bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of intestinal secretagogues and distension on small bowel myoelectric activity in fasted and fed conscious dogs
Authors: da Cunha Melo J. , Summers R. W. , Thompson H. H. , Wingate D. L. , Yanda R. 
Published: December 2014

1. Defined jejunal segments were perfused with solutions of bile salts and of ricinoleic acid during fasting and after feeding in two groups of conscious dogs, one with the segment in continuity, and the other with a Thirty‐Vella loop. Myoelectric activity was recorded from chronically implanted electrodes on the jejunal segment and also from the proximal and distal in situ bowel.2. The results in both groups were identical. During fasting, migrating complexes were present in the segment, but were replaced by intermittent spike activity during chenodeoxycholate without and with ricinoleic acid perfusion. After food, when migrating complexes were replaced by intermittent spike activity, none of the solutions produced any consistent effect.3. In fasted animals, low levels of distension (15 mmHg) interrupted the migrating complexes in the segment and induced intermittent spike activity which was similar to that seen with the secretagogues. The migrating complexes in the main bowel continued during distension. In fed animals, spike activity increased in the segment during distension at 25 mmHg and decreased in the main bowel. In both groups, distension of the segment to pressures between 37.5 and 50 mmHg abolished spike activity both in the distended segment and the main bowel in fasted and fed states, and, in fasted dogs, migrating complexes were also abolished.4. These results demonstrate that the inhibitory intestino‐intestinal reflex is mediated through extrinsic nerves and does not require an intact myenteric plexus, whereas the altered myoelectric activity induced by secretagogues is a local effect and does not spread to adjacent bowel through either intrinsic or extrinsic neural pathways. It seems likely that the local motor effect of secretagogues is a result of net secretion, producing distension to pressures below the threshold required to activate the intestino‐intestinal reflex.
Properties of high Q10 units in the conscious duck's hypothalamus responsive to changes of core temperature
Authors: Lin M. T. , Simon E. 
Published: December 2014

1. Five Pekin ducks were chronically implanted with a device allowing thermal stimulation of the hypothalamus and simultaneous recording of hypothalamic single unit activity on the conscious animals in repeated experiments. In addition, the core temperature of the animals could be lowered by means of a thermode tube which was placed in the colon and was perfused by a cold solution. Hypothalamic temperature was measured in the centre of the hypothalamic thermode array; core temperature was measured in the axillary pit.2. Each unit was tested in two periods of hypothalamic ramp cooling, one was performed at normal core temperature, and the other at a lowered core temperature during sustained intestinal cooling.3. Among forty‐six neurones exhibiting a local Q10 > 2 of their discharge rate, intestinal cooling was found to activate 26% (fall feed‐back units), to inhibit 44% (rise feed‐back units), and not to affect 30% (non‐reactive units). The local Q10 values of the fall feed‐back units were, on average, significantly higher than those of the rise feed‐back units.4. By multiple linear regression analysis the thermal coefficients (impulses/sec. °C) relating unit discharge to hypothalamic (local) and to core (remote) temperature changes were evaluated. The fall feed‐back units exhibited average local temperature coefficients of 0·79±0·11 and remote coefficients of ‐2·75±0·56 (means±
s.e. of mean); the corresponding coefficients of the rise feed‐back units were determined as 0·44±0·08 and +2·33±0·41.5. The results of this study support the hypothesis that the activity of hypothalamic neurones conveying extrahypothalamic cold signals is depressed more by hypothalamic cooling than that of the neurons conveying extrahypothalamic warm signals. This would explain the paradoxical effects of hypothalamic cooling on thermoregulatory effector activity in birds.
Acetylcholine‐induced membrane depolarization and potential fluctuations in the rat adrenal chromaffin cell
Authors: Kidokoro Y. , Miyazaki S. , Ozawa S. 
Published: December 2014

1. The effect of acetylcholine (ACh) on the rat adrenal chromaffin cell membrane was examined in culture by using an intracellular recording technique. ACh was applied with gas pressure through a pipette which had an internal tip diameter of about 3 μm.2. Upon application of ACh the chromaffin cell membrane depolarized with superimposed potential fluctuations. Occasionally repetitive spikes were observed during the entire period of ACh application up to 30 sec. In some cells a hyperpolarization with a slow time course followed the initial depolarization.3. The depolarization was detectable with 0·1 μ
m‐ACh; the amplitude increased with higher concentrations of ACh and saturated at 100 μ
m. The half‐maximal concentration was approximately 10 μ
m.4. The amplitude of the ACh depolarization increased when the membrane was hyperpolarized by passing current through the recording electrode, and decreased upon depolarization. This technique gave an apparent reversal potential of ‐24±4 mV (mean±S.D., n = 6).5. When the mean amplitude of the ACh depolarizations and the variance of the potential fluctuations in a given cell were plotted, a linear relation was found. The slope was 0·23±0·06 mV (n = 9) at the average membrane potential level of ‐60 mV. With a few assumptions this value approximates the amplitude of an elementary potential change.6. Temporal characteristics of the potential fluctuations were obtained by calculating an auto‐correlation function. The averaged auto‐correlation function in a given cell declined exponentially with time. The mean time constant at 31 °C was found to be 40±19 msec (n = 9) at the average membrane potential level of ‐60 mV. With a few assumptions this value provides an estimate of the mean duration of an elementary potential change.7. The ionic mechanism of the ACh depolarization was examined by changing the ion composition of the external solution. Na, K and Ca ions appear to be the current carriers during the ACh depolarization; Cl ions do not contribute.8. Various ACh receptor agonists and antagonists were applied to determine the pharmacological properties of these ACh receptors. The receptors were found to be nicotinic.9. The nature of the ACh‐induced membrane potential fluctuations is discussed.
Synaptic organization of sensory and motor neurones innervating triceps brachii muscles in the bullfrog
Authors: Frank Eric , Westerfield Monte 
Published: December 2014

1. The anatomy and physiology of sensory‐motor pathways were studied in the brachial spinal cord of adult bullfrogs to characterize the properties and specificity of these connexions.2. Motoneurones innervating a given forelimb muscle are located in discrete and reproducible regions of the lateral motor column. Yet only a fraction of the motoneurones in a particular region innervates any one muscle.3. The central projections of sensory afferent axons from the triceps muscles extend throughout the rostro‐caudal length of the brachial spinal cord. Within this region these projections terminate in an area containing many motoneuronal dendrites.4. Within the triceps motor pool sensory neurones from the triceps muscles produce monosynaptic potentials only in triceps motoneurones even though these motoneurones are mingled with motoneurones innervating other muscles.5. Motoneurones innervating each of the three heads of the triceps muscles, medial, internal and external, receive monosynaptic input from their own, homonymous muscle head. Sensory fibres from the medial head also innervate 98% of the heteronymous motoneurones projecting to the internal or external heads, and nearly 90% of the medial triceps motoneurones are innervated by sensory axons from the other two heads.6. Similarly, other brachial motoneurones receive monosynaptic input from sensory axons in their own muscle nerves. However, most of the synaptic potentials evoked in triceps motoneurones by stimulation of muscle nerves other than triceps are of longer latency and probably involve polysynaptic pathways.7. Thus, the pattern of synaptic connexions between muscle sensory afferents and motoneurones in the frog's spinal cord is specific. Furthermore, comparison with homologous pathways in the cat's spinal cord suggests that the strength and pattern of these connexions are similar.
Fluoride blocks an inactivation step of transduction in a locust photoreceptor
Authors: Payne Richard 
Published: December 2014

1. Photoreceptors in a superfused retina of a locust compound eye are treated with saline containing 10 mM‐NaF, while their intracellular resting potential and responses are recorded using glass micropipettes.2. Treatment for two minutes with 10 mM‐NaF, followed by a series of brief, bright flashes of light, results in an irreversible, noisy depolarization of approximately 10 mV. The final, stable level of depolarization is reached through the summed effect of each of the noisy, depolarizing afterpotentials that follow every response of the cell to a light flash. If kept in darkness after treatment with NaF, the noisy depolarization still develops, but more gradually, over a period of 5 min.3. The voltage noise induced by NaF mimics light‐induced voltage noise when the two are compared at mean depolarizations of more than 15 mV. At very small depolarizations, however, fluoride‐induced noise cannot be resolved into the large discrete events (bumps) that are typical of the response of a dark‐adapted photoreceptor to a single photon.4. The complete replacement of the superfusate sodium by choline reversibly reduces the fluoride‐induced noise and depolarization to the same extent as it does the light‐induced noise and depolarization of an illuminated cell.5. Increasing the superfusate calcium concentration from 0·5 to 10 mM also reversibly reduces fluoride‐induced noise and depolarization to the same extent as it does light‐induced noise and depolarization. This action of calcium is accompanied by an increase in a cell's input resistance which opposes the reduction caused by light or fluoride treatment.6. The results confirm the proposal (Payne, 1981) that anionic metabolic inhibitors cause spontaneous activity in sodium channels that are normally opened by light. A model is proposed in which fluoride acts by blocking the inactivation of a late stage in the transduction mechanism.
Ions and energy metabolism in duck salt‐gland: possible role of furosemide‐sensitive co‐transport of sodium and chloride
Authors: Ernst S. A. , van Rossum G. D. V. 
Published: December 2014

1. The effects of methacholine on net ionic movements and energy metabolism of the avian salt‐gland have been studied, using slices of glands taken from salt‐adapted Pekin ducks. The slices were equilibrated with media and drugs for 120 min at 1 °C before the experimental incubation at 38 °C.2. During incubation at 38 °C the slices accumulated K+ and lost Na+ and Cl−. In the presence of methacholine, they retained more Na+ and Cl− and accumulated less K+, the maximal effects being given by 0·5‐1·0 mM‐methacholine. Similar results were obtained whether the medium contained 10 mM‐Tris (used in most experiments) or 25 mM‐HCO3− as the major buffer.3. The higher final levels of cell Na+ and Cl− induced by methacholine were not seen when furosemide (1 mM) was also present. Methacholine did not induce a higher level of cell Na+ when medium Cl− was replaced by I−, NO3− or SO42-, and did not induce a higher Cl− content when medium Na+ was replaced by choline or Li+. The fall of K+ accumulation caused by methacholine was also prevented by furosemide or by replacing Cl− in the medium with other anions. The anion‐transport inhibitors, SCN− (up to 10 mM) and 4,4′‐diisothiocyano‐2,2′‐disulphonic acid stilbene (DIDS) (up to 2 mM) did not prevent the effects of methacholine.4. Methacholine stimulated respiration and lowered the slice ATP contents, and these effects were both prevented by ouabain or furosemide. Ouabain, but not furosemide, also reduced the basal (i.e. in the absence of methacholine) rate of respiration and raised the ATP level. SCN− and DIDS had no effect on basal or stimulated respiration or on ATP contents.5. The respiratory stimulation and fall of ATP induced by methacholine were totally prevented if medium Na+ was replaced by choline. Replacement of Na+ by Li+ caused some stimulation of basal respiration; it also permitted some loss of ATP in the presence of methacholine, but the loss was smaller than that seen in the normal Na+ medium.6. The respiratory stimulation and fall of ATP induced by methacholine were prevented if medium Cl− was replaced by SO42-. The effects of methacholine were partially blocked when NO3− replaced Cl−.7. The results are consistent with the stimulation by methacholine of a furosemide‐sensitive, coupled entry of Na+ and Cl− into the cells, associated with a loss of K+. This would result in a stimulation of Na+ extrusion by the ouabain‐sensitive transport system for Na+ and K+ with increased consumption of ATP.
The ‘late’ reflex responses to muscle stretch: the ‘resonance hypothesis’ versus the ‘long‐loop hypothesis’
Authors: Eklund G. , Hagbarth K.-E. , Hägglund J. V. , Wallin E. U. 
Published: December 2014

1. Experiments were performed to check the validity of previous claims concerning the ‘long‐loop’ aetiology of ‘late’ reflex electromyogram (e.m.g.) responses to muscle stretch in man. The primary aim was to investigate whether observations previously presented in favour of the ‘long‐loop hypothesis’ are explicable also in terms of the ‘resonance hypothesis’, according to which the ‘late’ reflex components represent spinal, short‐latency responses to intramuscular oscillations initiated by the impact.2. The contracting wrist flexors of healthy subjects were exposed to trains of recurrent 25‐50 Hz stretch stimuli (wrist torque pulses). Each of the initial two or three pulses in the train was followed by e.m.g. peaks with a latency of 20‐25 msec. The e.m.g. peaks driven in this way had the following characteristics in common with the successive two or three e.m.g. peaks which were induced by single ramp stretches or tendon taps. (a) Changes in stimulus parameters which altered the strength of the initial e.m.g. peak often had an opposite effect on the strength of the succeeding peak(s). Muscle vibration which attenuated the initial peak often enchanced the succeeding one(s). (b) The initial e.m.g. peak was less affected than the succeeding peak(s) by the subjects’ attempts to respond with rapid ‘resist’ or ‘let go’ reactions.3. Intramuscular oscillations (monitored by a needle accelerometer) and e.m.g. responses evoked by single ramp stretches and/or tendon taps were also studied in the long thumb flexor, the calf muscles and the masseter muscle. In the thumb flexor, the initial accelerometer deflexion was only rarely succeeded by a short latency e.m.g. peak, but the succeeding wave in the needle accelerogram was followed by such a peak, appearing about 40 msec after stimulus application. By contrast, the calf muscles and the jaw elevators exhibited a high amplitude, short‐latency e.m.g. response to the first but only rarely to the second intramuscular oscillation wave.4. The interval between initial and second e.m.g. peaks following tendon taps was longer for calf muscles than for wrist flexors and longer for wrist flexors than for jaw elevators. Similar differences were observed with respect to the intervals between the damped intramuscular oscillations initiated by the impacts.5. Without denying the existence of ‘long‐loop reflexes’ it is concluded that the characteristics of the ‘late’ reflex responses to muscle stretch in man are explicable also in terms of the ‘resonance hypothesis’.
Comparison of effects of denervation and botulinum toxin paralysis on muscle properties in mice
Authors: Brown M. C. , Hopkins W. G. , Keynes R. J. 
Published: December 2014

1. The properties of denervated and fully innervated but paralysed soleus and extensor digitorum longus (e.d.l.) muscles were compared in mice.2. Muscles were paralysed by single or repeated injections of botulinum toxin into the right lower leg. Contralateral muscles were denervated at the same time by sciatic nerve section. Muscles were excised 3‐20 days later and direct and indirect isometric twitch and tetanic tensions measured in vitro. ACh sensitivity was assessed from isometric contractions to various concentrations of bath‐applied ACh perchlorate.3. Denervated muscles as expected from the work of others developed sensitivity to ACh earlier and more rapidly than paralysed muscles. A transient peak of sensitivity was reached after 7 days of denervation in soleus and after 8 days in e.d.l. However 2 days later the sensitivity of muscles fully paralysed to nerve twitch and tetanic stimuli was not significantly different from that of denervated muscles.4. In both e.d.l. and soleus the direct tetanus/twitch ratios declined in paralysed and denervated muscles. The decline was initially more rapid in denervated than paralysed soleus, but the ratios for paralysed and denervated muscles were not significantly different after 10 days in either muscle. By this time there were no differences in the absolute strengths of the paralysed and denervated muscles.5. It is concluded that the ACh sensitivity and dynamic properties of fully paralysed mouse muscles become equal to those of denervated muscles once the acute effects associated with nerve degeneration are past. This result is consistent with the idea that normal neuronal control of extrajunctional mammalian skeletal muscle properties is mediated solely by means of activity.
Inverse effects of dansylation of red blood cell membrane on band 3 protein‐mediated transport of sulphate and chloride
Authors: Lepke Sigrid , Passow Hermann 
Published: December 2014

1. Dansylation of the red cell membrane produces inverse effects on SO42- and Cl− equilibrium exchange. The former is enhanced by several orders of magnitude (Legrum, Fasold & Passow, 1980), the latter is inhibited. Both effects are potentiated after dansylation in the presence of 2‐(4‐amino‐3‐sulphophenyl)‐6‐methyl‐7‐benzothiazol sulphonic acid (APMB), a disulphonic acid that combines non‐covalently with the 4,4′‐diisothiocyanate dihydrostilbene‐2,2′‐disulphonic acid (H2DIDS) binding site of the anion transport protein.2. After dansylation the maximum of the pH dependence of SO42- exchange near pH 6·3 is replaced by a plateau. When dansylation is performed in the presence of APMB, the plateau is reached at a much higher level at around pH 7·0 and resembles that observed by Funder & Wieth (1976) for Cl−.3. The mutual interactions between the transfer site, the H2DIDS binding site, and the as yet unidentified danysl chloride binding sites were studied in detail. Occupation of the H2DIDS binding site by the non‐covalently binding agents 4,4′‐dinitrostilbene‐2,2′‐disulphonate (DNDS), 4,4′‐bis(acetamido) stilbene‐2,2′‐disulphonate (DAS) or APMB inhibit the enhanced SO42- exchange across the previously dansylated membrane. The apparent KI value remains the same as in untreated membranes for DNDS, is reduced to 1/3 for DAS, and to 1/60 for APMB. Conversely, when dansylation is carried out while the H2DIDS binding site is occupied by DNDS, APMB or DAS, the enhancement of SO42- exchange (as measured after removal of excess dansyl chloride and the additional agent) is prevented by DNDS, augmented by APMB and not affected by DAS. This suggests that the agents stabilize different conformations of the H2DIDS binding site that are associated with different accessibilities of the dansyl chloride binding sites.4. The SO42- equilibrium exchange as measured at a fixed Cl− concentration is enhanced when the Cl− concentration at which dansylation is carried out is increased, indicating allosteric interactions between anion binding and the exposure of the dansyl chloride binding sites.5. The enhanced K+ efflux from dansylated red cells is independent of the described modifications of the dansylation reaction by APMB, DAS or DNDS, demonstrating that there exists no simple correlation between the changes of anion and cation movements that are induced by dansylation.
Combined effects of ATP and phosphate on rubidium exchange mediated by Na‐K‐ATPase reconstituted into phospholipid vesicles
Authors: Karlish S. J. D. , Lieb W. R. , Stein W. D. 
Published: December 2014

1. Phospholipid vesicles reconstituted with Na—K‐ATPase show an (ATP+phosphate)‐stimulated Rb—Rb exchange, with properties similar to the K—K exchange of human red cells. This includes a rate 15‐20% of the rate of active ATP‐dependent Na—K exchange.2. We have studied activation of this Rb—Rb exchange by ATP at fixed phosphate concentrations and by phosphate at fixed ATP concentrations. It is found for both ATP and phosphate that with low concentrations of the fixed ligand an increase in concentration of the complementary ligand produces first stimulation and then inhibition of Rb—Rb exchange. At high concentrations of the fixed ligand the complementary ligand shows only saturation behaviour.3. The pattern of activation and of inhibition by ATP and by phosphate is affected by the Rb0 concentration in the exterior medium, in that higher concentrations of Rb0 counteract inhibitory effects of high concentrations of ATP and phosphate.4. (ATP+phosphate)‐stimulated Rb—Rb exchange is activated by Rb0 in the exterior medium along a sigmoid curve. An increase of Rbi within the vesicles, which raises the maximal velocity of Rb—Rb exchange, is accompanied by a smaller increase in the Rb0 concentration required for half‐maximal stimulation of the Rb—Rb exchange.5. The data are interpreted in terms of a model similar to those proposed by Karlish & Stein (1982a,b), but extended to include simultaneous effects of ATP and phosphate. Inhibitions by high concentration of ATP or phosphate arise as a result of stabilization of E1 ATP or E2‐P forms respectively, in the presence of low concentrations of the complementary ligand. With high concentrations of the fixed ligand, saturation behaviour of the varying ligand is observed because the occluded Rb forms become the dominant transport intermediates. The occluded Rb forms bind both ATP and phosphate weakly and independently. The effects of ATP together with phosphate are accounted for by a simple combination of their separate effects on the Rb—Rb exchange.6. We suggest that the functional role of the occluded Rb form E2 (Rb)occ in active transport is to minimize passive cation leaks through the system and allow control of the direction of cation movements by binding of physiological ligands such as ATP or phosphate.