Biomedical subjects

Yun Mao

Publications and source records attributed to Yun Mao.

5 recordsLinked to original sources

PubMed2025

Perirenal Adipose Tissue and Hypertension: Observational and Genetic Analyses.

BACKGROUND: Perirenal adipose tissue (PRAT) consists of white and brown adipocytes with good vascularization and dense innervation, which could influence the blood pressure. We aim to investigate the association of PRAT thickness with risks of overall and specific forms of hypertension. METHODS: We measured PRAT thickness in the UK Biobank and CONPASS (Chongqing Primary Aldosteronism Study). We prospectively examined the correlation between PRAT thickness and incident hypertension in the UK Biobank. We cross-sectionally explored associations between PRAT thickness and common forms of hypertension in CONPASS. Integrating data from GWAS (Genome-Wide Association Study), we investigated the potential causal relationship between PRAT and hypertension forms by 2-sample Mendelian randomization analyses. RESULTS: In the prospective analysis of the UK Biobank, participants whose PRAT thickness was ≥46.1 mm showed a higher risk of developing hypertension than participants whose PRAT thickness was <16.4 mm (hazard ratio, 2.91 [95% CI, 1.97-4.32]). In the cross-sectional analysis of CONPASS, a 1 SD increment in PRAT thickness was associated with a 2.77-fold higher adjusted odds of low-renin essential hypertension and a 3.89-fold higher adjusted odds of idiopathic hyperaldosteronism. PRAT thickness was not significantly associated with other forms of hypertension, such as aldosterone-producing adenoma and obstructive sleep apnea. In 2-sample Mendelian randomization analyses, PRAT thickness was only significantly associated with a higher risk of idiopathic hyperaldosteronism (inverse variance weighted odds ratio, 1.33 [95% CI, 1.09-1.62]), with no evidence of significant heterogeneity or substantial directional pleiotropy. CONCLUSIONS: PRAT is causally associated with idiopathic hyperaldosteronism rather than essential hypertension and other forms of secondary hypertension.

Humans↗

PubMed2005

"Orthogonal" separations for reversed-phase liquid chromatography.

A general procedure is proposed for the rapid development of a reversed-phase liquid chromatographic (RP-LC) separation that is "orthogonal" to a pre-existing ("primary") method for the RP-LC separation of a given sample. The procedure involves a change of the mobile-phase organic solvent (B-solvent), the replacement of the primary column by one of very different selectivity, and (only if necessary) a change in mobile phase pH or the use of a third column. Following the selection of the "orthogonal" B-solvent, column and mobile phase pH, further optimization of peak spacing and resolution can be achieved by varying separation temperature and either isocratic %B or gradient time. The relative "orthogonality" of the primary and "orthogonal" RP-LC methods is then evaluated from plots of retention for one method versus the other. The present procedure was used to develop "orthogonal" methods for nine routine RP-LC methods from six pharmaceutical analysis laboratories. The relative success of this approach can be judged from the results reported here.

Chromatography, Liquid↗

PubMed2004

Quantitation of poloxamers in pharmaceutical formulations using size exclusion chromatography and colorimetric methods.

Poloxamers have been used as functional excipients in pharmaceutical products. They function as surfactants, emulsifying agents, solubilizing agents, dispersing agents, and in vivo absorbance enhancer. Despite their wide range of applications, limited analytical techniques have been reported in literature for characterizing poloxamers and few are targeted to quantify poloxamer contents in formulations with desired sensitivity and accuracy. In this paper, two distinct analytical methods for quantifying low levels of poloxamers in pharmaceutical formulations have been developed and optimized: a colorimetric method and a size exclusion chromatography method. The colorimetric method is based on the formation of a colored complex between poloxamers and cobalt(II) thiocyanate in aqueous medium, which has a maximum UV absorbance at 624 nm. The feasibility of this method is product specific. In this report, adequate specificity and sensitivity was demonstrated for only one of the several products tested. The size exclusion chromatography (SEC) method utilizes size exclusion columns with THF as mobile phase and refractive index detection. The SEC method provides a limit of quantitation (LOQ) of 0.005 mg/mL (0.0005%, w/w) and at least three orders of magnitudes of linear range. We applied the SEC method to pharmaceutical products containing 0.3-10% poloxamer 188 or poloxamer 407, such as Avapro, Neurontin, Sudafed and other developmental formulations. The results obtained with the SEC method agreed very well with literature and theoretical values with 97-102% recovery. The SEC method was proven to be widely applicable, accurate, precise and simple to use.

Amines↗

PubMed2002

Use of DRYLAB to compare octadecylsilane and carbon supports for reversed-phase chromatography of triazine herbicide test solutes.

One of the most important aspects of method development in reversed-phase high-performance liquid chromatography (RPLC) is the accurate prediction of the resolution as one or more experimental variables (usually the mobile-phase composition) are changed. By use of commercially available computer simulation programs, e.g. Drylab 2000, data from a few initial experimental runs are used to predict how the separation will vary with composition so that a computer program can then rapidly locate the optimum conditions. Assumption of a linear relationship between log k' (retention factor) and phi (volume fraction of organic modifier in the element) minimizes the number of initial runs required for a separation and is usually adequate when the range of phi is not large. In this work the linearity of plots of log k' against phi for octadecylsilane-coated silica (ODS) and carbon-coated zirconia (C-ZrO(2)) columns were compared and the plots were used to determine whether prediction of the separation of triazine herbicides was adequate. Analysis of the slopes and intercepts of such plots are presented for both types of columns.

Chromatography, High Pressure Liquid↗

PubMed1996

Photocatalytic Oxidation of Aromatic Hydrocarbons.

In acidic aqueous solutions UO(2)(2+) serves as a photocatalyst (lambda(irr) >/= 425 nm) for the oxidation of benzene by H(2)O(2). Under conditions where 50% of the excited state UO(2)(2+) is quenched by H(2)O(2) (k = 5.4 x 10(6) M(-)(1) s(-)(1)) and 50% by benzene (k = 2.9 x 10(8) M(-)(1) s(-)(1)), the quantum yield for the formation of phenol is 0.70. The yield does not change when benzene is replaced by benzene-d(6), but decreases by a factor of approximately 4 upon the change of solvent from H(2)O to D(2)O. Photocatalytic oxidation of toluene by UO(2)(2+)/H(2)O(2) produces PhCHO, PhCH(2)OH, and a mixture of cresols with a total quantum yield of 0.28 under conditions where 50% of UO(2)(2+) is quenched by H(2)O(2). The quenching of UO(2)(2+) by benzene and substituted benzenes takes place with k > 10(8) M(-)(1) s(-)(1). The system UO(2)(2+)/t-BuOOH/C(6)H(6)/hnu does not result in the oxidation of benzene, but instead yields methane and ethane.

Journal Article↗