Investigation of the genotoxic effects of fluoride on a bone tissue model.

Fluorides are thought to be a major cause of osteocarcinogenesis, due to their widespread industrial use, ability to accumulate in bone tissue, and genotoxic and probable carcinogenic properties. In vitro experiments investigating the genotoxic potential of fluorides in bone tissue models can provide valuable indirect information on their involvement in osteocarcinogenesis. Here, we investigated whether sodium fluoride (NaF) has the ability to induce DNA damage and chromosomal abnormalities in human osteosarcoma cells after 48 and 72 h of exposure. The cell cultures were treated with NaF in concentrations of 0, 20, 100 and 200 µg/ml. The level of DNA damage was assessed by the comet assay, and the frequency of chromosomal abnormalities by a micronucleus test. A significant increase in DNA damage indicators was noted in the samples treated with fluoride concentrations of 100 and 200 µg/ml, after 48 and 72 h of exposure. The micronucleus test revealed a dose-dependent increase in cells with micronuclei, nucleoplasmic bridges and nuclear protrusions. Increasing the concentration of NaF led to an increase in the prevalence of cytogenetic indicators after both treatment durations. This demonstrated ability of fluorine to exert genotoxic effects on bone cells indirectly indicates the possible importance of fluoride in the aetiology of osteosarcoma.

Polymers for mucoadhesive drug delivery system: a current status.

To overcome the relatively short gastrointestinal (GI) time and improve localization for oral controlled or sustained release drug delivery systems, bioadhesive polymers that adhere to the mucin/epithelial surface are effective and lead to significant improvement in oral drug delivery. Improvements are also expected for other mucus-covered sites of drug administration. Bioadhesive polymers find application in the eye, nose, and vaginal cavity as well as in the GI tract, including the buccal cavity and rectum. This article lays emphasis mainly on mucoadhesive polymers, their properties, and their applications in buccal, ocular, nasal, and vaginal drug delivery systems with its evaluation methods.

Protein cross-linking during oxidative denaturation of methaemoglobin.

Incubation of methaemoglobin in vitro for up to 4 h led to prominent cross-linking of globin subunits. This process was inhibited by superoxide dismutase, catalase and metal-chelator like diethylenetriamine penta-acetic acid but not by scavengers of hydroxyl radicals. Methaemoglobin in solution produced superoxide radical. It is suggested that damage to globin subunits is mediated by active oxygen species like hydroxyl radical involving a 'site-specific mechanism'. The formation of microprecipitates in incubated samples of methaemoglobin was also inhibited by anti-oxidant enzymes and transition metal-chelator indicating again the involvement of oxygen free-radicals. Such oxidative denaturation of methaemoglobin progresses independent of any formation of hemichrome and may have important physiological significance.

Erythrocyte membrane protein damage by oxidation products of phenylhydrazine.

Freshly prepared phenylhydrazine solution in buffer generated oxygen free-radicals and induced lipid peroxidation and aggregations of proteins when incubated with erythrocyte ghosts. The aggregation of protein was inhibitible by superoxide dismutase but not by catalase. When phenylhydrazine was allowed to autoxidize in buffer for several hours and subsequently added to a suspension of erythrocyte membrane, extensive aggregation of protein was still apparent although the membrane lipid peroxidation or generation of .OH radicals was insignificant under such condition. These results implicated oxidation products of phenylhydrazine but not oxygen free-radicals or lipid peroxidation products as major contributors to phenylhydrazine induced protein damages in red blood cells ghosts.

Membrane-associated protease activity of human erythrocytes.

Membrane-associated protease activity capable of digesting a number of membrane cytoskeletal proteins including band 3 protein was identified in human erythrocytes, almost totally free from contaminating leucocytes and platelets. This enzyme was inhibited by aprotinin (a specific inhibitor for a class of serine protease) and was distinct from the cytosolic calcium-dependent thiol protease (calpain), which is also known to bind to red cell membrane.

Phenylhydrazine mediated degradation of bovine serum albumin and membrane proteins of human erythrocytes.

Phenylhydrazine in solution has been shown to produce hydroxyl radicals, as measured by 2-deoxyribose degradation assay. In vitro incubation of bovine serum albumin with phenylhydrazine leads to extensive degradation of the former which, however, is not inhibited by hydroxyl-radical scavengers like mannitol, Tris or n-butanol. Metal chelators like EDTA, however, inhibits the breakdown of BSA. Erythrocyte ghosts incubated in vitro with phenylhydrazine also show extensive loss of membrane cytoskeletal proteins, inhibited by 5 mM EDTA but not by mannitol. In both the occasions a hydroxyl-radical mediated damage to protein takes place by a 'site-specific mechanism'. Further, such a damage to erythrocyte membrane proteins by phenylhydrazine may be related to well known action of this compound in producing accelerated aging of erythrocytes.