bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular features of organic anion permeablity in ox red blood cell.
Authors: Aubert L , Motais R
Published: December 2014

1. The penetration of organic anions into bovine red blood cells has been studied under experimental conditions where it could be distinguished from the penetration of undissociated acids which proceeds by diffusion through lipid zones of the membrane. 2. Several lines of evidence suggest that the entry of organic anions cannot be ascribed to simple diffusion across aqueous channels limited by positive charges but needs a specific interaction of the penetrating anion with a component of the membrane. 3. The structural requirements allowing for ionic transfer is a strong polar head for the smallest molecules and in addition an amphiphilic structure for acids with chain length greater than C4. Interaction between substrate and receptor requires at least a three point attachment involving three oxygen atoms in the substrate which react with complementary loci on the receptor to form ionic and hydrogen bonds. Such a three point attachment can be made by a sulphonic group or with carboxylic acid by alpha ketosubstitution, alpha hydroxysubstitution, addition of an amidegroup or addition of a second carboxyl group spatially close to the first. 4. As suggested by the behaviour of the formate anion, in such a transport system any carboxylic acid could interact transiently with the receptor and therefore interfere with the transport of an organic anion even though such ionic interaction with the receptor were insufficient to produce transport of the acid itself.
Linear and non‐linear performance of transducer and pupil in Calliphora retinula cells.
Authors: Leutscher‐Hazelhoff J T
Published: December 2014

1. Intracellular recordings have been made from the blowfly (Calliphora erythrocephala) retinula cell; apart from the transducer mechanism, these cells also feature a pupil mechanism. 2. At several mean intensity levels, within the apparently linear range of response, frequency characteristics of amplitude and phase and responses to ‘delta’‐flashes and ‘delta’‐flash pairs have been obtained. 3. Fourier methods have shown these responses to be mutually compatible, confirming linearity in these circumstances. 4. Non‐linear behaviour can be made to appear at the lower frequencies when the modulation depth is increased. 5. Non‐linearities can also appear through application of the superposition test: a low frequency sine wave, modulated so as to elicit an apparently linear response, and a high frequence sine wave which does not give rise to non‐linearity even at the highest modulation depths can, when superimposed, yield a greater response to the latter when situated at the minima of the former than at its maxima. 6. At frequencies above approximately 1 Hz these superposition non‐linearities are attributed to the transducer mechanism gain control. Below this frequency the pupil mechanism takes part considerably in the retinula cell's total observed gain control: its characteristics remain yet to be cleared up. 7. The transducer's linear and non‐linear properties fit in closely with those of the Fuortes‐Hodgkin model which couples increases in gain and time constants. 8. The Fuortes‐Hodgkin model will probably require some quantitative modifications in the originally treated case of Limulus, on account of its pupil. 9. Finally, the merits of Veringa's diffusion model, and the possibility of eventually joining this model with the Fuortes‐Hodgkin one are pointed out briefly.
Calcium dependent action potentials produced in leech Retzius cells by tetraethylammonium chloride.
Authors: Kleinhaus A L , Prichard J W
Published: December 2014

1. Retzius cells of leech segmental ganglia were exposed to tetraethylammonium chloride (TEA) presented both extracellularly, dissolved in the perfusing fluid, and intracellulary, by iontophoresis from a microelectrode. 2. Extracellular TEA, 10 and 25 mM, greatly prolonged the cells' action potentials, and the higher concentration increased their amplitude as well. At 10 mM the characteristic changes developed gradually over a period of about half an hour, while at 25 mM they appeared much more rapidly. However, at both concentrations the changes were reversible within minutes, even after long soaks in drug‐containing solution. It is therefore probable that the drug acted at the outer surface of the membrane. 3. Intracellular TEA also prolonged the action potentials but there were several differences from the response produced by extracellular application. The changes developed gradually, and for a time, each firing of the cell was a complex event consisting of several early, brief depolarizations followed by a single much larger and more prolonged one. The large, late depolarization eventually obliterated the early ones; its gradual development suggested that it was produced only after TEA diffused to some extrasomatic portion of the cell. Intracellular TEA always caused progressive depolarization; this and the changes in the action potential were both irreversible, suggesting that the site of action was on the inner surface of the membrane. 4. Manipulations of external Na and Ca provided evidence that (a) in the absence of TEA, Retzius cell action potentials were exclusively Na‐dependent, (b) that the early depolarizations in the complex action potentials produced by intracellular TEA were Na‐dependent, while the later, large depolarization was Ca‐dependent and (c) that the prolonged action potentials produced by extracellular TEA contained a large Ca‐dependent component. 5. We conclude that TEA, acting from either side of the membrane, caused a voltage‐sensitive, slowly activated Ca current to become a major contributor to the inward current of the action potential, probably by blocking the outward K current which ordinarily counteracts it. However, we cannot rule out the possibility that TEA enabled a Ca current by some means independent of its presumed action on K conductance. 6. Data resembling ours in some respects have been obtained from studies of the action of TEA on frog dorsal root ganglion cells, frog neuromuscular junction, and squid stellate ganglion. No clear counterpart of our findings has been reported form experiments on squid and amphibian axons, molluscan neurones, or frog skeletal muscle fibres.
Interactions between temperature and tonicity on cation transport in dog red cells.
Authors: Elford B C
Published: December 2014

1. The temperature‐dependence of the uptake of 24Na and 42K into dog red cells between 38 and 4 degrees C has been investigated. The effects on the cation fluxes of partial dehydration of the cells in hyperosmolar sucrose (50–125 mM) have also been studied. 2. A Hamilton gas‐tight syringe was used to pipette accurately reproducible volumes of packed cells which contained in addition to 24Na or 42K either [131I]albumin or [51Cr]EDTA as extracellular markers. 3. At 38 degrees C Na flux (m‐equiv/l. isosmolar cell volume. hr) increased from 2‐8 +/− 0–1 (n = 8) in cells of normal volume to 226 +/− 8 (n = 8) when the cells were shrunken by 27–4 +/− 0–6% (n = 8) in media containing sucrose (100 mM). K influx remained relatively constant under these conditions. 4. The exchange of 24Na in shrunken cells followed a single exponential time course but about 9% of the intracellular Na apparently did not exchange with 24Na in the bathing medium. 5. The steady‐state influx of Na in cells of normal volume was maximal at about 22 degrees C. The temperature dependence of the Na fluxes in shrunken cells was described by an Arrhenius relationship with a change in slope at about 22 degrees C. 6. The K influx in cells of normal volume decreased as the temperature was lowered from 38 degrees C, to about 12 degrees C, at which temperature the flux was at a well defined minimum. Above 12 degrees C, cell shrinkage had hardly any effect on K influx, but below 12 degrees C the influx in shrunken cells was significantly less than in cells of normal volume. 7. The selective increase in Na flux induced by cell shrinkage results from a Na:Na exchange process which cannot be explained in terms of Ussing's (1947) model of carrier‐mediated exchange diffusion. 8. The lack of coupling between the effects of temperature and cell volume on the fluxes of Na and K indicates that localized structural changes of lipid‐protein complexes specific for Na or K are responsible for the cation transport characteristics of dog red cells, and that phase transitions in the lipids of the cell membrane are unlikely to account for the temperature dependence of the fluxes.
Inhibition of adrenergic neurotransmission in isolated veins of the dog by potassium ions.
Authors: Lorenz R R , Vanhoutte P M
Published: December 2014

1. In the intact organism, an increase in K+ concentration decreases the reactivity of blood vessels to sympathetic stimulation. The present experiments were designed to determine whether or not K+ interferes with adrenergic neurotransmission. 2. Helical strips cut from dogs' saphenous veins were incubated (4 hr) in Krebs‐Ringer solution containing [7‐3H]norepinephrine (5 times 10(−8) g/ml). The preparations were mounted for superfusion and isometric tension recording; the superfusate was collected for estimation of total radioactivity and for chromatographic separation of 3H‐labelled norepinephrine and metabolites. 3. Supramaximal electric stimulation (5 Hz, 9 V, 2 msec) increased the tension and the [3H]norepinephrine efflux. Increasing the K+ concentration from 5‐9 to 1, 15, and 20 m‐equiv/l. caused a progressive depression of these contractions and diminished the total 3H efflux in proportion to the relaxation; the decrease in 3H efflux reflected a decrease in intact [3H]norepinephrine. The same increase in K+ concentration did not alter basal tension or basal 3H efflux. 4. Addition of tyramine (4 times 10(−6) g/ml. min) to the superfusate augmented both the tension and the efflux, but these actions were not depresesd by increasing the K+ concentration. 5. Cocaine, phentolamine, and phenoxybenzamine did not prevent the depression by K+ of the response to electric stimulation. 6. These experiments show that K+ causes relaxation of venous smooth muscle constricted by sympathetic stimulation and does so by inhibiting the release of norepinephrine from nerve endings. By contrast, K+ does not inhibit norepinephrine release in response to tyramine. 7. During submaximal electric stimulation (5 Hz, 1‐8‐‐3 V, 2 msec), increasing the K+ concentration from 5‐9 to 10 and 15 m‐equiv/l. potentiated the contractions and increased the [3H]norepinephrine efflux; at 20 m‐equil/l, K+ caused transient increases in tension and 3H efflux followed by relaxation and decreased norepinephrine release. After addition of cocaine (10(−5) g/ml. min), K+ only caused relaxation and decrease in 3H efflux, showing that, in addition to inhibition of norepinephrine release, K+ also inhibits the reuptake process. 8. In higher concentrations (40 m‐equil/l.), K+ caused both a liberation of norepinephrine and a direct activation of the smooth muscle cells.
The functional status and columnar organization of single cells responding to cutaneous stimulation in neonatal rat somatosensory cortex S1.
Authors: Armstrong‐James M
Published: December 2014

1. An investigation was carried out on single cells in 7 day old rat primary somatosensory cortex, which responded to cutaneous stimulation using mechanical pulses. 3 percent of cells encountered showed stable spontaneous activity, whereas 88 percent were silent in the absence of intentional stimulation. The remainder showed unstable spontaneous activity. In contrast, the great majority of adult cells were spontaneously active in the absence of stimulation, under similar conditions of urethane anaesthesia. 2. The distribution within cortical layers of cutaneously driven cells was similar in adult and 7 day old rats, and similar to that found in adult mammalian cortex by other workers. 3. 7 day old cells showed diminished excitability to cutaneous stimulation with stimuli at intervals below 10–15 sec, whereas adult cells could be successfully repetitively driven with stimuli at intervals of 500 msec. The low ability of the immature cells to follow repetitive cutaneous stimulation is not due to an overall depression of these cells excitability per se. Latencies of unitary responses in these immature cells were about sixfold those found in equivalent cells at maturity. 4. Columnar organization at seven days of age was similar in outline to that of the adult, but much less discrete. Receptive fields were considerably larger at 7 days and evidence is given that this may be due to inadequate surround inhibition. Immature vibrissae‐driven units were directionally selective. 5. At 7 days of age, long inter‐spike intervals were rare in spontaneously active cells with the result that inter‐spike interval histogram distributions (i.h.s.) were approximately normal. Corresponding i.h.s. of adult cells invariably showed skew distributions. 6. Tactile stimulation of centre receptive fields produced an increase in short and long intervals from spontaneously active cells at each age. In contrast to adult cells, the immature cells commonly responded cyclically, with alternating phases of increased and decreased firing rate for periods of up to 3 sec following punctate stimulation. 7. Decrease in spontaneous firing rate, following the first phase of excitation, was profound in 7 day old cells, and implied that inhibitory mechanisms operate at an early age in the rat somatosensory system. These mechanisms also appear to contribute to cyclical activity of 7 day old cells when driven by punctate cutaneous stimulation.
Volume adjustment by renal medullary cells in hypo‐ and hyperosmolal solutions containing permeant and impermeant solutes.
Authors: Law R O
Published: December 2014

1. The changes in the volumes of cells in slices (thickness 0‐3‐0‐4 mm) of rat renal outer and inner medulla have been investigated during aerobic incubation for 20 min at 37 degrees C in Krebs phosphate‐bicarbonate Ringer modified by the addition of urea or sucrose in order to produce a range of media hypo‐ and hyperosmolal with respect to the calculated tissue fluid osmolalities in these regions. 2. On the assumption that under these conditions the measured inulin space approximates to the true extracellular space (ECS), it was found that osmotic swelling or shrinkage of cells was not accompanied by any significant variation in the absolute size of the ECS. 3. Calculated cell volume changes in both regions were minimal when slices were incubated in urea‐containing media iso‐osmolal with tissue fluids in that region. In sucrose‐containing media minimal cell volume changes occurred when media were hypo‐osmolal in relation to tissue fluids by a factor of approximately 0–68. 4. In all except the most hypo‐osmolal media studied, calculated cell volume changes (as percentage of initial volume) were linearly related to the reciprocal of the incubation media osmolalities. The points of interception of the regression lines on the cell volume axis were dependent upon both the region studied and the composition of the incubation medium (urea or sucrose). 5. These changes were accompanied by variations in slice solute concentrations. Slice [Na] was greatest, and slice [K] least, following incubation in those media producing the greatest percentage changes in cell volume. 6. The volume of distribution [14‐C]sucrose within the inner medulla was 61‐7 plus or minus 2–5 mul./100 mg wet weight of tissue (mean plus or minus S.E., n equals 6) after 10 min incubation. The increase to 70–8 plus or minus 4‐2 mul./100 mg (n equals 6) after 100 min was not significant (0–1 greater than P greater than 0–05). The volume of distribution within the outer medulla rose markedly during this period, from 38–1 to 58–2 mul./100 mg.
Sodium fluxes in single amphibian oocytes: further studies and a new model.
Authors: Dick D A , Fry D J
Published: December 2014

1. The kinetics of Na efflux were studied in oocytes of Bufo bufo, Rana temporaria and R. pipiens. 2. Rate constants for Na efflux into Ringer solution varied from 0–002 min‐minus 1 to 0–017 min‐minus 1 and did not vary significantly from one species to another. 3. Na efflux is rapidly reduced by 30–50% on removing external K or applying ouabain but is reduced by 90% on cooling to 0 degrees C. The effects of K and cooling are also rapidly reversible. 4. Substitution of external Na by Li produces a slow decline of Na efflux. Reversal on restoring external Na is, however, rapid even in the presence of ouabain. 5. When external Na is replaced by Li in the presence of ouabain, the normal decline in Na efflux does not occur. 6. When external Na has been replaced by Li, application of ouabain causes little or no further decline in Na efflux. 7. These results are interpreted quantitatively by means of a model which proposes that intracellular membrane‐bounded channels (IMBC) contain 10–30% of the intracellular Na and provide a channel for its expulsion from the cell via connexions with the cell surface. It is supposed that Na is expelled actively from the cytoplasm into the IMBC as well as at the cell surface. Na expulsion via the IMBC is supposed to be insensitive to external K or ouabain. This model accounts for the results using parameters consistent with other investigations by autoradiography and Na‐sensitive micro‐electrodes. 8. Preliminary electron micrographic evidence shows channels which appear to lead from the cell surface into the cytoplasm and which may correspond with the proposed IMBC of the model.
On the association between transmitter secretion and the release of adenine nucleotides from mammalian motor nerve terminals.
Authors: Silinsky E M
Published: December 2014

1. Conventional electrophysiological techniques were used to record from isolated rat phrenic nerve‐hemidiaphragm preparations. After periods of rest (20 min) or nerve stimulation (7/sec for 20 min) the bathing medium of the preparation was removed and assayed for adenosine triphosphate (ATP) and adenosine diphosphate (ADP) using a sensitive modification of the firefly luciferase method (Silinsky, 1974). 2. In the presence of tubocurarine and normal (2 mM) calcium, fourteen periods of nerve stimulation (eight preparations) caused the appearance of ATP and/or ADP in amounts ranging from 28 to 641 p‐mole. Experiments using carbachol (30 muM or 1 mM) suggested that this nucleotide efflux was not produced by a secondary action of released acetylcholine (ACh). 3. Stimulation of isolate phrenic nerve trunks at 7/sec for 20 min did not cause the efflux of ATP or ADP. 4. In solutions of normal osmotic pressure and reduced calcium concentrations (0–1 mM or ‘calcium‐free’), stimulation failed to release adenine nucleotide from non‐contracting preparations. 5. Diaphragms were bathed in normal calcium and indirectly stimulated at 11/sec for 80–90 min in the presence of 5 times 10‐minus 5 M hemicholinium‐3. After all detectable signs of ACh release were eliminated, nerve stimulation failed to release ATP or ADP. 6. These results in conjunction with experiments on the hydrolysis of exogenous ATP suggest that ATP is released from the motor nerve ending and is subsequently degraded by enzymatic activity. It is also suggested that the released nucleotide may be derived from the cholinergic vesicle.
Membrane potentials in pinched‐off presynaptic nerve ternimals monitored with a fluorescent probe: evidence that synaptosomes have potassium diffusion potentials.
Authors: Blaustein M P , Goldring J M
Published: December 2014

1. Some physiological properties of tissue fractions from rat brain homogenates have been examined. Of the three fractions studied (presynaptic nerve terminals, mitochondria and fragmented membranes), only the nerve terminals (synaptosomes) have the ability to accumulate 42K from physiological salt solutions. 2. The ability to accumulate and retain K is lost if synaptosomes are exposed to very hypotonic solutions. The K uptake and total K content is reduced by ouabain and by inhibitors of glycolysis and oxidative phosphorylation. 3. These results suggest that synaptosomes in physiological saline accumulate K against a concentration gradient, and may have K diffusion potentials across their surface membranes. The voltage‐sensitive fluorescent probe, 3,3'‐dipentyl 2,2'‐oxacarbocyanine (CC5), was used to test this possibility. 4. In the squid axon, the fluorescent emission of CC5 is directly proportional to membrane potential; depolarization causes an increase in fluorescence. 5. The fluorescence of synaptosomes (‘synaptosome fluorescence’) treated with CC5 is increased when [K]o is increased or [K]o is reduced; replacement of external Na by Li or choline has little effect on the synaptosome fluorescence. In quantitative terms, synaptosome fluorescence is proportional to log ([K]o plus 0‐05[Na]o). Rb is about as effective as K in enhancing synaptosome fluorescence; Cs is about 1/4 as effective. The effect of increased [K]o is reversible. 6. The fluorescence data provide corroborative evidence that there is normally a large K gradient ([K]o smaller than [I]i) across the synaptosome surface membrane. The data suggest the [K]i may be in excess of 100 mM. 7. Replacement of Cl‐ by methylsulphate did not significantly affect the relationship between synaptosome fluorescence and [K]o, nor did removal of external Ca. 8. The fluorescence of CC5‐treated mitochondria, membrane fragmnets, or lysed synaptosomes is unaffected by changes in the K concentration of the medium. 9. Veratridine and gramicidin D, both of which enhance Na permeability (PNa) in some intact tissues, increase synaptosome fluorescence when added to the standard medium. The increment is greatly reduced or abolished when external Na is replaced by choline. 10. If synaptosomes are first Na‐loaded (by pre‐treatment with cyanide + iodoacetate), and then placed in a choline medium, addition of gramicidin D significantly decreases fluorescence. This effect could be explained if, with [Na]o smaller than [Na]i, the increase in PNa causes the synaptosomes to hyperpolarize. 11. The veratridine‐induced increase in synaptosome fluorescence was prevented by 3 times 10− minus 7M tetrodotoxin, which also blocks the depolarizing effect of veratridine in intact neurones. 12. The main conclusion is that synaptosomes may retain resting membrane potentials and the ability to increase Na permeability.
Absorption of two proline containing peptides by rat small intestine in vivo.
Authors: Lane A E , Silk D B , Clark M L
Published: December 2014

1. Glycyl‐L‐proline and L‐prolyl‐glycine are two dipeptides that are poorly hydrolysed by brush border peptide hydrolases in vitro. The present study was undertaken to investigate in vivo intestinal absorption of the two dipeptides in male Wistar rats. A steady‐state perfusion technique has been used and jejunal and ileal absorption studied by comparing rates of absorption of constituent amino acids from dipeptide and equivalent equimolar amino acid solutions. 2. Glycine and proline were absorbed at the same or faster rates during perfusion of 10 mM glycyl‐L‐proline than during perfusion of 10 mM‐L‐prolyl‐glycine than during perfusion of its equivalent equimolar amino acid solution. Conversely, the two constituent amino acids were absorbed at slower rates during perfusion of its equivalent amino acid solution. As expected very low concentrations of free amino acids were detected during the jejunal dipeptide perfusions but higher concentrations were detected during the ileal perfusions. 3. The addition of 40 mM L‐prolyl‐glycine to the 10 mM glycyl‐L‐proline solution did not affect the rates of disappearance of glycyl‐L‐proline. The addition of 40 mM glycyl‐L‐proline to 10 mM L‐prolyl‐glycine however had a significant inhibitory effect on the disappearance of L‐prolyl‐glycine. It is concluded that the two dipeptides may be absorbed by different peptide transport systems.
Responses of tendon organs in a lizard.
Authors: Gregory J E , Proske U
Published: December 2014

1. In the lizard Tiliqua the tendons of the caudo‐femoralis muscle are supplied by a nerve which runs separately from the muscle nerve. 2. Recordings of afferent discharges in the tendon nerve revealed the presence in the tendon of stretch‐sensitive mechanoreceptors which responded to both passive changes in limb position and to muscle contraction. 3. A preparation of the tendon and its nerve were dissected free of surrounding tissue and studied in isolation while recording the activity of single functional units. The minimum tension in the tendon necessary for a maintained response from a receptor lay in the range 5‐35 g (mean 16 g) and the firing rates at these tensions were in the range 5‐14 impulses/sec (mean 9 impulses/sec). 4. Receptors showed a steep increase in firing rate with increase in tension up to about 120 g. The firing rate 30 sec after the onset of a tension change did not exceed 40 impulses/sec. 5. During the tension change the receptor responded with a burst of impulses whose frequency depended on the velocity of stretch. With large, rapidly rising tension steps peak firing rates of up to 300 impulses/sec were observed. 6. Tension and length changes recorded during rapid tendon‐stretches were very similar, with little sag in tension at the new length. The response of all units however continued to fall throughout the stretch. Some of the possible causes of this adaptation have been discussed.
Ionic mechanism of a quasi‐stable depolarization in barnacle photoreceptor following red light.
Authors: Brown H M , Cornwall M C
Published: December 2014

1. The membrane mechanism of a quasi‐stable membrane depolarization (latch‐up) that persists in darkness following red light was examined in barnacle photoreceptor with micro‐electrode techniques including voltage‐clamp and Na+‐sensitive micro‐electrodes. 2. Current‐voltage (I–V) relations of the membrane in darkness following red light (latch‐up) and in darkness following termination of latch‐up with green light, indicate that latch‐up is associated with an increase of membrane conductance. 3. The latch‐current (membrane current in darkness following red light minus membrane current in darkness following a gree flash that terminates latch‐up) was inward at the resting potential, reversed sign at about +26mV (mean of six cells), and became outward at more positive membrance potentials. 4. Current‐voltage relations of the membrane during green light (no latch‐up) closely resembled those during latch‐up. The light‐induced current (LIC) elicited by green ligh (membrane current during the light flash minus membrane current in darkness following the light flash) was inward from the resting potential to +26mV (mean of six cells), then reversed sign and became outward. 5. The latch‐current and LIC were both augmented in reduced Ca2+ solutions and decreased as Na‐+ was reduced at a fixed Ca2+ concentration. 6. Both LIC and latch‐current reversed sign at a more negative membrane potential (increment V equals 14mV) in solutions containing one quarter the normal amount of Na+. 7. The internal Na‐+ activity (a‐iNa) of a photoreceptor increased from about 10–18 mM upon illumination with long steps of intense red or white illumination. Five minutes in darkness after white light, a‐iNa had recovered significantly, whereas a‐iNa remained elecated following red illumination. 8. Latch‐up seems to be a persistence in darkness of the same membrane mechanism that normally occurs during illumination; i.e. a conductance increase to Na+ ions. Ca2+ ions act primarily to suppress this current. There is evidence for a net Na+ influx during illumination that is sustained in darkness during latch‐up.
Transport of electrolytes across the helicoidal colon of the new‐born pig.
Authors: Bentley P J , Smith M W
Published: December 2014

1. The Na, K, Cl and water content of faeces removed from different parts of the pig helicoidal colon were determined for 1‐day‐old and adult animals. Faecal Na, Cl and water content fell in both cases during passage of contents through the colon. K content increased in the distal colon of the adult pig. This did not occur in the 1‐day‐old animal. 2. The colon of the 1‐day‐old pig removed a larger proportion of water from its contents than did that of the adult. The absorption of both water and Cl was found to extend into the distal colon of the 1‐day‐old animal; little or no net absorption took place in this region in the adult. 3. Colons taken from new‐born pigs maintained stable short‐circuit currents of about 60–80 muA cm‐2 with open‐circuit voltages of about 10 mV. Similar values were found for proximal and mid regions of colons taken from 1‐day‐old, suckled animals. In the distal colon, however, both short‐circuit current and open‐circuit potential doubled after suckling. 4. Measurements of Na flux in vitro showed no regional difference at birth. The amount of Na absorbed, about 4.5 muequiv cm‐2 h‐1, was twice that predicted from the short‐circuit current, supposing that to be due solely to the electrogenic transport of Na. 5. Colons taken from suckled pigs transported Na at double the rate found in the new‐born animal. This applied to both the proximal region, where the short‐circuit current remained constant, and the distal region, where the short‐circuit was double that of the new‐born. 6. Fluxes of Cl and K were also measured across the proximal colon of the one‐day‐old, suckled pig. There was a net absorption of Cl and secretion of K (1.3 and −0.05 muequiv cm‐2 h‐1 respectively). These fluxes, taken together with that for Na, could not wholly account for the short‐circuit current measured across these preparations. 7. The pig colon seems well able to cope with both electrolyte and water absorption during the first 24 hr of post‐natal life. Part of the absorbed sodium appears to follow a non‐electrogenic, possibly pinocytotic, route, but the full ionic contribution to the measured short circuit current has still to be determined.
Extracellular potassium changes in the spinal cord of the cat and their relation to slow potentials, active transport and impulse transmission.
Authors: Krív N , Syková E , Vyklický L
Published: December 2014

1. By means of K‐specific double‐barrelled micro‐electrodes the time course of changes in K+ concentration in the extracellular space of the lumbar spinal cord was examined after peripheral tetanic stimulation and after a single volley in a mixed peripheral nerve in non‐anaesthetized, intercollicularly decerebrated and spinalized cats. 2. Tetanic stimulation (100 Hz) which increases the [K]e from 3 to 9 mM is followed by a phase of reduced [K]e during which [K]e decreases by 0.5 mM below resting level, lasting 1–2 minutes before returning to its original resting level. Evidence is presented that this subnormal phase of [K]e reflects active processes redistributing accumulated K+ from extracellular space. 3. The subnormal phase of [K]e can be registered only when the microelectrode is located in very close vicinity of discharging neurones and is not primarily dependent on the absolute level of increased [K]e. This can be considered as evidence that the neurones and not the glial cells are responsible for active reabsorption of K+ from the extracellular space. 4. Increased E1K]e is reflected in focally recorded potentials as a negativity and decreased [K]e as a positivity. The latency of focally recorded positivity is, however, shorter than the latency of reduced [K]e. This makes it likely that the positivity reflects not only passive hyperpolarization of glial elements, but also an active, electrogenic ion transport across neuronal membrane. 5. The shortest latency of increased [K]e induced by a single volley in a mixed peripheral nerve was found to be 9 msec; the peak, representing 0.5 mM, was attained after 40 msec and the total duration was 200 msec. A theoretical consideration is put forward that the time course of transient increase in [K]e is consistent with the suggestion that K+ which accumulates in the spinal cord after neuronal discharge is responsible for primary afferent depolarization. 6. Evidence is presented that increased [K]e, induced by a long lasting peripheral stimulation, is accompanied by decreased efficacy of impulse transmission.
Voltage‐clamp studies of the calcium inward current in an identified snail neurone: comparison with the sodium inward current.
Authors: Standen N B
Published: December 2014

1. Membrane currents were recorded under voltage clamp from cell A of the snail Helix aspersa. 2. In sodium‐free saline the inward current was reduced to 75% of that in normal saline (containing both sodium and calcium). 3. The inward current in sodium‐free saline was dependent on the external calcium concentration. 4. Calcium‐free saline reduced the inward current to 30% of that in normal saline. (Na, Ca)‐free saline abolished the inward current. 5. Changes in calcium concentration shifted the curve relating calcium conductance to membrane potential along the voltage axis. 6. Inactivation of inward current in both normal saline and sodium‐free saline developed exponentially with time. 7. Steady‐state inactivation of calcium inward current was similar to that for sodium current and it is concluded that the conductance mechanisms for these two ions bear a close resemblance.
The response to stretch of human intercostal muscle spindles studied in vitro.
Authors: Davis J N
Published: December 2014

1. The discharge properties of human muscle spindles have been studied in vitro in a preparation based on the biopsied external intercostal muscle. 2. The static and dynamic responsiveness of thirty‐six endings in twenty visualized and histologically identified spindles have been investigated using amplitudes and velocities of stretch likely to encompass those occurring in vivo. 3. The dynamic index, measured at a stretch velocity of 3 mm/sec, ranged from 3 to 40 impulses/sec and was distributed bimodally, consitent with the presence of primary and secondary endings. 4. The relationship between the dynamic index and the velocity of stretch was approximately linear both for primary and secondary endings up to the maximum velocity tested (10 mm/sec). 5. The frequency/extension relationship was approximately linear for both primary and secondary endings. The mean values of the slope for primary and secondary endings were 16–1 +/− 8–3 S.D. of the observation and 12–1 +/− 6–5 impulses/sec per five per cent extension. 6. The slopes of the frequency/extension relationship for endings lying in the same spindle were positively correlated, significant at the 10% level. 7. It was estimated from the results in vitro that the position sensitivity of human intercostal spindles in vivo ranges from 2 to 21 impulses/sec per millimetre.
Prostaglandins, endotoxin and lipid A on body temperature in rats.
Authors: Feldberg W , Saxena P N
Published: December 2014

1. In unanaesthetized restrained rats kept at an ambient temperature of 21–23degrees C, rectal temperature was continuously monitored and the temperature effects of injections of prostaglandins, endotoxin from Salmonella abortus equi, lipid A, and antipyretics were examined. 2. Fever occurred when prostaglandin E1, E2, F1alpha or F2alpha (PGE1, PGE2, PGF1alpha, PGF2alpha) was injected into the cerebral ventricles in doses of 200 ng and 2 mug. PGE2 was the most potent prostaglandin followed in descending order by PGE1, PGF2alpha, and PGF1alpha. The fever produced by 2 mug of PGE1 and PGE2 was short and followed by a fall in temperature to below the pre‐injection level. 3. I.V. injections of endotoxin and lipid A in doses of 3 or 10 mug usually caused a long lasting fall in temperature, but when injected into the cerebral ventricles in doses of 400 ng or 1 mug, they produced long lasting fevers. 4. Injected I.V. or I.P., indomethacin and paracetamol had a hypothermic action of their own. Indomethacin was more potent than paracetamol and both were more potent than injected I.P. 5. I.V. and I.P. injections of indomethacin and paracetamol did not reverse the hypothermia in response to I.V. endotoxin or lipid A, but the fever responses to their injection into the cerebral ventricles were prevented and abolished by the antipyretics. 6. It is concluded that in rats endotoxin and lipid A, or the endogenous pyrogens produced by them, do not readily pass through the blood‐brain barrier into the brain tissue. If they do reach brain tissue, as when injected into the cerebral ventricles, they stimulate synthesis and release of prostaglandin in rats as they do in other species, and thereby produce fever. The hypothermia in response to I.V. endotoxin or lipid A, on the other hand, is thought to be independent of prostaglandin synthesis and to result from a direct toxic action on the skin vessels.
Drinking by dogs during and after running.
Authors: O'Connor W J
Published: December 2014

1. Drinking by dogs has been studied during and after running on a treadmill, and compared with the drinking produced by NaCl given by stomach tube or intravenously. 2. When water was offered with a delay of more than 5 min after the end of a run producing loss of 30–90 g water by panting, the drinking was similar to that produced by NaCl, assuming that loss of 100 g water produces the same increase in plasma sodium as 15 m‐mole NaCl. It is thus possible to explain drinking with a delay after the run as due to loss of water. 3. When water was offered immediately after a run or during pauses in the running there was drinking which cannot be explained as due to loss of water. Although the immediate stimulus to drinking is small, it may cause repeated small drinks by which the evaporative loss of water during running is matched by water intake. 4. Water (10–20 ml./kg body wt.) given by stomach tube before the run reduced or abolished drinking during running. Doses of water sufficient to stop drinking did not cause an increase in urine volume. 5. From these results a figure is produced placing in order mechanisms which may contribute to the control of water balance.
Comparison of thermal exchanges in men and women under neutral and hot conditions.
Authors: Bittel J , Henane R
Published: December 2014

1. The thermoregulatory responses in unacclimatized men and women were analysed and compared by means of standard heat exposure tests which allowed evaporative losses, body temperatures, heat storage and the complete thermal balance to be continuously recorded in all subjects. 2. The most pronounced differences were observed in delay before onset of sweating. Sweating always occurred faster with lower body temperatures in men than in women. The period immediately following ovulation was characterized by an increase in onset delay and a decrease in the sensitivity in sweating response compared with the pre‐ovulation period. 3. The evaporative rate in the steady state did not change significantly in the post‐ovulation period and was found to be higher in men who consequently had lower mean skin temperatures. Skin conductances, different under thermo‐neutral conditions, were the same in men and women under hot conditions. 4. Women showed a more definite increase of body temperatures and heat storage than men due to delayed sweating and decreased sweating sensitivity. The body heat content in the steady state increased more markedly in women than in men. Furthermore, the highest heat storage values were found during the post‐ovulation period. A high degree of correlation was found between body heat content and absolute onset delay. 5. The sweating kinetics and the transient phase just before the steady state of the thermal balance appeared to be decisive factors in the differentiation of the thermoregulatory behaviour in women before and after ovulation. Heat storage achieved during the transient phase and not made up by adequate evaporation seemed to be the cause of the large increase of body temperatures and heat content shown by women in hot environments.
Sweat gland function in isolated perfused skin.
Authors: Johnson K G
Published: December 2014

1. A technique for perfusion of skin has been used to investigate a possible neurochemical basis for the different patterns of sweating in domestic animals. Evaporative water loss was measured from excised trunk skin, ears or tails perfused with a nutrient Krebs solution, to which drugs were added as required. Perfused skin was observed to sweat in response to administration of sudorific drugs, and some features of the patterns of sweating were similar to those which could be induced by heating or by drugs in conscious animals. 2. In sheep and goat skin, injections of adrenaline, and to a lesser extent of noradrenaline, elicited brief sweat discharges but these were not sustained when the drugs were infused during 10–20 min. Injections of isoprenaline, carbachol, 5‐HT, bradykinin, oxytocin and histamine were all ineffective. 3. Injections of adrenaline into cattle skin evoked longer‐lasting sweat discharges, and infusions of adrenaline elicited continuous discharges. Injections of noradrenaline and sometimes of bradykinin caused only brief sweat discharges; other drugs were ineffective. 4. In horse and donkey skin, injections or infusions of noradrenaline, oxytocin and bradykinin elicited brief discharges of sweat. Infusions of isoprenaline caused a continuous and profuse outflow of sweat. Infusions of adrenaline also caused a continuous discharge which was usually biphasic in its onset. Other drugs were ineffective. 5. Assuming that the brief sweat discharges are due to myoepithelial contractions and the continuous discharges to sustained increases in secretion, equine sweat glands seem to have a alpha‐adrenergically controlled myoepithelium and a beta‐adrenergically controlled secretory mechanism. Sheep and goats may have a similar alpha‐adrenergic control of the sweat gland myoepithelium but only a feeble sweat secretory mechanism. In cattle, an alpha‐adrenergic mechanism appears to control sweat secretion, but the control of the myoepithelium is uncertain.
Gas transit times in the pig lung.
Authors: Davies A
Published: December 2014

1. A method of measuring the time taken by a front of gas to pass from the carina to individual small airways in the lung is described. 2. This method has been used to investigate the movement of a gas front through hollow lung casts, excised lungs, and excised lungs subjected to a gradient of pleural pressure. 3. The results obtained support the suggestion of morphometric studies that the asymmetrical anatomy of the bronchial tree plays a part in the uneven distribution of ventilation in the lung. 4. The effect of a gradient of pleural pressure over the surface of the upright lung was to increase the time taken by a gas front to reach dependent regions.
Myocardial sarcomere dynamics during isometric contraction.
Authors: Krueger J W , Pollack G H
Published: December 2014

1. Sarcomere lengths were measured during rest and throughout the time course of isometric contractions in thin, isolated rat papillary muscles using light diffraction techniques. 2. Shortening of the sarcomere length occurred upon contraction at all muscle lengths, averaging 7% at optimal length and more at shorter lengths. Relative to the narrow range of sarcomere lengths spanning the length‐‐tension curve, this degree of shortening was considerable. 3. Local changes of sarcomere length were quantitatively paralleled by local changes of tissue segment length, the latter demarcated by microspheres lodged within the muscle tissue. At all but the shortest muscle lengths, sarcomere shortening was fully accounted for by equivalent lengthening of the non‐striated regions near the clamped ends of the preparation. 4. It seems likely that these regions near the clamped ends of the preparation. 4. It seems constitute the source of the large series elasticity characteristic of isolated papillary muscle preparations such as this.
Quantitative aspects of ouabain binding to human erythrocyte and cardiac membranes.
Authors: Erdmann E , Hasse W
Published: December 2014

1. [3H]ouabain binding to human erythrocyte membranes is a time‐ and temperature‐dependent process. The association of ouabain to the membrane‐bound receptor follows second‐order kinetics, while the dissociation is a monomolecular reaction. An association rate constant of 4‐6 x 10(4) M‐1 sec‐1 and a dissociation rate constant of 1‐4 x 10(‐4) sec‐1 were measured at 37 degrees C. The dissociation constant calculated from these data agrees with that determined from equilibrium binding experiments. There is only one type of ouabain binding sites with high affinity for the drug as reflected by the low dissociation constant of 0‐28 x 10(‐8) M. 2. The dissociation constants of the ouabain‐receptor complexes from human erythrocyte and cardiac membranes are identical. 3. The maximal number of membrane‐bound ouabain binding sites was measured from equilibrium binding experiments as 288 +/‐ 28 per single erythrocyte. Thus one receptor site corresponds to less than 1 mum2 of the membrane, provided the receptors are diffusely distributed on the surface of the membrane. 4. Neither the maximal number of ouabain receptors nor the affinity for the drug changes with the age or sex of the blood donor. 5. A maximal transport capacity for sodium of 5‐6 m‐equiv/hr.1. is calculated from the number of receptor sites per erythrocyte and from the turn‐over number of the (Na+ + K+)‐ATPase.
Responses of neurones in motor cortex and in area 3A to controlled stretches of forelimb muscles in cebus monkeys.
Authors: Lucier G E , Rüegg D C , Wiesendanger M
Published: December 2014

1. The experiments were designed to investigate the effects of longitudinal muscle displacements on neurones of the motor cortex of anaesthetized Cebus monkeys and thus test the hypothesis that signals from muscle spindles may modify motor cortical output. The effects of sinusoidal stretching of the extensor digitorum communis (EDC) at frequencies varying from 6 to 300 Hz and of step and rhomboidal stretches were studied in neurones of the motor cortex. For comparison, neurones of the primary receiving area for low‐threshold muscle afferents, cortical area 3a, were also included in this study. Neurones of the motor cortex were subdivided into corticospinal (PT) neurones and non‐corticospinal (non‐PT) neurones. 2. Threshold stretch amplitudes were clearly higher for neurones of area 4 (PT and non‐PT) than for 3a neurones. However, a conspicuous fall in threshold stretch amplitude was observed for all three neurone populations when the frequency of sinusoidal stretching was increased (highest frequency: 300 Hz). A small number of non‐PT and PT neurones responded to vibration amplitudes of less than 100 mum and some of these low‐threshold cells of area 4 also responded to rhomboidal stretches of 8 mm/sec ramp velocity and 80 mum plateau amplitude. Increasing the stretch amplitude to twice threshold nearly doubled the output magnitude in all three cell types. Neurones of area 3a and non‐PT neurones of area 4 had similar latencies, and these were significantly shorter than the latencies of PT neurones tested with trains of high frequency vibration. Dynamic response patterns were observed in all three cell types, but most frequently in 3a neurones. 3. It is concluded that, in Cebus monkeys, signals from both primary and secondary muscle spindle endings from forelimb muscles reach the motor cortex. Under the present experimental conditions, the input from the primaries to the motor cortex was effective only if these spindle receptors were driven maximally by vibratory stimuli. The particularly low probability of stretch‐evoked discharges of cortico‐spinal neurones in the anaesthetized preparation may be explained by a low gain in transmission from input to output cells of the motor cortex.