bluuebunny/crossref_metadata_2025 huggingface dataset:
Cyclic changes in potential and resistance of the beta‐cell membrane induced by glucose in islets of Langerhans from mouse.
Authors: Atwater I , Ribalet B , Rojas E
Published: December 2014

1. The effects of KCl on the membrane potential were studied in cells from mouse islets of Langerhans identified as beta‐cells by the characteristic pattern of electrical activity induced by 11.1 mM glucose. 2. In the absence of glucose, when the beta‐cell membrane does not exhibit electrical activity, the dependence of the membrane potential upon external potassium [K+]o, could be described by the constant field equation using a PK/PNa ratio between 30 and 75. 3. In 11.1 mM glucose, when the beta‐cell membrane potential fluctuates between a silent phase at about ‐50 mV and an active phase at about ‐40 mV giving rise to a train of spikes, the dependence of the membrane potential upon [K+]o could also be described with the constant field equation using a smaller PK/PNa of about 15, during the silent phase, and of about 8, during the active phase (foot of the spikes during the burst). 4. A bridge amplifier for measuring the changes in membrane potential during the application of pulses of current through the same micro‐electrode was used to estimate the input resistance of a beta‐cell. In 11.1 mM glucose, rough estimates of the membrane resistance during the silent phase averaged 1.2 X 10(8) omega. 5. The time course of the changes in input resistance of the cell when switching from 0 to 11.1 mM glucose showed a transient decrease from 0.9 X 10(8) to 0.7 X 10(8) omega followed by an increase to 1.2 X 10(8) omega. 6. The burst pattern was shown to result from the superposition of two potential changes: (a) 5‐‐10 mV depolarization (lasting about 10 sec in 11.1 mM glucose), and (b) 10‐‐50 mM spikes (lasting about 0.1 sec). Only the latter could be suppressed by hyperpolarizing current injection. 7. Application of pulses of current during the various phases of the electrical activity in 11.1 mM glucose enable us to compare the resistance during the silent and active phases. This was found to be oscillating between a high resistance value at about 1.2 X 10(8) omega before each burst and a low resistance value at 0.9 X 10(8) omega during the active phase at the foot of the spikes. In some cells the resistance during the silent phase remained fairly constant. In other cells it increased gradually from 1.1 X 10(8) to 1.3 X 10(8) omega measured just before each burst of spikes. 8. The observed increase in resistance induced by glucose together with the measured dependency of the membrane potential on [K+]o with and without glucose can be explained by postulating that in the presence of glucose the K+ permeability of the beta‐cell membrane is reduced. 9. The oscillations between a high and a low resistance state in the presence of 11.1 mM glucose could be due to a sudden decrease in K+ permeability followed by a much larger increase in permeability to other ions, presumably Na+ and Ca2+.
Kinetics of bleaching and regeneration of rhodopsin in abnormal (RCS) and normal albino rats in vivo.
Authors: Perlman I
Published: December 2014

1. Rhodopsin concentration has been measured by the method of densitometry in retinae of rats with inherited retinal dystrophy (RCS) raised in darkness and compared with that of normal rats similarly reared. 2. In both RCS and normal rats the fraction of rhodopsin bleached is always directly proportional to the photon content of the light, I.t, where I is the light intensity in effective quanta (500 nm) cm‐2 sec‐1 and t is the duration of the bleaching exposure in seconds. 3. Rhodopsin photosensitivity for bleaching is slightly higher in RCS rats than in normals (2.3 (10)‐16 cm2 chromophore‐1 compared with 1.3 (10)‐16 cm2 chromophore‐1). 4. Rhodopsin regeneration in the dark in both RCS and normal rats cannot be described by the kinetics of a simple monomolecular chemical reaction. 5. Following 5 min bleaches, the regeneration rate becomes slower as the preceding bleach is made stronger. Regeneration in the dark is significantly faster in the RCS rats than in the normal ones. 6. In normal rats, after a full bleach, rhodopsin regenerates back to the dark‐adapted level within 3‐‐4 hr. In RCS rats rhodopsin regenerates to reach a plateau level, below the previous dark‐adapted level, that lasts for several hours. 7. The faction of total rhodopsin that can regenerate gradually declines with age until in 70 days old RCS rats no rhodopsin regeneration can be measured by the ensitometer. However, total rhodopsin density (fully bleached‐dark‐adapted) is still close to normal.
Influence of external potassium concentration on secretory responses to cholecystokinin‐pancreozymin and ionophore A23187 in the pancreatic acinar cell.
Authors: Kanno T , Saito A
Published: December 2014

1. The inhibitory effect of a diminution in [K+]o on the secretory processes of the pancreatic acinar cell was analysed in the isolated and perfused rat pancreas. 2. Partial replacement of KCl with NaCl produced falls in both amylase output and pancreatic juice flow which were induced by 5 m‐u. cholecystokinin‐pancreozymin (CCK‐PZ)/ml., and the responses were slowly regained after reintroduction of a standard concentration of KCl. 3. A quantitative relation was found between the amount of amylase released by CCK‐PZ and [K+]o over the range 1.0‐‐5.6 mM. A linear relation was obtained between the ratio of E1K+]3(0)/amylase output and [K+]3(0). 4. A quantitative relation was also found between the pancreatic juice flow induced by CCK‐PZ and [K+]o over the range 1.0‐‐5.6 mM. A linear relation was obtained between the ratio of [K+]3(0)/juice flow and [K+]3(0). 5. The results obtained may be explained by a model as follows: (1) amylase output and juice flow induced by CCK‐PZ are simply proportional to the amount of complex composed of a carrier molecule bearing one Ca and four Na atoms, (2) the inward movement of the complex is tightly linked to the CCK‐PZ‐induced activation of pumps which are postulated on both basal and apical sides of the membrane of the acinar cell, and (3) the Na:K coupling ratio of the pumps is close to 3:2. 6. A quantitative relation was also found between the amount of amylase released by Ca reintroduction after pre‐treatment with Ca‐ionophore A23187 and [K+]o. This may be explained by a model essentially similar to that mentioned above. 7. Total replacement of NaCl with NaBr slightly reduced the CCK‐PZ‐induced fluid and amylase secretion. Total replacement of NaCl with sodium isethionate or with sodium pyruvate, however, virtually abolished the CCK‐PZ‐induced fluid and amylase secretion.
The half‐lives of angiotensin II, angiotensin II‐amide, angiotensin III, Sar1‐Ala8‐angiotensin II and renin in the circulatory system of the rat.
Authors: Al-Merani S A , Brooks D P , Chapman B J , Munday K A
Published: December 2014

1. Methods are described for estimating the half‐life of angiotensin analogues and renin in the rat, from the time course of the blood pressure changes they evoke. 2. The following half‐life values were measured: angiotensin II, 16 +/‐ 1 sec; angiotensin III, 14 +/‐ 1 sec; angiotensin II‐amide, 15 +/‐ 1 sec; Sar1‐Ala8‐angiotensin II, 6.4 +/‐ 0.6 min; renin, 3.0 +/‐ 0.4 min. The distribution volume of angiotensin was found to be 18 ml./kg body wt. 3. It is inferred that the Asp1 residue does not reduce the rate of angiotensin II catabolism, but that substitution of this residue by sarcosine may inhibit catabolism while substitution by asparagine has no effect. 4. Five experimental criteria were identified which indicate that these methods give reliable estimates of the half‐life. It is suggested that these results are more accurate than most previous half‐life estimates. 5 When tachyphylaxis to angiotensin II‐amide occurs, the pressor activity of the plasma is not reduced.
Reactivation of membrane charge movement and delayed potassium conductance in skeletal muscle fibres.
Authors: Adrian R H , Rakowski R F
Published: December 2014

1. Intramembrane charge movement has been measured in striated muscle subjected to prolonged depolarization but repolarized to ‐100 mV for up to 100 sec. The method of measurement allows identification of charge or charges which are 'reprimed' by repolarization. 2. Charge 'reprimed' by repolarization appears to differ in its voltage distribution from charge detected in a permanently polarized fibre. The difference is probably due to the different pulse sequences used in the two measurements and to the fact that there appear to be several species of intramembrane charges with different transition potentials and different steepness of voltage distribution (V and k in eqn. (14): see below). 3. Potassium conductance is reprimed by repolarization following inactivation by depolarization. When the repriming potential is ‐100 mV the process appears to be in two stages; repriming to a value rather less than half the final value takes place exponentially with a time constant of approximately 40 sec; subsequently repriming to the final value is very slow. At a repriming potential of ‐140 mV repriming to the final value )1‐‐2 mmho/microF) takes place exponentially with a time constant of approximately 17 sec.
Reversal of 6‐hydroxydopamine‐induced hypotension in the rat without activation of the renin‐angiotensin system.
Authors: Bennett T , Gardiner S M
Published: December 2014

1. Male Wistar rats were housed individually in glass metabolic cages for 5 days during which time their food and water intakes reached plateau levels and they developed a significant systolic arterial hypertension. 2. After the initial 5‐day period, systolic blood pressure and water and electrolyte balances were measured for 4 days before and 7 days after I.P. injection of 6‐hydroxydopamine (100 mg/kg). In a separate experiment, plasma renin activity and glomerular filtration rate were measured 1 and 3 days after injection of 6‐hydroxydopamine. Haematocrit, plasma volume, osmolality and plasma concentrations of glucose, sodium, potassium and protein were also measured at intervals after treatment. 3. Systolic blood pressure fell within 24 hr after treatment with 6‐hydroxydopamine but was restored to pretreatment levels within 7 days. There was also a transient fall in glomerular filtration rate. 4. Plasma volume was significantly expanded on the first day after treatment and there was a fall in haemotocrit together with changes in plasma constituents indicative of a haemodilution, although plasma glucose levels were elevated. 5. There was a significant water retention on the third, fourth and fifth days after treatment but this was not accompanied by any measurable sodium retention and could not be attributed to renal compensation. Furthermore, plasma renin activity showed no significant change following 6‐hydroxydopamine treatment. 6. It is suggested that the return of systolic blood pressure to pre‐treatment levels was chiefly due to the return of vasoconstrictor function. The changes in plasma composition and volume were probably due to a fall in capillary hydrostatic pressure and an increase in the osmolality of extracellular fluid due to the elevated glucose levels.
The projection of jaw elevator muscle spindle afferents to fifth nerve motoneurones in the cat.
Authors: Appenteng K , O'Donovan M J , Somjen G , Stephens J A , Taylor A
Published: December 2014

1. By spike‐triggered averaging of intracellular synaptic noise it has been shown in pentobarbitone anaesthetized cats that jaw elevator muscle spindle afferents with their cell bodies in the mid‐brain have a relatively weak monosynaptic projection to masseter and temporalis motoneurones. 2. Extending the spike‐triggered averaging method to recording extracellular excitatory field potentials it has been shown that virtually all the spindles do project monosynaptically to the motoneurone pool. It is concluded that the general weakness of the projection is due to its restriction to a small proportion of the motoneurones, possibly those concerned most with tonic postural functions. 3. The shape of individual intracellular e.p.s.p.s together with the spatial distribution of extracellular excitatory potential fields provide some evidence for a dentrically weighted distribution of the synapses. 4. Evidence is presented that both primary‐ and secondary‐type spindle afferents project monosynaptically, the secondary effects being some 71% of the strength of the primary ones.
An ATPase dependent, radiosensitive acidic microclimate essential for intestinal folate absorption
Authors: Kesavan V. , Noronha J. M.
Published: December 2014

1. 5‐Methyltetrahydrofolic acid transport was studied across everted sacs of rat jejunal segments from control and whole body X‐irradiated (700 rad) rats at 10−5
M concentrations (at which optimum transport occurs) at various pHs.

2. The folate transport from mucosal to serosal compartment was inhibited by about 55% in irradiated rat at the pH of the intestinal chyme (6·5). Extraneous ATP in the incubation system could restore the defective transport of the irradiated intestine.

3. The maximum folate transport which occurred at pH 4·0 was not adversely affected by whole body irradiation. An acidic, pH dependent, passive uptake of 5‐methyltetrahydrofolic acid was observed.

4. The normal absorption barrier of the small bowel was not disrupted by the acidification process as practically no uptake was observed with irradiated segments pretreated at pH 4·0 except in the presence of ATP.

5. Leucine and serine transport at a zero concentration gradient indicated active transport mechanisms which were not affected by acidification. Their uptake was additively increased in the presence of glucose and ATP, further indicating that the normal physiology of the intestines was not affected by the acidification process.

6. An intestinal mucosal cell surface ATPase was observed which was Mg2+ dependent. It could hydrolyse solution phase ATP and thus generate the protons necessary for the acidification of a microenvironment where passive uptake of the neutral folate species could occur.

7. The ATPase activity was inhibited about 90% by 50 m
M‐Na azide at pH 6·5. Below this concentration folate transport was also inhibited.

8. Na azide did not inhibit folate transport at pH 4·0, suggesting that its inhibition of folate uptake at pH 6·5 is related to its inhibitory effect on ATPase, rather than on folate transport per se. ATPase activity was therefore essential for folate transport at the pH of the intestinal chyme.
Quantification of the morphological reaction of platelets to aggregating agents and of its reversal by aggregation inhibitors.
Authors: Born G V , Dearnley R , Foulks J G , Sharp D E
Published: December 2014

1. In rabbit citrated platelet‐rich plasma, the changes in shape of the platelets produced by adenosine diphosphate (ADP) or 5‐hydroxytryptamine (5‐HT) were observed by photometric and volumetric techniques and by measurements of platelet images on electron micrographs either directly or with an image analysing computer. This permitted the indirect manifestations of the shape changes to be correlated with the morphological features responsible for them, i.e. transformation of disks to more spherical forms and extrusion of blebs and spikes. 2. Following the addition of ADP, an initial brief peak in the light scattering records was associated with marked but transient irregularities in the surface of the platelets. These effects were absent when the other shape changes were produced by 5‐HT. 3. When the optical manifestations of the shape changes induced by ADP were reversed by the addition of antagonists adenosine triphosphate, 2‐chloroadenosine or prostaglandin E1, the morphological changes were reversed by a diminution in the number of spikes and the conversion of spherical platelet bodies to a more discoid form. 4. The volume of extracellular plasma trapped between platelets sedimented by centrifugation was proportional to the number of spikes which they extruded. Under all conditions, the volume of the platelets themselves remained remarkably constant at approximately 5 X 10(‐9) microliter./platelet. 5. Addition of a calcium chelating agent alone produced a rapid persistent alteration in the optical properties of platelet‐rich plasma. The magnitude of this alteration was proportional to chelator concentration but greater in some plasmas than in others. Similar optical effects were produced when the calcium concentration of platelet‐rich plasma was increased by adding calcium. The optical effects produced by calcium or its chelators were unusual in that the changes in transmitted and horizontally scattered light were in opposite directions (transmitted light decreased, scattered light increased) whereas, in all other circumstances so far examined, these changes were in the same direction. The chelators caused the formation of spikes on the platelets without appreciably altering their disk shape, which may explain the unusual nature of the optical effects.
Functional distinction between two transport mechanisms in rabbit gall‐bladder epithelium by use of ouabain, ethacrynic acid and metabolic inhibitors.
Authors: Frederiksen O
Published: December 2014

1. Net fluid transport rate, transepithelial p.d. and resistance, and unidirectional Na+‐fluxes were measured in rabbit gall‐bladder preparations exposed on both sides to bicarbonate‐Ringer solution in vitro. 2. Both ouabain and ethacrynic acid (ETCA) caused dose‐dependent decreases of net fluid transport rate; ouabain inhibited fluid transport predominantly from the serosal side, whereas the inhibitory effect of ETCA was elicited mainly from the mucosal (luminal) side. Applied bilaterally, the ID50 for ouabain was 2.5 X 10(‐6) M, and for ETCA 2.3 X 10(‐4) M. After maximal inhibition at each concentration level of the two inhibitors fluid transport could not be reversed. 3. 2,4‐Dinitrophenol (2,4‐DNP) (2 X 10(‐4) M) or substitution of O2 by N2 caused an 80% reversible decrease of net fluid transport. 4. The spontaneous p.d. across the rabbit gall‐bladder was about 2.7 mV, mucosal side positive. 2,4‐DNP, N2 and serosal application of ouabain depressed the p.d. after an initial hyperpolarization. This decrease was reversible during recovery from 2,4‐DNP and N2, but irreversible after removal of ouabain at concentrations greater than or equal to 10(‐4) M. Mucosal application of ETCA (10(‐3) M) caused no decrease in p.d., which actually increased slightly. 5. Calculated passive serosal‐to‐mucosal Na+‐fluxes changed in the same direction as did changes in conductance. 6. It is concluded that ETCA does not interfere primarily with the Na‐K‐ATPase or cellular oxidative metabolism. The data support the proposal that the pump responsible for isosmotic transepithelial fluid transfer is located in the luminal end of the cells. This pump is ETCA‐sensitive. The ATPase‐dependent Na‐K pump, which can be inhibited by ouabain, is localized in the serosa‐facing cell membrane. The data suggest that the inhibition of net fluid transport by ouabain is indirect and mediated by changes in intracellular ion concentrations. 7. The results support the concept that the transepithelial fluid transport mechanism is electroneutral, and suggest that the mucosa positive transepithelial p.d. is due to differences in electromotive forces arising from ion (mainly K+) diffusion across the mucosal and serosal cell membranes.
Transmission along and between rods in the tiger salamander retina.
Authors: Werblin F S
Published: December 2014

1. The electrical pathways that couple the rods and that link the outer segments of the rods to the coupled network, were evaluated. Two separate micro‐electrodes were inserted into the inner or outer segments of the same or neighbouring rods under visual control. Current was passed through one electrode, and the resulting potential recorded with the other. 2. The input resistance, measured at the inner or outer segment in a rod in the network, is strongly outward rectifying. It is typically near 40 Momega when the membrane is hyperpolarized 10 mV or more by extrinsic current, less than 10 Momega when the membrane is depolarized by 5 mV or more, and near 30 Momega at the no‐current level. 3. When current is injected into the outer segment, the response in the inner segment is nearly identical with that at the outer segment, suggesting that the resistance coupling the segments is not high relative to the input resistance of the rod in the network. 4. Under voltage clamp the light response current for a rod in the network is of constant magnitude for potential levels between ‐80 and ‐20 mV. This suggests that there is little or no measurable light elicited conductance change associated with the response, possibly a consequence of coupling between rods. 5. The rod response increases with increasing diameter of a concentric test flash up to about 200 micron, or about 16 rod diameters. 6. When current is injected into one rod, the response in its immediate neighbours is between a quarter and one tenth that recorded in the injected rod for all potential levels in the injected rod. 7. The membrane time constant, measured in a rod in the network, is proportional to the voltage‐dependent input resistance at 0.16 msec/Momega. With assumptions about the geometry of the rod network this represents a membrane capacitance of 1.5 muF/cm2. 8. The data can be approximated by a network model of square array. The model predicts that: the outer segment contributes less than half the current for the total rod response, the membrane resistance of an individual rod is greater than twice the measured input resistance for the rod in the network, near 60 Momega, and the coupling resistance for each arm of the network is about 4 times the individual rod resistance, near 240 Momega.
Acetylcholine noise in cultured chick myoballs: a voltage clamp analysis.
Authors: Fischbach G D , Lass Y
Published: December 2014

1. Large spherical muscle cells were grown in vitro by allowing dissociated chick myoblasts to fuse in suspension culture. 2. Myoball membranes could be adequately voltage clamped even in the face of large inward currents (ca. 100 nA) induced by ACh. 3. The single channel conductance, gamma, estimated from the ratio of the mean to the variance of ACh currents was 25‐40 pmho at temperatures between 25 degrees and 37 degrees C. 4. Spectra of ACh current fluctuations declined with 1/f2. The mean channel open time (tau) estimated from the half‐power frequency was 2 msec at 37 degrees C and ‐90 mV holding potential. At lower membrane potentials tau was decreased and on hyperpolarization tau was prolonged.
Ocular dominance in layer IV of the cat's visual cortex and the effects of monocular deprivation.
Authors: Shatz C J , Stryker M P
Published: December 2014

1. The relation between the physiological pattern of ocular dominance and the anatomical distribution of geniculocortical afferents serving each eye was studied in layer IV of the primary visual cortex of normal and monocularly deprived cats. 2. One eye was injected with radioactive label. After allowing sufficient time for transeuronal transport, micro‐electrode recordings were made, and the geniculocoritcal afferents serving the injected eye were located autoradiographically. 3. In layer IV of normal cats, cell were clustered according to eye preference, and fewer cells were binocularly driven than in other layers. Points of transition between groups of cells dominated by one eye and those dominated by the other were marked with electrolytic lesions. A good correspondence was found between the location of cells dominated by the injected eye and the patches of radioactively labelled geniculocortical afferents. 4. Following prolonged early monocular deprivation, the patches of geniculocortical afferents in layer IV serving the deprived eye were smaller, and those serving the non‐deprived eye larger, than normal. Again there was a coincidence between the patches of radioactively labelled afferents and the location of cells dominated by the injected eye. 5. The deprived eye was found to dominate a substantial fraction (22%) of cortical cells in the fourth layer. In other cortical layers, only 7% of the cells were dominated by the deprived eye. 6. These findings suggest that the thalamocortical projection is physically rearranged as a consequence of monocular deprivation, as has been demonstrated for layer IVc of the monkey's visual cortex (Hubel, Wiesel & Le Vay, 1977).
Fast axoplasmic transport of noradrenaline and dopamine in mammalian peripheral nerve.
Authors: Ben-Jonathan N , Maxson R E , Ochs S
Published: December 2014

A fast transport of noradrenaline (NA) at a velocity of 392 mm/day was found in cat peroneal nerve using a double‐ligation technique and a new sensitive radioenzymatic assay for catecholamines. The velocity of transport of NA is sufficiently close to that of 410 mm/day found for labelled proteins and polypeptides to be considered as moving down within the nerve fibres by the same transport mechanism. In addition, dopamine (DA) was also found to be moved down by anterograde transport at a fast, but not well defined, rate. Disulfiram, a dopamine‐beta‐hydroxylase inhibiting agent, reduced NA levels and increased DA both in control nerve segments and within the portion of the nerve isolated by ligations where NA‐containing densecore vesicles are present. The results are considered to support a dynamic turnover of NA and DA in the dense‐core vesicles as they are trasnported in the axons.
Vascular and metabolic responses to adrenergic stimulation in isolated canine subcutaneous adipose tissue at normal and reduced temperature.
Authors: Hjemdahl P , Sollevi A
Published: December 2014

1. The circulatory and metabolic effects of temperature reduction were studied in autoperfused canine subcutaneous adipose tissue in situ. 2. Cooling the adipose tissue sufficiently to reduce venous effluent temperature by 5‐‐6 degrees C decreased blood flow from an average of 6.4‐‐4.1 ml. min‐1 . 100g‐1. 3. Vasoconstrictor responses to sympathetic nerve stimulation (4 HZ) and injected noradrenaline (5 n‐mole) were potentiated by cooling while vasodilator components of the vascular responses, such as autoregulatory escape and post‐stimulatory hyperaemia, were virtually abolished by this treatment. 4. Oxygen uptake was reduced by cooling without signs of tissue hypoxia. This reduced oxygen demand may partly cause the decrease in adipose tissue blood flow. 5. Cooling inhibited glycerol mobilization from the adipose tissue during sympathetic nerve stimulation. Post‐stimulatory lipolysis was, however, not inhibited. In vitro studies with 'perifused' rat fat cells suggest that this may be due to impaired inactivation of the lipolytic process, rather than to changes in transmitter removal, following stimulation at low temperature. 6. Cooling inhibited the mobilization of fatty acids more than that of glycerol, suggesting increased re‐esterification of fatty acids within the tissue at low temperature. 7. It is concluded that cooling increases the sensitivity to vasoconstrictor stimuli and that inhibition of metabolic vasodilator mechanisms play a role for this effect. The stimultaneous inhibition of activating and inactivating mechanisms could explain the unchanged vascular and lipolytic responses to brief stimuli. Some possible implications of the present findings for the physiology of adipose tissue during cooling are discussed.
Renal bicarbonate reabsorption in the new‐born dog
Authors: Kleinman Leonard I.
Published: December 2014

1. Renal bicarbonate reabsorption was measured in thirty new‐born dogs 2‐27 days of age. Plasma bicarbonate was varied in the puppies by exchanging their blood with blood containing high levels of bicarbonate and low levels of chloride.

2. The exchange transfusion resulted in increases of plasma pH, PCO2 and bicarbonate in the puppies without changing plasma sodium and potassium or glomerular filtration rate (g.f.r.) and body weight.

3. There was no tubular reabsorption maximum (Tm) for bicarbonate and reabsorption values as high as 50 μequiv/ml. g.f.r. could be attained. No animals excreted bicarbonate at plasma levels below 25 m
M and some animals had plasma bicarbonate threshold values in excess of 40 m
M.

4. Bicarbonate reabsorption increased as arterial PCO2 rose (r = 0·62) but this was due to the rise of filtered bicarbonate since (a) there was no correlation between arterial PCO2 and bicarbonate reabsorption when factored by filtered bicarbonate and (b) lowering arterial PCO2 by mechanical hyperventilation did not reduce bicarbonate reabsorption corrected for filtered load.

5. Inhibition of renal carbonic anhydrase by acetazolamide (50 mg/kg) resulted in an inhibition of bicarbonate reabsorption of only 4·5 μequiv/ml. g.f.r. (less than 20% of the total). Even with renal carbonic anhydrase inhibited, there was no bicarbonate Tm and bicarbonate reabsorption values as high as 40 μequiv/ml. g.f.r. could be attained.

6. There was good correlation (r = 0·82) between inhibition of sodium and bicarbonate reabsorption during renal carbonic anhydrase inhibition. However, with carbonic anhydrase inhibited, there was no correlation between arterial PCO2 and bicarbonate reabsorption.

7. These results demonstrate that tubular bicarbonate reabsorption mechanisms in the new‐born dog are as efficient as those reported for the adult as long as body fluid and plasma sodium and potassium levels are carefully maintained.

8. The results are also consistent with a bicarbonate reabsorptive mechanism explained either by direct ionic bicarbonate reabsorption or by hydrogen ion secretion with diffusion of carbonic acid.
Inhibition of noradrenaline release by adenosine.
Authors: Wakade A R , Wakade T D
Published: December 2014

1. Release of [3H]noradrenaline evoked by stimulation (5 Hz) of the pre‐labelled rat vas deferens was reduced to 50% by adenosine (10(‐6) g/ml.). Inhibition of release was dependent on the concentration of adenosine and was inversely related to the frequency of stimulation. Phenoxybenzamine did not interfere with the action of adenosine on release. 2. Exposure of the pre‐labelled rat vas deferens to 135 mM‐K+ released almost 10 times more [3H]noradrenaline than exposure to 45 mM‐K+. Release induced by 45 mM‐K+ was almost abolished by adenosine (10(‐6) g/ml.) but that induced by 135 mM‐K+ was reduced to only 45%. 3. Inhibition of [3H]noradrenaline release was observed in salivary gland, heart and portal vein of the rat, and in the guinea‐pig heart and vas deferens. A very high concentration of adenosine (10(‐4) g/ml.) reduced the release (about 50%) in the rabbit heart, but the cat heart was totally insensitive to the inhibitory action of adenosine. 4. Aminophylline (2 x 10(‐4) g/ml.) antagonized the inhibitory action of adenosine (10(‐6) g/ml.) on the release of [3H]noradrenaline in the phenoxybenzamine‐treated vas deferens. 5. Tetraethylammonium (8 x 10(‐4) g/ml.) enhanced stimulation‐evoked release in the rat salivary gland by almost tenfold. In the presence of tetraethylammonium, even higher concentrations (2 x 10(‐5) g/ml.) of adenosine failed to interfere with release. 6. Elevation of external K+ (19 mM) blocked stimulation‐evoked release in the rat vas deferens by about 55%. Combination of high K+ and adenosine (10(‐6) g/ml.), which blocked release by about 40%, caused still greater inhibition (80%) of the release. 7. The possible mechanism of action of the inhibitory effect of adenosine on the stimulation‐evoked release of noradrenaline is discussed in relation to the calcium hypothesis.
Metabolic rate: its circadian rhythmicity in the female domestic fowl.
Authors: Berman A , Meltzer A
Published: December 2014

1. In quasi‐natural cyclic lighting, a circadian rhythm was observed in seven fowls; the range of oscillation of the rhythm was 50% of the mean metabolic level. Little variation was present between the individuals. 2. In fowls maintained for 15 days in isolation under 700 lx (ten fowls) or 0.07 lx (four fowls) constant lighting and at constant temperature free‐running rhythms were evident; the range of oscillation was about 12% of the mean level. Large variation prevailed between the individuals in the range of oscillation and in the portion of variance accounted for by periodic regression. In dim light, rhythmicity declined to become non‐significant by 8 days of exposure. 3. In four fowls maintained in a 6L/6D regimen for 12 days, metabolic rate was entrained to an ahemeral rhythm; there was no evidence of circadian influence on the metabolic response to light. Little variation was present between the individuals. Rhythmicity was maintained over the experimental period. 4. Metabolic levels were similar on 0.07 lx, 700 lx constant light, during the dark phase of the 6L/6D regimen and during night time in the quasi‐natural cyclic lighting. They were also similar on the light phase of the 6L/6D regimen and the quasi‐natural lighting.
Antidiuretic action of intravenous and intracerebral pyrogen in conscious rabbits.
Authors: Kruk B , Sadowski J
Published: December 2014

1. In conscious rabbits an i.v. infusion of 30 or 60 microgram E. coli pyrogen/kg body wt. decreased urine flow from control of 1.13 +/‐ 0.11 (S.E. of mean) ml./min to 0.43 +/‐ 0.09 ml./min while urine osmolality increased from 212 +/‐ 16 to 679 +/‐ 82 m‐osmole/kg H2O. Clearances of exogenous creatine and p‐aminohippurate did not change significantly. 2. Plasma antidiuretic activity (rat bio‐assay) increased from control of 15.5 +/‐ 4.2 to 56.8 +/‐ 5.5 muu./ml. at the top of antidiuresis. 3. Comparable urine flow and osmolality changes were evoked by a pyrogen dose of only 0.2 microgram per animal injected into the lateral cerebral ventricle. 4. The results suggest that in the rabbit pyrogen stimulates ADH release by an unknown central mechanism.
Vagal glucoreceptors in the small intestine of the cat.
Authors: Mei N
Published: December 2014

1. In anaesthetized cats, the unitary activity of seventy‐eight sensory vagal neurones was recorded in nodose ganglia by means of extracellular glass microelectrodes. 2. These neurones were stimulated by perfusion of the small intestine (duodenum and first part of jejunum) with glucose or other different carbohydrates at concentrations of 1‐‐20 g/l. (i.e. 55‐‐1100 m‐osmole/l.). 3. The neurones were slowly adapting to stimulation and their discharge frequency was always low (1‐‐30 Hz). 4. The activity of these neurones depended on the particular carbohydrate used and on its concentration: the discharge frequency generally increased when the concentration rose. 5. The neurones were of the C type (conduction velocities: 0.8‐‐1.4 m/sec; mean, 1.1 m/sec). 6. In contrast with the known neurones connected to the gastro‐intestinal tension receptors, they were not obviously activated by intestinal contractions or distensions. 7. In the same way, the stimuli which produced the response of other known endings, i.e. the mucosal receptors, were not effective; these stimuli included in particular stroking of the mucosa, over‐distension of the bowel, intestinal perfusion with alkaline or acid solutions. On the other hand, the use of substances other than glucose (KCl and NaCl of the same osmolarity) showed that the osmotic pressure was not directly related to the receptor activation. 8. Therefore it is proposed to call the endings corresponding to these neurones ‘glucoreceptors’. 9. The effect of glycaemia and intestinal motility were also studied. These variables acted presumably by changing the intestinal absorption rate. 10. The functional characteristics of the glucoreceptors (in particular the short latency of their response) strongly suggested that they were located close to the intestinal epithelium. 11. An ultrastructural study was performed in an attempt to identify the histological site of the receptors. Many non‐medullated fibres were observed in the villi, especially beneath the epithelial layer. They gave complex branchings with abundant swellings. Some of them, at least, belonged to the vagal sensory component, because they were less numerous after unilateral selective sensory vagotomy. Therefore these complex endings could serve as the vagal glucoreceptors. 12. The roles of vagal intestinal glucoreceptors are discussed. Their functional characteristics as well as the clinical and experimental data suggest that they may be involved in the regulation of different types of alimentary behaviour (hunger, thirst, alliesthesia) and energy balance.
The transplacental potential difference as distinguished from the maternal‐fetal potential difference of the guinea‐pig.
Authors: Binder N D , Faber J J , Thornburg K L
Published: December 2014

1. We measured the differences in electrical potential between mother and fetus in the guinea‐pig. The fetus was 33 +/‐ 2 (S.E. of mean) mV negative with respect to the mother. 2. Salts of bromine, sulphate, rubidium, and lithium were injected into pregnant sows and blood samples were obtained from the sows and their fetuses at various times after injection. The transplacental electrical potentials at which each of these ions would be in electrochemical equilibrium across the placental exchange barrier were calculated from the Nernst equation and the concentrations in maternal and fetal plasmas. 3. The differences in transplacental electrical potential calculated from the steady‐state concentrations of these ions in maternal and fetal plasmas were within 1 mV of zero. 4. These observations are consistent with a very small difference in electrical potential across the placental exchange barrier itself, and the generation of a potential difference between mother and fetus at a site other than the exchange barrier.
Involvement of uptake1 and uptake2 in terminating the cardiovascular activity of noradrenaline in normotensive and genetically hypertensive rats.
Authors: Bell C , Kushinsky R
Published: December 2014

1. In pithed, pancuronium‐treated rats, inhibition of Uptake1 with desmethylimipramine (2.5 mg/kg i.v.) increased the time course of the pressor response to vasomotor nerve stimulation (1 and 5 Hz for 5 sec) but not the time course of the pressor response to injected noradrenaline (10 and 50 ng i.v.). 2. Subsequent inhibition of Uptake2 with metanephrine (3 mg/kg, i.v.) did not affect the time course of responses to either vasomotor nerve stimulation or injected noradrenaline. 3. It is concluded that Uptake1 but not Uptake2 is important in terminating the activity of noradrenaline released from rat vasomotor nerves and that neither process inactivates intraluminal catecholamine. 4. By contrast, chronotropic responses of rat atria to adrenergic nerve stimulation were prolonged by blockade of both Uptake1 and Uptake2, in agreement with previous evidence for involvement of both processes in terminating sino‐atrial adrenergic responses. 5. Animals from the Otago strain of genetically hypertensive animals were identical to normotensives in their vascular handling of catecholamine. However, they lacked an atrial Uptake2 process. 6. This defect may be related to the high resting heart rate and abnormal cardiac catecholamine turnover observed to exist in the Otago hypertensive rats.
The blockade of GABA mediated responses in the frog spinal cord by ammonium ions and furosemide.
Authors: Nicoll R A
Published: December 2014

1. A variety of compounds which are known to block chloride transport in a variety of systems have been examined for their effects on amino acid and synaptic responses in the frog spinal cord in vitro. 2. A number of monocarboxylic aromatic acids, copper sulphate, and acetazolamide had no effect on any of the responses. 3. Ammonium ions blocked the motoneurone hyperpolarizing responses to all the neutral amino acids. In addition it selectively blocked dorsal root potentials and the action of GABA and beta‐alanine on primary afferents. 5. Intracellular recording from dorsal root ganglion cells demonstrated that furosemide had little effect on the reversal potential for the GABA response. These results suggest that furosemide acts primarily by blocking the conductance increase elicited by GABA. 6. The results with furosemide provide indirect evidence that chloride ions are involved in generating the GABA depolarizations of primary afferent terminals and dorsal root potentials.
Electrical activity of human colonic smooth muscle in vitro.
Authors: Duthie H L , Kirk D
Published: December 2014

1. Extracellular and intracellular recordings were made of the electrical activity of isolated strips of human colonic smooth muscle, cut from sixty surgical specimens. 2. Strips of taenia were spontaneously active. The myogenic activity consisted in half the strips of intermittent periods of regular spike activity (frequency 22 +/‐ 5 (S.D.) c/min) accompanied by tetanic contractions; in the other half of the strips activity was continuous. In half the specimens, slow potentials were recorded between periods of spike activity. Slow potentials were not accompanied by contractions. 3. Spikes in taenia were abolished by verapamil. Spikes disappeared in low Ca and low Na solutions, but in low Na solution spikes could be stimulated by 15 mM‐KCl. 4. ACh and physotigmine produced tetanic contractions in taenia. 5. Circular muscle was not spontaneously active within 1 h of incubation in the water bath, possibly due to inhibition by prostaglandins. 6. Circular muscle responded to ACh with irregular bursts of spikes associated with discrete contractions. Similar activity was seen after inhibition of prostaglandin synthesis with indomethacin. After treatment with tetrodotoxin, ACh produced regular spikes and tetanic contractions in circular muscle. 7. The possible relationships of these results to the myoelectrical activity of the human colon in vivo are discussed.
The force—velocity relation of isolated twitch and slow muscle fibres of Xenopus laevis
Authors: Lännergren J.
Published: December 2014

1. A study has been made of the relation between force and speed of shortening, or lengthening, in isolated twitch and slow muscle fibres, dissected from the iliofibularis muscle of Xenopus laevis. Both after‐loaded and quick‐release contractions were studied. Twitch fibres were stimulated electrically to give tetanic contractions (5‐20 °C); slow fibres were activated by a rapid change to solutions with high K concentration (30‐75 m
M; experiments at 21‐24 °C).

2. The velocity of slow fibres was constant during shortening over 10% length change in after‐loaded contractions, except at forces exceeding about 0·8 of isometric tension, P0. In quick‐release experiments, shortening velocity was found to depend not only on the relative load, P/P0, but also on the instant when the release was made. With increasing time after onset of contraction the initial rate of shortening decreased; also, a progressive fall in speed during shortening became more marked.

3. The fall in initial shortening speed with time of release from the onset of a contracture was more pronounced at high [K]o than at low.

4. The relation between the relative force, P/P0, and shortening velocity, V, in after‐loaded contractions (75 m
M‐K) and quick‐release contractions (45 m
M‐K, early releases) in slow fibres could be represented by a hyperbola with the constants a = 0·10P0, b = 0·11 lengths/sec; extrapolated Vmax. was 1·10 lengths/sec.

5. Isometric tension and maximum shortening velocity in slow fibres were very nearly constant between 32 and 75 m
M‐K. a/P0, however, was clearly reduced at 32 m
M‐K, representing a more curved P-V relation.

6. Force—velocity data for twitch fibres (quick‐release contractions, 20 °C) were reasonably well fitted by a hyperbola (a = 0·38P0, b = 1·97 lengths/sec, Vmax. = 5·20 lengths/sec), but a systematic deviation was observed for forces exceeding 0·6P0.

7. a/P0 for twitch fibres was found to be independent of temperature in the range 5‐20 °C. Q10 for b was 2·24 (10‐20 °C), and 2·86 (5‐10 °C).

8. Vmax. for twitch fibres was calculated to be 6·34 lengths/sec at 22·5 °C, the average temperature in the slow fibre experiments. The maximum shortening velocity in twitch fibres is thus 6 times higher than in slow fibres.

9. When loads in the range 1·1‐1·4P0 were quickly applied to an actively contracting slow fibre, lengthening of the fibre occurred in two phases, an initial rapid phase, followed by a phase of extremely slow lengthening. In corresponding experiments on twitch fibres lengthening was rapid at first and then gradually became slower.

10. Factors affecting the shape of the force—velocity curve are discussed. Calculations based on A. F. Huxley's (1957) model for muscle contraction indicated that cross‐bridge turnover rate is about 15 times lower in slow than in twitch fibres.
An electrophysiological study of the regulation of ciliary beating frequency in Paramecium.
Authors: Brehm P , Eckert R
Published: December 2014

1. The role of the surface membrane in the control of ciliary beat frequency in Paramecium was examined by intracellular electrophysiological techniques and pressure injection of Ca2+ and EGTA. Experiments were done on wild type P. caudatum and on both the wild type and a pawn mutant of P. tetraurelia. 2. The increased frequency of beating that accompanies reversal of power stroke orientation in response to depolarization in the wild type fails to occur during depolarization in the mutant pawn, which also fails to exhibit ciliary reversal upon depolarization. 3. Injection of moderate amounts of EGTA blocked the frequency increase without interfering with reversal of the beat in response to depolarization of the wild type. Larger injection of EGTA also prevented reversed beating. 4. The beat frequency in the normal (forward‐swimming) direction increased during hyperpolarization in pawn. The hyperpolarizing frequency‐voltage relations were quantitatively similar to those of the wild type. 5. Injection of EGTA to a final concentration of 10 mM into wild type cells neither modified the resting frequency nor blocked the frequency increase which normally accompanies hyperpolarization. 6. Transient ciliary reversal in both pawn and wild type produced by injection of Ca2+ could be terminated by the passage of inward current. The power stroke returned to the normal forward‐swimming direction and the ciliary beating frequency increased. Upon termination of the inward current the cilia of Ca2+‐injected cells again beat in reverse for many seconds. 7. The results support previous reports that increased frequency of beating and ciliary reversal seen in response to depolarization both require the entry of Ca2+ through the surface membrane. On the other hand, the results indicate that frequency increase with hyperpolarization is independent of an altered rate of Ca2+ entry. 8. Increased frequency during hyperpolarization appears to be related more closely to electrotonic membrane current than to membrane potential. It is proposed that inward current might activate high frequency beating by altering the ionic environment of the axoneme within the restricted volume of the cilium by electrophoretic means.