bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of the blood fibrinolytic enzyme system by platelets
Authors: Reid W. O. , Silver M. J.
Published: December 2017

Fibrinolytic activity in human blood develops after the occurrence of viscous metamorphosis (VM) of platelets. Freshly drawn venous blood was held at room temperature until spontaneous VM of platelets occurred and then introduced into oxalate solution to prevent coagulation. As compared to the control (blood added to anticoagulant before VM) plasma of such samples exhibited increased fibrinolytic activity, detected by increased serial thrombin times. Clots from platelet-rich plasma exhibited an increase in the convergence of branches of the thrombelastograph and a decrease in weight after incubation for 24 hr or more. The increase in branch convergence was roughly proportional to the platelet count and was reduced or absent in thrombocytopenic blood or platelet-poor plasma. Dimethylsulfoxide blocked VM and prevented branch convergence (without preventing clot retraction). Epsilon-aminocaproic acid, an inhibitor of plasminogen activator, blocked or inhibited fibrinolytic activity without arresting VM. This evidence suggests that platelets contain significant proactivator or activator of plasminogen (or a factor which initiates their activity) which is released when VM occurs.
Vascular volume changes in the dog forelimb
Authors: Baker Carleton H. , O'Brien L. J.
Published: December 2017

In an isolated dog forearm preparation perfusion pressure, venous pressure, and blood flow were determined. Blood flow and vascular volumes were estimated by arterial injection of red cells-Cr51 and albumin-I131. Measured blood flow agreed within ± 10% of that calculated from the indicator dilution. Vascular volume changes were determined from changes in limb weight. Measurements were made 1) during the control state, 2) during vasodilation with acetylcholine, and 3) after increasing the flow rate. The red cell-Cr51 volume averaged significantly less than that measured by the albumin-I131 at all three stages of the experiment. The ratio of the volumes (RBC-Cr51/albumin-I131) increased from 0.84 at the control to 0.93 in the dilated bed with elevated flow. Following vasodilation, the change in volume determined by weight change was significantly smaller than measured by the indicators. When flow was increased, the albumin-I131 measured a significantly smaller volume change than did the red cells-Cr51 or the weight. Three general types of time-concentration curves are described.
Urea production and excretion by the chicken kidney
Authors: Owen Edward E. , Robinson Roscoe R.
Published: December 2017

Using the Sperber technique, renal urea excretion was studied in the chicken during the constant unilateral infusion of either l-arginine, urea, or l-arginine-C14. After the prior injection of urea-C14 in some birds, the effect of a unilateral arginine infusion on the specific activities of plasma and urine urea-C14 was determined. During l-arginine infusion, urine urea excretion increased greatly from both kidneys. Urea/inulin clearance ratios always rose above 1.0 (maximum: 7.5). This response was not inhibited by pretreatment with 2,4-dinitrophenol. Urea/inulin clearance ratios greater than 1.0 were not observed during an infusion of exogenous urea. A constant unilateral infusion of tracer amounts of l-arginine-C14 was attended by a bilateral rise of urea-C14/inulin ratios to values much above 1.0 (higher on the side of infusion) at a time when total urea/inulin ratios remained less than 1.0. After equilibration of an administered dose of urea-C14, arginine infusion depressed the specific activity of urine urea-C14 much more than that of plasma. A double reciprocal plot indicated a straight-line relationship between the plasma arginine concentration and the simultaneous rate of urine urea excretion. These results provide conclusive in vivo evidence that the kidney of at least one species can synthesize urea from exogenous or endogenous plasma arginine via a rate-limited process, and that this urea is subsequently excreted by direct release into tubular urine.
A micropuncture study of the renal concentrating defect of potassium depletion
Authors: Bank Norman , Aynedjian Hagop S.
Published: December 2017

In order to study the renal concentrating defect of potassium depletion, tubular fluid osmolality and segmental water reabsorption were measured in surface nephrons of K-deficient rats and normal controls, using micropuncture methods. The osmolality of proximal and distal tubular fluid was found to follow the same pattern as in normal rats. Many of the proximal TF/PIn ratios and almost all of the distal TF/PIn ratios were higher in the K-deficient rats than in the normals. The data from the early distal tubule suggest that sodium chloride transport by the ascending limb of Henle's loop is not markedly impaired. Delivery of fluid to the collecting ducts was diminished, thus exlcuding the possibility that increased volume flow to this segment is responsible for the concentrating defect. The finding of elevated proximal TF/PIn ratios suggests that delivery of solute to the loops of Henle may be chronically decreased. This could account for low concentrations of sodium and urea in the medullary interstitium and thus play an important contributing role in the hyposthenuria of potassium depletion.
Electrolyte and nitrogen changes in skeletal muscle of developing rats
Authors: Vernadakis Antonia , Woodbury Dixon M.
Published: December 2017

Rats 1–45 days old were studied. Plasma Na and Cl concentrations changed little with age, whereas K concentration decreased. Total water content and total Na and Cl concentrations in muscle decreased progressively, whereas total K concentration increased during maturation. Intracellular Na concentration decreased whereas K concentration did not change during maturation. Adult muscle electrolyte values were attained at approximately 45 days. The changes in electrolyte and nitrogen content of muscle during maturation are discussed in relation to histological changes in this tissue with age.
Effects of rhinencephalic lesions on endocrine and somatic development in the rat
Authors: Kling Arthur
Published: December 2017

Lesions to the olfactory stalk, medial olfactory area, and hippocampus were produced in rats at 3–19 days of age. Delayed puberty occurred in the females with bilateral olfactory stalk and medial olfactory area lesions. Unilateral lesions of the olfactory stalk were also effective in delaying vaginal opening. Deficiencies in growth and smaller endocrine organs occurred in both sexes with a variety of lesions. Early handling affected final body and adrenal weights in both operated and control rats.
Mechanical properties of the collagenous framework of skin in rats of different ages
Authors: Fry Phyllis , Harkness Margaret L. R. , Harkness R. D.
Published: December 2017

The collagen content, tensile strength, and extensibility of the skin of rats have been examined in rats 3–85 weeks of age. Tensile strength calculated per unit cross-sectional area of collagen increased with age, the maximal value in the oldest group (5.5 kg/mm2 collagen) being about three times that in the youngest. The quantity present per unit area of surface also increased with age. An estimate of the total "surface mechanical resistance" obtained by multiplying collagen per unit area of skin and tensile strength rose continuously about twentyfold between the youngest to oldest of the groups. Application of a load produces after a time an elongation at constant rate ( K). Extensibility, measured by the ratio of this rate to length at zero time ( l0) obtained by extrapolation, and corrected to constant load of 100 g/mm2 cross-sectional area of collagen, was found to fall with age, the range being about eightyfold.
Some factors influencing short-term food intake of the goldfish
Authors: Rozin Paul N. , Mayer Jean
Published: December 2017

Goldfish press a lever in order to receive a food pellet during 1-hr sessions at the same time each day. They eat much less in 1 hr than when allowed to press the lever for a full day. The day-to-day 1-hr intake is stable. The intake in 1 hr is about the same when the fish have been deprived from 4 to 47 hr. This constancy cannot be accounted for by assuming a steady state in the gut. Four hours postfeeding virtually all undigested food from the previous feeding session remains in the gut; by 47 hr most or all has been excreted.
Abolition of autoregulation of renal blood flow by acetylcholine
Authors: Nahmod Victor E. , Lanari Alfredo
Published: December 2017

In order to study the mechanism of autoregulation of renal blood flow, 36 mongrel dogs were connected in parabiosis according to the Brull method. The following determinations were made: a) flow/pressure curves in innervated and denervated kidneys and b) acetylcholine and arterenol infusion in innervated kidneys. The critical closing pressure and the "run-off" index were also determined in all cases. The results of these experiments show the existence of renal blood flow autoregulation in innervated, denervated, and arterenol-infused kidneys, and the abolition of the autoregulatory mechanism in the acetylcholine-infused kidneys. The run-off index showed a better correlation with renal resistance than with critical closing pressure.
Alteration of vascular responses to endotoxin by adrenergic blockade
Authors: Brake Charles M. , Emerson Thomas E. , Wittmers Lorentz E. , Hinshaw Lerner B.
Published: December 2017

The effects of the adrenergic blocking agent phenoxybenzamine (Dibenzyline) on the vascular responses to injected histamine and endotoxin were studied in dogs utilizing a "venous return" preparation. A marked antihistaminic action of Dibenzyline was demonstrated in the hepatic portal system. Less effective blocking was seen in the arterial segment. The effectiveness of Dibenzyline for preventing increases in portal venous pressure and pooling of blood were similar with both histamine and endotoxin administration. These data show a basic similarity between the early vascular responses to histamine and endotoxin in the hepatic-portal system. A major dissimilarity between the vascular effects of histamine and endotoxin was the absence of an early drop in total peripheral resistance after endotoxin. Beneficial effects of Dibenzyline after endotoxin, during the first 100 min, could not be demonstrated in animals whose cardiac output was unsupported. The action of Dibenzyline alone is apparently incapable of reversing the detrimental effects of endotoxin.
A theory for the quantification of transcapillary exchange by tracer-dilution curves
Authors: Martin Pablo , Yudilevich David
Published: December 2017

A mathematical formulation of the simultaneously obtained indicator-dilution curves of two tracers: one confined to plasma and another diffusible through the capillary barrier, is made. The procedure allows the estimation for the permeable substance of the fractional extraction from the blood, and the interstitial fractional turnover rate and compartment size. The experimental data is obtained in 3–4 min in isolated perfused organs. Na22 (NaCl) and siderophilin-Fe59 first circulation dilution curves obtained in the isolated dog heart are used to exemplify the procedure.
Effect of hypothermia on excitation and propagation in the isolated atrium
Authors: Torres J. C. , Angelakos E. T.
Published: December 2017

Cooling rabbit right atria from 37 to 21 C resulted in only slight changes in excitability in contrast to a fivefold decrease in the spontaneous rate of excitation. Atrial arrest occurred at approximately 21 C and was characterized by a small nonpropagated electrical event associated with little or no tension development. In seven preparations repeatedly cooled and rewarmed no apparent relationship existed between changes in atrial excitability and either the onset of arrest or the resumption of activity subsequent to rewarming. Acetylcholine consistently restored normal electrical and mechanical activity in hypothermia-arrested atria for at least 20 min. This "excitatory" action of acetylcholine occurred independently of the existing level of atrial excitability. The continued presence of pacemaker activity and the lack of correlated changes in atrial excitability suggest that hypothermic atrial arrest is primarily the result of an impairment of sinoatrial conduction. The condition may be similar to the conduction block induced by elevated extracellular potassium.
Cardiac and peripheral failure in hemorrhagic shock in the dog
Authors: Rothe Carl F. , Selkurt Ewald E.
Published: December 2017

Cardiac output by the indocyanine-green-dilution technique, systemic arterial, right atrial, pulmonary arterial, and ventricular end-diastolic pressures were measured without thoracotomy to evaluate cardiac function in seven dogs. In other series of seven, mercury-in-rubber displacement transducers were placed around the left ventricles about 5 days before the experiments. In a third group of five, hemorrhagic hypotension was continued until 40% uptake of the maximum shed volume. Transfusions of blood, plasma, and dextran were given, as needed, to maintain arterial blood pressure above 100 mm Hg. Such therapy prolonged life. In a fourth group of 33, increases in hematocrit and plasma protein concentration, and decreases in central venous pressure suggested a progressive loss of intravascular fluid late in the hypotensive period and following transfusion. It appears that only with extreme degrees of oligemic hypotension, or with moderate hypotension plus prior cardiac damage does the cardiac weakness engendered by the prolonged hypotension become the most significant factor leading to death.
Venous oxygenation and circulatory responses to oxygen inhalation in acute anemia
Authors: Murray John F.
Published: December 2017

Studies were made in 20 dogs of the effects of acute normovolemic anemia on venous oxygenation and systemic oxygen transport. Ten dogs were given 100% oxygen to evaluate the circulatory effects of oxygen administration before and after anemia was induced. In anemia mean mixed venous oxygen tension decreased 2.3 mm Hg and a fall in venous oxygen saturation of 4.2% occurred. No shift in the oxyhemoglobin dissociation curve was demonstrated when oxygen tension was corrected for pH change. The administration of 100% oxygen to dogs with normal hematocrits resulted in a significant decrease in heart rate and cardiac output and a rise in peripheral vascular resistance. In anemia 100% oxygen raised mixed venous oxygen tension well above control values and systemic oxygen transport was increased nearly to normal amounts; these changes, however, did not modify the circulatory responses to anemia. It is concluded that the circulatory adjustments that are caused by acutely induced anemia do not result from a reduction in systemic oxygen transport or mixed venous oxygenation.
Effect of ACTH on total adrenal cholesterol in bursectomized chicks
Authors: Sato Koji , Glick Bruce
Published: December 2017

The effect of ACTH on the level of total adrenal cholesterol was studied in chemically or surgically bursectomized chicks. Total adrenal cholesterol was determined 12–15 hr after a single injection of 1 or 3 USP units of ACTH to 21-, 46-, and 60-day-old chicks. The adrenal cholesterol of control (12.9–16.7 µg/mg adrenal), surgically bursectomized (14.6– 18.2 µg/mg), and chemically bursectomized (13.3–14.2 µg/ mg) chicks receiving an injection of 3 USP units of ACTH was significantly lower than the cholesterol level (22.0–28.5 µg/ mg) of similar chicks not receiving ACTH. The results obtained from three trials suggest that the bursa of Fabricius does not influence the level of cholesterol in the adrenal gland. Also, it was found that ACTH will reduce the adrenal cholesterol of young birds.
Salt hunger unaffected by cadmium in rats allowed saline solution by choice
Authors: Schroeder Henry A.
Published: December 2017

Forty weanling rats were given choices of sodium chloride solution or water to drink until 8.4 months of age and again from 23 months of age until death, half of the rats receiving small doses of cadmium. No differences in intakes appeared in control and cadmium-fed groups. Young females drank two and one-half times as much salt solution as did males and older ones five times as much. When not exposed to salt, fluid intake of females remained elevated; that of males did not. Upon re-exposure, intake of salt solution by females almost doubled from previous levels, but changed little in males. Excessive intakes of more than 180 mg NaCl/100 g body wt. daily appeared in 6 of 20 older females, whereas 10 of 14 males exhibited aversion to salt. Young female rats allowed salt solution or water rapidly acquire salt hunger which may become excessive later in life.
Amylase and electrolyte changes after postganglionic parasympathectomy of parotid gland
Authors: Schneyer C. A. , Hall H. D.
Published: December 2017

Severance of the postganglionic parasympathetic innervation to the parotid gland of the rat resulted, at 4 weeks, in appreciable reduction in the size of the whole gland and of individual acinar cells, without evidence of an increase in the total number of these cells. Some increase in connective tissue was also observed in the denervated glands. Concentration of sodium in the denervated gland was increased, probably reflecting the increase in connective tissue. Sodium and potassium concentrations of the secretion and rate of secretory flow were essentially unchanged. Amylase was appreciably reduced in total amount and in concentration in the unstimulated parotid gland after denervation. Calculation of the concentration of amylase in acinar cells of the denervated gland showed that there was marked reduction in the concentration of this enzyme intracellularly. It was concluded that the parasympathetic innervation to the parotid gland is involved in maintenance of normal concentrations of amylase in the acinar cells but the mechanism of this regulation is not yet established.
Synergistic autonomic nervous regulation of accelerated salivary gland growth in rats
Authors: Wells Herbert , Peronace Angela A. V.
Published: December 2017

Within 8 days after a submandibular salivary gland is deprived of its parasympathetic nervous innervation, the gland undergoes a marked reduction in weight. After either sympathectomy or parasympathectomy, the increase in gland weight which usually follows incisor amputation or dietary pancreatin is partially inhibited. The gland weight response to these two stimuli is completely inhibited after combined sympathectomy and parasympathectomy. In contrast, the response of the glands to isoproterenol is not dependent upon nervous innervation since administration of the drug still causes glandular enlargement after partial or complete denervation. Compensatory growth of the remaining submandibular gland after removal of one gland and ligation of the ducts of the parotid glands is partially inhibited by section of either nervous branch alone and almost entirely inhibited after complete denervation. A small but definite compensatory response still occurs after complete denervation indicating that humoral as well as nervous factors may be involved in this response. In hypophysectomized rats the response of the submandibular glands to growth hormone administration is not impaired by partial or complete autonomic denervation, indicating that nervous factors do not have a role in this effect of growth hormone.
Hemodynamic correlates of the third heart sound
Authors: Arevalo F. , Meyer E. C. , MacCanon D. M. , Luisada A. A.
Published: December 2017

The third heart sound was related to hemodynamic events in 18 dogs using both external and intracardiac phonocardiograms, multiple catheterizations, and additional techniques. The third sound was found to be independent of atrioventricular or ventriculoatrial pressure gradients. The time of occurrence of the third sound was determined within certain limits by the duration of isovolumetric relaxation, which showed a definite rate dependency. The third heart sound persisted under conditions in which blood flow into the ventricle was prevented. The third heart sound coincided constantly with the return to the base line of the first derivative of the intraventricular pressure curve. Based on its independence from flow in marked systolic overload and on its relationships to parameters reflecting the state of the myocardium it seems that the third sound is associated with the end of ventricular muscle relaxation when ventricular volume and compliance equilibrate.
Effects of potassium on automaticity and conduction of canine hearts
Authors: Vassalle M. , Greenspan K. , Jomain S. , Hoffman B. F.
Published: December 2017

The action of potassium on cardiac automaticity and conduction was studied in dogs. It was found that idioventricular automaticity is depressed at an early stage of potassium administration. Apparent dissociation between P and QRS waves resulted from various degrees of atrioventricular block, but not complete block. The ventricles were driven by an atrial pacemaker even in absence of P waves in the limb lead ECG, as evidenced by the following findings. First, local atrial activity persisted in absence of P waves. Second, the His bundle electrogram maintained its control pattern. Finally, vagal stimulation inhibited the ventricular activity. Depression of ventricular conduction was found to involve Purkinje fibers, their junction with muscle, and the muscular fibers. Enlargement of the ventricular complexes in the ECG results in part from intermingling of depolarization and repolarization processes. Cardiac arrest results from failure of conduction since atrial activity often persisted after ventricular arrest. Ventricular flutter may occur in presence of reduced idioventricular automaticity; it is precipitated by a supraventricular beat under conditions of depressed ventricular conduction.
Reference sites not influenced by hydrostatic pressure for right and left atrial pressures
Authors: Armstrong George G. , Hancock John C.
Published: December 2017

Simultaneous recordings of left and right atrial pressures made in dogs being rotated into all positions in space allowed the location of rotational axes where right or left atrial pressure became independent of hydrostatic pressure. Utilization of these axes as zero reference levels made possible the measurement of right or left atrial pressure without the influence of hydrostatic factors. The right zero reference point lay 62.8% of the distance from the manubrium to the xiphoid, 61.2% of the posterior to anterior thoracic diameter, and 47.7% of the greatest transverse thoracic diameter as measured from the right lateral border. The left atrial zero reference point lay 62.1% of the manubrium to xiphoid distance, 57.2% of the posterior to anterior diameter of thorax, and 53.0% of the greatest transverse thoracic diameter as measured from the right lateral border. When referred to the anatomy of the dog, these points lay in the immediate vicinity of the right and left atrioventricular valves, respectively.
Action of natural angiotensin II and synthetic analogues on strips of rabbit aorta
Authors: Helmer Oscar M.
Published: December 2017

The pressor activity of pure natural asp1ileu5-angiotensin II, and synthetic asparginyl1-val5, asp1-val5, asp1-ileu5, and ß-asp1-val5-angiotensin II was determined in a nephrectomized pithed cat. All were of equal potency with the exception of ß-asp1-val5-angiotensin which was slightly more active. When assayed on the aortic strip asparginyl1-val5 had 25% and ß-asp1-val5-angiotensin had 75% of the activity of natural angiotensin. The difference in action of the angiotensin peptides can not be explained by their rate of destruction by peptidases. Marked variation in the specificity of different receptors might be responsible. Asparginyl1-val5-angiotensin II should not be used as a standard in assaying natural angiotensin unless the specificity of the test system has been determined.
Hypoglycemic action of D-ribose in the rabbit
Authors: Sloviter Henry A. , Ikeda Masakazu , Sakata Kazuki
Published: December 2017

The infusion of 0.05 ml/ min of a 2.5% solution of d-ribose in the rabbit produced a definite decrease in blood glucose concentration. A tenfold increase in the rate of infusion did not cause a significant change in the magnitude or duration of the hypoglycemia. The same degree of hypoglycemia was obtained whether the d-ribose was infused via the internal carotid artery or via a vein. Anesthesia did not prevent this hypoglycemic action. Injected epinephrine produced about the same hyperglycemic effect during the infusion of d-ribose as it did in the absence of an infusion of d-ribose. This indicates that the hypoglycemic action of d-ribose is probably not due to an inhibition of glycogenolysis.
Distribution of alloxan-C14 in islet and other tissues of the toadfish (Opsanus tau)
Authors: Cooperstein S. J. , Lazarow Arnold
Published: December 2017

These studies on the mechanism by which alloxan selectively destroys the ß cells in the islets of Langerhans have been carried out in the toadfish because the islet tissue in this species is segregated into a discrete mass, separated from the acinar tissue. We have measured the C14 content of several tissues at various times after intravenous injection of tracer doses of alloxan-2-C14. The islet C14 content never exceeded 50% of that of blood and was no greater than that found in many other tissues. Thus the selectivity of alloxan is not due to selective concentration by islet tissue. The distribution of alloxan-2-C14 was compared with that of d-mannitol-1-H3. A mixture of both isotopic substances was injected and the C14 and H3 in each tissue determined. The distribution of alloxan-2-C14 was very similar to that of d-mannitol-1-H3. This suggests that tracer doses of injected alloxan do not enter islet cells but remain in the extracellular compartment, and that the ß-cell membrane may be a primary site of alloxan action.
Temperature gradients in the legs of cold-acclimatized pheasants
Authors: Ederstrom H. E. , Brumleve S. J.
Published: December 2017

Ring-necked pheasants were kept outdoors throughout the year. Cloacal and subcutaneous leg temperatures were taken in January, February, and June. In cold-adapted birds the temperature averaged 37.5 C in the muscular, feather-covered region of the thigh. Within a distance of 2 cm below the termination of muscle and feathers the average subcutaneous temperature dropped to 9.7 C, and in the toe to 2.7 C. A more gradual fall in leg temperatures was found in summer. The leg vasculature was injected with latex and macro- and microstructure were observed. The preparations disclosed an extensive venous network surrounding the artery in the thigh, and a much reduced network in the lower leg. Anatomically the vasculature was similar to countercurrent heat-exchanger structures found in other animals. It was concluded that heat production and insulation accounted for the warm thigh, and that vasoconstriction and heat exchange between venous and arterial blood explained the steep temperature gradients in the legs of cold-adapted birds.
Angiographic analysis of renal vasoconstriction
Authors: Brody Michael J. , Fischer Harry W.
Published: December 2017

The effects of renal nerve stimulation, catecholamine infusion, and renal vein constriction on intrarenal vessel calibers were studied in dogs with a technique which combined renal perfusion at constant flow with selective angiography of the kidney. Equivalent elevations of total renal vascular resistance by nerve stimulation and catecholamine infusion resulted in different intrarenal hemodynamic changes. Nerve stimulation elicited constriction of both the large and small arterial segments, whereas the catecholamines constricted only the smaller segments while the renal and interlobar segments were passively dilated. Either no change or a decrease in the size of the interlobar and arcuate arteries was noted during renal vein constriction. It was concluded that intrarenal hemodynamics are affected differentially by the neurogenic and humoral components of the sympathetic nervous system.
Simultaneous study of capillary permeability to several macromolecules
Authors: Chien S. , Sinclair D. G. , Chang C. , Peric B. , Dellenback R. J.
Published: December 2017

Capillary permeability to three exogenous macromolecules (dextran with mol. wt. of 250,000; albumin-I131 with mol. wt. of 69,000, and dextran-C14 with mol. wt. of 16,000) and endogenous serum proteins were studied simultaneously in dogs by following the transfer of these substances from plasma into the thoracic duct lymph. Two hours after the administration of the macromolecules the lymph-to-plasma ratio for dextran 250,000 averaged 0.33 (sem 0.061) and that for albumin-I131 averaged 0.50 (sem 0.039). The lymph-to-plasma ratio for dextran-C14 exceeded unity because of the rapid decline in plasma concentration and the slow transit of fluid to the collecting cannula. The data reported here provide a basis for studying changes in capillary permeability under abnormal conditions.
Strontium-calcium interrelationships in the growing rat
Authors: Palmer Ray F. , Thompson Roy C.
Published: December 2017

The comparative metabolic behavior of strontium and calcium was studied in growing, female rats exposed either continuously or to single doses of Sr90 and Ca45 while on diets of various total calcium contents. At weaning the discrimination against ingested Sr90 relative to Ca45 was markedly less than that previously observed in mature rats. This discrimination increased and approached the levels observed in mature animals, while growth and Ca45 deposition was still proceeding at a rapid rate. The effect of a fourfold increase in dietary calcium (from 0.5 to 2.0%) over a 200-day feeding period was a twofold reduction in the steady-state level of Sr90 in bone. As previously shown in mature rats, the retention (as opposed to absorption) of a single dose of Sr90 was relatively unaffected by dietary calcium level, while that of Ca45 varied from almost total retention on a 0.1% calcium diet to retention on a 2.0% calcium diet which was similar to that observed for Sr90 on all diets.
Source of fat oxidation in exercising dogs
Authors: Issekutz B. , Miller H. I. , Paul P. , Rodahl K.
Published: December 2017

Dogs with indwelling arterial and venous catheters ran on a treadmill for 30–40 min. Palmitate-1-C14 was infused intravenously. The rate of FFA uptake increased linearly with FFA concentration during rest and exercise. At rest 20– 22% of the FFA uptake was oxidized; during exercise this figure rose to 80–90%. About 50% of the fat-CO2 could be ascribed to immediate oxidation of plasma FFA. The radioactivity and specific activity of the plasma EFA showed no marked change during exercise. When a 3-hr infusion was stopped 5 min before exercise, the radioactivity in the plasma FFA fraction decreased rapidly in the first 10 min of exercise, followed by a very low but constant disappearance rate. The disappearance of radioactivity from the plasma (FFA and EFA combined) during exercise was less than 1% of the C14O2 output. Therefore, it was concluded that the intracellular fat pool plays an important role as an energy source, whereas the plasma EFA did not seem to participate appreciably in the 6-fold elevated metabolism.
In vivo influences of hydrogen ions on lactate and pyruvate of blood
Authors: Tobin Richard B.
Published: December 2017

The effect of acidosis and alkalosis produced by various agents on the in vivo equilibrium of lactate and pyruvate concentrations in blood has been studied in cats. It was predicted from formulae for dissociation and for oxidation potential that acidosis should cause a rise in lactate-to-pyruvate (L/P) ratio and alkalosis should cause a fall in the ratio. Acetic acid and HCI both produced a rise in L/P ratio but d-malic acid caused a fall in ratio. NaHCO3 and THAM both caused an increase in L/P ratio by effecting a greater rise in lactate than in pyruvate. It is concluded that some other influence of pH must be responsible for the changes noted.
Number and distribution of capillaries as determinants of myocardial oxygen tension
Authors: Myers Wayne W. , Honig Carl R.
Published: December 2017

Blood content per gram of tissue was measured in various regions of the myocardium of the dog, by use of I131-labeled albumin and Cr51O4-labeled red cells. The ratio of I131 to Cr51O4 distributions was uniform, indicating that plasma skimming does not increase O2 delivery to the inner layers. Gradients in blood content were observed from epicardium to endocardium, and in the base-apex dimension of the heart. Both the transmural gradient and the amount of blood per gram of tissue were greatest at the left ventricular apex. In this region the deeper layers contained 1.5 times as much blood as superficial ones. The data permitted estimates of the number of open capillaries, and of intercapillary distances. These estimates indicate that only a fraction of the available capillaries are perfused at rest. Mean tissue oxygen tensions were computed for various conditions of flow, capillarity, and metabolism by use of the Kety modification of the Krogh equation. Results are discussed in relation to the regulation of tissue PO2.
Metabolic effects of glucagon in the perfused rat heart
Authors: Kreisberg Robert A. , Williamson John R.
Published: December 2017

The effect of glucagon on glycogenolysis and the utilization of acetate-2-C14 and glucose-U-C14 was studied in the isolated perfused rat heart. Significant effects of glucagon were obtained with a concentration of 5 µg/ml. Glucagon increased the uptake and oxidation to CO2 of glucose-U-C14 and acetate-2-C14 by 300 and 50%, respectively. The cardiac glycogen content fell to 60% of initial levels in 5 min and then remained constant. Lactate production reached a peak 30 sec after perfusion with glucagon, reflecting the early rapid glycogenolysis, and then fell to a constant rate within 5 min. Steady-state levels of hexose or triose phosphates were increased 300% at a time when glycogen levels had reached a plateau, indicating an increased rate of glucose phosphorylation, after the initial phase of rapid glycogenolysis, despite elevated levels of glucose 6-phosphate. Glucose transport was stimulated by glucagon although glucose entry remained the rate-limiting step of glucose uptake since no free intracellular glucose was detected. The increased fuel utilization produced by glucagon is shown to be dissociated from the glycogenolytic effect and is probably a consequence of the increased work of the heart. The effects of glucagon on the perfused rat heart are identical to those of epinephrine.
Delayed compliance in external jugular vein of the dog
Authors: Porciuncula C. I. , Armstrong G. G. , Guyton A. C. , Stone H. L.
Published: December 2017

The time course and magnitude of delayed compliance in a typical large vein, the external jugular vein of the dog, were studied in an effort to determine whether or not delayed compliance in the large veins is an important factor in allowing the circulatory system to accommodate to large changes in blood volume. These studies showed that essentially all delayed compliance is complete within approximately 20 min and that its magnitude was only one-third to one-fifth as great as the immediate elastic compliance of the vessel. Therefore, it was concluded that delayed compliance in the large veins plays little role in allowing the circulatory system to accommodate itself to large changes in blood volume, and that most of this accommodation must occur in other vascular beds.
Brain temperatures in the rat during exposure to low environmental temperatures
Authors: Lomax Peter , Malveaux E. , Smith R. E.
Published: December 2017

Exposure to cold is known to elicit a rise in metabolic rate in various tissues of homeothermic animals. The role of the hypothalamus in this response was investigated by exposing normal and cold-acclimated rats to environmental temperatures of 26 C, 6 C, and –8 C and comparing the temperature changes in the thalamus, hypothalamus, and rectum using chronically implanted thermocouples. At all environmental temperatures the cold-acclimated rats had lower hypothalamic temperatures than did the normal animals. Apart from this, pattern of response was similar in all animals; the hypothalamic temperature tends to increase on exposure of the animal to cold while the adjacent thalamic region shows a marked fall in temperature, the rectal temperature staying fairly constant. This difference in response suggests increased metabolic heat production in the hypothalamus on exposure of the rat to low temperatures.
Circulatory response to hypoxia in unanesthetized dogs with and without cardiac denervation
Authors: Glick Gerald , Plauth William H. , Braunwald Eugene
Published: December 2017

The generally held view that acute hypoxia stimulates the cardiovascular system was reinvestigated in ten normal, trained, unanesthetized dogs and in six dogs which had previously been subjected to total cardiac denervation. In the normal dogs, no significant or consistent changes were noted in cardiac output, stroke volume index, or in systemic arterial pressure 5 and 15 min after the onset of 8% O2 inhalation. Heart rate, however, rose significantly. The dogs which had been subjected to cardiac denervation responded with small elevations of cardiac output and heart rate during the late hypoxic period. Thus, these findings are contrary to the classical concept that hypoxia elevates the cardiac output. Moreover, despite the absence of both the sympathetic and parasympathetic innervations of the heart, subjecting the denervated animals to severe hypoxia revealed that they were at no apparent hemodynamic disadvantage in comparison to the intact animals.
120-Day study of cardiac output in unanesthetized rats
Authors: Popovic Vojin P. , Kent Kenneth M.
Published: December 2017

The technique of permanent cannulation of the aorta and right atrium which permits the simultaneous sampling of arterial and venous blood in unanesthetized small laboratory animals was modified so that the venous cannula is inserted in the right ventricle and the patency of the cannulas increased to well over 100 days. After cannulation rats were used for cardiac output determinations (Fick principle). The animals were unanesthetized and unrestrained. Oxygen consumption, oxygen contents of the blood, and cardiac output were determined seven times in 98 adult male rats during a period of 120 days. The mean value of the cardiac index was 286 ± 25 ml/min kg, remaining unchanged during a period in which the body weight of the animals increased from 300 to 500 g. The results indicate that the technique of permanent cannulation of the aorta and the right ventricle offers a reliable and reproducible method for cardiac output determinations in unanesthetized and unrestrained rats during a period of several months after the cannulation.
Increased plasma level of renin in experimental secondary hyperaldosteronism
Authors: Higgins James T. , Davis James O. , Urquhart John , Olichney Michael J.
Published: December 2017

Renal and peripheral venous plasma was prepared for assay of renin by the technique of Helmer and the formed angiotensin II was assayed for both pressor and steroidogenic activity. Both assays showed higher concentrations of renin in both renal and peripheral venous plasma from dogs with thoracic caval constriction than from normal dogs. The increase in aldosterone and corticosterone secretion by isolated adrenals in response to incubated plasma with its formed angiotensin II was qualitatively similar to that observed for synthetic angiotensin II. Thus, the steroid assay provided evidence that the final product formed for assay was angiotensin II. That the pressor activity in renal vein plasma was referable to a substance of renal origin is indicated by the lower level of activity in peripheral venous than in renal venous plasma and the fall in activity in peripheral venous plasma following nephrectomy. Further evidence for the validity of the assay for renin was obtained from studies of renin substrate. A large excess of renin substrate was found in normal dog plasma so that angiotensin II formed by incubation was not limited by substrate exhaustion. Also, the peripheral plasma level of renin substrate was essentially the same in dogs with thoracic caval constriction and in normal dogs.
Brown and white adipose tissue metabolism in cold-exposed rats
Authors: Steiner G. , Cahill G. F.
Published: December 2017

Brown and white adipose tissue from rats exposed to 5 C for 9 days has been studied with reference to its composition and handling of glucose-U-C14 in vivo and in vitro. Brown adipose tissue from cold-exposed rats demonstrated a decreased lipid content per milligram nitrogen, due mainly to decreased amounts of neutral lipid with little change in phospholipid. The incorporation of glucose into neutral lipids, glyceride glycerol, and fatty acids was increased in vivo and in vitro. There was increased incorporation into CO2 in vitro and there was no change in glucose conversion to phospholipid in vivo. No changes in any of these were noted in epididymal fat pads. These findings suggest that cold exposure leads to alterations in carbohydrate metabolism and lipogenesis in brown adipose tissue but not in epididymal fat pads. The possible role in thermogenesis is discussed.
Active transport of iron by intestine: mucosal iron pools
Authors: Manis James , Schachter David
Published: December 2017

Methods were developed for the specific estimation of Fe++, Fe+++, Fe59++ and Fe59+++ in homogenates of rat duodenal mucosa and applied to studies of iron transport by everted gut sacs in vitro and duodenal loops in vivo. In the course of active transport in vitro Fe++ is absorbed into a mucosal ferrous pool which turns over relatively rapidly by a) transport of Fe++ to the serosal surface and b) formation of a mucosal Fe+++ pool. The latter turns over more slowly and appears to be a storage depot for excess mineral. When rats are pretreated with oral iron, uptake of Fe++ at the mucosal surface is decreased, diversion of mucosal Fe++ to mucosal Fe+++ is increased, and transport toward the serosal surface is reduced. Corresponding effects, which tend to limit iron absorption in vivo, are observed with duodenal loops. A sensitive hemagglutination-inhibition method was developed to estimate apoferritin in normal rat mucosa, and this protein was detected and quantified. Ferritin could account for only 8.0% of the trivalent mucosal pool and appeared to play an insignificant role in the present studies.
Na-K activated adenosine triphosphatase and sodium transport in toad bladder
Authors: Bonting Sjoerd L. , Canady Mel Rose
Published: December 2017

The effect of several agents in vitro on sodium transport by the intact toad bladder and on sodium-potassium activated, magnesium-dependent ATPase (Na-K ATPase) activity has been examined in an attempt to elucidate the relationship between the agents, the Na-K ATPase system, and active sodium transport. Ouabain and erythrophleine inhibited sodium transport and Na-K ATPase activity, but had no effect on sodium-potassium independent, magnesium-dependent ATPase (Mg-ATPase) activity. Vasopressin, adenosine 3',5'-monophosphate (cyclic-AMP), and aldosterone had no effect on Na-K ATPase or Mg-ATPase activity. The results are compatible with the assumption that the Na-K ATPase system is closely related to the active sodium pump, and that ouabain and erythrophleine inhibit sodium transport by the bladder through inhibition of the Na-K ATPase system. The stimulatory effect on sodium transport of vasopressin, cyclic-AMP, and aldosterone is not due to direct stimulation of the Na-K ATPase system.
Endotoxin lethality and tryptophan pyrrolase induction in cold-exposed mice
Authors: Berry L. Joe
Published: December 2017

Mice singly housed and exposed to 5 C are almost as responsive as animals at 25 C in carrying out glyconeogenesis following a single injection of cortisone. An ld50 of endotoxin lowers liver glycogen about equally in mice housed at each of the two temperatures but the dose for mice at 5 C is 1/100 the dose at 25 C. Cortisone given concurrently with the endotoxin prevents glycogen depletion in mice at 25 C but not in those housed at 5 C, except, possibly, at certain critical doses. Cortisone also fails to induce an increase in liver tryptophan pyrrolase activity in cold-exposed mice, in contrast to those maintained at room temperature, and this failure cannot be ascribed to any alteration in hematin level, the cofactor for the enzyme. These findings are considered as evidence for an impaired capacity for protein (enzyme) synthesis in normothermic animals during acute exposure to cold.
Adenine nucleotide degradation in the rabbit heart
Authors: Richman Harold G. , Wyborny Leigh
Published: December 2017

Adenine nucleotide analysis of tissue and perfusates of the isolated rabbit heart were undertaken following hypoxia and uncoupled oxidative phosphorylation. During uncoupled oxidative phosphorylation, nucleotide degradation, primarily that of ATP, was three times as great as that observed during hypoxia. Although inosine and hypoxanthine were generally observed degradation products, adenosine was recovered only following uncoupled oxidative phosphorylation. Perfusion with 8-azaguanine, however, resulted in recovery of adenosine during both hypoxia and uncoupled oxidative phosphorylation. Washout studies demonstrated the rapid extracellular movement of adenosine and the total content of adenosine was uniformly greater in perfusates than in tissue. In no case was adenine nucleotide efflux observed nor phosphatase or deaminase activity in the perfusate demonstrated. In myocardium initial dephosphorylation to adenosine would appear to be the principal pathway of AMP degradation. The rapid extracellular movement of adenosine would justify its consideration as a mediator of metabolic control in the intact heart.
Activity of single neurons in the hypothalamic feeding centers: effect of glucose
Authors: Anand B. K. , Chhina G. S. , Sharma K. N. , Dua S. , Singh Baldev
Published: December 2017

Unit activity from neurons of hypothalamic feeding and satiety mechanisms, and from adjacent hypothalamic regions was recorded in anesthetized dogs with surgically exposed hypothalamus, and in Flaxedil-immobilized cats in which a stereotaxic approach was made. Intravenous glucose or insulin, or combinations of both, were given and the changes in spike activity observed. Glucose estimations were done on blood samples taken from femoral artery and vein. In starved animals the unit activity in satiety center neurons was slower than that obtained from feeding center neurons. Frequency of spikes recorded from satiety center neurons increased and that of feeding center neurons decreased significantly after glucose was given intravenously, while spike activity from these centers showed a reverse pattern of response after intravenous insulin. No significant changes were observed from other hypothalamic and cortical neurons. Activity of neurons of the satiety center did not show a significant correlation with blood glucose level per se, but a better correlation was found between unit activity and the A-V glucose difference. It is suggested that the satiety center is activated by increased glucose utilization in the body.
Factors influencing renal excretion of foreign organic acids
Authors: Weiner I. M. , Blanchard K. C. , Mudge G. H.
Published: December 2017

Renal excretory mechanisms for 16 organic acids (mostly benzoates) were examined by standard renal clearances in the dog to establish their participation in an active secretory system, and to ascertain the factors influencing their simultaneous tubular reabsorption. Active secretion was demonstrated by clearances greater than the glomerular filtration rate and by inhibition of excretion by presumably competitively transported acids, i.e., hippurates. Critical chemical substituents essential for transport could not be identified. For reabsorption by non-ionic diffusion, the relative roles of acidic strength, lipid solubility, and urinary pH are evaluated with emphasis on the variation in the importance of each of these factors.