Nombre chromosomique de quelques Angiospermes marocaines

Se indican los números cromosómicos de cinco taxones pertenecientes a cinco familias de Angiospermas de Marruecos: Allium porrum 2n=32; Armeria simplex 2n=18; Asphodelus ramosus subsp. ramosus n=28; Delphinium nanum subsp. nanum 2n=16 et Dipcadi serotinum 2n=8 et 32. Cada taxon se acompaña de una fotografía en mitosis o meiósis así como de un breve comentario."Chromosome numbers of some Moroccan angiosperm". Chromosome numbers of five taxa from five families of Moroccan angiosperms are reported: Allium porrum 2n=32; Armeria simplex 2n=18; Asphodelus ramosus subsp. ramosus n=28; Delphinium nanum subsp. nanum 2n=16 and Dipcadi serotinum 2n=8 and 32. Mitotic or meiotic metaphases microphotographs and brief comments are detailed for each taxa studied

The presence of valine at residue 129 in human prion protein accelerates amyloid formation

The polymorphism at residue 129 of the human PRNP gene modulates disease susceptibility and the clinicopathological phenotypes in human transmissible spongiform encephalopathies. The molecular mechanisms by which the effect of this polymorphism are mediated remain unclear. It has been shown that the folding, dynamics and stability of the physiological, alpha-helix-rich form of recombinant PrP are not affected by codon 129 polymorphism. Consistent with this, we have recently shown that the kinetics of amyloid formation do not differ between protein containing methionine at codon 129 and valine at codon 129 when the reaction is initiated from the a-monomeric PrPC-like state. In contrast, we have shown that the misfolding pathway leading to the formation of beta-sheet-rich, soluble oligomer waS favoured by the presence of methionine, compared with valine, at position 129. In the present work, we examine the effect of this polymorphism on the kinetics of an alternative misfolding pathway, that of amyloid formation using partially folded PrP allelomorphs. We show that the valine 129 allelomorph forms amyloids with a considerably shorter lag phase than the methionine 129 allelomorph both under spontaneous conditions and when seeded with pre-formed amyloid fibres. Taken together, our studies demonstrate that the effect of the codon 129 polymorphism depends on the specific misfolding pathway and on the initial conformation of the protein. The inverse propensities of the two allelomorphs to misfold in vitro through the alternative oligomeric and amyloidogenic pathways could explain some aspects of prion diseases linked to this polymorphism such as age at onset and disease incubation time. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved

Variabilité chromosomique de neuf plantes medicinales au Maroc

Se indican los números cromosómicos de 9 taxones usados como medicinales en Marruecos: Carum carvi 2n=20; Coriandrum sativum n=11 y 2n=22; Cuminum cyminum 2n=14; Foeniculum vulgare subsp. dulce 2n=22; Nigella sativa 2n=12; Pennisetum typhoides 2n=14; Petroselinum crispum n=11 y 2n=22; Pimpinella anisum 2n=20 y Trigonella foenum-graecum 2n=16. La mayoría de estos números se indican por primera vez en poblaciones de Marruecos. Cada taxon se acompaña de una fotrografía en mitosis así como de un breve comentario.Chromosomal variability of some medicinal plants in Morocco. Chromosome numbers of nine plants used in Moroccan pharmacopoeia are reported: Carum carvi 2n=20; Coriandrum sativum n=11 and 2n=22; Cuminum cyminum 2n=14; Foeniculum vulgare subsp. dulce 2n=22; Nigella sativa 2n=12; Pennisetum typhoides 2n=14; Petroselinum crispum n=11 and 2n=22; Pimpinella anisum 2n=20 and Trigonella foenum-graecum 2n=16. Most of those numbers are reported for the first time in Moroccan populations. Mitotic metaphases microphotographs and brief comments are detailed for each taxa studied

Nombre chromosomique de quelques plantes a fleurs du Maroc

Se indican los números cromosómicos de once taxones pertenecientes a nueve familias de Angiospermas de Marruecos: Armeria simplex n = 9; Atriplex semibaccata 2n = 18; Cistanche phelypaea n = 20; Echium velutinum subsp. velutinum 2n = 16; Linaria bipartita n = 6; Lupinus cosentinii n = 16; Mesembryanthemum nodiflorum 2n = 38; Plantago amplexicaulis 2n = 10; Sonchus bourgeaui 2n = 16; Vicia lutea et Vicia pseudocracca n = 7. Nueve de estos números se indican por primera vez en poblaciones de Marruecos. Cada taxon estudiado se acompaña de un breve comentario y de la mayoría de ellos se aportan observaciones en mitosis o meiosis.Chromosome numbers of some flowering plants from Morocco. Chromosome numbers of eleven taxa from nine families of Moroccan angiosperms are reported: Armeria simplex n = 9; Atriplex semibaccata 2n = 18; Cistanche phelypaea n = 20; Echium velutinum subsp. velutinum 2n = 16; Linaria bipartita n = 6; Lupinus cosentinii n = 16; Mesembryanthemum nodiflorum 2n = 38; Plantago amplexicaulis 2n = 10; Sonchus bourgeaui 2n = 16; Vicia lutea and Vicia pseudocracca n = 7. Nine of those numbers were reported for the first time in Moroccan populations. Mitotic or meiotic metaphases microphotographs and brief comments are detailed for each taxa studied.Ministère de l’Enseignement Supérieur SVT 04 / 0

Parasitoses caprines dans la région de Chefchaouen: épidémiologie et prophylaxie

Cette étude épidémiologique des parasitoses caprines a été effectuée, de septembre 1993 à août 1994, dans la région de Chefchaouen (Rif). Les caprins conduits en élevage extensif sont exposés à un polyparasitisme interne et externe très diversifié. La population des strongles gastro-intestinaux, constituée de sept espèces, est maximale en décembre et en avril. Les strongles respiratoires composés principalement de protostrongylidés montrent une forte charge parasitaire en septembre, décembre et mai. Au niveau hépatique, le trématode Fasciola hepatica manifeste un pic bicuspidal automno-hivernal. Les parasitoses de moindre importance sont la monieziose et l'oestrose. Parmi les parasitoses transmises au caprin par le chien, la cysticercose hépato-péritonéale prédomine l'hydatidose. Les ectoparasites dominants sont les mallophages en hiver et les ixodidés en été. Un programme de traitement anthelminthique est proposé

Spectre multifractal : Applications aux images médicales

Dans cet article, nous proposons une méthode puissante pour la caractérisation et la segmentation des images médicales basée sur la géométrie fractale. Le principe de cette méthode en analyse d’images est justifié par l’auto-similarité d’une texture sur une résolution finie qui repose principalement sur l’estimation d’attributs fractals. Diverses méthodes ont été proposées pour estimer la dimension fractale. Dans ce travail nous développons une méthode basée sur le spectre multifractal de Hausdorff pour caractériser des images médicales CT-Scan. Les résultats obtenus démontrent l’intérêt de cette géométrie et son adaptabilité pour caractériser les altérations des textures osseuses saines et ostéoporotiques

Critical Role of the Virus-Encoded MicroRNA-155 Ortholog in the Induction of Marek's Disease Lymphomas

Notwithstanding the well-characterised roles of a number of oncogenes in neoplastic transformation, microRNAs (miRNAs) are increasingly implicated in several human cancers. Discovery of miRNAs in several oncogenic herpesviruses such as KSHV has further highlighted the potential of virus-encoded miRNAs to contribute to their oncogenic capabilities. Nevertheless, despite the identification of several possible cancer-related genes as their targets, the direct in vivo role of virus-encoded miRNAs in neoplastic diseases such as those induced by KSHV is difficult to demonstrate in the absence of suitable models. However, excellent natural disease models of rapid-onset Marek's disease (MD) lymphomas in chickens allow examination of the oncogenic potential of virus-encoded miRNAs. Using viruses modified by reverse genetics of the infectious BAC clone of the oncogenic RB-1B strain of MDV, we show that the deletion of the six-miRNA cluster 1 from the viral genome abolished the oncogenicity of the virus. This loss of oncogenicity appeared to be primarily due to the single miRNA within the cluster, miR-M4, the ortholog of cellular miR-155, since its deletion or a 2-nucleotide mutation within its seed region was sufficient to inhibit the induction of lymphomas. The definitive role of this miR-155 ortholog in oncogenicity was further confirmed by the rescue of oncogenic phenotype by revertant viruses that expressed either the miR-M4 or the cellular homolog gga-miR-155. This is the first demonstration of the direct in vivo role of a virus-encoded miRNA in inducing tumors in a natural infection model. Furthermore, the use of viruses deleted in miRNAs as effective vaccines against virulent MDV challenge, enables the prospects of generating genetically defined attenuated vaccines

Heterologous Amyloid Seeding: Revisiting the Role of Acetylcholinesterase in Alzheimer's Disease

Neurodegenerative diseases associated with abnormal protein folding and ordered aggregation require an initial trigger which may be infectious, inherited, post-inflammatory or idiopathic. Proteolytic cleavage to generate vulnerable precursors, such as amyloid-β peptide (Aβ) production via β and γ secretases in Alzheimer's Disease (AD), is one such trigger, but the proteolytic removal of these fragments is also aetiologically important. The levels of Aβ in the central nervous system are regulated by several catabolic proteases, including insulysin (IDE) and neprilysin (NEP). The known association of human acetylcholinesterase (hAChE) with pathological aggregates in AD together with its ability to increase Aβ fibrilization prompted us to search for proteolytic triggers that could enhance this process. The hAChE C-terminal domain (T40, AChE575-614) is an exposed amphiphilic α-helix involved in enzyme oligomerisation, but it also contains a conformational switch region (CSR) with high propensity for conversion to non-native (hidden) β-strand, a property associated with amyloidogenicity. A synthetic peptide (AChE586-599) encompassing the CSR region shares homology with Aβ and forms β-sheet amyloid fibrils. We investigated the influence of IDE and NEP proteolysis on the formation and degradation of relevant hAChE β-sheet species. By combining reverse-phase HPLC and mass spectrometry, we established that the enzyme digestion profiles on T40 versus AChE586-599, or versus Aβ, differed. Moreover, IDE digestion of T40 triggered the conformational switch from α- to β-structures, resulting in surfactant CSR species that self-assembled into amyloid fibril precursors (oligomers). Crucially, these CSR species significantly increased Aβ fibril formation both by seeding the energetically unfavorable formation of amyloid nuclei and by enhancing the rate of amyloid elongation. Hence, these results may offer an explanation for observations that implicate hAChE in the extent of Aβ deposition in the brain. Furthermore, this process of heterologous amyloid seeding by a proteolytic fragment from another protein may represent a previously underestimated pathological trigger, implying that the abundance of the major amyloidogenic species (Aβ in AD, for example) may not be the only important factor in neurodegeneration

The Distribution of Prion Protein Allotypes Differs Between Sporadic and Iatrogenic Creutzfeldt-Jakob Disease Patients

Sporadic Creutzfeldt-Jakob disease (sCJD) is the most prevalent of the human prion diseases, which are fatal and transmissible neurodegenerative diseases caused by the infectious prion protein (PrP(Sc)). The origin of sCJD is unknown, although the initiating event is thought to be the stochastic misfolding of endogenous prion protein (PrP(C)) into infectious PrP(Sc). By contrast, human growth hormone-associated cases of iatrogenic CJD (iCJD) in the United Kingdom (UK) are associated with exposure to an exogenous source of PrP(Sc). In both forms of CJD, heterozygosity at residue 129 for methionine (M) or valine (V) in the prion protein gene may affect disease phenotype, onset and progression. However, the relative contribution of each PrP(C) allotype to PrP(Sc) in heterozygous cases of CJD is unknown. Using mass spectrometry, we determined that the relative abundance of PrP(Sc) with M or V at residue 129 in brain specimens from MV cases of sCJD was highly variable. This result is consistent with PrP(C) containing an M or V at residue 129 having a similar propensity to misfold into PrP(Sc) thus causing sCJD. By contrast, PrP(Sc) with V at residue 129 predominated in the majority of the UK human growth hormone associated iCJD cases, consistent with exposure to infectious PrP(Sc) containing V at residue 129. In both types of CJD, the PrP(Sc) allotype ratio had no correlation with CJD type, age at clinical onset, or disease duration. Therefore, factors other than PrP(Sc) allotype abundance must influence the clinical progression and phenotype of heterozygous cases of CJD