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Biomedical subjects

S Chou

Publications and source records attributed to S Chou.

At least 37 records · Page 2Linked to original sources
PubMed1999

Antiviral drug resistance in human cytomegalovirus.

Drug-resistant cytomegalovirus (CMV) should be considered when viral shedding persists after several weeks of therapy. The problem is most likely to arise in the setting of a severely immunosuppressed host with continuing or relapsing disease. Not all treatment failure can be attributed to drug resistance. The testing of CMV isolates for drug resistance in cell culture is time-consuming and labor-intensive, but recent advances in understanding of the genetics of resistance have resulted in rapid genotypic assays for specific mutations in the viral UL97 phosphotransferase or UL54 DNA polymerase genes that can predict resistance and cross-resistance to specific drugs. This information may help in the selection of alternative therapy.

Antiviral Agents↗
PubMed1999

Transcriptional activation in yeast cells lacking transcription factor IIA.

The general transcription factor IIA (TFIIA) forms a complex with TFIID at the TATA promoter element, and it inhibits the function of several negative regulators of the TATA-binding protein (TBP) subunit of TFIID. Biochemical experiments suggest that TFIIA is important in the response to transcriptional activators because activation domains can interact with TFIIA, increase recruitment of TFIID and TFIIA to the promoter, and promote isomerization of the TFIID-TFIIA-TATA complex. Here, we describe a double-shut-off approach to deplete yeast cells of Toa1, the large subunit of TFIIA, to <1% of the wild-type level. Interestingly, such TFIIA-depleted cells are essentially unaffected for activation by heat shock factor, Ace1, and Gal4-VP16. However, depletion of TFIIA causes a general two- to threefold decrease of transcription from most yeast promoters and a specific cell-cycle arrest at the G2-M boundary. These results indicate that transcriptional activation in vivo can occur in the absence of TFIIA.

Cell Cycle↗
PubMed1999

Molecular epidemiology of hepatitis C infection in U.S. veteran liver transplant recipients: evidence for decreasing relative prevalence of genotype 1B.

OBJECTIVE: The U.S. Veteran population represents a unique patient group to study different HCV genotypes because of geographically diverse exposures. The aim of this study was to characterize the distribution of HCV genotypes in U.S. veterans undergoing liver transplantation (OLT), trace genotypes to modes of acquisition (risk behavior and location), and evaluate the relative prevalence of HCV genotypes according to the time of acquisition. METHODS: Between 10/88 and 12/95, 110 primary OLTs were performed in U.S. Veterans at our center. Forty-nine (45%) patients had detectable HCV-RNA by PCR at the time of OLT. Determination of HCV genotypes was performed by restriction fragment length polymorphism of the 5' noncoding region and classified according to Simmonds et al. RESULTS: Twenty-three of 49 (47%) veterans had 1a, 17 (35%) 1b, two (4%) 2a, three (6%) 2b, two (4%) 3a, two (4%) mixed (1a/2a, 1b/2a). This distribution of HCV genotypes was comparable to the genotypic distribution of a contemporary cohort of nonveteran OLT recipients at the University of Washington. There was a statistically significant association between illicit injection drug use (IDU) and 1a, with 63% of 1a patients having IDU whereas only 14% of 1b patients admitted to IDU (p = 0.03). All patients in whom the mode of acquisition was unknown had genotype 1b (p = 0.04). Intranasal cocaine use was strongly correlated with IDU (p = 0.002). Patients who had tattoos but no history of blood transfusion (BT) or recreational drug use had genotype 1 (2 had 1a, 2 had 1b; p = NS). Twenty-two (45%) patients had serological evidence of prior hepatitis B (HBV) infection. Patients who had genotype 2a, 2b, 3a, or mixed were much more likely to have had HBV (seven of nine, 78%) than patients with genotype 1a or 1b (15 of 40, 37.5%) (p = 0.03). There was no significant correlation between BT, dates, or military branch of service, high risk behavior in Southeast Asia, level of education, ethnicity, and particular genotype(s). Whereas the proportion of 1b accounting for HCV infection in patients with a first exposure before 1968 was 50%, all patients with a first exposure post-1975 were non-1b (p = 0.04), suggesting a change in the epidemiology of HCV in our cohort. CONCLUSIONS: In U.S. Veterans undergoing OLT: 1) 45% had PCR-confirmed HCV infection, 2) 1a was the predominant genotype and was associated with IDU, and 3) a significant decrease in the prevalence of genotype 1b from the pre-Vietnam era to post-1975 suggests a changing epidemiology of HCV genotypes.

Cocaine-Related Disorders↗
PubMed1999

Interstrain variation in the human cytomegalovirus DNA polymerase sequence and its effect on genotypic diagnosis of antiviral drug resistance. Adult AIDS Clinical Trials Group CMV Laboratories.

The polymerase (pol) coding sequence was determined for 40 independent clinical cytomegalovirus isolates sensitive to ganciclovir and foscarnet. Sequence alignments showed >98% interstrain homology and amino acid variation in only 4% of the 1, 237 codons. Almost all variation occurred outside of conserved functional domains where resistance mutations have been identified.

Antiviral Agents↗
PubMed1998

Association of cytomegalovirus genotype with graft rejection after liver transplantation.

BACKGROUND: The envelope glycoprotein gB of human cytomegalovirus (CMV) occurs as one of four main genotypes. Some previous studies have proposed a relationship of CMV gB genotype to the frequency of symptomatic infection and to clinical outcomes in both transplant and human immunodeficiency virus-infected populations. Our aim was to define the distribution of CMV gB genotypes and the impact on acute cellular rejection and graft/patient survival after orthotopic liver transplantation (OLT). METHODS: Between October 1988 and December 1996, 325 patients underwent cyclosporine-based OLT at our center. CMV infection was surveyed prospectively and defined as viral isolation from blood or urine; 53 (16%) patients had detectable CMV. Isolates were genotyped by polymerase chain reaction amplification and restriction digest analysis. RESULTS: The distribution of CMV genotypes was: gB1, 19 (36%) patients; gB2, 15 (28%) patients; gB3, 13 (24%) patients; and gB4, 4 (8%) patients. Two patients (4%) had mixed infection (1 + 3, 1 + 4). Age, preOLT diagnosis, use of ganciclovir prophylaxis, basal immunosuppression, mean number of HLA donor/recipient mismatches, and United Network of Organ Sharing status were comparable among patients with different genotypes. Patients with gBl had a significantly higher mean number of acute rejection episodes (1.52+0.30 vs. 0.67+0.22; P=0.027). However, there was no difference in rejection severity, including OKT3 usage or FK506 conversion, or development of chronic rejection among patients with different genotypes. The gB genotype did not affect the development of symptomatic or tissue-invasive CMV disease, detected in 15 patients. Actuarial rates of patient (odds ratio [OR] 3.0; confidence interval [CI] 1.49-6.0) and graft (OR 2.57; CI 1.25-5.22) survival were significantly diminished in the group with CMV infection versus those without CMV (P<0.0001 for both), but there was no association with CMV genotype. CONCLUSIONS: (1) Patients with CMV infection had significantly reduced patient and graft survival rates at 1 and 5 years after OLT as compared with OLT recipients without CMV infection. (2) CMV genotype gB1 was associated with a higher mean number of acute rejection episodes.

Adult↗
PubMed1998

Indicators of glial activation and brain oxidative stress after intraventricular infusion of endotoxin.

Glial activation and oxidative stress are both consequences of brain aging. To investigate whether glial activation causes oxidative stress or not, the immune activator, lipopolysaccharide (LPS), was intraventricularly injected into the rat brain. The expression of candidate genes were examined by in situ hybridization histochemistry (ISHH) combined with immunohistochemistry for glial markers over a period of time up to 24 h after the LPS injection. The mRNA for glial fibrillary acidic protein (GFAP) was elevated around the injection site by 2 h, and the volume of elevated expression spread to the entire brain after 6 h, with higher levels present in the injected hemisphere. The level of inducible isoform of nitric oxide synthase (i-NOS) mRNA increased in a punctate-like pattern in the region of the injection by 6 h and this response spread to the entire brain after 12 h. These results indicate that the glia are activated for at least 24 h after a single LPS injection. The mRNAs for a heat-shock protein (HSP70) and for the manganese-dependent superoxide dismutase (Mn-SOD) were elevated in the ipsilateral hemisphere as early as 2 h post-injection, but these responses subsided nearly to basal levels by 4 h. These levels of mRNAs for these genes increased again after 6 h of the LPS injection; thus, the earlier increases of the messages appeared to be associated with the survival surgery procedure. With microautoradiographic analysis, scattered OX-42 positive cells expressed i-NOS mRNA after 6 h post-injection, but elevation of Mn-SOD mRNA was not detected in either microglia or astrocytes at any time point examined. The level for Cu/Zn-SOD mRNA did not alter at any time point. The beta-amyloid precursor protein (betaAPP) mRNAs were elevated beginning at 6 h. These results indicate that chronic glial activation leads to a condition of oxidative stress in the brain. The data also suggest that LPS injection could be used to study the effects of chronic glial activation on the survival of neuronal populations that could be at risk from oxidative stress.

Animals↗
PubMed1998

Recurrent thyroglossal duct cysts: a clinical and pathologic analysis.

OBJECTIVE: To analyze, in detail, the clinical and pathological findings in a patient population that had undergone previous Sistrunk procedures for the removal of thyroglossal duct cysts, in order to identify any possible factors that could be related to recurrence after 'definitive' surgery. SETTING: A large pediatric tertiary care center. METHODS: A retrospective chart review was performed to include all patients treated at a single center for thyroglossal duct cysts with a Sistrunk procedure, between 1978 and 1992 inclusive. RESULTS: A total of 108 consecutive patients were analyzed. We noted that the presence of recent preoperative infection of the cyst was the only statistically significant (P < 0.05) clinical difference noted between the successful and the unsuccessful surgical groups. However, pathological analysis revealed that there was a substantially greater number of multiple thyroglossal duct tracts (P < 0.05) noted in the group that failed a Sistrunk procedure. CONCLUSIONS: We feel that multiple thyroglossal tracts may play an etiologic role in some recurrent cysts. Thus, a wide conservative excision, including the middle two thirds of the hyoid bone, is necessary in order to include any multiple tracts in the resection.

Canada↗
PubMed1998

Mutation in region III of the DNA polymerase gene conferring foscarnet resistance in cytomegalovirus isolates from 3 subjects receiving prolonged antiviral therapy.

Three human immunodeficiency virus-infected subjects with progressive cytomegalovirus (CMV) retinitis despite prolonged antiviral therapy had buffy coat CMV isolates that were resistant to both ganciclovir and foscarnet. Genetic analysis of the resistant isolates showed that each contained a well-known ganciclovir resistance mutation in the viral UL97 phosphotransferase sequence, as well as a mutation (Ala to Val at codon 809, V809) in conserved region III of the DNA polymerase (Pol) sequence. A segment of the Pol sequence from one of the clinical isolates was transferred to CMV laboratory strain AD169 by homologous recombination. The recombinant virus containing V809 showed 6.3-fold increased foscarnet resistance and 2.6-fold increased ganciclovir resistance. Occurrence of the V809 mutation in 3 unrelated cases suggests that it is a clinically significant viral genetic marker for foscarnet resistance and decreased susceptibility to ganciclovir.

AIDS-Related Opportunistic Infections↗
PubMed1998

The capacity of a combined liposomal hepatitis B and C vaccine to stimulate humoral and cellular responses in mice.

Combined hepatitis B surface antigen and hepatitis C antigen were encapsulated into 1, 2, and 5 microm discrete liposomes and then lyophilized. Groups of adolescent CD-1 mice were given a single 0.3 mL oral dose of these liposomes containing 50 microg/mL hepatitis B surface antigen and hepatitis C antigen, 50 microg/mL of the same antigens or liposomes alone. Animals in each group were sacrificed every 2 weeks for 10 weeks and the humoral response investigated by enzyme-linked immunosorbent assay (ELISA) and the cellular response by splenic lymphocyte proliferation to 10 microg of either antigen. Seroconversion to both antigens in the mice receiving liposomal antigens occurred in 87.5% of animals sacrificed at 4 weeks and later. One animal (12.5%) receiving antigen alone seroconverted to hepatitis B virus at 6 weeks, but all animals receiving liposomes alone remained negative. Proliferation indexes (PI) greater than 3 were observed in all animals receiving liposomal antigens, with the greatest response seen at 10 weeks. PI was less than 2 for all animals in the other two groups. Thus, a single oral dose of liposomes of three sizes containing both hepatitis B and C antigens given to mice resulted in rapid seroconversion and a progressive robust cellular immune response, whereas the antigens alone or liposomes without antigen did not.

Animals↗
PubMed1998

Use of gas chromatographic fatty acid and mycolic acid cleavage product determination to differentiate among Mycobacterium genavense, Mycobacterium fortuitum, Mycobacterium simiae, and Mycobacterium tuberculosis.

Three Mycobacterium genavense strains and three American Type Culture Collection reference strains each of Mycobacterium fortuitum, Mycobacterium simiae, and Mycobacterium tuberculosis were subcultured onto Mycobacteria 7H11 agar (Difco Laboratories, Detroit, Mich.) supplemented with mycobactin J (Allied Laboratories, Fayette, Mo.). After 4 weeks of incubation at 37 degrees C in 10% CO2, the cultures were analyzed by gas-liquid chromatography (GLC) for their fatty acids and mycolic acid cleavage products. M. fortuitum was clearly differentiated from M. genavense by the presence of the specific marker 2-methyloctadecenoic acid in M. fortuitum and by the ratio of tetracosanoic acid to hexacosanoic acid. This ratio was <1 for M. genavense and >3 for M. fortuitum. M. fortuitum also contained docosanoic acid, which was not detected in M. genavense. M. genavense, M. simiae, and M. tuberculosis, which have similar GLC profiles, were also differentiated from each other by the presence of either cis-10-hexadecenoic acid or cis-11-hexadecenoic acid and by tetradecanoic acid content.

Chromatography, Gas↗
PubMed1997

Cytomegalovirus viremia: risk factor for allograft cirrhosis after liver transplantation for hepatitis C.

BACKGROUND: Despite recent advances in diagnosis and treatment, cytomegalovirus (CMV) infection continues to be a common cause of morbidity in liver transplant (LT) recipients. Because CMV infection suppresses cell-mediated immunity, which seems to be important in neutralizing hepatitis C virus (HCV) infection, we assessed the impact of CMV infection on histopathological HCV recurrence after LT. METHODS: The study group was comprised of 43 consecutive LT recipients with at least 6 months of histologic follow-up. Group 1 consisted of the 8 patients who developed CMV viremia after LT; group 2 comprised the 35 patients without CMV viremia. There was no significant difference with regard to age, initial immunosuppression, incidence of rejection, distribution of HCV genotypes, or mean follow-up between the groups. Semiquantitative histopathologic assessment of allograft hepatitis was performed using the Knodell's score. RESULTS: The mean total Knodell score of the final allograft biopsy was significantly greater in group 1 patients (P=0.016), with most of the difference due to periportal/bridging necrosis (P=0.009) and lobular activity subitem (P=0.01) scores. Half of the CMV viremic patients eventually developed allograft cirrhosis as compared with 11% of the CMV-negative patients (P=0.027). Accordingly, the cirrhosis-free actuarial survival by Kaplan-Meier estimates was significantly diminished in the CMV viremic patients. Glycoprotein B genotype analysis of CMV isolates revealed no significant differences between patients who did and those who did not develop allograft cirrhosis. CONCLUSIONS: After LT for chronic HCV, patients who develop CMV viremia incur a significantly greater risk of severe HCV recurrence.

Antiviral Agents↗
PubMed1997

Perianal fetal rhabdomyoma: case report.

A 4-week-old female was referred with a firm, enlarging perianal mass present since birth. At surgery, the lesion appeared to be arising from the subcutaneous external sphincter. Local excision was successful with preservation of the external sphincter. Histologic examination showed a mixture of undifferentiated spindle cells as well as immature and maturing myofibers consistent with a fetal rhabdomyoma. This report represents the second case of a fetal rhabdomyoma arising in the perianal location. All pediatric cases of fetal rhabdomyoma in the literature are reviewed.

Anal Canal↗
PubMed1997

Antiviral susceptibilities and analysis of UL97 and DNA polymerase sequences of clinical cytomegalovirus isolates from immunocompromised patients.

Antiviral susceptibilities to ganciclovir, foscarnet, and cidofovir and sequencing of UL97 and DNA polymerase were done on 23 cytomegalovirus (CMV) isolates from 10 immunocompromised persons with end-organ CMV disease who were treated with ganciclovir alone or ganciclovir followed by foscarnet. Screening of UL97 for ganciclovir resistance mutations was done by restriction digest analysis. Of 14 isolates resistant to ganciclovir, 11 (79%) contained one or more UL97 mutations at codons known to confer resistance to this compound, and 10 (91%) had a concordant mutant pattern by restriction digest analysis. Of 9 isolates containing mutations in conserved regions of the DNA polymerase, 8 were resistant to ganciclovir, and 4 were cross-resistant to cidofovir. All isolates were susceptible to foscarnet. It is concluded that ganciclovir-resistant clinical CMV isolates may contain UL97 mutations, DNA polymerase mutations, or mutations in both genes. Ganciclovir therapy may select for CMV isolates that are cross-resistant to cidofovir.

AIDS-Related Opportunistic Infections↗
PubMed1997

Evolution of mutations conferring multidrug resistance during prophylaxis and therapy for cytomegalovirus disease.

In a human immunodeficiency virus-infected subject, cytomegalovirus (CMV) isolated 9 months after the patient began oral ganciclovir prophylaxis was resistant to ganciclovir and cidofovir and contained mutations in both UL97 and Pol coding regions. At 1 year, retinitis developed, which progressed despite intravenous ganciclovir followed by foscarnet and then cidofovir. A subsequent buffy coat virus isolate was resistant to all three drugs and contained new mutations in UL97 and Pol. By individually transferring the observed mutations to laboratory strain AD169, it was shown that a mutation at codon 603 of UL97 conferred resistance to ganciclovir, a mutation at codon 412 of Pol conferred resistance to both ganciclovir and cidofovir, and a mutation at codon 802 of Pol conferred resistance to ganciclovir and foscarnet. This case illustrates the development of multidrug resistance during prolonged exposure to antiviral therapy for CMV and cross-resistance arising from point mutations in the CMV Pol gene.

AIDS-Related Opportunistic Infections↗
PubMed1997

Cytomegalovirus gB genotype distribution differs in human immunodeficiency virus-infected patients and immunocompromised allograft recipients.

Cytomegalovirus isolates can be grouped into 4 gB and 2 gH genotypes. gB genotypes were studied in patients infected with human immunodeficiency virus (HIV) and in allograft transplantation recipients. In allograft recipients, the distribution of gB 1, -2, -3, and -4 in leukocytes and urine, respectively, was 36%, 21%, 43%, and 0% and 39%, 30%, 17%, and 13%. However, in leukocytes of HIV-infected patients with <100/microL CD4 cells, gB1 was found significantly less often than in allograft recipients (11% vs. 36%) but gB2 was more frequent (56% vs. 21%; P < .05). The decreased incidence of gBl and increased incidence of gB2 compared with allograft recipients was also seen in urine of HIV-infected patients and reflected the distribution seen in leukocytes. gB4 was found significantly more often (P < .05) in semen than in leukocytes of HIV-infected patients with < 100/microL CD4 cells. gB1-4 genotypes were similar in patients with < 100/microL CD4 cells with or without retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Quantification of cytomegalovirus DNA in peripheral blood leukocytes by a branched-DNA signal amplification assay.

Quantification of cytomegalovirus (CMV) DNA in blood may aid in the identification of patients at highest risk for developing CMV disease, the evaluation of new therapeutics, and the prompt recognition of drug-resistant CMV strains. A branched-DNA (bDNA) assay was developed for the reliable quantification of CMV DNA in peripheral blood leukocytes. The bDNA assay allowed for the highly specific and reproducible quantification of CMV DNA in clinical specimens. Furthermore, the bDNA assay was at least as sensitive as culture techniques and displayed a nearly 3 log10 dynamic range in quantification. Changes in CMV DNA levels measured by the bDNA assay in a human immunodeficiency virus-positive patient undergoing therapy were consistent with CMV culture, antigen, and genotype results and correlated with disease progression and resistance markers. The bDNA assay for the quantification of CMV DNA may provide a useful tool that can be used to aid physicians in monitoring disease progression, evaluating therapeutic regimens, and recognizing viral resistance and drug failure.

AIDS-Related Opportunistic Infections↗
PubMed1997

Transcriptional activation by TFIIB mutants that are severely impaired in interaction with promoter DNA and acidic activation domains.

Biochemical experiments indicate that the general transcription factor IIB (TFIIB) can interact directly with acidic activation domains and that activators can stimulate transcription by increasing recruitment of TFIIB to promoters. For promoters at which recruitment of TFIIB to promoters is limiting in vivo, one would predict that transcriptional activity should be particularly sensitive to TFIIB mutations that decrease the association of TFIIB with promoter DNA and/or with activation domains; i.e., such TFIIB mutations should exacerbate a limiting step that occurs in wild-type cells. Here, we describe mutations on the DNA-binding surface of TFIIB that severely affect both TATA-binding protein (TBP)-TFIIB-TATA complex formation and interaction with the VP16 activation domain in vitro. These TFIIB mutations affect the stability of the TBP-TFIIB-TATA complex in vivo because they are synthetically lethal in combination with TBP mutants impaired for TFIIB binding. Interestingly, these TFIIB derivatives support viability, and they efficiently respond to Gal4-VP16 and natural acidic activators in different promoter contexts. These results suggest that in vivo, recruitment of TFIIB is not generally a limiting step for acidic activators. However, one TFIIB derivative shows reduced transcription of GAL4, suggesting that TFIIB may be limiting at a subset of promoters in vivo.

Amino Acid Sequence↗