bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of different functional types of neurones in the cat's rostral trigeminal nuclei responding to sinus hair stimulation
Authors: Gottschaldt K.-M. , Young D. W.
Published: December 2014

1. Properties of neurones in the trigeminal nuclei principalis and oralis responding to movements of facial sinus hairs were studied in cats anaesthetized by I. V. infusion of pentobarbitone.

2. Using electrophysiological methods trigeminal neurones were classified into primary afferent fibres, trigeminothalamic relay neurones, interneurones and other unspecified higher order neurones.

3. When receptive fields of synaptically activated neurones were compared with those of primary afferent fibres, an often extensive convergence from first order on to higher order neurones was established. Out of 119 relay neurones six received input from one sinus hair only. Spontaneous activity was encountered about twice as often in synaptically activated neurones than in primary afferent fibres.

4. The responsiveness of single neurones was unstable over time in about one fifth of the population and then the total number of impulses discharged in successive responses could vary by as much as 500%. Unstable responsiveness occurred sometimes alone but was often accompanied by marked changes in the size or the configuration of the receptive field. Such instabilities were observed in all kinds of synaptically activated neurones but not in primary afferent fibres.

5. Afferent inhibition in relay neurones could be elicited from within the excitatory receptive field and appeared to be related to the activation of distinct receptor populations responding to specific stimulus parameters. Inhibition was also seen in interneurones following both mechanical stimulation of the skin and electrical stimulation of lemniscal fibre terminals in the contralateral ventromedial thalamus.

6. The results are discussed and compared with previous findings about sinus hair representation in the trigeminal nucleus and the ascending lemniscal projection. The findings indicate that the concept of the ‘static properties’ of relay neurones is not adequate for all trigeminothalamic relay neurones and may require a critical reconsideration.

7. It is suggested that the afferent input from sinus hairs is effectively controlled at the level of the rostral trigeminal nuclei. This control may affect the spatial input to relay neurones, the temporal components of their responses and the intensity dimension of their transmission capacity. It is postulated that by these mechanisms tactile information from the sinus hair system is modulated according to the instantaneous sensory requirements of the behaving cat.
A comparison of ion concentrations, potentials and conductances of amphibian, bovine and cephalopod lenses
Authors: Delamere N. A. , Duncan G.
Published: December 2014

1. The concentrations of sodium, potassium and chloride in frog and bovine lenses showed a normal intracellular ion distribution with the sum of the internal cations approximately equal to the external sum. In the cephalopod lens, however, the sum inside was much lower than that outside.

2. The membrane potentials of frog, Sepiola and bovine lenses were ‐63, ‐63 and ‐23 mV respectively. A comparison of the electrical data with the Nernst potentials predicted from ion concentration data indicated that sodium and chloride ions as well as potassium contributed to the membrane potential in frog and bovine. In contrast, the membrane and Nernst potentials for potassium were equal in Sepiola.

3. Substituting potassium for sodium in the external medium depolarized lens potentials in all three species. Estimates of the relative permeabilities of sodium, potassium and chloride were obtained by fitting the Goldman‐Hodgkin‐Katz equation to the potential data.

4. The potassium permeability was determined directly by 42K efflux measurements and values of 2·99, 9·83 and 3·13 (× −8 m sec−1) were obtained for frog, Sepiola and bovine lenses respectively.

5. The effect of raising external potassium on the efflux rate constant was determined and there was reasonable agreement between experiment and theory (Kimizuka‐Koketsu) in frog and bovine lenses, but the Sepiola data indicated that the potassium permeability decreased by a factor of 2·6 when the external potassium was raised from 10 to 120 m
M‐K+.

6. The measured specific conductances, obtained using two internal micro‐electrodes, were 7·7, 15·9 and 9·9 (Sm−2) for frog, cephalopod and bovine lenses respectively. These data compare with computed values (Kimizuka‐Koketsu theory) of 7·5, 14·1 and 17·2 (Sm−2).

7. The effect of increasing external potassium on the conductance was also tested and there was good agreement between experiment and theory (assuming constant permeabilities) only in the amphibian lens. However, when the cephalopod data were corrected assuming a 2·6‐fold decrease in PK for a twelvefold increase in potassium, then there was excellent agreement between experiment and theory.

8. The bovine measured conductances were much lower than the theoretical values throughout the range of external potassium concentrations and several explanations were proposed to account for the discrepancies.
Movement of labelled decamethonium in muscle fibres of the rat.
Authors: Case R , Creese R , Dixon W J , Massey F J , Taylor D B
Published: December 2014

1. Tritium‐labelled decamethonium accumulated in diaphragm muscles of the rat in vitro with a peak at the end‐plate region and the distributions were fitted by Gaussian curves. 2. Prolonged wash in physiological saline (10 hr) produced some loss in radioactivity but no detectable spread of the labelled compound along the fibres, which indicated that the decamethonium was not in a mobile form. 3. Rats injected with labelled decamethonium showed radioactivity in the diaphragm muscles after 21 days. 4. A slow spread of the labelled compound along the fibres was detected, and from the widening of the Gaussian curves the apparent diffusion coefficient was 1.2 X 10(‐8) cm2sec‐1, which is less than 1/500 of that in free solution.
Analysis of electrical noise in turtle cones
Authors: Lamb T. D. , Simon E. J.
Published: December 2014

1. Properties of the light‐sensitive voltage noise in cones in the retina of the turtle, Pseudemys scripta elegans, have been studied by intracellular recording.

2. Suppression of the noise by light was a function of the hyperpolarizing response of a cone but not of the size or pattern of illumination.

3. Power density spectra of the noise were fitted in many cones by the product of two Lorentzians with characteristic time constants τ1 and τ2 averaging 40 and 7 msec respectively. The spectra of some cells were peaked and could be fitted by a resonance curve.

4. Spectra in dim light exhibited decreased low frequency power. They could often be fitted by a product of two Lorentzians using the same value of τ2 as used in darkness but decreasing τ1 and the zero frequency asymptote. An e‐fold reduction in τ1 occurred with lights which hyperpolarized by 4‐7 mV.

5. Injection of hyperpolarizing currents of about 0·1‐0·2 nA into weakly coupled cones reduced the noise, and also reduced the sensitivity to dim flashes.

6. The variance‐voltage relation during steady illumination of different intensities differed from cone to cone. Dim lights increased the noise in some cells and decreased it in others, but moderately bright lights which gave steady responses of more than about one third maximal reduced the noise in all cells.

7. When the cell was transiently depolarized during the differentiated component following steady illumination, the noise was less than it was after prolonged darkness.

8. In the after‐effect of bright light, the time course of recovery of noise was the same as that of flash sensitivity and voltage. The noise was reduced e‐fold for hyperpolarizations averaging 3 mV while for sensitivity this reduction occurred for 1·3 mV. For a given hyperpolarization the noise was lower during the after‐effect than during steady dim illumination.

9. When a series of dim flashes was delivered to a cone, no significant increase in variance over the dark noise was detected during the photo‐response. This implies that each photoisomerization evokes no more than about 1·5 μV at the peak of the response in a coupled cone, corresponding to about 50 μV in an isolated cone.

10. The elementary shot events underlying the noise are about 100 μV in amplitude in an isolated cone, have a characteristic time constant of 16‐60 msec and reflect unit conductance fluctuations of about 16 pS (S, Siemen ≡ Ω−1).

11. It is concluded that the noise source is internal to the cones. We postulate that the noise arises from opening and closing of the light‐sensitive ionic channels in the outer segment, and that in darkness there is a residual concentration of the blocking substance which on average closes up to about one third of the channels. It seems likely that the unit event involves a considerable number of blocking molecules and ionic channels.
Fluxes and distribution of calcium in rat liver cells: kinetic analysis and identification of pools
Authors: Claret-Berthon Brigitte , Claret M. , Mazet J. L.
Published: December 2014

1. Fluxes and distribution of Ca were studied in the perfused rat liver. Kinetic analysis of 45Ca exchange revealed three compartments with time constants of 4, 14 and 223 min, pool sizes of 250, 385 and 670 μmole.kg−1 wet wt. respectively, and one non‐exchangeable compartment of 400 μmole.kg−1.

2. 45Ca uptake by in situ mitochondria followed, as a function of cell loading time, a mono‐exponential function with a time constant of 16 min. This suggests that the second compartment may be identified as the intracellular pool of Ca. The calculated cell transmembrane flux of Ca was 28 μmole.kg−1 min−1 or 0·17 p‐mole.cm−2.sec−1.

3. The maximum 45Ca uptake by in situ mitochondria was 2·3 n‐mole.mg−1 of protein which represents, on the basis of 50 mg of mitochondrial protein per g of fresh liver, 115 μmole.kg−1 or 30% of the cytoplasmic pool. A pool of 10·8 n‐mole.mg−1 protein (or 540 μmole.kg−1) of non‐exchangeable Ca (at steady state) was probably in the form of Ca phosphate precipitated in the mitochondrial matrix.

4. Extracellular Ca pools were studied using competitor of Ca binding (La) or Ca chelators (EGTA). La displaced specifically a homogeneous pool of Ca (τ = 5·1 min) which represented a fraction (55 μmole.kg−1) of the rapidly exchangeable Ca (first compartment) without perturbing other external pools. On the other hand, EGTA displaced completely that compartment, and about 85% of the Ca of the third compartment. These results suggest that the first and the major fraction of the third compartments are extracellular. They account for 63% of total exchangeable Ca.

5. A model of distribution and exchange of Ca in hepatocytes is proposed.
Search for a natriuretic mechanism sensitive to sodium in the brain of the monkey.
Authors: Kumar M A , Swaminathan S
Published: December 2014

1. The effects of hypertonic saline infusion into the third ventricle were investigated in ten monkeys which were pre‐operated, trained, and used in the conscious state under controlled conditions. 2. In non‐hydrated monkeys, intraventricular infusion of NaCl 1.0 M, 0.01 ml./min for 30 min did not affect urine volume or Na output but produced a small increase in urine osmolality. Comparable infusion of NaCl 0.15 M had no effect on any parameter. 3. In monkeys undergoing water diuresis (with i.v. infusion of 5% dextrose), intraventricular hypertonic saline produced large reciprocal changes in urine volume and osmolality while urine Na showed no significant change. The effects on urine volume and osmolality were greater than those of lysine‐vasopressin 30 m‐u./kg i.v. 4. The absence of natriuresis after intraventricular hypertonic saline infusion in the monkey was in notable contrast to the results reported in lower species. However, the data suggested that the infusion probably released ADH as in other species.
Developmental changes in nephron number, proximal tubular length and superficial nephron glomerular filtration rate of rats.
Authors: Solomon S
Published: December 2014

1. Post‐natal development of single nephron glomerular filtration rate, superficial proximal tubular length, nephron number and kidney weight have been studied in Sprague Dawley and in Wistar rats. 2. Superficial tubular length is a non‐linear function of body weight or age. There seems to be a rapid growth until animals weigh about 150 g in Wistar rats. In this strain, growth is slower thereafter. This difference is not as evident in Sprague Dawley rats. 3. Nephron numbers increase over the same period at which rapid tubular growth occurs. 4. Sprague Dawley rats have somewhat fewer, but longer, proximal tubules than do Wistar rats. 5. In all animals weighing more than 100 g, SNGFR is linearly related to weight. For younger, smaller Sprague Dawley rats, the same linearity holds over the age range studied‐‐older than 20 days of age. In Wistar rats, SNGFR relative to weight is less in young animals. 6. By relating SNGFR to total kidney GFR, evidence is obtained that maturation of renal function also involves a greater increase in filtration by superficial than by juxtamedullary nephrons.
The reorganization of synaptic connexions in the rat submandibular ganglion during post‐natal development.
Authors: Lichtman J W
Published: December 2014

1. The innervation of neurones in the submandibular ganglion of neonatal and adult rats has been studied with intracellular recording, and light and electron microscopy. 2. Intracellular recordings from neurones in isolated ganglia from adult animals showed that about 75% of the ganglion cells are innervated by a single preganglionic fibre. 3. However multiple steps in the post‐synaptic potential (about five on average) were elicited in ganglion cells from neonatal animals by graded stimulation of the preganglionic nerve. The same result was obtained when the preganglionic fibres were stimulated at their emergence from the brainstem, indicating that neonatal neurones are innervated by several different preganglionic nerve cells. 4. The number of preganglionic fibres innervating individual ganglion cells gradually decreased during the first few weeks of life, and by about 5 weeks each ganglion cell was generally contacted by a single preganglionic axon. 5. Synapses were made on short protuberances in the immediate vicinity of the neuronal cell bodies in both neonatal and adult ganglia as shown by staining presynaptic boutons with the zinc‐iodide osmium method, injection of horseradish peroxidase into ganglion cells, and electron microscopical examination. 6. Electron microscopical counts of synaptic profiles per ganglion cell perimeter showed that the number of synaptic contacts made on ganglion cells actually increased during the first few post‐natal weeks, when the number of axons innervating each neurone was decreasing. 7. These results show that in the rat submandibular ganglion there is a reorganization of neuronal connexions during the first few weeks of life which results in a transition from multiple to generally single innervation of ganglion cells.
Kinetic analysis of sodium and chloride influxes across the gills of the trout in fresh water.
Authors: Girard J P , Payan P
Published: December 2014

1. Na and Cl intake through the gill of the perfused head of trout were studied in fresh water with (10(‐5)M) or without adrenaline in the perfusing solution. 2. Ionic influxes occur exclusively across the lamellae in fresh water while in the sea‐water adapted trout part of salt entry is extralamellar. 3. In absence of adrenaline, Na and Cl enter the gills at the same rate (respectively 6.9 +/‐ 1.30 and 6.6 +/‐ 1.55 muequiv/hr. 100 g). Adrenaline (10(‐5)M) increased the Na influx to 47.8 +/‐ 4.12 muequiv/hr. 100 g, a value similar to that observed in vivo. The Cl influx remains unchanged however (6.3 +/‐ 2.40 muequiv/hr. 100 g), a value much smaller than that found in vivo. 4. Radioactive loading experiments coupled with unloading experiments allowed the determination of the relative permeabilities of the serosal and mucosal barrier for Na+ and Cl‐. For both ions, the basal membrane is less permeable. Adrenaline by increasing the Na permeability across the apical barrier enhances the active Na pumping through the basal membrane. 5. Intracellular Na and Cl exchangeable pools were calculated. They represent less than 1% of the total ionic content of the epithelium. Adrenaline increased by sixfold the Na pool without modifying the Cl pool.
Left ventricular mechanoreceptors: a haemodynamic study
Authors: Fox I. J. , Gerasch D. A. , Leonard J. J.
Published: December 2014

1. To study the function of the left ventricular mechanoreceptors, a working left ventricle preparation was devised in dogs which permitted control of pressure and flow of the isolated perfused coronary circulation and of the flow of the isolated, separately perfused systemic circulation. The systemic circulation was perfused at a constant rate so that changes in systemic pressure reflected changes in systemic resistance.

2. Increases in myocardial contractility produced by injection of catecholamines into the isolated, perfused coronary circulation produced a fall in the pressure (resistance) of the isolated, separately perfused (at a constant rate) systemic circulation.

3. Completeness of isolation of the coronary and systemic circulations was shown by the marked difference in appearance times between the reflex hypotensive responses from catecholamine injections into the isolated coronary circulation and the direct hypertensive response from a similar injection when the circulations were connected as well as by the marked difference between the pressure pulses recorded simultaneously on both sides of the aortic balloon separating the two circulations.

4. Myocardial β receptor blockade produced by injection of propranolol into the isolated coronary circulation abolished or attenuated the changes in left ventricular myocardial contractility as well as the subsequent hypotensive responses following the similar injection of catecholamines.

5. Electrical stimulation of a sympathetic nerve innervating the heart resulted in increases in left ventricular myocardial contractility and subsequent systemic hypotensive responses indistinguishable from those following injection of catecholamines.

6. That distortion of the mechano‐ or stretch receptors in the left ventricular myocardium was the cause of the hypotensive responses was demonstrated by increasing left ventricular myocardial contractility by mechanically obstructing the left ventricular outflow which produced hypotensive responses similar to those following the injection of catecholamines or nerve stimulation.

7. Bilateral high cervical vagotomy abolished the hypotensive responses following injection of catecholamines into the isolated coronary circulation or following left ventricular outflow obstruction in all but one instance, indicating the importance of vagal fibres to the afferent arm of the reflex.

8. It is suggested that the left ventricular mechanoreceptors function normally to reduce the peripheral resistance in order to prepare the systemic circulation to receive the left ventricular output and, especially during exercise, to prepare the systemic circulation to receive the augmented cardiac output with a minimum alteration in the systemic blood pressure and to distribute this augmented output preferentially to the skeletal muscles.
The digestion and transmission of labelled immunoglobulin G by enterocytes of the proximal distal regions of the small intestine of young rats.
Authors: Morris B , Morris R
Published: December 2014

Density gradient centrifugation of samples prepared from proximal gut homogenates after intra‐lumenal injection of 125I‐labelled IgG, was used to prepare batches of IgG fragments according to sedimentation coefficients. 2. Ultrafiltration was employed to partition the radioactivity in the vascular compartments, viscera and carcasses of rats aged 14‐15 days, 2 hr after the injection of standard doses of labelled IgG into the proximal and distal regions of the small intestine. 3. Radioactive samples prepared by these methods were re‐introduced into young rats by intra‐cardiac injection, and the rate at which they were removed from the vascular compartment was assessed. 4. Proximal enterocytes transmitted about 39% of the IgG which had been removed from the intestine in intact form. Most of this was retained in the vascular compartment; they degraded up to about 57% of the total removed into fragments less than 1000 mol. wt. and about 4% into intermediate sized fragments. 5. Distal enterocytes degraded almost 90% of the IgG processed into fragments less than 1000 mol. wt., about 8% as fragments greater than 100,000 mol. wt. 6. Fragments, of all sizes, were cleared rapidly from the circulation into the viscera and carcass. 7. The relevance of these results to protein transmission and digestion by the rat small intestine is discussed.
Rabbit placental clearing‐factor lipase and transfer to the foetus of fatty acids derived from triglycerides injected into the mother.
Authors: Elphick M C , Hull D
Published: December 2014

1. Lipase activity was measured in rabbit placental tissue fragments in late pregnancy. The activity in incubated tissue was greater with heparin (69%), reduced by NaCl (90%), but not affected by acetone or ether. 2. Pregnant rabbits (28‐days gestation) were given triglyceride emulsions intravenously and the change in profile of fatty acids in the maternal and umbilical artery and vein plasma free fatty acid (FFA) measured. 3. Those fatty acids predominant in the emulsion were higher in concentration in the umbilical vein FFA than in the maternal plasma FFA and the venous‐arterial difference was altered such that the placental transfer of FFA was enriched in a pattern corresponding to the profile of the fatty acids in the emulsion. 4. It is concluded that (i) the rabbit placenta shows considerable lipase activity and the lipase has the same characteristics as clearing‐factor (lipoprotein) lipase, (ii) triglyceride infused into the mother is taken up by the placenta and hydrolysed, and (iii) the fatty acids so released pass through the placenta and are taken up by the foetus.
Kinetic evaluation of the Na‐K pump reaction mechanism.
Authors: Sachs J R
Published: December 2014

1. The ouabain‐sensitive K influx was measured at varying external K concentrations ([K]o) and at several fixed internal Na concentrations ([Na]c). The cells were nominally K‐free and the solutions Na‐free. Both the apparent maximal velocity (VM) and the apparent Michaelis constant for K (KK) increased as Nac increased. The ratio app. VM/app. KK increased with increasing Nac. 2. The ouabain‐sensitive Cs influx was measured at varying external Cs concentrations and at several fixed Nac in K‐free cells and Na‐free solutions. Both app. VM and app. Kcs increased as Nac increased and the ratio app. VM/app. Kcs increased with increasing Nac. 3. The data were evaluated in terms of ping‐pong model and a simultaneous model for the pump reaction mechanism. The simultaneous model described the data adequately and the ping‐pong models did not. 4. The K influx was measured at varying external K concentrations in solutions containing Na and at a low and high Nac; the cells contained K. The relation between the pump rate and the external K concentration was sigmoid. A Hill equation was fitted to the data. KK was higher in the high Nac cells, but the Hill coefficient (n) was not altered as Nac increased. 5. The K influx was measured at varying internal Na concentrations and two fixed external K concentrations; the cells contained K. The relation between the pump rate and Nac was sigmoid. When a Hill equation was fitted to the data, it was found that KNac was higher at the high external K concentration, but n was the same at both K concentrations.
Are there functionally important temperature sensors in the right heart or lungs?
Authors: Cranston W I , Hellon R F , Townsend Y
Published: December 2014

1. In conscious rabbits, paired hot or cold infusions were given into the left atrium or jugular vein. For each pair of infusions the volume and temperature of the fluid was identical. The time course of the displacement of brain temperature was measured. 2. The magnitude of the displacement of brain temperature was not influenced to any major extent by the route of infusion. 3. This evidence suggests that there are no temperature sensors of any importance in the right heart or lungs.
A possible origin of circulating gastrin component IV in cats.
Authors: Blair E L , Grund E R , Lund P K , Sanders D J
Published: December 2014

1. Blood circulating in the cat is known to contain relatively large concentrations of gastrin components corresponding to Rehfeld's Components III and IV, whereas human blood has mostly Components II and III. 2. Synthetic cat gastrin 17NS was continuously injected into chloralose anaesthetized cats and at 1, 10 and 40 min after the start of injection there were significantly greater concentrations of immunoreactive gastrin Component IV than Component III in arterial blood (P less than 0.025 in each case). These concentrations were also greater than the total arterial gastrin concentration in the basal state. 3. Cat blood with EDTA incubated at 37 degrees C with synthetic cat and natural porcine gastrins 17NS produced Component IV. Hunan blood with EDTA incubated in a similar way with natural and synthetic human gastrins 17NS did not produce any detectable Component IV. Cat blood incubated with natural porcine and synthetic cat gastrin 17NS at 0 degrees C did not produce any Component IV. 4. We conclude that there may be an enzyme or enzymes in cat blood which cause the conversion of gastrin 17NS to Component IV.
Inactivation of sodium channels: second order kinetics in myelinated nerve
Authors: Chiu S. Y.
Published: December 2014

1. Kinetics of inactivation of sodium channels in myelinated nerve from Rana pipiens were studied at 4·5 °C using the voltage clamp technique of Dodge & Frankenhaeuser (1958).

2. Potassium currents were blocked by cutting the internodes in 20 m
M‐TEA‐Cl + 100 m
M‐KCl and by adding 12 m
M‐TEA‐Cl to the external Ringer. Leakage and capacitative currents were subtracted electronically.

3. Kinetics of recovery from inactivation of the sodium channels were studied by inactivating the channels with a large depolarizing prepulse and allowing the channels to recover at different potentials; the extent of recovery was measured by applying a test pulse at various times after the prepulse.

4. Kinetics of development of inactivation were studied by two different methods. The first was to measure the decay of sodium current under a maintained depolarization. The second method was to measure the decay of the peak sodium current in a test pulse as a function of time after the onset of a maintained depolarization. These two methods yielded similar results for the kinetics of inactivation development.

5. Contrary to expectations of the Hodgkin—Huxley formalism, the time course of recovery from and development of inactivation is not strictly exponential. Rather, recovery from complete inactivation shows an initial delay which depends on recovery potentials. Development of inactivation at a fixed potential exhibits at least two exponentials.

6. The steady‐state inactivation curve h∞(E) is asymmetrical and is fitted better by 1/[1+exp (A1E+B1) +exp (A2E+B2)] than by 1/[1+exp (AE+B)].

7. Most of the above kinetic observation on inactivation can be fitted by the following modification of the h system of the Hodgkin—Huxley formalism: [Formula: see text]

8. In the analysis it was not necessary to modify the concept of two separate processes, activation and inactivation, governing the opening and closing of the sodium channels.
The spatial extent of excitatory and inhibitory zones in the receptive field of superficial layer hypercomplex cells
Authors: Sillito A. M.
Published: December 2014

1. An investigation has been made of the extent of inhibitory and excitatory components in the receptive field of superficial layer hypercomplex cells in the cat's striate cortex and the relation of the components to the length preference exhibited by these cells.

2. Maximal responses were produced by an optimal length stimulus moving through a restricted region of the receptive field. The length of this receptive field region was less than the total length of the excitatory zone as mapped with a very short slit. Slits of similar length to the excitatory zone produced a smaller response than an optimal length slit.

3. An increase of slit length so that it passed over receptive field regions either side of the excitatory zone resulted in an elimination of the response. When background discharge levels were increased by the iontophoretic application of
D, L‐homocysteic acid slits of this length were observed to produce a suppression of the resting discharge as they passed over the receptive field. They did not modify the resting discharge level when it was induced by the iontophoretic application of the GABA antagonist bicuculline. This data is taken to indicate that long slits activate a powerful post‐synaptic inhibitory input to the cell.

4. Maximal inhibitory effects were only observed if the testing slit passed over the receptive field centre. That is slits with a gap positioned midway along their length so as to exclude the optimal excitatory response region surprisingly tended to produce excitatory effects rather than the expected inhibitory effects. It appears that simultaneous stimulation of the receptive field centre is a precondition for the inhibitory effect of stimulation of regions either side of the excitatory zone to be activated.

5. It is suggested that the interneurones mediating the inhibitory input to the superficial layer hypercomplex cells are driven both by cells in adjacent hypercolumns with receptive fields spatially displaced to either side of the excitatory zone and by cells in the same column, optimal inhibitory effects only being achieved when both sets of input to the interneurone are activated.
The effects of position and skin temperature on the capillary pressures in the fingers and toes
Authors: Levick J. R. , Michel C. C.
Published: December 2014

1. Direct measurements of the capillary pressure (Pc) were made in capillaries at the base of the nails of the fingers and toes of two subjects (the authors of this paper).

2. With the hand or foot at heart level, Pc varied over the range of 7‐70 cm H2O with mean values of 43 cm H2O in both the fingers and the toes. Pc was higher in the arterial limb (mean 49 cm H2O) than in the venous limb (mean 34 cm H2O) of the capillary loops. The plasma colloid osmotic pressures for the two subjects were 33 and 34 cm H2O.

3. For capillaries at heart level there was a strong positive correlation between Pc and skin temperature when the latter was varied over the range 23‐36 °C.

4. When the hand or foot was lowered, Pc increased less than the local arterial (Pa) and venous pressures (Pv). Furthermore the variation in Pc was reduced. In fourteen measurements of Pc made on capillaries in the toes of standing subjects, Pc was no more than 10 cm H2O greater than Pv. It is argued that the increase in the ratio (Pa — Pc)/(Pc — Pv) with hydrostatic load represents an increase in the ratio of pre‐ to post‐capillary resistance.

5. When Pv was increased by inflating a sphygmomanometer cuff around the upper arm, (Pa — Pc)/(Pc — Pv) increased in the hand held at heart level. These changes were similar to those seen with changes in position.

6. The implications of the results are discussed with respect to fluid balance between the blood and tissues. It is argued that since Pc in the warm hand was never less than the plasma colloid osmotic pressure, fluid is not reabsorbed from the tissues into the capillaries of the warm skin of the hand even at heart level. Compensatory changes in the circulation appear to minimise the filtration of fluid into the feet of the standing subject but the mechanism of these changes remains obscure.
The morphology of group Ia afferent fibre collaterals in the spinal cord of the cat.
Authors: Brown A G , Fyffe R E
Published: December 2014

1. The enzyme horseradish peroxidase (HRP) was injected into single Ia muscle afferent fibres in anaesthetized cats. Subsequent histochemistry allowed the morphology of the axons and their collaterals in the lumbosacral spinal cord to be determined. 2. Fifteen Ia axons were stained, four from medial gastrocnemius, four from lateral gastrocnemius‐soleus and seven from muscles innervated by the posterior tibial nerve. All thirteen axons that could be traced into the dorsal roots bifurcated upon entering the cord. Between 4 and 11 mm of axons were stained and they gave off eighty seven collaterals over distances between 3 and 9 mm. Collaterals were given off at intervals of 100‐2600 micron at an average spacing of about 1000 micron. 3. All Ia collaterals had a characteristic morphology. After leaving the parent axon they ran ventrally to lamina VI and then ventrolaterally to the motor nuclei. The collaterals coursed cranially from their point of origin to the motor nuclei so that their lamina VI terminations were about 100‐300 micro caudal to their terminations in motor nuclei. Terminal arborizations were limited to three sites; lamina VI (the intermediate region), lamina VII (the Ia inhibitory interneurone region) and lamina IX (the motor nuclei). The three sets of terminals had characteristic arborizations and bouton arrangements. 4. The results are discussed in relation to previous anatomical studies. In particular the present results suggest that a single Ia collateral makes contact with many more motoneurones than has previously been suggested in fact with fifty to sixty rather than with about ten.
Hepatic portal vein infusion of glucose and sodium solutions on the control of saline drinking in the rat.
Authors: Blake W D , Lin K K
Published: December 2014

1. Rats were prepared under anaesthesia with non‐occlusive catheters in hepatic portal vein (HP) and inferior vena cava (VC) and maintained under standard conditions. 2. Each rat received a series (3 day intervals) of 30 min infusions of different solutions or sham into HP or VC. Oral intake of 0.15 M‐NaCl and water were measured for 30 min. Significant change in drinking behaviour was assumed when the response to HP infusion differed from both sham and VC infusion. 3. Saline drinking was inhibited by HP infusion of 1 M‐ or 2M‐NaCl, an effect blocked by right vagotomy or by addition of 16 mM‐KCl to the infusate. 4. Saline drinking was increased and water drinking decreased by HP infusion of 2 M‐glucose but not sucrose or fructose. 5. Saline drinking was decreased by HP infusion of deoxy‐D‐glucose to inhibit glucose utilization or ouabain to inhibit (Na4‐K+) ATPase. 6. Results are consistent with the presence of afferent nerve terminals in hepatic portal vessels which are sensitive to change in NaCl or glucose concentration and which, in response thereto, alter drinking behaviour. The effects of NaCl and glucose on the discharge rate of the nerve terminals may be interpreted in terms of changing activity or electrogenicity of a Na pump but changes in membrane conductance or Na influx cannot be ruled out.
THE POTASSIUM CURRENT UNDERLYING DELAYED RECTIFICATION IN CAT VENTRICULAR MUSCLE
Authors: McDonald T. F. , Trautwein W.
Published: December 2014

1. Outward currents in cat ventricular fibres have been studied using the single sucrose gap method. The time dependent outward currents can be separated into a fast component, IK, and a slow component, Ix. The voltage dependence of the IK time constant was bell‐shaped, being about 150 msec at ‐90 mV, 500 msec at ‐25 mV and 300 msec at +30 mV. The combination of much faster time constants and larger amplitudes relative to Ix allowed the estimation of IK amplitude, but not time course, from semilog plots of membrane currents accompanying 2 sec depolarizations.

2. The ‘steady‐state’ outward current at 2 sec (Iss) was separated into time independent background current (Ibg) and time dependent IK. The activation threshold for IK was about ‐50 mV and its amplitude increased steeply between ‐30 and +10 mV. The ratio of Ibg to IK was about 1 between ‐30 and +30 mV.

3. The current—voltage relations of Iss and Ibg showed inward going rectification but negative slope regions were not observed. Raising the external K concentration from 3 to 10, 20 and 30 m
M increased conductance and induced ‘cross‐overs’ in the current—voltage relations. Increases in conductance were offset by the reductions in driving force, i.e. currents at plateau potentials were not larger in high K solutions.

4. K accumulation occurs in response to prolonged membrane depolarization but conductance rather than accumulation appears to be responsible for the slowly rising outward current, Ix. However, the accumulation which takes place during the activation of Ix may preclude an accurate determination of its time course and reversal potential.

5. The potential at which outward IK tails declined to zero was strongly dependent on external K concentration in the range 3‐30 m
M. Inward going IK tails were difficult to detect because control hyperpolarization from the resting potential triggered large inward time dependent currents. Evidence is presented suggesting that much of this time dependency is due to the depletion of extracellular K from regions of restricted diffusion.

6. The steady‐state activation variable (n∞) of the IK‐system had to be calculated from isochronic (300 msec activating pulses) activation relations and τns because shifts in VK due to K accumulation precluded complete activations. The shape of n∞ was sigmoid approaching 0 at ‐60 mV, 0·5 at ‐20 mV and 1 at +20 mV.

7. The fully activated current—voltage relation of IK displayed inward going rectification.

8. It is concluded that there are strong similarities between IK in ventricular muscle and ix1 in Purkinje fibres. Possible counterparts in frog atrial muscle include the currents labelled I1 and ix.slow.
Modification by previous afferent discharge of the adaptation of frog muscle spindles following an extension.
Authors: Brokensha G , Westbury D R
Published: December 2014

1. Extension of a frog muscle spindle evoked a discharge of impulses in its sensory axon. The adaptation of the discharge after the dynamic phase of stretching occurred in two phases. At first the impulse train was almost regular and adapted quickly, but later this gave place to a phase of slower adaptation in which the variability of discharge was much increased. 2. The discharge of action potentials by the muscle spindle depressed the response of the receptor to a subsequent extension. This was true whether they were elicited antidromically by afferent stimulation or orthodromically by longitudinal vibration. This depression had its most marked effect on the first phase of adaptation where it greatly increased the rate of adaptation. The second, slower, phase of adaptation was little influenced. 3. The depression increased with the duration and with the frequency of afferent stimulation. It persisted for about 300 msec. 4. The results show that the properties of the spike generating mechanisms in the muscle spindle are modified by previous discharge and that this modification may influence the overall properties of the receptor. 5. The fact that afferent stimulation has different effects on the two phases of adaptation is consistent with the suggestion that the impulse train evoked by extension is derived from more than one spike generator within the muscle spindle.
Protein digestion and absorption in the rat.
Authors: Curtis K J , Kim Y S , Perdomo J M , Silk D B , Whitehead J S
Published: December 2014

1. A randomly labelled 14C protein was synthesized in order to investigate the site and rate of digestion and absorption of dietary protein in the rat. 2. A liquid test meal consisting of protein and a non‐absorbable marker, 51CrCl3, was administered to rats which were then sacrificed at intervals up to 4 hr after ingestion of the meal. Analysis of intestinal contents showed that as gastric emptying proceeded, the meal moved rapidly to the distal two thirds of the small intestine. 3. Protein digestion and absorption occurred predominantly in this area over a period of 1‐2 hr. 4. Amounts of endogenous protein present in the small intestine never exceeded amounts of exogenous protein during maximum absorption of exogenous protein (0‐1 hr). At later time periods (2‐4 hr), however, more endogenous than exogenous protein was detected in the intestinal lumen. 5. It is concluded that the digestion and absorption of dietary protein is a rapid process, taking place in the distal two‐thirds of the small intestine. Endogenous protein levels do not exceed exogenous protein levels until after the bulk of exogeneous protein is absorbed.
The control of enzyme secretion from fly salivary glands
Authors: Bay Christina M. Hansen
Published: December 2014

1. Stimulation of fluid secretion from fly salivary glands by 5‐hydroxytryptamine (5‐HT) is known to involve calcium and cyclic AMP. Isolated salivary glands were used to investigate the role of these second messengers in the control of enzyme (sucrase) secretion.

2. The protein component of secretion from isolated glands treated with 5‐HT appears to be identical to that of saliva secreted by flies during feeding.

3. Stimulation of fluid secretion by 5‐HT follows a definite dose‐response curve, but there is no consistent relationship between the rate of enzyme secretion and the stimulating concentration of 5‐HT.

4. Exogenous cyclic AMP causes secretion of enzymes as well as of fluid, thus mimicking the action of 5‐HT. The phosphodiesterase inhibitor theophylline enhances the rate of 5‐HT‐stimulated enzyme secretion.

5. Removal of calcium from the bathing medium enhances enzyme secretion in response to 5 or 10 n
M‐5‐HT but has no effect on enzyme secretion stimulated by 100 n
M‐5‐HT or by cyclic AMP.

6. Addition of 0·1 m
M‐lanthanum to medium containing 2 m
M‐calcium mimics the effect of calcium‐free solution on 5‐HT‐stimulated enzyme secretion.

7. The ionophore A 23187 causes secretion of both fluid and enzyme. The secretory rate is initially high but soon declines and ceases after about 40 min.

8. Enzyme secretion in response to 5‐HT or to cyclic AMP is progressively inhibited as the concentration of potassium is increased from 10 to 80 m
M. Secretion in response to A 23187 is initially inhibited by 80 m
M‐potassium but then partially recovers.

9. The rate of enzyme secretion appears to be affected by the intracellular concentrations of both calcium and cyclic AMP. It is possible that the rate of enzyme secretion increases as the intracellular calcium concentration rises, until the optimal calcium concentration is reached when further increase in the level of calcium progressively inhibits secretion. The optimal calcium concentration for enzyme secretion is lower than that for fluid secretion, and 5‐HT normally causes maximal fluid secretion and submaximal enzyme secretion.
The slowing of gastric emptying by proteins in test meals.
Authors: Burn-Murdoch R A , Fisher M A , Hunt J N
Published: December 2014

1. Test solutions containing either glucose, casein, partially hydrolysed gelatin or egg albumin, native or denatured, at concentrations up to 50 g/l. in 33 mM‐trisodium citrate solution, were given by tube into the stomachs of nine subjects in volumes of 600 or 750 ml. 2. The volume of the test solution recovered from the stomach after 20 min was measured. 3. The greater the concentration of solute the greater was the volume of the test solution recovered. 4. Gram for gram, gelatin hydrolysate was equivalent to glucose in slowing gastric emptying. Casein was slightly more effective than glucose and native egg albumin was less effective than glucose. 5. The results were explained by assuming that the products of hydrolysis of proteins stimulated osmoreceptors in the walls of the duodenum. 6. The results were in line with the suggestion that proteins in food contribute to the slowing of gastric emptying in such a way that isocaloric amounts of carbohydrate and mixed protein have the same effect. 7. There was a strong correlation between the concentration of glucose giving a recovery of 400 ml. and the corresponding concentration of casein within‐subject, but there was no such relationship for gelatin hydrolysate. It was concluded that the between‐subject variability in the digestion of casein was small, that for gelatin hydrolysate was large.
Effect of prior visual experience on cortical recovery from the effects of unilateral eyelid suture in kittens
Authors: Blasdel Gary G. , Pettigrew John D.
Published: December 2014

The reversibility of monocular deprivation was tested physiologically in twelve kittens which had received varying amounts of normal visual experience prior to unilateral eye closure. Recordings obtained from cells in cortical area 17 indicated that the effects of monocular deprivation are reversible in cats as old as 8 weeks if the animals have been allowed normal visual experience before eye closure.

1. Four kittens had their right eyes closed at 3, 4, and 5 weeks of age. All animals were reverse sutured at about 8 weeks of age, and after 2 weeks forced usage of the deprived eye, each animal was tested physiologically for recovery. Single unit recordings revealed a consistent relation between the extent to which the effects of initial deprivation could reverse and the age of the animal at the time of this deprivation. Recordings from a fifth, 8 week old kitten, which had been monocularly deprived for 3 weeks, ensured that our shortest period of deprivation induces a severe deficit.

2. Two kittens which were reared in the dark for 4 and 5 weeks before unilateral eye closure, failed to show substantial (greater than 20%) reversal when reverse lid‐sutured at 8 weeks of age. This failure suggests that kittens having their eyes closed after normal experience show enhanced reversibility, at least in part, on account of their early experience and not necessarily because of shorter deprivation. A litter‐mate of one of these kittens was allowed 9 days of normal vision after dark rearing and before lid suture. Recordings which were performed both before and after 6 days of reverse suture demonstrated a near total (85%) reversal in ocular dominance.

3. Three animals, monocularly deprived after some normal experience, recovered substantial numbers of binocular cells after both eyes had been allowed to remain open. In one of these cats the effectiveness of monocular deprivation was confirmed physiologically before eye opening. These findings contrast with those of other workers who have failed to find many binocular cells in kittens that had been allowed to recover, with eye opening, from monocular deprivation which had lasted since birth.

4. One kitten was reared for 2 weeks (3‐5 weeks of age) with alternating monocular deprivation. Single unit recordings from this cat, which were made after four additional weeks of unilateral eye closure, revealed some cells which had resisted monocular deprivation and which responded strongly to stimulation of the deprived eye. Reverse suture in the same animal led to the recovery of many cells (36%), dominated by the initially deprived eye, but did not result in a reversal in ocular dominance.