bluuebunny/crossref_metadata_2025 huggingface dataset:
Network thermodynamics: a candidate for a common language for theoretical and experimental biology
Authors: Mikulecky D. C.
Published: December 2017

Effective interaction between theory and experimentation in biology requires that there be a common language, which workers in both areas understand. Because the backgrounds of biomedical researchers are often more descriptive than quantitative, it would be useful to have a diagrammatic method for defining models of systems that would easily translate into a rigorous quantitative description susceptible to computer simulation. Network thermodynamics is the next logical step in the evolution of thermodynamic thinking and meets these criteria. Network thermodynamics has already begun to be used in a variety of areas in experimental biology and is accessible to direct use by the experimenter. Network thermodynamics is not restricted by the traditional constraints on classical and nonequilibrium thermodynamics, such as reversibility, linearity, nearness to equilibrium, etc. Since living systems are inherently hierarchical in their nature, the network approach incorporates this feature in a natural way and, in a sense, supplies the "missing link" between traditional physics and chemistry and the vitalists' concern for the complexity of living systems. In the future, the use of a common language for theoretical and experimental biology should result in an increased understanding of human biology by the scientific community.
Intracellular pH-temperature interactions of hepatocytes from American eels
Authors: Walsh P. J. , Moon T. W.
Published: December 2017

The effects of acclimation temperature and acute temperature changes on the intracellular pH (pHi) of hepatocytes isolated from the American eel, Anguilla rostrata, were studied by the measurement of the distribution ratio of dimethyloxizolidinedione (DMO). Varying the concentration of DMO (10(-7) to 10(-4) M) did not affect estimates of pHi, indicating that DMO acts as an ideal pHi probe in eel hepatocytes. In vitro studies yielded values of liver cell pHi identical to those previously measured in vivo (in vitro pHi = 7.556 +/- 0.010; in vivo pHi = 7.570 +/- 0.049 at 20 degrees C); hepatocyte pHi varied inversely with acclimation temperature (5-20 degrees C) in a manner consistent with alphastat regulation (delta pH/delta T = -0.0182 +/- 0.021). During acute temperature increases (5-20 degrees C) and decreases (20-5 degrees C) hepatocytes regulated pHi to the appropriate (acclimated) value within 30-45 min posttransfer under conditions of constant medium pH (pHe). The effects of medium pH were also studied, and although patterns of pHi regulation differed between 5 and 20 degrees C cells, a pHi difference consistent with alphastat regulation was maintained between 5 and 20 degrees C cells over the pHe range 7.8-8.3.
Stimulation of urinary acidification by insulin in the turtle bladder
Authors: Arruda J. A.
Published: December 2017

Addition of insulin to the substrate-containing serosal solution of freshly excised bladders or to that of bladders incubated overnight in substrate-enriched media increases the rate of H+ secretion to a greater extent in the latter (overnight group) than in the former. This effect can be blocked by pretreatment with anti-insulin antibody, suggesting that the stimulation of H+ secretion is a specific effect of insulin. The effect of insulin is concentration dependent with half-maximal stimulation of H+ secretion at 100 mU/ml and maximal stimulation at 250 mU/ml. Other characteristics of the insulin-induced stimulation of H+ secretion were its independence of any effect of Na transport and its absolute requirement for the presence of substrate (glucose or pyruvate) under aerobic conditions only. The proton-secreting action of insulin is associated with an increase in the proton-selective conductance in series with the proton pump while the estimated electromotive force of the proton pump remains constant. Finally, the insulin-induced and aldosterone-induced stimulations of proton secretion are mutually independent, as shown by the additivity of these events and by the fact that the effect of insulin was not blocked by pretreatment with cycloheximide. These data suggest that endogenous insulin modulates the rate of H+ secretion by the in vivo turtle bladder.
Parameter estimation in linear functional relationships
Authors: Haacke E. M. , Goldman M. D.
Published: December 2017

We present the application of a weighted least-squares technique to extract parameter estimates in linear models when all variables are subject to error and the goal of the investigation is the value of the parameters themselves. We assume that the relative variances of the variables are known and that the errors between variables are independent. The method of parameter estimation for linear functional relationships is presented, and we describe its differences from linear regression. We discuss how to obtain confidence intervals for the parameter estimates with an emphasis on computer Monte Carlo simulations. An explicit example related to measurements of lung volume changes is presented. An eigenvalue analysis of the data pertaining to the number of independent variables and a physical interpretation of the data space are also discussed.
Interhemispheric coupling coefficients: sex differences in brain neurochemistry
Authors: Denenberg V. H. , Rosen G. D.
Published: December 2017

Previously it was shown that the presence of a significant positive correlation between measures of the right and left hemispheres may be taken as evidence of a negative feedback loop linking the hemispheres [Denenberg, V. H. Am. J. Physiol. 238 (Regulatory Integrative Comp. Physiol. 7): R3-R13, 1980]. Such a finding is indicative of a different form of brain organization, compared with brains that lack this correlation. The purpose of this paper was to compare male and female rats with respect to correlations of left- and right-sided values for a set of brain neurochemicals. The variable of sex was chosen because there are ample data showing differences in brain organization. Neurochemical correlations in the nucleus accumbens and the striatum did not demonstrate any sex difference, but differences were found in neocortex: female rats had significantly greater hemispheric correlations than males for dopamine, 5-hydroxyindoleacetic acid, and serotonin turnover.
Diving responses in ducks after acute barodenervation
Authors: Jones D. R. , Milsom W. K. , Smith F. M. , West N. H. , Bamford O. S.
Published: December 2017

The contribution of systemic arterial baroreceptors to the cardiovascular adjustments to diving has been investigated in unanesthetized ducks after acute baroreceptor denervation. Both intact and denervated ducks exhibited bradycardia on diving, although denervated ducks showed a lesser and more variable fall in heart rate. Hindlimb vascular resistance rose significantly in both intact and denervated ducks. Continuous stimulation of one depressor nerve, through miniature electrodes implanted on the cut central end, resulted in a diving bradycardia intermediate between that recorded in intact and denervated animals. Intermittent stimulation of the depressor nerve, for 20-s periods, at intensities high enough to cause a large fall in mean arterial pressure (MAP) predive caused a smaller reduction in MAP as a dive was prolonged, due to a large decline in the ability of the baroreceptor reflex to affect peripheral resistance. There was no change in the effect of stimulation on cardiac control before or during diving. The present experiments indicate that a barostatic reflex, which exerts its effects primarily through cardiac control and not control of total peripheral resistance, is active through the dive but that the majority of the diving response in ducks is independent of baroreceptor integrity.
Neural control of renal excretory function during behavioral stress in conscious dogs
Authors: Koepke J. P. , Light K. C. , Obrist P. A.
Published: December 2017

The renal and neural mechanisms underlying the excretory response to behavioral stress (aversive conditioning) were examined in 30 conscious dogs. Twenty-one dogs decreased urine flow more than 20% during stress, whereas 9 dogs showed less than a 10% decrease. In 11 of the 21 renal-reactive dogs, decreases in urine flow (42%) and sodium excretion (45%) were associated with unchanged glomerular filtration (-1.5%; GFR; inulin clearance) and effective renal blood flow (-4%; RBF; p-aminohippurate clearance). In the other 10 renal-reactive dogs, similar declines in urine flow (54%) and sodium excretion (52%) occurred with decreases in GFR (24%) and RBF (27%). Among all 30 dogs, greater increases in cardiovascular activity during stress were associated with greater decreases in renal excretion. Surgical renal denervation abolished the excretory response to stress in 4 of 5 dogs. These findings suggest that excretory responses in most dogs are mediated 1) primarily via increased tubular reabsorption rather than decreased GFR, 2) via central integration with cardiovascular responses, and 3) via the renal nerves.
Selective regulation of brain and body temperatures in the squirrel monkey
Authors: Fuller C. A. , Baker M. A.
Published: December 2017

Many panting mammals can cool the brain below body core temperature during heat stress. Studies on human subjects suggest that primates may also be able selectively to regulate brain temperature. We examined this possibility by measuring hypothalamic (Thy) and colonic (Tco) temperatures of unanesthetized squirrel monkeys (Saimiri sciureus) in two different experiments. First, Thy and Tco were examined at four different ambient temperatures (Ta) between 20 and 36 degrees C. Over this range of Ta, Thy was regulated within a narrower range than Tco. In the cold Ta, Tco was lower than Thy; whereas in warm Ta, Tco was higher than Thy. Second, monkeys maintained at 35 degrees C Ta were acutely exposed to cool air blown on the face or abdomen. Air directed at the face cooled Thy more and faster than Tco, whereas air directed at the abdomen cooled Tco and Thy at the same rate. The second experiment was repeated in anesthetized animals with a thermocouple in the right atrium, and the results showed that this brain cooling was not produced by cooling of blood in the body core. These data demonstrate that the squirrel monkey is capable of selectively regulating Thy. Further the results suggest that venous blood returning from the face may be involved in selective brain cooling in warm environments.
Circadian and arousal state influences on thermoregulation in the pigeon
Authors: Heller H. C. , Graf R. , Rautenberg W.
Published: December 2017

We report here the characteristics of spinal thermosensitivity in pigeons as a function of arousal state and time of day. At any time in the light-dark (LD) cycle, the thresholds for shivering and panting were lower during non-rapid-eye-movement (NREM) sleep than during wakefulness. These thresholds in both awake and sleeping animals were lower during D than during L. The gain of the metabolic response to spinal cooling was nearly the same in wakefulness and NREM sleep. Shivering and panting responses to spinal thermal stimulations were impaired during REM sleep compared with wakefulness and NREM sleep. The results support the idea that central nervous system mechanisms controlling arousal states and circadian rhythmicity have separate and additive influences on temperature regulation in the pigeon.
Glycogenolytic rates and cAMP in livers of rats running at different treadmill speeds
Authors: Winder W. W. , Beattie M. A. , Fuller E. O.
Published: December 2017

The purposes of this study were to determine the effect of different work rates on the rate of liver glycogenolysis and to determine the relationship between liver adenosine 3',5'-cyclic monophosphate (cAMP) levels and the glycogenolytic rate. Rats were run at treadmill speeds ranging from 10 to 34 m/min up a 15% grade for either 30 or 60 min. Both the magnitude of the decrease in liver glycogen and the increase in hepatic cAMP were dependent on the running speed and the duration of running. At the highest work rate a disproportionate acceleration in the liver glycogenolytic rate was observed compared with that at lower work loads, thus resulting in a curvilinear relationship between work rate and liver glycogenolytic rate. A high degree of correlation was found between the liver glycogenolytic rate and hepatic cAMP concentration (r = 0.98). This observation is consistent with the idea that hepatic glycogenolytic rates are determined by cAMP-mediated mechanisms.
Increased beta-adrenergic receptors in brown fat of winter-acclimatized Alaskan voles
Authors: Feist D. D.
Published: December 2017

To assess a possible mechanism for the enhanced thermogenesis of cold-acclimated and winter-acclimatized red-backed voles (Clethrionomys rutilus), beta-adrenergic receptors of brown fat were characterized by specific binding of (-)-[3H]-dihydroalprenolol [( 3H]DHA) to isolated brown fat membranes from 23 degrees C-acclimated controls, cold-acclimated (5 wk or 5 mo at 5 degrees C), wild summer, and winter-acclimatized voles. Scatchard analysis to determine the equilibrium dissociation constant (Kd) and the maximum number of binding sites (Bmax) for control brown fat membranes gave a Kd of 4.45 nM [3H]DHA and Bmax of 249 fmol [3H]DHA bound per milligram of protein. beta-Adrenergic agonists competed for specific binding sites with an order of potency typical of the beta 1 subtype of adrenergic receptors: (-)-isoproterenol greater than (-)-norepinephrine greater than or equal to (-)-epinephrine. After cold acclimation for 5 wk or 5 mo, the Kd and Bmax for adrenergic binding sites were similar to those of controls. Brown fat mass was 1.5 times greater than that of controls after 5 wk cold acclimation but similar to controls after 5 mo cold acclimation. Winter voles had 1.7 times higher Bmax and 1.6 times more brown fat than summer voles. Thus seasonal acclimatization to winter in red-backed voles appears to involve an increase in beta-adrenergic receptors in brown fat, but cold acclimation does not. The results suggest quantitative and possibly qualitative differences in neural and hormonal stimulation of brown fat between cold acclimation and winter acclimatization in voles.
Kinetics of endogenously labeled plasma fibronectin: incorporation into tissues
Authors: Deno D. C. , Saba T. M. , Lewis E. P.
Published: December 2017

Fibronectin exists in a soluble form in plasma and lymph as well as in a relatively insoluble form in tissues. The disappearance of endogenously labeled fibronectin from plasma and its subsequent extravascular localization was studied over a 38-h period in normal rats (350-400 g) utilizing plasma fibronectin labeled in vivo with 75Se-selenomethionine. For comparative analysis, 125I-albumin was utilized in these dual isotopic experiments. After the simultaneous injection of 75Se plasma fibronectin (20 nCi) and 125I-albumin (2 microCi), all measured tissues demonstrated accumulation of both radiolabeled proteins in extravascular sites. Plasma fibronectin demonstrated a rather specific and high affinity for liver and spleen, which are enriched with reticuloendothelial cells. Albumin manifested the expected washout from extravascular sites, whereas fibronectin primarily displayed retention in tissues. The plasma disappearance of 75Se-labeled fibronectin was well described by two exponentials: an early phase with a half time of 0.52 h and a later phase with a half time of 21 h. To account for tissue retention of labeled fibronectin, a two-compartment kinetics model was required that included loss from the extravascular exchangeable compartment. Analysis of the disappearance kinetics and fibronectin distribution allowed estimation of the fractional turnover rate, pool size, and mean residence time. Accordingly the total rate of loss for plasma fibronectin was 0.51-0.54 mg/h. The calculated pool size of the soluble form of fibronectin was 15.5-16.3 mg. The mean residence time for exchangeable fibronectin was 29.6-29.9 h. These findings suggest that plasma fibronectin can be incorporated within the insoluble pool of fibronectin in tissues.
Cardiovascular responses to noxious radiant heat in anesthetized cats
Authors: Abram S. E. , Kostreva D. R. , Hopp F. A. , Kampine J. P.
Published: December 2017

The responses of heart rate and blood pressure to noxious radiant heat were studied in seven pentobarbital-anesthetized cats. Afferent activity recorded from the tibial nerve, systemic blood pressure, and heart rate were monitored as skin temperature of the hind footpad was raised to 53 degrees C for 20 s using radiant heat. The averaged tibial afferent nerve activity increased markedly as skin temperature approached 52 degrees C. Within 2-3 s of the onset of increased tibial nerve activity, systolic blood pressure increased an average of 32 mmHg and heart rate increased an average of 16 beats/min in the seven animals that were studied. The results of this study provide evidence for a somatosympathetic reflex that is initiated by cutaneous nociceptors. Under pentobarbital anesthesia, an increase in heart rate and blood pressure appears to be a reliable indicator of nociceptor activation.
Canine visual acuity: retinal and cortical field potentials evoked by pattern stimulation
Authors: Odom J. V. , Bromberg N. M. , Dawson W. W.
Published: December 2017

The visual acuities (i.e., visual thresholds for pattern detection) of four dogs under neuromuscular block were measured using visually evoked cortical potentials (VECP) and/or pattern-evoked retinal potentials (PERR). Stimuli were phase-reversing square-wave gratings with a mean luminance of 86 cd/m2 and 70% contrast. The mean of the VECP thresholds of two dogs tested was 12.59 cycles per degree (cycles/deg). The mean of the PERR thresholds of four dogs tested was 11.61 cycles/deg. The difference between VECP and PERR thresholds was not statistically significant. VECP acuities appear to be determined at or before the last stage of retinal processing (PERR). Our estimates of canine acuity are 1.3–2 times those reported for cats and 0.2–0.4 times those reported for primates when tested under comparable luminance and contrast conditions.
Simulation of calcium homeostasis: modeling and parameter estimation
Authors: Hurwitz S. , Fishman S. , Bar A. , Pines M. , Riesenfeld G. , Talpaz H.
Published: December 2017

The system that regulates plasma calcium in the bird has been formalized into a model based on a series of differential equations and solved by computer simulation. Bone, kidney, and intestine have been considered as the control subsystems, with parathyroid hormone and 1,25-dihydroxycholecalciferol as the regulating hormones. The parameters used in the simulation model have been computed either from published results or by specifically designed experiments described here. For the estimation of parameters, an iterative procedure has been developed that was designed to minimize the sum of square errors between observed and system-simulated values. Parameters of 1,25-dihydroxycholecalciferol metabolism were experimentally obtained from the kinetic behavior of the 3H-labeled hormone in rachitic birds after a single dose. Model parameters have been adjusted using the results of in vivo calcium loading and validated by an EDTA infusion experiment. The simulation model has been used to study the hierarchy of the activities of the three control subsystems and of the regulating hormones, at different calcium intakes. Positive or negative errors in plasma calcium resulted in an asymmetry in the activities of the controlling systems, bone and kidney, whereas the intestine is characterized by its relatively long response time.
Does the autonomic nervous system regulate whole-body lymph flow?
Authors: Power G. G. , Brace R. A.
Published: December 2017

We compared whole-body lymph flow responses with and without the autonomic nervous system intact in pentobarbital-anesthetized, acutely nephrectomized dogs. We measured left thoracic duct lymph flow, lymph and plasma protein concentrations, arterial and venous pressures, heart rate, and hematocrit in eight intact and six ganglion-blocked (hexamethonium, 15 mg/kg iv) animals. Ganglionic blockade lowered arterial pressure and heart rate but did not change lymph flow rate or the other variables. In the control and blocked groups at 30-min intervals, isotonic saline, lactated Ringer, and Dextran 70 solutions were serially infused, followed by hemorrhage and reinfusion of shed blood. Infusions or withdrawals were equal to 2% of body weight and were induced over 5-min intervals followed by 25 min of recovery. Lymph flow generally increased to a peak 5–7 min after each infusion was ended and then decayed back toward preinfusion levels; the extent of the rise in lymph flow, the time of the peak flow, and the extent of decay after the peak were unaffected by autonomic blockade. The absolute lymph flow rates in response to the infusions, hemorrhage, or blood infusion were not appreciably altered by ganglionic blockade. Thus the present studies provide little support to the hypothesis that the autonomic nervous system contributes to whole-body lymph flow.
Gasser and Graham and spinal cord electrophysiology
Authors: Allison T. , Wood C. C.
Published: December 2017

This year marks the 50th anniversary of the publication of the pioneering electrophysiological study of the spinal cord by H. S. Gasser and H. T. Graham (Am. J. Physiol. 103: 303-320, 1983). Gasser and Graham's paper is of historical interest, because it was the first study of the spinal cord to use a cathode ray tube. It is of scientific interest, because their careful recordings and insightful interpretations laid the groundwork for subsequent studies of spinal cord electrophysiology in anesthetized animals and, more recently, for the interpretation of noninvasive spinal cord recordings in awake, intact humans.
Influence of left ventricular receptor stimulation on plasma vasopressin in conscious dogs
Authors: Zucker I. H. , Gorman A. J. , Cornish K. G. , Huffman L. J. , Gilmore J. P.
Published: December 2017

The current study was undertaken to determine whether receptors in the left ventricle are capable, when stimulated, of inhibiting plasma arginine vasopressin (AVP) in the conscious dog. Dogs were instrumented to measure aortic pressure and heart rate. In addition, a catheter was implanted in the left circumflex coronary artery. Left ventricular receptors were stimulated by the intracoronary infusion of veratrine, which evoked a hypotension and bradycardia. Control experiments consisted of intravenous infusion of veratrine. Plasma AVP, osmolality, and sodium and potassium concentrations were measured at intervals following the infusion. Similar experiments were done during the intravenous infusion of sodium nitroprusside (NP) to lower aortic pressure to the same extent as that seen with intracoronary infusion of veratrine. Experiments were also performed in chronic sinoaortic-denervated dogs. Intracoronary infusion of veratrine resulted in a significant decrease in aortic pressure from 93.9 +/- 2.8 to 70.5 +/- 4.5 mmHg. Control plasma AVP averaged 2.13 +/- 0.25 pg/ml and did not change significantly during this time. NP infusion lowered aortic pressure to a similar degree, and plasma AVP rose to 21.17 +/- 3.79 pg/ml after 5 min. There were no significant changes in any other plasma constituents. The results were similar in sinoaortic-denervated dogs. We conclude from the results of this study that receptors in the left ventricle are not capable of decreasing plasma AVP from low basal levels or from augmented levels.
Viewing the ventromedial hypothalamus from the adrenal gland
Authors: Dallman M. F.
Published: December 2017

The relationships among food intake, insulin secretion, and adrenocortical function are reviewed. It is hypothesized that a major role of structures in, or passing through, the ventromedial hypothalamus is to inhibit food intake, insulin secretion, and adrenocortical function during the day (in the nocturnally active rat) and that this activity is normally driven by elements within the suprachiasmatic nuclei. Lesions of the ventromedial hypothalamus of rats result in nonrhythmic food intake, hyperinsulinemia, nonrhythmic adrenocortical function, and obesity. Adrenalectomy prevents or reverses the effects of lesions of the ventromedial hypothalamus on food intake, insulin secretion, and obesity, and corticosteroid replacement restores them. Because the actions of corticosteroids are both time- and dose-dependent, it is proposed that the effects of the tonic levels of corticosteroids observed after lesions of the ventromedial hypothalamus are to augment the hyperphagia, hyperinsulinemia, and substrate flow into fat to a greater extent than would occur if there were a normal circadian rhythm in adrenocortical function.
Beyond a pacemaker's entrainment limit: phase walk-through
Authors: Ermentrout G. B. , Rinzel J.
Published: December 2017

Desynchronization occurs when a pacemaker is externally stimulated at too high a rate, beyond the entrainment limit. One may then observe phase walk-through: the pacemaker and stimulus phase difference, rather than lock to a fixed pattern, may cycle repeatedly through all values. By means of a simple but nonlinear one-variable model we describe qualitatively the properties of entrainment, loss of entrainment, and phase walk-through for rhythmically stimulated pacemakers. We obtain an expression for the cycle length (beat period) of the repetitive phase walk-through. This shows, in contrast to the simplest treatment, that in general beat frequency is not a simple linear function of the difference between the pacemaker and stimulus frequencies. Our results are illustrated in the context of a model experimental pacemaker, the rhythmically flashing firefly. We discuss how these modeling results apply in a much more general setting.
Short photoperiods counteract the effects of ovariectomy on energy balance of voles
Authors: Dark J. , Zucker I. , Wade G. N.
Published: December 2017

Adult female meadow voles maintained from birth in a long photoperiod (14 h light, 10 h darkness; LD 14:10) were ovariectomized or sham-ovariectomized and housed subsequently in long or short (LD 10:14) photoperiods for 10 wk. Absolute and relative daily food intake, body mass, carcass lipid and water content, and lipoprotein lipase activity of white adipose tissue were reduced in voles housed in short photoperiods. Ovariectomy resulted in increases in food intake and body weight and altered carcass composition in long-day voles, but these changes were negated in voles kept in short photoperiods. Responsiveness to short photoperiods promotes winter weight loss and subsequent energy intake savings and counteracts the body weight increases normally associated with gonadal quiescence and diminished hormone secretion.
Differential renal and splenic nerve responses to vagal and spinal afferent inputs
Authors: Weaver L. C. , Fry H. K. , Meckler R. L.
Published: December 2017

Specific contributions of the kidney and spleen to cardiovascular homeostasis may be determined partially by differential sympathetic influences on each organ. This investigation was a comparison of renal and splenic sympathetic responses to stimulation of vagally innervated cardiac receptors and receptors of abdominal visceral and muscle spinal afferent nerves. Experiments were performed in anesthetized, sinoaortic-denervated cats in which upper thoracic sympathetic ganglia had been removed. Left atrial injections of veratridine depressed renal and splenic nerve discharges by 68 and 44%, respectively. In contrast, injections of bradykinin into the abdominal aorta caused 18 and 104% excitation of renal and splenic nerves, respectively. Visceral ischemia and mesenteric stretch by snare occlusion of the celiac artery caused 20 and 64% excitation of renal and splenic nerves, respectively. Left atrial injections of bradykinin caused biphasic renal nerve responses (range, 200% excitation to complete inhibition) and 246% excitation of splenic nerves; after vagotomy both renal and splenic nerves were excited (21 and 117%, respectively). In conclusion, sympathetic control of the kidney and spleen can be selective, illustrating significant potential discreteness of sympathetic outflow to the viscera.
Exaggerated wave reflection in the kangaroo simulates arterial counterpulsation
Authors: Avolio A. P. , Nichols W. W. , O'Rourke M. F.
Published: December 2017

The ascending aortic pressure wave in kangaroos is quite different from that seen in other experimental animals and in humans, despite an ascending aortic flow wave that is virtually identical. The diastolic pressure surge in the ascending aortic pressure wave of kangaroos is very prominent--so much so that peak diastolic pressure is often greater than peak systolic pressure, with the pressure wave resembling that recorded in humans during intra-aortic balloon counterpulsation. Ascending aortic impedance patterns in kangaroos indicate the presence of a single functionally discrete reflecting site in the peripheral circulation, with high reflection coefficient. All findings--of pulse contour and impedance patterns--are explicable on the basis of arterial anatomy and body shape. Wave reflection from the distant, large, and vascular lower body appears to dominate the effects of wave reflection from the short, small, and less vascular head and forelimb system.
Changes in glycerol kinetics after E. coli endotoxin administration in dogs
Authors: McGuinness O. P. , Spitzer J. J.
Published: December 2017

The metabolic clearance rate (MCR) and maximal rate of glycerol removal (Rd max) were determined in anesthetized dogs at two time periods after the intravenous administration of either Escherichia coli endotoxin or saline. The nonisotopic method employed in these studies to determine the MCR of glycerol consisted of a constant infusion of glycerol at three different infusion rates. At each infusion rate a steady-state glycerol concentration was obtained. The reciprocal of the slope of the linear relationship between the glycerol infusion rate and the change in the steady-state arterial glycerol concentration was equal to the MCR of glycerol. Administration of endotoxin significantly decreased the MCR of glycerol, whereas the volume of distribution of glycerol was not altered significantly. The arterial glycerol turnover remained unaltered, whereas arterial glycerol concentration increased after endotoxin administration. The studies demonstrate that the elevated arterial glycerol concentration maintained the rate of glycerol turnover in the face of decreased efficiency of glycerol removal after endotoxin administration.
Peripheral neural input to neurons of the middle cervical ganglion in the cat
Authors: Bosnjak Z. J. , Kampine J. P.
Published: December 2017

In vitro studies were conducted on the middle cervical ganglion (MCG) of the cat by recording intracellular action potentials from its neurons. The purpose of this study was to examine the possibility of a peripheral synaptic input to the MCG. Preganglionic electrical stimulation, via the ventral ansa (VA) and dorsal ansa (DA) subclavia, and post-ganglionic electrical stimulation, via the ventrolateral cardiac nerve (VCN), evoked graded synaptic responses that led to the discharge of one or more action potentials in the 14 ganglia studied. The conduction velocity of these pathways ranged from 0.4 to 0.9 m/s. Ten percent of the cells impaled were inexcitable, even with direct intracellular depolarizing current, whereas 80% of the neurons studied received a synaptic input from fibers of both central and peripheral origin. In addition, subthreshold synaptic inputs from peripheral and central origin sum to discharge the cell, suggesting an integration of neural inputs in the MCG. These responses were blocked by d-tubocurarine chloride. This evidence indicates that sympathetic efferent nerve activity can be modified by peripheral excitatory inputs and that these inputs may function as pathways for a peripheral reflex at the level of the MCG.
Further evidence that circadian rhythm of blinded rat pups is entrained by the nursing dam
Authors: Takahashi K. , Murakami N. , Hayafuji C. , Sasaki Y.
Published: December 2017

To determine the importance of the nursing mother in setting the phase of the endogenous rhythm in blinded rat pups, free-running rhythm of locomotor activity in the pups was observed during 4-5 wk after weaning. Blinded pups, optically enucleated on day 1, were raised by either an intact natural mother or an intact foster mother with a rhythm reversed to that of the natural mother. The locomotor activity was continuously recorded for 4-5 wk, starting between 3 and 5 postnatal wk. At 5 wk of age the offset time of activity phase was found during the periods corresponding to the middle half of the light phase in the nursing period, regardless of whether they were raised by a natural or a foster mother. The free-running periods, in the blinded pups tested, were fairly close, with the majority ranging between 24.3 and 24.5 h. These findings indicate that the endogenous rhythm of the blinded pups is entrained by the nursing mother during the nursing period.
Brain stem reticular influences on lumbar axial muscle activity. I. Effective sites
Authors: Femano P. A. , Schwartz-Giblin S. , Pfaff D. W.
Published: December 2017

Lumbar axial muscle responses to electrical stimulation of the brain stem reticular formation were used to characterize reticular influences on these muscles. Electromyographic recordings were obtained from the transversospinalis, medial longissimus, and lateral longissimus systems in the urethan-anesthetized rat. Ipsilateral stimulation of the pontomedullary reticular formation evoked excitatory responses in these muscles. Trains of pulses were required, but currents as low as 15 microA were effective. Contralateral reticular stimulation with currents similar to those that elicited activation during ipsilateral stimulation at the same brain stem levels could inhibit lumbar electromyographic activity. The results suggest that the motoneurons innervating the lumbar axial musculature in the rat receive strong reticulospinal influences that could be important for postural maintenance and the expression of certain behaviors.
Neuronal GABA release and GABA inhibition of ACh release in guinea pig urinary bladder
Authors: Kusunoki M. , Taniyama K. , Tanaka C.
Published: December 2017

gamma-Aminobutyric acid (GABA) and glutamate decarboxylase (GAD) are present in the urinary bladder of guinea pigs, and the possible correlation in regional distribution between GABA, GAD, and the number of vesical ganglion cells was studied. Electrical stimulation of the bladder strips produced an increase in the calcium-dependent and tetrodotoxin-sensitive [3H]GABA release and contractions in the strips preloaded with [3H]GABA. Nicotine, acetylcholine chloride (ACh), and hexamethonium did not significantly alter the release of [3H]GABA. Bicuculline significantly enhanced [3H]ACh release and cholinergic components of contractions evoked by electrical stimulation of the bladder strips preloaded with [3H]choline, thereby suggesting that this compound antagonizes the effect of endogenous GABA released during stimulation. GABA and muscimol but not baclofen reduced both the [3H]ACh release and contractions evoked by nicotine. These effects of GABA were antagonized by bicuculline and furosemide but not by alpha- and beta-adrenergic blockers. These findings suggest that GABA may be a noncholinergic nonadrenergic inhibitory neurotransmitter in the urinary bladder. The motility of the urinary bladder is thus inhibited by reducing the release of ACh from the postganglionic cholinergic neurons through bicuculline-sensitive GABA receptors probably associated with the chloride ion channel.
Role of intestinal calcium absorption in plasma calcium regulation of the rat
Authors: Bronner F.
Published: December 2017

Transmural calcium movement in the intestine involves both saturable and nonsaturable components, with the saturable movement subject to regulation by vitamin D and indirectly by parathyroid hormone. Under conditions of high-calcium intake, calcium absorption due to the saturable component is minimized and the numerical value of the nonsaturable component can equal that found in vitamin D-deficient or parathyroidectomized (PTX) animals on similar calcium intakes. Yet in PTX animals intestinal calcium represents a larger proportion of the calcium inflow into the central pool, and PTX animals are less able to regulate their plasma calcium than hormonally intact animals. This demonstrates that intestinal calcium input in the rat can be classified as a signal disturbing (raising) the plasma calcium.
A model for the distribution and clearance of inert substances in subcutaneous tissue
Authors: Ozisik M. N. , Hillman R. , Widmer F.
Published: December 2017

The subcutaneous space has received attention in recent years as a route for the continuous administration of drugs and implantation of drug delivery systems. Yet little work has been devoted to an examination of the mass transport (distribution) of drugs in the subcutaneous space and the factors that influence their rate of clearance. A mathematical model is developed to describe the spreading and resorption of substances infused into the subcutaneous space. It simulates radial diffusion and flow in the direction of spreading as well as lateral convection into the systemic circulation. An analytic solution is obtained for the distribution of the substance as a function of time and position in the subcutaneous space. Two independent parameters, v (Peclet no.) and H (generalized Biot no.), are found to control the transport. Examples are presented to illustrate the effects of these parameters on the distribution of substances in the subcutaneous space.
Passage of solutes through walls of Malpighian tubules of Rhodnius by paracellular and transcellular routes
Authors: O'Donnell M. J. , Maddrell S. H. , Gardiner B. O.
Published: December 2017

The walls of isolated upper Malpighian tubules of the insect, Rhodnius prolixus, are much more permeable to small relatively unchanged solutes (ethanol, xylose, and mannitol) than to larger or more charged solutes (acetate, glycine, tyrosine, and inulin). The more permeable solutes rapidly reach concentrations in the tubule cells equivalent to their concentrations in the bathing medium; the less permeable solutes do not penetrate into the cells. The time course of accumulation of permeable solute in the cells matches the time course of the appearance of solute in the lumen. Substances injected into the hemolymph of fed R. prolixus appear in the urine at concentrations predictable from the permeability of in vitro tubules, supporting the idea that the in vitro permeability of the tubules is representative of their properties in the intact insect. It is suggested that the rapid transcellular penetration of small solutes through the Malpighian tubules reflects the large areas of cell membrane. The area of cell membrane exceeds that of the paracellular clefts by a factor of 10(5).
Mechanisms of control of milk intake in suckling rats
Authors: Cramer Catherine P. , Blass Elliott M.
Published: December 2017

Page R154: Catherine P. Cramer and Elliott M. Blass. “Mechanisms of control of milk intake in suckling rats.” Page R157: Table 1 should read

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A discussion of apraxia, aphasia, and gestural language
Authors: Helm-Estabrooks N.
Published: December 2017

It is understood that damage to the left cerebral hemisphere in adulthood may result in syndromes of language disturbances called the aphasias. The study of these syndromes sheds light on normal language processes, the relationship between language behavior and the brain, and how best to treat aphasic individuals. Aphasia, for some, is a central communication disorder affecting all symbolic behavior in all modalities (i.e., speech, writing, and gesture). Difficulty producing symbolic gestures on command is called apraxia. Others view aphasia as a manifestation of a motor-sequencing disorder affecting all gestural systems including those required for speech movements. These divergent theories of the underlying nature of aphasia can be tested through examination of deaf individuals who use sign language before onset of aphasia. Poizner et al. [Am. J. Physiol. 246 (Regulatory Integrative Comp. Physiol. 15): R868-R883, 1984] studied three such patients with different aphasia syndromes: one patient had a nonsymbolic, motor-sequencing disorder; one had a gestural apraxia; and one had neither. These findings force the conclusion that neither the symbolic nor motor-sequencing theory of aphasia can account for the many varieties of that disorder.
Local cerebral metabolic rates of glucose in movement and language disorders from positron tomography
Authors: Metter E. J. , Riege W. H. , Hanson W. R. , Phelps M. E. , Kuhl D. E.
Published: December 2017

Positron-computed tomography with [18F]fluorodeoxyglucose to measure glucose metabolism has shown changes in the brain distant to a focal area of infarction, demonstrating that what appears as a focal abnormality represents a more widespread functional process. Several approaches are presented to better understand quantitative metabolic data and focus on caudate and basal ganglia function. Area-to-area correlations in Parkinson's and Huntington's diseases showed decreases in the number of cortical relationships compared with control subjects, suggesting that the basal ganglia are involved with the ability of cortical regions to function together. In aphasia, caudate metabolism correlated with several language measures that suggested a role in some undefined basic process, seemingly related to Broca's area function. The studies presented suggest that the caudate may involve integrating the processing of language and cognition with the execution of the resulting response. Motor and cognitive function seem related to similar and overlapping brain systems. The disruption of such systems may result in loss of both cognitive and motor aspects of a function.
Converging evidence in support of common dynamical principles for speech and movement coordination
Authors: Kelso J. A. , Tuller B.
Published: December 2017

We suggest that a principled analysis of language and action should begin with an understanding of the rate-dependent, dynamical processes that underlie their implementation. Here we present a summary of our ongoing speech production research, which reveals some striking similarities with other work on limb movements. Four design themes emerge for articulatory systems: 1) they are functionally rather than anatomically specific in the way they work; 2) they exhibit equifinality and in doing so fall under the generic category of a dynamical system called point attractor; 3) across transformations they preserve a relationally invariant topology; and 4) this, combined with their stable cyclic nature, suggests that they can function as nonlinear, limit cycle oscillators (periodic attractors). This brief inventory of regularities, though not mean to be inclusive, hints strongly that speech and other movements share a common, dynamical mode of operation.
Ventromedial hypothalamic knife-cut lesions in rats resistant to dietary obesity
Authors: Oku J. , Bray G. A. , Fisler J. S. , Schemmel R.
Published: December 2017

The effects of ventromedial hypothalamic (VMH) knife-cut lesions on food intake and body weight of S 5B/Pl rats, which are normally resistant to obesity when eating a high-fat diet, were examined in two experiments. In the first experiment body weight increased only slightly after VMH knife-cut lesions when animals were fed pelleted laboratory chow or a 10% corn oil diet. When eating the 30% corn oil diet, however, body weight increased in the VMH knife-cut rats. In the second experiment VMH knife-cut lesions produced a small weight gain in rats fed the 10% fat diet; this manipulation also increased food intake and disrupted the normal diurnal feeding pattern. Changes in the weight of the liver, interscapular brown adipose tissue, and white adipose tissue paralleled the changes in body weight. Plasma insulin increased in the rats eating the 30% corn oil diet ad libitum but not in the VMH-lesioned animals pair fed to the sham-operated rats. Incorporation of 3H from 3H2O into lipid was significantly increased in white fat of animals with VMH knife cuts. Similar results were obtained from incubation of adipose tissue in vitro with insulin and radioactively labeled glucose. These studies show that hypothalamic knife-cut lesions can remove the resistance of the S 5B/Pl rats to obesity when they are fed a high-fat diet.
Dissociation of circadian rhythms in rats with a hypothalamic island
Authors: Honma S. , Honma K. , Hiroshige T.
Published: December 2017

Complete isolation of the medial basal hypothalamus, including the suprachiasmatic nuclei in the isolated island, from the rest of the central nervous system was performed in rats. The circadian rhythm of plasma corticosterone level remained essentially intact in 5 of 16 rats with complete islands, whereas that of spontaneous locomotor activity was decomposed into ultradian bursts in 15 rats, resulting in a clear dissociation of the two rhythms in four rats. One rat, whose circadian rhythm of both variables persisted after the hypothalamic isolation, showed a diurnal activity. The 24-h patterns of plasma corticosterone of the other rats could be characterized as either episodic or continuously low throughout the day. A prefeeding corticosterone peak was detected under restricted feeding in rats with episodic fluctuations but not in those with continuously low hormone levels. It is concluded that the hypothalamic island includes the fundamental structures necessary for the manifestation of the entrained circadian rhythm of plasma corticosterone in rats under ad libitum feeding, whereas it contains only a part of that for spontaneous locomotor activity. The coupling pathways from the circadian oscillator(s) to these overt rhythms seem to be separate in the central nervous system, and the circadian rhythm of plasma corticosterone is not a direct consequence of that of locomotor activity.
Heart rate and energy expenditure in resting and running Svalbard and Norwegian reindeer
Authors: Nilssen K. J. , Johnsen H. K. , Rognmo A. , Blix A. S.
Published: December 2017

The purpose of this study was to determine whether a convenient relationship could be found between heart rate (HR) and energy expenditure at rest and during running in the high arctic Svalbard reindeer (SR) and the subarctic Norwegian reindeer (NR). Measurements of HR and energy expenditure (O2 consumption) were made at different ambient temperatures, at rest, and during running at different speeds during both summer and winter. Cost of transportation (Science 177: 222-228, 1972) was 3.56 and 2.67 J X g-1 X km-1 in SR and NR, respectively. The y-intercept value obtained for NR was close to the predicted value (J. Exp. Biol. 97: 1-22, 1982), whereas that of SR was much lower. In NR the relationship between HR and energy expenditure at running speeds from 0 to 9.2 km X h-1 is, regardless of ambient temperature (in the -30 to +10 degrees C range), described by the following equations: y = 8.04x + 48.70, r = 0.92, n = 27 (summer); and y = 7.48x + 31.20, r = 0.95, n = 52 (winter). In SR, the corresponding equations were y = 7.60x + 49.20, r = 0.94, n = 29 (summer); and y = 8.90x + 32.10, r = 0.96, n = 44 (winter), where y is HR (beats X min-1) and x is metabolic rate (W X kg-1).