bluuebunny/crossref_metadata_2025 huggingface dataset:
ON THE GENERAL EFFECTS OF EXPOSURE TO RADIUM ON METABOLISM AND TUMOUR GROWTH IN THE RAT AND THE SPECIAL EFFECTS ON TESTIS AND PITUITARY
Authors: Mottram J. C. , Cramer W.
Published: December 2014

When small doses of radiation from radium are applied over long periods to young male rats certain general changes are produced. These animals put on weight more rapidly than the controls and become very obese. The testes show intense atrophy of the seminiferous tubules and hypertrophy of the interstitial cells. The pituitary gland also shows changes in all three parts of the gland. The experimental analysis of these phenomena leads to the following conclusions :

The primary effect is the atrophy of the seminiferous tubules. The resulting shrinkage of these tubules allows the interstitial cells to hypertrophy. Comparison with the effects of castration shows that the elimination of the functional activity of the seminal epithelium does not lead to obesity. It only produces certain definite changes in the anterior portion of the pituitary gland. The obesity is, in this condition at any rate, the direct or indirect result of the hypertrophy of the interstitial cells, which also produces changes in the intermediate and posterior portions of the pituitary.

The observations show that the two component tissues of the testis, the spermatogenetic tissue and the interstitial tissue, have two distinct and independent effects on the organism, and that of these two effects that of the interstitial cells is the more profound one. Even in the absence of the spermatogenetic tissue they furnish an internal secretion which produces definite changes in the intermediate and nervous portions of the pituitary and which, through its action on this gland and possibly also some other endocrine organs, affects the metabolism. These effects on endocrine organs and metabolism represent probably the actual basis of the general changes stated by Steinach to occur after implantation of testicular tissue and, when induced in a senile organism, described vaguely as rejuvenescence.

The interrelationship of obesity and sterility is discussed and an explanation is given of the possible mode of production of the symptom complex of dystrophia adiposo‐genitalis.

Resection of the vasa deferentia produces no very obvious changes in either testis or pituitary, and does not produce obesity.

Rats which have been rendered obese by exposure to radium are more resistant to the growth of transplantable tumours.
THE EFFECT ON THE STOMACH OF STIMULATION OF THE PERIPHERAL END OF THE SPLANCHNIC NERVE
Authors: M'Crea E. D'A. , M'Swiney B. A.
Published: December 2014

Stimulation of the peripheral cut end of either splanchnic nerve will, if the organ be in a state of “hypotonus,” bring about a rise in the entogastric pressure. Should the viscus be initially in a condition of “hypertonus” a fall of entogastric pressure takes place and existing movements cease.

Our chief results may be summarised as follows:—

1. The primary effect of stimulation of the peripheral cut end of the splanchnic nerve on the stomach is dependent on the existing condition of the peripheral mechanism (“tonus”), and may be inhibitor or augmentor.

2. The inhibitor or augmentor effect may involve both “tonus” and movement.

The expenses of this investigation were in part defrayed from a grant from the Government Grant Committee of the Royal Society.
A METHOD OF DEMONSTRATING THE HUMORAL TRANSMISSION OF THE EFFECTS OF CARDIAC VAGUS STIMULATION IN THE FROG
Authors: Bain W. A.
Published: December 2014

A method is described whereby the humoral transmission of the effects of cardiac vagus stimulation in the frog may be strikingly demonstrated.
THE MECHANISM OF CAPILLARY CONTRACTION
Authors: Sanders A. G. , Ebert R. H. , Florey H. W.
Published: December 2014

(1) From this series of experiments carried out under good optical conditions, in one case as good as present lenses allow, we conclude that capillary contraction occurs in the rabbit's ear‐chamber, that this contraction is under the control of the sympathetic nervous system, and that endothelial swelling causes the obliteration of the vessels. No positive evidence was obtained of the participation of Rouget cells in this contraction.

(2) “Spikes” on the endothelium of slightly injured veins have been noted. Red corpuscles hang on these, often for several seconds.

The chambers have been made in the laboratory by Mr. S. W. Bush, to whose skill we are greatly indebted. Mr. J. Kent has had charge of the animals. The drawing is by Mr. H. Axtell.
PULMONARY VASOMOTOR RESPONSES OF ISOLATED PERFUSED CAT LUNGS TO ANOXIA AND HYPERCAPNIA
Authors: Duke Helen N.
Published: December 2014

1. A method for perfusing isolated cats' lungs with the animal's own heparinized blood is described, with some observations on the condition of the lungs during and after perfusion.

2. The pulmonary vasomotor responses to inhalation of various gas mixtures have been studied during perfusion of the pulmonary vessels at constant volume inflow.

3. Inhalation of gas mixtures containing 5–10 per cent. CO2 produces pulmonary vasoconstriction, as shown by an increase of pulmonary arterial pressure.

4. Inhalation of gas mixtures containing less than 15 per cent. O2 also produces a pressor response.

5. Ventilation of the lungs with pure O2 has no effect under the conditions of the experiments.

6. Ventilation of the lungs with pure neon or H2 produces similar effects to that produced by pure N2.

7. The pulmonary vasomotor responses to CO2 and O2 lack are not abolished by dihydroergotamine or atropine.
Temporary loss of activity prevents the increase of motor unit size in partially denervated rat soleus muscles.
Authors: Connold A L , Vrbová G
Published: December 2014

1. The effects of temporary short‐term paralysis on changes of motor unit size and amount of sprouting after partial denervation of the rat soleus were studied. 2. Two to ten months after section of the L5 ventral ramus combined with subsequent treatment with alpha‐bungarotoxin (BTX) the tension developed by the operated muscle was 39 +/‐ 8% (S.E.M., n = 8) of control unoperated soleus muscles. This is much less than the tension produced by partially denervated, NaCl‐treated or untreated muscles which was 66 +/‐ 9% (S.E.M., n = 5) and 66 +/‐ 12% (S.E.M., n = 5) respectively. The smaller tension developed by the BTX‐treated muscles was due to the relatively small size of their motor units. 3. The mean increase of tension output of individual motor units after partial denervation and treatment with NaCl when compared with controls was 194 +/‐ 15% (S.E.M., n = 4) while in the paralysed muscle this value was only 118 +/‐ 15% (S.E.M., n = 8). This reduced expansion of motor unit size in the BTX‐treated soleus was not caused by a decrease of the size of the muscle fibres. Thus a brief temporary paralysis prevents the expansion of motor unit territory that normally occurs in partially denervated muscles. 4. Examination of the innervation pattern and incidence of sprouting revealed that in partially denervated NaCl‐treated muscles 24 +/‐ 4% (S.E.M., n = 4) of endplates was contacted by either terminal or collateral sprouts, whereas in the BTX‐treated muscles only 5 +/‐ 2% (S.E.M., n = 3) of endplates had been contacted by sprouts. Treatment with BTX alone, without partial denervation, did not affect the tension output of the muscles, but caused 8 +/‐ 5% (S.E.M., n = 3) of the endplates to become innervated by collateral sprouts, as compared to only 3 +/‐ 2% (S.E.M., n = 3) in controls.
Adenosine triphosphate‐evoked currents in cultured neurones dissociated from rat parasympathetic cardiac ganglia.
Authors: Fieber L A , Adams D J
Published: December 2014

1. The excitatory response of cultured neurones of rat parasympathetic cardiac ganglia to extracellular adenosine 5'‐triphosphate (ATP) was examined using the whole‐cell isolated membrane patch recording configurations of the patch clamp technique. The short latency between ATP application and activation of the membrane current (less than 20 ms) suggests a direct coupling between purinergic receptor and ion channel. The response was maintained during exposure to ATP suggesting that receptor desensitization is not a factor in current decay. 2. The current‐voltage (I‐V) relationship for macroscopic ATP‐evoked currents showed strong inward rectification in the presence and absence of external divalent cations and a reversal potential of +10 mV (NaCl outside, CsCl inside). Unitary ATP‐activated currents in cell‐attached membrane patches exhibited a linear (ohmic) I‐V relationship with a slope conductance of approximately 60 pS. 3. The order of agonist potency for the purinergic receptor‐mediated response was 2‐methylthioATP = ATP greater than ADP greater than AMP greater than adenosine = alpha,beta‐methylene ATP greater than beta,gamma‐methylene ATP, a sequence consistent with a P2y receptor subtype. ATP‐evoked currents were attenuated by alpha,beta‐methylene ATP (IC50 approximately 10 microM) and reversibly inhibited in a dose‐dependent manner by Reactive Blue 2 (Kd = 1 microM). 4. The amplitude of the ATP‐evoked current was dependent on the extracellular Na+ concentration. The direction of the shift in reversal potential when NaCl was replaced with mannitol indicated that the purinergic receptor channel is cation selective. The cation permeability relative to Na+ followed the ionic selectivity sequence Ca2+ (1.48) greater than Na+ (1.0) greater than Cs+ (0.67). Anions were not measurably permeant. 5. ATP and ACh‐evoked responses in rat intracardiac neurones are mediated by distinct receptor channels. The ATP‐activated channels in cardiac neurones may contribute to non‐cholinergic, non‐adrenergic neurotransmission and mediate, in part, the vagal innervation of the mammalian heart.
Force decline due to fatigue and intracellular acidification in isolated fibres from mouse skeletal muscle.
Authors: Lännergren J , Westerblad H
Published: December 2014

1. Single, intact muscle fibres from the flexor brevis foot muscle of the mouse have been fatigued at 25 degrees C by 350 ms, 70 Hz stimulation trains, initially delivered every 3.8 s and then at stepwise decreasing intervals until tension was down to about 30% of the original (Po). Rested fibres generated a specific force of 372 +/‐ 8.4 kPa (mean +/‐ S.E.M., n = 25). 2. Endurance, defined as time to attain 0.5 Po, varied from 2.5 to 24 min, with the majority of fibres falling in the range 4‐8 min, corresponding to 70‐160 tetani. In all fibres where it was followed, tension recovery after cessation of stimulation was 90% or better. 3. Tetanic force declined in a characteristic way during fatiguing stimulation: initially tension fell to about 0.85 Po during eight to fourteen tetani (phase 1), then followed a long period of nearly steady tension generation (phase 2) and finally there was a rapid force decline (phase 3). 4. Caffeine (15 or 25 mM) caused a slight potentiation of tetanic force in the rested state (4.7 +/‐ 0.9%, n = 21) and slowed relaxation. No change in resting tension was seen with caffeine at concentrations up to 25 mM. 5. Caffeine (15‐25 mM) caused a rapid and dramatic increase in tetanic force when applied to severely fatigued fibres: force output rose from 29.8 +/‐ 1.5 to 82.5 +/‐ 1.2% (n = 13) of Po. During phase 2 force potentiation with caffeine was much smaller. 6. A 10 s pause resulted in a large, transient force increase when imposed during phase 3 but had little effect on force production during phase 2. 7. Intracellular acidosis, induced by superfusion with Tyrode solution gassed with 30% CO2 instead of the normal 5% (extracellular pH 6.5 vs. 7.3), resulted in a fall in tetanic tension to about 0.85 Po (n = 7). This depression could to some extent be counteracted by 15 mM‐caffeine, which brought tension back to about 0.90 Po. 8. It is concluded that there are at least two mechanisms for force decline during fatiguing stimulation: one which manifests itself early and is likely to be related to cross‐bridge function and another representing deficient Ca2+ handling which becomes prominent at a later stage. For severe fatigue (0.3 Po) the latter mechanism is dominant.
K+ and Cl‐ currents in enterocytes isolated from guinea‐pig small intestinal villi.
Authors: Sepúlveda F V , Fargon F , McNaughton P A
Published: December 2014

1. The whole‐cell configuration of the patch‐clamp technique has been used to investigate the conductance properties of villus enterocytes isolated from guinea‐pig small intestinal epithelium. 2. With near physiological ionic gradients inward and outward rectification was observed in the hyperpolarizing and depolarizing voltage domains respectively. 3. Replacement of intra‐ and extracellular K+ with N‐methyl‐D‐glucamine (NMG) eliminated inward rectification but did not alter outward currents. In symmetrical low Cl‐ solutions outward currents were reduced but inward rectification was not affected. Under these conditions increases in extracellular K+ shifted both the current‐voltage relation and the extrapolated reversal potential as expected for a K(+)‐selective current. 4. The inwardly rectifying nature of the K+ current observed here remained unaltered after chelation of internal Mg2+ with ATP or EDTA. 5. Extracellular application of 5 mM‐Ba2+ or 50 micrograms ml‐1 of the venom of the scorpion Leiurus quinquestriatus abolished the inward K+ current, while 5 mM‐extracellular tetraethylammonium (TEA) had little effect. 6. The current remaining in the presence of symmetrical Cl‐ solutions and in the complete absence of K+ rectified outwardly and reversed at 0 mV. The anionic nature of this current was confirmed by replacing Cl‐ with different anions. SCN‐ and Br‐ carried more current than Cl‐, while F‐ and gluconate were less permeant. 7. Anionic currents of villus guinea‐pig enterocytes were not stimulated by cyclic AMP and were strongly and reversibly inhibited by the Cl‐ channel blocker 5‐nitro‐2‐(3‐phenylpropylamino) benzoic acid (NPPB, 10(‐5) M). 8. The inwardly rectifying K+ current described here shares some, but not all, characteristics with others previously described. It is postulated that this conductance might function to couple K+ permeability and the Na(+)‐K+ pump rate in enterocytes. Absorption of chloride may be mediated by the Cl‐ channels.
The measurement of ox corneal swelling pressure by osmometry.
Authors: Hodson S , O'Leary D , Watkins S
Published: December 2014

1. Ox corneal stromal swelling pressure (gel pressure) may be measured by osmometry: polyethylene glycol of nominal molecular mass 10,000 Da (PEG 10K) is a suitable non‐penetrating solute. 2. Corneal hydrations equilibrate within 4 h of exposure to 154 mM‐NaCl including various concentrations (2‐8%) of PEG 10K, providing that the epithelium covers the anterior surface and Descemet's membrane covers the posterior surface. At equilibrium hydration, corneal gel pressure equals the external osmotic pressure contributed by PEG 10K. 3. The osmotic pressure of PEG 10K may be calibrated using Descemet's membrane as the semi‐permeable membrane. 4. Corneal gel pressure decreases with increasing hydration. 5. The relationship may be adequately explained by the Donnan theory of corneal swelling with a fixed negative matrix charge of 39.5 +/‐ 0.8 mequiv l‐1 at physiological hydration of 3.2 at this salt concentration (154 mM‐NaCl).
Dual effect of the local anaesthetic penticainide on the Na+ current of guinea‐pig ventricular myocytes.
Authors: Gruber R , Vereecke J , Carmeliet E
Published: December 2014

1. The effect of the local anaesthetic penticainide (2‐alkyl‐(4‐dialkylamino)‐2‐pyridyl‐butyramide) on macroscopic and single‐channel sodium current (INa) of guinea‐pig ventricular myocytes was studied with the patch‐clamp technique in the cell‐attached and inside‐out mode. 2. Penticainide (3‐60 microM) affected the INa from the outside as well as from the cytoplasmic side. 3. Peak INa was reduced by penticainide at concentrations of 6, 30 and 60 microM, and this decrease of peak INa was more pronounced when the holding potential was more negative. Despite a reduction of peak INa, the time integral of the Na+ current was not changed (60 microM) or was even enhanced (6 microM), and this enhancement became more pronounced at less negative potentials. 4. At a concentration of 3 microM, penticainide increased both the time integral of the current and peak INa. 5. The shape of the steady‐state current‐voltage relationship and the steady‐state inactivation curve were not influenced by penticainide. 6. In pronase‐modified inside‐out patches penticainide reduced INa at the beginning of a depolarizing pulse to the same extent as at the end (400 ms), indicating a very fast blockade of the bursting Na+ channel. The most prominent effects on pronase‐modified single‐channel INa were an increase of sweeps without activity, and a fast, repeatedly occurring block (flickering) of the bursting Na+ channel. 7. The amplitude of the unitary current was not altered. 8. It is concluded that penticainide blocks the open Na+ channel, and in addition shows the macroscopic inactivation.
Dependence of cytosolic calcium in differentiating rat pheochromocytoma cells on calcium channels and intracellular stores.
Authors: Reber B F , Reuter H
Published: December 2014

1. The rat clonal pheochromocytoma cell line (PC12) was used to study changes in the free intracellular Ca2+ concentration [( Ca2+]i) that are related to the distribution of L‐type (dihydropyridine‐sensitive) and N‐type (omega‐conotoxin‐sensitive) calcium channels during nerve growth factor (NGF)‐induced outgrowth of neurites. Changes in [Ca2+]i during K+ depolarization were recorded by means of Fura‐2 single‐cell microfluorimetry. 2. The basal [Ca2+]i of cells at rest was not altered by long‐term treatment with NGF, neither in the cell bodies nor in the growth cones. K+ depolarization of the cells caused a rise in [Ca2+]i. 3. The dihydropyridine (DHP) nifedipine alone, or together with omega‐conotoxin (omega‐CgTX), were similarly effective in inhibiting the K(+)‐induced increase in [Ca2+]i in untreated and NGF‐treated cell bodies, arguing for a preferential distribution of L‐type Ca2+ channels in this cell area. By contrast, after 6‐7 days exposure to NGF the K(+)‐induced initial transient rise of [Ca2+]i in growth cones was very sensitive to omega‐CgTX, whereas nifedipine affected only the sustained rise. 4. PC12 cells also contain caffeine‐ and inositol trisphosphate (IP3)‐sensitive intracellular Ca2+ stores. Addition of 30 mM‐caffeine caused a fast transient rise in [Ca2+]i. The extent of filling of the caffeine‐sensitive pool affected basal [Ca2+]i. These Ca2+ storage sites were empty under normal culture conditions. However, a single K+ depolarization caused filling of the stores, followed by spontaneous depletion (50% in about 5 min) after wash‐out of high [K+]o. When the caffeine‐sensitive stores were empty, the rise in [Ca2+]i was attenuated during submaximal depolarization. Caffeine‐sensitive Ca2+ stores were also present in some growth cones, though with much smaller capacities than in cell bodies. 5. Mobilization of Ca2+ from the IP3‐sensitive store, by bradykinin exposure, was found to be independent of the caffeine‐sensitive pool. There was no apparent ‘cross‐talk’ between both Ca2+ pools. 6. We conclude that changes in [Ca2+]i in cell bodies depend on both membrane Ca2+ channels and intracellular Ca2+ stores. During NGF‐induced differentiation there is a predominance of N‐type Ca2+ channels in growth cones, while Ca2+ stores are of minor importance in these structures.
Release of glucose from the liver of fetal and postnatal sheep by portal vein infusion of catecholamines or glucagon.
Authors: Apatu R S , Barnes R J
Published: December 2014

1. The blood flow to the liver in fetuses near term, newborn and adult sheep was measured by the Fick principle, using radionuclide‐labelled plastic microspheres, before and during infusion of adrenaline, noradrenaline or glucagon. 2. Glucose output and lactate consumption by the liver in sheep of each age group were calculated by application of the Fick principle using the concentration gradients of these metabolites measured in blood samples obtained, simultaneously with blood flow measurements, from catheters chronically implanted in the inflow and outflow vessels of the liver. 3. Catecholamines were infused into the portal vein of fetuses near term at a rate comparable with that at which they are known to be secreted in the sheep fetus during moderate to severe hypoxia. The cardiovascular and metabolic responses to these infusions were found to be comparable with those that occur in the fetus during hypoxia. 4. Catecholamines increased glucose output from the liver in all except the immediate post‐partum animals. Catecholamines were less effective than glucagon in promoting glucose release. The mean increments in glucose output during adrenaline infusion were 0.055 +/‐ 0.015 mmol min‐1 (100 g liver)‐1 in the fetus, 0.122 +/‐ 0.024 mmol min‐1 (100 g)‐1 in the 2‐week‐old lambs, 0.078 +/‐ 0.019 mmol min‐1 (100 g)‐1 in young lambs and 0.049 +/‐ 0.012 mmol min‐1 (100 g)‐1 in the adult sheep. During glucagon infusion the mean glucose output increments were 0.146 +/‐ 0.023 mmol min‐1 (100 g)‐1 in the fetus, 0.274 +/‐ 0.085 mmol min‐1 (100 g)‐1 in the 2‐week‐old and young lambs and 0.180 +/‐ 0.054 mmol min‐1 (100 g)‐1 in the adult. Adrenaline was more potent than noradrenaline, suggesting that the major glycogenolytic response might be beta‐receptor mediated. 5. In the immediate newborn period the output of glucose from the liver was high (0.20 +/‐ 0.05 mmol min‐1 (100 g liver)‐1 and was not statistically significantly increased by infusion either of glucagon or of catecholamines which resulted in similar increments of glucose output of about 0.128 +/‐ 0.133 mmol min‐1 (100 g)‐1. It is probable that the high output of glucose reflected the high endogenous circulating levels of catecholamines and glucagon in these animals at birth and that further infusions failed to add significantly to the already near‐maximal glucose release.(ABSTRACT TRUNCATED AT 400 WORDS)
Responses observed in individual arterioles and venules of rat skeletal muscle during systemic hypoxia.
Authors: Mian R , Marshall J M
Published: December 2014

1. In rats anaesthetized with Saffan, responses induced in individual arterial and venous vessels of the spinotrapezius muscle by systemic hypoxia (breathing 12 or 6% O2 for 3 min) were directly observed by in vivo microscopy. 2. Both 12 and 6% O2 induced gradual tachycardia and a fall in arterial pressure. Concommitantly, in each section of the vascular tree, some vessels showed a gradual increase in diameter, others, a gradual decrease. 3. During 12% O2, mean diameter changes were graded from mean increases of approximately 2% in main arteries (resting diameter 40‐90 microns) to approximately 20% in terminal arterioles (7‐13 microns) and ranged from mean increases of 5‐8% in collecting and secondary venules (9‐18 microns, 18‐30 microns), to a decrease of approximately 2% in main veins (65‐130 microns). 4. During 6% O2, constrictor responses were more common in arterial vessels. Thus, mean changes amounted to diameter decreases of less than 5% in main arteries and secondary arterioles (13‐18 microns), and increases of approximately 5% in primary arterioles (22‐50 microns) and terminal arterioles. By contrast, diameter increases predominated in venous vessels being graded from approximately 20% in collecting venules to approximately 2% in main veins. 5. In seventeen rats, 6% O2 was administered for eight 3 min periods separated by 30 min control periods. The changes evoked in arterial pressure and heart rate were consistent throughout. Diameter changes evoked in individual arterial and venous vessels were consistent in the first two hypoxic periods. However, diameter changes in the third and successive periods were significantly different from those recorded in the first period: increases in diameter became more common and pronounced. 6. These changes in vessel diameter, especially their variability, are considered in relation to recordings made previously of changes in gross blood flow and vascular conductance of limb muscle during systemic hypoxia.
Muscarinic receptor is coupled with a cation channel through a GTP‐binding protein in guinea‐pig chromaffin cells.
Authors: Inoue M , Kuriyama H
Published: December 2014

1. The ionic current evoked by muscarinic receptor agonists was investigated in dispersed chromaffin cells of the guinea‐pig adrenal medulla using the whole‐cell version of the patch‐clamp procedure. 2. Muscarine or oxotremorine (0.03‐10 microns) produced an inward current associated with an increase in current noise at a holding potential of ‐40 mV. The relationship between current and oxotremorine concentration fitted well to a rectangular hyperbole with an apparent dissociation constant (KA) of 0.23 micron. 3. The muscarinic antagonists pirenzepine (0.1 micronM) and AF‐DX 116 (0.3 microM) shifted the dose‐response curve to the right in a parallel manner. Dissociation constants (KB) for pirenzepine and AF‐DX 116 were estimated to be 50 and 70 nM, respectively. 4. The current‐voltage relation for the current induced by muscarine had a negative slope below ‐30 or ‐20 mV, and the current reversed its polarity at 0.4 +/‐ 0.8 mV (n = 4) in standard salt solution. Removal of Mg2+ or Ca2+ from the perfusate did not modify the muscarinic current‐voltage relationship. 5. When Na+ in the bath solution was replaced with Tris, the muscarinic current‐voltage relationship shifted to the left (the hyperpolarizing direction); the current reversed its polarity at ‐18.7 +/‐ 1.2 mV in a solution containing 72 mM‐Na+ (three cells) and at ‐57.5 +/‐ 2.7 mV in nominally Na(+)‐free solution (three cells). When Ca2+ was replaced by Mg2+, in Na(+)‐free solution, an inward current was not evoked by muscarinic stimulation. 6. Tetraethylammonium (TEA; 0.03‐3 mM) reduced the muscarinic current at ‐40 mV, and the KD value was 0.34 mM with a Hill coefficient of 1. Barium (4 mM) reduced the current to 0.69 +/‐ 0.06 of control (n = 3). 7. When the recording electrodes contained guanosine‐5'‐O‐(3‐thiophosphate) (GTP gamma S, 100 microM), an inward current developed at ‐55 mV during the first few minutes after breaking into the cell interior. This inward current was associated with an increase in noise and was not larger at ‐70 mV than at ‐55 mV; it reached a peak value about 3‐4 min after breaking into the cell interior and then declined over the next 2‐3 min. 8. Muscarinic agonists had no effect in those cells in which intracellular GTP gamma S had first evoked a transient inward current. The inward current caused by nicotine was unaffected by intracellular GTP gamma S.(ABSTRACT TRUNCATED AT 400 WORDS)
Dissociation between intracellular Ca2+ and modulation of [3H]noradrenaline release in chick sympathetic neurons.
Authors: Przywara D A , Bhave S V , Bhave A , Wakade T D , Wakade A R
Published: December 2014

1. We studied the relation between cyclic AMP, intracellular Ca2+ concentration and release of [3H]noradrenaline ([3H]NA) in sympathetic neurons cultured from chick embryos. 2. Forskolin (10 microM) and vasoactive intestinal polypeptide (VIP, 3 microM) increased cellular levels of cyclic AMP 8‐ and 3‐fold, respectively, either in the absence or presence of electrical stimulation. Electrical stimulation (1 Hz for 10 s) alone had no effect on cyclic AMP levels. 3. Electrically evoked (1 Hz for 10 s) release of [3H]NA was facilitated by 10 microM‐forskolin, 3 microM‐VIP and by the non‐hydrolysable cyclic AMP analogue, 8‐bromoadenosine 3': 5'‐cyclic monophosphate (8‐Br‐cyclic AMP). The inactive analogue of forskolin, dideoxyforskolin, had no effect on [3H]NA release. 4. The stimulation‐evoked release of [3H]NA was completely inhibited by the neuronal blocking drugs guanethidine (1 microM) and bretylium (3 microM). 5. Whole‐cell voltage‐clamp studies showed that forskolin and VIP did not facilitate and guanethidine and bretylium did not block voltage‐activated Ca2+ currents in the cell bodies of sympathetic neurons. 6. Fluorescence measurements using the Ca(2+)‐sensitive dye Indo‐1 revealed that forskolin and guanethidine had no effect on the electrically stimulated increase in intracellular Ca2+ concentration recorded from the cell bodies and the growth cones. 7. We conclude that release of [3H]NA can be enhanced or blocked without affecting the increase in intracellular Ca2+ concentration produced by electrical stimulation. Therefore, it is possible that pharmacological agents enhance or depress the release of [3H]NA by acting on steps of exocytosis that are down‐stream from Ca2+ mobilization.
Large conductance calcium‐activated non‐selective cation channel in smooth muscle cells isolated from rat portal vein.
Authors: Loirand G , Pacaud P , Baron A , Mironneau C , Mironneau J
Published: December 2014

1. Membrane currents of isolated smooth muscle cells from rat portal vein were studied using the whole‐cell patch‐clamp technique. 2. In addition to the Ca(2+)‐dependent Cl‐ current, single‐channel activities were recorded in response to external applications of 10 mM‐caffeine, in the absence of EGTA in the pipette solution. The conductance of this novel type of channel was around 200 pS for membrane potentials ranging from ‐100 to +60 mV. 3. The single‐channel activities were also induced by external application of noradrenaline (10(‐5)M) or acetylcholine (10(‐5)M), by Ca2+ entry through voltage‐dependent Ca2+ channels, and by intracellular application of ryanodine (10(‐5)M). The caffeine‐activated single‐channel currents disappeared when 10 mM‐EGTA was added to the pipette solution or after replacement of external Ca2+ with Ba2+. These results show that these channels are Ca2+ dependent. 4. Alterations of the Cl‐ equilibrium potential did not produce any change in the reversal potential of the caffeine‐activated single‐channel current indicating that it was not carried by Cl‐ ions. The value of the reversal potential was about +10 mV, irrespective of the CsCl‐, KCl‐ or NaCl‐containing solutions used to fill the pipette. This observation indicates that the channel was equally permeable to these monovalent cations. 5. Caffeine activated single‐channel currents when cells were bathed in 90 mM‐Ba2+ plus 1 mM‐Ca(2+)‐ or 91 mM‐Ca(2+)‐containing solutions, showing that divalent cations permeate the channels. The permeability for Ca2+ over Na+ was high as the ratio PCa/PNa was estimated to be 21. 6. Single‐channel activities induced by caffeine were not modified by Ca2+ channel blockers such as dihydropyridines and phenylalkylamines. 7. It is concluded that portal vein smooth muscle cells possess Ca(2+)‐activated nonspecific channels which are highly permeable to Ca2+ ions.
Kinetic properties and Na+ dependence of rheogenic Na(+)‐HCO3‐ co‐transport in frog retinal pigment epithelium.
Authors: la Cour M
Published: December 2014

1. Na(+)‐HCO3‐ co‐transport across the retinal membrane of the frog retinal pigment epithelium was studied by means of double‐barrelled pH‐selective microelectrodes. Transient changes in the intracellular pH were monitored in response to abrupt changes in the Na+ concentration on the retinal side of the epithelium. 2. The experiments were performed as follows. The Na(+)‐HCO3‐ co‐transport was inhibited by perfusing the retinal side of the epithelium with a Na(+)‐free solution. The co‐transport was then stimulated by changing the perfusate from the Na(+)‐free solution to a solution which contained from 5 to 110 mM‐Na+. The resulting inward Na(+)‐HCO3‐ co‐transport produced an intracellular alkalinization, the initial rate of which was used to calculate the initial rate of Na(+)‐HCO3‐ co‐transport, JHCO3‐. 3. The Na+ dependence of the Na(+)‐HCO3‐ co‐transport was studied at two different values of extracellular pH (7.40 and 7.10), at constant extracellular HCO3‐ concentration (27.5 mM) and at two different extracellular HCO3‐ concentrations (27.5 mM and 55 mM) at constant extracellular pH (7.40). In these experiments, the calculated values of JHCO3‐ followed single Michaelis‐Menten kinetics with respect to the extracellular Na+ concentration. 4. The data are consistent with a model in which the co‐transporter has a single binding site for the Na+ ion with an apparent affinity constant (apparent Km) of 37 mM. The apparent affinity constant for Na+ was independent of the extracellular concentration of CO3(2‐) in the range of 16‐65 microM, and of the extracellular HCO3‐ concentration in the range 27.5‐55 mM. 5. The NaCO3‐ ion‐pair hypothesis, in which sodium binds to the co‐transporter and is translocated across the cell membrane as the NaCO3‐ ion pair, was analysed. For stoichiometries 1:2 and 1:3 of the Na(+)‐HCO3‐ co‐transport, the NaCO3‐ ion‐pair hypothesis was found incompatible with the data. 6. The intracellular buffer capacity as measured by the CO2 method was 15 mM.
Conductance and kinetic properties of single nicotinic acetylcholine receptor channels in rat sympathetic neurones.
Authors: Mathie A , Cull‐Candy S G , Colquhoun D
Published: December 2014

1. The unitary conductance of nicotinic acetylcholine (ACh) receptor channels in rat sympathetic neurones has been studied. Conductance estimates varied from 26‐48 pS with a mean of 36.8 pS in 1 mM‐Ca2+. The main conductance level varied from patch to patch and the presence (or absence) of additional conductance levels also varied. 2. The channels showed large open channel noise and experiments with 300 mM‐NaCl in the patch pipette substantially increased the open channel noise. The appearance of detectable step‐like transitions within this noise strongly suggested the existence of closely spaced discrete levels. 3. Removal of divalent cations from the external solution increased the unitary channel conductance. Altering the main permeant ion in divalent‐free solutions gave the following conductance sequence: K+ (93 pS) greater than Cs+ (61 pS) greater than Na+ (51 pS) greater than Li+(23 pS). 4. Replacement of Na+ by Cs+ in the external solution considerably reduced the current evoked by ACh in whole‐cell recordings and the channel‐opening frequency in outside‐out patches. 5. The kinetic properties of channels activated by ACh and 1,1‐dimethyl‐4‐phenylpiperazinium iodide (DMPP) were also studied. At low concentrations of ACh and DMPP the gap distributions were complex and best fitted by the sum of four exponential components. Individual activations (bursts) were interrupted by the two shortest closed periods the briefer of which had time constants of 36 microseconds for ACh and 67 microseconds for DMPP. 6. The distribution of burst lengths had two components for each agonist, each component making up about 50% of the total area under the distribution. For ACh, the time constant of the longer component (12.2 ms) was similar to the decay time constant of excitatory postsynaptic potentials (EPSCs) at similar temperature and potential. For DMPP the time constant of the longer component was 17.6 ms. 7. The relative number of brief gaps per long burst was much larger for ACh than for DMPP. Therefore the corrected mean open time for ACh (0.86 ms) was much shorter than that for DMPP (2.3 ms). 8. In terms of receptor mechanism, the values of the channel opening equilibrium constant (beta/alpha) estimated from these numbers (ACh, 23; DMPP, 25) suggest that both agonists are efficaceous. 9. DMPP is a potent blocker of the channel with an equilibrium dissociation constant (KB) of around 50 microM and blockage gaps of around 1 ms duration. ACh also blocks the channel but with a higher KB of around 470 microM.(ABSTRACT TRUNCATED AT 400 WORDS)
Beta‐adrenergic and muscarinic regulation of the chloride current in guinea‐pig ventricular cells.
Authors: Tareen F M , Ono K , Noma A , Ehara T
Published: December 2014

1. Single guinea‐pig ventricular cells were voltage clamped using the patch clamp method combined with the pipette‐perfusion technique. The voltage‐dependent current systems were mostly blocked, and the background membrane conductance was measured by applying ramp pulses. 2. beta‐Adrenergic effectors and related substances such as adrenaline, isoprenaline, forskolin or internal application of cyclic AMP induced a current component which showed a reversal potential near the expected Cl‐ equilibrium potential as well as an outward rectification in the I‐V relation. It is suggested that the activation of this Cl‐ current was due to phosphorylation of the channel protein or related structure by the cyclic AMP‐dependent protein kinase. Coincidentally with the activation of the Cl‐ current, the membrane capacitance of the cell decreased reversibly. 3. Acetylcholine (ACh) depressed the responses induced by beta‐adrenergic stimulation and forskolin, but failed to interfere with the one induced by cyclic AMP. 4. The dose dependence of the Cl‐ current activation by isoprenaline or forskolin was fitted by the Hill equation, with a coefficient of 1.9 and a half‐maximum concentration K 1/2 = 13 nM for isoprenaline, and with a Hill coefficient of 3 and a K 1/2 = 1.2 microM for forskolin. In the presence of 5.5 microM‐ACh the dose‐response relation shifted to higher doses; K 1/2 was 65 nM for isoprenaline and 3.6 microM for forskolin. 5. Washing out ACh in the presence of isoprenaline frequently caused transient overshoots of the response. When a saturating concentration of isoprenaline was used, this rebound was not observed. 6. The internal application of cyclic GMP enhanced the response of the Cl‐ current induced by isoprenaline or adrenaline. 7. When cyclic AMP was applied internally, the response was small in most cells. When the cell was superfused with 20 microM‐IBMX (3‐isobutyl‐1‐methylxanthine), the Cl‐ current was consistently induced by the application of cyclic AMP. It is suggested that phosphodiesterase activity strongly buffered the influx of cyclic AMP through the patch pipette tip. 8. We suggest that the compensatory interaction between the beta‐adrenergic stimulation and the muscarinic inhibition is at the membrane level, most probably via GTP‐binding proteins in activating adenylate cyclase.
Decline in spindle support to alpha‐motoneurones during sustained voluntary contractions.
Authors: Macefield G , Hagbarth K E , Gorman R , Gandevia S C , Burke D
Published: December 2014

1. To address whether the muscle spindle support to alpha‐motoneurones is maintained during prolonged isometric voluntary contractions, the discharge of eighteen muscle spindle afferents, originating in the dorsiflexors of the ankle or toes, was recorded from the common peroneal nerve in eight subjects. Isometric contractions were generally sustained for 1 min, usually below 30% of the maximal voluntary dorsiflexion force. 2. Once the afferent had been identified, subjects were instructed to dorsiflex the foot slowly to recruit the spindle ending, to continue the ramp contraction until a predetermined target force was reached, and then to hold that force until requested to relax. 3. Five muscle spindle afferents maintained a constant discharge frequency during the hold phase of the isometric contraction. Following relaxation of the contraction two spindle afferents from tibialis anterior, exhibited a post‐contraction discharge despite the absence of detectable electromyographic activity (EMG). 4. The discharge frequency of most of the spindle afferents (72%) declined progressively during the isometric contraction. The mean firing rates had declined to two‐thirds of those at the onset of the contraction by 30 s, and to half after 1 min. The decline in spindle firing rate commenced during the ramp phase of the contraction and was statistically significant by 10 s, when force was held constant. The extent of the decline was greater for those units with the higher initial firing rates and for those units studied after many preceding contractions. 5. In the same contractions a progressive increase in EMG was required to maintain force and consequently the change in EMG was inversely related to the change in spindle discharge. While many mechanisms may contribute to the decline in spindle discharge during a sustained isometric contraction, it is argued that the result will be a progressive disfacilitation of alpha‐motoneurones, which may contribute to the decline in motor unit firing rates during a sustained contraction.
A physiological basis for variation in the contractile properties of isolated rat heart.
Authors: Lin L E , McClellan G , Weisberg A , Winegrad S
Published: December 2014

1. The maximum Ca(2+)‐activated force, maximum velocity of unloaded shortening and both Ca(2+)‐ and actin‐activated ATPase activities of myosin have been measured in detergent‐skinned preparations of isolated bundles of rat right ventricle after exposure of the intact tissue to different conditions of superfusion, mechanical activity and temperature. 2. Maximum Ca(2+)‐activated force per unit cross‐sectional area decreases with increasing cross‐sectional area, and, in the absence of electrical stimulation, with the duration of superfusion. Maximum velocity of unloaded shortening is not influenced by these differences. 3. Actin‐activated ATPase activity of myosin decreases as cross‐sectional area increases and duration of superfusion increases, but the extent of the decrease in enzymatic activity is less than that of developed force. Ca(2+)‐activated ATPase activity is independent of these differences. 4. Actin‐activated ATPase activity in cryostatic sections of quickly frozen tissue is not uniform across the transverse section. In thin bundles, it is highest in the centre and lowest at the edge of the section, which correspond, respectively, to the centre and the surface of the tissue bundle. Exposure of the tissue section to 1 microM‐cyclic AMP increases the actin‐activated ATPase activity of myosin with the largest increase in activity occurring at or near the surface of the bundle. 5. Ca(2+)‐activated ATPase activity of myosin is uniform across the transverse section and is not changed by cyclic AMP. 6. Electrical stimulation, elevated Ca2+ concentration in the superfusion medium, or isoprenaline partially or completely reverse the decline in maximum Ca(2+)‐activated force produced by prolonged superfusion of the bundle before its skinning. 7. These observations are similar in many ways to those made on frog skeletal muscles by Elzinga, Howarth, Rull, Wilson & Woledge (1989a). An explanation based on the existence of a physiological mechanism for regulating the properties of force generators is proposed. Regulation of the attachment of the cross‐bridge to an actin filament may be the basis for the regulatory mechanism.
Effects of chronic electrical stimulation on contractile properties of long‐term denervated rat skeletal muscle.
Authors: al‐Amood W S , Lewis D M , Schmalbruch H
Published: December 2014

1. The contractile properties of fast‐twitch (extensor digitorum longus or EDL) and slow‐twitch (soleus) muscles in the rat were followed for periods of between 4 and 10 months after denervation. The effects of chronic electrical stimulation during the last 3‐8 weeks of denervation were investigated. 2. The fall in tetanic tension that follows axotomy ended after about 4 months' denervation. The equilibrium tension was about 0.75% of control tension in EDL and 0.2‐0.3% in soleus. 3. The low tension in soleus was due partly to the small diameter of the muscle fibres (atrophy) and partly to their necrosis that resulted in an 8‐fold fall in specific tension (the force per unit cross‐sectional area). Similar but less extreme changes occurred in EDL. 4. It is speculated that the final level of tension reached by unstimulated denervated muscles is an equilibrium between decrease in force due to atrophy and necrosis and increase due to regeneration. Differences between the final tension levels in soleus and EDL cannot be accounted for quantitatively by known differences in atrophy alone. Therefore, the rate of necrosis in soleus and of regeneration in EDL may be higher. 5. Chronic stimulation of long‐term denervated muscle increased force generation by about 7‐fold in EDL and between 20 and 55 times in soleus. The final tension reached was between 4 and 5% of normal in both muscles. Specific tension of fibres was almost completely restored by stimulation and the number of fibres was normal. The failure to recover full tension was largely due to failure to reverse denervation atrophy completely. 6. Twitch contraction and relaxation times were identical in denervated‐stimulated soleus and EDL. There was no evidence for dependence on duration of stimulation or tension of the muscle. The normalized maximum rate of rise of tetanic tension remained higher in EDL than soleus.
Cardiac output, oxygen consumption and arteriovenous oxygen difference following a sudden rise in exercise level in humans.
Authors: De Cort S C , Innes J A , Barstow T J , Guz A
Published: December 2014

1. To investigate the relative contributions of increases in cardiac output and arteriovenous oxygen difference to the increase in oxygen consumption during exercise, the ventilatory and cardiovascular responses to a sudden transition from unloaded cycling to 70 or 80 W were measured in six normal healthy subjects. 2. Oxygen consumption (VO2) was measured breath‐by‐breath and corrected for changes in lung gas stores. Cardiac output (Q) was measured beat‐by‐beat using pulsed Doppler ultrasound, and blood pressure was measured beat‐by‐beat using a non‐invasive finger cuff (Finapres). All data were calculated off‐line, second‐by‐second. 3. Arteriovenous oxygen difference (A‐VO2) was calculated from Q and VO2 using the Fick Principle. Left ventricular afterload was calculated by dividing Q by mean blood pressure. 4. The data for Q and VO2 were closely fitted by single exponential curves (mean r2 0.84 and 0.90 respectively; r is the correlation coefficient). These curves yielded mean time constants for the increases in Q and VO2 of 28 and 55 s respectively following the increase in exercise level. In each individual subject, the time course of adjustment of Q was faster than that of VO2. There was a mean lag of 15 s from the start of the new exercise level before the derived A‐V O2 began to increase; the mean time constant for A‐V O2 was 57 s. 5. If A‐V O2 had remained constant, the observed rise in Q alone would have resulted in an average of 87% of the increase in VO2 which was observed after 5 s. If Q had remained constant, the observed increase in A‐V O2 would have led to only 8% of the actual increase in VO2 after 5 s. 6. Mean and systolic blood pressure rose and afterload fell immediately after the onset of the increased workload. The time constants of the systolic blood pressure and afterload responses to exercise varied widely and ranged from 37 to 81 and 10 to 26 s respectively (n = 4). 7. We conclude that Q is responsible for most of the early increase in VO2 following a sudden increase in exercise workload. Blood pressure responses to exercise are slower than Q and VO2 responses, probably due to the rapid decrease in afterload. 8. The dominant contribution of Q to adaptation to changing workload may be physiologically important particularly in heart disease, where decreased ability to increase cardiac output may limit the capacity to cope with changing metabolic needs during everyday activities.