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Large sets of electron microscopic images of the 30S ribosomal subunits of Bacillus stearothermophdus (914 molecules) and Escherichia coli (422 molecules) were analysed with image processing techniques. Using computer alignment and a new multivariate statistical classification scheme, three predominant views of the subunit were found for both species. These views, which together account for -90% of the population of images, were determined to a reproducible resolution of up to 1.7 nm, thus elucidating many new structural details. The angular spread of the molecular orientations around the three main stable positions is remarkably small (< 8°). Some of the current models for the small ribosomal subunit are incompatible with our new results.

Population-based data on sexually transmitted infections (STI), bacterial vaginosis (BV), Laboratory testing included polymerase chain reaction (PCR) for human papillomavirus (HPV), ligase chain reaction (LCR) for Chlamydia trachomatis and Neisseria gonorrhoeae, ELISA for human immunodeficiency virus (HIV), venereal disease research laboratory (VDRL) and fluorescent treponema antibody absorption test (FTA-ABS) for syphilis, and analysis of wet mounts, gram stains and Pap smears for trichomoniasis, candidiasis, and BV. Only women who had initiated sexual life were included in the analysis (n = 592). The prevalences of STI were , chlamydia 4. 5% (3.0-6.6), trichomoniasis 4.1% (2.7-6.1), gonorrhoea 1. 2% (0.5-2.6), syphilis 0. 2% (0.0-1.1), and HIV 0%. The prevalence of ) and 12. 5% (10.0-15.5 ), respectively. The most common gynaecological complaint was lower abdominal pain. STI are common in women in rural Brazil and represent an important health threat in view of the HIV pandemic.Key words: sexually transmitted infections -reproductive tract infections -prevalence -epidemiology -Brazil Sexually transmitted infections (STI) are a major cause of morbidity throughout the world, particularly in developing countries (Gerbase et al. 1998). In women, STI are often chronic and present with little or no symptoms, but eventually may lead to severe sequels, such as chronic pelvic inflammatory disease, ectopic pregnancy, and infertility (WHO 2000). The impact of STI on the health of women tends to be more severe in resourcepoor settings where diagnostic and treatment facilities are inappropriate. Here, women often are not aware of STI as health problems, and health care seeking behaviour is poor (Giffin & Lowndes 1999). Relatively high prevalences of STI have been documented in such settings e.g. from Brazil, Papua New Guinea, and The Gambia (Walraven et al. 2001, Mgone et al. 2002, Soares et al. 2003. STI, as well as bacterial vaginosis (BV), are considered to increase the risk of acquiring human immunodefiency virus (HIV) (Sewankambo et al. 1997, Rottingen et al. 2001.In Brazil, the HIV epidemic is characterized by changing dynamics, currently reaching new population groups, namely women, underprivileged individuals, and communities outside the great urban centres (Fonseca et al. 2000, Brazilian Ministry of Health 2006. Reliable epidemiological data from Brazilian women on STI and other reproductive tract infections (RTI), such as BV and candidiasis, are scanty. Syphilis and HIV in pregnant women, AIDS, and congenital syphilis are notifiable infections, but the epidemiologic situation of other RTI is rather enigmatic. Studies have addressed the issue of STI in certain specific groups, such as patients attending STI clinics, gynaecology and obstetric outpatient departments, female prisoners or commercial sex workers (Miranda et al. 2000, Benzaken et al. 2002, Codes et al. 2002, Cook et al. 2004. However, these studies do not allow to conclude on the burden of disease on the community level.To increase further the knowledge...

A three‐dimensional model for the arrangement of 29 of the 33 proteins from the Escherichia coli large ribosomal subunit has been generated by interactive computer graphics. The topographical information that served as input in the model building process was obtained by combining the immunoelectron microscopically determined network of epitope‐epitope distances on the surface of the large ribosomal subunit with in situ protein‐protein cross‐linking data. These two independent sets of data were shown to be compatible by geometric analysis, thus allowing the construction of an inherently consistent model. The model shows (i) that the lower third of the large subunit is protein‐poor, (ii) that proteins known to be functionally involved in peptide bond formation and translocation are clustered in two separate regions, (iii) that proteins functionally interdependent during the self‐assembly of the large subunit are close neighbours in the mature subunit and (iv) that proteins forming the early assembly nucleus are grouped together in a distinct region at the ‘back’ of the subunit.

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