In trypanosomes, the large mitochondrial genome within the kinetoplast is physically connected to the flagellar basal bodies and is segregated by them during cell growth. The structural linkage enabling these phenomena is unknown. We have developed novel extraction/fixation protocols to characterize the links involved in kinetoplast-flagellum attachment and segregation. We show that three specific components comprise a structure that we have termed the tripartite attachment complex (TAC). The TAC involves a set of filaments linking the basal bodies to a zone of differentiated outer and inner mitochondrial membranes and a further set of intramitochondrial filaments linking the inner face of the differentiated membrane zone to the kinetoplast. The TAC and flagellum-kinetoplast DNA connections are sustained throughout the cell cycle and are replicated and remodeled during the periodic kinetoplast DNA S phase. This understanding of the high-order trans-membrane linkage provides an explanation for the spatial position of the trypanosome mitochondrial genome and its mechanism of segregation. Moreover, the architecture of the TAC suggests that it may also function in providing a structural and vectorial role during replication of this catenated mass of mitochondrial DNA. We suggest that this complex may represent an extreme form of a more generally occurring mitochondrion/cytoskeleton interaction. INTRODUCTIONThe African trypanosome Trypanosoma brucei belongs to a large order of pathogenic and free-living flagellated protozoa designated the kinetoplastida. The majority of these organisms possess a single mitochondrion containing a structural mass of proteins and catenated circular DNA molecules, the kinetoplast. The kinetoplast is essential for survival and cyclical transmission of the parasite between mammalian host and tsetse fly. Early light microscope descriptions of trypanosomes recognized the precise location of the kinetoplast in proximity to the base of the flagellum (Robertson, 1912(Robertson, , 1913. The positions of the flagellum and kinetoplast have become the central features in classifying the different life cycle stages of kinetoplastids (Hoare and Wallace, 1966;Vickerman, 1976). Electron microscopy revealed the kinetoplast to be a highly complex disk-shaped structure located within a distended portion of the mitochondrial matrix adjacent to the flagellum basal bodies (Vickerman, 1973). The T. brucei kinetoplast consists of multiple copies of topologically interlocked circular DNA molecules termed maxicircles and minicircles, along with specific kinetoplast proteins. The maxicircle composition of the T. brucei network is 25-50 copies and represents 10% of the network mass (each maxicircle is 20 kb and all have identical DNA sequence). Maxicircles encode the mitochondrial proteins and some guide RNAs (gRNAs), whereas the minicircles are present in several thousand copies (1 kb in length), are heterogeneous in sequence, and encode gRNAs. The gRNAs are essential for the RNA editing process whereby the maxic...
The structural basis of mitosis, spindle organisation and chromosome segregation, in the unicellular parasite Trypanosoma brucei is poorly understood. Here, using immunocytochemistry, fluorescent in situ hybridisation and electron microscopy, we provide a detailed analysis of mitosis in this parasite. We describe the organisation of the mitotic spindle during different stages of mitosis, the complex ultrastructure of kinetochores and the identification of a potential spindle-organising centre in the mitotic nucleus. We investigate the dynamics of chromosome segregation using telomeric and chromosome-specific probes. We also discuss the problems involved in chromosome segregation in the light of the fact that the T. brucei karyotype has 22 chromosomes in the apparent presence of only eight ultrastructurally defined kinetochores.
Studies to determine the effect of some Nigerian Medicinal plants on some haematological parameters of rats infected with T. b. brucei was carried out. The plants investigated and the dose levels per kilogram body weights used are fresh Momordica balsamina pulp (150mg); fresh Aloe vera pulp (1ml); aqueous extracts of Securidaca longipenduculata root and root bark (100mg) and Annona senegalensis leaves (200mg). All the animals were treated orally for seven consecutive days after establishment of parasitaemia. Parasitaemia and some haematological parameters were determined before and after treatment as well as pathochemical composition of each plant. The result showed a significant (P < 0.05) improvement in Packed Cell Volume (PCV) values of rats treated with M. balsamina; A. vera and S. longipenduculata (root bark) when compared with the positive control. Total leukocyte and lymphocyte counts did not change significantly (P > 0.05) in groups treated with M. balsamina and S. longipenduculata (root bark) but increased in other treated and positive control groups. Similarly, no significant changes (P > 0.05) in neutrophils was observed in M. balsamina and S. longipenduculata (root) treated animals but an increase was seen in S. longipenduculata (root bark), A. vera and infected on treated groups. Treatment with M. balsamina, A. vera and S. longipenduculata (root and root bark) prolonged the lives of animals by 4, 1, 3 and 4 days respectively when compared with the positive control. Differences in the composition of various phytochemical of these plants could be responsible for the varied antitrypanosomal activities. Consequently, these plants have great potential which need to be exploited fully in the management of African trypanosomiasis.
an online international journal allowing free unlimited access to abstract and full-text of published articles. The journal is devoted to the promotion of health sciences and related disciplines (including medicine, pharmacy, nursing, biotechnology, cell and molecular biology, and related engineering fields). It seeks particularly (but not exclusively) to encourage multidisciplinary research and collaboration among scientists, the industry and the healthcare professionals. It will also provide an international forum for the communication and evaluation of data, methods and findings in health sciences and related disciplines. The journal welcomes original research papers, reviews and case reports on current topics of special interest and relevance. All manuscripts will be subject to rapid peer review. Those of high quality (not previously published and not under consideration for publication) will be published without delay. The maximum length of manuscripts should normally be 10,000 words (20 single-spaced typewritten pages) for review, 6,000 words for research articles, 3,000 for technical notes, case reports, commentaries and short communications. Submission of Manuscript:The International Journal of Health Research uses a journal management software to allow authors track the changes to their submission. All manuscripts must be in MS Word and in English and should be submitted online at http://www.ijhr.org. Authors who do not want to submit online or cannot submit online should send their manuscript by e-mail attachment (in single file) to the editorial office below. Submission of a manuscript is an indication that the content has not been published or under consideration for publication elsewhere. Authors may submit the names of expert reviewers or those they do not want to review their papers. Results: Hexane extract, at a dose of 400 mg/kg body weight and aqueous extract at a dose of 300 mg/kg body weight, cured the experimental infection in mice. Blood and CSF infectivity tests confirmed cure of infected animals. Enquiries Conclusion:The two different extracts of the same plant being efficacious brings hope that appropriate combinations of preparations from these extracts or preparations thereof may help in overcoming the problem of resistance, a major limitation of current chemotherapy, since the different extracts may be acting by different mechanisms.
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