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Biomedical subjects

L H Miller

Publications and source records attributed to L H Miller.

At least 217 records · Page 12Linked to original sources
PubMed1982

Plasmodium falciparum malaria. An amelanotic melanoma cell line bears receptors for the knob ligand on infected erythrocytes.

Erythrocytes infected with Plasmodium falciparum trophozoites and schizonts are not seen in the peripheral circulation because they attach to venular endothelium via knoblike structures on the infected erythrocyte membrane. We have recently shown that erythrocytes containing P. falciparum trophozoites and schizonts likewise attach to cultured human venous endothelial cells via knobs. In search of a more practical target cell for large scale binding studies designed to characterize and isolate the knob ligand, we tested various normal cells and continuous cell lines for their ability to bind P. falciparum-infected erythrocytes. Of the 18 cell types tested, binding of infected erythrocytes was observed to a human amelanotic melanoma cell line and amnion epithelial cells as well as to human aortic and umbilical vein endothelial cells. 96-100% of amelanotic melanoma cells bound 17+/-4 (+/-1 SEM) infected erythrocytes per positive cell, whereas fewer endothelial cells (4-59%) and amnion epithelial cells (8-19%) were capable of binding 12+/-5 and 4+/-1 infected erythrocytes per positive cell, respectively. Further studies designed to compare the mechanism of binding to the amelanotic melanoma cell line and endothelial cells showed the following results. First, that adhesion of infected erythrocytes to these two cell types was parasite stage-specific in that only erythrocytes containing late ring forms, trophozoites, and schizonts bound. Erythrocytes containing early ring forms, which do not attach to venular endothelium in vivo, did not bind to either cell type. Second, erythrocytes infected with trophozoites and schizonts of P. vivax or a knobless strain of P. falciparum, both of which continue to circulate in vivo, did not bind to either target cell type. Third, transmission electron microscopy showed that infected erythrocytes attached to the amelanotic melanoma cells via knobs. We conclude that cultured human endothelial cells and an amelanotic melanoma cell line share common determinants on their surface and that the mechanism of binding to these two different cell types is similar. The amelanotic melanoma cell line offers a useful substitute for endothelial cells in binding studies requiring large numbers of target cells.

Amnion↗
PubMed1982

Altered expression of Plasmodium knowlesi variant antigen on the erythrocyte membrane in splenectomized rhesus monkeys.

Variant antigens are present on the surface of Plasmodium knowlesi malaria-infected erythrocytes as detected by the schizont-infected cell agglutination (SICA) assay. We found that parasitized erythrocytes passaged in splenectomized monkeys did not agglutinate with immune sera. On the first passage from intact to splenectomized monkeys, the SICA titers decreased 4- to 16-fold; after the second and subsequent passages in splenectomized monkeys, the infected cells became nonagglutinable to all sera tested, including sera from animals infected with the nonagglutinating parasites. This loss of agglutinability could have resulted from selection of a genetically distinct subpopulation of the original parasites or the ability of the original parasites to alter their phenotypic expression. We have designated the new nonagglutinable phenotype, SICA [-], and the agglutinable phenotype, SICA [+]. The loss of agglutinability indicates that the variant antigen normally expressed on the erythrocyte membrane of infected cells is altered or absent. Because SICA [-] parasites developed in the absence of the spleen, the major organ of host defense against malaria, then this organ may in some manner influence or modulate antigenic expression in P. knowlesi and possibly other malaria parasites.

Animals↗
PubMed1982

Immunogenic antigens common to Plasmodium knowlesi and Plasmodium falciparum are expressed on the surface of infected erythrocytes.

Sera of Gambian individuals and rhesus monkeys immune against infections with Plasmodium falciparum and plasmodium knowlesi, respectively, were reacted with triton X-100-solubilized membranes of infected erythrocytes. Indirect immune precipitation with Staphylococcus aureus, Cowan strain A, followed by dodecylsulfate-polyacrylamide gel electrophoresis, were used to identify interspecies plasmodial antigens that were immunogenic in vivo. Both types of sera specifically precipitated Plasmodium-specific antigens with Mrs of 125,000, 90,000, and 65,000 to 50,000 from membranes of P. knowlesi-infected erythrocytes that had been labeled with 125I using the lactoperoxidase-catalyzed radioiodination or metabolically with 14C-amino acids. In addition, P. falciparum inhibited the precipitation of P. knowlesi antigens by the Gambian immune sera. Our results indicate, that during erythrocytic schizogony, interspecies Plasmodium antigens are exposed on the surfaces of infected erythrocytes.

Animals↗
PubMed1981

Falciparum malaria-infected erythrocytes specifically bind to cultured human endothelial cells.

Erythrocytes infected with the late stages of the human malarial parasite Plasmodium falciparum became attached to a subpopulation of cultured human endothelial cells by knoblike protrusions on the surface of the infected erythrocytes. Infected erythrocytes did not bind to cultured fibroblasts; uninfected erythrocytes did not bind to either endothelial cells or fibroblasts. The results suggest a specific receptor-ligand interaction between endothelial cells and a component, components, in the knobs of the infected erythrocytes.

Animals↗
PubMed1981

Invasion of erythrocytes by malaria merozoites: evidence for specific receptors involved in attachment and entry.

Invasion of erythrocytes by malaria merozoites involves attachment of the merozoite membrane at the point of collision with the erythrocytes, then reorientation of the merozoite such that its apex is opposed to the erythrocyte membrane, followed by invaginatin of the erythrocyte membrane and interiorization of the parasite. Specific recognition of erythrocyte surface components by the merozoite has been shown by studies on the specificity of merozoites of different malaria species for a limited range of host-species erythrocytes, for erythrocytes of particular maturity, and for erythrocytes possessing particular blood-group determinants. Different malaria species capable of invading erythrocytes of the same host also exhibit differences in specificity for components on enzyme-treated erythrocytes. The attachment phase of merozoite invasion has been isolated from subsequent steps by treatment of merozoites with cytochalasin B -- they then attach to but do not invade susceptible erythrocytes. There is now evidence for other differences between initial attachment steps and subsequent invasion steps form studies on merozoite treatments in vitro which affect invasion but not attachment. It has also been shown that addition of N-acetyl-D-glucosamine to cultures of Plasmodium falciparum inhibits merozoite invasion. Elucidation of the sequence and nature of molecular interactions of merozoite and erythrocyte membrane molecules during invasion will be based on the fundamental ultrastructural observations and on the specificity of attachment and invasion steps already described.

Acetylglucosamine↗
PubMed1981

Inverse relationship between onset and duration of EEG effects of six peripherally administered peptides.

Electrical activity in the rat brain after the peripheral injection of equimolar (0.1 mM) doses of Metenkephalin, Leu-enkephalin, beta-endorphin, gamma-endorphin, DSIP, and alpha-MSH was assessed by power spectral analysis. The mean onset of EEG activity for each peptide varied between 13.7 and 20.7 minutes and lasted between 27.8 and 40.8 minutes. The significant (p less than 0.001) interaction between duration and latency revealed that the longer the latency, the shorter the duration. Similar findings were observed after injection of the same peptides at a fixed dose of 80 microgram/kg body weight. Thus, the results demonstrate that peripherally injected peptides can exert EEG effects that last longer the sooner they start.

Animals↗
PubMed1981

Freeze-fracture study on the erythrocyte membrane during malarial parasite invasion.

Invasion of erythrocytes by malarial merozoites requires the formation of a junction between the merozoite and the erythrocyte. Migration of the junction parallel to the long axis of the merozoite occurs during the entry of the merozoite into an invagination of the erythrocyte. Freeze-fracture shows a narrow circumferential band of rhomboidally arrayed particles on the P face of the erythrocyte membrane at the neck of the erythrocyte invagination and matching rhomboidally arrayed pits on the E face. The band corresponds to the junction between the erythrocyte and merozoite membranes observed in thin sections and may represent the anchorage sites of the contractile proteins within the erythrocyte. Intramembrane particles (IMP) on the P face of the erythrocyte membrane disappear beyond this junction. When the erythrocytes and cytochalasin B-treated merozoites are incubated together, the merozoite attaches to the erythrocyte membrane and a junction is formed between the two, but the invasion process does not advance further and no movement of the junction occurs. Although there is no entry of the parasite, the erythrocyte membrane still invaginates. Freeze-fracture shows that the P face of the invaginated erythrocyte membrane is almost devoid of the IMP that are found elsewhere on the membrane, suggesting that the attachment process in and of itself is sufficient to create a relatively IMP-free bilayer.

Animals↗
PubMed1981

Identification of surface proteins on viable Plasmodium knowlesi merozoites.

Viable merozoites of Plasmodium knowlesi were isolated and the proteins that were labeled on intact merozoites by lactoperoxidase-catalyzed radioiodination were identified. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography of Triton soluble extracts of labeled merozoites demonstrated eight major bands ranging in apparent molecular weight from 150,000 D to 22,000 D. Exposure of intact merozoites to trypsin (10 microgram/ml) for 10 min resulted in the loss of the two highest molecular weight proteins (150,000 D and 105,000 D) and the appearance of two new bands at 70,000 D and 62,000 D. Trypsin treatment under these conditions also removed the receptor(s) for merozoite attachment to erythrocytes. Therefore, these high molecular weight proteins are candidates for the merozoite component that attaches to erythrocytes. There was no evidence that the labeled membrane components were serum or erythrocyte membrane components, two potential contaminants in the preparation. Anti-rhesus erythrocyte antibody did not precipitate labeled merozoite proteins. Furthermore, the immunoprecipitation of labeled merozoite proteins by rhesus anti-merozoite serum was not inhibited by erythrocyte ghosts.

Animals↗
PubMed1981

An electron microscopical study of the interaction of monoclonal antibodies with gametes of the malarial parasite Plasmodium gallinaceum.

Anti-malarial gamete antibodies prevent the fertilization of gametes in the mosquito midgut and prevent transmission of malaria. Recently, hybridoma cell lines secreting monoclonal antibodies (10G3 and 11C7) against gametes of the malarial parasite have been developed. These antibodies act synergistically to mediate 80--90% suppression of the infectivity of gametocytes, although neither monoclonal antibody alone has a significant effect on gametocyte infectivity. We performed immuno-electron microscopy to characterize the interactions of these monoclonal antibodies with gametes of Plasmodium gallinaceum. Male gametes exposed to either 10G3 or 11C7 agglutinated into loose clusters, while those exposed to a mixture of 10G3 and 11C7 agglutinated into long, rope-like bundles. This difference appears to be related to the distribution of the antibodies on the surface of the gametes. When 10G3 or 11C7 labeled with a ferritin-conjugated anti-mouse Ig were used singly, the ferritin particles were distributed in focal areas over the surface of the parasites. By contrast, when the male gametes were exposed to a mixture of 10G3 and 11C7, the ferritin particles were distributed over their entire surface. Female gametes reacted similarly to these antibodies. These observations indicate that combinations of antibody specificities that reduce fertilization efficiency coat the entire surface of the gametes. On the other hand, focal interactions resulting from a single antibody are unable to block fertilization.

Agglutination↗
PubMed1981

Rhesus monkeys protected against Plasmodium knowlesi malaria produce antibodies against a 65,000-MrP. knowlesi glycoprotein at the surface of infected erythrocytes.

Sera from 27 rhesus monkeys immunized in various ways against the H strain of Plasmodium knowlesi were analyzed by quantitative crossed immunoelectrophoresis. The reaction of the sera was compared with a reference immune serum only reactive with P. knowlesi-specific 65,000-Mr glycoprotein-immune component 13 (gp65/ic13) in membranes of infected rhesus monkey erythrocytes. Triton X-100-solubilized, 125I-labeled membranes of schizont-infected erythrocytes were used as an antigen. Sera from 9 or 10 monkeys immunized by repeated infections with P. knowlesi reacted with gp65/ic13. In 6 of 10 sera, anti-gp65/ic13 was the only antibody reacting with host cell membrane proteins. In contrast, vaccination of 15 monkeys with predominantly sexual stages or trophozoites of P. knowlesi in Freund complete adjuvant resulted in protection against blood challenges in 7 monkeys, only 2 of which contained precipitating antibody against gp65/ic13. None of the sera from monkeys not protected by infections or vaccinations contained detectable levels of precipitating antibodies against gp65/ic13. Our data indicate that gp65/ic13 acts as a prominent immunogen in vivo during natural p. knowlesi infections of rhesus monkeys. There is a positive correlation suggested between anti-gp65/ic13 antibody and protection in the monkeys analyzed. This correlation does not apply to monkeys protected against P. knowlesi malaria by vaccination, pointing to other effective immune defense mechanisms.

Animals↗
PubMed1981

Monoclonal antibodies against a specific surface determinant on malarial (Plasmodium knowlesi) merozoites block erythrocyte invasion.

Twelve hybridoma cell lines secreting monoclonal antibodies against Plasmodium knowlesi merozoites have been produced. Antibodies from 3 of the 12 lines agglutinated merozoites. The 2 monoclonal antibodies (13C11 and 16F8) that markedly agglutinated merozoites blocked merozoite invasion of erythrocytes. Of these 2 lines, the one that induced the most agglutination also blocked invasion most effectively. The third monoclonal antibody (53B3) caused minimal agglutination of merozoites and did not block invasion, nor did the other 9 nonagglutinating antibodies. The 2 blocking monoclonal antibodies bound to antigens around the entire surface of merozoites, as demonstrated by immunoelectron microscopy, and precipitated a single biosynthetically labeled protein of apparent m.w. of 250,000. None of the nonagglutinating lines precipitated this protein. Monoclonal antibodies 13C11 and 16F8 reacted with a common antigenic determinant on a Malaysian and a Philippine strain of P. knowlesi in that they blocked invasion and precipitated a 250,000 m.w. protein from both. Sera from immune monkeys also precipitated this 250,000 m.w. protein.

Agglutination↗
PubMed1980

Gametocytogenesis by malaria parasites in continuous culture.

Asexual proliferation of malaria parasites proceeds by multiplication of the parasites within red cells. Following rupture of the host cells the released merozoites re-invade other red cells. On re-invasion, a proportion of merozoites become, not asexual parasites but gametocytes, the sexual stages infective to the mosquito vectors. Conversion of asexual parasites to gametocytes occurs not only during natural infections but also in continuous in vitro culture as reported first by Trager and Jensen and by others. We showed previously that the proportion of early intra-erythrocytic stages (ring stages) of Plasmodium falciparum which developed into gametocytes in culture was influenced by culture conditions. Gametocyte formation was rare in conditions supporting rapid proliferation but frequent when parasite densisites were static. We now show that nearly 100% of ring stages develop into gametocytes in response to 1mM cyclic AMP in static cultures whereas in rapidly growing cultures few rings become gametocytes in response to cyclic AMP.

Animals↗
PubMed1980

Determinants on surface proteins of Plasmodium knowlesi merozoites common to Plasmodium falciparum schizonts.

In this report and (R. Schmidt-Ullrich, L. H. Miller, and D. F. H. Wallach. Manuscript in preparation.), we have demonstrated that malaria proteins on the surface of merozoites and infected erythrocytes cross-react between at least two primate malarias, Plasmodium knowlesi and P. falciparum. Sera from five Gambian adults who were highly immune to P. falciparum were used as a reagent to study the cross-reactivity between P. falciparum schizonts and surface proteins on P. knowlesi merozoites. Although the sera bound to the surface of viable, intact P. knowlesi merozoites, the sera did not block invasion of rhesus erythrocytes. 125I-lactoperoxidase-labeled surface proteins on merozoites formed complexes with the antibody. All major protein bands seen in the electrophoresis of the original Triton extract were bound by the immune sera. Because Gambians have never been exposed to P. knowlesi malaria, the antibodies that reacted with P. knowlesi merozoites must be directed against antigens of another parasite such as P. falciparum. We tested this hypothesis by competition for antibody in a Gambian serum between Triton-extracted antigens from P. falciparum schizont-infected erythrocytes and from surface-labeled P. knowlesi merozoites. P. falciparum inhibited the reaction, thus indicating cross-reaction between antigens in P. falciparum schizonts and P. knowlesi merozoites.

Animals↗
PubMed1980

A neuroheptapeptide influence on cognitive functioning in the elderly.

The heptapeptide core common to melanocyte-stimulating hormone (MSH) and adrenocorticotropin (ACTH) was administered as a single subcutaneous dose of 30 mg to 13 elderly human subjects (9 men, 4 women) in a double-blind, cross-over design. Significant improvement was found in the Benton Visual Retention Test after MSH/ACTH 4--10 as compared with administration of saline. This appeared to be greater in men than women. No side effects or laboratory abnormalities were observed. The behavioral results are consistent with our earlier findings in men and rats of improved visual attention after administration of MSH and extend them to the elderly population.

Adrenocorticotropic Hormone↗
PubMed1980

Factors affecting the ability of isolated Plasmodium knowlesi merozoites to attach to and invade erythrocytes.

Plasmodium knowlesi merozoites were prepared by the polycarbonate sieving method of Dennis, Mitchell, Butcher & Cohen (1975). Merozoite function was assayed by their attachment to and invasion of rhesus erythrocytes at 37 degrees C. The early merozoites from the culture chamber were the most invasive, although maximum numbers of merozoites appeared later. Merozoites were most stable when incubated at room temperature (23 degrees C). At 37 and 0 degrees C invasiveness rapidly declined to zero. Attachment was rapidly lost at 37 degrees C but was retained at 0 degrees C. Attachment was unchanged in the pH range 6.8--7.9 but invasion was reduced at pH 7.9. The presence of L-fucose, D-galactose, D-glucose, D-mannose, N-acetyl-D-galactosamine or N-acetyl-D-glucosamine did not reduce invasion. Attachment and invasion were greatly reduced or abolished by the presence of 2.5 mM EDTA or EGTA, by lactoperoxidase-catalysed iodination of the merozoites, or by treatment of the merozoites with trypsin at a concentration of 1 micrograms/ml or greater for 10 min at 23 degrees C.

Animals↗
PubMed1980

Anti-gamete monoclonal antibodies synergistically block transmission of malaria by preventing fertilization in the mosquito.

Experiments from our laboratory previously demonstrated that infected chickens immunized with gametes of the avian malaria parasite Plasmodium gallinaceum were no longer infectious to the mosquito vector Aedes aegypti and that this transmission-blocking immunity was mediated by antibody. To identify those antigens that are the targets of transmission-blocking immunity, hybrid mouse cell lines secreting monospecific antibodies to surface antigens on male and female gametes of P. gallinaceum have been produced. We describe two such anti-gamete antibodies, 10G3 and 11C7, which act synergistically both to agglutinate male gametes in vitro and to suppress infectivity of parasitized blood fed to mosquitoes. In the presence of a mixture of these antibodies, the male gametes became agglutinated during gametogenesis and failed to detach from the residual body of the gametocyte. In the presence of either antibody alone, the male gametes readily detached during gametogenesis. Neither antibody alone mediated more than a slight reduction in infectivity of gametocytes to mosquitoes. Although both 10G3 and 11C7 recognize surface antigens on both male and female gametes, agglutination and prevention of detachment of the male gametes from the residual body appears to be the primary mechanism by which the mixture of these antibodies prevents fertilization.

Agglutination↗
PubMed1980

A perspective on malaria vaccines.

The data obtained with adjuvant-antigen vaccines against asexual malaria parasites in different host-parasite systems are reviewed. From these data the problems associated with antimalarial vaccine development and testing are considered. The requirement for an adjuvant to induce immunity and the type of adjuvant required depends primarily on the host. Since the immune response of man to malaria vaccines is unknown, it is impossible to predict which animal infection is most likely to be a faithful model of malaria in man although it is generally assumed that the monkey is the most appropriate analogue. Therefore careful studies of the immune response of monkeys to purified malarial antigens are needed to develop vaccines for testing in man.

Animals↗