bluuebunny/crossref_metadata_2025 huggingface dataset:
Pyeloureteral dynamics in the intact and chronically obstructed multicalyceal kidney
Authors: Constantinou C. E. , Djurhuus J. C.
Published: December 2017

The transport of urine in the upper urinary tract of the multicalyceal kidney was studied in healthy and chronically obstructed pigs in terms of renal pelvic pressure, rate of and coordination of ureteral contractions, and bolus volume. The variations of these parameters to diuresis was examined by incremental elevation of urine output effected by intravenous infusion of mannitol. In 16 healthy animals the mean variation in urine flow was 0.01-3.20 ml/min, the change in peristaltic rate ranged from 0.763 to 5.125 min-1, and bolus volume from 0.003 to 2.083 ml.. In 14 chronically obstructed kidneys, for a mean variation in urine flow of 0.006-5.4 ml/min, peristaltic rate ranged from 0.237 to 6.095 min-1 and bolus volume from 0.00 to 1.80 ml. Discoordinated contractions, bursts of peristalsis, and incompletely transmitted pelvic contractions were characteristic of a chronically obstructed system. These observations are compared with the unobstructed unicalyceal and multicalyceal kidney. The disrupting impact of chronic ureteral obstruction on the hierarchical organization of the pyeloureteral pacemaker system is discussed.
Control of diving responses by carotid bodies and baroreceptors in ducks
Authors: Lillo R. S. , Jones D. R.
Published: December 2017

The precise role of carotid body chemoreceptors and systemic baroreceptors in cardiovascular responses during experimental diving in ducks is controversial. The diving responses of chronically baroreceptor-denervated, chemoreceptor-denervated, and combined baroreceptor- and chemoreceptor-denervated White Pekin ducks, Anas platyrhynchos, were compared with those of intact and sham-operated birds. All three types of denervation elevated predive heart rates on average by 100-150 beats/min. During submergence, the cardiac rate of the barodenervates quickly dropped and after 60 s stabilized at levels similar to those of submerged intact ducks for the remainder of a 2-min dive. However, arterial blood pressure declined drastically in the barodenervates. Ducks without functional carotid bodies showed significant bradycardia during submergence, although heart rate only fell to the predive rate of intact animals. Birds with combined baroreceptor and chemoreceptor denervation exhibited the same degree of bradycardia as chemoreceptor denervates, and arterial blood pressure rose spectacularly during a dive. It is concluded that during experimental diving in ducks 1) cardiac responses are not baroreflexive in origin, 2) the major portion of bradycardia is due to stimulation of carotid body chemoreceptors, and 3) intact system baroreceptors appear essential for maintenance of blood pressure.
Amygdaloid lesions impair ingestive responses to 2-deoxy-D-glucose but not insulin
Authors: Tordoff M. G. , Geiselman P. J. , Grijalva C. V. , Kiefer S. W. , Novin D.
Published: December 2017

Bilateral lesions of the amygdala in male rats impaired the feeding response to 2-deoxy-D-glucose (2-DG; 100, 200, and 400 mg/kg). During the first 3 h postinjection, control rats displayed a dose-related increase in both food and water consumption. Rats with amygdaloid lesions did not respond to 2-DG until the 3rd h postinjection, when only the two largest doses significantly increased food consumption. Their water intake remained unaffected throughout the 3-h postinjection period. During the 4th-24th h post-2-DG administration, both groups displayed a dose-related suppression of food and water intake. Following insulin (10 U/kg), amygdaloid and control animals were indistinguishable: both groups showed a significant short-term increase in food and water intake followed by a reduction in intakes during the 4th-24th h. Central visceral pathways that are important for the ingestive responses to 2-DG may be interrupted by amygdaloid lesions. However, pathways responsible for the ingestive behavior induced by insulin appear unaffected by damage to the amygdala.
Hypothalamic neurons with activity patterns related to sympathetic nerve discharge
Authors: Barman S. M. , Gebber G. L.
Published: December 2017

Spike-triggered averaging was used to identify hypothalamic neurons with activity patterns related to inferior cardiac sympathetic nerve discharge (SND). Three neuronal types were identified in baroreceptor-innervated cats. The discharges of SR units were temporally related to SND and the R wave of the electrocardiogram. The discharges of SER units were in addition related to electroencephalogram (EEG) activity. SE unit discharges were related to SND and EEG activity but not to the R wave. Two neuronal types were identified in baroreceptor-denervated cats. The discharges of S units were temporally related to SND but not to EEG activity. The second neuronal type exhibited activity patterns similar to those for SE neurons in the baroreceptor-innervated cat. With the exception of SER neurons, all unit types could be subdivided into two groups depending on whether their discharges were followed by an increase or a decrease in SND. The discharges of SER units were followed by a decrease in SND. These data are discussed with regard to the role played by the hypothalamus in generating the basal discharges of sympathetic nerves.xs
The good enough calculi of evolving control systems: evolution is not engineering
Authors: Partridge L. D.
Published: December 2017

In evolved aggregates of accidentally invented elements, retained when statistically good enough to identify limitations of antecedent systems, survival value might favor operators incorporating aspects of, while not identical with, feedback, feedforward, state varible, and "homeostatic" control. Generally, simple organizational increments should predominate. After invention, an internal controller with readily modifiable rules could facilitate evolution of compound inventions, but criteria controlling rule changes would be only indirectly (probably imperfectly) survival referent. Consequent to combination of independent invention with indirect criteria and statistical acceptance, evolved control logic could be: both redundant and incomplete; good enough with malefic aspects; built of loosely linked or autonomous sublogics; and a source of good enough solutions from incomplete information. The partially explicit rules are defined more by rejections than by ratifications. Study of the result based on formal logic, engineering conventions, and familiar coordinate systems could conceive illegitimate illusions of understanding.
Sperm motility-inhibiting factor in rat epididymis
Authors: Turner T. T. , Giles R. D.
Published: December 2017

Rat spermatozoa collected by micropuncture from the cauda epididymidis are immotile when diluted in cell-free cauda epididymidal fluid but are vigorously motile when diluted in 0.154 M NaCl. Removal of proteins from cauda fluid by heat precipitation or enzymatic digestion reduces the ability of cauda fluid to keep cauda sperm immotile. Cauda sperm diluted in trypsin-treated cauda fluid have motility initiation scores that are not significantly different (P less than 0.05) from cauda sperm motility scores after dilution in 0.154 M NaCl. Cell-free lumen fluids from the proximal epididymis have a reduced ability to enforce quiesence on cauda spermatozoa, and rete testis fluid does not keep cauda sperm immotile. However, concentrated rete testis fluid does prevent the initiation of motility. It is proposed that a proteinaceous factor, possibly of testicular origin, is important in preventing the initiation of motility while sperm reside in the distal reproductive tract of the male rat.
Influence of nutritional state on periodicity in plasma insulin levels in monkeys
Authors: Hansen B. C. , Jen K. L. , Koerker D. J. , Goodner C. J. , Wolfe R. A.
Published: December 2017

Rapid sustained oscillations in basal plasma levels of insulin, glucose, and glucagon (9-12 min/cycle) have been identified in rhesus monkeys and in humans. To assess the possible regulatory role of nutritional state in the control of these plasma fluctuations, 12 chronically cannulated conscious rhesus monkeys were studied at varying intervals following ingestion of a mixed meal. Blood samples were withdrawn at 2-min intervals for periods of 10-30 min. In the postprandial period both absolute and relative amplitudes (half amplitude percent) of oscillations increased up to 16 h postfeeding to maximal amplitudes of +/- 32% for insulin, +/- 4% for glucose, and +/- 22% for glucagon. Periods were consistently in the 9- to 12-min range for insulin and glucose. Progressive deprivation to 88 h produced decreases in amplitudes and more irregularity in fluctuations but did not affect the underlying periodicity of these oscillations in plasma levels of insulin, glucose, and glucagon. Results are consistent with the existence of one or more inherent oscillators in the pancreas that act to synchronize the release of hormones from particular types of islet cells. The amplitude of these oscillations but not the frequencies is associated with changes in liver metabolism and nutritional state.
Tardy occurrence of adipocyte hyperplasia in cafeteria-fed rat
Authors: Mandenoff A. , Lenoir T. , Apfelbaum M.
Published: December 2017

White adipose tissue cellularity was studied in rats during a diet characterized by a free choice of highly palatable items. At the 8th wk the increase in adipose stores is due to hypertrophy. Between the 8th and 20th wk hypertrophy persists, but hyperplasia appears both in retroperitoneal and epididymal sites. The probable role of carbohydrate intake in the onset of hyperplasia is discussed.
Cardiovascular adjustments to laboratory diving in beavers and nutria
Authors: McKean T.
Published: December 2017

Beavers (Castor canadensis) and nutria (Myocastor coypus) were anesthetized with halothane and catheters placed in the left ventricle, aorta and pulmonary artery, right ventricle or right atrium. The animals were strapped to a board and following recovery from anesthesia the following measurements were taken: regional distribution of blood flow, cardiac output, O2 consumption, arterial and venous blood gases, and pH. The animal was then immersed in 15-20 degrees C water for up to 2.75 min (nutria) or 4 min (beaver) and the measurements repeated. Heart rate and cardiac output decreased by 80 and 75%, respectively. Arterial and venous oxygen partial pressure and content fell as did pH whereas CO2 pressures rose during diving. Oxygen consumption at rest was 124 and 102% of that predicted on the basis of body mass for the beaver and nutria, respectively. Rate of decline of O2 stores during diving decreased by 93% in beavers and 89% in nutria compared to the predive value. Regional blood flow decreased to all organs except the adrenals, heart, and lungs. Blood flow to the brain increased during diving.
Hypothalamic and striatal dopamine receptor activation inhibits heat production in the rat
Authors: Lin M. T. , Chandra A. , Tsay B. L. , Chern Y. F.
Published: December 2017

Direct injection of dopaminergic agonist apomorphine into the lateral cerebral ventricle, the preoptic anterior hypothalamus, the caudate-putamen complex, or the globus pallidus caused hypothermia, decreased metabolism and cutaneous vasoconstriction at ambient temperature (Ta) 8 and 22 degrees C, and hyperthermia and cutaneous vasoconstriction in the rat at Ta 30 degrees C. On the other hand, local injection of dopaminergic antagonists such as haloperidol and pimozide into the preoptic anterior hypothalamus and the striatal nuclei caused hyperthermia, increased metabolism and cutaneous vasoconstriction at Ta 8, 22, and 30 degrees C. However, there was no change in respiratory evaporative heat loss in response to administration of either dopaminergic agonist or antagonists in the rat at all Ta studied. The data indicate that hypothalamic and striatal dopaminergic receptor activation inhibits metabolic heat production in rats. In addition, intrahypothalamic injection of 5-hydroxytryptamine caused hypothermia, decreased metabolism and cutaneous vasodilatation in the rat at Ta 8 and 22 degrees C, whereas at Ta 30 degrees C caused an insignificant change in the thermoregulatory responses. Furthermore, the thermal responses induced by intrahypothalamic injection of apomorphine were not altered by depletion of hypothalamic 5-hydroxytryptamine. These observations do not support the contention that there is a dopamineserotonin link in the hypothalamic pathways that mediate heat loss mechanisms in the rat.
Correlation of muscle activity with glycogen metabolism in muscle of Ascaris suum
Authors: Donahue M. J. , Yacoub N. J. , Harris B. G.
Published: December 2017

Isolated muscle segments from the parasitic roundworm Ascaris suum were shown to contract when perfused with acetylcholine (ACh). The muscle responded to ACh concentrations of 1 microM and was maximally contracted at 50 microM ACh. In fed muscle segments perfused with saturating levels of ACh the glycogen synthase Ka values for glucose 6-phosphate increased from 0.5 to 0.95 mM. In starved segments stimulated by ACh, the muscle utilized glycogen at a rate that was 1.41 micrograms.min-1.g tissue-1 greater than the saline-perfused controls. The cyclic AMP (cAMP) levels remained relatively constant at 0.34 +/- 0.08 nmol/g muscle during perfusion with ACh. Contraction in the muscle could be inhibited in a dose-dependent manner by gamma-aminobutyric acid (GABA). The presence of GABA in starved muscle prevented the decrease in Ka values and phosphorylase activity ratios brought about by glucose. Perfusion of GABA did not change cAMP levels in the muscle. Starved muscle perfused with GABA utilized glycogen at a rate that was 0.41 microgram.min-1.g-1 greater than saline-perfused controls. The results indicated that muscle contraction could be elicited by ACh, and that the energy for this process was derived from endogenous glycogen stores, which were depleted during contraction. Muscle contraction was also correlated with inactivation of glycogen synthase and activation of phosphorylase. These processes appeared to function via a cAMP-independent mechanisms.
Hormonal changes and enforced diving in the harbor seal Phoca vitulina. II. Plasma catecholamines
Authors: Hance A. J. , Robin E. D. , Halter J. B. , Lewiston N. , Robin D. A. , Cornell L. , Caligiuri M. , Theodore J.
Published: December 2017

Plasma epinephrine and norepinephrine concentrations were measured in five harbor seals, Phoca vitulina, during a control period, during a 6-min dive, and during a 30-min postdiving recovery period. Measurements were performed with and without prior glucose administration. Control epinephrine concentrations [189 +/- 118 (SD) pg/ml] and norepinephrine concentrations (340 +/- 191 pg/ml) were similar to resting values in humans. During diving there are dramatic increases in both epinephrine and norepinephrine concentrations, which returned to control values by 30 min of the postdiving recovery period. A similar pattern was found after glucose infusion. The increased catecholamines were not the primary mechanism responsible for arterial constriction during the dive. Persistent diving bradycardia suggests obliteration of the chronotropic effects of catecholamines during the dive. An unchanged stroke volume suggests obliteration of the inotropic effects of catecholamines during the dive. Catecholamines do not appear to be involved in postdiving hyperglycemia and hyperglucogenemia. Neither the regulatory role of increased catecholamines nor the physiological function of increased catecholamines was apparent from the studies. However, dramatic increases in plasma catecholamines during diving appear to be an important component of the hormonal response to prolonged diving in aquatic mammals.
Neural and vascular interaction in renin response to graded renal nerve stimulation
Authors: Ammons W. S. , Koyama S. , Manning J. W.
Published: December 2017

The effect of a 1-min period of renal nerve stimulation was studied in alpha-chloralose-anesthetized cats, whose left kidneys were pump perfused. Renal hemodynamics and filtration parameters were unaltered at stimulation frequencies of 2.0 Hz or less; however, renin secretion rates (RSR) increased with frequency reaching 3 times the control level. At higher frequencies renal vasoconstriction occurred and glomerular filtration rate (GFR) fell. RSR was increased but little more than at 2.0 Hz. The RSR response plots were similar to constant-flow and constant-pressure perfused preparations. beta-Adrenergic blockade with propranolol abolished low-frequency responses and resulted in progressive decreases in RSR at higher frequencies. alpha-Adrenergic blockade with phentolamine prevented renal vascular and GFR changes, whereas RSR continually increased up to 12.0 Hz (13.5 times control). Papaverine treatment, to prevent vascular-GFR changes without blocking alpha-receptors, resulted in similar renin responses. The results indicate that the beta-adrenergic receptor mediates increases in RSR in proportion to frequency when vascular-GFR factors are constant. When renal vasoconstriction occurs at high frequencies the beta-receptor mechanism interacts with an inhibiting mechanism indirectly mediated by alpha-adrenergic receptors.
Prediction of plasma amino acid concentration from diet amino acid content
Authors: Johnson D. J. , Anderson G. H.
Published: December 2017

The level of each plasma amino acid in male weanling rats was examined in relation to their intake from gluten, casein, synthetic amino acid, or zein diets. Plasma levels of valine, leucine, and isoleucine were found to be linearly related to the intake per gram diet regardless of the dietary source. Although levels of most other amino acids were not linearly related to intake, they were predictable if both the concentration of the amino acid in the diet and chronic level of protein intake were known. That is, a relationship, which applied to all diets, was found between the concentration of amino acid in the plasma, the concentration in the diet, and the total protein or amino acid nitrogen in the diet.
Systemic arterial hemodynamics in the diamond python Morelia spilotes
Authors: Avolio A. P. , O'Rourke M. F. , Bulliman B. T. , Webster M. E. , Mang K.
Published: December 2017

Studies of pulsatile systemic arterial hemodynamics were conducted in 10 diamond python snakes to test the hypothesis that body shape--through spatial dispersion of peripheral reflecting sites--is an important determinant of impedance patterns and of pulse wave contour. Findings support the hypothesis. Flow patterns in the aortic roots were similar to those in humans, sheep, dogs, rabbits, and guinea pigs, but in contrast to larger animals, little change in flow contour was seen in other arteries. Pressure wave contour was similar in all systemic arteries from which records were taken with no secondary diastolic wave under any circumstances. Impedance patterns at different sites showed none of the fluctuations that in other animals are attributable to discrete wave reflection. Discrete proximal wave reflection at the confluence of aortic arches was minimal. Data are explicable on the basis of widely distributed peripheral reflecting sites--a consequence of the snake's long and tapered body.
Blood flow in the rectal gland of Squalus acanthias
Authors: Kent B. , Olson K. R.
Published: December 2017

The percent of cardiac output distributed to the rectal gland of 33 free-swimming fish was quantitated by the isotopically labeled microsphere technique. In 21 fish less than 1% was found in the rectal gland; 12 fish had 2-7%, suggesting a pattern of intermittent blood flow. Methylmethacrylate corrosion casts were made for scanning electron microscopy study of the microvasculature. Blood entering the rectal gland artery is distributed via three pathways. The most extensive is along the rectal gland artery into 11 or 12 circumferential vessels, which branch along the capsule and give rise to the radially arranged sinusoids that perfuse the secretory tubules and then join to form the central rectal gland vein. A second is an arterial bypass that runs the length of the rectal gland and joins the circulation of the postvalvular intestine. The third is via arteriovenous anastomoses in the capsule between tightly packed small arteries and veins. The low to moderate blood flow in most rectal glands and the very high flow in others is consistent with the observation that in vivo the rectal gland secretes only intermittently. Blood pathways allowing bypass of the rectal gland parenchyma suggest a role of blood flow in the regulation of the secretory process.
Meaning of the cardiac output-blood volume relationship in essential hypertension
Authors: Chau N. P. , Coleman T. G. , London G. M. , Safar M. E.
Published: December 2017

This study interprets the cardiac output-blood volume relationship in essential hypertension. Previous reports indicated that the chronic volume-flow slope (i.e., the regression coefficient alpha, cardiac output = alpha blood volume + beta, obtained from steady-state volume and flow) and the transient volume-flow slope observed during a dextran infusion were both steeper in essential hypertensives than in normotensives. By applying the Guyton-Coleman circulatory model to essential hypertension, this reports demonstrates that: 1) several alterations of the circulatory system may theoretically change the steady state of volume and flow and generate a chronic volume-flow relationship. However, only alterations of the kidney function and of the autonomic nervous system may produce a volume-flow curve compatible with the available data. 2) As hypertension develops, vascular resistance and compliance have the greatest influence on the slope of the chronic volume-flow curve. 3) To account for the observed increase of this slope in the transition from normotension to essential hypertension, not only must resistance be increased but also compliance must be reduced in essential hypertension. The same conclusions are drawn from the study of the transient volume-flow relationship observed during the dextran infusion.
Liver glycogen content decreases during meals in rats
Authors: Langhans W. , Geary N. , Scharrer E.
Published: December 2017

The effects of feeding on liver glycogen content and blood glucose in the hepatic and hepatic portal veins were investigated in rats. Liver glycogen content decreased about 25% during meals both in rats refed after 12 h food deprivation (23 +/- 1 to 17 +/- 1 mg glycogen/g liver) and in ad libitum-fed rats taking fully spontaneous meals (44 +/- 2 to 32 +/- 2 mg/g). Liver glycogen began to increase within 30 min after meals in ad libitum-fed rats. Hepatic vein blood glucose levels at meal onset (118 +/- 4 mg/dl in the food-deprived rats, 127 +/- 4 in ad libitum-fed rats) and at meal end (155 +/- 3 and 166 +/- 5 mg/dl, respectively) were similar in the two groups. Portal vein blood glucose increased during meals in the previously food-deprived rats (83 +/- 4 to 116 +/- 6 mg/dl) but not in the ad libitum-fed rats (127 +/- 5 to 132 +/- 3 mg/dl). Mechanisms that may elicit prandial glycogenolysis and the possible role of this effect in the production of meal ending satiety are discussed.
Effect of synaptic blockade on thermosensitive neurons in hypothalamic tissue slices
Authors: Kelso S. R. , Boulant J. A.
Published: December 2017

To understand the basis of hypothalamic neuronal thermosensitivity, single-unit activity was recorded in vitro, from constantly perfused tissue slices of rat preoptic area and anterior hypothalamus, PO/AH. The firing rate and thermosensitivity of individual PO/AH neurons was determined before, during, and after tissue perfusion with a synaptic blocking medium, containing elevated magnesium and decreased calcium concentrations. During synaptic blockade, thermosensitivity was retained in nearly all of the warm-sensitive neurons, and some temperature-insensitive neurons showed increased warm sensitivity. The thermosensitivity of all cold-sensitive neurons was lost during synaptic blockade. These results support the hypothesis that PO/AH cold-sensitive neurons depend on synapses from nearby warm-sensitive neurons for their temperature sensitivity; whereas warm sensitivity is an independent property of certain PO/AH neurons.
Thirst and solute excretion: their effectiveness in osmostatic control of body fluid
Authors: Szczepanska-Sadowska E. , Niewiadomski W. , Sobocinska J. , Kozlowski S.
Published: December 2017

The effect of intravenous infusion of hypertonic NaCl at three different rates (series I, 4.0 mmol/min; series II, 8.0 mmol/min; series III, 16.0 mmol/min) on osmotic thirst threshold and postloading restitution of plasma osmolality (Posm) has been determined in dogs. Osmotic thirst threshold increased proportionally to the rate of delivery of the osmotic load. Relative suppression of osmotic thirst at the higher rates of infusion was temporary and largely disappeared within 10 min after the end of hypertonic infusion. During the postloading period excretion of osmotic load and water intake was proportional to the magnitude of the load administered. However, the animals with high osmotic thirst threshold stopped drinking at a higher Posm than those with a low osmotic thirst threshold. In series I and II, Posm decreased during 1 h to a level not significantly different from the preloading value. In each series renal excretion of osmotic load was more important than water intake for restitution of Posm during 1 h. Amount of water ingested during this period was significantly smaller than that theoretically required to restore resting Posm when excretion of osmotic load was not taken into account. However, total amount of water intake and osmotic load excreted during 1 h were together well adjusted to restore preloading Posm.
Release of tonin and of kallikrein by perfused rat submaxillary gland
Authors: Garcia R. , Thibault G. , Gutkowska J. , Genest J.
Published: December 2017

The release of tonin and kallikrein was investigated in the venous effluent of the perfused rat submaxillary gland (SMG). The SMG was perfused through the common carotid artery after all branches except the SMG artery had been ligated. The venous outflow was collected from the SMG vein. The contralateral nonperfused gland was used as control. The infusion of isoproterenol increased tonin release without affecting its concentration in the SMG. Theophylline increases both tonin secretion and tonin concentration in the SMG. These results suggest that beta-adrenergic stimulation enhances tonin release by increasing synthesis in the SMG, and that these effects might be mediated by cAMP. The infusion of norepinephrine did not affect either tonin release or tonin concentration in the gland. Kallikrein release was significantly increased by norepinephrine, isoproterenol, and theophylline. However, whereas alpha-stimulation produced a significant decrease in kallikrein concentration in the stimulated SMG, beta-adrenergic and theophylline stimulation produced no significant changes in tissue kallikrein. These results suggest that alpha-adrenergic stimulation increases kallikrein release by depleting the enzyme from the gland, whereas beta-adrenergic stimulation might increase kallikrein release by stimulating its synthesis in the gland.
Effects of dietary sodium restriction on heart rate control in rats
Authors: Bush E. N. , Vollmer R. R.
Published: December 2017

The effects of dietary sodium restriction on heart rate control were evaluated in male Wistar rats maintained for 4 wk on a low- (22 meq/kg diet) or standard (141 meq/kg diet) sodium diet. In conscious low-sodium rats, atropine produced heart rate increases greater than in standard sodium animals, indicating that basal parasympathetic tone was elevated. Sodium restriction did not affect basal sympathetic tone, since similar reductions in heart rate were produced by propranolol in both dietary groups. However, sympathetically mediated tachycardic responses to sodium nitroprusside were augmented in low-sodium rats. This enhancement of sympathetic function was also observed in low-sodium animals after pithing. The increases in heart rate produced by spinal sympathetic stimulation were significantly accentuated; whereas, responses to norepinephrine were not affected by the diets. This finding is in agreement with the observation that the chronotropic responses elicited by isoproterenol in isolated atria were not altered. When neuronal influences on heart rate were blocked by combined administration of atropine and propranolol or chlorisondamine in conscious rats, the underlying intrinsic cardiac rate was found to be significantly higher in low-sodium rats. In summary, the present study identifies three effects of sodium restriction on heart rate control in the rat: 1) basal parasympathetic tone is increased, 2) heart rate responses to sympathetic activation are enhanced, and 3) the intrinsic cardiac rate is elevated.
Interactions between baroreceptor and sympathetic pathways
Authors: McCall R. B. , Humphrey S. J.
Published: December 2017

The interactions between baroreceptor and sympathetic pathways were determined in anesthetized cats using computer summation techniques. Electrical stimuli applied to baroreceptor afferent nerves produced an early and late period of inhibition of sympathetic nervous discharge (SND) recorded from the external carotid or inferior cardiac nerves. The late period of baroreceptor-induced inhibition summated algebraically with the cardiac-locked slow wave of SND during all phases of the cardiac cycle. Increases in the intensity of baroreceptor stimulation resulted in an increase in the amplitude and duration of the late inhibition. Alterations in the periodicity of SND failed to effect the late phase of inhibition. Picrotoxin blocked the late period of baroreceptor-induced inhibition but enhanced the cardiac locking of SND. These data indicate that the late period of inhibition reflects the ability of afferent nerves to modulate the amplitude of central sympathetic outflow, regardless of its periodicity. In addition, the central baroreceptor pathways involved in amplitude modulation and temporal locking of SND to the cardiac cycle are distinct and are located at the level of the brain stem. A spinal component of baroreceptor-induced sympathoinhibition is also described.
Theoretical analysis of "metabolic indices" of blood buffer system
Authors: Sato T. , Ikeda N. , Tsuruta H. , Shirataka M.
Published: December 2017

The well-known base excess (BE) and buffer base (BB) curves of Siggaard-Andersen's nomogram are based on their empirical finding that the blood buffer lines in the pH-log PCO2 coordinates with the same BE (or BB) always pass through a single point irrespective of the hemoglobin concentration. We have analytically derived the BE and BB curves on the assumption of a two-compartmental model of blood buffer system comprised of plasma and red blood cells. These hyperbolic functions of BE and BB curves fitted the Siggaard-Andersen's observation very well. The simple formulas derived from the buffer equation with the parameters obtained on the least-square basis were shown to estimate “metabolic indices” of blood as accurately as the computer reading of the nomographic curves. These results seem to indicate that the buffer equation based on the two-compartmental model describes the acid-base status of blood satisfactorily, and that it can entirely replace the Siggaard-Andersen's nomogram.
Weaning in the rat: a study of hormonal influences
Authors: Blake H. H. , Henning S. J.
Published: December 2017

The control of weaning was studied in rat pups aged 17-24 days. The influence of two hormones, thyroxine (T4) and corticosterone, and the effect of declining intestinal lactase activity were evaluated. Hypothyroidism was induced by administration of n-propylthiouracil and hyperthyroidism was induced by injection of T4. Hypothyroid pups failed to begin nibbling chow while littermates injected with T4 weaned normally. Two abnormalities resulting from hypothyroidism, hypothermia and stunted incisors, were not responsible for the lack of weaning in hypothyroid pups. Hyperthyroidism did not cause precocious weaning. Glucocorticoid levels were manipulated by both adrenalectomy (ADX) and administration of corticosterone. ADX pups exhibited a delayed pattern of weaning while both ADX pups injected with corticosterone and sham-operated pups weaned normally. Corticosterone injected before its normal developmental surge did not cause precocious weaning. Lactase activity, measured throughout these experiments, did not consistently reflect the degree of weaning progression. We conclude that 1) the hormones, T4 and corticosterone, are necessary for the onset of weaning, but neither is a sufficient stimulus to initiate weaning, and 2) low lactase activity does not initiate weaning.
Role of similarity principles in data extrapolation
Authors: Rosen R.
Published: December 2017

This paper addresses the problem of extrapolating from data set gathered on a particular system to problems of more general physiological interest. It asks: what are the limits of the extrapolability of data? Under what circumstances can data derived from a particular system be transformed into data about another, different system? Such questions address the general problem of similarity analysis. A mathematical exploration of the meaning and usefulness of the concept of similarity is presented, and the necessity for a "prototype" is introduced. The discussion shows what we mean by the relationship between natural systems and the purest form of model of such systems, the mathematical model. The value and limitations of Dimensional Analysis are considered. It is concluded that the principle of dimensional homogeneity which underlies Dimensional Analysis is not strong enough to cope effectively with situations involving many phases, as arise in biological studies. Therefore, a more general approach is used. It is shown that the problems associated with data extrapolation are very deep and lead to some of the deepest issues in all of science. The extrapolation of data from animal models to human beings has been a general characteristic of pharmacologic research and, for that matter, biomedical investigations generally. Attention to limitations and dangers of such extrapolations seems overdue. With proper understanding of the essential nature of the extrapolatory action, and modeling relations, models can be validated.
Temperature dependence of the hamster circadian pacemaker
Authors: Gibbs F. P.
Published: December 2017

Blind male hamsters were maintained in running-wheel cages in a LD 12:12 light-dark cycle. After regular running patterns were established hypothermia was induced by ether anesthesia, wetting of the fur with ethanol, and cooling with ice. The hamsters were kept hypothermic for 3-24 h at colonic temperatures from 10 to 20 degrees C. Following hypothermia the animals were rewarmed and replaced in their home cages. Examination of the locomotor activity records showed phase shifts (delays) in activity onset that were correlated with the temperature and duration of the hypothermia but not with the circadian time at which the hypothermia was administered. The data were interpreted to mean that the circadian pacemaker was running at a reduced rate during the hypothermic bout. Calculation of the Q10 for the rate of the clock during hypothermia produced a range from 1.08 to 1.34 depending on the method of calculation. When compared with earlier data gathered from rats under similar conditions, the hamsters circadian pacemaker appears to be better temperature compensated.
Dual mechanism for catecholamine secretion in the dogfish shark Squalus acanthias
Authors: Opdyke D. F. , Bullock J. , Keller N. E. , Holmes K.
Published: December 2017

Both 1,1-dimethyl-4-phenylpiperazinium iodide, a ganglionic stimulating drug (DMPP), and potassium ion (K+) cause a pressor response when injected into Squalus acanthias, an elasmobranch. The pressor responses are due to increased secretion of epinephrine and norepinephrine. The pressor response to DMPP can be blocked by prior infusion of hexamethonium, a ganglionic blocking drug. However, ganglionic blockade does not inhibit the pressor response to K+. Plasma catecholamine concentrations do not increase significantly in response to challenge with DMPP after hexamethonium infusion, but exceedingly high levels of plasma catecholamines quickly appear after K+ injection following hexamethonium infusion. It is concluded that there are at least two mechanisms controlling catecholamine secretion in the dogfish, one of which involves the ganglion cells that are intimately associated with chromaffin cells in the chromophil bodies that are so characteristic of this species and elasmobranchs in general.
Electrophysiological study on nervous pathway from splanchnic nerve to vagus nerve in rat
Authors: Niijima A.
Published: December 2017

Action potentials evoked by the stimulation of the hepatic branch of the splanchnic nerve were recorded from the peripheral cut end of the dorsal celiac branch of the vagus nerve in the rat. Action potentials were clearly demonstrated after averaging over 100 times by a computer. The observations indicate the existence of a nervous pathway from the hepatic branch of the splanchnic nerve to the dorsal celiac branch of the vagus nerve in the rat.
Neonatal hyperthyroidism: effects on sympathetic responses to stress in adult rats
Authors: McCarty R. , Kirby R. F. , Brunjes P. C.
Published: December 2017

Treatment of developing rats with thyroid hormone results in accelerated maturation of sympathetic and adrenal medullary responses to reflex activation of central sympathetic outflow. In this study, we examined the effects of neonatal hyperthyroidism on the responsiveness of the sympathetic nervous system of adult rats to acute stress. Hyperthyroidism was produced in Long-Evans hooded rats by injections of thyroxine (neo-T4, 1 mg/kg body wt) on postnatal days 1-4. Littermate controls received injections of vehicle only. In adulthood, male rats of the two groups were prepared with chronic tail artery catheters to allow repeated sampling of blood and direct measurements of mean arterial pressure (MAP, mmHg) and heart rate (HR, beats/min). Two days after surgery, rats were stressed by exposure to 1 min of inescapable foot shock (2.0 mA, 0.6-s duration, every 6 s). The activity of the sympathetic nervous system was assessed by measuring plasma levels of norepinephrine (NE) and epinephrine (E). Basal plasma levels of NE and E and resting MAP did not differ between neo-T4 and control rats. However, basal HR was elevated in neo-T4 rats. Footshock-induced increments in plasma levels of both catecholamines were greater in neo-T4 compared with control rats even though behavioral responses to footshock were similar across groups. However, neo-T4 rats were more active when tested in an open field on each of 3 consecutive days. These findings indicate that neonatal treatment with T4 results in hyperresponsiveness of the sympathoadrenal medullary system to acute stress that persists into adulthood.
Mechanisms of control of milk intake in suckling rats
Authors: Cramer C. P. , Blass E. M.
Published: December 2017

To reconcile reported differences in the development of internal controls over milk intake via suckling, infant rats 5-20 days of age were allowed to withdraw milk from anesthetized dams periodically induced to let down milk by intravenous infusion of oxytocin. In experiment 1, milk supply was made unlimited by providing pups with a series of milk-replete dams. Five- and ten-day-old pups withdrew inappropriately large volumes of milk, whereas 15- and 20-day-old pups limited intake to moderate volumes. In experiment 2, intake of deprived and nondeprived pups was measured after only 10 oxytocin-induced milk letdowns, comparable to the normal nursing bout. When milk availability was thus limited, pups of all ages consumed volumes of milk dependent on their level of deprivation. Moreover intake of pups 10-20 days of age was highly correlated with incidence of nipple shifting. Thus rats as young as 5 days of age can vary the rate at which milk is taken from a limited source; however, not until 15 days are they able to control the volume withdrawn from an unlimited source.
Effects of training on cardiorespiratory function in the horse
Authors: Thomas D. P. , Fregin G. F. , Gerber N. H. , Ailes N. B.
Published: December 2017

The effects of 5- and 10-wk treadmill exercise training on cardiorespiratory function were evaluated in the horse. Cardiac output (Q), heart rate (HR), and stroke volume (SV), as well as left ventricular (LVP), aortic (AoP), and mean right atrial (RAP) pressures and the peak first time derivative of LVP (LV dP/dtmax), were measured at rest and at five different levels of exercise up to 90% of initial predicted maximal HR (HRmax). Oxygen uptake (VO2) and respiratory exchange ratio (R) were also obtained under the same conditions. At rest, although HR was no different after training, LV dP/dtmax was lower at 10 wk (2,369 +/- 502 vs. 1,615 +/- 302 mmHg/s). At the different measured work loads during exercise, Q and VO2 remained unchanged with training, whereas there were consistent trends toward lower LVP, AoP, and LV dP/dtmax and significant reductions in HR and R (both P less than 0.05). In contrast, SV and mean RAP were elevated (P less than 0.05) during exercise after the 10-wk training program. Although the observed changes in cardiorespiratory function in response to a training program in the horse are generally similar to those reported for other species, our data also suggest a training-induced increase in venous pressures during exercise as measured by elevated mean RAP values.
Renal hemodynamic actions of angiotensin II: interaction with tubuloglomerular feedback
Authors: Hall J. E. , Granger J. P.
Published: December 2017

The present study was designed to investigate the importance of interactions between angiotensin II (ANG II) and other intrinsic control mechanisms, including tubuloglomerular feedback (TGF), in controlling renal hemodynamics. When endogenous ANG II formation was blocked by SQ 14225 infusion and changes in myogenic activity were minimized by servo controlling renal arterial pressure, ANG II infusion (20 ng . kg-1 . min-1 iv) did not change glomerular filtration rate but decreased renal blood flow (RBF) from 286 +/- 36 to 179 +/- 31 ml/min due to increases in calculated preglomerular (54%) and efferent (100%) arteriolar resistances. After inhibition of TGF by occluding the ureter during mannitol diuresis, ANG II infusion (20 ng . kg-1 . min-1) decreased RBF from 229 +/- 25 to 151 +/- 19 ml/min while increasing glomerular hydrostatic pressure (calculated from ureteral stop-flow pressure and plasma colloid osmotic pressure) from 56.7 +/- 2.5 to 62.3 +/- 2.2 mmHg. Postglomerular resistance increased to 173 +/- 17% of control, but preglomerular resistance did not change significantly during ANG II infusion after inhibition of TGF. These data suggest that the direct renal vasoconstrictor action of ANG II is confined mainly to postglomerular vessels and that changes in preglomerular resistance that occur when ANG II levels are inappropriately elevated in normal animals are caused by other intrinsic control mechanisms, such as TGF.
Duodenal osmoconcentration and food intake in pigs after ingestion of hypertonic nutrients
Authors: Houpt T. R. , Houpt K. A. , Swan A. A.
Published: December 2017

Samples were taken from the duodenum of young pigs via indwelling catheters after ingestion of liquid meals. They had been deprived of feed and water overnight. Samples were taken every minute for 15 min and then at 20, 25, 30, 40, 50, and 60 min. After ingestion of hypertonic glucose solutions, duodenal osmolality rose rapidly to maximal levels within 10-15 min when osmoconcentrations were as follows: for 10% glucose, 480 mosmol/kg H2O; for 20%, 680; and for 40%, 1,200. After 5% glucose, osmolality was about 280 mosmol/kg H2O and did not change appreciably during the hour. Water ingestion caused a fall to 60 mosmol/kg H2O at 3 min and then a slow recovery. Ingestion of glucose-in-milk solutions gave similar but slightly higher values. When the glucose-in-water or -milk solutions were ingested just before a meal of feed pellets, meal size was depressed proportional to glucose concentration.
Effect of clorgyline (a MAO type A inhibitor) on locomotor activity in the Syrian hamster
Authors: Tamarkin L. , Craig C. J. , Garrick N. A. , Wehr T. A.
Published: December 2017

Syrian hamsters in a lighting schedule of 14 h of light per day (LD 14:10) and housed in cages equipped with running wheels exhibited a clear onset of locomotor activity during the 1st h after lights off. Implantation of osmotic minipumps containing clorgyline (2 mg . kg-1 . day-1), an irreversible inhibitor of monoamine oxidase type A, caused a 1.5-h delay in the onset of wheel running by the 7th day of treatment. Increasing dosages of clorgyline (0.5, 1, 2, or 4 mg . kg-1 . day-1) caused increasing delays. Hamsters shifted from LD 14:10 to LD 10:14 underwent a 3-h advance in the onset of wheel running. Animals treated with clorgyline (2 mg . kg-1 . day-1) exhibited a markedly slowed rate of advance in activity onset, which did not prevent the short photoperiod from inhibiting reproductive function. Additionally, removal of the pineal gland did not affect wheel-running onset and did not prevent the delay in activity onset during clorgyline treatment. Hamsters in LD 14:10 were "released" into constant darkness (DD) for 3 days to prevent masking of activity onsets and offsets by light. Delays in activity onset in LD 14:10 caused by clorgyline (2 mg . kg-1 . day-1) persisted when these animals were released into DD. Activity offset in LD 14:10 occurred at lights on before and during clorgyline treatment but was delayed when the treated animals were maintained in DD. Drug-induced delays in both activity onset and offset suggest that clorgyline is not simply shortening the duration of activity or changing the expression of activity relative to the light-dark cycle, but is delaying the phase position of the circadian rhythm in locomotor activity. Clorgyline may act directly on the central oscillatory mechanism that drives the rhythm.
Regulatory aspects of Na+ transport in complex epithelia (frog skin)
Authors: Huf E. G. , Mikulecky D. C.
Published: December 2017

In the multilayered epithelial membranes, topological factors, in addition to factors operating in cell units, must be considered in the regulation of ion transport. One such factor, i.e., the role of cell-to-cell junctions as regulators, is considered in the present computer simulation study. The primary aim was to correlate electron microprobe data on cellular Na+ pool sizes of frog skin with well-known rates of transepidermal Na+ influx and efflux under several laboratory conditions, including single or combined application of ouabain and amiloride. A complete kinetic analysis of data obtained on a simplified multicompartmental model of the epidermis suggests, on purely topological grounds, the occurrence in the epidermis of multiple physiological steady states in which Na+ is pumped transepidermally at equal rates but associated with very different states of intercellular Na+ flow dynamics. The possible significance of these multiple states for the understanding of the responses of the epidermis to perturbing influences is discussed.