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Biomedical subjects

B Hope

Publications and source records attributed to B Hope.

16 recordsLinked to original sources
PubMed2005

Orthopaedic manifestations of the hip in haemophilia--impaction bone grafting used in revision total hip arthroplasty in a haemophilic patient.

The condition of haemophilia presents many challenges to the orthopaedic surgeon. Two such challenges include the haemophilic pseudotumour, a rare complication occurring in 1-2% of haemophiliacs, and the phenomenon of aseptic loosening of arthroplasty implants. This report presents a case involving the separate management of a pseudotumour and revision hip arthroplasty in the same hip using impaction bone grafting.

Acetabulum↗
PubMed2003

Sexual sensation seeking, reduced concern about HIV and sexual risk behaviour among gay men in primary relationships.

Gay and bisexual men who indicated they were currently in a primary relationship with another man (N = 230) completed measures of HIV treatment attitudes, sexual risk behaviour and sexual sensation seeking. Results indicate non-primary partner sexual activity is common in many gay relationships and men in non-exclusive relationships possessed greater levels of sexual sensation seeking and treatment-related reduced concern about the dangerousness of HIV than men in exclusive relationships. Results also suggest that individuals who were members of HIV-seroconcordant relationships were more likely to engage in unprotected sexual activity with their primary sexual partners than gay men who were members of HIV-discordant couples. A series of regression analyses revealed that reduced concern about HIV mediated the relationship between sexual sensation seeking and sexual risk behaviour. The next generation of HIV prevention interventions must address the attitudinal shifts that have occurred among some gay men regarding the seriousness of HIV and should be sensitive to the dynamics of gay relationships.

Adult↗
PubMed2001

Time-dependent changes in extinction behavior and stress-induced reinstatement of drug seeking following withdrawal from heroin in rats.

RATIONALE AND OBJECTIVES: Footshock stress reliably reinstates heroin seeking in rats, but the time course of the development of this effect following drug withdrawal is not known. Here we studied the effect of intermittent footshock stress on reinstatement of heroin seeking following different withdrawal periods (1-66 days). We also studied whether changes in corticotropin-releasing factor (CRF) mRNA in the central nucleus of the amygdala (CeA) and the bed nucleus of the stria terminalis (BNST) are correlated with this reinstatement after 1 day and 6 days of heroin withdrawal. METHODS: Rats were trained to self-administer heroin (9 h/day; 0.1 mg/kg per infusion) for 10 days. Tests for extinction behavior and footshock-induced reinstatement of heroin seeking were then conducted after 1, 6, 12, 25, or 66 days of heroin withdrawal. On the test day, rats were given five to ten 60-min extinction sessions until they reached the extinction criterion of less than 15 responses per 60 min on the lever previously associated with heroin. Rats were then exposed to intermittent foot-shock (0.8 mA; 10 min), and lever-pressing behavior was recorded for 120 min. RESULTS: Reinstatement of lever-pressing behavior by footshock followed an inverted U-shaped curve with maximal responding after 6 days and 12 days of heroin withdrawal. Surprisingly, foot-shock did not reinstate lever-pressing behavior on day 1 of withdrawal. Lever pressing during extinction, prior to exposure to footshock, also followed an inverted U-shaped curve, with higher responding after 6, 12, and 25 days of heroin withdrawal. Finally, compared with control groups not exposed to shock, CRF mRNA levels in response to footshock were increased in the CeA (day 1 of withdrawal) and the dorsal BNST (day 1 and day 6), but not in the ventral BNST. CONCLUSIONS: The duration of the heroin withdrawal period is an important factor in the manifestation of (1) footshock stress-induced reinstatement of heroin seeking and (2) extinction of the heroin-reinforced behavior. Finally, the time-dependent changes in footshock stress-induced reinstatement following withdrawal from heroin were not correlated with alterations in CRF mRNA in the CeA and BNST.

Animals↗
PubMed2001

Expectancies of sexual "escape" and sexual risk among drug and alcohol-involved gay and bisexual men.

PURPOSE: We tested the hypotheses that sexual risk would relate to gay/bisexual men's patterns of combining alcohol or drugs with sex, their motivation to use drugs to cognitively "escape" awareness of HIV risk, and their use of bars as social and sexual settings. METHODS: We conducted extensive interviews among African-American (n = 139) and White (n = 112) gay and bisexual men who were attending a behavioral intervention for safer sex results. Those who frequently combined drugs with sex reported higher rates of sexual risk and Hepatitis B infection than did men who infrequently combined substances with sex, or who combined only alcohol with sex. Sexual risk was pronounced among more frequent drug users who also reported strong expectancies that alcohol or drugs facilitate sex and cognitively escape from awareness of HIV risk. Frequenting bars per se was not an important factor in sexual risk. IMPLICATIONS: Men who use alcohol or drugs to enhance sexuality and escape self-awareness of HIV risk have a significantly diminished capacity to avoid sexual risk.

Adult↗
PubMed2000

Kappa-opioid receptor activation prevents alterations in mesocortical dopamine neurotransmission that occur during abstinence from cocaine.

In vivo microdialysis was used to characterize basal dopamine dynamics and cocaine-evoked dopamine levels in the medial prefrontal cortex of male Sprague-Dawley rats that had previously received once daily injections of cocaine (days 1-5; 20mg/kg, i.p.) in combination with the selective kappa-opioid receptor agonist U-69593 (days 3-5; 0.32mg/kg, s.c.) or its vehicle. The influence of these treatments on [3H]dopamine uptake in medial prefrontal cortex synaptosomes was also determined. Three days following the cessation of drug treatment, animals with prior history of cocaine administration exhibited enhanced psychomotor stimulation in response to a subsequent cocaine challenge. This effect was not apparent in animals that had previously received the cocaine treatment regimen in combination with the kappa-opioid receptor agonist U-69593. Cocaine challenge increased prefrontal dopamine levels in all pretreatment groups, but cocaine-pre-exposed animals had lower cocaine-evoked dopamine levels and higher basal in vivo extraction fraction, indicative of an increase in basal dopamine uptake relative to controls. Pretreatment with U-69593 prevented these effects of cocaine. Measurement of [3H]dopamine uptake in synaptosomes revealed a significant increase in uptake three days after the cessation of cocaine treatment. No increase in uptake was observed in animals that had received the cocaine treatment regimen in combination with U-69593. These results demonstrate that the early phase of abstinence from cocaine is associated with marked alterations in medial prefrontal cortex dopamine neurotransmission and that these neuroadaptations are prevented by the activation of kappa-opioid receptors. Furthermore, they raise the possibility that mesocortical dopamine neurons may be an important neural substrate upon which kappa-opioid agonists act to prevent the development of cocaine-induced behavioral sensitization.

Analgesics↗
PubMed1998

Bioconcentration of chlorinated biphenyls in biota from the North Pacific Ocean.

This study examined polychlorinated biphenyl (PCB) congener bioconcentration patterns in tissues of marine biota (macrophytes, urchins, mollusks, sea cucumbers, fishes) at Midway Atoll, North Pacific Ocean. Calculated mean lipid-normalized logarithmic bioconcentration factors (log BCFL) for PCB congeners in various marine species ranged from 3.75 to 6.97. The relationship between log BCFL and the logarithmic n-octanol-water partition coefficient (log Kow) can be adequately described by species-specific parabolic models wherein log BCFL generally increases then decreases with increases in log Kow. With the exception of a bilinear model, a variety of hydrophobicity models were generally not successful in closely predicting measured tissue residue concentrations as a function of log Kow. There is no evidence of a consistent pattern of progressive increase in bioconcentration of PCB congeners with increasing trophic level in this nearshore aquatic ecosystem.

Animals↗
PubMed1996

Sex, drugs and escape: a psychological model of HIV-risk sexual behaviours.

The lack of an effective HIV vaccine or other biomedical intervention means that behavioural change will continue to be critical to the prevention of HIV infection. Despite near universal knowledge of HIV and sexual safety, and widespread intentions to be safe, rates of unprotected sex and HIV sero-conversion remain high among gay and bisexual men. Explanatory models that link risk-taking and prevention to rational processes such as knowledge, social norms, behavioural intentions, or perceived vulnerability to infection, cannot fully account for the continued risk behaviours observed in virtually all cohorts of gay men. We feel that innovative conceptions of risk and risk prevention are needed, that emphasize non-rational, affective processes in risk-taking and decision-making. Consistent with recent models from social psychology, we propose that for many people sexual risk does not stem from a lack of community norms or personal standards, but from a desire to escape cognitive awareness of very rigorous norms and standards. Being self-aware of HIV risk arouses anxiety and precludes highly-desired activities: fatigue, fatalism, or other negative affect over HIV may lead people to 'cognitively disengage' within the sexual situation, and not to follow their norms or intentions toward safety. We propose that both substance use and the approach of high stimulation or other sexual settings facilitates this cognitive disengagement, wherein people enact 'automatic' sexual scripts and/or become more responsive to external pressures toward risk. We briefly review current psychosocial models of HIV risk behaviour, outline a cognitive escape model with particular emphasis on substance use as a behavioural risk factor, and discuss implications of an escape model for behavioural interventions among gay and bisexual men.

Bisexuality↗
PubMed1992

Regulation of immediate early gene expression and AP-1 binding in the rat nucleus accumbens by chronic cocaine.

Chronic treatment of rats with cocaine leads to long-term biochemical changes in the nucleus accumbens (NAc), a brain region implicated in mediating the reinforcing effects of cocaine and other drugs of abuse. Immediate early genes (IEGs) and their protein products appear to play an important role in transducing extracellular stimuli into altered patterns of cellular gene expression and, therefore, into long-term changes in cellular functioning. We therefore examined changes in the mRNA levels for the IEGs c-fos, c-jun, fosB, junB, and zif268 in the NAc of rats treated acutely and chronically with cocaine. A single cocaine injection increased the mRNA levels of all of the IEGs examined. Following chronic cocaine treatment, however, IEG expression had returned to control levels and was not significantly increased following a further acute challenge with cocaine, suggesting desensitization in the ability of cocaine to induce these IEGs. Similarly, levels of Fos-like immunoreactivity, which are increased in the NAc by acute cocaine, were reduced to control levels in chronic cocaine-treated rats. Fos, Jun, and a number of related proteins activate or repress transcription of genes by binding to DNA response elements called AP-1 sites. As would be expected from the RNA data and immunohistochemistry, acute cocaine administration increased AP-1 binding activity in the NAc, an effect that reverted completely to control levels within 8-12 hr. In contrast, AP-1 binding activity in the NAc of animals treated chronically with cocaine remained elevated at acute levels 18 hr after the last chronic injection, a time at which c-fos and c-jun mRNA levels and Fos-like immunoreactivity had returned to control values. An additional acute cocaine challenge did not further increase AP-1 binding. The data suggest that chronic cocaine treatment leads to a persistent increase in AP-1 binding activity, which may be involved in some of the physiological and behavioral aspects of cocaine addiction.

Animals↗