Evaluation d'un nouveau cholécystocinétique

Boyden''s test meal (egg yolk beaten with cream), used during cholecystography, remains in the stomach for a long time and could interfere with the radiological findings on barium meal examination performed after cholecystography.A new preparation based on corn oil emulsion (G.P. Prep) was evaluated in 33 patients with and without symptoms of gallbladder disease. The criteria used in the evaluation of results were three: reduction in the gallbladder dimensions, variations in the cholecystovertebral angle, and visualization of the extrahepatic bile ducts.The gallbladder dimensions were determined before and after contraction with the aid of a metallic perforated ruler (Colcher''s) placed at the estimated level of the gallbladder at the time of exposure.     

Vieillissement de l'appareil photosynthétique

Summary The variations and characteristics of o-diphenoloxidase activity (O-diphenol-O₂-oxidoreductase EC 1.10.3.1) were examined in aging, isolated spinach chloroplasts to determine whether this activity, measured in the presence of 4-methylcatechol as substrate, could be responsible for the inhibition of O₂ evolution during aging of these organelles in dark and light.The rate of the Hill reaction (oxygen evolution and the corresponding photoreduction of ferricyanide) during aging in the dark was inhibited at pH 8.0 and stimulated at pH 6.5. This difference did not depend on the nature of the buffer used (Tris-HCl or phosphate). Furthermore, the pH optimum for the ferricyanide-Hill reaction was shifted to lower values (from pH 8.0 to 6.5) on aging of chloroplasts. This phenomenon is probably due to uncoupling during aging. In the light, the Hill reaction was markedly inhibited. However, the ratio moles O₂ evolved/moles ferricyanide reduced diminished slowly in darkness and rapidly when the chloroplasts were aged in the light.Aging of chloroplasts in darkness was accompanied by a slow decrease in the latent period which precedes the initiation of the oxidation, followed by an increase in O-diphenoloxidase activity. Light-aged chloroplasts showed an initial stimulation and then a smaller increase in enzyme activity compared with that of the dark-aged chloroplasts. This latter phenomenon was probably due to secondary reactions caused by photo-inactivation. Under light conditions, the latent period decreased rapidly and disappeared after one hour.This latent period varied considerably with the season and was reduced or obliterated by treatments with light, fatty acids, Triton-X, hypotonic medium and increasing concentrations of substrate: that is by treatments which generally enhance chloroplast swelling. Thus it appears that the latent period is not a characteristic of O-diphenoloxidase but depends on the integrity of chloroplast structure.The enzyme activity was characterized by a stoichiometry of about 1 moles O₂ consumed per 1.2 moles substrate oxidized, indicating that oxidation was probably proceeding further than conversion of O-diphenol to O-diquinone. The latter compound could be used as a Hill oxidant and it permitted measurement of O₂ evolution in the same reaction mixture in the presence of light. Under these experimental conditions, O₂ evolution (a DCMU sensitive reaction) was first stimulated in dark-aged chloroplasts and rapidly inhibited in light-aged chloroplasts.At appropriate concentrations, KCN, a potent inhibitor of oxidases, enhanced O₂ evolution, suggesting that O-diphenoloxidase activity interferes with O₂ evolution. This possibility is discussed in view of our previous findings on chloroplast aging in vitro.     

Syndrome de klinefelter et conseil génétique

Klinefelter’s syndrome is a common sex chromosomal aberration generally characterized by hypergonadotrophic hypogonadism and azoospermia. However, spermatogenesis impairment is variable and severe oligozoospermia can be found in some men, particularly those exhibiting a mosaic karyotype 47,XXY/ 46,XY. New reproductive technologies, such as intracytoplasmic sperm injection (ICSI), allow Klinefelter patients to have a progeny, even those who are azoospermic after testicular sperm recovery. The question therefore arises of whether or not there is a genetic risk for pregnancies from affected fathers. Sperm karyotyping, by in vitro penetration of zona-free hamster eggs or by fluorescence in-situ hybridization (FISH), is a method of choice for measuring aneuploidy rate in spermatozoa of patients carrying gonosomal abnormalities. A theoretical model would predict a high level of 24,XX and/or 24,XY disomic sperm cells in Klinefelter patients if 47,XXY spermatogonia were able to complete meiosis and achieve spermatogenesis. Interestingly, current observations show that the rate of abnormal spermatozoa in these patients is low, around 1–2%, which indicates that only 46,XY spermatogonia can produce mature sperm cells and that oligozoospermic Klinefelter patients probably carry a 47,XXY / 46,XY mosaicism, at least at the testicular level. However, this low but statistically significant level of disomic spermatozoa emphasizes the fact that their spermatogenesis occurs in a compromised environment which could increase the risk of meiotic errors. Therefore, the possible occurrence of autosomal aneuploidies in children born from Klinefelter fathers leads to the following recommendations: a) individual analysis by FISH of the sperm aneuploidy rate in each Klinefelter patient candidate for ICSI; b) proposal of fetal karyotyping after amniocentesis in pregnancies obtained by this technique.     

Génétique moléculaire des dysgénésies testiculaires

The first step of male differentiation is the testis determination which is genetically controled. The key role of SRY gene is now established. However, a number of clinical and genetic data favoured the role of other genes taking place upstream or downstream SRY. Most of 46, XX males possess a translocated SRY gene and thus develop testis, but SRY gene is not found in 10% of such patients. Likewise, the molecular study of 46, XY females participated in the identification of SRY as testis determining factor, but 80% of XY gonadal dysgenesis are not explained by an abnormality of SRY gene. Several clinical situations permitted to suspect the role of autosomal (chromosome 1, 9, 10 17 …) and X chromosome loci in the pathology of sex determination. Some recent works concern, in particular, the testis determining factor of the X chromosome (TDF-X) that could act as a repressor of the testis differentiation. In conclusion, molecular mechanisms of sexual determination appear to be much complex, involving probably several genes in a pathway that remain to be elucidated.     

Génétique et infertilité masculine: données actuelles

Intracytoplasmic sperm injection (ICSI) and testicular biopsies (TESE) have revolutionized the treatment of male infertility, introducing a risk of an increased frequency of genetic defects in the offspring. These risks and their consequences must therefore be evaluated when proposing ICSI to an infertile man. Karyotype and molecular analysis should be performed to detect any genetic defects responsible for male infertility. Y microdeletion screening is important, not only to define the aetiology of spermatogenic failure, but also to provide information allowing a more appropriate management of both the infertile male and his future male child. Genetic counselling is then advised before deciding to attempt ICSI.     

Le syndrome de kallmann de morsier aspect génétique

Kallmann syndrome (KS) is a rare, heterogeneous disorder consisting of congenital hypogonadotropic hypogonadism, associated with anosmia (or hyposmia) and other clinical manifestations such as mirror movements, and renal, urological and neurosensory disorders. The presence of anosmia with micropenis in boys is suggestive of the diagnostic of KS. In KS, the GnRH neurons do not migrate correctly from the olfactory placode to the hypothalamus during development and olfactory bulbs also fail to form, leading to anosmia. Mutations in KAL1 which encodes Anosmin-1, are responsible for the X-linked form of KS. Anosmin-1 is normally expressed in the brain, facial mesenchyme, mesonephros and metanephros. It is required to promote migration of GnRH neurons into the hypothalamus. It also allows migration of olfactory neurons from the olfactory bulbs to the hypothalamus. The loss of function mutations in FGFR1 “fibroblast growth factor” were identified in 2003 as a cause of autosomal forms of this disease. An additional autosomal cause of Kallmann syndrome was recently identified by a mutation in the prokineticin receptor-2 gene (PROKR2) (KAL-3) and its ligand prokineticin 2 (PROK2) (KAL-4). Mutations in these genes induce various degrees of olfactory and reproductive dysfunction, but not the other symptoms seen in KAL-1 and KAL-2 forms of KS. Neuropilin2, which has an important role in migration of GnRH neurons, is a recent candidate gene for KS. The authors describe the genetic features and recent findings of KS, necessary to understand this disease.     

Cinétique de dégradation des hydrocarbures par Candida lipolytica

Résumé Le mécanisme d'assimilation des hydrocarbures par une levure, Candida lipolytica est étudié au moyen de l'analyse cinétique de la croissance du microorganisme et de la disparition du substrat hydrocarboné. Les hydrocarbures utilisés sont des n-paraffines. On ajoute au milieu soit un seul hydrocarbure (n-tetradécane ou n-hexadécane), soit un mélange binaire (n-dodécane et n-heptadécane), soit un mélange complexe (du n-undécane au n-octadécane). Contrairement à d'autres auteurs, nous pensons qu'il est peu probable que l'essentiel de la réaction s'effectue par contact des gouttes de substrat et des microorganismes puisque l'on observe des retards d'assimilation de certains hydrocarbures: ceux de faible poids moléculaire (les plus solubles) sont assimilés plus rapidement. Il semble donc que l'assimilation se fasse en grande partie à partir d'hydrocarbures préablement solubilisés.

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Kinetics of hydrocarbon assimilation by Candida lipolytica

Summary The mechanism of hydrocarbon uptake by a yeast, Candida lipolytica has been studied by means of the kinetic analysis of micro-organism growth and substrate assimilation. Hydrocarbons used as only source of carbon are normal alkanes either pure (n-tetradecane or n-hexadecane) or in mixture of two paraffins (n-dodecane and n-heptadecane) or eight paraffins (n-undecane to n-octadecane). In these last cases delays in n-alkanes consumption are observed. They show that the most soluble substrates (lower molecular weight) are first consumed. In opposition to other authors we think that there is little probability for main reaction occurring by direct contact between drops and micro-organisms. The evidence indicates that n-alkanes are mainly utilized in the dissolved state.