bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of specific chemical factors in the solvent on the absorption of macromolecular substances from the small intestine of the new‐born calf
Authors: Hardy R. N.
Published: December 2014

1. The absorption, without change, of [131I] and [125I]solutes of high molecular weight after duodenal infusion has been measured in anaesthetized calves less than 20 hr old by analysis of lymph collected from the thoracic or intestinal duct.

2. Factors present in boiled bovine colostrum whey known to be necessary for the rapid absorption of [131I]bovine serum γ‐globulin have now been shown to accelerate the passage of [131I]polyvinyl pyrrolidone (PVP) of mean mol. wt. 160,000 (K.60) into the lymph in a comparable manner.

3. [131I]PVP K.30 (mean mol. wt. 40,000) and [131I]human serum albumin could be absorbed to some degree in the absence of solvent factors necessary for the absorption of solutes of higher mol. wt. and a large proportion of the solute thus absorbed passed directly into the portal capillaries.

4. Lactate and pyruvate and salts of certain lower volatile fatty acids resemble factors in colostrum whey in their facilitation of the absorption of both γ‐globulin and PVP K.60: these active compounds were not however found in colostrum in significant quantities.

5. Potassium isobutyrate was the most effective of the compounds tested and at concentrations of 56·7 m‐mole/l. generally accelerated absorption to a greater degree than did colostrum whey itself.

6. Absorption of both γ‐globulin and PVP K.60 from colostrum whey was characterized by a profuse flow of lymph containing relatively low concentrations of labelled solute. In contrast, when these solutes were fed in solutions containing simple compounds such as potassium isobutyrate they appeared in very high concentrations in the lymph, the flow of which remained relatively scant.

7. When [125I]PVP was administered in water, little was absorbed. If, however, such an infusion was followed 3 hr later by a duodenal infusion of colostrum, [125I]PVP passed into the lymph almost immediately. This response was too rapid for the colostrum to have reached the absorbing cells in the terminal ileum.

8. Intravenous infusions of
L+lactate have been found to facilitate the absorption of [125I]PVP K.60 introduced into the duodenum in water. This indicates that some of the solvent factors which accelerate absorption may reach the terminal ileum via the blood vascular system after they themselves have been absorbed from the upper small intestine.
The role of the antrum and the vagus nerve in the formation of gastric mucosal histamine
Authors: Rosengren Elsa , Svensson S. E.
Published: December 2014

1. The effects of the vagus nerve and of antral gastrin on the rate of histamine formation (histamine forming capacity, HFC, i.e. histidine decarboxylase activity) in the parietal cell region of the gastric mucosa has been investigated in the following stomach preparations: gastric fistula, denervated Heidenhain pouch, antral resection with gastrojejunostomy, gastrojejunostomy with exclusion of the duodenum and in the intact stomach. The determinations of mucosal HFC were made on fasting rats and on re‐fed animals when the effect of feeding was studied.

2. In fasting rats with a gastrojejunostomy and the antrum intact the mucosal HFC of the innervated stomach was about 4 times higher than in the corresponding preparation with the antrum resected. In the innervated main stomach the mucosal HFC was about twice as high as in the denervated pouch, indicating that the vagus and endogenous antral gastrin each contribute to maintaining mucosal HFC in the fasting state.

3. Acidifying the stomach caused a substantial lowering of the mucosal HFC presumably by inhibiting antral gastrin release, whereas acid in the stomach did not interfere with the elevation of mucosal HFC evoked by injection of gastrin.

4. Injection of gastrin elevated mucosal HFC in the innervated main stomach and in the denervated pouch to approximately equal levels. With the dose of gastrin employed there was about a fourfold increase in the HFC of the pouch mucosa.

5. In antrectomized rats enhanced vagal influence, evoked by insulin injection or by feeding, raised the mucosal HFC. In rats with the antrum intact and the stomach acidified, insulin injection produced an increased HFC. Thus, a vagal effect on mucosal HFC exists independent of participation of antral gastrin.

6. The stable choline esters carbachol and methacholine act directly on the parietal cell without involving mucosal HFC. The vagus nerve and gastrin, however, are assumed to provide secretory stimulation by means of accelerated histamine formation.

7. The interrelation between increased histamine formation and hydrochloric acid secretion is discussed.
Indirect cholinergic vasomotor control of intestinal blood flow in the domestic chicken
Authors: Bell Christopher
Published: December 2014

1. A histochemical and pharmacological study has been made of the relationship between the medial circular and adventitial longitudinal smooth muscle coats of the anterior mesenteric artery of the domestic chicken.

2. The longitudinal (LM) coat was found to be innervated by excitatory cholinergic and inhibitory adrenergic nerves, confirming previous reports.

3. The circular (CM) coat was found to be innervated by adrenergic vasoconstrictor nerves. There was no evidence for the existence of cholinergic nerves supplying the circular muscle.

4. Contraction of the LM had little effect on the resting perfusion pressure of the isolated artery, but caused potentiation of perfusion pressure responses to vasoconstrictor stimuli directly affecting the CM.

5. It is suggested that the function of the LM is to modulate the reactivity of the anterior mesenteric artery to vasomotor stimuli, and that this may be particularly implicated in the cardiovascular response to sudden stress.
After‐effects of fusimotor stimulation on the response of muscle spindle primary afferent endings
Authors: Brown M. C. , Goodwin G. M. , Matthews P. B. C.
Published: December 2014

1. The experiments were performed on the soleus muscle of the anaesthetized cat in which the ventral roots had been cut.

2. A short period of repetitive stimulation of a single fusimotor fibre which influenced a particular spindle primary ending invariably caused a characteristic alteration in the response of the same ending to a subsequently applied ramp stretch of the muscle. The change consisted in the appearance of a burst of impulses at the beginning of the stretch where none had been present before. Occasionally, such an ‘initial burst’ was spontaneously present; it was then enhanced following fusimotor stimulation.

3. This after‐effect of fusimotor stimulation was abolished by a subsequent stretch of the muscle, but otherwise persisted for over a minute.

4. When the muscle was released to below the length at which the spindle had been facilitated and a testing stretch applied from the new initial length there was no burst of impulses at the beginning of stretch. There was, however, a burst as the muscle was stretched through the length at which the fusimotor fibre had been stimulated.

5. These effects are suggested to be due to the persistence of stable bonds between the actin and myosin filaments of the intrafusal fibres, so that their previously activated regions were ‘stuck’ at the length they were when the fusimotor stimulation was applied.

6. Such effects were produced both by static and by dynamic fusimotor fibres. The effects of the two kinds of fusimotor fibre, however, appeared to be mediated by different intrafusal muscle fibres. This was shown by stimulating one kind of fibre with the muscle slightly stretched, then releasing the muscle a few mm and stimulating the other kind of fibre to the same spindle. A subsequent testing stretch then elicited two bursts, one at the beginning and one in the middle of the stretch.
Responses to directional stimuli in retinal preganglionic units
Authors: Norton A. L. , Spekreijse H. , Wagner H. G. , Wolbarsht M. L.
Published: December 2014

1. Extracellular recordings were made from directionally selective ganglion cell units in the isolated frog retina and decapitated Necturus preparation.

2. Intracellular recordings were made from individual photoreceptor cells in the frog and Necturus retinae while stimuli which had evoked directionally selective responses at the ganglion cell level were presented. No evidence for inhibition of photoreceptors for any direction of movement of the light stimulus was found. This appeared to rule out a mechanism for directional selectivity involving inhibition of photoreceptor potentials.

3. Intracellular recordings were made from the nuclear layer between photoreceptors and ganglion cells in Necturus. The responses were of two types: either transitory or sustained.

4. The sustained type responses could be divided into two classes depending on their receptive field organization. One type of sustained potential had a large receptive field without any evidence for a centre‐surround antagonism and corresponded to the luminosity type S‐potential recorded in fish. The other type had a smaller receptive field and showed a difference in sign of response between centre and surround if the centre was flooded with a steady light. This is very similar to what has been described for a type of on‐centre, off‐surround ganglion cell.

5. The transitory type of responses showed some centre‐surround antagonistic organization. Some of these transitory units also appeared to show some discrimination in response as a function of the distribution of light on the retina.

6. No specific directional selectivity was found from units at the inner nuclear layer. This further excluded any mechanism of directional sensitivity which involves selectivity at the photoreceptor level.

7. It was concluded that although inner nuclear layer units may play a role in the mechanism of directional selectivity, no specific directionality was found at the first synaptic level of the retina.
Rod‐cone independence for sensitizing interaction in the human retina
Authors: Westheimer Gerald
Published: December 2014

1. Illumination of a retinal area adjoining a tested area can cause either desensitization or sensitization through lateral interaction, depending on whether the distance separating the illuminated and tested areas is small or large. This interaction occurs both in the rod and the cone mechanisms of the retina when each is tested separately by selection of appropriate adapting and testing stimuli.

2. In the mixed rod/cone region of the near periphery of the human retina the spatial parameters of interaction within the rod and cone systems were different when mapped out by using only one kind of adapting stimulus and sampling the excitatory state of the rod and cone systems by different probing stimuli.

3. Sensitizing interaction signals generated by the rod system are incapable of causing sensitization of the cone system.
The series elastic component of frog gastrocnemius
Authors: Cavagna Giovanni A.
Published: December 2014

1. The force—extension curve of the series elastic elements of the frog gastrocnemius has been determined up to the force attained during stretching by means of the isotonic quick‐release method, modified in order to allow the release of the muscle immediately after stretching.

2. The series compliance decreases progressively up to a stress value of about 2 kg/cm2 and then it remains constant up to the maximal values of stress attained (about 10 kg/cm2).

3. The lengthening of the series elastic elements when the stress rises to its full isometric value (P0l0/M = 5·2 kg/cm2) is about 3% of the muscle resting length, l0. The Young's modulus in the linear part of the diagram is 294 kg/cm2.

4. The elastic energy stored up to P0 is on average 55 g cm/g; an additional amount of 63 g cm/g is stored during stretching the contracted muscle.
The secretion of pancreatic juice in response to stimulation of the vagus nerves in the pig
Authors: Hickson J. C. D.
Published: December 2014

1. The secretory response to stimulation of the vagus nerves has been examined in the pig and compared with that in the dog under similar experimental conditions.

2. In the pig, stimulation of the vagus nerves caused a profuse flow of pancreatic juice with a high content of bicarbonate, in addition to a secretion of digestive enzymes; atropine suppressed the secretion of enzymes but failed to diminish the flow of bicarbonate‐rich juice.

3. Intra‐arterial injections of acetylcholine closely imitated the effects of stimulation of the nerves, with the difference that both the flow of juice and the secretion of enzymes were abolished together by atropine.

4. Stimulation of the nerves and injections of acetylcholine were effective after resection of the stomach and intestine: these stimuli can therefore act directly on the pancreas, independently of the release of gastro‐intestinal hormones.

5. In the dog, the pancreas differed from that of the pig in that stimulation of the vagus nerves and injections of acetylcholine acted predominantly on the secretion of enzymes and caused only a sparse flow of juice. Atropine annulled all these effects together.

6. The results show that the vagus nerves can exert a much wider control of the secretion of pancreatic juice in the pig than in the dog. Possible mechanisms for this action are discussed.
Studies on the excretion of [14C]histamine and its metabolites by the rabbit kidney
Authors: Lippert T. H. , Quasthoff Ursula
Published: December 2014

1. After intravenous administration of [14C]histamine in rabbits, the urinary excretion of [14C]histamine and [14C]histamine metabolites was examined over a period of 4 hr.

2. It was found that [14C]histamine was excreted in the unchanged form only in small amounts (6–7%), while 54–71% was eliminated in the form of its metabolites.

3. Under normal conditions, the percentage excretion of metabolites, but not of histamine, showed a dose dependence. With the higher [14C]histamine dose, a significantly smaller proportion of the dose given was excreted as metabolites than with the lower dose. The proportion of unchanged [14C]histamine excreted remained constant.

4. Pre‐treatment with histamine infusions, or with mepyramine maleate, caused an increase in the excretion of [14C]histamine metabolites while the excretion of [14C]histamine remained unchanged.

5. Pre‐treatment with a diuretic, a combination of mersalyl and theophylline, did not influence the excretion of [14C]histamine nor of its metabolites.
Consequences of monocular deprivation on visual behaviour in kittens
Authors: Dews P. B. , Wiesel T. N.
Published: December 2014

1. Kittens were raised for a period with one of their eyes closed by suture of the lids. The age at suture and the duration of deprivation were varied systematically. When the cat was a year or more old, the normal and deprived eyes were compared using behavioural procedures which made graded demands on visual function.

2. In kittens deprived from birth, the duration of eye closure determined the severity of the defect in vision with the deprived eye. A cat with an eye closed for the first 4‐6 weeks showed as a permanent effect only a lowering of the visual acuity. When closure was extended through the first 7 weeks the visual acuity was further lowered but the animal still showed good visual guidance of paw placement. Further extension of deprivation through the first 16 weeks led to a still more severe defect; such animals showed no indication of visual guidance of paw placement or of pattern discrimination. They were influenced visually by stimuli that differed in luminosity.

3. The upper age limit of the susceptibility to deprivation was determined by varying the age at eye closure. Waiting until 1 month of age before closing the eye conferred no appreciable protection. Waiting until 2 months of age, however, reduced the damage. Deprivation starting at 4 months of age or later produced no effect we could detect. Thus, susceptibility is greatest during the second month after birth and then falls until by 4 months of age the kitten, like the adult cat, suffers no permanent consequences of monocular light and form deprivation.

4. After exclusive use of the deprived eye for a period, brought about by closure of the normal eye, visual control with the deprived eye was better than in similarly deprived cats whose normal eye was never closed. Improvement in the deprived eye was also seen in an animal whose normal eye was closed after both eyes had been open for more than one year.

5. Relating the behavioural results to the neurophysiological findings in the visual cortex in the same or similarly deprived cats shows that the grading of visual defects with age and length of deprivation was generally paralleled by a change in proportion of cortical cells driven by stimulation of the deprived eye. The effect of reversal of eye closure in improving behavioural control was not, however, accompanied by an increase in the ability of the deprived eye to drive cortical cells.
Abomasal secretory responses to teasing with food and feeding in the sheep
Authors: McLeay L. M. , Titchen D. A.
Published: December 2014

1. Secretion of acid and pepsin from abomasal pouches and contractions of the reticulum and rumen were studied in sheep. Observations were made in sheep after being fasted and when they had food available ad libitum.

2. The abomasal pouches were of fundic regions alone and also of the fundic region with a rim of antral mucosa.

3. The secretion from both types of pouch was continuous, was increased by feeding and decreased by fasting.

4. The volume, pepsin concentration and acid concentration of the secretion from fundic pouches increased within 15–30 min of the sheep being teased with food or fed. These responses were observed in sheep which had food available ad libitum or had been fasted.

5. Reticulum contractions and the rumen contractions associated with them (A sequences) increased in frequency when sheep with either type of pouch were teased with food or when they ate.

6. Consistent associations between rumination and abomasal secretory activity were not established.

7. Mixed fundic‐antral pouches did not characteristically show responses to teasing with food and sustained secretory responses were delayed by up to 90 min after feeding commenced.

8. It is suggested that a cephalic phase of gastric (abomasal) secretion was revealed in the studies on fundic pouches of the abomasum.
Blood levels of oxytocin and vasopressin during suckling in the rabbit and the problem of their independent release
Authors: Bisset G. W. , Clark Barbara J. , Haldar Jaya
Published: December 2014

1. Oxytocin and vasopressin were assayed in samples of blood collected from conscious rabbits during suckling. The milk yields were determined from the weight gain of the litters.

2. With normal milk yields (35–155 g), relatively high concentrations (31–375 μu./ml.) of oxytocin were present in the blood but vasopressin was detected in only one out of eight samples. It is concluded that the release of oxytocin by the milk‐ejection reflex is essential for normal milk removal in the rabbit and that this hormone is released independently of vasopressin.

3. When the milk yield did not exceed 15 g, an amount which could be removed by passive withdrawal from the mammary gland, vasopressin was detected in four out of five blood samples but none contained a detectable concentration of oxytocin. This result can be explained by the intervention of emotional stress which is known to block the milk‐ejection reflex but which acts as a stimulus for the release of vasopressin.

4. Emotional stress could inhibit the milk‐ejection reflex either centrally by blocking the release of oxytocin, or peripherally by blocking the response of the mammary gland to circulating oxytocin. The absence of the hormone in blood during ineffectual suckling suggests that the block is central.
The mechanism of functional vasodilatation in rabbit epigastric adipose tissue
Authors: Lewis G. P. , Matthews J.
Published: December 2014

1. The effect of close‐arterial infusions of fat‐mobilizing substances has been examined on the release of free fatty acids and blood flow in the epigastric adipose tissue of rabbits.

2. All the fat mobilizers in addition to causing the release of free fatty acids also caused an increased blood flow in the fat tissue.

3. Both the fat mobilization and the vasodilatation continued for an hour or so after the end of infusion.

4. Although no vasodilator substance could be detected in the venous effluent from the activated adipose tissue, a vasodilator could be detected in acid—ether extracts of adipose tissue excised during a period of fat mobilization.

5. It is suggested that a vasodilator substance is released or formed in adipose tissue during fat mobilization and that this substance accounts for the vasodilatation accompanying activity in the tissue.
Electrical responses of single cones in the retina of the turtle
Authors: Baylor D. A. , Fuortes M. G. F.
Published: December 2014

1. Intracellular recordings have been made from single photoreceptors in the retina of the turtle. Histological sections of the retina made after injection of dye through the recording electrode reveal dye in the inner segments of single cones.

2. Following a brief flash of light the cone undergoes a hyperpolarization which is graded with the intensity of the flash.

3. The excitatory receptive field of a receptor is probably as small as the cross‐section of a single cone, but accurate measurements are rendered difficult by scattering of light within the retina.

4. The voltage drop produced by a current injected into the cell is increased during the response to light. Steady hyperpolarizing currents increase the size of the response to light; depolarizing currents of increasing strength reduce and then reverse the response.

5. The results are consistent with the hypothesis that light activates the visual cell by decreasing the permeability of membrane channels which in darkness act as a shunt of the membrane.
Direct measurements of membrane unstirred layers
Authors: Green K. , Otori T.
Published: December 2014

1. The unstirred layer of fluid bounding the posterior surface of the rabbit cornea and contact lens has been directly measured using an optical apparatus.

2. Small polystyrene latex spheres (< 0·25 μ diameter) were used as an indicator because of the excellent light‐reflective properties; other indicators were used (e.g. carmine particles) and had a similar behaviour.

3. With the bulk solution unstirred the layer was 350 μ thick on the cornea and 150 μ thick on the contact lens. Following vigorous stirring the layer was reduced to 65 μ on the cornea and < 20 μ on the contact lens.

4. The present direct measurements of the unstirred layers thickness confirm previous indirect measurements.
Water uptake by the crab‐eating frog Rana cancrivora, as affected by osmotic gradients and by neurohypophysial hormones
Authors: Dicker S. E. , Elliott Annie B.
Published: December 2014

1. The rate of water uptake across the skin was investigated in live Rana cancrivora, an euryhaline frog which has been reported to tolerate sea water. When they were exposed to distilled water at 29° C, the rate of water uptake was 8·4 ± 0·4 μl./cm2.hr; when bathed in solutions ranging from 30 to 570 m‐osmole/l., irrespective of whether the solute was sucrose, urea or NaCl, the rate of fluid uptake during the first day was inversely related to the osmolarity of the solution. No appreciable fluid movement was observed when the bathing solution had an osmolar concentration of 270 m‐osmole/l.

2. The rate of fluid uptake was not affected by injections of vasopressin, oxytocin or of extracts of amphibian or rat pituitary glands, irrespective of whether R. cancrivora were bathed in distilled water or in solutions of NaCl or sucrose.

3. In Bufo melanostictus, in contrast with R. cancrivora, injections of neurohypophysial extracts produced a marked increase of the rate of fluid uptake.

4. In the laboratory, R. cancrivora could be acclimatized stepwise to tolerate NaCl solutions up to 700 m‐osmole/l. for 7 days.

5. After 24 hr exposure either to distilled water or to NaCl solutions from 100 to 670 m‐osmole/l., the osmolar concentration of the plasma of R. cancrivora was always higher than that of the bathing fluid. In R. pipiens or R. temporaria plasma osmolar concentration was higher than that of the bathing fluid only when the latter did not exceed 300 m‐osmole/l.

6. Under all conditions investigated, the osmolar concentration of the urine of R. cancrivora was always lower than that of the plasma.

7. The amounts of pressor and oxytocic activities of pituitary glands of R. cancrivora kept in distilled water or in NaCl solutions up to 300 m‐osmole/l. were 8·9 ± 0·8 and 1·8 ± 0·3 m‐u./gland, irrespective of sex or body weight within the range 30–50 g. After 3 days exposure to hypertonic NaCl solutions, the amounts of pressor and oxytocic activities were 14·7 ± 1·2 and 3·1 ± 0·3 m‐u./gland. In both instances the pressor/oxytocic ratio was 4·9. Pituitary glands of R. temporaria similarly showed increased pressor and oxytocic activities after exposure to NaCl solutions of 300–360 m‐osmole/l.
Perfusion from cerebral ventricle to cisterna magna in the unanaesthetized cat. Effect of calcium on body temperature
Authors: Feldberg W. , Myers R. D. , Veale W. L.
Published: December 2014

1. A method is described for the perfusion of the liquor space from a lateral cerebral ventricle to the cisterna magna in the unanaesthetized cat. Perfusions were carried out for 30–40 min using various physiological salt solutions whilst rectal temperature was recorded.

2. When the salt solution used contained calcium in the physiological concentration, rectal temperature remained unchanged, but when it contained no calcium an intense hyperthermia developed during the perfusion. The finding that calcium must be present in the perfusion fluid for preventing temperature from rising may lead to a new understanding of the working of the ‘set‐point’ in the control of body temperature and of the mechanism of action of pyrogens.

3. Independent of the nature of the perfusion fluid a long‐lasting late rise in temperature developed after a perfusion. This happened regularly when the infusion needle was inserted only into the hub of the ventricular cannula, but rarely when the needle was extended beyond the tip of the cannula shaft and the cannula had been flushed out during the preceding days. It is therefore thought that an unknown pyrogenic factor present in the lumen of the cannula and washed into the ventricle with the perfusion fluid is responsible for this effect.

4. The effluent collected from the cisterna contracted the fundus strip of the rat stomach. As the contractions were little affected by BOL, they are attributed mainly to an action of prostaglandin E1 and not to an action of 5‐HT. There was no difference in the biological activity of the effluent whether the perfusion fluid contained calcium or not.
An electrophysiological investigation of the slow fibre system in the frog rectus abdominis muscle
Authors: Forrester T. , Schmidt H.
Published: December 2014

1. Junctional potentials were recorded with a micro‐electrode inserted into muscle fibres of the rectus abdominis muscle of the frog. Large and small nerve fibres were stimulated separately, using a selective stimulation technique. In a few muscle fibres rectangular current pulses were applied through a second micro‐electrode to examine current—voltage relations.

2. Two groups of muscle fibres could be distinguished: (a) Muscle fibres with resting potentials less negative than −75 mV, being localized at the ventral surface only and representing about 9% of the superficial fibres. These fibres were found to be innervated by small (high‐threshold) nerve fibres and responded to single indirect stimuli with a typical s.j.p. (long latency, multiple components, after‐hyperpolarization); upon repetitive stimulation summation of s.j.p.s and a slowly increasing tension could be recorded. The fibres showed a slow time course of electrotonic potentials, relatively high membrane resistance and ‘delayed rectification’. (b) Muscle fibres with generally much higher resting potentials, being innervated by large (low‐threshold) nerve fibres only. Upon indirect stimulation a short‐latency end‐plate or action potential (followed by a twitch) was recorded. The membrane time constant and input resistance of these fibres were similar to those of twitch fibres in other frog muscles.

3. No evidence was found in the present work for the existence of an intermediate type of muscle fibre.

4. It is concluded that the rectus muscle, similar to other frog muscles, contains two distinct types of muscle fibres, twitch and slow.
The binding of tritiated ouabain to mammalian non‐myelinated nerve fibres
Authors: Landowne D. , Ritchie J. M.
Published: December 2014

1. A study has been made of the binding of radioactively labelled ouabain by desheathed rabbit vagus nerves, which consist mainly of non‐myelinated fibres. The corresponding inhibition of the electrogenic sodium pump was also measured.

2. By varying the ouabain concentration and the external potassium concentration two kinds of binding sites could be distinguished: a first site specifically associated with pumping and whose ability to bind ouabain is dependent on the external presence of potassium; and a second site not associated with pumping and unaffected by external potassium.

3. Just complete inhibition of the sodium pumping mechanism is associated with a specific binding of ouabain of about 4·3 p‐mole/mg dry nerve.

4. This gives an upper limit for the density of sodium pumping sites of about 750 per square micron.

5. The turnover rate (i.e. (cation pumped)/(number of sites)) at 20° C is about 22 sec−1.
Electrophysiological evidence for the existence of orientation and size detectors in the human visual system
Authors: Campbell F. W. , Maffei L.
Published: December 2014

1. The evoked potential in response to a grating alternating in phase at 8 c/s was recorded as a function of contrast from the occiput of man.

2. It was found that a linear relation exists between the log. of contrast and the amplitude of the evoked potential.

3. Extrapolation to zero amplitude voltage of the regression line between the amplitude of the evoked potential and log. contrast predicts the psychophysical threshold. This law was found to hold over the wide range of spatial frequencies tested.

4. Below 3 c/deg the results are best fitted with two regression lines; one of these is generated from the foveal and the other from the parafoveal representation in the cortex.

5. The slope of the regression lines was found to be almost independent of either the spatial frequency or the area of the stimulus grating.

6. The slope of the regression lines could be markedly increased by using as a stimulus either two different spatial frequencies, or two different orientations, presented simultaneously.

7. Using the evoked potential the selectivity to orientation was found to be so high that a channel was not influenced by another orientation 15° away.

8. The channels selectively sensitive to spatial frequency were highly selective and were not influenced by another spatial frequency one octave removed in spatial frequency.

9. It is concluded that in man there exist neurones highly selective to both orientation and spatial frequency.
The diuretic actions of prostaglandin E1 and of noradrenaline and the occurrence of a prostaglandin E1‐like substance in the renal lymph of cats
Authors: Fujimoto S. , Lockett Mary F.
Published: December 2014

1. The actions of noradrenaline, prostaglandin E1 and angiotensin II‐amide on various parameters of renal function and on the flow of renal lymph and its equivalent content of prostaglandin E1‐like activity have been compared in cats under chloralose anaesthesia.

2. All three compounds produced diuresis and natriuresis. Noradrenaline (0·1–0·3 μg/kg.min) and angiotensin II (0·1–0·2 μg/kg.min) with rise of the filtration fraction (FF) and GFR; prostaglandin E1 (0·13–0·19μg kg.min) with increase in GFR but without change in FF. Noradrenaline and angiotensin markedly raised renal perfusion pressure, prostaglandin E1 lowered it by approximately 10 mm Hg.

3. All three compounds increased the renal lymph flow. Only PGE1 and noradrenaline markedly raised the equivalent concentration of PGE1 in the renal lymph.

4. Complete block of α and β adrenergic receptors prevented the vasopressor effect and the rise in FF caused by noradrenaline but did not markedly reduce the diuretic and natriuretic effects nor the influence on renal lymph.

5. Effects of PGE1 and of angiotensin were unaffected by α and β adrenergic block and atropinization did not prevent the release of PGE1‐like material or the diuresis caused by noradrenaline.

6. It is suggested that the diuretic and natriutetic actions of noradrenaline are in large part attributable to the intrarenal action of this PGE1‐like substance of unknown origin.
The response of some sympathetic neurones to volleys in various afferent nerves
Authors: Coote J. H. , Perez‐Gonzalez J. F.
Published: December 2014

1. Responses of sympathetic neurones to various afferent inputs have been analysed both in anaesthetized cats with intact neuraxis and in spinal cats.

2. In anaesthetized cats electrical stimulation of low threshold group III afferent fibres in skin and muscle nerves inhibited sympathetic neurones and gave depressor responses. The silent period following a sympathetic reflex discharge is most likely due to inhibition brought on by a particular subgroup within this afferent group.

3. High threshold group III and group IV afferent fibres excited sympathetic neurones and elicited pressor responses.

4. Sympathetic reflex arcs could be temporally facilitated during the somatic afferent induced inhibition, by group IV, and to a lesser extent by group III volleys.

5. Section of the spinal cord shortened the time course and lessened the degree of group III inhibition suggesting that suprasegmental pathways are involved in the long‐lasting depression following a reflex.

6. Baroreceptor afferent stimulation inhibited group III‐ and group IV‐ evoked reflexes even with some temporal facilitation in the pathway.

7. The special properties of the sympathetic reflex arcs and the relation of the results to other work on
B.P. reflexes are discussed. It is suggested that the group III and IV muscle afferents have a chemoreceptor function and are responsible for mediation of the pressor reflex during muscle exercise.
Slow changes in potassium permeability in skeletal muscle
Authors: Adrian R. H. , Chandler W. K. , Hodgkin A. L.
Published: December 2014

1. Voltage clamp experiments on sartorius muscle fibres at 3° C showed that the potassium current is divisible into three components, namely:

(a) Current in the delayed rectifier channel, which reached a maximum in about 0·1 sec at −30 mV, and declined with a time constant of about 4 msec when the fibre was repolarized to −100 mV; this component had an approximately linear instantaneous current—voltage relation and an equilibrium potential E1 at 10–15 mV positive to the resting potential.

(b) A slow component which reached a maximum in about 3 sec at −30 mV, and declined with a time constant of about 0·5 sec when the fibre was repolarized to −100 mV; this component had an approximately linear instantaneous current—voltage relation and a mean equilibrium potential E2 at ‒83 mV in fibres where E1 averaged −75 mV.

(c) Current in the inward rectifier channel which decreased with a time constant of about 0·25 sec when the fibre was hyperpolarized to −150 mV. This component had an equilibrium potential close to the resting potential and an instantaneous current—voltage relation which was that of an inward rectifier.

2. The general characteristics of the late after‐potential in muscles in hypertonic solutions at 3° C are consistent with those of the slow conductance change. The sign of the late after‐potentials was reversed by depolarizing below −80 mV.

3. The decline of current during a maintained hyperpolarization cannot be attributed solely to a decrease in tubular potassium concentration, since there may be a large decrease in current without much alteration of equilibrium potential. The negative slope conductance often seen at −150 mV is also difficult to reconcile with the tubular depletion hypothesis.

4. Replacement of 10 m
M‐K by 10 m
M‐Rb abolished inward rectification but had less effect on the fast and slow components of the potassium conductance.
Gallamine thiethiodide (Flaxedil) and cat retinal ganglion cell responses
Authors: Enroth‐Cugell Christina , Pinto L. H.
Published: December 2014

1. Repeated flashes of diffuse light were presented to the cat's eye over long periods of time (hours) while the mixed ganglion cell response was recorded from single axons in the optic tract. This was done for cats receiving gallamine triethiodide intravenously and for cats who did not receive the drug.

2. All responses were transformed into instantaneous pulse density tracings. Such tracings from control and gallamine cells were compared to observe possible effects of gallamine: (a) the shape (time course) did not change during gallamine administration; (b) maximum firing frequency, total number of spikes and latency was measured for both the on‐ and the off‐component on the pulse density tracings and plotted versus time. Statistical methods failed to reveal any difference between the manner in which these response features of control cells and of gallamine cells varied with time.
On the mode of action of ACTH on the isolated perfused adrenal gland
Authors: Jaanus Siret D. , Rosenstein M. J. , Rubin R. P.
Published: December 2014

1. Isolated cat adrenal glands were perfused with Locke solution, and the corticosteroid outputs in response to adrenocorticotrophin (ACTH) were studied.

2. Steroid outputs varied with the ACTH concentration, as well as with the duration of exposure to a given ACTH concentration.

3. Omission of calcium from the perfusion medium markedly depressed ACTH‐evoked steroid release. The steroid output was directly related to the extracellular calcium concentration up to 0·5 m
M.

4. During a constant exposure to ACTH, steroid output was maintained for at least 2‐3 hr, provided that calcium was present in the perfusion medium.

5. Strontium, but not barium or magnesium, replaced calcium in maintaining the secretory response to ACTH.

6. Magnesium depressed ACTH‐evoked secretion in the presence of calcium, and this depression of secretion was antagonized by increasing the calcium concentration.

7. Prolonged perfusion with sodium‐free or potassium‐free solutions did not markedly inhibit steroid output in response to ACTH. Excess potassium (56 m
M) did not produce a consistent or marked increase in spontaneous steroid output and did not affect the response to ACTH.

8. The steroid content of adrenal glands perfused with Locke solution and exposed to ACTH was about 10% of the amount which was secreted. By contrast, adrenal glands perfused with calcium‐free media and exposed to ACTH contained much higher amounts of steroid, despite the negligible amount secreted.

9. These data suggest that calcium plays a critical role in the mechanism of corticosteroid secretion from the adrenal cortex.
Effects of 0·9% saline infusion on urinary and renal tissue composition in the hydropaenic, normal and hydrated conscious rat
Authors: Atherton J. C. , Green R. , Thomas S.
Published: December 2014

1. Changes in water and solute outputs of hydropaenic, normal and hydrated conscious rats were determined during intravenous infusion (0·2 ml./min) of isotonic (0·9%) saline for 4 hr; renal tissue composition was determined before, and after 1 or 2 hr, infusion.

2. In normal and hydrated rats increased excretion of water and sodium was such that urinary output matched intravenous input from about 2 hr. In hydropaenic rats, the diuretic and natriuretic response was much reduced; a retention of infused saline, equivalent to 15% body weight, occurred over 4 hr.

3. A considerable increase in urea output and clearance, and a smaller increase in potassium and ammonium outputs, occurred in all groups.

4. The corticomedullary osmolal gradients characteristic of non‐diuretic rats were largely dissipated during saline infusion: by 1 hr in normal and hydrated rats, and by 2 hr in the hydropaenic group.

5. These changes were ascribable mainly to an increase in tissue water content in all segments, particularly in the hydropaenic group; and to a profound decrease in urea content in all groups.

6. Changes in tissue sodium content were smaller, and differed between segments and between the differently hydrated groups. A decrease in papillary content occurred in hydropaenic and normal groups and an increase in cortical and outer medullary content occurred in all groups.

7. After 2 hr saline infusion, incomplete papillary—urinary osmotic equilibration was evident in all groups.

8. These changes in medullary osmolality and in papillary—urinary osmotic equilibration preceded the maximal diuresis, and must contribute to the diuresis induced by saline infusion, as in water and osmotic diureses.
The dependence of the transmembrane salivary secretory potential on the external potassium and sodium concentration
Authors: Petersen O. H.
Published: December 2014

1. The submandibular gland of the cat was perfused with equi‐osmolar Locke solutions of different cationic composition. The increase in acinar membrane potential (secretory potential), measured with a glass capillary micro‐electrode, was recorded after intra‐arterial injection of acetylcholine.

2. When nearly all Na in the perfusion fluid was replaced by tetraethylammonium (TEA), the size of the secretory potentials was significantly (P < 0·001) greater than of those recorded during perfusion with normal Locke solution.

3. When the K concentration in the TEA Locke solution was augmented, the size of the secretory potentials was greatly diminished. Thus at a [K]o of 4 m‐equiv/l. the size of the secretory potentials was 43·3 mV ± 2·5 (n = 19) but at a [K]o of 10 m‐equiv/l. the size was only 24·7 mV ± 2·0 (n = 13) and at a [K]o of 20 m‐equiv/l. the size of the secretory potentials was 12·0 mV ± 1·0 (n = 21). When the submandibular gland was perfused with a K‐free TEA Locke solution the size of the secretory potentials was 49·7 mV ± 2·2 (n = 17).

4. The size of the secretory potentials recorded during perfusion with normal (Na) Locke solution increased significantly (P < 0·001) when K was omitted from the perfusion fluid. The decrease of the size with increasing [K]o was considerably less marked than that found during perfusion with TEA Locke solution. Increasing [K]o by a factor of 5 diminished the size of the secretory potentials recorded in Na Locke solution by a factor of 2, whereas the size of the secretory potentials recorded in TEA Locke solution, with the same changes in [K]o, diminished by a factor of 3·5.

5. The results seem to indicate that the increase in acinar membrane potential obtained after stimulation of the gland is due to an enhanced permeability of the basal acinar cell membrane to K. However, it seems that the permeability to Na is also enhanced so that the outwardly directed K current is partly short‐circuited by an inward Na current.
Accessibility of heart water to pentoses
Authors: Fisher R. B. , Gilbert J. C.
Published: December 2014

1. The raffinose space, the inulin space and the weight loss on compression of perfused rat hearts are indistinguishable in magnitude.

2. The inulin space shows systematic variations from day to day and is also affected by the procedure used for removing surplus water from the perfused heart. It is therefore not safe to use a mean figure of extracellular space in permeability experiments.

3. Perfusion of hearts with arabinose solutions alters the intracellular water content. These alterations can be accounted for if it is assumed that the arabinose which penetrates the cells is uniformly distributed in the cell water.

4. By appropriate choice of pentose concentration and of time of perfusion it can be shown that all the estimated cell water is accessible to pentose.

5. It is concluded that no detectable fraction of the extracellular water is inaccessible to inulin and that no detectable fraction of the intracellular water is inaccessible to pentose.
Properties of kallikrein‐containing granules isolated from the submaxillary gland of the guinea‐pig
Authors: Bhoola K. D. , Heap P. F.
Published: December 2014

1. Granular fractions of high purity consisting of subcellular kallikrein‐ and amylase‐storing organelles have been isolated from homogenates of guinea‐pig submaxillary gland.

2. The isolated kallikrein‐ and amylase‐containing granules closely resembled secretory granules observed in situ in serous acinar cells in intra‐granular appearance, size and histochemical reaction.

3. The subcellular, histochemical and ultrastructural studies indicate that the serine protease, kallikrein, is like amylase an exocrine enzyme with a functional role in saliva.
The effect of changes in lung volume on the size and shape of alveoli
Authors: Forrest J. B.
Published: December 2014

1. A technique is described by which living anaesthetized guinea‐pigs were artificially ventilated with a positive and negative pressure cycle, and rapidly frozen at the instant of cessation of ventilation at a preselected point on the respiratory cycle.

2. The dimensions of alveoli and alveolar ducts were measured by histological morphometric methods, and related to the degree of lung inflation at the instant of freezing.

3. The alveolar volume fraction increased from 0·52 at low lung volumes, up to 0·62 at lung volumes in the mid‐inflation range, then decreased to 0·51 at high lung volumes. The alveolar duct volumetric fraction remained constant at all lung volumes.

4. The total volume of alveoli increased linearly with increase in lung volume. The total alveolar duct volume increased little until the lungs were 40% inflated, above which it increased steeply.

5. The total number of alveoli was linearly related to the body weight.

6. The total alveolar surface area increased steeply between lungs of low lung volume and those which were up to 50% inflated, above which the increase levelled off. The absolute values of total alveolar surface depended on the body weight as well as the degree of lung inflation.

7. The mean alveolar duct diameter was 40% greater, and the mean alveolar mouth diameter 35% greater in lungs which were fully inflated than in lungs which were nearly collapsed. The average geometrical shape of alveoli was not related to the degree of lung inflation.

8. The harmonic mean thickness of the air—blood barrier was 33% less in lungs which were fully inflated than in lungs which were nearly collapsed. The alveolar surface membrane was smooth whether the lungs were fully inflated or collapsed.
Modification of transmitter release by ions which prolong the presynaptic action potential
Authors: Benoit P. R. , Mambrini J.
Published: December 2014

1. The action of ions which increase the nerve spike duration at Ranvier's node has been studied at the neuromuscular junction of the frog.

The duration of the presynaptic action potential is increased by UO2, Ni, Nz and TEA ions.

2. The release of transmitter after a nerve impulse is delayed and prolonged in the presence of the four ions, but the amount of evoked transmitter release estimated from the mean quantal content of e.p.p. is increased only by UO22+ and TEA. Both Ni2+ and Zn2+ decrease it.

3. The frequency of m.e.p.p.s is increased by UO22+ and decreased by Ni2+ and Zn2+ at KCl‐depolarized junctions. It is not affected by TEA.

4. It has been concluded that the increased presynaptic spike duration is responsible for the delayed and prolonged transmitter release in the presence of ions which increase the nerve spike duration at Ranvier's node.

It is demonstrated that some ‘specific’ effects possibly resulting from ionic competition for presynaptic sites between UO22+, Ni2+ or Zn2+ and other ions present in the Ringer may increase, interfere with, or hide the increased transmitter release that may be predicted from the lengthened presynaptic depolarization.