Female mammals typically become hyperphagic from mid- to late pregnancy and during lactation. Mexican free-tailed bats, Tadarida brasiliensis mexicana, double their nightly food intake from late pregnancy to peak lactation and consume an insect diet that is exceptionally high in fat. During late pregnancy and throughout lactation, fasting plasma levels of cholesterol in this insectivorous bat are high (215 +/- 8 mg/dl) and are nearly 10-fold higher than in three species of Old World frugivorous bats. Fasting triglycerides were unexpectedly low in T. brasiliensis (25 +/- 2 mg/dl), despite evidence of high fat intake during nightly feeding bouts (postprandial cholesterol and triglycerides, 268 +/- 18 and 122 +/- 20 mg/dl, respectively). High-density lipoprotein (HDL) cholesterol levels were extraordinarily high (124 +/- 5 mg/dl) and unaffected by feeding. Low-density lipoprotein cholesterol levels were correspondingly low (86 +/- 7 mg/dl). This unusual plasma lipid profile was not associated with coronary or aortic atherosclerosis, nor was there evidence of hyperglycemia or hyperinsulinemia. A high-fat diet and high levels of cholesterol in T. brasiliensis are not correlated with cardiovascular disease or (possibly) insulin resistance. Among several possible factors that might account for these observations, nightly bouts of powered flight (commuting and foraging for food) may contribute to elevated HDL cholesterol, which may protect this species from developing atherosclerosis.

The mechanisms of Cl- transfer across the rat placenta have been investigated. Clearance across the intact placenta from mother to fetus (m-->f) of 51Cr-EDTA (paracellular diffusion marker) and 36Cl- (Kmf) was 1.9 +/- 0.1 and 37.3 +/- 4.1 microliters/min, respectively (mean +/- SE, n = 10), the large difference indicating that most m-->f transfer of Cl- is transcellular. The clearance of 36Cl- across the dually perfused placenta in m-->f and fetal-to-maternal directions was symmetrical and highly sensitive to the anion-exchange inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (0.1 mM). The Kmf of 36Cl- was not inhibited by anoxia and had a low temperature quotient (Q10 between 32 and 37 degrees C was 1.52). The m --> f transfer of Cl- seemed to be fully saturated at physiological concentrations of Cl-. 36Cl- could be displaced from the transporter on the maternal side by other anions with the following order of affinity: Cl- approximately NO3- > Br- > lactate- >> gluconate. It is concluded that most of the Cl- transfer across the rat placenta is effected by an anion exchanger.

We previously showed that, although cold-induced thermoregulation is attenuated in 26-mo-old male Fischer 344 (F344) rats, not all rats this age exhibit the same degree of cold-exposed hypothermia or diminished brown adipose tissue nonshivering thermogenic capacity. Examination of this heterogeneity suggested the hypothesis that it was associated with a difference in the physiological state between aged rats that were maintaining stable body weight versus those showing the rapid weight loss often occurring near the end of the rat's natural life span. To test this, we acutely exposed male F344 rats to cold (4 h at 6 degrees C) beginning at 24 mo of age. This exposure was weekly for the first 2 wk and then on alternate weeks as long as the rat's body weight was stable. If body weight progressively declined for 3-5 consecutive days, the rat's response to the acute cold exposure was again measured, as was that of two additional rats not displaying this rapid loss in body weight. If body temperature decreased during the cold exposure to intraperitoneal temperatures < or = 32.5 degrees C, the rat was killed with pentobarbital sodium and interscapular brown adipose tissue was removed. One of the age-matched controls was also killed at this time. The age at which body weight showed a spontaneous rapid decline ranged from 24.5 to 29 mos. All eight rats displaying spontaneous rapid weight loss had significant hypothermia during the acute cold exposure, whereas none of the eight weight-stable rats did. The development of hypothermia in the spontaneous rapid weight loss group was not, in general, observed before their weight loss. The weight loss and hypothermia were associated with lower levels of brown fat uncoupling protein and significant changes in body fat and protein. These data suggest that the development of senescence-related hypothermia occurs rapidly and is not a simple function of chronological age or the median life span of the animals. Furthermore, these data imply that the rate of aging in terms of maintenance of thermoregulatory homeostasis has both a gradual and rapid component, the latter being associated with a different physiological state than the former.

Expression of Na(+)-K(+)-adenosinetriphosphatase (ATPase) in tissues from obese and lean Zucker rats was monitored. The phosphatase activity of the sodium pump was increased in liver and intestinal mucosa from obese animals but was unaltered in skeletal muscle, brown adipose tissue, kidney, and heart. Induction of Na(+)-K(+)-ATPase activity was correlated with increased alpha 1-subunit protein amounts in liver and intestinal mucosa, although alpha 1-subunit mRNA levels were increased only in liver tissue. Neither protein nor mRNA amounts for both subunits were significantly altered in the other tissues analyzed. The only exception was a decrease in the amount of beta 1-protein in kidney from obese rats. alpha 2-Subunit protein and alpha 2- and beta 2-mRNA levels were not altered in brown adipose tissue, heart, and soleus. In summary, this study shows that in obese Zucker rats the expression of the sodium pump is enhanced in tissues that are directly involved in nutrient uptake and processing. This adaptation may be related to the ongoing hyperphagia and to tissue hypertrophia but develops in a different manner in each tissue, suggesting differential regulation of alpha 1-subunit expression.

We determined whether the triple vascular occlusion pressure (Pto), the equilibration pressure obtained when the hepatic artery, portal, and hepatic veins were occluded simultaneously, represented the capillary pressure (Pc) in isolated bivascularly blood-perfused canine livers. Effects of a bolus injection of histamine (0.1-60 micrograms), norepinephrine (NE; 1-600 micrograms), or acetylcholine (ACh; 0.01-10 micrograms) into the portal vein or the hepatic artery were also studied on vascular resistance distribution using Pto as a measure of Pc. The livers were perfused at constant flow via the portal vein and at constant pressure via the hepatic artery. Pto was compared with Pc measured using the traditional gravimetric method (Pc,i). Pto and Pc,i showed a strong correlation (Pto = -0.02 + 0.98 Pc,i; r = 0.83, P = 0.0018). With comparisons, the intercept was not significantly different from zero, and the slope was not different from 1.00, indicating that Pto accurately represented Pc. The resting postsinusoidal vascular resistance comprised 54% of the total hepatic vascular resistance (Rt). Portal or arterial injection of histamine increased predominantly hepatic venous resistance (Rhv) over portal resistance with liver weight gain. NE constricted both the portal vein and the hepatic artery in greater magnitude than the hepatic vein, as evidenced by a significant decrease in the Rhv/Rt ratio. This precapillary constriction was accompanied by a significant decrease in liver weight. In contrast, ACh contracted both portal and hepatic veins similarly without liver weight change. We conclude that Pto is an excellent estimate of Pc in isolated blood-perfused canine livers and that the hepatic vascular resistance sites in the resting states are located evenly in the pre- and postsinusoidal vessels. Intraportal or intra-arterial infusion of histamine, NE, and ACh produced characteristically different changes in hepatic vascular resistances and hepatic volume. The Pto technique could be applied in experimental research on hepatic hemodynamics.

Interleukin-1 (IL-1) and interleukin-6 (IL-6) are thought to play a role in mediating weight loss, net protein catabolism, anorexia, and fever after infection or injury. Because IL-1 and IL-6 can be synthesized in the brain and have been shown to be increased in central nervous system (CNS) infections, we investigated the metabolic consequences of prolonged CNS exposure to these cytokines. At equivalent doses, intracerebroventricular infusion of IL-1, but not IL-6, caused negative nitrogen balance, weight loss, and anorexia. Intracerebroventricular infusion of IL-1 also caused adrenocortical activation, as indicated by increased adrenal weight and plasma corticosterone, and decreased thymus weight. However, clamping plasma glucocorticoids at low levels by adrenalectomy and corticosterone pellet replacement did not attenuate IL-1-induced losses of body weight and nitrogen. We conclude that centrally produced IL-1 could play an important role in the metabolic alterations associated with CNS injury or infection and that these effects may not be solely attributable to increased secretion of glucocorticoids.

This study was designed to test the hypothesis that endogenous arginine synthesis plays an important role in maintaining arginine homeostasis in neonatal pigs. Gabaculine was used as a suicide inhibitor of ornithine aminotransferase to decrease the intestinal conversion of glutamine-derived pyrroline-5-carboxylate (P-5-C) into ornithine, the precursor of both citrulline and arginine. Four-day-old suckling pigs received oral administration of 0.0 or 0.83 mg gabaculine/kg body wt every 4 h during a 12-h period from 6 A.M. to 6 P.M. Blood was collected from piglet's jugular vein at 6 A.M. and 6 P.M. after a 2-h isolation from sows. Gabaculine treatment decreased plasma concentrations of ornithine, citrulline, and arginine by 59, 52, and 76%, respectively, and increased those of glutamine and proline by 74 and 220%, respectively. The gabaculine treatment also increased plasma concentrations of leucine, taurine, and ammonia by 29, 42, and 20%, respectively. There were no differences in intramuscular concentrations of amino acids between control and gabaculine-treated pigs. Because P-5-C synthase (the enzyme required for synthesis of P-5-C from glutamate) was almost exclusively located in enterocytes of 4-day-old pigs, our data suggest that the intestinal production of citrulline plays an important role in endogenous synthesis of arginine and its homeostasis in neonatal pigs.

Electrolytic lesions of the posterodorsal aspects of the medial division of the extended amygdala in female rats result in hyperphagia and excessive weight gain. In the present study, the effects of such lesions on plasma insulin, glucose, corticosterone, and adrenocorticotropic hormone were assessed during a period of food restriction and again after a 15-day period of food ad libitum. Compared with control animals, the rats with amygdaloid lesions were hyperinsulinemic under both conditions and gained substantially more weight when fed ad libitum. No difference between groups was observed for the other hormones. It is concluded that damage to the posterodorsal aspects of the medial amygdala results in a primary metabolic dysfunction that accounts, at least in part, for the overeating and excessive weight gain.

In the present study, we test whether thyrotropin-releasing hormone (TRH) stimulates respiratory frequency in perinatal rats by acting at regions of the medulla responsible for respiratory rhythmogenesis, the pre-Botzinger complex. We also test whether TRH stimulates respiration in the fetal rat at a time shortly after the inception of respiratory rhythmogenesis [embryonic days (E) 17-18]. Two in vitro experimental models were utilized: the isolated brain stem-spinal cord preparation from fetal (E17-E18) and neonatal [postnatal days (P) 0-2] rats and the medullary slice preparation isolated from neonatal rats (P1-P2). Bath application of TRH caused a dose-dependent, reversible increase (maximum increase approximately 60%) in the frequency of respiratory rhythmic neural discharge generated by brain stem-spinal cord [half-maximal effective concentration (EC50) approximately 9 nM] and medullary slice (EC50 approximately 2.5 nM) neonatal rat preparations. Pressure injection of TRH unilaterally into the region of the pre-Botzinger complex of the neonatal medullary slice caused an approximately 28% increase in the frequency of respiratory discharge. Application of TRH to the medium bathing fetal rat brain stem-spinal cord preparations caused an approximately threefold increase in respiratory discharge frequency. We conclude that TRH stimulates respiratory discharge frequency from the time near inception of respiratory motor discharge and acts directly at the pre-Botzinger complex.

The aims of this work were to establish whether glutamine infusion via alanyl-glutamine dipeptide provides effective therapy against muscle atrophy from glucorticoids and whether the glucocorticoid induction of glutamine synthetase (GS) is downregulated by dipeptide supplementation. Rats were given hydrocortisone 21-acetate or the dosing vehicle and were infused with alanine (AA) or alanyl-glutamine (AG) at the same concentrations and rates (1.15 mumol.min-1.100 g body wt-1, 0.75 ml/h) for 7 days. Compared with AA infusion in hormone-treated animals, AG infusion prevented total body and fast-twitch muscle mass losses by over 70%. Glucocorticoid treatment did not reduce muscle glutamine levels. Higher serum glutamine was found in the AG-infused (1.72 +/- 0.28 mumol/ml) compared with the AA-infused group (1.32 +/- 0.06 mumol/ml), but muscle glutamine concentrations were not elevated by AG infusion. Following glucocorticoid injections, GS enzyme activity was increased by two- to threefold in plantaris, fast-twitch white (superficial quadriceps), and fast-twitch red (deep quadriceps) muscle/fiber types of the AA group. Similarly, GS mRNA was elevated by 3.3- to 4.1-fold in these same muscles of hormone-treated, AA-infused rats. AG infusion diminished glucocorticoid effects on GS enzyme activity to 52-65% and on GS mRNA to 31-37% of the values with AA infusion. These results provide firsthand evidence of atrophy prevention from a catabolic state using glutamine in dipeptide form. Despite higher serum and muscle alanine levels with AA infusion than with AG infusion, alanine alone is not a sufficient stimulus to counteract muscle atrophy. The AG-induced muscle sparing is accompanied by diminished expression of a glucocorticoid-inducible gene in skeletal muscle. However, glutamine regulation of GS appears complex and may involve more regulators than muscle glutamine concentration alone.

Bispectral analysis was used to demonstrate quadratic nonlinear coupling (i.e., phase locking) of different frequency components in inferior cardiac sympathetic nerve discharge (SND) of urethan-anesthetized rats. The complex patterns of SND analyzed included mixtures of 1) the cardiac-related and 10-Hz rhythms, 2) the 10-Hz rhythm and irregular 2-to 6-Hz oscillations, and 3) the 10-Hz rhythm and a lower frequency non-cardiac-related rhythm near 4 Hz. In some cases, the bicoherence function (normalized bispectrum) showed no phase locking of these frequency components. Cases of nil bicoherence are equated with linear superposition of frequency components, which implies the existence of multiple and noninteractive central circuits. Increased complexity of SND was observed in other cases, as evidenced by significant phase locking of different frequency components with or without frequency locking. Frequency locking (higher frequency rhythm is a multiple of lower) was confirmed by constructing Lissajous orbital plots showing covariation of voltages in selectively filtered bands of SND. We equate frequency locking with nonlinear coupling of the central generators of different sympathetic nerve rhythms and phase locking without frequency locking possibly with nonlinearities arising at levels below noncoupled central rhythm generators.

The mechanisms and mediators of hypertrophic growth secondary to infravesical urinary outflow obstruction are unknown. The renin-angiotensin system has been implicated in vascular and cardiac hypertrophy, but the involvement of angiotensin II (ANG II) as a trophic factor in the lower urinary tract has not been investigated. In this study, the ANG II subtype AT1 receptor antagonist losartan (DuP 753) was administered perorally (15 mg.kg-1.day-1) for 28 days to rats subjected to partial urethral obstruction or sham surgery. Partial urethral obstruction caused a 3.5-fold increase in bladder weight and a 3-fold increase in bladder protein content compared with sham rats. However, no difference was observed in bladder weight or bladder protein content between losartan-treated rats and rats receiving no drug. Cystometric evaluation of bladder function revealed significant increases in micturition volume, bladder capacity, bladder compliance, and spontaneous contractile activity in rats subjected to partial urethral obstruction compared with sham rats. However, bladder function in rats treated with losartan was not different from bladder function in rats receiving no drug. In vitro studies of isolated bladder tissue showed a weak contractile response to ANG II (1 microM) that amounted to 4.4 +/- 1.0% of the response to K+ (124 mM). The ANG II-induced contraction was abolished by losartan (10 microM) and indomethacin (10 microM). The contractile response to ANG II (1 microM), K+ (124 mM), and transmural nerve stimulation (2 Hz) was reduced in bladder strips from obstructed rats. In conclusion, no evidence was found for involvement of ANG II in development of bladder hypertrophy. The effect of ANG II on bladder smooth muscle tone was minor but was mediated by stimulation of the AT1 subtype receptor.

Tumor necrosis factor (TNF) and interleukin (IL)-1 are two cytokines for which naturally occurring inhibitors have been identified. The present study was undertaken to evaluate the extent to which scavenging of TNF in bacteremia attenuates the plasma levels of IL-1 receptor antagonist (IL-1ra) and soluble TNF receptors (sTNFR). Ten male baboons received 2 x 10(9) colony-forming units/kg live Escherichia coli over 2 h and were subjected to either placebo or anti-TNF antibody (anti-TNF Ab) treatment (1 mg/kg CDP571, Celltech, UK) 2 h before E. coli infusion (observation time: 72h). IL-1ra (range: 50-100 ng/ml) and sTNFR (range: 55kDa, 20-25 ng/ml; 75 kDa, 30-35 ng/ml) release was more sustained than that of IL-1 and TNF and was significantly attenuated by anti-TNF treatment, as were the circulating levels of IL-1, IL-8, and monocyte chemotactic peptide-1 (MCP-1) in the anti-TNF Ab group. We conclude that the increase in circulating natural cytokine modulators observed in nonhuman primate bacteremia is under the partial control of endogenous TNF because it was influenced by anti-TNF pretreatment. This attenuation is comparable to the anti-TNF effect on the chemokine MCP-1.

To characterize the renin secretory profile in Lyon hypertensive (LH) rats, renin responses to reductions of arterial pressure and beta-adrenoceptor stimulation were assessed in conscious unrestrained LH (n = 13) and Lyon normotensive (LN, n = 14) rats under normal-salt diet. Mean arterial pressure (MAP) in the infrarenal aorta was recorded beat to beat for 3 h. Then, plasma renin concentration (PRC) was measured 1) in basal conditions, 2) during 10-mmHg stepwise reductions of MAP down to 60 mmHg using a chronically implanted aortic inflatable cuff, and 3) during isoprenaline infusion (62.5, 125, and 250 ng.kg-1.min-1 iv). Compared with LN, LH rats had an elevated MAP (146 +/- 3 vs. 111 +/- 1 mmHg, P < 0.001) and decreased PRC [4.2 +/- 0.6 vs. 8.2 +/- 0.8 ng angiotensin (ANG) I.ml-1.h-1, P < 0.001] and kidney renin content (216 +/- 14 vs. 1,149 +/- 103 micrograms ANG I.h-1.g-1, P < 0.001). Pressure-dependent renin release occurred below 90 mmHg in LN rats and below 80 mmHg in LH rats, and its sensitivity in the low-pressure range did not differ between strains. Isoprenaline-induced increases in PRC were weaker (P < 0.01) in LH than in LN rats. In additional LH and LN rats (n = 6-8), acute ANG II AT1-receptor blockade with losartan (20 mg/kg, followed by 10 mg.kg-1.h-1 iv for 2 h) induced lesser (P < 0.001) PRC increases in LH than in LN rats. Renin responses to isoprenaline remained blunted (P < 0.01) during losartan infusion in LH rats. We conclude that, in LH rats, renin secretion is independent of MAP in the range of its spontaneous variations and is poorly responsive to beta-adrenoceptor stimulation, the alteration of which cannot be explained by an enhanced feedback inhibition by ANG II.

Changes in the percentage of adenosine 3', 5'-cyclic monophosphate (cAMP)-dependent protein kinase present as the active catalytic subunit (PKAc) and in the levels of the second messengers cAMP, guanosine 3',5'-cyclic monophosphate (cGMP), and D-myo-inositol 1,4,5-trisphosphate (IP3) were quantified in tissues of the freeze-tolerant wood frog Rana sylvatica over the course of freezing at -2.5 degrees C and thawing at 5 degrees C. Freezing exposure rapidly raised liver cAMP concentration and %PKAc (by 2- and 6-fold, respectively) within 2 min postnucleation; both peaked and stabilized between 5 and 60 min postnucleation but declined with longer freezing. Other organs also showed elevated PKAc during freezing, particularly skeletal muscle. By contrast, cGMP concentration was reduced in muscle and kidney after 24 h of freezing but rose after thawing in muscle. Liver also showed a twofold elevation of cGMP during thawing. The protein kinase C (PKC) second messenger, IP3, rose throughout freezing in liver, reaching levels 11-fold higher than control values after 24 h of freezing. IP3 was also elevated in brain after 4 and 8 h of freezing. The different patterns of cAMP, protein kinase A (PKA), and IP3 changes in liver suggest that, whereas cAMP and PKA clearly mediate the rapid activation of glucose output as a cryoprotectant, IP3 and PKC may be involved instead with metabolic responses that deal with the consequences of long-term freezing, such as ischemia resistance or cell volume control.

We examined the efficiency and intracellular fate of oligodeoxy-nucleotides (ODN) in the central nervous system (CNS) after delivery with a hemagglutinating virus of Japan (HVJ)-liposome vector in vivo and in vitro. In primary cultured granular cells of the rat cerebellum, application of fluorescein isothiocyanate (FITC)-labeled ODN complexed with HVJ-liposomes in vitro resulted in strong fluorescence localized in nuclei that persisted for > or = 2 wk, in contrast to 3 days with ODN alone. In vivo ODN transfer was attempted by different approaches: infusions into the paraventricular nuclei of the hypothalamus and the lateral cerebroventricle. Injection of FITC-labeled ODN into the hypothalamus by the HVJ-liposome method produced a higher concentration and more persistent fluorescence than did injection of ODN alone. Administration of ODN into the lateral cerebroventricle with HVJ-liposomes yielded more conspicuous and prolonged fluorescence in the periventricular layer, predominantly in cell nuclei. Furthermore, the distribution of fluorescent cells was broader with the HVJ-liposome method. These results indicate that the HVJ-liposome method prolongs the half-life of ODN and concentrates them in cell nuclei. Thus it is an efficient method for ODN transfer and holds promise as a gene delivery method in the CNS.

The role of (+/-)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA)-kainate and N-methyl-D-aspartate (NMDA) receptors in the rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM) on the central respiratory drive (CRD)-related activity of splanchnic sympathetic nerve activity (SNA) was examined in rats. SNA increased during inspiration (I peak) and postinspiration (PI peak). Bilateral microinjections of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; AMPA-kainate antagonist) or DL-2-amino-5-phosphonovaleric acid (APV; NMDA antagonist) into RVLM abolished the PI, but not the I, peak. Blockade of all excitatory amino acid receptors in RVLM with kynurenate, or mixtures of APV and CNQX, also failed to eliminate the I peak. Somatosympathetic responses were abolished by CNQX injection into RVLM, but were unaffected by APV. CNQX, but not APV, injection into CVLM increased the PI peak of SNA. Our findings suggest the following. 1) Both NMDA and AMPA-kainate receptors in RVLM are involved in the coupling between the sympathetic nervous system and CRD, which generates the PI peak seen in SNA. 2) The I peak of SNA is independent of excitatory amino acid transmission within RVLM. 3) There are different relative amounts of NMDA and AMPA-kainate receptors at synapses where respiratory and somatic inputs converge onto RVLM neurons. 4) Glutamatergic inputs to CVLM neurons modulate the coupling between SNA and CRD in RVLM.

Two series of experiments were conducted to investigate the role of corticotropin-releasing hormone (CRH) in the effects of 5-hydroxytryptamine (5-HT) on energy intake and energy expenditure. The first set of experiments was carried out to confirm the influence of 5-HT1A-, 5-HT1B-, 5-HT2A/2C-receptor agonists on the activation of the hypothalamic-pituitary-adrenal axis. Plasma corticosterone levels were measured, and a double-immunolabeling procedure was used to determine whether the neuronal activity marker, c-Fos protein (Fos), could be found within brain neurons containing CRH after treatments with 5-HT1A-, 5-HT1B-, 5-HT2A/2C-receptor agonists. The second series of experiments was conducted to assess the involvement of CRH in the effects of 5-HT on food intake and metabolic rate (VO2). The effects of the 5-HT1A-, 5-HT1B-, 5-HT2A/2C-receptor agonists on food intake and VO2 were measured in rats treated with the CRH antagonist, alpha-helical CRH-(9-41). In both experiments rats were intraperitoneally injected with either a vehicle (NaCl 0.9%), the 5-HT1A-receptor agonist (+/-)-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide (8-OH-DPAT), the 5-HT1B-receptor agonist 5-methoxy-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole succinate (RU-24969), or the 5-HT2A/2C-receptor agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl (DOI). Fos immunoreactivity was detectable within the CRH-containing neurons of the paraventricular nucleus of the hypothalamus (PVH) after injection of each of the 5-HT-receptor agonists used. The CRH antagonist alpha-helical CRH-(9-41) attenuated the increases in metabolic rate induced by DOI and 8-OH-DPAT. alpha-Helical CRH did not, however, prevent the effects of RU-24969 and DOI on either nocturnal metabolic rate or food intake. The present results provide further evidence for a role of CRH in 5-HT-mediated thermogenic effect, which likely involves the 5-HT2A/2C receptor during the day and the 5-HT1A receptor during the night. Moreover, these results do not support a role for CRH in 5-HT anorectic effects, which likely involves 5-HT1B and 5-HT2A/2C receptors. Finally, the results of this study indicate that the stimulation of CRH-containing neurons located in the PVH does not necessarily predict changes in food intake and energy expenditure.

An isolated-perfused tail-trunk preparation was employed to study the influence of transmembrane pH gradient and membrane potential on the transport and distribution of L(+)-lactate (Lac), metabolic H+ (delta Hm+), and related parameters in rainbow trout white muscle after exhaustive exercise. One resting [arterial pH (pHa) approximately 7.9] and four postexercise treatments (pHa approximately 7.4, 7.9, 8.4, and, high K+, pHa approximately 7.9, partially depolarized by 15 mM K+) were examined. Variations in HCO3- concentration (2-18 mM) at a constant PCO2 approximately 2 Torr were used to alter pHa. The elevated intracellular Lac (approximately 50 mM) remained unchanged after 60 min of perfusion because of very low rates of lactate efflux and oxidation. H+, HCO3-, and Lac- distributions were all well out of electrochemical equilibrium. Total CO2 efflux was reduced at high extracellular pH (pHe); alterations in the net driving force on HCO3- may have overshadowed the influence of PCO2 gradients in driving total CO2 efflux. Lac efflux and delta Hm+ flux were completely uncoupled. delta Hm+ flux reacted to both acid-base and electrochemical gradients as delta Hm+ efflux dropped and even reversed when pHe decreased, whereas partial depolarization in conjunction with depressed intracellular pH resulted in elevated delta Hm+ efflux. Lac efflux did not respond to changes in pHe. Changes in Lac efflux corresponded more closely to changes in the Lac- concentration gradient than in the lactic acid gradient. This study provides circumstantial evidence for the involvement of electroneutral mechanisms (i.e., Lac(-)-H+ cotransport and/or Lac-/anion exchange) in lactate efflux, but does not eliminate the possibility of an active transport mechanism contributing to the retention of Lac.

This study examined the effects of elevated muscle temperature on muscle metabolism during exercise. Seven active but untrained men completed two cycle ergometer trials for 2 min at a workload estimated to require 115% maximal oxygen uptake (VO2) either without pretreatment (CT) or after having their thigh wrapped in a heating blanket for 60 min before exercise (HT). HT increased (P < 0.01) muscle temperature (Tm) and resulted in a difference in Tm between the two trials before (delta = 1.9 +/- 0.1 degrees C, P < 0.01) and after exercise (delta = 0.6 +/- 0.2 degree C, P < 0.05). HT did not affect rectal temperature or plasma catecholamines. In addition, these parameters were not different between CT and HT either before or after exercise. No differences in resting intramuscular concentrations of the adenine nucleotides (ATP, ADP, AMP) or their degradation products (inosine 5'-monophosphate, ammonia), lactate, glycogen, creatine phosphate, or creatine were observed between HT and CT. During exercise, the magnitude of ATP degradation and inosine 5'-monophosphate and ammonia accumulation was higher (P < 0.05) in HT compared with CT. Although preexercise concentrations of glycogen and lactate were not different between the two trials, postexercise lactate concentration was higher (P < 0.05) and glycogen lower (P < 0.05) in HT compared with CT. In addition, net muscle glycogen use was higher (P < 0.05) in HT. It is concluded that an elevated Tm per se increases muscle glycogenolysis, glycolysis, and high-energy phosphate degradation during exercise. These alterations may be the result of an increased rate of ATP turnover associated with the exercise and/or changes in the anaerobic/aerobic contribution to ATP resynthesis.

Human peritoneal mesothelial cells (HMC) play a critical role in maintaining the intraperitoneal balance between fibrinolysis and coagulation by expressing the fibrinolytic enzyme tissue-type plasminogen activator (t-PA) as well as a specific plasminogen activator inhibitor, PAI-1, and the procoagulant protein tissue factor (TF). Of three compounds known to stimulate t-PA synthesis in cultured human endothelial cells, i.e., retinoic acid, the protein kinase C activator 4 beta-phorbol 12-myristate 13-acetate (PMA), and sodium butyrate, only butyrate (1 mM) caused about a threefold increase in t-PA synthesis and mRNA expression in HMC after 24 h of incubation, without markedly affecting PAI-1 synthesis. PMA (10 nM) induced a threefold increase in urokinase-type plasminogen activator (u-PA) mRNA, but u-PA antigen levels in the HMC conditioned media remained below the detection level (0.5 ng/ml), possibly as a result of rapid uptake and degradation by the u-PA receptor. The u-PA receptor mRNA levels were about fivefold enhanced above control levels after PMA treatment of the cells. An increase in intracellular adenosine 3',5'-cyclic monophosphate levels by forskolin (10 microM) diminished t-PA and PAI-1 levels 43 and 17%, respectively. Among the inflammatory mediators tested [tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha, and bacterial lipopolysaccharide], TNF-alpha (10-1,000 U/ml) showed the strongest procoagulant effects. We found that the isoflavone compound genistein (25 micrograms/ml) prevented the TNF-alpha-induced expression of PAI-1 and TF while also slightly counteracting the decrease in t-PA synthesis. The protein kinase C inhibitor R0-318220 (3 microM) only moderately opposed the TNF-alpha-induced changes in t-PA and PAI-1 synthesis but completely prevented the induction of TF mRNA. In summary, our results demonstrate that t-PA synthesis in HMC is relatively insensitive to pharmacological stimulation. To restore the balance between fibrinolysis and coagulation under inflammatory conditions, attempts to interfere with the TNF-alpha-signaling pathway were more successful.

We tested the hypothesis that sustained increases in mean arterial pressure (MAP) produce nonuniform changes in regional sympathetic nerve discharges (SND) after the return of MAP to control levels. Renal, adrenal, splanchnic, and lumbar SND were recorded before, during, and after a 30-min elevation in MAP produced by phenylephrine (PE) infusion in alpha-chloralose-anesthetized spontaneously hypertensive (SH) rats. SND remained reduced from control values after PE infusion, despite the return of MAP to control levels. Importantly, the duration of poststimulus sympathoinhibition was significantly less in adrenal and splanchnic SND compared with renal and lumbar SND. In sinoaortic-denervated SH rats, SND remained at control levels during and after PE infusion. Simultaneous recordings of aortic depressor nerve (ADN) activity and SND demonstrated that prolonged renal and lumbar sympathoinhibition occurred even when ADN activity fell below control levels after PE infusion. We conclude that poststimulus responses of efferent SND in SH rats are regionally nonuniform and that renal and lumbar sympathoinhibitory responses are not mediated solely by prolonged increases in afferent baroreceptor nerve activity.

Stressful life events may be important causative or precipitating factors for functional gastrointestinal disorders such as the irritable bowel syndrome in humans. In the rat, a single session of foot shocks is known to sensitize the behavioral and hormonal responses to subsequent stress, but intestinal responses have not been investigated. Rats were fitted with bipolar electrodes on proximal colon and exposed to a single session of foot shocks (10 x 6 s in 15 min; preshocked) or no shocks (control). Weight gain after foot shocks was identical to that in controls. Two weeks after foot shocks, basal colonic spike burst frequency did not differ from controls or from that recorded before shock treatment. Unlike controls, however, preshocked rats showed a significant increase in colonic spike burst frequency to a novel stressful challenge in the home cage, an electrified prod. Because the behavioral responses to this challenge did not differ, colonic hyperresponsiveness in preshocked rats may represent a form of stress-induced autonomic sensitization. The model should be a useful tool to study mechanisms and pharmacotherapeutic approaches of the gastrointestinal consequences of traumatic stress.

Metabolites of cytochrome P-450 are produced in cells when arachidonic acid cascade is activated. Fever genesis depends largely on the cyclooxygenase branch of arachidonic acid cascade, which is caused by many stimuli, such as interleukin (IL)-1, IL-6, and interferon-alpha. To assess the significance of cytochrome P-450 branch in fever, murine recombinant IL-1 beta was bilaterally microinjected (1 ng/microliter) into the medial preoptic area and anterior hypothalamus in conscious rats treated 60 min previously with or without the cytochrome P-450 inhibitor econazole (15 mg/kg im). The IL-1 beta-induced rise in colonic temperature was enhanced after the plateau phase of fever (from 240 min after IL-1 beta) in econazole-pretreated rats (P < 0.001). Another cytochrome P-450 inhibitor, clotrimazole (15 mg/kg im), also enhanced IL-1 beta-induced fever from 160 min after IL-1 beta injection (P < 0.001). Econazole also enhanced the fever when it was given 120 min before injection of IL-1 beta (P < 0.001). The cytochrome P-450 inhibitor, however, did not affect the fever when given 10 min after IL-1 beta (P = 0.95). Econazole and clotrimazole did not alter normal body temperature (P = 0.65 and 0.73, respectively). The results suggest that the metabolite(s) of cytochrome P-450 affect the falling phase after the plateau phase of fever and act as putative endogenous antipyretic(s).

Lipoprotein lipase (LPL) is a hydrolytic enzyme, involved in lipoprotein metabolism and nutrient partitioning, that is subject to tissue-specific regulation. Evidence for divergent regulation of the lipase by insulin has been demonstrated, but alterations in the tissue-specific response of LPL to catecholamines has not been studied in humans. The regulation of LPL in gluteal adipose tissue and vastus lateralis muscle by isoproterenol (epinephrine isopropyl homologue) in humans was examined over 2 h in subjects infused with 0 (saline) or 8 or 24 ng.kg-1.min-1 isoproterenol. The infusion of normal saline into control subjects failed to alter adipose tissue or skeletal muscle LPL activity. However, in the saline-infused subjects there was a positive correlation between the percent change in plasma norepinephrine concentrations and the percent change in muscle LPL activity (r = 0.826, P < 0.05). Isoproterenol infusion did not change LPL in either adipose tissue or muscle compared with saline-infused controls, but plasma insulin levels in addition to plasma glucose, free fatty acids, and glycerol were increased. To prevent the isoproterenol-induced hyperinsulinemia, a pancreatic clamp technique was utilized. An increase in muscle LPL was demonstrated (P = 0.037) with no change in adipose tissue LPL. The change in muscle LPL activity after the 2-h infusion correlated with the change in muscle mRNA (P = 0.021). Overall, these studies indicate that in humans the response of LPL to catecholamines is tissue specific with no effect in adipose tissue but a stimulation in skeletal muscle. Endogenous regulation of LPL in muscle by catecholamines could be important in muscle fuel metabolism and could relate to effects of adenosine 3',5'-cyclic monophosphate and/or fatty acids at the level of the LPL gene.

Previous research has shown ectotherms to have markedly lower sodium pump metabolism than endotherms. Direct measurement of enzymatic activity of the sodium pump (Na(+)-K(+)-adenosinetriphosphatase) confirmed this difference. To determine the source of this difference, sodium pump density was measured with the use of [3H]ouabain binding. Ectotherms and endotherms were found to share similar sodium pump numbers. Approximate densities (in pmol/g) were 250 for skeletal muscle, 500 for liver, 900 for heart, and 8,000 for kidney and brain. Therefore, differences in sodium pump activity between endotherms and ectotherms were due to differences in turnover rates or molecular activities of sodium pumps. Molecular activities of sodium pumps (in ATP/min) of tissues from endotherms were between 6,000 and 12,000 and, for ectotherms, between 1,500 and 2,500. Exceptions were found that included the heart of Bufo marinus. In a single invertebrate species studied, Charax destructor, the sodium pumps of the heart had a low molecular activity characteristic of ectothermic tissues. These results suggest that during the evolution of endothermy there was a general increase in the molecular activity of the sodium pump.

To examine the presence of metabolic cold adaptation in Antarctic isopods, whole animal rates of oxygen uptake (MVo2) and protein synthesis were measured in Glyptonotus antarcticus at 0 degree C and compared with the temperature isopod Idotea rescata at 4 and 14 degrees C. The specific relationship between rates of metabolism and protein synthesis was investigated by injecting animals with cycloheximide, a protein synthesis inhibitor. In G. antarcticus, routine MVo2 was 11.10 +/- 0.89 mumol.kg-1.min-1 (n = 19 animals), and ks was 0.24 +/- 0.04% protein synthesized/day (n = 8 animals). Comparison with I. rescata showed that standardized whole animal MVo2 decreased with temperature (temperature quotient = 1.99), but whole animal ks was considerably lower in the Antarctic isopod; 66 and 22% of total MVo2 was attributable to protein synthesis in G. antarcticus at 0 degree C and I. rescata at 4 degrees C, respectively. The energetic cost of protein synthesis was four times higher in G. antarcticus at 885 +/- 141 mmol ATP/g protein (n = 5 animals) compared with 237 +/- 76 mmol ATP/g protein (n = 6) in I. rescata. G. antarcticus does not show metabolic rate compensation and maintains extremely low ks levels because of the relatively high energetic cost of protein synthesis.

In anesthetized rats, iontophoresis of the gamma-aminobutyric acid (GABAB)-receptor agonist and antispastic drug baclofen inhibits the bulbospinal vasomotor neurons of the rostral ventrolateral medulla (RVLM). The present study was carried out to determine whether C1 adrenergic and other bulbospinal neurons of the RVLM have postsynaptic GABAB receptors. Retrogradely labeled RVLM bulbospinal neurons (n = 52) were recorded in 120-micron-thick slices from neonatal rat brain (3-10 days old). Most neurons (48/52) were tonically active (3 +/- 0.6 spikes/s). Twenty-six neurons were recovered histologically, and 18 of them were immunoreactive for tyrosine hydroxylase (TH). In current clamp, baclofen (0.3-10 microM) hyperpolarized RVLM bulbospinal cells in a dose-dependent manner (16 +/- 0.5 mV hyperpolarization by 3 microM baclofen; n = 19) and decreased input resistance by 40% (n = 10). In voltage clamp (1 microM tetrodotoxin present; holding potential: -40 to -60 mV), 3 microM baclofen induced an outward current of 21 +/- 2 pA (n = 29). This current exhibited inward rectification and reversed polarity close to the K+ equilibrium potential (external K+ from 2.5 to 10 mM). The current induced by baclofen was reduced 90% by 0.1-0.2 mM BaCl2 (n = 6) and was blocked reversibly by the selective GABAB-receptor antagonist CGP-55845A (0.5-1 microM; n = 6). All histologically verified TH-immunoreactive cells (n = 18) were sensitive to baclofen. In summary, RVLM bulbospinal neurons including C1 adrenergic cells possess GABAB receptors. Activation of these receptors increases an inwardly rectifying K+ conductance. This effect reduces the intrinsic firing frequency of RVLM vasomotor neurons "in vitro" and may contribute to the sympatholytic action of baclofen "in vivo."

Hepatic cytokine gene expression is independently stimulated by circulating microbial products and reductions in the cellular O2 supply. Although these stimuli occur sequentially after gram-negative bacteremia, it is unknown whether their interplay augments production of interleukin (IL)-1 by the liver. We studied the effects of intraportal Escherichia coli (EC) bacteremia and secondary constant-flow hypoxia (Po2, approximately 46 Torr for 30 min) on IL-1 alpha and IL-1 beta gene expression in ex situ buffer-perfused rat livers over 180 min (n = 67). At t = 0, normoxic EC and normal saline (NS) controls received 10(9) live EC serotype 055:B5 and 0.9% NaCl, respectively; in livers subjected to EC+hypoxia-reoxygenation (H/R) and NS+H/R, hypoxia began 0.5 h after EC or NS and was followed by 120 min of reoxygenation. Portal and hepatic venous perfusates were serially analyzed for bacterial colony-forming units, O2 uptake, and aspartate aminotransferase. At 60 min (peak hypoxia) and 180 min, cDNAs for IL-1 alpha and IL-1 beta were hybridized to whole liver RNA, and IL-1 beta protein levels in venous perfusates were assessed. Intrahepatic levels of reduced glutathione (GSH) were measured as an index of oxidative stress. Compared with normoxic EC, IL-1 alpha transcripts decreased at 180 min in EC+H/R livers (P < 0.0001) as did IL-1 beta mRNA (P < 0.05), despite similar EC clearance, GSH levels, posthypoxic O2 uptake, and aspartate aminotransferase release. Hepatic secretion of IL-1 beta likewise fell in EC+H/R vs. EC controls (P < 0.005). Prostaglandin H synthase-2 (COX-2) message accumulation was not enhanced by H/R, and indomethacin did not reverse H/R-mediated suppression of IL-1 production. In contrast, H/R-related falls in EC-induced IL-1S expression were reversed by allopurinol or catalase. Thus brief hypoxic stress of the liver causing neither GSH depletion nor functional impairment downregulates postbacteremic IL-1 expression by a mechanism involving O2 radicals but not cyclooxygenase metabolites.

In the present study, the time course of change in sucrose-induced insulin resistance, triglyceride (TG) concentration, and liver fatty acid composition was examined. Male rats (n = 8-10/group per time point) was fed a high-starch (ST) diet for 2 wk and were then equicalorically fed ST or a high-sucrose (SU) diet for 1, 2, 5, or 8 wk. Body weight and percent body fat were similar between ST and SU diets at all time points. Glucose infusion rate (GIR) was significantly (P < 0.05) lower in the SU diet (9.2 +/- 0.9, 7.4 +/- 0.5, 6.2 +/- 1.0, and 6.0 +/- 0.9 mg.kg-1.min-1) vs. the ST diet (15.1 +/- 1.7, 15.7 +/- 0.7, 14.7 +/- 1.9, and 14.2 +/- 0.9 mg.kg-1.min-1) at 1, 2, 5, and 8 wk, respectively. Reduced suppression of glucose appearance accounted for 85, 50, 45, and 40% of the reduction in GIR at these same time points. Muscle glycogen synthesis was reduced (P < 0.05 vs. ST diet) in the SU diet at 2, 5, and 8 wk. Fasting plasma TG concentration was inversely related (r = -0.79, P < 0.001) to muscle glycogen synthesis, and liver TG concentration was positively related (r = 0.59, P < 0.01) to glucose appearance. Liver fatty acid composition was similar between diet groups. In summary, the SU diet produced insulin resistance in liver before muscle. TG concentration appears to be related to sucrose-induced insulin resistance in liver and muscle.

We investigated the physiological regulation of renal function by nitric oxide (NO) and its interactions with the endothelial cyclooxygenase products in the conscious, chronically catheterized rat. A subpressor dose of NO inhibitor nitro-L-arginine methyl ester (L-NAME) produced renal vasoconstriction that was unaffected by cyclooxygenase inhibition with indomethacin (Indo). Acute, high-dose L-NAME produced a pressor response of approximately 40 mmHg and marked renal vasoconstriction. Indo selectively amplified the renal vasoconstriction, whereas inhibition of the thromboxane-endoperoxide receptor had no effect. Chronic NO inhibition for 5 wk led to sustained hypertension and renal vasoconstriction; the latter was amplified by acute Indo. These data suggest that in the normal, conscious rat the kidney is under important NO-dependent tone. There is no obvious interaction between NO and the cyclooxygenase products in control of basal renal function. When systemic NO inhibition is produced with either acute or chronic high-dose L-NAME, the kidney is severely vasoconstricted. The renal vasoconstriction is not ameliorated by thromboxane-endoperoxide antagonism but is exacerbated by cyclooxygenase blockade, suggesting that vasodilator cyclooxygenase products compensate for the renal hypoperfusion because of severe NO deficiency.

The central and peripheral cardiovascular effects of synthetic trout urotensin II (UII) were investigated in the conscious rainbow trout. Intracerebroventricular injection of 50 pmol UII produced a slight (3%) but significant (P < 0.05) increase in heart rate but had no effect on mean arterial blood pressure. Injection of 500 pmol UII icv produced a significant (P < 0.05) rise (8%) in blood pressure with no change in heart rate. In contrast to the weak pressor effect of centrally administered UII, intra-arterial injection of UII produced a dose-dependent increase in arterial blood pressure and decrease in heart rate with significant (P < 0.05) effects on both parameters observed at a dose of 25 pmol. Higher doses of the peptide produced a sustained decrease in cardiac output that accompanied the bradycardia and rise in arterial blood pressure. The UII-induced bradycardia, but not the increase in pressure, was abolished by pretreatment with phentolamine. Trout UII produced a sustained and dose-dependent contraction of isolated vascular rings prepared from trout efferent branchial [-log 50% of the concentration producing maximal contraction (pD2) = 8.30] and celiacomesenteric (pD2 = 8.22) arteries but was without effects on vascular rings from the anterior cardinal vein. The data indicate that the pressor effect of UII in trout is mediated predominantly, if not exclusively, by an increase in systemic vascular resistance. The UII-induced hypertensive response does not seem to involve release of catecholamines, but the bradycardia may arise from adrenergic-mediated activation of cardioinhibitory baroreflexes.

Exposure to stressors can affect various aspects of immune function, including the antibody response. We have previously reported that rats exposed to an acute session of inescapable tail shock (IS) show long-term reductions in anti-keyhole limpet hemocyanin (KLH) immunoglobulin (Ig) M and IgG and a failure to expand Th1-like cells in response to KLH. To further investigate the potential role of decreased Th1-like cells in the IS-induced reduction of anti-KLH Ig, we examined two isotypes of IgG, IgG1 and IgG2a. Isotype switching is under cytokine control. Interleukin-4 helps B cells switch from making IgM to making IgG1, whereas interferon (IFN)-gamma helps B cells switch from making IgM to making IgG2a. In this paper we report that IS exposure reduces IFN-gamma levels 4 days after exposure to IS+KLH compared with immunized home cage controls. In addition, IS exposure reduced the Th1 cytokine-sensitive anti-KLH IgG2a but not Th2 cytokine-sensitive anti-KLH IgG1. This pattern of isotype reduction suggests that a failure to expand the Th1 cell, which results in less IFN-gamma, may contribute to the the IS-induced reduction in anti-KLH Ig. Glucocorticoids (GCs) differentially regulate Th1 and Th2 cells. Administration of the type II GC receptor antagonist RU-486 before IS blocked the IS-induced suppression in anti-KLH IgM, IgG, and IgG2a. Corticosterone (2.5 mg/kg), however, did not produce the suppression in anti-KLH Ig. These results support a role of corticosterone in mediating IS-induced reductions in in vivo antibody.

The purpose of this study was to determine whether high plasma levels of atrial natriuretic peptide (ANP) in compensated heart failure are important in the maintenance of sodium balance. This was achieved by subjecting eight dogs to bilateral atrial appendectomy (APX) to blunt the ANP response to pacing-induced heart failure. Five intact dogs served as controls. In controls, 14 days of left ventricular pacing at 240 beats/min produced a sustained fall in cardiac output and mean arterial pressure of approximately 40 and 20%, respectively; compared with cardiac output, reductions in renal blood flow (up to approximately 25%) were less pronounced and even smaller decrements in GFR occurred (up to 9%). Despite these changes and a threefold elevation in plasma norepinephrine concentration, plasma renin activity (PRA) did not increase and sodium balance was achieved during the second week of pacing in association with a six- to eightfold rise in plasma levels of ANP. Similar responses occurred in four dogs in which APX was relatively ineffective in blunting the ANP response to pacing. In marked contrast, there were substantial increments in PRA and in plasma norepinephrine concentration, and marked sodium and water retention during the last week of pacing in four dogs with APX and severely deficient ANP. These results indicate that ANP plays a critical role in promoting sodium excretion in the early stages of cardiac dysfunction.

Sleep, daily torpor, and hibernation have been considered to be homologous processes. However, in the Djungarian hamster, daily torpor is followed by an increase in slow-wave activity (SWA; electroencephalogram power density 0.75-4.0 Hz) that is similar to the increase observed after sleep deprivation. A positive correlation was found between torpor episode length and the subsequent increase in SWA, which was highest when SWA was assumed to increase with a saturating exponential function. Thus the increase in SWA propensity during daily torpor followed similar kinetics as during waking, supporting the hypothesis that when the animal is in torpor it is incurring a sleep debt. An alternative hypothesis, proposing that the mode of arousal causes the subsequent SWA increase, was tested by warming the animals during emergence from daily torpor. Irrespective of mode of arousal, more non-rapid eye movement (NREM) sleep and a similar SWA increase was found after torpor. The data are compatible with a putative neuronal restorative function for sleep associated with the expression of SWA in NREM sleep. During torpor, when brain temperature is low, this function is inhibited, whereas the need for restoration accumulates. Recovery takes place only after return to euthermia.

To examine possible regulatory control of renal proximal tubule organic anion secretion, winter flounder (Pleuronectes americanus) proximal tubule primary cultures were mounted in Ussing chambers. Unidirectional fluxes of [2,4-(14)C]dichlorophenoxyacetic acid were determined under short-circuited conditions. Phorbol 12-myristate 13-acetate (1 microM) caused a significant (P < 0.01) inhibition of net 2,4-dichlorophenoxyacetic acid secretion. Preincubation with staurosporine (1 microM) blocked the phorbol 12-myristate 13-acetate-induced decrease in secretion. Neither forskolin (10 microM) nor W-7 (20 microM) had any effect on net transport. Elevation of intracellular calcium activity with either A-23187 or thapsigargin produced a slight, transient decrease in transport. Addition of dopamine (1 microM) to the peritubular side, but not the luminal side, caused a significant (P < 0.01) decrease in net secretion. Both the alpha-adrenergic agonist oxymetazoline (10 microM) and depletion of intracellular Na+ transiently, but significantly (P < 0.05), increased net transport. The data indicate that renal organic anion excretion may be regulated through dopaminergic inhibition and alpha-adrenergic stimulation of net transepithelial secretion.

The present study examined the contribution of energy expenditure to the recovery of body weight after a period of overfeeding. Three groups of 2-mo-old female rats (n = 24) were fed, respectively, a 10% (wt/wt)-fat diet (control), a 35% (wt/wt)-fat diet (high fat) or were force fed 130% of the control diet (tube fed). After 30 days, all groups received the control diet for 18 days of recovery. Both overfeeding protocols significantly increased weight above control levels. This difference disappeared after 7 days of recovery. Increases in resting oxygen consumption, serum 3,5,3'-triiodothyronine (T3) levels, and the thermogenic response to norepinephrine were observed at the end of overfeeding. Serum T3 and resting oxygen consumption returned to control levels by day 3 of recovery from overfeeding, whereas the thermogenic response to norepinephrine required 9 days to recover. Whereas total energy expenditure was not significantly elevated during overfeeding, significant increases of 9.6 and 13.9% were observed in the formerly high-fat and tube-fed animals, respectively, during recovery. These data indicate that changes in energy expenditure play an important role in maintaining the stability of body weight.

We investigated the importance of pre- and postnatal maternal rhythmicity for the development and synchronization of the juvenile circadian core temperature (Tc) rhythm in rats by evaluating the Tc of artificially reared pups in six litters derived from mothers maintained in continuous bright light (LL) and impregnated after drinking behavior stopped showing circadian periodicity. Pups removed from their aperiodic mothers on postnatal day 9 and artificially reared for 3 days showed a free-running Tc rhythm whose amplitude (3.1 +/- 0.1 degrees C, n = 47) was only slightly smaller than that of control pups born to mothers maintained in a 12:12-h light-dark cycle. In four litters the acrophases were not much less synchronized than in the four control litters (mean vector lengths 0.79 +/- 0.05 vs. 0.94 +/- 0.04). In two litters synchronization among littermates was not significant. Additional experiments with cross-fostered pups showed that synchronization is not caused by the time of birth. We conclude that synchronization among littermates can develop even when maternal rhythmicity has been suppressed even before conception, possibly because the Tc decrease of several littermates happening to have similar phases at birth acts as zeitgeber.

Increases of plasma arginine vasopressin (AVP) and plasma renin activity (PRA) during controlled mechanical ventilation (CMV) with positive end-expiratory pressure (PEEP) induce positive fluid balances by decreasing renal excretion. We investigated whether elevated levels of AVP and/or PRA maintain mean arterial pressure (MAP) during PEEP under conditions where plasma volume is not expanded. Six conscious chronically tracheotomized beagle dogs, kept under standardized conditions, were investigated in four protocols. They were 1) control: 1 h spontaneous breathing with a continuous positive airway pressure of 4 cmH2O (CPAP 4) followed by 2 h CMV with PEEP, resulting in a mean airway pressure of approximately 20 cmH2O (CMV 20 referred to as "PEEP"); 2) vasopressin blockade: 1 h CPAP 4, 2 h PEEP after intravenous application of an AVP V1-receptor antagonist (AVPA); 3) converting enzyme inhibition: 1 h CPAP 4, 2 h PEEP plus angiotensin-converting enzyme inhibition (ACEI); and 4) combined blockade: 1 h CPAP 4, 2 h PEEP plus AVPA + ACEI. In AVPA + ACEI, MAP decreased during PEEP from 101 +/- 4 to 75 +/- 10 mmHg, glomerular filtration rate (GFR) decreased from 3.6 +/- 0.3 to 1.7 +/- 0.7 ml.min-1.kg body wt-1, heart rate increased from 95 +/- 10 to 122 +/- 7 beats/min, plasma aldosterone increased from 62 +/- 26 to 353 +/- 63 pg/ml, plasma epinephrine increased from 81 +/- 15 to 352 +/- 89 pg/ml (all changes P < 0.05), and plasma norepinephrine did not change. Neither MAP nor GFR changed during PEEP in control experiments in which both PRA and AVP increased, in AVPA experiments in which PRA increased, or in ACEI experiments in which AVP increased. We conclude that both AVP and angiotensin II contribute to the maintenance of MAP and GFR during PEEP. When both hormones are inhibited, no immediate compensation exists to prevent an acute fall in MAP and GFR.

Squid (Lolliguncula brevis) were exercised at increasing swimming speeds to allow us to analyze the correlated changes in intracellular metabolic, acid-base, and energy status of the mantle musculature. Beyond a critical swimming velocity of 1.5 mantle lengths/s, an intracellular acidosis developed that was caused by an initial base loss from the cells, the onset of respiratory acidification, and, predominantly, octopine formation. The acidosis was correlated with decreasing levels of phospho-L-arginine and, thus, supported ATP buffering at the expense of the phosphagen. Monohydrogenphosphate, the actual substrate of glycogen phosphorylase accumulated, enabling glycogen degradation, despite progressive acidosis. In addition to octopine, succinate, and glycerophosphate accumulation, the onset of acidosis characterizes the critical velocity and indicates the transition to a non-steady-state time-limited situation. Accordingly, swimming above the critical velocity caused cellular energy levels (in vivo Gibbs free energy change of ATP hydrolysis) to fall. A minimal value was reached at about -45 kJ/mol. Model calculations demonstrate that changes in free Mg2+ levels only minimally affect ATP free energy, but minimum levels are relevant in maintaining functional concentrations of Mg(2+)-complexed adenylates. Model calculations also reveal that phosphagen breakdown enabled L. brevis to reach swimming speeds about three times higher than the critical velocity. Comparison of two offshore squid species (Loligo pealei and Illex illecebrosus) with the estuarine squid L.brevis indicates that the latter uses a strategy to delay the exploitation of high-energy phosphates and protect energy levels at higher than the minimum levels (-42 kJ/mol) characterizing fatigue in the other species. A more economical use of anaerobic resources and an early reduction in performance may enable L. brevis to tolerate more extreme environmental conditions in shallow estuarine waters and even hypoxic environments and to prevent a fatal depletion of energy stores.

We examined blood pressure and heart rate (HR) in relation to glucose and arterial PO2 (PaO2) at approximately 121 days (early) and at approximately 140 days (late) gestation in 12 growth-restricted and 10 control fetal lambs. Mild growth restriction (relative to maternal weight) was produced by withdrawal of 25 ml/day of maternal blood during the second half of pregnancy (P < 0.05). Fetuses from this model are hypoglycemic during early and late gestation but hypoxemic only during late study. Mean systolic and diastolic pressures in the experimental group were approximately 8.0 mmHg lower than the corresponding values in controls at both studies (P < 0.05). Fetal HR (FHR) was 15.4 beats/min lower (P < 0.05) in 10 but was higher than control in 2 experimental fetuses that were also not growth restricted. There were significant correlations between late systolic pressure and HR and PaO2 (r = 0.54, P = 0.046 and r = 0.50, P = 0.049, respectively) and between FHR and blood pressure and birth weight/maternal weight (P < 0.05). We conclude that, in this model, fetal blood pressure and HR may serve as good indicators of hypoxemia and growth restriction.

Recombinant human ciliary neurotrophic factor (rh-CNTF) was reported to attenuate skeletal muscle wasting in rats after unilateral transection of the sciatic nerve (M. E. Helgren, S. P. Squinto, H. L. Davis, D. J. Parry, T. G. Bolton, C. S. Heck, Y. Zhu, G. D. Yancopoulos, R. M. Lindsay, and P. S. DiStefano. Cell 76: 493-504, 1994). Under the experimental conditions reported herein, the absolute masses of the denervated gastrocnemius and soleus muscles were not increased in mature or immature rats of either sex by treatment with rhCNTF. At the highest doses of rhCNTF (1 and 0.1 mg/kg), increases in the ratio of the masses of the denervated to the contralateral innervated gastrocnemius and soleus muscles could be attributed entirely to a muscle-wasting effect on the contralateral innervated muscle rather than any muscle-sparing effect on the denervated muscle. The muscle-wasting effects of rhCNTF were associated with reductions in body weight gain and reduced food intake. Pair-fed rats lost less body weight and skeletal muscle mass than rhCNTF-injected freely fed rats but experienced significantly greater loss of visceral mass. Male rats displayed greater loss of body weight and skeletal muscle mass than female rats. Recombinant inhibitors of the cachectic cytokines, tumor necrosis factor and interleukin-1, did not significantly alter the wasting effects of rhCNTF. These findings demonstrate that, in contrast to its well-characterized trophic effects on cells of the nervous system, rhCNTF causes atrophy of skeletal muscle by mechanisms involving both anorexia and cachexia based on the results of pair-feeding experiments.

In conditions of chronic cold exposure, ducklings develop a nonshivering thermogenesis that requires a high energy expenditure. Therefore, energy supply becomes essential to cold-acclimated ducklings, which increase their intake of carbohydrate-rich food. The aim of this work was to investigate the effect of cold acclimation on the activity of the intestinal brush-border Na(+)-D-glucose cotransport, which is the first major step controlling glucose entrance into an organism. Cotransport activity was determined by measuring D-glucose uptake in brush-border membrane vesicles isolated from different parts of the small intestine of thermoneutral control (25 degrees C) or cold-acclimated (4 degrees C) ducklings (Cairina moschata). Two D-glucose transport sites were described in ducklings: a high-affinity/low-capacity site and a low-affinity/high-capacity site. The former was mainly located in the ileum and the latter in the duodenum. These two transport sites were altered differently by cold exposure. Major alterations occur in the ileum where 1) a reduction in the Michaelis-Menten constant and maximal transport rate of the high-affinity site was observed, and 2) the occurrence of low-affinity site activity was noted in cold-acclimated ducklings, although it was not detected in the thermoneutral control group. Cold effect on the high-affinity site could be related to the changes in the ileal brush-border membrane vesicle lipids, whereas cold effect on the low-affinity site could be due, at least in part, to the higher glycosyl content found in this segment. The small intestine appears then able to react to cold exposure by increasing both its mucosa mass in proximal segments and D-glucose uptake capacity in ileum to respond to the higher energy demand induced by thermoregulatory requirements.

The influence of altered dietary sodium on angiotensinogen and renin gene expression was examined in young normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Artificial rearing was used to increase or decrease dietary sodium intake during the preweanling period. In normally reared control animals, renal renin and liver angiotensinogen mRNA decreased between 6 and 30 postnatal days of age. In contrast, in the central nervous system, angiotensinogen mRNA increased between 6 and 30 days of age, and renin mRNA remained stable. Dietary sodium manipulation between postnatal days (PD) 6 and 18 significantly influenced renal renin gene expression, with low-sodium diet increasing renin mRNA on PD12 and PD18 and high-sodium diet decreasing renin mRNA on PD18. Liver angiotensinogen mRNA decreased for animals on either diet on PD12 and PD18. Brain angiotensinogen and renin mRNA were not affected by dietary sodium levels. There were no strain-related differences in the response to high and low dietary sodium. These results demonstrate that 1) the peripheral and central renin-angiotensin systems do not have a common ontogenetic pattern of development, 2) they are independently regulated in response to dietary sodium variations, and 3) young WKY and SHR share very similar ontogenetic patterns of angiotensinogen and renin gene expression.

Changes in liver and skeletal muscle fructose-2,6-bisphosphate (Fru-2,6-P2) concentrations were compared during fasting, exercise, and recovery in the lizard Dipsosaurus dorsalis and in outbred mice (Mus musculus). We present the first correlative evidence that suggests that a decrease in the content of Fru-2,6-P2 may mediate elevated gluconeogenesis in lizard skeletal muscle. Contents of Fru-2,6-P2 in lizard gastrocnemius and red and white iliofibularis (IF) were significantly lower (as much as 55% in white IF) during recovery from exhaustive exercise than at rest. Recovery from exhaustive exercise had no significant effect on Fru-2,6-P2 concentrations in any mouse muscle examined. Fasting significantly depressed lizard and mouse liver Fru-2,6-P2 contents and decreased lizard red IF by over 84% from the fed condition. Lizard red and white muscle fiber bundles incubated in 20 mM lactate had significantly lower Fru-2,6-P2 (94 and 61% depression, respectively) than those incubated in 8.5 mM glucose. These results are consistent with the hypothesis that Fru-2,6-P2 acts as a signal for controlling gluconeogenesis in lizard skeletal muscle.

Zinc is an essential nutrient for growth; however, little is known about zinc kinetics (absorption, distribution, and excretion) in preterm infants (< 38-wk gestation). Zinc kinetics were studied in two preterm infants (gestational ages, 32 and 33 wk) following oral or intravenous administration of a stable isotope (70Zn). Plasma, red blood cells (RBC), urine, and feces were sampled for up to 30 days. Isotope enrichment was measured in tissues by inductively coupled plasma (ICP)-mass spectrometry, and zinc was determined by ICP-atomic emission spectrometry. Data were analyzed by compartmental analysis using SAAM31. Zinc intake increased during the studies, and, because body zinc was not in steady state, both tracer (70Zn) and tracee (Zn) data were fitted using analogous models. A model for adults [M. E. Wastney, R. L. Aamodt, W. F. Rumble, and R. I. Henkin. Am. J. Physiol. 251 (Regulatory Integrative Comp. Physiol. 20): R398-R408, 1986] was modified to fit data from the preterm infants. RBC data were fitted using one compartment (vs. 2 in adults), and an adult RBC subsystem was included in the model to account for zinc introduced during blood transfusions. Exchange of zinc between compartments that were not sampled was based on zinc distribution in neonates. Absorption was 42 and 34%, and endogenous fecal excretion, based on intravenous data, was 15 micrograms.kg-1.day-1. The model can be used to quantify changes in zinc kinetics of preterm infants with age, weight, and zinc intake for evaluating nutritional requirements with growth.

To assess the effect of chronic sleep deprivation on host defense, we observed growth and regression of a subdermal allogenic carcinoma (Walker 256 rat tumor) in rats undergoing 10 days of total sleep deprivation (TSD rats), yoked stimulus control (TSC) rats that were partially sleep deprived, and home cage control (HCC) rats. Tumor size was measured daily. Integrated tumor size was smaller in TSD rats than in both TSC (P = 0.04) and HCC rats (P = 0.0003). Thus host defense against these tumors (as defined by reduction in tumor size) was improved by sleep deprivation. This improvement could be a nonspecific effect, e.g., tumor growth can be inhibited by a catabolic state (dietary restriction). TSD and TSC rats lost body weight, indicating a catabolic state. However, tumor size was not predicted by body weight change, but was predicted by change in sleep time (P = 0.02). Host defense enhancement could alternatively result from enhanced immune response. Early tumor size (5 days) was similar in the three groups, but peaked sooner in TSD rats than in both TSC (P = 0.05) and HCC rats (P = 0.01), leading to large differences in size later. Immune-suppressed rats also showed little difference from HCC rats in early growth but large differences later. Thus host defense in an in vivo model that manifests a systemic immune response can be enhanced by sleep deprivation with timing, which is consistent with an enhancement of the immune response.