Factors affecting the acquisition of resistance against Schistosoma mansoni in the mouse. The effect of varying the route and the number of primary infections, and the correlation between the size of the primary infection and the degree of resistance that is acquired

Mice given primary infections of Schistosoma mansoni by percutaneous or subcutaneous routes were found to acquire a higher degree of resistance against homologous challenge after 7--8 weeks than mice infected intraperitoneally. Mice infected by the intraperitoneal route tended to have smaller worm burdens than those infected with the same number of cercariae by the other two routes and this may, in part, have contributed to the relative lack of efficacy of intraperitoneal infections in inducing resistance to re-infection. The same degree of resistance was acquired after primary percutaneous infection irrespective of whether it was administered in 3 equivalent weekly doses, or the same total number of cercariae was administered as a single infection. The same degree of resistance was also observed when a percutaneous challenge was administered on the same or a different skin site to that which received the percutaneous primary infection. The degree of resistance to re-infection acquired after a percutaneous primary infection correlated well with the size of the primary worm burden and the number of eggs in the intestine and liver, but did not correlate with the number of eggs in the lungs.

Factors affecting the acquisition of resistance against Schistosoma mansoni in the mouse. V. Reduction in the degree of resistance to reinfection after chemotherapeutic elimination of recently patent primary infections

Effective treatment of mice with six to eight week-old patent S. mansoni infections with any one of five schistosomicidal agents (Oxamniquine, Praziquantel, potassium antimony tartrate, Niridazole and Hycanthone) resulted in a reduction in the degree of resistance to homologous challenge in the treated animals when compared with the level of resistance to reinfection observed in untreated mice with intact primary infections. Mice challenged five to six weeks after treatment with Praziquantel, Niridazole or Hycanthone demonstrated a lower level of resistance than mice challenged within 10 days of the termination of the chemotherapeutic schedules. Direct comparison of Praziquantel with potassium antimony tartrate indicated that treatment with the former drug allowed retention of a greater level of acquired resistance than the antimonial in the immediate post-treatment period. Resistance to reinfection in Hycanthone-treated mice was not restored by intravenous injection of S. mansoni eggs before challenge.

Chronically and acutely suicidal persons one month after contact with a crisis intervention centre

This paper describes a follow-up study of 31 suicidal people who contacted Klinic (a crisis intervention centre in Winnipeg) during a 28-day period, and who gave their names and addresses. The suicidal persons were classified as either 'chronically suicidal' (those having a history of psychological instability and/or suicide attempts) or 'acutely' suicidal (those having fairly stable lives with no previous psychological instability or suicide attempts). The majority were classified as chronically suicidal, and they reported that they were still experiencing suicidal feelings with little improvement in their life situations. In contrast, none of the acutely suicidal persons were still experiencing suicidal feelings and all felt that their life situation had improved considerably. The majority of suicidal contacts was made by chronically suicidal persons and crisis intervention had a negligible impact on their suicidal feelings and psychological problems. Alternative treatment approaches for this group are recommended.

The role of anonymity in suicidal contacts with a crisis intervention centre

In follow-up studies of telephone crisis centres the clients who choose to remain anonymous cannot be included in any follow-up group. It is therefore important to try to determine if there are some ways in which the anonymous group is unrepresentative of the total sample. The results of this study indicate that tha anonymous group tend to be more lonely and more likely to withhold information than the non-anonymous group. However, it would seem that follow-up studies would not be seriously invalidated by the non-availability of the anonymous group. A possible explanation of the role of anonymity in suicidal calls is presented, and the results are further discussed in terms of a counselling approach for anonymous suicidal callers and implications for further research.

Complications with the use of bioabsorbable pins in the foot

The authors present a brief history and overview of the usage of bioabsorbable pins in Podiatric Surgery. A retrospective study of 49 patients who had been implanted with Biofix pins is presented. The number of patients who displayed reactions to the pin sufficient to require subsequent surgical intervention was found to be 10.2%. Three specific cases are presented in detail. All of the patients who displayed reactions were over 40 years of age and the majority were between 55 and 60 years of age. A discussion of these facts is presented with the authors' views on why bioabsorbable pin reactions may be expected to occur in older age groups.