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M D Bates

Publications and source records attributed to M D Bates.

23 records · Page 2Linked to original sources
PubMed1987

Plasmodium vivax: exoerythrocytic schizonts recognized by monoclonal antibodies against blood-stage schizonts.

Exoerythrocytic parasites of Plasmodium vivax grown in human hepatoma cells in vitro were probed with monoclonal antibodies raised against other stages of P. vivax. Monoclonal antibodies specific for four independent antigens on blood-stage merozoites all reacted with exoerythrocytic schizonts and merozoites by immunostaining. The characteristic staining pattern of each monoclonal antibody was similar on both blood- and exoerythrocytic-stage parasites and appeared only in mature schizont segmenters. In contrast, a monoclonal antibody specific for the caveolar-vesicle complex of the infected host cell membrane and a second monoclonal antibody reacting with an unknown internal antigen did not appear to react with exoerythrocytic parasites. We confirm prior reports that monoclonal antibodies against the sporozoite immunodominant repeat antigen react with all exoerythrocytic-stage parasites, but note that as the exoerythrocytic parasite matures the immunostaining is concentrated in plaques reminiscent of germinal centers and apparently distinct from mature merozoites. These results indicate that mature merozoites from either exoerythrocytic or blood-stage parasites are antigenically very similar, but that stage-specific antigens may be found in specialized structures present only in a specific host cell type.

Animals↗
PubMed1986

Synthetic peptides from the circumsporozoite proteins of Plasmodium falciparum and Plasmodium knowlesi recognize the human hepatoma cell line HepG2-A16 in vitro.

Several lines of evidence have emphasized the importance of the malaria circumsporozoite (CS) protein as a factor in sporozoite invasion of the hepatocyte; however, the specific mechanism of cell recognition and invasion has not been explained. In this study we present evidence that a highly conserved region of the CS protein immediately adjacent to the repeat region, the N1 region, specifically recognizes receptors on the human hepatoma cell line HepG2-A16 under conditions where invasion by sporozoites can occur. Peptides consisting of sequences from the repeat region or of the more extensive N2 region showed no such specific association. Antibody against the N1 peptide could inhibit sporozoite invasion in vitro. Covalent coupling of radiolabeled N1 peptide to HepG2-A16 cells identified two hepatic cell proteins to be closely associated with the peptide. We suggest that these proteins could act as receptors or mediators, via the N1 region of the CS protein, for the P. falciparum sporozoite in the process of invasion of the hepatocyte.

Amino Acid Sequence↗
PubMed1984

Calcium mobilization in the pituitary gonadotrope: relative roles of intra- and extracellular sources.

GnRH stimulates pituitary gonadotropin release by a Ca+2-dependent mechanism. Indeed, while it is clear that Ca+2 fulfills the requirements of a second messenger, the relative roles of Ca+2 mobilized from intra- and extracellular sources have never been distinguished. In the present study we examined the requirements for intra- and extracellular Ca+2 by three different means. First, in static cultures we used a specific Ca+2 ion channel blocker, methoxyverapamil (D600), to block entry of extracellular Ca+2 into pituitary cell cultures to determine if brief elevation of intracellular Ca+2 (whether derived from external or internal sources) could support continued gonadotropin release. Studies over a wide range of GnRH concentrations indicated that blockade of Ca+2 entry into the gonadotrope (in the presence of continued occupancy of the GnRH receptor by the releasing hormone) resulted in termination of LH release. Second, compounds that stabilize intracellular Ca+2 (preventing its mobilization), such as 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate-HCl (TMB-8) and dantrolene (Dantrium), were shown not to alter the potency or efficacy of GnRH in stimulating LH release. Third, we used a system of perifused cells to measure the actions of D600, EGTA, or the removal of GnRH on stimulated LH release to correlate precisely the release process with access to Ca+2 in the extracellular compartment. The results of these studies suggest that LH release in response to GnRH is primarily dependent on Ca+2 mobilized from extracellular sources. Termination of accessibility to this Ca+2 pool also results in termination of release. The data are consistent with a model in which GnRH occupancy of its receptor regulates a plasma membrane Ca+2 ion channel; continued access to the extracellular Ca+2 pool is required for continued LH release.

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