Catabolism of newly synthesized decorin in vitro by human peritoneal mesothelial cells.

OBJECTIVE: Previous studies have shown that decorin and biglycan account for over 70% of the proteoglycans (PGs) synthesized by human peritoneal mesothelial cells (HPMCs). Since these PGs are involved in the control of cell growth, cell differentiation, and matrix assembly, we investigated their turnover in cultured HPMCs. METHODS: Confluent HPMCs were metabolically labeled with [35S]-sulfate and the labeled products isolated from the cell medium and the cell layer characterized by sensitivity to bacterial eliminases. Experiments were undertaken with exogenous labeled decorin, and its metabolic state was studied. RESULTS: In a 24-hour labeling period, 75% of the newly synthesized chondroitin sulfate/dermatan sulfate (CS/DS) PGs appeared in the culture medium, the majority of which (90%) was decorin. In the cell layer, protein-free glycosaminoglycan (GAG) chains accounted for 21% of the total CS/DS at 24 hours and exhibited constant specific activity at 12-16 hours. The latter material was turned over with a half-life of approximately 2.5 hours. Exogenous decorin underwent receptor-mediated endocytosis and subsequent intracellular degradation. Uptake but not degradation could be inhibited by heparin. CONCLUSIONS: HPMCs are distinguished by a rapid turnover of decorin. A characteristic metabolic feature is the existence of a large intracellular pool of protein-free DS-GAGs. Understanding the control of decorin turnover in HPMCs might lead to delineation of its potential role in both the physiology and pathophysiology of the membrane in PD patients.     

Genetic differentiation between and within strains of the saw-toothed grain beetle, Oryzaephilus surinamensis (Coleoptera: Silvanidae) at RAPD loci

Nine strains of Oryzaephilus surinamensis have been kept in laboratory culture for periods ranging from 5 to 30 years (30–180 generations). Two RAPD primers provided sufficient information to separate the strains reliably and unambiguously. The strains are maintained at a population size of 200 breeding adults. The marked divergence between strains is consistent with the small population size, which for the older strains, according to population genetics theory, implies that roughly half the original genetic variation should now be lost from within strains. However, there is no indication that the older strains have less inter-strain variation. The results demonstrate RAPD loci can reliably detect population subdivision, which in field populations of pest species is of fundamental importance in understanding the population genetics of insecticide resistance.     

Minimising neonatal brain injury: how research in the past five years has changed my clinical practice.

With improving neonatal survival for extremely premature babies, the challenge for neonatology is to improve outcome of surviving babies. This review concentrates on best evidence emerging in recent years on prevention of brain damage by early administration of drugs as well as avoidance of induced brain damage by hyperventilation and dexamethasone therapy given postnatally for chronic lung disease.