Search PubMed⌕ Search

Biomedical subjects

S Chou

Publications and source records attributed to S Chou.

At least 55 records · Page 3Linked to original sources
PubMed1997

Low multiplicity cytomegalovirus infection of human aortic smooth muscle cells increases levels of major histocompatibility complex class I antigens and induces a proinflammatory cytokine milieu in the absence of cytopathology.

BACKGROUND: Cytomegalovirus has been implicated in the development of allograft vasculopathy in heart transplant recipients. Given that allograft vasculopathy is a form of chronic rejection, it is conceivable that cytomegalovirus somehow alters the allogeneic response to the vasculature. Prior work has demonstrated that smooth muscle cells (SMCs) are highly permissive for cytomegalovirus and exhibit cytopathologic characteristics and alterations in MHC class I antigens in response to cytomegalovirus at a high multiplicity of infection (MOI). METHODS: To determine whether cytomegalovirus at low, more clinically relevant MOI, can alter SMCs phenotypically, human aortic SMCs were infected with approximately 1 plaque forming units/3000 cells of cytomegalovirus strain AD169. RESULTS: One week after infection, human aortic SMCs (compared with human foreskin fibroblasts) demonstrated no cytopathologic characteristics (n = 6), released reduced amounts of intact virion into the culture media (assessed by exposing naive monolayers of human foreskin fibroblasts to media and staining for cytomegalovirus immediate-early antigen, n = 3), yet had at least, if not greater detectable total cytomegalovirus vital DNA levels. Infected HASMCs uniformly increased their expression of MHC class I antigen by 55% +/- 21% above constitutive levels (assessed by flow cytometry (n = 5, p < 0.0001). Cytomegalovirus infection resulted in an increase in interleukin-6 mRNA expression compared to control (297 +/- 63 vs 188 +/- 50, respectively; p = 0.02, n = 6) and reduced the expression of transforming growth factor-beta mRNA (802 +/- 152 vs 1201 +/- 236, respectively; p = 0.05). CONCLUSIONS: These data suggest that low MOI of cytomegalovirus can infect SMCs without producing cell cytolysis and, in spite of this lack of overt infection, modulate cell surface antigens and cytokine mRNA levels that can influence allogeneic responses.

Antigens, Viral↗
PubMed1996

Detection of ganciclovir resistance mutations quantitation of cytomegalovirus (CMV) DNA in leukocytes of patients with fatal disseminated CMV disease.

Cytomegalovirus (CMV) UL97 mutations associated with ganciclovir resistance at codons 460, 594, and 595 were detected by polymerase chain reaction (PCR) followed by restriction enzyme analysis in CMV blood isolates and directly in polymorphonuclear leukocyte (PMNL) DNA extracts of 4 subjects who died of progressive disseminated CMV disease due to ganciclovir-resistant CMV strains. The CMV DNA load was also serially determined in leukocyte fractions of these patients using a quantitative-competitive PCR assay. There was excellent concordance between specific UL97 mutations in blood culture isolates and those detected in PMNL fractions for all patients. Emergence of such UL97 mutations during ganciclovir therapy was associated with an increasing CMV DNA burden in leukocytes of the 2 patients with AIDS but not in the 2 subjects with chronic lymphocytic leukemia. Rapid molecular strategies, including detection of common CMV UL97 mutations and CMV DNA quantitation, can be used directly in leukocytes of immunocompromised subjects with CMV disease to monitor antiviral therapy.

AIDS-Related Opportunistic Infections↗
PubMed1996

Direct identification of Mycobacterium species in Bactec 7H12B medium by gas-liquid chromatography.

Twenty-nine Mycobacterium reference strains representing 10 species and 60 mycobacterial cultures isolated from sputum specimens were studied. These cultures were grown in Bactec 7H12B medium (Becton Dickinson and Co., Paramus, N.J.) supplemented with oleic acid-albumin-dextrose-catalase enrichment broth (Becton Dickinson and Co., Cockeysville, Md.). The cultures were analyzed by gas-liquid chromatography for their fatty acids, secondary alcohols, and mycolic acid cleavage products. All of the clinical isolates could be identified by comparing their gas-liquid chromatography profiles with those of the reference strains. The data indicate that this method significantly shortens the turnaround time and could be used for the early detection and identification of mycobacterial species.

Alcohols↗
PubMed1996

Single amino acid changes in the DNA polymerase confer foscarnet resistance and slow-growth phenotype, while mutations in the UL97-encoded phosphotransferase confer ganciclovir resistance in three double-resistant human cytomegalovirus strains recovered from patients with AIDS.

Three human cytomegalovirus (HCMV) strains (VR4760, VR4955, and VR5120) showing double resistance to ganciclovir (GCV) and foscarnet (PFA) were isolated from three patients with AIDS who underwent multiple sequential courses of therapy with GCV and PFA (A. Sarasini, F. Baldanti, M. Furione, E. Percivalle, R. Brerra, M. Barbi, and G. Gerna, J. Med. Virol., 47:237-244, 1995). We previously demonstrated that the three strains were genetically unrelated and that each of them was present as a single viral population in vivo. Thus, in each of the three cases, a single viral strain was resistant to both GCV and PFA. In the present paper, we report the characterization of the molecular bases of the double resistance and demonstrate that the PFA resistance is associated with a slower replication of HCMV strains in cell cultures. Sequencing of the UL97 and UL54 genes, GCV anabolism assays, and marker transfer experiments showed that GCV resistance was due to single amino acid changes in the UL97 gene product (VR4760, Met-460 --> Ile; VR4955, Ala-594 --> Val; VR5120, Leu595 --> Ser), while single amino acid changes in domain II of the DNA polymerase (VR4760 and VR5120, Val-715 --> Met; VR4955, Thr-700 --> Ala) were responsible for both the PFA resistance and the slow-growth phenotype. Thus, in these three cases, double resistance to GCV and PFA was not due to a single mutation conferring cross-resistance or to the presence of a mixture of strains with different drug susceptibilities. The HCMV DNA polymerase recombinant strains carrying the mutations conferring PFA resistance were sensitive to GCV and (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC). In addition, the same UL54 mutations were responsible for the slow growth of the clinical isolates, since the recombinant strains showed a marked delay in immediate-early antigen plaque formation and a reduction of infectious virus yield compared with AD169, from which they were derived. These results may have some important implications for the successful isolation, propagation, and characterization of PFA-resistant strains from clinical samples containing mixed viral populations.

AIDS-Related Opportunistic Infections↗
PubMed1996

Folic acid and prevention of neural tube defects: a study of Canadian mothers of infants with spina bifida.

OBJECTIVES: To determine the diffusion of information about preventing neural tube defects (NTDs) through folic acid consumption by examining whether mothers of Canadian children born with spina bifida, who had become pregnant at least a year after evidence of the preventive effect of folic acid had been published, had taken sufficient amounts of folic acid in the periconceptional period and were aware of this important new information. DESIGN: Validated food-frequency questionnaire to assess folate intake. SETTING: The Hospital for Sick Children in Toronto between Jan. 4 and Aug. 16, 1994. PARTICIPANTS: Thirty mothers whose infants were being treated for spina bifida. MAIN OUTCOME MEASURES: The mothers' mean folate intake and knowledge about the protective effect of folic acid; demographic and health information. RESULTS: The mothers' mean folate intake was 0.182 mg/d (standard deviation 0.076 mg/d, range 0.02 to 0.53 mg/d), less than half the protective dose. Only 4 (13%) of the mothers had been aware of the relation between nutritional folate and NTDs when they conceived, but even they did not supplement their diets with sufficient folic acid. The medical data showed that, in addition to the failure of primary prevention of NTDs, secondary prevention through diagnostic tests during pregnancy were also inadequate. CONCLUSIONS: Our study, one of the first to be conducted after the role of folate in preventing NTDs was confirmed, reveals that, in one of the most advanced countries in the world, this new information has had no effect on patients' folate intake. Unless food is fortified with folate, the estimated 400 to 800 annual cases of NTDs in Canada will not be prevented.

Canada↗
PubMed1996

[Allergic granulomatous angiitis in a patient with positive reactions on serological tests for parasite antigens].

A 68-year-old woman with bronchial asthma complained of fever, right thigh pain, sensory disturbance at the tips of the upper and lower limbs, and abdominal pain. She had severe eosinophilia and radiologic examination showed a mass-like shadow in the left lower lobe of the lung. Allergic granulomatous angiitis was diagnosed on the basis of findings from a muscle biopsy (gangrenous vasculitis with eosinophilia). This patient also had positive results of serological tests (Ouchterlony method) for various parasite antigens, despite the fact that no eggs of parasites were found in her feces. After steroid administration, the serological reactivity to parasite antigens had decreased. The positive reactions to parasite antigens was probably related to the cause of the vasculitis.

Aged↗
PubMed1995

Analysis of the UL97 phosphotransferase coding sequence in clinical cytomegalovirus isolates and identification of mutations conferring ganciclovir resistance.

The UL97 phosphotransferase coding sequences of clinical cytomegalovirus (CMV) isolates, 10 resistant and 11 sensitive to ganciclovir, were compared to define mutations associated with drug resistance. In each ganciclovir-resistant isolate, a mutation was found that resulted in an amino acid substitution at codon 460 (4 isolates), codon 594 (2 isolates), or codon 595 (4 isolates). No sensitive isolate carried any of these mutations. Marker transfer studies showed that each mutation was capable of conferring ganciclovir resistance to the laboratory CMV strain AD169. Rapid diagnostic tests based on DNA amplification and restriction enzyme analysis were developed for these mutations. Specific mutant DNAs were detected when they constituted at least 10% of the population in the specimen. Several mutations in UL97 appear to be common markers for ganciclovir resistance, and their detection may be a rapid alternative to conventional cell culture susceptibility testing.

Amino Acid Sequence↗
PubMed1995

Frequency of UL97 phosphotransferase mutations related to ganciclovir resistance in clinical cytomegalovirus isolates.

Cytomegalovirus (CMV) isolates from subjects who received ganciclovir therapy were tested for susceptibility to ganciclovir by a plaque reduction assay. Results were correlated with restriction enzyme and sequence analysis of the CMV UL97 phosphotransferase gene. Of the 30 isolates, 20 had one or more mutations in UL97 affecting amino acid encoding at codons 460, 520, or 591-596. All 20 were resistant to ganciclovir, with an IC50 of > 6.0 microM (range, 6.7-50.0). The remaining 10 isolates had no mutations at these loci; 8 were susceptible to ganciclovir while the other 2 were borderline resistant (IC50s, 6.6 and 7.2 microM). None of 40 control CMV isolates from untreated subjects contained any amino acid changes at these loci. The three most common mutations at codons 460, 594, and 595 were detected by restriction digest analysis in 16 (80%) of 20 isolates and in 16 (73%) of 22 isolates with ganciclovir IC50s > 6.0 microM. These results indicate that the majority of ganciclovir-resistant clinical isolates contain diagnostically useful mutations in UL97.

Amino Acid Sequence↗
PubMed1995

Novel mutation in the UL97 gene of a clinical cytomegalovirus strain conferring resistance to ganciclovir.

Characterization of a ganciclovir-resistant cytomegalovirus strain from a patient with AIDS showed a histidine-to-glutamine change at residue 520 of UL97 (Q520 mutation). In anabolism studies, Q520 was associated with impaired phosphorylation of ganciclovir. Transfer of Q520 to a recombinant virus resulted in a ganciclovir-resistant phenotype.

AIDS-Related Opportunistic Infections↗
PubMed1995

[ATPase activity of erythrocytic membrane and intraerythrocytic ionic levels in pregnancy with intrahepatic cholestasis].

To study the relationship between lithocholic acid and intrahepatic cholestasis of pregnancy (ICP), the ATPase activity of erythrocytic membrane and intraerythrocytic ionic levels were determined in 24 non-pregnant women, 38 normal pregnant women and 34 gravida with ICP. The activities of Na(+)-K+ ATPase, Ca++ ATPase and Mg++ ATPase of the membrane were found significantly lower in ICP group than in the controls. Intraerythrocytic Na+ and Ca++ levels were higher and Mg++ was significantly lower in ICP group than in the controls, and K+ showed no difference among the three groups. A negative correlation existed between lithocholic acid level and the activity of ATPase (Na(+)-K+, Ca++). The conclusion is that the high levels of lithocholic acid affected the morphology and function of the red blood cells.

Adenosine Triphosphatases↗
PubMed1994

Analysis of interstrain variation in a putative immediate-early region of human herpesvirus 6 DNA and definition of variant-specific sequences.

Sequences of a 2.6- to 2.9-kb open reading frame in a putative immediate-early region of the human herpesvirus 6 (HHV6) genome were determined and compared in three reference and six local isolates of HHV6. The sequences segregated into two variant groups (A and B) having only 75% nucleotide homology and 62% peptide homology, in part because of deletions in the variant A strains. Among the variant B isolates, further sequence grouping was evident; two clinical isolates segregated with reference strain Z29 into a cluster that had 96.6% nucleotide homology and 92.6% peptide homology when compared to a second variant B cluster of four isolates. Within each cluster of variant B isolates, nucleotide homology was 99.4% or more. Two pairs of isolates had identical sequences. The marked divergence of variants A and B permitted the design of variant-specific oligonucleotide primers that could detect in a single polymerase chain reaction the presence of either or both variant A and B HHV6 DNA. Variation in this gene region of HHV6 is more extensive than in the envelope glycoprotein (gB and gH) coding regions and could be related to known biological differences between variant groups.

Amino Acid Sequence↗
PubMed1994

Frequency distribution of cytomegalovirus envelope glycoprotein genotypes in bone marrow transplant recipients.

Using restriction analysis of polymerase chain reaction (PCR)-amplified DNA, the cytomegalovirus (CMV) envelope glycoprotein (gB and gH) genotypes were determined for virus isolates from 128 bone marrow transplant recipients with fatal or nonfatal CMV. All isolates could be assigned to one of four gB and gH genotypes previously identified by DNA sequencing studies. Isolates of gB type 1 were more commonly found to be of gH type 2, whereas gB types 2-4 were more commonly linked to gH type 1. A small frequency of recombination with gB was detected by restriction analysis of DNA from variable regions of the gp55 and gp116 domains. Multiple isolates from various sites of 29 patients were typed and, with three exceptions, the gB genotype remained constant in all isolates from a single patient. Patients who survived CMV infection more commonly shed virus of gB type 1 than those who died (P = .003). This significant difference of gB types among patient subsets is unexplained but raises the possibility that gB genotypes may serve as a marker for pathogenicity of CMV strains in marrow transplant patients.

Adolescent↗
PubMed1993

Fibromatosis in infancy and childhood: the spectrum.

Fibromatoses form an interesting group of tumors occupying a midposition in the spectrum of fibrous tissue neoplasms. Within the fibromatoses subgroups there exists a variety of tumors whose clinical behavior spans the range from completely benign to locally aggressive. Four case histories are presented to illustrate this point. All four patients were initially seen with asymptomatic head or neck masses. The first had complete excision with no recurrence to date. The second underwent spontaneous regression after confirmation of diagnosis with biopsy. The third case had a very locally aggressive disease requiring three surgical resections to date, while the last case had one recurrence after the initial resection. With certain exceptions, initial wide local excision offers the best possible chance for cure.

Biopsy↗
PubMed1993

Antibodies induced by a primary cytomegalovirus infection react with human herpesvirus 6 proteins.

After a primary human cytomegalovirus (HCMV) infection, antibody titer to human herpes-virus 6 (HHV-6) rises. To determine if this occurs because of simultaneous infection with both viruses, serologic responses to these viruses were investigated among healthy women who received a live HCMV vaccine or acquired HCMV from an infected child. Both vaccination and natural infection caused four-fold or greater titer rises to HHV-6. Analysis of sera from 5 children with primary HHV-6 showed no serologic response to HCMV. Absorption of 7 sera with HCMV antigens reduced titers to HHV-6 by two- to fourfold. Immunoblot analysis of sera obtained from 10 persons before and after a primary HCMV infection revealed that after HCMV infection, 2 persons developed IgG reactivity to the 116-kDa protein (gp116) of HHV-6 and to two cleavage products of this protein. Reactivity to HHV-6 gp116 appeared after HCMV sero-conversion and was removed by absorption of sera with HCMV glycoprotein gB (gB), indicating that antibodies to HCMV gB cross-react with HHV-6 gp116, the likely gB homologue of HHV-6. The serologic diagnosis of HHV-6 infection requires excluding a primary HCMV infection.

Antibody Formation↗
PubMed1992

Homology of the envelope glycoprotein B of human herpesvirus-6 and cytomegalovirus.

The envelope glycoprotein B (gB) coding sequences of two strains of human herpesvirus-6 (HHV6 GS and Z29) were determined by sequencing a 2.5-kb open reading frame adjacent to the DNA polymerase sequence. The deduced primary translation product is 830 amino acids in length and is 96% conserved between the two divergent strains with no localized hypervariability noted. It contains the expected signal and transmembrane sequence motifs as well as a putative site of protease cleavage. There was 39% amino acid identity with the gB of human cytomegalovirus (CMV, strain AD169). HHV6-CMV gB peptide homology was evident through the entire sequence, but was especially strong in the amino-terminal portion of CMV gp55, which contains linear and conformational epitopes recognized by CMV-neutralizing antibodies. All 10 cysteine residues of HHV6 gB match corresponding residues of CMV gB. Sequence data suggest strong structural similarity and possible immunologic cross-reactivity of gB from the two viruses.

Amino Acid Sequence↗
PubMed1992

Comparative analysis of sequence variation in gp116 and gp55 components of glycoprotein B of human cytomegalovirus.

Sequence variation in the gp116 component of cytomegalovirus envelope glycoprotein B was examined in 11 clinical strains and compared with variation in gp55. The peptide variation in gp116 was found to be strongly clustered at codons 27-67, 440-460, and to a lesser extent at codons 181-194, 311-317, and 387-397. Strains adopted one of three to four peptide configurations at these loci, usually consistent with their gp55 sequence configuration. Two instances were observed of a sequence variation arising from recombination within gB. The limited, largely group-specific nature of variation in both gp116 and gp55 facilitates functional and immunologic analyses.

Amino Acid Sequence↗