bluuebunny/crossref_metadata_2025 huggingface dataset:
Sympathetic nerve development in the brown adipose tissue of the rat
Authors: Berry D. M. , Daniel H.
Published: April 2011

With the Falck fluorescent histochemical method for catecholamines, the development of sympathetic nerve fibers in the brown fat of the rat was studied. At birth a low level of catecholamine fluorescence was found in preterminal axon bundles, which have been called here sheathed axons. The fluorescence in these bundles reached a maximum at about 5 days of age. Parenchymal nerve catecholamine fluorescence was discernible at 2 to 3 days of age. These nerves progressively got brighter until adult levels had been reached at about 10–15 days. The sympathetic nerve fiber network seen on arterial blood vessels in the adult was not seen in the young rat until 8–10 days of age. These blood vessel nerves reached maturity at about 15–21 days. The parenchymal nerve innervation was shown to originate in the sympathetic chain. The sympathetic chain gave off sheathed axon bundles which reach the parenchyma by passing along septa or beside blood vessels.
Induction of superovulation in mature rats with gonadotrophins
Authors: Husain S. M. , Saucier R.
Published: April 2011

Ovulation was induced in mature female rats by appropriately timed injections of pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (HCG). Various combinations of the gonadotrophins were used. Maximal ovulatory response was consistently obtained with 50 I.U. PMSG and any combination of HCG between 50 I.U. and 5000 I.U. On the basis of the results obtained it is recommended that 50 I.U. PMSG and 50 I.U. HCG be injected to obtain a maximal ovulatory response in mature rats. High doses of PMSG (but not HCG) suppress ovulation markedly.
A comparison of salbutamol with isoproterenol and norepinephrine in activating rat cardiac phosphorylase
Authors: McNeill John H. , Commarato Michael A.
Published: April 2011

Salbutamol (AH 3365) was administered by intravenous infusion to rats, and its effect on cardiac phosphorylase activation was compared with that of isoproterenol and norepinephrine. The dose–response curve obtained with salbutamol demonstrated that the maximum effect was less than that obtained with the other two amines. Salbutamol was approximately 1/400 as potent as isoproterenol and 1/40 as potent as norepinephrine in activating cardiac phosphorylase. The phosphorylase-activating effect of both isoproterenol and salbutamol was blocked by propranolol. The results indicate that salbutamol has much less affinity for the cardiac β-receptor responsible for activating phosphorylase. The results also indicate that this receptor is probably of the β1 type.
Influence of energy supply and calcium on the low sodium induced changes in the transmembrane potential and contraction of guinea pig papillary muscle
Authors: Prasad K.
Published: April 2011

The effects of changes in extracellular concentrations (25, 50, 100, 140 mM) of NaCl on the simultaneously recorded action potential (AP) and contraction of guinea pig papillary muscle in the presence of various concentrations of glucose (0, 5, 20, 30, 50 mM) and CaCl2 (0, 0.5, 1.0, 2.5 mM) were investigated. Low sodium (25 mM) produced a marked shortening of the action potential duration (APD) associated with a marked increase in the force of contraction but a small change in AP amplitude. A direct relation between extracellular NaCl and cardiac contraction was observed. There was no relation between AP amplitude and cardiac contraction. Low sodium induced shortening of the APD was greater in the absence of glucose than in its presence while the increase in the force contraction induced by low Na was markedly reduced in the absence of glucose. Low sodium was practically ineffective in restoring the contraction of papillary muscle in the absence of CaCl2. A calcium concentration dependent increase in the force of contraction was associated with a corresponding shortening of the APD in low sodium. Anoxia markedly reduced the positive inotropic effects of low sodium and enhanced the low sodium induced shortening of the APD in the papillary muscle. Glucose produced a marked lengthening of the APD which was shortened during anoxia but it was effective only slightly in lengthening the APD shortened by low sodium. The effects of ouabain in the muscles in the presence of low sodium were reduced. It is suggested that the changes in the APD accompanied by changes in the contraction in the guinea pig papillary muscle might be associated with NaCl-induced changes in the membrane ATPase. The low sodium induced increase in the force of contraction seems to be dependent upon both calcium and energy supply.
Effect of dihydroergotamine and growth hormone on lipolysis in isolated fat cells of the rat
Authors: Hotta N. , Sirek O. V. , Sirek A.
Published: April 2011

Dihydroergotamine (DHE) is lipolytic in the isolated fat cell preparation of Rodbell. Bovine growth hormone (GH) alone or in combination with dexamethasone causes lipolysis that is barely measurable. The combination of GH and DHE is equally ineffective. Incubation of fat cells with all three agents produces massive lipolysis that is by far greater than the sum of effects of individual components. The augmented lipolytic effect is suppressible with puromycin. The exact mechanism of interaction between GH, dexamethasone, and DHE has to be elucidated.
Rationalization and optimization of the hemodialysis procedure. II
Authors: Stinson Robert H. , Boer Jan de
Published: April 2011

The concepts of dialysance and clearance, as applied in hemodialysis, were closely examined. Strict application of Wolf's definition shows dialysance to be a flow-independent function of the membrane area and thickness as well as of the diffusion coefficient of the substance to be removed. Clearance is a flow-dependent function of dialysance except in a non-flow situation, where clearance equals dialysance. Flow-dependent clearance equations and time-dependent equations for removal of substances from blood, both with and without concurrent metabolic production, are developed for Kolff and Kiil hemodialyzers. Since clearance increases with increase of any variable, only practical considerations need be considered in hemodialyzer design.
The effect of chronic hypoxia on in vitro lipolysis in the rat
Authors: Alpert Arnold
Published: April 2011

The responsiveness of the lipolytic system in chronically hypoxic rats (14 500 ft) was assessed by the in vitro release of free fatty acids (FFA) and glycerol, measured aerobically and anaerobically, in epididymal fat pads from fed, fasted, and fasted–refed animals. Basal aerobic release of FFA for fed rats was significantly higher in the altitude (ALT) group. In fasted rats both basal and norepinephrine (NE)-stimulated release of FFA and glycerol was higher when compared with heavier sea level (SL) controls. However, weight-matched (younger) controls showed no difference in release rates. Anaerobic NE-stimulated release of FFA, glycerol, and lactate was higher in ALT rats than in weight-matched SL controls only in those animals fasted and refed a high carbohydrate diet. Fat pad glycogen content in such animals was 0.207 mg/100 mg tissue for SL and 0.384 for ALT. Anaerobic in vitro FFA mobilization in adipose tissue from fasted–refed ALT rats is more sensitive to NE, and this physiological advantage may be a reflection of a greater potential for glycogen storage in the fat tissue of these acclimated animals. Additionally, weight matching is necessary in evaluating altitude-stressed animals, and use of dietary restrictions to obtain controls of equal age and weight may yield misleading metabolic data.
Pressor action of beta blocking agents in rats
Authors: Regoli D.
Published: April 2011

Propranolol (10 to 30 μg/kg), oxprenolol (trasicor) (5 to 10 μg/kg), and sotalol (10 to 50 μg/kg) evoke an acute and prolonged increase of arterial pressure in normal and nephrectomized rats, while after adrenalectomy the arterial pressure remains unchanged or is reduced. The pressor effect is accompanied by a reduction of heart rate. The dose of the three beta blockers evoking an arterial pressure increase does not antagonize the effect of isopropylnoradrenaline. To block the beta receptors, doses 10 to 100 times higher than those effective on arterial pressure have to be used. The block of the beta receptors is accompanied by an initial fall of the blood pressure and by a significant decrease of the heart rate. The pressor effect of beta blockers is not antagonized but rather is potentiated by phenoxybenzamine and phentolamine. Moreover, in the presence of an alpha receptor blockade, the administration of beta blockers partially restores the response to catecholamines. These results support the hypothesis that the pressor effect evoked by beta receptor blocking agents may be due: (a) to the release of endogenous catecholamines and (b) to the interference by beta blockers with phenoxybenzamine and phentolamine on the alpha receptors.
Influence of glucose metabolism on ouabain-induced changes in the transmembrane potential and contraction of human heart in vitro
Authors: Prasad K. , Callaghan John C.
Published: April 2011

Effects of glucose, anoxia, iodoacetate, and 2,4-dinitrophenol on the ouabin-induced changes in the simultaneously recorded transmembrane action potential and contraction of 72 human papillary muscle strips obtained from 36 patients undergoing corrective open heart surgery were investigated. Ouabain (10−8M, 10−9M, 10−10M) produced a shortening of the action potential duration (APD) and an increase in the force of contraction in the muscle. Non-oxygenated glucose-free solution, iodoacetate (10−5M), and 2,4-dinitrophenol (10−6M) produced partial to complete inhibition of the positive inotropic effects of ouabain (10−8M or 10−9M) in the papillary muscles. The shortening of the APD produced by ouabain was further enhanced in the presence of the above metabolic inhibitors. As the glucose level was raised (0, 5, 10, 20, 30 mM), anoxic papillary muscles responded to ouabain by a progressive increase in the force of contraction and a parallel increase in the APD. Glucose (30 mM) was effective in restoring the positive inotropic effects of ouabain in DNP-poisoned muscle while it was ineffective in doing so in the muscle poisoned with both IAA and DNP. These results indicate the requirement of energy for the positive inotropic effects of ouabain in cardiac muscle.
The effect of nitrate ion on glycerol-treated frog skeletal muscle fibers
Authors: Luff A. R. , Atwood H. L.
Published: April 2011

The effect of nitrate ion on glycerol-treated, frog sartorius muscle fibers was investigated. Glycerol treatment alone (which has been shown to disrupt the transverse tubular system of the fiber) caused a considerable reduction in the time constant of the fiber membrane, but the effective resistance was virtually unchanged. Exposure of normal fibers to nitrate ion produced an increase in both the effective resistance and the time constant. Glycerol-treated fibers exposed to nitrate ion showed an increase in both the effective resistance and the time constant. The latter increased to a value in excess of that found in the normal fibers. The effect of nitrate ion on membrane electrical properties appeared to result from its action on the surface membrane as opposed to the transverse tubules.
Penetration of Circulating GABA into Long-Isolated Cortical Slabs
Authors: Gottesfeld Zehava , Krnjević K. , Reiffenstein R. J.
Published: April 2011

Small slabs of suprasylvian cortex were isolated unilaterally in six cats. After an interval of 3–4 months, single units were recorded in the slabs and in the contralateral control areas. Intravenous injections of GABA and glutamate (mostly 2–8 mmole) failed to alter the discharge of these units in any clear and predictable way that could not be ascribed to large changes in blood pressure. In this respect there was no difference between long-isolated and control neurons. 14C-GABA injected i.v. did not penetrate the slabs more rapidly than the control areas. It is concluded that the convulsive tendency of long-isolated slabs cannot be ascribed to a general increase in permeability of the blood–brain barrier. There was some evidence that slabs have a higher blood content than normal cortex.
Detection and Analysis of Parpanit in Blood by Gas–Liquid Chromatography
Authors: Casselman A. A. , Bannard R. A. B.
Published: April 2011

A method has been developed for the extraction of Parpanit free base (caramiphen) from human blood and for determination of the drug by gas–liquid chromatography. The method is reliable and nearly quantitative but insufficiently sensitive for use in peak build-up and clearance studies in humans. Factors such as the age of the blood and time of contact of the drug with the blood on the efficiency of recovery were examined. The Parpanit content of fresh rabbit blood could be measured accurately, but there was considerable variability in the results obtained with fresh blood from different rabbits. The drug was degraded or absorbed by contact with rabbit blood in vitro and in vivo, more rapidly by the serum than by the cells.
The Effect of Vitamin A Deficiency in Rabbits on the Elastic Properties of the Lung and Thoracic Aorta
Authors: Saksena J. S. , Mehta J. A. , Naimark A.
Published: April 2011

Weanling rabbits were fed a vitamin A deficient diet for 6 weeks. During this period they failed to gain weight normally and exhibited significantly lower serum vitamin A levels when compared with their littermates fed a vitamin A supplemented diet. These findings indicated that vitamin A deficiency was established, and the lungs and specimens of aorta were removed for study. The pressure–volume relationships of saline-filled lungs revealed that test lungs were more compliant than control lungs and this difference was associated with a decrease in elastin content in test lungs. The absence of such changes in pair-fed controls suggests that the effects are due to vitamin A deficiency per se rather than the general effects of retarded growth. A decrease was also noted in the elastance of the aorta, confirming that vitamin A deficiency has an effect on elasticity of tissues generally. When vitamin A deficient animals were given vitamin A supplemented diets the elastance of the aorta returned to control values but the compliance of the lung, although somewhat decreased, did not reach control values. The mechanism by which vitamin A deficiency affects tissue elasticity is not known.
The Effect of Preganglionic Stimulation on the Acetylcholine and Choline Content of a Sympathetic Ganglion
Authors: Friesen A. J. D. , Khatter J. C.
Published: April 2011

Preganglionic stimulation of the cat's superior cervical ganglion at 60/s for 2–8 min reduced the ganglion's acetylcholine (ACh) content by about 30%. With continued stimulation, the ACh stores gradually recovered within 15 min. However, when ganglia were allowed to rest following 4 min of stimulation at 60/s not only was there a rapid restoration of the ACh content, but the ACh levels rose to 130% of control after 10 min of rest. Under either of these experimental conditions the choline content increased transiently only after the ACh stores had returned to control values. The above data suggest that there may be a delay in the onset of maximal rates of ACh resynthesis induced by nerve stimulation and that ACh synthesis continues for several minutes after the cessation of the stimulus. In addition, the results are consistent with the concept that about one-third or more of the total ACh stores of a rested ganglion is in a form that can be readily mobilized for release. The observed rebound increase in the ACh content probably means that the ACh storage capacity is not normally saturable and that under most physiological conditions the ACh levels are maintained within certain limits by a precise control of ACh synthesis.
Multigeneration Studies on the Effect of Dietary DDT on the Vitamin A Status of the Weanling Rat
Authors: Phillips W. E. J. , Hatina G. , Villeneuve D. C. , Grant D. L.
Published: April 2011

The feeding of a nutritionally adequate stock diet containing 20 p.p.m. p,p′-DDT to rats for three generations demonstrated that this pesticide decreased liver stores of vitamin A in weanling rats. The lower vitamin A levels were not modified in successive generations of weanlings. The DDT effect was not apparent in the dams at maturity. Possible public health implications are discussed.
The Effect of Ouabain on Substrate Metabolism in the Isolated Perfused Rat Heart
Authors: Hoeschen Robert J.
Published: April 2011

The effect of ouabain (2, 5, and 10 μg/ml) on the uptake and oxidation of 5 mM glucose-U-14C and 0.4 mM palmitate-1-14C was determined in the isolated perfused rat heart. During 30-min perfusions, 5 and 10 μg/ml ouabain enhanced glucose uptake and 10 μg/ml also increased glucose oxidation. Palmitate uptake, oxidation, and incorporation into tissue lipids were unaffected by ouabain. The addition of glucose did not alter the lack of effect of ouabain on palmitate metabolism, but the presence of palmitate inhibited the stimulatory effect of ouabain on glucose uptake. The ouabain enhancement of glucose uptake was not associated with any change in glycerol release from the perfused heart, nor did ouabain increase the stimulated glucose utilization due to insulin. The concentrations of ouabain used in these experiments were shown to have an inotropic effect when the glycoside was added after 45 min of control perfusion. Thus, ouabain had no effect on palmitate metabolism. The enhancement of glucose uptake and oxidation was not due to an antilipolytic effect, nor did ouabain potentiate the effect of insulin on glucose transport. The ouabain effect on glucose utilization was associated with, but not necessarily a result of, increased contractility.
Lactate and Pyruvate Levels in Brain and Skeletal Muscle During Hyperthermia in Dogs
Authors: Dunn Robert B. , Lioy Franco
Published: April 2011

Tissue hypoxia, as shown by an increase of the arterial concentration of lactate and of the lactate–pyruvate (L/P) ratio, has been observed during hyperthermia in free-breathing animals with high arterial [Formula: see text]. The effect of raising body temperature to 41.9 °C for 2 h on lactate and pyruvate concentrations in arterial, muscle venous, and sagittal sinus blood and cerebrospinal fluid was studied in anesthetized dogs. The animals were paralyzed with gallamine, and arterial pH and [Formula: see text] maintained at normal levels by artificial ventilation with 50% O2[Formula: see text]. A slight increase in lactate and pyruvate took place in the arterial blood and parallel changes were observed both in the muscle venous and sagittal sinus blood. The L/P ratio did not change. Lactate and pyruvate increased markedly in the CSF, without a change in the L/P ratio. Therefore hyperthermia, in the absence of respiratory alkalosis, does not appear to induce tissue hypoxia associated with an increase in L/P ratio. The lack of correlation between lactate and pyruvate concentrations in sagittal sinus blood and cerebrospinal fluid confirms the fact that the A–V differences of these substrates across the brain are not a good index of cerebral metabolism.
The Renal Response to Blood Volume Expansion in the Rat: Proximal Tubular Function and Urinary Excretion
Authors: Sonnenberg H.
Published: April 2011

Chronically salt- and deoxycorticosterone-acetate-loaded (DOCA) rats and chronically salt-deficient (NaD) rats were infused with blood, and consequent changes in renal excretion of water and electrolytes were compared with simultaneous alterations in proximal tubular function. During the period of intravascular expansion maintained by reinfusion of urine, diuresis and natriuresis, significant compared to control excretion, were seen in both groups. Although absolute levels of diuresis were not statistically different, DOCA rats excreted more sodium and less potassium than NaD rats; total cation excretion (Na+K) was comparable. A 10% reduction in proximal fractional reabsorption occurred in both series, associated, however, with large similar increases in single nephron filtration rate, so that absolute rates of proximal fluid reabsorption were actually increased. No correlation was found between changes in fractional or absolute reabsorption and renal excretion. Since vascular expansion results in similar alterations of filtration rate and proximal transport in both groups, the different ratios of excretion of sodium and potassium must be due to differences in tubular function at sites distal to the proximal convolution. The lack of direct correlation between proximal function and magnitude of renal excretion in these experiments further suggests that the excretory response to blood volume increase is determined ultimately by tubular mechanisms located in the distal part of the nephron.
Metabolic Control Mechanisms in Mammalian Systems. XIII. Thyroid Hormone Control of α-Glycerophosphate Dehydrogenase Activity in Rat Cerebral Cortex and Cerebellum
Authors: Schwark W. S. , Singhal R. L. , Ling G. M.
Published: April 2011

The influence of thyroid hormone on soluble NAD-linked α-glycerophosphate dehydrogenase (α-GPDH) activity as well as the ontogeny and relative distribution of this enzyme were investigated in certain regions of the rat brain. In adult female rats, highest levels of enzyme activity were found in the brain stem and spinal cord; lowest activity was present in the cerebellum. Studies on the development of α-GPDH in the cerebral cortex and cerebellum revealed the presence of extremely low levels of enzyme activity at birth with rapid increases occurring within the first 30 days of life. These developmental increases in α-GPDH activity of the cerebral cortex and cerebellum were markedly impaired in rats made hypothyroid by treatment with 131I at 1 day of age. Whereas 50 μCi of 131I exerted no appreciable effect on the brain enzyme, 60% inhibition of α-GPDH was produced by 200 μCi of the radioisotope. Much less inhibition of enzyme activity in both cerebral cortex and cerebellum was observed when thyroidectomy was delayed for 20 days after birth. Treatment of young hypothyroid animals with L-triiodothyronine (T3) produced increases in cerebrocortical and cerebellar α-GPDH activity which were both time- and dose-dependent. However, when the initiation of T3 treatment was delayed until thyroidectomized animals reached adulthood, the hormone failed to produce any appreciable change in enzyme activity. Cycloheximide, an inhibitor of protein synthesis, prevented the T3-induced increases in brain α-GPDH in neonatally thyroidectomized animals, suggesting that the observed hormone-stimulated increases in enzyme activity may be the result of new enzyme synthesis. Evidence indicates that thyroid hormone plays an important role in the regulation of α-GPDH activity of the developing cerebral cortex and cerebellum.
The Excretion of Catecholamines in Rats During Acute and Chronic Exposure to Altitude
Authors: Myles W. S. , Ducker A. J.
Published: April 2011

The response of the sympathoadrenal medullary system in rats exposed to altitude has been assessed in terms of excretion of free noradrenaline (NA) and adrenaline (A) in the urine. Male Sprague–Dawley rats were either exposed acutely to simulated altitudes of 18 000 ft and 24 000 ft for 6 h or chronically to 18 000 ft for 5 weeks. Acutely exposed animals showed a considerable increase in the excretion of both catecholamines at 18 000 ft and 24 000 ft accompanied by a fall in body temperature. Acclimation to 18 000 ft by chronic exposure was achieved either by allowing the animals to reach the final altitude in stages during the 1st week, or by placing them directly at 18 000 ft. Body weight measurements confirmed that the second exposure condition was the more stressful. Although both groups showed an increase in NA excretion in the initial stages, only the second group exhibited an increase in A excretion. As the exposure continued, NA excretion returned towards sea level values. Preexposed animals maintained their body temperature at 18 000 ft and, when subsequently exposed to 24 000 ft for 6 h, did not excrete increased levels of NA or A. Increased activity of the sympathoadrenal medullary system appears to be involved only in the initial stages of acclimation to altitude.
Circulating Adrenocorticotropin (ACTH) as a Controlled Variable in the Regulation of ACTH Secretion
Authors: Kraicer J. , Conrad R. G.
Published: April 2011

Rats received 21 daily injections of hydrocortisone acetate, beginning 5 days after bilateral adrenalectomy. Immediately following cessation of hydrocortisone administration, adenohypo-physial adrenocorticotropin (ACTH) concentration was reduced to about 40% of intact, control levels and remained at this low level for 16 days. There followed a gradual increase to intact control levels by 32 days, to 150% of control by 48 days, and to 170% of control by 64 days. The daily administration of a long-acting ACTH preparation following the cessation of hydrocortisone administration altered this response. Adenohypophysial ACTH levels remained lower than in the animals not receiving ACTH, reaching only 50% of control at 32 days and 93% of control at 48 days. At 64 days, ACTH concentration was actually higher in the ACTH-treated group, reaching over 300% of control values. These findings demonstrate (a) that the circulating level of ACTH can, in itself, alter adenohypophysial ACTH concentration, and (b) the importance of timed studies, since, depending on the time chosen, ACTH administration will depress, augment, or indeed produce no change in adenohypophysial ACTH concentration. We conclude that the circulating levels of ACTH can alter ACTH secretion.
Human Serum Pseudocholinesterases: Molecular Weight Estimation of a Subunit Structure
Authors: Boutin Denis , Brodeur Jules
Published: April 2011

Molecular weight determinations by gel filtration on Sephadex G-200 were performed on fractions of human serum cholinesterases as obtained after ultrafiltration through a semipermeable membrane. The molecular weight of the fraction filtering through a membrane with molecular weight exclusion limits of 100 000 was estimated to be 86 000, whereas that of the fraction retained by the filter was higher than 300 000, approximating the value of 348 000 previously reported in the literature. Both fractions were shown to be interconvertible under the experimental conditions used. These results provide further evidence in favor of the existence of an enzymatically active subunit structure of cholinesterases and suggest that subunits combine into tetramers to form the major component of the cholinesterase activity in human serum.
Résistance Electrique de la Paroi d'une Microélectrode
Authors: Caillé Jean Pierre , Gagné Simon
Published: April 2011

The electrical resistance (R) and tip potential (Ep) of the conventional microelectrode (outside diameter at the tip < 0.5 μ) was measured as it passed through the interface between a KCl solution and pure CCl4. The microelectrode was pulled from Pyrex (No. 7740 Corning) glass capillaries and filled with 1.0 M KCl. In the 40 microelectrodes studied, the electrical resistance was found to increase with depth of penetration in the CCl4, although with considerable variation. Depending on the electrode, a 10-fold increase in resistance (R10) could be recorded after as little as 1.5 (μ) or as much as 7.0 (μ) penetration (defined here as Z10). At the depth of penetration producing R10, the tip potential of the electrode was found to vary with the KCl concentration in the aqueous phase. Specifically, the stable Ep versus log (aK) plotted for a KCl range between 1.0–0.02 M produced a straight line (slope varied from 33–55 mV depending on the electrode).
Vascular Capacity and Hematocrit in Experimental Cardiomegaly due to Aortic Constriction in Rats
Authors: Rakušan Karel
Published: April 2011

Cardiomegaly in rats was induced by experimental aortic stenosis caused by slowly constricting rings placed on the abdominal aorta. The capacity of the terminal vessels per gram of left ventricle was significantly lower in these animals as compared to normal rats. Chronic treatment with heart extract prevented this decrease without influencing heart growth. Tissue hematocrit in hypertrophied hearts due to aortic constriction was also significantly lower than in the normal heart. The results indicate that capillary capacity in cardiomegaly depends on the age of animals in which pathological growth of the heart occurs. On the other hand, the values of hematocrit in the coronary vessels in the same situation are determined by the type of mechanism which induces the pathological growth.
The Effects of Pharmacological Agents on the Electrical Responses of Cells of Nitella flexilis
Authors: Belton P. , Netten C. Van
Published: April 2011

Procaine hydrochloride decreases potential and effective resistance of the membrane and does not produce prolonged spikes. Tetraethylammonium (TEA) and barium ions prolong the spikes of internodal cells of Nitella evidently by delaying K+ activation as is the case in many other excitable cells. The last two agents do not increase the amplitude of the spikes in contrast to their effect on some arthropod muscle fibers. The other effects of Ba2+ and TEA on the spikes of Nitella and animal cells are almost identical. We conclude that the same molecular mechanism is involved in K+ activation in animals and plants.
Cold-Induced Vasodilatation in the Sheep
Authors: Meyer A. A. , Webster A. J. F.
Published: April 2011

Experiments were performed to investigate the nature and control of cold-induced vasodilatation (C.I.V.D.) in the extremities of sheep exposed to air temperatures below 0 °C. Two distinct patterns of C.I.V.D. were observed, the 'hunting' phenomenon and continuous proportional control of skin temperature. The different patterns were characteristic of individual sheep and not influenced by cold acclimation. Temperature fluctuations (hunts) were usually asynchronous in different extremities. Infusion of noradrenaline (NA) usually initiated a synchronous rise in skin temperature as blood pressure rose but thereafter reduced the intensity and frequency of hunting. During infusion of NA one sheep regularly exhibited cardiac arrhythmia except during a 5-week period of cold acclimation. Following section of the left vagosympathetic trunk, the sympathectomized left ear remained close to +40 °C at air temperatures of −25 °C. Infusion of NA for 100 min reduced temperature of the sympathectomized ear to about +15 °C after which point regular hunting ensued. Angiotensin and vasopressin did not reduce temperature in the sympathectomized ear. The results indicate that sympathetic nervous control is essential to cold vasoconstriction in the sheep and suggest that it is the dominant factor regulating skin temperature during the process of C.I.V.D.
Biochemical Basis of Heart Function. IV. Energy Metabolism and Calcium Transport in Hearts of Vitamin E Deficient Rats
Authors: Fedelesova Margaret , Sulakhe Prakash V. , Yates John C. , Dhalla Naranjan S.
Published: April 2011

Feeding a vitamin E deficient diet to rats for 10 weeks was found to decrease myocardial creatine phosphate, ATP, ATP/ADP ratio, NAD+, NADP+, and NADPH, whereas the level of ADP was increased without any changes in the levels of AMP, total adenine nucleotides, NADH, and ATP/AMP ratio. The levels of ATP and pyridine nucleotides were restored fully, whereas creatine phosphate was restored partially on feeding a normal diet for 4 weeks to animals previously on the vitamin E deficient diet for 10 weeks. Vitamin E deficiency was found to increase cardiac lactate, pyruvate, and lactate/pyruvate ratio and decrease the activities of lactate dehydrogenase and malate dehydrogenase. The activity of Na+–K+-stimulated, ouabain-sensitive ATPase was markedly elevated in the hearts of animals on the vitamin E deficient diet. The ATP-dependent calcium accumulation by the sarcoplasmic reticular fraction in the absence and presence of P1 or oxalate was greater in the vitamin E deficient heart. Vitamin E deficiency also increased the Ca2+-stimulated ATPase activity of the cardiac sarcoplasmic reticulum. Although myocardial contractility of the hearts from vitamin E deficient rats was depressed, no damage to the ultrastructures of mitochondria and sarcoplasmic reticulum was apparent. These results indicate marked alterations in myocardial metabolism due to vitamin E deficiency and it is suggested that such changes are due to abnormalities in the processes of both energy production and utilization.
Hymenolepis diminuta: The Microbial Fauna, Nutritional Gradients, and Physicochemical Characteristics of the Small Intestine of Uninfected and Parasitized Rats
Authors: Mettrick D. F.
Published: April 2011

In uninfected rats the amount of trichloroacetic acid (TCA) soluble and insoluble carbohydrate in the small intestine declined steadily from duodenum to ileum. In rats infected with 10 16-day-old Hymenolepis diminuta these gradients were reversed and there was a 54% increase in the amount of TCA-soluble carbohydrate, and a 110% increase in the amount of glucose present in the luminal contents.In uninfected rats the amounts of TCA-soluble and -insoluble nitrogen and of total lipid in the small intestine were considerably more than in the intestine of infected rats. The differences may represent utilization by the worms of these nutrients.In parasitized rats the concentrations and molar ratios of the amino acids of the intestinal amino acid pool were significantly different (P < 0.001) in every region of the gut from those in uninfected animals.The intestinal pH of parasitized rats was lower than that in uninfected rats, and the pH gradient showed an inverse correlation with worm biomass and lactic acid distribution.The number of microorganisms present in the small intestine and colon of parasitized rats was less than half that in uninfected animals. Escherichia coli and the coliforms showed the greatest decrease in numbers. Other common aerobes were also markedly reduced in number. Anaerobic enterococci and yeasts were absent in the parasitized animals; anaerobic streptococci and micrococci were restricted to the ileum.
Regional Differences in Rates of Insorption of Sodium and Water from the Human Large Intestine
Authors: Devroede Ghislain J. , Phillips Sidney F. , Code Charles F. , Lind James F.
Published: April 2011

Regional differences in sodium and water fluxes across the mucosa of the human colon were sought by comparing the arterial appearances of isotopes of sodium and water after instillation of test solutions containing them into four parts of the large intestine. Deuterium oxide and 24Na, in isotonic sodium chloride (154 mM), were placed in the cecum, transverse colon, descending colon, or rectum. The times of appearance and concentration of isotopes in serial samples of arterial blood were integrated with known plasma–disappearance curves to obtain rates of unidirectional flux from colonic lumen to blood (insorption). A gradient of insorption was found. Insorption was most rapid in the cecum and decreased progressively in the transverse colon, descending colon, and rectum. During steady-state perfusion of the entire large intestine the insorption rates of sodium and water, calculated by disappearance of isotopes from the lumen, were intermediate between those observed in the cecum and transverse colon during regional studies. Perfusion studies also revealed a close correlation between insorption and net absorption of sodium and water, implying that a regional gradient of net absorption may exist in the large intestine, analogous to the observed insorption gradient.
Comparative Effects of Ethacrynic Acid, Furosemide, and Diazoxide in the Perfused Dog Hindlimb
Authors: Ogilvie R. I. , Schlieper E.
Published: April 2011

The vasodilator effects of intravenous ethacrynic acid (EA), furosemide (F), and diazoxide (DZ) were compared in the hindlimb of anesthetized anephric dogs, perfused with a constant inflow of arterial blood. A dose-response relationship was demonstrated for all three agents. The curves for EA and F were parallel and relatively flat, with EA being 10 times more potent than F in producing vasodilatation of the perfused limb. The dose–response for DZ was steep and the maximal vasodilator response observed at the lowest dose of DZ (5 mg/kg) did not differ from that at the highest doses of EA (10 mg/kg) or F (100 mg/kg). The maximal vasodilator effect of DZ in the perfused hindlimb occurred within 2 min after intravenous administration. After the higher doses of F there was a transitory vasodilator effect within 2 min but the maximal and more persistent effect was not observed until much later. The mean time for maximal effect was 40 min for EA, 46 min for F, and 2 min for DZ. The time course of vasodilator effect and maximal observed effect for EA and F was not altered by intraarterial administration nor by sympathetic decentralization of the perfused hindlimb. We conclude that F, like EA, has a direct vasodilating effect on peripheral arterioles and both EA and F probably act by a different mechanism than DZ.
Lactate Turnover and Oxidation in Normal and Adrenal-Demedullated Dogs during Cold Exposure
Authors: Minaire Yves , Pernod André , Jomain Marie-Josèphe , Mottaz Michel
Published: April 2011

Plasma lactate turnover and oxidation rates have been measured by primed continuous infusion of L-14C-lactate in normal and adrenal-demedullated dogs shivering in a cold environment. In normal dogs, oxygen consumption due to shivering in the cold increased by a factor of 5.2 relative to the resting state in a thermoneutral environment. Plasma lactate concentration did not change but the rates of production and utilization of this metabolite were more than doubled. The increase in turnover of lactate in the cold was accompanied by an increase in its rate of oxidation. Over two-thirds of the lactate produced was promptly oxidized accounting for 12% of the expired CO2. Relative to normal dogs exposed to cold, cold-exposed adrenal-demedullated dogs showed increases of 40–60% of plasma lactate concentration, turnover rate, and conversion to respiratory CO2.
Constriction of Human Umbilical Vein Under Aerobic and Anaerobic Conditions
Authors: Nair Xina , Dyer Donald C.
Published: April 2011

In the presence of metabolic inhibitors, the responses to serotonin of helically cut strips of human umbilical vein in Krebs–Henseleit solution at 37 °C were recorded isotonically. The tissues contracted to serotonin in a 95% nitrogen – 5% carbon dioxide atmosphere and in the presence of sodium cyanide (NaCN, 10−3M) and 2,4-dinitrophenol (DNP, 10−3M). The results indicate that human umbilical vein is capable of responding quite well to serotonin at very low oxygen levels and in the presence of sodium cyanide. The average maximum contractions to serotonin in the presence of NaCN and in the 95% nitrogen – 5% carbon dioxide atmosphere were, respectively, 91% and 88% of control. The contractile responses to serotonin were quite inhibited in the presence of 2,4-dinitrophenol. The combination of NaCN plus DNP did not inhibit the contractions to serotonin over that inhibited by DNP alone.
The Mechanisms of Tolerance Towards Histamine in the Rat and Mouse
Authors: Lewis A. J. , Nicholls P. J.
Published: April 2011

Rats and mice were rendered tolerant to histamine by prolonged treatment with the amine. Possible mechanisms of adaptation were examined in these species. Increased binding of histamine to nonmast cell sites in the skin and lung of the mouse and the lung and ileum of the rat was observed. The ability of the blood serum to bind histamine (histaminopexy) was increased in the histamine-treated mouse although serum from the rat possessed a lower binding capacity compared with controls. Prolonged administration of histamine to both species resulted in significant but relatively small increases in both in vivo and in vitro catabolism of histamine in several tissues. A reduction in the histamine-forming capacity of the kidney was observed in histamine-adapted rats. Adrenal changes were noted after histamine treatment and included increased weight in both species, lowered noradrenaline, and an increased level of adrenaline in the rat adrenals. It appears that no single mechanism examined explains the tolerance obtained but that the effect is a combination of factors.
Seasonal Changes in Catecholamine Content and Composition of Interscapular Brown Fat in Rats Fed a Commercial Chow or a Semipurified Diet
Authors: Héroux O. , Johnson G. E. , Flattery K. V.
Published: April 2011

Catecholamine content and composition of interscapular brown fat pads have been determined in rats fed a commercial chow (MLC) or a semipurified diet (T4F) and exposed in groups of 15 to outdoor winter, spring, or summer conditions. Brown fat pads were heavier in all seasons in T4F-fed rats than in MLC-fed rats; they contained more of every constituent, which means that the diet did not affect the composition of the fat but favored its growth. Under winter conditions the brown fat pads in T4F-fed rats showed a greater reduction of lipid and in severe winter (1967–1968), they contained more noradrenaline. The greater trophic changes during winter in brown fat of T4F-fed rats than of MLC-fed rats suggest a greater metabolic potential of that tissue in T4F-fed rats which could in part explain the greater cold resistance provided by that diet.
The Threshold for Potassium-Induced Contractures of Frog Skeletal Muscle. Potentiation of Potassium-Induced Contractures by Preexposure to Subthreshold Potassium Concentrations
Authors: Vos E. C. , Frank G. B.
Published: April 2011

A brief exposure (about 10–30 s) of a frog's toe muscle or a small bundle of fibers from the semi-tendinosus muscle to just subthreshold potassium concentrations potentiated contractures subsequently produced by exposing the muscles to a potassium concentration slightly above the threshold. The contractures thus potentiated had greater maximum tensions, and greater rates of tension development and relaxation than control contractures elicited by the same final potassium concentration. The resistance to stretch (R.T.S.) in the first few seconds of the potentiated contractures was about twice that of control contractures. Maximum potentiation occurred with preexposures of about 30 s; longer preexposures led to a decrease of potentiation and eventually to a depression of the contracture. The potentiation was not immediately abolished when the muscle was reexposed to Ringer solution but persisted for 2 min or longer (the 'washout effect'). It was concluded that exposing a muscle to low subcontracture threshold concentrations of potassium for a few seconds primes the intracellular contractile apparatus, probably by causing an increased sarcoplasmic concentration of Ca2+ ions, resulting in a potentiation of subsequently induced submaximal potassium contractures. The increase in metabolism (or 'Solandt effect') seen under these conditions is temporally related to the decline and eventual loss of the potentiation and is probably a reflection of active processes involved in reducing the sarcoplasmic concentration of Ca2+ ions.
Evidence for a Functional Connection Between the Sarcoplasmic Reticulum and the Extracellular Space in Frog Sartorius Muscle
Authors: Kulczycky S. , Mainwood G. W.
Published: April 2011

Electron microscopy of muscles soaked in Ringer solution containing horseradish peroxidase shows a considerable penetration of peroxidase into the terminal cisternae and the longitudinal tubules of the sarcoplasmic reticulum (SR). Taken together with observations on the effects of hypertonic solution on the dimensions of the tubular system and the terminal cisternae it seems clear that there must be a functional continuity of the sarcoplasmic reticulum and the external solution, probably through connections with the T tubes at the triad junction. These findings conflict with other reports that the probe molecules do not penetrate into the SR. The reason for these discrepancies is not yet clear. One factor which may limit the penetration of probe molecules in the tubular system is the fluid dynamics associated with active transport. The effect of ouabain on peroxidase penetration provides some support for this suggestion.
The Enzymatic Degradation of Angiotensin II Analogues by proteolytic enzyme in vitro
Authors: Carrara M. C. , Regoli D. , Park W. K.
Published: April 2011

Angiotensin II (ATII), angiotensin I (ATI), and Acpc analogues of ATII, 8-Achc-ATII, 8-D-Phe-ATII, and 8-Ala-ATII, were incubated in vitro with carboxypeptidase, chymotrypsin, and leucine-aminopeptidase in order to study the influence of unnatural amino acids (Acpc, Achc, and D-Phe) and of L-Ala on the activity of peptidases.Fragments occurring during the breakdown of peptides were demonstrated by paper chromatography in an ascending system.ATII and ATI are rapidly inactivated by carboxypeptidase and chymotrypsin, while the degradation by leucine-aminopeptidase is slower.Substitution of L-Phe with Acpc, Achc, D-Phe, or L-Ala in position 8 prevents the degradation by carboxypeptidase. Chymotrypsin degrades 3-Acpc-ATII and 5-Acpc-ATII but not 4-Acpc-ATII. The action of leucine-aminopeptidase is not influenced by substituting Acpc to each one of the first five amino acids composing the molecule of angiotensin.The possible implications of these findings for the peptide-receptor interaction is discussed.
Suppression by Corticosterone of Adrenocorticotropin Release from Adenohypophyses Incubated in Krebs–Ringer Bicarbonate Ultrafiltered Plasma
Authors: Kraicer Jacob , Milligan John V. , Sinclair Duncan G.
Published: April 2011

Adenohypophyses were incubated in plasma obtained from adrenalectomized rats and pressure dialyzed against Krebs–Ringer bicarbonate. Corticosterone, in concentrations between 20 and 40 μg/100 ml of ultrafiltered plasma protein, suppressed the augmented release of adrenocorticotropin induced by a crude acid extract of rat hypothalamus–stalk–median eminence. Thus corticosterone, in concentrations and conditions comparable to those found in the circulation, will act directly on the adenohypophysis to decrease its response to corticosterone-releasing factor activity.
Effect of Phytol on the Incidence of Muscular Dystrophy in Rabbits
Authors: Hidiroglou M. , Jenkins K. J.
Published: April 2011

In an experiment with 60 rabbits fed a vitamin E deficient diet, 1% of phytol was ineffective in prevention of muscular dystrophy, whereas vitamin E supplementation at 100 p.p.m. completely prevented onset of the disease. This observation with rabbits contrasts with the reported antidystrophic activity of phytol in chicks.
Evidence for Na Sequestration in muscle from Na Diffusion Measurements
Authors: Caillé J. P. , Hinke J. A. M.
Published: April 2011

Intrafiber diffusion of 22Na and 14C-sorbitol was measured along the longitudinal axis of a single muscle fiber which had been placed inside the lumen of a glass capillary at least 24 h beforehand. Compared to their diffusion in 1% agar, the self-diffusion coefficients of 22Na at 10 °C (0.438 × 10−5 cm2/s) and 14C-sorbitol (0.216 × 10−5 cm2/s) were reduced by a factor of 2 when intrafiber pH was 7.5. However, the theoretical and experimental concentration–distance profile curves only matched for 14C-sorbitol but not for 22Na. In the latter case, the experimental curves were consistently higher than the theoretical curve indicating an excess accumulation of 22Na at all x values (axis distance). This Na accumulation was found to be highly dependent on the pH inside the fiber. From pH 10.1 to 5.2, the fraction of excess Na (excess 22Na per total 22Na at a given x) decreased from 0.34 to zero. We interpret this excess Na to be a measure of the amount of myoplasmic Na which is acting as counterion for the fixed negative charge on the contractile filaments.