[The expression of mutation sy2 causing nonhomologous synapsis in meiosis of diploid rye Secale cereale L]. / Proiavlenie mutatsii sy2, vyzyvaiushchei negomologichnyi sinapsis v meioze diploidnoi rzhi Secale cereale L.

The cytological expression of spontaneous mutation sy2 isolated from a population of weedy rye was examined. It was demonstrated that the primary defect of meiosis in the mutant plants is nonhomologous synapsis, which occurs simultaneously with the homologous one. An electron microscope study of the synaptonemal complex (SC) at prophase I showed synaptic abnormalities that manifested as "switches" of synapting axial elements to the nonhomologous partner and the formation of foldbacks of lateral SC elements. The sy2 mutants are characterized by one to two such events per meiosis. Nonhomologous synapsis leads to the appearance of univalents at metaphase I (on average 4.16 +/- 0.022 per meiocyte) and multivalents (on average 0.12 +/- 0.007 per meiocyte). The presence of multivalents in 12.0% of meiocytes at metaphase I may result from recombination in ectopic regions of homology. It is suggested that the sy2 mutation impairs a component of the system that limits synapsis in meiocytes to only homologous chromosome pairs.

[Damaging effect of antibiotics on the structure of synaptonemal complexes of meiotic chromosome of mice]. / Povrezhdaiushchee deistvie antibiotikov na strukturu sinaptonemnykh kompleksov meioticheskikh khromosom myshi.

The structure of synaptonemal complexes (SCs) of chromosomes of mouse primary spermatocytes were studied using electron microscopy on days 1, 10, and 36 after the completion of per os administration of drugs belonging to three groups of antibiotics: tetracyclins, macrolides, and fluoroquinolones. The antibiotics were administered to mice during ten days. At the substages of early and middle pachytene, heteromorphic SC bivalents and fragments of chromosome-core elements were detected in spermatocytes at all times studied after the administration of the antibiotics of three groups. As cells passed through the period from early to middle pachytene, the number of cells containing heteromorphic SC bivalents and the fragments of chromosome cores gradually decreased, which could be an indication of selection of cells with chromosomal aberrations. A high level of associations between the X chromosome and autosome bivalents (including heteromorphic ones) also favors this suggestion. A gradual decrease in the number of chromosomal aberrations was detected, as time elapsed from the completion of antibiotics administration. The study of sperm obtained from epididymises of males did not reveal significant differences in both morphology and motility of sperm between males of the control and experimental groups.

[Synaptonemal complexes of chromosomes of male mice after prolonged administration of neoaquasept]. / Issledovanie sinaptonemnykh kompleksov khromosom samtsov myshei posle dlitel'nogo vvedeniia neoakvasepta.

A long-term (during 4 months) daily peroral injections of neoaquasept (NA) (a drinking water disinfections agent) at a dose corresponding to the normal level of consumption increases the number of spermatocytes in which the sexual bivalent associates with normal autosomal bivalents (up to 18.2%). In single cells a premature desynapsis of sex chromosomes at late pachytene was observed. There was the appearance of single cells with the X0 karyotype. A 3-fold excess of the normal consumption of NA causes an increase in the number of cells with the above disturbance in the SC structure and behaviour and causes the appearance of heteromorphic bivalents. On the 7th day after a single MTD injection of NA male mice displayed a sharp (up to 27.9%) increase in the number of cells in which the sexual bivalent associated with autosomal bivalents, formation of univalents of autosomal and sex chromosomes, SC degeneration.

[Electron microscopic analysis of synaptonemal complexes of male laboratory mice exposed during the period of embryogenesis in the vicinity of the Chernobyl Nuclear Power Station]. / Elektronno-mikroskopicheskii analiz sinaptonemnykh kompleksov samtsov laboratornykh myshei, éksponirovannykh v period émbriogeneza v raione Chernobylskoi AES.

Four male mice were shown to have decreased fertility among 74 laboratory male mice exposed in the Chernobyl APP area during embryogenesis. Electron microscopic analysis of synaptonemal complexes (SC) of at zygotene-diplotene and light-optic analysis of chromosome aberrations at diakinesis-metaphase 1 demonstrated the presence of interchromosome translocations in autosomal chromosomes, and also intrachromosome translocations in two of four animals. The frequency of chromosome translocations in SC preparations was on the average 1.8 times higher than their frequency at the diakinesis-metaphase 1 stage. High percentage of cells in which associations of sex bivalent axes (XY) with the axes of autosomal bivalents were observed in the SC preparations and reduced fertility in the animals studied confirmed the Forejt's hypothesis that such associations caused the arrest of cells at pachytene and, as a consequence, disturbed the process of embryogenesis.

[Association between synaptonemal complexes of sex and autosomal bivalents in male tx/ty mice as a possible cause of their sterility]. / Assotsiatsiia mezhdu sinaptonemnymi kompleksami polovykh i autosomnykh bivalentov u samtsov myshei tx/ty kak vozmozhnaia prichina ikh steril'nosti.

Electron microscopic study of total preparations of synaptonemal complexes of spermatocytes I from sterile heterozygous male mice--t12/tw18; tw5/twPa-1; twPa-1/tw18 was performed. T/tw18 and C3H/N fertile heterozygotes were used in each variant as control. The cells are karyotyped in all experiments, as based on the measurements of the length of 19 SC autosomes and SC sex complex. All sterile compounds (spermatocytes) demonstrate high frequency of different types of associations (72%) between sex chromosomes and the autosome 17 carrying a chromosomal aberration in the region of the T-locus. The heterozygotes tx/ty used in our experiments show no disruption of chromosome synapsis, when even studied under electron microscope, though some atypical changes in the ultrastructure of chromosome axes and frequent atypical associations of the axes of XY-sex bivalents in sterile heterozygous animals exist.

Synaptonemal complexes and chromosome chains in the rodent Ellobius talpinus heterozygous for ten Robertsonian translocations.

Synaptonemal complexes (SC) in four Ellobius talpinus males heterozygous for ten Robertsonian translocations were examined with an electron microscope using a surface-spreading technique. A total of 136 late zygotene and pachytene spermatocytes were examined. From one to three completely paired SC trivalents were found in each early pachytene spermatocyte. The lateral elements of the short arms of the acrocentric chromosomes in these trivalents were joined with an SC thus forming the third arm of the SC trivalent. At the same stage a few SC trivalents did not contain lateral elements in the pericentromeric region of the metacentric chromosomes and remained unpaired in this region up to mid pachytene. At zygotene and pachytene from two to eight SC trivalents were joined into chains due to formation of SCs between the short arms of acrocentrics of other SC trivalents. These chains are frequent at late zygotene, but are resolved during pachytene into individual trivalents. It is proposed that pairing and SC formation between the short arms of he acrocentric chromosomes results from the monosomy of the short arms and partial DNA homology between these heterochromatic regions. Since crossing over probably does not take place in these segments, the chromosomal chains may subsequently be corrected into trivalents by a dissolution of the SCs combining adjacent trivalents. The correction and disjoining of chains may not be effective in all cells. The cells in which the chains are retained are assumed to be arrested at the pachytene stage.