Microstructure and biocompatibility of titanium oxides produced on nitrided surface layer under glow discharge conditions.

The disadvantages of titanium implants are their low wear resistance and the release of titanium elements into surrounding tissue. These can be eliminated by modifying the surface by surface engineering methods, among them nitriding under glow discharge conditions which allow to produce diffusive surface layers. Their combining with an oxide layer might be valuable for biological events occurring at the bone implant interface. The aim of this study was to enhance the titanium biomaterial performance via combining nitriding and oxidizing treatments in one process under glow discharge conditions. The oxynitrided surface layers were produced at 680 degrees C. The obtained layer was TiO + TiN + Ti2N + alphaTi(N) type and about 4-microm thick and was of diffusive character. This layer significantly increased wear resistance and slightly corrosion resistance compared to that of the reference titanium alloy. The produced titanium oxide was about 400-nm thick and built from fine crystallites. This oxide exhibits bioactivity in SBF (simulated body fluid). Osteoblasts of Saos-2 line incubated on this surface exhibited good adhesion and proliferation and ALP release comparable with cells cultured on the reference titanium alloy and TiN + Ti2N + alphaTi(N) surface layers. A quantitative analysis of blood platelets adhering to this layer revealed their highest amount in comparison to that on both the nitrided surface layer and titanium alloy. The presented study provided a simple and reproducible method of combining oxidizing and nitriding under glow discharge in one process. Experimental data in vitro suggests that titanium alloy oxynitriding under low temperatures at glow discharge conditions improves titanium alloy properties and biocompatibility and tissue healing. Therefore, the layer of TiO + TiN +Ti2N + alphaTi(N) type could be valuable for long-term bone implants.

Interactions of hydrogen with Pd and Pd/Ni alloy chain-functionalized single walled carbon nanotubes from density functional theory.

Density functional theory is employed to study Pd and Pd/Ni alloy monatomic chain-functionalized metallic single walled carbon nanotubes (SWNT(6,6)) and semiconducting SWNT(10,0), and their interactions with hydrogen molecules. The stable geometries and binding energies have been determined for both isolated chains and chains on SWNT surfaces. We found that continuous Pd and Pd/Ni chains form on SWNTs with geometries close to stable geometries in the isolated chains. Ni alloying improves stability of the chains owing to a higher binding energy to both Pd and C atoms. The physical properties of SWNTs are significantly modified by chain functionalization. SWNT(10,0) is transformed to metal by either Pd or alloy chains, or to a smaller band gap semiconductor, depending on the Pd binding site. From calculations for H(2) interactions with the optimized chain-SWNT systems, the adsorption energy per H atom is found to be about 2.6 times larger for Pd/Ni chain-functionalized SWNTs than for pure Pd chain-functionalized SWNTs. Band structure calculations show that the SWNT(10,0) reverts back to semiconductor and SWNT(6,6) has reduced density of states at the Fermi level upon H(2) adsorption. This result is consistent with the experimentally observed increase of electrical resistance when Pd-coated SWNTs are used as H(2) sensing materials. Finally, our results suggest that Pd/Ni-SWNT materials are potentially good H(2)-sensing materials.

Effect of testosterone replacement therapy on lipids and lipoproteins in hypogonadal and elderly men.

We investigated the effects of long-term testosterone replacement in hypogonadal and elderly men on lipids and lipoproteins. Twenty-two men with initial serum testosterone concentrations below 3.5 ng/ml took part in the study: 11 with hypopituitarism (1st group) and 11 otherwise healthy elderly men with low testosterone levels (2nd group). Testosterone deficiency was replaced by intramuscular injections of testosterone enanthate 200 mg every second week. Plasma levels of sex hormones, gonadotropins, SHBG, lipids and lipoproteins were determined before the treatment and after 3, 6 and 12 months of treatment. During the treatment serum testosterone and estradiol increased significantly, reaching normal levels. This was associated with a decrease in total cholesterol (from 225 +/- 16.9 mg/dl to 202 +/- 13.6 mg/dl after 6 months and 198 +/- 12.8 mg/dl after 1 year of testosterone administration, P < 0.0001 in men with hypoandrogenism associated with aging and from 255 +/- 12.1 mg/dl to 214 +/- 10.6 mg/dl after 6 months and 206 +/- 9 mg/dl after 1 year of treatment, P < 0.0001 in men with hypopituitarism) and LDL-cholesterol concentrations (from 139 +/- 12.5 mg/dl to 126 +/- 10.7 mg/dl after 6 months and 118 +/- 9.8 mg/dl after 1 year of testosterone administration, P < 0.0001 in men with hypoandrogenism associated with aging and from 178 +/- 10.3 mg/dl to 149 +/- 10.2 mg/dl after 6 months and 140 +/- 7.3 mg/dl after 1 year of treatment, P < 0.001 in men with hypopituitarism). However, no significant decrease in HDL-cholesterol levels or HDL2- and HDL3-cholesterol subfractions was observed. The effects of testosterone replacement therapy on lipids and lipoproteins were similar in both groups with different aetiology of hypogonadism. No side effects on the prostate were observed. The results of this study indicate that testosterone replacement therapy in hypogonadal and elderly men may have a beneficial effect on lipid metabolism through decreasing total cholesterol and atherogenic fraction of LDL-cholesterol without significant alterations in HDL-cholesterol levels or its subfractions HDL2-C and HDL3-C.

Hyperinsulinaemia and decreased plasma levels of dehydroepiandrosterone sulfate in premenopausal women with coronary heart disease.

OBJECTIVES: The purpose of the study was to establish plasma levels of insulin, ovarian sex hormones and dehydroepiandrosterone sulfate (DHEA-S) and to evaluate their correlations with lipids in premenopausal women with angiographically demonstrated coronary stenosis. DESIGN: Differences in plasma levels of insulin, ovarian sex hormones, DHEA-S and lipids between groups were compared by analysis of variance. SETTING: From January 1993 until December 1993 patients were diagnosed in the Outpatient Clinic of the Department of Endocrinology Medical Centre for Postgraduate Education, Warsaw. SUBJECTS: Premenopausal women with normal oral glucose tolerance test (OGTT) results, with and without coronary stenosis were studied: 21 women after acute myocardial infarction with angiographically demonstrated coronary stenosis (women with CHD), and 14 women with chest pain, a positive exercise test without significant changes of coronary arteries on coronarography (women with normal coronarography, NC). The control group consisted of nine, healthy women with no risk factors for CHD. MAIN OUTCOME MEASURES: In premenopausal women with CHD, the decreased plasma level of DHEA-S and hyperinsulinaemia were anticipated. RESULTS: In women with CHD, the plasma levels of DHEA-S (926.5 +/- 83 ng mL-1) were significantly lower than those in women with NC (1375.7 +/- 181 ng mL-1) and in healthy controls (1984 +/- 127 ng mL-1), P < 0.02 and P < 0.001, respectively. The fasting insulin and insulin response to an OGTT in women with CHD and with NC was higher than in healthy subjects. A significant decrease of high-density lipoprotein (HDL) cholesterol, HDL-2 cholesterol and apolipoprotein A-I, and an increase of total cholesterol, low-density lipoprotein cholesterol C and apolipoprotein B levels in women with CHD compared to healthy controls were observed. A negative correlation between fasting insulin and the plasma levels of DHEA-S was established. CONCLUSION: In premenopausal women, hyperinsulinaemia and decreased DHEA-S levels may contribute to the development of coronary atherosclerosis.