Osteogenesis enhanced by chitosan (poly-N-acetyl glucosaminoglycan) in vitro.

Chitosan, with a chemical structure similar to hyaluronic acid, has been implicated as a wound healing agent. The purpose of this research was to evaluate the effect of chitosan on osteoblast differentiation and bone formation in vitro. Mesenchymal stem cells were harvested from fetal Swiss Webster mice calvariae prior to osteoblast differentiation and calcification (12 to 13 days in utero). Stem cells were seeded into 6-well culture plates at a density of 350,000 cells per well. Using this model, it was possible to quantify the influence of chitosan on osteoprogenitor differentiation and osteogenesis. Experimental wells were pretreated with 200 microliters chitosan (2 mg/ml in 0.2% acetic acid vehicle). Control wells were pretreated with 200 microliters vehicle (0.2% acetic acid) or remained untreated. Cells were allowed to grow under optimal conditions for 14 days. Cell cultures were fixed with glutaraldehyde and stained with Von Kossa stain to identify bone forming colonies. Positive staining colonies were identified and counted under light microscopy. Histologic cross-sections of representative positively stained colonies identified osteoblasts and confirmed bone formation. Examination of control wells revealed 3.6 +/- 0.6 colonies per well while experimental wells revealed a significantly greater average of 6.2 +/- 1.2 colonies per well (P < or = 0.01). Computer-assisted image analysis of the average area of bone formed by control colonies was 0.34 +/- 0.09 (relative units) while that of experimental colonies was 0.39 +/- 0.06 (relative units) per average bone forming colony. The difference in mean size (control versus chitosan bone forming colony) was not statistically significant (P = 0.4691). The results of this in vitro experiment suggest that chitosan potentiates the differentiation of osteoprogenitor cells and may facilitate the formation of bone.

Effects of sodium bicarbonate, magnesium oxide, and a commercial buffer mixture in early lactation cows fed hay crop silage.

Sixteen early lactation Holstein cows fed 70% concentrate: 30% hay crop silage were used to determine effects of .7% sodium bicarbonate, .7% sodium bicarbonate plus .28% magnesium oxide, or 1.8% commercial buffer mixture (total ration dry basis). This mixture contained a variety of buffers, alkalis, and other compounds known to affect milk production or composition in some circumstances. Buffers did not affect dry matter intake, milk yield, or milk composition but decreased efficiency of milk production. Ruminal fluid pH was not affected, but fecal pH and digestibilities of dry matter, organic matter, energy, acid detergent fiber, and cellulose were increased by the mixed buffers compared with sodium bicarbonate alone. Total ruminal volatile fatty acid concentration was reduced by buffers. Compared with sodium bicarbonate alone, mixed buffers increased ruminal ammonia concentration, acetate proportion, and acetate:propionate ratio and decreased proportions of propionate and butyrate. Valerate was reduced by all three buffers. Ruminal volume and liquid dilution rate were unaffected, but buffers increased total fluid outflow from the rumen. Higher amounts of buffers or alkalis may be necessary to offset low rumen pH and affect production with hay crop silage-based diets.