bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the localization of pulmonary carbonic anhydrase in the cat.
Authors: Hanson M A , Nye P C , Torrance R W
Published: December 2014

1. We considered whether some of the carbonic anhydrase of the lung is on the surface of the pulmonary capillaries so that it acts directly on plasma as it traverses the pulmonary capillaries to accelerate CO2/pH equilibration. 2. Experiments were performed on spontaneously breathing cats or saline‐perfused cat lungs. 3. In intact cats, Tris buffer injected suddenly into the right atrium transiently lowered end‐tidal CO2, FET, CO2. The rate of CO2 uptake came within an order of magnitude of taxing the calculated diffusing capacity of the lungs. The fall in FET, CO2 was much reduced by giving the carbonic anhydrase inhibitors benzolamide or acetazolamide intravenously, or even by adding benzolamide to the injected Tris. The fall in FET, CO2 could be increased by adding carbonic anhydrase to the injected Tris. 4. In saline‐perfused lungs ventilated with 5% CO2 in O2, Tris or alkalinized albumin solution injected into the pulmonary artery transiently lowered FET, CO2 and the effect was reduced by the addition of benzolamide or acetazolamide to the injectate. Injecting Tris bubbled with 15% CO2 caused a rise in FET, CO2, also reduced by benzolamide. 5. We conclude that pulmonary carbonic anhydrase is readily accessible to large or small molecular wight buffers in the capillaries and to inhibitors, and we suggest that it is located on the luminal surface of the capillary endothelium.
Inward rectification in frog skeletal muscle fibres and its dependence on membrane potential and external potassium.
Authors: Leech C A , Stanfield P R
Published: December 2014

1. Experiments were carried out using a voltage‐clamp technique to investigate the dependence of inward rectification on membrane potential and on the equilibrium potential for K+, changed either by changing [K]o or changing [K]i. 2. The relationship between gK, the potassium chord conductance, and membrane potential depended on membrane potential and [K]o, but not on [K]i. 3. Under hyperpolarization, K currents increased with time, but instantaneous current‐voltage relations also showed inward rectification. The time constants for activation fell with hyperpolarization, e ‐fold for an 18 mV change in membrane potential. 4. The time constants for activation depended on [K]o but not on [K]i. 5. Under depolarization, the activation of K currents was partly reversed, but between activation and membrane potential, determined from two‐pulse experiments, also appeared to depend on [K]o but not on [K]i. 5. Under depolarization, the activation of K currents was partly reversed, but between activation and membrane potential, determined from two‐pulse experiments, also appeared to depend on [K]o but not on [K]i. 6. The rate of activation of K currents under hyperpolarization had a Q10 of 2.64 +/‐ 0.08 (n = 5). Currents, measured per unit length, increased with temperature, with a Q10 of 1.66 +/‐ 0.11 (n = 5).
Alterations of myocardial capillary permeability by albumin in the isolated, perfused rabbit heart.
Authors: Mann G E
Published: December 2014

1. Capillary permeability‐surface area products for 22Na, 51Cr‐EDTA (mol. wt. 357), [57Co]cyanocobalamin (mol. wt. 1353) and 125I‐labelled insulin (mol. wt. approximately or equal to 6000) were measured using the single‐passage, multiple‐tracer dilution technique in isolated rabbit hearts perfused at constant flows between 0.2 and 4.7 ml. min‐1 . g‐1. 2. In hearts perfused with a Krebs‐Ringer solution containing bovine albumin (10 g . l . ‐1), the permeability‐surface area products for 51Cr‐EDTA and [57Co]cyanocobalamin increased as the perfusion rate increased, but reached constant values at flows above 2 ml . min‐1 . g‐1. For 125I‐labelled insulin a diffusion‐limited value of 0.06 +/‐ 0.02 ml . min‐1 . g‐1 (mean +/‐ S.E., n = 10) was measured at significantly lower perfusion rates. As the value for 22Na increased continuously with increments in flow, only a flow‐limited value could be estimated. 3. When hearts were initially perfused with albumin (10 g . l . ‐1) and then with an albumin‐free Krebs‐Ringer solution, a significant increase in the permeability‐surface area for 22Na, 51Cr‐EDTA and [57Co]cyanocobalamin was observed. 4. In hearts perfused with albumin capillary permeability coefficients calculated for 22Na, 51Cr‐EDTA. [57Co]cyanocobalamin and 125I‐labelled insulin were respectively: 10.5, 3.5, 2.1 and 0.21 x 10(‐5) cm.sec‐1. 5. These findings confirm that bovine albumin reduces the permeability of myocardial capillaries to hydrophilic solutes of varying molecular sizes and this effect may be the result of an interaction of albumin with the pathways for transcapillary exchange.
Connexions between hair follicle afferent fibres and spinocervical tract neurones in the cat: the synthesis of receptive fields.
Authors: Brown A G , Noble R
Published: December 2014

1. Relationships between the terminal arborizations of hair follicle afferent fibres and dendritic trees of spinocervical tract (s.c.t.) neurones were studied using intra‐axonal and intracellular injections of horseradish peroxidase in chloralose‐anaesthetized, paralysed cats. 2. Seventeen afferent‐neurone pairs were successfully stained and their receptive fields determined. Ten of the pairs had s.c.t. neurones with a field containing that of the hair follicle afferent and seven pairs had separate fields on the hind limb. 3. Where the afferent fibre's field was outside the neurone's field there were no indications of synaptic contacts between the two neuronal elements. 4. Synaptic contacts were always observed (at the light microscope level) for the ten pairs with the hair afferent's receptive field contained within the s.c.t. cell's field. Contacts were always made by the branches of only a single collateral from the hair follicle afferent fibre. The numbers and locations of synaptic contacts were related to the relative positions of the receptive field: where the hair follicle afferent's field was centrally placed there were many (forty to sixty) contacts on proximal dendrites; where the hair follicle afferent's field was peripherally placed in the s.c.t. cell's receptive field there were few contacts (two to thirteen) and these were peripherally placed on the dendritic tree. Where the primary afferent fibre had a centrally placed field contacts upon dendritic spines were observed. 5. The results are discussed in terms of the synthesis of receptive fields and the organization of neuronal connexions within the mammalian spinal cord.
Gastric acid response to pylorus ligation in rats: is gastrin or histamine involved?
Authors: Alumets J. , Ekelund M. , Håkanson R. , Hedenbro J. , Rehfeld J. F. , Sundler F. , Vallgren S.
Published: December 2014

1. Pylorus ligation stimulated the acid output in vagally intact rats. The serum gastrin concentration and the gastric mucosal histamine content were not affected. The gastric histidine decarboxylase activity was initially slightly elevated and then greatly reduced (12‐20 hr after ligation).

2. Pylorus ligation stimulated the acid output in chronically, but not in acutely, vagotomized rats. Chronic vagotomy raises the serum gastrin concentration, the gastric histamine content and histidine decarboxylase activity. The serum gastrin concentration was further raised by pylorus ligation. The histamine content was initially lowered but returned to preligation values after 20 hr. The histidine decarboxylase activity first decreased, but increased to very high levels 5‐6 hr after ligation. Twelve hours after ligation it was lower than before ligation.

3. Following pylorus ligation pentagastrin and histamine stimulated the acid output in vagally intact and in acutely vagotomized but not in chronically vagotomized rats. By contrast, pentagastrin raised the histidine decarboxylase activity in vagally intact and in chronically vagotomized, but not in acutely vagotomized rats.

4. The two major populations of endocrine cells of the oxyntic gland area (ECL cells and A‐like cells) are argyrophil, store histamine and are capable of taking up exogenous DOPA and of decarboxylating it to dopamine which is retained in the cytoplasm for several hours. As evidenced by light and fluorescence microscopy pylorus ligation did not affect their argyrophilia or their ability to produce and store dopamine.

5. Pylorus ligation caused ultrastructural changes in the gastrin cells of the pyloric gland area and in the histamine‐storing ECL and A‐like cells of the oxyntic gland area. The two endocrine cell types in the oxyntic gland area were enlarged by pylorus ligation, more so after 16 hr than after 4 hr. The size of the gastrin cells seemed unaffected. In all three cell types pylorus ligation reduced the number of cytoplasmic granules. There was no increase in the Golgi area or in the endoplasmic reticulum in any of the endocrine cell types of the oxyntic gland area. It appears unlikely that the ultrastructural changes of the ECL and A‐like cells reflect an increased rate of histamine mobilization.

6. The acid response to pylorus ligation probably reflects neuronal reflex mechanisms exclusively. There is no evidence that gastrin or histamine released from gastric endocrine cells mediate the response.
Electrophysiological studies of new‐born rat nodose neurones in cell culture.
Authors: Baccaglini P I , Cooper E
Published: December 2014

1. Neurones of the nodose ganglion of the vagus nerve were dissociated from new‐born rats and grown in the virtual absence of non‐neuronal cells and in the presence of nerve growth factor. 2. The resting potentials of the neurones ranged from ‐40 to ‐80 mV. Action potentials were of short duration, with no inflexion on the falling phase; others were of longer duration with a hump on the falling phase. 3. The inward current of the action potential was carried either predominantly by Na+ or by Na+ and Ca2+. 4. Tetrodotoxin (1 microM) blocked the Na+ channels of some neurones but in other neurones the Na+ channels were partially or completely resistant to tetrodotoxin (1‐10 microM). 5. Many neurones formed excitatory synapses on neighbouring neurones which were blocked or greatly reduced by conventional ganglionic nicotinic antagonists. This indicates that these neurones secreted ACh and expressed ACh receptors at these synapses. 6. The accompanying paper (Baccaglini & Cooper, 1981) reports the effect of co‐culturing nodose neurones with non‐neuronal cells on the expression of functional nicotinic receptors.
Changes in spectral reflexions from the iridophores of the neon tetra.
Authors: Lythgoe J N , Shand J
Published: December 2014

1. The iridescent stripe of the freshwater teleost, the neon tetra, changes from green in the daytime to violet‐blue at night. 2. Spectral reflectance measurements were used to follow these colour changes. 3. Light causes a shift in reflectance to longer wavelengths in living fish and in isolated tissue from the lateral stripe. The change is reversed in darkness. 4. The spectral reflectance shifts to longer wavelengths when the fish is disturbed in darkness. No such colour changes were seen in fishes kept alive in 10(‐4) M‐reserpine. 5. Hypotonic Ringer solution causes a reflectance shift to longer wavelengths and hypertonic solution causes a shift to shorter wavelengths. 6. The iridescent reflexions from the lateral stripe which is continued across the iris originate from iridophores in the dermis. These iridophores contain regular stacks of broad, double‐sided hexagonal plates that are about 10 nm thick. Each plate is contained within a pouch in the cytoplasm and is separated from its neighbour by approximately one quarter the wavelength of light. 7. A distinction is drawn between the physiologically active iridophores in the lateral stripe and iris that have broad hexagonal crystal plates which are very thin and the physiologically inactive iridophores that are also found in the iris, but in addition are found on the flanks below the lateral stripe, and on the head. These iridophores contain hexagonal crystals that are usually narrower than the active type, but are about 60‐100 nm thick.
Feline cerebral veins and arteries: comparison of autonomic innervation and vasomotor responses
Authors: Edvinsson Lars , McCulloch James , Uddman Rolf
Published: December 2014

1. The innervation of feline cerebral (pial) vessels by nerve fibres containing noradrenaline, substance P or vasoactive intestinal polypeptide (VIP) has been examined using the Falck—Hillarp histo‐fluorescence method and immunohistochemical techniques. Cerebral veins were shown to be innervated by nerve fibres containing noradrenaline, substance P or VIP. Nerve fibres containing noradrenaline were the most numerous, while fibres containing substance P were observed least frequently in both types of vessel. For each putative neurotransmitter, the density of the innervation of the cerebral veins was less than that of cerebral arteries.

2. The vasomotor responses of individual pial arteries and veins on the convexity of the cerebral cortex to perivascular micro‐injection of noradrenaline, substance P and VIP were examined in twenty‐five cats anaesthetized with α‐chloralose.

3. The perivascular micro‐application of noradrenaline resulted in pronounced dose‐dependent reductions in the diameter of pial veins (maximum calibre reduction: 32±3% noradrenaline 10−5 M) and arteries (22±3% noradrenaline 10−5 M). Pial veins were more sensitive to noradrenaline than were pial arteries tested under similar conditions. The reductions in the diameter of cerebral veins and arteries resulting from the administration of noradrenaline could be attenuated by the concomitant micro‐application of phentolamine (10−6 M).

4. The perivascular micro‐application of substance P effected significant dose‐dependent increases in the calibre of pial veins (maximum calibre increase: 16±4% substance P 10−7 M) which were of a similar magnitude to those observed in pial arteries in response to this peptide (21±4% substance P 10−6 M).

5. The perivascular micro‐application of VIP resulted in small increases in the calibre of pial veins (maximum calibre increase: 9±2% VIP 10−8 M) which were proportionately smaller than those observed in pial arteries in response to this peptide (23±5% VIP 10−7 M).
Slowing effects of dopamine and calcium‐channel blockers on frequency of sodium spikes in rat pars intermedia cells
Authors: Douglas W. W. , Taraskevich P. S.
Published: December 2014

1. Spontaneous discharge of action potentials (Na spikes) in cells isolated from rat pars intermedia was slowed or arrested by Co2+, Ni2+ or Mn2+, which block voltage‐dependent Ca channels in these cells. The amplitude of persisting spikes was undiminished. The effects resembled those of dopamine.

2. Action potential frequency decreased when the Ca2+ concentration was lowered to 0·1 mM and increased when the Ca2+ concentration was raised from this level to 1 mM or 2 mM or when Ba2+ (2 mM) was introduced. These effects, together with those of Co2+, Ni2+ and Mn2+, are consistent with the possibility that Ca2+ participates in the regulation of spike discharge.

3. Verapamil, methoxyverapamil (D600), and nifedipine reduced the amplitude of the individual Na spikes in concentrations that had little effect on voltage‐dependent Ca channels. Action potential frequency was comparatively little affected by these drugs.

4. K+ (15 mM) stimulated action potential frequency and this effect too was suppressed by dopamine or Co2+.

5. The effect which dopamine had of slowing spontaneous discharge, like the inhibitory effect on secretion, was blocked by metoclopramide. But otherwise the mechanism is unclear: dopamine blocked voltage‐dependent Ca channels in some cells but not in most others.

6. The effects of K+ and Ba2+ of eliciting spikes, the suppression of Na‐spike discharge by Co2+ and related Ca‐channel blocking cations, and the unspecific effects of the organic ‘Ca channel blockers’, all have implications for the use of these substances as tools to analyse stimulus—secretion coupling.
The effects of nucleus raphe magnus lesions on an ascending thermal pathway in the rat.
Authors: Taylor D C
Published: December 2014

1. In the thalamus and hypothalamus of rats, anaesthetized with Urethane, single unit recordings have been made from cells which respond to small innocuous changes in scrotal skin temperature applied with a water‐perfused brass thermode. 2. Once a scrotal temperature‐sensitive neurone had been isolated the brain stem was electrolytically lesioned through implanted tungsten electrodes to determine whether the input from the scrotal skin temperature sensors ascends through the brain stem lemniscal pathways or the mid‐line raphe nuclei. All recordings sites and lesions were identified histologically. 3. Thirty‐six neurones have been studied of which half were located in the ventrobasal thalamus, six were located in the anterior thalamic nuclei and the remainder were in the medial hypothalamus. 4. The nucleus raphe magnus was lesioned on eighteen separate occasions; in each case the temperature‐responsive activity of the thalamic or hypothalamic neurone was abolished. 5. Extensive brain‐stem lesions which spared only the mid‐line nucleus raphe magnus had no discernible effect on the responses of the thalamic or hypothalamic neurones to scrotal skin temperature. 6. The ascending pathway from the thermal sensors of the rat scrotal skin must pass through, or relay in, the nucleus raphe magnus.
Feed‐forward dendritic inhibition in rat hippocampal pyramidal cells studied in vitro
Authors: Alger B. E. , Nicoll R. A.
Published: December 2014

1. Intracellular recordings from CA1 pyramidal cells in the rat hippocampal slice preparation have been used to study the neuronal pathways involved in hippocampal synaptic inhibition.

2. When direct comparisons are made in a single pyramidal cell, orthodromic stimulation delivered to stratum (s.) radiatum in normal recording conditions is found to be more effective than antidromic stimulation in producing inhibitory post‐synaptic potentials (i.p.s.p.s).

3. Orthodromic i.p.s.p.s in normal conditions appear to be complex, multiphasic events, whereas antidromic i.p.s.p.s are relatively simple. The orthodromic i.p.s.p. involves both a GABA‐mediated dendritic component and a non‐GABA‐mediated component neither of which is activated by antidromic stimulation.

4. Barbiturates induce a late depolarizing phase of the orthodromic response, a ‘depolarizing i.p.s.p.’, which is mediated by GABA. The depolarizing i.p.s.p. is not produced by antidromic stimulation.

5. Injections of tetrodotoxin and bicuculline methiodide localized to either somatic or apical dendritic regions reveal that the depolarizing i.p.s.p. is produced by GABA released from neuronal elements in the dendritic field which acts on pyramidal cell dendrites.

6. The depolarizing i.p.s.p. is strongly temperature‐dependent and increases in amplitude and duration progressively as slices are cooled from 37 to 22 °C.

7. Depolarizing i.p.s.p.s can be produced by orthodromic stimulation in s. oriens as well as in s. radiatum. In each case the depolarizing i.p.s.p.s appear localized to the dendrites in the field stimulated.

8. We conclude that the depolarizing i.p.s.p. evident in the presence of barbiturates is caused by the same synaptic release of GABA which in normal conditions produces hyperpolarizing dendritic i.p.s.p.s.

9. Numerous comparisons between orthodromic and antidromic stimulation indicate that dendritic i.p.s.p.s are activated by feed‐forward pathways.
Pharmacological evidence for two kinds of GABA receptors on rat hippocampal pyramidal cells studied in vitro
Authors: Alger B. E. , Nicoll R. A.
Published: December 2014

1. The rat hippocampal slice preparation has been used in conjunction with intracellular recording and ionophoresis to study the action of γ‐aminobutyric acid (GABA) on CA1 pyramidal cells.

2. GABA elicits a hyperpolarizing (h.) response at the soma. The reversal potential of this h. response is the same as for inhibitory post‐synaptic potentials (i.p.s.p.s) evoked by stimulating pyramidal cell axons.

3. GABA elicits primarily depolarizing (d.) responses when applied to the apical dendrites, but h. responses can also be found.

4. The GABA antagonists bicuculline methiodide, picrotoxin, penicillin, and pentylenetetrazole are all ten to one hundred times more potent on the d. response than on the h. response. Hyperpolarizing responses are uncovered in the dendrites when intermediate doses of these drugs block the d. response.

5. The GABA analogue, 4,5,6,7‐tetrahydroisoxazolo [5,4‐c]pyridine‐3‐ol (THIP), which has been proposed to activate synaptic receptors preferentially in other systems, elicits h. responses in the dendrites. It is one seventh as potent as GABA in eliciting d. responses.

6. Pentobarbitone enhances d. responses to a much greater extent than h. responses, while diazepam enhances h. responses to a greater extent.

7. Nipecotic acid, low temperature, and low sodium media all increase the size of d. responses to ionophoretically applied GABA indicating that an active uptake process limits their size.

8. We conclude that h. responses reflect the activation of synaptic receptors which are highly concentrated on the pyramidal cell soma—initial segment, but are also present on the dendrites. Depolarizing responses, which are evoked in the dendrites, reflect the activation of extrasynaptic receptors.

9. We propose that an ordinarily undetectable amount of synaptically released GABA can ‘spill’ over onto extrasynaptic (d.) receptors. Depolarizing receptor activation can be detected in the presence of pentobarbitone. Spillover is markedly enhanced at subphysiological temperatures presumably due to enhanced release of GABA and impairment of the GABA uptake system.
Cholinergic and catecholaminergic receptors in the Xenopus oocyte membrane
Authors: Kusano K. , Miledi R. , Stinnakre J.
Published: December 2014

1. Neurotransmitter‐receptors in the membrane of Xenopus oocytes have been studied using electrophysiological techniques. Neurotransmitters and related agents were applied while recording either membrane potential or membrane current. The majority of ovarian oocytes used were at stages IV and V.

2. Three types of oocytes were examined: inner ovarian epithelium covered (e.c.) oocytes; epithelium manually removed (e.r.) oocytes; and collagenase treated (c.t.) ooctyes.

3. Ovarian oocytes are sensitive to some cholinergic and catecholaminergic agents. Responses to serotonin were seldom observed and when present were much weaker than responses to other agents. No responses were observed to the amino acids: aspartate, glutamate, γ‐aminobutyric acid, and glycine; or to octopamine and histamine.

4. Acetylcholine (ACh) usually depolarized the membrane, in a dose‐dependent manner, with threshold concentrations as low as 10−9
m. The ACh‐potential was due to an increase in Cl permeability and had a reversal potential around — 19 mV. The intracellular Cl ion activity, measured with a Cl‐ion sensitive micro‐electrode, was about 65 m
m and the estimated Cl‐ion equilibrium potential, ECl, agreed with the reversal potential of the ACh‐potential.

5. Curare (10−4
m), tetrodotoxin (10−6
m), or α‐bungarotoxin (10−6 g/ml.) did not block the response to 10−6
m‐ACh; whereas atropine (10−7
m) blocked it. No response to nicotinic agents (e.g. nicotine, 1,1‐dimethyl‐4‐phenylpiperazinium) was observed. These results suggest that the ACh receptors in the oocyte membrane are muscarinic in nature.

6. The apparent latency of the ACh potential, examined by ionophoretic application of ACh to e.r. oocytes and c.t. oocytes, ranged from 0·5 sec to over 20 sec. Intracellular injection of ACh was without effect.

7. Responses to catecholamines were observed mostly in e.c. oocytes; while in e.r. and c.t. oocytes they were rare and of very small amplitudes.

8. The usual response to both dopamine and (—)‐epinephrine was a transient hyperpolarization manifested by an initial increase in K‐permeability followed by a decrease. The latency of these responses ranged from 10 sec to over 30 sec and their reversal potential was nearly — 100 mV, which coincided with EK.

9. Oocytes responded to the β‐adrenergic receptor agonist, isoproterenol, as well as (—)‐epinephrine. Pre‐treatment with the β‐adrenergic receptor blocker, propranolol, abolished the response to both (—)‐epinephrine and (—)‐isoproterenol. The dopamine potential was also reduced considerably. Both the α‐adrenergic receptor agonist, phenylephrine, and the α‐adrenergic receptor blocker, phentolamine, were without effect.

10. Maturation of the oocytes, induced in vivo by gonadotropin or in vitro by progesterone, led to loss of responsiveness to both cholinergic and catecholaminergic agents.
An electrophysiological study of somatic and visceral convergence in the reflex control of the external sphincters
Authors: McMahon S. B. , Morrison J. F. B. , Spillane Kathy
Published: December 2014

1. Mass wave and single unit discharges have been recorded from pudendal efferents innervating the external anal and urethral sphincters in chloralose anaesthetized or decerebrate cats.

2. Reflex discharges in these neurones were elicited by electrical stimulation of the contralateral pudendal nerve, the posterior cutaneous nerve of thigh, or the vesical or colonic branches of the pelvic nerve. The latencies of the evoked responses were 5·5‐20 msec. The vesical branches of the pelvic nerve produced discharges less consistently than the other nerves.

3. Irrespective of whether afferent stimulation produced an early evoked response there was always a prolonged period of depression of pudendal nerve excitability following the stimulus. Condition—test interactions showed that this depression began within 50 msec of the stimulus and that its duration varied between 150 and 2500 msec in single units, with a modal value of 500 msec.

4. No evoked response or depression of excitability was seen when afferents in the hypogastric or lumbar colonic nerves were stimulated.

5. Increasing intravesical or intracolonic pressure, within physiological limits, produced a graded reduction in the size of evoked discharges.

6. Short trains of stimuli (four shocks in 20 msec) applied to the raphé nucleus, were capable of inhibiting test responses in pudendal efferents for periods of up to 800 msec.

7. The possible functional roles of two groups of sphincteric reflex interneurones, with either excitatory or inhibitory receptive fields, are discussed.
The effect of horizontal‐plane environment on the development of binocular receptive fields of cells in cat visual cortex
Authors: Hänny P. , von der Heydt R.
Published: December 2014

1. The different perception of vertical in the two eyes (Helmholtz, 1864) was interpreted as an adaptation of cortical binocular receptive fields to the bias distribution of orientation disparity in the visual environment resulting from the relative frequency of contours in horizontal planes below eye level (ground, table) compared to other orientations in space.

2. Kittens were reared in environments where visible contours were confined to a horizontal plane which was the floor for two kittens and the ceiling for two other kittens. The floor tended to produce negative, the ceiling positive, orientation disparities. In either case, the disparities were maximal about the vertical retinal meridians and zero at the horizontal meridian. The preferred stimulus orientations of binocular neurones in area 17 of the visual cortex were determined at 3‐4 months age in these four kittens and in seven normal cats for control. Automatic stimulus variation, quantitative analysis, and eye drift correction were used.

3. In the ‘floor cats’ neurones with near‐vertical orientations showed a mean interocular angle between the preferred orientations of ‐8.7° relative to neurones with near‐horizontal orientations; in the ‘ceiling cats’, the angle was +2.8°; in the normal cats it was ‐0.4°.

4. Since these angles are independent of the alignment of the eyes, the difference between floor cats and ceiling cats reflects different functional connexions at cortical level. This indicates that the orientations of the developing receptive fields can be modified by visual experience.

5. These observations in kittens suggest that the perceptual difference between the eyes in man is also caused by early visual experience.
Behaviour of human motor units in different muscles during linearly varying contractions
Authors: de Luca C. J. , LeFever R. S. , McCue M. P. , Xenakis A. P.
Published: December 2014

1. The electrical activity of up to eight concurrently active motor units has been recorded from the human deltoid and first dorsal interosseous (f.d.i.) muscles. The detected myoelectric signals have been decomposed into their constituent motor‐unit action potential trains using a recently developed technique.

2. Concurrently active motor unit behaviour has been examined during triangular force‐varying isometric contractions reaching 40 and 80% of maximal voluntary contraction (m.v.c.). Experiments were performed on four normal subjects and three groups of highly trained performers (long‐distance swimmers, powerlifters and pianists).

3. Results revealed a highly ordered recruitment and decruitment scheme, based on motoneurone excitability, in both muscles and in all subject groups.

4. Differences were observed between the initial (recruitment) and final (decruitment) firing rates in each muscle. These parameters were invariant with respect to the force rates studied, although some differences were observed among subject groups.

5. In general, firing rates of f.d.i. motor units increased steadily with increasing force (up to 80% m.v.c.). The firing rates of deltoid motor units rose sharply just after recruitment and then increased only slightly thereafter.

6. Recruitment was found to be the major mechanism for generating extra force between 40 and 80% m.v.c. in the deltoid, while rate coding played the major role in the f.d.i.

7. The potential of rate coding for increasing force levels up to m.v.c. is discussed.
Stimulation of calcium‐dependent release of labelled protein from pulse‐labelled mouse pituitary intermediate lobe tissue
Authors: Thornton V. F.
Published: December 2014

1. The effect of K depolarization on the release of labelled protein from pulse‐labelled intermediate lobe tissue of mouse pituitaries has been studied.

2. Depolarization briefly stimulated Ca‐dependent release of labelled protein. Co (2·5 mM) and verapamil (0·08 mM) reversibly blocked stimulation. Efflux of 45Ca was also briefly stimulated by depolarization, but not in the presence of Co or verapamil, nor in the absence of Ca.

3. The response to maintained depolarization quickly inactivated. Inactivation probably resulted from Ca‐channel inactivation rather than exhaustion of available labelled protein, since responses different in magnitude but of constant time course could be obtained by depolarization in different concentrations of Ca. In addition, much more labelled protein could be released by exposure to Ba.

4. Depolarization did not cause a response if the Ca concentration was 0·4 mM or less; neither did inactivation occur in these conditions, and a response occurred as soon as the Ca concentration was raised. Two separate responses could be generated by a stepwise increase in the Ca concentration during maintained depolarization. The magnitude of the two responses together was similar to the magnitude of one response at the higher Ca concentration.

5. Recovery from inactivation was complete after about 20 min in normal K. However, recovery also occurred during maintained depolarization provided the Ca concentration was reduced sufficiently. Recovery was complete at 0·4 mM‐Ca or less, and at higher concentrations the extent of recovery depended on the Ca concentration selected.

6. It is concluded that depolarization opened potential‐dependent Ca channels permitting Ca entry and causing the release of labelled products. The response was brief probably because the Ca channels were inactivated. Since the channels were not inactivated by depolarization in low Ca, inactivation may result from Ca entry.
Short‐ and long‐term effects of paralysis on the motor innervation of two different neonatal mouse muscles
Authors: Brown M. C. , Hopkins W. G. , Keynes R. J.
Published: December 2014

1. A study was made of short‐ and long‐term effects of paralysis induced by type A botulinum toxin on the development of innervation of mouse muscles. The toxin was injected locally over the tensor fasciae latae (t.f.l.) and gluteus muscles at various times after birth, and the innervation was later examined by intracellular recording and by a histological technique using a reduced silver stain for axons.

2. Paralysis induced at 0‐4 days of age delayed but did not prevent the eventual elimination of nearly all focal multiple innervation in gluteus muscle fibres, whereas in t.f.l. up to 50% of the fibres remained focally innervated by more than one axon for at least 120 days. There was an associated reduction in the number of muscle fibres in t.f.l. of between 50 and 70%. The biggest reduction in the number of gluteus fibres was under 40%.

3. In the t.f.l., paralysis begun at 6‐9 days caused the extent of single‐site polyneuronal innervation to increase above the level existing at the time of paralysis. Histologically this increase was seen to be due at least in part to the stimulation of nodal sprout growth from a limited number of nodes.

4. Motor nerve terminal sprouts were evoked by paralysis at all ages. In mice injected before 4 days of age recovery from the toxin occurred rapidly and without the formation of ectopic synapses by sprouted motor terminals; however, intrafusal motor nerves also sprouted and established a permanent ectopic innervation on surrounding extrafusal muscle fibres.

5. The following conclusions are drawn. (a) In some but not all muscles, neonatally induced paralysis can not only temporarily halt elimination of polyneuronal innervation but actually lead to an increase; it is suggested tentatively that this occurs only during the neonatal period because of the availability at that time of endoneurial pathways associated with normal polyneuronal innervation, rather than because of any special neuronal growth potential then. (b) Permanent establishment of focal polyneuronal innervation is due not to stability of presynaptic elements maintained past a critical developmental stage but is associated with substantial losses of muscle fibres, leading to a high ratio of nerve fibres to muscle fibres.
Inotropic and electrophysiological effects of histamine on human ventricular heart muscle.
Authors: Eckel L , Gristwood R W , Nawrath H , Owen D A , Satter P
Published: December 2014

1. The effects of histamine were investigated on mechanical and electrophysiological parameters in isolated electrically driven human ventricular papillary muscles. The effects of cimetidine and propranolol on histamine responses were also investigated. 2. The effects of histamine were compared with those of noradrenaline, isoprenaline, dimaprit, a selective H2‐receptor agonist, and a cyclic AMP derivative, 8‐(4‐chlorphenylthio) cyclic AMP. 3. The effects of histamine and dimaprit and the effects of cimetidine on histamine responses were also investigated in guinea‐pig right ventricular papillary muscles in order to allow a comparison with human papillary muscles. 4. In human papillary muscles, histamine caused concentration‐dependent increases in the force of contraction and reductions in both time‐to‐peak tension and time‐to‐half‐maximal relaxation. Histamine simultaneously caused distinct changes in the action potential configuration with increases in the height and duration of the plateau phase and an increase in the over‐all action potential duration. 5. Noradrenaline and isoprenaline produced similar responses to histamine, as did 8‐(4‐chlorphenylthio) cyclic AMP, consistent with the view that the effects of histamine as well as the beta‐adrenoceptor agonists on human ventricle, were associated with cyclic AMP mediated increases in calcium‐dependent slow inward current.
Effect of pancreatic juice on basal pancreatic and gastric secretion in dogs.
Authors: Magee D F , Naruse S
Published: December 2014

1. The effect of duodenal infusion of pancreatic juice on basal pancreatic and gastric secretion was studied in five conscious dogs provided with pancreatic fistulae, gastric fistulae and Heidenhain fundic pouches. 2. Pancreatic juice and trypsin stimulated a pancreatic secretion rich in protein. 3. Autodigested juice without proteolytic activities also stimulated the secretion. Boiling the juice or addition of trypsin inhibitor to the juice diminished the augmented secretion. 4. It seems, therefore, that trypsin is necessary even in proteolytically inactive autodigested juice for pancreatic stimulation. 5. In dogs, unlike rats and pigs, basal pancreatic secretion is not under negative feed‐back control by duodenal tryptic activity. 6. Basal gastric secretion was not significantly changed by duodenal infusion of pancreatic juice.
Fibre types in chicken skeletal muscles and their changes in muscular dystrophy
Authors: Barnard E. A. , Lyles Joan M. , Pizzey J. A.
Published: December 2014

1. Five major fibre types in chicken skeletal muscles are recognized, based upon their histochemical and morphological characteristics. A classification of these which is readily related to a commonly used classification of mammalian muscle fibre types is given.

2. Seven muscles of the chicken were analysed in recognizing this range of fibre types. The proportions of the different types in each of these were determined. In some cases a gradient of fibre type composition exists across a single muscle.

3. Measurements of muscle contraction were used in defining tonic muscles, which contain two fibre types. It was shown that in addition to the anterior latissimus dorsi (a.l.d.), previously well known to be a tonic muscle, two other muscles, the plantaris and the adductor profundus, are of the same class, but differ subtly from the a.l.d. in certain features. Gross red colouration is not a useful diagnostic feature of slow muscles, since the tonic adductor profundus, for example, is white.

4. Fibres similar histochemically to mammalian type I (slow‐twitch) occur in some of the avian twitch muscles investigated. These are oxidative in character, and despite the fact that they are multiply innervated we suggest that these are avian slow‐twitch fibres.

5. The patterns of cholinesterases found in a skeletal muscle correspond to its fibre type composition, with regard to both the concentrations and the proportions of the multiple forms of enzyme present. The distinctive patterns of those forms of acetylcholinesterase in the different fibre types are described.

6. The fibre type composition is changed by inherited muscular dystrophy in a characteristic manner. This change has so far been found (at the earlier stages of the disease) only in the muscles with a predominance of type II B fibres in the normal chicken. Pathological changes within the fibres occur selectively in the type II B fibres, but there are exceptions to this and the effect can be greatly modified by the type of neighbouring fibres.
Origin of the light peak: in vitro study of Gekko gekko
Authors: Griff Edwin R. , Steinberg Roy H.
Published: December 2014

1. The light peak is a large, light‐evoked increase in standing potential recorded in mammals, birds and reptiles. We have studied the cellular origin of the light peak in an in vitro preparation of neural retina‐pigment epithelium (r.p.e)—choroid from the lizard, Gekko gekko. The tissue was mounted between two separate bathing solutions; the trans‐tissue potential was recorded retinal‐side positive; micro‐electrodes were introduced to measure the trans‐epithelial potential (t.e.p.) and to record intracellularly from the r.p.e.

2. A 10 min stimulus of diffuse white light evoked an increase in trans‐tissue potential that reached maximum amplitude, the light peak, about 15 min after stimulus onset. Since the light peak is present in vitro, it must originate in either the neural retina or the r.p.e.

3. A micro‐electrode was positioned in the subretinal space and the trans‐retinal potential and t.e.p. were measured simultaneously. A 10 min stimulus produced an increase in t.e.p. equal in magnitude and time course to the trans‐tissue light peak; no potential was present across the retina. The light peak is therefore generated solely across the r.p.e.

4. Intracellular r.p.e. recordings were made to determine whether the light peak was generated at the apical or basal membrane or across the paracellular shunt. A 10 min stimulus first caused a hyperpolarization of both membranes with a time course similar to the r.p.e. c‐wave followed by a depolarization of both membranes with the time course of the light peak. We conclude that whereas the r.p.e. c‐wave results from a hyperpolarization of the apical membrane, the light peak is generated by a depolarization of the basal membrane of the r.p.e.

5. Changes in tissue resistance, Rt, and the ratio of apical to basal membrane resistances, a, were monitored during the light peak by passing current across the tissue and measuring the appropriate current‐induced voltages. Rt decreased and a increased with the time course of the light peak. Assuming that the paracellular shunt resistance is constant, we conclude that the light peak is accompanied by an increase in basal membrane conductance.

6. This and the following paper present the first direct demonstration of an interaction between the neural retina and the basal membrane of the r.p.e. The light peak, initiated by absorption of light by photoreceptors, results in a depolarization and conductance increase of the basal membrane.
Compensatory increases in milk secretion in response to unilateral inhibition by colchicine during lactation in the goat.
Authors: Henderson A J , Peaker M
Published: December 2014

1. Milk secretion in one mammary gland of goats was temporarily inhibited by intramammary treatment with colchicine at weeks 6, 12, 18, 24 and 30 of lactation. The magnitude of the inhibition was similar at all stages when compared with milk yield before the experiment. 2. The untreated gland partially compensated for the decreased rate of milk secretion by significantly increasing its own rate of secretion. There was no significant effect of stage of lactation on this response. 3. The rapidity of the compensatory response suggests that existing secretory cells increased their rate of secretion, and therefore that the mammary secretory cells are not secreting at their intrinsic maximum at any stage of lactation. 4. In later stages of lactation (weeks 18, 24 and 30) the increases in the untreated gland were more pronounced in afternoon milkings (8 h milking interval) than in morning milkings (16 h interval. At week 30 only, the rate of secretion before treatment was similarly lower in the 16 h period. It is proposed that an additional limitation is imposed on secretion during the relatively long period of milk accumulation as lactation advances and declines. 5. The results are discussed in relation to rate‐limitations on milk secretion with respect to substrate supply and possible systemically active mammary factors.
Uptake and action of a disulphonic stilbene (SITS) in the perfused guinea‐pig liver: a comparison with bromsulphthalein.
Authors: Rutishauser S C
Published: December 2014

1. Livers were perfused with a Krebs‐Ringer bicarbonate buffer in a single‐pass perfusion system. Bile secretion was maintained by infusion of secretin. 4‐Acetamido‐4'‐isothiocyano‐2,2'‐stilbene disulphonic acid (SITS) was added to the perfusate to give concentrations ranging between 5 x 10(‐6) and 10(‐4) M. 2. SITS was extracted from the perfusate by the liver (V, 0 . 15 mumol/min per g liver; Km 8 . 6 x 10(‐5) M) and excreted in bile in a modified form (bile/plasma ratio: 50‐170; maximum rate of excretion: 25 nmol/min per g liver wet wt). 3. The rates of uptake and excretion of bromsulphthalein (BSP) were similar to those for SITS, with the exception that the affinity of BSP for hepatic uptake was greater (Km 1 . 8 x 10(‐5) M). 4. Both SITS and BSP decreased the rate of bile flow. A 50% reduction in bile flow was attained in each case at an estimated drug content of the liver of 1 . 5 mumol/g wet wt. 5. Unlike other cells the hepatocyte appears to be readily penetrated by SITS, and it is suggested that SITS inhibits bile secretion by inhibiting an intracellular mechanism which could be mitochondrial in location.
The calcium component of the action potential in spinal motoneurones of the rat.
Authors: Harada Y , Takahashi T
Published: December 2014

Intracellular recordings were made from motoneurones of the neonatal rat (1‐14 days old) spinal cord isolated and perfused in vitro. An increase in extracellular Ca2+ concentration from 2 to 20 mM produced an increase in the amplitude of the after‐depolarization (a.d.p.), while replacement of Ca2+ by Mn2+ virtually abolished the a.d.p. These changes in the a.d.p. occurred in parallel with those in the after‐hyperpolarization (a.h.p.). The amplitudes of the a.d.p. and the a.h.p. were dependent upon the membrane potential: hyperpolarization increased the a.d.p. and decreased the a.h.p.; the opposite effects were produced by depolarization. The presence of Ca2+ spikes was demonstrated either by suppression of the voltage‐dependent K+ conductance with tetraethylammonium (TEA) or after blocking the Na+ spike. The Ca2+ spike was all‐or‐none in nature and blocked by Mn2+ or Co2+. The a.h.p. amplitude was dependent upon the extracellular K+ concentration but also correlated with the amplitude of the Ca2+‐dependent response. It is concluded that the a.d.p. is a Ca2+‐dependent potential whose amplitude is under normal conditions markedly reduced by the voltage‐dependent K+ conductance; the a.h.p. seems to be produced by an increase in the Ca2+‐dependent K+ conductance.
Measurement of pulmonary venous and arterial pH oscillations in dogs using catheter tip pH electrodes.
Authors: Chakrabarti M K , Cobbe S M , Loh L , Poole‐Wilson P A
Published: December 2014

Respiratory pH oscillations were studied in situ in the aorta and superior vena cava of rabbits, and in the pulmonary vein and aorta of open‐chested dogs, using catheter tip pH electrodes. Preliminary experiments on two spontaneously breathing rabbits showed pH oscillations of 0.006‐0.010 pH units in the ascending aorta at a respiratory rate of 40/min. No oscillations were apparent in the superior vena cava. In anaesthetized, ventilated dogs, the delay from the upstroke in airway pressure to the onset of the alkaline limb of the pH oscillation was 1.15 +/‐ 0.9 s in the pulmonary vein and 4.1 +/‐ 0.1 s in the descending aorta (mean + S.E. of mean, n = 28 tracings in four dogs). Pulmonary venous oscillations were equal to or larger in amplitude than those in the aorta. Aortic oscillations became proportionately smaller at shorter respiratory cycle lengths, although both were related to tidal volume. Stop flow experiments were performed using a pH electrode placed in situ in the left atrium inside a wide‐bore tube. A small fall in pH occurred when flow was stopped (‐0.0036 +/‐ 0.0012, mean +/‐ S.E. of mean, n = 22 recordings in four dogs). The findings were not dependent upon the phase of the oscillation at which flow was stopped. Mean plasma free haemoglobin was very low (1.6 mg/dl), indicating minimal haemolysis of the blood withdrawn past the electrode. It is concluded that the plasma CO2 hydration reaction is virtually at equilibrium by the time blood reaches the pulmonary vein.