X chromosome heterochromatic pattern and nucleolar synthesis in pupal ovaries of Aedes aegypti

C-banding and silver-staining techniques were used to examine pupal ovaries of Aedes aegypti from Sao Jose do Rio Preto (Brazil). Silver staining in ovary cystocytes showed two basic patterns relative to the nucleolar morphology: viz (1) a single, compact small body; and (2) multiple bodies encompassing large nuclear areas. These two types of cystocytes were present in the ratio of 7:1, which is the same as the number of nurse cells and oocytes, respectively, in each follicle. This suggests the possibility of eventually using such a nucleolar morphological difference to recognize both cell types in developmental stages before emergence. Silver nitrate staining in metaphase chromosomes revealed centromeric bands on all six chromosomes. The C-banding pattern in metaphase chromosomes showed an intercalary band in one of the X arms, as described previously in other populations. In ovary cystocytes (pachytene stage) this C-positive band seemed to consist of two chromomeres. Phase contrast microscopy showed that the nucleolus was associated with the distal chromomere of this intercalary C-band, indicating that the nucleolus organizer region was located in that part of the heterochromatic band.

CHROMOSOME-STUDIES IN MALES AFFECTED BY DUCHENNE OR BECKER MUSCULAR-DYSTROPHY

We studied cytogenetically 48 male patients with Duchenne or Becker muscular dystrophy. All of them showed normal X chromosomes. Fragility of Xp21 was investigated in 1400 G-banded chromosomes of 28 patients and only one break was observed at this band (0.07%). This low frequency of breakage excludes Xp21 as a fragile site in these patients.

SYNAPTONEMAL COMPLEX-ANALYSIS IN SPERMATOCYTES AND OOCYTES OF RAINBOW-TROUT, ONCORHYNCHUS-MYKISS (PISCES, SALMONIDAE) - THE PROCESS OF AUTOSOME AND SEX-CHROMOSOME SYNAPSIS

The surface-spreading synaptonemal complex (SC) technique was employed to analyze spermatocytes and oocytes of rainbow trout in order to visualize the process of autosome and sex chromosome synapsis in this species. The structure of lateral elements (LEs) of the SC and the chromosome synapsis process at the stages of leptotene, zygotene and pachytene are described. Comparative analysis of SCs of spermatocytes and oocytes showed a difference in the synaptic process, i.e. in spermatocytes all LEs were synapsed before the appearance of centromeric regions in the biarmed elements, while in the oocytes some fully synapsed LEs, including the centromeric region of the biarmed elements, were found together with fully or partially unsynapsed LEs. In males the sex chromosome synapsis starts only after all autosomes have synapsed. Irregular synapses involving three or four LEs were found in 3.4% of the cells analyzed in mid or late zygotene. Multivalents were found in males and females. Some aspects of initial meiotic development and their implications in rainbow trout cytogenetics, genetics and evolution are discussed.

CYTOGENETIC EVIDENCE OF INVOLVEMENT OF CHROMOSOME REGION-15Q12 AND REGION-12Q15 IN CONDITIONS WITH ASSOCIATED OVERGROWTH

Syndromes with associated overgrowth are poorly understood. Besides their mode of inheritance, nothing is known regarding the basic genetic alterations that lead to their abnormal phenotypic manifestations. The chromosome localization of the genes involved remains unknown for this group of syndromes, with the only exception being the Wiedemann-Beckwith syndrome.

LOSS OF THE SEX-CHROMOSOME IN HUMAN NEOPLASIAS OF THE NERVOUS-SYSTEM

Thirty-eight tumors (five grade I-II astrocytomas, three grade III astrocytomas, four glioblastomas, one oligodendroglioma, four ependymomas, one pineocytoma, three medulloblastomas, four acoustic nerve neurinomas, one intraspinal neurinoma, one neurofibroma, 10 meningiomas, and one craniopharyngioma) and three benign lesions of the nervous system were evaluated cytogenetically after in vitro culture. Sex chromosome loss was detected in 56% of the cases (-X in 13 of the 25 female patients and -Y in nine of the 16 male patients). The objective of the present report was to study the role of this abnormality in cells of the nervous system.

Detection and differentiation of Leptospira spp. serovars in bovine semen by polymerase chain reaction and restriction fragment length polymorphism

In view of the importance of venereal transmission of bovine leptospirosis, the objective of the present study was to apply the polymerase chain reaction (PCR) to 26 serovars of Leptospira interrogans, L. borgpetersenii, L. santarosai, L. noguchii and L. biflexa, to determine the detection threshold in semen samples and to evaluate the possibility of differentiation among serovars using 19 restriction endonucleases. The results showed that all serovars were amplified and the detection threshold in semen samples of a bull was 100 bacteria/ml. Using endonucleases we could classify the 26 serovars into eight groups. The present results show that PCR is a method of great potential for the detection of Leptospira spp, at bovine artificial insemination centers. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Use of primers derived from a new sequence of the bovine Y chromosome for sexing Bos taurus and Bos indicus embryos

A bovine male-specific marker was identified in our laboratory through random amplified polymorphic DNA (RAPD) analysis. This fragment of 3216 bp was cloned, sequenced and mapped by fluorescent in situ hybridization (FISH) on the taurine Yq. Primers derived from this sequence were initially screened by polymerase chain reaction (PCR) for their ability to detect Y-specific segments in zebu and taurine genomic DNA. Two of these primers amplified a 655 bp Y-specific sequence present in taurine and zebu male genomic DNA. These primers were then used for detecting the 655 bp male sequence in DNA from 173 zebu and 30 taurine embryos, which had been previously sexed using primers for the sequence BC 1.2. The results revealed an accuracy of 100%. (C) 2002 Elsevier B.V. All rights reserved.

Evaluation of the genetic diversity of Xylella fastidiosa strains from citrus and coffee hosts by single-nucleotide polymorphism markers

The aim of this study was to obtain information about genetic diversity and make some inferences about the relationship of 27 strains of Xylella fastidiosa from different hosts and distinct geographical areas. Single-nucleotide polymorphism (SNP) molecular markers were identified in DNA sequences from 16 distinct regions of the genome of 24 strains of X. fastidiosa from coffee and citrus plants. Among the Brazilian strains, coffee-dependent strains have a greater number of SNPs (10 to 24 SNPs) than the citrus-based strains (2 to 12 SNPs); all the strains were compared with the sequenced strain 9a5c. The identified SNP markers were able to distinguish, for the first time, strains from citrus plants and coffee and showed that strains from coffee present higher genetic diversity than the others. These markers also have proven to be efficient for discriminating strains from the same host obtained from different geographic regions. X. fastidiosa, the causal agent of citrus variegated chlorosis, possesses genetic diversity, and the SNP markers were highly efficient for discriminating genetically close organisms.