bluuebunny/crossref_metadata_2025_split huggingface dataset:
Membrane potential and ion content in the smooth muscle of the guinea‐pig's taenia coli at different external potassium concentrations
Authors: Casteels R. , Kuriyama H. 
Published: December 2014

1. The relation between the membrane potential and the intracellular ion concentration of the taenia coli was studied in solutions with different external potassium concentrations.2. Isotonic solution in which the sum of NaCl+KCl was constant did not produce swelling of the smooth muscle of taenia coli, even at high [K]o, and did not change the intracellular chloride concentration.3. Addition of an equivalent amount (118 m
M) of NaCl or KCl to Krebs solution produced the same loss of water.4. Solutions in which the product [K][Cl] was kept constant decreased the internal chloride concentration so that the chloride equilibrium potential became temporarily positive and returned only after 2 hr to a negative value.5. From these results and the finding that even in normal Krebs solution ECl was about 35 mV more positive than the membrane potential, it is concluded that the chloride ions are not passively distributed. The potassium equilibrium potential is the main factor in the generation of the membrane potential. The large discrepancy between the two can be explained by the non‐passive chloride distribution and by the sodium permeability of the membrane. The maintenance of the normal cell volume in solutions with constant sum of NaCl+KCl is explained by the constant intracellular chloride concentration.
Tension development in highly stretched vertebrate muscle fibres
Authors: Gordon A. M. , Huxley A. F. , Julian F. J. 
Published: December 2014

1. An apparatus is described by which the length of a selected part of an isolated muscle fibre can be held constant, giving isometric conditions, or alternatively its length can be measured while tension is held constant (isotonic). Control can be switched between length and tension so as to carry out afterloaded contractions with a shortening stop.2. When a part of a fibre with uniform striation spacing is stretched so far that there is presumably no overlap of filaments, the tension developed during an isometric tetanus with this apparatus is very small (not more than 3‐5% of the tension developed at optimum length).3. If the tendon ends are held stationary, a fibre with the same initial length develops a large amount of tension (order of 30‐40% of tension at optimum length) with a slow time course. This additional tension is due to shortening of the end parts of the fibre, where the striation spacing is smaller and overlap of filaments still exists.4. The resistance to elongation of a part of a fibre where there is no overlap is only slightly increased on stimulation.5. To a first approximation, the results are in good agreement with expectations based on the sliding filament theory. The development of detectable amounts of tension, and of a slight increase of stiffness, on stimulation, are however not expected on the simplest form of this theory; possible explanations are discussed.
The flow and lipoid composition of thoracic duct lymph in the grazing cow
Authors: Hartmann P. E. , Lascelles A. K. 
Published: December 2014

1. A technique is described for the collection of thoracic duct lymph from the grazing cow.2. The effects of continuing drainage of lymph were overcome by establishing an exteriorized lymphatico‐venous shunt from which lymph and blood samples were obtained when required. The shunt functioned satisfactorily for periods of 10, 14 and 28 days in the three cows.3. The rate of lymph flow and concentration of lipids in the lymph were low during and immediately after the operation. Higher sustained levels of flow of 1·37 ± 0·43 (
S.D.), 1·88 ± 0·40 (
S.D.) and 1·90 ± 0·45 (
S.D.) 1./hr, for the dry and two lactating cows respectively, were observed during the period 3‐9 days after the operation.4. More than 200% of the volume and 100% of the protein of the blood plasma compartment passed through the thoracic duct each day.5. Chlyomicron triglyceride comprised 50‐70% and phospholipid 20% of the total lipid in lymph.6. The results indicated that at least 200 and 400 g of esterified fatty acid were transported daily in the lymph of the dry and lactating cows respectively.
The local training effect of secretory activity on the response of eccrine sweat glands
Authors: Collins K. J. , Crockford G. W. , Weiner J. S. 
Published: December 2014

1. The influence of repeatedly raising the body temperature by radiant heat to a level at which acclimatization to heat is normally acquired was investigated in two series of experiments, the first without the subjects sweating, the second with sweating.2. In a second investigation local sweat‐gland activity was induced by drug injections on successive days without raising the body temperature.3. These experiments show that the increased sweating capacity characteristic of acclimatization to heat is a result of sweat‐gland activity and does not appear to be induced by or to depend on an elevated body temperature.4. Secretory activity results in a loss of glycogen from sweat‐gland cells on the first day of heat exposure but not after the glands have been ‘trained’ by acclimatization to heat.5. The state of acclimatization has no influence on the threshold concentration of acetylcholine required to elicit sweating when injected intradermally.
The placental transfer of hexoses and polyols in the guinea‐pig, as shown by umbilical perfusion of the placenta
Authors: Ely Pauline A. 
Published: December 2014

1. Experiments involving polyol and sugar transfer across the guineapig placenta have been described.2. Regarding the former, sorbitol, dulcitol and mannitol are all transferred at approximately the same rate and more slowly than meso‐inositol. Erythritol is not transferred.3. Concerning the hexose transfers, glucose and galactose are transferred at approximately the same rate and more rapidly than fructose.4. With regard to glucose transfer, there appears to be a mechanism with the following properties: (a) It tends towards saturation under certain conditions. (b) It favours saturation rather than diffusion kinetics for forward flows. (c) It exhibits competition with fructose and with galactose. Glucose/galactose competition has been used to demonstrate uphill transport by counterflow. (d) Competitive inhibition by phlorrhizin or phloretin could not be demonstrated.
Circulatory control in hypoxia by the sympathetic nerves and adrenal medulla
Authors: Korner P. I. , White S. W. 
Published: December 2014

1. The effects of severe arterial and primary tissue (carbon monoxide) hypoxia on cardiac output, arterial and right atrial pressures, heart rate and ventilation, have been studied in unanaesthetized normal rabbits, and in animals subjected to adrenalectomy, ‘sympathectomy’ (guanethidine), adrenalectomy + ‘sympathectomy’, and section of the carotid sinus and aortic nerves.2. In both arterial and primary tissue hypoxia the sympathetic nerves play a more important part in the normal circulatory response than the adrenal medullary hormones.3. Provided one adrenergic effector pathway remains intact, animals with intact chemoreceptors and baroreceptors tolerate both types of hypoxia well. Circulatory control during both types of hypoxia by means of sympathetic nerves alone produces relatively more peripheral vasoconstriction than is observed during reflex control through increased adrenal catecholamine secretion.4. The occurrence of tonic sympathetic activity in animals with section of carotid sinus and aortic nerves permits maintenance of a high cardiac output during hypoxia but the arterial pressure is low and there is probably less selective distribution of blood flow to the periphery than in animals with normal reflex control.5. Absence of any adrenergic activity in adrenalectomized and ‘sympathectomized’ animals results in a gradual fall in cardiac output during prolonged hypoxia, after an initial small rise.6. The results in guanethidine‐treated animals suggest that the sympathetic discharge to the arterial chemoreceptors is a factor sustaining chemoreceptor discharge during prolonged arterial hypoxia.
The dual effect of calcium on the action potential of the frog's heart
Authors: Niedergerke R. , Orkand R. K. 
Published: December 2014

1. Using ventricle strips of the frog's heart stimulated at the low rate of about 1 shock/min intracellular action potentials were recorded under conditions of varying calcium concentrations.2. Overshoots of action potentials were increased by about 18·3 mV as a result of a 10‐fold increase, within the range of 0·1‐5 m
M, of the calcium concentration.3. A similar effect was obtained by strontium, but magnesium was ineffective.4. The increase of the overshoot by high calcium was associated with an increased rate of rise of the potential during the later part of its ascending phase. The initial fast upstroke remained unaltered.5. Another effect, a depression of the overshoot, developed during periods of repetitive stimulation, at the rate of 20/min, and this was followed by a gradual recovery during subsequent periods of rest.6. The depression of the overshoot increased with increasing calcium concentrations reaching values of over 40 mV.7. High concentrations of strontium and low concentrations of sodium also induced depression of the overshoot, but high magnesium was ineffective.8. A tentative hypothesis has been proposed attributing these two effects: (a) to an entry of calcium through the excitable membrane thus contributing to the ionic inward current, and (b) to a resulting accumulation of calcium in some cellular store.
The preparation and properties of porcine neurophysin and the influence of calcium on the hormone‐neurophysin complex
Authors: Ginsburg M. , Jayasena K. , Thomas P. J. 
Published: December 2014

1. The preparation of a hormone‐binding protein fraction (neurophysin) from porcine neurohypophyses is described.2. It was shown by gel‐filtration that the protein (which sedimented as a single component on analytical ultracentrifugation) forms complexes with oxytocin and lysine vasopressin. The maximum capacity of porcine neurophysin to bind oxytocin and lysine vasopressin was estimated from the results of dialysis experiments as 232 u. oxytocin and 48 u. lysine vasopressin/mg protein.3. Binding of oxytocin and lysine vasopressin by neurophysin was completely inhibited in the presence of calcium in concentrations greater than 10−6
M but is unaffected at less than 10−7
M‐Ca. The concentration of calcium required to inhibit binding did not appear to be dependent on hormone or protein concentrations.4. No evidence was obtained that calcium was bound by neurophysin or by the peptide hormones either alone or in combination.5. These results are discussed in the light of the hypothesis that release of the hormone from the neurohypophysis is mediated by calcium.
Contraction kinetics of striated muscle fibres following quick changes in load
Authors: Civan M. M. , Podolsky R. J. 
Published: December 2014

1. The contraction kinetics of single striated muscle fibres and small fibre bundles from the frog and the toad were measured when the load was changed from P0 to L < P0. Simultaneous recordings were made of displacement at one end and force at the other end of the preparation.2. After the load was changed, the contractile force generally reached a steady value before the contraction velocity became steady. The amount of time required for isotonic contraction to become steady depended on the change in fractional load and on the temperature; it did not depend on sarcomere length in the range 2·2‐3·0 μ or on the number of fibres in the preparation. The characteristics of the non‐steady state are described in terms of the displacement deviation (the difference between the actual displacement at a given time and the back extrapolation of the steady phase of the displacement record) and the null times (the times at which the displacement deviation became zero, measured relative to the time at which the contractile force first reached the value of the load).3. The time average of the transient velocity was approximately equal to the final steady velocity.4. The product of the null time following a given relative force step and Vmax, the steady velocity of unloaded contraction, was found to be independent of temperature. This is taken as evidence that the isotonic velocity transients originate in the contractile mechanism.5. The non‐steady state following step changes in load is identified with the motion of cyclic contraction mechanisms. The motion of the specific model formulated by A. F. Huxley (1957) was compared with that of frog muscle fibres and, although the transients in the two systems differ in detail, the characteristic dimensions are of the same order.
The effects of cyclopropane, halothane and ether on central baroreceptor pathways
Authors: Biscoe T. J. , Millar R. A. 
Published: December 2014

1. The reductions in arterial pressure and preganglionic sympathetic activity evoked by aortic nerve stimulation in the rabbit were studied before and during administration of constant inspired concentrations of the inhalation anaesthetics cyclopropane, halothane, and ether. The background anaesthetic was pentobarbitone, gallamine triethiodide was given, and pulmonary ventilation was with 100% oxygen.2. During light pentobarbitone anaesthesia, aortic nerve stimulation usually induced similar reductions in arterial pressure and preganglionic discharge, expressed as the maximum percentage reduction from prestimulation levels. There were two components in the sympathetic responses, attributable to A and C fibre excitation in the aortic nerve, which was also shown to contain a third fibre group with properties similar to those of B fibres.3. The arterial pressure, heart rate, and preganglionic sympathetic responses to aortic nerve stimulation were rapidly and profoundly inhibited by 50% cyclopropane, which also produced arterial hypertension.4. Halothane (3%) significantly inhibited the depressor responses, but even in the presence of severe hypotension the arterial pressure could usually be further reduced by aortic nerve stimulation. The inhibitory effects of 2% halothane were slow in onset and not pronounced. In the concentrations used, these actions of halothane were significantly less than those of cyclopropane.5. The inhibitory effects of ether on the depressor responses were roughly intermediate between those of cyclopropane and halothane; complete suppression of the responses occurred with high ether concentrations, which were also liable to cause circulatory collapse.6. It is concluded that the three anaesthetics significantly inhibit impulse transmission through central baroreceptor pathways; the implications of the findings are discussed in relation to the different circulatory actions of these anaesthetics.
In vitro absorption of γ‐globulin by neonatal intestinal epithelium of the pig
Authors: Lecce James G. 
Published: December 2014

1. An in vitro method, using fluorescent γ‐globulin and everted neonatal pig's intestinal slices, for the study of the active transport of large molecules is described.2. Uptake of γ‐globulin occurred within 15 min and required no exogenous substrates.3. In vitro absorption of γ‐globulin by intestinal epithelium was limited to the neonatal pig and 5‐day‐old mouse. No uptake was seen in intestines from a mature mouse, a pig with diarrhoea, a normal pig, a mature rabbit, a guinea‐pig, a chick, and a chick embryo. Chick embryo yolk sac readily took up γ‐globulin.4. Rings of everted intestinal epithelium remained active (still absorbed γ‐globulin) after incubating for 4‐6 hr in balanced salt solution (BSS).5. Uptake of γ‐globulin required oxygen and sodium and was reversibly inhibited by metabolic antagonists such as iodoacetate, arsenate, fluoride, 4,6‐dinitro‐ϕ‐cresol, phlorrhizin, anaerobiosis and cold. Under the conditions of the test, large colloidal molecules did not inhibit uptake of γ‐globulin.6. Similar results (although not as clear‐cut) with metabolic inhibitors were obtained with preparations of chick embryo yolk sacs.7. Injuring mature pig's intestinal epithelium with surface‐active agents did not produce non‐specific absorption artifacts that resembled the specific absorption found in immature pig's intestinal epithelium.
The importance of peripheral changes in determining the sensitivity of striated muscle to depolarizing drugs
Authors: Maclagan Jennifer , Vrbová Gerta 
Published: December 2014

1. The sensitivity of the flexor digitorum longus and soleus muscles to depolarizing drugs was tested after cross‐union of their respective motor nerves.2. The alien innervation did not affect the sensitivity of either the flexor digitorum longus (FDL) or soleus muscles, which retained their normal characteristic responses to decamethonium and suxamethonium. The time course of muscle contractions was, however, altered by the cross‐union operation.3. A considerable increase in sensitivity to depolarizing drugs was shown after de‐afferentation and after tenotomy of the soleus muscles. Both these conditions are associated with muscle atrophy.4. It is suggested that hypersensitivity to depolarizing drugs can be expected in any situation where the muscle is undergoing atrophy.
The subcellular localization of kallikrein, amylase and acetylcholine in the submaxillary gland of the guinea‐pig
Authors: Bhoola K. D. , Ogle C. W. 
Published: December 2014

1. The subcellular distribution pattern of kallikrein was compared with that of amylase and acetylcholine in submaxillary gland homogenates of the guinea‐pig.2. Kallikrein was located in particles which sedimented in the nuclear (46%) and mitochondrial (17%) fractions. These particles were probably similar if not identical to zymogen granules.3. The above observations would support a digestive role for salivary kallikrein.
Amino acid transport in the goldfish intestine
Authors: Mepham T. B. , Smith M. W. 
Published: December 2014

1. The serosal transfer of the following eight amino acids: threonine, alanine, serine, histidine, valine, methionine, phenylalanine and leucine, was measured using everted sacs of anterior intestine taken from goldfish acclimatized to 8° C and incubated at 25° C.2. All eight amino acids were actively transported and the serosal transfer correlated with the steady potential (P < 0·001) and with the amino acid‐evoked potential (P < 0·05) measured on the same preparations.3. The goldfish rectum actively transported alanine and the steady potential was raised when alanine bathed the mucosa of the everted preparation.4.
L‐aspartic acid was partly transaminated to alanine by the goldfish anterior intestine; the rectum transaminated alanine to an unidentified amino acid which might have been serine, asparagine or glutamine or some mixture of these three.5. It is suggested that
L‐amino acids increase the ease by which sodium enters the mucosal cell but that it is the rate at which this sodium is transported across the basal membrane which determines the net serosal transfer of amino acids.
The influence of diameter of medullated nerve fibres of cats on the rising and falling phases of the spike and its recovery
Authors: Paintal A. S. 
Published: December 2014

1. The relation of conduction velocity, i.e. fibre diameter (Hursh, 1939a) to certain temporal dimensions of the nerve impulse recorded monophasically was studied in medullated fibres of cats in vivo at temperatures mostly ranging between 21 and 37° C.2. Contrary to existing belief, it was demonstrated unequivocally that spike duration varies inversely with the conduction velocities of the fibres; so also the durations of the rising and the falling phases (rise‐time and fall‐time) of the impulse. The fall‐time is linearly related to conduction velocity at all recorded temperatures. The rise‐time varies steeply with conduction velocity at the lower levels of conduction rate, and very gradually at the higher conduction rates.3. The spike duration of preganglionic sympathetic fibres is identical with that of somatic medullated fibres with similar conduction velocities. There is therefore little justification for classifying them separately as so‐called B fibres.4. The rate of recovery of spike amplitude following a preceding impulse also varies inversely with conduction velocity, and in the same manner as the absolute refractory period (ARP). In fact the relation of time for 40% recovery of spike amplitude to conduction velocity is identical with the relation of conduction velocity to ARP. The Q10 for 40% recovery of spike amplitude is 4·7 between 13 and 29° C.5. Rise‐time increases exponentially with fall in temperature in all medullated fibres, fast (say 64 m/sec) and slow (say 16 m/sec), the Q10 being 2·5. Fall‐time varies exponentially with temperature in slow fibres (Q10 = 3·5); in fast fibres it varies linearly. The Q10 for spike duration is the same in all fibres between 27 and 37° C only, its value being about 3·4. Below 27° C the Q10 depends on the conduction velocity of the fibres. Only in slow fibres does spike duration tend to vary exponentially with temperature.6. Only abortive spikes are generated during the interval between the end of a preceding spike and the end of the ARP which is about 1½ times spike duration in fast fibres and about twice spike duration in slow fibres.
A gastric phase of pancreatic secretion
Authors: Blair E. L. , Brown J. C. , Harper A. A. , Scratcherd T. 
Published: December 2014

1. Extracts of antral mucosa increase the output of pancreatic amylase. They do not stimulate the resting pancreas of the anaesthetized cat to secrete juice, but have a slight ‘secretin‐like’ effect on a pancreas already responding to endogenous or exogenous secretin.2. In animals with the vagus and splanchnic nerves cut instillation of meat extracts or acetylcholine into the antrum stimulates gastric acid and pancreatic amylase secretion. These responses can be prevented by injection of atropine or cocainization of the antral mucosa.3. In animals with the splanchnic nerves cut but the vagus nerves intact, distension of the body or antrum increases the output of amylase. After vagal section distension of the body has no effect on the pancreas, but the response to antral distension is still present.4. It is concluded that there is a gastric phase of pancreatic secretion which, in the cat, is almost entirely a stimulation of enzyme output. A vago‐vagal reflex pathway is required for the pancreatic response to mechanical stimulation of the body of the stomach, and may be involved in the response to antral stimulation. Chemical and mechanical stimulation of the antrum produces a hormonally mediated increase in pancreatic enzyme secretion. The effects of atropine and cocaine on this response are consistent with the view that the release of the antral stimulant depends on a local cholinergic reflex pathway in the antrum.