Michael Gross

Cerebral glucose metabolic rates in obsessive compulsive disorder

Brain metabolism was measured with positron emission tomography and [18F] 2-fluoro-2-deoxyglucose in normal subjects and in patients with obsessive compulsive disorder (OCD) while they performed a continuous auditory discrimination task designed to evaluate the functional localization of sustained attention. Data on 8 nondepressed patients with OCD were compared with 30 normal volunteers. We observed significantly higher normalized regional metabolism both in the right orbital frontal cortex (p = 0.002, two-tailed t test) and in the left anterior orbital frontal cortex (p = 0.017, one-tailed t test) and in patients with OCD as compared to normal controls. We observed no normalized glucose metabolic differences in basal ganglia structures in patients with OCD as compared to our normal controls. There were no statistical differences in global glucose metabolic values between the OCD and the control group. Our findings are consistent with the findings of Baxter et al. (Arch Gen Psychiatry 44:211-218, 1987). Regions in the parietal cortex also appear to show differences in this preliminary study.

Dysfunction in a prefrontal substrate of sustained attention in schizophrenia

Regional brain metabolism was measured in normal subjects and patients with schizophrenia while they performed an auditory discrimination task designed to emphasize sustained attention. A direct relationship was found in the normal subjects between metabolic rate in the middle prefrontal cortex and accuracy of performance. The metabolic rate in the middle prefrontal cortex of patients with schizophrenia, even those who performed as well as normals, was found to be significantly lower than normal and unrelated to performance. The findings point to a role of the mid-prefrontal region in sustained attention and to dysfunction of this region in schizophrenia.

Readiness of high-risk populations in the HIV network for prevention trials to participate in HIV vaccine efficacy trials in the United States

Objective:To determine the willingness of populations at high risk of HIV-1 infection to participate in HIV vaccine efficacy trials, determine factors influencing decision-making, and evaluate knowledge levels of vaccine trial concepts. Design:Cross-sectional study. Methods:HIV-1-negative homosexual men, male and female injecting drug users and non-injecting women at heterosexual risk were recruited in eight cities in the United States (n = 4892). Results:A substantial proportion of the study population (77%) would definitely (27%) or probably (50%) be willing to participate in a randomized vaccine efficacy trial. Increased willingness was associated with high-risk behaviors, lower education level, being uninsured or covered by public insurance, and not having been in a previous vaccine preparedness study. Altruism and a desire for protection from the vaccine were major motivators for participation. Major concerns included positive HIV-1 antibody test due to vaccine, safety of the vaccine, and possible problems with insurance or foreign travel. Baseline knowledge of vaccine trial concepts was low. Conclusions:It is likely that high-risk volunteers will be willing to enroll in HIV vaccine efficacy trials. A variety of participant and community educational strategies are needed to address participant concerns, and to ensure understanding of key concepts prior to giving consent for participation.

Evidence for common alterations in cerebral glucose metabolism in major affective disorders and schizophrenia

Regional glucose metabolic rates were measured in affectively disordered patients during the performance of auditory discrimination. Those regions previously observed as abnormal in schizophrenia were examined to see if similar alterations might be associated with affective disorder. The abnormalities observed in the mid-prefrontal cortex, an area that appears to be an important biologic determinant of the sustained attention required of subjects in this task, are similar to those previously observed in schizophrenia. Moreover, the abnormalities do not appear to relate directly to symptomatology or the subjects performance. The authors discuss the possibility that this abnormality may reflect dysfunction in the integrating component of the attention network critical for the maintenance of goal-directed behavior and thus represent a psychosis vulnerability factor in some patients.

Non-injection substance use correlates with risky sex among men having sex with men: data from HIVNET.

Associations between substance use and sexual behavior were examined among 3220 seronegative men who have sex with men (MSM) in a HIV vaccine preparedness study. Relationships between current and past substance use and current sexual risk were evaluated using crude odds ratios and logistic regression to adjust for confounding variables. Heroin and injection drug use were uncommon (< 2%). Substances most often used were alcohol (89%), marijuana (49%), nitrite inhalants (29%), amphetamines or similarly acting stimulants (21%), cocaine 14% and hallucinogens (14%). Increased adjusted odds for unprotected sex were significantly associated with current heavy alcohol use (OR 1.66; CI 1.18, 2.33), past alcohol problems (OR 1.25; CI 1.05, 1.48), and current drug use (OR 1.26; CI 1.08, 1.48). When associations with specific drugs and nitrite inhalants were examined separately, current use of cocaine and other stimulants (OR 1.25; CI 1.01, 1.55), hallucinogens (OR 1.40; CI 1.10, 1.77), and nitrite inhalants (some (OR 1.61; CI 1.35, 1.92); heavy (OR 2.18; CI 1.48, 3.20)), were independently associated with unprotected sex. Those with past drug use or past heavy alcohol use but not currently using demonstrated no increase in sexual risk, suggesting an important role for substance-focused interventions in risk reduction efforts among MSM.

Anal sex among HIV-seronegative women at high risk of HIV exposure.

To assess the prevalence and the sociodemographic and behavioral correlates of anal sex in a cohort of HIV-seronegative U.S. women at high risk of HIV exposure, we administered a risk assessment using audio computer-assisted self-interview (A-CASI). Of 1268 sexually active women, 432 (32%) reported anal sex in the previous 6 months. Compared with women who did not report anal sex, those who did had more unprotected vaginal sex (median of 11 versus 7 episodes; p <. 001) and a higher proportion of unprotected sexual (vaginal plus anal) episodes (median of 0.90 versus 0.81; p =.01). Anal sex was reported by higher proportions of women who did not always use condoms, who used crack in the past year, who were </=35 years of age, with no formal education beyond high school, who had had a diagnosed sexually transmitted disease in the previous year, a primary male sex partner, and a male sex partner with a history of injecting use. Women were more likely to report anal sex by A-CASI than during interviewer-administered risk assessments (odds ratio [OR], 9.00; 95% confidence interval [CI], 1.14-71.0). A less biased method of ascertainment may account for the large proportion of women reporting anal sex. Given increased vaginal risk among women reporting anal sex, the relative importance of anal sex in heterosexual transmission merits further study. Behavioral and biomedical prevention strategies effective for anal as well as vaginal sex are needed.

Effects of Acute Stimulant Medication on Cerebral Metabolism in Adults with Hyperactivity

Recent work in our laboratory has demonstrated both global and regional reductions in cerebral glucose metabolism in adult subjects with attention-deficit typeractivity disorder (ADHD). The purpose of the present study was to examine the effects of an acute dose of stimulant medication on cerebral metabolism in adults with ADHD using positron emission tomography with flurodeoxyglucose-18 as the tracer. Each subject underwent scanning twice, once off-drug and again after receiving a single oral dose of either dextroamphetamine (0.25 mg/kg) or methylphenidate (0.35 mg/kg). Subjects completed behavioral self-report measures before and after the scan and performed an auditory continuous performance task during the tracer uptake period. Neither drug changed global metabolism. Both drugs increased systolic blood pressure, and dextroamphetamine improved performance on the auditory attention task. Each stimulant produced a differential pattern of increases and decreases in regional metabolism throughout the regions of interest that were sampled. Rather than increasing glucose utilization in specific brain regions with lowered metabolic rates in adults with ADHD, stimulants may act by altering glucose use throughout the brain.

Metabolic brain pattern of sustained auditory discrimination

SummaryPositron emission tomography of [18F]-2-fluorodeoxyglucose was used to assess the functional brain activity of normal subjects while performing auditory discrimination (CPT), while receiving an identical set of tones as in CPT, but with the instructions that they were background noise, or while at rest. The present study: (1) confirms earlier findings of an association between the functional activity of the right midprefrontal cortex and the performance of auditory discrimination, (2) localizes this increase in right prefrontal cortex activity to the middle prefrontal gyrus; and (3) provides a framework of specific testable hypotheses for the evaluation of the importance of certain limbic and paralimbic areas in the biological determination of sustained attention to be addressed in future studies. The framework accounts for the now confirmed finding that the middle cingulate has lower metabolic activity in CPT than at rest, and new findings of alterations in temporal lobe processing of tones in response to attention.

Correlates of condom failure in a sexually active cohort of men who have sex with men

Condom failure (slippage or breakage) has been shown to be associated with HIV seroconversion among men who have sex with men (MSM), but predictors of failure have been poorly elucidated. Of 2592 HIV-seronegative MSM participants in the HIV Network for Prevention Trials (HIVNET) multisite Vaccine Preparedness Study who reported condom use for anal sex in the 6 months before enrollment, condom failure was reported by 16.6%, with failure rates of 2.1/100 episodes of condom usage (2.5 failures/100 episodes for receptive anal sex and 1.9/100 episodes for insertive anal sex). In separate multivariate models evaluating predictors of condom failure reported by the insertive and receptive partners, more frequent condom use was associated with a decreased per-condom failure rate and amphetamine and heavy alcohol use with increased rates in both models. Being employed, having private medical insurance, and using lubricants for >80% of anal sex acts were significantly associated with decreased failure rates in the insertive model. Safer sex counseling should particularly target men of lower socioeconomic status, promote proper and consistent use of condoms with appropriate lubricants, and address the impact of drug use, especially amphetamines and alcohol, on condom failure.

The social context of drinking, drug use, and unsafe sex in the Boston Young Men Study.

The objective of this study was to evaluate the relation between drinking, drug use, and unprotected anal intercourse in young men who have sex with men. A cross-sectional analysis of first-visit data from a prospective cohort of 508 young gay men recruited from 1993 through 1994 from bars, college campuses, and the Fenway Community Health Center in Boston was performed. The major outcome measures were any unprotected anal intercourse, after drinking and when sober, stratified by type of sexual partner (steady or nonsteady) during the previous 6 months and during the most recent sexual encounter. The average age of the cohort was 23.3 years; 77.6% were white, and 76.4% were in college. These young men had a median of 10.5 male sexual partners in their lifetimes, and 3 sexual partners in the previous 6 months before enrollment. One hundred and thirty-four (26%) reported unprotected anal intercourse during the previous 6 months. Individuals who had unprotected anal intercourse were more likely to have a drinking problem (odds ratio [OR] = 1.95; 95% confidence interval [CI] = 1.26-3.01) and drank more (20.4 ml/day versus 13.9 ml/day; p < or = 0.01), compared with individuals who did not engage in unprotected anal intercourse. Overall, men were significantly less likely to have unprotected anal intercourse after alcohol or drug use, based on a series of paired analysis (OR = 0.27; 95% CI = 0.15-0.48). However, when we stratified by type of sexual partner, men were significantly more likely to have unprotected anal intercourse with their nonsteady sexual partners after drinking than when sober (OR = 4.33; 95% CI = 1.37-13.7), but were significantly less likely to have unprotected anal intercourse with steady partners (OR = 0.27; 95% CI = 0.15-0.48). The patterns observed as already mentioned for drinking were also found for substance use in general. Men who were more likely to have unprotected anal intercourse after substance use were significantly more likely to have a drinking problem (OR = 7.65; 95% CI = 2.34-24.59). These results suggest that the role of alcohol and unsafe sex in young gay men is complex, with the role of situational factors of paramount importance. Alcohol and substance use interventions designed to reduce HIV risk need to specify the role of substance use in the sexual context to be successful.