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Biomedical subjects

R Rockwell

Publications and source records attributed to R Rockwell.

10 recordsLinked to original sources
PubMed2001

Factors associated with prevalent hepatitis C: differences among young adult injection drug users in lower and upper Manhattan, New York City.

OBJECTIVES: This study examined correlates of prevalent hepatitis C virus (HCV) infection among young adult injection drug users in 2 neighborhoods in New York City. METHODS: Injection drug users aged 18 to 29 years were street recruited from the Lower East Side and Harlem. Participants were interviewed about drug use and sex practices; venipuncture was performed for hepatitis B virus (HBV), HCV, and HIV serologies. RESULTS: In both sites, testing positive for HCV antibody (anti-HCV) was associated with having injected for more than 3 years. Additionally, HCV infection was positively associated with injecting with someone known to have had hepatitis (but the association was significant only in the Lower East Side) and with sharing cotton (but the association was statistically significant only in Harlem). Being in drug treatment and older than 24 years were associated with HCV in the Lower East Side but not in Harlem. Receiving money for sex was associated with anti-HCV positivity in Harlem but not in the Lower East Side. CONCLUSIONS: Several differences in factors associated with prevalent HCV infection existed among 2 populations of young injection drug users from the same city. Indirect transmission of HCV may occur.

Adolescent↗
PubMed2000

Behavioral risk reduction in a declining HIV epidemic: injection drug users in New York City, 1990-1997.

OBJECTIVES: This study assessed trends in HIV risk behaviors among injection drug users in New York City from 1990 to 1997. METHODS: Injection drug users were recruited continuously from a large drug detoxification treatment program (N = 2588) and a research storefront located in a high-drug-use area (N = 2701). Informed consent was obtained, and a trained interviewer administered a structured interview covering sociodemographics, drug use history, HIV risk behavior, and participation in syringe exchange. RESULTS: Trends were assessed for 5 risk behaviors in the 6-month period before the interview. The 3 injection risk behaviors declined significantly over time at each site (all P < .01). When data were pooled across sites, all 5 risk behaviors declined significantly over time (all P < .01). Participation in syringe exchange programs and in HIV counseling and testing increased greatly from 1990 to 1997. CONCLUSIONS: The continuing risk reduction among injection drug users indicates a "declining phase" in the large HIV epidemic in New York City. HIV prevention programs appear to be making an important contribution to the declining phase.

Adult↗
PubMed1999

Similarities and differences by race/ethnicity in changes of HIV seroprevalence and related behaviors among drug injectors in New York City, 1991-1996.

OBJECTIVE: To measure differences and similarities in the prevalence of HIV infection and of related risk and protective behaviors among New York City black, white, and Hispanic drug injectors during a period of decreasing HIV prevalence. METHODS: Drug injectors were interviewed at a drug detoxification clinic and a research storefront in New York City from 1990 to 1996. All subjects had injected drugs within the last six months. Phlebotomy for HIV testing was conducted after pretest counseling. Analysis compares the first half (period) of this recruitment interval with the second half. RESULTS: HIV seroprevalence declined among each racial/ethnic group. In each period, white drug injectors were significantly less likely to be infected than either blacks or Hispanics. Similar declines were found in separate analyses by gender, length of time since first injection, and by recruitment site. After adjustment for changes in sample composition over time, blacks and Hispanics remained significantly more likely to be infected than whites. Interactions indicate that the decline may be greatest among Hispanics and slowest among blacks. A wide variety of risk behaviors declined in each racial/ethnic group; and syringe exchange use increased in each group. Few respondents reported injecting with members of a different racial group at their last injection event. CONCLUSIONS: HIV prevalence and risk behaviors seem to be falling among each racial/ethnic group of drug injectors. Black and Hispanic injectors continue to be more likely to be infected. Declining prevalence among whites poses some risk of politically based decisions to reduce prevention efforts. Overall, these results show that risk reduction can be successful among all racial/ethnic groups of drug injectors and suggest that continued risk reduction programs may be able to attain further declines in infection rates in each group.

Adult↗
PubMed1999

Geographic proximity, policy and utilization of syringe exchange programmes.

The objective of the research was to assess the effects of geographic proximity on the utilization of syringe exchange among injection drug users (IDUs) in New York City. Between 1994 and 1996, 805 IDUs were interviewed with a structured questionnaire. Geographic proximity was defined as living within a ten-minute walk. Eighty-one per cent of IDUs who lived close typically used a syringe exchange compared to 59% of those who lived further away. In multiple logistic regression analysis, those who lived close remained (adjusted odds ratio of 2.89; 95% CI 2.06 to 4.06, p = 0.001) more likely to use syringe exchange. Those who lived close were less likely to have engaged in receptive syringe sharing at last injection (adjusted odds ratio = 0.45, 95% CI 0.24 to 0.86, p = 0.015). In conclusion, locating exchange services in areas convenient to large numbers of IDUs may be critical for prevention of HIV infection.

Adult↗
PubMed1995

Genetic variation for resistance to chlorpyrifos in Drosophila melanogaster (Diptera: Drosophilidae) infesting grapes in Israel.

Five species of drosophilid flies were observed breeding in grapes growing in Israel; of these, 2 species, Drosophila melanogaster (Meigen) and D. simulans Sturtevant, are major pests. Natural populations of both species were sampled and tested for resistance to chlorpyrifos; the 2 more intensively sampled populations were D. melanogaster in commercial vineyards. One vineyard had been treated repeatedly with chlorpyrifos to control this secondary pest species; the other had never been treated with an organophosphorus compound. The LC50 to chlorpyrifos of a genetically heterogeneous line of D. melanogaster from the exposed population (Be'er Tuvia) was 99 ng/cm2, and the LC50 of a corresponding line from the unexposed population (Sde Eliahu) was 52 ng/cm2; the wild-caught lines were much more resistant than a laboratory strain, Canton-S, whose LC50 was 0.25 ng/cm2. Genetic variance for resistance existed in both natural populations but realized heritability did not differ significantly between the populations. In crosses between a highly resistant strain and several sensitive laboratory strains of D. melanogaster, resistance was dominant. A resistance factor was mapped to a locus on chromosome 2 (approximately 2-72).

Animals↗
PubMed1978

Experimental Haemophilus influenzae type b meningitis: immunological investigation of the infant rat model.

Infant rats inoculated intraperitoneally with Haemophilus influenzae type b develop bacteremia and meningitis. Rats were infected at 10 to 12 days of age and studied for the development of serum anticapsular antibody and bactericidal and opsonizing activity. Seven and 11 weeks after inoculation, convalescent animals showed a higher frequency of anticapsular antibody responses than uninfected controls, but 35 to 40% of the infected group had undetectable levels of anticapsular antibody (<0.10 mug/ml). In contrast, all of the convalescent animals, but none of the controls, showed moderate titers of serum bactericidal activity; and bactericidal activity persisted after absorption of the convalescent sera with type b capsule. Bactericidal activity was detected primarily in the eluted fraction corresponding to a molecular weight of 150,000 and was present in the offspring of convalescent females. Offspring of convalescent females were protected against challenge with H. influenzae type b, and control offspring could also be protected by passive immunization with convalescent serum which lacked detectable anticapsular antibody. Convalescent serum samples efficiently opsonized H. influenzae type b, and this activity persisted after absorption of the serum with capsular antigen. These data are consistent with the hypothesis that antibody to the noncapsular surface antigens of H. influenzae type b play an important role in host defenses.

Animals↗
PubMed1978

Ampicillin-resistant Hemophilus influenzae.

Ampicillin-resistant Hemophilus influenzae had not been identified in Fresno, California, before June 1976. In the 12 months that followed, eight resistant type B strains and three resistant nontypable isolates were cultured from patients treated at two hospitals that provide nearly all of the acute pediatric inpatient care for the area. Two of the resistant strains were obtained from patients with invasive infections and represented 4.2 percent of Hemophilus influenzae isolated from blood, cerebrospinal fluid or joint aspirates during the 12 months. The remaining six resistant type B strains were obtained from 117 patients, and were the predominant organism in cultures of other sites, primarily respiratory secretions. In two of three patients infected with nontypable organisms, resistance appeared to emerge during therapy with ampicillin. Measurement of beta lactamase was a practical and accurate method for differentiating between ampicillin-sensitive and resistant strains. All ten of the beta lactamase-positive isolates tested had minimal inhibitory concentrations (MIC) for ampicillin of 15 mug per ml, or less. In contrast 30 beta lactamase-negative strains had MIC's of 1.5 mug per ml, or less, of ampicillin. Our results indicate that ampicillin resistance has become a significant problem in the Central Valley of California and probably the entire state.

Adolescent↗