bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gastric emptying in young pigs
Authors: Ochia B. A. 
Published: December 2014

1. Gastric emptying in young pigs has been studied by using a serial test meal procedure.2. Phenol red was used as a reference substance. In acute experiments the recovery of phenol red from the stomach with the pylorus occluded was 94·8 ± 2·2 (
S.E.)% of that introduced.3. Gastric emptying was examined in seven fasted conscious pigs provided with a chronic gastric cannula. After emptying the stomach 500 ml. of a liquid meal containing 20 g citrus pectin, 35·0 g sucrose and 100 mg phenol red made up to 1 l. was introduced. After 5–60 min the meal was withdrawn, the volume of meal that had left the stomach was assessed from the recovery of phenol red and the secretion of gastric juice was calculated from the dilution of phenol red and the rate of emptying. After an initial very rapid outflow, the rate of emptying fell with time, as did the rate of secretion.4. In three pigs 200, 400, 600 or 800 ml. meal was introduced into the stomach and the stomach was emptied 20 min later. The rate of gastric emptying varied directly with the volume of meal introduced.5. Atropine sulphate, 0·5 mg/kg body weight, injected
I.M. 30 min before the test, greatly inhibited gastric emptying and secretion.
The formation of synapses in reinnervated mammalian striated muscle
Authors: Bennett M. R. , McLachlan Elspeth M. , Taylor R. S. 
Published: December 2014

1. The hemidiaphragm of the adult rabbit has a single band of end‐plates running around the middle of the muscle. A study has been made of the formation of synapses during spontaneous reinnervation of this muscle, using histological, ultrastructural and electrophysiological techniques.2. Following spontaneous reinnervation, silver‐stained nerve terminals were found in association with cholinesterase‐stained end‐plates only in the region of the muscle corresponding to the original innervation band.3. The regenerated nerve terminals were observed with the electronmicroscope in positions overlying or adjacent to the old synaptic folds.4. Spontaneous miniature end‐plate potentials and evoked synaptic potentials were recorded only in the middle of the muscle fibres after reinnervation.5. The growth of the regenerating axons was not oriented towards the end‐plate zone but followed muscle fibres and blood vessels in random directions.6. It is concluded that, in adult mammalian striated muscle, the old end‐plate region is preferentially reinnervated as a consequence of some special property of the muscle fibre at this site.
Effects of cold exposure on tissue blood flow in the new‐born lamb
Authors: Alexander G. , Bell A. W. , Hales J. R. S. 
Published: December 2014

1. Conscious lambs less than 2 days old were exposed to thermoneutral and to cold environments, and the radioactive microsphere technique was used to obtain measurements of blood flow to most tissues of the body.2. Cold stress was such as to evoke a summit metabolic response. Deep body temperature was within the normal range for thermoneutral conditions, while metabolic rate increased by about 300%, cardiac output by about 30%, and blood pressure by about 25%.3. Blood flow to the thermogenic tissues increased: perirenal, inguinal, pericardial, prescapular and cervical brown fat depots showed a five‐ to sixfold increase, while the longissimus dorsi, trapezius, gastrocnemius and biceps femoris muscles showed a five‐ to ninefold increase.4. There was an increase in blood flow in the diaphragm, intercostal, panniculus and cardiac muscles, but a decrease in flow in the skin of the leg, ear and midside, the maxillo turbinals, thyroids, spleen, kidneys, liver and gut. There were no significant changes in total or regional blood flow in the brain or spinal cord, or in the adrenals, nasal mucosa or tongue.5. Results support other evidence that thermogenesis in both brown fat and skeletal muscle is very important in the new‐born lamb exposed to cold. Changes in flow in other tissues correlated with known functions in the cold animal. The redistribution of cardiac output during cold stress is a further example of circulatory adjustments which enable animals to cope with stress states.6. Many differences between blood flow values obtained by the radio‐active microsphere and other techniques for measuring blood flow are noted and discussed.
The role of a reactive disulphide bond in the function of the acetylcholine receptor at the frog neuromuscular junction
Authors: Ben-Haim D. , Landau E. M. , Silman I. 
Published: December 2014

1. The effects of disulphide bond reduction and reoxidation on synaptic transmission in the frog neuromuscular preparation have been studied.2. The amplitudes of end‐plate potentials (e.p.p.s) and miniature e.p.p.s (m.e.p.p.s) were decreased irreversibly by the reducing agent dithiothreitol (DTT). Recovery of e.p.p.s and m.e.p.p.s could be achieved, however, by subsequent reoxidation employing 5,5'‐dithio‐bis‐(2‐nitrobenzoic acid) (DTNB).3. No change in e.p.p. quantal content was produced by treatment with DTT and DTNB. The reduction of m.e.p.p. frequency found in DTT was attributed mainly to our inability to distinguish small m.e.p.p.s from the background noise. However, a genuine reduction in m.e.p.p.s frequency could not be ruled out.4. The ‘reactive’ disulphide bond which is acted upon by DTT and DTNB could be located within a few Ångstrom from the anionic site of the receptor for acetylcholine (ACh), by employing the active‐site directed reagent bromoacetylcholamine (BACA).5. Reduction of the ‘reactive’ disulphide bond did not cause changes in the post‐synaptic membrane input impedance nor was the e.p.p. reversal potential affected. Treatment with DTT and DTNB was found to modify only the conductance of the synaptic membrane.6. No synaptic effects were produced by DTT in a non‐cholinergic synapse, the crab neuromuscular preparation.7. It is concluded that the receptor for ACh, besides including the well‐known anionic site for binding quaternary ammonium groups, also contains a unique ‘reactive’ disulphide bond. This bond controls synaptic conductance but not the relative permeability of the synaptic membrane to Na+ and K+. It is not yet clear whether the ‘reactive’ bond controls the interaction of ACh with the receptor or the translation of this interaction into ionic permeability changes.
Presbyopia and the water content of the human crystalline lens
Authors: Fisher R. F. , Pettet Barbara E. 
Published: December 2014

1. The water content of the human crystallaline lens nucleus is 63·4%
S.D. ± 2·9%, and cortex 68·6%
S.D. ± 4·3%.2. Neither the total water content of the cortex, nor that of the nucleus show any significant changes with age, so ‘sclerosis’ of the lens due to loss of water is not a cause of presbyopia.3. The initial loss of water from the nucleus of the lens substance obtained by drying in vacuo at 20° C for 2 hr is related to age (P = 0·05) and deformability (0·02 > P > 0·01).4. The lens fibres of the ageing nucleus have an increased resistance to deformation associated with a decrease in initial water loss. These characteristics can be explained by a common physical property of the fibres, namely increased adhesion to each other as the lens nucleus ages. The newly formed cortical fibres do not appear to show these changes.
The attenuation of passively propagating dendritic potentials in a motoneurone cable model
Authors: Redman S. J. 
Published: December 2014

1. The Rall model of the motoneurone, which consists of a lumped resistance and capacitance, representing the soma, in parallel with a number of distributed resistance‐capacitance networks of finite and equal electrical length, representing equivalent dendritic cables, has been used to study the effects of varying electrical and geometrical parameters on the time course and amplitude of transients generated at different locations on the dendritic cables.2. An analytical solution has been obtained for the time course of the voltage transient generated at the point of current injection on the parallel combination of all dendritic cables, in terms of the distance from the soma to the current injection point, the electrotonic length of the equivalent dendritic cable, the dendritic to soma conductance ratio and the membrane time constant. The current applied is a current impulse, and the response to any synaptic current time course may be obtained from the analytical expression for the current impulse response. A smooth current time course of the form Te—αT has been used in computations.3. An analytical expression has been obtained for the early part of the voltage response at the point of current injection, when the current is applied to a fraction of the total dendritic cable. This response is in terms of all the cable parameters, and the assumed fraction of the dendritic cable which receives the synaptic current. Computations of this response have been carried out assuming a smooth time course of synaptic current.4. The computations of the peak amplitude of the voltage transient obtained from these expressions, together with similar computations for the peak amplitude of the voltage transient after propagation to the soma (Jack & Redman, 1971b), have been used to derive a set of attenuation curves for dendritic propagation. These curves give the ratio of the peak amplitude of the voltage transient at the synaptic location on the dendritic cable, and the peak amplitude after propagation to the soma, in terms of the electrotonic distance to the synaptic location, the time course of current injection, and the cable parameters for the motoneurone model.
Blood flow and fatty acid release by cervical adipose tissue of rabbits
Authors: Hardman M. J. , Hull D. 
Published: December 2014

1. A direct technique was used to measure blood flow and exchange of metabolites by cervical adipose tissue in 3‐month‐old and adult rabbits.2. The initial blood flow from adipose tissue of fed 3‐month‐old rabbits was 0·45 ml./g tissue.min and the tissue released fatty acids and glycerol. In similar rabbits unfed for 24 hr, fatty acid release increased fourfold. Both the rate of blood flow and the arterio‐venous difference of fatty acid increased. In fed adult rabbits blood flow was 0·16 ml./g tissue.min.3. Noradrenaline infusion in both young and adult rabbits stimulated a rapid and large increase in cervical adipose tissue blood flow together with an increase in fatty acid and glycerol release. Glucose uptake remained small. No increase in local heat production in cervical adipose tissue was detected during noradrenaline infusion.4. It is concluded that cervical adipose tissue in adult rabbits is actively concerned in energy storage and supply.
Some effects of preganglionic nerve stimulation on synaptic vesicle populations in the rat superior cervical ganglion
Authors: Quilliam J. P. , Tamarind D. L. 
Published: December 2014

1. The ‘local vesicle population’, namely the population of synaptic vesicles lying within a zone 0·25 μm wide adjacent to the presynaptic membrane and expressed as ‘vesicles μm−2’ has been estimated in rat superior cervical ganglia maintained in vitro for 1 h. Ganglia were either unstimulated or stimulated tetanically during the last few minutes of the in vitro period.2. Individual local vesicle populations at synapses in groups of ganglia which had received the same treatment showed an approximately normal frequency distribution.3. The technique of stimulation did not permit fixation during tetanus, but the mean local vesicle population in ganglia fixed a few seconds after 10 Hz tetani of up to 10 min duration were significantly (P < 0·001) higher than the unstimulated control value of 124·0 ±
S.E. 3·2. Ganglia fixed a few seconds after 3 min tetani at 10 Hz had a mean local vesicle population of 155·7 ±
S.E. 5·7, rising slightly but not significantly to 165·0 ±
S.E. 4·3 at 1 min and 163·1 ±
S.E. 5·2 at 2 min after tetanus. Thereafter the mean local vesicle population fell slowly, reaching control level between 10 and 20 min after tetanus.4. In terms of the vesicle hypothesis, the observations suggest that post‐tetanic potentiation might arise from a closer clustering of vesicles about release areas resulting in an increase in fractional release. It is suggested that stimulation increased the local vesicle population by promoting vesicle mobilization rather than by altering the size or shape of the presynaptic terminals. The ‘mobilizing agent’ might be intracellular Ca2+.5. The results appear to be consistent with those of other workers where experimental conditions and the region in which vesicles were counted were comparable.6. Alternative interpretations for the findings, not involving the vesicle hypothesis, are considered.
The post‐synaptic action of efferent fibres in the lateral line organ of the burbot Lota lota
Authors: Flock Åke , Russell Ian J. 
Published: December 2014

1. The post‐synaptic action of efferent fibres on lateral line organs in the burbot was investigated with extracellular electrodes.2. Selective excitation of efferent fibres or stimulation of the lateral line nerve causes a negative efferent potential in the epithelium, an increase in the microphonic potential, and inhibition of afferent nerve impulses.3. Stimulation of the lateral line nerve causes antidromic impulses in the afferent fibres in addition to exciting the efferent fibres. However, stimulation of the lateral line nerve has no post‐synaptic influence on lateral line organs when the efferent synapses are selectively blocked by gallamine.4. The influence of efferent stimulation on the microphonic potential is greater at large amplitudes of mechanical stimulation than at low.5. The similarities between the effects of efferent stimulation in the lateral line organ and in the cochlea suggest similar synaptic mechanisms.
Kinetics of rhodopsin bleaching in the isolated human retina
Authors: Baumann Ch. , Bender Silvia 
Published: December 2014

1. Pieces of human retina were dissected from eyes enucleated because of malignant tumours. The isolated retinas were perfused by an ionic medium (36° C) and investigated spectrophotometrically.2. Rhodopsin was identified on the basis of its difference spectrum. The maximum absorbance change on bleaching was about 0·1 (λ = 500 nm).3. The process of bleaching was quantitatively analysed in terms of four slow reactions, viz. (a) conversion of metarhodopsin II into metarhodopsin III, (b) hydrolysis of metarhodopsin II into retinal and opsin, (c) decay of metarhodopsin III to retinal, and (d) reduction of retinal to retinol.4. First‐order rate constants for the reactions in 3 were 9 × 10−3 sec−1 (a), 3 × 10−3 sec−1 (b), 4 × 10−3 sec−1 (c), and 3 × 10−2 sec−1 (d).5. With two simplified versions of the model summarized in 3 and 4, the description of experimental data was less accurate.
Localization of pulmonary stretch receptors in the airways of the dog
Authors: Miserocchi G. , Mortola J. , Sant'Ambrogio G. 
Published: December 2014

1. During respiratory efforts against a closed airway, the afferent activity of vagal fibres from pulmonary stretch receptors does not appreciably increase during the inspiratory phase because the lung is prevented from expanding.2. Occlusion at different levels of the airways allows the localization of pulmonary stretch receptors in the tracheo‐bronchial tree.3. 144 fibres from pulmonary stretch receptors on the left side of the tracheo‐bronchial tree have been studied in eleven dogs and their localization was as follows: 17·4% in the upper half of the intrathoracic trachea, 27·1% in the lower half of the intrathoracic trachea and the carina, 11·1% in the main bronchus, 13·9% in the upper lobe and 30·5% in the lower lobe.4. From the surface area of the tracheo‐bronchial tree at different levels on the assumption of a total of 2000 stretch receptors on each side, their average concentration was as follows: 34·8% receptors/cm2 in the upper half of the intrathoracic trachea, 54·2/cm2 in the lower half of the intrathoracic trachea, 56·8/cm2 in the main bronchus, 0·37/cm2 in the intrapulmonary airways.5. Occlusion of the main bronchus caused an increase of the eupnoeic oesophageal pressure swing by about 75% whereas occlusion of the inferior lobar bronchus led to an increase of only 20%. Therefore the reflex effects induced on the respiratory activity by occluding the airways at various levels show the greatest importance of the hilar portions of the airways where the concentration of pulmonary stretch receptors has been found to be greater.
Plasma aldosterone, cortisol and corticosterone concentrations in the new‐born guinea‐pig
Authors: Malinowska K. W. , Nathanielsz P. W. 
Published: December 2014

1. Plasma aldosterone concentrations have been measured by radio‐immunoassay in the new‐born and adult guinea‐pig and related to plasma cortisol and corticosterone concentrations.2. Plasma aldosterone concentrations were high in the hours immediately after birth with peak values of 552 pg/ml. at between 6 and 24 hr of age. Adult male plasma concentrations were 72 pg/ml. in plasma taken by cardiac puncture and 126 pg/ml. when measured in blood taken from an indwelling arterial catheter.3. The major plasma glucocorticoid was cortisol and earlier reports of values above 1 μg/ml. were confirmed by more exacting column chromatography with Sephadex LH 20.4. There was no constant relation between aldosterone and glucocorticoid concentrations in the animals studied, either new‐born or adult.5. Plasma cortisol: corticosterone ratios were not constant but varied considerably. In the adult a sevenfold rise in plasma cortisol concentration occurred under certain conditions without any change in plasma corticosterone concentrations.
Electrophysiological investigation of GABA‐mediated inhibition at the hermit crab neuromuscular junction
Authors: Earl Janet , Large W. A. 
Published: December 2014

1. The inhibitory neuromuscular junction of the abductor muscle of the large claw of the hermit crab (Eupagurus bernhardus) was investigated using electrophysiological intracellular techniques in order to elucidate further the relative contributions of the pre‐ and post‐synaptic mechanisms of action of GABA and of neural inhibition.2. The electrical constants of the post‐synaptic membrane, calculated using the equations for a ‘short cable’ model, were characteristic of a poorly developed electrical excitability; the specific membrane resistance was usually < 1000 Ω cm2 and the specific membrane capacitance was > 40 μF/cm2.3. Stimulation of the excitatory axon to the abductor muscle of the large claw at a frequency of 20 Hz evoked highly facilitating excitatory junction potentials (e.j.p.s); stimulation of the inhibitory axon (60‐220 Hz) during the excitatory train elicited inhibition which was manifest as an attenuation of the e.j.p.s.4. The addition of γ‐aminobutyric acid (GABA) to the bathing solution produced a dose‐dependent reduction of e.j.p. amplitude and membrane resistance. The inhibitory effect of concentrations (5 × 10−5 and 1 × 10−4
M) which caused a 40–75% e.j.p. attenuation could largely be accounted for by a post‐synaptic action on membrane conductance.5. Experiments with picrotoxin suggest that presynaptic inhibitory mechanisms have an important role in neurally evoked inhibition.6. Picrotoxin (1–5 × 10−5
M) effectively blocked neural inhibition and the actions of GABA in this preparation, whereas bicuculline proved to be considerably less potent and therefore less useful as a physiological tool for studying GABA‐mediated inhibition in crustacea.
Does the vestibular apparatus play a role in the development of the visual system?
Authors: Blakemore C. , Papaioannou J. 
Published: December 2014

1. The receptive field properties of visual cortical neurones were investigated in kittens that had been subjected to either unilateral or bilateral labyrinthectomy shortly after birth.2. Two kittens were reared in a normal visual environment. Another two were reared in the dark with recurrent exposures to vertically oriented black and white stripes, which in normal kittens is known to bias the distribution of receptive field orientations.3. For both normally reared and stripe‐reared labyrinthectomized kittens, no differences were detected in cell types, preferred orientations, binocularity, columnar organization, or any other neuronal properties, compared with similarly reared intact kittens.4. The failure to detect deficits in visual development after labyrinthectomy is discussed in relation to other reports of vestibular influences on the visual system of the adult cat.
Analysis of the role of cyclic adenosine 3′,5′‐monophosphate in catecholamine release
Authors: Jaanus Siret D. , Rubin R. P. 
Published: December 2014

1. Cyclic adenosine 3′,5′‐monophosphate (cyclic AMP) levels and catecholamine release were measured in cat adrenal glands perfused in situ with Locke solution.2. Cyclic AMP was present in the medulla in an amount which represented approximately one fifth of that present in the cortex.3. Perfusion with acetylcholine (ACh) or nicotine increased cyclic AMP both in the intact adrenal and in the perfusate. The time course of the changes in tissue cyclic AMP during stimulation was out of phase with the time course of catecholamine release. Maximal increases in cyclic AMP were not manifest until after 8 min of exposure to the secretogogue, whereas maximal rates of secretion occurred during the first minute.4. Theophylline (0·5 m
M) increased basal and stimulated adrenal cyclic AMP levels, but did not potentiate the secretory response to ACh or nicotine.5. Perfusion with cyclic AMP or its dibutyryl derivative (0·2–4 m
M) failed to effect a consistent or significant increase in the rate of catecholamine release and was unable to potentiate the secretory response to a submaximal concentration of ACh or calcium.6. The results suggest that, unlike calcium, cyclic AMP is not a direct mediator of medullary secretion.
The development of a blood‐brain barrier mechanism in foetal sheep
Authors: Evans C. A. N. , Reynolds J. M. , Reynolds M. L. , Saunders N. R. , Segal M. B. 
Published: December 2014

1. The penetration of a metabolically inert, small molecular radius lipid insoluble substance ([13C] and [4H]sucrose), from blood into brain and c.s.f., has been studied in developing sheep from 50 days gestation (term, 150 days) through to the new‐born stage. Around 50 days gestation sucrose accumulated rapidly into brain and c.s.f., and reached a steady‐state level in brain of about 12% of the plasma level by 3 hr. By 60 days sucrose penetrated less freely into brain and c.s.f.; the brain steady‐state level was 10% by 4½ hr. A large decrease in sucrose penetration occurred by 70 days gestation, and by 123 days (just before the time when a foetal lamb becomes viable) both the rate of penetration and the brain steady‐state level of sucrose were similar to those of the adult of other species.2. The rate of c.s.f. secretion at different ages has been estimated by dye dilution during ventriculo‐cisternal perfusion. The turnover of c.s.f. in 60 day foetuses was high (1·36%/min.g wet weight brain). From 123 days gestation to the adult stage the turnover was much lower, 0·02%/min.g at 123 and 137 days gestation and 0·01%/min.g in the adult ewe.3. A simple new method for measuring c.s.f. volume is described. The volume at 51 days was estimated to be 0·14 ml.,
S.E. ± 0·03, n = 4 (brain weight = 0·87 g ± 0·11), at 59 days it was 0·45 ml.,
S.E. ± 0·04, n = 6 (brain weight = 2·0 g ± 0·1) and near term it was 7·28 ml
S.E. ± 1·29, n = 4 (brain weight 42·0 g ± 0·5).4. The results are discussed in relation to possible changes in permeability of the cerebral capillary endothelium, the sink effect of c.s.f., and changes in extracellular space of the brain during its development. It is concluded that the high rate of penetration and raised brain steady‐state level of sucrose in immature sheep foetuses is probably due to immaturity of a permeability barrier at the level of the cerebral capillary endothelium or its associated glial processes. Some clinical implications of these findings are considered briefly.