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Biomedical subjects

M Mayer

Publications and source records attributed to M Mayer.

At least 271 records · Page 15Linked to original sources
PubMed1985

Aging and aneuploidy: evidence for the preferential involvement of the inactive X chromosome.

It has been known for some time that there is an association between chronological aging and X-chromosome aneuploidy in peripheral blood lymphocyte cultures from females. In an attempt to elucidate the mechanism of X-chromosome aneuploidy in aging females, we used a BrdU late-labeling technique to determine the X-inactivation pattern in 45,X and 47,XXX lymphocytes of older women. In 50 of 58 X-aneuploid cells the inactive X chromosome was missing or extra. This implies that either the inactive X has a special propensity for mitotic errors or mitotic errors occur at random but subsequent selection is less stringent against cells with a missing or additional inactive X chromosome than against aneuploid cells involving the active X chromosome. Evidence is presented in favor of the former hypothesis.

Aged↗
PubMed1985

Proteolytic enzymes in human fetal membranes and amniotic fluid. A comparison of normal and premature ruptured membranes.

The amniotic and chorionic membranes obtained at term and term amniotic fluid contain a soluble protease activity which cleaves [14C]-labeled globin at acid pH. In contrast, a salt extract of the pellet fraction obtained from the fetal membranes displays only negligible protease activities at the pH range of 4-8. Specific activities of the proteases in the soluble and salt-extractable fractions of fetal membranes which were intact before onset of labor were not significantly different from the respective activities in cases of premature rupture of fetal membranes (PROM). However, the protease activity of the amniotic fluid was found to increase with advancing gestational age and to reach maximal activity at term. A heat-sensitive and nondializable protease inhibitory activity was found in term amniotic fluid. This inhibitory activity acted on the cytosolic protease of amniotic membranes from control and PROM cases, but not on the soluble protease of chorionic membranes, and had a similar potency in fluids from PROM cases or fluids collected at term. These results do not support a role for fetal membrane proteases, amniotic fluid proteases, or amniotic fluid protease inhibitory activities in the etiology of PROM. However, the observed changes in amniotic fluid protease activity with fetal age suggest a physiological role for the enzyme in normal fetal development.

Amniotic Fluid↗
PubMed1985

The effect of methionine and 5-azacytidine on fragile X expression.

The cellular mechanism for the expression of the fragile site at Xq28 is unknown. We tested the effect of 5-azacytidine and methionine on fragile X expression in lymphocytes and lymphoblastoid cells in an attempt to determine if DNA methylation was involved. We were unable to demonstrate a consistent dosage effect of methionine on fragile X expression. While 5-azacytidine was found to inhibit the fragile X in both males and females, it did so only at relatively high concentrations. We conclude that the role, if any, of DNA methylation in fragile X expression is likely to be secondary, the primary effect being due to thymidylate depletion.

Azacitidine↗
PubMed1985

Bile levels of imipenem following different dose regimens.

Seventeen patients received either 500 mg (9 patients) or 1000 mg (8 patients) of imipenem following bile duct surgery with indwelling Kehr-T-drainage which permitted the measurement of bile levels. Bile and blood specimens were taken at the following time intervals: control value prior to the 20 min-imipenem-infusion, then at 10, 15, 20, 30, 45, 60, 90, 120, 150, 180, 240 and 300 min after administration of imipenem. In addition, a blood specimen was drawn after 360 min. Three patients of the 500 mg-group and 6 patients of the 1000 mg-group received a second dose after 4 h. The specimens were taken at the same intervals as mentioned above. It was shown that a spaced dose of 500 mg imipenem thrice daily would be sufficient to treat infections by sensitive pathogens of the bile ducts.

Aged↗
PubMed1985

[Psychotic symptoms during the evolution of dementia in muco- polysaccharidosis of Hurler-Scheie phenotype].

The case reported concerns a 17 1/2 year-old adolescent presenting with complete alpha-L-iduronidase deficiency. Its phenotype intermediate between Hurler's and Scheie's syndromes and the occurrence of a delirious and hallucinatory condition evolving with acute exacerbations on a constant subdelirious and excited state made this case particular. This case report is compared to the 30 in the Anglo-Saxon literature which shows, in addition to the rarity of psychiatric symptoms (one single case), the multiplicity of the possible phenotypes, reinforcing the hypothesis of a polyallelic or even non allelic mutation.

Adolescent↗
PubMed1984

Plasminogen activator activity in differentiating leukemia cells.

Plasminogen activator (PA) activity of human promyelocytic leukemia cell line HL-60 was assayed by following the conversion of plasminogen to plasmin and the plasmin-mediated hydrolysis of 14C-labeled globin. When HL-60 cells were induced to differentiate into macrophages by 12-O-tetradecanoyl-phorbol-13-acetate (TPA), cell-associated PA activity and secretion of PA into the conditioned medium increased profoundly. PA activity increased earlier and as a result of lower concentrations of TPA than the ability of the cells to adhere. Exposure to 10(-6)M dexamethasone did not prevent TPA-induced adherence and produced a slight inhibition of cellular PA activity. These findings imply that TPA-induced differentiation of HL-60 cells to macrophage-like cells is associated with induction of PA activity.

Cell Adhesion↗
PubMed1984

Structure and mitotic stability of minichromosomes originating in yeast cells transformed with tandem dimers of CEN11 plasmids.

Large (10.5-13.5 kbp) circular minichromosomes containing the centromere of chromosome 11 (CEN11) and the MET14 gene of Saccharomyces cerevisiae in the YRp7 vector are considerably more stable during mitosis than smaller ones containing only the 1.6 kbp CEN11 SalI-fragment. Yeast transformants obtained with a tandem dimeric and thus dicentric form derived from this DNA varied in the mitotic stability of the TRP1 marker of the vector. The largest group of transformants contained minichromosomes which carried deletions located quite specifically at one of the two centromeres in the dimer, eliminating its function in mitosis. This group included also some minichromosomes which had been modified by intramolecular tandem amplification of the subunit carrying the deletion without losing the centromere within the unmodified subunit. The second major group carried minichromosomes which had been monomerized. Monomerized minichromosomes showed the relative low degree of mitotic stability typical for the original minichromosomes containing the 1.6 kbp CEN11 SalI-fragment. Increasing numbers of additional subunits carrying the TRP1-ARS1 sequences but lacking additional centromeres improved the mitotic stability considerably.

Base Sequence↗
PubMed1984

Inhibition of phorbol-ester-induced adhesion of differentiating human myeloid leukemic cells by pentamidine-isethionate.

Human myeloid leukemia cells can be induced to differentiate into macrophage-like cells by various phorbol esters, particularly 12-O-tetradecanoyl-phorbol-14-acetate (TPA). In this study, the effect of several known protease inhibitors on TPA-induced differentiation of human acute promyelocytic leukemia cells (line HL-60) was tested. Among the test compounds, only pentamidine-isethionate (PI), an inhibitor of trypsin-like enzymes, prevented one early marker of differentiation, e.g. cell adherence to plastic and glass surfaces. However, PI failed to affect other markers of differentiation and did not inhibit readherence of scraped and resuspended TPA-treated cells. Exposure to TPA resulted in a decrease in the cellular alkaline proteolytic activity and an increase in the acid proteolytic activity. PI further inhibited the residual activity of the alkaline protease in the 36,000 g pellet fraction of the TPA-treated cells, but did not reduce this activity in control cells. The present results indicate, on the basis of the differential effects of PI, that the emergence of differentiation markers in HL-60 cells following exposure to TPA is independent of the induction of adherence.

Amidines↗
PubMed1984

Protease activity in fibromyoma and normal human myometrium.

The potential involvement of intracellular proteases in the pathophysiology of fibromyoma was studied by assay of activity of two proteolytic enzymes in fibromyoma and adjacent normal myometrium. Protease I, a soluble acid protease and protease II, a particulate protease optimally active at the neutral pH range are present in fibromyoma as well as in normal myometrial tissue. No consistent difference was observed between the specific activities of these enzymes in the fibromyoma and the surrounding myometrium. The large variation in the specific activity of the protease noted among normal and fibroid tissue samples from different patients cannot be ascribed to differences in cellularity. This variance might suggest differences in rate of processing of steroid hormones or different degrees of vascularization. The present findings do not support a major role for modulation of intracellular protease activities in the development of fibromyoma.

Adult↗