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Biomedical subjects

J B Page

Publications and source records attributed to J B Page.

At least 19 recordsLinked to original sources
PubMed2001

Breathers in Josephson junction ladders: resonances and electromagnetic wave spectroscopy.

We present a theoretical study of the resonant interaction between dynamical localized states (discrete breathers) and linear electromagnetic excitations (EE's) in Josephson junction ladders. By making use of direct numerical simulations we find that such an interaction manifests itself by resonant steps and various sharp switchings (voltage jumps) in the current-voltage characteristics. Moreover, the power of ac oscillations away from the breather center (the breather tail) displays singularities as the externally applied dc bias decreases. All these features may be mapped to the spectrum of EE's that has been derived analytically and numerically. Using an improved analysis of the breather tail, a spectroscopy of the EE's is developed. The nature of breather instability driven by localized EE's is established.

Journal Article↗
PubMed2001

Penetration of dynamic localized states in dc-driven Josephson junction ladders by discrete jumps.

We give a theoretical study of unusual resistive (dynamic) localized states in anisotropic Josephson junction ladders, driven by a dc current at one edge. These states comprise nonlinearly coupled rotating Josephson phases in adjacent cells, and with increasing current they are found to expand into neighboring cells by a sequence of sudden jumps. We argue that the jumps arise from instabilities in the ladder's superconducting part, and our analytic expressions for the peculiar voltage (rotational frequency) ratios and I-V curves are in very good agreement with direct numerical simulations.

Journal Article↗
PubMed2001

Where you live and where you shoot: suggestive data from Valencia, Spain.

Residence appears to exert influence over choices of venues for injection among intravenous drug users (IDUs) in Valencia, Spain. While living in their parents' homes, young IDUs may resort to high-risk venues for injection, particularly chutaderos in which used needles and syringes are often reused. Residence patterns of young IDUs in Spain may be highly similar to residence of IDUs in Italy and Puerto Rico, which also have AIDS epidemics dominated by IDUs rather than men who have sex with men. Intervention in these places needs to take contextual factors of residence into account for effective prevention of HIV infection.

Adult↗
PubMed2001

High-risk behaviours in men from Bogotá, Colombia and the spread of HIV.

Our objective was to identify sexual behaviours related to risk of HIV infection. A cluster survey of sexually experienced men from diverse sociodemographic settings in Bogotá, Colombia was carried out using a standardized self-administered questionnaire. A high response rate (96%) resulted in the enrollment of 553 men. Most participants 129/442 reported having intercourse with women and 51/111 reported having sex with other men. Most respondents (90%) engaged in high-risk sexual practices; only 2% knew their HIV-1 serostatus. Consistent condom use was reported by 20% of those who practised anal sex, and was even lower (5%) among men who had sex with women during menses. Heterosexuals exhibited a higher degree of risky sexual patterns than homosexual/bisexuals (P=0.01). In conclusion, high-risk sexual practices are prevalent among men in Bogotá, particularly heterosexuals, attesting to the urgent need for effective and specific interventions to prevent HIV transmission.

Adult↗
PubMed2000

HIV-1 RNA load in needles/syringes from shooting galleries in Miami: a preliminary laboratory report.

We quantified HIV-1 RNA load in rinses from needles/syringes (N/S) obtained at shooting galleries in Miami and also analyzed the rinses for antibodies for viral proteins. In rinses from 36 N/S that contained visible blood, 14 (39%) had detectable amounts of HIV-1 RNA. Numbers of copies of HIV-1 RNA ranged from the detection limit (400 copies/ml) to 268,000 copies/ml. We also detected antibodies to HIV-1 polypeptides in 34/36 (94%) of rinses from visibly contaminated N/S using Western blots specific for the HIV-1 proteins. No antibodies were detected in laboratory rinses from six visibly clean needles. The presence of HIV-1 RNA in N/S is an important indication of the risk created by N/S sharing as well as by shared paraphernalia and wash waters by injecting drug users.

Blotting, Western↗
PubMed2000

When obesity is desirable: a longitudinal study of the Miami HIV-1-infected drug abusers (MIDAS) cohort.

Despite widespread nutrient deficiencies, a substantial proportion of the MIDAS cohort exhibits obesity, which has been linked to immune dysregulation in other clinical settings. Herein, the effects of obesity on immune function, disease progression, and mortality were evaluated longitudinally in 125 HIV-1-seropositive drug users, with comparison measures in 148 HIV-1-seronegative controls. Data were collected at a community clinic from 1992 to 1996, before administration of highly active antiretroviral therapy. Results indicated that overweight/obesity, defined as body mass index (BMI; kg/m2) > or =27, was evident in 18% of the HIV-1-seropositive patients and 29% of the seronegative patients. At baseline, no significant immunologic differences were observed among lean, nonobese, and obese groups. Over an 18-month period, 60.5% of the nonobese HIV-1-seropositive patients exhibited a 25% decline in CD4 cell count, compared with 18% of the obese patients (p<.004). During the follow-up period, 38% of the lean and 13% of the nonobese study subjects died of HIV-1-related causes. Measurements of BMI were inversely associated with progression to death, independent of CD4 count <200 cells/mm3 (p<.02). These data suggest that mild-to-moderate obesity in HIV-1-infected chronic drug users does not impair immune function and is associated with better HIV-1-related survival.

Adult↗
PubMed2000

Quality of life measures in the Miami HIV-1 infected drug abusers cohort: relationship to gender and disease status.

PURPOSE: This study examined activity, daily living, health, support, and outlook in HIV+ drug users. METHODS: Using the physician-administered Spitzer Index, the study assessed 75 HIV-1 seropositive men (n = 51) and women (n = 24) enrolled in the Miami HIV-1 Infected Drug Abusers Study (MIDAS). RESULTS: Total composite scores were significantly lower in the HIV-1 infected women than the men (p = .03). Significant gender differences were observed in activity assessment, independent of disease status, with women six times as likely to have lower activity scores (p = .0038). Most women (45%) in this category were homeless or marginally housed, compared to 11 percent of the men. Additionally, women with low activity scores had less social support than women with high activity scores. Cocaine use was significantly related to reports of normal activity, and varied across genders; more men used cocaine than women (p = .03). Compared to non-AIDS participants, AIDS patients were more likely to have lower scores in health (p = .009) and poorer outlook (p = .03). IMPLICATIONS: These findings reveal specific deficits in areas of psychosocial capacity, particularly in HIV-1 infected women who abuse drugs, that may need to be strengthened in order to enhance function and adherence to treatment, as well as well-being.

Activities of Daily Living↗
PubMed2000

First injection and current risk factors for HIV among new and long-term injection drug users.

The purpose of this paper is to estimate HIV seroprevalence and to examine the injection and sexual risk behaviours of a cohort of active new heroin injectors who have initiated injection within the past four years and to compare their risk behaviours with those of long-term heroin injectors who initiated injection prior to January 1, 1985. A stratified network-based sample was used to recruit injection drug users (IDUs) from the streets of Miami-Dade, Florida. New IDUs displayed a significantly lower HIV seroprevalence than long-term injectors (13.3 versus 24.7%). Both new and long-term drug injectors exhibited a high level of current HIV risk behaviour. While new injectors were more likely than long-term injectors to practise safer injection behaviours at the initial injection episode, the current risk behaviours of new and long-term injectors are similar.

Adult↗
PubMed2000

The association between cigarette smoking and drug abuse in the United States.

Cigarette smoking has been identified as an independent risk factor for many human diseases. However, the association between cigarette smoking and illegal drug use has not been thoroughly investigated. We have analyzed the 1994 National Household Survey on Drug Abuse to clarify whether cigarette smoking has any effect on the initiation of illegal drug use. Data from 17,809 respondents completing the 1994 "new" (1994-B) questionnaire were analyzed. Logistic regression analyses were performed with the use of statistical package SUDAAN, taking into consideration the multistage sampling design. The results show that those who had smoked cigarettes were far more likely to use cocaine (OR = 7.5; 95% CI: 5.7-9.9), heroin (OR = 16.0; 95% CI: 6.8-37.9), crack (OR = 13.9; 95% CI: 7.9-24.5) and marijuana (OR = 7.3; 95% CI: 6.2-8.7). The associations are consistent across age-strata and remain after adjusting for race and gender. This study suggests that cigarette smoking may be a gateway drug to illegal drug use.

Adolescent↗
PubMed1999

Intrinsic localized modes and chaos in damped driven rotator lattices.

It is shown that intrinsic localized rotational modes (ILRMs) in parametrically driven damped lattices of coupled classical dipole rotators can become chaotic without losing their localized character. Insight into this behavior is obtained by means of a nonlinear stability analysis. Moreover, we discuss a robust scheme for exploiting a spatially extended chaotic state to generate stationary randomly spaced arrays of driven ILRMs, and show that the associated absorption exhibits unusual signatures.

Journal Article↗
PubMed1999

Use of needles and syringes in Miami and Valencia: observations of high and low availability.

Two studies engaged in gathering data on injecting drug users (IDUs) employed supplementary resources to enhance their ethnographic components and compare patterns of use of needles/syringes (n/s) in two geographically similar but culturally distinct cities. Despite its policy of making n/s highly available at fair prices, Valencia, Spain, has markedly higher rates of HIV seroprevalence among its IDUs than does Miami, Florida, where possession of n/s is illegal. Ethnographically based models that track IDUs through choices of injection venues help to explain this difference. Inability of IDUs in Valencia to use their own domiciles as venues for injection contrasts sharply with problems of Miami IDUs, who have access to houses but have difficulty finding n/s. This research suggests that intervention in Valencia needs to focus on how people select places where they inject, and intervention in Miami needs to focus on improving availability of n/s.

Adolescent↗
PubMed1999

Lemon juice as a solvent for heroin in Spain.

Preliminary observations and responses to interviews in Valencia, Spain reveal that injecting drug users (IDUs) dissolve heroin before injection with two or three drops of lemon juice. Solution in lemon juice makes heating of heroin in water unnecessary. This pattern apparently developed spontaneously in Spain, but is almost unknown elsewhere in the world. Its implications for IDUs' health remain speculative, but use of lemon juice to dissolve heroin for injection deserves further scientific study.

Acetic Acid↗
PubMed1997

HIV-1 infection in women is associated with severe nutritional deficiencies.

Nutritional deficiencies may contribute to immune dysregulation, and have been shown to be sensitive markers of HIV-1 disease progression. Only limited information exists, however, regarding the nutritional profile of HIV-1-seropositive drug abusers. Immune and nutritional measurements were obtained in a subsample of 125 subjects from a larger cohort of drug users being followed for HIV-1 infection and cofactors of disease progression. Nutritional deficiencies, particularly vitamins A, E, and zinc, were widespread with up to 86% of the drug users exhibiting at least one nutritional alteration. Although immune parameters (CD4 count, CD8 count, beta2-microglobulin) were similar in the HIV-1-infected men and women, women had significantly poorer overall nutritional status, as measured by plasma proteins, which are considered to be sensitive markers of malnutrition. A comparison of individuals with advanced disease (CD4 count <200/mm3) revealed significantly lower levels of plasma prealbumin (p < .01), selenium, (p < .05), and greater deficiency of vitamins A (p < .01) and E (p < .05) in women than in men. The greater severity of nutritional deficiencies noted in HIV-1-infected women may be an important determinant of disease progression and survival.

Adult↗
PubMed1997

High risk of HIV-related mortality is associated with selenium deficiency.

To determine the independent contribution of specific immunologic and nutritional factors on survival in HIV-1 disease, CD4 cell count, antiretroviral treatment, plasma levels of vitamins A, E, B6, and B12 and minerals selenium and zinc were considered in relation to relative risk for HIV-related mortality. Immune parameters and nutrients known to affect immune function were evaluated at 6-month intervals in 125 HIV-1-seropositive drug-using men and women in Miami, FL, over 3.5 years. A total of 21 of the HIV-1-infected participants died of HIV-related causes during the 3.5-year longitudinal study. Subclinical malnutrition (i.e., overly low levels of prealbumin, relative risk [RR] = 4.01, p < 0.007), deficiency of vitamin A (RR = 3.23, p < 0.03), vitamin B12 deficiency (RR = 8.33, p < 0.009), zinc deficiency (RR = 2.29.1, p < 0.04), and selenium deficiency (RR = 19.9, p < 0.0001) over time, but not zidovudine treatment, were shown to each be associated with HIV-1-related mortality independent of CD4 cell counts <200/mm3 at baseline, and CD4 counts over time. When all factors that could affect survival, including CD4 counts <200/mm3 at baseline, CD4 levels over time, and nutrient deficiencies were considered jointly, only CD4 counts over time (RR = 0.69, p < 0.04) and selenium deficiency (RR = 10.8, p < 0.002) were significantly associated with mortality. These results indicate that selenium deficiency is an independent predictor of survival for those with HIV-1 infection.

Adult↗
PubMed1997

Needle exchange and reduction of harm: an anthropological view.

Overwhelming evidence from all over the world confirms that needle exchange programs (NEPs) in widely varied forms have value in prevention of HIV infection among injecting drug users (IDUs). Unfortunately, the United States has relatively few active NEPs because of political opposition to adoption of any policy that would give the appearance of condoning use of illegal drugs. Some additional opposition comes from the affected communities themselves. NEPs that assiduously construct links with affected communities have highest probabilities of effectiveness. Studies of NEPs, with some notable exceptions, still lack anthropological evaluations of their impact, and this deficiency needs more attention in future efforts to frame, implement, and evaluate NEPs.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Injection drug users' practices and attitudes toward intervention and potential for reducing the transmission of HIV.

Miami is one of the major centers of illegal drug activity and has a significant proportion of AIDS cases among injection drug users (IDUs). Since Needle Exchange Programs (NEP) are illegal and therefore do not exist in the state of Florida, other strategies must play a large role in reducing the transmission of HIV among IDUs. In order to effectively communicate with IDUs about needle safety, it is necessary to understand the practices and culture of IDUs, including where and how the needle/syringes are obtained and used. Data from recent studies conducted in Miami and other local sites indicate that IDUs inject frequently, averaging more than 1,000 per year, per person. While the vast majority of IDUs feel it is very important to clean needles and to use a needle only one time, these sentiments are not always practiced. Furthermore, data indicate that the context where shooting takes place must be considered in the planning of HIV risk reduction interventions. These findings suggest the importance of understanding patterns of drug use, attitudes toward intervention, and the cultural context where risky behaviors occur. Although Needle Exchange Programs are illegal in Florida, intervention programs must still stress the importance of using only new needles, but since new needles cannot always be obtained, IDUs should be taught and motivated not to use contaminated drug paraphernalia.

Acquired Immunodeficiency Syndrome↗