bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of body core temperature and peripheral temperatures on oxygen consumption in the pig
Authors: Carlisle H. J. , Ingram D. L.
Published: December 2014

1. The rate of oxygen consumption was measured in young pigs exposed to different ambient temperatures and the effect on metabolic rate of changing the temperature of thermodes implanted in the hypothalamus and over the spinal cord was determined. In some experiments the temperature of the skin over the trunk was changed by means of a water‐perfused coat.

2. Cooling the hypothalamus or the spinal cord in a warm ambient did not change the rate of oxygen consumption. At a thermoneutral ambient temperature, cooling either thermode increased oxygen consumption. In a cold environment, cooling either thermode increased the rate of oxygen consumption more than at a thermoneutral temperature. The increase in the rate of oxygen consumption was greatest during cooling of the spinal cord and it appeared that the pigs also shivered more violently. Heating either thermode tended to decrease oxygen consumption in a cold environment.

3. In pigs with thermodes both in the hypothalamus and over the spinal cord, cooling both thermodes was accompanied by a greater increase in oxygen consumption than cooling either thermode alone. The increase in oxygen consumption on cooling one thermode could be reduced by heating the other.

4. The skin temperature (fixed by the water perfused coat, or the ambient temperature) at which the rate of oxygen consumption increased, was lowered during heating of the thermodes, but the rate of increase in oxygen consumption appeared not to change as a function of falling skin or ambient temperature.
Separate channels for the analysis of the shape and the movement of a moving visual stimulus
Authors: Tolhurst D. J.
Published: December 2014

1. The effects of temporal modulation on the properties of spatial frequency channels have been investigated using adaptation.

2. Adapting to drifting sinusoidal gratings caused threshold elevation that was both spatial frequency and direction specific. Little systematic difference was found between the band widths of the elevation curves for drifting and stationary gratings.

3. It was confirmed that adaptation fails to reveal channels at low spatial frequencies when stationary gratings are used. However, channels were revealed at frequencies at least as low as 0·66 c/deg when the test gratings were made to move. These channels are adapted only a little by stationary gratings, confirming their dependence on movement.

4. The existence of movement‐sensitive channels at low spatial frequencies explains the well known observation that temporal modulation greatly increases the sensitivity of the visual system to low spatial frequencies.

5. Temporal modulation was effective at revealing these channels only when the flicker or movement of the test patterns was apparent to the observer; only at low spatial frequencies did patterns, modulated at low rates, actually appear to be temporarily modulated at threshold. At higher spatial frequencies, they were indistinguishable from stationary patterns until the contrast was some way above the detection threshold.

6. It is suggested, therefore, that the movement‐sensitive channels are responsible for signalling the occurrence of movement; the channels at higher spatial frequencies give no information about temporal changes. These two systems of channels are compared to the Y‐ and X‐cells respectively of the cat.
Neurones in the ventrobasal complex of the rat thalamus responding to scrotal skin temperature changes
Authors: Hellon R. F. , Misra N. K.
Published: December 2014

1. In rats the scrotal temperature was raised or lowered with a water‐perfused thermode while micro‐electrode recordings were made of unit activity in the ventrobasal complex of the thalamus. The electrodes were aimed at the region where evoked responses had been found by electrical stimulation of the scrotum. Recording sites were marked by iontophoresis of dye from the micro‐electrode.

2. Changes in firing rate of thalamic neurones were only found in the scrotal temperature range of 31–40° C. Within this range, 72% of the 123 cells tested were excited or suppressed by skin warming. At temperatures above or below this range, activity was not affected. Most of the cells responded just to temperature and only 7% were also excited by touch.

3. Raising temperature in the range 31–40° C caused 82% of the thermally responding cells to increase their firing rate and 18% to decrease their rate. Individual neurones showed a sudden and maintained change in their activity for scrotal temperature increases of only 2, 1 or even 0·5° C. Mean firing rates changed by factors of about 8 or more with these temperature increases and further warming did not change the rate. These step‐like changes in firing rate were found at different points over the whole skin temperature range of 31–40° C, but most were between 33 and 38° C.

4. For a given neurone the step‐like change in activity occurred once its critical temperature was reached, irrespective of whether this was achieved by a step increase of skin temperature over 1–2 sec or by a slow ramp increase lasting several minutes.

5. It is not possible to say whether the skin warm receptors, cold receptors or both were responsible for these thalamic responses, but the results do show that incoming thermal information is considerably processed when it reaches the thalamic level.
Placental iron transfer in the cat
Authors: Baker Erica , Morgan E. H.
Published: December 2014

1. The transfer of iron from maternal plasma to the foetus was studied in the cat using cat transferrin labelled with 59Fe and radioiodine.

2. Pregnancy was accompanied by a fall in maternal haematocrit, a rise in serum total iron‐binding capacity and iron stores, but no change in serum iron concentration or plasma iron turnover.

3. Near‐term foetal haematocrit and serum iron concentration were higher and iron binding capacity lower than in the pregnant animals.

4. The uptake of 59Fe from maternal plasma by the placenta and transfer to the foetuses were slow and small in amount. The daily transfer of iron to the foetuses calculated from these data was only 5 μg.

5. There was a small, transient uptake of 59Fe from the plasma by the foetal membranes.

6. Small amounts of plasma transferrin and albumin were slowly taken up by the placenta.

7. It was concluded that the maternal endothelium of the placenta of the cat acts as a barrier for the uptake of plasma transferrin‐bound iron. As a result the rate of iron transfer to the foetuses from maternal plasma is inadequate to account for their rate of iron accumulation, and another source, such as maternal erythrocytes, must supply most of the iron to the foetuses.
Adaptation and dynamics of cat retinal ganglion cells
Authors: Enroth‐Cugell Christina , Shapley R. M.
Published: December 2014

1. The impulse/quantum (I/Q) ratio was measured as a function of background illumination for rod‐dominated, pure central, linear square‐wave responses of retinal ganglion cells in the cat.

2. The I/Q ratio was constant at low backgrounds (dark adapted state) and inversely proportional to the 0·9 power of the background at high backgrounds (the light adapted state). There was an abrupt transition from the dark‐adapted state to the light‐adapted state.

3. It was possible to define the adaptation level at a particular background as the ratio (I/Q ratio at that background)/(dark adapted I/Q ratio).

4. The time course of the square‐wave response was correlated with the adaptation level. The response was sustained in the dark‐adapted state, partially transient at the transition level, and progressively more transient the lower the impulse/quantum ratio of the ganglion cell became. This was true both for on‐centre and off‐centre cells.

5. The frequency response of the central response mechanism at different adaptation levels was measured. It was a low‐pass characteristic in the dark‐adapted state and became progressively more of a bandpass characteristic as the cell became more light‐adapted.

6. The rapidity of onset of adaptation was measured with a time‐varying adapting light. The impulse/quantum ratio is reset within 100 msec of the onset of the conditioning light, and is kept at the new value throughout the time the conditioning light is on.

7. These results can be explained by a nonlinear feedback model. In the model, it is postulated that the exponential function of the horizontal cell potential controls transmission from rods to bipolars. This model has an abrupt transition from dark‐ to light‐adapted states, and its response dynamics are correlated with adaptation level.
Characteristics of a sulphydryl group essential for sodium exchange diffusion in beef erythrocytes
Authors: Motais R. , Sola F.
Published: December 2014

1. In the beef red blood cell, the component of the Na efflux which is insensitive to ouabain but depends on the presence of external Na, is not affected by furosemide but is reduced by several agents: ethacrynic acid, dinitrofluorobenzene, p‐chloromercuribenzene (PCMB),
N‐ethylmaleimide and p‐chloromercuribenzene sulphonate (PCMBS). Some of these agents increased a parallel passive permeability which could mask the reduction of efflux.

2.
N‐ethylmaleimide and PCMBS, which in our experimental conditions (initial concentration 5 × 10−4
M and 5 × 10−6
M respectively, haematocrit 7·7%) do not increase the leak, inhibit Na influx and efflux markedly and equally. This provides further evidence of the existence of a typical ouabain‐insensitive Na exchange diffusion in beef red blood cell.

3. Inhibition of the exchange diffusion mechanism by
N‐ethylmaleimide or PCMBS is not total and their inhibitory effects are slightly additive. Various arguments suggest that their effects on exchange diffusion can be attributed to a reaction with sulphydryl groups.

4. These sulphydryl groups are rapidly titrable by a poorly penetrating agent such as PCMBS, and the inhibitory effect is rapidly reversible. Thus, it is assumed that the sulphydryl groups containing proteins are superficially located on the outer border of the membrane.

5. After inhibition, there is no change in half saturation constant for the complexing reaction for transfer, suggesting that the inhibited sites are no longer functioning but that the uninhibited sites are in every way normal.

6.
N‐ethylmaleimide and PCMBS act similarly in sheep red blood cells.

7. PCMBS does not affect sodium movement in human erythrocytes, but
N‐ethylmaleimide inhibits markedly the ouabain‐insensitive Na efflux.
Development of a mammalian fast muscle: dynamic and biochemical properties correlated
Authors: Drachman D. B. , Johnston D. M.
Published: December 2014

1. The isometric properties and related biochemical properties of a developing rat fast muscle (extensor digitorum longus, EDL) have been determined during the 21 days after birth.

2. At birth the maximum rate of rise of tension in a tetanus, a measure of speed of contraction, is slow; it begins to increase only after the 5th day and reaches adult values by 21 days.

3. The increase in actomyosin ATPase activity of the rat EDL correlates closely (P ≪ 0·001) with the changes in the maximum rate of rise during the same period of development.

4. The relaxation phase of a tetanic response begins to increase in speed promptly after birth, and reaches adult values by the 21st day. The rate of calcium accumulation by the isolated sarcoplasmic reticulum (SR) increases with a similar time course.

5. The separate contributions of contraction and relaxation mechanisms to the changes in the more conventional isometric properties of maturing muscles have been analysed.
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.
Negative feedback regulation of noradrenaline release by nerve stimulation in the perfused cat's spleen: differences in potency of phenoxybenzamine in blocking the pre‐ and post‐synaptic adrenergic receptors
Authors: Dubocovich Margarita L. , Langer S. Z.
Published: December 2014

1. The effects of low concentrations of phenoxybenzamine (8·8 × 10−10 to 2·9 × 10−7
M) on responses and on noradrenaline overflow elicited by nerve stimulation were studied in the perfused cat's spleen.

2. In the presence of 8·8 × 10−10
M or 2·9 × 10−9
M phenoxybenzamine there was a significant reduction in responses to nerve stimulation while the overflow of the transmitter did not increase at the two frequencies of stimulation employed: 5 and 30 Hz.

3. In the presence of 2·9 × 10−8
M or 2·9 × 10−7
M phenoxybenzamine the responses to nerve stimulation were practically abolished and a significant increase in transmitter overflow was obtained at both frequencies of stimulation. The drug was more effective in increasing transmitter overflow at 5 Hz when compared with 30 Hz.

4. The higher effectiveness of phenoxybenzamine in blocking the post‐synaptic α‐receptor when compared with the blockade of the presynaptic α‐receptor that regulates transmitter release is compatible with the view that these two receptors are not identical.

5. A second alternative for the difference in effectiveness of phenoxybenzamine is that both types of α receptors are identical, but the spare receptor capacity for the presynaptic adrenergic receptors is higher than that of the post‐synaptic receptors.
The effects of pentobarbitone anaesthesia on the volume and composition of the extracellular fluid of dogs
Authors: Rampton D. S. , Ramsay D. J.
Published: December 2014

1. The effects of pentobarbitone sodium (Nembutal) anaesthesia in dogs on extracellular fluid and plasma volumes, plasma protein concentration, haematocrit and extracellular fluid electrolyte composition were measured.

2. Induction of pentobarbitone anaesthesia caused a rapid rise in extracellular fluid volume, accompanied by decreases in the haematocrit, in extracellular fluid potassium concentration, and in plasma calcium, magnesium, and protein concentrations. There were no significant changes in plasma osmolality and extracellular fluid concentrations of sodium and chloride.

3. Extracellular fluid volume did not alter significantly during six hours of anaesthesia, but the haematocrit and extracellular fluid potassium concentration showed an increase towards control values.

4. The relevance of these findings to the interpretation of experiments carried out under pentobarbitone anaesthesia is noted.
Studies of radiocalcium efflux in single barnacle muscle fibres: effects of procaine and external divalent cations
Authors: Chen Stephen S.
Published: December 2014

1. 45Ca efflux from single barnacle muscle fibres loaded with radio‐calcium by microinjection was studied.

2. The 45Ca washout curve consisted of three exponential phases with half‐times of 4·8, 12·6 and 111·1 min.

3. Removal of external Ca2+ reduced 45Ca efflux by 65%. The 45Ca efflux recovered upon restoring external Ca2+, the magnitude of the recovery being dependent upon the external Ca2+ concentration. 10 m
M procaine was found to reduce the magnitude of the recovery.

4. Removal of external Mg2+ resulted in a 38% increase in 45Ca efflux.

5. External application of procaine at pH 7·8 caused a dose‐dependent inhibition of 45Ca efflux. The magnitude of the inhibition was reduced in the presence of low external Ca2+ concentrations. 10 m
M procaine at pH 9·3 caused a biphasic effect: inhibition was followed by stimulation.

6. Microinjection of 0·5
M procaine caused only inhibition of 45Ca efflux, whereas microinjection of 1·5
M procaine caused stimulation followed by inhibition. These effects were observed at an external pH of 7·8 and 9·3.

7. Injection of 100 m
M‐EGTA abolished the stimulatory but not the inhibitory effect produced by procaine injection.

8. These results are interpreted as indicating that a major fraction of the 45Ca efflux involves Ca‐Ca exchange which is inhibited by the charged form of procaine in a non‐competitive manner at the external surface of the muscle fibre. The stimulatory action is attributed to release by procaine of Ca2+ from internal binding sites.
Polysensory interactions in the cuneate nucleus
Authors: Atweh S. F. , Banna N. R. , Jabbur S. J. , To'mey G. F.
Published: December 2014

1. The effects of light flashes or sound clicks on somatic sensory activity in the cuneate nucleus of the cat were studied. Polysensory interactions were demonstrated by means of gross potential recording in the cuneate nucleus or medial lemniscus, single unit recording in the cuneate nucleus, and excitability testing of tract terminals.

2. Brief flashes or clicks were found to produce negative (N) and positive (P) waves in the cuneate nucleus similar to those produced by cutaneous stimulation. Furthermore, the P wave evoked by conditioning photic or acoustic stimuli depressed the P wave produced by cutaneous test stimuli.

3. Conditioning photic or acoustic stimuli inhibited spontaneously firing cuneate neurones as well as those driven by cutaneous test stimuli.

4. Conditioning photic or acoustic stimuli depressed the test discharge in the medial lemniscus evoked by cutaneous test stimuli.

5. Micro‐electrode stimulation within the cuneate nucleus evoked an antidromic response in the superficial radial nerve consisting of two spike complexes. Conditioning photic or acoustic stimuli caused an increase in the size of the initial spike complex and a depression in the secondary spike complex. These changes and the time courses of all the interactions observed were suggestive of presynaptic inhibition.

6. The modulatory influences of photic and acoustic stimuli on the cuneate nucleus were present under α‐chloralose or pentobarbitone anaesthesia and the acoustic influence persisted after midcollicular decerebration. When added to other evidence, the above findings suggest that the reticular formation of the brain stem plays an important role in these polysensory interactions.
Membrane properties underlying spontaneous activity of denervated muscle fibres
Authors: Purves D. , Sakmann B.
Published: December 2014

We have examined the events underlying the initiation of spontaneous action potentials (fibrillation) in fibres of previously denervated rat diaphragm maintained in organ culture for up to 10 days.

1. Based on discharge pattern, two classes of spontaneously active fibres were found: rhythmically discharging fibres, and fibres in which action potentials occur at irregular intervals.

2. Sites of action potentials initiation were located by exploration along the fibre length with two independent extracellular recording electrodes. The majority of sites of origin in both regular and irregular fibres were at the former end‐plate zone; however, there was no region along the length that could not, at least in some fibres, be a site of origin.

3. Intracellular recording at or near sites of origin of action potential discharge showed two types of initiating events. Irregularly discharging fibres were brought to threshold by discrete depolarizations of up to 15 mV in amplitude, while regularly occurring action potentials were associated with oscillations of the membrane potential.

4. Discrete depolarizations (called fibrillatory origin potentials or f.o.p.s) at sites of origin in irregularly discharging fibres have the following properties: (a) random occurrence and nearly constant amplitude outside a refractory period during which both amplitude and probability of a second f.o.p. are reduced; (b) associated inward current flow which is localized to about 100 μm or less along the fibre length, and (c) dependence of amplitude and frequency on membrane potential.

5. Oscillation of membrane potential found at sites of origin of action potential discharge in regular fibres also occurred locally along the fibre length and was sensitive to changes in membrane potential.

6. Both f.o.p.s and oscillations of membrane potential were reversibly abolished by low Na+—Ringer fluid or tetrodotoxin.

7. Neither type of initiating event was appreciably affected by concentrations of
D‐tubocurarine which blocked extrajunctional sensitivity to acetylcholine.

8. We conclude that spontaneous action potentials under these conditions arise from a localized Na+‐conductance change in the membrane of the active fibre; this conductance change is distinct from the increased Na+‐conductance which follows the interaction of acetylcholine with its receptor. Spontaneous activity in single, denervated muscle fibres is cyclical and self‐inhibiting (Purves & Sakmann, 1974); thus the Na+‐conductance change underlying the initiation of spontaneous action potentials is affected by muscle fibre activity.
The response of laryngeal afferent fibres to mechanical and chemical stimuli
Authors: Boushey H. A. , Richardson P. S. , Widdicombe J. G. , Wise J. C. M.
Published: December 2014

1. We have recorded afferent activity from ‘single fibres’ dissected from the superior laryngeal nerve of anaesthetized cats.

2. Units which responded to gentle mechanical stimulation of the larynx epithelium were chosen for study.

3. Receptors with myelinated fibres were grouped according to their spontaneous activity. Group 1 fibres had little or no spontaneous activity: group 2 fibres had constant and continuous spontaneous activity.

4. Group 1 fibres had a wide range of adaptation rates. Their conduction velocities lay between 3·0 and 30 m/sec. The receptors were generally stimulated by ammonia and distilled water and often by CS riot control agent, 5 and 10% CO2, 200 ppm SO2, and cigarette smoke. Histamine, phenyl diguanide, graphite dust, 100 ppm SO2 and saline drops did not generally excite the fibres.

5. Group 2 fibres were slowly adapting. Their conduction velocities ranged between 8·0 and 26·5 m/sec. Ammonia usually, and distilled water sometimes, excited these fibres while 5 and 10% CO2 mixtures inhibited them. A minority of group 2 fibres were pH sensitive, inhibited by acids and stimulated by alkaline buffers. Cigarette smoke had complex actions, either excitation, inhibition or, at different times, both. Histamine, P.d.g., CS, SO2, saline drops and dust had no action on these fibres.

6. Recordings were made from one unmyelinated fibre (conduction velocity 1·9 m/sec) which responded to stroking of the epithelium with a thread and to histamine, P.d.g. and ammonia vapour applied to the epithelium.

7. We consider the site, method of excitation and reflex actions of the different receptors described.
Cloacal resorption of salt and water in the Galah (Cacatua roseicapilla)
Authors: Skadhauge Erik
Published: December 2014

1. The transmural net flow of salt and water in the coprodeum and large intestine of the Galah (Cacatua roseicapilla), an Australian xerophilic parrot, was measured by an in vivo perfusion technique. The main goal of the study was to understand what happens when the hyperosmotic ureteral urine formed in the dehydrated state is regurgitated into the cloaca. Buffered perfusion fluids, hyper‐ and isosmotic to plasma, with varying NaCl and KCl concentrations, were used. [14C]polyethylene glycol served as an unabsorbable water marker.

2. The cloacal Na+ and Cl− absorption rates were nearly parallel and at low luminal concentrations roughly proportional to the intraluminal concentrations. At higher concentrations the Na+ absorption rate showed saturation. The maximal Na+ flow was 217 μequiv/kg.hr, the concentration at half maximal flow 181 m‐equiv/l. The Na+ absorption rate was not impaired by a high K+ concentration. K+ was secreted into the intestine, except at high intraluminal K+ concentrations where resorption was observed.

4. The apparent osmotic permeability coefficient was 0·85 μl./kg.hr.m‐osmole at an average osmotic difference of 446 m‐osmole between lumen and plasma; it was higher at lower differences. In the (near) absence of an osmotic difference across the cloacal epithelium the solute‐linked water flow was 5·0 μl. H2O/μequiv Na+.

5. It is concluded that the hyperosmotic ureteral urine formed in the dehydrated state can pass into the cloaca without a water loss. A Na+ absorption of around 70% of the ureteral output is likely.