Nitric oxide mediates the effects of pulsed electromagnetic field stimulation on the osteoblast proliferation and differentiation.

The purpose of this research was to investigate whether the effects of pulsed electromagnetic field (PEMF) stimulation on the osteoblast proliferation and differentiation are mediated by the increase in the nitric oxide (NO, nitrogen monoxide) synthesis. The osteoblasts (MC3T3-E1 cell line) were cultured in the absence (-NMMA group) or in the presence (+NMMA group) of the NO synthase inhibitor L-NMMA. First, osteoblasts were subjected to PEMF stimulation (15 Hz and 0.6 mT) up to 15 days. The DNA content and the NO concentration in the conditioned medium were determined on the 3rd, 7th, and 15th days of culture. Following, osteoblasts were stimulated in the proliferation (P-NMMA and P+NMMA groups) or in the differentiation (D-NMMA and D+NMMA groups) stages of maturation, and the alkaline phosphatase (AlPase) activity was determined on the 15th day of culture for all groups. PEMF stimulation increased significantly the nitrite concentration in the -NMMA group on the 3rd, 7th, and 15th days of culture. However, this effect was partially blocked in the +NMMA group. The DNA content in the -NMMA group, but not in the +NMMA group, increased significantly on the 3rd and 7th days of culture. The AlPase activity in the P-NMMA and D-NMMA groups, but not in the P+NMMA and D+NMMA groups, also increased significantly. In conclusion, the PEMF stimulatory effects on the osteoblasts proliferation and differentiation were mediated by the increase in the NO synthesis.     

Genetic analysis of a local population of <Emphasis Type="Italic">Oryza glumaepatula</Emphasis> using SSR markers: implications for management and conservation programs

Knowledge of natural diversity and population structures of wild species, which might be related to cultivated species, is fundamental for conservation and breeding purposes. In this study, a genetic characterization of a large population of Oryza glumaepatula, occurring in a 10 km² area located at Tamengo Basin (Paraguay River, Brazil), was performed using SSR markers. This population is annually dragged from the river to permit navigation; one goal of this study was to examine the impact of this removal on genetic variability. From 18 polymorphic SSR markers, a total of 190 alleles were detected in a sample of 126 individuals, with an average of 10.3 alleles/locus, and a H _e of 0.67. The five QTL-related markers showed an average H _e value of 0.56, while the remaining 13 markers detected an average estimate of 0.70. An apparent outcrossing rate of 30%, a high proportion of alleles at low frequencies (56%), and the presence of exclusive alleles (9.5%) were found, with strong evidence of the establishment of individuals from different populations upstream in the Paraguay River. For conservation purposes, the river drag has no effect on the population. However, periodical seed collection from the Corumbá population can preserve part of the genetic variability present in upstream populations reducing the need for upriver collecting expeditions.