Search PubMed⌕ Search

Biomedical subjects

C C Pao

Publications and source records attributed to C C Pao.

At least 73 records · Page 4Linked to original sources
PubMed1990

Endocervical chlamydial deoxyribonucleic acid in infertile women.

The presence of chlamydial deoxyribonucleic acid (DNA) was evaluated by DNA hybridization in endocervical cells of infertile and normal fertile women. Chlamydial DNA was detected in 49 of 186 (26.3%) infertile patients, which is significantly more common than in fertile control individuals (12.5%, or 8 of 64 individuals). Among infertile patients, 49.3% (33 of 67) of those with tubal factors as cause of infertility and 13.4% (16 of 119) of those with nontubal factors were found to contain chlamydial DNA in their endocervical cells. The results show that chlamydial DNA could be found significantly more frequently in endocervical cells of infertile patients with tubal factor than those without tubal factors or in normal controls.

Adolescent↗
PubMed1989

The etiology of acute hepatitis superimposed upon previously unrecognized asymptomatic HBsAg carriers.

To study the etiology of acute hepatitis superimposed upon previously unrecognized asymptomatic HBsAg carriers, paired sera were collected in acute and convalescence phases for measurement of HBeAg, anti-HBe, hepatitis B virus DNA and anti-delta from 76 adult patients with acute hepatitis who were HBsAg positive but IgM anti-HBc negative or positive only at low titer. None of them were IgM anti-hepatitis A virus positive on admission. Of the 34 patients who were HBeAg positive initially, two (5.9%) were diagnosed as having delta superinfection, and another two (5.9%) were suspected to have non-A, non-B virus superinfection because of a transient decrease of serum hepatitis B virus DNA. The remaining 30 (88.2%) cases were hepatitis B virus DNA negative with or without anti-HBe seroconversion on follow-up. The episodes of acute hepatitis in these cases may represent "immune clearance of HBeAg" or "immune clearance of hepatitis B virus with delayed anti-HBe seroconversion," respectively, in the natural course of chronic hepatitis B virus infection. Of the patients who were anti-HBe positive initially, 23 (54.8%) were diagnosed as having delta superinfection, including eight with de novo seroconversion of anti-delta and 15 with a rising titer of anti-delta; 10 (23.8%) were positive for hepatitis B virus DNA and were considered as reactivation of hepatitis B virus, and the other nine (21.4%) were suspected as having non-A, non-B virus superinfection.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

Detection of human papillomaviruses in exfoliated cervicovaginal cells by in situ DNA hybridization analysis.

A total of 851 specimens of exfoliated cervicovaginal cells and 27 specimens of male urethral smears obtained from 706 individuals with various clinical findings were examined for the presence of human papillomavirus (HPV) types 6, 11, 16, 18, 31, and 33 by in situ DNA hybridization analysis. The nonradioactive DNA in situ hybridization method used in this study showed no detectable cross-hybridization either among different types of HPV (except between types 6 and 11) or between HPV DNA and human cellular DNA. Furthermore, this system was found to be more sensitive than the Southern blotting method in detecting HPV. HPV was found in 233 of 276 (84.4%) and in 34 of 47 (72.3%) samples of cervicovaginal cells from patients with urogenital condylomata and cervical dysplasia, respectively. HPV was also detected in 6 of 39 (15.4%) women with normal cytological findings who were also symptom-free. Young women who were at low risk but were infected with HPV showed significantly reduced ratios of helper-inducer T lymphocytes to suppressor-cytotoxic T lymphocytes compared with those of uninfected normal controls (1.28 +/- 0.31 versus 2.47 +/- 0.64; P less than 0.001). This in situ DNA hybridization method can have broad application to the screening of HPV in early lesions and in normal-looking tissues and may be used to identify patients at risk of more serious or possibly malignant progression.

Blotting, Southern↗
PubMed1988

The detection of mycobacterial DNA sequences in uncultured clinical specimens with cloned Mycobacterium tuberculosis DNA as probes.

A plasmid DNA library was constructed from restriction endonuclease digested genomic deoxyribonucleic acid (DNA) of a virulent strain of Mycobacterium tuberculosis isolated from sputum of a patient. The sensitivity and specificity of two of the cloned DNA fragments in detecting M. tuberculosis and its related DNA sequences were analysed by DNA-to-DNA hybridization. The level of detection was determined to be 50 picograms of M. tuberculosis DNA, which is approximately equivalent to 10,000 mycobacterial genomes. These two M. tuberculosis DNA probes did not cross-hybridize to DNA of non-mycobacterial origin, nor with DNA from 9 out of 11 other mycobacterial species. Mycobacterial DNA sequences could be detected in 134 of 441, or 30.4%, of various types of uncultured clinical specimens from 365 patients by the DNA probes, whereas traditional culture method showed only a 19.0% positivity rate for the same specimens (p less than 0.001). The overall sensitivity and specificity of the DNA probes in detecting M. tuberculosis are 90.5% and 83.8% respectively. The DNA hybridization test may become a useful tool for the early and rapid determination of mycobacterial infection in uncultured clinical specimens.

Autoradiography↗
PubMed1988

Changes of serum HBV-DNA in relation to serum transaminase level during acute exacerbation in patients with chronic type B hepatitis.

To examine the relationship between changes of serum hepatitis B virus-dexoyribonucleic acid (HBV-DNA) and transaminase levels during acute exacerbation of chronic type B hepatitis, serial serum specimens from 74 patients were assayed for HBV-DNA by slot blot hybridization with 32P-labeled cloned HBV-DNA as probe. Of these patients, serial serum specimens were obtained with an interval of 2-7 days in 22 patients (Group I), 8-14 days in 30 patients (Group II) and 15-30 days in 22 patients (Group III). The peak of serum HBV-DNA was reached shortly before or simultaneously with the maximum elevation of serum alanine transaminase (ALT) in most (greater than 90%) of the acute exacerbations. In contrast, the peak of serum ALT was reached before maximum elevation of serum HBV-DNA in only 13.6% of Group I, 3.3% of Group II and 13.6% of Group III (9.5% of whole series). The results suggest that the increase of serum HBV-DNA is an event preceding, rather than the result of, hepatocytolysis in most of the acute exacerbations occurring in patients with chronic type B hepatitis.

Alanine Transaminase↗
PubMed1988

Screening for hepatitis B virus in healthy blood donors by molecular DNA hybridization analysis.

A DNA molecular hybridization technique employing a purified adw subtype hepatitis B virus (HBV) cloned DNA of 3.2 kilobase pairs as a probe was used to screen for the presence of HBV DNA in blood samples collected from 486 apparently healthy blood donors. Eighteen of 104 (17.3%) hepatitis B surface antigen (HBsAg) carriers and 7 of 382 (1.8%) HBsAg-negative individuals had circulating HBV DNA in their sera. Among the seven individuals who were positive for HBV DNA but negative for HBsAg, three had antibodies against both HBsAg (anti-HBsAg) and hepatitis B core antigen, one had only anti-HBsAg, one had both anti-hepatitis B core antigen and anti-hepatitis B e antigen and two were negative for all the above HBV markers. The results suggest that the absence of HBsAg in otherwise apparently healthy individuals may not be enough to ensure lack of circulating HBV.

Adult↗
PubMed1988

Enhanced production of hepatitis B virus surface antigen in mouse C127 cell on a bovine papillomavirus-metallothionein vector.

We have constructed a recombinant plasmid pCPS12 containing the hepatitis B viral surface antigen (HBsAg) gene linked to the mouse metallothionein promoter on a BPV-pML2 vector. Two stable clones S12-8 and S12-2, obtained by transfection of the mouse C127 cells with pCPS12 propagated in dam+ dcm+ and dam- dcm- Escherichia coli respectively, exhibited different types of response to 5-azacytidine (5-aza-CR) and cadmium (Cd) induction. In S12-8, the productivity of HBsAg was enhanced by 5-aza-CR or 5-aza-CR plus Cd, but not by Cd alone. In S12-2, the expression of HBsAg was not affected by 5-aza-CR but was induced by Cd in the presence or absence of 5-aza-CR. This suggests that methylation may be important in controlling the HBsAg expression and the inducibility of Cd in the transfectants.

Animals↗
PubMed1987

Intra blood-cerebrospinal fluid-barrier detection of hepatitis B virus.

Hepatitis B, a major public health concern worldwide, is caused by hepatitis type B virus, a hepdnavirus that infects only human and certain nonhuman primates, and replicates strictly in hepatocytes. By using the techniques of slot and Southern blot DNA hybridization, and electron microscopy, the presence of HBV was identified in the cerebrospinal fluid of three affected individuals.

Blood-Brain Barrier↗
PubMed1987

Deoxyribonucleic acid hybridization analysis for the detection of urogenital Chlamydia trachomatis infections in women.

The presence of Chlamydia trachomatis-related deoxyribonucleic acid sequences in endocervical specimens of 317 women was analyzed by deoxyribonucleic acid hybridization techniques with deoxyribonucleic acid from C. trachomatis used as probes. Samples from 56 of 172 high-risk patients (32.6%) and 16 of 145 low-risk patients (11.0%) contained C. trachomatis-related deoxyribonucleic acid sequences. Direct detection of chlamydial antigen with enzyme-linked immunoassay on the same patients yielded positive rates of 26.3% and 7.3% for the high- and low-risk patients, respectively. C. trachomatis culture confirmed 86.3% of deoxyribonucleic acid-positive results and 84.0% of antigen-positive results. The overall sensitivities of chlamydial deoxyribonucleic acid and antigen assays were 91.7% and 68.8%, respectively, whereas the specificities were 95.3% and 94.7%. Results also suggested that the test of the C. trachomatis deoxyribonucleic acid correlated better with the female urogenital chlamydial infections than did the antigen test of C. trachomatis. The combined results of higher sensitivity in detecting the microorganism and better correlation with disease activity may make the deoxyribonucleic acid hybridization test a useful tool for the early and accurate diagnosis of C. trachomatis infections in female patients.

Antigens, Bacterial↗
PubMed1987

Presence of hepatitis B virus DNA in serum of surface-antigen-seronegative immunocompromised patients.

We compared the prevalence of serum hepatitis B virus (HBV) DNA in cancer patients who were immunocompromised with that in healthy subjects. Testing positive for serum HBV DNA were 27 of the 232 (11.6%) surface-antigen-negative cancer patients and 7 of the 382 (1.8%) surface-antigen-negative healthy subjects. These data suggest that the negative serology, at least in immunocompromised individuals, is probably not sufficient to exclude HBV infection.

DNA, Viral↗
PubMed1987

Hepatitis type B virus DNA in patients receiving hemodialysis: correlation with other HBV serological markers.

Possible presence of hepatitis type B virus (HBV) was assessed in 239 end-stage renal failure patients who were receiving long-term maintenance hemodialysis (average 30.8 months; duration: 1-94 months), and who had not shown any other symptom of HBV infection. Their HBV serological markers, including HBV DNA, were evaluated together with those of normal control individuals. HBV surface antigen (HBsAg) was detected in 42 of the 239 dialysis patients, 15 of whom also positive for HBV DNA (mean +/- SD = 56.2 +/- 23.7 pg/100 microliters of serum). HBV DNA was also found in 22 of the 197 (11.2%) dialysis patients who were negative for HBsAg, with an average of 36.2 +/- 19.0 pg/100 microliters of serum. This rate of detecting HBV DNA in HBV seronegative dialysis individuals was significantly higher than the rate of 1.83% found among healthy HBsAg(-) individuals. Among these 22 dialysis patients who were HBsAg(-) but HBV DNA(+), 15 were found to possess antibodies against HBsAg (anti-HBs) and/or antibody against HBV e antigen (anti-HBe). These data suggested that the absence of serum HBV antigen or the presence of antibodies against HBV markers might not be sufficient to identify possible HBV infection in immunocompromised hosts such as hemodialysis patients.

Adult↗
PubMed1986

Early detection of hepatocellular carcinoma in patients with chronic type B hepatitis. A prospective study.

A prospective surveillance of hepatocellular carcinoma (HCC) using serum alpha-fetoprotein and high-resolution, linear-array, real-time ultrasonography was carried out in 432 patients with clinicopathologically proven chronic type B hepatitis. During a follow-up period of 6-85 mo (median 23, mean 26.9 +/- 16.8 mo), asymptomatic HCC was identified in 8 patients, with a calculated annual incidence of 826/100,000, and 2768/100,000 for patients over age 35 yr. The relative risk of developing HCC in hepatitis B surface antigen-positive chronic hepatitis patients was 2 when compared to those that were hepatitis B surface antigen-negative, and was 5 when compared in patients over age 35 yr. Hepatocellular carcinomas detected by these methods were in a relatively early stage as most tumors were small, only 50% were associated with cirrhosis, 37.5% were positive for hepatitis B e antibody, and most were still resectable. We, therefore, recommend a combination of alpha-fetoprotein and ultrasonography surveillance in patients with chronic hepatitis in order to improve the chance of early HCC detection as well as the chance for successful resection. In addition, the low incidence of cirrhosis and hepatitis B e antibody in these patients with "early" HCCs and the occurrence of hepatitis B e antigen/hepatitis B e antibody seroconversion after HCC had developed suggest that the development of HCC and progression from hepatitis to cirrhosis were two independent (though related) sequelae of chronic hepatitis B virus infection.

Adolescent↗
PubMed1981

Effect of unusual guanosine nucleotides on the activities of some Escherichia coli cellular enzymes.

Unusual guanosine nucleotides guanosine 5'-diphosphate 3'-diphosphate (ppGpp, also known as MSI) and guanosine 5'-diphosphate 3'-monophosphate (ppGp, also known as MSIII) accumulate to high concentrations in wild-type cells of Escherichia coli during amino acid starvation. We reported here that both nucleotides strongly inhibit the activity of enzymes IMP dehydrogenase and adenylosuccinate synthetase, the first enzymes of the guanylate and adenylate biosynthetic pathways. In both cases, ppGP (MSII) is a stronger inhibitor than ppGpp (MSI). On the other hand, these two nucleotides exhibited opposite effects on the activity of phosphoenolpyruvate carboxylase, the enzyme that utilizes phosphoenolpyruvate. At their respective physiological concentrations, the activity of phosphoenolpyruvate carboxylase is activated by ppGpp and inhibited by ppGp.

Adenylosuccinate Synthase↗
PubMed1981

Regulation of small RNAs in Escherichia coli. Alteration in the intracellular concentrations of small RNAs during amino acid and energy starvation.

The accumulation of low molecular weight RNAs in Escherichia coli cells following amino acid or energy source starvation was examined using two-dimensional polyacrylamide gel electrophoresis. 32P-labeled small RNA prepared from serine- or isoleucine-starved stringent strain (relA+) cells was shown to display gel patterns that were grossly different from that of unstarved cells. It appears that the deprivation of serine or isoleucine has little or no inhibitory effect on the accumulation of transfer RNA cognate to the deprived amino acid. This is demonstrated by a relative increase in the concentrations of small RNAs that can be charged with serine or isoleucine following starvation of these amino acids. However, small RNAs labeled during starvation of phenylalanine or energy source showed gel patterns similar to that of control cells. This suggested a heterogenous response in the accumulation of some low molecular weight RNAs, presumably transfer RNAs, following starvation of different amino acids.

Amino Acids↗
PubMed1981

Stringent control of RNA synthesis in the absence of guanosine 5'-diphosphate-3'-diphosphate.

Severe curtailment of RNA synthesis and widespread readjustment of cellular activities, together with an increase of guanosine 5'-diphosphate-3'-diphosphate (ppGpp) have been demonstrated in Escherichia coli cells starved for amino acid or energy. The rates of growth and RNA synthesis are reduced by shifting the growth temperature from 40 degrees C to 20 degrees C. The intracellular pool of ppGpp diminishes under such conditions. Furthermore, the accumulation of ppGpp normally attainable by either amino acid- or energy-limitation can be totally blocked by a downshift of temperature imposed prior to the starvation. However, the synthesis of stable RNA is still stringently restricted under these conditions. Two other nucleotides were also effected. The intracellular level of phantom spot (Gallant, J., Shell, L., and Bittner, R. (1976) Cell 7, 75-84) decreased upon temperature fall. Guanosine 5'-diphosphate-3'-monophosphate, whose concentrations have been linked to stringent response and stable RNA synthesis, did not change by the simple temperature downshift, but increased following amino acid limitation even when a downshift of temperature was imposed before the starvation. These results suggest that ppGpp is not always needed for inhibition of stable RNA synthesis during stringent response, and that a compound such as guanosine 5'-diphosphate-3-monophosphate may be involved in the stringent regulation of stable RNA synthesis, at least under the temperature downshift conditions.

Escherichia coli↗
PubMed1981

Role of peptide chain elongation factor G in guanosine 5'-diphosphate 3'-diphosphate synthesis.

In a wild-type strain (relA+) of Escherichia coli, starvation of amino acid led to an immediate cessation of the synthesis of stable ribonucleic acids, together with the accumulation of an unusual nucleotide, guanosine 5'-diphosphate 3'-diphosphate, commonly known as ppGpp. This compound also accumulated during heat shock. When temperature-sensitive protein synthesis elongation factor G (EF-G) was introduced into E. coli NF859, a relA+ strain, the synthesis of ppGpp was reduced to approximately one-half that of wild-type EF-G+ cells at a nonpermissive temperature of 40 degrees C. Furthermore, fusidic acid, an inhibitor of protein synthesis which specifically inactivates EF-G, prevented any accumulation of ppGpp during the heat shock. We suggest that a functional EF-G protein is necessary for ppGpp accumulation under temperature shift conditions, possibly by mediating changes in the function of another protein, the relA gene product. However, EF-G is probably not required for the synthesis of ppGpp during the stringent response, since its inactivation did not prevent ppGpp accumulation during amino acid starvation.

Amino Acids↗
PubMed1980

Regulation of ribosomal and transfer RNA synthesis by guanosine 5'-diphosphate-3'-monophosphate.

Permeabilized cells of Escherichia coli were used to examine the effect on RNA synthesis of guanosine 5'-diphosphate-3'-monophosphate (ppGp). Electrophoretic and hybridization analysis of bulk RNA demonstrated that ppGp selectively reduced the accumulation of both ribosomal and transfer RNAs. The experiments further suggested that the observed reduction in stable RNA accumulation resulted from a reduction in stable RNA chain initiation rather than an effect on elongation, processing, or maturation of stable RNA transcripts. In contrast, the expression of the lac Z gene was not affected by ppGp. These results suggest that ppG, a nucleotide produced in E. coli during the stringent response, could play a direct role in the stringent regulation of stable RNA synthesis.

Escherichia coli↗