Amnios et problèmes de surface oculaire

La membrane amniotique, enclave interne de la vie naissante, présente diverses propriétés exploitées en ophtalmologie. Elle est utile pour : (1) limiter la formation d’adhésions fibreuses entre la paupière et le globe oculaire (symblépharon) ou la progression d’excroissances fibrovasculaires vers la cornée (ptérygion) ; (2) contribuer à la guérison d’ulcères cornéens, de kératites bulleuses et des déficiences en cellules souches de la cornée dues à des brûlures thermiques, chimiques ou d’autre origine. L’amnios, alors greffé avec des cellules limbiques saines, favoriserait la prolifération de cellules moins différenciées, aptes à reconstruire l’épithélium cornéen. La membrane amniotique contient des cytokines, réduit l’acuité des réactions immunologiques et possède des propriétés antalgiques, anti-bactériennes et anti-inflammatoires ; de plus, elle favorise, comme le fait la peau foetale, une guérison avec un minimum de cicatrices. La connaissance des mécanismes d’action de la membrane amniotique obtenue grâce à la recherche pourrait fournir de nouvelles avenues pharmacologiques afin de traiter des maladies de la surface oculaire.The amniotic membrane, the most internal placental membrane, has various properties useful in ophthalmology. Collected on delivery by elective Caesarean section, the amnion is prepared under sterile conditions, and, usually, cryopreserved until its use as a biological bandage or as a substrate for epithelial growth in the management of various ocular surface conditions. Specifically, the amnion is used to : (1) limit formation of adhesive bands between eyelids and eyeball (symblepharon) or the progression of a fibrovascular outgrowth towards the cornea (pterygium) or to (2) facilitate the healing of corneal ulcers, bullous keratopathy, and corneal stem cell deficiency. In this last condition, either hereditary or acquired after a thermal or a chemical burn, corneal stem cells, located at a transitional zone between the cornea and conjunctiva, are lost. These cells are essential for renewal of corneal epithelium in normal and in diseased states. The loss of these cells leaves the corneal surface free for invasion by conjunctival epithelium. Not only, does conjunctival epithelium support the development of vascularisation on the normally avascular cornea, but some conjunctival cells differentiate into mucus secreting goblet cells. Such a change in phenotype leads to loss of corneal transparency and visual disability. The removal of this fibro-vascular outgrowth in combination with transplantation of both amniotic membrane and corneal stem cells are used to treat this condition. The amnion stimulates the proliferation of less differentiated cells which have the potential to reconstruct the cornea. This potential is at the origin of the hypothesis that the amnion may provide an alternative niche for limbal stem cells of the corneal epithelium. It abounds in cytokines and has antalgic, anti-bacterial, anti-inflammatory and anti-immunogenic properties, in addition to allowing, like fetal skin does, wound healing with minimal scar formation. These desirable properties are responsible for the increasing use of amniotic membrane in ophthalmology. The complete understanding of the mechanisms of action of amniotic membrane for ocular surface diseases has yet to be understood. Once revealed by research, they may provide new pharmacological avenues to treat ocular surface diseases

Slow Motion: Economic Mobility of Young Workers in the 1970s and 1980s

This paper investigates the question of how long it takes young male workers to earn enough to reach a given standard of living, e.g., enough to support a family. We use the Panel Study of Income Dynamics data on the earnings of children and their parents to answer these questions. Our findings are that all groups of men, classified by race, ethnicity, and education level, are taking longer to reach a given standard of living. Some, e.g., undereducated black males, will never reach middle class standards of living for themselves. Implications for household formation, marriage, and public policy are discussed in closing

Peer Effects in Drug Use and Sex Among College Students

Past research suggests that congregating delinquent youth increases their likelihood of problem behavior. We test for analogous peer effects in the drug use and sexual behavior of male ( n = 279) and female ( n = 435) college students, using data on the characteristics of first-year roommates to whom they were randomly assigned. We find that males who reported binge drinking in high school drink much more in college if assigned a roommate who also binge drank in high school than if assigned a nonbinge-drinking roommate. No such multiplier effect is observed for females, nor are multiplier effects observed for marijuana use or sexual behavior for either males or females. Students who did not engage in these behaviors in high school do not appear to be affected by their roommates’ high school behavior.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44594/1/10802_2005_Article_3576.pd

Empathy or Antipathy? The Impact of Diversity

Mixing across racial and ethnic lines could spur understanding or inflame tensions between groups. We find that white students at a large state university randomly assigned African American roommates in their first year were more likely to endorse affirmative action and view a diverse student body as essential for a high-quality education. They were also more likely to say they have more personal contact with, and interact more comfortably with, members of minority groups. Although sample sizes are too small to provide definitive evidence, these results suggest students become more empathetic with the social groups to which their roommates belong. (JEL I28, J15, J18, Z13)