Micro abrasive blasting delivers 21st century stents.

As the applications for stents expand, contract manufacturers have responded with improvements in manufacturing operations.

A three-dimensional structural dissection of Drosophila polytene chromosomes.

We have analyzed the three-dimensional structural details of Drosophila melanogaster polytene chromosome bands and interbands using three-dimensional light microscopy and a novel method of sample preparation that does not involve flattening or stretching the chromosomes. Bands have been visualized in unfixed chromosomes stained with the DNA specific dye 4,6-Diamidino-2-phenylindole (DAPI). Interbands have been visualized using fixed chromosomes that have been immunostained with an antibody to RNA polymerase II. Additionally, these structures have been analyzed using in situ hybridization with probes from specific genetic loci (Notch and white). Bands are seen to be composed of approximately 36 substructural features that measure 0.2-0.4 micron in diameter. We suggest that these substructural features are in fact longitudinal fibers made up of bundles of chromatids. Band shape can be a reproducible characteristic of a particular band and is dependent on the spatial relationship of these bundles, varying from bands with a uniform distribution of bundles to bands with a peripheral concentration of chromatin. Interbands are composed of bundles of chromatids of a similar size and number as those seen in the bands. The distribution of bundles is similar between a band and the neighboring interband, implying that there is a long range organization to the DNA that includes both the coding and the noncoding portions of genes. Finally, we note that the polytene chromosome has a circular shape when viewed in cross section, whether there are one or two homologs present.

The onset of homologous chromosome pairing during Drosophila melanogaster embryogenesis.

We have determined the position within the nucleus of homologous sites of the histone gene cluster in Drosophila melanogaster using in situ hybridization and high-resolution, three-dimensional wide field fluorescence microscopy. A 4.8-kb biotinylated probe for the histone gene repeat, located approximately midway along the short arm of chromosome 2, was hybridized to whole-mount embryos in late syncytial and early cellular blastoderm stages. Our results show that the two homologous histone loci are distinct and separate through all stages of the cell cycle up to nuclear cycle 13. By dramatic contrast, the two homologous clusters were found to colocalize with high frequency during interphase of cycle 14. Concomitant with homolog pairing at cycle 14, both histone loci were also found to move from their position near the midline of the nucleus toward the apical side. This result suggests that coincident with the initiation of zygotic transcription, there is dramatic chromosome and nuclear reorganization between nuclear cycles 13 and 14.

Precise determination of the molecular limits of a polytene chromosome band: regulatory sequences for the Notch gene are in the interband.

We have aligned the molecular map of the Notch locus to the cytological features of the salivary gland polytene chromosomes of D. melanogaster in order to determine the interphase chromatin structure of this gene. Using high-resolution in situ hybridization and computer-aided optical microscope data collection and image analysis, we have determined that the coding portions and introns of the Notch gene, which is not expressed in this tissue, are all contained within the polytene chromosome band 3C7. The portion of the Notch gene that resides 5' to the start of transcription lies in an open chromatin conformation, the interband between bands 3C6 and 3C7. Our data are most consistent with condensation of the chromosomal DNA into 30 nm fibers in this polytene band.

Studies on the turnover of methionine oxidized alpha-1-protease inhibitor in rats.

Alpha-1-protease inhibitor (alpha-1-PI) is the major regulator of extracellular leukocyte elastase activity and can be rendered impotent against elastase by oxidation of a critical methionine, residue 358. Alpha-1-PI was isolated from rat plasma by affinity chromatography on Sepharose-bound anhydrochymotrypsin, DEAE-cellulose anion-exchange, and Sephadex G-150 gel filtration. The product was radiolabeled using non-oxidative conditions with Bolton-Hunter reagent, and an aliquot subsequently oxidized with N-chlorosuccinimide. Turnover studies in rats indicated that both native and oxidized alpha-1-PI had half-lives of 170 min. Using partially purified human neutrophil methionine sulfoxide-peptide reductase (Met(O)PR), it was demonstrated that oxidized product could be converted back "in vitro" to an active inhibitor of elastase. To assess whether oxidized alpha-1-PI underwent reduction "in vivo," methionine-oxidized rat inhibitor was injected into the rats, aliquots of plasma samples were withdrawan and passed through a Sepharose-bound anhydrochymotrypsin affinity resin, and bound functional alpha-1-PI was eluted with 0.1 M chymostatin. Radioactive counting of bound and unbound fractions indicated that reduction does not occur in vivo and suggested that, at least under homeostatic conditions, the Met(O)PR is confined to intracellular sites where it does not have access to the circulating protein.

Multiply resistant pneumococcus causing meningitis: its epidemiology within a day-care centre.

An 11 month-old infant had meningitis caused by a strain of Streptococcus pneumoniae, serotype 6b, resistant to penicillin, chloramphenicol, and several other antimicrobials. The minimum inhibitory concentrations (MIC) by agar dilution were 1.0 microgram/ml for penicillin and 16 microgram/ml for chloramphenicol. The infant did not respond to high-dose intravenous penicillin G but was cured by a combination of ampicillin, chloramphenicol, and rifampicin. At the infant's day-care centre this multiply resistant strain was isolated from throat cultures of 27% of the children (age less than or equal to 26 months) assigned to the same room as the index case, and from 11% of older children and staff. There was a 33% carriage rate in family contacts of colonised children. Antibiotic use during the previous 2 months was more frequent among the carriers than among non-carriers. No resistant pneumococci were found in on hundred and twenty-five children and staff in six other Denver day-care centres, in 300 consecutive routine throat cultures processed by our clinical microbiology laboratory, or among 150 pneumococcal isolates collected from Denver area hospitals. The carriers were not treated, and there have been no other cases of infection due to this strain. The emergence of multiply resistant pneumococci in the United States indicates the need to screen important pneumococcal isolates for resistance to both penicillin and chloramphenicol, especially in cases of meningitis.