[HIV infection and risk behavior among drug users served by a program of syringe exchange].
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Adult↗
Biomedical subjects
M J Bravo
Publications and source records attributed to M J Bravo.
Stereo matching precedes dichoptic masking.
Stereo matching can intervene to prevent dichoptic masking. In a dichoptic masking paradigm we measured the contrast threshold for a bar target, presented to one eye, as a function of the contrast of an identical masking bar, presented at retinal correspondence in the other eye. Confirming previous studies of dichoptic masking with sinusoidal gratings, the test bar thresholds rose proportionally with increasing masking contrast. This threshold elevation was almost nullified when an extra bar was presented to the eye seeing the test stimulus. Release from masking occurred when the disparity between the masking bar and extra bar was < 20 min arc over a range of contrast levels (8-45%), and for bars containing either broad spatial frequency spectra or bars with only high spatial frequencies (peak = 12 c/deg). The latter result rules out an explanation for the release from masking based on contrast discrimination in low spatial frequency channels. The extra bar was effective in releasing the test bar from masking as long as the extra bar's contrast was greater than about one-fifth the contrast of the mask, a result that suggests that there is a contrast threshold for stereo matching. We interpret our findings to indicate that a stage of stereo matching occurs prior to the neural site limiting dichoptic contrast discrimination.
Contrast Sensitivity↗
HIV-transmission knowledge in drug users from outpatient facilities in Spain. A national survey.
Knowledge of AIDS and its transmission was studied in patients undergoing drug-dependence treatment for opiates and/or cocaine. The study area included all of Spain and was carried out via a questionnaire assessing information about risk practices, HIV serostatus, etc, and 13 true or false questions concerning HIV-transmission knowledge. The main purpose of the present study was to analyse the relationship between the level of information found in patients and factors potentially related to it, including the practice of high-risk activities for HIV transmission, the sources of information and behaviour modification. Findings indicate that poor information was associated with the use of non-sterile needles, anal-penis sexual relations, non-use of condoms, lack of preventive measures in daily cohabitation, and lack of previous drug-dependence treatment. Determining factors of being well-informed were a high level of education, a longer duration of intravenous drug use, and contact with the Health Service as a source of information. These findings partially support the need to implement programs aimed at improving knowledge about HIV in the population of drug users.
Acquired Immunodeficiency Syndrome↗
Intravenous administration among heroin users having treatment in Spain.
BACKGROUND: Of critical importance to AIDS control in Spain is the analysis of geographical variation and trend over time in the prevalence of intravenous administration in heroin users, as well as the factors associated with the use of this route. METHODS: We carried out a cross-sectional study of 27,655 people admitted to outpatient treatment for heroin dependence in 15 of the 17 Autonomous Communities of Spain during 1991, using data provided by the State Information System on Drug Abuse (SEIT). To assess the association of some factors with use of the intravenous route crude and logistic analysis was performed. RESULTS: The prevalence of intravenous administration in this population was 64.4% with regional differences ranging between 33% and 90%. Crude and logistic analysis demonstrated a strong association with two factors in addition to geography: the year of first use and the age at first use (the earlier the first use, the greater the strength of the association). CONCLUSIONS: These findings are of paramount importance for the control of the HIV epidemic in Spain and further study in this area could help to guide policy development.
Acquired Immunodeficiency Syndrome↗
IV drug users: changes in risk behaviour according to HIV status in a national survey in Spain.
STUDY OBJECTIVE: To determine whether HIV positive intravenous drug users (IVDUs) who were receiving outpatient treatment for opiate and cocaine abuse or dependence used practices aimed at reducing the spread of HIV. DESIGN: Cross sectional study of behaviour and HIV serostatus in IVDUs. SETTING: A nationwide sample, from 83 health centres for outpatient treatment, stratified by autonomous regions. PARTICIPANTS: Altogether 1074 IVDUs were recruited. HIV serostatus could be verified in 738 (68.7%) of these. MEASUREMENTS AND MAIN RESULTS: Crude and adjusted odds ratios and their 95% confidence intervals were estimated to assess the association between HIV serostatus and behavioural changes. In their daily interactions with other members of the same household, seropositive subjects more frequently used preventive methods aimed at avoiding transmission than seronegative patients. Treatment for abuse or dependency before the current regimen had a greater impact in HIV positive than HIV negative subjects in terms of abstaining from risk behaviours. There was a significant trend toward lower drug consumption in HIV positive subjects, and the number of seropositive and seronegative IVDUs who stopped injecting their drugs was significantly higher among the former. Seropositive subjects were also more likely to stop sharing drug injecting equipment and to change their sexual habits; they reported an increased consistent use of condoms. CONCLUSIONS: HIV positive IVDUs were more likely to change their risk behaviours than their HIV negative counterparts.
Adolescent↗
Sharing injecting equipment and sexual behavior in ambulatory intravenous drug users: a national survey (Spain).
This article examines the relationship between sharing and sexual behavior in a nationwide sample of 1,074 intravenous drug users (IVDUs) in ambulatory treatment in Spain. Of our sample, 31.9% shared or had shared injecting equipment. Sharing was associated with sex-less frequent in males--and yielded an inverse relationship with age, years of education, and age at first intravenous drug use. Sharers, especially women, engaged more frequently in sex in exchange for money. A small proportion (6.3%) of male IVDUs had bisexual or homosexual relations. Condoms were always used by 18.4% of males and 15.9% of females. The sharing of injecting equipment was not generally associated with a particular type of penetrative sexual encounter, although condom use was less frequent among IVDUs who shared injecting equipment. The limitations of the present study are discussed.
Adult↗
Geographical variations in the prevalence of HIV infection among drug users receiving ambulatory treatment in Spain.
To identify the factors responsible for the regional differences in HIV-positive serostatus among drug users in Spain receiving outpatient treatment, the 17 autonomous regions into which Spain is divided were classified as high (mean 52%) or low prevalence groups (mean 34%) depending on the prevalence of seropositivity. In regions where the prevalence of positive serostatus was high, unemployment was more markedly associated with HIV infection than in low prevalence regions, while other potential risk factors yielded the same strength of association. Even so, adjustment for all the factors only accounted for 13% of the total difference in HIV+ prevalence between regions. The current distribution of risk factors among the two groups of autonomous regions does not explain these differences.
Acquired Immunodeficiency Syndrome↗
The contributions of figure and ground textures to segmentation.
Several models of texture segmentation use spatial gradients in the activity of early filters to locate texture boundaries. The models assume that these filters are identical to those involved in the detection and discrimination of near threshold patterns. The models differ in how activity gradients from different types of filters are combined. We examined this question by measuring the respective contributions of a figure and a ground texture to segmentation. Vertical and horizontal line segments were used to construct two perfectly discriminable textures and these textures were used to construct four types of displays. Each display contained an obliquely oriented figure, but the displays differed in the way this figure was defined. Displays consisted of either (1) a horizontally textured figure on a blank background, (2) a blank figure on a vertically textured background, (3) a horizontally textured figure on a vertically textured background or (4) a figure with a mixed texture (50% vertical lines, 50% horizontal lines) on a blank background. In a two-alternative forced-choice experiment, observers were asked to judge the figure's orientation (right or left oblique), and the contrast of the textures was varied across trials. The resulting psychometric functions for segmentation were very similar for the four types of displays, suggesting ways in which a simple model of segmentation should be modified.
Contrast Sensitivity↗
The role of attention in different visual-search tasks.
Observers viewed displays containing a variable number of distractors of one color and a target of another color. In some experiments, the target and distractors maintained their color from trial to trial; in others, they reversed unpredictably. Observers made a speeded two-choice judgment concerning either the presence, the color, or the shape of the odd-colored target. With only one exception, all of these conditions produced the same pattern of results: reaction times remained constant as the number of distractors increased. The exceptional result occurred when observers judged the shape of the odd-colored target and the color of the target and distractors reversed unpredictably. In this case, reaction times decreased as the number of distractors increased. These results are interpreted in terms of the attentional requirements of the different judgments and the mechanisms that guide attention.
Adult↗
[The persistence of risky conduct for HIV transmission among intravenous drug users in Madrid, Seville, and Valencia. The Working Group of the Médicos del Mundo for the Monitoring of HIV Infection and the Risk Practices of Intravenous Drug Users].
OBJECTIVE: To determine the prevalence of HIV infection and risk-taking behavior for infection among intravenous drug users in Madrid, Seville, and Valencia (Spain). To study the main factors associated with such behavior. MATERIAL AND METHODS: Personal interviews were carried out with 821 intravenous drug users recruited in 1994 and 1995 among recent participants in three needle-exchange programs. Subjects were asked about their risk-taking behavior in the 30 days preceding the interview. Bivariate statistical methods and logistical regression techniques were used. RESULTS: In the month before the interview, 13.8% of the subjects in Valencia, 18.1% in Madrid, and 26.9% in Seville used needles that had been used by other people, usually (73-88%) without disinfecting them effectively. Condom use during the reference period was 50% in Seville, 42.5% in Madrid, and 34.2% in Valencia. The prevalence of HIV infection ranged from 30.1% in Seville to 43. 2% in Madrid. Multivariate analysis showed that the factors most closely associated with accepting used needles were: needle sharing (OR = 12.2), residence in Seville (OR = 6.6), and HIV positivity (OR = 4.6). The factors most closely associated with not using condoms systematically were: ignorance of personal HIV serological state (OR = 4.1), needle sharing (OR = 3.7), and HIV negativity (OR = 3.3). CONCLUSIONS: The risk of HIV transmission among intra-venous drug users in Spain is high (infection and risk-taking behavior have a high prevalence), so programs designed to reduce this risk should be increased quickly.
Adult↗