D. S. Ellis

Recent observations on the behaviour of certain trypanosomes within their insect hosts.

Publisher Summary The parasites responsible for the diseases, such as sleeping sickness and related trypanosomiases belong to the Trypanosoma brucei group. The methods used for studying the developmental cycles of trypanosomes within the tsetse fly are summarized in the chapter. The penetration of the fully developed peritrophic membrane can occur in the midgut region, and this penetration is outward into the ectoperitrophic space. It is related to the concentration of parasites within the lumen—that is, it occurs in those areas of the midgut that contain the highest concentration of trypanosomes–– and its frequency tails off on either side of these areas of maximum parasite density. The mechanics of penetration require a minimum of two trypanosome enzymes: a protease to allow passage across a chitin-containing layer of the peritrophic membrane and an obligatory enzyme, such as lipase, to attack the inner lipid-containing layer of the peritrophic membrane. A lipase is also necessary for the trypanosomes to cross the cell membranes of the tsetse gut cells. There is also the possibility that the parasites may travel up (or down) within the haemocoelomic membrane; outside the gut epithelial cells, to some suitable point of exit; or possibly remain within the membrane near the external membrane of the salivary gland.

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.

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 bugRhodnius prolixus byTrypanosoma 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 appeared similar to, and often actually part of, the basement membrane of the gland cells. These outer “membranes” were found to enclose large numbers of multinuleate “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.

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

SummaryCongo-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.

The behaviour of trypanosomes within the midguts of wild-caught tsetse from Zimbabwe

Trypanosomes infecting the midgut of wild-caught tsetse from Zimbabwe were found on electron microscopic examination to be penetrating the peritrophic membranes and so entering the ecto-peritrophic space in the mycetome region of the midgut. Other trypanosomes entered midgut cells, behaviour similar to that previously reported in laboratory-infected tsetse colonies.

Acute Liver Failure Due to Adenoviral Hepatitis in a Pediatric Liver Transplant

Adenoviral infection is a significant cause of morbidity and mortality in immunocompromised patients in the pediatric age group, hepatitis caused by the serotype 5 being the most common manifestation in the liver transplant recipient. The authors report a case of a 3 1/2-year-old child in whom fatal adenoviral hepatitis developed after liver transplantation for syndromic paucity of the intrahepatic bile ducts. Allograft biopsy at 14 days showed early changes of microabscesses in the parenchyma but no inclusions. Immunohistochemistry using an adenovirus-group antibody (MAB805, Chemicon International, Harrow, England), however, demonstrated nuclear positivity in hepatocytes related to and at a distance from the lesions. As antibody titers are unreliable in an immunocompromised patient and culture results take time, immunohistochemistry for adenovirus offers a rapid diagnosis. The technique is economic and has a clear advantage on the more demanding electron microscopic screening, which was performed in the case as additional evidence. Immunohistochemistry for adenovirus should be done routinely in the presence of microabscesses to differentiate the lesion from hepatitis due to cytomegalovirus. Int J Surg Pathol 3(3) :189-194, 1996

A Simple Vacuum Pipette For Processing Groups Of Specimens For Electron Microscopy

A standard sink filter pump attached to a special glass adaptor, holding pipettes, enables groups of specimens to be fixed and dehydrated for electron microscopy with speed and safety.

A brief note on an arrangement of sub-pellicular tubules in trypanosomes

Early work using electron microscopy in the study of trypanosomes revealed fibrillar structures beneath the pellicle (Kleinschmidt 1951). As better techniques of fixation (Sabatini et al. 1963) and embedding (Glauert et al. 1956) were introduced, it was found that these structures were tubules and that they decreased in number at each end of the trypanosome (Figs. 1 and 2) down to as few as five or six, while over 100 could be counted in central regions (Fig. 3). These tubules spiralled around the organism, making it difficult to obtain easily countable transverse sections of them in serial sections, though the decrease in numbers towards the ends of the organism was always obvious, Meyer and De Sousa (1976) demonstrated a clear spacing pattern in Trypanosoma cruzi which was further analysed by Dvorak (1979), but a minor problem has existed as to how the numbers of these tubules were reduced; did adjacent tubules fuse to reduce the total number, or did some tubules simply end and their neighbours close ranks to maintain to regular spacing pattern s e e n throughout the length of this trypanosome? The sections shown in the figures are of metacyclic forms of Trypanosoma brucei brucei stock, LUMP 1144 (one mouse passage from TREU 667) found in the salivary glands of Glossina morsitans morsitans (from the Tsetse Research Laboratory, Bristol, England). The glands were fixed by the special technique of Ledingham and Simpson (1972), using p-phenylene-diamine to enhance the contrast in the salivary glands. Although this fixation technique does not provide for as good preparations as the glutaraldehyde-osmium tetroxide method employed for blood stream and midgut forms of salivarian trypanosomes (eg, Evans et al. 1979), it yields quite satisfactory preparations of the salivary gland forms, which are notoriously difficult to fix. Figure 4 shows the ending of two tubules beneath the pellicle of a trypomastigote in the lumen of the salivary gland, where no fusion has taken place, but where the adjacent tubules have closed up to maintain the regular spacing intervals. Presumably this is the mechanism used in trypanosomes to reduce the number of subpellicular tubules progressively towards each end of the body of the organism. This information came from a section cut at just the right