bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat production and chemical change in tortoise muscle
Authors: Walsh T. H. , Woledge R. C.
Published: December 2014

1. Measurements have been made of heat production and changes in levels of phosphorylcreatine (PC), ATP and lactic acid resulting from contraction of tortoise muscle under anaerobic conditions.

2. The only significant chemical change found was a break‐down of PC.

3. The amount of heat produced per mole of PC split (−ΔH) was 13·18 ± 1·04 kcal/mole (mean and
S.E. from thirty‐five observations).

4. (−ΔH) is probably rather greater in tortoise than in frog muscle. The value of (−ΔH) cannot easily be accounted for by the known processes accompanying PC splitting in either type of muscle.
Functional specializations of the vascular bed of soleus
Authors: Hilton S. M. , Jeffries M. G. , Vrbová G.
Published: December 2014

1. The venous outflow from the slow soleus muscle, at rest and during exercise, was compared with that of fast muscles. The blood flow through the soleus at rest was found to be, on average, 52 ml./100 g.min, which is about 4 times that of fast muscles.

2. On stimulation of soleus through its motor nerve at low frequencies, up to 8/sec, hardly any increase in flow was observed, whereas fast muscles stimulated at the same rates showed a marked increase, the maximal functional hyperaemia being reached at 8/sec. Even when the soleus muscle was stimulated at frequencies of 40/sec the post‐contraction hyperaemia was very small and sometimes absent.

3. The relative absence of functional hyperaemia in the soleus does not appear to be due to low vascular tone, for small amounts of acetylcholine, injected close arterially, produced a considerable increase in blood flow. Further, in experiments in which the vascular tone was increased by lumbar sympathetic stimulation, no functional hyperaemia was seen.

It is concluded that a contracting soleus does not release in adequate amounts the substance causing functional vasodilatation in fast muscles.

4. No vasodilator effect of adrenaline could be demonstrated in soleus, and the vasodilator effect of isoprenaline was much smaller than that seen in fast muscles.

5. The vasoconstrictor effect of lumbar sympathetic stimulation on the resistance vessels of soleus was much smaller than the effect seen in fast muscles. However, the responses of the resistance vessels in soleus to close arterial injections of noradrenaline were not very different from those of fast muscles, and it is suggested that the density of the terminal sympathetic innervation of the vessels of soleus differs from that of fast muscles.
Responses of cat retinal ganglion cells to brief flashes of light
Authors: Levick W. R. , Zacks J. L.
Published: December 2014

1. The responses of cat retinal ganglion cells to brief flashes of light have been illustrated and described with a view to providing material for comparison with psychophysical experiments in the scotopic (rod‐dominated) range of performance.

2. There is a minimum response duration of 50–70 msec no matter how brief the flash is made. This duration is reached with stimuli lasting 32 msec or shorter.

3. Reducing the background illumination obviously increases the latency of responses to stimuli at 4 times threshold intensity (about 10 msec increment per log. unit decrement) but has no obvious effect on the minimum response duration.

4. The relation between intensity and duration of a flash for threshold responses closely resembles that in human psychophysical experiments. The Bunsen—Roscoe law is applicable for flash durations up to 64 msec.

5. If equal amounts of energy are delivered in the form of a pair of flashes of varying separation rather than by rectangular pulses, the shape of the response changes more abruptly with the temporal factor.

6. Non‐linear performance is apparent for stimuli as weak as 4 times threshold.

7. A method is developed for quantitative analysis of individual responses. It is based upon cross‐correlation of the train of impulses with a Gaussian smoothing function and represents local impulse frequency as a smooth function of time. The method also improves the signal‐to‐noise ratio of post‐stimulus time‐histograms of the sum of many responses.

8. The measurement of variability of individual responses is the main result of the method; its magnitude indicates that it is a significant new factor limiting temporal resolution with suprathreshold stimuli.
Independent release of oxytocin and vasopressin during parturition in the rabbit
Authors: Haldar Jaya
Published: December 2014

1. Oxytocin and vasopressin were assayed in samples of blood collected from seven conscious rabbits during parturition.

2. Oxytocin was detected in the blood in ten out of fourteen samples collected during the expulsion of one or more foetuses. Four samples contained 6–100 μu./ml., three 100–200 μu./ml. and three 200–500 μu./ml.

3. Vasopressin was detected in six blood samples collected during the delivery of foetuses but in only one experiment did the amount exceed that found in the corresponding control sample collected before or after delivery.

4. When both hormones were detected in the same blood sample, the ratio of oxytocin to vasopressin varied from 5:1 to at least 26:1.

5. It is concluded that, while oxytocin may not be essential for parturition in the rabbit, stretching of the birth canal during the expulsion of foetuses normally acts as a stimulus for the reflex release of oxytocin from the neurohypophysis and that oxytocin is released independently of vasopressin.
The effect of high oxygen tensions on the mechanical properties of rat lungs
Authors: Hurley R. M. , Rosenberg Edith
Published: December 2014

1. The average mechanical properties of groups of lungs or lung—thorax systems from pathogen‐free rats weighing approximately 200 g were determined. Static pressure—volume curves and resistances to air‐flow were obtained.

2. Six series, each of sixteen rats, were studied. Eight experimental rats in each series were exposed to 4 atm O2 (OHP) in a transparent pressure chamber; the other eight rats, which served as controls, were obtained from the breeder at the same time and studied at the same time.

3. In four series, the experimental animals were killed 10 min after gasping due to OHP had been definitely established. One series was a control in which experimental animals were exposed to 4 atm of pressure in an atmosphere containing oxygen at a tension of 150 mm Hg for 190 min. The experimental animals in the sixth series were exposed to 4 atm O2 for 2 hr and none of them gasped.

4. Gross and histological examination of sixteen rats, eight of which were killed after 10 min of gasping at 4 atm O2, showed that at this stage of intoxication there was no evidence of pulmonary pathology.

5. In none of the series studied were the static pressure—volume curves for deflation shifted, i.e. OHP did not affect the elastic properties of the lungs or the alveolar surfactant.

6. In two series studied 10 min after gasping behaviour had been established there was a significant decrease of resistance to air‐flow and a shift to the left of the static pressure—volume curve for inflation with air. The rats in both these series were sedated with pentobarbitone and then killed with pentobarbitone injected into the jugular vein.

7. The decrease in resistance to air‐flow was interpreted as broncho‐dilatation and a possible mechanism whereby OHP produces broncho‐dilatation is discussed.
Time course of the sodium influx in squid giant axon during a single voltage clamp pulse
Authors: Bezanilla Francisco , Rojas Eduardo , Taylor Robert E.
Published: December 2014

1. Sodium influx measurements were carried out on internally perfused squid giant axons under conditions of membrane potential control.

2. The ratio ‘measured extra sodium influx/calculated ionic influx from the inward current record’ is close to unity and is independent of the duration of the rectangular pulse of membrane potential.

3. The variation of the sodium permeability with time during the voltage clamp pulse is obtained by subtracting the sodium influx obtained from the ‘tail’ current record from the measured extra sodium influx.

4. Evidence was obtained indicating that the measured change in sodium permeability during a sudden decrease of the membrane potential from its resting level involves two processes, namely, a transient increase in sodium permeability (activation), and a decrease in sodium permeability (inactivation).

5. The extra influx of sodium during a voltage clamp pulse is not decreased by raising the internal sodium concentration from 0 to 100 m
M, supporting the validity of the independence principle.
The involvement of phosphatidylserine in adenosine triphosphatase activity of the sodium pump
Authors: Wheeler K. P. , Whittam R.
Published: December 2014

1. A study has been made to see whether the ATPase of the Na pump is activated by phospholipids.

2. Solubilization of a membrane‐containing (microsomal) fraction from ox brain cortex with deoxycholate removed most or all of the ouabain‐inhibited ATPase and p‐nitrophenylphosphatase (pNPPase) activities. Addition of sonicated dispersions of crude commercial samples of phosphatidic acid, phosphatidylinositol or phosphatidylserine stimulated both enzymic activities, but neither phosphatidylcholine nor phosphatidylethanolamine affected them. After partial purification by chromatography, however, definite activation was demonstrated only with that component of crude samples which migrated like phosphatidylserine.

3. The ATPase activity dependent on phosphatidylserine was eliminated by removal of Na and K or by addition of ouabain and was substantially inhibited by oligomycin. The corresponding component of pNPPase activity was partially inhibited by ouabain or by removal of most of the K, but was little affected by oligomycin. The phosphatidylserine‐dependent enzyme(s) therefore exhibited properties characteristic of the ATPase of the Na pump.

4. Phosphatidylserine dispersions similarly activated both the ATPase and the pNPPase of the particulate enzyme preparations, untreated with deoxycholate.

5. The results suggest that the system for active transport of Na and K involves a complex unit of phosphatidylserine and the protein of the ATPase.
The permanence of tissue binding of thyroxine in the rat
Authors: Harland W. A. , Orr J. S.
Published: December 2014

1. Male rats were given radiothyroxine and after 24 hr, approximately half the blood volume was replaced by exchange transfusion.

2. Plasma concentration of radiothyroxine 2 hr after exchange averaged 81·1% of the value before exchange. This compared with a predicted mean of 97·1% assuming a free and rapid exchange of thyroxine throughout the thyroxine distribution space. The difference between the observed and expected value was highly significant.

3. The effective exchangeable pool of thyroxine was found to be approximately twice the plasma volume.

4. From these and other observations it is suggested that the liver and plasma constitute most of the exchangeable pool of thyroxine.

5. This experiment supports a model of thyroxine metabolism which envisages essentially permanent binding of thyroxine by tissues other than the liver.
Paradoxical temperature dependence of Na and K fluxes in human red cells
Authors: Wieth Jens Otto
Published: December 2014

1. The effect of temperature on passive movements of sodium and potassium through the red cell membrane has been determined in the presence of various monovalent anions.

2. Passive sodium and potassium fluxes varied in a complex way with temperature, when the isotonic electrolyte media contained 120 m
M thiocyanate or salicylate. Between 0 and 18° C the fluxes decreased with increasing temperature. Above 18° C the rate of permeation increased when temperature was increased.

3. The ability of anions to induce an increased sodium influx at 0° C was gradually intensified through the following sequence of anions:HCO3− < Cl− = Br− < NO3− < I− « SCN− « salicylate.

4. It is proposed that the anion induced effects on the cation permeability are secondary to binding of anions to fixed cations in the red cell membrane. The temperature dependence of the cation fluxes is assumed to reflect the binding on anions to fixed charges at temperatures between 0 and 18° C.
Effect of some monovalent anions on chloride and sulphate permeability of human red cells
Authors: Wieth Jens Otto
Published: December 2014

1. The permeability of human red cells to 36Cl− and to [35S]SO42‐ was studied in the presence of various monovalent anions.

2. A maximum decrease of anion permeability was found in a study of the steady‐state exchange of 36Cl in a medium containing 120 m
M salicylate. The exchange had a half‐time of 3 hr at 0° C, a reduction of normal chloride permeability by a factor of 105. The activation energy of chloride exchange decreased from a value of 45 to 22 kcal/mole in the interval between 0 and 10° C. Simultaneous determination of the permeability to potassium and chloride proved that salicylate induced a reversal of the normal selectivity of red cells at 0° C (permeability coefficient PK of 3·5 × 10−9 cm/sec to be compared with a PCl of 2 × 10−9 cm/sec).

3. In contradistinction to the slow movement of 36Cl, the exchange of [14C]salicylate was completed within 4 min, when red cells were suspended at 0° C in the salicylate medium.

4. A study of the sulphate permeability at 38° C showed that the rate of steady‐state exchange decreased, when chloride was replaced by lyotropic anions other than bromide. The sequence of the permeability decrease was: Cl− = Br− < I− < NO3 < SCN− < salicylate, the same sequence which previously has been shown to increase the permeability to sodium and potassium. The activation energies of sulphate exchange were 32 kcal/mole (chloride medium), and 38 kcal/mole (thiocyanate medium).

5. Sufficient data were obtained during the study to demonstrate that when equilibrium has been obtained, there is a good agreement between the values of 36Cl (cell water)/36Cl (extracellular water) and of {[35S]SO4 (cell water)/[35S]SO4 (extracellular water)}½.

6. It is concluded that the anion‐induced changes of permeability are due to binding of anions to fixed cationic charges in the red cell membrane.
The range of thermal insulation in the tissues of the new‐born baby
Authors: Hey E. N. , Katz G.
Published: December 2014

1. Rectal temperature and skin temperatures were measured in twenty‐eight naked babies weighing 1·1–4·5 kg, lying supine in environments of 25–31 °C when air speed was 4‐7 cm/sec. The ratio of external insulation to internal or tissue insulation for the whole body averaged 2·7 but varied inversely with body weight; the ratio was higher than this on the trunk, and five times lower than this on the hand and foot. The mean ratio rose threefold when environmental temperature was increased to 34–35° C.

2. Direct measurements of heat flow from the back of a hand placed in a water jacket maintained at 32° C were made in thirty‐three babies. Heat loss averaged 3 kcal/m2.hr.° C at low environmental temperature, but the loss was often rather less than this in the first 24 hr of life. Heat loss from the hand increased three‐ to fourfold, during exposure to an environment of 35° C.

3. When babies more than 48 hr old were exposed to an environment of 34–35° C, heat loss from the hand only increased when rectal temperature reached between 36·6 and 37·3° C; a slightly higher rectal temperature was usually reached before heat loss rose in babies less than 24 hr old.

4. Similar methods were used to study specific tissue insulation in three babies with congenital defects of the brain who lacked evidence of temperature control. No changes in insulation were detected in these three babies following changes in environmental temperature.

5. It is concluded that the range and pattern of control that can be exerted over the specific thermal insulation of the tissues is essentially the same in babies 2‐20 days old as it is in adult life.
Summit metabolism and cardiovascular function in young lambs during hyperoxia and hypoxia
Authors: Alexander G. , Williams D.
Published: December 2014

1. Exposure of lambs at sea level to air containing more than 33% oxygen resulted in a small increase in summit metabolism (maximum oxygen consumption on severe cold exposure) in some lambs, and in an improvement in the ability to maintain summit metabolism in others; there was a concomitant improvement in the maintenance of cardiac output, but no change in the degree of right to left shunting.

2. Hypoxia (12–13% oxygen in inspired air) reduced summit metabolism of new‐born lambs by 25%; but there was no effect in lambs 6–11 days old. Hypoxia neither reduced cardiac output, nor affected the degree of right to left shunting.

3. The results suggest that in very young lambs there is some limitation of summit metabolism imposed by the supply of either oxygen or substrate to thermogenic tissues.
The production of adenosine triphosphate in perfused giant axons of Loligo
Authors: Martin K. , Shaw T. I.
Published: December 2014

1. The light production by squid giant axons perfused with solutions containing extract of firefly tails has been studied to give information about the production of ATP in such axons.

2. An initial flash occurs when the perfusion fluid first enters the fibre. There is a secondary production of light, noticeable when the perfusion is halted, providing glutamate or aspartate are present in the perfusion medium.

3. There is no secondary light production if glutamate is replaced by sulphate, succinate or α‐ketoglutarate in the perfusion fluid.

4. Ouabain has no effect whereas cyanide and oligomycin both block the secondary light production, the latter irreversibly.

5. When the sodium outside the fibre is replaced by lithium or choline the secondary light production is often reduced and occasionally abolished.

6. A raised internal sodium does not enhance secondary light production.

7. The secondary light production is dependent upon the concentration of AMP in the perfusion solution.

8. Fresh axoplasm generates a powerful light on immersion in perfusion fluid whereas dialysed axoplasm, even in the presence of added glutamate, generates no light whatever.

9. The evidence, on balance, suggests that, under the conditions of the experiments described, there is no detectable reversal of active transport in perfused nerve fibres but that there is an enzyme system, probably membrane bound, capable of generating ATP from glutamate or aspartate and AMP by oxidative phosphorylation. The enzyme system can be inhibited by the replacement of external sodium.
Responses of unshorn and shorn sheep to thermal stress
Authors: Phillips G. D. , Raghavan G. V.
Published: December 2014

1. The effect of close shearing upon the respiratory frequency of ewes at ambient temperature of 20° C and 55% relative humidity has been described.

2. Removal of an adequate area of fleece (3000 cm2 or more) on the thoraco‐lumbar region resulted in a depression of respiratory responses and this was attributed to the exposure of cold receptors located beneath the fleece.

3. The continued depression of respiratory frequency of partially shorn sheep (3000 cm2) during rising ambient temperature appears to be due to persistence of cold receptor drive originating from the shorn area.

4. The absence of any rise in carotid blood temperature before the onset of polypnoea in unshorn sheep, during rising ambient temperature, suggests that the onset of panting in sheep can occur almost immediately upon a rise in ambient temperature even in the absence of any rise in the temperature of the blood supplying the brain.
Efflux mechanism contributing to the stability of the potassium concentration in cerebrospinal fluid
Authors: Bradbury M. W. B. , Štulcová Barbora
Published: December 2014

1. The clearance of 42K from c.s.f. has been separated into two components by means of ventriculo‐cisternal perfusion in the rabbit. At 2 hr the largest fraction of radioactivity is recoverable from brain. A smaller fraction passes into the bloodstream and this loss can be expressed as a barrier clearance.

2. The clearance into brain was largely independent of potassium concentrations in the perfusion fluid of 15 m‐equiv/l. and below. It was depressed by ouabain, 10−2 m
M.

3. The barrier clearance was small, about 9% of the total, when the perfusion fluid contained potassium (1·5 m‐equiv/l. or below). Above this concentration it increased steeply reaching 32 μl./min or 37% of the total at 10 m‐equiv/l. A similar high barrier clearance was caused by replacing 84% of the sodium in the perfusion fluid with choline. Ouabain, 10−2 m
M, abolished the increased barrier clearance due to potassium (10 m‐equiv/l.).

4. The clearance of [14C]urea into both brain and blood was unaffected by the potassium concentration in c.s.f. The barrier clearance of [14C]urea was, if anything, increased by 10−2 m
M ouabain.

5. Perfusion of the low sodium fluid caused a net loss of potassium from c.s.f.

6. The influx of 42K into c.s.f. from blood was the same, when the perfusion fluid contained potassium (2·9 or 10 m‐equiv/l.).

7. The potential between c.s.f. and blood of about 4 mV (c.s.f. positive) was little affected by the potassium or sodium concentration in the perfusion fluid.

8. These observations indicate that the net flux of potassium ions from c.s.f. to blood begins to increase very steeply with the potassium concentration in c.s.f., when the latter is between 2 and 3 m‐equiv/l. This relation, taken together with the variation of influx with the potassium concentration in blood plasma, can largely explain the known stability of the potassium concentration in the c.s.f. of the rabbit at 2·8–2·9 m‐equiv/l.

9. The increased flux of potassium from c.s.f. at raised concentrations of potassium in this fluid appears to depend on a sodium—potassium pump inhibitable by ouabain.
The effect of temperature on the resting tension of frog's muscle in hypertonic solutions
Authors: Hill D. K.
Published: December 2014

1. It has long been known that the tension of a resting muscle rises when it is warmed and falls on cooling. It is shown here that treatment with hypertonic solution causes an alteration in this effect; the usual rise or fall of tension with warming or cooling is then preceded by a transient change in the opposite direction.

2. The magnitude of the abnormal reversed phase does not depend in a simple, linear, manner on the temperature change. For instance, the effect for cooling from 20 to 0° C is much greater than twice that for 10 to 0° C.

3. The results lead to the suggestion that the tension, in both normal and hypertonic muscle, comes from an active process. It is proposed that a temperature change operates by altering the concentration of an ‘activating substance’, and that the change of concentration becomes delayed by hypertonicity.
Further purification of a polypeptide demonstrating enterogastrone activity
Authors: Brown J. C. , Mutt V. , Pederson R. A.
Published: December 2014

1. The further purification of a polypeptide having potent enterogastrone activity, without CCK—PZ effects, is described.

2. The material was inhibitory when doses of 1·0 μg/kg.hr were administered intravenously. Amino acid analyses demonstrated the absence of proline, a high content of glutamine and a preponderance of lysine over arginine. Tryptic degradation destroys the inhibitory effect of the polypeptide. Further studies must be performed before the physiological status of the polypeptide can be ascertained.
The representation of three‐dimensional visual space in the cat's striate cortex
Authors: Blakemore Colin
Published: December 2014

1. Binocularly driven single units were recorded in the cat's striate cortex. For each neurone the two monocular receptive fields were stimulated simultaneously in order to assess the optimal positioning of the image in both eyes to give the best binocular response.

2. The electrode was driven perpendicular to the surface of the brain to explore cortical columns, all the cells of which are known to have the same preferred target orientation.

3. All orientation columns were found to fit into one of two classes according to their binocular organization.

4. In a constant depth column the receptive fields of binocular neurones cover a small retinal area and they are laid out in almost identical arrays in the two eyes. Consequently, the horizontal disparity is practically the same for all the units. The depth column as a whole is viewing a thin sheet of visual space, a few degrees wide, floating at some distance from the cat. There may be about 0·6° disparity difference between neighbouring depth columns.

5. In a constant direction column the binocular units' fields are all super‐imposed on the retina contralateral to the hemisphere containing the column. In the ipsilateral eye they are more scattered horizontally. Therefore the horizontal disparity varies enormously from cell to cell and the column as a whole is viewing a cylinder of visual space directed towards the contralateral eye. Neighbouring direction columns may vary by about 4° in their oculocentric visual direction.

6. This columnar arrangement is probably important for space perception in the cat. Activity in only one depth and one direction column would specify the orientation and the three‐dimensional locus of an object in space.

7. The two types of column may be involved in the control of disjunctive and conjugate eye movements.
Daily changes in foetal and maternal blood of conscious pregnant ewes, with catheters in umbilical and uterine vessels
Authors: Comline R. S. , Silver Marian
Published: December 2014

1. Blood gas tensions, pH, packed cell volume (PCV) and the levels of glucose, fructose and lactic acid have been followed in foetal and maternal blood for periods of 3‐30 days in conscious ewes between 80 days gestation and term (∼ 147 days).

2. Blood samples were withdrawn through indwelling catheters placed in one or both umbilical vessels, a uterine vein and a maternal artery.

3. The success of the operation appeared to depend on the maintenance of maternal blood gas and pH levels within normal limits as well as on the final position of the tip of the catheter. The difficulties and limitations of the technique are discussed.

4. Foetal blood gas tensions, pH, PCV, lactic acid and glucose levels did not change markedly during the last 50–60 days of gestation. The fructose concentration fell during this period, the greatest change was between 100 and 120 days gestation.

5. Small fluctuations in PO2, PCO2 and pH in umbilical venous blood were associated with similar changes in the uterine vein, so that the gradients across the placenta appeared to remain constant.

6. Daily changes in maternal plasma glucose levels were reflected in similar changes in foetal plasma fructose and by much smaller alterations in the foetal glucose levels. The glucose concentration in the foetal plasma was less than 25% of that in maternal plasma.

7. The existence of a general relationship between maternal plasma glucose and foetal plasma fructose was masked by the independent fall in fructose levels with age. However, at any given stage of gestation, there was a significant correlation between foetal fructose and maternal glucose.

8. Few changes in the umbilical blood were associated with impending abortion or birth. Blood gas tensions remained constant, but a sharp fall in fructose levels often occurred 48 hr before any changes in pH, PCV and lactate concentration.

9. Present and other findings on conscious animals are compared with previous observations on acute, anaesthetized preparations.
Medullary activation of intercostal fusimotor and alpha motoneurones
Authors: Andersen P. , Sears T. A.
Published: December 2014

1. Studies have been made of the anatomical localization in the brain stem of the sites at which tetanic stimulation evoke inspiratory and expiratory apneusis.

2. The inspiratory responses arise from a relatively circumscribed region within the medulla corresponding to the nucleus reticularis giganto‐cellularis and ventralis which give rise to the medullary contingent of the long reticulo‐spinal tracts. Expiratory responses were obtained dorsal and lateral to this area, but not localized to any cyto‐architectonically distinct region of the reticular formation.

3. During the apneustic responses there was co‐activation of the intercostal alpha and fusimotor neurones with reciprocal inhibition of the antagonistic motoneurones. The threshold for activation of the fusimotor neurones was usually lower than for the alpha motoneurones.

4. Results with brief tetanic stimulation suggest that the long reticulospinal tracts are responsible for the apneustic responses and that the effects are mediated at segmental level over an interneuronal pathway.

5. The response of the intercostal motoneurones during the apneustic responses is shown to be dependent on the integrity of the dorsal spinal roots.
The origin and secretion of pancreatic juice bicarbonate
Authors: Case R. M. , Scratcherd T. , Wynne R. D'A.
Published: December 2014

1. The rate of secretion from a saline‐perfused preparation of the cat's pancreas is directly proportional to the perfusate bicarbonate concentration. When all bicarbonate is omitted, secretion completely or almost completely ceases.

2. Incorporation of [14C]bicarbonate into the perfusion fluid results in its prompt appearance in the juice. The radioactive label is concentrated four to five times in the juice just as the total juice bicarbonate is four to five times greater than perfusate bicarbonate.

3. These two observations suggest that about 95% of pancreatic juice bicarbonate is derived from perfusate (plasma) bicarbonate.

4. The inhibition of pancreatic secretion from the perfused gland by acetazolamide is similar to that observed in the intact animal.

5. There is a fall in pH and rise in PCO2 in the perfusion fluid leaving the gland which is greater during secretion than at rest.

6. It is therefore suggested that during secretion, hydrogen ions pass from the gland into the perfusate (plasma), thus increasing the production of carbon dioxide from circulating bicarbonate. This carbon dioxide diffuses into the cell, is rehydrated (partly under the influence of carbonic anhydrase) and finally is secreted, thus establishing the necessary gradient for the continued diffusion of carbon dioxide into the cell.
Presynaptic and post‐synaptic inhibition elicited in the cat's dorsal column nuclei by mechanical stimulation of skin
Authors: Andersen P. , Etholm B. , Gordon G.
Published: December 2014

1. Primary afferent depolarization (PAD), with a time course comparable with that of the PAD following limb nerve stimulation, was produced in the cuneate nucleus by mechanical stimulation of the skin of the ipsilateral forepaw. Brushing or blowing on hairs was as effective as any other form of stimulation and there was a rapid adaptation to a sustained stimulus. Up to 55% increase in excitability was produced by blowing on hairs.

2. The P‐wave and the PAD produced by mechanical stimulation were at a minimum in the rostral part of the cuneate nucleus and at a maximum 2‐6 mm caudal to the obex.

3. The distribution of the PAD produced in the gracile nucleus by blowing on the skin of the hind foot was studied by a technique allowing measurement of excitability changes near the terminals of single fibres. Minimal values were obtained rostral to the obex and maximal values 1‐4 mm caudal to the obex, a distribution matching that previously determined for single cells subject to surround inhibition.

4. Post‐synaptic inhibition was produced in the cuneate nucleus by gentle blowing on the ipsilateral forepaw. Up to 20% fall in excitability occurred in populations of cells tested by direct electrical stimulation. IPSPs lasting up to 160 msec were observed in single cells following light mechanical stimulation in the immediate neighbourhood of these cells' receptive fields. Blocking of antidromic invasion of single cells was occasionally produced by mechanical skin stimulation.

5. It is concluded that both pre‐ and post‐synaptic inhibition must be concerned in the phenomenon of afferent surround inhibition, though there was no evidence to indicate their relative roles, qualitatively or quantitatively.

6. It is shown that up to 20% reduction in transmission through the gracile or cuneate nucleus could be produced by blowing on the ipsilateral hind paw or forepaw respectively, measured as reduction in the area of the monophasically recorded lemniscal response. A single electrical stimulus to the skin of the contralateral forepaw reduced transmission through the cuneate nucleus by less than 5%.
The characteristics of the cochlear after‐potential studied in the guinea‐pig by perfusion and stimulation
Authors: Panayiotopoulos C. P. , Stopp Phyllis E.
Published: December 2014

1. An after‐potential which comprises three components can be recorded from scala tympani or scala vestibuli following the termination of a tone burst of more than 20–30 msec duration. The major component is of opposite polarity to the negative summating potential (SP) when recorded from scala tympani (ST) and of the same polarity as the SP when recorded from scala vestibuli.

2. The size of this after‐potential is dependent on the duration and strength of the tonal stimulus but not on the stimulus frequency or its rate of turn‐off.

3. A single short tone‐pip (10 msec) produces no visible after‐potential, but an after‐potential is seen following the end of a train of such pips separated by intervals of similar duration.

4. Replacement of the perilymph in ST by Ringer solution has a negligible effect on the cochlear responses. However, replacing the sodium ion in Ringer solution by lithium or adding DNP to the perfusate abolishes the after‐potential just as in the case of a neuronal after‐potential. The latter manoeuvre affects also the N1, CM and SP, while the former does not.

5. It is suggested that there exists an active membrane mechanism at the hair cell/nerve junction, which is responsible for the after‐potential and which can be influenced by perfusion of ST. It is further suggested that this neural mechanism makes a contribution to the recorded SP over and above the SP component due to non‐linear factors.
Development of the differential response to succinylcholine in the fast and slow‐twitch skeletal muscle of the kitten
Authors: Mann William S. , Salafsky B.
Published: December 2014

1. The response to SCh has been studied in anterior tibialis and soleus muscles of new‐born and neonate cat while, in a separate group of animals of similar ages, the end‐plate development in these muscles has been examined.

2. At birth, when the contraction times of the anterior tibialis and soleus are not statistically different, the anterior tibialis is 1·4 times more sensitive to SCh blocking action than the soleus, but both muscles were 20–40 times less sensitive than their adult counterparts.

3. With maturation, the ratio of the soleus/anterior tibialis contraction time increased to 2·7 while the ratio of the 50% blocking dose of SCh in the soleus/anterior tibialis increased to 2·8, the increases being parallel. The time to 50% recovery at 50% blocking doses of SCh was similar for both muscles at all ages although it was 3 times longer in new‐born and 1‐week‐old animals than in animals 3 weeks of age and older.

4. The areas of individual end‐plates from these muscles were very similar at birth but by three weeks of age the areas of end‐plates from the anterior tibialis were substantially greater than those obtained from soleus.

5. We have speculated that the relationship between SCh sensitivity and end‐plate area in fast and slow muscle may find its origins in the frequency of the MEPP.
Autonomic effector responses to stimulation of nucleus fastigius
Authors: Achari N. K. , Downman C. B. B.
Published: December 2014

1. In anaesthetized cats electrical stimulation of the nucleus fastigius caused cardiovascular responses, electrodermal responses of the paws and pupil dilation with retraction of the nictitating membranes.

2. The cardiovascular responses included rise of arterial pressure and peripheral vasoconstriction. Increase of pulse pressure and tachycardia also occurred.

3. The effects of sympathetic blocking drugs indicate that fastigial stimulation causes sympathetic discharge to the heart and to the peripheral vessels. There was no evidence of alteration of vagal activity.

4. Fastigial stimulation inhibited reflex bradycardia due to carotid sinus distension, vagal afferent stimulation or phenyl diguanide.

5. Fastigial and hypothalamic influences on cardiovascular responses could be evoked after severing the nervous pathways connecting the two.

6. The pressor response to fastigial stimulation was still present after bilateral division of the carotid sinus and vagus nerves.
Direct and indirect activation of the hippocampus by tubocurarine
Authors: Feldberg W. , Lotti V. J.
Published: December 2014

1. In cats anaesthetized with intravenous chloralose, tubocurarine was either perfused through the inferior horn of a lateral ventricle or applied by micro‐injection into the hippocampus, and the electrical activity was recorded from the surfaces of the occipital cortices and from the cannulae used for the perfusion or injection which, insulated except at their tips, served as recording electrodes as well.

2. With both methods, the hippocampus became activated by tubocurarine acting directly on the hippocampus. The activation resulted in an abnormal spike discharge interrupted from time to time by short bursts of fast activity, termed episodes, followed by periods of electrical silence during which no abnormal activity was recorded. This abnormal discharge was recorded in all leads. The spikes were negative when recorded from the surface of the hippocampus, but changed polarity when the electrode was lowered and penetrated the pyramidal cell layer, and on further lowering the electrode the positive spikes increased in voltage up to 15 mV and then decreased.

3. With both methods, signs of indirect activation of the hippocampus were observed when the tubocurarine set up foci of excitation in one of the following three areas of cerebral cortex which lie ventral to the hippocampus, the Area entorhinica, the Area perirhinica and the Area post‐splenialis. The foci of excitation resulted in a continuous discharge of negative spikes which were recorded in the leads from these areas only. A characteristic feature of the indirect hippocampal activation arising from the continuous discharge set up in the Area post‐splenialis was the periodicity. Activation lasting 20–60 sec occurred every few minutes or at shorter intervals, often leading to an episode.
Effects of changes of ionic environment on the negative after‐potential of the spike in rat uterine muscle
Authors: Ohashi H.
Published: December 2014

1. The spontaneous activity of the smooth muscle of rat uterus consists of bursts of spikes, each spike being followed by a negative after‐potential. The effect of changes in ionic environment on the negative after‐potential was investigated at various stages of pregnancy and in the non‐pregnant condition.

2. The amplitude of the negative after‐potential was the same in spontaneously generated and electrically evoked spikes. During repetitive discharge, whether spontaneous or in response to depolarizing current application, the amplitude of the after‐potential was smallest in the first spike of a burst and it increased gradually with repetition of discharge.

3. The decay of the negative after‐potential was slower than the passive return of the membrane potential to its resting level.

4. The amplitude of the negative after‐potential was larger in non‐pregnant uterus than during late pregnancy.

5. In pregnant uterus, the replacement of the Cl in the medium with benzene sulphonate transiently augmented the negative after‐potential and then gradually reduced it. Eventually, the negative after‐potential disappeared and, instead, a positive after‐potential was observed. This conversion took place without a noticeable change in the resting potential or in the initial falling phase of the action potential itself. Replacement of Cl with NO3 had no appreciable effect on the negative after‐potential.

6. In non‐pregnant uterus, the conversion of the negative to a positive after‐potential was never observed. However, in Cl‐deficient solution the size and duration of the negative after‐potential were reduced.

7. In Cl‐deficient solution (benzene sulphonate substitution), the decay of the electrotonic potential following the break of cathodal current became faster than that in normal solution. On the other hand the development of the anodic electrotonic potential became slower.

8. Replacement of the NaCl in the medium with sucrose converted the negative after‐potential to a positive after‐potential. On the other hand, reduction of Na only by replacement of NaCl with Tris‐Cl had no noticeable effect on the negative after‐potential.

9. It is concluded that the negative after‐potential of the spike in rat uterine muscle is largely due to an increase of Cl conductance of the membrane.
Alterations of synaptic action in chromatolysed motoneurones of the cat
Authors: Kuno M. , Llinás R.
Published: December 2014

1. Monosynaptic EPSPs in lumbosacral motoneurones undergoing chromatolysis were studied by intracellular recording from 7 to 20 days after section of the appropriate ventral roots of the cat.

2. The maximum monosynaptic EPSPs evoked in chromatolysed motoneurones by afferent volleys from the biceps‐semitendinosus or the triceps surae muscles ranged from 1·0 to 9·5 mV in amplitude. The time‐to‐peak of these EPSPs was 1·7 msec on the average. These values were significantly smaller and longer, respectively, than the amplitude and the time‐to‐peak of monosynaptic EPSPs observed in normal motoneurones. The long time‐to‐peak of EPSPs in chromatolysed motoneurones could not be accounted for by asynchronous transmitter release.

3. The mean number of unit EPSPs responding to a single afferent impulse (m) in chromatolysed motoneurones was comparable to that found in normal motoneurones.

4. The amplitude of unit EPSPs estimated from the mean EPSP amplitude and the m value following stimulation of a single afferent fibre was significantly smaller in chromatolysed motoneurones than in normal motoneurones. This difference was attributed to a difference in synaptic location.

5. The shape of monosynaptic EPSPs evoked in chromatolysed motoneurones by stimulation of single afferent fibres was analysed on the basis of Rall's compartment model. The analysis suggested that there is a lack of the excitatory synaptic input to the cell body in chromatolysed motoneurones.

6. Similar alterations were also found in IPSPs. The degree of change in synaptic responses evoked by stimulation of various pathways appears to depend on the synaptic location.

7. Following the study of the interaction of several inputs on the motoneurone and of their dependence on membrane potential, a tentative model of the synaptic distribution of different pathways is proposed.
Osmosensitive single neurones in the hypothalamus of unanaesthetized monkeys
Authors: Hayward James N. , Vincent Jean D.
Published: December 2014

1. We recorded with tungsten micro‐electrodes the activity of single neurones in the supraoptic nucleus (NSO) and adjacent regions of the hypothalamus while repeatedly injecting solutions of varying tonicity into the common carotid artery of trained, unanaesthetized monkeys who accepted the experimental restraints without anxiety.

2. Intracarotid injections of mildly hypertonic solutions of sodium chloride produced a characteristic behavioural response during and immediately after injection: e.e.g. ‘arousal,’ lip and tongue smacking, chewing, irregular sniffing respiration and associated mildly increased movement of face, eyes and body.

3. Of the 130 cells analysed during hypertonic intracarotid injections, 105 (81%) were osmosensitive. Twenty‐five (19%) of the cells studied during similar injections were non‐osmosensitive. On the basis of the anatomical location of the cells, the pattern of discharge to intracarotid osmotic stimuli and the response to arousing sensory stimuli, we divided the osmosensitive cells into two major groups, ‘specific’ and ‘non‐specific’ osmosensitive cells.

4. Fifty‐two (50%) of the osmosensitive cells we labelled ‘specific’ because they responded to an intracarotid injection of hypertonic sodium chloride, generally did not respond to non‐noxious arousing sensory stimuli and were located in or near the supraoptic nucleus. We found two subtypes of these ‘specific’ osmosensitive cells: (a) twenty‐one (20%) NSO cells with ‘biphasic’ responses, that is, acceleration followed by inhibition; (b) thirty‐one (30%) cells in the immediate perinuclear zone of the NSO with ‘monophasic’ responses, subdivided into twenty‐one (20%) cells that accelerated and ten (10%) that were inhibited.

5. Fifty‐three osmosensitive cells (50%), located diffusely in the anterolateral hypothalamus, were ‘non‐specific’, responding both to intracarotid injections of hypertonic sodium chloride and also to sensory stimuli that were mildly arousing. Two groups of ‘non‐specific’ osmosensitive cells showed monophasic responses; thirty‐five (34%) cells accelerated and seventeen (16%) of them were inhibited.

6. The ‘monophasic’ specific osmosensitive neurones lying in the immediate perinuclear zone of the supraoptic nucleus in the primate could conceivably be the ‘osmoreceptors’ of Verney. The ‘biphasic’ specific osmosensitive neurones in the NSO may well represent the secretory cells of this system. From our data, the ‘non‐specific’ osmosensitive neurones, scattered diffusely in the anterolateral hypothalamus, have little to do with osmoregulation. Some of these cells located in the perinuclear zone of the NSO could act as interneurones, however, conveying afferent input to the osmoreceptor‐secretory complex of the supraoptic nucleus.
Variations in deep body temperature in the young unrestrained pig over the 24 hour period
Authors: Ingram D. L. , Legge K. F.
Published: December 2014

1. The temperature near the carotid artery has been measured in the unrestrained pig by means of radiotelemetry. When the animals were housed singly under constant conditions of temperature and lighting the temperature rhythm appeared to be related only to the time of feeding. A similar record was obtained from temperature measurements made in the hypothalamus.

2. Over the range of ambient temperatures 10–30° C the mean body temperature was 38·8° C. No consistent variation occurred with ambient temperature, but on initial transfer from 10 to 30° C ambient temperature the body temperature decreased, while on initial transfer from 30 to 10° C it increased.

3. When one pig was housed in a hut with a small outside yard a nychthemeral rhythm was sometimes superimposed on that imposed by feeding. When two pigs were kept in a paddock containing a hut the nychthemeral rhythm was more pronounced.

4. It is concluded that in the pig there is very little innate circadian temperature rhythm and that the temperature variations seen are related chiefly to feeding and activity.