bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption and intestinal catabolism of fatty acids in the rat: effect of chain length and unsaturation
Authors: Bernard A , Carlier H
Published: December 2014

Simultaneous portal blood absorption and intestinal mucosal catabolism of labelled fatty acids were investigated. Anaesthetized adult Wistar rats were infused intraduodenally either with 90 mumol of capric (C10:0), oleic (C18:1), linoleic (C18:2) or arachidonic (C20:4) 1–14C acids or with 30 mumol of each labelled fatty acid in addition to 30 mumol of oleic acid and 30 mumol of monopalmitin. For mixed infusates, experiments were carried out with two additional long‐chain fatty acids: palmitic (C16:0) and erucic (C22:1) 1–14C acids. Radioactivity was quantified in the lipids and in the catabolic products in portal blood recovered at 5 min intervals for 1 h after infusion. At the end of the experiment, the disappearance of radioactivity from the mucosa was quantified. When labelled fatty acids were infused alone, 49% of the radiolabelled lipid disappearing from the mucosa was recovered in the blood for C10:0, but only 7.8% for C18:1, 6.4% for C18:2 and 10.6% for C20:4. With mixed infusates, 41% of the radiolabelled lipid disappearing from the mucosa was recovered in the blood for C10:0 compared with 12% for C18:1, 10.2% for C18:2, 10.5% for C20:4 and 2.7% for C16:0 and 2% for C22:1. Labelled catabolites appear with the same profiles as those of the respective fatty acids in blood. These studies confirm a minor absorption into blood of long‐chain fatty acids compared to the medium‐chain fatty acids and highlight differences in the catabolism of the fatty acids according to their chain length and their degree of unsaturation. The differences might be related to the differences in the fatty acid hydrosolubility and to their different affinities for the I‐ and L‐cytosolic fatty acid binding proteins. These phenomena may be important in nutrition in relation to the availability of essential fatty acids.
Effects of the prostaglandin analogue misoprostol on cell proliferation in the canine small intestine
Authors: Goodlad RA , Lee CY , Levin S , Wright NA
Published: December 2014

While there are several reports of prostaglandins of the E series being associated with increased mucosal mass in the stomach, their effects on the small intestine are less well documented. A microdissection‐based technique was used to measure proliferation and crypt size in the duodenum, jejunum and ileum of dogs given the prostaglandin analogue misoprostol. Six test and six control animals were given an oral dose of 300 micrograms kg‐1 day‐1 of misoprostol for 11 weeks, a dose‐duration combination chosen to optimize the development of gastric hyperplasia. Misoprostol increased both the area of the crypts (P less than 0.001) and the number of mitoses per crypt (P = 0.002) throughout the small intestine. The technique also demonstrated a significant gradient in crypt size and in crypt area from the duodenum to the ileum. There was no statistical interaction between misoprostol and the site studied, suggesting that this trophic effect was systemic or systemically mediated.
Parotid protein secretion from the rabbit during feeding
Authors: Ikawa M , Hector MP , Proctor GB
Published: December 2014

Rabbits were trained to accept a standardized feeding regime. Under anaesthesia both parotid ducts were cannulated in a retrograde direction and saliva was subsequently collected in feeding sessions involving pellets and carrots before and after the administration of propranolol. Salivary total protein and amylase concentrations were assayed and protein analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS‐PAGE). Propranolol produced a reduction in protein secretion but not fluid secretion, indicating that protein secretion is partly under beta‐adrenergic control. A transient increase in protein secretion was seen 8 h after the administration of propranolol and suggested the existence of different neural mechanisms involved in protein secretion compared to synthesis. Protein output (with high fluid secretion) during feeding on pellets was higher than on carrots (with high protein concentration) and suggested a significant role of the parasympathetic nervous system. The pattern of protein secretion as seen by SDS‐PAGE was similar in individual rabbits and remained largely unchanged with the different foods and in the presence of propranolol.
Regulation of cellular water and ionic content in lungs of fetal and adult rats
Authors: Mariani MF , Thomas L , Russo MA , van Rossum GD
Published: December 2014

Slices of lungs from late‐fetal (1 day pre‐partum) and adult rats lost K+ and gained Na+, Cl‐, water and Ca2+ during pre‐incubation at 1 degrees C. These changes were reversed upon restoration to 37 degrees C. The recovery of composition at 37 degrees C was completely dependent on cell respiration in adult slices; by contrast, glycolysis could support partial recovery in the fetal slices. Ouabain completely inhibited K+ reaccumulation at both ages but inhibited net extrusion of water by no more than 50%. Replacement of medium Cl‐ with NO3‐ prevented the extrusion of water in the presence of ouabain in adult but not fetal slices. Transmission electron microscopy of type II epithelial cells in slices of both ages showed that ouabain induced the formation of many cytoplasmic vesicles, apparently derived from the Golgi apparatus. Regulation of cell ionic and water content is thus generally similar in late‐fetal and adult lung tissue, but there are differences in the source of ATP and in some features of ouabain‐resistant volume regulation.
The effect of level of contraction on the electromyographic power spectrum of the diaphragm in pigs
Authors: Hussain SN , Clement MG , Vanelli G , Albertini M , Aguggini G
Published: December 2014

We investigated the relationship between the frequency components of myoelectric power spectra of the diaphragm and the level of diaphragmatic contraction in seven anaesthetized spontaneously breathing pigs. Electromyographic activity of the costal and crural portions of the diaphragm were recorded with fish‐hook electrodes and the frequency‐power spectra during inspiration were computed and expressed in terms of centroid frequency (fc). Diaphragmatic force was indirectly assessed as transdiaphragmatic pressure (Pdi) which was measured with balloon‐catheter systems placed in the abdomen and oesophagus. The relationships between Pdi and costal and crural fc were assessed during brief (2 min) and incremental increases in diaphragmatic contraction, achieved by gradual occlusion of the inspiratory line of the breathing circuit. When Pdi was increased to 128, 191, 287 and 421% of the value measured during unobstructed breathing, costal and crural fc rose significantly in all animals because of an increase in the power of high‐frequency components and a decline in the power of low‐frequency components. Both costal and crural fc returned to control values within 5 min of the release of inspiratory occlusion. Our results indicate that the level of contraction is an important determinant of the diaphragmatic myoelectric power spectrum and should be taken into consideration when using power spectral analysis to diagnose diaphragmatic mechanical failure.
Correlates of osteoclast function in the presence of perchlorate ions in the rat
Authors: Moonga BS , Datta HK , Bevis PJ , Huang CL , MacIntyre I , Zaidi M
Published: December 2014

The effects of perchlorate anion (ClO4‐) on osteoclast properties were investigated through a number of independent in vivo and in vitro procedures. Intravenous infusion of ClO4‐ significantly reduced plasma [Ca] in young (50 g) Wistar rats, in the absence of changes in plasma [Mg] or [albumin]. This effect was maximal at 20 min after administration, and at a dose of 600 mumol/rat. Scanning electron‐microscope images suggested that the presence of 10 mM‐perchlorate reduced both the total area of cortical bone resorbed by freshly disaggregated rat osteoclasts, and the number of osteoclastic excavations in vitro. Similar effects were observed in the presence of 5 mM [Ca2+]. The effects of Ca2+ were potentiated by otherwise ineffective (1 mM) doses of perchlorate. Indo‐1 dual‐emission microspectrofluorimetry indicated a transient sixfold elevation of cytosolic free [Ca2+], in isolated cultured osteoclasts, with addition of 10 mM‐perchlorate. Records of time‐lapse video images indicated that this was followed by a marked and sustained cell retraction, by up to 70% of control cell area. Such effects were not observed at thiocyanate concentrations (10 mM) that would have produced comparable lyotropic effects as perchlorate. However, perchlorate did not alter morphometric measures for pseudopodial motility and cell migration. Nor did it influence supernatant concentrations of tartrate‐resistant (osteoclastic) acid phosphatase in cultures of resorbing osteoclasts. These findings suggest that perchlorate is a potent inhibitor of osteoclast function, and acts through an influence on intracellular [Ca2+], and in turn upon the degree of cell retraction.
Intracellular pH changes induced by hypoxia and anoxia in isolated sheep heart Purkinje fibres
Authors: Bright CM , Ellis D
Published: December 2014

The effects were studied of hypoxia on intracellular ion activities in sheep heart Purkinje fibres. The intracellular pH (pHi), surface pH (pHs), intracellular potassium activity (aki), and intracellular sodium activity (aNai) of the cells were recorded using liquid ion exchanger‐filled microelectrodes. Various methods of inhibiting oxidative phosphorylation were compared for their effect on pHi. These methods were the use of hypoxia, anoxia or NaCN (2 mM). Hypoxia was produced by degassing solutions under reduced pressure then bubbling with 100% nitrogen gas. Anoxia was produced in a similar manner but with the addition of the reducing agent sodium dithionite (0.5 mM) to remove all traces of oxygen from the solutions. Anoxia caused the most marked changes. Concentration of sodium dithionite between 0.1 and 1 mM produced similar maximum rates of acidification. High concentrations (5 or 20 mM) could produce larger intracellular acidifications apparently unrelated to anoxia. The effects of hypoxia and NaCN were similar. Inhibition of Na(+)−H+ exchange with amiloride (1 mM) had little effect on the pH changes produced by hypoxia. Periods of hypoxia exceeding 1 h still resulted in rapid, readily reversible changes in pHi. Hypoxia caused a rise in aNai, the effect being larger in anoxic conditions. The intracellular K+ activity decreased in hypoxia with further decreases in anoxic conditions. The intracellular ion changes produced during hypoxia are discussed in terms of the production of lactic acid by the cells and changes in the ATP supply to the Na(+)−K+ pump.
Contribution of joint and muscle afferents to position sense at the human proximal interphalangeal joint
Authors: Ferrell WR , Craske B
Published: December 2014

Experiments were carried out to examine the perceived position of the human index finger about the proximal interphalangeal joint. In protocol I, the finger was moved from an intermediate position at velocities ranging from 200 deg/min to 2 deg/min, then held still at one of three positions. The subject's task was visually to align a finger silhouette that was coaxial with the joint to the kinaesthetically perceived position of the unseen finger. Judgements of position were found to be quite accurate, and unaffected by previous velocity. Protocol II showed that although the direction of joint displacements of 0.01 and 0.1 deg could not be detected at any velocity, 1 deg could be detected at 200 deg/min and 10 deg at 20 and 2 deg/min. In protocol III the finger was moved at 2 deg/min and maintained at either 105 or 175 deg. It was found that the position of the unanaesthetized finger was quite accurately known, but with digital nerve block, subjects clearly perceived the finger to be at the mid‐position (approximately 130‐150 deg). This suggests that the absence of joint and cutaneous afference is interpreted by the CNS as indicating mid‐position. The slight bias of the sensed position towards the objective position shown by the results also indicates that muscle afferents can provide a crude signal related to joint position. This finding was further supported by the observation that splinting the distal interphalangeal joint into flexion resulted in flexion bias in the perceived angle of the proximal interphalangeal joint. Anaesthesia of the middle finger, thumb and distal portion of the index finger (leaving proximal joint unaffected), had little effect on position matching performance, suggesting that the large error in position sense during anaesthesia of the whole finger is due to loss of afference specifically related to the proximal interphalangeal joint, and not due to loss of non‐specific facilitatory influences from cutaneous and joint afferents. The results argue for an important proprioceptive role for joint afferents at finger joints.
Oxytocin‐evoked repetitive rises of intracellular calcium in single cultured human myometrial cells
Authors: Thornton S , Gillespie JI , Greenwell  , Dunlop W
Published: December 2014

Repetitive transient increases in intracellular calcium were recorded in single cultured human myometrial cells exposed continuously to oxytocin (1 pM‐1 nM). Each transient was preceded by a pacemaker‐like gradual increase in baseline [Ca2+]i. Removal of extracellular Ca2+ reversibly stopped the transients although small fluctuations in [Ca2+]i were observed in seven out of eleven cells studied. In a proportion of cells (1–2%) repetitive Ca2+ transients were observed in the absence of exogenous oxytocin. The pattern of activity was similar to that seen in cells exposed to oxytocin. These spontaneous elevations in [Ca2+]i were reversibly inhibited by removing extracellular calcium. These experiments demonstrate for the first time repetitive agonist‐induced and spontaneous transient increases in [Ca2+]i in single cultured human myometrial cells.
Effects of lengthened immobilization on functional and histochemical properties of rabbit tibialis anterior muscle
Authors: Pattullo MC , Cotter MA , Cameron NE , Barry JA
Published: December 2014

The imposition of long‐term lengthened immobilization on rabbit tibialis anterior (TA) muscles resulted in rapid increases in slow oxidative (SO) fibre number. After 2 weeks, SO number had increased 2‐fold and was 5 times greater after 6 weeks immobilization. There were also fibre‐type‐specific effects on SO, fast oxidative glycolytic (FOG) and fast glycolytic (FG) fibre areas. Twitch strength was unchanged throughout immobilization whilst production of tetanic tension was impaired during the initial period but had returned to control levels by 6 weeks. Twitch contraction times and isometrically determined rates of rise and relaxation were largely unaffected by immobilization despite the marked increase in expression of slow myosin. The change in phenotypic expression of the lengthened TA was not attributable to chronically increased levels of activation since integrated EMG activity was unchanged from control values throughout the immobilization period. Thus it is suggested that a chronic increase in tension consequent on the lengthening procedure is a potent stimulus for fast‐to‐slow myosin transformation.
Osteoclasts from medullary bone of egg‐laying Japanese quail do not express the putative calcium ‘receptor’
Authors: Bascal ZA , Moonga BS , Dacke CG , Zaidi M
Published: December 2014

The present study reports the contrasting effects of extracellular calcium ([Ca2+]e) elevation on cytosolic free calcium levels ([Ca2+]i) of osteoclasts, freshly isolated either from medullary bone of the egg‐laying Japanese quail or from rat cortical bone. [Ca2+]i was measured in single osteoclasts using the Ca(2+)‐sensitive fluorochrome, Indo‐1. We found that elevation of [Ca2+]e failed to induce a rise of [Ca2+]i in quail osteoclasts, whilst causing an elevation of [Ca2+]i in rat osteoclasts. The calcium ionophore, ionomycin, led to a sustained elevation of [Ca2+]i in both cell types. These findings suggest that osteoclasts isolated from egg‐laying quail do not possess the calcium sensor or 'receptor' that appears to be vital for the survival and function of rat osteoclasts.
Appearance of phloridzin‐sensitive glucose transport is not controlled at mRNA level in rabbit jejunal enterocytes
Authors: Smith MW , Turvey A , Freeman TC
Published: December 2014

Glucose uptake by rabbit intestine has been shown to be confined to the upper two‐thirds of jejunal villi. Inhibition by phloridzin shows most of this transport to take place through the Na(+)‐glucose linked transporter (SGLT1). Parallel measurements on the other hand show SGLT1 mRNA expression to increase rapidly as enterocytes reach the crypt‐villus junction. Levels of SGLT1 mRNA then remain elevated in all villus enterocytes. These results provide direct evidence that SGLT1‐mediated glucose transport is subject to post‐transcriptional control.
Electrical resistances of cultured bovine arterial endothelium in solutions of various resistivities
Authors: Turner MR
Published: December 2014

Relationships between the electrical resistance (Rm) of cultured endothelium and the resistivity (rho) of the bathing solution have been investigated, using eight monolayers of bovine arterial endothelium. Bathing solutions of differing rho were prepared by mixing culture medium and isosmolar (290 mM) sucrose in various proportions. Relationships between 1/Rm and 1/rho were linear, as predicted, with a mean 1/Rm intercept of zero. The slopes of the relationships give a mean fractional area per unit path length (Ap/delta chi) of 12.7 cm‐1 for the paracellular pathways of the cultured endothelium. This resembles previous estimates of Ap/delta chi for mammalian endothelium in arteries. The 1/Rm intercept of zero indicates that the major electrical conducting pathways of cultured arterial endothelium are paracellular.
Transients in intracellular free calcium in subconfluent and confluent cultures of a rat smooth muscle cell line
Authors: Otun H , Gillespie JI , Nicholls JA , Greenwell  , Dunlop W
Published: December 2014

The Ca2+ mobilizing mechanisms in the smooth muscle cell line A7r5 were found to undergo changes related to the degree of confluence of the cultures. In sparse cultures resting calcium was stable and exposure to arginine vasopressin (AVP) resulted in a single transient increase in intracellular free calcium (Ca2+i). In confluent cultures the cells could be divided into two general groups, those with a stable resting Ca2+i and those which demonstrated spontaneous brief elevations in Ca2+i of variable frequency. Application of AVP elevated Ca2+i, induced oscillations in quiescent confluent cells, increased the frequency of oscillatory activity in cells which were already active and, in cells which exhibited high frequency spontaneous fluctuations, inhibited this activity. Isotonic K+ depolarizing solution and normal solutions containing Co2+ inhibited Ca2+ spikes. These data suggest that the mechanism underlying the transients involves cyclical electrical phenomena at the cell membrane possibly utilizing calcium channels. There is no indication that the mechanism involves cytoplasmic oscillators.
An analysis of the action of an analogue of almitrine bismesylate in the rat model of hypoxic lung disease
Authors: Bee D , Emery CJ , Howard P
Published: December 2014

Chronically hypoxic (CH) and normoxic control rats were used to assess the action of S9581, a water‐soluble analogue of almitrine bismesylate. S9581 increased ventilation (Ve) by 34% in control and 20% in CH rats. During acute hypoxia Ve was raised and S9581 caused a further increase of 20% in both groups. Low doses of S9581 and almitrine enhanced the hypoxic ventilatory response in CH rats while high doses depressed it in both groups. Effects of S9581 on the pulmonary circulation were assessed in the isolated perfused lung of rats. As with almitrine a complex relationship of dose‐dependent vasoconstriction and dilatation was revealed. In low doses, S9581 enhanced the hypoxic pulmonary vasoconstrictor response to 2% O2 whilst this was attenuated by high doses in both control and CH rats. S9581 seemed to act like almitrine bismesylate on both the ventilation (peripheral chemoreceptor) and the pulmonary circulation. For studying almitrine‐like activity the water solubility of S9581 provides considerable advantages for the researcher.
Avoidance of endotoxin‐induced inflammation during studies of albumin clearance from caprine joints
Authors: Bassett JE , Simkin PA , Jacobs C , Roux E
Published: December 2014

Intra‐articular injection of radiolabelled, commercial goat serum albumin (GSA) produces acute arthritis in caprine joints. This inflammation distorts clearance values and vitiates studies of normal lymphatic function. Endotoxin, routinely found in commercial albumin preparations, appears to cause this local reaction. We describe a simple method for the preparation of low‐endotoxin, radioiodinated serum albumin from aseptically collected serum. We have used this technique to prepare GSA for use as a tracer molecule in clearance studies of synovial joint lymphatic function. The isolated protein exhibits antigenic and chemical characteristics indistinguishable from those of commercial GSA but contains at least 1000‐fold less endotoxin. In contrast to commercial GSA preparations, this albumin does not produce local inflammation when injected into synovial joints and is cleared from caprine joints in the normal monoexponential manner. Low levels of endotoxin seriously distort studies of articular albumin kinetics and may induce comparable artifacts when commercial protein preparations are used to study other physiological systems.
Confocal analysis of fluorescent bead uptake by mouse Peyer's patch follicle‐associated M cells
Authors: Porta C , James PS , Phillips AD , Savidge TC , Smith MW , Cremaschi D
Published: December 2014

Latex beads coated with secretory immunoglobulin (IgA) instilled into mouse intestinal loops are taken up by M cells present in Peyer's patch follicle‐associated epithelial tissue. Bead adsorption and uptake is greater at the edge compared with the apex of follicle domes. Coating beads with bovine serum albumin (BSA) causes a fourfold reduction in adsorption and a twentyfold reduction in uptake. Results demonstrate selectivity between adsorption and uptake and between the ability of different proteins to facilitate uptake.
Neutral endopeptidase (EC 3.4.24.11) modulates the contractile effects of neuropeptides on muscle cells from the guinea‐pig stomach
Authors: Gu ZF , Menozzi D , Okamoto A , Maton PN , Bunnett NW
Published: December 2014

The objectives of this investigation were to characterize neuropeptide‐degrading enzymes on the surface of gastric muscle cells and to determine their physiological function. Neutral endopeptidase (NEP, EC 3.4.24.11) activity was measured using the fluorogenic substrate glutaryl‐Ala‐Ala‐Phe‐4‐methoxy‐2‐naphthylamine. The NEP inhibitors phosphoramidon and DL‐thiorphan (1 microM) inhibited degradation of the substrate by gastric muscle membranes by 100% and by freshly dispersed gastric muscle cells by 55‐60%. The phosphoramidon or DL‐thiorphan‐inhibitable activity, attributed to NEP, of membranes was 112 +/− 4.0 pmol h‐1 (micrograms protein)−1 and of cells was 4.2 +/− 0.8 nmol h‐1 (10(6) cells)−1. This activity was associated with membranes prepared from cells and was not detected in the cytoplasm or in the cell incubation solution. Gastric muscle membranes were fractionated by electrophoresis and analysed by Western blotting using two NEP antisera. Both antisera recognized a protein in membranes with an electrophoretic mobility identical to that of recombinant human NEP and an apparent molecular mass of approximately 95 kDa. Neuropeptides were degraded by membranes with specific activities in the order of [Leu5]enkephalin > [Met5]enkephalin > gastrin‐releasing peptide‐10 (GRP‐10) > [D‐Ala2][Leu5]enkephalin > somatostatin‐14. Phosphoramidon and DL‐thiorphan similarly inhibited the degradation of GRP‐10 (mean of 35% inhibition), somatostatin‐14 (57%) and the aminopeptidase‐resistant analogue, [D‐Ala2][Leu5]enkephalin (75%). When aminopeptidases were inhibited with amastatin (10 microM) phosphoramidon inhibited degradation of [Leu5]enkephalin (54%) and [Met5]enkephalin (100%). Phosphoramidon increased the potency of the contractile effects of neuropeptides on muscle cells by > 280‐fold for somatostatin‐14, 17‐fold for GRP‐10, 18‐fold for [Met5]enkephalin and 14‐fold for [Leu5]enkephalin. The results show that an NEP‐like enzyme on the surface of gastric muscle cells degrades and inactivates enkephalins, GRP‐10 and somatostatin‐14 and acts in a manner analogous to that of acetylcholinesterase in the neuromuscular junction of skeletal muscle.
Amylin inhibits bone resorption by a direct effect on the motility of rat osteoclasts
Authors: Alam AS , Moonga BS , Bevis PJ , Huang CL , Zaidi M
Published: December 2014

We have performed a set of independent studies on the effects of the circulating pancreatic polypeptide, amylin, on rat osteoclast function, in vitro. Time‐lapse video observations, measuring cell protrusions and retraction, showed that 250 nmol l‐1 amylin or 250 nmol l‐1 beta‐calcitonin gene‐related peptide (beta‐CGRP) inhibited osteoclast motility (quiescence or Q effect). Both amylin and beta‐CGRP produced inhibitory responses with a significant first‐order regression over time (half‐times, 19 and 28 min respectively). In contrast, 250 nmol l‐1 amylin or 250 nmol l‐1 beta‐CGRP produced no change of osteoclast spread area, whilst 300 pmol l‐1 calcitonin (CT) application resulted in cell retraction (R effect). Forskolin (10 mumol l‐1) mimicked amylin and CGRP in inhibiting osteoclast motility (half‐time, 8.6 min), and similarly lacked an effect on cell spread area. Neither amylin nor beta‐CGRP (62.5–1250 nmol l‐1) elevated cytosolic free calcium levels ([Ca2+]i) in single osteoclasts whilst 300 pmol l‐1 salmon calcitonin (sCT) produced a rapid phasic elevation of [Ca2+]i, confirming previous results with asusuberic (1‐7) eel calcitonin. The osteoclast‐bone resorption assay revealed the following potency difference in direct comparison of the area of resorption per bone slice: beta‐CGRP/amylin, 0.1; sCT/amylin, 800 and human CT/amylin, 12. The potency of deamidated amylin approached that of beta‐CGRP. Assay precision ranged between 0.3 and 0.8. Amylin (250 nmol l‐1) also significantly (P < 0.05) reduced supernatant (tartrate‐resistant) acid phosphatase in the bone‐osteoclast cultures. These measures independently indicate an effect of amylin on osteoclast motility through mechanisms distinct from those of calcitonin, possibly through different selectivities for receptor subtypes, the cyclic AMP‐linked 'amylin subtype' and the [Ca2+]i‐linked 'calcitonin subtype'.
Short‐term oscillations of aortic core temperature and thermogenic organ blood flow in the rat
Authors: Closa D , Gomez-Sierra JM , Latres E , Alemany M , Remesar X
Published: December 2014

Core and organ temperatures in the rat have been found to be subject to regular periodic oscillations (with a frequency of ca 12 cycles per day, i.e. 143 mu Hz) within set limits, by using a chronic thermocouple implant procedure. These cycles consisted of consecutive warming (the temperature increased steadily) and cooling periods (the temperature decreased regularly). There were sustained temperature differences between several tissues and that of the aortic blood (core temperature), higher for brown adipose tissue, kidney and liver, and lower for muscle, white adipose tissue and skin. Organ blood flows and cardiac output were measured by a radioactive microsphere retention method applied to unanaesthetized rats. Blood flow measurements were done on unaware rats (see Methods), during either the warming or cooling phases. During the warming phases, there was a higher blood flow across the brown adipose tissue, kidney and skin, with a cardiac output about twice that found in the cooling periods. The haemodynamic changes observed, as well as the organ temperature differences observed with respect to the blood, suggest that periodic changes in blood flow are an essential part of the operation of the thermogenic system.
Changes in voltage‐operated calcium channels modify ethanol withdrawal hyperexcitability in mouse hippocampal slices
Authors: Whittington MA , Little HJ
Published: December 2014

Measurements of hippocampal excitability were made from area CA1 of isolated mouse hippocampal slices, prepared after chronic ethanol treatment in vivo, and the effects of the stereoisomers of the dihydropyridine Bay K 8644, that act at calcium channels, were investigated. The decrease in the threshold stimulation required to produce a single population spike, the leftward shift in the population spike input‐output curves, and the increase in population spike amplitude, that were seen during ethanol withdrawal, were all increased by the (‐) isomer of Bay K 8644. This isomer has been shown to increase opening of calcium channels. These effects of ethanol withdrawal were decreased by the (+) isomer of Bay K 8644, that is a calcium channel blocker. In contrast, the increase in paired‐pulse potentiation of the population spike, seen during the initial phase of ethanol withdrawal, was significantly decreased by both isomers of Bay K 8644. After the chronic ethanol treatment, single orthodromic stimuli produced epileptiform field potentials, consisting of two independent phases, a short latency series of multiple population spikes, superimposed upon the initial observed EPSP, and a longer latency train of spikes, occurring on a second EPSP, temporally distinct from the first. The (‐) isomer of Bay K 8644 increased both these phases of epileptiform activity during ethanol withdrawal in a dose‐dependent manner, while (+)−Bay K 8644 reduced the initial phase of multiple spiking and abolished the later phase. In slices from control animals, the higher concentration of (‐)‐Bay K 8644 (2 microM), but not the lower concentration (500 nM) decreased the stimulation required to produce multiple population spikes. Neither produced the long latency epileptiform activity. The (+) isomer of Bay K 8644 had no effect on control recordings. Lesioning the Schaffer collateral‐commissural fibre pathway, or removing area CA3, in slices from ethanol‐treated animals, abolished the later phase of epileptiform activity without affecting the initial multiple spiking. Intracellular recordings from area CA1 showed both the short latency and the longer latency epileptiform activities in slices from ethanol‐treated mice and in control hippocampal slices after application of the (‐) isomer of Bay K 8644, but these patterns of activity were not seen in control slices in the absence of Bay K 8644. Spontaneous activity during ethanol withdrawal was seen in intracellular recordings, but such activity was not seen in the field potential recordings.(ABSTRACT TRUNCATED AT 400 WORDS)
Intestinal transport of sodium, glucose and immunoglobulin in neonatal pigs. Effect of glucocorticoids
Authors: Sangild PT , Diernaes L , Christiansen IJ , Skadhauge E
Published: December 2014

The effect of cortisol on plasma immunoglobulin G (IgG) levels and on jejunal transport of sodium and glucose has been investigated in neonatal pigs (0–7 days of age). Five pigs were delivered vaginally (VD) at term (114–115 days gestation) and thirty‐five by caesarean section (CS) 2–4 days before term (to circumvent a neonatal cortisol surge). Postnatally, twenty‐seven CS pigs were injected with adrenocorticotrophic hormone (ACTH; n = 13), metyrapone (an inhibitor of adrenal 11 beta‐hydroxylase activity, n = 7) or physiological saline (n = 7). Pigs were killed at birth, at 3 days, or at 6‐7 days of age. Plasma concentrations of cortisol and IgG were determined and unidirectional fluxes of sodium and glucose measured across the proximal jejunum in vitro. Newborn CS pigs had significantly lower plasma cortisol but higher net fluxes of sodium and glucose than newborn VD pigs. At 3–7 days, metyrapone‐treated pigs had significantly lower concentrations of cortisol and IgG in plasma and lower net fluxes of sodium and glucose than ACTH‐treated pigs. Differences in net fluxes between treatment groups resulted from changes in both electrogenic and non‐electrogenic sodium transport. Furthermore, sodium‐glucose co‐transport accounted for a major proportion of net sodium transport. High unidirectional fluxes in newborn CS pigs may be explained by the passage of large amounts of sodium through tight junctions and paracellular pathways in the prepartum period. The results indicate that cortisol stimulates net transport of sodium, glucose and immunoglobulins in the postnatal period of caesarean‐delivered pigs. However, cortisol is unlikely to play a major regulatory role in the postnatal maturation of intestinal transport in normally delivered pigs.
Functional consequences of the interaction of Ni2+ with the osteoclast Ca2+ ‘receptor’
Authors: Bax BE , Shankar VS , Bax CM , Alam AS , Zara S , Moonga BS , Pazianas M , Huang CL , Zaidi M
Published: December 2014

Ni2+ was used as an extracellular activator of the Ca2+ 'receptor' in order to study the regulation of osteoclast function in vitro. Application of different micromolar concentrations of Ni2+ to osteoclasts bathed in 1.25 mM [Ca2+] and 0.8 mM [Mg2+] caused a concentration‐dependent elevation of cytosolic [Ca2+] measured in single cells using fura‐2 fluorescence. Cytosolic [Ca2+] responses to 5 mM [Ni2+] showed a rapidly developing and use‐dependent inactivation, unlike those induced by the application of 10 mM [Ca2+]. Pre‐treatment with 5 mM [Ni2+] reduced the magnitude of responses to a subsequent extracellular application of 10 mM [Ca2+] and vice versa. Ni2+ treatment elicited a number of functional effects. It produced an inhibition of osteoclastic bone resorption which was sustained over hours. This was associated with a pronounced cell retraction or R effect over the 40 min period following Ni2+ exposure as observed by time‐lapse video image analysis. Both these effects varied with concentration. In contrast, granule movement, cell migration, and quantitative indicators of margin ruffling were all unchanged. These findings are consistent with the initiation of a causally related set of specific functional and morphometric events following activation of a specific membrane receptor sensitive to divalent cations.
Thermoregulatory responses to beta‐adrenergic agonists at low ambient temperatures in the rat
Authors: Carlisle HJ , Stock MJ
Published: December 2014

Dose‐response effects on heat production (HP) and dry heat loss (DHL) following injection with the non‐selective (beta 1/beta 2) adrenergic agonist isoprenaline (ISO) and the atypical B3 agonist BRL 35135 (BRL) were established at an ambient temperature of 25 degrees C in rats. Subsequently, the effects of HP and DHL of a maximal thermogenic dose of ISO (75 micrograms/kg) and a supramaximal dose of BRL (40 micrograms/kg) were tested at ambient temperatures of 5, 10 and 15 degrees C. In terms of heat production, BRL was no different from saline at 5 degrees C, but its thermogenic activity became increasingly evident as ambient temperature increased. For ISO, HP was lower than, or no different from, saline at 5 and 10 degrees C, respectively, but DHL exceeded HP at both temperatures, and colonic temperature fell significantly; ISO and BRL responses were similar at 15 degrees C. ISO was also capable of producing a decrease in HP at 10 degrees C if the rats were shaven. Substitution for endogenous, sympathetically mediated thermogenesis would explain the attenuation of the BRL and ISO effects at cool ambient temperatures, whereas the hypothermic effects of ISO in the cold appeared to be due to an inappropriate increase in DHL, which was exacerbated at 5 degrees C by a reduction in HP below saline values. The increase in DHL was consistent with beta 2‐mediated effects of ISO on peripheral blood flow, but the mechanism responsible for the reduction in HP in the cold is unknown, although reduced vascular thermogenesis has been offered as a putative explanation.
Effect of raised extracellular calcium on cell spread area in quail medullary bone osteoclasts
Authors: Bascal ZA , Alam AS , Zaidi M , Dacke CG
Published: December 2014

The present study reports on the effects of extracellular calcium ([Ca2+]o) elevation and ionomycin on cell spread area of medullary bone osteoclasts freshly isolated from egg‐laying Japanese quail. The responses were compared with those demonstrated in osteoclasts cultured for periods of 5–8 days and also to those previously demonstrated in neonatal rat osteoclasts. Freshly isolated medullary bone osteoclasts, unlike rat osteoclasts, were refractory to 20 mM [Ca2+]o, in that they showed no change in cell spread area. They did, however, show a modest (15%) reduction in cell spread area to ionomycin (7–50 microM), applied for 15–30 min. When medullary bone osteoclasts were precultured for 5–8 days, they exhibited a well‐developed response to 20 mM [Ca2+]o with a 46% reduction in cell spread area. They also showed a similar reduction in cell spread area in response to ionomycin (4 microM). It is concluded that, unlike freshly isolated neonatal rat osteoclasts, those obtained from quail medullary bone appear refractory to inhibitory factors such as [Ca2+]o. However, when the avian cells are cultured for a few days they appear to recover their ability to respond to [Ca2+]o.
Contractile properties of rat gastrocnemius muscle during staircase, fatigue and recovery
Authors: MacIntosh BR , Grange RW , Cory CR , Houston ME
Published: December 2014

Slowing of relaxation is one of the anticipated changes in the contraction of fatigued skeletal muscle. However, interpretation of the mechanism(s) contributing to slowed relaxation may be affected by the measurement technique employed. In this study, relaxation was measured in three ways: (i) traditional half‐relaxation time; (ii) peak rate of relaxation; and (iii) late relaxation time, measured from 50 to 25% of peak developed tension. When rat gastrocnemius muscle was stimulated indirectly in situ at 10 Hz, developed tension increased in 10 s to 185%, then decreased to 39% after 1 min with little additional change over the next 4 min. After 10 s of inactivity, developed tension was 60% of the initial value, but did not recover further over the next 20 min. The half‐relaxation time transiently decreased at the start of stimulation, then by 20 s was considerably prolonged. Within 10 s of recovery, half‐relaxation time returned to prestimulation values but became prolonged again by 10 min of recovery. The peak rate of relaxation was proportional to the developed tension at all times except 2.5–10 s of 10 Hz stimulation, at which time acceleration of relaxation was evident, and 15–20 s of the 10 Hz stimulation when it was relatively decreased. The late relaxation time increased during the repetitive stimulation, returned to control level early in recovery, then increased again, by 5 min of recovery. The diverse responses indicated by these indices of relaxation potentially discriminate different mechanisms which contribute to slowing of relaxation in fatigue, a point which would be missed if a single method of measurement of relaxation was employed.
Ethanol augments the baroreflex‐inhibitory effects of sciatic nerve stimulation in the anaesthetized dog
Authors: Kirkman E , Marshall HW , Banks  , Little RA
Published: December 2014

Electrical stimulation of somatic afferent fibres in the sciatic nerve has been used as a model of injury in the anaesthetized dog. Stimulation of the sciatic nerve (during reflexly induced periods of apnoea to obviate any respiratory effects of sciatic stimulation) led to a simultaneous increase in arterial blood pressure and heart rate and a decrease in baroreflex sensitivity. Infusion of ethanol sufficient to produce clinically relevant plasma ethanol levels (100–200 mg %) had no consistent effects on baroreflex sensitivity, but enhanced the pressor response and significantly augmented the inhibitory effects of sciatic stimulation on the baroreflex. Since ethanol is commonly associated with injury in man, such changes in the response to ‘injury’ may modify the patients' cardiovascular response to the injury and complicate diagnosis.
Secretion of acid, gastrin, and cobalamin‐binding proteins by the fetal pig stomach: developmental regulation by cortisol
Authors: Sangild PT , Hilsted L , Nexo E , Fowden AL , Silver M
Published: December 2014

The role of cortisol in the development of gastric function was investigated in the fetal pig. Pregnant sows (term = 114 +/− 2 days, n = 10) were anaesthetized (pentobarbitone) and osmotic minipumps containing either saline or cortisol inserted subcutaneously into fetuses at 82‐84 (n = 11) or 91‐96 (n = 14) days gestation. Six days later the infused pigs were removed by Caesarean section and the stomach and its contents collected for analysis. Samples were also obtained from unoperated (control) fetal pigs (n = 51) removed under anaesthesia at intervals from 70 days gestation until term. The concentrations of acid in gastric fluid, gastrin in plasma and antral tissue (bioactive as well as precursor forms), and cobalamin(CBL)‐binding proteins in fundic tissue were low in control pigs until 100 days gestation. During the last 2 weeks before term, large increases occurred in gastric fluid acidity (from pH 6‐7 to pH 3 at birth), plasma amidated gastrin (from 10 to 90 pM) and CBL‐binding protein concentration (from 10 to 80 pmol (g fundus)‐1). These changes occurred in parallel with a surge in plasma cortisol (from 20 to 200 ng ml‐1). Immature fetuses infused with cortisol had significantly higher gastric acidity, plasma amidated gastrin, and concentration of CBL‐binding proteins than the corresponding control fetuses (P < 0.05). Across age and treatment groups, significant correlations were found between log10 plasma cortisol values and the above parameters (r = 0.59‐0.76, P < 0.01). The results suggest that endogenous cortisol secretion stimulates the secretion of gastric acid, gastrin and CBL‐binding proteins in the prenatal period of the pig.
The effect of high phosphorus intake on calcium and phosphorus retention and bone turnover in growing lambs
Authors: Wan Zahari M , Scott D , Loveridge N , Buchan W , Milne J
Published: December 2014

Growing lambs were fed diets that just met their requirement for Ca but which supplied either 1 or 3 times their requirement for P and the effects on Ca and P retention and on bone turnover were monitored. Feeding the high P diet had no adverse effect on Ca and P absorption or retention or on bone formation rate. Bone resorption rate was a little higher in lambs fed the high P diet but there were no differences between treatments in plasma parathyroid hormone, 1,25‐dihydroxyvitamin D3 or 25‐hydroxyvitamin D3 levels or in bone mineral content. It would appear from these results that feeding diets that are rich in P is unlikely to have any adverse effect on skeletal mineralization in the lamb provided that their minimum requirement for Ca is met.
Effect of hypoxia on arterial potassium concentration at rest and during exercise in man
Authors: Barlow CW , Qayyum MS , Davey PP , Paterson DJ , Robbins PA
Published: December 2014

Hypoxia has been reported to increase arterial potassium concentration ([K+]a) in anaesthetized cats (Paterson, Estavillo & Nye, 1988). The purpose of this study was to determine whether this phenomenon occurs in humans. The effect of hypoxia on [K+]a was measured in ten male subjects, at rest and during light exercise, before and after 8 weeks of physical training. The [K+]a increased by 0.15 +/− 0.04 mM (mean +/− S.E.M.) at rest, when end‐tidal PO2 (PET,O2) was lowered from 100 to 51 +/− 1.6 Torr, and by 0.10 +/− 0.02 mM during exercise, when PET,O2 was lowered from 100 to 66 +/− 6.2 Torr. Physical training did not alter the rise in [K+]a significantly. The magnitude of this effect is small in comparison with that of exercise‐induced hyperkalaemia, and is unlikely to be of great physiological significance at moderate levels of hypoxia.
Evidence for downregulation of hypothalamic 5‐hydroxytryptamine receptor function in endurance‐trained athletes
Authors: Jakeman PM , Hawthorne JE , Maxwell SR , Kendall MJ , Holder G
Published: December 2014

Serum prolactin (PRL) was used as a hormone marker of serotoninergic function following oral administration of an acute dose of a serotoninergic agonist. Five male endurance‐trained athletes (ET) and five healthy non‐endurance‐trained controls (NT) were studied. The peak PRL concentration was lower (P = 0.031) for the ET athletes (486 +/‐ 208 mU l‐1; mean +/‐ S.D.) than for the NT controls (1000 +/‐ 385 mU l‐1); the total release of PRL was also lower (P = 0.042) for the ET subjects. The lower neuroendocrine response to a serotoninergic agonist in the endurance‐trained athletes suggests a downregulation of central serotoninergic receptor function in response to endurance training in man.
A novel method for recording whole‐cell and single‐channel currents from differentiating cerebellar granule cells in situ
Authors: Radden E , Behrens M , Pehlemann FW , Schmidtmayer J
Published: December 2014

A preparation procedure is described yielding very thin tissue layers (1‐3 cells) of the rat cerebellum. One‐week‐old rat cerebellum was embedded in agarose and cut in 1 mm slices, which then were mounted by a fresh fibrin preparation on the bottom of a culture dish. After coagulation of the fibrin the slice was gently lifted, leaving a thin fingerprint‐like layer of cells on the bottom of the dish. Individual cells could be identified by their topographical positions. From these preparations patch‐clamp recordings were made of cells in the external and the internal granule layer and of migrating cells. Whole‐cell currents of cells in the external granule layer, recorded using the perforated‐patch method, show that these neuroblasts already possess a full complement of ionic currents, consisting of a transient sodium current and a transient and a sustained potassium current. Whereas the potassium currents are predominant, the maximum sodium peak currents are minute (42 +/− 5 pA, mean +/− S.E.M., n = 21), i.e. too small for generating action potentials. There were no significant differences between cells of the external and the internal granule layer. The ionic channels passing these currents were identified and characterized in single‐channel studies on cell‐attached patches. Two types of potassium channel were found: a non‐inactivating channel with a single‐channel conductance of 21 pS and an inactivating channel with a conductance of 6 pS.
Increased mammary blood flow in the lactating goat induced by parathyroid hormone‐related protein
Authors: Prosser CG , Farr VC , Davis SR
Published: December 2014

Human synthetic parathyroid hormone‐related protein (PTHrP) increased mammary blood flow (MBF) following close‐arterial infusion via the external pudic artery in goats during mid‐lactation. MBF increased 74 +/− 8% within 30 min of the start of continuous infusion of PTHrP compared with 10 +/− 3% in controls. MBF decreased by 90 min, however, and was not different from control values for the remainder of the infusion. The increase in plasma concentrations of calcium and decrease in phosphate during PTHrP suggests that this was not due to altered activity of PTHrP, but may relate to downregulation of response or production of counter‐regulatory vasoconstrictive agents within the gland. This problem was alleviated when PTHrP was infused in a pulsatile fashion. An average 14‐40% increase in MBF was achieved over 6 h, but this did not alter the rate of milk secretion, suggesting that mammary hyperaemia is not sufficient by itself to increase milk yield in the normally lactating goat. MBF increased in a dose‐dependent fashion, although the lowest dose used to give a detectable response was approximately 40‐fold higher than the concentration normally present in the mammary venous circulation. Thus, endogenous PTHrP may not be an important regulator of MBF during lactation in the goat.