bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulus—response functions of rapidly adapting mechanoreceptors in the human glabrous skin area
Authors: Knibestöl M. 
Published: December 2014

1. Single unit impulses were recorded from the ulnar and median nerves of awake human subjects with tungsten electrodes inserted percutaneously in the upper arm.2. Forty‐nine rapidly adapting mechanoreceptors with receptive fields in the glabrous skin area were studied. Thirty‐nine units had small receptive fields with distinct borders (RA‐receptors) while ten units had large fields with indistinct borders (PC‐receptors).3. The afferent response to stimuli of varying indentation amplitude and velocity of indentation, was analysed.4. Amplitude thresholds varied from 0·05 to 1·65 mm for the RA‐receptors. For the PC‐receptors amplitude thresholds ranged from less than 0·05 to 1·95 mm.5. Velocity thresholds varied for the RA‐receptors from 0·4 to 39·3 mm/sec, and for the PC‐receptors from 0·5 to 19·6 mm/sec.6. The conduction velocities of the afferents were all in the A α—β range. For the RA‐receptors the conduction velocities ranged from 26 to 91 m/sec (mean = 55·3 ± 3·4), and for PC‐receptors the range was from 34 to 61 m/sec (mean = 46·9 ± 3·6).7. The nerve impulse frequency as a function of indentation velocity was analysed for nineteen RA‐receptors and four PC‐receptors. A hyperbolic log tangent function of the type first introduced by Naka & Rushton (1966) in studies on S‐potentials in the fish retina was found to be the best description of the stimulus—response function for sixteen RA‐receptors and two PC‐receptors. For the remaining units a pure logarithmic function was the best description. However, the logarithmic function may be, as found in the present study, a special case of the more general log tanh function.
Photoreceptors in the crayfish compound eye: electrical interactions between cells as related to polarized‐light sensitivity
Authors: Muller Kenneth J. 
Published: December 2014

1. The sensitivity to plane‐polarized light and the electrical interactions of photoreceptors were examined with intracellular and extracellular micro‐electrodes in excised compound eyes of the crayfish.2. There are two types of photoreceptor: each photoreceptor cell responds best to polarized light when the electric‐vector of the light is oriented in one of two orthogonal directions. Seven cells, representing each type, are grouped together to form ommatidia.3. In each ommatidium, cells that are sensitive to the same orientation of the electric‐vector of polarized light are coupled electrically. Cells having orthogonal polarized‐light sensitivities are not coupled.4. Nearly all cells studied were sensitive to orange light. A few cells of both types were found that were sensitive to blue light. Blue‐sensitive cells were not coupled to orange‐sensitive cells.5. The photocurrents of both cell types produce negative extracellular potentials which can be greater than 10 mV when measured near the photoreceptive membranes within ommatidia. Evidence suggests that the extracellular potentials produced by one type of cell can effectively reduce the receptor potentials recorded in the other cell type. It is proposed that such a mutual non‐synaptic interaction can make a cell more sensitive to the orientation of polarized‐light than would be predicted from the cell's differential absorption of polarized light (i.e. its dichroic ratio).
Further effects of chlorpromazine on the hexose permeability of the human erythrocyte
Authors: Baker G. F. , Rogers H. J. 
Published: December 2014

1. The effect of chlorpromazine on hexose transfer across the human erythrocyte membrane was investigated by optical and isotopic techniques in intact erythrocytes.2. Chlorpromazine produces two phases of inhibition of glucose exit at 17° C in both types of experiment.3. Glucose exchange flux shows a much smaller decrease in flux rate at the same concentrations of chlorpromazine at 17° C.4. Sorbose and glucose entry at 36° C show a similarly complex inhibition by chlorpromazine. The inhibitor constant (Ki) for these effects with the two sugars is similar.5. An Arrhenius plot shows that the average energy change for the reaction of the carrier with chlorpromazine is −46 kJ mole−1 and suggests that a drug‐induced conformational change in the carrier may occur.6. These findings require models of hexose permeation to contain separate terms in their kinetics for net and exchange fluxes and the predictions of one such model have been compared with the experimental results.
Efflux of potassium from isolated rod outer segments: a photic effect
Authors: Cavaggioni A. , Sorbi R. T. , Turini S. 
Published: December 2014

1. Illumination of the isolated outer segments of rod photoreceptors loaded with 42K or 86Rb reduces the efflux of these ions.2. During the perfusion of the isolated rod outer segments with a solution containing only 2·36 m
M‐Na the effect of light is absent, and the amplitude of the photic effect is linearly related to the logarithm of the extracellular Na concentration.3. In darkness, raising the concentration of K in the fluid of perfusion gives an increase of the efflux of 86Rb and increasing the extracellular concentration of Ca yields a retention. The efflux of 86Rb and 42K is greater in darkness when sucrose or choline substitute for Na.4. It is suggested that in darkness the isolated outer segments are permeable both to Na and to K. Light appears to decrease the permeability for Na ions. There is no evidence that the permeability for K ions is modified by light.
The physiological role of calcitonin assessed through chronic calcitonin deficiency in rats
Authors: Kumar M. Ashwini , Sturtridge W. C. 
Published: December 2014

1. An attempt was made to assess the physiological role of calcitonin by producing its prolonged deficiency in rats.2. Three groups of young rats viz. (I) sham‐operated controls, (II) thyroidectomized with thyroxine replacement and (III) thyroidectomized with thyroxine as well as calcitonin replacement, all with parathyroid autografts, were studied for 5 weeks. Groups II and III showed impaired Ca tolerance and group II also showed significant reduction in total (organic and inorganic) mass of femora as compared to group I.3. Three similar groups of old mature rats were studied as under (2) for 9 weeks. Groups II and III in this case showed no significant changes as compared to group I.4. In intact mature rats, Ca tolerance is impaired, thyroid content of calcitonin is high and the hypocalcaemic action of calcitonin is much reduced as compared to intact young rats.5. It is concluded that calcitonin plays a useful but non‐essential role in Ca metabolism and bone development of young growing rats. Its function, if any, in mature rats on a normal diet remains doubtful.
Excitation‐contraction coupling in voltage clamped uterine smooth muscle
Authors: Mironneau Jean 
Published: December 2014

1. The relationship between ionic currents and contraction has been investigated in uterine strips of pregnant rat by means of a double sucrose gap apparatus combined with an optical method which permits the measurement of the contraction of the small muscular bundle where potential and current are recorded.2. Effects of duration, size and frequency of imposed potentials upon contraction have been studied. The uterine muscle shows summation and tetanus phenomena. Tension elicited by depolarizing pulses of different durations and amplitudes can be considered as made of two components.3. The first component of the contraction evoked by short depolarizing steps (about 50 ms) depends on the slow inward current. This contraction is abolished by manganese and lanthanum ions and by compound D 600. The amplitude of the tension can be related to the external calcium concentration and consequently to the calcium influx. The slow inward current is supposed to release a part of the bound calcium without excluding, however, a direct activation of myofibrils.4. The second component of the contraction is observed in manganese containing solution with depolarizations longer than 200 ms and without inward current. Such a component of tension suggests the possibility of release of calcium from intracellular stores which could be located in the sarcoplasmic membrane of the uterine smooth muscle.
Relationship between the velocity of rolling granulocytes and that of the blood flow in venules
Authors: Atherton Anne , Born G. V. R. 
Published: December 2014

1. The mean velocities at which granulocytes roll along the walls of small venules have been related to their mean blood flow velocities in preparations of hamster cheek pouch and mouse mesentery. In animals anaesthetized with Nembutal, 30–200 μm venules were observed microscopically and the movement of rolling granulocytes quantitated on films. Apparent mean blood flow velocity was determined from films of embolizing platelet thrombi.2. In four venules the velocity distribution of about 100 rolling cells was almost symmetrical about the mode, with a small proportion moving at up to three times the mode velocity. Therefore, the mean and mode velocities were very similar.3. In two mesenteric and two cheek‐pouch venules, blood flow velocity was temporarily altered during and after gentle compression with a fine glass fibre; this was associated with proportional changes in mean cell velocities.4. In four different venules of a hamster cheek pouch, the mean velocity of rolling granulocytes increased in proportion to the mean blood flow velocity (r = 0·963).5. In thirty‐six venules of ten mouse mesenteries, the velocities were proportional (r = 0·915) between blood velocities of about 300 and 1000 μm/sec. Above this the velocity of the cells did not increase further.6. The rolling of granulocytes is presumably governed by two forces, the shear force of the flowing blood and an adhesive force between the surfaces of granulocytes and vascular endothelium. Our results suggest that, within limits, the proportionality between the velocities of blood flow and rolling cells is due to shear force, the adhesive force being similar for all the cells. The results suggest that this adhesion force per granulocyte is of the order of 10−5 dynes.
The rate of action of tetrodotoxin on myelinated nerve fibres of Xenopus laevis and Rana esculenta
Authors: Schwarz J. R. , Ulbricht W. , Wagner H.‐H. 
Published: December 2014

1. The experiments were done on single Ranvier nodes of Xenopus laevis (voltage clamp) and Rana esculenta (action potentials). Rate and size of the effect of tetrodotoxin were determined by the reversible reduction of either the sodium inward current (Xenopus) or of V̇A, the maximum rate of rise of the action potential (Rana).2. The results of tetrodotoxin block at equilibrium could be excellently fitted by assuming a one‐to‐one reaction between toxin molecules and sodium channels of the Xenopus membrane with an equilibrium dissociation constant K = 3·60 n
M at room temperature. V̇A was not linearly related to the fraction of unblocked sodium channels and 10·9 n
M tetrodotoxin was necessary on the average to reduce V̇A to 50% in Rana motor fibres; in sensory fibres a lower concentration sufficed.3. Onset and offset of the tetrodotoxin effect on Xenopus nodes could be quantitatively interpreted as being determined by the rates of the tetrodotoxin channel reaction. Experiments with 3·1 and 15·5 n
M tetrodotoxin at room temperature yielded an association rate constant, k1, of 2·94 × 106
M−1 sec−1 and a dissociation rate constant, k2, of 1·42 × 10−2 sec−1. In these experiments the equilibrium dissociation constant, K, was 3·31 n
M. If determined solely from the onset in the two tetrodotoxin concentrations, k1 = 3·25 × 106
M−1 sec−1 and K = k2/k1 = 4·08 n
M was calculated.4. In Rana fibres the onset and offset of V̇A reduction by 15·5 and 31 n
M tetrodotoxin was evaluated using the equilibrium effects of intermediary tetrodotoxin concentrations for calibration. The average results at room temperature were k1 = 4 × 106
M−1 sec−1, k2 = 1·4 × 10−2 sec−1 and K = 3·4 n
M.5. The very short latency with which V̇A started to decline when tetrodotoxin was suddenly applied proved that the toxin had ready access to the membrane.6. The temperature dependence of k1, k2 and K in the Xenopus experiments could be described by Arrhenius plots yielding activation energies, Ea, of 9·8, 20·5 and 7·0 kcal/mole, respectively, corresponding to Q10 values of 1·82, 3·42 and 1·53 (between 12 and 22° C). For k1, determined from onset alone, Ea = 13·7 kcal/mole (Q10 = 2·25) was obtained. Although in Rana the temperature dependence of the rate constants could not be determined directly, the Q10 for k2 must have been of the order of 3.7. The results suggest that the rate of the toxin action on the nodal membrane of Xenopus and Rana is limited by the tetrodotoxin‐sodium site reaction.
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.