bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial interaction in human cone vision
Authors: Westheimer Gerald 
Published: December 2014

1. The adaptation state of a uniformly illuminated patch of human cone retina was determined by finding the threshold for a small, brief light spot seen flashing in its centre.2. When the illuminated patch of the retina is increased in diameter, the adaptation state is first raised, and beyond a critical background diameter, lowered.3. This is interpreted as a manifestation of excitatory and inhibitory interaction of adaptation stimuli: illumination of retinal regions in the immediate neighbourhood of the area tested acts to raise the adaptation level, and of those further removed acts to lower it.4. The critical area beyond which adapting light produces inhibition is about 5 min of arc in diameter in the eye's object space for foveal observation. For peripheral cone vision it increases much as the minimum angle of resolution.5. The inhibiting action of outlying areas is substantially reduced, or perhaps even eliminated, by lowering the background luminance.6. Surrounding the retinal patch with a pair of juxtaposed narrow concentric black and white rings superimposed on a uniform field, simulating a border, irrespective of diameter, does not influence the threshold of the probing spot. This argues against a possible threshold raising effect of the border of the background.7. The inhibiting action on a patch of cone retina of a surrounding annulus occurs only when the annulus is seen by the same eye and not when it is seen by the other eye: the site of inhibitory interaction is, therefore, retinal.
Body temperature responses in cats and rabbits to the monoamine oxidase inhibitor tranylcypromine
Authors: Feldberg W. , Lotti V. J. 
Published: December 2014

1. In unanaesthetized cats tranylcypromine (1‐10 mg/kg) had scarcely any effect on rectal temperature when injected intraperitoneally, yet such injections prevented the deep and long‐lasting fall in rectal temperature which normally occurs when the cat is anaesthetized by intraperitoneal pentobarbitone sodium or intravenous chloralose. The anaesthesia itself, however, was not affected. In some of the experiments with pentobarbitone sodium rectal temperature even rose to fever level.2. In anaesthetized as well as in unanaesthetized cats injections of tranylcypromine (0·1‐1 mg) into the cerebral ventricles caused a rise in rectal temperature.3. In rabbits, rectal temperature was scarcely affected when surgical anaesthesia was produced by intravenous infusions of pentobarbitone sodium under the same condition in which, in cats, intraperitoneal pentobarbitone sodium produced a deep and long‐lasting fall in temperature, i.e. when no external heat was applied but excessive dissipation of heat was prevented by placing the rabbit on a cotton‐wool pad. However, when it was placed on the metal surface of an operating table, the anaesthesia was associated with a deep fall in rectal temperature.5. In anaesthetized and unanaesthetized rabbits tranylcypromine had no effect on rectal temperature when injected intraperitoneally (10 mg/kg) or into the cerebral ventricles (1 mg).5. These results are discussed in relation to the theory that the three monoamines in the hypothalamus, 5—hydroxytryptamine (5‐HT), adrenaline and noradrenaline, act as central transmitters in temperature regulation.
The effect of withdrawal of visual presentation of errors upon the frequency spectrum of tremor in a manual task
Authors: Sutton G. G. , Sykes K. 
Published: December 2014

1. When a subject attempts to exert a steady pressure on a joystick he makes small unavoidable errors which, irrespective of their origin or frequency, may be called tremor.2. Frequency analysis shows that low frequencies always contribute much more to the total error than high frequencies. If the subject is not allowed to check his performance visually, but has to rely on sensations of pressure in the finger tips, etc., the error power spectrum plotted on logarithmic co‐ordinates approximates to a straight line falling at 6 db/octave from 0·4 to 9 c/s. In other words the amplitude of the tremor component at each frequency is inversely proportional to frequency.3. When the subject is given a visual indication of his errors on an oscilloscope the shape of the tremor spectrum alters. The most striking change is the appearance of a tremor peak at about 9 c/s, but there is also a significant increase of error in the range 1‐4 c/s. The extent of these changes varies from subject to subject.4. If the 9 c/s peak represents oscillation of a muscle length‐servo it would appear that greater use is made of this servo when positional information is available from the eyes than when proprioceptive impulses from the limbs have to be relied on.
Acetate metabolism in the isolated sheep foetus
Authors: Alexander D. Pauline , Britton H. G. , Nixon D. A. 
Published: December 2014

1. Sheep foetuses over the age range 105‐142 days and maintained on an extracorporeal circuit removed exogenous acetate at 2·0‐4·9 mg/kg.min.2. Urinary loss of acetate was less than 12·5% of the administered amount.3. The rate of acetate removal appeared to be unaffected by the addition of glucose to the circuit. The removal of glucose also seemed to be unaffected by the presence of acetate.4. A decline in the plasma concentration of free fatty acids and ketone bodies was also observed during the perfusion.5. It is concluded that under these conditions acetate may have accounted for about one half of the oxygen consumption. The contribution of free fatty acids and ketone bodies must have been small. The relevance of these findings to the nutrition of the foetus in utero is discussed.
The effect of a non‐ionic detergent (Triton WR 1339) on the removal of triglyceride fatty acids from the blood of the rat
Authors: Otway Sheila , Robinson D. S. 
Published: December 2014

1. The initial rate of removal from the circulation of injected [14C] labelled chylomicron triglyceride is much slower in rats that have been injected with the non‐ionic detergent, Triton WR 1339, than in normal animals. Pre‐incubation of the lipid with Triton before its injection causes a further reduction in removal rate.2. After the injection of [14C]labelled chyle triglyceride into animals given Triton, the rate of disappearance of radioactivity falls markedly as the percentage of the labelled material remaining in the blood declines.3. A much smaller decrease in the rate of removal of injected chylomicron triglyceride occurs with increase in the size of the injected dose and with increase in the time interval between Triton and chylomicron triglyceride injections.4. Serum triglycerides labelled with 14C are removed from the circulation of rats that have been given Triton at a much slower rate than [14C] labelled chylomicron triglycerides.
The effect of very frequent milking and of oxytocin on the yield and composition of milk in fed and fasted goats
Authors: Linzell J. L. 
Published: December 2014

1. The effect of milking goats 1‐4 times an hour for 3‐12 hr on the yield and composition of milk has been studied in fed and fasted animals at all stages of lactation.2. It was essential to inject oxytocin (50‐400 m‐u.
I.V.) just before each milking to remove all the milk already in the udder and then the yield was similar to that obtained on twice daily milking (105 ± 2·1
S.E.%). There were no significant differences between goats or between the two glands of one goat, even if one had been denervated by autotransplantation. However, the variation from hour to hour was 1·5 times greater than from day to day.3. The claim of Zaks (1964) and Zaks, Natochin, Sokolova, Tanasichuk & Tverskoy (1965) that milking every 15 min always produces a large rise in milk Na and a fall in K and lactose, which is characteristic of alveolar milk, is not substantiated. In high yielding goats milking gently by hand or with a cannula caused a small change in K only, but vigorous hand milking exacerbated this fall and also caused a fall in lactose and a rise in Na and Cl. Still larger changes were produced by using excessively large doses of oxytocin (2500 m‐u.) when there was also a rise in citrate and total nitrogen. Hourly milking in goats fasted for 24 hr had the same effect.4. In fasted goats the milk yield fell to 90% within 8 hr and to 56 ± 2·1% of the previous level by 24 hr. It remained at this level for a further 10‐12 hr on twice daily or on hourly milking. The yields of autotransplanted glands usually fell slightly but significantly more than that of the glands in situ. In most goats mammary blood flow was halved but in all animals there were large falls in mammary uptake of glucose, acetate and amino acids and greatly increased uptake of free fatty acids. There were significant differences between fasted goats on hourly milking.5. It is concluded that, in spite of changes in milk composition, milking hourly can be a useful technique for studying milk secretion. The striking effects of a short fast in a lactating animal are emphasized.
The effect of subthreshold potentials on the membrane current in cardiac Purkinje fibres
Authors: McAllister R. E. , Noble D. 
Published: December 2014

1. In sodium‐containing solutions, up to 60% of the slow outward current in Purkinje fibres can be activated by depolarizations which are too small to activate the fast sodium conductance responsible for the depolarization phase of the action potential. This result reinforces the view that the slow outward current results from slow activation of the potassium conductance rather than from slow inactivation of the sodium conductance.2. These subthreshold changes in membrane conductance are probably responsible for the dependence of the action potential and pace‐maker potential durations on small changes in membrane potential in the subthreshold region.
Energetics of cardiac contractions
Authors: Gibbs C. L. , Mommaerts W. F. H. M. , Ricchiuti N. V. 
Published: December 2014

1. The average resting heat production of a muscle under zero tension is 24·8 mcal/g muscle .min at 20° C. In the majority of muscles examined the resting heat production increases when the resting tension and muscle length are increased.2. The relation between actively developed tension and heat produced is similar to that existing in skeletal muscle. The plot of heat against developed tension can be obtained either by altering muscle length or by varying the stimulus frequency.3. The mean maximum total efficiency work/(work + heat) in the work experiments was 11·6%. The total energy produced (work + heat) correlates with the load rather than with the work done.4. In isotonic contractions more heat is liberated than the heat versus tension plot predicts. This extra heat is load‐dependent.
Effects of water content upon the respiration and the cations of kidney slices
Authors: Little J. R. , Robinson J. R. 
Published: December 2014

1. Cortical slices from the kidneys of adult rats were incubated aerobically at 38·5° C in Warburg manometers in an ordinary balanced saline medium and also in ‘low‐ion’ media consisting of 20 m
M Tris buffer to which 0‐30 g polyethylene glycol (‘PEG 6000’)/100 ml. was added to control the swelling of the tissue.2. Oxygen uptake in the low ion media containing less than 2 m‐equiv/l. of Na+ and K+ was maximal when the water content of the slices was kept normal by 14% PEG 6000 in the medium, and was about two thirds of the oxygen consumption in a balanced saline medium.3. Slices respiring in the low‐ion media retained potassium in concentrations 10‐20 times the concentration in the medium; the ratio of tissue to external concentration of K+ was inversely related to the water content of the tissue.4. Ratios of K+/Na+ concentration in tissue water were maximal and equal to 10‐25 when water content was near normal and the ratio Na+/K+ in the medium was between 1·5 and 2·0.5. Cryoscopic measurements showed that 14% of PEG 6000 contributed 140 m‐osmole/kg to the osmolality of the low‐ion media in which slices maintained a normal water content.6. It was not possible to interpret the volume of the cells as determined by the balance between the osmotic effect of PEG 6000 in the medium and the colloid osmotic pressure of intracellular proteins.
Influence of the ionic environment on the membrane potential of adrenal chromaffin cells and on the depolarizing effect of acetycholine
Authors: Douglas W. W. , Kanno T. , Sampson S. R. 
Published: December 2014

1. Intracellular recordings were made from chromaffin cells isolated from adrenal medullae of gerbils to examine the effects, on membrane potential, of changes in the ionic environment that are known, from other experiments, to influence the rate of catecholamine secretion.2. Depolarization in response to acetylcholine fell linearly with the logarithm of the extracellular sodium concentration over the range 154‐3 m
M and reached a value, in sodium‐free medium, of about 30% of the control value.3. The depolarizing effect of acetylcholine in sodium‐free media increased linearly with the logarithm of the extracellular calcium concentration over the range 1‐117 m
M.It is concluded that depolarization in response to acetylcholine involves inward movement of both sodium and calcium ions.4. Depolarization was also observed in response to the secretagogues, excess potassium and barium, both in sodium‐rich and sodium‐free media. The effect of barium was antagonized by calcium, and it is suggested that these two cations interact at the level of the plasma membrane.5. Depolarization does not appear to be tightly coupled to secretion, for acetylcholine or excess potassium still depolarized the chromaffin cells when the environment was calcium‐free or contained an excess of magnesium, conditions that inhibit secretion. Furthermore, although acetylcholine had some depolarizing effect in sodium‐free media, the level to which the membrane potential fell was not below the control ‘resting’ potential since the cells in sodium‐free medium were hyperpolarized; yet, secretory responses are augmented in such conditions.6. It is proposed that depolarization in response to acetylcholine may be no more than the electrical sign of increased permeability to ions such as sodium and calcium, and that depolarization is not, in itself, a key event in stimulus—secretion coupling. The evidence is held to favour the view that movement of calcium into the chromaffin cells on exposure to acetylcholine is responsible for evoking secretion.
Potassium‐stimulated respiration and intracellular calcium release in frog skeletal muscle
Authors: Van Der Kloot William G. 
Published: December 2014

1. In 1931 Fenn showed that the respiration of frog twitch muscles increases when [K+]o is raised. The present paper is a further study of potassium‐stimulated respiration. Stimulation depends on membrane potential, since respiration is also stimulated by elevated [Rb+]o or [Cs+]o in direct relation to their ability to depolarize.2. When [K+]o is elevated to 25 m
M there is an increase in respiration which is sustained for hours. If [K+]o is 30 m
M or above, there is a transitory burst of stimulated respiration, followed by a decline back to the basal level.3. If [K+]o is raised in steps from 20 to 30 m
M, there may never be a burst of increased oxygen consumption. Often a rise in [K+]o from 20 to 24 m
M decreases respiration.4. The response to elevated [K+]o can be blocked by divalent cations or by local anaesthetics; the blocking agents do not interfere with the depolarization of the membrane. The blocking agents act rapidly; they probably take effect soon after they contact the cell membrane.5. Either extracellular Ca2+ or Sr2+ is important for the stimulation of respiration. The burst produced by 50 m
M [K+]o is transformed into a sustained rise in respiration when [Ca2+]o or [Sr2+]o are also raised. If a muscle is stimulated with 25 m
M [K+]o in the absence of extracellular calcium, respiration is elevated as usual, but now the rise is transitory unless Ca2+ or Sr2+ are added back to the extracellular solution.6. Depolarization seems to stimulate respiration by causing the release of Ca2+ into the sarcoplasm. Since respiration is increased by a depolarization below the threshold for producing a contracture, respiration is more sensitive than contraction as an indicator of sarcoplasmic calcium concentration.7. A model for the relation between sarcoplasmic calcium and membrane potential is proposed. The model accounts for the time course of the stimulation of respiration and also for much of the available data on potassium contracture. In the model, Ca2+ is released into the sarcoplasm from a store in the cell. With depolarization, the release of Ca2+ from the store is increased, but the rate at which extracellular Ca2+ can replenish the store is decreased. The ability of the longitudinal reticulum to pump Ca2+ from the sarcoplasm does not vary with membrane potential.
An electrophysiological study of single vagal efferent units associated with gastric movements in sheep
Authors: Iggo A. , Leek B. F. 
Published: December 2014

1. A method for obtaining reticulo‐ruminal movements for up to 19 hr in halothane‐anaesthetized sheep is described. The duration, wave form and frequency of the movements resembles those in the conscious animal except that ruminal movements have a lower amplitude.2. A method of recording for up to 5½ hr single efferent unit discharges from fibres presumed to innervate the reticulo‐rumen is described.3. At least seven distinguishable types of discharge pattern were recorded. By relating these temporally to movements of the reticulum and rumen it was concluded that Types I, II and III occurred in fibres innervating the reticulum or associated structures, Type IV the rumen and Types V, VI and VII other gastric structures not yet identified. Apart from Type VII units there was no ‘resting discharge’ in efferent fibres during the quiescent phase of the gastric cycle.4. We conclude that the co‐ordination of the complex sequence of gastric movements in ruminant animals is a function of the ‘gastric centres’ in the hind‐brain through their ability to determine the pattern, durations, spike frequencies and temporal interrelationships of discharges in gastric motoneurons innervating the different parts of the forestomach.
Nervous factors influencing the membrane activity of intestinal smooth muscle
Authors: Kuriyama H. , Osa T. , Toida N. 
Published: December 2014

The effects of various chemical agents on the spontaneous membrane activities and those electrically elicited in the smooth muscles of small intestine were investigated.1. The effects of various chemicals on the spontaneously active membrane might be summarized as follows. (a) Cholinergic agents; atropine slightly hyperpolarized the membrane and reduced the amplitude of slow potential changes even in aged preparations. Prostigmine depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. Atropine prevented the actions of prostigmine on the membrane. (b) Ba2+ depolarized the membrane, and enhanced the amplitude and prolonged the duration of the slow potential changes. The spike frequency was initially increased, then reduced. Atropine and tetrodotoxin partially prevented the action of Ba2+ on the membrane activities.2. Effects of chemical agents on the membrane activity elicited by electrical stimulation might be summarized as follows. (a) Short pulse stimulation (0·5‐1 msec) generated the spike as a direct response of the muscle cell membrane, then it was followed by slow depolarization, delayed hyperpolarization, i.e. the ‘inhibitory potential’, and post‐inhibitory rebound successively. (b) The slow depolarization and the post‐inhibitory rebound were reduced in amplitude by treatment with atropine, and enhanced by treatments with prostigmine and Ba2+. Tetrodotoxin blocked all activities except the spike.3. When repetitive stimulation (20 c/s) was applied to the membrane, the membrane hyperpolarized; then, after 3‐5 sec, it gradually depolarized even if the stimulation was continued, and triggered spikes. The hyperpolarization always preceded depolarization. The duration and the amplitude of the delayed depolarization was proportionally increased by the increased intensity and duration of stimulation. Atropine and tetrodotoxin blocked the generation of the post‐inhibitory rebound.4. Effects of repetitive stimulation on the stored tissues were observed. The responses to repetitive stimulation of the membrane of muscles which had been stored 50 hr at 4 °C, were the same as those observed in the fresh tissue. The response of the tissue which had been stored 100 hr was the same as that observed in the fresh tissue treated with tetrodotoxin, i.e. all activities except the spikes were blocked.
The effect of progressive hypoxia on the respiratory and cardiovascular systems of the chicken
Authors: Butler P. J. 
Published: December 2014

1. During the initial stages of progressive hypoxia the intact, unanaesthetized chicken shows increases in heart rate and respiratory frequency with no change in arterial blood pressure and oxygen consumption. During the later stages, heart rate, diastolic and mean blood pressure and oxygen consumption fall, while respiratory frequency increases further.2. Following bilateral cervical vagotomy and adrenergic β‐receptor blockage there is no tachycardia, but the late bradycardia and fall in blood pressure do occur during progressive hypoxia. Respiratory frequency remains at a low level after vagotomy.3. It is suggested that the initial tachycardia is dependent on both the sympathetic and parasympathetic nervous systems, and that the former helps maintain arterial pressure during the early stages of hypoxia. Bradycardia and hypotension seem to be due to anoxia itself, and the vagus is essential for the increase in respiratory frequency.
Observations on the site and mode of action of pyrogens in the rabbit brain
Authors: Cooper K. E. , Cranston W. I. , Honour A. J. 
Published: December 2014

1. Leucocyte pyrogen has been injected bilaterally into various parts of the rabbit brain. It caused fever when injected into the pre‐optic area and the anterior hypothalamus, but not when injected into the posterior hypothalamus, the mid‐brain, the pons, the cerebellum or the cerebral cortex.2. The mean time which elapsed between a leucocyte pyrogen injection into the anterior hypothalamus and the onset of fever was 7·8 min. For similar injections of bacterial pyrogen the time lag was 24·8 min. The mean time lag between bilateral injections of noradrenaline into the anterior hypothalamus and the onset of fever was 7·4 min.3. The amount of leucocyte pyrogen required to cause fever when injected into the anterior hypothalamus was less than 1/100 of that required to cause a similar fever on intravenous injection. The quantity of bacterial pyrogen injected into the hypothalamus was of the same order as that which would cause a similar fever on intravenous injection.4. Control injections of saline, plasma, cerebrospinal fluid, heated leucocyte pyrogen and red cells into the anterior hypothalamus did not cause fever.5. After attempts to deplete the hypothalamus of its monoamine stores by intraventricular injections of reserpine, the rabbit had fever as a result of an intravenous injection of bacterial pyrogen.6. We conclude that the anterior hypothalamus and the pre‐optic area are sites at which leucocyte pyrogen acts to cause fever in the rabbit. The mechanism of this febrile response is not clear, but it appears that part, at least, of the response could be mediated by a mechanism other than release of noradrenaline or failure to release 5‐HT.