bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrogenic sodium pump in smooth muscle cells of the guinea‐pig's taenia coli
Authors: Casteels R. , Droogmans G. , Hendrickx H. 
Published: December 2014

1. The changes of the membrane potential, of the K equilibrium potential, and of the membrane conductance during K accumulation by K‐depleted tissues have been studied. Three subsequent characteristic periods can be described.2. Readmission of 5·9 m
M‐K after complete depletion results in a rapid extrusion of Na and uptake of K, and in a rapid hyperpolarization of the cells. Initially the time course of the K equilibrium potential and the membrane potential are similar except in propionate solution. This initial period is characterized by a high membrane conductance. No change of membrane potential occurs if 10−5
M ouabain is present.3. After 5‐7 min the membrane potential becomes more negative than the K equilibrium potential. The difference between both values is larger in solutions containing propionate or in hypertonic solutions. This second phase of the recovery period is characterized by a progressive decrease of the membrane conductance.4. In a third phase both the membrane potential and the membrane resistance return to their steady‐state value.5. If the external K concentration in the recovery solution is increased, the maximal hyperpolarization is less and has a shorter duration. A decrease of the temperature of the recovery solution results in a slower initial rate of repolarization and in a decrease of the maximal value of the hyperpolarization.6. These observations demonstrate the existence of an electrogenic sodium pump in smooth muscle cells during stimulation of the Na pump. An analysis of the experimental data obtained under steady‐state conditions in normal Krebs solution suggests that also under these conditions an electrogenic Na pump might take part in the maintenance of the resting potential.
Different types of extrafusal muscle fibres in snake costocutaneous muscles
Authors: Ridge R. M. A. P. 
Published: December 2014

1. Tonic and twitch muscle fibres were identified physiologically in m. costocutanei superiores and inferiores of garter snakes and grass snakes.2. Tonic fibres were multiterminally innervated and showed s.j.p.s in response to nerve stimulation. They did not show propagated A.P.s. They were innervated by motor axons with lower conduction velocities than those to twitch fibres, and often gave a contraction and developed tension in response to a single shock to the nerve. Intracellular square pulse analysis showed that Cm = 1 μF/cm2 and Rm = 40,000 Ω cm2.3. Twitch fibres showed a conducted action potential in response to nerve stimulation, and focal, as opposed to diffuse, innervation. They showed a variety of isometric twitch contraction times (times‐to‐peak of about 30–65 msec). Groups of similar motor units contained fibres of approximately similar contraction times. Slow twitch (and tonic) fibres often appeared silvery under dark field illumination, while faster twitch fibres appeared clear. No difference in Cm, Rm or λ was found between faster and slow twitch fibres. Values were approximately 3‐4 μF/cm2, 3000–4000 Ω cm2 and 2 mm respectively.
The resting membrane potential of the somatic muscle cells of Ascaris lumbricoides
Authors: Brading Alison F. , Caldwell P. C. 
Published: December 2014

1. The resting membrane potential of Ascaris muscle fibres, which is normally relatively insensitive to ion changes in the medium, has been measured under a wide variety of conditions.2. The results have been interpreted in terms of a form of the constant field equation containing additional terms for the contribution of ions and charged groups other than potassium, sodium and chloride.3. Normally the contribution of the additional terms is large and tends to outweigh the contributions of potassium, sodium and chloride.4. The contribution of the additional terms is considerably reduced in the absence of sodium and in the presence of γ‐amino butyric acid and acetylcholine.5. It is suggested that the additional terms may represent the contribution of an electrogenic active transport mechanism to the factors determining the membrane potential.
The form and distribution of the receptive fields of Pacinian corpuscles found in and around the cat's large foot pad
Authors: Lynn Bruce 
Published: December 2014

1. Firing thresholds of Pacinian corpuscles situated within or close to the large pad of the cat's hind foot have been determined following step displacements applied to various points on the pad surface.2. The most sensitive positions on the receptive fields of thirty‐one corpuscles were distributed unevenly over the pad. About half were situated close to the interlobular crease lines, and most of the others were at the edge of the pad.3. Threshold receptive fields were usually of complex form, with more than one region of low threshold.4. The approximate locations of a number of Pacinian corpuscles whose fields had been mapped were determined by dissection.5. The most sensitive position on the pad was usually at the closest point to the corpuscle. If the corpuscle was situated outside the pad itself, it was therefore usually most easily excited from some point at the edge of the pad. However, a minority of Pacinian corpuscles were most easily stimulated from some region other than that closest to them.6. It is suggested that previous estimates of the ability of this population of receptors to transmit information about the positions of stimuli (Gray, 1966) must be re‐evaluated in the light of the non‐uniform distribution and asymmetry of their cutaneous receptive fields.
The responses of frog muscle spindles and fast and slow muscle fibres to a variety of mechanical inputs
Authors: Brown M. C. 
Published: December 2014

1. The tension in the iliofibularis muscle of frogs was recorded while the muscle was stretched or released. At the same time recordings were made from single spindle afferents in dorsal root filaments. Either large or small motor nerve fibres were stimulated in split ventral root filaments.2. While small motor nerve fibres were stimulated the discharge from muscle spindle afferents was greatly increased by stretching, and greatly reduced by shortening the muscle. This sensitivity to movement was shown even if the movements were small, so that a stretch of 0·2% of the muscle length was sufficient to cause a pronounced increase in the afferent discharge.3. In contrast, during stimulation of the large motor nerve fibres the spindle was much less sensitive to movements with the result that even stretches or releases of the muscle by 1 mm did not cause very large changes in the discharge frequency.4. The tension in slow extrafusal muscle fibres in many ways mirrored the spindle discharge during the stimulation of small motor nerve fibres, for the tension was greatly increased by stretching, even through small distances, and greatly reduced by releasing the muscle. The tension in fast extrafusal muscle fibres was much less changed by such movements, and thus was rather like the spindle discharge during stimulation of large motor nerve fibres.5. As the extrafusal muscle fibres do not directly pull on and excite the spindle afferents, the simplest explanation for the similarities between the muscle tension and the spindle discharge is that the mechanical properties of the intrafusal muscle fibres innervated by the large motor nerve fibres are like those of fast extrafusal muscle fibres, and that the mechanical properties of the small intrafusal fibres are similar to those of slow extrafusal muscle fibres.6. It is shown that the cross‐bridge sliding filament mechanism of muscle contraction provides a ready explanation for the differences found between fast and slow muscles, and it is concluded that a most important functional difference between the two sorts of intrafusal muscle fibres is the speed of their contractions, for it is this which determines their contrasting actions on the spindle.7. It was also found that low rates (< 4/sec) of small motor nerve fibre stimulation were often very effective in exciting the spindles. These rates produced rather little extrafusal tension.
Effect of electrical stimulation on the fluorescence intensity of catecholamine‐containing tuberal nerve cells*
Authors: Lichtensteiger W. 
Published: December 2014

1. By means of a microfluorimetric technique, the intensity of the catecholamine fluorescence was measured in nerve cells of the arcuate and periventricular hypothalamic nuclei of ovariectomized rats pre‐treated with oestrogen and progesterone. In such animals the fluorescence intensity is in the range of the lowest intensities that were observed during the oestrous cycle.2. Unilateral intermittent electrical stimulation of the arcuate nucleus or of the medial preoptic area induced an acute increase of the fluorescence intensity in the cell bodies of the tuberal catecholamine‐containing nerve cell group. The change was already manifest 5 min after the onset of stimulation and within 10 min the mean fluorescence intensity reached levels that are among the highest so far observed in this cell group. Prolonged stimulation of the medial preoptic area led to a biphasic response, as shown by a decrease in intensity between 30 and 60 min of stimulation.3. The increase in fluorescence intensity caused by stimulation of the arcuate nucleus was completely prevented by pre‐treatment with the tyrosine hydroxylase inhibitor α‐methyl‐tyrosine. Thus, the effect appears to be due to an enhancement of amine synthesis.4. The intensity values found after synthesis inhibition were used for a preliminary estimation of the catecholamine turnover time in the nerve cell bodies of the arcuate nucleus.5. In conclusion, electrical stimulation appears to induce a characteristic type of concentration change in the nerve cell body, at least under certain experimental conditions. It is compared with similar responses to physiological changes such as the reaction to acute cold exposure.
Selective effects of an octopus toxin on action potentials
Authors: Dulhunty Angela , Gage Peter W. 
Published: December 2014

1. A lethal, water soluble toxin (Maculotoxin, MTX) with a molecular weight less than 540, can be extracted from the salivary glands of an octopus (Hapalochlaena maculosa).2. MTX blocks action potentials in sartorius muscle fibres of toads without affecting the membrane potential. Delayed rectification is not inhibited by the toxin.3. At low concentrations (10−6‐10−5 g/ml.) MTX blocks action potentials only after a certain number have been elicited. The number of action potentials, which can be defined accurately, depends on the concentration of MTX and the concentration of sodium ions in the extracellular solution.4. The toxin has no post‐synaptic effect at the neuromuscular junction and it is concluded that it blocks neuromuscular transmission by inhibiting action potentials in motor nerve terminals.
Neuronal pathway of the recurrent facilitation of motoneurones
Authors: Hultborn H. , Jankowska Elżbieta , Lindström S. , Roberts W. 
Published: December 2014

1. The recurrent facilitation of motoneurones is a disinhibition, i.e. a release of the motoneurones from a sustained hyperpolarization evoked by tonically active inhibitory interneurones. Only two groups of interneurones are known to receive recurrent inhibition from motor axon collaterals via Renshaw cells; the interneurones mediating the reciprocal Ia inhibition and the Renshaw cells themselves. The properties of these two groups of neurones were studied to determine if they could produce the tonic inhibition of motoneurones removed during recurrent facilitation.2. It was found that the tonic firing of Ia inhibitory interneurones is sensitive to anaesthetics to the same degree as is recurrent facilitation. The range of frequencies of tonic discharges of Renshaw cells appeared to be similarly low in unanaesthetized and anaesthetized preparations although in individual cells the discharge rates were decreased by anaesthesia.3. The recurrent inhibition of Ia interneurones inhibiting a given group of motoneurones and the recurrent facilitation of the same group of motoneurones were, as a rule, evoked from the same nerves, although in some cats the origin of the recurrent facilitation was somewhat wider. In contrast no evidence could be found that the Renshaw cells which inhibit a functional group of motoneurones are inhibited by volleys in the nerves from which recurrent facilitation is regularly evoked.4. It was concluded that the recurrent facilitation is caused mainly by inhibition of the tonic activity of Ia inhibitory interneurones and that it is thus a manifestation of the recurrent control of Ia reciprocal inhibition of motoneurones.
The independence of electrogenic sodium transport and membrane potential in a molluscan neurone
Authors: Marmor Michael F. 
Published: December 2014

1. The current—voltage relations of the Anisodoris giant neurone (G cell) were studied in the presence and absence of Na pump activity.2. Inhibition of the electrogenic Na pump with ouabain had no effect on either the presence at warm temperatures (10–15° C), or absence at cold temperatures (0–5° C), of inward‐going rectification.3. Abolition of inward‐going rectification in the warm, by replacement of external K with Rb, did not affect the electrogenic Na pump.4. The current generated by the electrogenic pump was essentially constant between the membrane potentials of — 30 and — 100 mV.5. The potential produced by the electrogenic pump can be predicted by a modification of the constant field equation.6. It is estimated that the energy required to extrude Na was between 3160 and 3700 cal/g‐atom, and that uncoupled Na efflux during pump activity was typically between 0·2 and 4·0 p‐mole/cm2.sec.
Maternal hyperventilation and foetal hypocapnia in sheep
Authors: Baillie P. , Dawes G. S. , Merlet Claudie L. , Richards R. 
Published: December 2014

1. In anaesthetized foetal lambs near term, hypocapnia induced by maternal hyperventilation abolished the rise of arterial pressure and femoral vasoconstriction caused by hypoxaemia. This is consistent with interaction of PCO2 and PO2 on the foetal aortic bodies.2. In immature lambs (0·6−0·77 of term) maternal hyperventilation caused a fall in foetal carotid PCO2 commensurate with that in the maternal blood. In mature lambs (at 0·9 or more of term) the fall in foetal carotid PCO2 was less than that in maternal blood, whether the foetus was exteriorized or in utero.3. The mean transplacental gradient for PCO2 (maternal arterial‐umbilical vascular), when the foetus was replaced with a mechanical pump recirculating foetal blood, was 6·3 mm Hg. This is attributed to placental CO2 production, and is nearly half the mean PCO2 gradient (maternal artery‐foetal carotid) of about 14 mm Hg during normal maternal ventilation.4. The mean maternal‐umbilical transcotyledonary venous gradients (avoiding vascular shunts through the myometrium and intercotyledonary chorion) were for PCO2 1·7 mm Hg and for PO2 13·4 mm Hg.5. Maternal hyperventilation (Pa, CO2 ∼ 20 mm Hg) caused a small fall in mean foetal carotid PO2 (5 mm Hg), which was readily reversible with no evidence of progressive acidaemia.
The action of carbon dioxide on afferent transmission in the dorsal column—lemniscal system
Authors: Morris Mary E. 
Published: December 2014

1. Transmission in the lemniscal afferent pathway was studied in thirteen decerebrate, unanaesthetized cats while changing the concentration of inspired PCO2.2. 2‐20% CO2, when inhaled for ≤ 10 min, raised the mean tissue PCO2, recorded from the surface of the medulla or cerebellum, from 22 torr to between 26 and 93 torr.3. Medial lemniscal potentials were evoked by stimulation of a forelimb nerve and recorded from the transected surface of the contralateral mid‐brain. The transmission of supramaximal responses was progressively and reversibly depressed as tissue levels of PCO2 were raised and lowered. The time course of the changes in transmission corresponded closely to changes in the tissue PCO2.4. The amplitude of the main early lemniscal peak was decreased to 80% by the inhalation of 20% CO2. A late component of the lemniscal response, presumably due to repetitive firing and conduction in smaller fibres and polysynaptic pathways, was more affected than the early main response.5. The failure of transmission was unrelated to threshold changes in the peripheral nerve, since potentials recorded close to the site of stimulation showed no changes.6. Increases in the transmission time of the main lemniscal potentials were uniform and < 10% during the administration of CO2 and did not appear to contribute to amplitude changes.7. The inhibition of afferent transmission from one nerve by a preceding conditioning volley in a second nerve was not altered by hypercarbia.8. It is concluded that CO2 has a blocking action on afferent transmission in the pre‐thalamic lemniscal system. The site of this block may be at the synapses and/or other regions of low safety factor in the afferent fibres.
The origin of the basal cell potential in frog corneal epithelium
Authors: Akaike Norio 
Published: December 2014

1. As the micro‐electrode penetrated through the epithelial cell membranes of frog cornea, a stepwise increase in the potential reaching a maximum value of — 60 mV (‘basal cell potential’) was observed. Upon penetrating the stroma, the potential dropped abruptly but remained negative (‘stroma potential’).2. The basal cell potential was determined as a K+ or a Cl− electrode, but the cell membrane was far more permeable to Cl− than to K+. It was also permeable to Na+, but to a smaller extent.3. When the product [K]o.[Cl]o was kept constant, for a tenfold increase in [K]o the slope of the basal cell potential approached 58 mV at high [K]o. The slope was greater in the excised cornea than in the whole eye.4. The basal cell membrane was more permeable to SCN− than to Cl−. Its selectivity towards cations was in the order K+ > Rb+ > Cs+ > NH4+.5. In Li+ solution the basal cell membrane in the excised cornea caused a hyperpolarization, followed by a gradual depolarization. In contrast, a slow progressive hyperpolarization occurred in the whole eye.6. Ouabain applied to the epithelial surface of both kinds of preparations did not affect the basal cell potential, but the potential was reduced when applied to the endothelium. MIAA and FDNB also depolarized when applied to both sides of the basal cell.7. With 90 m
M‐K+ solution containing Cl− or CH3SO4− applied to the epithelial surface, the potential change occurred only in the high K+ solution with CH3SO4−.8. The significance of these results for understanding the role of the epithelial boundary regulating the influence of Na+, K+, Cl− and drugs is discussed.
Frequency—response analysis of central vestibular unit activity resulting from rotational stimulation of the semicircular canals
Authors: Jones G. Melvill , Milsum J. H. 
Published: December 2014

1. The neural response of semicircular canal‐dependent units in the vestibular nuclei of cats has been examined over a frequency range of sinusoidal rotation extending from 0·004 to 0·9 Hz.2. Frequency—response analysis indicates that, over the range examined, the information contained in the neural signal received by the brain stem was similar to that expected from the mechanical end‐organ.3. Over the experimental frequency range, the relation between neural response and mechanical stimulus was found to be dominated by a single time constant of about 4 sec, such that two response regions can be defined above and below a stimulus frequency of ¼ rad/sec (≃ ≃ Hz).4. Above this frequency the information content of the neural signal tends towards that of angular velocity and below that frequency it tends towards that of angular acceleration.5. It is inferred (a) that the so‐called ‘long’ time constant of the cat's horizontal canal is about 4 sec and (b) that during most normal head movements containing frequencies below about 1 Hz the informational mode of neural signals generated in the canal and received in the brain stem probably tends towards that of head angular velocity.6. This seems appropriate for the generation of vestibulo‐ocular reflex compensation for head movement and for reflex damping (negative velocity feed‐back) of unintended head and body movements.7. The average neural gain of central unit responses is estimated at 1264 action potentials/sec, per degree of cupular deflexion. This high value reflects the very small angles of cupular deflexion assessed on the basis of physical characteristics of the canal.8. The results permit a rough estimate of the elastic restoring coefficient of the cupula in the horizontal canal as 2·05 × 10−3 dyne. cm.
Excitation—contraction coupling in amphioxus muscle cells
Authors: Hagiwara S. , Henkart Maryanna P. , Kidokoro Y. 
Published: December 2014

1. Excitation‐contraction coupling was studied in myotomal muscles of amphioxus, Branchiostoma californiense.2. The action potential of a muscle cell produces a twitch with a rise time of 30–40 msec at 11° C and its Q10 is about 2·2.3. The twitch increases in amplitude with increasing external Ca concentration and is abolished in Ca‐free saline (1 m
M‐EGTA and 55·7 m
M‐MgCl2); the twitch amplitude is suppressed by Co or La ions.4. Caffeine at concentrations above 1 m
M in the external saline causes a prolongation of the action potential and a contracture which lasts several minutes.5. After exposure to caffeine the responsiveness of the muscle to subsequent applications of caffeine recovers in normal saline in 20–30 minutes but not in Ca‐free saline.6. The amplitude of the caffeine contracture is independent of the external Ca concentration and is unaltered after the twitch is eliminated in Ca‐free saline.7. After exposure to caffeine a full‐sized twitch can be obtained before the responsiveness to caffeine shows any significant recovery.8. It is concluded that the twitch is produced by the Ca influx resulting from the increased permeability of the muscle cell membrane to Ca during the action potential and that the Ca mobilized by caffeine is not necessary to the initiation of the twitch.9. Electronmicroscopy shows the existence of sarcoplasmic reticulum.
Central neural regulation by adrenergic nerves of the daily rhythm in hepatic tyrosine transaminase activity
Authors: Black Ira B. , Reis Donald J. 
Published: December 2014

1. In adrenalectomized fasted rats transection of the spinal cord at C7‐C8 or placement of bilateral electrolytic lesions in the lateral hypothalamus when performed in the morning interrupted the daily rhythm of hepatic tyrosine transaminase by elevating low (AM) enzyme activities to high (PM) levels; lesions placed in PM did not affect the late afternoon rise in enzyme activity.2. Bilateral thalamic lesions had no affect on enzyme activity.3. The activity of hepatic catechol‐O‐methyl transferase was unaffected by hypothalamic lesions.4. The lesion‐evoked rise of tyrosine transaminase activity was abolished by exogenously administered norepinephrine.5. Cycloheximide blocked the rise of tyrosine transaminase activity caused by hypothalamic lesions.6. The results suggest that rhythmic activity of sympathetic nerves governed by lateral hypothalamus contribute to regulation of the daily rhythm in tyrosine transaminase by regulating the release of norepinephrine peripherally; norepinephrine may block the daily rise of enzyme by interfering with protein synthesis, possibly of new enzyme, by competing with pyridoxal co‐factor.7. It is proposed that alternating activity of sympathetic‐adrenergic and vagal‐cholinergic nerves to liver, controlled by the
C.N.S., contribute to rhythmic activity of hepatic tyrosine transaminase.