Positive effect of oral supplementation with glycosaminoglycans and antioxidants on the regeneration of osteochondral defects in the knee joint.

The effect of oral supplementation with glycosaminoglycans (GAG) and radical scavengers (vitamin E/selenium) on the regeneration of osteochondral defects was investigated in rabbits. After introduction of defined osteochondral defects in the knee joint, groups of ten animals were given a GAG/vitamin E/selenium mixture or a placebo (milk sugar) for 6 weeks. Following sacrifice, histological and histochemical analysis was performed. The amount of synovial fluid was increased in the placebo group, while the viscosity of the synovial fluid was significantly enhanced in the GAG group. The amount of sulfated GAG in the osteochondral regenerates (8.8 +/- 3.6 % vs. 6.0 +/- 5.6 %; p <0.03) was significantly higher in the GAG group. In both groups, the GAG amount in the cartilage of the operated knee was significantly higher than in the non-involved knee (p <0.05). Histological analysis of the regenerates in the GAG group was superior in comparison with the placebo group. For the first time, a biological effect following oral supplementation with GAG was demonstrated in healing of osteochondral defects in vivo. These findings support the known positive clinical results.

Effects of a ferrate-containing preparation on diverse metabolic processes in yeast.

A plant-sap-derived preparation containing bi- and tervalent ferrate anions was tested on growth, respiration on glucose, and membrane transport of 6-deoxy-D-glucose (6-dGlc) and 2-aminoisobutyric acid (Aib) in several yeast species, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Lodderomyces elongisporus, Rhodotorula gracilis, and Dipodascus magnusii. Growth was enhanced by as much as 65%, respiration was not affected significantly except for a decrease in R. gracilis, transport of 6-dGlc was not affected while that of Aib was increased by up to 45% in R. gracilis and up to 27% in L. elongisporus.

Isolation of sulphate transport defective mutants of Candida utilis: further evidence for a common transport system for sulphate, sulphite and thiosulphate.

Selenate-resistant mutants of Candida utilis were isolated. They did not take up sulphate while incorporation of an organic sulphur source, such as L-methionine, was similar to the wild-type strain. They grew poorly on sulphate, sulphite and thiosulphate and, as expected, grew well on methionine. Sulphite reductase activities of the mutants were similar to the wild type strain. The properties of these mutants support the view of a common transport system for sulphate, sulphite and thiosulphate.

Stimulation of amino acid transport in Saccharomyces cerevisiae by metabolic inhibitors.

Inhibitors of energy metabolism (3-chlorophenylhydrazonomalononitrile, antimycin A, iodoacetamide, dicyclohexylcarbodiimide) but not of transport (uranyl ions) stimulate at low concentrations the uptake of L-leucine, L-glutamic acid, L-arginine and, to a lesser degree, of 2-aminoisobutyric acid in Saccharomyces cerevisiae. The effect is apparent only after augmenting the energy reserves of cells by preincubation with D-glucose or, more strikingly, with ethanol. It is absent in a mutant (op1) lacking the translocation system for ADP--ATP in mitochondria. The presence of two different energy reserves for amino acid transport is indicated (one in energy-poor, the other in energy-rich cells). The stimulating effect appears to be caused by a retarded degradation of the transport proteins as occurs at a lowered level of mitochondria-produced ATP.

Loss of inducible D-galactose transport by baker's yeast after osmotic treatment.

The ability of Saccharomyces cerevisiae to transport D-galactose and related sugars with an axial hydroxyl group at C-4, acquired by induction with D-galactose, was lost either by exposing early exponential-phase cells to an osmotic shock involving incubation in 0.6M NaC1O4, 0.66M sucrose and 1mM histidine and transfer to 5mM Tris-HC1 with 2mM dithiothreitol, or simply by transferring them to distilled water. The total amount of protein thus released was 0.1--0.35 and 0.1 mg per mg dry wt., respectively. The shock fluid contained at least six proteins, among them a galactose-binding component. L-Arabinose transport could not be restored by adding the concentrated shock fluid to depleted cells but cells remained viable after the shock and resynthesized the transport system if incubated in a galactose-containing growth medium.

Transport of 4-deoxy- and 6-deoxy-D-glucose in baker's yeast.

Tritium-labelled 4-deoxy-D-glucose (4-dglc) and 6-deoxy-D-glucose (6-dgcl) were prepared by catalytic hydrogenolysis of the corresponding deoxyiodo derivatives with gaseous tritium. The two sugars are transported into Saccharomyces cerevisiae by both the constitutive glucose and the inducible galactose carrier. Uranyl ions are powerful inhibitors. The pH optimum in uninduced cells lies at 5.5 for both sugars, the apparent activation energies (between 15 and 35 degrees C) are 25.1 kJ/mol and 16.5 kJ/mol, respectively. The steady-state intracellular concentration of both sugars is less than the extracellular one (no uphill transport). Neither of them is a substrate of yeast hexokinase. 4-Deoxy-D-glucose undergoes a dinitrophenol-sensitive conversion to an unknown metabolite which is not phosphorylated and may represent one of its oxidation products.

Transport of acyclic polyols in Saccharomyces cerevisiae.

Acyclic polyols (erythritol, xylitol, ribitol, D-arabinitol, mannitol, sorbitol and galactitol) are not metabolized by Saccharomyces cerevisiae. They are taken up by a fast non-active process, reaching 40-70% distribution referred to total cell water. The uptake is insensitive to temperature, pH (between 4 and 8), 2,4-dinitrophenol and uranyl ions. Its initial rate rises linearly with concentration from 10(-5)M to 1M. The process resembles simple diffusion through large pores or the trapping of the whole solution on the surface. Protoplasts behave like whole cells in this respect. Only erythritol shows a second type of uptake which is inhibitor-insensitive but temperature-dependent.