634 resultados para GTG-banding


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Polymers tied together by constraints exhibit an internal pressure; this idea is used to analyze physical properties of the bottle-brush–like chromosomes of meiotic prophase that consist of polymer-like flexible chromatin loops, attached to a central axis. Using a minimal number of experimental parameters, semiquantitative predictions are made for the bending rigidity, radius, and axial tension of such brushes, and the repulsion acting between brushes whose bristles are forced to overlap. The retraction of lampbrush loops when the nascent transcripts are stripped away, the oval shape of diplotene bivalents between chiasmata, and the rigidity of pachytene chromosomes are all manifestations of chromatin pressure. This two-phase (chromatin plus buffer) picture that suffices for meiotic chromosomes has to be supplemented by a third constituent, a chromatin glue to understand mitotic chromosomes, and explain how condensation can drive the resolution of entanglements. This process resembles a thermal annealing in that a parameter (the affinity of the glue for chromatin and/or the affinity of the chromatin for buffer) has to be tuned to achieve optimal results. Mechanical measurements to characterize this protein–chromatin matrix are proposed. Finally, the propensity for even slightly chemically dissimilar polymers to phase separate (cluster like with like) can explain the apparent segregation of the chromatin into A+T- and G+C-rich regions revealed by chromosome banding.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Chromosome painting in placental mammalians illustrates that genome evolution is marked by chromosomal synteny conservation and that the association of chromosomes 3 and 21 may be the largest widely conserved syntenic block known for mammals. We studied intrachromosomal rearrangements of the syntenic block 3/21 by using probes derived from chromosomal subregions with a resolution of up to 10–15 Mbp. We demonstrate that the rearrangements visualized by chromosome painting, mostly translocations, are only a fraction of the actual chromosomal changes that have occurred during evolution. The ancestral segment order for both primates and carnivores is still found in some species in both orders. From the ancestral primate/carnivore condition an inversion is needed to derive the pig homolog, and a fission of chromosome 21 and a pericentric inversion is needed to derive the Bornean orangutan condition. Two overlapping inversions in the chromosome 3 homolog then would lead to the chromosome form found in humans and African apes. This reconstruction of the origin of human chromosome 3 contrasts with the generally accepted scenario derived from chromosome banding in which it was proposed that only one pericentric inversion was needed. From the ancestral form for Old World primates (now found in the Bornean orangutan) a pericentric inversion and centromere shift leads to the chromosome ancestral for all Old World monkeys. Intrachromosomal rearrangements, as shown here, make up a set of potentially plentiful and informative markers that can be used for phylogenetic reconstruction and a more refined comparative mapping of the genome.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Phyllosphere microbial communities were evaluated on leaves of field-grown plant species by culture-dependent and -independent methods. Denaturing gradient gel electrophoresis (DGGE) with 16S rDNA primers generally indicated that microbial community structures were similar on different individuals of the same plant species, but unique on different plant species. Phyllosphere bacteria were identified from Citrus sinesis (cv. Valencia) by using DGGE analysis followed by cloning and sequencing of the dominant rDNA bands. Of the 17 unique sequences obtained, database queries showed only four strains that had been described previously as phyllosphere bacteria. Five of the 17 sequences had 16S similarities lower than 90% to database entries, suggesting that they represent previously undescribed species. In addition, three fungal species were also identified. Very different 16S rDNA DGGE banding profiles were obtained when replicate cv. Valencia leaf samples were cultured in BIOLOG EcoPlates for 4.5 days. All of these rDNA sequences had 97–100% similarity to those of known phyllosphere bacteria, but only two of them matched those identified by the culture independent DGGE analysis. Like other studied ecosystems, microbial phyllosphere communities therefore are more complex than previously thought, based on conventional culture-based methods.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper presents a discussion of the status of the field of coral geochemistry as it relates to the recovery of past records of ocean chemistry, ocean circulation, and climate. The first part is a brief review of coral biology, density banding, and other important factors involved in understanding corals as proxies of environmental variables. The second part is a synthesis of the information available to date on extracting records of the carbon cycle and climate change. It is clear from these proxy records that decade time-scale variability of mixing processes in the oceans is a dominant signal. That Western and Eastern tropical Pacific El Niño-Southern Oscillation (ENSO) records differ is an important piece of the puzzle for understanding regional and global climate change. Input of anthropogenic CO2 to the oceans as observed by 13C and 14C isotopes in corals is partially obscured by natural variability. Nonetheless, the general trend over time toward lower δ18O values at numerous sites in the world’s tropical oceans suggests a gradual warming and/or freshening of the surface ocean over the past century.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Aberrations of the long arm of chromosome 11 are among the most common chromosome abnormalities in lymphoproliferative disorders (LPD). Translocations involving BCL1 at 11q13 are strongly associated with mantle cell lymphoma. other nonrandom aberrations, especially deletions and, less frequently, translocations, involving bands 11q21-923 have been identified by chromosome banding analysis. To date, the critical genomic segment and candidate genes involved in these deletions have not been identified. In the present study, we have analyzed tumors from 43 patients with LPD (B-cell chronic lymphocytic leukemia, n = 40; mantle cell lymphoma, n = 3) showing aberrations of bands 11q21-923 by fluorescence in situ hybridization. As probes we used Alu-PCR products from 17 yeast artificial chromosome clones spanning chromosome bands 11q14.3-923.3, including a panel of yeast artificial chromosome clones recognizing a contiguous genomic DNA fragment of approximately 9-10 Mb in bands 11q22.3-923.3. In the 41 tumors exhibiting deletions, we identified a commonly deleted segment in band 11q22.3-923.1; this region is approximately 2-3 Mb in size and contains the genes coding for ATM (ataxia telangiectasia mutated), RDX (radixin), and FDX1 (ferredoxin 1). Furthermore, two translocation break-points were localized to a 1.8-Mb genomic fragment contained within the commonly deleted segment. Thus, we have identified a single critical region of 2-3 Mb in size in which 11q14-923 aberrations in LPD cluster. This provides the basis for the identification of the gene(s) at 11q22.3-923.1 that are involved in the pathogenesis of LPD.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Introdução: A obesidade é uma afecção com alta prevalência no Brasil e no mundo. É fator de risco para comorbidades como Diabetes tipo 2 (DM2), Hipertensão Arterial Sistêmica (HAS), Dislipidemia, Apneia Obstrutiva do Sono (AOS), entre outras. Seu tratamento é complexo e a cirurgia bariátrica, executada por diferentes técnicas, tem sido uma das opções. Objetivo: Analisar os resultados publicados na literatura em relação às técnicas cirúrgicas de Banda Gástrica Ajustável (BGA), Gastrectomia Vertical (GV), Gastroplastia com derivação em Y de Roux (GDYR) e Derivação Biliopancreática (DBP) - técnica de \"Scopinaro\" e de \"Duodenal Switch\" quanto às complicações operatórias, à mortalidade, à perda do excesso de peso (PEP) e ao reganho, e a resolução das comorbidades após a operação. Método: Foram analisados 116 estudos selecionados na base de dados MEDLINE por meio da PubMed publicados na Língua Inglesa entre 2003 e 2014. Para comparar as diferentes técnicas cirúrgicas (BGA, GV, GDYR e DBP), realizou-se estudo estatístico por meio da análise de variância (ANOVA) aplicando os testes de Duncan e de Kruskal Wallis avaliando: complicações pós-operatórias (fístula, sangramento e óbito); perda e reganho do excesso de peso, e resolução das comorbidades. Resultados: A ocorrência de sangramento foi de 0,6% na média entre todos os estudos, sendo 0,44% na BGA; 1,29% na GV; 0,81% na GDYR e 2,09% na DBP. Já a ocorrência de fístulas foi de 1,3% na média entre todos os estudos, 0,68% para BGA; 1,93% para GV; 2,18% para GDYR e 5,23% para DBP. A mortalidade nos primeiros 30 dias pós-operatórios foi de 0,9% na média entre todos os estudos, 0,05% na BGA; 0,16% na GV; 0,60% na GDYR e 2,52% na DBP. A PEP após cinco anos na média entre todos os estudos foi de 63,86%, especificamente na BGA, foi de 48,35%; 52,7% na GV; 71,04% na GDYR e 77,90% na DBP. A taxa de DM2 resolvida foi de 76,9% na média entre todos os estudos, sendo 46,80% na BGA; 79,38% na GV; 79,86% na GDYR e 90,78% na DBP. A taxa de Dislipidemia resolvida após a operação foi de 74,0% na média de todo o estudo, sendo 51,28% na BGA; 58,00% na GV; 73,28% na GDYR e 90,75% na DBP. A taxa de HAS resolvida após a operação foi de 61,80% na média de todo o estudo, sendo 54,50% na BGA; 52,27% na GV; 68,11% na GDYR e 82,12% na DBP. A taxa de AOS resolvida após a operação foi de 75,0% na média de todo o estudo, sendo 56,85% na BGA; 51,43% na GV; 80,31% na GDYR e 92,50% na DBP. Conclusão: quando analisadas e comparada as quatro técnicas observa-se que nos primeiros 30 dias pós-operatório a taxa de sangramento é superior nos pacientes submetidos à DBP e taxa de fístula inferior nos pacientes da BGA. Quanto à mortalidade observou-se taxa mais pronunciada nos pacientes submetidos à DBP e menos nos submetidos à BGA. Quanto à PEP observou-se uma uniformidade entre os pacientes submetidos à GV, GDYR E DBP até o terceiro ano. Após esse período observa-se reganho de peso nos submetidos à GV até o quinto ano de seguimento. Já nos pacientes submetidos à BGA observou-se taxas de PEP menos pronunciadas em relação às demais desde o início do seguimento. Quanto à resolução das comorbidades observou-se taxas de resolução de DM2 inferiores nos pacientes submetidos à BGA, e não houve diferença entre nenhuma técnica quanto à resolução das demais comorbidades: HAS, AOS e dislipidemia