bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of spinal and skin temperatures on the firing rate and thermosensitivity of preoptic neurones
Authors: Boulant J. A. , Hardy J. D.
Published: December 2014

1. In anaesthetized rabbits, preoptic single unit activity was recorded while preoptic, spinal cord and skin temperatures were independently manipulated.

2. The units that were insensitive to preoptic temperature were characterized by low firing rates and also by a very low incidence of extrahypothalamic thermosensitivity.

3. Thirty‐seven units having positive coefficients to preoptic temperature were tested for their response to spinal or skin temperature. Of these, twenty‐two units responded to extrahypothalamic temperature, seventeen with positive thermal coefficients. In addition, the incidence of extrahypothalamic thermosensitivity generally increased among the higher firing units.

4. Twenty‐two units had negative coefficients for preoptic temperature and were tested for their extrahypothalamic thermosensitivities. Of these, sixteen units had dual thermosensitivities, ten with negative coefficients for the extrahypothalamic temperatures. In addition, there was no correlation between the incidence of extrahypothalamic thermosensitivity and the level of firing rate.

5. In the units having positive coefficients for preoptic temperature, an increased firing rate, due to extrahypothalamic temperature, generally resulted in a decreased preoptic thermosensitivity. Conversely, a decreased firing rate usually resulted in an increased preoptic thermosensitivity.

6. In the units having negative coefficients for preoptic temperature, an increased firing rate, due to extrahypothalamic temperature, usually increased the preoptic thermosensitivity; while a decreased firing rate tended to decrease the sensitivity to preoptic temperature.
Behavioural contrast sensitivity of the cat in various visual meridians
Authors: Bisti S. , Maffei L.
Published: December 2014

1. The contrast sensitivity of the cat as a function of the spatial frequency of the visual stimulus was determined by using behavioural techniques.

2. No statistically significant difference was found for the contrast sensitivity thresholds at various orientations of the stimulus.

3. A comparison of the contrast sensitivity curve of the cat with that of the human shows that the two species have rather different characteristics of visual spatial resolution.
The formation of synapses in striated muscle during development
Authors: Bennett M. R. , Pettigrew A. G.
Published: December 2014

1. A study has been made of the formation of synapses in developing striated muscles which receive either a focal (the rat hemidiaphragm) or a distributed (the avian anterior latissimus dorsi) innervation using histological, ultrastructural and electrophysiological techniques.

2. In the developing diaphragm only a single synaptic contact was initially established at random along the length of the short (300 μm) myotubes by a single axon; in the developing ALD more than one synaptic contact could be established initially along the length of the long (2500 μm) myotubes by axons, but the distance between these was never less than 170 μm.

3. Each synapse established by the initial axonal contact in either the diaphragm or the ALD subsequently received a multiple innervation from further exploring axons in the muscles, and all such additional innervation of muscle cells was constrained to the sites of the initial synaptic contacts; this multiple innervation of synaptic sites was lost in the subsequent 4 weeks.

4. It is suggested that the axon forming the initial synaptic contact on myotubes induces a property over an adjacent length of myotube which makes its membrane refractory to synapse formation over this length; this characteristic length is longer for axons forming a focal innervation than it is for those forming distributed innervation.
Long‐term effect of ouabain and sodium pump inhibition on a neuronal membrane
Authors: Gorman A. L. F. , Marmor M. F.
Published: December 2014

1. The long‐term effects of ouabain on the membrane potential of the Anisodoris giant neurone (G cell) were examined in cells maintained for periods of up to 15 hr at 11–13° C.

2. In the presence of ouabain (5 × 10−4
M), the membrane potential depolarized to a constant level for 1‐4 hr, then hyperpolarized for 5‐7 hr after which it gradually depolarized again.

3. During the hyperpolarizing phase, after 6–8 hr in ouabain, [K]1 fell approximately 50%, [Na]1 increased 50–100% and the PNa/PK ratio decreased to 25% of its initial value.

4. After 8 hr in ouabain the membrane conductance increased two‐ to fourfold. This increase was independent of temperature and membrane rectification.

5. The K permeability (PK) was calculated from the constant field equation, and showed a fourfold increase after long‐term treatment with ouabain. This rise in PK probably underlies the membrane hyperpolarization and the decrease in the PNa/PK ratio.

6. It is suggested that inhibition of the Na+ pump with ouabain causes a gradual rise in [Na]1 which secondarily leads to Ca2+ uptake, an increase in [Ca]1, and thereby an increase in PK.
A comparative study of blood gas tensions, oxygen affinity and red cell 2,3 DPG concentrations in foetal and maternal blood in the mare, cow and sow
Authors: Comline R. S. , Silver Marian
Published: December 2014

1. Blood gas tensions, pH, PCV, O2 affinity and red cell 2,3‐diphosphoglycerate (DPG) levels have been measured in uterine and umbilical blood in conscious cows and mares with indwelling vascular catheters and in sows under sodium pentobarbitone anaesthesia.

2. Large PO2 gradients (20–24 mmHg) were observed between the uterine and umbilical venous blood in the cow and pig, while in the mare the corresponding PO2 difference was only 2·7 ± 1·7 mmHg. Alterations in maternal arterial PO2 did not affect the large vein‐to‐vein PO2 difference in either ruminant or pig.

3. In the cow the presence of different haemoglobin types in the adult (A, AB or B) did not appear to affect the O2 affinity. In six animals the mean P50 of the foetal blood (24·8 mmHg) was considerably lower than that of the mother (35·5 mmHg); no changes in P50 were observed during the last month of gestation. Red cell 2,3‐DPG levels were higher in the calf foetus than in the mother, but in the ruminant 2,3‐DPG has no effect on the affinity of haemoglobin for O2 and the differences in P50 between foetus and mother could be ascribed to the presence of a foetal haemoglobin.

4. In the sow large differences in O2 affinity between foetal and maternal blood were observed, which were related to red cell 2,3‐DPG concentration. A rise in foetal blood P50 during the last half of gestation was associated with increased foetal weight and a rise in red cell 2,3‐DPG.

5. In the mare the P50 of the foetal blood was 2‐5 mmHg below that of the mother. This difference appeared to be due to the lower 2,3‐DPG concentration in the foetal red cells as in the sow; in both species the haemoglobin of the foetus is similar to that of the mother.

6. The differences in foetal and maternal O2 affinity found in the various species and the changes which may occur during gestation or in the perinatal period are discussed in relation to the observed transplacental PO2 gradients and the O2 requirements of the foetus and neonate.
The rate and depth of breathing in new‐born infants in different sleep states
Authors: Hathorn M. K. S.
Published: December 2014

1. Ventilation was recorded on ten male and ten female healthy full‐term infants during the first week after delivery, using a trunk plethysmograph. Tidal volume (VT), respiration rate (f) and pulmonary ventilation (V̇) for each respiratory cycle were measured during periods of rapid eye movement sleep (REM) and during quiet sleep when eye movements were absent (NREM).

2. It was found that mean instantaneous V̇ and f were significantly higher in all infants during REM than during NREM sleep, while mean VT was either unchanged or showed a decrease. In addition, there was significantly greater variation in instantaneous V̇, VT and f during REM as compared with NREM sleep.

3. Positive correlations were found in most infants in both sleep states between individual values of VT and the duration of the respiratory cycle (T).

4. Periodic changes in T were found in all infants during both sleep states; these periodicities may reflect the behaviour of respiratory control mechanisms operating over a longer time span than the individual respiratory cycle.
Foetal respiratory movements, electrocortical and cardiovascular responses to hypoxaemia and hypercapnia in sheep
Authors: Boddy K. , Dawes G. S. , Fisher R. , Pinter S. , Robinson J. S.
Published: December 2014

1. Foetal breathing movements, electrocortical activity, arterial pressure and heart rate were recorded continuously in chronically catheterized sheep, 97–145 days pregnant.

2. With increasing gestational age there was a fall in heart rate of 0·67 beats/day and a rise in arterial pressure of 0·46 mmHg/day.

3. Hypoxaemia in the foetus was induced by allowing the ewe to breathe low oxygen mixtures, 9% O2 with 3% CO2 in N2. In the younger foetuses there was an initial rise in heart rate whereas in the older foetuses there was a fall. After the end of hypoxia there was a persistent tachycardia in both groups. In the older foetuses there was a rise of arterial pressure.

4. Two vagotomized older foetuses showed cardiovascular responses similar to those of the younger foetuses.

5. Foetal breathing movements were abolished by hypoxaemia in twenty‐two of twenty‐five experiments. In the three exceptional experiments there was a small rise in Pa, CO2.

6. The proportion of time occupied by low voltage electrocortical activity in the foetus was reduced by hypoxaemia.

7. Hypercapnia was induced by giving the ewe 4‐6% CO2 with 18% O2 in N2 to breathe. After an initial slight fall the foetal heart rate increased and there was a small rise in foetal arterial pressure.

8. The proportion of time occupied by low voltage electrocortical activity and breathing movements was increased by hypercapnia.

9. Maternal hyperoxia, induced by giving 50% O2 in N2, did not significantly increase foetal breathing movements unless the ewe was in labour. In labour the foetuses had lower Pa, O2 values initially and a reduced incidence of foetal breathing, both of which were increased by maternal hyperoxia.
Forced convection around the human head.
Authors: Clark R P , Toy N
Published: December 2014

1. The parameters determining the forced convective heat loss from a heated body in an air stream are outlined. 2. Local forced convective heat transfer distributions around the human head and a heated vertical cylinder at various wind speeds in a climatic chamber have been found to be similar and related to the aerodynamic flow patterns. 3. From the local convective coefficient distribution, values for the overall convective coefficient h‐c at various wind speeds have been evaluated. These are seen to agree closely with existing whole body coefficients determined by other methods.
The relationship between elevated water intake and oedema associated with congestive cardiac failure in the dog.
Authors: Ramsay D J , Rolls B J , Wood R J
Published: December 2014

1. In the dog constriction of the thoracic region of the inferior vena cava increases water intake and extracellular and plasma fluid volumes. 2. Restriction of water intake to the pre‐operative level for 2 weeks reduces the measured extracellular fluid volume to the pre‐operative level. 3. Administration of the competitive angiotensin inhibitor, saralasin acetate, to two dogs in congestive cardiac failure following thoracic caval constriction markedly reduced their water intake. 4. These results suggest that increased fluid intake is probably important in the aetiology of the oedema associated with congestive cardiac failure, probably through the renin‐angiotensin system.
Excitatory, inhibitory and biphasic synaptic potentials mediated by an identified dopamine‐containing neurone.
Authors: Berry M S , Cottrell G A
Published: December 2014

1. A giant dopamine‐containing cell, situated in the left pedal ganglion of the water snail Planorbis corneus, was identified in isolated living preparations of the central nervous system. Spectrophotofluorimetric analysis confirms that the cell contains dopamine, whereas noradrenaline appears to be absent. The cell is unique in being a repeatedly identifiable dopamine‐containing neurone. 2. Stimulation of the giant dopamine‐containing cell resulted in excitatory, inhibitory or biphasic (depolarizing‐hyperpolarizing) synaptic potentials in a number of follower neurones. The duration of the e.p.s.p.s and i.p.s.p.s was 0–3–5 sec; they ranged from barely detectable responses to ones 7 mV in amplitude in different cells. The depolarizing phase of a biphasic synaptic potential (b.p.s.p.) was usually less than 1 mV in amplitude (max. 3mV) and lasted 40–400 msec. The latency of i.p.s.p.s was long (70–120 msec) compared with that of e.p.s.p.s and b.p.s.p.s (20 msec). Abolition of the depolarizing phase of b.p.s.ps. by tubocurarine left a long‐latency (70–120 msec) i.p.s.p. All responses showed summation and marked facilitation. 3. Evidence is presented that the post‐synaptic potentials are produced by direct connections from the giant cell and result from a release of dopamine. Of eight putative transmitter substances tested on these different groups of neurones, only dopamine produced a potential change which in each case was of the same polarity as the post‐synaptic potential when this was monophasic. However, generally applied dopamine produced only a hyperpolarization in follower cells showing b.p.s.p.s. This result is probably partly due to rapid desensitization of the receptors mediating the depolarization and also to a masking of the depolarization by the more effective hyperpolarizing response. 4. Erogometrine and 6‐hydroxydopamine specifically antagonized the i.p.s.p.s and dopamine receptors mediating inhibition. Neither the e.p.s.p.s nor the excitatory dopamine response were blocked by high concentrations of hexamethonium. Hexamethonium was also ineffective in blocking the depolarizing phase of a b.p.s.p., which was, however, selectively eliminated by tubocurarine. 5. It is suggested that dopamine is the transmitter released from the giant cell and that it can mediate excitatory, inhibitory or biphasic responses in different follower neurones.
Effect of destruction of the posterior pituitary on the diuresis from left atrial receptors.
Authors: Kappagoda C T , Linden R J , Snow H M , Whitaker E M
Published: December 2014

1. In anaesthetized dogs, stimulation of atrial receptors after destruction of the pituitary gland results in a diuresis. This response was not abolished by the administration of bretylium tosylate and was also observed in a surgically denervated kidney. 2. The diuresis is qualitatively similar to that observed in anaesthetized dogs with intact pituitary glands. 3. It is concluded that the diuresis which results from stimulation of the left atrial receptors is mediated by a blood‐borne agent which is not the antidiuretic hormone.
A dual effect of repetitive stimulation on post‐tetanic potentiation of transmitter release at the frog neuromuscular junction.
Authors: Magleby K L , Zengel J E
Published: December 2014

1. End‐plate potentials (e.p.p.s) were recorded with a surface electrode from frog neuromuscular junctions blocked with high Mg and low Ca to study post‐tetanic potentiation(potentiation). 2. Potentiation is found to decay exponentially over most of its time course. 3. The time constant tsu(H) characterizing this exponential decay is a function of the previous history (frequency and duration) of stimulation. For example, tsu(H) increased from about 20 sec following a few impulses to over 70 sec following more than 1000 impulses. 4. A new method is presented to obtain estimates of the rise of potentiation (uncontaminated by facilitation or an intermediate facilitatory process) during repetitive stimulation. It is found that potentiation is present following short trains of impulses and continually increases in magnitude with the duration of the conditioning stimulation. Potentiation was at a maximum immediately following the conditioning trains. 5. The relationship between P(T), the magnitude of potentiation immediately following repetitive stimulation, and tsu(H), the time constant for the decay of this potentiation, is given by tsu(H)=Ae‐P(T)/B, where A=19‐8 plus or minus 5‐1 sec (mean plus or minus S.D. of an observation) and B increases from 2.2plus or minus 2‐1 to 5‐7 plus or minus 2‐7 as the stimulation rate increases from 5 to 30/sec. 6. The value of A in the above equation can be considered to represent the minimal time constant for the decay of potentiation‐‐that is, the time constant for decay after a simgle impulse. 7. Evidence is presented for a afacilitatory process with a time constant of decay of about 3 sec which is intermediate in duration between facilitation and potentiation. 8. It is suggested that repetitive stimulation has a dual effect on potentiation; each impulse (1) adds an increment of potentiation and (2) increases tsu(H), the time constant for the decay of potentiation.
Climbing fibre inputs to cerebellar Purkinje cells from trigeminal cutaneous afferents and the SI face area of the cerebral cortex in the cat.
Authors: Miles T S , Wiesendanger M
Published: December 2014

1. An investigation was made of climbing fibre (CF) activity evoked in single Purkinje cells in the cerebellum by electrical stimulation of trigeminal cutaneous afferents, the face area of the SI cortex, and the superficial radial nerve, in Nembutal‐anaesthetized cats. In addition, both the extent of the cutaneous receptive fields of individual Purkinje cells on the face and the CF responses evoked in these cells by controlled natural stimulation were examined. 2. The pattern of convergence from these inputs on to individual Purkinje cells was found to be complex. DF responses were evoked in 67% of trigeminally‐activated cells by electrical stimulation of more than one trigeminal branch. An excitatory CF convergence from the face area of the SI cortex was found on 68% of trigeminally activated cells; 23% also responded to stimulation of the superficial radial nerve. 3. In 81% of the Purkinje cells which were activated by trigeminal nerve stimulation, CF responses were readily elicited by gentle mechanical stimulation of the facial skin. A qualitative relationship was established between the size of the peripheral field of a Purkinje cell, and the probability of convergence on to that cell from the SI cortex. 4. Recordings were made from a limited number of Purkinje cells which were responsive to electrical stimulation of bilateral trigeminal branches and the superficial radial nerve. However, CF responses in these cells often could be elicited only by high intensity stimulation. It is suggested that these cells are analogous to, or perhaps an extension of the population of Purkinje cells described in the anterior lobe which are excited via the ventral funiculus pathway in the spinal cord only by stimulation of ‘flexor reflex afferents’ in bilateral limb nerves.
The interdigestive myo‐electric complex of the stomach and small bowel of dogs.
Authors: Code C F , Marlett J A
Published: December 2014

1. Szurszewski (1969) described a cyclic recurring, caudally migrating band of intense action potential activity, the activity fromt, in the small bowel of dogs fasted 18–21 hr. The finding has been confirmed by Carlson, Bedi & Code (1972) and by Grivel & Ruckebusch (1972). The objectives of the present study were to extend these observations first by indentifying the full sequence of myo‐electric events in the stomach and small bowel of healthy conscious dogs fasted for 24–48 hr and for longer periods and second by determining the effect of ingestion of mild and of saline solution on the complex and the role of gastric distension in their action. 2. Under surgical anaesthesia, silver‐silver chloride electrodes were implanted on the serosal surface of the stomach and small bowel of seven dogs, and recordings of electric activity were started when the dogs had recovered. One hundred and nine interdigestive complexes were studied in detail in five of the dogs during period ranging from 5 to 14 months. All observations were made while the dogs were healthy, conscious, and fasted. 3. The period of intense action potential activity, the activity frot or band, was found to be one phase of a cyclic‐recurring sequence of changes in action potential activity. The entire sequence, composed of four phases, occured almost simultaneously in the stomach and duodenun and then migrated distally in sequence over the entire small bowel. As one cycle terminated in the distal ileum, another had started in the stomach and duodenum, and this cyclic recurrence continued during fasts of 4 and 5 days. 4. The cycles of the interdigestive complex tended to recur at the same time each day in three of the dogs. The mean periods of the cycles ranged from 90 to 114 min, and the mean time of their propagation from stomach to terminal ileim ranged from 105 to 134 min. The mean velocity of the activity fronts (phase III of the cycles) was 5‐7‐11‐7 cm/min in the orad portion of the small bowel and 0‐9‐2‐5 cm/min in the distal half. The mean calculated length of the activity front diminished from a range of 42–62 cm in the duodenum to 5‐10 cm in the ileum. 5. Intragastric instillation of 400 ml. milk always interrupted the complex present in the bowel at the time of instillation and usually suppressed the next, whereas 400 ml. saline solution interrupted the complex present in the bowel only at the time of instillation. Distension of the stomach with a ballon always suppressed the interdigestive complex in the stomach and duodenum but sometimes failed to interrupt its migration along the bowe.
Acetylcholine responses on clonal myogenic cells in vitro.
Authors: Steinbach J H
Published: December 2014

1. Some electrophysiological properties of the acetylcholine response shown by clonal rat myogenic cells were studied in vitro. Some mononucleate myoblasts showed a slow hyperpolarizing response. 2. Multinucleate myotubes showed a fast depolarizing response that was very similar to that of mammalian skeletal muscle in vivo, and differed from the hyperpolarizing response of myoblasts. 3. The depolarizing response involved Na, K and Ca ions, but not Cl ions. The dependence of the reversal potential on external ion concentrations was generally similar to that shown by frog muscle, but some quantitative differences were seen. 4. The reversal potential determined at sites of nerve‐muscle interaction did not differ from those at background or non‐interacted sites.
Pancreatic acinar cells: effect of acetylcholine, pancreozymin, gastrin and secretin on membrane potential and resistance in vivo and in vitro.
Authors: Petersen O H , Ueda N
Published: December 2014

1. Intracellular recordings of membrane potential and input resistance have been made in vivo and in vitro from the exocrine acinar cells of rat pancreas using indwelling glass micro‐electrodes. 2. The resting cell membrane potential and input resistance in the in vivo experiments were not markedly different from the values obtained in the in vitro experiments. The effect of both acetylcholine (ACh) and pancreozymin (CCK‐Pz) on the pancreas in vivo as well as in vitro was to reduce both the acinar cell membrane potential and the input resistance narkedly. The amplitude of the evoked depolarization and the change in input resistance evoked by supramaximal stimuli were of the same magnitude in both types of preparations. 3. Gastrin had an effect on the acinar cell potential and resistance which was indistinguishable from that of CCK‐Pz or ACh. The effect of gastrin or CCK‐Pz was, in contrast to that of ACh, not influenced by the presence of atropine. The reversal potential for the gastrin evoked potential change was about −20 mV. 4. Secretin in doses producing maximal volume secretion in vivo had no effect on acinar cell membrane potential and input resistance. 5. Dibutyryl cyclic AMP (5mM) and cyclic GMP (1mM) had no effect on cell membrane potential or resistance. 6. It is concluded that the in vitro superfused pancreas segment preparation is a useful model system in electrophysiological studies since it functions essentially as the in vivo preparation. In contrast to both gastrin and CCK‐Pz, secretin has no effect on the bioelectrical properties of the acinar cells, indicating that there are no physiologically important secretin receptors in rat acinar cells.
Light path and photon capture in turtle photoreceptors.
Authors: Baylor D A , Fettiplace R
Published: December 2014

1. The directional selectivity of individual cones was examined by intracellular recording in the eye of the turtle. Sensitivites were determined from linear responses to dim flashes of monochromatic light incident on a cell over a range of angles to its long axis. 2. With light near the optimum wave‐length, some red‐ and green‐sensitive cones showed a high sensitivity for light entering axially and lower sensitivities for light entering obliquely. In contrast, other cells had lower peak sensitivities and less pronounced directional selectivities. The highest axial sensitivities observed in red receptors were about 320 muV photon(−1) mu2; in these cells, the sensitivity declined to half for rays 6–9 degrees off the axis as measured in the retina. Green receptors had lower axial sensitivities and broader angular profiles. 3. On the assumption that rays at all angles contribute independently to the over‐all sensitivity, the sensitivity of a cell to large cones of rays was successfully predicted from the angular selectivity determined with a narrow pencil of rays. The shape of small responses to dim stimuli delivered on and off the axis of the cell was invariant, implying that a cone signals the number of photons absorbed but not their angle of incidence. 4. Short wave‐lengths have previously been shown to be filtered out by the oil droplets present in turtle cones. At short wave‐lengths, the angular profiles showed a depression in axial sensitivity consistent with this filtering action. 5. Diameters of inner segments, oil droplets, and outer segments were measured in red‐, green‐, and blue‐sensitive cones, since these dimensions are expected to influence the cones' angular acceptances and ability to collect light. The diameters of the structure were in approximately the same proportions for each type of receptor, but the absolute values of the diameters were found to be scaled in relation to the wave‐length of maximum sensitivity. 6. Optical determinations of the efficiency with which axial rays are concentrated by red receptors gave a mean value of 55%. 7. Receptors in histological sections of the whole eye were found to be oriented with their long axes directed approximately toward the pupil. 8. The observed directional selectivities and collecting efficiencies agree well with the behaviour of a model retinal cone developed by Winston & Enoch (1971) on a geometrical optical treatment. 9. Effective collecting areas are derived for red‐, green‐ and blue‐sensitive cones; these permit conversion of observed flash sensitivities into the mean peak hyperpolarization produced by isomerization of a visual pigment molecule. The figure obtained is about 25 muV for red‐sensitive cones and 21muV for green‐sensitive cones.
Contrast sensitivity of individual colour mechanisms of human vision.
Authors: Cavonius C R , Estévez O
Published: December 2014

1. Contrast sensitivity functions of isolated colour mechanisms were measured at spatial frequencies from 0–2 to 32 c/deg. The contrast sensitivity vs. spatial‐frequency functions of the red (pi5) and green (pi4) mechanisms are similar, while the blue (pi3) mechanism has lower absolute sensitivity and lower resolving power. Isolation of a single mechanism never increases its maximum sensitivity. 2. The shape of the contrast sensitivity function of a colour mechanism is established within the mechanism. Little if any inhibitory interaction takes place among colour mechanisms. 3. Differences that have been reported between the sensitivities of the red and green mechanisms, as well as the apparent “supersensitivity” of the isolated green mechanism, may be artifacts that result from the extrapolation procedures that were used to estimate the absolute sensitivities of the colour mechanisms.
Innate and environmental factors in the development of the kitten's visual cortex.
Authors: Blakemore C , Van Sluyters R C
Published: December 2014

1. This is a study of the receptive fields of 771 cells recorded in the visual cortex of twenty‐five kittens reared normally or subjected to various kinds of visual deprivation or environmental manipulation. 2. Kittens deprived of patterned visual experience, by dark rearing or diffuse occlusion of the eyes, have a majority of cirtical neurones with little or no specificity for the orientation or axis of movement of visual stimuli. However, in such deprived animals, especially those younger than 3 weeks, there are a number of genuinely orientation selective cells. They are broadly "turned" (by adult standards), they are almost always of the simple type, are heavily dominated by one eye, and are found mainly in the deeper layers of the cortex, especially layer IV. 3...
An analysis of the representation of the forelimb in the ventrobasal thalamic complex of the albino rat.
Authors: Angel A , Clarke K A
Published: December 2014

1. Glass micro‐electrodes have been used to record from a total of 998 units situated in the ventrobasal thalamic complex in the deeply anaesthetized albino rat. 2. Of these units 889 responded to electrical stimulation of the contralateral forelimb and fifty‐one to the contralateral hind limb. The remaining units consisted of those with receptive fields on the trunk, head and those which responded to stimulation of more than one limb. Only the latter group of units showed any spontaneous activity in the absence of intentional stimulation. 2. Of the units which responded to electrical stimulation of the contralateral forelimb the receptive fields, modality and latencies of response were accurately determined for 505 units. The mean latency to supramaximal stimulation at the wrist was 4.49 (+/− 0.04 S.E. of mean) msec; and to mechanical stimulation (for 146 of these units) at the centre of the receptive field 6.58 (+/− 0.12) msec. The modalities were distributed as follows: light pressure, 391; heavy pressure, 47; hair movement, 40; claw sensitive, 15 and joint movement, 12 units. 4. The forelimb representation within the ventrobasal thalamic complex was somatotopically organized, the over‐all appearance being that of an incompletely closed fist, palmar surface uppermost, thumb media, with the wrist caudal and the digital tips rostral and dorsal. 5. The central projection was distorted, some parts showing expanded representation, notably the tips of digits II and III and the medial wrist pad. Other parts were contracted, e.g. the wrist, forearm and shoulder. 6. Units with receptive fields consisting of the whole of a walking pad had shorter mean latencies, to tactile stimulation, than those whose field was a single spot on a pad. 7. Units were found to show an abolute unresponsive time to the second of a pair of identical supramaximal electrical stimuli of up to 50 msec, and a relative unresponsive time which could last up to 500 msec. The absolute unresponsive and relative unresponsive times to the second of a pair of tactile stimuli was shorter being 30 and 150 msec respectively. 8. The effect of decortication was to increase the excitability of thalamic units to peripheral stimulation both in the initial and later discharges.
The velocity tuning of single units in cat striate cortex.
Authors: Movshon J A
Published: December 2014

1. The activity of single units was recorded from the striate cortex (area 17) of anaesthetized, paralysed cats. Responses to stimuli moving at different velocities were examined. 2. Peak evoked firing frequency, rather than fotal evoked spikes, is used throughout as a measure of response. The former mea‐ure gives curves of response vs. velocity that correlate well with curves of contrast sensitivity vs. velocity, wheras the latter does not. 3. Cortical receptive fields were classified according to the criteria of Hubel & Wiesel. Simple cells were found to prefer lower velocities (mean 2‐2 deg sec‐1) than complex cells (mean 18–8 deg sec‐1). The response of simple cells to stimuli moving faster than 20 deg sec‐1 is generally poor; complex cells usually discharge briskly to these speeds. 4. Cells classified as hypercomplex by the end‐inhibition criterion were further chara‐terized as type I or type II, according to the suggestion of Dreher (1972). Type I units are indistinguishable from simple cells in their velocity tuning, and type II units equally clearly resemble complex cells. These results are therefor consistent with Dreher's sbudivision. 5. Teh selectivity of cells for velocity is variable but can be quite marked. The average selectivities of simple and complex cells are not significantly different. There is an inverse correlation between preferred velocity and the sharpness of velocity selectivity for simple cells; no trend is apparent for other cell types. 6. No clear correlation is observed between the velocity preferances of units and their degree of direction selectivity, or receptive field arrangement. Simple cells with ‘sustainef’ temporal responses to flashed stimuli tend to prefer slower rates of movement than ‘transient’ ones, and to be less selective for velocity. 7. The results for different cortical cell‐types are compared with the velocity tuning of X‐ and Y‐cells in the lateral geniculate nucleus.
Contractions induced by a calcium‐triggered release of calcium from the sarcoplasmic reticulum of single skinned cardiac cells.
Authors: Fabiato A , Fabiato F
Published: December 2014

1. Fragments of single cardiac cells were obtained by homogenization of ventricular tissue from adult rats. Remaining pieces of sacrolemma were removed by micro‐dissection. Tension was recorded from the ends of the skinned (sarcolemma‐free) cells with a photodiode force transducer. 2. In the presence of a strong buffering of the free [Ca2+] with 4‐0 mM total EGTA, a tonic tension was obtained that increased according to t sigmoid curve when the free ([Ca2+] was increased from 10(−6–75)M to 10(−5–0)M. This curve was not modified by the destruction of the sarcoplasmic reticulum (SR) by the detergent Brij 58. Therefore, the tonic tension corresponded to the direct effect of the free [Ca2+] present in the buffer on the myofilaments. 3. In the presence of a slight buffering of the free [Ca2+] with 0–050 mM total EGTA, cyclic contractions were observed that were attributed to cyclic releases and re‐sequestrations of Ca2+ by the SR. The absence of effect of azide and ruthenium red on the cyclic contractions obtained at a free [Ca2+] lower than 10(−6–50)M demonstrated that the mitochondria played no role in the triggering of these contractions. 4. Cyclic contractions were induced by a slight variation of free [Ca2+] in the buffer from 10(−7–65)M to 10(−7–40)M. Their amplitude at 10(−7–40)M free Ca2+ was equal to the tonic tension developed by a free [Ca2+] 20 times higher applied to the myofilaments when the SR was destroyed by detergent or functionally inhibited by high total [EGTA]. It was concluded that these cyclic contractions corresponded to a Ca2+‐triggered release of Ca2+ from the SR. 5. The cyclic contractions were induced by the filling of the SR with Ca2+ to a critical level at which it released a fraction of the Ca2+ it contained. Each contraction was followed by a re‐sequestration of Ca2+, the kinetics of which conditioned the duration of the cycles. 6. The amplitude of the cyclic contractions increased when the free [Ca2+] that triggered them was increased. This gradation was deemed incompatible with a simple regenerative process, which should produce an all‐or‐nothing response. Additional process, such as a modulation of the Ca2+ release by free [Mg2+] and [ADP] may help to explain the gradation of the contractions. 7. It was concluded that a Ca2+‐triggered release of Ca2+ from the SR of rat ventricular cells may amplify the Ca2+ flux crossing the sarcolemma during the plateau of the action potential, thereby permitting the activation of the myofilaments.
Atrial receptors and heart rate: the efferent pathway.
Authors: Kappagoda C T , Linden R J , Scott E M , Snow H M
Published: December 2014

1. Stimulation of left atrial receptors by distension of the junctions between the pulmonary veins and the left atrium is known to cause a reflex increase in heart rate. It was suggested that the efferent path of this reflex was solely in the sympathetic nerves to the heart but more recently the existence of a vagal efferent component has been postulated by Albrook, Bennion & Ledsome (1972). 3. The junctions between the pulmonary veins and the levt atrium were distended before and after the administration of I.C.I. 66082 and bretylium tosylate. The response of an increase in heart rate was significantly decreased after the administration of I.C.I. 66082 (5 mg/kg) and abolished after the administration of bretylium tosylate (10 mg/kg). 3. It is concluded that the efferent pathway of the reflex is solely in the sympathetic nerves to the heart.
The contribution of inhibitory mechanisms to the receptive field properties of neurones in the striate cortex of the cat.
Authors: Sillito A M
Published: December 2014

1. The iontophoretic application of the GABA antagonist bicuculline to simple and complex cells in the striate cortex of the cat produced extensive modifications of receptive field properties. These modifications appear to relate to a block or reduction of GABA‐mediated intracortical inhibitory influences acting on the cells examined. 2. For simple cells the effects of bicuculline on receptive field properties involved a loss of the subdivision of the receptive field into antagonistic "on" and "off" regions, a reduction in orientation specificity and a reduction or elimination of directional specificity. 3. The effect on the "on" and "off" subdivisions of the simple cell receptive field was such that all stationary flashing stimuli, whether covering the whole receptive field, or located within the receptive field over a previously determined "on" or "off" region, resulted in an "on and off" response. 4. The orientation specificity of complex cells was reduced during the application of bicuculline such that in many cases the original specificity of the cell was virtually lost with the response to the orientation at 90 degrees to the optimal being of similar magnitude to the optimal. The directional specificity of complex cells was generally less affected than that of simple cells. Often when large changes in orientation specificity were observed the directional specificity was relatively unaffected. 5. For some cells apparently showing to all visual stimuli only inhibitory responses, the application of bicuculline resulted in the appearance of excitatory responses. 6. In all cases receptive field properties reverted to the original state after termination of the bicuculline application. It was not generally possible to duplicate the effects of bicuculline by raising neuronal excitability with iontophoretically applied glutamate. 7. On the basis of these results it is suggested that the normal subdivision of the simple cell receptive field into separate "on" and "off" regions and its directional specificity are dependent on intracortical inhibitory processes that are blocked by bicuculline. The orientational tuning of simple cells conversely appears to be largely determined by the excitatory input but normally enhanced by lateral type inhibitory processes acting in the orientation domain. 8. It also appears that the excitatory input to some complex cells is not orientation specific. This suggests that for these cells it is extremely unlikely that they receive an orientation specific excitatory input from simple cells.
Factors governing the periodic activation of supraoptic and paraventricular neurosecretory cells during suckling in the rat.
Authors: Lincoln D W , Wakerley J B
Published: December 2014

1. One hundred and thirty‐two antidromically identified paraventricular (PV) and supraoptic (SO) neurones were studied during milk ejection evoked by the suckling of the young, in thirty‐four lactating rats anaesthetized with urethane (1.1 g/kg I.P.). The spike activity of these neurones was analysed to determine some of the factors governing their orthodromic activation. Changes in spike activity were compared with the amount of oxytocin released from the neurohypophysis, as measured by the rise in intramammary pressure at milk ejection. 2. Sixty‐five units, from both the PV and SO nuclei, displayed a characteristic burst of accelerated activity 12–18 sec before milk ejection. With a suckling stimulus of nine or ten pups, these neurosecretory responses were both regular in their occurrence (recurring evey 4‐8 min) and uniform in character, i.e. all responsive cells accelerated to 30–80 spikes/sec for 1‐4 sec. Two units deviated from this pattern and both were recorded in animals which failed to display a detectable milk ejection...
The relative contributions of the folds and caveolae to the surface membrane of frog skeletal muscle fibres at different sarcomere lengths.
Authors: Dulhunty A F , Franzini‐Armstrong C
Published: December 2014

The plasmalemmal area of striated muscle fibres is greater than the apparent surface area (A = circumference x length) because of variable folds and the invaginations of the caveolae and T‐tubules. Freeze‐fracture replicas of the surface membrane of sartorius and semitendinosus muscles from Rana pipiens have been used to determine the numbers and distribution of folds and caveolae at different sarcomere lengths. (1) The plasmalemma folds are variable in size and shape, but are always oriented perpendicular to the long axis of the fibre. The folds vary with stretch, being more prominent at short sarcomere lengths. The caveolae are elliptical invaginations of the plasmalemma which open to the outside by a narrow “neck” of approximately 20 nm. The caveolar lumen has an average long dimension of 81.6 +/‐ 11.7 nm and an average short dimension of 66.9 +/− 7.9 nm. The caveolar “necks” only can be seen in freeze‐fracture replicas and these are distributed in two circumferential bands on either side of the Z‐line, and in longitudinal bands separated by distances of 1‐5 mum. In the sartorius muscle, at a sarcomere length of 2.8 mum, there is an average number of thirty‐seven caveolae per square micrometer of fibre surface. (2) During passive stretch the opening of folds provides membrane for the necessary increase in surface area up to a sarcomere length of about 3.0 mum. This length is defined as the critical sarcomere length (Sc). The number of caveolae remains constant at all sarcomere lengths less than Sc and thus their “necks” have been used as membrane markers to determine the amount of folding at different sarcomere lengths. The membrane area contained in folds and caveolae is expressed as a fraction of the apparent surface area (A). For example, in the sartorius muscle, at a sarcomere length of 2.4 mum, the membrane area, excluding the T‐tubules, is: A + 0.1A (folding) + 0.7A (caveolae) = 1.8A. (3) For stretch beyond Sc membrane is provided by the opening of caveolae. At a sarcomere length of about 8 mum all the caveolae are open and the fibres rupture with further stretch. (4) The relative contributions of folds and caveolae vary with sarcomere length in a way that is consistent with assumptions of constant volume and plasmalemma area. The maintenance of constant plasmalemma area, even after excessive stretch, suggests that the plasmalemma is relatively inelastic in this situation.
Reconstruction of the electrical activity of cardiac Purkinje fibres.
Authors: McAllister R E , Noble D , Tsien R W
Published: December 2014

1. The electrical activity of Cardiac Purkinje fibres was reconstructed using a mathematical model of the membrane current. The individual components of ionic curent were described by equations which wee based as closely as possible on previous experiments using the voltage clamp technique. 2. Membrane action potentials and pace‐maker activity were calculated and compared with time course of underlying changes in two functionally distinct outeard currents, iX1 and iK2. 3. The repolarization of the theoretical action potential is triggered by the onset of iX1, which becomes activated over the plateau range of potentials. iK2 also activates during the plateau but does not play a controlling role in the repolarization. Hwever, iK2 does govern the slow pace‐maker depolarization through its subsequent deactivation at negative potentials. 4. The individual phases of the calculated action potential and their 'experimental' modifications were compared with published records. The upstroke is generated by a Hodgkin‐Huxley type sodium conductance (gNa), and rises with a maximum rate of 478 V/sec, somewhat less than experimentally observed values ( up to 800 V/sec). The discrepancy is discussed in relation to experimental attempts at measuring gNa. 5. The ole of the transient outward chloride current (called igr) was studied in calculations of the rapid phase of repolarization and 'notch' configuration...
Functional properties of ganglion cells of the rhesus monkey retina.
Authors: De Monasterio F M , Gouras P
Published: December 2014

Three general classes of cells were identified in a sample of 460 cells recorded from all areas of the retina subserving the central 40 degrees of vision in the rhesus monkey. 2. One class (colour‐opponent) had sustained colour‐opponent responses and concentrically organized receptive fields, in which usually one cone mechanism mediated the centre response and one or two different cone mechanisms mediated the antagonistic surround. A few cells of this class had non‐concentric (co‐extensive) receptive field organization. 3. A second class (broad‐band) had transient responses and concentrically organized receptive fields, in which usually two cone mechanisms mediated the centre response. In most cells, the surround had the same spectral sensitivity as the centre and the cells had non‐colour opponent responses. In other cells, the surround had a spectral sensitivity different to that of the centre and the cells had colour‐opponent responses. 4. The third class (non‐concentric) did not have concentrically organized receptive fields. One group of cells had extremely phasic on‐, off‐ or on‐off responses and no spontaneous activity, another group had characteristically regular spontaneous activity and was responsive only to moving stimuli. 5. Cells of the colour‐opponent class with concentric receptive fields had the smallest centre‐sizes, which did not vary markedly from cell to cell (mean 15 mum); cells of the non‐concentric class with phasic responses had the largest centre‐sizes, which varied from cell to cell. 6. Colour‐opponent cells comprised the highest proportion of cells near the foveola; broad‐band cells comprised the highest proportion in the more peripheral areas of the retina; non‐concentric cells were equally represented in all areas.