bluuebunny/crossref_metadata_2025 huggingface dataset:
REINNERVATION OF MUSCLE IN THE MOUSE FOLLOWING NERVE CRUSH AND X‐IRRADIATION
Authors: Gomez S. , Love S.
Published: December 2014

The effects of X‐irradiation on nerve regeneration were examined in adult mice. The right sciatic nerve was crushed focally and 3 d later the hind limb was exposed to 20 Gy X‐rays. Compound muscle action potentials (m.a.p.s) were recorded in vivo from the posterior crural muscles. Stimulation of the sciatic nerve proximal to the crush injury evoked m.a.p. s of low amplitude with marked temporal dispersion. Stimulation at 20 or 50 Hz resulted in almost immediate intermittent failure of the longer latency m.a.p.s. In vitro physiological examination showed X‐irradiation to have no effect on the timing of reinnervation. However, the latency of evoked end‐plate potentials was prolonged and, on repetitive nerve stimulation, increased markedly until failure occurred. Nerves which regenerated after X‐irradiation showed impaired conduction, particularly of trains of impulses.
ENHANCEMENT OF MAXIMAL BILIRUBIN EXCRETION BY BILE SALTS IN THE ANAESTHETIZED RABBIT
Authors: Esteller A. , González J. , López M. A. , Hidalgo F.
Published: December 2014

The influence of glycodeoxycholate, taurocholate and dehydrocholate on the maximal hepatic excretion of bilirubin was investigated in rabbits anaesthetized with sodium pentobarbitone. Biliary secretion of dehydrocholate was much less than that of the other two bile salts, which could be explained by its metabolism in the hepatocytes. Glycodeoxycholate and dehydrocholate had a greater choleretic effect than taurocholate. Only glycodeoxycholate and taurocholate increased the secretion of biliary lipids, suggesting that dehydrocholate or its metabolites were unable to form micelles. All three bile salts, however, increased maximal bilirubin excretion to a similar extent. These results indicate that the action of bile salts on the excretion of bilirubin cannot be fully explained in terms of binding to mixed micelles.
POTASSIUM‐INDUCED DEPOLARIZATIONS AND GENERATION OF TENSION IN BARNACLE MUSCLE FIBRES: EFFECTS OF EXTERNAL CALCIUM, STRONTIUM AND BARIUM
Authors: Luxoro M. , Nassar-Gentina Verónica
Published: December 2014

Potassium‐induced contractions were studied in muscle fibres from Megabalanus psittacus (Darwin) in an attempt to establish the requirement of extracellular calcium for the development of force. A sudden elevation of external potassium induced the production of contractures and/or twitches only if calcium was present. In calcium‐free solutions no contraction or action potential occurred. When external calcium was replaced by barium, potassium‐induced depolarizations accompanied by several action potentials did not generate either contractures or twitches. With strontium in place of calcium, action potentials of different duration were observed. Only the long‐lasting ones (a few seconds) induced twitches.
INCREASE IN WEIGHT AND WATER RETENTION ON OVERFEEDING DOGS
Authors: Golob P. , O'Connor W. J. , Potts D. J.
Published: December 2014

Dogs, kept in metabolism cages, were weighed daily and the daily water intake, urine volume and evaporative loss of water measured or calculated. When the daily meal was doubled, the weight increased in two phases: during the first 4 d the increase in weight was more than could be accounted for by the deposition of protein, glycogen and fat so that water retention must have occurred; after the fourth day the increase in weight was slower and could have been due to the deposition of solids, without water retention. When carbohydrate was added to the meal either as starch or glucose, the increase in weight in the first 3 d was more than the weight of the added carbohydrate, showing water retention. After the third day the slower increase in weight could be explained by the deposition of solids. When the daily meal was supplemented with fat, increase in weight occurred uniformly throughout the period of overfeeding and was equal to or less than the added fat. There was thus no evidence for water retention. Addition of meat to the daily meal caused an increase in weight larger than the fat and protein of the extra meat. Meat therefore caused water retention. The results indicate that during overfeeding, deposition in the body of protein and glycogen, but not fat, determines water retention.
AN ANALYSIS OF THE EFFECT OF SYNOVIAL CAPILLARY DISTRIBUTION UPON TRANS‐SYNOVIAL CONCENTRATION PROFILES AND EXCHANGE
Authors: Levick J. R.
Published: December 2014

Recent morphometric studies of synovium lining the rabbit knee showed that capillaries extend to 〉 200 µm below the synovial surface; that a proportion of the superficial capillaries are fenestrated; and that the numerical density of the capillaries varies with depth (Knight & Levick, 1983, 1984). Such observations raised the question ‘Down to what depth do capillaries contribute significantly to the diffusional flux of a small extracellular solute (e.g. sulphate) into the joint cavity?’ This problem was addressed by a mathematical model of trans‐synovial diffusion. The periarticular tissue was considered as a stack of thin slices (Δx = 2–5 µm), each of known depth and capillary population. An expression for interstitial concentration normal to the surface was derived from the Fick diffusion equations and the mass‐balance equation for each slice. Morphometric values were substituted into the area and distance terms of the Fick equation. A range of values was explored for two permeability terms, namely Dt/Di (diffusivity across unit fenestral matrix relative to that across unit interstitial matrix) and PS/Q (permeability‐surface area product/blood flow for synovial fenestrated capillaries); the ranges lay between the estimated extreme values. Steady‐state concentrations and transcapillary fluxes at each depth were obtained by iterative calculation on a microcomputer. The thickness of tissue from which 80% of the joint influx arose (T0·8) was 7–13 µm for diffusion‐limited transcapillary exchange (PS/Q = 0·05; Dt/Di = 1–0·03); or 9–17, µm for flow‐limited exchange (PS/Q = 5; Dt/Di = 1–0·03) in areolar synovium, which is the most extensive tissue. The relative independence of the results from the permeability conditions was due to the dominant effect of a peak in capillary density just below the synovial surface. The resistance of the capillary endothelial wall as a fraction of total blood‐joint barrier resistance was calculated to be 0·18‐0·80 in areolar synovium under conditions of diffusion‐limited exchange.
CALCIUM ACTION POTENTIALS IN UNFERTILIZED EGGS OF MICE AND HAMSTERS
Authors: Georgiou P. , Bountra C. , Bland K. P. , House C. R.
Published: December 2014

Measurements of membrane potential and resistance have been made in zona‐free eggs of mice and hamsters. The mean±S.D. values for membrane potential were −91 ± 28 mV (mouse) and −97 ± 29 mV (hamster) and for input resistance were 430 ± 230 MΩ (mouse) and 410 ± 150 MΩ (hamster) respectively. Large fluctuations (20 mV) of membrane potential occurred apparently at random and these were accompanied by changes of membrane resistance. Depolarizing current pulses passed through the recording micro‐electrode evoked action potentials in eggs of both species. The threshold for excitation was about −50 mV, the maximum rate of rise of the action potential was about 3V.s−1 and its peak value was about + 13 mV. Action potentials could be evoked in eggs bathed in sodium‐free solution or in normal solution containing tetrodotoxin (3 µM). The presence of cobalt (5–20 mM), lanthanum (1 mM) or verapamil (200–400 µM) in the bathing solution suppressed the action potential. Raising the extracellular calcium concentration from 4 to 40 mM increased the peak value of the action potential by 25 mV. It is concluded that the plasma membranes of mouse and hamster eggs have voltage‐dependent calcium channels.
PROTEIN TURNOVER WITH SPECIAL REFERENCE TO MAN
Authors: Waterlow J. C.
Published: December 2014

This review is concerned with rates of N flux in the living animal rather than with mechanisms of protein synthesis and breakdown at the cellular level. Methods of measuring protein turnover in the whole body are discussed, with special emphasis on studies in man, and results obtained by different methods have been compared.

Aspects of whole body protein turnover which are of physiological interest include its relation to body size, growth and development, energy metabolism and food intake. There are substantial increases in protein turnover in injury, and changes that occur in exercise are beginning to be explored.

From the physiological point of view these results point the need for future research along two main lines. The first is that of regulation: a wide variety of hormones stimulate or repress protein synthesis and breakdown, with varying actions in different tissues. These effects, however, do not in themselves explain the mechanism by which a balance between synthesis and breakdown is maintained. Secondly, the fact that all cellular proteins are in a dynamic state poses questions about the relation between structure and function in tissues such as muscle and brain, which physiologists have hardly begun to tackle.
THE EFFECT OF VARIATION IN PHOSPHORUS INTAKE ON NET INTESTINAL PHOSPHORUS ABSORPTION, SALIVARY PHOSPHORUS SECRETION AND PATHWAY OF EXCRETION IN SHEEP FED ROUGHAGE DIETS
Authors: Scott D. , McLean A. F. , Buchan W.
Published: December 2014

Mature sheep fitted with rumen and duodenal cannulae and fed either pelleted hay or grass diets were given supplements of Na2HPO4 by continuous infusion into the rumen and the effects on salivary phosphorus secretion, intestinal phosphorus absorption and pathway of excretion were studied. Little phosphorus was excreted in the urine in control periods and little increase was seen in response to phosphorus supplementation, most of the extra phosphorus given being recovered in the faeces. Infusion of phosphorus into the rumen led to an increase in the flow of phosphorus to the intestine, an increase in absorption, a rise in plasma phosphate level and an increase in salivary phosphorus secretion while withdrawal of supplementary phosphorus was seen to have the opposite effects. In separate studies short sections of the upper small intestine temporarily isolated from the normal flow of digesta were perfused with solutions containing NaH2PO4 (5‐50 mmol. l−1). Phosphorus absorption increased with increasing concentration though the relationship was curvilinear such that absorptive efficiency fell from around 0·7 at 5 mmol. l−1 to around 0·35 at a concentration of 50 mmol. l−1. The significance of these results in relation to the control of phosphorus balance in ruminants is discussed.
EFFECT OF REGION OF INTESTINE AND UNSTIRRED LAYERS ON UPTAKE OF SUGARS INTO RABBIT INTESTINE
Authors: Thomson A. B. R.
Published: December 2014

The kinetic characteristics of the transport of four sugars were determined in rabbit jejunum and ileum. The effective resistance of the intestinal unstirred layer and the rates of uptake of glucose, galactose, 3‐O‐methyl glucose and fructose were assessed in vitro. The unstirred layer resistance was higher in jejunum than in ileum at all rates of stirring of the bulk phase. The maximal transport rates, Jmd, of galactose and 3‐O‐methyl glucose were higher than the Jmd of glucose, which in turn was higher than that for fructose. The Jmd of glucose, galactose, and fructose were each lower in ileum than in jejunum, but the Jmd of 3‐O‐methyl glucose in the ileum was similar to both regions. For the single Michaelis‐Menten model, the values of the Michaelis constant, Km, for glucose and galactose were slightly lower in the jejunum than in the ileum, whereas the value of the Km for 3‐O‐methyl glucose and for fructose were similar in the two sites. In the jejunum, the relative values of the Km were 3‐O‐methyl glucose = fructose 〉 galactose 〉 glucose. It is regarded that variations in sugar absorption between the jejunum and ileum are due to differences in the values of the effective resistance of the unstirred water layer, the maximal transport rate, and the Michaelis constant.
THE EFFECTS OF L‐ALANINE AND ACETYLCHOLINE ON MEMBRANE POTENTIAL, 45Ca2+ AND 86Rb+ EFFLUX AND AMYLASE SECRETION IN THE ISOLATED MOUSE PANCREAS
Authors: Singh J. , Petersen O. H.
Published: December 2014

A comparative study was made of the effects of acetylcholine (ACh) and the neutral amino acid L‐alanine on membrane potential, 45Ca2+ and 86Rb+ fractional efflux, and amylase secretion in segments of the isolated mouse pancreas. Both ACh and L‐alanine evoked similar dose‐dependent depolarizations of pancreatic acinar cells. ACh, but not L‐alanine, caused a marked reduction in input resistance and evoked electrical uncoupling of acinar cells at high concentrations. Measurements of 45Ca2+ release from pre‐labelled tissue showed that ACh increased the fractional efflux of 45Ca2+ whereas L‐alanine had no such effect. Both ACh and L‐alanine stimulated the release of 86Rb+ from pre‐labelled tissues. The L‐alanine‐evoked 86Rb+ efflux was markedly reduced by pre‐treatment with 10–3 M ouabain which had no effect on the ACh‐induced response. L‐alanine had no significant effect on amylase secretion whereas ACh elicited a marked increase in amylase output. These results show that although both ACh and L‐alanine evoke depolarization of the pancreatic acinar cell membrane, the mechanisms underlying their actions on the cells are different.
MECHANORECEPTORS OF THE RABBIT DUODENUM
Authors: Cottrell David F.
Published: December 2014

A preparation is described which allowed the investigation of single‐unit afferent activity in non‐myelinated mesenteric nerves in urethane‐anaesthetized rabbits. Three classes of mechano‐receptors were isolated and were located in the muscularis externa (n = 17), the serosa (n = 5) and the mesentery (n = 2). Intraluminal perfusion of chemical solutions containing glucose and hypertonic saline caused increased movement in the loop and also excited mechanoreceptors. No specific chemoreceptors were identified. The results demonstrate that duodenal mechano‐receptors with non‐myelinated axons in the rabbit are indirectly sensitive to the chemical composition of duodenal chyme.
COMPONENTS OF INJURY (HAEMORRHAGE AND TISSUE ISCHAEMIA) AFFECTING CARDIOVASCULAR REFLEXES IN MAN AND RAT
Authors: Little R. A. , Randall P. E. , Stoner H. B. , Marshall H. W. , Redfern W. S.
Published: December 2014

The effects of two components of tissue injury, namely fluid loss from the circulation and tissue ischaemia, on cardiovascular reflex activity have been studied. Moderate blood loss ( 10–20% blood volume) in the unanaesthetized rat increased the slope of the regression line relating heart period to mean arterial blood pressure and usually displaced it to the left (i.e. towards a relative bradycardia). A blood donation of 500 ml (approximately 10% blood volume) increased the Valsalva ratio in conscious man without a change in resting pulse rate. However, a 15 min period of unilateral limb ischaemia in man reduced the Valsalva ratio. The pattern of change in the pulse rat response to the Valsalva manoeuvre produced by limb ischaemia closely resembles that found previously after limb injury in man. There was no evidence that the endogenous opioids were involved in the interaction between limb ischaemia and cardiovascular reflex activity in man.
EFFECT OF LIMB ISCHAEMIA ON BLOOD PRESSURE AND THE BLOOD PRESSURE‐HEART RATE REFLEX IN THE RAT
Authors: Redfern W. S. , Little R. A. , Stoner H. B. , Marshall H. W.
Published: December 2014

The effects of bilateral hind‐limb ischaemia on blood pressure and on the blood pressure‐heart rate reflex have been studied in the rat. Limb ischaemia increased blood pressure and decreased the elevation and slope of the regression line describing the relationship between heart period (H.P.) and mean arterial pressure (M.A.P.). Nociceptive afferents from muscle receptors using long fibre tracts in the anterolateral part of the spinal cord seem to be responsible for the changes seen. The changes in the blood pressure‐heart rate reflex were mediated by a combination of vagal inhibition and sympathetic activation. The efferent pathway for the pressor effect was in the sympathetic outflow. Central catecholaminergic neurones were involved in the pressor effect of limb ischaemia but not in the changes in the blood pressure‐heart rate reflex. Electrolytic lesions in the posterior hypothalamus attenuated the inhibition of the reflex and it is suggested that neurones in the defence area may be activated by limb ischaemia. The interaction between limb ischaemia and the H.P.‐M.A.P. relationship was not affected by opioid antagonists. After the period of ischaemia there was an increase in the elevation of the regression line describing the relationship between H.P. and M.A.P. which was secondary to the fall in body temperature characteristic of this phase of the response to injury.
THE RESPONSE OF PANCREATIC β‐CELL MEMBRANE POTENTIAL TO POTASSIUM‐INDUCED CALCIUM INFLUX IN THE PRESENCE OF GLUCOSE
Authors: Dawson Christine M. , Atwater Illani , Rojas E.
Published: December 2014

Membrane potential measurements were made in pancreatic β‐cells from microdissected islets from normal mice. In the presence of 11 mM glucose, depolarization of the membrane for 1 min with 50 mM potassium is followed by an inhibition of electrical activity before the normal burst pattern resumes. This inhibitory period, called the recovery time, is steady for each β‐cell after three consecutive pulses of 50 mM potassium. The mean recovery time is 109 s. During the recovery time, the membrane is hyperpolarized and the input resistance is decreased, indicating that potassium permeability is high over this period. The recovery time is dependent on the size of the depolarization: 1 min exposure to potassium concentrations below 50 mM reduces the recovery time with a half‐maximal effect at 38·5 mm potassium, corresponding to ‐27 mV. Also, increasing the extracellular calcium concentration lengthens the recovery time. Increasing the glucose concentration, however, shortens the recovery time. It is postulated that the recovery time represents activation of the calcium‐gated potassium permeability and is a reflexion of the time taken for the β‐cell to buffer the increased intracellular calcium resulting from the potassium depolarization.
VASCULARLY PERFUSED FROG LUNG: EFFECTS OF METABOLIC CONDITIONS ON ADENINE NUCLEOTIDES AND INORGANIC IONS
Authors: van Rossum G. D. V. , Parsons D. S.
Published: December 2014

The metabolic activity of frog lung perfused through its vascular bed has been assessed by determining changes in metabolites in the perfusion medium and by measuring the adenine nucleotides, ions and water in the tissue after perfusion under a variety of conditions. The addition of respiratory inhibitors, CN− or antimycin A, reduced the adenylate energy charge when a glucose‐free perfusate was used but not when glucose was present. CN− and anaerobiosis stimulated lactate production while iodoacetate reduced lactate production and the adenylate energy charge. The addition of fatty acids, glutamine or lactate to the perfusate had no effect on the adenylate energy charge or ionic contents. With plasma albumin depleted of fatty acids in the perfusate, there was an increased production of NH4+; this could be partially suppressed by the addition of butyrate or octanoate. Glutamine increased NH4+ production and lactate was consumed by the lung, indicating that both of these substrates are metabolized. The tissue levels of Na+ and K+ were remarkably resistant to ouabain, a concentration of 2 mmol.l−1 being required to produce significant reduction of K+ and increase in the tissue Na+; the contents of adenine nucleotides, Ca2+ and Mg2+ were unaffected. During April‐June, the tissue ATP and adenylate energy charge appeared to be particularly sensitive to PO2 in the perfusate.
ACIDAEMIA AND HYPERKALAEMIA FOLLOWING LOW‐VOLTAGE ELECTRIC SHOCK IN THE ANAESTHETIZED CAT
Authors: Bradford A. , O'Regan R. G.
Published: December 2014

Plasma K+ and Na+ concentrations ([K+], [Na+]), gas tensions (PO2, PCO2), pH levels and lactate concentrations ([lactate]) were measured in blood samples obtained before and after applying low‐voltage electric shocks (13–130 V a.c., 5–50 mA, 50 Hz) from forelimb to opposite hind limb in cats anaesthetized with pentobarbitone. The current intensities used did not induce any changes either in rectal temperature or in the electrocardiogram in post‐shock periods. Marked reductions in pH, increases in [K+] and elevations in [lactate] relative to control values were measured in arterial blood samples following shocks lasting between 10 and 30 s, with the changes in pH and [lactate] more prolonged (45–90 min) than the [K+] alterations (5–10 min). Post‐shock acidaemia and hyperkalaemia were significantly attenuated by neuromuscular blockade and were more pronounced in samples obtained from blood draining the skinned hind limb than in arterial blood. In the immediate post‐shock periods both arterial and venous blood samples showed elevations in PCO2 and decreases in PO2 compared with control levels. No differences in [Na+] were noted in arterial and venous blood samples obtained before and after shocks. The sequelae of electric shocks noted in this study mainly arose from changes occurring in tetanically contracted muscles during the passage of current and similar residual effects would be expected to be present in human subjects in circumstances where victims of electrical accidents cannot release contact from a low‐voltage source. Some of these sequelae may have relevance in explaining the ‘delayed deaths’ which occasionally follow human electrical accidents.
THE EFFECTS OF VINCRISTINE ON MILK SECRETION AND MILK COMPOSITION IN THE GOAT
Authors: Henderson A. J. , Faulkner A.
Published: December 2014

The effects of intramammary injection of vincristine on milk secretion were studied in goats. Vincristine inhibited milk secretion in a dose‐dependent manner, with 1 mg decreasing milk yield to approximately 40% of previous yield. The inhibition was reversible with a full recovery of milk yield within a few days. During inhibition, there were significant changes in milk composition; Na concentration increased and K and lactose concentrations decreased, while Cl concentration was unaffected. Fat, protein, citrate and Ca concentrations all increased, particularly as milk yield was recovering. The concentrations in milk of the two lactose precursors, glucose and UDP‐galactose, both increased. During inhibition and recovery, the secretion rates of three major components of milk, lactose, protein and fat, were affected to a different degree, with lactose secretion being inhibited to the greatest extent. The results are discussed in relation to the action of vincristine on milk secretion. It is proposed that vincristine's actions include a specific inhibition of lactose synthesis.
THE EFFECT OF VARIATION IN PHOSPHORUS INTAKE ON NET INTESTINAL PHOSPHORUS ABSORPTION, SALIVARY PHOSPHORUS SECRETION AND PATHWAY OF EXCRETION IN SHEEP FED ROUGHAGE DIETS
Authors: Scott D. , McLean A. F. , Buchan W.
Published: December 2014

Quarterly Journal of Experimental Physiology 69–3 (1984)

On page 448 the sentence 3 lines from the bottom should read

The sheep were fitted with a re‐entrant cannula in the duodenum close to the pylorus and digesta was collected through this cannula for 30 h after dosing, unlabelled donor material being used to replace that removed.
EFFECTS OF BOTULINUM TOXIN ON SYNAPSE FORMATION AND ACETYLCHOLINE SENSITIVITY IN SKELETAL MUSCLE IN THE NEWT
Authors: Sayres Helen , Tonge D. A.
Published: December 2014

A sublethal dose of botulinum toxin (type E) was injected into the biceps muscle of the forelimb of adult newts, Triturus cristatus, causing local paralysis for up to 3 weeks and impaired transmission for about 3 months. The paralysed muscles became supersensitive to the acetylcholine analogue, carbachol, and also accepted innervation from an implanted foreign nerve. These results suggest that in the newt activity is important in the control of muscle sensitivity to acetylcholine and synapse formation. During the first 2 months after botulinum toxin, stimulation of the implanted nerve caused contraction in every muscle examined (n = 13). In muscles examined between 3 and 14 months after toxin injection there was no contraction in response to stimulation of the implanted nerve in eight out of nineteen cases, suggesting that regression of the foreign innervation might have occurred. Further evidence for regression of foreign innervation was obtained by intracellular recordings from those muscles which contracted in response to stimulation of both nerves. The proportion of muscle fibres responding to stimulation of the implanted nerve fell significantly (P 〈 0·05) from 65·7 ± 7·1% (±S.E.M., n = 239) in thirteen muscles examined during the first 4 months to 39·5 ± 5·5% (±S.E.M., n = 188) in nine muscles examined between 9 and 14 months after toxin injection. There was a strong negative correlation (r = ‐0·81; P 〈 0·001) between the proportion of muscle fibres responding to stimulation of the original and implanted nerves in individual muscles.
PHOSPHATE EXCRETION AND REABSORPTION IN THE CONSCIOUS DOG
Authors: Summerill R. A. , Lee K. E.
Published: December 2014

When normal conscious dogs were given small doses of (NH4)2HPO4 by stomach tube to increase their plasma PO4, the rate of excretion of PO4 increased without change in creatinine clearance. After eating meat, increased PO4 excretion was accompanied by increase in both creatinine caearance and plasma PO4. The calculated rate of tubular reabsorption of PO4 did not change significantly after (NH4)2HPO4 administration, but there was a significant increase in PO4 reabsorption after meat; in comparison there was no change in SO4 reabsorption. Similarly, administration of certain amino acids, which caused an increase in creatinine clearance, also caused a significant increase in PO4 reabsorption. Administration of SO4 with PO4 had no significant effect on PO4 reabsorption. It appears from the results, that PO4 has an apparent tubular maximum rate of reabsorption (Tm) when plasma PO4 alone is varied; but this Tm is not a real maximum because PO4 reabsorption increases above this value after the administration of meat or amino acids, both of which cause an increase in glomerular filtration rate. There is no evidence to suggest that there is any inhibition of PO4 reabsorption by SO4 or amino acids.
CONTRIBUTION OF INTERNAL AND EXTERNAL CAROTID BEDS TO COMMON CAROTID ARTERY INPUT IMPEDANCE IN THE DOG
Authors: Taylor David E. M. , Tukmachi Emad S. A.
Published: December 2014

The input impedance of the canine common carotid artery has been obtained using high fidelity pressure and flow recordings at the level of the superior thyroid artery. From the impedance spectra initially, and following internal and external carotid artery occlusion, separate estimations of internal carotid, external carotid and external/internal collateral bed impedances were derived by the use of network theory. Studies were carried out on six dogs. The common carotid input resistance was 10·98±1·42 (S.E.M.) x 106 kN.m−5.s, while those for the internal, external and collateral beds were 48·80±7·12, 14·94±2·37 and 171·42±46·83 x 106 kN.m−5.s respectively. The impedance spectrum of the common carotid, external carotid and collateral beds were of a high impedance type with major reflexions, while that for the internal carotid bed was of low impedance type with much less reflexion. On standardization of impedance for tissue mass the resistance levels became 17·44±2·91 x 106 kN.m−5.s. 100 g−1 for internal and 85·41±4·75 x 106 kN.m−5.s. 100 g−1 for external carotid beds. Thus, common carotid input impedance differences between dog and man are due to differences in relative mass of tissue perfused by internal and external carotid arteries, rather than to different peripheral‐bed characteristrics in the two species.
THE ORIGINS AND CHARACTERISTICS OF CROSS‐CORRELATED ACTIVITY BETWEEN γ‐MOTONEURONES IN THE CAT
Authors: Ellaway P. H. , Murthy K. S. K.
Published: December 2014

Cross‐correlation analysis of the naturally occurring discharges of γ‐motoneurones to gastrocnemius and soleus muscles has revealed a tendency towards synchronized firing in the decerebrated, spinal cat. The primary feature of the cross‐correlation between two γ‐motoneurones is a symmetrical peak centred at time zero with reference to discharges at the level of the cell bodies in the ventral horn of the spinal cord. The peak has a half‐width in the range 3‐10 ms. Secondary features of the correlograms are frequently present, especially when the primary peak is large. They consist of dips to either side of the peak and are mirrored in the respective autocorrelation functions of the two contributory neurones. This suggests that they arise as a result of periodicity in firing patterns of the neurones. The degree of synchrony has been measured as the ratio (k') of the total counts contributing to the peak over the number expected by chance. The value of k' was found to be dependent upon the firing frequencies of the neurones. Plots of k' against the geometric mean frequency of discharge showed a falling curvilinear relation as frequency increased. There was a weak inverse relation between the width of the cross‐correlation peak and firing frequency. These relations had to be acknowledged before any assessment of change in the degree of synchrony could be made. The correlation between discharges is absent or weak in the decerebrated cat with an intact spinal cord and in intact cats anaesthetized with pentobarbitone or chloralose. Anaesthetics administered to a spinal animal did not suppress synchrony. The synchrony between γ‐motoneurones is characteristic of the short‐term synchrony (Sears & Stagg, 1976) which arises from activity in shared presynaptic axons. In a few instances a stronger, more‐tightly coupled synchrony was observed. The cross‐correlogram peak had a half‐width of 0·5‐l·0 ms and was superimposed upon the usual wider‐based peak. We presume that this intense form of synchrony has a different origin. The properties of the short‐term synchrony are discussed with respect to (a) the mechanism of supraspinal control, and (b) a plausible model of the membrane properties of γ‐motoneurones which could account for the dependency of k' on frequency of firing. Experiments to determine the afferent source of synchronous firing and its distribution are presented in the following paper (Ellaway & Murthy, 1985).
SECRETION OF PAROTID ACINAR GRANULES IN RATS DURING REFLEX STIMULATION AFTER CHRONIC SYMPATHECTOMY
Authors: Garrett J. R. , Harrop T. J. , Thulin A.
Published: December 2014

After chronic post‐ganglionic sympathectomy the ultrastructure of ‘resting’ parotid acinar cells in rats remains relatively normal, despite the loss of nerve impulses normally causing secretion of acinar granules from this gland. The question whether eating hard chow still induces some acinar degranulation weeks after superior cervical ganglionectomy, has now been tested. It was found that scattered pockets of parotid acinar degranulation did occur. Some of these changes after unilateral denervation may have been attributable to intact sympathetic nerves arising from the contralateral superior cervical ganglion (Alm, Asking, Emmelin & Gjörstrup, 1984), but this cannot explain similar changes that occurred in glands after bilateral ganglionectomy. The possibility that some degranulation may be induced by circulating catecholamines was tested, 9‐16 weeks after unilateral sympathectomy, by placing animals in the cold (0‐4°C) for 2 h before removal of tissues. Animals not given food during that time showed no evidence of parotid acinar degranulation, but those given hard chow showed extensive acinar degranulation in both parotid glands. On the sympathectomized side the degranulation was, however, less uniform and more patchy than on the side with an intact innervation. These findings agree with the belief that circulating catecholamines can, at times, induce degranulation of parotid acinar cells made supersensitive by chronic sympathetic denervation but, for it to occur, the cells must also be receiving parasympathetic stimulation at the same time. This interaction probably permits a sufficient turnover of granules to maintain a relative homoeostasis of the parotid acinar cells in rats.
CHANGES IN INTRAPULMONARY CHEMORECEPTOR DISCHARGE IN RESPONSE TO THE ADJUSTMENT OF RESPIRATORY PATTERN DURING HYPERVENTILATION IN DOMESTIC FOWL
Authors: Gleeson M.
Published: December 2014

It has been suggested that avian vagal intrapulmonary CO2‐sensitive receptors (i.p.c.) may be capable of monitoring the rate and extent of CO2 wash‐out from the lung during spontaneous breathing. The purpose of this study was to record i.p.c. discharge activity in spontaneously breathing domestic fowl when minute volume (V1) was elevated from resting levels. This was accomplished by administration of almitrine (2 mg. kg−1 i.v.), a respiratory stimulant drug that has been shown to have a specific long‐lasting stimulatory action on carotid body chemoreceptors. Unanaesthetized decerebrate fowl were tracheotomized and single‐unit activity was recorded from sixteen vagal i.p.c. When ventilation was elevated 2·2‐fold by, almitrine (initially by increases in tidal volume (VT)) i.p.c. discharge was increased in both inspiration and expiration, and the delay period before the onset of i.p.c. discharge in inspiration was markedly shortened. Within 5‐10 min after the administration of almitrine, the breathing pattern changed to one of rapid, shallow breathing, although the 2·2‐fold elevation of the rate of gas flow through the parabronchi (V) and mean inspiratory flow rate (VT/T1) were maintained. The i.p.c. continued to fire phasically, with peaks of discharge in both inspiration and expiration, though there were fewer spikes per breath and mean inspiratory peak discharge rate returned to control (eupnoeic) levels. It is concluded that i.p.c. discharge is increased when V1 is elevated in the spontaneously breathing fowl and that the pattern of discharge is dependent on the pattern of breathing. I.p.c. show high dynamic sensitivity to changes in the PC02 of their microenvironment and it is possible to explain the changes in discharge pattern observed in terms of the PCO2 changes in the lungs and air sacs. These results support proposals that the pattern of breathing is to some extent dependent upon the intensity and timing of i.p.c. activity.
FLOW IN GLASS MODELS SIMULATING VASCULAR JUNCTIONS UNDER STEADY FLOW CONDITIONS
Authors: Stehbens William E. , Stehbens Gilbert R.
Published: December 2014

The dye‐injection technique was used to study flow patterns in twelve glass models of the union of two streams to form a common stem as occurs in veins and, less often, in arteries. The angle of union and the sharpness of the apex of the union varied. Flow disturbances, though minor at low flow rates, were observed in the stem beyond the junction in all models at Reynolds numbers below 2000. The disturbances were attributed to instability in the wake of the junction and to boundary layer separation at the apex. The results indicate possible applicability to the human vascular system.
WOUND CONTRACTION. CORRELATIONS BETWEEN THE TENSION GENERATED BY GRANULATION TISSUE, CELLULAR CONTENT AND RATE OF CONTRACTION
Authors: Snowden John M. , Cliff Walter J.
Published: December 2014

The tension generated in vitro by samples of granulation tissue taken from wounds at various times after wounding has been measured. Throughout the period when in vivo contraction was occurring with a constant linear rate of movement of the wound margins the in vitro tension produced by samples of the granulation tissue remained constant at ∼80 mg/mm2. With cessation of contraction in vivo, the tension generated by the granulation tissue fell to 40 mg/mm2. Morphometric studies demonstrated that total cellularity paralleled the tension developed. However, the decrease in cellularity preceded by ∼4 d the decrease in the tension developed. Strong correlation between the rate of contraction and the maximum thickness of the granulation tissue was demonstrated.
EFFECTS OF LUNG INFLATION ON ABDOMINAL VASCULAR RESISTANCE IN ANAESTHETIZED DOGS
Authors: Wood L. M. , Hainsworth R. , McGregor K. H.
Published: December 2014

In chloralose‐anaesthetized dogs, the airways to each lung were separated by cuffed endobronchial cannulae and one vagus nerve was cut. We determined the effects of inflation of the innervated lung on abdominal vascular resistance, assessed in the unopened abdomen from changes in perfusion pressure at constant flow. Both static and. phasic lung inflation resulted in variable responses of heart rate and abdominal vascular resistance. However, there was a significant correlation between the responses and when heart rate increased there was a significant vasoconstriction. When vasodilatation occurred this was unaffected by vascular isolation of the abdomen indicating that it could not have resulted directly from a blood‐borne agent. The bradycardia and vasodilatation were prevented by administration of antagonists to histamine and prostaglandin synthesis. These experiments indicate that, when lung inflation results in tachycardia, abdominal vascular resistance increases. The responses of bradycardia and vasodilatation appear to involve the action of histamine and/or prostaglandins.
EFFECT OF DRUGS AND ELECTRICAL FIELD STIMULATION ON CIRCULAR MUSCLE STRIPS FROM HUMAN LOWER OESOPHAGUS
Authors: McKirdy H. C. , Marshall R. W.
Published: December 2014

Sphincteric muscle from human lower oesophagus may be identifiable in vitro by its ability to develop a very high level of tone (sustained resting tension). Circular muscle strips from human lower oesophagus generally behave in a similar manner to strips from the opossum oesophagus with respect to development of tone, responses to electrical field stimulation and responses to a variety of drugs. Pharmacological analysis of responses to field stimulation in strips from the region of the oesophago‐gastric junction suggests that the typical biphasic response (relaxation followed by an after‐contraction) is mediated by nerves which are neither adrenergic nor cholinergic. Of the substances examined only vasoactive intestinal peptide (VIP) cannot be excluded as a possible candidate for the role of inhibitory transmitter. The mechanism producing the after‐contraction is not clear but it would seem unlikely that this is simply a rebound contraction. The after‐contraction can be blocked independently of the relaxation by a variety of agents and is potentiated by metoclopramide.
PHOSPHATE ABSORPTION AT DIFFERENT INTESTINAL SITES IN THE DEVELOPING LAMB
Authors: Scharrer E.
Published: December 2014

Net phosphate absorption was studied at different sites of the intestine in milk‐fed lambs of different age (1 week, 3‐4 weeks, 10‐13 weeks) and also in lambs fed a solid diet (age: 10‐13 weeks). Disappearance of phosphate from ligated intestinal segments filled or perfused with an electrolyte solution containing 1.2 mmol/l phosphate was employed as measure for phosphate absorption. In all groups of animals the mid‐jejunum absorbed phosphate with the greatest velocity. In the 1‐week‐old lambs the proximal colon descendens was almost as efficient, though phosphate absorption at this site was minimal in the other groups of animals. With the exception of the distal jejunum, phosphate absorption appeared to decrease with age. Between animals of the same age fed either a liquid milk diet or a solid diet phosphate absorption did not differ significantly. Phosphate absorption from the mid‐jejunum was inhibited by galactose and glucose in the 1‐week‐old lambs. The significance of these findings in relation to control of phosphate absorption in the developing lamb is discussed.
EFFECTS OF PHONEUTRIA NIGRIVENTER SPIDER VENOM ON MOUSE PERIPHERAL NERVE
Authors: Cruz-Höfling M. A. , Love S. , Brook G. , Duchen L. W.
Published: December 2014

A physiological and morphological study has been made of the effects of the venom of the spider Phoneutria nigriventer on peripheral nerve and skeletal muscle of the mouse. Venom was injected either into the sciatic nerve, via a glass micropipette, or into the calf muscles. Repetitive firing of nerve fibres commenced within seconds of injection and caused fasciculation of muscles and irregular trains of end‐plate potentials. These physiological disturbances were associated with swelling of the nodal and paranodal axoplasm and the development of vacuoles in the periaxonal space. The segments of internode between the vacuoles became attenuated, with an increase in the density of axoplasmic organelles and a reduction in axonal calibre. The repetitive firing ceased after 1‐3 h with development of conduction block. Both the physiological and the morphological abnormalities gradually resolved and by 24 h nerve conduction and morphology had largely returned to normal. It seems likely that these short‐lived abnormalities are a consequence of the influx of sodium ions at the nodes of Ranvier, caused by the action of the venom on sodium channels.
RESECTION OF RABBIT ILEUM: EFFECT ON JEJUNAL STRUCTURE AND CARRIER‐MEDIATED AND PASSIVE UPTAKE
Authors: Thomson A. B. R.
Published: December 2014

Adaptive changes occur in nutrient uptake following intestinal resection. A previously validated in vitro technique was used to measure the rate of uptake of solutes six weeks following surgical removal of the distal half of the small intestine in the rabbit. The rate of jejunal uptake of a homologous series of fatty alcohols, cholesterol, and six bile acids was unchanged in the resected animals. The uptake of short‐ and long‐chain length fatty acids was also unchanged following resection, although there was a modest but significant increase in the uptake of decanoic and dodecanoic acid. The incremental change in free energy, ∫ ΔFw → l, was increased in the jejunum of resected animals when assessed with the medium chain‐length fatty acids, but was unchanged when estimated from the uptake of long chain‐length fatty acids. The value of ∫ ΔFw → l for bile acids was similar in the jejunum of control and resected animals. There was an increase in the maximal transport rate (Jmd) for D‐glucose, galactose and L‐leucine, an increase in the Michaelis constant (Km) for 3‐O‐methylglucose, and an increase in both the Jmd and Km for fructose. There was no change in the passive component of the uptake of these solutes following intestinal resection. In the resected animals there was no significant increase in the height, width, and surface area of the jejunal villi, the number of mucosal cells per villus, or in the mucosal surface area, although there was a significant increase in the weight of the scraped mucosa and in the height of the microvilli. The modifications in the active and passive kinetic constants were not related to the alterations in the microvillus surface area, and changes in the Km or ∫ ΔFw → l were not due to any variation between control and resected animals in the effective resistance of the intestinal unstirred water layer. These results indicate that, (1) ileal resection was not associated with changes in the effective resistance of the intestinal unstirred water layer; (2) the variable changes in the uptake of passively adsorbed solutes following resection suggests a functional heterogeneity of the villus towards passive permeation; (3) estimation of the incremental change in free energy of the intestine using a homologous series of saturated fatty acids may provide variable results depending upon the chain length of the probes; (4) the estimation of the permeability properties of the membrane based on the uptake of one group of probes cannot be generally applied to describe the permeability properties of the membrane towards all passively transported solutes; (5) it is likely that at least one major adaptive response to ileal resection was an increase in the number of active transport sites per unit area of mucosa, leading to an increase in the value of Jmd; and (6) those signals responsible for changes in intestinal transport following resection may differ from those signals influencing alterations in morphology.
OBJECTIVE MEASUREMENTS OF CUSTOMARY PHYSICAL ACTIVITY IN ELDERLY MEN AND WOMEN BEFORE AND AFTER RETIREMENT
Authors: Patrick J. M. , Bassey E. J. , Irving J. M. , Blecher A. , Fentem P. H.
Published: December 2014

An objective method for assessing customary physical activity has been described, based on heart rate and footfall signals recorded on magnetic tape using small body‐borne recorders. Computer analyses were used to obtain indices of the intensity and duration of periods of physical activity using both biosignals. Threshold values were set for each individual at a heart rate related to a standard walking speed of 4·8 km.h−1 (3 miles per hour). Four activity indices were defined in terms of time spent above this threshold and the intensity of the heart rate elevation above it, applying criteria relating to the duration of periods of activity or the concurrent activation of the walking signal. The choice and validity of these indices are discussed, and results for several groups of subjects presented. Three groups of subjects aged over 60 years were studied before and after retirement: twenty‐five were steel‐workers and thirty‐nine were factory‐workers (men and women). Rather low levels of activity were recorded. After one year of retirement the female factory workers showed a significant decrease in activity. In men this was found only after several years of retirement had elapsed.
MATERNAL HEART RATE AND STROKE VOLUME IN THE PYGMY GOAT: EFFECTS OF EXERCISE AND CARDIAC AUTONOMIC BLOCKADE
Authors: Hosenpud Jeffrey D. , Hart Mark V. , Rowles John R. , Morton Mark J.
Published: December 2014

To determine the normal maternal heart rate and stroke volume response to exercise and the role of the autonomic nervous system in this response, pregnant and non‐pregnant pygmy goats were studied at rest, during and following treadmill exercise, and after autonomic blockade. Resting heart rates, stroke volumes and cardiac outputs were 10%, 60%, and 76% higher in pregnant compared to non‐pregnant animals (P 〈 0·05, 0·001, and 0·001 respectively). During exercise, heart rate and stroke volume rose in both pregnant and non‐pregnant animals by similar amounts. Immediately post‐exercise, stroke volume in pregnant animals dropped precipitously below resting levels by 15% (P 〈 0·005) but cardiac output was preserved by heart rate. This fall in stroke volume was not seen in control animals. Autonomic blockade lowered resting and exercise heart rates in both groups without changing stroke volume. The elevations in heart rate and stroke volume in pregnancy are not primarily mediated via the autonomic nervous system. Although the maternal cardiac output response to exercise appears normal, the post‐exercise fall in stroke volume, presumed secondary to a reduction in preload, could potentially be harmful to both mother and fetus.
COLD EXPOSURE AND MAMMARY EXCHANGES OF CIRCULATING THYROXINE AND OESTRONE SULPHATE IN THE GOAT
Authors: Goode J. , Thompson G. E.
Published: December 2014

The effects of cold exposure on arterial and mammary venous concentrations of thyroxine and oestrone sulphate, and on mammary blood flow, were measured in goats during different stages of pregnancy and lactation. There were no significant differences in net mammary uptake of thyroxine in four non‐pregnant lactating goats exposed for 30 h to cold (‐3 ± 2° C) or control (20 ± 2 °C) temperatures. Cold exposure for 30 h of six lactating goats (approximately 85 d pregnant) stimulated a net mammary release into the circulation of oestrone sulphate (mean 294 ng/min); plasma cortisol concentrations also increased. Cold exposure at approximately 30 d of pregnancy increased cortisol concentrations but had no effect on release of oestrone sulphate.