bluuebunny/crossref_metadata_2025_split huggingface dataset:
Indomethacin and the prostaglandin hypothesis of coronary blood flow regulation
Authors: Afonso Skoda , Bandow George T. , Rowe George G. 
Published: December 2014

1. Recent experimental data support the view that prostaglandins might be involved in autoregulation of coronary blood flow. Since indomethacin blocks prostaglandin synthesis, the present study was performed to determine whether indomethacin also inhibits coronary vasodilatation induced by hypoxia.2. Coronary and systemic haemodynamic and metabolic effects of hypoxia (5% and 8% oxygen in nitrogen) were studied in intact, anaesthetized and vagotomized dogs before and after indomethacin.3. 30 and 60 min after administration of indomethacin coronary blood flow increases produced by hypoxia were considerably lower than those before indomethacin.4. These results are held to lend support to the hypothesis that prostaglandins are involved in the autoregulation of coronary blood flow.
Stimulation of the hypothalamus and ovulation in the guinea‐pig
Authors: Booth Janet E. , Donovan B. T. 
Published: December 2014

1. Various methods of stimulating the hypothalamus were applied to the guinea‐pig with the aim of inducing ovulation.2. Electrochemical stimulation of the hypothalamus, or gross stimulation of the brain, was ineffective.3. Electrical stimulation of the medial basal hypothalamus or rostral hypothalamus elicited gonadotrophin release.4. Despite variation of the time and intensity of stimulation, follicular luteinization was more common than the formation of new corpora lutea.5. Electrical stimulation of the medial basal hypothalamus often caused luteinization of follicles. Fewer animals responded to excitation of the rostral hypothalamus, but in those that did, ovulation occurred more frequently.6. The present observations contrast markedly with comparable studies on the rat, where both electrochemical and electrical stimulation of the hypothalamus readily induce ovulation.
Histamine metabolism of the gastric mucosa following antrectomy
Authors: Lundell L. 
Published: December 2014

1. Histamine metabolism of the gastric mucosa in rats subjected to antrectomy, antrectomy and substitution with pentagastrin and exclusion of the antrum has been investigated employing various in vivo and in vitro methods.2. Mucosal histamine formation after antrectomy fell to about one third, whereas after antrum exclusion histamine formation increased many‐fold.3. After antrectomy, mucosal histamine content decreased, and increased after antrum exclusion.4. After total gastrectomy, (a) whole‐body histamine formation was reduced to about half, as judged by determining histamine excretion, and (b) pentagastrin infusion did not increase histamine excretion, showing absence of histamine mobilization from extra‐gastric sources. In rats with the stomach retained, infusion of pentagastrin induced a dose‐dependent increase in histamine excretion.5. Kinetic studies in which [14C]histidine was injected and the resulting urinary [14C]histamine determined showed that on pentagastrin infusion after antrectomy newly formed histamine was initially mobilized to a larger extent than in the controls.6. Antrectomized rats were subjected to substitution treatment by three injections per day of pentagastrin. After 3 weeks of substitution, histamine excretion was considerably higher than without substitution. After 6 weeks of substitution, histamine excretion was about the same in the substituted antrectomized, non‐substituted antrectomized and sham‐operated groups. Neither time nor substitution could, however, normalize the excretion of histamine on pentagastrin stimulation after antrectomy.7. In non‐substituted antrectomized rats, pentagastrin was less effective in elevating mucosal histamine formation than in the substituted and sham‐operated groups.8. The indispensability of the rat in this kind of study is emphasized.
Intracellular sodium and potassium concentrations in toad and frog oocytes during development
Authors: Cannon J. D. , Dick D. A. T. , Ho‐Yen D. O. 
Published: December 2014

1. During growth of oocytes of Bufo bufo from approximately 700–2000 μm in diameter, intracellular Na rose from 20 to 120 m‐mole/l. cell water while K fell from 120 to 15 m‐mole/l. cell water.2. In Rana temporaria Na similarly rose from 9 to 190 m‐mole/l. cell water and K fell from 126 to 28 m‐mole/l. cell water.3. At the same time in both Bufo and Rana the ouabain‐sensitive Na efflux, the ouabain‐insensitive Na efflux, and the total Na influx all increased.4. It is concluded that the predominant process is an increase of passive Na permeability. The increase of apparently active Na efflux may be secondary to the consequent rise in intracellular Na.
The dispersion of solutes during blood flow through a straight tube
Authors: Lane D. A. , Sirs J. A. 
Published: December 2014

1. The dispersion of solutes in plasma and blood has been studied by observing the clearance at a point down‐stream of a bolus of labelled solution by the steady flow of unlabelled solution.2. With a low molecular weight solute the clearance curve is qualitatively similar in 2
N‐KCl solution, plasma and whole blood.3. The dispersion of a high molecular weight protein, [131I]HSA, in plasma is dominated by the velocity profile of the flow.4. The clearance curves for HSA in whole blood are similar to those of plasma, except that the red blood cells speed the clearance of protein in the tail region of the curve.5. An analysis of the data suggests that the dispersion of solutes during blood flow through a straight tube can be attributed to the combined effects of solute diffusion and laminar convection. There is no evidence that induced motion of the erythrocytes produces significant mixing, in the bulk of the flow.
Synaptic transmission and cell death during normal ganglionic development
Authors: Landmesser Lynn , Pilar G. 
Published: December 2014

1. During normal embryonic development of the chick ciliary ganglion, cell death over a 4‐day period (Stages 35–39) reduces the number of ganglion cells by half, from 6500 to 3200. Both ciliary and choroid populations are affected by approximately the same amount.2. Previous to cell death, preganglionic fibres form functional synapses on all ganglion cells, indicating that synapses form on cells which are destined to die.3. Shortly before the period of cell death, there is a failure of transmission in approximately half the cells. Some evidence suggests that transmission failure in at least some of the cells is of preganglionic origin.4. Cell death is nearly synchronous with the establishment of peripheral connexions by ganglion cells, at least with respect to the ciliary population which forms functional synapses with iris muscle. This implies that those cells which die do so because they have failed to form adequate peripheral connexions.5. It is suggested that many of the cells in which transmission has failed die, bringing transmission through the ganglion back to 100%. However, transmission failure appears to be a transitory phenomenon in other cells which survive and probably results from death of their preganglionic elements. Restoration of transmission would then be brought about by the formation of new or more effective synapses by surviving preganglionic fibres.
The absorption of 125I‐labelled immunoglobulin G by different regions of the gut in young rats
Authors: Morris B. , Morris R. 
Published: December 2014

1. 125I‐labelled homologous IgG was injected into different regions of the small intestine of rats aged 12, 16, 18, 20 and 22 days. At 12 days the proximal and middle regions of the intestine readily absorbed globulin and transmitted it to the circulation. The distal region of the intestine transmitted little to the circulation at all ages tested.2. The intestine loses its ability to transmit globulin to the circulation in a distal‐proximal direction. At 16 and 18 days the ability of the middle region had declined significantly, and this decline continued so that little globulin was transmitted from this region at 20 and 22 days.3. The proximal intestine retained the ability to transmit globulin to the circulation in significant amounts up to 20 days.4. There is a close negative correlation between body weight and total radioactivity of the sera of rats which had received doses of labelled globulin into the proximal and middle regions of the intestine. There was no such correlation after injection into the distal intestine — suggesting a restricted throughput of radioactive material by the absorptive cells of this region.5. These results are discussed in the context of the termination of antibody absorption, and in relation to the results obtained using polyvinyl pyrrolidone.
Evidence for the genetic control of the sodium pump density in HeLa cells
Authors: Boardman Lesley , Huett Marian , Lamb J. F. , Newton J. P. , Polson Jean M. 
Published: December 2014

1. HeLa cells were grown in normal and altered growth solutions; the ion contents, volumes, K sensitive ouabain binding, the Na‐K‐ATPase and the Na and K transport measured.2. Cells grown in 1 × 10−4
M ethacrynate or low‐K media for 24 hr have a raised [Na]i, a decreased [K]i, and an increased ouabain binding. Those grown in low‐K also have an increased Na‐K‐ATPase activity.3. When cells are put into low‐K solutions the [Na]i initially rises to a high value, and then starts to fall some 8 hours later as the ouabain binding increases, suggesting that these additional sites represent working Na pumps. Flux measurements on low‐K cells provide some support for this view.4. Experiments in which sorbitol replaced [Na]o showed that the increased ouabain binding and Na‐K‐ATPase was related to the increase in [Na]i rather than the decrease in [K]i and was not due to a non‐specific effect of [K]o change.5. The protein synthesis inhibitors cycloheximide and puromycin stopped the effect of ethacrynate and low‐K solutions on increased ouabain binding. They also decreased the ouabain binding and K influx in normal cells over 24 hr. Cycloheximide had similar effects on Na‐K‐ATPase in low‐K treated and normal cells. These results suggest that protein synthesis is required for the appearance of more ouabain sensitive sites in the cell membrane, both in response to ethacrynate and low‐K treatment and for normal replacement during the cell's life.6. The RNA synthesis inhibitors actinomycin D (AMD) and cordycepin had complex effects on ouabain binding in fresh and ethacrynate treated cells. These inhibitors increased the ouabain binding but decreased the K influx. This discrepancy was due to the appearance of ouabain binding sites with different characteristics from normal sites. A limited investigation of this phenomenon was carried out. Probably AMD stops the normal replacement of sites in the membrane.7. These results are consistent with the hypothesis that HeLa cells have a system for controlling the number of Na pumps in their membranes. This system responds to the level of [Na]i within the cell and involves protein synthesis. It is not clear to what extent the nucleus is normally involved in this process.
Steady‐state contribution of the sodium pump to the resting potential of a molluscan neurone
Authors: Gorman A. L. F. , Marmor M. F. 
Published: December 2014

1. The electrogenic contribution of the Na+‐K+ exchange pump to the membrane potential of the Anisodoris giant neurone (G cell) was examined under steady‐state and Na+ loaded conditions.2. The membrane potential was variable for the first 1‐4 hr after impalement, but, in the absence of experimental manipulation, remained constant thereafter. The average membrane potential for ten cells maintained at 11–13 °C and measured 5‐36 hr after impalement was 55·8 ± 1·0 mV (
S.E. of mean).3. Low concentrations of external ACh caused a reversible increase in membrane Na+ conductance. Brief exposure to ACh proved a fast and reversible technique to load the cell with Na+ ions, and transiently stimulate the electrogenic Na+ pump.4. In ten cells maintained from 5 to 36 hr at 11–13° C the reduction in membrane potential produced by inhibition of the Na+ pump with ouabain was remarkably constant between cells and averaged + 9·7 mV.5. Cells maintained under steady‐state conditions (at 11–13° C) for extended periods of time were shown to be relatively insensitive to changes in temperature and to small changes in external K+.6. It is estimated that the Na+‐K+ exchange pump contributes approximately ‐ 10 mV to the steady‐state resting potential of the G cell, and that two Na+ ions are extruded for every K+ ion transported into the cell per pump cycle.
Membrane potential and resistance measurement in acinar cells from salivary glands in vitro: effect of acetylcholine
Authors: Nishiyama A. , Petersen O. H. 
Published: December 2014

1. Cell membrane potential and input resistance measurements were made on segments of submaxillary glands from mice, rabbits or cats placed in a tissue bath, which was perfused with physiological salt solutions.2. During exposure to a standard Krebs—Henseleit solution, ACh stimulation always evoked a marked decrease in input resistance and time constant. The change in potential evoked by ACh stimulation was either a monophasic hyperpolarization (low resting potential) or a depolarization followed by hyperpolarization (high resting potential).3. Increasing [Ca]o from 2·56 to 10 m
M resulted in an enhanced input resistance. Under this condition it was sometimes possible to obtain current—voltage relations. The relationship was linear in the range −50 to −10 mV. In the absence of extracellular Ca the resting potential was reduced and ACh mostly evoked hyperpolarizations. In those cases when the resting potential remained high biphasic potentials were still observed.4. During exposure to Na‐free solutions the resting potential was either unchanged or slightly enhanced. ACh never evoked biphasic potentials, but always large hyperpolarizations.5. In the first period (1 hr) after exposure to a K‐free solution ACh normally evoked very large hyperpolarizations, often to more than −100 mV. After several hours of exposure to K‐free solution the input resistance gradually increased and ACh evoked a tremendous fall in input resistance and time constant with only a small potential change. Re‐introducing control solution, ([K]o = 4·7) for a short period at this stage, caused a very marked hyperpolarization (about 30 mV) unaccompanied by a change in input resistance and time constant.6. Replacing extracellular Cl by SO4 hyperpolarized the cell membrane. ACh mostly evoked hyperpolarization under this condition, but occasionally biphasic potentials were observed. Increasing [K] of the sulphate solution depolarized the cell membrane by about 49 mV per tenfold increase in [K]. In the presence of ACh the membrane behaved as a K‐selective membrane with a slope of the linear curve relating membrane potential to [K]o of 59 mV per tenfold increase in [K]o.7. It is concluded that ACh evokes a marked increase in surface cell membrane permeability of salivary acinar cells. The ACh evoked hyperpolarization is due to an increase in PK: the depolarization frequently preceding the hyperpolarization is probably mainly related to an increase in PNa. The membrane Na—K pump can act electrogenically at least under conditions of Na loading.
The bleaching and regeneration of rhodopsin in the cat
Authors: Bonds A. B. , MacLeod Donald I. A. 
Published: December 2014

1. The processes of bleaching and regeneration were monitored by retinal densitometry in living cats.2. Neither bleaching nor regeneration of rhodopsin can be described by the simple kinetic equation (Alpern, 1971) found valid for man.3. After a strong 1 min bleach, the retina contains more unbleached rhodopsin than expected on the basis of the initial bleaching rate.4. During the first 9 min after a 1 min bleach, cats regenerate rhodopsin only slowly; density changes during this period are dominated by formation and decay of metarhodopsin III. Subsequently, rhodopsin regeneration accelerates to a rate of 50%/11 min.5. No such delay precedes recovery from a prolonged (20 min) bleach.
Mechanism of nerve membrane depolarization caused by grayanotoxin I
Authors: Narahashi Toshio , Seyama Issei 
Published: December 2014

1. The mechanism of depolarization of squid axon membranes caused by grayanotoxin I has been studied by means of internal perfusion and voltage clamp techniques.2. The depolarization induced by either internal or external application of grayanotoxin I was reversed by decreasing the external sodium concentration from 449 to 1 m
m.3. No depolarization was observed when both external and internal media were devoid of sodium ions, indicating that the depolarization by grayanotoxin I in normal media is due to a specific increase in resting sodium permeability.4. The resting sodium permeability as measured by voltage clamp was increased to 1·31 × 10−6 cm/sec by internal application of 1 × 10−5
m grayanotoxin I, an increase by a factor of about 90.5. The apparent dissociation constant of internally applied grayanotoxin I in increasing the resting sodium permeability was estimated to be 4·12 × 10−5
m, and the toxin interacts with the membrane receptor on a one‐to‐one stoichiometric basis.6. Tetrodotoxin antagonized the action of grayanotoxin I in increasing the resting sodium permeability in a non‐competitive manner.
Effects of acetylcholine and carbamylcholine on the axon and Schwann cell electrical potentials in the squid nerve fibre
Authors: Villegas Jorge 
Published: December 2014

1. The effect of acetylcholine and carbamylcholine on the axon and Schwann cell membrane potential have been studied in the giant nerve fibre of the squid. The addition of carbamylcholine (10−6
M) to the external sea‐water medium has no appreciable effects on the resting and action potentials of the axon. However, it induces a long‐lasting hyperpolarization in the surrounding Schwann cells of the unstimulated intact or slit nerve fibres which is completely blocked by
D‐tubocurarine (10−9
M). Eserine (10−9
M) prolongs the Schwann cell hyperpolarizations induced by a 1 min exposure of the unstimulated nerve fibres to acetylcholine (10−7
M).2. The addition of carbamylcholine (10−6
M) to the external medium increases the relative permeability of the Schwann cell membrane to the potassium ion in slit nerve fibres. Yet, a hundredfold reduction in external sodium concentration has no appreciable effect on the hyperpolarization of the Schwann cells of the slit nerve fibre under similar conditions.3. Tetrodotoxin at a concentration of 5 × 10−8
M has no appreciable effects on either the Schwann cell electrical potential or on the hyperpolarizing action of carbamylcholine on the Schwann cells of the unstimulated intact nerve fibres.4. These findings indicate the presence of acetylcholine receptors in the plasma membrane of the Schwann cell in these nerve fibres and give further support to the hypothesis on the role of the cholinergic system in the genesis of the long‐lasting Schwann cell hyperpolarizations caused by the conduction of nerve impulse trains by the axon.
Changes in colostrum composition and in the permeability of the mammary epithelium at about the time of parturition in the goat
Authors: Linzell J. L. , Peaker M. 
Published: December 2014

1. Changes in milk composition and in mammary permeability to labelled sucrose and monovalent ions have been studied in late pregnancy and at the time of parturition. These data have been compared with those obtained previously in lactating goats.2. Colostrum contained more sodium, chloride, protein, immunoglobulins and less potassium and lactose than milk. The composition of the aqueous phase changed near term and normal milk composition was reached either several days before or several days after parturition. The main decrease in the immunoglobulin concentration occurred when the animal was first milked or suckled.3. In contrast to lactating animals, [14C]sucrose passed from blood to milk and [14C]lactose from milk to blood. There was a significant correlation between the entry of labelled sucrose into milk and the sodium concentration.4. The rate of passage of 24Na and 36Cl into milk from blood was higher in late pregnancy than in lactation.5. In late pregnancy, the concentrations of both sodium and chloride were inversely correlated with the concentration of lactose while there was a positive correlation between potassium and lactose.6. Hydrostatic pressure in the lumen of the mammary gland increased during late pregnancy but there was no significant correlation with the composition of the aqueous phase of milk.7. When one gland of 4 animals was milked twice‐daily starting 9–19 days before parturition, the composition of the secretion changed to that of normal milk only in the gland that was being milked. Similarly, [14C]sucrose, 24Na and 36Cl entry from blood decreased. Milk yield also increased but a further increase occurred post‐partum.8. Comparison of the passage of 3HOH, 24Na and 36Cl into different fractions of milk during
I.A. infusions indicates that the mammary ducts are less permeable to ions than the alveoli, but it was not possible to decide whether the ducts are as impermeable as during lactation.9. It is suggested that ion and lactose movements occur via a para‐cellular route and these results are discussed in relation to transport mechanisms and in terms of local and systemic controlling mechanisms.
Ionic relations and electrical properties of isolated oocytes of Bufo bufo with special reference to removal of extracellular chloride
Authors: Hannibal O. H. , Lea E. J. A. 
Published: December 2014

1. The efflux rate coefficients of sodium, potassium and chloride from immature oocytes of the toad Bufo bufo have been measured and found to be respectively, 0·0069, 0·0023 and 0·0034 min−1.2. Replacement of external chloride by sulphate resulted in a fall in chloride efflux of about 50%. This has been interpreted in terms of exchange diffusion.3. The membrane conductance has been measured and found to be 0·14 × 10−3 mhos cm−2 in good agreement with the value calculated from the flux data, 0·12 × 10−3 mhos cm−2, after taking account of the chloride exchange diffusion fraction.