bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction between myocardial depressant factor and vasoactive mediators with ischemia and shock
Authors: Lefer A. M.
Published: December 2017

A variety of endogenously formed vasoconstrictor substances circulate in the blood and act as mediators in ischemia and shock states. These humoral substances are chemically diverse and include peptides, lipids, and aromatic amines. One of the novel peptides, myocardial depressant factor (MDF) and several interesting lipids, including thromboxane A2 (TxA2), leukotriene D4 (LTD4), and platelet-activating factor (PAF) are very potent substances having a broad profile of pathophysiological actions. Some of the effects of MDF include myocardial depression, constriction of splanchnic vessels, and impairment of phagocytosis. TxA2 primarily constricts blood vessels, aggregates platelets, and increases membrane permeability. LTD4 is a potent vasoconstrictor and bronchoconstrictor and promotes leakage of fluid out of blood vessels. PAF activates platelets, depresses cardiac function, constricts airways, and enhances fluid leakage from the intravascular compartment. Thus vasoconstriction is common to all these mediators. Moreover, these vasoactive substances have common mechanisms of release and interact to exacerbate ischemia and contribute to the pathogenesis of a variety of shock states. New pharmacological approaches to blocking the formation and action of these mediators have provided interesting insights into the pathophysiology of shock.
Role of adrenergic-dependent H+ release from red cells in acidosis induced by hypoxia in trout
Authors: Fievet B. , Motais R. , Thomas S.
Published: December 2017

The response to severe hypoxia is characterized in trout by a sudden drop in blood pH, which is of metabolic origin, and by an increase in the blood concentration of adrenaline. This acidification is biphasic in nature. The first phase of acidification is not associated with a rise in the blood lactate concentration and no longer occurs after pretreatment of the fish with a beta-blocker agent, propranolol. Thus an acid other than lactic acid is released into the blood at the onset of hypoxia and this release, which is under beta-adrenergic control, is responsible for the first phase of acidification. On the other hand the second phase of acidification is related to an increase in blood lactate and is not modified by a beta-blocker agent. We have also demonstrated that deep hypoxia promotes a rapid increase in red blood cell volume and that this cell enlargement is coincident with a large net uptake of Na+ and Cl-. In the presence of beta-blocking agents the Na+ uptake is blocked and the swelling of the cells is considerably inhibited. The residual swelling is clearly due to the chloride shift induced by both deoxygenation of hemoglobin and change in blood pH. In the light of data obtained in vitro on the effect of catecholamines on trout erythrocytes, it can be considered that the first phase of acidification occurring at the onset of hypoxia, and that is under beta-adrenergic control, is due essentially to the release of H+ by red blood cells in exchange with external sodium mediated by a beta-adrenergic-stimulated Na+-H+ exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)
Age-related changes in circannual rhythms of lymphocyte blastogenic responses in mice
Authors: Brock M. A.
Published: December 2017

Blastogenic responses to T- and B-lymphocyte mitogens were tested in suspensions of splenocytes from 15- and 24- to 28-mo-old C57BL/6 mice and compared with analogous responses in young animals. The mice were housed under constant environmental conditions with alternating light-dark cycles (LD 12:12). Single cell suspensions were cultured in vitro with mitogens, and the induced incorporation of tritiated thymidine by dividing cells was determined. Increases in periodicity of responses to concanavalin A and phytohemagglutinin by T cells and to lipopolysaccharide by B cells and lower mean levels of activation characterized rhythms in cells from 15-mo-old and senescent mice compared with young animals. Amplitudes of the rhythms were unchanged at 15 mo, but by 24 mo of age rhythmic responses of T but not B cells were damped. The separable effects of age on expression of circannual rhythms by T and B lymphocytes suggest another mechanism for imbalance in the immune system. Phases of depressed responses that are extended for several months in populations of older mice could provide increased opportunities for environmental assaults.
Cardiorenal-endocrine dynamics during and following volume expansion
Authors: Zimmerman R. S. , Edwards B. S. , Schwab T. R. , Heublein D. M. , Burnett J. C.
Published: December 2017

The relationship between atrial pressure, atrial natriuretic peptide (ANP), the renin-angiotensin-aldosterone system, and renal hemodynamic and excretory function was examined during and following acute 10% body weight saline volume expansion and measurements were made at 3.3, 6.6, and 10% body weight volume expansion in pentobarbital anesthetized dogs (n = 10). Right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP), fractional excretion of Na (FENa), and ANP all increased in parallel during volume expansion. Plasma renin activity (PRA) and aldosterone decreased in parallel during 10% volume expansion. Following 10% volume expansion, saline was infused at the peak urine flow rate to maintain peak volume expansion. Despite continued saline infusion, RAP, PCWP, and ANP decreased in parallel. In contrast, FENa remained increased, and aldosterone and PRA remained depressed. These studies demonstrate that atrial pressures, ANP, and FENa increase in parallel during volume expansion; this suggests a role for ANP in modulating acute atrial volume overload. During stable volume expansion periods, however, despite a decrease in ANP levels, Na excretion remains elevated, suggesting that non-ANP mechanisms may be important in maintaining natriuresis during stable volume expansion.
Contraction of major artery segments of rat by fish neuropeptide urotensin II
Authors: Itoh H. , Itoh Y. , Rivier J. , Lederis K.
Published: December 2017

Urotensin II (U II) caused marked concentration-dependent contractions of helical strips from several major arteries of the rat. The thoracic aorta was most sensitive; the apparent concentration of U II producing half-maximal contraction was 6.8 X 10(-10) M. Papaverine, dibutyryl cyclic AMP, forskolin, and nitroprusside antagonized the contractile responses to U II at the apparent concentrations producing 50% inhibition (IC50) of 7.6 X 10(-6), 2.1 X 10(-4), 2.5 X 10(-6), and 1.5 X 10(-8) M, respectively. Verapamil, a calcium channel-blocking agent, partially inhibited the contractile response to U II at IC50 = 6.5 X 10(-6) M. Maximal relaxation, i.e., a complete inhibition, could not be obtained even at a concentration of 3 X 10(-5) M verapamil. Cyproheptadine reduced the U II-induced contraction at higher concentrations. Phentolamine (10(-5) M), propranolol (10(-5) M), atropine (10(-4) M), tetrodotoxin (10(-6) M), burimamide (10(-5) M), and indomethacin (10(-5) M) did not change the U II-induced contraction. At higher concentration, U II (10(-8) M) induced a small contraction of aortic strips in Ca2+-free Krebs Henseleit solution similar to that of norepinephrine, but the U II-induced contraction was not inhibited by phentolamine or propranolol. The action of U II did not require the presence of endothelial cells. It is concluded that U II acts on vascular smooth muscle and induces the contraction partly through intracellular Ca2+ mobilization but mainly by stimulating the influx of extracellular Ca2+ via potential dependent and potential independent calcium channels.(ABSTRACT TRUNCATED AT 250 WORDS)
Amniotic fluid volume regulation: basal volumes and responses to fluid infusion or withdrawal in sheep
Authors: Tomoda S. , Brace R. A. , Longo L. D.
Published: December 2017

To better understand the mechanisms that regulate amniotic fluid (AF) volume, we measured AF volume and the rates of fetal swallowing and urination in 33 pregnant sheep at 124-142 days gestation. In four of five ewes over 9-18 days, the spontaneous changes in amniotic fluid volume correlated positively with urine flow rate and negatively with the rate of swallowing (R = 0.686, P less than 0.01), such that 47% of the AF volume changes could be attributed to changes in rates of urination and swallowing. Following infusion of one liter of isotonic amniotic saline (n = 12) or mannitol (n = 5), AF volume increased 110%, and after 24 h returned to the control value in the saline group but it remained elevated 59% above control in the mannitol group. AF sodium was unchanged following saline infusion but remained reduced following mannitol. Following withdrawal of 61% of AF over 20-40 min, AF volume averaged 51 and 71% of control at 24 and 48 h, respectively, whereas AF sodium was unchanged. Variations in rates of fetal swallowing or urine formation could not explain the entire changes in AF volume following either the volume infusion or withdrawal. These data suggest that AF volume is regulated within a relatively narrow range and fetal urine formation and swallowing together and transplacental fluid flux each appear to contribute equally to the regulation of AF volume.
Pulmonary depressor reflex elicited by capsaicin in conscious intact and lung-denervated dogs
Authors: Clifford P. S. , Litzow J. T. , Coon R. L.
Published: December 2017

A pulmonary depressor reflex has been shown to be elicited in anesthetized cats, dogs, and rats by intravenous injection of capsaicin. The effects observed include apnea, hypotension, and bradycardia with some investigators reporting tachypnea following the apneic period. We investigated the response to a bolus injection of capsaicin (20 micrograms/kg) into the cephalic vein in 11 conscious beagle dogs. Five control dogs underwent sham thoracotomies, and six dogs underwent selective denervation of the lungs. A low dead-space latex rubber mask was used to monitor ventilation, and arterial blood pressure was obtained by catheterizing an exteriorized carotid artery. In four of the five control dogs the observed response was apnea concomitant with hypotension and bradycardia, followed by tachypnea. In five of the six lung-denervated dogs there was a slight tachypnea along with hypertension. It is concluded that the pulmonary depressor reflex can be elicited in conscious dogs by intravenous injection of capsaicin but is absent in lung-denervated dogs.
Effects of dopamine in the renal vascular bed of fetal, newborn, and adult sheep
Authors: Nakamura K. T. , Felder R. A. , Jose P. A. , Robillard J. E.
Published: December 2017

The renal hemodynamic response to renal arterial dopamine infusions was compared in unanesthetized fetal (129-137 days gestation, full term 145 days), newborn, and adult sheep. Mean arterial blood pressure and heart rate remained unchanged during intrarenal dopamine infusions. Dopamine produced dose-related decreases in mean renal blood flow velocity in all three groups. When compared with adult sheep fetal sheep were slightly more sensitive to the vasoconstrictive effects of dopamine ED50 (mean effective dose ratio: fetus/ED50 adult = 0.368 +/- 0.047, P less than 0.05). Increases in mean renal blood flow velocity were not seen at any dose given (1-16 micrograms/kg body wt in fetuses, 2-32 micrograms/kg body wt in newborns and adults) until dopamine was infused during alpha- and beta-adrenoceptor blockade. The largest mean increase in renal flow velocity was 13 +/- 3, 16 +/- 3, and 17 +/- 4% in fetal, newborn, and adult sheep, respectively. cis-Flupentixol inhibited the vasodilation. This study demonstrates the presence of renal vasodilation following renal arterial dopamine infusions in fetal, newborn, and adult sheep when renal alpha- and beta-adrenoceptors are blocked. Vasodilator responses are similar in all three groups, and increases in renal blood flow velocity are small compared with that of other experimental models.
Prevention of genetic fa/fa obesity with an ephedrine-methylxanthines thermogenic mixture
Authors: Dulloo A. G. , Miller D. S.
Published: December 2017

A thermogenic mixture containing ephedrine and methylxanthines was administered to 8-wk-old genetically obese fa/fa rats (O-E/Mx group) for a period of 15 wk. Their energy balance and the final body composition were compared with an untreated ad libitum-fed (O-AL) group, as well as to other fa/fa obese animals that were either pair fed to lean controls (O-PF group), or that were food restricted to such an extent they maintained a similar body weight to that of lean animals (O-WF group). Energy intake was elevated above lean or O-PF levels by approximately 27 and 10% in the O-AL and O-E/Mx groups, respectively, but lower by 18% in the O-WF group. Energy expenditure, compared with the lean values, was 10% higher in both the O-AL and O-E/Mx groups, but reduced by 13 and 30% in the O-PF and O-WF groups, respectively. The gain in body energy and the efficiency of energy deposition remained elevated above the lean values by 2.3- to 3.5-fold in the O-AL, O-PF, and O-WF groups but were reduced to lean levels in the O-E/Mx groups. These studies indicate that, unlike food restriction, the ephedrine-methylxanthine mixture prevents or arrests the development of the obesity in the fa/fa mutant by normalizing their energetic efficiency to that of the lean.
High-NaCl diet reduces cardiac vagal afferent nerve response to volume expansion
Authors: Dibona G. F. , Sawin L. L.
Published: December 2017

To localize the mechanism by which high dietary NaCl intake decreases the reflex inhibitory effects of intravenous volume expansion on efferent renal sympathetic nerve activity, experiments were performed in anesthetized normal rats prepared for separate examination of the afferent and efferent limbs of the cardiopulmonary baroreceptor reflex. When left ventricular end-diastolic pressure, an index of left heart filling pressure, was progressively increased by intravenous isotonic saline administration in sinoaortic-denervated rats, the increase in cardiac vagal afferent nerve activity was less in rats consuming high compared with normal dietary NaCl intake. During electrical stimulation of the central vagus nerve in sinoaortic-denervated rats, the decreases in efferent renal sympathetic nerve activity were similar in rats consuming high and normal dietary NaCl intake. Thus the effect of high dietary NaCl intake to decrease overall cardiopulmonary baroreceptor reflex gain during intravenous volume expansion is located in the afferent limb of the reflex arc.
Enhancement of cold-stimulated thermogenesis in the corpulent rat (LA/N cp) by aminophylline
Authors: Lee T. F. , Wang L. C. , Russell J. C.
Published: December 2017

Previous studies on obese strains of rats (e.g., Zucker and LA/N cp) have shown that they are deficient in nonshivering thermogenesis and poor in cold tolerance. Our earlier studies have established that aminophylline (AMPY; 85% theophylline-15% ethylenediamine) is effective in significantly improving cold tolerance in the lean Sprague-Dawley rat regardless of age or thermogenic capacity. The present study tested whether AMPY may be also effective in improving cold tolerance in both young (12-18 wk) and older (36-42 wk) lean and corpulent LA/N cp rats. Contrary to previous reports, however, the norepinephrine (NE)-stimulated nonshivering thermogenesis was not only present but also equal in magnitude in the corpulent rats to that of their lean controls. Further, no difference in cold tolerance was observed between the two groups regardless of age. Similarly, AMPY (18.7 mg/kg ip) significantly improved thermogenesis and cold tolerance in both lean and corpulent rats, again without any age-related difference in response. These results indicate that, despite the existence of obesity, no difference in thermogenic capacity to either NE or cold stimulation is evident in the LA/N cp rats. Thus the ontogeny of obesity in this strain may be caused by factors other than deficiency in NE- or cold-stimulated thermogenesis at the end-organ level.
Thoracic duct lymph flow during head-out water immersion in conscious dogs
Authors: Miki K. , Pazik M. M. , Krasney E. , Hong S. K. , Krasney J. A.
Published: December 2017

Water immersion (WI) increases plasma volume in awake dogs. The contribution of lymph flow to this fluid shift was studied in six splenectomized conscious dogs with a side fistula of the thoracic duct. Lymph flow, hematocrit (Hct), and plasma (CP) and lymph (CL) protein concentration were measured during 60 min in air and 120 min of WI (37 degrees C). Lymph flow in air averaged 0.96 +/- 1.0 (SE) ml/min. Lymph flow tended to decrease immediately in WI and was maintained at a level averaging 0.66 ml/min. CP/CL did not change significantly, whereas Hct fell significantly by 1.51 +/- 0.2% (Hct units) at 40 min of WI. Urine flow increased significantly to a maximum value of 1.5 +/- 0.5 ml/min at 40-60 min of WI compared with a mean value in air of 0.3 +/- 0.1 ml/min. The Hct and urine flow responses indicate that fluid shifted into the intravascular space during WI. Since lymph flow tended to decrease, the fluid shift in WI occurs across the capillary wall and not via lymphatic channels.
Brain ECF pH and central chemical control of ventilation during anoxia in turtles
Authors: Davies D. G. , Sexton J. A.
Published: December 2017

The role of changes in brain extracellular fluid [H+] in the control of breathing during anoxia was studied in unanesthetized turtles, Chrysemys scripta. Ventilation, [minute ventilation (VE), tidal volume (VT), and breathing frequency (f)], cerebral extracellular fluid (ECF) pH, and arterial blood gases were measured at 25 degrees C during a 30-min control period (room air), 30 min of anoxia (100% N2 breathing), and 60 min of recovery (room air). ECF pH was measured in the cerebral cortex with a glass microelectrode (1-2 micron tip diam). Large changes in ventilation, ECF [H+], and arterial blood gases were observed. The predominant ventilatory response was an increase in f with a slight increase in VT. A correlation was observed between ECF [H+] and f, which suggested that central chemoreceptor stimulation was involved in the ventilatory response.
Intravenous insulin infusions in rats decrease gustatory-evoked responses to sugars
Authors: Giza B. K. , Scott T. R.
Published: December 2017

Physiological factors that affect food intake have been shown to influence taste-evoked activity in the rat's central nervous system. Insulin appears to have a bimodal effect on feeding, inhibiting intake when its rise is within the normal physiological range, but, with further increases, causing hyperphagia. We studied the effect of low intravenous doses (0.5 U/kg) of regular insulin on taste-evoked responses in the nucleus tractus solitarius. Taste activity was elicited by application to the tongue of glucose, fructose, NaCl, HCl, and quinine. We monitored responses before and after intrajugular injections of insulin or a control vehicle. Taste responsiveness to glucose and fructose was significantly reduced for the period 7-22 min following the injection. Activity representing NaCl, HCl, and quinine was unaffected. The suppression of responsiveness to sweet stimuli could decrease the hedonic appeal of tastants and so serve as a mechanism by which physiological doses of insulin could contribute to a reduction in feeding.
Natriuretic response to homologous heart extract in aglomerular toadfish
Authors: Lee J. , Malvin R. L.
Published: December 2017

Although the renal effects of the atrial natriuretic factor (ANF) have been widely investigated, the mechanism of its natriuretic and diuretic effect is still controversial. The purpose of this study was to investigate whether ANF has a specific tubular action distinct from any renal or systemic hemodynamic effects. Renal responses to homologous heart extract (HE) or synthetic ANF were examined in the aglomerular toadfish. A significant natriuresis and diuresis were observed following an intra-arterial injection of either HE (amount derived from 1 heart) or ANF (atriopeptin III, 20 micrograms). However, neither affected urinary excretion of K+. Synthetic ANF did not alter the excretion of Mg2+ or Ca2+. In addition HE showed a hypotensive effect, and ANF did not alter the mean arterial pressure significantly. Neither HE nor ANF affected heart rate. Injection of skeletal muscle extract or saline vehicle alone was without effect on renal function, mean arterial pressure, or heart rate. These results support the hypothesis that ANF has a specific tubular action to increase urinary Na+ and water excretion. The presence of a natriuretic factor was demonstrated in the heart of the fish.
Changes in physiological properties of rabbit oviduct by ovarian steroids
Authors: Nozaki M. , Ito Y.
Published: December 2017

Effects of estrogen and progesterone on electrical and mechanical properties of longitudinal smooth muscle cells of the rabbit fallopian tubes were investigated using microelectrode and isometric tension recording methods. In tissues from the estrogen-treated rabbits, there was a decrease in frequency of spontaneous contractions, whereas an increase was seen in tissues from the progesterone-treated rabbits. The membrane potential of smooth muscle cells of the fallopian tube was -58.5 mV. Following treatment with progesterone or estrogen, the membrane was either depolarized (-53.7 mV, P less than 0.05) or hyperpolarized (-63.2 mV, P less than 0.05), respectively. Spontaneous burst discharges were recorded from these smooth muscle cells, and changes in the frequency of the bursts induced by treatment with progesterone or estrogen corresponded well with changes in the spontaneous contractions. Passive electrical parameters such as the time and space constants were increased by treatment with progesterone and decreased by treatment with estrogen. Therefore endogenous ovarian steroids probably participate in transport of the ovum by controlling spontaneous membrane and mechanical activities of the smooth muscle cells of the fallopian tube.
Role of local neurons in cerebrocortical vasodilation elicited from cerebellum
Authors: Iadecola C. , Arneric S. P. , Baker H. D. , Tucker L. W. , Reis D. J.
Published: December 2017

The vasodilation elicited in cerebral cortex by stimulation of the cerebellar fastigial nucleus (FN) is mediated by input pathways coming from the basal forebrain. We studied whether these pathways mediate the cortical vasodilation via a direct action on local blood vessels or via interposed local neurons. Neurons were destroyed in the primary sensory cortex by local microinjection of the excitotoxin ibotenic acid (IBO) (10 micrograms/l microliter). Five days later rats were anesthetized (alpha-chloralose), paralyzed, and ventilated. Arterial pressure and blood gases were controlled, and FN was stimulated electrically. Local cerebral blood flow (LCBF) was measured using the [14C]iodoantipyrine technique with autoradiography. Five days after IBO, neurons were destroyed in a restricted cortical area, and afferent fibers and terminals were preserved. The selectivity of the neuronal loss was established by histological and biochemical criteria and by transport of horseradish peroxidase from or into the lesion. Within the lesion, resting LCBF (n = 7) was unaffected, but the increase in LCBF evoked from the FN was abolished (P greater than 0.05); n = 6). In contrast the vasodilation elicited by hypercapnia (arterial CO2 partial pressure = 62.7 +/- 3; n = 5) was preserved. In the rest of the brain the vasodilation elicited from FN was largely unaffected. We conclude that the vasodilation evoked from FN in cerebral cortex depends on the integrity of a restricted population of local neurons that interact with the local microvasculature.
Adrenal gland denervation and diving in ducks
Authors: Mangalam H. J. , Jones D. R. , Lacombe A. M.
Published: December 2017

The extreme elevation in plasma levels of free norepinephrine (NE) and free epinephrine (EP), which occurs during forced diving of ducks (Anas platyrhynchos), was studied before and after denervation of the adrenal glands. In intact animals both NE and EP concentration increased by up to two orders of magnitude in a 4-min dive but by a significantly lesser amount if the duck breathed O2 before the dive. Denervating the adrenal glands reduced the amounts of both catecholamines (CA) released during dives, plasma EP decreased to 10%, and NE to 50% of values obtained before denervation. Breathing O2 before a dive virtually eliminated CA release in denervates, indicating that hypoxia was the important non-neural releasing agent. Hypoxia was also the most important neural releasing agent compared with hypercapnia, acidosis, or hypoglycemia. Adrenal denervation did not cause significant changes in heart rate, blood pressure, arterial blood gas tensions, pH, or plasma glucose during dives, although denervation caused increased variation in some of these variables. In ducks CA release in dives is largely due to decreasing arterial O2 partial pressure, and full expression of the response is dependent on intact innervation of the adrenal gland.
Expiratory effects of cerebellar stimulation in developing opossums
Authors: Farber J. P.
Published: December 2017

Positive-pressure breathing (PPB) causes expiratory activation of abdominal (ABD) and intercostal (IC) muscles in anesthetized opossums. Developmentally these responses begin to appear at about the 30th postnatal day and become prevalent over the next 3-4 wk. The purpose of the present study was to examine effects of constant-current cerebellar stimulation, applied over a single breath, on respiratory timing and expiratory electromyogram (EMG) activity in ABD and IC muscles during PPB in anesthetized opossums from 30-35 days of age to weaning. Electrode placements in the region of the deep cerebellar nuclei showed strong expiration-phased effects. For animals showing expiratory activation of both ABD and IC muscles during PPB, the response at low-current density consisted of suppression of the IC and ABD EMGs; relative inhibition often differed, with reduction of the ABD EMG being greater than for IC muscles. In animals of all ages tested, cerebellar stimulation prolonged the expiratory phase of the stimulated breath. Frequency of cerebellar stimulation needed to achieve maximum prolongation of the breath was significantly lower for younger vs. older animals. Pathways from deep cerebellar nuclei may differentially influence the activity of motor groups with comparable respiratory functions; this may be related to a cerebellar function of coordinating respiratory and nonrespiratory (i.e., movement and posture) functions of specific motor groups.
Evolution of mammalian endothermic metabolism: "leaky" membranes as a source of heat
Authors: Else P. L. , Hulbert A. J.
Published: December 2017

O2 consumption was measured at 37 degrees C in tissue slices of liver, kidney, and brain from Amphibolurus vitticeps and Rattus norvegicus (a reptile and mammal with same weight and body temperature) both in the presence and absence of ouabain. O2 consumption of the mammalian tissues was two to four times that of the reptilian tissues and the mammalian tissues used three to six times the energy for Na+-K+ transport than the reptilian tissues. Passive permeability to 42K+ was measured at 37 degrees C in liver and kidney slices, and passive permeability to 22Na+ was measured at 37 degrees C in isolated and cultured liver cells from each species. The mammalian cell membrane was severalfold "leakier" to both these ions than was the reptilian cell membrane, and thus the membrane pumps must use more energy to maintain the transmembrane ion gradients. It is postulated that this is a general difference between the cells of ectotherms and endotherms and thus partly explains the much higher levels of metabolism found in endothermic mammals.
Significance of vessel size and type in vascular heat transfer
Authors: Lemons D. E. , Chien S. , Crawshaw L. I. , Weinbaum S. , Jiji L. M.
Published: December 2017

This study was undertaken to gain a better understanding of the fundamental mechanisms of micro- and macrovascular heat transfer by experimentally identifying those vessels most important in the process. Tissue temperature fields around thermally nonequilibrated vessels were determined using a small temperature sensor that was guided through the rabbit thigh to generate a detailed temperature map. The measurements revealed that the lower limit of vessel size for thermal nonequilibration was 100 microns for arteries and 400 microns for veins. Local temperature fields were found around four of the five (80%) arteries that were greater than 300 microns in diameter but in only 3 of the 12 (25%) veins greater than 400 microns. These experimental results are in good agreement with previously published theoretical studies (5) in which it was concluded that thermal equilibration in the branching countercurrent vascular network of the rabbit limb occurs in vessels an order of magnitude larger than the capillaries. In those studies the smallest vessels capable of carrying heat were predicted to be 50 microns ID with the major blood tissue heat exchange occurring in vessels greater than 100 micron ID. These findings contrast with the view that most heat transfer occurs in the capillaries and suggest that vascular heat transfer analysis must take into account the vascular architecture of the 50- to 1,000-micron vessels where most heat transfer occurs.
Dimensional analysis does not determine a mass exponent for metabolic scaling
Authors: Butler J. P. , Feldman H. A. , Fredberg J. J.
Published: December 2017

In several recent article, Heusner used dimensional reasoning to derive important biological conclusions regarding the scaling of metabolism with body mass [Respir. Physiol. 48: 13-25, 1982; J. Appl. Physiol. 54: 867-873, 1983; Am. J. Physiol. 246 (Regulatory Integrative Comp. Physiol. 15): R839-R845, 1984]. We demonstrate errors in the derivation and show that dimensional analysis, correctly applied, not only fails to determine the mass scaling exponent but also fails to constrain the relationship to a power law at all.
Cadmium inhibition of Ca2+ uptake in rainbow trout gills
Authors: Verbost P. M. , Flik G. , Lock R. A. , Wendelaar Bonga S. E.
Published: December 2017

The effects of cadmium (Cd2+) on calcium (Ca2+) transport in the gills of rainbow trout (Salmo gairdneri) were studied. The gill epithelium of freshwater fish represents a model for a Ca2+-transporting tight epithelium. Unidirectional Ca2+ fluxes in the gills were estimated in an isolated saline-perfused head preparation. Ca2+ influx was not affected when up to 10 microM Cd were added to the ventilatory water at the start of flux determinations (in vitro exposure). However, after 16 h in vivo preexposure of the fish to 0.1 microM Cd in the water, a 79% inhibition of Ca2+ influx was observed. Ca2+ efflux was not affected when up to 10 microM Cd were added to the ventilatory water during the flux determination. Ca2+ efflux in fish preexposed to 0.1 microM Cd for 16 h was also not affected; a preexposure to 1 microM Cd, however, resulted in a 173% increase in Ca2+ efflux rates. Tracer retention in the gill tissue indicated that both Ca2+ and Cd2+ enter the gill epithelium via a lanthanum (La3+)-inhibitable pathway. It is concluded that Cd2+ readily enters the branchial epithelial cells, similarly as Ca2+ does via La3+-sensitive apical Ca2+ channels. The inhibitory action of Cd2+ on transepithelial Ca2+ influx seems to result from an inhibition of the basolateral Ca2+ transport, occurring after a critical intracellular Cd2+ concentration has been reached.
Adrenal, thyroid, and testicular hormone rhythms in male golden hamsters on long and short days
Authors: Ottenweller J. E. , Tapp W. N. , Pitman D. L. , Natelson B. H.
Published: December 2017

Plasma concentrations of adrenal, thyroid, and testicular hormones were measured at 4-h intervals around the clock in male hamsters on long (14:10-h light-dark cycle) and short (10:14-h light-dark cycle) days. Plasma corticosterone, cortisol, thyroxine (T4), triiodothyronine (T3), and testosterone rhythms were present on long days. The only one of these hormones to have a significant rhythm on short days was cortisol, but even its amplitude was suppressed compared with the cortisol rhythm on long days. Short days also lowered mean plasma levels of cortisol, T4, T3, and testosterone. Finally, short days raised the ratio of corticosterone to cortisol and lowered the ratio of T4 to T3. Both ratios had significant rhythms on long days but not on short days. Because of the many interactions among adrenal, thyroid, and testicular hormone axes, it is unclear whether the primary effect of short days is on one of these endocrine systems or on another factor that has separate effects on each of the hormone rhythms that was measured. Nonetheless, it is clear that a major effect of short day lengths in hamsters is to suppress hormone rhythms. Explanations of photoperiodic effects that depend on endocrine mediation should take this into account.
Patterns of reproductive hormone secretion in hibernating Turkish hamsters
Authors: Darrow J. M. , Yogev L. , Goldman B. D.
Published: December 2017

Changes in gonadal state and in circulating reproductive hormones [follicle-stimulating hormone (FSH), prolactin (PRL), and testosterone] were studied for 30 wk in male Turkish hamsters (Mesocricetus brandti) induced to hibernate by exposure to a short-day, cold environment [10:14-h light-dark (LD) cycle, 6 +/- 1 degree C]. Similar measures were compared in hamsters maintained under short-day warm conditions (10:14-h LD, 21 +/- 2 degrees C). A decrease in testicular size and in hormone levels was observed after 9-12 wk of short-day exposure in all animals. After 24 wk, hormone levels rose again, accompanied by testicular recrudescence, in short-day warm hamsters and in hamsters that failed to hibernate in the cold. For animals that hibernated the temporal pattern of endocrine and gonadal changes differed only slightly in comparison. Testicular recrudescence of hibernators lagged approximately 3 wk behind that of short-day warm hamsters. Hormone levels were generally lower in hibernators sampled during bouts of torpor than during bouts of spontaneous arousal from torpor. A marked elevation of serum FSH was observed in aroused hibernators well before the end of the hibernation season (at 21 wk of short-day exposure). Mean testosterone and PRL values had increased by wk 27, after hibernation was terminated in the majority of animals. These results indicate that testosterone may not be essential for the termination of the hibernation season. The data also suggest that an endogenous timing mechanism, resistant to the decreased body temperature experienced during torpor, may function to trigger a resurgence of the neuroendocrine-gonadal axis at the end of the winter season.
Endogenous and exogenous cholecystokinin may reduce food intake by different mechanisms
Authors: Shillabeer G. , Davison J. S.
Published: December 2017

To determine whether exogenous cholecystokinin (CCK) and endogenous CCK evoke different gastrointestinal motor responses, we investigated the motility induced by CCK by use of standard manometric methods. Injection (ip) of 500 ng/kg CCK caused immediate profound gastric inhibition and duodenal phasic excitation that did not resemble the postprandial pattern. Similar profound gastric inhibition has been associated with nausea. The contribution of endogenous CCK to the fed pattern of motility was investigated using proglumide; intraperitoneal injection of the antagonist before feeding caused no change, but injection before a second meal induced a decrease (P less than 0.025, n = 6) in gastric pressure with no accompanying duodenal change. This suggests that CCK causes an increase in gastric pressure that could result from a delay in gastric emptying. In support of this hypothesis, we have previously demonstrated, by use of proglumide, that endogenous CCK delays gastric emptying. Therefore exogenous CCK may reduce food intake by evoking an abnormal gastrointestinal motor pattern that may induce malaise, whereas endogenous CCK may decrease food intake by delaying gastric emptying, thus prolonging gastric satiety signals.
Ouabain binding in tadpole ventral skin. II. Localization of Na pump sites
Authors: Robinson D. H. , Mills J. W.
Published: December 2017

By use of [3H]ouabain autoradiography, the distribution of ouabain binding sites in the tadpole ventral skin and the change in the pattern of binding during metamorphosis were examined. In the tadpole the greatest grain density, and hence density of Na pumps, was found in the outer one-third of the epidermis. The pattern of binding changed at (Anat. Rec. 94: 7-23, 1946) stage 20 to a homogenous distribution. At stage 21 the highest grain density was in the middle third of the epidermis. The adultlike pattern of binding, with the highest density in the serosal two-thirds of the epidermis, was noted at stages 22 and 23. The average grain density through the entire tissue is approximately 2.4-fold higher in the stage 23 animal than in the tadpole with the significant increase in density occurring between stages 20 and 21. Since the adult Na transport characteristics are also not fully developed until stage 22 (Biochim. Biophys. Acta 692: 455-461, 1982), it is proposed that the development of the Na-pump characteristics is coincident with the development of other adult transport properties.
Blood volume restitution after hemorrhage in adult sheep
Authors: Grimes J. M. , Buss L. A. , Brace R. A.
Published: December 2017

Indirect experimental evidence suggested the possibility that the restoration of blood volume to normal hemorrhage in adult sheep may occur more quickly than in other species that have been studied. To test this hypothesis, we studied unanesthetized chronically catheterized adult female sheep 1-2 wk after splenectomy. An average of 19.6 +/- 1.4% (SE) of their initial blood volume was removed over 10 min. Blood volume restitution at 0.5, 1, 3, 5, 7, 24, and 48 h posthemorrhage averaged 12 +/- 3, 34 +/- 3, 41 +/- 3, 50 +/- 4, 62 +/- 10, 79 +/- 10, and 124 +/- 25%, respectively. Arterial pressure decreased during the hemorrhage and returned to normal within 2 h, whereas venous pressure did not change significantly. No change in blood osmolality occurred. There was a highly significant correlation between blood volume and plasma protein mass (r = 0.98, P less than 10(-6)) during and after the hemorrhage. Thus it appears that the posthemorrhage restoration of blood volume in adult sheep occurs over essentially the same time course as in other species and this appears to be mediated by a restoration of plasma protein mass.
Interaction of vasopressin with area postrema during volume expansion
Authors: Hasser E. M. , Undesser K. P. , Bishop V. S.
Published: December 2017

Effects of arginine vasopressin (AVP) on inhibition of renal sympathetic nerve activity (RSNA) during activation of cardiopulmonary reflexes by volume expansion were examined in conscious sinoaortic-denervated rabbits. The role of the area postrema in mediating these effects was also evaluated in rabbits subjected to area postrema lesion. Animals were subjected to 12% volume expansion with whole blood alone or during infusion of AVP (0.6 mU . kg-1 . min-1). Volume expansion in area postrema-intact animals caused a progressive reflex inhibition of RSNA (maximum = -36.5 +/- 3.3% delta RSNA). Vasopressin infusion did not significantly alter resting arterial pressure, right atrial pressure, heart rate, or RSNA. However, maximum inhibition of RSNA during volume expansion (-62.6 +/- 3.2% delta RSNA) was significantly augmented during AVP infusion, and the augmentation was reversed by a specific vascular (V1) AVP receptor antagonist. Vagotomy eliminated RSNA responses to volume expansion with or without AVP. In area postrema-lesioned animals, the RSNA response to volume expansion was similar to that of intact animals (-31.8 +/- 2.3% delta RSNA). However, AVP did not augment the RSNA response to volume expansion in lesioned animals (-30.4 +/- 2.5% delta RSNA). Thus exogenous AVP augmented cardiopulmonary reflex-mediated inhibition of RSNA due to volume expansion. This effect appeared to be mediated by the V1 AVP receptor and to require the presence of an intact area postrema.
Extracted and nonextracted atrial natriuretic peptide in rabbits during tachycardia
Authors: Rankin A. J. , Ledsome J. R. , Keeler R. , Wilson N.
Published: December 2017

The time course of changes in the plasma concentration of immunoreactive atrial natriuretic peptide (iANP) accompanying tachycardia was measured in anesthetized rabbits. In contrast to the hemodynamic changes, which occurred within the 1st min of tachycardia, the plasma iANP increased gradually and did not reach significantly elevated levels until 10 min into the stimulation period. After 20 min of tachycardia iANP was almost 200 pg/ml. Immunoreactive ANP was measured prior to and following extraction. Although the basal levels of iANP were higher in the unextracted than in extracted plasma (62 vs. 22 pg/ml), the time course of changes in iANP was identical in both. The gradual increase in iANP suggests that the release of iANP in this model may not simply be a consequence of the increase in atrial pressure.
Cardiovascular responses to chemical and electrical stimulation of amygdala in rats
Authors: Gelsema A. J. , McKitrick D. J. , Calaresu F. R.
Published: December 2017

Electrical stimulation of the amygdala has been shown to produce changes in cardiovascular variables. To locate neuronal cell bodies responsible for these changes, responses of arterial pressure (AP) and heart rate (HR) to DL-homocysteate (DLH, 0.15 M, 50-100 nl) microinjected into sites in three amygdaloid nuclei were compared with responses to electrical (90-150 microA) stimulation of the same sites in 35 artificially ventilated, paralyzed, urethan-anesthetized rats. Electrical stimulation resulted in depressor responses in most sites (89%). Changes in AP were accompanied by variable changes in HR. Chemical stimulation produced significantly fewer (25%) depressor responses. Similar results were obtained with injections of 1.0 M DLH. To eliminate the influence of the anesthetic on these responses, AP was recorded in nine conscious rats while stimulating the amygdala. Changes in behavior and AP in these animals could be obtained only by electrical stimulation. These results may be interpreted to indicate either that cell bodies responsible for changes in cardiovascular variables during electrical stimulation are not located in the amygdala or that chemical and electrical stimulation affect different neuronal elements in circuits located in the same anatomic site.
Control of discharge patterns of medullary respiratory neurons by pulmonary vagal afferent inputs
Authors: Zuperku E. J. , Hopp F. A.
Published: December 2017

To provide a better understanding of the central mechanisms by which pulmonary afferents reflexly control breathing, the responses of single respiratory neurons to vagal afferent patterns were analyzed. Respiratory-related unit (RRU) recordings were obtained from inspiratory (I), expiratory (E), and phase-spanning neurons in the ventral medulla of halothane-anesthetized, paralyzed, ventilated, vagotomized, mongrel dogs. Electrical stimulation of the largest vagal fibers was used to reflexly alter I and E durations (TI and TE) and to present various temporal input patterns to RRU. The net response was quantified by taking the difference between cycle-triggered histograms (CTH) of activity obtained during an input and the spontaneous control (no input) CTH. For step frequency patterns confined to either the I or E phase, 127 responses in 41 neurons were analyzed. The average step response time was greater than 500 ms. In general the time courses of the control and test-input discharge patterns were linearly related to one another. For I neurons the slopes (beta) of these relationships were linear functions of the vagal step frequency (Fv). Linear relationships were also obtained for 1/TI vs. Fv and 1/beta vs. TI. These results suggest that the vagal control of the discharge patterns of these neurons and phase timing is mediated via a process similar to gain modulation.
Interaction of carotid chemoreceptor and baroreceptor reflexes in anesthetized dogs
Authors: Brunner M. J. , Wallace A. , MacAnespie C. L.
Published: December 2017

Interaction between baroreceptors and chemoreceptors during simultaneous activation of the reflexes was studied in eight pentobarbital sodium-anesthetized vagotomized dogs. The carotid sinus reflexogenic area was isolated and perfused at controlled carotid sinus pressure (CSP), PO2, and PCO2. Random combinations of CSP, PO2, and PCO2 were delivered to the carotid sinus. Results were analyzed by multiple linear regression. For the arterial pressure response, increasing CO2 resulted in an upward shift of the baroreceptor reflex response curve and an increased slope of the linear portion of the curve. The heart rate-CSP curve was also shifted upward by CO2, with the effect being greatest at high levels of CSP. The respiratory frequency-CO2 relationship had an increased slope and was shifted upward when CSP was decreased. The responses of tidal volume and ventilation (VE) depended on all three inputs. At any level of PO2, decreasing CSP resulted in a parallel shift of the VE-CO2 relationship. The results indicate that there is a significant interaction between chemoreceptor and baroreceptor reflex sensitivities.
Effects of exercise training on energy balance of ovariectomized rats
Authors: Richard Denis , Rochon Louise , Deshaies Yves
Published: December 2017

Pages R740–R745: the authors of “Effects of exercise training on energy balance of ovariectomized rats” are Denis Richard, Louise Rochon, and Yves Deshaies.
Noradrenergic turnover increases in locus coeruleus after hemorrhage in cats
Authors: Thrivikraman K. V. , Carlson D. E. , Gann D. S.
Published: December 2017

Push-pull perfusion was used to determine monoaminergic activity in the locus coeruleus (LC) of alpha-chloralose-urethan-anesthetized cats after 20% hemorrhage. Blood was withdrawn from 0 to 3 min and reinfused from 10 to 13 min. Continuous 5-min interval samples of perfusate were collected from -5 to 15 min. Concentrations of the monoamines were determined using high-performance liquid chromatography with electrochemical detection. The perfusion sites (n = 21) were identified histologically. In a group of eight contiguous sites in the ventral LC (vLC), 4-hydroxy-3-methoxy-phenyl(ethylene)glycol (MHPG) increased significantly from 0.50 +/- 0.22 (control) to 1.19 +/- 0.42 pmol/5 min during the first 5 min after hemorrhage (P less than 0.05). This response differed significantly from that obtained at the remaining 13 sites. Other metabolites were not often detectable for many sites either within or outside vLC, and their responses to hemorrhage were not significant. The response of MHPG in the vLC indicates that norepinephrine (NE) turnover increases in this area selectively and implicates NE in the increase in the catecholamine oxidation current reported previously using in vivo voltammetry. Since the vLC was shown previously to facilitate adrenocorticotropin (ACTH) release, the increase in NE turnover after hemorrhage could induce ACTH release. This increase may also act locally to modulate the ascending hemodynamic signal.