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Biomedical subjects

Y Yan

Publications and source records attributed to Y Yan.

At least 145 records · Page 8Linked to original sources

[Arsenic exposure of residents in areas near Shimen arsenic mine].

OBJECTIVES: To investigate the levels of arsenic exposure of residents in the arsenic polluted areas near an arsenic mine. METHODS: To analyse the arsenic levels in environmental samples and hair in the polluted areas and a control area. RESULTS: In three villages of the polluted areas, arsenic levels in soil were 84.17 to 296.19 mg/kg, in river water 0.5 to 14.5 mg/L, in well water and tap water lower than 0.05 mg/L, in rice 0.196 to 0.620 mg/kg. Arsenic intake amounted 195 to 1129 micrograms/day. In the hair, the arsenic contents were from 0.972 to 2.459 micrograms/g, increasing with aging. CONCLUSION: In the areas near Shimen arsenic mine, arsenic pollution was serious. The levels of arsenic exposure of residents were equal to or even over that of the severe cases of chronic arsenic poisoning reported domestically and abroad.

Adult↗

Metal-ion binding and limited proteolysis of betabellin 15D, a designed beta-sandwich protein.

Betabellin 15D is a 64-residue, disulfide-bridged homodimer. When folded into a beta structure, the protein is predicted to have two clusters of three histidine residues, each cluster able to bind a divalent metal ion. When the protein was incubated with Cu2+, Zn2+, Co2+, or Mn2+, metal complexes of betabellin 15D were observed by electrospray-ionization mass spectrometry. The relative abundances of the ionic complexes suggested an order of affinities of Cu2+ > Zn2+ > Co2+ > Mn2+, consistent with solution-phase affinities for nitrogen- or sulfur-containing ligands. Limited proteolysis of betabellin 15D by immobilized pepsin, as measured by nanoelectrospray-ionization mass spectrometry, showed that the Phe12-Ser13 peptide bond of betabellin 15D was cleaved more slowly in the presence of Cu2+ than in its absence. Because Cu2+ has little or no effect on the catalytic rate of pepsin, the slower cleavage of the Phe12-Ser13 peptide bond may be due to its decreased accessibility caused by Cu(2+)-induced folding of betabellin 15D.

Amino Acid Sequence↗

Atomic Structures of Oxygen-associated Defects in Sintered Aluminum Nitride Ceramics.

: Convergent-beam electron diffraction and Z-contrast imaging are used to study oxygen-associated defects, flat inversion domain boundaries, dislocations, and interfaces in sintered AlN ceramics. The structures of these defects are directly derived from atomic-resolution Z-contrast images. The flat inversion domain boundaries contain a single Al-O octahedral layer and have a stacking sequence of.bAaB-bAc-CaAc., where -cAb- indicates the single octahedral layer. The expansion at the flat inversion domain boundaries is measured to be 0.06 (+/-0.02) nm. The interfaces between 2H- and polytypoid-AlN are found to be also inversion domain boundaries but their stacking sequence differs from that of the flat inversion domain boundaries.

Journal Article↗

Rural youth and youth culture in north China.

This article describes how economic reforms have transformed the local world of village life in North China, specifically the emergence of a rural "youth culture" that reflects urban values and styles. This culture has both challenged and enriched rural China's tradition and its more recent communal structure, a change that reshapes the relations amongst family members of different age cohorts as well as between peasants and cadres, it is argued that this transformation in the Chinese countryside holds opportunities to improve living conditions and unmake the constraints of tradition and the modern nation-state on life chances and everyday experience. The sheer number of rural youth in China suggests that the future impact of this transformation on social realities could be enormous.

Adolescent↗

Increased expression of hepatic DNA methyltransferase in smokers.

The DNA methyltransferase enzyme (DNA MTase) catalyzes DNA methylation at cytosines in CpG dinucleotides. 5-Methylcytosine modification of DNA is important in gene regulation, DNA replication, chromatin organization and disease. Increased levels of DNA MTase have been associated with the initiation and promotion of cancer. This study was conducted to assess whether cigarette smoking and other factors, such as age and gender, influence DNA MTase expression in nontumorous tissue. DNA MTase was significantly (p<0.05) higher in samples from cigarette smokers; the mean level of DNA MTase mRNA was almost 2-fold higher in these samples than in those from nonsmokers. Levels of DNA MTase mRNA were higher in samples from females than in those from males, but the difference was not statistically significant. Age was not associated with DNA MTase levels. Increased levels of DNA MTase in individuals who smoke may indicate a greater susceptibility to the risk of cancer since increased levels of this enzyme are found in cancer cell lines and human tumors. The results of this study suggest that further investigations of increased expression of this enzyme as a predisposing factor for cancer susceptibility are needed.

Adolescent↗

Absence of cancer-associated changes in human fibroblasts immortalized with telomerase.

The ectopic expression of telomerase in normal human cells results in an extended lifespan, indicating that telomere shortening regulates the timing of cellular senescence. As telomerase expression is a hallmark of cancer, we investigated the long-term effects of forced expression of human telomerase catalytic component (hTERT) in normal human fibroblasts. In vitro growth requirements, cell-cycle checkpoints and karyotypic stability in telomerase-expressing cells are similar to those of untransfected controls. In addition, co-expression of telomerase, the viral oncoproteins HPV16 E6/E7 (which inactivate p53 and pRB) and oncogenic HRAS does not result in growth in soft agar. Thus, although ectopic expression of telomerase in human fibroblasts is sufficient for immortalization, it does not result in changes typically associated with malignant transformation.

Catalytic Domain↗

In planta localization of a beta-1,4-endoglucanase secreted by Heterodera glycines.

Polyclonal sera specific to beta-1,4-endoglucanases (cellulases) synthesized in the subventral esophageal gland cells of the soybean cyst nematode, Heterodera glycines, were used to provide the first identification of a nematode esophageal gland protein that is secreted into host plant tissue. Sera generated to proteins encoded by Hg-eng-1 and Hg-eng-2 (endoglucanases) did not cross-react with soybean root proteins on Western blots (immunoblots) or in immunofluorescence microscopy of noninoculated (control) soybean root sections. In cross sections of soybean roots at 24 h after inoculation of roots with second-stage juveniles of H. glycines, HG-ENG-1 was localized within the nematode's subventral gland cells and was not detected in root tissue. HG-ENG-2 was localized within the subventral gland cells and was secreted from the juvenile's stylet into root cortical tissue at 24 h after inoculation of roots with second-stage juveniles of H. glycines. HG-ENG-2 was localized along the juvenile's migratory path through the root cortex.

Animals↗

Developmental expression of secretory beta-1,4-endoglucanases in the subventral esophageal glands of Heterodera glycines.

Two beta-1,4-endoglucanases (EGases), Hg-eng-1 and Hg-eng-2, were recently cloned from the soybean cyst nematode, Heterodera glycines, and their expression was shown in the subventral esophageal glands of hatched second-stage juveniles (J2). We examined the expression of these EGases in the subventral glands of all post-embryonic life stages of H. glycines by in situ hybridization and immunolocalization. The first detectable accumulation of EGase mRNAs occurred in the subventral glands of unhatched J2. EGase transcripts remained detectable in J2 after hatching and during subsequent root invasion. However, in late parasitic J2 and third-stage juveniles (J3), the percentage of individuals that showed EGase transcripts decreased. In female fourth-stage juveniles and adult females, EGase transcripts were no longer detected in the subventral glands. EGase hybridization signal reappeared in unhatched males coiled within the J3 cuticle, and transcripts were also present in the subventral glands of migratory adult males. Immunofluorescence labeling showed that EGase translation products are most abundantly present in the subventral glands of preparasitic J2, migratory parasitic J2, and adult males. The presence of EGases predominantly in the migratory stages suggests that the enzymes are used by the nematodes to soften the walls of root cells during penetration and intracellular migration.

Animals↗

Removal of strontium by the chelating agent acetylamino propylidene diphosphonic acid in rats.

Studies of the effects of the chelating agent, calcium acetylamino propylidene diphosphonic acid (Ca-APDA), on the removal of radioactive strontium with two administration modalities were carried out in rats. The parenteral (intraperitoneal) administration of 150, 300, or 600 mg kg(-1) Ca-APDA was carried out for 3 d, 10 min after exposure of the animals to the strontium injection. On the first day post-treatment, the retention of strontium in the whole body decreased to 90.1%, 83.9%, and 35.1% that of the control level, respectively. The strontium deposited in femur of 600 mg kg(-1) Ca-APDA group was lowered to 28.4% of the control value. A single oral dose of 600 mg kg(-1) Ca-APDA administered simultaneously with, or 10 min after, oral administration of strontium, radionuclide retention in the whole body was reduced after 1 d to 42.9% and 31.9% of the control, respectively; meanwhile the strontium deposited in the femur was reduced to 16.9% and 29.3% of the control. In conclusion, the results indicate the efficacy of the new agent, Ca-APDA, to remove radioactive strontium from the body, or to inhibit the strontium intestinal absorption, in radio-strontium contaminated individuals.

Administration, Oral↗

Correlates of dissatisfaction with treatment in patients with prostate cancer diagnosed through screening.

PURPOSE: We evaluated correlates of patient reported dissatisfaction with treatment of prostate cancer detected by screening. MATERIALS AND METHODS: We performed a cross-sectional retrospective study to evaluate the correlates of dissatisfaction with treatment in 1,651 patients in whom prostate cancer was detected through serial screening. We included demographic and clinical characteristics in the independent and control variables, and we validated measurements of quality of life outcomes. RESULTS: Overall 11% of patients were dissatisfied with the treatment received. Differences in the rates of dissatisfaction with treatment were not statistically significant across treatment groups (11% for retropubic radical prostatectomy, 21% for perineal radical prostatectomy, 14% for radiotherapy, 8% for observation, 8% for hormonal treatment and 4% for cryoablation, p = 0.1). Patient age, race, followup interval, marital status, education and co-morbid conditions were not significant correlates of dissatisfaction with treatment (for all characteristics p> or =0.05). Urinary function and bothersomeness were associated with dissatisfaction with treatment (p<0.0001), whereas sexual function and bothersomeness were not (p>0.05). Multivariate analysis revealed that urinary function and bothersomeness were also the only significant correlates of dissatisfaction with treatment. CONCLUSIONS: Of patients in whom prostate cancer was detected by screening 11% were dissatisfied with treatment. Urinary function and bothersomeness were the only important correlates of dissatisfaction.

Aged↗

The septal chondromucosal island pedicle flap: anatomic study and clinical application.

A study was made of the facial regions of 10 fresh cadavers. The vascular anatomy of the perinasal region and the septum consistently confirmed the existence of a nasal alar basal artery and a nasal alar basal nerve to the septum. A new septal chondromucosal flap, supplied by the nasal alar basal artery and nerve, is proposed in this article. The composite flap can be used safely to restore partial or entire tarsoconjunctival defects of the upper or lower eyelid or combined defects of the upper and lower eyelid.

Adult↗

Purification, solution properties and crystallization of SIV integrase containing a continuous core and C-terminal domain.

The C-terminal two-thirds segment of integrase derived from the simian immunodeficiency virus has been cloned, expressed in Escherichia coli, and purified to greater than 95% homogeneity. The protein encompasses amino-acid residues 50-293 and contains a F185H substitution to enhance solubility. In dilute solutions at concentrations below 1 mg ml(-1), the enzyme is predominantly dimeric. At the higher concentrations (>10 mg ml(-1)) required to enable crystallization, the enzyme self-associates to form species with molecular weights greater than 200 kDa. Despite the apparent high aggregation in solution, the enzyme crystallizes from a 8%(v/v) polyethylene glycol (molecular weight 6000) solution in a form suitable for X-ray diffraction studies. The resulting single crystals belong to the space group P2(1)2(1)2(1), with unit-cell parameters a = 79.76, b = 99.98, c = 150.2 A, alpha = beta = gamma = 90 degrees and Z = 4. Under X-ray irradiation generated with a rotating-anode generator, the crystals diffract to 2.8 A resolution and allow collection of a native 3 A resolution diffraction data set.

Cloning, Molecular↗

Crystallization and preliminary X-ray analysis of the Escherichia coli UDP-MurNAc-tripeptide D-alanyl-D-alanine-adding enzyme (MurF).

Crystals of the Escherichia coli UDP-MurNAc-tripeptide D-Ala-D-Ala-adding protein (MurF), which catalyzes the formation of the last metabolite of the bacterial cell-wall building block, have been grown in hanging-drop vapor-diffusion trials using PEG 8K as a precipitating agent. The crystals belong to hexagonal space group P6(1) or P6(5), with unit-cell dimensions a = b = 74, c = 425 A. The asymmetric unit contains two molecules, with a crystal volume per protein mass (V(m)) of 3.4 A(3) Da(-1) and a solvent content of about 64% by volume. A native data set to 2.8 A resolution has been obtained from a frozen crystal using a synchrotron X-ray source.

Base Sequence↗

Appropriate regulation of renin and blood pressure in 45-kb human renin/human angiotensinogen transgenic mice.

The renin-angiotensin system is normally subject to servo control mechanisms that suppress plasma renin levels in response to increased blood pressure and increase plasma renin levels when blood pressure falls. In most species, renin is rate limiting, and angiotensinogen circulates at a concentration close to the Km, so varying the concentration of either can affect the rate of angiotensin formation. However, only the plasma renin level responds to changes in blood pressure and sodium balance to maintain blood pressure homeostasis. Therefore, the high plasma human renin levels and the hypertension of mice and rats containing both human renin and angiotensinogen transgenes indicate inappropriate regulation of renin and blood pressure. These anomalies led us to develop new lines of transgenic mice with a longer human renin gene fragment (45 kb) than earlier lines (13 to 15 kb). Unlike their predecessors, the 45-kb hREN mice secrete human renin only from the kidneys, and both the human and mouse renins respond appropriately to physiological stimuli. To determine whether blood pressure is also regulated appropriately, we crossed these new 45-kb hREN mice with mice containing the human angiotensinogen gene. All doubly transgenic mice were normotensive like their singly transgenic and nontransgenic littermates. Moreover, among doubly transgenic mice, both human and mouse plasma renin concentrations were suppressed relative to the singly transgenic 45-kb hREN mice. These findings demonstrate the importance of appropriate cell and tissue specificity of gene expression in constructing transgenic models and affirm the pivotal role played by renal renin secretion in blood pressure control.

Aging↗

Chemopreventive effects of tea extracts and various components on human pancreatic and prostate tumor cells in vitro.

Pancreatic and prostate cancers pose serious problems to human health. To determine the potential for chemopreventive intervention against pancreatic and prostate cancers, black and green tea extracts and components of these extracts were examined in vitro for their effect on tumor cell growth. Components included a mixture of polyphenols from green tea (GTP), mixtures of polyphenols (BTP) and of theaflavins (MF) from black tea, and the purified components epicatechin-3-gallate (ECG) and epigallocatechin-3-gallate (EGCG). Two human cell lines, pancreatic adenocarcinoma (HPAC) and prostate tumor (LNCaP), were exposed to these agents for 24 hours. Results showed inhibition (approx 90%) of cell growth in pancreatic tumor cells by black and green tea extracts (0.02%). GTP (10 micrograms/ml) and MF (100 micrograms/ml) significantly inhibited growth (approx 90%); ECG and EGCG inhibited growth as well (approx 95%). Black and green tea extracts, GTP, and EGCG decreased the expression of the K-ras gene, as determined by reverse transcription-polymerase chain reaction. Green and black tea extracts decreased the multidrug-resistant gene (mdr-1), although GTP and EGCG increased expression. Similar data were obtained in the prostate cell line LNCaP. All agents significantly inhibited growth. These agents increased expression of the mdr-1 gene. This study suggests that components from black and green tea extracts can modulate the expression of genes known to play a role in the carcinogenesis process and, therefore, may be potential agents for chemoprevention against pancreatic cancer.

Anticarcinogenic Agents↗

The relationship between normal erythrocyte sedimentation rate of Chinese young people and geographical factors.

In order to provide a scientific basis for the layout of a unified standard of the reference value of Chinese young people's erythrocyte sedimentation rate (ESR), the relationship between the reference values of the Chinese healthy young's ESR and five geographical factors was tested according to the Wintrobe methods. The altitude was found to be the most important factor affecting the reference value of the Chinese young's ESR. The altitude increase correlates with the decrease of the reference value of the young's ESR. The method of stepwise regression analysis was used to deduce two multivariate regression equations. If the geographical index values of a particular area of China are known, the reference value of the young's ESR of this region can be calculated by means of the regression equations. Furthermore, the depending on geographical factors, China can be divided into six districts: Qingzang, Southwest, Northwest, Southeast, North and Northeast District, according to the reference values of the Chinese young's ESR.

Adult↗

DNA sequence recognition by a novel series of minor groove-binding ligands.

We have used quantitative DNase I and hydroxyl radical footprinting with three DNA fragments to examine the sequence-specific recognition of DNA by five novel minor groove-binding ligands which contain a structural motif in which a para-disubstituted benzene ring is flanked by two meta-disubstituted benzene rings. The compounds are all AT-selective and bind better to (AT)6 than (AT)4 sites. The ligands bind more tightly to AATT and TAAT than TTAA, TATA and ATAT, and avoid sequences containing central TpA steps. Different side groups cause subtle changes to the sequence recognition properties of these ligands.

Adenine↗

New buccinator myomucosal island flap: anatomic study and clinical application.

The authors studied the vascular anatomy of the buccinator muscle by dissecting fresh cadavers. The anatomy of the buccal branches of the facial artery consistently confirmed the existence of a posterior buccal branch, a few inferior buccal branches, and anterior buccal branches to the posterior, inferior, and anterior portions of the buccinator. The buccal artery and posterior buccal branch anastomose to each other and ramify over the muscle. Several veins originate from the lateral aspect of the muscle, converge into the buccal venous plexus, and drain into the facial vein (from two to four tributaries) or into the pterygoid plexus and the internal maxillary vein (from the buccal vein). These vessels and nerves enter the posterior half of the buccinator posterolaterally. The facial artery and vein are located at variable distances from each other around the oral commissure and the nasal base. Two patterns of buccinator musculomucosal island flaps supplied by these buccal arterial branches are proposed in this article. The buccal musculomucosal neurovascular island flap (posteriorly based), supplied by the buccal artery, its posterior buccal branch, and the long buccal nerve, can be passed through a tunnel under the pterygomandibular ligament for closure of mucosal defects in the palate, pharyngeal sites, the alveolus, and the floor of the mouth. The buccal musculomucosal reversed-flow arterial island flap (superiorly based), supplied by the distal portion of the facial artery through the anterior buccal branches, can be used to close mucosal defects in the anterior hard palate, alveolus, maxillary antrum, nasal floor and septum, lip, and orbit. The authors have used the flaps in 12 patients. There has been no flap necrosis, and results have been satisfactory, both aesthetically and functionally.

Adult↗