bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of plasma fibronectin: increased lung tissue incorporation after postoperative bacteremia
Authors: Charash W. E. , Vincent P. A. , McKeown-Longo P. J. , Saba T. M. , Lewis E. , Lewis M. A.
Published: December 2017

Fibronectin is an adhesive glycoprotein that may influence the permeability of the vascular barrier. We compared the plasma disappearance of purified human fibronectin (hFn) and its incorporation into lung tissue in control nonbacteremic and bacteremic sheep after surgery to determine the influence of postoperative bacteremia on the plasma clearance and lung deposition of hFn. Lymph fistulas were surgically prepared 48 h before either saline or bacterial challenge to allow for collection of timed samples of plasma, lung lymph, and peripheral lymph. On the day of the study, the sheep were anesthetized and given either 5 X 10(8) Pseudomonas aeruginosa in saline or saline alone. In parallel, they were infused intravenously with 100 mg of hFn, and the hFn concentration in plasma, lymph, and tissue extracts was subsequently determined by enzyme-linked immunosorbent assay over an 8-h experimental interval. Localization of endogenous sheep fibronectin (sFn) and the injected hFn in serial lung tissue samples was determined by dual-label immunofluorescence. In nonbacteremic control sheep, plasma hFn levels declined with an initial rapid slope (t1/2 = 0.53 +/- 0.19 min), followed by a second, gradual slope (t1/2 = 21.7 +/- 2.5 h), whereas the concentration of hFn in lung lymph and peripheral lymph rose exponentially with time. In bacteremic sheep, the early plasma disappearance of hFn was similar, but the second phase of plasma clearance was faster (t1/2 = 7.4 +/- 0.3 h). Lung tissue from control and bacteremic sheep contained the same level of extractable hFn. However, tissue extraction followed by immunofluorescence microscopy indicated that lung tissue from bacteremic sheep contained more nonextractable hFn than lung tissue from nonbacteremic sheep. Thus postoperative bacteremia that elicits acute lung vascular injury will increase the plasma disappearance of hFn and its incorporation into the lung tissue.
Effect of outflow pressure on intestinal lymph flow in unanesthetized sheep
Authors: Drake R. E. , Gabel J. C.
Published: December 2017

Lymphatic vessels are important in removing excess fluid from the intestines and preventing intestinal edema. In this study we used the relationship between intestinal lymph flow rate (QL) and lymphatic outflow pressure (PO) to analyze the flow from intestinal lymphatics in unanesthetized sheep. We cannulated intestinal lymphatic vessels in six anesthetized sheep. One to 3 days after the surgery, we measured QL as we increased PO in steps. We found no QL decrease until PO greater than 15 cmH2O, but QL decreased significantly for PO greater than 15 cmH2O and was decreased to zero at PO = 34 +/- 13 (SD) cmH2O. In three experiments, we used the pressure pulses generated by the active lymphatic pump to estimate the pump stroke volume and frequency. These data indicate that increases in lymphatic pumping prevented a QL decreased for PO less than 15 cmH2O and the QL decrease for PO greater than 15 cmH2O was associated with lymphatic pump failure. When we increased portal venous pressure from baseline (10.1 +/- 4.1 cmH2O) to 24.3 +/- 6.2 cmH2O, lymph flow increased, but it was much more sensitive to outflow pressure. These results are important because they indicate that the ability of the lymphatics to remove fluid from edematous intestines may be compromised by small increases in lymphatic outflow pressure.
Seasonal changes in CSF insulin levels in marmots: insulin may not be a satiety signal for fasting in winter
Authors: Florant G. L. , Richardson R. D. , Mahan S. , Singer L. , Woods S. C.
Published: December 2017

Plasma insulin (PI) reportedly crosses the blood-brain barrier in mammals and acts with the central nervous system (CNS) to reduce food intake. Animals that hibernate (hibernators) eat little or no food from early winter (November) to spring (April). This lack of food intake may be due to elevated PI concentrations acting within the CNS. In this study, we determined whether hibernators have altered insulin levels within the CNS at different times during the circannual cycle of metabolism and feeding. Plasma and cerebrospinal fluid (CSF) immunoreactive insulin concentrations were measured in marmots (Marmota flaviventris) during the feeding phase of the body weight cycle and during the fasting period (hibernation). Basal plasma and CSF samples were collected in September, November, January, and April. In addition, plasma and CSF insulin levels were monitored during a 2-h intravenous infusion of glucose (20% wt/vol) that stimulated pancreatic B-cell production of insulin. During the spring feeding period, we found that as PI levels rise, so do CSF insulin concentrations. However, in fall and winter when marmots are fasting, very little insulin entered the CSF even when PI levels were significantly elevated. Furthermore, the longer the fast, the lower was the CSF insulin under both basal and infusion conditions. These results lead us to conclude that elevated CSF insulin is not a likely cause of suppressed food intake in fasting marmots.
Spontaneously hypertensive rats demonstrate increased renal vascular alpha 1-adrenergic receptor responsiveness
Authors: Uchino K. , Frohlich E. D. , Nishikimi T. , Isshiki T. , Kardon M. B.
Published: December 2017

To determine alpha 1-adrenergic receptor responsiveness of the renal vasculature in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR), phenylephrine (2.5 or 5.0 micrograms.kg-1.min-1 iv) or saline was infused. Effective renal blood flow (ERBF) and glomerular filtration rate were determined by p-aminohippuric acid and inulin clearances, respectively. Peritubular capillary, proximal tubular, and stop-flow pressures (SFP) were measured by micropuncture. Phenylephrine decreased ERBF (6.27 +/- 0.48 to 4.55 +/- 0.65 ml.min-1.g-1; P less than 0.05) and increased arterial pressure and SFP (31.5 +/- 0.9 to 34.2 +/- 1.0 mmHg) in SHR. It only increased arterial pressure and ERBF in WKY without changing SFP. Afferent arteriolar resistance (RA) and glomerular capillary pressure (PG) remained unchanged, whereas efferent resistance (RE) decreased in WKY; in contrast, RA, RE, and PG increased in SHR (RA 21.2 +/- 2.0 to 38.1 +/- 7.1 mmHg.ml-1.min.g, RE 6.9 +/- 0.6 to 13.9 +/- 3.8 mmHg.ml-1.min.g; and PG 49.6 +/- 0.9 to 53.7 +/- 1.1 mmHg; all P less than 0.05). These data demonstrated increased SHR afferent and efferent arteriolar responsiveness; WKY efferent arteriolar hyperresponsiveness was not observed. The findings support the concept of augmented intrarenal vascular alpha 1-adrenergic responsiveness in hypertension that may predispose to subsequent glomerular hypertension.
Sodium excretion and renal precession of sodium over inulin
Authors: Keeler R. , Azzarolo A. M.
Published: December 2017

Renal excretory patterns for inulin and 22Na were measured in rats after simultaneous injection into a renal artery. In normal rats, the excretion of 22Na was much faster than inulin. This is referred to as “precession of sodium” and showed that some of the excreted 22Na had bypassed the intratubular route. During water diuresis, 65% of excreted 22Na was excreted before inulin. The quantity of 22Na preceding inulin (0.10 +/- 0.03% of the amount injected) increased eightfold during infusion of atrial natriuretic peptide (ANP). In saline diuresis, 45% of excreted 22Na (1.47 +/- 0.39% of the amount injected) preceded inulin, but precession was not affected by ANP. In rats with a nephrotic syndrome, 13% of excreted 22Na (0.34 +/- 0.12% of the amount injected) preceded inulin during saline diuresis and increased to 1.66 +/- 0.53% of the amount injected during the infusion of ANP. Precession of sodium was completely abolished in kidneys with papillary necrosis, suggesting that 22Na entered the tubular lumen in the inner medulla. These experiments demonstrate that, in rats, a large fraction of excreted sodium enters the tubules by a route other than filtration. The quantity of sodium entering the tubules by this route shows a 10- to 15-fold variation under conditions that modify the rate of sodium excretion.
Dopamine modulation of prolactin and vasopressin but not behavior on satiation of sheep
Authors: Bell F. R. , Lightman S. L. , Simmonds A.
Published: December 2017

We have investigated the rapid changes in plasma prolactin and arginine vasopressin (AVP) associated with water satiation in ruminants. Sheep deprived of water for 72 h were allowed voluntary access to ad libitum water. Each sheep drank approximately 5 liters in a single draft. This was performed in a head-down position, which was maintained for approximately 2-3 min and ceased rapidly with an abrupt movement to the upright position. During dehydration, plasma sodium, osmolality, and AVP all increased significantly, but prolactin was unaffected. On rehydration, AVP fell to basal levels within 5 min, but prolactin increased as a short pulse, after which it rapidly fell again. Plasma sodium and osmolality returned to predehydration levels within 6 h of satiation. A possible role of dopaminergic mechanisms in these responses was investigated by the administration of the dopamine agonist bromocriptine or the antagonist metoclopramide. Neither of these agents had any observable effects on the drinking behavior of the sheep during water satiation. During metoclopramide treatment, dehydration was associated with a marked fall in prolactin, and on rehydration there was a prompt and very marked increase in prolactin level. There was also an exaggerated increase of AVP during dehydration and a decrease on rehydration. Bromocriptine had relatively little effect on prolactin responses but prevented the drinking-associated inhibition of AVP, demonstrating an unexpected dissociation between AVP secretion and the stereotyped drinking response.
Sleep deprivation in rats: effects on EEG power spectra, vigilance states, and cortical temperature
Authors: Franken P. , Dijk D. J. , Tobler I. , Borbely A. A.
Published: December 2017

Vigilance states, electroencephalogram (EEG) power spectra (0.25-25.0 Hz), and cortical temperature (TCRT) of 10 rats were obtained during a baseline day, a 24-h sleep deprivation (SD) period, and 2 days of recovery (recoveries 1 and 2). EEG power density in waking gradually increased in most frequencies during the SD period. Non-rapid-eye-movement (NREM) sleep was enhanced on both recovery days, and rapid-eye-movement sleep was enhanced only on recovery 1. In the initial 4 h of recovery 1, EEG slow-wave activity (SWA; mean power density 0.75-4.0 Hz) in NREM sleep was elevated relative to baseline, and the number of brief awakenings (nBA) was reduced. In the dark period of recovery 1 and the light period of recovery 2, SWA was below baseline, and nBA was increased. During the entire recovery period, SWA and nBA, both expressed as deviation from baseline values, were negatively correlated. During the SD period, TCRT was above baseline, and in the initial 16 h of recovery 1 it was below baseline. Whereas TCRT was negatively correlated with NREM sleep, no significant correlation was found between TCRT and SWA within NREM sleep. It is concluded that SD causes a short-lasting intensification of sleep, as indicated by the enhanced SWA and the reduced nBA, and a long-lasting increase in sleep duration. The different time courses of SWA and TCRT suggest that variations in NREM sleep intensity are not directly related to changes in TCRT.
Pentobarbital produces dissimilar changes in glucose influx and utilization in brain
Authors: Otsuka T. , Wei L. , Bereczki D. , Acuff V. , Patlak C. , Fenstermacher J.
Published: December 2017

The effects of pentobarbital sodium on local cerebral glucose utilization (LCGU) and 3-O-methylglucose (3-MG) influx were measured by quantitative autoradiography in 52 brain areas of control and treated rats. Pentobarbital (50 mg/kg ip) lowered LCGU to a relatively uniform rate (approximately 35 mumol.100 g-1.min-1) in 24 of 25 forebrain areas. Among the 18 hindbrain areas, LCGU was decreased by pentobarbital by 15-55% (range 50-157 and 28-110 mumol.100 g-1.min-1 in control and treated rats, respectively). In contrast, pentobarbital lowered the 3-MG influx rate constant and permeability-surface area product by 20-30% in nearly all brain structures. The 3-MG results fit a model in which both the half-saturation constant and the maximal velocity of the glucose carrier are decreased by pentobarbital. After pentobarbital treatment, the ratio of local cerebral plasma flow (LCPF) to LCGU was the same as in controls for brain areas in which LCGU was less than 35 mumol.100 g-1.min-1 but was higher in brain areas where LCGU exceeded 35 mumol.100 g-1.min-1. Pentobarbital produced dissimilar changes in LCGU, 3-MG influx, and LCPF; these processes may thus not be closely linked during pentobarbital anesthesia.
2,5-anhydro-D-mannitol acts in liver to initiate feeding
Authors: Tordoff M. G. , Rawson N. , Friedman M. I.
Published: December 2017

We determined the site at which the fructose analogue 2,5-anhydro-D-mannitol (2,5-AM) acts to increase food intake in rats. Rats began eating sooner and ate more food during hepatic portal than during jugular infusions of 2,5-AM (50, 100, or 150 mg/h). After rats were intubated with 2,5-[14C]AM (1.15 microCi in 200 mg/kg), significant quantities of radioactivity were found in liver but not in brain. Hepatic vagotomy prevented the eating response to 200 mg/kg 2,5-AM without altering the effect of the analogue on plasma fuels. These results indicate that low doses of 2,5-AM act in the liver to increase food intake and suggest that the signal for feeding generated in the liver is transmitted to the brain through the hepatic vagus nerve. Taken together, this work provides the strongest evidence to date that a signal initiating feeding behavior originates in the liver.
Influence of fatty acid oxidation in lateral hypothalamus on food intake and body composition
Authors: Beverly J. L. , Martin R. J.
Published: December 2017

This study tested the concept that the level of fatty acid oxidation in the ventrolateral hypothalamus (VLH) reflects peripheral energy stores and elicits compensatory responses to changes in energy balance status. Fatty acid oxidation rates in the VLH were chronically altered over a 14-day period by infusing into the VLH either 0.1 mM 4-pentenoic acid (4-PA; 5 ng/h) or 1.0 mM L-carnitine (L-Carn; 98 ng/h). Fatty acid oxidation rates in the VLH were altered to a similar extent as by overfeeding (reduced 37% by 4-PA) and dietary restriction (increased 28% by L-Carn). Diffusion of infusates was limited, since there were normal rates of fatty acid oxidation in the ventromedial hypothalamus and cortex. There were no significant effects of altering fatty acid oxidation in the VLH on food intake, body weight, body composition, or serum levels of glucose, insulin, and free fatty acids. The results of this experiment indicate that the level of fatty acid oxidation in the VLH is unlikely to independently elicit changes in food intake or peripheral metabolism.
Pethidine (meperidine) inhibition of oxytocin secretion and action in parturient rats
Authors: Russell J. A. , Leng G. , Coombes J. E. , Crockett S. A. , Douglas A. J. , Murray I. , Way S.
Published: December 2017

Pethidine (also known as meperidine and as Demerol) injected subcutaneously at 10 mg/kg into parturient rats on the birth of the second pup resulted in a marked slowing of the progress of parturition, associated with reduced plasma oxytocin concentrations. Injection of the opiate antagonist naloxone counteracted the inhibition of oxytocin secretion and largely prevented the slowing of parturition. In vitro, pethidine inhibited spontaneous, oxytocin-induced and acetylcholine-induced contractions of uteri from rats immediately post partum, and these effects were not reversed by naloxone. In anesthetized lactating rats, pethidine inhibited the suckling-induced milk-ejection reflex and attenuated oxytocin-induced contractions of mammary myoepithelium. Finally, pethidine depressed plasma oxytocin concentrations in rats given 2% saline to drink for 24 h to stimulate oxytocin secretion. Thus pethidine inhibits oxytocin secretion in all three conditions; this inhibition is probably mediated by central opioid receptors. In addition, however, pethidine depresses the oxytocin responsiveness both of mammary myoepithelium and of myometrium. The latter effect at least is not opioid mediated.
Sodium-dependent magnesium transport across in situ perfused rat placenta
Authors: Shaw A. J. , Mughal M. Z. , Maresh M. J. , Sibley C. P.
Published: December 2017

Placentas of anesthetized rats were perfused in situ on the fetal side to study mechanisms of Mg2+ transport. The perfusate was a Mg(2+)-free Krebs-Ringer, and the unidirectional transfer of Mg2+ from maternal plasma to this Ringer was compared with that of 45Ca and 51Cr-EDTA, the latter being employed as a paracellular diffusional marker. Placental perfusion with amiloride (0.5 mM) or ouabain (1 mM) both rapidly (4 min) reduced maternal-fetal clearance (Kmf) for Mg2+ but had no effect on Kmf for 45Ca. In contrast, perfusion of the carbonic anhydrase inhibitor acetazolamide (1 mM) did not affect Kmf for Mg2+ or 45Ca. Placental perfusion with a Na+-free Ringer reduced Kmf for both Mg2+ and 45Ca, although the latter response was delayed. Kmf for 51Cr-EDTA was increased by amiloride and was unaffected by perfusion of ouabain, acetazolamide, or Na+-free Ringer, indicating that the effects of these treatments on Kmf of Mg2+ do not reflect nonspecific effects on placental permeability. These data suggest that maternal-fetal transfer of Mg2+ across the perfused rat placenta is Na+ dependent.
Endometrial transport generates the maternal-fetal electrical potential difference in guinea pigs
Authors: McNaughton T. G. , Power L. A. , Gilbert R. D. , Power G. G.
Published: December 2017

These studies examined the transport characteristics of the uterine endometrium with respect to the origin and mechanism of generation of the maternal-fetal electrical potential difference (PD) in pregnant guinea pigs. Late-gestation animals were used in two experimental preparations. In vivo, a sealed uterine pouch that preserved blood flow to the endometrium was prepared by removal of the fetus, placenta, and fetal membranes from the uterus and replacement with Earle's solution, a balanced electrolyte solution. In vitro, sections of uterine wall comprised of myometrium and endometrium without fetal membranes were mounted in Ussing chambers. Transuterine PDs (fetal side negative) were indistinguishable in vivo and in vitro, averaging 29.6 +/- 4.5 and 32.6 +/- 6.1 (95% confidence interval) mV in the respective preparations. Both values are within the range of maternal-fetal PD measured in intact guinea pigs, indicating that the fetoplacental unit is not essential in generating an intrauterine PD. The maternal-fetal PD, therefore, is likely a passive result of the fetus and placenta being immersed in fluids at the intrauterine potential. In vitro, both PD and short-circuit current (Isc) were completely inhibited by ouabain (10(-3) M) at the serosal (maternal) side of the uterine wall but unaffected by the inhibitor from the luminal (fetal) side. Amiloride (10(-5) M) and valinomycin (10(-5) M) caused decreases in the PD when added to the luminal side, both in vivo and in vitro, and were both ineffective from the serosal side in vitro. Isc was reduced 83% from 315 +/- 24 to 53 +/- 6 (SE) microA/cm2 after luminal amiloride (5 x 10(-4) M), indicating that Na+ is the predominant ion actively transported.(ABSTRACT TRUNCATED AT 250 WORDS)
DNA synthesis is reduced in selected fetal tissues during prolonged hypoxemia
Authors: Hooper S. B. , Bocking A. D. , White S. , Challis J. R. , Han V. K.
Published: December 2017

The effects of 24 h of reduced maternal uterine blood flow (RUBF) on relative DNA synthesis rates in different tissues and on blood glucose and lactate concentrations were studied in fetal sheep. In six sheep, RUBF was induced for 24 h, whereas in another six sheep (controls), uterine blood flow was not reduced. To estimate DNA synthesis rate, [3H]thymidine (1 mCi/kg) was injected intravenously into each fetus 8 h before the end of the 24-h experimental period. Fetal arterial oxygen saturation decreased from 59.1 +/- 3.3 to 25.7 +/- 5.6% after 1 h of RUBF and remained significantly reduced for the duration of the experiment. Fetal blood lactate concentrations were significantly increased by RUBF from 14.3 +/- 6.5 to 57.8 +/- 12.4 mg/dl at 1 h and remained elevated, whereas fetal blood glucose concentrations were not affected. A 24-h period of RUBF did not significantly alter fetal body weights, tissue weights, tissue-to-body weight ratios, or tissue DNA content. Over the last 8 h of the 24-h experimental period, RUBF was found to significantly reduce the relative rate of DNA synthesis (as assessed by [3H]thymidine incorporation into DNA) in the lung (104.7 +/- 26.6 vs. 17.1 +/- 3.1 dpm/micrograms DNA), quadriceps muscle (92.8 +/- 20.7 vs. 14.4 +/- 5.3 dpm/micrograms DNA), and thymus gland (87.5 +/- 7.1 vs. 32.9 +/- 12.2 dpm/micrograms DNA). Relative DNA synthesis rates in the fetal liver, kidney, small intestine, cerebral cortex, cerebellum, placenta, thyroid gland, and adrenal gland were not significantly affected by RUBF. In this study, we have shown that DNA synthesis was greatly reduced in selected fetal tissues (lung, quadriceps muscle, and thymus gland) by a 24-h period of RUBF, although it is not known why a reduction was only observed in these tissues.
Effects of pylorectomy on cholecystokinin-induced inhibition of liquid gastric emptying
Authors: Moran T. H. , Crosby R. J. , McHugh P. R.
Published: December 2017

The present study was designed to investigate a role for the pyloric sphincter and its population of cholecystokinin (CCK) receptors localized to the circular muscle layer in the inhibition of gastric emptying produced by exogenously administered CCK in rats. We examined the ability of two doses of CCK to inhibit the gastric emptying of 10-ml saline (0.9% NaCl) and glucose (0.125 g/ml) test meals in rats equipped with chronic gastric fistulas before and after surgical removal of the region of the pylorus containing CCK receptors. Preoperatively, CCK (2 and 8 micrograms/kg) inhibited gastric emptying of both saline and glucose. Pylorectomy did not significantly alter the baseline saline and glucose emptying and did not alter the ability of CCK to inhibit the emptying of the saline test meals. In contrast, pylorectomy eliminated the ability of CCK to inhibit glucose emptying. These results demonstrate that the inhibition of gastric emptying by CCK may involve multiple mechanisms depending on the character of the gastrointestinal contents.
Development of mammalian endothermic metabolism: quantitative changes in tissue mitochondria
Authors: Hulbert A. J. , Mantaj W. , Janssens P. A.
Published: December 2017

The development of energy metabolism of mammalian tissues was assessed in the tammar wallaby Macropus eugenii by the measurement of mitochondrial parameters in the liver, heart, kidney, and brain. Tissues taken from wallabies (n = 27) ranging from 10-day-old pouch young (weighing approximately 4 g) to adults (averaging 6.2 kg) were weighed and fixed, and mitochondrial volume and mitochondrial membrane surface area (MMSA) were determined by quantitative electron microscopy techniques. Developmental changes in these parameters were analyzed chronologically and allometrically. Relative growth rates of all four tissues decreased during development. Liver and heart showed constant allometric growth throughout development, whereas kidney and brain showed biphasic allometric growth. Tissue metabolic intensity assessed by MMSA (m2/cm3 tissue) was constant in liver, showed a threefold increase in brain during pouch life, showed a fourfold increase in the heart between 100 and 200 days of age, and showed a twofold increase in the kidney at the end of pouch life. In all tissues, adult levels of tissue metabolic capacity were present at pouch exit. In all four tissues, total MMSAs were at "reptilian" levels at birth and gradually increased to "mammalian" levels. Each tissue exhibited a different developmental timetable. When the total MMSAs for all four tissues were summed there was a similar pattern of allometric development between summed MMSA and whole animal metabolic rate.
Intracellular pH regulation in trout urinary bladder epithelium: Na(+)-H+(NH4+) exchange
Authors: Marshall W. S. , Bryson S. E.
Published: December 2017

We measured intracellular pH (pHi) of single epithelial cells in situ in the urinary bladder epithelium using microspectrofluorometry and the cytoplasmically trapped pH-sensitive fluorophore, 2',7'-bis(2-carboxyethyl)-5(6)- carboxyfluorescein (BCECF). The resting pHi was 7.21 +/- 0.03 (n = 40 bladders, 489 cells) in pH 7.8 bathing solutions, indicating that H+ is not passively distributed across the plasma membrane and is extruded against its electrochemical gradient. Whereas exposure to hypercapnia (5% CO2 saturation) reversibly decreased pHi, mucosally added 20 mM NH4+ reversibly increased pHi. Recovery from the NH4+ effect was slow and lacked an acid-load pHi undershoot; this is interpreted as suggesting significant NH4+ permeability. Recovery from hypercapnic acidosis was blocked by mucosally added amiloride, indicating that apical Na(+)-H+ exchange is involved in pHi regulation. Addition of 0.5 mM NH4+ to the basolateral side when the mucosal side was bathed in mock urine (2 mM NaCl) significantly increased undirectional mucosal-to-serosal Na+ flux, and the increase was blocked by mucosally added amiloride. We conclude that an apically located Na(+)-H+ exchange is important in pHi regulation and may also accept NH4+ as the counterion for Na+.
Reduced renal responses to an acute saline load in obese Zucker rats
Authors: Zeigler D. W. , Patel K. P.
Published: December 2017

The purpose of this study was to determine if the reflex response to a saline load is altered in the obese Zucker rat. The obese Zucker rat is a genetic model of obesity and insulin-resistant diabetes that has been reported to have high blood pressure. We examined the reflux renal responses to volume expansion in both anesthetized obese and lean Zucker rats. Initial blood pressure was significantly elevated in the obese Zucker rats compared with the lean controls. Urine flow and sodium excretion from innervated and denervated kidneys were measured before and after volume expansion with normal saline. Volume expansion resulted in significantly less urine flow and sodium excretion in the obese than the lean Zucker rats. This response was evident in both the intact and denervated kidneys. Rats were then infused with atrial natriuretic peptide (ANP) to determine if natriuretic and diuretic responses were altered in these rats. The diuretic action of ANP was not significantly reduced in the obese Zucker rat. However, the natriuretic action of ANP was significantly attenuated in the obese rats. These results indicate that the reflux response to an acute saline load is attenuated in the obese Zucker rat and that this decreased response may be due to a reduction in the direct action of ANP on the kidney.
Medial medullary contribution to tonic descending inhibition of visceral input
Authors: Holt I. L. , Akeyson E. W. , Knuepfer M. M.
Published: December 2017

In the present study, we sought to define the extent and source of tonic descending modulation of spinal neurons receiving visceral input from the afferent renal nerve (ARN). Spinal gray neurons responding to stimulation of the ARN in 64 chloralose-anesthetized rats were located primarily in laminae IV and V (70%), with fewer neurons located in laminae I and VII. ARN stimulation excited 76 and inhibited 8 neurons. Analysis of response latencies demonstrated that responses were due to activation of A delta- and/or C-fiber afferents. Reversible spinalization with cervical cold block (2-5 degrees C) affected activity in most neurons excited by ARN stimulation without affecting inhibited neurons. Cervical cold block increased the spontaneous activity of (disinhibited) the majority of neurons (54 of 76 neurons) and disfacilitated the spontaneous activity of 14 neurons. The evoked response to ARN stimulation was disinhibited by cold block in 51% and disfacilitated in 17% of the neurons, and there was a good correlation between neurons with disinhibited spontaneous activity and those with disinhibited evoked activity. Microinjections of muscimol (0.5-1 nmol) into the rostral medial medulla affected spontaneous and ARN-evoked activities similarly to cold block in 14 of 15 neurons, although the responses to muscimol were usually smaller in magnitude. We conclude that ARN input is modulated supraspinally and that the nucleus raphe magnus and adjacent neuropil contain neurons that contribute to tonic supraspinal inhibition of renal input in the rat.
Microdialysis of cat pons reveals enhanced acetylcholine release during state-dependent respiratory depression
Authors: Lydic R. , Baghdoyan H. A. , Lorinc Z.
Published: December 2017

Microinjection of cholinergic agonists and acetylcholinesterase inhibitors into the medial pontine reticular formation (mPRF) causes a state that is polygraphically similar to rapid-eye-movement (REM) sleep. Respiratory studies of intact unanesthetized cats during this cholinergically induced REM sleep-like state have shown that the same cholinoceptive pontine reticular regions that mediate REM sleep can also cause state-dependent respiratory depression. The present study investigated the hypothesis that acetylcholine (ACh) release in the mPRF is increased during the respiratory depression that accompanies the cholinergically induced REM sleep-like state. Cats were implanted for polygraphic recording of sleep and wakefulness and with guide tubes aimed for placing a microinjector in one mPRF and a microdialysis probe in the contralateral mPRF. ACh release was measured with high-performance liquid chromatography and electrochemical detection. Compared with waking levels, ACh was significantly increased and respiratory frequency was significantly decreased during the carbachol-induced REM sleep-like state. These results support the hypothesis that endogenous cholinergic neurotransmission in brain regions known to regulate REM sleep can also cause state-dependent changes in respiratory control.
Dietary regulation of intestinal brush-border sugar and amino acid transport in carnivores
Authors: Buddington R. K. , Chen J. W. , Diamond J. M.
Published: December 2017

The ability of omnivores and herbivores to regulate reversibly their intestinal brush-border nutrient transporters is functionally related to the unpredictably variable composition of their natural diets. To determine whether carnivores are able similarly to regulate the activities of their intestinal nutrient transporters, we fed to three species of vertebrates that are carnivorous as adults (cats, mink, and leopard frogs) diets with either at least 50% digestible carbohydrate or with negligible carbohydrate levels. Rates of transport for the sugars glucose and fructose and the amino acids (AAs) aspartate, leucine, lysine, and proline were measured throughout the intestine (only proline and glucose in the frogs) by an in vitro everted-sleeve method. Although all three species consume much carbohydrate during early development, only the mink was able to regulate sugar transporter activity in response to changes in levels of dietary carbohydrate. In contrast, the sugar transporters of the cat were unresponsive to varying carbohydrate levels, and long-term feeding of a high-carbohydrate diet caused down-regulation of sugar transport in frogs. Of the three species, only the mink is a member of a family that includes omnivorous species, whereas all members of the families to which the cat and frog belong are carnivorous as adults. All three species were able to regulate rates of AA transport, though the patterns and magnitude of the responses differed between species as well as between AAs, suggesting independent regulation of some AA transporters.(ABSTRACT TRUNCATED AT 250 WORDS)
Active urea transport independent of H+ and Na+ transport in frog skin epithelium
Authors: Lacoste I. , Dunel-Erb S. , Harvey B. J. , Laurent P. , Ehrenfeld J.
Published: December 2017

We investigated the relationship between H+ secretion (JH), Na+ absorption (JNa), and urea transport (Ju) in skin of frogs (Rana esculenta) adapted to running tap water, NaCl (100 mM), and KCl (100 mM). In addition, cell morphological changes, particularly in the mitochondria-rich cells (MRC), were followed. NaCl adaptation stimulated an active Ju, reduced JNa and JH, and caused a decrease in the apical surface of MRC. After KCl adaptation, JNa and JH were increased and highly correlated, with a twofold increase in Ju, whereas the numerous MRC developed infoldings on their apical membranes. No correlation was found between JH and Ju. Clamping the skins in a range of +/- 50 mV or changing the external pH from 7.4 to 5.4 (at high cellular buffering power) had no effect on Ju. Depolarization of the basolateral membranes (serosal KCl-Ringer) had no effect on Ju. Ju was reversibly blocked by acidification of the cells by oxygen-free solution and sulfhydryl reagents (Hg2+, p-chloromercuribenzenesulfonic acid, and N-ethylmaleimide). Diethylstilbestrol, a proton transport blocker, had no effect on Ju. Apical addition of amiloride and derivatives (phenamil and ethylisopropyl amiloride) reversibly blocked Ju, whereas ouabain had no effect. We conclude that a cation (Na+ or H+)-dependent process is unlikely to exist in R. esculenta skin. A primary active transport in a two-step process is the simplest hypothesis to account for the energy-dependent Ju that develops in NaCl-adapted frogs.
Zucker and Wistar diabetic fatty rats show different response to adrenalectomy
Authors: Turkenkopf I. J. , Kava R. A. , Feldweg A. , Horowitz C. , Greenwood M. R. , Johnson P. R.
Published: December 2017

The short-term effects of adrenalectomy on certain aspects of glucose homeostasis and adiposity were examined in Zucker and Wistar diabetic fatty (WDF) rats. Ten-week-old male obese and lean WDF and Zucker rats were adrenalectomized or underwent sham operation. Obese rats of each strain were pair fed the intake of obese adrenalectomized rats. Intragastric glucose tolerance tests showed that sham-operated obese rats of both strains were severely hyperinsulinemic compared with leans; adrenalectomy and pair feeding reduced palsma insulin to lean levels in Zucker but not WDF rats. At the time they were killed, sham-operated obese WDF rats were significantly hyperglycemic and hyperinsulinemic compared with other groups, but adrenalectomy reduced plasma glucose and insulin to lean levels in both strains. Adrenalectomy reduced inguinal and retroperitoneal fat pad weights more in Zucker than WDF obese rats. Although adrenalectomy decreased epididymal and inguinal fat cell size in both obese rat strains, the effect was greater in Zucker compared with WDF rats. These data suggest that the basis for the differential response to adrenalectomy in obese WDF and Zucker rats may reside in their different genetic backgrounds.
Olfactory bulbectomy lengthens circadian period of locomotor activity in golden hamsters
Authors: Pieper D. R. , Lobocki C. A.
Published: December 2017

Removal of the olfactory bulbs (BX) of rats or mice lengthens the circadian period of locomotor activity. In golden hamsters, BX elevates serum gonadotropin levels of hamsters maintained in long or short photoperiod and prevents the testicular regression associated with short days without altering the secretion or action of pineal melatonin. The present study examined the influence of BX on circadian wheel-running activity in hamsters and tested whether this effect was related to changes in serum testosterone levels. BX lengthened the free-running period of locomotor activity in gonadally intact hamsters by a mean of 21.0 min, and BX had a similar effect in orchidectomized animals with or without testosterone replacement. These results suggest that the olfactory bulbs normally tend to increase the frequency of the hamster's circadian oscillator and that this effect is unrelated to altering gonadal steroid levels.
Effects of central and intravascular angiotensin I and II on the choroid plexus
Authors: Maktabi M. A. , Heistad D. D. , Faraci F. M.
Published: December 2017

The choroid plexus contains receptors for angiotensin II (ANG II) and a very high concentration of angiotensin-converting enzyme. The goal of this study was to test the hypothesis that central, as well as circulating, ANG I and II decrease blood flow to the choroid plexus. Under control conditions in anesthetized rabbits, blood flow (microspheres) to the choroid plexus was 449 +/- 21 (mean +/- SE) ml.min-1.100 g(-1). Intravascular ANG I (30 and 100 ng.kg-1.min-1) decreased blood flow to the choroid plexus by 19 +/- 14 and 28 +/- 18%, respectively. Intravascular ANG II (30 and 100 ng.kg-1.min-1) also produced a decrease in blood flow by 28 +/- 9 and 47 +/- 7%, respectively. When administered into the lateral ventricle, ANG I and II (10 and 100 ng.kg-1.min-1) decreased blood flow to a similar degree: 22 +/- 11 and 31 +/- 10% and 12 +/- 10 and 27 +/- 8%, respectively. Cerebral blood flow was not decreased by intravascular or central ANG I or II. The angiotensin-converting enzyme inhibitor quinaprilat prevented the decrease in blood flow to the choroid plexus in response to ANG I without affecting responses to ANG II. Thus 1) circulating ANG I and II are potent constrictors of blood vessels of the choroid plexus, 2) the constrictor effect of ANG I on the blood vessels of the choroid plexus appears mediated primarily by generation of ANG II, and 3) intracerebroventricular ANG I produces large reductions in the blood flow to the choroid plexus, which suggests that there is an effective central system that converts ANG I to ANG II.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of thyroidectomy on development of skeletal muscle in fetal sheep
Authors: Finkelstein D. I. , Andrianakis P. , Luff A. R. , Walker D.
Published: December 2017

The influence of the thyroid gland on the functional and histochemical development of fast- and slow-twitch skeletal muscle of fetal sheep has been studied in euthyroid fetal sheep (n = 6) and athyroid fetuses (n = 4) surgically thyroid-ectomized at 70-75 days of gestation. Two fast-twitch muscles, the medial gastrocnemius and extensor digitorum longus, and the slow-twitch soleus muscle were studied at the fetal age of 140 days gestation. The athyroid fetuses had significantly slower twitch contraction and relaxation times in both the medial gastrocnemius and extensor digitorum longus muscles compared with the euthyroid fetuses. Twitch contraction and relaxation times of the soleus were not different in the two groups. Thyroidectomy resulted in an increase in the proportion of fast (type II) muscle fibers and myosin, as shown histochemically and by gel electrophoresis of heavy-chain myosins. These results indicate that the functional maturation of the fast-twitch muscles of sheep is influenced by the presence of an intact thyroid gland from at least 70 days of gestation. In contrast, the slow-twitch soleus muscle fiber diameter and twitch contraction and relaxation times were not different in the two groups.
Glucose increases rat plasma norepinephrine levels by direct action on the brain
Authors: Levin B. E.
Published: December 2017

The hypothesis that glucose can selectively activate the sympathetic nervous system (SNS) by direct action on the brain was tested using plasma norepinephrine (NE) and epinephrine (Epi) responses to intracarotid and intravenous glucose injections as indexes of SNS and adrenal medullary responses, respectively. Intracarotid glucose bolus injections (0.1 g/kg) transiently raised plasma glucose (22%) and insulin (98%) levels at 2 min and increased plasma NE, but not Epi, levels from 2 to 60 min. Areas under the NE curve were 700% higher than equiosmolar doses of mannitol. An intravenous glucose bolus (1 g/kg) gave quantitatively similar but delayed (30 min) NE responses to the 0.1 g/kg intracarotid dose but raised plasma glucose 500% and insulin 1,700% above baseline at 2 min postinjection. Slow intracarotid glucose infusions for 60 min at 4 mg.kg-1.min-1 raised plasma NE levels from 30 to 60 min with 250% higher areas under the NE curve than the intracarotid and intravenous bolus doses but without a change in plasma glucose, insulin, or Epi levels. Infusions at 6 mg.kg-1.min-1 transiently raised plasma NE levels at 30 min without altering glucose, insulin, or Epi levels. These results suggest that glucose alone can produce a selective, delayed SNS activation by a direct action on the brain.
Role of angiotensin in ameliorating the renal actions of norepinephrine
Authors: Yang H. M. , Lohmeier T. E.
Published: December 2017

To determine the importance of the arterial pressure effects of angiotensin II (ANG II) on renal function during acute renal adrenergic stimulation, we examined the effects of a 2-h intrarenal arterial infusion of norepinephrine (NE) at 0.1 and 0.25 micrograms.kg-1.min-1 on renal function in five conscious dogs during 1) control conditions, 2) servo-control of renal arterial pressure (RAP) at control levels, and 3) chronic captopril administration. The low rate of NE infusion produced an approximately 20% decrease in glomerular filtration rate (GFR) and renal plasma flow (RPF) and an approximately 8-mmHg increase in RAP in association with an approximately 2.5-fold rise in plasma renin activity (PRA). The high rate of NE infusion produced greater increments in both PRA and RAP and an approximately 50% reduction in GFR and RPF. Neither servo-control of RAP nor captopril administration significantly affected the above renal responses to the low rate of NE infusion. In marked contrast, when increases in RAP (approximately 20 mmHg) were prevented at the high rate of NE infusion by servo-control of RAP, both the PRA and renal responses were enhanced. Furthermore, when RAP was reduced (approximately 25 mmHg) as a result of chronically blocking the renin-angiotensin system with captopril, the renal responses to the high rate of NE infusion were exaggerated even further; in four of five dogs, total renal ischemia occurred in response to NE. These results indicate that ANG II indirectly ameliorates the renal actions of renal adrenergic stimulation by increasing RAP.
Dietary modulation of intestinal nutrient transport in the teleost fish tilapia
Authors: Titus E. , Karasov W. H. , Ahearn G. A.
Published: December 2017

Tilapia (Oreochromis mossambicus) were fed a diet with either 60% carbohydrate (70% grain-4% fish meal) or 17% carbohydrate (11% grain-65% fish meal) for greater than or equal to 4 wk. Intestinal uptake of radiolabeled acetate, D-glucose, and L-proline was measured in brush-border membrane vesicles. As expected, fish fed high carbohydrate had significantly higher D-glucose uptake than those fed low carbohydrate [maximal uptake rate (Vmax), respectively, 84.2 +/- 18.2 vs. 37.4 +/- 10.9 pmol.mg protein-1.s-1; n = 4 batches of vesicles in each case; t test, P less than 0.025]. The change in glucose transport was specific, because in the same batches of vesicles there was no significant diet effect on carrier-mediated uptake of L-proline or acetate. Also as expected, dietary modulation of carrier-mediated transport was effected primarily by alterations in Vmax and not apparent Michaelis constant (Km); Km was not significantly altered by diet for either D-glucose (high carbohydrate vs. low carbohydrate, respectively, 0.34 +/- 0.17 vs. 0.12 +/- 0.03 mM; P greater than 0.2), L-proline (respectively, 0.10 +/- 0.03 vs. mM 0.13 +/- 0.05), or acetate (respectively, 4.8 +/- 1.4 vs. mM 6.5 +/- 2.2).
Oxygen consumption and sodium pump thermogenesis in a developing mammal
Authors: Else P. L.
Published: December 2017

During development the liver undergoes large changes in its oxygen consumption. The energy requirements of the sodium pump (i.e., ouabain-sensitive respiration) would appear to account for a major part of these changes. In very young rats (birth to 9 days), the sodium pump accounted for approximately 50% of a high weight-specific liver metabolism (LMR). In rats greater than or equal to 20 days of age, the sodium pump accounted for a smaller percentage (33%) of a much lower LMR. These changes scaled with body mass. LMR scaled with an allometric slope of -0.258, ouabain-sensitive respiration with a slope of -0.355, and ouabain-insensitive respiration with a slope of -0.194. It is proposed that changes in LMR of rats during development are due primarily to the changing energy requirements of the sodium pump.
Blood ion regulation during repeated maximal exercise and recovery in humans
Authors: Lindinger M. I. , Heigenhauser G. J. , McKelvie R. S. , Jones N. L.
Published: December 2017

We investigated the ionic changes in arterial (a) and femoral venous (fv) blood that accompany muscle fatigue with repeated maximal exercise. Measurements were made on separated plasma and hemolysed whole blood to quantify the relative contributions of plasma and erythrocytes to this acid-base challenge. Five healthy males performed four 30-s bouts of maximal isokinetic cycling exercise, with 4 min of rest between bouts, and recovery was followed for 90 min. In whole blood, maximal increases in [K+]a amounted to 10 +/- 2.0 meq/l and in [K+]fv to 7 +/- 4.3 meq/l and occurred at the end of bout 2. Whole blood lactate concentration ([Lac-]) peaked at 15.3 +/- 1.39 ([Lac-]a) and 16.7 +/- 1.59 meq/l ([Lac-]fv) at the end of bout 4. In plasma, peak [Lac-]a and [Lac-]fv were both 21 meq/l at the end of bout 4. Plasma [H+]a increased from 36 +/- 1.0 neq/l at rest to 44 +/- 2.9 neq/l at the end of the first bout of exercise; 80% of this increase was due to a 2.9 meq/l decrease in arterial strong ion difference ([SID]), and 20% was due to an increase in plasma protein ([Atot]a); a reduction in arterial PCO2 to 29 mmHg had an alkalinizing effect. In contrast, plasma [H+]fv increased from 39 +/- 0.5 neq/l at rest to 93 +/- 4.1 neq/l, with an increase in PfvCO2 to 97 +/- 7 mmHg contributing 75%, a decrease in [SID]fv 15%, and an increase in [Atot]fv 10% to the increase in [H+]fv. In later exercise bouts, the relative contributions of [SID]a, [Atot]a, and arterial PCO2 to plasma [H+]a were similar, but the contribution of [SID]fv to [H+]fv increased and that of femoral venous PCO2 decreased, with the contribution of [Atot]fv remaining unchanged (8-12%). During exercise and recovery, the changes in both arterial and femoral venous PCO2 and [K+] were more rapid than changes in [Lac-], and the time course of whole blood [K+] was slower than that of plasma [K+]. Erythrocytes may play an important role in regulating plasma [Lac-] and [K+] with intense exercise.
Cerebral metabolic responses and vasopressin and oxytocin secretions during progressive water deprivation in rats
Authors: Kadekaro M. , Summy-Long J. Y. , Freeman S. , Harris J. S. , Terrell M. L. , Eisenberg H. M.
Published: December 2017

Pages R310–R317: M. Kadekaro, J. Y. Summy-Long, S. Freeman, J. S. Harris, M. L. Terrell, and H. M. Eisenberg. “Cerebral metabolic responses and vasopressin and oxytocin secretions during progressive water deprivation in rats.” Page R314: In several places in Table 6 the word “nerve” was incorrectly substituted for the word “nucleus.” The correct table appears below.

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