Localization of chromosomal DNA sequences homologous to ribosomal gene type I insertion DNA in Drosophila melanogaster

Chromosomal sites which have DNA homology to the 1 kb (kilobase pair) Bam HI restrictable fragment of the 5 kb type I insertion present in many ribosomal genes in Drosophila melanogaster , were identified by using in situ hybridization and autoradiography. XX and XY complements of polytene chromosomes showed the nucleolus and chromocenter to be heavily labeled. Of the light label over euchromatic regions, the 102C band of chromosome 4 labeled particularly intensely. In mitotic XX and XY complements, the NORs (nucleolus organizer regions) of both sex chromosomes labeled as did the centromeric heterochromatin of autosomes. Label also appeared less frequently over telomeric and euchromatic regions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47555/1/438_2004_Article_BF00328069.pd

Evidence for heterogeneity in heterochromatin of Drosophila melanogaster

In Drosophila melanogaster the heterochromatin comprises the whole of the Y chromosome, about the proximal third of the X chromosome and the centromeric areas of chromosomes 2 and 3. It appears throughout the cell cycle as darkly staining and highly condensed chromatin and replicates later than euchromatin during the synthetic period. The heterochromatin of Drosophila is considered genetically inert because it contains very few mappable genes, although it has marked genetic effects in determining the well known position effect. It has recently been found that the heterochromatin of Drosophila corresponds to the C bands and contains highly repetitive DNA. None of these characteristics has, however, so far been of any use in solving the problem of the functional role of the heterochromatin. The heterochromatin regions of D. melanogaster fluoresce differently after staining both with quinacrine and with the compound 33258 Hoechst. Here are described experiments in which the heterochromatin of Drosophila was differentiated by means of treatment of the living ganglia cells with 33258 Hoechst, which is known to decondense the centric heterochromatin of the mouse

Surgical Patterns of Care in Patients with Invasive Breast Cancer Treated with Neoadjuvant Systemic Therapy and Breast Magnetic Resonance Imaging: Results of a Secondary Analysis of TBCRC 017

BACKGROUND: Neoadjuvant chemotherapy (NCT) down-stages advanced primary tumors, with magnetic resonance imaging (MRI) being the most sensitive imaging predictor of response. However, the impact of MRI evaluation on surgical treatment decisions in the neoadjuvant setting has not been well described. We report surgical patterns of care across 8 National Cancer Institute comprehensive cancer centers in women receiving both NCT and MRI to evaluate the impact of MRI findings on surgical planning. METHODS: Seven hundred seventy women from 8 institutions received NCT with MRI obtained both before and after systemic treatment. Univariate and multivariate analyses of imaging, patient-, and tumor-related covariates associated with choice of breast surgery were conducted. RESULTS: MRI and surgical data were available on 759 of 770 patients. A total of 345 of 759 (45 %) patients received breast-conserving surgery and 414 of 759 (55 %) received mastectomy. Mastectomy occurred more commonly in patients with incomplete MRI response versus complete (58 vs. 43 %) (p = 0.0003). On multivariate analysis, positive estrogen receptor status (p = 0.02), incomplete MRI response (p = 0.0003), higher baseline T classification (p < 0.0001), younger age (p < 0.0006), and institution (p = 0.003) were independent predictors of mastectomy. A statistically significant trend toward increasing use of mastectomy with increasing T stage at presentation (p < 0.0001) was observed in patients with incomplete response by MRI only. Among women with complete response on MRI, 43 % underwent mastectomy. CONCLUSIONS: Within a multi-institutional cohort of women undergoing neoadjuvant treatment for breast cancer, MRI findings were not clearly associated with extent of surgery. This study shows that receptor status, T stage at diagnosis, young age, and treating institution are more significant determinants of surgical treatment choice than MRI response data