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Biomedical subjects

R Montgomery

Publications and source records attributed to R Montgomery.

At least 73 records · Page 4Linked to original sources
PubMed1980

Effects of cesalin on the ultrastructure and biological properties of cultured mammalian cells.

Cesalin rapidly inhibits the incorporation of uridine and thymidine into KB, MCF-7, HBL-100, and HTC cells but has no measurable effect on AlAb cells. Protein syntheiss is inhibited only after the effect on DNA and RNA is observed. After 12 to 48 hr, the cells in cultures containing cesalin increasingly lose adhesion to the flask surface and float in the medium. Both the inhibition of nucleotide incorporation and the inhibition of the cell growth, used as assays for cytotoxicity, show a varying sensitivity of these cell lines to cesalin, with AlAb cells being the most resistant and KB cells being the most sensitive. The ultrastructural changes induced by cesalin in KB cells demonstrate alteration in the nucleolus, increase in rough endoplasmic reticulum, extensive blebbing of the plasma membrane, and invagination of the nuclear membrane. The blebbing of the plasma membrane decreases after 24 hr with the appearance of a highly disorganized nuclear structure and numerous vacuoles containing insoluble fragments.

Cell Line↗
PubMed1979

Biological effects of cesalin, an anti-tumor protein, on cultured mammalian cells.

The effects of the protein cesalin were studied to determine the site of its toxic action in KB cells for which the ID50 is 0.9 pg/ml. Several effects have been noted: (i) respiration in KB cells was reduced by greater than 50% within 1 h after cesalin addition, which could not be explained on the basis of mitochondrial damage or from elevated intracellular ATP levels, since these did not rise significantly until about 3 h after cesalin addition; (ii) both DNA and RNA synthesis were inhibited, starting about 3 h after addition of cesalin to KB cells, but the transport of nucleosides and amino acids does not appear to be affected; (iii) no decrease is observed in protein synthesis for at least 5 to 6 h; (iv) cesalin can inhibit DNA synthesis and mitotic division independently of one another. The interaction of cesalin with the cell surface is rapid and after 5 min at 37 degrees C less than 10% of treated cells can be rescued by addition of excess antiserum to cesalin. The cell surface receptors are exposed throughout the cell cycle and the toxicity of cesalin is not restricted to a particular phase of this cycle.

Amino Acids↗
PubMed1979

Effects of macromomycin on the ultrastructure and biological properties of cultured mammalian cells.

Macromomycin is shown to inhibit the biosynthesis of RNA, DNA, and protein in cultured cells of KB, HBL-100, SW-613, MCF-7, and A1Ab. There was no substantial increase in cell numbers in cultures containing macromomycin (5 microgram/ml), but after 24 to 48 hr the cells were two to three times the diameter of control cells with concomitant increase in cell protein. The ultrastructural changes induced by macromomycin in KB cells demonstrate an increase in nuclear size without similar changes in the size of other cytoplasmic subcellular units. It was of interest to note the general proliferation of cellular organelles and the increased occurrence of annulate lamellae followed, after prolonged treatment, by the appearance of larger numbers of lipid droplets and lysosomes; vacuoles developed to a significant extent after the cells detached from the monolayer. A1Ab cells show ultrastructural changes similar to those of KB cells when treated with macromomycin.

Antibiotics, Antineoplastic↗
PubMed1979

Attitude changes following a sexual counseling program for spinal cord injured persons.

The attitudes of a sample of spinal cord injured outpatients toward a range of sexual behaviors were measured before and after participation in a counseling program. In comparison to the sexual attitudes of an untreated control group those of the sample group were found to be more permissive after than before the program. In addition, the counseling program, which operated in a workshop format over a period of 6 weeks, was favorably evaluated by participants on a number of criteria.

Adolescent↗
PubMed1978

Interaction of ovalbumin and its asparaginyl-carbohydrate fractions with concanavalin A.

The interaction of ovalbumin and its asparaginyl-carbohydrate fractions with concanavalin A was studied. Relative affinities were obtained by competitive binding studies using p-nitrophenyl alpha-D-mannopyranoside. Ovalbumin was separated into two fractions, I and II, by chromatography on concanavalin A-Sepharose. Ovalbumin and its fractions I and II interacted with concanavalin A in solution with binding affinities at 10 degrees C of 2 . 10(5) M-1, 3 . 10(4) M-1 and 2 . 10(6) M-1, respectively. The seven asparaginyl-carbohydrate fractions, obtained by fractionation on Dowex 50W-X2 (H+) and Durrum DA-4 (borate)columns, bound to concanavalin A with approximately the same affinity as native ovalbumin, suggesting that the sugar residues for binding in the isolated carbohydrates are exposed in the native protein. The binding of ovalbumin to concanavalin A was minimal after treatment with alpha-D-mannosidase in spite of the fact that only one half of the available mannose residues were hydrolyzed when compared to those removed by similar treatment of the asparaginyl-carbohydrate before fractionation. It is concluded that those alpha-D-mannosyl residues in ovalbumin that are required for binding to concanavalin A are accessible to alpha-D-mannosidase while the residual mannosyl groups are "buried" from interaction with concanavalin A and the enzyme.

Asparagine↗
PubMed1978

Studies on macromomycin, an antitumor protein.

Macromomycin is a protein isolated from the culture filtrate of Streptomyces macromomyceticus. It is an antibiotic and also cytotoxic to a broad spectrum of carcinoma cells, the ID50 for P388 leukemia cells being 1 X 10(-9) M. Macromomycin binds rapidly and tightly to the P388 cell membrane and the eventual death of the cell cannot be reversed by either washing the toxin away or treating the cell with trypsin. The cytotoxicity does not appear to be specific for any phase of the P388 cell cycle. Macromomycin is a single polypeptide, pI 5.38, devoid of methionine and arginine residues and contains 4 cysteine residues joined by two intramolecular disulfide bonds. The cytotoxicity results in inhibition of DNA, RNA, and protein synthesis in P388, the latter inhibition occurring a few hours after the inhibition of nucleic acid synthesis. The antibiotic and antitumor activities are destroyed rapidly by ultraviolet light, which gives a product that differs little in amino acid composition, molecular weight, and antigenic property, but can be separated from the native macromomycin by ion exchange chromatography. It is proposed that macromomycin has an ultraviolet-sensitive prosthetic group upon which much of the biological activity is based.

Amino Acids↗
PubMed1976

Alpha-D-Mannosidase. Preparation and properties of free and insolubilized enzyme.

Alpha-D-Mannosidase (alpha-D-mannoside mannohydrolase, EC 3.2.1.24) has been purified to homogeneity as demonstrated by polyacrylamide gel electrophoresis and ultracentrifugation. The molecular weight of the enzyme is approx. 200000; the protein appears to contain 4 subunits, with molecular weights of 66000 and 44000. The enzyme was immobilized on Sepharose and the properties of the coupled and free enzyme were compared. Both were stable up to 70 degrees C with rapid loss of activity between 75-80 degrees C; both retained 25-30% activity in 6 M urea and 65% of the original activity could be restored in the coupled preparation by removal of the urea. The pH maximum of each form was approximately the same, with the maximum of the immobilized enzyme shifted slightly to a lower pH. The coupled alpha-D-mannosidase presented in this report offers the possibility of digesting high molecular weight substrates, such as glycoproteins, with the advantages of (1) recovering large quantities of digested substrate; (2) recovery of the active glycosidase; and (3) digestion at high temperatures and under conditions that denature many proteins.

Disaccharidases↗