bluuebunny/crossref_metadata_2025 huggingface dataset:
Conformational and Biological Properties of Partial Sequences of Glucagon
Authors: Epand Richard M. , Grey Vijaylaxmi
Published: April 2011

We have investigated the properties of derivatives of the 29-amino-acid polypeptide hormone, glucagon, which had varying numbers of amino acids cleaved from the carboxyl terminal portion of the molecule. These derivatives included a 27-amino-acid fragment made by cleavage of the native molecule with cyanogen bromide and a 23-amino-acid fragment made synthetically. We found both of these derivatives capable of stimulating the conversion of ATP to cyclic AMP in in vitro assays using rat liver homogenates. The concentration of these peptides, which were required to produce enhanced adenyl cyclase activity, was higher than that of glucagon, and in the case of the 1–23 derivative it was several orders of magnitude larger. The requirement for higher concentrations of peptide is expected, as removal of a large portion of the total number of amino acids will proportionately decrease the free energy of dissociation of the peptide from the membrane receptor, thus changing the equilibrium constant for binding by several orders of magnitude. Circular dichroism and ultra-centrifuge studies of these peptides, as well as a 21-amino-acid fragment made by cleavage of the native molecule with carboxypeptidase, indicated that the shorter glucagon analogues have structures similar to that of the native molecule although somewhat less ordered.
Rat Blood and Muscle Lactate After Prolonged Exercise
Authors: Taylor A. W. , Rao S.
Published: April 2011

The effects of reserpine upon skeletal muscle and blood lactate levels have been studied in exercised and control rats. The exercise program consisted of 12 weeks of running on a motor-driven treadmill at 26.8 m/min for 1 h per day, 5 days per week. Animals received reserpine doses of 2.5, 5.0, and 12.5 mg/kg (i.p.) 24 h prior to sacrifice. Skeletal muscle and blood lactate levels were measured from animals sacrificed at rest or immediately after a fatiguing run. Tissue lactate levels were elevated only in those animals receiving 2.5 mg/kg of reserpine and exhaustive exercise. Blood lactate levels were unaffected by the drug and by the run to exhaustion. The results indicate that elevated muscle lactate levels are not the sole cause of muscular fatigue.
The Influence of Lysine-8-vasopressin, Oxytocin, and Adrenaline on Vascular Smooth Muscle in the Human Finger
Authors: Gaskell Peter
Published: April 2011

Lysine-8-vasopressin, oxytocin, or adrenaline was administered by intravenous infusion to young women, and their effect on the critical opening pressure (COP) of digital vessels, vascular resistance in the finger, and systemic blood pressure was measured. All doses of lysine-8-vasopressin between 0.001 and 0.08 U/min increased the COP of digital vessels but only the largest dose raised blood pressure slightly. A dose of 0.04 U/min had little if any effect on overall vascular resistance in the finger. Nevertheless the smallest dose given (0.001 U/min), which is within the physiological range of secretion rate by the pituitary gland, increased the COP of digital vessels substantially. Oxytocin at doses of 5–160 mU/min had no apparent effect on COP or vascular resistance of digital vessels or on blood pressure. Adrenaline at 4 μg/min increased the COP of digital vessels substantially. The latter observation is consistent with the absence of β receptors in vessels of the skin of the fingers.
Serum Glycoprotein Synthesis in Intact and Hepatectomized Walker 256 Tumor-Bearing Rats Following Glucosamine-1-14C Administration
Authors: Macbeth R. A. , Boorman M. G. , Gellatly J.
Published: April 2011

Incorporation of administered free glucosamine-1-14C into protein-bound hexosamine of the various fractions of the total serum proteins, as obtained by disc electrophoresis, has been studied in normal and in Walker 256 tumor-bearing rats, both in the intact state and following hepatectomy. Normal intact animals demonstrate greater incorporation of labeled glucosamine into a band in the transferrin zone than into the other disc electrophoretic fractions during the 3 h period of observation. The response of tumor-bearing intact animals is characterized by increased incorporation of labeled glucosamine into glycoproteins of the post-albumin zone and decreased incorporation into that in the transferrin zone in comparison with normal animals. Non-tumor-bearing hepatectomized animals fail to incorporate significant labeled glucosamine into any of the glycoprotein fractions of the serum. Tumor-bearing hepatectomized animals, on the other hand, incorporate labeled glucosamine into glycoproteins of the post-albumin zone. These studies support the suggestion that malignant tumor tissue is capable of glycoprotein synthesis and release into the circulation and indicate the gross characteristics of the tumor-produced glycoproteins.
Effects of Feeding a Zero- or High-Roughage Diet to Cattle upon Adipose Tissue Lipogenesis
Authors: Buchanan-Smith J. G. , Horney F. D. , Usborne W. R. , Burgess T. D.
Published: April 2011

Hereford steer calves were fed whole shelled corn or corn silage diets to determine the effect of dietary roughage level on lipogenic enzymes of adipose tissue. In Trial 1, perirenal and subcutaneous adipose tissue were taken post-mortem from 32 steers who had been fed either diet ad libitum for at least 175 days and weighed 450 kg live. In Trial 2, for which a changeover design was used, six cattle were fed both diets so that energy intake was calculated to be equal for each. Perirenal adipose tissue was taken in the second trial by biopsy when the steers weighed 200 kg live. In Trial 1, compared to high-roughage, the zero-roughage diet elicited from a two- to fourfold increase (P < 0.05) in activity of pentose phosphate pathway dehydrogenases of adipose tissue. This dietary effect was not observed in Trial 2. In both trials, acetyl-CoA synthetase activity and fatty acid synthesizing capacity from acetate of adipose tissue were unaffected by diet. Carcasses from animals fed the zero-roughage diet in Trial 1 contained 6% more separable fat (P < 0.05) than carcasses from animals fed the high-roughage diet. The mean of both trials for plasma acetate from animals fed the zero-roughage diet was 0.61 μmol/ml, which was less (P < 0.05) than 0.95 μmol/ml, which was the comparable value determined from animals fed the high-roughage diet. Plasma propionate was increased (P < 0.05) by feeding the zero-roughage diet in both trials but accounted for less than 20% of volatile fatty acids in all samples examined.
Stimulation of Bone Resorption by Increasing Dietary Protein Intake in Rats Fed Diets Low in Phosphorus and Calcium
Authors: Denis G. , Kuczerpa A. , Nikolaiczuk N.
Published: April 2011

The effect of three levels (3.3, 11, and 33%) of dietary protein on bone resorption was studied in young rats fed diets deficient in P and Ca. Plasma P decreased and plasma Ca rose with an increase in dietary protein and returned to near normal values 8 h after food withdrawal. Urinary Ca rose linearly with increasing levels of dietary protein while urinary P was insignificant in the animals fed 11 and 33% protein. Assuming a molar ratio of Ca/P of 8.13/6 in young bones, estimates of the amount of P liberated from bone were calculated from urinary Ca and evaluated at 0.07,1.05, and 3.29 mg/100 g body weight per 8 h for the animals fed 3.3, 11, and 33% protein, respectively. Histological sections of the tibia revealed a progressive widening of the epiphyseal plate. Correlations between Ca excretion, levels of dietary protein, and width of epiphyseal plate were linear. Plasma P and Ca variations and Ca and P excretions in thyroparathyroidectomized and thyroxin replaced and in parathyroidectomized rats fed diets deficient in P and Ca containing 33% protein were similar to those of sham-operated controls. From this study we concluded that dietary protein independently of parathormone or calcitonin determines the magnitude of the physiological and histological changes observed in growing animals fed diets inadequate in P and Ca.
Hypercoagulabilité Sanguine avec Administration de Noréthynodrel : Correction par Purification de la Progestine
Authors: Brazeau P. , Dansereau M. , Gervais M. H. , Banerjee R. C.
Published: April 2011

Blood clotting induced by non-purified norethynodrel is no longer observed in adult female rats when purified norethynodrel (99.7% pure) is used. Analysis of the times of bleeding and of coagulation of these rats treated with purified and non-purified norethynodrel clearly demonstrate that the purification of progestin eliminates the thromboembolic side effects. It is debated whether or not the concentration of estrogens can fully explain these side effects associated with the use of oral contraceptives. Furthermore, degradation products and/or contaminants during synthesis of this progestin would be, in large part, responsible for this blood clotting side effect in the female rat.
Effect of Hydrochlorothiazide on Calcium Kinetics in Blood Vessels
Authors: Zsotér Thomas T. , Suffiad Kadar
Published: April 2011

Prolonged administration of hydrochlorothiazide (HCT) depresses norepinephrine vasoconstriction. In an attempt to explain these findings, the effect of HCT on calcium kinetics in the vessels was investigated in the present study. Mesenteric veins of rabbits treated with HCT for 6–10 weeks took up considerably more 45Ca in vitro (p < 0.01) than veins of control animals. The efflux of 45Ca was similar in treated and control animals. Residual radioactivity was almost three times as high in vessels of HCT-treated rabbits. After a 4 week long administration of HCT, Ca kinetics were not yet altered, indicating the importance of the time element in the action of the drug. As a working hypothesis we suggest that prolonged treatment with HCT causes trapping of Ca in an intracellular compartment of vascular smooth muscle, making it less available for norepinephrine vasoconstriction.
Serum and Pituitary Prolactin Changes in the Band-tailed Pigeon (Columba fasciata) in Relation to the Reproductive Cycle
Authors: March G. L. , McKeown B. A.
Published: April 2011

Relative changes in serum and pituitary prolactin in the band-tailed pigeon were measured by radioimmunoassay. It was found that serum prolactin concentrations rose substantially prior to crop gland development and reached a maximum during the period of ovulation. At the same time, there was a corresponding depletion of pituitary prolactin. The reciprocal nature of these changes continued for the remainder of the reproductive cycle. Although the lack of antigonadal response to increased levels of prolactin is clearly demonstrated by the male of this species, this problem remains unresolved in the female.
Experiments on Rouleau Formation
Authors: Kernick D. , Jay A. W. L. , Rowlands S. , Skibo L.
Published: April 2011

Rouleau formation was measured by an adaptation of an old method used by Ponder (1927, Q. J. Exp. Physiol. 16, 173–194). Blood was depleted of red cells to a low hematocrit. It was stirred under standardized conditions, and after various times, samples were examined by microscope. Mean rouleau length was taken as an index of rouleau formation. The method was used to observe changes of rouleau formation with time and temperature and with variations in erythrocyte sedimentation rate (E.S.R.). Under these experimental conditions, mean rouleau length increases with time up to 40 min. Over a range of hematocrit values between 0 and 4%, rouleau length is a linear function of hematocrit. At higher hematocrits random aggregations based on columnar units are seen. Rouleau formation is temperature dependent and maximum mean rouleau length occurs around 37 °C. Subjects with a high erythrocyte sedimentation rate tend to form long rouleaux. By exchanging red blood cells (R.B.C.) between two ABO Rh compatible patients with greatly differing E.S.R. and mean rouleau length, it was shown that the agent responsible was in the plasma and not on the R.B.C. The results were compared with a theory of aggregation which proved inadequate in some respects.
Drug-Induced Porphyrin Biosynthesis. X. Potentiation of Propanidid-Induced Elevation of δ-Aminolevulinic Acid Synthetase and Porphyrins in Chick Embryo Liver by the Carboxylesterase Inhibitor Bis-[p-nitrophenyl] Phosphate
Authors: Taub Hillel , Marks G. S.
Published: April 2011

Propanidid, an ultra short-acting non-barbiturate anesthetic containing an ester group, induces δ-aminolevulinic acid (ALA)-synthetase and porphyrin accumulation in 17-day-old chick embryo liver. The potency and duration of action of propanidid in inducing ALA-synthetase activity and porphyrin accumulation was markedly increased when administered to chick embryos which had been pretreated with bis-[p-nitrophenyl] phosphate, an inhibitor of liver carboxylesterase.
Suppression of Food Intake in the Rat by Tung Oil
Authors: McPherson Jr. James C.
Published: April 2011

Tung oil has previously been found to suppress voluntary food intake when mixed with the diet. When tung oil or corn oil were fed by stomach tube to weanling and adult rats, the voluntary intake of laboratory chow was depressed by both lipids. The corn-oil fed animals readjusted their caloric intake to their prefeeding level in adults and to the level consumed by chow-only fed weanlings of the same age. However, the tung-oil fed adult animals consumed only one-half the dry food intake of the corn-oil fed animals (p < 0.001). Consequently the adult tung-oil fed animals lost significantly more (p < 0.01) of their body weight than did the corn-oil fed controls. This suggests that the mechanism of suppression of food intake by tung oil operates at some level other than taste or consistency of the diet.
Effect of Bilateral Adrenalectomy on Production of Restraint Ulcers in the Stomach of Albino Rats
Authors: Ganguly A. K. , Bhatnagar O. P.
Published: April 2011

To assess the specific role played by adrenals in the production of restraint ulcers in the stomach of albino rats, bilaterally adrenalectomized rats were exposed to stress by a restraint technique and the gastric ulcers that developed were compared with those of adrenal-intact rats under similar conditions.The results show that in vagus-intact, bilaterally adrenalectomized rats, the ulcer index comes down to 0.016 from 0.11 in vagus-intact, adrenal-intact rats. This clearly demonstrates that adrenals play a significant role in the production of restraint ulcers in the gastric mucosa of the albino rats.
The Effects of Lidocaine, Propranolol, Procaine Amide, and Bretylium Tosylate on the Contractility of Isolated Cat Papillary Muscles
Authors: Graham James D. , Chandler Brian M.
Published: April 2011

Depression of myocardial contractility by certain anti-arrhythmic agents may be a major clinical hazard to the use of these drugs. In order to study this problem further, cat right ventricular papillary muscles contracting 15 times/min in oxygenated Krebs (25 °C) were exposed to increasing concentrations of lidocaine, propranolol, procaine amide, and bretylium tosylate every 15 min. Measurements of rate of development of tension (dp/dt), peak active tension (AT) and time to peak tension (TPP) were made in the drug-treated muscles and compared to controls. In dosages comparable to human therapeutic levels, only propranolol depressed contractility; dp/dt was decreased 27% at 0.1 μg/ml (p < 0.01). At 10 times the "therapeutic level," lidocaine also depressed contractility; dp/dt was decreased 29% at 100 μg/ml (p < 0.001), and 70% at 200 μg/ml. Bretylium was positively inotropic at this level; at 200 μg/ml, dp/dt was increased 25%. The positive inotropism of bretylium was still seen with cats pretreated with reserpine. Procaine amide unexpectedly produced an increase in dp/dt of 44% at 500 μg/ml (p < 0.01). Reserpine prevented the inotropism of procaine amide. In general AT paralleled dp/dt. TTP was shortened by higher doses of all drugs except propranolol. In summary, lidocaine caused severe depression of contractility at higher doses, propranolol was negatively inotropic, and procaine amide and bretylium were positively inotropic.
γ-Aminobutyric Acid Antagonists in Crustacea
Authors: McLennan H.
Published: April 2011

The potency of picrotoxin, bicuculline, and bicuculline methochloride as antagonists of the inhibitory actions of γ-aminobutyric acid on the discharge of the stretch receptor neurones and on neuromuscular transmission in crayfish have been examined. On the stretch receptor the three antagonists were roughly equipotent; at the neuromuscular junction however the bicucullines were considerably less effective than picrotoxin.
Interaction of Local Anesthetics and Salicylate with Phospholipid Membranes
Authors: Singer M. A.
Published: April 2011

Local anesthetics reduce both the surface charge and cation permeability of phosphatidylcholine (PC) liposomes containing the long chain anion dicetylphosphate. These agents also reduce the negative surface charge of PC vesicles dispersed in a salicylate solution, but in this case cation permeability is enhanced. It is proposed that the local anesthetic, by reducing the negative surface potential on the PC–salicylate liposome, permits the adsorption of more salicylate anions. The resultant higher salicylate surface concentration is responsible for the increased cation permeability.
Microtubule and Neurofilament Densities in Amphibian Spinal Root Nerve Fibers: Relationship to Axoplasmic Transport
Authors: Smith Richard S.
Published: April 2011

Dark-field microscopy of living myelinated nerve fibers from the spinal roots of Xenopus laevis revealed many spherical organelles moving in the axoplasm of fibers from the ventral roots and in fibers just distal to the dorsal root ganglion. Similar organelles were present but few were seen to move along fibers from the dorsal roots central to the ganglion. This observation prompted an ultrastructural study of microtubule and neurofilament densities in the myelinated fibers of the spinal roots. The density of microtubules was significantly less in fibers from the central part of the dorsal roots than in the rest of the spinal root system. Neurofilament densities were equivalent in all parts of the roots. Microtubules showed a significant association with mitochondria in the ventral roots and in the dorsal roots distal to the ganglion, but no significant association was obtained for the dorsal roots central to the ganglion. The meaning of these results in the axoplasmic transport of large organelles is discussed.
Carbon Tetrachloride and Cation Transport by Rat Liver Slices
Authors: Nestruck A. C. , Furneaux R. W.
Published: April 2011

The ability of liver slices prepared from normal rats and from isolated perfused livers following a 1 h control perfusion to reverse a cold-imposed shift in cations when rewarmed was confirmed as a control parameter of rat liver tissue. Three hours after normal rats had received a standard dose of CCl4 via a gastric tube, a decreased ability for the membrane transport of sodium was found. The infusion of CCl4 directly into the perfusate line was shown to cause acute toxic damage in isolated livers. Further, at the end of the 1 h perfusion, the infusion of CCl4 was shown to result in an increased tissue sodium level and a decreased capacity for the membrane transport of sodium and potassium by slices. It is suggested that a generalized change in plasmalemma function, as evidenced in alterations in the membrane transport of cations and tissue cation level, may be an early manifestation of CCl4 hepatotoxicity.
Histochemistry and Ultrastructure of the Juxtaglomerular Apparatus in Magnesium-Deficient Rats
Authors: Cantin Marc , Huet Madeleine
Published: April 2011

The activity of glucose-6-phosphate dehydrogenase and of 6-phosphogluconate dehydrogenase at the level of the macula densa as well as the ultrastructure of the juxtaglomerular apparatus have been studied in magnesium-deficient rats and the results correlated with changes in hematocrit and hemoglobin values, in number of red blood cells, and in systemic blood pressure. The results indicate that magnesium deficiency induces hyperplasia and hypertrophy of epithelioid juxtaglomerular cells without any increase in the enzymatic activity of the macula densa. The ultrastructure of lacis cells is not altered while slight modifications are noted in the cells of the macula densa. These changes are ascribed to systemic hypotension and possibly to hypoxia.
Binding of 3H-γ-aminobutyric Acid and 14C-glycine to Synaptosomal–Mitochondrial Fractions of Rat Cerebral Cortex and Spinal Cord
Authors: DeFeudis Francis V.
Published: April 2011

The "binding" of γ-aminobutyric acid (GABA) and glycine to subcellular particles of rat cerebral cortex and spinal cord has been studied using differential centrifugation and double-isotope methods. When cerebral cortices and spinal cords were homogenized in isosmotic sucrose solutions containing 40 mM NaCl plus "tracer" amounts of 3H-GABA and 14C-glycine and then subjected to differential centrifugation, 3H-GABA was bound preferentially to particles prepared from cerebral cortex while 14C-glycine was bound to a similar extent to particles of both cerebral cortex and spinal cord. However, when P2 fractions, enriched in synaptosomes and mitochondria, were first isolated using unlabelled Na+-free sucrose solution and then resuspended in solutions containing 40 mM NaCl plus the labelled amino acids, preferential binding of the amino acids occurred. Under these latter conditions 3H-GABA was bound to a greater extent to synaptosomal–mitochondrial particles of cerebral cortex while 14C-glycine was bound to a greater extent to identically prepared particles of spinal cord. Although the retentions of both 3H-GABA and 14C-glycine were increased by allowing the particles to stand at 23 °C for 15 min, preferential binding still existed.
Cyclic 3′,5′-Adenosine Monophosphate Dependent Protein Kinase From Dog Prostate
Authors: Tsang Benjamin K. , Singhal Radhey L.
Published: April 2011

Protein kinase, which is stimulated two- to fourfold by cyclic 3′,5′-adenosine monophosphate (cyclic AMP), has been isolated and partially purified from the cytosol of dog prostate. Two peaks having the cyclic AMP binding and kinase activities were separated by using diethylaminoethylcellulose chromatography. While the major activity peak (fraction II) was eluted at 0.17 M NaCl, the minor peak (fraction I) was observed at a lower salt concentration. In the presence of cyclic AMP, maximum stimulation of the enzyme (fraction II) was observed at 7 min during which enzyme activity was found to be linear with time. The enzyme was half maximally activated by 5 × 10−8 M cyclic AMP whereas maximal stimulation was seen with 5 × 10−6 M concentration of the cyclic nucleotide. Binding studies revealed that the association constant (Kassoc) of prostatic enzyme to cyclic AMP at pH 5.0, 0 °C, was 1 × 10−8 M−1. In comparing the ability of casein, protamine, and different histone subfractions to serve as the substrate for protein kinase, highest cyclic AMP stimulation was demonstrated with histones. It is postulated that the effect of cyclic AMP on this enzyme may be related to its ability to exert marked "andromimetic" effects on the prostate gland.
Degradation of Hyaluronic Acid by Baboon Sex-Skin Tissue
Authors: Naidoo S. S. , Qureshi A. M.
Published: April 2011

Baboon sex-skin tissue as well as interstitial fluid obtained from the sex skin contain an endogenous enzyme capable of depolymerizing hyaluronic acid. The degradation products, fractionated by DEAE-cellulose, are a series of oligosaccharides that contain N-acetylhexosamine at the reducing end. The major end-products of the reaction are tetra-, hexa-, and octasaccharides. The pH optimum of the enzyme is 4.1. It is concluded that the enzyme in sex-skin tissue is a β-endohexosaminidase similar to hyaluronidases present in serum, bone, and liver.
The Bronchodilator Activity of AY-22093, a Prostanoic Acid Derivative
Authors: Greenberg R. , Beaulieu G.
Published: April 2011

The bronchodilator activities of AY-22093, prostaglandin E2 (PGE2), and isoproterenol were compared using in vivo and in vitro techniques. In the conscious guinea pig, an aerosol of AY-22093, PGE2, and isoproterenol afforded significant protection against histamine-induced bronchospasm; AY-22093 and isoproterenol were equally effective in protecting against antigen-induced anaphylaxis. In the anesthetized guinea pig, using the Konzett and Rössler technique, PGE2 (1 μg/kg, intravenously (i.v.)) inhibited the bronchoconstriction induced by histamine (10 μg/kg, i.v.) by 63% as compared with 37% inhibition after AY-22093 (1 μg/kg, i.v.). Larger intravenous doses of PGE2 and AY-22093 (10 and 20 μg/kg) caused almost complete inhibition of the histamine-induced bronchoconstriction. The administration of PGE2 (0.5–10 μg) or AY-22093 (5–100 μg) by aerosol inhibited the bronchoconstriction induced by histamine (10 μg/kg, i.v.) by 20–70%. Maximum bronchodilator effects occurred within 3 min and lasted for as long as 30 min after either route of administration. Both compounds caused a fall in blood pressure after intravenous but not after aerosol administration. AY-22093 relaxed the guinea pig tracheal strip where tone was induced by carbachol. This relaxation was not altered by propranolol. The results indicate that AY-22093 is a bronchodilator qualitatively similar to PGE2, having a direct effect on smooth muscle but less potent than PGE2.
Role of the N-terminal Amino Acid for the Biological Activities of Angiotensin and Inhibitory Analogues
Authors: Regoli D. , Rioux F. , Park W. K. , Choi C.
Published: April 2011

Aspartic acid was replaced in position 1 of angiotensin II (ATII) with several amino acids, to assess the possible influence of the N-terminal amino acid for (a) the intrinsic activity, (b) the affinity, and (c) the metabolic degradation of agonist analogues of ATII. Some of the substitutions in position 1 were used in combination with replacement of Phe by Gly or Leu in position 8, to obtain the corresponding antagonist.The compounds were tested in vivo (rat blood pressure) and in two in vitro preparations (rat stomach and rabbit aorta strips). The oil immersion technique, described by Kalsner and Nickerson (1968) (Can. J. Physiol. Pharmacol. 46, 719–730), was used to study the disposition of the peptides by vascular smooth muscles (rabbit aorta strips). Degradation of the peptides by purified aminopeptidases was evaluated in vitro by measuring the fragments on paper chromatography. Potency of antagonists was estimated in vivo (ID50) and in vitro (pA2 values): duration of action was established by infusing the inhibitors intravenously into anesthetized rats and testing the effect of standard doses of angiotensin before and after.The results indicate that replacement of Asp with other amino acids does not influence the intrinsic activity, but can either increase or decrease the affinity in vitro or the potency in vivo. 1-Sar-ATII, and 1-D-Ala-ATII are more potent and longer acting than 1-Asp-ATII on isolated intestinal and vascular smooth muscles, but not in vivo. On the contrary, 1-β-Asp-ATII and 1-β-D-Asp-ATII are more potent than 1-Asp-ATIIin vivo, but not on rabbit aorta strips. Rate of relaxation of rabbit aorta strips suspended in oil, after contraction with submaximal doses of several analogues of ATII, are significantly slower than relaxation after 1-Asn2-ATII and 1-Asp-ATII. A close parallelism between the diminution of the relaxation rate in oil and the degradation by aminopeptideses in vitro was observed, suggesting that metabolic degradation may be the major factor determining relaxation of rabbit aorta in oil after contraction with one of these peptides. Potencies of antagonists in vivo and in vitro are increased by replacing Asp with Sar. Substitution of Asp with β-Asp or β-D-Asp brings about a slight increase of potency in vivo but not in vitro. It appears that firm binding and prolonged occupation of receptors by sarcosyl derivatives are the primary factors contributing to increase the potency and to prolong the duration of action of antagonists, while prevention or reduction of metabolic breakdown by aminopeptidases is much less efficient.
Oxidative Phosphorylation in Hypoxic Airway Smooth Muscle
Authors: Stephens N. L. , Vogel J.
Published: April 2011

The impairment of mechanical function that we have previously reported in tracheal smooth muscle under conditions of hypoxia and substrate depletion may be due to a defect in the utilization of the energy produced, to a decrease in energy production in the muscle after the hypoxic inhibition of mitochondria, or to a combination of these. To test the second hypothesis mitochondria were isolated from the trachealis smooth muscle of dogs whose [Formula: see text] had been maintained at 30 mm Hg ± 7 (S.E.), for 1 h before death. Studies of oxidative phosphorylation revealed no significant differences in ADP/O ratios in these mitochondria as compared with normal nor was there any significant difference in rate of O2 uptake as long as ADP was available (state 3 respiration). However, there was a significant difference in respiratory control ratios (R.C.R.), generally regarded as the most sensitive biochemical index of the function integrity of mitochondria, as well as a significant difference between control and experimental conditions in the rate of O2 uptake when ADP was not available (state 4 respiration). These findings suggested loose coupling between electron transport and oxidative phosphorylation.
Interactions of Ca, P, Zn, and Alkaline Phosphatase in the Chick. II. Effect of Dietary Ca Level
Authors: McCuaig L. W. , Motzok I.
Published: April 2011

Chicks were fed a semi-purified diet, containing 0.75% Ca, 0.5% inorganic phosphate (Pi), and 50 p.p.m. Zn, to 2 weeks of age. They were then divided into groups and fed the same diet with 0, 0.75, 1.50, 2.25, or 3.00% Ca, for 4 or 7 days before being killed. Plasma was analyzed for Ca, Pi, and Zn, and duodenal mucosa for Ca, Pi, Zn, Mn, and alkaline phosphatase (AP). The low Ca treatment decreased plasma and mucosa Ca and increased mucosa Zn, whereas the high Ca diets increased mucosa Ca and decreased mucosa Zn, plasma Pi, and mucosa AP activity. There was an overall positive correlation of AP with plasma and mucosa Zn, and plasma and mucosa Pi, and a negative overall correlation of AP with plasma and mucosa Ca. Mucosa Mn content did not seem to be related to the enzyme activity.
On the Mechanism of Isoosmotic Transport of Fluid Across the Small Intestine. The Effect of the Staverman Reflection Coefficient of the Solute Used to Increase the Osmolality of the Mucosal Solution on the Composition of the Absorbate
Authors: Beck I. T. , Dinda P. K.
Published: April 2011

The objective of the present study was to investigate the mechanism by which the fluid transported across the small intestine becomes isoosmotic with the mucosal solution. The osmolality of the mucosal solution of a unilateral preparation (the serosal side was not bathed) was increased with water soluble, nonelectrolyte solutes of different Staverman reflection coefficients (σ), and the composition of the undiluted absorbate was studied. The solutes ('hyperosmotic agents') used were formamide, urea, erythritol, and mannitol. In a series of separate experiments, utilizing a method based on potential difference depression, we found that the σ's of these solutes in the hamster small intestine were 0.26, 0.85, 0.93, and 1.00, respectively. Our data on transport across the unilateral preparation showed that when the intestine was incubated in an isotonic mucosal solution (Krebs–Ringer bicarbonate solution containing 10 mM glucose, 292 mosmol/kg), the absorbate was essentially isotonic, although its composition was significantly different from that of the mucosal solution. When the osmolality of the mucosal solution was increased to 342, 392, or to 442 mosmol/kg with any of the hyperosmotic agents, the absorbate was always isoosmotic with the mucosal solution. With formamide (low σ) as the hyperosmotic agent, the concentration of electrolytes and glucose in the absorbate was the same as that in the absorbate of the control preparation (incubated in the isotonic mucosal solution), and the transported fluid became isoosmotic with the mucosal solution exclusively due to the presence of formamide in the absorbate. When the osmolality of the mucosal solution was increased with urea, erythritol, or mannitol, the concentration of these hyperosmotic agents in the absorbate decreased linearly with the increase in their σ, and the absorbate became isoosmotic with the mucosal solution due to a linear increase in the concentration of electrolytes and glucose. In addition, we found that the transport of fluid, solutes, and fluid/solute (ml/mmol per gram dry intestine) decreased linearly with the increase in σ of the hyperosmotic agents. Further calculation of the data showed that the increase in the concentration of electrolytes and glucose with the increase in σ of the hyperosmotic agents was almost exclusively due to a linear decrease in fluid/solute transport.
Human Skeletal Muscle Glycogen Branching Enzyme Activities with Exercise and Training
Authors: Taylor A. W. , Stothart J. , Booth M. A. , Thayer R. , Rao S.
Published: April 2011

Sixteen healthy male subjects classified as sedentary (8) or active (8), exercised to exhaustion on a bicycle ergometer at a load requiring 70% of their maximal aerobic capacity. Biopsy samples of the vastus lateralis muscle were taken at rest and at the time of fatigue. A 12 week training program increased skeletal muscle glycogen content and branching enzyme activities twofold. The exhaustive submaximal exercise reduced the glycogen levels of the trained group to values similar to the fatigue levels of the non-trained subjects. Skeletal muscle glycogen branching enzyme activities decreased with submaximal exercise to fatigue in all groups. Maximal exercise to fatigue resulted in small increases in the activities of the enzyme. The results of the present study and a previous study (Taylor et al. 1972. Can. J. Physiol. Pharmacol. 50, 411–415) indicate that the activities of the glycogen synthesizing enzymes are highly correlated with the skeletal muscle resting glycogen concentration and the relative fitness of the subjects.
Alterations by Anesthetic Agents of the Responses of Rat Striatal Neurons to Iontophoretically Applied Amphetamine, Acetylcholine, Noradrenaline, and Dopamine
Authors: Spencer Hugh J. , Havlicek Viktor
Published: April 2011

The effect of two anesthetic agents, Penthrane and diallylbarbiturate (Dial, CIBA), was investigated on the responses of rat striatal neurons to iontophoretically applied noradrenaline (NA), dopamine (DA), acetylcholine (ACh), and d-amphetamine (d-Amph).At both high (50 mg/kg) and low (35 mg/kg) dose levels of Dial there was a highly significant [Formula: see text] change in the nature of the responses to all the substances tested. This change was primarily a decrease in the frequency of excitatory responses observed to catecholamine and ACh, compared with those observed under Penthrane.Although the dosage of Dial also affected the nature of the responses, it was to a much lesser degree; d-Amph responses were not affected and were almost purely inhibitory.Under both anesthetics, there was no evident correlation between the responses to d-amphetamine and to catecholamines.
The Volume Available to Diffusion in the Muscle Fiber
Authors: Caillé J. P. , Hinke J. A. M.
Published: April 2011

Intrafiber diffusion of 3HOH, dimethyl-3H-sulfoxide (DMSO), D-14C-sorbitol, and 36Cl was measured along the longitudinal axis of the single muscle fiber (Balanus nubilus) that had been placed inside the lumen of a glass capillary at least 24 h beforehand. When the fiber contained 75% water, the mean self-diffusion coefficients (× 10−5 cm2/s) at 10 °C and at pH 7.5 were 0.908 ± 0.008 for water, 0.418 ± 0.008 for DMSO, 0.216 ± 0.005 for sorbitol, and 0.683 ± 0.006 for chloride. These diffusion coefficients in myoplasm were 0.53–0.58 times the values in pure water. Diffusions of the above were also measured in fibers with reduced water content, as low as 45% by weight. In all cases, the diffusion coefficient decreased in proportion to the reduction in the fiber water. With the aid of Wang's theory for diffusion in polyelectrolyte solutions, we have attempted to separate the "obstruction effect" from the "binding effect", both of which operate to reduce the diffusion coefficient of substances in the myoplasm. Our analysis indicates that the diffusible volume in myoplasm (75% water) for all substances is about 80% of the water volume or 65% of the fiber volume. So-called "bound" water in myoplasm is estimated to be 0.57 g water per gram dry weight.
Immobilization-induced Bone Alterations in Chickens
Authors: Nightingale T. E. , Littlefield L. H. , Merkley J. W. , Richardi J. C.
Published: April 2011

Unilateral wing immobilization was used to study bone changes associated with lack of exercise in young chickens. With disuse, humerus bone weight, diameter, cortical thickness, radiographic density, and breaking strength were reduced significantly, whereas bone length, ash, calcium, and phosphorus were unchanged. The results of this study indicate that exercise-related bone changes can best be shown by radiographic density and breaking strength, but not by bone ash or mineral determinations.
A Study of Prostaglandins and Prostaglandin Antagonists in Relation to Anaphylaxis in Calves
Authors: Burka J. F. , Eyre P.
Published: April 2011

Actions of prostaglandins (PG) E1, E2, and F2α on the cardiovascular–respiratory systems of anesthetized calves were studied in conjunction with the effects of a series of prostaglandin antagonists on acute systemic anaphylaxis. Meclofenamate, acetylsalicylic acid (ASA), phenylbutazone, and indomethacin, all inhibitors of PG synthesis, were particularly effective in protecting calves from anaphylactic cardiovascular shock. Meclofenamate showed "broad spectrum" antagonism of the mediators of anaphylaxis. Indomthacin and ASA eliminated the biphasic fall in systemic arterial pressure, suggesting that prostaglandins may be involved, together with biogenic amines, in the early stages of anaphylaxis. SC-19220, polyphloretin phosphate, and diethylcarbamazine citrate (DECC) had little or no inhibitory effects against exogenous prostaglandins and afforded only weak protection against systemic anaphylaxis. "Broad spectrum" inhibition of amine and PG receptors, as well as inhibition of slow-reacting substance of anaphylaxis formation and release, may account for part of the protective effects of DECC. A blood-bathed superfusion system suggested participation by PG F2α in bovine anaphylaxis. Cardiovascular–respiratory changes induced by exogenous prostaglandins in calves suggest that PG F2α may be responsible for the transient rise in systemic arterial pressure and increase in pulmonary arterial pressure in anaphylaxis, whereas PG E1 and E2 may be participating in the primary fall in systemic arterial pressure.
Effect of Vitamin D Deficiency on Aminoaciduria and Intestinal Transport of Amino Acids in the Rat
Authors: Morin Claude L. , Léveillé Jean , Ling Victor
Published: April 2011

Generalized hyperaminoaciduria and hyperphosphaturia are associated with human vitamin D deficiency rickets and the effect has been reproduced in animals. The basis for the renal transport impairment was attributed to secondary hyperparathyroidism resulting from hypocalcemia.In this study we attempted over a 16-week period to induce hyperaminoaciduria in Holtzman rats with vitamin D deficient diets of varying calcium content (0.4% and 0.04%) so as to investigate the possibility of a concomitant defect in intestinal transport of amino acids. Despite signs of secondary hyperparathyroidism, generalized hyperaminoaciduria was not in evidence in any of the groups. However, increased urinary excretion of lysine and taurine was demonstrated in rats fed a low calcium diet without vitamin D (LCa−D). The same observation was also made for taurine in rats deprived of vitamin D and on a normal calcium diet (NCa−D) and in animals fed a low calcium diet with vitamin D (LCa+D). The results failed to show any effect of vitamin D deficiency, hypocalcemia, or secondary hyperparathyroidism on the intestinal transport of lysine, alanine, and cycloleucine.
Characteristics of the Plasma Disappearance of [3H]-Thyrotropin-Releasing Hormone in the Rat
Authors: Dupont A. , Labrie F. , Levasseur L. , Schally A. V.
Published: April 2011

Thirty seconds after an intravenous injection of 0.5 ml of 2.5 × 10−6 M [3H]thyrotropin-releasing hormone (TRH) to male rats, the radioactivity was distributed in an apparent volume of 134 ml, thus reflecting its rapid disappearance from the blood. The pattern of plasma radioactivity after intravenous injection of [3H]TRH could be represented by the sum of three exponentials, suggesting a three-compartment model of plasma disappearance of radioactivity. The half-life of TRH and of its metabolites calculated from the first exponential curve was 2.2 min. Thin-layer electrophoresis of methanol extracts of plasma collected 1, 7, 20, and 30 min after injection of [3H]TRH showed that the neurohormone was transformed into TRH-free acid in proportions of 58, 58, 52, and 47%, respectively. The first 60 min seemed to be the most important period for elimination of the hormone and its metabolites by the kidney. In fact, 60 min after injection, 38% of the total radioactivity was found in the bladder. At 2, 15, and 30 min after injection of [3H]TRH, high accumulation of radioactivity occurred in kidneys, pineal gland, and anterior and posterior (including intermediate) lobes of the pituitary. High levels of radioactivity were seen in kidneys and anterior pituitary gland at all time intervals studied.
Effects on the Acquisition of DRL-20 Performance of Propranolol or Isoproterenol Injected into the Basolateral Amygdala of Rats
Authors: Richardson J. Steven , Musty Richard E.
Published: April 2011

The acquisition of DRL-20 performance by rats is significantly disrupted by 20 μg of propranolol and significantly improved by 37 μg of isoproterenol injected into the basolateral amygdala prior to each daily testing session. Autoradiography of [14C]propranolol injected into the basolateral amygdala indicates that the injected propranolol remains within 1 mm of the injection site. This suggests that the β-adrenergic receptors in the basolateral amygdala are somehow involved in the elimination of maladaptive behavior.
Heat Vasodilatation of the Rat Tail
Authors: Hellström B.
Published: April 2011

The vasomotor response of the tail of the albino rat to total-body heating and cooling was studied by skin-temperature recording and plethysmography with the tail at 25 °C air temperature. Tail vasodilatation started at core temperatures slightly above 37 °C and increased to a core temperature up to about 39 °C. During cooling of warm rats, tail vasoconstriction started at significantly higher levels of core temperature than the values at which vasodilatation appeared when the rat was warmed.
Responses of Spinal Neurons to Iontophoretically Applied Prostaglandin E1 in the Frog
Authors: Coceani F. , Viti A.
Published: April 2011

Prostaglandin E1 (PGE1) has been tested by microiontophoresis on intemeurons and motoneurons in the isolated spinal cord of the frog. PGE1 action was almost exclusively excitatory, regardless of the cell type and the test condition used. In general, the excitatory response had rapid onset and termination, and was susceptible to tachyphylaxis. Responsive intemeurons were scattered throughout the tissue, and the incidence of responses showed no obvious relation to the mono- vs. polysynaptic connection of cells to primary afferents and descending fibers of the lateral funiculus. PGE1-sensitive intemeurons were encountered more often in preparations from summer than from winter animals. These findings, coupled with the demonstration of prostaglandin biosynthesis and catabolism in the tissue, suggest that PGE1 plays a role in the normal function of spinal neurons. The intimate mechanism of PGE1 action remains to be elucidated.
Effect of Chronic Intake of Ethanol on Lactate/Pyruvate and β-Hydroxybutyrate/Acetoacetate Ratios in Rat Liver
Authors: Khanna J. M. , Kalant H. , Loth J.
Published: April 2011

Adult male rats were fed a liquid diet providing 35% of the calories as ethanol, while pair-fed controls received the corresponding diet with alcohol replaced by an equicaloric concentration of sucrose. After 1 month, lactate/pyruvate (L/P) and β-hydroxybutyrate/acetoacetate (β-HB/AcAc) ratios in the livers were determined under five different conditions: (1) both diets present up to the time of sacrifice, (2) ethanol diet replaced by control diet for 24 h before sacrifice, (3) ethanol diet replaced by control diet for 48 h before sacrifice, (4) as in the preceding, followed by intraperitoneal (i.p.) injection of ethanol, 1 g/kg, 1 h before sacrifice, (5) as in the preceding, but i.p. injection 3 h before sacrifice.The L/P ratio was significantly higher in the alcohol group than in controls under the first experimental condition, but the groups did not differ under the other four conditions. The β-HB/AcAc ratio was also significantly higher in the alcohol group under the first condition. This difference disappeared in the second and third conditions. Under the fourth and fifth conditions the β-HB/AcAc ratio was significantly higher in the controls. The results are compatible with an adaptive increase in mitochondrial reoxidation of NADH in the chronic alcohol groups, but the possibility of a change due to alcohol withdrawal can not be excluded.
Effect of Central Cholinergic Blockade on the Hyperthermia Evoked by Prostaglandin E1 Injected Into the Rostral Hypothalamus of the Rat
Authors: Rudy Thomas A. , Viswanathan C. T.
Published: April 2011

The possibility of a cholinergic involvement in the hyperthermic action produced by the injection of prostaglandin E1 (PGE1) into the anterior hypothalamic/preoptic region of the rat brain was examined. Intracerebral injection of either atropine or mecamylamine prior to the injection of PGE1 failed to attenuate the PGE1-induced hyperthermia. Both atropine and mecamylamine by themselves produced a rise in colonic temperature. It thus seems unlikely that PGE1 evokes hyperthermia in the rat by releasing endogenous acetylcholine at muscarinic or nicotinic synapses in the rostral hypothalamus. The possibility that PGE1 acts by inhibiting the release of acetylcholine within this region requires additional investigation.
Storage and release of labelled acetylcholine in the myenteric plexus of the guinea-pig ileum
Authors: Szerb J. C.
Published: April 2011

Guinea-pig ileum myenteric plexus–longitudinal muscle preparation was superfused with [3H]choline for 15 min either without being stimulated or during field stimulation at 0.1 or 16 Hz; the preparation was then either removed immediately or after 75- or 135-min superfusion with hemicholinium-3 (HC-3) and the total acetylcholine (ACh) and [3H]ACh contents were determined. For measuring the release of [3H]ACh the preparation was stimulated for 60 min the second time at 0.1 or 16 Hz in the presence of hemicholinium. Exposure to [3H]choline without stimulation resulted in the formation of [3H]ACh which decreased without further stimulation in the presence of HC-3 at the same rate as did total ACh. Labelling during 0.1-Hz stimulation resulted in [3H]ACh stores which were maintained in the first 75 min but decreased thereafter. Labelling during stimulation at 16 Hz produced the largest and best maintained [3H]ACh content. Following labelling during 0.1-Hz stimulation, more label could be released than following labelling in the absence of stimulation. Labelling during 16-Hz stimulation did not increase any further the pool of [3H]Ch accessible to release by 0-Hz stimulation, but caused a 2.5 times increase in the pool from which 16-Hz stimulation released [3H]ACH. These results suggest that two populations of cholinergic neurons exist in the myenteric plexus, one activated only by high frequency stimulation, the other by both high and low frequency stimulation.