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G Chen

Publications and source records attributed to G Chen.

At least 649 records · Page 36Linked to original sources
PubMed1996

Accuracy of MR imaging for estimating intraosseous extent of osteosarcoma.

OBJECTIVE: We compared how well T1-weighted and short inversion time inversion recovery (STIR) MR images obtained before and after preoperative chemotherapy reveal the extent of longitudinal intraosseous tumor involvement in osteosarcoma of children. MATERIALS AND METHODS: MR images were obtained at diagnosis and after preoperative multiagent chemotherapy in 20 children with osteosarcoma arising in the long bones. Images were reviewed to determine the length of the abnormal intraosseous signal intensity on paired longitudinal T1-weighted and STIR images taken at diagnosis and after chemotherapy. These measurements were compared with those made during a review of similarly oriented pathologic sections of the resected bone. Median differences were calculated and analyzed using Wilcoxon's signed-rank test. RESULTS: Abnormalities detected on T1-weighted images corresponded more closely to pathologic findings than did abnormalities detected on STIR images. On STIR images, readers overestimated tumor extent in 73% of both pre- and postchemotherapy studies. Readers overestimated tumor length on 29 of the 40 STIR images and on 13 of the 40 T1-weighted images. Readers underestimated tumor length on five STIR images and 11 T1-weighted images. Median differences between measurements made at the pathologic examination and on STIR images were statistically significant, both for imaging at diagnosis (p = .001) and for imaging after chemotherapy (p = .005); however, no significant differences were found between measurements made at the pathologic examination and measurements made on T1-weighted images. Measurements of tumor length on either type of imaging did not change significantly after chemotherapy. MR imaging showed 100% sensitivity for epiphyseal tumor spread but poor specificity. False-positive readings occurred in seven of 13 patients with abnormal signal intensity that extended into the adjacent epiphyses. CONCLUSION: Readers estimated intraosseous tumor extent more accurately on T1-weighted images than on STIR images. Readers overestimated tumor length on STIR images. T1-weighted longitudinal images taken before chemotherapy can be used for early planning of surgical approaches to osteosarcoma in children.

Adolescent↗
PubMed1996

Spin trapping study in the lungs and liver of F344 rats after exposure to ozone.

Fischer 344 rats were injected with the spin traps C-phenyl N-tert-butyl nitrone (PBN, 150 mg/kg bw, ip) or 4-pyridine-N-oxide N-tert-butyl nitrone (POBN, 775 mg/kg bw, ip), and exposed to clean air or 2 ppm ozone for two hours. The presence of spin adducts was determined by electron paramagnetic resonance (EPR) spectroscopy of chloroform extracts of lung and liver homogenates. No significant levels of adducts were detected in the lungs of air control animals. Benzoyl N-tert-butyl aminoxyl, attributed to direct reaction of ozone with PBN, and tert-butyl hydroaminoxyl, the scission product of the hydroxyl adduct of PBN, were detected in the lungs of ozone exposed rats. EPR signals for carbon-centred alkoxyl and alkyl adducts were also detected with PBN in the lungs and liver of animals exposed to ozone. With POBN, only carbon-centred alkyl radicals were detected. Senescent, 24 months old rats were found to retain about twice more 14C-PBN in blood, heart and lungs by comparison to juvenile, 2 months old animals. Accordingly, the EPR signals were generally stronger in the lungs of the senescent rats by comparison to juvenile rats. Together, the observations were consistent with the previously proposed notion that a significant flux of hydrogen peroxide produced from the reaction of ozone with lipids of the extracellular lining, or from activated macrophages in the lungs could be a source of biologically relevant amounts of hydroxyl radical.

Animals↗
PubMed1996

[Suppression of granulopoiesis by vesnarinone].

The effects of vesnarinone (3,4-dihydro-6-[4(3,4-dimethoxybenzoyl)-1-piperanizyl]-2 (1H)-quinolinone) on the hematopoietic precursors in 5 healthy volunteers and leukemic blast progenitors in 11 acute myeloid leukemia (AML) patients, 1 chronic myelocytic leukemia patient (CML) in blast crisis, and 3 leukemic cell lines were studied in methylcellulose and suspension cultures. Normal erythroid precursors (colony-forming unit erythroid: CFU-E and burst-forming unit erythroid: BFU-E) and granulopoietic precursors (colony-forming unit granulocyte/macrophage: CFU-GM) were suppressed in methylcellulose culture by vesnarinone in a dose-dependent manner. Leukemic blast progenitors may replicate themselves and/or undergo terminal divisions with limited differentiation. The plating efficiency of primary blast colony formation (PE1) in methylcellulose, which is considered to reflect the terminal divisions of leukemic blast progenitors, was suppressed by vesnarinone in a dose-dependent manner in all cases tested. The plating efficiency of secondary blast colony-formation (PE2) in methylcellulose culture and the recovery of clonogenic cells in the suspension culture, which are considered to reflect the self-replication function of leukemic blast progenitors, were also suppressed by vesnarinone in a dose-dependent manner in all cases tested. The results suggest that vesnarinone inhibits the growth of normal and leukemic hematopoietic progenitors. To determine the mechanism by which vesnarinone inhibits hematopoiesis, the effect of the agent on apoptosis (programmed cell death) of leukemic cells was studied. DNA ladder formation was recognized in OCI/AML 1 a cells after exposure to 100 micrograms/ml vesnarinone for 18 hours; this means that vesnarinone induced apoptosis in this cell line. Therefore, vesnarinone is considered to be the cause of apoptosis of granulopoietic precursors.

Adult↗
PubMed1996

Genetic evidence for the neuronal nitric oxide synthase gene (NOS1) as a susceptibility locus for infantile pyloric stenosis.

The etiological role of the gene for neuronal nitric oxide synthase (NOS1) in infantile pyloric stenosis (PS) was investigated by analysis of two intragenic polymorphisms (NOS1a and NOS1b) in 27 families. There was significant overall transmission disequilibrium between PS and NOS1a (P = .006). Consideration of each allele independently revealed a highly significant tendency for allele 7 (210 bp) to be preferentially transmitted to the affected offspring (P = .0006). These observations suggest that NOS1 is a susceptibility locus for PS.

Alleles↗
PubMed1996

Replication error phenotype and p53 gene mutation in lymphomas of mucosa-associated lymphoid tissue.

Low grade mucosa-associated lymphoid tissue (MALT) lymphomas commonly arise from a background of chronic inflammatory lesions and can transform into high grade tumors at a late stage. Because chronic inflammation is closely associated with genetic instability, which is one of the mechanisms leading to activation of oncogenes and inactivation of tumor suppressor genes, it is possible that genetic instability plays an important role in MALT lymphomagenesis. In this study, we have examined the frequency of replication error (RER+) phenotype, a newly defined manifestation of genetic instability, and its relationship to p53 mutations in 40 MALT lymphomas (16 high grade and 24 low grade). RER+ phenotype was detected in 21/40 (52.5%) MALT lymphomas (12/24, 50% in low grade; 9/16, 56.2% in high grade). Five of seven reactive lymphoid infiltrates adjacent to tumors also showed one microsatellite alteration, four of which were identified in the corresponding lymphoma lesions in the same patient. In five RER+ high grade lymphomas with low grade lesions, homogeneous and heterogeneous microsatellite alterations were observed between the two components. The same 40 cases were investigated for p53 gene mutations at exons 5 to 8 by PCR-SSCP and direct sequencing. p53 point mutations were found in 11 (27.5%) of the 40 cases. These mutations were statistically related to RER+ phenotype (P < 0.05). Our results demonstrate that the RER+ phenotype is a common genetic feature of MALT lymphomas. Genetic instability occurs throughout the spectrum of the lymphoma development and may be related to the accumulation of genetic aberrations such as p53 mutations. The observation of identical microsatellite alterations between the adjacent lymphoid infiltrates and their corresponding lymphomas provides genetic evidence for evolutionary link of the two lesions. The homogeneous and heterogeneous microsatellite alterations observed between low and high grade components indicate their clonal lineage and genetic diversity.

Base Sequence↗
PubMed1996

[Studies on microcystin contents in different drinking water in highly endemic area of liver cancer].

In order to study the pollution with microcystin (MC), a potent liver promoter, in drinking water in highly endemic area of liver cancer, cyanobacteria and its product MC were detected in drinking water in Haimen, Jiangsu Province during 1992 to 1993. Oscillatoria was identified as the most common species of cyanobacteria in pond-ditch and river water in Haimen, Jiangsu Province, which can produce MC. MC was detected in two of 65 water samples with high performance liquid chromatography, liquid chromatography and mass spectrography. In addition, studies were conducted in 989 samples collected from drinking water in Haimen, Jiangsu Province and more sensitive ELISA was used to detect their MC contents. Results showed proportions of samples with positive MC (greater than 50 pg/ml) were 17.3%, 31.9%, 4.3% and 0 for pond-ditch, river, shallow and deep well water, respectively, with average contents of 101, 160, 68 and 0 pg/ml, respectively. Proportions of positive MC samples and average MC contents for pond-ditch water were significantly greater than those in shallow and deep well water. It suggests studies on relationship between MC and liver cancer should be conducted further.

Carcinogens↗
PubMed1996

[Population pharmacokinetics/pharmacodynamics of magnesium sulfate in pregnancy induced hypertensive gravidas treated with the drug].

NONMEM program was applied for analyzing population pharmacokinetics/pharmacodynamics of magnesium sulfate in pregnancy induced hypertensive patients treated with the drug. A 2-compartment open model with fast and slow consecutive intravenous infusion was used to estimate population pharmacokinetics from 60 patients. A 3-compartment model comprised an effect compartment linked to the central compartment, sigmoid Emax effect model and parametric method were used to estimate population pharmacodynamic parameters from 26 patients. Serum magnesium concentration was determined by spectrophotometric method ant it was adjusted with basic value determined before dosage. The diastolic blood pressure lowering effect was chosen as index of effect of cardiovascular response. The population pharmacokinetic parameters of magnesium sulfate were: the standard value of K10(h-1), K12(h-1), K21(h-1), and Vc(L.kg-1) were estimated to be 1.62, 20.8, 2.70, and 27.0, respectively. Their interindividual varibilities were estimated to be 25.70%, 14.13%, 24.33%, and 34.04%, respectively. The residual error of concentrations was 15.03%. The population pharmacodynamic parameters of magnesium sulfate were: the standard value of Emax (%), Ce(50) (microgram.ml-1), upsilon, and Keo (h-1) were estimated to be 28.73, 28.39, 4.22, and 0.43. Their interindividual variability were estimated to be 56.32%, 62.24%, 33.47% and 42.76%. The residual error of effect was 28.54%.

Adult↗
PubMed1996

[Multi-drug resistance of serovar E strains in clinically isolated Pseudomonas aeruginosa and analysis of genome pattern].

We analyzed the in vitro antibiotic susceptible pattern and serovar for 132 strains of pseudomonas aeruginosa (98 from inpatients and 34 from outpatients) isolated at Showa University hospital from September to December of 1993. The ratio of resistant strains was 38.6% for carbenicillin, 12.1% for piperacillin, 12.9% for ceftazidime, 12.1% for cefsulodin, 17.4% for cefoperazone, 9.1% for cefclidin, 24.2% for cefpirome, 7.6% for imipenem, 17.4% for amikacin, 16.7% for aztreonam, 89.4% for minocycline and 33.3% for ofloxacin. The incidence of resistance against minocycline, carbenicillin, ofloxacin was markedly high. Among the 132 tested strains of Pseudomonas aeruginosa, 16 were multi-drug resistant strains (i.e., resistant to more than 8 drugs out of 12 drugs), and 14 of the multi-drug resistant strains (87.5%) were isolated from inpatients. Multi-drug resistant strains were isolated most frequently from urine specimens. The antibiotics that remained effective against the multi-drug resistant strains included amikacin, imipenem, cefclidin and cefsulodin. The serovar of 116 strains (resistant to up to 7 drugs) was 27 for G, 24 for B, and 19 for E, and 15 of the 16 multi-drug resistant strains showed serovar E. Restriction enzyme SpeI digestion analysis (using pulse field electrophoresis) of P. aeruginosa having serovar E revealed common 650kb and 540kb bands in multi-drug resistant strains. The genome pattern was quoted for serovar E strain according to the restriction enzyme digestion pattern and was shown to be useful for tracing the route of infection.

Drug Resistance, Microbial↗
PubMed1996

Regulation of signal transduction pathways by mood-stabilizing agents: implications for the delayed onset of therapeutic efficacy.

A series of investigations were performed to elucidate the mechanisms of action of lithium, valproate, and carbamazepine. We have found that lithium exerts major effects on G proteins, most likely via a posttranslational process stabilizing the inactive heterotrimeric (alpha beta gamma) form of the protein. We also find that chronic lithium and valproate exert major, very similar effects on the PKC signaling pathway, with both drugs decreasing the levels of membrane-associated PKC alpha and epsilon, and have similar effects on the DNA binding activity of the transcription factor, AP-1. By contrast, we find that carbamazepine exerts major, direct inhibitory effect at the level of adenylyl cyclases. Overall, the results suggest that signal transduction pathways are targets for the actions of mood-stabilizing agents; given their key roles in the amplification and integration of signals in the central nervous system, these findings have clear implications not only for research into the etiology/pathophysiology of manic-depressive illness, but also for the development of innovative treatment strategies.

Adenylyl Cyclases↗
PubMed1996

Cryopreservation of embryos in an IVF-ET program.

OBJECTIVE: To evaluate the use of cryopreservation of embryos in an in vitro fertilization and embryo transfer (IVF-ET) program. METHODS: Three cases of successful pregnancy after frozen-thawed embryo transfer were reviewed. The Testart's slow freezing and rapid thawing method was chosen. RESULTS: The first case was a Turner's syndrome patient and her husband had azoospermia. Donated frozen-thawed embryo transfer was done after hormonal replacement therapy. Pregnancy was achieved and a normal baby was delivered. The other two cases of IVF-ET did not achieve pregnancy during the stimulated cycle but became pregnant with frozen-thawed embryos in the natural cycle 4-5 months later. CONCLUSIONS: Pregnancy could be achieved in couples with incurable reproductive defects with donated embryos cryopreserved and ready for use whenever the endometrium is prepared by hormonal replacement therapy to be synchronous with the embryo development. In an IVF-ET program, one egg-retrieval may serve for many future chances of embryo transfer and therefore increase the cumulative pregnancy success rate.

Adult↗
PubMed1996

[Phacoemulsification aspiration and intraocular lens implantation].

OBJECTIVE: To investigate the characteristics of phacoemulsification of cataract in our country and management and prevention of its complications. METHODS: The procedure of phacoemulsification with small incision (6 mm) intraocular lens implantation was improved and was performed on 40 eyes of 40 cases. They had been followed up for 3-6 months postoperatively and their follow-up results were summarized. RESULTS: The uncorrected visual acuity 1.0 or better was in 57.5%, 0.8 or better in 82.5% and 0.5 or better in 97.5%. The postoperative mean astigmatism was 0.50 +/- 0.25 D, which was less than that in the large incision group (9-12 mm) performed on 40 cases in the same period (P < 0.001). Cataract with hard nucleus can be successfully taken out by the technique of peripheral rotation engraving method. CONCLUSION: The operation is a safe reliable one for restoration of visual acuity in patients with cataract, and is superior to extracapsular cataract extraction.

Adult↗
PubMed1996

Surgical treatment of coronary artery fistulae associated with other cardiovascular anomalies.

OBJECTIVE: To evaluate retrospectively our surgical experience, techniques and long-term results in 11 patients with coronary artery fistulae associated with other cardiovascular anomalies. METHODS: From January 1980 to April 1995, 11 patients with coronary artery fistulae associated with other cardiovascular anomalies were found among 20,000 open-heart procedures and treated surgically. Besides closure of the fistulae, coronary artery bypass grafting was performed in 5 patients with atherosclerotic coronary artery disease, and aneurysm angioplasty was done in 4 patients with coronary artery aneurysm. Ventricular septal defect and patent ductus arteriosus were closed in one patient and mitral valve replacement was performed in another patient. RESULTS: There were no surgical deaths, but one late death due to acute myocardial infarction occurred 6 months after surgery. The mean follow-up time was 75.7 months and all patients' functional status improved by an average 1.4 judged by the New York Heart Association functional classification. CONCLUSIONS: Coronary artery fistula associated with other cardiovascular anomalies will aggravate symptoms and cause deterioration of heart function. Therefore, evaluation and surgical intervention should be done as soon as possible to restore coronary blood flow and correct concomitant cardiovascular anomalies. The surgical results are excellent with a low operative risk and good long-term results.

Adult↗
PubMed1996

Rat as an animal model carrying human hepatitis B virus in hepatocytes.

OBJECTIVE: To establish an experimental animal model of rat carrying human hepatitis B virus in the hepatocytes using a simple and reproducible method. MATERIALS AND METHODS: Human serum rich in hepatitis B virus was injected into portal veins and caudalis veins of young male Wistar rats. One and two months after the injection, liver biopsies were done. In situ hybridization and immunohistochemical study of liver specimens were carried out. Sera were also examined for HBV DNA by polymerase chain reaction. RESULTS: All of seven rats in this experiment were HBV DNA and HBV surface antigen (HBsAg) positive in their hepatocytes. Most HBV positive hepatocytes were distributed around the central vein and scattered in the liver lobules, and HBV DNA and HBsAg were located in cytoplasm. HBsAg exists mainly as the forms of diffuses and inclusion body. No hepatocytic damage or inflammation was observed. Neither viremia nor antigenemia was detected. CONCLUSIONS: Our studies showed for the first time that natural human HBV can enter Wistar rat liver cells through intravenous injection efficiently and express for a long period. This animal model can be used in the studies of HBV molecular biology, therapeutic regimens and prophylaxis against HBV. A possible mechanism of HBV entering rat hepatocytes is also proposed.

Animals↗
PubMed1996

[Hormonal therapy for the synchronization between donor and recipient in an oocyte donation and surrogacy fertilization in vitro-embryo transfer program].

OBJECTIVE: To evaluate the efficacy of hormonal therapy for the establishment of endometrium synchronous with the embryo in an oocyte donation and surrogacy fertilization in vitro-embryo transfer (IVF-ET) program. METHODS: The IVF-ET routine of the Beijing Medical University was employed. The recipients included cases with (1) premature menopause and (2) abnormal chromosomal karyotypes; surrogate mothers. For (1) surrogate mother, low constant doses of estradiol (E2) (17-beta estradiol-Estrace or E2 valerate) 2-4 mg was started 3-5 days before the expected menstruation of the donor progesterone (P) was started intramuscularly 30 mg daily from the day of hCG injection, 50 mg from the day of oocyte pick-up, 100 mg from the day of embryo transfer and 150 mg from the day of positive urinary beta-hCG; E2 was maintained at the 4 mg dose. Both E2 and P were continued until after the luteo-placental shift-about 90 to 100 days of pregnancy with gradual tapering doses. The serum E2 and P levels were measured by radioimmunoassay and compared with those of normal pregnancy. For (2) women with normal menstrual periods, the Chinese made gonadotropin-releasing hormone-A (GnRH-A) 400-600 micrograms was given for down-regulation of pituitary and artificial agonadism when at least amenorrhea of two months was achieved and a quiescent state of the endometrium and ovaries was ascertained by vaginal ultrasonography. Then the E2 and P therapy was started as described above. GnRH-A was stopped on the day of hCG injection. RESULTS: In the hormonal therapy group, the serum E2 levels were quite similar to those of the normal pregnancy, while the P levels were about 3-5 times higher. Two full term deliveries of normal female babies and one in her 36th week of pregnancy were achieved in the premature menopause group. In the normal menstruation group, one was in her 15th week of pregnancy and the surrogate mother was in h34 4 1/2 months of pregnancy. CONCLUSION: The proposed hormonal therapy to synchronize the donor and the recipient may be used with satisfactory clinical outcome in an oocyte donation and surrogacy IVF-ET program.

Chorionic Gonadotropin, beta Subunit, Human↗
PubMed1996

Collagen gene expression in the neomatrix of carcinoma of the breast.

Excessive deposition of extracellular matrix or neomatrix is a characteristic of desmoplastic invasive breast carcinomas. Type I and III collagens are abundant neomatrix components. Archival breast tissue sections were studied using 35S-labeled cDNA probes for alpha 1(I) and alpha 1(III) procollagen and in situ hybridization. Among the 33 invasive breast cancers, hybridization was seen forming a gradient-like pattern in fibroblasts closest to tumor cells. In the 10 ductal carcinomas in situ studied, a ring-like pattern of hybridization was seen in proximity to the basement membrane zone. Adjacent normal and benign tissues did not demonstrate the patterns of hybridization described in malignant tissues. Gene expression for neomatrix interstitial collagens occurs before there is evidence of invasion in carcinoma of the breast.

Breast Neoplasms↗
PubMed1996

Effect of vasopressin on delayed neuronal damage in hippocampus following cerebral ischemia and reperfusion in gerbils.

Mongolian gerbils were used as delayed neuronal damage (DND) animal models. At the end of 15 minute cerebral ischemia and at various reperfusion time ranging from 1 to 96 hours, the content of water and arginine vasopressin (AVP) in the CA1 sector of hippocampus were measured by the specific gravity method and radioimmunoassay. Furthermore, we also examined the effect of intracerebroventricular (ICV) injection of AVP, AVP antiserum on calcium, Na+, K(+)-ATPase activity in the CA1 sector after ischemia and 96 hour reperfusion. The results showed that AVP contents of CA1 sector of hippocampus during 6 to 96 hour recirculation, and the water content of CA1 sector during 24 to 96 hour were significantly and continuously increased. After ICV injection of AVP, the water content and calcium in CA1 sector of hippocampus at cerebral ischemia and 96 hour recirculation further increased, and the Na+, K(+)-ATPase activity in CA1 sector was remarkably decreased as compared with that of control. While ICV injection of AVP antiserum, the water content and calcium in CA1 sector were significantly decreased as compared with that of control. These suggested that AVP was involved in the pathophysiologic process of DND in hippocampus following cerebral ischemia and reperfusion. Its mechanism might be through the change of intracellular action mediated by specific AVP receptor to lead to Ca ions over-load of neuron and inhibit the Na+, K(+)-ATPase activity, thereby to exacerbate the DND in hippocampus.

Animals↗