Browsing by Author "Jura, W.G.Z.O."
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Item Fine Structure and Invasive Behaviour of the Early Developmental Stages of Theileria Annulata In Vitro(1983) Jura, W.G.Z.O.; Brown, C.G.D.; Kelly, B.J.V.P.; Centre for Tropical Veterinary Medicine, Easter Bush, Roslin, Midlothian, EH25 9RG Gt. BritainThe interaction, in vitro, between bovine peripheral blood by lymphocytes and sporozoites of Theileria annulata (Ankara) was studied by light and electron microscopy. Beginning five minutes following incubations, samples were taken for Giesma-stained smears and glutaraldehyde-fixed pelletes, for light and electron microscopy, respectively. Sporozoites of T. annulata measure an average of 0.9 μm long, 0.8 μm broad and posses a limiting unit membrane, the pellicle; a round-to-ovoid, eccentrically situated, non-chromocentric nucleus, double-membraned, tubular, acristate mitochondria, varying numbers of anisocytic, densely osmiophilic and pleomorphic organelles, the rhoptries which together with the polar ring form the apical complex; and numerous, loosely scattered, electron-dense ribosomal particles. As early as 5 min of incubation, sporozoites had made contact with, and penetrated, lymphocytes. Sporozoites consistently attached to the lymphocyte plasmalemma by their basal end, possibly at specific receptor sites. Apparently only a proportion of lymphocytes (up to 40% and more commonly 10–20%) were susceptible. Two subpopulations of the susceptible lymphocytes were observed; one which appeared to have receptor sits localized on one pole of the plasmalemma and the other subpopulation in which the receptor sites were distributed evenly around the plasmalemmal surface. With individual susceptible lymphocytes, the number of interiorized sporozoites increased from 1 to 3 at 5–10 min to as many as 15 or more parasites at around 60 min of incubation. Theileria annulata sporozoites were interiorized by the invagination of the host cell palsmalemma which remained intact throughout the process but the later fragmented. Within 30 min of interiorization, each sporozoite underwent dedifferentiation by the loss of its rhoptries and transformed into a trophozoite. Around 24 h, the trophozoite, a uninucleate, motile and feeding stage of the parasite, developed into a schizont an acentric, closed mitosis.Item An In Vitro Study of the Relative Importance of Bile and Carbon Dioxide in the Activation of Fasciola Gigantica Metacercariae(1976) Hanna, R.E.B.; Jura, W.G.Z.O.; East African Veterinary Research Organisation, Muguga, PO Box 32, Kikuyu, KenyaThe relative importance of bile and atmospheric stimuli in activating metacercariae of Fasciola gigantica prior to excystment has been studied by omitting each in turn from the in vitro excystment medium, and by separating each from the period of incubation at 37°C. The results indicate that bile is less important than carbon dioxide in triggering excystment, and may serve only to increase the permeability of the cyst wall to carbon dioxide. It is speculated that activation involves initiation of carbon dioxide fixation and anaerobic metabolism due to the high concentration of carbon dioxide and low redox potential prevalent in the gut.Item The Integrity of Host Lymphocyte Plasma lemma During Its Invasion by Theileria Annulata Sporozoites as Demonstrated by Ruthenium Red Staining(1984/1985) Jura, W.G.Z.O.; Veterinary Research Department, K.A.R.I., Muguga,The integrity of host lymphocyte plasma membrane during its invasion by Theileria annulata sporozoites !was examined in an in vitro system using ruthenium red staining. It was demonstrated that during interiorisation of the sporozoites, the dye was completely excluded from the intracellular milieu, indicating that the continuity of the host-cell plasmalemma was not disrupted throughout the process of penetration, and confirmed a previous observation that the fragmentation of the host lymphocyte membrane only occurs later, after the parasite is intracellular.Item Metabolic Energy Pathways in Theileria Annulata Sporozoites and Their Significance in Sporozoite-Bovine Lymphocyte Interactions in Vitro(1984/1985) Jura, W.G.Z.O.; Brown, C.G.D.; Brocklesby, D.W.; Centre for Tropical Veterinary Medicine,The existence of metabolic energy pathways has been studied in extracellular T. annulata sporozoites using chemicals known to inhibit specific energy-generating pathways, and their role during invasion of bovine peripheral blood lymphocytes (PBL) by thesporozoites determined in an in vitro system. An inverse relationship was depicted between the dose of various chemicals and the number of T. annulata sporozoites invading PBL: as the concentrations of the inhibitor drugs increased, the number of T. annulata sporozoites within the lymphocytes decreased. An ultracytochemical study demonstrated the presence of the respective pathway marker enzymes, i.e., lactic dehydrogenase (LDH) in the cytosol and within mitochondria, succinic dehydrogenase (SDH) on the mitochondrial membranes and in the contiguous matrix, and cytochrome oxidase (CO) between the inner and outer mitochondrial membranes, in infective T. annulata sporozoites fixed in situ within whole salivary glands of 3-day fed Hyalomma anatolicum anatolicum ticks.Item Ultrastructural Characteristics of In Vitro Parasite-Lymphocyte Behaviour in Invasions with Theileria Annulata and Theileria Parva(1983) Jura, W.G.Z.O.; Brown, C.G.D.; Rowland, A.C.; Centre for Tropical Veterinary Medicine, The University of Edinburgh, Easter Bush, Roslin, Midlothian, EH25 9RG Gt. Britain; Department of Veterinary Pathology, Veterinary Field Station, The University of Edinburgh, Easter Bush, Roslin, Midlothian, EH25 9RG Gt. BritainHost-parasite relationships have been studied by electron microscopy using glutaraldehyde—OsO4 -fixed pellets of lymphoid cultures infected in vitro by Theileria annulata and T. parva. Intracellular presence of the parasite resulted in a progressive and marked lymphoblastoid transformation. The schizont stage periodically provoked the formation of, and adopted an intimate association with, cytoplasmic annulate lamellae in the interphase cell. Annulate lamellae developed from the outer nuclear membrane of the host cell by a delamination process and were taken into the cytoplasmic matrix of the schizont by phagotrophy through the cytostome. Schizont nuclei themselves were seen to divide at the prometaphase stage of host cell mitosis, the division being characterized by the development of intranuclear spindle microtubules anchored in spindle pole bodies. A hypothesis is propounded that Theileria parasites, consequent on interiorization, provoke the blastoid transformation and the formation of annulate lamellae through the influence of components of their genomic material on host cell deoxyribonucleic acid (DNA) and that the annulate lamellae represent a species of messenger ribonucleic acid (mRNA) and serve as a monitoring device for the schizont, facilitating the accurate timing of the host cell cyclical events.
