Chromosome studies in some Stevia. Cav. (Compositae) species from Southern Brazil

Karyotypes of six species of the genus Stevia from Southern Brazil were studied, utilizing root tip metaphases. All species were diploid with 2n = 22 chromosomes. It was possible to identify each species by chromosome morphology. The basic chromosome number for Brazilian species of Stevia is X = 11. This number is also found in almost all South American species. We suggest that in Stevia there is an evolutionary trend toward chromosomal rearrangement, caused mainly by pericentric inversions. It was found that, in addition to aneuploidy and polyploidy, chromosomal rearrangements are common in the tribe Eupatorieae.

Atypical chromosome abnormalities in acute myeloid leukemia type M4

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Determination of the probable ontogenic time of action of lethal factors on the second chromosome of Drosophila melanogaster derived from a natural population

From the study of the genetic load of second chromosome factors in a natural population of Drosophila melanogaster, 15 lethal-bearing strains were recovered and maintained in the laboratory balanced against Ins (2L + 2R), Cy, L-4. For each lethal factor, the probable time of action during development was determined by the appearance of a sharp reduction, at any given stage, in the frequency of individuals compared to that expected in the absence of the lethal factor. Carried out in this way, the analysis suggested that seven were embryonic lethals, two larval lethals and three pupal lethals. Additionally, three gave no evidence of affecting any of the above-mentioned stages; these are interpreted as gametic lethals.

Chromosome banding in three species of Brazilian toads (Amphibia-Bufonidae)

The chromosomes of Bufo crucifer, B. ictericus, and B. pamacnemis were studied by conventional staining as well as with C banding and NOR techniques. These species have a diploid number of 2n = 22 and identical karyotypes, composed of metacentric and submetacentric chromosomes. The C banding patterns and NOR data indicate that these species of Bufo are not differentiated by the distribution and amount of constitutive heterochromatin or the position of the nucleolar organizer regions.

KARYOTYPIC ANALYSIS AND CHROMOSOME BIOMETRY OF CELL-CULTURES OF THE YELLOW-THROATED ALLIGATOR (CAIMAN-LATIROSTRIS DAUDIN)

Blood from eight specimens of both sexes of the alligator Caiman latirostris was collected and incubated in culture medium. Conventional as well as chromosomal banding (C and NOR) techniques were used.The diploid number was determined as 42, being 24 telocentric, 12 metacentric and six submetacentric, with real lengths varying from 1.49 to 6.08, 1.63 to 3.71, and 2.41 to 3.19 mum, respectively. The fundamental number was 60. About 81% of the chromosomes were small and 19% medium in size. NOR-banding was presented for the first time for this species and it was verified that only one submetacentric pair (no. 20) was marked on arm q, and under conventional staining it presented a secondary constriction. There was no association between NOR marked chromosomes.

Chromosomal evolution in Gekkonidae. I. Chromosome painting between Gekko and Hemidactylus species reveals phylogenetic relationships within the group

Geckos are a large group of lizards characterized by a rich variety of species, different modes of sex determination and diverse karyotypes. In spite of many unresolved questions on lizards' phylogeny and taxonomy, the karyotypes of most geckos have been studied by conventional cytogenetic methods only. We used flow-sorted chromosome-specific painting probes of Japanese gecko (Gekko japonicus), Mediterranean house gecko (Hemidactylus turcicus) and flat-tailed house gecko (Hemidactylus platyurus) to reveal homologous regions and to study karyotype evolution in seven gecko species (Gekko gecko, G. japonicus, G. ulikovskii, G. vittatus, Hemidactylus frenatus, H. platyurus and H. turcicus). Generally, the karyotypes of geckos were found to be conserved, but we revealed some characteristic rearrangements including both fissions and fusions in Hemidactylus. The karyotype of H. platyurus contained a heteromorphic pair in all female individuals, where one of the homologues had a terminal DAPI-negative and C-positive heterochromatic block that might indicate a putative sex chromosome. Among two male individuals studied, only one carried such a polymorphism, and the second one had none, suggesting a possible ZZ/ZW sex determination in some populations of this species. We found that all Gekko species have retained the putative ancestral karyotype, whilst the fission of the largest ancestral chromosome occurred in the ancestor of modern Hemidactylus species. Three common fissions occurred in the ancestor of Mediterranean house and flat-tailed house geckos, suggesting their sister group relationships. PCR-assisted mapping on flow-sorted chromosome libraries with conserved DMRT1 gene primers in G. japonicus indicates the localization of DMRT1 gene on chromosome 6.

Application of dissociation curve analysis to radiation hybrid panel marker scoring: generation of a map of river buffalo (B-bubalis) chromosome 20

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

Paracentric inversion involving a NOR-bearing chromosome of rainbow trout (Oncorhyncus mykiss): Electron microscopy studies of the synaptonemal complex

Cytogenetic studies conduced on a sample of 19 specimens of rainbow trout (Oncorhyncus mykiss) showed that 6 presented two chromosomes with a single subterminal AgNOR on the short arms and 13 presented one chromosome with a single subterminal Ag-NOR and a second chromosome with two small subterminal Ag-NORs. Synaptonemal complex studies showed the presence of a pairing failure involving the two lateral elements (LEs) of the NOR-bearing chromosomes only in those specimens with two different NOR-bearing chromosomes, suggesting that the chromosomes with two Ag-NORs originated from a paracentric inversion involving a terminal segment of the original NOR-bearing chromosome. A comparative analysis between three normal and three heterozygous fishes suggest that in the latter group the LEs of the NOR-bearing chromosomes initiate the synaptic process in a more delayed manner, the synapsis develops more quickly, and the nucleolus stays associated with chromosomes for a longer time.

Chromosome numbers of some Brazilian species of diplopods (Diplopoda, Arthropoda)

The present paper presents the chromosome numbers of five brazilian species of diplopods: Plusioporus setiger (2n = 10 and 2n= 10+ lB, the distinction of the sexual pair was not possible), Pseudonannolene ophiulus (2n=12, XY), Pseudonannolene halophila (2n=16, XY), Rhinocricus sp. (2n=28, XY) and Rhinocricus padbergi (2n=20, the distinction of the sexual pair was not possible).

Frequent p53 mutations and occasional loss of chromosome 4 in invasive bladder carcinoma induced by N-butyl-N-(4-hydroxybutil)nitrosamine in B6D2F1 mice

B6D2F1 mice (45/group) were treated with N-butyl-N-(4- hydroxybutyl)nitrosamine (BBN) or uracil as follows: Group 1 received 0.05% BBN in drinking water for the entire experiment, Group 2 received 5 mg of BBN by gastric gavage in 0.1 mL of 20% ethanol twice per week for 10 wk, Group 3 received a 2.5% uracil-containing diet for the entire experiment, and Group 4 was controls (received 0.1 mL of 20% ethanol by gavage twice per week for 10 wk). The surviving mice in Group 1 were killed after week 26 and those in the other groups after week 30. By week 15, three of 11 Group 1 and one of 15 Group 2 mice had bladder carcinoma. By 26 and 30 wk, respectively, invasive carcinomas were observed in 33 of 34 and six of 21 mice in Groups 1 and 2 and renal pelvic carcinomas in 11 of 34 and three of 21 mice in Groups 1 and 2. Four of 19 uracil-treated mice had bladder nodular hyperplasia. By polymerase chain reaction-single-strand conformation polymorphism and sequence analyses, 16 of 20 and two of five bladder carcinomas from Groups 1 and 2, respectively, showed mutations in the p53 gene. Ha-ras mutation was present in one case. Loss of heterozygosity analysis with simple-sequence length polymorphism markers for chromosome 4 showed that 10 of 21, two of 15, and nine of 13 mice in Groups 1-3, respectively, had heterozygous or homozygous deletions. B6D2F1 mice are therefore susceptible to the urothelial carcinogenic effects of BBN and develop frequent p53 mutations and chromosome 4 deletions. Chromosome 4 deletions were also seen with uracil.

Clonal chromosome abnormalities found in three non-neoplastic proliferative brain lesions

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

A cytogenetic study of Diplomystes mesembrinus (Teleostei, Siluriformes, Diplomystidae) with a discussion of chromosome evolution in siluriforms

The mitotic chromosomes, nucleolus organizer regions (NORs), C-banding pattern and nuclear DNA content of Diplomystes mesembrinus were studied. The karyotype, with 2n=56 chromosomes (22m+24sm+6st+4a), has a high chromosome arm number (NF = 102), one chromosome pair with NORs, and a very small amount of heterochromatin. The NOR-bearing arm is entirely heterochromatic and exhibits a marked size polymorphism. The diploid DNA content detected in erythrocyte nuclei of D. mesembrinus was 2.57 ± 0.15 pg/nucleus. The chromosome evolution in Siluriformes is discussed on the basis of available cytogenetic data and it is proposed that 2n=56 is synapomorphic for the order.

Chromosome analysis of two species of sugar cane pests of the genus Mahanarva (Homoptera, Cercopidae)

Studies on the cytogenetics of Homoptera are scarce. Some references in the literature have reported a chromosome number for the genus ranging from n=5 to 19 and 2n=10 to 2n=39 chromosomes. The genus Mahanarva includes two species of agricultural importance as pests of sugar cane culture in Brazil. We report here the first data concerning the chromosome number and morphology of the species Mahanarva fimbriolata and M. posticata. The chromosome number observed for the two species was 2n=19 for males and 2n=20 for females. The sex determining mechanism of these species was of the XX/X0 type (for males and females, respectively), with chromosome X being the smallest in the complement.