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S An

Publications and source records attributed to S An.

At least 19 recordsLinked to original sources
PubMed2006

Expression profiling of radiation-induced genes in radiodermatitis of hairless mice.

BACKGROUND: Radiation induces many cellular events leading to radiodermatitis. OBJECTIVES: The aim of this study was to establish a radiodermatitis model using experimental animals, and to examine the expression profile of radiation-induced genes. METHODS: Hairless mice were irradiated on the dorsal skin; then total RNAs were isolated and microarray hybridizations were performed. RESULTS: Irradiation with a total of 40 Gy (10 Gy day-1 for four consecutive days) provokes radiodermatitis in the hairless mouse. After microarray analysis, 130 genes that showed upregulation by radiation were selected and organized into four different clusters, depending on the time-kinetic pattern. Classification of these genes into several functional categories revealed that various biological processes were globally affected by radiation. These include transcription regulation, signal transduction, cell communication, cell death regulation and metabolism. CONCLUSIONS: These results demonstrate the complexity of the transcriptional profile of the radiation response, providing important clues on which to base further investigations of the molecular events underlying radiodermatitis.

Animals↗
PubMed2003

Gas analysis reveals novel aerobic deammonification in thermophilic aerobic digestion.

A laboratory-scale thermophilic aerobic digester was operated with piggery wastewater. The operating temperature varied from 50-70 degrees C. It has been found that excessive nitrogen removal occurred in the laboratory-scale thermophilic system at various HRTs. Nitrite and nitrate were not observed in the effluent. Gas measurement reveals the presence of significant amount of N2O along with NH3 gas. The rational production of N2O gas in accordance with temperature and HRT suggests that biologically mediated deammonification processes significantly contribute to the N removal. Although further microbiological investigation is required to clarify the exact nitrogen removal mechanism, the large production of N2O gas seems to be a result of the existence of a rapid growing heterotrophic deammonification process in the thermophilic system.

Agriculture↗
PubMed2001

Identification and characterization of a melanin-concentrating hormone receptor.

Melanin-concentrating hormone (MCH), a neuropeptide expressed in central and peripheral nervous systems, plays an important role in the control of feeding behaviors and energy metabolism. An orphan G protein-coupled receptor (SLC-1/GPR24) has recently been identified as a receptor for MCH (MCHR1). We report here the identification and characterization of a G protein-coupled receptor as the MCH receptor subtype 2 (MCHR2). MCHR2 has higher protein sequence homology to MCHR1 than any other G protein-coupled receptor. The expression of MCHR2 has been detected in many regions of the brain. In contrast to MCHR1, which is intronless in the coding region and is located at the chromosomal locus 22q13.3, the MCHR2 gene has multiple exons and is mapped to locus 6q21. MCHR2 is specifically activated by nanomolar concentrations of MCH, binds to MCH with high affinity, and signals through Gq protein. This discovery is important for a full understanding of MCH biology and the development of potential therapeutics for diseases involving MCH, including obesity.

Alternative Splicing↗
PubMed2001

Endothelial differentiation gene-2 receptor is involved in lysophosphatidic acid-dependent control of 3T3F442A preadipocyte proliferation and spreading.

EDG-2, EDG-4, EDG-7, and PSP24 genes encode distinct lysophosphatidic acid (LPA) receptors. The aim of the present study was to determine which receptor subtype is involved in the biological responses generated by LPA in preadipocytes. Growing 3T3F442A preadipocytes express EDG-2 and EDG-4 mRNAs, with no expression of EDG-7 or PSP24 mRNAs. Quantitative reverse transcriptase-polymerase chain reaction revealed that EDG-2 transcripts were 10-fold more abundant than that of EDG-4. To determine the involvement of the EDG-2 receptor in the responses of growing preadipocytes to LPA, stable transfection of antisense EDG-2 cDNA was performed in growing 3T3F442A preadipocytes. This procedure, led to a significant and specific reduction in EDG-2 mRNA and protein. This was associated with a significant alteration in the effect of LPA on both cell proliferation and cell spreading. Finally, the differentiation of growing preadipocytes into quiescent adipocytes led to a strong reduction in the level of EDG-2 transcripts. Results demonstrate the significant contribution of the EDG-2 receptor in the biological responses generated by LPA in 3T3F442A preadipocytes.

3T3 Cells↗
PubMed2001

Computer simulation of the distribution of aluminum speciation in soil solutions in equilibrium with the mineral phase imogolite.

The speciation of aluminum (Al) is a critical issue when evaluating the environmental and biological significance of elevated Al concentrations in soil solutions caused by acidic precipitation. Numerous studies have revealed that, with increased concentrations of silica acid in soil, the activity of Al species in soil solutions is greatly modified by SiO(4)(2-). However, thus far there has been little thorough theoretical modeling of this subject. This paper reports a computer simulation of the distribution of Al speciation in soil solutions in equilibrium with the mineral phase imogolite based on a chemical equilibrium calculation. The unique characteristic associated with imogolite reported by previous researchers can be explained theoretically by the proposed model. The dissolved silica has a remarkable influence on Al speciation: increasing concentrations of silica acid may effectively inhibit the formation of polymeric alumino-hydroxo species, and, furthermore, detoxify Al toxicity to plants.

Aluminum↗
PubMed2001

Simultaneous measurement of denitrification and nitrogen fixation using isotope pairing with membrane inlet mass spectrometry analysis.

A method for estimating denitrification and nitrogen fixation simultaneously in coastal sediments was developed. An isotope-pairing technique was applied to dissolved gas measurements with a membrane inlet mass spectrometer (MIMS). The relative fluxes of three N(2) gas species ((28)N(2), (29)N(2), and (30)N(2)) were monitored during incubation experiments after the addition of (15)NO(3)(-). Formulas were developed to estimate the production (denitrification) and consumption (N(2) fixation) of N(2) gas from the fluxes of the different isotopic forms of N(2). Proportions of the three isotopic forms produced from (15)NO(3)(-) and (14)NO(3)(-) agreed with expectations in a sediment slurry incubation experiment designed to optimize conditions for denitrification. Nitrogen fixation rates from an algal mat measured with intact sediment cores ranged from 32 to 390 microg-atoms of N m(-2) h(-1). They were enhanced by light and organic matter enrichment. In this environment of high nitrogen fixation, low N(2) production rates due to denitrification could be separated from high N(2) consumption rates due to nitrogen fixation. Denitrification and nitrogen fixation rates were estimated in April 2000 on sediments from a Texas sea grass bed (Laguna Madre). Denitrification rates (average, 20 microg-atoms of N m(-2) h(-1)) were lower than nitrogen fixation rates (average, 60 microg-atoms of N m(-2) h(-1)). The developed method benefits from simple and accurate dissolved-gas measurement by the MIMS system. By adding the N(2) isotope capability, it was possible to do isotope-pairing experiments with the MIMS system.

Geologic Sediments↗
PubMed2000

A sphingosine-1-phosphate receptor regulates cell migration during vertebrate heart development.

Coordinated cell migration is essential in many fundamental biological processes including embryonic development, organogenesis, wound healing and the immune response. During organogenesis, groups of cells are directed to specific locations within the embryo. Here we show that the zebrafish miles apart (mil) mutation specifically affects the migration of the heart precursors to the midline. We found that mutant cells transplanted into a wild-type embryo migrate normally and that wild-type cells in a mutant embryo fail to migrate, suggesting that mil may be involved in generating an environment permissive for migration. We isolated mil by positional cloning and show that it encodes a member of the lysosphingolipid G-protein-coupled receptor family. We also show that sphingosine-1-phosphate is a ligand for Mil, and that it activates several downstream signalling events that are not activated by the mutant alleles. These data reveal a new role for lysosphingolipids in regulating cell migration during vertebrate development and provide the first molecular clues into the fusion of the bilateral heart primordia during organogenesis of the heart.

Alleles↗
PubMed2000

Sphingosine 1-phosphate-induced cell proliferation, survival, and related signaling events mediated by G protein-coupled receptors Edg3 and Edg5.

Sphingosine 1-phosphate (S1P) regulates cell proliferation, apoptosis, motility, and neurite retraction. Contradictory reports propose that S1P acts as either an intracellular second messenger or an extracellular ligand for cell-surface receptors. Hence, the precise signaling mechanisms mediating the diverse cellular effects of S1P remain to be determined. Here, we investigate whether S1P stimulation of cell proliferation, survival, and related signaling events can be mediated by the recently cloned Edg family members of G protein-coupled receptors. We observed that S1P treatment significantly increased proliferation of HTC4 hepatoma cells stably transfected with human S1P receptor Edg3 or Edg5, which was attributable to stimulation of cell growth and inhibition of apoptosis caused by serum starvation. Edg3 and Edg5 transduced S1P-evoked signaling events relevant to cell proliferation and survival, including activation of the ERK/MAP kinases, and immediate-early induction of c-Jun and c-Fos. Trancriptional activation of reporter genes for the c-fos promoter and the serum response element by Edg3 and Edg5 transfected in Jurkat cells was inhibited by pertussis toxin and C3 exoenzyme, implicating G(i/o)- and Rho-dependent pathways. Our data also indicated that Edg3 and Edg5 mediated the serum response element activation through transcriptional factors Elk-1 and serum response factor. Thus, specific G protein-coupled receptors Edg3 and Edg5 account for, at least in part, S1P-induced cell proliferation, survival, and related signaling events.

Cell Division↗
PubMed2000

Molecular identification and characterization of G protein-coupled receptors for lysophosphatidic acid and sphingosine 1-phosphate.

Lysophospholipid mediators, lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), play important roles in diverse biological processes, including cell proliferation, survival, cytoskeleton changes, migration, wound healing, angiogenesis, tumor invasion, and embryonic development. The recent breakthrough in cloning and identification of several G-protein-coupled receptors for LPA and S1P has provided tools to dissect the complex mechanisms by which these lysophospholipids exert their (patho)physiological functions. Here, strategies and efforts in cloning and identifying the Edg family receptors for LPA and S1P are reviewed. Reporter gene assays used to take advantage of signaling properties of LPA and S1P, and to overcome intrinsic difficulties unique to this system, are described. From these experimental approaches, important lessons can be learned and applied to future studies of signal transduction of lysophospholipid receptors.

Animals↗
PubMed2000

RNase L-independent specific 28S rRNA cleavage in murine coronavirus-infected cells.

We characterized a novel 28S rRNA cleavage in cells infected with the murine coronavirus mouse hepatitis virus (MHV). The 28S rRNA cleavage occurred as early as 4 h postinfection (p.i.) in MHV-infected DBT cells, with the appearance of subsequent cleavage products and a decrease in the amount of intact 28S rRNA with increasing times of infection; almost all of the intact 28S rRNA disappeared by 24 h p.i. In contrast, no specific 18S rRNA cleavage was detected in infected cells. MHV-induced 28S rRNA cleavage was detected in all MHV-susceptible cell lines and all MHV strains tested. MHV replication was required for the 28S rRNA cleavage, and mature cytoplasmic 28S rRNA underwent cleavage. In certain combination of cells and viruses, pretreatment of virus-infected cells with interferon activates a cellular endoribonuclease, RNase L, that causes rRNA degradation. No interferon was detected in the inoculum used for MHV infection. Addition of anti-interferon antibody to MHV-infected cells did not inhibit 28S rRNA cleavage. Furthermore, 28S rRNA cleavage occurred in an MHV-infected mouse embryonic fibroblast cell line derived from RNase L knockout mice. Thus, MHV-induced 28S rRNA cleavage was independent of the activation of RNase L. MHV-induced 28S rRNA cleavage was also different from apoptosis-related rRNA degradation, which usually occurs concomitantly with DNA fragmentation. In MHV-infected 17Cl-1 cells, 28S rRNA cleavage preceded DNA fragmentation by at least 18 h. Blockage of apoptosis in MHV-infected 17Cl-1 cells by treatment with a caspase inhibitor did not block 28S rRNA cleavage. Furthermore, MHV-induced 28S rRNA cleavage occurred in MHV-infected DBT cells that do not show apoptotic signs, including activation of caspase-3 and DNA fragmentation. Thus, MHV-induced 28S rRNA cleavage appeared to differ from any rRNA degradation mechanism described previously.

Animals↗
PubMed2000

Lysophosphatidic acid and sphingosine 1-phosphate stimulate endothelial cell wound healing.

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) are potent lipid growth factors with similar abilities to stimulate cytoskeleton-based cellular functions. Their effects are mediated by a subfamily of G protein-coupled receptors (GPCRs) encoded by endothelial differentiation genes (edgs). We hypothesize that large quantities of LPA and S1P generated by activated platelets may influence endothelial cell functions. Using an in vitro wound healing assay, we observed that LPA and S1P stimulated closure of wounded monolayers of human umbilical vein endothelial cells and adult bovine aortic endothelial cells, which express LPA receptor Edg2, and S1P receptors Edg1 and Edg3. The two major components of wound healing, cell migration and proliferation, were stimulated individually by both lipids. LPA and S1P also stimulated intracellular Ca(2+) mobilization and mitogen-activated protein kinase (MAPK) phosphorylation. Pertussis toxin partially blocked the effects of both lipids on endothelial cell migration, MAPK phosphorylation, and Ca(2+) mobilization, implicating G(i)/(o)-coupled Edg receptor signaling in endothelial cells. LPA and S1P did not cross-desensitize each other in Ca(2+) responses, suggesting involvement of distinct receptors. Thus LPA and S1P affect endothelial cell functions through signaling pathways activated by distinct GPCRs and may contribute to the healing of wounded vasculatures.

Animals↗
PubMed2000

[Effect of kidney-replenishing herbs on ovarian function of dexamethasone-induced osteoporosis in rats].

OBJECTIVE: To investigate the effect of Kidney-replenishing herbs (KRH) on ovarian function of experimental rats with dexamethasone-induced osteoporosis (OP). METHODS: Radioimmunoassay was used to analyse blood level of growth hormone (GH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol (E2), progesterone (P), testosterone (T) and prolactin (PRL) of animals and data of three groups, the normal control group, the pathologic control group (non-treated OP model) and the treated group (model rats treated with KRH) were compared. Weight and histomorphological features of ovary and uterus of the rats were also observed. RESULTS: As compared with the normal control group, levels of GH, LH, FSH, E2 and P in the pathologic control group were significantly lowered (P < 0.05), and the weight of ovary and uterus decreased (P < 0.05). In comparison of the treated group and the pathologic group, GH, LH, FSH, E2 and P levels were significantly higher and weight of ovary and uterus heavier in the treated group (P < 0.05). No obvious changes occurred in T and PRL levels. KRH showed markedly improving effect on the ovarian and uterine morphological construction of rats. CONCLUSIONS: KRH could elevate the level of GH, LH, FSH, E2 and P, increase the weight and improve the histomorphologic features of ovary and uterus in OP rats, it demonstrated that KRH has therapeutic effect in treating dexamethasone-induced OP rats.

Animals↗
PubMed2000

[Study on relationship between estrogen receptor gene polymorphism and syndrome differentiation typing of female postmenopausal osteoporosis in Traditional Chinese medicine].

OBJECTIVE: To study the relationship between estrogen gene polymorphism and TCM Syndrome Differentiation of female postmenopausal osteoporosis in China. METHODS: Two hundred and forty-six Chinese postmenopausal women, age 44-80 years, mean 65.8 years, using molecular biological method to analyze the endonuclease Pvu II, Xba I restriction fragment length polymorphisms (RFLPs), with dual X-ray bone mineral density absorption meter to determine the bone mineral densities of lumbar vertebra (L1-4) and femur (intertrochanter, femur neck, Ward's region) separately. The subjects were divided into Kidney Yin deficiency type, Kidney Yang deficiency type and both Kidney Yin-Yang deficiency type, to observe the relationship between TCM and bone density as well as estrogen receptor gene polymorphism, Pp(Pvu II) and Xx(Xba I) were used to express RFLPs, the capital P and X to express the deficit of restricting sites. RESULTS: Bone mineral density of PPxx gene type (n = 21) was obviously lower than that of other gene types (n = 225), lumbar (-0.71 +/- 0.46) g/cm2, intertrochanter (-0.31 +/- 0.58) g/cm2, femur neck (-0.84 +/- 0.66) g/cm2, Ward's region (-0.96 +/- 0.85) g/cm2, the TCM Syndrome Differentiation typing of this gene type belonged to both Kidney Yin-Yang deficiency type. CONCLUSION: Estrogen receptor gene RFLPs is related to TCM Syndrome Differentiation typing.

Adult↗
PubMed1999

Differential coupling of the sphingosine 1-phosphate receptors Edg-1, Edg-3, and H218/Edg-5 to the G(i), G(q), and G(12) families of heterotrimeric G proteins.

Sphingosine 1-phosphate (S1P) is one of several bioactive phospholipids that exert profound mitogenic and morphogenic actions. Originally characterized as a second messenger, S1P is now recognized to achieve many of its effects through cell surface, G protein-coupled receptors. We used a subunit-selective [(35)S]GTPgammaS binding assay to investigate whether the variety of actions exerted through Edg-1, a recently identified receptor for S1P, might be achieved through multiple G proteins. We found, employing both Sf9 and HEK293 cells, that Edg-1 activates only members of the G(i) family, and not G(s), G(q), G(12), or G(13). We additionally established that Edg-1 activates G(i) in response not only to S1P but also sphingosylphosphorylcholine; no effects of lysophosphatidic acid through Edg-1 were evident. Our assays further revealed a receptor(s) for S1P endogenous to HEK293 cells that mediates activation of G(13) as well as G(i). Because several of the biological actions of S1P are assumed to proceed through the G(12/13) family, we tested whether Edg-3 and H218/Edg-5, two other receptors for S1P, might have a broader coupling profile than Edg-1. Indeed, Edg-3 and H218/Edg-5 communicate not only with G(i) but also with G(q) and G(13). These studies represent the first characterization of S1P receptor activity through G proteins directly and establish fundamental differences in coupling.

Animals↗
PubMed1999

Prostaglandin E2 enhancement of interferon-gamma production by antigen-stimulated type 1 helper T cells.

Prostaglandin E2 (PGE2) is a potent mediator generated in immune tissues by cyclooxygenation of arachidonic acid. PGE2 affects T cell functions through four homologous G protein-coupled receptors termed EP1R, EP2R, EP3R, and EP4R that differ in tissue distribution and signaling. Antigen-evoked secretion of interferon-gamma (IFN-gamma) by sperm whale myoglobin-specific Th1 cells of DBA/2 mouse I-Ed-restricted clones, that express EP3Rs and EP4Rs, was enhanced a maximum of 3-fold by 10(-10) to 10(-8) M PGE2 and 2.5-fold each for the EP1R/EP3R-directed agonist sulprostone (10(-8) and 10(-7) M) and for the EP4R/EP3R/EP2R agonist misoprostol (10(-9) M). Neither PGE2 nor the synthetic analogs affected secretion of IFN-gamma by PMA plus ionomycin-stimulated clones of Th1 cells. Antigen-evoked secretion of IFN-gamma by influenza hemagglutinin-specific mouse lymph node Th1 cells, that also express EP3Rs and EP4Rs, was increased a maximum of 12-fold by 10(-9) to 10(-8) M PGE2, 14-fold by 10(-9) M sulprostone, and 10-fold by 10(-9) M misoprostol. Production of IFN-gamma by either type of Th1 cell was not affected significantly by 10(-6) M PGE2 alone. The generation of IFN-gamma by antigen-stimulated Th1 cells thus is significantly enhanced by physiologically relevant concentrations of PGE2.

Animals↗
PubMed1999

Predominance of CCR5-dependent HIV-1 subtype E isolates in Cambodia.

To investigate the genetic and biologic features of HIV-1 strains circulating in Cambodia, viruses from 95 HIV-1-seropositive individuals were subtyped by heteroduplex mobility assay (HMA) and 23 were further analyzed for their biologic characteristics. Eighty-nine individuals were clearly infected by HIV-1 subtype E. The other six samples were sequenced, together with 17 HMA subtype E samples. All but one of the 23 Cambodian env sequences clustered with previously described Thai and Vietnamese subtype E sequences, bearing a GPGQ motif at the tip of the V3 loop; the last had a GPGR motif and was phylogenetically equidistant from Asian and African subtype E viruses. Nonsyncytium-inducing, CCR5-dependent viruses predominated in patients of clinical stage B even in some with a high viral load and were detected in about 50% of the patients of stage C. All syncytium-inducing strains, mostly from AIDS patients, used both CCR5 and CXCR4. The presence of syncytium-inducing viruses did not correlate with the plasma viral load. These data show that CCR5-dependent HIV-1 subtype E is currently predominant in Cambodia. The analysis of clinical and virologic markers strongly supports the idea that dynamics of the viral population during subtype E infection in Southeast Asia is similar to that of subtype B infection in Europe and the United States.

Base Sequence↗