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Biomedical subjects

J Hansen

Publications and source records attributed to J Hansen.

At least 145 records · Page 8Linked to original sources
PubMed1996

[Occupational exposure to formaldehyde and risk of cancer].

Formaldehyde is a widespread animal carcinogen with limited evidence of carcinogenesis in humans. We investigated the occupational risk of cancer (1970-84) among men and women in Denmark. Relative risks (RR) were estimated from standardized proportionate incidence ratios among patients whose longest employment had been held since 1964, at least 10 years before diagnosis, in 265 companies in which exposure to formaldehyde was identified. The only biologically plausible increased risk was for nasal cancer, for which relative risks of 2.3 (95% confidence interval = 1.3-4.0) and 2.4 (0.6-6.0) appeared for men and women, respectively. In the subgroup of blue-collar men with no probable exposure to wood-dust, the major confounder, the relative risk for this cancer was 3.0 (1.4-5.7). It is concluded that occupational exposure to formaldehyde may increase the risk of nasal cancer, but formaldehyde does probably not affect other cancers.

Adult↗
PubMed1996

Prenatal and postnatal prevalence of Turner's syndrome: a registry study.

OBJECTIVE: To study prevalence of Turner's syndrome in Denmark and to assess validity of prenatal diagnosis. DESIGN: Study of data on prenatal and postnatal Turner's syndrome in Danish Cytogenetic Central Register. SUBJECTS: All registered Turner's syndrome karyotypes (100 prenatal cases and 215 postnatal cases) during 1970-93. MAIN OUTCOME MEASURES: Prevalence of Turner's syndrome karyotypes among prenatally tested fetuses and Turner's syndrome among liveborn infants. RESULTS: Among infant girls, prevalence of Turner's syndrome was 32/100,000. Among female fetuses tested by amniocentesis, prevalence of Turner's syndrome karyotypes was 176/100,000 (relative risk of syndrome, 6.74 compared with prevalence among untested pregnancies). Among female fetuses tested by chorion villus sampling, prevalence of syndrome karyotypes was 392/100,000 (relative risk, 16.8). We excluded prenatal tests referred because of results of ultrasound scanning: among fetuses tested by amniocentesis revised relative risk was 5.68, while revised relative risk among fetuses tested by chorion villus sampling was 13.3. For 29 fetuses with prenatal diagnosis of possible Turner's syndrome, pregnancy was allowed to continue and 24 children were live born. Thirteen of these children were karyotyped postnatally, and diagnosis of Turner's syndrome had to be revised for eight, seven being normal girls and one boy. This gives tentative predictive value of amniocentesis in diagnosing Turner's syndrome of between 21% and 67%. There was no significant relation between mother's age and risk of Turner's syndrome. CONCLUSIONS: Discrepancy between prenatal and postnatal prevalence of Turner's syndrome challenges specificity of prenatal examination in diagnosing Turner's syndrome.

Adolescent↗
PubMed1996

Cleavage site analysis in picornaviral polyproteins: discovering cellular targets by neural networks.

Picornaviral proteinases are responsible for maturation cleavages of the viral polyprotein, but also catalyze the degradation of cellular targets. Using graphical visualization techniques and neural network algorithms, we have investigated the sequence specificity of the two proteinases 2Apro and 3Cpro. The cleavage of VP0 (giving rise to VP2 and VP4), which is carried out by a so-far unknown proteinase, was also examined. In combination with a novel surface exposure prediction algorithm, our neural network approach successfully distinguishes known cleavage sites from noncleavage sites and yields a more consistent definition of features common to these sites. The method is able to predict experimentally determined cleavage sites in cellular proteins. We present a list of mammalian and other proteins that are predicted to be possible targets for the viral proteinases. Whether these proteins are indeed cleaved awaits experimental verification. Additionally, we report several errors detected in the protein databases. A computer server for prediction of cleavage sites by picornaviral proteinases is publicly available at the e-mail address NetPicoRNA@cbs.dtu.dk or via WWW at http:@www.cbs.dtu.dk/services/NetPicoRNA/.

Amino Acid Sequence↗
PubMed1996

Relationship between protein structure and geometrical constraints.

We evaluate to what extent the structure of proteins can be deduced from incomplete knowledge of disulfide bridges, surface assignments, secondary structure assignments, and additional distance constraints. A cost function taking such constraints into account was used to obtain protein structures using a simple minimization algorithm. For small proteins, the approximate structure could be obtained using one additional distance constraint for each amino acid in the protein. We also studied the effect of using predicted secondary structure and surface assignments. The constraints used in this approach typically may be obtained from low-resolution experimental data. When using a cost function based on distances, half of the resulting structures will be mirrored, because the resulting structure and its mirror image will have the same cost. The secondary structure assignments were therefore divided into chirality constraints and distance constraints. Here we report that the problem of mirrored structures, in some cases, can be solved by using a chirality term in the cost function.

Protein Structure, Secondary↗
PubMed1996

Radiation dose by spiral CT and conventional tomography of the sternoclavicular joints and the manubrium sterni.

UNLABELLED: OBJECTIVE DESIGN AND PATIENTS: Conventional frontal tomography of the sternum has to some extent been replaced by spiral computed tomography (CT). The objective of this study was to analyse this change of procedure in terms of dosimetry by measurement of the radiation dose to individual organs using an anthropomorphic Rando Alderson phantom. RESULTS: The total effective radiation dose in examination of the sternoclavicular joints and the manubrium sterni was found to be lower using spiral CT than conventional tomography, the values being 0.6 and 0.8 mSv, respectively. CONCLUSION: As spiral CT is diagnostically comparable and in some respects superior to tomography, its use is recommended for studies of the sternum.

Humans↗
PubMed1996

Management of accidentally found pathological lymph nodes on routine screening mammography.

Normal lymph nodes in the anterior part of the axilla are readily seen on routine mammography. It is important, however, to recognize pathological lymph nodes, characterized by increased attenuation, high density, a round or irregular shape and lack of fat in the hilus, as they often indicate significant diseases. We examined the final diagnosis in 22 patients referred for clinical examination from a mammographic screening programme because of pathological lymph nodes without concomitant breast malignancy. Ten of them were found to have a malignant lesion, and one had sarcoidosis. None of the malignancies had been diagnosed before screening. Among women with abnormal but impalpable nodes, only one malignancy was found (in a woman with previous breast cancer), whereas nine of 13 women with palpable nodes had malignancies. Seven malignant lymphomas were discovered, but among all 60 women of the age group in question with newly diagnosed lymphomas in the region, only 13 had pathological axillary nodes. Mammography cannot therefore be used as a screening method for lymphoma. We conclude that mammographically pathological lymph nodes in the axilla should be examined clinically and propose a simple programme for patient management.

Adult↗
PubMed1996

Occurrence of cancer in women with Turner syndrome.

A study of cancer incidence in a cohort of 597 women with Turner syndrome (TS) and a virtually complete follow-up is presented. The cohort was established from the Danish Cytogenetic Register. Information on cancer incidence was obtained from the Danish Cancer Registry and compared with the expected number calculated from the age-, period- and site-specific cancer rates for Danish women. A total of 21 neoplasms was observed, of which 13 occurred more than 1 year after diagnosis of TS, corresponding to a relative risk of cancer of 1.1. Wilms' tumour was the only identified childhood cancer. No case of gonadoblastoma or dysgerminoma was identified in the 29 women with a Y chromosome or in the women in whom no Y chromosome material was detected by standard cytogenetic methods, suggesting that the risk of ovarian germ cell tumours may be lower than previously estimated. Colon cancer was observed in five patients (relative risk 6.9, 95% confidence interval 2.2-16.2). Further studies are needed to assess whether colon cancer in TS is related to Turner-associated genes on the sex chromosome(s).

Adolescent↗
PubMed1996

Inactivation of MET10 in brewer's yeast specifically increases SO2 formation during beer production.

Sulfite is widely used as an antioxidant in food production. In beer brewing, sulfite has the additional role of stabilizing the flavor by forming adducts with aldehydes. Inadequate amounts of sulfite are sometimes produced by brewer's yeasts, so means of controlling the sulfite production are desired. In Saccharomyces yeasts, MET10 encodes a subunit of sulfite reductase. Partial or full elimination of MET10 gene activity in a brewer's yeast resulted in increased sulfite accumulation. Beer produced with such yeasts was quite satisfactory and showed increased flavor stability.

Alleles↗
PubMed1996

Exposure to crocidolite and the incidence of different histological types of lung cancer.

OBJECTIVES: To estimate the relations between exposure to both tobacco smoke and crocidolite and the incidence of various histological types of lung cancer. METHODS: In 1979 all former workers from the Wittenoom asbestos industry who could be traced were sent a questionnaire on smoking history. Of 2928 questionnaires sent, satisfactory replies were received from 2400 men and 149 women. Of the men, 80% had smoked at some time and 50% still smoked. Occupational exposure to crocidolite was known from employment records and follow up was maintained through death and cancer registries in Australia with histological diagnoses obtained from the relevant State Cancer Registry. Conditional logistic regression was used to estimate the effects of tobacco and asbestos exposure on incidence of different cell types of lung cancer in a nested case-control design. RESULTS: Between 1979 and 1990, 71 cases of lung cancer occurred among men in this cohort: 27% squamous cell carcinoma, 31% adenocarcinoma, 18% small cell carcinoma, 11% large cell carcinoma, and 13% unclassified or indeterminate. Two of the classified cases and one unclassified case had never smoked. The incidence of both squamous and adenocarcinoma types of lung cancer were greatest in ex-smokers and in those subjects with the highest levels of exposure to crocidolite. After adjustment for smoking habit, the increase in incidence of lung cancer with increasing exposure to crocidolite was greater for squamous cell carcinoma than for adenocarcinoma. CONCLUSIONS: The results from this study have shown significant exposure-response effects for exposure to crocidolite, and both adenocarcinoma and squamous cell carcinoma of the lung. They also provide some further evidence against the theory that parenchymal fibrosis induced by asbestos is a necessary precursor to asbestos induced lung cancer.

Adenocarcinoma↗
PubMed1996

Total effective radiation dose from spiral CT and conventional radiography of the pelvis with regard to fracture classification.

PURPOSE: In most departments CT has replaced special radiographic projections with regard to classification of pelvic fractures. This change of procedure calls for analysis in terms of dosimetry. METHODS: The total effective radiation doses given with spiral CT and conventional 5 projection radiography were determined according to ICRP 60 by measuring organ doses with an anthropomorphic Rando Alderson phantom packed with thermoluminescence dosimeters. For comparison, easily obtainable calculated effective doses were also determined, based on the CT dose index (CTDI), measured free-in-air and as entrance surface dose using organ conversion factors according to NRPB-R250 and NRPB-R262. RESULTS: The total effective radiation dose was lower in spiral CT than in conventional 5 projection radiography, 4.4 and 5.0 mSv, respectively. In spiral CT the calculated effective dose was 11% lower and in conventional radiography 68% higher than the dose obtained by actual measurement using the Alderson phantom. CONCLUSION: As CT gives important diagnostic information with regard to classification of pelvic fractures, and without a greater radiation risk than impacted by 5 projection conventional radiography, we recommend the performance of spiral CT instead of special projections.

Acetabulum↗