Geology topics

Xiaotian Chang

Publications and source records attributed to Xiaotian Chang.

4 recordsLinked to original sources

USGS2010

Determination of antibiotics in sewage from hospitals, nursery and slaughter house, wastewater treatment plant and source water in Chongqing region of Three Gorge Reservoir in China

Sewage samples from 4 hospitals, 1 nursery, 1 slaughter house, 1 wastewater treatment plant and 5 source water samples of Chongqing region of Three Gorge Reservoir were analyzed for macrolide, lincosamide, trimethoprim, fluorouinolone, sulfonamide and tetracycline antibiotics by online solid-phase extraction and liquid chromatography-tandem mass spectrometry. Results showed that the concentration of ofloxacin (OFX) in hospital was the highest among all water environments ranged from 1.660 μg/L to 4.240 μg/L and norfloxacin (NOR, 0.136–1.620 μg/L), ciproflaxacin (CIP, ranged from 0.011 μg/L to 0.136 μg/L), trimethoprim (TMP, 0.061–0.174 μg/L) were commonly detected. Removal range of antibiotics in the wastewater treatment plant was 18–100% and the removal ratio of tylosin, oxytetracycline and tetracycline were 100%. Relatively higher removal efficiencies were observed for tylosin (TYL), oxytetracycline (OXY) and tetracycline (TET)(100%), while lower removal efficiencies were observed for Trimethoprim (TMP, 1%), Epi-iso-chlorotetracycline (EICIC, 18%) and Erythromycin-H 2 O (ERY-H 2 O, 24%). Antibiotics were removed more efficiently in primary treatment compared with those in secondary treatment.

Chongqing region, Three Gorge Reservoir↗

USGS2001

Effects of maturation-inducing hormone on heterologous gap junctional coupling in ovarian follicles of Atlantic croaker

A previous ultrastructural study of heterologous (granulosa cell-oocyte) gap junction (GJ) contacts in ovarian follicles of Atlantic croaker suggested that these contacts disappear late during the process of resumption of oocyte meiosis. This observation suggested that, unlike scenarios proposed for a number of other species, uncoupling of GJ is not necessary for the onset of meiotic resumption in croaker follicles. However, the functionality of heterologous GJ contacts and the temporal association between maturation-inducing hormone (MIH)-induced changes in heterologous coupling and resumption of oocyte meiosis have not been examined in Atlantic croaker. These questions were addressed with a cell-cell coupling assay that is based on the transfer of a GJ marker, Lucifer Yellow, from oocytes to granulosa cells. Follicle-enclosed oocytes injected with Lucifer Yellow allowed transfer of the dye into the follicle cell layer, thus confirming that there is functional heterologous coupling between the oocyte and the granulosa cells. Dye transfer was observed in vitellogenic, full-grown/maturation-incompetent, and full-grown /maturation-competent follicles. Treatment of maturation-competent follicles with MIH caused a time-dependent decline in the number of follicles transferring dye. However, although GJ uncoupling in some of the follicles was observed before germinal vesicle breakdown (GVBD, index of meiotic resumption), about 50% of the follicles maintained the ability to transfer dye even after GVBD had occurred. Further, a known GJ inhibitor (phorbol 12-myristate 13-acetate) blocked heterologous GJ within a time frame similar to that seen with MIH but without inducing any of the morphological changes (including GVBD) associated with follicular maturation. In conclusion, uncoupling of heterologous GJ seems insufficient and unnecessary for the onset of meiotic resumption in ovarian follicles of Atlantic croaker. ?? 2001 Elsevier Science.

General and Comparative Endocrinology↗

USGS2000

Phylogenetic sequence analysis, recombinant expression, and tissue distribution of a channel catfish estrogen receptor beta

An estrogen receptor β (ERβ) cDNA fragment was amplified by RT-PCR of total RNA extracted from liver and ovary of immature channel catfish. This cDNA fragment was used to screen an ovarian cDNA library made from an immature female fish. A clone was obtained that contained an open reading frame encoding a 575-amino-acid protein with a deduced molecular weight of 63.9 kDa. Maximum parsimony and Neighbor Joining analyses were used to generate a phylogenetic classification of channel catfish ERβ on the basis of 25 full-length teleost and tetrapod ER sequences. The consensus tree obtained indicated the existence of two major vertebrate ER subtypes , α and β. Within each subtype, and in accordance with established phylogenetic relationships , teleost and tetrapod ER were monophyletic confirming the results of a previous analysis (Z. Xia et al ., 1999, Gen. Comp. Endocrinol . 113, 360–368). Extracts of COS-7 cells transfected with channel catfish ERβ cDNA bound estrogen with high affinity ( K d = 0.21 nM) and specificity. The affinity of channel catfish ERβ for estrogen was higher than previously reported for channel catfish ERα. As determined by qualitative RT-PCR, the tissue distributions of ERα and ERβ were similar but not identical. Both ER subtypes were present in ovary and testis. ERα was found in all other tissues examined from juvenile and mature fish of both sexes. ERβ was also found in most tissues except, in most cases, whole blood and head kidney. Interestingly, the pattern of expression of ER subtypes in head kidney always corresponded to the pattern in whole blood. In conclusion, we isolated a channel catfish ERβ with ligand-binding affinity and tissue expression patterns different from ERα. Also, we confirmed the validity of our previously proposed general classification scheme for vertebrate ER into α and β subtypes and within each subtype, into teleost and tetrapod clades.

General and Comparative Endocrinology↗

USGS2000

Novel transcripts of the estrogen receptor α gene in channel catfish

Complementary DNA libraries from liver and ovary of an immature female channel catfish were screened with a homologous ERα cDNA probe. The hepatic library yielded two new channel catfish ER cDNAs that encode N-terminal ERα variants of different sizes. Relative to the catfish ERα (medium size; 581 residues) previously reported, these new cDNAs encode Long-ERα (36 residues longer) and Short-ERα (389 residues shorter). The 5′-end of Long-ERα cDNA is identical to that of Medium-ERα but has an additional 503-bp segment with an upstream, in-frame translation-start codon. Recombinant Long-ERα binds estrogen with high affinity ( K d = 3.4 nM), similar to that previously reported for Medium-ERα but lower than reported for catfish ERβ. Short-ERα cDNA encodes a protein that lacks most of the receptor protein and does not bind estrogen. Northern hybridization confirmed the existence of multiple hepatic ERα RNAs that include the size range of the ERα cDNAs obtained from the libraries as well as additional sizes. Using primers for RT-PCR that target locations internal to the protein-coding sequence, we also established the presence of several ERα cDNA variants with in-frame insertions in the ligand-binding and DNA-binding domains and in-frame or out-of-frame deletions in the ligand-binding domain. These internal variants showed patterns of expression that differed between the ovary and liver. Further, the ovarian library yielded a full-length, ERα antisense cDNA containing a poly(A) signal and tail. A limited survey of histological preparations from juvenile catfish by in situ hybridization using directionally synthesized cRNA probes also suggested the expression of ERα antisense RNA in a tissue-specific manner. In conclusion, channel catfish seemingly have three broad classes of ERα mRNA variants: those encoding N-terminal truncated variants, those encoding internal variants (including C-terminal truncated variants), and antisense mRNA. The sense variants may encode functional ERα or related proteins that modulate ERα or ERβ activity. The existence of ER antisense mRNA is reported in this study for the first time. Its role may be to participate in the regulation of ER gene expression.

General and Comparative Endocrinology↗