bluuebunny/crossref_metadata_2025 huggingface dataset:
TWO TYPES OF STATIC γ‐AXON IN CAT MUSCLE SPINDLES
Authors: Boyd I. A.
Published: December 2014

The action of single static γ‐axons in ‘single fibre’ ventral root filaments was tested on the responses of from two to eight spindles in the same tenuissimus muscle in anaesthetized cats. The type of intrafusal fibre activated in each spindle by a particular axon was diagnosed from its effect on the discharge of primary and secondary sensory endings, frequently in the same spindle. One or two spindles were subsequently isolated in most experiments and the type of intrafusal fibre activated by the axon was observed directly. Except in the case of a few weak actions which could not be interpreted, the diagnosis made from the afferent recordings was always correct. Twenty‐four static γ‐axons activated the chain fibres in every spindle they supplied on which their action was tested; the static bag2 fibre was also involved in about 20% of the spindles though its contraction was quite often weak. Eleven static γ‐axons activated the static bag2 fibre in every spindle they supplied on which their action was tested; some chain fibres were activated as well in about 20% of the spindles. There were only two possible exceptions to the general rule that a static γ‐axon activates either the chain fibres or the static bag2 fibre in every spindle it supplies and never activates only the chain fibres in one spindle, and only the static bag2 fibre in another spindle. Direct observation of isolated spindles provided preliminary evidence that some non‐selective connexions of static γ‐axons have a pronounced physiological action by way of their terminals on one type of intrafusal fibre while the terminal(s) on the other type of fibre produce such a weak contraction that the sensory endings are not affected. Other non‐selective connexions do, however, have a significant physiological effect by way of their terminals on both the static bag2 fibre and the chain fibres. It is proposed that there are two types of static γ‐motoneurone. ‘Static bag γ‐motoneurones’, through their terminals on the static bag2 fibre in every spindle, bias the discharge from primary endings (and to a lesser extent from some secondary endings) but leave their length sensitivity largely unaltered; connexions to chain fibres in some spindles have a weak action on primary endings but may greatly increase the length sensitivity of secondary endings. ‘Static chain γ‐moto‐neurones’, through their terminals on chain fibres in every spindle, drive the discharge of primary endings in such a way that, if several axons are activated together, the sensitivity of the primary endings to changes in muscle length may be abolished; connexions to the static bag2 fibre in a few spindles seem to enhance this effect. Static chain γ‐motoneurones probably bias the discharge of secondary endings substantially but have a variable action on their length sensitivity.
EFFECT OF SERUM ON SODIUM PUMP ACTIVITY AT VARIOUS CONCENTRATIONS OF INTERNAL AND EXTERNAL SODIUM IN MOUSE (3T3) AND HUMAN (HeLa) CELLS
Authors: Lamb J. F. , Ogden P. , Singh J.
Published: December 2014

Serum causes a large rise in the ouabain‐sensitive K influx in 3T3 and other cells. It has been argued that this is secondary to the increased Na and K leaks which are also caused by serum. We have measured the K influx into 3T3 and HeLa cells at various values of intracellular Na concentration ([Na]i), and from Na‐free medium in 1 and 20% (v/v) serum. Raising [Na]i increases the K influx, but saturation does not occur over the range of [Na]i studied. The estimated Km for [Na]i is around 130 mM and the Vmax some 10 times that of the resting K influx at normal (20 mM) [Na]i. Serum stimulates the K influx by a constant proportion at all values of [Na]i studied, and in Na‐free medium. These results are inconsistent with previous explanations of the serum stimulation of pumping.
INSULIN AND THE PARASYMPATHETIC DEPENDENCE OF PANCREATIC JUICE SECRETION IN HEALTHY AND ALLOXAN DIABETIC SHEEP
Authors: Pierzynowski Stefan G. , Podgurniak Paweł , Mikołajczyk Marioletta , Szczesny Wiesław
Published: December 2014

Pancreatic function was measured in four ewes following vagal stimulation under control conditions and after the induction of alloxan diabetes. The volume and protein content of the pancreatic juice was measured along with simultaneous measurement of blood glucose and plasma insulin. The volume of pancreatic juice and its protein content decreased markedly in the diabetic state and returned to the initial value after insulin treatment. In normal animals, vagal stimulation markedly increased; the volume of pancreatic secretion and its protein content as well as the plasma insulin concentration. In the diabetic animals vagal stimulation caused only a slight increase in the protein content of pancreatic juice and plasma insulin concentration. It is suggested that insulin is probably one of the more important factors directly regulating the secretion of pancreatic juice.
EFFECT OF INTRARUMINAL SODIUM AND POTASSIUM CONCENTRATIONS AND OF THE TRANSMURAL POTENTIAL DIFFERENCE ON MAGNESIUM ABSORPTION FROM THE TEMPORARILY ISOLATED RUMEN OF SHEEP
Authors: Martens H. , Blume Ingrid
Published: December 2014

The net absorption of magnesium from the temporarily isolated and washed reticulo‐rumen of sheep has been studied using buffer solutions with different sodium, potassium and chloride concentrations. An increased potassium concentration led to an increased potential difference (p.d.) and a decreased magnesium absorption. The exchange of chloride in the buffer solutions with sulphate (at constant sodium and potassium concentrations) caused a significant increase of the p.d. and again a reduced net magnesium absorption indicating that the p.d. is an important factor associated with decreased net magnesium absorption. The replacement of sodium with lithium (at constant potassium concentrations) did not influence the net magnesium absorption. It is concluded that the low apparent availability of magnesium after an oral load of potassium is mainly caused by the high transmural potential difference across the rumen wall under such feeding conditions. However, the presented data cannot rule out an effect of potassium per se independent of the effect of the p.d.
INTERACTIONS BETWEEN MONOSACCHARIDES AND DISACCHARIDES DURING UPTAKE BY THE PERFUSED LIVER OF RAT
Authors: Ibu J. O. , Short A. H.
Published: December 2014

The extractions of D‐glucose, L‐glucose, D‐fructose and D‐galactose by the isolated liver of rat perfused at constant flow were estimated by paired tracer dilution. The effects on these of 25 mM concentrations of these monosaccharides, of α‐methyl‐glucoside and of the disaccharides sucrose, maltose, and lactose were measured. Inferences were drawn from these data about the transport of monosaccharides at the sinusoidal surface of the liver cells. The hepatic clearances of the isomeric monosaccharides consistently ranked D‐glucose (at 5·5 x 10−3 M) 〉 D‐galactose (2·5 x 10−5 M) 〉 D‐fructose (3·2 x 10−7 M) » L‐glucose (2 x 10−6 M). This implies at least that there are membrane transport mechanisms with distinctly lower affinity for the other sugars than for D‐glucose. Glucose entry was stereoselective, and interactions amongst some of the sugars were demonstrated. A reproducible pattern of differential inhibition of D‐glucose entry by the competing sugars at 25 mM was found. The consistent lack of effect of sucrose excluded a mere osmotic effect. The pattern of inhibition of D‐fructose entry by the same sugars was qualitatively similar to that of D‐glucose, whereas that of D‐galactose was distinctive. The disaccharide competitors, lacking cell entry, can exert their effects only at the external surface. These markedly discriminate between D‐glucose and D‐galactose. The penetrating sugars, however, show mutual competition. The hypothesis is proposed that the external surface of the rat hepatocyte has distinct populations of hexose transport sites which discriminate between D‐glucose and D‐galactose, whereas internal sites participating in the same fluxes are unselective.
THE INFLUENCE OF VAGOTOMY ON THE RESPIRATORY EFFECTS OF INJECTED PHENYL DIGUANIDE IN ANAESTHETIZED RABBITS
Authors: Davies A. , Jones H.
Published: December 2014

The effects of intravenous injections of phenyl diguanide (PDG) on pattern of breathing were studied before, immediately after, and some time after bilateral cervical vagotomy in anaesthetized rabbits. The characteristic tachypnoea observed in the intact animals could not be produced for several minutes after bilateral vagotomy, but after 15 min could be elicited again. This sequence of events was not essentially modified by cutting the glossopharyngeal nerves nor by injection of local anaesthetic into the pericardial sac. We suggest that the respiratory effects of PDG in the rabbit, previously considered to originate mainly from peripheral receptors, including those of the lungs, has a considerable central component which has previously been obscured by the short‐term effects of vagotomy.
IRON CONTENT AND DISTRIBUTION IN JAPANESE QUAIL
Authors: Sánchez J. , García F. , Planas J.
Published: December 2014

Determination of blood haematocrit and haemoglobin, plasma iron content, total iron binding capacity and phosphoprotein (vitellogenin), and the iron content of different organs (pectoral muscle, liver, spleen, intestine, femur bone marrow, blood, gonad and eggs, and feathers) were carried out in prelaying, onset of laying and full laying females, as well as in adult males. The whole iron content was also determined on incinerated specimens giving these results: 53·7 parts per million (p.p.m.) iron in the prelaying group, 54·5 p.p.m. iron at the onset of laying, 64·3 p.p.m. iron in full laying and 53·5 p.p.m. iron in males. The plumage represented 5‐8% of the total body weight, and its iron content oscillated between 152‐163 p.p.m. iron in males and non‐laying females and 177·3 p.p.m. iron at full laying. The laying period induced important variations in plasma levels and in organ distribution, but not in haematological values. The first eggs laid were smaller (9·2 g) and richer in iron (427 µg iron) than those laid by older layers (11·8 g and 305 µg iron). The percentage distribution of the total iron content of organs was, in prelaying females: feathers, 21·9; blood, 56·6; pectoral muscle 8·1; liver, 9·7; intestine, 2·7. In laying females: 29·1; 46·6; 11·5; 7·4; 4·2. In males: 17·4; 59·6; 11·4; 7·9; 2·3. The increase in intestinal iron content in laying quails coincided with a double intake of food. This distribution differs from the mammalian model, as egg production (where each egg represented 2·5‐5·5% of the total iron) and the great inert iron deposits in the plumage require an elaborate iron metabolism control system to cover all the iron needs in birds.
LUNG REFLEXES AFFECTING THE LARYNX IN THE PIG, AND THE EFFECT OF PULMONARY MICROEMBOLISM
Authors: Aguggini G. , Clement M. G. , Widdicombe J. G.
Published: December 2014

Laryngeal airflow resistance was measured in anaesthetized pigs during stimulation of lung vagal reflexes by injection of phenylbiguanide and of capsaicin, before and during pulmonary microembolism due to intravenous injection of hardened red blood cells; the microembolism caused pulmonary hypertension. The Breuer‐Hering reflex was also assessed before and after pulmonary microembolism. Phenylbiguanide and capsaicin caused apnoea followed by rapid shallow breathing, hypertension, bradycardia and laryngeal constriction in inspiration and expiration. Most of these effects were abolished by bilateral cervical vagotomy. Pulmonary microembolism caused only small changes in breathing pattern, mainly a decrease in inspiratory time. After microembolism the Breuer‐Hering reflex was enhanced, and injections of phenylbiguanide and capsaicin caused longer apnoeas by a vagal reflex. The changes in pattern of breathing and in lung reflexes after lung microembolism and during the associated pulmonary hypertension are consistent with an enhancement of pulmonary stretch receptor activity in this condition, but do not indicate any important role for C fibre reflexes.
THE EFFECT OF POTASSIUM AND THE TRANSMURAL POTENTIAL DIFFERENCE ON MAGNESIUM TRANSPORT ACROSS AN ISOLATED PREPARATION OF SHEEP RUMEN EPITHELIUM
Authors: Martens H. , Gäbel G. , Strozyk H.
Published: December 2014

Isolated mucosal sheets of sheep rumen were studied in vitro in Ussing chambers using a computer‐controlled voltage clamp. Undirectional Mg2+ fluxes were measured at high (70 mmol.l−1) or low (5 mmol.l−1) mucosal concentrations of K+ under open‐ or voltage‐clamp conditions. A high mucosal concentration of K+ caused a potential difference (p.d.) of 25·1 ± 1·8 mV, blood side positive. The Mg2+ fluxes were 52·2 ± 6·5 nmol.cm−2.h−1 from the mucosal to serosal side, JMgms, and 11·6 ± 1·4 nmol.cm−2.h−1 from the serosal to mucosal side, JMgsm. The net flux, JMgnet, was 40·6 ± 5·9 nmol.cm−2.h−1. When, at high mucosal K+ concentrations the p.d. was abolished by an external current (short‐circuit conditions) significantly different flux data were obtained: JMgms, 76·1 ± 8·3; JMgsm, 8·0 ± 1·4; and JMgnet 68·1 ± 7·7 nmol.cm−2.h−1. The results of the low (control) and high mucosal K+ group did not differ significantly when Mg2+ fluxes were measured under short‐circuit conditions: JMgms, 72·1 ± 8·7; JMgsm, 6·5 ± 2·6; and JMgnet, 65·5 ± 9·0 nmol.cm−2.h−1. An increase of the p.d. to 26·6 ± 2·0 mV (control) by an external current led to significant alterations of the fluxes in the control group: JMgms, 47·4 ± 3·0; JMgsm, 12·3 ± 2·3; and JMgnet, 35·2 ± 4·1 nmol.cm−2.h−1. Although it is suggested that an increased p.d. caused an enhanced passive flux of Mg2+ from the serosal to the mucosal side through the shunt pathway, the magnitude of the decrease in JMgms cannot solely be explained by a reduction in the passive, putative paracellular part of JMgms.
METABOLIC ADAPTATIONS IN MOUSE MAMMARY GLAND DURING A NORMAL LACTATION CYCLE AND IN EXTENDED LACTATION
Authors: Shipman Lorna J. , Docherty Ann H. , Knight Christopher H. , Wilde Colin J.
Published: December 2014

The development and involution of mouse mammary tissue was measured in terms of changes in the cell population and the synthetic capacity of cells during the course of pregnancy, lactation and natural weaning, and after lactation was extended by introduction of foster litters of younger pups. Synthetic capacity was assessed by measuring the activities of several key enzymes closely concerned with the synthesis of milk constituents together with other constitutive enzymes. The capacity of the tissue to synthesize lactose and casein was also measured using short‐term cultures of freshly prepared mammary explants. Results showed that the mammary cell population began to increase and differentiate around the time of parturition. Cell numbers increased up to day 5 of lactation, whereas cellular differentiation continued through lactation until day 15, around the time of peak milk yield. After day 15 there was a sharp drop, followed by a gradual decline in synthetic capacity and cell population, as pups were weaned. Substitution of younger pups for the natural litter at day 15 prevented the normal fall in milk secretion. In this case, mammary cell number remained at day 15 levels; cellular differentiation was also maintained to a considerable degree, although several markers of differentiation decreased during extended lactation.
FACTORS AFFECTING THE SECRETION OF SUBMANDIBULAR SALIVARY KALLIKREIN IN CATS
Authors: Garrett J. R. , Kidd A. , Smith R. E. , Kyriacou K. , Liao J.
Published: December 2014

Glandular kallikrein has been assessed in submandibular saliva, homogenates and plasma by the fluorimetric substrate D‐Val‐Leu‐Arg‐7‐amino‐4‐trifluoromethylcoumarin (AFC) and histochemically in tissue sections by the 4‐methoxy‐2‐naphthylamide (MNA) analogue. Nerve stimulation was used to produce salivary secretion. Parasympathetic saliva contained low concentrations of kallikrein, independently of any circulating catecholamines from the adrenals. Sympathetic saliva contained very high concentrations of kallikrein; the amounts in individual drops rapidly reached a peak then declined gradually. Adrenergic blocking drugs during mixed parasympathetic and sympathetic stimulation showed that β‐adrenergic effects normally increase the secretion of kallikrein in response to the α‐adrenergic influence from sympathetic nerve impulses. Small amounts of a glandular kallikrein‐like activity are present in the plasma. Effluent blood from the submandibular gland before, during and after stimulation of either nerve gave no indication that submandibular kallikrein passes from the glandular compartment to the blood under conditions of unobstructed salivary flow. Excision of the chorda tympani indicated that parasympathetic nerve impulses are required for the normal resynthesis of submandibular kallikrein. The secretion of salivary kallikrein is essentially an exocrine function but its role in the saliva remains obscure. The results suggest that sudden mobilization of kallikrein may occur at times into the saliva and that a separate population of adrenergic axons, under separate central control, may pass to the striated ducts specially for this purpose.
A HIGH‐CONDUCTANCE CALCIUM‐DEPENDENT CHLORIDE CHANNEL IN ASCARIS SUUM MUSCLE
Authors: Thorn P. , Martin R. J.
Published: December 2014

Quarterly Journal of Experimental Physiology 72 (1987)

Page 44, eqn. (10), should read:

Pr = n! / r!(n‐r)! Pr(1‐P)n‐r
BIOLOGY OF PEPTIDES FROM THE CALCITONIN GENES
Authors: Zaidi M. , Breimer L. H. , MacIntyre I.
Published: December 2014

Despite being products from the same gene, there is clearly a marked divergence in the distribution and physiological role of calcitonin and CGRP. Whereas calcitonin is predominantly distributed in the thyroid, CGRP is abundant in the nervous system throughout the body. Though the peptides have only weak structural homologies, a generally similar conformation enables them to interact at each other's receptors. Hence the pharmacological effects of the peptides faintly resemble one another. Calcitonin receptors are mainly found on osteoclasts and at certain sites in the nervous system. CGRP binding sites are abundant in the cerebellum and blood vessels. Calcitonin is a circulating hormone controlling osteoclastic activity. CGRP acts as a neurotransmitter or neuromodulator centrally, and released from perivascular nerve terminals, it modulates arteriolar tone. Released from motoneurones, CGRP may also play a trophic role regulating the muscle acetylcholine receptor state. The next decade should establish the physiological role of CGRP and the regulation of the expression of the calcitonin/CGRP gene complex.
FLOW THROUGH INTERSTITIUM AND OTHER FIBROUS MATRICES
Authors: Levick J. R.
Published: December 2014

This review examined the relation between interstitial hydraulic permeability and chemical composition, using porous matrix theory, and assessed the view that interstitial conductivity is governed by GAG concentration. Conductivity correlates negatively with both GAG and collagen concentration over a wide variety of tissues. Conductivities of GAG matrices in vitro, coupled with other quantitative considerations, indicate, however, that no single class of fixed fibrous element exists at a sufficiently high concentration to account by itself for the low conductivity in most tissues. It seems that the low interstitial conductivity arises from the combined interactive effects of three main classes of fibrous element: collagen fibrils, GAG and proteoglycan core protein. In most cases the proteoglycan complex plays a major role which is significantly amplified, however, by the collagen fibril network.
THE EFFECT OF β‐BLOCKADE ON THE TRANSIENT INCREASE IN CORONARY VASCULAR RESISTANCE RESULTING FROM HAEMORRHAGE
Authors: Dambrosio M. , Gattullo D. , Mary D. A.S.G. , Vacca G.
Published: December 2014

Abrupt reduction in aortic blood pressure by haemorrhage in the anaesthetized dog has previously been used to assess the effect of elastic recoil and myogenic properties of the coronary vascular wall on diastolic coronary resistance. Using such assessments this study examines whether β‐blockade influences the magnitude of the effect of the vessel wall on coronary resistance. In two groups of dogs abrupt reduction in aortic blood pressure caused by haemorrhage resulted in an initial increase in diastolic coronary resistance, followed by its decline to the control value. In the first group with intact vagi, β‐blockade resulted in a greater initial increase in resistance and attenuation of its subsequent decline. Vagotomy in the second group did not abolish the effect of β‐blockade on diastolic coronary resistance. The findings suggest that during abrupt reduction in perfusion pressure, β‐blockade and reduction in heart rate and coronary blood flow resulted in a greater elastic recoil of the coronary vascular wall associated with an initial increase in diastolic coronary resistance and attenuation of myogenic properties related to return of diastolic coronary resistance to the control level.
THE DEVELOPMENT OF TETRODOTOXIN‐RESISTANT ACTION POTENTIALS IN LONG‐TERM ORGAN CULTURE OF RAT MUSCLE
Authors: Lee S. , Miledi R. , Ruzzier F.
Published: December 2014

The development and long‐term maintenance of tetrodotoxin (TTX)‐resistant action potentials in culture was examined. The amplitude and maximum rate of rise of the action potential in normal Ringer solution fell during culture. At the same time the amplitude and maximum rate of rise of the TTX‐resistant action potential increased, demonstrating that TTX resistance can develop fully in culture. Actinomycin D inhibited the onset of denervation changes in culture and was also able to delay the fall in the maximum rate of rise of the action potential in normal Ringer solution. When applied to muscle after 48 h of culture, it was relatively ineffectual, showing that de novo protein synthesis during the first 48 h of culture result in denervation changes which are not reversed by subsequent exposure to actinomycin D. The onset of TTX resistance occurred more rapidly in dissociated muscle fibres, presumably as a result of the early removal of the nerve stump.
INFLUENCES OF SHORT‐TERM SYMPATHECTOMY ON THE COMPOSITION OF PROTEINS IN RAT PAROTID SALIVA
Authors: Proctor G. B. , Garrett J. R. , Asking B.
Published: December 2014

The protein constituents in parasympathetically evoked saliva from normal and short‐term sympathectomized parotid glands were compared. There was a reduction in all proline‐rich proteins (PRP) in the saliva following sympathectomy. The decrease was quantified for acidic PRP by high‐performance ion‐exchange chromatography, which showed an increase in the ratio of amylase to other proteins. These results suggest that sympathetic impulses influence the synthesis of PRP and amylase in opposite directions.
MAGNESIUM METABOLISM IN THE RUMENS OF LACTATING DAIRY COWS FED ON SPRING GRASS
Authors: Johnson C. L. , Helliwell S. H. , Jones D. A. Aubrey
Published: December 2014

Six rumen cannulated lactating Jersey cows were used to study the effects of an abrupt change from a dry diet to young spring grass on mineral metabolism in the rumen, on plasma Mg2+ levels and on water intake. There was an increase in the intake of dietary Mg2+ and concentration of ultrafilterable Mg2+ in rumen fluid when the grass was fed associated with a fall in plasma Mg2+ concentration and percentage urinary Mg2+ excretion. The pH of rumen fluid fell when the cows were fed grass and there was a close inverse relationship with the concentration of ultrafilterable Mg2+ and Ca2+. Changes occurred in the mineral composition of rumen fluid that interact to affect the absorption of Mg2+. The concentrations of NH3, ultrafilterable K+ and ultrafilterable Ca2+ increased and the concentration of ultrafilterable Na+ decreased. These changes were associated with an increase in the potential difference between rumen fluid and blood (positive). Water consumption fell abruptly when the grass was fed and some cows drank no water on several days. However, total water intake was almost doubled resulting in an increased rumen volume.
INHIBITION OF 3β‐HYDROXYSTEROID DEHYDROGENASE IN THE SOW NEAR TERM: EFFECTS ON FETAL AND MATERNAL STEROIDS AND ON DELIVERY
Authors: Silver Marian , Fowden Abigail L.
Published: December 2014

The effect of Epostane, a 3β‐hydroxysteroid dehydrogenase inhibitor, on maternal and fetal plasma progesterone and other steroids has been investigated in chronically catheterized pregnant sows near term. Epostane (1‐2 mg/kg) was given I.V. and samples withdrawn from the uterine vein and artery and a fetal artery. In seven sows tested at 106‐110 d gestation (term 115 d) Epostane induced parturition 25 ± 2·1 h later with the birth of live viable young (group 1). In four sows tested with the same dose of Epostane at 106‐111 d gestation parturition was not induced (group 2). A rapid drop in maternal and fetal plasma progesterone occurred after Epostane; in group 1 maternal progesterone remained below 4 ng/ml until delivery whereas in group 2 the drop was temporary, as was the decrease in fetal progesterone in all animals. Epostane also resulted in a rapid fall in maternal and fetal plasma cortisol with a gradual recovery over the following 9‐12 h which was accompanied by increased ACTH (adreno‐corticotrophic hormone) levels in the fetus. In group 1 fetuses a further escalation in both cortisol and ACTH occurred up to and during delivery while in group 2 basal concentrations were restored after 24 h. Epostane also reduced maternal oestrone concentrations in both groups over the 6‐9 h after drug treatment. In group 2 the basal oestrone concentrations and the oestrone/progesterone ratio before and after Epostane administration were lower than in group 1 which may in part explain the failure of Epostane to induce labour in the former despite their similar gestational age. It is concluded that Epostane is not a reliable inducing agent in the sow when infused within 5‐10 d of term although enhanced adrenocortical activity probably ensures the viability of the piglets if delivered.
EFFECT OF EXTERNAL SODIUM SUBSTITUTION ON POTASSIUM CONTRACTURES OF MAMMALIAN MUSCLES: POSSIBLE INVOLVEMENT OF SARCOLEMMA‐BOUND CALCIUM AND Na+‐Ca2+ EXCHANGE
Authors: Noireaud J. , Leoty C.
Published: December 2014

Isometric tension of K+ contractures, membrane potential, internal Na+ activity (aiNa) and intracellular pH (pHi) have been measured in vitro under conditions which modify sarcolemma‐bound calcium and the activity of the Na+‐Ca2+ exchange of normal mammalian soleus muscle. In the absence of external Na+ and for a given high external K+, the maximum amplitude of the contracture was increased (Na+ replaced by TEA+) or decreased (Na+ replaced by Li+ or Cs+) compared with that obtained in the presence of Na+. Replacement of external Na+ by another monovalent cation (TEA+) did not induce any change of pHi. However the concomitant decrease of aiNa was related to a Na+‐Ca2+ exchange across the sarcolemmal membrane. The data suggest that in soleus muscle, a sarcolemmal calcium pool is involved during the development of K+ contractures.
PHOTOPERIOD: AN IMPORTANT REGULATOR OF PLASMA PROLACTIN CONCENTRATION IN FETAL LAMBS DURING LATE GESTATION
Authors: Bassett J. M. , Bomford J. , Mott J. C.
Published: December 2014

Measurement of prolactin (PRL) at 120‐140 days gestation in chronically‐cannulated fetal lambs and their mothers during hormonally‐extended breeding seasons shows that photoperiod is a major determinant of PRL secretion in the fetal lamb as well as in its mother. About 80% of the variance between fetuses in plasma PRL concentration is associated with variation in ambient photoperiod. The magnitude of this effect far exceeds the range of previously reported diurnal or ontogenetic changes in PRL in the fetal lamb.
THE DORSAL LATERAL GENICULATE NUCLEUS OF THE SHEEP AND ITS RETINAL CONNECTIONS
Authors: Clarke P. G. H. , Martin K. A. C. , Whitteridge D. , Rao V. M.
Published: December 2014

Layers 1 and 2 of the sheep's LGN have similar properties to layers A and A1 in the cat. In layer 3 of the sheep the cell size is the same as that of the main group in layers 1 and 2, and it is contralaterally driven but has no sublamination. There is a medial interlaminar nucleus in the sheep which consists of two incomplete laminae, each driven by one eye. Scattered cells from the whole of the retina temporal to the decussation line project to the contralateral LGN. There is only a band of cells 1·5 mm wide nasal to the decussation line which project to the ipsilateral LGN. Cells with corresponding ipsilateral fields are found on the medial side of the nucleus in layers 1 and 2. A few cells with orientation sensitivity have been seen in the LGN. The area of the greatest cell density in the retina, the streak, is accommodated in the LGN by expansion vertically, not horizontally.
FLUX OF INORGANIC PHOSPHATE ACROSS THE SHEEP RUMEN WALL IN VIVO AND IN VITRO
Authors: Breves G. , Höller H. , Packheiser P. , Gäbel G. , Martens H.
Published: December 2014

Experiments were done in vivo and in vitro to study the flux of inorganic phosphate (Pi) across the rumen wall in sheep. The technique of the temporarily isolated and washed reticulo‐rumen was applied to measure Pi net flux at nine different Pi concentrations in the buffer solutions introduced into the reticulo‐rumen for 1 h. Six sheep were either P replete (4·25 g P d−l) or in a P‐depleted state (1·05 g P d−1). Under both dietary treatments Pi net secretion into the reticulo‐rumen was found at Pi concentrations between 0·1 and 2·2 mmol 1−1 whereas Pi net absorption was observed at Pi concentrations between 4·1 and 15·8 mmol 1−1. There were positive linear relationships between Pi concentration and Pi net flux for the whole concentration range studied in repleted and in depleted sheep. There were no indications of active transport components or saturation phenomena. Unidirectional Pi fluxes were then measured in Ussing chambers with 32p using a total of 100 rumen wall epithelia obtained from eighteen sheep of different ages. No Pi net flux was found under short‐circuit conditions. Experiments with changed potential differences (+25 or ‐25 mV at serosal side) showed that Pi flux was influenced by the electrical gradient indicating electrogenic phosphate ion diffusion without involvement of active transport processes. Critical evaluation of the obtained unidirectional flux ratios suggests that part of the Pi flux was electroneutral, e.g. by ion exchange or co‐transport. The results from these studies show that the reticulo‐rumen substantially contributes to phosphate absorption from the sheep gastrointestinal tract.
FEED‐BACK INHIBITION OF MILK SECRETION: THE EFFECT OF A FRACTION OF GOAT MILK ON MILK YIELD AND COMPOSITION
Authors: Wilde Colin J. , Addey Caroline V. P. , Blatchford David R. , Peaker Malcolm , Casey Michael J.
Published: December 2014

A milk fraction containing whey proteins of 10‐30 kDa was injected into one mammary gland of lactating goats via the teat canal. This fraction produced a temporary dose‐dependent reduction in milk yield in the treated gland; the milk yield of the other gland, which received an equal volume of carrier solution, was not affected. Injection of a second fraction, containing whey proteins of 〉 30 kDa, affected milk secretion only at high doses, and this effect was not wholly specific to the treated gland. The 10‐30 kDa fraction and the 〉 30 kDa fraction produced similar transient changes in the concentrations of several ions and lactose in milk of the treated gland, but not in that of the untreated gland. These data indicate that a milk constituent present in the 10‐30 kDa whey inhibits milk secretion in a temporary and reversible manner. The results are discussed in relation to regulation of milk secretion through local feed‐back inhibition.
EFFECTS OF PEPTIDES FROM THE CALCITONIN GENES ON BONE AND BONE CELLS
Authors: Zaidi Mone , Bevis Peter J. R. , Beacham Jeremy L. , MacIntyre Iain , Chambers Timothy J. , Gaines Das Rose E.
Published: December 2014

The calcitonin‐calcitonin gene‐related peptide (CGRP) gene complex encodes a family of novel peptides ‐ calcitonin, CGRP and katacalcin. Whereas calcitonin is a circulating hormone involved in skeletal maintenance, the physiological function of CGRP still remains unclear. In the present study we have compared the biological activity of CGRP with that of calcitonin using three experimental systems. We have demonstrated that both peptides inhibit bone resorption by active rat osteoclasts and thus lower plasma calcium when injected into young rats. In both respects the CGRP homologues (rat, human α and human β) were found to be 100‐ to 1000‐fold less potent than human calcitonin. The effects of the CGRP peptides and calcitonin were only additive. Human CGRP (α) also caused a marked dose‐dependent elevation of bone cyclic AMP levels in mice, somewhat like calcitonin. Though from our studies it would seem reasonably clear that CGRP is weakly agonistic for the calcitonin receptor on the osteoclast to produce effects on bone resorption and plasma calcium, it is still unclear whether the elevation of bone cyclic AMP simply represents an osteoclastic effect or an additional, more important, effect on osteoblasts. It is highly unlikely that CGRP may exert systemic effects on bone. Nevertheless, the peptide may be an important local regulator of bone cell function.
THIXOTROPIC CHANGES IN HUMAN MUSCLE STIFFNESS AND THE EFFECTS OF FATIGUE
Authors: Lakie M. , Robson Lesley G.
Published: December 2014

Two methods have been used to study the stiffness of the relaxed finger musculature after movement followed by various times at rest. The muscles stiffen considerably as the time at rest increases. The time course of this change has been plotted; it continues at a declining rate for at least 30 min. The increased stiffness after resting can be immediately reduced by active or passive movements but not by isometric efforts. These changes characterize a thixotropic system and suggest a long‐term molecular rearrangement in relaxed muscle. Extensive eccentric exercise of the muscles under investigation reduces the overall stiffness and there is a concomitant increase in tremor on movement.
THE ROLES OF HEPATIC NERVES IN THE REDUCTION OF FOOD INTAKE AS A CONSEQUENCE OF INTRAPORTAL SODIUM PROPIONATE ADMINISTRATION IN SHEEP
Authors: Anil M. H. , Forbes J. M.
Published: December 2014

Like other mammals, ruminants can also control their food intake. One of the potential sites where feed‐back signals arise is the liver. We have already shown in our previous study that intraportal administration of propionate depresses intake and that this action is dependent on an intact nerve supply to the liver because sectioning the hepatic plexus abolishes the effect of propionate. In the following work the relative importance and the possible roles of different hepatic nerves were investigated. Three‐hour continuous infusions of sodium propionate or saline into the hepatic portal vein of sheep were carried out following applications of different surgical procedures and food intakes were measured. In experiment 1 bilateral splanchnotomies were sufficient to prevent the effect of propionate on food intake. The subsequent total hepatic denervations also resulted in the removal of the depressing effect of propionate. Experiment 2 was designed to compare the involvement of the splanchnic afferents from the liver and the hepatic vagal afferents. Intraportal propionate was demonstrated to depress feeding in the intact animal whereas splanchnic nerve blockade with local anaesthetic removed this effect. Paradoxically selective hepatic vagotomy also abolished this effect. It was concluded that there may be more than one pathway involved in transmitting information from the liver to the central nervous system. Possible implications of the results are discussed and attempts are made to explain the mechanism of action and compare different theories by other workers.
THE EFFECT OF HYPOXIA ON PLASMA POTASSIUM CONCENTRATION AND THE EXCITATION OF ARTERIAL CHEMORECEPTORS IN THE CAT
Authors: Paterson David J. , Nye Piers C. G. , Estavillo Jaime A.
Published: December 2014

Intra‐arterial recordings of potassium concentration ([K+]a) and arterial chemoreceptor discharge were made in six anaesthetized cats while tracheal PO2 was stepped every 2 min (end‐tidal PO2 ca. 140, 60, 40 and 95 Torr) at constant PCO2 (33 Torr). [K+]a increased hyperbolically from 3·0 mM to 4·5 mM as arterial PO2 was lowered from 95 to 40 Torr. Because the discharge of arterial chemoreceptors is excited by hyperkalaemia as well as hypoxia, the hypoxic discharge of arterial chemoreceptors may have a component mediated by [K+]a. The mechanisms underlying the arterial K+ increase in hypoxia remain unknown.
SODIUM‐DEPLETION‐INDUCED CONTRACTURES IN ISOLATED RAT VAS DEFERENS: POSSIBLE ROLE OF ENDOGENOUS CATECHOLAMINES
Authors: Mishra S. K. , Das P. K. , Sanyal A. K.
Published: December 2014

The mechanism involved in the development of contracture in an isolated smooth muscle in Na+‐depleted saline solution is not clearly understood. Whereas most of the reported studies attribute it to direct myogenic action of Na+ depletion, a few suggested the contracture to be an indirect mechanism through the release of the neurotransmitter from presynaptic nerve endings. The present study employed rat vas deferens and it showed that the slowly developing contracture in Na+‐depleted saline solution was blocked by prior treatment with in vitro prazosin and in vivo reserpine. Prior exposure of the tissue to verapamil caused the development of rhythmic contractions in Na+‐free medium and these rhythmic contractions were blocked by prazosin. Exposure of the tissue to a Ca2+‐free solution abolished the contractures induced by Na+‐free solution. Na+‐depletion increased the sensitivity of the vas deferens to exogenous noradrenaline. It is concluded that the contractures induced by Na+ depletion result from the stimulation of postjunctional α‐adrenoceptors by endogenously released catecholamines from the adrenergic nerve terminals innervating the vas deferens smooth muscle. Further, these contractures result from an influx of extracellular Ca2+ through both voltage‐dependent and receptor‐operated calcium channels.
SODIUM DEPENDENCE OF AMINO ACID‐STIMULATED ACID SECRETION IN THE CONSCIOUS RAT
Authors: Martin V. , Dimaline R.
Published: December 2014

Gastric acid secretion in conscious gastric‐fistulated rats was measured by non‐recirculating constant gastric perfusion, and extragastric autotitration. Luminal L‐amino acids stimulated acid secretion with a potency histidine 〉 alanine 〉 tryptophan. The response to histidine was concentration dependent, and was inhibited by low pH and by low luminal sodium. These results are consistent with the idea that a sodium‐dependent uptake mechanism might, in part, mediate the acid secretory response to intragastric amino acids.
ADVANTAGES OF BURST STIMULATION FOR INDUCING SYMPATHETIC SALIVARY SECRETION IN RATS
Authors: Anderson L. C. , Garrett J. R. , Proctor G. B.
Published: December 2014

Electrical stimulation of the cervical sympathetic nerve trunk delivered at 50 Hz in bursts of 1 s every 10 s, evoked a more copious, uniform and reproducible flow of saliva than when delivered at 10 Hz continuously. This advantage of burst stimulation occurred with parotid secretion and was especially evident with secretion from submandibular glands, where the oedema, commonly seen after stimulating the sympathetic nerve continuously, was avoided. Therefore stimulation in bursts is recommended for obtaining sympathetic salivary responses in rats.
THE EFFECTS OF PANCREATECTOMY ON THE RATES OF GLUCOSE UTILIZATION, OXIDATION AND PRODUCTION IN THE SHEEP FETUS
Authors: Fowden Abigail L. , Hay William W.
Published: December 2014

The effects of fetal pancreatectomy on the uptake and metabolism of glucose were investigated in chronically catheterized sheep fetuses during late gestation by using tracer methodology. Rates of glucose uptake and metabolism were also measured in pancreatectomized fetuses during the infusion of insulin. Pancreatectomy produced hypoinsulinaemia and significantly reduced the rates of fetal glucose utilization and umbilical glucose uptake in comparison to intact fetuses of a similar gestational age. There was no significant alteration in the glucose oxidation fraction after pancreatectomy but because glucose utilization was low in the pancreatectomized fetuses, the rate of fetal glucose oxidation was significantly less after pancreatectomy than in intact animals. No apparent endogenous production of glucose was observed in the pancreatectomized fetuses. Insulin infusion into the pancreatectomized fetuses raised the rates of umbilical glucose uptake and of fetal glucose utilization and oxidation by 40‐50% to values similar to those observed in intact animals. The endogenous production of glucose remained negligible during the infusion of insulin into the pancreatectomized fetuses. There was a net flux of radioactive glucose from the pancreatectomized fetus to the uteroplacental tissues and from the uteroplacental tissues into the uterine circulation. These net fluxes and the rate of placental metabolism of tracer glucose decreased significantly during the infusion of insulin into the pancreatectomized fetus. When all the data were combined, partial correlation analyses of the net uteroplacental uptake of tracer glucose and the fetal concentrations of plasma insulin and blood glucose showed that the fetal arterial glucose concentration was the major influence on the net flux of tracer from the fetus to the uteroplacental tissues. These observations demonstrate that the endogenous concentration of insulin has an important role in regulating glucose metabolism in sheep fetus during late gestation.
EFFECT OF PROTEIN INTAKE ON GASTRIN SECRETION IN RUMINANTS
Authors: Perry K. W. , Weekes T. E. C. , Rooke J. A. , Parker D. S. , Aarmstrong D. G.
Published: December 2014

Plasma gastrin concentrations were measured in portal and peripheral circulations in sheep and in cows in response to feeding diets of varying protein content. Mean plasma gastrin concentrations did not increase in response to feeding at either sampling site in contrast with the known response in non‐ruminants. Plasma gastrin levels were similar when feeding diets of varying protein content to both sheep and cows and also when comparing portal and peripheral concentrations in sheep. Basal jugular venous gastrin concentrations in the cow at 40·5 ± 4·13 pg gastrin 17/ml were lower than values measured in sheep portal blood at 67·6 ± 12·70. The latter, however, was comparable with known values for humans.
GLYCOGEN METABOLISM AND POST‐EXERCISE KETOSIS IN CARBOHYDRATE‐RESTRICTED TRAINED AND UNTRAINED RATS
Authors: Adams J. H. , Koeslag J. H.
Published: December 2014

Liver and muscle glycogen, and blood 3‐hydroxybutyrate concentrations were studied during and for 2 h after treadmill running for 1 h, in 144 carbohydrate‐starved trained and untrained rats. The resting liver glycogen concentration of the trained animals was 227 ± 8 (mean ± S.E.M.) µmol glucosyl units/g wet mass, compared with 162 ± 12 µmol/g in the untrained animals. The muscle glycogen levels were 42 ± 1 and 28 ± 1 µmol/g respectively. Exercise reduced muscle and liver glycogen concentrations by approximately the same absolute amounts in both animal groups, leaving the trained rats with nearly 3 times as much residual glycogen as the untrained animals. There was very little resynthesis of muscle glycogen recovery, but the trained animals replenished approximately 43% of the liver glycogen used during exercise. The blood 3‐hydroxybutyrate concentrations were negatively correlated with the simultaneous liver glycogen concentration of our experimental animals (r = −0·55; P 〈 0·001). It is concluded that trained animals primarily owe their resistance to post‐exercise ketosis to their large stores of glycogen.
PARASYMPATHETIC ACTIVATION OF AMYLASE SECRETION IN THE INTACT AND SYMPATHETICALLY DENERVATED RAT PAROTID GLAND
Authors: Asking B. , Proctor G. B.
Published: December 2014

Observations were made on amylase secretion from the rat parotid gland induced by parasympathetic nerve stimulation in vivo. In spite of a low salivary amylase concentration a large total amylase output, equivalent to 36% of initial gland content, was found on prolonged activation (5 Hz, 120 min). However, no decrease in gland amylase content was found, which indicates that the output of amylase was balanced by synthesis. We suggest that prolonged, parasympathetically induced amylase secretion is dependent on activation of amylase synthesis and that the secretion is mainly of non‐granular origin. Parasympathetic nerve stimulation produced an even larger amylase output from sympathectomized glands. Even under these conditions gland amylase content was unchanged and no obvious degranulation was found when the glands were examined after stimulation. This is in marked contrast to the decrease in amylase content and to the degranulation which are found after sympathetic activation.
MECHANISMS AND SIGNIFICANCE OF CALCIUM ENTRY AT POSITIVE MEMBRANE POTENTIALS IN GUINEA‐PIG VENTRICULAR MUSCLE CELLS
Authors: Terrar D. A. , White E.
Published: December 2014

Possible mechanisms for calcium entry at positive membrane potentials were investigated in single cells isolated from guinea‐pig ventricular muscle. The cells were voltage clamped and contraction was measured by an optical technique. When prolonged (200 ms to 2 s) depolarizations at +60 mV were applied, contraction amplitude increased with pulse duration, in contrast to the contraction at 0 mV. When a ‘pre‐pulse’ to 0 mV was applied for 200 ms to inactivate current through ‘L‐type’ calcium channels, contraction nevertheless increased with membrane potential during a subsequent test pulse applied over the range ‐40 to +60 mV. Contraction during the test pulse at +60 mV was abolished when extracellular calcium was reduced to zero. This effect developed more rapidly than abolition of the contraction in response to the pre‐pulse to 0 mV. Reduction of extracellular calcium from 2·5 to 1 mM reduced the contraction at +60 mV to a greater extent than that at 0 mV and caused an inward shift in the current at +60 mV. Nifedipine (5 µM) substantially reduced the contraction during the test pulse to 0 mV but had little effect on the contraction at +60 mV. Conversely, dodecylamine (20 µM) caused little or no decrease in the contraction at 0 mV but substantially reduced the contraction at +60 mV. Following a conditioning pre‐pulse to 0 mV the contraction at +60 mV was not consistently reduced by exposure to 3 µM‐ryanodine. The interpolation of a single 200 ms pulse to +60 mV in a train of pulses to 0 mV potentiated the following contraction to 0 mV. This potentiation decayed over the first four steps to 0 mV following an interpolated pulse and increased with the voltage of the interpolated pulse over the range ‐20 to +60 mV. Potentiation was abolished on exposure to 3 µM‐ryanodine. These observations are consistent with entry of calcium at positive membrane potentials through voltage‐dependent, non‐inactivating pathways which are insensitive to nifedipine but inhibited by dodecylamine. The observations support the hypothesis that calcium entry via this mechanism may contribute, at least under some conditions, to the loading of intracellular stores of calcium during the late plateau of the action potential, and thus influence subsequent contraction. Calcium entry through Na+‐Ca2+ exchange is a possibility which would allow calcium entry to increase over the range of membrane potentials at which contraction was increased. However, additional calcium entry through other nifedipine‐insensitive pathways, such as calcium‐activated non‐selective channels, cannot be excluded.