bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differentiation of t-e circadian system in the golden hamster
Authors: Zucker I. , Fitzgerald K. M. , Morin L. P.
Published: December 2017

The effect of estradiol benzoate (EB) on free-running circadian activity rhythms was studied in gonadectomized hamsters maintained in constant dim illumination. EB shortened the period (tau) of the female, but not of the male circadian activity rhythm. Responsiveness of the circadian system to EB was subject to sexual differentiation. The circadian period of wheel running by female hamsters given a single injection of testosterone propionate on the day of birth did not shorten in response to EB in adulthood. This failure to respond to EB also was observed in normal male hamsters, and was different from the response shown by normal females. Preliminary data suggest that tau of the activity rhythm of males castrated on the day of birth is shortened during EB treatment in adulthood. The differential effects of estradiol on tau are related to anatomic differences between the sexes in neural connections of the substrate for circadian rhythms.
Comparison of vertebrate salt-excreting organs
Authors: Kirschner L. B.
Published: December 2017

Many marine vertebrates must excrete NaCl against a substantial chemical gradient to remain hypoionic to the environment. Salt secretion appears to be mediated by “chloride cells” found in the gills of many fish or in salt glands in elasmobranchs, reptiles, and birds. The ultrastructure of the cells is similar in all animals possessing them, as is the composition of the fluid they produce, and a common mode of function is suggested. However, the extant flux-force data cannot be reconciled with a single mechanism. They appear to suggest that various combinations of Na+-, K+-, and Cl--transport systems can operate in different epithelia, and that epithelial permeabilities may also differ. However, a solution approximately seawater in monovalent ion concentrations is produced in every case.
Comparison of storage- and signal-limited models of pancreatic insulin secretion
Authors: O'Connor M. D. , Landahl H. , Grodsky G. M.
Published: December 2017

Kinetic patterns of glucose-stimulated insulin secretion from the in vitro perfused pancreas were used to test different types of secretion models of similar complexity. A storage-limited, two-compartment model, modified slightly from that previously, was compared with signal-limited models incorporating delta or feedback characteristics. Mathematical relationships for all models were fixed by single-step, dose-response experiments and models were compared in a series of glucose test patterns including steps, step restimulations, staircases, pulses, ramps, and ramp restimulations. The work quantifies previously unreported characteristics of hypersensitivity and low-glucose rest/restimulation behavior in the pancreas. All models simulated staircase and ramp experiments. The two-compartment model contains an inherent hypersensitivity factor required for repeated pulse-type experiments. However, the kinetics of hypersensitivity were too rapid to be simulated in all types of pulse and ramp/pulse experiments by the restricted refilling characteristics as written into this model. The signal-limited, delta-feedback model did not inherently produce potentiation, but required add-on modification that then more closely simulated some pulse and ramp/pulse experiments. This model simulated experimental negative spikes, whereas the storage-limited model would require additional complexity to do so. These and other results suggest that both storage- and signal-limited models, although currently insufficient, could be elaborated to simulate available data. Therefore, a choice between the two to describe the underlying physiological mechanism of multiphasic insulin secretion is premature. The alternate possibility that the secretion mechanism may be reflected by a combination of the two models is presented.
Urea recycling in active golden-mantled ground squirrels (Spermophilus lateralis)
Authors: Steffen J. M. , Rigler G. L. , Moore A. K. , Riedesel M. L.
Published: December 2017

In response to fasting or fasting combined with water deprivation urine urea excretion declined sharply in normothermic ground squirrels (Spermophilus lateralis) when compared with laboratory rats. Intraperitoneal injection of urea equivalent to 0.3% of body weight failed to increase blood urea in 12-h fasted ground squirrels, and led to little urine urea excretion when compared with similarly treated rats. Collection of expired CO2 from fasted or fasted water-deprived ground squirrels that were urea loaded and injected with a tracer dose of 14C-tagged urea revealed a 1,000- to 1,500-fold greater 14CO2 expiration than controls. Treatment of fasted squirrels with antibiotics (penicillin, tetracycline, or sulfamethazine) to reduce intestinal microflora reduced expired 14CO2 to control levels. In fasted squirrels, drug treatment also enhanced urine urea excretion with values approaching those of controls. The results of these experiments point to the possibility of urea nitrogen recycling in nutritionally stressed ground squirrels.
Regulatory drinking in the pigeon Columba livia
Authors: Kaufman S. , Peters G.
Published: December 2017

Pigeons were subjected to stimuli known to induce regulatory drinking in mammals. Water-satiated birds drank in response to intravenous (iv) hypertonic NaCl, intraperitoneal (ip) hyperoncotic polyethylene glycol (PEG) (20 M), iv infusions of angiotensinamide, subcutaneous (sc) isoprenaline, and iv chicken kidney extract. Intravenous porcine renin failed to elicit a major drinking response. Drinking after water deprivation was reduced by an iv preload of isotonic saline. Water intake after iv hypertonic NaCl equaled the volume required for dilution to isotonicity. Water intake in response to ip PEG was larger than in rats and resulted in a parallel increase in body weight. Sensitivity to isoprenaline and angiotensinamide was less than or equal to that of rats although pigeons drank much more. Drinking responses to iv hypertonic NaCl plus ip hyperoncotic PEG were additive. Small (5 ml/kg body wt) blood losses induced delayed (after 4 h) drinking; larger blood losses were ineffective. There was no simple additive relationship between the responses to hemorrhage and hypertonic saline. In summary, the dipsogenic response of pigeons was much greater than that of mammals although sensitivity was sometimes higher and sometimes lower.
Temperature dependence of blood viscosity in frogs and turtles: effect on heat exchange with environment
Authors: Langille B. L. , Crisp B.
Published: December 2017

The temperature dependence of the viscosity of blood from frogs and turtles has been assessed for temperatures between 5 and 40 degrees C. Viscosity of turtles' blood was, on average, reduced from 3.50 +/- 0.16 to 2.13 +/- 0.10 cP between 10 and 30 degrees C, a decline of 39%. Even larger changes in viscosity were observed for frogs' blood with viscosity falling from 4.55 +/- 0.32 to 2.55 +/- 0.25 cP over the same temperature range, a change of 44%. Blood viscosity was highly correlated with hematocrit in both species at all temperatures. Viscosity of blood from both frogs and turtles showed a large standard deviation at all temperatures and this was attributed to large individual-to-individual variations in hematocrit. Turtles heat faster than they cool, regardless of whether tests are performed at temperatures above or below the range of thermal preference. The effect of temperature dependence of blood viscosity on heating and cooling rates is demonstrated.
In vitro studies of sodium transport across the lower intestine of a desert parrot
Authors: Skadhauge E. , Dawson T. J.
Published: December 2017

The lower intestine (coprodeum and colon) of the Australian parrot, the galah, was mounted in Ussing chambers. Short-circuit current (SCC), electrical potential difference (PD), and unidirectional fluxes of Na and Cl were measured in birds that were fed mixed seeds or were NaCl loaded. The net Na transport of both coprodeum and colon was nearly equal to the SCC, and the flux ratio for Cl was unity. In birds which received mixed seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but increased colonic Na transport. The coprodeal and colonic SCC and NA transport of birds receiving mixed seeds were inhibited by amiloride on the mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by amiloride (by 17%), but stimulated by amino acids (by 18%).
Mathematical model of the fetal cardiovascular system: the uncontrolled case
Authors: Huikeshoven F. , Coleman T. G. , Jongsma H. W.
Published: December 2017

A mathematical model was developed to study and to interpret the results of different experiments undertaken in the field of fetal cardiovascular physiology. This model consists of a total of six peripheral blood compartments and a detailed description of the heart. The unique characteristics of the fetal circulation, particularly the ductus arteriosus, the foramen ovale, and the placenta are incorporated into this model. No control mechanisms are incorporated. The model was validated by simulating several previously described experiments. First, the performance of the individual ventricles was measured. The results indicate that, in the normal physiological situation, the right ventricle is working near the upper limits of its function while the left ventricle works below its limits. Second, the circulatory system was stressed by increasing the blood volume and the results show a shift from right to left in the relative contributions of each ventricle to the total cardiac output. Finally, effects of clamping the several blood vessels of the umbilical cord were studied.
Cerebral energy metabolism in mallard ducks during apneic asphyxia: the role of oxygen conservation
Authors: Bryan R. M. , Jones D. R.
Published: December 2017

Cerebral energy metabolism during apneic asphyxia was studied in ducks. Fluctuations in the reduced form of respiratory chain nicotinamide adenine dinucleotide (NADH) were monitored from the left cerebral hemisphere and used as an indicator of mitochondrial hypoxia. Electroencephalogram (EEG) and surface PO2 were recorded from the right hemisphere. Forced dives of 4- to 7-min duration on restrained ducks were characterized by bradycardia and an accumulation of NADH, which increased throughout the diving period. NADH returned to the preasphyxic level when breathing was resumed. In later experiments, asphyxia was produced by stopping artificial ventilation in paralyzed ducks. Asphyxia produced by this means caused similar changes in the measured variables (heart rate, blood pressure, and NADH fluorescence) to those obtained in forced submergence of nonparalyzed ducks. The inhibition of cardiovascular adjustments by atropine caused NADH to increase faster and tissue PO2 to decrease faster during apneic asphyxia than in nonatropinized ducks. We conclude that the oxygen-conserving cardiovascular adjustments play a key role in the increased cerebral tolerance to apneic asphyxia in ducks.
Choosing the right fictions of scientific law
Authors: Walter D. O.
Published: December 2017

Fictions are well established in the theory and practice of civil law; similar importance is here claimed for fictions in the theory and application of scientific law. A puzzle from quantum mechanics, previously referred to in this Journal [Am. J. Physiol. 238 (Regulatory Integrative Comp. Physiol. 7(: R277-R290, 1980], is reinterpreted by suggesting quantum logic as a source of relevant fictions, which indicate a solution to that puzzle. Another physiological application of quantum theory suggests that the concept of "the state of the brain" may, in its usual classical sense, not be useful for an individual brain--but may well be suggestively modeled by a quantum state. The notion of "myths," usually only pejoratively applied in positivistic writings, is suggested for rehabilitation, in view of their helpful function (often unnoticed) even in positivistic thinking. Finally, an example of a biological simulation (of a tumor by a cell culture) is presented, to show that its multilayered fictionalizations illustrate the surprising fact that a simulation that is insulated from the system being simulated can be logically more powerful than any uninsulated simulation.
Ion transport by the urinary bladder of the gobiid teleost, Gillichthys mirabilis
Authors: Loretz C. A. , Bern H. A.
Published: December 2017

Transport characteristics of the two epithelial cell types lining the urinary bladder of the goby can be studied in Ussing-type chambers. Cuboidal cell regions from seawater- and 5% seawater-acclimated fish exhibit little mucosal-to-serosal Na or Cl transport. In contrast, columnar cell regions from both seawater- and 5% seawater-acclimated fish transport substantial amounts of Na and Cl. Whereas all electrolyte transport in 5% seawater-acclimated fish is electrically silent (neutral), columnar cell regions from seawater-acclimated fish possess an electrogenic Na transport component in addition to the neutral transport. Columnar cell regions also possess a Cl/Cl exchange diffusion mechanism. Neutral Na and Cl transport are not altered in response to external salinity; electrogenic transport varies both with acclimation to salinity and season. Reabsorption of Na and Cl from urine reduces excretory losses of these ions from 5% seawater-acclimated fish and drives urinary bladder water reabsorption in seawater-acclimated fish.
Separation of drinking and pressor responses to central angiotensin by monoamines
Authors: Camacho A. , Phillips M. I.
Published: December 2017

This study investigated the neurotransmitters involved in the increase in blood pressure and drinking produced when angiotension II is injected intraventricularly (ivt). Using pharmacologic manipulations of the monoamines norepinephrine, dopamine, and serotonin it has been possible to separate the pressor response from dipsogenic responses to angiotension II. Alpha-adrenergic blockade with phentolamine restricted to the brain blocked the pressor response to angiotensin II in a dose-related manner, while drinking remained unaffected. Norepinephrine alone, injected into the ventricles elevated blood pressure, but did not produce drinking. The norepinephrine effect was also blocked by phentolamine by the same ventricular route. Other monoamines were not involved. Dopamine alone did not produce thirst. Cardiovascular effects with dopamine were observed only with large doses. The dopaminergic agonist apomorphine produced no change in blood pressure or drinking. Reduction of central serotonin stores by p-chlorophenylalanine intraperitoneally or 5,7-dihydroxytryptamine intraventricularly had no effect on the pressor or dipsogenic effects of angiotensin II. The serotonin agonist N,N-dimethyl-5-methoxytryptamine ivt did not produce a rise in blood pressure or drinking. It is concluded that the pressor effect of angiotensin II, but not the drinking effect is mediated by noradrenergic stimulation of alpha-receptors. The drinking response does not appear to be mediated by the monoamines.
Intravenous adenosine triphosphate (ATP) in hemorrhagic shock in rats
Authors: Schloerb P. R. , Sieracki L. , Botwin A. J. , Winblad J. M. , Maguire M. H.
Published: December 2017

The effect of intravenous (iv) infusion of 6.25 mumol of ATP-MgCl2 on survival and tissue ATP levels in hemorrhagic shock was investigated using a rat model. Mortality in ATP-MgCl2-treated shocked rats was 50% compared with 53% in saline-treated controls. Tissue ATP levels in ATP-MgCl2-treated shocked rats did not differ from those in saline-treated shocked rats nor from those in sham-operated controls. After iv infusion of 6.25 mumol of [8-14C]ATP-MgCl2, shocked, sham-operated, and nephrectomized rats had similar tissue distributions of 14C. The 14C in heart, lung, kidney, and liver of shocked and sham-operated rats was present almost entirely as nonphosphorylated [8-14C]ATP catabolites. It is concluded that ATP-MgCl2 iv did not benefit survival or enhance tissue ATP levels in shocked animals and that the administered ATP was rapidly and extensively degraded.
Scope for activity in the crayfish Pacifastacus leniusculus
Authors: Rutledge P. S. , Pritchard A. W.
Published: December 2017

The scope for activity of the crayfish Pacifastacus leniusculus was determined between 5 and 30 degrees C (incipient lethal of 33 degrees C). Standard oxygen consumption rate (VO2) ws low (e.g., 17 ml x kg-1 x h-1 at 20 degrees C); and it increased with temperature over the entire range (Q10 = 2.09 for 5-25 degrees C). Active VO2 increased with temperature (Q10 = 1.76) to a maximum at 20 degrees C (VO2 = 176 ml x kg-1 x h-1), and then decreased. Scope for activity likewise showed a maximum at 20 degrees C (VO2 - 158 ml x kg-1 x h-1) and decreased at higher temperatures. Comparison with fish studies indicates these values represent a relatively well-developed oxygen uptake ability in this decapod crustacean. At 20 degrees C crayfish active VO2 is a significant fraction of that shown by highly active VO2 is a significant fraction of that shown by highly active species such as sockeye (29%), and moderately active species such as goldfish (57%), bullhead (62%), and bass (78%); and it is much greater than active VO2 for sluggish species such as gobiids (> 300%). Also, crayfish scope for activity between 5 and 20 degrees C is virtually identical to scopes for bullhead and bass because crayfish have lower standard VO2 than either of these fish.
Circulation, oxygen transport, and activity in the crayfish
Authors: Rutledge P. S.
Published: December 2017

Heart and ventilation frequencies, oxygen uptake rate, hemocyanin concentration, and pre- and postbranchial PO2 and pH were measured in unrestrained crayfish (Pacifastacus leniuculus) immediately following routine and forced (maximum) activity. Experiments were performed at 20 degrees C, the temperature of maximum scope for activity in this species, and at 10 and 25 degrees C. A procedure for using N-ethylmaleimide as an anticoagulant in hemolymph sampling is described. Hemocyanin oxygen saturation, oxygen content of pre- and postbranchial hemolymph, cardiac output, and stroke volume were estimated from the measured parameters. PO2 of postbranchial hemolymph sampled immediately after routine activity was low (9-12 Torr), accompanied by hemocyanin oxygen saturations of 55-75%. Maximum forced activity for 10 min caused further reduction in these values. Thus hemocyanin is apparently not usually saturated with oxygen in these crayfish. Cardiac output, as estimated by the Fick principle, was high (at 20 degrees C, 236 ml x kg-1 x min-1 for routine activity and 969 ml x kg-1 x min-1 for forced activity). Evidence is presented that ventilation, rather than circulation, limits active oxygen uptake and scope for activity both above and below 20 degrees C.
Vascular response of the dogfish and sculpin to angiotensin II
Authors: Carroll R. G.
Published: December 2017

The mechanism by which angiotensin II (AII) exerts its pressor effect was examined in a saltwater teleost and elasmobranch. In vivo application of AII failed to elicit any changes in dogfish (Squalus acanthias) mesenteric microcirculatory blood flow, but the sculpin (Myoxocephalus octodecimspinosus) mesentery bed showed consistent reversible decreases in blood flow following AII application. Topical treatment with 0.5 mg phentolamine did not attenuate the AII response. In vitro addition of AII did not alter the mean resting tension of the dogfish celiac artery or intestinal vein, but significantly contracted the sculpin aorta. Addition of chromaffin tissue to the dogfish arterial muscle bath imparted significant vasoaction to AII when compared to saline. Both in vivo and in vitro experiments demonstrate the absence of functional AII vascular receptors in dogfish and their presence in the sculpin. Additional evidence for the mediation of AII vascular action in the dogfish by catecholamine release has been demonstrated.
Amino acid gluconeogenesis and glucose turnover in kelp bass (Paralabrax sp.)
Authors: Bever K. , Chenoweth M. , Dunn A.
Published: December 2017

The glucose replacement rate, plasma glucose concentration, glucose body mass, and amino acid gluconeogenesis were determined in vivo in fed and fasted kelp bass (Paralabrax clathratus) using [6-3H]glucose administered with [U-14C]glutamate, [U-14C]aspartate, or [U-14C]alanine. Fasting (14 days) and prolonged starvation (72 days) do not produce changes in the replacement rate, body mass, or plasma concentration of glucose. The removal of amino acids from the circulation is rapid in both fed and fasting states with nearly 50% of the administered 14Ctracer disappearing by 5 min. The incorporation of [14C]amino acid carbon into the body glucose mass is also rapid with significant amounts of tracer appearing within 15 min after administration. Gluconeogenesis from alanine and glutamate is increased by fasting whereas that from aspartate is diminished. The gluconeogenic rate is comparable to that previously observed in rats (Dunn, A., M. Chenoweth, and J. G. Hemington. The relationship of adrenal glucocorticoids to transaminase activity and gluconeogenesis in the intact rat. Biochim. Biophys. Acta 237: 192-202, 1971), although the glucose replacement rate is significantly lower. We propose that the paradoxically high rate of gluconeogenesis in fish may serve to provide carbohydrate precursors for mucus synthesis in these carnivorous animals with limited carbohydrate intake.
A new method for long-term monitoring of the ballistocardiogram, heart rate, and respiration
Authors: Alihanka J. , Vaahtoranta K. , Saarikivi I.
Published: December 2017

The principle of the static charge-sensitive-bed (SCSB) method is described. The method is simple and inexpensive. From the SCSB recording the ballistocardiogram (BCG) and respiratory movement can be simultaneously recorded by selective filtering of the original signal. The SCSB recording thus enables continuous long-term monitoring of the BCG, heart rate, respiratory rate, respiratory amplitude, and body movements. There are no electrodes or cables connected to the subject. The SCSB-BCG signal was studied by comparing the SCSB method with the conventional ultralow-frequency (ULF) acceleration BCG. The wave forms at rest and the amplitude responses to physical exercise were studied by both methods. Multiple recordings of the BCG, heart rate, respiratory movement, respiratory rate, and body movements after exercise and during sleep using the SCSB method are presented. The SCSB method opens new approaches to long-term studies of the regulation of myocardial performance, heart rate, and respiration. Applications of the SCSB method for clinical sleep studies, patient monitoring and cardiovascular screening examinations are discussed.
Right atrial stretch decreases supraoptic neurosecretory activity and plasma vasopressin
Authors: Menninger R. P.
Published: December 2017

It is generally held that left atrial stretch (LAS) but not right atrial stretch (RAS) reflexly inhibits vasopressin release and results in a diuresis. To reexamine the influence of RAS on the release of vasopressin and on the behavior of antidromically identified supraoptic neurosecretory neurons, RAS and LAS were applied in pentobarbital-anesthetized cats. Weighted 20 or 30 g sutures were placed in the left atrium pulmonary vein junction and at the base of the right atrial appendage. Antidromically identified supraoptic nucleus neurons were inhibited by both RAS and LAS applied independently and together, although fewer neurons were responsive to RAS alone. Simultaneous stretch of both atria resulted in greater inhibition of these neurons than did stretch of either atrium alone. Stretch of the right atrium alone also resulted in a significant decrease in plasma arginine vasopressin measured by radioimmunoassay. Differences between these results and other reports may stem from differences in the method of RAS or the specific right atrial receptors affected.
Active urea transport through isolated skins of frog and toad
Authors: Garcia-Romeu F. , Masoni A. , Isaia J.
Published: December 2017

Urea influxes (Ji) and effluxes (Je) were studied across the isolated skins of Rana esculenta, Bufo bufo, and B. viridis. Two symmetrical pieces of the same skin, bathed in Ringer + 2 mM urea, were used for the two fluxes. In R. esculenta the urea fluxes are passive when the animals are kept in running water but become active after dehydration in air or preadaptation in saline solutions. The ratio Ji/Je can vary between 3 and 27 and the Ji between 2 and 22 nmol . h-1 . cm-2 according to preadaptation. Only the active fluxes obey saturation kinetics. Urea absorption is always independent of sodium transport. In toads, active urea transport occurs even when hydrated. It is markedly stimulated by saline preadaptation. A correlation between the degree of active urea transport across the skin and the capacity of the species to endure dehydrating conditions would appear to exist. The physiological significance of this transport mechanism is discussed.
Role of sympathetic system in morphine-induced mydriasis in rat
Authors: Wallenstein M. C.
Published: December 2017

The effects of three doses (5, 30, and 60 mg/kg) of morphine on pupillary diameter (PD) were studied in rats that were either normal, neurotransmitter antagonist pretreated, guanethidine pretreated, cervical sympathectomized, or adrenalectomized. Morphine produced a dose-dependent increase in PD and exophthalmos. In addition, the PD concurrently underwent fluctuations. alpha-Adrenergic antagonists blocked both mydriasis and exophthalmos, whereas a beta-adrenergic antagonist had no significant effect. This suggested a role for the sympathetic nervous system. However, cervical sympathectomy or guanethidine pretreatment only partially blocked the increase in PD or exophthalmos. Adrenalectomy also partially blocked the mydriasis and exophthalmos. Adrenalectomy combined with guanethidine pretreatment completely blocked morphine-induced mydriasis but no exophthalmos. Thus, the results suggest that both direct sympathetic innervation and hormonal action from the adrenals are involved in morphine-induced mydriasis in the rat.
Pyrogens fail to produce fever in a cordylid lizard
Authors: Laburn H. P. , Mitchell D. , Kenedi E. , Louw G. N.
Published: December 2017

We investigated the effects on body temperature of the lizard Cordylus cataphractus of intracardiac injections of leucocyte pyrogen (LP) synthesized from rabbit blood and of killed Aeromonas hydrophila, a gram-negative bacterium reputed to be pathogenic in lizards. Lizards were placed in a photothermal gradient that allowed them to select a preferred body temperature following the injections. Neither injection of 0.5 ml rabbit LP nor of 4 X 10(9) organisms of A. hydrophila in 0.2 ml sterile saline caused body temperature of lizards to differ from that of control lizards injected with sterile saline. Following injection of these solutions in the lizards placed in a thermal gradient where ambient temperature ranged from 20-88 degrees C, body temperature was maintained between 32 and 34 degrees C. Pyrogens failed to elevate body temperature even when body temperature was elevated artificially to 36 degrees C before injection. We conclude that C. cataphractus does not respond with fever to either rabbit LP or A. hydrophila. Fever may not be ubiquitous even among lizards.
Endogenous cryogen excreted by the kidneys
Authors: Kluger M. J. , Turnbull A. J. , Cranston W. I. , Wing A. J. , Gross M. P. , Rothenburg B. A.
Published: December 2017

Injection (iv) of human urine into rabbits results in a fall in body temperature accompanied by peripheral vasodilation in a thermoneutral ambient temperature and suppression of shivering metabolism in the cold. There were no consistent changes in mean arterial pressure in response to the injection of urine. If the production of urine is prevented by occlusion of the ureters of rabbits, body temperature falls. Injection of endogenous pyrogen (iv) into rabbits, which have had their ureters occluded, results in a significant attenuation in the magnitude of the fever as compared to controls. These observations suggest that there is an endogenously produced cryogenic substance (“endogenous cryogen”) normally excreted in an active form by the kidneys and which when either injected, or prevented from being excreted (by clamping the ureters), results in a regulated fall in body temperature. In addition, in human patients on regular dialysis treatment who still had residual renal function, the oral temperature was slightly below normal before hemodialysis and slightly above normal after hemodialysis, a difference averaging 0.39 degrees C (P less than 0.001). These data are in agreement with the hypothesis that endogenous cryogen is a dialyzable substance, and that its concentration is reduced (and therefore the patient's body temperature rises) during hemodialysis.
Statics of the respiratory system and growth: an experimental and allometric approach
Authors: Fisher J. T. , Mortola J. P.
Published: December 2017

Static mechanical properties of the respiratory system have been examined during growth. Static inflation limb pressure-volume curves were obtained in rats and rabbits of three age groups, newborn, 2 wk, and adult. Lung weight-to-body weight ratio (LW/BW) decreased with age. Functional residual capacity (FRC) decreased with age when expressed per unit BW but increased when expressed per unit LW. Elastic recoil pressure of the lung at FRC increased during growth. Respiratory system and chest wall compliance per unit body weight (Crs/BW, Cw/BW) decreased during growth while lung compliance (CL/LW) increased. Examination of the newborn and adult allometric functions with respect to each other, suggests that, in general, changes in respiratory variables during growth are age dependent rather than size dependent. The slopes of these functions during growth tend to be less than the allometric slopes found in either the newborn or adult. In the adult the respiratory system and lung-specific compliances are interspecific constants, whereas chest wall specific compliance decreases with body size. In contrast, all the specific compliances of the newborn are size independent. The allometric ratio of Cw to CL decreases with body size in the adult, whereas this ratio is larger in the newborn and is an interspecific constant.
Total body sodium, calcium, and chloride measured chemically and by neutron activation in guinea pigs
Authors: Sheng H. P. , Huggins R. A. , Garza C. , Evans H. J. , LeBlanc A. D. , Nichols B. L. , Johnson P. C.
Published: December 2017

Body sodium (Na), calcium (Ca), and chloride (Cl) of guinea pigs weighing between 227 and 600 g were measured by total body neutron activation analysis (TBNAA) followed by chemical analysis (CA) on 12-17 animals. Paired t test was used to compare any differences in the results obtained by the two methods. There was no significant difference in the results for the three elements. The means and standard deviation for Ca (g/100 g body wt) 1.070 +/- 0.132 (TBNAA) and 1.107 +/- 0.125 (CA); for Na 0.149 +/- 0.019 (TBNAA) and 0.143 +/- 0.021 (CA); and for Cl 0.126 +/- 0.009 (TBNAA) and 0.132 +/- 0.024 (CA). Neutron activation analysis alone, in a series of 27 animals, gave means (g/100 g body wt) and standard deviation of 1.110 +/- 0.084 for Ca, 0.120 +/- 0.009 for Cl, and 0.153 +/- 0.011 for Na. TBNAA has potential usefulness, particularly in longitudinal studies in the same animal, because of its accuracy and the rapidity and ease with which the measurements can be made.
Mechanism of captopril-induced drinking
Authors: Schiffrin E. L. , Genest J.
Published: December 2017

Captopril (SQ 14,225), an orally active angiotensin I-converting enzyme (ACE) inhibitor, increased drinking and produced water diuresis in rats when given orally at a dose of 100 mg.kg-1.day-1. Chronic intraperitoneal infusion of angiotensin (ANG) II or the ANG II antagonist [Sar1, Ile8]ANG II abolished this response. Intracerebroventricular (icv) captopril infused chronically reduced the dipsogenic response to oral captopril. [Sar1, Ile8]ANG II (icv) was without effect on captopril-induced drinking. These results suggest that drinking produced by chronic oral treatment of rats with captopril may be caused by the effects of the elevated ANG I concentrations achieved after blockade of ACE and stimulation of renin secretion by captopril. Systemic ANG II may reduce this response by decreasing renin secretion. Systemic [Sar1, Ile8]ANG II presumably blocks brain ANG receptors for blood-borne ANG. Since icv [Sar1, Ile8]ANG II is ineffective, the receptors for systemic and icv ANG appear to be distinct. Orally administered captopril does not diffuse into the brain.
Mathematical model of the human circadian system with two interacting oscillators
Authors: Kronauer R. E. , Czeisler C. A. , Pilato S. F. , Moore-Ede M. C. , Weitzman E. D.
Published: December 2017

Human subjects during extended isolation from environmental time cues show complex variations in timing and duration of sleep with a progressive pattern, which eventually results in rest-activity and body temperature rhythms having different average periods. We present a model where temperature and rest-activity are each governed by an oscillator of the van der Pol type, denoted x and y, respectively. The oscillators affect one another through “velocity” type coupling, the effect of x on y being about four times greater than y on x. Periodic zeitgeber, z, is modeled as forcing only on y. We find that the entire pattern sequence can be realistically reproduced by causing only the intrinsic period of the y oscillator to increase while that of x remains stable. Desynchronization between x and y is the result of the intrinsic periods of the two oscillators becoming so disparate that the coupling is no longer able to enforce synchrony. Prior to desynchronization both human subjects and our model exhibit “phase trapping” wherein the relative phase of x and y is slowly modulated although the average x and y periods match. The model phase relations between temperature and both the timing and duration of sleep are, throughout, in good agreement with entrained and free-running human data. Most importantly, the model shows that the dramatic change in the length of the rest-activity cycle when desynchronization occurs is actually due to a relatively small variation in the governing variable, y.
Failure of pinealectomy or melatonin to alter circadian activity rhythm of the rat
Authors: Cheung P. W. , McCormack C. E.
Published: December 2017

These experiments were undertaken to determine if the pineal gland is involved in the physiological mechanism by which the rat alters its free-running period (tau) in response to changes in illuminance. Spontaneous wheel-running activity was recorded from pinealectomized or sham-operated female Charles River rats. The tau of running activity was determined in continuous darkness (DD) or in continuous dim light (LL). Pinealectomized rats and sham-operated rats lengthened their tau's to approximately the same extent when shifted from DD to LL and shortened their tau's when shifted back to DD. Continuous melatonin administration via Silastic capsules failed to alter tau of rats kept in dim LL. These results indicate that the pineal is not primarily involved in the mechanism by which the rat alters tau in response to changes in illuminance.
Open-loop gain of evaporative heat loss during radiant heat exposure in the mouse
Authors: Gordon C. J.
Published: December 2017

Whole-body evaporative water loss of the mouse during radiant heating was determined at ambient temperatures of 20-35 degrees C. The ratio of evaporated to absorbed heat per gram body weight, which is equal to open-loop gain (OLGEHL), increased over sixfold with each 1 degrees C increase in ambient temperature. At 35 degrees C, OLGEHL was equal to 0.8, which implies that the mouse evaporates 80% of the absorbed radiant heat. At 20 degrees C, less than 1% of the absorbed heat is evaporated and the remainder of the heat load is dissipated passively. A previous estimate of OLG for the mouse is similar to the data from this study at an ambient temperature of 35 degrees C. Determining OLG with natural ambient stimulation may make future studies in thermoregulation comparable.
Transmitterlike action of serotonin in phase shifting a rhythm from the Aplysia eye
Authors: Corrent G. , Eskin A.
Published: December 2017

The presence of serotonin (5-HT) and the characteristics of the phase-response curve for 5-HT indicate that 5-HT acts as a transmitter of circadian information in the Aplysia eye. Additional evidence for such a neurotransmitter role of 5-HT in the eye is presented. The isolated eye has the capacity to synthesize 5-HT from exogenous tryptophan. The receptors mediating the phase-shifting effect of 5-HT have a high affinity for 5-HT (threshold for phase shifting is less than or equal to 10(-7) M). Also these receptors demonstrate a high degree of structural specificity for 5-HT. Some structurally similar indoles to 5-HT do not cause phase shifts (5-hydroxytryptophan, 5-hydroxyindoleacetic acid), whereas others (bufotenine, tryptamine, LSD) do cause phase shifts but are less effective than 5-HT. Furthermore phase shifts in the rhythm are not produced by other monoamine neurotransmitters (dopamine, octopamine) or acetylcholine. Changes in membrane conductance to Na+, Cl-, or Ca2+ do not appear to be involved in phase shifting by 5-HT. Since large reductions in extracellular Ca2+ did not affect phase shifting by 5-HT, 5-HT is acting either directly on the circadian pacemaker cell(s) or on cells electronically coupled to the pacemaker cell(s).
Pulmonary vein-atrial junction stretch receptors and the inhibition of drinking
Authors: Moore-Gillon M. J. , Fitzsimons J. T.
Published: December 2017

A chronically implanted inflatable balloon was used to produce distension of a left pulmonary vein at its junction with the left atrium in trained conscious dogs. Balloon inflation caused a fall in the amounts of water drunk in response to injection of isoproterenol, infusion of hypertonic NaCl, or overnight water deprivation. There was also a significant increase in heart rate, but arterial, central venous, and left atrial pressures were unaltered. Blockade of the left vagosympathetic nerve prevented the inhibitory action of distension of a pulmonary vein on water intake in response to injection of isoproterenol. In experiments where the balloon was left inflated for 24 h, distension also caused a fall in the spontaneous daily water intake, whereas food intake was unaffected. Despite the fall in water intake, urine flow increased so that the dog went into negative fluid balance. In conclusion, distension of a pulmonary vein at its junction with the left atrium causes reduction in both spontaneous and induced water intake, and this inhibition is not secondary to circulatory changes or fluid retention by the kidney. The action of the receptors concerned may complement the actions of the same or similar receptors on renal function whose effects have been observed previously in acute experiments in anesthetized animals and here for the first time in conscious animals.
Renal function, heart rate, and blood pressure during exercise and avoidance in dogs
Authors: Grignolo A. , Koepke J. P. , Obrist P. A.
Published: December 2017

The effects of two behavioral tasks, treadmill exercise and shock avoidance, on renal and cardiovascular function were examined in dogs during intravenous infusion of isotonic saline. Urine was collected with a bladder catheter. Control experiments established steady base lines of urine flow (V), sodium excretion (UNaV), glomerular filtration rate (GFR), free water clearance (CH2O), heart rate (HR), and arterial pressure (Pa). Exercise led to increased V, UNaV, GFR, HR, and Pa with no change in CH2O. Avoidance caused decreases in V and UNaV, increases in HR and Pa but no change in either GFR or CH2O. The hematocrit increased significantly during both tasks. Exercise and avoidance led to opposite urinary changes even when HR accelerations were identical. The natriuretic effect of exercise was the consequence of an increased filtered load, while the antinatriuretic effect of shock avoidance was apparently due to an increased rate of tubular reabsorption of filtrate. The results show that exercise and shock avoidance, while eliciting similar cardiovascular changes, lead to opposite adjustments in urine and sodium output.
Mechanisms involved in central cardiovascular effects of prostaglandin F2 alpha
Authors: Feuerstein G. , Helke C. J. , Zerbe R. L. , Jacobowitz D. M. , Kopin I. J.
Published: December 2017

Prostaglandin F2 alpha (PGF2 alpha) injected into the cerebroventricular system (icv) of halothane-anesthetized rats increased the arterial blood pressure, heart rate, and rectal temperature. These effects were accompanied by a preferential increase in plasma norepinephrine concentration. Plasma levels of epinephrine, renin, and vasopressin were not changed in the PGF2 alpha-icv-treated rats. Bilateral vagotomy did not affect the PGF2 alpha-induced hypertension and tachycardia nor was there any change in the selective increase in plasma norepinephrine concentration. Hexamethonium pretreatment suppressed, in a dose-response manner, the increases in blood pressure, heart rate, and rectal temperature in response to PGF2 alpha-icv. Plasma norepinephrine and epinephrine levels were not altered by PGF2 alpha-icv in hexamethonium-treated rats, but plasma vasopressin concentration was markedly elevated in all hexamethonium-infused rats. These results suggest that selective central activation of the sympathetic nervous system underlies the profound cardiovascular and temperature responses elicited by central administration of PGF2 alpha.
Increased left atrial pressure does not alter renal function in the conscious primate
Authors: Cornish K. G. , Gilmore J. P.
Published: December 2017

To study the functional role of the atriorenal reflex in the nonhuman primate, we chronically instrumented six Macaca fascicularis with left atrial snares and left atrial and aortic catheters. After inserting a bladder catheter, we determined hemodynamic and renal responses of the conscious chair-restrained monkey to increased left atrial pressure. In 23 snare experiments, no significant changes in renal or cardiovascular function were observed even though left atrial pressure increased from 6.5 +/- 3.3 to 16.2 +/- 3.4 mmHg. The animals were subjected also to blood volume expansion with isoncotic isotonic dextran solutions (+15% of calculated blood volume). They responded normally to this volume stimulus. Conscious dogs prepared in the same manner as the nonhuman primate exhibited diuresis in response to elevations of atrial pressure. We conclude that left atrial stretch receptors are not importantly involved in volume homeostasis in the nonhuman primate.
Transient response of the calcium homeostatic system of the conscious pig to bolus calcium injections
Authors: Jaros G. G. , Maier H. , Podzuweit T. , von Gulich M. , Schindler J. G.
Published: December 2017

Calcium injection in the pig elicits a fast transient response which reinstates the calcium concentration to within normal limits between 30 and 40 min after injection. Although the fate of the calcium that disappeared is not known, the present experiments eliminate the kidneys and the bone remodeling cells as the main short-term regulators. The fast response is independent of parathyroid hormone but is greatly dependent of calcitonin. Further experiments are being performed to discover the nature and site of the regulating mechanisms.
Breath-to-breath variations in rate and depth of ventilation in sleeping infants
Authors: Haddad G. G. , Lai T. L. , Epstein M. A. , Epstein R. A. , Yu K. F. , Leistner H. L. , Mellins R. B.
Published: December 2017

Ventilatory measurements were made noninvasively over 2- to 3-h periods during sleep in each of nine normal infants at 1 mo of age. To assess the changes that occur in ventilation on a breath-to-breath basis, we 1) examined the variations of each of tidal volume (VT), respiratory cycle time (Ttot), expiratory time (TE), and inspiratory time (TI) and 2) studied their interrelationships. We found that the variations of VT, Ttot, and TE but not of TI were significantly greater in rapid-eye-movement (REM) than in quiet sleep. In addition, on a breath-to-breath basis, VT had a positive linear relationship and strong correlation with TI; however, the correlation between VT and TE was weak in both sleep states. VT/Ttot was found to be moderately and negatively correlated with Ttot in both REM and quiet sleep. VT was weakly correlated with Ttot in REM sleep and was, on the average, more correlated with Ttot in quiet sleep. We suggest that in infants 1) on a breath-to-breath basis, VT/Ttot is likely to drop if respiratory frequency is decreased and 2) VT is nonlinearly related to Ttot during sleep; this lack of linearity depends on the lack of constancy of VT/Ttot, which is in turn closely related to the variability of the "on-switching" of inspiratory activity.
Vagal cardiac preganglionic neurons: distribution, cell types, and reflex discharges
Authors: Nosaka S. , Yasunaga K. , Tamai S.
Published: December 2017

In chloralose- and urethan-anesthetized rats, the cardiac branch (CB) of the vagus nerve was electrically stimulated, and antidromic responses of medullary cells were recorded. The cells identified as the vagal cardiac preganglionic neurons (VCPN) were localized in the dorsal motor nucleus (ND group, 8 cells), a region in and around the nucleus ambiguus (NA group, 7 cells) and an intermediary zone (IM group, 2 cells) lying in between. Latencies of the antidromic responses were distinctly different among the three groups, and calculated conduction velocities indicated that the VCPN of the ND group possess C-fiber axons whereas those of the NA group and probably of the IM group, B-fiber axons. In another series of experiments, the right carotid sinus nerve (CSN) or the left cervical vagus nerve was stimulated, and efferent fiber group(s) mediating reflexly evoked discharges to the CB was determined by means of two-point recordings. Among reflex discharges evoked by stimulation of the CSN the shortest latency reflex was proved to be mediated by B-efferent fibers. In contrast, among reflex discharges evoked by stimulation of the vagus nerve, the greatest reflex component was found to be conveyed by C-efferent fibers. It was concluded that the VCPN consist of two types of cells, each located in a different region of the medulla oblongata and contributing to vagal cardiac reflex mechanisms in a different manner.
Lipoprotein lipase and lipid metabolism in muscle and adipose tissues of Zucker rats
Authors: McNamara J. P. , Azain M. , Kasser T. R. , Martin R. J.
Published: December 2017

To determine the relative rates of lipid metabolism in muscle and adipose tissues in obesity, we measured uptake and oxidation of free palmitate or tripalmitin into tissue slices in vitro. We also measured lipoprotein lipase (LPL) activity of soleus muscle and perirenal adipose tissues. Muscle took up more liquid from tripalmitin than from free palmitate (FFA) at 6 and 12 wk of age, whereas adipose took up more from FFA. The relative uptake of tripalmitin in adipose decreased from twofold that of muscle at 6 wk to 60% of muscle at 12 wk. Uptake from FFA in adipose was faster than in soleus at both ages. LPL/g of soleus muscle at 12 wk was higher than that of adipose. LPL/g protein was higher in adipose tissue than in muscle at 12 wk. Muscle oxidized 15-32% of FFA, obese muscles more than lean at 12 wk. AT 15-h fast decreased lean adipose tripalmitin uptake 50%, did not affect obese adipose lipid uptake, and decreased obese soleus palmitate uptake. In soleus muscle, triglyceride uptake is as active as in adipose. Obese muscles at 12 wk oxidized more FFA than lean and respond to a short fast by increasing the percent lipid oxidized.