Biomedical subjects

G Xing

Publications and source records attributed to G Xing.

At least 19 recordsLinked to original sources

PubMed2005

Thyroid cancer in pregnancy.

OBJECTIVE: To compare stage at diagnosis, treatment and survival among pregnant women with thyroid cancer to non-pregnant women with thyroid cancer, and to assess the impact of treatment on maternal and perinatal outcomes. METHODS: A database containing maternal and newborn discharge records linked to the California Cancer Registry was queried to obtain information on all thyroid cancers from 1991-1999. Women with thyroid cancer occurring during pregnancy were compared to age-matched non-pregnant women with thyroid cancer. RESULTS: 595 cases of thyroid cancers were identified (129 antepartum and 466 postpartum). About 64% of thyroid cancers were diagnosed at stage 2 among pregnant women versus 58% among non-pregnant controls. The odds of thyroid cancer were 1.5 times higher among Asian/Pacific Islanders than among Non-Hispanic White women. Pregnancy had no significant effect on mortality after diagnosis of thyroid cancer. Thyroidectomy during pregnancy was not associated with adverse maternal or neonatal outcomes. CONCLUSIONS: Thyroid cancer discovered during or after pregnancy does not appear to have a significant impact on the prognosis of the disease.

Adenocarcinoma, Follicular↗

PubMed2002

The effects of isolation rearing on glutamate receptor NMDAR1A mRNA expression determined by in situ hybridization in Fawn hooded and Wistar rats.

Rats reared in social isolation exhibit a syndrome of behavioral and biochemical effects indicative of enhanced mesolimbic dopamine (DA) function. The precise nature of the neurodevelopmental changes that produce this state are unknown but result in enhanced DA neurotransmission in the nucleus accumbens (NAC). It was hypothesized that this may be the indirect result of chronic changes in glutamate NMDA receptor function. The same prediction has been made for Fawn hooded (FH) rats that exhibit some of the characteristic effects of isolation-reared rats when compared to Wistar rats. Therefore, mRNA levels of the NMDAR1A receptor subunit were determined by in situ hybridization and were quantified in the striatum, hippocampus and prefrontal cortex of FH and Wistar rats. Isolation rearing alone was not found to have an effect on the expression of NMDAR1A, while FH rats had reduced levels across most brain regions examined. In some areas of the striatum and prefrontal cortex, this effect was greater in FH isolates than in FH socials, while in the hippocampus, the opposite was observed.

Animals↗

PubMed2001

Increased sensitivity to seizures in repeated exposures to hyperbaric oxygen: role of NOS activation.

Nitric oxide is involved in the mechanism of hyperbaric oxygen (HBO(2)) brain toxicity as nitric oxide synthase (NOS) inhibitors delay latent time before the onset of seizures. The purpose of this study was to investigate if seizures affect sensitivity to convulsions during subsequent exposure to HBO(2) and to determine if NOS activity and expression is changed after HBO(2) seizures. Rats were exposed to 5 atm (gauge pressure) 100% O(2) until seizures recorded by electroencephalograph (EEG) and reexposed 1, 2, or 6 days later. Latency to seizures was significantly shorter (P<0.05) in animals reexposed 1 or 2 days after the first exposure. Activity of calcium-dependent NOS activity in cortex was significantly higher 1 and 2 days after seizures compared with controls (P<0.05), while calcium-independent NOS activity was not changed during the 6-day post-seizure interval. The expression of neuronal NOS (nNOS) protein determined by Western blot was higher 1 and 2 days after seizures (P<0.05), while the expression of endothelial (eNOS) and inducible (iNOS) remained unchanged. nNOS upregulation 1 and 2 days after seizures and protection against HBO(2) seizures by nNOS-specific inhibitor 7-nitroindazole (7-NI) suggest possible involvement of NO in the mechanism of increased sensitivity to HBO(2) in reexposures.

Animals↗

PubMed2001

Functional characterization of novel human ARFGAP3.

ADP ribosylation factors (ARFs) are critical in the vesicular trafficking pathway. ARF activity is controlled by GTPase-activating proteins (GAPs). We have identified recently a novel tentative ARF GAP derived from human fetal liver, ARFGAP3 (originally named as ARFGAP1). In the present study, we demonstrated that ARFGAP3 had GAP activity in vitro and remarked that the GAP activity of ARFGAP3 was regulated by phospholipids, i.e. phosphatidylinositol 4,5-diphosphate as agonist and phosphatidylcholine as antagonist. ARFGAP3 is a predominantly cytosolic protein, and concentrated in the perinuclear region. Its transient ectopic overexpression in cultured mammalian cells reduced the constitutive secretion of secreted alkaline phosphatase, indicating that ectopic overexpression of ARFGAP3 inhibits the early secretory pathway of proteins in vivo. These results demonstrated that ARFGAP3 is a novel GAP for ARF1 and might be involved in intracellular traffic of proteins and vesicular transport as predicted.

ADP-Ribosylation Factors↗

PubMed2001

Characterization and tissue expression of a novel human gene npdc1.

We report the molecular characterization of a novel human homologue of mouse npdc1 (neural proliferation, differentiation and control, 1) gene, designated human npdc1 (hnpdc1). hnpdc1 was identified by large-scale sequencing of fetal liver cDNA libraries and the full-length cDNA was obtained by PCR amplification. The hnpdc1 gene, which contains nine exons, was mapped to human chromosome 15. It encodes a polypeptide of 325 amino acids, which shows high homology (77% identity) to the mouse NPDC1. Sequence analysis has shown that hNPDC1 protein contains a putative signal peptide of 34 amino acids, a transmembrane segment, and a typical bipartite nuclear localization signal. Northern blot and dot blot hybridization indicates that, just like mnpdc1, hnpdc1 mRNA is strongly expressed in adult brain (especially in hippocampus, frontal lobe and temporal lobe) and about 1.82-fold higher in adult brain than that in fetal brain. Unlike mnpdc1, however, hnpdc1 contains two transcripts instead of only one (1.5 kb), and has high expression levels in prostate, pituitary gland, and mammary glands. These results support that hNPDC1 plays a role in the control of neural cell proliferation and differentiation, and suggest that it may be involved in the development of several secretion glands.

Amino Acid Sequence↗

PubMed2001

Proteomic analysis of apoptosis initiation induced by all-trans retinoic acid in human acute promyelocytic leukemia cells.

The irreversible destiny of apoptosis in its early stage might play a critical role in the apoptosis of human acute promyelocytic leukemia (APL) cell line induced by all-trans retinoic acid (ATRA). To characterize protein alterations during the apoptosis-initiation phase and to understand the metabolic status at that time, we investigated the protein profiles in the apoptosis-initiation phase of APL cell line HL-60 by proteomic analysis. ATRA-withdrawal was conducted to demonstrate that there was committed initiation phase of apoptosis triggered by 10(-6) M ATRA at day 3. Only after that time point, ATRA-treated cells irreversibly went to apoptosis. Also at that time point, the positive regulators of apoptosis such as STAT3 increased at protein level, whereas negative regulators (Bcl-2 and p-STAT3) decreased. In addition, caspase-3 also increased after that time. Furthermore, comparative proteomic analysis was utilized to examine the protein expression profiles during the initiation stage of apoptosis. Our results showed 12 upregulated and 7 downregulated proteins experiencing twofold alteration, including key regulators of signal transduction such as G-proteins and nucleic receptors, proteins related with metabolism, oxidation and reduction, proteins associated with the nucleus and cytoskeleton-related proteins. Some of them could be positive modulators to trigger apoptosis, whereas others could contribute to intracellular defense against apoptosis induced by exogenous triggers. The results above suggest that there is a subtle balance between apoptosis and the intracellular defense against apoptosis. Once the balance is disturbed, cells would irreversibly initiate to undergo the execution of apoptosis.

Amino Acids↗

PubMed2001

Designing metal-peptide models for protein structure and function.

Recent progress in the rational design of metal sites within peptide model systems shows increasing control in the placement of metals within helical bundles and inclusion of sophisticated elements such as second-sphere ligand interactions. A crystallographically characterized two-metal peptide model for diiron proteins represents a major achievement in de novo design methodologies. Increasingly complex and robust models for electron transfer through and between helices, and electrode-supported electron-transfer peptides, have been constructed. Design elements for peptide-supported ferredoxins and mononuclear Fe(II) and Zn(II) sites have been refined.

Amino Acid Sequence↗

PubMed2001

Developmental vulnerabilities to the onset and course of bipolar disorder.

Different types of psychosocial stressors have long been recognized as potential precipitants of both unipolar and bipolar affective episodes and the causative agents in posttraumatic stress disorder (PTSD). New preclinical data have revealed some of the neurobiological mechanisms that could convey the long-term behavioral and biochemical consequences of early stressors. Depending on the timing, quality, quantity, and degree of repetition, maternal deprivation stress in the neonatal rodent can be associated with lifelong anxiety-like behaviors, increases in stress hormones and peptides. and proneness to drug and alcohol administration, in association with acute changes in the rate of neurogenesis and apoptosis (preprogrammed cell death) and decrements in neurotrophic factors and signal transduction enzymes necessary for learning and memory. Patients with bipolar illness who have a history of early extreme adversity (physical or sexual abuse in childhood or adolescence), compared with those without, show an earlier onset of illness, faster cycling frequencies, increased suicidality, more Axis I and Axis II comorbidities (including alcohol and substance abuse), and more time ill in more than 2 years of prospective follow-up. These findings are subject to a variety of interpretations, but to the extent that the more severe course of bipolar illness characteristics are directly and causally related to these early stressful experiences, early recognition and treatment of high-risk children could be crucial in helping to prevent or ameliorate the long-term adverse consequences of these stressors.

Bipolar Disorder↗

PubMed2001

Water stress and accumulation of beta-N-oxalyl-L-alpha,beta-diaminopropionic acid in grass pea (Lathyrus sativus).

Grass pea seedlings were grown in an irrigated field. Roots of 15-day-old seedlings were treated with PEG, and leaves were studied. With the duration of PEG treatment, changes in the lipid peroxidation and activities of superoxide dismutase, catalase, peroxidase, and glutathione reductase as well as contents of hydrogen peroxide and beta-N-oxalyl-L-alpha,beta-diaminopropionic acid (ODAP) were assayed. The results indicate that with the duration of PEG treatment, activities of superoxide dismutase, peroxidase, and catalase decreased, whereas contents of hydrogen peroxide and ODAP, extent of lipid peroxidation, and activity of glutathione reductase increased. Both diethyldithiocarbamate and aminotriazole strongly inhibit activities of superoxide dismutase and catalase, respectively. At same time, the extent of lipid peroxidation was obviously increased. However, mannitol decreased the extent of lipid peroxidation. Diethyldithiocarbamate, aminotriazole, and mannitol do not affect the accumulation of ODAP. The observations suggest that there is no direct relationship between the accumulation of ODAP and the metabolism of free radicals. In addition, the relationship between water stress and ODAP accumulation in grass pea is discussed.

Amino Acids, Diamino↗

PubMed2001

Kainate receptor-mediated heterosynaptic facilitation in the amygdala.

Prolonged low-frequency stimulation of excitatory afferents to basolateral amygdala neurons results in enduring enhancement of excitatory synaptic responses. The induction of this form of synaptic plasticity is eliminated by selective antagonists of GluR5 kainate receptors and can be mimicked by the GluR5 agonist ATPA. Kainate receptor-mediated synaptic facilitation generalizes to include inactive afferent synapses on the target neurons, and therefore contrasts with other types of activity-dependent enduring synaptic facilitation that are input-pathway specific. Such heterosynaptic spread of synaptic facilitation could account for adaptive and pathological expansion in the set of critical internal and external stimuli that trigger amygdala-dependent behavioral responses.

Amygdala↗

PubMed2001

cDNA transfection of amino-terminal fragment of urokinase efficiently inhibits cancer cell invasion and metastasis.

Focusing of urokinase-type plasminogen activator (uPA) to the cell surface via binding to its specific receptor (uPAR, CD87) is critical for tumor invasion and metastasis. Consequently, the inhibition of uPA-uPAR interaction on the cell surface might be a promising anti-invasion and anti-metastasis strategy. We examined the effects of cDNA transfection of the human uPA amino-terminal fragment (ATF) on invasion and metastasis of cancer cells. First, a highly metastatic human lung giant-cell carcinoma cell line (PG), used as the target cell for evaluation of this effect, was demonstrated to express both uPA and uPAR. Then, ATF, which contains an intact uPAR binding site but is catalytically inactive, was designed as an antagonist of uPA-uPAR interaction and was transfected into PG cells. [(3)H]-Thymidine incorporation and cell growth curves indicated that expressed ATF did not affect the proliferation of transfected cells. However, analysis by scanning electron microscopy revealed that ATF changed the host cells from the typical invasive phenotype to a noninvasive one. Correspondingly, the modified Boyden chamber test in vitro showed that ATF expression significantly decreased the invasive capacity of transfected cells. Furthermore, in the spontaneous metastasis model, it was confirmed in vivo that expressed ATF remarkably inhibited lung metastasis of implanted ATF-transfected PG cells. In summary, autocrine ATF could act as an antagonist of uPA-uPAR interaction, and ATF cDNA transfection could efficiently inhibit the invasion and metastasis of the cancer cells. Inhibition of uPA-uPAR interaction on the cell surface might be a promising anti-invasion and anti-metastasis strategy.

Animals↗

PubMed2001

Hepatopoietin acts as an autocrine growth factor in hepatoma cells.

Hepatopoietin (HPO) is a novel human hepatotrophic factor. Its known function is mainly limited to supporting liver regeneration. Recently, it was shown by our laboratory that HPO acts as a mitogen for hepatoma cell lines and that there are HPO-specific receptors on the surface of these cells (Wang, G., et al., J Biol Chem 1999;274:11469-11472), indicating that HPO might be involved in oncogenesis in the liver. To study this hypothesis, we first conducted experiments in vitro to identify the existence of an autocrine loop of HPO/HPO receptor in hepatoma cell lines. It was demonstrated that HPO was actually expressed by hepatoma cells, such as HepG2, Bel 7402, and SMMC-7721, and secreted into the culture medium. Furthermore, it was shown that HPO-neutralizing antibody has an inhibitory effect on the uptake of tritiated thymidine by hepatoma cells. The results strongly suggest that HPO acts as an autocrine factor for hepatoma cells in vitro.

Aged↗

PubMed2001

Gene expression profiling in human fetal liver and identification of tissue- and developmental-stage-specific genes through compiled expression profiles and efficient cloning of full-length cDNAs.

Fetal liver intriguingly consists of hepatic parenchymal cells and hematopoietic stem/progenitor cells. Human fetal liver aged 22 wk of gestation (HFL22w) corresponds to the turning point between immigration and emigration of the hematopoietic system. To gain further molecular insight into its developmental and functional characteristics, HFL22w was studied by generating expressed sequence tags (ESTs) and by analyzing the compiled expression profiles of liver at different developmental stages. A total of 13,077 ESTs were sequenced from a 3'-directed cDNA library of HFL22w, and classified as follows: 5819 (44.5%) matched to known genes; 5460 (41.8%) exhibited no significant homology to known genes; and the remaining 1798 (13.7%) were genomic sequences of unknown function, mitochondrial genomic sequences, or repetitive sequences. Integration of ESTs of known human genes generated a profile including 1660 genes that could be divided into 15 gene categories according to their functions. Genes related to general housekeeping, ESTs associated with hematopoiesis, and liver-specific genes were highly expressed. Genes for signal transduction and those associated with diseases, abnormalities, or transcription regulation were also noticeably active. By comparing the expression profiles, we identified six gene groups that were associated with different developmental stages of human fetal liver, tumorigenesis, different physiological functions of Itoh cells against the other types of hepatic cells, and fetal hematopoiesis. The gene expression profile therefore reflected the unique functional characteristics of HFL22w remarkably. Meanwhile, 110 full-length cDNAs of novel genes were cloned and sequenced. These novel genes might contribute to our understanding of the unique functional characteristics of the human fetal liver at 22 wk.

Cloning, Molecular↗

PubMed2001

[Characteristics of N2O emissions from vegetal soils on Fildes peninsula, Antarctica].

The N2O fluxes from the vegetal soils were first measured on the Fildes peninsula, Antarctica, and the total N2O emission was also estimated in the summer 2 months. The daily variations of N2O fluxes appeared single-peak trend under the sunshine or rainy weather conditions but they were irregular under the snow weather conditions and inconsistent with the atmospheric temperatures. The seasonal variations of the N2O fluxes were affected by the temperature and rainfall. The conditions during the transitions between dry and wet seasons improved the N2O emission. The total N2O emissions from moss and lichen soils were 3.7152 kg and 2.5344 kg, respectively. It follows that the vegetal soils are the sources for the atmospheric N2O on the Fildes peninsula, Antarctica.

Antarctic Regions↗

PubMed2001

[Experimental study of anti-metastasis effect of urokinase amino-terminal fragment gene on human breast cancer cells].

OBJECTIVE: To explore the suppressive effects of urokinase amino-terminal fragment (ATF) gene on metastatic potential of human breast cancer cell line MCF-7. METHODS: A pcDNA3-ATF plasmid containing ATF cDNA under CMV promotor/enhancer control was constructed and transfected into MCF-7 cells by lipofectin. The expression of of uPA/uPAR and ATF in MCF-7 cells were analyzed by RT-PCR and Western blot. The effect of ATF expression on invasiveness in vitro, tumorigenesis and metastasis in vivo of MCF-7 cell was investigated. RESULTS: MCF-7 cells displayed an overexpression of uPA/uPAR. Expression of ATF was detected after ATF gene-transfection. The invasive capacity of ATF gene-transfected MCF-7 cells was decreased significantly. Although the tumorigenesis was not affected, the in vivo metastasis of ATF gene-transfected MCF-7 cells was remarkably inhibited. CONCLUSION: Suppression of invasiveness and metastasis of ATF-transfected MCF-7 cells is perhaps due to a competitive inhibition of interaction with endogenous uPA/uPAR.

3T3 Cells↗

PubMed2001

[Diagnosis and treatment of horizontal canal benign paroxysmal positional vertigo].

OBJECTIVE: To explore effective methods for the diagnosis and treatment of horizontal-canal benign paroxysmal positional vertigo (HC-BPPV). METHODS: Medical records from nine patients with HC-BPPV, treated between July 1996 and March 2000, were retrospectively analyzed. Data of complete history, audiograms, positional tests and neuro-otological examinations were collected. All patients were treated with a particle repositioning maneuver called the "barbecue rotation" which starts with the patient in the supine position and consists of three 90-degree head rotations towards the unaffected ear. RESULTS: HC-BPPV was characterized by brief attacks of intense vertigo that were induced mainly by rolling over in bed (9/9) and turning the head to either side while upright (5/9). In most cases, rotation to the pathological side from supine position caused a very intense horizontal nystagmus beating towards the undermost ear. Findings such as latency and fatigability, which are common features of posterior-canal BPPV (PC-BPPV), were not present. After the barbecue rotation, all patients had immediate and sustained relief of their attacks during the 4 to 15 months' follow up. CONCLUSION: HC-BPPV is different from PC-BPPV and other vertiginous diseases in typical presentations and positional testing results. The barbecue rotation is a successful method for curing the disorder.

Adult↗

PubMed2001

[A preliminary study of a hearing screening model for newborn].

OBJECTIVE: To search for a hearing screening model for newborn and to investigate the prevalence of newborn hearing loss in our country. METHODS: The distortion product otoacoustic emissions (DPOAE) was used to test the hearing in 2,998 of 3,075 newborns before discharge. Otoacoustic emissions (OAE) was again used for cases failed in the hospital screening 4 weeks later. Those cases failed in both screening steps were finally tested by auditory brainstem response (ABR). All infants failed in ABR test received diagnostic evaluation audiologically to identify the category and degree of hearing loss. The pass criterion of DPOAE was defined as signal-noise-ratio (SNR) exceeding 6 dB in 4 of 5 frequencies between 1.5-6 kHz. The pass criterion of ABR was the presence of wave V in response to 35 dB nHL click stimuli. RESULTS: The OAE screening in the hospital showed that 2,710 (90.4%) newborns passed the first test. Two hundred and sixty three of 288 newborns passed the second OAE screening after one month. Six of 25 infants failed in ABR test were eventually identified to be hearing impaired. CONCLUSION: Two-stages screening, combining OAE and ABR tests, may be an ideal model for newborn hearing screening. The prevalence of congenital hearing loss is similar to that reported in the literature.

Evoked Potentials, Auditory, Brain Stem↗

PubMed2000

Stimulation of the mitogen-activated protein kinase cascade and tyrosine phosphorylation of the epidermal growth factor receptor by hepatopoietin.

Hepatopoietin (HPO) is a novel human hepatotrophic growth factor, which specifically stimulates proliferation of cultured primary hepatocytes in vitro and liver regeneration after liver partial hepatectomy in vivo. Recently, the identification of the mitogenic effect of HPO on hepatoma cell lines and the existence of HPO-specific receptors indicate that HPO acts via its specific cell surface receptor. However, the molecular mechanism of HPO action is not fully elucidated. In this report, we examined the signal transduction events induced by HPO in hepatoma cell line (HepG2). Our results demonstrated that HPO induces phosphorylation of mitogen-activated protein kinase kinase and mitogen-activated protein kinase (MAPK) in a rapid and transient manner. HPO stimulates tyrosine phosphorylation of epidermal growth factor receptor (EGFR). Furthermore, we observed that both MAPK activation and the mitogenic effect of HPO on HepG2 cells were completely blocked by AG1478, a specific inhibitor of EGFR tyrosine kinase activity. However, the effects of HPO were not antagonized by an EGFR-blocking antibody, mAb528, which blocks the interaction between epidermal growth factor and EGFR, indicating that stimulation of tyrosine phosphorylation of EGFR by HPO was not mediated by epidermal growth factor. In contrast, genistein, a general tyrosine kinase inhibitor, significantly attenuated the tyrosine phosphorylation of EGFR in response to HPO. In conclusion, our results suggest that tyrosine phosphorylation of EGFR may play a critical role in MAPK activation and mitogenic stimulation by HPO.

Enzyme Inhibitors↗