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X Tang

Publications and source records attributed to X Tang.

At least 163 records · Page 9Linked to original sources
PubMed1998

Temperature-induced conformational changes in prosomatostatin-II: implications for processing.

Somatostatin (SRIF) is a 14-residue peptide hormone synthesized in the hypothalamus and pancreatic islets. SRIF-14 and an N-terminally extended form, SRIF-28, are generated by the proteolytic processing of an approx. 102-residue precursor prosomatostatin (proSRIF) at a single set of paired basic residues (Arg-Lys) and at a monobasic (Arg) site respectively. Previous work in our laboratory demonstrated that the propeptide of SRIF mediates intracellular sorting; we suggested that this information resides in the prohormone structure. To identify putative sorting domains we have investigated structural features of recombinant anglerfish proSRIF-II purified from Escherichia coli. Two species of proSRIF-II were obtained: a monomeric form and a disulphide-linked dimer. CD analyses revealed that monomeric proSRIF-II lacks appreciable periodic secondary structure; however, on slow heating (2 degrees C/min) and cooling, it assumed a predominantly alpha-helical conformation. When subjected to a second heating-and-cooling cycle, the alpha-helical conformation was maintained. In contrast, the dimeric form of proSRIF-II was predominantly alpha-helical and its helicity did not increase in response to heating and recooling. Our results suggest that proSRIF-II might exist in several different folding intermediate states.

Amino Acid Sequence↗
PubMed1998

Genomic organization and expression of a human gene for Myc-associated zinc finger protein (MAZ).

We have cloned and characterized the genomic structure of the human gene for Myc-associated zinc finger protein (MAZ), which is located on chromosome 16p11.2. This gene is transcribed as an mRNA of 2.7 kilobases (kb) that encodes a 60-kDa MAZ protein. A 40-kb cosmid clone was isolated that includes the promoter, five exons, four introns, and one 3'-untranslated region. All exon-intron junction sequences conform to the GT/AG rule. The promoter region has features typical of a housekeeping gene: a high G + C content (88. 4%); a high frequency of CpG dinucleotides, in particular within the region 0.5 kb upstream of the site of initiation of translation; and the absence of canonical TATA and CAAT boxes. An S1 nuclease protection assay demonstrated the presence of multiple sites for initiation of transcription around a site 174 nucleotides (nt) upstream of the ATG codon and such expression was reflected by the promoter activity of a MAZ promoter/CAT (chloramphenicol acetyltransferase) reporter gene. Cis-acting positive and negative elements controlling basal transcription of the human MAZ gene were found from nucleotides (nt) -383 to -248 and nt -2500 to -948. Moreover, positive and negative autoregulatory elements were also identified in the regions from nt -248 to -189 and from nt -383 to -248 after co-transfection of HeLa cells with plasmids that carried the MAZ promoter/CAT construct and the MAZ-expression vector. Our results indicate that the 5'-end flanking sequences are responsible for the promoter activities of the MAZ gene.

Amino Acid Sequence↗
PubMed1998

A novel integrin-activated pathway forms PKB/Akt-stimulatory phosphatidylinositol 3,4-bisphosphate via phosphatidylinositol 3-phosphate in platelets.

The aggregation of human platelets is an important physiological hemostatic event contingent upon receptor-dependent activation of the surface integrin alphaIIbbeta3 and subsequent binding of fibrinogen. Aggregating platelets form phosphatidylinositol 3, 4-bisphosphate (PtdIns(3,4)P2), which has been reported to stimulate in vitro the activity of the proto-oncogenic protein kinase PKB/Akt, as has phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3). It has been assumed that PtdIns(3,4)P2 is synthesized by either 5-phosphatase-catalyzed hydrolysis of PtdIns(3,4,5)P3 produced by phosphoinositide 3-kinase (PI3K) or phosphorylation by PI3K of PtdIns4P. We investigated the route(s) by which PtdIns(3,4)P2 is formed after directly activating alphaIIbbeta3 with anti-ligand-induced binding site Fab fragment and report that aggregation does not lead to the generation of PtdIns(3,4,5)P3, but to transient formation of PtdIns3P and generation of PtdIns(3,4)P2, the latter primarily by PtdIns3P 4-kinase. Both this novel pathway and the activation of PKB/Akt are inhibited by the PI3K inhibitor, wortmannin, and the calpain inhibitor, calpeptin, constituting the first evidence that PtdIns(3,4)P2 can stimulate PKB/Akt in vivo in the absence of PtdIns(3,4,5)P3. Integrin-activated generation of the second messenger PtdIns(3,4)P2 thus depends upon a route distinct from that known to be utilized initially by growth factors. This pathway is of potential general relevance to the function of integrins.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed1998

Alignment echo of spin-3/2 9Be nuclei: detection of ultraslow motion

It is demonstrated that the alignment echo of 9Be is quite useful for detecting ultraslow atomic motions in the metallic glass Zr46. 75Ti8.25Cu7.5Ni10Be27.5. The time scale of detectable atomic motion is between T2 = 1.5 ms and T1 of a few seconds. Similar to previous works of 2H NMR, the Jeener-Broekaert sequence is used to create quadrupolar order for spin-32 nuclei upon nonselective excitations. Since the chemical and Knight shift distributions are not negligible for 9Be, the proper choice of the dephasing time between the first and the second pulses is essential for achieving pure quadrupolar order. It is demonstrated experimentally that slow atomic motions contribute significantly to the decay of the alignment echo near the glass transition temperature. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Changes in tropospheric composition and air quality.

Reductions in stratospheric ozone (O3) cause increased penetration of ultraviolet-B (UV-B) radiation to the troposphere, and therefore increases in the chemical activity in the lower atmosphere (the troposphere). Tropospheric ozone levels are sensitive to local concentrations of nitrogen oxides (NOx) and hydrocarbons. Model studies suggest that additional UV-B radiation reduces tropospheric ozone in clean environments (low NOx), and increases tropospheric ozone in polluted areas (high NOx). Assuming other factors remain constant, additional UV-B will increase the rate at which primary pollutants are removed from the troposphere. Increased UV-B is expected to increase the concentration of hydroxyl radicals (OH) and result in faster removal of pollutants such as carbon monoxide (CO), methane (CH4), non-methane hydrocarbons (NMHCs), sulfur and nitrogen oxides, hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Concentrations of peroxy radicals (both inorganic and organic) are expected to increase, leading to higher atmospheric levels of hydrogen peroxide (H2O2) and organic peroxides. The effects of UV-B increases on tropospheric O3, OH, methane, CO, and possibly other tropospheric constituents, while not negligible, will be difficult to detect because the concentrations of these species are also influenced by many other variable factors (e.g., emissions). Trifluoroacetic acid (TFA, CF3COOH) is produced in the atmosphere by the degradation of HCFC-123 (CF3CHCl2), HCFC-124 (CF3CHFCl), and HFC-134a (CF3CH2F), which are used as substitutes for ozone-depleting substances. The atmospheric oxidation mechanisms of these replacement compounds are well established. Reported measurements of TFA in rain, rivers, lakes, and oceans show it to be a ubiquitous component of the hydrosphere, present at levels much higher than can be explained by reported sources. The levels of TFA produced by the atmospheric degradation of HFCs and HCFCs emitted up to the year 2020 are estimated to be orders of magnitude below those of concern, and to make only a minor contribution to the current environmental burden of TFA. No significant effects on humans or the environment have been identified from TFA produced by atmospheric degradation of HCFCs and HFCs. Numerous standard short-term studies have shown that TFA has, at most, moderate toxicity.

Air↗
PubMed1998

Biological and genetic differences between lung- and brain-derived isolates of maedi-visna virus.

During the epidemic caused by maedi-visna virus (MVV) of sheep in Iceland, the pulmonary affection, maedi, was the predominant clinical manifestation. In some flocks, however, a central nervous system (CNS) affection, visna, was the main cause of morbidity and mortality. As there is only one breed of sheep in the country, host factors did apparently not play an important role in the different clinical manifestations. To obtain some information on possible viral genetic determinants of neurotropism and neurovirulence we studied both phenotypic and genotypic properties of two maedi-visna virus strains; a strain that was originally isolated from the brain of sheep with encephalitis (visna), and another strain isolated from the lungs of a sheep suffering from pneumonia (maedi). The brain isolate was found to grow faster in sheep choroid plexus cells than the lung isolate, whereas the growth rate in macrophages was similar for the maedi and visna virus strains. Intracerebral inoculation indicated that the visna virus isolate induced more severe brain lesions than the maedi isolate. In addition, a pathogenic molecular clone derived from a visna strain (KV1772kv72/67) was tested for growth in sheep choroid plexus cells and macrophages. The molecularly cloned virus retained the fast growth rate in choroid plexus cells. The nucleotide sequence of the env gene and the U3 of the LTR was determined for the maedi strain and compared to that of the visna strains. There was an 11.7% difference in deduced amino acid sequence in the Env protein and a 6% difference in the LTR. The molecular clone KV1772kv72/67 will be a useful reagent for characterization of viral determinants of cell tropism in vitro and possibly neurovirulence in vivo.

Amino Acid Sequence↗
PubMed1998

Clinicopathological factors predicting retroperitoneal lymph node metastasis and survival in endometrial cancer.

BACKGROUND: By clarifying the significance of clinicopathological factors for retroperitoneal lymph node metastasis and survival of patients with endometrial cancer, we suggest ideas for optimal treatment of this disease. METHODS: A retrospective study was conducted in 310 women with endometrial cancer who underwent surgery with retroperitoneal lymphadenectomy. To evaluate retroperitoneal lymph node metastasis, age-adjusted and multivariable analyses were carried out for six clinicopathological factors including pathological grade, myometrial invasion, cervical invasion, peritoneal cytology, lymphatic permeation and vascular invasion. To evaluate survival, besides the above factors, a positive rate of metastasis of dissected retroperitoneal lymph nodes was included. RESULTS: In 40 patients (13%) with nodal metastasis, the average positive rate of metastasis of dissected retroperitoneal lymph nodes was 22%. For retroperitoneal lymph node metastasis, the odds ratio of deep myometrial invasion, cervical invasion and severe lymphatic permeation were 5.97, 2.72 and 12.01, respectively. For survival, the hazard ratios of the positive rates of metastasis of dissected retroperitoneal lymph nodes (both 25% and < 25%), positive peritoneal cytology and poor pathological grade were 7.10, 3.24, 3.82 and 3.27, respectively, and 5-year survival rates for them were 0, 50, 72 and 77%, respectively. CONCLUSIONS: For retroperitoneal lymph node metastasis, lymphatic permeation, deep myometrial invasion and cervical invasion were the independent prognostic factors. For survival, retroperitoneal lymph metastasis, poor pathological grades and positive peritoneal cytology were the independent prognostic factors. The positive rate of metastasis of dissected retroperitoneal lymph metastasis plays an important role in predicting survival of endometrial cancer. Lymph node biopsy is insufficient in treatment of this disease.

Adenocarcinoma↗
PubMed1998

Immunoreactive endothelin-1 and its receptors in human adrenal tissues.

To elucidate the pathophysiologic significance of endothelin-1 (ET-1) in adrenal and the mechanism for reduced responsiveness to exogenous ET-1 in aldosterone-producing adenoma (APA), we have investigated ET-1 receptors by radioligand binding assay (RBA) in human normal adrenal (NA), APA, idiopathic hyperaldosteronism (IHA), and pheochromocytoma (PHEO), immunoreactive (ir-) ET-1 content in NA, APA and PHEO by radioimmunoassay (RIA), and immunohistochemical staining of ET-1 with the peroxidase-anti-peroxidase (PAP) method in NA, APA, and PHEO. A single class of high-affinity binding sites for ET-1 was found in human NA and tumor tissues. Dissociation constant (Kd) values of ET-1 receptors were similar in NA, APA, and IHA, but maximal binding capacity (Bmax) of ET-1 receptors was lower in APA than in NA and IHA. Both Kd and Bmax in PHEO were higher than those in NA, APA, and IHA. Ir-ET-1 content in tumors of APA and PHEO were higher than in NA. Immunohistochemical staining was more intense in the tumor cells of APA and PHEO than in NA. These results suggest that the reduced response to exogenous ET-1 in APA could be related to downregulation of ET-1 receptors in the tumor. Increased ET-1 content and receptors may lead to hypersecretion of catecholamine in PHEO. ET-1 produced in normal and tumor adrenal tissues may regulate aldosterone and catecholamine secretion from adrenals in a paracrine/autocrine fashion.

Adrenal Gland Neoplasms↗
PubMed1998

Update on Pneumocystis carinii f. sp. hominis typing based on nucleotide sequence variations in internal transcribed spacer regions of rRNA genes.

Pneumocystis carinii f. sp. hominis isolates from 207 clinical specimens from nine countries were typed based on nucleotide sequence variations in the internal transcribed spacer regions I and II (ITS1 and ITS2, respectively) of rRNA genes. The number of ITS1 nucleotides has been revised from the previously reported 157 bp to 161 bp. Likewise, the number of ITS2 nucleotides has been changed from 177 to 192 bp. The number of ITS1 sequence types has increased from 2 to 15, and that of ITS2 has increased from 3 to 14. The 15 ITS1 sequence types are designated types A through O, and the 14 ITS2 types are named types a through n. A total of 59 types of P. carinii f. sp. hominis were found in this study.

Base Sequence↗
PubMed1998

Determination of copy number of rRNA genes in Pneumocystis carinii f. sp. hominis.

Differential PCR was performed to determine the copy number of rRNA genes in Pneumocystis carinii f. sp. hominis. Two different reference genes, thymidylate synthase (TS) and beta-tubulin (BTU) genes, were used. Primers for the internal transcribed spacer (ITS) region of nuclear rRNA genes and either the TS or BTU gene were mixed together to perform PCR on seven different bronchoalveolar lavage specimens from patients with P. carinii pneumonia. The radioactivity derived from the incorporated radioactive nucleotides of each PCR product band was then used to calculate the copy number of the ITS relative to that of the TS or BTU gene. The copy number ratio between the ITS and the TS gene was determined to be 0.8, and that between the ITS and the BTU gene was also 0.8. These results suggest that the ITS has the same copy number as the TS or BTU gene. Since the copy number of the TS or BTU gene is presumed to be 1, the results also suggest that P. carinii f. sp. hominis has only one copy of the ITS and thus one copy of the nuclear rRNA genes. Therefore, two types of ITS sequences derived from a specimen would indicate that the patient is infected by two types of P. carinii f. sp. hominis.

Bronchoalveolar Lavage Fluid↗
PubMed1998

[Effects of perinatal care on low birth weight].

OBJECTIVE: To explore the relationship between low birth weight and maternal factors during perinatal period. METHODS: Data of perinatal care were collected, sorted out and analyzed for 9,337 live births during 1993 to 1996, including 269 with low birth weight, in Xiucheng District of Jiaxing City, Zhejiang Province. RESULTS: Incidence of infants with low birth weight (less than 2,500 grams) averaged 2.88%, and appeared a gradual decreasing trend during the four years. Low birth weight correlated with maternal education, body height, number of gestations, antenatal check-ups, gestational age and the sex of babies. CONCLUSION: Systematic management of perinatal care for pregnant women will benefit to lowering the incidence of low birth weight, and perinatal and infant mortalies.

Adult↗
PubMed1998

[Regulatory factors of osteogenic phenotypical experession by fibroblasts in vitro].

In order to explore further the regulatory factors to the potentiality in inducing osteogenesis by fibroblasts, the fibroblasts were isolated, and purified from human skin, and were grown in incubation in the media of EGF, IL-6, TNF-alpha and BMP2 at different concentrations for two weeks, then, the markers for osteogenic features were investigated by biochemistry, histochemistry and electron microscopic observations. It was found that the combined use of TNF-alpha and BMP2 could stimulate fibroblasts to secrete alkaline phosphatase, osteocalcin and collagen, and the morphological changes of the fibroblasts were also very striking. In the extracellular matrix, the collagen fibrils, with or without periodicity, were arranged regularly or randomly oriented, and numerous minute calcium granules were interspersed among them. The fibroblasts were interwoven one on top of another in the form of multilayer structure and on the surface, there were secreting granules and piling up of calcium crystals which coalessed steadily and increased in size in forming bony nodules. It was considered that TNF-alpha and BMP2 were capable of inducing the fibroblasts to form bone.

Alkaline Phosphatase↗
PubMed1998

[Reversal of cancer multidrug resistance by Chinese medicine Ams-11, Fw-13 and Tul-17].

The aim of this project was to find some kinds of Chinese materia medica as effective agents for in vitro reversal of cancer multidrug resistance. Based on the present authors' previous researches, thirty-two kinds of Chinese medicine as research meterials were selected and examined. Using cell growth inhibit assay, the authors found that three of them--Ams-11, Fw-13 and Tul-17 in the doses free from cytotoxity could enhance the sensitivity of multidrug resistant cells to anti-cancer drugs in a dose-dependent way. It seemed that these three kinds of Chinese medicine might be potential effective reversal agents.

Cell Survival↗
PubMed1998

[Effect of vasectomy on apoptosis in spermatogenic cells of the male rat].

To explore the effect of vasectomy on apoptosis of spermatogenic cells, we have detected apoptosis in the testis of vasectomized and sham-operated adult rats within a period of 12 postoperative weeks by means of flow cytometry and TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuride triphosphate nick-end labeling) method. Flow cytometry found that, in vasectomized rat, the sub-haploid peak was higher and the percentage of cells with sub-haploid was increased. The total number of positive TUNEL cells in the vasectomized group was greater than that in the sham-operated group (P < 0.001). Compared with the same time-phased sham-operated subgroups, the number of apoptotic spermatogonia and primary spermatocytes in the testes of the subgroups 2 weeks, 6 weeks and 10 weeks after vasectomy as well as the number of spermatogonia of the subgroup 12 weeks after vasectomy were significantly higher (P < 0.05). These findings demonstrate that vasectomy could enhance the apoptosis of spermatogenic cells.

Animals↗
PubMed1998

[The prognostic value of heart rate variety on congestive heart failure of pregnant women].

OBJECTIVE: To explore the prognostic value of heart rate variety (HRV) on congestive heart failure (CHF) of pregnant women complicated with organic heart disease. METHOD: One hour ambulatary electrocardiography was performed in 61 pregnant women complicated with organic heart dieases at about the 28th-32th week in gestational period and 7 days after delivery respectively. RESULT: 9 patients occured CHF later, their HRV time domain index were significantly decreased (P < 0.001, P < 0.05), compared with patients without CHF as control group. 7 days after delivery, When the condition of CHF patients was improved. Their SD, SD SD value increased. CONCLUSION: HRV has some value of assessing the cardiac reserve and predicting the happen of Congestive Heart Failure in pregnant women complicated with organic heart disease.

Adult↗