bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of NO on vasopressin and oxytocin release and blood pressure responses during osmotic stimulation in rats
Authors: Kadekaro M. , Liu H. , Terrell M. L. , Gestl S. , Bui V. , Summy-Long J. Y.
Published: December 2017

NG-nitro-L-arginine methyl ester (L-NAME, 250 micrograms/5 microliters), an inhibitor of nitric oxide (NO) synthase, or artificial cerebrospinal fluid (5 microliters) was administered intracerebroventricularly to conscious naive rats or to rats treated subcutaneously (15 microliters/kg) with NaCl (0.15, 0.45, or 1.0 M) or given a needle prick only. Intracerebroventricular injection of L-NAME increased plasma concentration of vasopressin (VP) and oxytocin (OT) in control naive rats, indicating that NO tonically inhibits basal secretion of both hormones during isosmotic isovolemic conditions. Osmotic stimulation with hypertonic saline (0.45 and 1.0 M NaCl) elevated plasma levels of both hormones as expected. Central blockade of NO synthase further enhanced secretion of OT during mild, but not strong, osmotic stimulation, whereas the high levels of VP remained unaffected by L-NAME. In animals treated with the needle prick or 0.15 M NaCl, only OT levels were increased after L-NAME. Therefore, NO selectively inhibits OT release in response to a painful stimulus (needle prick) and moderate osmotic stimulation to promote a preferential release of VP. A transient pressor response was observed after subcutaneous injection of 0.15 and 0.45 M NaCl, but a sustained response was obtained after 1.0 M NaCl. Regardless of whether the animals received NaCl solutions, however, treatment with L-NAME elevated blood pressure in all animals. Thus NO-induced vasodilation maintains basal arterial blood pressure and limits the pressor response to osmotic stimulation.
Effects of NO synthase inhibitors, arginine-deficient diet, and amiloride in pregnant rats
Authors: Greenberg S. S. , Lancaster J. R. , Xie J. , Sarphie T. G. , Zhao X. , Hua L. , Freeman T. , Kapusta D. R. , Giles T. D. , Powers D. R.
Published: December 2017

This study tests the hypothesis that nitric oxide synthase (NOS) inhibition is linked to NG-nitro-L-arginine methyl ester (L-NAME)-mediated intrauterine growth retardation (IUGR) and fetal limb reduction deficits (LRD) in pregnant dams. Administration of L-NAME (1 mg/ml) or aminoguanidine (AG, 500 micrograms/ml) in the drinking water or intraperitoneal administration of L-N5-(1-iminoethyl)-ornithine (L-NIO, 10 mg.kg-1.day-1) on gestational days 13-20 decreased nitrite and nitrate plus nitrate (RNI) levels in the urine and plasma and decreased RNI in incubates of aorta and fetal limbs compared with pregnant rats given amiloride (50 micrograms/ml) or water (control). Although all drugs caused fetal IUGR, only L-NAME and amiloride caused fetal deaths and LRD. Urine and tissue levels of RNI were unchanged in rats fed and arginine-free diet (AFD) on gestational days 13-20, and yet fetal IUGR, deaths, and LRD were prevalent. L-NAME potentiated the fetal abnormalities and resorptions. Plasma arginine concentrations decreased with AFD > > L-NAME > L-NIO. Plasma ornithine, a precursor for polyamine synthesis, decreased with AFD and increased with L-NAME. Thus inhibition of NOS is not linked to LRD. The ability of L-NAME and amiloride to produce fetal IUGR and LRD may result from L-NAME-mediated modulation of amino acid delivery to the fetus and amiloride-mediated inhibition of protein synthesis. Finally, IUGR appears unrelated to LRD.
Erythropoietin gene expression is suppressed after lipopolysaccharide or interleukin-1 beta injections in rats
Authors: Frede S. , Fandrey J. , Pagel H. , Hellwig T. , Jelkmann W.
Published: December 2017

Proinflammatory cytokines play an important role in the pathogenesis of anemia in inflammatory diseases. Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) have been reported to inhibit the synthesis of erythropoietin (EPO) in vitro. To evaluate the in vivo significance of this observation, we have investigated effects of the administration of bacterial lipopolysaccharide (LPS) and IL-1 beta on renal EPO production in rats. Measurements by competitive reverse-transcription polymerase chain reaction showed that EPO mRNA levels were significantly reduced in the kidneys of normoxic rats 6 h after the injection of LPS (0.1 or 1 mg/kg). In addition, LPS and IL-1 beta (1 microgram/kg) inhibited the increase in EPO mRNA and plasma EPO levels when administered to rats before hypoxia exposure (8% O2 in the inspiratory gas). Evidence for an inflammatory reaction in the kidneys of LPS-treated rats was provided by measurements of greatly elevated renal TNF-alpha mRNA levels. Furthermore, kidneys isolated from LPS-created rats produced less immunoreactive EPO when perfused hypoxically in vitro for 2 h. Thus mediators of the immune response inhibit renal EPO gene expression in vivo, which is relevant with respect to the impaired synthesis of EPO in inflammatory diseases in humans.
The subtype 2 angiotensin receptor regulates renal prostaglandin F2 alpha formation in conscious rats
Authors: Siragy H. M. , Carey R. M.
Published: December 2017

The angiotensin AT1 receptor mediates renal prostaglandin (PG) E2 production through stimulation of phospholipase A2. Blockade of the AT2 receptor potentiates the angiotensin II-induced increase in PGE2 levels. In the kidney, PGE2 is converted to PGF2 alpha mainly by the enzyme PGE 9-ketoreductase. We hypothesized that the conversion of PGE2 to PGF2 alpha is inhibited by AT2 receptor blockade, resulting in the observed increase in PGE2 levels. Using a microdialysis technique, we monitored changes in renal interstitial fluid PGE2 and PGF2 alpha in response to 5 days of sodium depletion alone or a combination of sodium depletion and intravenous infusion of the AT1 receptor blocker losartan or the AT2 receptor blocker PD-123319 in conscious rats. We utilized the PGF2 alpha-to-PGE2 ratio as an indirect measure of the rate of renal PGF2 alpha formation. Sodium depletion increased PGE2, PGF2 alpha, and the PGF2 alpha-to-PGE2 ratio. During sodium depletion, losartan decreased PGE2 and PGF2 alpha and did not change the PGF2 alpha-to-PGE2 ratio. In contrast, PD-123319 increased PGE2, decreased PGF2 alpha, and decreased the PGF2 alpha-to-PGE2 ratio. These data demonstrate that activation of the renin-angiotensin system during sodium depletion physiologically increases renal conversion of PGE2 to PGF2 alpha. The increase in renal production of PGF2 alpha is mediated through stimulation of the angiotensin AT2 receptor.
Sexual dimorphism in regional blood flow responses to vasopressin in conscious rats
Authors: Wang Y. X. , Crofton J. T. , Bealer S. L. , Share L.
Published: December 2017

The greater pressor response to vasopressin in male than in nonestrous female rats results from a greater increase in total peripheral resistance in males. The present study was performed to identify the vascular beds that contribute to this difference. Mean arterial blood pressure (MABP) and changes in blood flow in the mesenteric and renal arteries and terminal aorta were measured in conscious male and nonestrous female rats 3 h after surgery. Graded intravenous infusions of vasopressin induced greater increases in MABP and mesenteric vascular resistance and a greater decrease in mesenteric blood flow in males. Vasopressin also increased renal vascular resistance to a greater extent in males. Because renal blood flow remained unchanged, this difference may be due to autoregulation. The vasopressin-induced reduction in blood flow and increased resistance in the hindquarters were moderate and did not differ between sexes. Thus the greater vasoconstrictor response to vasopressin in the mesenteric vascular bed of male than nonestrous females contributed importantly to the sexually dimorphic pressor response to vasopressin in these experiments.
Adrenal vasoactive intestinal peptide participates in neonatal corticosteroid production in the rat
Authors: Bodnar M. , Sarrieau A. , Deschepper C. F. , Walker C. D.
Published: December 2017

Neonatal rats (3-14 days old) exhibit a period of adrenal hyporesponsiveness characterized by blunted corticosterone (B) responses to stress and reduced adrenal sensitivity to adrenocorticotropic hormone (ACTH). Several adrenomedullary peptidergic systems like vasoactive intestinal peptide (VIP) are postulated to influence cortical function. VIP is known to stimulate corticosterone secretion in vitro and to be released from the adrenal medulla following splanchnic nerve stimulation. Here, we tested whether 1) accelerated sympathetic innervation of the adrenal gland by daily L-thyroxine (T4) treatment modified the ontogeny of adrenal VIP and 2) an increase in VIP synthesis could prematurely increase adrenal sensitivity and corticosteroid output during neonatal life. Immunohistochemical VIP staining revealed a different ontogenetic pattern between adrenal regions from days 2-18 and different sensitivities to T4 treatment. Capsular staining was most abundant at all ages and increased with T4 treatment, whereas medullary staining was seen by day 18 and was not affected by T4. Throughout development, VIP receptors were detected mostly in the capsular region, but not in the adrenal cortex. Although receptor levels were not modified by T4 injections, T4 significantly enhanced VIP mRNA levels in the whole adrenal at all ages. In vivo administration of VIP (0.1-2.0 mg/kg body wt ip) to 9- to 12-day-old neonates increased pituitary ACTH, adrenal B, and aldosterone secretion significantly. Corticotropin-releasing factor immunoneutralization before VIP injection diminished VIP-induced ACTH release but still produced small but significant B and aldosterone secretion. Our results show that 1) VIP innervation of the adrenal capsule is present soon after birth and is increased by sympathetic activity whereas VIP appears only much later in the medulla and does not coincide with the onset of splanchnic innervation and 2) exogenous VIP stimulates ACTH, B, and aldosterone release during development and the effect of VIP on steroidogenic secretion is occurring through ACTH secretion, but also, at least in part, directly at the level of the adrenal gland.
Effect of heat stress on LPS-induced fever and tumor necrosis factor
Authors: Kluger M. J. , Rudolph K. , Soszynski D. , Conn C. A. , Leon L. R. , Kozak W. , Wallen E. S. , Moseley P. L.
Published: December 2017

Exposure to heat stress leads to both short-term and long-term effects on morbidity. Male rats were exposed to a high ambient temperature of 40 degrees C, which resulted in biotelemetered core body temperature rising to approximately 42 degrees C. This treatment led to a marked enhancement in lipopolysaccharide (LPS)-induced fever at 24 h after exposure to heat stress. The increase in fever was accompanied by a significant suppression in the circulating concentration of tumor necrosis factor. Heat-shock protein-70 measured in liver was elevated by the heat exposure (but not further elevated by the injection of LPS). An enhanced fever to LPS and other inflammatory stimuli found in heat-stressed human subjects could explain the apparent increase in susceptibility to disease.
Central opiate mu-receptor-mediated suppression of tissue protein synthesis
Authors: Hashiguchi Y. , Molina P. E. , Dorton S. , McNurlan M. A. , Garlick P. J. , Reddy D. , Abumrad N. N.
Published: December 2017

We determined the dose-dependent effects of central mu-opioid receptor stimulation on rates of tissue protein synthesis. Chronically catheterized conscious rats received an intracerebroventricular injection of [D-Ala2, N-Me-Phe4,Gly5-ol]enkephalin (DAGO, 0.5, 2, or 8 nmol/rat) or water (5 microliters) 45 min before determination of protein synthesis by the flooding dose technique. DAGO produced a significant decrease in tissue protein synthesis in liver (57%), spleen (54%), gut mucosa (36%), gut serosa (23%), kidney (48%), gastrocnemius (33%), and plantaris muscle (27%), but it did not alter rates of protein synthesis in the brain, heart, and soleus muscle. DAGO produced an acute dose-dependent respiratory depression 30 min after intracerebroventricular injection; this depression resulted in acidosis, hypoxia, and hypercapnia (pH 7.19 +/- 0.04, arterial partial O2, pressure 44.2 +/- 3.4 Torr, arterial O2 saturation 65.3 +/- 5.5%, and PCO2 66.3 +/- 4.4 Torr). Intracerebroventricular DAGO increased circulating levels of catecholamines, corticosterone, and growth hormone but did not alter those of insulin and insulin-like growth factor I. Significant positive correlations between protein synthesis and pH were observed in the tissues studied (i.e., liver protein synthesis vs. pH, P < 0.0001, r = 0.902; gastrocnemius protein synthesis vs. pH, P < 0.0001, r = 0.830). Our results indicate that mu-receptor stimulation inhibits tissue protein synthesis, and this effect appears to be secondary to respiratory depression and the resulting acidosis and/or hypoxia. Furthermore, our findings suggest differential sensitivity in tissue response to alterations in pH, hypoxia, and stress hormone elevation.
Cholecystokinin octapeptide inhibits carbohydrate but not protein intake
Authors: Mamoun A. H. , Bergstrom J. , Sodersten P.
Published: December 2017

Male rats ingested about half as much of an intraorally infused (1 ml/min) carbohydrate solution compared with a protein solution. Blood levels of cholecystokinin octapeptide (CCK-8) had increased to 13.6 +/- 1.4 and 16.7 +/- 1.7 pmol/l when the rats stopped ingesting carbohydrate or protein and continued to increase to 35.6 +/- 3.2 pmol/l 30 min after the carbohydrate meal and 34.4 +/- 3.5 pmol/l 60 min after the protein meal. Intraperitoneal injection of CCK-8 (0.6-5.0 micrograms) inhibited and injection of the CCKA-receptor antagonist L-364, 718 (20-80 micrograms) facilitated carbohydrate intake, but neither CCK-8 nor L-364,718 affected protein intake. The results suggest that CCK-8 is not involved in regulating the duration of a protein meal but may be involved in regulating carbohydrate intake. The postprandial period of suppression of protein intake correlated with the disappearance of some amino acids, e.g., Arg, Tyr, and Trp, in the blood, and this may be of importance for protein ingestion, since these amino acids are neurotransmitter precursors.
Methotrexate potentiates bradykinin-induced increase in macromolecular efflux from the hamster oral mucosa
Authors: Gao Xiao-Pei , Rubinstein Israel
Published: December 2017

The purpose of this study was to determine whether methotrexate modulates bradykinin-induced increase in macromolecular efflux from the in situ oral mucosa and whether this response is mediated by thel-arginine/nitric oxide biosynthetic pathway. Using intravital microscopy, we found that suffusion of methotrexate alone onto the hamster cheek pouch had no significant effects on leaky site formation and increase in clearance of fluorescein isothiocyanate-labeled dextran (molecular mass, 70 kDa). However, methotrexate significantly potentiated bradykinin-induced responses ( P < 0.05). These effects were associated with significant increases in nitrites concentration and guanosine 3′,5′-cyclic monophosphate-like immunoreactivity in the suffusate and were abrogated by NG-nitro-l-arginine methyl ester (l-NAME) but not NG-nitro-d-arginine methyl ester (d-NAME).l-Arginine, but notd-arginine, abolishedl-NAME-induced responses. ZnCI2and indomethacin had no significant effects on methotrexate-induced responses. Methotrexate had no significant effects on adenosine- and ionomycin-induced increases in macromolecular efflux. Collectively, these data indicate that methotrexate amplifies bradykinin-induced increase in macromolecular efflux from the in situ oral mucosa in a specific, receptor- andl-arginine/nitric oxide biosynthetic pathway-dependent fashion.
Long-term effects of maternal deprivation on the corticosterone response to stress in rats
Authors: Suchecki Deborah , Tufik Sergio
Published: December 2017

Twenty-four hours of maternal deprivation result in activation of the infant rat’s adrenocortical axis. In the present study we examined the long-term effects of maternal deprivation on the corticosterone (Cort) response to stress. Pups were maternally deprived (Dep) on postnatal day( PND) 11 and tested immediately ( PND 12) or returned to their mothers and tested at later ages. Testing consisted of a time course of the Cort response to a saline injection (5, 15, 30, and 60 min). At PND 12, the response of Dep pups was higher than that of nondeprived (non-Dep) pups. No group differences were observed at PND 16 and 22. On PND 30, Dep rats showed lower Cort levels than non-Dep pups at 0, 5, and 30 min after saline. At PND 60, non-Dep females showed higher Cort levels than males at 5, 15, and 30 min. This gender difference for Dep pups was observed only at 5 min. Male and female Dep animals presented lower Cort levels than non-Dep counterparts at 60 and 30 min after saline, respectively. These findings indicate that maternal deprivation effects on Cort secretion are long lasting. Dep rats showed a smaller adrenal response to stress at PND 30, whereas as adults the stress response was similar but the turnoff was different.
Role of L-type Ca2+ channel in PACAP-induced adrenal catecholamine release in vivo
Authors: Geng Guoju , Gaspo Rania , Trabelsi Fethi , Yamaguchi Nobuharu
Published: December 2017

The aim of the present study was to investigate whether the dihydropyridine-sensitive L-type Ca2+ channel is operative in adrenal catecholamine (CA) secretion induced by a novel neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), in anesthetized dogs. Plasma CA concentrations in adrenal venous and aortic blood were determined by a high-performance liquid chromatography method. All drugs tested were locally infused into the left adrenal gland via the left adrenolumbar artery. PACAP, with the isoform consisting of 27 (PACAP-27) and 38 (PACAP-38) amino acid residues, significantly increased CA output in a dose-dependent manner, with doses ranging from 5 to 500 ng and 7 to 700 ng, respectively. However, the amplitude of epinephrine response to PACAP-27 was three times greater than that obtained with PACAP-38 at the highest dose tested. In a separate group, a single dose of PACAP-27 (50 ng) induced highly reproducible CA responses when the same dose was repeated with an interval of 35 min. In dogs treated with nifedipine (50 μg), 5 min before the second administration of PACAP-27, the net CA response was significantly inhibited by ∼50% compared with that obtained in the presence of vehicle. A similar CA response to BAY K 8644 (5 μg) was completely abolished by the same dose of nifedipine. The present results indicate that both PACAP-27 and PACAP-38 have the direct local secretagogue effect on the adrenal medulla in vivo and that CA responses to PACAP-27 were greater than those observed with PACAP-38 at equivalent mole doses. The study suggests that the dihydropyridine-sensitive L-type Ca2+ channel is functionally involved in PACAP-induced adrenal CA secretion in the canine adrenal medulla in vivo.
Insulin-like growth factor I is suppressed in socially subordinate male baboons
Authors: Sapolsky Robert M. , Spencer E. Martin
Published: December 2017

Insulin-like growth factor (IGF) I is a potent growth-promoting and anabolic hormone with major roles in cellular growth and differentiation, protein metabolism and muscle physiology, wound healing, erythropoiesis, and immune stimulation. Few, if any, studies have examined social or psychological factors that could give rise to individual differences in IGF-I levels. As part of a long-term psychoendocrine study of a population of male baboons living freely in a national reserve in East Africa, we examined the relationship between social rank and IGF-I concentrations. We observed that social subordinance was associated with a relative suppression of IGF-I concentrations; no rank-related differences in concentrations of IGF-II or IGF-binding protein were observed. Extensive psychoendocrine literature suggests that the individual differences in IGF-I profiles were a consequence, rather than a cause, of the rank difference. We were able to rule out a number of possible proximal explanations for the rank-IGF-I correlation: 1) the correlation was not a function of age (which involves both an adolescent spurt in IGF-I concentrations as well as a decline in concentrations in aged individuals); 2) the IGF-I suppression in subordinate individuals could not be explained by the basal hypercortisolism typical of such subordinate animals; and 3) neither differences in the quality or quantity of food consumed, in basal testosterone concentrations, nor in genetics could explain the rank difference. Although the mediating mechanisms responsible for this rank difference were not discernible in this study, the magnitude of difference in IGF-I levels among baboons of differing ranks might be of physiological significance.
Lack of locomotor-cardiac coupling in trotting dogs
Authors: Simmons Adam D. , Carrier David R. , Farmer Colleen G. , Gregersen Colin S.
Published: December 2017

Coupling of locomotor and cardiac cycles has been suggested to facilitate effective arterial delivery and venous return during vigorous exercise. In an attempt to document locomotor-cardiac coupling, we ran five dogs on a motorized treadmill while monitoring heart activity with surface electrocardiogram electrodes and locomotor events with high-speed video and an accelerometer mounted on the dog’s back. Analysis of the cardiac and locomotor frequencies revealed that heart rate was usually slightly greater than stride frequency. Hence the timing of the cardiac cycles varied with respect to the phase of the locomotor cycles, and therefore consistent coupling of the locomotor and cardiac cycles was not observed in any of the dogs. However, the period of the cardiac cycle sometimes varied in a rhythmic way that caused brief periods of transient coupling of the locomotor and cardiac cycles in three of the five dogs. These brief periods of coupling (5–20 heartbeats) occurred at approximately the same phase relationship in each of the three dogs. We hypothesize that the variation in cardiac period and the resulting transient coupling are a function of locomotor and ventilatory influences on venous return and/or ventricular ejection. Because venous return and ejection fraction are likely to vary in an unpredictable manner when animals run in a complex environment, we suggest that reflex control of heart rate will be important during locomotion and strict integer coupling of the locomotor and cardiac cycles is unlikely to evolve.
Maturation alters cerebral NOS kinetics in the spontaneously hypertensive rat
Authors: Pearce William J. , Tone Beatriz , Ashwal Stephen
Published: December 2017

Using14C-labeled arginine to14C-labeled citrulline conversion assays in brain homogenates from 14- to 18-day-old and adult spontaneously hypertensive rats, we tested the hypotheses that maturation increases neuronal nitric oxide synthase (nNOS) activity and that this increase involves changes in cofactor availability and/or nNOS kinetics. nNOS activity (in pmol ⋅ mg−1⋅ min−1) was 46% higher in adults (19 ± 2) than in pups (13 ± 1). The addition of 264 μM calmodulin (CaM), 3 μM FAD, 3 μM flavin adenine mononucleotide (FMN), and 10 μM tetrahydrobiopterin (BH4) increased NOS activity by 3, 46, 45, and 88% in pups and by 19, 40, 36, and 102% in adults, respectively. All cofactor effects were significant except for CaM in the pup homogenates. Cofactor effects were not significantly different between pup and adult homogenates, except for BH4, which increased absolute NOS activity more in adults than in pups. Values of maximal enzyme velocity ( Vmax) for nNOS in the absence of added cofactors were greater in adults than in pups (104 ± 5 vs. 53 ± 3, P < 0.05). Addition of 3 μM FAD or 3 μM FMN increased pup Vmaxvalues to 68 ± 2 and 99 ± 5, respectively, but had no effect in adults. BH4did not affect Vmaxin either group. Control values of the Michaelis-Menten constant ( Km) forl-arginine were greater ( P < 0.05) in pups (5.7 ± 0.4 μM) than in adults (4.3 ± 0.2 μM) and were significantly reduced by 10 μM BH4to 3.8 ± 0.2 and 2.9 ± 0.1 μM, respectively. Neither FAD nor FMN affected Kmvalues in either group. The results indicate that endogenous nNOS cofactor levels are not saturating in either pups or adults, changes in cofactor levels differentially affect NOS kinetics in pups and adults, and age-related differences in NOS activity result from fundamental differences in NOS kinetics. These findings support the general hypothesis that the increased vulnerability to ischemic stroke associated with maturation is due in part to corresponding increases in the capacity for nitric oxide synthesis.
Role of guanylyl cyclase receptors for CNP in salt secretion by shark rectal gland
Authors: Gunning Mark , Solomon Richard J. , Epstein Franklin H. , Silva Patricio
Published: December 2017

The role of C-type natriuretic peptide (CNP) and its guanylyl cyclase-linked receptors in mediating salt secretion by the rectal gland of the spiny dogfish shark ( Squalus acanthias) was investigated using HS-142–1, a competitive inhibitor of the binding of natriuretic peptides to their guanylyl cyclase receptors. CNP binds to receptors and activates guanylyl cyclase in rectal gland membranes in a way that is inhibited by HS-142–1. Guanylyl cyclase activation in rectal gland membranes is far more sensitive to CNP than to atrial natriuretic peptide, whereas the reverse is true for membranes derived from mammalian (rabbit) renal collecting duct cells. HS-142–1 inhibited the stimulatory effect of CNP on ouabain-inhibitable oxygen consumption by rectal gland tubules. In explanted rectal glands continuously perfused with blood from intact donor sharks, HS-142–1 inhibited the increase in salt secretion normally provoked by infusing isotonic saline solutions into the donor animal. These results strongly support the view that CNP released into the systemic circulation in response to volume expansion mediates the secretion of chloride by the rectal gland via receptors linked to guanylyl cyclase.
Renal adaptation to dietary sodium restriction and loading in rats treated neonatally with enalapril
Authors: Guron Gregor , Nilsson Annika , Dibona Gerald F. , Sundelin Birgitta , Nitescu Nicoletta , Friberg Peter
Published: December 2017

Neonatal treatment of rats with angiotensin-converting enzyme inhibitors or the angiotensin II type 1 receptor antagonist losartan induces irreversible renal histological abnormalities, mainly papillary atrophy, in association with an impairment in urinary concentrating ability. In the present study, sodium and potassium balance were assessed during high and low sodium intake and dietary potassium restriction in adult Wistar rats treated neonatally with enalapril (10 mg ⋅ kg−1⋅ day−1) from 3 to 24 days of age. During balance studies, neonatally enalapril-treated rats showed 1) normal adaptation to dietary sodium restriction, 2) sodium retention during dietary sodium loading, and 3) a transient, modest, renal potassium wastage during dietary potassium restriction. Renal clearance determinations under pentobarbital anesthesia showed elevated fractional excretions of sodium and potassium and osmolar clearance without changes in glomerular filtration rate or effective renal plasma flow in enalapril-treated compared with vehicle-treated rats. Thus, in addition to the impaired urinary concentrating ability, adult rats treated neonatally with enalapril demonstrated alterations in renal sodium and potassium handling, which may be related to the prevailing papillary atrophy.
Effects of active vasoconstriction and total flow on perfusion distribution in the rabbit lung
Authors: Oyamada Yoshitaka , Mori Masaaki , Kuwahira Ichiro , Aoki Takuya , Suzuki Yukio , Suzuki Koichi , Miyata Atsushi , Nishio Kazumi , Sato Nagato , Naoki Katsuhiko , Kudo Hiroyasu , Ohta Yasuyo , Yamaguchi Kazuhiro
Published: December 2017

We analyzed the effects of hypoxic vasoconstriction and total flow on the distribution of pulmonary perfusion in 38 isolated left rabbit lungs perfused under zone 3 conditions. Lungs were suspended in an upright position, oriented to the apicobasal line. Distributions of regional perfusion rates (RPR) along the vertical and horizontal axes were determined using nonradioactive microspheres labeled with heavy metal elements, which were detectable with X-ray fluorescence spectrometry. Changing the O2 concentration of a respirator and an extracorporeal membrane oxygenator independently, respective influences of active vasoconstriction induced by alveolar hypoxia and pulmonary artery hypoxia (PA hypoxia) on the RPR distribution were examined at a flow rate of 0.4 ml ⋅ min−1 ⋅ g wet lung tissue−1. To analyze the effects of changes in total flow, we investigated the RPR distribution at a perfusion rate of 1.2 ml ⋅ min−1 ⋅ g wet lung tissue−1. The RPR distribution in the absence of hypoxia was inhomogeneous and was augmented in the lower lung fields, whereas alveolar hypoxia shifted the RPR upward and significantly diminished the RPR in the lung base. RPR distributions along the horizontal axes under alveolar hypoxia conditions demonstrated that remarkable hypoxic pulmonary vasoconstriction (HPV) takes place in medial regions at the lung base. PA hypoxia altered the RPR distribution in qualitatively the same manner as alveolar hypoxia. Increased flow rate augmented the RPR in the lung, except in the dorsobasal region. These results suggest that the occurrence of HPV and the vascular conductance are not uniform throughout the lung.
Lysosomal proteolysis in distally or proximally denervated rat soleus muscle
Authors: Weinstein Randi B. , Slentz Michael J. , Webster Kimberly , Takeuchi Julie A. , Tischler Marc E.
Published: December 2017

We examined the mechanism of accelerated proteolysis in denervated rat soleus muscles. The soleus was denervated by severing either the tibial nerve (proximal, short stump) or sciatic nerve (distal, long stump) at 24, 48, 72, or 96 h before excision. Twenty-four hours after denervation, the extent of atrophy was similar for proximal and distal denervation, although lysosomal latency declined in both groups. After 48 and 72 h, denervation resulted in a decline in protein content, an increase in in vitro protein degradation, and a decline in lysosomal latency, all of which were greater in proximally denervated than in contralateral distally denervated muscles. These differences between acute responses of proximally and distally denervated muscles suggest the retention of some factor in the longer nerve stump that attenuates atrophy. After 96 h, total protein loss, protein degradation, and lysosomal latency were similar for proximal and distal denervation, suggesting the loss of axoplasmic flow from the long nerve stump.
Development of independent ingestive responding to blockade of fatty acid oxidation in rats
Authors: Swithers Susan E.
Published: December 2017

The present studies examined the development of ingestive responsiveness to blockade of fatty acid oxidation in rat pups using 2-mercaptoacetate (MA), an inhibitor of mitochondrial acyl-coenzyme A dehydrogenases, or methyl palmoxirate (MP), an inhibitor of carnitine palmitoyltransferase I (CPT-I). Rat pups aged 6, 9, 12, or 15 days of age received an intraperitoneal injection of 0, 100, 200, 400, or 800 μmol/kg MA, and intake of a commercial half-and-half or 15% glucose diet from the floor of test containers was assessed in a 30-min test beginning 1 h after administration of MA. The results demonstrate that, although no dose of MA affected intake of either diet in pups 9 days or younger, low doses of MA increased intake and the highest dose suppressed intake of both diets in pups 12 days of age or older. Physiological measurements indicated that levels of β-hydroxybutyrate were significantly lower following doses of 400 or 800 μmol/kg MA in 9-, 12-, and 15-day-old pups and that gastric emptying was inhibited in 12 and 15 day olds by 800 μmol/kg MA. Intake of a commercial half-and-half diet from the floor of test containers was also assessed in 12- to 18-day-old rat pups 6.5 h after they received a gavage load of 0, 1.25, 2.5, 5, or 10 mg/kg MP. Unlike MA, MP did not increase intake of a commercial half-and-half diet in rat pups 12 or 15–18 days of age; instead, the highest dose of MP suppressed intake in 15- to 18-day-old pups. The failure of MP to enhance intake in pups at the ages tested is likely related to composition of dam’s milk; rat milk is high in medium-chain fatty acids that do not require CPT-I for entry into mitochondria. Thus it is likely that MP does not significantly block fatty acid oxidation in pups at the ages tested. On the other hand, blockade of fatty acid oxidation produced by MA significantly affects intake by 12 days of age, suggesting it may be the first metabolic signal that influences intake in rat pups.
Muramyl dipeptide and IL-1 effects on sleep and brain temperature after inhibition of serotonin synthesis
Authors: Imeri Luca , Bianchi Susanna , Mancia Mauro
Published: December 2017

The role of the interactions between serotonin (5-HT) and muramyl dipeptide (MDP) and interleukin-1 (IL-1) in sleep control and thermoregulation was evaluated. To this purpose, MDP and IL-1 were injected intracerebroventricularly at dark onset into freely moving rats pretreated twice intraperitoneally with para-chlorophenylalanine (PCPA) (300 mg/kg), which depletes brain 5-HT and causes insomnia. Fever and slow-wave sleep (SWS) enhancement induced by 150 pmol MDP were completely blocked in PCPA-pretreated rats. Only the first phase of the biphasic increase in SWS induced by 2.5 ng IL-1 was suppressed by PCPA pretreatment, whereas fever remained unaffected. These results suggest that 1) MDP effects on both sleep-wake activity and brain cortical temperature are mediated by the serotonergic system; 2) the mechanisms mediating the first and the second phases of IL-1-induced SWS excess are different: 5-HT could be involved in the first phase, but not in the second one; and 3) the 5-HT system does not appear to be involved in IL-1-induced fever.
Sepsis-induced depression of rat glucose-6-phosphatase gene expression and activity
Authors: Deutschman Clifford S. , Andrejko Kenneth M. , Haber Barbara A. , Bellin Lisa , Elenko Eric , Harrison Rachel , Taub Rebecca
Published: December 2017

Sepsis in rats decreases the hepatic expression of the gluconeogenic enzyme glucose-6-phosphatase (G6Pase). The aim of this study was to investigate the relationship among G6Pase transcription, mRNA, enzymatic activity, and serum glucose levels at different intervals during mild or fulminant sepsis. Both fulminant and mild sepsis immediately decreased hepatic G6Pase mRNA levels. In mild sepsis, levels began to recover late in the time course. Serum glucose levels were maintained in mild sepsis but decreased markedly in fulminant sepsis. G6Pase transcription after fulminant sepsis decreased and never recovered. A similar transcriptional decrease was noted in mild sepsis, but some recovery occurred in this state. Histochemistry after mild sepsis revealed a decrease in G6Pase protein and enzymatic activity that paralleled transcription. These studies suggest that changes in G6Pase transcription and activity are early markers for sepsis-induced alterations in hepatic function. Mechanisms other than gene expression and enzymatic activity serve to maintain glucose levels in mild sepsis, but in the fulminant disorder, compensatory mechanisms fail and hypoglycemia develops.
Evidence for the presence of smooth muscle α-actin within pericytes of the renal medulla
Authors: Park Frank , Mattson David L. , Roberts Lou A. , Cowley Allen W.
Published: December 2017

This study was designed to determine whether smooth muscle α-actin mRNA and smooth muscle α-actin contractile protein elements were present within the renal medullary pericytes. Extraction of total RNA from microdissected outer medullary descending vasa recta allowed for the detection of smooth muscle α-actin mRNA expression using reverse transcription-polymerase chain reaction (RT-PCR). Expression of smooth muscle α-actin was specific to the descending vasa recta and not a result of tubular contamination because RT-PCR amplification of the vasopressin V2 receptor, which is a specific tubular marker, did not occur. To determine the exact cell type(s) that translate the mRNA into protein, we performed immunohistochemistry on the renal outer and inner medulla using a monoclonal smooth muscle α-actin antibody, whose specificity was determined by immunoblot analysis. Smooth muscle α-actin protein was found selectively within the pericytes surrounding the descending vasa recta from the outer and inner medullary tissue sections. This study demonstrates that the pericytes alone that surround the descending vasa recta within the outer and inner medulla contain smooth muscle α-actin mRNA and protein and are therefore the site of the contractile elements that could play a vasomodulatory role in the control of renal medullary blood flow and its distribution within the renal medulla.
Regulation of intracellular pH in proximal tubules of avian loopless reptilian-type nephrons
Authors: Martinez Christina L. , Brokl Olga H. , Shuprisha Apichai , Abbott Diane E. , Dantzler William H.
Published: December 2017

In proximal tubules isolated from chicken superficial loopless reptilian-type nephrons, intracellular pH (pHi), measured with pH-sensitive fluorescent dye 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein, was ∼7.1–7.2 under control conditions ( N-2-hydroxyethylpiperazine- N′-2-ethanesulfonic acid-buffered medium with pH 7.4 at 37°C), and was reduced to ∼6.9 in response to NH4Cl pulse. The rate of recovery of pHi(control value ≅ 5 × 10−3pH U/s) from this acid level was 1) significantly decreased by removal of Na+or both Na+and Cl−from the bath or addition of 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (0.25 mM) to the bath, 2) significantly increased by high bath K+(75 mM), and 3) unchanged by removal of Cl−alone from the bath or addition of ethylisopropylamiloride (1 mM) or Ba2+(5 mM) to the bath. Resting pHiwas 1) significantly decreased by Na+or simultaneous Na+and Cl−removal, 2) significantly increased by high K+, and 3) unchanged by Cl−removal alone or addition of Ba2+. The data do not fit the concept of pHiregulation by the most commonly suggested basolateral transporters (Na+/H+exchanger, Na+-dependent and Na+-independent Cl−/[Formula: see text]exchangers, or Na+-[Formula: see text]-[Formula: see text]cotransporter).
Persistent T lymphocyte rhythms despite suppressed circadian clock outputs in rats
Authors: Deprés-Brummer Petra , Bourin Philippe , Pages Nicole , Metzger Gérard , Lévi Francis
Published: December 2017

Circadian rhythms in circulating leukocyte and lymphocyte counts persisted with halved amplitudes in constant light (LL) of 300 lx intensity for 8 wk, whereas circadian rhythms in body temperature, locomotor activity, and plasma catecholamines were completely suppressed. Subsequent exposure to constant darkness (DD) normalized all circadian rhythms within 2 wk. Rhythms in circulating T lymphocyte subsets were studied in LL or DD using double labeling with monoclonal antibodies and flow cytometry. Circadian rhythms were suppressed for leukocytes and lymphocytes but were maintained for both T helper cells (Th) and T cytotoxic cells (Ts) lymphocytes after 11 wk in LL. A group 24-h rhythm was only validated for total lymphocytes after 16 wk in LL. However, individual total, Th, and Ts lymphocytes maintained their usual respective phase relationships in each rat. The alteration of immune cell circulatory rhythms likely stemmed from a progressive loss of circadian synchronization among rats kept in LL. Conversely, after 11 or 16 wk in DD, leukocytes and lymphocyte subsets circadian rhythms were maintained. Thus catecholamines do not drive circulatory T cell rhythms. The loss of coupling between T lymphocyte rhythms and three major outputs of the circadian system further supports the hypothesis of an independent immunologic oscillator.
Meal pattern analysis to investigate the satiating potential of fat, carbohydrate, and protein in rats
Authors: Burton-Freeman Britt , Gietzen Dorothy W. , Schneeman Barbara O.
Published: December 2017

We examined meal patterns after isocaloric duodenal infusions of fat, carbohydrate (CHO), and protein by measuring meal size, intermeal interval (IMI) and total food intake (TFI). Wistar rats were adapted to normal feeding 6 h/day, with continuous computer monitoring of feeding patterns. One of five solutions (10 ml of 1 kcal/ml at 0.45 ml/min; 0, 20, 50, 80, or 100% of energy from fat) or saline (control) was infused 10 min after initiation of eating. Separate rats received casein or casein hydrolysate at 18.5 or 37% energy. Equivalent energy loads varying in fat, CHO, and protein content compared with saline resulted in similar reductions in first meal intakes. The second meal did not differ among fat and CHO treatments including saline; however, infusion with a protein-containing solution increased the size of meal 2. The IMI was doubled by protein infusion independently of dose or source but extended dose dependently by fat. TFI was lower after high fat and higher after protein than after saline infusion. The results indicate that the concentrations of fat, CHO, and protein differentially affect the qualitative and quantitative aspects of feeding in rats.
Responses of ventral respiratory group neurons of the cat to natural vestibular stimulation
Authors: Woodring S. F. , Yates B. J.
Published: December 2017

Stimulation of vestibular otolith afferents by fore-aft tilt (pitch) elicits changes in activity of nerves innervating respiratory muscles, including the diaphragm, abdominal muscles, and tongue musculature. To determine the role of ventral respiratory group (VRG) neurons in producing these vestibular-respiratory responses, the activity of VRG neurons was recorded during natural vestibular stimulation in multiple transverse planes. Only a small fraction of VRG neurons with inspiratory (I, 20 of 80 cells), expiratory (E, 11 of 59 cells), or phase spanning (4 of 16 cells) activity responded to tilts up to 15° in amplitude delivered at frequencies from 0.02 to 2 Hz. In particular, responses were infrequent in VRG neurons with projections to the spinal cord (0 of 23 E cells and 2 of 15° I cells), despite the fact that the tilts employed produced robust modulation of the activity of abdominal (expiratory) nerves. Furthermore, the characteristics of responses to tilt of the small fraction of VRG neurons with vestibular inputs did not match those of respiratory muscles. These data suggest that neurons in addition to those in the VRG must participate in generating vestibular-respiratory responses.
Single-breath diffusing capacity of NO independent of inspiratory NO concentration in rabbits
Authors: Heller Hartmut , Schuster Klaus-Dieter
Published: December 2017

Pulmonary diffusing capacity of NO (DlNO) was determined by performing single-breath experiments on six anesthetized paralyzed supine rabbits, applying inspiratory concentrations of NO (FiNO) within a range of 10 parts per million (ppm) ≤ FiNO≤ 800 ppm. Starting from residual volume, the rabbit lungs were inflated by 50 ml of a NO-nitrogen-containing indicator gas mixture. Breath-holding time was set at 0.1, 1, 3, 5, and 7 s. Alveolar partial pressure of NO was determined by analyzing the end-tidal portion from expirates, with the use of respiratory mass spectrometry. In the six animals, pulmonary diffusing capacity of NO averaged DlNO= 1.92 ± 0.21 ml ⋅ mmHg−1⋅ min−1(mean ± SD value). Despite extreme variations in FiNO, we found very similar DlNOvalues, and in three rabbits we found identical values even at such different FiNOlevels of 80 ppm or 500, 20, or 200 ppm as well as 10 or 800 ppm. There was also no dependence of DlNOon the respective duration of the single-breath maneuvers. In addition, the time course of NO removal from alveolar space was independent of applied FiNOlevels. These results suggest that DlNOdeterminations are neither affected by chemical reactions of NO in alveolar gas phase as well as in lung tissue nor biased by endogenous release of NO from pulmonary tissue. It is our conclusion that the single-breath diffusing capacity of NO is able to provide a measure of alveolar-capillary gas conductance that is not influenced by the biochemical reactions of NO.
Different modulation of steroidogenesis and prostaglandin production in frog ovary in vitro by ACE and ANG II
Authors: Bramucci Massimo , Miano Antonino , Gobbetti Anna , Zerani Massimo , Quassinti Luana , Maccari Ennio , Murri Oretta , Amici Domenico
Published: December 2017

Our aim was to study the role of angiotensin-converting enzyme (ACE) and angiotensin II (ANG II) on ovarian steroidogenesis and prostaglandin production of amphibian. Hormonal effects of ACE, ACE inhibitors, synthetic bullfrog angiotensin I (ANG I), and [Val5]ANG II were compared on frog ovaries of postreproductive and prereproductive periods. Very high ACE activity was found in ovary of water frog ( Rana esculenta) compared with other frog tissues, and this activity was inhibited by the typical ACE inhibitors, captopril and lisinopril. Frog ovary tissue in postreproductive and prereproductive periods was incubated in vitro in the presence of ACE (2.5 mU/ml), captopril (0.1 mM), lisinopril (0.1 mM), [Val5]ANG II (1 μM), and synthetic bullfrog ANG I (1 μM). Production of 17β-estradiol, progesterone, androgens, and prostaglandins E2and F2αwas determined. The data showed a modulation of 17β-estradiol, progesterone, and prostaglandin E2production by ovary ACE; on the other hand, [Val5]ANG II modulated the production of progesterone and prostaglandin F2α, whereas androgen production was not influenced. The present in vitro studies suggest the existence of two pathways independently regulated by ACE and ANG II modulating ovarian steroidogenesis and prostaglandin production.
Development of the pituitary adrenal axis in fetal sheep twins
Authors: Schwartz Jeffrey , Rose James C.
Published: December 2017

Plasma cortisol increases in fetuses at term and is important for overall development. This study was designed to determine whether cortisol increases synchronously in twin fetal sheep and whether differences between twins contribute to the respective timing. Catheters were surgically implanted in fetal arteries in twins, the amniotic sac, and a maternal artery and vein. Blood was drawn daily until labor was imminent or the twins were delivered. Fetal pituitaries and adrenals were removed for in vitro measurements. Analyses included blood gases and cortisol (daily) and plasma cortisol, adrenocorticotropic hormone (ACTH), and estrogens (at completion). Twins were assigned retrospectively to group A or B, depending on which cortisol was first elevated ( group A) above baseline. Group A fetuses consistently had higher cortisol until term. All group A fetuses also first had elevated ACTH. In four of four sets of twins of both sexes, the male was in group A. There were no differences between fetuses in plasma estrogens or pituitary ACTH response to stimulation, but adrenal cells from group A fetuses were more responsive. These data suggest that adrenal activity is increased in one twin consistently, with the difference being attributable to the responsiveness of adrenal cells to ACTH rather than pituitary responsiveness to either corticotropin-releasing hormone or vasopressin. Difference between sexes may also be involved.