[Fréquence des maladies transmises sexuellement chez des étudiants universitaires.]

OBJECTIVE: To estimate the incidence rate of sexually transmitted diseases (STDs) among university students and evaluate the associated sociodemographic factors. DESIGN: Mail survey in April 1990. Included in the questionnaire were questions about the subjects'' STD experience since their admission to the university and the type and date of the infection. SUBJECTS: Of the 19,682 undergraduate students 2920 subjects, in 10 groups of 292, were randomly selected. A total of 1731 (59.4%) completed the questionnaire. MAIN OUTCOME MEASURES: Estimated annualized incidence rates of genital human papillomavirus infection and Chlamydia infection. RESULTS: The estimated annualized incidence rates of genital human papillomavirus and Chlamydia infections were 2.2% and 1.5% respectively. Among the students who indicated being infected with genital human papillomavirus 59% were 18 to 21 years old (p < 0.05), 76% were women (p < 0.01) and 69% had more than one sexual partner (p < 0.01). No statistically significant associations were observed between age, sex and Chlamydia infection. On the other hand, 95% of the cases of Chlamydia infection were found among those who had more than one sexual partner (p < 0.01). CONCLUSION: University students continue to have sexual activities at risk for STDs and should be specifically targetted by general practitioners and health services in an effort to slow the spread of STDs.     

The distance dependence prediction of the Janzen-Connell hypothesis: a meta-analysis

The Janzen-Connell hypothesis explains the maintenance of tropical diversity through the interacting effects of parent-centered dispersal patterns and distance- and density-dependent propagule survival. These effects were thought to support regular spacing of species within tropical forest, enhancing diversity. One of the predictions of the hypothesis is that seed and seedling survival should improve with increased parental distance. Although there are many independent tests of this hypothesis for individual species, there are few synthetic studies that have brought these data together to test its validity across species. This paper reports the results of a meta-analysis of the effect of distance on enhancing propagule survival, employing an odds-ratio effect size metric. We found no general support for the distance-dependent prediction of the hypothesis, and conclude that further testing to explore this hypothesis as a diversity-maintaining mechanism is unnecessary. However, we did find that distance from parent slightly reduces survivorship in the temperate zone, as contrasted with the tropics, and we saw stronger evidence in support of the hypothesis for seedlings than for seeds. The phenomenon of enhanced propagule survival with distance from the parent may be important for the population biology of particular species, but it is not a general phenomenon across communities, life history stages or life forms.     

Detection and identification of ferricrocin produced by ectendomycorrhizal fungi in the genusWilcoxina

The ectendomycorrhizal fungiWilcoxina mikolae isolates CSY-14 and RMD-947 andW. rehmii isolate CSY-85 were grown in pure culture under iron-limiting conditions. All three isolates tested positive for siderophore formation using both the ferric perchlorate assay and a sensitive HPLC iron-binding assay. A peptide siderophore was isolated from the culture medium by HPLC and shown to contain the amino acids serine, glycine and ornithine in a 1:2:3 ratio. This siderophore was identified as ferricrocin on the basis of electrospray mass spectroscopy and its co-chromatography in two different HPLC systems with ferricrocin isolated fromAspergillus fumigatus. Ferricrocin was the only siderophore isolated from theseWilcoxina cultures. This is the first report of siderophore formation by ectendomycorrhizal fungi.     

What studies of turbellarian embryos can tell us about the evolution of development mechanisms

In spiralian embryos determination of the axes of bilateral symmetry is associated with D quadrant specification. This can occur late through equal cleavage and cell interactions (conditional specification) or by the four-cell stage through unequal cleavage and cytoplasmic localization (autonomous specification). Freeman & Lundelius (1992) suggest that in spiralian coelomates the former method is ancestral and the latter derived, with evolutionary pressure to shorten metamorphosis resulting in early D quadrant determination through unequal cleavage and appearance of adult features in the larvae. Because of the key phylogenetic position of the turbellarian platyhelminthes, understanding the method of axis specification in this group is important in evaluating the hypothesis. Polyclad development, with equal quartet spiral cleavage, is believed to represent the most primitive condition among living turbellarians and has been examined experimentally in Hoploplana inquilina. Blastomere deletions at the two and four-cell stage produce larvae that are abnormal in morphology and symmetry, indicating that early development is not regulative, and also establish that the embryo does not have an invariant cell lineage. Deletions of micromeres and macromeres at the eight-cell stage indicate that cell interactions are involved in dorso-ventral axis determination, with cross-furrow macromeres playing a more significant role than non-cross-furrow cells. The results support the idea that conditional specification is the primitive developmental mode that characterized the common ancestor of the turbellarians and spiralian coelomates. Evolutionary trends in development in polyclads and other turbellarian orders are discussed.     

HIV-1 Nef protein: purification, crystallizations, and preliminary X-ray diffraction studies.

Human immunodeficiency virus Nef protein accelerates virulent progression of AIDS by its interaction with specific cellular proteins involved in cellular activation and signal transduction. Here we report the purification and crystallization of the conserved core of HIV-1LAI Nef protein in the unliganded form and in complex with the wild-type SH3 domain of the P59fyn protein-tyrosine kinase. One-dimensional NMR experiments show that full-length protein and truncated fragment corresponding to the product of HIV-1 protease cleavage have a well-folded compact tertiary structure. The ligand-free HIV-1 Nefcore protein forms cubic crystals belonging to space group P23 with unit cell dimensions of a = b = c = 86.4 A. The Nef-Fyn SH3 cocrystals belong to the space group P6(1)22 or its enantiomorph, P6(5)22, with unit cell dimensions of a = b = 108.2 A and c = 223.7 A. Both crystal forms diffract to a resolution limit of 3.0 A resolution using synchrotron radiation, and are thus suitable for X-ray structure determination.     

Genetic control of plastid carotenoids and transformation in the skin of Cucurbita pepo L. fruit

Summary The influence of allelic state of gene B on skin pigmentation in two cultivars of Cucurbita pepo L. has been studied. Total carotenoids were lower at early stages of fruit development in cultivar (cv.) Early Prolific (EP) BB YY fruit skin, than in EP B ⁺ B ⁺ YY fruit skin, but no differences were observed in total skin carotenoids twenty days after anthesis. Total carotenoids were lower in cv. Fordhook Zucchini (FZ) BB yy fruit skin, than in FZ B ⁺ B ⁺ yy fruit skin at all developmental stages from anthesis to maturity. Both green and yellow tissues contained typical foliar carotenoids. The carotenoids from yellow fruit skin of both EP genotypes and of FZ BB were characterized by a low carotene: xanthophyll ratio, with a high proportion of the xanthophylls esterified to fatty acids. The xanthophylls of the yellow tissues were esterified with 120, 140, 160 fatty acids. The carotenoids from the green fruit skin of FZ B ⁺ B ⁺ had a higher percentage of carotenes (primarily -carotene) and a lower percentage of esterified xanthophylls. Spectral shapes of carotenoid fractions from all yellow tissues were similar and distinguishable from those of green FZ B ⁺ B ⁺ tissue. The results of these studies are discussed in terms of the genetic control of plastid transformation in Cucurbita pepo L.New Jersey Agricultural Experiment Station No. D99201 (NE-9) 32-83, supported by state funds and funds from the Rutgers University Research Council     

Habitat,diet, and activity patterns of free-ranging woolly spider monkeys (Brachyteles arachnoides E. Geoffroy 1806)

Results of a 10-month study of the ecology and behavior of free- ranging woolly spider monkeys (Brachyteles arachnoides)in Brazil show that these animals are strongly folivorous. Leaf-eating accounted for more than 50% of the total feeding time in all samples but one and accounted for more than 80% of the total feeding time in three samples. Mature foliage was routinely eaten. Woolly spider monkeys consistently spend more than 50% of each day quietly resting and sleeping. Animals travel little except when actively feeding and show low levels of social interaction. Such an activity profile suggests that woolly spider monkeys may often be living near the limits of their energetic resources. The social organization of the species is unusual for a folivorous primate in that small groups of females and associated immature animals confine their activities to discrete home-range areas, whereas males are itinerant, traveling over the home ranges of various female groups. Animals sharing a common home-range area show no permanent daily pattern of association other than that of mother-dependent offspring. Foraging alone or with few conspecifics should maximize each individual’s returns from foraging by minimizing the day range that must be traveled each day to locate foods while simultaneously lowering interference competition for higher-quality dietary resources.     

Sequence of the 3''-noncoding and adjacent coding regions of human gamma-globin mRNA.

In cloning human fetal globin cDNA in bacterial plasmids, we obtained a recombinant which contained a fragment of gammg-globin cDNA corresponding to the region from amino acid 99 to the poly A. We determined a sequence of 169 nucleotides which included the complete 3' non-coding region of the gamma-globin mRNA. The codon for amino acid 136 was GCA, indicating that this cloned fragment was derived from the Agamma-globin gene. In conjunction with the surrounding sequences, the GCA codon provides the Agamma-species with a unique CTGCAG hexanucleotide that is recognized by the restriction enzyme Pst I. The 3'-untranslated region of the gamma-globin mRNA consists of 90 nucleotides, and shares little homology with that of the human beta-globin mRNA. As in other mammalian mRNAs, a symmetrical sequence and the hexanucleotide AAUAAA are present.