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By examining published, empirical data we show that men and women consistently differ in the shape of the distribution of the number of sexual partners. The female distribution is always relatively narrow-variance is low-with a big majority of women having a number of partners close to the average. The male distribution is much wider-variance is high-with many men having few sex partners and many others having more partners than most females. Using stochastic modelling we demonstrate that this difference in variance is, in principle, sufficient to cause a difference in the gender prevalence of sexually transmitted diseases: compared to the situation where the genders have identical sex partner distributions, men will reach a lower equilibrium value, while women will stay at the same level (meaning that female prevalence becomes higher than male). We carefully analyse model behaviour and derive approximate expressions for equilibrium prevalences in the two different scenarios. We find that the size of the difference in gender prevalence depends on the variance ratio (the ratio between the variances of the male and female sex partner distributions), on the expected number of life-time partners, and on the probability of disease transmission. We note that in addition to humans, the variance phenomenon described here is likely to play a role for sexually transmitted diseases in other species also. We also show, again by examining published, empirical data, that the female to male prevalence ratio increases with the overall prevalence of a sexually transmitted disease (i.e., the more widespread the disease, the more women are affected). We suggest that this pattern may be caused by the effect described above in highly prevalent sexually transmitted diseases, while its impact in low-prevalence epidemics is surpassed by the action of high-risk individuals (mostly males).

We have performed a computational analysis of DNA structural features in 18 fully sequenced prokaryotic genomes using models for DNA curvature, DNA flexibility, and DNA stability. The structural values that are computed for the Escherichia coli chromosome are significantly different from (and generally more extreme than) that expected from the nucleotide composition. To aid this analysis, we have constructed tools that plot structural measures for all positions in a long DNA sequence (e.g. an entire chromosome) in the form of color-coded wheels (http://www.cbs.dtu. dk/services/GenomeAtlas/). We find that these "structural atlases" are useful for the discovery of interesting features that may then be investigated in more depth using statistical methods. From investigation of the E. coli structural atlas, we discovered a genome-wide trend, where an extended region encompassing the terminus displays a high of level curvature, a low level of flexibility, and a low degree of helix stability. The same situation is found in the distantly related Gram-positive bacterium Bacillus subtilis, suggesting that the phenomenon is biologically relevant. Based on a search for long DNA segments where all the independent structural measures agree, we have found a set of 20 regions with identical and very extreme structural properties. Due to their strong inherent curvature, we suggest that these may function as topological domain boundaries by efficiently organizing plectonemically supercoiled DNA. Interestingly, we find that in practically all the investigated eubacterial and archaeal genomes, there is a trend for promoter DNA being more curved, less flexible, and less stable than DNA in coding regions and in intergenic DNA without promoters. This trend is present regardless of the absolute levels of the structural parameters, and we suggest that this may be related to the requirement for helix unwinding during initiation of transcription, or perhaps to the previously observed location of promoters at the apex of plectonemically supercoiled DNA. We have also analyzed the structural similarities between groups of genes by clustering all RNA and protein-encoding genes in E. coli, based on the average structural parameters. We find that most ribosomal genes (protein-encoding as well as rRNA genes) cluster together, and we suggest that DNA structure may play a role in the transcription of these highly expressed genes., (Copyright 2000 Academic Press.)

The fact that DNA three-dimensional structure is important for transcriptional regulation begs the question of whether eukaryotic promoters contain general structural features independently of what genes they control. We present an analysis of a large set of human RNA polymerase II promoters with a very low level of sequence similarity. The sequences, which include both TATA-containing and TATA-less promoters, are aligned by hidden Markov models. Using three different models of sequence-derived DNA bendability, the aligned promoters display a common structural profile with bendability being low in a region upstream of the transcriptional start point and significantly higher downstream. Investigation of the sequence composition in the two regions shows that the bendability profile originates from the sequential structure of the DNA, rather than the general nucleotide composition. Several trinucleotides known to have high propensity for major groove compression are found much more frequently in the regions downstream of the transcriptional start point, while the upstream regions contain more low-bendability triplets. Within the region downstream of the start point, we observe a periodic pattern in sequence and bendability, which is in phase with the DNA helical pitch. The periodic bendability profile shows bending peaks roughly at every 10 bp with stronger bending at 20 bp intervals. These observations suggest that DNA in the region downstream of the transcriptional start point is able to wrap around protein in a manner reminiscent of DNA in a nucleosome. This notion is further supported by the finding that the periodic bendability is caused mainly by the complementary triplet pairs CAG/CTG and GGC/GCC, which previously have been found to correlate with nucleosome positioning. We present models where the high-bendability regions position nucleosomes at the downstream end of the transcriptional start point, and consider the possibility of interaction between histone-like TAFs and this area. We also propose the use of this structural signature in computational promoter-finding algorithms., (Copyright 1998 Academic Press.)

The outcome of two different alternating regimens of chemotherapy was investigated in a prospective controlled trial in limited-stage small-cell lung cancer (SCLC). Both regimens comprised cyclophosphamide, lomustine, vincristine, methotrexate, doxorubicin and etoposide administered in different schedules. The investigative regimen (B) included simultaneous administration of cyclophosphamide + lomustine alternating with cyclophosphamide + doxorubicin, and with doxorubicin + lomustine. The hypothetical superiority of this regimen was based on data from experimental animal tumors suggesting potentiated efficacy of the three specific combinations. A total of 234 patients were included, and 113 vs 108 patients were eligible. Median survival in both groups was 48 weeks (p = 0.89). Complete remissions were observed in 36/101 and in 42/99 patients evaluable for response. There was no significant difference in response duration. At restaging after 18 months of chemotherapy 27 patients (16%) and 22 patients (16%), respectively, were free of disease. Six patients, three in each arm, are still alive, 8+ to 10.5+ years after diagnosis. Scheduled doses of the six agents were the same in the two regimens except for a 30% reduction of every second dose of cyclophosphamide in regimen B. Nevertheless, regimen B resulted in significantly more leukopenic patients, septicemic episodes, and blood transfusions, and the dosage of etoposide was more often reduced in arm B than in arm A. The increased toxicity was not associated with improved treatment results.

Six of 796 patients treated with intensive combination chemotherapy for small cell carcinoma of the lung developed overt acute nonlymphocytic leukemia (ANLL) (three patients) or preleukemia with severe refractory cytopenia and clonal cytogenetic abnormalities in bone marrow cells (three patients). The latent period to development of preleukemia or leukemia was less than two years in four of the six patients. The cumulative risk of preleukemia and leukemia according to a Kaplan-Meier estimate was 14.0% +/- 6.9% (mean +/- SE) four years after the start of treatment. The relative risk of overt ANLL was 77, since three cases were observed v 0.039 cases expected, based on the age- and sex-specific incidence of acute nonlymphocytic leukemia in the general Danish population. The risk of secondary solid tumors was not increased. The possible causes of the exceptionally early appearance and very high cumulative risk of leukemic complications found in the present study, as compared to previous experience in other malignant diseases, is discussed, including the implications for future therapy of patients with small cell lung cancer.

The most examined tumor markers in lung cancer patients are CEA, hormonal peptides, and some neurogenic enzymes in small cell carcinoma. Calcitonin, ACTH, ADH, CEA, neurophysin, oxytocin, beta-endorphin, neuron-specific enolase, and CK BB are elevated in serum specimens in 25-75% of cases of small cell carcinoma. The level of these markers is related to the stage of the disease in groups of patients; elevated pretreatment levels decrease with tumor regression. Marker levels are not valid in defining the tumor load and the presence of disease in the individual patient. It has not yet been documented that the markers can be used for clinical decisions on antineoplastic therapy. A recent development is the finding that measurement of CSF and plasma concentrations of ADH, calcitonin, CK BB, bombesin, and neuron-specific enolase may contribute in the diagnosis of CNS metastases including meningeal carcinomatosis.