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Biomedical subjects

D Tan

Publications and source records attributed to D Tan.

At least 91 records · Page 5Linked to original sources
PubMed1997

[PCR-SSCP analysis of p53 gene in human primary brain tumor].

In this study PCR-SSCP alalysis was made to detect the mutation of the exon 5-7 of p53 gene in 37 cases of human primary brain tumor. The results showed that 10 human primary brain tumors had mutation, of which 9 were gliomas (37.5%) and 1 was meningioma (7.7%), and that the higher the grade of tumor was, the higher would be the frequency of mutation. These results suggest that human primary brain tumor is related to p53 gene mutation and such mutation may be the major reason for human primary brain tumor genesis and malignancy.

Astrocytoma↗
PubMed1997

[Determination of metronidazole in gastric juice by high performance liquid chromatography].

Metronidazole (MTZ) is the first chosen drug of anti-anaerobe which was recommended by World Health Organization. In this paper a high performance liquid chromatographic (HPLC) method has been developed to determine the concertration of MTZ in human gastric juice. Gastric juice was obtained by intubation after taking drug, then the sample was precipitated with ethanol to remove proteins, centrifuged, filtered and finally assayed by HPLC. The operating conditions were reversed phase C18 column (4mm x 150mm), CH3OH:KH2PO4 (5mmol/L, pH 4.0) = 10:90 mobile phase with flow rate of 1.5mL/min and detection wavelength at 320nm. The standard working curve was Y = -1.63 + 1.15X, with r = 0.9999, n = 7. The linear range was 2.5-200mg/L. The detection limit was 0.4mg/L. The average recovery was 96.0% and the coefficient of variation was 3.07%. This method can be applied to guide clinical therapy and pharmaceutical research.

Adult↗
PubMed1997

[Detection of the level of serum IgG antibody to hepatitis E virus].

The levels of serum IgG antibody to hepatitis E virus (anti-HEV-IgG) was detected in serum specimens from 50 patients with acute sporadic hepatitis E and 20 healthy donors who were positive for anti-HEV-IgG by ELISA titration. The results showed that the level of anti-HEV-IgG in acute hepatitis E patients was significantly higher than that in healthy donors and the average titer is 1:121 and 1:22, respectively (P < 0.01). So acute viral hepatitis E should be diagnozed when the titer of anti-HEV-IgG was over 1:40.

Antibodies, Viral↗
PubMed1996

Active site of 5-aminolevulinate synthase resides at the subunit interface. Evidence from in vivo heterodimer formation.

5-Aminolevulinate synthase (EC 2.3.1.37) is the first enzyme in the heme biosynthetic pathway of animals, fungi and some bacteria. It functions as a homodimer and requires pyridoxal 5'-phosphate as an essential cofactor. In mouse erythroid 5-aminolevulinate synthase, lysine 313 has been identified as the residue involved in the Schiff base linkage with pyridoxal 5'-phosphate [Ferreira, G. C., et al. (1993) Protein Sci. 2, 1959-1965], while arginine 149, a conserved residue among all known 5-aminolevulinate synthase sequences, is essential for function [Gong & Ferreira (1995) Biochemistry 34, 1678-1685]. To determine whether each subunit contains an independent active site (i.e., intrasubunit arrangement) or whether the active site resides at the subunit interface (i.e., intersubunit arrangement), in vivo complementation studies were used to generate heterodimers from site-directed, catalytically inactive mouse 5-aminolevulinate synthase mutants. When R149A and K313A mutants were co-expressed in a hem A- Escherichia coli strain, which can only grow in the presence of 5-aminolevulinate or when it is transformed with an active 5-aminolevulinate synthase expression plasmid, the hem A- E. coli strain acquired heme prototrophy. The purified K313A/R149A heterodimer mixture exhibited K(m) values for the substrates similar to those of the wild-type enzyme and approximately 26% of the wild-type enzyme activity which is in agreement with the expected 25% value for the K313A/R149A coexpression system. In addition, DNA sequencing of four Saccharomyces cerevisiae 5-aminolevulinate synthase mutants, which lack ALAS activity but exhibit enzymatic complementation, revealed that mutant G101 with mutations N157Y and N162S can complement mutant G220 with mutation T452R, and mutant G205 with mutation C145R can complement mutant Ole3 with mutation G344C. Taken together, these results provide conclusive evidence that the 5-aminolevulinate synthase active site is located at the subunit interface and contains catalytically essential residues from the two subunits.

5-Aminolevulinate Synthetase↗
PubMed1996

Consecutive evaluation of immunoglobulin M and G antibodies against hepatitis E virus.

Hepatitis E virus (HEV) infection is sporadic in the Guangzhou city southern China. However, the evaluation of antibodies to HEV during consecutive time periods after infection has not been reported. We utilized enzyme immunosorbent assay (ELISA) to defect IgM and IgG anti-HEV in consecutive serum specimens from patients with acute hepatitis E and compared that data with detection rates of IgM and IgG anti-HAV in patients with acute hepatitis A. IgM anti-HEV can be detected as early as 4 days after onset of disease symptoms in some patients. The detection rate of IgM anti-HEV is significantly higher in specimens collected within 4 weeks (95%) of onset than in those specimens collected 4 to 18 weeks after onset (67.6%) (P < 0.005). IgM anti-HEV had a similar pattern to IgM anti-HAV and can be used as a marker of acute HEV infection. In contrast with IgG anti-HAV, 56.8% of the specimens did not contain detectable levels of IgG anti-HEV (P < 0.005). One should be cautioned against making a diagnosis of HEV infection solely by the currently available assays for IgG anti-HEV. In conclusion, IgM anti-HEV can be used as a reliable and sensitive marker for recent HEV infection, but serum specimens should be collected within 4 weeks after onset of symptoms to avoid false-negative results. In contrast, we should be aware of the failure to develop IgG anti-HEV in some patients. These patients carry the risk of reinfection.

Acute Disease↗
PubMed1996

Role of endothelin in the pathophysiology of renal ischemia-reperfusion in normal rabbits.

The present study addressed the acute effects of endothelin-1 on renal function and neutrophils accumulation in the setting of in vivo severe (60 min) acute ischemia/reperfusion. Ischemia/reperfusion decreased renal functional parameters and increased renal neutrophil accumulation and medullary congestion. All these parameters markedly improved with the intrarenal administration of anti-endothelin-1 antiserum. Comparatively, the intrarenal infusion of endothelin-1 decreased renal function and increased neutrophil accumulation. Abnormalities in renal histology were, however, less pronounced than with ischemia/ reperfusion. In experiments using rabbit isolated perfused kidneys, endothelin-1 induced the accumulation of labeled neutrophils. This accumulation was similar to that observed in kidneys obtained after 60 minutes of ischemia plus 60 minutes of reperfusion. Both endothelin and ischemia/ reperfusion effects were counteracted by an anti-endothelin antibody. In further in vitro studies, we found that endothelin-1-induced the expression of the CD18 antigens on the neutrophil surface. In subsequent experiments based on this effect of ET-1 on CD18 antigens, a blockade of both ischemia/reperfusion-induced and endothelin-1-induced neutrophil accumulation was obtained by infusion an anti-CD18 antibody. In conclusion, our experiments disclosed the critical role of endothelin-1 as a major promoter of early neutrophil accumulation after ischemia/reperfusion, which occurred through an integrin-mediated mechanism.

Animals↗
PubMed1996

Role of endothelium-related mechanisms in the pathophysiology of renal ischemia/reperfusion in normal rabbits.

The present study addressed the effect of interventions aimed to increase NO in the setting of acute renal ischemia/reperfusion (I/R) in uninephrectomized rabbits. In the 60-minute post-I/R period, L-arginine+superoxide (O2.-) dismutase (SOD) synergistically improved the renal functional (69.4% versus 10.4% of the pre-I/R glomerular filtration rate with or without L-arginine+SOD, respectively; p < .01) and histological parameters (82.9% decrease of medullary congestion in L-arginine+SOD, P < .01 versus vehicle) and blocked the I/R-dependent neutrophil accumulation (89.3% reduction). In spite of these results over the short term, a second set of experiments disclosed that the protection by L-arginine+SOD was no longer present at 24 and 48 hours (plasma creatinine in vehicle-treated versus L-arginine+SOD-treated animals [mg/100 mL]: 24 hours after I/R, 9.4 +/- 1.9 versus 8.07 +/- 0.65; 48 hours after I/R, 11.6 +/- 3.6 versus 9.7 +/- 0.9; P = NS in all the cases). Additional experiments were conducted using a milder 30-minute ischemic model, which showed no significant functional or histological protection by using L-arginine+SOD. In conclusion, our experiments disclosed the following: (1) the critical importance of the interaction between NO and O2.- in the acute protective effect of L-arginine (this effect not only improved renal function and histology but also reduced neutrophil accumulation) and (2) the discordance existing between the immediate protection afforded by L-arginine+SOD and the lack of protection observed at 24 and 48 hours. This finding suggests that a punctual intervention on the NO system at the time of I/R is not sufficient to reduce renal damage over the long term.

Animals↗
PubMed1996

Cervicofacial actinomycosis with paravertebral spread: a case report.

We report a case of cervicofacial actinomycosis with paravertebral extension in a 60-year-old man who presented with recurrent neck masses. Diagnosis was confirmed on culture and histology of pus and debris obtained from surgical drainage. He improved only after lengthy in-hospital high dose penicillin therapy. He is currently well and is on maintenance doxycycline therapy for 6 months following the high dose penicillin therapy.

Abscess↗
PubMed1995

Typing and subtyping of influenza viruses in clinical samples by PCR.

Type A and B influenza viruses can cause a wide spectrum of illness, and these viruses are responsible for considerable mortality and morbidity. Rapid typing of isolates is desirable when amantadine treatment or prophylaxis of contacts of type A influenza virus carriers is considered, but the available rapid techniques lack sensitivity and standard diagnostic methods require expansion of virus in tissue culture or embryonated hens' eggs. We developed a series of oligonucleotide primers able to detect, type, and subtype type A influenza viruses in a single reverse transcription-PCR. RNA was isolated from clinical specimens, and cDNA was generated with random primers. PCR was carried out with a mixture of primers specific for influenza viruses of types B, A/H1 and A/H3, and subtyping of the neuraminidase was carried out on the same cDNA template under identical conditions. Amplified products were detected by ethidium bromide staining of amplified products after agarose gel electrophoresis. When it was used to test 98 clinical specimens, this method was comparable to standard culture techniques in the detection, typing, and subtyping of influenza viruses.

Base Sequence↗
PubMed1995

[Treatment of recurrent carcinoma of the uterine cervix].

One hundred thirty seven patients with recurrent carcinoma of the uterine cervix were treated from 1964 through 1985. The primary treatment was surgery in 64 cases and radiation of 73 cases. Treatment consisted of surgery (n = 13) radiotherapy with or without Chinese medicine (n = 92), chemotherapy (n = 26), and chemotherapy plus radiation (n = 6). The mean 5-year survival rate of this series was 40.9%. One patient survived 28 year without tumor. Seven of 13 surgically treated patients were alive and free of disease for 5 to 28 years with an average 5-year survival rate of 53.8%. Thirty recurrent cases following radiotherapy were again treated by radiation, 11 of them (36.7%) were alive for 5 years.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

[The effect of estrogen and its receptor antagonist on the growth of human gastric cancer cell line in vitro].

In this study, the effect was studied of estradiol (E2) and tamoxifen on the growth of a human gastric adenocarcinoma SGC-7901 cell line in vitro. Estrogen receptor as revealed by immunohistochemical staining was positive when added at various concentrations. E2 could significantly stimulate cell growth. The effect was most marked at concentration of 0.1 mumol/L. The cell doubling time was reduced, the plating efficiency was increased and c-myc oncogene expression was enhanced. Flow cytometric analysis indicated that cell] proliferation index was greater in the E2-treated than in the control. All these effects caused by E2 could be partially inhibited by the estrogen receptor inhibitor tamoxifen.

Adenocarcinoma↗
PubMed1995

Acute sporadic hepatitis E virus infection in southern China.

BACKGROUND/AIMS: The hepatitis E virus is responsible for epidemic and sporadic hepatitis in northwestern China, but its role as a cause of acute sporadic hepatitis in southern China has not been reported. METHODS: We applied the most practical current methods for diagnosis of hepatitis E virus infection, IgM and IgG anti-HEV detection by enzyme linked immunosorbent assay, to investigate the prevalence of hepatitis E virus infection among acute sporadic hepatitis. RESULTS: Anti-HEV IgM was found in 1 of 26 (3.8%), 4 of 20 (20.0%), 4 of 19 (21.1%), and 51 of 142 (35.9%), with acute hepatitis A, B, C and non-ABC, respectively. Anti-HEV IgM was not detectable in healthy subjects, while IgG anti-HEV was found in 14 of 77 healthy subjects (18.2%) and was long-lasting. Ninety-one cases without any evidence of hepatitis A, B or C infections and anti-HEV IgM were tentatively classified as non-A, B, C, D, E (non-ABCDE) hepatitis. By comparison with non-ABCDE, cases with hepatitis E were more frequently icteric and exhibited higher alanine aminotransferase levels (92.2% vs. 45.1%, 770 iu/l vs 377 iu/l, respectively, p < 0.005). Chronic cases were not observed in hepatitis E virus infections. However, 14 of 91 (15.4%) cases with non-ABCDE developed to chronicity (p < 0.005). CONCLUSIONS: Hepatitis E virus infection is sporadic as well as endemic in southern China. Only IgM anti-HEV but not IgG anti-HEV can be used as an appropriate marker of acute hepatitis E virus infection. Superinfection of hepatitis E virus with other types of hepatitis viruses is frequent in this area. While the disease was associated with more severe clinical manifestations, patients usually recovered completely.

Acute Disease↗
PubMed1995

Chinese character operating system of traditional Chinese medicine and pharmacology (TCMP).

With the development in research, teaching and literature work in traditional Chinese medicine and pharmacology (TCMP) by means of computers, it has been found that the existing Chinese character operative systems cannot meet the need of carrying out information processing and software development in this field, since these systems do not include many of the common and special terms in TCMP. This makes it inconvenient to exchange academic thoughts in information processing in this field with our colleagues at home and abroad and greatly affects the sharing of the literature data in TCMP. It is therefore necessary to develop a Chinese character operating system applicable to the use of computers in the research of TCMP. Recently, we have developed jointly a Chinese character operating system of TCMP. This system is based on the original GB2312-80 Chinese character international code, to which are added 1,150 Chinese characters commonly used in TCMP. The five-stroke code, which make input possible according to word forms, are used for the input of expanded words. Besides, the system also provides the codes of a number of common names of Chinese materia medica, acupoint names, common terms in traditional Chinese medicine (TCM), TCM disease names, names of classic TCM works, etc. It also provides a convenient character-creating software. We hope that our work will lead to discussions concerning the difficult problems in computer processing of TCMP literature, i.e. the Chinese character.

Database Management Systems↗
PubMed1994

Follow-up study of acute hepatitis C.

An extended follow-up study of hepatitis C virus (HVC) infection was conducted in Guangzhou and its nearby regions on patients hospitalized with acute hepatitis. Routine screening of blood donors for HCV was not yet instituted at the time of this study. HCV was found to be a common cause of the disease, and the infection had a close association with recent histories of blood transfusion. Sequential sera obtained from patients during hospitalization and after discharge were tested for the presence of HCV antibodies by the first and the second generation of commercial test kits, for levels of alanine aminotransferase (ALT), and for the presence of HCV-RNA. The development of HCV antibodies in some of the patients may be delayed for protracted period following clinical onset. HCV-RNA was only intermittently detectable both before and after seroconversion. Six of 33 patients studied showed seroreversion and 5 of them were accompanied by loss of HCV-RNA and serum ALT returned to normal levels. The disease persisted in 24 of 27 patients without seroreversion, accompanied by intermittent detection of HCV-RNA throughout the protracted course of the infection. Our results indicate that both EIA for detection of HCV antibodies and PCR for serum HCV-RNA should be used in combination for reliable diagnosis of HCV infection and screening of blood for transfusion.

Acute Disease↗