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Biomedical subjects

M Zi

Publications and source records attributed to M Zi.

3 recordsLinked to original sources

Autonomic function in elderly patients with chronic heart failure.

AIMS: Autonomic function (AF) is attenuated by heart failure (HF). Reports have been based on studies of young patients with systolic heart failure (SHF). However, HF is a disease of older patients who are more likely to have diastolic heart failure (DHF). We investigated whether age alters AF in elderly HF patients and whether the haemodynamic type of HF influences AF. METHOD AND RESULTS: Thirty-six elderly HF (Framingham criteria) patients (11 with SHF, 25 with DHF) and 21 matched healthy subjects underwent simple bedside AF tests. Compared with the reference values for healthy adults, the mean E:I ratios and the median 30:15 ratios standing were all essentially normal. The median 30:15 ratios tilt and the mean Valsalva ratios were all significantly below the reference value (P for all cases <<0.050). Comparing three groups, there were no significant differences for mean E:I ratio (P=0.111), 30:15 tilt (P=0.619) and 30:15 standing (P=0.167), whereas there were significant differences for the mean Valsalva ratios (P=0.001). The mean Valsalva ratio of the SHF patients was significantly lower than that for the DHF patients (P<0.001) which in turn was significantly lower than the result of the healthy subjects (P<0.001). CONCLUSION: There is an age-related impairment in AF with further impairment occurring in patients with HF. However, the severity of autonomic dysfunction is less in patients with DHF compared with patients with SHF.

Aged↗

Versatile two-phase solvent system for alkaloid separation by high-speed counter-current chromatography.

In order to find a versatile high speed counter-current chromatography solvent system that can be used as a general prefractionation system for most alkaloids, the crude extracts of five Chinese traditional medicinal herbs, Cortex phellodendri, Semen strychni, green tea, Sophora flavescens ait, and Datura mete L. were resolved. All separations were performed only with a two-phase system composed of CHCl3-CH3OH-water (4:3:2). The water had different acidities controlled by adding NaH2PO4 or HCl to each sample. The fractionated components were identified by thin-layer chromatography, which confirmed this solvent system was versatile and very useful for the separation of alkaloids.

Alkaloids↗

Voltammetric determination of dopamine in the presence of ascorbic acid at over-oxidized polypyrrole-indigo carmine film-coated electrodes.

Over-oxidized polypyrrole films doped with indigo carmine (PPy-IC) offer substantial improvements in voltammetric sensitivity and selectivity towards dopamine. This polymer coating attenuates the voltammetric response of ascorbic acid while the oxidation peak current of dopamine is enhanced by over one order of magnitude compared with that at the bare electrode. The high sensitivity and selectivity for dopamine appears to be mainly due to the charge discrimination and the analyte accumulation. The detection limit is dependent on both film thickness and preconcentration time. At a 0.25 micron thick PPy-IC film-coated electrode, for a 2 min preconcentration time, the detection limit is 10(-8) mol l-1, over two orders of magnitude lower than at a bare glassy carbon electrode. The concomitant ascorbic acid shows no interference although its concentration is as high as 0.1 mmol l-1. The effects of various experimental parameters on the voltammetric response of dopamine were also investigated. The attractive permselective and preconcentrating properties of the PPy-IC films make them valuable for in vivo electrochemistry.

Ascorbic Acid↗