bluuebunny/crossref_metadata_2025_split huggingface dataset:
The site and receptors responsible for the inhibition by sympathetic nerves of intestinal smooth muscle and its parasympathetic motor nerves
Authors: Gillespie J. S. , Khoyi M. A. 
Published: December 2014

1. The effects of three inhibitory stimuli, sympathetic nerve stimulation, noradrenaline (NA) and isoprenaline have been examined on three forms of motor activity in the rabbit colon, the response to pelvic (parasympathetic) nerve stimulation, acetylcholine (ACh) and spontaneous tone.2. The response to pelvic nerve stimulation is most effectively inhibited by sympathetic nerve stimulation, much less effectively by NA and hardly at all by isoprenaline. The sympathetic nerves can inhibit the pelvic response at frequencies of stimulation which do not affect spontaneous tone. The inhibitory effect of sympathetic stimulation, and of NA, on the pelvic response is reduced by phentolamine 5 × 10−6
M and unaffected by propranolol 5 × 10−6
M suggesting the effect is mediated via α receptors.3. The response to ACh is inhibited by all three stimuli equally. The inhibitory effect of sympathetic nerve stimulation and of isoprenaline is reduced by propranolol 5 × 10−6
M. The inhibitory effect of NA is also reduced by propranolol but to a lesser extent. Phentolamine 5 × 10−6
M has a small effect in reducing the inhibitory effect of sympathetic nerve stimulation or of NA. This effect of phentolamine is lost if the participation of motor nerves in the response to ACh is excluded by either tetrodotoxin 10−7 g/ml. or cold storage for 10‐14 days. These results suggest that inhibition of the ACh response takes place mainly at the muscle by activation of β receptors but that ACh may have a small indirect stimulant action through motor nerves and this is susceptible to inhibition through α receptors.4. All three stimuli are equally effective in lowering smooth muscle tone. This inhibitory effect of sympathetic nerve stimulation and of isoprenaline is reduced by propranolol 5 × 10−6
M and unaffected by phentolamine 5 × 10−6
M. The inhibitory effect of NA is reduced by propranolol but again is less sensitive to block than the other two inhibitory stimuli. Phentolamine is without effect on the inhibitory action of NA and the combination of phentolamine with propranolol is no more effective than propranolol alone. These results suggest that NA liberated by sympathetic nerves and isoprenaline inhibit myogenic tone in the smooth muscle by an action on β receptors but the action of NA added to the bath cannot be fully explained in this way.
The gecko visual pigments: a microspectrophotometric study
Authors: Crescitelli Frederick , Dartnall H. J. A. , Loew E. R. 
Published: December 2014

1. A dual system of visual pigments having absorbance maxima in the green and blue respectively has been found in the retinas of geckos both by single cell microspectrophotometry and by the method of extraction. Microspectrophotometry has shown the system to be present in four species of geckos representing four genera. Along with previous work with extracts (Crescitelli, 1972) this indicates a fundamental property in this family of lizards. No other photopigments have been detected.2. For Gekko gekko, the species most intensively studied, the two pigments have absorbance maxima at 521 and 467 nm respectively. Both are based on vitamin A1 and both are characterized by absorbance spectra that nearly conform to the Dartnall nomogram.3. In situ, the 521‐pigment is not temperature‐sensitive, and has virtually the same absorbance spectrum at 23° C as at 5° C. On extraction into digitonin solution, however, the absorbance spectrum of the pigment becomes temperature‐dependent and, though identical when measured at low temperature (2‐5° C) with the constant in situ curve, is displaced to shorter wave‐lengths at higher temperatures (10‐25° C). Thus the extract spectrum is relevant to the in situ spectrum only at low temperature (and in the presence of chloride ions).4. Unlike the rhodopsins of several vertebrates, the gecko 521‐pigment displays no evidence of a meta‐III stage in the sequence of products following photic bleaching, even at low temperatures. This is true for the pigment in situ as well as in the extracted condition.
Effects of injections of calcium and EGTA into the outer segments of retinal rods of Bufo marinus
Authors: Brown J. E. , Coles J. A. , Pinto L. H. 
Published: December 2014

1. Intracellular recordings were made from the outer segments of rods in the isolated, superfused retina of Bufo marinus. Cells were impaled under observation with a compound microscope fitted with an infra‐red image converter. Changes of membrane voltage and some concomitant changes of input resistance were measured in response to light, membrane polarization and iontophoretic injections.2. By means of a double barrel micropipette, charge was passed into a rod from a micropipette barrel that contained Ca2+ while no net current crossed the plasma membrane. In about half the cells, immediately after the injection, a hyperpolarization was observed that decayed with a time course similar to the decay of the receptor potential.3. Membrane hyperpolarization also occurred after a depolarizing current stopped flowing into a rod through a single barrel pipette that contained only K‐acetate. This hyperpolarization was accompanied by an increase of membrane conductance. The reversal potential for the conductance‐increase was between the voltage in the dark and the voltage in the absence of [Na+]out. A larger hyperpolarization became evident after an equal depolarizing current stopped flowing into a rod through a pipette that also contained Ca2+; this larger after‐hyperpolarization was due to both the cessation of depolarizing current and the injection of Ca2+.4. A depolarization of 10‐20 mV that lasted 2‐60 sec became evident after hyperpolarizing current stopped flowing into a rod through a single‐barrel pipette filled with K‐EGTA. During the after‐depolarization, the responses to small, dim spots of light were attenuated. No depolarization was observed after passing hyperpolarizing currents into rods through pipettes that contained either acetate−, SO2-4 or MOPS−.5. These results show that sequestration of [Ca2+]in depolarizes the plasma membrane and that an increase in [Ca2+]in hyperpolarizes the membrane mimicking the later part of the receptor potential. These findings support the hypothesis of Yoshikami & Hagins (1971) that Ca2+ is an intracellular messenger for excitation in vertebrate rods.
The effects of external sodium substitution on cell sodium and potassium in vascular smooth muscle
Authors: Friedman Sydney M. 
Published: December 2014

1. The entry of Li into the vascular smooth muscle cells of the rat tail artery follows first‐order kinetics with a rate constant of approximately 1·3 hr−1 at 10 m
M‐[Li]o. The rate constant decreases gradually to ca. 0·5 hr−1 when the [Li]o/[Na]o ratio is increased.2. Replacement of Na with Li over the range of [Li]o from 1 to 115 m
M, accomplished at constant ionic strength and osmolarity of the bathing solution, produces changes in cell Na and K without apparent change in cell water. At equilibrium, cell Li increases in linear proportion to [Li]o, at a ratio of 2:1 throughout the range. The increase in cell Li is associated with inverse falls in both cell K and Na such that the ratio of cell K to cell Na remains constant at ca. 10:1 throughout.3. The changes in the ionic contents, induced by equilibration of the tissue with a Na‐free, Li‐substituted solution, are reversible.4. Replacement of Na with sucrose over the range of 40‐115 m
M results, at equilibrium, in a linear fall in cell Na without conspicuous change in cell K. A constant portion of the cell Na, ca. 10 m‐mole/kg dry wt., does not participate in this exchange.5. At equilibrium, reductions in [Na]o are reflected in corresponding reductions in apparent [Na]i such that the [Na]o/[Na]i ratio remains constant.
The effect of catecholamines on Na—K transport and membrane potential in rat soleus muscle
Authors: Clausen Torben , Flatman John A. 
Published: December 2014

1. The action of catecholamines on the transport and the distribution of Na and K and the resting membrane potential (EM) has been investigated in soleus muscles isolated from fed rats.2. In a substrate‐free Krebs—Ringer bicarbonate buffer adrenaline (ADR) (6 × 10−6
M) increased 22Na efflux by 83%, 42K influx by 34%, and EM by 10%. Similar effects were exerted by noradrenaline (NA), phenylephrine, salbutamol and isoprenaline. The effects of ADR on Na—K transport and EM were suppressed by ouabain (10−3
M) and propranolol (10−5
M), but not by thymoxamine (10−5
M) or tetracaine (10−4
M).3. Following 90 min of incubation in the presence of ADR (6 × 10−6
M), the intracellular K/Na‐ratio was increased threefold. NA produced almost the same change, and both catecholamines seem to induce a new steady‐state distribution of Na and K which can be maintained for several hours in vitro.4. The effect of ADR on 22Na efflux and EM could be detected at concentrations down to 6 × 10−9 and 6 × 10−10
M, respectively, and half‐maximum increase was obtained at around 2 × 10−8
M. NA was at least one order of magnitude less potent.5. The effect of low concentrations of ADR on 22Na efflux was potentiated by theophylline (2 m
M). When added together, dibutyryl‐cyclic AMP and theophylline mimicked the action of ADR on 22Na efflux, 42K influx, Na/K content and EM. Ouabain (10−3
M) also suppressed the effect of dibutyryl‐cyclic AMP and theophylline on Na—K transport.6. Following the addition of ouabain (10−3
M), EM rapidly dropped from a mean of ‐71 to ‐63 mV, and then showed a slow linear fall for up to 4hr.7. The hyperpolarization induced by ADR was associated with a decrease in membrane conductance, 22Na influx and 42K efflux. The time course and the response to ouabain suggests that all of these effects are secondary to stimulation of the active coupled transport of Na and K.8. It is concluded that in rat soleus muscle, the active Na—K transport is electrogenic and susceptible to stimulation by catecholamines via beta‐adrenoceptors. This effect is mediated by adenyl cyclase activation and may account for the increase in EM and the intracellular K/Na ratio.
Endocytosis and immunoglobulin transport across the small intestine of the new‐born pig
Authors: Burton K. A. , Smith M. W. 
Published: December 2014

1. Measurements of porcine and human IgG transport across the small intestine of the new‐born pig have been made in vivo and related to the amount of endocytosis taking place.2. The amount of immunoglobulins transported, following intraduodenal administration to conscious animals, is directly related to the degree of endocytosis which these proteins produce. Administration of protein in amounts sufficient to cause a maximal endocytotic response causes saturation of the protein transporting process.3. Absorption of small amounts of human IgG from the small intestine can be accelerated by the addition of sow colostrum or porcine IgG in quantities sufficient to stimulate endocytosis. These effects disappear when the amount of human IgG administered is itself sufficient to fully stimulate endocytosis.4. Preferential transport of porcine over human IgG can be demonstrated when both are given as a single solution to individual pigs. The degree of preference is, however, small in relation to the total amount of immunoglobulin transported.5. The initial formation of endocytotic vacuoles in the pig intestine seems, unlike the situation in rats and mice, to provide a major route for the trans‐cellular movement of macromolecules including immunoglobulins. Present evidence suggests that, though sow colostrum can on occasion stimulate such transport, it does so merely by acting as a protein‐containing solution to increase the amount of endocytosis taking place.
Training induced adaptation of skeletal muscle and metabolism during submaximal exercise
Authors: Henriksson Jan 
Published: December 2014

1. Six subjects were trained using a one‐leg bicycle exercise for 2 months. The untrained leg served as control. After the training period, muscle oxidative capacity, determined as succinate dehydrogenase activity, was 27% higher in the trained (as opposed to the control) leg (P < 0·05).2. When the subjects in this situation performed a 1 h two‐legged submaximal bicycle exercise bout (150‐225 W), determinations of VO2 of the single leg (leg blood flow × (A—V)O2 difference) revealed that they appeared to choose to work harder with their trained than with their untrained leg, so as to make the relative loads for the two legs the same.3. Determinations of O2 and CO2 on femoral arterial and venous blood demonstrated that the
R.Q. was lower in the trained as compared to the untrained leg, 0·91 cf. 0·96 (10 min) and 0·91 cf. 0·94 (50 min) (P < 0·05).4. That metabolism of fat was more pronounced in the trained leg was further supported by the finding of a significant net uptake of free fatty acids in this leg only. Moreover, a lower release of lactate from the trained leg was demonstrated.5. It is suggested that the shift towards a more pronounced metabolism of fat in the trained leg is a function of an increased muscle oxidative capacity.
A study of excitatory neuromuscular transmission in the bovine trachea
Authors: Cameron A. R. , Kirkpatrick C. T. 
Published: December 2014

1. The excitatory innervation of bovine tracheal smooth muscle has been studied with the sucrose‐gap apparatus.2. Single 2 ms electrical stimuli applied to the whole tissue excited intrinsic nerves, and produced a small transient depolarization of the smooth muscle, the excitatory junction potential (e.j.p.). The e.j.p. caused a twitch‐type contraction; twitches and e.j.p.s summated during repetitive stimulation but facilitation was not observed, and action potentials were never elicited.3. The effects of electrical stimulation could be abolished by atropine (5 × 10−7 mol/l) and augmented by neostigmine (4 × 10−6 mol/l), and were mimicked by exogenous acetylcholine (1·0 μg/ml).4. With the electron microscope, the density of innervation was found to be low (one axon per ninety smooth muscle cells). Axons were found in small groups in the clefts between bundles of cells, but no axons penetrated within the muscle bundles. Naked axon varicosities containing agranular vesicles were seen, but no axon approached within 200 nm of a smooth muscle cell.5. It is difficult to reconcile the sparsity of innervation with the dependence of the tissue on nerve excitation to initiate activity.
Transmission from photoreceptors to ganglion cells in turtle retina
Authors: Baylor D. A. , Fettiplace R. 
Published: December 2014

1. Synaptic transfer between photoreceptors and impulse‐generating cells was studied in isolated eyecups from turtles. Single red‐sensitive cones or rods were stimulated by current passed through an intracellular electrode, and impulses generated by the resulting synaptic action were recorded with an external micro‐electrode. This technique permits study of retinal transmission without the operation of the visual transduction mechanism. Antidromic stimulation of the optic nerve indicated that most of the impulse‐generating cells were ganglion cells.2. Individual ganglion cells responded transiently to changes in the membrane potential of a receptor and could be classified into three groups on the basis of the direction of the effective change in potential. Off centre ganglion cells responded selectively to depolarizations of a receptor, while on centre ganglion cells responded selectively to hyperpolarizations. On‐off ganglion cells responded to both depolarizations and hyperpolarizations of a receptor.3. Ganglion cells gave the same pattern of response to electrical hyperpolarization of a receptor and to light in the centre of their receptive fields. Subthreshold depolarizing currents passed in a receptor antagonized the ganglion cell's response to light, and subthreshold hyperpolarizing currents reinforced the response. These observations are consistent with the view that the hyperpolarization generated by visual transduction is responsible for regulating the release of transmitter at the first retinal synapse.4. When a receptor was stimulated with weak current pulses of fixed intensity the number and latency of the ganglion cell impulses fluctuated randomly in successive trials. The relation between the fraction of trials yielding a response and the stimulus intensity was broad. These results indicate that the link between retinal input and output is noisy.5. In the most sensitive pairs of cells, a response of one or more impulses could be obtained in half the trials with a current of about 2 × 10−11 A, which changed the potential of the receptor by 1‐2 mV. A current of similar magnitude would be developed by about 130 photoisomerizations in a red‐sensitive cone or 50 photoisomerizations in a rod.6. Dim background light producing a steady hyperpolarization of a few millivolts in the rods raised the threshold for electrically‐evoked transmission from a rod to a ganglion cell. In experiments on red‐sensitive cones, background light raised the threshold in the off pathway, in which depolarization was the effective stimulus, and lowered the threshold in the on pathway, in which hyperpolarization was the effective stimulus. These changes in sensitivity were not accompanied by obvious changes in the input resistance of the stimulated receptor. Regulation of retinal sensitivity in background light thus involves changes in synaptic transfer as well as changes in the sensitivity of the visual transduction mechanism.
Morphology and responses to light of the somata, axons, and terminal regions of individual photoreceptors of the giant barnacle
Authors: Hudspeth A. J. , Stuart Ann E. 
Published: December 2014

1. The median eye of the giant barnacle, B. nubilus, comprises four large photoreceptor neurones which are visible under the dissecting microscope for almost their entire length. We have studied the structure of, and the responses to light recorded in, the somata, axons, and terminal regions of these neurones.2. The photoreceptor somata, each 40‐70 μm in diameter, extend numerous light‐sensitive dendritic processes whose membranes form rhabdomeric microvilli. Recordings from the soma show that dim light evokes a steady, noisy depolarization; brighter light elicits a transient depolarization which decays to a maintained plateau, followed by a hyperpolarization when the light is turned off.3. Light‐induced voltage changes spread decrementally along the photoreceptor axons, which average 10 mm in length and 25 μm in diameter. In distal parts of the axon, near the presynaptic terminals, depolarizations and hyperpolarizations can be as large as 50% or more of their values in the soma.4. There is no demonstrable electrical coupling between photoreceptor neurones as shown by simultaneous recordings from two receptor somata or axons.5. Each photoreceptor axon enters the mid line commissure of the supraoesophageal ganglion, bifurcates, and arborizes in a restricted zone of neuropil in each hemiganglion. The large size of the terminal processes of these neurones and their characteristic cytoplasmic inclusions enable one to trace them with the electron microscope as they branch in the neuropil.6. The terminal processes subdivide and end in 1‐3 μm diameter branches which are the sites of apparently chemical synapses. Vesicle‐containing, presynaptic loci on these processes of the receptor cell are invariably apposed to two post‐synaptic processes from cells as yet unidentified.
Analysis of the onset phase of olfactory bulb unit responses to odour pulses in the salamander
Authors: Kauer John S. , Shepherd Gordon M. 
Published: December 2014

1. A method for delivering odour pulses of controlled onset, steady plateau and abrupt termination, has been developed and applied to a single unit study of mitral cell responses in the olfactory bulb of the salamander. The pulses have been monitored during the experiments near the site of stimulation on the olfactory mucosa.2. Responses have been categorized as excitatory or suppressive based on the initial response to the odour pulse.3. Initially excitatory responses had sustained discharges near threshold. With increasing concentration, the discharge changed to a brief burst followed by suppression. The briefest latency of a unit response was 120 msec, using stimulation of medium concentration, after the start of the pulse; the majority of units appeared to be excited within 200‐300 msec. Ramp stimuli gave increasing periods of excitation as the rise time of the odour front became less abrupt.4. Initially suppressive responses showed suppression at all levels of concentration. The majority of units appeared to have an onset of suppression about 300‐400 msec after the start of the pulse.5. These basic responses, involving suppression or excitatory—suppressive sequences, can be correlated with some basic properties of the synaptic circuits in the olfactory bulb. The time courses of the initial responses appear to be within the time periods of the inhalation cycle of the salamander, and therefore may reflect mechanisms of processing of natural olfactory stimuli.
Vagal control of lower oesophageal sphincter motility in the cat
Authors: Gonella J. , Niel J. P. , Roman C. 
Published: December 2014

1. The effects of vagal efferent fibre stimulation on the smooth muscle of the lower oesophageal sphincter have been studied on the anaesthetized animal and on the isolated and perfused organ.2. In both muscle layers (longitudinal and circular) vagal stimulation elicits two types of electromyographic (e.m.g.) potentials: (a) excitatory junction potentials (e.j.p.s) where there is a depolarization of the smooth muscle fibres. E.j.p.s can give rise to spike potentials inducing a contraction of the sphincter; (b) inhibitory junction potentials (i.j.p.s) where there is hyperpolarization of the smooth muscle fibres, often followed by a transient depolarization which may initiate spikes (post‐inhibitory rebound).3. Pure i.j.p.s are observed after atropine treatment which suppresses e.j.p.s. Under these conditions, a long lasting vagal stimulation induces a long duration hyperpolarization concomitant with an opening of the lower oesophageal sphincter followed after the cessation of stimulation by a powerful rebound leading to a strong contraction which closes the sphincter.4. Several arguments, pharmacological (action of acetylcholine (ACh), atropine and hexamethonium) and physiological (threshold and latency of responses) lead to the following conclusions.Preganglionic vagal fibres are cholinergic and they activate (a) intramural excitatory cholinergic neurones; (b) intramural non‐adrenergic inhibitory neurones (purinergic neurones). Preganglionic fibres leading to inhibition have a higher threshold than those leading to excitation.Both excitatory and inhibitory pathways are interconnected inside the intramural network. In particular, activation of intramural inhibitory neurones, by relaxing the oesophagus orally to the lower oesophageal sphincter, inhibits intramural excitatory neurones and subsequently blocks vagal excitatory responses.5. Two functions may be attributed to the vagal extrinsic innervation: (a) closure of the lower oesophageal sphincter by maintaining the basal tone of the sphincter; this would imply that at rest the inhibitory control is supplanted by the excitatory one; (b) sphincter opening during swallowing by suppressing the excitatory stimulus and reinforcing the inhibitory one (it may be recalled that after bilateral vagotomy, swallowing is no longer followed by a relaxation of the sphincter).