bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.