bluuebunny/crossref_metadata_2025 huggingface dataset:
Discharge patterns of principal cells and interneurones in lateral geniculate nucleus of rat
Authors: Burke W. , Sefton Ann Jervie
Published: December 2014

1. The cells of the lateral geniculate nucleus of the rat are classified into one of two distinct groups on the basis of their responses to a single shock to optic nerve or visual cortex. The distinctive difference between these two groups is that the P cells (87% of all cells) responded with short bursts of 1‐5 spikes, whereas the I cells (13%) responded with long bursts of about 10 spikes. Both groups give recurring bursts at intervals of 100 msec or more for a total duration of up to about 5 sec.

2. The majority of P cells (75%) have a lower threshold for late firing than for early firing. The majority of I cells (62%) have about the same threshold and all I cells have very low thresholds.

3. To stimulation of the optic nerve the mean latency of the first spikes of all P cells is 4·4 msec. The mean latency of the first spikes of all I cells is 5·8 msec. The latency of the earliest spike in an I cell is 0·9 msec longer than the earliest spike in a P cell.

4. To stimulation of the visual cortex the latency of the earliest spike in an I cell is 1·0 msec longer than the earliest spike in a P cell. Most P cells (78%) respond with either very short latency (less than 1·7 msec) or with a wave form characteristic of antidromic invasion or both. No I cell has either of these characterstics.

5. It is concluded that P cells are principal cells projecting to visual cortex and that I cells are interneurones.
Oxygen consumption during pouch development of the macropod marsupial Setonix brachyurus
Authors: Shield John
Published: December 2014

1. Measurements of O2 consumption at 9 or 10 temperatures in the 20‐40° C ambient temperature range were made on joeys with ages selected to cover the 180‐day period of pouch occupancy.

2. The rate of O2 consumption of joeys younger than 100 days increased directly with ambient temperature.

3. After 100 days of age the O2 consumption rate at low temperatures rose and at about 140 days of age a constant rate was maintained over the full ambient temperature range.

4. Heat transfer from joey to mother commenced after 100 days of age.

5. At 150‐180 days of age the rate of O2 consumption at 20° C was approximately 12 times greater than at ages less than 100 days. A thermal neutral zone was established in the range 32‐36° C by joeys older than 150 days.

6. At the usual pouch temperature of 36·5° C, O2 consumption per unit wet body weight rose from 12 ml./kg.min at birth to 17 ml./kg.min at the end of pouch life. On a unit dry body weight basis it fell from 120 to 56 ml./kg.min. This decline parallels the decrease in growth rate.
The diffusion of radiopotassium across intercalated disks of mammalian cardiac muscle
Authors: Weidmann Silvio , Hodgkin A. L.
Published: December 2014

1. Experiments were performed to determine whether intercalated disks represent a high or a low resistance to the diffusion of K ions.

2. Bundles of sheep ventricular fibres, 0·6‐0·8 mm thick and 7‐11 mm long, were pulled through a hole in a partition. One half was charged by radiopotassium (K*); the other half was washed by inactive Tyrode solution.

3. A steady state with respect to the distribution of K* along the bundle was reached 6 hr after the exposure to radioactivity.

4. On the ‘washed’ side [K*] fell along a relatively smooth curve and did not tend to the value zero towards the cut end of the bundle. The average space constant for the decrease of [K*] was 1·55 mm, corresponding to a distance of about 12 × the length of a cell. This indicates that the disk resistance is low and that the fibres are healed over at their cut ends.

5. Rhythmical contraction had no detectable effect on the space constant. This may mean either that shortening and thickening of a cell does not effectively mix its content, or that stirring goes on even in resting cells.

6. On the assumption of mixing between disks the average resistance of 1 cm2 of disk to the movement of K ions is 3 Ω. If there is no mixing this value would be even lower.

7. The assumption that K* distribution within the ‘washed’ half of the bundle is a consequence of cell‐to‐cell rather than of extracellular movement is supported by the results of several control experiments.

8. It is concluded that the propagation of the cardiac action potential is possible by local circuit currents.
The effect of hyperthermia and localized heating of the anterior hypothalamus on the sympatho‐adrenal system of the ox (Bos taurus)
Authors: Robertshaw D. , Whittow G. C.
Published: December 2014

1. Arterial plasma catecholamine concentrations, rectal temperatures and respiratory rates were measured in the unanaesthetized ox in a cool environment (15/11·5° C dry bulb/wet bulb (
D.B./W.B.) in a hot, dry environment (40/22° C), in a hot, humid environment (40/39·1° C) and during localized heating of the hypothalamus.

2. There was no significant difference in the plasma catecholamine levels of animals exposed to a cool environment (15/11·5° C) and to a hot, dry (40/22° C) environment.

3. When the animals became hyperthermic in the hot, humid environment, considerable increases in the plasma levels of adrenaline and smaller increases in noradrenaline concentration occurred.

4. Bilateral adreno‐medullary denervation abolished the changes in plasma catecholamine levels associated with hyperthermia.

5. Localized heating of the anterior hypothalamus in either a cool or a warm environment did not result in any change in plasma catecholamine levels.

6. It was concluded that the source of the increased levels of plasma catecholamines during hyperthermia was the adrenal medulla and that the stimulus for their release was a nervous one rather than direct chemical or thermal stimulation of the adrenal medulla. The cause of the increased sympatho‐adrenal activity was not apparent, but neither thermal stimulation of cutaneous and hypothalamic receptors nor the associated changes in respiratory activity seemed to be implicated in the response.
Energy barriers to sodium extrusion from sodium‐rich kidney cortex slices
Authors: Smyth Honor
Published: December 2014

1. Rat and guinea‐pig kidney cortex slices were made Na‐rich by leaching in cold NaCl and then allowed to recover in Ringer solution at 30 or 25° C. Net Na extrusion was systematically decreased by the use of re‐immersion media with constant Na and diminishing K, or with constant K and increasing Na, and the energy requirements for Na extrusion under these conditions were calculated.

2. The critical energy barrier at which no net Na loss can be achieved was somewhat lower in these tissues than found by other authors for frog sartorius muscle.

3. Inclusion of pyruvate or insulin and lactate in the recovery fluid had no effect.

4. Methylsulphate apparently enters renal cells during incubation and is therefore unsuitable for use with this tissue as a source of impermeant anion.
Synaptic stimulation superimposed on motoneurones firing in the ‘secondary range’ to injected current
Authors: Granit R. , Kernell D. , Lamarre Y.
Published: December 2014

1. This paper extends the work on the ‘primary range’ of firing (Granit, Kernell & Lamarre, 1966), in lumbar motoneurones to the ‘secondary range’. By definition the latter begins when, with stronger currents, the linear curve relating firing rate to injected current in the primary range undergoes a fairly sudden increase of slope.

2. It was shown that motoneurones firing at the higher frequencies of the secondary range were partially inactivated. Yet such firing rates were within the physiological range.

3. Algebraical summation of firing rates, when present in the secondary range, implied at the same time that the synaptic amount added was diminished by comparison with what it had been within the primary range.

4. Superimposed synaptic excitatory stimuli did not (as in the ‘primary range’) regularly add their effect algebraically on to the rate of firing achieved by injected currents alone. More commonly the synaptic effect of the constant input underwent a progressive increase throughout the secondary range.

5. Superimposed inhibitory stimuli regularly reduced the slope constant as determined by trans‐membrane current alone and, by counter‐acting inactivation, made the motoneurone approach the mode of firing characteristic of the ‘primary range’.

6. The latter finding emphasizes the significance of analysing firing motoneurones with the aid of ‘slope constants’ and provides inhibition with a new role in the integrative behaviour of motoneurones, as considered in the Discussion.
A species comparison of the effects of changing perfusion pressure on blood flow and metabolic heat production in the myocardium
Authors: Grayson J. , Parratt J. R.
Published: December 2014

1. A heated thermocouple technique (internal calorimetry) has been used to investigate blood flow and heat production responses in the myocardium to changing blood pressure in monkeys, dogs, rabbits, guinea‐pigs and rats.

2. Perfusion experiments (isolated guinea‐pig and dog hearts) showed linear relations between conductivity increment and coronary blood flow up to 1·5 ml. g−1 min−1 (dog heart perfused with blood) and 5 ml. g−1 min−1 (guinea‐pig heart perfused with saline). This relation was the same in the beating and non‐beating heart.

3. In rabbits, guinea‐pigs and rats the relation between flow (conductivity increment) and blood pressure was linear. In contrast, in monkeys and dogs, over the range 100‐40 mm Hg, little change in blood flow occurred. After the injection of procaine around the stellate ganglion, the relation between pressure and flow in both species was linear. It is suggested that the constancy of blood flow displayed in the monkey and dog over this blood pressure range was due to the activity of adrenergic vasodilator fibres.

4. Evidence is adduced to show an increased myocardial heat production when systemic arterial pressure fell below about 60 mm Hg. This was not affected by cardiac denervation. The possible significance of this effect is discussed.
Dynamic and static contributions to the rhythmic γ activation of primary and secondary spindle endings in external intercostal muscle
Authors: von Euler C. , Peretti G.
Published: December 2014

1. In cats anaesthetized with sodium pentobarbital 160 external intercostal muscle spindle afferents were identified by their pause in response to ventral root stimulation; the internal intercostal muscle was denervated.

2. In order to assignate the afferents to either primary or secondary endings they were tested for their responsiveness to vibration (Bianconi & Van Der Meulen, 1963). The maximal frequency which they were able to follow regularly for at least four cycles, termed ‘critical frequency’, was determined.

3. The endings fell into two groups: low‐f (frequency) sensitive endings with critical frequencies below 400 c/s and high‐f sensitive endings with critical frequencies above 400 c/s. The latter were regarded as primary endings and the former as secondary ones.

4. The manner in which the spindle endings resumed activity after a pause produced by shocks to the ventral root, i.e. whether ‘phasic’ or ‘tonic’ (Granit & Van Der Meulen, 1962) was studied in all the spindle afferents.

5. All the secondary (low‐f sensitive) endings were ‘tonic’ except three for which the determination of critical frequency was questionable. Both ‘tonic’ and ‘phasic’ properties were found among the primary (high‐f sensitive) endings.

6. The majority of the secondary endings (74%) showed inspiratory rhythmic fusimotor activation in parallel with the skeletomotor contraction as did the primary endings (79%).

7. Fifty‐seven spindle endings which all showed marked rhythmic inspiratory γ activation were tested for respiratory variations in their dynamic responses to steady stretch and length changes introduced at low repetition rates.

8. The results indicate that both ‘dynamic’ and ‘static’ γ fibres are represented among the rhythmic γ fibres controlling primary muscle spindle endings, whereas rhythmic activation of secondary endings seems to be mediated only by ‘static’ fibres.
Responses in the inferior olive to stimulation of the cerebellar and cerebral cortices in the cat
Authors: Armstrong D. M. , Harvey R. J.
Published: December 2014

1. Extracellular field potentials and single unit responses have been recorded from the inferior olive of the cat following stimulation of the surface of the contralateral paramedian lobule of the cerebellum, and of the ipsilateral cerebral cortex.

2. Cerebellar stimulation results in antidromic invasion of inferior olivary neurones via the climbing fibres. These responses are followed by synaptic discharges which may be generated through climbing fibre recurrent collaterals.

3. Precise histological controls have shown that these responses to stimulation of the paramedian lobule are located in the ventral lamella of the principal olive.

4. Unifocal stimulation of the sensori‐motor cortex with surface‐anodal pulses evokes synaptically generated discharges of neurones in the ventral lamella, with a latency of 8‐9 msec. The area of cortex yielding responses has been mapped at chosen stimulus intensities and the limitations of the maps have been discussed.

5. It has been shown that the initial excitatory responses obtained from either cortex are followed by an inhibition which lasts about 100 msec, and gives way to a period of recovery or facilitation. This, in turn, is succeeded by a further period of inhibition. Possible neural substrates for these changes have been discussed.
The effects of stimulating cutaneous and splanchnic afferents on cerebellar unit discharges
Authors: Newman P. P. , Paul D. H.
Published: December 2014

1. Electrical stimulation of the right splanchnic nerve evoked the discharge of single units in the right cerebellar cortex of the anaesthetized cat. The majority of the units also responded to electrical stimulation of an area of skin on the right side of the anterior abdominal wall. The units were all located in lobules Vb‐f (culmen) of the anterior lobe of the cerebellum, lateral to the paravermian vein.

2. The response evoked by a conditioning stimulus (C) to one afferent pathway was followed by a period during which the response of a testing stimulus (T) to another pathway was diminished or absent. Diminished responsiveness was indicated by a reduction in the probability of the unit firing and a prolongation of the mean latency of the test response.

3. The effects of interaction depended on the interval between conditioning and testing stimuli and could be demonstrated with intervals as long as 150 msec. Complete blocking of the test response occurred with C—T intervals between 30 and 40 msec; at intervals shorter than 25 msec the effects were less intense.

4. If the C—T interval was constant, increasing the strength of the conditioning stimulus or decreasing the strength of the testing stimulus produced in each case a more powerful and prolonged inhibitory effect on the test response.

5. When two successive stimuli were applied to the splanchnic nerve, the discharge evoked by the first stimulus was invariably followed by complete block of the response to the second stimulus over a wide range of intervals.
Observations on the potential across the rumen of the sheep
Authors: Ferreira H. G. , Harrison F. A. , Keynes R. D. , Nauss A. H.
Published: December 2014

1. The electric potential difference between rumen contents and jugular venous blood was measured in anaesthetized sheep. In order to investigate the effect on the potential of changing the ionic concentrations within the rumen, the digesta were removed from the rumen and various salt solutions were substituted. The reticulo‐rumen sac was isolated before the experiment by ligation of the oesophagus and the reticulo‐omasal junction.

2. The observation of Dobson & Phillipson (1958) that the rumen contents are normally of the order of 30 mV negative to the blood was confirmed.

3. For potassium concentrations between 25 and 100 m
M the potential at constant [Na+] varied linearly with log [K+]. With sulphate as the anion, the slope for a 10‐fold concentration change was 39·7 ± 3·0 mV when [Na+] was around 50 m
M. The slope showed a tendency to increase when [Na+] was lowered, and to decrease when [Na+] was raised.

4. When chloride was substituted for sulphate, both the slope and the absolute size of the potential were slightly reduced.

5. When the sodium concentration was varied at constant [K+], the potential increased as an approximately linear function of [Na+]. At around 10 m
M‐K the mean slope was 0·32 ± 0·07 mV/m
M; at the highest potassium concentrations it fell to 0·13 ± 0·05 mV/m
M.

6. In most of these experiments isotonicity was maintained with sucrose. The results of a few tests in which Li+ was substituted for Na+ or K+ suggested that the rumen epithelium behaves in a relatively inert fashion towards this ion.
The potential and short‐circuit current across isolated rumen epithelium of the sheep
Authors: Ferreira H. G. , Harrison F. A. , Keynes R. D.
Published: December 2014

1. A technique is described for working with isolated sheets of rumen epithelium. Epithelium was obtained at operations for rumen fistulation or in acute experiments and was rapidly mounted between two cone‐shaped chambers each of which held 40 ml. of bathing fluid. The fluids were gassed with 95% O2/5% CO2 and 20 cm2 of epithelium was exposed to the fluids.

2. Electrical measurements were made of (a) the potential generated across the epithelium, (b) the short‐circuit current which flowed and (c) the resistance of the epithelium.

3. The results are grouped according to the composition of the sheep Ringer solution used to bathe the epithelium. The most stable preparation was obtained when the solutions contained 5 m
M each of glucose, acetate, propionate and butyrate as well as bicarbonate and phosphate buffers.

4. In Cl− media, the average initial p.d., short‐circuit current (s.‐c.c.) and resistance were 9·3 mV, 11·6 μA/cm2 and 1156 Ω. cm2 respectively. Higher values of 17·6 mV, 17·3 μA/cm2 and 1501 Ω. cm2 were recorded in SO42- media. In both media, the s.‐c.c. declined at approximately 1·5 μA/cm2.hr and preparations were suitable for study over periods from 4 to 6 hr.

5. When the concentration of potassium was varied on either side of the epithelium at constant [Na+], the potential showed a linear relation with log [K+] for both sides of the epithelium.

6. Changing the sodium concentrations at constant [K+] on either side of the epithelium caused negligible alterations in the potential.

7. Exclusion of sodium from the media bathing both sides of the epithelium abolished the potential and s.‐c.c.

8. The addition of ouabain to the blood side of the preparation abolished the potential and s.‐c.c. whereas on the rumen side these parameters were unaffected.
Monoamine oxidase inhibition: effect on 5‐hydroxytryptamine output from perfused third ventricle and body temperature
Authors: El Hawary M. B. E. , Feldberg W. , Lotti V. J.
Published: December 2014

1. In cats anaesthetized with pentobarbitone sodium the third ventricle was perfused with artificial c.s.f., the effluent was collected in 30 min samples and assayed for 5‐hydroxytryptamine (5‐HT) on the rat stomach‐strip preparation. Rectal temperature was monitored continuously.

2. On perfusion of artificial c.s.f. through the third ventricle, small amounts of 5‐HT appeared in the effluent; the amounts decreased with successive samples.

3. When tranylcypromine (Parnate), an inhibitor of amine oxidase, was added to the perfusion fluid and perfusion was continued, the 5‐HT output increased. This increase was associated with shivering and a rise in temperature which was not, however, maintained.

4. When tranylcypromine was injected intraperitoneally, during the fall in temperature produced by the pentobarbitone sodium anaesthesia, the 5‐HT output also increased, shivering occurred and the fall in temperature was halted or reversed. The effect on temperature was maintained.

5. When the cat was killed and perfusion was continued, the 5‐HT output, already elevated by the tranylcypromine before death, increased even further in the next few samples.
The reflex effects of alterations in lung volume on systemic vascular resistance in the dog
Authors: Daly M. de Burgh , Hazzledine Julie L. , Ungar A.
Published: December 2014

1. The reflex effects of alterations in lung volume on systemic vascular resistance have been studied in anaesthetized dogs under conditions in which the systemic circulation was perfused at constant blood flow. The pressures in the isolated perfused carotid sinuses and aortic arch, and the arterial blood PO2 and PCO2 were maintained constant.

2. A maintained inflation of the lungs produced by injection of air into the trachea caused a fall in systemic arterial perfusion pressure, indicating vasodilatation. The size of the systemic vasodilator response varied directly with the pressure and volume of gas used to inflate the lungs. A similar effect was observed when the tidal volume of lungs ventilated by an intermittent positive pressure was increased.

3. Collapse of the lungs by creating a pneumothorax in closed‐chest spontaneously breathing animals evoked a systemic vasoconstrictor response which was reversed when the lungs were re‐expanded.

4. These vasodilator responses were abolished by dividing the pulmonary branches of the thoracic vagosympathetic nerves. Evidence is presented that the afferent fibres run in the cervical vagosympathetic nerves and through the stellate ganglia.

5. The responses were unaffected by atropine, but were abolished by hexamethonium, guanethidine and by bretylium tosylate, indicating that they are mediated via the sympathetic nervous system.

6. Evidence is presented that the lungs are a constant course of afferent impulses inhibiting the ‘vasomotor centre’, and that the lung inflation—systemic vasodilator reflex is a potential mechanism operating in eupnoeic breathing.
The effect of noradrenaline on the permeability of depolarized intestinal smooth muscle to inorganic ions
Authors: Jenkinson D. H. , Morton I. K. M.
Published: December 2014

1. Radio‐isotopes have been used to study the effect of noradrenaline on the permeability of the taenia of the guinea‐pig caecum to inorganic ions. The preparations were bathed at either 10 or 20° C in solutions containing a high concentration of potassium, in order to depolarize the fibres and so avoid ionic movements secondary to changes in membrane potential.

2. Under these conditions noradrenaline increased both inward and outward fluxes of potassium whilst having little effect on the exchange of chloride.

3. No effect of noradrenaline on the uptake of sodium could be detected, whereas carbachol (carbamyl choline chloride), applied under identical conditions, caused a significant increase at a concentration chosen to match the effect of noradrenaline on potassium exchange.

4. These results are discussed in relation to the hypothesis that an increase in potassium permeability contributes to the inhibitory actions of noradrenaline on intestinal smooth muscle.
The intestinal absorption of pig and bovine immune lactoglobulin and human serum albumin by the new‐born pig
Authors: Pierce A. E. , Smith M. W.
Published: December 2014

1. Homologous and heterologous colostral immune globulins and human serum albumin were fed to new‐born pigs and an attempt was made to estimate the amounts appearing subsequently in serum.

2. All three proteins, fed separately in large amounts to different pigs, appeared in the serum in low concentration about 45 min after feeding, and then rose quickly to a high level. No difference could be detected between the amounts absorbed when equal amounts had been fed but there was a wide variation between pigs. Previous dialysis of pig colostrum against bicarbonate saline did not affect the rate or amount of pig immune globulin absorbed after feeding.

3. When pig and bovine colostral IgG were fed together at equal concentrations in bovine colostrum, the absorption of pig IgG was greater than that of bovine IgG. Human serum albumin, added to bovine colostral IgG in bovine colostrum, was absorbed readily and this did not interfere significantly with the absorption of bovine colostral IgG.

4. The efficiency with which the pig intestine absorbed bovine colostral IgG depended on the dose and/or concentration fed, increasing as the dose fed was increased to 2 g and remaining constant for higher doses.

5. Some of the absorbed immune globulin was shown to exist in a partly degraded form.

6. The process of protein transfer across the intestine of the new‐born pig may select, to a limited degree, between different proteins, but the digestion of protein shown to take place and the large variation between individual pigs makes interpretation of these results uncertain.
The in vitro transfer of bovine immune lactoglobulin across the intestine of new‐born pigs
Authors: Pierce A. E. , Smith M. W.
Published: December 2014

1. Everted sacs of pig intestine, used soon after birth, maintained transmural potentials and transferred water and glucose to the serosal surface.

2. Immune globulin, fed as bovine colostrum to the new‐born pig, appeared in the serosal fluid of everted sacs during incubation in bicarbonate saline. The particular segment showing maximum transferring ability varied between limits and appeared to depend on the amount or concentration of colostrum fed to the pig. Sacs from unfed pigs incubated in bovine colostrum also transferred colostral IgG to the serosal fluid. This transfer was dependent on the concentration of colostral IgG in the incubation medium and became more pronounced in the middle third of the small intestine.

3. Human serum albumin inhibited the transfer of colostral IgG and about twenty molecules of albumin were transferred for every molecule of colostral IgG, when both were presented together in equal concentration on the basis of weight, to the middle segment of the small intestine.

4. Some of the immune globulin collected in vitro after feeding bovine colostrum was found in a degraded form, but the amounts present could not be estimated. There was no apparent degradation of immune globulin in the purely in vitro experiments.

5. The in vitro transfer of bovine colostral IgG showed selectivity between molecules of albumin and colostral IgG, the nature of which warrants further study.
The distribution of [14C]sucrose within the skeletal muscle of the rat in vitro
Authors: Law R. O.
Published: December 2014

1. The distribution of [14C]sucrose within the plantaris muscle of the rat has been examined by suspending muscles in oxygenated Ringer containing this marker and subsequent analysis of the muscle.

2. Histological examination of sections of muscle treated in this way indicates considerable distortion of muscle fibre pattern; this has been held to cast doubt upon the validity of such a method as a means of extracellular space examination.

3. The rate of K+ loss from muscles under these conditions has been examined by flame photometry. Up to 50% of the original muscle K+ has been shown to be lost by efflux within approximately 1 hr from the commencement of soaking.

4. It is considered that these findings indicate severe deterioration in the physiological condition of the muscle, and it is suggested that tissue hypoxia is chiefly responsible for this.
Studies on the mechanism of kinin formation in inflammation
Authors: Zachariae H. , Malmquist J. , Oates J. A. , Pettinger W.
Published: December 2014

1. Injection of autologous plasma into the subcutaneous space leads to kinin formation in man. Kinin formation was also observed after similar injections of homologous plasma in the rat, dog and guinea‐pig. The material withdrawn from the subcutaneous tissue following the injection of plasma was characterized as kinin by inhibition of its formation with trasylol, by inactivation with chymotrypsin and by its pharmacologic effects.

2. Kinins were also demonstrated in subcutaneous tissue following injections of compound 48/80, a histamine liberator.

3. A slightly acid pH greatly favours the accumulation of kinins in subcutis.

4. Human plasma kallikrein was not activated in vitro by histamine, serotonin, nicotonic acid or endotoxin. Human polymorphonuclear leukocytes initiated the formation of kinins in plasma.

5. It is suggested that in inflammation, ‘primary mediators’ such as histamine, do not activate plasma kallikrein directly, but rather increase vascular permeability, permitting plasma to enter the extravascular space where conditions for activation exist. Kinin accumulation is enhanced in inflammation where pH is slightly lowered.
Release of neurophypophysial hormones in vitro
Authors: Daniel A. R. , Lederis K.
Published: December 2014

1. The rate of release of neurohypophysial hormones in vitro, using isolated, halved neural lobes of the rat in an incubation medium containing excess K+ and Ca2+, was measured. The highest average rate of release was observed between 10 and 20 min after commencement of incubation.

2. Incubation of isolated, halved rat neural lobes in the presence of acetylcholine, with or without eserine, did not stimulate hormone release. When complete isolated hypothalamo‐neurohypophysial systems were incubated in a suspension medium containing 10−7 mg/ml. acetylcholine a significant increase in the release of oxytocin occurred (P < 0·01); the increase in vasopressin release was less pronounced (P < 0·05).

3. Uptake of O2 by the isolated, halved neural lobes and the hypothalamo‐neurohypophysial systems continued for 2‐3 hr, i.e. in excess of the experimental incubation time.

4. During the first 40 min of incubation the control halved neural lobes increased in weight; the neural lobes incubated in buffer containing high potassium and calcium showed no increase in weight.

5. Neural lobes incubated in buffer containing excess K+ and Ca2+ contained about 3 times as much potassium as controls. The sodium content was not affected significantly.

6. Factors involved in the process of neurohypophysial hormone release are discussed.
The effect of infusions of glucose, acetate and amino acids in hourly milk yield in fed, fasted and insulin‐treated goats
Authors: Linzell J. L.
Published: December 2014

1. Experiments have been carried out in lactating goats milked hourly to assess the value of this technique in studies of milk secretion.

2. On refeeding 24 hr‐fasted goats there was an increase in arterial concentration and mammary uptake of volatile fatty acids within an hour, but little increase in hourly milk and lactose yield until the mammary uptake of glucose had also increased (after 2‐3 hr).

3. Intravascular infusions of acetate had no effect on milk secretion in 24 hr‐fasted goats but glucose infusions increased milk yield by 62 ± 5% and lactose yield by 87 ± 12% within 3 hr, with no effect on fat secretion. The addition of acetate or acetate plus amino acids had no more effect than glucose alone.

4. The yield of milk and lactose could be reduced within an hour by insulin (2 u./kg
I.V.) and this was prevented or reversed by injecting glucose. In one goat, where in spite of a fall in blood sugar, mammary arteriovenous difference and blood flow did not fall, there was little or no fall in milk yield.

5. In fasted or insulin treated goats an increase in milk and lactose secretion could be obtained within an hour by infusing glucose into the artery of one gland autotransplanted to the neck, which responded before the control gland in situ, thus showing that the effect of glucose is directly on the mammary tissue.

6. In two normally fed goats with a low blood sugar, glucose infusions increased the milk or lactose yield by 30% within 3 hr.

7. It is concluded that frequent milking, using minimal doses of oxytocin, is a valid method of studying factors controlling milk secretion and that, in the lactating goat, the availability of glucose to the mammary gland can be a limiting factor for maximum milk secretion.
The relation between spontaneous activity, metabolic rate and the 24 hour cycle in mice at different environmental temperatures
Authors: Mount L. E. , Willmott Jane V.
Published: December 2014

1. Oxygen consumption rates and levels of spontaneous activity were recorded simultaneously for mice, both singly and in groups, over 24 hr periods at temperatures ranging from 8 to 37° C.

2. There was marked 24 hr variation in both metabolic rate and activity, with maxima during the night; the amplitude of the variation diminished at the lower environmental temperatures.

3. At 28‐33° C environmental temperatures, increased activity was associated with an increased oxygen consumption rate.

4. At 8 and 15° C, increased activity was accompanied by only a small increase in oxygen consumption.

5. These results show that thermogenesis from spontaneous activity can take the place of thermoregulatory heat production in the cold.
Penetration of sugars across the blood—brain barrier
Authors: Eidelberg E. , Fishman J. , Hams M. L.
Published: December 2014

1. A cerebral perfusion method was used to measure the net uptake of arabinose from the circulatory system in cats.

2. There was found to be discrimination between the optical isomers of this substance, with apparently greater uptake of the (—)‐form.

3. The uptake process was highly temperature dependent, with a Q10 of 3·0.

4. The uptake of arabinose was partially inhibited by 1 m
M ouabain perfused concurrently. It was not significantly inhibited by dinitrophenol or phlorrhizin.

5. Glucose inhibited competitively the uptake of (—)‐arabinose.

6. We conclude that the mechanism involved is of the carrier‐mediated or of the active transport type, and that at least part of it is shared with glucose and probably other sugars.
The relation of blood volume to body weight and arterial haemoglobin levels in rabbits
Authors: Mott Joan C.
Published: December 2014

1. Relative blood volume (ml./kg) of rabbits calculated from total circulating haemoglobin and blood haemoglobin concentration decreases rapidly during the first few weeks of life and more slowly thereafter.

2. In anaemic rabbits over 1 kg body weight, relative blood volume is significantly increased.

3. Rabbits under 1 kg body weight have larger blood volumes than would be expected from their anaemia alone, were the relationship deduced in rabbits over 1 kg in body weight applicable. Blood volume was not related to haemoglobin concentration in these immature rabbits.
Further studies of the metabolism of thyroxine and 3,5,3′‐triiodothyronine in the guinea‐pig
Authors: Brown-Grant K.
Published: December 2014

1. Thyroxine labelled with 125I and triiodothyronine labelled with 131I have been administered simultaneously to guinea‐pigs and their metabolism studied by whole body counting and measurement of radioactivity in urine, faeces, and blood.

2. The half‐life of triiodothyronine in the body is about 19 hr, significantly less than that of thyroxine (41 hr).

3. After triiodothyronine administration, an unidentified iodinated compound appears in the blood which complicates the estimation of the half‐life of this hormone by measurement of the radioactivity in peripheral blood.

4. A previous report, based on measurements of blood radioactivity, that the half‐lives of the two hormones are similar in the guinea‐pig was not confirmed.
Impulse frequency in secretory nerves of salivary glands
Authors: Emmelin N. , Holmberg J.
Published: December 2014

1. In dogs under pentothal anaesthesia the submaxillary duct was exposed in the neck and a polythene tube tied into it. During the following days the dogs were examined repeatedly, standing in a frame. The highest rates of submaxillary secretion evoked by introducing various foodstuffs or rejectable substances into the mouth were estimated. Finally, the dogs were anaesthetized and the rates of salivary flow recorded during electrical stimulation of the chordalingual nerve at different frequencies.

2. The frequency—response curve for electrical stimulation has a steep slope up to a frequency of 10/sec, where a salivary flow at a rate of about 90% of the maximal is evoked.

3. The fastest secretion that is obtained reflexly on feeding corresponds to a flow which in different experiments varies between 4 and 8 shocks/sec. The very rapid secretion caused by rejectable substances can be reproduced by stimulating at 10‐30/sec.

4. In similar experiments on the parotid gland foodstuffs were often, and rejectable substances always found to cause a salivary flow at a rate which exceeded that obtained on maximal stimulation of the auriculotemporal nerve. This supports the view expressed by previous investigators that additional secretory fibres reach the parotid gland of the dog by anatomically unknown routes.
Confirmation from choline acetylase analyses of a massive cholinergic innervation to the rat hippocampus
Authors: Lewis P. R. , Shute C. C. D. , Silver Ann
Published: December 2014

1. Unilateral lesions were made in the fimbria of adult rats with a stereotaxically‐applied, radio‐frequency current. After 3‐23 days survival, fresh, unfixed, transverse sections were cut of the forebrain. Half the sections were stained histochemically to show the distribution of acetylcholinesterase (AChE) activity. From the other sections, small, anatomically defined areas were dissected out and assayed for choline acetylase (ChAc) activity (acetyl‐CoA: choline‐O‐acetyltransferase EC2.3.1.6).

2. In the fimbria, anterior to the lesion, ChAc activity rises sharply and is still approximately twice the normal after 7 days. In the hippocampus, ChAc activity falls: in most experiments activity on the operated side was 20‐40% of that on the control side, but in some experiments values below 10% were obtained. These changes closely parallel those observed in the staining for AChE.

3. The results go far towards proving that the hippocampus receives a massive cholinergic innervation via the fimbria. The fibres concerned appear to be those which stain characteristically for AChE and it seems likely that other pathways showing the same histochemical behaviour are also cholinergic.
Electrophysiological study of the intestinal smooth muscle of the guinea‐pig
Authors: Kuriyama H. , Osa T. , Toida N.
Published: December 2014

The membrane properties of single cells of intestinal smooth muscle of duodenum, jejunum, ileum, caecum and rectum of guinea‐pig have been studied.

1. The membrane potentials of longitudinal muscles of the duodenum, jejunum, ileum, caecum and rectum varied from 54 to 56 mV and those of circular muscles of jejunum, ileum, caecum and rectum varied from 57 to 60 mV. The ablated longitudinal muscle had a slightly lower value (50 mV) than the intact one.

2. The longitudinal muscle generated spontaneous discharges but these were rare in the circular muscles of the intestine except for the caecum. Overshoot potentials could be observed in all regions of the intestine. The maximum rate of rise of the spontaneously discharging longitudinal muscles varied from 11 to 18 V/sec.

3. Not all of the slow potential changes (but at least some) were generated by the nervous elements distributed between the muscle layers and in them.

4. The conduction velocities measured from the longitudinal muscles of jejunum and rectum in the presence of tetrodotoxin were 2·1 cm/sec and 4·0 cm/sec respectively.

5. Chronaxies of the longitudinal muscles of jejunum and rectum were 2‐5 msec and 5‐18 msec respectively.

6. Intracellular stimulation of the single cells of the duodenum and caecum could trigger a spike, similar to that observed in the taenia coli. The spikes were mostly graded ones; a spike of full size was rarely elicited. When the spikes were triggered, the after‐hyperpolarization appeared consistently presumably caused by the increased potassium conductance.

7. The effective membrane resistance and the time constant were measured for the longitudinal muscles of the jejunum and rectum. When spikes were generated by intracellular stimulation the observed values were 40‐50 MΩ and 3‐5 msec in both tissues. These values were the same as those observed in the taenia coli.

8. When the time constant of the membrane was measured by the extracellular polarizing method, the longitudinal muscles of the jejunum especially and the rectum had smaller time constants than the taenia coli.

9. The differences of conduction velocity and chronaxie of the different regions of the intestine are discussed in relation to the cable properties of the tissues which are directly influenced by the morphological arrangements of the tissues.
The partition of sodium fluxes in isolated toad oocytes
Authors: Dick D. A. T. , Lea E. J. A.
Published: December 2014

1. The rate constant for Na efflux from the oocyte calculated from (d/dt) (ln [Na*]i]) is only approximately 52% of that calculated from (d/dt)[(ln(d[Na*]i)dt)]. The difference may be interpreted by supposing that 48% of the internal Na of the oocyte is either bound to proteins or sequestered in cell organelles.

2. The mean rate constant for Na efflux was 6·4 × 10−3 min−1 corresponding to an apparent Na efflux rate of 13·3 p‐mole/cm2.sec. When this is corrected for the increase in surface area produced by microvilli the true efflux rate is 1·1‐1·3 p‐mole/cm2.sec.

3. The action of ouabain (1‐5 μ
M) appears to involve two different effects: (a) there is 48‐65% inhibition of the membrane Na pump, and (b) there is a release of some of the sequestered Na in the cell.

4. Removal of external K causes a 40% reduction in Na efflux although this value may be an underestimation owing to the presence of K which has leaked from the cell and may be retained near the cell surface.

5. Raising the external K concentration to 15 m
M reduces the inhibitory effect of ouabain by approximately a half.

6. It was concluded that the Na pump in the toad oocyte may have a slightly lower level of activity than that in frog muscle, but that its general properties are similar to those in frog muscle and some other animal cells.
A search for pulmonary arterial chemoreceptors in the cat, with a comparison of the blood supply of the aortic bodies in the new‐born and adult animal
Authors: Coleridge Hazel , Coleridge J. C. G. , Howe A.
Published: December 2014

1. Electrophysiological and histological techniques have been employed to search for pulmonary arterial chemoreceptors in kittens and cats.

2. In cats, impulses were recorded from vagal fibres arising from chemoreceptors in the aortico‐pulmonary region. The receptors were identified by their response to hypoxia, and their location was investigated by comparing the effects of injecting drugs at various sites in the pulmonary and systemic circulations. In only one of a large number of experiments did a chemoreceptor appear to receive pulmonary rather than systemic arterial blood.

3. No chemoreceptor impulses were evoked when a segment of the pulmonary artery was perfused as described by Duke, Green, Heffron & Stubbens (1963).

4. The vasculature of the aortico‐pulmonary bodies was displayed by micro‐dissection following injection of coloured gelatin masses, and the bodies were examined histologically. In the new‐born kitten, the pulmonary artery invariably furnished a branch to some aortic bodies but the vessel frequently anastomosed with systemic arteries. As post‐natal development proceeded the vessel became occluded, and in most kittens more than a month old and in forty‐one of forty‐three cats the aortic bodies were supplied wholly by systemic arteries.

5. It was concluded that a pulmonary arterial supply to aortic bodies in the adult animal is an uncommon variation owing to the abnormal persistence of a foetal condition.

6. Results indicated that the nomenclature introduced by Howe (1956) is, with slight modification, a useful method of classifying the various groups of aortic bodies according to their position, blood supply and innervation.
The effect of heating and cooling the hypothalamus on behavioural thermoregulation in the pig
Authors: Baldwin B. A. , Ingram D. L.
Published: December 2014

1. Pigs were trained to push a switch with their snouts in order to obtain a short burst of infra‐red heat on the skin.

2. When the preoptic region of the hypothalamus was cooled by means of an implanted thermode, the rate at which the heaters were turned on increased at environmental temperatures ranging from 0 to 25° C. At 30 and 35° C cooling sometimes had no effect.

3. The preoptic region was warmed either by means of a thermode or using radio‐frequency heating from implanted electrodes. Warming the preoptic region decreased the rate at which the infra‐red heaters were turned on, but the effect was not as obvious as the increases observed during cooling.

4. Pigs placed in a cold or neutral environment did not learn to push a switch in order to obtain radio frequency heating of the preoptic region.
The demonstration of luteinizing hormone releasing factor in hypophysial portal blood of pro‐oestrous and hypophysectomized rats
Authors: Fink G. , Nallar R. , Worthington W. C.
Published: December 2014

1. A method for the routine collection of hypophysial portal blood from rats under direct vision has been described.

2. This method has been used to obtain portal blood from adult female rats in pro‐oestrus and adult female rats which had been hypophysectomized at least 14 days before collection.

3. The pooled plasma from this blood was assayed for activity, resembling that of luteinizing hormone releasing factor (LRF), by the ovarian ascorbic acid depletion method.

4. The portal plasma from both groups of donor animals exhibited significant activity when compared to peripheral plasma controls.

5. It is concluded that the ovarian ascorbic acid depleting activity of portal plasma was due to LRF.

6. The possibility that some of the activity exhibited by portal plasma from pro‐oestrous rats was due to contamination of the samples by LH containing backflow blood from pituitary sinusoids is discussed.

7. The possibility that the ovarian ascorbic acid depleting activity of the hypophysial portal plasma was due to either vasopressin or a nonspecific factor has been excluded.
Hypothalamic control of thyrotrophin secretion*
Authors: Panda J. N. , Turner C. W.
Published: December 2014

1. By means of the haemagglutination‐inhibition technique, it has been possible to measure the plasma and pituitary levels of thyroid‐stimulating hormone (TSH) following unilateral and bilateral electrolytic lesions placed in the supraoptic area of the hypothalamus of female rats.

2. Unilateral lesions after 8 and 48 hr caused a temporary decrease in the percentage of circulating TSH followed by a return to normal.

3. Bilateral lesions caused a fall in plasma TSH to a level 41% below normal at 10 days whereas the pituitary level increased 70%.

4. Rats with bilateral symmetrical supraoptic lesions, kept for 3 days at 4° C, had a lower plasma TSH content (23%) and a higher pituitary TSH content (16%) than the sham operated control animals but the levels of pituitary TSH did not show any significant difference (0·100 > P > 0·050).

5. Thyroidectomized rats with bilateral lesions kept at 26° C for 3 days had a much lower plasma TSH (39%) and a slightly higher pituitary TSH as compared to the normal intact animals, suggesting that the hypothalamus also influences the synthesis of TSH in the pituitary.

6. Thyroidectomized rats with bilateral lesions kept at 4° C for 3 days showed both a plasma and pituitary TSH increase compared to controls at 26° C, suggesting that when a higher demand for thyroid function is present the pituitary gland has some autonomy for both secretion and release of TSH. This autonomy appears to be slight, as there was no statistically significant difference between the pituitary TSH levels of the thyroidectomized animals bearing similar supraoptic lesions and exposed to 4 and 26° C.