Estimated cumulative X-ray exposure and additional cancer risk during the evaluation and treatment of scoliosis in children and young people requiring surgery.

INTRODUCTION: Clinicians and patients must weigh the benefits of radiological imaging against the risks of radiation exposure in the diagnosis and treatment of scoliosis. This report aims to estimate the cumulative absorbed and equivalent dose of radiation in patients undergoing surgical treatment for scoliosis, and to present this as an estimated risk of cancer compared to background radiation levels. METHODS: Retrospective review of estimated absorbed dose on the Computerised Radiology Information System (CRIS®). Patients undergoing surgical correction of scoliosis (age ≤ 25) from August 2010 to August 2015 investigated. Estimated absorbed dose [milligrays (mGy)] recorded. Pedicle screws inserted using image intensification. Equivalent dose [millisieverts (mSv)] and additional cancer risk calculated from the National Research Council document 'Health risks from exposure to low levels of ionising radiation' (2006). RESULTS: 271 patients identified. Mean age 15 (range 2-25). Mean total absorbed dose 2136 mGy [standard deviation (SD) 1700 mGy]. Mean number of plain spine radiographs was 8 (SD 3) with total 1884 mGy exposure (SD 1609 mGy). Additional dose provided by CT (mean 0.17 episodes), plain chest and abdominal radiographs and image intensification. Mean number of image intensification episodes was 1.1 with mean estimated exposure 180 mGy (SD 238 mGy). Image intensification accounted for 8% of the estimated absorbed dose during treatment. Estimated mean effective dose delivered was 20.952 mSv equating to an additional cancer risk of 0.27-0.45%. CONCLUSION: Additional cancer risk from cumulative imaging is small and equivalent to approximately 8 years of natural background radiation. Use of image intensification for pedicle screw insertion is a minor contribution (8%) to the total patient dose.

The genome sequence of Schizosaccharomyces pombe.

We have sequenced and annotated the genome of fission yeast (Schizosaccharomyces pombe), which contains the smallest number of protein-coding genes yet recorded for a eukaryote: 4,824. The centromeres are between 35 and 110 kilobases (kb) and contain related repeats including a highly conserved 1.8-kb element. Regions upstream of genes are longer than in budding yeast (Saccharomyces cerevisiae), possibly reflecting more-extended control regions. Some 43% of the genes contain introns, of which there are 4,730. Fifty genes have significant similarity with human disease genes; half of these are cancer related. We identify highly conserved genes important for eukaryotic cell organization including those required for the cytoskeleton, compartmentation, cell-cycle control, proteolysis, protein phosphorylation and RNA splicing. These genes may have originated with the appearance of eukaryotic life. Few similarly conserved genes that are important for multicellular organization were identified, suggesting that the transition from prokaryotes to eukaryotes required more new genes than did the transition from unicellular to multicellular organization.

The complete nucleotide sequence of chromosome 3 of Plasmodium falciparum.

Analysis of Plasmodium falciparum chromosome 3, and comparison with chromosome 2, highlights novel features of chromosome organization and gene structure. The sub-telomeric regions of chromosome 3 show a conserved order of features, including repetitive DNA sequences, members of multigene families involved in pathogenesis and antigenic variation, a number of conserved pseudogenes, and several genes of unknown function. A putative centromere has been identified that has a core region of about 2 kilobases with an extremely high (adenine + thymidine) composition and arrays of tandem repeats. We have predicted 215 protein-coding genes and two transfer RNA genes in the 1,060,106-base-pair chromosome sequence. The predicted protein-coding genes can be divided into three main classes: 52.6% are not spliced, 45.1% have a large exon with short additional 5' or 3' exons, and 2.3% have a multiple exon structure more typical of higher eukaryotes.

Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence.

Countless millions of people have died from tuberculosis, a chronic infectious disease caused by the tubercle bacillus. The complete genome sequence of the best-characterized strain of Mycobacterium tuberculosis, H37Rv, has been determined and analysed in order to improve our understanding of the biology of this slow-growing pathogen and to help the conception of new prophylactic and therapeutic interventions. The genome comprises 4,411,529 base pairs, contains around 4,000 genes, and has a very high guanine + cytosine content that is reflected in the biased amino-acid content of the proteins. M. tuberculosis differs radically from other bacteria in that a very large portion of its coding capacity is devoted to the production of enzymes involved in lipogenesis and lipolysis, and to two new families of glycine-rich proteins with a repetitive structure that may represent a source of antigenic variation.

The nucleotide sequence of Saccharomyces cerevisiae chromosome IX.

Large-scale systematic sequencing has generally depended on the availability of an ordered library of large-insert bacterial or viral genomic clones for the organism under study. The generation of these large insert libraries, and the location of each clone on a genome map, is a laborious and time-consuming process. In an effort to overcome these problems, several groups have successfully demonstrated the viability of the whole-genome random 'shotgun' method in large-scale sequencing of both viruses and prokaryotes. Here we report the sequence of Saccharomyces cerevisiae chromosome IX, determined in part by a whole-chromosome 'shotgun', and describe the particular difficulties encountered in the random 'shotgun' sequencing of an entire eukaryotic chromosome. Analysis of this sequence shows that chromosome IX contains 221 open reading frames (ORFs), of which approximately 30% have been sequenced previously. This chromosome shows features typical of a small Saccharomyces cerevisiae chromosome.

The nucleotide sequence of Saccharomyces cerevisiae chromosome XIII.

Systematic sequencing of the genome of Saccharomyces cerevisiae has revealed thousands of new predicted genes and allowed analysis of long-range features of chromosomal organization. Generally, genes and predicted genes seem to be distributed evenly throughout the genome, having no overall preference for DNA strand. Apart from the smaller chromosomes, which can have substantially lower gene density in their telomeric regions, there is a consistent average of one open reading frame (ORF) approximately every two kilobases. However, one of the most surprising findings for a eukaryote with approximately 6,000 genes was the amount of apparent redundancy in its genome. This redundancy occurs both between individual ORFs and over more extensive chromosome regions, which have been duplicated preserving gene order and orientation. Here we report the entire nucleotide sequence of chromosome XIII, the sixth-largest S. cerevisiae chromosome, and demonstrate that its features and organization are consistent with those observed for other S. cerevisiae chromosomes. Analysis revealed 459 ORFs, 284 have not been identified previously. Both intra- and interchromosomal duplications of regions of this chromosome have occurred.

Adolescent blood pressure in a cohort study of sickle cell disease.

BACKGROUND: Previous studies on low blood pressure in patients with homozygous sickle cell (SS) disease have sought new hypotheses on the mechanism of low blood pressure but have not analyzed the role of known determinants such as weight. METHODS: Blood pressure has been measured by an automated oscillometric method in 220 patients with SS disease, 144 with sickle cell-hemoglobin C disease (both groups aged, 9.5 to 18.5 years) and 122 control subjects with a normal hemoglobin genotype (aged 16.0 to 18.5 years) participating in a cohort study from birth. RESULTS: Significant age-related increases in systolic and mean arterial pressure occurred in sickle cell-hemoglobin C disease but not in SS disease. Further analyses were confined to a subgroup of 51 patients with SS, 41 patients with sickle cell-hemoglobin C, and 97 subjects with normal hemoglobin, aged 16.0 to 18.5 years in whom simultaneous measurements of height, weight, arm circumference, and hematologic test results were also available. Crude analyses showed significantly lower systolic, diastolic, and mean arterial pressure in SS disease compared with control subjects with normal hemoglobin, but further analysis showed the systolic difference to be confined to males and all differences disappeared after adjustment for weight. No differences occurred in sickle cell-hemoglobin C disease. CONCLUSIONS: These results suggest that the lower blood pressure in SS disease is attributable to low weight and that no further mechanisms need be postulated.

Adolescent blood pressure in a cohort study of sickle cell disease

BACKGROUND: Previous studies on low blood pressure in patients with homozygous sickle cell (SS) disease have sought new hypothesis on the mechanism of low blood pressure but have not analyzed the role of known determinants such as weight. METHODS: Blood pressure has been measured by an automated oscillometric method in 220 patients with SS disease, 144 with sickle cell-hemoglobin C disease (both groups aged, 9.5 to 18.5 years) and 122 control subjects with a normal hemoglobin genotype (aged 16.0 to 18.5 years) participating in a cohort study from birth. RESULTS: Significant age-related increases in systolic and mean arterial pressure occurred in sickle cell-hemoglobin C disease but not in SS disease. Further analysis were confined to a subgroup of 51 patients with SS, 41 patients with sickle cell-hemoglobin C, and 97 subjects with normal hemoglobin, aged 16.0 to 18.5 years in whom simultaneous measurements of height, weight, arm circumference, and hematologic test results were also available. Crude analysis showed significantly lower systolic, diastolic, and mean arterial pressure in SS disease compared with control subjects with normal hemaglobin, but further analysis showed the systolic difference to be confined to males and all differences disapperared after ajustment for weight. No difference occurred in sickle cell-hemoglobin C disease. CONCLUSIONS: These results suggest that the lower blood pressure in SS disease is attributable to low weight and that no further mechanisms need be postulated (AU)

Selective utilization of serum vitamin A for visual pigment synthesis.

Two groups of goldfish (Carassius auratus) were subjected to light and temperature conditions known to promote a contrast in their scotopic visual pigment compositions. After 3 weeks, the porphyropsin/rhodopsin ratio in the neuroretina of these goldfish ranged from 99% porphyropsin in one group to 59% in the other. Samples of blood, liver and retinal pigment epithelium (RPE) were also removed from these animals and analysed by high-performance liquid chromatography (HPLC) for vitamin A composition. There was consistently more vitamin A2 than vitamin A1 (over 50% vitamin A2) in both vitamin A alcohol and vitamin A esters extracted from the liver and the RPE. In contrast, only 30% of all vitamin A extracted from the blood was vitamin A2. These observations suggest that it is mainly vitamin A1 that is transported in the blood, whereas vitamin A2 is selectively retained in the liver and in the RPE and used to form porphyropsin in the eye.