bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of the action of picrotoxin on the inhibitory neuromuscular junction of the crayfish
Authors: Takeuchi A. , Takeuchi Noriko 
Published: December 2014

1. The effect of picrotoxin on the neuromuscular junction of the crayfish (Cambarus clarkii) was investigated. The potential changes were recorded intracellularly and extracellularly with micro‐electrodes. The membrane conductance of the muscle fibre was also measured.2. Picrotoxin depressed the amplitudes of the inhibitory junctional potentials and the potential changes produced by iontophoretically applied γ‐aminobutyric acid (GABA), but had no appreciable effect on the excitatory junctional potentials and the potential changes produced by
L‐glutamate.3. The presynaptic action of GABA and the neural transmitter was depressed by picrotoxin. The presynaptic action of β‐guanidinopropionic acid was also depressed by picrotoxin.4. The increase in the membrane conductance produced by the addition of GABA in the bath fluid was depressed by picrotoxin. The dose—response relation showed that picrotoxin depressed the conductance increase produced by GABA in a non‐competitive manner. The action of picrotoxin on the conductance increase produced by GABA was more effective in low Cl‐ solution.5. The analysis of the dose—response curves showed that the action of picrotoxin was well expressed by the Michaelis—Menten equation, but the slope of the dose—response curve of GABA was steeper than this relation. It is proposed that the conductance of the junctional membrane was increased by the combination of two molecules of GABA with a receptor, and the attachment of one molecule of picrotoxin to a specific site depressed the conductance increase.
The role of brown adipose tissue in the calorigenic effect of adrenaline and noradrenaline in cold‐acclimated rats
Authors: Himms‐Hagen Jean 
Published: December 2014

1. Removal of the interscapular brown adipose tissue of the cold‐acclimated rat has no immediate effect on the calorigenic response of the rat to adrenaline or noradrenaline.2. There is a progressive loss of the enhanced response to adrenaline and to noradrenaline during the 4 days following removal of the interscapular brown adipose tissue from cold‐acclimated rats. There is no loss of response in sham‐operated cold‐acclimated rats.3. Removal of the interscapular brown adipose tissue from rats living at room temperature has no effect on the calorigenic response to adrenaline or noradrenaline, neither immediately afterwards nor 2‐4 days later.4. It is concluded that interscapular brown adipose tissue is not the major site of oxygen consumption in the enhanced calorigenic response to adrenaline or noradrenaline in cold‐acclimated rats. However, it does play an important role in this enhanced metabolic response, probably as an endocrine gland whose secretory product modifies the ability of other tissues to respond calorigenically to catecholamines.
The effect of altered thyroid state on atrial intracellular potentials
Authors: Freedberg A. S. , Papp J. Gy. , Williams E. M. Vaughan 
Published: December 2014

1. A group of rabbits was made hypothyroid by thyroidectomy, and another group was injected daily with
L‐thyroxine. After an appropriate interval respective alterations in thyroid state were confirmed by measurement of heart weight and of plasma iodine, and the animals' atria were isolated for recording.2. Measurements were made of atrial contractions, conduction velocity, spontaneous heart rate and maximum driven frequency, and action potentials were recorded with intracellular micro‐electrodes.3. The resting potential and action potential heights were not affected by differences of thyroid state.4. Atrial arrhythmias are common in hyperthyroidism, rare in myxoedema. The possibility that hypothyroidism might reduce the rate of rise of the action potential, as do anti‐arrhythmic drugs, and hyperthyroidism increase it, was investigated. Although the rate of rise was slower in hypothyroid atria at some driving frequencies, this could not alone account for an anti‐arrhythmic effect, because at frequencies near the spontaneous heart rate the rate of rise of the action potential was not reduced.5. The duration of the repolarization phase of the action potential was greatly prolonged in atria from thyroidectomized rabbits, and was shortened in hyperthyroid atria. These changes could account for a reduced probability of arrhythmias in hypothyroidism, and the converse in hyperthyroidism.
The total thermal insulation of the new‐born baby
Authors: Hey E. N. , Katz G. , O'Connell Bridget 
Published: December 2014

1. One hundred and seventeen healthy new‐born babies weighing between 0·9 and 4·8 kg at delivery have been studied during the first ten days of life, and sixteen of these babies have been studied serially for 6 weeks after birth. The babies lay supine in a draught‐free environment (air speed 4‐5 cm/sec) of moderate humidity. The operative temperature was between 26 and 38° C for the babies who were studied naked.2. Total non‐evaporative heat loss was calculated from simultaneous measurements of oxygen consumption, evaporative water loss and the concomitant change in mean body temperature.3. Approximately 10% of the total body surface area was in contact with the mattress or floor. Conductive heat loss accounted for only about 5% of all non‐evaporative heat loss when the naked baby was lying on a thick foam mattress, but for as much as 25% when the baby was lying in a water‐jacketed chamber with a floor of clear plastic ∼ 5 mm thick.4. Insulation to heat loss by convection and radiation varied with environmental temperature. Total specific insulation was low in a warm environment when the naked baby vasodilated, and rose by between 16 and 25% to a maximum in an environment of 31° C. It decreased significantly when the baby became physically active in environments with a temperature less than this.5. Total specific insulation in an environment of 31° C varied with body size: it averaged 0·156° C.m2.hr/kcal in seven naked babies weighing 0·9–1·2 kg, rose to 0·190° C.m2.hr/kcal in twelve babies weighing 1·8–2·2 kg, and averaged 0·201° C.m2.hr/kcal in the thirty‐four babies who weighed over 3 kg. Tissue insulation accounted for 23% of this total specific insulation in the smaller babies, and about 28% of the total in babies weighing over 3 kg.6. Clothing ten babies in a vest, napkin and long cotton nightdress increased the total specific insulation by an average of 0·23° C.m2.hr/kcal.
The partition of nutrients between mother and conceptuses in the pregnant rat
Authors: Frazer J. F. D. , Huggett A. St G. 
Published: December 2014

1. Diminishing the food supply to pregnant rats was associated with a subnormal degree of foetal loss among the larger litters, but a greatly lowered intake increased this foetal loss.2. Whether the food intake was lowered, normal or increased, the increase in conceptus weight over the last half of pregnancy could be related to the total maternal weight increase over this period by the formula y = ¼x + 4·5n, where n was the number of foetuses.3. With values of x below 20 g, this no longer held, but y never fell below 4·5 (n + 1).4. It is concluded that Hammond's theory of the partition of nutrients is confirmed, so far as mother and conceptuses are concerned, in the rat.
Further study of the role of calcium in synaptic transmission
Authors: Katz B. , Miledi R. 
Published: December 2014

1. The effect of calcium on synaptic transmission has been studied by intracellular recording of pre‐ and post‐synaptic potential changes in the stellate ganglion of the squid.2. For a given presynaptic ‘input’ (propagated spike, or local depolarizing pulse after tetrodotoxin treatment), the post‐synaptic response increases with external calcium concentration [Ca]o in a highly non‐linear fashion, indicating that transmitter output varies with more than the second power of [Ca]o over a certain concentration range.
Enzymic and physiological studies on normal and disused developing fast and slow cat muscles
Authors: Mann William S. , Salafsky B. 
Published: December 2014

1. Contraction time (CT), ½ relaxation time (½ RT), maximum twitch‐tetanus tensions and the activity of two glycolytic enzymes (aldolase, pyruvic kinase) and two oxidative enzymes (malic and isocitric dehydrogenase) was studied in anterior tibialis (AT) and soleus (SOL) muscles from birth to 18 weeks of age.2. One hind leg of each of six kittens was casted at birth and the above parameters were examined in both casted and contralateral AT and SOL at 18 weeks of age.3. Differentiation of the contraction properties in normal developing fast muscle (AT) was closely paralleled by a marked elevation in glycolytic enzyme activity. Oxidative enzymic activity in AT and SOL was relatively unchanged from birth to 18 weeks of age, as was glycolytic activity in SOL.4. Disuse, due to immobilization, produced atrophy in AT and SOL muscles at 18 weeks of age. The CT of the casted SOL was slightly quicker than normal while the CT of the AT was unchanged. The glycolytic and oxidative enzymic activity in both casted muscles was generally unchanged but the contralateral AT had higher glycolytic activity than normal muscles.
The relation between carotid body chemoreceptor discharge, carotid sinus pressure and carotid body venous flow
Authors: Biscoe T. J. , Bradley G. W. , Purves M. J. 
Published: December 2014

1. Activity in forty‐two single chemoreceptor afferent fibres from the carotid body in thirty‐nine cats was measured when the carotid body was naturally and artificially perfused. In nine of these cats, carotid body venous flow was also measured.2. When pressure within the carotid sinus segment was suddenly raised or lowered, chemoreceptor activity changed in the opposite direction within the first 5‐10 sec by an amount which was significantly greater than the variation of activity in the control period. Thereafter activity stabilized at a level which was not different from control.3. Whether the carotid body was naturally or artificially perfused, carotid body chemoreceptor activity, following this initial transient change, was unaffected in eight out of twelve fibres by alterations in carotid sinus pressure within the range 60–160 mm Hg and carotid body venous flow 10–60 μl./min, blood gas tensions and pH being maintained constant. In the four remaining fibres, chemoreceptor activity increased slightly but significantly as pressure was lowered in this range. Chemoreceptor activity increased in all fibres tested when pressure was lowered below 50–60 mm Hg.4. Chemoreceptor response curves to changes in Pa,O2 (30–450 mm Hg), Pa,CO2 (27–62 mm Hg) or [H+]a (3–7 × 10−5 m‐equiv/l.) were not significantly different whether the carotid body was perfused (a) naturally at the prevalent systemic pressure, (b) artificially at the same pressure, or (c) artificially at one higher pressure, 130 or 140 mm Hg.5. These results indicate that the carotid body chemoreceptors are relatively unaffected by sustained changes in arterial pressure or in total carotid body flow within the physiological range.
The effect of adenosine triphosphate on the transmural potential in rat small intestine
Authors: Kohn P. G. , Newey H. , Smyth D. H. 
Published: December 2014

1. ATP either in the mucosal or serosal fluid caused a transient increase in the potential difference and short‐circuit current across the wall of rat jejunum in vitro, the serosal solution becoming more positive.2. Similar responses were observed in the ileum and colon, and in in vivo preparations of small intestine.3. The response is relatively specific for ATP.4. The transient nature of the response is not due to rapid hydrolysis of extracellular ATP.5. High concentrations of K+ in the mucosal medium, serosal ouabain or mucosal 2,4‐dinitrophenol all inhibit the response without altering the time course.6. Significant inhibition was not observed in the presence of ADP or in Mg2+‐free salines.7. The results are consistent with an intracellular action of ATP in the epithelium to stimulate net ion transport. The results do not demonstrate whether or not extracellular ATP can act as an energy donor for an electrogenic ion pump.8. Theophylline prolongs the time course of the response, and the involvement of the adenyl cyclase system cannot be excluded as an explanation for the findings.
The half‐life of exogenous gastrin in the circulation
Authors: Blair E. L. , Farra Yvonne , Richardson Diana D. , Steinbok P. 
Published: December 2014

1. A method of gastrin bio‐assay is described which can be used on as little as 30 ng synthetic human gastrin I at a minimum concentration of 2·5 ng/ml.2. Pentagastrin or synthetic human gastrin I added to cat plasma can be stored on ice or at 4° C, for periods up to 27 hr without apparent loss of gastrin activity.3. Between 1½ and 13 min after the rapid
I.V. injection of pentagastrin in the anaesthetized cat and between 1½ and 15 min after the injection of synthetic human gastrin I, there is a rapid reduction of the gastrin concentration in the arterial plasma. The data relating log10 gastrin concentration in arterial plasma with time can be fitted by a single term.4. Studies in vitro show that over the periods of time involved in the in vivo studies, both pentagastrin and synthetic human gastrin I are stable in cat plasma at 37° C in concentrations which occurred in the circulating plasma.5. The half‐life of pentagastrin in the circulating arterial plasma of the anaesthetized cat is 1·50 min (
S.E. ± 0·08) and the half‐life of synthetic human gastrin I is 2·65 min (
S.E. ± 0·09).
Intracellular hydrolysis of short chain glycerides by rat small intestine in vitro and transfer of glycerol
Authors: Howard J. , Jackson M. J. , Smyth D. H. 
Published: December 2014

1. When triacetin, tripropionin and tributyrin are incubated with sacs of rat everted intestine, they enter the epithelial cells and are completely hydrolysed to free fatty acids and glycerol.2. The distribution between the mucosal and serosal fluids of the glycerol released is very different from that of the fatty acid. Although both hydrolytic products are accumulated in the serosal fluid, a much higher fraction of the fatty acid appears in this compartment.3. When glycerol is initially present in the mucosal fluid there is no evidence of its movement against a concentration gradient.4. The results confirm the existence of a transport mechanism for fatty acids released intracellularly but do not require the hypothesis of a special mechanism for glycerol transfer.
Cervico‐lumbar reflex interactions involving a proprioceptive receiving area of the cerebral cortex
Authors: Abrahams V. C. 
Published: December 2014

1. In the decerebrate cat descending cervico‐lumbar reflex interactions from neck muscle nerves are absent, and those from forepaw nerves are reduced or absent.2. Lesions restricted to the anterior pole of the suprasylvian gyrus regularly abolish descending cervico‐lumbar reflex interactions from neck muscle nerves. The same lesions may reduce or abolish descending cervico‐lumbar reflex interactions from forepaw nerves.3. The ascending cortical looping pathway utilized in descending cervico‐lumbar reflex interactions is crossed, and the descending pathway from the cerebral cortex is bilateral.
Mesopic increment threshold spectral sensitivity of single optic tract fibres in the cat: cone—rod interaction
Authors: Andrews D. P. , Hammond P. 
Published: December 2014

1. Mesopic increment threshold spectral sensitivities of sixty‐six on‐centre and twenty‐five off‐centre ganglion cells in the cat were determined by recording from single fibres of the left optic tract at a level posterior to the optic chiasma.2. All units were monocularly driven; receptive fields were located almost exclusively in the right visual half‐fields within 30° of the area centralis, but with slight overlap across each retinal mid line to the left half‐fields. The extent of field spread to the right temporal hemi‐retina was significantly larger than that to the left nasal hemi‐retina. Field centre diameters ranged from less than 0·25° for central units to 2° for more peripheral units.3. At high mesopic adaptation of 1 log cd/m2 all responsive units (forty‐four fibres) received mixed cone—rod input. Threshold curves could always be fitted by the absorption spectra of visual pigment 556 together with varying contributions from visual pigment 507, each derived from the Dartnall nomogram.4. Of forty‐seven fibres analysed under low mesopic background (0 log cd/m2) 92% received similar cone—rod input, being fitted predominantly by visual pigment 507 with slight cone contamination. The remaining 8% received pure rod input and could be matched by visual pigment 507 alone.5. In conclusion, the cat retina presumably contains a single class of cones with absorption maxima at 556 nm, and a single class of rods. Discrepancy between the presumed rod absorption maximum (502 nm) and the low‐mesopic sensitivity maxima of tract fibres (507 nm) is considered in terms of tapetal reflectivity, and absorption by ocular media. Both mechanisms input to the great majority of retinal ganglion cells. At high mesopic levels the cone mechanism predominates. At low mesopic levels the rod mechanism predominates. A small proportion of ganglion cells within the central 30° of the retina receive input only from rods, and in these the rod mechanism saturates completely below 1 log cd/m2.
On the relationships between membrane potential, calcium transient and tension in single barnacle muscle fibres
Authors: Ashley C. C. , Ridgway E. B. 
Published: December 2014

1. The calcium‐sensitive photoprotein aequorin has been used to follow the rapid changes in intracellular calcium concentration that occur during the contraction of single muscle fibres from the barnacle Balanus nubilus, Darwin.2. The transient change in calcium‐mediated light emission (calcium transient) and the changes in membrane potential and tension were recorded simultaneously, thus permitting an examination of the relationships between the chemical, electrical, and mechanical events of excitation—contraction coupling.3. With short‐duration stimuli (< 200 msec), the calcium transient shows an S‐shaped rising phase reaching a maximum soon after the cessation of the stimulus pulse. During membrane repolarization the calcium transient begins an exponential falling phase which has a time constant of 50–80 msec at 11–12° C.4. The shape of the calcium transient resembles the first derivative of the rising phase of the isometric tension response, thus suggesting that calcium controls the rate of tension development.5. There is no detectable increase of the light emission above resting values, during the falling phase of isometric tension.6. A plot of the calcium transient area (lumen × sec) versus peak isometric force (g. cm−2) is linear over, at least, a range of forces from ca. 50–400 g. cm−2.7. When the fibre is capable of producing an active membrane response following the intracellular injection of potassium citrate, the onset and cessation of the calcium transient follow closely the onset and cessation of the active membrane response. Tension responses under these conditions are much suppressed, suggesting that excitation—contraction coupling may be partially blocked between calcium release and the development of tension.8. Hypertonic salines (1
M sucrose or 1
M glycerol) cause little change in the membrane response, but greatly suppress the calcium transient and completely abolish the tension responses. These effects are readily reversible when normal saline is reintroduced, suggesting that excitation—contraction coupling may be temporarily blocked between the membrane response and calcium release.9. If the stimulus is prolonged (> 250–300 msec), the calcium transient falls slowly from its maximum value despite continued membrane depolarization, suggesting a time‐dependent change in the ratio of the rate of release of calcium to the rate of calcium binding. The results from brief tetanic stimulation also support this suggestion.
Miniature potentials in denervated slow muscle fibres of the frog
Authors: Miledi R. , Stefani E. 
Published: December 2014

1. Pyriformis and iliofibularis muscles of the frog were studied with micro‐electrodes. Both muscles contain a mixture of fast and slow muscle fibres, which can be distinguished by differences in their miniature end‐plate potentials (min.e.p.p.s).2. In addition, the membrane time constant of fast fibres is < 20 msec, while that of slow fibres is > 200 msec.3. The characteristic difference in time constant persisted after denervation and allowed the identification of fibre type.4. Denervated slow fibres had min.e.p.p.s of variable time courses and skew amplitude distributions. Their frequency was lower than in normally innervated fibres, and could be increased by hypotonic solutions.5. In analogy with similar observations made previously in fast muscle fibres, it is suggested that after nerve degeneration the Schwann cells of small motor nerve fibres release packages of transmitter which give rise to min.e.p.p.s.
The effect of the tetraethylammonium ion on the delayed currents of frog skeletal muscle
Authors: Stanfield P. R. 
Published: December 2014

1. A method which permitted control of the membrane potential near the end of a muscle fibre and measurement of an approximation of the membrane current was used to investigate the effects of the tetraethylammonium (TEA) ion on the delayed outward potassium current obtained on depolarizing.2. Assuming Ri to be 250 Ω cm and a fibre diameter of 80 μ, the mean value for the maximum potassium conductance (ḡK) was 23·2 ± 3·2 mmho.cm−2.3. 58 m
M‐TEA, in two series of experiments, reduced ḡK by about 90%. A concentration—effect relation for TEA in its action on the delayed rectifier could be fitted by a curve for a drug‐receptor complex assuming one molecule of TEA to combine reversibly with one receptor, and a dissociation constant of 8 × 10−3
M.4. TEA tended to shift the threshold for delayed rectification to slightly more negative membrane potentials. TEA caused a similar shift in the relation between n∞ and membrane potential, but did not much alter the form of the relation.5. The relation between n∞ and membrane potential and between τn−1 and membrane potential were well fitted by the model of Adrian, Chandler & Hodgkin (1970a) assuming that the Q10 was 2·5.6. TEA slowed the rate of onset of the delayed potassium currents, decreasing τn−1 (the reciprocal of the time constant of the fourth power function which described the current's development) by about 80%.7. The inactivation of the delayed current with time was shown to follow a complex time course. A fast phase decays with a time constant of 270 msec and a slow phase with a time constant of 2·3 sec at a membrane potential of + 10 mV.8. The fast phase of the delayed current is much more susceptible to the action of TEA than the slow phase, and these are interpreted in terms of different potassium channels. TEA has little effect on the time constant with which either the fast current or the slow current inactivates.