bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction of cortical evoked potentials in the rat
Authors: Holmes O. , Short A. D.
Published: December 2014

1. Unitary and mass potentials were recorded with glass micropipettes at different depths in and around the primary somatosensory area of the cortex in rats anaesthetized with urethane; in addition, surface mass potentials were recorded with chlorided silver ball electrodes. Potentials were evoked by stimuli to the contralateral forepaw and the contralateral cortex. Observations were confined to potentials evoked within 20 msec of stimulation.

2. If forepaw stimuli were applied at times when the cortex was not showing spontaneous activity, one component of the evoked response was a widespread depth negativity. This was accompanied by a smaller surface positivity which had the same time course. It could be recorded over the same area of cortex. Unitary activity was found with the same latent period and spatial distribution as the depth negativity. These components of the evoked mass and unitary responses to forepaw stimulation were absent if times of spontaneous cortical activity were chosen for delivering the stimuli.

3. Contralateral cortical stimuli evoked mass activity similar to the component of the mass response to forepaw stimulation described in 2. Stimuli given simultaneously to the two sites elicited less unitary activity than the sum of the unitary activity evoked by the two stimuli separately. The mass activity exhibited the interactions which would be expected on the hypothesis that it is generated by the unitary activity. The time course of the interaction is described.

4. The interaction was confined to the components of the evoked potentials which were only present if stimuli were applied when the cortex was quiescent. Stimuli applied when the cortex was active evoked mass and unitary potentials which showed no interaction.
Intrapulmonary receptor response to changes in airway‐gas composition in Gallus domesticus
Authors: Fedde M. R. , Peterson D. F.
Published: December 2014

1. A unidirectional, artificial ventilating system was used to observe respiratory and neural responses to changes in CO2 concentration in pulmonary airways of the chicken.

2. Sectioning any of the three pulmonary branches of the vagus slowed the respiratory response to sudden removal of CO2 from unidirectional ventilating gas stream.

3. The impulse frequency of CO2‐sensitive units was inversely related to the CO2 content in the ventilating gas stream.

4. Abrupt elimination of CO2 from the ventilatory gas stream caused a transient burst of activity from CO2‐sensitive receptors, which quickly adapted to a constant discharge frequency. Fifty percent of the units responded within 0·35 sec after CO2‐free gas reached the lungs. The neural response to abrupt re‐addition of CO2 to the gas stream was less rapid.

5. Acetylcholine or NaCN injected into the pulmonary artery had no apparent effect on the discharge of CO2‐sensitive receptors. Veratridine temporarily reduced discharge and occasionally produced short, rapid bursts of activity.

6. Hypoxia and hyperoxia (5% and 80% O2) produced no significant change in the discharge of CO2‐sensitive receptors.

7. Carbon dioxide‐sensitive units in spontaneously breathing chickens were silenced by adding 10% CO2 to the inspired gas; the units responded vigorously to inflation of the respiratory system with a gas containing no CO2 but remained silent during inflation with gas containing 15% CO2. Units insensitive to CO2, which increased their impulse frequency during inflation regardless of the CO2 content of the inflating gas, also were observed.
Effects of prolonged saline exposure on water, sodium and urea transport and on electron‐microscopical characteristics of the isolated urinary bladder of the toad Bufo bufo
Authors: Ackrill P. , Dixon J. S. , Green R. , Thomas S.
Published: December 2014

1. A comparison was made of various transport properties and electron‐microscopical characteristics of isolated urinary bladders from toads (Bufo bufo) maintained in either tap water or 0·7% saline (0·7 g NaCl in 100 ml. H2O) for 10 days to 2 months.

2. In the absence of Pitressin, isolated bladders from saline‐adapted toads showed:

(a) markedly, and significantly, lower osmotic water flow;

(b) moderately, but not significantly, lower urea permeability;

(c) no significant change in net sodium transport (measured as short‐circuit current, Isc); and

(d) significantly smaller intercellular space/mucosal cell ratios in electron‐micrographs.

3. Differences in the transport and electron‐microscopical characteristics between bladders from water‐exposed and saline‐adapted toads became more evident in the presence of exogenous Pitressin (10 m‐u./ml. serosal solution):

(a) the stimulating influence of Pitressin on osmotic water flow, short‐circuit current and urea permeability was considerably smaller in bladders from saline‐adapted toads than in those from water‐exposed toads;

(b) the influence of Pitressin on short‐circuit current was reduced more profoundly than that on either water flow or urea permeability;

(c) the Pitressin‐induced increment in intercellular space/mucosal cell ratio was significantly smaller in electron‐micrographs of bladders from saline‐adapted toads than in those from water exposed toads.

4. The effects of saline adaptation are discussed in relation to decreased permeability of mucosal membrane barriers.
Neuronal and subcellular localization of acetylcholine in the posterior pituitary of the rabbit
Authors: Lederis K. , Livingston A.
Published: December 2014

1. Acetylcholine and neurohypophysial hormones were measured in subcellular fractions of rabbit neurohypophysis.

2. Differential and density gradient centrifugation, followed by bio‐assay and electron microscopy were used to separate and characterize the subcellular particles, or isolated nerve endings.

3. Acetylcholine in the rabbit neurohypophysis was found to occur in small vesicles of about 40 nm diameter which had similar characteristics to the synaptic vesicles from central nervous tissue.

4. Examination of intact nerve endings isolated from the rabbit neurohypophysis indicated that at least some acetylcholine and neurohypophysial hormones occurred in separate nerve endings.
The effect of insulin on the kinetics of pentose permeation of the rat heart
Authors: Fisher R. B. , Gilbert J. C.
Published: December 2014

1. The kinetics of permeation of pentoses into the rat heart in the presence of insulin are similar in nature to those in the absence of insulin.

2. The half‐saturation concentration of the carrier system is increased by insulin in a manner which is independent of insulin concentration.

3. The Vmax of the carrier system is altered by insulin in a graded fashion: at low insulin concentrations it may be lower than in the absence of insulin.

4. It is shown that these effects can be accounted for if insulin combines with the carrier and thereby increases either the rate constant governing the mobility of the carrier in the membrane or the rate constant governing dissociation of the sugar‐carrier complex.

5. The effects cannot be accounted for by a graded action of insulin on the membrane as distinct from the carrier.
Sodium transport and short‐circuit current in rat colon in vivo and the effect of aldosterone
Authors: Edmonds C. J. , Marriott Jane
Published: December 2014

1. A method for measurement of short‐circuit current and for applying a voltage clamp to segments of rat colon in vivo is described.

2. The mucosa behaved as an ohmic resistor of average resistance 154 Ω/cm2 although brief transient effects were frequently observed. Tissue resistance was independent of considerable changes in ionic strength and composition of the luminal solution.

3. The short‐circuit current averaged 120 μA/cm2 in normal rats. Aldosterone intravenously raised the p.d., short‐circuit current rising proportionately and tissue resistance being unchanged. The effects of various modifications of the intraluminal solution in respect to composition, hydrostatic pressure and pH were examined. An increase in the osmolality of the luminal solution sufficient to abolish water absorption did not affect p.d. or short‐circuit current.

4. The short‐circuit current measured with 150 m
M‐NaCl in the lumen was almost completely accounted for by active Na absorption both in normal and aldosterone‐treated rats. The changes in Na efflux rate produced by voltage clamping suggested that only part of Na efflux was due to simple diffusion. With lower [NaCl] in the lumen, the short‐circuit current exceeded that atributable to active Na absorption, the discrepancy increasing with reduction of [NaCl].

5. The luminal [Na] at which Na efflux and influx rates were equal was reduced by aldosterone, an effect which is probably responsible for the low stool [Na] of aldosterone treated animals. The significance of this finding in terms of the mode of action of aldosterone is discussed.
Rate constants associated with changes in sodium conductance in axons perfused with sodium fluoride
Authors: Chandler W. K. , Meves H.
Published: December 2014

1. Membrane currents during step depolarizations were measured in axons which were perfused with 300 m
M‐NaF and placed in K‐free artificial sea‐water, −0·3–4° C. The Na conductance was fitted by the modified Hodgkin—Huxley model, gNa = ḡNam3(h1 + h2). Changes in h1 and h2 were assumed to follow [Formula: see text] where x represents the inactive state.

2. The rate constants and steady‐state values for m were in agreement with the Hodgkin—Huxley equations except that the experimental relationship of m∞3 against V was shifted 10–15 mV in the negative direction. This discrepancy, which was not found in an experiment with choline sea‐water, can be explained on the basis of a resistance in series with the membrane between the voltage measuring electrodes.

3. At 0° C the rate constants (in msec−1) associated with changes in h1 and h2 were fitted using the following equations: βh1 = 0·5/{exp [− (V + 32)/10] + D1exp (− V/V1)}, αh2 = pexp (V/V2), βh2 = pexp (V/V2 − V/23·5) + pD2, with the condition that at 0 mV, (αh2 + βh2) = p(D2 + 2) = 0·55 msec−1. The experiments gave average values D1 = 3·6, V1 = 240 mV, p = 0·08 msec−1 and V2 = 70 mV. The average value of ḡNa was 66 mmho/cm2.

4. At negative voltages where m∞3 against V is steep, the points for βh1 and αh2/βh2 from axons in Na sea‐water were not fitted well by the above equations whereas data from an axon in choline sea‐water were. These discrepancies can be explained on the basis of a series resistance.

5. Measurements made at 16–17° C indicated that ḡNa has a Q10 of 1·6, τm−1 a Q10 of 2·8 and βh1 a Q10 of 3·5. The ratio αh2/βh2 was decreased relative to the value at 0° C and could be fitted by using Q10 = 0·6.

6. Measurements made with 250 m
M‐NaF + 50 m
M‐KF inside gave rate constants which were very similar to those obtained with 300 m
M‐NaF. Perfusion with 300 m
M‐KF appeared to double the value of βh1, relative to that obtained with 300 m
M‐NaF, and to reduce αh2/βh2 by about half.

7. The voltage dependence of αh2 makes it likely that following depolarization recovery from the inactive state x occurs via x → h1 rather than x → h2 → h1.
Relationships between disaccharide hydrolysis and sugar transport in amphibian small intestine
Authors: Parsons D. S. , Prichard J. S.
Published: December 2014

1. A study is described of the relationships which exist between disaccharide hydrolysis and glucose transport in the small intestine of Rana pipiens and Bufo vulgaris. The experiments were undertaken on the intestine perfused in vitro through the vascular system and with fluid circulating through the intestinal lumen. For this system it was found that, with [U‐14C]glucose in the intestinal lumen, the apparent specific activity of the glucose appearing in the vascular effluent was not significantly different from that in the lumen.

2. Changes of ionic composition of vascular and luminal fluids, and the presence of phloridzin or strophanthin, had little effect upon the maltase activity in situ in R. pipiens, although this activity was somewhat reduced when the sodium of the intestinal lumen was replaced by lithium. In contrast, in all cases a marked reduction was found in the rate of glucose translocation in the vascular effluent.

3. With Tris substituted for the luminal sodium, there was evidence of a competitive inhibition of the maltase activity in situ by the buffer cation. At the same time, the rate of glucose translocation into the vascular effluent was but little affected and there was an apparent increase in the efficiency with which the cellular systems responsible for the translocation were able to capture the glucose liberated.

4. It was found that competition for transepithelial translocation occurred between the glucose initially present in the intestinal lumen, and glucose derived from either maltose or trehalose. There was no evidence for competition for hydrolysis between maltose and trehalose, yet the glucose units derived from these two disaccharides competed with each other for translocation.

5. The significance is discussed of the finding that it is possible to dissociate the processes of disaccharide hydrolysis from those underlying the translocation of hexose units into the vascular effluent. It is suggested that monosaccharide units released by the hydrolysis of disaccharide molecules have access to a pool of glucose which is equally accessible to glucose free in the intestinal lumen. It is also suggested that the rate of transport of glucose from the pool into the vascular effluent (i.e. glucose translocation) is determined by the concentration of glucose within the pool. From consideration of the properties of a model operating upon these principles, it is possible to predict the relative contribution of disaccharides and monosaccharides in the intestinal lumen to the glucose appearing in the vascular effluent. The experimentally determined contributions of the two sources are very similar to those predicted from the model. The implications of possible sites for the postulated pool are discussed.
Some reflective properties of the tapetum lucidum of the cat's eye
Authors: Coles J. A.
Published: December 2014

1. Observation of the fresh, isolated tapetum of the cat with a low‐power microscope showed it to be composed of multilayer reflectors (domains) each being less than 6 μm in diameter. It is concluded that these are subdivisions of the intracellular bundles of rodlets seen in electron micrographs.

2. Apparatus was devised for illuminating a single domain with a pencil of white light and observing the colour and direction of the reflected light.

3. Those domains which lie near the vitreal surface of the tapetum tend to reflect blue light and deeper ones reflect longer wave‐lengths; this is attributed to differences in the layer spacings of the domains.

4. Each domain has a set of reflecting planes lying within 15° of the general plane of the tapetal surface. In addition, many domains have surfaces inclined to these at angles greater than 20° which also can reflect visible light.

5. The mechanism of reflexion is discussed in relation to the latticelike structure of the domain.

6. It is suggested that under some conditions the nature of the tapetum may lead to significant local variations in the spectral sensitivity of the visual system.
Factors influencing the uptake of [125I]polyvinyl pyrrolidone by the intestine of the young rat
Authors: Clarke Rufus M. , Hardy R. N. , Oakes D.
Published: December 2014

1. The uptake of orally administered [125I]polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000 (K. 60) by the small intestine of young rats was determined 4 hr after feeding by measurement of the radioactivity remaining in the wall after flushing out the intestinal contents.

2. PVP uptake was proportional to the administered dose of PVP for doses of 1 mg and below. At higher doses, uptake was no longer in linear proportion, suggesting a degree of saturation of uptake.

3. Litters were reared in one of three environmental temperatures: 13, 20 and 30° C, and were tested to determine the age at which PVP uptake ceased (‘closure’). The results were evaluated statistically (see Appendix).

4. There was no significant difference between the time of closure in animals reared at 20 and 30° C, but, relative to these groups, closure was significantly delayed, by approximately 48 hr, in animals reared at 13° C.

5. Once closure had begun, there were no significant differences in the rate of decline in PVP uptake with age between animals reared at different environmental temperatures.

6. Separation of the young rats from their mother both before and after the test‐feed of PVP caused a considerable reduction in PVP uptake. Provided that the body temperature of the young rats was maintained, the main factor contributing to the reduction in PVP uptake appeared to be the absence of milk, rather than separation from the mother.
Spinal and supraspinal components of the reflex discharges into lumbar and thoracic white rami
Authors: Sato Akio , Schmidt Robert F.
Published: December 2014

1. In chloralose anaesthetized cats reflex discharges in thoracic and lumbar white rami were elicited by single shock stimulation of intercostal, spinal and hind limb nerves.

2. In animals with an intact neuraxis single stimuli of sufficient strength usually elicited a white rami mass discharge having two distinct components. Following spinal transection only the late reflex component disappeared.

3. The early (spinal) reflex component had its largest amplitude if the afferent volley entered the spinal cord at the same or an adjacent segment of the white ramus under observation, whereas the size of the late (supraspinal) component was rather independent of the segmental level of the afferent input.

4. It was concluded that somatic afferent volleys have a twofold action on the sympathetic nervous system: a more generalized action via the supraspinal sympathetic reflex centres and a more circumscribed action on the preganglionic neurones at the segmental level.
Spontaneous activity of cerebellar Purkinje cells and their responses to impulses in climbing fibres
Authors: Latham Ann , Paul D. H.
Published: December 2014

1. Spontaneous discharges and evoked responses of Purkinje cells have been studied in the anterior lobe vermis of the cerebellum in cats anaesthetized with thiopentone sodium.

2. Spontaneous activity was of two kinds: (a) single spikes which occurred in long trains and were discharged at average frequencies of 50–125/sec and (b) burst responses due to climbing fibre (CF) activation of the cell. These occurred at an average frequency close to 1/sec.

3. CF responses were evoked by either stimulation of the Aβ fibres of the superficial radial nerve (SRN) or by an electrode inserted into the deep white matter near the fastigial nucleus (JF electrode).

4. A suppression of the discharge of single spikes was frequently observed to follow a CF response, whether it occurred naturally or was produced by a stimulus. These pauses in spontaneous discharge (post‐CF pause) lasted for approximately 100 msec, but they did not have a one‐to‐one relationship with the CF responses. Occasionally a pause in the spontaneous activity was elicited by stimuli that failed to evoke the cell.

5. For a period following a peripheral stimulus, a Purkinje cell could not be further excited by a second peripheral stimulus (interaction). JF stimulation could still excite the cell. Evidence was obtained that there was no significant inhibition during the period of depressed excitability to peripheral stimulation.

6. The control over the input of activity to the cerebellum through the CF system appears to be imposed at an extra‐cerebellar site. The olivary nuscles was suggested as a strong possibility.

7. Some possible mechanisms responsible for the post‐CF pause were discussed. Disfacilitation of Purkinje cells by suppression of granule cell discharges seems to give the best fit to the data.
Brown adipose tissue metabolism in vivo and serum insulin concentrations in rabbits soon after birth
Authors: Hardman M. J. , Hull D. , Milner A. D.
Published: December 2014

1. In rabbits kept unfed for 4 or 24 or 48 hr after delivery by Caesarean section at term, noradrenaline infusion (I.V. for 30 min) caused a similar increase in oxygen consumption but the increase in serum free fatty acid concentration was greatest in rabbits kept unfed for 48 hr.

2. The brown adipose tissue of anaesthetized rabbits under 3 hr old took glucose from the circulation but did not release fatty acids. In similar rabbits noradrenaline infusion stimulated the tissue to generate heat, but there was no release of fatty acids even though the rate of triglyceride hydrolysis was high (as judged by the rate of glycerol release).

3. In rabbits kept unfed for 48 hr from birth in a warm environment, brown adipose tissue released small amounts of fatty acids but continued to take glucose from the circulation. Heat production in response to noradrenaline infusion was accompanied by an increased release of fatty acids. The fat content of the brown adipose tissue did not fall with starvation.

4. The mean serum insulin concentration of rabbits at birth was 54 μu./ml. compared to 23 μu./ml. in the mother. In new‐born rabbits kept unfed for 48 hr the insulin concentration had fallen to 14 μu./ml.

5. It is concluded (i) that at birth brown adipose tissue has the capacity to generate heat but the tissue is slow to release its stores of fat in response to starvation, (ii) that brown adipose tissue has a high rate of glucose uptake even during starvation and (iii) that the high circulating concentration of insulin may be responsible for the tissue's slow adaptation to the demands of starvation.
Micropuncture studies of the electrochemical aspects of fluid and electrolyte transport in individual seminiferous tubules, the epididymis and the vas deferens in rats
Authors: Levine Norman , Marsh Donald J.
Published: December 2014

1. Micropuncture and micro‐analytical techniques were used to study some of the electrochemical aspects of fluid and electrolyte transport in single seminiferous tubules, the epididymis and vas deferens.

2. Seminiferous tubules contain a fluid that is slightly hypertonic to plasma, has a high potassium and chloride ion concentration, a lower sodium ion concentration and is slightly acidic relative to plasma.

3. The lumen of the seminiferous tubule is about 5 mV negative to a Ringers bathing solution.

4. Potassium and chloride ions enter the seminiferous tubule lumen against an electrochemical gradient, while the gradient for sodium ion favours its entry. This does not preclude possible active transport of sodium ion.

5. Between the seminiferous tubules and the beginning of the caput epididymis spermatocrit changes indicate that about 50% of the fluid leaving the testis is reabsorbed. Chloride ion and potassium ion are reabsorbed in concentrations greater than in lumen while sodium ion is reabsorbed in a concentration equal to that in the lumen. This region is also the site of intense hydrogen ion secretion.

6. The region between the seminiferous tubules and the caput is isopotential. Reabsorption of sodium and chloride ions are against electrochemical gradient. Potassium ion reabsorption is favoured by the electrochemical gradient.

7. Osmolar and electrical considerations indicate the probable secretion of organic acids between the seminiferous tubules and the caput epididymis.

8. Between the caput and the vas deferens 50% of the remaining fluid is reabsorbed. Sodium ion is reabsorbed in concentrations much greater than in lumen, potassium ion enters the lumen and the pH rises. Sodium reabsorption in this region is essentially independent of chloride reabsorption.

9. The corpus epididymis is 20 mV negative to a Ringers bathing medium while the beginning of the vas deferens is 27 mV negative. Reabsorption of sodium ion is against an electrochemical gradient as is potassium entry. Osmolality data and the concentration of sodium in the reabsorbate require further secretion of organic compounds in this region.
Some properties of an SH group essential for choline transport in human erythrocytes
Authors: Martin K.
Published: December 2014

1. The choline transport system in human erythrocytes is inhibited by N‐ethylmaleimide (NEM), cystamine and p‐chloromercuribenzene sulphonic acid (PCMBS).

2. External choline increases the rate of inhibition by NEM and cystamine but decreases the rate of inhibition by PCMBS. Intracellular choline has the opposite effect.

3. Competitive inhibitors of choline transport that are not themselves transported protect the carrier against all three thiol reagents.

4. Some thiol reagents with a very low lipid solubility do not inhibit choline transport.

5. The transport inhibition by cystamine is reversed by various reducing agents.

6. Cystamine protects the transport system against NEM and PCMBS.

7. It is suggested that NEM and cystamine react with an SH group of the transport system and that this SH group is more reactive when the carrier is facing inside. PCMBS penetrates erythrocytes only very slowly and is assumed to react preferentially with the outward facing carrier.

8. The reactive SH group seems to be located in a lipophilic environment.
The effect of splanchnic nerve stimulation on gastric acid secretion and mucosal blood flow in the anaesthetized cat
Authors: Reed J. D. , Sanders D. J. , Thorpe Valerie
Published: December 2014

1. Electrical stimulation of the vagus nerves produced a parallel increase in gastric acid secretion and gastric mucosal blood flow.

2. Gastric acid secretion and mucosal blood flow, stimulated by pentapeptide infusions or by vagal stimulation, were markedly and equally reduced by electrical stimulation of splanchnic nerve fibres.

3. The splanchnic stimulated reduction in acid and mucosal blood flow occurred only when the rise in blood pressure, normally associated with splanchnic stimulation, was prevented by inclusion of a pressure reservoir in the circulation.

4. There was evidence that the effect of the splanchnic nerves was not mediated by release of adrenaline from the adrenal medulla.
The intracellular localization of kallikrein, trypsin and amylase in dog pancreas
Authors: Bhoola K. D. , Dorey Gundula
Published: December 2014

1. Subcellular organelles containing kallikrein (‐ogen), trypsinogen and amylase have been isolated from homogenates of dog pancreas and found on discontinuous sucrose density‐gradients to equilibrate with 1·7–1·775
M sucrose.

2. The electron microscopic appearance of the isolated enzyme‐containing organelles appeared to be identical with that of the secretory (zymogen) granules seen in situ in the acinar cells of the pancreas.

3. The sequence of events associated with the storage and intracellular transport of pancreatic secretory enzymes is reviewed. The results obtained in this study have been used to delineate the probable intracellular pathway taken by kallikrein, trypsin and amylase from synthesis to secretion.

4. The physiological role of the glandular kallikreins is discussed.
Hyperplasia of the gastric mucosa during pregnancy and lactation in the rat
Authors: Crean G. P. , Rumsey R. D. E.
Published: December 2014

1. The growth of the gastric mucosa during pregnancy and afterwards has been studied by comparing the stomachs of rats, killed at weekly intervals after impregnation, with the stomachs of virgin rats of the same age and starting weight. The rate of growth of the gastric mucosa in both groups was determined from the changes observed in the weight of the whole stomach, the weight and surface area of the fundus, the volume (mass) of the fundic mucosa and the total parietal and total peptic cell populations.

2. Hyperplasia of the gastric mucosa occurred during pregnancy and lactation, the effect being characterized by increases in the surface area and volume (mass) of the gastric mucosa, and in the total parietal and total peptic cell populations.

3. The data suggest that the effect developed shortly after conception. Hyperplasia of the gastric mucosa continued throughout pregnancy and reached maximal values after the second week of lactation and waned thereafter; the maximal changes obtained for individual observations such as surface area and the total parietal and total peptic cell populations represented increases of the order of 40% above corresponding control values.

4. From the observations that were made on food intake it seemed unlikely that the hyperplasia of the gastric mucosa was due to hyperphagia. It also seemed unlikely that the effect could be accounted for by the increase that occurred in body weight during pregnancy.
Recurrent inhibition from motor axon collaterals of transmission in the Ia inhibitory pathway to motoneurones
Authors: Hultborn H. , Jankowska Elẓbieta , Lindström S.
Published: December 2014

1. The effects of impulses in recurrent motor axon collaterals on reflex transmission from different types of primary afferents to motoneurones were investigated in the cat by conditioning of PSPs evoked in motoneurones.

2. IPSPs evoked by volleys in large muscle spindle (Ia) afferents were effectively decreased when preceded by an antidromic stimulation of ventral roots. Some IPSPs from group II muscle afferents and low threshold cutaneous afferents were also slightly depressed, while other PSPs were unaffected.

3. The depression of the IPSPs could be evoked by antidromic volleys, which produced neither conductance changes in the motoneurones nor depolarization of Ia afferent terminals.

4. The effect on the Ia IPSPs is most likely due to post‐synaptic inhibition of the Ia inhibitory interneurones, evoked through α‐motor axon collaterals and Renshaw cells. The depression of some IPSPs from flexor reflex afferents is explained by a convergence of excitatory effects from these afferents on the Ia inhibitory interneurones.

5. The results indicate a selective recurrent control from motor axon collaterals of the interneurones in the reciprocal Ia inhibitory pathway to motoneurones.
The Purkinje shift in cat: extent of the mesopic range
Authors: Hammond P. , James C. R.
Published: December 2014

1. The mesopic range, defined for cats with fully dilated pupils, extends from −1·0 to +1·4 log cd/m2. The technique employed involves measurement of the relative shift in threshold with adaptation level, between two wave‐lengths respectively selective for cones and rods at threshold. The magnitude of this shift is compared with that predicted from the Dartnall nomogram for visual pigments 556 and 507 (the in situ cone and rod absorption maxima).

2. The result is based on monochromatic increment threshold determinations for 149 on‐centre or off‐centre fibres, isolated in the optic tract posterior to the chiasma, under a variety of adaptation levels. All units included receive dual input — from 500 nm rods and from a single class of cones with maximum sensitivity at 556 nm. No units receive input from 450 nm cones; six units with input mediated purely by rods are excluded from the sample.
The effects of hypercapnia, hypoxia and ventilation on the baroreflex regulation of the pulse interval
Authors: Bristow J. D. , Brown E. B. , Cunningham D. J. C. , Goode R. C. , Howson M. G. , Sleight P.
Published: December 2014

1. The effects of moderate degrees of hypercapnia in hypoxia and in hyperoxia on the baroreceptor‐cardiodepressor reflex have been studied in nine normal men.

2. The beat‐by‐beat relation between pulse interval (I) and systolic pressure (P) during transient elevations of arterial pressure induced by intravenous injections of angiotensin II and phenylephrine was used to assess the sensitivity (ΔI/ΔP) and setting (I at a single reference arterial pressure) of the reflex.

3. There was no consistent change in reflex sensitivity in any of the conditions studied.

4. In hyperoxia (PA, O2 ∼ 200 torr) hypercapnia was associated with significant re‐setting of the reflex in the direction of tachycardia. The extent of the re‐setting was correlated with the degree of hypercapnia and with the accompanying increase in breathing.

5. When hyperoxia with hypercapnia was replaced by hypoxia (PA, O2 ∼ 55 torr) with hypercapnia (which causes substantial arterial chemoreceptor activity), pulse interval at constant arterial pressure was further decreased.

6. The tachycardia of hypoxia could not be accounted for by change of arterial pressure, PA, CO2 or pulmonary ventilation, since it was most clearly demonstrable at constant values of pressure and either PA, CO2 or ventilation.
Removal of an insulin inhibitor from the rat heart by perfusion
Authors: Young D. A. B.
Published: December 2014

1. Insulin‐stimulated efflux of galactose from the perfused rat heart increased when the Krebs bicarbonate medium was prepared with gassing with CO2.

2. Analysis of the kinetics of efflux in the light of the carrier theory is used to justify the interpretation of the increased rate of efflux as an increased response to insulin.

3. With medium prepared with CO2 gassing, the photoperiodic reduction in insulin response seen previously was not found; but it was seen when cardiac contractility was reduced or eliminated during the period of galactose loading.

4. The relation between the increase in galactose efflux with insulin and the insulin concentration conforms to the Michaelis—Menten equation, for perfusates prepared both with and without CO2 gassing, indicating in the latter case the presence of a competitive inhibitor of insulin.

5. It has been previously shown that preparing the perfusate with CO2 gassing results in increased contractility of the perfused heart and a much increased rate of interstitial washout. The conditions of the enhanced response to insulin are consistent with the removal of the inhibitor from the heart due to the increased rate of interstitial washout. The possible role of the inhibitor in the control of lipid and carbohydrate metabolism is discussed.
The effect of quinine on tension development, membrane potentials and excitation‐contraction coupling of crab skeletal muscle fibres
Authors: Huddart H.
Published: December 2014

1. The effect of quinine on tension development and membrane potentials of crab skeletal muscle was examined using strain gauges and intracellular electrodes.

2. In low concentrations (0·1–0·5 m
M), quinine caused transient potentiation of twitch tension which then rapidly declined along with progressive depression of the tetanus. These actions are correlated with the decline of both action and resting potentials during quinine treatment.

3. In moderate concentrations (1–5 m
M), quinine induced phasic contractures, but the attendant depolarization made the muscles refractory to stimulation and potassium activation, but not to caffeine activation.

4. Quinine did not induce contractures in depolarized muscle, which suggests that the action of quinine in inducing calcium release from the sarcoplasmic reticulum may be blocked by potassium depolarization, unlike the calcium‐releasing action of caffeine. Quinine appeared to have no effect on the mechanical threshold of crab skeletal muscle fibres.

5. To explain its depression of contractility in crab muscle, it is suggested that quinine may deplete the calcium store of the sarcoplasmic reticulum, leading to extinction of the terminal stages of the excitation—contraction coupling process and loss of contractility.
Noradrenaline action on nerve terminal in the rat diaphragm
Authors: Kuba K. , Tomita T.
Published: December 2014

1. The mechanism by which noradrenaline increases the release of transmitter from the nerve terminal was investigated in the rat diaphragm.

2. Increase of the frequency of the miniature end‐plate potential (m.e.p.p.) was exponential when plotted against the intensity of a constant current which depolarized the nerve terminal. Noradrenaline (5 × 10−6 g/ml.) did not change the slope of the curve showing the relationship between the logarithm of the frequency of m.e.p.p.s and the depolarizing current (m.e.p.p.‐current relationship), but simply shifted the curve along the axis of the current towards weaker intensities.

3. End‐plate potentials (e.p.p.s) were evoked by passing a brief depolarizing pulse to the nerve terminal in the presence of tetrodotoxin (1 × 10−7 g/ml.). A sigmoidal relationship was obtained between the amplitude of e.p.p. and the intensity of the current pulse (e.p.p.‐current intensity relationship). Noradrenaline (5 × 10−6 g/ml.) shifted the e.p.p.‐current intensity relationship along the axis of the current intensity to smaller values, without any change in the maximum amplitude of e.p.p.s.

4. The frequency of m.e.p.p. was increased, as the [Ca]0 was raised from 0·01 to 7·5 m
M. An increase in [Ca]0 beyond the normal concentration (2·5 m
M) had no remarkable effect on the action of noradrenaline. However, when [Ca]0 was reduced, the action of noradrenaline became weaker.

5. A kinetic model in which the transmitter release is modified by the binding of Ca with a specific site in the nerve terminal may explain the results. According to this model, noradrenaline did not change the dissociation constant of the reaction between Ca and the specific site (X), but increased the rate constant of the Ca complex (CaX) for releasing acetylcholine.

6. The action of noradrenaline was potentiated when [Na]0 was reduced, and suppressed when [Mg]0 was increased. The results may be summarized: that noradrenaline augments the probability of release of transmitter quanta from the resting nerve terminals and that this action can be intensified by first raising the probability of release by some other means. Depolarization of the nerve terminals by current, increase of the external Ca concentration, decrease of Na and decrease of Mg are all effective in promoting the action of noradrenaline.
Inhibition of gastric secretion by atropine in conscious rats
Authors: Johansson Irene , Lundell L. , Svensson S. E.
Published: December 2014

1. The effect of atropine on acid and pepsin secretion, stimulated by feeding, vagus excitation or infusions of gastrin, histamine and methacholine, was studied in conscious rats provided with a Pavlov or a Heidenhain pouch.

2. The acid and pepsin secretion in response to food was substantially suppressed by atropine in the Pavlov pouch.

3. The strong stimulatory effect of 2‐deoxy‐D‐glucose on acid and pepsin secretion in the Pavlov pouch was almost abolished by atropine.

4. A plateau secretion of acid obtained by infusion of submaximal doses of hog gastrin II, was significantly inhibited by atropine in the Pavlov and the Heidenhain pouch.

5. Methacholine‐induced acid and pepsin secretion in the denervated Heidenhain pouch was nearly completely inhibited by atropine.

6. A plateau secretion of acid evoked by infusing histamine in a near maximal dosage was inhibited by atropine to the same extent as the gastrin‐induced secretion in the Pavlov pouch.

7. The mode of action of atropine as a gastric secretory inhibitor is discussed.
An analysis of acetylcholine responses of junctional and extrajunctional receptors of frog muscle fibres. With an Appendix
Authors: Feltz Anne , Mallart Alberto , Kahn R. , le Yaouanc A.
Published: December 2014

1. An analysis has been made of the distribution and rise time of the responses induced by electrophoretic application of ACh on junctional and extrajunctional receptors of the neuromuscular junction of the frog.

2. The junctional and the extrajunctional responses appear to constitute two independent groups with no overlapping characteristics: (a) the responses evoked from junctional receptors show always a high ‘sensitivity’ (30–100 mV/nC) and a rise time usually shorter than 10 msec that does not lengthen as the ACh dose is increased; (b) the responses evoked from extrajunctional area show a lower sensitivity (0·5–10 mV/nC) and a slow rise time that is a linear function of the dose Q⅔ of ACh.

3. The lengthening of the rise time of extrajunctional response with increasing doses of ACh is interpreted by supposing that larger doses saturate larger areas of a membrane of low sensitivity uniformly covered with receptors. On the contrary, at junctional spots the does of ACh would be insufficient to saturate the receptors and rise time will be independent of dose.

4. Relatively unresponsive zones may exist between junctional spots and extrajunctional areas and between neighbouring extrajunctional areas.

5. Extrajunctional areas are subjected to significant seasonal variations; in summer they are practically absent, in autumn they appear as elongated areas of about 20 μ wide and 50 μ long, and late in winter they fuse together and all the ‘end‐plate’ zone becomes sensitive to ACh.
Experimental alteration of the relationshp between the external calcium concentration and the contractile force generated by auricular trabeculae isolated from the heart of the frog, Rana pipiens
Authors: Chapman R. A.
Published: December 2014

1. The contractile strength generated by isolated frog auricular trabeculae has been determined by perfusion with high‐K Ringer over a range of [Ca]o.

2. Experiments are described in which the cubic relationship between the contracture tension and [Ca]o has been changed to a square or a linear relationship.

3. These results have been interpreted by proposing that three Ca compounds, whose concentrations are proportional to [Ca]o, act co‐operatively at some stage of the process leading to the generation of tension.

4. The change in contractile strength, determined by regular electrically evoked twitches, has been investigated at different temperatures and the results have been explained by assuming that the concentrations of the three hypothetical activating compounds vary at different rates when [Ca]o is altered.

5. The staircase response is supposed to develop as the consequence of an increase in the concentrations of the two activating Ca compounds with the slowest time constants.

6. The possible physical representations of the hypothetical activating compounds are discussed.
Inhibition by prostaglandin E1 of gastric secretion in the dog
Authors: Nezamis James E. , Robert André , Stowe David F.
Published: December 2014

1. The effect of prostaglandin E1 (PGE1) on gastric secretion was studied in dogs equipped with gastric fundic pouches, either innervated (Pavlov) or denervated (Heidenhain).

2. PGE1 inhibited gastric secretion (volume, acid concentration, acid output, pepsin output) when given either by constant intravenous infusion or by single intravenous injection. The degree of inhibition was dose dependent.

3. The antisecretory effect of PGE1 was demonstrated against gastric stimulants which operate through different mechanisms. Thus, PGE1 counteracted the secretogogue effect of:

(a) histamine dihydrochloride; the ED50 was 0·5–1·0 μg/kg. min for a submaximal dose, and 1·0–1·5 μg/kg. min for a maximal dose;

(b) pentagastrin; the ED50 was around 0·25 μg/kg. min;

(c) food; the ED50 was 0·5 to 0·75 μg/kg. min;

(d) 2‐deoxyglucose; the ED50 was less than 0·1 μg/kg. min.

4. Although in some experiments, nausea and vomiting were observed during administration of PGE1, the antisecretory property of the substance is not related to a vomiting reflex, since

(a) an antiemetic, such as atropine, prevented vomiting without interfering with the effect of PGE1, and

(b) profuse vomiting elicited by apomorphine did not reduce gastric secretion stimulated by either histamine or pentagastrin.

5. The mechanism by which PGE1 inhibits gastric secretion is unknown. Studies by others have shown that the compound reduces gastric mucosal blood flow, inhibits acid formation from gastric mucosa when applied in vitro and may change the rate of formation of gastric cyclic AMP. It is likely that PGE1 interferes with biochemical processes, within parietal and chief cells, which lead to elaboration of gastric juice.

6. Unlike most gastric inhibitors, PGE1 appears to act as a protective shield against most, if not all, gastric stimulants. Since prostaglandins of the E series are naturally occurring substances and are normally present in the stomach, they may play a role in the regulation of gastric secretion.
A study of the inferior mesenteric and pelvic ganglia of guinea‐pigs with intracellular electrodes
Authors: Crowcroft P. J. , Szurszewski J. H.
Published: December 2014

1. Ganglion cells in the inferior mesenteric ganglion (IMG) and the pelvic plexus of the guinea‐pig were studied using intracellular micro‐electrodes.

2. Ganglion cells had resting membrane potentials of 55–65 mV. Threshold for initiation of an action potential ranged from 10 to 20 mV depolarization. Action potentials often exceeded 100 mV in amplitude and were followed by an after‐hyperpolarization of up to 20 mV.

3. Synaptic responses were recorded from cells in the IMG in response to stimulation of the right and left hypogastric nerves, ascending mesenteric, inferior splanchnic and colonic nerves. It has been established that more than forty preganglionic fibres converge on any one cell. Preganglionic fibres to the IMG were also observed in the pelvic nerves.

4. In contrast to the IMG, ganglion cells in the pelvic plexus received up to ten preganglionic fibres.

5. Ganglion cells responded to supramaximal preganglionic stimulation with up to four action potentials.

6. In the IMG, action potentials in response to synaptic action were followed by a prolonged period of hyperpolarization (after‐hyperpolarization) and a later phase of prolonged depolarization (after‐depolarization). The time course of these after potentials depended on the pattern of firing of action potentials during the period of stimulation. In the presence of dihydro‐β‐erythroidine, or if synaptic action was insufficient to evoke action potentials, only the after‐depolarization was observed.

7. Other cells were impaled whose properties differed from those described above. In one group of cells the resting membrane potentials were higher (up to 85 mV), input resistances lower and the threshold for initiation of an action potential was higher. The other group were inexcitable, had high resting membrane potentials (up to 85 mV), low input resistances and underwent a slow depolarization in response to repetitive stimulation of preganglionic fibres.

8. This study indicates that marked convergence of presynaptic fibres occurs on to ganglion cells of the IMG. The ganglion cells in the pelvic plexus receive a relatively small number of fibres, many of which exert intense synaptic activity ensuring a direct connexion to the central nervous system.
Further evidence for the involvement of microtubules in the intra‐axonal movement of noradrenaline storage granules
Authors: Banks P. , Mayor D. , Tomlinson D. R.
Published: December 2014

1. Constricted cat hypogastric nerve/inferior mesenteric ganglion preparations maintained in vitro for 48 hr have been used to study the effects of different concentrations of colchicine on axonal microtubules and on the proximo‐distal movement of catecholamine containing dense‐cored vesicles in non‐myelinated axons.

2. In low concentrations (0·03–0·3 μg/ml.), colchicine had no effect on the number of microtubules per axon and did not diminish the amount of noradrenaline accumulating proximal to the constriction.

3. Higher concentrations of colchicine (1·0–10 μg/ml.) produced a dramatic reduction in the number of microtubules per axon. This was associated with marked reductions in the number of dense‐cored vesicles and the amount of noradrenaline accumulating above the constriction.

4. There was some morphological evidence for a structural relationship between dense‐cored vesicles and microtubules.

5. These results further support the view that axonal microtubules are involved in the relatively fast proximo‐distal transport of noradrenaline containing dense‐cored vesicles in non‐myelinated sympathetic axons.