bluuebunny/crossref_metadata_2025 huggingface dataset:
The hyperthermic effect of intracerebroventricular cholera enterotoxin in the unanaesthetized cat
Authors: Clark Wesley G. , Cumby H. Rick , Davis Henry E.
Published: December 2014

1. Cholera enterotoxin was used to evaluate a possible role of endogenous cyclic AMP in production of hyperthermia. Injection of purified toxin (0·10‐1·0 μg in 0·10 ml.) into the lateral cerebral ventricle of unanaesthetized cats caused dose‐related hyperthermic responses. Heating the toxin for 40 min at 90° C abolished its hyperthermic activity.

2. Intraventricular administration of dibutyryl cyclic AMP (250‐1000 μg) also caused hyperthermia which, however, was preceded by transient periods of hypothermia and/or excitation in about half of the tests.

3. Paracetamol, indomethacin and sodium salicylate inhibited hyperthermic responses to cholera enterotoxin. Paracetamol and indomethacin also inhibited hyperthermia induced by dibutyryl cyclic AMP (sodium salicylate was not tested).

4. It is likely that the hyperthermic effect of cholera enterotoxin in the cat is mediated via endogenous cyclic AMP and that the antipyretics inhibit this effect by an action subsequent to the increase in cyclic AMP.

5. It is unlikely that prostaglandin‐induced hyperthermia in the cat is mediated via cyclic AMP since these antipyretics do not inhibit this response to prostaglandin E1.
Correlation of food intake in lambs with adipocyte glucose metabolism and NEFA release
Authors: Mears G. J. , Mendel V. E.
Published: December 2014

1. Experiments were conducted with lambs to determine the correlation between food intake, rate of glucose incorporation into CO2 and lipids, and rate of lipid mobilization by their isolated omental adipocytes.

2. During the interval between weaning and slaughter average daily dry matter (ADDM) intakes of the individual lambs were significantly correlated with average daily gains; however, the ratio of ADDM intake to body wt.¾ was similar in all individuals.

3. The average size of adipocytes for each lamb, as determined by lipid: protein ratios, was not significantly correlated with food intake.

4. Oxidation of glucose to CO2 and the total measured glucose incorporation by the adipocytes were significantly and negatively correlated with lamb ADDM intakes at low levels of glucose (0·1 mg/ml.), whereas rates of lipogenesis from glucose were similar for all intake levels.

5. Insulin‐induced increases in glucose utilization were positively and significantly correlated with ADDM intakes to the extent that insulin had over twice the effect on the adipocytes from high‐intake lambs as it had on those from low‐intake lambs. The minimum effective dose of insulin necessary to significantly increase glucose utilization by the adipocytes was also positively and significantly correlated with the ADDM intakes of the lambs.

6. Basal NEFA release rates were higher for adipocytes from low‐intake lambs. Epinephrine significantly increased NEFA release rates, independent of lamb intakes.

7. A larger number of adipocytes in the high‐intake lambs means that they would have a greater total potential to lower blood glucose, particularly when they are under the effects of normal circulating levels of insulin. The amount of glucose removed from the glucose pool could be the feed‐back signal which results in a high long‐term food intake.
Thyroid hormone responses to prolonged cold exposure in man
Authors: Eastman C. J. , Ekins R. P. , Leith I. M. , Williams E. S.
Published: December 2014

1. Four men, of ages varying from 23 to 28 years, living at Halley Bay, Antarctica (75° 31′ S, 26° 39′ W), were exposed to a mean air temperature of 6·6° C.

2. The concentration of serum triiodothyronine (T3) rose significantly by the second day, remained raised, and returned to pre‐exposure levels within 2 days of return to a normal environment.

3. The concentration of serum thyroxine (T4) rose more slowly than did the T3, reaching a maximum in 3‐4 days and also returning to normal within 2 days of return to a normal environment.

4. There was a wide individual variation in the change of concentration of serum cortisol.
The influence of bulbospinal monoaminergic pathways on sympathetic nerve activity
Authors: Coote J. H. , Macleod Valerie H.
Published: December 2014

1. Spontaneous and reflex activity was recorded from renal and splanchnic nerves and thoracic white rami during discrete electrical stimulation within the medulla oblongata of anaesthetized cats.

2. Inhibition or excitation of spontaneous sympathetic nerve activity was obtained from several medullary regions.

3. The long‐circuited reflex elicited in renal nerves and the spinally mediated reflex discharge produced in white rami by single shock stimulation of intercostal nerves were inhibited by stimulation within the sympatho‐inhibitory areas of the medulla.

4. Activation of spontaneous sympathetic nerve activity or inhibition of spontaneous and reflex sympathetic nerve activity was obtained during electrical stimulation within the lateral funiculi of the cervical spinal cord in unanaesthetized decerebrate cats, spinalized at C1.

5. There was a correlation between the position of some sympatho‐inhibitory regions of the medulla and spinal cord and the position of the cell bodies and axons of descending monoamine‐containing neurones.

6. Intravenous administration of the precursor of noradrenaline,
L‐DOPA, to unanaesthetized decerebrate cats, spinalized at C1, was followed by a depression of spontaneous activity in renal nerves and reflex responses elicited in renal nerves and white rami.

7. Similarly the precursor of 5‐hydroxytryptamine, 5‐HTP, caused a depression of reflex activity elicited in renal nerves and white rami, but had no effect on spontaneous renal nerve activity.

8. It is suggested that there exist both noradrenergic and tryptaminergic pathways which descend to the spinal cord from the medulla and which are inhibitory to sympathetic outflow.
Fall in blood pressure produced from discrete regions of the ventral surface of the medulla by glycine and lesions
Authors: Guertzenstein P. G. , Silver Ann
Published: December 2014

1. In cats anaesthetized with pentobarbitone sodium, atropinized by
i.v. atropine methyl nitrate and artificially ventilated, experiments were carried out (a) to localize the site where glycine acts on the ventral surface of the medulla when, on topical application through paired Perspex rings caudal to the trapezoid bodies, it produces a fall in arterial blood pressure, (b) to compare the effects of uni‐ and bilateral application, and (c) to study the blood pressure effects produced by electrolytic lesions of the glycine‐sensitive areas.

2. Blood pressure fell only a little on unilateral application of glycine through one of the Perspex rings, but a pronounced fall occurred on its bilateral application. The fall was too large to be explained by two minimal responses added together. Thus the application of glycine to one side potentiated the depressor effect of glycine applied to the other side.

3. By moving the paired Perspex rings rostrally or caudally to different positions on the medulla and determining for each position the effectiveness of glycine, the glycine‐sensitive areas were found to be restricted to a 1·5 mm wide strip situated 1–2·5 mm caudal to the trapezoid bodies. By making electrolytic lesions within the limits of this strip the glycine‐sensitive areas were found to be not wider than 1·5 mm in the mediolateral direction and to be situated about 4 mm lateral to the mid line. Histologically, such lesions involved the cells of the parvicellular part of the lateral reticular nucleus.

4. Placing an electrode, with a diameter of 1 mm, under light pressure on the glycine‐sensitive area produced a short‐lasting steep rise in blood pressure. The same effect was produced when a current was passed through the electrode to destroy the underlying tissue, but after its destruction the passage of current no longer produced the pressor effect.

5. Once the glycine‐sensitive area of one side was destroyed, glycine applied to the destroyed area through one of the Perspex rings no longer produced its small depressor effect, but when applied to the intact area of the other side, a pronounced fall in blood pressure occurred. Thus unilateral destruction had the same effect as unilateral glycine application. It potentiated the depressor effect of glycine applied to the other side.

6. Following unilateral destruction of the glycine‐sensitive area there was only a small fall in blood pressure; following its bilateral destruction blood pressure fell to a low level.

7. It is concluded that the cells in the small circumscribed glycine‐sensitive areas on the ventral surface of the medulla may play a key role in the maintenance of arterial blood pressure and that the cells of one side are sufficient for this function.
Effect of ouabain on renin secretion in anaesthetized dogs
Authors: Churchill Paul C. , McDonald Franklin D.
Published: December 2014

1. Pentobarbitone anaesthetized dogs were used to study the effects on renin secretion of ureteral occlusion and partial aortic clamping before and after intrarenal arterial administration of ouabain.

2. Arterial plasma renin activity (A renin) and renal venous minus arterial plasma renin activity (RV‐A renin) were both increased by either ureteral occlusion during mannitol diuresis or partial aortic clamping to reduce renal perfusion pressure. Intrarenal arterial ouabain administration blunted or abolished the effects of these manoeuvres on A and RV‐A renins.

3. The observations are not consistent with the hypothesis that renin secretion is uniquely controlled by afferent arteriolar transmural pressure. Both ureteral occlusion and aortic clamping reduce this pressure and increase renin secretion, yet evidence presented herein suggests that ouabain, which also decreases this pressure, decreases renin secretion.

4. The observations are consistent with the hypothesis that renin secretion is controlled by tubular fluid flow and/or composition in the region of macula densa cells. Possibly changes in flow and/or composition are detected as changes in macula densa intracellular sodium concentration.
Changes in time scale and sensitivity in turtle photoreceptors
Authors: Baylor D. A. , Hodgkin A. L.
Published: December 2014

1. In turtle cones the steady‐state relation between the internal potential and log light intensity was much flatter in the steady state than it was at 30 msec after the beginning of a step of light; this is attributed to a desensitization which develops with a delay of 50–100 msec.

2. When a weak flash was superposed on a steady background light which hyperpolarized the cone by 3‐6 mV the amplitude of the linear response to a flash was reduced to 1/e and the time to maximum was shortened from about 110 to 70 msec; the response also became diphasic. With stronger background lights the flash sensitivity continued to fall, but the time to maximum did not become shorter than 40–50 msec and lengthened again with very strong lights.

3. In cones the flash sensitivity SF was reduced to half its dark value SFD by a light intensity of 1/SFDζ where ζ is about 20 sec/V.

4. At low levels of background light, about two‐thirds of the change in sensitivity was time‐dependent and one‐third was attributable to the ‘instantaneous non‐linearity’ described in the previous paper.

5. The reduction in time to peak and the decrease in sensitivity produced by a background light which hyperpolarized by about 3 mV was little affected by changing the diameter of the area illuminated from 12 to 800 μm.

6. An experiment with a rod showed that a very weak light which hyperpolarized by only 0·5 mV decreased the linear response to 1/e and shortened the time to maximum from 300 to 180 msec.

7. With weak or moderate flashes the time‐dependent desensitization lagged behind the potential by 50–100 msec.

8. The desensitization and shortening of time scale which persisted after a flash or step were associated with an after‐hyperpolarization. The relaxation of potential, sensitivity and time scale became slower as the preceding illumination was increased from 103 to 1010 photons μm−2; the increase seemed to occur in steps involving components which relaxed with time constants of the order of 0·1, 1, 10 and 100 sec. A rebound phenomenon was observed after steps longer than 30 sec and with equivalent intensities greater than 105 photons μm−2 sec−1.

9. Several of the observations are explained by a hypothesis in which the central assumption is that the particles which block the ionic channels are degraded or removed by an autocatalytic reaction.
Light scattering associated with tension changes in the short‐range elastic component of resting frog's muscle.
Authors: Flitney F W
Published: December 2014

1. A study has been made of some optical and associated mechanical properties of resting frog's sartorius muscles in isotonic and hypertonic solutions. Tension and transparency changes accompanying small alterations of muscle length (smaller than 1‐5%) were recorded simultaneously. 2. The form of the transparency change is complex. It has three phases, two of which occur during the length change and the third (delayed phase) after it is complete. Directional recording of the response reveals both scattering and diffraction components. 3. The change of light scattering is associated with tension changes in the short‐range elastic component (SREC) of the muscle. Its magnitude is related to the stiffness of the SREC; both increase when the osmotic strength of the external solution is raised and when muscle length is increased. 4. The change of light scattering is not much affected by the velocity of the applied length change. This is true also of the mechanical stiffness of the SREC. 5. The origin of the diffraction change is not known. 6. It is concluded that the scattering effect is caused by conformational changes in the SREC.
A central osmosensitive receptor for renal sodium excretion.
Authors: Blaine E H , Denton D A , McKinley M J , Weller S
Published: December 2014

1. The effect on renal Na and water excretion of increasing the NaCl concentration of blood supplying the brain was investigated in conscious water‐loaded sheep. Intracarotid infusion ot 4 M‐NACl at 0–8 ml./min for 60 min was compared with equivalent intrajugular infusion. 2. A more rapid increase in renal Na excretion and urine osmolality occurred with the intracarotid infusions than with intrajugular infusions. 3. Intracarotid infusions of 2 M sucrose or fructose at 1–6 ml./min for greater increase in renal Na excretion, urine osmolality and a decrease in urine flow rate. 4. The results suggest that there are receptors in the brain sensitive to changes in extracellular tonicity which influence renal Na excretion. It is possible that changes in ADH secretion alone mediate the early natriuresis seen with intracarotid hypertonic infusions although an alternative concurrent mechanism cannot be ruled out.
Membrane permeability changes during stimulation of isolated salivary glands of Calliphora by 5‐hydroxytryptamine.
Authors: Berridge M J , Lindley B D , Prince W T
Published: December 2014

1. The membrane resistance of isolated salivary glands was found to decrease in response to 5‐HT. The change in resistance was calcium‐dependent. 2. The resistance change of the apical membrane was found to be much greater than the change in resistance of the basal membrane. 3. Potential responses under current‐clamped conditions showed that one part of the biphasic response to 5‐HT (attributed to an increase in chloride permeability) could be reversed and the other part (attributed to an increase in a potassium pump) could not. 4. These observations have been incorporated into a model which, on evaluation, predicts all of the observed potential changes during the action of 5‐HT. It suggests that the potential responses reflect changes in the internal chloride concentration produced by the calcium‐dependent increases in chloride permeability.
Endocrine responses to insulin hypoglycaemia in the young calf.
Authors: Bloom S R , Edwards A V , Hardy R N , Malinowska K W , Silver M
Published: December 2014

1. Variations in the output of glucocorticoids and catecholamines from the right adrenal gland, in response to insulin hypoglycaemia, have been investigated in calves 2‐5 weeks after birth. These have been correlated with changes in the concentration of glucocorticoids and glucagon in arterial plasma. 2. Moderate hypoglycaemia for a limited period (0–1 u. insulin/kg), elicited a prompt increase in steroid output from the adrenal gland followed by a significant rise in plasma glucagon concentration. By comparison, changes in both catecholamine output and peripheral plasma glucocorticoid concentrations were found to be trivial in this group of animals. 3. Administration of a larger dose of insulin (0–5 u./kg) produced a more substantial fall in plasma glucose concentration followed by spontaneous recovery within 2‐3 hr. This stimulus elicited the release of greater amounts of both cortisol and corticosterone, followed by a significant increase both in the output of adrenaline and in plasma glucagon concentration. Increase in steroid output was accompanied by an increase in adrenal blood flow and was associated with elevated concentrations of both steroids in arterial plasma. 4. The adrenal cortical response and associated changes in plasma steroid concentration were found to be transient even in response to persistent and intense hypoglycaemia (4 u. insulin/kg). The increase in plasma glucagon concentration in this group of animals was not significantly greater than that produced by smaller doses of insulin. However, substantial amounts of adrenaline (78 plus or minus 14 ng. kg‐minus 1 min‐minus 1; maximum; n equals 9) together with a little noradrenaline (10 plus or minus 3 ng.kg‐minus 1 min‐minus 1; maximum; n equals 9) were released from the right adrenal gland under these conditions. 5. Changes in adrenal blood flow could be related to adrenal glucocorticoid output in calves given 0–1 or 0–5 u. insulin/kg. In animals given the largest dose of insulin adrenal blood flow was found to increase coincidentally with rising steroid output but this hyperaemia then persisted after steroid output had subsided to values within the normal range. 6. Calves given the largest dose of insulin (4–0 u./kg) invariably collapsed and convulsed after 2‐3 hr, but these symptoms could not be related to any particular endocrine response. No clinical signs of hypoglycaemia were observed in the other animals. 7. The results are discussed in relation to previous studies of adrenal function in this and other species.
Characteristics of renin release from isolated superfused glomeruli in vitro.
Authors: Blendstrup K , Leyssac P P , Poulsen K , Skinner S L
Published: December 2014

1. A method is described for studying renin release from superfused rat glomeruli following their rapid isolation by a magnetic iron‐oxide technique. 2. Microscopically selected glomeruli were free of tubular components. Some possessed vascular pole protrusions of up to 20 mum, unrelated to renin content. 3. Renin content of 102 batches, each of 400 glomeruli, was 1.34 plus or minus 0.08 times 10‐4 Goldblatt hog units per 100 glomeruli (plus or minus S.E. of mean). Different osmolarities (305, 355 and 400 m‐osmole/1.), sodium concentrations (110 and 135 mM) and buffer compositions of the preparation solution did not alter this value. Renin content per glomerulus in intact kidney was 100‐fold higher. 4. At 30 degrees C the contained juxtaglomerular cells released renin at consistent but decreasing rates over 4‐6 hr. Initial release rate in 110 mM sodium, 305 m‐osmole/1. solutions were 0.86 plus or minus 0.068 times 10‐6 units per 100 glomeruli per 30 min (plus or minus S.E. of mean, n = 42) or 0.546 plus or minus 0.046 percent of content per 30 min. In 135 mM sodium, 305 m‐osmole/1. solutions, release was 2.4‐fold higher (P less than 0.001) and remained elevated for at least 3 hr. When related to renin content per glomerulus resting release rate in vitro was higher by at most one order of magnitude than calculated in vivo values. 5. Release was augmented by gentle physical agitation of the glomeruli. 6. Release rate was inversely ralated to temperature. On reducing temperature from 30 degrees C, release increased 2.6‐fold at 20 degrees C and 6.7‐fold at 10 degrees C (P less than 0.001, n = 11). The response was reversible. 7. 3 mM sodium cyanide plus 3 mM sodium iodoacetate caused a variable release of renin associated with depletion of content within 4 hr. The response was progressive and reached a peak after 60 min. 8. Sensitivity of renin release to temperature and metabolic blockade indicates that energy is required for retention of renin by the cell. This, together with the release observed with increased sodium concentration at constant osmolarity, suggests a dependence of renin release upon the mechanism controlling the volume of the juxtaglomerular cell or its organelles.
Effects of adapting lights on the time course of the receptor potential of the anuran retinal rod.
Authors: Coles J A , Yamane S
Published: December 2014

1. The intracellular receptor potential of the retinal rod cell was recorded in the unperfused, isolated retina of Rana catesbiana and in the perfused, isolated retina of Bufo marinus. Qualitatively, the responses from the two preparations were similar. 2. The rate at which the receptor potential returned to the dark level at the termination of a pulse of light (Voff) was measured at a fixed potential chosen to be about 0–6 of the way from the dark level to the peak of the response. 3. When the light intensity was such that less than about 10‐minus 5 of the photopigment was bleached per second, Voff increased as the duration of the pulse was increased, reaching a maximum in 50–100 s. 4. When a brief test flash was presented at various intervals after an adapting pulse lasting about 50 s, Voff for the test flash was greater than the value in the dark adapted state for times up to about 80 s after the adapting pulse. 5. It has been hypothesized that in the vertebrate rod light causes release from the disk sacs of particles which block conducting channels in the surface membrane (Yoshikami & Hagins, 1971, 1973). A modification is proposed in which the blocking particles are converted to an inactive state can be increased by light adaptation. 6. This modified hypothesis will account qualitatively for the further observations that (a) during the response to illumination lasting several seconds the membrane potential recovers part of the way to the dark level and (b) if a second light pulse is superimposed on this background illumination then after the superimposed pulse the depolarization is increased.
Potassium and sodium ion current noise in the membrane of the squid giant axon.
Authors: Conti F , De Felice L J , Wanke E
Published: December 2014

1. The spectral density of current noise power from 20 mm segments of giant axons of the squid Loligo vulgaris has been measured under space‐clamp and voltage‐clamp conditions. From 4 to 1000 Hz the measured noise is larger by several orders of magnitude than the theoretical thermal noise. The amplifier's noise, which may yield appreciable contributions above 200 Hz, could be evaluated and subtracted from the total noise using direct measurements of the membrane impedance...
On the role of mitochondria in transmitter release from motor nerve terminals.
Authors: Alnaes E , Rahamimoff R
Published: December 2014

1. The changes in transmitter release produced by mitochondrial inhibitors has been studied at the frog neuromuscular junction using conventional electrophysiological techniques for stimulation and intracellular recording. 2. Inhibitors of the electron transport chain and inhibitors of oxidative phosphorylation produce an increase in the frequency of appearance of the miniature end‐plate potentials. This increase in frequency is observed also in calcium‐free media. Mitochondrial inhibitors also augment the amount of transmitter liberated by a nerve impulse. 3. Ruthenium red, which is an inhibitor of calcium uptake by mitochondria, increases the spontaneous transmitter release but decreases the quantal content. The latter effect of Ruthenium red is antagonized by calcium. 4. The mitochondrial content of the motor nerve terminals is, on the average, 6.59%. 5. The experimental results are explained on the hypothesis that spontaneous release of transmitter reflects the resting level of intracellular free calcium and the evoked release reflects the sum of the resting calcium and the calcium brought in by the action potential. The mitochondria play a role in transmitter release by participating in the regulation of the intracellular free Ca.
Gastric, antral and fundic pouch secretion in sheep.
Authors: McLeay L M , Titchen D A
Published: December 2014

1. Fundic secretion of HCl and pepsin was studied in sheep with both fundic and antral pouches. The antral pouches were of the entire pyloric region. Continuity of the alimentary tract was restored by an abomasoduodenal anastomosis. 2. Secretion from fundic pouches was continuous. It was reduced in volume and acidity, was pepsin output, by resection of the antral pouches. 3. Teasing with food, feeding and injection of pentagastrin stimulated fundic acid and pepsin secretion in animals with antral pouches before and after antrectomy. 4. Pouches prepared from the entire pyloric region showed continuous secretion with variations not related to feeding or fasting. Antral secretion was increased after s.c. injections of histamine, carbachol and pentagastrin. 5. It is concluded that although the pyloric antrum contributes to the magnitude of the secretory response of an abomasal fundic pouch, the direction of the secretory response is similar whether or not the pyloric antrum is present as a separated pouch, or is removed.
The effects of intra‐ruminal loading with cold water on thermoregulatory behaviour in sheep.
Authors: Baldwin B A
Published: December 2014

1. Shorn sheep exposed to ambient termperatures of 5 degrees C soon learned to turn on infra‐red heaters by placing their muzzles through a photoelectric beam, although before shearing they did not operate the heaters. 2. The duration of infra‐red heating obtained decreased at higher ambient temperatures and at 25 degrees C very little heat was obtained. 3. When infra‐red heaters totalling 900 or 1800 W were suspended above the sheep they turned on the 900 W heaters for almost exactly twice as long as they did the 1800 W heaters when exposed to 10 degrees C for 24 hr periods. 4. Loading the rumen with 1 l. water at 0–1 degree C produced an increment in the duration of infra‐red heating obtained in a 1 hr period. At ambient temperatures of 0, 10 and 20 degrees C the increment observed after intraruminal loading with 2 l. water at 0–1 degree C was almost exactly double that obtained with a 1 l. loading. 5. Loading the rumen with 1 l. water at 0–1 degree C did not result in the sheep increasing the duration of infra‐red heating obtained at ambient temperatures of 30 degrees C but a 2 l. loading was effective. At an ambient temperature of 40 degrees C the 2 l. load was ineffective.
Is brain prostaglandin synthesis involved in responses to cold?
Authors: Cranston W I , Hellon R F , Mitchell D
Published: December 2014

1. Experiments with rats have suggested that prostaglandin synthesis in the C.N.S. may mediate thermoregulatory reactions to cold. This possibility was investigated in cats using two types of experiment. 2. In one series of experiments, c.s.f. collected from the cisterna magna of conscious cats exposed to a cold and a hot environment was assayed for prostaglandin‐like activity. During cold exposure there was a slight increase in activity which persisted after return to neutral ambient temperature. There was no correlation between prostaglandin‐like activity and rectal temperature. During the heat exposure there was no demonstrable change in activity. 3. In the second series, conscious cats were exposed to cold conditions and given intravenous injections of salicylate, paracetamol, or indomethacin, all of which inhibit prostaglandin synthesis. Indomethacin salicylate nor paracetamol caused any significant change in rectal temperature. 4. The results do not support a role for C.N.S. prostaglandin synthesis in thermoregulatory reactions to cold in cats.
The effects of cyclic adenosine 3',5'‐monophosphate and other adenine nucleotides on body temperature.
Authors: Dascombe M J , Milton A S
Published: December 2014

1. Adenosine 3',5'‐monophosphate (cAMP), its dibutyryl derivative (Db‐cAMP) and other adenine nucleotides have been micro‐injected into the hypothalamic region of the unanaesthetized cat and the effects on body temperature, and on behavioural and autonomic thermoregulatory activities observed. 2. Db‐cAMP and cAMP both produced hypothermia when applied to the pre‐optic anterior hypothalamus. With Db‐cAMP the hypothermia was shown to be dose dependent between 50 and 500 mug (0‐096‐0‐96 mumole). 3. AMP, ADP and ATP also produced hypothermia when injected into the pre‐optic anterior hypothalamus. 4. The order of relative potencies of the adenine nucleotides with respect both to the hypothermia produced and to the autonomic thermoregulatory effects observed were similar. Db‐cAMP was most potent and cAMP least. 5. Micro‐injection into the pre‐optic anterior hypothalamus of many substances including saline produced in most cats a non‐specific rise in body temperature apparently the result of tissue damage. Intraperitoneal injection of 4‐acetamidophenol (paracetamol 50 mg/kg) reduced or abolished this febrile response. 6. The hypothermic effect of the adenine nucleotides has been compared with the effects produced in these same cats by micro‐injections of noradrenaline, 5‐hydroxytryptamine, a mixture of acetylcholine and physostigmine (1:1), EDTA and excess Ca2+ ions. 7. It is concluded that as Db‐cAMP and cAMP both produce hypothermia, it is unlikely that endogenous cAMP in the pre‐optic anterior hypothalamus mediates the hyperthermic responses to pyrogens and prostaglandins.
Pulmonary vasomotor nerve responses in isolated perfused lungs of Macaca mulatta and Papio species.
Authors: de Burgh Daly I , Ramsay D J , Waaler B A
Published: December 2014

1. Lung lobes of Macaca mulatta and Papio species were isolated from the body and perfused by a pump delivering a constant volume inflow. The left atrial pressure was kept constant and therefore any recorded change in pulmonary arterial pressure reflected a change in pulmonary vascular resistance. 2. In five Macaca mulatta preparations stimulation of the upper thoracic sympathetic chain, the stellate ganglion, the middle cervical ganglion and the thoracic vagosympathetic nerve caused a small increase in calculated pulmonary vascular resistance usually followed by a larger decrease. Evidence is produced which suggests that the depressor response is mediated by adrenergic beta‐receptors. In three preparations no change in pulmonary vascular resistance occurred. 3. In four Papio preparations stimulation of similar nerves invariably caused an increase in calculated pulmonary vascular resistance. In one animal no change in vascular resistance occurred. 4. A regression analysis of the results showed an inverse relationship between the magnitude of the pulmonary vascular response to nerve stimulation and the degree of excitement of the animals during capture, restraint and anaesthesia (P less than 0.01).
Cell electrical potentials during enhanced sodium extrusion in guinea‐pig kidney cortex slices.
Authors: Proverbio F , Whittembury G
Published: December 2014

1. Experiments were performed on outermost slices of the guinea‐pig kidney which are mainly made up of proximal tubular cells. 2. Kidney cells loaded with Na+ by chilling at 0.6 degrees C for 2.5 hr, when subsequently rewarmed to 25 degrees C in a medium containing 16 mM‐K+ extrude Na+ at enhanced speed for about 10 min. This Na+ movement is accompanied by efflux of Cl and influx of K+. 3. Measurements of cell potential during enhanced Na+ extrusion show that cells hyperpolarize to values about 30 mV more negative than the K+ equilibrium potential. 4. This hyperpolarization is only partly inhibited by 1 mM ouabain or by 2 mM ethacrynic acid but both agents added together suppress it completely. 5. With 16 mM‐Rb instead of 16 mM‐K the hyperpolarization is smaller. 6. A diminished extracellular K+ concentration outside of the cells, within the slice, can account for only a small part of the hyperpolarization. 7. The hyperpolarization is proportional to the rate of Na+ pumping. 8. Cl‐ seems to shunt the hyperpolarization to a greater extent than K+. 9. It is concluded that Na+ extrusion is capable of transferring electric charge across the membrane.
The aortic arch baroreceptor response to static and dynamic stretches in an isolated aorta‐depressor nerve preparation of cats in vitro.
Authors: Arndt J O , Dörrenhaus A , Wiecken H
Published: December 2014

1. The aortic arch baroreceptors of cats were studied in an isolated aortic arch‐depressor nerve preparation in vitro to analyse their transmission properties. 2. Sinusoidal length changes of varying amplitudes (0‐34‐1‐2 mm) and frequencies (1‐10 Hz) at a given pre‐stretch were imposed on the isolated receptor zone to quantitate the velocity sensitivity of these receptors and to test the linearity of the system. 3. The receptor response was evaluated from the spike activity of single fibres of the depressor nerve in number of spikes per stimulus period, average discharge rate, instantaneous frequency, and phase angle between forcing function and instantaneous frequency. 4. The static response is characterized by a threshold, saturation range, and a relatively large linear part between these two non‐linearities. 5. The aortic receptors exhibit rate sensitivity. Depending on the stimulus amplitude and frequency the phase angles between the forcing function and the instantaneous frequency ranged from ‐14 to ‐68 degrees. 6. The average discharge rate (spikes/sec) is sensitive to stimulus amplitude but not to stimulus frequency at near‐threshold operation; in the linear part of the static response curve, the receptor response becomes independent of the stimulus mode. 7. The baroreceptors of the aorta share many properties with other mechanoreceptors of different species and organ systems, particularly with those of the rest of the circulation. They exhibit static and to some degree rate sensitivity and operate physiologically near their thresholds, i.e. the afferent arc of the baroreflexes is highly non‐linear.
Retention and redistribution of proteins in mammalian nerve fibres by axoplasmic transport.
Authors: Ochs S
Published: December 2014

Fast axoplasmic transport is characterized by a crest of labelled activity moving down nerve fibres after injection of the L7 dorsal root ganglion with the amino acid precursor (3H) leucine, the crest followed by a plateau which represents in part a later egress of labelled components from compartments in the cell bodies and in part materials left behind the advancing crest. 2. after making ligations just below the ganglia at different times after injection of the precursor, a small downward slope of locally retained activity of incorporated materials is seen in the plateau remaining in the nerves. The slope becomes changed to a horizontal level when in addition a distal ligation is made as a result of the redistribution of labelled materials within the doubly ligated nerve segments. 3. the outlfow pattern at later times, at a day and longer after injection, shows an additional spread of activity from the cell body region. The pattern of outflow gradually levels off at later times as additions of activity are made to the more distal part of the nerves. The activity retained in the nerves becomes less free to become redistributed in the course of several days. 4. The temporal changes in the outflow patterns can be accounted for by the local retention and redistribution of the labelled materials within the fibres. Later additions of labelled materials compartmented in the cell bodies also contribute to the later pattern of outflow. A "unitary" view for fast and slow transport is presented based on the transport filament hypothesis earlier proposed to account for fast axoplasmic transport.
The formation of synapses between chick embryo skeletal muscle and ciliary ganglia grown in vitro.
Authors: Betz W
Published: December 2014

1. Chick embryo ciliary ganglia (explanted) and skeletal muscle (dissociated) were grown together in vitro for up to 3 weeks. Nerve processes sprouted from the ganglia and contacted neighbouring myotubes and striated muscle fibres. 2. Spontaneous action potentials and subthreshold e.p.p.s. were recorded from muscle fibres with intracellular micropipettes. Similar potentials could be evoked by electrical stimulation of the ganglion. The pharmacological effects of curare and tetrodotoxin were identical to those observed at adult vertebrate neuromuscular junctions. 3. The amplitude, but not the frequency, of the spontaneous potentials was affected by changing the muscle fibre membrane potential. The reversal potential of evoked synaptic potentials occurred at a membrane potential of about 0 mV.
Activation and inhibition of the lateral hypothalamic neurones elicited by medial forebrain bundle stimulation.
Authors: Muneyuki I
Published: December 2014

1. Single neurone discharges were recorded from the lateral hypothalamus (LH) at the level of the ventromedial nucleus. Single stimulation of the medial forebrain bundle (MFB) at the level of the mesodiencephalic junction elicited a strong inhibition lasting for 100‐300 msec in these neurones. 2. However, by the use of multiple stimulating electrodes, it was possible to find a circumscribed locus in the MFB which gave rise to an initial activation of firing discharges with a latency of 1‐15 msec (in different neurones) preceding the period of inhibition. 3. One class of the LH neurones was antidromically activated, and was thought to give off axons into the descending MFB. The other was activated orthodromically through a highly efficient synaptic connexion, and was viewed as 'relay' neurones of the ascending MFB. 4. Although the former could also be activated orthodromically, the efficacy of driving was distinctly lower than that observed in the latter. Presumably they integrate the messages from the visceral centres of the medulla and pons, thus participating in the viscero‐motor outflow from the hypothalamus. 5. Intracellularly recorded spike potentials of these neurones deteriorated rapidly leaving only hyperpolarization which corresponded in its time course to the suppression of extracellular spike discharges following MFB stimulation. It was suggested that the inhibition was elicited via recurrent routes localized within the hypothalamus.
An electrophysiological study of chemical and electrical synapses on neurones in the parasympathetic cardiac ganglion of the mudpuppy, Necturus maculosus: evidence for intrinsic ganglionic innervation.
Authors: Roper S
Published: December 2014

1. The cardiac ganglion of the mudpuppy is situated on a thin sheet of tissue. Two nerve cell types can be distinguished readily in the living preparation ‐ principal cells and smaller interneurones which synapse with the principal cells. The purpose of this study was to investigate synaptic transmission and the functional organization of neuronal connections of ganglion cells with intracellular micro‐electrodes. 2. Stimulation of the preganglionic, vagus, nerves evoked a large excitatory response in principal cells. About three quarters of these neurones were innervated by a single vagal axon. The remaining cells received two or more preganglionic nerve fibres. 3. The quantum content of vagal excitatory post‐synaptic potentials (e.p.s.p.s) was measured. Normally, the e.p.s.p. was suprathreshold and consisted of about twenty‐two quanta, whereas only about nine quanta were required to reach threshold and initiate an action potential. 4. Intracellular stimulation of principal cells evoked e.p.s.p.s in neighbouring principal cells. The responses were blocked by cholinergic antagonists. These potentials were caused by excitation of principal cell axon collateral synapses. 5. Principal cells also formed electrical junctions with each other. These electrical junctions were very weak. Although they transmitted slow potential changes, only a small response was recorded in one cell when an electrically coupled neighbouring cell fired an impulse. The resistance of the electrical junction between principal cells was calculated to be about 5‐8 X 10(8) omega. 6. Stable penetrations of interneurones were only rarely achieved, making it difficult to study their functional relationship to principal cells. Action potentials were recorded from interneurones in a few instances. 7. These data demonstrate that parasympathetic ganglion cells in the heart of the mudpuppy receive innervation from more than one source involving both chemical and electrical synapses, and that some of the synapses are intrinsic to the ganglion.
Secretin‐like choleretic effect of prostaglandins E1 and E2 in cats.
Authors: Krarup N , Larsen J A , Munck A
Published: December 2014

1. The effects of intraportal and hepatic arterial infusion of prostaglandins E1 and E2 on liver function and circulation was studied in fasting chloralose anaesthetized cats. 2. Infusion of the prostaglandins at rates of 0‐1, 1‐0 and 5‐0 mug/kg.min caused a 35‐40% increase in bile flow. This may be explained by a decrease in the reabsorption or a secretion of sodium ions by the ductular cells. The canalicular bile production and bile flow. This may be explained by a decrease in the reabsorption or a secretion of sodium ions by the ductular cells. The canalicular bile production and bile acid excretion was not affected by the prostaglandins. 3. Infused at rates of 1‐0 and 5‐0 mug/kg.min the prostaglandins caused a transient decrease in mean arterial blood pressure and mesenteric vascular resistance. The resistance in the intrahepatic arterioles and low‐pressure vessels was not affected. 4. The prostaglandins did not influence the splanchnic uptake of oxygen and ethanol, whereas a slight increase in the splanchnic glucose output occurred. 5. The effects of the two prostaglandins were identical and not related to the route of administration.
Frequency‐related inhibitory mechanisms controlling rhythmical activity in the septal area.
Authors: McLennan H , Miller J J
Published: December 2014

1. The response patterns of identified neurones in the medical and lateral septal regions to varying rates of repetitive stimulation of the fimbria were investigated in rats anaesthetized with urethane. 2. Neurones in the lateral septum which characteristically respond to single pulse stimulation of the fimbria with an activation‐inhibition sequence, exhibited a reduction or complete elimination of the inhibitory component both during and following tetanic volleys delivered at 7‐12 HZ. Stimulation at lower frequencies did not alter the response. 3. Concurrently with this effect on the inhibitory component of the response exhibited by lateral septal cells, repetitive volleys eliminate the small amplitude burst discharges which are correlated with the onset of the inhibitory period and are considered to indicate the firing of inhibitory interneurones. 4. Tetanic stimulation of the fimbria at rates which eliminate this interneuronal response in the lateral septum, produce an irregular pattern of firing in medial septal neurones which previously exhibited a synchronized bursting discharge to single pulses. 5. Ipsilateral section of the fimbrial input to the septum resulted in the elimination of the burst discharge pattern exhibited by medial septal neurones. 6. The results suggest that a frequency gating mechanism in the lateral septum, activation of which is dependent upon the level of hippocampal output, is responsible for controlling the firing pattern of medical septal neurones.
Quantitative assessment of the transmission of labelled protein by the proximal and distal regions of the small intestine of young rats.
Authors: Morris B , Morris R
Published: December 2014

1. The plasma volume in rats aged 15‐16 days was measured by dilution analysis using homologous, 125I‐labelled immunoglobulin G. A mean plasma volume of 5‐53 ml./100 g and a mean blood volume of 8‐01 ml./100 g were obtained.2. After the injection of labelled immunoglobulin G into the heart, homogenates of various abdominal organs and of the carcass were prepared. Labelled immunoglobulin G left the vascular compartment at a rate of about 9‐10%/hr over a 3 hr period. About 11% of the labelled immunoglobulin G was catabolized in 2 hr. 3. The data obtained from these studies was used to make quantitative estimates of the amount of intact immunoglobulin G transmitted from the proximal intestine and from the ileum after the intra‐intestinal injection of 1000 mug of labelled immunoglobulin G.Homogenates of the experimental animals were prepared and it was estimated that over 40% of the labelled immunoglobulin G was transmitted as intact protein from the proximal intestine. The results suggest that no intact immunoglobulin G was transmitted from the ileum, but about 15% of the protein removed from the ileum was recovered in the whole body as degraded fragments precipitable with trichloroacetic acid. 4. These observations are discussed in the context of the transmission of antibodies, and their relevance to the receptor hypothesis is considered.
The effect of low amplitude muscle vibration on the discharge of fusimotor neurones in the decerebrate cat.
Authors: Trott J R
Published: December 2014

1. Longitudinal vibration (50‐100 mum, 100‐300 Hz) has been applied to the triceps surae tendon to examine its effect on the tonic discharges of gastrocnemius medialis fusimotor neurones in the decerebrated cat. 2. For nineteen out of twenty‐seven fusimotor neurones vibration consistently caused a small rise in discharge frequency. The remaining eight neurones showed no respose to the vibration which always evoked a considerable discharge in alpha motoneurones. 3. The reflex excitation of fusimotor neurones is attributed to activity in primary endings of muscle spindles since control experiments confirmed that these receptors were powerfully excited by the vibration used whereas secondary endings and Golgi tendon organs remained unaffected. 4. Tonic discharges of fusimotor neurones of unknown destination were also recorded from lumbar 7 and sacral 1 ventral root filaments in decerebrated cats. Of thirty cells, seven were inhibited, five were excited and the remaining eighteen units were unaffected by vibration of the triceps surae. 5. These findings are discussed in relation to the role of muscle stretch receptors in the autogenetic control of fusimotor neurones.