bluuebunny/crossref_metadata_2025 huggingface dataset:
Lithium protection against oxygen toxicity in rats: ammonia and amino acid metabolism.
Authors: Banister E W , Bhakthan N M , Singh A K
Published: December 2014

1. The use of Li pre‐treatment in rats before high pressure oxygen exposure has been reported effective in controlling convulsions. This is an effect which is better demonstrated if exposure to oxygen follows shortly after Li injection than exposure following several hours later. 2. This study has investigated the hypothesis that the protective action of Li may be exerted, in the short term, by its removing ammonia from the blood and alleviating the latter's known toxic action. 3. A normal Li distribution time profile in unstressed rat brain and blood following intraperitoneal injection has been established. Brain and blood ammonia, amino acids and Li concentrations were also measured in Li‐treated animals exposed and convulsed by oxygen. These measurements were made both shortly (15 min) and also several hours after (24 hr) Li treatment. Ammonia and amino acid values in Li‐protected groups were compared to normal unstressed animal values and also to values in animals convulsed by oxygen unprotected by Li pre‐treatment. 4. In rat brain abd blood significant (P less than 0‐001) elevation of ammonia and glutamine and depression of gamma‐amino butyric acid (brain only) and glutamate was noted following oxygen treatment in unprotected animals. Prior injection of Li 15 min before high pressure oxygen exposure delayed convulsions twice as long. Additionally if these animals were only exposed to oxygen for a period of time equal to that which would normally produce convulsions in unprotected animals, brain and blood ammonia and amino acids were maintained near to unstressed animal levels. Concomitantly, blood Li concentrations were considerably depressed below the values one would expect from the previously determined Li distribution time profile. 5. In rats exposed to high pressure oxygen 24 hr after Li treatment there was no protective action against high pressure oxygen convulsion, rather a potentiating effect for convulsion was seen. 6. These data present compelling evidence for the controlling effect of Li in rats, on rising blood ammonia concentration which occurs in high pressure oxygen exposure. The effect might well be due to the known chelating properties of Li with ammonia.
Sulphate excretion by dogs following ingestion of ammonium sulphate or meat.
Authors: O'Connor W J , Summerill R A
Published: December 2014

1. When normal conscious dogs were given small doses of (NH4)2SO4 by stomach tube, the rate of excretion of SO4 increased due to increase in plasma SO4 without change in creatinine clearance. After eating meat, increased SO4 excretion was due to increase in glomerular filtration rate without change in plasma SO4. 2. The calculated rate of tubular reabsorption of SO4 did not change significantly either after (NH4)2SO4 or after meat. 3. The rate of production of SO4 after meat was estimated. In 4 hr approximately one fifth of the S in meat was converted to inorganic SO4; in the same time approximately one third of the N in the meat was converted into urea. 4. Half of the SO4 in the doses of (NH4)2SO4 was absorbed from the gut; all of the NH was converted into urea. (NH4)2SO4 thus produced acidosis. 5. After (NH4)2SO4, increased excretion of NH4+ accompanied the increased excretion of SO4‐but Na+, K+ in urine also increased.
The secretion of citrate into milk.
Authors: Linzell J L , Mepham T B , Peaker M
Published: December 2014

1. The time course of changes in specific activities of citrate, lactose and fatty acids in milk during frequent milking, following the I.V. administration of labelled glucose, acetate and chylomicrons in goats has been studied. Peak specific activities of lactose and citrate in milk were reached at 2‐3 hr, while peak specific activites of fatty acids were reached at 5‐7 hr. 2. Following short I.A. infusions of 24Na, 36Cl, and 42K, peak specific activities in milk were reached in 1 hr or less. 3. The mammary epithelium of lactating goats was found to be virtually impermeable to labelled citrate in both directions. 4. Labelled citrate had an apparent volume of distribution in lactating guinea‐pigs mammary slices in vitro similar to that of extracellular space markers. 5. Treatment of goats with large doses of oxytocin markedly increased the permeability of the secretory epithelium to labelled citrate. 6. In the goat mammary gland, citrate, protein and calcium failed to enter milk which had been diluted with isosmotic lactose by intraductal injection, whereas Na, K and Cl did enter, thus tending to restore the concentrations of these ions to normal. 7. It is suggested that citrate, which is formed within the sucretory cell, enters milk not by passage across the apical cell membrane but, in common with lactose and milk protein, by exocytosis of Golgi vesicles. It appears that citrate is held at high concentrations in milk by virtue of the impermeability of the mammary epithelium to the forms in which it occurs in milk.
Reversal of the physiological effects of monocular deprivation in the kitten's visual cortex.
Authors: Movshon J A
Published: December 2014

1. Twenty‐three kittens were monocularly deprived of vision until the age of 4, 5, 6 or 7 weeks. Their deprived eyes were then opened, and their experienced eyes shut for a further 3‐63 days. After this time physiological recordings were made in the visual cortex, area 17. Three control kittens, monocularly deprived for various periods, showed that at the time of reverse‐suturing, few neurones could be influenced at all from the deprived eye. 2. Following reverse‐suturing, the initially deprived eye regained control of cortical neurones. This switch of cortical ocular dominance was most rapid following reverse‐suturing at the age of 4 weeks. Delaying the age of reverse‐suturing reduced the rate and then the extent of the cortical ocular dominance changes. 3. The cortex of reverse‐sutured kittens is divided into regions of cells dominated by one eye or the other. The relative sizes of these ocular dominance columns changed during reversed deprivation. The columns devoted to the initially deprived eye were very small in animals reverse‐sutured for brief periods, but in animals that underwent longer periods of reversed deprivation, the columns driven by that eye were larger, while those devoted to the initially open eye were smaller. 4. Clear progressions of orientation columns across the cortex were apparent in many of the kittens, but, in contrast to the situation in normal or strabismic kittens, these sequences were disrupted at the borders of eye dominance columns: the cortical representations of orientation and ocular dominance were not independent. 5. Binocular units in these kittens were rather rare, but those that could be found often had dissimilar receptive field properties in the two eyes. Commonly, a cell would have a normal orientation selective receptive field in one eye, and an immature, unselective receptive field in the other. Cells that had orientation selective receptive fields in both eyes often had greatly differing orientation preferences in the two eyes, occasionally by nearly 90 degrees. 6. During the reversal of deprivation effects, the proportion of receptive fields exhibiting mature properties declined in the initially experienced eye, while the proportion increased in the initially deprived eye. Similarly, the average band width of orientation tuning of receptive fields in the initially deprived eye decreased, while that of receptive fields in the initially experienced eye increased. 7. One kitten was reverse‐sutured twice, to demonstrate that cortical ocular dominance may be reversed a second time, even after one reversal of ocular dominance. 8. It is suggested that the sensitive period for cortical binocular development consists of two phases. In the first phase, all cortical neurones may be modified by experience, but the rate at which they may be modified decreases with age. In the second phase, an increasing number of cortical neurones becomes fixed in their properties, while those that remain modifiable are as modifiable as they were at the end of the first phase. 9...
The effect of noradrenaline and 5‐hydroxytryptamine injected into a lateral cerebral ventricle, on thermoregulation in the new‐born lamb.
Authors: Cooper K E , Pittman Q J , Veale W L
Published: December 2014

1. Respiratory frequency, shivering, ear skin temperatures and rectal temperatures were observed following intraventricular injections of noradrenaline (NA), 5‐hydroxytryptamine (5‐HT) and saline (NaCl) into new‐born lambs exposed to ambient temperatures of 4, 21, or 30 degrees C. 2. Intraventricular NA caused respiratory rate to decrease and body temperature to increase in the 30 degrees C environment. At 21 degrees C, it increased ear skin temperature but did not significantly affect rectal temperature. At 4 degrees C, NA decreased shivering and rectal temperature fell. 3. 5‐HT elevated respiratory rate in the 30 degrees C environment and increased ear skin temperature in the 21 and 4 degrees C environments. In the 4 degrees C environment rectal temperature decreased. 4. In general, the change in rectal temperature was related to the dosage of drug administered. Control injections of NaCl had no significant effect on any of the variables measured. 5. The monoaminergic pathways involved in thermoregulation in the new‐born lamb appear to be organized in a manner similar to that of the adult sheep and are functional at birth.
Adrenal and pancreatic endocrine responses to hypoxia in the conscious calf.
Authors: Bloom S R , Edwards A V , Hardy R N , Silver M
Published: December 2014

1. Pancreatic and adrenal responses to intense hypoxia have been examined in conscious unrestrained calves 3‐5 weeks after birth. 2. The outputs of both cortisol and corticosterone from the right adrenal gland rose steadily in response to hypoxia and this cortical secretory response was accompanied by a pronounced increase in blood flow through the gland. The changes in both steroid output and adrenal blood flow corresponded with those which occur in response to supramaximal doses of corticotrophin in calves of the same age. 3. Neither adrenaline nor noradrenaline were released in significant amounts from the adrenal medulla until the arterial PO2 had fallen below 15 mmHg. Such severe hypoxia caused secretion of catecholamines at rates comparable with those recorded during maximal stimulation of the sympathetic innervation to the gland in anaesthetized calves. The response to intense hypoxia in these conscious calves differed from that which occurs under anaesthesia in that the amount of adrenaline released was invariably greater than that of noradrenaline. 4. Severe hypoxia produced a rapid but transient increase in plasma glucagon concentration, followed by a pronounced rise in plasma glucose concentration in animals with abundant liver glycogen. No change in plasma insulin concentration was observed during hypoxia although it rose subsequently in response to hyperglycaemia. 5. Bilateral section of the splanchnic nerves virtually abolished the release of catecholamines in response to hypoxia but the adrenal cortical and pancreatic responses did not appear to be affected.
Properties of the larval neuromuscular junction in Drosophila melanogaster.
Authors: Jan L Y , Jan Y N
Published: December 2014

The anatomy and physiology of the Drosophila larval neuromuscular junction were studied. 2. The dependence of muscle resting potentials on [K+]o and [Na+]o follows the Goldman‐Hodgkin‐Katz equation (PNa/PK=0‐23). Chloride ions distribute passively across the membrane. 3. The mean specific membrane resistance of muscle fibres is 4‐3 X 10(3) omega cm2, and the mean specific membrane capacitance is 7‐1 muF/cm2. The muscle fibre is virtually isopotential. 4.Transmitter release is quantal. Both the miniature excitatory junctional potential and the evoked release follow the Poisson distribution. 5. Transmitter release depends on approximately the fourth power of [Ca2+]o. If Sr2+ replaces Ca2+, it depends on approximately the fourth power of [Sr2+]o. Mg2+ reduces transmitter release without altering the fourth power dependence on [Ca2+]o.
Linear and nonlinear spatial subunits in Y cat retinal ganglion cells.
Authors: Hochstein S , Shapley R M
Published: December 2014

1. The mechanism which makes Y cells different from X cells was investigated. 2. Spatial frequency contrast sensitivity functions for the fundamental and second harmonic responses of Y cells to alternating phase gratings were determined. 3. The fundamental spatial frequency response was predicted by the Fourier transform of the sensitivity profile of the Y cell. The high spatial frequency cut‐off of a Y cell's fundamental response was in this way related to the centre of the cell's receptive field. 4. The second harmonic response of a Y cell did not cut off at such a low spatial frequency as the fundamental response. This result indicated that the source of the second harmonic was a spatial subunit of the receptive field smaller in spatial extent than the centre. 5. Contrast sensitivity vs. spatial phase for a Y cell was measured under three conditions: a full grating, a grating seen through a centrally located window, a grating partially obscured by a visual shutter. The 2nd/1st harmonic sensitivity ratio went down with the window and up with the shutter. These results implied that the centre of Y cells was linear and also that the nonlinear subunits extended into the receptive field surround. 6. Spatial localization of the nonlinear subunits was determined by means of a spatial dipole stimulus. The nonlinear subunits overlapped the centre and surround of the receptive field and extended beyond both. 7. The nature of the Y cell nonlinearity was found to be rectification, as determined from measurements of the second harmonic response as a function of contrast. 8. Spatial models for the Y cell receptive field are proposed.
Permeability of individual human erythrocytes to thiourea.
Authors: Jay A W
Published: December 2014

The osmotic swelling to haemolysis of individual red blood cells by isosmotic thiourea has been studied using microcine photography. 2. Crenation occurs immediately upon addition of isosmotic thiourea. The cell becomes a crenated sphere without volume decrease. 3. Subsequently, the cell volume increases linearly with time with maximum swelling occurring at about 102 sec which is 81% of the total haemolysis time. 4. At maximum swelling, the cell volume is 92% greater than the initial cell volume. This volume increase is about double that measured with other permeating substances. 5. The much larger maximum volume implies that thiourea increases the area of the cell membrane. This increase varies from 0 to 75% for individual cells, with a mean of 22%. 6. Membrane expansion varies inversely as the initial cell membrane area and cell volume (r=0‐790). 7. Using the increased surface area, increased maximum volume and the swelling time, the mean permeability is calculated to be 5‐52 X 10(‐7) cm/sec (S.D. of mean=+/‐1‐19 X 10(‐7) cm/sec). The distribution of permeabilities represents a normal distribution. 8. The pre‐lytic potassium loss ranged from 0 to 36% with a mean value of 16‐5%. This is consistent with values reported in the literature for slow haemolysis. As with other permeants the distribution is skewed towards lower values. 9. Membrane permeability of individual cells varies with the amount of membrane expansion observed. Coefficient of correlation between permeability and expansion index is 0‐674. 10. There is no correlation between permeability and the reciprocal of the haemolysis time (r=‐0‐035). The correlation between permeability and the reciprocal of the swelling time is also poor (r=0‐303), probably owing to the variability in membrane expansion by thiourea in individual cells. 11. As has been shown previously for faster permeants, the permeability coefficient cannot be calculated from the haemolysis time. Because thiourea alters the membrane area and the haemolytic volume, the coefficient cannot be calculated from the swelling time unless the changes in the membrane area are also taken into account.
The responses to nerve stimulation of the salivary gland of Nauphoeta cinerea Olivier.
Authors: Ginsborg B L , House C R
Published: December 2014

A study has been made with intracellular electrodes of the responses of acini of the salivary gland of Nauphoeta cinerea Olivier to salivary duct nerve stimulation. The gland is a paired structure and offers the possibility of investigating the interaction between ipsi‐ and contralateral nerve stimulation. 2. The characteristics of the responses are as previously described for field stimulation (House, 1973). The latency is of the order of 1 sec and almost independent of the amplitude of the response which may attain a hyperpolarization of about 80 mV. The depolarization which sometimes follows can be disassociated from the preceding hyperpolarization and is presumably an independent response. 3. The stimulus‐response relationship shows that acini are multiply innervated. Those close to the mid line recieve axons from both ipsi‐ and contralateral salivary duct nerves. The response to a test stimulus T can be augmented by an immediately preceding conditioning stimulus C, the joint response being greater than the sum of the separate responses. This effect occurs even when C and T are delivered to different nerves. For longer intervals between C and T, the response to T is depressed.
A study of the ion selectivity and the kinetic properties of the calcium dependent slow inward current in mammalian cardiac muscle.
Authors: Reuter H , Scholz H
Published: December 2014

1. A voltage‐clamp method combining a single surcose gap and two intracellular micro‐electrodes was used to measure membrane currents in ventricullar myocardial fibres. 2. The adequacy of the voltage‐clamp method is demonstrated by comparing the total current, It, across the gap with the voltage difference, delta V, between the two intracellular micro‐electrodes, i.e. another independent way of measuring membrane currents. With both current measurements the slow inward current, Is, shows the same voltage‐ and time‐dependences. 3. The sensitivity of the slow inward current to variation in external Ca and Na concentrations was investigated systematically. The reversal potential of the slow inward current was sensitive to variation of both ion species. 4. From the reversal potential measurements relative permeabilities of the conductance channels of the slow inward current were estimated as PCa/PNa approximately 1/0‐01 and PCa/PK approximately 1/0‐01 by means of the constant field equation. 5. The activation and inactivation kinetics of the slow inward current were explored in detail and related to the plateau of the action potential.
A quantitative analysis of local anaesthetic alteration of miniature end‐plate currents and end‐plate current fluctuations.
Authors: Ruff R L
Published: December 2014

1. The effect of the local anaesthetic QX222 on the kinetics of miniature end‐plate currents (m.e.p.c.s) and acetylcholine (ACh) induced end‐plate current (e.p.c) fluctuations was studied in voltage‐clamped frog cutaneous pectoris neuromuscular junctions made visible with Nomarski differential interference contrast optics. 2. In Ringer solution the m.e.p.c.s decayed with a single exponential time course and the e.p.c. fluctuation spectra were characterized by single Lorentzian functions, with the spectral cut‐off frequency well predicted by the m.e.p.c. decay rate. 3. In the presence of 0‐1‐0‐5 mm QX222 at‐50 to ‐100 mV holding potential both the e.p.c. fluctuation spectrum and the m.e.p.c. decay consisted of a fast and a slow component, with the cut‐off frequency of each spectral component predicted by the decay rate of the corresponding constituent of the m.e.p.c. 4. Hyperpolarization increased the decay rate and relative amplitude of the fast component of the m.e.p.c. and decreased the decay rate of the slow m.e.p.c. component. 5. With 0‐05 mm QX222 and ‐70 mV holding potential the m.e.p.c.s. and e.p.c. fluctuation spectra consisted of three components. The third component of the m.e.p.c. and e.p.c. spectra had nearly the same decay rate and cut‐off frequency as was found at the same end‐plate under equivalent conditions before drug exposure. 6. The kinetic predictions of four different schemes for local anaesthetic action were compared with observed m.e.p.c.s. and e.p.c. fluctuations. 7. Schemes in which the local anaesthetic acted by creating two kinetically distinct populations of acetylcholine receptors or by interacting with ACh receptor to produce a biphasic exponential decay of the end‐plate channel conductance did not accurately predict the e.p.c. fluctuation spectrum. 8. The variance of the e.p.c. fluctuations vanished at the reversal potential indicating that local anaesthetic action was not due to the presence of different ion selective end‐plate channels. 9. QX222 action could be explained by alteration of the ACh receptors such that they sequentially c‐hanged from one conductance state to another. A specific case in which QX222 binds to the ACh receptors in its open state creating a partially blocked state, was found to be the most parisimonious. 10. The conductance, gamma, of a single end‐plate channel was estimated from e.p.c. fluctuations. In Ringer's solution gama = 24‐4 +/‐ 1‐2 (s.d.) pmho. In the presence of 0‐1 mm to 0‐5 mm QX222 the effective single channel conductance, gamma, varied from 14‐2 to 1‐39 pmho. 11. gamma decreased with increased local anesthetic concentration, hyperpolarization, or decreased temperature. The variation in gamma is thought to reflect the dependence on the experimental conditions of the relative probability that the ACh receptors is in an open vs a partially blocked state.
The optical properties of birefringence signals from single muscle fibres.
Authors: Baylor S M , Oetliker H
Published: December 2014

1. The optical retardation of single muscle fibres at rest and the optical properties of the large, early birefringence signal detectable during a twitch (Baylor & Oetliker, 1975, 1977a) were investigated. 2. The resting birefringence, B, which is the factor relating resting retardation, R, to the light path length through the fibre, L, was found to be 2.25 x 10‐3 (i.e. R = 2.25 X 10‐3 X L) and to be independent of wavelength ( lambda = 480‐660 nm). 3. When the angle of incidence, psi, of the crossed polarizers with respect to the fibre axis was varied, the resting light intensity and large, early change in light intensity were related by the function sin2 psi‐cos2psi. When the net phase shift, phi lambda, of a narrow longitudinal strip of fibre plus compensator was varied, the resting light intensity was described by the function (1‐cos phi lambda), whereas the early change in light intensity followed sin phi lambda. These results make it likely that the optical mechanism underlying the early birefringence signal is a change in retardation. 4. When a narrow longitudinal strip of fibre was illuminated by monochromatic light in the range 480‐690 nm, the magnitude of the signal varied approximately as expected if the retardation change is independent of wave‐length. 5. The spatial characteristics of the signal were examined by moving a small slit of light across the fibre width as well as by measuring the signal collected from the entire fibre width as a function of wave‐length. The results from both experiments support the idea that the large, early change in retardation is due to a volume‐related rather than surface‐related structure. 6. Under the assumption that the retardation change is distributed as fibre volume, its average magnitude was calculated. For fibres in normal Ringer the peak of the early retardation change compared with resting is about 1.7 x 10‐3, and for fibres in D2O Ringer about 0.7 x 10‐3.
Drinking caused by exposing dogs to radiant heat.
Authors: O'Connor W J
Published: December 2014

1. Exposure to radiant heat caused dogs to pant and lose water by evaporation at rates of 40‐70 g/hr. 2. When water was offered at intervals during the heating, the dogs drank at about half of the opportunities. The individual drinks were small but, by their repetition, loss of water by evaporation during heating was approximately matched by drinking. 3. Water given by stomach tube reduced drinking during a subsequent period of heating. 4. When water was offered more than 15 min after the end of a period of heating, after panting had ceased, drinking occurred only if the water loss exceeded 50‐70 g, about 0‐6% of the body water. This is regarded as drinking due to loss of water, beyond a threshold of dehydration necessary to stimulate drinking with the dog at rest. When water was offered during heating, drinking occurred with dehydration less than this threshold. 5. The drinking produced by heating was similar to that produced by running (O'Connor, 1975). When the animal ran under heat, panting was more severe and the water loss greater (85‐150 g/hr); it was approximately matched by more drinking.
Quantitative evaluation of the loss of human platelet dense bodies following stimulation by thrombin or A23187.
Authors: Costa J L , Detwiler T C , Feinman R D , Murphy D L , Patlak C S , Pettigrew K D
Published: December 2014

1. Distributions of dense bodies per platelet were evaluated in unstimulated human platelets and in platelets stimulated to secrete by the addition of varying amounts of thrombin or the ionophore A23187. Since distributions were not Gaussian, they were compared by non‐parametric methods. 2. Most distribution obtained following varying levels of dense‐body release differed significantly from the control (unstimulated) distribution. In general, distribution from points widely separated in terms of per cent release of total dense‐body content also differed significantly. Distributions obtained at points where the total number of dense bodies lost was approximately the same did not differ significantly, regardless of the drug and incubation conditions used to produce the dense‐body loss. 3. Dense bodies were lose from platelets during the secretory process (measured as the release of either calcium or ATP), and the number of dense bodies lost correlated at a significant level with the amounts of both substances secreted. 4. Following maximal secretion produced by either thrombin or A23187, a population of dense bodies (refractory dense bodies) remained in platelets. The refractory dense bodies could not have been distributed uniformly among the control populations of either platelets or dense bodies. The distribution of refractory dense bodies could, however, be described by a model in which platelets containing large numbers of dense bodies had a greater proportion of their dense‐body complement refractory than did platelets containing fewer dense bodies.
Kinetics of the inhibition of the Na‐K pump by tetrapropylammonium chloride.
Authors: Kropp D L , Sachs J R
Published: December 2014

1. The tetrapropylammonium ion (TPA) acts as a mixed‐type (with K) inhibitor of the Na‐K pump. The kinetics of the process suggest that combination of the pump with a single TPA ion is sufficient for inhibition. 2. TPA inhibits the partial reactions of the Na‐K pump (the uncoupled Na outflux, the Na‐Na exchange, and K‐K exchange). 3. TPA inhibits ouabain binding to the pump and this inhibitory effect is enhanced by external Na. The inhibitory effect of TPA on the pump rate is also promoted by external Na. 4. A Lineweaver‐Burk plot of the reciprocal of the ouabain‐sensitive K influx versus the reciprocal of the external K concentration is approximately a straight line if the measurements are made in Na‐free solutions. TPA increases the apparent Michaelis constant (K 1/2) for K and the plot remains straight. 5. The Lineweaver‐Burk plot is parabolic when the measurements are made in solutions which contain Na. TPA both increases the apparent K 1/2 for K and makes the curve more parabolic. 6. The characteristics of pump inhibition by TPA are similar to those for strophanthidin. In both cases the kinetic behaviour is consistent with a model in which the inhibitor binds: with greatest affinity to the pump form free of K; with less affinity to the pump form with a single bound K; and with least affinity to the pump form with two bound K.
Effects of cytochalasin B and dimethylsulphoxide on isosmotic fluid transport by rabbit gall‐bladder in vitro.
Authors: Frederiksen O , Leyssac P P
Published: December 2014

1. Net fluid transport rate, transepithelial ohmic resistance and potential difference (p.d.), and unidirectional fluxes of Na+ were measured in rabbit gall‐bladder preparations in vitro exposed on both sides to Ringer solutions of identical electrolyte composition. 2. Bilateral application of 1% dimethylsulphoxide (DMSO), the solvent for cytochalasin B, rapidly and reversibly depressed net fluid transport rate by 15% and increased the lumen positive p.d. by 1‐5‐2‐0 mV. Resistance did not change significantly. These effects of DMSO were shown to be non‐specific osmotic effects. 3. Cytochalasin B (10(‐5)M) applied bilaterally caused: (a) a progressive inhibition of net fluid transfer rate to 40‐50% of its control value within 60 min; the effect was partly reversible within 60 min and independent of the substrates glucose, glutamate and pyruvate; (b) a progressive depression of the mucosal‐to‐serosal Na+ flux within the first 30 min with no further change in the flux during the following 30 min of exposure to cytochalasin B; the effect was partly reversible within 70 min; (c) a rapid but moderate increase in the passive serosal‐to‐mucosal Na+ flux, which continued to increase gradually during the entire 60 min period of exposure to cytochalasin B; the effect was completely reversible within 70 min; (d) a prompt drop in ohmic resistance (30%) and p.d. (40%) with no further changes in these parameters during the following 60 min of exposure to cytochalasin B. The effect on resistance was partly reversible within 90 min; the effect on p.d. was completely reversible within 30 min. 4. The results are interpreted to indicate an early inhibitory action of cytochalasin B on the active transcellular pump mechanism and to suggest a cytochalasin B‐mediated progressive increase in cell membrane permeability to sodium resulting ultimately in a highly leaky epithelium. The results are compatible with the concept that a mechanochemical process is involved in isosmotic transcellular transport of fluid across low‐resistance epithelia.
The orderly recruitment of motor units of the masseter and temporal muscles during voluntary isometric contraction in man.
Authors: Yemm R
Published: December 2014

1. The contractile properties of the motor units of the masseter and temporal muscles of human subjects were studied during voluntary isometric contractions, using a method previously employed to examine units of a small hand muscle. 2. Over the range of forces studied (0‐6 kg), the units of both muscles were recruited in an orderly fashion, with a nearly linear relationship between the voluntary force at which units were recruited and their measured twitch tensions. 3. The range of contraction times (25‐90 msec) was similar to that observed for the hand muscle. In some subjects it seemed that small units, recruited at low forces, exhibited shorter contraction times.
Reduction of potassium permeability by chloride substitution in cardiac cells.
Authors: Carmeliet E , Verdonck F
Published: December 2014

1. The efflux of radioactive K and Cl ions was measured in cow Purkinje fibres and ventricular preparations of cow, cat and frog. The effect of K and Cl was studied by changing the extracellular K concentration between zero and 54 mM, and by substituting Cl ions by acetylglycinate, isethionate, benzenesulphonate, propionate and nitrate. 2. In the absence of Cl the rate coefficient for 42K efflux showed a pronounced fall, which was more pronounced the higher the K concentration. This effect was not related to the change in membrane potential. The rate coefficient for 42K efflux increased in the presence of higher extracellular K concentrations. 3. 36Cl efflux increased in the presence of reduced as well as increased extracellular K concentrations. 4. The calculated permeability coefficient for K (PK) was maximal at 5‐4 mM‐K, decreased slightly at higher K concentrations, but fell markedly in K‐free solutions, (to about 1/5 of the value in 5‐4 mM‐K). In Cl‐free medium PK reduced to 0‐67 of the value in the Cl medium, irrespective of the K concentration. 5. The calculated PCl was greater in K‐free and 16‐2 mM‐K than in 5‐4 mM‐K. 6. The ratio PK/PCl showed important changes as a function of extracellular K concentration: the value was 5 in 5‐4 mM‐K and fell to 2 and 0‐5 respectively in 16‐2 and K‐free solutions. 7. The results suggest that part of the changes in membrane resistance measured by electrical methods in Cl‐free media is due to a simultaneous decrease in K conductance.
The electrical properties and active ion transport across the urinary bladder of the urodele, Amphiuma means.
Authors: Degnan K J , Zadunaisky J A
Published: December 2014

1. The electrical properties and the active transport processes of the isolated urinary bladder of the urodele, Amphiuma means, were studied by mounting this tissue as a flat sheet between two halves of a lucite chamber. The mean transepithelial potential difference was 70‐2 +/‐ 2‐3 mV (serosa positive), the mean short‐circuit current was 10‐9 +/‐ 0‐5 micrionA/mg of dry weight and the mean transepithelial d.c. resistance was 6540 +/‐ 374 omega mg of dry weight. 2. The short‐circuit current (Isc) accounted for 92% of the net 22Na+ flux from the mucosa to the serosa. The difference resulted from a transport of 36Cl‐ in the same direction as sodium. 3. The active sodium transport exhibited typical saturation kinetics, having a Km of 15‐4 m‐equiv/l. and approaching zero order at 60‐70 m‐equiv/l. The transepithelial potential difference increased linearly with the log of the mucosal sodium concentration at a rate of 50‐3 mV per tenfold concentration change. 4. In the absence of the major anions (HCO3‐ and Cl‐) from the bathing solutions, the electrical properties and the sodium influx decreased to less than 40% of their control values. The presence of only one of these two anions in the serosal bathing solution was sufficient to maintain these parameters. 5. Amiloride (10(‐5)M) and ouabain (10(‐6)M) inhibited the sodium transport 97% and 85% respectively. Amphotericin B (10(‐6)M) stimulated the sodium transport 47%. Furosemide (10(‐3)M) inhibited the chloride transport 43%. The sodium transport was insensitive to the action of two enurohypophyseal peptides tested, lysine‐vasotocin and pitocin.
Long‐lasting increases in the tremor of human hand muscles following brief, strong effort.
Authors: Furness P , Jessop J , Lippold O C
Published: December 2014

1. Long‐lasting (up to 4 h) increases in finger tremor were produced by intense brief effort to contract the muscle. 2. Similar increases resulted from intense effort which did not contract the muscle because the motor nerve was blocked. 3. Comparable contractions induced electrically failed to give rise to increased tremor. 4. Power spectral analysis (1‐15 HZ) revealed that all frequencies of tremor were approximately equally increased. 5. It is concluded that these long‐lasting increases in tremor are of central nervous origin.
Specific patterns of neuronal connexions involved in the control of the rabbit's vestibulo‐ocular reflexes by the cerebellar flocculus.
Authors: Ito M , Nisimaru N , Yamamoto M
Published: December 2014

1. In anaesthetized albino rabbits, the occurrence of Purkinje cell inhibition on canal‐ocular reflexes was surveyed with a reflex testing method. 2. Test reflexes were elicited by electrical stimulation of the semicircular canals. The results were appaised by recording potentials and tension from extraocular muscles. Twelve reflexes were defined in terms of the receptor canal and the effector muscle. 3. Conditioning electrical stimuli were applied to the flocculus, the inferior olive, and optic pathways at the retinae, optic chiasm, pretectal area and upper medulla. 4. The conditioning stimulation at the ipsilateral flocculus induced depression in six of the twelve canal‐ocular reflexes; four of the six arose from the anterior canal and the remaining two from the horizontal canal. 5. The effect of stimulation of the contralateral inferior olive was similar to that of the ipsilateral flocculus, though less clear in two of the four reflexes from the anterior canal because of a contaminating effect. 6. The two reflexes from the horizontal canal were depressed by stimulation of the ipsilateral optic pathway which reached the ipsilateral flocculus via the contralateral pretectal area and inferior olive. 7. The four reflexes from the anterior canal were affected by stimulation of optic pathways in a different manner from each other. One was depressed from the contralateral retina via the ipsilateral pretectal area, while another was depressed from the ipsilateral retina via the contralateral pretectal area, though only occasionally. The third reflex was depressed from the ipsilateral pretectal area but not from the retina. The fourth was affected from neither the retina nor the pretectal area. 8. On the basis of latency measurements, it was concluded that the depression of canal‐ocular reflexes was due to inhibition of relay neurones of the testing reflexes by flocculus Purkinje cells which were activated either directly, or indirectly through olivocerebellar climbing fibre afferents. 9. The above conclusion was supported by the observation that the depression induced by stimulation of the inferior olive and optic pathways was abolished by acute destruction of the ipsilateral flocculus. 10. The possible functional significance of the specific patterns of connexions from flocculus Purkinje cells to canal‐ocular reflex pathways is discussed, and specialization among flocculus Purkinje cells in relationship with vestibulo‐ocular reflexes is postulated.
Possible explanations for the differences in secretory characteristics between conjugated and free bile acids.
Authors: O'Máille E R , Richards T G
Published: December 2014

1. The hepatic extraction fraction and maximum excretory rate of conjugated cholate are greater than those of free cholate (studied after acute taurine depletion); the possibility that this difference might be due to greater bile‐to‐blood back‐diffusion of un‐ionized cholic acid (pKa 5‐5) compared to that of taurocholic acid (pKa 2) has been investigated by varying the pH of bile by secretin or acetazolamide administration in the anaesthetized dog. 2. The mean biliary pH during free cholate excretion in the control state in twenty‐three experiments was 7‐5 (at which approximately 1% of cholate is un‐ionized). Three to fourfold changes in the hydrogen ion activity of bile (which resulted in changes of the same magnitude in the percentage of un‐ionized cholic acid) had no significant effect on the total (mainly free) cholate maximum excretory rate. It is concluded that back‐diffusion of un‐ionized cholic acid in the bile ducts is not an important determinant of the secretory performance of free cholate. 3. The bile flow rate associated with mainly free cholate excretion is much higher than that associated with taurocholate excretion at the same rate; the extra bile flow appears to arise largely by means that are independent of the osmotic effect of cholate excretion, as the osmotic coefficient (osmolality/total solute concentration) of bile containing mainly free free cholate (calculated directly) was only slightly greater than that of bile containing mainly taurocholate (obtained by extrapolation) at the same total cholate concentration. 4. The peak hepatic excretory rate of taurocholate following the instillation of the entire contents of the gall‐bladder of a fasted dog into the distal ileum was only about one fifth of the maximum rate attainable; at the peak rate taurocholate is almost completely removed in the first passage of blood through the liver.
Rectification in Aplysia statocyst receptor cells.
Authors: Wiederhold M L
Published: December 2014

1. Membrane slope resistance of Aplysia statocyst receptor cells was measured by passing constant current pulses, using a bridge circuit. In response to downward tilt all cells which responded exhibited depolarization but this could be accompanied by either decrease, increase or no measurable change in slope resistance, depending on resting membrane potential. 2. By altering membrane potential with d.c. and measuring slope resistance with constant current pulses, these cells are shown to exhibit both anomalous and delayed rectification. Either hyperpolarization or depolarization from one potential can cause the slope resistance to decrease by as much as a factor of 5. 3. The response to standard tilt can be changed from an increase in slope resistance to a decrease, or vice versa, by altering membrane potential. 4. When membrane potential was held constant during downward tilt, the slope resistance always decreased. 5. Slope resistance, the voltage response to standard tilts and the amplitude of membrane potential fluctuations all vary with average membrane potential in a similar manner. 6. These findings are incorporated into a circuit model in which anomalous and delayed rectification are represented by voltage‐controlled elements. the response to tilt is always modelled as introducing a parallel conductance pathway with a large positive reversal potential. 7. The model demonstrates that slope resistance can be increased by adding a parallel shunt pathway if the latter brings the membrane out of the anomalous rectification region. 8. The model also demonstrates how delayed rectification can greatly alter the reversal potential inferred from measurements at potentials below actual reversal.
Comparison of vagal and meat stimulation on gastric acid secretion and serum gastrin.
Authors: Blair E L , Grund E R , Lund P K , Piercy A , Reed J D , Sanders D J , Shale D , Shaw B , Wilkinson J
Published: December 2014

The gastric acid secreted per unit of serum gastrin concentration or per unit of gastrin delivered to the gastric mucosa was significantly greater during electrical vagal stimulation than during stimulation by meat extract in the pyloric antrum. There was no significant difference in the concentrations of big, big gastrin or Components I and II in gastric venous serum during the two forms of stimulation. There were significantly greater concentrations of Components II and IV in gastric venous serum during meat extract stimulation than during vagal stimulation. The gastrin in gastric venous serum when meat extract was in the pyloric antrum was comprised of Component IV in addition to Component III whereas gastrin in extracts of cat antral mucosa was predominantly Component III. Gastric acid secretion in response to vagal stimulation was greater than can be accounted for by the action of gastrin alone and cannot be explained by differences in the known gastrin variants in the circulation during the two forms of stimulation.
Factors affecting the distribution of chloride ions in rat renal outer medulla.
Authors: Law R O
Published: December 2014

1. The intracellular Cl‐ concentration, [Cl‐]1, of rat renal outer medullary slices has been studied in iso‐osmolal media containing 42, 93, 144, 189 or 225 mM chloride, [Cl‐]0. Equilibrium values for [Cl‐]1 were attained within 25‐50 min from the start of incubation such that [Cl‐]1/[Cl‐]0 = 0‐46. This ratio was independent of [Cl‐]0 within the range studied. Intracellular Na+ was unaffected, and only minor variations of cell volume were observed (calculated from slice weight changes and [14C]carboxyl inulin spaces. 2. When [Cl‐]0 = 189 mM, [Cl‐]1 remained constant at 87 mM for up to 50 min, indicating that these figures may represnet the interstitial [Cl‐] and mean intracellular [Cl‐] respectively in outer medulla. 3. Omission of bicarbonate from medium containing 189 mM‐Cl‐ caused an increase in [Cl‐]1/[Cl‐]0 to 0‐58, which was not significantly affected by anoxia or by the presence of arsenite (5 X 10(‐3) M) or 2,4‐dinitrophenol (10(‐3) M). Significant further increases were observed in the presence of iodoacetic acid (5 X 10(‐3) M) (0‐70), acetazolamide (10(‐3) M or 5 M 10(‐3) M) (0‐71) and iodacetic acid plus 2,4‐dinitrophenol (0‐85). The addition of the diuretic agents ouabain, ethacrynic acid‐cysteine and frusemide (all 10(‐3) M) to 189 mM‐Cl‐ media containing bicarbonate reduced [Cl‐]1/[Cl‐]0 to 0‐36, 0‐37 and 0‐42 respectively. 4. The mean 36Cl‐ space of outer medulla after 50 min incubation in 189 mM Cl‐ medium was 49‐7 +/‐ 2‐1 micronl./100 mg wet wt. The volume of distribution was not significantly affected by ouabain, ethacrynic acid‐cysteine or frusemide (10(‐3) mM). 5. Net efflux of 36Cl‐ from slices loaded with isotope into 'cold' 189 mM Cl medium showed three components with rate constants of 69 X 10(‐3), 18 X 10(‐3) and 9‐9 X 10(‐5) sec‐1 respectively. Efflux was not affected by ouabain, ethacrynic acid‐cysteine or frusemide (10(‐3) mM). 6. The main conclusions drawn from this study are: (i) the interstitial fluid Cl‐ concentration of normally hydrated rat outer medulla is approx. 189 mM; (ii) the [Cl‐]1/[Cl‐]0 ratio 0‐46 may represent a chiefly passive distribution maintained by the opposing gradient of a second anion, probably bicarbonate; (iii) the energy required to maintain unequal distribution of Cl‐ in the absence of external bicarbonate is derived chiefly from glycolysis, with a small aerobic component; (iv) there may be two intracellular chloride pools whose net rates of Cl‐ exchange differ by a factor of approx. 180.