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Biomedical subjects

J W Robinson

Publications and source records attributed to J W Robinson.

At least 91 records · Page 5Linked to original sources
PubMed1978

The relationship between the functional and structural alterations in the rat small intestine following proximal resection of varying extents.

The functional and structural characteristics of the ileal remnant of rat intestine were examined four weeks after 45%, 70% or 95% proximal resection. The increase in villus height in the ileal remnant had alfread reached its maximum after a resection of 45%, whereas a further increment in the length of the crypts occurred after 70% resection. There was an increase in the number of enterocytes per unit length of villus and a rise in the DNA content per unit weight of mucosal scrapings, which testifies to the development of mucosal hyperplasia in this situation. The specific activities of sucrase, measured biochemically, and of nonspecific esterase, determined histochemically, were reduced in proportion to the extent of the resection. Similarly, the uptakes of L-phenylalanine and of beta-methyl-D-glucoside by intestinal rings in vitro were progressively diminished in the ileal remnant. There was an increase in the rate of disappearance of glucose from a perfused loop in vivo, when expressed in terms of unit intestinal length. Galactose absorption remained unchanged, but when expressed in terms of unit dry tissue, was significantly reduced, in agreement with the diminished transport of both amino-acids and monosaccharides in vitro.

Animals↗
PubMed1978

Bullous pemphigoid in children.

Bullous pemphigoid in children appears to be the same disease as its adult counterpart based on a case in a 3-year-old boy. Generalized tense bullae over the skin and oral mucosa, characteristic direct and indirect immunofluorescence, elevated IgE levels, blood eosinophilla, and therapeutic response to corticosteroids parallel the disease in adults. The long-term prognosis, however, is still unknown. A review of bullous pemphigoid in children is presented.

Child↗
PubMed1978

Binding of platinum to human transferrin.

A complex of platinum and human transferrin has been formed by appropriately combining apotransferrin (metal free protein) and potassiumchloroplatinate (K2PtCl4). Atomic absorption spectroscopy indicated that both primary bind sites on the protein participated in the complex. Electron paramagnetic resonance (EPR) examination showed that the bound platinum was not paramagnetic, and thus it is highly probable that the Pt ion is in the +2 oxidation state. The results suggest a possible mechanism for physiological distribution of third-transition-series metals.

Chemical Phenomena↗
PubMed1978

Glucose transport by brush-border membrane vesicles after proximal resection or ileo-jejunal transposition in the rat.

1. The functional properties of the ileal mucosa following jejunal resection or interposition in the jejunum were studied with the help of membrane vesicles. 2. Despite the development of functional and morphological features in the mucosa which are more generally associated with the jejunum than with the ileum, examination of brush-border vesicles derived from ileal and jejunal enterocytes from resected or transposed intestines reveals that the functional characteristics of apical membranes isolated from the different regions of the intestine are maintained after these surgical manoeuvres. Vesicles from control ileum develop an 'overshoot' uptake of glucose that is 3-4 times smaller than that of jejunal vesicles, a difference that is still observed in membranes prepared from mucosa of ileal loops following proximal resection or interposition in the jejunum.

Animals↗
PubMed1978

Lack of effect of bile in pathogenesis of secretion in mechanical small bowel obstruction.

In dogs, the principal lesion in the ileal mucosa above a mechanical obstruction is the induction of a secretory state in which there is a net loss of water and electrolytes into the intestinal lumen. The role of stagnated bile as a possible agent provoking this secretion was explored by ligating the common bile duct and diverting the bile by means of an anastomosis between the gall bladder and the ileum distal to the obstruction. 7 days after creation of an obstruction with bile diversion, the functional and morphological changes in the obstructed loop were almost identical to those occurring in animals with obstructions without bile diversion. The secretory response above the obstruction continued unabated, with levels of cAMP in the secreting mucosae lower than in control tissues. These results suggest: (a) that the secretion in the obstructed intestine is not influenced by the presence of bile, and (b) that this secretion may not be secondary to an increase in mucosal cAMP levels.

Animals↗
PubMed1978

Functional and structural characteristics of the rat intestinal mucosa following ileo-jejunal transposition.

The transformation of the rat ileal mucosa following interposition into the jejunum has been examined with respect to its functional and structural characteristics. Morphometric studies show that there is an increase in the size of the villi and crypts in the same proportions, such that the structures become longer than those of normal jejunal mucosa. There is no change in villus width or epithelial cell height and no evidence of mucosal damage. In agreement with these observations, there is an increase in the amount of DNA per unit weight mucosa in the transposed ileum. L-phenylalanine accumulation in vitro by transposed loops is reduced to the level of the control jejunum, whereas beta-methyl-D-glucose uptake is unchanged. Biochemical and histochemical determinations of various enzyme activities reveal that the levels in the transposed mucosa are much lower than in the controls. The results show that although certain features of the transposed ileum resemble those of the normal jejunum, this does not apply to all characteristics. It is argued that the ileal mucosa retains its normal functional properties, but undergoes hyperplastic changes, possibly as a result of contact with chyme that is richer in nutritive material, resulting in the establishment of a more immature cell population with a global reduction in enzyme levels and transport capacities.

Animals↗
PubMed1978

[Role of the bile in lesions of the intestinal mucosa above a mechanical occlusion].

In dogs, the principal lesion in the ileal mucosa above a mechanical obstruction is the induction of a secretory state in which there is a net loss of water and electrolytes into the intestinal lumen. The role of stagnated bile as a possible agent provoking this secretion was explored by ligating the common bile duct and diverting the bile by means of an anastomosis between the gall bladder and the ileum distal to the obstruction. Seven days after creation of an obstruction with bile derivation, the functional and morphological changes in the obstructed loop were almost identical to those occurring in animals with obstructions without bile diversion. The secretory response above the obstruction continued unabated. These results suggest that the secretion in the obstructed intestine is not influeced by the presence of bile.

Animals↗
PubMed1978

Kinetics of the co-transport of phenylalanine and sodium ions in the guinea-pig small intestine. 1. Phenylalanine fluxes.

The kinetics of phenylalanine influx into guinea-pig small intestinal rings at different external sodium-ion concentrations have been examined. A change in the sodium concentration alters the value of Kt for phenylalanine influx without affecting the Jmax for the process. By studying the relationship between the value of Kt and the sodium-ion concentration, the applicability of various models to the overall process of sodium-coupled phenylalanine influx has been considered. The results are most consistent with a general non-compulsory model for the formation of a ternary complex between carrier, phenylalanine molecule and a sodium ion, which can be formed from either binary complex, i.e., either species can combine first to the carrier. The consistency of the model was tested by determining phenylalanine influx as a function of the sodium-ion concentraion at different amino-acid concentrations, and a good fit was obtained with the predictions of the non-compulsory model.

Animals↗
PubMed1978

Kinetics of the co-transport of phenylalanine and sodium ions in the guinea-pig small intestine. II. Sodium fluxes and flux ratios.

The validity of a general non-compulsory model for the description of the co-transport of sodium and phenylalanine in the small intestinal mucosa of the guinea-pig has been examined by measuring the influx of sodium and the flux ratios. The simultaneous influxes of sodium and phenylalanine have been determined by incubating intestinal tissues at a fixed sodium and variable phenylalanine concentrations. The experiment was repeated at a number of sodium concentrations, and a straight-line relationship between the fluxes was always obtained. The slope of this line, the flux ratio, is dependent on the sodium concentration; the function is biphasic inasmuch as it rises with sodium concentration at low external sodium, but decreases when the sodium concentration is raised above a level of about 70 mM. This response is compatible with the model under examination. No saturable component of sodium influx could be detected in the absence of phenylalanine, but the values of this influx corresponded with those predicted from the flux ratio experiment. In the presence of phenylalanine, sodium influx could be resolved into saturable and non-saturable components, and the Kt for sodium influx via the saturable mechanism agreed with that predicted from the constants derived from measurements of phenylalanine influx. The maximal velocity for sodium influx was similar to the maximal velocity for phenylalaline influx. Equations were derived to examine the behaviour of sodium influx as a function of the external phenylalanine concentration, and a Kt for phenylalanine was deduced which agrees closely with that obtained by studying phenylalanine fluxes directly. These results provide evidence in favour the applicability, in this species, of a model involving no compulsory pathway for the formation of a ternary complex between the carrier, a sodium ion and the phenylalanine molecule. Examination of the literature suggests that in other species different models may describe more accurately this co-transport mechanism.

Animals↗
PubMed1978

Kinetics of the co-transport of sodium and phenylalanine in the guinea-pig samll intestine. III - Influence of harmaline on sodium and phenylalanine fluxes.

The effect of harmaline on sodium and phenylalanine influxes in guinea-pig small intestine has been examined kinetically. Harmaline behaves as a fully competitive inhibitor of the saturable component of sodium influx; this property has been revealed from experiments in which the sodium concentration was varied and the harmaline concentration maintained constant, and from a second series in which sodium was constant and harmaline levels were altered. A Ki-value for harmaline of 1.61 mM was deduced from these experiments. The effect of harmaline on phenylalanine influx is more complex, since only that component of entry which occurs in the form of the ternary complex is sensitive to the drug. Within the framework of a non-compulsory model for co-transport which appears to describe phenylalanine influx in this tissue, equations were derived to calculate the different components of influx under given experimental conditions. tJøala, the influx to phenylalanine in the form of the ternary complex, was found to be a Michaelis-Menten function of the sodium concentration. Assuming that the component in the form of the binary complex is unchanged by harmaline, that occurring in the ternary form in the presence of the drug can be evaluated by subtraction. This fraction is also a Michaelis-Menten function of the sodium concentration; the inhibition by harmaline is released on raising the sodium concentration. From these expressions, a Ki for harmaline under these conditions of 1.66 mM was derived. These observations support the proposal that harmaline interferes with the interaction of sodium with its specific sites on the carrier in the intestinal brush-border membrane.

Alkaloids↗
PubMed1977

The reversibility of the inhibition of intestinal amino-acid transport by harmaline.

The inhibitory aciton of harmaline on L-phenylalanine uptake by guinea-pig intestinal rings is fully reversible provided only low concentrations of the inhibitor are used; if the concentration is raised to a sufficient extent to enable the drug to interfere with sodium pumping or cellular metabolic reactions, as witnessed by its effect on tissue oxygen consumption, then the inhibition of L-phenylalanine uptake is only reversible if short contact times are employed.

Alkaloids↗