bluuebunny/crossref_metadata_2025_split huggingface dataset:
An analysis of the mechanism of cessation of uptake of macro‐molecular substances by the intestine of the young rat (‘closure’)
Authors: Clarke Rufus M. , Hardy R. N. 
Published: December 2014

1. The longitudinal distribution of cells capable of absorbing macro‐molecular material has been determined in the small intestine of the young rat by measurements of the uptake of [125I]polyvinyl pyrrolidone (PVP).2. PVP uptake was never seen in the duodenum and became restricted to the distal half of the small intestine by the 18th day of life. The subsequent decline to zero in PVP uptake was due to an almost uniform decrease in PVP uptake by the distal half of the small intestine.3. Histological studies indicate that this rapid decline in PVP uptake did not reflect a decrease in uptake by individual cells, but rather their replacement by new cells incapable of taking up PVP.4. Autoradiographic estimates of turnover time in the intestinal epithelium using tritiated thymidine reveal good agreement between the time needed to replace completely the epithelium of the ileum (62 hr) and the duration of the rapid decline in PVP uptake (approximately 3 days).5. It is concluded that on or about the 18th post‐natal day there is an abrupt change in the functional characteristics of the apical plasma membrane of cells produced by the crypts of Lieberkühn in the distal half of the small intestine. The stimulus for this change is unknown, but cells produced subsequently cannot take up PVP.
Composition of alveolar liquid in the foetal lamb
Authors: Adamson T. M. , Boyd R. D. H. , Platt H. S. , Strang L. B. 
Published: December 2014

1. Experiments were performed on foetal lambs at gestations between 125 days and term. The foetus was exteriorized at Caesarean section with the umbilical cord and placental attachment maintained intact. Samples of liquid from the alveolar parts of the lung were withdrawn through a tracheal cannula and samples of lung lymph, plasma and amniotic liquid were also obtained. Measurements were made of total osmolality, concentrations of electrolytes and urea, pH and PCO2. Titrations were carried out with
N/10 HCl and
N/10 NaOH. The water content of the liquids was estimated and concentrations expressed per kg H2O.2. In alveolar liquid [H+], [K+] and [Cl−] were higher and [Ca2+], [phosphates] and [HCO3−] were lower than in plasma or lymph. In amniotic liquid osmolality [Na+], [Cl−] and [Ca2+] were lower and [phosphates] higher than in plasma or lymph. Alveolar liquid/plasma ratios of [HCO3−], [Ca2+], [Cl−] and [K+] differed from ultra filtrate/plasma ratios of these ions.3. Titration curves demonstrated a very small amount of buffering in alveolar liquid at its in vivo pH of 6·27 mostly due to HCO3− at an average concentration of 2·8 m
M/kg H2O.4. It is concluded that foetal alveolar liquid is not an ultrafiltrate of plasma nor a mixture of amniotic liquid and plasma ultrafiltrate, but a special material elaborated by the foetal lung.
The effect of chronic osmotic disturbance on the concentrations of cations in cerebrospinal fluid
Authors: Bradbury M. W. B. , Kleeman C. R. 
Published: December 2014

1. Adult cats were rendered hypo‐ and hypernatraemic by peritoneal dialysis. These states were maintained for periods of 2‐5 days.2. The concentrations in cerebrospinal fluid (c.s.f.) of the cations, potassium, calcium and magnesium all decreased in the hyponatraemic animals and increased in the hypernatraemic animals. These shifts in c.s.f. cation concentrations did not relate to plasma changes in the same cations, which were often in the opposite direction.3. The relations of the cation concentrations to c.s.f. sodium were not linear and, in the cases of calcium and magnesium, the relevant cation concentration related better to the square rather than the first power of the c.s.f. sodium concentration.4. Brain water changed much less in the hypo‐ and hypernatraemic animals than might be anticipated from the shifts in blood osmolarity, plasma sodium concentration and muscle water.5. Isotonicity of the fluids in brain with blood plasma and c.s.f. appeared to be largely maintained by loss or gain of sodium and chloride ions by this tissue.6. The c.s.f. results may be partly due to a constant influx of the cation in question being diluted with more formed c.s.f. in hyponatraemia and less c.s.f. in hypernatraemia, but the deviations from linearity in the plots of c.s.f. cation against c.s.f. sodium suggest the influence of other factors.
The isolation of a substance very closely resembling the 18‐monoacetate of D‐aldosterone from the venous blood of activated muscle and from contracting muscle
Authors: Lockett Mary F. , Retallack R. W. 
Published: December 2014

1. A renally active substance can be extracted in detectable quantity from 150 g flash‐frozen active but not from 150 g flash‐frozen flaccid striped muscle. This substance is identical to the 18‐monoacetate of
D‐aldosterone (18‐MA) in RF value in three solvent systems and in biological activity.2. The renally active substance is secreted into the blood stream by active but not by flaccid muscles.3. Bilateral stimulation of decentralized sciatic nerves causes diuresis, natriuresis, a rise in the clearances of creatinine and PAH without change in heart or respiratory rates, in cats under chloralose anaesthesia. These changes can be matched by
I.V. infusion of ADH, 0·3–0·45 m‐u./kg.min.4. The urinary changes caused by sciatic stimulation are not prevented by transection of the spinal cord but are abolished by hypophysectomy.5. Hence, like 18‐MA, the muscle substance liberates ADH from the neurohypophysis.
Isotonic lengthening and shortening movements of cat soleus muscle
Authors: Joyce G. C. , Rack P. M. H. 
Published: December 2014

1. By supplying pulses to different subdivisions of the ventral nerve roots in rotation it was possible to obtain smooth contractions of cat soleus with low rates of stimulation.2. After contracting isometrically the muscle was subjected to ‘step’ changes in tension after which it lengthened or shortened isotonically.3. Isotonic lengthening movements usually began relatively slowly but proceeded with increasing velocity; this acceleration was most conspicuous when low rates of stimulation were used.4. At low rates of stimulation the isotonic lengthening movement often continued beyond the length at which the muscle could have generated that tension in an isometric contraction. The muscle then shortened slowly back toward that length.5. Isotonic shortening movements began relatively rapidly, but as shortening continued the movement became slower, and often had an irregular oscillatory course.6. The isotonic movements are discussed in relation to the sliding filament theory of muscle contraction.7. The compliance of the series elastic elements was calculated from the relative amplitudes of the ‘step’ changes in tension and length. The stiffness of this component increased with increasing muscle tension.
The distribution of dopamine in the brain of a tortoise, Geochelone chilensis (Gray)
Authors: Juorio A. V. 
Published: December 2014

1. Dopamine was found in the tortoise brain; the highest concentration (3·7 μg/g) occurred in a region of the telencephalon containing the nucleus basalis and cortex olfactoria. This region may be considered similar to the mammalian and avian corpus striatum with respect to dopamine.2. The administration of reserpine or prenylamine substantially decreased the concentration of dopamine in the tortoise brain. This effect appeared later and lasted longer than in birds or mammals. When these drugs were given in doses which nearly depleted brain dopamine the characteristic signs observed in birds or mammals were not present.
The steps between depolarization and the increase in the respiration of frog skeletal muscle
Authors: van der Kloot William 
Published: December 2014

1. For many years it has been known that when muscles are depolarized by raising [K+]out there is an increase in respiration, even at levels of depolarization below the threshold for a detectable contracture.2. K+‐stimulated respiration occurs in muscles in which protein synthesis is blocked with puromycin. Stimulation does not depend upon activation of phosphorylase kinase. In muscle poisoned with IIA and kept in N2, depolarizations below the threshold for contracture cause a fall in creatine phosphate. Apparently an ATPase is activated by depolarization; the resulting ADP is probably the trigger for the increase in oxygen uptake.3. When the T‐tubules are destroyed by the glycerol‐osmotic shock method depolarization does not produce an increase in respiration.4. Caffeine is known to stimulate respiration at concentrations below the threshold for producing a contracture. Muscles that have been made refractory to stimulation by potassium are still stimulated by caffeine: the action of caffeine is not antagonized by an increase in extracellular Mg2+. Caffeine must act on a later step in excitation—contraction coupling.5. K+‐stimulated respiration ultimately depends on the presence of Ca2+ in the Ringer. However, the Ca2+ can be replaced by Ni2+. It is known that Ni2+ does not activate actomyosin. Ni2+ is not sequestered by isolated fragments of the sarcoplasmic reticulum. It seems that the Ni2+ or Ca2+ in the extracellular solution is required for a superficial step in excitation—contraction coupling.6. Respiration is also often stimulated when muscles are placed in an isotonic sucrose solution, even though the fibres are hyperpolarized. A trace amount of Ca2+ in the sucrose solution is probably necessary for the response.7. An interaction between Ca2+ and a superficial membrane receptor appears to be an essential, early step in excitation—contraction coupling.
Distribution of granular vesicles in normal and constricted sympathetic neurones
Authors: Geffen L. B. , Ostberg Anna 
Published: December 2014

1. A quantitative analysis has been made of the characteristics of granular vesicles in different parts of normal and ligated post‐ganglionic sympathetic neurones supplying the cat spleen. The least diameter of the vesicle membrane and its electron‐dense core was measured from electron micrographs with an automated particle size analyser.2. Vesicles of average diameter 443 Å, with and without electron‐dense cores (192 Å), were concentrated in the axon terminals of the spleen, whereas in the cell bodies in the coeliac ganglion and their axons there were only a few large vesicles (787 Å) with large granules (562 Å).3. Ligation of the splenic nerves for 24 hr resulted in an accumulation proximal to the constriction of granular vesicles significantly larger (688 Å) and more completely granulated (478 Å) than those in the terminals.4. Reserpine reduced the number of vesicles with granular cores without discrimination between the two populations.5. Since the distribution of noradrenaline in sympathetic neurones can be correlated with the presence of large as well as small granular vesicles, it is suggested that the larger, more granular type found mainly proximally in the neurone is in transit from its perikaryal site of synthesis to the axon terminals, where it is transformed into the smaller synaptic vesicles.
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.