Manisha Shah

Matrix metalloproteinase 13–deficient mice are resistant to osteoarthritic cartilage erosion but not chondrocyte hypertrophy or osteophyte development

OBJECTIVE To investigate the role of matrix metalloproteinase 13 (MMP-13; collagenase 3) in osteoarthritis (OA). METHODS OA was surgically induced in the knees of MMP-13-knockout mice and wild-type mice, and mice were compared. Histologic scoring of femoral and tibial cartilage aggrecan loss (0-3 scale), erosion (0-7 scale), and chondrocyte hypertrophy (0-1 scale), as well as osteophyte size (0-3 scale) and maturity (0-3 scale) was performed. Serial sections were stained for type X collagen and the MMP-generated aggrecan neoepitope DIPEN. RESULTS Following surgery, aggrecan loss and cartilage erosion were more severe in the tibia than femur (P<0.01) and tibial cartilage erosion increased with time (P<0.05) in wild-type mice. Cartilaginous osteophytes were present at 4 weeks and underwent ossification, with size and maturity increasing by 8 weeks (P<0.01). There was no difference between genotypes in aggrecan loss or cartilage erosion at 4 weeks. There was less tibial cartilage erosion in knockout mice than in wild-type mice at 8 weeks (P<0.02). Cartilaginous osteophytes were larger in knockout mice at 4 weeks (P<0.01), but by 8 weeks osteophyte maturity and size were no different from those in wild-type mice. Articular chondrocyte hypertrophy with positive type X collagen and DIPEN staining occurred in both wild-type and knockout mouse joints. CONCLUSION Our findings indicate that structural cartilage damage in a mouse model of OA is dependent on MMP-13 activity. Chondrocyte hypertrophy is not regulated by MMP-13 activity in this model and does not in itself lead to cartilage erosion. MMP-13 deficiency can inhibit cartilage erosion in the presence of aggrecan depletion, supporting the potential for therapeutic intervention in established OA with MMP-13 inhibitors.

Risky Business: The Market for Unprotected Commercial Sex

While condoms are an effective defense against the transmission of HIV, large numbers of sex workers are not using them. We argue that some sex workers are willing to take the risk because clients are willing to pay more to avoid using condoms. Using data from Mexico, we estimate that sex workers received a 23 percent premium for unprotected sex. The premium represents a value of one life year of between

Nature's Experiment?: Handedness and Early Childhood Development

14,760 and

Impact Evaluation of a Large-scale Rural Sanitation Project in Indonesia

51,832 or one to five times annual earnings. The premium jumped to 46 percent if the sex worker was considered very attractive, a measure of bargaining power.

Compensated for Life: Sex Work and Disease Risk

In recent years, a large body of research has investigated the various factors affecting child development and the consequent impact of child development on future educational and labor market outcomes. In this article, we contribute to this literature by investigating the effect of handedness on child development. This is an important issue given that around 10% of the world’s population is left-handed and given recent research demonstrating that child development strongly affects adult outcomes. Using a large, nationally representative sample of young children, we find that the probability of a child being left-handed is not significantly related to child health at birth, family composition, parental employment, or household income. We also find robust evidence that left-handed (and mixed-handed) children perform significantly worse in nearly all measures of development than right-handed children, with the relative disadvantage being larger for boys than girls. Importantly, these differentials cannot be explained by different socioeconomic characteristics of the household, parental attitudes, or investments in learning resources.

Sex Work and Infection: What's Law Enforcement Got to Do with It?

Lack of sanitation and poor hygiene behavior cause a tremendous disease burden among the poor. This paper evaluates the impact of the Total Sanitation and Sanitation Marketing project in Indonesia, where about 11 percent of children have diarrhea in any two-week period and more than 33,000 children die each year from diarrhea. The evaluation utilizes a randomized controlled trial but is unusual in that the program was evaluated when implemented at scale across the province of rural East Java in a way that was designed to strengthen the enabling environment and so be sustainable. One hundred and sixty communities across eight rural districts participated, and approximately 2,100 households were interviewed before and after the intervention. The authors found that the project increased toilet construction by approximately 3 percentage points (a 31 percent increase in the rate of toilet construction). The changes were primarily among non-poor households that did not have access to sanitation at baseline. Open defecation among these households decreased by 6 percentage points (or 17 percent). Diarrhea prevalence was 30 percent lower in treatment communities than in control communities at endline (3.3 versus 4.6 percent). The analysis cannot rule out that the differences in drinking water and handwashing behavior drove the decline in diarrhea. Reductions in parasitic infestations and improvements in height and weight were found for the non-poor sample with no sanitation at baseline.

Can Mistargeting Destroy Social Capital and Stimulate Crime? Evidence from a Cash Transfer Program in Indonesia

Sex workers draw a premium for engaging in unprotected sex. We theoretically motivate a test of whether this premium represents a compensating differential for disease, thereby mitigating sex workers’ propensity to use condoms. Using transaction-level data and biological STI markers from sex workers in Ecuador, we exploit within-worker variation across local disease environments. We find that locations with low disease prevalence exhibit a very low, insignificant premium for unprotected sex. A one percentage point increase in the local disease rate increases the premium for noncondom sex by 33 percent. Market forces may curb the self-limiting nature of STI epidemics.

Face Value: Information and Signaling in an Illegal Market

A number of countries are pursuing the regulation of sex work to decrease the spread of sexually transmitted infections (STIs) and to reduce the probability of a generalized human immunodeficiency virus/acquired immunodeficiency syndrome epidemic. We study the effects of enforcing licensing regulation laws on sex worker STI rates, using nationally representative sex worker data from Ecuador. We find that increasing enforcement in the street sector significantly decreases STIs. However, increasing enforcement in the brothel sector increases the probability of a sex worker ever being infected with any STI. Increasing enforcement in the street shifts some sex workers from the more risky street into the less risky brothels and increases street prices, reducing the overall number of street clients. As a result, overall infection rates decrease. In contrast, increasing enforcement in the brothel sector can exacerbate public health problems by inducing some unlicensed brothel sex workers into the riskier street sector.

The Prostitute's Allure: The Return to Beauty in Commercial Sex Work

Cash transfer programs can provide important financial support for poor households in developing countries and are becoming increasingly common. However the potential for mistargeting of program funds is high. This article focuses on the social consequences arising from misallocation of resources in close-knit communities. We find that the mistargeting of a cash transfer program in Indonesia had significant negative social consequences. The prevalence of crime within communities increased and participation in community groups declined. Hence poorly administered transfer programs have a potentially large negative downside that extends beyond the pure financial costs that have been the focus of the literature to date.

Early Child Development and Maternal Labor Force Participation: Using Handedness as an Instrument

Economists argue that rich information environments and formal enforcement of contracts are necessary to prevent market failures when information asymmetries exist. We test for the necessity of formal enforcement to overcome the problems of asymmetric information by estimating the value of information in an illegal market with a particularly rich information structure: the online market for male sex work. We assemble a rich data set from the largest and most comprehensive online male sex worker Web site to estimate the effect of information on pricing. We show how clients of male sex workers informally police the market in a way that makes signaling credible. Using institutional knowledge, we identify the specific signal male sex workers use to communicate quality to clients: face pictures. We find that there is a substantial return to the signal in this market. The findings provide novel evidence on the ability of rich information environments to overcome problems of asymmetric information without formal enforcement mechanisms.