Low noise constant current source for bias dependent noise measurements.

A low noise constant current source used for measuring the 1∕f noise in disordered systems in ohmic as well as nonohmic regime is described. The source can supply low noise constant current starting from as low as 1 µA to a few tens of milliampere with a high voltage compliance limit of around 20 V. The constant current source has several stages, which can work in a standalone manner or together to supply the desired value of load current. The noise contributed by the current source is very low in the entire current range. The fabrication of a low noise voltage preamplifier modified for bias dependent noise measurements and based on the existing design available in the MAT04 data sheet is also described.

Critical evaluation of toxic versus beneficial effects of methylglyoxal.

In various organisms, an array of enzymes is involved in the synthesis and breakdown of methylglyoxal. Through these enzymes, it is intimately linked to several other physiologically important metabolites, suggesting that methylglyoxal has some important role to play in the host organism. Several in vitro and in vivo studies showed that methylglyoxal acts specifically against different types of malignant cells. These studies culminated in a recent investigation to evaluate a methylglyoxal-based formulation in treating a small group of cancer patients, and the results were promising. Methylglyoxal acts against a number of pathogenic microorganisms. However, recent literature abounds with the toxic effects of methylglyoxal, which are supposed to be mediated through methylglyoxal-derived advanced glycation end products (AGE). Many diseases such as diabetes, cataract formation, hypertension, and uremia are proposed to be intimately linked with methylglyoxal-derived AGE. However methylglyoxal-derived AGE formation and subsequent pathogenesis might be a very minor event because AGE are nonspecific reaction products that are derived through the reactions of carbonyl groups of reducing sugars with amino groups present in the side chains of lysine and arginine and in terminal amino groups of proteins. Moreover, the results of some in vitro experiments with methylglyoxal under non-physiological conditions were extrapolated to the in vivo situation. Some experiments even showed contradictory results and were differently interpreted. For this reason conclusions about the potential beneficial effects of methylglyoxal have often been neglected, thus hindering the advancement of medical science and causing some confusion in fundamental understanding. Overall, the potential beneficial effects of methylglyoxal far outweigh its possible toxic role in vivo, and it should be utilized for the benefit of suffering humanity.

Calcium phosphate ceramics as bone graft substitutes in filling bone tumor defects.

BACKGROUND: Synthetic bio-inert materials are currently used as an alternative to autogenous bone graft. Calcium hydroxyapatite (HA) and Beta tri-calcium phosphate (beta-TCP), which belong to the calcium phosphate ceramics group, are biocompatible and osteo-conductive. The purpose of this study is to analyse the use of HA and beta-TCP in their ceramic forms as a bone graft substitute in filling bone voids after curettage of benign bone tumors. MATERIALS AND METHODS: Twenty-four patients in the age range of 3.5-55 years (mean 14.3 years) having benign bone tumors with bone defects were filled with bone graft substitute following curettage. In 20 patients bone defects were filled with block/granules of HA ceramic and in four with beta-TCP. Fibular strut graft was packed with HA in four patients. The patients were followed up for an average of 18 months (range 12-36 months). RESULTS: The functional status of the patients at follow-up was evaluated and compared with preoperative functional status. Early incorporation of graft substitutes became evident radiologically between 6 and 10 weeks (Stage I). Complete incorporation (Stage III) was observed in an average of nine months (6-18 months). Clinical healing was observed before radiological healing. The average time taken to return to preoperative function was 14 weeks. There was no recurrence of lesion or growth retardation. CONCLUSION: Calcium hydroxyapatite and beta-TCP are excellent bone graft substitutes for autogenous bone graft in filling voids after curettage of benign bone tumors.