The associations between risk behaviour and reported history of sexually transmitted diseases, among young women: a population-based study

The aim of this study was to determine the associations between risk behaviour and women's reported sexually transmitted diseases (STDs). All the women aged 19, 21, 23 and 25, residing in a specified housing area, were invited to answer a questionnaire regarding their sexual behaviour, smoking and alcohol consumption and previous history of STD. Of the 611 women participating, one out of 4 women had a history of at least one STD. In an univariate analysis, self-reported STD was found to be related to age, having more than 4 lifetime sexual partners, having practised intercourse at first date, inconsistent use of condoms, alcohol consumption of more than 3 bottles of wine per month and smoking. These factors were, however, not independent of each other and when subjected to a multivariate logistic regression analysis 2 factors, i.e. the lifetime number of sexual partners (more than 4 partners vs one; OR 7.94, (3.41-18.50)) and coitus on first date (practised more than once vs never, OR 2.99 (1.55-5.78)) emerged as independently associated with a previous STD.

Characterization of a mutant profilin with reduced actin-binding capacity: effects in vitro and in vivo

We are investigating structure-function relationships in profilin and actin by site-specific mutagenesis using a yeast, Saccharomyces cerevisiae, expression system to produce wild-type and mutant proteins. This paper shows that deleting proline 96 and threonine 97, which are located close to the major actin binding site on profilin, did not significantly alter the interaction between profilin and phosphatidylinositol 4,5-bisphosphate, nor did it affect the profilin:poly(L-proline) interaction. The mutant protein, however, had a lower capacity to bind to actin in vitro than wild-type profilin, though it showed a slightly increased profilin-enhanced nucleotide exchange on the actin. When microinjected into Swiss 3T3 mouse fibroblasts or porcine aortic endothelial cells, the mutant profilin did not change the organization of the microfilament system like the wild-type profilin did. This provides further evidence that profilin controls microfilament organization in the cell by interacting directly with actin.

Experimental design for kinetic analysis of protein-protein interactions with surface plasmon resonance biosensors

The reaction between antibody immobilized to surfaces, with and without a dextran matrix, and antigen in solution was studied using surface plasmon resonance detection. The use of a reference surface made it possible to identify conditions where a response related to changes in matrix conformation could be ignored. It was possible therefore to improve data quality by separating signals related to binding events from signals due to differences in refractive index between sample and running buffer. When antigen was injected over antibody immobilized to surfaces with and without dextran matrix the binding curves were virtually superimposable. Consequently, no binding artifacts associated with the dextran matrix were observed. Sets of binding curves obtained with different antigen concentrations were analyzed using numerical integration of differential rate equations and global fitting. When data was inconsistent with a one to one reaction it was possible to obtain good fits to an entire data set assuming several other reaction schemes including parallel, competitive and two-state reactions. Thus data analysis alone was not sufficient to discriminate between different reaction schemes. In contrast several reaction schemes could be ruled out with simple experiments; the duration of antigen injection, and reanalysis of antigen recovered in fractions from the antibody surface. In view of these findings experimental design appears to be the key to successful interaction analysis.

Potentiation by estramustine of the cytotoxic effect of vinblastine and doxorubicin in prostatic tumor cells

The effects of combining estramustine (EM) with vinblastine (VLB) or doxorubicin (DOX) on cellular uptake, cellular retention and cell survival were investigated in Dunning hormone-insensitive rat prostate AT-1 tumor cells and DU-145 human prostatic tumor cells. Accumulation of VLB and DOX by AT-1 cells was less than one-half of that in DU-145 cells. Inclusion of EM or estromustine considerably increased uptake of both VLB and DOX in AT-1 cells but not in DU-145 cells. Verapamil and tamoxifen also potentiated VLB uptake in AT-1 cells. A combination of VLB and EM resulted in a considerable synergistic effect on both cytotoxicity and cellular retention of VLB. The presence of P-glycoprotein (Pgp) in AT-1 cells could be demonstrated by both Western blots and immunocytochemical detection. Photoaffinity labeling of Pgp by [3H]-azidopine was clearly inhibited by VLB, verapamil and EM. Our data strongly support the argument for a combination of EM with not only VLB but also DOX to improve the therapeutic index in patients with prostate cancer.

Binding of autoreactive mouse anti-type II collagen antibodies derived from the primary and the secondary immune response investigated with the biosensor technique

The reactivity of autoantibodies to type II collagen, secreted by B cells isolated from the primary and the secondary immune response to rat type II collagen in DBA/1 mice, was investigated using BIAcore 2000 instrumentation. Assays were performed on both collagen and antibody surfaces. These assays demonstrated a 100-fold difference in affinity between primary and secondary immune response antibodies. The difference in affinity was almost entirely due to differences in the dissociation rate constant. Somatic mutations in secondary clones were in one case associated with a 3-4-fold difference in affinity and in another case appeared to be without any effect on the binding activity.

The influence of sexual and social factors on the risk of Chlamydia trachomatis infections: a population-based serologic study

BACKGROUND

Genital chlamydia infections often are asymptomatic, which promotes their spread in the population. In women, the possible consequences of infection are pelvic inflammatory disease and infertility. Most studies on the prevalence of Chlamydia trachomatis have been based on clinical series, and prevalences tend to vary with the clinical setting. Few seroepidemiologic studies have emerged from industrialized countries.

GOAL OF THIS STUDY

To assess the prevalence of Chlamydia trachomatis using culture and serology, and its relationship with possible risk factors.

STUDY DESIGN

This was a population-based study involving completion of a self-administered questionnaire, analysis of cervical samples for Chlamydia trachomatis, and serologic tests for Chlamydia trachomatis antibodies.

RESULTS

The prevalence of Chlamydia trachomatis infection was 2.7%, and the seroprevalence was 24.7% among the sexually active women. Seropositivity was correlated with sexual behavior variables, and the incidence of serologic cross-reactivity with respiratory infections (strain TWAR) was low. Multivariate logistic regression analysis showed the number of sexual partners, age at first coitus, history of therapeutic abortion, and previous pelvic inflammatory disease to be independently correlated with seropositivity.

CONCLUSION

Early sexual experience and multiple lifetime sexual partners are independent risk factors for Chlamydia trachomatis infection.

The structure of OmpF porin in a tetragonal crystal form

BACKGROUND

OmpF porin is a trimeric integral membrane protein responsible for the passive transport of small hydrophilic molecules, such as nutrients and waste products, across the outer membrane of Escherichia coli. Very few membrane proteins have been crystallized in three dimensions, yet this stable protein can be obtained in several crystal forms. Comparison of the structures of the same membrane protein in two different packing environments is of major interest, because it allows us to explore the integrity of the structure outside the natural membrane environment.

RESULTS

The structure of OmpF porin in a tetragonal crystal form with two trimers per asymmetric unit has been determined at 3.2 A resolution and compared with that obtained previously in a trigonal crystal form. The lattice contacts involve only polar atoms, whereas extensive hydrophobic protein-protein interactions were found in the trigonal lattice. The trimer structure is virtually identical in both.

CONCLUSIONS

Our comparison reveals that the overall structure of OmpF is not influenced by crystal lattice constraints and, thus, presumably bears close resemblance to the in vivo structure. The tetragonal crystal structure has provided the starting model for the phasing of neutron diffraction data obtained from this crystal form, as described in an accompanying article.

Kinetic analysis of the interaction between protein A domain variants and human Fc using plasmon resonance detection

A real-time biospecific interaction analysis (BIA) was performed to study the specific interaction between the Fc portion of human immunoglobulin G1 (Fc1) and a one domain analogue (designated Z) of staphylococcal protein A, in monovalent (Z) and divalent (ZZ) forms, and five different single amino acid substituted Z variants (L17D, N28A, F30A, I31A, K35A). Experimental BIA data were used to calculate association rate constants (kon), dissociation rate constants (koff) and affinity constants (Kaff). The divalent form (ZZ) showed a higher affinity for Fc1 mainly because of a slower off rate. Out of the five mutant Z proteins, four (L17D, N28A, I31A, K35A) showed a decreased affinity to Fc1 compared to the parent Z molecule. Surprisingly, two (L17D, I31A) of these four had the major effect of a decreased binding energy as a lowered kon while the other two (N28A, K35A) mutant proteins showed an increased koff as the major kinetic difference from Z in their binding to Fc1. For five of the six different Z variants, as well as for the ZZ molecule, calculated Kaff and calculated differences in binding free energies relative to the parent Z molecule (delta delta G), are in good agreement with the corresponding values obtained in a competitive displacement assay using radioactively labeled Z as a tracer (Cedergren et al., (1993) Prot. Eng. 6, 441-448). However, the I31A variant, with a measured kon that was more than three orders of magnitude lower than that of Z in the BIA assay, showed a significantly weaker affinity to Fc1 when calculated from the BIA data compared to the competitive displacement assay. The discrepancy between these two methods for Z(I31A) is discussed as well as possible explanations for the unexpected large effect of lowered kon for two of the mutant Z proteins.

Surface plasmon resonance detection and multispot sensing for direct monitoring of interactions involving low-molecular-weight analytes and for determination of low affinities

Surface plasmon resonance detection allows direct observation of molecular interactions between an analyte in solution and its immobilized binding partner. The use of simultaneous monitoring of interaction events on multiple sensing surfaces, with varying amounts of immobilized receptor, for detection of low-molecular-weight analytes and for determination of low affinities was investigated. Using multispot sensing and BIAcore 2000 instrumentation, analytes as small as 180 Da were detected and affinities in the 50 microM range could be determined. The use of multispot sensing thus extends direct interaction analysis to include low-molecular-weight analytes and low-affinity interactions.

Direct and competitive kinetic analysis of the interaction between human IgG1 and a one domain analogue of protein A

Direct and competitive kinetic analysis of the binding between a one domain analogue of protein A, and mutants thereof, to immobilised hIgG1 was compared using a biosensor system based on surface plasmon resonance detection. Rate constants determined from both assays were almost identical. The experiments demonstrate that competitive kinetic analysis can be used in combination with biosensor technology, and indicate that competitive kinetic analysis may extend the use of the technology to include low molecular weight analytes.

The silent suffering women--a population based study on the association between reported symptoms and past and present infections of the lower genital tract

OBJECTIVES

To assess the prevalence of lower genital tract symptoms and the association between reported symptoms and past and present signs of sexually transmitted diseases (STD) in young women.

DESIGN

All women belonging to the 19-, 21-, 23- and 25-year age cohorts and living in the catchment area of the community health centre, were invited by mail to take part in a population-based study. The participants answered a structured questionnaire and a gynaecologic examination was performed. Samples for wet smear, cervical Pap smear, HPV DNA determination and Chlamydia trachomatis culture were taken at the gynaecologic examination. The presence of genital warts was noted. A blood sample was analysed for antibodies against C trachomatis and HSV-2.

SETTING

The community health care centre was located in Umeå, a city in Northern Sweden.

RESULTS

Of the 886 women who were eligible, 611 (70%) participated in the investigation. One out of four women reported symptoms from the lower genital tract. The most commonly reported symptoms were itching, followed by discharge, and soreness. The most commonly reported STD was C trachomatis (15%). The most prevalent present STD was HPV infection (20%) whereas C trachomatis infection could be isolated from 2.7% of the women. Antibodies against C trachomatis and HSV-2 were present among 22% and 6% of the women, respectively. There was a significant correlation between the women's complaint of vaginal discharge and previous C trachomatis infection, lack of lactobacilli and presence of leucocytosis in wet smear.

CONCLUSIONS

We have in a population-based study of young healthy women found that one out of four women had some kind of lower genital tract complaint. Itching was the most commonly reported symptom and was associated with pseudohyphae and acetowhite patches. Reported vaginal discharge and soreness were associated with the history of a past C trachomatis infection and signs of a disturbed vaginal flora.

Human papillomavirus infection is transient in young women: a population-based cohort study

The prevalence of human papillomavirus (HPV) infection in cervical cell scrapes from a cohort of 276 young women was determined by a general two-step polymerase chain reaction. HPV infection fluctuated among young women during a 2-year interval. The total prevalence of HPV infection decreased from 21% to 8.3%. The most prevalent HPV types at enrollment were HPV-16 (3.3%) and HPV-6 (2.9%). At follow-up, the most common type was HPV-16 (2.9%), while no HPV-6 was detected. In 2 women only, the same HPV type persisted. Regression of HPV infection was found in 80% of the women. A new HPV type-specific infection was detected in 7.2% of the women and was independently associated with a new sex partner or an abnormal smear since enrollment.

Identification of the trapped calcium in the gelsolin segment 1-actin complex: implications for the role of calcium in the control of gelsolin activity

The X-ray structure of the complex of actin with gelsolin segment 1 revealed the presence of two calcium ions, one bound at an intramolecular site within segment 1 and the other bridging the segment directly to actin. Although earlier calcium binding studies at pH 8.0 revealed only a single calcium trapped in the complex (and also in the binary gelsolin-actin complex), it is here shown that two calcium ions are bound under the conditions of crystallization at physiological pH. Mutation of acidic residues in either actin or segment 1 involved in ligation of the intermolecular calcium ion resulted in loss of one of the bound calcium ions at pH < 7, but not at pH 8. Thus the calcium ion trapped in the segment 1-actin complex is that located at the intramolecular site. The implications of this for gelsolin function are discussed.

Lifetime number of partners as the only independent risk factor for human papillomavirus infection: a population-based study

BACKGROUND AND OBJECTIVES

Previous studies of relationships between genital human papillomavirus infection and tentative risk factors have yielded conflicting results, possibly because of inaccuracy of the viral detection methods used and differences in selection criteria.

GOAL OF THIS STUDY

To determine human papillomavirus prevalence and identify risk factors in a group of young Swedish women.

STUDY DESIGN

This was a population-based study involving completion of a structured questionnaire, analysis of cervical scrapings for human papillomavirus and Chlamydia trachomatis, and serologic tests for C. trachomatis and herpes simplex virus antibodies.

RESULTS

The prevalence of human papillomavirus infection was 22% among the sexually active women and 4% among the virgins. A number of factors were associated with human papillomavirus prevalence in univariate analysis, but logistic regression analysis showed that lifetime number of male sexual partners was the only independent risk factor for human papillomavirus infection (adjusted odds ratio, 7.45; 95% CI, 2.79-19.92 for six or more partners vs. one partner).

CONCLUSION

Human papillomavirus infection is a prevalent sexually transmitted disease among young Swedish women, and the lifetime number of male sexual partners is a major risk factor.

Real-time competitive kinetic analysis of interactions between low-molecular-weight ligands in solution and surface-immobilized receptors

With surface plasmon resonance detection it is possible to measure the binding kinetics between a macromolecule in solution and a receptor immobilized on a sensor surface. The detector response is proportional to the mass of the analyte that binds to the surface, and therefore, a direct observation of a low-molecular-weight (lmw) analyte ( < 5000 Da) interacting with its immobilized binding partner is normally not possible. I describe here a competitive approach in which a lmw analyte and a high-molecular-weight analyte react at the same time with the immobilized receptor. Using this approach it is possible to extend kinetic analysis to lmw analyte-receptor interactions. A qualitative analysis allows rapid affinity ranking of different lmw analytes interacting with the same receptor, and a quantitative analysis of binding data allows the calculation of rate constants for the lmw analyte-receptor interaction. The competitive kinetics approach may therefore be used as an alternative to other affinity techniques for the characterization of lmw ligands, for identification of inhibitors, and for drug screening.

The effect of a new oral hygiene training program on approximal caries in 12-15-year-old Brazilian children: results after three years

This study evaluated the effects of a new oral hygiene training program on approximal caries in a population of 12-13-year-old Brazilian schoolchildren with a well-established habit of daily toothbrushing with a F dentifrice. Two hundred twenty-two children were randomly allocated into two test groups (I and II) and one control group (III). Group I subjects were trained to establish needs-related oral hygiene habits based on self-diagnosis and a new behavioral principle, the 'linking method', for establishment of habits. The first three visits (20 minutes each) were scheduled at two-day intervals. They were recalled for a monthly check-up during the first 4 months, and then every 3 months for reevaluation of the results based on self-diagnosis. Group II subjects were recalled at the same intervals for detailed oral hygiene instruction on how to clean every tooth surface using dental tape, toothbrush, and fluoride dentifrice. Group I developed significantly fewer (p < 0.001) new approximal manifest (dentin) caries lesions than groups II and III. The mean values (SEM) were 2.3 (0.29), 4.7 (0.59), and 5.3 (0.68), respectively. The conclusions from our study are: In a toothbrushing population using fluoride dentifrices and fluoridated drinking water, the oral hygiene training program with behavioral modification significantly reduced caries incidence on approximal surfaces. Frequent repetition of training in meticulous oral hygiene is almost redundant.

Serum profiles of oxytocin during oral contraceptive treatment

Serum profiles of oxytocin were studied by means of a continuous blood sampling system in five young healthy women before and during treatment with a combined oral contraceptive. Oxytocin levels were determined by a specific radioimmunoassay in blood samples collected in 10-min fractions from 22.00 to 06.00. The values were further analyzed by the pulse detection program PULSAR. Great individual differences in oxytocin profiles were observed, and in some of the women these differences were also pronounced between the two sampling occasions. All 10 profiles demonstrated irregular peaks which occurred with varying frequency. Although the baseline level of oxytocin increased in all women and the average concentration increased in four of the women during treatment, there was no clear-cut effect on the peak frequency. Based on results from animal experiments, it is suggested that the increase in oxytocin levels may be related to an excitatory effect exerted by estrogen on oxytocin secreting neurons.

Working on a moving surface--a biomechanical analysis of musculo-skeletal load due to ship motions in combination with work

Ship motions are recognized by fishermen as a cause of high musculo-skeletal load. In the present study, the motions of a Swedish trawler at sea were registered over three degrees of freedom. Simultaneously, the working postures of a fisherman on board were registered in the sagittal plane during five different working situations: (1) standing erect in still conditions; (2) holding a load of 21 kg in still conditions; (3) standing erect during motion of the ship; (4) standing during motion of the ship, holding a load of 21 kg; and (5) repeatedly lifting and lowering a 21 kg load during motion of the ship. All registrations were sampled using a computer where data were processed in a two-dimensional, dynamic biomechanics model, developed for this particular purpose. Vertical and horizontal forces as well as moments were calculated for seven major joint systems of the body, as was compression at the L4/L5 vertebral level. In situation (3), ship motions were mainly counteracted by motions in the lower extremity and lumbar back, thus inducing increased strain in these parts of the body; other parts of the body were little affected. Holding a load considerably increased the load on most joints. Lifting the load further increased the musculo-skeletal strain and also increased the range of moments in each joint as well as the range of lumbar compression. Moment at the C7 vertebral level was relatively unaffected by ship motions and by handling external loads.

Analysis of active antibody concentration. Separation of affinity and concentration parameters

Antibody binding to surfaces with differing amounts of immobilised antigen was measured in a biosensor system using surface plasmon resonance detection. Binding rates obtained during the initial binding phase on high density antigen surfaces were proportional to antibody concentration and independent of antigen-antibody affinity. One antibody calibration curve covering the range from 0.5 to 160 nM (0.08-25 micrograms/ml) antibody was valid for IgG antibodies with different antigen specificities. To illustrate the use of this methodology active antibody concentrations were analysed in culture media and in rabbit serum.

Mutagenesis of human profilin locates its poly(L-proline)-binding site to a hydrophobic patch of aromatic amino acids

The actin-binding protein, profilin, contains a src-homology (SH) 3-like fold (Schutt, C.E. et al., submitted), and its tight interaction with poly(L-proline) is reminiscent of the binding activity exhibited by SH3-domains. Here we demonstrate that replacements of aromatic amino acids in a hydrophobic patch on the surface of the profilin molecule abolish its poly(L-proline)-binding capacity. However, the location of this hydrophobic patch is found in another region of the molecule than that displaying structural similarities with SH3 domains.

Mutations in beta-actin: influence on polymer formation and on interactions with myosin and profilin

Two beta-actin mutants, one with proline 38 replaced with alanine (P38A) and the other with cysteine-374 replaced with serine (C374S), as well as the wild-type beta-actin, were expressed in the yeast, S. cerevisiae, purified to homogeneity, and analyzed in vitro for polymerizability and interaction with DNase I, myosin, and profilin. Both mutations interfered with the polymerization of the actin, and with its interaction with myosin. The C374S mutation had the most pronounced effect; it reduced the polymerizability of the actin, abolished its binding to profilin, and filaments containing this mutation moved at reduced rates in the in vitro 'motility assay'. The ATPase activity measured in solutions containing myosin subfragment 1 was similar for both the mutant and wild-type actins.