bluuebunny/crossref_metadata_2025 huggingface dataset:
Sodium and water contents of sarcoplasm and sacroplasmic reticulum in rat skeletal muscle: effects of anisotonic media, ouabain and external sodium
Authors: Rogus Ellen , Zierler Kenneth L.
Published: December 2014

1. During the first 2 hr washout of 24Na from rat extensor digitorum longus muscle fits a sum of two exponentials, neither of which represents loss of extracellular tracer. This implies a model with two intracellular components.

2. Results of suitably designed experiments indicate that the two components are bidirectionally connected to each other as well as to extracellular space. These results are incompatible with a model in which every fibre is homogeneous with respect to Na concentration and flux, but in which there is a distribution of these properties among fibres.

3. Results are consistent with identification of the more slowly exchanging component as sarcoplasm and the more rapidly exchanging component as sarcoplasmic reticulum (SR).

4. Parameters of the general model include six transport coefficients, two volumes, and contents of two Na pools. The number of equations is inadequate to yield unique solutions by which the values of these parameters can be calculated. However, we derive inequalities that place upper and lower limits on the parameters.

5. If the model is correct, the rate constant for Na efflux from SR to extracellular space is at least five times greater than that across sarcolemma. Under standard conditions flux (per muscle weight) from SR is at least 100 times greater than that from sarcoplasm.

6. Under standard conditions, only 2–4% of intracellular Na, or 0·5‐0·9 m‐equiv/kg wet wt., is in sarcoplasm, and the rest is in SR.

7. Bounds on fluid volumes of sarcoplasm and SR under standard conditions are calculated with the assumption that Na concentration in SR is the same as in extracellular space. According to the calculations, fluid volume of sarcoplasm is 0·54 ml./g wet wt. Fluid volume of SR is about 0·124 ml./g wet wt., or 14·3% of fibre volume, in agreement with Peachey's estimate (1965) of volume of SR in frog muscle.

8. Three tests are applied to the model, with the following results: (a) volume of sarcoplasm increases in hypotonic solution and decreases in hypertonic solutions, as predicted for an osmometer. Volume of SR tends to change in the opposite direction, in agreement with results of Birks & Davey (1969) from electron microscopy on frog muscle; (b) the major effect of partial substitution of external Na by Li is a reduction in Na content of SR, with no significant change in that of sarcoplasm or in volume of either component; (c) the major effect of 10−5
M ouabain is an increase in Na content of sarcoplasm, with no demonstrable change in that of SR or in volume of either component.

9. These results support the model, particularly our identification of the slowly exchanging component as sarcoplasm, identification of the rapidly exchanging component as SR, and the assumption that Na concentration in SR is close to that in extracellular fluid.
The role of the sympathetic innervation in the control of plasma glucagon concentration in the calf
Authors: Bloom S. R. , Edwards A. V. , Vaughan N. J. A.
Published: December 2014

1. The extent to which the splanchnic sympathetic innervation is implicated in the control of plasma glucagon concentration has been investigated in the young calf.

2. Stimulation of the peripheral ends of both splanchnic nerves (0·5–10·0 c/s for 10 min) caused an abrupt increase in plasma glucagon concentration in adrenalectomized calves 3–5 weeks after birth. This effect was found to be statistically significant (P < 0·01) at each of these frequencies. In calves tested during the first 24 hr after birth comparatively small responses were obtained.

3. The hyperglycaemia produced by splanchnic nerve stimulation in older calves caused an abrupt rise in plasma insulin concentration when stimulation was discontinued but insulin release was completely inhibited throughout the period of stimulation at all frequencies tested.

4. It is concluded that tonic changes in sympathetic efferent activity are likely to modify plasma glucagon concentration in the normal conscious calf.
Ionic dependence of adrenal steroidogenesis and ACTH‐induced changes in the membrane potential of adrenocortical cells
Authors: Matthews E. K. , Saffran M.
Published: December 2014

1. The effects of changes of ionic environment upon corticosteroid production by rabbit adrenal glands have been investigated in vitro using a superfusion technique and on‐line steroid analysis by an automated fluorescence method. In some experiments micro‐electrode recordings of adrenocortical transmembrane potentials were made concomitantly with measurement of steroid output.

2. Adrenocorticotrophic hormone (ACTH), 10 m‐u./ml., induced a sevenfold increase in corticosteroid production rate in normal Krebs solution.

3. The steroidogenic response to ACTH was not impaired after omission of [K]o for 1 hr but was inhibited following exposure to K+‐free medium for 3 hr. Increase of [K]o tenfold to 47 m
M increased the basal but not the ACTH‐stimulated output of corticosteroid whereas raising [K]o twentyfold to 94 m
M enhanced both the basal and ACTH‐stimulated steroid production rate. In K+‐free solution the adrenocortical cells hyperpolarized from ‐ 67 to ‐ 86 mV; subsequently on addition of ACTH they depolarized. Reintroduction of K+ restored the membrane potential.

4. Omission of Ca2+ partially depolarized the cells but only affected the steroidogenic response to ACTH in the presence of EDTA. A threefold increase of [Ca]o, to 7·68 m
M, had no effect on either membrane potentials or steroid formation, but increasing [Ca]o tenfold to 25·6 m
M partially blocked ACTH action. Increasing [Mg]o twentyfold to 22·6 m
M had little effect on ACTH‐stimulated corticosteroid output and Sr 2·56 m
M, in substitution for Ca2+, supported ACTH action, but La, 0·25 m
M, completely blocked the steroidogenic effect of ACTH.

5. Replacement of NaCl, 118 m
M by choline chloride, 118 m
M, was without effect on ACTH‐induced steroidogenesis, whereas LiCl, 118 m
M, reduced it by 50%. NaF, 1 and 10 m
M, inhibited ACTH‐induced steroidogenesis by approximately 60%.

6. Nupercaine, 10−4
M, inhibited the steroid response to ACTH with no effect upon membrane potentials: increasing the nupercaine concentration to 10−3
M inhibited the steroid response and depolarized the cells. Ouabain, 10−5
M, induced complete depolarization and suppression of the steroidogenic response to ACTH.

7. Action‐potential‐like changes in membrane potential appeared in cells exposed to ACTH in a K+‐free medium. The amplitude of the action potentials ranged from 10 to 60 mV according to cell, with a frequency up to 36/min; the frequency tended to increase with time. Tetrodotoxin, 10−6 g/ml., did not inhibit ACTH‐induced action potentials in K+‐free medium.

8. These observations are discussed in relation to the ionic requirements for the steroidogenic action of ACTH. The results further emphasize the dissociation of membrane polarization and the secretion of steroid. The mechanism of output of steroid hormone from the adrenocortical cell may thus differ fundamentally from the secretory mechanisms in other, particle‐storing cells.
The effect of a water load on cutaneous water loss in man
Authors: Allen Judith A. , Roddie I. C.
Published: December 2014

1. Ingestion of 1 l. water at 37° C had no effect on the rate of water loss from forearm and hand skin although ingestion of a similar volume at 16° C significantly decreased the rate.

2. Ingestion of 1 l. water at 37° C had no physiologically significant effect on the expiratory minute volume.

3. Ingestion of 500 ml. water at 37° C caused small increases in total body weight loss in environmental temperatures of 29 and 40° C.

4. It is concluded that neither cutaneous nor respiratory water loss play an important part in the excretion of a water load in man.
Effects of thermal stimulation of medulla oblongata and spinal cord on decerebrate rabbits
Authors: Chai C. Y. , Lin M. T.
Published: December 2014

1. Changes of rectal and ear temperatures, and respiratory and heart rates, during external thermal stress and during thermal displacement of the medulla oblongata and spinal cord have been investigated in rabbits, before and after decerebration, with ether inhalation only during the operation.

2. Abrupt exposure of the intact animals to heat (35° C) or cold (5° C) produced appropriate thermoregulatory adjustments such as vasodilatation or vasoconstriction of the ear skin, and increase or decrease of respiratory frequency with little change in rectal temperature. After decerebration, these responses to heat and cold were reduced and rectal temperature was moderately altered.

3. In intact animals, heating (42‐43° C) and cooling (32‐33° C) the medulla and spinal cord also produced appropriate thermoregulatory vasomotor and respiratory responses, although these were smaller than those caused by ambient heating and cooling. Heating these structures also produced bradycardia and cooling tachycardia. In addition, shivering‐like movements over extremities and trunks or jaws were elicited, respectively, during spinal or medullary cooling. None of these responses was altered after decerebration.

4. These results suggest that while the hypothalamus may be the principal site of thermoregulation, some independent but less powerful thermoregulatory structures exist in the medulla oblongata and spinal cord. Thermal responses to stimulating the latter structures are not results of afferent activation of the hypothalamic mechanism.
Evidence that axoplasmic transport of trophic factors is involved in the regulation of peripheral nerve fields in salamanders
Authors: Aguilar C. E. , Bisby M. A. , Cooper E. , Diamond J.
Published: December 2014

1. We have compared the effects of partial denervation with those of colchicine‐induced block of axoplasmic flow, on the peripheral fields of nerves innervating the hind limb of salamanders.

2. Acute application of colchicine solution (0·03‐0·10
M) to spinal nerve 16 results in a dose‐dependent increase in skin and muscle fields of the adjacent nerves (15 and 17). The time course, magnitude and distribution of the response to 0·10
M colchicine is not distinguishable from that of the compensatory sprouting of nerves 15 and 17 that occurs after section of nerve 16.

3. In contrast to the situation with nerve section, sprouting of adjacent nerves occurred after colchicine applications which produced no behavioural deficit, no change in the peripheral field of the treated nerve, and no interference with impulse conduction in it; nor was there subsequent degeneration in the nerve.

4. The same concentrations of colchicine reduced the axoplasmic flow of catecholamines and cholinesterase; treated nerves contained fewer microtubules than untreated controls.

5. A similar application of colchicine solution to nerve 15 prevented it from sprouting in response to the stimulus provided by section of nerve 16.

6. We conclude that nerve terminals are continuously supplied by axoplasmic flow with a trophic factor concerned with the regulation of nerve fields. When the supply of this factor is reduced, adjacent nerves sprout and invade the territory of the treated nerve. In addition, the ability of nerves to sprout is itself dependent upon the maintenance of axoplasmic flow.
Cardiorespiratory and metabolic costs of continuous and intermittent exercise in man
Authors: Edwards R. H. T. , Ekelund L.-G. , Harris R. C. , Hesser C. M. , Hultman E. , Melcher A. , Wigertz O.
Published: December 2014

1. Cardiorespiratory and metabolic responses to paired patterns of continuous and intermittent exercise with the same average power output were studied in eight men. Heart rate, ventilation and pulmonary gas exchange were measured during the different patterns of exercise performed on a cycle ergometer. The recovery oxygen volume was measured over 30 min of loadless pedalling. Needle biopsy samples of the vastus lateralis muscle were taken before, during and after completion of the exercise for measurement of muscle metabolites.

2. Heart rate, ventilation, oxygen intake, respiratory exchange ratio, and blood lactate concentration were generally higher with intermittent compared with continuous exercise as were the accumulated totals for heart beats, ventilation and oxygen intake. Muscle biopsy samples tended to have higher lactate and lower phosphocreatine contents in intermittent exercise. The lactate concentration in muscle and blood water was the same during loadless pedalling before exercise but was significantly higher in muscle than blood during exercise. This concentration gradient was larger in intermittent than in continuous exercise.

3. Work efficiency, calculated from the total oxygen cost of work in excess of a loadless pedalling control, was significantly lower in intermittent exercise. The explanation is thought to be connected with the observation that when the work was performed at a high rate in short bursts a large part of the oxidative recovery took place after the contraction during the rest periods, whereas in the low intensity continuous exercise the oxygen was mainly utilized while the work was being performed. This indicates that for part of the time in the intermittent exercise the muscle was working under anaerobic conditions. Although the possibility exists that the efficiency of resynthesis of phosphagen may be reduced in this form of activity, it is more likely that the result described is due to the greater amount of lactate formed in the intermittent exercise.
Physiological types and histochemical profiles in motor units of the cat gastrocnemius
Authors: Burke R. E. , Levine D. N. , Tsairis P. , Zajac F. E.
Published: December 2014

1. A variety of physiological properties of single motor units have been studied in the gastrocnemius muscle (primarily in the medial head) of pentobarbitone‐anaesthetized cats. Intracellular stimulation of individual motoneurones ensured functional isolation of the muscle units innervated by them.

2. A system for muscle unit classification was developed using a combination of two physiological properties. Almost all of the units studied could be classified into one of three major types, including two groups with relatively short twitch contraction times (types FF and FR, which were differentiable from one another on the basis of sensitivity to fatigue) and one group with relatively long contraction times (type S, which were extremely resistant to fatigue and were differentiable from FF and FR units on the basis of the shape of unfused tetani). Post‐tetanic potentiation of twitch responses was observed in all three muscle unit types. The distributions of axonal conduction velocities for motoneurones innervating FF and FR muscle units were essentially the same, while conduction velocities for motoneurones innervating type S units were, in general, slower.

3. Histochemical profiles of muscle units representative of each of the physiological classes present in the gastrocnemius pool were determined using a method of glycogen depletion for muscle unit identification. Each of the physiological categories of muscle units exhibited a corresponding unique set of muscle fibre staining reactions, or histochemical profile. Within each physiological type, all of the units examined had the same histochemical profile. The results generally support the hypothesis that the histochemical characteristics of muscle fibres are meaningfully related to the physiological properties of the same fibres. However, certain limitations in the detailed application of the hypothesis were also apparent.

4. Systematic assessment of the histochemical profiles of relatively large numbers of fibres belonging to single muscle units provided strong support for the hypothesis that all of the muscle fibres innervated by a single α‐motoneurone are histochemically identical.
Depolarization of sensory nerve endings and impulse initiation in common carotid baroreceptors
Authors: Matsuura S.
Published: December 2014

1. Electrical events in the peripheral nerve terminals of baroreceptors were investigated following isolation and identification of receptive fields innervated by single baroreceptor fibres. A slow potential change, that is a local depolarization which had the characteristics of a generator (receptor) potential, was recorded from the common carotid baroreceptor fibres at a point close to the sensory terminals.

2. The slow potential increased in amplitude with increasing stimulus strength and its time course increased with increasing duration of the mechanical stimulus. Action potentials were initiated from the slow potential when the applied mechanical stimulus was suprathreshold.

3. The slow potentials evoked by a train of subthreshold stimuli summed to evoke action potentials.

4. When a high‐frequency train of suprathreshold stimuli was applied to the baroreceptors, the slow potential following a preceding one from which an action potential was initiated failed to fire the nerve fibre.

5. When the sodium content of the Ringer—Locke solution was decreased, the slow potential remained after blockage of the action potential.

6. The slow potential remained after abolishing the spike potential by application of tetrodotoxin.
Ionic analysis of photoreceptor membrane currents
Authors: Zuckerman Ralph
Published: December 2014

1. Membrane current was derived from simultaneous measurements of interstitial ‘dark’ voltages and conductivities along the radial axis of frog photoreceptor cells. Membrane current was subsequently resolved into its component ionic currents or fluxes by means of ionic substitution and by the use of inhibitors of active transport.

2. The plasma membrane of the frog rod outer segment was found to be permeable to Na+ and Cl−, with a ratio of Na+ to K+ permeabilities higher than that found in most neuronal cells. A net inward flux of 1·5 × 108 Na+/sec.rod flows across the outer segment plasma membrane in the dark.

3. The proximal portion of the rod receptor, extending from the proximal region of the inner segment to the synaptic terminal, is mainly permeable to K+, although some degree of Na+ permeability is also presumed.

4. A hyperpolarizing electrogenic Na pump was localized to the base of the outer segment and inner segment of the cell. The pump transfers at least 108 charges/sec out of the cell at this level, the pump current dividing and re‐entering the cell at both the outer segment and proximal portion of the photoreceptor including the synaptic terminal.

5. These findings have been incorporated into an ionic model of the photoreceptor, and its implications for cellular functioning considered.
Net placental transfer of free amino acids against varying concentrations
Authors: Hill Penny M. M. , Young Maureen
Published: December 2014

1. The patterns of the free plasma amino acids in the pregnant guinea‐pig and her foetuses, near term, are described. The concentration of each amino acid was higher in the foetal plasma than in the maternal. The foetal:maternal gradients (F:M) varied for each amino acid; the straight chain amino acids had the highest F:M ratios.

2. Net transfer of endogenous plasma amino acids, from the maternal circulation across the placental membrane, was studied. The foetus was removed and the foetal placenta perfused in situ via the umbilical arteries, with an artificial fluid containing varying concentrations of amino acids.

3. All the amino acids, both essential and non‐essential, could be transferred from the maternal to the foetal circulation against the F:M gradients. With ‘closed circuit’ perfusion, this transport increased the concentration of total amino N in the perfusate until it was twice that of the normal F:M gradient of 5. The concentrations of the individual amino acids was increased to 1·7–4·2 times those normally present in foetal plasma, and the final values reached were similar to the concentrations of free amino acid found in placental tissue.

4. The umbilical vein—artery differences were small, with the placenta perfused ‘open circuit’ in the steady state, using physiological flow rates and amino acid concentrations. The average net placental transfer of amino N found was 1·14 m‐mole min−1. This is about 60% of the calculated net rate of accumulation of N by the 60 g guinea‐pig foetus.

5. The influence of foetal placental perfusion concentration on transfer was small but significant. In the steady state, the transfer of amino N, and each individual amino acid, was found to be inversely proportional to the concentrations in the perfusate when the placenta was perfused ‘open circuit’. The slopes of the regression of transfer on concentration had an average value of 0·13 n‐mole min−1 g−1 per μmole. No significant difference in the slopes was found between the three amino acid transport groups.

6. Net transfer was independent of perfusate flow, within the physiological range, which suggests a secretory process across the membrane from maternal to foetal circulation.
Influence of eye movements on geniculo‐striate excitability in the cat
Authors: Adey W. Ross , Noda Hiroharu
Published: December 2014

1. The excitability of the geniculo‐striate pathway during a saccadic eye movement was studied in alert cats with chronically implanted electrodes. Excitability was assessed by the amplitude of post‐synaptic components of field responses in both lateral geniculate nucleus and visual cortex to electrical stimulation of the optic chiasm. Modifications in amplitude were evaluated during the period following eye movements, by triggering a stimulator from potential shifts in the electrooculograms and altering delays in the stimulus pulse.

2. The post‐synaptic component of the geniculate response was markedly depressed for about 150 msec, reaching a trough at approximately 100 msec after the initiation of an eye movement. This effect was dependent on the visual environment and was not observed in complete darkness. A similar depression occurred when the visual field was abruptly moved by retinal impulses generated by a quick displacement of the image of the visual world associated with an eye movement. The depression reflected a reduction of cellular discharge to the orthodromic volley and hence a suppression of the transmission of visual information through the lateral geniculate nucleus. This may be a mechanism for saccadic suppression.

3. The post‐synaptic components of the cortical response were enhanced for about 200 msec, reaching a peak at approximately 150 msec after the initiation of an eye movement. Although this facilitation occurred also in complete darkness, it did not occur when the visual field was abruptly shifted while the eyes were stationary. The fact that it occurred with eye movements and exclusively in the post‐synaptic components suggests that it was caused by signals from a system closely related to eye movements. This may be a manifestation of the corollary mechanism.
Light‐induced resistance changes in retinal rods and cones of the tiger Salamander
Authors: Lasansky A. , Marchiafava P. L.
Published: December 2014

1. The electrical properties of retinal rods and cones of the larval tiger salamander were investigated with intracellular electrodes, and the cells identified by means of dye injections.

2. Both types of photoreceptors are hyperpolarized by illumination. Following stimulation with brief flashes of dim light, rod responses show a slower time course than cone responses; with bright flashes, rod responses can be recognized because of their long recovery time.

3. Values of input resistance were derived from the voltage displacement induced by constant current pulses in darkness or at the peak of the photoresponse. The input resistance following illumination was also calculated from the effect of steady polarizing currents on the amplitude of the photoresponse.

4. In darkness, the input resistance of the rod cells is time‐ and voltage‐dependent, but the voltage—current relations of most cells have a linear region which includes the physiological limits of membrane potential. At the peak of the photoresponse, the input resistance (slope of the linear region of the v—i relations) is decreased.

5. Cone cells show approximately linear v—i relations. As reported by previous authors, illumination increases the input resistance.

6. These results support the current view that the cone photoresponse is the consequence of a reduction in the permeability of channels which in darkness shunt the membrane. In rods, however, it appears that the main effect of illumination is to increase the permeability of the membrane to ions for which the equilibrium potential is more negative than the membrane potential in darkness.
Stochastic properties of spontaneous transmitter release at the crayfish neuromuscular junction
Authors: Cohen Ira , Kita Hiroshi , Van Der Kloot William
Published: December 2014

1. Miniature excitatory junctional potentials (min.e.j.p.s) were recorded with an intracellular electrode from the adductor muscle of the dactyl of the first or second walking leg of the crayfish, Orconectes virilis.

2. The intervals between the min.e.j.p.s were compared to the exponential prediction by five goodness of fit tests. The results indicate that the intervals are not exponentially distributed.

3. The autocorrelogram of intervals shows that the intervals are unlikely to be independent.

4. A stochastic analysis that includes the power spectrum of intervals, the variance—time curve, and the ln‐survivor curve suggest that there is a clustering of min.e.j.p.s. The results are similar to those on the frog neuromuscular junction.

5. An autocorrelogram of the min.e.j.p. amplitudes suggests that sizes are not independently distributed.

6. These results, which are similar to those previously reported from the frog neuromuscular junction, support the use of the branching Poisson process as a theoretical model for the stochastic properties of spontaneous quantal release of transmitter.
The kinetics of the reaction of carbon monoxide with fully oxygenated haemoglobin in solution and erythrocytes
Authors: Sirs John A.
Published: December 2014

1. Spectrophotometric measurements, using a rapid mixing and stopped flow technique, have been made of the rate at which CO displaces O2 from its combination with haemoglobin.

2. In haemoglobin solutions, buffered at pH 7·2 and 9·1, the reaction proceeds by a unimolecular dissociation as proposed by Gibson & Roughton (1955). In a Ringer—Locke solution, equilibrated with a PCO2 of 3 cmHg and at pH 7·4, the reaction of HbO2 with CO is a two‐stage process, with a transition from one form of Hb4O6 to another.

3. An investigation of the reaction between CO and HbO2 in erythrocytes, suspended in Ringer—Locke solution, indicates that the rate is determined by the chemical reaction and this also is a two‐stage process.

4. The transition is probably associated with the reaction of CO2 with Hb4O6, following the dissociation from fully saturated oxyhaemoglobin of an oxygen molecule. It alters the relative velocity constants of the reactions of O2 and CO with Hb4O6 by 100:1.

5. The implications of these proposals of the equilibria of haemoglobin with CO and O2 are discussed. The difference between the sigmoid equilibria curves at high HbO2 and HbCO values can be explained as due to the different reaction pathways.
The influence of the splanchnic nerves on the external secretion, blood flow and electrical conductance of the cat pancreas
Authors: Barlow T. E. , Greenwell J. R. , Harper A. A. , Scratcherd T.
Published: December 2014

1. Electrical stimulation of the cut peripheral end of the splanchnic nerves results in a biphasic change in electrical conductance measured across the tail of the pancreas. A phase of decreased conductance is followed by a more prolonged phase of increased conductance.

2. Simultaneous measurements of pancreatic blood flow indicate that the phase of decreased conductance occurs as a result of vasoconstriction, whilst the phase of increased conductance is due to vasodilatation.

3. The initial phase of decreased conductance and vasoconstriction is abolished by α‐receptor blocking agents such as phenoxybenzamine and the phase of increased conductance blocked by β‐receptor blocking agents such as pronethalol.

4. Short periods of electrical stimulation applied to the splanchnic nerves result in a secretion of amylase and a reduction in the volume rate of secretion.

5. When the vasoconstrictor response was abolished by phenoxybenzamine, nerve stimulation still reduced the rate of secretion, suggesting that the inhibitory effect is in part due to a direct action of the secretory cells.

6. After bretylium tosylate, splanchnic nerve stimulation no longer produced vasomotor changes in the pancreas and the inhibitory effect on the volume response was converted to one of augmentation, but the secretion of enzymes was unaffected.

7. The secretion of amylase on splanchnic stimulation was abolished by intravenous injection of atropine, suggesting that a cholinergic mechanism is involved.

8. Noradrenaline did not mobilize pancreatic enzymes.
Lipogenesis and insulin sensitivity of single fat cells*
Authors: Gliemann J. , Vinten J. , Vølund Aa.
Published: December 2014

1. A method for measuring the lipogenesis from [14C]glucose by single fat cells is described: (i) after incubation with ‘carrier‐free’ [U‐14C]glucose (0·55 μ‐mole/ml.), collagenase‐isolated fat cells were fixed with osmium tetroxide; (ii) similarly incubated pieces of epididymal fat pads were treated with osmium tetroxide for 90 sec, whereby only the superficial cells are fixed, and the tissue was then disintegrated by shaking with collagenase. The osmium‐fixed free cells were washed, sucked into a micropipette, measured under a microscope and assayed individually for 14C‐activity.

2. There was a quantitative recovery of 14C‐lipid activity from osmium‐fixed single cells.

3. Both collagenase‐isolated cells and in situ fixed surface cells were normally distributed with respect to diameters (for both cell groups from ad lib. fed rats of ca. 110 g; mean diameter, about 55 μm;
S.D. about 7 μm).

4. Frequency distribution curves (number of fat cells versus 14C‐lipogenesis per cell) were asymmetric and very broad (coefficient of variation about 50%) for collagenase‐isolated cells incubated with insulin (103 μ‐u./ml.). Frequency distribution curves for surface cells obtained from similarly incubated pieces of epididymal fat pads showed a coefficient of variation of the same magnitude, whereas the mean lipogenesis of these cells was only about one third of that of the isolated cells.

5. Collagenase‐isolated cells incubated in the presence of insulin (103 μ‐u./ml.) showed a weak but highly significant positive correlation between fat cell diameter and 14C‐lipogenesis (eight rats, r about 0·5 and P < 0·001 for each rat). Analysis of the relationship: lipogenesis = k × diameter to the exponent of β showed that the estimates of β varied significantly from rat to rat (range: 1·3–2·9). Similar correlations between cell size and lipogenesis were found both for cells incubated with insulin in various submaximal concentrations and for cells incubated without insulin.

6. Small and large cells from the same rat were equally sensitive to insulin.

7. Statistical analysis of frequency distribution curves (number of cells versus 14C‐lipogenesis per unit surface area) representing cells from the same rat incubated with insulin 0, 2·5, 5, 10, and 103 μ‐u./ml., respectively, suggests that insulin exerts a graded influence on the lipogenesis of each fat cell.
Functional organization of a visual area in the posterior bank of the superior temporal sulcus of the rhesus monkey
Authors: Zeki S. M.
Published: December 2014

1. Anatomical studies have shown the cortex of the posterior bank of the superior temporal sulcus to receive a projection from visual cortical areas, including areas 17, 18 and 19. In this paper the response of single neurones in this area to simple visual stimulation is reported. Ten monkeys were studied.

2. A clear but relatively crude topographic representation of the visual field was found. There was a large variation in the size of the receptive fields of individual cells, even in a single penetration. Some cells, with the central parts of their receptive fields located from between 1 and 5° from the centre of gaze had receptive fields averaging about 10° × 10° or even larger. Other cells with central receptive fields had much smaller field sizes.

3. Two main types of neurones were encountered, with subdivisions within each type. The first type responded to movement irrespective of form. These could be subdivided into neurones which responded to movement in any direction within the receptive field and neurones which responded to movement in one direction only (directionally selective neurones). Another type of cell was responsive to both contour and movement, much like the complex and lower order hypercomplex cells. Almost all such neurones were directionally selective.

4. In oblique penetrations through this cortical region, there tended frequently to be an orderly shift in preferred directions of motion, thus suggesting the possibility of a columnar organization for movement.

5. Combined anatomical (degeneration) and electrophysiological experiments showed that these types of neurones are found in those regions of the posterior bank of the superior temporal sulcus receiving a direct projection from area 17.
Sensitization and centre‐surround antagonism in Necturus retina
Authors: Burkhardt Dwight A.
Published: December 2014

1. The impulse discharge of ganglion cells and the proximal negative response were recorded with extracellular micro‐electrodes in Necturus retina and spatial influences of background illumination studied.

2. When a steady background of constant illuminance was extended in diameter from 0·25 to 1 mm, the response to a small concentrically placed test flash was enhanced (sensitization).

3. This sensitization was tonic, showed marked spatial summation, was also found by surrounding a central background with an annulus, and when quantified by threshold measurements, closely resembled the sensitization effect found psychophysically in human vision.

4. Sensitization was prominent in intracellular recordings from bipolar cells and usually apparent in horizontal cells. In bipolar cells, a background change which produced sensitization evoked a large but predominantly transient potential whose polarity was opposite to that evoked by a central flash.

5. The tonicity and large spatial extent of the sensitization effect strongly suggest that it is mediated by horizontal cells. They might do this by either acting upon receptors, bipolar cells, or both.
The effect of sodium and calcium ions on the release of catecholamines from the adrenal medulla: sodium deprivation induces release by exocytosis in the absence of extracellular calcium
Authors: Lastowecka Anna , Trifaró J. M.
Published: December 2014

1. Perfusing bovine adrenal glands with Na+‐free Locke solution for 15–40 min did not modify the increase in the release of catecholamines from glands stimulated by acetylcholine. However, after 80–100 min of perfusion with Na+‐free solution, the response to acetylcholine stimulation was decreased or abolished.

2. Immediately after switching the perfusion medium to Na+‐free solution, there was a sharp increase (6–10 times over control values) in catecholamine output.

3. Graded substitution of Na+ in the perfusion fluid enhanced the output of catecholamines. This increase in the output of amines was linearly related to the logarithm of the extracellular Na+ concentration.

4. The release of catecholamines in the absence of Na+ was not reduced by the presence of atropine and hexamethonium nor by the omission of Ca2+ in the presence of EDTA or EGTA.

5. Excess of Mg2+ in the perfusion fluid reduced (10 m
M‐Mg2+) or blocked (20 m
M‐Mg2+) the increase in the output of catecholamines induced by Na+ deprivation in the presence or absence of extracellular Ca2+.

6. Na+ deprivation induced release of catecholamines during perfusion of the glands with depolarizing concentrations (56 m
M) of K+.

7. In the presence or the absence of extracellular Ca2+, the increase in the output of catecholamines induced by Na+ deprivation was accompanied by an increase in the output of dopamine β‐hydroxylase, but not of lactate dehydrogenase. In addition, during perfusion with Ca2+ free solution, Na+ deprivation induced a parallel increase in both catecholamine and adenosine triphosphate outputs.

8. The ratios of catecholamines to dopamine β‐hydroxylase and catecholamines to adenosine triphosphate determined in the perfusates collected from glands during perfusion with Na+‐free medium were similar to those measured in the soluble contents of isolated chromaffin granules. These results provided biochemical evidence in favour of exocytosis as the mechanism of secretion during Na+ deprivation.
Isometric contractions of motor units in self‐reinnervated fast and slow twitch muscles of the cat
Authors: Bagust J. , Lewis D. M.
Published: December 2014

1. Isometric contractions of motor units have been studied in self‐reinnervated soleus and flexor digitorum longus muscles, the motor nerves of which had been transected 6 months earlier.

2. The distributions of motor unit tetanic tensions in both muscles were skewed towards large values and showed greater variance than normal: there were motor units which produced more tension and others which developed less tension than in control muscles. Mean tensions of motor units are compared with those of the controls.

3. The variance of times to peak of motor units in both muscles was significantly smaller than normal.

4. Conduction velocities of axons were slower than normal above the point of nerve section. A number of axons did not functionally cross this point and those that did conducted slowly below the neuroma.

5. Many of the correlations seen in normal muscle between axon conduction velocity, motor unit tetanic tension, twitch time to peak and ratio of twitch to tetanic tension were demonstrated in reinnervated muscle.

6. We suggest that the pattern of motor unit organization in self‐reinnervated muscle can in part be due to random regrowth of axons but is largely produced by specific processes related to axon size which are not identical in fast and slow muscle.
Effect of glycylglycine and glycine on jejunal absorption rate of L‐histidine in man in vivo
Authors: Cook G. C.
Published: December 2014

1. Using a double‐lumen tube jejunal perfusion system in vivo, the effects of glycylglycine and glycine on the jejunal transfer rate of
L‐histidine have been studied in a 30 cm jejunal segment, in six Zambian African men. Data on the effect of
L‐histidine on glycylglycine transfer rate have also been obtained. The solutions perfused in each subject contained (A)
L‐histidine (100 m‐mole l.−1), (B)
L‐histidine (100 m‐mole l.−1) and glycylglycine (50 m‐mole l.−1), (C) glycylglycine (50 m‐mole l.−1), and (D)
L‐histidine (100 m‐mole l.−1) and glycine (100 m‐mole l.−1).

2. Whereas the presence of glycine in the perfusing fluid significantly impaired the absorption rate of
L‐histidine (P < 0·01), glycylglycine had no significant effect. The presence of
L‐histidine in the perfusing fluid had no significant effect on the rate of glycylglycine absorption. When compared with results for glycine absorption rate in twelve Zambian African subjects in another study, the presence of
L‐histidine produced a significant impairment in the rate of glycine absorption (P < 0·001).

3. The results demonstrate a mutual inhibition between the rates of
L‐histidine and glycine absorption. The lack of a similar inhibition between
L‐histidine and glycylglycine is consistent with the concept of independent transfer mechanisms for amino acids and dipeptides in the human jejunum.
The formation of synapses in mammalian sympathetic ganglia reinnervated with preganglionic or somatic nerves
Authors: McLachlan Elspeth M.
Published: December 2014

1. A study has been made of the formation of synapses in the superior cervical ganglion of the guinea‐pig, during reinnervation either with axons of the cervical sympathetic trunk, or with somatic axons of the nerve to the sternohyoid muscle.

2. No significant changes in either the geometry or electrical parameters of sympathetic motorneurones were detected following denervation for periods of 3–6 weeks, or after reinnervation with either preganglionic or somatic axons.

3. The post‐ganglionic action potential reappeared about 4 weeks after preganglionic trunk section (eighteen of eighteen ganglia); its amplitude increased progressively and was almost normal by more than 10 weeks after nerve section. A very small response was detected from thirteen of eighteen ganglia after periods longer than 8 weeks after cross‐reinnervation with somatic axons.

4. Regenerated preganglionic or somatic nerve terminals were demonstrated around the ganglion cells using ZIO impregnation and electron‐microscopy; the structure of these terminals was unchanged following regeneration into the ganglia, although many more synapses were formed by preganglionic terminals than by somatic terminals.

5. The facilitation of evoked synaptic potentials which occurs during repetitive stimulation of preganglionic axons was retained following their regeneration, whereas most synapses formed on ganglion cells by regenerating somatic axons showed facilitation of transmitter release during trains of stimuli, rather than the normal depression.

6. These observations suggest that the structure and electrical properties of adult mammalian autonomic motorneurones are not under neural control, but that these neurones do show some selectivity in the type of nerve which they will permit to form synapses on them.
The density and photosensitivity of human rhodopsin in the living retina
Authors: Alpern M. , Pugh E. N.
Published: December 2014

1. The visual pigment in a 5° circular patch of the living human retina 18° temporal from the fovea was studied with the Rushton retinal densitometer. The measuring light (570 nm) was selected to obviate artifacts from colour photoproducts.

2. The action spectrum of a 10% bleach agrees well with the action spectrum at absolute threshold for the same patch of retina. The quantized C.I.E. scotopic spectral sensitivity curve is a good description of both spectra. Therefore, the visual pigment studied must be human rhodopsin.

3. Its density has been estimated in five different ways. The results are in reasonable agreement. The optical density of human rhodopsin in vivo is about 0·35 (common logarithmic units) at its γmax.

4. The photosensitivity of human rhodopsin in vivo was determined by studying its rate of bleaching in response to steps of monochromatic light exposed to the dark adapted eye, by measuring the amount bleached in the steady state by monochromatic lights as well as the amount bleached by 10 sec flashes of white light.

5. The results obtained by the different methods are in good agreement with each other and with previous estimates made by others using white light.

6. The photosensitivity of human rhodopsin in vivo [εγmax = 62,000 to 120,000 l./cm mole] is much higher than expected from in vitro measurements.
The projection of the posterior knee joint nerve to the cerebellar cortex
Authors: Belcari Paola , Carli G. , Strata P.
Published: December 2014

1. In decerebrate cats, electrical stimulation of the posterior knee joint nerve evokes in the depth of the cerebellar cortex field potentials which have been identified as due to both mossy and climbing fibre inputs.

2. The potentials evoked through the mossy fibres have a latency of 15–17 msec and are more widespread. Those evoked through the climbing fibres have a latency of 26–33 msec and are more restricted.

3. Stimulation of the larger fibres originating from the Golgi receptors gives only a very restricted projection. When the fibres originating from the Ruffini receptors are also activated, the effect on the cerebellar cortex is more widespread.

4. The results have been confirmed by recording unitary activity.
Fluorescent staining of acetylcholine receptors in vertebrate skeletal muscle
Authors: Anderson M. J. , Cohen M. W.
Published: December 2014

1. α‐Bungarotoxin was labelled with fluorescent dyes and used as a stain for visualizing the distribution of acetylcholine receptors in vertebrate skeletal muscle fibres.

2. Dye‐toxin conjugates had the same pharmacological properties as native toxin, but their potencies were lower.

3. Fluorescent staining was examined in teased muscle fibres. The stain was found to be confined to the neuromuscular junction and associated with the subsynaptic membrane.

4. Staining intensity was reduced by curare and even more so by carbachol, but not by atropine or neostigmine. Pre‐treatment of muscles with unlabelled α‐bungarotoxin entirely prevented staining.

5. The staining at amphibian neuromuscular junctions was characterized by a pattern of intense transverse bands occurring at intervals of approximately 0·5‐1 μm, with fluorescence of lower intensity between them. Fluorescent staining was not detected on adjacent, extrasynaptic, muscle membrane. In side views the staining appeared as a fine line with small protuberances occurring at the same intervals as the intense bands seen face‐on. These results indicate that acetylcholine receptors are associated with the entire subsynaptic membrane, including the membrane of the junctional folds and that their density changes abruptly at the border between synaptic and extrasynaptic muscle membrane.
The velocity of lymph flow in the canine thoracic duct
Authors: Browse N. L. , Rutt D. R. , Sizeland D. , Taylor Alexis
Published: December 2014

1. The velocity and pattern of movement of lymph in the thoracic duct of anaesthetized and conscious dogs has been studied by observing the movement of droplets of ultrafluid lipiodol in the duct.

2. The velocity of flow when anaesthetized varied from 0·1–2·0 cm/sec, to 5·0 cm/sec when conscious.

3. The pattern of flow was affected by respiration and the cardiac cycle. Most movement occurred at the end of inspiration.

4. The duct of five autopsy preparations was perfused with saline to assess the volume and velocity of flow produced by the level of pressure gradients previously observed in the duct. These studies show that the small gradients (2–5 mmHg) observed during life are more than sufficient to produce the normal volume and velocity of flow measured. The mean resistance of the duct was 0·5 mmHg/ml. min.
γ‐Aminobutyric acid and inhibition in the septal nuclei of the rat
Authors: McLennan H. , Miller J. J.
Published: December 2014

1. The electrophoretic application of γ‐aminobutyrate (GABA) and glycine to septal neurones inhibited their discharge, but the currents required to cause equivalent degrees of inhibition were always smaller for GABA than for glycine.

2. The actions of GABA but not those of glycine were antagonized by bicuculline and not by strychnine and vice versa.

3. The recurrent collateral inhibition of lateral septal neurones and the direct inhibition of medial cells evoked by stimulation of the fimbria were blocked by bicuculline but not by strychnine.

4. The bursting patterns of discharge of laterally situated medial septal neurones was disrupted by bicuculline, but required a longer application of the drug than was needed to block the direct fimbrial inhibition. It is suggested that this disruption is due to diffusion of the drug to affect the inhibitory interneurones of the lateral septum.

5. It is concluded that the inhibitory processes in the septum involve GABA as the synaptic transmitter.