bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.