Managing the uncertainties of low-level radioactive waste disposal

A special program developed by the authors, called Pombe, identifies protein coding regions in the Schizosaccharomyces pombe genome. Linear discriminant analysis was applied to predict 5'-terminal, internal, 3'-terminal exons (coding-exon) and introns. The accuracy of the prediction was tested by cross verifications. The sensitivity, specificity and correlation coefficient for the internal exon prediction were 98.5%, 99.9% and 98.3% respectively at the nucleotide level. Open reading frames were studied and used to predict intron-less genes: 99.0% of such genes were identified with correct stopping sites. The gene structure was determined by dynamic programming and the prediction achieved 97.0% correlation coefficient at the nucleotide level. The program is available at http:(/)/clio.cshl.org/genefinder.     

Assessment of the biodegradation potential of psychrotrophic microorganisms

These experiments were designed to establish an animal model of acute carbon monoxide (CO) poisoning in awake habituated rats. On the day before exposure, under a brief anesthesia, a Levine preparation (unilateral common carotid artery occlusion) was performed on group 1 (n = 8) and 2 (n = 28), but not on group 3 rats (n = 8). Group 1 rats were exposed to air as control. Groups 2 and 3 rats were exposed to 0.27% CO in air for 60 min [carboxyhemoglobin (HbCO) = 70%] followed by a 2-day recovery in air. The Levine preparation per se did not induce any detectable physiologic effects on group 1 rats. Identical cardiovascular and metabolic responses to CO occurred in groups 2 and 3. After the CO exposure, all group 3 rats lived for 2 days with normal neurologic index (NI). In group 2 (n = 25 post-CO), 84% of the rats showed increased NI and edema of the ipsilateral cerebral hemisphere, and 76% of the rats died 8.7 +/- 1.7 h after the CO exposure. NI correlated with the brain edema (rs = 0.748, P < 0.001) and inversely correlated with the survival time after the CO exposure (rs = -0.777, P < 0.001). We therefore may conclude that exposure of the Levine-prepared rats to 0.27% CO in air for 60 min will provide a valuable model for testing of different treatments for CO poisoning.     

Prevalence of Cyclospora species and other enteric pathogens among children less than 5 years of age in Nepal

Stools from 124 Nepalese children aged 6 to 60 months with diarrhea were examined for organisms of the coccidian genus Cyclospora and for other enteric pathogens. Enterotoxigenic Escherichia coli, Giardia Lamblia, Campylobacter species, Cyclospora species, and Cryptosporidium species were the most common pathogens identified. Cyclospora species were detected in none of 74 children < 18 months of age compared with 6 (12%) of 50 children > or = 18 months of age (P = 0.004).     

Carcinoma of the male breast: a review and recommendations for management

OBJECTIVES: To investigate whether occupational exposure to organic solvents increases the risk of dementia. METHODS: Cases of dementia were identified from the computed tomography records of eight neuroradiology centres in England and Wales, and were compared with two sets of controls investigated at the same centres. The first set of controls were patients with brain cancer and the second set were patients with other disorders that were not chronically disabling. Lifetime occupational histories were obtained through a postal questionnaire completed by the subjects or their next of kin. Associations between dementia and occupation were examined by logistic regression. RESULTS: Usable questionnaires were returned for 204 (61%) of the cases, 225 (51%) of the controls with brain cancer, and 441 (61%) of the other controls. The findings with each of the two sets of controls were similar. In comparison with all controls combined, cases had less often worked ever as a painter or printer (odds ratio (OR) 0.6, 95% confidence interval (95% CI) 0.3 to 1.2), and were less likely to have worked for > 1 year as a printer, painter, or launderer or dry cleaner (OR 0.6, 95% CI 0.3 to 1.4). CONCLUSIONS: These findings provide no support for the hypothesis that occupational exposure to solvents is a cause of dementia. An excess risk in subsets of workers with extremes of exposure cannot be discounted, but the data indicate that any influence of exposure to solvents on the overall incidence of severe dementia in the general population of England and Wales is small.     

The yeast spindle pole body is assembled around a central crystal of Spc42p

The spindle pole body (SPB) is the microtubule organizing center (MTOC) in the yeast Saccharomyces that plays a pivotal role in such diverse processes as mitosis, budding, and mating. We have used cryoelectron microscopy and image processing to study the structure of isolated diploid SPBs. We show that SPBs are present in two lateral-size classes, sharing a similar vertical architecture comprised of six major layers. Tomographic reconstructions of heparin-stripped SPBs reveal a central hexagonally packed layer. Overexpression of Spc42p results in the growth of a similar layer, forming a crystal that encircles the SPB. Hence, the SPB is an MTOC that utilizes crystallographic packing of subunits in its construction.     

Circular dichroism and electron microscopy of a core Y61F mutant of the F1 gene 5 single-stranded DNA-binding protein and theoretical analysis of CD spectra of four Tyr --> Phe substitutions

A core Y61F mutant of the gene 5 single-stranded DNA-binding protein (g5p) of f1 bacterial virus aggregated when expressed from a plasmid, but, after refolding in vitro, it behaved much like wild-type and may be a stability or folding mutant. Circular dichroism (CD) titrations showed the same cooperative polynucleotide binding modes for Y61F and wild-type g5p. There are n = 4 and n congruent with 2.5 modes for binding to poly[d(A)] at low ionic strengths, but n = 4, n = 3, and n congruent with 2-2.5 modes for binding to fd single-stranded viral DNA (fd ssDNA), where n is the number of nucleotides occluded by each bound g5p monomer in a given mode. Y61F g5p has slightly reduced affinity in the n = 4 mode. Electron microscopy showed that Y61F g5p forms left-handed nucleoprotein superhelices indistinguishable from wild-type. Progression from binding to fd ssDNA in the n = 4 to n = 3 to n congruent with 2-2.5 mode is accompanied by an increase in the number of helical turns, an increase from (7.7 +/- 0.3) to (9.5 +/- 0.3) to ( approximately 10-13) g5p dimers per turn, and a decrease in the number of DNA nucleotides per turn. From CD spectra for four of five possible Y --> F g5p mutants, we infer that the fifth tyrosine, Tyr 56, contributes strongly to the CD. Retention of a strong 229 nm CD band in all mutants indicates that all retain elements of the native structure. Spectra of Y26F, Y34F, and Y61F g5p imply limited mobility of the replacement Phe. Comparison of measured with calculated CD spectra also suggests limited mobility for Tyr 26 and Tyr 34 in g5p in solution, and provides new information that the g5p structure in solution may be dominated by Tyr 41 rotamers differing from that stabilized in the crystal.     

Molecular genetic studies of sporadic pituitary tumors

Tumor formation may result from the activation of dominant oncogenes or by inactivation of recessive, tumor suppressor genes. The role of such mutations in the development of pituitary tumors has been studied. Tumors from 88 patients, representing the 4 major classes of adenoma, were investigated. In DNA extracted from matched leukocyte and tumor samples, allelic deletions were sought with 15 probes identifying restriction fragment length polymorphisms on chromosomes 1, 5, 10, 11, 13, 17, 20, and 22. Evidence of amplification or rearrangement of 10 recognized cellular oncogenes (N-ras, mycL1, mycN, myc, H-ras, bcl1, H-stf1, sea, kraS2, and fos) was sought in tumor DNA. Activating dominant mutations of Gs alpha were detected using the polymerase chain reaction to amplify exons 7-10 and hybridizing the product to normal and mutant allele-specific oligonucleotides. Allelic deletions on chromosome 11 were identified in 16 tumors (18%) representing all 4 major subtypes. Deletions on other autosomes were observed in less than 6% of tumors. Three adenomas had deletions on multiple autosomes, 2 of these were aggressive and recurrent. Mutations of Gs alpha were confirmed to be specific to somatotrophinomas, being identified in 36% of such tumors in this series. No evidence of amplification or rearrangement of other recognized cellular oncogenes was found. Inactivation of a recessive oncogene on chromosome 11 is an important and possibly early event in the development of the four major types of pituitary adenoma, whereas activating mutations of Gs alpha are confirmed to be specific to somatotropinomas. Two aggressive tumors were found to have multiple autosomal losses, suggesting a multistep progression in the development of tumors of this phenotype.     

Evolution of rhizobia by acquisition of a 500-kb symbiosis island that integrates into a phe-tRNA gene

Nodulation and nitrogen fixation genes of Mesorhizobium loti are encoded on the chromosome of the bacterium. Nevertheless, there is strong evidence that these genes can be transferred from an inoculant strain to nonsymbiotic mesorhizobia in the field environment. Here we report that the chromosomal symbiotic element of M. loti strain ICMP3153 is transmissible in laboratory matings to at least three genomic species of nonsymbiotic mesorhizobia. The element is 500 kb in size, integrates into a phe-tRNA gene, and encodes an integrase of the phage P4 family just within its left end. The entire phe-tRNA gene is reconstructed at the left end of the element upon integration, whereas the 3' 17 nucleotides of the tRNA gene are present as a direct repeat at the right end. We termed the element a symbiosis island on the basis of its many similarities to pathogenicity islands. It may represent a class of genetic element that contributes to microbial evolution by acquisition.