Type III secretion à la Chlamydia

Type III secretion (T3S) is a mechanism that is central to the biology of the Chlamydiaceae and many other pathogens whose virulence depends on the translocation of toxic effector proteins to cytosolic targets within infected eukaryotic cells. Biomathematical simulations, using a previously described model of contact-dependent, T3S-mediated chlamydial growth and late differentiation, suggest that chlamydiae contained in small non-fusogenic inclusions will persist. Here, we further discuss the model in the context of in vitro-persistent, stress-induced aberrantly enlarged forms and of recent studies using small molecule inhibitors of T3S. A general mechanism is emerging whereby both early- and mid-cycle T3S-mediated activities and late T3S inactivation upon detachment of chlamydiae from the inclusion membrane are crucial for chlamydial intracellular development.     

L'adaptation à la vie arboricole chez les fourmis

Arboreal ants constitute one of the largest animal groups in the tropical forest canopy not just in terms of their individual number and overall biomass, but also in terms of diversity. Because the arboreal habitat has particular characteristics which clearly differentiate it from the ground, the ants' ecological success depends on developing adaptations designed to overcome the constraints peculiar to this environment in order to best exploit its resources. Although it is not always possible to identify all of the characteristics common to all arboreal ants species, those species said to be ‘dominant’ share morphological, physiological and behavioural traits which differentiate them from other ants. The most important difference is the type of food sources exploited. These dominant species feed principally on the nectar of the extra-floral nectaries of plants or on the honeydew of Homoptera. These products are extremely rich in sugary substances and low in nitrogen. The exploitation of these food sources has, then, repercussions on the growth and reproduction of ant colonies, given the importance of nitrogen as a limiting factor. Obtaining the necessary amount of nitrogen involves exploiting large volumes of liquid. From a purely morphological point of view, it is interesting to note that the digestive system of most of the dominant ant species has a modified proventriculus and a thin cuticle which means less need for proteins. These modifications permit individual foragers to transport large volumes of liquid by holding them in their crops in order to distribute them to the rest of the colony. The venom of many of these species also differs from that of other ants in that it lacks nitrogen. Dominant species have, thus, developed adaptations related to their feeding habits, lowering the need for nitrogen in individuals and, in this way, permitting the greater development of the colony. The exploitation of this type of food source is also facilitated by the type of nests constructed by the ants. Indeed, the elaboration of a nest independently of any structure provided by the plant offers numerous advantages, despite the important energetic costs involved. These types of nests allow the ant to (1) ‘choose’ the nest site and thus to install the nest on plants providing the best resources (extra-floral nectaries or Homoptera attendance) and (2) exploit a greater number of resources with lower energy costs by placing parts of the colonies near food sources. In addition, even if part of the sugary food substances are destined for the synthesis of molecules necessary to the survival and proper functioning of individuals, there is a large surplus. This surplus might indirectly reinforce these species' defensive systems on both an inter- as well as intraspecific level by serving as an energy source enabling individuals to have high level of activity and aggressiveness. The remaining arboreal species, which — in terms of diversity — make up the majority, do not share common traits which permit them to be clearly differentiated from terricolous species. Nevertheless, comparisons conducted within a genus show that certain arboreal species have developed adaptations to their way of life, and not only those species living in the domatia of ant plants, but also other, strictly arboreal species. As is the case for dominant species, the modifications observed originate especially in response to the two principal limiting factors in the arboreal habitat: available food resources and a limited number of nest sites.     

Hommage à rené delépine à l'occasion de son départ à la retraite

A tribute to René Delépine on the occasion of his retirement. The career of René Delépine is reviewed on the occasion of his retirement. When he was a student, a meeting with Jean Feldmann led to a lifelong inclination towards phycology. Eventually appointed to the position of assistant professor at the University of Paris-VI (University Pierre-et-Marie-Curie), René Delépine worked and published primarily on the taxonomy of antarctic and subantarctic marine algae but he was also interested in seaweed aquaculture and utilizations. After organizing the national colloque ValVA (Valorisation des végétaux aquatiques), he became increasingly involved in the commercial application of seaweeds. His main activity, however, remained university teaching for which he was always enthusiastic, especially for teaching in the field and on the subject of the utilizations of algae. A list of his publications is given at the end of this article.     

Contribution à la systématique du genre Pichia

The presence of intracellular osidases, nitrite and nitrate reductases, vitamin requirements and GC content in the DNA, have been investigated for in 18 species of Pichia.According to their typical characters and their biocaracters, a pattern is suggested for the integration of these new species into the formerly existing groups of the genus Pichia. A new way of classifying the species of the genus Pichia is proposed.     

De la gonorrhée à la blennorragie: Les grandes étapes historiques

This paper examines the history of gonorrhoea and its treatment. It is very probably a very ancient disease that was confused with syphilis for centuries.     

Contribution à l'étude de la bryoflore Lorraine

Contribution to the knowledge of the bryophyte flora of Lorraine (France). The bryophyte flora of Lorraine (France), which was not extensively studied during the second half of this century, has been visited again over the last four years. Seligeria acutifolia Lindb. has been collected for the first time in that region. New localities of several rare or poorly known bryophytes are given. A perspective view is proposed as to the future of bryological research in Lorraine.     

Contribution à la connaissance des fungi keratinophiles de l'ouest de la France V. Étude au microscope électronique à balayage

Résumé La recherche des Fungi kératinophiles dans 301 prélèvements de sol de la Loire-Atlantique a permis de trouver une fois sur troisArthroderma uncinatum. A. curreyi est assez abondant.Nannizzia cajetani, A. quadrifidum etA. tuberculatum ont été également assez souvent mis en évidence.Chrysosporium keratinophilum semble rare. Plus rares également sont les espèces plus spécialement pathogènes:A. benhamiae, N. fulva etN. incurvata.L'étude au microscope électronique à balayage permet de séparer et définir différentes espèces par l'observation des ornementations: verrues, granules, érosions planes, crêtes. C'est ainsi que nous pouvons confirmer la séparation des deux espècesN. fulva etN. incurvata.     

Quand l’évolution parle à la biologie fondamentale

Like many results in comparative anatomy, the works on bone histology led by Armand de Ricqlès have found their whole sense within the framework of the theory of evolution. It seems to be the same thing in genomics and molecular biology. However, some examples show that the fluidity of genomes is not realized by the same processes in eukaryotes and in prokaryotes. In the first taxon, transposons play a fundamental role, since in the other case horizontal gene transfers are essential. These dynamics seem to be necessary for understanding the bases of genomic evolution both from fundamental and applied points of view.     

Applications à la conchyliculture des récentes acquisitions sur la biologie des mollusques bivalves

Today, mollusc farming represents the fourth part of the mundial aquaculture production. These results have been permitted by the improvement of farming techniques commercially important but also by advances in the biology of a species. Valuable reproductive studies have been carried out in s.a. hatcheries on triploids and tetraploids animals. Since the last decade, advances in the knowledge of metabolism and growth mechanisms has helped the improvement of the brood stock. Nevertheless, the mundial expansion of bivalve farming increases the outbreak of strong epizooties. Investigations allow a valuable knowledge on the scope of molluscan defence mechanisms against pathogen agents. The results are discussed in relation to a possible selection for bivalve farming.     

Effets d’une exposition à la Vinclozoline et à la Génistéine de la gestation à l’âge adulte sur la fonction de reproduction du ratWistar mâle: protocole et résultats préliminaires

Current evidence indicates that endocrine disrupters (EDs) can induce adverse effects on the male reproductive tract in various mammalian species. Recent reports indicate deterioration in male reproductive health in several human populations, but the evidence for a causal link with endocrine disruption is still weak. In addition, the experimental conditions of most of the reportedin vivo studies are not representative of environmental exposures (for example, high doses, short-term exposure, a single ED) and the mechanisms by which EDs disrupt the reproductive system are poorly understood. The objective of the present study is to develop an animal model to assess the reproductive effects and study the putative cellular and molecular mechanisms involved after exposure to genistein (phytoestrogen) and vinclozolin (fungicide with a known antiandrogenic potential) alone or in combination. The study will be performed in male Wistar rats, with administration of low and high doses of the compounds from conception to adulthood and a subset of the males in each treatment group will be mated with unexposed females. We plan to assess the level of sperm production, histology of the reproductive organs, motility and morphometry of spermatozoa and hormone levels, as well as DNA fragmentation of spermatozoa and determination of the number of germ cells, Sertoli cells and the diameters of seminiferous tubules. Estrogen, androgen, progesterone and FSH receptors will be detected and quantified and the level of testicular apoptosis and several apoptosis pathways will be studied to determine the putative cellular and molecular mechanisms involved. The preliminary results confirmed the developmental effects previously reported for high doses of vinclozolin. More interestingly, they indicated a number of deleterious effects for male rats exposed to low dosages alone or mixtures of low and high dosages compared to controls and rats exposed to high dosages alone. For example, a number of developmental anomalies of the genitalia were observed and a significant decrease of sperm motility and motion and fertilizing ability were observed. These preliminary results provide evidence that chronic exposure to environmental levels of EDs or mixtures of EDs have a detrimental impact on the male reproductive tract. The next step involves assessment of the anatomical disorders and the study of some of the cellular and molecular mechanisms possibly involved.     

Contribution à l'etude des thecamoebiens de la Province de Buenos Aires

Résumé La faune des Thécamoebiens fut étudiée dans deux étangs (La Brava et De los Padres) situe dans la Province de Buenos Aires (Argentina). Le nombre d'espèces trouvé en tout a été de 14, quelques-unes desquelles représentées par de différentes formae. Une nouvelle forma Centropyxis compressa (Cushman), forma brava n.f. a été trouvée et décrite, et une espèce de Pontigulasia a été proposée en nomenclatura aperta.

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Summary The Thecamoebiens of two lakes (La Brava and de los Padres) located in the Province of Buenos Aires (Argentina) were studied. The total number of species found is 14, several of them are represented by various formae. A new forma was found and described, namely Centropyxis compressa (Cushman), forma brava n.f. and one species of Pontigulasia was put in nomenclatura aperta.

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Departamento de Ciencias Biologicas, Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires     

Les traumatismes de la verge: à propos de 23 cas

The authors report 23 cases of penile injuries based on a retrospective study of their urological practice in Senegal. The various cases were distributed as follows: fracture of the penis (19 cases), corpora cavernosa and urethral gunshot injuries (2 cases), rupture of the superficial dorsal vein of the penis (1 case) and laceration of the penile skin (1 case). The mean age of these patients was 32.4 years. Early surgical treatment of all penile fractures reduces the complication rate.     

Contribution à la connaissance des Desmidiées du Congo belge

Résumé Le présent travail s'occupe de 85 Desmidiées, dont la plupart ont été trouvées dans le matériel que j'ai recueilli au Congo, à Stanley-Ville.Quant aux Micrasterias, ce genre a été étudié avant tout sur du matériel provenant des environs de Léopoldville et recueilli par les Docteurs W. Bervoets et Fr. Evens. Une partie des déterminations et des figures ont été faites par le Dr. Evens. Je l'en remercie ici tout spécialement.Les espèces et variétés traitées se répartissent comme suit:Des 85 espèces trouvées dans le matériel examiné, 76 sont nouvelles pour le Congo et 5 variétés sont décrites comme nouvelles pour la science. Ce sont: Pleurotaenium subcoronulatum (Turner) W. & G. S. West, var. maximum Euastrum malmei Borge, var. congolense Micrasterias tropica Nordstedt, var. ndjiliensis van Oye & Evens Cosmarium obsoletum Reinsch, var. glabra Staurastrum orbiculare Ralfs, var. maxima De beaucoup d'espèces des données systématiques sont mentionées et discutées.La dispersion des différentes espèces est examinée là o\u on dispose d'assez de données.Enfin, des conclusions générales sont faites quand le matériel le permettait. En général, les données du travail permettent de confirmer les conclusions faites antérieurement.     

Efficacité de la mémoire associative inhérente à la potentiation post-tétanique

An associative memory is modeled in networks of cells that are assumed to have the short-term plasticity of the neuromuscular junction of the frog. The data relating synaptic transmission efficiency and stimulation frequency for post-tetanic potentiation of the neuromuscular junction are represented by polynomial expansions. Simulation of storage and retrieval demonstrates that functional associative memory is feasible based on this particular synaptic plasticity. Retrieval reaches a maximum efficiency at a delay of three minutes after storage and is lost after about 9 min. The signal to noise ratio of the retrieved pattern drops steadily as additional associations are stored in memory but retrieval appears to be possible with up to four stored associations. Although the data are derived from synapses not normally proposed as a basis for memory functions, the results here will generalize to other synaptic junctions located more centrally that have similar characteristics. This simulation technique allows the efficiency of associative memory based on various types of synaptic plasticity to be evaluated.     

Insuffisance rénale chronique : de la maladie osseuse à la maladie osseuse et vasculaire

The accelarated atherosclerosis occurring in patients with chronic renal failure (CRF) is a well-known complication since the beginning of dialysis. The relationship between vascular lesions and phosphocalcic abnormalities is a more recent concept. The relationship between increase in phosphate × calcium product and cardiac valvular calcifications was demonstrated in 1980. The relationship between high serum phosphate levels and mortality was shown in 1998. The strong prevalence of coronary calcifications in CRF patients was shown in 1996. In 2000, the association between these calcifications and the oral dose of calcium was strongly suggested. Thereafter, the mechanism of these calcifications appeared much more complex, involving hypercholesterolemia, inflammation, and other factors. The relationships between hyperparathyroidism and mortality were shown during the years 2000. There is also an association between hypoparathyroidism and mortality in dialysis patients but not in CRF patients before the dialysis stage. Another new concept is the discovery of a relationship between vitamin D deficiency, very frequent is CRF patients, and mortality. Treatment with active 1,25(OH)D is associated with a better survival. There is also an new interest in treatment with the 25(OH)D form since the enzyme 1-alpha-hydroxylase, which is responsible for its transformation in active form, is present in multiple organs.