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Biomedical subjects

D S Ellis

Publications and source records attributed to D S Ellis.

At least 73 records · Page 4Linked to original sources
PubMed1983

The chemotherapy of rodent malaria, XXXIV. Causal prophylaxis Part III: Ultrastructural changes induced in exo-erythrocytic schizonts of Plasmodium yoelii yoelii by primaquine.

Wistar rats were injected intravenously with sporozoites from Anopheles stephensi infected with Plasmodium yoelii yoelii. The animals were subsequently treated with primaquine at doses of 30, 50 or 100 mg kg-1 at various times. Liver biopsies were made and the exoerythrocytic schizonts examined by light and electron microscopy between 45 and 50 hours. The action of the drug appeared to be principally on the parasite mitochondria, the membranes of which became thickened, then proliferated into multiple layers. Finally the whole organelles swelled up losing all structural organisation. Other parasite membranes were affected similarly and the peripheral enzyme granules disappeared. Following treatment the small, disrupted schizonts were apparently absorbed by their host cells which appeared unaffected by primaquine.

Animals↗
PubMed1982

The interaction of monoclonal antibodies directed against envelope glycoprotein E1 of Sindbis virus with virus-infected cells.

Two monoclonal antibodies specific for the Sindbis virus envelope glycoprotein E1 were evaluated for their ability to maintain long-term infection when present in the medium of virus-infected cells. One of them, previously shown to have neutralizing activity and to inhibit haemagglutination, caused suppression of both virus expression at the cell surface and prolonged intracellular virus presence. The other monoclonal antibody which lacked neutralizing activity but inhibited virus-specific haemolysis caused redistribution of viral antigens on the cell surface but only slightly prolonged cell survival. Both epitopes were located on the surface of the virus. By electron microscopy it was demonstrated that the determinant associated with haemolytic activity resided near the virus membrane while the haemagglutination inhibition antibody attached near the apex of the virus spikes.

Animals↗
PubMed1982

Studies by electron microscopy of the giant forms of some African and South American trypanosomes found other than within their mammalian host.

Giant multinucleate cyst forms of 3 brucei group trypanosomes and 2 South American species were found in culture systems and within the insect host cells by electron microscopy; the African stocks within the tsetse mid-gut cells, an unidentified Brazilian trypanosome within the bug's gut cells and Trypanosoma rangeli within the muscle layers surrounding the bug's salivary gland. The various forms found were similar in that they contained varying numbers of large vacuoles, usually lined by subpellicular tubules into which appeared to bud the various organelles seen in normal trypanosomes and which were produced in considerable numbers within the body of these giant forms. These large vacuoles were seen opening to the exterior and liberating what could be small new forms. Sometimes direct budding of new small forms was observed directly from the pellicle of the giant form. The possibility that these giant forms may arise from some type of fusing of individual trypanosomes, that they may perhaps give rise to new individuals and that such a process might provide a mechanism for genetic exchange is discussed.

Animals↗
PubMed1981

Congo/Crimean haemorrhagic fever virus from Iraq 1979: I. Morphology in BHK21 cells.

Congo-Crimean Haemorrhagic Fever virus, isolated from a patient in Iraq, was grown, after passage in suckling mouse brain, in BHK cells. The particles matured after 8-9 days in these cells by budding, usually singly, into cytoplasmic vacuoles throughout the host cells. The virions had an overall diameter of 115 to 125 nm, including rounded surface spikes 15 nm long and 10 nm wide. The viral cores, surrounded by a lipid unit membrane, contained discrete electron-dense elements. It is suggested that the spikes, dimpled at their outer end and possibly hollow throughout their length, passed out through "pores" in the unit membrane.

Animals↗
PubMed1981

Notes on midgut cell nuclear coats in various tsetse species.

Coats were found on the midgut cell nuclei of G.m. morsitans, G. austeni, G. tachinoides, G. f. fuscipes and G. p. palpalis. No coat was found in G. p. gambiensis. The coats were of differing ultrastructural design and of different dimensions in each species. The appearance of the coat seems to be linked to the physiological train of events following the bloodmeal rather than to novel events such as viral or protozoal infection. The timing of its appearance varied among the different species examined.

Animals↗
PubMed1980

The penetration of the salivary glands of Rhodnius prolixus by Trypanosoma rangeli.

Ultrastructural studies of the mechanism of penetration of the salivary gland of the reduviid bug Rhodnius prolixus by Trypanosoma rangeli showed that trypanosomes from the haemocoele penetrate the outer "membranes" of the gland flagellum foremost, disrupting the inner layers, to pass between the muscle cells to reach the gland cell basement membrane. This latter is also penetrated flagellum foremost, the parasite invaginating the gland cell plasmalemma beneath, to create a vacuole in which the trypanosome crosses the gland cells to reach the central lumen, often only losing its containing vacuole just before leaving the cell. The structure of the outer "membranes" surrounding the salivary gland appearland cells. These outer "membranes" were found to enclose large numbers of multinucleate "giant form" trypanosomes, whose significance is as yet unknown, but could perhaps represent a stage in the life cycle of the parasite where genetic interchange could take place.

Animals↗
PubMed1980

Evaluation of plaque size reduction as a method for the detection of Pichinde virus antibody.

The reaction between Pichinde virus and homologous antisera has been studied using a plaque size reduction method. The incorporation of antiserum in the overlay of infected Vero cell monolayers revealed a pattern of virus-cell interactions which were manifested by both a significant reduction in the diameter of virus plaques, and regeneration of cells in the centre of each. Electron microscopy demonstrated that antibody molecules were bound to virus particles budding from the surface of infected cells resulting in the formation of extracellular virus-antibody complexes. These aggregates were subsequently detected in vacuoles of freshly-infected cells. In the absence of virus neutralization, reaction of Pichinde virus with homologous antiserum leads to the formation of infectious aggregates which due to their larger size restrict the rate of plaque development.

Animals↗
PubMed1979

Ebola and Marburg viruses: I. Some ultrastructural differences between strains when grown in Vero cells.

A strain of Marburg virus and two strains of Ebola virus grown in Vero cells were compared by electron microscopy. The outer coat of the Marburg virion appeared to be more resistant to erosion by negative staining techniques than that of the Epbola strains. Marburg virus commonly produced "torus" forms and short filaments; the Zaire strain of Ebola produced extensive branched forms and very long filaments; the Sudan strain of Ebola produced shorter, less branched structures but very many aberrant forms. The mechanism for the production of these aberrant forms is described.

Animals↗
PubMed1979

Ebola and Marburg viruses: II. Thier development within Vero cells and the extra-cellular formation of branched and torus forms.

The development of Marburg virus and the Sudanese and Zaire strains of Ebola virus in Vero cells as visualized by electron microscopy is described. Despite differences in timing, all three strains appear to pass through identical stages of development. Initially there is a large increase in nucleolus material, and viral precursor material arranges itself in spirals and then into tubes. The cells fill with core material, which passes to the plasmalemma, which often proliferates. Each virion passes through the plasmalemma, acquiring a coat of host material. The formation of torus forms is discussed; the branched appearance that is often seen is believed to be an aberrant form. The reasons for this view are put forward.

Animals↗
PubMed1979

Rift Valley fever virus: some ultrastructural observations on material from the outbreak in Egypt 1977.

Rift Valley fever virus isolates from the 1977 outbreak in Egypt were studied at an ultrastructural level. The particles measured 90 to 110 nm in diam. using negative staining and sectioning techniques, with a core component of 80 to 85 nm. The surface of the virions was calculated to be covered by approx. 160 sub-units. The particles were found in smooth endoplasmic reticular systems, which were made up of either multi-tubular complexes, or of a single large vacuole. The majority of these membrane systems were found to be unassociated with Golgi apparatus. Inclusion bodies were found within the host cell nuclei (made up of rods and fine granules) and in the cytoplasm (aggregates of fine or coarse granules). The possible relationship of these structures to virus replication is discussed.

Animals↗
PubMed1979

Ultrastructural studies of certain aspects of the development of Trypanosoma congolense in Glossina morsitans morsitans.

The course of Trypanosoma congolense infections in Glossina morsitans morsitans was followed by electron-microscopic examination of ultrathin sections of the guts and proboscises of infected flies. Guts dissected from flies 7 days after infection with culture procyclic forms of T. congolense had heavy trypanosome infections in the midgut involving both the endo- and ectoperitrophic spaces. Trypanosomes were also seen in the process of penetrating the fully formed peritrophic membrane in the central region of the midgut. By post infection day 21, trypanosomes had reached the proboscis of the fly and were found as clumps of epimastigote forms attached to the labrum by hemidesmosomes between their flagella and the chitinous lining of the food canal. Desmosome connections were observed between the flagella of adjacent epimastigotes. Flies examined at postinfection days 28 and 42 had, in addition to the attached forms in the labrum, free forms in the hypopharynx.

Animals↗
PubMed1978

Intrauterine development of the microfilariae of Dipetalonema viteae.

The egg shell of Dipetalonema viteae separated from the oolemma and became highly convoluted at an early stage of development. No second oolemma or trilaminate membrane was seen. Channels containing electron dense material (thought to be nutrient material from the uterine wall) were formed between adjacent embryos. Many developing embryos died. Microvilli were formed by the uterine wall and developing embryos were closely apposed to these (again presumably to obtain nutrient). Embryos emerged from the egg in the uterus and were born as unsheathed microfilariae.

Animals↗
PubMed1978

Ultrastructure of Ebola virus particles in human liver.

Electron microscopy of tissues from two necropsies carried out in the Sudan on patients with Ebola virus infection identified virus particles in lung and spleen, but the main concentrations of Ebola particles were seen in liver sections. Viral precursor proteins and cores were found in functional liver cells, often aligned in membrane-bound aggregations. Complete virions, usually found only extracellularly, were mainly seen as long tubular forms, some without cores. Many tubular forms had 'enlarged heads' or 'spores' and some branched and torus forms were identified. The size and structure of the Ebola virus forms appear to be virtually indistinguishable from those of Marburg virus.

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