bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate of generation of myocardial power density normalized by cardiac frequency
Authors: Moreno A. H. , Bloomfield M. E. , Grossi E. A.
Published: December 2017

We introduce a frequency normalized, power averaged, rate of generation of power density (FARPD) that extends the range of applicability of the averaged rate of generation of power density (ARPD) to any cardiac frequency encountered in experimental or clinical situations. Normalization eliminates the frequency-dependent mathematical artifacts arising during the computation of quantities containing time derivatives of the pressure, while preserving the effects of changes in heart rate on the cardiac muscle itself (Bowditch type of phenomena). The distribution of normal values in a group of 51 control dogs was very close to the standard normal distribution. These values had no statistically significant differences with those of a smaller control group studied by independent investigators. Isoproterenol and propranolol produced highly significant statistical changes in FARPD. Alterations in pre- and afterload produced changes that were not significant for the former and significant at the 5% level for the latter. These changes were small when compared to those resulting from typical inotropic interventions.
Zinc metabolism in humans: a kinetic model
Authors: Foster D. M. , Aamodt R. L. , Henkin R. I. , Berman M.
Published: December 2017

A quantitative model is developed that describes the kinetics of the early phases of zinc metabolism in humans. The model is based on averaged data obtained over 5 days from 17 atients with smell and/or taste dysfunction who were given 69mZn in trace amounts orally and intravenously. A function describing the rate of entry of 69mZn into systemic plasma following ingestion of the isotope is derived showing that about 37% of the ingested zinc enters plasma. Gastrointestinal absorption is essentially completed by 4 h. Sixty-seven percent of the absorbed zinc in the portal circulation is extracted by the liver before being released into the systemic circulation and agrees with the calculated extraction efficiency from the systemic circulation. There are both rapid and slow exchnage phases between plasma and liver and between plasma and red cells. The calculated steady-state zinc values for plasma, red cells, and liver agree with previously reported measured values implying there are no additional zinc pools in these tissues. The tracer data, however, account for only 10% of total body zinc, the remaining 90% in tissues whose kinetics are too slow to be resolved from a 5-day study.
Noncoordinate regulation of cytoplasmic RNA in compensatory renal hypertrophy
Authors: Ouellette A. J. , Malt R. A.
Published: December 2017

To examine the regulatory role of mRNA in compensatory renal hypertrophy, the accumulation and decay of [3H]orotic acid in poly(A)-containing mRNA in mouse kidney was analyzed after unilateral nephrectomy during the period of maximal rRNA accretion. The distribution of radioactivity between newly synthesized poly(A)-containing and poly(A)-lacing polysomal RNA was altered, but no differences in mRNA half-life were observed in growth compared with effects of sham nephrectomy. Radioactivity in polysomal polyadenylated RNA was diminished by approximately 25% during growth where mice were labeled after nephrectomy, but if mice were labeled 18 h before operation, no difference was noted. Thus, accumulation of newly synthesized poly(A)-containing mRNA relative to RNAs that lack poly(A) is changed early in the course of renal hypertrophy. This noncoordinate regulation may represent a control mechanism effective early in induced cell growth involving mRNAs that lack poly(A).
Water balance in the California newt, Taricha torosa
Authors: Brown S. C. , Brown P. S.
Published: December 2017

Both dehydration to 87% of original body weight (Wo) and arginine vasotocin (AVT: 20 mU/g) elicited rapid weight gains (ca. 9% of Wo in the 1st h) when terrestrial-phase T. torosa were given access to water. In each case, net weight gain resulted from increased integumental osmosis and antidiuresis. Mesotocin (0.001 -- 0.1 micrograms/g) elicited modest but significant weight gains (ca. 1%/h) caused solely by increased integumental osmosis. Integumental water uptake from wet moss was 66% that of totally immersed animals. Water movement from ventral to dorsal body surface occurred along channels on the skin. Urinary bladder storage capacities in excess of 50% of Wo were observed. Following AVT administration, bladder water resorption increased significantly, while glomerular filtration rate dropped to 16% of control values. The structural and physiological adaptations for water balance in T. torosa are comparable to those found in some terrestrial anurans.
Salt balance in embryos of Fundulus heteroclitus and F. bermudae adapted to seawater
Authors: Guggino W. B.
Published: December 2017

22Na+ and 36Cl- tracer flux experiments of embryos of Fundulus heteroclitus show that a significant influx and efflux of Na+ and Cl- occur during development. The average influx for Na+ and Cl-, respectively, are 5.0 +/- 0.76 and 1.1 +/- 0.1 nmol . mg-1 . h-1. The average effluxes are 4.9 +/- 0.95 and 3.0 +/- 0.01 nmol . mg-1 . h-1 for Na+ and Cl-, respectively. The electrical potential across the embryonic cavity epithelium of F. heteroclitus and F. bermudae is 50 +/- 1.7 mV and 40 +/- 1.3 mV, respectively (inside positive). Diluting the artificial seawater bathing medium with distilled water decreases the potential across the embryonic cavity of F. bermudae to -11 +/- 5.0 mV at 5% artificial seawater. Because in seawater the potential across the embryonic cavity epithelium is inside positive, the efflux of Cl- is against its electrical potential gradient indicating an active extrusion mechanism for Cl-. The site of the active extrusion mechanism for chloride is located in the yolk sac where chloride cells associated with blood vessels are common.
Role of Na-K-ATPase in chloride cell function
Authors: Epstein F. H. , Silva P. , Kormanik G.
Published: December 2017

In seawater eels the efflux of sodium (and chloride) across the gill is directly proportional to the activity of Na-K-ATPase in homogenates of gill filaments. The rate of ion movement, however, is substantially greater than at the temperature of seawater. Na-K-ATPase is localized predominantly on the basolateral surface of the chloride cell so that ouabain inhibits from the blood side rather than from the apical or mucosal surface of chloride cells. Chloride, rather than sodium, is probably the actively transported ion species, and an attractive hypothesis for active chloride transport is one that invokes the cotransport of chloride with sodium across the basolateral membrane, the energy for which is supplied indirectly by the operation of the Na-K-ATPase pump. Exposure to freshwater sharply dissociates ion movements from Na-K-ATPase activity, possibly by changing the permeability of cell membranes to chloride movements.
Thirst and vasopressin release in the dog: an osmoreceptor or sodium receptor mechanism?
Authors: Thrasher T. N. , Brown C. J. , Keil L. C. , Ramsay D. J.
Published: December 2017

The effects of intravenous infusion of hypertonic NaCl, sucrose, glucose, urea, or isotonic NaCl solution on thirst and plasma arginine vasopressin concentration (AVP) were studied in five conscious dogs. The changes in osmolality and sodium concentration of plasma and cerebrospinal fluid (CSF) were measured at the threshold of drinking, or after 45 min if no drinking occurred. Hypertonic NaCl and sucrose stimulated drinking in all dogs and significantly elevated plasma AVP. Equally hypertonic glucose, urea, or isotonic NaCl failed to stimulate any drinking or vasopressin secretion. All hypertonic solutions caused significant and similar increases in the osmolality and sodium concentration of CSF. Plasma osmolality was increased by the hypertonic solutions. Plasma sodium was increased by hypertonic NaCl, decreased by sucrose and glucose, and not changed by urea. Isotonic NaCl had no effect on either plasma or CSF composition. These data are not consistent with either a sodium or an osmoreceptor mechanism located within the blood-brain barrier (BBB) or with a peripheral sodium receptor mechanism. An intracranial osmoreceptor located on the blood side of the BBB is proposed to explain these results.
Age-related differences in angiotensin I metabolism by isolated perfused rat lungs
Authors: Wallace K. B. , Roth R. A. , Hook J. B. , Bailie M. D.
Published: December 2017

The pulmonary vasculature has been implicated in the clearance of several vasoactive substances from the circulation including angiotensin I (AI). In view of the previously reported age-related differences in angiotensin-converting enzyme (ACE) activity of lung homogenates, it was of interest to examine the ability of intact perfused lungs to metabolize AI. Lungs from newborn and adult rats were perfused with Krebs bicarbonate buffer containing 1.0 ng/ml AI in a single-pass, nonrecirculating system. The rate of perfusion was normalized to lung mass. Removal of AI was determined from the transpulmonary difference in radioimmunoassayable AI. Lungs from 7-day-old rats removed a smaller fraction of AI from the circulation than did adult lungs. The age-related increase in AI clearance was accompanied by an increase in pulmonary ACE content; however, enzyme content alone could not account for the observed differences. The increased metabolism of AI by the pulmonary vasculature during development may contribute to the age-related increase in circulating angiotensin II concentrations.
Quantitative aspects of reversible osmotic opening of the blood-brain barrier
Authors: Rapoport S. I. , Fredericks W. R. , Ohno K. , Pettigrew K. D.
Published: December 2017

Retrograde infusion of a hypertonic arabinose solution into the right external carotid artery of rats reversibly increases cerebrovascular permeability to [14C]sucrose in the right cerebral hemisphere. PA ([14C]sucrose permeability x capillary surface area) rises from a control mean of 11 x 10(-6) S-1 to above 200 x 10(-6) S-1. The rise correlates with an increased staining of the brain by intravascular Evans blue, and is followed by a transient, 1-1.5% increase in brain water content. At least 20 s of infusion is required for 1.6 M arabinose solution to effectively open the blood-brain barrier. The increase in cerebrovascular permeability is temporary, however, because PA remains slightly elevated 1-2 h after infusion and is normal 6 h after infusion. It is suggested that osmotic barrier opening is mediated by cerebrovascular dilatation as well as by shrinkage of the vascular endothelium. By quantitatively defining thresholds of infusate concentration and infusion time for osmotic barrier opening, and by characterizing the time course of increased PA, the experiments establish criteria for applying the osmotic method to experimental pharmacology of the central nervous system.
Effect of saralasin and indomethacin on renal function in developing piglets
Authors: Osborn J. L. , Hook J. B. , Bailie M. D.
Published: December 2017

To investigate the influence of angiotensin II (AII) and renal prostaglandins on neonatal renal hemodynamics and sodium excretion, unanesthetized piglets 1-5, 18-20, and 45-50 days of age were treated with saralasin and indomethacin prior to volume expansion (VE) with isotonic saline. Saralasin did not affect basal renal blood flow (RBF) or the intrarenal distribution of blood flow as calculated as the ratio of outer-to-inner slice counts (O/I) in piglets 1-50 days of age. VE increased fractional sodium excretion equally in all animals. In 1- to 5-day-old piglets, saralasin blunted this natriuresis without affecting renal hemodynamics. Therefore, low neonatal RBF and O/I do not appear to be due to AII. In addition, indomethacin did not change renal hemodynamics in newborn piglets and did not affect the natriuresis after VE in any age group. Indomethacin decreased RBF and increased O/I of conscious 45- to 50-day-old animals. Renal prostaglandins do not appear to be a factor in control of renal hemodynamic in newborn pigs and do not influence the natriuresis in neonates following saline loading.
Angiotensin and drinking rates in the euryhaline killifish
Authors: Malvin R. L. , Schiff D. , Eiger S.
Published: December 2017

Drinking rates were measured in the euryhaline fish Fundulus heteroclitus in the presence and absence of angiotensin II or its competitive inhibitor P-113 and converting enzyme inhibitor (SQ20881). Angiotensin stimulated drinking in Fundalus adapted to salt- or freshwater. More significant, P-113 decreased drinking rates in saltwater-adapted fish and to ones acutely exposed to saltwater. SQ20881 was also effective in inhibiting drinking. These data are interpreted to support the hypothesis that endogenously produced angiotensin is a physiological stimulus for drinking in fish.
Comparative nephron function in reptiles, birds, and mammals
Authors: Dantzler W. H. , Braun E. J.
Published: December 2017

Volume and osmolarity of urine produced by kidneys of reptiles, birds, and mammals depend on anatomic relationships among nephrons, epithelial permeability to water controlled by antidiuretic hormone, and, for reptiles and birds, probably on volume flow rate through collecting ducts and excretion of uric acid. Urine volume and volume flow rate through collecting ducts in reptiles and birds depend on number of filtering nephrons controlled by antidiuretic hormone. Mammalian nephrons do not filter intermittently but control of nephron filtration rates in all three vertebrate classes may have important similarities and differences. Uric acid excretion by birds and many reptiles permits excretion of inorganic cations in excess of amounts permitted by osmolarity of urine. This process may require tubular absorption of water without sodium. Such absorption, which has been found in reptilian proximal tubules, may be very important for osmoregulation in all birds and uricotelic reptiles and may provide insight into the mechanism of fluid absorption in mammals. Urea excretion in mammals may be important for enhancing concentrating ability. Much more must be learned about these processes, but similarities and differences among them in the three vertebrate classes may help illuminate details of each.
Heat intolerance as a function of percent of body surface involved with miliaria rubra
Authors: Pandolf K. B. , Griffin T. B. , Munro E. H. , Goldman R. F.
Published: December 2017

Twenty-four heat-acclimatized male volunteers were wrapped as previously described (Am. J. Physiol. 239 (Regulatory Integrative Comp. Physiol. 8): R226-R232, 1980) but to produce miliaria rubra (heat rash) in specific regions of the body. Three experimental rash groups were involved: 1) the torso (17% total skin surface rashed, n = 6), 2) torso and arms (38%, n = 8), or 3) legs (41%, n = 6), while four subjects served as controls. All subjects were reexposed to walking in the heat on the 7th day after unwrapping, and again 14, 21, and 28 days after unwrapping. When compared to responses for the last heat acclimatization day, tolerance time and sweat rate were lower and mean body temperature and delta heat storage significantly higher for experimental rash subjects contrasted to the controls for up to 21 days; however, no significant differences between the three rashed groups were found. The critical amount of surface area for heat intolerance from heat rash appears to be related to the specific region of the body and associated sweating responses; smaller rashed areas of the trunk, because they have greater potential for abundant sweating, may produce similar responses to heat stress as larger rashed areas of the limbs. Heat intolerance due to rash was not resolved until after 21 days.
Temperature effects on ventilation and acid-base balance of the green turtle
Authors: Kraus D. R. , Jackson D. C.
Published: December 2017

Ventilation (VE), pulmonary gas exchange (MO2 and MCO2), and arterial acid-base status (pH and PaCO2) were measured in immature green turtles. Chelonia mydas, equilibrated at 15, 25, and 35 degrees C. From 25 to 35 degrees C, pH decreased by 0.0134 U/degrees C and PaCO2 increased from 30.1 +/- 1.1 to 46.0 +/- 2.4 Torr (mean +/- SE, n = 8) in conformity with results from other ectotherms. From 15 to 25 degrees C, however, pH fell on the average by 0.06 U/degrees C but the change was not significant. PaCO2 rose over this range from 25.3 +/- 1.6 to 30.1 +/- 1.1 Torr. Calculated plasma [HCO3-], 27-28 meq/l, did not change over the entire temperature range. Both VE and MO2 increased with temperature, but the ratio, VE/MO2 (the air convection requirement), fell with temperature (1.01 +/- 0.10 l/mmol at 35 degrees C, 0.64 +/- 0.03 l/mmol at 25 degrees C, and 0.45 +/- 0.04 l/mmol at 15 degrees C). We conclude that the green turtle adheres to the typical ectotherm blood acid-base pattern over their usual temperature range (25-35 degrees C), but that pH control deviates from this pattern at temperatures below this range.
Evidence for a circulating ergostatic factor: studies on parabiotic rats
Authors: Nishizawa Y. , Bray G. A.
Published: December 2017

The effect of electrolytic ventromedial hypothalamic lesions or forced overfeeding through gastric cannulas was studied in parabiotic rats. In one experiment a ventromedial hypothalamic lesion in one member of the parabiotic union was associated with an increased fatness in the lesioned rat and a decrease in fat pad weight and a rise in body density (loss of fat) of the unlesioned animal. In the other two experiments a high fat or high carbohydrate diet was tube fed to one member of a parabiotic union. The average preinfusion intake per rat was 56 kcal/day. When 90 kcal/day were given through the intragastric cannula, oral intake of calories for the two animals fell to approximately 44 kcal/day. Body fat of the non-tube-fed animal was less than in the tube-fed controls. These studies suggest the presence of an ergostatic (energy stabilizing) factor that enters and is transported in the blood with passage from one animal to another.
Analysis of errors in parameter estimation with application to physiological systems
Authors: Grove T. M. , Bekey G. A. , Haywood L. J.
Published: December 2017

The accuracy of parameter estimation applied to physiological systems is analyzed. The method of analysis is applicable to procedures utilizing minimization of squared output error and a nonlinear dynamic system model. Three major sources of estimation error are described: 1) measurement error, 2) modeling error, and 3) optimization error. Measurement errors affect values used for the system output, the model input, and nonestimated parameters of the model. Modeling errors are due to failure to adequately describe the structure of the system and to numerical errors that occur in the digital computer solution of the model equations. Linearization by use of Taylor series expansions in the region of the nominal solution is used to obtain an expression for the covariance matrix of the parameter estimates in terms of the covariance matrix of each error source. The analysis is applied to the example of cardiac output estimation from respiratory measurements. The results demonstrate that an analysis of system identifiability is not sufficient to ensure usable estimates and that systematic error analysis is essential for assessing the usefulness of parameter estimation techniques.
Angiotensin and single nephron glomerular function in the trout Salmo gairdneri
Authors: Brown J. A. , Oliver J. A. , Henderson I. W. , Jackson B. A.
Published: December 2017

Glomerular filtration rate (GFR), urine flow (UV), renal tubular transport maximum for glucose (TMG), and single nephron glomerular filtration rate (SNGFR), determined in anesthetized norepinephrine-infused trout (Salmo gairdneri), were 18.51 +/- 5.78 microliter x min-1 x kg body wt-1, 5.31 +/- 1.38 microliter x min-1 x kg body wt-1, 105.21 +/- 46.84 microgram x min-1 x kg body wt-1, and 3.74 +/- 1.12 nl/min, respectively, when in seawater (SW) and 140.39 +/- 17.24, 76.38 +/- 10.41, 626.16 +/- 77.46, and 1.31 +/- 0.20 in freshwater (FW). Angiotensin II infusions, to reduce UV, GFR, and TMG by 50%, had no effect on the average SNGFR of FW trout, but reduced that of SW fish to 1.42 +/- 0.19 nl/min. Infusions of 20% ferrocyanide, visualized as Prussian blue (PB), identified three glomerular populations: filtering (F) with PB in glomerular vessels and tubular lumen; nonfiltering (NF)--PB in glomerular vessels only; nonperfused (NP)--no PB associated with the nephron. SW and FW kidneys contained about 40% NF tubules. In FW, 45% were F tubules compared with 5% in SW, whereas NP tubules comprised 51% of SW tubules and 13% of FW. During angiotensin II infusions the distributions were 9% and 46% NF in FW and 6% F and 12% NF in SW trout.
Lack of ingestive compensation to osmotic stimuli in chronic decerebrate rats
Authors: Grill H. J. , Miselis R. R.
Published: December 2017

Chronic decerebrate rats fitted with oral fistulas for remote injection of water or nutrient were tested for their capacity to behaviorally compensate for dehydration by increasing their ingestion of water. Decerebrates and their controls were given water for ingestion via the oral fistula in 50-microliter aliquots following various challenges. The rats' ejection of water from the mouth marked behavioral termination of the drinking. The volume of water was measured 1 and 24 h after an intragastric meal of regular diet; 0.5, 4, 8, and 24 h following subcutaneous isotonic or hypertonic NaCl injection; and 1, 4, 8, and 24 h following an intragastric meal of regular or 3% NaCl adulterated diet. Unlike controls, decerebrates failed to increase the amount of water ingested following intracellular dehydration regardless of the means of producing dehydration or the duration of time permitted for a response. However, both control and decerebrate rats increased their ingestion of a sweet solution (0.03 M sucrose) demonstrating their capacity to respond and confirming their ability to compensate for food deprivation. This lack of increased water intake in response to dehydration for decerebrate rats favors the existence of at least some aspects of the regulatory circuitry for this behavioral control of water balance to lie in the forebrain.
Effects of temperature acclimation on crayfish hemocyanin oxygen binding
Authors: Rutledge P. S.
Published: December 2017

Crayfish, Pacifastacus leniusculus, were acclimated to 10, 20, and 25 degrees C for 1 mo. Hemocyanin from animals at these three acclimation temperatures showed distinctly different oxygen binding patterns. At any particular set of test temperature and pH, hemocyanin from 10 degrees C-acclimated animals had the lowest oxygen affinity and the greatest cooperativity, whereas hemocyanin from 25 degrees C-acclimated animals had the highest oxygen affinity and the lowest cooperativity. When tested at their own acclimation temperature, and at normal hemolymph pH for that temperature, all three hemocyanins showed oxygen pressure for half-saturation of hemoglobin of 6-7 Torr. Thus acclimation keeps oxygen affinity centered around a narrow range of values. The acclimation response probably eliminates hemocyanin oxygen affinity as a major factor in the decline of oxygen uptake ability in the crayfish above 20 degrees C. The structural basis for the observed functional changes in the hemocyanin is not yet clear.
Effects of localized low-temperature pulses on the cockroach circadian pacemaker
Authors: Page T. L.
Published: December 2017

The hypothesis that the circadian pacemaker that controls the activity rhythm in the cockroach, Leucophaea maderae, is composed of mutually coupled optic lobe oscillators was investigated using localized low-temperature pulses. Following section of one optic tract cooling the intact optic lobe for 6 h (7.5 degrees C) beginning at activity onset consistently caused a phase delay of several hours. Cooling the neurally isolated lobe had little or no effect. The results suggested the low-temperature phase delays the rhythm via a phase shift in an oscillator in the optic lobe. To determine if optic lobe oscillators were coupled, low-temperature pulses were given to one optic lobe of intact animals. If the treated lobe was isolated by optic tract section 4 days after the pulse, the rhythm (driven by the untreated lobe) was delayed; but if the tract was cut 0.5 h after the pulse the phase shift was prevented. The interaction between the optic lobes in intact animals was also found to reduce the delay caused by a low-temperature pulse. These results suggest the cockroach circadian pacemaker is composed of two mutually coupled optic lobe oscillators.
Prostaglandins, catecholamines, and cardiovascular responses to hemorrhage
Authors: Feuerstein G. , Jimerson D. C. , Kopin I. J.
Published: December 2017

The effects of prostaglandins (PGE2 and 16,16-dimethyl-PGE1) on epinephrine (E) and norepinephrine (NE) release, in response to a hypotensive stimulus (bleeding 5 ml/300 g), were studied in relation to blood pressure and heart rate responses in the rat. PGE2 (10 micrograms/kg-1 . min-1) and 16,16-dimethyl-PGE1 (1 microgram . kg-1 . min-1) accelerated blood pressure and heart rate recovery rate following acute hemorrhage and increased plasma E and NE levels. Plasma levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) and 3,4-dihydroxyphenylglycol (DHPG) were not affected by PG infusion. In bilaterally nephrectomized rats, PGE2 increased plasma levels of E, NE, and DHPG but failed to enhance the blood pressure and had only a mild effect on heart rate recovery following bleeding. In hexamethonium-treated rats, infusion of PGE2 had a small and transient effect on blood pressure recovery, but its effect on the heart rate was not affected; NE and E levels in the plasma of the hexamethonium-treated rats were still higher in the PGE2-infused rats. These studies indicate that in the intact rat, administered PGE potentiate the release of E and NE and facilitate blood pressure and heart rate recovery following acute hemorrhage. The hemodynamic effects of the PGE appear to be mediated by a renal factor whereas the effects of PGE on E and NE response to hemorrhage are independent of the presence of intact kidneys.
Optimized blood sampling protocols and sequential design of kinetic experiments
Authors: DiStefano J. J.
Published: December 2017

Design of optimal blood sampling protocols for kinetic experiments is discussed and evaluated, with the aid of several examples--including an endocrine system case study. The criterion of optimality is maximum accuracy of kinetic model parameter estimates. A simple example illustrates why a sequential experiment approach is required; optimal designs depend on the true model parameter values, knowledge of which is usually a primary objective of the experiment, as well as the structure of the model and the measurement error (e.g., assay) variance. The methodology is evaluated from the results of a series of experiments designed to quantify the dynamics of distribution and metabolism of three iodothyronines, T3, T4, and reverse-T3. This analysis indicates that 1) the sequential optimal experiment approach can be effective and efficient in the laboratory, 2) it works in the presence of reasonably controlled biological variation, producing sufficiently robust sampling protocols, and 3) optimal designs can be highly efficient designs in practice, requiring for maximum accuracy a number of blood samples equal to the number of independently adjustable model parameters, no more or less.
Spinal sympathetic reflex and random activity in the isolated amphibian spinal cord
Authors: Undesser E. K. , Shinnick-Gallagher P. , Gallagher J. P.
Published: December 2017

Preganglionic sympathetic neurons in the fourth ramus communicantes discharged in response to electrical stimulation of somatic or visceral afferents entering the spinal cord at segments 2, 3, or 4. Intrasegmental reflexes consisted of a large peak followed by a second, smaller one, whereas only a single peak was observed in intrasegmental reflex. Reflex wave forms were similar to those in the cats except a monosynaptic component was not usually observed. In addition latencies and central delays were different in frogs and cats. Spontaneous activity was rarely recorded although poststimulus random activity was usually observed. Medium to high threshold afferents were responsible for eliciting spinal sympathetic reflexes from spinal nerve two. In frogs the interaction between spinal sympathetic reflexes elicited by the same or different afferents was qualitatively similar to that in cats. It appears therefore that the amphibian spinal cord is a suitable preparation for analyzing sympathetic preganglionic neurons.
Effect of acclimation temperature and pH on contraction of frog sartorius muscle
Authors: Renaud J. M. , Stevens E. D.
Published: December 2017

The effect of acclimation temperature and pH on the isometric twitch and tetanus of sartorius muscle from frog, Rana pipiens, was studied at different experimental temperatures. Seven variables were measured, namely: tension, latent period, time to maximum tension, half-relaxation time, mean rate, maximum rate, and maximum acceleration of tension development. The effect of experimental temperature was similar to that reported in the literature. The effects of acclimation temperature were small and were not compensatory. Different pH's were obtained by varying CO2 in the gas phase, while the HCO3- concentration was kept constant. The main effects of a decrease in pH on the isometric twitch and tetanus were a reduction in tension and rate of tension development and an increase in latent period. A decrease in pH had no effect on the time to maximum tension or the half-relaxation time. Analysis of variance showed that the test temperature had the greatest effect of all three treatments on each variable, the effects of test and acclimation temperature were dependent on neither the test nor the acclimation temperatures. The in vivo relationships between these three treatments are discussed.
Cholecystokinin and satiety in pigs
Authors: Anika S. M. , Houpt T. R. , Houpt K. A.
Published: December 2017

Twenty-three pigs, 1-3 mo of age, were fitted variously with intraperitoneal, intrajugular, intraportal, and intraduodenal catheters. After a 4-h fast, porcine cholecystokinin (CCK), 5-40 Ivy dog units/kg body wt (IDU/kg); caerulein, 0.25-2 micrograms/kg; or the octapeptide of cholecystokinin (CCK-OP), 5-40 IDU/kg, was given parenterally; or 2-5% sodium oleate or 5% protein hydrolysate (5 ml/kg) was injected intraduodenally. Pelleted feed intake was then measured for 10 min. Food intake was depressed in a dose-related fashion in all instances as compared to after 0.9% NaCl control injections. For example, feed consumption following 5 and 40 IDU/kg of CCK intrajugularly was 84 +/- 2 and 6 +/- 4 (SE) %, respectively, of control intake. Intraportal infusion produced a greater depression of feeding. A conditioned taste aversion could not be formed to CCK, caerulein, or CCK-OP. Sodium oleate or protein hydrolysate, releasers of endogenous CCK, depressed feeding, and this satiety effect was attenuated when given with 0.5% tetracaine. The results support the hypothesis that CCK participates in rapid, presumably preabsorptive, satiety.
Effect of endurance training on liver cAMP response to prolonged submaximal exercise
Authors: Winder W. W. , Holman R. T. , Garhart S. J.
Published: December 2017

Endurance-trained rats utilize liver glycogen at a reduced rate during exercise compared to nontrained rats. We have compared liver cAMP responses to exercise in trained and nontrained rats in an attempt to elucidate the mechanism of this adaptation. Rats were trained on a motor-driven rodent treadmill 5 days/wk for 12 wk. On the day of the test, trained and nontrained rats were quickly anesthetized after running at 21 m/min up a 15% grade for periods up to 90 min. After 45 min of running, liver cAMP had increased from 0.60 +/- 0.01 to 0.90 +/- 0.03 pmol/mg in nontrained rats whereas no significant increase had occurred in livers of trained rats. Plasma glucagon and norepinephrine levels were significantly lower in trained rats at this point. At the end of 90 min hepatic cAMP was 1.28 +/- 0.12 in nontrained compared to 0.83 +/- 0.06 pmol/mg in trained rats. Plasma glucagon was markedly elevated in nontrained but not in trained rats at this time. The lower rate of liver glycogen utilization in trained rats is consistent with the lower cAMP levels maintained early in exercise.
Geometric similarity of aorta, venae cavae, and certain of their branches in mammals
Authors: Holt J. P. , Rhode E. A. , Holt W. W. , Kines H.
Published: December 2017

The diameters of the aorta and venae cavae at various points throughout their lengths, the diameters of their major branches, and the lengths of various aortic and vena caval segments were measured in plastic corrosion casts of the arterial and venous systems of the normal adult mouse, rat, rabbit, dog, goat, horse, and cow, extending over a body weight range of 38,000-fold (arterial) and 1,100-fold (venous). It is shown that the diameters and lengths of these vessels are described by power-law equations relating the particular diameter or length to body weight (BW) raised to a particular diameter or length to body weight (BW) raised to a particular power, i.e., diameter = a BWb. Equations for the diameters and lengths of the vessels are given for slightly distended vessels and for vessels distended in the physiological range.
Nonlinearity, multistability, and fluctuations: reviewing the reviewers
Authors: Landauer R.
Published: December 2017

Mathematicians, physicists, and physical chemists have generated a number of viewpoints related to systems with nonlinearity, multistability, and fluctuations. The viewpoints tend to be characterized by slogans generated by the respective advocates, e.g., Catastrophe Theory, Dissipative Structures, and Synergetics. The advocates also usually stress the applicability of their work to biology and to self-organization. Have the discussions in the semipopular and broader technical journals served to give proper guidance to the outsider through their assessment of these viewpoints? We discuss this, with particular emphasis on book reviews.
Pituitary beta-endorphin, naloxone, and feeding in several experimental obesities
Authors: Gunion M. W. , Peters R. H.
Published: December 2017

The role of beta-endorphin in the development of several obesity syndromes was examined. Adult female hooded rats received ventromedial hypothalamic lesions, dorsolateral tegmental lesions, parasagittal hypothalamic knife cuts, intraventricular 5,7-dihydroxytryptamine, ovariectomy, control surgery, or were deprived to 75% of normal body weight. Dose-dependent suppression of food intake by the opiate antagonist naloxone (0.5, 1.8, 6.8, or 25.0 mg/kg, ip) was measured during once-daily 4-h food access periods. No difference was found among the groups at any dose. Pituitary beta-endorphinlike immunoreactivity (BELI) was substantially decreased in knife-cut rats, but was unaltered by other treatments. Obesity had no effect on BELI. In another experiment, rats made obese by prolonged maintenance on palatable foods had elevated pituitary BELI levels. Feeding mechanisms involving opioid peptides do not appear to be of etiological significance in the syndromes examined.
Role of autonomics in the initiation of electromechanical dissociation
Authors: Kostreva D. R. , Castaner A. , Kampine J. P.
Published: December 2017

The onset of electromechanical dissociation during acute cardiac tamponade in mongrel dogs is significantly prolonged by either surgical or pharmacologic sympathectomy. Bilateral vagotomy does not have any apparent effect on the initiation of electromechanical dissociation. Pretreatment with isoproterenol just prior to tamponade does not significantly increase heart rate or the double product. Cardiopulmonary sympathetic efferent stimulation significantly decreases the time to the onset of electromechanical dissociation by increasing the heart rate and double product. The early onset of electromechanical dissociation appears to be related to cardiac work and oxygen consumption.
Automatic detection of eye movements in REM sleep using the electrooculogram
Authors: Gopal I. S. , Haddad G. G.
Published: December 2017

An automated method for detecting and counting eye movements using the electrooculogram (EOG) wave form during rapid-eye-movement (REM) sleep is presented. The method is formulated as a sequential decision process with decisions based on slope and amplitude threshold criteria. Signal processing techniques such as digital filtering and smoothing are used to improve the effectiveness of the method. Validation is done by using the method on EOG data from three infants and comparing the automated count of eye movements with the visual counts of human observers. The correlation coefficient between the automated and visual count is greater than 0.9, the first-order regression coefficient close to 1.0, and the zero-order regression coefficient close to 0. We believe that this method will be useful in differentiating between the substates of REM sleep in studies of cardiorespiratory physiology.
Glucoregulation and simulated diving in the harbor seal Phoca vitulina
Authors: Robin E. D. , Ensinck J. , Hance A. J. , Newman A. , Lewiston N. , Cornell L. , Davis R. W. , Theodore J.
Published: December 2017

Plasma glucose, glucagon, and insulin concentrations were measured in the harbor seal, Phoca vitulina, during a 6-min dive and a 30-min recovery period. Studies were performed in the fasting state and following intravenous glucose. During diving in the fasting state, values of plasma glucose, glucagon, and insulin are not significantly different from prediving values, presumably because of the loss of perfusion to the pancreas. In the postdiving period, plasma glucagon increases significantly. The increased glucagon levels reach a peak at 6 min into the postdiving period. By 4 min postdiving, plasma glucose values increase. The hyperglycemia appears to be at least partially related to hyperglucagonemia. Despite hyperglycemia, insulin levels do not change significantly. The net effect is to increase glucose availability, particularly for non-insulin-requiring tissues (brain). Preadministration of glucose eliminates the postdiving increase in glucagon. Plasma glucose and insulin concentrations also show no significant changes during the diving and postdiving periods. These results suggest that hormonally mediated glucose conservation serves to maintain brain glucose supplies and to restore peripheral carbohydrate stores during the postdiving period.
A critical examination of the dual system theory in Ostrinia nubilalis
Authors: Skopik S. D. , Takeda M. , Holyoke C. W.
Published: December 2017

Beck's dual system theory (DST) is examined theoretically and experimentally by investigating the oviposition rhythm of Ostrinia nubilalis and its entrainment by light cycles. Several well-known circadian phenomena are not accounted for by the DST. 1) It does not generate transient cycles when light pulses fall during the advance portion of the circadian cycle. This is also reflected in DST-predicted phase-response curves (PRC's) for both Drosophila pseudoobscura and O. nubilalis. Steady-state phase advances are predicted to occur on day 1 after the light pulses by the DST, not several cycles later as has been observed in many cases. 2) It does not account for the observation that the magnitude of a phase shift (delta phi) is often a function of pulse duration of both delays and advances. The DST predicts the same + delta phi, for example, for a 0.5-h and a 6.0-h light pulse beginning 5.0 h after dusk. 3) The DST does not accurately predict steady-state phase relationships between the light cycle and the gating oscillation (P-system) in non-24-h light cycles. 4) The driver (S-system) is given the property of being temperature sensitive whereas the driven rhythm (P-system) is temperature compensated. This is contrary to accumulated data suggesting that the circadian pacemaker is temperature compensated.
Circadian rhythm of body temperature persists after suprachiasmatic lesions in the squirrel monkey
Authors: Fuller C. A. , Lydic R. , Sulzman F. M. , Albers H. E. , Tepper B. , Moore-Ede M. C.
Published: December 2017

Squirrel monkeys (Saimiri sciureus) demonstrate prominent circadian (approx 24 h) rhythms in many behavioral and physiological variables including drinking and body temperature. Both of these rhythms can be entrained by a 24-h light-dark cycle (LD 12:12) but will free-run with an endogenous period in a constantly illuminated (LL:600 lx) environment free of time cues. After radio-frequency lesions were placed stereotaxically in the suprachiasmatic nuclei (SCN) of five monkeys, the circadian rhythm of drinking behavior was disrupted when the monkeys were maintained in LL. However, the circadian rhythm in core body temperature in these animals persisted in LL with a significant circadian spectral component following destruction of the SCN. The SCN thus appear to be of fundamental importance for regulating the circadian organization of drinking; however, an oscillator located elsewhere in the squirrel monkey is capable of generating the core body temperature rhythm.
PAH transport in rock crab urinary bladder. II. Luminal and serosal steps
Authors: Holliday C. W. , Miller D. S.
Published: December 2017

To characterize the organic anion transport properties of the luminal (1) and serosal (s) membranes of crab urinary bladder, initial (10 min) fluxes (J) and tissue accumulations (Ac) of 10 microM PAH were measured in the absence and presence of 1 mM BCG (nontransported, high-affinity competitor). Control bladders exhibited net reabsorptive transport with a mean Jl leads to s/Js leads to 1 of about 7; concentrative transport of p-aminohippuric acid (PAH) occurred only across the luminal cell (c) membrane. With luminal PAH, luminal bromocresol green (BCG) reduced Jl leads to c, Jc leads to s, and Ac by about 85%; serosal BCG reduced Jc leads to s, increased Ac but had no effect on Jl leads to c. With serosal PAH, serosal BCG reduced Js leads to c, Jc leads to l, and Ac; luminal BCG had no effects on either fluxes or tissue accumulation. When bladder sheets were loaded with radiolabeled PAH, mounted in a chamber, and exposed to flowing crab Ringer solution on both sides, Jc leads to s was nearly twice as large as Jc leads to l; BCG significantly reduced Jc leads to s but not Jc leads to l. With unlabeled PAH in the efflux media, Jc leads to s was increased. The data are consistent with a model featuring an inwardly directed pump at the luminal membrane, a facilitated carrier at the serosal membrane, and nonmediated pathways at both membranes.
Effect of tilting on blood pressure and interstitial fluid pressures of bluefish and smooth dogfish
Authors: Ogilvy C. S. , DuBois A. B.
Published: December 2017

Tolerance of the circulatory system of fish for gravitational stress has not been measured previously. We examined this in bluefish (Pomatomus saltatrix) and smooth dogfish (Mustelus canis) by placing them horizontally on a V-board in air while their gills were perfused with aerated seawater, then tilting them head up for 0.5 h, and finally returning them to horizontal. Meanwhile, we recorded the blood pressure, pulse pressure, and heart rate in the ventral aorta, and interstitial fluid pressure in the head and tail. All four bluefish tolerated a 30 degrees tilt or even a 60 degrees tilt with little change in blood pressure or interstitial pressure in the anterior and posterior regions. All recovered afterward. However, in the seven dogfish examined, the posterior interstitial fluid pressure increased from 2.8 +/- 1.0 cmH2O before tilting to 11.8 +/- 3.3 cmH2O toward the end of a 30 degrees tilt lasting 30 min. The blood pressure decreased as the pulse pressure approached zero, showing that circulatory insufficiency had developed due to insufficient venous return to the heart. Most of the dogfish died within a few hours after the experiment. These findings are in keeping with the conclusion that the vasculature of bluefish has more rigidity, less permeability, and perhaps more compensatory tone than that of smooth dogfish. We speculate that bluefish may have evolved their circulatory tolerance for gravity as a cross-adaptation to the stresses imposed on the circulation by forward acceleration and by regional differences of transcutaneous pressure occurring during fast carangiform swimming.
Roles of the skin and gills in sodium and water exchanges in neotenic urodele amphibians
Authors: Baldwin G. F. , Bentley P. J.
Published: December 2017

Neotenic urodele amphibians that possess prominent external gills absorb substantial amounts of water and sodium across their integument. Ligation of the gills did not change the uptake of either water or sodium in Necturus maculosus or Ambystoma tigrinum. In anuran tadpoles and fish the gills are known to be a major site of such exchanges. The possible physiological significance of such a restricted branchial permeability in aquatic urodeles is discussed as well as the bases for these special properties.
The tides of human consciousness: descriptions and questions
Authors: Winfree A. T.
Published: December 2017

A Rosetta Stone has appeared in our midst in the form of R. A. Wever's monograph The Circadian System of Man (New York: Springer-Verlag, 1979), describing the results of 20 years' experiments with J. Aschoff. In the January 1982 issue of this journal, Kronauer, Czeisler, Pilato, Moore-Ede, and Weitzman offer their decipherment: a mathematical description of man's circadian temperature rhythm and sleep timing based on their own experimental observations in the Bronx, confirming and substantially extending Wever's in Bavaria. This paper might have been as happily received by the Journal of Mathematical Biology or Biological Cybernetics. Accordingly I here attempt to disentangle numerical description from physiological hypothesis, emphasizing items that seem, at least in principle, susceptible to experimental test.
Dogfish pressor response to potassium blocked by magnesium and phentolamine
Authors: Carroll R. G. , Opdyke D. F. , Keller N. E.
Published: December 2017

In vivo infusion of MgCl2 blocks the dogfish pressor response to K+. This action of Mg2+ was contrasted to phentolamine in in vivo and in vitro experiments. Mg2+ blocks the spontaneous release of catecholamines from dogfish chromaffin tissue but does not alter the norepinephrine-induced contraction of the isolated dogfish artery. In vivo infusion of Mg2+ causes a significant decrease in resting catecholamine levels and diminishes the catecholamine release caused by K+ challenge. Both Mg2+ and phentolamine block the pressor action of K+, Mg2+ by preventing the K+-induced release of catecholamines and phentolamine by preventing the circulating catecholamines from interacting with alpha-adrenergic receptor sites.
Ventral medullary extracellular fluid pH and blood flow during hypoxia
Authors: Nolan W. F. , Houck P. C. , Thomas J. L. , Davies D. G.
Published: December 2017

Vascular responses of the ventral medulla and total brain to 30-60 min of isocapnic hypoxia (PaO2 = 32 +/- 2 Torr) were examined using radioactive microspheres in anesthetized, paralyzed, and artificially ventilated cats. Ventral medullary extracellular fluid (ECF) pH was measured using pH microelectrodes with tip diameters of 1-2 micrometers. Total brain blood flow (Q) increased significantly from a control value of 53 +/- 8 (mean +/- SE) to 160 +/- 42 ml.100 g-1.min-1 following 30-60 min of hypoxia. Ventral medullary Q increased from 28 +/- 5 to 97 +/- 20 ml.100 g-1.min-1 and ECF pH decreased by 0.15 +/- 0.06 pH U. Q responses are attributable to decreased vascular resistance as arterial pressure remained constant. The sensitivity of the ventral medullary vasculature to isocapnic hypoxia did not differ from that of the brain as a whole. The results show that under the conditions of our experiment, the ventral medullary vascular response to hypoxia is not sufficient to stabilize local ECF pH. The observation of simultaneously reduced pH and increased Q is consistent with a role for ECF H+ in mediating the cerebrovascular response to hypoxia.