bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of metoclopramide on intestinal muscle responses and the peristaltic reflex in vitro
Authors: Okwuasaba Francis K. , Hamilton John T.
Published: April 2011

Metoclopramide (Mcp) is known to facilitate gastrointestinal emptying in vivo and to stimulate various isolated intestinal muscle preparations. On the guinea pig ileum, taenia coli, rabbit ileum and rat duodenum, Mcp increased the tone and responses to acetylcholine, carbachol and nicotine; had no effect on responses to histamine, potassium chloride and prostaglandin E1; decreased responses to 5-hydroxytryptaminc (5-HT).Atropine, methysergide, morphine, and tetrodotoxin, alone or in combination, partially blocked the stimulatory responses to Mcp, but hexamethonium, mepyramine and indo-methacin did not.Mcp (1.0 μM) lowered the threshold for elicitation of the peristaltic reflex to a subthreshold intraluminal pressure (2.5 cm water), facilitated the peristaltic response to threshold pressures (3–4 cm water) and restored the reflex in fatigued preparations, but not that depressed by cooling to 24 °C.During block of peristalsis by atropine, hexamethonium or methysergide (applied serosally) 5-HT (0.25 μM) but not Mcp (1.0 μM) effectively restored the peristaltic reflex, but neither antagonized the inhibition by morphine or procaine acting serosally. However, Mcp (1.0 μM) re-established peristalsis inhibited by a high concentration of 5-HT (4 × 10 μM).These results do not support the hypotheses that the stimulatory action of Mcp is entirely dependent on either peripheral sensitization of muscarinic receptors or an action on tryptaminergic mechanisms but are consistent with our previous conclusion that an additional component may be a blockade of some intrinsic inhibitory (possibly purinergic) substance normally restraining intestinal motility or tone.
Brown adipose tissue—a factor in the survival of harp seal pups
Authors: Grav Hans J. , Blix Arnoldus Schytte
Published: April 2011

The respiratory characteristics of mitochondria isolated from the subcutaneous brown adipose tissue of newborn harp seals indicate that the tissue is thermogenically active. Temperature recordings in vivo revealed, in fact, that the tissue was maintained at a temperature close to that of the body core during immersion of the pups in ice-water. Beta-adrenergic blockade markedly increased the cooling rates at both locations in ice-water, while curarization, accompanied by artificial respiration did not. We conclude that nonshivering thermogenesis through activated brown adipose tissue plays a decisive role in the defence against cold in the newborn harp seal.
Forearm oscillation during cooling of the dentate nucleus in the monkey
Authors: Cooke J. D. , Thomas J. S.
Published: April 2011

A study was made of oscillations in arm acceleration in monkeys performing a self-paced manual step-tracking task. Power spectral density analyses of segments of arm acceleration data from normal monkeys containing both flexion and extension movements and intermovement holding periods showed three major peaks at 1–1.5 Hz, 3–5 Hz and 5–7 Hz. Cooling of the dentate nucleus produced a marked increase in the relative magnitude of the 3–5 Hz spectral band. The spectral peak in this frequency range was larger than the other two which were also present during cooling. Autocorrelation functions from long segments of data containing flexion and extension movements and intermovement holding periods showed regular periodic variations in both normal and cooled animals. This suggests that the ongoing oscillations were not changed in phase by the occurrence of the self-initiated arm movements.
Induced rouleaux formation in interspecies populations of red cells
Authors: Sewchand Lionel , Canham Peter B.
Published: April 2011

A study was made of rouleaux formation between erythrocytes of different species when suspended in Ringer solution with polyvinylpyrrolidone added (PVP with M.W. 360 000, 4.0 g/l). PVP was shown previously to be a suitable asymmetric macromolecule for promoting rouleaux formation. For the present study fresh samples of blood were obtained from humans, cats, rats, mice, dogs, rabbits and guinea pigs. Initially homogeneous populations of cells were allowed to form rouleaux in the microscope chamber for the purpose of determining the average cellular dimensions for each species. Subsequently red cells from two species at a time were mixed in equal proportions to assess the degree of preference for the cells of one species to form rouleaux among themselves rather than with cells of the other species. The sequencing of the cells in the mixed rouleaux which formed on the coverslip was determined from photomicrographs, using the previously determined knowledge of the cellular dimensions. Although the visual impression was that the rouleaux were composed of a random selection of cells from the mixed population, a preference for cells to join in rouleaux with cells of the same species was demonstrated statistically in nine of the ten combinations tested. Only the rat–mouse mixture of cells was excepted, perhaps because these animals are closely related members of the same family.
The electrophysiological basis of the motor inhibitory effect of adrenaline on rabbit small intestinal smooth muscle
Authors: El-Sharkawy T. Y. , Daniel E. E.
Published: April 2011

The spontaneous electrical activity of small intestinal smooth muscle cells consists of repetitive depolarizations (control activity) on which spikes (response activity) may be superimposed; each spike is preceded by a prepotential. Response activity is associated with contractions. Adrenaline initially abolished the response activity and any prepotentials, as well as the contractions, without altering the control activity or the membrane potential. This effect was followed by hyperpolarization and slight increase in the control potential amplitude. The hyperpolarization was insensitive to temperature (Q10 = 1.01) and was larger when the membrane was initially depolarized by K withdrawal but did not occur after the membrane was hyperpolarized by replacing Cl by propionate or by prolonged K withdrawal. It is suggested that adrenaline inhibits intestinal motility by uncoupling the control activity to response activity through suppression of the prepotentials. The adrenaline-induced hyperpolarization may be due to an increase in K permeability but not to stimulation of electrogenic Na pumping. The increase in K permeability may depend upon the presence of Cl ions.
Release of red cells from the slowly-exchanging splenic pool after noradrenaline administration
Authors: Geiger H. B. , Song S. H. , Groom A. C.
Published: April 2011

Isolated, denervated, cat spleens were perfused at constant flow with modified Ringer solution. Perfusion pressure, outflow rate, and outflow red cell concentration were measured against time. After splenic perfusion by 500 ml solution the cell washout curve became a single exponential function, indicating that only cells from the most slowly exchanging red cell compartment remained (these are immature and abnormal cells which adhere to the fine structures of the red pulp). Splenic contraction was induced by injection of 5 μg noradrenaline into the inflow after perfusion by 600 and 1000 ml of fluid, respectively; outflow cell concentration rose 17-fold before returning to baseline value and 32% of red cells in the spleen were expelled. The time course of changes in cell concentration was similar in shape but delayed with respect to that of outflow rate. The transit time of the cells from the site of release to the splenic vein must have exceeded 40 s, which is consistent only with release from the red pulp. Furthermore, at the peak of the cell concentration curve the mean reticulocyte count was 37.8%. Thus immature and abnormal red cells, which comprise the slowly-exchanging compartment, are indeed released from the spleen during contraction.
Neostriatal administration of somatostatin: differential effect of small and large doses on behavior and motor control
Authors: Rezek M. , Havlicek V. , Leybin L. , Pinsky C. , Kroeger E. A. , Hughes K. R. , Friesen H.
Published: April 2011

The administration of small doses of somatostatin (SRIF) (0.01 and 0.1 μg) into the neostriatal complex of unrestrained, freely moving rats induced general behavioral excitation associated with a variety of stereotyped movements, tremors, and a reduction of rapid eye movements (REM) and deep slow wave sleep (SWS). In contrast, the higher doses of SRIF (1.0 and 10.0 μg) caused movements to be uncoordinated and frequently induced more severe difficulties in motor control such as contralateral hemiplegia-in-extension which restricted or completely prevented the expression of normal behavioral patterns. As a result, the animals appeared drowsy and inhibited. Analysis of the sleep-waking cycle revealed prolonged periods of a shallow SWS while REM sleep and deep SWS were markedly reduced; electroencephalogram recordings revealed periods of dissociation from behavior. The administration of endocrinologically inactive as well as the active analogues of SRIF failed to induce effects comparable with those observed after the administration of the same dose of the native hormone (10.0 μg).
Can nonadrenergic inhibitory varicosities be Identified structurally
Authors: Daniel E. E. , Taylor G. S. , Daniel V. P. , Holman M. E.
Published: April 2011

The distribution of vesicles in axon varicosities was examined in rabbit jejunum and opossum esophagus. Circular muscle cells of both rabbit jejunum and opossum esophagus responded to stimulation of intrinsic nerves with inhibitory junction potential in nearly all cases. Inhibitory junction potentials were rare and small in longitudinal muscle cells of rabbit jejunum. There were few axon varicosities with a predominance of large opaque vesicles or large dense-cored vesicles in any muscle layer of rabbit or opossum or in the plexuses of rabbit jejunum. There were almost as high a proportion of such varicosities in longitudinal as in circular muscle of rabbit jejunum, and there were almost none in circular muscle of opossum esophagus. The distribution of vesicles in varicosities was found often to be heterogeneous and could account for the observed occurrence of a small proportion of varicosities with a predominance of large vesicles. It is suggested that there is no structural distinction in vertebrates between axons which are cholinergic and axons which are nonadrenergic inhibitory.
Microiontophoresis of 5-hydroxytryptamine, epinephrine, and prostaglandin E1 on spinal neurons in the frog
Authors: Caulford P. G. , Coceani F.
Published: April 2011

5-Hydroxytryptamine (5-HT) and epinephrine were applied by microiontophoresis to single neurons in the isolated spinal cord of the frog. 5-HT depressed all but two of the responsive cells, whereas the response to epinephrine consisted exclusively of depression. 5-HT action was more marked than that of epinephrine on most cells. With either compound, responsive units were diffusely distributed throughout the tissue. While it was proven that prostaglandin E1 (PGE1) exerts a direct excitatory action on spinal neurons, no evidence of an antagonism between PGE1 and the monoamines was obtained. These findings provide additional support to the hypothesis that 5-HT and epinephrine are transmitters in the frog spinal cord. The possibility that PGE1 may 'modulate' the responsiveness of spinal neurons to the monoamines was not confirmed.
Dynamic elasticity of human mitral valve chordae tendineae
Authors: Lim Koon Ong , Boughner Derek R. , Smith Carol A.
Published: April 2011

Chordae tendineae are under constant dynamic stress and, therefore, measurements of static properties alone cannot provide a complete analysis of their mechanical response under stress. This study investigated the dynamic viscoelastic properties of human mitral valve chordae tendineae. The tissue was subjected to sinusoidal strain variations over a frequency range of 0.42 to 6.68 Hz. At a fixed strain, the storage modulus, E′, was found to be independent of applied frequency but varied inversely with chordal thickness. Values in the order of 108 dyn cm−2 (1 dyn = 10 μN) were found. E′ also increased with strain level. The phase lag, [Formula: see text], between stressing function and response was found to be small (0.2–0.058 rad) and decreased with frequency. Values of [Formula: see text] at each frequency were found to be independent of chordal size and strain level. This property would enable a smooth and even closure of the valve and provide a more rapid response at elevated heart rates. The loss modulus, E″, was found to be 18 to 50 times smaller than E′. This implied an almost complete recovery on removal of any stress on the tissue. E″, which also decreased with frequency, was found to be smaller for the larger chordae.
Dopamine β-hydroxylase and cytochrome oxidase activities in brown adipose tissue of newborn rats following sympathectomy with 6-hydroxydopamine
Authors: Behrens W. A. , Depocas Florent
Published: April 2011

Dopamine-β-hydroxylase (DBH) (EC 1.14.17.1) activity is present in the interscapular brown adipose tissue (IBAT) as early as 2 days of age in the white rat. The specific and the total activities of this enzyme, as well as those of cytochrome oxidase (COX) (EC 1.9.3.1) in IBAT increase up to at least 20 days of age. Daily administration of 6-hydroxydopamine (6-OHDA) between the second and the twelfth day after birth does not significantly alter IBAT weight gain relative to untreated controls, but the increase in protein content with age is reduced to about half the normal value at the end of the treatment. The treatment with 6-OHDA also results in a drastic lowering of DBH specific and total activities, and a much smaller rate of increase of COX specific and total activities with age in IBAT compared with controls. These results provide additional evidence for a previously proposed role of sympathetic nervous system activity in the development of the thermogenic potential of IBAT in the newborn rat.
Substance P selectively blocks excitation of Renshaw cell by acetylcholine
Authors: Krnjević K. , Lekić Dušan
Published: April 2011

In cats, under Dial anaesthesia, Renshaw cells were excited by microiontophoretic applications of acetylcholine (ACh), aspartate, and glutamate. Substance P, in small doses (10–30 nA), selectively abolished the responses to ACh, leaving the discharges evoked by the amino acids unchanged or enhanced. Higher doses (> 50 nA) depressed all responses, but those evoked by amino acids went down last and recovered sooner. By contrast, neither synaptic responses to ventral root stimulation nor spontaneous discharges were affected by substance P, presumably owing to the high efficacy of synaptic transmission and the presence of diffusion barriers around junctional sites.
Effect in vivo of β-adrenergic stimulation, angiotensin II, dibutyryl cyclic AMP, and theophylline on tonin concentration in rat saliva and submaxillary gland
Authors: Garcia R. , Kondo K. , Scholkens B. , Boucher R. , Genest J.
Published: April 2011

Tonin (an enzyme present in rat submaxillary gland and saliva) has previously been shown to be able, unlike renin and reninlike substances, to release angiontensin II either directly by acting on an appropriate substrate or from angiotensin I. The administration of a β-adrenergic drug, isoproterenol, produces a rise of tonin concentration in saliva without affecting its concentration in the submaxillary gland. Prior administration of a β blocker, propranolol, partially prevents this effect. The administration of theophylline increases the tonin concentration in both saliva and the submaxillary gland, whereas dibutyryl cyclic AMP increases tonin concentration in the former. These results suggest that β-adrenergic stimulation enhances both tonin release into the saliva and tonin synthesis in the submaxillary gland, and that these effects might be mediated by cyclic AMP. Infusion of angiotensin II blocked the stimulatory effect of isoproterenol on salivary tonin. 1Sar-8Ile-angiotensin II is both a weak antagonist of angiotensin II in this respect and a strong agonist in terms of blocking the effect of isoproterenol, another role mirrored in other physiological mechanisms of derivatives of angiotensin II.
The effects of Ca2+ antagonists on Ca2+ accumulation by subcellular fractions of rat myometrium
Authors: Crankshaw D. J. , Janis R. A. , Daniel E. E.
Published: April 2011

Several agents which antagonize or interact with Ca2+ in the excitation–contraction coupling of smooth muscle have been tested for their effects on Ca2+ accumulation by subcellular fractions of the rat uterus. Na+, but not K+, reduced the amount of Ca2+ that could be accumulated by the plasma membrane fraction (PM) and the endoplasmic reticular fraction (ER). Sr2+ considerably reduced Ca2+ accumulation by PM, ER, and the mitochondrial fraction; Ba2+ had a similar effect but was not as potent as Sr2+ La3+ at concentrations up to 10 mM was unable to block Ca2+ accumulation by PM and ER completely. The pharmacological agents D600, verapamil, and chlorpromazine all inhibited Ca2+ accumulation at dose levels much higher than those required to inhibit contractility, and were ineffective at lower doses. The action of Ca2+ antagonists is seen to be complex, involving interactions at different sites and on different processes. For a fuller understanding of their mechanisms of action further studies upon passive binding and on the release of Ca2+ from subcellular sites are required.
A study of soma isopotentiality in Aplysia neurons
Authors: Roberge Fernand A. , Jacob Robert , Gulrajani Ramesh M. , Mathieu Pierre A.
Published: April 2011

Soma isopotentiality in small, approximately spherical nerve cells during an action potential results in the total transmembrane current being proportional to the first time derivative of the membrane potential. The analytical results of earlier workers are used to obtain quantitative estimates of the deviations in soma isopotentiality to be expected when cells R2 and R15 in the abdominal ganglion of Aplysia californica are subjected to subthreshold stimulation. The deviations in isopotentiality during an action potential are determined experimentally in a small number of cells by noting the instantaneous potential difference between two widely spaced microelectrodes inserted in the cell soma. These analytical and experimental investigations showed that the soma of the endogenously active cell R15 could be considered isopotential both for subthreshold stimulation as well as during an action potential. On the other hand, a clear deviation from isopotentiality was observed in the silent cell R2 where activity was elicited by antidromic stimulation of the axon. Accordingly for the spontaneous action potentials observed in cell R15, a phase–plane diagram transforms into a current–voltage plot and is discussed from this point of view. The lack of soma isopotentiality for antidromic stimulation is presumably due to differing contributions of the triggering axon spike at the two separate microelectrode locations.
CNS control of the PNS-mediated gill withdrawal reflex and its habituation
Authors: Lukowiak Ken
Published: April 2011

Removal of the branchial (Br) nerve input to the gill significantly reduced the latency and increased the amplitude of the gill withdrawal reflex evoked by siphon stimulation. Further, after Br removal repeated siphon stimulation which previously resulted in habituation now resulted in facilitation of the reflex. However, the synaptic input to gill motor neurons in the abdominal ganglion continued to decrement as before. In preparations without the peripheral nervous system (PNS), removal of Br did not produce similar results. The gill withdrawal reflex and its habituation are mediated by the PNS, but the CNS exerts facilitatory and suppressive control. Thus, changes in synaptic efficacy to gill motor neurons in the abdominal ganglion are not the ultimate cause of gill reflex habituation. Habituation is the result of adaptive neural processes which occur together in the abdominal ganglion, the PNS, and the peripheral terminations of the central motor pathways to the gill. Therefore, in any analysis of the underlying neural mechanisms of habituation all these loci must be included and taken into account.
Effects of lidocaine in rabbit atria
Authors: Illanes A. , Betancourt O. J. , Dresel P. E.
Published: April 2011

Standard microelectrode recordings were obtained from rabbit right and left atria. Lidocaine (1 × 10−5 M) had no effect on these, but 5 × 10−5 M lidocaine significantly slowed rate and Vmax. This concentration had no effect on the duration of the action potential, a result clearly different from the effect of this drug in Purkinje tissue. Lidocaine had much less effect on the 'steady-state' relation of membrane potential to Vmax of phase 0 of the action potential than on the 'membrane responsiveness curve obtained by the extra stimulus technique. We have demonstrated time-related recovery from sodium inactivation in rabbit left atria and have shown that lidocaine slows recovery in this tissue as it does in Purkinje fibres.
Maternal dietary deficiency and its effect on the metabolism of nucleic acids and proteins. "Effect of exchanging the young, during the lactation period, between the control and undernourished female rats"
Authors: Goswami Tapas , Srivastava Uma
Published: April 2011

The effect of maternal dietary deficiency on the metabolism of nucleic acids and proteins was studied by exchanging the pups of control and undernourished dams during the lactation period. In the pups of control dams fostered by undernourished dams during the lactation period (E3), it was observed that the body and organ weight, and RNA, DNA, and protein content failed to increase normally. Contrary to this, the free leucine and nucleotide contents were higher and their specific activities lower in the plasma and various organs of the E3 group as compared with the control group.Specific activity of protein was higher in the liver, brain, kidney, and lung, and was lower in the spleen and heart of the E3 group as compared with the control group. Specific activity of RNA was higher in the liver, spleen, and lung, and was lower in the brain, kidney, and heart of the E3 group as compared with the control group.In the pups of undernourished dams fostered by the control dams during the lactation period (E1), the body and organ weights, the RNA, DNA, and protein content, the content of free leucine and nucleotides as well as their specific activities, and the specific activity of protein and RNA were partially or completely restored. However, the DNA content of the brain remained unchanged in comparison with those pups of undernourished dams nursed by their own mother (E2). In the brain, kidney, spleen, and lung of the E1 group, the specific activity of RNA increased considerably and even exceeded the control values.The radioactivity results discussed above clearly demonstrate an accelerated metabolism of protein and RNA in the various organs of the E3 group and a partial or complete normalization in the E1 group.
Effects of thyroid status on plasma adrenaline and noradrenaline concentrations in sheep during acute and chronic cold exposure
Authors: Christopherson R. J. , Thompson J. R. , Hammond V. A. , Hills G. A.
Published: April 2011

In the first of two experiments, plasma concentrations of adrenaline (A), noradrenaline (NA), and glucose were determined in intact sheep and in surgically thyroidectomized sheep treated intramuscularly with either 0.125 or 0.25 mg triiodothyronine (T3) per day. On day 28 of exposure to temperatures of 22–25 or 2–5 °C, overall mean plasma concentrations of A were 0.07 and 0.15 ng/ml, respectively, and of NA were 0.30 and 0.45 ng/ml, respectively. Plasma A concentrations were higher in intact compared with thyroidectomized sheep on T3 therapy. Plasma glucose concentrations were increased by exposure to 2–5 °C and by T3 treatment. In a second experiment thyroidectomized sheep were kept at 22–26 °C and were either T3 treated (0.07 mg T3/day, im) or untreated. After 3 weeks, mean concentrations in the untreated sheep before acute cold and during the last hour of cold exposure (−23 °C) were, respectively: for A, 0.09 and 0.47 ng/ml; for NA, 0.46 and 3.15 ng/ml; and for glucose, 62.1 and 122.1 mg/100 ml. In T3-treated sheep the mean concentrations before and during cold were, respectively: for A, 0.07 and 0.22 ng/ml; for NA, 0.30 and 1.71 ng/ml; and for glucose, 59.6 and 82.3 mg/100 ml. The untreated sheep showed greater increases in plasma concentrations of A, NA, and glucose and in hematocrit values than T3-treated sheep, but had slightly smaller increases in metabolic rate, greater decreases in rectal temperature, and similar heart rates during cold exposure.
Antagonism by phosphate buffer of the twitch loss in isolated muscle fibers produced by calcium-free solutions
Authors: Frank G. B.
Published: April 2011

In 37 of 41 isolated frog skeletal muscle fiber preparations (one, two, or three fibers) the twitch was eliminated or reduced to < 10% of control by exposing the fibers to a 0-caicium, bicarbonate-buffered solution for 10 min or less. Replacing the bicarbonate by a phosphate buffer either prevented twitch inhibition or increased the 0-calcium exposure time required for its production. It is concluded that surface membrane-bound calcium ions (presumably in the t-tubules) are required to couple the action potential to the mechanical response and that phosphate ions inhibit the loss of the membrane-bound calcium ions into an external calcium-free solution.
Flow correlation of loop of Henle potassium influx
Authors: Levine D. Z. , McLeod R. A. , Byers M. K.
Published: April 2011

Potassium influx in short loops of Henle was assessed using end proximal to early distal perfusion with potassium-free saline. Over a wide range of perfusion rates influx was highly correlated with collected flow rates. The magnitude of the influx was comparable with the delivery rate of potassium to the early distal site seen during free flow, over a narrower range of collected flow rates.
Relationship between analgesia and turnover of brain biogenic amines
Authors: Bensemana D. , Gascon A. L.
Published: April 2011

The analgesic activity of morphine, Δ9THC, and sodium salicylate was studied concomitantly with changes in brainstem and cortex turnover of dopamine (DA), noradrenaline (NA), and serotonin (5HT). The results show that a correlation exists between the presence of analgesia and the increased turnover rates of the three biogenic amines.Morphine and sodium salicylate induced analgesia is accompanied by an increased turnover rate of all three biogenic amines; Δ9THC-induced analgesia is accompanied by an increased turnover rate of DA and 5HT only. There is, however, no consistent relationship between the degree of analgesia and the degree of change in the turnover rates.The existence of the endogenous morphine-like substances, endorphines, may explain why morphine analgesia is distinct from that of Δ9THC and sodium salicylate. The possible relationship between this morphine-like substance and biogenic amines is discussed.
Time course of mesenteric vasodilatation following hypophysectomy and the stopping of a vasopressin infusion
Authors: Pang Catherine C. Y. , Wilcox William C. , McNeill J. Robert
Published: April 2011

Hypophysectomy caused an increase in superior mesenteric arterial conductance that reached a new plateau approximately 20 min after removal of the gland in four pentobarbital-anesthetized cats. Intravenous infusion of arginine vasopressin (0.74 ± 0.21 mU min−1 kg−1) caused conductance to decrease to approximately prehypophysectomy control values. Stopping the infusion resulted in an increase in conductance and the time course of this vasodilatation was virtually identical to that which occurred following hypophysectomy. The results are consistent with the interpretation that the effects of acute hypophysectomy on the mesenteric resistance vessels are due primarily to removal of the vasopressin system and the concomitant elimination of circulating vasopressin.
Alterations in polyamines and nucleic acids in the rat ventral prostate during cyproterone acetate treatment and subsequent withdrawal
Authors: Tsang B. K. , Singhal R. L.
Published: April 2011

The effect of cyproterone acetate (CA) was examined on polyamines and nucleic acid levels of the ventral prostate at various time intervals after daily administration of this antiandrogen (1.25 mg/100 g, sc) to adult rats. While CA markedly reduced prostatic spermine, spermidine, and putrescine levels after 10 days of treatment, changes in the latter two polyamines appeared to be biphasic with significant elevations being observed at day 1, followed by marked decreases that were evident as early as the 3rd day. Cessation of antiandrogen treatment for 10 days in rats that had been pretreated with CA significantly elevated prostatic spermine levels, while the concentration of spermidine and putrescine remained slightly lower than controls. In contrast, CA failed to exert any marked effect on prostatic spermine and putrescine levels when animals were treated concomitantly with testosterone (5 mg/100 g per day, sc; 10 days). Like prostatic spermidine and putrescine, RNA levels and the RNA:DNA ratio were significantly elevated 24 h after CA administration, but decreased thereafter to levels markedly lower than controls by the 10th day of treatment. DNA concentration was increased slightly during CA administration, although the total content of this nucleic acid remained unaltered. While cessation of CA administration restored RNA and the RNA:DNA ratio to control values, these were significantly increased in rats given both CA and testosterone. Results of the present investigation support the hypothesis that changes in cellular polyamines may be related to alterations in RNA metabolism, and thus cellular differentiation of the prostate gland following androgenic deprivation and (or) depletion.
Metabolism of the isolated perfused rabbit heart. I. Responses to anoxia and reoxygenation, II. Energy stores
Authors: Chiong Miguel A. , Berezny Gary M. , Winton Timothy L.
Published: April 2011

Cardiac performance, substrate utilization, and creatine kinase (CK) release were studied in Langendorff rabbit hearts during aerobic perfusion, 25 min of anoxia, and 75 min of reoxygenation. In study I (n = 40), increasing glucose availability during aerobic perfusion enhanced substrate utilization without influencing cardiac performance, and this effect was not modified by insulin. Reoxygenation with glucose decreased CK (milliunits per millilitre) in the coronary sinus effluent but the best early recovery occurred in hearts protected with the 'cocktail' (see Table 1) during anoxia and perfused with glucose and insulin during recovery. This early recovery of performance was associated with transient higher CK loss, an effect that may have been related to one or more of the following factors: squeezing out of interstitial CK, heterogeneous anoxic injury to the myocardium, severe sarcolemmal damage, and preferential energy utilization by the contractile apparatus.In study II (n = 82), increasing recovery of cardiac performance was associated with increasing rate of CK loss (milliunits per minute) during reoxygenation. At 15 min of recovery, creatine phosphate (CP) and ATP stores were 400 and 50% of the aerobic group suggesting the presence of a defect in energy transfer from CP to the cytosolic ADP: ATP system. Thereafter, CP levels gradually declined while ATP reached a peak concentration of 85% of the aerobic group at 30 min. By the end of recovery, ATP stores were low at 23% of control, at a time when cardiac performance and the rate of CK loss were maximal. The significance of these depleted ATP stores remains to be elucidated.
Effect of a local cold stress on peripheral temperatures of Inuit, Oriental, and Caucasian subjects
Authors: Livingstone S. D. , Grayson J. , Reed L. D. , Gordon D.
Published: April 2011

Male subjects comprised of six Inuit from Igloolik, N.W.T., and five Orientals and six Caucasians from Toronto, Ont., volunteered for tests to determine the effect of localized cold stress on peripheral temperatures. In each subject, skin temperatures of the right index finger, the arm, and the cheek, as well as blood pressure and heart rate, were measured before, during, and after foot immersion in water of 10 °C temperature for 10 min. There was an immediate decrease in finger temperature on foot immersion in all three subject groups; however, the Inuit finger temperatures recovered very quickly to control values, the Caucasian finger temperatures began to increase after decreasing for 7.5 min, and the Oriental finger temperatures decreased continuously during the foot immersion and remained cool even 10 min after the removal of the cold stimulus. The cold stimulus did not affect the cheek or arm temperatures of any of the groups. In all subjects, systolic and diastolic blood pressures and heart rates increased on foot immersion, gradually returning towards normal values. No intergroup differences were seen in these parameters.
Effect of ketamine on thermoregulation in rats
Authors: Lin M. T. , Chen C. F. , Pang I. H.
Published: April 2011

Intraperitoneal administration of ketamine produced dose-dependent hypothermia at the ambient temperatures (Ta) of both 8 and 23 °C in unanesthetized rats. At a Ta of 8 °C, the hypothermia was brought about solely by a decrease in metabolic heat production. There were no changes in either the tail skin temperature (Ttail) or the sole skin temperature (Tsole). At a Ta of 23 °C, the hypothermia was due to an increase in Ttail, an increase in Tsole, and a decrease in metabolic heat production. However, at a Ta of 31 °C, there were no changes in rectal temperature in response to ketamine application, since neither heat production nor skin temperatures (e.g., Ttail and Tsole) was affected by ketamine at this Ta. The data indicate that the effect of the drug treatment may be to decrease heat production and (or) increase heat loss.
Characterization of the energy-dependent calcium binding of a mitochondrial fraction isolated from bovine intrapulmonary vein
Authors: McNamara Dennis B. , Roulet Marie-Jeanne , Hyman Albert L. , Kadowitz Philip J.
Published: April 2011

A mitochondrial-enriched fraction was isolated from bovine intrapulmonary vein; this fraction had a three- to four-fold enrichment factor for succinic dehydrogenase, a mitochondrial marker enzyme, and bound calcium in an azide-sensitive, energy-dependent fashion using either ATP or succinate as substrate. The calcium binding was sensitive to the concentrations of H+, ATP, Ca2+, and mitochondrial fraction. Binding and accumulation were time dependent, reaching at 10–12 min a plateau which was maintained over the time interval studied, i.e. 18 min. At the plateau, maximal binding was 221 ± 8.64 and maximal accumulation was 285 ± 20.2 nmol Ca2+/mg protein. The mitochondrial-enriched fraction contained an azide-sensitive, Mg2+-dependent, Ca2+-stimulated ATPase (Mg2+ + Ca2+ = 25.59 ± 1.03, Ca2+ = 3.96 ± 1.06 μmol P1/mg protein per hour). This study is the first to report the isolation from intrapulmonary vein of a subcellular organelle capable of binding calcium in an energy-dependent fashion; furthermore, it confirms and extends the observations of others that mitochondria may contribute to intracellular calcium homeostasis in vascular smooth muscle.
Taurolithochoiic acid and chlorpromazine cholestasis in the rhesus monkey
Authors: Strasberg S. M. , Kay R. M. , Ilson R. G. , Petrunka C. N. , Paloheimo J. E.
Published: April 2011

Taurolithocholic acid (TLC) and chlorpromazine (CPZ) cholestasis were studied in reversible primate models in order to determine the level of injury, changes in canalicular permeability, and the effects of taurocholic acid (TC) on the production of cholestasis. TLC produced dose-dependent cholestasis. Reductions in bile acid secretion rate and concentration, larger decreases in [14C]erythritol clearance than in total bile flow, and increased bicarbonate concentration in bile indicated that the cholestasis was canalicular in origin. TC prevented cholestasis; it also caused an increased secretion of TLC in bile, but the TLC:TC concentration ratio was unchanged, providing evidence that TC is beneficial because it hastens excretion of TLC from the liver cell in micelles. Permeability to [3H]inulin was increased during the recovery period. CPZ caused reductions in bile flow, bile acid secretion rate, and [14C]erythritol clearance, and almost completely eliminated biliary bicarbonate secretion, suggesting a mixed canalicular and ductular form of cholestasis. When TC was given with CPZ, no reductions in bile acid secretion rate or [14C]erythritol clearance were found but bicarbonate secretion was markedly reduced, bicarbonate concentration diminished, and bile acid concentration increased, i.e., TC protected against the canalicular component of CPZ cholestasis and unmasked the ductular component. Permeability to inulin was increased in three of four animals. TLC cholestasis occurs predominately at the canalicular level, whereas CPZ probably affects bile flow at the ductular level as well. TC protects the hepatocyte against the effects of both agents.
Rapid disappearance of nitroglycerin following incubation with human blood
Authors: Armstrong Joyce A. , Slaughter Susan E. , Marks Gerald S. , Armstrong Paul W.
Published: April 2011

Nitroglycerin (GTN) (at a concentration of 50 ng/mL) was incubated aerobically at 37 °C with whole blood, resuspended cells, and plasma from five normal volunteers. At several time periods following the initiation of the incubation (0, 1.5, 3, 5, 10, and 20 min for blood and resuspended cells, and 0, 30, 45, 60, 120, and 180 min for plasma) the samples were assayed for GTN in the incubation medium. Linear regression analyses were performed between the logarithm of the percentage GTN remaining and incubation time in order to determine the rate of disappearance of GTN from each system. A short t1/2 for GTN was found in blood (6.2 min) and resuspended red cells (6.6 min) whereas a longer t1/2 of 53.4 min was determined in plasma. These data indicate that the metabolism of GTN in human blood is rapid and predominantly localized in the cellular compartment of the blood. It is concluded that (a) the short circulatory t1/2 of GTN following clinical administration is explained, at least in part, by rapid metabolism in blood and (b) it is necessary to rapidly centrifuge blood from GTN-treated patients and to freeze the plasma in order to prevent the breakdown of GTN prior to analysis.
Kinin receptors in experimental inflammation
Authors: Marceau F. , Barabé J. , St-Pierre S. , Regoli D.
Published: April 2011

The contractile response of the rat isolated urinary bladder to kinins is mediated by receptors of the B1 and of the B2 types, as this preparation responds to des-Arg9-bradykinin (des-Arg9-BK), a fairly selective stimulant of receptor B1 and to [Tyr(Me)8]-BK, a potent agonist on receptor B2. Des-Arg10-[Leu9]-kallidin, a specific and competitive antagonist of the action of kinins on receptor B1, has been found to block the effect of des-Arg9-BK in concentrations similar to those required in the rabbit aorta; therefore, the B1 receptor of the rat urinary bladder is analogous to that of the rabbit vascular tissue.The response of the rat urinary bladder to des-Arg9-BK increases progressively from near null level during the incubation in vitro and can be abolished by cycloheximide; this suggests that receptor B1 of the rat urinary bladder is formed de novo.The inflammation of the bladder induced by intravesical injection of the detergent Triton X-100 enhances the initial response to des-Arg9-BK without modifying the response to other agents. The B1 receptor is formed in vivo in the rat urinary bladder submitted to the Triton X-100 treatment but not in the control untreated organ. The local de novo synthesis of B1 receptors for kinins that follows a noxious stimulus is proposed as a possible mechanism implicated in the chemical mediation of the inflammatory process.
Vasopressin increases the central nervous system suppressive control over gill reflex behaviours and associated neural activity in Aplysia
Authors: Lukowiak Ken , Thornhill J. A. , Cooper K. E. , Veale W. L.
Published: April 2011

Exposure of the abdominal ganglion of Aplysia to arginine vasopressin (10−12 M) reduces the amplitude of the gill withdrawal reflex, accelerates its rate of habituation, and causes a concomitant decrease in the number of action potentials evoked in gill motor neuron L7. The effects of vasopressin on both the reflex and the concomitant neural activity evoked in L7 were completely reversible. Vasopressin did not affect the passive membrane properties of L7. The results indicate that a vertebrate neurohypophyseal hormone can affect behavioural responses as well as modify the synaptic efficacy of the reflex pathway.
Noradrenaline-induced calorigenesis in warm- or cold-acclimated rats. In vivo estimation of adrenoceptor concentration of noradrenaline effecting half-maximal response
Authors: Depocas Florent , Zaror-Behrens Gloria , Lacelle Suzanne
Published: April 2011

Desmethylimipramine (DMI, 1 mg DMI∙HCl kg−1) and normetanephrine (NMN, 1 μg min−1 g−0.74) were used to inhibit, respectively, neuronal and extraneuronal uptakes of noradrenaline (NA) during calorigenesis induced in barbital-sedated warm-acclimated (WA) or cold-acclimated (CA) rats by infusion of NA, a procedure which mimics the effects of NA released within calorigenic tissues in response to cold exposure. The doses of the inhibitors were selected for maximal effectiveness in potentiating calorigenic response and for minimal side effects. For rats of either acclimation group treated with DMI and NMN, with DMI only, or with neither inhibitor the doses of NA required to evoke approximately half-maximal calorigenic responses were, respectively, 0.5, 1.0, and 3.5 ng min−1 g−0.74. The corresponding steady-state concentrations of NA in arterial plasma averaged 14.3, 21.7, and 43.2 nM in the three groups of WA rats and 10.0, 14.8, and 31.9 nM in the three groups of CA rats. Reduction by NA uptake inhibitors of the circulating levels of NA necessary to stimulate calorigenesis, half-maximally, presumably in brown adipose tissue, indicates a reduction in the steepness of the NA concentration gradient between capillary plasma and synaptic clefts in that tissue. The steady-state concentration of NA in blood plasma of rats treated with DMI and NMN and infused with NA at a dose of 0.5 ng min−1 g−0.74 (~1 × 10−8 M) is a good estimate of the NA concentration required at calorigenic adrenoceptors to effect half-maximal activation. Presumably, this concentration is also an estimate of that resulting from NA released at nerve endings during cold-induced activation of nonshivering thermogenesis at half-maximal rates in brown adipose tissue.
Fractionation and Ca uptake studies on membranes of rabbit longitudinal and circular intestinal smooth muscle
Authors: Grover A. K. , Kwan C. Y. , Garfield R. E. , McLean J. , Fox J. E. T. , Daniel E. E.
Published: April 2011

Membrane fractionation studies using circular and longitudinal muscles from rabbit small intestine showed that optimal methods for preparation of microsomes and their fractionation on discontinuous sucrose density gradients were identical for the two muscles. 5′-Nucleotidase was maximally enriched in the F2 (20–28% (w/w) sucrose) fraction, NADPH: cytochrome c oxidoreductase was maximal in the F3 Fraction, and cytochrome oxidase specific activity was highest in the mitochondrial fraction. The ATP-dependent Ca uptake was highest in the F2 fraction. All membrane fractions, including F2, from the longitudinal muscle exhibited much higher ATP-dependent Ca uptake than the corresponding fractions from the circular muscle. Azide inhibited Ca uptake, in the presence of ATP, by mitochondrial fractions from the longitudinal muscle. Oxalate potentiated the ATP-dependent Ca uptake by the various subcellular fractions from the longitudinal muscle. Azide and oxalate had no effects on Ca uptake by any of the fractions derived from the circular muscle. A23187 abolished the Ca uptake in presence of ATP by F2 from either muscle. When F2 vesicles after Ca uptake in presence of ATP were diluted in hypotonic EGTA, they lost 70–80% of the stored Ca in <10 s. However, a similar dilution in isotonic EGTA led to significantly smaller loss of the stored Ca in <10 s and the remainder was lost with a half-life of 5.6 min from the circular muscle F2 vesicles and 6.2 min from the longitudinal muscle F2 vesicles. Passive Ca uptake capacities of F2 from the two muscles were similar. Thus the higher Ca uptake in presence of ATP, by longitudinal muscle F2 vesicles than by the circular muscle F2 vesicles, may be due to a higher specific activity of the Ca pump in the longitudinal muscle than in the circular muscle. The contribution due to differences in intactness and orientation of the vesicles in the two muscles is unknown at this time.
Dissociation of the antiaggression and serotonin-depleting effects of fenfluramine
Authors: McKenzie G. M.
Published: April 2011

Fenfluramine or norfenfluramine produced a marked and persistent depletion of whole-brain serotonin and antagonized potently the apomorphine-induced aggression response in Long Evans male rats. Chronic treatment with fenfluramine or norfenfluramine resulted in the development of complete tolerance to the antiaggression action of fenfluramine whereas tolerance to the serotonin-depleting action was not observed. Pretreatment with chlorimipramine antagonized both the antiaggression and the serotonin-depleting activity of fenfluramine yet the antiaggression activity of haloperidol was unaffected. Neither p-chlorophenylalanine nor the combination of α-methyl-p-tyrosine and reserpine affected the antiaggression activity of fenfluramine. It is concluded that the serotonin-depleting and antiaggression effects are dependent upon the ability of fenfluramine to gain access into the serotonergic neuron and that whereas serotonin release can account for the antiaggression action, release does not seem to explain adequately the depleting action of fenfluramine.
Distribution of amylase and chymotrypsin in four regions of the rat pancreas
Authors: Beaudoin Adrien R. , St-Jean Pierre , Girard Ginette
Published: April 2011

Recent observations have confirmed the existence of more than one pool of secretory proteins in the rat pancreatic tissue. To determine if these different pools could be located in the different regions of the rat pancreas, the amylase and chymotrypsin contents have been measured in the biliary, duodenal, gastric, and splenic regions. On a tissue DNA content, protein content, or a fresh weight basis, the proportions of these two enzymes are comparable in the four regions. It is therefore postulated that heterogeneity of enzyme composition exists either within these regions or within the acinar cell itself.