bluuebunny/crossref_metadata_2025_split huggingface dataset:
Excitatory input from the distal colon to the inferior mesenteric ganglion in the guinea‐pig
Authors: Crowcroft P. J. , Holman Mollie E. , Szurszewski J. H. 
Published: December 2014

1. Intracellular recordings were obtained from ganglion cells in the guinea‐pig inferior mesenteric ganglion (IMG) with a segment of the distal colon attached to the lumbar colonic nerves.2. Continuous electrical activity consisting of excitatory synaptic potentials and action potentials was recorded from ganglion cells in all regions of the IMG.3. The ‘spontaneous’ synaptic potentials were indistinguishable from those elicited by submaximal stimulation of any of the nerve trunks connected to the IMG.4. The excitatory activity was irreversibly abolished when the lumbar colonic nerves were cut and reversibly abolished when tetrodotoxin (5 × 10−7 g/ml.) was added to the colon side of a two‐compartment organ bath.5. Addition of dihydro‐β‐erythroidine (5 × 10−6 g/ml.) to the ganglion side of the bath abolished the synaptic activity of colonic origin and the synaptic responses to stimulation of any of the nerve trunks connected to the IMG.6. Addition of dihydro‐β‐erythroidine (1 × 10−5 g/ml.) to the colon side of the bath markedly depressed the synaptic input of colonic origin but had no effect on synaptic responses produced by preganglionic nerve stimulation.7. Distension of the colonic segment and the application of 5‐HT (1 × 10−5 g/ml.) to the mucosal surface of the colon increased the frequency of synaptic input.8. The synaptic input from the colon was transiently blocked following repetitive stimulation of any of the nerve trunks connected to the IMG. The discharge of miniature synaptic potentials was unaffected.9. Addition of noradrenaline (1 × 10−7 to 1 × 10−6 g/ml.) to the colon side of the bath reduced, and in some cases completely abolished, the synaptic input to the IMG. Phentolamine (1 × 10−6 g/ml.), when added to the colon side of the bath, blocked the effect of noradrenaline and the transient inhibition following repetitive nerve stimulation.10. Addition of noradrenaline (1 × 10−4 g/ml.) to the ganglion side of the bath reduced but never abolished the amplitude of the synaptic potentials of colonic origin.11. It was concluded that in the guinea‐pig, the IMG is involved in a peripheral reflex whose afferent limit of this reflex consists of the axons of cholinergic neurones within the wall of the colon. Many of these neurones are driven either directly or indirectly by cholinergic synapses. The efferent noradrenergic neurones of the IMG function as a group of inhibitory neurones which depress the activity of the excitatory neurones of the colon which are driving them.
Splanchnic nerve inhibition of gastric acid secretion and mucosal blood flow in anaesthetized cats
Authors: Reed J. D. , Sanders D. J. 
Published: December 2014

1. Efferent electrical splanchnic nerve stimulation will significantly inhibit gastric acid secretion and mucosal blood flow (MBF) stimulated by either large
I.V. doses of pentapeptide or histamine, if the rise in blood pressure is prevented.2. Splanchnic stimulation will also reduce the increase in MBF in response to infusions of isopropylnoradrenaline, if the blood pressure rise is prevented.3. Evidence is presented which suggests that the splanchnic nerve inhibitory effect is not due to reducing the amount of stimulant arriving at the gastric mucosa.4. By analysing the responses to histamine, when acid secretion is accompanied by a large MBF relative to the pentapeptide responses, it is suggested that the inhibitory effect of splanchnic nerve stimulation is due to vasoconstriction.5. It remains possible that there is a direct inhibitory effect on the parietal cells.
Peristalsis in the rabbit distal colon
Authors: Mackenna B. R. , McKirdy H. C. 
Published: December 2014

1. The motility of the distal colon of the rabbit has been examined by the conventional Trendelenburg method and by an isometric, isovolumic modification of this method.2. The colon shows a range of movements, and tetrodotoxin and cold‐storage have been used in an attempt to differentiate between myogenic and neurally integrated activities.3. The observable myogenic movements are pendulum movements, ‘tone rings’ and ‘tone waves’; the last of these can be weakly propulsive. The rabbit colon also shows a neurally organized and powerfully propulsive movement which corresponds to the peristaltic wave.4. The implication of a role for nervous structures in the propulsive activity of the rabbit distal colon is at variance with the view of Lee (1960).5. The myenteric reflex arc in the colon has been examined pharmacologically. Cholinergic neural transmission has been implicated at the ganglionic‐synaptic and neuroeffector junctions, but additional noncholinergic mechanisms of chemical transmission have not been excluded.
Recurrent inhibition of antidromically identified rat supraoptic neurones
Authors: Dreifuss J. J. , Kelly J. S. 
Published: December 2014

1. In anaesthetized male rats, the hypothalamus and pituitary stalk were exposed by a transpharyngeal approach. The compound field potential of the supraoptic nucleus evoked by stimulation of the pituitary stalk, was recorded with glass electrodes inserted near the origin of the anterior cerebral artery.2. The mean latency of 169 antidromically evoked action potentials isolated from the field was 9·9 msec with an extreme range of 6–26 msec. Although the wave form of the antidromic action potential showed a variety of shapes and sizes and the initial wave could be of either polarity, the majority were strikingly similar in form. The initial wave was positive with an inflexion on the rising phase and was followed by a shallow rather longer lasting negative potential.3. The antidromic nature of the action potential was confirmed when the action potential evoked at constant latency after the stimulus was observed to be cancelled by another occurring spontaneously. Although the antidromic action potentials followed stimulation frequencies greater than 100 Hz, the response to high frequency stimulation was seldom tested since the amplitude of the action potential was greatly reduced at frequencies above 30 Hz if the number of shocks exceeded a critical number, as few as 3‐6 at 100 Hz.4. Stimulation of the pituitary stalk at intensities below and near threshold for antidromic invasion of the cell under study was shown by means of post‐stimulus time histograms to be associated with an inhibitory period lasting on average 80 msec (
S.D. = 13, N = 30).5. An increase in the intensity and duration of the inhibitory period occurred as the intensity of the stimulation was increased as might be expected if the response was mediated synaptically. The inhibitory pathway is believed to involve the recurrent collateral axons already demonstrated anatomically since the stimulation intensities necessary to produce either a marked inhibitory response or antidromic invasion of the cell in question are in most instances nearly the same.
Adrenergic re‐innervation of smooth muscle of nictitating membrane by preganglionic sympathetic fibres
Authors: Ceccarelli B. , Clementi F. , Mantegazza P. 
Published: December 2014

1. The preganglionic and post‐ganglionic trunks of the cervical sympathetic nerve were joined in an end‐to‐end anastomosis after excision of the superior cervical ganglion in the cat.2. Seventy‐five days after the anastomosis the diameter of the pupil was nearly normal and there was almost complete recovery of the prolapsed palpebra and of the nictitating membrane. The contraction of the nictitating membrane, induced by electrical stimulation, caudally to the point of anastomosis, showed that the smooth muscle of the nictitating membrane had been re‐innervated.3. Neither hexamethonium nor nicotine had any marked effect on the contraction of the nictitating membrane. Severing the regenerated nerve trunk produced a degeneration contraction. These results are strong evidence that the denervated membranes were re‐innervated by true cholinergic preganglionic fibres.4. Our pharmacological studies indicated that in the re‐innervated preparations neuromuscular transmission was adrenergic in the sense that it was blocked by phentolamine and not by atropine. These results were confirmed by the histochemical‐fluorescence studies which showed that the endings of the regenerated axons contained high concentrations of catecholamines.5. Electron microscopy showed that the regenerated terminals contained none of the small dense‐core vesicles, considered to be typical of adrenergic nerve endings, but contained clear synaptic vesicles and an unusually great number of large granular vesicles.6. Our results suggest that the denervated nictitating membranes were re‐innervated by cholinergic presynaptic sympathetic fibres that had been modified so that they could release catecholamines in addition to, or instead of, acetylcholine.
The isoenzymes of carbonic anhydrase: kinetic properties with particular reference to the functions in the intestinal tract
Authors: Carter M. J. , Parsons D. S. 
Published: December 2014

1. Details are given of an electrometric method for measuring the activity of isoenzymes of carbonic anhydrase (EC 4.2.1.1) in catalysing the hydration of carbon dioxide under different conditions at 0° C. In the method, a measured volume of water saturated with carbon dioxide at a known partial pressure and appropriate temperature is introduced into a buffered solution. Using a sensitive electrometer and recording instrument, the subsequent change in hydrogen ion concentration is recorded as a function of time. Under the conditions of assay, the pH change induced in the presence of substrate is very small (ΔpH < 0·05 units) and the period of observation need not exceed 10 sec.2. For enzymes isolated from guinea‐pig tissues, it is found that the specific activity of the ‘high activity’ isoenzyme (carbonic anhydrase C, carbonic anhydrase II, HACA) is about eighteen times that of the ‘low activity’ counterpart (carbonic anhydrase B, carbonic anhydrase I, LACA) when measured at 0° C, pH 7·2, and ionic strength 0·19. Under the same conditions, the Km was found to be 10 m
M for the ‘high activity’ isoenzyme and 23 m
M for the ‘low activity’ isoenzyme. No differences were found between the equivalent kinetic parameters of the corresponding isoenzymes isolated from different tissues.3. The isoenzymes isolated from guinea‐pig tissues are found to be inhibited by acetazolamide in a non‐competitive manner. It is also found that the ‘high activity’ isoenzyme is many times more sensitive to this inhibitor than is the ‘low activity’ isoenzyme. Evidence is presented which indicates that one acetazolamide binding site is present on each molecule of either isoenzyme.4. While chloride ions specifically inhibit the ‘low activity’ component of guinea‐pig carbonic anhydrase (I0·5 = 40 m
M), acetate, butyrate and pyruvate inhibit both isoenzymes. Under the conditions employed, acetate and pyruvate are more strongly inhibitory to the ‘low activity’ isoenzyme than to the ‘high activity’ isoenzyme, while butyrate is more strongly inhibitory to the ‘high activity’ isoenzyme.5. The findings are discussed with particular reference to the physiological significance of the presence of the isoenzymes in the gastro‐intestinal tract. Also considered are possible relationships between the distribution of the ‘low activity’ isoenzyme in these tissues and the transport and metabolism of products of fermentation occurring in the intestinal lumen.
A comparison of the behaviour to ions of the P III component of the pigeon cone and rat rod electroretinogram
Authors: Arden G. B. , Ernst W. 
Published: December 2014

1. Isolated pigeon and rat retinas were incubated in various media and the effect of changing ions on the P III component of the electroretinogram was studied, with particular regard to the influence of calcium on other ions.2. In pigeon, without calcium, reduction of sodium and chloride both reduce P III. This behaviour continues in the presence of calcium but only if the retina has been treated with ouabain. Under these conditions, the effect of calcium is to prevent the appearance of inverted responses.3. Under other conditions, calcium renders the pigeon P III insensitive to change in chloride. Sensitivity is rapidly restored by the use of ouabain, 2,4‐DNP, or by cooling.4. Calcium does not alter the linear relationship between sodium and response amplitude.5. In pigeon, increasing potassium increases P III amplitude, though the exact relationship is altered by calcium.6. In the rat retina treated with ouabain, increasing sodium increases P III, and increasing potassium decreases P III. This result is similar to that of Sillman, Ito & Tomita (1969b). If calcium is absent, inverted P IIIs can be obtained.7. If calcium is present in the medium, reducing sodium also reduces rat P III.8. If calcium is reduced below 10−7
M, then reducing sodium increases P III, and large responses are obtainable from solutions which contain almost no ions. These responses vanish very rapidly if the retina is cooled or treated with ouabain.
Resting tension and the form of the twitch of rat skeletal muscle at low temperature
Authors: Hill D. K. 
Published: December 2014

1. A study has been made of the effect of temperature on the resting tension and on the form of the isometric twitch of isolated rat skeletal muscle. The soleus and the extensor digitorum longus (EDL) were used as representatives of slow and fast types of muscle. The main interest is in the behaviour at low temperature, when rat muscle shows characteristics which are not found with frog muscle.2. At higher temperatures both soleus and EDL of the rat resemble frog muscle in showing a ‘rubber‐like’ form of resting tension, i.e. the tension increases with warming: this has not previously been demonstrated in mammalian muscle. But at low temperatures (below 15° C) the converse is observed; tension then increases as temperature falls. This ‘cold tension’ is much larger with soleus than with EDL. The ‘cold tension’ is the converse of the ‘rubber‐like’ tension also in its dependence on length; it becomes smaller when the muscle is stretched.3. These muscles remain excitable and give consistent twitches with transverse stimulation at temperatures down to about 3° C provided the exposure to cold is not prolonged beyond a few minutes. The amplitude of the twitch is reduced by cooling, e.g. at 3° C it is about 30–50% of that at 25° C.4. The twitch becomes very prolonged at low temperatures. With a soleus at 3‐4° C it may last 40 sec. The temperature coefficient of the rate constant of the relaxation phase is very high compared with that of frog's muscle.5. The rate constant of relaxation in a twitch at low temperature increases when the muscle is stretched. This is the reverse of what happens at higher temperature.6. The extreme prolongation of the twitch with cooling indicates a very large decrease in the rate of decay of the active state, and it is suggested that the increase of resting tension at low temperature is due to an accumulation of ‘activator’.
Visual acuity in the blue cone monochromat
Authors: Green Daniel G. 
Published: December 2014

1. To isolate the blue cones of the normal eye, blue sine‐wave gratings were superimposed on a bright yellow background. Threshold contrasts for resolution of the gratings were then determined.2. Under these conditions visual acuity for high contrast gratings on four normal subjects was on the average 0·31 min−1. This is about a factor of 6 lower than grating acuity under optimal conditions.3. The contrast sensitivity of two subjects who lack the normal red and green receptor mechanisms was measured using blue sinusoidally modulated gratings. Visual acuity was found to be greatly reduced from normal. The low acuity of these individuals is due to both a reduction in contrast sensitivity and a reduction in resolution.4. The spatial resolving characteristics of these subjects resembles the vision of the normal eye under conditions which isolate the blue sensitive mechanisms.5. The vision of the cone monochromat differs significantly from that of the more typical rod monochromat. The rod monochromat has even lower acuity than the blue cone monochromat for high contrast gratings but has much greater contrast sensitivity for gratings of low spatial frequency.
Effects of denervation and reinnervation on the responses of kitten muscles to acetylcholine and suxamethonium
Authors: Jones Rosemary , Vrbová Gerta 
Published: December 2014

1. The development of the high sensitivity of the adult neuromuscular junction to the blocking and depolarizing action of suxamethonium was studied in kittens of different ages.2. It was found that the sensitivity to the depolarizing effects of suxamethonium increases simultaneously with that to the blocking effects of the drug during the 3rd–6th week of life. The increase of sensitivity to the blocking effects of suxamethonium during development can therefore be accounted for by the depolarizing effect of the drug.3. When the nerve is crushed during the first week of the animal's life and then left to regenerate, the development of the high sensitivity of the neuromuscular junction to suxamethonium and acetylcholine is impaired. Thus during development the nerve is essential for the induction of the high sensitivity of the neuromuscular junction to acetylcholine as well as to other depolarizing drugs.4. The blocking and depolarizing effects of suxamethonium on reinnervated muscles of cats at different ages were compared. The depolarizing action of suxamethonium on reinnervated end‐plates is always smaller, but its blocking effect is not. In young animals the blocking effect of suxamethonium on reinnervated muscles is smaller, whereas reinnervated muscles of adult animals are extremely sensitive to the blocking effects of the drug.5. 24–36 hr after denervation cat muscles were more sensitive to the blocking effects of suxamethonium but the depolarizing effect of the drug on the end‐plate region was smaller. It thus appears that the nerve not only induces but also maintains the high sensitivity of the end‐plate region to depolarizing drugs.
Time course of changes in renal tissue and urinary composition after cessation of constant infusion of lysine vasopressin in the conscious, hydrated rat
Authors: Atherton J. C. , Green R. , Thomas S. , Wood Jeanne A. 
Published: December 2014

1. The changes in urinary and renal tissue composition in conscious rats were determined for up to 2 hr following the cessation of intravenous infusion of lysine vasopressin, LVP (at 60 μu./min. 100 g body wt. for 4½ hr). A constant water load (4% body wt.) was maintained during and after lysine vasopressin infusion, by quantitative replacement of excreted water. In these circumstances, any changes in urinary and renal tissue composition are presumed to represent direct consequences of the rapid plasma and tissue clearance of lysine vasopressin.2. Urinary flow increased and osmolality decreased, rapidly, reaching stable values characteristic of sustained water diuresis after about 60 min.3. The steepness of the corticomedullary solute concentration gradients also decreased rapidly. Papillary Na and urea concentrations fell to values characteristic of sustained water diuresis in about 45 min.4. The changes in medullary composition were compounded of a moderate significant increase in water content, a moderate, significant decrease in Na content, and a profound decrease in urea content.5. In the eventual steady‐state water diuresis, urinary outputs of Na and K were significantly lower, and of NH4 significantly higher, than those observed in control experiments where LVP infusion was continued for the corresponding 2 hr.6. It is concluded that the diuresis following the cessation of LVP infusion is due not merely to reduced nephron permeability to water but also to a rapid reduction in the osmotic force responsible for water reabsorption from the collecting duct.
The onset and development of transmission in the chick ciliary ganglion
Authors: Landmesser Lynn , Pilar G. 
Published: December 2014

1. The onset and development of transmission has been studied electro‐physiologically in the isolated chick ciliary ganglion from Stage 25 (Hamburger & Hamilton, 1951) until 28 days after hatching. Ultrastructure of the synapses was concomitantly investigated.2. Synaptic transmission began at Stage 26½ and was 100% in both cell groups, ciliary and choroid, by Stage 33. It was initially chemical until Stage 41 when effective electrical coupling first appeared in the ciliary population. The proportion of electrically transmitting synapses increased to 80% by 1‐2 days post‐hatching.3. Few morphological synapses were present at Stage 33½ when all ganglion cells were transmitting. A scarcity of synaptic vesicles persisted until late in embryonic development when all ciliary cells possessed calyces. At hatching the calyces were filled with synaptic vesicles.4. Initial synaptic contacts were by fine terminal branches often on the intricate processes of early ganglion cells. Calyces formed from Stage 36½ and there was a concomitant retraction of ganglion cell processes, so that by Stage 40 all ciliary cells had simple calyces. The calyx was a transitory structure, which from the first week post‐hatching began to break up into a cluster of boutons.5. Chemical post‐synaptic potentials (PSPs) were at Stage 40 long (30 × the membrane time constant) and further prolonged by eserine. By Stage 43, PSPs had become markedly shortened and were unaffected by eserine. No simple explanation can be offered for the changes in PSP time course and sensitivity to anticholinesterases during development.6. Intracellular records from Stage 40 ciliary cells, which all possess calyces, showed 1‐2 mV amplitude, diphasic, fast decaying electrical coupling potentials (CPs). Later in development the CPs became 20–40 mV amplitude, more slowly decaying and monophasic. This seemed to be correlated with faster presynaptic conduction velocities and myelination of the cell soma. Such changes in CPs may reflect a shift from capacitative to more resistive coupling and point to several factors contributing in varying degrees to the electrical transmission.7. Presynaptic fibres innervating ciliary cells were from the start of lower threshold and faster conduction velocity than those innervating ciliary cells, as occurred in the adult. It is concluded that these preganglionic fibres were probably specified by the time transmission starts and that they selectively innervated the proper post‐synaptic cells.
Hypothalamic endogenous noradrenaline and thermoregulation in the cat and rabbit
Authors: Cranston W. I. , Hellon R. F. , Luff R. H. , Rawlins M. D. 
Published: December 2014

1. The imino‐dibenzyl drugs, imipramine and desipramine, which inhibit the uptake by neurones of noradrenaline, were injected into the lateral cerebral ventricles of cats and rabbits: changes in body temperature resulted which were different for the two species, but nevertheless closely resembled those following intraventricular injection of relatively large quantities of exogenous noradrenaline.2. The endogenous noradrenaline content of the hypothalamus in both species was reduced by repeated injections into the lateral ventricle of the methyl ester of
DL‐α‐methyl‐p‐tyrosine: in animals so treated the hypothalamic content of 5‐hydroxytryptamine was not significantly changed.3. Noradrenaline‐depleted animals showed significantly reduced responses to intraventricular imipramine and desipramine. The diminished responses were primarily due to reduction in endogenous noradrenaline.4. These observations indicate that endogenous noradrenaline, present in the hypothalamus, can influence body temperature in cats and rabbits.