Biomedical subjects

X J Han

Publications and source records attributed to X J Han.

7 recordsLinked to original sources

PubMed1998

Pharmacokinetics of medroxyprogesterone acetate after single and multiple injection of Cyclofem in Chinese women.

To provide pharmacokinetic data for safety evaluation on prolonged treatment with Cyclofem, which contains 25 mg medroxyprogesterone acetate (MPA) and 5 mg estradiol cypionate in 0.5 mL microcrystalline aqueous suspension, the pharmacokinetic profiles of MPA after single and multiple administration of this monthly injectable contraceptive were investigated in Chinese women. Nine healthy fertile women received Cyclofem based on a once-a-month regiment for up to 1 year. Blood samples were collected immediately prior to drug administration and on days 1, 3, 5, 7, 14, 21, and 28 after injection. After the 1st, 6th, and 12th injection, the maximum serum concentrations (Cmax) of MPA were observed on days 3.4 +/- 0.9, 4.3 +/- 2.2, and 3.7 +/- 2.6, respectively. Cmax of serum MPA during the 1st, 6th, and 12th treatment cycles were 3.75 +/- 1.27, 5.54 +/- 1.79, and 5.55 +/- 1.80 nmol/L, whereas the areas under the curve (AUC0-28 days) were 55.84 +/- 28.15, 95.45 +/- 26.56, and 98.81 +/- 21.84 nmol/L.day, respectively. There was significant interindividual variation in the pharmacokinetics of MPA after intramuscular injection of Cyclofem. No significant change was demonstrated in mean residence time (MRT) of MPA after single and multiple injection. There was a tendency of increase in Cmax and AUC0-28 days of MPA during the first 6 months of treatment, whereas no further enhancement was found between the 6th and 12th injection (p > 0.05). Peak levels of estradiol (E2) observed in Cyclofem users were within the normal range of the preovulatory phase. Results of this long-term study suggest that no drug accumulation occurred after repeated administration of Cyclofem in the Chinese women.

Adult↗

PubMed1995

Lectin affinity electrophoresis.

Lectin affinity electrophoresis is a powerful technique to investigate the interaction between a lectin and its ligand. Affinity electrophoresis results from the reduced mobility of a charged species owing to its interaction with an immobile species. In this protocol, a two-dimensional lectin affinity electrophoresis experiment is described that affords separation of oligosaccharides. The first-dimension is composed of a weak, polyacrylamide, capillary tube gel containing a lectin. The example described involves a mixture of fluorescently labeled disaccharides. The mobility of only the lectin-binding disaccharide is reduced affording a separation in the first-dimension. The tube gel is then extruded and placed onto the second-dimension gradient polyacrylamide gel and subjected to electrophoresis. Mobility in the second-dimension is dependent on molecular size and visualization si by fluorescence under transillumination. This method is also applicable, with appropriate modifications, for the separation and analysis of glycopeptides and glycoproteins.

Carbohydrate Sequence↗

PubMed1995

Analysis of fluorescently labeled sugars by reversed-phase ion-pairing high-performance liquid chromatography.

Reducing sugars, including monosaccharides, disaccharides, and a trisaccharide, are derivatized by reductive amination with 7-amino-1,3-naphthalene disulfonic acid. Reversed-phase ion-pairing high-performance liquid chromatography is then used to separate these visibly fluorescent, charged conjugates. Isocratic elution with triethylamine-acetic acid from a phenyl column, a C18 column, and C18 and phenyl columns in series gives good separations of a mixture of monosaccharides and a mixture of disaccharides and trisaccharides. Resolution of certain monosaccharides is enhanced by replacing triethylamine with a chiral amine and using gradient elution. Further enhancement of resolution is achieved by adding phenylboronic acid, an agent capable of complexing with the vicinal diol functionality present in many sugars. The trimethylamine-acetic acid eluant permits detection by either ultraviolet absorbance or fluorescence, and the addition of a chiral ion-pairing agent or a phenylboronic acid complexing agent necessitates fluorescence detection. A reversible Schiff base form of the fluorescent sugar conjugate is prepared; it is sufficiently stable to perform fractionations but sufficiently unstable to be converted to a fluorescent label and reducing sugar.

Carbohydrate Sequence↗

PubMed1995

Preparation and structural characterization of large heparin-derived oligosaccharides.

Porcine mucosal heparin was partially depolymerized with heparin lyase I and then fractionated into low-molecular-weight (< 5000) and high-molecular-weight (> 5000) oligosaccharides by pressure filtration. The high-molecular-weight oligosaccharide mixture (approximately 50 wt% of the starting heparin) also contained intact heparin. This intact polymer complicates oligosaccharide purification. Thus, the low-molecular-weight fraction was used to prepare homogeneous oligosaccharides for structural characterization. The low-molecular-weight oligosaccharide mixture was first fractionated by low-pressure gel permeation chromatography into size-uniform mixtures of disaccharides, tetrasaccharides, hexasaccharides, octasaccharides, decasaccharides, dodecasaccharides, tetradecasaccharides and higher oligosaccharides. Each size-fractionated mixture was then purified on the basis of charge by repetitive semi-preparative strong-anion-exchange high-performance liquid chromatography. This approach has led to the isolation of 14 homogeneous oligosaccharides from disaccharide to tetradecasaccharide. The purity of these heparin-derived oligosaccharides was determined by gradient polyacrylamide gel electrophoresis, analytical strong-anion-exchange high-performance liquid chromatography, capillary electrophoresis and one-dimensional nuclear resonance spectroscopy. The structure of these oligosaccharides was established using 600 MHz two-dimensional nuclear resonance spectroscopy. The spectral methods used included homonuclear correlation spectroscopy, nuclear Overhauser effect spectroscopy and heteronuclear multiple quantum coherence spectroscopy. The 1H/1H connectivities of the protons of each sugar residue in an oligosaccharide were established by two-dimensional homonuclear correlation spectroscopy, while 1H/13C assignments were made using 1H inverse detection. One- and two-dimensional nuclear resonance spectroscopic analysis of these heparin oligosaccharides showed two closely related groups of heparin-oligosaccharides are afforded by enzymatic depolymerization of heparin. One group is fully sulphated, having the structures delta UAp2S(1[-->4)-alpha-D-GlcNpS6S(1-->4)-alpha-L-IdoAp2S( 1]n-->4)-alpha- D-GlcNpS6S, where delta UAp is 4-deoxy-alpha-L-threo-hex-4-eno-pyranosyluronic acid, GlcNp is 2-deoxy-2-aminoglucopyranose, IdoAp is idopyranosyluronic acid, S is sulphate and n = 0-6. The other group of oligosaccharides differ in that they contain beta-D-glucuronic acid in place of the alpha-L-iduronic acid residue nearest to the reducing end. The present study describes the isolation and structural elucidation of seven new oligosaccharides: an octasaccharide, two decasaccharides, two dodecasaccharides and two tetradecasaccharides. The utility of two-dimensional nuclear resonance spectroscopy to determine the structure of complex heparin oligosaccharides is also illustrated.

Animals↗

PubMed1995

Strategy for the sequence analysis of heparin.

The versatile biological activities of proteoglycans are mainly mediated by their glycosaminoglycan (GAG) components. Unlike proteins and nucleic acids, no satisfactory method for sequencing GAGs has been developed. This paper describes a strategy to sequence the GAG chains of heparin. Heparin, prepared from animal tissue, and processed by proteinases and endoglucuronidases, is 90% GAG heparin and 10% peptidoglycan heparin (containing small remnants of core protein). Raw porcine mucosal heparin was labelled on the amino termini of these core protein remnants with a hydrophobic, fluorescent tag [N-4-(6-dimethylamino-2-benzofuranyl) phenyl (NDBP)-isothiocyanate]. Enrichment of the NDBP-heparin using phenyl-Sepharose chromatography, followed by treatment with a mixture of heparin lyase I and III, resulted in a single NDBP-linkage region tetrasaccharide, which was characterized as deltaUAp(1-->3)-beta-D-Galp(1-->3)-beta-D-Galp(1-->4)-beta-Xylp -(1-->O-Ser-NDBP (deltaUAp is 4-deoxy-alpha-L-threo-hex-4-enopyranosyl uronic acid). Several NDBP-octasaccharides were isolated when NDBP-heparin was treated with only heparin lyase I. The structure of one of these NDBP-octasaccharides, deltaUAp2S(1-->4)-alpha-D-GlcNpAc(1-->4)-alpha-L-IdoAp (1-->4)-alpha-D-GlcNpAc6S(1-->4)-beta-D-GlcAp(1-->3)-beta-D- Galp(1-->3)-beta-D-Galp(1-->4)-beta-Xylp-(1-->O-Ser NDBP (S is sulphate, Ac is acetate), was determined by 1H-NMR and enzymatic methods. Enriched NDBP-heparin was treated with lithium hydroxide to release heparin, and the GAG chain was then labelled at xylose with 7-amino-1,3-naphthalene disulphonic acid (AGA). The resulting AGA-Xyl-heparin was sequenced on gradient PAGE using heparin lyase I and heparin lyase III. A predominant sequence in heparin at the protein core attachment site was deduced to be -D-GlcNp2S6S(or 6OH)(1-->4)-alpha-L-IdoAp2S-(1-->4)-alpha-D-GlcNp2S6S (or60H) (1-->4)-alpha-L-IdoAp2S(1-->4)-alpha-D-GlcNp2S6S( or 6OH)(1-->4)-alpha-L-IdoAp2S(1-->4)-alpha-D-GlcNpAc (1- ->4)-alpha-L-IdoAp(1-->4)-alpha-D-GlcNpAc6S(1-->4)-beta-D-++ +GlcAp(1-->3)-beta-D-Galp(1-->3)-beta-D-Galp(1-->4)-beta-Xyl-AGA.

Animals↗

PubMed1992

Control of inhibin production by dispersed human luteal cells in vitro.

The production of inhibin in vitro by dispersed cells from early to mid (Days 16-19) and late stage (Day 23) human corpus luteum (CL) was examined, and the effects of human chorionic gonadotrophin (hCG), follicle stimulating hormone (FSH), oestradiol and testosterone on inhibin production were determined. Corpora lutea from five subjects in the early to mid luteal stage and three subjects in late luteal stage were dispersed with enzymes and the luteal cells cultured in medium supplemented with 5% calf serum and either FSH (1, 10 or 100 ng mL-1), oestradiol-17 beta (2.5, 5 or 10 micrograms mL-1) or testosterone (0.25, 1 or 5 micrograms mL-1) with or without hCG (1 I.U. mL-1). Cells were cultured for 1 to 3 days without changes of medium, and the concentrations of progesterone, oestradiol and immunoreactive inhibin in the medium were measured by radioimmunoassay. Cells from both types of CL produced inhibin in vitro under basal conditions, but only cells from early to mid CLs responded to hCG with a significant increase in inhibin production. Both progesterone and oestradiol production were stimulated by hCG in both groups of CL. Inhibin concentrations in the cell cultures declined with time in culture, particularly in the late CL group, whereas the concentration of steroids increased. Neither FSH, oestradiol nor testosterone significantly changed inhibin production in either CL group. It was concluded that inhibin production by human luteal cells in vitro is influenced by the age of the CL, and is dependent on LH (hCG) but not on FSH or sex steroids.

Adult↗

PubMed1992

Inhibitory effect of interferon and tumor necrosis factor on human luteal function in vitro.

OBJECTIVE: To investigate whether immunological mechanisms may be involved in human luteal function. DESIGN: The effects of the cytokines, interferon-alpha (IFN-alpha), interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) on steroidogenesis by human luteal cells were examined in vitro. The dispersed human luteal cells, obtained from a total of 17 women at laparotomy, were cultured separately in the presence or absence of human chorionic gonadotropin (hCG) and IFNs/TNF-alpha with the medium being replaced at 48 hours. The medium was collected at 48 and 96 hours for steroid assays. RESULTS: The IFN-alpha had no significant effect on the production of estradiol or progesterone (P), whereas a dose-related inhibition of basal, as well as hCG-stimulated P formation, was observed after the addition of IFN-gamma (10 to 1,000 U/mL). Progesterone production was inhibited to about 45% of the control at 48 hours and even lower at 96 hours (n = 6, P < 0.001). The combination of IFN-gamma and low doses of TNF-alpha induced a further significant inhibition, whereas there was no effect of TNF-alpha alone. This inhibitory effect of IFN-gamma could be completely neutralized with a monoclonal antibody to IFN-gamma. Incubation with the antibody alone increased the production of P from luteal cells in culture, suggesting a local tonic inhibitory action of endogenous IFN-gamma. CONCLUSION: Interferon-gamma and TNF-alpha, whose function classically is known as antiviral, also may play a role in human luteal regression by inhibiting luteal P production.

Adult↗