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Biomedical subjects

W A Hemmings

Publications and source records attributed to W A Hemmings.

At least 19 recordsLinked to original sources
PubMed1980

Distributed digestion.

It is proposed the classical theory of digestion, that all dietary protein is broken down to amino acid before absorption, be abandoned as disproved. Evidence reviewed elsewhere has shown that a large part of the intake is in the form of high molecular mass protein which passes through the bloodstream rapidly and is taken up by the tissues throughout the body, there to be finally broken down by way of smaller polypeptide intermediates which may have important pharmacological roles as agents in cell function.

Absorption↗
PubMed1978

Intestinal uptake and transport of proteins in the adult rat.

The transport of immunoglobulin and ferritin across the intestinal mucosa of adult rats provides an excellent model for transcellular protein transport study. Intestinal uptake and transcellular transport have been extensively studied in the neonatal rat, but not to such an extent in the adult rat. The transport of 125I labelled bovine immunoglobulin G and ferritin was studied in 100 days old rats using intestinally administered proteins. Antigen was estimated in the tissues by reacting extracts against specific immune antiserum prepared in rats, and visualization studies were carried out by fluorescence microscopy and direct deposition autoradiography at electron microscopic level. From these studies, it can be seen that these proteins are taken up by the intestinal cells and transported, antigenically intact, across the barriers to the body organs.

Animals↗
PubMed1978

Food allergy.

Explore the source record for details and available documents.

Dietary Proteins↗
PubMed1978

Transport of large breakdown products of dietary protein through the gut wall.

Ferritin or tritium labelled immunoglobulin G may, by electron microscopy, be demonstrated entering, within, and leaving the epithelial cells. Quantitative studies using various proteins labelled with radioiodine show that large amounts of protein bound radioactivity may be demonstrated in the tissues after feeding the labelled protein to adult rats by stomach tube. The molecular size of this material as determined by sugar gradient ultracentrifugation of tissue extracts ranges when IgG is fed from 50,000-20,000 Daltons. The material retains its ability to react as antigen with antisera specific to the original molecule: precipitation reactions may be obtained in gels and quantitative studies show that cnosiderable amounts of the protein-bound radioactivity are still specifically precipitable. Such studies have been carried out with alpha-gliadin as well as bovine IgG. At 100 days old rats may absorb as much as 40% of a dose of bovine IgG in the form of these large molecular breakdown products.

Animals↗
PubMed1976

The use of direct deposition electron microscope autoradiography in studies of protein transport.

The use of direct deposition autoradiography in studies of the localization of proteins labelled with radio-iodine or tritium in the epithelia of fetal, suckling, and adult animals is described. Using a single marker in the first place, rabbit IgG and bovine IgG have been seen both in the vacuolar apparatus and also free in the cytoplasm of endodermal cells of the rabbit yolk-sac splanchnopleur. This has been confirmed in those cells using a combination of bovine IgG marked with tritium and rabbit IgG marked with 125I, presented simultaneously to the cells. Both proteins are present, apparently equally, attached to the brush border and distributed through the cytoplasm, as well as within vacuoles. Selection does not take place before or during entry to the cell, as has been suggested by quantitative results which have been reported elsewhere. It is hoped that the use of two markers together will permit localization of the selective process. In the adult rat gut, both isotopes have been demonstrated entering and within and leaving the ileal cell, confirming quantitative results reported elsewhere.

Animals↗
PubMed1975

Transport across the rabbit foetal yolk-sac of fractions of IgG from several mammalian species.

Electrophoretically migrating fast and slow IgG fractions of rabbit, mouse, human, guinea-pig, dog, horse and cow sera were prepared by DEAE-cellulose chromatography, labelled with either 131I or 125I, and tested in passage across yolk-sac splanchnopleur of rabbits. In foetal sera, slow IgG generally reached higher concentrations than fast IgG, but even with mouse Ig, which has a high ratio between the two fractions, the difference was only four-fold. This differential between fast and slow IgG was not sufficient to explain the absorptive selectivity between IgG of different species. The capacity of isotopically labelled rabbit and equine IgG to be transported across the rabbit foetal yolk sac was also studied using fractions prepared by isoelectric focusing. Marked differences in concentration quotient (CQ) values (CQ equals (concentration in foetal serum)/(concentration in injected material)) between individual pI peaks for these species were found.

Animals↗