Ultrastructural localization and distribution of Nardilysin in mammalian male germ cells.

BACKGROUND: NRD convertase, also termed Nardilysin, is a Zn(++) metalloendopeptidase that specifically cleaves the N-terminus of arginine and lysine residues into dibasic moieties. Although this enzyme was found located within the testis, its function in male reproduction is largely unknown. In addition, the precise distribution of this enzyme within germ cells remains to be determined. METHODS: To answer these questions, we developed an immuno-gold electron microscopy analysis to detect Nardilysin at ultrastructural level in mice. In addition, we performed a quantitative analysis of these gold particles to statistically estimate the distribution of Nardilysin in the different subcellular compartments of differentiating late spermatids/spermatozoa. RESULTS: Expression of Nardilysin in wild-type mice was restricted to germ cells and markedly increased during the last steps of spermiogenesis. In elongated spermatids, we found the enzyme mainly localized in the cytoplasm, more precisely associated with two microtubular structures, the manchette and the axoneme. No labelling was detected over the membranous organelles of the spermatids. To test whether this localization is dependent of the functional microtubules organization of the flagella, we analysed the localization into a specific mouse mutant ebo/ebo (ébouriffé) known to be sterile due to an impairment of the final organization of the flagellum. In the ebo/ebo, the enzyme was still localized over the microtubules of the axoneme and over the isolated cytoplasmic microtubules doublets. Quantification of gold particles in wild-type and mutant flagella revealed the specific association of the enzyme within the microtubular area of the axoneme. CONCLUSIONS: The strong and specific accumulation of Nardilysin in the manchette and axoneme suggests that the enzyme probably contributes either to the establishment of these specific microtubular structures and/or to their functional properties.

OBJECTIFS: La NRD convertase aussi appelée Nardilysine, une Zn++ metalloendopeptidase qui clive spécifiquement dans la région N terminale des résidus arginine et lysine des sites dibasiques, est impliquée dans la transformation/maturation des proprotéines. Le but de cette étude est de localiser cette enzyme durant la spermiogénèse afin de comprendre son rôle au cours de la maturation des spermatides. MÉTHODES: La Nardilysine est révélée par immunohistochimie au niveau ultrastructural chez des souris contrôles fertiles et chez un mutant stérile (ébouriffé : ebo/ebo). Des analyses quantitatives sont effectuées par comptage des grains d'or colloïdal qui permettent de détecter la localisation spécifique de l'enzyme au cours de la croissance des spermatides dans des régions particulières. RÉSULTATS: L'expression de la Nardilysine chez les souris sauvages et stériles ebo/ebo est limitée aux cellules germinales avec une augmentation significative dans les étapes ultimes de la spermiogénèse. L'enzyme est fortement exprimée dans le cytoplasme des spermatides allongées et dans les structures microtubulaires, la manchette et le flagelle. Aucun marquage n'est observé au niveau des organites cellulaires des spermatides. Chez le mutant ebo/ebo, dont le flagelle est anormal, l'enzyme est toujours présente sur les doublets de microtubules du flagelle. La quantification des particules d'or chez la souris sauvage et chez le mutant révèle une association spécifique de l'enzyme avec les microtubules du flagelle. CONCLUSIONS: L'accumulation spécifique de la Nardilysine au niveau de la manchette et du flagelle suggère que cette enzyme pourrait contribuer à l'établissement de ces structures microtubulaires particulières et/ou à leurs propriétés fonctionnelles.

Drinking patterns are associated with variations in atherosclerotic risk factors in French men.

BACKGROUND: While a relationship between alcohol and cardiovascular risk factors is well established, data suggest that the type of alcoholic beverage could modulate this relationship. AIM OF THE STUDY: To determine whether drinking patterns modulate the relationship between alcohol and cardiovascular risk factors. METHODS: We tested the relationship between preference of alcoholic beverages and atherosclerotic risk factors in a cross-sectional study of 2,126 men. A hierarchical clustering method determined six drinking patterns, 'low drinkers', 'high quality wines', 'beer and cider', 'digestives', 'local wines', and 'table wines', according to the preferential intake of alcoholic beverages. Logistic models estimated the relative risk of abnormal markers in the drinking patterns compared with low drinkers. Unadjusted estimates investigated the relationship with the cluster as a group, while adjustment on alcohol, nutritional and socio-demographic factors investigated the relationship with the preference of alcoholic beverage in itself. RESULTS: Abstainers had high total plasma homocysteine (tHcy), even after full adjustment (odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.8). Drinkers of high quality wine had low lipoprotein( a), high tHcy and high body mass index; beer and cider drinkers had high tHcy and waist circumference. Drinkers of digestives had high triacylglycerol; after adjustment they were at risk of low apolipoprotein A-I (OR = 3.1, 95% CI: 1.2, 7.3), and high tHcy (OR = 4.9, 95% CI: 1.2, 33.3). Local wines drinkers were similar to low drinkers. Table wine drinkers had high apolipoprotein B, high triacylglycerol, and high waist-to-hip ratio. CONCLUSION: Our data suggest that preference of alcoholic beverage could indicate groups at specific risks of atherosclerotic disease.

A point pattern model of the spread of foot-and-mouth disease.

The spatial spread of foot-and-mouth disease (FMD) is influenced by several sources of spatial heterogeneity: heterogeneity of the exposure to the virus, heterogeneity of the animal density and heterogeneity of the networks formed by the contacts between farms. A discrete space model assuming that farms can be reduced to points is proposed to handle these different factors. The farm-to-farm process of transmission of the infection is studied using point-pattern methodology. Farm management, commercial exchanges, possible airborne transmission, etc. cannot be explicitly taken into account because of lack of data. These latter factors are introduced via surrogate variables such as herd size and distance between farms. The model is built on the calculation of an infectious potential for each farm. This method has been applied to the study of the 1967-1968 FMD epidemic in UK and allowed us to evaluate the spatial variation of the probability of infection during this epidemic. Maximum likelihood estimation has been conducted conditional on the absence of data concerning the farms which were not infected during the epidemic. Model parameters have then been tested using an approximated conditional-likelihood ratio test. In this case study, results and validation are limited by the lack of data, but this model can easily be extended to include other information such as the effect of wind direction and velocity on airborne spread of the virus or the complex interactions between the locations of farms and the herd size. It can also be applied to other diseases where point approximation is convenient. In the context of an increase of animal density in some areas, the model explicitly incorporates the density and known epidemiological characteristics (e.g. incubation period) in the calculation of the probability of FMD infection. Control measures such as vaccination or slaughter can be simply introduced, respectively, as a reduction of the susceptible population or as a reduction of the source of infection.

Sequence alignment: an approximation law for the Z-value with applications to databank scanning.

The Z-value is an attempt to estimate the statistical significance of a Smith and Waterman dynamic programming alignment score (H-score) through the use of a Monte-Carlo procedure. In this paper, we give an approximation for the Z-value law deduced from the Poisson clumping heuristic developed by Waterman and Vingron (Stat. Sci. 9 (1994) 367) in the case of independent and identically distributed sequences comparison. As for non-gapped alignment scores, our approximation is of Gumbel type but with parameters that are sequence independent. This result makes clear the related experimental results mentioned by Comet et al. (Comput. Chem. 23 (1999) 317). Using 'quasi-real' sequences (i.e. randomly shuffled sequences of the same length and amino acid composition as the real ones) we investigate the relevance of our approximation result. Since the Monte-Carlo approach we use generates a bias for the Gumbel decay parameter estimation, a correction procedure is proposed. Applications to real sequences are considered and we show how our results can be used to detect the potential biological relationships between real sequences.

Brief communication: estimates of some demographic parameters in a Neolithic rock-cut chamber (approximately 2000 BC) using iterative techniques for aging and demographic estimators.

Two new techniques-one anthropological, which estimates the mean age at death for adult skeletons, the other demographic, which gives main survivorship curve parameters-are used on a sample of skeletons (N approximately 170) discovered in a Neolithic rock-cut chamber (Loisy-en-Brie, France). The iterative technique for aging used a stochastic sampled F matrix derived from the trabecular involution of the femoral head observed in the reference collection of Coimbra (Portugal; N = 421). The results, obtained from techniques and data, independent of each other, are strongly consistent. Overall, they give a life expectancy at birth of about 25-28 years and the probability of death at 1 and 5 years, respectively, of about .271-.249 and .429-.380.

Isolation by distance, trend surface analysis, and spatial autocorrelation.

The isolation by distance model is both a population process and a surface model. In this model the surface is, on average, flat in every direction. By contrast, probably most observed genetic surfaces exhibit trends generated by complex long-distance populational processes. When one estimates the parameters of a Malécot-Morton equation for those surfaces, the isolation by distance model does not fit. In the simplest case, in first-order trends (two-dimensional clines) the genetic differentiation increases dramatically, faster per unit distance than it would by isolation by distance alone. When isolation by distance takes place but is hidden through the apparent and complicated relief of a surface, another surface model incorporating trend spatial analysis can bypass the difficulty of estimating the isolation by distance process if approached through the Malécot-Morton equation or through a measure of spatial autocorrelation.