2,071 research outputs found
Disruption of the developmental programme of Trypanosoma brucei by genetic ablation of TbZFP1, a differentiation-enriched CCCH protein
Full text linkThe regulation of differentiation is particularly important in microbial eukaryotes that inhabit multiple environments. The parasite Trypanosoma brucei is an extreme example of this, requiring exquisite gene regulation during transmission from mammals to the tsetse fly vector. Unusually, trypanosomes rely almost exclusively on post-transcriptional mechanisms for regulated gene expression. Hence, RNA binding proteins are potentially of great significance in controlling stage-regulated processes. We have previously identified TbZFP1 as a trypanosome molecule transiently enriched during differentiation to tsetse midgut procyclic forms. This small protein (101 amino acids) contains the unusual CCCH zinc finger, an RNA binding motif. Here, we show that genetic ablation of TbZFP1 compromises repositioning of the mitochondrial genome, a specific event in the strictly regulated differentiation programme. Despite this, other events that occur both before and after this remain intact. Significantly, this phenotype correlates with the TbZFP1 expression profile during differentiation. This is the first genetic disruption of a developmental regulator in T. brucei. It demonstrates that programmed events in parasite development can be uncoupled at the molecular level. It also further supports the importance of CCCH proteins in key aspects of trypanosome cell function
Theoretical frameworks for the learning of geometrical reasoning
No full textWith the growth in interest in geometrical ideas it is important to be clear about the nature of geometrical reasoning and how it develops. This paper provides an overview of three theoretical frameworks for the learning of geometrical reasoning: the van Hiele model of thinking in geometry, Fischbein’s theory of figural concepts, and Duval’s cognitive model of geometrical reasoning. Each of these frameworks provides theoretical resources to support research into the development of geometrical reasoning in students and related aspects of visualisation and construction. This overview concludes that much research about the deep process of the development and the learning of visualisation and reasoning is still needed
Michael Rodriguez interviews historian and author Keith Widder
No full textHistorian and author Keith Widder talks about his move to Michigan from Wisconsin, his career as Curator of History for the Mackinac Island State Park Commission, his research interests, his book "Michigan Agricultural College", and his current projects. Widder is interviewed by Michigan State University Librarian Michael Rodriguez for the MSU Libraries' Michigan Writers Series. Held in the MSU Main Library
Canthochilum ciboney Matthews 1969
No full textCanthochilum ciboney Matthews, 1969 Figs. 39, 47 A single male was reported from Mt. Trou d'Eau, Haiti (18 º42.1’N 72 º03.1’W) by Matthews (1969). This locality is just north of the Enriquillo Depression, near the Dominican border. We have seen additional specimens from the Sierra de Baoruco in the southwest Dominican Republic. Specific records include: DOMINI- CAN REPUBLIC: 3 — Prov. Pedernales, 26 km N. Cabo Rojo, 825m, 21 AUG 1992 – 09 SEP 1992, D. S. Sikes & P. Ward, flight intercept trap (WIBF); 3 — Prov. Pedernales, 24 km N. Cabo Rojo, 610m, 20 AUG – 0 9 SEP 1988, M. A. Ivie, T. K. Philips & K. A. Johnson, flight intercept trap (WIBF); 7 — Prov. Barahona, nr. Filipinas, Larimar Mine, 20–26 JUNE 1992, R. E. Woodruff & P. E. Skelly (PESC); 3 – Pedernales Prov. Sierra Baoruco, 31 km N. Cabo Rojo, 2500 ’, XII- 29-1986, Doyen & Santiago/ broad leaf mesophyll association/ ex flight trap (UCBC). 1 — Prov. Pedernales, 24 km N. Cabo Rojo, 665m, 22 JULY –09 AUG 1999, M. A. Ivie, K. A. Guerrero, R. S. Miller & M. Branham (WIBF).Published as part of Philips, Keith & Ivie, Michael A., 2008, Seven new species of Canthochilum Chapin from Hispaniola (Coleoptera: Scarabaeidae: Scarabaeinae), pp. 27-42 in Zootaxa 1730 on page 38, DOI: 10.5281/zenodo.18129
Interview with Keith R. A. DeCandido
No full textTWC interviews Keith R. A. DeCandido, author of Supernatural tie-in novels Nevermore, Bone Key, and Heart of the Dragon
The shaping of student knowledge: learning with dynamic geometry software
No full textThe focus of this paper is a software genre usually referred to as ‘dynamic geometry’ because of the ability of the user to dynamically manipulate geometrical figures created with the software tool. Using data from a longitudinal study of 12-13 students’ use of dynamic geometry software, the focus of the analysis is on the interpretations the students make of geometrical objects and relationships when using this form of software. The analysis suggests that the students’ mathematical reasoning is shaped by their interactions with the software in that their ability to explain geometrical facts and relationships evolves from imprecise, ‘everyday’ expressions, through reasoning that is overtly mediated by the software environment, to mathematical explanations of the geometric situation that transcend the particular tool being used. Such findings suggest that curriculum initiatives that encourage the use of dynamic geometry software are appropriate but that the incorporation of such software into classroom practices is unlikely to be straightforward
The developmental cell biology of Trypanosoma brucei
Full text linkTrypanosoma brucei provides an excellent system for studies of many aspects of cell biology, including cell structure and morphology, organelle positioning, cell division and protein trafficking. However, the trypanosome has a complex life cycle in which it must adapt either to the mammalian bloodstream or to different compartments within the tsetse fly. These differentiation events require stage-specific changes to basic cell biological processes and reflect responses to environmental stimuli and programmed differentiation events that must occur within a single cell. The organization of cell structure is fundamental to the trypanosome throughout its life cycle. Modulations of the overall cell morphology and positioning of the specialized mitochondrial genome, flagellum and associated basal body provide the classical descriptions of the different life cycle stages of the parasite. The dependency relationships that govern these morphological changes are now beginning to be understood and their molecular basis identified. The overall picture emerging is of a highly organized cell in which the rules established for cell division and morphogenesis in organisms such as yeast and mammalian cells do not necessarily apply. Therefore, understanding the developmental cell biology of the African trypanosome is providing insight into both fundamentally conserved and fundamentally different aspects of the organization of the eukaryotic cell
Canthochilum darlingtoni Matthews 1969
No full textCanthochilum darlingtoni Matthews, 1969 Fig. 41 Matthews (1969) described this species from Sánchez, on the north coast of the Dominican Republic, and Pico Quita Espuela, highest peak in the Cordillera Septentrional, in Prov. Duarte. We have seen additional specimens from the Cordillera Central and Parque Nacional Los Haitises. Specific records include: DOMINI- CAN REPUBLIC: 1 — Prov. La Vega, nr. Buena Vista, Hotel LaMontafta (19 º12.1’N 70 º35.1’W), 610m, 04– 10 APR 1992, M. A. Ivie, carrion trap (WIBF); 3 — ibid, 9–12 APR 1992, dung baited pitfal (WIBF); 4 — Prov. LaVega, 12 km NE Jarabacoa, 550m, 01–07 SEP 1988, M. A. Ivie, T. K. Philips & K. A. Johnson (WIBF); 8 — Prov. Hato Mayor, W. of Sabana de la Mar, Parque Nacional Los Haitises, bosque humido, 01– 16 APR 1992, M. A. Ivie, D. S. Sikes & W. Lanier, dung baited pitfall trap (WIBF); 2 — ibid, flight intercept trap (WIBF); 4 — ibid, 16 APR 1992, pitfall trap (WIBF); 2 — ibid, flight intercept trap (WIBF); 2 — ibid, 0 1 July 1992, M. A. & R. 0. Ivie (WIBF); 1 — Prov. Hato Mayor, Parque Nacional Los Haitises, 19 º 51 ’N 69 º29.1’W, 0 m, 16 July 1993, litter in butresses, D. Sikes (WIBF); 1 — La Vega Prov., 10 km NE Jarabacoa, Hotel Montana, forest, 18.VII– 4.VIII. 95, 550 m, FIT, S + J Peck, 95 - 30 (TKPC).Published as part of Philips, Keith & Ivie, Michael A., 2008, Seven new species of Canthochilum Chapin from Hispaniola (Coleoptera: Scarabaeidae: Scarabaeinae), pp. 27-42 in Zootaxa 1730 on page 39, DOI: 10.5281/zenodo.18129
Developmental incompetence in selected and naturally occurring Trypanosoma isolates
Full text linkTrypanosoma brucei has two distinct life stages in its mammalian host. The proliferative ‘slender’ form develops into a cell-cycle arrested ‘stumpy’ form at high parasite density.
This transition occurs in a density-dependent quorum sensing (QS) like process, for which critical molecular regulators have been identified. Naturally occurring T. brucei subspecies (T. b. evansi and T. b. equiperdum) have reduced ability to generate the stumpy form and are described as ‘monomorphic’.
Utilising whole genome sequences of 41 naturally occurring monomorphic isolates, we corroborate previous studies in identifying at least four independent monomorphic T. brucei clades. Mutations in six genes were then explored for their contribution to monomorphism. The orthologous gene sequences were synthesised and used to replace wild-type alleles, via CRISPR-Cas9, in developmentally competent T. brucei. The replacement of two targets with the monomorphic mutant sequence reduced the ability to generate stumpy forms in developmentally competent cells. Furthermore, we identified mutations associated with cell proliferation and motility phenotypes. We also selected monomorphic cell lines from a pleomorphic population and confirmed significant downregulation of transcripts of a developmental regulator, ZC3H20, during the progression to monomorphism. In vitro overexpression of ZC3H20 in the selected monomorphic cells restored pleomorphism.
Independently selected monomorphic lines generated in vitro were also found to show consistently altered regulation of several transcripts, hinting that the initial steps to monomorphism may share similarities in discrete populations. We suggest that, in the field, monomorphism develops on a spectrum via modifications to the regulation of key QS genes, which can be reversed in the first instance. As the scale tips towards developmental incompetence, mutations accrue in key QS genes which lock the parasites in a monomorphic phenotype. This provides insight into the molecular control of the QS process and possible diagnostic tools to anticipate increased virulence in the field
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