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H J Els

Publications and source records attributed to H J Els.

At least 37 records · Page 2Linked to original sources
PubMed1979

An electron microscopic study of intra-erythrocytic stages of Babesia bovis in the brain capillaries of infected splenectomized calves.

Splenectomized vaccine donor calves undergoing primary reactions to Babesia bovis infections may develop cerebral babesiosis which leads to death if not treated in time. A brain biopsy was performed on an artificially-infected animal showing nervous symptoms and the tissue was immediately processed for electron microscopic examination. Virtually every erythrocyte in the brain capillaries sectioned was infected with B. bovis. Intra-erythrocytic merozoites, trophozoites and dividing trophozoites were indentified. Important features of the piriform merozoites included a reduced apical complex consisting of the anterior polar ring, microtubules, rhoptries and micronemes. Unidentified membrane-bound bodies, mostly spherical in shape, were observed anterior to the nucleus. The trophozoites showed very little structural differentiation and no food vacuoles or micropores could be detected. Each trophozoite produced 2 identical merozoites and the parent cell became totally incorporated in the daughter merozoites in the multiplication process. Projections were seen radiating from the surface of infected erythrocytes which appeared to adhere to other surfaces on contact. This probably resulted in the sludging of infected erythrocytes in the capillaries. The latter observations coincide with those described for Babesia argentina.

Animals↗
PubMed1979

Viruses isolated from Culicoides midges in South Africa during unsuccessful attempts to isolate bovine ephemeral fever virus.

Five viruses, unrelated to bovine ephemeral fever virus (BEFV), were isolated from Culicoides biting-midges collected during the summer months of the years 1968-69 and 1969-70 near a cattle herd in which cases of BEF occurred and at an open horse stable at Onderstepoort. These viruses were investigated by means of serological, electron-microscopical and physicochemical tests. It was established that 2 isolates, Cul. 1/69 and Cul. 2/69, were related to each other and belonged to the Palyam subgroup of the genus Orbivirus, that isolate Cul. 3/69 belonged to the equine encephalosis subgroup of the genus Orbivirus, while Cul. 1/70 was related to Akabane virus, which belongs to the Simbu subgroup of the family Bunyaviridae. One isolate, Cul. 5/69, though prevalent in the cattle population, could not be identified at this point. A brief serological survey indicated that the cattle in the nearby herd possessed antibodies against all the isolates except Cul. 3/69. BEFV could not be isolated in mice or in cultured cells from the wild-caught Culicoides.

Animals↗
PubMed1977

Light and electron microscopic observations on the development of Babesia bigemina in larvae, nymphae and non-replete females of Boophilus decoloratus.

In Boophilus decoloratus infected by transovarian passage with B. bigemina, primary schizogony occurred as a continuous repetitive process in all 3 stages of the tick's life cycle spent on the host. The primary schizonts and the large merozoites (= vermicules) produced by them were observed in the gut epithelium, haemocytes, muscles, ad peritracheal cells. Secondary schizogony which led to the formation of small merozoites (= infective forms) occurred mainly in the salivary glands, but was also observed in the cortex of the synganglion. Mature small merozoites were observed in nymphal and adult ticks only. An infective stabilate was prepared from nymphae collected on Day 14 and Day 15 post larval infestation. The infections resulting from intravenous injection of the stabilate had a prepatent period of 8 days.

Animals↗
PubMed1977

The fine structure of intra-erythrocytic stages of Babesia bigemina.

The electron microscope was used to study the structure of merozoites, merozoites in the process of transformation to trophozoites, trophozoites, and the method of multiplication of B. bigemina. The merozoites were piriform in shape and surrounded by 3 peripheral membranes of which the 2 inner ones often appeared as a single thick osmiophilic structure (inner membrane). Anterior and posterior polar rings, microtubules, micronemes, rhoptries and mitochondria with and without tubular cristae were discernible. A single large unidentified spherical body was present in most of the mature merozoites. After penetration of an erythrocyte, merozoites developed into trophozoites through a transformation process which involved the loss of the inner membrane of the pellicle, rhoptries, most of the micronemes and the spherical body. The trophozoites were surrounded by a single membrane, were pleomorphic in shape and contained large inclusions of host cell cytoplasm, but no cytostomes or food vacuoles could be identified. Reproduction took place through a process resembling schizogony resulting in the production of 2 merozoites, the cytoplasmic constituents of the original trophozoite (mother cell) being virtually entirely incorporated into the daughter cells in the process. None of the parasites were contained in parasitophorous vacuoles.

Animals↗
PubMed1977

Negative staining of a non-haemadsorbing strain of African swine fever virus.

Since the application of negative staining, preceded by fixation, prevents the disruption and distortion of the capsid of the African swine fever virus, improved contrast and evaluation of the appearance and size of virus particles in the electron microscope is possible and, in addition, the icosahedral shape of the virus is demonstrable. The mature virus particle contains at least 2 capsid layers and an outer envelope.

African Swine Fever Virus↗
PubMed1976

Light and electron microscopic observations on the development of small merozoites of Babesia bovis in Boophilus microplus larvae.

The development of small pyriform merozoites of B. bovis in the granule-secreting cells of the salivary glands of B. microplus larvae, studied with a light microscope, showed a close resemblance to that of B. argentina described by Riek (1966) in the same tick vector. Dvelopment took place through a process of schizogony and resulted in the formation of many merozoites. A study of the ultrastructure of developing merozoites in the schizont revealed the following: a poorly defined outer membrane; a granular osmiophilic inner membrane; anterior and posterior polar rings; rhoptries; micronemes; microtubules; a nucleus; spherical bodies of varying size. The schizonts were membrane-bound but no parasitophorous vacuoles were seen.

Animals↗
PubMed1976

Transmission of jaagsiekte (ovine pulmonary adenomatosis) by means of a permanent epithelial cell line established from affected lungs.

An epithelial cell line, designated JS-15,4, has been established in culture from jaagiekte lesions and subcultured in vitro for almost 2 years. It exhibits morphological and other features of transformed cells and has been shown by electron microscopy to consist of type B ovine alveolar epithelial cells. Jaagiekte was successfully transmitted to 3 new-born lambs by the intratracheal injection of cells following immunosuppressive treatment with either anti-thymocyte immunoglobulin alone or combined with anti-macrophage immunoglobulin. Incubation periods as short as 10 weeks were recorded. Evidence was also obtained that natural transmission may result from the inhalation of viable cells.

Aneuploidy↗
PubMed1976

The fine structure of merozoites of Babesia bovis in the gut epithelium of Boophilus microplus.

Electron microscopic studies on merozoites of Babesia bovis in epithelial cells of the gut of Boophilus microplus revealed that the pellicle apparently consists of 3 membranes, and an osmiophilic layer intimately associated with microtubules. Micropores in the pellicle were often associated with micronemes. An unidentified tubular structure extended from the anterior polar ring to the nuclear region where it appeared to be associated with the nuclear envelope. A Golgi complex, typical protozoan mitochondria, food vacuoles and rhoptries could not be identified.

Animals↗
PubMed1975

Characteristics of an ovine herpesvirus associated with pulmonary adenomatosis (jaagsiekte) in sheep.

The isolation of an ovine herpesvirus from a cell culture of an adenomatous sheep lung is reported, confirming previous observations of a possible association of a herpesvirus with this tumour. Some growth properties and morphological characteristics of the virus are described, as well as serological data supporting a possible relationship between tumour and virus. Attempts to produce jaagsiekte by intratracheal injection of virus into lambs were unsuccessful, suggesting that a second factor may be involved inthe oncogenic process possibly similar to that proposed for the well-known EBV-Burkitt's lymphoma system.

Animals↗
PubMed1972

Structure of the bluetongue virus capsid.

Seven polypeptides were found to be present in the capsid of the bluetongue virus (BTV), four of which are major and three are minor components. This number and size distribution is the same as that found in reovirus, which has a similar segmented, double-stranded ribonucleic acid genome. In both viruses an excellent correlation is found between the molecular weights of certain genome segments and those of the polypeptides, suggesting a direct coding relationship between them. Careful comparison, however, indicates that the correlation patterns of the two viruses are different, suggesting that different genome segments may be utilized to code for certain capsid proteins. This phenomenon may be related to the fact that these viruses can be distinguished morphologically, reovirus having a larger diameter and possessing a double-layered capsid against the smaller single capsid of the BTV. Utilizing the degrading effect of CsCl gradients, it was demonstrated, however, that two of the BTV polypeptides are present as a diffuse protein layer surrounding the capsid. This outer layer probably has some of the functions of the reovirus outer capsid, one being the "masking" of a viral transcriptase which could be demonstrated after its removal.

Animals↗