Biomedical subjects

Jun Xiao

Publications and source records attributed to Jun Xiao.

21 records · Page 2Linked to original sources

PubMed2003

[A study on the relationship between urinary 1-hydroxypyrene level and early genetic effect among coke oven workers].

OBJECTIVE: To investigate the relationship between the urinary 1-hydroxypyrene level and cytokinesis-block micronucleus and the olive moment of comet assay in peripheral blood lymphocyte in coke oven workers. METHODS: One hundred and thirty-three workers from a coke plant and 28 referents without occupational PAH exposure were recruited in this study. Urinary level of 1-hydroxypyrene was measured by alkaline hydrolysis combined with high performance liquid chromatography as an internal exposure dose, and the DNA and chromosomal damage of peripheral blood lymphocyte were evaluated with comet assay and cytokinesis-block micronucleus method. Personal information including occupational history, age, sex, smoking and alcohol drinking, was collected by questionnaire. RESULTS: There existed a good correlationship between the urinary level of 1-hydroxypyrene and frequency of micronuclei per 1 000 binucleated cells or the olive moment of comet assay in the study subjects, after adjusting for sex, age, smoking and alcohol drinking (r > 0.25, P < 0.01). One hundred and sixty-one subjects were divided into three groups by their urine 1-hydroxypyrene level (expressed as 0.30 - 2.44, 2.45 - 7.09 and 7.10 - 33.10 micro mol/mol Cr), and the geometric means of their urinary levels of 1-hydroxypyrene were 1.14, 4.32 and 12.49 micro mol/mol Cr, respectively. After adjusting for age, sex, smoking and alcohol drinking by multiple nonparametric analysis of covariance, the median of olive moment of comet assay in the group of 7.10 - 33.10 micro mol/mol Cr was 3.67, significantly higher than that in the groups of 0.30 - 2.44 and 2.45 - 7.09; and the micronuclei frequencies in the groups of 2.45 - 7.09 and 7.10 - 33.10 micro mol/mol Cr were 8.00 per thousand and 7.50 per thousand, respectively, significantly higher than that in the group of 0.30 - 2.44 micro mol/mol Cr (6.00 per thousand ). CONCLUSIONS: The comet assay of peripheral blood lymphocyte was more suitable to detect the PAHs-induced early genotoxicity, than the cytokinesis-block micronucleus.

Adult↗

PubMed1996

Kinetics and Mechanism of the Reaction between Serum Albumin and Auranofin (and Its Isopropyl Analogue) in Vitro.

The first detailed kinetic analysis and mechanistic interpretation of the reactions between serum albumin and the second-generation gold drug Auranofin [Et(3)PAuSATg = (triethylphosphine)(2,3,4,6-tetra-O-acetyl-1-beta-D-glucopyranosato-S-) gold(I)] and its triisopropylphosphine analogue, iPr(3)PAuSATg, in vitro are reported. The reactions were investigated using Penefsky spun columns and NMR saturation transfer methods. Under the Penefsky chromatography conditions with 0.4-0.6 mM albumin and a wide range of Et(3)PAuSATg concentrations, the reaction is biphasic. The fast phase is apparently first order in albumin with a rate constant [k(1) = 3.4 +/- 0.3 x 10(-)(2) s(-)(1)] that decreases slightly in magnitude and becomes intermediate in order at low gold concentrations, [Et(3)PAuSATg] < [AlbSH]; it accounts for approximately 95% of the Au(I) that binds. A minor, slower step [k(2) = 2.3 +/- 0.3 x 10(-)(3) s(-)(1)), which accounts for only 5% of the reaction, is also first order with respect to albumin, and zero order with respect to auranofin. For iPr(3)PAuSATg, only the first step was observed, k(1) = (1.4 +/- 0.1) x 10(-)(2) s(-)(1), and is first order in albumin and independent of the iPr(3)PAuSATg concentration. (31)P-NMR saturation transfer experiments utilizing iPr(3)PAuSATg, under equilibrium conditions, yielded second-order rate constants for both the forward (1.2 x 10(2) M(-)(1) s(-)(1)) and the reverse (3.9 x 10(1) M(-)(1) s(-)(1)) directions. A multistep mechanism involving a conformationally altered albumin species was developed. Albumin domain IA opens with concomitant Cys-34 rearrangement, allowing facile gold binding and exchange, and then closes. In conjunction with the steady-state approximation, this mechanism accounts for the different reaction orders observed under the two set of conditions. The rate-determining conformational change of albumin governs the reaction as monitored by the Penefsky columns. Rapid second order exchange of R(3)PAuSATg at the exposed Cys-34 residue is observed under the NMR conditions. The mechanism predicts that under physiological conditions where [Et(3)PAuSATg] is 10-25 &mgr;M, the reaction will be second order and rapid with a rate constant of 8 +/- 2 x 10(2) M(-)(1) s(-)(1). The Penefsky spun columns revealed a previously unreported and novel binding mechanism, association of auranofin in the pocket of albumin-disulfide species, which was confirmed by Hummel-Dreyer gel chromatographic techniques under equilibrium conditions. This albumin-auranofin complex (AlbSSR-Et(3)PAuSATg) is weakly bound and readily dissociates during conventional gel exclusion chromatography.

Journal Article↗

PubMedDate not supplied

Retinotopic organization of ferret suprasylvian cortex.

The retinotopic organization of striate and several extrastriate areas of ferret cortex has been established. Here we describe the representation of the visual field on the Suprasylvian visual area (Ssy). This cortical region runs mediolaterally along the posterior bank of the suprasylvian sulcus, and is distinct from adjoining areas in anatomical architecture. The Ssy lies immediately rostral to visual area 21, medial to lateral temporal areas, and lateral to posterior parietal areas. In electrophysiological experiments we made extracellular recordings in adult ferrets. We find that single and multiunit receptive fields range in size from 2 deg x 4 deg to 21 deg x 52 deg. The total visual field representation in Ssy spans over 70 deg in azimuth in the contralateral hemifield (with a small incursion into the ipsilateral hemifield), and from +36 deg to -30 deg in elevation. There are often two representations of the horizontal meridian. Furthermore, the location of the transition from upper to lower fields varies among animals. General features of topography are confirmed in anatomical experiments in which we made tracer injections into different locations in Ssy, and determined the location of retrograde label in area 17. Both isoelevation and isoazimuth lines can span substantial rostrocaudal and mediolateral distances in cortex, sometimes forming closed contours. This topography results in cortical magnifications averaging 0.07 mm/deg in elevation and 0.06 mm/deg in azimuth; however, some contours can run in such a way that it is possible to move a large distance on cortex without moving in the visual field. Because of these irregularities, Ssy contains a coarse representation of the contralateral visual field.

Animals↗