Biomedical subjects

X Xia

Publications and source records attributed to X Xia.

At least 91 records · Page 5Linked to original sources

PubMed1998

How optimized is the translational machinery in Escherichia coli, Salmonella typhimurium and Saccharomyces cerevisiae?

The optimization of the translational machinery in cells requires the mutual adaptation of codon usage and tRNA concentration, and the adaptation of tRNA concentration to amino acid usage. Two predictions were derived based on a simple deterministic model of translation which assumes that elongation of the peptide chain is rate-limiting. The highest translational efficiency is achieved when the codon recognized by the most abundant tRNA reaches the maximum frequency. For each codon family, the tRNA concentration is optimally adapted to codon usage when the concentration of different tRNA species matches the square-root of the frequency of their corresponding synonymous codons. When tRNA concentration and codon usage are well adapted to each other, the optimal content of all tRNA species carrying the same amino acid should match the square-root of the frequency of the amino acid. These predictions are examined against empirical data from Escherichia coli, Salmonella typhimurium, and Saccharomyces cerevisiae.

Codon↗

PubMed1998

The rate heterogeneity of nonsynonymous substitutions in mammalian mitochondrial genes.

Substitution rates at the three codon positions (r1, r2, and r3) of mammalian mitochondrial genes are in the order of r3 > r1 > r2, and the rate heterogeneity at the three positions, as measured by the shape parameter of the gamma distribution (alpha 1, alpha 2, and alpha 3), is in the order of alpha 3 > alpha 1 > alpha 2. The causes for the rate heterogeneity at the three codon positions remain unclear and, in particular, there has been no satisfactory explanation for the observation of alpha 1 > alpha 2. I attempted to dissect the causes of rate heterogeneity by studying the pattern of nonsynonymous substitutions with respect to codon positions in 10 mitochondrial genes from 19 mammalian species. Nonsynonymous substitutions involve more different amino acid replacements at the second than at the first codon position, which results in r1 > r2. The difference between r1 and r2 increases with the intensity of purifying selection, and so does the rate heterogeneity in nonsynonymous substitutions among sites at the same codon position. All mitochondrial genes appear to have functionally important and unimportant codons, with the latter having all three codon positions prone to nonsynonymous substitutions. Within the functionally important codons, the second codon position is much more conservative than the codon position. This explains why alpha 1 > alpha 2. The result suggests that overweighting of the second codon position in phylogenetic analysis may be a misguided practice.

Animals↗

PubMed1998

[Investigation on the epidemiology of Histoplasma capsulatum infection in Nanjing district].

Two hundred and ninety-two permanent or temporary residents in Nanjing district were tested with histoplasmin (Histolyn-CYL, ALK/Berkeley Laboratories, USA) and PPD. Forty-nine (16.78%) subjects reacted to histoplasmin with 5.0-23.0 (9.5 +/- 4.2) mm induration. Positive reaction rate among people without pulmonary diseases (normal group) was 15.10% comparing to 17.74% to patients with pulmonary diseases. Positive reaction to PPD with 5-50 (14.2 +/- 4.7) mm induration was 56.16%, with 59.43% in normal group and 54.30% in patients with pulmonary diseases while 8.90% subjects reacted to both histoplasmin and PPD, 7.88% of the research subjects reacted to histoplasmin but not to PPD. Result suggested that there was herd infection of Histoplasma capsulatum in Nanjing district.

Adult↗

PubMed1998

[A preliminary report of antiscar formation effect by subconjunctival injection of mitomycin C before trabeculectomy in glaucoma].

To improve the function of filtering blebs and increase the successful rate of the trabeculectomy, mitomycin C injection 0.02 mg.ml-1 was given subconjunctivally at the operative site before trabeculectomy in 32 patients (38 eyes) with moderate or late glaucoma. All patients were followed up for 6 to 12 months. The results showed that the rate of functional blebs were 93.7%. The successful rate of the operation was 94.7%. The common postoperative complication was shallow anterior chamber (7.9%). These findings indicate that the subconjunctival injection of mitomycin C before operation is a safe, effective method for antiscar formation.

Adult↗

PubMed1998

[Prognostic significance of P-glycoprotein expression in acute leukemia in adults].

OBJECTIVE: To explore the prognostic significance of P-glycoprotein (P-gp) expression in previously untreated acute leukemia in adults. METHODS: P-gp expression in 151 acute myeloblastic leukemia (AML) and 47 acute lymphoblastic leukemia (ALL) was determined by monoclonal antibody UIC2 and flow cytometry. RESULTS: The rate of complete remission (CR) differed between P-gp+ and P-gp- AML (20.5% vs 78.5%, P < 0.001), but the CR rate did not significantly differ between P-gp+ and P-gp- ALL(66.7% vs 80%, P > 0.05). The six-month relapse rate was significantly higher in P-gp+ group than that of P-gp- group (AML: 66.7% vs 8.7%, P < 0.001; ALL: 50% vs 9.5%, P < 0.05). The median disease-free survival time was shorter in P-gp+ group than in P-gp- group (AML: 5 months vs 13 months; ALL: 4 months vs 13 months). CONCLUSION: Overexpression of P-gp is a poor prognostic factor in adult acute leukemia and P-gp detection is useful for the prediction of treatment response and early relapse.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

[Clinical study on acute respiratory infection caused by chlamydia pneumoniae].

OBJECTIVE: To find out the infected rate and the clinical features of patients with acute respiratory infection caused by chlamydia pneumonia(C. pneumoniae). METHOD: A prospective study for chlamydia pneumoniae infection was conducted in 110 patients with respiratory tract infection from January to December 1995 in Nanjing. Sputum and throat swab specimens were taken and C. pneumoniae DNA were detected by polymerase chain reaction (PCR) with the HM-1-HR-1 primer pair. At the same time, serum samples were taken and immunoglobulins G and M (IgG and IgM) fractions of antibodies to C. pneumoniae were studied by microimmunofluorescence test. RESULT: Prevalence of specific IgG was 70% in patients with respiratory tract infection. Seventeen patients (16%) were serologically diagnosed as having recent C. pneumoniae infection and 12 patients (11%) had the positive PCR in sputum and/or swab specimens. The total positive rate was 23% (25/110) combining PCR with serology. Acute infection of C. pneumoniae was common in the patients with asthma (57%), pneumonia (35%), COPD (26%) and bronchitis (25%). The clinical feature between C. pneumonia infection (n = 5) and non-C. pneumonia infection (n = 85) was not significanty different. CONCLUSION: Data suggest that Chlamydia pneumonia is an important pathogen that causes infections of the human respiratory tract and attention should be drawn to this special illness.

Acute Disease↗

PubMed1998

[Detection of oncogenic mutations in sputum and its diagnostic value of lung cancer].

OBJECTIVE: To find a new method to molecular biological detection of lung cancer. METHOD: The sputum specimens from 96 cases of lung cancer and other lung patients were detected for K-ras and p53 mutations by using polymerase chain reaction(PCR) and restriction fragment length polymorphism and and immunohistochemistry (IHC) techniques. RESULT: 38 out of 62 sputum specimens of lung cancer patients were positive for cytology: Sensitivity was 61%. NPV (negative predictive value) was 59%; p53 was overexpressed in 48 cases: Sensitivity was 77%. NPV was 66%; k-ras was positive in 21 cases: Sensitivity was 34%, NPV 42%; The combination of conventional cytology and molecular screening(k-ras + p53) produced a sensitivity value of 92%(P < 0.05) with an NPV of 84%(P < 0.05); In 24 cases of patients whose cytology of sputum was false negative, 17 were found either p53 or k-ras positive of which 7 patients were identified to be lung cancer in the follow-up study. CONCLUSION: These results suggest that detection of oncogene mutation in sputum enhanced and added to the diagnostic value of conventional cytology. It is a promising approach to early lung cancer detection and massive screening in terms of its rapidity, economy and simplicity.

Adenocarcinoma↗

PubMed1998

[Cytotoxic effect of mitomycin C on the nonpigmented epithelium of ciliary body in rabbit eyes].

OBJECTIVE: To observe pathomorphological changes of nonpigmented epithelial cells (NECs) of ciliary body after local single application of mitomycin C (MMC) during sclerectomy in rabbit eyes, and to explore cytotoxic effect of MMC on ciliary body. METHODS: A single five minutes intraoperative exposure to the agent MMC (0.2 mg/ml, 0.1 ml) was used during sclerectomy in rabbit eyes. The treated area was rinsed with 20 ml normal saline. The NECs of ciliary body at the operated area were observed under light microscope and transmission electron microscope on the 7th and 28th day postoperatively. RESULTS: On the 7th day postoperatively, the NECs were swollen, and the intracellular abundant mitochondria were swollen and vacuolized. String pearls-like membrane-encapsulated vacuoles were present in the intervals of beta-cell membrane of the NECs. On the 28th day postoperatively, these damages were gradually recovered. CONCLUSIONS: These findings suggest a toxic effect of MMC on the NECs of ciliary body, possibly that can decrease the aqueous production and intraocular pressure, even causing persistent hypotony.

Animals↗

PubMed1998

[Internalization and replication of Edwardsiella tarda in HEp-2 cells].

It is demonstrated that Edwardsiella tarda possesses the ability to invade cultured epithelial HEp-2 cells by both lysis-counting assay and thin-section electron microscopy. Among fifteen strains of E. tarda, 6 strains internalized into HEp-2 cells and located mainly in vesicles. After internalization, the bacteria replicated in the host cells and then released into medium. Pretreatment of the HEp-2 cells with various concentration of cytochalasin D (0.1-5.0 micrograms/ml) or cytochalasin B (2.5-10.0 micrograms/ml) significantly reduced the amount of internalized bacteria in a dose-dependent manner. While pretreatment of HEp-2 cells with 0.25-100 mumol/L colchicine did not show any effect on the invasiveness of E. tarda. This strongly indicates that microfilaments are required for the internalization of E. tarda into HEp-2 cells and that microtubules are not involved in the entrance of E. tarda into HEp-2 cells.

Cells, Cultured↗

PubMed1998

[Appllcation of PYGC and the hierarchical clustering analysis to recognization of viruses].

The pyrolysis gas chromatography of 29 strains nuclear polyhedrosis viruses, 11 strains cytoplasmic polyhedrosis viruses and 16 strains granulosis viruses were performed on a shimadzu GV-9A capillary gas chromatography equipped with a pyrolyser model PYR-2A. The differences among the inclusion bodies of NPV, CPV and GV could clearly be distinguished and also beidentified through analysis of fingerprinting the hierarchical clustering analysis of GC, This procedure has provided a usefel method for the classification and identification of viruses.

Algorithms↗

PubMed1998

[Effects of polysaccharide of Polygala aureocauda on the immunnity functions of normal mouse].

The effects of polysaccharide of polygala aureocauda on the immunity functions of the normal mouse were researched by the tests of clearing away carbon granules, hemolysin antibodies production and lymphocyte transformation. The results showed that the polysaccharide of polygala aureocauda Dunn. (PADTP) could strengthen the phagocytosis of the single nucleus phagocytes, promote the production of the antibodies, and raise the transformable rate of the lympocytes. That proved the PADTP could strengthen immunity function of the normal mouse.

Adjuvants, Immunologic↗

PubMed1998

[Effect of AHMED valve implantation surgery for the treatment of neovascular glaucoma].

PURPOSE: To evaluate the efficacy of the valve implantation for the treatment of neovascular glaucoma. METHODS: 15 cases (15 eyes) neovascular glaucoma were treated with AHMED valve implantation surgery, and followed up for 6 to 42 months. RESULTS: The IOP of the cases is lowered from 6.01 +/- 1.28 kPa (1 kPa = 7.5 mmHg) preoperatively to 1.96 +/- 0.68 kPa postoperatively. The success rate was 80.0% (The criteria of success is 0.80 kPa < or = IOP < or = 2.80 kPa and without severe complication that influence the visual acuity). The common postoperative complications included hyphema, shallow anterior chamber. CONCLUSION: The AHMED valve implantation surgery can lower the IOP, increase the operative success rate and preserve the visual function effectively. It is regarded to be an effective, safe method to treat neovascular glaucoma.

Adult↗

PubMed1997

Identification of quantitative trait loci controlling levels of radiation-induced thymocyte apoptosis in mice.

Thymocyte apoptosis levels are higher in C57BL/6J mice than in C3Hf/Kam mice. Low-dose irradiation increases the numbers of thymocytes undergoing apoptosis, but the strain difference persists. We mapped three loci controlling radiation-induced thymocyte apoptosis levels in F2 intercross progeny of these strains. The strongest association of a genomic region with an apoptosis level occurred in a region of chromosome 11 known to harbor a locus (or loci) important in the pathogenesis of several rodent models of autoimmune disease. Additional loci influencing radiation-induced thymocyte apoptosis were identified on chromosomes 9 and 16. The genetic polymorphisms underlying these loci may have an evolutionary role in fine-tuning the apoptotic response in T cells and may be important in the etiology of lymphoproliferative disorders and autoimmunity.

Animals↗

PubMed1997

Glutathione S-transferase expression in hepatitis B virus-associated human hepatocellular carcinogenesis.

Hepatitis B virus (HBV) and aflatoxin B1 represent the main risk factors for the development of hepatocellular carcinoma (HCC) in areas endemic for liver cancer. The glutathione S-transferases (GSTs) are a family of Phase II detoxification enzymes that catalyze the conjugation of a wide variety of endogenous and exogenous toxins, including aflatoxin B1, with glutathione. This study characterizes the GST isoenzyme composition (alpha, mu, and pi) of both HBV-infected normal hepatic tissues and HCCs. Analysis of matched pairs of hepatic tissue (normal and tumor) from 32 HCC patients indicated that total GST activity was significantly higher in normal tissues than in tumor tissues, although the percentage of samples expressing GST alpha and pi was equivalent. GST mu was detected by Western blot in the normal tissue from 87.5% of the subjects possessing the GST M1 gene but only 28.6% of the corresponding tumor tissues. The GST activity of normal tissue from GST M1 null patients was significantly decreased as compared to that of subjects possessing the GST M1 gene (264.6 and 422.2 nmol/min/mg, respectively; P = 0.005). GST pi appeared to be overexpressed in the normal tissue of GST M1 null patients, a potential compensatory effect. Patients positive for HBV DNA had significantly lower GST activity than those who were HBV negative (302.1 versus 450.0 nmol/min/mg, respectively; P = 0.02). These results suggest that cellular protection within the human liver is compromised by HBV infection and further decreased during hepatocellular tumorigenesis.

Adult↗

PubMed1997

Mutation in the mitochondrial 12S rRNA gene in two families from Mongolia with matrilineal aminoglycoside ototoxicity.

Irreversible hearing loss is a catastrophic complication of treatment with aminoglycoside antibiotics such as streptomycin, gentamycin, and kanamycin. Many kindreds showing a matrilineal pattern of inheritance of this trait have been described in China where the widespread use of aminoglycoside antibiotics accounts for approximately 25% of profound deafness in some districts. Because of the characteristic inheritance pattern, mitochondrial DNA (mtDNA) mutations were postulated to be the cause of the deafness in these pedigrees. In 1993 it was shown that an A to G substitution at base pair 1555 of the mitochondrial 12S ribosomal RNA gene was the only mutation common to all the families with aminoglycoside ototoxicity. We ascertained three Mongolian pedigrees from the School for the Deaf and Blind in Ulaanbaatar, all of which contained multiple affected subjects with streptomycin induced deafness in a pattern consistent with matrilineal transmission. Amplified mtDNA, obtained from transformed lymphoblastoid cell lines using previously described primers, showed the A to G point mutation in the 12S rRNA gene in two of the three families by restriction analysis as well as direct sequencing. No other example of this substitution was found among 400 control samples from Mongolians with normal hearing. We have thus confirmed the clinical relevance of the 1555 A to G mitochondrial mutation in the 12S rRNA gene by identifying it in affected subjects with familial aminoglycoside ototoxicity in another ethnic group. In countries where aminoglycosides are widely used, genetic counselling and screening of high risk families before the use of these drugs could have a dramatic effect on the incidence of deafness.

Anti-Bacterial Agents↗

PubMed1997

A novel case of unilateral blepharophimosis syndrome and mental retardation associated with de novo trisomy for chromosome 3q.

We have evaluated a 3 2/12 year old girl who presented with unilateral blepharophimosis, ptosis of the eyelid, and mental retardation. Additional dysmorphic features include microcephaly, high, narrow forehead, short stubby fingers, and adduction of the right first toe. Cytogenetic analysis showed an unbalanced karyotype consisting of 46,XX,add(7)(q+) that was de novo in origin. Fluorescence in situ hybridisation (FISH) using microdissected library probe pools from chromosomes 1,2,3,7, and 3q26-qter showed that the additional material on 7q was derived from the distal end of the long arm of chromosome 3. Our results indicate that the patient had an unbalanced translocation, 46,XX,der(7)t(3;7)(q26-qter;q+) which resulted in trisomy for distal 3q. All currently reported cases of BPES (blepharophimosis-ptosis-epicanthus inversus syndrome) with associated cytogenetic abnormalities show interstitial deletions or balanced translocations involving 3q22-q23 or 3p25.3. Our patient shares similar features to BPES, except for the unilateral ptosis and absence of epicanthus inversus. It is possible that our patient has a contiguous gene defect including at least one locus for a type of blepharophimosis, further suggesting that multiple loci exist for eyelid development.

Adult↗

PubMed1997

[One-year-result of excimer laser for photorefractive keratectomy in very high myopia].

We corrected 53 cases (84 eyes) of very high myopia using photorefractive keratectomy (PRK) with VISX 20/20 excimer laser, and followed up the cases more than one year. The rates of visual acuity more than or equal to 0.5 or 1.0 were 81.0% and 23.9%, 75.0% eyes were within +/- 2.00 diopter of the desired emmetropia. Grade 2 or more severe corneal haze were presented in 13.1% eyes. PRK with VISX 20/20 excimer laser may be an effective method to correct very high myopia from -10.00 to -16.00 diopters.

Adolescent↗

PubMed1997

[Photorefractive keratectomy to correct myopic astigmatism].

The VISX 20/20 excimer laser was used to treat 260 eyes with myopia and myopic astigmatism of 166 patients. All patients were followed up for one year. The diopter of preoperative astigmatism was from -0.25-(- 4.00 D (-1.00 +/- 0.62 D). The diopter was lowered to -0.07 +/- 0.40 D at 6 months postoperatively (P < 0.05) and -0.06 +/- 0.39 D at 12 months postoperatively (P < 0.01). Photorefractive keratectomy (PRK) is effective and safe for myopic astigmatism.

Adolescent↗