Biomedical subjects

R H Meints

Publications and source records attributed to R H Meints.

30 records · Page 2Linked to original sources

PubMed1984

Infection of a Chlorella-like alga with the virus, PBCV-1: ultrastructural studies.

Ultrastructural studies revealed that the virus, PBCV-1, adsorbs to the surface of the Chlorella-like green alga NC64A and enzymatically digests a portion of the host cell wall. The viral DNA is then released into the interior of the cell leaving an empty capsid on the surface. Thus uncoating of the viral genome occurs at the surface of its host. PBCV-1 also adsorbs to and digests the host wall of either heat-killed, methanol-extracted, or purified cell wall fragments.

Chlorella↗

PubMed1984

Structural proteins and lipids in a virus, PBCV-1, which replicates in a Chlorella-like alga.

PBCV-1, a large dsDNA-containing virus which replicates in a Chlorella-like green alga, is composed of approximately 64% protein, 25% DNA, and 5-10% lipid on a weight basis. Polyacrylamide gel electrophoresis of the dissociated virus particle resolves 50 to 60 proteins which range in apparent molecular weight from 10,000 to 135,000. Two of these proteins are glycoproteins and at least four are located on the viral surface. The major lipids are phosphatidyl choline, phosphatidyl ethanolamine, and an unidentified component. The effect of organic solvents, surfactants, and chelating and reducing agents on viral infectivity and ultrastructure are reported. Inhibitor studies established that PBCV-1 protein synthesis occurs on cytoplasmic ribosomes.

Chlorella↗

PubMed1982

Viruses of symbiotic Chlorella-like algae isolated from Paramecium bursaria and Hydra viridis.

We previously reported that isolation of symbiotic Chlorella-like algae from the Florida strain of Hydra viridis induced replication of a virus (designated HVCV-1) in the algae. We now report that isolation of symbiotic Chlorella-like algae from four other sources of green hydra and one source of the protozoan Paramecium bursaria also induced virus synthesis. Algae from one of these hydra contained a virus identical to HVCV-1 (based on its rate of sedimentation, buoyant density, reaction to HVCV-1 antiserum, and DNA restriction fragments) whereas algae from the other three hydra contained another similar, but distinct, virus (designated HVCV-2). The virus from the paramecium algae (designated PBCV-1) was distinct from both HVCV-1 and HVCV-2. The symbiotic algae in the hydra could also be distinguished ultrastructurally. Chloroplasts of both algae that produced HVCV-1 lacked a pyrenoid whereas chloroplasts of the other three symbiotic algae contained pyrenoids. Since all symbiotic eukaryotic algae we have examined have had virus, a potential viral role in symbiosis is suggested.

Journal Article↗

PubMed1980

Quantitative demonstration of cell surface involvement in a plant-animal symbiosis: lectin inhibition of reassociation.

The freshwater hydra, Hydra viridis is normally associated with Chlorella-like, algal symbionts which inhabit the host's digestive cells. Under experimental conditions bleached hydra will reassociate with algae harvested from green hydra, but not from our cultures of wild type Chlorella or strain NC64A which when originally isolated from Paramecium bursaria was symbiotically competent. Because of its demonstrated selectivity, the reassociation process is hypothesized to involve a recognition interface whose active participants are the algae cell wall and the digestive cell membrane. The data presented here confirm the hypothesis and suggest some potential molecular characteristics of the interacting partners. Concanavalin A (Con A), a plant lectin, used widely for similar studies in other systems totally inhibits reassociation; Wheat Germ Agglutinin (WGA), ricin and Lens culinaris lectin do so to a lesser degree. These results are consistent with the hypothesis that glycoproteins on the cells' peripheries are involved in cell-cell recognition in this system.

Binding Sites↗

PubMed1979

Enhancement of erythroid colony growth in culture by hemin.

Hemin was found to enhance the growth of murine erythroid colonies in culture. In the presence of 100 mU/ml erythropoietin (EPO), the addition of hemin (0.05-0.2 mM) resulted in the growth of twice as many colonies as were obtained with EPO alone. Hemin also significantly increased erythroid colony formation in culture in the absence of added EPO. Hemoglobin synthesis as measured by the incorporation of 59Fe into cyclohexanone extractable heme was augmented in culture by hemin. Neither delta-aminolevulinic acid, a hemin precursor, nor FeCl3 increased colony number.

Animals↗

PubMed1978

Sialic acid: a specific role in hematopoietic spleen colony formation.

Vibrio cholerae neuraminidase (VCN) treatment of donor bone marrow cells results in a reduction in the number of hematopoietic colonies (CFUs) formed in the spleens of lethally irradiated mice. Treatment of marrow cells with sodium periodate under mild conditions, known to preferentially oxidize sialic acid, also reduced CFUs while subsequent potassium borohydride reduction restored CFUs to 80% of control levels. Innoculum viability as measured by in vitro incorporation of tritiated precursors into proteins, nucleic acids, and oligosaccharides was unaffected by VCN treatment. The ability of bone marrow cells in culture to respond to the hormone erythropoietin, as measured by the incorporation of 59Fe into cyclohexanone-extractable heme, was also not affected by neuraminidase, making a cytotoxic effect of the VCN preparation unlikely. Incubation of VCN-treated marrow with either beta-galactosidase or trypsin had no effect on the VCN-induced reduction in CFUs. These results are consistent with the idea that membrane sialic acid plays a direct and specific role in the implantation and development of CFUs.

Animals↗

PubMed1977

Studies of the development of frog hemopoietic tissue in vitro. I. Spleen culture assay of an erythropoietic factor in anemic frog blood.

A new in vitro technique has been described for demonstrating the presence of an erythropoietic factor in the circulating blood of frogs. The assay system consisted of MC33 medium, erythropoietically active spleen cells from Rana pipiens, and plasma or serum from frogs made anemic via phenylhydrazine or bleeding. The spleen cells, which remain erythropoietically active for up to nine days, were found to incorporate 59Fe, [3H]thymidine, [3H]uridine, and [3H]leucine at a greater rate in the presence of plasma or serum from anemic versus normal frogs. The hormones triiodothyronine, prolactin, and erythropoietin were not effective in eliciting an hemopoietic response. The data presented suggest that the spleen from that adult frog is a major site of erythroid differentiation and maturation.

Anemia↗

PubMed1975