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The Science Citation Index, Journal Citation Reports (JCR), published by the Institute for Scientific Information (ISI) and designed to rank, evaluate, categorize and compare journals, is used in a wide scientific context as a tool for evaluating researchers and research work, through the use of just one of its indicators, the impact factor. With the aim of obtaining an overall and synthetic perspective of impact factor values, we studied the frequency distributions of this indicator using the box-plot method. Using this method we divided the journals listed in the JCR into five groups (low, lower central, upper central, high and extreme). These groups position the journal in relation to its competitors. Thus, the group designated as extreme contains the journals with high impact factors which are deemed to be prestigious by the scientific community. We used the JCR data from 1996 to determine these groups, firstly for all subject categories combined (all 4779 journals) and then for each of the 183 ISI subject categories. We then substituted the indicator value for each journal by the name of the group in which it was classified. The journal group may differ from one subject category to another. In this article, we present a guide for evaluating journals constructed as described above. It provides a comprehensive and synthetic view of two of the most used sections of the JCR. It makes it possible to make more accurate and complete judgements on and through the journals, and avoids an oversimplified view of the complex reality of the world of journals. It immediately reveals the scientific subject category where the journal is best positioned. Also, whereas it used to be difficult to make intra- and interdisciplinary comparisons, this is now possible without having to consult the different sections of the JCR. We construct this guide each year using indicators published in the JCR by the ISI.

In this paper, we analysed six indicators of the SCI Journal Citation Reports (JCR) over a 19-year period: number of total citations, number of citations to the two previous years, number of source items, impact factor, immediacy index and cited half-life. The JCR seems to have become more or less an authority for evaluating scientific and technical journals, essentially through its impact factor. However it is difficult to find one's way about in the impressive mass of quantitative data that JCR provides each year. We proposed the box plot method to aggregate the values of each indicator so as to obtain, at a glance, portrayals of the JCR population from 1974 to 1993. These images reflected the distribution of the journals into 4 groups designated low, central, high and extreme. The limits of the groups became a reference system with which, for example, it was rapidly possible to situate visually a given journal within the overall JCR population. Moreover, the box plot method, which gives a zoom effect, made it possible to visualize a large sub-population of the JCR usually overshadowed by the journals at the top of the rankings. These top level journals implicitly play the role of reference in evaluation processes. This often incites categorical judgements when the journals to be evaluated are not part of the top level. Our «rereading» of the JCR, which presented the JCR product differently, made it possible to qualify these judgements and bring a new light on journals.

The influence of testosterone on plasma and pituitary levels of gonadotrophin (GTH) as well as on gonadal development was studied in immature rainbow trout. Among the animals receiving a testosterone-cocoa butter implant (200 micrograms) at the age of 5 months, gonadal puberty occurred 8 months later in half of the males (opposite to the controls which remained immature) and the beginning of oocyte maturation was observed in only one female. These animals were characterized by a higher pituitary GTH level. Owing to the multivariate statistical analyses made, it was possible to provide evidence for the presence of two populations with different reactions to the same steroid treatment. They also confirmed the existence of a positive testosterone feedback, in the male, leading to a precocious gonadal development. The pituitary GTH load obtained with 200 micrograms of testosterone seemed to be related to the age of first maturation. The secretion of an appropriate level of GTH resulting in the stimulation of gametogenesis required the availability of a relatively large pituitary GTH level and seemed to be possible because the animals were already in the pubertal period. The fact that the highest pituitary GTH level of the treated lot was found in the only female showing a beginning of sexual maturation suggests that testosterone may also act in females.

Two groups, A and B, of 5 adult Ile-de-France rams each of the same age were exposed for 52 weeks (October 1975 to October 1976) to an artificial light regime reproducing natural variations of daylength (DL). In group A, DL increased from 8 to 16 h during the first 26 weeks and then decreased. In group B, DL varied in an opposite manner. Light intensity was constant (300 lux/m2) and ambient temperature was controlled (20 +/- 4 degrees C). The rams were collected using an artificial vagina twice weekly (2 X 2 ejaculates/male/week) during the whole experimental period (EP). The volume and concentration of each ejaculate were recorded. The pH of the raw semen was also measured on the first ejaculate once a week or every two weeks, according to material possibilities. The unselected ejaculates of all rams were used for artificial insemination (AI) on the same days in the same flocks between January and October 1976. AI (980 ewes) was always carried out after oestrus synchronization (FGA + PMSG). Amongst these ejaculates, some (3 ejaculates/male/group/period) could be used for both in vitro (pH) and in vivo (AI) measurements: - Weekly sperm production (SP) varied in an opposite manner in both groups during the whole EP. In group A, minimal (10.6 +/- 4.0.10(9) and maximal (25.5 +/- 5.1.10(9] levels were reached from weeks 12 to 28 and weeks 38 to 52, respectively. In group B, SP was maximal (21.8 +/- 2.3.10(9] from weeks 9 to 24 and minimal (12.7 +/- 5.2.10(9] from weeks 36 to 49. The differences between rams were significant within periods of high and low production. - The sperm pH was somewhat higher in both groups when DL increased and vice-versa. Fertility after AI was higher with rams exposed to short days than with rams exposed to long days (65.7 vs 56.7%; P less than 0.01). The season of AI had no effect on mean fertility (61.0 vs 62.3% for ewes inseminated from January to June and from July to October, respectively), whatever the DL. No correlation was found between the pH of the sperm and its fertilizing ability. From January to April, a highly significant correlation existed between fertility and prolificacy in the 10 rams (r = + 0.607). These results show that photoperiodism has an important effect on both ejaculated sperm production and fertility in rams.(ABSTRACT TRUNCATED AT 400 WORDS)

International audience; The influence of the gonads and/or of LHRH on gonadotropic function, and possibly on gonadal development, was studied in juvenile rainbow trout treated with low doses of testosterone or untreated. Whatever the treatment, all fish of both sexes remained sexually immature, although large individual variations in plasma GTH were observed in all experimental and control groups. This dispersion in the individual values of plasma GTH seemed to be the first sign of an increase in the previously low gonadotropic activity and might announce the beginning of a pubertal period several months before the onset of meiosis in males and of vitellogenesis in females. Castration did not change the plasma and pituitary GTH values, suggesting that control of the gonadotropic function did not depend mainly on sexual steroids during this period. In our experimental conditions, LHRH administration did not lead to any change in plasma or pituitary levels of GTH. Only the testosterone treatment (20 μg) had an effect, causing a higher pituitary GTH load in some fish which was not modified either by castration or by LHRH and decreased with time ; neither of these treatments changed the plasma GTH levels. Thus, the fact that the required amount of GTH was not released to initiate early onset of gametogenesis did not seem to be due to a repressive control by the gonads or to the absence of stimulation by an LHRH-like hypothalamic factor. The quantity of GTH accumulated in the pituitary gland and the dose of steroid used have been discussed.

This article presents a method for estimating the variability of measurements in radio-immunoassays. Repeated assays are carried out on the same plasma used as a reference. The variances of repeatability (or intraassay) and reproducibility are calculated from the values obtained from the reference. These variances are used to calculate the agreement between two or more values obtained from unknown plasma. Analysis of the values of the plasma reference completes information obtained from standard curves.

Changes in sexual behavior and progesterone, oestrone, oestradiol, testosterone and androstenedione concentrations have been studied in the follicular fluid of 25 pseudopregnant rabbits on Days 6, 9, 12, 15 and 18. The sexual behavior score seemed to rise at the end of pseudopregnancy and follicular steroid levels were higher on Days 6 and 18 of pseudopregnancy than on Days 9, 12 or 15. The generalized distance D2 of Mahalanobis showed the existence of four periods during pseudopregnancy: Day 6, Days 9 and 12 which were similar, Day 15 and Day 18. These stages were found to differ by a compound of the sexual behavior score and the concentrations of androgens and oestradiol in follicular fluid. There was no relationship between sexual behavior and follicular steroid concentrations. Nevertheless, undetectable levels of oestradiol in the follicular fluid were only observed in deeply dioestrus females.

International audience; Une technique de mesure spectrophotométrique de la concentration en spermatozoïdes du sperme de truite a été mise en oeuvre et un certain nombre de mesures pratiquées pendant la période de reproduction ont montré que :- la concentration varie entre 10.109 et 25.109 spermatozoïdes par ml au début de la fraie (fig. 2) et diminue ensuite ;- la concentration du sperme dans le canal déférent n'est pas constante et diminue dans le sens antéro-postérieur (fig. 4) ;- la quantité de spermatozoïdes par gramme de testicule est très élevée au début de la fraie et diminue ensuite (fig.5 ) ;- quelle que soit la fréquence des prélèvements, la quantité de spermatozoïdes récoltés dans les conditions de la pratique piscicole reste toujours faible par rapport à la quantité totale de spermatozoïdes présents dans les testicules au moment de la fraie : 22 p.100 dans le cas le plus favorable c'est-à-dire lorsque les spermatozoïdes sont collectés tous les 2 jours (tabl. I).

International audience; Afin d'étudier quantitativement et rapidement la spermatogenèse des poissons téléostéens, nous avons évalué la part de volume occupée par les cellules germinales dans le testicule par la méthode des numérations ponctuelles (oculaire intégrateur I de Zeiss). On peut ainsi constater chez Cavassius auratus des différentes dans la répartition des catégories cellulaires entre les parties antérieure médiane et postérieure. Cependant l'observation de 5o à 60 champs microscopiques sur une seule coupe transversale de la partie médiane du testicule, fournit un échantillon représentatif de la totalité de celui-ci. La méthode d'échantillonnage ainsi mise au point a été appliquée sur des testicules d'animaux soumis à des traitements différents mais d'effets connus comme l'hypophysectomie seule ou suivie d'une supplémentation avec de la poudre hypophysaire brute de Carpe ou HCG. On montre ainsi que les volumes occupés par les cellules germinales rapportés au poids corporel permettent la discrimination nette entre les lots considérés ici et complètent l'information apportée par le rapport gonado-somatique.