bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of neutral α‐ and ω‐amino acids and basic α‐amino acids on uptake of l‐histidine by intestinal mucosa, testis, spleen and kidney in vitro: a comparison with effect in brain
Authors: Neame K. D. 
Published: December 2014

1. The effect of the
D‐ and
L‐isomer of neutral α‐amino acids, of ω‐amino acids, and of basic
L‐α‐amino acids on uptake of
L‐histidine in vitro has been investigated in intestinal mucosa, testis, spleen and kidney cortex, and compared with the effect in brain.2. Neutral α‐amino acids produced inhibition that was in general greater the longer the carbon chain of the inhibiting amino acid. There were minor variations with different tissues.3. ω‐amino acids produced little or no inhibition, with only slight variation between tissues. There was a tendency towards less inhibition the longer the carbon chain.4. The effect of basic amino acids varied with different tissues. With one exception, all produced significant inhibition with intestinal mucosa and testis. With spleen and kidney, inhibition was slight or absent, and resembled the effect produced by the ω‐amino acids. With brain (previously reported elsewhere) the short‐chain amino acids produced considerable inhibition, those having longer carbon chains little or none.5. Proline produced significant inhibition in brain and spleen, but none in the other tissues. Tryptophan had no effect with kidney.6. The findings are considered as further evidence for a relation between the extent to which an amino acid can be taken up by a given tissue and the specificity of the transport systems in that tissue. They also support the view that the nature of certain transport systems may vary considerably between different tissues.
Decremental and incremental visual thresholds
Authors: Short A. D. 
Published: December 2014

1. Extrafoveal decremental and incremental visual thresholds have been measured with a circular test‐object of 57′ diameter, an exposure time of 0·1 sec and background luminance ranging from 2·5 to 7·3 log. quanta (equivalent to 507 nm) per second per square degree at the cornea.2. The decremental threshold is lower than the incremental threshold by factors up to 0·4 log. unit when the background luminance is low; and the two thresholds are virtually the same when the background luminance is high.
The extracellular space of the smooth muscle of the guinea‐pig taenia coli
Authors: Goodford P. J. , Leach E. H. 
Published: December 2014

1. The measured extracellular space of the taenia coli is large when small ions or molecules are used for the determination, and small when large molecules are used, even with identical experimental procedures.2. Extracellular hyaluronic acid has been detected histologically. It is apparently reduced by hyaluronidase.3. The extracellular inulin space increases after the tissue has been pretreated with hyaluronidase, although the ionic composition and wet weight are unchanged.4. It is suggested that the hyaluronic acid prevents the free entry of macromolecules such as inulin into the extracellular space by steric hindrance. Monatomic ions such as Na+, Li+, Cl−, Ca2+ therefore have a larger extracellular space available than is calculated on the basis of the inulin space.5. A slight shrinkage of the muscle cells can be detected when the incubation period is prolonged.
An interaction between potassium and sodium in the smooth muscle of the guinea‐pig taenia coli
Authors: Goodford P. J. 
Published: December 2014

1. The potassium content of the guinea‐pig taenia coli was 72 m‐mole K/kg fr. wt. after equilibration with normal Krebs‐type solution at 35° C in vitro.2. It fell to 13 m‐mole K/kg fr. wt. when Ca2+ and Mg2+ were omitted from the bathing solution, but this fall was reversed in part when [Na+]o was also reduced.3. The taeniae relaxed when Ca2+ and Mg2+ were omitted from the normal solution. However, they contracted if Na+ was also omitted.4. Effects 2 and 3 may show some antagonism between sodium and divalent cations in smooth muscle.5. The extracellular space of the same muscles was measured with [14C]sorbitol. It was 440 ml./kg fr. wt. in normal solution.6. The uptake of 42K was measured in the same muscles at the same time. An initial rapid exchange was followed within 2 min by a slow (half‐time [unk] 50 min in normal solution) and presumably intracellular uptake of tracer.7. In normal solution the initial rapid phase of 42K exchange corresponded to 3·0 m‐mole K/kg fr. wt. A value of 2·6 m‐mole K/kg fr. wt. would have been calculated from [K+]o and the [14C]sorbitol space, and these estimates did not differ significantly.8. The [14C]sorbitol space fell slightly when [Ca2+]o, [Mg2+]o, and [Na+]o were reduced, but the amount of rapidly exchanging potassium increased significantly reaching 4·6 m‐mole K/kg fr. wt. in solutions from which Ca2+, Mg2+ and Na+ were omitted. The [14C]sorbitol space only accounted for 2·4 m‐mole K/kg fr. wt. under these conditions, a significantly smaller quantity.9. The observations have been interpreted on Wilbrandt & Koller's (1948) hypothesis that there may be a superficial anionic region in muscle cells. On this model the present results suggest that K+ rather than Na+ is favoured as a monovalent counter‐cation in the taenia coli.
Pharmacological studies on feline Betz cells
Authors: Crawford J. M. , Curtis D. R. 
Published: December 2014

1. A study has been made of the sensitivity of single neurones in the pericruciate cortex of anaesthetized and unanaesthetized cats to cholinomimetics administered electrophoretically from multibarrel micropipettes.2. A high proportion of deep pyramidal cells, including Betz cells, were excited by these substances, and the receptors involved have muscarinic characteristics.3. Atropine specifically reduced the sensitivity of cortical neurones to acetylcholine, but no such action could be demonstrated for dihydro‐β‐erythroidine, gallamine or general anaesthetics.4. The significance of these results is discussed in relation to the possible synaptic or non‐synaptic action of acetylcholine upon cortical neurones.
Skin temperature, thermal comfort, sweating, clothing and activity of men sledging in Antarctica
Authors: Budd G. M. 
Published: December 2014

1. Three men were studied while dog‐sledging 320 km in 12 days in Antarctica. Conventional Antarctic clothing (‘sweaters and windproofs’) was worn. Four hundred observations were made of medial thigh skin temperature, thermal comfort, sweating, clothing, activity and environmental conditions.2. Work occupied an average of 11·0 hr/day and sleep 7·5 hr. Estimated daily energy expenditure averaged 5100 kcal (range 2740‐6660 kcal).3. Skin temperature fell on exposure to cold despite the clothing worn, but was not changed by the level of activity. Sweating, and thermal comfort, were directly related to both skin temperature and activity.4. Inside the tent, the modal value of skin temperature was 33° C (range 27‐36° C) and the men were comfortable in 94% of observations.5. During the 9·2 hr/day spent outdoors the modal value of skin temperature was 27° C (range 18‐33° C) and the men felt too cold (but did not shiver) in 11% (range 7‐20%) of observations, suggesting that cold stress was not negligible. However, they also felt too hot in 20% of observations and were sweating in 23%.
Body temperature, shivering, blood pressure and heart rate during a standard cold stress in Australia and Antarctica
Authors: Budd G. M. , Warhaft N. 
Published: December 2014

1. Four men of European descent were exposed naked to an air temperature of 10° C for 2 hr in Australia, and again after 24 weeks' residence at Mawson, Antarctica.2. Their ability to maintain rectal temperature during the test cold exposure significantly improved at Mawson. Shivering and cold diuresis did not change. The response of skin temperature did not change significantly except for a small increase in toe temperature. Bradycardia caused by the cold exposure was significantly greater at Mawson, but the rise in blood pressure did not change. Spontaneous fluctuations in rectal temperature that occurred during the cold exposure were intensified at Mawson.3. The results confirm those of a previous study at Mawson, and are attributed to general acclimatization to cold. It is suggested that tissue insulation increased as a result of enhanced vasoconstriction.
Effect of 5‐hydroxytryptophan acting from the cerebral ventricles on 5‐hydroxytryptamine output and body temperature
Authors: El Hawary M. B. E. , Feldberg W. 
Published: December 2014

1. In cats anaesthetized with intraperitoneal pentobarbitone sodium the third ventricle, the anterior or inferior horn of the left lateral ventricle, was perfused with 5‐hydroxytryptophan (5‐HTP) in different concentrations, and the effluent assayed for 5‐hydroxytryptamine (5‐HT) on the rat stomach strip preparation of Vane (1957).2. On perfusion of the third ventricle with 5‐HTP the output of 5‐HT in effluent increased, the increase depending on the 5‐HTP concentration: with 1/50,000 it increased 44‐69 times (mean 55), with 1/25,000, 81‐83 times (mean 82) and with 1/10,000, 71‐200 times (mean 128). The 5‐HT output depended also on the initial output during the preceding perfusion with artificial c.s.f. The greater this initial output the greater was the maximum output reached during the 5‐HTP perfusion.3. The increase in 5‐HT output during perfusion of the third ventricle with 5‐HTP was usually associated with shivering and a rise in rectal temperature. This association, however, was not invariably obtained, probably because of a central depressant effect of 5‐HTP itself.4. On perfusion of the anterior or inferior horn of the left lateral ventricle with 5‐HTP, the output of 5‐HT in the effluent also increased, but to a lesser extent than in the effluent from the third ventricle. There was no association with shivering nor with a rise in rectal temperature.5. An injection of 1 or 2 mg 5—HTP into the cerebral ventricles of unanaesthetized cats produced a biphasic rise in temperature, shivering, constriction of the skin vessels followed by vasodilatation, tachypnoea, wiping and scratching movements, miaowing and long lasting sleep.6. The biphasic rise in temperature is explained as the result of two opposing effects: increased formation of 5‐HT which would raise body temperature, and a central depressant effect of 5‐HTP itself or of one of its metabolites which would lower body temperature.7. The initial rise in temperature and the shivering in response to an intraventricular injection of 5‐HTP varied from cat to cat. In those in which these effects were strong the 5‐HT output during a subsequent perfusion of the third ventricle with artificial c.s.f. was higher, and the maximum 5—HT output reached on perfusion with 5‐HTP was greater than in those in which these effects had been weak.
Location of sites of 5‐hydroxytryptamine storage and metabolism by radioautography
Authors: Gershon M. D. , Ross L. L. 
Published: December 2014

1. A technique for the radioautographic identification, localization, and study of the turnover of cellular depots of 5‐hydroxytryptamine (5‐HT) has been evaluated. A light microscopic survey was made of the uptake and turnover of 5‐HT, synthesized in vivo from its administered tritium‐labelled precursor, 5‐hydroxytryptophan (5‐HTP).2. 5‐HT was taken up rapidly and retained for long periods of time by adrenal medullary chromaffin cells, gastric enterochromaffin cells, blood platelets, thyroid parafollicular cells, beta cells of pancreatic islets, mast cells, and septal cells of the lung. Reticulo‐endothelial cells of liver and spleen took up radioactive 5‐HT more slowly but also retained it for days.3. Specific uptake, and a rapid turnover of radioactive 5‐HT, was found in pancreatic exocrine cells, neurones of the superior cervical ganglion, terminal axons of gastro‐intestinal myenteric plexus, carotid body cells, and pinealocytes.4. A supranuclear localization of radioactive 5‐HT in renal proximal tubular cells may represent tubular secretion of 5‐HT.5. The localization of 5‐HT by radioautography generally corresponds to that found by formaldehyde‐induced fluorescence. It makes possible the study of 5‐HT turnover and is capable of greater resolution than the fluorescence technique. Freeze‐drying may also be avoided.
An analysis of spontaneous impulse activity of units in the striate cortex of unrestrained cats
Authors: Griffith J. S. , Horn G. 
Published: December 2014

1. Recordings were made from sixty‐five cells in the visual cortex of unanaesthetized, dark‐adapted cats and transferred automatically to computer input paper tape.2. The activity of each cell was measured as a function of time (the running mean). The unit of time used was inversely proportional to the mean firing rate, in order to give comparable results for different cells.3. For sixty‐nine sections of discharge from fifty‐two cells, the length of time recorded was sufficient to test for the long‐term stability of the running mean. In twenty‐six sections, various kinds of trend and long‐term irregularity were found.4. The interspike interval histogram was computed for the forty‐one sections (from thirty‐one cells) in which there were more than 2000 discharges. Only eight histograms approximated closely to the exponential form. A test was also made of the distribution of the longer intervals alone and in twenty‐five sections they did not deviate significantly from the exponential form.5. There was no significant correlation between the behaviour of the longer interspike intervals and the long‐term stability or otherwise of the running mean.
Optical quality of the human eye
Authors: Campbell F. W. , Gubisch R. W. 
Published: December 2014

1. Optical quality of the eye was measured at eight pupil sizes between 1·5 and 6·6 mm diameter by recording the faint light emerging from the eye; this light was reflected from the bright image of a thin line on the fundus.2. The nature of the fundus reflexion was examined; it was found that the fundus acts very much like a perfect diffuser while retaining polarization.3. Using the result that the fundus acts like a diffuser, the recorded line images were Fourier analysed to provide modulation transfer functions. These functions indicate an optical quality considerably higher than that found in previous physical studies.4. Linespread profiles were then derived from the modulation transfer functions. These profiles are 40% narrower than those of previous physical studies for a 3·0 mm pupil. The narrowest profile occurred with a 2·4 mm pupil.5. Our results demonstrate that physical and psychophysical studies can yield similar estimates of optical quality. The influence of optical factors not common to both techniques is discussed. Evidence for the existence of neural ‘image sharpening’ mechanisms is reviewed.
Potassium contractures in single muscle fibres of the crayfish
Authors: Zachar J. , Zacharová Daria 
Published: December 2014

1. Contractures were evoked in isolated muscle fibres of the extensor carpopoditi muscle of the crayfish (Astacus fluviatilis) by increasing [K]o at constant [Cl]o or at constant [K]o[Cl]o product.2. The relation between tension and log [K]o is S‐shaped with a less steep slope if [K]o was increased at constant [Cl]o. This is due to a smaller drop in membrane potential for a given change in [K]o in the latter case.3. The curves relating the tension to the membrane potential overlap in either case. In the linear part of the curve, the slope is around 0·3 kg cm−2m V−1.4. The mechanical threshold of contracture is about ‐55 mV and mechanical saturation is at ‐20 mV.5. Fibres exert the greatest tension when stretched to 1·25 lo (8 kg/cm2), where lo is the length at which the fibres are just taut in the solution. Tension falls on either side of this optimal length. Tension vanishes when the fibre is stretched to 1·95 lo.6. Sarcomere length at optimal fibre length is 10·5 ± 0·3 μ. The A band is 3·95 ± 0·8 μ long and does not alter during stretch.7. The crayfish muscle fibres were of the phasic type, since they relaxed spontaneously at maintained high [K]o.8. At [K]o near saturation point, contractures attain the maximum tension in 5 ± 1·3 sec and the time to half decay is 8·1 ± 0·5 sec.9. If the contracture is allowed to relax spontaneously, it is not possible to obtain initial tension until after 20‐30 min. When the contracture is terminated by a return to low [K]o after reaching its maximum, but before spontaneous relaxation appears, the fibre is capable of repeatedly exerting the initial tension.10. The rate of recovery after a spontaneously relaxed contracture depends on [K]o in the solution, in which the fibre lies before evoking the test contracture. The relation of recovery upon log [K]o is S‐shaped and the tension is the greater, the lower the [K]o in the solution in which recovery is taking place.
Properties of stretch receptors in cat extraocular muscles*
Authors: Bach-Y-Rita P. , Ito F. 
Published: December 2014

1. The properties of fifty‐two stretch receptors in the extraocular muscles were studied in thirty cats. Between ten and twenty‐eight receptors were observed in each preparation.2. In four preparations, spontaneously discharging receptors were observed, with afferent fibre conduction velocities ranging from 16·9 to 41·1 m/sec.3. In the remaining twenty‐six cats, the minimal threshold receptors ranged from 3 to 130 g, with a peak distribution between 10 and 20 g, and afferent fibre conduction velocities ranging from 6·5 to 52·0 m/sec, the peak being between 10 and 15 m/sec. Of these receptors, nineteen were quickly adapting and seven were slowly adapting.4. The dynamic and static indexes of all the receptors were essentially similar; they both increased markedly on increasing the initial length. This suggests that the receptors do not lie in contact with regions of reduced viscosity on the muscle fibres comparable to the equatorial region of the intrafusal muscle fibres.5. All of the receptors were located in the muscle; none was located in the tendon. Forty‐seven of forty‐nine receptors were in parallel and two receptors were in series with the contractile elements.6. The properties of all the receptors studied appeared to be similar, suggesting that a single type of stretch receptor is located in the inferior oblique muscle of cats.
Kidney composition and renal concentration ability in young rabbits
Authors: Forrest J. N. , Stanier Margaret W. 
Published: December 2014

1. The water, sodium, urea, potassium and ammonia concentrations of the kidney cortex and inner medulla of adult rabbits, and of rabbits 1, 4, 14 and 21 days old, were measured after mild dehydration. The urine osmolarity and serum and urine urea concentrations were also measured.2. Potassium and ammonia showed no consistent variation in the different parts of the kidney or at the different ages. Sodium concentrations expressed as m‐equiv/100 g fresh weight were about twice as high in the medulla as in the cortex at all ages.3. The medulla/cortex ratio of urea concentration increased markedly between the fourteenth and twenty‐first day after birth. So also did the urine osmolarity of the mildly dehydrated animals.4. The rise in the medulla/cortex urea ratio between birth and 21 days, and the even higher ratio found in adult animals, was due to a decrease in the concentration of urea in the cortex rather than to an increase in its concentration in the medulla.
Effects of sodium extrusion and local anaesthetics on muscle membrane resistance and potential
Authors: Harris E. J. , Ochs S. 
Published: December 2014

1. Membrane potentials and resistances of K‐depleted muscles were measured in the cold and again after warming in K‐containing media so that active ion movements occurred.2. On warming there was a fall of resistance and a gradual rise of potential which passed through a maximum. Later measurements of resistance in a chloride medium showed that values were, if anything, higher than initially in the warm.3. The excess potentials measured approximated to those required to induce passive inward movement of the K ions through the measured K resistance.4. Permeabilities for K+ and Cl− were deduced. When cocaine, procaine, amytal or mepyramine were added or when K+ was replaced by Rb+ in the Cl−‐free solution the K+ permeability was eventually reduced. The same agents led to an enhanced initial response of potential to warming, but later the potentials in Cl−‐free media fell to less than the K+ equilibrium values.5. A method for obtaining the resistivity of the membrane from measurements made in conditions of non‐linear voltage—current dependence was applied.
Effect of inhibitors and uncouplers on the Na pump of the Maia muscle fibre
Authors: Bittar E. E. 
Published: December 2014

1. A study has been made of sodium efflux from single muscle fibres of the crab Maia squinado, and of the effect of inhibitors and uncouplers on this efflux, using the microsyringe technique.2. (i) Externally applied ethacrynic acid or injected ethacrynic acid produces 50% inhibition. The inhibitory state due to externally applied ethacrynic acid is shown to be sensitive to 40 m
M‐K+ in the bathing medium.(ii) Internally applied chlorpromazine causes 40% inhibition.(iii) Internally applied ethyl alcohol causes a slight increase or a slight decrease in Na efflux or no effect.(iv) Internally applied antimycin A produces a net inhibitory effect of almost 50%.(v) Internally applied rotenone produces a 60% inhibitory effect while fibres that fail to contract initially show about a 90% fall in efflux.(vi) The response pattern to internally applied oligomycin is similar to that of antimycin but the net inhibitory effect is only 25%.(vii) Internally applied atractylate produces 45% inhibition.(viii) Internally applied gramicidin A produces about 40% inhibition.(ix) Internally applied valinomycin is without an effect, but in the presence of 40 m
M‐K+ in the external medium there is marked inhibition of Na efflux.3. The evidence put forward suggests that the Na pump of the Maia fibre is divided into two parts, one the Na+‐K+‐ATPase, driven by ATP and arginine phosphate (ArP), and the other, an electrogenic mechanism, driven by respiration and possibly direct coupling of glycolytic energy. The process of reverse electron flow can be invoked as a reasonable explanation of some of the observations made.
Post‐tetanic hyperpolarization and electrogenic Na pump in stretch receptor neurone of crayfish
Authors: Nakajima S. , Takahashi K. 
Published: December 2014

1. Two types of after‐potentials in the stretch receptor neurone of crayfish are described.2. A short‐duration after‐hyperpolarization associated with a single spike or a few spikes is diminished and reversed on applying hyperpolarizing currents. However, a much longer‐lasting post‐tetanic hyperpolarization (PTH) is enhanced by conditioning hyperpolarization; thus, no reversal potential can be obtained.3. No changes in membrane conductance occur during PTH.4. Reducing K concentration in the bathing fluid diminishes PTH, while it shifts the reversal potential of the short after‐potential toward greater negativity.5. Replacement of Na with Li, or addition of 2,4‐dinitrophenol in the bathing fluid suppresses PTH in a reversible manner.6. Electrophoretic injection of Na into the cell induces a long‐lasting hyperpolarization.7. No change in K‐equilibrium potential, as indicated by the reversal point of the short after‐potential, is detected during PTH.8. It is concluded that the short after‐potential is caused by a permeability increase for potassium ion, whereas PTH is produced by an electrogenic Na‐pump.