The Effect of Systemic Racism and Homophobia on Police Enforcement and Sexual and Emotional Violence among Sex Workers in East London: Findings from a Cohort Study.

There is extensive qualitative evidence of violence and enforcement impacting sex workers who are ethnically or racially minoritized, and gender or sexual minority sex workers, but there is little quantitative evidence. Baseline and follow-up data were collected among 288 sex workers of diverse genders (cis/transgender women and men and non-binary people) in London (2018-2019). Interviewer-administered and self-completed questionnaires included reports of rape, emotional violence, and (un)lawful police encounters. We used generalized estimating equation models (Stata vs 16.1) to measure associations between (i) ethnic/racial identity (Black, Asian, mixed or multiple vs White) and recent (6 months) or past police enforcement and (ii) ethnic/racial and sexual identity (lesbian, gay or bisexual (LGB) vs. heterosexual) with recent rape and emotional violence (there was insufficient data to examine the association with transgender/non-binary identities). Ethnically/racially minoritized sex workers (26.4%) reported more police encounters partly due to increased representation in street settings (51.4% vs 30.7% off-street, p = 0.002). After accounting for street setting, ethnically/racially minoritized sex workers had higher odds of recent arrest (adjusted odds ratio 2.8, 95% CI 1.3-5.8), past imprisonment (aOR 2.3, 95% CI 1.1-5.0), police extortion (aOR 3.3, 95% CI 1.4-7.8), and rape (aOR 3.6, 95% CI 1.1-11.5). LGB-identifying sex workers (55.4%) were more vulnerable to rape (aOR 2.4, 95% CI 1.1-5.2) and emotional violence. Sex workers identifying as ethnically/racially minoritized (aOR 2.1, 95% CI 1.0-4.5), LGB (aOR 2.0, 95% CI 1.0-4.0), or who use drugs (aOR 2.0, 95% CI 1.1-3.8) were more likely to have experienced emotional violence than white-identifying, heterosexual or those who did not use drugs. Experience of any recent police enforcement was associated with increased odds of rape (aOR 3.6, 95% CI 1.3-8.4) and emotional violence (aOR 4.9, 95% CI 1.8-13.0). Findings show how police enforcement disproportionately targets ethnically/racially minoritized sex workers and contributes to increased risk of rape and emotional violence, which is elevated among sexual and ethnically/racially minoritized workers.

Gait risk factors for disease progression differ between non-traumatic and post-traumatic knee osteoarthritis.

OBJECTIVE: To examine if relationships between knee osteoarthritis (OA) progression with knee moments and muscle activation during gait vary between patients with non-traumatic and post-traumatic knee OA. DESIGN: This longitudinal study included participants with non-traumatic (n = 17) and post-traumatic (n = 18) knee OA; the latter group had a previous anterior cruciate ligament rupture. Motion capture cameras, force plates, and surface electromyography measured knee moments and lower extremity muscle activation during gait. Cartilage volume change were determined over 2 years using magnetic resonance imaging in four regions: medial and lateral plateau and condyle. Linear regression analysis examined relationships between cartilage change with gait metrics (moments, muscle activation), group, and their interaction. RESULTS: Measures from knee adduction and rotation moments were related to lateral condyle cartilage loss in both groups, and knee adduction moment to lateral plateau cartilage loss in the non-traumatic group only [ß = -1.336, 95% confidence intervals (CI) = -2.653 to -0.019]. Generally, lower levels of stance phase muscle activation were related to greater cartilage loss. The relationship between cartilage loss in some regions with muscle activation characteristics varied between non-traumatic and post-traumatic groups including for: lateral hamstring (lateral condyle ß = 0.128, 95%CI = 0.003 to 0.253; medial plateau ß = 0.199, 95%CI = 0.059 to 0.339), rectus femoris (medial condyle ß = -0.267, 95%CI = -0.460 to -0.073), and medial hamstrings (medial plateau; ß = -0.146, 95%CI = -0.244 to -0.048). CONCLUSION: Findings indicate that gait risk factors for OA progression may vary between patients with non-traumatic and post-traumatic knee OA. These OA subtypes should be considered in studies that investigate gait metrics as risk factors for OA progression.

The countryside or the city: Which environment is better for the honeybee?

For a number of years, the decline of honeybee (Apis mellifera) in North America and Europe has been the subject of much debate. Among the many factors proposed by hundreds of studies to explain this phenomenon is the hypothesis that agricultural activities using pesticides contribute to the weakness of bee colonies. Moreover, while urban beekeeping is presently booming in several cities, we do not know if this environment is more beneficial for bees than the typical, rural area. In the summer of 2018, we sampled honeybees (foragers and larvae) in rural (Laurentians) and urban (city of Montreal) areas and compared them using the following biomarkers: carotenoids, retinoids, α-tocopherol, metallothionein-like proteins (MTLPs), lipid peroxidation, triglycerides, acetylcholinesterase activity (AChE) and proteins. Pesticides, pharmaceuticals and personal care products (PPCPs) and metals were also quantified in honeybees' tissues. Our result revealed that, globally, urban foragers had higher levels of insecticides and PPCPs and that metals were in greater concentrations in urban larvae. Compared to rural foragers, urban foragers had higher concentrations of MTLPs, triglycerides, protein and AChE activity. The multifactorial analysis confirmed that insecticides, some metals and PPCPs were the most influential components in the contaminant‒biomarker relationships for both foragers and larvae.

Impact of the T2-weighted axial oblique MRI sequence in the assessment of peroneal tendons.

AIM: To define the role of the T2-weighted axial oblique sequence for the magnetic resonance imaging (MRI) assessment of peroneal tendon pathologies. MATERIALS AND METHODS: Two radiologists interpreted 180 ankle MRI examinations using standard sequences alone and then in combination with an axial oblique sequence. The readers indicated how likely a peroneal pathology was present using a five-level confidence scale. Diagnostic confidence, interobserver agreement, and clinical correlation were compared. Changes in diagnosis were recorded. RESULTS: For both readers, the diagnostic confidence was significantly higher using the axial oblique sequence for tendinosis and inframalleolar tenosynovitis for both tendons and for peroneus brevis partial and longitudinal split tears (p<0.001). For reader 1, the diagnostic confidence was also higher using the axial oblique sequence for peroneus longus partial tears (p=0.007). Changes in diagnosis were seen for tendinosis and tenosynovitis of both tendons and for peroneus brevis partial and longitudinal split tears in 0.6-10.8% of cases. Inter-rater reliability was significantly higher with the axial oblique sequence for the diagnosis of tendinosis, inframalleolar tenosynovitis, and partial tear for both tendons, and for peroneus brevis longitudinal split tear. Amongst 105 examinations with clinical information, peroneal pathologies were most frequently diagnosed as present in cases with lateral symptoms (17% versus 14%) and absent in cases without lateral symptoms (92% versus 86%) on the axial oblique sequence. CONCLUSION: The axial oblique sequence for the assessment of peroneal tendons allows for higher diagnostic confidence, inter-rater reliability, and clinical correlation and can lead to changes in diagnosis.

Relationship between alignment and cartilage thickness in patients with non-traumatic and post-traumatic knee osteoarthritis.

OBJECTIVE: To compare cartilage thickness between patients with non-traumatic and post-traumatic knee osteoarthritis (OA) and healthy controls and to determine if disease severity and alignment impact these differences. DESIGN: Participants with non-traumatic (n = 22) and post-traumatic (n = 19) knee OA, and healthy controls (n = 22) were recruited for this cross-sectional study. Participants underwent 3T magnetic resonance imaging (T1-weighted, 3D sagittal gradient echo sequence) and cartilage thickness was determined in four regions: medial and lateral condyle, and medial and lateral plateau. Lower extremity alignment (mechanical axis angle) and disease severity (Kellgren-Lawrence scores) were measured from full length radiographs. Statistical analysis included one-way analysis of variance (ANOVA) and modified Bonferroni test adjusting for multiple pairwise comparisons. Linear regression analyses examined the relationship between cartilage thickness and knee OA group after controlling for disease severity, meniscal status, and alignment. RESULTS: In participants with predominantly medial compartment knee OA, compared to healthy controls, those with non-traumatic knee OA had diminished cartilage thickness in the medial plateau (p = 0.035) and those with post-traumatic knee OA had greater cartilage thickness in the lateral condyle (p = 0.044). In the lateral condyle, data revealed that alignment accounted for the variance in cartilage thickness (p = 0.035), in which a stronger relationship was found in the non-traumatic (r = -0.61) than the post-traumatic (r = -0.12) OA group. CONCLUSIONS: Emerging data demonstrated that participants with non-traumatic knee OA have a stronger relationship between alignment and cartilage thickness than those with post-traumatic knee OA. This indicates that factors involved in knee OA initiation and progression may differ between these OA subtypes.

A comparison of muscle activation and knee mechanics during gait between patients with non-traumatic and post-traumatic knee osteoarthritis.

OBJECTIVE: The objective was to compare muscle activation and knee mechanics during gait between participants with non-traumatic knee osteoarthritis (OA), post-traumatic knee OA, and healthy adults. DESIGN: Participants with non-traumatic knee OA (n = 22), post-traumatic knee OA (n = 19), and healthy adults (n = 22) completed gait trials for this observational, cross-sectional study. Post-traumatic OA group had a history of traumatic anterior cruciate ligament (ACL) rupture. Surface electromyography (EMG) measured activation of seven lower extremity muscles. Motion capture cameras and force plates measured motion and force data. Principal component analysis (PCA) determined waveform characteristics (principal components) from EMG, knee angle, and knee external moment waveforms. Analysis of variance (ANOVA) examined group differences in principal component scores (PC-scores). Regression analyses examined if a variable that coded for OA group could predict PC-scores after accounting for disease severity, alignment, and lateral OA. RESULTS: There was lower gastrocnemius EMG amplitudes (P < 0.01; ANOVA) in the post-traumatic OA group compared to healthy group. Non-traumatic OA group had higher vastus lateralis, vastus medialis, and rectus femoris EMG compared to post-traumatic OA group (P = 0.01 to 0.04) in regression analyses. Also, non-traumatic OA group had higher and prolonged lateral hamstring EMG compared to healthy (P = 0.03; ANOVA) and post-traumatic OA (P = 0.04; regression) groups respectively. The non-traumatic OA group had lower knee extension (P < 0.05) and medial rotation (P < 0.05) moments than post-traumatic and healthy groups. CONCLUSIONS: Muscle activation and knee mechanics differed between participants with non-traumatic and post-traumatic knee OA and healthy adults. These OA subtypes had differences in disease characteristics that may impact disease progression.

Assortative mixing as a source of bias in epidemiological studies of sexually transmitted infections: the case of smoking and human papillomavirus.

For studies examining risk factors of sexually transmitted infections (STIs), confounding can stem from characteristics of partners of study subjects, and persist after adjustment for the subjects' individual-level characteristics. Two conditions that can result in confounding by the subjects' partners are: (C1) partner choice is assortative by the risk factor examined and, (C2) sexual activity is associated with the risk factor. The objective of this paper is to illustrate the potential impact of the assortativity bias in studies examining STI risk factors, using smoking and human papillomavirus (HPV) as an example. We developed an HPV transmission-dynamic mathematical model in which we nested a cross-sectional study assessing the smoking-HPV association. In our base case, we assumed (1) no effect of smoking on HPV, and (2) conditions C1-C2 hold for smoking (based on empirical data). The assortativity bias caused an overestimation of the odds ratio (OR) in the simulated study after perfect adjustment for the subjects' individual-level characteristics (adjusted OR 1·51 instead of 1·00). The bias was amplified by a lower basic reproductive number (R 0), greater mixing assortativity and stronger association of smoking with sexual activity. Adjustment for characteristics of partners is needed to mitigate assortativity bias.

Who mixes with whom among men who have sex with men? Implications for modelling the HIV epidemic in southern India.

In India, the identity of men who have sex with men (MSM) is closely related to the role taken in anal sex (insertive, receptive or both), but little is known about sexual mixing between identity groups. Both role segregation (taking only the insertive or receptive role) and the extent of assortative (within-group) mixing are known to affect HIV epidemic size in other settings and populations. This study explores how different possible mixing scenarios, consistent with behavioural data collected in Bangalore, south India, affect both the HIV epidemic, and the impact of a targeted intervention. Deterministic models describing HIV transmission between three MSM identity groups (mostly insertive Panthis/Bisexuals, mostly receptive Kothis/Hijras and versatile Double Deckers), were parameterised with behavioural data from Bangalore. We extended previous models of MSM role segregation to allow each of the identity groups to have both insertive and receptive acts, in differing ratios, in line with field data. The models were used to explore four different mixing scenarios ranging from assortative (maximising within-group mixing) to disassortative (minimising within-group mixing). A simple model was used to obtain insights into the relationship between the degree of within-group mixing, R0 and equilibrium HIV prevalence under different mixing scenarios. A more complex, extended version of the model was used to compare the predicted HIV prevalence trends and impact of an HIV intervention when fitted to data from Bangalore. With the simple model, mixing scenarios with increased amounts of assortative (within-group) mixing tended to give rise to a higher R0 and increased the likelihood that an epidemic would occur. When the complex model was fit to HIV prevalence data, large differences in the level of assortative mixing were seen between the fits identified using different mixing scenarios, but little difference was projected in future HIV prevalence trends. An oral pre-exposure prophylaxis (PrEP) intervention was modelled, targeted at the different identity groups. For intervention strategies targeting the receptive or receptive and versatile MSM together, the overall impact was very similar for different mixing patterns. However, for PrEP scenarios targeting insertive or versatile MSM alone, the overall impact varied considerably for different mixing scenarios; more impact was achieved with greater levels of disassortative mixing.

Differences between seven measures of self-reported numbers of clients of female sex workers in southern India: implications for individual- and population-level analysis.

Quantifying sexual activity of sub-populations with high-risk sexual behaviour is important in understanding HIV epidemiology. This study examined inconsistency of seven outcomes measuring self-reported clients per month (CPM) of female sex workers (FSWs) in southern India and implications for individual/population-level analysis. Multivariate negative binomial regression was used to compare key social/environmental factors associated with each outcome. A transmission dynamics model was used to assess the impact of differences between outcomes on population-level FSW/client HIV prevalence. Outcomes based on 'clients per last working day' produced lower estimates than those based on 'clients per typical day'. Although the outcomes were strongly correlated, their averages differed by approximately two-fold (range 39.0-79.1 CPM). The CPM measure chosen did not greatly influence standard epidemiological 'risk factor' analysis. Differences across outcomes influenced HIV prevalence predictions. Due to this uncertainty, we recommend basing population-based estimates on the range of outcomes, particularly when assessing the impact of interventions.

Men who have sex with men and women in Bangalore, South India, and potential impact on the HIV epidemic.

OBJECTIVE: The aim of this study was to quantify differences in patterns of sexual behaviour among men who have sex with men and women (MSMW) compared with men who have sex with men only (MSMO), and to examine the extent to which bisexual behaviour may act as a bridge for introducing HIV infection into the general population. METHODS: A cross-sectional survey in Bangalore city in 2006, which sampled men seeking sex with men in public places and hammams (bath houses where transgender individuals sell sex to men). RESULTS: Among a sample of 357 men reporting same-sex behaviour; 41% also reported sex with a woman in the past year and 14% were currently married to a woman, only two of whom had informed their wives about having sex with men. Condom use was very inconsistent with all male partners, while 98% reported unprotected vaginal sex with their wives. MSMW reported lower rates of risky behaviour with other men than MSMO: fewer reported selling sex (17% vs 58%), or receptive anal sex with known (28% vs 70%) or unknown (30% vs 59%) non-commercial partners. CONCLUSION: Bisexual behaviour was common among men seeking sex with men sampled in this survey. Although MSMW reported lower rates of risky sexual behaviour with male partners than MSMO, inconsistent condom use with both male and female partners indicates a potential means of HIV transmission into the general population. HIV prevention programmes and services should reach bisexual men who potentially expose their male and female partners to HIV.

Biological markers to establish a relationship between the health status of the St. Lawrence River yellow perch (Perca flavescens) with a gradient of anthropogenic disturbances.

Since the mid-1990s, the decline of the yellow perch population of Lake Saint-Pierre (hereinafter LSP) in Quebec, Canada has been the subject of several research programs. The combined effect of habitat deterioration, the presence of invasive species, and poor water quality negatively affected the yellow perch population in this lake. In 2013, we sampled yellow perch (larvae, juveniles and adults) at six sites along the St. Lawrence River representing a gradient of increasing human influences from upstream to downstream and measured several biomarkers including retinoid compounds (vitamin A). In the most contaminated sites (LSP, north and south shores), we found that retinoid stores were decreased in all three stages of development. To corroborate these results and to test other biomarkers, we once again sampled yellow perch (adults only) from the same sites. Results from our 2014 and 2015 samplings confirmed that LSP yellow perch appeared to be at a disadvantage compared to fish from upstream populations. Individuals from LSP have lower acetylcholinesterase (AChE) activity as well as lower retinoid levels in liver and plasma. These fish were also marked by lower levels of antioxidants such as lycopene and vitamin E. A discriminant analysis of this set of results confirmed that the yellow perch of the LSP could be easily discriminated from those of the other sites (2014 and 2015) on the basis of liver retinoid and, to a lesser extent, of the liver tocopherol and protein concentration of the muscle, as well as AChE activity and DROH (all-trans-3,4-dehydroretinol) measured in plasma.

Incremental role of male circumcision on a generalised HIV epidemic through its protective effect against other sexually transmitted infections: from efficacy to effectiveness to population-level impact.

BACKGROUND: Male circumcision (MC) can reduce HIV acquisition. However, a better understanding of the indirect protective effect of MC on sexually transmitted infections (STIs) is required. OBJECTIVE: To assess the incremental benefits conferred by MC on HIV infection at the individual level in circumcision trials (no herd immunity effect) and at the population level (with herd immunity effect) owing to its protective effect against other STIs. METHODS: A dynamic stochastic model of HIV and STI infections in a Kenyan population was used to simulate the impact of MC offered to a few trial participants or to a large proportion of men in order to study the protective role of MC on HIV infection at the individual and population levels. RESULTS: Fewer than 20% of the HIV infections prevented in the circumcised arm of the circumcision trials (individual level) could be attributable to the efficacy of MC against STIs rather than against HIV. At the population level, MC can significantly reduce the prevalence of HIV, especially among men and women in the longer term. However, even at the population level, the long-term incremental impact of MC on HIV due to the protection against STI is modest (even if MC efficacy against the STI and STI prevalence was high). CONCLUSIONS: The protection of MC against STI contributes little to the overall effect of MC on HIV. Additional work is needed to determine whether, and under what conditions, the protective effect of MC efficacy against STIs can have a significant incremental benefit on the HIV epidemic.

Nonlocal Coherent Denoising of RF Data for Ultrasound Elastography.

Ultrasound elastography infers mechanical properties of living tissues from ultrasound radiofrequency (RF) data recorded while the tissues are undergoing deformation. A challenging yet critical step in ultrasound elastography is to estimate the tissue displacement (or, equivalently the time delay estimate) fields from pairs of RF data. The RF data are often corrupted with noise, which causes the displacement estimator to fail in many in vivo experiments. To address this problem, we present a nonlocal, coherent denoising approach based on Bayesian estimation to reduce the impact of noise. Despite incoherent denoising algorithms that smooth the B-mode images, the proposed denoising algorithm is used to suppress noise while maintaining useful information such as speckle patterns. We refer to the proposed approach as COherent Denoising for Elastography (CODE) and evaluate its performance when CODE is used in conjunction with the two state-of-art elastography algorithms, namely: (i) GLobal Ultrasound Elastography (GLUE) and (ii) Dynamic Programming Analytic Minimization elastography (DPAM). Our results show that CODE substantially improves the strain result of both GLUE and DPAM.

Evaluating large-scale HIV prevention interventions: study design for an integrated mathematical modelling approach.

BACKGROUND: There is an urgent need to evaluate HIV prevention interventions, thereby improving our understanding of what works, under what circumstances and what is cost effective. OBJECTIVES: To describe an integrated mathematical evaluation framework designed to assess the population-level impact of large-scale HIV interventions and applied in the context of Avahan, the Indian AIDS Initiative, in southern India. The Avahan Initiative is a large-scale HIV prevention intervention, funded by the Bill & Melinda Gates Foundation, which targets high-risk groups in selected districts of the six states most affected by the HIV/AIDS epidemic (Maharashtra, Karnataka, Tamil Nadu, Andhra Pradesh, Nagaland and Manipur) and along the national highways. METHODS: One important component of the monitoring and evaluation of Avahan relies on an integrated mathematical framework that combines empirical biological and behavioural data from different subpopulations in the intervention areas, with the use of tailor-made transmission dynamics models embedded within a Bayesian framework. RESULTS: An overview of the Avahan Initiative and the objectives of the monitoring and evaluation of the intervention is given. The rationale for choosing this evaluation design compared with other possible designs is presented, and the different components of the evaluation framework are described and its advantages and challenges are discussed, with illustrated examples. CONCLUSIONS: This is the first time such an approach has been applied on such a large scale. Lessons learnt from the CHARME project could help in the design of future evaluations of large-scale interventions in other settings, whereas the results of the evaluation will be of programmatic and public health relevance.

A Bayesian approach to estimate changes in condom use from limited human immunodeficiency virus prevalence data.

Evaluation of large-scale intervention programmes against human immunodeficiency virus (HIV) is becoming increasingly important, but impact estimates frequently hinge on knowledge of changes in behaviour such as the frequency of condom use over time, or other self-reported behaviour changes, for which we generally have limited or potentially biased data. We employ a Bayesian inference methodology that incorporates an HIV transmission dynamics model to estimate condom use time trends from HIV prevalence data. Estimation is implemented via particle Markov chain Monte Carlo methods, applied for the first time in this context. The preliminary choice of the formulation for the time varying parameter reflecting the proportion of condom use is critical in the context studied, because of the very limited amount of condom use and HIV data available. We consider various novel formulations to explore the trajectory of condom use over time, based on diffusion-driven trajectories and smooth sigmoid curves. Numerical simulations indicate that informative results can be obtained regarding the amplitude of the increase in condom use during an intervention, with good levels of sensitivity and specificity performance in effectively detecting changes. The application of this method to a real life problem demonstrates how it can help in evaluating HIV interventions based on a small number of prevalence estimates, and it opens the way to similar applications in different contexts.

Complementary hypothesis concerning the community sexually transmitted disease mass treatment puzzle in Rakai, Uganda.

OBJECTIVES: To study the dynamics of a mass treatment programme for sexually transmitted diseases (STD) on prevalence of STD and HIV incidence in order to help explain the results of the STD mass treatment community trial in Rakai, Uganda. METHODS: The analysis is based on simulations of STD mass treatment interventions using a deterministic model describing the course of STD and HIV transmission over time and incorporating demographic, biological and behavioural parameters. The mass intervention modelled mimics that used in the Rakai community trial. RESULTS: Mass treatment decreases STD prevalence to a very low level compared with baseline but is unsuccessful at eradicating the infection. STD prevalences return to baseline fairly rapidly after each round of mass treatment. Under different realistic scenarios, the fraction of HIV cases prevented by STD mass treatment assuming uniform 80% coverage of high- and low-risk groups, over the 20-month period following the first round of treatment, was greater than 35%. If, however, differential coverage is assumed, for example that while the total coverage is still 80%, only 40 or 25% of those at high risk are treated, the HIV preventable fraction is reduced, to 19 and 15% respectively (undetectable given the statistical power of the study). The tremendous impact of differential coverage can also be observed even in the early stage of the HIV epidemic. CONCLUSIONS: In the Rakai trial, mass treatment may have had an effect, although transient, on all STD prevalences, which could have had positive repercussions for HIV incidence. This modelling exercise suggests that although an 80% coverage appears high, the differential coverage of low- and high-risk populations may seriously impair our ability to test the STD-HIV interaction hypothesis.

Effects of N-acetylcysteine in the rat heart reperfused after low-flow ischemia: evidence for a direct scavenging of hydroxyl radicals and a nitric oxide-dependent increase in coronary flow.

The capacity of N-acetylcysteine to directly scavenge hydroxyl radical produced by rat hearts reperfused after 90 min of low-flow ischemia was assessed by the hydroxylation of 4-hydroxybenzoate into 3,4-dihydroxybenzoate using a gas chromatography-mass spectrometric assay. Reperfused hearts showed a massive release of 3,4-dihydroxybenzoate, lactate dehydrogenase, and total glutathione, contained less reduced and oxidized glutathione, but maintained spontaneous beating and coronary flow rates close to preischemic values. Compared to untreated hearts: reperfused hearts treated with N-acetylcysteine from the start of ischemia (i) released four times less 3,4-dihydroxybenzoate, but similar amounts of lactate dehydrogenase or glutathione, (ii) showed a nitric oxide-dependent increase in coronary flow rate, and (iii) contained less oxidized glutathione, but similar amounts of reduced glutathione. Reperfused hearts receiving N-acetylcysteine since the last 5 min of ischemia had also a four-times lower 3,4-dihydroxybenzoate release, but their coronary flow rate response was similar to that of untreated hearts. These results indicate that N-acetylcysteine can directly scavenge hydroxyl radicals produced by reperfused ischemic hearts, although this effect is not associated with any protective effects as indicated by the lactate dehydrogenase and glutathione release and cannot explain the nitric oxide-dependent reperfusion hyperemia.

The influence of different sexual-contact patterns between age classes on the predicted demographic impact of AIDS in developing countries.

A model is developed to describe the spread of HIV within heterosexual communities and the demographic impact of AIDS. The model combines epidemiologic and demographic processes and is designed to mirror the impact of AIDS in sub-Saharan Africa. Refinements on past work in this area include unequal probabilities for transmission from females to males and from males to females, the inclusion of an age- and sex-dependent sexual-partner choice function and distributed incubation plus infectious periods. Numerical studies suggest that unequal transmission probabilities (weighted to a greater probability from males to females than vice versa), and the tendency of males to choose sexual partners of the opposite sex younger than themselves, both act to increase the demographic impact of AIDS over that predicted with equal transmission between the sexes and partner choice restricted within given age classes. Analyses support the conclusions of past work that the epidemic will only have a small detrimental impact on the dependency ratio of a population (the ratio of dependents to working adults) even when a weighting is added to take account of the extra burden imposed by the care of adult AIDS patients. However, a small increase in the ratio can imply a significant rise in the number of dependents within the population. Stimulation studies of the impact of changes in behavior to reduce transmission highlight to the need to induce such changes as early as possible in the course of the epidemic in order to minimize its impact. Directions for future research are discussed emphasizing the need to acquire quantitative data on sexual habits and to construct models to represent heterogeneity in sexual behavior.

PIP: A mathematical model of the likely demographic impact of acquired immunodeficiency syndrome (AIDS) suggest that, in the countries of sub- Saharan Africa, this impact can be expected to increase in the years ahead as a result of unequal transmission probabilities (weighted toward a greater probability from males to females) and the tendency of men to select female sexual partners from a younger class. The model refines earlier work in its consideration of predicted influence of human immunodeficiency virus (HIV) infection on the age structure and dependency ratio of the population, the significance of patterns of sexual contact between the age classes of the 2 sexes, and the impact of control measures such as health education and condom use. The assumptions of a doubling time of 1.5 years in the early stages of the epidemic and a 3 times greater probability of transmission from infected males to susceptible females rather than vice versa produce the observation that net population growth rate will change from positive to negative 25 years after introduction of the AIDS virus. The dependency ration is not significantly affected by AIDS due to the counterbalancing effects of deaths from vertical and horizontal transmission. On the other hand, if dependency ratio is defined to encompass the burden created by the care of AIDS patients, the disease-related ratio will increase over time. The most significant social factor in terms of the impact of AIDS on net fertility is the tendency of African men to choose female sexual partners at least 5 years younger than themselves. Finally, the numerical analyses indicate that the introduction of AIDS control measures 10 years after the onset of the epidemic will slow the progression of the epidemic and prevent a change in the population growth rate from positive to negative over a 100-year period.

The impact of HIV and other STDs on human populations. Are predictions possible?

This article presents an overview of the use of mathematical models to study the demographic impact of STDs. Written for the nonmathematician, the article introduces the basic concepts of mathematical epidemiology for infectious diseases, such as the mass-action principle, the threshold density concept, and the basic reproductive rate. Described are the main features that characterize the epidemiology of STDs and those features that differentiate them from other directly transmitted diseases, such as measles, rubella, and others. Also presented are major findings concerning the importance of sexual behavior on the dynamics of STD transmission, and the numerical analysis of the demographic impact on gonococcal and HIV infections using a mathematical model. The epidemiology of these two STDs is explored, as well as how the growth rate of the population can influence the epidemiology of these STDs. Finally, the authors demonstrate how, under some circumstances, early treatment of gonorrhea can reduce the demographic impact of HIV in regions most affected by both diseases.

Mathematical models of disease transmission: a precious tool for the study of sexually transmitted diseases.

This paper is an introduction to the mathematical epidemiology of sexually transmitted diseases (STDs) and its application to public health. After a brief introduction to transmission dynamics models, the construction of a deterministic compartmental mathematical model of HIV transmission in a population is described. As a background to STD transmission dynamics, basic reproductive rate, intergroup mixing, rate of partner change, and duration of infectivity are discussed. Use of the models illustrates the effect of sexual mixing (proportionate to highly assortative), of preventive intervention campaigns, and of HIV-chlamydia interaction on HIV prevalence in the different population groups. In particular, planned prevention campaigns can benefit the targeted intervention group but surprisingly can be disadvantageous for the general population. Through examples, mathematical models are shown to be helpful in our understanding of disease transmission, in interpretation of observed trends, in planning of prevention strategies, and in guiding data collection.