bluuebunny/crossref_metadata_2025_split huggingface dataset:
Speed of repolarization and morphology of glycerol‐treated frog muscle fibre
Authors: Nakajima S. , Nakajima Yasuko , Peachey L. D. 
Published: December 2014

1. Single muscle fibres from frog semitendinosus were subjected to sudden changes in [K]o, while recording membrane potential.2. In agreement with Hodgkin & Horowicz (1960), a sudden increase in [K]o in normal fibres produced a rapid depolarization (half‐time 0·3 sec), whereas a sudden decrease in [K]o produced a slower repolarization (half‐time 2‐3 sec).3. Fibres were subjected to ‘glycerol‐treatment’, a procedure which was supposed to produce a functional disconnexion of the T‐system from the surface. In these glycerol‐treated fibres both depolarization and repolarization induced by changes of [K]o took place rapidly.4. The results suggest that the slowness of the repolarization in normal fibres is due to a retention of K ions inside the T‐tubules.5. Electron microscopical observation of single fibres or bundles of fibres, which have been soaked in a Ringer containing ferritin, revealed that normal fibres contained ferritin particles in the T‐system, while glycerol‐treated fibres showed no ferritin. Except for the presence of some large vacuoles and some swelling of the T‐system, glycerol‐treated fibres appeared morphologically normal.6. Prolonged soaking in a high potassium solution produced electrical effects suggesting that K ions can enter the tubules of treated fibres very slowly, in spite of their inaccessibility to ferritin.7. The main effect of glycerol‐treatment does not seem to be a total disconnexion of the T‐system from the fibre surface, but rather constriction of the T‐tubules near their openings to the exterior.
Effects of low temperature on the positive dynamic current of cardiac Purkinje fibres
Authors: Hiraoka Mari , Hiraoka Masayasu 
Published: December 2014

1. The effects of low temperature on the positive dynamic current (mainly Cl− current) of sheep cardiac Purkinje fibres were studied using the ‘voltage clamp’ technique.2. Cooling of Purkinje fibres from 37° C to room temperature (25° C) slowed the time course of the current and decreased its peak amplitude. The Q10 of the decay of the current was 2·67 over 25–37° C. Removal of inactivation was also delayed and the Q10 of the rate constant was 2·62 over 30–37° C.3. The decreased peak amplitude of the current on cooling could not be restored by pre‐step hyperpolarization. Thus the curve for the steady‐state inactivation was simply depressed downward. The Q10 of the maximum current response was 3·05 over 25–37° C.4. During deep hypothermia (less than 10° C), no Cl− current was demonstrated by depolarization up to + 60 mV.5. The high sensitivity to temperature suggests that the current contributes significantly to the prolongation of action potentials during low temperature, but its quantitative role cannot be evaluated without simultaneous evaluation of other plateau currents.
The action of cobalt ions on neuromuscular transmission in the frog
Authors: Weakly J. N. 
Published: December 2014

1. Cobalt ions, in concentrations of 0·05‐2 m
M, block neuromuscular transmission in the frog sartorius muscle.2. The reduction in the e.p.p. amplitude produced by Co2+ is due to a decrease in the amount of transmitter released by a nerve impulse (mean quantum content). This reduction is associated with little change in the resting membrane potential of the muscle fibre or in the mean amplitude of spontaneous m.e.p.p.s.3. The reduction in evoked transmitter release produced by Co2+ may be antagonized by elevation of the external Ca2+ concentration. It is suggested that the antagonism between Co2+ and Ca2+ is competitive in nature.4. The mean dissociation constant for Co2+ and its hypothetical membrane complex was found to be 0·18 m
M. On this basis, it is concluded that Co2+ is about 20 times more potent than Mg2+ in suppressing evoked transmitter release.5. In contrast to the inhibitory action on evoked release, Co2+ increases spontaneous transmitter release. However, concentrations of Co2+ 20–60 times greater than those which decrease the e.p.p. amplitude are needed to produce a significant increase in m.e.p.p. frequency.
Anatomy and innervation ratios in motor units of cat gastrocnemius
Authors: Burke R. E. , Tsairis P. 
Published: December 2014

1. Muscle fibres belonging to single motor units of identified type were studied in frozen sections of cat medial and lateral gastrocnemius muscles. Reconstruction of the distribution of fibres in individual units showed that the territories of all three physiological types present in the cat medial gastrocnemius were quite extensive. Within its territory, fibres belonging to the studied unit were distributed more or less uniformly without localized collections. The density of unit fibres suggests that, in cat medial gastrocnemius, a given region of the muscle may be shared by as many as fifty different muscle units.2. Direct determination of innervation ratios in identified muscle units required complete reconstruction of the three‐dimensional distribution of unit fibres within the whole medial gastrocnemius. Satisfactory results were obtained with two type FF units and one type FR unit.3. Indirect estimates of the average innervation ratios expected for muscle units of different physiological type were obtained using counts of muscle fibres with characteristic histochemical profiles and data on relative frequencies of motor units of known type in the medial gastrocnemius unit pool. Such indirect estimates of innervation ratios agreed with the results of direct fibre counts in identified units for types FF and FR muscle units. Taken in sum, the available evidence suggests that an average muscle unit in the cat medial gastrocnemius contains between 400 and 800 muscle fibres, irrespective of physiological type.4. Tension production by single muscle units depends on a number of factors, including innervation ratio, the cross‐sectional areas of unit fibres and the specific tension outputs of the unit fibres. The present results suggest that the specific tension output of gastrocnemius type S unit muscle fibres is considerably smaller (about 0·6 kg/cm2) than in either FF units (about 1·5–2·0 kg/cm2) or type FR units (2·6–2·9 kg/cm2).
Daily loss of calcium and sodium from the skin of two healthy men
Authors: Carr T. E. F. , Harrison G. E. , Nolan J. 
Published: December 2014

1. The daily losses from the skin of Ca and Na have been measured for two healthy men. The losses included Ca and Na in exfoliated skin cells as well as in insensible perspiration. The daily output of Ca in urine was also measured.2. In five measurements, the total daily skin loss of Ca ranged from 8·0 to 21·1 mg with mean values of 16·7 and 10·8 mg for the two subjects. The total daily skin loss of Na under the same conditions ranged from 45 to 146 mg with mean values of 97 and 77 mg respectively.3. The ratio of the daily skin loss to the urinary excretion of Ca was 6·8 and 3·4%.4. There was no correlation between the daily skin loss of Ca and atmospheric humidity.5. In the last experiment, the fraction of the total skin loss of Ca due to fluid secretion was assessed by giving an
I.V. dose of 47Ca to each subject. The values derived for this fraction were 0·37 and 0·38.
Evidence for the existence of neural mechanisms selectively sensitive to the direction of movement in space
Authors: Beverley K. I. , Regan D. 
Published: December 2014

1. Visual sensitivity to movement in depth was measured as a function of the relative distances through which the left and right retinal images moved. This relative distance (left:right ratio) provides a sensitive cue to the direction along which a target moves in three‐dimensional space.2. Gazing at a target which moved along a fixed direction in space produced a gross reduction of visual sensitivity to movements in depth along that direction. For other directions of movement, visual sensitivity was not affected.3. Sensitivity to depth movement rapidly rose almost to the preadaptation level within the first 20–60 sec after removing the adapting target, but recovery was not complete until 100–300 min had elapsed.4. Any adapting target whose left:right ratio fell within a definite range gave similar reductions of visual sensitivity to movements in depth. There were five such ranges.5. The effects of adapting to movement in depth suggest that eight mechanisms underlie depth perception. These mechanisms are ‘tuned’ to the direction of movement in three‐dimensional space. Four mechanisms are wholly concerned with movements along directions very close to the line which cuts midway between the eyes, and do not respond to movements whose direction departs by more than 1·5° from the preferred direction.6. Neural mechanisms ‘tuned’ to different left:right ratios could provide a physiological basis for sensing the direction in which an object moves in three‐dimensional space.
The contribution of articular receptors to cardiovascular reflexes elicited by passive limb movement
Authors: Barron Wendy , Coote J. H. 
Published: December 2014

1. In decerebrate cats, passive movements of one hind limb led to increases in arterial blood pressure, heart rate and ventilation. When both limbs were moved the magnitude of the changes was approximately doubled.2. Section of the nerves to the limb abolished the responses to movement. The responses are, therefore, dependent on a reflex originating in the moving limb.3. The magnitude of the cardiovascular responses was significantly reduced following section of the sensory nerve fibres from the knee joint, in an otherwise partially denervated limb. This indicates that part of the reflex changes associated with limb movement arise from sensory endings in the joints.4. Electrical stimulation of articular nerves led to similar cardiovascular responses. The afferent fibres involved were identified as those having conduction velocities below 18 m/sec, whose terminations are classified as the type IV joint receptors. The possibility that these subserve some other function than pain is discussed.
Lymph flow and lymph protein concentration in the skin and muscle of the rabbit hind limb
Authors: Bach Catherine , Lewis G. P. 
Published: December 2014

1. Three lymphatic beds have been found in the rabbit hind limb:(i) the lymph from the foot and ankle drains into lymphatics which run with the deep veins to the popliteal node;(ii) the superficial lymphatics of the medial skin from mid‐calf to the groin enter the inguinal node while those of the lateral skin drain into the popliteal node;(iii) the lymph draining the muscles collects in vessels which do not enter the popliteal node but join the femoral lymphatic post‐nodally.2. The lymphatic system of the hind limb is regionalized so that lymph from a specific area enters the popliteal node in one specific lobe and no other.3. By cannulating the femoral lymphatic and ligating the post‐nodal lymph vessel close to the point at which it leaves the node it was possible to collect pure muscle lymph.4. The mean muscle lymph flow was 21 μl./100 g.min whilst the skin lymph flow was 240 μl./100 g.min. The mean protein concentration of muscle lymph was usually somewhat higher than that of skin lymph.5. After nerve stimulation there was an increase in muscle lymph flow but no increase in protein concentration.6. After a mild thermal injury there was no change in muscle lymph flow or its protein concentration, but there was an enormous increase in the leakage of lactic dehydrogenase indicating considerable cellular injury. On the other hand a significant increase in both protein concentration and flow of skin lymph occurred after thermal injury.
Effect of stimulating right atrial receptors on urine flow in the dog
Authors: Kappagoda C. T. , Linden R. J. , Snow H. M. 
Published: December 2014

1. Complex unencapsulated nerve endings (right atrial receptors) have previously been found in the endocardium of the right atrial appendage and the junction between the superior vena cava and the right atrium.2. Distension of balloons located in the right atrial appendage and at the junction between the superior vena cava and the right atrium resulted in an increase in urine flow. This diuresis was accompanied by a small increase in the excretion of sodium.3. Cooling the right cervical vagus caused a reduction in the response to distension of the right atrial appendage.4. It is concluded that stimulation of right atrial receptors by the distension of balloons located in the right atrial appendage and at the junction between the right atrium and the superior vena cava results in a reflex increase in urine flow.
Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells
Authors: Schatzmann H. J. 
Published: December 2014

1. In resealed human red cells loaded with Ca‐EGTA buffer solutions it was found that the intracellular free Ca2+ concentration for half saturation of the Ca transport system (which pumps Ca out of the cell) is equal to or smaller than 4 × 10−6
M and thus closely agrees with the dissociation constant of the Ca + Mg activated membrane ATPase.2. The maximal rate of Ca transport from resealed cells to medium was found to be 0·148 ± 0·009 μmole/ml. cells.min at 28° C.3. The rate of Ca transport was unaffected by a variation of the extracellular Ca2+ concentration from 3·10−7 to 5·10−3
M.4. Evidence is presented making it probable that the stoichiometric relation between Ca transported and ATP hydrolysed is 1:1 rather than 2:1.5. As the Ca transport is quite rapid even at half saturation and the passive leak for Ca negligible in intact cells it can be predicted that the steady‐state cellular Ca2+ concentration must be low, most probably less than 10−6 μmole/ml. cells. Transport from cells containing 5·10−7 μmole/ml. into blood plasma is thermodynamically compatible with the normal plasma Ca2+ concentration and the normal cellular ATP, ADP and Pi content.6. Treatment with the mercurial PCMBS in the cold for 15 hr allows to load red cells with 1 μmole Ca/ml. cells without destroying their ability to transport Ca after removal of the mercurial.7. It is shown that at high cellular Ca concentrations (0·1–3 μmole/ml. cells) about 50% of the total is free Ca2+ on account of binding mainly to dialysable cell constituents.
The action of carbon dioxide on constricted airways
Authors: Astin T. W. , Barer Gwenda R. , Shaw J. W. , Warren Patricia M. 
Published: December 2014

1. In artificially ventilated open‐chest cats and dogs ventilation with 5–15% CO2 reversed the bronchoconstriction caused by drugs or by pulmonary artery occlusion. Total lung resistance, ‘static’ lung compliance, and intratracheal or intrabronchial pressure at constant pump stroke were measured.2. CO2 reduced resistance and increased compliance of the lung during infusions of 5‐hydroxytryptamine (5‐HT), histamine and acetylcholine in cats. In dogs CO2 reduced resistance during 5‐HT infusions; it caused small reductions in intratracheal pressure but no significant change in resistance during infusions of histamine and acetylcholine. Even in cats CO2 had a larger effect during 5‐HT than during histamine and acetylcholine infusions.3. Occlusion of a pulmonary artery caused increases in resistance and decreases in compliance in the affected lobes of both cats and dogs. These changes were partly reversed by ventilation with high CO2 mixtures.4. The bronchodilator action of CO2 took place over a wide range of Pa, CO2 values (20–100 torr).
The effect of pain on human sweating
Authors: Abram W. P. , Allen Judith A. , Roddif I. C. 
Published: December 2014

1. Attempts were made to induce emotional sweating in normal subjects by subjecting them to painful stimuli such as compression of pins on the forearm skin, immersion of the fingers in iced water, compression of the thoracic cage by rib calipers and ischaemic exercise of the forearm muscles.2. Changes in sweating were estimated by continuously monitoring the rate of total body weight loss.3. Of the painful stimuli used, only ischaemic forearm exercise significantly increased the rate of sweat secretion.4. Tasks in mental arithmetic caused much greater increases in sweat secretion than any of the pain stimuli except ischaemic pain.5. It is concluded that many varieties of pain, even when severe, do not induce sweating under laboratory conditions.
Release of endogenous noradrenaline from an isolated elastic artery
Authors: Bell Christopher 
Published: December 2014

1. The overflow of noradrenaline following field stimulation of vasoconstrictor nerves has been studied in isolated preparations of the guineapig thoracic aorta.2. Stimulation with trains of 3000 pulses at 5 and 25 pulses.s−1 resulted in mean overflows of 0·15 and 0·17 (ng.g−1).pulse−1 respectively.3. These overflows were not affected by pre‐treatment of the aortae with the inhibitor of neuronal amine re‐uptake desmethylimipramine (10−5
M) or with the inhibitors of extraneuronal amine uptake metanephrine (5 × 10−4
M) or desoxycorticosterone (2·5 × 10−5
M).4. In contrast, inhibition of monoamine oxidase and catechol‐O‐methyl transferase with pargyline (1 × 10−4
M) and tropolone (2·5 × 10−4
M) caused the mean overflows to be increased to 0·27 and 0·31 (ng.g−1).pulse−1 in response to stimulation at 5 and 25 pulses.s−1 respectively. Inhibition of either enzyme alone had little effect.5. It is concluded that in the guinea‐pig aorta nervously released noradrenaline is inactivated primarily by enzymic metabolism, while neural re‐uptake is insignificant. This situation is the reverse of that existing in the uterine artery of the same species.6. Phenoxybenzamine (10−5
M) also caused pronounced increases in overflow at both high and low frequencies of stimulation. This could be due to an effect of phenoxybenzamine on release of noradrenaline or on some tissue uptake mechanism distinct from the normal neuronal and extraneuronal pathways.7. Calculations based on the overflow at 5 pulses.s−1 following total enzyme inhibition indicated that a single stimulating pulse liberated 2·1 × 10−4 of the total transmitter store.
The oxygen and carbon monoxide capacities of foetal and adult blood
Authors: Gregory I. C. 
Published: December 2014

1. The oxygen capacities of foetal and adult blood have been compared by direct measurement of their oxygen and carbon monoxide combining power. Corrections have been applied to the capacities obtained from oxygen content determinations for the presence of carboxyhaemoglobin and methaemoglobin.2. Mean values for the capacities of foetal blood derived from oxygen and carbon monoxide content were 1·312 ml./g (
S.E. ± 0·007) and 1·331 (
S.E. ± 0·002) respectively, while those for adult blood were 1·306 ml./g (
S.E. ± 0·006) and 1·331 (
S.E. ± 0·0005) respectively.3. For neither carbon monoxide nor oxygen was there a significant difference (P > 0·05) of capacity between adult and foetal blood. There was, however, a significant difference (P < 0·05) on comparing the two methods of measurement on each form of blood and values from both methods were significantly different (P < 0·001) from the theoretical value of 1·39 ml. oxygen/g haemoglobin derived from the molecular weight of haemoglobin.4. These results suggest that the International Cyanmethaemoglobin Standard gives values of haemoglobin concentration which are approximately 6% higher than levels indicated by oxygen combining power.
Absorption of folic acid by everted segments of rat jejunum
Authors: Blair J. A. , Johnson I. T. , Matty A. J. 
Published: December 2014

1. Everted rings of rat intestine were used to study the initial uptake rate of folic acid at various concentrations and incubation temperatures in vitro.2. Folic acid was accumulated linearly for periods of at least 30 min.3. The initial uptake rate was found to reach a constant value as the concentration of folic acid in the incubation medium was increased above 5 × 10−6
M.4. Reducing the temperature of incubation from 37 to 27° C gave small Q10 values at either end of the concentration range.5. Transfer of folic acid into the serosal compartment of everted sacs was shown to undergo a rate reduction in the same concentration range.6. A mechanism for folic acid transport is suggested in which folic acid is converted to the neutral species at the mucosal surface in an acid microclimate.
Actions of glucose and potassium chloride on osmoreceptors slowing gastric emptying
Authors: Barker G. R. , Cochrane G. McL. , Corbett G. A. , Hunt J. N. , Roberts Susan Kemp 
Published: December 2014

1. Five subjects were given 373 test meals of 750 ml. water containing a range of concentrations of glucose or potassium chloride.2. The greater the concentration of solute in the meals, the greater was the volume of the test meal recovered from the stomach after a fixed time.3. When the concentrations of the solutes were expressed as m‐osmole/l. corrected by osmotic coefficients based on vapour pressures at 37° C, glucose and potassium chloride were indistinguishable in slowing gastric emptying.4. These results are consistent with the regulation of gastric emptying by a duodenal receptor responding to osmotic pressure.5. Potassium chloride was more nauseating than glucose on an osmolar basis.
Tension responses to quick length changes of glycerinated skeletal muscle fibres from the frog and tortoise
Authors: Heinl P. , Kuhn H. J. , Rüegg J. C. 
Published: December 2014

1. Twitch fibres isolated from the sartorius muscle of the frog were glycerinated (cf. Heinl, 1972) and thin fibre bundles dissected from the m. ileofibularis of the tortoise were briefly glycerinated as described by Julian (1971).2. The glycerinated fibres (length 0·3–0·5 cm) were fixed to an apparatus which performed length changes within 5 msec and recorded the time course of tension changes in the fibres.3. The fibres were suspended in a relaxing medium, containing ATP and 4 m
M‐EGTA. Contraction was induced by raising the calcium concentration to 4 m
M‐CaEGTA.4. The tension time course of activated fibres following quick length changes (0·1–1% L0) was studied. The tension records produced by quick releases and stretches could be resolved into four phases similar to the kind shown in Fig. 1 a.5. The phase of quick tension recovery was found to take place more rapidly in frog than in tortoise fibres: it was completed in ∼ 30 msec (after stretch) and in ∼ 20 msec (after release) in frog fibres (3° C). The corresponding values obtained for tortoise fibres were ∼ 300 and ∼ 400 msec (3° C).6. In tortoise fibres the size of the elastic and quick recovery phase increased with rising isometric tension (induced by raising the calcium concentration (pCa 8 to 5)), and decreased with increasing sarcomere length (2·5–4·2 μm). In fibres, in which the rigor state was induced by withdrawal of ATP, no quick tension recovery was recorded.7. It is suggested that the rotational movement of the crossbridge head on the actin filament, postulated by Huxley & Simmons (1971 b) is taking place more slowly in the tortoise than in the frog muscle. Furthermore, it is suggested that this rotational movement does not occur in the rigor state, as no quick tension recovery was recorded there.