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Jiangang Chen

Publications and source records attributed to Jiangang Chen.

13 recordsLinked to original sources
PubMed2006

Circulating bioactive androgens in midlife women.

CONTEXT: It is important to characterize the biological activity of circulating androgenic steroid hormones during the menopausal transition because these appear to impact the metabolic and cardiovascular health risk factors of women. OBJECTIVE: The objective of the study was to develop and characterize a cell-based bioassay that measures the androgen receptor-mediated signal transduction in serum. DESIGN: This was a clinically relevant experimental study nested in a sample population of a longitudinal cohort study. SETTING: The study was conducted at a university laboratory. METHODS: A receptor-mediated luciferase expression bioassay based on HEK 293 cells that were stably cotransfected with plasmids containing the human androgen receptor and luciferase gene was developed. In 49 samples from menstruating women aged 42-52 yr, total testosterone (T) and SHBG concentrations were measured by immunoassay; free T concentrations were calculated from the total T and SHBG concentrations. RESULTS: Mean total T concentration of the sample was 1.15 nm (sd 0.46, range 0.57-3.86 nm). The mean bioactive androgen detected was 1.00 nm (sd 0.24, range 0.53-1.60 nm). Calculated free T (mean 0.0156 nm) was significantly lower than the levels of bioactive androgens measured by receptor-mediated bioassay. There was significant positive correlation between bioactive androgen levels and total T values in young women and polycystic ovarian disorder patients, whereas no correlation was found between the two values in middle-aged women. CONCLUSIONS: An androgen receptor-mediated bioassay can provide additional information in the evaluation of total bioactive androgens in midlife women. Our data suggest that levels of circulating SHBG may have a significant impact on the levels of total circulating bioavailable androgens.

Adult↗
PubMed2006

Phosphate immobilization from aqueous solution by fly ashes in relation to their composition.

Phosphate sorption capacities of 15 Chinese fly ashes were determined and related to their composition. The data of P sorption were best fitted to Langmuir equation, and the calculated sorption maxima of phosphate (Qm) ranged from 5.51 to 42.55 mg/g. The Qm value showed a significantly positive correlation with total Ca content (r=0.9836**) and total Fe content (r=0.8049**), but negative correlation with total Si and total Al content. Correlation coefficients of CaO (r=0.9647**) and CaSO4 (r=0.9399**) were much greater than that of CaCO3 (r=0.6361*). Correlation coefficients of Qm with Fe2O3d and Al2O3d were much higher than those of total Fe and total Al contents, respectively. Fractionation of P sorbed by fly ash revealed that loosely bound P fraction and/or Ca+Mg-P fraction were the dominant form of immobilized phosphate. Ca content was strongly correlated with the Ca+Mg-P fraction instead of Mg content, whereas Fe content was highly correlated with Fe-Al-P fraction compared with Al content. The loosely bound P was correlated well with both Ca and Fe content. The greatest removal of phosphate occurred at alkaline conditions for high calcium fly ash, at neutral pH levels for medium calcium fly ash, while low calcium fly ash immobilized little phosphate at all pH values. This behavior was explained by the reaction of phosphate with Ca and Fe related components. It was concluded that P immobilization by fly ash was governed by Ca ingredient (especially CaO and CaSO4) and Fe ingredient (especially Fe2O3d).

Adsorption↗
PubMed2006

Removal of phosphate from aqueous solution by zeolite synthesized from fly ash.

Fifteen Chinese fly ashes were converted hydrothermally into zeolites, and phosphate immobilization capacity (PIC) of the synthesized zeolites and the corresponding raw fly ashes were determined using an initial phosphate concentration of 1000 mg/L. Results showed that there was a remarkable increase in PIC (from 1.2 to 7.6 times) following the synthesis process. Fractionation of immobilized phosphorus indicated that Fe+Al-P increased most significantly and consistently among all the phosphorus fractions following the conversion of fly ash to zeolite. The PIC and Ca+Mg-P were closely related to Ca content (with r values of 0.9683 and 0.9651, respectively) rather than Mg content (with r values of 0.3920 and 0.3212, respectively). The r values of PIC and Fe+Al-P with Fe content (with r values of 0.4686 and 0.6385, respectively) were higher than those with Al content (with r values of -0.7857 and -0.3770, respectively). Although calcium and iron components were mainly involved in phosphate immobilization, there was no significant change of Ca and Fe content following the conversion of fly ash to zeolite. Increase in dissociated Fe(2)O(3) and specific surface area probably accounted for the enhancement in PIC of synthesized zeolites compared with corresponding fly ashes. The PIC value of zeolites showed a significant correlation with dissociated Fe(2)O(3) (r=0.6186). The specific surface area increased 26.0-89.4 times as a result of the conversion of fly ash to zeolite. The maximum removal of phosphate occurred within different pH ranges for zeolites which were synthesized from high, medium and low calcium fly ashes and this behavior was explained by the reaction of phosphate with calcium and iron components.

Adsorption↗
PubMed2006

Daily immunoactive and bioactive human chorionic gonadotropin profiles in periimplantation urine samples.

A need exists for broadly applicable biomarkers of pregnancy outcome in population-based studies that assess environmental hazards to human reproduction. Previous studies have demonstrated that during the periimplantation period, measures of the circulating levels of immunoreactive hCG (IhCG) are not predictive of pregnancy outcome, whereas measurements of the circulating levels of bioactive hCG (BhCG) provide information relating to pregnancy outcome and might provide the basis for an early biomarker of pregnancy outcome. However, for this biomarker to have broad application in population-based studies, it must be adapted to urinary hCG metabolites. The principle objective of the present study was to characterize the periimplantation excretion patterns of urinary hCG metabolites of pregnancies that resulted in live birth (LB), early pregnancy loss (EPL), and recognized clinical abortion (CAB) with an immunoenzymometric assay specific to intact hCG and an LH/chorionic gonadotropin cellular bioassay as the basis for a preliminary comparison between successful (LB) and failing (EPL and CAB) outcome groups. Automated immunoassays for FSH and hCG were used to define each conceptive cycle's implantation window. The timing of first hCG detection was significantly later for the EPL group. Pregnancies that resulted in LB had consistently rising average daily IhCG and BhCG levels, with no significant differences when average daily IhCG and BhCG measurements were compared (Student t-test, P>0.05), whereas pregnancies that resulted in CAB and EFL had lower average daily IhCG and BhCG levels that increased inconsistently. These findings demonstrate that critical information related to pregnancy outcome may be present when multiple urinary hCG isoforms are measured. Further data suggest that the rate of change for the ratio of daily BhCG over IhCG levels might be useful as the basis of a broadly applicable early biomarker for pregnancy outcome.

Abortion, Spontaneous↗
PubMed2003

Bromodichloromethane inhibits human placental trophoblast differentiation.

Epidemiological data suggest an association between exposures to bromodichloromethane (BDCM), a trihalomethane found in drinking water as a result of drinking water disinfection, and an increased risk of spontaneous abortion. We previously hypothesized that BDCM targets the placenta and showed that the secretion of chorionic gonadotrophin (CG) was reduced in primary cultures of human term syncytiotrophoblasts exposed to BDCM. In the present study we extend this observation by evaluating the effects of BDCM on the morphological differentiation of mononucleated cytotrophoblast cells to multinucleated syncytiotrophoblast-like colonies. Addition of BDCM to cytotrophoblast cultures inhibited the subsequent formation of multinucleated colonies in a dose-dependent manner, as determined by immunocytochemical staining for desmosomes and nuclei. The effect was seen at BDCM concentrations between 0.02 and 2 mM and was confirmed by quantitative image analysis. Secretion of bioactive and immunoreactive chorionic gonadotropin was also significantly inhibited in a dose-dependent manner under these culture conditions, and cellular levels of CG were also reduced. Trophoblast viability was not compromised by exposure to BDCM. We conclude that BDCM disrupts syncytiotrophoblast formation and inhibits CG secretion in vitro. Although other tissue targets are not ruled out, these data substantiate the idea that BDCM targets the placenta and could have implications for understanding the adverse pregnancy outcomes associated with BDCM exposure in humans.

Adult↗
PubMed2003

Effect of bromodichloromethane on chorionic gonadotrophin secretion by human placental trophoblast cultures.

Bromodichloromethane (BDCM) is a trihalomethane found in drinking water as a by-product of disinfection processes. BDCM is hepatotoxic and nephrotoxic in rodents and has been reported to cause strain-specific full-litter resorption in F344 rats during the luteinizing hormone-dependent phase of pregnancy. In humans, epidemiological studies suggest an association between exposure to BDCM in drinking water and increased risk of spontaneous abortion. To begin to address the mechanism(s) of BDCM-induced spontaneous abortion, we hypothesized that BDCM targets the placenta. Primary cultures of human term trophoblast cells were used as an in vitro model to test this hypothesis. Trophoblasts were allowed to differentiate into multinucleated syncytiotrophoblast-like colonies, after which they were incubated for 24 h with different concentrations of BDCM (20 nM to 2 mM). Culture media were collected and assayed for immunoreactive and bioactive chorionic gonadotropin (CG). Cultures exposed to BDCM showed a dose-dependent decrease in the secretion of immunoreactive CG as well as bioactive CG. The lowest effective BDCM concentration was 20 nM, approximately 35-times higher than the maximum concentration reported in human blood (0.57 nM). Trophoblast morphology and viability were similar in controls and cultures exposed to BDCM. We conclude that BDCM perturbs CG secretion by differentiated trophoblasts in vitro. This suggests that the placenta is a likely target of BDCM toxicity in the human and that this could be related to the adverse pregnancy outcomes associated with BDCM.

Cell Survival↗
PubMed2003

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on chorionic gonadotrophin activity in pregnant macaques.

As many as 62% of all human conceptions are lost prior to 12 weeks of pregnancy and it is unknown how many of these losses result from environmental hazards. Previous studies have shown that single doses of 1, 2, and 4 microg/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) administrated orally to cynomolgus macaques during the peri-implantation period leads to early fetal loss (EFL) within 10-20 days. TCDD induced EFL is associated with a reduction in the biological activity of monkey chorionic gonadotrophin (mCG) but no change in the immunoreactive mCG profile. These studies are consistent with either a direct effect of TCDD on differentiation of the trophoblast and an indirect effect on mCG synthesis, or a direct effect on mCG synthesis and secretion independent of trophoblast development. The present study was designed to test the hypothesis that the action of TCDD is directly on mCG synthesis rather than on the differentiation of the trophoblast. Female macaques (Macaca fascicularis) were treated with a single dose of TCDD (4 microg/kg b.wt.) on Gestational Day 20, a stage of pregnancy following initial trophoblast differentiation and invasion. Circulating mCG concentrations were monitored for the next 6 days. Compared to the controls, the peak level of serum bioactive mCG was lower in the treated group (P<0.05), with a decrease observed on the day following exposure. The bioactive/immunoreactive mCG ratio was also lower in the treated group compared to the controls (P<0.05). There was no difference in serum immunoreactive mCG levels between the groups. Histological evaluation of the embryo-placental unit showed increased apoptosis and vascular congestion after treatment but was otherwise grossly normal. Because exposure of the conceptus to TCDD following differentiation of the trophoblast decreased the bioactivity of circulating mCG, we conclude that the action of TCDD in the placenta is directly on mCG synthesis.

Animals↗
PubMed2003

Bone resorption is affected by follicular phase length in female rotating shift workers.

Stressors as subtle as night work or shift work can lead to irregular menstrual cycles, and changes in reproductive hormone profiles can adversely affect bone health. This study was conducted to determine if stresses associated with the disruption of regular work schedule can induce alterations in ovarian function which, in turn, are associated with transient bone resorption. Urine samples from 12 rotating shift workers from a textile mill in Anqing, China, were collected in 1996-1998 during pairs of sequential menstrual cycles, of which one was longer than the other (28.4 vs. 37.4 days). Longer cycles were characterized by a prolonged follicular phase. Work schedules during the luteal-follicular phase transition (LFPT) preceding each of the two cycles were evaluated. All but one of the shorter cycles were associated with regular, forward phase work shift progression during the preceding LFPT. In contrast, five longer cycles were preceded by a work shift interrupted either by an irregular shift or a number of "off days." Urinary follicle-stimulating hormone levels were reduced in the LFPT preceding longer cycles compared with those in the LFPT preceding shorter cycles. There was greater bone resorption in the follicular phase of longer cycles than in that of shorter cycles, as measured by urinary deoxypyridinoline. These data confirm reports that changes in work shift can lead to irregularity in menstrual cycle length. In addition, these data indicate that there may be an association between accelerated bone resorption in menstrual cycles and changes of regularity in work schedule during the preceding LFPT.

Adult↗
PubMed2003

Hormonal characteristics in the early luteal phase of conceptive and nonconceptive menstrual cycles.

To determine whether serum hormone profiles are different in nonconceptive and conceptive menstrual cycles after ovulation and before implantation. Daily blood samples obtained during the luteal phase of nonconceptive cycles (n = 31) and conceptive cycles (n = 19) were analyzed (intersubject comparison). Samples obtained in sequential nonconceptive and conceptive cycles from five subjects (intrasubject comparisons) were analyzed to confirm results obtained with intersubject analysis. Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E(2)), progesterone, and relaxin were measured by immunoassay. A cell-based bioassay was used to determine whether the measurement of serum immunoreactive LH is a result of cross-reaction with human chorionic gonadotropin (hCG). Intersubject analysis showed that mean serum LH levels were significantly higher in conceptive cycles on day 4 and day 5 after the FSH peak in urine, and this was confirmed by intrasubject analysis. The addition of antibodies that precipitate hCG did not affect the activity of LH receptor ligand molecules in serum samples collected during the early luteal phase of conceptive cycles, as measured by bioassay. In contrast, this LH receptor binding activity was completely removed when precipitating antibodies for LH were added. The mean levels of serum E(2) were higher in conceptive cycles after day 4 following the FSH peak in urine. The mean values of serum FSH, progesterone, and relaxin were not significantly different in nonconceptive and conceptive cycles during the same time interval. The differences in luteal phase hormones may reflect alterations in signaling in the hypothalamic-pituitary-ovarian axis that begin during the preovulatory period of nonconceptive cycles.

Adult↗
PubMed2002

Urinary follicle-stimulating hormone peak as a biomarker for estimating the day of ovulation.

OBJECTIVE: To evaluate urinary follicle-stimulating hormone (FSH) as a biomarker for the day of ovulation. DESIGN: Prospective observational study. SETTING: Clinical research center. PATIENT(S): Thirteen women were monitored with measurements of serum and urinary hormones and ovarian ultrasonography during 20 menstrual cycles. Data on urinary hormones and ultrasound evaluations from a total of 65 menstrual cycles from 42 women were analyzed. INTERVENTION(S): Blood and/or urine samples were collected daily. Daily transvaginal ultrasonography was used to detect follicular collapse. MAIN OUTCOME MEASURE(S): LH, FSH, and E(2) were measured in serum. FSH, estrone conjugates (E1C), and pregnanediol-3-glucuronide (PdG) were analyzed in urine. The day of luteal transition (DLT) was calculated using two algorithms. RESULT(S): In 20 cycles, the urinary FSH peak was closer to the day of follicular collapse (-0.85 days) than was the peak day of serum E(2) and the day of luteal transition, as calculated by one algorithm. The FSH peak was not closer to the day of follicular collapse than the peak values of urinary LH, serum FSH, or the day of luteal transition as calculated by a second algorithm. The most consistent correspondence between a hormone peak and ovulation was for serum E(2), serum FSH, serum LH, and urinary FSH. In 65 cycles for which urinary hormone data and ultrasound evaluations were available, the urinary FSH peak occurred within 1 day of follicular collapse in 97% of cycles. CONCLUSION(S): Urinary FSH is a useful biomarker for estimating the day of ovulation in population-based studies.

Adult↗
PubMed2002

Detection of xenoestrogens in serum after immunoprecipitation of endogenous steroidal estrogens.

In this article we report a simple and efficient method for detecting nonsteroidal estrogens in a biologic sample. This method uses polyclonal antibodies to estradiol (E2) to immunoprecipitate these major biologically active steroidal estrogens, leaving behind the nonsteroidal estrogens, which are then detected in a cell-based transcriptional activation bioassay for estrogen receptor agonist. The immunoprecipitation method efficiently removed 99% of radiolabeled E2 and estrone (E1) from human serum. In experiments in which supraphysiologic concentrations of E2 and E1 to human serum, all of the immunoreactive estrogens were still removed by the immunoprecipitation protocol. We carried out an in vivo validation study of this method in which we treated female macaques with the xenoestrogen nonylphenol (NP), during the late follicular phase of the menstrual cycle. We used blood samples collected before and after treatment to evaluate and characterize endogenous and exogenous serum estrogens. An immunoassay for E2 did not detect the NP in treated monkeys. The cell-based bioassay also did not detect the estrogenic activity of NP because of its saturation by the endogenous serum steroidal estrogens. However, when steroidal estrogens were removed by immunoprecipitation, we detected the estrogenic activity of NP in the bioassay. Thus, this approach is appropriate for detecting exogenous, nonsteroidal estrogens in serum samples.

Animals↗
PubMedDate not supplied

Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on chorionic gonadotropin secretion by human trophoblasts.

This study tests the idea that the environmental toxicant, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), affects human trophoblast differentiation and alters the secretion of chorionic gonadotropin (CG). Primary cultures of cytotrophoblast cells were incubated under differentiation-inducing and nondifferentiation-inducing conditions in the presence or absence of different concentrations of TCDD. Levels of immunoreactive CG as well as bioactive CG were measured in culture supernatants. TCDD caused a significant increase in the secretion of immunoreactive CG from differentiated trophoblast cultures but had no effect on the secretion of bioactive hormone. The net effect was a TCDD-dependent reduction in the CG bioactive/immunoreactive (B/I) ratio for differentiated trophoblast cultures. TCDD had no effect on immunoreactive or bioactive CG secretion by undifferentiated trophoblasts. Immunocytochemical studies showed that TCDD had no effect on the morphologic differentiation of trophoblast cells as determined by staining nuclei and desmosomal proteins. On the other hand, immunocytochemical staining for CG was increased in cells exposed to TCDD compared to control cells. These in vitro results support earlier in vivo studies in macaques suggesting that trophoblast is a target for TCCD and that TCDD-induced early pregnancy loss is accompanied by a decrease in the CG B/I ratio.

Cell Nucleus↗