bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of unmyelinated afferent fibres by mechanical stimuli and inflammation of the urinary bladder in the cat.
Authors: Häbler H J , Jänig W , Koltzenburg M
Published: December 2014

1. We examined the functional properties of unmyelinated primary afferent neurones innervating the pelvic viscera in twenty‐five anaesthetized cats. The axons were isolated from the intact dorsal root and the intact or chronically de‐efferented ventral root of the segment S2. All units were electrically identified with electrical stimulation of the pelvic nerve. 2. The responses of the neurones were studied with natural stimulation of the urinary bladder using innocuous and noxious increases of intravesical pressure and at the onset of an acute artificial inflammation induced by intraluminal injection of mustard or turpentine oil. 3. Out of 297 unmyelinated afferent units isolated from the dorsal root, seven were excited by an increase of the intravesical pressure during contractions and distension of the urinary bladder. These units were silent when the bladder was empty and had thresholds of 30‐50 mmHg which are presumed to be noxious. Further increases of the intravesical pressure were accurately encoded by the discharge rate of the fibres. Out of sixty‐eight unmyelinated afferent units isolated from the ventral root none was activated by these stimuli. 4. Intraluminal injection of mustard oil excited mechanosensitive units at short latency. The discharge was not closely related to changes of the intravesical pressure and the units displayed on‐going activity after the irritant had been removed. This observation suggests that the units had also chemosensitive properties and that the receptive endings were located in the bladder wall. 5. In sixteen cats ninety‐five afferent fibres that were not activated by noxious mechanical stimuli of the urinary bladder were systematically tested with intraluminal injections of mustard oil. This excited 7/67 dorsal root units and 4/28 ventral root units with short latency. Intraluminal application of turpentine oil, tested on twenty‐six afferents in four animals, did not produce a rapid excitation. 6. Following the induction of an inflammation some previously non‐mechanosensitive units started to respond to changes of intravesical pressure in the biologically relevant pressure range of the urinary bladder. 7. In conclusion, a small subpopulation (2.4%) of unmyelinated visceral afferents responds to high, presumably noxious, intravesical pressure and intraluminal application of chemical irritants. Acute inflammation excites a larger proportion of afferents (9.5%) that are not activated by acute noxious mechanical stimulation of the normal urinary bladder. In the inflamed bladder some previously non‐mechanosensitive units started to respond to increases of intravesical pressure. These novel types of chemosensitive receptors may contribute considerably to the pathogenesis of visceral pain states.
Effects of caffeine on calcium release from the sarcoplasmic reticulum in frog skeletal muscle fibres.
Authors: Klein M G , Simon B J , Schneider M F
Published: December 2014

1. Resting myoplasmic [Ca2+] and [Ca2+] transients (delta [Ca2+]) were monitored using Fura‐2 fluorescence and Antipyrylazo III absorbance signals from voltage‐clamped segments of cut frog skeletal muscle fibres in the presence and absence of 0.5 mM‐caffeine. The rate of release (Rrel) of calcium from the sarcoplasmic reticulum was calculated from delta [Ca2+]. 2. delta [Ca2+] and Rrel were increased in caffeine for all pulses. The decline of delta [Ca2+] was slower after a given pulse in caffeine than without caffeine. Resting [Ca2+] was slightly elevated in caffeine. 3. The voltage dependence of the peak value of Rrel and of the steady level of Rrel at the end of a 60‐120 ms pulse were both shifted towards more negative voltages in caffeine. For relatively small pulses the voltage at which a given release waveform was observed was also shifted to more negative voltages. 4. Intramembrane charge movements measured in the same fibres in which the above changes in Rrel were observed showed no significant changes in caffeine. 5. In caffeine calcium release continued for many milliseconds after the end of a short (10 ms) pulse. Continued release after a pulse was not observed without caffeine and was probably due to positive feedback of elevated [Ca2+] on calcium release resulting from calcium‐induced calcium release in caffeine. 6. Intramembrane charge movements after short pulses showed no change in caffeine that could account for the continued calcium release after the pulse. 7. Continued release after short pulses in caffeine decreased as the pulse duration was increased and was absent for pulses of 60 ms or longer. Rrel also inactivated during such pulses. 8. Relatively large and long conditioning pulses in caffeine suppressed both the peak Rrel and the continued release after short pulses. Peak release and continued release after short pulses recovered in parallel with increasing recovery time following suppression by a conditioning pulse in caffeine. 9. These results indicate that in the presence of caffeine, charge movement and calcium‐induced calcium release both contribute significantly to the activation of sarcoplasmic reticulum calcium release during fibre depolarization. Release activated by either mechanism appears to be inactivated by calcium‐dependent inactivation. A significant contribution of calcium‐induced calcium release during depolarization in the absence of caffeine is not ruled out by present observations.
Electrophysiology of glutamate and sodium co‐transport in a glial cell of the salamander retina.
Authors: Schwartz E A , Tachibana M
Published: December 2014

1. Müller cells were isolated from salamander retinas and their membrane voltage was controlled with a whole‐cell voltage clamp. External D‐aspartate, L‐aspartate and L‐glutamate each induced a membrane current. D‐Glutamate, kainate, quisqualate and N‐methyl‐D‐aspartate were more than 100x less effective than L‐aspartate. Kynurenic acid had no effect on the current produced by L‐glutamate, L‐aspartate or D‐aspartate. 2. The current induced by an acidic amino acid (AAA) was completely dependent on the presence of external Na+. Neither Li+, Cs+, choline nor TEA+ were able to substitute for Na+. The relationship between external Na+ concentration and current amplitude can be explained if the binding of three Na+ ions enabled transport. The apparent affinity constant for Na+ binding was 41 mM. Altering K+, H+ and Cl‐ concentrations demonstrated that these ions are not required for transport. 3. The shape of the current‐voltage relation did not depend on the external amino acid concentration. The relationship between D‐aspartate concentration and current amplitude can be described by the binding of D‐aspartate to a single site with an apparent affinity constant of 20 microM. 4. Influx and efflux of AAA were not symmetric. Although influx was electrogenic, efflux did not produce a current. Moreover, influx stimulated efflux; but efflux inhibited influx. 5. Removing external Na+ demonstrated that Na+ carried a current in the absence of an AAA. Li+ was a very poor substitute for Na+. This current may be due to the uncoupled movement of Na+ through the transporter. The relationship between the external Na+ concentration and the amplitude of the uncoupled current can be explained if the binding of two or three Na+ ions enabled the translocation of Na+ in the absence of an AAA. The apparent affinity constant for Na+ binding was approximately 90 mM. 6. The temperature dependence of the AAA‐induced current had a Q10 between 8 and 18 degrees C of 1.95. The Q10 is consistent with a rate constant for influx of 10(4) s‐1 (at ‐70 mV and 20 degrees C). The maximum rate of influx was measured following a concentration jump produced by the photolysis of ‘caged’ L‐glutamate. The onset of the observed current was limited by the 1.3 ms resolution of the recording system. Hence, the rate constant for influx must be faster than 10(3) s‐1.(ABSTRACT TRUNCATED AT 400 WORDS)
Leucocytosis induced in rabbits by intravenous or central injection of granulocyte colony stimulating factor.
Authors: Morimoto A , Sakata Y , Watanabe T , Murakami N
Published: December 2014

1. We investigated the effect of intravenous, intracerebroventricular and intrapreoptic injections of human recombinant granulocyte colony stimulating factor (GCSF) on body temperature and acute phase responses in the rabbit, including changes in the plasma concentration of iron, zinc, copper and fibrinogen and in circulating leucocyte count. 2. Neither intravenous nor intracerebroventricular injection of GCSF had any effect on the body temperature. 3. Both the intravenous and the intracerebroventricular injections of GCSF induced a dose‐dependent increase in the circulating leucocyte count but neither affected the plasma concentration of iron, zinc, copper and fibrinogen. Furthermore, intrapreoptic injection of GCSF produced leucocytosis but had no effect on the red blood cell count. 4. The present results suggest that GCSF induces leucocytosis through its action on both the peripheral target organs and the central nervous system.
Voltage dependence and stability of the gating kinetics of the fast chloride channel from rat skeletal muscle.
Authors: Weiss D S , Magleby K L
Published: December 2014

1. The voltage dependence and stability of the gating kinetics of the fast Cl‐channel in excised patches of membrane from cultured rat skeletal muscle were studied with the patch clamp technique. Up to 10(6) open and shut intervals were analysed from each of five different patches containing a single fast Cl‐channel. 2. To test for kinetic stability, plots of the mean durations of consecutive groups of 5‐500 open and shut intervals were examined at each voltage. After excluding infrequent entries into both an apparent subconductance state and a long‐lived (inactive) shut state, there were no abrupt and sustained changes in the moving means, indicating the absence of obvious shifts to other kinetic modes. The moving means did, however, fluctuate about the overall mean. 3. A comparison of experimental and simulated data indicated that most, but not all, of the fluctuation in the moving means was due to the stochastic variation inherent in the gating process. The fluctuation not accounted for by stochastic variation was mainly expressed as a slow, low‐amplitude, component of drift about the mean. This slow component was unlikely to have arisen from measurement errors. 4. To examine whether the slow drift reflected detectable changes in kinetic modes, the data were divided into consecutive groups of 50,000 intervals. The exponential components describing the distributions were remarkably similar among the different groups, with stochastic variation accounting for most of the observed differences. This finding implies a single kinetic mode throughout the experiment. Thus, any changes in channel activity associated with the slow drift would have little effect on the analysis of gating kinetics presented here. 5. Depolarization increased channel open probability, Popen, for all five channels. This increase had a voltage sensitivity of 17 +/‐ 4 mV per e‐fold change (effective gating charge of 1.6 +/‐ 0.32 electronic charges at 23 degrees C). Popen was 0.5 at ‐31 +/‐ 4 mV. 6. The depolarization‐induced increase in Popen typically arose from a decrease in the mean shut time (19 +/‐ 4 mV per e‐fold change; effective gating charge of 1.3 +/‐ 0.3 at 23 degrees C) and an increase in the mean open time (109 +/‐ 61 mV per e‐fold change; effective gating charge of ‐0.24 +/‐ 0.13). 7. Neither plots of Popen versus voltage nor plots of the mean open and mean shut time versus voltage were completely described by a single Boltzmann distribution, suggesting multiple voltage‐sensitive steps in channel gating.(ABSTRACT TRUNCATED AT 400 WORDS)
The control of limb geometry in cat posture.
Authors: Lacquaniti F , Le Taillanter M , Lopiano L , Maioli C
Published: December 2014

1. The aim of this study is to address the problem of the controlled variable in quadrupedal stance. In particular, we considered whether the projection of the centre of mass of the body on the support surface or the joint torques or the geometrical configuration of the limbs are primarily controlled. 2. Cats were trained to stand freely on a platform which could be tilted in the sagittal plane by up to +/‐ 20 deg. The normal and tangential components of the contact forces at each paw were measured by means of load cells. The position of limb joints was recorded by means of the ELITE system. 3. The projection of the centre of body mass on the platform, as well as the orientation and length of limb axes, varied to only a limited extent with tilt angle. In particular, the limb axes were closely lined up with the vertical, as were the vectors of the contact forces at the paws. As a result, the torques at the proximal joints (scapula and hip) were close to zero and the torques at the other joints varied little with table tilt. 4. In order to test the different hypotheses on postural control, an external load (10‐20% of the animal weight) was applied to the cat forequarters. The projected centre of mass consistently shifted forwards, contrary to the hypothesis that this parameter is controlled in stance. Instead, the geometry of limb posture remained unmodified after load application, even though the torques at forelimb joints were much greater than in the control. 5. This postural behaviour showed no sign of adaptation over a period of 24 h of continuous load application. 6. It is concluded that limb geometry is primarily controlled in stance. The results are discussed in the context of current notions on hierarchical control and body scheme.
Response behaviour of cat dorsal horn neurones receiving input from skeletal muscle and other deep somatic tissues.
Authors: Hoheisel U , Mense S
Published: December 2014

1. In chloralose‐anaesthetized cats, lumbosacral dorsal horn neurones driven by receptors in skeletal muscle and other deep tissues (tendon, joint, bone) were studied. 2. Upon mechanical stimulation two main types of neurones were found: units having exclusive input from deep tissues (D cells, 28.8%) and units with input from both cutaneous (C) and deep (D) receptors (C‐D cells, 71.2%). In both categories, low‐threshold mechanosensitive (LTM) and high‐threshold mechanosensitive (HTM) elements were present. 3. Neurones responding exclusively to noxious stimulation of skeletal muscle were not found; the input from muscle nociceptors converged on the dorsal horn cells together with other deep or cutaneous input. D cells with exclusively HTM input were numerous; these could from the anatomical basis for a specific spinal pathway for deep pain. 4. For C‐D neurones with input from deep nociceptors the cutaneous receptive field (RF) was usually located distal to the deep one. This arrangement might be of relevance for the occurrence of hyperaesthetic skin distal to painful deep lesions. 5. Cold block of the spinal cord resulted in a marked increase in the neurones' mechanical responsiveness and in the number of RFs per neurone. Simultaneously, the proportion of HTM RFs increased, particularly in cells with input from skeletal muscle. 6. The recording sites in the dorsal horn were located in the superficial dorsal horn and in and around laminae V/VI. Evidence is presented that in dorsal horn cells with deep input not only the mechanical excitability but also the degree of convergence is controlled by descending spinal pathways.
Brown adipose tissue thermogenic responses of rats induced by central stimulation: effect of age and cold acclimation.
Authors: Thornhill J , Halvorson I
Published: December 2014

1. Urethane‐anaesthetized, age‐matched cold‐(4 degrees C) and room (21 degrees C)‐acclimated groups of Sprague‐Dawley rats were given repeated (three) ventromedial hypothalamic electrical stimulations. Interscapular brown adipose tissue (IBAT), colonic, surface tail temperatures and blood pressure were monitored before and after each electrical stimulation. Propranolol HCl (2.5 mg kg‐1 i.v.) was given 10 min prior to the last (third) ventromedial hypothalamic stimulation. 2. Repeated electrical stimulation of the ventromedial hypothalamic (VMH) nucleus to either small or large rats (kept at 21 degrees C) caused no significant change in interscapular brown fat, colonic or surface temperatures compared to respective pre‐stimulation control values whereas mean arterial pressure was slightly but significantly increased during the 30 s stimulation period. 3. Electrical stimulation of the ventromedial hypothalamic nucleus of small or large rats, kept at 4 degrees C for 3 weeks prior to testing, caused significant (greater than 0.25 and greater than 0.40 degrees C, respectively) rises in interscapular BAT temperature from respective prestimulation control values. Colonic temperatures increased following ventromedial hypothalamic electrical stimulation only in the small, 4 degrees C‐acclimated group whereas surface tail temperatures did not significantly change after stimulation of either cold‐exposed group. Mean arterial pressures were significantly increased during ventromedial hypothalamic electrical stimulation in both 4 degrees C‐acclimated groups, compared to pre‐stimulation control levels and, in addition, were above those of age‐matched rats kept at 21 degrees C. Intravenous propranolol, which decreased interscapular brown fat and colonic temperatures in all groups, blocked the rise in interscapular brown fat and colonic temperatures of the 4 degrees C‐acclimated rats following the last electrical stimulation of the ventromedial hypothalamic nucleus. 4. In vitro biochemical analysis of the interscapular brown fat pads of another four groups of age‐matched, small and large 21 and 4 degrees C‐acclimated rats revealed that the thermogenic capacity of the 4 degrees C‐acclimated groups was, in all cases, significantly increased from age‐matched groups previously kept at 21 degrees C, as shown by significant increases in brown adipose tissue mass, BAT DNA and protein content, BAT mitochondrial protein and BAT mitochondrial GDP binding.(ABSTRACT TRUNCATED AT 400 WORDS)
Modulation of inwardly rectifying channels by substance P in cholinergic neurones from rat brain in culture.
Authors: Yamaguchi K , Nakajima Y , Nakajima S , Stanfield P R
Published: December 2014

1. Whole‐cell recording was used to investigate the effects of substance P on cultured neurones from the rat nucleus basalis. 2. Brief applications of substance P produced a reduction, about 1 min in duration, of resting membrane conductance. The concentration producing a half‐maximal effect was approximately 40 nM, with the continuous presence of substance P resulting in desensitization of the response. 3. The control current‐voltage relation exhibited inward rectification over the voltage range ‐70 to ‐150 mV, and hyperpolarization produced a time‐dependent decrease of current (inactivation). 4. The substance P‐sensitive current, obtained by subtracting the current during the presence of the tachykinin from the control current, showed no time‐dependent inactivation, though its current‐voltage relation also revealed inward rectification, with the reversal potential being approximately equal to the potassium equilibrium potential, Vk. 5. The relation between the substance P‐sensitive chord conductance and voltage could be fitted by a Boltzmann equation, with changes in [K+]o shifting this relation along the voltage axis roughly in parallel with the shift in Vk. The maximum conductance was proportional to [( K+]o). 6. Cs+ (0.1 mM) blocked the substance P‐sensitive current in a voltage‐dependent manner, with an equivalent valency for Cs+ of 1.9. Barium blockage of the substance P‐sensitive current was less voltage dependent. 7. Replacement of external Na+ by tetramethylammonium (TMA+) ions reduced the substance P‐sensitive current by only 18%. 8. These results indicate that substance P inhibits potassium channels with inward rectifier properties very similar to those of skeletal muscle. 9. Application of sodium nitroprusside did not alter the effect of substance P, suggesting that cyclic GMP plays no role in the channel modulation.
Superposition of H reflexes on steady contractions in man.
Authors: Rüegg D G , Krauer R , Drews H
Published: December 2014

1. The aim of the investigation was to study the influence of steady isometric contractions on H reflexes of human soleus muscle. 2. Stimulating and recording conditions were hardly affected by plantar flexions which subjects maintained in a force matching task. 3. If the interval between a preceding control and the test stimulus was less than 8 s the test H reflex was depressed in the relaxed subject. The depression was diminished or removed if the test reflex was superimposed on a background activity. The interval between control and test H reflex was at least 8 s in the following experiments. 4. H reflexes were nearly independent of steady plantar flexions on which they were superimposed. In some subjects, there was a slight increase with increasing torque. During dorsal flexions, H reflexes in all subjects were inhibited with increasing torque. 5. The relationship between test H reflexes, control H reflexes and background activity was evaluated by varying pseudo‐randomly stimulus intensity and steady flexion torque. The surface defined by this three‐dimensional relation approximated a plane suggesting linear properties of the H reflex. In some subjects threshold intensity decreased slightly with torque, in others it was constant. 6. In response to a warning signal, human subjects initiated steady plantar or dorsal flexions in both feet and, at the same time, they started to concentrate on a light at the onset of which they performed a unilateral ballistic plantar contraction as fast as possible. The relations between H reflex and maintained flexion force during the warning period of the reaction time task were identical to those during force matching, showing that the behavioural context did not modulate the relations. 7. The relations were also the same if reflexes were evoked bi‐ or unilaterally, illustrating the absence of a mutual modification of simultaneously evoked H reflexes. 8. The relation was the same with ipsilateral matching and relaxed contralateral muscles as with bilateral matching. If the ipsilateral side stayed flaccid contralateral matching increased H reflexes by about 20% above control values. 9. It was concluded that various factors can combine to produce an increase of H reflexes with torque, the most important of them being the use of short intervals between H reflexes. We have various evidence from the present experiments for believing that, in the relaxed subjects, the subliminal fringe was small and that although stimulus intensities below threshold could evoke an afferent volley, the effect of this on low‐threshold motor units was prevented by presynaptic inhibition at the Ia terminals.
Use‐dependent changes in synaptic efficacy in rat prefrontal neurons in vitro.
Authors: Hirsch J C , Crepel F
Published: December 2014

1. An in vitro slice preparation of rat prefrontal cortex was used to analyse the responses of layer V pyramidal cells to electrical stimulation of layer II. We also studied the long‐lasting modifications of synaptic efficacy following high‐frequency stimulation of the same region. 2. Stable intracellular recordings were obtained from forty‐three regular spiking pyramidal cells. The input resistance was 56 +/‐ 18 M omega (mean +/‐ S.D.) at a resting membrane potential of ‐71 +/‐ 4 mV. 3. At rest, a single stimulus of increasing strength evoked a monophasic, purely depolarizing postsynaptic potential (PSP) of increasing amplitude. In neurons recorded with potassium acetate‐filled micropipettes, membrane depolarization disclosed an excitatory‐inhibitory (EPSP‐IPSP) sequence (onset latency of the EPSP, 3.6 +/‐ 0.6 ms). 4. Superfusion with the non‐N‐methyl‐D‐aspartate (NMDA) receptor antagonist, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) reduced the EPSP and suppressed the IPSP. The small EPSP which remained was blocked by the NMDA receptor antagonist, D,L‐2‐amino‐5‐phosphonovalerate (APV). 5. In five cells, administration of 0.5 mumol l‐1 bicuculline revealed a postsynaptic NMDA component in the evoked response as evidenced by its anomalous voltage dependence in the presence of Mg2+ and its sensitivity to APV. In these cells the latency of the APV‐sensitive EPSP was the same as that of the APV‐insensitive EPSP. 6. In six cells superfused with a high‐Mg2+, low‐Ca2+ artificial cerebrospinal fluid (ACSF) a small monosynaptic EPSP remained which had the same latency as the PSP recorded in control ACSF. 7. Patterned high‐frequency stimulation (50‐100 Hz) was applied to the afferents of twenty‐eight neurons (twenty‐three of them were recorded in the presence of bicuculline). During the train the membrane potential depolarized some 20 mV and each stimulus evoked a small PSP. The tetanic stimulation was followed by a short‐term enhancement of the PSP amplitude and a slight increase in membrane input resistance. 8. Out of the twenty‐eight cells, twenty‐four showed long‐lasting (over 30 min) modifications of the PSP. Long‐term depression (LTD) of the evoked PSP was observed in fourteen cells and long‐term potentiation (LTP) in ten cells. There was no significant change in the steady‐state membrane properties and in the latency of the response. 9. In 64% of the cells that showed LTD and 70% of those that showed LTP of synaptic efficacy, the latency of the enhanced or depressed component of the PSP was the same as the control.(ABSTRACT TRUNCATED AT 400 WORDS)
Chloride conductance and intracellular chloride accumulation in mouse Peyer's patch enterocytes.
Authors: Cremaschi D , James P S , Rossetti C , Smith M W
Published: December 2014

1. Measurements of membrane potential, Cl‐ conductance and intracellular Cl‐, K+, Na+ and H+ activities have been carried out in the follicle‐associated epithelium of the mouse Peyer's patch to characterize further the physiological properties of antigen‐transporting M cells, enterocytes and intraepithelial lymphocytes. 2. Intraepithelial lymphocytes, identified in random impalements as a second negative jump in membrane potential (Vm), were found to have higher K+ and H+ activities, lower Na+ and Cl‐ activities and higher negative values for Vm than either of the other two epithelial cell types. Cl‐ activity in these cells was higher than that predicted from the Nernst equation. 3. M cells identified as having the first negative jump in Vm in impalements involving intraepithelial lymphocytes were unable to accumulate Cl‐. They also had a lower Vm than that found in apparently fully differentiated enterocytes. This Vm was partly depolarized at a low Cl‐ concentration. 4. Apparently fully differentiated enterocytes could be further divided into two populations depending on whether the Vm could or could not be partly depolarized by a low Cl‐ concentration. The mean Vm and intracellular Cl‐ activity of Cl(‐)‐sensitive cells, measured in high Cl‐ medium, were less than values found for Cl(‐)‐insensitive enterocytes. Cl‐ was only accumulated by enterocytes showing no depolarization at low external Cl‐ concentration. 5. The Vm of mature villus enterocytes was the same as that determined for Cl(‐)‐insensitive follicle‐associated enterocytes. Villus enterocyte Vm was not depolarized at a low Cl‐ concentration. 6. The present ability to distinguish two apparently large populations of follicle‐associated enterocytes having M cell‐like or villus enterocyte‐like properties is discussed in relation to current theories describing how M cells might be formed. The presence of a Cl‐ conductance in M cell enterocytes, the inability to accumulate Cl‐ and the maintenance of a low Vm could aid endocytosis of macromolecules across the apical membrane.
Mechanism of action of GABA on intracellular pH and on surface pH in crayfish muscle fibres.
Authors: Kaila K , Saarikoski J , Voipio J
Published: December 2014

1. The mode of action of gamma‐aminobutyric acid (GABA) on intracellular pH (pHi) and surface pH (pHs) was studied in crayfish muscle fibres using H(+)‐selective microelectrodes. The extracellular HCO3‐ concentration was varied (0‐30 mM) at constant pH (7.4). 2. GABA (5 x 10(‐6)‐10(‐3) M) produced a reversible fall in pHi which showed a dependence on the concentrations of both GABA and HCO3‐. The fall in pHi was associated with a transient increase in pHs and it was inhibited by a K(+)‐induced depolarization. 3. In the presence of 30 mM‐HCO3‐, a near‐saturating concentration of GABA (0.5 mM) produced a mean fall in pHi of 0.43 units. This change in pHi accounted for about two‐thirds of the GABA‐induced decrease (from ‐66 to ‐29 mV) in the sarcolemmal H+ driving force, while the rest was due to the simultaneous depolarization. 4. The apparent net efflux of HCO3‐ (JHCO3e) produced by a given concentration of GABA was estimated on the basis of the instantaneous rate of change of pHi. In the presence of 30 mM‐HCO3‐, JHCO3e following exposure to 0.5 mM‐GABA had a mean value of 8.0 mmol l‐1 min‐1. Under steady‐state conditions (at plateau acidosis), the intracellular acid load produced by 0.5 mM‐GABA was about 25% of that seen at the onset of the application. 5. The GABA‐induced HCO3‐ permeability, calculated on the basis of the flux data, showed a concentration dependence similar to that of the GABA‐activated conductance described in previous work. 6. The GABA‐induced increase in pHs was immediately blocked by both a membrane‐permeant inhibitor of carbonic anhydrase (acetazolamide, 10(‐6) M) and by a poorly permeant inhibitor (benzolamide, 10(‐6) M). 7. Application of acetazolamide (10(‐4) M) for 5 min or more produced a decrease of up to 60% in the maximum rate of fall of pHi at GABA concentrations higher than 20 microM. 8. The recovery of the GABA‐induced acidosis was associated with a fall in pHs. The recovery was completely blocked in solutions devoid of Na+ or of Cl‐, as well as by DIDS (4,4'‐diisothiocyanostilbene‐2,2'‐disulphonic acid, 10(‐5) M). This indicates that the maintenance of a non‐equilibrium H+ gradient at plateau acidosis and the recovery of pHi are attributable to Na(+)‐dependent Cl(‐)‐HCO3‐ exchange. 9. We conclude that the effects of GABA on pHi and pHs are due to electrodiffusion of HCO3‐ across postsynaptic anion channels.(ABSTRACT TRUNCATED AT 400 WORDS)
A bladder‐to‐bladder cooling reflex in the cat.
Authors: Fall M , Lindström S , Mazières L
Published: December 2014

1. Reflex effects of cold stimulation of the lower urinary tract were studied in cats anaesthetized with alpha‐chloralose. The bladder and the urethra were catheterized for separate fluid instillations and the bladder pressure was monitored together with the evoked efferent nerve responses in pelvic nerve filaments. 2. A bladder cooling reflex could be evoked from both the bladder and the urethra. The response was an efferent discharge in preganglionic pelvic motor fibres to the bladder. 3. Bladder mechanoreceptors that drive the normal micturition reflex were not directly involved in the cooling reflex. Their tension sensitivity was decreased by cooling and the efferent reflex response typically occurred before any activation of these receptors. The efferent activity of the cooling reflex also survived an intentional unloading of the mechanoreceptors, a manipulation that abolishes the normal micturition reflex. 4. The dynamic threshold temperature of the cooling reflex was about 30‐32 degrees C, which was at the thermal neutral point of the bladder in our experimental situation. 5. The bladder‐evoked component of the reflex was greatly reduced or abolished by an intravesical infusion of the local anaesthetic Xylocaine. It was also abolished by total bladder denervation. 6. The vesical component of the reflex was unchanged by bilateral transections of the hypogastric nerves but abolished by pelvic nerve transection. The cooling reflex from the distal urethra was abolished by transection of the pudendal nerves. 7. It was proposed that the cooling reflex originates from cold receptors in the bladder and urethral walls and that the responsible afferent fibres are unmyelinated C fibres. The function of the reflex may be to rid the body of a thermal ballast when under cooling stress.
Glucose uptake and transport in contracting, perfused rat muscle with different pre‐contraction glycogen concentrations.
Authors: Hespel P , Richter E A
Published: December 2014

1. Glucose uptake and transport, muscle glycogen, free glucose and glucose‐6‐phosphate concentrations were studied in perfused resting and contracting rat skeletal muscle with different pre‐contraction glycogen concentrations. Rats were pre‐conditioned by a combination of swimming exercise and diet, resulting in either low (glycogen‐depleted rats), normal (control rats) or high (supercompensated rats) muscle glycogen concentrations at the time their hindlimbs were perfused. 2. Compared with control rats, pre‐contraction muscle glycogen concentration was approximately 40% lower in glycogen‐depleted rats, whereas it was 40% higher in supercompensated rats. Muscle glycogen break‐down correlated positively (r = 0.76; P less than 0.001) with pre‐contraction muscle glycogen concentration. 3. Glucose uptake during contractions was approximately 50% higher in glycogen‐depleted hindquarters than in control hindquarters; in supercompensated hindquarters it was 30% lower. When rats with similar muscle glycogen concentrations were compared, glucose uptake in hindquarters from rats that had exercised on the preceding day was approximately 20% higher than in hindquarters from rats that had not exercised on the preceding day. 4. Muscle membrane glucose transport, as measured by the rate of accumulation of 14C‐3‐O‐methylglucose in the contracting muscles, was 25% lower in supercompensated than in glycogen‐depleted muscles at the onset as well as at the end of the 15 min contraction period. 5. Intracellular concentrations of free glucose and glucose‐6‐phosphate were higher at rest and during the entire 15‐min stimulation period in supercompensated muscles than in glycogen‐depleted muscles, and glucose uptake during contractions correlated negatively with free glucose (r = ‐0.52; P less than 0.01) as well as with glucose‐6‐phosphate (r = ‐0.49; P less than 0.01) concentrations. 6. It is concluded that: (a) The rate of glucose uptake in contracting skeletal muscle is dependent on the pre‐contraction muscle glycogen concentration. Regulating mechanisms include limitations of membrane glucose transport as well as of glucose metabolism. (b) Contractions on the preceding day have a stimulating effect on glucose uptake during contractions of the same muscles on the next day.
Effect of vasoactive intestinal peptide, bombesin and substance P on fluid secretion by isolated rat pancreatic ducts.
Authors: Ashton N , Argent B E , Green R
Published: December 2014

1. We have used micropuncture techniques to study the regulation of fluid secretion by interlobular ducts isolated from the pancreas of copper‐deficient rats. 2. Ducts isolated from different strains of Wistar rats exhibited quantitative differences in basal fluid secretion; however, secretion rates measured in the presence of secretin were similar. 3. Vasoactive intestinal peptide had no effect on fluid transport. 4. Bombesin stimulated fluid secretion, and this effect was abolished by removal of extracellular bicarbonate. 5. Substance P inhibited basal secretion, and that stimulated by bombesin and secretin. These inhibitory effects were partially reversed by spantide. 6. Substance P also inhibited fluid secretion stimulated by dibutyryl cyclic AMP and forskolin. This places the site of inhibition mediated by substance P at a point in the secretory mechanism distal to the generation of cyclic AMP. 7. We conclude that rat pancreatic duct cells possess receptors for bombesin and substance P, in addition to 'secretin‐preferring’ receptors. Since VIP had no effect on fluid transport, it is unlikely that ‘VIP‐preferring’ receptors are present on rat duct cells.
Modulation of secretion by dopamine involves decreases in calcium and nicotinic currents in bovine chromaffin cells.
Authors: Sontag J M , Sanderson P , Klepper M , Aunis D , Takeda K , Bader M F
Published: December 2014

1. Catecholamine secretion from cultured bovine adrenal chromaffin cells was decreased in a dose‐dependent manner by the D2 dopamine agonists apomorphine and LY 17 1555. 2. 45Ca2+ uptake was similarly inhibited and whole‐cell Ca2+ currents were reduced by apomorphine. 3. These inhibitory effects of D2 agonists depended on the secretagogue used, being much more pronounced for nicotine‐evoked responses compared to high K+ stimulation, indicating another possible site of action of apomorphine up‐stream of Ca2+ entry. 4. Inhibition by apomorphine of nicotine‐evoked responses could not be explained by competitive antagonism against nicotine or DMPP (1,1‐dimethyl‐4‐phenyl‐piperazinium iodide). 5. Apomorphine caused reductions of inward whole‐cell nicotinic current evoked by ACh and nicotine. 6. Inhibition of nicotine‐evoked secretion and 22Na+ influx by apomorphine were not affected by tetrodotoxin, and voltage‐dependent, whole‐cell Na+ currents were unaltered by apomorphine. 7. No evidence was obtained for increases in K+ conductance by apomorphine. 8. Action potentials recorded in whole‐cell current clamp were blocked by apomorphine when they were triggered by nicotinic depolarization but not when they were elicited by direct electrical stimulation. 9. Inclusion of GDP‐beta‐S in the pipette internal solution did not affect apomorphine‐dependent inhibition of nicotinic‐evoked responses, while the decrease in whole‐cell Ca2+ current induced by apomorphine was completely inhibited in the presence of GDP‐beta‐S. 10. Increases in cyclic AMP caused by cholera toxin and forskolin did not change the apomorphine‐dependent inhibitory effects on nicotine‐evoked secretion, indicating that changes in cyclic AMP levels caused by dopamine receptor stimulation are probably not involved.
Inhibition of barosensitive neurones evoked by lobule IXb of the posterior cerebellar cortex in the decerebrate rabbit.
Authors: Paton J F , Silva‐Carvalho L , Goldsmith G E , Spyer K M
Published: December 2014

1. Electrical stimulation of lobule IXb of the posterior cerebellar vermis evoked an increase in heart rate and arterial pressure in the decerebrate rabbit. This pattern of response was followed by a rebound bradycardia which was maintained until arterial pressure had returned to control levels. Activation of the arterial baroreceptors during IXb stimulation failed to elicit reflex changes in heart rate and arterial blood pressure. 2. Extracellular recordings were made from eighty‐one single neurones in the nucleus tractus solitarius (NTS), and adjacent structures, that received inputs from the carotid sinus nerve, aortic nerve and/or vagus. A proportion of these were characterized as baro‐ or chemosensitive by physiological stimuli. The nature of the input from lobule IXb onto these cells was studied subsequently. 3. In twenty‐seven out of thirty‐five barosensitive neurones, stimulation of lobule IXb either decreased or abolished on‐going activity. The latency to onset of inhibition was 21 ms in fourteen cells. In a further twenty‐one neurones the spikes evoked orthodromically by electrical stimulation of either the aortic or sinus nerves were either inhibited or severely reduced in number during short‐train conditioning stimulation of lobule IXb. This effect was most potent when the cortical conditioning stimulus was timed to occur 25 ms before the aortic or carotid sinus nerves were stimulated. 4. It is suggested that stimulation of lobule IXb in the decerebrate rabbit expresses its influence on the cardiovascular system in part by an inhibitory action on neurones receiving baroreceptor inputs at the level of the NTS.
Induced neural‐type differentiation in the cleavage‐arrested blastomere isolated from early ascidian embryos.
Authors: Okado H , Takahashi K
Published: December 2014

1. Isolated blastomeres and pairs of blastomeres from 8‐cell embryos of Halocynthia roretzi and Halocynthia aurantium were cleavage‐arrested with cytochalasin B and cultured. Their differentiation was examined in terms of membrane excitability, immunoreactivity to an epidermis‐specific monoclonal antibody (2C5), and the presence of acetylcholinesterase. 2. The blastomeres that showed epidermal‐type differentiation had Ca2(+)‐dependent action potentials and membrane currents, and immunoreactivity to 2C5. The blastomeres that showed neural‐type differentiation had Na(+)‐, Ca2(+)‐ and TEA‐sensitive delayed K+ channels, and lacked immunoreactivity to 2C5. 3. Cleavage‐arrested anterior‐animal blastomeres, a4‐2, when cultured in isolation from an 8‐cell embryo, differentiated exclusively into epidermal‐type cells. However, when cultured in contact with anterior‐vegetal blastomeres, A4‐1, they mostly showed neural‐type differentiation (seventeen out of twenty‐four cells in H. roretzi). 4. Reduction of the cytochalasin B concentration enhanced neural‐type development of a4‐2 blastomeres in contact with A4‐1 blastomeres in H. aurantium, possibly by tightening the physical contact between the blastomeres. 5. When a cleavage‐arrested and isolated a4‐2 blastomere was treated with 2% pronase at 10 degrees C for 15 min at the time when sister control embryos reached the 32‐cell stage, the blastomere underwent neural‐type differentiation in a manner identical to that of a4‐2 blastomeres contacted by A4‐1 cells. 6. The period during which neural‐type differentiation of a4‐2 blastomeres could be induced by treatment with pronase was from the 8‐cell to the 110‐cell stage. At the late gastrula stage neural‐type differentiation of a4‐2 blastomeres was not induced by pronase. The effective period for neural‐type differentiation of a4‐2 blastomeres in contact with A4‐1 cells was between the 64‐cell stage and late gastrula stage. Competence of the a4‐2 blastomere to undergo neural‐type differentiation decreased during gastrula stages, while the inducing ability of the A4‐1 blastomere lasted longer. 7. In a few cases the posterior‐animal blastomere, b4‐2, could also be induced to undergo neural‐type differentiation after contact with A4‐1 cells or after pronase treatment. 8. The appearance of Na+ spikes in a4‐2 blastomeres in contact with A4‐1 cells was considered a manifestation of neural induction, similar in principle to the induction of ectoderm by the chorda‐mesoderm in higher vertebrates.
Calcium currents in isolated rabbit coronary arterial smooth muscle myocytes.
Authors: Matsuda J J , Volk K A , Shibata E F
Published: December 2014

1. Calcium inward currents were recorded from relaxed enzymatically isolated smooth muscle cells from the rabbit epicardial left descending coronary artery using a single‐pipette voltage‐clamp technique. Outward K+ currents were blocked with CsCl‐tetraethylammonium‐filled pipette solutions. 2. Relaxed coronary smooth muscle cells had a maximum diameter of 8.6 +/‐ 0.6 microns and a cell length of 96.7 +/‐ 3.3 microns when bathed in 2.5 mM [Ca2+]o. The average resting membrane potential at room temperature was ‐32 +/‐ 10 mV. The mean cell capacitance was 18.5 +/‐ 1.7 pF and the input resistance was 3.79 +/‐ 0.58 G omega. 3. Depolarizing voltage‐clamp steps from a holding potential of ‐80 mV elicited a single time‐ and voltage‐dependent inward current which was dependent upon extracellular [Ca2+]. In 2.5 mM [Ca2+]o, the inward current was activated at a potential of ‐40 mV and peaked at +10 mV. This current was inhibited by 0.5 mM‐CdCl2 and 1 microM‐nifedipine and was enhanced with 1 microM‐Bay K 8644. No detectable low‐threshold, rapidly inactivating T‐type calcium current was observed. 4. The apparent reversal potential of this inward current in 2.5 mM [Ca2+]o was +70 mV and shifted by 33.0 mV per tenfold increase in [Ca2+]o. This channel was also more permeable to barium and strontium ions than to calcium ions. 5. Single calcium channel recordings with 110 mM‐Ba2+ as the charge carrier revealed a mean slope conductance of 20.7 +/‐ 0.8 pS. 6. This calcium current (ICa) exhibited a strong voltage‐dependent inactivation process. However, the steady‐state inactivation curve (f infinity) displayed a slight nonmonotonic, U‐shaped dependence upon membrane potential. The potential at which half of the channels were inactivated was ‐27.9 mV with a slope factor of 6.9 mV. The steady‐state activation curve (d infinity) was also well‐described by a Boltzmann distribution with a half‐activation potential at ‐4.4 mV and a slope factor of ‐63 mV. ICa was fully activated at approximately +20 mV. 7. The rate of inactivation was dependent upon the species of ion carrying the current. Both Sr2+ and Ba2+ decreased the rate as well as the degree of inactivation. The tau f (fitted time constant of inactivation) curve displayed a U‐shaped relationship in 2.5 mM [Ca2+]o. The reactivation process was voltage dependent and could be described by a single exponential. 8. The current amplitude and the inactivation kinetics were temperature dependent.(ABSTRACT TRUNCATED AT 400 WORDS)
Permeability of frog mesenteric capillaries after partial pronase digestion of the endothelial glycocalyx.
Authors: Adamson R H
Published: December 2014

1. The proteolytic enzyme pronase, which degrades the endothelial cell glycocalyx, was perfused through single capillaries of frog mesentery. Hydraulic conductivity (Lp) of each vessel was determined before and after pronase perfusion. In three vessels in which Lp increased, the ultrastructure of interendothelial clefts was examined. In a separate group of frogs the effect of pronase on the endothelial glycocalyx was assessed by using cationized ferritin to label the capillary luminal surface. 2. Control Lp was 2.0 x 10(‐7) cm s‐1 cmH2O‐1 (10 mg ml‐1 bovine serum albumin, BSA, in frog Ringer solution). Vessels were then perfused with a solution containing 0.1 mg ml‐1 pronase and 10 mg ml‐1 BSA for 1 min. Lp measured in the same eleven vessels increased to 4.9 x 10(‐7) cm s‐1 cmH2O‐1 (P less than 0.005). 3. Transverse sections of three of these vessels were examined by transmission electron microscopy at eight sites along each vessel. In these sections a total of 156 interendothelial cell clefts were found and photographed. No morphological features, such as fenestrations, transendothelial channels, or intercellular gaps associated with inflammation, were found which might account for the increases in Lp. 4. Measurement of cleft dimensions yielded a harmonic mean cleft depth (delta x) of 0.32 microns and an arithmetic mean cleft depth of 0.64 microns. Mean width (w) of the clefts outside the tight regions was 0.012 microns and the cleft length per unit area (L) was 1330 cm‐1. The mean fractional pore area of vessel wall per unit cleft depth, Ap/delta x, calculated as Lw/delta x, was 48.7 cm‐1. 5. There was less cationic ferritin (CF) labelling of the luminal glycocalyx in pronase‐perfused than in control capillaries. On average, the proportion of the luminal surface covered by CF was 85% in controls and 42% in pronase‐treated capillaries (P less than 0.01). In some vessels the CF pattern was greatly disrupted, indicating large changes in the glycocalyx structure. 6. It is concluded that the moderate increases in Lp induced by pronase perfusion are associated with partial digestion of the endothelial glycocalyx but are not accompanied by changes in the dimensions of the intercellular cleft. These observations support the fibre matrix hypothesis of capillary permeability and suggest that the endothelial glycocalyx contributes as much as 60% of the hydraulic resistance of the capillary wall.