bluuebunny/crossref_metadata_2025 huggingface dataset:
The localization of pupilloconstrictor function within the mid‐brain of the cat
Authors: Sillito A. M. , Zbrożyna A. W.
Published: December 2014

1. Electrical stimulation techniques have been used to examine the localization of pupilloconstrictor function in the mid‐brain of the cat.

2. The results show the preganglionic pupilloconstrictor neurones to be localized to a discrete part of the small celled component of the oculomotor nucleus.

3. The area described comprises both the Edinger—Westphal and anteromedian nuclei at the level where they adjoin and the caudal continuation of the anteromedian nucleus. It does not include the rostral anteromedian nucleus or the Edinger—Westphal nucleus caudal to the level where its cells are continuous with those of the anteromedian nucleus. These regions do not appear to relate to pupilloconstrictor function.

4. The preganglionic nature of the pupilloconstrictor area within the small celled component was verified by an examination of the distribution of the antidromic evoked potential produced by stimulation of the preganglionic fibres at the ciliary ganglion.

5. The distribution of pupilloconstrictor responses obtained from extranuclear structures suggested the presence of an excitatory tract from the region of the posterior commissure to the pupilloconstrictor nucleus.

6. There was no indication of a lateral division of function within the pupilloconstrictor nucleus. All the responses obtained from nuclear or supranuclear structures were bilaterally equal.
Effects of ouabain and diphenylhydantoin on transmembrane potentials, intracellular electrolytes and cell pH of rat muscle and liver in vivo
Authors: Williams J. A. , Withrow C. D. , Woodbury D. M.
Published: December 2014

1. The effects of ouabain and diphenylhydantoin (DPH) to inhibit and stimulate, respectively, the Na+—K+ pump were used to correlate transmembrane resting potentials (RP), ionic gradients, and cell pH (DMO method) in rat muscle and liver in vivo.

2. Ouabain effects included a rise in K+ and fall in Na+ concentration in plasma, a rise in intracellular Na+ and Cl− and a fall in K+ concentration and pHi in muscle, and a rise in intracellular K+ concentration in liver.

3. Measured muscle RP was decreased from −90 to −65 mV by ouabain with the RP predictable from the Goldman equation for Na+ and K+ with PNa/PK = 0·01.

4. Measured hepatic RP was increased from −44 to −48 mV by ouabain, whereas the Goldman equation predicts the potential should decrease. A change in permeability of some ion or activation of an electrogenic pump component is necessary to explain this result.

5. DPH produced no significant effect on muscle electrolytes or RP and failed to reverse the effect of ouabain at the time measured and in the doses used.

6. DPH produced a slight rise in hepatic cell K+ and a rise from −42 to −47 mV in hepatic RP. This hyperpolarization also cannot be explained without invoking a permeability change or activation of an electrogenic pump.

In all cases intracellular Cl− in both muscle and liver changed in the direction expected from the change in the RP. Muscle Cl− appears passively distributed if a constant amount of extra or bound Cl− is first subtracted from each group. Hepatic intracellular Cl− is always less than expected on the basis of passive distribution, although errors in determination do not allow elimination of the possibility that Cl− distribution is determined only by the RP.

8. Cell pH and RP data were used to calculate H+ gradients. DPH had no effect on cell pH and only slightly increased the H+ gradient in liver. Ouabain produced a slight fall in muscle cell pH but reduced the H+ gradient by half. In liver only the H+ gradient was increased slightly. The data support the concept of a loose coupling between active H+ and Na+—K+ transport.
Changes in light scattering associated with the action potential in crab nerves
Authors: Cohen L. B. , Keynes R. D.
Published: December 2014

1. Changes in light scattering from stimulated crab leg nerves were measured in an effort to study changes in structure that occur during the action potential.

2. The peak changes in scattering after individual stimuli were 10−4‐10−5 of the resting scattering; signal averaging techniques were used to increase the signal‐to‐noise ratio.

3. During the compound action potential there was a transient increase in the 90° scattering which reached a peak about 20 msec after the stimulus. This increase was probably not due to a change in axon volume. Its time course was somewhat slower than that of birefringence changes measured at the same time.

4. In normal sea water the transient increase was followed by a longer lasting (persistent) decrease in scattering. This persistent decrease could be converted to an increase by reducing the tonicity of the sea water or by raising the external refractive index. This scattering change may represent a swelling of the axon resulting from the ionic exchanges that occur during the action potential.
Influence of ambient temperature on the thermoregulatory responses to 5‐hydroxytryptamine, noradrenaline and acetylcholine injected into the lateral cerebral ventricles of sheep, goats and rabbits
Authors: Bligh J. , Cottle W. H. , Maskrey M.
Published: December 2014

1. The influences of ambient temperature (Ta) on the thermoregulatory effector activities and the body temperature (Tb) of intraventricular injections into the sheep, goat and rabbit of 5‐hydroxytryptamine (5‐HT), noradrenaline (NA), acetylcholine (ACh), carbachol and eserine, have been interpreted in terms of a simple neuronal model of the pathways between thermosensors and thermoregulatory effectors.

2. In all three species 5‐HT in minimal doses caused a rise in respiratory frequency (RF) and a fall in Tb at high Ta, and a reduction in EMG activity and a fall in Tb at low Ta. These effects could be interpreted as those of an excitatory transmitter acting on the warm receptor—heat loss pathway.

3. In all three species NA caused a reduction in RF and a rise in Tb at high Ta, and a reduction in EMG activity and a fall in Tb at low Ta. These effects are interpreted as those of an inhibitory transmitter acting both on the warm sensor—heat loss pathways and on the cold sensor—heat production pathway.

4. The effects of ACh and the cholinomimetic substances carbachol and eserine are complex and more difficult to interpret. In small doses the effects on the sheep and goat are those of an excitatory transmitter on the cold sensor—heat production pathway. There was an increase in EMG activity and a rise in Tb at low Ta, and a reduction in RF and a rise in Tb at high Ta. At higher dose levels in the goat and at all dose levels in the rabbit these substances had the reverse effects which are attributed to a synaptic block due to the excess of the excitatory substance.

5. The effects of ambient temperature and injected substances upon ear temperature are consistent with the predictions of the model if it is assumed (a) that at high and low ambient temperatures direct thermal effects on ear vessels dominate those of the sympathetic innervation, and (b) that the warm sensor influence is to lower peripheral vasomotor tone, and the cold sensor influence is to increase it.

6. The conclusion reached is that when consideration is given to species differences in the thermoneutral ambient temperature and to the possibility that excitatory substances have reversed effects at high dose levels, the effects of 5‐HT, NA and ACh in the control of body temperature are very similar in the sheep, goat and rabbit: 5‐HT is excitatory on the heat loss pathway, ACh is excitatory on the heat production pathway and NA has an inhibitory influence on both pathways.
An examination of the extent of reversibility of thyroxine binding within the thyroxine distribution space in the rabbit
Authors: Nathanielsz P. W.
Published: December 2014

1. New Zealand white rabbits were injected intraperitoneally with [125]
L‐thyroxine. Experiments were performed after 24 hr had elapsed.

2. Thyroxine distribution space was calculated as 129 ml. kg−1. Half‐life of disappearance of thyroxine from the blood of the urethane anaesthetized rabbit was 653 min.

3. After exchange of approximately 20 ml. kg−1 whole blood with heparinized blood from a non‐radioactive donor, equilibration of radioactivity in the recipient had produced a peak radioactivity by 2 hr.

4. The thyroxine space in which complete exchange took place within 2 hr was 102·7 ± 4·7 ml. kg−1 in six rabbits. This is 79·6% of the thyroxine distribution space.

5. These results are compared with observations in the rat.
Studies on the nature of sweat gland ‘fatigue’ in the goat
Authors: Jenkinson D. McEwan , Robertshaw D.
Published: December 2014

1. The nature of the ‘fatigue’ of sweating that occurs in the goat upon exposure to environmental conditions of 40° C/26° C (dry bulb/wet bulb) has been examined.

2. Heat exposure activated all the sweat glands and the decrement in sweating which occurred was due to a decline in the amount of sweat produced by each gland.

3. The decline in sweating activity was associated with a decrease in sweat gland volume and a thickening of the glandular wall. The restoration of sweat gland function took approximately 5‐6 hr after removing the animal from the hot environment but the restoration of sweat gland volume took longer.

4. The volume of sweat produced was greater than the decrease in sweat gland volume and it is concluded that ‘fatigue’ is due to the rate of expulsion exceeding the rate of sweat production.

5. Repeated intravenous injections of adrenaline at 40° C resulted in a decline in sweat output and reduced the normal glandular response to heat exposure.
The separation of renal activity from lung and from the venous effluent from perfused lungs
Authors: Lockett Mary F.
Published: December 2014

1. Antidiuretic and salt‐retaining activity has been separated from cat and ox lung, and from the venous effluent of blood‐perfused cat lungs, by acetone extraction, gel filtration, partition and thin‐layer chromatography.

2. The chromatographic properties of the renally active substance from lung and from pulmonary venous blood are similar.

3. The renal actions of these substances, demonstrable in vivo and in the isolated organ, are characterized by reduction in the excretion of water and Na. Renal blood flow, glomerular filtration rate and the urinary Na/K are not significantly affected.

4. Concentrations of the lung substance which equate with angiotensin II‐val5‐amide in reduction of urinary Na in rats during water diuresis and under alcohol sedation do not raise the mean arterial pressure of the anaesthetized rat nor contract the superfused rat colon. At these dose levels angiotensin II is markedly vasopressor and contracts the superfused rat colon.
A study of the electrochemistry and osmotic relationships of the cochlear fluids in the neonatal rat at the time of the development of the endocochlear potential
Authors: Bosher S. K. , Warren R. L.
Published: December 2014

1. Changes in the endocochlear potential between the 8th and 18th days after birth were investigated in the rat. Initially the potential was low but its magnitude increased rapidly between the 11th and 16th day. During the 13th and 14th days the rate of increase was approximately 1 mV/hr.

2. The rapid potential increase arose virtually simultaneously in all three turns of the cochlea.

3. Histological examination revealed the cochlea, including the hair cells of Corti's organ and the stria vascularis, to be fully mature before the period of rapid change in the endocochlear potential, apart from the cells of Claudius, whose final development coincided with the latter part of this phase.

4. The endolymphatic sodium concentration (average 1·0 m‐equiv/l.) had attained the very low adult level in the earliest period studied. The potassium and chloride concentrations were slightly below the normal adult levels, the result of some degree of general hypo‐osmolality present at this time.

5. The endolymphatic ionic concentrations remained unchanged during the phase of rapid increase in the endocochlear potential.

6. The findings thus indicate that the distinctive endolymphatic ionic composition and the endocochlear potential arise largely independently and in succession during cochlear maturation.

7. No differences in osmotic pressure were demonstrated between endolymph, perilymph and serum. The problems concerning the homoeostasis of the inner ear fluids do not consequently seem to be complicated by unusual hydrodynamic aspects.

8. Alterations in body fluid osmolality, produced by intraperitoneal injection of water or hypertonic glycerol, were accompanied by simultaneous changes in the osmotic pressures of the inner ear fluids. Some portion of the membranes bounding the endolymphatic space is therefore considered to be freely permeable to water.

9. The investigations provide no further information about the nature of the endocochlear potential, although an increase in the electrical resistance of the cochlear duct membranes is thought responsible for its appearance. The time relationships of this period support the concept that the potential is an essential feature of the mechano‐electric transduction process.
Salt‐gland secretion and blood flow in the goose
Authors: Hanwell Ann , Linzell J. L. , Peaker M.
Published: December 2014

1. Salt‐gland blood flow in the domestic goose has been measured using a combination of Sapirstein's indicator fractionation technique for organ blood flow and Fegler's thermodilution method for cardiac output.

2. Nasal salt secretion was induced by giving 0·5
M‐NaCl or 0·154
M‐NaCl
I.V. or by giving artificial sea water by stomach tube into the proventriculus.

3. During secretion, salt‐gland blood flow increased from 82·7 ± 21·9 ml./100 g tissue. min to as high as 2179 ml./100 g. min (mean 1209 ± 140).

4. The rate of secretion in response to salt loading was very variable and was not correlated with the rate of blood flow.

5. From the data obtained, it could be calculated that the median values for the percentage extraction of ions from the arterial plasma were Na 15%, K 35%, Cl 21% and water 5·8%.

6. Atropine abolished secretion but not the increase in blood flow produced by salt loading.

7. Unilateral complete denervation abolished secretion from and the increase in blood flow through the operated but not the control gland.

8. Anaesthesia, induced by pentobarbitone sodium, almost completely blocked secretion and the increase in blood flow in the salt‐gland in response to salt loading.

9. In geese given 0·5 or 0·154
M‐NaCl
I.V. a positive, significant correlation was found between the total amount of nasal secretion collected over 30 min and the concentrations of Na and Cl in the nasal fluid. However, when the time course of secretion was followed in any one bird, the rate of secretion was inversely related to the concentrations of Na and Cl.

10. Harderian gland blood flow was not affected by salt loading.
Spatial synaptic distribution of recurrent and group Ia inhibitory systems in cat spinal motoneurones
Authors: Burke R. E. , Fedina L. , Lundberg A.
Published: December 2014

1. The reversal potentials of several types of inhibitory post‐synaptic potentials (IPSPs) have been studied in cat spinal motoneurones with and without modification of intracellular chloride ion (Cl−) concentration. Single barrel intracellular micropipette electrodes have been used.

2. When studied with potassium citrate filled micropipettes, the reversal potential for IPSPs evoked by stimulation of antagonist group Ia afferents is the same as that for recurrent IPSPs evoked by antidromic stimulation of motoneurone axon collaterals, confirming earlier observations (Araki, Ito & Oscarsson, 1961; Coombs, Eccles & Fatt, 1955).

3. Studied with potassium chloride filled micropipettes. the reversal potential for the group Ia IPSP was found to be different from that for the recurrent IPSP when the amount of Cl− diffusing or iontophoretically injected into the motoneurone was small. The amount of difference in reversal potential varied from cell to cell but when present the group Ia IPSP reversed to a depolarizing potential more readily than the recurrent IPSP in all cases.

4. Interaction between recurrent IPSPs and monosynaptic excitatory post‐synaptic potentials (EPSPs) was also studied and the amount of non‐linearity of potential summation was measured.

5. The results are consistent with the hypothesis that the terminations of Renshaw cells responsible for the recurrent IPSP are located largely on the proximal dendrites of motoneurones, while the terminations of the interneurones generating the group Ia IPSP appear to be closer to or on the cell somata.
Contractions of the caudal region of the oesophagus of the cat
Authors: Titchen D. A. , Wheeler J. S.
Published: December 2014

1. The motility of the most caudal part of the oesophagus has been investigated in cats which were decerebrated, had the whole of the central nervous system pithed or were anaesthetized with chloralose.

2. Contractions of the most caudal region of the oesophagus were evoked by its stretch and the presence in it of HCl. These reactions were obtained in all types of preparations used.

3. In decerebrate preparations oesophageal contractions occurred in response to the introduction of acid into the stomach. These were not obtained after the vagus ṅerves had been cut.

4. Slight degrees of gastric distension stimulated oesophageal contractions, greater distension was inhibitory.

5. Both reductions in oesophageal activity and contractions of the oesophagus were obtained with different parameters of stimulation of efferent vagal fibres.

6. Excitatory and inhibitory effects on the oesophagus were obtained from stimulation of the central end of the vagus nerves cut in the abdomen or in the neck.

7. In totally pithed preparations of cats stretch of one region of the oesophagus was found to modify the activity of a distant region of the oesophagus cranial or caudal to the site of distension.

8. The reactions of the caudal oesophagus were abolished by atropine.

9. The importance of vago‐vagal reflexes in the modification of basically direct oesophageal responses has been discussed.
Actions of dinitrophenol and some other metabolic inhibitors on cortical neurones
Authors: Godfraind J. M. , Kawamura H. , Krnjević K. , Pumain R.
Published: December 2014

1. In cats under methoxyflurane, DNP and other metabolic inhibitors were tested on cortical neurones by iontophoresis from micropipettes.

2. DNP, dinitro‐o‐cresol, iodoacetate, pentachlorophenol and oligomycin (uncouplers or inhibitors of oxidative phosphorylation), as well as moderate anoxia, blocked selectively and reversibly spontaneous firing and discharges evoked by ACh; responses evoked by glutamate were facilitated by moderate doses of DNP and blocked only by large amounts.

3. Azide, cyanide, ouabain and strophanthidine had a mainly excitatory effect; the cardiac glycosides tended to depress more strongly responses to glutamate.

4. Intracellular observations showed that DNP causes a sharp fall in electrical excitability, associated with a hyperpolarization and fall in membrane resistance.

5. The hyperpolarizing action of DNP had a mean reversal level (EDNP) nearly 30 mV more negative than the resting potential; EDNP was identical with the mean reversal level for the depolarizing action of ACh, measured on the same cells.

6. DNP had its usual hyperpolarizing effect on neurones whose IPSPs had been made positive by raising the internal [Cl]; the mean EIPSP was over 30 mV more positive than EDNP.

7. It is concluded that DNP lowers excitability by raising the membrane conductance to K+ (gK) and that it blocks ACh responses selectively because ACh has a precisely opposite action on these neurones.

8. In the Discussion, it is suggested that the rise in gK is mediated by an increase in internal free Ca2+, caused by a slowing of mitochondrial activity, and that a similar mechanism may play a significant role in general anaesthesia.
Thermoregulation in intensively lactating cows in near‐natural conditions
Authors: Berman A.
Published: December 2014

1. Thermoregulatory reactions of lactating cows (33 kg milk/day) have been measured in summer (25–39° C) and in winter (9·5–24° C) at 3 hr intervals, during four nychthemeral (24 hr) cycles in each season.

2. The rectal‐to‐tympanic temperature gradient increased with rising body temperatures. The seasonal changes were larger for the rectal temperatures than for the tympanic membrane temperatures. These and the significantly lower correlations between rectal temperatures and regulatory responses suggest that in the ruminant rectal temperatures are considerably affected by rumen metabolism and do not represent a reliable index of the regulated temperature.

3. In the winter the regulatory responses were correlated with skin temperatures only. In the summer responses were correlated with both skin and tympanic temperatures, excepting for skin water loss.

4. The seasonal difference in the effects of skin and tympanic temperatures on regulatory responses was associated with a small change in mean tympanic temperature. The twofold larger nychthemeral fluctuation in the summer tympanic temperature is suggested to cause the seasonal difference in the thermoregulatory mode.

5. The winter range of nychthemeral fluctuations in tympanic temperature suggests a range of permitted core thermolability. A wider permitted core thermolability in summer is unlikely to be a mechanism of acclimatization in the cow.
Local blood flow, cerebrovascular autoregulation and CO2 responsiveness in the rabbit hypothalamus
Authors: Cranston W. I. , Rosendorff C.
Published: December 2014

1. Local blood flow has been measured in the hypothalamus and other areas of the brain in the conscious rabbit, by measuring the rate of clearance of small volumes (2·5–10 μl.) of a saline solution of the inert tracer 133Xe injected locally.

2. Increasing the arterial PCO2 caused a mean rise in the hypothalamic blood flow of 34%.

3. The hypothalamic blood flow remained relatively constant over a mean arterial blood pressure range of 41–140 mm Hg.

4. Hypothalamic blood flow was relatively unaffected by anaesthesia with intravenous pentobarbitone; by contrast, blood flow in the cerebral cortex was greatly reduced.

5. It is concluded that the technique is a valid and useful one, since CO2 responsiveness and autoregulation is maintained. Different areas of grey matter have different flow rates, and vary in their responsiveness to barbiturate anaesthesia.
Activation of transmitter release by strontium and calcium ions at the neuromuscular junction
Authors: Meiri U. , Rahamimoff R.
Published: December 2014

1. The interaction between Ca and Sr ions on quantal transmitter release at the frog neuromuscular junction was studied, using conventional electrophysiological techniques.

2. While Ca ions always activate transmitter release, the activating action of Sr ions depends on the Ca ion concentration in the medium; at low [Ca], strontium ions enhance the release, but at higher [Ca] they inhibit it. It is postulated that there is a [Ca] at which Sr ions do not affect transmitter liberation.

3. When Sr activates release, its effect and the effect of Ca add in a more than linear fashion.

4. Magnesium ions inhibit the release induced by Sr.

5. The results can be explained by assuming that Ca and Sr act on the same site, at some stage of the process of quantal transmitter release. The affinity of both ions towards the sites is approximately the same, but the effectiveness of Sr is much smaller.
The short‐latency projection from the baboon's motor cortex to fusimotor neurones of the forearm and hand
Authors: Clough J. F. M. , Phillips C. G. , Sheridan J. D.
Published: December 2014

1. The corticospinal connexions that are responsible for the firing of fusimotor impulses at short latency in response to brief, high‐frequency stimulation of the baboon's motor cortex have been investigated by micro‐electrode recording from antidromically identified fusimotor neurones of the forearm and hand.

2. Of nineteen fusimotor neurones investigated by intracellular recording, six showed EPSPs at monosynaptic latency.

3. In extracellular records, the latency of firing of an early fusimotor impulse was always too long to be explained by monosynaptic excitation by the corticospinal D volley, but could be explained by monosynaptic excitation from an I volley.

4. Four of the nineteen intracellularly recorded fusimotor neurones showed short‐latency (?disynaptic) IPSPs in response to brief high frequency cortical bursts.
Modification of the reflex response to stimulation of carotid sinus baroreceptors during and following stimulation of the hypothalamic defence area in the cat
Authors: Humphreys P. W. , Joels N. , McAllen R. M.
Published: December 2014

1. The effects of stimulation of the hypothalamic defence area on carotid sinus baroreceptor reflexes have been investigated by examining the cardiovascular responses to a 15 sec period of increased pressure within the vascularly isolated carotid sinus before, during, and immediately following a 25 sec period of hypothalamic stimulation.

2. Identification of the hypothalamic defence area was based on the occurence of atropine‐sensitive muscle vasodilatation. Electrode positions were confirmed by histological examination.

3. During hypothalamic stimulation the reflex fall in blood pressure resulting from a rise in sinus pressure was found to be undiminished whether sinus pressure was raised at the onset or at the 10th sec of hypothalamic stimulation.

4. By contrast, in at least half the cats in which a reflex bradycardia could be evoked from the sinus, this bradycardia was largely if not completely suppressed during hypothalamic stimulation. This suppression of reflex bradycardia occurred when sinus pressure was raised at the onset as well as at the 10th sec of stimulation.

5. During the first 5 sec after hypothalamic stimulation the hypotensive response to an increase in carotid sinus pressure was much reduced; on the other hand the reduction in heart rate was exaggerated, sometimes to a very marked degree.

6. The results suggest that stimulation of the hypothalamic defence area can modify baroreceptor reflexes and that this modification can include selective alterations in the various components of the reflex response.
Studies of temporal frequency adaptation in visual contrast sensitivity
Authors: Smith Robert A.
Published: December 2014

1. A short adaptation to sinusoidal flicker produces a temporary elevation in the temporal contrast threshold of a human observer.

2. The frequency specificity of this adaptation effect is much less than that observed with adaptation to spatial frequencies; thus it does not seem warranted to postulate the existence of distinct channels for the detection of specific temporal frequencies, as has been done in the case of spatial frequencies (Blakemore & Campbell, 1969).

3. At low frequencies, a substantial adapting modulation is necessary to produce an effect, but at high frequencies an effect can be seen even with adaptation which is below threshold (as determined by the method of adjustment).

4. This subthreshold adaptation appears to explain the observation that thresholds set by the method of adjustment rise by as much as a factor of two during the first minute of exposure.

5. No interocular transfer of the adaptation effect was observed.

6. Adaptation first appears at mesopic luminances, but its appearance is not dependent on the change from rod to cone vision. Under several conditions, however, the first appearance of flicker adaptation did coincide with a change in the deLange curve, which is attributable to the appearance of the antagonistic surround of visual receptive fields. Thus it was hypothesized that the surround is essential for adaptation.
Sodium chloride absorption and solute‐linked water flow across the epithelium of the coprodeum and large intestine in the normal and dehydrated fowl (Gallus domesticus). In vivo perfusion studies
Authors: Bindslev Niels , Skadhauge Erik
Published: December 2014

1. The transmural net flow of salt and water in the coprodeum and large intestine of normal and dehydrated hens was investigated by means of an intraluminal in vivo perfusion technique. The lumen was perfused with hypo‐, iso‐, and hyperosmotic salt solutions. Polyethylene glycol (PEG 4000) and [14C]inulin served as water markers.

2. The maximal net Na+ flow (JNa) from the mucosal to the serosal side was nearly the same in the two states of hydration: normal birds 308 μ‐equiv/kg.hr, dehydrated birds 281 μ‐equiv/kg.hr, while the JNa was half maximal at luminal Na+ concentrations of 99 and 43 μ‐equiv/l. respectively. The ‘affinity’ for Na+ in the dehydrated bird was thus twice that in the normal bird. K+ was secreted into the gut lumen at a constant rate against the electrochemical gradient, JK = −97 μ‐equiv/kg.hr (
S.E. = 5). Clμ was absorbed from lumen to plasma down the electrochemical gradient with JCl ranging from 0 to 94 μ‐equiv/kg.hr. The low JCl was observed at low luminal NaCl concentrations when the JNa was also small.

3. The solute‐linked water flow, Jvs, occurring in the absence of an osmolality difference across the epithelium, was 1·1 μl. H2O/μ‐equiv Na+ in normal birds and 1·5 in dehydrated birds. The Jvs was calculated as an operational parameter in experiments with luminal osmolalities different from plasma osmolality by subtracting the water flow observed in an experiment without Na+ in the perfusion fluid from the water flow in an experiment with Na+ containing perfusion fluids, both fluids being of the same osmolality. Jvs was maximal at luminal osmolalities close to plasma osmolality. These observations are compatible with the hypothesis that the Jvs is due to an osmotic flow into a confined region between the cells.

4. When the perfusion rate was lowered from 5‐9 ml./kg.hr to 0·8–1·0 the incoming perfusion fluid osmolality at which net water flow across the epithelium was zero went up from 100 to 180 m‐osmolal higher than plasma osmolality. This observation suggests that a significant fraction of ureteral urine in the dehydrated bird may be absorbed in the coprodeum and large intestine.
The parasympathetic secretory nerves of the lacrimal gland of the cat
Authors: Arenson M. S. , Wilson H.
Published: December 2014

1. Electrical stimulation of the brain stem of the anaesthetized cat induces a secretion from the lacrimal gland.

2. The secretion is abolished either by Vidian nerve section or by the application of nicotine to the sphenopalatine ganglion.

3. In contrast to stimulation of the peripheral end of the cut Vidian nerve, stimulation of the central end induces lacrimal secretion.

4. A new pathway is proposed in the light of the experimental findings.
Adrenal catecholamine secretion during stimulation of the nasal mucous membrane in the rabbit
Authors: Allison D. J. , Powis D. A.
Published: December 2014

1. Left adrenal venous blood was collected in anaesthetized rabbits and analysed for catecholamine content by either a fluorimetric technique or a bio‐assay method using the blood pressure of the pithed rat.

2. Stimulation of the nasal mucous membrane with ether vapour or water caused apnoea, bradycardia, a rise in arterial blood pressure and an increase in adrenal medullary catecholamine secretion.

3. During the pre‐stimulation control periods adrenaline constituted 66% of the total catecholamine present in adrenal venous blood and noradrenaline 34%. These proportions altered during stimulation of the nasal mucous membrane to 72 and 28% respectively. Electrical stimulation of the left splanchnic nerve produced a secretion composed almost entirely of adrenaline.

4. The increased catecholamine output elicited during stimulation of the nose occurred in animals whose pulmonary ventilation was maintained constant by means of a pump. It was abolished, however, by local anaesthesia of the nasal passages or by surgical division of the left splanchnic nerve.

5. The increased secretion of catecholamines is therefore reflex in nature, and evidence is presented that it is the result of a primary reflex from the nose.
The mechanism of thyroxine transfer from plasma to tissue binding sites
Authors: Hillier A. P.
Published: December 2014

1. An examination has been made of the uptake of thyroxine by rat livers perfused with very dilute solutions of thyroxine‐binding globulin (TBG) and thyroxine‐binding pre‐albumin (TBPA).

2. Under these circumstances the rate of transfer of thyroxine to the liver is very similar to the rate of thyroxine dissociation for both TBG and TBPA.

3. It is concluded that thyroxine transfer from plasma to tissue‐binding sites involves its initial release into the free state and not, as has been suggested, directed exchange.
The effect of adrenaline and noradrenaline on the blood flow, electrical conductance and external secretion of the pancreas
Authors: Barlow T. E. , Greenwell J. R. , Harper A. A. , Scratcherd T.
Published: December 2014

1. Adrenaline and noradrenaline cause a biphasic change in the transverse electrical conductance across the cat pancreas. After a latent period of from 5 to 30 sec a phase of decreased conductance lasting about 30 sec occurs which gives way to a phase of increased conductance lasting from 5 to 8 min.

2. Coincidentally with the phase of decreased conductance, vasoconstriction and a reduction in blood flow occurs and an increased blood flow with the phase of increased conductance. The blood flow and conductance records run a parallel time course.

3. Weight for weight adrenaline produces changes of greater magnitude than noradrenaline.

4. The phase of decreased conductance and blood flow was abolished by an α‐receptor blocking agent and the phase of increased conductance and blood flow by a combination of α‐ and β‐receptor blocking agents.

5. Inhibition of the volume rate of secretion coincident with the phase of decreased conductance followed rapid intravenous injection of adrenaline or noradrenaline. During the phase of increased conductance secretion either returned to control values or was transiently augmented.

6. Inhibition of secretion occurred after α‐receptor blockade in the absence of vasoconstriction, suggesting that the catecholamines have a direct action on the cell.

7. β‐receptor blockade increased the effectiveness of adrenaline to inhibit pancreatic secretion.

When the effects of the catecholamines on secretion were tested, secretion was always induced by secretin.
The binomial nature of transmitter release at the crayfish neuromuscular junction
Authors: Johnson E. W. , Wernig A.
Published: December 2014

1. Transmitter release at excitatory junctions on the opener muscle of the crayfish dactyl was studied by recording junctional potentials with extracellular micro‐electrodes.

2. At low temperatures, evoked release was dispersed sufficiently in time for potentials produced by individual quanta to be counted, and the mean (m) and variance (σ2) of the quantum content distribution for a series of trials measured directly. These values were used to calculate the average probability of quantal release (p), assuming a binomial distribution.

3. For all values of m and p, the observed release pattern (number of 0, 1, 2, 3,... quantal releases during a series of trials) was approximated closely by the corresponding binomial distribution. However, Poisson predictions differed significantly from the observed quantal distribution for values of p > 0·2.
Release of an antidiuretic substance by bradykinin in the rat
Authors: Harris M. C.
Published: December 2014

1. Water‐loaded rats under ethanol anaesthesia were used to determine whether bradykinin releases ADH and whether the release is a reflex response to hypotension or the result of direct stimulation of the central nervous system by the peptide.

2. Intravenous injections of bradykinin caused hypotension followed by prolonged antidiuresis; both responses were dose dependent.

3. The antidiuresis caused by bradykinin could not be accounted for by hypotension alone. Haemorrhage and intravenous injections of isoprenaline, which caused falls in arterial blood pressure similar to those caused by bradykinin, produced only short‐lasting antidiuretic responses.

4. Intracarotid injections of bradykinin caused antidiuresis with little or no preceding hypotension. No antidiuresis was produced by intracarotid injections of isoprenaline.

5. After intravenous injection of bradykinin, small amounts of ADH were identified in whole blood and, on a few occasions only, in concentrated urine. However, ADH was not detected in blood extracts.

6. After intravenous injection of nicotine in doses which caused antidiureses similar to that caused by bradykinin, ADH was regularly detected in large amounts in blood extracts and in unconcentrated urine.

7. Bradykinin did not cause prolonged antidiureses when injected into a rat with congenital diabetes insipidus.

8. ADH release was not increased when isolated rat neural lobes were incubated with bradykinin although release was elevated by an increase in the K+ concentration of the incubation medium.

9. It is suggested that bradykinin causes release of an antidiuretic substance by a direct action on the central nervous system. The possibility that this substance is ADH is discussed.
Mechanism of compensatory renal hypertrophy
Authors: Dicker S. E. , Shirley D. G.
Published: December 2014

1. Adult rats were unilaterally nephrectomized and the weight of the remaining kidney up to 42 days after the operation compared with that of rats of comparable weight which underwent a sham operation.

2. After unilateral nephrectomy the rate of renal hypertrophy varied with the protein content of the diet: it was faster when animals were fed on a high protein diet (22% casein) and lowest in animals fed on a low protein diet (7% casein).

3. In rats fed on a standard diet (18% casein), after unilateral nephrectomy there was a sharp increase in glomerular filtration rate (
G.F.R.), as measured by inulin clearance estimations; this was accompanied by an enhanced oxygen uptake and by an increase of RNA/DNA ratios in the renal cortex. Changes in rate of oxygen uptake and of RNA/DNA ratios in the medulla were negligible.

4. A marked increase in mitotic activity of cells of the cortex occurred only 48 hr after the operation. It lasted for about 2 days. No significant changes in mitotic activity of cells in the medulla were observed.

5. After its initial marked rise glomerular filtration rate in the renoprival kidney settled down to about 30–40% above its pre‐operative level, and remained at that level for the whole period of observation (6 weeks), while the increase of oxygen uptake returned to its control level in some 10–14 days. RNA/DNA ratios in the cortex remained high, but did not increase further.

6. The increase of RNA/DNA ratios in the renal cortex was correlated with a steady increase in the dry weight of the renoprival kidney.

7. Water and solutes excretion were restored to normal in about 3‐5 days after the operation.

8. Though the increase in glomerular filtration rate may be the prime mover in the mechanism of compensatory renal hypertrophy, it does not explain why there is an increase in the size of tubules.
Further studies on prostaglandin E1 fever in cats
Authors: Feldberg W. , Saxena P. N.
Published: December 2014

1. Micro‐injections of a few nanograms of prostaglandin E1 (PGE1) into the anterior hypothalamus of unanaesthetized cats produced a rise in rectal temperature, whereas temperature was not affected when micro‐injections of even larger doses were made into the posterior hypothalamus. The hyperthermia produced by injections of PGE1 into the cerebral ventricles is therefore attributed to an action of PGE1 on the anterior hypothalamus.

2. During a pentobarbitone sodium anaesthesia the sensitivity of cats to the hyperthermic effect of PGE1 injected into the cerebral ventricles was found to be greatly reduced, particularly during the early stage of anaesthesia when body temperature was falling steeply.
Intracellular sodium activity and the sodium pump in snail neurones
Authors: Thomas R. C.
Published: December 2014

1. Recessed‐tip Na+‐sensitive micro‐electrodes were used to measure [Na+]i continuously in snail neurones for experiments lasting up to several hours. The average resting [Na+]i in twenty‐two cells was 3·6 m
M.

2. Inhibition of the Na pump by ouabain caused [Na+]i to increase at an average rate of 0·54 m‐mole/min. This corresponds to a passive influx of Na quantitatively similar to that observed in squid axons.

3. Changing external K over the range 1‐8 m
M had little effect on [Na+]i, but K‐free or 0·25 m
M‐K Ringer caused a rise in [Na+]i.

4. Increasing membrane potential by up to 90 mV caused an increased influx of Na, but did not inhibit the pump.

5. Reducing external Na caused a decrease in [Na+]i but did not affect the pump rate at a given [Na+]i. The pump rate at low [Na+]i was proportional to [Na+]i minus a threshold value of about 1 m
M.

6. The Na pump appeared still to be electrogenic at subnormal rates of activity.

7. It is concluded that, given sufficient external K, the rate of the Na pump depends principally on [Na+]i. Changes in external Na or membrane potential appear to affect the pump only indirectly, by changing the Na influx and thus [Na+]i.
A reflex increase in heart rate from distension of the junction between the superior vena cava and the right atrium
Authors: Kappagoda C. T. , Linden R. J. , Snow H. M.
Published: December 2014

1. Localized distension of the junction between the superior vena cava and the right atrium without obstructing venous return caused an increase in heart rate.

2. This increase in heart rate was a reflex response; the afferent path was in the vagi and the efferent solely in the sympathetic nerves.

3. The receptors most likely to be stimulated by the distension of the junction between the superior vena cava and the right atrium are the right atrial receptors located on the endocardial surface of the intrapericardial portion of the superior vena caval—right atrial junction.
Pure central responses from off‐centre cells and pure surround responses from on‐centre cells
Authors: Enroth-Cugell Christina , Pinto L. H.
Published: December 2014

1. Pure responses generated by the centre response mechanism of off‐centre cells or the surround response mechanism of on‐centre cells were studied in the cat by recording from single optic tract fibres while applying slow square‐waves of light of varying duration but constant luminance.

2. The response, whether due to a centre or a surround mechanism, consisted of a rapid decrease in firing frequency at onset of light, followed by a gradual recovery of firing rate while the light was on. The time course of the recovery was exponential. At ‘off’ there was a sudden increase in firing rate (off‐discharge) followed by an exponential, more gradual, decay of impulse frequency. Both the gradual recovery during illumination and the off‐discharge were absent for the shortest flashes.

3. Perhaps the most significant result was that the behaviour exhibited by responses generated by one only of the response mechanisms, centre or surround, is predictable and much simpler than that exhibited by mixed responses; the magnitude of the off‐discharge increased, the latency decreased monotonically with increased flash duration and the magnitude of the off‐discharge was linearly related to the level of firing at the moment when the light went off.

4. For two off‐centre cells gain was studied by recording the response to a brief test flash superimposed upon a slow gain changing square‐wave stimulus. Centre mechanism gain decreased promptly upon application of the gain changing light, stayed low while it was on, only to return promptly to its former value when the gain changing light went off.

5. A simple model which qualitatively accounts for the results (excluding latency) was suggested. The onset of light initiates both an inhibitory and excitatory process whose sum constitutes the transient input to the cell. The excitatory process grows at a slower rate so that ‘excitation wins more and more as the light remains on’. Similarly after ‘off’ the excitatory process decays slower than the inhibitory one, thus leaving the cell with a transient excess of net‐excitation.
The effect of vasopressin (Pitressin) administration and dehydration on the concentration of solutes in renal fluids of rats with and without hereditary hypothalamic diabetes insipidus
Authors: Lee J. , Williams P. G.
Published: December 2014

1. The method of sequential centrifugation has been used to obtain fluid samples from both the renal papilla and inner medulla of the rat.

2. Experiments were carried out on Brattleboro rats with hereditary hypothalamic diabetes insipidus (DI; homozygous recessive), and on their (heterozygous) litter‐mates with normal quantities of neurohypophysial vasopressin. Initial classification of the animals by measurement of urine volume and osmolality was confirmed by post‐mortem bio‐assay of the pituitary glands, in thirty‐five out of forty‐seven animals.

3. In rats with DI, urine osmolalities comparable to those of heterozygous rats were obtained after four daily injections of 1 u. Pitressin Tannate in Oil (PTO). Under these conditions, when dehydration was superimposed for 72 hr, urine osmolality did not increase markedly. In heterozygous rats dehydrated for the same period of time, urine osmolality increased by some twofold.

4. In rats with DI, the administration of PTO induced a rise of both sodium and urea concentrations in renal fluids and in urine. Dehydration during PTO administration caused a further rise of urea concentrations only. Dehydration per se significantly raised urinary and renal fluid urea concentrations, but sodium concentrations did not rise.

5. In heterozygous rats dehydration per se increased both urea and sodium concentrations in renal fluids and urine.

6. The evidence is discussed that the action of vasopressin involves factors apart from increasing the permeability of the distal nephron to water and urea.
The relations between sarcomere length and characteristics of isometric twitch contractions of frog sartorius muscle
Authors: Close R. I.
Published: December 2014

1. Relations between sarcomere length, tension and time course of isometric twitches at 20° C were determined for thirty‐two sartorius muscles from Rana temporaria.

2. The maximum isometric twitch tension per unit cross‐sectional area of muscle ranged from 0·56 to 2·2 kg/cm2 at 20° C and initial sarcomere length about 2·1 μ. This variation was not correlated with the corresponding measure of tetanic tension.

3. The maximum isometric twitch tension per unit cross‐sectional area of muscle at 2·1 μ sarcomere length was directly correlated with twitch contraction time and inversely correlated with the cross‐sectional area of the muscle.

4. The isometric twitch contraction was potentiated with increase in initial sarcomere length from about 2·1 to about 2·8 μ at 20° C, and the degree of potentiation was inversely correlated with the maximum isometric twitch tension per unit cross‐sectional area of muscle at 2·1 μ sarcomere length.

5. The sarcomere length: twitch tension relation is labile and may be altered by changes in temperature and the after‐effects of repetitive stimulation.

6. Variation in twitch contractions at different sarcomere lengths are discussed in connexion with excitation—contraction coupling and the degree of activation of muscle fibres during twitch contractions at 20° C.