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Resume Objectif – Dans le but d’evaluer si les atteintes tres severes de la spermatogenese necessitant une microinjection ICSI sont prejudiciables a la qualite embryonnaire, nous avons compare les resultats de cette technique a ceux de la fecondation in vitro classique pratiquee pour indication masculine (FIV IM). Materiel et methodes – Cent trente-quatre cycles de FIV (groupe 1) ont ete selectionnes a partir d’oligoasthenoteratospermies definies selon les criteres de Who et permettant d’obtenir un nombre total de spermatozoides mobiles selectionnes compris entre 500 000 et 1 million. Nous avons obtenu 1 088 ovocytes matures et 486 embryons. Cent quarante-trois cycles d’ICSI (groupe 2) ont ete selectionnes sur la base d’alterations spermatiques severes rendant impraticable une FIV classique. Au total, 1 147 ovocytes matures ont ete injectes et 626 embryons ont ete obtenus. Resultats – Les taux de grossesses par transfert etaient respectivement de 22,7 % et de 37,1 % dans les groupes 1 et 2 et les taux d’implantation de 12,3 % et 17 %. L’analyse statistique des embryons obtenus dans les deux techniques n’a pas montre de difference dans la distribution des embryons les plus reguliers et les moins fragmentes (groupe A) ni dans celle des embryons irreguliers et fragmentes (groupe B). La chronologie des divisions embryonnaires (groupes 1 et 2) n’etait pas non plus statistiquement differente. Conclusion – Le taux de grossesse par cycle et par transfert retrouve en ICSI ( p p p

The meiotic prophase behavior of three human reciprocal autosomal translocations is presented. Each translocation was ascertained among men attending an infertility clinic. Two involved chromosomes 3 and 5, with breakpoints in different places. Quadrivalents were seen in every cell. The third translocation was a rare t(11 q;15q) rearrangement in a 45-chromosome individual with tertiary monosomy. The long product of the translocation was retained in the karyotype over two generations of the family, the short product having been lost. At meiotic prophase, a trivalent was seen in every cell; in 60% of the nuclei, the short arm of the trivalent was closely associated with the XY bivalent. The transmission and phenotypic effects of tertiary monosomy in man and the mouse are discussed.

A study of XY-autosome relationships at the pachytene stage in an infertile 17-21 reciprocal translocation carrier was undertaken by means of three dimensional reconstruction. Synaptonemal complexes and the sex vesicle were analysed on electron microscopic serial sections and the reconstruction was performed on transparent sheets and on a Samba 2000 (Alcatel TITN) image analysis system. All asynapsed segments were entirely included in the sex vesicle, the chromatin fibre of the autosomes and sex chromosomes being tightly intermingled. In one nucleus, the four arms of the quadrivalent were paired, except around the breakpoints where an interstitial asynapsis was observed. In the other nuclei, a terminal asynapsis involving one or two arms of the quadrivalent was found. In the sex vesicle, autosomal asynapsed segments showed the same morphological characteristics as those of X and Y chromosomes. This observation agrees with the hypothesis of the extension of gene inactivation from sex chromosomes to autosomes.

To whom correspondence should be addressed at: Laboratory of Cytogenetics, National Research Center of MentalHealth, Russian Academy of Medical Sciences, Zagorodnoe sh.2, Moscow 113152, RussiaA rapid fluorescence in-situ hybridization (FISH) technique was used for direct chromosomal analysis on germcells from an infertile male with large-headed spermatozoa. The interphase chromosomes were fluorescently-labelled using an extremely bright cyanine dye during a 5-15 min FISH procedure. Germ cells were analysedusing a battery of chromosome-specific DNA probes in several consecutive rapid FISH experiments, rt wasfound that the majority of large-headed spermatozoa contained a diploid chromosome number probably dueto errors in meiosis I or II divisions, whereas the majority of spermatozoa with normal sized heads are haploidand may be utilized for selective in-vrtro fertilization procedures. Rapid FISH may be useful for the detectionof major chromosomal aneuploidies in germ cells as an alternative technique to standard or multicolour FISH,and may find an additional application for the chromosomal analysis of human preimplantation embryos.

Acrocentric bivalent associations were studied in 232 human male germ cells at pachytene in order to understand better the preferential involvement of chromosomes 13, 14, and 21 in Robertsonian translocations. The tendency of each acrocentric bivalent to associate with another was not correlated with NOR activity, as measured by silver staining. Good agreement was noticed between their ability to associate and the amount of satellite DNA in human acrocentric chromosomes. The distribution of two-by-two acrocentric bivalent associations was random. In order to reconcile this result with the nonrandom distribution of Robertsonian translocations, a molecular hypothesis is proposed. The model is based on homology of recom-binational sites, interspersed at regular interval in satellite DNA, which could increase the probability of accidental unequal crossing-over between two specific acrocentric chromosomes.