bluuebunny/crossref_metadata_2025 huggingface dataset:
Low‐threshold mechanoreceptive and nociceptive units with unmyelinated (C) fibres in the human supraorbital nerve.
Authors: Nordin M
Published: December 2014

1. In recordings from the human supraorbital nerve with tungsten microelectrodes, eleven afferent units with unmyelinated (C) axons were identified on the basis of their conduction velocities (0.6‐1.4 m/s). 2. Eight units had low mechanical thresholds (less than or equal to 0.23 g) and could be activated up to their maximal firing rates of about 100 impulses/s by weak tactile stimuli, whereas three units had higher thresholds (5.5 g) and responded vigorously to noxious stimuli only. 3. During a skin indentation the low‐threshold units adapted to an irregular low‐frequency discharge, and release of the stimulus elicited a prominent off‐response often ending with an after‐discharge. Slow stroking was a particularly effective stimulus, even when done with cotton wool, whereas rapid stroking reduced the response. All types of stroking stimuli were occasionally followed by after‐discharges. Repeated mechanical stimulation at short intervals resulted in a decline of the response, indicating receptor fatigue. For two units a response to skin cooling was observed. 4. The above low‐threshold C units have all the main characteristics of the C mechanoreceptors known from the cat and primates but not previously proven to exist in man. The high‐threshold C units are similar to the polymodal nociceptors found in other human skin areas.
Respiratory‐related discharge pattern of sympathetic nerve activity in the spontaneously hypertensive rat.
Authors: Czyzyk‐Krzeska M F , Trzebski A
Published: December 2014

1. Synchronization of spontaneous sympathetic discharge during the respiratory cycle was studied in the cervical and renal nerves of vagotomized, normotensive Wistar‐Kyoto rats (WKYs) and age‐matched spontaneously hypertensive rats (SHRs). Phrenic nerve discharge was used as an index of central inspiratory activity. 2. In normotensive Wistar‐Kyoto rats depression of sympathetic activity appeared at the onset of inspiration reaching a minimum at mid‐inspiration. Peak maximal sympathetic discharge corresponded to postinspiratory phase; a second increase sometimes appeared in late expiration. Variations of respiratory frequency over wide range of experimental conditions by hypoxia, hyperoxia, hyper‐ or hypocapnia and transection of carotid sinus nerves did not affect this pattern. 3. In SHRs the respiratory‐phase‐related timing of sympathetic discharge was variable. In normoxia, the maximal sympathetic activity occurred in late inspiration, preceded by short depression at early inspiration and followed by postinspiratory depression. A second increase in sympathetic activity was observed in mid‐expiration. 4. The pattern of respiratory phase modulated sympathetic activity in SHRs was altered by hypoxic stimulation of the peripheral chemoreceptors. The early inspiratory depression of sympathetic activity was substantially prolonged and the maximal sympathetic discharge was shifted from inspiration to early expiration. This effect was abolished after carotid sinus nerves had been cut. 5. Hypercapnic stimulation of central chemoreceptors in SHRs with carotid sinus nerves cut did not influence the timing of the sympathetic activity in relation to the respiratory phase, though the magnitude of rhythmical sympathetic discharges was increased. 6. We discuss the possibility that altered synchronization between central respiratory drive and sympathetic neuronal system may contribute to the neurogenic mechanisms of arterial hypertension in SHRs.
Cutaneous effects on presynaptic inhibition of flexor Ia afferents in the human forearm.
Authors: Nakashima K , Rothwell J C , Day B L , Thompson P D , Marsden C D
Published: December 2014

1. In six subjects, H reflexes obtained in the flexor muscles in the forearm were inhibited by single motor threshold shocks to the radial nerve in the spiral groove. The first two phases of the inhibitory time course were studied: with intervals between the radial and median nerve shocks of ‐1 to +1 ms, and +5 to +30 ms. These two phases are thought to be due respectively to disynaptic inhibition between radial Ia afferents and flexor alpha‐motoneurones, and to presynaptic inhibition of flexor Ia afferents. 2. Single or short trains (10 ms, 400 Hz) of cutaneous stimuli to the dorsal or palmar aspect of the proximal phalanx of the index finger or to the superficial radial nerve at the wrist, reduced the amount of presynaptic inhibition by 10‐20%, but had no effect on the earlier disynaptic inhibition. Single stimuli to either side of the index finger or trains of stimuli to the ventral side, had no effect on the size of control H reflexes elicited alone. 3. Effects of cutaneous nerve shocks on presynaptic inhibition could be seen with stimuli as small as 1.5 x perceptual threshold. 4. Anaesthesia of the hand in one subject reversibly increased the amount of presynaptic inhibition and decreased the amount of disynaptic inhibition. 5. We conclude that, as in the cat, cutaneous input can modulate transmission in presynaptic inhibitory pathways in man.
Release of adrenocorticotrophin from the adrenal gland in the conscious calf.
Authors: Jones C T , Edwards A V
Published: December 2014

1. The effect of stimulation of the splanchnic nerve on the output of ACTH‐related peptides from the adrenal gland has been investigated in conscious, functionally hypophysectomized calves, previously fitted with an ‘adrenal clamp’. 2. Stimulation of the splanchnic nerve elicited a small, but statistically significant, increase in the output of ACTH‐like immunoreactivity at each frequency tested. This response was frequency‐dependent over the range 40‐70 Hz when stimulating intermittently for 1 s at 10 s intervals and was potentiated by stimulating intermittently. Thus, the average mean output during stimulation in burst at 70 Hz (25 +/‐ 5 fmol min‐1 kg‐1) was significantly higher than the corresponding value during continuous stimulation at 7 Hz (6 +/‐ 1 fmol min‐1 kg‐1; P less than 0.01) even though the total number of impulses delivered was identical in each case. 3. There was also a small but significant rise in the output of cortisol from the gland with intermittent stimulation, which was linearly related to the output of ACTH‐like immunoreactivity at the lower frequencies (4 and 7 Hz). 4. Separation of the ACTH‐related peptides which were extracted from the adrenal effluent plasma of these animals during splanchnic nerve stimulation revealed the existence of two clear forms: ACTH (1‐39) accounted for about 60% of total ACTH immunoreactivity and pro‐opiomelanocortin (POMC) for about 30%. 5. It is concluded that small amounts of ACTH are released within the adrenal gland during splanchnic nerve stimulation in the functionally hypophysectomized calf and that this may possibly contribute towards the steroidogenic effect of stimulating the splanchnic nerve.
Dynamics and dimensions of cardiac output changes in humans at the onset and at the end of moderate rhythmic exercise.
Authors: Eriksen M , Waaler B A , Walløe L , Wesche J
Published: December 2014

1. An improved Doppler ultrasound technique was used to measure stroke volume (SV) and cardiac output (CO) on a beat‐to‐beat basis in a group of supine humans before, during and after periods of standardized, rhythmic exercise, involving the quadriceps muscle groups on both sides. The development of CO on such bouts of exercise was compared to Doppler ultrasound records of the simultaneous femoral arterial flow (FF) response. 2. Records of CO at rest revealed spontaneous fluctuations around a mean level, with differences between the minimal and maximal values of the order of 1 l min‐1. The mean CO level at rest again varied considerably from one day to another and from test run to test run. 3. Upon start of exercise an immediate and rapid increase in heart rate (HR) and CO took place. The entire increase, the size of which varied appreciably from test run to test run, was completed within 10‐15 s. No or only minor changes were seen in the mean SV level during the exercise periods. 4. The time course of the increase in FF was indistinguishable from that of the increase in CO, which occurred without any detectable delay relative to the changes in FF. These closely parallel developments indicate a tight regulatory coupling between the two types of flow changes. 5. In the majority of tests the total and two‐sided increase in FF seen in the steady‐state situation in the last part of an exercise period was significantly larger than the recorded increase in CO. This discrepancy implies that some redistribution of flow from tissues other than the working muscles might take place, even at this moderate level of work. 6. Upon the end of exercise a striking but transient increase in CO occurred, resulting from an increase in SV concomitant with a maintained HR. In the course of five to eight post‐exercise cardiac cycles about 100 extra milliliters of blood were expelled from the heart. This cardiac outflow overshoot was found to occur during a post‐exercise fall in mean arterial blood pressure (MAP).
Reduction of the N‐type calcium current by noradrenaline in neurones of rabbit vesical parasympathetic ganglia.
Authors: Akasu T , Tsurusaki M , Tokimasa T
Published: December 2014

1. Intracellular and single‐electrode voltage‐clamp recordings were made from neurones of vesical parasympathetic ganglia (VPG) isolated from the rabbit urinary bladder. 2. Noradrenaline (NA, 0.5‐5 microM) shortened the duration of the action potentials and depressed the amplitudes of both spike after‐hyperpolarization and after‐current. 3. Voltage‐dependent calcium currents (ICa) were recorded by using microelectrodes filled with 2 M‐caesium chloride in a superfusing solution containing tetraethylammonium (TEA, 50 mM) and tetrodotoxin (TTX, 500 nM). Noradrenaline (0.5‐5 microM) depressed both the ICa and the tail current evoked by depolarizing voltage jumps from ‐100 to ‐50 mV to ‐30 to +20 mV. 4. Substitution of barium for calcium also produced an inward current (IBa) with no obvious tail current. Noradrenaline (1 microM) reduced the magnitude of the IBa without affecting the voltage dependence of the current‐voltage relationship for IBa. 5. Yohimbine (1 microM), but not prazosin (1 microM) or propranolol (1 microM), antagonized the NA‐induced inhibition of the IBa. UK 14304, a potent alpha 2‐adrenoceptor agonist, mimicked NA in depressing the IBa. 6. The transient low‐threshold (T), the transient high‐threshold (N) and the slowly inactivating high‐threshold (L) calcium currents co‐existed in VPG neurones. 7. Noradrenaline reduced the IBa evoked at clamp potentials more positive than ‐20 mV from holding potentials near the resting membrane potential (‐70 to ‐50 mV). Under these conditions, the IBa consisted primarily of N‐ and L‐current components. In contrast, NA had no effect on the isolated T‐ and L‐currents. It is concluded that NA selectively inhibits the N‐type calcium channels by an action at alpha 2‐adrenoceptors in the rabbit VPG neurones.
Brush‐border membrane alkaline phosphatase activity in mouse Peyer's patch follicle‐associated enterocytes.
Authors: Brown D , Cremaschi D , James P S , Rossetti C , Smith M W
Published: December 2014

1. Using a new method of quantitative cytochemistry to determine alkaline phosphatase activity, it was possible to identify M cells and distinguish two further types of enterocytes present in mouse Peyer's patch follicle‐associated epithelial tissue. 2. A quantitative description of these three cell types was provided by making direct absorbance measurements of enzyme reaction product on the luminal surface of individual follicle‐associated enterocytes. M cells having a negligible alkaline phosphatase activity had a mean absorbance of 6 +/‐ 2 arbitrary units. The other two populations of enterocytes had overlapping but significantly different mean absorbances of 20 +/‐ 2 and 30 +/‐ 3 arbitrary units. 3. M cells accounted for 3.2 +/‐ 1% of the total number of cells present in the apical part of the follicle‐associated epithelium. This percentage is a minimum value describing an extreme example of cells having M cell‐like characteristics. The remaining epithelial cells were divided equally between those having high and low alkaline phosphatase activities in their brush‐border membranes. A small percentage of cells having low alkaline phosphatase activities could perform M cell functions. 4. Results obtained suggest that reduced alkaline phosphatase activity and brush‐border membrane Cl‐ conductance can both be used as differentiation markers to identify a large population of poorly differentiated enterocytes present in mouse follicle‐associated epithelial tissue.
Agonist‐dependent Ca2+ and Mn2+ entry dependent on state of filling of Ca2+ stores in aortic smooth muscle cells of the rat.
Authors: Missiaen L , Declerck I , Droogmans G , Plessers L , De Smedt H , Raeymaekers L , Casteels R
Published: December 2014

1. The properties of intracellular Ca2+ stores of intact‐ and of saponin‐skinned A7r5 (an established cell line from embryonic rat aorta) smooth muscle cells were studied by measuring 45Ca2+ and 54Mn2+ fluxes. 2. Application of 5 microM‐vasopressin to intact cells increased the fractional loss of 45Ca2+ in Ca2(+)‐free solution by a factor of 5.2. This effect was not influenced by a pre‐incubation with 10 microM‐ryanodine. Caffeine (25 mM) did not stimulate the fractional loss of 45Ca2+ from intact cells. 3. In skinned cells 10 microM‐IP3 (inositol 1,4,5‐trisphosphate) and 5 microM‐A23187 (a calcium ionophore) released the same amount of 45Ca2+. This release did not require GTP and was not affected by a pre‐incubation with 10 microM‐ryanodine. Caffeine (25 mM) did not release stored Ca2+. 4. NaF (1 mM) plus 10 microM‐AlCl3 inhibited by 72% the 45Ca2+ uptake by the IP3‐sensitive store of skinned cells at 0.15 microM‐Ca2+. Cyclic AMP‐dependent protein kinase did not stimulate this ATP‐dependent 45Ca2+ uptake, nor could the presence of phospholamban be demonstrated immunologically. 5. The 45Ca2+ uptake by cells which had been depleted of Ca2+ with 5 microM‐vasopressin was 69% higher than the uptake obtained without such proceeding depletion. This enhanced 45Ca2+ uptake did not occur through voltage‐operated Ca2+ channels, because blockade of these channels with verapamil, or depolarization of the plasma membrane by increasing [K+] from 5.9 to 59 mM in the presence of verapamil, did not modify this uptake. 6. A similar increase of the 54Mn2+ uptake occurred in intact cells with a depleted Ca2+ store. If, however, the cells were first skinned and subsequently exposed to 54Mn2+, the ATP‐dependent 54Mn2+ uptake amounted to less than 6% of the ATP‐dependent 45Ca2+ uptake. 7. If intact cells were first exposed to a 45Ca2(+)‐ or 54Mn2(+)‐containing solution, and subsequently skinned in a non‐radioactive intracellular solution, the addition of 10 microM‐A23187 to these cells released stored Ca2+ or Mn2+. The amount of released Ca2+ was only slightly larger than the amount of released Mn2+. If the intracellular store was depleted before loading, the amount of Ca2+ or Mn2+ released by the ionophore increased by 68 and 28%, respectively. 8. It is concluded that A7r5 smooth muscle cells do not express a Ca2(+)‐induced Ca2+ release mechanism, but do contain an IP3‐induced Ca2+ release mechanism which can release approximately all intracellularly accumulated 45Ca2+.(ABSTRACT TRUNCATED AT 400 WORDS)
Deoxygenation permeabilizes sickle cell anaemia red cells to magnesium and reverses its gradient in the dense cells.
Authors: Ortiz O E , Lew V L , Bookchin R M
Published: December 2014

1. Our findings of a low total magnesium content in the dense fraction (over 1.118 g ml‐1) of sickle cell anaemia (SS) red cells seemed inconsistent with the low Mg2+ permeability and outward Mg2+ gradient seen in normal red cells, and prompted studies of the Mg2+ permeability and equilibria in the SS cells. 2. Deoxygenation and sickling induced Mg2+ permeabilization in SS cells, supporting non‐specificity of the sickling‐induced cation permeabilization, previously described for Na+, K+ and Ca2+. The extent of Mg2+ permeabilization was comparable in SS cells with normal or high density. 3. Compared with normal‐density SS cells and normal red cells, the dense SS cells showed a much larger increase in the fraction of ionized magnesium ([Mg2+]i) on deoxygenation, resulting in [Mg2+]i levels sufficient to reverse the normal inward direction of the transmembrane Mg2+ gradient. 4. The molar ratio of 2,3‐diphosphoglycerate (2,3‐DPG) to haemoglobin was markedly reduced in the dense SS cells. Since 2,3‐DPG and ATP are the main cytoplasmic Mg2+ buffers, their further reduction upon binding to deoxyhaemoglobin accounts for the high [Mg2+]i in the deoxygenated dense SS cells; the resulting outward electrochemical Mg2+ gradient, together with sickling‐induced Mg2+ permeabilization, could explain the decreased total magnesium content of these cells. 5. The above findings suggested that the documented low sodium pump fluxes in dense SS cells may result from an increased Mg2+:ATP ratio, which is known to inhibit Na(+)‐K+ exchange fluxes through the sodium pump. If so, deoxygenation, by increasing the Mg2+:ATP ratio, should inhibit the pump further, whereas increasing ATP should relieve the inhibition. Experiments designed to test this possibility showed that in these dense SS cells, the ouabain‐sensitive K(86Rb) influx was low in oxygenated cells, was reduced further by deoxygenation, but was substantially increased after treatment with inosine, pyruvate and phosphate to increase their organic phosphate pool. These results were thus consistent with such a mechanism for Na+ pump inhibition in the dense SS cells.
Functional and structural differences in febrile mechanism between rabbits and rats.
Authors: Morimoto A , Murakami N , Sakata Y , Watanabe T , Yamaguchi K
Published: December 2014

1. Febrile responsiveness of rabbits and rats to intravenous (I.V.) or intracerebroventricular injection of human recombinant interleukin‐1 alpha (IL‐1 alpha), human recombinant interleukin‐1 beta (IL‐1 beta) and prostaglandin E2 was examined. 2. The I.V. injection of both IL‐1 alpha and IL‐1 beta produced dose‐dependent fever over a range of 0.05‐2.0 micrograms/kg. A small dose of IL‐1 alpha (0.5 micrograms/kg) or IL‐1 beta (0.5 micrograms/kg) produced a monophasic patterned fever in both rabbits and rats. A large dose (2.0 micrograms/kg) of IL‐1 alpha or IL‐1 beta produced a biphasic fever in rabbits, but monophasic fever in rats. Febrile responses in rabbits induced by I.V. injection of IL‐1 alpha or IL‐1 beta were significantly greater than those in rats induced by these same injections. Furthermore, in both species, the pyrogenicity of I.V. IL‐1 beta was greater than that of IL‐1 alpha. 3. The intracerebroventricular injection of both IL‐1 alpha and IL‐1 beta produced dose‐dependent fever over a range of 0.2‐20 ng. In rabbits and rats, the ventricular injections of IL‐1 alpha and IL‐1 beta produced fever with almost the same pattern‐‐monophasic, regardless of injection doses. Although febrile responsiveness of rabbits to ventricular injection of IL‐1 alpha was greater than that of rats, responsiveness to IL‐1 beta was almost the same in both species. Pyrogenicity of ventricular IL‐1 beta was greater than that of IL‐1 alpha. However, febrile responses in rats induced by ventricular injections of several doses (2‐2000 ng) of prostaglandin E2 were greater than those in rabbits. 4. The present results show that febrile responsiveness of rabbits to I.V. IL‐1 is significantly greater than that of rats. However, fever sensitivity within the central nervous system (CNS) of rats is not lower compared with that of rabbits. Therefore, we considered that between the two species there exist structural differences in the organum vasculosum laminae terminalis (OVLT), which is currently believed to be the pathway of pyrogen to the CNS and/or the site of production of pyrogenic prostaglandins. 5. Histological examinations showed that the rabbit's OVLT has two vascular components with capillaries, one in the layer near the third ventricle and the other in the layer near the subarachnoideal space. However, the rat's OVLT only has a single component, in the layer near the subarachnoideal space.(ABSTRACT TRUNCATED AT 400 WORDS)
Characteristics of transient outward currents in single smooth muscle cells from the ureter of the guinea‐pig.
Authors: Imaizumi Y , Muraki K , Watanabe M
Published: December 2014

1. Two kinds of transient outward currents were observed upon depolarization of single smooth muscle cells isolated from guinea‐pig ureter. The major transient outward current was through Ca2(+)‐activated K+ channels (IK(Ca) which had a large conductance (130 pS; 126 mM [K+]i/5.9 mM [K+]o). 2. The smaller transient outward current (ITO) was pharmacologically separated from other membrane currents in the presence of 1 mM‐Cd2+ and 2 mM‐tetraethylammonium(TEA+) and was selectively blocked by 3 mM‐4‐aminopyridine. It peaked (approximately 200 pA) within 10 ms upon depolarization from ‐80 to +20 mV and its half‐inactivation time was approximately 50 ms at +20 mV. Half‐maximum voltages (V 1/2) for activation and inactivation were about ‐8 and ‐50 mV, respectively, in the presence of 1 mM‐Cd2+ and 2 mM‐TEA+. The time course of recovery from inactivation of ITO was fitted with a single‐exponential function (tau = 100 ms at ‐80 mV). A tenfold change of [K+]o resulted in a 53 mV change in the reversal potential of the tail of ITO. 3. Cadmium reduced peak ITO and shifted the voltage dependence of activation and inactivation in the positive direction in a concentration‐dependent manner. The V 1/2 for inactivation in the absence of Cd2+ was estimated to be approximately ‐64 mV. 4. Single‐channel outward currents which appeared only in the initial part of a depolarizing pulse from about ‐100 mV were recorded using the cell‐attached patch clamp. The decay of the ensemble average of the current was similar to the macroscopic ITO under whole‐cell clamp. When the holding potential was less negative, the opening probability of the channel greatly decreased. The channel conductance in normal extracellular medium was 14 pS. 5. In ureter cells ITO resembles A‐type current. ITO does not contribute significantly to the repolarization of the action potential but it may regulate membrane excitability by opposing Ca2+ current activated around the threshold of the action potential.
Long‐lasting facilitation of excitatory postsynaptic potentials in the rat hippocampus by acetylcholine.
Authors: Markram H , Segal M
Published: December 2014

1. The effects of acetylcholine (ACh) on excitatory postsynaptic potentials (EPSPs) evoked by stimulating Schaffer‐commissural afferents and on ionophoretically applied L‐glutamate ligands, were investigated in CA1 neurones of hippocampal slices using current‐ and voltage‐clamp techniques. 2. ACh produced a transient suppression followed by a long‐lasting facilitation of EPSPs. The facilitation was also seen in Cs(+)‐filled cells under voltage‐clamp conditions. Both suppressing and facilitating effects were blocked by atropine. 3. All components of the EPSP were reduced in the initial phase of ACh action, while only the slow component was enhanced during the later phase. The facilitation was blocked by an N‐methyl‐D‐aspartate (NMDA) receptor antagonist, d‐2‐amino‐5‐phosphonovalerate (2‐APV) and by hyperpolarization. 4. ACh also facilitated responses to ionophoretically applied NMDA in voltage‐clamped, Cs(+)‐filled cells in Ba2(+)‐treated slices. ACh facilitated responses to L‐glutamate which was blocked by 2‐APV. ACh failed to affect responses to kainate or quisqualate. 5. We conclude that ACh, acting on muscarinic receptors, exerts a primary effect in the hippocampus to specifically amplify NMDA receptor‐mediated synaptic responses and thereby facilitate EPSPs.
Proprioceptive guidance of human voluntary wrist movements studied using muscle vibration.
Authors: Cody F W , Schwartz M P , Smit G P
Published: December 2014

1. The alterations in voluntary wrist extension and flexion movement trajectories induced by application of vibration to the tendon of flexor carpi radialis throughout the course of the movement, together with the associated EMG patterns, have been studied in normal human subjects. Both extension and flexion movements were routinely of a target amplitude of 30 deg and made against a torque load of 0.32 N m. Flexor tendon vibration consistently produced undershooting of voluntary extension movements. In contrast, voluntary flexion movements were relatively unaffected. 2. The degree of vibration‐induced undershooting of 1 s voluntary extension movements was graded according to the amplitude (0.75, 1.0 and 1.5 mm) of flexor tendon vibration. 3. As flexor vibration was initiated progressively later (at greater angular thresholds) during the course of 1 s voluntary extension movements, and the period of vibration was proportionately reduced, so the degree of vibration‐induced undershooting showed a corresponding decline. 4. Varying the torque loads (0.32, 0.65 and 0.97 N m) against which 1 s extension movements were made, and thereby the strength of voluntary extensor contraction, produced no systematic changes in the degree of flexor vibration‐induced undershooting. 5. Analysis of EMG patterns recorded from wrist flexor and extensor muscles indicated that vibration‐induced undershooting of extension movements resulted largely from a reduction in activity in the prime‐mover rather than increased antagonist activity. The earliest reductions in extensor EMG commenced some 40 ms after the onset of vibration, i.e. well before voluntary reaction time; these initial responses were considered to be ‘automatic’ in nature. 6. These results support the view that the central nervous system utilizes proprioceptive information in the continuous regulation of moderately slow voluntary wrist movements. Proprioceptive sensory input from the passively lengthening antagonist muscle, presumably arising mainly from muscle spindle I a afferents, appears to be particularly important and to act mainly in the reciprocal control of the prime‐mover.
Brain stem regions mediating the cardiovascular responses elicited from the posterior cerebellar cortex in the rabbit.
Authors: Paton J F , Spyer K M
Published: December 2014

1. In this study we have examined the roles of the lateral parabrachial nucleus (lateral PBN) and nucleus tractus solitarius (NTS) as sites mediating the circulatory responses evoked from lobule IX b of the posterior cerebellar vermis in the decerebrate and anaesthetized decerebrate rabbit. Microinjection of either kainic acid or bicuculline into the lateral PBN and NTS was undertaken to assess the importance of neurones and GABAergic mechanisms, respectively, in expressing the cardiovascular responses evoked from lobule IX b. 2. In both the decerebrate and anaesthetized decerebrate rabbit activation of neurones within the lateral PBN with a microinjection of glutamate elicited tachycardia and a pressor response together with an increase in renal sympathetic nerve discharge and vasoconstriction in the hindlimb. A microinjection of GABA into the lateral PBN evoked an opposite pattern of response. Chemical lesioning of neurones within the rostral region of the lateral PBN or pharmacological blockade of GABAA receptor, abolished or significantly attenuated the cardiovascular response (bradycardia/depressor effect) evoked from lobule IX b in the anaesthetized decerebrate rabbit. 3. In the decerebrate animal the tachycardia/pressor response elicited from lobule IX b was suppressed when either kainic acid or bicuculline was microinjected into the caudal division of the lateral PBN. 4. A bradycardia, depressor response, an abolition of on‐going renal nerve activity and vasodilatation in the femoral bed were evoked by activating neurones within a restricted region of the NTS with glutamate in the decerebrate and anaesthetized decerebrate rabbit. A microinjection of GABA into the NTS produced a qualitatively opposite pattern of response. The bradycardia/depressor response evoked from lobule IX b in the anaesthetized decerebrate rabbit was not altered significantly following a microinjection of either kainic acid or bicuculline into the ipsilateral NTS. However, in the decerebrate preparation following a microinjection of bicuculline into the ipsilateral NTS the tachycardia/pressor response evoked from IX b was either abolished or in many cases reversed to the pattern of response seen in the anaesthetized decerebrate rabbit. 5. The present experiments provide evidence for two functionally distinct pathways from the cardiovascular region of lobule IX b to the lateral PBN.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of millimolar concentrations of glutaraldehyde on the electrical properties of frog skin.
Authors: Mărgineanu D G , Van Driessche W
Published: December 2014

1. The effects of millimolar concentrations of glutaraldehyde on the electrophysiological properties of the epithelium of frog skin (Rana temporaria) were investigated. We recorded short‐circuit current (Isc), transepithelial conductance (Gt) and impedance (Zt), fractional resistance (fRo) and the potential difference across the apical membrane (Vo). We used either Na+ or K+ as major mucosal cations to compare the effects on transepithelial Na+ and K+ currents (INa and IK) and thus on the apical Na+ and K+ permeabilities. 2. At concentrations above 0.005% (w/v) or 0.5 mM, glutaraldehyde irreversibly and completely inhibits both INa and IK within 2‐3 h. The initial time courses of the inhibition of transepithelial currents following serosal and mucosal applications of the compound markedly differ. 3. Glutaraldehyde decreased Gt in sulphate Ringer solutions while it augmented Gt severalfold in chloride Ringer solution. 4. Measurements of the transepithelial impedance of tissues incubated with sulphate solutions showed that glutaraldehyde increased the resistances of both apical and basolateral membranes significantly. The capacitance of the apical membrane was augmented, while the basolateral membrane capacitance was drastically decreased. 5. Microelectrode impalements of the granulosum cells showed that glutaraldehyde decreased Vo by more than 40 mV and increased fRo, which reached values around 90%. 6. The role of free amino groups in ion‐transporting proteins and the potential non‐fixative uses of protein cross‐linkers in epithelia are discussed.
Differentiation of membrane excitability in isolated cleavage‐arrested blastomeres from early ascidian embryos.
Authors: Okado H , Takahashi K
Published: December 2014

1. Differentiation of excitable cells was studied electrophysiologically and histochemically in cleavage‐arrested blastomeres isolated from early ascidian embryos. Blastomeres were isolated at the 4‐ or 8‐cell stage, and cultured in sea water containing cytochalasin B until the time of hatching of control larvae. Electrical responses, immunoreactivity to epidermis‐specific monoclonal antibody (2C5) and activity of muscle‐specific acetylcholinesterase were examined. 2. All cleavage‐arrested blastomeres isolated from an 8‐cell embryo differentiated to elicit either muscular‐ or epidermal‐type action potentials, but no neural‐type action potentials were observed in these blastomeres. The anterior‐animal and the posterior‐animal blastomeres developed only epidermal‐type action potentials, which involved expression of Ca2+ channels and immunoreactivity to 2C5. One‐third of anterior‐vegetal blastomeres developed epidermal‐type action potentials which are mediated by Ca2+ channels though the immunoreactivity to 2C5 was absent. A majority of remaining blastomeres showed action potentials composed of Ca2+ currents and TEA‐sensitive delayed K+ currents (type I response), and a few of them had fast transient K+ currents (A‐currents) in addition (type II response). One‐third of posterior‐vegetal blastomeres developed epidermal‐type action potentials without expression of the immunoreactivity to 2C5. The remainder differentiated into muscular‐type cells, which expressed Ca2+ currents, TEA‐sensitive and TEA‐insensitive delayed K+ currents, and showed acetylcholinesterase activity. 3. Cleavage‐arrested blastomeres isolated from a 4‐cell embryo also differentiated into epidermal‐ or muscular‐type cells, but not neural‐type cells. The anterior blastomere, which is the parent cell of anterior‐animal and anterior‐vegetal blastomeres of an 8‐cell embryo, developed epidermal‐type, type I or type II responses, as was the case in the anterior‐vegetal blastomere isolated from an 8‐cell embryo. The posterior blastomere, which was the parent cell of posterior‐animal and posterior‐vegetal blastomeres of an 8‐cell embryo, differentiated into either epidermal‐type or muscular‐type cells in terms of both membrane excitability and immunochemical reactivity. 4. Cleavage‐arrested 1‐cell embryos differentiated exclusively into epidermal‐type cells in terms of membrane excitability and 2C5 immunoreactivity, even when the cytochalasin B concentration was decreased below 0.1 microgram/ml.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of anions on the Na(+)‐H+ exchange of trout red blood cells.
Authors: Guizouarn H , Scheuring U , Borgese F , Motais R , Garcia‐Romeu F
Published: December 2014

1. Replacement of chloride by foreign anions in the suspending medium of trout erythrocytes can affect in a complex manner both the activation by catecholamines of the latent Na(+)‐H+ exchanger and its subsequent desensitization. These changes are discussed in relation to other cellular modifications (distribution of permeant anions and accumulation of cyclic AMP) induced by foreign anions. 2. The transfer of trout erythrocytes from a chloride‐containing medium to media containing lyophilic permeable anions, NO3‐ or SCN‐, immediately induces a decrease of distribution ratios of permeable anions across the red cell membrane (i.e. Donnan ratios). It is probable that the binding of lyophilic anions to haemoglobin, by altering the amount of negative fixed charges, results in changes of distribution of permeant anions across the membrane. 3. The effectiveness of anions in decreasing both the activation of the Na(+)‐H+ exchanger and the Donnan ratio follows the same sequence in both cases, i.e., SCN‐ greater than NO3‐ greater than Cl‐ = propionate. It was demonstrated that a change in Donnan ratio affects antiport activity possibly through a shift in intracellular pH; such a mechanism however cannot account for all the effects of foreign anions on antiport activity. 4. The present results show that lyophilic anions do not modify the affinity of the antiporter for sodium ions but greatly decrease the transport capacity of the exchange system. This is interpreted as indicating that the binding of lyophilic anions to some component of the transport system prevents antiporters from establishing their activated configuration once stimulated. Since the inhibitory effect of anions on Na(+)‐H+ exchange has been demonstrated in all erythrocytes studied but in no other cell, the crucial substance involved in this inhibition could well be haemoglobin, which appears to control antiport activity in erythrocytes. 5. Some anions affect desensitization of the exchanger. This effect is not related to the lyophilic character of the anion and is not mediated by a change in intracellular cyclic AMP. 6. Propionate and acetate drastically reduce the intracellular level of cyclic AMP and seem to facilitate the activated configuration of the exchanger.
Control of intracellular calcium by ATP in isolated outer hair cells of the guinea‐pig cochlea.
Authors: Ashmore J F , Ohmori H
Published: December 2014

1. Intracellular calcium levels were monitored in isolated outer hair cells of the guinea‐pig cochlea using the calcium‐sensitive dye Fura‐2. 2. The calcium in the cells was studied during application of ATP externally applied from a pipette. ATP induced a rise of intracellular calcium which could be separated into two components: a rapid rise, peaking in 20 s, localized around the apical end of the cell, and a slower rise, peaking in 50‐150 s but spread throughout the cell. The effects were observed with 5, 25 and 100 microM‐ATP concentrations. 3. In the absence of external Ca2+, ATP was still able to trigger a rise in Ca2+, but with a longer delay. Under these conditions, the cells did not show the initial rapid Ca2+ rise. The result suggests that ATP can mobilize intracellular stores. 4. A rise in intracellular Ca2+ was also observed when 5 mM‐caffeine was applied to the bath. 5. Simultaneous measurements were made of whole‐cell currents and intracellular calcium. ATP activated an inward current at resting potentials of ‐60 mV. Internal Ca2+ levels increased during the inward current. In current‐clamped cells Ca2+ levels also increased during the associated depolarization produced by ATP. 6. Adenosine (150 microM) did not produce any measurable inward current. Acetylcholine (ACh, 100 microM‐1 mM) produced only a small rise in Ca2+. However, applied simultaneously with ATP, ACh suppressed the rise in intracellular Ca2+ produced by ATP, with the kinetics of a competitive antagonist. 7. Intracellular Ca2+ increased with step depolarizations of the cell above ‐20 mV during whole‐cell clamp. Large rises in Ca2+ were also observed on depolarizing the cell with isotonic KCl. 8. Calcium levels in supporting cells of the organ of Corti were sensitive to ATP. In these cells, rises in intracellular Ca2+ did not require the presence of extracellular Ca2+. 9. It is concluded that the organ of Corti contains receptors for ATP on a variety of the cells. ATP controls a direct entry of Ca2+ through the membrane and also may mobilize intracellular stores.
Selective control of sympathetic pathways to the kidney, spleen and intestine by the ventrolateral medulla in rats.
Authors: Hayes K , Weaver L C
Published: December 2014

1. Electrical activity of multifibre renal, splenic, mesenteric and greater splanchnic nerves and 13th thoracic white rami was recorded in artificially respired, urethane‐anaesthetized rats. Discharge of neurones in the rostral ventrolateral medulla was blocked by unilateral microinjections of the inhibitory amino acid glycine and effects on the electrical activity of these sympathetic nerves were compared. 2. Blockade of the rostral ventrolateral medulla caused greater decreases in discharge of renal than splenic nerves and had no consistent effect on mesenteric nerves. This blockade also decreased the discharge of the preganglionic white rami more than that of the preganglionic splanchnic nerves. 3. Postganglionic responses to rostral ventrolateral medulla blockade were always greater than preganglionic responses. 4. The arterial pressure and renal nerve responses to rostral ventrolateral medulla blockade in urethane‐anaesthetized rats were not different from those in rats anaesthetized with alpha‐chloralose. 5. These findings demonstrate that pre‐ and postganglionic sympathetic pathways to the kidney are more dependent upon excitatory drive from the rostral ventrolateral medulla than pathways directed to the spleen and intestine.
Mirror movements studied in a patient with Klippel‐Feil syndrome.
Authors: Farmer S F , Ingram D A , Stephens J A
Published: December 2014

1. Electromyographic (EMG) recordings have been made from upper limb muscles in a patient with well‐defined congenital mirror movements occurring in association with Klippel‐Feil syndrome and the results compared to those obtained in normal control subjects. 2. In the patient, liminal percutaneous electrical or magnetic brain stimulation applied over either hemisphere elicited bilateral and symmetrical short‐latency muscle responses in relaxed intrinsic hand muscles. In the normal subjects unilateral brain stimulation only elicited contralateral muscle responses. 3. F response and H reflex studies for the patient's ulnar‐supplied intrinsic hand muscles were normal. No crossed responses were recorded in the homologous muscles of the contralateral hand. 4. Scalp‐recorded somatosensory‐evoked responses following ulnar or median nerve stimulation were of normal latency and distribution in the patient. 5. In the patient, cross‐correlation analysis of on‐going single and multiunit needle EMGs recorded between muscles of left and right hands revealed a central peak in the cross‐correlogram. No cross‐correlogram peaks were found between left‐ and right‐hand muscles in normal subjects. The magnitude and time course of the central peaks in the cross‐correlograms constructed between the firing of motor units on opposite sides of the body in the patient were similar to those found in cross‐correlograms constructed between the firing of motor units from muscles on the same side of the body in the patient and in normal subjects. 6. The magnitude of cross‐correlogram peaks detected within a muscle and those detected between left and right homologous muscles showed a gradient in which the largest peaks were found in the intrinsic hand and forearm extensor muscles. The smallest peaks were observed in the forearm flexor muscles. No peaks were detected between left and right biceps brachii muscles. In intrinsic hand muscles, the size of the cross‐correlogram peak detected between the EMGs of homologous muscle pairs was greater than that found for non‐homologous muscle pairs. 7. Cutaneous reflex responses were recorded from first dorsal interosseous muscle following unilateral electrical stimulation of the digital nerves of the index finger. In the patient, this produced an early excitatory (E1) response on the stimulated side. Later excitatory (E2 and E3) responses, of approximately equal size and latency, were distributed bilaterally. In the normal subjects, reflex responses were confined to the stimulated side.(ABSTRACT TRUNCATED AT 400 WORDS)
Measurement of intracellular calcium and pH in avian neural crest cells.
Authors: Dickens C J , Gillespie J I , Greenwell J R
Published: December 2014

1. Intracellular pH (pHi) and calcium (Cai2+) were studied in freely migrating neural crest cells and in closely packed non‐migrating cells derived from avian neural tubes in vitro, using the fluorescent dyes 2,3‐dicyanohydroquinone (DCH) and Indo‐1 to measure pHi and Cai2+ respectively. 2. In freely migrating crest cells the pHi was approximately 0.2 pH units more alkaline and Cai2+ 90 nM lower than in closely packed cells. 3. Experiments to establish the cellular mechanisms regulating pHi in isolated neural crest cells demonstrate the presence of Na(+)‐H+ exchange in 66% of the cells and Na(+)‐HCO3(‐)‐dependent pHi‐regulating mechanisms in all cells examined. 4. Interactions between pHi and Cai2+ were examined. pHi was altered using either NH4Cl pulses resulting in small changes in Cai2+ or using a weak acid and base (propionate and trimethylamine), which produced a fall and a rise in Cai2+ respectively. 5. Exposure to Ca2(+)‐free media caused a lowering of Cai2+ and induced a transient acidification. 6. Application of BAPTA‐AM (50 microM), a cell‐permeant analogue of EGTA, resulted in a fall in Cai2+ and an intracellular acidification. 7. Co2+ and La3+ (2 mM) each induced a reversible fall in Cai2+ that was accompanied by intracellular acidification. These data suggest the presence of a transmembrane flux of Ca2+ in the resting cells. 8. It would appear that the mechanisms influencing Cai2+ and pHi are linked. This idea is discussed in terms of possible mechanisms and roles for Ca2+ and pH as modulators of neural crest cell behaviour.
Neuronal activity in the lateral cerebellum of trained monkeys, related to visual stimuli or to eye movements.
Authors: Marple‐Horvat D E , Stein J F
Published: December 2014

1. The responses of neurones in the lateral cerebellar cortex to visual stimuli and to eye movements were recorded in rhesus monkeys trained to perform visually guided arm and eye movements in a tracking task. 2. Twenty‐two of 134 units recorded (16%) modulated their discharge in response to a bright Xenon flash. They were mainly located in the dorsal paraflocculus. Among those identified as Purkinje cells both simple spike and climbing fibre responses to the flash were seen. (72% of the units were related to arm movements; these were centred in the paramedian lobule, and have been described fully in Marple‐Horvat & Stein (1987).) 3. The visual responsiveness of one of the units varied according to the phase of the monkey's task. Around the time that the target stepped, which was the monkey's cue to move, its sensitivity to other stimuli disappeared. 4. Only two neurones responded to the movements of the tracking target. These responses were conditional upon the monkey using visual signals to guide his movements; they did not respond to the target step if he moved before the target did. 5. Fourteen units (10%) located in crus I and II and lobulus simplex correlated strongly with the velocity of horizontal eye movements. Only one of these also responded to visual stimuli. 6. Thus most neurones were found to carry only visual, or eye movement, or limb movement information rather than combinations of these signals; they were located in different but overlapping regions of lateral cerebellar cortex. Visually responsive neurones are probably involved in planning the visual goal of movements, while eye and arm movement neurones probably help to create co‐ordinative structures for executing voluntary eye and arm movements.
Stimulation‐dependent facilitation of the high threshold calcium current in guinea‐pig ventricular myocytes.
Authors: Zygmunt A C , Maylie J
Published: December 2014

1. Stimulation‐dependent modulation of Ca currents was examined in guinea‐pig ventricular myocytes at room temperature. Whole‐cell recordings of Ca currents were made under conditions which minimized ionic fluxes through other channels. 2. Stimulation from rest at a rate of 2 Hz resulted in a decrease of the low threshold Ca current within one pulse and facilitation of the high threshold Ca current within five pulses. Facilitation was associated with a reduction in the rate of inactivation. 3. Pulse durations as short as 10 ms facilitated the high threshold Ca current in subsequent pulses. Facilitation produced by a single pulse decayed with a half‐time of several seconds. 4. Substitution of Ba2+ or Sr2+ for external Ca2+ reduced the rate of inactivation of the high threshold Ca current and abolished facilitation of the current. 5. Facilitation persisted with 40 microM‐Ruthenium Red added to the internal solution or 0.2‐2 microM‐ryanodine added to the bath solution to reduce Ca2+ release from the sarcoplasmic reticulum. 6. Facilitation was modulated by isoprenaline. Low concentrations of isoprenaline (5‐10 nM) increased the amount of facilitation. Isoprenaline (1 microM) increased the Ca current approximately 3‐fold, however, facilitation was nearly abolished. 7. Caffeine (0.5 and 1 mM) affected the Ca current and facilitation in a manner similar to 1 microM‐isoprenaline. It increased the Ca currents approximately 2.5‐fold and facilitation was not observed. 8. We conclude that stimulation‐dependent facilitation of the high threshold Ca current is mediated by calcium and hypothesize that calcium affects a site near the Ca channel that modifies the rate of inactivation. The common actions of caffeine and high concentrations of isoprenaline suggest that calcium modulates a phosphorylation step.