Effect of Rooibos tea (Aspalathus linearis) on chick skeletal muscle cell growth in culture.

Rooibos tea (RT) extract contains natural antioxidants and scavenging agents. We investigated the effects of different concentrations of RT extract in medium on growth and changes of growth parameters of cultured chick embryonic skeletal muscle cells. Presence of 2, 10 and 100% of RT extract in the culture of primary cells significantly inhibited cell proliferation. The inhibition of cell growth reflected on decreased DNA, RNA and protein contents in primary cell culture and fibroblasts and myoblasts. The ability of the primary cells, fibroblasts and myoblasts to synthesize DNA and protein in the presence of RT extract, measured as an amount of [3H]thymidine and [3H]leucine incorporated into DNA and de novo synthesized protein, corresponded with decreasing DNA and protein contents in all three cell types. The inhibition effect of RT rose with increasing concentration of the tea extract in the culture medium. Ornithine decarboxylase activity was significantly affected only by 100% RT extract in every examined cell types. These results suggest that the inhibitory effect of RT extract on the growth of primary cells, fibroblasts and myoblasts is due to the potent scavenging activity of the RT extract.

Enhanced ornithine decarboxylase activity of chick muscle cells in culture by beta-adrenergic agonists.

The ability of beta-adrenergic agonists to stimulate ornithine decarboxylase activity (ODC) in chick muscle cell culture prepared from 11-day old embryos was evaluated. After 72 h of preincubation (myotube formation) the medium was supplemented for 4 h with noradrenaline, ritodrine, isoproterenol or clenbuterol, at concentrations of 10(-12), 10(-9) and 10(-6) mol/l. No significant response of ODC activity to noradrenaline was observed. The highest concentration (10(-6) mol/l) of the beta-adrenergic agonists ritodrine and isoproterenol elevated the activity of ODC. Clenbuterol was the most active beta-adrenergic agonist. The lowest concentration (10(-12) mol/l) had an apparent effect on ODC activity in muscle cell culture, and the substitution of media at levels of 10(-9) and 10(-6) mol/l had a similar effect in comparison to controls. The potency of beta-adrenergic agonists in increasing ODC activity was on the following order: noradrenaline, ritodrine, isoproterenol, clenbuterol. Results indicate that beta-adrenergic agonists may directly stimulate ODC activity followed by physiological processes in the muscle cells in the early stage of chick embryonic development.

Effects of thyroid hormones on chick embryo muscle cell culture.

The importance of thyroid hormones (TH) in the normal development of muscles has been repeatedly postulated. The effects of physiological TH doses on ornithine decarboxylase (ODC) and protein synthesis in muscle cells have been studied using cell cultures prepared from 11-day-old chick embryos. Triiodothyronine nuclear receptors in primary muscle cell culture were characterized on the basis of the specific binding analysis as a single receptor class with the equilibrium dissociation constant Kd = 1.2 +/- 0.4 x 10(-10) mol/l and binding capacity Bmax = 0.21 +/- 0.09 fmol/micrograms DNA. While the physiological amounts of both triiodothyronine (T3) and thyroxine (T4) stimulated ODC activity after 2 hr of treatment, only T3 had the same stimulatory effect after 4 hr of treatment. Twenty-four hour exposure of muscle cell culture to TH did not change ODC activity. The incorporation of [3H]leucine into proteins was elevated only after 120 hr incubation in the presence of T4. Application of T4 caused also an increase in the protein content after 24 hr.

In vitro separation of embryonic chick skeletal muscle myoblasts and fibroblasts: comparison of their characteristics.

The aim of the present experiments was to test two methods of separating myoblasts and fibroblasts (selective plating, differential trypsinization) from chick embryonal skeletal muscle and to compare their characteristics. Ornithine decarboxylase (ODC) activity, the amount of incorporated [3H]leucine into proteins and incorporation of [3H]thymidine into DNA were significantly higher in myoblasts than in fibroblasts separated by selective plating. When comparing myoblasts and fibroblasts separated by differential trypsinization, significantly higher ODC activity and greater incorporation of [3H]leucine into protein, but no incorporation of [3H]thymidine into DNA, were found in myoblasts. Higher ODC activity and greater incorporation of labelled leucine were found in fibroblasts separated by the selective plating than in fibroblasts separated by differential trypsinization. The incorporation of labelled thymidine into DNA was higher in myoblasts separated by selective plating than in myoblasts obtained by differential trypsinization. The method of selective plating appears to be simpler and adequate for obtaining myoblastic and fibroblastic cell cultures with sufficiently low mutual contamination. The method of differential trypsinization involves a more drastic treatment of cells and is more time consuming.

[Detection of leukosis on brown Leghorn chicken farms]. / Detekcia leukózý v chove sliepok plemena Brown Leghorn.

Samples taken on the Brown Leghorn hen farms were tested for the leucosis virus. Out of 21 samples the leucosis virus was present in five cases (24%). Viruses are detectable in chicken embryonic cells, accompanied by transformation and focus formation. Viruses are not transformed by the guniea pig and quail embryonic cells. The results were achieved by fusion but not by co-cultivation of the tested cells with permanent line 16 Q. These viruses appear to belong to the sub-group B, it is less probable that they belong to the sub-group C. The isolated viruses document spontaneous infection of the originally leucosis-free hen farm during five years when leucosis-free conditions were not secured.