bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of sodium chloride intake by rats
Authors: Fregly M. J. , Harper J. M. , Radford E. P.
Published: December 2017

Regulation of NaCl intake was studied in rats by allowing them choice between distilled water and a NaCl solution to drink during experiments in which food was loaded with NaCl to levels of 6% by weight. The level of dietary NaCl failed to influence spontaneous intake of NaCl solutions but increased water intake in proportion to the concentration of NaCl in food. Increases in the concentration of NaCl solution offered to rats whose food was salt loaded resulted in proportional decreases in volume intake of NaCl solution such that total amount of sodium ingested by way of NaCl solution was maintained at 1.3–1.5 mEq/100 g body wt per day. The results suggest, but do not prove, that NaCl intake is "regulated" by way of NaCl in solution rather than by way of NaCl in food. The mechanism regulating NaCl intake is separate from that regulating water intake and appears to be located somewhere within either the mouth or pharyngeal region or both. Bypass of these regions by intraperitoneal injection of saline failed to alter the pattern of spontaneous NaCl intake of rats.
Alterations in gastric secretion following hypothalamic lesions producing hyperphagia
Authors: Ridley Peter T. , Brooks Frank P.
Published: December 2017

Fasting gastric secretion and secretion during insulin hypoglycemia were collected from hypothalamic hyperphagic rats equipped with chronic gastric fistula in an attempt to correlate the hypothalamic neural mechanisms controlling food intake with gastric secretion. The interdigestive or basal fasting secretion of rats rendered hyperphagic by stereotaxic ablation of the ventromedial nuclei was significantly increased in volume, acid concentration and output, and pepsin output when compared with control and sham-operated rats and rats with hypothalamic lesions without hyperphagia. Hypothalamic hyperphagic rats did not show a significant increase in gastric secretion during insulin hypoglycemia, whereas the other groups did. The levels of hypoglycemia induced by insulin were comparable in all groups. These studies suggest an important role of the ventromedial nuclei in the central regulation of acid and pepsin secretion, and also relate the hypothalamic neural control of gastric secretion to that of food intake. The results also indicate that this nucleus is involved either as a "center" or pathway in the augmentation of gastric secretion by insulin hypoglycemia.
Venous and arterial responses to stimulation of beta adrenergic receptors
Authors: Abboud Francois M. , Eckstein John W. , Zimmerman Ben G.
Published: December 2017

The effects of intra-arterial injections of isoproterenol on small vessels, arteries, and veins were studied in the paw and muscle of the foreleg of dog. Total blood flow to the foreleg was held constant. Blood pressures were measured in large and small arteries and veins. In some experiments venous outflow from paw and muscle was measured. The small vessel segment was the site of major dilatation. Venodilator responses were small, but they were enhanced when isoproterenol was injected in the presence of venous constriction induced by intra-arterial infusions of norepinephrine. Dichloroisoproterenol and nethalide blocked the dilator responses to isoproterenol in all segments but they did not block the dilator responses to acetylcholine or glyceryl trinitrate. Isoproterenol did not change the distribution of blood flow within the foreleg; responses in muscle and paw were not significantly different. The results indicate that stimulation of beta receptors with isoproterenol causes much more dilatation in small vessels than in veins in the foreleg and that small vessels of both paw and muscle dilate equally.
Mechanism of circulatory responses to systemic hypoxia in the anesthetized dog
Authors: Kontos Hermes A. , Mauck H. Page , Richardson David W. , Patterson John L.
Published: December 2017

The possibility that mechanisms secondary to the increased ventilation may contribute significantly to the circulatory responses to systemic hypoxia was explored in anesthetized dogs. In 14 spontaneously breathing dogs systemic hypoxia induced by breathing 7.5% oxygen in nitrogen increased cardiac output, heart rate, mean arterial blood pressure, and femoral arterial flow, and decreased systemic and hindlimb vascular resistances. In 14 dogs whose ventilation was kept constant by means of a respirator pump and intravenous decamethonium, systemic hypoxia did not change cardiac output, femoral arterial flow, or limb vascular resistance; it significantly decreased heart rate and significantly increased systemic vascular resistance. In seven spontaneously breathing dogs arterial blood pCO2 was maintained at the resting level during systemic hypoxia. The increase in heart rate was significantly less pronounced but the other circulatory findings were not different from those found during hypocapnic hypoxia. Thus, mechanisms secondary to increased ventilation contribute significantly to the circulatory responses to systemic hypoxia. Hypocapnia accounts partly for the increased heart rate, but not for the other circulatory responses.
Action of 2-deoxy-D-glucose on frog gastric mucosa
Authors: Sachs George , Shoemaker R. , Hirschowitz B. I.
Published: December 2017

2-Deoxyglucose (2-DG) has been found to inhibit chloride and acid secretion by the in vitro frog mucosa, with a fall in short-circuit current and potential difference and a rise in resistance. The ATP levels and phosphohexoisomerase activity were essentially unchanged following 2-DG treatment. 3-Methyl-O-glucose uptake was reduced by about 50% following preincubation with 2-DG. The O2 consumption was only slightly reduced with 10 mmoles 2-DG, but the CO2 ratio from glucose-6-C14/glucose-1-C14 fell from 0.98 to 0.37, indicating activation of the hexosemonophosphate (HMP) shunt.
Comparison of rat salivas evoked by auriculo-temporal and pilocarpine stimulation
Authors: Schneyer C. A. , Hall H. D.
Published: December 2017

Stimulation of rat parotid gland by way of the auriculotemporal nerve was used to delineate the relationship between flow rate and concentration of Na and K in the saliva. It was found that [Na] increased with increasing flow rate, whereas [K] hardly changed. Comparison of the electrolyte composition of saliva evoked by supramaximal stimulation of the nerve with that evoked by supramaximal doses of pilocarpine showed only small differences in [Na] and [K], and these were attributable to differences in flow rate. On the other hand, levels of amylase activity and total protein were 5–20 times higher in pilocarpine-evoked saliva than in saliva obtained by stimulation of the auriculotemporal nerve; these differences could not be attributed to differences in flow rate. Pilocarpine is, therefore, an adequate substitute for stimulation of the parotid gland by the parasympathetic nerve if only electrolytes and flow rate are considered, and is not a satisfactory substitute when the protein and amylase activity are considered.
Descending respiratory pathways in the medulla oblongata of the cat1
Authors: Kahn Norman , Wang S. C.
Published: December 2017

Midsagittal sections of the medulla oblongata, extending between levels 3–4 mm caudal to 2–6 mm rostral to the obex, were made in 29 midcollicular decerebrate cats. Respiratory activity was recorded by monitoring spontaneous ventilatory movements in cats breathing air or phrenic nerve potentials in cats immobilized with gallamine and artificially ventilated with 95% O2-5% CO2. Midline sections produced definite changes in the rate and depth of respiration and of the phrenic nerve discharge, but cessation of respiratory activity was not usually seen. Despite these alterations in the spontaneous nerve activity, it was possible to elicit, with stimulation of a point in the medullary reticular formation, a marked sustained discharge of the homolateral phrenic nerve. The changes in the spontaneous respiratory pattern probably resulted from disturbances of the neural structures responsible for the genesis of rhythmic respiration rather than of the motor pathways. It is concluded that the efferent respiratory pathways descend from the medulla oblongata into the spinal cord predominantly uncrossed.
Hereditary obesity and hormone deficiencies in yellow dwarf mice
Authors: Wolff George L.
Published: December 2017

Daily injection of 0.05 USPU of ovine growth hormone had no effect on greater fat deposition in yellow dwarf ( Ayadwdw) mice of either sex as compared with nonyellow dwarf mice ( aadwdw). No differences between the accelerated growth rates of both genotypes during the injection period were noted nor were there any marked differences in the increase in tail length between the genotypes. Yellow dwarf mice continued gaining weight more rapidly than nonyellow dwarf mice after the end of the injection period. Analysis of the fat and water content of the carcasses indicates that the greater rate of weight gain of yellow dwarf mice is due almost entirely to increased fat deposition. The results of this experiment suggest that the obesity of yellow mice is not due to deficiencies of growth hormone or thyrotrophin.
Effect of angiotensin on maximal tubular transport of PAH and glucose in dogs
Authors: Healy John K. , Barcena Carlos , Schreiner George E.
Published: December 2017

Although the physiological actions of angiotensin have attracted considerable interest, its effects on the maximal renal tubular transport rates for p-aminohippuric acid (PAH) and glucose (Tmpah and Tmg) have not previously been described in any species. This study therefore comprised an examination of Tmpah at three dose levels and Tmg at two dose levels of angiotensin. The Tm of neither substance was reduced. In the course of the experiments, glucose was found to elevate control PAH clearance measurements and to offer some protection against the renal vasoconstrictive effect of angiotensin. It was concluded that angiotensin does not cause focal renal cortical deprivation of blood flow, nor does it interfere with the tubular transport of PAH or glucose. Other aspects of the renal response to angiotensin are altered by glucose.
Factors affecting distribution of iodide in brain and cerebrospinal fluid
Authors: Reed Donal J , Woodbury Dixon M. , Jacobs Lyle , Squires Russell
Published: December 2017

The effects of acetazolamide, sodium perchlorate, ouabain, and of iodide loading on the processes controlling I131 and inulin-C14 distribution in the brain and CSF were studied in nephrectomized rats. It was observed that the first three drugs increased the concentration of both iodide and inulin in the brain and CSF after intracisternal administration of the tracers. It was concluded that acetazolamide reduced the rate of formation and flow of CSF, that perchlorate primarily decreased active iodide transport, and that ouabain slightly reduced CSF formation and flow. Iodide loading increased the CSF/plasma iodide ratio, expressed as percent (CSF iodide space), from 1.97 to 42.17, and the comparable values for brain were 2.02 and 11.76, respectively. The results suggest that the primary factors in the control of iodide distribution in the CNS are the following: 1) an active iodide transport system between CSF and blood, 2) limited permeability to iodide of the structures between blood and CSF and between blood and brain, and 3) relatively free diffusion of iodide between brain and CSF.
Comparison of subcutaneous and intravenous administration of pancreatic stimulants
Authors: Preshaw R. M. , Grossman Morton I.
Published: December 2017

In conscious dogs with permanent gastric and pancreatic fistulas, the response to single injections of extracts of mucosa of the gastrointestinal tract by intravenous and subcutaneous routes was compared. Both crude and highly purified secretin preparations were weak stimulants of the pancreas by subcutaneous administration, in contrast to the large effect of the same doses given intravenously. An extract containing pancreozymin was effective in causing increased protein secretion by the pancreas by both routes of injection. Gastrin stimulated pancreatic volume flow by subcutaneous administration but not by intravenous administration, in contrast to secretin. This indicates that crude extracts of the mucosa of the pyloric gland area of the hog do not contain enough secretin to be easily detectable. Attempts to show that supramaximal doses of secretin, pancreozymin, and gastrin exhibit self-inhibitory properties when tested on pancreatic secretion were unsuccessful, although self-inhibition of gastrin-stimulated gastric secretion was confirmed.
Corticosterone secretion in rats as a function of ACTH input and adrenal blood flow
Authors: Porter John C. , Klaiber M. S.
Published: December 2017

The rate of secretion of corticosterone from the left adrenal of rats receiving a constant input of ACTH was determined for different flows of blood through the adrenal during the 2- to 3-hr interval following hypophysectomy. Two hours after hypophysectomy the secretion of corticosterone was low in all groups regardless of flow. An input of 0.26 mU ACTH/min caused a steady increase in secretion for 30–40 min before a steady-state rate was attained. The average steady-state rate of secretion was 1.1, 2.4, 3.5, 6.2, 7.2, 6.2, and 6.2 µg/5 min for flows of 0.005, 0.012, 0.023, 0.034, 0.039, 0.051, and 0.058 ml/min, respectively. Under the conditions of these experiments where the input of ACTH was 0.26 mU/min the secretion of corticosterone increased significantly with time of input of ACTH and with flow of blood through the adrenal.
Effect of renal arterial pressure on the stop-flow sodium minimum
Authors: Wilkins James W. , Greene James A. , Weller John M.
Published: December 2017

An increase in renal perfusion pressure in the rat and dog elevates the stop-flow distal sodium minimum concentration. The following studies were done to define the mechanism of this change. Dog kidneys were perfused at selected pressures during stop flow. The sodium minimum concentration changed 0.8 mEq Na/liter urine for each 10 mm Hg change in perfusion pressure. This was not modified by infusion of angiotension II. Ureteral pressure varied directly with perfusion pressure. The point of maximum PAH secretion showed proximal displacement with increased perfusion pressure. The entrance of postocclusive filtration markers into more distal samples increased with elevated perfusion pressure. It is concluded that the increase in distal sodium minimum concentration occurring with increased perfusion pressure is probably due to an increase in filtration, intratubular pressure, and tubular dilatation, causing stop-flow distal sodium minimum concentration to equilibrate at a higher level.
Lipoprotein lipid transport by livers from normal and CCl4-poisoned animals
Authors: Heimberg Murray , Weinstein Ira , Dishmon Guinn , Fried Melvin
Published: December 2017

Triglyceride release by livers isolated from normal fed animals has been shown previously to be stimulated by the addition of palmitate to the perfusate. It may be concluded from the data reported herein that the output of cholesterol and phospholipid into the d < 1.006 lipoprotein class is proportional to release of triglyceride into this fraction. Triglyceride, cholesterol, and phospholipid may be secreted in constant proportion in order to maintain a physical-chemical stability and solubility of the very low density lipoprotein whose primary function is transport of triglyceride from liver to extrahepatic tissues. CCl4, which inhibits triglyceride release by the liver, also inhibits output of cholesterol and phospholipid into the d < 1.006 lipoprotein. Release of cholesterol into the d < 1.063 lipoprotein is not clearly related to non-esterified fatty acid levels in the medium, to triglyceride release by the liver, or to other lipids present in this fraction. The serum lipoprotein class containing the largest initial concentration of any lipid is not necessarily identical with the fraction having the major net hepatic release of that lipid. Thus, each lipoprotein class released may have specific and different lipid carrier functions.
Some sensory influences on savage (affective) behavior in cats
Authors: Kaelber William W. , Mitchell Clifford L. , Way John S.
Published: December 2017

Since it is well established that cats rendered "savage" following bilateral lesions in the ventromedial hypothalamic nuclei manifest this type of behavior only when an external stimulus, e.g., tactile, auditory, or visual, is directed at them, a study was made of the degree to which some of the long ascending sensory systems participate in this phenomenon. After the hypothalamic lesions were made and the animals exhibited such adverse behavior, they were subjected to secondary bilateral lesions of the medial lemniscus and spinothalamic tracts in the lateral mesencephalic tegmentum. It was found that following destruction of these tracts (including part of the magnocellular division of the medial geniculate bodies) most animals no longer responded to external stimuli with the somatic and autonomic manifestations that characterize "rage," or that such responses were extremely altered and fragmentary.
Relationship of blood pressure to renal concentrating defect in hemorrhagic shock
Authors: Wright Hastings K. , Gann Donald S.
Published: December 2017

The osmolalities of renal papillary and cortical tissue extracts, urine, and peripheral plasma were measured in Pitressin-loaded dogs in hemorrhagic shock after 1 hr of anuria. The excretion of urine during hypotension was induced by an infusion of mannitol. After 1 hr of anuria at 60 mm Hg mean blood pressure, the renal papilla, cortex, peripheral plasma, and urine were essentially isoosmotic. After 1 hr of anuria at 40 mm Hg, the renal papilla and urine were hypertonic to cortex and plasma. The results indicate that medullary solute washout in hemorrhagic shock is a function of blood pressure, and suggest that the rate of washout is related to the rate of medullary blood flow.
Autonomic involvement in the lymphatic delivery of fibrinogen
Authors: Kolmen S. N. , Daily L. J. , Traber D. L.
Published: December 2017

Fibrinogen concentrations in thoracic duct lymph and plasma were measured in 64 dogs before and following the intravenous administration of one of the following agents: saline, ephedrine, methacholine, or neostigmine. Measurements of hematocrit, lymphatic flow, arterial pressure, heart rate, and respiratory rate were recorded also. Half of the dogs in each of the above groups were premedicated with atropine, the other half with saline. The rate of lymphatic flow increased only in dogs premedicated with saline and receiving ephedrine, methacholine, or neostigmine. Blood and lymph fibrinogen concentrations increased only in dogs receiving ephedrine; this increase was not observed in any dog premedicated with atropine. Fibrinogen delivery (milligrams fibrinogen delivered via the thoracic duct per minute), therefore, was dependent on parasympathetic activity and primarily was a reflection of the induced increase in rate of lymphatic flow. The increased flow was related to changes in hematocrit and to a lesser extent to changes in respiratory rate. Evidence and inductive reasoning are presented to support the concept of extravascular storage of fibrinogen and to propose a possible mechanism by which depletion and repletion of these stores is accomplished.
Role of calcium ions and phospholipids in platelet aggregation and plug formation
Authors: Silver Melvin J.
Published: December 2017

Certain phospholipids aggregate and form "plugs" in a simple system in which all variables are easily controlled. Aggregation requires the presence of divalent cations. Suspensions of lecithin are totally inactive whereas those of phosphatidylethanolamine and interaction products of lecithin and phosphatidylserine (molar ratio 1/1) aggregate and form plugs. Phosphatidylserine and lecithin-phosphatidylserine interaction products at higher molar ratios produce some aggregation but do not form plugs. Adenosine diphosphate (in the presence of small amounts of calcium) can accelerate the formation of small aggregates of platelets or exogenous phospholipids, but cannot bring about the formation of large aggregates or plugs. The hypothesis is presented that aggregation of platelets in physiological thrombus formation occurs after a triggering mechanism "uncovers" phospholipid micelles in platelets. The newly available negative charges on the polar ends of phospholipids would then be bridged by divalent cations present in the surrounding plasma, producing aggregates and plugs.
Rhythmic changes in renal function in the rat
Authors: Bray George A.
Published: December 2017

Cold exposure causes rats to increase their urine output. This increase in urine output was found to occur in 5- to 8-day cycles with peak urine volumes three or more times the volumes prior to exposure to the cold. Cycles in urine volume occurred on a constant electrolyte intake and in animals receiving exogenous Pitressin. The peaks in urine volume were accompanied by a threefold increase in the variability of sodium excretion but not potassium excretion. The increase in urine volume which occurred at the same time in all rats in a group began at night and continued through the following day. These data have been discussed in the light of a possible mechanism controlling sodium intake with water intake and electrolyte excretion.
Potassium exchange between cerebrospinal fluid, plasma, and brain
Authors: Cserr Helen
Published: December 2017

Potassium exchange between cerebrospinal fluid (CSF), plasma, and brain was investigated in anesthetized dogs and rats using the technique of ventriculocisternal perfusion. Transport via bulk secretion and absorption of CSF accounts for only 20% of total potassium exchange, unidirectional ionic fluxes across the ependyma for 80%. This large transependymal exchange is primarily between CSF and brain intracellular potassium pools, since two-thirds of the K42 outflux can be recovered from brain tissue. Conversely, much of transependymal influx comes from brain, as demonstrated by the low specific activity of influx relative to that of plasma following intravenous injection of K42. Potassium outflux is almost proportional to CSF [K+] in the range 0–10 mEq/liter but is independent of plasma [K+]. Perfusion with 10–5 m ouabain reduces transependymal K42 outflux to 25% of control; the residual outflux may be accounted for by passive processes. Results are discussed in terms of 1) regulation of CSF potassium concentration and 2) the relationship between CSF and brain extracellular fluid.
Effects of denervation on normal and dystrophic muscle: DNA and nucleotide enzymes
Authors: McCaman M. W. , McCaman R. E.
Published: December 2017

Page 495: M. W. McCaman and R. E. McCaman. "Effects of denervation on normal and dystrophic muscle: DNA and nucleotide enzymes." Page 495, column 2, lines 20, 22, and 23, "C56B-F1- dydy" for dystrophic mice and "C56B- DyDy" for normal mice should read, "(129B6)F1- dy/dy" for dystrophies and "(129B6)F1- Dy/Dy" for normals.
Behavioral regulation of internal temperature in the lizard Tiliqua scincoides
Authors: Myhre K. , Hammel H. T.
Published: December 2017

To study behavioral thermoregulation in the lizard, Tiliqua scincoides, two animals were implanted with two thermodes astraddle the preoptic region of the brainstem. These and four others without thermodes wandered between warm and cold environments, keeping the brain or colonic temperature cycling about a mean preferred temperature of 29.3 C during activity. When inactive, they voluntarily moved to a cool place and let their internal temperatures drop. When put into a hot test chamber, the lizards returned to a neutral environment when their colonic temperatures reached a reproducible level, designated the colonic exit temperature. Increasing the temperature of the test environment decreased the colonic exit temperature, the difference being highly significant when increasing the ambient temperature from 40 to 55 C. Warming the rostral brainstem by circulating water of 42 C through the thermodes also lowered the colonic exit temperature significantly at an ambient temperature of 40 and 45 C. Cooling the brainstem by 25 C water caused an increase of the colonic exit temperatures. We believe that the behavioral regulation of the internal temperature in Tiliqua scincoides is activated by a combination of brain and peripheral temperatures.
Influence of hematocrit and colloid on whole blood viscosity during volume expansion
Authors: Schrier R. W. , McDonald K. M. , Wells R. E. , Lauler D. P.
Published: December 2017

Page 346: R. W. Schrier, K. M. McDonald, R. E. Wells, and D. P. Lauler. "Influence of hematocrit and colloid on whole blood viscosity during volume expansion." Page 346, column 2, line 16: "Bohlmann" should read "Bahlmann"; line 19: "oral" should read "renal."
Mechanical properties of smooth muscle. II. Active state
Authors: Gordon A. R. , Siegman M. J.
Published: December 2017

Page 1250: A. R. Gordon and M. J. Siegman. "Mechanical properties of smooth muscle. II. Active state." Page 1254, column 1, equation 5 should read:

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Page 1254, column 2, the equation in lines 1 and 2 should read:

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Circulatory transport of L-glutamine in fasted mammals: cellular sources of urine ammonia
Authors: Hills A. G. , Reid E. L. , Kerr W. D.
Published: December 2017

Page 1470: A. G. Hills, E. L. Reid, and W. D. Kerr. "Circulatory transport of L-glutamine in fasted mammals: cellular sources of urine ammonia." Page 1472, the legends to Figs. 3 and 4 should be interchanged. Page 1473, in the footnote to Table 1, line 7, Fig. 3 should read Fig. 4; line 8, Fig. 4 should read Fig. 5; and line 9, Fig. 5 should read Fig. 6. In Table 1 the unit of measure is micromoles per period.
Water and ion transport by the urinary bladder of the teleost Pseudopleuronectes americanus
Authors: Renfro JL
Published: December 2017

Water and ion transport by the isolated teleost urinary bladder were studied. The transepithelial electrical PD across sac-type bladder preparations was unstable, i.e., initially mucosa positive but becoming more negative with time. Perfused bladders maintained a low mucosa positive PD which was stable. Both Na and Cl appeared to be actively transported from mucosal side (M) to serosal side (S). Voltage clamping the bladder at 0, -50, or +50 mV had almost no effect on active or passive Na or Cl flux in either direction. Na and Cl transport seemed electrically neutral. Fluid absorption (M to S) was directly correlated with absorption of osmotically active solutes. These solutes were almost all Na and Cl. The bladder acidified and secreted K+ into the mucosal fluid. Divalent ions were concentrated in the mucosal fluid as a result of fluid absorption. Although furosemide and ethacrynic acid inhibited ion and water transport by the bladder, ouabain was effective at a much lower concentration. Ouabain (10(-4) M) inhibited active Na transport when applied only to the mucosal or only to the serosal surface. Ouabain abolished the PD only from the serosal surface.
Neuroendocrine conditioning: conditioned feeding after alterations in glucose utilization
Authors: Balagura S , Harrell LE
Published: December 2017

We have demonstrated that it is possible to condition the feeding behavior induced by either 2-deoxy-D-glucose (a chemical that induces glucopenia) or tolbutamide (an oral hypoglycemic agent). Such behavioral conditioning is also accompanied by a conditioning of neuroendocrine responses. A model for both overt and covert conditioned responses is proposed.
Uremic inhibition of purine uptake by rat hepatic slices
Authors: White AG , Nachev P
Published: December 2017

Measurements were made of the production of allantoin by liver slices prepared either from bilaterally nephrectomized rats or from normal, control rats in flasks containing either a) no added substrate, b) hypoxanthine, or c) xanthine. Uremic liver slices showed a 72.3% inhibition of augmented allantoin production with hypoxanthine as substrate and a 68.3% inhibition with xanthine as substrate. Next, uremic rat serum was added to liver slices prepared from normal rats along with either a) no added substrate, b) hypoxanthine, or c) xanthine. Normal rat serum replaced uremic rat serum in control experiments. In these paired experiments, uremic serum exerted an inhibitory effect on allantoin production of 78.0% when hypoxanthine was the substrate and of 83.6% when xanthine was the substrate. Studies on possible underlying mechanisms showed that the observed uremic inhibition of allantoin production by hepatic slices, in the presence of substrate (e.g., hypoxanthine), represents a decreased production of uric acid, secondary to the decreased hepatic uptake of substrate.
Cardiovascular responsiveness to beta-adrenergic stimulation and blockade in chronic hypoxia
Authors: Maher JT , Manchanda SC , Cymerman A , Wolfe DL , Hartley LH
Published: December 2017

Previous studies have shown that exposure to high altitude results in an initial increase in heart rate, followed by a return to sea-level values within several days; circulating catecholamines rise progressively during this time. Nine conscious dogs were studied in normoxia (N) and after 10 days' exposure to 445 torr (CH). The mean (plus or minus SE) hematocrit was higher in CH (50 plus or minus 2 vs. 42 plus or minus 1%) while Pa-o2 (53 plus or minus 1 vs. 97 plus or minus 2 torr) and PaCO2 (27 plus or minus 1 vs. 35 plus or minus 1 torr) were lower than in N. A 3.5-fold increase in plasma norepinephrine above the N value was found in CH. Arterial pH, heart rate (HR), and mean femoral arterial pressure (MAP) did not differ significantly in N and CH. Isoproterenol (ISO), 0.5 mug/kg iv, produced an average increase in HR of 92 plus or minus 9 beats/min in N, but only 66 plus or minus 8 beats/min in CH (P smaller than .02). Reduction in MAP after ISO were similar. Pretreatment with propranolol, 0.15 mg/kg iv, reduced HR equally in N and CH without affecting MAP, but diminished the HR response to ISO significantly more in CH than in N. The attenuated chronotropic response to beta-adrenoceptor stimulation following chronic hypobaric hypoxia suggests a relative cardiac refractoriness secondary to an increased level of sympathetic activity.
Oxidative energy metabolism in germ-free and conventional rat liver mitochondria
Authors: Sewell DL , Wostmann BS , Gairola C , Aleem MI
Published: December 2017

The ADP:O ratios and State 3 (ADP-stimulated) and State 4 (controlled) rates of succinate, beta-hydroxybutyrate, isocitrate, glutamate, pyruvate + malate, alpha-ketoglutarate, and ascorbate + N,N,N',N'-tetramethylphenylenediamine (TMPD) oxidation were examined in liver mitochondria from germ-free and conventional rats of both Lobund Wistar (100-day-old) and Fisher (120-day-old) strains. The State 3 respiration rates of isolated mitochondria from germ-free and conventional rats were comparable except for the rate of succinate oxidation in the Wistar rats, which was significantly lower (approx. 10%). The State 4 respiration rates were generally lower in mitochondria isolated from germ-free Fisher rats (approx. 8%) and significantly lower (approx. 18%) in germ-free Wistar rats. The ADP:O ratios were similar in germ-free and conventional rats. Serum thyroxine concentrations indicated delayed maturation of thyroid function in young germ-free rats, but adult animals had concentrations similar to those found in conventional rats. The results indicate that, although absence of a microflora results in a 20-30% reduction in metabolic rate, the germ-free state has little influence on the functional respiration or oxidative phosphorylation of mitochondria isolated from the liver of the adult rat.
Intratubular hydrostatic pressure in testis and epididymis before and after vasectomy
Authors: Johnson AL , Howards SS
Published: December 2017

A method is described for the measurement of intratubular hydrostatic pressure in the testis, caput epididymidis, and cauda epididymidis of the golden hamster. Pressures in these locations in normal animals ranged from 3 to 6 cmH2O. Mean pressure in the tubules of the caput was significantly higher than that in the seminiferous tubules (P smaller than 0.05) and in the proximal caudal tubules (P smaller than 0.02). There was a small, significant increase in pressure from the proximal cauda to the distal cauda (P smaller than 0.04). Two weeks after vasectomy, the mean pressure in the seminiferous tubules of 3.3 cmH2O was significantly lower (P smaller than 0.004) than the mean pressure in the normal seminiferous tubules of 4.4 cmH2O. Pressures in the cauda at 2 wk of 10-18 cmH2O were significantly greater than normal (P smaller than 0.0005) and reflected the accumulation of sperm and fluid. The high incidence of spermatic granuloma formation and/or rupture of the epididymis observed after vasectomy emphasized that there are definite limits to both distensibility and reabsorptive capacity of the epididymis in some species. Pressures at 1 mo after vasectomy were similar to those at 2 wk in animals that were still obstructed and comparable to normal in animals with granulomas and/or large epididymal leaks. Testicular weight was slightly but significantly decreased 2 wk after vasectomy. At 4 wk, there was no detectable effect of vasectomy on the weights of the testes.
Secretion of salt and water into the medullary collecting duct of Ringer-infused rats
Authors: Sonnenberg H
Published: December 2017

Using a microcatheterization technique, the contribution of the collecting duct to the renal response to extracellular fluid volume expansion was studied in anesthetized rats. During intravenous infusion of Ringer solution (0.25 ml/min per 100 g body wt), urinary excretion of fluid, sodium, and potassium was 365 mul/min per g kidney wt (V), 52.6 mueq/min per g kidney wt (UNaV), and 3.86 mueq/min per g kidney wt (UKV), representing 23, 24, and 65% of filtered load, respectively. Analysis of collecting duct fluid from cortex and outer medulla indicated continued net reabsorption of ions and water in these nephron segments; in contrast, in inner medulla net secretion of Na, K, and fluid into the collecting duct was demonstrated. Addition of sodium and water was equivalent to approximately 10% of filtered load. It is concluded that under the stress of extreme intravenous fluid loading tubular secretion of salt and water into the inner medullary collecting duct contributes importantly to diuresis and natriuresis. The mechanism of such secretion remains undetermined.
Hypothalamic heating and cooling in monoamine-depleted rabbits
Authors: Woolf CJ , Laburn HP , Willies GH , Rosendorff C
Published: December 2017

The role of monoamines in the thermoregulatory responses induced by hypothalamic heating and cooling was investigated in conscious rabbits. Depletion of hypothalamic catecholamines by pretreatment with 6-hydroxydopamine (6-OHDA) greatly attenuated the rectal temperature and vasomotor responses to hypothalamic heating and cooling. Pretreatment with p-chlorophenylalanine (PCPA) depleted the animals of 5-hydroxytryptamine (5-HT). The results obtained are consistent with 5-HT having an inhibitory role in the rabbit's vasomotor response to heat stress and activating heat conservation during cold stress. Reserpinized rabbit were depleted of both norepinephrine (NE) and 5-HT and were found to be unresponsive to hypothalamic temperature changes. We conclude that the integrity of the monoaminergic system is viral for the correct functioning of the hypothalamus in maintaining a constant body temperature.
Regulation of body mass in rats exposed to chronic acceleration
Authors: Pitts GC , Bull LS , Oyama J
Published: December 2017

Female rats approximately 6 mo old were chronically centrifuged for up to 30 days at 2.76 G or 3.18 G and sacrificed at intervals for body-composition study. Both fat and the fat-free body mass (FFBM) were reduced during the 1st wk of centrifugation, with the fat showing considerably more variation both within and between groups. The FFBM was reduced below control level to the same extent in rats fed commercial chow, a high-fat diet, or a high-protein diet or in rats prefasted to produce a body-mass deficit at the start of centrifugation. There were no centrifugation-associated changes in body water content. It was concluded that body fat showed no evidence of regulation, FFBM is regulated at any constant level of acceleration between 1 and 4.15 G, and the change in FFBM induced by a change in acceleration is probably not regulated.
Increased uptake and utilization of glucose by diaphragms of rats exposed to chronic centrifugation
Authors: Daligcon BC , Oyama J
Published: December 2017

Weaning female Sprague-Dawley rats were exposed to 2.76 or 4.15 G for periods ranging from 2 to 20 wk. The isolated diaphragm tissues from these rats were studied in vitro to determine the uptake of glucose and its utilization to CO2 and glycogen. The diaphragm muscle tissues obtained from centrifuged rats showed higher rates of glucose uptake and 14CO2 production from [U-14C]glucose than those obtained from noncentrifuged controls, but no significant differences in the rate of incorporation of [U-14C]glucose into glycogen were observed. Rats centrifuged for 12 wk at 4.15 G continued to show an increase in diaphragm tissue glucose uptake for periods up to 2 wk after return to normal gravity. The stimulating effect of insulin on the uptake of glucose and its incorporation into glycogen was much higher in the diaphragms of centrifuged rats. From the results of this study, it is concluded that one of the adaptive responses of rats to chronic centrifugation is an increase in glucose metabolism of their muscle tissues.
ATPase activity of kidney mitochondria stimulated by sodium
Authors: Weiner MW
Published: December 2017

ATPase activity of intact mitochondria may be induced by the presence of sodium. Mitochondria obtained from kidney cortex or medulla demonstrate a higher sodium-stimulated ATPase than mitochondria prepared from liver. This difference is not due to a greater capacity of kidney mitochondria for ATP hydrolysis. Sodium-stimulated ATPase activity of mitochondria is not further enhanced by magnesium or potassium, nor is it inhibited by ouabain. Furthermore, the ATPase of submitochondrial particles is not enhanced by the presence of sodium. These results indicate that the ATPase activity of mitochondria which is stimulated by sodium is unrelated to the microsomal Na-K-ATPase. mitochondrial sodium-stimulated ATPase is affected by pH, anionic composition, furosemide, and ethacrynic acid. The demonstration that mitochondrial ATP hydrolysis can be activated by sodium suggests that intracellular sodium may directly influence intracellular energy metabolism.
Regulation of intestinal calcium-binding protein calcium intake in the rat
Authors: Freund T , Bronner F
Published: December 2017

Analytical gel electrophoresis of the vitamin D-dependent intestinal calcium-binding protein (CaBP) has demonstrated two protein bands (1 and 2) of similar molecular weight and similar specific binding activity. The mucosal concentration of CaBP, measured by a quantitative competitive binding assay, has been shown to vary reproducibly and inversely with calcium intake and the mucosal calcium concentration. These same factors also influence the relationship of bands 1 and 2. When animals on a high-calcium diet were placed on a low-calcium diet, their CaBP increased by 35% in 24 h and by 48% in 48 h and reached a level typical of animals on a low-calcium diet. Measurement of the diurnal variation of CaBP and mucosal calcium in animals allowed access to feed only at night revealed significant, but inverse, oscillations. These observations are interpreted as reflecting a regulation of CaBP by the mucosal calcium concentration, which appears to reflect absorbed calcium in transit.
Thermoregulation of myocardial protein synthesis
Authors: Taegtmeyer H , Ferguson AG , Lesch M
Published: December 2017

The effect of temperature on myocardial protein synthesis was evaluated using L-[14C]phenylalanine incorporation into total protein of isolated rabbit right ventricular papillary muscles. Muscles were incubated in oxygenated Krebs-Ringer buffer containing tracer amino acid at temperatures of 25-43 degrees C or incubated without tracer at varying temperatures up to 120 min and then incubated at 37 degrees C for an additional 2 h with the tracer present for the final hour of incubation. Higher as well as lower than physiological temperatures depressed tracer amino acid incorporation. Recovery of myocardial protein synthesis from thermal injury was incomplete when the experimental temperature deviated by 6 degrees C or more from the control and exposure exceeded 60 min. In addition, tracer amino acid incorporation on reoxygenation and return to 37 degrees C in muscles exposed to anoxia at 25 degrees C did not differ from that in muscles exposed to anoxia at 37 degrees C. Specific activity of the intracellular amino acid pool was directly measured in appropriate experiments and variation of this parameter could not account for the depressed tracer amino acid incorporation. Likewise methylprednisolone (10-5 M), chloroquine phosphate (10-5 M), and glucose (15 mM), if present during hyperthemia, did not ameliorate thermal damage. It is concluded that hyperthermia as well as hypothermia can cause irreversible alterations rather than reversible inhibition of myocardial protein synthesis.
Carbohydrate metabolism and its response to catecholamines as modified in alkalotic rat
Authors: Yajima M , Ui M
Published: December 2017

Metabolic activities and their responses to catecholamines were studied in fasted rats exposed to simulated altitudes. Analysis of hepatic levels of gluconeogenic intermediates revealed the inhibition of gluconeogenesis between glyceric acid 3-P and fructose 6-P associated with a rise of the ratios of redox pairs such as lactate to pyruvate in livers of alkalotic rats. Inhibition of gluconeogenesis was indicated also by the suppressed incorporation of glutamate 14C into blood glucose. Since no activation was detected on glycolytic pathway of skeletal muscles, marked hyperlactacidemia during alkalosis appeared to result from the suppression of hepatic gluconeogenesis. Most of metabolic actions of epinephrine and isoproterenal known to be mediated via the beta receptor were significantly reduced but not completely abolished during alkalosis. Exceptionally, hyperinsulinemia induced by isoproterenol was completely reversed and replaced by hypoinsulinemia during alkalosis. Despite hypoinsulinemia, hyperglycemia induced by glucose load decreased more rapidly in alkalotic than in normal rats. In view of the fact that the adrenergic alpha receptor is involved in theinhibition of insulin secretion, the observed irregular modifications of catecholamine actions could be explained on the basis of a postulate that the adrenergic alpha-receptor functions are potentiated in alkalosis.
Kinetics of Na+ uptake and transcellular transit by the pancreas
Authors: Rossier M , Rothman SS
Published: December 2017

22Na uptake into strips of rabbit pancreas was measured for up to 10 min. The uptake curve was characterized by the presence of two plateaus separated by an inflexion point; a first "plateau" or an approximation of steady-state uptake was observed between 1 and 3 min; betwen 3 and 4 min the slope of the uptake curve increased again, finally decreasing to a new and higher steady-state uptake between 4 and 6 min. The data suggest that the first part of the uptake curve (from 0 to 3 min) represents uptake into most if not all cells, and the second part (from 3 to 10 min) represents the sum of "quasi" steady-state cellular uptake and of the equilibration of the ductal compartment in series with the cells. In this model a substantial delay (2.5-3.25 min) elapses between the filling of cellular and ductal compartments which is apparently of intracellular origin, implying restricted Na+ diffusion within the cytoplasm and an intracellular Na+ gradient. If this model is correct, then the mean transit time for Na+ across the whole organ should be approximately 3-4 min and be primarily the result of transcellular transit. The mean transit time for Na+ across the whole organ in vitro was measured and found to be 3.5 min on the average. The step that accounts for most of this time appears to be the transepithelial transit of Na+.
Effects of vagotomy on urecholine-modified histamine dose responses in dogs
Authors: Hirschowitz BI , Hutchison GA
Published: December 2017

Histamine step-dose responses, 2-100 mug/kg-h in 6 successive 45-min steps, were studied in nine dogs with gastric cannula. In three of the dogs the gastric fundus was selectively vagally denervated and the dose responses were repeated. In both groups of dogs the dose responses were then studied against background intravenous infusions of urecholine (10, 20, 40, and 80 mug/kg-h). Vagotomy acted as a competitive inhibitor (Km doubled from 14 to 29 mug/kg-h, while Vmax was unchanged) and this effect could be reversed by smaller than 10 mug urecholine/kg-h. In both groups increasing backgrounds of urecholine increased Vmax from similar to 14 meq H+/30 min to similar to 23-24 meq/30 min and decreased histamine km from 14 mug/kg-h to about 1-2 mug/kg-h. Both changes were log linear. The effects of urecholine on histamine-stimulated H+ secretion thus showed synergism (decreased Km) and potentiation (increased Vmax), the former interpreted as a cholinergic effect on the parietal cell histamine receptors and the latter as the probable existence of spare cholinergic receptors not (normally) accessible to histamine. There were no intrinsic qualitative or quantitative differences in these responses between the vagotomized and the innervated stomachs.
Estimate of relative thickness of peritubular interstitial space in Necturus kidney
Authors: Asterita MF , Windhager EE
Published: December 2017

Electrophysiological techniques were used to evaluate volume changes of compartments interposed between the peritubular membrane of proximal tubue cells and capillary wall or peritoneal surface of Necturus kidney. The time courseof potassium-induced peritubular membrane depolarization was measured during a switch from 3- to 90-meq potassium sulfate solution in superfusion as well as in vascular perfusion experiments. When superfusion fluids contained 6, 2, and 0 g dextran/100 ml, mean half times of depolarization in normal kidneys were 4.1, 1.9, and 5.8 s. Decreasing the colloid osmotic pressure of superfusion fluids resulted in a significant increase in half-time values. Similar results were obtained in saline expansion. In controls the mean half time was 4.5s; in saline expansion it was 7.7 s. In vascular perfusions, mean half-time values were 225, 350, 355, and 450 s for dextran concentrations of 6, 4, 2, and 0 g/100 ml, respectively. These results indicate that the half time of depolarization increases significantly as the colloid osmotic pressure of perfusion fluids decreases. Estimates of effective unstirred-layer thickness on the peritubular side of proximal tubular epithelium indicate a decrease by about 25% when vascular colloid osmotic pressure is increased from 0 to 54 mmHg.