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Biomedical subjects

J L Meyer

Publications and source records attributed to J L Meyer.

At least 37 records · Page 2Linked to original sources
PubMed1990

Distribution of rDNA and 28S, 18S, and 5S rRNA in micronuclei containing a single chromosome.

Investigating genes and their transcription products in nuclear compartments corresponding to one mammalian chromosome, the ribosomal genes 18S-28S and 5S were localized in PtK1 micronucleated cells and rRNA was characterized in sorted micronuclei containing single identified chromosomes. In situ hybridization revealed the presence of 18S-28S rRNA genes in two micronuclei per cell and 5S rRNA genes in four micronuclei per cell. Flow cytometry histograms of isolated micronuclei stained with Hoechst 33342 exhibited five peaks (a-e) in which peaks b and c, respectively, corresponded to chromosomes 4 and X. Restricted genomic DNA from sorted peak c micronuclei showed the presence of 28S gene sequences. Direct sorting of the micronuclei from each peak on nitrocellulose and their hybridization with the 18S-28S rDNA probe revealed that the rRNA genes were exclusively located in micronuclei containing X chromosomes. Northern blotting showed the presence of 18S-28S and 5S rRNAs in peak c micronuclei and their absence from peak b micronuclei. Consequently, these procedures allowed us to show the presence of ribosomal genes and the corresponding rRNA in micronuclei containing single X chromosomes, and the absence of rRNA from micronuclei that do not contain the ribosomal genes. In regards to the transcription of these genes, the micronuclei from peak c can be considered as functional interphase X chromosomes.

Animals↗
PubMed1988

[Prognostic significance of the T4 lymphocyte count in patients infected with CDC Class II and III HIV].

From 1985 to 1987 101 patients infected with the human immunodeficiency virus (HIV) were seen at our outpatient clinic and prospectively analyzed in a cohort study. We evaluated the follow-up in 41 patients of CDC classes II and III with regard to the number of T-helper lymphocytes (T4) and clinical progression. The patients consisted of 24 i.v. drug addicts, 11 homosexuals and 6 persons with other or multiple risk factors for HIV infection. Patients with a T4 count of less than 400/mm3 at the first visit did not differ significantly with regard to development of AIDS from those with a count of greater than 400/mm3 after a mean follow-up of approximately 1 year. The course of the infection for the individual patient was extremely varied and not predictable by the T4 value. We conclude that the number of the T4-lymphocytes is of no help in assessment of prognosis in the individual patient of CDC classes II and III.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Production of calcification inhibitors by rat calvaria and bone cells in culture.

Inhibition of calcium phosphate crystal formation was assessed in conditioned medium from cultured rat calvaria and rat calvaria cells. The amount of inhibitor activity was measured by determining the amount of hydroxyapatite needed to induce calcium phosphate precipitation in a solution with a constant calcium phosphate supersaturation. Rat calvaria in culture released inhibitor activity. This activity was separated by chromatography on a Bio-Gel P4 column into a high molecular weight (HMW) fraction and a low molecular weight (LMW) fraction. The latter contained, among others, citrate and pyrophosphate (PPi), but the concentration of these was too low to account for the total activity observed. The identity of the HMW and the remaining LMW inhibitors are at present unknown. Various populations of calvaria cells also produced these two types of inhibitors, 20% of the LMW being due to PPi. Fibroblasts produced only the HMW type of inhibitors. These results suggest that cells might control the process of biologic calcification by regulating the amount of inhibitors they produce.

Animals↗
PubMed1987

[A simple rapid method of culturing chorionic villi. Identification and description of maternal cells in culture].

Chorionic villi cell cultures is a complement to direct chromosome analysis. It is indispensable for the determination of certain enzymatic activities. A rapid, simple and reliable method of culture is described which allows height quality karyotyping in a week. Confusion with maternal cells is a possible source of error. The authors identified and described these maternal cell types.

Cells, Cultured↗
PubMed1986

Influence of aluminum on mineralization during matrix-induced bone development.

A model of de novo mineralization employing matrix-induced endochondral bone formation in rats was used to study the short-term effects of aluminum on the deposition of calcium and phosphate in vivo. In experiments where systemic aluminum concentrations were elevated, the cellular processes associated with bone development appeared to be normal, if somewhat delayed, however precipitation of the mineral phase was prevented. This suggests a primary direct physical chemical effect of aluminum in vivo on calcification, as suggested by in vitro studies which demonstrate that aluminum is a potent inhibitor of calcium phosphate precipitation. Aluminum salts implanted locally with the matrix appeared to be toxic to the cellular processes leading to chondrogenesis and osteogenesis.

Alkaline Phosphatase↗
PubMed1986

Production and turnover of planktonic bacteria in two southeastern blackwater rivers.

Production by attached and free-living planktonic bacteria in two blackwater rivers in the Southeastern United States was measured over a period of 14 months by using the rate of incorporation of [methyl-H]thymidine into DNA. Production rates and biomass dynamics were compared to determine the potential for in situ production to supply planktonic biomass. Bacterial production in these rivers was moderate and varied seasonally. Rates varied from 0.058 to 2.120 mg of C m h in the Ogeechee River and from 0.002 to 2.418 mg of C m h in Black Creek. Regressions of growth rate on various environmental variables showed that temperature and total dissolved organic carbon concentration were the best predictors of growth. Although attached bacteria were <21% of the total biomass, they accounted for up to 53% of the total production. Turnover times for attached bacteria ranged from <1 day to >3 years depending on season. Turnover times of free-living bacteria varied from 4.4 days to 11.8 years. Comparisons of biomass with production indicated that during most seasons, the majority of bacterial biomass in these rivers was of allochthonous origin. During summer, when water temperatures were high, bacterial growth in the river may have supplied a greater percentage of the standing stock of bacteria than allochthonous inputs.

Journal Article↗