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Biomedical subjects

D M Nelson

Publications and source records attributed to D M Nelson.

At least 91 records · Page 5Linked to original sources
PubMed1979

Instrumental analysis of trace elements in thumbnails of human subjects.

Human thumbnails were analyzed for trace elements by instrumental analysis using thermal neutron activation technique. The average concentration of metals studied in clinically symptom-free adult female and male subjects were: zinc, 184 vs. 153 ppm; chromium, 6.8 vs. 4.2; selenium, 0.9 vs. 0.6; gold, 2.6 vs. 0.4; mercury, 1.9 vs. 0.4; silver, 0.7 vs. 0.3; cobalt, 0.07 vs. 0.04. A summary of literature reported concentration of metals in human nail is also presented.

Adult↗
PubMed1978

Cytological events involved in protein synthesis in cellular and syncytial trophoblast of human placenta. An electron microscope autoradiographic study of [3H]leucine incorporation.

Electron microscope autoradiography has been used to study protein synthesis in syncytial and cellular trophoblast of term human placental villi incubated in vitro with tritiated leucine ([3H]leu). Autoradiographs were analyzed using the hypothetical grain analysis of Blackett and Parry (1973. J. Cell Biol. 57:9-15). The results of this study demonstrated that both cellular and syncytial trophoblast have marked capacities for protein synthesis. Cellular trophoblast synthesized protein in both its rough endoplasmic reticulum (RER) and its ground plasm which contained abundant free ribosomes. The vast majority of 3H-proteins remained within the cell, with some of the proteins synthesized ultimately appearing in the nucleus. A small percentage of grains was ultimately associated with the trophoblast basement membrane. In syncytial trophoblast, the RER was the dominant site for protein synthesis. The autoradiographic data suggested that, as in the cellular trophoblast, the vast majority of 3H-proteins synthesized by the syncytial trophoblast remained within the syncytial trophoblast throughout the incubation period. The major portion of [3H]leu-labeling present in the syncytial trophoblast of villi incubated the longest times (4 h+) remained in association with the RER. Labeled proteins did not become concentrated in syncytial trophoblast Golgi apparatus, vesicles, or granules. In contrast to cellular trophoblast, the nuclei in the syncytium did not contain 3H-proteins at any time-point studied.

Autoradiography↗
PubMed1978

Cytological events involved in glycoprotein synthesis in cellular and syncytial trophoblast of human placenta. An electron microscope autoradiographic study of [3H]galactose incorporation.

Electron microscope autoradiography was used to study glycoprotein synthesis in cellular trophoblast (cytotrophoblast) and syncytial trophoblast of term human placental villi incubated in vitro with D-[1-3H]galactose ([3H]gal). Autoradiographs were analyzed using the hypothetical grain analysis of Blackett and Parry (1973. J. Cell Biol. 57:9-15). The results of this study indicated that [3H]gal incorporation into term placental villi was predominantly localized to cytotrophoblast. Utilization of [3H]gal by term syncytial trophoblast was extremely low and yielded too few grains for a quantitative grain analysis. This result is in striking contrast to that found in the preceding study of [3H]leucine incorporation (Nelson, D. M., A. C. Enders, and B. F. King. 1978). Within cytotrophoblast, the rough endoplasmic reticulum incorporated the most [3H]gal into glycoprotein. The Golgi apparatus was another site of [3H]gal incorporation. The vast majority of the [3H]gal incorporated into cytotrophoblast during the pulse incubation remained intracellular through the duration of the experiment. There was little autoradiographic evidence for secretion of tritiated macromolecules. Cytotrophoblast incubated for the longest time period studied (4 h+) showed a substantial concentration of tritiated macromolecules in the Golgi complex and in the ground plasm but not in the rough endoplasmic reticulum.

Autoradiography↗
PubMed1978

Nonuniform distribution and grouping of insulin receptors on the surface of human placental syncytial trophoblast.

These studies were designed to investigate the cytologic localization and topographic distribution of insulin receptors in human placental villi. Biochemical studies showed placental villi to specifically bind 125I-insulin. Radioautographic studies showed the specific binding to be localized to the surface of the syncytial trophoblast. Topographic distribution of insulin binding was determined with ferritin-insulin. Initial studies using ferritin-insulin containing some oligomers of ferritin revealed the insulin receptors to be specifically associated with the glycocalyx region of the surface membranes of microvilli. No insulin receptors were detectable in association with the intermicrovillous plasma membrane even though its glycocalyx is in direct continuity with the glycocalyx of microvilli. Monomeric ferritin-insulin showed the same nonuniform distribution of the insulin receptor, which suggests that there is not complete freedom of lateral mobility of the insulin receptors in the surface membrane of this tissue. The insulin receptors were found to occur as singletons or in groups of two or more. Incubations with monomeric ferritin-insulin at 4 degrees or with tissue prefixed with formaldehyde showed that the groups of insulin receptors were naturally occurring, i.e., they are present prior to and independent of insulin binding and thus not secondary to ligand-induced aggregation. The physiologic meaning of the nonuniform distribution and the groups of insulin receptors is unclear at present.

Cell Membrane↗
PubMed1977

Characterization of a microvillous membrane preparation from human placental syncytiotrophoblast: a morphologic, biochemical, and physiologic, study.

The syncytiotrophoblast microvillous membrane must play a vital role in many essential functions of the placenta. In order to better understand the functional characteristics of this membrane, we have investigated an isolated membrane preparation by a variety of techniques. Electron microscopic observations showed membranous structures similar to microvilli of intact placental villi in size, shape, and microfilamentous content. Similarities in colloidal iron staining and transferrin localization were also shown. The preparation was enriched in enzymes characteristic of surface membranes and diminished in enzymes characteristic of intracellular organelles. Sialic acid content was also increased. SDS gel electrophoresis revealed the presence of a 45,000 molecular weight band, which may be actin. The preparation transported serine, glycine, and alpha-aminoisobutyric acid by a temperature-dependent, saturable process.

Alkaline Phosphatase↗
PubMed1977

Galactosyltransferase activity of the microvillous surface of human placental syncytial trophoblast.

The syncytial trophoblast has previously been shown to have minimal intrasyncytial galactosyltransferase activity at term. The biochemical and autoradiographic study reported here shows that the microvillous surface of term human placental syncytial trophoblast has a galactosyltransferase activity capable of transferring 3H-galactose from uridine diphosphate-D-galactose-1-3H to trichloroacetic-acid precipitable, endogenous acceptors. This capability of resynthesizing cleaved galactose moieties in the glycocalyx, without dependence on cytoplasmically located galactosyltransferases, would allow for reinstatement of the original surface molecular configuration without requiring synthesis and insertion of a completely new membrane molecule. It is suggested that the surface galactosyltransferase might function to repair damage to syncytial trophoblast glycocalyx induced by the enzymes in maternal blood.

Autoradiography↗
PubMed1976

The nonuniform distribution of acidic components on the human placental syncytial trophoblast surface membrane: a cytochemical and analytical study.

The surface coat of syncytial trophoblast from term human placentas was studied using cytochemical methods (colloidal iron, alcian blue-lanthanum nitrate, dialyzed iron) in coordination with tissue enzyme digestions (trypsin, neuraminidase) and sialic acid analyses. The presence of at least two highly acidic anionic components that contribute significantly to the surface negativity of trophoblast has been demonstrated. The first of these, sialic acid, was removed with neuraminidase. Tissue digestion with this glycosidase was accompanied by a decrease in trophoblast surface staining with colloidal iron, a decrease in tissue sialic acid, and an increase in the concentration of sialic acid in the incubating medium. Results from methylation experiments were consistent with the presence of sialic acid. The second anionic component(s) was identified by removal with trypsin of a glycocalyx constituent that stained with both colloidal iron and lanthanum. After trypsinization, tissue sialic acid levels were not significantly different from control values, and no detectable sialic acid was present in the incubating medium. The identity of this anionic component has not been established. Both sialic acid and nonsialic acid acidic components are distributed in higher density on membrane of microvilli than on intermicrovillous surface membrane. In addition, the sialic acid moieties appear to be clustered in the glycocalyx.

Acids↗
PubMed1976

Lead poisoning among migrant children in New York State.

Potentially hazardous painted surfaces were found in 40% of 166 dwelling units surveyed in 97 upstate New York migrant labor camps, a figure substantially lower than comparable surveys in upstate New York high risk urban areas. Blood samples obtained from 79 migrant children in 1972 revealed only one child with blood lead level above 40 mug per 100 ml as compared to a 21.6% yield from 5,733 high risk urban area children. A second screening program in 1974 yielded only three children of 190 tested with proven blood lead levels above 40 mug per 100 ml, although seven additional children with possible elevations were lost to follow-up.

Child↗