RGD-tethered silk substrate stimulates the differentiation of human tendon cells.

Tendon reconstruction surgery often requires healing of the tendon to bone. The development of a more rapid and strong interaction at the tendon to bone interface would be invaluable to patients having orthopaedic surgery. Therefore, our rationale was to modify sutures so that they would be anabolic for tendon to bone healing. It has been shown that silk stimulates bone formation in osteoblast cultures. In the current study, we tested the ability of silk and silk-RGD (arginine-glycine-aspartic acid) to stimulate human tenocyte adhesion, proliferation, and differentiation. A 1.3-fold increase in tenocyte adhesion was found on silk-RGD compared with tissue culture plastic. By 72 hours, proliferation had increased on all substrates but was particularly enhanced on silk-RGD compared with the control. At 6 weeks, Northern blot analysis of decorin and Type I collagen mRNA levels showed a 2-3-fold increase in message levels on silk-RGD and silk compared with tissue culture plastic. The data suggest cultured human tenocytes adhere, proliferate, and differentiate on silk and silk-RGD substrates. A suture material, such as silk, decorated with RGD, may have the potential to facilitate tendon-bone healing with widespread applications in tendon reconstruction surgery.

Cardiac myocytes express mRNA for ten RGS proteins: changes in RGS mRNA expression in ventricular myocytes and cultured atria.

Regulators of G-protein signalling (RGS) are recently identified proteins that shorten the lifetime of the activated G protein. We now show that rat cardiac myocytes express mRNA for at least 10 RGS. The mRNA for RGS-r is barely detectable in rat ventricles, but increases more than 20-fold during the 60- to 90-min process of isolating ventricular myocytes, and after 90 min of culture of atrial pieces in medium with Ca2+. Both in myocytes and in atria, the rise in RGS-r is transient. The mRNA for cardiac RGS5, but not RGS-r, is developmentally regulated. These studies suggest that rapid regulation of RGS levels may be a new mechanism that governs how signals are transmitted across the cardiac cell membrane.

Systemic lupus erythematosus in relation to environmental pollution: an investigation in an African-American community in North Georgia.

The etiology of systemic lupus erythematosus is not well understood, although gender, race, genetic predisposition, and certain drugs are risk factors. Several environmental exposures have been implicated. In this study, we examined the prevalence and incidence of lupus in an African-American community that experienced long-standing exposures to industrial emissions. We hypothesized that lupus was elevated among residents of a specific community in Gainesville, Georgia. We included both a retrospective cohort study and a cross-sectional study designed to assess the incidence and prevalence, respectively, of lupus. The prevalence of lupus was 3 cases/300 persons (1000/100,000). Compared with the highest reported prevalence, this represents a 6-fold increase. The incidence of lupus was 3 cases/4709 person-years (63.7 cases/100,000 person-years). Compared with the highest reported incidence, this represents a 9-fold increase. The hypothesis that environmental toxins may induce lupus is consistent with the known ability of certain medications to do the same. The results suggest that long-standing exposure to industrial emissions may be associated with an increased risk of lupus.