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Biomedical subjects

S H Chen

Publications and source records attributed to S H Chen.

At least 19 recordsLinked to original sources
PubMed1992

Accurate and rapid detection of heterozygous carriers of a deletion by combined polymerase chain reaction and high-performance liquid chromatography.

We have developed a technique to detect accurately heterozygous carriers of a deletion. Specific target sequences were amplified by the polymerase chain reaction (PCR), and the products subsequently were analyzed by high-performance liquid chromatography. Examples from four loci demonstrated that 24-27 cycles of amplification for a single-copy DNA, based on 50 ng of genomic DNA, results in excellent quantitation that readily permits the detection of heterozygous carriers of a deletion. We have demonstrated that triplex PCR (three targets in a single PCR) entails no loss of precision. We also have demonstrated that this method can accurately differentiate the heterozygous carriers of a deletion from normal individuals in four family studies, three for Duchenne muscular dystrophy patients and one for a hemophilia B patient.

Base Sequence↗
PubMed1992

The effect of pepsin digestion in relation to the pre-S region on hepatitis B surface antigen-induced hypersensitivity.

The role of the pre-S region of the hepatitis B surface Ag (HBsAg) particle in hypersensitivity to HBsAg was evaluated in mice. Plasma-derived or recombinant HBsAg was digested with pepsin to prepare different forms of HBsAg with or without pre-S region. Strains of mice including AKR/J (H-2k), A.SW (H-2s), C3H/He (H-2k), and CBA/J (H-2k) did not respond to the major S protein with regard to hypersensitivity. However, the pre-S-containing HBsAg overcame this nonresponsiveness. In BALB/c (H-2d) and A/J (H-2a) mice, the pre-S-containing HBsAg induced higher hypersensitivity than did the major S protein. The enhancement induced by the pre-S region was demonstrated to occur during the induction phase by crisscross assay using pre-S-containing HBsAg and major S protein as Ag. The patterns of hypersensitivity induced by the major S, middle S (composed of major S and pre-S2), and large S (composed of middle S and pre-S1 proteins) were also compared. The middle S protein induced responses of 1-h and 24-h hypersensitivities in major S non-responder (C3H/He and CBA/J) mice, whereas the large S protein circumvented only the 1-h one. The effectiveness to stimulate hypersensitivities in vivo by HBsAg is in the following order: middle S greater than large S greater than major S. These data suggest that the pre-S region of HBsAg particle can enhance both the 1-h and 24-h hypersensitivities in the afferent phase.

Animals↗
PubMed1992

Similar-sized daughter-strand gaps are produced in the leading and lagging strands of DNA in UV-irradiated E. coli uvrA cells.

The nascent DNA synthesized after UV irradiation contained discontinuity, i.e., daughter-strand gaps. The sizes of these gaps produced in the leading and lagging strands of UV-irradiated Escherichia coli cells were determined by using strand-specific DNA probes. The DNA isolated from irradiated uvrA delta(lac-pro) cells was hybridized with the 32P-labeled single-stranded DNA probes. After digestion with S1 nuclease, the sizes of the bound radioactive DNA fragments were determined by electrophoresis in an alkaline agarose gel. It was found that the average size of gaps produced in the leading strand was about 0.12 kb, whereas those produced in the lagging strand was slightly smaller than 0.12 kb. No gaps larger than 0.5 kb were detected.

Coliphages↗
PubMed1992

Stereochemical analysis of betamethasone and dexamethasone by derivatization and high-performance liquid chromatography.

A simple and economical high-performance liquid chromatographic method has been developed for the simultaneous determination of betamethasone and dexamethasone. The method is based on the derivatization of the structural epimers of betamethasone and dexamethasone with a homochiral reagent, N-carbobenzoxy-L-phenylalanine. The derivatives obtained were easily recognized by a non-chiral silica column with n-hexane-dichloromethane-isopropanol (100:100:4, v/v/v) as a mobile phase and a good separation was obtained for quantitation. The method was satisfactorily applied to the determination of betamethasone and dexamethasone in tablets.

Betamethasone↗
PubMed1992

Hepatitis B virus replication in well differentiated mouse hepatocyte cell lines immortalized by plasmid DNA.

The primary hepatocytes cultured from adult BALB/c mice were readily transfected by plasmid DNA and could be immortalized at a frequency of approximately 0.1 to 0.6 x 10(-7) cells/micrograms of the transfected DNA. There was no detectable plasmid DNA at the tenth cell passages. A total of five mouse hepatocyte cell lines were established. Most of them were tumorigenic. Three of the established mouse hepatocyte cell lines were well differentiated, since they expressed liver-specific genes. Further transfection of these three well differentiated mouse hepatocyte cell lines with hepatitis B virus (HBV) DNA showed that the HBV-transfected cells had integrated HBV genomes, HBV-specific mRNA transcripts, and expression of hepatitis B surface and hepatitis B core antigens. One of the lines, ML-3Neo (HBV), even secreted HBV-like particles. Furthermore, circulating hepatitis B surface antigens were detected in the sera of BALB/c mice bearing ML-3Neo (HBV) tumors. These cell lines provide a convenient model for future studies on the host immune reaction against HBV and on the transformation of hepatocytes by HBV and other cellular oncogenes and the determination of their effects on hepatocellular differentiation.

Animals↗
PubMed1992

Cytoprotective effect of reduced glutathione in hydrogen peroxide-induced endothelial cell injury.

The kinetic effects of hydrogen peroxide (H2O2) on cultured endothelial cells isolated from bovine carotid artery were studied. The cytoprotective effects of glutathione (GSH) on H2O2-induced cell injury were also investigated. H2O2-induced a dose- and time-dependent cell injury in cultured endothelial cells. H2O2-induced cell injury was blocked by simultaneous treatment by catalase, but not by superoxide dismutase. H2O2 also induced endogenous PGI2 biosynthesis, and the maximum PGI2 production was reached after 1 h treatment. Stimulation of PGI2 production was parallel with arachidonate release from H2O2-treated cells. However the prostaglandin biosynthesis enzyme activity in cells was inhibited by H2O2 treatment. When the cells were treated with GSH, the intracellular GSH reached a plateau after 3 h treatment. Both H2O2-induced cell injury and PGI2 production were significantly inhibited by the 3 h pretreatment with GSH. The cytoprotective effect of GSH was completely inhibited by buthionine sulfoximine which is a specific inhibitor of gamma-glutamylcysteine synthetase. The results indicate that the cytoprotective effect of GSH on H2O2-induced cell injury in cultured bovine carotid artery endothelial cells depends on the increase in intracellular GSH content.

Animals↗
PubMed1992

Methylation analysis of CGG sites in the CpG island of the human FMR1 gene.

The fragile-X syndrome of mental retardation is associated with an expansion in the number of CGG repeats present in the FMR1 gene. The repeat region is within sequences characteristic of a CpG island. Methylation of CpG dinucleotides that are 5' to the CGG repeat has been shown to occur on the inactive X chromosome of normal females and on the X chromosome of affected fragile-X males, and is correlated with silencing of the FMR1 gene. The methylation status of CpG sites 3' to the repeat and within the repeat itself has not previously been reported. We have used two methylation-sensitive restriction enzymes, AciI and Fnu4HI, to further characterize the methylation pattern of the FMR1 CpG island in normal individuals and in those carrying fragile-X mutations. Our results indicate that: (i) CpG dinucleotides on the 3' side of the CGG repeat are part of the CpG island that is methylated during inactivation of a normal X chromosome in females; (ii) the CGG repeats are also part of the CpG island and are extensively methylated as a result of normal X-chromosome inactivation; (iii) similar to normal males, unaffected fragile-X males with small CGG expansions are unmethylated in the CpG island; for affected males, the patterns of methylation are similar to those of a normal, inactive X chromosome; (iv) in contrast to the partial methylation observed for certain sites in lymphocyte DNA, complete methylation was observed in DNA from cell lines containing either a normal inactive X chromosome or a fragile-X chromosome from an affected male.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Free vascularized joint transfers in acute complex hand injuries: case reports.

The loss of function of the metacarpophalangeal joint is a significant disability. Simultaneous reconstruction of the soft tissue, extensor mechanism, joint, and flexor tendon in a complex hand injury is difficult and challenging. Free vascularized autogenous toe joint transplantation is a useful technique that provides not only joint replacement but also the soft tissue, extensor mechanism, and flexor tendon in more severe complex hand injuries. Two patients underwent immediate, free vascularized metatarsophalangeal joint transfer of the second toe to replace the long and ring finger metacarpophalangeal joint in acute complex hand injuries. The follow-up results at 16 months and 8 months postoperatively are presented.

Acute Disease↗
PubMed1992

A statistical model based fundamental frequency synthesizer for Mandarin speech.

A novel method based on a statistical model for the fundamental-frequency (F0) synthesis in Mandarin text-to-speech is proposed. Specifically, a statistical model is employed to determine the relationship between F0 contour patterns of syllables and linguistic features representing the context. Parameters of the model were empirically estimated from a large training set of sentential utterances. Phonologic rules are then automatically deduced through the training process and implicitly memorized in the model. In the synthesis process, contextual features are extracted from a given input text, and the best estimates of F0 contour patterns of syllable are then found by a Viterbi algorithm using the well-trained model. This method can be regarded as employing a stochastic grammar to reduce the number of candidates of F0 contour pattern at each decision point of synthesis. Although linguistic features on various levels of input text can be incorporated into the model, only some relevant contextual features extracted from neighboring syllables were used in this study. Performance of this method was examined by simulation using a database composed of nine repetitions of 112 declarative sentential utterances of the same text, all spoken by a single speaker. By closely examining the well-trained model, some evidence was found to show that the declination effect as well as several sandhi rules are implicitly contained in the model. Experimental results show that 77.56% of synthesized F0 contours coincide with the VQ-quantized counterpart of the original natural speech. Naturalness of the synthesized speech was confirmed by an informal listening test.

China↗
PubMed1992

Haplotype analysis and polymorphic frequency data at two factor IX loci (F9-192 and F9-Hha1) in a Chinese population.

Gene frequencies and haplotypes for two factor IX markers, F9-192 and F9-Hha1, were determined in a Chinese population. The frequencies for F9-192 are 0.86 for A and 0.14 for G. For F9-Hha1, the gene frequencies are 0.69 for - and 0.31 for +. Haplotype analysis revealed that the two polymorphic sites are in linkage equilibrium and, thus, are useful markers for genetic counseling of Asian families in which hemophilia B exists.

Alleles↗
PubMed1992

Electronystagmographic features in some peripheral and central vestibular disorders: application of multiple discriminant analysis of electronystagmographic parameters.

In routine clinical electronystagmographic (ENG) tests (postrotatory, optokinetic, caloric and tracking tests), eye movement signals were analyzed and a multiple discriminant analysis was carried out with the aid of a microcomputer. Six parameters were selected and, based on these, two functions for discriminating between peripheral and central disorders were established. Discrimination between 35 patients with peripheral lesions and 15 patients with central lesions was made with a correct classification rate of 97.1 and 86.7%, respectively. These rates are significantly higher than that of any single ENG test analysis. Our results indicate that the clinical application of ENG can be improved by searching for more sensitive ENG parameters and adopting the comprehensive analysis approach.

Adult↗
PubMed1992

Variable severity of pulmonary disease in adults with identical cystic fibrosis mutations.

Adults with CF followed in a university center were assessed for the presence of the most common CF gene mutation, delta-F508. Excluding one member of a sibling pair, 29 of 55 subjects had two copies of delta-F508 (homozygotes), 23 had one copy of delta-F508 with the other CF mutation not identified (complex heterozygotes) and three were lacking delta-F508. A wide range of clinical severity was seen among individuals carrying two copies of the delta-F508 gene, who are genetically identical at the CF gene locus. The number of individuals diagnosed with CF as adults was significantly lower in the homozygote group (1 of 29) as compared with the heterozygote group (7 of 24). No differences were detected between groups in pulmonary function, non-pulmonary complications or overall clinical severity. These results suggest that environmental or background genetic factors contribute significantly to the variability in pulmonary and other complications seen among individuals with CF.

Adolescent↗
PubMed1992

Noninvasive fetal ECG mode fetal heart rate monitoring by adaptive digital filtering.

Beat-to-beat variability (BTBV) of the fetal heart rate (FHR) is considered an indication of the neural integrity and is an important prognostic indicator of fetal well-being. We report the initial evaluation of a recently developed abdominal fetal ECG (AFECG) mode of FHR monitoring using Adaptive Digital Filtering (ADF) to accurately obtain BTBV noninvasively. Five women in labor at term were monitored with the direct fetal scalp electrode (FSE) and simultaneously with the AFECG using ADF. A computer analysis of 3298 seconds (55 minutes) of data provided a one-to-one comparison of the R-R intervals. One analysis of the direct FSE data with a second simultaneous analysis from the same electrode, to serve as control, was compared with the noninvasive AFECG data. The study group has a standard deviation of only 1.50 bpm compared to 0.79 bpm for the control group. The AFECG method agrees with the direct FSE method within 1 bpm for 92.6% of the reported R-R intervals and within 2 bpm for 98.9% of the reported intervals. This new noninvasive AFECG technique with ADF provides a continuous record of instantaneous FHR and BTBV that may be relied upon to provide an accurate continuous clinical record. The reliability of the technique has yet to be determined over a wide range of subjects.

Computers↗
PubMed1992

Superior mesenteric artery syndrome as a complication in hip spica application for immobilization: report of a case.

A 10-year-old girl who had a pelvic and femoral osteotomy for congenital dislocation of her right hip was immobilized with a hip spica. On the 28th postoperative day, she had upper abdominal pain, distention and bilious vomiting. An upper GI series demonstrated complete obstruction of the duodenum at the third portion of the duodenum in a supine position; however, the barium passed the obstruction site slowly when the patient assumed a lateral or prone position. She was successfully treated conservatively with nasogastric decompression, fluid replacement, proper positioning and hyperalimentation. Superior mesenteric artery syndrome is a rare complication in patients immobilized in a body cast or hip spica. Early diagnosis and proper treatment usually leads to an uneventful convalescence.

Barium Sulfate↗
PubMed1992

[Clinical analysis of chronic renal function failure accompanied by pulmonary tuberculosis].

In 592 patients with chronic renal function failure (CRFF), 31 were accompanied by pulmonary tuberculosis, the incidence was 5.2%. The incidence of the First Affiliated Hospital of Sun Yat-sen University (6.6%) is higher than that of Zun Yi District Hospital (3.9%). The difference may be associated with dialysis therapy and regional TB natural population incidence. The data also showed that accompanied TB may be a reversible factor of deteriorating CRFF. Details of diagnosis and treatment of CRFF accompanied by TB are presented.

Adult↗
PubMed1992

Osteogenic activity of cells from dental pulp, periodontal ligament, bone marrow and muscle in vitro: an ultrastructural study and alkaline-phosphatase activity.

Dental pulp, periodontal ligament, bone marrow and muscle tissue from the same rat were cultured in vitro in order to investigate their osteogenic activity by transmission electron microscope. Immunohistochemical methods with various antibodies were utilized and alkaline-phosphatase (ALPase) activities of these cells were also measured biochemically. Dental pulp cells were stellate in shape, showed an intense ALPase reaction, and had lipid-like droplets. Periodontal ligament cells were composed of spindle fibroblasts and epithelial cells. The former revealed a positive reaction for ALPase and possessed microfilaments. Bone marrow cells were spindle shaped, resembling fibroblasts, but some of them were similar to osteoblasts. Muscle cells were long, slender in shape, and showed no positive reaction for ALPase. The cells from pulp tissue showed the highest activity of ALPase, followed by periodontal ligament and bone marrow; there was no activity in muscle tissue. All the cells except the epithelial-like cells of the periodontal ligament and muscle cells were positive in reaction with ALPase which is a marker for osteogenic cells, and vimentin which is a marker of fibroblastic characteristics. Osteogenic activity and cellular differentiation of these cells were discussed.

Alkaline Phosphatase↗