|
|
|
| Registros recuperados: 8.210 | |
|
|
| Chaud-Netto,José; Cruz-Landim,Carminda da. |
| This study describes the ultrastructural differences between the compound eyes of ch li/ch li and Ch/ch li honeybee queens. Heterozygous "limão" bees had an almost normal ultrastructural organization of the ommatidia, but there were some alterations, including small vacuoles in the crystalline cones and a loss of pigment by primary pigmentary cells. In homozygous bees many ommatidia had very deformed crystalline cones and there were some bipartite rhabdoma. There was a reduction in the amount of pigment in the primary and secondary pigmentary cells and receptor cells (retinulae) of mutant eyes. However, the eyes of both heterozygous and homozygous queens had the same type of pigment granules. Certain membrane-limited structures containing pigment granules... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000100017 |
| |
|
|
| Félix,Leonardo Pessoa; Guerra,Marcelo. |
| The Cymbidioid phylad presents the widest chromosome number variation among orchids, with records varying from 2n = 10 in Psygmorchis pusilla to 2n = 168 in two species of Oncidium. In the present work, a total of 44 species were studied belonging to 20 Cymbidioid genera, as a contribution to clarifying the karyological evolution of the group. All the plants investigated were collected in Brazil, mainly in the northeast region. The chromosome variation found was similar to that previously registered in the literature. Chromosome numbers observed were: 2n = 54 (subtribe Eulophiinae), 2n = 44, 46, 92 (subtribe Cyrtopodiinae), 2n = 54, ca. 108 (subtribe Catasetinae), 2n = 52, ca. 96 (subtribe Zygopetalinae), 2n = 40, 80 (subtribe Lycastinae), 2n = 40, 42... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000400041 |
| |
|
|
| Cifuentes O.,Lucía; Armanet B.,Leonor; Aguirre A.,Raúl; Vargas B.,Juana; Acuña P.,Mónica. |
| DNA polymorphism is very useful in paternity analysis. The present paper describes paternity studies done using DNA profiles obtained with the (CAC)5 probe. All of the subjects studied were involved in nonjudicial cases of paternity. Genomic DNA digested with HaeIII was run on agarose gels and hybridized in the gel with the (CAC)5 probe labeled with 32P. The mean number of bands larger than the 4.3 kb per individual was 16.1. The mean proportion of bands shared among unrelated individuals was 0.08 and the mean number of test bands was 7.1. This corresponded to an exclusion probability greater than 0.999999. Paternity was excluded in 34.5% of the cases. The mutation frequency estimated from non-excluded cases was 0.01143 bands per child. In these cases, the... |
| Tipo: Info:eu-repo/semantics/other |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000400005 |
| |
|
|
| Mello,Maria Luiza S.; Maria,Sílvya S.; Tavares,Maria Cristina H.. |
| The survival of Triatoma infestans and of somatic cells from this species is affected by heat shock. In this study, we examined the cell death responses of male germ line cells from 5th instar nymphs 7 and 30 days after heat shock exposure (40ºC, 1 h). The preparations were stained by the Feulgen reaction and the TUNEL immunocytochemical assay. Apoptosis was elicited by heat shock, with positive TUNEL responses in spermatogonial chromatin and chromosomes, spermatids and sperm cells. Spermatogonia were most affected seven days after the shock whereas some spermatids and sperm cells exhibited DNA fragmentation only thirty days after heat shock. The rate of cell death varied among the cells. In some cases, cellular differentiation was unaffected by heat... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000200011 |
| |
|
|
| Loreto,Vilma; Souza,Maria José de. |
| Several techniques including C-banding, fluorochromes and silver staining were used to obtain information about heterochromatin patterns in the grasshopper B. coccineipes. Conventional staining showed a karyotype with 2n = 23 chromosomes in males and 2n = 24 in females, as well as XO:XX sex determination and acrotelocentric chromosomes. The medium-sized X chromosome was heteropycnotic positive at the beginning of prophase I and negative in metaphase I. C-banding revealed heterochromatic blocks in the pericentromeric regions of all chromosomes. Silver nitrate staining in this species showed three small bivalents (S9-S11) as nucleolar organizers with NORs located in the pericentromeric regions. CMA3-positive blocks were seen in pericentromeric regions of... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000300013 |
| |
|
|
| Telles,Mariana Pires de Campos; Diniz-Filho,José Alexandre Felizola. |
| An Ornstein-Uhlenbeck process was used to simulate the exponential relationship between genetic divergence and geographic distances, as predicted by stochastic processes of population differentiation, such as isolation-by-distance, stepping-stone or coalescence models. These simulations were based only on the spatial coordinates of the local populations that defined a spatial unweighted pair-group method using arithmetic averages (UPGMA) link among them. The simulated gene frequency surfaces were then analyzed using spatial autocorrelation procedures and Nei's genetic distances, constructed with different numbers of variables (gene frequencies). Stochastic divergence in space produced strong spatial patterns at univariate and mutivariate levels. Using a... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000400007 |
| |
|
| |
|
| |
|
|
| Vallente-Samonte,Rhea U.; Conte,Robert A.; Verma,Ram S.. |
| Homologies between chromosome banding patterns and DNA sequences in the great apes and humans suggest an apparent common origin for these two lineages. The availability of DNA probes for specific regions of human chromosomes (5q31, 10q22, 13q32-33 and 19q13.1) led us to cross-hybridize these to chimpanzee (Pan troglodytes, PTR), gorilla (Gorilla gorilla, GGO) and orangutan (Pongo pygmaeus, PPY) chromosomes in a search for equivalent regions in the great apes. Positive hybridization signals to the chromosome 5q31-specific DNA probe were observed at HSA 5q31, PTR 4q31, GGO 4q31 and PPY 4q31, while fluorescent signals using the chromosome 10q22-specific DNA probe were noted at HSA 10q22, PTR 8q22, GGO 8q22 and PPY 7q22. The chromosome arms showing... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000300004 |
| |
|
|
| Pereira,Sérgio Luiz. |
| With the advent of DNA sequencing techniques the organization of the vertebrate mitochondrial genome shows variation between higher taxonomic levels. The most conserved gene order is found in placental mammals, turtles, fishes, some lizards and Xenopus. Birds, other species of lizards, crocodilians, marsupial mammals, snakes, tuatara, lamprey, and some other amphibians and one species of fish have gene orders that are less conserved. The most probable mechanism for new gene rearrangements seems to be tandem duplication and multiple deletion events, always associated with tRNA sequences. Some new rearrangements seem to be typical of monophyletic groups and the use of data from these groups may be useful for answering phylogenetic questions involving... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000400008 |
| |
|
|
| Rodrigues,Luís R.R.; Barros,Regina M.S.; Assis,Maria de Fátima L.; Marques-Aguiar,Suely A.; Pieczarka,Julio C.; Nagamachi,Cleusa Y.. |
| The karyotypes of Phyllostomus discolor and P. hastatus from Eastern Amazonia were studied by G-, C-, G/C sequential and Ag-NOR techniques. Both species presented 2n = 32, with the autosome complement composed of 30 bi-armed in P. discolor and 28 bi-armed plus 1 acrocentric in P. hastatus. In both species, the X chromosome is medium submetacentric while the Y is minute acrocentric. The present study found only one difference between the karyotypes of P. discolor and P. hastatus: the smallest autosome (pair 15) is bi-armed in discolor and acrocentric in hastatus, a result best explained by pericentric inversion. The C-banding revealed constitutive heterochromatin only at the centromeric regions of all chromosomes, with the NOR site located at the distal... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000300016 |
| |
|
|
| Chauffaille,Maria de Lourdes L.F.; Marques,Eliana Azevedo; Oliveira,Jose Salvador Rodrigues de; Rodrigues,Maria Madalena; Figueiredo,Maria Stella; Romeo,Maura; Yamamoto,Mihoko; Kerbauy,José. |
| Chronic lymphocytic leukemia (CLL) presents a varying incidence of karyotypic abnormalities whose detection is complicated by difficulties in obtaining mitosis for analysis in this type of mature lymphocyte disorder. Since the introduction of molecular cytogenetics (FISH = fluorescent in situ hybridization), applying centromeric probes for chromosome 12 has made it possible to detect a higher percentage of trisomy 12 cases. The objective of the present study was to detect trisomy 12 by FISH (alpha satellite probe) in 13 patients with CLL whose karyotypes by G-banding were either normal or inadequate. Using this method trisomy 12 was detected in three patients in a percentage of positive cells varying from 55.5% to 79%, showing that FISH is a sensitive and... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000300005 |
| |
|
|
| Bassi,Loredana; Palitti,Fabrizio. |
| DNA topoisomerases catalyze topological changes in DNA that are essential for normal cell cycle progression and therefore they are a preferential target for the development of anticancer drugs. Anti-topoisomerase drugs can be divided into two main classes: "cleavable complex" poisons and catalytic inhibitors. The "cleavable complex" poisons are very effective as anticancer drugs but are also potent inducers of chromosome aberrations so they can cause secondary malignancies. Catalytic inhibitors are cytotoxic but they do not induce chromosome aberrations. Knowledge about the mechanism of action of topoisomerase inhibitors is important to determine the best anti-topoisomerase combinations, with a reduced risk of induction of secondary malignancies. |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000400052 |
| |
|
|
| De Luca,J.C.; Ortiz Jaureguizar,E.; Dulout,F.N.. |
| The degree of similarity between chemical and physical agents in their capacity to induce reciprocal translocations was analyzed by means of multivariate analysis techniques. The effect of three different doses of gamma rays, four doses of X-rays and different doses of adriamycin, mitomycin C, thio-tepa and bleomycin was analyzed. Data were arranged in a basic matrix by two methods: cluster analysis and ordination. Two main groups were found, one including doses of 9 and 10 Gy and the other including the remaining lower doses of ionizing radiation and the other chemicals. Various subgroups were found within the second group. Accordingly, using presence/absence data there was not a specific pattern of chromosomal damage induction for physical and chemical... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000300014 |
| |
|
|
| Beiguelman,Bernardo; Franchi-Pinto,Carla. |
| Analysis of 116,699 deliveries (1062 twin pairs and 115,637 singletons) which occurred from 1984 to 1996 at the largest obstetric center in Campinas, SP, Brazil, provided the following conclusions: 1) despite the low percentage of twin births (0.9%), 10.7% of all early neonatal deaths and 3.5% of all stillbirths were twins. Compared to singletons, the likelihood of stillbirths and early neonatal deaths among twins was 1.9 and 6.5 times greater, respectively. 2) The proportion of twins among early neonatal deaths tended to decrease, probably because of improvements in prenatal and perinatal care. 3) The critical period for early neonatal deaths in singletons and twins lasted for the three first days after birth. 4) The incidence of perinatal deaths among... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000100003 |
| |
|
| |
|
| |
|
|
| Di Masso,Ricardo J.; Silva,Patricia S.; Font,María Teresa. |
| Growth patterns of four lines of mice selected for body conformation were analyzed with the logistic function, in order to provide baseline information about the relationship between asymptotic weight and maturing rate of body weight. Two lines were divergently selected favoring the phenotypic correlation between body weight and tail length (agonistic selection: CBi+, high body weight and long tail; CBi-, low body weight and short tail), whereas the other two lines were generated by a disruptive selection performed against the correlation between the aforementioned traits (antagonistic selection: CBi/C, high body weight and short tail; CBi/L, low body weight and long tail). The logistic parameters A (asymptotic weight) and k (maturing rate) behaved in... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000200016 |
| |
|
|
| Cruz-Landim,Carminda da. |
| Morphological studies of Meliponine worker ovaries in five species indicated a possible stimulatory effect of the queen on ovary development and on the production of trophic eggs in some of them. There are also indications that the queen inhibits the production of fertile eggs by the workers. This inhibition may involve a delay in the development of fertile eggs by the worker, until she is out of direct contact with the queen, or a lack of ovary development in the queen's presence, as seen in Leurotrigona muelleri. The evolutionary tendency toward inability to produce fertile eggs has its extreme representation in the pupal worker ovary reabsorption found in Frieseomelitta silvestri. On the other hand, the finding, in some species, of dwarf queens with the... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000100015 |
| |
|
|
| Vallinoto,Marcelo; Sena,Leonardo; Sampaio,Iracilda; Schneider,Horacio; Schneider,Maria Paula. |
| Mitochondrial DNA-like sequences have been found in the nuclei of a variety of organisms. These nuclear pseudogenes can be used to estimate relative evolutionary rates of mitochondrial genes, and can be used as outgroups in phylogenetic analyses. In this study, mitochondrial sequences with pseudogene-like characteristics, including deletions and/or insertions and stop codons, were found in tamarins (Saguinus spp., Callitrichinae, Primates). Phylogenetic analysis allowed estimation of the timing of the migration of these sequences to the nuclear genome, and also permitted inferences on the phylogeny of the genus. The choice of an inadequate outgroup (Aotus infulatus) prevented a good phylogenetic resolution of the subfamily Callitrichinae. The relatively... |
| Tipo: Info:eu-repo/semantics/article |
|
| Ano: 2000 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-47572000000100006 |
| |
| Registros recuperados: 8.210 | |
|
|
|
