Description and chromosome number of a species of Pseudonannolene Silvestri (Arthropoda, Diplopoda, Pseudonannolenidae)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Cytogenetic analysis of Cycloramphus boraceiensis Heyer (Anura, Leptodactylidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Análise cromossômica em bulbilhos de sisal (Agave spp.) cultivados em diferentes municípios baianos, Brasil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of NOR distribution in cultivated and naturalized stocks of rainbow trout (Oncorhynchus mykiss)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Karyological characterization of four Neotropical fish species of the genus Hisonotus (Teleostei, Loricariidae, Hypoptopomatinae) from distinct Brazilian river basins

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evidence of an XX/XY sex chromosome system in the fish Dormitator maculatus (Teleostei, Eleotrididae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Extensive polymorphism and chromosomal characteristics of ribosomal DNA in the characid fish Triportheus venezuelensis (Characiformes, Characidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic analysis of three sea catfish species (Teleostei, Siluriformes, Ariidae) with the first report of Ag-NOR in this fish family

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comparative genomic hybridization analysis detects frequent over-representation of DNA sequences at 3q, 7p, and 8q in head and neck carcinomas

Comparative genomic hybridization (CGH) was used to identify chromosomal imbalances in 19 samples of squamous cell carcinoma of the head and neck (HNSCC). The chromosome arms most often or er-represented were 3q (48%), 8q (42%), and 7p (32%); in many cases, these changes were observed at high copy number. Other commonly over-represented sites were 1q, 2q, 6p, 6q, and 18q. The most frequently under-represented segments were 3p and 22q. Loss of heterozygosity of two polymorphic microsatellite loci from chromosome 22 was observed in two tongue tumors, in agreement with the CGH analysis. Gains of 1q and 2q material were detected in patients exhibiting a clinical history of recurrence and/or metastasis followed by terminal disease. This association suggests that gain of 1q and 2q map be a new marker of head and neck tumors with a refractory clinical response. (C) 2000 Elsevier B.V. All rights reserved.

NUCLEOLAR CHROMOSOME VARIANTS IN STERNOPYGUS-MACRURUS (PISCES, STERNOPYGIDAE) FROM 3 BRAZILIAN RIVER BASINS

The karyotypes, location of nucleolus organizer regions (NOR) and constitutive heterochromatin pattern of Sternopygus macrurus (Pisces, Gymnotoidei) of natural populations from the Amazon River, Sao Francisco River and Tiete River (the last belonging to the Upper Parana River system) are reported. All specimens had 2n = 46 chromosomes and presented small differences in karyotypic formulae, but populations of each river basin had a different fixed NOR phenotype. The loss of the satellite and a gradual deletion of the heterochromatin block adjacent to the NOR may be the origin of the variants. The possible mechanism of fixation of the NOR phenotypes, and the implications of the occurrence of intraspecific differences in fixed NOR phenotype in this species are discussed.

TELOMERIC FUSIONS IN A WILMS-TUMOR

The present report describes the karyotypic findings in cells from a Wilms' tumor. The most consistent cytogenetic abnormalities detected consisted of translocations involving break and fusion of chromosomal telomeres and telomeric associations frequently affecting the terminus of the short arms of chromosomes 14 and 17.

Karyotypic patterns of seven species of molossid bats (Molossidae, Chiroptera)

G- and C- banding patterns of seven species of the bat family Molossidae, Eumops glaucinus, E. perotis; Molossops abrasus, M. remminckii, Molossus ater, M. molossus, and Nyctinomops laticaudatus, were identified. Comparisons among the karyotypes of these species showed extensive homologies between E. perotis, M. ater, M. molossus, M. abrasus, and N. laticaudatus, demonstrating inter- and intrageneric conservatism, and a lesser degree of homologies in M. temminckii and glaucinus, reflecting intrageneric variation, Chromosomal variation was due to inversions, Robertsonian rearrangements, translocations, and variations in the location of constitutive heterochromatin and nucleolus organizer regions. The chromosome corresponding to No. 5 in the M. ater karyotype is discussed. We suggest that the Nyctinomops and Molossops karyotypes represent the primitive condition and that Molossus and Eumops have derived karyotypes.

NATURAL TRIPLOIDY IN ASTYANAX-SCABRIPINNIS (PISCES, CHARACIDAE) AND SIMULTANEOUS OCCURRENCE OF MACRO B-CHROMOSOMES

The occurrence of natural triploidy in two specimens of Astyanax scabripinnis collected in the Araqua river and in the Corrego das Pedras stream, respectively, is noticed. The triploid specimen from the Araqua river presented one macro B-chromosome and the triploid specimen from Corrego das Pedras stream presented two macro B-chromosomes. The C-banding performed in the specimen from the Araqua river confirmed the triploidy and showed that the macro B-chromosome was entirely heterochromatic. Ag-NOR characterization showed two chromosomes involved in the nucleolar activity in both specimens. Some aspects related to the origin of triploid fishes are described.

CHROMOSOME-STUDIES IN HYPOPTOPOMATINAE (PISCES, SILURIFORMES, LORICARIIDAE) .2. ZZ ZW SEX-CHROMOSOME SYSTEM, B-CHROMOSOMES, AND CONSTITUTIVE HETEROCHROMATIN DIFFERENTIATION IN MICROLEPIDOGASTER-LEUCOFRENATUS

Cytogenetic analysis of two local populations of microlepidogaster leucofrenatus showed a basic diploid chromosome number (2N) of 54 in both populations. Some fishes were found to have a 2N = 55 or 56 chromosomes due to the presence of one or two large heterochromatic B chromosomes. Specimens of M. leucofrenatus from the Poco Grande stream had 24 metacentrics, 24 submetacentrics, four subtelocentrics, and one submetacentric homomorphic pair in males and one submetacentric/subtelocentric heteromorphic pair in females, whereas individuals of this species from the Marumbi River had 22 metacentrics, 24 submetacentrics, four subtelocentrics, two acrocentrics, and one submetacentric/subtelocentric heteromorphic pair in females. The occurrence of the heteromorphic pair in the females was due to the presence of an extra C-banded segment on the W chromosome. Ag-NORs in both populations were located interstitially on the short arm of the largest metacentric pair. The Poco Grande population had less constitutive heterochromatin than did the Marumbi River population. The speciation process in this fish species is discussed on the basis of heterochromatin distribution.

Karyotype analysis in Brachiaria (Poaceae) species

This is the first karyotype characterization of Brachiaria species. Twelve accessions belonging to five species were analysed. The basic chromosome number was x = 9 and 7, the same reported for the tribe Paniceae. Variations in the chromosome number were observed in B. decumbens (2n = 18; 36) and B. humidicola (20 = 36; 42; 54). Chromosome numbers of 20 = 18 in B. ruziziensis and 20 = 36 in B. brizantha and B. jubata were recorded. Inter- and intraspecific karyotype differentiation of the accessions analysed was facilitated by variations in karyotypic symmetry. The karyotypes were generally considered symmetrical, with a tendency to asymmetry in the direction of the polyploids. It is suggested that addition, deletions and mainly polyploidy have been the most direct causes involved in the chromosome evolution of this genus.