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Biomedical subjects

A Whyte

Publications and source records attributed to A Whyte.

At least 91 records · Page 5Linked to original sources
PubMed1985

Human syncytiotrophoblast membrane proteins defined using a heterologous antiserum.

Detergent extracts of human trophoblast plasma membranes (TrPM) and of other fetal tissues from the same conceptus were prepared and the proteins separated by use of isoelectric focusing. A major band of isoelectric point (pI) 4.1 was present in TrPM together with minor bands of (pI) 4.9, 5.9, 7.3, 7.8 and 7.9. These bands were absent from non-trophoblastic fetal tissues. The pI 4.1 protein reacted with an 125I-labelled IgG fraction of a heterologous antiserum raised against TrPM and was found to have an apparent molecular weight of 100,000. This protein did not appear to be placental alkaline phosphatase, SP1, transferrin or human chorionic gonadotrophin. Many neoplastic cell lines tested also revealed a major protein band of pI 4.1 but it has not been established that this was the same protein as found in the TrPM preparations.

Antigens, Surface↗
PubMed1984

A monoclonal antibody to an antigen present on the microvillous membrane of the trophectoderm of the preimplantation blastocyst of the pig.

Immunization of BALB/c mice with 14-day pig preimplantation blastocyst material followed by fusion of spleen cells with NS-0 myeloma cells resulted in a clone, SN 1/38, which secreted IgG1 which reacted specifically with the microvillous border of the pig trophectoderm and trophoblast as assessed by immunohistology. SN 1/38 did not react with other fetal tissues, or with blastocysts from other animal species. It was shown by absorption studies and by enzyme-linked immunoabsorbent assay that SN 1/38 was not directed against the placental form of pig alkaline phosphatase. The location of this antigen and its apparent presence throughout gestation indicate a functional role in the materno-fetal interaction.

Animals↗
PubMed1981

Propidium iodide as a nuclear marker in immunofluorescence. I. Use with tissue and cytoskeleton studies.

Some examples are given of immunofluorescence with tissue sections and microtubular cytoskeletons of cultured cells where the fluorescent dye propidium iodide (PI) has been used as marker of nuclei. The emission wave length of IP is longer than that of fluorescein, making it possible to use several different and commonly available filter combinations. The use of nuclei as positional indicators is often a more suitable method than phase microscopy combined with immunofluorescence because of low background illumination against which morphology is viewed, circumventing the need for often expensive phase optics.

Antibodies↗
PubMed1980

Differential expression of trophoblast-specific membrane antigens by normal and abnormal human placentae and by neoplasms of trophoblastic and non-trophoblastic origin.

Using a specific antiserum to human syncytial trophoblast plasma membrane (TrPM), we have investigated the expression of these antigens on a variety of trophoblastic and non-trophoblastic tissues by a standard peroxidase/anti-peroxidase staining method. Normal placenta (first-trimester as well as full-term), placenta from tubal pregnancy and placenta accreta were all found to express TrPM antigens. However, malignant change in trophoblast neoplasms appeared to by accompanied by a loss of these antigens, with 7 out of 10 specimens of hydatidiform mole staining positively while 3 specimens of invasive mole and 7 specimens of choriocarcinoma were all negative. In contrast, a number of malignant tumours of non-trophoblastic origin such as carcinomas of the colon, cervix, bladder and hepatomas were found to express TrPM antigens. The possible significance of the reversal to a trophoblast phenotype by malignant neoplasms of non-trophoblastic origin is discussed.

Antigens, Neoplasm↗
PubMed1980

Lectin binding by microvillous membranes and coated-pit regions of human syncytial trophoblast.

The distribution of saccharides on the microvillous membrane of the human syncytial trophoblast was investigated using ferritin conjugates of four lectins: concanavalin A (specific for alpha-D-manno- and alpha-D-glucopyranosyl residues), wheatgerm agglutinin (specific for N-acetylglucosamine), Limulus polyphemus lectin (specific for N-acetylneuraminic acid), and Lotus tetragonolobus lectin (specific for alpha-L-fucose). Concanavalin A and wheatgerm agglutinin (WGA) reacted strongly with the surface membrane and ferritin deposits were also observed in coated pit regions of the membrane. Lectins from L. polyphemus and L. tetragonolobus, however, reacted only weakly with the microvillous border and neither reacted with coated pits. Enhanced agglutinability of trophoblast cells in comparison with other foetal cells from the same conceptus was seen with WGA. This agglutination was inhibited by addition of acetylglucosamine or by a solubilized membrane fraction which was bound by a column of WGA-Sepharose. The membrane fraction which did not bind to the column did not inhibit agglutination. Electrophoresis of the WGA-bound membrane proteins revealed six subunits, the major band having an apparent mol. wt. of 55 000. A protein of this mol. wt was also seen in coated vesicles isolated from equivalent human placentae.

Agglutination↗
PubMed1980

Immunoferritin localisation of antigens of the microvillous membrane of human trophoblast.

Antiserum raised to purified plasma membranes of the human trophoblast (TrPM) was used in an indirect immunoferritin method to investigate the expression of specific membrane antigens in explants of human trophoblast and in cultured cells. Ferritin deposits occurred in discrete regions on the microvillous membrane of the syncytiotrophoblast, and these deposits also occurred in coated areas of the membrane. Discrete staining was also seen in cultured trophoblast cells and HeLa cells. Human amnion cells had a strong positive reaction for the TrPM antigens, but foetal skin cells and HEp-2 (larynx carcinoma) cells were negative. TrPM antigens appear to be highly specific for trophoblast and amnion, only being found otherwise as a result of placental genomic re-expression in neoplasia.

Antigens, Surface↗
PubMed1979

Antigens of the human trophoblast plasma membrane.

Using purified plasma membranes of human syncytial trophoblast as immunogen, we have raised heterologous antisera which reacted by indirect immunohistological methods with the surface of the trophoblast. This antigenic activity appears to be absent from other adult and foetal tissues. Its absence from maternal sera and its resistance to mild detergents treatment suggest that it is intimately associated with the surface membrane of the syncytial trophoblast. This antigen was found to be immunologically different to a number of proteins, including those known to be produced by the trophoblast. The identification of this antigen may indicate a potential line of research for the immunological regulation of human fertility.

Adult↗
PubMed1978

Increased sialylation of surface glycopeptides of human trophoblast compared with fetal cells from the same conceptus.

The surface glycopeptides of human trophoblastic cells have been compared with those of fetal cells from the same embryos using double-labeling methods with isotopes of L-fucose and D-glucosamine. A faster eluting, neuraminidase-sensitive, fraction was observed on Sephadex chromatography of the trophoblast spectra when D-glucosamine was used as precursor. Labeling with fucose did not appear to result in any differences, thus suggesting that the glycopeptides characertistic of trophoblast contained glucosamine-derived metabolic products, including sialic acid, but excluding fucose. This increased sialylation is similar to, but not identical with, modifications observed in neoplastic cells, and on this basis it is postulated that two species of glycopeptides may be involved in atypical cellular behavior. The first contains sialic acid and other sugars excluding fucose, and is associated with localized cellular growth and invasion. The second contains both sialic acid and fucose and is characteristic of neoplastic cells.

Fetus↗
PubMed1978

Saccharide distribution in human trophoblast demonstrated using fluorescein-labelled lectins.

The reaction of six Flourescein-conjugated lectins with human trophoblast and foetal limb are described. The trophoblast had marked membrane fluorescence after treatment with wheatgerm and Lotus tetragonolobus lectins. Concanavalin A reacted strongly with the trophoblastic cytoplasm but did not react with the nuclei. Most of the lectins had only weak reactions with foetal tissue, apart from the cartilage matrix which fluoresced strongly after treatment with several of the lectins. In addition, concanavalin A reacted with amylase-labile material, probably glycogen, in the skin epidermis and chondrocyte cytoplasm. Various substances were tested in order to determine the nature of the wheatgerm lectin receptor of trophoblast. Several secretory and binding proteins were found not to be responsible, and the identity of the receptor remains unknown.

Carbohydrate Metabolism↗
PubMed1978

Saccharide alterations in rat kidney associated with malignant transformation by injection of dimethylnitrosamine.

Renal tumours were induced in dietary-primed rats by injection of dimethylnitrosamine. Control and tumour tissue was excised at varying periods and maintained in short-term organ culture in the presence of 3H- or 14C-fucose. The plasma membranes were then isolated, and the isotopic profiles of normal kidney and renal tumour membrane proteins were established, using polyacrylamide-gel electrophoresis in dodecyl sulphate. Several fucose-containing glycoproteins of the plasma membranes were found to alter upon neoplastic transformation: 4 increased and 3 decreased. The probable identity of 2 of these proteins is indicated: alpha-foetoprotein is one of the glycoproteins which increased, whereas neutral endopeptidase decreased in the tumour membranes. Fluorescein-labelled lectin binding by the kidney tissue was also found to alter upon transformation. The most marked changes were an increase in sialic acid (neuraminidase-sensitive) and galactosamine (Ricinus communis agglutinin Type I) in the nuclei of some neoplastic cells and some hyperplastic-tubule cells.

Animals↗
PubMed1977

Variation in the volume of coated vesicles isoalted from human placenta.

Electron microscopic analysis of 500 negatively stained coated vesicles isolated from human placenta showed that they exist within limits in a continuous range of volumes with an unimodal distribution. Some vesicles were larger than the frequently quoted maximum size of these organelles (diameter 100nm). The ratio of hexagonal to pentagonal facets in the clathrin lattice of the vesicle wall appears to be variable. This feature may be important in morphogenesis since the mean volume of prolate vesicles is larger than that of spherical vesicles. Empty lattices had a mean volume smaller than that of lattices containing phospholipid bilayers.

Female↗
PubMed1977

Differeniated regions of human placental cell surface associated with exchange of materials between maternal and foetal blood: coated vesicles.

Coated vesicles may be an important component of the micropinocytic system of the human placenta. Regions of very dense reaction with glycocalyx stains are restricted to membranes within forming and fully formed coated vesicles. This is interpreted as evidence against permanently grouped specific binding sites having a role in the selective uptake of materials by micropinocytosis, and as support for theories of coated-vesicle formation which take into account the dynamic nature of membrane components. The pyroantimonate precipitation technique which was employed in an attempt to localize cations in placental tissue at term resulted in the deposition of electron-dense material in coated vesicles and basement membrane. Examination of the distribution of coated vesicles in placental tissue explants at 8--12 weeks of gestation revealed a restricted distribution of these organelles. Probably more than 89% of coated vesicles lie within the largest vesicles' diameter from the cell surface. Placental coated vesicles were isolated and examined using negative staining. A polygonally patterened structure was apparent on their surfaces. Analysis of the isolated fraction of coated vesicles using sodium dodecyl sulphate polyacrylamide gel electrophoresis shows the presence of a major protein of molecular weight 180000. This is the same molecular weight that has been given for clathrin, the major protein of the raised polygonally patterned structure on the cytoplasmic surface of coated vesicles from other sources.

Cell Fractionation↗