Mycologie medicale dans l'ouest de la France: Contribution du service de Parasitologie de l'Universite de NANTES (1963–1973)

Résumé Le service de Parasitologie de l'Université de NANTES s'est intéressé aux problèmes de Mycologie hospitalière, d'épidémiologie des mycoses ainsi que d'expérimentation sur les affinités fongiques, à l'échelon régional, et de 1963 à 1973.La contribution clinique a porté essentiellement sur les levuroses étudiées soit au niveau des cavités buccales irradiées, soit chez les malades des services de Réanimation où l'interprétation du rôle pathogène de Candida parapsilosis nécessite des épreuves immunologiques.Nous avons décrit une forme de Blastomycose chéloïdienne à Aureobasidium pullulans.Nos études morphologiques ont surtout porté sur l'observation au microscope électronique à balayage des ultrasculptures présentées par les champignons kératinophiles, ce qui nous a permis de distinguer les différentes espèces du complexe Microsporum gypseum. Il ne semble pourtant pas que cette technique d'observation permette de résoudre tous les problèmes. La conservation des Dermatophytes en eaudistillée par la méthode de Castellani s'est révélée particulièrement remarquable: une souche de M. gypseum a été récupérée après 6 ans de conservation par ce procédé.Notons, en matière d'épidémiologie la prédominance de Trichophyton rubrum sur T. mentagrophytes, survenue récemment: la recrudescence passagère d'Epidermophyton floccosum; la présence d'Arthroderma simii sur une plage. Une étude des champignons kératinophiles telluriques du massif armoricain a porté sur près de 3000 échantillons de terre, ce qui a permis de retrouver, assez rarement d'ailleurs, Arthroderma benhamiae.Nos expérimentations ont porté sur les réponses sérologiques et histologiques de lapins à une imprégnation aspergillaire par instillation intra-trachéale: les résultats obtenus ont été comparés aux examens sérologiques obtenus chez l'homme atteint d'aspergillose. Enfin, nous avons remarqué que le contact levures-cellules sarcomateuses opéré in vitro permet aux levures d'acquérir un pouvoir immunisant antitumoral par emprunt antigénique. La création d'un service de Parasitologie, Mycologie et Immunologie Parasitaire à l'Unité d'Enseignement et de Recherche des Techniques Médicales de NANTES nous a permis non seulement d'aborder les problèmes du diagnostic biologique des mycoses humaines, mais aussi d'entreprendre des enquêtes épidémiologiques dans la région nantaise ainsi que des expériences sur les affinités fongiques.

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The physico-chemical mechanism of mediated transport. I. Facilitated diffusion

On the basis of the currently accepted model for the cell membrane structure, a physico-chemical model for mediated transport is developed and solved for the case of polar non-electrolyte migration through the cell membrane. The model considers the interstitial space defined by the transport protein subunits to be the migration pathway for polar solutes. A Langmuir-type adsorption equilibrium is assumed at the interfaces and a multicomponent diffusion mechanism of solute and water is postulated within the migration pathway, where the polar residues of the transport protein represent another component of the system. Membrane selectivity is governed by the adsorption constants, which are shown to affect strongly the kinetics of transport. Isosmotic transport and the volume change of the cell are important features incorporated in the model, which is shown to fulfill the peculiar properties of facilitated diffusion systems. It is concluded that the same type of pathway can be used for the transport of other polar solutes through existing or induced hydrophilic channels, for which a similar approach is suggested.     

Reaction of forest soil microflora to environmental stress along a moderate pollution gradient next to an oil refinery

Twenty-five study sites were established along a 57-km-long transect in order to estimate the impact of an oil refinery, mainly emitting sulphur dioxide (24000 t yr⁻¹), on forest soil (F/H-horizon) chemistry and microbiology. The study demonstrated the existence of a pollution gradient which was best represented by the logarithm of the concentration of vanadium in the analyzed F/H soil layer. Of the soil microbial characteristics measured, including length of fungal hyphae, soil respiration, microbial biomass C and N, and percentage mass loss of Scots pine (Pinus sylvestris) needle litter, only fungal hyphal length was suppressed by the pollution load. No reduction in basic cations (Ca, Mg, K, and Na) in the F/H-horizon, or enrichment of soluble aluminum in the F/H-horizon of the Scots pine forest could be detected to result from the deposition.     

Changes in Prokaryote and Eukaryote Assemblages Along a Gradient of Hydrocarbon Contamination in Groundwater

Groundwater biota are particularly sensitive to environmental perturbations such as groundwater contamination. The diversity of prokaryotic and eukaryotic biota has been examined along a gradient of chlorinated hydrocarbon (CHC) contamination in the Botany Sands, an urban coastal sand-bed aquifer (Sydney, Australia). Molecular techniques were used to analyze the richness and composition of prokaryote and eukaryote assemblages using 16S and 18S rDNA, respectively. Taxon richness did not change significantly along the gradient for either prokaryotes or eukaryotes; however, significant shifts in assemblage composition were evident for both groups. Assemblage changes were most strongly correlated with concentrations of the major CHC, cis-1,2-dichloroethene, but the concentrations of a number of the contaminants were also correlated, making it difficult to infer if effects were due to any particular contaminant. The presence of cis-1,2-dichloroethene and other secondary ethenes suggests in situ breakdown of the primary CHCs via natural attenuation. The current focus of management of the Botany aquifer is to stop the contaminant plume reaching the adjoining estuary. This approach is clearly justified given the changes evident in the microbial assemblages in the groundwater, which are a likely consequence of the contamination.     

Antibody formation by one or both lymphoid populations present in chimeric marmosets

Development of an isoimmune serum capable of identifying a specific leukocyte antigen in the marmoset, Saguinus fuscicollis illigeri, permitted detection of lymphoid cell chimerism in this species by the cytotoxic test. This reagent was then used to identify the cell population in the chimera responsible for antibody production against a test antigen, sheep red blood cells. Primary in vitro antibody formation as measured by plaque-forming cells with blood leukocytes or splenic lymphocytes of six animals chimeric for the leukocyte antigen, MLA-1, revealed an immune response by both cell types of the chimeric population from three animals and a response by only one cell type in the other three.     

Estrogen target cells. Establishment of a cell line derived from the rat pituitary tumor MtT/F4.

Pretreatment of rabbit kidney cells with cytochalasins B and D (CB, CD) enhanced herpes simplex virus type 2 (HSV-2) DNA infectivity 3- to 6-fold over values obtained using the standard CaCl₂ technique. Cells were pretreated with CB for 4–6 h to achieve infectivity enhancement. A lower concentration of CD, and shorter pretreatment periods, resulted in comparable DNA infectivity. Separate exposure of cells to colchicine, colcemid, or vinblastine increased DNA infectivity 7-, 6-, and 5-fold, respectively, over control values. Additional enhancement was obtained when CD was used together with any one of the aforementioned drugs. Maximal enhancement of HSV-2 DNA infectivity was obtained by pretreating recipient cells with a drug mixture containing colchicine, colcemid, and CD. This treatment maximized infectivity levels 20- to 30-fold over CaCl₂ control values.     

The induction of cell-mediated immunity and tolerance to insulin with insulin coupled to syngeneic lymphoid cells

The induction of delayed type hypersensitivity (DTH) and tolerance to DTH against bovine insulin in mice were explored. DTH was induced with insulin in complete Freund's adjuvant (CFA) and was assessed by ear swelling in vivo and by antigen-driven cell proliferation in vitro. Using the concept that thymus cell unresponsiveness is most easily accomplished via antigen on syngeneic membranes, tolerance was induced by iv injection of syngeneic lymphoid cells which had been coupled to insulin with carbodiimide. Mice tolerized with insulin-coupled cells and then sensitized with insulin-CFA had diminished ear swelling in vivo and decreased insulin-driven cell proliferation in vitro. This unresponsiveness was antigen specific but was also inconstant in degree with regard to suppression of ear swelling, most likely because of variability in coupling of insulin to cells. Proliferative responses were more uniformly suppressed, suggesting the possibility that two target cells were being tolerized. Thus, as with other proteins, the biologically active insulin can be used to induce tolerance.     

Understanding of Aquifer Microbiology is Tightly Linked to Sampling Approaches

Primary samples of groundwater or core are collected and analyzed to characterize the microbiology of aquifers and to predict biogeochemical transformations. Alternative sampling devices have been developed that are incubated for some length of time in the aquifer to accrue biomass for analysis. Considering data generated from different types of aquifer samples, it appears that the type of sample collected and analyzed may strongly influence the resulting view of aquifer microbiology. Borehole artifacts need to be rigorously considered when incubated substrata are used. The indigenous attached populations in deeper, fractured rock aquifers remain understudied and await new sampling approaches.     

Long-Term m5C Methylome Dynamics Parallel Phenotypic Adaptation in the Cyanobacterium Trichodesmium

A major challenge in modern biology is understanding how the effects of short-term biological responses influence long-term evolutionary adaptation, defined as a genetically determined increase in fitness to novel environments. This is particularly important in globally important microbes experiencing rapid global change, due to their influence on food webs, biogeochemical cycles, and climate. Epigenetic modifications like methylation have been demonstrated to influence short-term plastic responses, which ultimately impact long-term adaptive responses to environmental change. However, there remains a paucity of empirical research examining long-term methylation dynamics during environmental adaptation in nonmodel, ecologically important microbes. Here, we show the first empirical evidence in a marine prokaryote for long-term m5C methylome modifications correlated with phenotypic adaptation to CO₂, using a 7-year evolution experiment (1,000+ generations) with the biogeochemically important marine cyanobacterium Trichodesmium. We identify m5C methylated sites that rapidly changed in response to high (750 µatm) CO₂ exposure and were maintained for at least 4.5 years of CO₂ selection. After 7 years of CO₂ selection, however, m5C methylation levels that initially responded to high-CO₂ returned to ancestral, ambient CO₂ levels. Concurrently, high-CO₂ adapted growth and N₂ fixation rates remained significantly higher than those of ambient CO₂ adapted cell lines irrespective of CO₂ concentration, a trend consistent with genetic assimilation theory. These data demonstrate the maintenance of CO₂-responsive m5C methylation for 4.5 years alongside phenotypic adaptation before returning to ancestral methylation levels. These observations in a globally distributed marine prokaryote provide critical evolutionary insights into biogeochemically important traits under global change.     

The ability of nonspecific T-cell stimulators to induce helper-cell-dependent increases in either polyclonal or isotype-restricted Ig production in vivo

In order to delineate the various roles of T cells in B-cell activation, mice were exposed to a variety of specific or nonspecific T-cell stimuli including mitogens, e.g., concanavalin A, adjuvants, e.g., complete Freund's adjuvant, and colchicine plus nonimmunogenic doses of antigen, anti-lymphocyte serum, and pathogens and their spleens analyzed for total class-specific immunoglobulin-secreting cells as indicators of helper cell generation. The results demonstrate that, depending on the mode of stimulation, markedly different Ig-secreting cell response patterns were induced, differing with respect to their kinetics and the isotype induced. In contrast to polyclonal T-cell stimuli such as concanavalin A and 17X lethal malaria which induced increases in all classes of Ig-recruiting cells, injection of many T-cell-activating agents resulted in the selective production of IgG clones in particular IgG 1. Such findings are discussed in terms of the different mechanisms of T-cell help and provide further evidence for functional heterogeneity in the T-helper-cell pool.