bluuebunny/crossref_metadata_2025 huggingface dataset:
The period of susceptibility to the physiological effects of unilateral eye closure in kittens
Authors: Hubel D. H. , Wiesel T. N.
Published: December 2014

1. Kittens were visually deprived by suturing the lids of the right eye for various periods of time at different ages. Recordings were subsequently made from the striate cortex, and responses from the two eyes compared. As previously reported, monocular eye closure during the first few months of life causes a sharp decline in the number of cells that can be influenced by the previously closed eye.

2. Susceptibility to the effects of eye closure begins suddenly near the start of the fourth week, remains high until some time between the sixth and eighth weeks, and then declines, disappearing finally around the end of the third month. Monocular closure for over a year in an adult cat produces no detectable effects.

3. During the period of high susceptibility in the fourth and fifth weeks eye closure for as little as 3‐4 days leads to a sharp decline in the number of cells that can be driven from both eyes, as well as an over‐all decline in the relative influence of the previously closed eye. A 6‐day closure is enough to give a reduction in the number of cells that can be driven by the closed eye to a fraction of the normal. The physiological picture is similar to that following a 3‐month monocular deprivation from birth, in which the proportion of cells the eye can influence drops from 85 to about 7%.

4. Cells of the lateral geniculate receiving input from a deprived eye are noticeably smaller and paler to Nissl stain following 3 or 6 days' deprivation during the fourth week.

5. Following 3 months of monocular deprivation, opening the eye for up to 5 yr produces only a very limited recovery in the cortical physiology, and no obvious recovery of the geniculate atrophy, even though behaviourally there is some return of vision in the deprived eye. Closing the normal eye, though necessary for behavioural recovery, has no detectable effect on the cortical physiology. The amount of possible recovery in the striate cortex is probably no greater if the period of eye closure is limited to weeks, but after a 5‐week closure there is a definite enhancement of the recovery, even though it is far from complete.
Influence of oestrogen on thyroid function in the ewe
Authors: Falconer Ian R.
Published: December 2014

1. Thyroid activation at oestrus occurs in several species, which may be related to oestrogen secretion occurring at the same time. In the ewe this relationship has been examined by measuring thyroid activity before and after oestrogen administration.

2. Measurements have been made of thyroid 131I release rate and protein‐bound 131I concentration in the plasma in normal and ovariectomized ewes and of protein‐bound 125I in plasma from thyroid vein blood in ewes with exteriorized thyroid glands.

3. No evidence of an activation of the thyroid by oestrogen was observed in immature ewes or adult oestrous cycle, anoestrous or ovariectomized ewes, given oestrone or oestradiol dibenzoate in doses of 25–1000 μg by injection.

4. It was concluded that oestrogen may not be responsible for thyroid activation observed in normal oestrous ewes.
The extraneuronal uptake and localization of noradrenaline in the cat spleen and the effect on this of some drugs, of cold and of denervation
Authors: Gillespie J. S. , Hamilton D. N. H. , Hosie R. Jeanette A.
Published: December 2014

1. Extraneuronal uptake of noradrenaline (NA) was examined in the cat spleen first by perfusing with NA for 10 min, followed by a 2‐min wash to clear the extracellular fluid, then measuring the amount retained, its subcellular distribution and the tissue components involved as revealed by the development of the characteristic fluorescence. Secondly, thin spleen slices were exposed to NA in vitro and the development of fluorescence in various structures, particularly arterial smooth muscle, measured.

2. The cat spleen accumulated large quantities of NA and this, like the development of fluorescence, was concentration‐dependent. After particle separation most of the retained amine appeared in the high‐speed supernatant, with a lesser amount in the coarse granule fraction. There was little amine in either the mitochondrial or microsomal fraction. The microsomal fraction from unperfused spleens was rich in NA, presumably from storage granules from the adrenergic nerves. On an intermittent sucrose density gradient the NA‐rich particles sedimented between 1·0 and 1·5
M sucrose, corresponding to the recently described dense granules from bovine splenic nerves.

3. Fluorescence histochemistry revealed several tissues accumulating NA. At an NA concentration of 10−5 g/ml., arterial smooth muscle and endothelium showed intracellular fluorescence; at 10−4 g/ml., collagen, the perimeter of the smooth muscle cells of the capsule‐trabecula‐vein system and the reticular cells forming the framework of the spleen developed fluorescence. In the reticular cells the fluorescence was intracellular. The fluorescence pattern on the perimeter of non‐arterial smooth muscle corresponded to the pattern of basement membrane as shown by PAS staining. The red pulp, lymphoid tissue and the phagocytic cells of the ellipsoids did not fluoresce.

4. Cooling the tissue to 15° C or less, phenoxybenzamine in a concentration of 5 × 10−5 g/ml. or normetanephrine in a concentration of 10−4 g/ml. prevented both uptake and loss of NA in arterial smooth muscle but had no effect on collagen.

5. Chronic post‐ganglionic denervation or reserpine had no effect on the development of fluorescence in any extraneuronal tissue.
Depression of transmitter release at the neuromuscular junction of the frog
Authors: Betz W. J.
Published: December 2014

1. Depression of transmitter release produced by preceding conditioning stimulation was studied at the frog's neuromuscular junction.

2. Depression occurred when transmitter release was restricted to a short length of nerve terminal, or when release was initiated by electrotonic depolarization of the terminals after action potentials were abolished by tetrodotoxin.

3. Quantitative studies revealed a non‐linear relationship between the estimated magnitude of ‘zero‐time’ depression and the amount of transmitter released by conditioning stimulation.

4. Two stimuli separated by 20–200 msec were given and the ratio of the end‐plate potential amplitudes (V2/V1) was measured. This amplitude ratio increased during depression produced by stimuli preceding the test pair.

5. These observations may be explained by assuming that depression is associated with a reduction in release probability as well as a depletion of transmitter available for release.
Centrifugal dorsal root discharges induced by motoneurone activation
Authors: Decima E. E. , Goldberg L. J.
Published: December 2014

1. It has been confirmed that antidromic stimulation of motoneurones in the cat lumbar cord can induce, when properly conditioned, a centrifugal discharge in dorsal root afferent fibres.

2. The effective conditioning can be (a) an orthodromic volley to the same or an adjacent dorsal root, (b) a volley to the dorsal column one or two segments above the tested level, or (c) a natural stimulus applied to the ipsi‐ or contralateral hind limb.

3. The conditioning stimulus acts by increasing presynaptic excitability; the peak of its effect (maximum presynaptic depolarization) occurs 7–10 msec after the arrival of the conditioning volley to the cord and then quickly decays.

4. A large antidromic field potential in the ventral horn is not necessary for the production of a centrifugal dorsal root discharge. Activation of a ventral root filament of approximately 100 μ in diameter can still induce such a discharge in a single dorsal root fibre. Furthermore, antidromic stimulation of the remaining fibres of the same ventral root cannot affect the terminals activated by the thin ventral root filament.

5. The phenomenon of motoneurone—presynaptic interaction was obtained in different types of experimental preparations: acute and chronic spinal, anaemic and midcollicular decerebrate, animals with intact supraspinal centres, and one animal without acute laminectomy.
Distribution of ions and electrical potential differences between mother and foetus at different gestational ages in goats and sheep
Authors: Mellor David J.
Published: December 2014

1. Potential differences associated with the compartments of goat and sheep conceptuses have been measured in vivo and in vitro during the last half of gestation and the osmolarity, and the [Na+], [K+], and [Cl−] of maternal and foetal plasma and amniotic and allantoic fluid taken from these animals were determined.

2. The potential difference (p.d.) patterns of both goats and sheep were the same.

(a) The transplacental p.d. was about 71 mV (foetus negative) in the goat, and about 51 mV (foetus negative) in the sheep.

(b) The amniotic fluid p.d. (i.e. the p.d. measured between the maternal extracellular fluid and the amniotic fluid) decreased as gestation advanced (from 110 to 70 mV in the goat, and 90 to 50 mV in the sheep) and was equal to the sum of the transplacental p.d. and a p.d. between the foetal blood and the amniotic fluid. The amniotic fluid was negative relative to both maternal and foetal blood.

(c) An allantoic fluid p.d. (measured between the maternal extracellular fluid and the allantoic fluid) of about 107 mV in the goat, and about 96 mV in the sheep, was equal to the sum of the transplacental p.d. and a p.d. between the foetal blood and the allantoic fluid. The allantoic fluid was negative relative to both maternal and foetal blood.

(d) The results suggest that p.d.s of the fluid sacs arise from activity between the foetal fluids and the blood perfusing the foetal membranes, and not from activity across the full thickness of the foetal membranes.

3. The ionic concentrations were considered in relation to the electrochemical gradients found between the maternal and foetal fluid compartments to determine whether the ions were distributed according to electrochemical equilibrium.

(a) It seems that ions in the amniotic fluid tend to equilibrate with foetal plasma, and not with maternal plasma or allantoic fluid, that changes in the [Na+] and [K+] of amniotic fluid can be accounted for largely in terms of passive factors, and that variations in the [Cl−] are associated with activity of an electrogenic Cl− pump directed from the foetal blood into the amniotic fluid.

(b) It appears that ions in the allantoic fluid can exchange with those of both maternal and foetal plasma, that an electrogenic pump effects absorption of Na+ from the allantoic fluid into the foetal blood, and that the [K+] and [Cl−] of allantoic fluid are maintained largely by passive exchange under the action of electrochemical gradients between maternal plasma and allantoic fluid, and between foetal plasma and allantoic fluid.

4. The results considered in the context of Na+ passage between mother and foetus call in question the general assumption that all Na+ reaches the foetus by passing across the placenta.
Voltage clamp experiments on ventricular myocardial fibres
Authors: Beeler G. W. , Reuter H.
Published: December 2014

1. A voltage clamp method utilizing a sucrose gap and glass microelectrodes was developed and used to study dog ventricular myocardial fibre bundles. The limitations and the reliability of this method are demonstrated by a series of tests.

2. A dynamic sodium current, excited at membrane potentials more positive than −65 mV, was measured. The equilibrium potential for this large, rapid inward current depends directly on [Na]o, shifting 29·0 ± 2·3 mV (±
S.E. of mean), as opposed to a theoretically expected value of 30·6 mV, when [Na]o is reduced to 31% of normal.

3. Sodium current is inactivated by conditioning depolarizations. Complete inactivation occurs with conditioning potentials more positive than −45 mV, and 50% inactivation occurs at about −55 mV. The location of the inactivation curve shifts along the voltage axis, when [Ca]o is varied between 0·2 and 7·2 m
M.

4. A second, much smaller and slower net inward current, with a threshold around −30 mV, and an equilibrium potential above +40 mV was also observed.

5. The ‘steady‐state’ current—voltage relationship (after 300–600 msec) exhibits inward‐going (anomalous) rectification with negative slope between −50 and −25 mV.

6. A small, very slowly developing component of outward current was observed at inside positive potentials. The equilibrium potential for this current, although slightly dependent on [K]o, is neither identical with the potassium equilibrium potential nor with the resting potential in normal Tyrode solution.

7. Anatomical limitations, primarily resistance in the extracellular space within the bundle, prevent complete characterization of the rapid, large sodium current, but do not limit the application of the clamp method to the study of other, smaller and slower currents. The evidence for this is discussed extensively in the Appendix.
Membrane calcium current in ventricular myocardial fibres
Authors: Beeler G. W. , Reuter H.
Published: December 2014

1. A slow inward current in ventricular preparations of the dog heart can be measured by the voltage clamp method without interference from the initial rapid sodium current if the sodium system is inactivated by conditioning depolarization.

2. The slow inward current is very sensitive to variation in [Ca]o. It occurs above the equilibrium potential of INa immediately after changing the bathing fluid to a sodium‐free solution and persists under this condition for a long time without much alteration, while INa is rapidly abolished. Tetrodotoxin and [Mg]o have no effect on this current component. These results strongly support the view that the slow inward current in cardiac tissue is carried by calcium ions.

3. The threshold for initiation of the calcium current is around −35 mV in Tyrode solution and is shifted to more negative potentials by either increasing [Ca]o or reducing [Na]o.

4. Calcium sensitive inward current tails associated with repolarization are assumed to represent a proportional measure of calcium conductance activated during the preceding depolarization. Calcium conductance declines rapidly with time in the inside negative potential range and slowly at positive potentials. The time constants for this ‘inactivation’ process vary between 40 and 700 msec in the potential range −35 to +50 mV.

5. By using instantaneous current—voltage relations the reversal potential of calcium current was estimated to be about +60 mV in normal Tyrode solution. As shown in the Appendix, however, the calcium equilibrium potential cannot be considered to be constant.

6. The importance of the calcium current for the plateau of the cardiac action potential is discussed.
The influx of orthophosphate into squid giant axons
Authors: Caldwell P. C. , Lowe A. G.
Published: December 2014

1. The influx of 32P, applied externally as orthophosphate, into the axoplasm of squid giant axons has been studied.

2. An average orthophosphate influx of 20·9 f‐mole/cm2.sec is obtained if the 32P found in the axoplasm is assumed to be indicative of orthophosphate which has crossed the axolemma.

3. The influx does not show very much dependence on external orthophosphate concentration in the range 0·02–0·5 m
M.

4. The influx is reduced by cyanide, 2,4‐dinitrophenol, ouabain and by the absence of external potassium.

5. The 32P appears to arrive in the axoplasm as orthophosphate.

6. It is concluded that there is an inward movement of orthophosphate into the axons which is mediated by an active transport process and that this may have some connexion with the active transport of sodium and potassium.
The effect of duodenal and mid small bowel transection on the frequency gradient of the pacesetter potential in the canine small intestine
Authors: Code Charles F. , Szurszewski Joseph H.
Published: December 2014

1. The effect of surgical transection and reunion of the small bowel on its pacesetter potenial (PP) frequency gradient was studied over periods of 3 months in six conscious, healthy dogs, using fourteen platinum electrodes previously implanted along the bowel.

2. Duodenal transection and reunion abolished the gradient of the pacesetter potential distal to the transection and this effect persisted throughout 3 months of observation.

3. In dogs with two transections, one in the duodenum and another in the mid small bowel, the mid small bowel transection and reunion further reduced the frequency of the PP caudad to it and this effect also persisted throughout the 3 months of observation.

4. We conclude that the gradient in intact bowel occurs because the frequency of the duodenal pace‐maker is considerably more rapid than the natural frequency of the PP in the rest of the bowel, and because the bowel is composed of collections or populations of smooth muscle cells with differing natural or intrinsic PP frequencies arranged in a progression of diminishing frequencies from orad to caudad location. The natural frequency of a segment is unmasked by transection of the bowel just orad to it because this eliminates the influence or drive of the orad pace‐maker. The findings are in agreement with the concept that in intact bowel, as the PP passes caudadward, distal populations of cells are eventually encountered which cannot follow the faster orad pacesetter because of the slowness of their natural frequency. Thus, during caudad passage, some cycles of the PP are not transmitted and this, occurring over the length of the bowel, accounts in part, at least, for the gradient of frequency of PP over the small bowel.
Regional variations in the visual acuity for interference fringes on the retina
Authors: Green Daniel G.
Published: December 2014

1. The visual acuity of the peripheral retina was measured using both sinusoidal gratings viewed in the usual way and interference fringes formed on the retina directly.

2. It is shown that optical aberrations cause a reduction in peripheral visual acuity for eccentricities of less than 5°. However, the hypothesis that optical defects are a major cause of the well‐known decrease in acuity with eccentricity is rejected.

3. The fringe acuities at various retinal positions are compared with Osterberg's counts of the distribution of cones. It is shown that at eccentricities of less than 2°, resolution approaches the theoretical limits for a mosaic of receptors.
Invariant features of spatial summation with changing locus in the visual field
Authors: Wilson M. E.
Published: December 2014

1. Spatial summation curves have been determined under photopic conditions for loci between 5 and 55° from fixation. At each locus the area and Weber fraction for the largest stimulus showing complete summation (Sc) has been estimated. While the area of Sc increases progressively towards the periphery, its Weber fraction remains constant.

2. The invariance of the Weber fraction for Sc, coupled with changes in its area, have been compared with similar findings observed during changes in adaptation level, in impaired fields, and during accommodative and convergence changes. It is suggested that the Weber fraction for Sc may be an important parameter of visual function which is maintained under changing conditions by alterations in the area over which background energy is summated.

3. It has been shown that, for stimulus areas up to at least 1 log unit greater than Sc, all the summation curves from 5 to 55° from fixation can be superimposed by simple displacement along the log area axis. For loci closer together, the superimposition has been shown for larger ranges of areas beyond Sc. This suggests that, so far as spatial summation is concerned, changes in locus serve only to change the spatial scale of the visual system.

4. Comparisons have been made between the area of Sc at various loci and the sizes of the central regions of the receptive fields of retinal ganglion cells determined electrophysiologically in the primate.
Evidence for the release of two atropine‐resistant spasmogens from Auerbach's plexus
Authors: Ambache N. , Verney J. , Zar M. Aboo
Published: December 2014

1. Two atropine‐resistant response‐components of nervous origin have been detected in plexus‐containing preparations of the longitudinal muscle from the guinea‐pig ileum, by alternate field stimulation with equal numbers of pulses at 50 Hz (response A) and at 5 Hz (response B). With trains of ten or more pulses, response A is always larger than B; the ratio of A/B (1·2–21·3) is subject to animal variation.

2. Both responses are abolished by tetrodotoxin and are absent from plexus‐free preparations.

3. Neither response is reduced by ganglion‐block with (+)‐tubocurarine, dimethyltubocurarine or hexamethonium, or by ganglion‐paralysing doses of nicotine; the contribution of excited preganglionic endings to these responses is therefore negligible.

4. Neither response is due to a release of histamine, 5‐hydroxytryptamine (5‐HT) or prostaglandins, since both A and B persist in the presence of mepyramine, methysergide and the prostaglandin‐antagonist SC‐19220 (1‐acetyl‐2(8‐chloro‐10,11‐dihydrodibenz [b,f] [1,4]oxazepine‐10‐carbonyl) hydrazine).

5. The two response‐components are affected differentially by a number of drugs.

6. Histamine, 0·1 μg/ml., reduces response A to the level of B; this selective inhibition of the histamine‐sensitive component in A is specifically antagonized by nicotine, 1‐2·5 × 10−5 g/ml.

7. 5‐HT, 0·1 μg/ml., and strychnine, 20–40 μg/ml., also reduce response A to the level of B, but these selective inhibitions are not antagonized by nicotine.

8. Diphenhydramine, 10 μg/ml., produces equality of the two responses by depressing A and potentiating B.

9. The inhibitory effects of the foregoing drugs are not due to catecholamine release, since they persist after α + β adrenoceptor blockade with phentolamine and pronethalol, and after previous reserpinization of the guinea‐pigs.

10. In atropinized plexus‐containing preparations of the longitudinal muscle from the guinea‐pig descending colon, the responses elicited at 50 Hz and at 5 Hz are virtually equal and both appear to be of Type B since they are not inhibited by histamine, 5‐HT or strychnine; diphenhydramine produces strong contractions.
Cardiovascular function in young lambs during summit metabolism
Authors: Alexander G. , Williams D.
Published: December 2014

1. Cardiac output in lambs less than 3 days old was 50–100% higher during summit metabolism than during exposure to thermoneutral conditions.

2. The Fick method, based on oxygen consumption, and the dye dilution method for determination of cardiac output, gave qualitatively similar results, but there were considerable quantitative discrepancies.

3. The thermogenic tissues, muscle and brown fat, extracted some 80% of the oxygen from the blood perfusing them during summit metabolism.

4. Significant right to left shunts through the foramen ovale were detected in about half of the lambs during the first few days of life; the size and incidence of shunts decreased with advancing age but were apparently independent of environmental conditions.

5. During exposure to extreme cold, left to right shunts through the ductus arteriosus were detected in a high proportion of lambs, < 12 hr old, with detectable foramen ovale shunts. Pressure measurements in pulmonary and systemic arteries in very young lambs indicated that right to left shunting via the ductus was unlikely to occur; none was detected.

6. Summit metabolism was poorly related to oxygen carrying capacity of blood, but significant correlations of summit metabolism with cardiac output (positive) and with oxygen saturation of mixed venous blood (negative) were observed, though not consistently.

7. It is concluded that the great variability of summit metabolism between lambs older than 6 hr is not readily explained in terms of cardiovascular phenomena, but that the quantity and efficiency of thermogenic tissues probably play an important role in limiting summit metabolism.
The luteinizing hormone releasing activity of extracts of blood from the hypophysial portal vessels of rats
Authors: Fink George , Harris G. W.
Published: December 2014

1. A method of acid ethanol extraction and gel filtration was used to obtain a ‘luteinizing hormone (LH)‐free’ fraction of blood collected from the cut pituitary stalk of rats (termed hypophysial portal blood).

2. The ‘LH‐free’ fraction of hypophysial portal plasma from hypophysectomized and from ovariectomized rats caused a greater depletion of ovarian ascorbic acid in immature rats, pretreated with gonadotrophins, than a similar fraction of systemic plasma obtained from the same donor animals.

3. The ‘LH‐free’ fraction of hypophysial portal plasma from ovariectomized rats evoked a rise in the level of LH in the systemic plasma of ovariectomized, oestrogen and progesterone treated, rats. This fraction also caused ovulation in rabbits when infused directly into the anterior pituitary gland of these animals. The activity of the ‘LH‐free’ fraction of systemic plasma was considerably less than that of portal plasma in either of these assay systems.

4. The results of these experiments suggest the presence of a factor in the ‘LH‐free’ fraction of hypophysial portal plasma which is capable of causing the release of luteinizing hormone from the anterior pituitary gland. The molecular weight of this factor, as assessed by its behaviour on filtration through ‘Sephadex G‐25’, is probably less than 5000.

5. The LRF activity of the ‘LH‐free’ fraction of hypophysial portal plasma obtained from rats at various phases of the oestrous cycle was measured by the ovarian ascorbic acid depletion method. There appears to be a decrease in the level of activity at oestrus. However, a rise in LRF activity, which was expected to occur at the ‘critical period’ of prooestrus, was not evident. The significance of these findings is discussed.
The effects of salicylate on temperature regulation in the rabbit
Authors: Cranston W. I. , Luff R. H. , Rawlins M. D. , Rosendorff C.
Published: December 2014

1. A stable pyrexia has been produced in rabbits by intravenous injection of leucocyte pyrogen followed by a continuous infusion.

2. Intravenous sodium salicylate, given 4 hr after the start of pyrogen infusion, induced rapid and progressive defervescence. The rate of fall of temperature was dose dependent.

3. Intravenous injection of sodium salicylate had no effect on the temperature of afebrile rabbits.

4. The intraventricular injection of small doses of sodium salicylate, given 4 hr after the start of a pyrogen infusion, caused a rapid, dose‐dependent defervescence, but had no significant effect on the temperature of afebrile rabbits.

5. Salicylates exert at least part of their antipyretic activity through an action on the central nervous system.
The origin of human placental oxytocinase
Authors: Mathur V. S. , Walker J. M.
Published: December 2014

1. Placentas from normal women and from those with pre‐eclamptic toxaemia, taken immediately after labour, were examined for oxytocinase activity and analysed morphometrically.

2. Both enzyme activity and volume of syncytiotrophoblast were significantly reduced in placentas from patients with toxaemia.

3. There was a positive correlation between the enzyme activity and the proportion of trophoblast in the placenta. When the activity was expressed per unit volume trophoblast, there was very little difference between placentas, whether from normal subjects or from patients with toxaemia.

4. It is concluded that human placental oxytocinase is located in the syncytiotrophoblast.
Reflex onset of polypnoea in sheep
Authors: Phillips G. D. , Raghavan G. V.
Published: December 2014

1. Measurements have been made of the cardio‐respiratory activities, ear and lumbar skin temperatures, and temperature of the blood in the carotid artery and jugular vein of partially shorn and unshorn sheep during mammary heating at ambient temperatures of 20/55, 15/55 and 10/55 (dry bulb temperature, ° C/relative humidity,%).

2. Heating the mammary region resulted in a marked rise in respiratory and heart rates of unshorn sheep, whereas, in partially shorn sheep, the heart rates increased without being accompanied by a similar rise in respiratory rates.

3. With decrease in ambient temperature from 20 to 10° C, there was a decrease in respiratory response of unshorn sheep during mammary heat treatment suggesting that the magnitude of respiratory response during mammary heat treatment depends on the environmental temperature to which the sheep is exposed.

4. The carotid blood temperature declined following mammary heat treatment at all ambient temperatures studied, both in unshorn and partially shorn sheep, but the magnitude of decline was greater in unshorn than in partially shorn sheep.

5. The rise in respiratory rates following mammary heating of unshorn sheep at all ambient temperatures, in spite of a decline in carotid blood temperature and the absence of similar responses during flank heating, is attributed to the stimulation of warm receptors in the mammary region.
Actions of noradrenaline and acetylcholine on sympathetic ganglion cells
Authors: Kobayashi H. , Libet B.
Published: December 2014

1. The responses of the post‐synaptic membrane of sympathetic ganglion cells to noradrenaline (NA) and to acetylcholine (ACh) were studied in relation to the slow inhibitory post‐synaptic potential (S‐IPSP) and slow excitatory one (S‐EPSP) respectively.

2. NA produced an hyperpolarization of about 4 mV in cells of rabbit superior cervical ganglia.

3. The hyperpolarizing response to NA was not accompanied by any detectable change in membrane resistance, and it was depressed by conditioning depolarization.

4. NA also depressed all the post‐synaptic potentials, presumably by an action on presynaptic function.

5. ACh produced a large depolarization in ganglion cells of rabbit and of frog (paravertebral) ganglia, which was accompanied by a large decrease in membrane resistance.

6. When ACh was applied during nicotinic blockade, achieved with high concentration of nicotine (frog ganglia) or
D‐tubocurarine (rabbit ganglia), it still produced a considerable depolarization. This response could be blocked by atropine, and is presumably a muscarinic type of action.

7. The muscarinic‐ACh response was not accompanied by a decrease in membrane resistance. Instead, the frog ganglion cells exhibited increased resistances of up to more than twice the resting value during both the muscarinic‐ACh depolarization and the S‐EPSP.

8. The muscarinic‐ACh depolarization and the S‐EPSP were both depressed by conditioning hyperpolarization (in nicotinized frog cells). An initial hyperpolarizing phase now appeared in both of these responses.

9. It is concluded that the hyperpolarizing response to NA and the depolarizing response to muscarinic‐ACh action are not generated by increases in ionic mobilities in the post‐synaptic membrane; and that these two responses are produced by the same electrogenic mechanisms which underlie the S‐IPSP and the S‐EPSP respectively.
Stimulation and desensitization of the hypothalamic heat‐sensitive structures by capsaicin in rats
Authors: Jancsó-Gábor Aurelia , Szolcsányi J. , Jancsó N.
Published: December 2014

1. In rats the injection of capsaicin into the pre‐optic area of the anterior hypothalamus produces a prompt fall in body temperature and abolishes shivering. With repeated injections of capsaicin the hypothermic effect gradually diminishes and finally vanishes (local desensitization).

2. Rats desensitized by hypothalamic injections exhibit a behaviour similar to rats pre‐treated parenterally with capsaicin: put in a heat box at 37–39° C they lose their ability to regulate against overheating of their bodies and respond with an enhanced hyperthermia to strong sensory stimuli such as repeated pinching of the tail.

3. Parenteral desensitization strongly inhibits the effect of capsaicin given into the hypothalamus. On the other hand in intrahypothalamically desensitized rats the hypothermic response to subcutaneously given capsaicin is also reduced.

4. The hypothermic response to local heating of the anterior hypothalamus by diathermy (from 1 to 4° C above the initial temperature) was markedly reduced or even abolished in rats pre‐treated parenterally with large doses of capsaicin.

5. It is concluded that the hypothalamic warmth detectors are stimulated and subsequently desensitized by capsaicin. Thus, in the thermoregulatory disturbances caused by capsaicin the impairment of the hypothalamic warmth detectors plays an important role.

6. Capsaicin is proposed as a tool in studying the function of the hypothalamic warmth detectors.
Observations on coronary collateral communications and the control of flow in the coronary circulation of the dog
Authors: Coulson R. L. , Grayson J. , Irvine M.
Published: December 2014

1. Pressure was measured in the small arterial anastomosing branches of the coronary vascular network. The mean value was 30 mm Hg not significantly different from the mean value of 33 mm Hg for peripheral coronary pressure measured distal to a ligature on the anterior descending branch of the left coronary artery. Evidence was adduced to show that either the anterior descending or the circumflex artery had the capacity to maintain network pressure at levels adequate for tissue perfusion.

2. The network has both capacity and compliance. Filling of the network compliance during systole probably accounts for the systolic phase of coronary flow. Flow through the microcirculation is probably entirely diastolic, the combined compliance of the aorta and large vessels together with the network provides the necessary reservoir, the potential energy indicated by diastolic pressure provides the perfusion pressure head.

3. Resistance of vessels between the aorta and network cannula (pre‐net) was approximately double that of the microcirculation (post‐net). The smaller pre‐network vessels are of the order 70 μm in diameter. Both pre‐ and post‐network vessels are vaso‐active and respond similarly to adrenaline and haemorrhage.
Interactions between histamine and bradykinin assessed by continuous recording of increased vascular permeability
Authors: Baumgarten A. , Melrose G. J. H. , Vagg W. J.
Published: December 2014

1. The responses of the cutaneous blood vessels of the guinea‐pig to histamine and bradykinin have been studied in order to determine whether these factors mediate vascular changes by acting on different blood vessel receptors.

2. In animals injected intravenously with bovine serum albumin labelled with phosphorus 32P the reactions to histamine and bradykinin have been studied by continuously recording the local radioactive emission from the skin.

3. Histamine increased the intensity of radioactive emission for 7–15 min. The level of radioactivity then remained almost constant for at least 1 hr. Bradykinin increased the rate of emission for 5‐7 min but the radioactivity decreased by approx. 30% in 1 hr.

4. The intensity of the response to histamine was markedly diminished in sites previously treated with either histamine or bradykinin, compared with the reaction in normal skin. However, a response of similar intensity to that in normal skin was evoked by histamine earlier in sites previously treated with bradykinin than in sites treated with histamine. By contrast, bradykinin evoked a similar reaction to that in normal skin, in sites previously treated with either histamine or bradykinin.

5. The dissimilarity of the responses evoked by histamine and bradykinin suggests that there are two types of blood vessel receptors. One type may be activated by both histamine and bradykinin but becomes refractory to further stimulation with histamine. The other type of receptor is activated only by bradykinin and does not become refractory.
The effects of some inhibitors and accelerators of sodium transport on the turnover of 22Na in the cerebrospinal fluid and the brain
Authors: Davson H. , Segal M. B.
Published: December 2014

1. The purpose of the experiments was to discover whether the turnover of 22Na in the c.s.f., which is largely determined by its rate of secretion, is affected in the same manner by inhibitors or accelerators of active transport as the turnover in the brain tissue since there is reason to believe that the composition of the extracellular fluid of brain is controlled by active processes.

2. Although acetazolamide (Diamox) inhibits rate of secretion of c.s.f. and the turnover of 22Na in this fluid it does not appreciably affect the turnover of 22Na in the brain tissue of either rat or rabbit, the small inhibition observed being probably secondary to the effects on the c.s.f.

3. Ouabain inhibits secretion of c.s.f. and turnover of 22Na in this fluid, but it, also, has no effect on turnover of 22Na in the brain tissue alone or in combination with Diamox.

4. Amphotericin B and amiloride, the anti‐aldosterone spirolactone S.C. 114266, all inhibited secretion of c.s.f. without affecting turnover of 22Na in the brain tissue; actinomycin D, puromycin and cycloheximide, however, had no effect on secretion of c.s.f.

5. Vasopressin inhibited secretion of c.s.f. and turnover of 22Na in this fluid but increased the turnover in the brain by some 16%.

6. In the ventriculo—cisternally perfused rabbit, replacement of 80% of the NaCl in the perfusion fluid by choline chloride caused a slowing of the passage of 22Na from blood into the perfusion fluid.

7. On the basis of these results it is concluded that the brain extracellular fluid is not renewed by appreciable bulk‐flow, in contrast with the c.s.f.
Passage of macromolecules between alveolar and interstitial spaces in foetal and newly ventilated lungs of the lamb
Authors: Normand I. C. S. , Reynolds E. O. R. , Strang L. B.
Published: December 2014

1. Experiments were performed on exteriorized foetal lambs to measure transfer of macromolecules (proteins and [125I]PVP) between lung alveolar liquid (Al) and lung interstitial liquid as represented by lung lymph (Lly). Transfer was measured in the foetus and during a 2 hr period of positive pressure ventilation.

2. In thirteen experiments [125I]PVP was introduced into Al and, after a control period, the lungs were ventilated for 2 hr. In six other experiments the [125I]PVP was injected intravenously; and in two of these the lungs were ventilated for 2 hr. Measurements were made of protein and of [125I]PVP concentration in plasma and Lly collected at intervals throughout the experiment, as well as in Al obtained before ventilation and at the end of ventilation after degassing the lung. [125I]PVP in the samples was separated into fractions of different Stokes—Einstein radius by gel filtration using Sephadex G‐200.

3. Before ventilation there was evidence of a negligible transfer of protein from Lly to Al (mean protein Al/Lly = 0·014) or of [125I]PVP from Al to Lly (mean [125I]PVP Lly/Al = 0·00017). The effect of ventilation for 2 hr was to produce an increase in both ratios, but by a variable amount (after 2 hr ventilation mean protein Al/Lly = 0·70 ± 0·08 (
S.E. of mean) and mean [125I]PVP Lly/Al = 0·48 ± 0·09). By calculating Lly/Al ratios for [125I]PVP fractions obtained by gel filtration it was shown that in transfer from Al to Lly during ventilation molecular sieving could be detected, the degree of which was expressed by means of a Relative Sieving Index (RSI). Significant correlations were found between the minimum surface tension of lung extracts, and two other indicators of lung maturity on the one hand, and the protein and [125I]PVP ratios and RSI on the other; so that the more mature the lamb the less the transfer of macromolecules during ventilation and the greater the degree of molecular sieving.

4. By comparing concentrations of [125I]PVP gel filtration fractions in lymph and plasma, when the [125I]PVP had been placed in Al, we demonstrated some sieving of molecules (in the range 34–15 Å) in their absorption from interstitial space to plasma.

5. It was concluded that in the lungs of the foetal lamb there is an almost complete barrier to the transfer of macromolecules between alveolar and interstitial spaces; that positive pressure ventilation for 2 hr causes a very variable degree of break‐down in this barrier, and that the degree of break‐down is usually greater in immature than in mature lungs.
Effects of Ca removal on the smooth muscle of the guinea‐pig taenia coli
Authors: Bülbring Edith , Tomita T.
Published: December 2014

1. The effects of removing the external Ca ions on the spontaneous and evoked activity of the smooth muscle of the guinea‐pig taenia coli were investigated with the double sucrose‐gap method.

2. In Ca‐free Locke solution the membrane was depolarized, the membrane resistance became low, the spike amplitude became small and the mechanical response decreased. In most preparations the electrical and mechanical activity was abolished within 10 min, but in some preparations the electrical activity continued for more than 30 min.

3. In Ca‐free solution containing 0·1 m
M‐EGTA, the membrane was depolarized and the electrical and mechanical activity was abolished within 5 min in every preparation. When NaCl was replaced with sucrose, the effects of Ca removal on the spike activity and contraction appeared very slowly and the membrane potential and membrane resistance remained unchanged.

4. When Ca was replaced with Mg (2 m
M) the spike was blocked within 1 min without depolarization or reduction of the membrane resistance. In Na‐deficient (sucrose) solution, the presence of Mg accelerated the disappearance of the spike caused by Ca removal.

5. In Ca‐free solution containing 0·5 m
M‐Mg, a spike‐like activity was observed without accompanying mechanical response. This activity was blocked by increasing the Mg concentration above 2 m
M. It was Na‐dependent, since it was abolished by removing Na from the external solution, but it was not influenced by tetrodotoxin (2 × 10−6 g/ml.).

6. It was concluded that calcium has at least two functions, one as current carrier for the action potential and another as controller of the Na permeability of the membrane. It was also suggested that the Ca which is bound at the membrane may be utilized as a source of Ca ions to carry the current for the action potential.
Some metabolic responses of axotomized neurones to contact between their axons and denervated muscle
Authors: Watson W. E.
Published: December 2014

1. The nucleolar and cell body dry mass and nucleic acid content of hypoglossal neurones were measured in adult rats using interference microscopy and ultra‐violet absorption microspectrography.

2. The left hypoglossal nerve was transplanted into the ipsilateral sternomastoid. Seventy days later the sternomastoid was denervated by dividing the ipsilateral spinal accessory nerve. This was followed by metabolic changes in hypoglossal nerve cells.

3. The changes induced in hypoglossal neurones by division of the ipsilateral accessory nerve did not occur if botulinum toxin was injected locally at the same time.

4. In other rats the left hypoglossal nerve was anastomosed to the proximal stump of the ipsilateral median nerve simultaneously divided at the level of the wrist. Seventy days later this median nerve was divided in the axilla. This was followed by metabolic changes in hypoglossal nerve cells.

5. These results are discussed in relation to the possible roles of reacting Schwann cells, degenerating axoplasm and denervated muscle in maintaining aspects of the metabolic response of nerve cells to injury.

6. It is suggested that the synthesis of acetylcholine by an axonal ending, or its release, is dependent upon the presence of an adjacent membrane which can respond to it, and that the metabolic changes measured in the nerve cell body are secondary to this response of the axon terminal.
An estimate of the proportion of the resting membrane conductance of the smooth muscle of guinea‐pig taenia coli attributable to chloride
Authors: Ohashi H.
Published: December 2014

1. The contribution of Cl and K to the steady‐state membrane conductance of the smooth muscle of the guinea‐pig taenia coli has been investigated by measuring the increase in membrane resistance in Cl‐deficient and K‐deficient solutions. A large external electrode was used for passing current and the voltage change was recorded with an intracellular electrode. The experiments were carried out in hypertonic solution in order to suppress spontaneous activity.

2. When the tissue was exposed to K‐deficient solution, the amplitude and time course of the electrotonic potential was increased and the membrane was hyperpolarized.

3. When the tissue was exposed to Cl‐deficient solutions in which Cl was replaced with an impermeant anion, benzene sulphonate, the size and time course of the electrotonic potential was increased whereas the membrane potential, after 20–30 min equilibration, was unchanged. The magnitude of the increase of the electrotonic potential depended on the substituted amount of Cl.

4. When the tissue was exposed to low K the relation between the membrane conductance and the remaining external K concentration was the same in the presence of the normal Cl concentration and in Cl‐deficient solution (7 m
M‐Cl). It was therefore concluded that any effect of benzene sulphonate on the K conductance is negligible.

5. The effects of Cl or K deficiency on the electrotonic potential indicate that Cl and K ions account for most of the membrane conductance and that the contribution by Cl is about 40%.

6. The ratio of PCl/PK was calculated from the constant field theory on the assumption that the contribution of ions other than K and Cl to the membrane conductance is negligibly small. The mean value was 0·40.
Dependence of acetylcholine desensitization on the membrane potential of frog muscle fibre and on the ionic changes in the medium
Authors: Magazanik L. G. , Vyskočil F.
Published: December 2014

1. The rate of desensitization of the post‐synaptic membrane to prolonged action of acetylcholine was investigated during (a) potassium depolarization of the frog muscle fibre, (b) artificial changes of the membrane potential and (c) in the presence of some multivalent cations and of caffeine.

2. Depolarization of the muscle fibre by 15 m
M‐K+ led to a slowing down in the development of desensitization by 80%. This effect on desensitization produced by membrane potential changes could account for the previously described effect of increased K+ concentration.

3. Electrotonically produced depolarization of the muscle fibre membrane resulted in a decrease, hyperpolarization in an increase of the rate of desensitization.

4. Several multivalent cations can be, according to their ability to increase rate of desensitization, arranged in the following series: [Formula: see text]

5. Caffeine in a concentration of 1·5 m
M does not affect the rate of desensitization.

6. A hypothesis is presented suggesting that desensitization is not only restricted to the receptor level but that it also occurs, at least partly, at the terminal stages of the activation system.