bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of route of delivery and ambient temperature on thermoregulation in newborn lambs
Authors: Clarke L. , Heasman L. , Firth K. , Symonds M. E.
Published: December 2017

We examined the effect of route of delivery on brown adipose tissue (BAT) function and thermoregulation in lambs born either vaginally at term or by cesarean section close to term. Immediately after birth, lambs were placed in a warm (30 degrees C; WD) or cool (15 degrees C; CD) ambient temperature, and measurements of colonic temperature, plus heat production (i.e., oxygen consumption and carbon dioxide production), were recorded for 6 h. Over the first 30 min of life, colonic temperature remained constant in vaginally delivered lambs and was lower in the WD group. Following cesarean section delivery, colonic temperature declined rapidly, a response that was greater in the CD group. Cesarean section-delivered lambs had an increased reliance on shivering thermogenesis and restored colonic temperature after 2 h, and by 6 h these parameters were higher than in lambs born vaginally. Irrespective of delivery, temperature, plasma thyroid hormone concentrations and norepinephrine content of BAT were lower in lambs born by cesarean section compared with those born vaginally. Plasma cortisol concentrations and epinephrine content of BAT were greater in lambs born by cesarean section. The amount of uncoupling protein and level of guanosine 5'-diphosphate binding in BAT were higher in vaginally delivered than in cesarean section-delivered lambs, and for each group mean values were greater for CD than WD lambs. Cesarean section delivery results in altered thyroidal, adrenal, and sympathetic activity, which appears to have a marked influence on BAT function, thereby contributing to distinct differences in thermoregulation compared with lambs born vaginally.
Role of brain angiotensin II in thirst and sodium appetite of sheep
Authors: Weisinger R. S. , Blair-West J. R. , Denton D. A. , Tarjan E.
Published: December 2017

The contribution of brain angiotensin II (ANG II) to thirst and Na+ appetite of sheep was evaluated. Thirst was stimulated by water deprivation, intracarotid or intracerebroventricular infusion of ANG II, or intracarotid or intracerebroventricular infusion of hypertonic solution. Intracerebroventricular infusion, over 1-3 h, of the ANG II type 1 (AT1) receptor antagonist, losartan, decreased or abolished water intake caused by all of the stimuli tested. Intracerebroventricular infusion of ZD-7155, another AT1-receptor antagonist, blocked ANG II-induced water intake. Neither losartan nor ZD-7155 infused intracerebroventricularly altered the Na+ appetite of Na(+)-depleted sheep. Intracerebroventricular infusion of losartan over 3 h, however, did block the increase in water intake and the decrease in Na+ intake caused by intracerebroventricular infusion of hypertonic NaCl in Na(+)-depleted sheep. Intracerebroventricular infusion of the ANG II type 2 (AT2) receptor antagonist, PD-123319, over 1-3 h, did not alter ANG II-induced water intake or Na+ depletion-induced Na+ intake. These results are consistent with the proposition that brain ANG II, working via AT1 receptors, is involved in the neural system controlling some aspects of physiological thirst and Na+ appetite. A role for AT2 receptors in physiological thirst or Na+ appetite is not supported by the present results.
Peptide YY and the Y2 agonist PYY-(13-36) inhibit neurons of the dorsal motor nucleus of the vagus
Authors: Chen C. H. , Rogers R. C.
Published: December 2017

Peptide YY (PYY) is released by endocrine cells in the ileum in response to the presence of fatty acids in the intestinal lumen. Circulating PYY suppresses vagally mediated digestive functions as a consequence of direct action on neurons in the dorsal medulla. Recent evidence from our laboratory suggests that this PYY-mediated inhibition of digestion occurs because of peptide action at the Y2-type receptor in the dorsal medullary region encompassing vago-vagal reflex circuitry. The present study describes the effects of PYY and the specific Y2 agonist peptide PYY-(13-36) on neurons of the dorsal motor nucleus of the vagus (DMN) in both the 1) intact in vivo and 2) in vitro brain stem slice preparation. Our results show that 50% of DMN neurons recorded under in vivo or in vitro conditions, including synaptic blockade, are inhibited by the application of PYY or PYY-(13-36). Approximately 45% are not affected, and only approximately 5% are activated. These results suggest that one of the principal means by which PYY suppresses digestive functions is by the direct inhibition of cholinergic vagal efferent neurons of the DMN via action at a Y2 receptor.
Na-K-2Cl cotransporters are present and regulated in simian eccrine clear cells
Authors: Toyomoto T. , Knutsen D. , Soos G. , Sato K.
Published: December 2017

In freshly dissociated rhesus palm eccrine clear cells, regulatory volume increase (RVI) was studied using image analysis as a measure of Na-K-2Cl cotransport activity. Pseudo-RVIs, as well as RVI during methacholine (MCh)-induced cell shrinkage, were observed in clear cells and were inhibited by 100 microM bumetanide or in Na-free medium, but were not inhibited by amiloride or ouabain. RVI in hypertonic medium and RVI after MCh-induced cell shrinkage were accelerated by adenosine 3',5'-cyclic monophosphate (cAMP)-elevating agents (forskolin+isoproterenol) and inhibited by phorbol ester. RVI in hypertonic medium was enhanced by a phosphatase inhibitor, okadaic acid. mRNA for Na-K-2Cl cotransporter (NaKCC) was demonstrated in freshly isolated rhesus sweat secretory coils by polymerase chain reaction (PCR) after reverse transcription using a set of primers derived from the published human NaKCC (hNaKCC) 1 sequence, i.e., nucleotides 2,043-2,810. The deduced amino acid sequence of the PCR-amplified 767-base pair segment was identical to that of hNaKCC 1 from a human colon cell line (T84). The data are interpreted to indicate that NaKCC, showing strong homology to secretory type hNaKCC 1, is present in rhesus eccrine secretory coils and may participate in the cotransport component of eccrine sweat secretion and cell volume regulation, especially during cholinergic stimulation. The data also raise the possibility that sweat gland NaKCC may be upregulated by cAMP-mediated protein phosphorylation and downregulated by protein kinase C.
Baroreceptor-independent renal nerve inhibition by intracerebroventricular angiotensin II in conscious sheep
Authors: May C. N. , McAllen R. M.
Published: December 2017

The effect of central administration of angiotensin II (ANG II) on efferent renal sympathetic nerve activity (RSNA) was studied in conscious sheep. ANG II (1 nmol/h), infused for 30 min into the lateral cerebral ventricles in five sheep, did not alter mean arterial pressure (MAP) but reduced RSNA to 38 +/- 5% of control. Intracerebroventricular infusion of higher doses of ANG II (3 and 10 nmol/h), which increased MAP by 12 +/- 2 and 14 +/- 3 mmHg, respectively, reduced RSNA to 9 +/- 5 and 11 +/- 7% of control. MAP and RSNA gradually returned to control over a period of 2 h after the infusions. Intracerebroventricular losartan (1 mg/h for 1 h before, and then during, angiotensin infusion) blocked all the effects of angiotensin (3 nmol/h). Baroreflex relationships constructed from the beat-to-beat relationship of RSNA to diastolic pressure showed a significant leftward shift during intracerebroventricular ANG II compared with the control relationship. The beat-to-beat relationship between central venous pressure and RSNA was abolished during intracerebroventricular infusion of ANG II. These findings demonstrate that intracerebroventricular ANG II has a direct central inhibitory action on RSNA that is independent of both arterial and low-pressure baroreceptors. This effect of angiotensin is mediated by central angiotensin AT-1 receptors.
Role of lysophosphatidic acid in endothelin-1- and hematoma-induced alteration of cerebral microcirculation
Authors: Yakubu M. A. , Liliom K. , Tigyi G. J. , Leffler C. W.
Published: December 2017

Cerebral hematoma increases cerebrospinal fluid (CSF) endothelin-1 (ET-1). Inhibitors of ET-1 synthesis prevent this increment and hematoma-induced modification of cerebral arteriolar reactivity. We hypothesized that intrathecal ET-1 injection could 1) modify pial arteriolar reactivity similarly to hematoma; 2) increase CSF lysophosphatidic acid (LPA), a potential contributor to altered cerebrovascular reactivity; and 3) reduce the level of adenosine 3',5'-cyclic monophosphate (cAMP) in the CSF. Either ET-1 (10(-7) M) or artificial CSF was injected over the left parietal cortex of newborn pigs. Four days later, cranial windows were implanted. CSF ET was increased from a basal level of 11 fmol/ml to 18 fmol/ml 4 days after ET-1 injection, whereas CSF cAMP was reduced from 2,700 to 950 fmol/ml. The mean diameter of pial arterioles was reduced 31%. In control animals, 10(-12) M ET caused dilation, and higher concentrations induced vasoconstriction. Four days after ET-1 injection topical ET-1 caused constriction instead of dilation at 10(-12) M, and constrictions at higher doses were enhanced. Norepinephrine-induced constrictions were potentiated in the ET-1-injected group. Dilations to cAMP-dependent (but not independent) vasodilators were attenuated after ET-1. The concentration of the vasoconstrictor lipid mediator LPA increased approximately fourfold. Thus intrathecal injection of ET-1 mimics hematoma-induced modification of cerebral vascular reactivity and increase in LPA production. The mechanism(s) of ET-1- and hematoma-induced modifications may involve LPA, which is known to contribute to the loss of dilator responses by inhibition of cAMP product on. The present study further suggests that ET-1 together with LPA could be causing changes in cerebrovascular reactivity following cerebral hemorrhage. ET-1 stimulates the release of LPA from brain parenchyma independent of serum so that LPA could serve as a secondary mediator.
Magnesium kinetics in adolescent girls determined using stable isotopes: effects of high and low calcium intake
Authors: Sojka J. , Wastney M. , Abrams S. , Lewis S. F. , Martin B. , Weaver C. , Peacock M.
Published: December 2017

Magnesium kinetics were measured in five adolescent girls who were participating in a calcium balance study. Two calcium levels were fed in a randomized crossover design. After an acclimation period, 26Mg was consumed orally and 25Mg was given intravenously, and then blood, urine, and feces were collected for 14 days. Total magnesium and percent enrichment were determined, and data were fitted to a eight-compartment model. There was no significant difference between high and low calcium intakes for any of the parameters examined. Mean values for control (800 mg/day) and high (1,800 mg/day) calcium intake were as follows: Mg intake, 305 +/- 30 and 286 +/- 9 mg/day; absorption (percent), 44 +/- 7 and 39 +/- 9; absorption (mg/day), 134 +/- 35 and 110 +/- 28; urinary excretion, 96 +/- 22 and 101 +/- 31 mg/day; fecal excretion, 175 +/- 32 and 200 +/- 11 mg/day; and magnesium balance, 13 +/- 35 and -34 +/- 48 mg/day, respectively. In conclusion, high calcium intake did not alter magnesium kinetics or balance in adolescent girls.
Acute hypoxia upregulates NOS gene expression in rats
Authors: Gess B. , Schricker K. , Pfeifer M. , Kurtz A.
Published: December 2017

This study aimed to investigate the influence of acute tissue hypoxygenation on the expression of NO synthase (NOS) genes in vivo. To this end, male Sprague-Dawley rats were exposed either to 9% oxygen or to 0.1% carbon monoxide for 6 h, and mRNA levels of NOS-I, -II, and -III in kidneys, livers, lungs, and left and right heart ventricles were assayed by ribonuclease protection. For comparison, mRNA levels of erythropoietin were also measured in these tissues. NOS-III mRNA was highly abundant in all organs investigated. NOS-II mRNA was detected in lungs and hearts but not in kidneys and livers. NOS-I mRNA was found in kidneys, lungs, and hearts but not in livers. NOS-III mRNA levels were upregulated by hypoxia in all tissues examined, with the least effect (1.2-fold) in the left ventricle and the greatest effect (2.6-fold) in the lung. NOS-II mRNA was substantially downregulated in the ventricles by both treatments but not changed in the lung. NOS-I mRNA was upregulated by carbon monoxide in kidneys and lungs and by 9% oxygen in the lung. These findings suggest that NOS-III and possibly also NOS-I gene expression behave like oxygen-regulated genes, whereas the general effect of tissue hypoxygenation on NOS-II gene expression is less clear. Because NOS-III is primarily expressed in endothelial cells, a general upregulation of NOS in these cells may be of relevance for the regulation and maintenance of blood flow through hypoxic tissues.
A1 adenosine receptors potently regulate heart rate in mammalian embryos
Authors: Hofman Paul L. , Hiatt Kelly , Yoder Mervin C. , Rivkees Scott A.
Published: December 2017

A1adenosine receptors (A1ARs) have been recently shown to be expressed in rodent embryonic hearts at very early stages of development. To determine the functional significance of fetal cardiac A1AR expression during embryogenesis, murine fetal heart preparations were studied between postconceptual days 9 and 12. Dose-response curves generated using a variety of adenosine agonists revealed that A1AR activation potently regulated fetal heart rates. The A1AR agonist, N 6-cyclopentyladenosine, inhibited heart rates in a dose-dependent manner (half-maximal effective concentration = 3.6 × 10−8 M) and stopped fetal cardiac contractions in 63% of preparations. In contrast, A2a and A2b receptor activation did not alter heart rates, and activation of A3 receptors produced modest declines in heart rates. Endogenous adenosine also acted tonically to suppress fetal heart rates, as demonstrated by the A1AR antagonist 1,3-dipropyl-8-cyclopentylxanthine, increasing heart rates, whereas the adenosine reuptake blocker dipyridamole lowered fetal heart rates. Pertussis toxin treatment blocked A1AR action, showing that A1AR action was G protein mediated. Using drugs that alter cAMP levels and ion channel action, we were able to show that A1AR action involves events mediated by cAMP, ATP-dependent K, L-type calcium, sodium, and chloride channels, and the pacemaker current. These data show that adenosine and A1ARs potently regulate mammalian heart rates via multiple effector systems at very early stages of prenatal development.
Chronic nitric oxide inhibition with l-NAME: effects on autonomic control of the cardiovascular system
Authors: Scrogin Karie E. , Hatton Daniel C. , Chi Yue , Luft Friedrich C.
Published: December 2017

To determine whether increased sympathetic activity contributes to the hypertension induced by chronic exposure to moderate nitric oxide synthase (NOS) inhibition, various indexes of autonomic function were measured in rats given the NOS inhibitor N G-nitro-l-arginine methyl ester (l-NAME, 10 mg/100 ml, ≅16 mg ⋅ kg−1 ⋅ day−1) in the drinking water. One week of treatment raised blood pressure (139 ± 3 vs. 106 ± 1 mmHg; P < 0.01) and lowered heart rate (319 ± 4 vs. 379 ± 6 beats/min, P < 0.01).l-NAME had no effect on cardiac sympathetic tone, but elevated cardiac parasympathetic tone (−73 ± 4 vs. −56 ± 7 beats/min; P< 0.05). Depressor responses to ganglionic blockade were greater inl-NAME-treated rats (−50 ± 5 vs. −34 ± 5 mmHg; P < 0.05), whereas resting plasma, renal, and adrenal catecholamine values did not differ between groups. Treated rats also showed evidence of reduced baroreflex sympathetic stimulation of heart rate during hypotension and reduced parasympathetic activation during hypertension. Together, these data provide only very limited, indirect evidence that sympathetic stimulation contributes to the hypertension associated with moderate NOS inhibition.
Temperature-dependent feeding: lack of role for leptin and defect in brown adipose tissue-ablated obese mice
Authors: Melnyk Anna , Himms-Hagen Jean
Published: December 2017

The objective was to characterize the ability of control and transgenic brown adipose tissue (BAT)-ablated uncoupling protein diphtheria toxin A chain (UCP-DTA) mice to adjust food intake in relation to changes in environmental temperature and to assess the involvement of leptin in this adjustment. We measured serum leptin in mice from a previous study of UCP-DTA mice raised at thermoneutrality (35°C) or at the usual rearing temperature (24°C) from weaning [Melnyk, A., M.-E. Harper, and J. Himms-Hagen. Am. J. Physiol. 272 ( Regulatory Integrative Comp. Physiol. 41): R1088–R1093, 1997] and extended the study by acclimating control and obese UCP-DTA mice at 18 wk of age to cold (14°C) for up to 14 days. Leptin levels did not change in control mice at 14°C; however, food intake increased threefold within 1 day and remained at this level. Serum leptin level was elevated in UCP-DTA mice at 24°C compared with control mice at 24°C; this elevated level decreased within 1 day at 14°C and was not different from the level in control mice by 14 days. Food intake of UCP-DTA mice that were hyperphagic at 24°C did not change during 7 days at 14°C, then increased slowly. Similar low leptin levels were present in control mice raised at 24 or 35°C and in UCP-DTA mice raised at 35°C. Food intake of control mice raised at 24°C was two times that of control mice raised at 35°C. UCP-DTA mice raised at 35°C ate the same low amount as control mice raised at 35°C. UCP-DTA mice at 24°C were hyperphagic relative to control mice at 24°C yet had elevated leptin levels in their serum. Two principal conclusions are drawn. First, adjustment of food intake over a fourfold range by control mice acclimated to temperatures from 35 down to 14°C is independent of changes in serum leptin levels. Second, this adjustment of food intake in relation to temperature is defective in the UCP-DTA mouse; the defect leads to hyperphagia at 24°C and a failure to increase food intake as rapidly as control mice when exposed to 14°C. Because lack of UCP-1-mediated thermogenesis in BAT of knockout mice is known not to induce hyperphagia, we propose that deficiency of UCP-1-expressing brown adipocytes in BAT of UCP-DTA mice results in lack of a satiety factor, secreted by these cells in BAT of control mice in inverse relationship to sympathetic nervous system activity.
Gastrointestinal osmoreceptors and renal sodium excretion in humans
Authors: Andersen Lars Juel , Jensen Thomas Ulrik Skram , Bestle Morten Heiberg , Bie Peter
Published: December 2017

The hypothesis that natriuresis can be induced by stimulation of gastrointestinal osmoreceptors was tested in eight supine subjects on constant sodium intake (150 mmol NaCl/day). A sodium load equivalent to the amount contained in 10% of measured extracellular volume was administered by a nasogastric tube as isotonic or hypertonic saline (850 mM). In additional experiments, salt loading was replaced by oral water loading (3.5% of total body water). Plasma sodium concentration increased after hypertonic saline (+3.1 ± 0.7 mM), decreased after water loading (−3.8 ± 0.8 mM), and remained unchanged after isotonic saline. Oncotic pressure decreased by 9.4 ± 1.2, 3.7 ± 1.2, and 10.7 ± 1.3%, respectively. Isotonic saline induced an increase in renal sodium excretion (104 ± 15 to 406 ± 39 μmol/min) that was larger than seen with hypertonic saline (85 ± 15 to 325 ± 39 μmol/min) and water loading (88 ± 11 to 304 ± 28 μmol/min). Plasma ANG II decreased to 22 ± 6, 35 ± 6, and 47 ± 5% of baseline after isotonic saline, hypertonic saline, and water loading, respectively. Plasma atrial natriuretic peptide (ANP) concentrations and urinary excretion rates of endothelin-1 were unchanged. In conclusion, stimulation of osmoreceptors by intragastric infusion of hypertonic saline is not an important natriuretic stimulus in sodium-replete subjects. The natriuresis after intragastric salt loading was independent of ANP but can be explained by inhibition of the renin-angiotensin system.
Norepinephrine turnover in peripheral tissues of rats with heart failure
Authors: Patel Kaushik P. , Zhang Kun , Carmines Pamela K.
Published: December 2017

Experiments were performed to determine if there is regional heterogeneity in sympathetic neural activation of peripheral tissues in rats with chronic heart failure (HF; 6–8 wk after coronary artery ligation). Norepinephrine (NE) turnover, an index of sympathetic activation, was determined on the basis of the decline in tissue NE levels that occurs during the 8-h after tyrosine hydroxylase inhibition (α-methyl-dl-p-tyrosine, 300 mg/kg ip at 4-h intervals). Compared with sham-operated rats, NE turnover was increased in the cardiac left ventricle, skeletal muscle, duodenum, and kidney of rats with HF, but was unaltered in liver and spleen. The increased renal NE turnover in HF was largely a reflection of increased turnover in the cortex, with no change evident in the medulla. Blockade of sympathetic ganglionic traffic (hexamethonium, 2 mg/kg sc at 2-h intervals) eliminated the tissue-specific effects of HF on tissue NE levels measured 8-h after tyrosine hydroxylase inhibition. These data support the contention that chronic HF evokes a central nervous system-mediated increase in basal sympathetic tone that exhibits regional heterogeneity (both between and within organs), a phenomenon that likely contributes to the functional consequences of this pathophysiological state.
Functional status of the regenerated chorda tympani nerve as assessed in a salt taste discrimination task
Authors: Kopka Stacy L. , Geran Laura C. , Spector Alan C.
Published: December 2017

We tested whether the recovered ability of rats to discriminate NaCl from KCl after chorda tympani nerve transection (CTX) is causally linked to nerve regeneration or some other compensatory process. Rats were presurgically trained in an operant NaCl vs. KCl discrimination task. Rats with regenerated nerves, histologically confirmed by anterior tongue taste pore counts and tested 62 days after CTX (CTX-62R; n = 5), performed as well as those tested 62 days after sham surgery (Sham-62; n = 5), but both of these groups initially performed slightly worse than animals tested 7 days after sham surgery (Sham-7; n = 4). Performance of rats tested either 7 (CTX-7P; n = 5) or 62 (CTX-62P; n = 4) days after CTX in which nerve regeneration was prevented was severely disrupted. Adulteration of the stimuli with amiloride, an epithelial sodium channel blocker, impaired discrimination performance in a similar dose-dependent manner in the Sham-7 ( n = 2), Sham-62 ( n = 5), and CTX-62R ( n = 5) groups, suggesting that the functional status of the amiloride-sensitive transduction pathway returns to normal in rats with regenerated chorda tympani nerves. Performance of CTX rats without regenerated nerves (CTX-7P, n = 2; CTX-62P, n = 4) was further degraded by amiloride treatment, suggesting that taste receptors innervated by other nerves are sensitive to amiloride. In conclusion, nerve regeneration is an essential component underlying full recovery of salt discrimination function after CTX.
Central effects of leptin on cardiovascular and neurohormonal responses in conscious rabbits
Authors: Matsumura Kiyoshi , Abe Isao , Tsuchihashi Takuya , Fujishima Masatoshi
Published: December 2017

We determined the cardiovascular and neurohormonal responses to intracerebroventricular injection of leptin in conscious rabbits. Intracerebroventricular injection of leptin elicited dose-related increases in mean arterial pressure and renal sympathetic nerve activity while producing no consistent, significant increases in heart rate. Peak values of mean arterial pressure and renal sympathetic nerve activity induced by intracerebroventricular injection of 50 μg of leptin (+17.3 ± 1.2 mmHg and +47.9 ± 12.0%) were obtained at 10 and 20 min after injection, respectively. Plasma catecholamine concentrations significantly increased at 60 min after intracerebroventricular injection of leptin (control vs. 60 min; epinephrine: 33 ± 12 vs. 97 ± 27 pg/ml, P < 0.05; norepinephrine: 298 ± 39 vs. 503 ± 86 pg/ml, P < 0.05). Intracerebroventricular injection of leptin also caused significant increases in plasma vasopressin and glucose levels. However, pretreatment with intravenous injection of pentolinium (5 mg/kg), a ganglion blocking agent, abolished these cardiovascular and neurohormonal responses. On the other hand, intravenous injection of the same dose of leptin (50 μg) as used in the intracerebroventricular experiment failed to cause any cardiovascular and renal sympathetic nerve responses. These results suggest that intracerebroventricular leptin acts in the central nervous system and activates sympathoadrenal outflow, resulting in increases in arterial pressure and plasma glucose levels in conscious rabbits.
Increased expression of spinal cord Fos protein induced by bladder stimulation after spinal cord injury
Authors: Vizzard Margaret A.
Published: December 2017

These studies examined Fos protein expression in spinal cord neurons synaptically activated by stimulation of bladder afferent pathways after spinal cord injury (SCI). In urethan-anesthetized Wistar rats after SCI for 6 wk, intravesical saline distension significantly ( P ≤ 0.005) increased the number of Fos-immunoreactive (IR) cells in the rostrolumbar (L1, 38 cells/section; L2, 29 cells/section) and caudal lumbosacral (L6, 140 cells/section; S1, 110 cells/section) spinal cord compared with control animals, but Fos expression in the L5 segment was not altered. The distribution of Fos-IR cells was also altered in the lumbosacral spinal cord. Significantly greater numbers of Fos-IR cells were distributed in the dorsal commissure and medial and lateral dorsal horn after intravesical distension in SCI animals. Large percentages of parasympathetic (75%) and sympathetic (85%) preganglionic neurons also expressed Fos-IR after intravesical distension in SCI animals. These results demonstrate that bladder distension produces increased numbers and an altered distribution pattern of Fos-IR cells after SCI. This pattern resembles that after noxious irritation of the bladder in control animals. Pretreatment with capsaicin significantly reduced the number of Fos-IR cells induced by bladder distension after SCI. These data suggest that SCI can reveal an altered Fos expression pattern in response to a nonnoxious bladder stimulus that is partially mediated by capsaicin-sensitive bladder afferents.
Renal responses to diuretic drugs in freshwater catfish Ictalurus punctatus
Authors: Nishimura H.
Published: December 2017

Renal tubules of freshwater teleosts consist of proximal, intermediate, distal, and collecting segments. Diuretic drugs were injected into freshwater channel catfish to define the mode of natriuresis and diuresis. Although the catfish lack a loop of Henle, ethacrynic acid (1 mg/kg), furosemide (1 mg/kg) and, to a smaller extent, hydrochlorothiazide (2 mg/kg) produced marked chloruresis and natriuresis. The amount of sodium and chloride reabsorbed decreased, and the decrease in fractional reabsorption of chloride was greater than that of sodium. All three drugs, however, elicited only mild diuresis. This finding suggests that these drugs inhibit sodium and chloride reabsorption in tubules which are highly impermeable to water, most likely along distal segments of the nephron. Ethacrynic acid and furosemide appear to inhibit both reabsorption and secretion of potassium. Acetazolamide (50 mg/kg) induced moderate diuresis which seemed to reflect increased glomerular filtration rate. Smaller doses of acetazolamide increased urinary bicarbonate excretion without the increase in filtration rate, suggesting a possible inhibition of carbonic anhydrase in the renal tubules.
Effect of chronic furosemide administration on hydrogen and sodium excretion in the dog
Authors: Bosch J. P. , Goldstein M. H. , Levitt M. F. , Kahn T.
Published: December 2017

Studies were performed to evaluate the effects of the chronic administration of furosemide on hydrogen and electrolyte excretion in dogs on a normal electrolyte diet and in the absence of electrolyte or volume depletion. Control daily excretion in five dogs averaged 64 meq for Na, 51 meq for K, 66 meq for Cl, and 17 meq for net H. Furosemide, 40 mg, in the drinking water 3 times daily was given for 4 days. On day 1 Na excretion averaged 128 meq, but thereafter was not significantly different from control levels. Over 4 days cumulative net H excretion increased 63.6 meq and plasma HCO3 rose 6.6 meq/liter. The same dogs were restudied by the same protocol except that, to obviate electrolyte depletion, NaCl and KCl were administered daily in quantities sufficient to replace urinary losses. All dogs remained in positive Na, K, and Cl balance. Body weight, hematocrit, plasma albumin, creatinine, and plasma renin activity were unchanged, indicating the absence of electrolyte or volume depletion. Nonetheless, cumulative net H excretion increased 61.2 meq and plasma HCO3 increased 4.3 meq/liter. Two adrenalectomized dogs receiving steroid replacement showed similar changes in net H excretion and plasma HCO3. These experiments suggest that chronic furosemide administration may enhance H excretion and generate alkalosis even in the absence of volume or electrolyte depletion and without increased aldosterone secretion.
Renal tubular transport of prostaglandins: inhibition by probenecid and indomethacin
Authors: Rennick B. R.
Published: December 2017

With use of the Sperber technique in chickens, labeled prostaglandin E2 and F2alpha were infused and resulted in renal tubular excretion of the label into the urine. A labeled metabolite, 12,14-dihydro,15-keto-PGF2alpha, was infused exogenously and this label was also excreted by active tubular transport. Tubular excretion of the label from PGE2, PGF2alpha, and 13,14-dihydro,15-keto-PGF2alpha was inhibited by probenecid, indomethacin, and PAH. The PAH was 10 times weaker as an inhibitor than probenecid and indomethacin. These results indicate that the prostaglandins are actively transported across the renal tubule by the classic anionic transport system which transports PAH. Since the transport of the prostaglandins is blocked by nonsteroidal anti-inflammatory agents such as indomethacin, the anti-inflammatory action of indomethacin may be produced not only by the inhibition of prostaglandin synthesis but also by restriction of the distribution of endogenous prostaglnadins. Thin-layer chromatography of an ethyl acetate extract of urine collected during infusion of [3H]PGF2alpha revealed three discrete radioactive peaks, one of which corresponded to authentic PGF2alpha. This signified tubular excretion of PGF2alpha. One metabolite in the ethyl acetate extract was found to be of renal origin.
Ionic composition of arterial and mixed venous plasma in the unanesthetized dog
Authors: Zweens J. , Frankena H. , van Kampen E. J. , Rispens P. , Zijlstra W. G.
Published: December 2017

The use of permanent catheters in the aorta and pulmonary artery permitted the establishment of normal values for hemoglobin concentration in blood and -or pH, PCO2, osmolality, and protein and electrolyte concentrations in the plasma of arterial and venous samples from unanesthetized, undisturbed dogs, and the comparison of the ionic composition of simultaneously taken arterial and venous samples. Arterial samples yielded the following mean values: CHb, 143 g liter-1; pHP, 7.427; PCO2, 32.5 mmHg; CPosmol, 295 mmol kg-1; CPpr, 73.1 g liter-1, CPNa+, 148.0; CPK+, 3.9; CPCa2+, 2.38; CPMg2+, 0.85; CPCl-, 116.0; CPHCO3-, 21.1; CPlact-, 1.4; CPphosph, 1.21; net cation equivalency, 16.4; and anion gap, 1.03 mmol liter-1 in eight male mongrel dogs with seven or eight samplings from each dog. The anion gap in arterial and venous plasma was small, indicating that the contribution of sulfate and organic acids to the ionic composition of dog plasma is quantitatively unimportant. In simultaneously taken arterial and venous samples the following significant arteriovenous differences were found: HP, +0.038; PCO2, -5.6 mmHg; CPosmol, -1.8 mmol kg-1; protein, -0.8 g liter-1; CPNa+, -1.0; CPK+, -0.1; CPCl-, +1.3; and CPHCO3-, -1.7 mmol liter-1. These differences are explained on the basis of the changes that occur in blood upon the addition of CO2 and the ensuing chloride and water shifts.
Permeability changes in Necturus proximal tubule during volume expansion
Authors: Bentzel C. J. , Reczek P. R.
Published: December 2017

The permeability of Necturus proximal tubule to hydrophilic nonelectrolytes of varying molecular size was studied under control conditions and during isotonic expansion of the animal's extracellular volume. Transepithelial permeability was measured in perfused tubular segments under conditions of zero net water flux. During volume expansion, tubular permeability to urea increased slightly, whereas mannitol decreased slightly and permeability to sucrose was significantly decreased. Volume expansion had a greater effect on osmotic flow parameters; the NaCl reflection coefficient decreased from 0.64 to 0.47 (summer animals) and from 0.41 to 0.27 (winter animals). Osmotic water flux and hydraulic conductivity increased but only in the lumen-to-capillary direction. Reflection coefficients of nonelectrolytes measured at the apical surface were reduced during volume expansion for probing molecules greater than 3 A in radius and were unchanged for smaller molecules, less than 3 A, suggesting two pore populations. We propose that an increase in tight-junction permeability can account for modification of osmotic flow parameters, whereas the whole thickness of the epithelium, particularly the intercellular space, plays the dominant role in regulation of diffusional permeability.
Antidiuretic hormone increases renal prostaglandin synthesis in vivo
Authors: Walker L. A. , Whorton A. R. , Smigel M. , France R. , Frolich J. C.
Published: December 2017

Studies demonstrating the antagonism by prostaglandins (PGs) of antidiuretic hormone (ADH) action led to the proposal that renal medullary PGs may act to attenuate the physiologic effects of ADH via a negative-feedback loop. Therefore, we examined urinary PG excretion, an indicator of renal PG synthesis, in rats with hereditary diabetes insipidus (DI) utilizing gas chromatography-mass spectrometry. The DI rats, devoid of ADH, excrete much less prostaglandin E2 (PGE2) than normal Long-Evans rats (39 +/- 5 vs. 228 +/- 53 ng/24 h, means +/- SE, P less than 0.005). DI and normal rats were treated for 35 days with ADH while separate groups of DI and normal controls received vehicle only. The ADH treatment increased urinary PGE2 excretion in DI rats to 233 +/- 35 ng/24 h whereas PGE2 excretion was unaffected by vehicle treatment. ADH treatment in normal rats similarly increased PGE2 excretion from 215 +/- 49 to 410 +/- 63 ng/24 h (P less than 0.05). To determine whether the rise in PGE2 excretion is the result of the rise in papillary osmolality, we subjected DI rats to dehydration, which increased urine osmolality from 130 +/- 10 to 302 +/- 12 mosmol/kg H2O but left urinary PGE2 unaffected. We conclude that ADH stimulates renal medullary PGE2 synthesis in vivo.
Transcellular and paracellular tracer chloride fluxes in Necturus proximal tubule
Authors: Kimura G. , Spring K. R.
Published: December 2017

Necturus proximal tubule lumen was filled with solutions of Na36Cl or [36Cl]tetramethylammonium ([36Cl]TMA) and the tracer disappearance was measured. With these tracers it was possible to differentiate between chloride fluxes across the cellular and the extracellular shunt pathways. Since it was previously shown that chloride does not enter tubule cells from the lumen unless Na is also present in the lumen, the [36Cl]TMA disappearance rate gave the shunt flux of chloride while the Na36Cl disappearance rate gave the sum of the transcellular and the shunt fluxes. The transcellular tracer chloride flux was unaffected by changes in the transepithelial potential difference, and the rate constant for the chloride flux from lumen to cell was identical to that previously reported for luminal sodium entry. These observations support the conclusion that a coupled transport of NaCl, in an electrically silent form, occurs across the luminal membrane of the Necturus proximal tubule cell. Shunt chloride flux was directly proportional to the electrical driving force, indicating diffusional chloride movement out of the lumen into the shunt pathway.
Temperature dependence of transepithelial potential in isolated perfused rabbit proximal tubules
Authors: Biagi B. A. , Giebisch G.
Published: December 2017

The response of the transepithelial potential to rapid cooling in isolated perfused proximal convoluted (PCT) and proximal straight (PST) tubules has been studied. Tubules were perfused with solutions which simulated glomerular filtrate (A), filtrate minus glucose and alanine (B), and late proximal tubular fluid (C). The values of the potentials at 37 and 10 degrees C as well as the temperature-sensitive component were found to vary with perfusate composition. Temperature sensifound to vary with perfusate composition. Temperature sensitivity in PCT was seen only when glucose and alanine were present in the perfusate. In contrast, a portion of the potential difference in PST was temperature dependent under each of the perfusion conditions. Temperature sensitivity in PST was inhibited by 10(-5) M ouabain in the bath. It is concluded that the lumen-negative, temperature-sensitive component of PCT potential may reflect the coupled luminal entry of Na+ along with glucose and alanine. In PST, the temperature-sensitive component can be associated with Na+ transport but is not dependent on luminal concentrations of glucose, alanine, HCO3- or Cl- over the ranges examined. Potentials in both segments at 10 degrees C are interpreted as resulting from processes that are passive in nature.
Effects of electrochemical gradients on active sodium transport in toad urinary bladder
Authors: Chen J. S. , Walser M.
Published: December 2017

To determine the concentration dependence of active sodium transport in toad urinary bladder, bidirectional fluxes of sodium were measured at three mucosal sodium concentrations (Cm) (114, 27, and 3 mM), before and after addition of sufficient ouabain to eliminate active transport. The results permit estimation of E, the electromotive force of the sodium pump, and its conductance, ga. E averaged 137 mV and was unaffected by depolarization or by reduction of Cm; ga fell by only 40%, suggesting that a Cm of 3 mM was still above the half-maximal value for the sodium pump. However, net open-circuit transport was estimated to become zero at Cm = 6 mM, owing to backflux through the shunt path, which did not vary with Cm. The flux ratio in the active path exhibited the type of abnormality first described as "single-file pore diffusion," which is attributed to relatively tight coupling between transport and metabolism.
Use of mass spectrometer to measure CO2 and O2 fluxes in voltage-clamped epithelia
Authors: Rosenthal S. J. , King J. G. , Essig A.
Published: December 2017

A quadrupole mass spectrometer was coupled to an Ussing chamber in order to evaluate rates of oxidative metabolism in voltage-clamped epithelia. Well-defined mixing characteristics of the continuously perfused chamber allowed CO2 and O2 concentrations to be related to rates of CO2 efflux, JCO2, and oxygen influx, JO2. The use of a model tissue to simulate step changes in JCO2 validated the treatment, with response within a minute. Monitoring of metabolism was facilitated by use of a desk-top computer, which evaluated JCO2 at 6-s intervals. Concurrent measurements of electrical current and JCO2 were made in the toad urinary bladder in order to relate active sodium transport to metabolism; the use of amiloride to eliminate active transport and the associated metabolism then allowed evaluation of the rates of active Na transport (JNa) and suprabasal metabolism (JsbCO2), and their ratio JNa/JsbCO2. We report the ability to resolve a 5 pmol/s change in CO2 efflux or an 11 pmol/s change in O2 influx rates.
Studies of renal cell function using cell culture techniques
Authors: Handler J. S. , Perkins F. M. , Johnson J. P.
Published: December 2017

Cell culture, a powerful tool for the study of cell biology, offers advantages for the study of renal cell function. Epithelial cells derived from a variety of organs, including the kidney, form oriented epithelial sheets in culture that have many structural characteristics (microvilli, tight junctions) of epithelia in situ. There is evidence of transepithelial transport of salt and water by cells of two lines (MDCK and LLC-PK1) derived from mammalian kidney. LLC-PK1 cells may also manifest the glucose transport system of the proximal tubule. Cells of both lines have adenylate cyclase activity sensitive to hormones. Two lines of cells derived from toad urinary bladder form epithelia with a high transepithelial resistance and transport sodium actively from apical to basolateral surface. The rate of sodium transport in both lines is stimulated by cyclic AMP and by aldosterone. There are important differences in the characteristics of the response of the two lines to aldosterone as well as in their sensitivity to inhibition of sodium transport by amiloride. These differences may lead to new insights regarding the molecular events in the response to aldosterone and in the inhibitory action of amiloride. Cultures of kidney cells have also been used effectively to study the biosynthesis of the hormonal derivative of vitamin D and to study prostaglandin production. In addition, cell culture is ideally suited for study of the developmental biology of the kidney.
Bath and lumen effects of SITS on PAH transport by isolated perfused renal tubules
Authors: Dantzler W. H. , Bentley S. K.
Published: December 2017

Effects of 4-acetamido-4'-isothiocyano-2,2'-disulfonic stilbene (SITS) in bath or lumen on p-aminohippurate (PAH) transport by isolated perfused snake (Thamnophis spp.) distal-proximal renal tubules were studied. Addition of SITS to the bath in concentrations as low as 10(-10) M irreversibly depressed net PAH secretion. Addition of 10(-4) M SITS in the bath depressed net PAH secretion by about 60% without affecting apparent permeability of luminal membrane to PAH (PL) or net fluid absorption. Cellular PAH concentration was reduced by about 70% at this time but was still greater than that in the bath. Apparent permeability of peritubular membrane, determined from PAH efflux from tubules with oil-filled lumens, was unchanged even with 10(-3) M SITS in bath. These data indicate that SITS in the bath inhibits PAH transport from bath into cells without enhancing passive efflux from cells to bath. Addition of 10(-4) M SITS to the lumen alone depressed net PAH secretion and PL by about 60%, but this depression was reversed when SITS was removed from the lumen. These data suggest that PAH moves from cells to lumen by a mediated process distinctly different from that fro transport into cells from bath.
Effect of verapamil on the hydroosmotic response to antidiuretic hormone in toad urinary bladder
Authors: Humes H. D. , Simmons C. F. , Brenner B. M.
Published: December 2017

To investigate the role of the calcium ion in the hydroosmotic response to antidiuretic hormone (ADH), the effects of verapamil, an inhibitor of calcium ion entry into cells, on stimulated water flow was examined in vitro in the toad urinary bladder. Verapamil, 50 micro M, decreased ADH-stimulated osmotic water flow from 23.4 +/- 4.1 to 9.9 +/- 3.3 mg . min-1 . hemibladder-1 (mean +/- SE, n = 12, P < 0.001). That this inhibitory effect was due to a verapamil-induced alteration in cellular calcium metabolism is suggested by the findings that 45Ca2+ uptake by isolated toad bladder epithelial cells was reduced nearly 50% in the presence of verapamil and that reversibility of verapamil's inhibitory action was calcium dependent. Additionally, verapamil reduced theophylline- (20 mM) stimulated water flow from 22.8 +/- 2.7 to 9.5 +/- 2.9 mg . min-1 . hemibladder-1 (n = 7, P < 0.001) but enhanced cAMP- (10 mM) induced water flow from 12.8 +/- 2.5 to 21.6 +/- 1.1 ng . min-1 . hemibladder-1 (n = 7, P < 0.001). The latter effect was due, at least in part, to a direct inhibitory effect by verapamil on phosphodiesterase activity of toad bladder homogenates. These results, therefore, suggest that the calcium ion is an important coupling factor at the level of the adenylate cyclase enzyme complex for the stimulus-reabsorption coupling between ADH and the transporting epithelia of the toad urinary bladder.
Modification of Na and Cl transport in canine tracheal mucosa by prostaglandins
Authors: Al-Bazzaz F. , Yadava V. P. , Westenfelder C.
Published: December 2017

We tested the effect of prostaglandins PGF2 alpha and PGE1 on the transport of 36Cl and 22Na by canine tracheal epithelium. Sheets of epithelium were mounted in Ussing chambers and short-circuited. Addition of PGF2 alpha to the mucosal side resulted in an increase of net Cl secretion from 0.71 +/- 0.41 to 2.40 +/- 0.67 mu eq . cm-2 . h-1 without significant effect on net Na absorption. Prostaglandin E1 on the mucosal side increased net Cl secretion from 1.36 +/- 0.31 to 2.69 +/- 0.35 and decreased Na absorption from 0.87 +/- 0.16 to 0.49 +/- 0.09. Indomethacin significantly depressed net Cl secretion from 1.36 +/- 0.36 to 0.57 +/- 0.22. Subsequent addition of PGE1 augmented net Cl secretion to 3.88 +/- 0.75. PGE1 did not enhance [14C]mannitol fluxes across this epithelium. Cellular levels of cAMP increased in response to PGE1 from 130 +/- 12.7 to 642 +/- 33.4 pmol . mg prot-1 . 10 min-1, whereas PGF2 alpha had no effect. These data suggest that although effects of PGF2 alpha and PGE1 are similar as pertains to net Cl secretion, they differ in their effects on Na transport and their capacity to increase cAMP levels. Alterations in Cl and Na transport in response to PGE1 are likely to be mediated, at least in part, by the adenylate cyclase-cAMP system. Furthermore, endogenous prostaglandins may have an important regulatory role in ion transport by airways epithelium.
Aldosterone binding along the rabbit nephron: an autoradiographic study on isolated tubules
Authors: Vandewalle A. , Farman N. , Bencsath P. , Bonvalet J. P.
Published: December 2017

The sites of action of aldosterone (A) along the tubule of rabbit kidney were studied by autoradiographic localization of mineralocorticoid-binding sites on microdissected tubular segments. Kidney pyramids were incubated at 30 degrees C for 1 h in a collagenase solution with [3H]aldosterone at a concentration of 1.5 X 10(-9) M with and without an excess unlabeled A. Tubular segments were then microdissected and transferred onto dry film; fixation and staining were done only after exposure of the film 4 mo later in order to avoid diffusion. Specific nuclear labeling was 19.0 +/- 1.3 silver grains/100 micrometers2 in distal convoluted tubules (n = 28) and 21.0 +/- 1.8 in cortical collecting ducts (n = 18). No difference between these two structures was observed (P greater than 0.1, paired t test, n = 15). No specific binding was found in the proximal tubule (0.5 +/- 0.4, n = 17). In the thick ascending limb of Henle's loop, the labeling was low (3.9 +/- 0.9, n = 16). We conclude that, in the rabbit kidney, nuclear mineralocorticoid-binding sites, presumably receptors, are present in the distal and cortical collecting tubule.