bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell structure and function in the visual cortex of the cat
Authors: Kelly J. P. , Van Essen D. C. 
Published: December 2014

1. The organization of the visual cortex was studied with a technique that allows one to determine the physiology and morphology of individual cells. Micro‐electrodes filled with the fluorescent dye Procion yellow were used to record intracellularly from cells in area 17 of the cat. The visual receptive field of each neurone was classified as simple, complex, or hypercomplex, and the cell was then stained by the iontophoretic injection of dye.2. Fifty neurones were successfully examined in this way, and their structural features were compared to the varieties of cell types seen in Golgi preparations of area 17. The majority of simple units were stellate cells, whereas the majority of complex and hypercomplex units were pyramidal cells. Several neurones belonged to less common morphological types, such as double bouquet cells. Simple cells were concentrated in layer IV, hypercomplex cells in layer II + III, and complex cells in layers II + III, V and VI.3. Electrically inexcitable cells that had high resting potentials but no impulse activity were stained and identified as glial cells. Glial cells responded to visual stimuli with slow graded depolarizations, and many of them showed a preference for a stimulus orientation similar to the optimal orientation for adjacent neurones.4. The results show that there is a clear, but not absolute correlation between the major structural and functional classes of cells in the visual cortex. This approach, linking the physiological properties of a single cell to a given morphological type, will help in furthering our understanding of the cerebral cortex.
Influence of dendritic location and membrane properties on the effectiveness of synapses on cat motoneurones
Authors: Barrett J. N. , Crill W. E. 
Published: December 2014

1. Measurements of the specific membrane properties and neuronal geometry of cat motoneurones were used to calculate the excitatory postsynaptic potentials (e.p.s.p.s) produced by unit (quantal) conductance changes occurring at various locations on the dendritic tree.2. Calculations demonstrate that conductance changes of 80–190 × 10−10 mho are required to produce e.p.s.p.s having the same rise time and peak amplitude as the quantal e.p.s.p.s recorded in motoneurones by Kuno & Miyahara (1969b). Because quantal conductance changes are so large, synaptic activity can significantly reduce the effective specific resistance of the motoneuronal membrane.3. A quantal conductance change occurring at a high‐impedance distal dendritic site is calculated to produce an e.p.s.p. of 15–20 mV peak amplitude at that site. Significant non‐linear summation will occur between the e.p.s.p.s produced by conductance changes occurring simultaneously on the same dendritic branch.4. Calculations which take into account both non‐linear summation and the loss of synaptic charge through dendritic membranes predict that for these motoneurones the time integral of soma‐recorded quantal e.p.s.p.s originating on distal dendrites should be at least 20% as great as the time integral of a quantal e.p.s.p. originating directly on the soma. Quantal conductance changes occurring on 76% of the dendritic tree should produce soma e.p.s.p. time integrals at least 50% as great as those produced by somatic synapses.
Blood flow in resting (contralateral) arm and leg during isometric contraction
Authors: Eklund Brita , Kaijser L. , Knutsson E. 
Published: December 2014

1. Blood flow in resting forearm and calf were measured plethysmographically in healthy young men during isometric contraction performed both as a handgrip and as a dorsiflexion of the foot. The isometric contraction was maintained for 2 min at one third maximal voluntary contraction for the handgrip and half maximal voluntary contraction for the dorsiflexion of the foot. In some experiments the possible influence on blood flow of inadvertent muscle activation in the resting limb was checked by recording the e.m.g.2. Both handgrip and dorsiflexion of the foot produced substantial increases in heart rate and mean arterial pressure, the pressure rise being almost linear with time throughout the contraction.3. Isometric contraction produced a rapid increase in forearm blood flow which reached a maximum on average two and a half times the resting value after 1 min and then declined slightly. Similar increases in forearm blood flow were produced by handgrip and dorsiflexion of the foot.4. Unlike in the resting forearm, the blood flow in the resting calf increased only slightly during the first minute of contraction and then decreased again to the resting level.5. The flow increase in the resting limbs could not be ascribed to inadvertent muscle activation as judged from the e.m.g. recordings.6. It is concluded that isometric muscle contraction produces a rapid increase in blood flow in the resting forearm, but only a very slight flow increase in the calf. Since the flow increased faster than the arterial pressure it must to a certain extent be induced by active neurogenic vasodilatation. Similarly, the relative flow decrease during the latter half of the contraction concomitantly with a progressively rising arterial pressure suggests that the neurogenic effect on the resistance vessels changes character, becoming more vasoconstrictive, and this might be related to increased effort in sustaining the contraction.
Properties of rarely encountered types of ganglion cells in the cat's retina and on overall classification
Authors: Cleland B. G. , Levick W. R. 
Published: December 2014

1. In a reference sample of 960 cat retinal ganglion cells, seventy‐three had receptive fields departing from the concentric centre—surround pattern.2. Five classes were distinguished among the subset: local edge detectors, direction‐selective cells, colour‐coded cells, uniformity detectors, edge inhibitory off‐centre cells.3. Local edge detectors (forty‐five) possessed a radially symmetrical pattern of responses to both centrifugal and centripetal movements of both black and white small targets, an on—off receptive field with a silent inhibitory surround and a low or zero maintained discharge. Their operation could be interpreted as the detection of a contrasting border confined to a small region of the visual field.4. With direction‐selective units (eleven) it was possible to find an axis through the receptive field along which sharply different responses could be obtained for opposite directions of movement of small black or white targets.5. Colour units (six) were mostly of the single opponent type having excitatory input from blue‐sensitive cones and inhibitory input from long wave‐length cones. Both inputs coexisted at the centre of the field and either could be spatially more extensive than the other. One example changed over to rod input under scotopic conditions, another did not.6. Uniformity detectors (five) had a brisk maintained discharge which was reduced or abolished temporarily by all forms of visual stimulation.7. Edge inhibitory off‐centre units (three) behaved like uniformity detectors for small targets and fine gratings but like off‐centre on‐surround units for large targets. Their receptive fields consisted of three concentric regions: a small sized, central edge inhibitory region; a larger zone of off‐responsiveness; and an outlying annulus of on‐responsiveness.8. It is argued that the above physiological types belong to the morphologically heterogeneous class of cells called γ cells. The argument is based on similarity in the sizes of receptive fields and dendritic trees and on evidence that the axons are thinner than those of the brisk‐sustained and brisk‐transient ganglion cells.9. The physiological classification of cat retinal ganglion cells developed in this paper and the preceding one is summarized in a Table.10. It now appears that cat and rabbit possess a qualitatively similar complement of receptive field types among their ganglion cells; the differences reside in the quantitative expression of the various classes.
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.
Facilitated transport of prostaglandins across the blood—cerebrospinal fluid and blood—brain barriers
Authors: Bito L. Z. , Davson H. , Hollingsworth Jillian R. 
Published: December 2014

1. Ventriculo‐cisternal perfusions were performed on rabbits with artificial cerebrospinal fluid containing blue dextran and tritium‐labelled prostaglandin F2α ([3H]PGF2α). In order to study the nature of prostaglandin (PG) transfer across the blood—brain barrier, high concentrations of PGF2α or potential PG transport inhibitors were added to the perfusion fluid after the normal rate of [3H]PGF2α clearance was established.2. The [3H]PGF2α clearance was inhibited by 10−6 to 10−3
M PGF2α, PGF2β, probenecid, iodipamide or bromcresol green but not by perchlorate.3. The 3H content of the brain, relative to the 3H‐activity in the ventricular system, was also increased by high concentrations of PGF2α, iodipamide or bromcresol green.4. It is concluded that the removal of PGs from the extracellular fluids of the brain is mediated by saturable, facilitated transport processes across both the choroidal and extrachoroidal regions of the blood—brain barrier system. In the case of the mammalian brain, such facilitated PG transport appears to be the primary mechanism for the termination of the action of these potent, endogenously produced autacoids.
Genetic dissection of the photoreceptor system in the compound eye of Drosophila melanogaster
Authors: Stark William S. , Walker John A. , Harris William A. 
Published: December 2014

1. Three mutations which eliminate specific types of photoreceptors in Drosophila were characterized.2. Of the eight photoreceptors in each facet, two mutations delete the outer six (R 1‐6). The third eliminates R 7, one of the two central photoreceptors. Double mutants can be constructed in which only photoreceptor R 8 is present.3. The spectral sensitivities, photopigments, and behavioural properties of these mutants were investigated.4. R 1‐6 have two sensitivity peaks, near 350 and 470 nm. These receptors contain a rhodopsin with these absorption peaks. It interconverts with a metarhodopsin that absorbs around 570 nm.5. R 7 is a U.V.‐receptor, containing rhodopsin that absorbs around 370 nm and interconverts with a metarhodopsin which absorbs around 470 nm.6. R 8 is a non‐adapting blue‐receptor with a third type of rhodopsin.7. The properties of these photopigments explain the different sensitivities and spectral adaptation phenomena of the various photoreceptors.8. All the photoreceptors have input into phototaxis. Spectral analysis of this behaviour provides evidence for integration of the input from the different photoreceptors.
The association between acidification and electrogenic events in the rat proximal jejunum
Authors: Lucas M. L. 
Published: December 2014

1. Simultaneous measurement of hydrogen ion production, transmural potential difference and intermittent short‐circuit current (SCC) was made in the rat proximal jejunum in vitro: similarly, potassium and sodium ion movements were measured to investigate the relationship of acidification to electrogenic events and associated ion movements in the jejunum.2. Acidification correlated significantly with the short‐circuit current and both were inhibited by 10 m
M serosal ouabain or 10 m
M mucosal aminophylline. Both inhibitors had effects on net potassium movement but not on net sodium movement. Moreover, in isotope studies whereas 10 m
M serosal ouabain reduced the Jms sodium flux, 10 m
M mucosal aminophylline had no effect, i.e. aminophylline can reduce both short‐circuit current and acidification without perceptibly altering the serosally directed sodium flux.3. In low‐sodium buffers in which acidification still occurs although reduced, transmural potential differences occur of reversed polarity that are apparently unrelated to sodium diffusion potential differences (as evidenced by isotopic sodium efflux experiments) and which could be caused by hydrogen ion production. In low sodium buffers however the inhibitors have opposing effects, ouabain causing an increase and aminophylline a decrease in the reversed potential differences.4. A model for acidification (that of potassium rather than sodium ion exchange for the hydrogen ion and hydroxyl for chloride ion exchange) is proposed to explain the present experimental findings and other diverse observations in the literature: although either step might be the electrogenic step, acidification must be also considered as a component of the jejunal short‐circuit current.