Enzymatic activity of adenylate cyclase toxin from Bordetella pertussis is not required for hemolysis

Adenylate cyclase (AC) toxin from Bordetella pertussis enters cells to cause supraphysiologic increases in cAMP. AC toxin is also hemolytic. Substitution of Lys-58 with a methionine residue by site-directed mutagenesis of the structural gene for AC toxin, cyaA, and introduction of this mutation onto the B. pertussis chromosome results in an organism that synthesizes an enzyme-deficient AC toxin molecule. This mutant toxin molecule exhibits 1000-fold reduction in enzymatic activity relative to wild-type and has no toxin activity in J774 cells. The enzyme-deficient toxin molecule is not, however, impaired in its ability to lyse sheep red blood cells. In order to ascertain the importance of these two separate activities of AC toxin in vivo the enzyme-deficient organisms were used to infect infant mice. The hemolytic, enzyme-deficient mutant organisms are reduced in virulence relative to wild-type organisms after intranasal challenge indicating that, although the enzymatic activity of AC toxin does not contribute to hemolysis, it is this property of the toxin which is important for virulence of B. pertussis.

Lethal infection by Bordetella pertussis mutants in the infant mouse model

Different aspects of lethal infection of infant mice with Bordetella pertussis were examined. Mutants deficient in vir-regulated genes were tested for the ability to cause a lethal infection in the infant mouse model. Adenylate cyclase toxin-hemolysin and pertussis toxin were required to cause a lethal infection at low doses. Mixed infection caused by challenging the mice with an equal number of pertussis toxin and adenylate cyclase toxin-hemolysin mutants at a dose at which neither alone was lethal was also unable to cause a lethal infection. Production of the filamentous hemagglutinin and the dermonecrotic toxin was not required to cause a lethal infection. Nine other mutants in vir-regulated genes whose phenotypes have yet to be determined were also tested. Only two of these mutants were impaired in the ability to cause a lethal infection. Expression of fimbriae does not appear to affect the dose required to cause a lethal infection; however, fimbrial expression was correlated with the later stages of a nonlethal, persistent infection. Growth of the bacteria in MgSO4, a condition which reversibly suppresses expression of the genes required for virulence, did not alter the ability of the bacteria to cause a lethal infection. Auxotrophic mutants deficient in leucine biosynthesis were as virulent as the parental strain; however, mutants deficient in methionine biosynthesis were less virulent. A B. parapertussis strain was much less effective in promoting a lethal infection than any of the wild-type B. pertussis strains examined. A persistent infection in the lungs was observed for weeks after challenge for mice given a sublethal dose of B. pertussis, and transmission from infected infants to the mother was never observed.

Reasons given by female virgins for not having premarital intercourse

By analyzing reasons given by virgin women for not engaging in premarital coitus, we can attain greater insight into the decision-making process involved in maintaining virginity as well as in the transition to nonvirginity. Among virgin women, there is a subgroup who are likely to have premarital coitus if they should meet the right person. On the other hand, women who give moral reasons for not engaging in coitus are the least likely to engage in premarital coitus even if they should become involved in a love relationship. Our results suggest that counsellors and educators should be aware of the diversity of reasons for not engaging in premarital intercourse as well as factors influencing these reasons in order to gain a more complete understanding of premarital sexual decision-making.

Comparison of younger and older adolescent females attending birth control clinics

Sexual and contraceptive attitudes and practices were assessed for 486 single females aged 13-20, attending ten birth control centres in Ontario. At last intercourse, 28% were not using any contraception and only 33% reported they had used contraceptives all of the time. Younger adolescents were less likely than older ones to have used effective methods of contraception or to have used contraceptive methods effectively. Younger adolescents expressed greater embarrassment about obtaining oral contraceptives, particularly from the family physician, and were more likely to perceive oral contraceptives as being difficult to obtain.

Self-esteem and sexual permissiveness

Assessed the relationship between self-esteem and sexual permissiveness for 486 single females aged 13--20 who were attending 10 birth control centers in Ontario. Consistent with Stratton and Spitzer's social deviance model, which predicts that the nature of the permissiveness/self-esteem relationship is dependent on cultural norms, in this liberal sample high esteem Ss were accepting of premarital intercourse with affection. Those who deviated from the permissiveness with affection norm by endorsing sexual abstinence had lower esteem, but there was no relationship between esteem and endorsement of premarital intercourse without affection or esteem and number of coital partners. High self-esteem Ss were more willing to take sexual initiative and had lower sex guilt.

Self-esteem, locus of control, and adolescent contraception

The relationships between locus of control, self-esteem, and attitudes to contraception and contraceptive behaviors were assessed for 486 single women of ages 13 to 20, attending 10 birth control centers in Southern Ontario, Canada. The Ss voluntarily filled out a questionnaire, and the data were measured with the Fatalism scale of Reid and Ware's I-E scale, a Likert-type self-esteem scale, and a semantic differential birth control pill scale. There were no significant relationships between locus of control and any of the contraception variables. Ss with high self-esteem were found to have positive attitudes toward using birth control pills, to be less embarrassed about obtaining contraception, and to be more effective and consistent contraceptive users.