Biomedical subjects

M Gu

Publications and source records attributed to M Gu.

At least 91 records · Page 5Linked to original sources

PubMed1997

Mitochondrial respiratory chain function in multiple system atrophy.

Multiple system atrophy (MSA) is a clinico-pathological entity distinct from idiopathic Parkinson's disease (PD) that is responsible for 5-10% of cases of parkinsonism. Degeneration of nigral neurones is a feature of both diseases. A specific deficiency of mitochondrial complex I activity has been found in PD substantia nigra. We have analysed mitochondrial function in substantia nigra and platelets from MSA patients to identify any respiratory chain defect in this disorder and to determine its tissue specificity. As our MSA patients had been on L-DOPA, we also sought to establish whether this treatment could cause the complex I defect as seen in PD. We found no significant difference in respiratory chain activity corrected for mitochondrial mass between control and MSA patients in either of the tissues studied. These results provide a biochemical dimension to the differences between MSA and idiopathic PD. In addition, the fact that L-DOPA failed to induce a complex I defect in MSA substantia nigra suggests that this treatment is unlikely to cause the complex I deficiency in PD, without additional factors that may operate in PD.

Aged↗

PubMed1997

DNA vaccines: safety and efficacy issues.

DNA technology has been harnessed to produce a variety of plasmid-based vaccines designed to prevent viral, bacterial and parasitic infections. The rapid adoption and implementation of this novel vaccine strategy carries with it important safety and efficacy concerns. This review will focus on whether DNA vaccines (1) are likely to induce systemic or organ-specific autoimmune disease, (2) have the potential to induce tolerance rather than immunity, and (3) are as effective in individuals with depressed immune function as they are in healthy adults.

Aging↗

PubMed1997

Cloning and expression of the human tumor-specific antibody GM4.

The human monoclonal antibody GM4 was generated by fusing pooled lymphocytes from cancer patients with the lymphoblastoid cell line SHFP-1. Immunohistochemical staining of tumor and normal tissue indicated that this human IgG4 antibody preferentially reacted with melanomas and neuroblastomas. In this study, we demonstrate that GM4 recognizes a "vimentin-like" peptide sequence that we have termed AgGM4. To generate a recombinant derivative of this human antibody, we isolated and expressed the complete heavy and light chain genes. The entire coding sequence for both the heavy and light chains was isolated by RT-PCR using a set of degenerate 5' signal sequence specific primers and a 3' constant region primer. High level antibody synthesis and secretion was achieved in Chinese hamster ovary (CHO) cells using a vector designed to maximize expression. Western blot and FACS analysis indicated recombinant GM4 reacted with human tumor cell lines and AgGM4 in a manner similar to the antibody produced by the hybridoma cell line, demonstrating that the specificity of the antibody was not altered during molecular cloning.

Amino Acid Sequence↗

PubMed1997

Effect of nitric oxide on DNA replication induced by angiotensin II in rat cardiac fibroblasts.

Our previous in vivo studies (Hou et al. J Clin Invest. 1995;96:2469-2477.) demonstrated that chronic inhibition of nitric oxide synthase led to an exaggerated response to relatively low doses of angiotensin II, resulting in a rapid and marked cardiac fibrosis. To examine further the importance of angiotensin II in inducing cardiac fibrosis and the possibility that nitric oxide serves as a modulator of the proliferative effects of angiotensin II, we used cultured rat cardiac fibroblasts to study the interrelationships between these substances. Angiotensin II induced a delayed DNA synthetic response in quiescent cells that occurred 30 hours after exposure to the hormone. The most pronounced effect of angiotensin II on thymidine uptake occurred 36 to 42 hours after the addition to cells. This response was inhibited in a dose-dependent manner by the addition of either S-nitroso-N-acetylpenicillamine or sodium nitroprusside, each a source of nitric oxide. The nitric oxide donor was most effective in reducing thymidine incorporation when added 12 hours after angiotensin II, whereas the metabolite N-acetylpenicillamine had no effect at any time. The inhibitory effect of S-nitroso-N-acetylpenicillamine was mimicked by 8-bromoguanosine 3':5'-cyclic monophosphate but not by 8-bromoadenosine 3':5'-cyclic monophosphate. Nitric oxide donors did not appear to inhibit the induction of c-fos, Egr-1, or other immediate-early genes in response to angiotensin II. The results suggest that nitric oxide affects the cell cycle following the transition into G, and modulates the proliferation of fibroblasts during cardiac fibrosis induced by angiotensin II.

Angiotensin II↗

PubMed1997

[Chlamydia trachomatis and Ureaplasma urealyticum infection in patients with tubal pregnancy].

OBJECTIVE: To explore the relationship between genital infections with chlamydia trachomatis (CT) and ureaplasma urealyticum (UU) and tubal pregnancy. METHODS: 34 patients with tubal pregnancy (case group), 28 women undergoing tubal ligation (control group A) and 40 women with normal early intrauterine pregnancy (control group B) were investigated as a case-control study. The polymerase chain reaction (PCR) technique was used to detect CT DNA and UU DNA in samples from the secretion of cervix, fallopian tube and pelvic fluid. RESULTS: Case group was more likely to have detectable CT DNA (47.1%) and UU DNA (55.9%) from cervical secretion than control group A and B (P < 0.05). CT DNA detective rate from fallopian tube was significantly higher in case group than the control group A (26.5% versus 3.6%, P < 0.05). There were no significant differences in the positive rates of UU DNA from fallopian tube, CT DNA and UU DNA from pelvic fluid between case group and control group A. CONCLUSION: There is a strong association between tubal pregnancy and genital infection with CT and UU.

Adult↗

PubMed1997

[Expression of glutathione S-transferase-pi in operative specimens as marker of chemoresistance in patients with ovarian cancer].

OBJECTIVE: To study the relationship between the expression of glutathione S-transferase-pi (GST-pi) in operative specimens and chemoresistance in patients with ovarian cancer. METHODS: The expression of GST-pi in 87 epithelial ovarian cancer tissues and 30 normal ovarian epithelial tissues was determined with labelled streptavidin biotin method (LSAB). All the patients had not received chemotherapy before operation. We used Chi-Square and Cox-Mantel test to analyze the relativity between the expression of GST-pi and clinical pathological data, chemotherapeutic response, prognosis in patients with ovarian cancer. RESULTS: (1) 59 (67.8%) of 87 ovarian cancer tissue were demonstrated to be positive expression with GST-pi, but all 30 normal ovarian epithelial tissue were negative. (2) There was no direct correlation between the expression of GST-pi and clinical pathological data. (3) 43 (43/59) of GST-pi positive cases were chemoresistant, while only 3 (3/28) of GST-pi negative ones were chemoresistant. (4) The difference in the chemotherapeutic response between the two groups was obviously significant (P < 0.005). The survival period of the patients with GST-pi positive expression was also obviously shorter than that of those with GST-pi negative expression (P = 0.004). CONCLUSION: These results strongly suggest that GST-pi expression in epithelial ovarian cancer tissues is closely related to chemoresistance clinically and it may be served as a useful marker to predict the prognosis of patients.

Antineoplastic Agents↗

PubMed1997

[Animal experiment on gene therapy of ovarian cancer by adenovirus-mediated thymidine kinase gene transduction and ganciclovir administration in vivo].

OBJECTIVE: The efficacy and toxicity of adenovirus-mediated transduction of herpes simplex virus thymidine kinase gene started by Rous sarcoma virus (ADV/RSV-tk) followed by administration of ganciclovir (GCV) were studied in vivo. METHODS: An animal model of human epithelial ovarian cancer was established in nude mice using the serous ovarian adenocarcinoma cell lines Ov-ca-2774, then mice were treated by ADV/RSV-Tk and GCV, or GCV and HSV-tk respectively. The average survival time of mice and toxicity were assessed. RESULTS: The mice treated with GCV or HSV tk alone died from 14.4 +/- 1.7 to 19.3 +/- 3.5 days after treatment. The survival time had no difference with control group. The mice treated with ADV/RSV-tk followed by GCV lived at least two times longer than controls and the difference in both groups was significant. The earlier the treatment began, the longer the average survival time was. Treatment efficacy was dependent on dose of ADV/RSV-tk and tumor burden of mice. CONCLUSION: ADV/RSV-tk gene therapy is a safe and efficient approach to ovarian cancer treatment in the experiment.

Adenoviridae↗

PubMed1996

The effect of overexpression of the protein tyrosine phosphatase PTPMEG on cell growth and on colony formation in soft agar in COS-7 cells.

We established stable COS-7 cell lines overexpressing recombinant PTPMEG and an inactive mutant form in which the active site cysteine is mutated to serine (PTPMEGCS). We found that both endogenous and recombinant enzyme were primarily located in the membrane and cytoskeletal fractions of COS-7 cells. Endogenous PTPMEG accounts for only 1/3000th of the total tyrosine phosphatase activity in COS-7 cells and transfected cells expressed 2- to 7-fold higher levels of the enzyme. These levels of overexpression did not result in detectable changes in either total tyrosine phosphatase activity or the state of protein tyrosine phosphorylation as determined by immunoblotting of cell homogenates with anti-phosphotyrosine antibodies. Despite the low levels of activity for PTPMEG, we found that overexpressing cells grew slower and reached confluence at a lower density than vector transfected cells. Surprisingly, PTPMEGCS-transfected cells also reach confluence at a lower density than vector-transfected cells, although they grow to higher density than PTPMEG-transfected cells. Both constructs inhibited the ability of COS-7 cells to form colonies in soft agar, with the native PTPMEG having a greater effect (30-fold) than PTPMEGCS (10-fold). These results indicate that in COS-7 cells both PTPMEG and PTPMEGCS inhibit cell proliferation, reduce the saturation density, and block the ability of these cells to grow without adhering to a solid matrix.

Animals↗

PubMed1996

The properties of the protein tyrosine phosphatase PTPMEG.

We previously cloned a cDNA encoding a protein tyrosine phosphatase (PTP) containing sequence homology to protein 4.1, designated PTPMEG. Recombinant protein and amino- and carboxyl-terminal peptides were used to obtain polyclonal antibodies against PTPMEG to identify endogenous PTPMEG in A172 cells and to show that the enzyme is primarily localized to the membrane and cytoskeletal fractions of these cells. We prepared recombinant protein in Sf9 and COS-7 cells to further characterize it. The protein was phosphorylated in both cell types on serine and threonine residues. The multiple sites of phosphorylation were all within the intermediate domain of the protein between amino acids 386 and 503. This region also contains two PEST sequences and two proline-rich motifs that may confer binding to Src homology 3 domains. The recombinant protein was cleaved by trypsin and calpain in this region and thereby activated 4-8-fold as assayed using Raytide as substrate. We immunoprecipitated the protein from human platelets with both amino- and carboxyl-terminal antipeptide antibodies to assess the state of the enzyme in these cells. The full-length molecule was found in extracts from unstimulated platelets, whereas extracts from both calcium ionophore- and thrombin-treated platelets contained proteolyzed and activated forms of the enzyme, indicating that proteolysis by calpain is evoked in response to thrombin. Prior incubation of platelets with calpeptin, an inhibitor of calpain, blocked the agonist-induced proteolysis.

Amino Acid Sequence↗

PubMed1996

A pilot study of blood antioxidant and free radical marker profiles in patients awaiting coronary artery bypass grafting.

Coronary artery bypass grafting (CABG) carries a high risk of acute pancreatitis. We report a pilot study to investigate whether pre-existing oxidative stress might underlie this susceptibility, in that a burst of free radical activity not only accompanies the reperfusion stage of CABG but seems to be a pivotal step in the pathogenesis of pancreatitis. Samples of peripheral venous blood were obtained on the morning of surgery from 8 consecutive patients (age, median and range, 62, 35-70 years) with > 75% stenosis in at least three coronary vessels and a further 8 (64, 49-70 years) who had received 1200 mg allopurinol in divided doses in the previous 48 h: the results were compared with profiles of 8 healthy controls (56, 50-60 years) with normal exercise ECG. None of the patients or controls currently smoked cigarettes and the majority drank alcohol on a social basis. Compared with controls, untreated patients had lower levels of glutathione (P < 0.001) and ascorbate (P < 0.05) in plasma, alpha-tocopherol (vitamin E as molar ratio of cholesterol, P < 0.025 and beta-carotene (P < 0.05) in serum. There was no difference in serum selenium levels, but values in patients and controls were lower than in younger controls from this area (P < 0.02). Samples from the patients contained higher concentrations of lipid peroxides than control samples (P < 0.25) but there was no evidence of excessive isomerisation of linoleic acid or oxidation of ascorbate and erythrocytes showed normal ATP and energy charge with no increase in membrane lipid peroxidisability. Treatment with allopurinol did not alter this pattern, such that the ratio of oxidised to total glutathione in plasma was higher among the 16 patients than 8 controls (P < 0.025). Habitually inadequate intakes are the best explanation for the patients' deficits in aqueous phase antioxidants; prescribed low cholesterol diets would exacerbate any prior insufficiency of lipid-phase antioxidants. Correction of these deficits during the months leading up to surgery should reduce the risk of CABG-induced acute pancreatitis.

Adult↗

PubMed1996

Mitochondrial defect in Huntington's disease caudate nucleus.

Although the Huntington's disease (HD) gene defect has been identified, the structure and function of the abnormal gene product and the pathogenetic mechanisms involved in producing death of selective neuronal populations are not understood. Indirect evidence from several sources indicates that a defect of energy metabolism and consequent excitotoxicity are involved in HD. Toxin models of HD may be induced by 3-nitropropionic acid or malonate, both inhibitors of succinate dehydrogenase, complex II of the mitochondrial respiratory chain. We analyzed mitochondrial respiratory chain function in the caudate nucleus (n = 10) and platelets (n = 11) from patients with HD. In the caudate nucleus, severe defects of complexes II and III (53-59%, p < 0.0005) and a 32-38% (p < 0.01) deficiency of complex IV activity were demonstrated. No deficiencies were found in platelet mitochondrial function. The mitochondrial defect identified in HD caudate parallels that induced by HD neurotoxin models and further supports the role of abnormal energy metabolism in HD. The relationship of the mitochondrial defect to the role of huntingtin is not known.

Aged↗

PubMed1996

Primary inflammatory fibrosarcoma of the esophagus.

Primary sarcomas of the esophagus are rare. We report the radiologic, surgical, and pathologic findings of a primary inflammatory fibrosarcoma of the esophagus in a 33-year-old woman, and review the prognostic features and management options of this tumor.

Adult↗

PubMed1996

Furin regulates both the activation of Pseudomonas exotoxin A and the Quantity of the toxin receptor expressed on target cells.

Pseudomonas exotoxin A (PE) binds and enters mammalian cells via the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP). The toxin then requires proteolytic cleavage to generate an enzymatically active fragment with translocates to the cell cytosol and inhibits protein synthesis. To assess the role of furin in determining toxin susceptibility, CHO cells were transfected with a mouse furin gene (CHO+fur cells) and maintained under neomycin selection. Cells expressing the transfected gene were about two- to threefold more sensitive to PE than were cells expressing only a neomycin resistance gene (CHO+neo cells). Possible reasons for the increased toxin sensitivity include the cleavage of a greater number of PE molecules and/or the conversion of more single-chain LRP to the processed, two-chain form. Processing of LRP appears to be necessary to allow the surface display of this receptor. Results of ligand binding studies indicated that the CHO+fur cells displayed about twofold more surface-expressed LRP than did CHO+neo cells. In addition, the in vitro cleavage of PE by recombinant furin enhanced toxin potency about threefold for CHO+neo cells but enhanced it very little for CHO+fur cells. This suggested that CHO+fur cells were processing PE at close to the maximum usable rate. Together these findings suggest that furin is involved in at least two separate protein processing pathways that each contribute to the sensitivity of cells to PE.

ADP Ribose Transferases↗

PubMed1996

Longitudinal study of molecular epidemiology of small round-structured viruses in a pediatric population.

Small round-structured viruses (SRSV), recently designated members of the family Caliciviridae, can now be readily subtyped by amplification of a defined portion of their genome by reverse transcription-PCR and then by identification of the amplicons with specific probes by Southern blotting. A longitudinal survey (from 1991 to 1995) was conducted to determine the genotypes of the SRSV present in pediatric stool specimens from patients with sporadic cases of gastroenteritis. It was found that almost all viruses were of the G-2 genotype, and on probing, the subtype P2-B was predominant but the frequencies of the different subtypes varied from year to year. A survey of the genotypes of SRSV from community outbreaks from 1995 showed that the G-2 genotype was also predominant and that the distribution of its subtypes was similar to that seen in sporadic cases of diarrhea in pediatric patients over the same time period. It was concluded that there is a succession of subtypes of SRSV in our pediatric population over time. This distribution of genotypes in sporadic cases of pediatric gastroenteritis may reflect the distribution in community outbreaks occurring at the same time.

Caliciviridae Infections↗

PubMed1996

[The evaluation of adenosine triphosphate bioluminescence assay for chemosensitivity testing of ovarian cancer cell line].

OBJECTIVE: To assess the efficacy of adenosine triphosphate (ATP) assay for chemosensitity testing of ovarian cancer cell line and to compare its predicting value with that of diphenyltetrazolium bromide (MTT) test. METHODS: By using ATP assay and MTT test the cytotoxic effect of 7 anticancer drugs on ovarian cancer cell line AO were determined. The sensitivity and stability of ATP assay were compared with those of MTT test. The optimal time of exposure of the cells to the drugs before doing ATP chemosensitity assay is investigated. RESULTS: (1) The results obtained by ATP assay correlate well with that by MTT test (r = 0.918 1). However, in 90% of the assay samples the cytotoxic effect of the chemotherapeutic agents on cancer cells detected by ATP assay was 10% or more stronger as compared with that determined by MTT test. The difference in sensitivity of the two assays was also demonstrated by the least number of living cells. A change of living cells of 60 per well could be detected by ATP assay while that detected by MTT test should be 200 per well. (2) By repeating the tests of a same batch of samples for 5 times, it revealed that the results obtained by ATP assay was more stable than MTT test. The difference between the sx- (standard error) of the two tests was significant (P < 0.05). (3) The optimal time of exposure of the cancer cells to the anticancer drugs for testing its chemosensitivity was 5 days. CONCLUSIONS: The method of ATP assay for chemosensitivity test is simple and convenient with high sensitivity and stability. It may be used as a new in vitro chemosensitivity test in patients with ovarian cancer.

Adenosine Triphosphate↗

PubMed1995

Furin is important but not essential for the proteolytic maturation of gp160 of HIV-1.

The envelope glycoproteins of HIV are required for viral infectivity. Proteolysis of the precursor envelope glycoprotein gp160 results in the formation of gp120 and gp41. Cleavage occurs after the sequence Arg-Glu-Lys-Arg. This sequence is expected to be a substrate for the cellular protease furin. We examined whether furin is responsible for cleavage of gp160 by using a furin-deficient CHO cell line and the same cell line transfected with furin cDNA. Data obtained from viral transmission assays suggested that furin increased viral infectivity but was not essential for the maturation of gp160, implying that other proprotein processing enzymes also recognize this putative furin cleavage site.

Amino Acid Sequence↗

PubMed1995

Mutational spectra in the lacl gene in skin from 7,12-dimethylbenz[a]anthracene-treated and untreated transgenic mice.

Transgenic mice carrying the bacterial lacl gene in a lambda shuttle vector were used to isolate and characterize background and 7,12-dimethylbenz[a]anthracene (DMBA)-induced mutations in skin. Adult male mice were treated once topically with either DMBA or acetone or were left untreated. Seven days later, DMBA treatment had significantly increased the mutant frequency in the skin (mean +/- SEM, 36 +/- 3 x 10(-5)) versus in vehicle-treated (6.4 +/- 1.2 x 10(-5)) and untreated mice (7.1 x 1.0 x 10(-5)). At least 10 mutants from each of three DMBA-treated and three untreated mice were selected for DNA sequence analysis. In each case, the entire 1080-bp target gene was sequenced. Base-pair substitutions predominated (86 of 96 mutations), although frameshift and deletion mutations were also detected. Twelve percent of the mutants carried more than one mutation. In controls, the mutations were predominantly GC-->AT transitions (26 of 42), and no AT-->TA transversions were recovered. In contrast, in the DMBA-treated mice, AT-->TA transversions represented 42% of the mutations (23 of 54) and GC-->AT transitions accounted for only 11%. The AT-->TA transversions occurred mostly at 5'-CA sites. This class of mutation has been recovered frequently in ras genes from DMBA-treated mice and probably represents an early event in carcinogenesis (Nelson MA et al., Proc Natl Acad Sci USA 89:6398-6402, 1992). Our present results are consistent with the types of DNA damage induced by DMBA. The observation of different mutant frequencies and spectra in treated and control mice demonstrates the utility of this approach in the study of mutagenesis in vivo.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1995

Identification of salivary proteins inhibiting herpes simplex virus 1 replication.

Salivary proteins play an important role in the maintenance of the oral ecology. Previous studies have indicated that human submandibular-sublingual and parotid salivas can selectively suppress the in vitro infectivity of herpes simplex virus 1. The purpose of this study was to identify the salivary components in human submandibular-sublingual saliva that modulate in vitro infectivity. Assessment of the interaction of viral particles with salivary components was accomplished using an in vitro solid-phase assay. These experiments revealed that herpes simplex virus particles selectively interact with the members of the salivary proline-rich protein and cystatin families. Subsequent yield reduction assays demonstrated the ability of proline-rich proteins and salivary cystatins to inhibit the viral replication, with basic proline-rich peptides being more effective. Subsequent assays suggest that basic proline-rich peptides reduced the virus titer by interfering with penetration and/or cellular processing of virus within the target cell. Collectively, these results further suggest that salivary proteins have an important role in the host defense mechanism against recurrent herpesvirus infection.

Animals↗