Search PubMed⌕ Search

Biomedical subjects

J T Parsons

Publications and source records attributed to J T Parsons.

At least 19 recordsLinked to original sources
PubMed2006

Transtheoretical Model and substance use in HIV-positive youth.

The purpose of the study was to test constructs of the Transtheoretical Model (TTM) for predicting alcohol and other drug use in HIV-positive youth (ages 16-25). Questionnaires and interviews about alcohol and other drug use, stage of change, self-efficacy, emotional distress and social support were obtained from 64 HIV-positive youth. Structural equation modeling with standard errors determined by methods appropriate to small samples, demonstrated that self-efficacy mediated the relationship between stage of change and alcohol use and between social support and alcohol use. The same pattern of results emerged for marijuana use. The models predicted 47% of the variance in alcohol use and 69% of the variance in marijuana use. Results supported the TTM and highlight the potential of interventions that seek to boost self-efficacy and social support specific to reducing substance use.

Adolescent↗
PubMed2005

Knowledge of human papillomavirus and effects on sexual behaviour of gay/bisexual men: a brief report.

The objective of this study was to examine the knowledge and misinformation about human papillomavirus (HPV) and differences in sexual risk practices. Self-report surveys assessing the history of HPV/genital warts and sexual practices were completed by 1065 gay/bisexual men in New York City. Of the men reporting a history of HPV, genital warts, or both, the majority reported having warts but not HPV, demonstrating inaccurate knowledge. A significantly greater percentage of men who reported both HPV and warts (HPV+) reported having unsafe sex compared with men reporting neither (HPV-) and men reporting warts but not HPV (HPV+ uninformed). HPV+ and HPV+ uninformed men reported significantly more men non-primary sex partners in the past three months than HPV- men. Findings indicate that many gay/bisexual men, a population at risk for HPV, are misinformed about its various permutations. Men who are HPV+ report increased sexual risk practices and more sexual partners. Comprehensive gay men's health programmes must include HPV education.

Bisexuality↗
PubMed2004

The use of the Internet by gay and bisexual male escorts: sex workers as sex educators.

While prior studies have targeted street-based male sex workers as potential vectors of disease transmission, the number of men who work independently through Internet chat-rooms and other online endeavors has steadily increased. It is likely that these men differ substantially from their street-based counterparts in terms of sexual risk behaviors with their clients. The purpose of this study was to explore the ways in which the Internet has impacted the work of male escorts and their sexual practices with clients. Semi-structured qualitative interviews and quantitative surveys were administered to 46 such men. Less than half the men reported unprotected anal sex with clients. The qualitative data lend support to this finding, in that the majority talked about refusing any unsafe sex with clients, and many reported taking the extra step of educating their clients about the dangers of risky sex. Some of the escorts described the methods used to incorporate safer sex practices into sessions with their clients. Internet-based male escorts can play an important role as potential sex educators on the front lines of the fight against HIV and other sexually transmitted infections.

Adult↗
PubMed2003

Promoting safer sex among HIV-positive youth with haemophilia: theory, intervention, and outcome.

The goal of the project was to develop and evaluate theory-based interventions designed to change sexual behaviour and promote safer sex practices of HIV seropositive young men and adolescents with haemophilia to prevent transmission to sexual partners and offspring. Safer sex was defined as abstinence, consistent condom use, or 'outercourse' (intimate, non-intercourse sexual behaviour). This project utilized the Transtheoretical Model developed by Prochaska and DiClemente, which describes behaviour change as an incremental, stage-based process. The 1-year intervention protocol consisted of two individual sessions and two peer-centred activities. One hundred and four adolescents, residing in 22 states, participated. Pre- and post-intervention evaluations were conducted to measure stage progression for participants. The number who were in the action or maintenance stage of change for safer sex was significantly greater at post-test than at pre-test (79 vs. 62%, P < 0.0001). Participants also reported an increased use of outercourse. In addition, significant increases in self-efficacy and knowledge regarding safer sex were demonstrated. Following these stage-based interventions, participants were significantly more likely to be engaging in safer sex behaviours than they were previously. These intervention activities can be adapted for use with other adolescent populations and for other behaviour change goals in adolescents with haemophilia.

Adolescent↗
PubMed2003

Intentional unsafe sex (barebacking) among HIV-positive gay men who seek sexual partners on the internet.

While unsafe sex has been reported throughout the HIV epidemic, the underlying assumption has been that most persons do not seek to purposely ham unprotected sex. Within the gay community, the term 'barebacking' has emerged to refer to intentional unsafe anal sex. The prevalence of barebacking is evidenced among gay men, particularly those who are HIV-positive, by the number of internet sites devoted to barebacking and the number of men seeking sexual partners through the use of the internet. To gain insight into barebacking, a sample of 112 HIV-positive gay men were recruited from internet sites where men seek to meet each other for sex. The major it of participants (84%)reported engaging in barebacking in the past three months, and 43% of the men reported recent bareback sex with a partner of unknown serostatus. These results indicate the potential for widespread transmission of HIV to uninfected men by the partners they meet on the internet. Analyses revealed that men who reported bareback sex only with HIV-positive partners scored lower in sexual adventurism than those who had bareback sex regardless of partner serostatus. A significant correlation was observed between defining masculinity as sexual prowess and intentional unprotected anal sex. There are serious implications for HIV prevention efforts, in that internet-based education should be a priority in order to reach men who rely on this mechanism to find sexual partners.

Adult↗
PubMed2003

Correlates of depressive symptoms among HIV-positive injection drug users: the role of social support.

Using cross-sectional data from an ethnically diverse sample of HIV-positive injection drug users (IDUs), we sought to identify correlates of depressive symptoms. We were particularly interested in whether perceived social support was associated with depression among HIV-positive IDUs and whether social support buffered adverse effects of other correlates. Data were collected from a sample of HIV-positive IDUs recruited from a variety of venues in the New York City and San Francisco metropolitan areas in the USA. Multiple regression analysis identified four significant correlates of depressive symptoms. Perceived social support and having a regular place for HIV medical care were significantly associated with lower levels of depressive symptoms, while history of mental health problems and non-injection polydrug use were significantly associated with higher levels of depressive symptoms. Moreover, a significant interaction effect was found between social support and non-injection polydrug use, indicating that social support buffers the association between non-injection polydrug use and depression. These results suggest that increasing social support might be a useful tool for HIV-positive IDUs in reducing depression and the adverse effect of non-injection polydrug use.

Adult↗
PubMed2003

Characteristics of HIV antiretroviral treatments, access and adherence in an ethnically diverse sample of men who have sex with men.

Data regarding HIV antiretroviral treatment regimens, access to treatment and medical care, and adherence to medications were collected as part of the Seropositive Urban Men's Study, a formative study of HIV-positive men who have sex with men. Participants (N = 456) were recruited from AIDS service organizations, mainstream gay venues and public/commercial sex environments. The sample was 94% gay or bisexually-identified; 29% were African American, 24% Latino and 30% white. The majority (71%) indicated being on antiretroviral treatment, and most were taking a protease inhibitor/nucleoside reverse transcriptase inhibitor combination. African American men in New York City were less likely to be on treatment. Among those on treatment (n = 322), 51% reported at least one day in which they had missed a dose of their medication and the mean number of days in which a dose was missed (in the past 30 days) was 1.72. Multivariate analyses indicated that avoidant coping, frequency of drinking alcohol and difficulty in communicating with sex partners about HIV were related to days of missed doses, suggesting the need or desire to escape from the reality of life with HIV as a potential explanation for poor adherence.

Adult↗
PubMed2002

Sexual and drug-using practices of HIV-positive men who frequent public and commercial sex environments.

An ethnically diverse sample (69.7% men of colour) of HIV-seropositive MSM from the New York City and San Francisco metropolitan areas were recruited from a variety of social settings. While only 27.0% of the participants were recruited from PSEs (public sex environments where men 'cruise' for potential sex partners, such as parks) and CSEs (commercial sex environments where an admission is paid for entrance, such as bathhouses and sex clubs), 49.6% reported attending PSEs and 40.7% reported attending CSEs. Only a minority of participants from the full sample reported sexual behaviours that would have placed a partner at highest risk for HIV seroconversion. However, differences between those who frequented CSEs and those who did not emerged on several psychosocial factors (sexual sensation seeking, depression, perceived responsibility towards protecting sexual partners from HIV infection), sexual risk behaviours (unprotected oral and anal sex) and types of recreational drugs used. Fewer differences were found between those who frequented PSEs and those who did not.

Adolescent↗
PubMed2001

Cortactin: coupling membrane dynamics to cortical actin assembly.

Exposure of cells to a variety of external signals causes rapid changes in plasma membrane morphology. Plasma membrane dynamics, including membrane ruffle and microspike formation, fusion or fission of intracellular vesicles, and the spatial organization of transmembrane proteins, is directly controlled by the dynamic reorganization of the underlying actin cytoskeleton. Two members of the Rho family of small GTPases, Cdc42 and Rac, have been well established as mediators of extracellular signaling events that impact cortical actin organization. Actin-based signaling through Cdc42 and Rac ultimately results in activation of the actin-related protein (Arp) 2/3 complex, which promotes the formation of branched actin networks. In addition, the activity of both receptor and non-receptor protein tyrosine kinases along with numerous actin binding proteins works in concert with Arp2/3-mediated actin polymerization in regulating the formation of dynamic cortical actin-associated structures. In this review we discuss the structure and role of the cortical actin binding protein cortactin in Rho GTPase and tyrosine kinase signaling events, with the emphasis on the roles cortactin plays in tyrosine phosphorylation-based signal transduction, regulating cortical actin assembly, transmembrane receptor organization and membrane dynamics. We also consider how aberrant regulation of cortactin levels contributes to tumor cell invasion and metastasis.

Actins↗
PubMed2001

Cell-cycle-dependent association of protein phosphatase 1 and focal adhesion kinase.

Immunofluorescence studies with protein phosphatase-1 (PP1) isoforms-specific antibodies detected PP1delta, but not alpha or gamma1, at focal adhesions. PP1delta also co-immunoprecipitated with the focal adhesion kinase (FAK) and the alphav-integrin. In the present study glutathione S-transferase (GST)-PP1delta pulled-down FAK from fibroblasts extract and the interaction domain localized between residues 159 and 295 of delta. The association was confirmed by the ability to GST-FAK-related non-kinase (FRNK) to pull-down PP1delta from fibroblasts extract. GST-FRNK also pulled-down purified muscle PP1 catalytic subunit, thus indicating direct interaction between FAK and PP1. FAK displays consensus sequences for phosphorylation by cell division cycle kinase-2-cyclin B, and might be a PP1 substrate. In fact, FAK immunoprecipitated from metabolically-labelled mitotic HeLa cells without tyrosine phosphatase inhibitors was phosphorylated on Ser only and was dephosphorylated in vitro by purified muscle PP1, with loss of phospho-Ser. No PP1 was associated with FAK immunoprecipitated from mitotic HeLa cells. However, progressively more PP1 activity was assayed in FAK-immunoprecipitates obtained from cells released from mitosis. The associated activity was maximal at 2 h from the mitotic release (when 85-90% of the cells remained round) and decreased to basal level by 8 h (when cells were all polygonal). At the same time FAK underwent dephosphorylation, which was completed by 4 h. FAK obtained from cells at 1.5 h was Ser-phosphorylated, and underwent dephosphorylation during in vitro incubation, with loss of phospho-Ser, indicating the presence of active FAK-bound phosphatase. The only FAK-associated PP1 isoform between 1 and 8 h was PP1delta. The results suggest that FAK dephosphorylation by PP1delta occurs in cells released from mitosis, and confirmed the specific association of PP1delta, as detected previously in adherent cells.

Animals↗
PubMed2001

Treatment of early and moderately advanced vocal cord carcinoma with 6-MV X-rays.

PURPOSE: Whereas there are many reports regarding treatment of early vocal cord cancer with cobalt 60 or 2-4-MV X-rays, there are still few reports on the results of treatment with 6-MV X-rays. Theoretically, 6-MV X-rays result in greater underdosage of tumor at the air-tissue interface and at the anterior commissure. This paper analyzes the results of irradiation of early and moderately advanced squamous cell carcinoma of the true vocal cord treated exclusively with 6-MV X-rays in a community hospital. The literature pertinent to the issue is reviewed. METHODS AND MATERIALS: Eighty-three patients with Tis, T1, T2, or T3 squamous cell carcinoma of the true vocal cord were treated with curative intent at Bethesda Memorial Hospital in Boynton Beach, Florida between April 1986 and April 1998. The dose schedules most commonly used were 63 Gy in 28 fractions (2.25 Gy per fraction once a day) for T1 tumors or 74.40 Gy in 62 fractions (1.2 Gy per fraction twice a day) for T2 and T3 tumors. All patients have minimum 2-year follow-up; 63 (76%) have 5-year minimum follow-up. RESULTS: Local control was achieved in 6 of 6 Tis, 53 of 54 (98%) T1, 8 of 8 T2, and 6 of 6 T3 lesions. No complications were encountered. CONCLUSIONS: A recent literature review indicates that the treatment of early vocal cord cancer with 6-MV X-rays remains controversial. The dose schedules used in the present paper produced a high rate of local control, a finding that is consistent with reports of other investigators who used dose schedules similar to those used in the present series. However, several other investigators have reported significantly lower rates of local control for T1 or T2 glottic cancer treated with 6-MV X-rays when compared to results obtained with cobalt 60 or 4 MV at their own institution. The latter institutions used lower total doses and/or lower dose per fraction than those institutions reporting high rates of local control with 6 MV. Data from the literature, as well as our own data, are consistent with the following hypotheses: (1) the lower rates of local control reported by several institutions when using 6 MV compared with cobalt or 2-4 MV, using the same radiation dose schedules for each beam energy, indicate that underdosage of mucosal surfaces in the laryngeal air cavity may be a clinically important phenomenon, and (2) time-dose factors, although certainly important for lower energy beams, may be even more important when using 6 MV.

Aged↗
PubMed2001

Alterations in the focal adhesion kinase/Src signal transduction pathway correlate with increased migratory capacity of prostate carcinoma cells.

Focal adhesion kinase (FAK) has been implicated in the regulation of cell migration. In addition, FAK expression is increased in a number of highly metastatic tumor cell lines. Therefore, we investigated the role of FAK in regulating migration of prostate carcinoma cell lines with increasing metastatic potential. We show that highly tumorigenic PC3 and DU145 cells exhibit intrinsic migratory capacity, while poorly tumorigenic LNCaP cells require a stimulus to migrate. Increased metastatic potential of PC3 and DU145 cells correlates with increased FAK expression, overall tyrosine phosphorylation and activity, as measured by autophosphorylation of tyrosine 397. However, in PC3 and DU145 cells, FAK autophosphorylation is adhesion dependent whereas a second site of tyrosine phosphorylation, tyrosine 861, a Src specific site, is uncoupled from adhesion-dependent signaling events. Finally, inhibiting the FAK/Src signal transduction pathway by over expressing FRNK (Focal adhesion kinase-Related Non-Kinase), an inhibitor of FAK activation, or treatment with PP2, a Src family kinase inhibitor, significantly inhibited migration of prostate carcinoma cell lines, demonstrating that tumor cell migration continues to be dependent on signals emanating from this pathway.

Adenoviridae↗
PubMed2001

Cortactin promotes and stabilizes Arp2/3-induced actin filament network formation.

Cortactin is a c-src substrate associated with sites of dynamic actin assembly at the leading edge of migrating cells. We previously showed that cortactin binds to Arp2/3 complex, the essential molecular machine for nucleating actin filament assembly. In this study, we demonstrate that cortactin activates Arp2/3 complex based on direct visualization of filament networks and pyrene actin assays. Strikingly, cortactin potently inhibited the debranching of filament networks. When cortactin was added in combination with the active VCA fragment of N-WASp, they synergistically enhanced Arp2/3-induced actin filament branching. The N-terminal acidic and F-actin binding domains of cortactin were both necessary to activate Arp2/3 complex. These results support a model in which cortactin modulates actin filament dendritic nucleation by two mechanisms, (1) direct activation of Arp2/3 complex and (2) stabilization of newly generated filament branch points. By these mechanisms, cortactin may promote the formation and stabilization of the actin network that drives protrusion at the leading edge of migrating cells.

Actin Cytoskeleton↗
PubMed2001

The role of radiotherapy and limb-conserving surgery in the management of soft-tissue sarcomas in adults.

The treatment of soft-tissue sarcomas has undergone significant changes over the past several decades. Previously, patients were often treated with surgery alone, which frequently necessitated amputation of the affected extremity. Less extensive, limb-sparing operations combined with adjuvant irradiation are now feasible for most patients without compromising the likelihood of cure.

Adult↗
PubMed2001

Substance use and sexual transmission risk behavior of HIV-positive men who have sex with men.

We examined substance use in relationship to transmission risk behavior (unprotected insertive, UIAI, or receptive anal intercourse, URAI) between HIV-positive men who have sex with men (MSM) and their HIV-negative or unknown serostatus partners. Men who engaged in transmission risk behavior with casual partners were more likely than men who did not engage in such behavior to have used various substances. Users of certain drugs were specifically less likely to use condoms with HIV-negative or unknown status partners than users. Of men who drank alcohol, those who drank more frequently before or during sex engaged in significantly more UIAI with casual partners. Of men who used drugs, those who used more frequently before or during sex were more likely to engage in URAI with casual partners. In multivariate analyses, use of inhalants as well as drinking before or during sex predicted UIAI, while use of inhalants as well as noninjection drug use before or during sex predicted URAI. HIV prevention programs for HIV-positive MSM should focus on decreasing substance use and use specifically before or during sex. Developing prevention programs for substance-using MSM is critical to improve community health and decrease HIV transmissions.

Adult↗
PubMed2001

Safer sex decision-making among men with haemophilia and HIV and their female partners.

An exploratory qualitative study of adult heterosexual men with haemophilia and HIV and women who were their sexual partners was conducted as formative research to better understand cognitive factors involved in behavioural intentions and practices which comprise HIV risk-reduction for sexual transmission. The study sought to generate hypotheses, uncover themes, and develop a broad perspective on possible determinants of behaviours related to HIV transmission risk reduction. Qualitative analysis of these data served as a basis for developing a subsequent quantitative, hypothesis-testing survey and an intervention. Face-to-face interviews were conducted with 23 single men and 28 married men with haemophilia and HIV infection, and 28 married women partners selected through stratified, purposeful sampling. The interviews identified beliefs, attitudes, and values underlying decisions regarding target behaviours related to preventing sexual transmission of HIV, including (1) using condoms consistently during vaginal intercourse and (2) talking to partners about risk reduction. The interviews elicited information about perceived advantages and disadvantages of performing each of the targeted behaviours, and factors that facilitate or prevent performing them. Qualitative analysis of coded responses yielded important themes regarding how choices are made about sexual activity and safer sex. Most notably, communication between partners (1) plays a direct, key role in facilitating condom use and (2) forms the basis for maintaining emotional intimacy in these relationships. The link between condom use and communicating about safer sex was viewed as pivotal in achieving HIV prevention for individuals in serodiscordant couples. Recommendations for risk reduction intervention development are discussed.

Adult↗