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Biomedical subjects

R Abraham

Publications and source records attributed to R Abraham.

At least 127 records · Page 7Linked to original sources
PubMed1981

Differential fluorescent staining of porcine heterochromatin by chromomycin A3/distamycin A/DAPI and D 287/170.

R banding of porcine chromosomes by chromomycin A3 plus distamycin A and DAPI (DA-DAPI) revealed two distinct types of heterochromatin: The GC-rich centromeric heterochromatin of the biarmed autosomes (Nos. 1-12) and of the X chromosome exhibited bright chromomycin A3 fluorescence, while the heterochromatin of the acrocentric chromosomes (Nos. 13-18) stained brightly by DA-DAPI. The latter also fluoresced brightly when stained by D 287/170. In addition, significant fluorescent polymorphism was observed among both acrocentric and metacentric chromosomes.

Animals↗
PubMed1979

Effect of hydrophobic detergent on lipid absorption in the rat and on lipid and sterol balance in the swine.

The effects of hydrophobic detergent on fat absorption in the rat were determined under two conditions. In the first, a high dose of detergent was given in a test lipid meal to rats not previously exposed to this agent. A marked delay in digestion of triglyceride in association with malabsorption was observed. In the second, a relatively small dose of detergent was given to rats pretreated with dietary supplement of detergent. No delay of digestion or uptake was observed but absorbed, reesterified lipid was noted to accumulate in the mucosa. Morphologic studies showed abnormal collections of fat droplets in the enterocytes. Sterol and fat balance studies were done on swine on chronic dietary detergent supplement. Mild steatorrhea with excess fecal excretion of neutral sterols was observed. It is concluded that hydrophobic detergents can have an inhibitory effect on both intraluminal and intracellular events of fat absorption.

Animals↗
PubMed1978

Lysosomal enzymes in macrophages of colonic tumors induced in rats by 1,2-dimethylhydrazine dihydrochloride.

Ten weekly doses of dimethylhydrazine (30 mg/kg) were given to rats to induce colonic tumors. Histochemical and electron cytochemical studies revealed a distinct pattern of lysosomal acid phosphatase and beta-glucuronidase activity in macrophages in the stroma of these neoplasms. A dramatic increase in the number of acid phosphatase-rich macrophages was present in adenomas when compared to that in normal colonic mucosa. Fewer numbers of these cells were seen in well-differentiated adenocarcinomas, and they were barely detectable in highly invasive mucinous adenocarcinomas. It is postulated that these macrophages may play a role in preventing the invasion of adenomatous neoplasms into the submucosa. Application of histochemical techniques to study macrophage lysosomal enzymes may prove a useful diagnostic tool in differentiation of human colonic tumors for prognostic evaluation.

Acid Phosphatase↗
PubMed1977

Species differences in the hepatic response to mirex: ultrastructural and histochemical studies.

Mirex was fed at levels of 1, 5, 15, and 30 ppm to mice, 5 and 30 ppm to rats, while monkeys received the chemical by stomach tube at levels of 0.25 and 1 mg/kg (equal to 5 and 20 ppm). Mice were killed and their livers obtained at 2, 4, 6, 9, 10, 15 and 18 months, whereas rats were killed and surgical biopsies were taken at 16, 19, 26, and 36 months. Cytochemical techniques were employed to detect activities of lysosomal beta-glycerol phosphatase (ACpase) and glucose 6-phosphatase (G-6-pase). ACpase and G-6-pase remained unchanged and comparable to controls in livers of mice receiving 1 ppm. G-6-pase decreased in centrilobular areas while ACpase increased with time in the higher groups. At 12 months, liver cells that lost their G-6-pase activity surrounded by Kupffer cells that contained strong ACpase. In contrast, rat livers had no increase in ACpase and little loss in G-6-pase. Surprisingly, and in spite of the high levels of mirex ingested, monkey livers showed no loss of G-6-pase or activation of ACpase. Ultrastructurally, the underlying feature in all livers was proliferation of smooth endoplasmic reticulum (SER) displaying species variation. Thus, in mice, intense proliferation of SER that was both time- and dose-dependent was localized in specific regions of the cytosol. Hepatic cells, damaged and necrotic in mice fed 5, 15, and 30 ppm, were phagocytosed by activated Kupffer cells. SER proliferation in rat and monkey liver cells was less conspicuous than in mice. Except for this change, rat and monkey liver cells were normal. There studies emphasize species and enzyme variations in response to mirex. An interesting aspect observed was the lack of lysosomal catabolism during liver enlargement.

Acid Phosphatase↗
PubMed1976

A receptor for antibody on B lymphocytes. III. Relationship to immunoglobulin and ia determinants.

The physicochemical structure of the receptor for antibody (FcR) on B cells and its interrelationship with Ig and H-2 gene complex associated antigens were examined. FcR were found to be sensitive to treatment with phospholipase C and pronase, but resistant to neuraminidase, phospholipase A and chymotrypsin. They would therefore appear to be composed of phospholipoproteins. Several lines of evidence indicated that FcR and Ig receptors were discrete entities: thus, FcR (1) were resistant to chymotrypsin; (2) capped independently of Ig, as demonstrated by means of Fab fragments of anti-Ig, and (3) were closely associated with at least some Ia determinants, which are known to be distinct from Ig determinants. The relationship between FcR and H-2 gene complex associated antigens was confirmed by demonstrating inhibition of binding of aggregates by anti-Ia serum and vice versa. If, however, FcR were capped, anti-Ia serum applied under non-capping conditions was still found to bind diffusely to the great majority of B cells. Although this could be explained in part by the presence of residual FcR, some Ia determinants appeared to be distinct from FcR. The finding of residual FcR after capping with aggregates or immune complexes implied that FcR are a more integral part of the cell membrane than Ig receptors and could therefore act as proreceptors for the latter. Consistent with this was the demonstration of a significant polar distribution of Ig on B cells capped for FcR and then labelled under non-capping conditions with anti-Ig.

Animals↗
PubMed1975

Relationship between Fc receptors, antigen-binding sites on T and B cells, and H-2 complex-associated determinants.

The relationship between H-2 complex-associated determinants, Fc receptors, and specific antigen-recognition sites on T and B cells was examined by binding and functional assays. The Fc receptor was detected by radiolabeled immune complexes or aggregated human IgG. Both these reagents selectively bound to B cells, not to T cells. When spleen cells, from mice primed to several antigens, were exposed to highly substituted radioactive aggregates, their capacity to transfer both a direct and indirect plaque-forming cell response to these antigens was abrogated. Addition of B cells, but not of T cells, restored responsiveness. Complexed Ig binding to Fc receptors was prevented by pretreatment of mixed lymphoid cell populations with antisera directed against membrane components on the same cell (e.g., H-2) and on other cells (e.g., theta). The lack of specificity of inhibition was thought to be due to the formation on cell surfaces of antigen-antibody complexes which would then attach to the Fc receptor during the incubation precedure. Specific blockade of the Fc receptor during the incubation procedure. Specific blockade of the Fc receptor however occurred when B cells were pretreated with the Fab fragments of anti-H-2 antibody. This was demonstrated autoradiographically and by inhibition of aggregate-induced suicide. The blocking activity of ante-H-2 Fab was removed by absorption with spleen cells from thymectomized irradiated mice but not with thymus cells of appropriate specificity. This suggested that the antibodies involved had specificity for determinants on the B-cell membrane distinct from those coded by the K or D end of the H-2 complex, and either absent from, or poorly represented on, thymus cells. Specific antigen-induced suicide of B cells was achieved simply by incubating the cells with radioactive antigen in the cold. T-cell suicide on the other hand required that the 125I-labeled antigen be presented to the T cells at 37 degrees-C on the surface of spleen cells from antigen-primed mice. Pretreatment of T cells with the Fab fragment of anti-H-2 antibody protected them from the suicide effect. By contrast no such protection of B cells could be achieved by this procedure. In other words H-2 (? Ir)-associated determinants may not only be in close proximity to the antigen-binding site on T cells but, in addition, may be involved in the effective operation of the receptor.

Animals↗