bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adrenal secretion rates and adrenal tissue concentrations of pregnenolone, progesterone, 11βOH‐androstenedione and some other steroids in young pigs and dogs
Authors: Holzbauer Margarethe , Newport Helen M. 
Published: December 2014

1. The rates were measured at which a number of different steroids were secreted by the adrenal gland of the eviscerated and nephrectomized young pig and dog.2. In addition to cortisol and corticosterone the following steroids were consistently found to be present in the adrenal venous blood: pregnenolone, progesterone, 11βOH‐progesterone, androstenedione, 11βOH‐androstenedione and adrenosterone.3. The sum of the latter steroids could amount to as much as 30% of the total steroid secretion.4. A severe deficit in the blood volume increased the secretion of pregnenolone and the 17‐oxo steroids in the pig.5. α‐ethyltryptamine failed to inhibit ACTH release if the animals were eviscerated and nephrectomized, or if they were anaesthetized with chloralose instead of pentobarbitone sodium.6. The same steroids as in the adrenal venous blood were found in extracts from the adrenal glands of a number of species.7. The amount of individual steroids present in the adrenal gland of the stressed pig and dog was compared with the rate at which each had been secreted immediately before the excision of the gland.8. There was a positive correlation between the adrenal concentrations and the secretion rates of cortisol, the major glucocorticoid secreted by the pig and the dog.9. In contrast, the rate at which pregnenolone was secreted did not show a consistent relationship to its concentration in the gland.10. A storage mechanism for pregnenolone in the adrenal cortex is proposed.
Hypoxaemia and aortic chemoreceptor function in foetal lambs
Authors: Dawes G. S. , Duncan Sheila L. B. , Lewis B. V. , Merlet Claudie L. , Owen-Thomas J. B. , Reeves J. T. 
Published: December 2014

1. In foetal lambs the effect of raising and lowering arterial PO2 (by varying the O2 content of the maternal inspired gas mixture) was studied in order to determine whether the systemic arterial chemoreceptors regulated the circulation.2. From 0·7 of term relative hypoxaemia (e.g. reducing carotid PO2 from 40 to 20 mm Hg) caused a rise of arterial pressure and femoral vaso‐constriction. These changes were unaffected or even increased by bilateral section of the nerves from the carotid sinus and body. They were abolished by section of the vagi or aortic nerves.3. It is concluded that in foetal lambs during the last third of gestation the circulation is under reflex control by the aortic chemoreceptors.
Spontaneous activity of single neurones in the hypothalamus of rabbits during sleep and waking
Authors: Findlay Alan L. R. , Hayward James N. 
Published: December 2014

1. A method is described for recording from single cells in the hypothalamus of unanaesthetized freely moving rabbits. Behaviour, bodily movement, skin and brain temperatures and e.e.g. were monitored.2. Patterns of unit firing during slow sleep, paradoxical sleep and waking were studied in several regions of the hypothalamus, thalamus and in the septum.3. Of the 144 cells analysed from waking to slow sleep, fifty‐six (39%) decreased mean firing rates, thirty (21%) increased spike discharges and fifty‐eight (40%) showed no marked change. Dorsal hypothalamic and massa intermedia thalamic cells fired in brief high frequency clusters during slow sleep with a characteristic ‘bimodal’ interspike interval histogram. Waking and paradoxical sleep abolished these cluster discharges with a concomitant change to an ‘asymmetric’ histogram.4. Of the thirty‐two cells observed during the three states of waking, slow sleep and paradoxical sleep, a majority (twenty‐five or 78%) showed their highest rates of spontaneous discharge during paradoxical sleep. Discharge rates of cells sometimes changed in the course of paradoxical sleep according to the presence or absence of phasic events such as myoclonic motor activity. Two hypothalmic cells were almost totally arrested during paradoxical sleep.5. Analysis of unit firing rates during spontaneous rises in brain temperature during waking and paradoxical sleep revealed that a majority of the neurones (22/24) changed their discharge rates in relation to behaviour rather than to brain temperature. Two cells did appear to respond specifically to the central thermal stimulus.6. Hypothalamic cells do not behave as a homogeneous population in relation to changes in the state of arousal of the rabbit. Spontaneous changes in cell discharge related to sleep‐waking behaviour must be considered in any interpretation of hypothalamic unit activity as related to neuroendocrine or autonomic mechanisms.
The role of a renal thirst factor in drinking induced by extracellular stimuli
Authors: Fitzsimons J. T. 
Published: December 2014

1. Rats in normal fluid balance drank water 1–2 hr after complete ligation of the inferior vena cava either above or below the renal veins. At the same time there was a fall in urine flow and excretion of electrolyte, especially after caval ligation above the renal veins, so that the animals ended the initial 6 hr period in positive fluid balance.2. Caval ligation was relatively ineffective as a stimulus to drinking after bilateral nephrectomy, but was effective in rats made anuric by ureteric ligation.3. Rats subjected to caval ligation and offered a choice between water and 1·8% saline (w/v) drank water, despite the increasing hypotonicity of the body fluids thereby resulting.4. During the secondary polydipsia, which generally occurred on about the third day after caval ligation as renal function was recovering, there was an increased preference for 1·8% saline.5. Constriction of the aorta above the renal arteries, or constriction of both renal arteries, also caused drinking, oliguria and the development of positive fluid balance.6. Constriction of the aorta below the renal arteries, or after nephrectomy, was ineffective as a stimulus to drinking.7. Saline extracts of renal cortex caused rats in normal water balance to drink. Activity was destroyed by boiling the extract for 10 min. Renal medullary and hepatic extracts were without effect on drinking.8. It proved impossible to separate dipsogenic and pressor activities of renal extracts during the different stages of fractionation which lead to the production of renin; disappearance of one activity was invariably accompanied by disappearance of the other.9. Dipsogenic and pressor actions were greater in nephrectomized rats than in normal rats.10. Both extractable dipsogenic factor and extractable pressor activity were reduced by treating the rat with DOCA and saline for several weeks beforehand.11. The renal dipsogen therefore has similar properties to renin. It may prove to be identical with renin, particularly in view of the fact that angiotensin also stimulates drinking.12. Adrenalectomy did not affect drinking induced by renin or by caval ligation.13. It is concluded that the renin angiotensin system may play a role in the genesis of the thirst which follows certain extracellular stimuli.
The time course of red cell lysis in hypotonic electrolyte solutions
Authors: Bowdler A. J. , Chan T. K. 
Published: December 2014

1. Osmotic haemolysis of a standard suspension of human red cells was followed using a recording spectrophotometer at wave‐lengths between 600 and 650 mμ.2. Optical density changes in the cell suspensions were related to turbulence of the suspension, cell swelling and loss of haemoglobin‐containing cells.3. The time course of the loss of cells from suspension in hypotonic electrolyte solutions showed two phases: an early rapid phase was followed by a smaller phase of longer half‐time.4. The second phase was most prominent in the middle ranges of partial haemolysis and less when total haemolysis was at the extremes of the detectable range.5. The second phase was eliminated by the inclusion of 20 m
M sucrose in the suspension, and was slowed by the presence of 0·005% tannic acid without alteration of magnitude.6. The magnitude of the second phase was dependent on the dominant external cation, becoming progressively greater through the series: Mg2+ < Na+ < Li+ < K+ < Rb+.7. The slow phase is interpreted as arising from passive cation permeability in cells swollen to a volume close to that critical for haemolysis, with water influx secondary to the unopposed colloid osmotic pressure of intracellular protein.
Analysis of synaptic efficacy in spinal motoneurones from ‘quantum’ aspects
Authors: Kuno M. , Miyahara J. T. 
Published: December 2014

1. Synaptic responses of triceps surae motoneurones of the cat following stimulation of single afferent fibres were examined by intracellular recording techniques.2. The mean quantum content (m) of monosynaptic excitatory postsynaptic potentials (EPSPs) was independent of the type of motoneurone recorded and of the afferent fibre stimulated. There was no significant difference in m value between homonymous and heteronymous synapses.3. A positive correlation was found between the amplitude of unit EPSPs and the input resistance of motoneurones. The difference in the amplitude of unit EPSPs appears to be responsible for the higher synaptic efficacy in slow‐conducting motoneurones than in fast‐conducting motoneurones.4. There was no significant difference in the time course of monosynaptic EPSPs evoked by impulses from homonymous and heteronymous afferent fibres.5. The ratio of monosynaptic connexions from a given afferent fibre was significantly greater on to homonymous than to heteronymous motoneurones. It is concluded that the difference in efficacy between homonymous and heteronymous synaptic transmission is due to the difference in the number of afferent fibres converging upon these motoneurones.
Cat colour vision: one cone process or several?
Authors: Daw N. W. , Pearlman A. L. 
Published: December 2014

1. Peripheral mechanisms that might contribute to colour vision in the cat have been investigated by recording from single units in the lateral geniculate and optic tract. Evidence is presented that the input to these cells comes from a single class of cones with a single spectral sensitivity.2. In cats with pupils dilated a background level of 10–30 cd/m2 was sufficient to saturate the rod system for all units. When the rods were saturated, the spectral sensitivity of all units peaked at 556 nm; this was true both for centre and periphery of the receptive field. The spectral sensitivity curve was slightly narrower than the Dartnall nomogram. It could not be shifted by chromatic adaptation with red, green, blue or yellow backgrounds.3. In the mesopic range (0·1–10 cd/m2), the threshold could be predicted in terms of two mechanisms, a cone mechanism with spectral sensitivity peaking at 556 nm, and a rod mechanism with spectral sensitivity at 500 nm. The mechanisms were separated and their increment threshold curves measured by testing with one colour against a background of another colour. All units had input from both rods and cones. The changeover from rods to cones occurred at the same level of adaptation in both centre and periphery of the receptive field. Threshold for the cones was between 0·04 and 0·25 cd/m2 with the pupil dilated, for a spot covering the centre of the receptive field.4. None of the results was found to vary between lateral geniculate and optic tract, with layer in the lateral geniculate, or with distance from area centralis in the visual field.5. The lack of evidence for more than one cone type suggests that colour discrimination in the cat may be a phenomenon of mesopic vision, based on differences in spectral sensitivity of the rods and a single class of cones.
Rat brain amines, blood histamine and glucose levels in relationship to circadian changes in sleep induced by pentobarbitone sodium
Authors: Friedman Alexander H. , Walker Charles A. 
Published: December 2014

1. The circadian patterns for onset and duration of sleep after the administration of a constant dose of pentobarbitone sodium have been measured in rats adapted to and maintained under a fixed illumination cycle. The relationship of these patterns to others for rectal temperature and motor activity as well as for noradrenaline (NA), 5‐hydroxytryptamine (5‐HT) and histamine in mid‐brain and caudate nucleus, and histamine and glucose in blood serum, has been examined.2. The onset of sleep is longest and duration shortest during the phase of the illumination cycle when motor activity and rectal temperature are maximal. An inverse relationship for these parameters is found during the light phase of the illumination cycle.3. In untreated rats, mid‐brain NA and histamine and caudate nucleus histamine levels are maximal and 5‐HT minimal during the dark phase of the illumination cycle. An inverse relationship for these parameters is found during the light phase of the illumination cycle.4. Pentobarbitone sodium treatment significantly elevates mid‐brain NA and histamine and caudate nucleus histamine levels during the dark phase of the illumination cycle. Although 5‐HT levels are reduced over the entire circadian cycle this change is significant only during the light phase of the illumination cycle.5. Pentobarbitone sodium treatment reverses the circadian pattern for body temperature, producing a mirror image of the control pattern.6. The circadian pattern for blood serum histamine levels differs from the
C.N.S. pattern for histamine. Peak levels occur at the end of the light phase of the illumination cycle. After pentobarbitone sodium these levels are reduced, although the circadian pattern is similar to the control.7. Circadian blood glucose patterns have bimodal peaks; a primary peak at the end of the dark phase, a secondary peak at the end of the light phase of the illumination cycle. Pentobarbitone sodium did not significantly alter the pattern. The relationship between this pattern and
C.N.S. and peripheral histamine and catechol amines is discussed.
Chloride fluxes in crab muscle fibres
Authors: Richards C. D. 
Published: December 2014

1. Isotopic techniques were used to study the efflux of Cl− from single cannulated muscle fibres of the crab Maia squinado.2. The efflux of 36Cl− was found to be exponential with steady rate constants ranging from 0·01 to 0·07 min−1. The steady efflux was ca. 1000–2000 p
M cm−2 sec−1. The efflux was slightly depressed by K+‐free saline and was unaffected by 40 m
M‐K+ saline and NO3− saline. The influx and efflux of Cl− were presumed independent.3. The membrane conductance calculated from 36Cl− flux data was consistent with that determined by the method of electrotonic spread for other marine crustacean muscle fibres. Cl− accounted for most of the membrane conductance.
Reticulo‐ruminal mechanoreceptors in sheep
Authors: Leek B. F. 
Published: December 2014

1. The nervous activity in single afferent gastric vagal units was recorded electrophysiologically from halothane‐anaesthetized sheep with spontaneous reticulo‐ruminal movements present.2. Sixty‐six afferent units innervating gastric mechanoreceptors were isolated from fifteen sheep. The receptors were located mainly in the medial walls of the reticulum and the cranial sac of the dorsal rumen, and also in the reticular groove, the reticulo‐ruminal fold, the dorsal and ventral sacs of the rumen and the omasal canal.3. The mean conduction velocity (
C.V.) for twenty‐seven units was 12·4 ± 1·0 m/sec (
S.E.). For units with a pathway in the dorsal vagal trunk, the mean
C.V. was 14·5 ± 1·0 m/sec (
S.E.) and for units with a pathway in the ventral vagal trunk the mean
C.V. was 6·6 ± 0·5 m/sec (
S.E.).4. From the receptors a slowly adapting response was elicited by tangential lengthening. These were tension receptors in series with contractile elements, as they were excited by increased tensions developed both passively by inflation of the viscus and actively by muscular contractions.5. Receptors in the reticulum and the rumen appeared to be situated deep in the muscle layers, whereas those in the reticular groove structures seemed to be more superficial and gave the in series tension receptor response as well as a response to light pressure.6. A resting discharge in tension receptor units was usually absent at low levels of distension but appeared and increased as the level of distension was raised. Intermittency and fluctuations in the resting discharge were related to intrinsic local movement involving the receptive fields. Increasing distension enhanced the intrinsic movements.7. Even after the removal of the abomasum, reticular and ruminal (primary cycle) movements were evoked by distending the reticulum. It is possible that this manoeuvre enhanced intrinsic movements, which, in turn, caused an increased excitatory afferent input to the ‘gastric centres’ from in series reticular tension receptors.8. The enhanced afferent discharge from reticular tension receptors elicited by an isometrically recorded reticular contraction reflexly inhibited the subsequent (primary cycle) contraction of the rumen.9. Very few receptors were located in the caudal regions of the rumen whereas the cranial sac is richly supplied with tension receptors. The idea that the cranial sac may serve as the reflexogenic zone for secondary cycle movements of the rumen is discussed.
The respiratory efficiency and flexibility of erythrocytes stored in acid‐citrate‐dextrose solution
Authors: Sirs John A. 
Published: December 2014

1. Measurements have been made of the flexibility and respiratory efficiency of erythrocytes stored in acid‐citrate‐dextrose (ACD).2. The rate of packing of stored blood, during centrifugation, indicates that the red blood cells are relatively inflexible.3. Spectrophotometric observations, using the rapid‐mixing and stopped‐flow technique, indicate that the rate of egress of oxygen from HbO2 in these erythrocytes is significantly reduced. This is not due to a change of the chemical rate of dissociation of HbO2.4. Neither factor is significantly reversed by resuspending the cells in Ringer‐Locke solution or adjusting to pH 7·4.5. A small improvement is obtained by adding hypertonic NaCl or incubating the blood at 37° C for 1 hr.6. Incubation with adenosine, 25 μ‐mole/ml. blood, at 37° C for at least 1 hr, restored both the respiratory function and flexibility to normal.
Resting potential and electrical properties of frog slow muscle fibres. Effect of different external solutions
Authors: Stefani E. , Steinbach A. B. 
Published: December 2014

1. The electrical properties of frog slow muscle fibres were investigated with intracellular micropipettes to determine their characteristic length (λ), specific membrane resistance (Rm) and specific membrane capacitance.2. The value of λ was about 1 cm in fibres of 1·2 cm length. The ‘short cable model’ was used to calculate Rm. Its mean value was 1·12 × 105 ohm cm2, about 10–20 times larger than the value for twitch fibres. The mean value for Cm was 3·24 × 10−6 F/cm2.3. Resting potentials measured immediately after penetration with a single micropipette were about — 80 mV. Lower values can be attributed to the effects of damage or leakage produced by micropipette insertion.4. Changes in external K concentration produced changes in the initially recorded resting potentials which follow the constant field theory using a ratio of Na: K permeabilities PNa/PK = 0·02. Changes in external Cl concentration produced little or no change in the resting potential or membrane resistance, indicating a low Cl permeability.5. In agreement with previous work, slow fibres showed a time‐dependent decrease in resistance (‘delayed rectification’) for membrane potentials more positive than — 60 mV. ‘Anomalous rectification’ observed in twitch fibres was not seen in slow fibres. In high external K concentrations the resistance of slow fibres is almost unaffected by changes in membrane potential.6. Increasing the concentration of external Ca (up to isotonic) has two distinct effects on slow fibres. It increases Rm up to ten times, and it improves the stability of trans‐membrane recordings, probably by reducing the leakage due to micropipette penetrations. Magnesium does not appear to have either of these effects.
Epipharyngeal receptors responding to mechanical stimulation
Authors: Nail B. S. , Sterling G. M. , Widdicombe J. G. 
Published: December 2014

1. Action potentials were recorded from twenty‐one afferent nerve fibres from receptors in the epipharynx in anaesthetized, paralysed cats. Sixteen of the fibres had no spontaneous discharge.2. Gentle mechanical stimulation of the epithelium of the epipharynx with a nylon fibre caused all twenty‐one receptors to discharge with rapidly adapting bursts of impulses at a mean peak frequency of 197 impulses/sec.3. Stimulation with a stream of air through the epipharynx sufficient to distend the whole pharynx caused seven out of twelve receptors to discharge in rapidly adapting bursts. Stimulation with a jet of air directly on to the epithelium of the epipharynx caused seven out of nine receptors to discharge.4. Chemical stimulation of the epipharynx with ammonia vapour caused an increased discharge in only three out of twenty receptors, and intravenous histamine had no effect on the four units tested.5. It is concluded that the receptors mediate the ‘aspiration reflex’ elicited by mechanical stimulation of the epipharyngeal mucosa.
The mechanism of salt and water absorption in the intestine of the eel (Anguilla anguilla) adapted to waters of various salinities
Authors: Skadhauge Erik 
Published: December 2014

1. The absorption of NaCl and water was studied by intraluminal in vivo perfusion of the intestine of the yellow European eel (Anguilla anguilla) adapted to fresh water (FW), to sea water (SW), and to double strength SW (DSW).2. The net lumen to plasma NaCl transport from diluted SW perfusion fluids was independent of the NaCl concentration in the Na+ concentration range tested. The NaCl absorption (expressed as μ‐equiv/100 g.hr.) increased from FW (mean ±
S.E.): Na+ 166 ± 17, Cl− 205 ± 24 to SW: Na+ 363 ± 33, Cl− 423 ± 37, and again in DSW: Na+ 640 ± 110, Cl− 676 ± 149.3. The osmolality of the perfusion fluid which resulted in zero net water transport was higher than plasma osmolality by 73 ± 3 m‐osmole in FW, 126 ± 5 m‐osmole in SW, and 244 ± 32 m‐osmole in DSW (mean ±
S.E.). A fairly constant ratio between net NaCl transport and this osmolality difference prevailed.4. The general osmotic permeability to water in the serosa—mucosa direction (expressed as μl./100 g. hr. m‐osmole) measured from experiments with impermeant solute increased from FW: 3·7 ± 0·5 to SW: 7·2 ± 1·0 (mean ±
S.E.).5. These results are compatible with the interpretation that the water flow occurring in the absence of a general transmural osmotic gradient, the ‘solute‐linked water flow’, is linearly related both to net NaCl transport and to the osmotic permeability to water. The findings support the view that the ‘solute‐linked water flow’ is, indeed, secondary to the salt movement and is due to osmotic force.6. The amount of water absorbed from dilute SW perfusion fluids isosmotic with plasma was larger than in most other intestinal epithelia. FW: 650, SW: 1620 μl./100 g. hr. The NaCl concentration of the absorbate was hypertonic to plasma.7. The passive permeability of the intestine to NaCl was very low, and the reflexion coefficient was close to unity. Therefore metabolic energy will be used to absorb NaCl, even when the NaCl concentration in the gut is higher than that of plasma due to ingestion of SW. There appears to be a limited interaction in the intestinal wall between passive salt and water flow.8. In DSW the Na+ ingestion with the oral intake of the surrounding fluid matched the gut absorption capacity. Since DSW is close to the tolerance limit, it is concluded that the gut NaCl transport capacity may be one of the factors limiting the tolerance to water or higher salinity.