bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rod and cone independence in the electroretinogram of the dark‐adapted monkey's perifovea
Authors: Gouras P. 
Published: December 2014

1. Rod and cone interaction has been studied in the vitreal and intraretinal e.r.g. in the perifovea of the dark‐adapted Rhesus monkey retina.2. Rod and cone responses can be completely isolated in the e.r.g. using dim, monochromatic stimuli. The threshold cone response begins at about 50 msec whereas that of the rods begins at 150 msec. There is no detectable interaction between these two responses.3. By comparing the e.r.g. with ganglion cell responses, it is concluded that the time delays and interactions of rod and cone signals arriving at the ganglion cell layer are determined respectively before and after the origin of the b‐wave.
The contrast sensitivity of retinal ganglion cells of the cat
Authors: Enroth-Cugell Christina , Robson J. G. 
Published: December 2014

1. Spatial summation within cat retinal receptive fields was studied by recording from optic‐tract fibres the responses of ganglion cells to grating patterns whose luminance perpendicular to the bars varied sinusoidally about the mean level.2. Summation over the receptive fields of some cells (X‐cells) was found to be approximately linear, while for other cells (Y‐cells) summation was very non‐linear.3. The mean discharge frequency of Y‐cells (unlike that of X‐cells) was greatly increased when grating patterns drifted across their receptive fields.4. In twenty‐one X‐cells the relation between the contrast and spatial frequency of drifting sinusoidal gratings which evoked the same small response was measured. In every case it was found that the reciprocal of this relation, the contrast sensitivity function, could be satisfactorily described by the difference of two Gaussian functions.5. This finding supports the hypothesis that the sensitivities of the antagonistic centre and surround summating regions of ganglion cell receptive fields fall off as Gaussian functions of the distance from the field centre.6. The way in which the sensitivity of an X‐cell for a contrast‐edge pattern varied with the distance of the edge from the receptive field centre was determined and found to be consistent with the cell's measured contrast sensitivity function.7. Reducing the retinal illumination produced changes in the contrast sensitivity function of an X‐cell which suggested that the diameters of the summating regions of the receptive field increased while the surround region became relatively ineffective.
Mean carbon dioxide tension in the brain after carbonic anhydrase inhibition
Authors: Brzezinski J. , Kjällquist Å. , Siesjö B. K. 
Published: December 2014

1. Measurements of the CO2 tensions in arterial blood, in blood from the superior sagittal sinus, in cisternal cerebrospinal fluid, and on the surface of the cerebral cortex were made in spontaneously breathing anaesthetized cats and rats after inhibition of carbonic anhydrase with acetazolamide in doses of 50‐150 mg/kg.2. After an acetazolamide dose of 50 mg/kg in cats there was a mean increase in the c.s.f. CO2 tension of 8 mm Hg; after a dose of 100 mg/kg the corresponding mean increase was 13 mm Hg.3. Since the CO2 tension measured in venous blood was only moderately influenced by the acetazolamide, the normal PCO2 difference between venous blood and c.s.f. was markedly reduced. The apparent arterial CO2 tension, i.e. the CO2 tension measured in vitro, always changed to the same extent as the c.s.f. CO2 tension.4. The findings were confirmed by measurements of the CO2 tension on the surface of the cerebral cortex, and by measurements of the blood and c.s.f. CO2 tensions in the rat.5. It is concluded that the mean tissue CO2 tension of the brain can be estimated from the measured arterial CO2 tension, even under conditions of carbonic anhydrase inhibition.
The lymphatic and venous pathways for the outflow of thyroxine, iodoprotein and inorganic iodide from the thyroid gland
Authors: Daniel P. M. , Plaskett L. G. , Pratt O. E. 
Published: December 2014

1. Baboons and cats were given radioactive iodine and, at varying times after the injection, samples of thyroid and non‐thyroid lymph and of thyroid venous and peripheral venous blood were collected. The radioactive material in these samples was separated by paper chromatography or by differential precipitation and solvent extraction into three main fractions: inorganic iodide, iodoamino acid iodine and high molecular‐weight material (retained at the origin of chromatograms and not extractable by butanol or ethanol). The latter was considered to be iodoprotein.2. Thyroxine was the main component of the radioactive iodoamino acid iodine in thyroid lymph, in thyroid venous and in peripheral blood. The concentration of thyroxine radioactivity in the thyroid lymph was several times greater than that in either thyroid venous or peripheral blood plasma, both before and after giving thyroid stimulating hormone.3. An unidentified thyronine compound that was frequently found in thyroid lymph and also in blood samples contained an appreciable proportion of the radioactive iodine. This substance was probably a metabolite of one of the iodothyronines. In addition, iodotyrosines probably accounted for up to 4% of the radioactivity in the lymph and blood samples but radioactive triiodothyronine could not be detected with certainty.4. In some experiments lymph was obtained from the cervical lymph trunk at a considerable distance from the thyroid gland, in order to avoid operative trauma to the gland. This cervical lymph contained diluted thyroid lymph but even so it contained more radioactivity in the form of iodoamino acid and iodoprotein than did peripheral blood or non‐thyroid lymph. Cervical lymph and thyroid lymph both contained less radioactive inorganic iodide than did non‐thyroid lymph.5. The administration of thyroid stimulating hormone caused a prolonged rise in the output of radioactive iodoamino acid in the thyroid venous blood and, for a limited period, an increase in the output of radioactive inorganic iodide. At the same time there was an increase in the output of radioactive material in the thyroid lymph. The main part of the latter was due to a rise in the output of iodoprotein.6. The lymphatics and the venous system provide alternative pathways for the outflow of iodine compounds from the thyroid gland. These pathways differ in relative importance for different iodine compounds. For iodoprotein the lymphatic pathway is the important one since there is no appreciable release of this substance into the thyroid venous blood. In the case of inorganic iodide, where there is no appreciable difference in concentration between thyroid lymph and blood, the greater flow of blood makes the venous pathway relatively more important than the lymphatic one. Thyroxine is released into the thyroid lymph in higher concentration than into the blood but the faster flow of blood makes the venous pathway relatively more important.
The inhibition of induced motor activity in transplanted fundic pouches
Authors: Brown J. C. , Johnson L. P. , Magee D. F. 
Published: December 2014

1. An increase in motor activity of transplanted fundic pouches can be produced repeatedly by an alkaline buffer solution in the duodenum.2. The response can be abolished by small doses of a cholecystokinin‐pancreozymin extract.3. The secretagogues, olive oil and peptone will inhibit the response when introduced into the duodenum.4. Acetylcholine in the duodenum will also inhibit the effect.5. Hydrochloric acid will inhibit the motor activity produced by alkaline buffer in the duodenum and also resting activity of the pouches.
Effects of acetylcholine and other medullary secretagogues and antagonists on the membrane potential of adrenal chromaffin cells: an analysis employing techniques of tissue culture
Authors: Douglas W. W. , Kanno T. , Sampson S. R. 
Published: December 2014

1. A method has been devised for isolating adrenal chromaffin cells (from gerbils) and maintaining them in vitro. Transmembrane potentials of these cells were recorded with intracellular micro‐electrodes.2. Acetylcholine depolarized the chromaffin cells and so did various other substances known to evoke catecholamine secretion: nicotine, pilocarpine, histamine, 5‐hydroxytryptamine, angiotensin, and bradykinin.3. The depolarizing effect of acetylcholine was partially antagonized by hexamethonium and was blocked completely by hexamethonium in combination with atropine.4. Hexamethonium alone completely blocked the response to nicotine; and atropine alone abolished the response to pilocarpine. Thus both nicotinic and muscarinic receptors are present in gerbil chromaffin cells.5. The experiments demonstrate that the various secretagogues and antagonists tested act on the plasma membrane of the chromaffin cell and raise the question whether depolarization may be an important event in stimulus‐secretion coupling.
The significance of adenosine cyclic 3′,5′‐monophosphate for the contraction of smooth muscle
Authors: Bartelstone H. J. , Nasmyth P. A. , Telford J. M. 
Published: December 2014

1. The influence of adenosine cyclic 3′,5′‐monophosphate (3′,5′‐AMP) and of drugs believed to increase or decrease its concentration in the tissues has been determined on the response of vascular and uterine smooth muscles to catecholamines. Generally, drugs believed to increase tissue content of 3′,5′‐AMP potentiated the responses and those believed to decrease it depressed them.2. The cardiovascular responses of dogs (with major vessels occluded in the chest) to carotid occlusion were potentiated by infusions of theophylline and sodium fluoride. Infusion of theophylline also potentiated the response of the occluded abdominal vessels to noradrenaline.3. Intravenous infusions of theophylline and sodium fluoride potentiated pressor responses to catecholamines in the pithed rat. Infusions of iminazole depressed the responses in two animals and was without effect in two others.4. In spinal cats intravenous infusions of theophylline potentiated pressor responses to catecholamines, but sodium fluoride was without effect.5. Contractions of the isolated rat aortic strip to noradrenaline were always potentiated by sodium fluoride and by theophylline, and depressed by iminazole, when they were recorded isometrically. Theophylline always potentiated the contractions, when they were recorded isotonically but sodium fluoride was mostly, and iminazole always, ineffective.6. 3′,5′‐AMP in concentrations from 0·1 to 20 μg/ml. potentiated the responses of the isolated rat aortic strip to noradrenaline in thirty‐eight experiments out of hundred. Concentrations from 10 to 500 μg/ml. sometimes depressed contractions recorded isometrically. In five experiments, exposure to low concentrations for 3 hr increased the resting tension of the preparation.7. Responses to noradrenaline of uteri from oestradiol‐treated rabbits were potentiated by vasopressin and by sodium fluoride, but not by theophylline or iminazole. In progesterone‐treated animals the responses were unaffected by vasopressin and sodium fluoride, but potentiated by theophylline and depressed by iminazole. 3′,5′‐AMP was without effect on the uterine responses.8. It is concluded that the results support the view that an increase in the tissue content of 3′,5′‐AMP potentiates the contraction of vascular and uterine smooth muscle in response to catecholamine. This view is supported by the observation that the nucleotide itself can potentiate the responses of the rat aortic strip to noradrenaline.
Release of noradrenaline by splenic nerve stimulation and its dependence on calcium
Authors: Kirpekar S. M. , Misu Y. 
Published: December 2014

1. Cat spleens were perfused with Krebs bicarbonate solution using a constant flow pump. The amount of noradrenaline released during splenic nerve stimulation was measured at various frequencies. The dependence of noradrenaline release on the ionic composition of perfusion medium was also determined.2. The effect of frequency of stimulation on the output of noradrenaline was studied in both normal and phenoxybenzamine treated cats. In normal cats, the output was 0·33 ng/stimulus at 10/sec, whereas it was 1·21 ng/stimulus at 30/sec. In phenoxybenzamine‐treated cats, the maximum output of noradrenaline of 4 ng/stimulus was obtained at 5 or 10/sec. Higher or lower frequencies of stimulation produced lower output.3. In both normal and phenoxybenzamine treated cats, removal of calcium from the perfusing medium nearly abolished the release of noradrenaline in response to nerve stimulation. Replacement of calcium restored the noradrenaline release. The noradrenaline output/stimulus was linearly related to the log of the external calcium concentration.4. Increasing the concentration of magnesium to (10‐20 m
M) reduced the noradrenaline output. This depressant effect of magnesium was partially antagonized by increasing the calcium concentration of the perfusion solution.5. Divalent alkali metal earths such as barium and strontium were able to substitute for calcium. Barium substitution nearly doubled the noradrenaline output/stimulus and increased the pressor activity of the samples taken just before nerve stimulation.6. Removal of potassium from the perfusion fluid or lowering the sodium concentration to 50 m
M had little effect on the release of noradrenaline. Lowering the sodium concentration to 37·5 m
M or less usually abolished the noradrenaline output; this effect is attributed to blockade of nerve conduction.7. It is suggested that depolarization of post‐ganglionic sympathetic nerve terminals may increase the influx of calcium ions which in turn leads to the release of noradrenaline from the nerve terminals.
The effect of adrenaline and noradrenaline on hormone secretion and blood flow from the thyroid vein in sheep with exteriorized thyroids
Authors: Falconer I. R. 
Published: December 2014

1. Emotional stimulus to the sheep has previously been shown to cause increased thyroid hormone secretion; the influence of adrenaline and noradrenaline in this process has been investigated.2. Sheep bearing exteriorized thyroid glands on carotid artery—jugular vein loops were used. Thyroid vein blood was collected through a cannula in the jugular vein within the loop, and blood flow was measured by a plethysmographic technique.3. 131I (50 μc) was injected intramuscularly (
I.M.) into the sheep, and 4‐7 days later the concentration of total and protein bound 131I in thyroid vein blood was measured in samples taken every 10 min for 4 hr. Intracarotid injections of 1 μg,
I.V. injections of 5 μg, or
I.V. infusions at 10 μg/min for 10 min, of adrenaline or noradrenaline were administered 1·5 hr after commencement of sampling. Blood flow from the thyroid was measured in similar experiments.4. No significant changes in thyroid hormone secretion could be attributed to adrenaline or noradrenaline, and it was concluded that circulating catecholamines do not influence the release of thyroid hormone observed after brief emotional stimulus in the sheep.
The progressive pressor response to angiotensin in the rabbit
Authors: Dickinson C. J. , Yu R. 
Published: December 2014

1. The threshold for any detectable rise of systemic arterial pressure during the prolonged intravenous administration of angiotensin to conscious rabbits was observed to be an infusion rate of 0·003‐0·006 μg.kg−1.min−1.2. At infusion rates between threshold and 0·04 μg.kg−1.min−1 the systemic arterial pressure rose progressively over a 3‐ to 7‐day period to a plateau.3. On stopping the angiotensin infusion the blood pressure fell rapidly back to its base line much faster than it rose during the infusion. The time taken to reach control values was approximately related to the duration of the infusion.4. At infusion rates of about 0·05 μg.kg−1.min−1 the full rise of blood pressure developed within a few minutes, and could be sustained without change for many days. At higher rates the blood pressure diminished with time.5. Diurnal fluctuations of blood pressure were often seen during prolonged infusions of angiotensin at low rates; and more rapid fluctuations of blood pressure over an hour or two were frequently encountered immediately after an infusion was turned off.6. The possible role of angiotensin in producing chronic renal hypertension is discussed in the light of these observations.
The effects of a single injection of progesterone on the oestrous cycle, thyroid gland activity and uterus‐plasma concentration ratio for radio‐iodide in the rat
Authors: Brown-Grant K. 
Published: December 2014

1. A single subcutaneous injection of 5 mg, 1·25 mg or 625 μg, but not 312 μg, of progesterone in oil delayed ovulation in the rat by 1 or more days, when injected at the dioestrous stage of a 4‐day oestrous cycle.2. When ovulation was delayed in this way the expected increase in the thyroid‐serum concentration ratio for 131I was also delayed but the ratio did increase when delayed ovulation occurred.3. A single injection of progesterone resulted in an increase in the uterus‐plasma and oviduct‐plasma concentration ratios for 131I; the increase was greatest when steroid was injected at the dioestrous stage of the cycle and was delayed and least when the steroid was given at the pro‐oestrous stage.4. Ovulation was advanced by 1 day when progesterone was injected on the second day of dioestrus in rats showing regular 5‐day cycles; this ovulation was not accompanied by an increase in the thyroid‐serum concentration ratio. In these experiments a dose of progesterone that failed to advance ovulation produced a rise in uterus‐plasma and oviduct‐plasma ratio for 131I but no rise was seen when ovulation was induced, suggesting that oestrogen secretion had been stimulated.5. 20α‐Dihydroprogesterone (pregn‐4‐en‐20α‐o1‐3‐one) was not effective in delaying or advancing ovulation at a dose level of 2·5 mg per rat and had no effect on the uterus‐plasma concentration ratio for radio‐iodide.6. These results are discussed in relation to the hypothesis that the increase in thyroid gland activity at the oestrous stage of the cycle is related to the neuro‐endocrine changes that lead to ovulation.
Actions of calcium and certain multivalent cations on potassium contracture of guinea‐pig's taenia coli
Authors: Imai S. , Takeda K. 
Published: December 2014

1. Using a calcium buffer system, the effect of severe calcium lack on the shape of K‐contracture of the guinea‐pig's taenia coli was studied. Under conditions of calcium lack, the initial phasic response was preferentially affected and it disappeared completely at concentrations below 10−7
M, while the ensuing tonic response persisted, though considerably diminished in size, even at the concentration of 10−8
M.2. In calcium‐free media, various multivalent cations, which according to Frank (1962) can support the K‐contracture of a skeletal twitch muscle fibre in calcium‐free solution, augmented the remaining tonic response, but did not restore the phasic response, when it was eliminated in calcium free environment.3. When K‐contractures were induced in normal calcium media, these cations produced, in contrast, an abolition of the phasic response together with a partial depression of the tonic phase. They also inhibited a part of the fully developed contracture. The last effect was no longer obtainable in calcium‐free media.4. It is concluded that the phasic response and a part of the tonic response of taenia coli depend upon the extracellular calcium for their initiation (and also for maintenance of tension in the case of the latter) and that the rest of the tonic response draws on a store of ‘bound’ calcium for its evolution.
Motor activity following the silent period in human muscle
Authors: Alston W. , Angel R. W. , Fink F. S. , Hofmann W. W. 
Published: December 2014

1. When a muscle is unloaded during voluntary contraction, there is normally a silent period in the electromyogram. The silence is terminated by a sudden return of muscle action potentials.2. In order to investigate the mechanism of the terminal motor volley, the unloading reflex was studied in six human subjects. The independent variables were the initial muscular force, the inertia of the limb and the amount of motion permitted. The dependent variables were the size and latency of the terminal volley.3. During isometric contraction, the amplitude of the surface‐recorded muscle action potentials increased monotonically with increasing muscular tension.4. The action potentials were significantly larger during the terminal volley than during the period before unloading.5. When acceleration of the limb was reduced by increasing the inertia, the terminal volley was decreased in size, but the latency was not affected.6. When movement was interrupted by a mechanical block, the latency of the terminal volley was reduced, but the size was not affected.7. The results suggest that the terminal motor volley is not the result of a decrease in Renshaw feed‐back or in autogenetic inhibition.8. The motor volley must be regulated by proprioceptive feed‐back, because it is affected by the velocity and displacement of the limb.9. The muscle frequently responded within 20 msec after motion of the limb was blocked. Hence it appears that the mechanism involves a spinal reflex.10. Because the motor discharge occurs while the muscle is shortening, it cannot be an ordinary stretch reflex. If the discharge is attributed to spindle afferent driving, one must assume that the gamma motor neurones are active during the silent period.11. The authors postulate a fusimotor reflex, which is driven by afferent impulses from the moving limb and excites the alpha motoneurones by way of the ‘gamma loop’.
Some observations on ‘autoregulatory escape’ in cat intestine
Authors: Baker Rosemary , Mendel D. 
Published: December 2014

1. ‘Autoregulatory escape’ (Folkow, Lewis, Lundgren, Mellander & Wallentin, 1964a) in which intestinal blood flow escapes from the constrictor influence of splanchnic nerve stimulation, was investigated in the cat. Measurements were made of intestinal blood flow, movements and portal venous pH and oxygen content.2. ‘Autoregulatory escape’ was observed with sympathetic nerve stimulation and noradrenaline infusion. It did not occur during haemorrhage.3. The recovery of flow during noradrenaline infusion could not be explained by changes in intestinal motility or loss of effect of noradrenaline due to changes in portal venous hydrogen ion concentration.4. During a noradrenaline infusion there was a reduction in oxygen consumption associated with a fall in blood flow. During the period of ‘autoregulatory escape’, however, oxygen consumption increased. The significance of these observations is discussed.