bluuebunny/crossref_metadata_2025 huggingface dataset:
Carotid bifurcation sympathectomy and deafferentation: respiration during hypercapnia
Authors: Jennings D. B. , Szlyk P. C.
Published: December 2017

The respiratory effects of hypercapnia were studied in six awake cats 1) after bilateral sympathectomy of the carotid bifurcations and 2) after bilateral section of the carotid sinus nerves. When cats breathed either 2 or 4% CO2 in air, neither denervation affected the absolute level of ventilation, the percent change in ventilation, or the range of breath-to-breath variability in ventilation (V). However, in all six cats tidal volume (VT) increased for some levels of breath V after sympathectomy of the carotid bifurcations during inhalation of 4% CO2 in air. Moreover, after the subsequent carotid deafferentation, increased VT during fractional concentration of inspired CO2 (FICO2) of 4% persisted in four of six cats. Thus increased VT after sympathectomy could not be attributed to increased carotid chemoreceptor afferent activity but may have been due to reduced baroreceptor activity. On the other hand, sympathectomy-induced differences in breath timing, present during inhalation of 2% CO2, were reversed to intact values after sinus nerve section. In contrast to 2% CO2, changes in respiratory timing in intact cats associated with 4% CO2 were not altered significantly by sympathectomy or deafferentation of the carotid bifurcations. The latter indicates that above a critical FICO2 central mechanisms, unrelated to the carotid bifurcation, dominated respiratory timing in the hypercapnic awake cats.
Evidence for rapid inhibition of ACTH by corticosteroids in dogs
Authors: Keller-Wood M. , Bell M. E.
Published: December 2017

These experiments were designed to determine whether stimulated adrenocorticotropic hormone (ACTH) secretion in dogs can be rapidly inhibited by increases in plasma corticosteroid concentrations. Five dogs were injected with a 2:1 mixture of cortisol to corticosterone (corticosteroids; total doses of 22.5, 45, or 90 micrograms/kg) or vehicle simultaneously with the injection of insulin (0.5 U/kg). These dogs were also injected with corticosteroids (45 micrograms/kg) with ovine corticotropin-releasing factor (oCRF-41; 1 micrograms/kg) or with the same dose of corticosteroids alone. Plasma ACTH and corticosteroid concentrations were measured for 90 min after the injections. The inhibition of ACTH secretion was significant 10 min after injection of oCRF-41 and 40 min after injection of insulin. The first significant increase in ACTH during insulin-induced hypoglycemia does not occur until 30 min, however. Therefore, after both of these stimuli to ACTH, the ACTH response is inhibited within approximately 10 min of its onset. The results suggest that canine ACTH responses to stimuli can be rapidly inhibited and that one site of this inhibition is the pituitary.
Plasma dopamine in regulation of canine renal blood flow
Authors: Kapusta D. R. , Robie N. W.
Published: December 2017

Studies were performed in pentobarbital-anesthetized dogs to determine whether circulating plasma dopamine (DA) is involved in renal blood flow (RBF) regulation. During graded reductions in renal perfusion pressure (RPP), total renal venous (RV) DA content significantly increased at RPPs below the autoregulatory range. The RBF response to decrements in RPP was also examined during control, infusion of DA (1.2 micrograms.kg(-1).min(-1)ia), and after DA receptor blockade by SCH 23390 (30 micrograms/kg iv). During DA infusion, autoregulation was still evident over the same RPPs, although at higher flow rates. At pressures below the autoregulatory range, RBF decreased linearly and the autoregulatory curve merged with control at 50 mmHg. After SCH 23390, autoregulation ceased at a higher RPP than during control, and RBF was significantly less than control rates at pressures of 80 mmHg and below. To elucidate reasons for this latter response, reductions in RPP were repeated before and after administration of both prazosin (0.1 mg/kg iv) and SCH 23390. The results indicated that RBF rates were not different from control at any RPP. Further, prazosin alone did not alter renal autoregulation but significantly increased RBF at RPP below the autoregulatory range. Thus these results indicate that dopamine does not participate in RBF control at pressures above the inflection point for the lowest limit of RBF autoregulation but may be released at lower RPP to act as a vasodilator agent to oppose alpha-adrenoceptor-mediated reductions in RBF. Moreover, tonic DA receptor activation may influence the setting of the lower limit of canine RBF autoregulation.
Renal nerves and renal responses to volume expansion in conscious monkeys
Authors: Peterson T. V. , Benjamin B. A. , Hurst N. L.
Published: December 2017

Experiments were performed in conscious macaque monkeys to determine the effect of renal denervation on the diuresis and natriuresis of blood volume expansion. When the kidneys were innervated, expansion of estimated blood volume by 20% with 3% dextran in isotonic saline caused increases in urine flow (V), from 0.28 +/- 0.07 ml/min to a peak response of 1.08 +/- 0.20 ml/min, absolute sodium excretion (UNaV), from 30.0 +/- 11.2 to 99.8 +/- 11.7 mueq/min, and fractional sodium excretion (FENa+), from 1.24 +/- 0.51 to 3.19 +/- 0.56%. The animals then underwent bilateral renal denervation and were volume expanded a second time 6-13 days postdenervation. Under this condition, V increased from 0.32 +/- 0.05 to 0.64 +/- 0.08 ml/min, UNaV, from 22.2 +/- 4.6 to 46.2 +/- 8.0 mueq/min, and FENa+, from 0.91 +/- 0.26 to 1.92 +/- 0.41%, these increases being significantly less than when the kidneys were innervated. These results demonstrate that the renal nerves play an important role in the nonhuman primate in mediating increases in renal excretion during hypervolemia.
Glomerular permselectivity to serum proteins in rainbow trout (Salmo gairdneri)
Authors: Elger B. , Ruhs H. , Hentschel H.
Published: December 2017

Changes in glomerular filtration rate (GFR) were induced in the unanesthetized rainbow trout by short-term adaptation from freshwater (FW) to brackish water (BW, 50% seawater) to investigate the effect of altered glomerular function on the glomerular permselectivity to endogenous serum proteins in vivo. Protein patterns of serum and urine were obtained by nondenaturing polyacrylamide gradient gel electrophoresis. In the serum, high-molecular-weight proteins dominate by 83.1 +/- 8.16%, and total serum protein concentrations were 3.25 +/- 0.32 (FW) and 3.12 +/- 0.16 g/100 ml (BW). The urinary protein concentration increased from 16.0 +/- 1.41 (FW) to 42.8 +/- 11.0 mg/100 ml (BW), whereas GFR and urine flow rate, both linearly related, decreased from 4.55 +/- 0.34 (FW) to 1.84 +/- 0.11 (BW) ml.h-1.kg-1 and from 2.31 +/- 0.19 (FW) to 0.56 +/- 0.02 (BW) ml.h-1.kg-1, respectively. The fractional clearance of protein increased exponentially at decreased GFR. This suggests increased glomerular filtration of serum proteins due to altered glomerular hemodynamics.
Renal response of anesthetized rats to low-dose infusion of atrial natriuretic peptide
Authors: Soejima H. , Grekin R. J. , Briggs J. P. , Schnermann J.
Published: December 2017

Studies were performed in rats to determine the minimum infusion rate of atrial natriuretic peptide (ANP) associated with detectable changes in renal function and to determine the change in plasma levels of the peptide produced by these infusion rates. Synthetic ANP-(4-28) was administered to anesthetized euvolemic rats at rates ranging between 10 and 230 ng.kg-1.min-1 for 30 min. Significant natriuresis and diuresis were seen with an infusion of 20 ng.kg-1.min-1. At this rate of infusion, plasma ANP averaged 279 +/- 19.9 pmol/l (vs. 158 +/- 11.8 pmol/l in control rats). A transient increase in K excretion was seen with infusions higher than 100 ng.kg-1.min-1. There was no measurable change in glomerular filtration rate up to an infusion of 160 ng.kg-1.min-1. A significant decrease in mean arterial pressure was only seen with an infusion of 230 ng.kg-1.min-1. In volume-expanded rats, infusion of ANP at 10 ng.kg-1.min-1 induced a significant natriuresis. Our results indicate that natriuresis and diuresis are caused by an infusion of ANP which produces changes in plasma ANP concentration that may well result from stimulation of endogenous ANP release. In contrast, changes in K excretion, glomerular filtration rate, and arterial blood pressure may require changes in plasma ANP that are not easily achievable by physiological interventions.
Orthodromic field potentials and recurrent inhibition during anoxia in turtle brain
Authors: Feng Z. C. , Sick T. J. , Rosenthal M.
Published: December 2017

Recent evidence suggests that suppression of electrical activity, with the likely reduction of energy use, provides a necessary strategy for prolonged anoxic tolerance of turtle brain. The present study was aimed toward defining mechanisms underlying anoxia-induced suppression of electrical activity in turtle brain. Goals were to determine whether effects of anoxia were selective to excitatory or inhibitory processes and to test the hypothesis that enhanced inhibition underlies suppression of orthodromic field potentials in olfactory bulb. Amplitudes of "conditioning" and "test" responses, provoked by pairs of stimulus pulses to the olfactory nerve, were evaluated before, during, and after anoxic insults in the brains of turtles anesthetized with pentobarbital sodium. Suppression of conditioning responses was proportionally greater than that of test responses, indicating that inhibition was decreased and that enhanced inhibitory activity is not responsible for suppression of field potentials in turtle olfactory bulb during anoxia. When normoxia was restored, conditioning responses recovered but test responses remained suppressed. These data confirm that the inhibitory effect of a conditioning pulse on responses to a second pulse of stimulation results from a recurrent circuit and suggest that anoxia-induced changes in field potentials are independent of this recurrent circuit. Enhanced inhibition during the early period of recovery after anoxic insults may provide advantages for restoring energy status and cell physiology by suppressing electrical activity and energy use.
Metabolic changes in skeletal muscle and blood of greyhounds during 800-m track sprint
Authors: Dobson G. P. , Parkhouse W. S. , Weber J. M. , Stuttard E. , Harman J. , Snow D. H. , Hochachka P. W.
Published: December 2017

The aim of this study was to examine some metabolic properties and changes that occur in skeletal muscle and blood of greyhounds after an 800-m sprint. Three prime moving fast-twitch muscles were selected: biceps femoris (BF), gastrocnemius (G), and vastus lateralis (VL). The amount of glycogen utilized during the event was 42.57, 43.86, and 42.73 mumol glucosyl units/g wet wt, respectively. Expressed as a function of race time (48.3 +/- 0.7 s, n = 3), the mean rate of glycogen breakdown was 53.48 +/- 0.5 mumol.g wet wt-1.min-1 during the sprint. This is equivalent to an ATP turnover of 160 mumol.g wet wt-1.min-1, assuming 100% anaerobic conversion to lactate. This represents a conservative estimate, since greyhound muscle is heterogeneous and comprised of a large percentage of fast-twitch oxidative fibers (Armstrong et al., Am. J. Anat. 163: 87-98, 1982). The large decrease in muscle glycogen was accompanied by a 6- to 7-fold increase in muscle lactate from 3.48 +/- 0.13 to 25.42 +/- 3.54 (BF), 2.54 +/- 1.05 to 18.96 +/- 2.60 (G), and 4.57 +/- 0.44 to 30.09 +/- 1.94 mumol.g wet wt (VL), and a fall in muscle pH from 6.88 +/- 0.03 to 6.40 +/- 0.02 (BF), 6.92 +/- 0.02 to 6.56 +/- 0.02 (G), and 6.93 +/- 0.02 to 6.47 +/- 0.01 (VL). Cytosolic phosphorylation potential in BF decreased 10-fold from 11,360 +/- 680 to 1,184 +/- 347, and redox potential decreased 5-fold, indicating a marked reduction in the cytosol at this time.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of indomethacin on febrile response to recombinant human interleukin 1-alpha in rabbits
Authors: Hashimoto M. , Bando T. , Iriki M. , Hashimoto K.
Published: December 2017

Effects of indomethacin, a potent inhibitor of prostaglandin (PG) synthesis, on the fever induced by recombinant human interleukin 1-alpha (rhIL 1-alpha) was studied in conscious rabbits. Intracerebroventricularly administered rhIL 1-alpha induced a dose-dependent increase in colonic temperature that was prominently suppressed by pretreatment with indomethacin given either intracerebroventricularly or subcutaneously. On the other hand, fever induced by intravenous administration of rhIL 1-alpha was not completely suppressed by either subcutaneous or intracerebroventricular indomethacin; a small rise in colonic temperature persisted at approximately 45 min after rhIL 1-alpha injection. This rise in colonic temperature was suppressed when indomethacin was given both intracerebroventricularly and subcutaneously. It is suggested that PGs synthesized in the central nervous system contribute to the IL 1 fever and that part of IL 1-alpha given peripherally is also transmitted into the central nervous system to contribute to IL 1 fever.
Adrenoceptors and temperature regulation in goldfish
Authors: Wollmuth L. P. , Crawshaw L. I. , Rausch R. N.
Published: December 2017

In goldfish, microinjections of norepinephrine (NE) into the anterior aspect of the nucleus preopticus periventricularis result in dose-dependent decreases in selected temperature (21). To determine the characteristics of the adrenoceptors involved in this response, noradrenergic antagonists were injected 10 min before an injection of 50 ng norepinephrine. In comparison to control injections, injections of 50 ng phentolamine, an alpha-antagonist, significantly attenuated the effect of NE. In contrast, 50 ng propranolol, a beta-antagonist, produced a nonsignificant attenuation. These antagonists injected by themselves had no thermoregulatory effect. For noradrenergic agonists, thermoregulatory effects comparable to a dose of 10-25 ng NE were obtained at the following doses (in microgram): 1.0 clonidine (alpha 2), 5.0 phenylephrine (alpha 1), and 25 isoproterenol (beta). In fish, both alpha 1 and alpha 2-adrenoceptors appear to subserve the NE-induced decrease in selected temperature. Because antagonists injected by themselves do not have a thermoregulatory effect, NE may not have a role in the short-term regulation of body temperature in fish but rather may modulate this system in response to altered environmental conditions.
Time course of thermal adaptation in plasma membranes of trout kidney. II. Molecular species composition
Authors: Hazel J. R. , Landrey S. R.
Published: December 2017

The molecular species composition of phosphatidylcholine (PC) was determined in plasma membranes of kidney for rainbow trout, Salmo gairdneri, undergoing thermal acclimation between 5 and 20 degrees C. Species of PC from 5 degrees C-acclimated trout were characterized by significantly higher values of unsaturation ratio (8.78 vs. 3.15), unsaturation index (2.32 vs. 1.84), and average chain length (34.18 vs. 33.12 carbons) than those of 20 degrees C-acclimated trout, primarily because of elevated proportions of 16:0/20:4 (8.67 vs. 4.42%) and 16:0/22:6 (15.61 vs. 7.18%) and reduced levels of 14:0/16:0 (3.34 vs. 12.41%). Proportions of saturated and monoenoic species responded most rapidly (within 16-48 h) to temperature change, whereas species containing long-chain, polyunsaturated fatty acids increased only after 10-21 days of cold acclimation. The combined results of the present and preceding paper [Hazel and Landrey, Am. J. Physiol. 255 (Regulatory Integrative Comp. Physiol. 24): R352-R357, 1988] indicate that the metabolic adaptation responsible for the thermal compensation of membrane structure differ in response times, which range from rapid adjustments in both headgroup and molecular species composition to considerably slower changes in the proportions of species containing long-chain polyunsaturated fatty acids. Furthermore, the restructuring of phospholipid molecular species composition modifies membrane structure in different ways at different times during the acclimation response.
Polyriboinosinic:polyribocytidylic acid enhances rabbit slow-wave sleep
Authors: Krueger J. M. , Majde J. A. , Blatteis C. M. , Endsley J. , Ahokas R. A. , Cady A. B.
Published: December 2017

Drowsiness and fever are common symptoms of many viral diseases. It has been postulated that double-stranded RNA (dsRNA) produced during viral replication may cause these symptoms by direct toxic effects or by inducing interferon (IFN) or other cytokine production. Polyriboinosinic:polyribocytidylic acid (poly I:C), a pyrogenic and IFN-inducing synthetic dsRNA, and polyriboadenylic:polyribouridylic acid (poly A:U), a less effective pyrogen and IFN-inducing substance, were used as models of viral dsRNA to further characterize the physiological response to dsRNA. Poly I:C was injected either intravenously or intracerebroventricularly into rabbits, and electroencephalograph, body movement, and brain temperature were monitored over the next 6 h; blood samples were taken 24 h postinjection. Poly I:C increased slow-wave sleep duration, suppressed rapid-eye-movement sleep, and induced fever but failed to raise plasma Cu. Dose-dependent responses occurred after intravenous or intracerebroventricular injections; minimal effective doses were 0.3 micrograms/kg (iv) and 1.0 ng (icv). Poly A:U failed to alter the sleep or temperature parameters measured. Responses elicited by poly I:C were distinct from those elicited by bacterial products, e.g., endotoxin enhances plasma Cu levels, thus implying different mechanisms. We conclude that poly I:C enhances slow-wave sleep and body temperature without provoking the acute-phase rise in plasma Cu. These effects may be initiated through an IFN-mediated process.
Organ-specific control of glycolysis in anoxic turtles
Authors: Kelly D. A. , Storey K. B.
Published: December 2017

Control of glycolysis during anoxia was investigated in five organs (heart, brain, liver, and red and white skeletal muscles) of the freshwater turtle, Pseudemys scripta, after 1 or 5 h of submergence in N2-bubbled water. Lactate was produced as the metabolic end product, with distinct organ differences in the amount (net lactate accumulation was 2.4-fold higher in brain than white muscle) and rate (lactate production in liver dropped 16-fold after the 1st h) of lactate accumulation. ATP and total adenylate contents of all organs were reduced (by 15-32%) after 1 h of submergence, but energy charge was maintained; after 5 h, adenylate contents had fully recovered. Changes in the levels of hexose and triose phosphate intermediates of glycolysis indicated an activation of glycolysis within the 1st h of anoxia exposure in brain, heart, and skeletal muscles. By 5 h, however, these were reversed, and a glycolytic rate depression was indicated, consistent with the overall metabolic rate depression accompanying long-term anaerobiosis in the turtle. Crossover analysis indicated glycolytic control at the pyruvate kinase reaction in all organs during both glycolytic activation and metabolic depression; regulatory control at the phosphofructokinase locus was primarily important only during glycolytic activation in heart and red muscle. The same analysis indicated a very rapid glycolytic inhibition in liver occurring within the 1st h of anoxia exposure; this allows glycogenolysis to be directed toward glucose export yielding the fermentative fuel used by other organs during anoxia.
Food restriction normalizes somatic growth and diabetes in adrenalectomized ob/ob mice
Authors: Dubuc P. U. , Carlisle H. J.
Published: December 2017

Carcass composition was determined in intact and adrenalectomized (ADX) ob/ob mice after 6 wk of food restriction from weaning (21 days). Diets (2.6 or 3.2 g/day) led to reduced weight gain in intact ob/ob mice, but fat deposition was still greater, and lean growth was less than isocalorically fed lean mice. When diet was combined with ADX, obese mice fed 3.2 g/day had rates of fat-free body growth equal to ad libitum-fed lean mice but still gained more weight and deposited more fat. With 2.6 g/day, however, body weight gain, fat deposition, fat-free body growth, and protein deposition were all similar to intact lean mice receiving the same diet. Neither diet nor diet combined with ADX improved the defective thermoregulation of obese mice tested at 23 degrees C, 8 degrees C, or in response to food deprivation or food ingestion. Together, diet and adrenalectomy reduced blood glucose and insulin levels in ob/ob mice, and with the 2.6 g/day diet, the values of each were the same as littermate lean controls. The present results indicate that adrenal glucocorticoids are necessary for maintaining elevated fat deposition at the expense of lean body growth in dieted ob/ob mice, whereas hyperphagia, defective thermoregulation, energy efficiency, and diabetes are still expressed after surgery.
Cardiovascular, renal, and endocrine responses to intravenous endothelin in conscious dogs
Authors: Goetz K. L. , Wang B. C. , Madwed J. B. , Zhu J. L. , Leadley R. J.
Published: December 2017

Endothelin is a recently discovered vasoconstrictor peptide that is synthesized in certain vascular endothelial cells. We have identified the cardiovascular, renal, and hormonal responses that can be elicited in conscious dogs by intravenous administration of endothelin at rates of 10 and 30 ng.kg-1.min-1 for 60 min (0.24 and 0.72 nmol.kg-1/1-h infusion). Each dose of endothelin increased total peripheral resistance, arterial pressure, and left atrial pressure and decreased heart rate and cardiac output. Hematocrit increased by 4.8% (NS) and 22.9% (P less than 0.01) in response to the lower and higher infusion rates, respectively. Urinary sodium excretion, urine osmolality, and osmolar clearance decreased and free water clearance increased. The lower dose of endothelin decreased plasma norepinephrine and increased plasma atriopeptin. The higher dose increased plasma levels of vasopressin, renin, aldosterone, norepinephrine, epinephrine, and atriopeptin. The higher infusion rate of the peptide caused one or more brief vomiting episodes in four of five dogs. Although it is not yet known whether endothelin is a circulating hormone, it is clear that this peptide is capable of causing profound cardiovascular, renal, and endocrine alterations in conscious dogs. The possible relevance of these observations to physiological processes and to pathological conditions such as hypertension remains to be established.
Neural influences on trophic changes in brown adipose tissue during cold acclimation
Authors: Park I. R. , Himms-Hagen J.
Published: December 2017

We studied the role of the sympathetic innervation in development and maintenance of increased levels of uncoupling protein (UCP) and of thyroxine 5'-deiodinase (TD) during cold-induced growth of brown adipose tissue (BAT). Interscapular BAT was unilaterally (and in some experiments, bilaterally) denervated either before acclimation to cold (4 degrees C) for 12 days or after 14 days of a total 28-day period of acclimation to cold. BAT norepinephrine was reduced to 3-7% of the normal level in denervated BAT for up to 26 days. Denervation slowed, but did not prevent, cold-induced increases in total protein, in mitochondrial GDP binding, and in mitochondrial UCP concentration, which all reached 50% or more of the elevated level in intact tissue. In contrast, TD activity did not exceed 10% of the elevated level in intact tissue at any time. Denervation after cold acclimation resulted in a very rapid loss of TD activity, a slower and selective loss (after a lag of 1 day) of UCP, and a much slower loss of tissue protein. We conclude that the sympathetic innervation is required for an optimal trophic response of BAT to cold acclimation and for maintenance in the hypertrophied state but that other factors are also involved. Induction and maintenance of TD in BAT does need the sympathetic innervation.
Proximal tubule response in aldosterone escape
Authors: Gonzalez-Campoy J. M. , Kachelski J. , Burnett J. C. , Romero J. C. , Granger J. P. , Knox F. G.
Published: December 2017

The response of the proximal tubule to chronic aldosterone administration (15 micrograms.kg-1.day-1) was evaluated in eight conscious female mongrel dogs. Temporal profiles between hemodynamic and hormonal changes and the fractional excretions of sodium and lithium were established. Aldosterone infusion resulted in a significant decrease in urinary sodium excretion from 9.2 +/- 1.3 to 5.8 +/- 0.9 meq/h after 1 day, returning to normal by the 5th day. These changes in urinary sodium excretion were associated with significant elevations of the mean arterial pressure (MAP) from 105 +/- 5 to 111 +/- 6 mmHg and plasma atrial natriuretic factor concentrations (ANF) from 30 +/- 2 to 57 +/- 7 pg/ml beginning the 1st day of infusion. Plasma renin activity (PRA), on the other hand, was depressed by aldosterone, falling below the level of detectability. The fractional excretion of lithium increased significantly by day 2 of aldosterone infusion (from 29 +/- 3 to 44 +/- 6%), reflecting the proximal tubular response to the above changes. We conclude that the proximal tubule responds to increases in MAP and ANF and decreases in PRA during aldosterone infusion by decreasing sodium reabsorption. Subsequent nephron segments must also respond to the volume expansion produced by aldosterone, since the sustained proximal tubule natriuretic response is insufficient to explain all of escape.
Muscular contraction stimulates posterior hypothalamic neurons
Authors: Waldrop T. G. , Stremel R. W.
Published: December 2017

Recent studies have suggested that the subthalamic locomotor region (STLR) of the posterior hypothalamus is involved in modulating cardiorespiratory responses to feedback from contracting muscles. The purpose of this study was to determine whether neurons in this hypothalamic region alter their discharge frequency during contraction of hindlimb muscles. Stainless steel electrodes were used to record single-unit activity of STLR neurons during static and rhythmic contractions of hindlimb muscles in anesthetized cats. Recordings were also made from neurons in areas outside but surrounding the subthalamic locomotor region. Contraction of the triceps surae muscles was induced by stimulation of the peripheral cut ends of the L7 and S1 ventral roots. Both static and rhythmic contractions of the triceps surae evoked an increase in the discharge rate of the majority of the STLR cells studied. Two types of excitatory responses were observed: 1) abrupt increases in discharge frequency at the onset of muscular contraction and 2) a delayed more gradual increase in firing. Most of the cells that responded to muscular contraction could be activated by mechanical probing of the triceps surae muscles. However, the changes in discharge frequency were unrelated to changes in arterial pressure occurring during muscular contraction. Most of the neurons located outside the STLR were slightly inhibited by or did not respond to muscular contraction. Thus input from contracting muscles exerts predominantly an excitatory effect on neurons in the posterior hypothalamus. These results are consistent with other studies which have concluded that this hypothalamic site is involved in influencing the cardiorespiratory responses to muscular contraction.
Carotid baroreflex resetting during drug-induced arterial pressure changes in humans
Authors: Fritsch J. M. , Rea R. F. , Eckberg D. L.
Published: December 2017

We studied human baroreflex resetting during 25 min of drug-induced arterial pressure changes in 10 healthy volunteers. Average (+/- SE) base-line systolic pressure of 113 +/- 4 fell to 102 +/- 3 during nitroprusside infusions and rose to 135 +/- 6 mmHg during phenylephrine infusions. Average base-line R-R intervals of 932 +/- 37 shortened to 820 +/- 39 during nitroprusside infusions and lengthened to 1,251 +/- 61 ms during phenylephrine infusions. Carotid baroreceptor-cardiac reflex responses were evaluated with a complex series of neck chamber pressure changes, and R-R intervals were plotted as functions of carotid distending pressure. Baroreceptor-cardiac reflex relations shifted on both R-R interval and arterial pressure axes during drug infusions, but there was no significant change of the maximum slope or range of R-R interval responses. The position of baseline R-R intervals on the reflex relation (operational point) changed significantly. Resting R-R intervals were closer to threshold during pressure reductions and closer to saturation for baroreceptor-cardiac responses during pressure elevations. These results document short-term partial resetting of human baroreceptor-cardiac reflex responses as early as 25 min after the onset of arterial pressure changes.
Effects of fentanyl on carotid sinus baroreflex control of circulation in rabbits
Authors: Ohsumi H. , Sakamoto M. , Yamazaki T. , Okumura F.
Published: December 2017

The effects of intravenous administration of fentanyl on carotid sinus baroreflex control of hemodynamics were investigated in chronically instrumented rabbits. Carotid sinus baroreflex was assessed by bilateral carotid occlusion (BCO), and the responses of mean arterial pressure (MAP), heart rate (HR), mean ascending aortic flow (MAF), and total peripheral resistance (TPR) were obtained. Hemodynamic responses to BCO were examined with cumulative doses of 5, 10, and 15 micrograms/kg of fentanyl. Fentanyl did not affect MAP and TPR but reduced HR and MAF dose dependently. Fentanyl did not attenuate the MAP response to BCO significantly. In contrast, fentanyl significantly attenuated the TPR response from 0.126 +/- 0.003 to 0.104 +/- 0.005 mmHg.min-1.ml-1 and augmented the HR response from 31 +/- 2 to 47 +/- 3 beats/min in the conscious state and at 15 micrograms/kg of fentanyl, respectively. The administration of atropine after the fentanyl attenuated MAP and HR responses to 79.9 and 27.7% of those of 10 micrograms/kg of fentanyl, respectively. We suggest that these dissociated hemodynamic responses reflect the vagotonic and sympatholytic effects of fentanyl on the baroreflex pathways.
Failure of chronic beta-adrenergic blockade to inhibit overfeeding-induced thermogenesis in humans
Authors: Welle S. L. , Nair K. S. , Campbell R. G.
Published: December 2017

The effect of the beta-adrenergic antagonist propranolol on the increase in resting metabolic rate (RMR) induced by overfeeding was examined to determine whether increased beta-adrenergic activity contributes to this response. Six male subjects who were overfed with carbohydrate (1,600 excess kcal/day) for 10 days without drug treatment (control group) had increases (compared with values after 10 days of weight maintenance) in RMR after 6 days [0.24 +/- 0.06 kcal/min (22%)] and 10 days of overfeeding [0.17 +/- 0.03 kcal/min (15%)]. Eight male subjects were given a weight-maintenance diet for 10 days with oral propranolol treatment (40-60 mg every 6 h) over the last 7 days of this period. Five of these subjects were then overfed for 10 days, and three remained on the weight-maintenance diet; propranolol treatment continued until the end of the study. Propranolol significantly reduced RMR (mean 9%) before the onset of overfeeding but did not prevent increases in RMR after 6 days [0.18 +/- 0.05 kcal/min (16%)] and 10 days of overfeeding [0.17 +/- 0.03 kcal/min (15%)]. In the subjects who remained on the weight-maintenance diet throughout the study, there was no reversal of propranolol's initial reduction of RMR that would have falsely elevated the overfeeding effect. These data provide further evidence that the increase in RMR induced by overfeeding in humans is not mediated by increased beta-adrenergic activity.
Prolactin stimulates food intake in the absence of ovarian progesterone
Authors: Gerardo-Gettens T. , Moore B. J. , Stern J. S. , Horwitz B. A.
Published: December 2017

Increases in serum estrogen inhibit food intake. Conversely, progesterone stimulates food intake, probably via its antiestrogenic action. We have reported that elevated serum prolactin also stimulates food intake in female rats. It is unclear whether this effect is mediated through elevated levels of progesterone. The present study investigated the effects of prolactin on food intake and brown fat activity in the absence of progesterone. Female Osborne-Mendel rats were assigned to one of six groups: sham operated (Sham, n = 10), ovariectomized (OVX, n = 10), OVX + low estrogen (EL, n = 11), OVX + EL + prolactin (PIT, n = 9), OVX + high estrogen (EH, n = 10), and OVX + EH + PIT (n = 8). Estrogen levels were elevated by Silastic implants. Prolactin levels were elevated through pituitary transplants placed under the kidney capsule. Nine days postsurgery, food intake was significantly higher in OVX vs. Sham rats. Estrogen-treated rats (OVX + EL and OVX + EH) had significantly suppressed food intake values compared with both Sham and OVX animals. Finally, hyperprolactinemic rats (OVX + EL + PIT and OVX + EH + PIT) ate significantly more food than did estrogen-treated rats without pituitary explants. Despite the hyperphagia, no significant differences in brown fat GDP binding were observed. These data indicate that prolactin stimulates food intake in the absence of ovarian progesterone.
Effect of diltiazem on skeletal muscle 3-O-methylglucose transport in bacteremic rats
Authors: Westfall M. V. , Sayeed M. M.
Published: December 2017

This study examined whether alterations in cellular Ca2+ regulation contribute to previously observed changes in skeletal muscle sugar transport during bacteremia. Fasted male rats received saline (control) or bacteria (4 X 10(10) Escherichia coli/kg) intraperitoneally. Twelve hours later, basal and insulin-mediated 3-O-methylglucose (3MG) transport was measured in isolated soleus muscles. Measurements of 3MG transport in the presence of cytochalasin b or at a low temperature (0.5 degree C) indicated that altered sugar transport in bacteremic rat muscles was not due to nonspecific membrane permeability changes. To determine the role of Ca2+ in the pathogenesis of altered sugar transport during bacteremia, rats were treated with the Ca2+ antagonist diltiazem (DZ, 0.6-2.4 mg/kg) at various times (0, 0 + 7.5, 10 h) after saline or bacterial injection. In bacteremic rats given 2.4 mg/kg DZ at 10 h, basal and insulin-mediated transport were similar to control values. This dose of DZ had little effect on control muscles. The addition of 20 microM DZ to the incubation media did not affect basal or insulin-mediated 3MG transport in bacteremic rat muscles. Addition of the Ca2+ agonist BAY K 8644 to the incubation media had no effect on sugar transport in bacteremic rat muscles but caused alterations in control rat muscles that were comparable to those observed in bacteremia. These results suggest that alterations in Ca2+ regulation could contribute to the previously observed changes in sugar transport in skeletal muscles from bacteremic rats.
Central administration of interleukin 1 elicits hyperinsulinemia in rats
Authors: Cornell R. P. , Schwartz D. B.
Published: December 2017

This laboratory previously demonstrated that human natural interleukin 1 (IL-1) administered intravenously at a dose of 50 U to conscious fasted male Holtzman rats elicited unstimulated as well as glucose- and arginine-stimulated hyperinsulinemia. The major question posed in the present investigation is whether the monokine IL-1 can act centrally on an area of the brain such as the preoptic area of the anterior hypothalamus, which participates in mediating the IL-1-induced febrile response, to elicit insulin secretion by the pancreas. Therefore, for this study, injections of IL-1 were administered intravenously (iv), intracerebroventricularly (icv), or into the preoptic area of the anterior hypothalamus (iPO) in pentobarbital-anesthetized fasted rats. Preliminary experiments determined that the hyperinsulinemic response was enhanced in anesthetized compared with conscious animals treated iv with IL-1. An icv administered 10-U dose of the monokine produced a delayed hyperinsulinemia equal to two times the saline control value starting near 20 min postinjection but declining quickly. When injected iPO, 5 U of IL-1 elicited a prompt substantial hyperinsulinemia equal to more than three times control beginning at 5 min postinjection and persisting through the 30-min experimental period. These findings indicate that an IL-1-induced signal for pancreatic insulin secretion can be generated within the central nervous system.
Effect of sympathetic blockade on diurnal variation of hemodynamic patterns
Authors: Talan M. I. , Engel B. T.
Published: December 2017

Heart rate, stroke volume, and intra-arterial blood pressure were monitored continuously in each of four monkeys, 18 consecutive h/day for several weeks. The mean heart rate, stroke volume, cardiac output, systolic and diastolic blood pressure, and total peripheral resistance were calculated for each minute and reduced to hourly means. After base-line data were collected for approximately 20 days, observation was continued for equal periods of time under conditions of alpha-sympathetic blockade, beta-sympathetic blockade, and double sympathetic blockade. This was achieved by intra-arterial infusion of prazosin, atenolol, or a combination of both in concentration sufficient for at least 75% reduction of response to injection of agonists. The results confirmed previous findings of a diurnal pattern characterized by a fall in cardiac output and a rise in total peripheral resistance throughout the night. This pattern was not eliminated by selective blockade, of alpha- or beta-sympathetic receptors or by double sympathetic blockade; in fact, it was exacerbated by sympathetic blockade, indicating that the sympathetic nervous system attenuates these events. Because these findings indicate that blood volume redistribution is probably not the mechanism mediating the observed effects, we have hypothesized that a diurnal loss in plasma volume may mediate the fall in cardiac output and that the rise in total peripheral resistance reflects a homeostatic regulation of arterial pressure.
Glomerular filtration rate in conscious unrestrained starlings under dehydration
Authors: Roberts J. R. , Dantzler W. H.
Published: December 2017

Glomerular filtration rate (GFR) was measured in conscious unrestrained starlings, Sturnis vulgaris. Alzet osmotic minipumps were inserted into the peritoneal cavity under lidocaine local anesthesia and served to infuse the GFR marker [14C]sodium ferrocyanide. GFR was measured in hydrated birds and again after a 24-h period of water deprivation. GFR in dehydrated birds was 1.15 +/- 0.09 ml.min-1.kg-1, significantly lower (P less than 0.001) than the 2.71 +/- 0.31 ml.min-1.kg-1 in fully hydrated animals. In addition, the GFR of the hydrated birds was significantly lower (P less than 0.01) than values of 4.43 +/- 0.24 ml.min-1.kg-1 measured in hydrated anesthetized birds during micropuncture studies. A 24-h period of water deprivation caused significant increases in plasma osmolality and concentration of sodium, chloride, and phosphate. The osmolality and concentrations of calcium, magnesium, and phosphate were significantly elevated in both cloacal urine supernatant and in ureteral urine of dehydrated birds. In both hydrated and dehydrated states, the concentration of magnesium, phosphate, potassium, and total osmolality were significantly higher in cloacal urine than in ureteral urine.
Flow dynamics of the crocodilian heart
Authors: Axelsson M. , Holm S. , Nilsson S.
Published: December 2017

We report for the first time the flow events corresponding to the pressure patterns in the left and right aorta (LAo and RAo) during the cardiac cycle in the caiman (Caiman crocodylus ssp). These experiments show a complex LAo flow pattern; an initial small anterograde flow in the early systole is reversed to a backflow at midsystole. At the end of systole there is again a small anterograde flow. This second flow pulse corresponds to a pressure peak ("foramen spike") in the LAo pressure trace. The observed pattern is compatible with the view that the foramen Panizzae is obstructed by the medial cusp of the RAo valve during part of the systole. LAo pressure remains normally above right ventricular pressure throughout the cardiac cycle and there is thus no contribution to LAo flow from the right ventricle. The net flow in the LAo normally equals the flow through the foramen Panizzae and is very small compared with the systemic flow in the RAo.
Fish muscle energy metabolism measured by in vivo 31P-NMR during anoxia and recovery
Authors: van den Thillart G. , van Waarde A. , Muller H. J. , Erkelens C. , Addink A. , Lugtenburg J.
Published: December 2017

By means of in vivo 31P nuclear magnetic resonance (NMR) we measured energy stores and intracellular pH at 10-min intervals in the myotome of unanesthetized carp and goldfish before, during, and after a period of anoxia (1 h for carp and 4 h for goldfish). The fish were mounted in a modified bioprobe, and their gills were irrigated with a constant flow of aerated or anoxic water. Anoxia caused a steep decline of phosphocreatine and intracellular pH in carp muscle. After the phosphocreatine stores had been exhausted by greater than 85%, [ATP] fell, whereas IMP and phosphodiesters accumulated. In goldfish muscle, initial changes followed the same pattern, but after 20 min a steady state of high-energy phosphates was reached and the development of acidosis was dampened. The resistance of goldfish to anoxia is due to metabolic suppression and a switch from lactate to ethanol and CO2 as the anaerobic end products. In both species, recovery was complete within 3 h. The fast pH recovery seems to be mainly caused by H+ and lactic acid efflux.
Cardiovascular responses to denervation of pulmocutaneous baroreceptors in toads
Authors: Van Vliet B. N. , West N. H.
Published: December 2017

Toad pulmocutaneous arterial baroreceptors are connected to afferent fibers carried in the recurrent laryngeal nerves (rLNs). Bilateral rLN denervation in conscious toads (Bufo marinus) caused 34 and 78% increases in heart rate (Fh) and systemic arterial blood pressure (Pa) within 10-15 min, respectively. The variance of Pa was significantly increased 2 days after denervation, but Pa and Fh were not. In additional chronic experiments, 5 of 17 baroreceptor-denervated toads died within the 2-wk recovery period. No deaths occurred in sham-operated toads. The mean Pa, Fh, and cardiac interval (Ic), the mean variance of Pa, Fh, and Ic, and Pa and Fh responses to stress, plasma composition, and the dry-to-wet weight ratio of skeletal muscle and lung were not statistically different in denervated and sham-operated toads. However, the sensitivity of Ic to changes in Pa, exposed by intra-arterial injections of phenylephrine and nitroprusside, was attenuated in denervated toads. Postmortem examination revealed occasional pulmonary lesions, the incidence of which appeared correlated with causes of pulmonary hypertension: baroreceptor denervation and phenylephrine injections. We conclude that pulmocutaneous arterial baroreflex is tonically active but is not essential for the long-term maintenance of Pa in conscious undisturbed toads.
Interaction among unitary spike trains: implications for whole nerve measurements
Authors: Andresen M. C. , Yang M.
Published: December 2017

Interaction among action potential trains was examined in electroneurograms (ENGs) from filaments containing several fibers. In an in vitro preparation, increasing aortic pressure generated trains of action potentials (spikes) from regularly discharging aortic baroreceptors. Multifiber records were electronically sorted, and spikes from each separate baroreceptor were identified. "True" discharge rates, measured as the instantaneous frequency of the sorted records, were compared with the results of three quantitation approaches commonly used for multifiber or whole nerve activity in mass ENGs: "spike" counts per unit time, ENG voltage integration, and normalizations of counts or integration. Even in ENGs containing only two active baroreceptors, numerous interactions of the two spike trains occurred. Of 33 paired recordings (66 baroreceptors), 77.3% of the individual baroreceptors had spike trains that could not be clearly discriminated because of interactions with signals from other baroreceptors. Virtually all baroreceptors (96.3%) in nine three-fiber ENGs (27 baroreceptors) showed evidence of missed spikes. Corrected or true spike rates were always greater than activity rates measured by simple counting. Similarity of discharge frequencies in the different baroreceptors was the most important determinant of the rate of voltage signal interaction. Simple count or integration methods underestimated slopes of pressure-response curves and peak activity values by 20-40% compared with sorted instantaneous frequency. Not all coincidence of action potentials in the ENG resulted in simple additions of peak voltages. We conclude that simple counting and integrative techniques substantially underestimate multifiber nerve activity and such quantitation techniques should be used cautiously, particularly in experimental comparisons across groups of animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of cardiovascular and behavioral responses to alerting stimuli in rats
Authors: Casto R. , Nguyen T. , Printz M. P.
Published: December 2017

Freely moving rats exhibit complex motor and cardiovascular responses to tactile stimulation (12.5 psi air puff, 100-ms duration). In naive Wistar-Kyoto rats, the behavioral response is characterized by a short-latency (25 +/- 1 ms) jumping event, the magnitude of which habituates to repeated stimuli. In a paradigm of consecutive tactile stimuli, each delivered at 30-s intervals, the arterial pressure (AP) response is consistent in profile (36.4 +/- 1.7 mmHg, initial stimulus) and habituates rapidly (15.4 +/- 2.2 mmHg, at 20th stimulus). Rates of habituation of the jumping behavior and AP increase are similar and significantly correlated (P less than 0.01), suggesting partial common mediation. Heart rate changes are bimodal and highly dependent on stimulus number. Initial stimuli elicit bradycardia (-42 +/- 7 beats/min), habituating to extinction by stimulus 10. A temporally delayed tachycardia becomes evident by trial 5 (19 +/- 5 beats/min) and persists unchanged throughout the remainder of the 30-stimulus session. Delayed tachycardia may represent activation of secondary autonomic mechanisms. The nature of cardiovascular responses elicited by the tactile stimulus suggests a somatomotor reflex mediated through the ventrolateral medulla. Adrenal enucleation exaggerated the magnitude of transient bradycardia and abolished extinction of bradycardia with repeated stimuli. Adrenal medullary secretion has only minor importance in direct mediation of the response, but this study suggests that adrenal function plays an important role in tonically setting the level of cardiac responsiveness to parasympathetic vs. sympathetic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)