Annual incidence rates of hip symptoms and three hip OA outcomes from a U.S. population-based cohort study: the Johnston County Osteoarthritis Project.

OBJECTIVE: Estimate annual incidence rates (IRs) of hip symptoms and three osteoarthritis (OA) outcomes (radiographic, symptomatic, and severe radiographic) overall and by race, sociodemographic characteristics, and hip OA risk factors. DESIGN: Analyze baseline (1991-1997) and first follow-up (1999-2003) data (n = 1446) from the Johnston County Osteoarthritis Project, a population-based, prospective study of adults ≥45 years in North Carolina. Hip symptoms were pain, aching, and/or stiffness on most days, or groin pain. Radiographic and severe radiographic OA were Kellgren-Lawrence (KL) grades ≥2 and ≥3, respectively. Symptomatic OA was radiographic OA with symptoms in the same hip. Sociodemographics were age, gender, race, highest attained education, and annual household income. Hip OA risk factors were self-reported body mass index (BMI) at age 18 years, clinically measured BMI at baseline, and history of hip injury. RESULTS: Annual IRs (median = 5.5 years follow-up) were 37, 23, 13, and 2.9 per 1000 person-years for hip symptoms, and radiographic, symptomatic, and severe radiographic hip OA, respectively. We found low IRs of radiographic and symptomatic hip OA among African Americans and high IRs of hip symptoms among the obese and the very poor. Across outcomes, IRs were highest for those with hip injury. CONCLUSION: No prior studies have reported IRs of hip symptoms; IRs of radiographic and severe radiographic hip OA were similar to, and the IR of symptomatic hip OA was higher than, previous estimates. Prevention efforts should target low socioeconomic status (SES) populations and obese adults; interventions for hip OA and hip symptoms are imperative for those with hip injuries.

Batrachochytrium dendrobatidis can infect and cause mortality in the nematode Caenorhabditis elegans.

Batrachochytrium dendrobatidis (Bd) has been identified as a causative agent in the precipitous decline of amphibians worldwide. Studies on the fungus including its ability to infect and kill the host require use of frogs, a precious resource. Therefore, the development of an alternate host model to study the virulence of the fungus would be useful. Here, we show that Bd can cause mortality in the nematode Caenorhabditis elegans. Incubation of Bd with C. elegans resulted in greater than 70% mortality in the nematodes over a period of 24 h. Fluorescence microscopy using propidium iodide, a fluorescent dye used to determine cell viability, and tactile assays were used to discriminate between live and dead nematodes. These observations suggest that C. elegans may be a useful model organism to study the pathogenicity and virulence mechanisms of Bd.

Identification and partial characterization of an elastolytic protease in the amphibian pathogen Batrachochytrium dendrobatidis.

Batrachochytrium dendrobatidis (Bd) is a fungus that causes chytridiomycosis, a disease that has been implicated as a cause of amphibian population declines worldwide. Infected animals experience hyperkeratosis and sloughing of the epidermis due to penetration of the keratinized tissues by the fungus. These symptoms have led us to postulate that Bd produces proteases that play a role in the infection process. Here, we show that Bd is capable of degrading elastin in vitro, a protein found in the extracellular matrix of the host animal. Elastolytic enzyme activity was partially purified using ion exchange chromatography and size-exclusion filtration from cultures grown in inducing media. The elastolytic activity of the purified fraction had a pH optimum of 8, was strongly inhibited by EDTA and phenylmethylsulfonyl fluoride (PMSF), and was partially inhibited by an elastase-specific inhibitor. This activity was also enhanced by the presence of Mg2+ and Ca2+ but not Zn2+. An antiserum directed against Aspergillus fumigatus serine protease (Alp) was found to react with a polypeptide of approximately 110 kDa from the purified material. Using immunofluorescence, this antiserum was also observed to react with zoospores and sporangia grown on toad skin. These observations suggest that Bd may produce proteases similar to those produced by other pathogenic fungi that are capable of degrading proteins found in the extracellular matrix. The proteolytic activity exhibited in vitro might aid the organism in its ability to colonize and destroy the epidermis of its amphibian host.