bluuebunny/crossref_metadata_2025_split huggingface dataset:
Post‐synaptic effects of cortical stimulation on forelimb motoneurones in the baboon
Authors: Kernell D. , Chien-Ping Wu 
Published: December 2014

1. The arm area of the baboon's precentral motor cortex was stimulated by brief surface‐anodal pulses, and the post‐synaptic potentials elicited in contralateral forelimb motoneurones were studied by intracellular recording.2. Strong cortical stimuli elicited a rapid series of excitatory and, in some cells, inhibitory post‐synaptic potentials (EPSPs and IPSPs respectively). Comparisons with the simultaneously recorded response of the pyramidal tract indicated that these post‐synaptic potentials were due to a repetitive discharge of fast pyramidal fibres. Thus, the later synaptic events were mostly due to a repetition of the early monosynaptic EPSP and early IPSP respectively.3. Inhibition was seen more often in cells whose monosynaptic EPSP had a small maximal size than in those whose monosynaptic EPSP was larger. The net depolarization produced by a strong cortical stimulus was related to the maximal size of the early monosynaptic EPSP.4. In the Discussion, an interpretation is suggested for previous findings concerning the spinal distribution of late synaptic effects elicited by cortical stimulation.
Responses in the dorsal accessory olive of the cat to stimulation of hind limb afferents
Authors: Armstrong D. M. , Eccles J. C. , Harvey R. J. , Matthews P. B. C. 
Published: December 2014

1. Field potentials and single unit discharges were recorded in the dorsal accessory olive of the cat following stimulation of nerves of the contralateral hind limb.2. The largest field potentials were evoked when nerves were stimulated with brief trains at 200‐300/sec. Responses were sometimes evoked from quadriceps nerve by volleys restricted to low threshold group I afferents, but responses were not usually evoked from other muscle nerves unless both group I and II afferents were excited.3. The spatial distributions of the field potentials evoked from different nerves were very similar and individual units were made to discharge by stimulation of each of a wide range of nerves including muscle, skin and joint nerves. Single units were also made to discharge by stimulation of both the ipsilateral and the contralateral quadriceps nerve.4. The latency of the field potentials evoked by stimulation of quadriceps nerve ranged from 14 to 23 msec in different preparations. The latency of responses evoked from various branches of the sciatic nerve was consistently longer and was usually between 20 and 30 msec.5. The activity was conveyed by a tract which, at the upper lumbar level of the spinal cord, lay in the ventral quadrant ipsilateral to the olive. In the upper cervical region the tract lay close to the ventral surface of the cord. Values between 24 and 30 m/sec were found for the conduction velocity of the tract.6. An excitatory response in the dorsal accessory olive was followed by a period of about 100 msec during which the amplitude of a second response was reduced.
The distribution of the T‐system along the sarcomeres of frog and toad sartorius muscles
Authors: Peachey L. D. , Schild Renée F. 
Published: December 2014

1. Frog and toad sartorius muscles were soaked in ferritin suspensions and then fixed and prepared for electron microscopy. Ferritin particles were counted in micrographs of regions where fibril striations were in good register, and the number of particles plotted according to position along the sarcomeres.2. The distribution of ferritin particles in both frog and toad muscle sarcomeres could be accounted for by a single peak centred at the Z‐line, with a total width of about 0·4 μ.3. The peak in toad fibres was slightly broader than that in frog fibres, and this was due to more frequent branching of the T‐system in the toad. In both frog and toad sartorius muscles branching increases the total quantity of T‐system by around 30%.4. No peak was found in the ferritin distribution which could account for the peak of albumin distribution observed near the A—I boundary of toad sartorius muscles by Hill (1964).
The evolution of fatigue associated with isometric contraction in toad sartorius
Authors: Aljure Emilio F. , Borrero Luis M. 
Published: December 2014

1. The development of fatigue in isolated toad sartorius undergoing short, periodic, isometric tetani of controlled duration, was studied. Stimulation was direct and curare was used.2. In the great majority of cases extratension decreased very regularly towards a steady value, following a simple exponential equation.3. The final steady tension (expressed as percentage of the maximum) and the constant of exponential decay varied as simple functions of the mean frequency of stimulation and their product was a constant.
Renal contribution to thoracic duct lymph in dogs
Authors: O'Morchoe C. C. C. , O'Morchoe P. Jean 
Published: December 2014

1. The renal contribution to thoracic duct lymph was measured in seventeen anaesthetized fasting dogs by measurement of thoracic duct flow before and after renal arterial occlusion.2. In eight experiments it was shown that thoracic duct flow and glomerular filtration rate were not significantly affected by the operation to expose the renal artery.3. In three experiments occlusion of the renal vein, after release of arterial occlusion, resulted in a sudden increase in thoracic duct flow.4. In animals infused with isotonic saline or dextrose (approximately 1 ml./min) the average values obtained for control thoracic duct flow, left renal flow and right renal flow were approximately 2·0, 0·7 and 0·3 ml./hr/kg body wt.: in non‐infused animals these values were 1·4, 0·4 and 0·35 ml./hr/kg body wt. respectively.5. Possible reasons for the apparently smaller lymph flow from the right than the left kidney, and the relationship between the renal contribution to thoracic duct flow and actual renal lymph flow are discussed.6. Close correlation was found between control thoracic duct flow and body weight and between renal lymph flow and control thoracic duct flow.
The slowing of gastric emptying by monosaccharides and disaccharides in test meals
Authors: Elias E. , Gibson G. J. , Greenwood Linda F. , Hunt J. N. , Tripp J. H. 
Published: December 2014

1. Test meals containing various concentrations of glucose, maltose, sucrose, fructose, lactose, galactose and mixtures of these solutes were given to six healthy subjects. All meals contained 40 m
M sodium citrate.2. The slowing of gastric emptying produced by the disaccharides in test meals was generally consistent with the stimulation of duodenal osmoreceptors occuring after the hydrolysis of the disaccharides.3. Glucose was slightly more effective, per osmole, in slowing gastric emptying than was galactose.4. By comparison with glucose or galactose, fructose was much less effective in slowing gastric emptying. In three subjects out of six there was a threshold for its effect.5. The results may be indicative of the relative activities of disaccharidases in the brush border of the small intestine. They are consistent with there being an osmoreceptor deep to these enzymes which slows gastric emptying.
Effects of tetrodotoxin on the slowly adapting stretch receptor neurone of lobster
Authors: Albuquerque E. X. , Grampp W. 
Published: December 2014

1. A study has been made of the effects of tetrodotoxin on the impulse activity, resting membrane potential, input resistance, and the generator potential and its after‐hyperpolarization of the slowly adapting stretch receptor neurone of the lobster.2. Tetrodotoxin was able to abolish completely within about 2 min the impulse activity in most cells, when given in a dose of 2 × 10−8 g/ml., but in all cells, when administered in a dose of 4 × 10−8 g/ml. After blockage by the toxin in concentrations as high as 4 × 10−6 g/ml. for periods of up to 30 min the action potential was restored by washing the preparation in physiological solution for 1 hr.3. In a concentration of 4 × 10−8 g/ml. tetrodotoxin produced within 1–2 min an average increase of 4·8 mV of the resting membrane potential and a simultaneous 47% reduction of the resting input resistance. These effects were reversed by washing the preparation in physiological solution for 1 hr.4. Tetrodotoxin administered in doses as high as 4 × 10−6 g/ml. for periods of up to 30 min had no effect on the amplitude of the steady phase of the generator potential.5. In a concentration of 4 × 10−8 g/ml. tetrodotoxin produced within 5 min a 65% reduction of the amplitude of the hyperpolarization following the generator potential. This effect was reversed by washing the preparation in physiological solution for 1 hr.6. The simultaneous increase in resting membrane potential and decrease in membrane resistance is suggested to be due to an elevated potassium permeability besides a reduced sodium conductance. The constancy in height of the generator potential in the presence of a decreased membrane resistance makes necessary the assumption of an augmented generator current. The decrease in amplitude of the hyperpolarization following the generator potential may be the result of an increase in potassium conductance and/or a reduction in acceleration of an electrogenic pump in consequence of a diminished sodium influx during the generator potential.
Heat work and phosphorylcreatine break‐down in muscle
Authors: Wilkie D. R. 
Published: December 2014

1. A new instrument, the integrating thermopile, is described for measuring the total quantity of heat produced during muscular contraction.2. This instrument has been used to investigate the relation between change of enthalpy (‐ (heat produced + work produced)) and break‐down of phosphorylcreatine (ΔPC) in iodoacetate‐poisoned frog sartorii at 0° C. In a variety of different types of contraction—series of isometric twitches, isometric tetani, contractions with positive and with negative work—the relation between enthalpy change and ΔPC was always the same, and corresponded to an in vivo molar enthalpy change (ΔH) of ‐11·0 ± 0·23 (
S.E.; n = 52) kcal/mole.3. This value of ΔH is used to estimate the in vivo ΔH for ATP splitting and also the number of rephosphorylations to be expected per hexose unit oxidized by normal unpoisoned muscle.
The kinetics and rectifier properties of the slow potassium current in cardiac Purkinje fibres
Authors: Noble D. , Tsien R. W. 
Published: December 2014

1. The reversal potential of the slow outward current in Purkinje fibres varies with [K]o in accordance with the expected potassium equilibrium potential. It is concluded that virtually all of this current is carried by potassium ions.2. The magnitude of the current is determined by two separable factors. The first factor is directly proportional to a variable obeying first‐order voltage‐dependent kinetics of the Hodgkin—Huxley type but with extremely long time constants. The time constants of this variable are extremely sensitive to temperature and the Q10 over the range 26‐38° C is 6.3. The second factor shows inward‐going rectification with a marked negative slope in the current—voltage relation beyond about 25 mV positive to the K equilibrium potential. The current—voltage relations measured at different values of [K]o cross each other on the outward current side of the equilibrium potential.4. The changes in slow potassium current during pace‐maker activity have been calculated. It is shown that the mechanism of the pace‐maker potential differs in several important respects from that described by Noble's (1962) model. The negative slope in the current—voltage relation appears to be an important factor in generating the last phase of pace‐maker depolarization.5. The role of the slow potassium current during the action potential and the consequences of the high temperature dependence of the kinetics are discussed.
Amiloride: a potent inhibitor of sodium transport across the toad bladder
Authors: Bentley P. J. 
Published: December 2014

1 Amiloride inhibits Na transport and short‐circuit current (SCC) across the toad bladder. It is 1000 times more active at the mucosal than serosal surface. The lowest effective concentration was 10−7
M.2. The inhibition was non‐competitive with the sodium on the mucosal side of the bladder.3. Vasopressin, cyclic adenosine monophosphate (AMP) and aldosterone increased Na transport and SCC across the bladder and these effects were inhibited by amiloride.4. The antagonism of amiloride for vasopressin was non‐competitive.5. Amphotericin B also increases Na transport across the bladder but its action was not changed by amiloride.6. Amiloride was without effects on SCC and diffusion potentials in bladders metabolically inhibited with CN− and iodoacetic acid (IAA).7. Neither plasma albumin, Ca2+ nor adenosine triphosphate (ATP) altered the effects of amiloride.8. The only structural analogue of amiloride found to reduce SCC similarly was guanidine which was 1000 times less active. Pyrazine and a substituted pyrazine analogue were without effect. Neither guanidine nor the substituted pyrazine compound were competitive with amiloride.9. Amiloride had no effect on the osmotic permeability of the toad bladder either in the presence or absence of vasopressin.10. Na transport across the toad colon was also reduced by 10−5
M amiloride at the mucosal surface.11. The possible mechanism of action of amiloride is discussed.
A dual effect of calcium ions on neuromuscular facilitation
Authors: Rahamimoff R. 
Published: December 2014

1. The changes in neuromuscular facilitation produced by varying extracellular calcium and magnesium concentrations have been studied at the frog neuromuscular junction using intracellular recording and automatic averaging of responses.2. When [Ca] was elevated three effects were observed: a large increase in transmitter release by the first impulse; a decrease in facilitation at short intervals between impulses; and a prolongation of the time course of the facilitated release. If the release by the first impulse is kept at constant level, by raising both [Ca] and [Mg], facilitation becomes greater at all impulse intervals.3. The results have been discussed in terms of the hypothesis that the action of calcium is responsible for neuromuscular facilitation.
Renal sodium reabsorption after acute renal denervation in the rabbit
Authors: Blake William D. , Jurf Amin N. 
Published: December 2014

1. Separate effects on the functions of left and right kidneys were examined after left‐sided renal handling and acute denervation. Studies were done on pentobarbital‐anaesthetized rabbits using clearance techniques to evaluate renal haemodynamics and water and electrolyte excretion.2. When compared with its counterpart, the handled kidney exhibited some decrease in function for at least 20 min. Recovery of most functions occurred in 40‐60 min.3. The effects of denervation on renal functions were observed when the effects of handling had subsided. Renal plasma flow (
R.P.F.) and glomerular filtration rate (
G.F.R.) were not significantly changed, whereas the decrease in Na, K and water excretion, which was usually observed for no ascertained reason in the innervated kidney, was prevented.4. The magnitude of the denervation natriuresis was greater in these rabbits than in dogs studied previously; other functions studied were comparable in the two species.5. The results from thirty‐five experiments are interpreted to indicate that denervation decreases Na reabsorption independently of
G.F.R., perhaps by a direct effect on tubular transport, but more probably by a redistribution of filtration to nephrons of lesser reabsorptive capacity.
On the increase in rate of heat production caused by stretch in frog's skeletal muscle
Authors: Clinch N. F. 
Published: December 2014

1. The increase in rate of heat production caused by stretch in the unstimulated frog's sartorius (stretch response) has been measured using a conventional thermopile technique.2. The rate of heat production was found constant between l0 (the distance in vivo between the tendons when the legs were in a straight line) and 1·2 l0, and rose rapidly above this length to reach 3‐5 times the basal rate at 1·3 l0. Stretching to greater lengths appeared to damage the muscles.3. The stretch response is increased by several substances which increase the duration of the active state.4. Unlike the rate of heat production at l0, the stretch response is increased by procaine; while the presence of CO2 greatly reduces it.5. Evidence is presented supporting the hypothesis that the stretch response is associated with the appearance of tension in the sarcolemma.
Factors influencing the sensitivity of the rat to vasopressin
Authors: Forsling Mary L. , Jones J. J. , Lee J. 
Published: December 2014

1. Indirect evidence suggests that the concentration of arginine vasopressin in the plasma of normally hydrated man is about 1 μ‐u./ml., but this is usually considered to be below the limit of sensitivity of the standard assay preparation, the water‐loaded Wistar rat under ethanol anaesthesia.2. It was found that there was a surprising variation in sensitivity to vasopressin between batches of Wistar rats, and that other varieties of rat (including those with diabetes insipidus) were no more sensitive.3. Three modifications of the standard assay procedure produced an increase in sensitivity:(a) using Wistar rats weighing 100‐150 g, rather than larger animals;(b) commencing the assay shortly after surgery, i.e. as soon as the urine flow reached 25 μl./min;(c) infusing vasopressin intravenously (0·5‐3 μ‐u./min). By using modification (a) with either (b) or (c) it was possible to detect as little as 0·5 μ‐u.4. With these modifications antidiuretic activity equivalent to 0·5‐2·0 μ‐u./ml. of arginine vasopressin was measured in nine samples of plasma from a normally hydrated subject.5. It is suggested that the frequent reports of enhanced sensitivity may have been due to the fortuitous use of a particularly sensitive batch of rats, or to a high endogenous secretion of vasopressin due to operative trauma.
Effects of amino acids, dipeptides and disaccharides on the electric potential across rat small intestine
Authors: Kohn P. G. , Smyth D. H. , Wright E. M. 
Published: December 2014

1. The effects of a number of amino acids, peptides and disaccharides on the potential difference across the wall of the rat small intestine have been studied.2. All the
L‐amino acids tested, except lysine and arginine, and the three
D‐amino acids tested stimulate the potential when present in the mucosal fluid.3. The concentration dependence and time course of the potential differs between different amino acids.4. The results suggest a close correlation between the active transport of an amino acid and the potential change which it evokes.5. Glycyl‐glycine, glycyl‐
L‐alanine and tri‐glycine stimulate the potential and this appears to be due to the amino acids liberated by hydrolysis.6. Maltose and sucrose, but not lactose, stimulate the potential, and the effect appears to depend on the extent of hydrolysis of the disaccharide.7. The magnitude of the potential varies in different parts of the intestine. For the amino acids tested the maximum potential occurred in the distal ileum, while in the case of hexoses the maximum potential was found in the mid‐intestine.8. The results are discussed in relation to the mechanisms of transfer of hexoses and amino acids.
The time course of changes in renal tissue composition during mannitol diuresis in the rat
Authors: Atherton J. C. , Hai M. A. , Thomas S. 
Published: December 2014

1. The time course and extent of changes in the composition of renal tissue slices in osmotic diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of mannitol (15 g/100 ml.) for up to 7½ hr.2. Very rapid changes in tissue water and solute contents occurred within 15 min, preceding the times of maximal diuresis, with little subsequent change even up to 7½ hr.3. The main changes were:(a) an increase in water content in all slices, particularly the papilla; (b) a very profound decrease in papillary and medullary urea content in the first 15 min, with a small, but significant, further decrease, subsequently; (c) a small, but significant, rapid decrease in papillary sodium, and small non‐significant increases in the outer medulla and cortex. Subsequent changes in any segment were small and non‐significant; (d) apart from small changes in the first 15 min ammonium and potassium contents remained fairly constant.4. The rates of change in papillary and urinary urea concentrations were similar, so that after 30 min, any differences between tip and urinary concentrations were small and non‐significant.5. The findings are discussed in terms of factors influencing counter‐current mechanisms. It is concluded that altered medullary blood flow is mainly responsible for the rapid changes in medullary composition.6. The relation between papillary and urinary urea concentrations is explicable in terms of passive handling, with equilibration across a freely permeable collecting duct membrane.
The time course of changes in renal tissue composition during water diuresis in the rat
Authors: Atherton J. C. , Hai M. A. , Thomas S. 
Published: December 2014

1. The time course and extent of changes in the composition of renal tissue slices in water diuresis were determined by sacrificing groups of rats before and during the intravenous infusion of dextrose (2·5 g/100 ml.) in amounts sufficient to administer over 2 hr, and subsequently to maintain for up to 7½ hr, a positive fluid load of 4% body weight.2. The corticomedullary osmolal gradient characteristic of the nondiuretic rats was progressively dissipated until, at 7½ hr, only papillary tip concentrations were higher than those of other segments.3. The changes in individual constituents followed different time courses: (i) an increase in water content in all segments, particularly the papilla, was almost complete by 1 hr, preceding the maximal increases in urine flow; (ii) a marked decrease in papillary and medullary urea content in the first hour was followed by a slower, progressive decrease leading to an almost complete dissipation of the urea gradient by 7½ hr; (iii) small, non‐significant decreases in sodium content occurred in all segments in the first hr, followed by a further small, progressive decrease in papillary sodium content; (iv) changes in ammonium and potassium concentrations were mainly related to those in water content, since the contents of these solutes showed only small changes.4. By 2 hr, differences in the rates of decline of osmolal and urea concentrations in urine and papilla led to urinary concentrations significantly lower than papillary values. The steep papilla‐urine urea concentration difference became smaller, but remained significant even at 7½ hr.5. The findings are discussed in terms of changes in countercurrent mechanisms, particularly as influenced by anti‐diuretic hormone.6. The development of papilla/urine urea concentration ratio greater than unity is also considered in terms of passive transport with changes in membrane permeability.