bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of exercise on protein and electrolyte secretion in parotid saliva.
Authors: Dawes C
Published: December 2014

1. Ten subjects collected ten 1 min samples of parotid saliva at a constant flow rate 1‐2 hr before exercise, immediately after running 3‐8 miles and 3 hr after exercise. 2. Exercise had no significant effects on the concentration of sodium, potassium, calcium, magnesium, chloride, bicarbonate or inorganic phosphate. 3. Exercise caused a marked elevation in total protein concentration and in seven of the subjects the initial samples after exercise were cloudy due to protein precipitation. The precipitated protein could be dissolved in sodium EDTA. 4. The saliva samples collected immediately after exercise from the seven subjects in which precipitation occurred contained higher concentrations of protein, calcium and phosphate than in those of the other three subjects. 5. Electrophoretic analysis revealed that all proteins appeared to show a proportional increase in the cloudy saliva, as compared with the clear saliva but differential precipitation of certain proteins occurred in the former which was largely restricted to proteins having a high affinity for calcium phosphate. 6. Electronmicroscopic examination of centrifuged cloudy saliva produced after exercise revealed the presence of rounded droplets of homogeneous structure in contrast to the fine granular deposits produced in clear parotid saliva by in vitro procedures causing precipitation of calcium phosphate crystals on which protein adsorbed.
Arterial chemoreceptor‐like activity in the abdominal vagus of the rat.
Authors: Howe A , Pack R J , Wise J C
Published: December 2014

1. Centripetal activity in fibres in the ventral abdominal vagus nerve of the rat has been studied by recording from fine strands of the divided nerve within the abdomen. 2. In the starved animal, few spontaneously active fibres were located. A proportion of these, however, showed changes in activity in response to changes in F1 oxygen which were typical of arterial chemoreceptor afferent nerves. The resting discharge in these preparations was 0.8‐8.0 impulses/sec. In response to extreme hypoxic hypoxia, histotoxic hypoxia or acetylcholine, this discharge increased markedly, with a maximum mean activity of up to 25 impulses/sec. 3. Both the mean/S.D. ratio and statistical comparison with a ‘noise’ equation were used to assess the apparent random nature of the spike intervals. The former indicated that the spike intervals were random but the latter test was inconclusive. 4. We suggest that this chemoreceptor‐like activity originates from the abdominal vagal paraganglia and that these structures may be part of a more generally distributed chemoreceptor system.
Renin‐dependence of drinking induced by partial aortic obstruction in the dog
Authors: Fitzsimons J. T. , Moore‐Gillon M. J.
Published: December 2014

1. Inflation of a balloon implanted in the abdominal aorta above the level of the renal arteries was used to produce partial obstruction to aortic blood flow in trained, conscious mongrel dogs.

2. Following inflation, heart rate and arterial blood pressure downstream from the point of inflation fell, whilst arterial blood pressure upstream from the point of inflation rose. Central venous pressure was unaltered.

3. In sixteen out of eighteen experiments, balloon inflation led to drinking. Inflations maintained for 3 days led to a sustained increase in daily water intakes, but intakes of 0.9% NaCl were unaltered when both water and 0.9% NaCl were available to drink.

4. There was a significant inverse correlation between the amount drunk in the first 60 min following balloon inflation and the ratio of the change in the arterial pressure upstream of the obstruction to the change in pressure downstream of the obstruction.

5. In experiments where the inflation was maintained for 90 min, there was no further drinking between the 60th and 90th min. In experiments where the inflation was released after 60 min, there was another bout of drinking between the 60th and 90th min.

6. Plasma renin activity and plasma renin concentration both rose following balloon inflation. Drinking following balloon inflation was abolished by infusion of the competitive angiotensin II antagonist saralasin.

7. Inflation of an aortic balloon to a size that produced drinking in other experiments also led to a reduction in urinary water and electrolyte loss in fluid pre‐loaded dogs.

8. In conclusion, water intake in response to partial aortic obstruction above the level of the kidneys is caused by renin released from the kidneys. However, the dipsogenic effectiveness of the endogenous renin released is reduced as a result of the simultaneous increase in arterial pressure above the obstruction.
Age changes in neuromuscular junction morphology and acetylcholine receptor distribution on rat skeletal muscle fibres.
Authors: Courtney J , Steinbach J H
Published: December 2014

1. Neuromuscular junctions in the sternomastoid muscles of female Lewis rats were examined in animals up to 917 d old. 2. The average number of myelinated branches of terminal axons entering a junction increased with age of the animal, up to 400 d. This change could be described by a simple kinetic model which assumed that there was no influence of age on the ability of motoneurones to produce or maintain terminal branches, but that axons could produce or maintain only a limited number of branches. 3. There was a change in the over‐all junctional length with age, but there was a significant increase in the number of discrete regions of high ACh receptor density in junctions from older animals. 4. There was a gradual decrease in the number of ACh receptors per junction with age after about 500 d, and muscles from some rats older than 500 d had detectable numbers of extrajunctional ACh receptors. 5. The changes in the neuromuscular junction with increased age occurred gradually over adult life.
Mechanisms involved in the renal responses to intravenous and renal artery infusions of noradrenaline in conscious dogs.
Authors: Anderson W P , Korner P I , Selig S E
Published: December 2014

1. The renal haemodynamic and glomerular filtration rate (G.F.R.) responses to intravenous and intrarenal infusions of noradrenaline were studied in conscious dogs, either with or without prior blockade of angiotensin II formation with teprotide. 2. Infusion noradrenaline by either route resulted in dose‐related rises in plasma renin activity. 3. Pretreatment with teprotide reduced the rise in mean arterial pressure and abolished the rise in G.F.R. seen during intravenous infusions of noradrenaline (0.1, 0.2 and 0.4 microgram/kg . min). Noradrenaline also reduced filtration fraction more after teprotide pretreatment. 4. Renal blood flow rose and renal vascular resistance fell in response to I.V. noradrenaline infusions. This renal vasodilatation was unaffected by pretreatment of the dogs with teprotide, indomethacin or DL‐propranolol. However after pentolinium pretreatment, I.V. noradrenaline infusion caused a dose‐related renal vasoconstriction. 5. Infusion of noradrenaline into the renal artery (0.02, 0.05 and 0.1 microgram/kg . min) resulted in rises in mean arterial pressure and G.F.R. which were abolished by teprotide pretreatment. Filtration fraction rose when noradrenaline was administered alone but fell when it was infused after teprotide treatment. 6. Thus angiotensin II formed as the result of increased renin release acted to maintain G.F.R. and filtration fraction during noradrenaline infusion. In addition, I.V. noradrenaline infusions in conscious dogs caused reflex vasodilatation of the renal vasculature.
Effects of substance P on neurones of the inferior mesenteric ganglia of the guinea‐pig
Authors: Dun N. J. , Minota S.
Published: December 2014

1. The membrane effects of substance P on neurones of isolated inferior mesenteric ganglia and the underlying ionic mechanisms were investigated by means of intracellular recording techniques.

2. When applied to the neurones by superfusion, substance P (0.5 μ
m) caused a membrane depolarization; in a few neurones, the depolarization was preceded by a small hyperpolarization. Substance P effects were not altered in a low Ca2+/high Mg2+ solution or in a solution containing
d‐tubocurarine and atropine.

3. When the membrane potential was clamped manually at the resting level between ‐50 and ‐60 mV, substance P caused, in about an equal number of neurones, a slight to moderate decrease and also increase of membrane resistance; a brief increase occurred prior to the decrease of membrane resistance.

4. In neurones with high resting membrane potential (> ‐70 mV), substance P elicited a large depolarization accompanied by a marked increase in membrane resistance; the latter was probably due to anomalous rectification.

5. Conditioning hyperpolarization of the membrane close to the level of EK increased and decreased substance P‐induced depolarization in eleven and two neurones, respectively.

6. Substitution of external Na+ with an equimolar amount of either sucrose or Tris buffer markedly attenuated the depolarizing effect of substance P.

7. The substance P‐induced depolarization was diminished in a high K+ (10 m
m) solution, and it could be augmented when membrane was hyperpolarized to EK. On the other hand, the effect of substance P was not appreciably affected in a low Cl− solution.

8. It is concluded that substance P depolarizes the sympathetic neurones by increasing and decreasing membrane permeability to Na+ and K+, respectively, and that the concomitant membrane resistance change depends on interaction of GNa activation and GK inactivation.

9. The possibility that substance P is the transmitter mediating the non‐cholinergic slow excitatory potential elicited by repetitive preganglionic stimulation in the neurones of the inferior mesenteric ganglia is suggested.
Spinal neurones with long projections activated from the abdominal viscera of the cat
Authors: McMahon S. B. , Morrison J. F. B.
Published: December 2014

1. Recordings have been made from seventy‐three neurones responding to electrical stimulation of pelvic, hypogastric or lumbar colonic nerves, in decerebrate or anaesthetized cats. Fifty‐two of the units had long projections that ascended to the first cervical segment, and no units with visceral inputs were found to belong to the spino‐cervical tract. Twenty‐one units had long descending projections.

2. Twenty percent (i.e. 11/46) responded to parasympathetic (pelvic) nerve stimulation (group 1) whilst 80% (35/46) responded to stimulation of hypogastric and/or lumbar colonic nerves (group 2). Ninety percent of group 2 neurones also responded to pelvic nerve stimulation.

3. The electrical thresholds for activation of the units indicated that the largest peripheral nerve fibres responsible for the response were of the Aδ size.

4. Thirty‐one of the neurones had visceral mechanosensitive receptive fields; twenty‐one had simple receptive fields in the bladder (seven) or in the colon (fourteen), ten units had compound receptive fields. The response of units with simple receptive fields to mechanical stimulation were either inhibitory or excitatory, and slowly adapting or rapidly adapting. Forty‐two units appeared to have no visceral mechano‐sensitive receptive fields in spite of showing responses to visceral nerve stimulation.

5. Fifty percent of the units tested responded to innocuous somatic stimuli, mostly derived from muscle or joint receptors. Some of the units were found to respond to injections of bradykinin (10‐15 μg) into a hindlimb artery.

6. Group 1 had predominantly inhibitory visceral receptive fields, and somatic receptive fields in structures innervated from sacral segments of the spinal cord. Group 2 units all received inputs from visceral nerves entering the spinal cord over lumbar segments; many also received projections from sacral segmental inputs. These inputs showed an equal mixture of excitatory and inhibitory visceral receptive fields and convergence from somatic inputs arising from lumbar as well as sacral dermatomes. It seems likely that this group represents units originating in lumbar as well as sacral segments of the cord.

7. The possible role of these neurones as mediators of visceral sensations and visceral reflexes is discussed.
Cellular swelling in slices of rat renal outer medulla incubated in the presence of bovine serum albumin.
Authors: Law R O
Published: December 2014

1. Cells in slices of rat renal outer medulla incubated for up to 100 min in modified phosphate‐bicarbonate Ringer undergo reversible, concentration‐dependent swelling (increase in water content) in the presence of bovine serum albumin (b.s.a). 2. Swelling also takes place in the presence of dextran sulphate, but neutral dextran or polyvinylpyrrolidone are without effect. 3. Swelling due to b.s.a. is pH‐dependent, decreasing (relative to cell volume in the absence of b.s.a.) as pH is reduced. 4. Swelling due to b.s.a. is associated with the net cellular gain of Na+, the magnitude of which increases at pH is raised. 5. There is an accompanying pH‐independent net loss of cellular K+; at pH greater than about 6.20 this loss is smaller than the uptake of Na+, and cells thus show net gain of monovalent cation. 6. The relationships between pH and percentage increase in cell water content and between pH and percentage increase in cell osmotic content due to net gain of cation in the presence of 8% b.s.a. are coincident within the range pH 6.15‐‐7.60. 7. Studies on the volume of distribution of [125I]b.s.a. within slices suggests that more may bind to cells at low pH than at high pH.
The effects of electrical stimulation on sprouting after partial denervation of guinea‐pig sympathetic ganglion cells.
Authors: Maehlen J , Njå A
Published: December 2014

1. The effects of electrical stimulation of presynaptic and post‐synaptic cells on sprouting after partial denervation were examined in the guinea‐pig superior cervical ganglion with intracellular recording. The partial denervation reduced the mean number of preganglionic axons innervating each ganglion cell from about eleven to about two (Maehlen & Njå, 1981). 2. One week after partial denervation alone, the number of residual preganglionic axons innervating each superior cervical ganglion cell was increased by about 30%. This means that the number of ganglion cells contacted by each residual preganglionic axon was increased by the same amount, which represents an early stage of sprouting. 3. Preganglionic stimulation for 1 hr immediately after the partial denervation (with 100 pulses at 20 Hz every 25 sec) increased the rate of sprouting. Thus 1 week after partial denervation and preganglionic stimulation the number of residual preganglionic axons innervating each ganglion cell was increased by about 70%. Preganglionic stimulation had no similar effect on the innervation of normal ganglia. 4. The acceleration of sprouting caused by preganglionic stimulation was abolished by blocking ganglionic transmission with hexamethonium (30‐‐60 mg kg‐1 hr‐1 I.V.) during the stimulation. 5. Furthermore, the rate of sprouting of residual preganglionic axons was increased by electrical stimulation of the ganglion cells alone. 6. These results show that after partial denervation of the superior cervical ganglion, a period of impulse activity in ganglion cells enhances their subsequent ability to receive innervation from sprouts arising from residual preganglionic axons.
The ionic basis of concentration‐related effects of noradrenaline on the action potential of calf cardiac purkinje fibres.
Authors: Kass R S , Wiegers S E
Published: December 2014

1. Noradrenaline has paradoxical concentration‐dependent effects on the Purkinje fibre action potential. At concentrations greater than 500 nM, it shortens the action potential whereas at lower concentrations it prolongs the action potential. 2. We determined the dose‐‐response relation for Isi to noradrenaline in Purkinje fibres and found that a noradrenaline concentration of 126 nM produces a half maximal effect. 3. A maintained component of Isi was shown to have a similar response to noradrenaline. 4. The dose‐dependence of noradrenaline‐induced changes in Ix was determined. The half maximal noradrenaline concentration for this relationship was shown to be 133 nM. 5. The dose‐‐response relationships for Ix and Isi were not altered by variation in extracellular Ca2+. 6. Ix appears to be approximately twice as responsive as Isi to saturating doses of noradrenaline. 7. These data were incorporated in a computer‐generated reconstruction of the effects of noradrenaline on the action potential and are sufficient to account for the paradoxical effects of noradrenaline.
Inhibition of acetylcholine responses by intracellular calcium in Lymnaea stagnalis neurones.
Authors: Chemeris N K , Kazachenko V N , Kislov A N , Kurchikov A L
Published: December 2014

1. Acetylcholine (ACh)‐induced currents were studied in completely isolated Lymnaea stagnalis neurones using the voltage‐clamp technique. 2. The ACh‐activated pathways were shown to be selective for Cl‐ ions. 3. It was shown that membrane depolarization inhibits ACh‐induced conductance. This phenomenon was called ‘ACh response inactivation’. 4. Inactivation decreases after lowering the extracellular Ca2+ concentration or after blockade by Mn2+ of the electrically excitable Ca2+ channels. 5. In dialysed neurones an increase of the intracellular Ca2+ concentration inhibits the ACh‐induced conductance. 6. The conclusion is made that the inactivation of ACh response by depolarization is initiated by Ca2+ entering the neurone through the electrically excitable Ca channels. 7. The onset and the decay of the ACh response inactivation were studied by analysing the relaxations of the ACh‐induced current during and after the application of depolarizing pulses. The most conspicuous relaxation is a slow relaxation observed at the end of a long depolarizing pulse, which appears to reflect the return of the system from the inactivated state to the non‐inactivated one. 8. The slow relaxations observed during and after a depolarizing pulse appear correlated with variations of the intracellular Ca2+ concentration, and are distinct from faster relaxations observed in the hyperpolarizing range and attributed to the voltage dependence of the channel open‐time.
Structural and functional definition of the motor cortex in the monkey (Macaca fascicularis)
Authors: Sessle B. J. , Wiesendanger M.
Published: December 2014

1. The details of the organization of the motor cortex and its anterior and posterior border were investigated in three monkeys by a combination of techniques including intracortical microstimulation (i.c.m.s.), electrophysiological recording of cutaneous and muscle afferent inputs to single cortical neurones, and electrophysiological and anatomical identification of corticospinal neurones; in addition, data from these methods were related to cortical cytoarchitecture.

2. Almost 5000 individual cortical loci were tested with i.c.m.s. in the unanaesthetized monkeys. In this paper, we particularly consider the organization of the forelimb motor representation, and its relation to the representation of other parts of the body. I.c.m.s. thresholds of about 5 μA were common for evoking twitch movements and e.m.g. responses in distal forelimb and face, jaw and tongue muscles, but proximal forelimb, trunk and hind‐limb movements also sometimes had such low thresholds.

3. The fingers were found to be represented nearest the central sulcus, with horseshoe‐shaped bands of cortical tissue representing progressively more proximal muscles situated around this central ‘finger core’.

4. Cytoarchitectonically, the cortex having these low‐threshold motor effects was characteristic of area 4. There was also a close fit between the extent of this ‘excitable cortex’ and the extent of densely spaced corticospinal neurones identified electro‐physiologically or with horseradish peroxidase labelling. In subsequent mapping of forelimb afferents to the cortex when the animal was deeply anaesthetized, low‐threshold and short‐latency responses to muscle nerve stimulation were rarely found in this ‘excitable cortex’.

5. The anterior border could be clearly established by i.c.m.s. and by the sharp boundary of corticospinal neurones. It was noted that the motor cortex extends rostrally beyond area 4 and its anterior border appears to reside in the posterior part of area 6aα (Vogt & Vogt, 1919) although it is difficult to establish the precise transition from area 4 to area 6.

6. Posteriorly, the ‘micro‐excitable cortex’ was found to be limited to regions cytoarchitectonically delineated as area 4 and did not include area 3a. On the other hand, low‐threshold forelimb proprioceptive afferent inputs appeared restricted to area 3a neurones in the deeply anaesthetized animal. Corticospinal neurones were very dense in area 4, and there was a clear decrease in their occurrence in more caudal areas. However, scattered nests of corticospinal neurones were noted in areas 3a, 3b, 2, 1 and 5. It remains to be seen whether these scattered nests could be directly involved in motor control or whether they may modulate ascending somatosensory transmission, and whether they rely on sensory feed‐back or inputs from other central areas for their spinal effects.
Changes in holding and ion‐channel currents during activation of an ascidian egg under voltage clamp
Authors: Kozuka Masao , Takahashi Kunitaro
Published: December 2014

1. The unfertilized egg of an ascidian, Halocynthia roretzi, was activated by the divalent ionophore A23187 in natural or artificial sea water (nSW or ASW) or by an external solution containing a high concentration of Ca ions (high‐Ca ASW) under voltage‐clamp condition.

2. Activation current began with an abrupt increase in the holding current and decayed relatively slowly with a common time course in various ASWs. Activation current was both Na‐ and Ca‐dependent. The peak time, Tp, and the peak amplitude, D, of the activation current in nSW at 15 °C and ‐90 mV were 27 ± 4 sec and ‐1·50 ± 0·47 nA, respectively.

3. The currents through Na, Ca and anomalous K channels were evoked by test pulses with constant intervals in nSW and high‐Sr, high‐Ca and high‐K ASWs. Na‐channel current was enhanced during activation. In contrast, Ca‐channel current decreased. In high‐Ca, Na‐free ASW the Ca current through Na channels increased while the Ca current through Ca channels decreased. The time for the maximum of Na current, Tmax, was (7·2 ± 1·5) × 10 sec at 15 °C and index R, the ratio of the maximum amplitude to the amplitude before activation, was 2·31 ± 0·18 in nSW. The time for the minimum of Ca‐channel current, Tmin, was about 70 sec, being almost the same as Tmax of Na current.

4. The current through anomalous K channels increased initially and decreased later with a time lag behind the decrease in Ca‐channel current.

5. Both Tp of activation current and Tmax of Na current were reduced by raising the temperature. Q10 for Tp and Tmax was 2·2 and 2·3, respectively.

6. When the egg was activated in ASW containing scorpion toxin, the Na current through normal channels increased strongly while the Na current through toxinmodified channels increased less markedly.

7. There was no significant change in the total membrane capacity before and during activation.
Effect of castration on medial preoptic/anterior hypothalamic neurone responses to stimulation of the fimbria in the rat
Authors: Kendrick Keith M.
Published: December 2014

1. Single unit extracellular recordings were made from medial preoptic/anterior hypothalamic neurones in response to electrical stimulation of the ipsilateral fimbria. The effects of castration on neuronal responses were investigated and the pathway of the fimbria input analysed using multiple stimulation and selective lesions. The percentage of responsive medial preoptic/anterior hypothalamic neurones which had connexions with the medial forebrain bundle was also investigated.

2. Orthodromic action potentials were recorded from 192 medial preoptic/anterior hypothalamic neurones in twenty animals (ten gonadally intact and ten castrated). These neurones responded to a single shock stimulus applied to the ipsilateral fimbria by producing one or one to three action potentials followed by an inhibitory period (similar to simple and complex spikes found in hippocampus and cerebellum). A further forty‐eight neurones showed a post‐stimulus inhibition. Castration significantly reduced the percentage of medial preoptic/anterior hypothalamic neurones that responded reliably to 0·6 Hz stimulation, lengthened the inhibitory periods, reduced the percentage of neurones producing one to three action potentials and lengthened their interspike intervals.

3. Further experiments using ten animals showed that medial preoptic/anterior hypothalamic neurones orthodromically stimulated from the fimbria were also driven by stimulation of the ipsilateral stria terminalis and the cortico‐medial and basolateral amygdala. Lesioning the stria terminalis abolished the responses of medial preoptic/anterior hypothalamic neurones to stimulation of the fimbria.

4. In five animals the responses of fifty‐seven medial preoptic/anterior hypothalamic neurones orthodromically stimulated from the fimbria were recorded after stimulation of the medial forebrain bundle. 44·5% of these neurones were stimulated antidromically and 25·6% orthodromically from the medial forebrain bundle. Neurones responding to fimbria stimulation by producing one to three action potentials were more likely to have connexions with the medial forebrain bundle.

5. The relevance of these findings to local neuronal circuitry and the control of sexual behaviour are discussed.
Erythrocyte nucleoside transport: asymmetrical binding of nitrobenzylthioinosine to nucleoside permeation sites
Authors: Jarvis S. M. , McBride D. , Young J. D.
Published: December 2014

1. Nitrobenzylthioinosine is a potent and specific inhibitor of nucleoside translocation in animal cells. Kinetic and inhibitor binding studies were undertaken to clarify how this inhibitor interacts with the nucleoside transporter from human and nucleoside‐permeable type sheep erythrocytes.

2. [3H]nitrobenzylthioinosine inhibition of zero‐trans [U‐14C]uridine influx into nucleoside‐permeable type sheep cells was consistent with simple competitive inhibition (apparent Ki 1 nmol/l). Analysis of results using total inhibitor levels instead of cell‐free inhibitor concentrations did not affect the inhibition pattern, but increased the apparent Ki value by 5‐fold.

3. In contrast, [3H]nitrobenzylthioinosine was a non‐competitive inhibitor of zero‐trans [U‐14C]uridine efflux (apparent Ki 1·5 nmol/l). Dipyridamole, another potent inhibitor of nucleoside translocation, also inhibited zero‐trans [U‐14C]uridine influx in a competitive manner (apparent Ki 20‐40 nmol/l).

4. [3H]nitrobenzylthioinosine bound to high‐affinity sites on cell membranes from human and nucleoside‐permeable type sheep cells (apparent KD values ≃ 1 nmol/l). Binding of inhibitor to these sites was competitively blocked by uridine, a well characterized substrate for the nucleoside transporter (apparent Ki 1·25 and 0·9 mmol/l, respectively). These apparent Ki values are close to the apparent Km for uridine equilibrium exchange in human erythrocytes.

5. Similarly, deoxycytidine was found to be a competitive inhibitor of high‐affinity [3H]nitrobenzylthioinosine binding activity (apparent Ki 1·0 and 1·2 mmol/l for human and nucleoside‐permeable type sheep cell membranes, respectively). This contrasts with a previous report that this nucleoside had no effect on inhibitor binding activity. Transport studies confirmed that deoxycytidine is a substrate for the erythrocyte nucleoside transporter. Apparent Km and Vmax values for [U‐14C]‐deoxycytidine zero‐trans influx into human and nucleoside‐permeable type sheep cells were comparable to those obtained for [U‐14C]uridine.

6. It is suggested from these results that nitrobenzylthioinosine competes directly with nucleosides for the permeation site of the nucleoside transporter, but that inhibitor binds preferentially to the external membrane surface.
Pharmacological analysis of directionally sensitive rabbit retinal ganglion cells
Authors: Ariel M. , Daw N. W.
Published: December 2014

1. Cholinergic drugs were infused into the retinal circulation of the rabbit while we analysed the receptive field properties of directionally sensitive retinal ganglion cells. Physostigmine eliminated the trigger feature, directional specificity, of both types (on‐centre and on—off) of these cells. In this respect the action of physostigmine (an ACh potentiator) was very like that of picrotoxin (a GABA antagonist). Therefore, a detailed analysis of the receptive field properties of directionally sensitive ganglion cells was made to analyse the effects of physostigmine and picrotoxin.

2. Size specificity and radial grating inhibition were not abolished by physostigmine, but were often affected by picrotoxin. The optimal velocity in the preferred direction (as measured by maximum firing frequency) was not much changed by physostigmine, but was higher during infusion of picrotoxin. Infusion of nicotine, a depolarizing ACh agonist which increases the activity of retinal ganglion cells, revealed the presence of inhibition to movement in the null direction. The null direction response during picrotoxin started slightly later than this inhibition. The null direction response during physostigmine was weaker and started later still. Mecamylamine and dihydro‐β‐erythroidine, nicrotinic receptor antagonists, totally blocked the effect of physostigmine and reduced the control light response by about half.

3. From this analysis, it appears that on—off ACh release onto directionally sensitive cells provides a substantial excitation which, when potentiated by physostigmine, overcomes or outlasts the null direction GABA inhibition within the receptive field. The spatial extent of GABA inhibition is asymmetric to and larger than the spatial extent of ACh excitation. Similar pathways appear to be involved in both the on‐centre and on—off directionally sensitive ganglion cells, yet the on‐centre cell pathway may receive an additional input which suppresses the ACh excitation at light offset. Possible schemes for the cellular mechanism of directional sensitivity are discussed in light of these results and recent anatomical and pharmacological findings.
Evidence for long‐term functional plasticity in the visual cortex of adult cats
Authors: Singer W. , Tretter F. , Yinon U.
Published: December 2014

1. Vision was investigated with behavioural and electrophysiological techniques in three groups of cats: (a) two normally raised kittens in which one eye was rotated at an age of 3 months, (b) three adult cats in which one eye had been rotated and the other closed 6 months prior to recording, (c) two adult cats in which first one eye had been rotated and the other closed and subsequently, after one year, the rotated eye had been closed and the normal eye re‐opened. The latter two cats were investigated 6 and 12 months after reverse suture, respectively. All adult cats were at least 2 years old when operated on for the first time.

2. Behavioural analysis revealed that the kittens of the first group no longer used the rotated eye for fixation, visuo‐motor behaviour being impaired when tested through this eye. Binocularity was found to be disrupted to nearly the same extent as in kittens made strabismic at the beginning of the critical period. In addition, ocular dominance was shifted towards the normal eye.

3. The adult cats in the second group developed a virtually complete neglect of the visual modality subsequent to a period of severely disturbed visuo‐motor behaviour.

4. These behavioural abnormalities were associated with clear alterations in the functional state of striate cortex. Only 47% of the recorded cells could be driven with light, the majority of these reactive neurones yielding only sluggish responses to optimally aligned stimuli. The ocular dominance distribution showed a significant reduction of binocular cells but gave no indication of a shift in ocular dominance towards either of the two eyes. Moreover, contrast sensitivity as assessed with pattern‐evoked potentials was significantly reduced.

5. The remaining two animals that were reverse sutured after the visual neglect had developed showed complete behavioural recovery when tested through the re‐opened normal eye. However, this recovery was not instantaneous and occurred only after the cats had been forced to use their visual sense.

6. Behavioural recovery was paralleled by an increase of cortical reactivity to normal levels and by a marked increase in binocularity. This gain increase of excitatory transmission was, however, selective for neurones dominated by the normal eye, leading to a bias in ocular dominance towards this eye.

7. The observed modifications in the functional state of striate cortex indicate that reversible changes in the gain of excitatory transmission can still occur beyond the end of the classical critical period. These long‐lasting changes in synaptic efficiency appear to follow the rules postulated by Hebb for adaptive synaptic connexions.
Input‐output relationships of the central respiratory controller during peripheral muscle stimulation in cats.
Authors: Eldridge F L , Millhorn D E , Waldrop T G
Published: December 2014

1. Inspiratory output responses, measured as integrated phrenic activity, to hypercapnia, to carotid sinus nerve stimulation, to unilateral and bilateral stimulation of calf muscles and to combinations of these stimuli were determined in paralysed, vagotomized and glomectomized cats whose end‐tidal PCO2 was kept constant by means of a servo‐controlled ventilator. 2. Confirming an earlier report (Eldridge, Gill‐Kumar & Millhorn, 1981), the inspiratory response to progressive hypercapnic stimulation of the central chemoreceptors was not linear, and the responses to a constant carotid sinus nerve test stimulus were progressively decreased in magnitude as the pre‐stimulus level of respiratory activity was increased by hypercapnia. 3. In contrast, the response to a test stimulus from calf muscles remained the same at all pre‐stimulus levels of respiratory activity, whether conditioned by hypercapnia or by carotid sinus nerve stimulation. 4. Unlike the findings with chemoreceptor inputs, the combining of stimuli from right and left muscles exhibited an algebraically additive effect on output. 5. We suggested before that the decreasing responses to identical chemoreceptor inputs were due to progressive neuronal saturation of a common central pathway between these inputs and the respiratory controller. The absence of such behaviour with muscular afferent input indicates that this input does not travel to the respiratory controller by the same pathway as that common to the chemoreceptors.
Fast charge movements in skeletal muscle fibres from Rana temporaria
Authors: Collins Carol A. , Rojas E. , Suarez‐Isla B. A.
Published: December 2014

1. Fast charge movements were measured in cut skeletal muscle fibres from Rana temporaria.

2. The initial time course of the current in response to a sudden displacement of the membrane potential from ‐110 to ‐60 mV was analysed in terms of an electrical equivalent circuit modified from Falk & Fatt (1964).

3. The specific resistance in series with the sarcolemma was estimated as 7·4 Ω cm2. The total capacity (surface sarcolemma plus tubular membrane) was estimated as 3·43 μF/cm2.

4. The asymmetry currents settling within 1 ms during depolarizing pulses of increasing size (on‐response), from a holding potential around ‐120 mV, could be described in terms of a single exponential. The asymmetry currents after the pulses (off‐response) exhibited at least two components.

5. The integral of the on‐response, Qon, as a function of Vp, could be fitted using a function of the Boltzmann type. At the mid‐point of the distribution curve, equal to ‐38 mV, the slope was 0·012 mV−1. A saturating value of 28 pC was reached at 40 mV.

6. The off‐response to pulses not exceeding 3 ms exhibited two components. The first one had an exponential time course. The charge Qoff associated with this fast component was always equal to Qon.

7. τon (the relaxation time constant), as a function of membrane potential was asymmetrical, exhibiting a maximum value of 233 μs at about ‐38 mV.

8. For Vp values smaller than ‐20 mV the Qon—Vp and τon—Vp curves could be analysed using the two‐state transition model. From this analysis the average transition potential V′ was estimated as ‐38 mV and the effective valence of the mobile charges as 1·36.

9. Double‐pulse protocols (duration of pre‐pulses referred to as T in the range 0‐3 s) showed that Qon and τon decreased as T increased. Single transient analysis shows that the changes are confined to the transient for depolarizing pulses.

10. This immobilization of the charges is reversible and follows a similar time course to the slow inactivation of the Na+ conductance described in the preceding paper.

11. A differential effect of the depolarizing pre‐pulse on the ionic and asymmetry currents is seen in the decrease of τon with increasing T while τm remains constant.
The control of liver regeneration after partial hepatectomy in the rat.
Authors: Dicker S E , Morris C A , Shirley D G
Published: December 2014

1. Normal rat liver slices were incubated for 24 h in culture medium to which had been added freeze‐dried plasma, prepared from the blood of rats which had undergone partial hepatectomy (60‐70% of liver removed) 10 min, 4 or 24 h previously. No changes in the dry weight of the slices were observed. 2. Similarly, there were no changes in the dry weight or protein content of incubated liver slices when freeze‐dried plasma prepared from the blood of rats unilaterally nephrectomized 10 min, 4 or 24 h previously was added to the culture medium. 3. Slices from the remaining liver stump, taken 4 h after partial hepatectomy (60‐70% of liver removed) and incubated for 4 h in culture medium, did not release a factor capable of increasing the dry weight of normal liver slices incubated in the same medium. 4. After partial hepatectomy (60‐70% of liver removed), there was no increase of guanosine 3':5'‐cyclic monophosphate in the remaining part of the liver. 5. No measurable amount of esterase activity was found in normal liver or in the remaining liver stump after partial hepatectomy (60‐70% of liver removed). 6. It is suggested that the stimulatory mechanism for liver regeneration is of a different nature from that involved in compensatory renal hypertrophy.
Influences on the expression of acetylcholine receptors on rat nodose neurones in cell culture.
Authors: Baccaglini P I , Cooper E
Published: December 2014

1. Nodose neurones dissociated from new‐born rats were grown in culture in the absence or presence of cells from neonatal skeletal muscle or heart. 2. In cultures devoid of non‐neuronal cells cholinergic interactions between the neurones were common. In the presence of non‐neuronal cells such interactions were rare. 3. A decrease in the proportion of neurones responsive to ACh was primarily responsible for the reduced incidence of synaptic interactions. Non‐neuronal cells influenced the expression of ACh receptors in developing nodose neurones in culture. 4. Most neurones appeared susceptible to the non‐neuronal influence during the first week in culture. 5. Many nodose ganglion neurones, whether grown in the presence or absence of non‐neuronal cells, were sensitive to gamma‐aminobutyric acid and serotonin but were insensitive to glutamate, glycine and L‐epinephrine.
Possible zeitgebers for external entrainment of the circadian rhythm of plasma corticosterone in blind infantile rats.
Authors: Hiroshige T , Honma K , Watanabe K
Published: December 2014

1. The phase angle of circadian rhythm of plasma corticosterone in individual blind pups was followed in order to find out an effective zeitgeber(s) during the post‐natal development. 2. The retinal light pathway before the opening of eyes was not essential for the entrainment of pups' rhythm to the environmental light‐dark (LD) cycle. 3. In blinded pups whose eyes were enucleated on the day of birth, no evidence was obtained for effective extra‐retinal pathways for photic inputs. 4. Free‐running circadian hormone rhythm of blind pups was not entrained by 'social contact' with other sighted pups in the same cage. 5. Even when the duration of nursing was varied from 2 to 4 weeks, the phase angle of pups' rhythm at the fourth week was not affected. 6. In mother‐pups exchange experiments in which pups born from LD mother were reared by DL mother (LD‐DL pups) and conversely, pups from DL original mother were reared by LD foster mother (DL‐LD pups), about one half of the pups at the fourth post‐natal week of both groups exhibited phase angles belonging to their original mothers and the other half showed phase angles of their foster mothers. 7. It is suggested that blind pups may retain the phase angle of circadian rhythm of the original mother and the overt hormone rhythm may be modifiable by the foster mother during the early phase of post‐natal life.
Dialysable and non‐dialysable hydroxyproline in the rat's urine: age related and diurnal variations
Authors: Gaggi Renato , Gianni Anna Maria , Montanaro Nicola
Published: December 2014

1. Urinary dialysable and non‐dialysable hydroxyproline, which are considered good indices of bone resorption and neoformation respectively, were determined in rats under conditions that modify skeleton metabolism, such as body growth and parathyroid or calcitonin administration. It was also investigated whether dialysable and non‐dialysable hydroxyproline excretions showed significant circadian fluctuations in rats of different ages.

2. Dialysable hydroxyproline excretion sharply decreased from the first to the fifth months of age and underwent further gradual reduction up to the fourteenth month of life. Non‐dialysable hydroxyproline excretion followed a smoother decrease up to the fifth month, then remained constant. Urinary excretion of non‐dialysable hydroxyproline expressed as a percentage of the total hydroxyprolinuria (n.d.%) slowly increased with advancing rat age.

3. In 2‐, 4‐ and 6‐month old rats, dialysable hydroxyproline excretion showed significant circadian fluctuations with minima and maxima at the end of the dark and light fraction of the cycle respectively. Daily fluctuations were greater in young and adult rats (50‐65% of the respective average levels) than in 4‐month old rats (25%). Non‐dialysable hydroxyproline excretion followed similar but less pronounced patterns. Significant circadian fluctuations of n.d.% were detectable only in 2‐ and 4‐month old rats, with peaks at 04.00‐05.00 hr, thus indicating that the bone formation/resorption ratio increased in the nocturnal fraction of the cycle.

4. Young rats administered with calcitonin exhibited reduced levels of urinary dialysable but not of non‐dialysable hydroxyproline when the hormone was given at 13.30 hr. No changes were observed when calcitonin was injected at 19.30 hr. On the contrary, both diurnal and nocturnal parathyroid hormone administration to young rats caused increased levels of dialysable and non‐dialysable hydroxyproline of the same magnitude.
Amiloride‐sensitive sodium channels in rabbit and guinea‐pig gall‐bladder.
Authors: Cremaschi D , Meyer G
Published: December 2014

1. The effects of low amiloride concentrations (less than 2.5 x 10(‐5) M) on the apical membrane (Vm) and transepithelial (Vms) potential differences, transepithelial resistance (Rep) and apical/basolateral membrane resistance ratio (Rm/Rs) have been determined in the gall‐bladders of the rabbit and guinea‐pig. 2. Vm was hyperpolarized, Vms decreased towards negative values, Rm/Rs increased, but Rep remained unchanged. 3. K+ selectivity of the apical membrane was also checked by increasing luminal K+ concentration from 5.9 to 29.4 mM; the corresponding change in the apical electromotive force was much higher in the rabbit than in the guinea‐pig. 4. Pre‐incubations with Cl‐‐and HCO3‐‐free salines did not modify K+ selectivity in the rabbit, but nearly doubled it in the guinea‐pig. 5. Pre‐incubations with control solutions containing 10(‐5) M‐amiloride in the lumen converted the apical membrane of rabbit gall‐bladder into a perfectly K+‐perm‐selective membrane; the same results were obtained in the guinea‐pig only on bathing the tissue with Cl‐‐ and HCO3‐‐free salines together with 10(‐5) M‐amiloride. 6. It is suggested that in the apical membrane of rabbit gall‐bladder K+ and Na+ conductances exist, whereas in guinea‐pig gall‐bladder both K+, Na+ and anion (Cl‐ and/or HCO3‐) conductances are present; in both species conductive Na+ pathways are inhibited by amiloride. .
Sustained synaptic input to ganglion cells of mudpuppy retina
Authors: Belgum Jack H. , Dvorak David R. , McReynolds John S.
Published: December 2014

1. Intracellular responses were recorded from on‐centre and off‐centre ganglion cells in isolated eyecups of the mudpuppy, Necturus maculosus.

2. Current—voltage relations were measured in darkness, during illumination of the receptive field centre, and after chemically mediated synaptic inputs were blocked by 4 mM‐cobalt chloride.

3. In on‐centre cells the membrane potential in darkness was ‐56±6 mV (mean±S.D.). Addition of Co2+ resulted in an average depolarization of 10 mV and an average decrease in conductance of 2·1 nS. These results suggest that in darkness on‐centre cells are tonically inhibited by synaptic input which increases conductance and has a reversal potential more negative than the dark membrane potential.

In off‐centre cells the membrane potential in darkness was ‐46±5 mV. Addition of Co2+ caused an average hyperpolarization of 6 mV and an average decrease in conductance of 1·5 nS. These results suggest that in darkness off‐centre cells receive a tonic excitatory input which increases conductance and has a reversal potential more positive than the dark membrane potential.

4. In on‐centre cells light causes a sustained depolarization. This response involves an increase in a tonic excitatory input which increases conductance and has a reversal potential more positive than the dark membrane potential.

5. In off‐centre cells, light causes a sustained hyperpolarization. This response involves an increase in a sustained inhibitory input which increases conductance and has a reversal potential more negative than the dark membrane potential.

6. The depolarizing off‐response of off‐centre cells is associated with an increase in an excitatory input which increases conductance and has a reversal potential more positive than the dark membrane potential. This response may be due to a temporary increase in the excitatory input which is tonically active in darkness or may reflect an additional excitatory input.

7. It is suggested that in both on‐ and off‐centre ganglion cells the balance of sustained excitatory and inhibitory synaptic inputs determines the resting potential in darkness. Centre illumination alters the balance of these inputs, by increasing one and decreasing the other, to produce the characteristic sustained light responses.

8. The possible presynaptic sources of the sustained excitatory and inhibitory inputs are discussed.