ABSTRACT
After two diode laser treatments for hair removal, a 39-year-old woman was noted to have pili bigemini within the treated areas. It resolved after a third treatment. Pili bigemini, the appearance of two hairs coming from the same follicular opening, can be induced by intermediate doses of laser energy. It follows sublethal damage to the hair follicule apparatus.
ABSTRACT
Homocysteine present in human blood plasma is derivatized with thiol selective ultraviolet labelling reagent, 2-chloro-1-methylpyridinium iodide, and separated from other plasma thiol derivatives by high-performance liquid chromatography (HPLC) with detection at 312 nm. The separation is carried out isocratically on LiChrospher RP-18 column using mobile phase consisting of pH 2.5 0.04 M trichloroacetic acid buffer and methanol in the ratio 9:1 (v/v) pumped at 0.5 ml min(-1) at 40 degrees C. The homocysteine S-pyridinium derivative elutes at 6.5 min. To determine total and protein-bound homocysteine it is necessary to cleave disulphide bounds by the use of tri-n-butylphosphine in order to form free sulfhydryl group. The method provides quantitative information on total and protein-bound homocysteine based on assays with derivatization after reduction of whole plasma, and derivatization after reduction of acid precipitated proteins. The calibration graph is linear over the concentration range covering most experimental and clinical cases. The assay has a low pmol sensitivity and is reproducible; intra- and inter-day, relative standard deviation range from 1.79 to 5.09% and from 2.80 to 5.60%, respectively. The method is applied to the determination of total and protein-bound homocysteine in the plasma of healthy individuals.
ABSTRACT
Several human diseases, in particular metabolic disorders, often lead to the accumulation of characteristic metabolites in plasma, urine and cells. The selected diseases of this type include cystinuria and homocystinuria. In the typical laboratory diagnosis of these two diseases, a positive nitroprusside test is followed by quantitative analysis of urine cysteine and homocysteine in order to differentiate between cystinuria and homocystinuria. A sensitive and reproducible assay for total urine cysteine and homocysteine has been developed. The essential steps in the assay include conversion of disulphides to free thiols with tributylphosphine, conjugation of the thiols with 2-chloro-1-methyl pyridinium iodide, separation of S-pyridinium derivatives of cysteine and homocysteine from other endogenous urine thiol derivatives by reversed-phase high-performance liquid chromatography, and detection and quantitation by spectrophotometry. The method has a sensitivity of 4 pmol and is reproducible, intra- and inter-day coefficients of variation are from 1.37 to 4.14% and from 2.38 to 5.01%, respectively. The mean concentration of total urine cysteine and homocysteine in healthy donors (7 men and 7 women) were for women. 92.0 +/- 45.8 and 16.4 +/- 4.8 respectively, and for men 120.9 +/- 46.6 and 21.5 +/- 7.4 nmol/ml, respectively. Total urine homocysteine represents approximately 17.7% of cysteine in the urine of normal individuals.
