bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of lysergic acid diethylamide on autonomic post‐ganglionic transmission.
Authors: Ambache N , Killick S W , Srinivasan V , Zar M A
Published: December 2014

1. Six sites of autonomic post‐ganglionic transmission were examined for susceptibility to LSD. Inhibition of transmission by LSD was confined to the three sympathetic junctions. 2. Inhibition of sympathetic transmission was maximal with short trains of pulses and declined considerably as train length was increased. 3. Evidence for a presynaptic mode of action was obtained. This was the predominant effect of LSD in the rat anococcygeus and dog retractor penis because alpha‐adrenoceptor‐blocking properties were feeble or absent; but in dog splenic strips LSD produced marked post‐synaptic alpha‐blockade. 4. The presynaptic inhibitory effect of LSD was unrelated to its 5‐hydroxytryptamine‐blocking property because it was not shared by methysergide. Neither was it mediated by prostaglandin release because it was unaltered by indomethacin, which suppresses prostaglandin synthesis. 5. In the rat anococcygeus and dog retractor penis larger doses of LSD induced slow contractions and, as a result of the concurrent block of motor transmission, revealed relaxation responses on transmural stimulation, caused by the excitation of sacral inhibitory fibres present in these muscles. 6. The LSD contractions were due to stimulation of post‐synaptic alpha‐adrenoceptors because they were abolished by phentolamine or yohimbine but were present as usual in preparations taken from reserpinized animals. 7. LSD blocked presynaptic alpha‐adrenoceptors in the cholinergic motor fibres to the longitudinal muscle of the guinea‐pig ileum.
Rod‐rod interaction in the retina of the turtle.
Authors: Schwartz E A
Published: December 2014

Intracellular responses were recorded from rods in isolated eye‐cups of the snapping turtle, Chelydra serpentina. Responses to small and large diameter spots of 500 nm light were studied. 1. The peak amplitudes of responses smaller than approximately 2 mV were directly proportional to irradiance. Small spots (less than 100 mum diameter) produced approximately 30 muV/rhodopsin molecule bleached. Increasing stimulus diameter to 400–500 mum increased this five to seven times to about 200 muV/rhodopsin molecule bleached in the impaled receptor. The difference is attributed to a neural “enhancement” produced by stimulating neighbouring rods. 2. Enlarging the diameter of a spot altered the shape of responses produced by very dim lights. 3. The variance of responses to a small spot was only slightly less than the mean. The variance of responses to a large spot was much less than the mean. 4. Responses evoked by a small spot of dim light obeyed the superposition principle in that the response to a very dim step of light was the integral of the response of a very dim flash. Responses evoked by a large spot did not obey the superposition principle. The response to a step of dim light covering a spot of large diameter was less than predicted from the integral of the response to a flash. The difference is attributed to a neural “disenhancement” produced by stimulating neighbouring rods. 5. The time course of this disenhancement could be observed by presenting two large diameter, dim flashes within a short interval. The time course of disenhancement did not coincide with that of the voltage response but was delayed such that its maximum occurred after the peak amplitude. 6. Dim background lights of different diameter, which delivered the same quantity of light to the impaled cell but very different quantities of light to neighbouring cells, left the response produced by a small diameter test spot unaltered. It is concluded that rod‐rod interaction can modify the intracellular responses of rods in two ways; it produces an early enhancement which increases response amplitude nearly tenfold and also a delayed disenhancement which replaces the wave of enhancement that follows a flash.
The inulin space, solute concentrations, and weight changes in rat renal medullary slices incubated in iso‐osmolal media, and their modification during anoxia and hypothermia.
Authors: Law R O
Published: December 2014

1. The volume of distribution of [14‐C]carboxyl inulin has been studied in slices of outer and inner medulla from rat kidney incubated in Krebs phosphate‐bicarbonate Ringer, modified to render it iso‐osmolal with the tissue fluids in these zones, under three conditions, (a) aerobically at 37 degrees C (control), (b) anoxically at 37 degrees C, and (c) aerobically at 0 degrees C. 2. Under control conditions near steady‐state volumes of approximately 24 and 42 mul./100 mg wet weight slice were obtained for outer and inner medulla respectively during the period 10–30 min from the start of incubation. In the outer medulla the volumes of distribution in anoxic and hypothermic slices exceeded that in control slices during this time, but control values increased from 30 to 100 min so that after 100 min the distribution volumes were approximately 30 mul./100 mg under each set of conditions. 3. In the inner medulla control and anoxic slices had inulin distribution volumes of approximately 42 mul./100 mg during 10–30 min, rising to over 50 mul./u99 mg by 100 min. Slices incubated hypothermically reached a steady‐state value of approximately 40 mul./100 mg by 30 min, which did not increase further for up to 100 min. 4. All slices lost about 10% of their initial weight during the first 3 min of incubation. Thereafter control slices maintained weight constancy for at least 30 min (outer medulla) or 100 min (inner medulla); slices incubated anoxically or hypothermically gained weight, the gains being greatest in anoxic outer and hypothermic inner medulla. 5. The K concentration within control slices (both zones), hypothermic outer and anoxic inner medulla attained equilibrium when slice [K] was approximately 8 times medium [K] (5–9 mM). In anoxic outer and hypothermic inner medullary slices [K] fell to a significantly greater extent, but interpretation of these findings in terms of slice K loss is subject to modification in respect of the increases in slice weight (water content) accompanying the [K] decreases. 6. There was a transient (1–3 min) rise in [Na] in all slices. This was followed by a [Na] decrease, which was most apparent in control slices, and finally a gradual increase towards medium [Na] (141 and 180 mM for outer and inner medulla respectively).
The spinal course and distribution of fore and hind limb muscle afferent projections to the superior colliculus of the cat.
Authors: Abrahams V C , Rose P K
Published: December 2014

1. Projections to the superior colliculus from fore and hind limb muscle nerves have been examined. 2. Hind leg nerve stimulation at strengths sufficient to excite Group II and III fibres elicited unit discharge in all layers of the superior colliculus and underlying tegmentum. 3. Forelimb nerve stimulation excited units in all layers of the superior colliculus and underlying tegmentum. Twenty per cent were activated by stimulation below Group II threshold, the remainder by stimulation above Group II threshold. 4. Most units activated by limb afferent nerve stimulation were also activated by visual stimuli. There was considerable convergence from both flexor and extensor nerves and most units were excited by stimulation of nerves in more than one limb. 5. Units fired either with a short or long latency or with a paired discharge. Short latency units were most common in deep collicular layers and the tegmentum, long latency units were most common in superficial layers. 6. The spinal pathway of the afferents is mainly in the dorsolateral quadrant contralateral to the recording site. The anatomical characteristics of the pathway are similar to the lateral funiculus climbing fibrespinocerebellar pathway.
The effects of prolonged repetitive stimulation in hemicholinium on the frog neuromuscular junction.
Authors: Ceccarelli B , Hurlbut W P
Published: December 2014

1. Cutaneous pectoris nerve‐muscle preparations from the frog were stimulated for prolonged periods in solutions with curare alone, curare and hemicholinium no. 3 (HC‐3), or curare and glucose plus choline. End‐plate potentials (e.p.p.s) and miniature end‐plate potentials (m.e.p.p.s) were recorded intracellularly. Black widow spider venom (BWSV) was applied to determine the degree of depletion of the transmitter stores. 2. The ultrastructure of the neuromuscular junctions was studied in the electron microscope. Some of the preparations were fixed immediately at the end of the period of stimulation and others were fixed about an hour after BWSV had been applied. In some experiments horseradish peroxidase (HRP) was present during the period of stimulation and the fixed tissue was treated to reveal the distribution of the tracer. 3. The amplitude of the e.p.p. fell rapidly to almost zero during 2 hr of stimulation at 2/sec in 100 muM HC‐3 and little recovery occurred during a subsequent hour of rest. About 2‐7 times 10‐5 quanta were secreted. The e.p.p.s usually persisted throughout the period of stimulation in the other solutions and 2‐2‐6 times as much transmitter was secreted. 4. When BWSV was applied immediately at the end of the period of stimulation in HC‐3, almost no m.e.p.p.s were discharged and only small m.e.p.p.s were discharged when the venom was applied after an hour of rest. 5. When BWSV was applied to unstimulated terminals that had been bathed in HC‐3, or to terminals that had been stimulated and rested for an hour in glucose plus choline, m.e.p.p.s of nearly normal amplitude were discharged. 6. Terminals stimulated for 2 hr at 2/sec in 100 muM HC‐3 contained a normal complement of synaptic vesicles and a large proportion of vesicles were labelled with HRP when the tracer was present during the period of stimulation. 7. BWSV induced the almost complete depletion of vesicles from terminals that had been stimulated in HC‐3. 8. Depletion of vesicles also occurred when terminals were stimulated for 20 min at 10/sec after they had been previously stimulated for 2 hr at 2/sec in HC‐3. These terminals showed extensive infolding of the axolemma and they contained swollen mitochondria. 9. These results indicate that stimulation in HC‐3 depletes terminals of their store of transmitter but not of their population of vesicles and that vesicles empty of transmitter can fuse with and reform from the axolemma of the nerve terminal.
The distribution time of intravenously injected raffinose and inulin in intact animals and the effect thereon of sex and infusion of oxytocin.
Authors: Pickford M
Published: December 2014

1. In anaesthetized dogs whose renal pedicles were ligated the distribution time for I.V. administered raffinose was noted. In males the plasma concentration of raffinose fell for 7–10 min from the time of injection and in females it fell for 12–15 min; thereafter in both sexes the plasma concentration remained constant. 2. During I.V. infusion of oxytocin 10 mug/kg. min, the distribution time for raffinose was 12–16 min in males and 4‐6 min in females. 3. During the period before stabilization of plasma concentration the concentration of raffinose was higher in the femoral artery than in the vein in both sexes. 4. In anaesthetized rats whose renal pedicles were ligated the distribution time for I.V. injected inulin was 7–8 min in males and 5 min in females. 5. Following alpha‐adrenoceptor blockade with phentolamine the distribution time in both male and female rats was 14–15 min. 6. The sex differences in distribution time, both in normal and oxytocin‐treated dogs, may be related to the state of contraction and differential sensitivity or pre‐ and post‐capillary blood vessels and hence, of capillary pressure.
Multiple interneuronal afferents to the giant cells in Aplysia.
Authors: Shimahara T , Tauc L
Published: December 2014

1. Several different types of presynaptic neurones to the giant cells of Aplysia have been found in the pleural ganglion. Some of these presynaptic neurones are common to the left giant cell in the pleural ganglion and to the right giant cell in the abdominal ganglion but others make contact only with one. 2. Interneurones of the left giant cell were studied in detail. They can be identified not only physiologically from the type of post‐synapitc potential (p.s.p.) which they produce in the left giant cell, but also by their localization in the ganglion. 3. Direct stimulation of these presynaptic neurones produced not only the classical types of post‐synaptic potentials known as e.p.s.p. or i.p.s.p. but also a slow e.p.s.p. and more complex post‐synaptic potentials consisting of a rapid depolarizing or hyperpolarizing component (e for excitatory; i for inhibitory). According the p.s.p.s. which have been found were classified as being of eight different types: e.p.s.p., slow e.p.s.p., pseudo‐slow e.p.s.p., e.i.p.s.p., i.e.p.s.p., i.i.p.s.p., to which is added the biphasic p.s.p. (b.p.s.p.) of electrical origin. 4. The monosynaptic nature of each of these p.s.p.s. was established by four criteria: (a) ability to follow one to one the presynaptic spike, (b) short and constant latency, (c) change of p.s.p. with the presynaptic spike when the duration is prolonged by iontophoretic injection of TEA, (d) sensitivity of the synaptic efficacy to presynaptic polarization. 5. For all p.s.p.s., the hyperpolarization of the interneurone was followed by a decrease in the corresponding amplitude; on the contrary depolarization produced an increase in p.s.p. amplitude. 6. The physiological role of these p.s.p.s. and their possible mechanism are discussed.
The effects of temperature and 2,4‐dinitrophenol on transmembrane potentials of submandibular acinar cells.
Authors: Creed K E , McDonald I R
Published: December 2014

1. Micro‐electrodes were used to investigate the effect of different temperatures and of DNP on salivary secretory potentials of the cat and the possum produced in response to parasympathetic nerve stimulation. 2. The mean resting potential was unchanged between temperatures of 15 and 40 degrees C in both species. 3. The amplitude of the secretory potential decreased as the temperature was lowered. Below 25 degrees C there was often no response to 1 Hz stimulation but a poorly maintained response to higher frequencies could still be obtained at 20 degrees C. 4. Decrease in temperature prolonged both the latency and time course of the secretory potential. In both species and at all frequencies the latency was increased with a Q10 of about 2‐0; the increase in hyperpolarization time had a Q10 of about 1‐6. 5. Close arterial injection of DNP (1 times 10‐ minus 4 M) decreased the amplitude of the parasympathetic secretory potential without affecting its latency and time course or the resting potential. The electrical response to close arterial injection of acetylcholine was also abolished. 6. It was concluded that metabolic energy is required to activate the hyperpolarization mechanism, and this may involve the formation of high‐energy phosphate bonds.
Contrast sensitivity in humans with abnormal visual experience.
Authors: Freedman R D , Thibos L N
Published: December 2014

1. Grating contrast sensitivities have been determined over a range of spatial frequencies for a normal subject and for subjects who are visually biased in that they have a lower resolution capacity for targets of specific orientations. The bias si only found in astigmatic subjects and the grating orientation yielding poorest acuity coincides with the most defocused astigmatic meridian. However this resolution anisotropy remains when optical factors are accounted for. 2. For the normal subject, high and low frequency attenuation is found and a typical reduction in contrast sensitivity is exhibited for oblique target orientations. 3. The biased subjects, called meridional amblyopes because they have reduced acuity for a given grating orientation, show markedly abnormal contrast sensitivity functions. Their cut‐off spatial frequencies are different for various target orientations and this difference applies also to contrast sensitivity over nearly the entire spatial frequency range tested (0‐5‐16 cycles/deg). The differences are of about the same magnitude for most frequencies and they are found in all types of meridional amblyopes. 4. Optical explanations of these differences are ruled out by laser‐interference fringe tests and by varying effective pupil size. 5. Theoretical effects of defocus have been calculated to compare predicted visual deprivation with performance. Results indicate that reduced contrast sensitivity functions can be equivalent to a small defocus effect. 6. To examine the results in the spatial domain, inverse Fourier transforms of representative contrast sensitivity functions have been computed. The optical portion of the resulting spatial weighting functions has been parcelled out to obtain neural spatial weighting functions.
Uptake of orthophosphate by rabbit vagus nerve fibres.
Authors: Anner B , Ferrero J , Jirounek P , Straub R W
Published: December 2014

1. The uptake of orthophosphate and its incorporation into ATP, ADP, and creatine phosphate (CrP) were studied in desheathed rabbit vagus nerve. 2. Using −32P labelled orthophosphate, the total amount of labelled phosphate taken up by the preparation was continuously recorded in a perfusion apparatus. For measuring the incorporation into phosphorylated compounds, phosphate esters and inorganic phosphate were extracted, separated and their total amount and radioactivity determined. 3. The total uptake of phosphate was found to be a biexponential function of time. 4. The time constant of the first process was 10–20 min and independent of the extracellular phosphate concentration, the final amount labelled by this process was relatively small and proportional to external phosphate, increasing from 0.026 m‐mole/kg wet nerve at 0–04 mM phosphate to 1‐14 m‐mole/kg at 5nM. 5. The time constant of the second process depended on the extracellular phosphate concentration varying from 4624 min at 0–04 mM to 210 min at 5 mM. The final amount labelled by this process was 5‐6 m‐mole/kg wet wt. and independent of the extracellular phosphate. 6. The kinetics of the slow uptake were consistent with the presence of a saturable process and a non‐saturable one. 7. Extraction of ATP, ADP, and the sum of CrP and Pi, showed that the total amount of these compounds remained constant for 2 hr while their radioactivity increased slowly, approximately at the same rate as the slow fraction. 8. Increasing the external phosphate from 0–04 to 5 nM increased the amount of labelled ATP. 9. A comparison with the metabolic turnover of phosphate, estimated from the oxygen consumption, shows that uptake is much slower than metabolism, so that the slow appearance of labelled nucleotides is very probably due to a limitation of the influx. 10. From the experimental data the influx can then be calculated for various phosphate concentrations. It is close to that found in squid axons.
The turnover of phosphorus compounds in crab muscle fibres.
Authors: Caldwell P C , Walster G E
Published: December 2014

1. The exchange of 32P injected into single crab muscle fibres as either orthophosphate or ATP has been studied. The results have been analysed in terms of a simple kinetic model. 2. The exchange of 32P between ATP and arginine phosphate is considerably faster than that between ATP and orthophosphate during rest and during contraction in caffeine. 3. The rate constants obtained at rest after the injection of either orthophosphate or ATP labelled with 32P were of the same order. They were also of the same order as those which have been obtained previously for squid axons. 4. The exchange during caffeine contraction of 32P unjected as orthophosphate gave rate constants which were consistent with an increased rate of splitting of ATP and with the rate constants needed to account for the observed net formation of orthophosphate. The results obtained after the injection of 32P‐labelled ATP during caffeine contraction were less clear cut.
The bioelectric parameters of the vagina during the oestrous cycle of the rat.
Authors: Frances Edwards D , Levin R J
Published: December 2014

1. A new in vitro preparation of the rat vagina was devised to allow the measurement of the electrical potential difference (p.d.), short‐circuit current (s‐c.c.) and tissue resistance. 2. In vivo and in vitro, the magnitude of the transvaginal p.d. (adventitia positive to lumen) was greatest at oestrus and smallest at dioestrus and metoestrus. The p.d. at pro‐oestrus was not significantly different from the latter values. 3. The s‐c.c. was significantly greater at oestrus than at metoestrus, dioestrus and pro‐oestrus. 4. The vaginal resistance was maximal at pro‐oestrus and was significantly greater than that at metoestrus, dioestrus and oestrus. The value at oestrus was significantly greater than that at metoestrus and dioestrus. These changes in resistance correlate well with known changes in vaginal morphology during the oestrous cycle. 5. It is proposed that the cellular site for the generation of vaginal bioelectric activity is the basal cell layer of the vagina and that the variations of the transvaginal p.d. measured in vivo are caused by the changes in vaginal current and tissue resistance.
The effect of duodenal infusion on the electromyogram of gastric muscle during activation and inhibition of gastric emptying.
Authors: Bell F R , Grivel M‐L
Published: December 2014

1. When the abomasum of the conscious calf is partially distended, rhythmic motility can readily be recorded from the e.m.g. of the smooth muscle of the fundus (body) and antrum. 2. In gastric evacuation rhythmic contractions of the antrum are reinforced by both rhythmic and tonic fundic contractions. 3. The output volume of the stomach can be directly correlated with e.m.g. activity. 4. Intragastric fluid is usually emptied in gushes coinciding with a strong contraction of the antrum but fluid may be evacuated, when the antrum is inactive, through the force generated by persisting rhythmic fundic contractions. 5. Using re‐entrant cannulae so that the duodenum can be infused separately from the gastric effluent, isotonic sodium bicarbonate produced almost 100% gastric evacuation with greatly enhanced e.m.g. activity of fundus and antrum. Infusion of the duodenum with a solution of HCl, 60 m‐equiv/l., produced the opposite effect, the gastric muscle becoming quiescent and 100% of the gastric test meal being retained. 6. These results show that the activating or inhibitory effects of a duodenal infusate are produced through an activating or inhibitory effect on the smooth muscle of the stomach. 7. The mechanism of the interrelation between duodenal receptor and gastric effector has not yet been elucidated but the connexion is not intramural since it continues when the duodenum is transected near to the pylorus.
Sensorimotor cortical representation in the rat and the role of the cortex in the production of sensory myoclonic jerks.
Authors: Angel A , Lemon R N
Published: December 2014

1. After administration of 1,2‐dihydroxybenzene (catechol) to anaesthetized rats, rabbits and cats, a reflex jerk consisting of three distinct components was evoked in the limb muscles by peripheral stimulation. The second component of the jerk in the forelimb muscles of all three animals was specifically abolished by lesions confined to the contralateral forelimb sensorimotor cortex. 2. These lesions had no effect on the second response in either the hind limbs or in the forelimb ipsilateral to the lesion. The first and third responses were also unaffected. 3. Lesions in the cat hind‐limb cortex abolished the contralateral hind‐limb second response, but not the ipsilateral hind‐limb or forelimb response. 4. In the rat and rabbit, unilateral hind‐limb sensorimotor lesions were ineffective in completely abolishing the second response in the contralateral hind‐leg muscles, and in addition, reduced the probability of occurrence of the response in the ipsilateral hind leg. Bilateral lesions abolished the response. 5. Re‐investigation of the sensory and motor representation of the hind limb in the rat cortex revealed that this is bilateral in nature. Short‐latency cortical responses (ca. 7–0 msec) could be evoked in one cortex by stimulation of either hind paw. The geometric centre of the cortical area from which these responses could be recorded was identical for each hind paw. 6. After catechol injection, stimulation of the cortical surface with single anodal shocks of threshold strength produced responses at similar latency (ca. 8–0 msec) in both hind limbs. 7. The behaviour of the second response after cortical lesions corresponds closely with the pattern of the somatosensorimotor cortical representation. The latency of the response is such as to allow its production by a long‐loop cortical reflex, and this possibility is discussed.
Spectral correlates of a quasi‐stable depolarization in barnacle photoreceptor following red light.
Authors: Brown H M , Cornwall M C
Published: December 2014

1. Illumination of B. eburneus photoreceptors with intense red light produces a membrane depolarization that persists in darkness. This quasistable depolarization (latch‐up) can be terminated with green light. The phenomenon was investigated with electrophysiological, spectrochemical, and microspectrophotometric techniques. 2. Latch‐up was associated with a stable inward current in cells with the membrane potential voltage‐clamped at the resting potential in darkness. The stable current could only be elicited at wave‐lengths greater than 580 nm. 3. Light‐induced current (LIC) was measured at various wave‐lengths in dark‐adapted photoreceptors with the membrane voltage‐clamped to the resting potential. The minimum number of photons required to elicit a fixed amount of LIC occurred at 540 nm, indicating that the photoreceptor is maximally sensitive to this wave‐length of light. The photoreceptor was also sensitive to wave‐lengths in the near‐U.V. region of the spectrum (380–420 nm). 4. Steady red adapting light reduced the magnitude of the LIC uniformly at all wave‐lengths except in the near‐U.V. region of the spectrum; sensitivity was reduced less in this region. 5. The spectrum for termination of the stable inward current following or during red light was shifted to the blue (peak about 510 nm) compared to the peak for LIC (peak about 540 nm). 6. Absorbance of single cells prepared under bright, red light decreased maximally at 480 nm following exposure to wave‐lengths of light longer than 540 nm. 7. A pigment extract of 1000 barnacle ocelli prepared under dim, red light had a maximum absorbance change at 480 nm when bleached with blue‐gree light. 8. There was no evidence in the latter two experiments of photointerconversion of pigments with absorbance maxima at 480 and 540 nm. Rather, the maximum absorption of the bleaching products seemed to occur at wave‐lengths shorter than 420 nm. 9. Since latch‐up induction occurs at wave‐lengths longer than 580 nm, it may depend on the 540 pigment or on an undetected red absorbing pigment. 10. A photolabile pigment at 480 nm correlated most closely with termination of the stable inward current associated with latch‐up.
The effect of sympathetic nerve stimulation on acid secretion, regional blood flows and oxygen usage by stomachs of anaesthetized cats.
Authors: Grund E R , Reed J D , Sanders D J
Published: December 2014

1. Gastric acid secretion, and total gastric and mucosal blood flows (amidopyrine technique) were measured in anaesthetized cats. Oxygen contents of arterial and gastric venous blood were measured using an oximeter. 2. Splanchnic nerve stimulation (10 Hz) significantly reduced the acid output and total gastric and mucosal blood flows produced in response to maximal gastrin pentapeptide infusions. 3. The arterial haemoglobin concentration was significantly reduced during splanchnic nerve stimulation, and this is consistent with the hypothesis that the splanchnic nerve effect is directed against precapillary sphincters. 4. During the period of inhibition, gastric oxygen consumption and acid secretion were reduced to similar degrees. There was no significant change in oxygen extraction by the stomach. 5. It remains possible that the splanchnic nerves directly inhibit the parietal cell activity.
The mechanical properties of oesophageal striated muscle in the cat and sheep.
Authors: Floyd K , Morrison J F
Published: December 2014

1. A study has been made of the mechanical behaviour of isolated strips of cat and sheep oesophageal muscle. 2. At 37 degrees C, time to peak tension in an isometric twitch was about 80 ms in both muscles. Tetanic fusion frequency was 30 s‐minus 1, twitch: tetanus ratio 0.4–0.47, and maximum velocity of shortening was 3 lengths. s‐minus1. 3. The results are compared with the prperties of other muscles.
Intracellular pH and distribution of weak acids across cell membranes. A study of D‐ and L‐lactate and of DMO in rat diaphragm.
Authors: Roos A
Published: December 2014

1. The steady‐state distribution ratios of D‐ and L‐lactate between fibre water and external fluid were measured in ‘intact’ rat hemidiaphragm preparations exposed for 2–5 hr to a variety of solutions of normal ionic strength and osmolarity. The studies were designed to minimize the effects, on these distributions, of conversion of lactate and of generation of lactic acid by the muscle. 2. At D‐lactate concentrations between 2.3 and 118 mM, at normal pH and PCO2, the D‐lactate distribution ratio, obtained from the distribution of [2‐(3)H]D‐lactate was independent of concentration; it averaged 0.349. As the concentration of D‐lactate was reduced below 2.3 mM, its distribution ratio progressively fell to less than 0.1. 3. Radiochromatograms of extracts of incubated muscle showed that the tritium label was not attached to substances other than lactate. 4. At L‐lactate concentrations of 59 and 108 mM, at normal pH and PCO2, the average L‐lactate distribution ratios, obtained by enzymatic analysis, were respectively 0.395 and 0392. 5. At 19–89 mM D‐lactate, depolarizing the muscle fibres by high K(49–127 mM), at normal pH, PCO2, and [K]0[Cl]0 product, only slightly affected the D‐lactate distribution ratio which averaged 0.405. 6. The D‐lactate distribution ratio and intracellular pH (pHi), obtained with the DMO method (5,5‐dimethyl‐2,4‐oxazolidinedione), were measured in thirty sets of studies after exposure of the muscle to solutions buffered to pH values ranging between 5.99 and 8.13, and containing 18.5–118 mM D‐lactate and 6–129 mM‐K. 7. The relation between the distribution ratios of D‐lactate ([TL]i/[TL]O) and of H ions ([Ho/[H]i) in these studies could be expressed by [TL]i/[T]O = 0.646 [H]o/[H]i+0.056. 8. It was concluded that it is predominantly the undissociated lactic acid molecules, rather than the much more numerous lactate ions, which permeate the fibre membrane; and that the steady‐state lactate distribution ratio is determined by the transmembrane pH gradient, and not by membrane potential. 9. The expression of the steady‐state lactate distribution ratio as function of relative membrane permeabilities of lactic acid molecule and lactate ion, membrane voltage, and internal and external H ion concentrations indicates that a finite permeability to the ion, three or four orders of magnitude less than that to the molecule, is compatible with the experimental data. When both ion and molecule of any weak acid are permeable, they act as a carrier system for the movement of protons down their electrochemical gradient. 10. Near‐maintenance of pHi in the face of high fibre D‐lactate (19–44 mM) and DMO (8–42 mM) indicates stimulation of proton extrusion by acid loans. 11. This extrusion is insensitive to ouabain, as judged from the lack of effect of the drug of pHi with acid loading.
The differential effect of cooling on responses of cerebellar cortex.
Authors: Eccles J C , Rosén I , Scheid P , Táboríková H
Published: December 2014

1. Responses of the cerebellar cortex in anaesthetized cats were evoked by mossy fibre and/or climbing fibre inputs, and the effects of graded cooling of the cerebellar cortex were investigated. Cooling was applied either globally by flooding the exposed cortex with cooled Ringer Locke, or in later experiments locally be passing cooled fluid through a silver tube in contact with the cerebellar cortex. The cortical temperature was continuously monitored by a thermistor inserted to a depth of 0.5 mm close to the recording site. 2. In the granular layer the cooling caused a large increase in the diphasic P1N1 wave generated by the afferent mossy fibre volley. The waves generated by synaptic excitation and discharge of granule cells, N2P2, were not diminished until the temperature fell towards 20 degrees C. In contrast the N3 wave of the molecular layer was largest with cooling in the range of 35 to 25 degrees C, often several times larger than at 38 to 40 degrees C. Associated with the enhanced N3 wave there was an enhanced N4 wave, which indicates an increased discharge by Purkynĕ cells. 3. Climbing fibre inputs generate a negative field potential in the molecular layer due to the powerful excitation of Purkynĕ cells. In contrast to the N3 potential this climbing fibre wave was largest at the higher temperatures 35–40 degrees C and declined progressively with cooling, being usually suppressed at moderate coolings of 31–27 degrees C. Intracellular recording revealed that the diminution was due both to the elimination of all but the first impulses of the normal burst discharge of the climbing fibre impulses and to the diminution of the synaptic excitation of a single climbing fibre impulse. 4. It is shown that the negative potentials produced in the molecular layer by combinations of mossy fibre and climbing fibre inputs can be very effectively distinguished by this differential effect of cooling. 5. The effects of cooling even to a severe level are immediately recoverable on warming. Repeated cooling has no untoward effects and there is no sign of the hysteresis reported for the cuneate nucleus. 6. There is a discussion of the factors that could cause cooling to differentiate between the actions of the mossy fibre and climbing fibre impulses on Purkynĕ cells.
Skeleto‐fusimotor axons in the hind‐limb muscles of the cat.
Authors: Emonet‐Dénand F , Jami L , Laporte Y
Published: December 2014

1. Motor axons supplying various hind‐limb muscles of the cat (flexor hallucis lingus, peroneus brevis, peroneus digiti quinti, tibialis anterior, soleus and tenuissimus) were identified as skeleto‐fusimotor or beta axons because their repetitive stimulation elicited both the contraction of extrafusal muscle fibres and an increase in the rate of discharge of spindle primary endings which perisited after selective blockade of extrafusal neuromuscular junctions. 2. The conduction velocity of these axons ranged from 39 to 92 m/sec. 3. Of seventy‐six beta axons, seventy‐two had a dynamic action on the sensitivity to velocity of stretching of primary endings, four had a static action. 4. The dynamic action of six beta axons was observed only after the contraction of extrafusal muscle fibres was selectively suppressed. 5. Tendon organs can be activated by beta motor units.
The effect of procaine on the action of acetylcholine at the neuromuscular junction.
Authors: Katz B , Miledi R
Published: December 2014

1. The effect of procaine on acetylcholine‐induced membrane fluctuations (ACh noise) was studied by intracellular and focal external recording from end‐plates of frog sartorius muscle. 2. With intracellular recording, ACh noise (the ratio of variance to mean depolarization) was substantially reduced by procaine, suggesting a greatly decreased amplitude of the elementary potential change. 3. Spectral analysis of the ACh noise indicated a dual average time course of the underlying “shot effects", similar to the complex shape (brief spike followed by a long tail of low intensity) of the end‐plate current in pro‐aine‐treated muscle. 4. The post‐synaptic blocking action of procaine can be largely explained by the drastic shortening of the initial high‐intensity phase of the end‐plate conductance change. 5. The average time course of the ACh shot effects is discussed in terms of alternative hypotheses, one attributing the complex shape to each elementary event, the other involving sequential reaction steps which produce two unequal populations of ion gates of different “life‐times”.
The effect of temperature on desensitization kinetics at the post‐synaptic membrane of the frog muscle fibre.
Authors: Magazanik L G , Vyskocit F
Published: December 2014

1. The time course of acetylcholine (ACh) potentials during development of desensitization was prolonged when a double‐barrel ACh pipette was used for evoking desensitization. When a single‐barrel ACh pipette was used, no change in the time course of ACh potential was to be seen during desensitization. 2. The recovery after desensitization did not depend on the rate of onset or on its level when a single ACh pipette was used. The half‐time of recovery had a constant value of about 5.8 sec in the presence of chlorpromazine or SKF‐525 A in a muscle bath at 22 degrees C. 3. Unlike the rate of onset, recovery from desensitization does not depend on the membrane potential. 4. The rate of onset of desensitization, i.e. time taken for reduction of ACh potentials to half‐way between the initial amplitude and final steady value, decreased when temperature of the muscle bath was lowered. 5. Q10 of desensitization onset was found to be 1.5 for a change of temperature from 32 to 22 degrees C, 1.9 from 22 to 12 degrees C, 2.6 from 12 to 5 degrees C and 3.3 from 12 to 2 degrees C. 6. A similar temperature effect was observed in the case of desensitization recovery, the Q10 being 1.2 for temperature changes from 32 to 22 degrees C, 1.3 from 22 to 12 degrees C and 2.36 from 12 to 2 degrees C. 7. Intracellular application of quaternary methiodide of SKF‐525 A or chloropromazine caused more rapid desensitization by ACh. The rate of desensitization onset depends on the ACh dose and on the frequency of application. The rate of recovery, however, has a constant value with a half‐time of 5.5–5.7 sec at 22 degrees C. 8. Both the rate of onset and the rate of recovery changed with temperature in the case of intracellular potentiation of desensitization, in a similar manner to that observed after extracellular application of these drugs. 9. The onset of desensitization can thus be influenced by different substances as well as by changes in temperature. Recovery apparently has a different mechanism from the onset, because its time course can be altered only by changes in temperature of the muscle.
The relation between discrimination and sensitivity in the perception of motion in depth.
Authors: Beverley K I , Regan D
Published: December 2014

1. Binocular discrimination of the direction of a target's motion in depth was measured in terms of the smallest angular difference in direction that could be detected with a probability 50% better than chance. Directional discrimination was measured for targets moving along 16 different trajectories directed to the left and right of the nose. 2. The relative velocities of the retinal images in the left and right eyes gave a sensitive cue to the direction of the target's motion in depth. 3. The direction of motion was bets discriminated when the target moved along a line directed close to the nose. A change in direction of only 0.2 degrees from this direction of motion could be detected. Discrimination showed two other maxima, one on each side of the central maximum. Discrimination fell to about 0.6–0.8 degrees when the target's direction was changed by only 6 degrees to either side of the nose. 4. The curve of sensitivity to movement in depth had a generally inverse shape to the directional discrimination curve: sensitivity was minimal for trajectories directed near the nose and increased for trajectories directed so as to miss the head. 5. The directional discrimination curve can be related to the sensitivity curves of the four postulated neural mechanisms tuned to different directions of motion in depth; there are three discrimination maxima and, correspondingly, three trajectories for which the slopes of adjacent sensitivity curves differ maximally. This suggests that binocular psychophysical judgements of the direction along which a target moves in depth are to some extent mediated by neural mechanisms that compare (e.g. subtract) the outputs of directionally tuned movement detectors. One function of such neural comparators might be to enhance psychophysical sensitivity to the direction along which a target moves in depth, and thus to provide a physiological basis for precisely judging whether or not an object will hit the head. 6. We suggest that the neural basis for judging the direction of moving objects has an analogy in colour vision where opponent‐colour mechanisms enhance sensitivity to wave‐length differences in such a way that wave‐lengths are more easily discriminated in those parts of the spectrum where the slopes of the pigment action spectra differ maximally.
Effects of magnesium on contractile activation of skinned cardiac cells.
Authors: Fabiato A , Fabiato F
Published: December 2014

1. In the presence of a slight buffering of the free [Ca2+] with 0.050 mM total EGTA cyclic contractions were induced by a Ca2+‐triggered release of Ca2+ on skinned (sarcolemma‐free) segments of single cardiac cells from rat ventricle. The threshold of the free [Ca2+] trigger was elevated when the free [Mg2+] was increased. 2. At a suprathreshold free [Ca2+] increasing the free [Mg2+] resulted in a decrease in frequency and in an increase in amplitude of the phasic contractions. Addition of caffeine at a specified interval after a cyclic contraction produced a larger contraction when free [Mg2+] was higher. It was concluded that an increase of free [Mg2+] increased the capacity and the rate of binding for Ca2+ by the sarcoplasmic reticulum (SR). 3. Small skinned fibres of skeletal muscle which were perfused with 10 mM caffeine yielded results similar to those obtained in skinned cardiac cells. It was concluded that the mechanism of action of free Mg2+ was similar in both preparations, but that the SR of skeletal muscle had a higher capacity and rate of binding for Ca2+ than the cardiac SR. 4. With a strong buffering of the free [Ca2+] with 4‐0 mM total EGTA, a smaller tonic tension was developed for a given pCa in the presence of a higher free [Mg2+]. This result was nearly identical in skinned cells from cardiac and skeletal muscle tissue. 5. A decrease of the [MgATP2‐] produced a tension in the skinned cardiac cells that were perfused in Ca2+ free media. The maximum tension was observed for [MgATP2‐] 10(−5–50)M as in skinned fibres of skeletal muscle. A further decrease of [MgATP2‐] resulted in a decrease of tension.
Chloride transport in human red cells.
Authors: Dalmark M
Published: December 2014

1. The chloride equilibrium flux (chloride self‐exchange) was determined by measuring the rate of 36Cl efflux from radioactively labelled human red cells. The cellular chloride concentration was varied between 5 and 700 mM by the nystatin technique (Cass & Dalmark, 1973). The chloride transport capacity was not affected by the nystatin technique. 2. The chloride equilibrium flux showed saturation kinetics in the pH range between 6–2 and 9–2 (0 degrees C). The chloride transport decreased at chloride concentrations higher than those which gave the maximum transport. 3. The apparent half‐saturation constant, (K1/2), depended on the pH and whether the chloride transport was perceived as a function of the chloride concentration in the medium or in the cell water. The (K1/2)m increased and the (K1/2)c decreased with increasing pH. The dependence of the chloride transport on the chloride concentration was described by Michaelis‐Menten kinetics at pH 7–2, but at values of pH outside pH 7–8 S‐shaped or steeper graphs were observed. 4. The chloride equilibrium flux varied with the pH at constant chloride concentration in the medium (pH 5‐7‐9‐5). The transport had a bell‐shaped pH dependence at chloride concentrations below 200 mM. At chloride concentrations between 300 and 600 mM the chloride transport increased with increasing pH to reach a plateau around pH 8. The position of the acidic branches of the pH graphs was independent of the chloride concentration (25–600 mM), but the position of the alkaline branches moved towards higher values of pH with increasing chloride concentration (5–150 mM). Thus, the position of the pH optimum increased with increasing chloride concentration. The chloride transport at low pH values was a function of the inverse second power of the hydrogen ion concentration. The pK of the groups which caused the inhibition was approximately 6 and independent of the temperature (0–18 degrees C). 5. The chloride equilibrium flux as a function of chloride concentration, pH, and temperature could be described by a transport model with a mobile, positively charged, chloride binding carrier with a single chloride dissociation constant of 33 mM, a transport capacity of 900 m‐mole/3 x 10(13) cells.min (pH 7–2, 0 degrees C), and an Arrhenius activation energy of 30 kcal/mole. The pH dependence of the transport of inorganic monovalent and divalent anions is discussed in relation to the suggested model.
Chloride and water distribution in human red cells.
Authors: Dalmark M
Published: December 2014

1. The influence of the pH and the temperature on the cellular chloride and water content was investigated in human red cells, the cellular KC1 concentrations of which varied between 10 and 600 mM. The compositions of the media (10–600 mM‐KC1, 1 mM‐NaC1, 27 mM sucrose) at each single KC1 concentration were constant at the different values of the pH and the temperature. 2. The variation of the cellular KC1 concentration was obtained by washing the cells with KC1 salt solutions containing nystatin...
Effect of adrenal hormones on thyroid secretion and thyroid hormones on adrenal secretion in the sheep.
Authors: Falconer I R , Jacks F
Published: December 2014

1. Previous work has shown that after stressful stimuli, sheep initially secrete increased amounts of thyroid hormone, at a time when adrenal secretion is also elevated. 2. This study was designed to evaluate (a) any short‐term activation or inhibition of thyroid secretion by exogenous cortisol or ACTH administered in quantities comparable to those secreted after stress in sheep and (b) any short‐term effect that exogenous thyroxine or triiodothyronine may have on the concentration of plasma cortisol in the sheep. 3. Thyroid activity was measured by determination of plasma protein bound 125I (PB125I) and total 125I in thyroid vein and mixed venous (jugular) blood. Plasma cortisol and thyroxine concentrations were measured by a competitive protein‐binding assay at intervals for up to 5 hr after commencement of the experiment. 4. No evidence of an activation of thyroid secretion was found during cortisol or ACTH infusion, as monitored by thyroid vein PB125I. Similarly there was no evidence of any inhibition of thyroid function, as measured by continued secretion of thyroid hormones into thyroid vein blood. 5. No effect on plasma cortisol concentration due to thyroid hormone treatment was observed. 6. It was concluded that (a) elevated circulating corticosteroids in physiological concentrations have no short‐term effects on thyroid activity in the sheep and (b) the short‐term alterations in thyroid and adrenal cortical secretion observed during stress in the sheep could not be attributed to direct interaction of elevated thyroid hormone concentrations with adrenal cortical secretion.