Perception of the risk of sexual transmission of HIV among Congolese and Japanese university students.

OBJECTIVE: Sub-Saharan Africa remains the region most heavily affected by HIV infection. This study aimed to evaluate the knowledge, attitudes, and practices of Congolese students of risk behaviors for sexual transmission of HIV in comparison with their Japanese counterparts. METHODS: Of the 1,747 undergraduate students who participated in the survey, there were 1,326 respondents (752 Japanese, 574 Congolese) who voluntarily and fully filled out the auto-administered questionnaire. RESULTS: The proportion of Congolese respondents who do not always use condoms with an occasional sex partner was significantly higher, 57%, as compared with their Japanese counterparts (15%; p < 0.001). Fewer than 40% (9.9-39.7%) of Congolese respondents had accurate knowledge about multiple sex partnership (MSP), men sex with men (MSM), precocious sex, and commercial sex work (CSW) being high-risk behaviors (p < 0.001) for the sexual transmission of HIV infection. However, the proportion of Congolese tested or willing to get tested for HIV was significantly higher (97.2%) than that in the Japanese group (72.4%, p < 0.001). In Congolese students, we observed an absence of adherence to preventive measures such as condom use with an occasional sex partner, and a greater proportion of students having inaccurate knowledge of major risk behaviors such as MSM, precocious sex, and MSP, compared with their Japanese counterparts. CONCLUSIONS: This study showed that, though sexual contact remains the main mode of HIV transmission in the region, Congolese students tend to have inaccurate knowledge of risk behaviors that expose people to the sexual transmission of HIV. This suggests that continuous education targeting those risk behaviors is of great importance to reduce the spread of the HIV epidemic.

Effect of copper substitution on the local chemical structure and dissolution property of copper-doped ß-tricalcium phosphate.

Substitution of inorganic ions into ß-tricalcium phosphate (ß-TCP) is a well-known approach for facilitating biological functions of bioceramics. However, the dissolution mechanism of those ß-TCPs is still under intensive debates. In the present study, the effect of copper substitution into ß-TCP crystal structure on the local chemical structure and dissolution property of the copper-doped ß-TCP (CuTCP) was investigated to clarify the dissolution mechanism of ß-TCP. A copper-dependent decrease in the dissolution rate of CuTCP with time was observed. The 1H → 31P nuclear magnetic resonance (NMR) spectra of 10 mol% copper-doped ß-TCP after the dissolution test demonstrated an amorphous hydrated layer on the surface of ß-TCP core particles, which contained hydroxyapatite and dicalcium phosphate dihydrate and anhydrate. As such, all the dissolution curves could be curve-fitted by a heterogeneous dissolution model composing of fast and slow dissolution components. Overall, dissolution mechanism could be proposed as follows: the CuTCP particles initially dissolved by hydrolysis based on the fast dissolution component. Subsequently, the amorphous hydrated layers were formed on their surface, and caused the diffusion-controlled dissolution. As the result, the slow dissolution component would be dominant, and led to the decreased dissolution rate. STATEMENT OF SIGNIFICANCE: Understanding the dissolution mechanism of copper doped ß-tricalcium phosphate (CuTCP) is crucial for designing an angiogenetic controlled copper release CuTCP for therapeutic biomaterials. However, dissolution mechanism of ß-TCP or CuTCP is still under intensive debates. This study demonstrated for the first time, that amorphous hydrated layers were formed on the CuTCP particle surface during its dissolution process, which caused a diffusion-controlled dissolution, and decreased the dissolution rate of CuTCP. This work not only provided a novel dissolution mechanism of ß-TCP or CuTCP, but also a new finding for designing an angiogenetic controlled copper release CuTCP for therapeutic biomaterials.