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Biomedical subjects

S M Wang

Publications and source records attributed to S M Wang.

At least 109 records · Page 6Linked to original sources
PubMed1997

Surface gene mutants of hepatitis B virus in infants who develop acute or chronic infections despite immunoprophylaxis.

Serum hepatitis B virus (HBV) DNA from 4 infants with fulminant hepatitis B, 3 infants with acute self-limited hepatitis B, and 15 infants with chronic HBV infection were amplified by polymerase chain reaction followed by direct sequencing of the region of HBV genome encoding the major antigenic epitopes of hepatitis B surface antigen (HBsAg). All infants were born to carrier mothers and administered immunoprophylaxis from birth. Serum HBV DNA from 13 carrier children born to carrier mothers who did not receive immunoprophylaxis and had comparable length of infection were studied as controls. An S mutant (residue 126, Thr to Ala) initially found in an infant with fulminant hepatitis was replaced by another S mutant (residue 145, Gly to Arg) 4 days later. In a girl with chronic hepatitis B, Ala-126 variant and Arg-145 variant were found at 17 and 25 months of age, respectively. The Arg-145 variant persisted for 8 years in an asymptomatic male carrier and for 1 year in an infant with chronic hepatitis B. The Ala-126 variant persisted for 11 years in one child who had an early loss of hepatitis B e antigen. In the majority of the infants' mothers, corresponding mutations in HBsAg were not detected in serum by direct sequencing. The S mutants detected in three carrier infants were not found in their mothers' serum after cloning and sequencing of 10 DNA clones from each maternal sample. None of the 13 control patients had detectable S mutants. These results suggest that S variants emerge or are selected under the immune pressure generated by the host or by administration of hepatitis B immune globulin and hepatitis B vaccination. An S mutant (residue 129, Gln to Arg) found in one mother-infant pair suggested a direct maternal-infant transmission, resulting in immunoprophylaxis failure. None of the family members of children infected with Arg-145 variant had the same variant infection, implying this variant's low transmissability.

Alanine Transaminase↗
PubMed1997

Congenital bilateral agenesis of diaphragm: report of a case.

UNLABELLED: Bilateral agenesis of the diaphragm is a rare, life-threatening malformation. Infants with this defect rarely survive to have surgical intervention. We report a 32-week premature female infant who was born to a 36-year-old mother via vaginal delivery. The pregnancy course was complicated by hypertension and polyhydramnios. Cytogenetic study showed a normal 46 XX female karyotype. She had cyanosis, respiratory distress and scaphoid abdomen at birth. A roentgenograph confirmed the diagnosis of diaphragmatic hernia. Surgery was performed at 21 h of age. Bilateral agenesis of diaphragm, herniation of abdominal organs and oesophagus and pulmonary hypoplasia were noted. Furthermore, stomach and spleen were adherent to the mediastinum and vertebrae. The patient developed hypotension and persistent hypoxaemia and expired at age of 26 h. Autopsy revealed bilateral agenesis of diaphragm, hypoplasia of lungs, and pancreas fibrosis with mild hypoplasia of islets of Langerhans. CONCLUSION: Bilateral agenesis of diaphragm associated with pancreas fibrosis is a rare entity, and its clinical significance needs further investigation.

Abnormalities, Multiple↗
PubMed1997

Angiotensinogen and angiotensin-I converting enzyme gene polymorphisms and the risk of coronary artery disease in Chinese.

The homozygous deletion allele (DD) of the angiotensin-I converting enzyme (ACE) gene and the T235 homozygote of the angiotensinogen (AGT) gene have been reported to be correlated with an increased prevalence of coronary artery disease (CAD) and myocardial infarction (MI). The importance of the DD genotype and T235 homozygote as genetic risk factors for CAD in Chinese remains uncertain. This study included 426 patients who underwent coronary angiography and 180 healthy subjects without clinical evidence of CAD. Coronary angiography identified 268 patients with CAD (CAD group) and 158 patients without CAD. The healthy subjects and patients without angiographic evidence of CAD constituted the control group. Three polymorphisms were studied: an insertion/deletion (I/D) polymorphism of the ACE gene and the T174 M and M235T polymorphisms of the AGT gene. No association was found between any of the three studied polymorphisms and the risk of CAD or MI in Chinese using univariate or multivariate analysis. In multivariate analysis, the relative risks were 1.20 (95% confidence interval = 0.91-1.61, P = 0.20) for the DD genotype, 1.05 (95% CI = 0.82-1.35, P = 0.69) for the T174 homozygote, and 1.19 (95% CI = 0.91-1.55, P = 0.20) for the T235 homozygote. Similarly, no significant difference was found in the frequencies of the DD genotype and the T174 and T235 homozygotes between the control group, the CAD group, the non-MI group, and the MI group when analyzed according to sex, age, or degree of risk. Our data suggest that neither the DD genotype of the ACE I/D polymorphism nor the T174 and T235 homozygotes of the AGT gene confer significant risk for CAD or MI in Chinese.

Angiotensinogen↗
PubMed1997

adg2-1 represents a missense mutation in the ADPG pyrophosphorylase large subunit gene of Arabidopsis thaliana.

Arabidopsis mutants affecting ADPG pyrophosphorylase (ADGase) activity can be divided into two complementation groups, adg1 and adg2. Previous biochemical studies of adg2-1 mutant indicated that mutant plants do not accumulate ADGase large subunit protein and that ADGase small subunits assemble as homotetramers. This suggested that the ADG2 gene may encode the large subunit of ADGase. In this paper, it is shown that adg2-1 mutant plants accumulate near wild-type levels of transcripts encoding both the large and small subunits of ADGase. However, by RFLP analysis and complementation of adg2-1 with the ADGase large subunit gene, we show that the adg2-1 mutant does represent a mutation of the ADGase large subunit gene. Sequence analysis of the adg2-1 allele revealed a missense mutation. The results therefore suggest either that the missense mutation affects the stability of the ADGase large subunit protein or that it prevents assembly of the large subunit into holoenzyme.

Amino Acid Sequence↗
PubMed1997

Parental desire for perioperative information and informed consent: a two-phase study.

The purpose of this investigation was to identify the perioperative anesthetic information parents want from the anesthesiologist, and to determine whether the provision of detailed anesthetic risk information is associated with increased parental anxiety. The investigation consisted of a cross-sectional study followed by a randomized controlled trial. In Phase 1, baseline and situational anxiety, coping strategy, and temperament were obtained from parents of children undergoing surgery (n = 334). A questionnaire examining the desire for perioperative information was administered to all parents. In Phase 2, 47 parents were randomly assigned to receive either routine anesthetic risk information (control) or detailed anesthetic risk information (intervention). The effect of the intervention on parental anxiety was assessed over four time points: prior to the intervention, immediately after the intervention, day of surgery in the holding area, and at separation to the operating room. For Phase 1, the majority of parents (> 95%) preferred to have comprehensive information concerning their child's perioperative period, including information about all possible complications. For selected items, increased parental educational level was associated with increased desire for information (P < 0.05). For Phase 2, when the intervention group was compared with the control group, there were no significant differences in parental anxiety over the four time points [F(1,45) = 0.6, P = 0.4]. Also, the interaction between time and group assignment was not significant [F(3,135) = 1.66, P = 0.18]. We conclude that parents of children undergoing surgery desire comprehensive perioperative information. Moreover, when provided with highly detailed anesthetic risk information, the parental anxiety level did not increase.

Adaptation, Psychological↗
PubMed1997

Characterization of a maize beta-amylase cDNA clone and its expression during seed germination.

A maize (Zea mays L.) cDNA clone (pZMB2) encoding beta-amylase was isolated from a cDNA library prepared from the aleurone RNA of germinating kernels. The cDNA encodes a predicted product of 488 amino acids with significant similarity to known beta-amylases from barley (Hordeum vulgare), rye (Secale cereale), and rice (Oryza sativa). Glycine-rich repeats found in the carboxyl terminus of the endosperm-specific beta-amylase of barley and rye are absent from the maize gene product. The N-terminal sequence of the first 20 amino acids of a beta-amylase peptide derived from purified protein is identical to the 5th through 24th amino acids of the predicted cDNA product, indicating the absence of a conventional signal peptide in the maize protein. Recombinant inbred mapping data indicate that the cDNA clone is single-copy gene that maps to chromosome 7L at position 83 centimorgans. Northern blot analysis and in vitro translation-immunoprecipitation data indicate that the maize beta-amylase is synthesized de novo in the aleurone cells but not in the scutellum during seed germination.

Amino Acid Sequence↗
PubMed1997

Myocardial mechanics and titin in experimental insulin-resistant rats.

We investigated the intrinsic cardiac mechanics of myocardium and changes in titin in insulin-resistant rats. Microsonometry and micromanometry were used to evaluate the maximal elastance (Emax) and myocardial stiffness constant (Km) of the left ventricle, in addition to the traditional systolic and diastolic cardiac function, with an isolated working heart preparation. Thirty 150 g Wistar rats were divided into three groups of 10. Group A was fed rat chow, while groups B and C were fed a 66% fructose diet for 7-8 months. Group C also received clonidine. Group B rats developed insulin resistance, as well as elevated plasma glucose and blood pressure. Group C rats also had insulin resistance and elevated plasma glucose, but not higher blood pressure. Group B rats had decreased Emax, decreased peak-dp/dt, prolonged Tau and increased Km compared to normal control rats. Group C rats, which mimicked the clinical condition of diabetic cardiomyopathy, maintained normal global left ventricular function as revealed by cardiac output, peak + dp/dt, peak-dp/dt and Tau of relaxation. However, they had a lower Emax slope (355 +/- 51 vs 535 +/- 56 mmHg.mm than group A rats, p < 0.05) and increased Km (81.6 +/- 9.9 vs 25.5 +/- 4.8 in group A, p < 0.001), even though the extent of elevation of plasma glucose was only mild (71.3 +/- 2.0 to 108.9 +/- 4.4 mg/dl, p < 0.001). Their left ventricular mass, myocyte size, interstitial fibrosis and vascular picture did not change. However, the content of myocardial titin decreased significantly (intensity ratio of titin/actin was 0.23 +/- 0.01 and 0.29 +/- 0.02 in group C and group A rats respectively, p < 0.05). These findings suggest that changes in titin play a role in the change in myocardial functional characteristics and may be one of the causes of diabetic cardiomyopathy.

Animals↗
PubMed1997

Dissection of the signaling mechanism for capsule detachment of lipid droplets in rat adrenocortical cells.

In a previous study, we used a monoclonal antibody, A2, to demonstrate the presence of the lipid droplet-specific capsule in adrenocortical cells and the stimulation of steroid secretion with adrenocorticotrophic hormone (ACTH), resulting in the detachment of this capsule from the droplet surface into the cytosol. To investigate the signaling pathway for this event, we tested the role of adenylate cyclase, cAMP, and protein kinases A and C (PKA and PKC) in this response. ACTH-induced decapsulation of lipid droplets was blocked by either adenylate cyclase inhibitor or PKA inhibitor and stimulated by Bt2cAMP. We conclude that the signaling mechanism involved in lipid droplet decapsulation is the cascade consisting of adenylate cyclase activation, cAMP elevation, and subsequent PKA activation. Furthermore, the cytosolic detached capsular protein was able to relocate to the lipid droplet surface on cessation of ACTH or Bt2cAMP stimulation. In addition to PKA-mediated decapsulation, inhibition of PKC by calphostin C alone was enough to induce decapsulation, a process that was independent of PKA activity, whereas activation of PKC could prevent Bt2cAMP-induced decapsulation. A cAMP radioimmunoassay also confirmed that ACTH caused a marked increase in intracellular levels of cAMP, while PMA or calphostin C caused no significant changes. We conclude that PKA and PKC are reciprocally operated to regulate the decapsulation of lipid droplets, the same mechanism adopted in steroidogenesis. A time-course study also indicates that decapsulation of lipid droplets was accompanied by detectable changes in the size and the area of lipid droplets upon the stimulation of Bt2cAMP or calphostin C, implying a possible coupling between the capsule detachment and steroidogenesis.

Adenocarcinoma↗
PubMed1997

Streptococcal toxic shock syndrome complicating varicella in children.

The most common complication in children with varicella is cutaneous superimposed infection with pyogenic bacteria. Group A beta-hemolytic streptococci, which are known to cause life-threatening infections in both previously healthy children and those with underlying diseases, are the most frequently associated pathogens. A newly recognized disease, called streptococcal toxic shock syndrome, is associated with severe morbidity and mortality. We report a 3-year-old boy with a diagnosis of this syndrome who presented with increasing fever, vomiting, and lethargy 7 days after the development of a classic varicella skin lesion. In spite of aggressive fluid supply, administration of inotropic agents, and cardiopulmonary resuscitation, a rapidly deteriorating clinical course led to death 4 hours after hospitalization. This is the first report of this association in Taiwan. Pediatricians evaluating children with varicella must be mindful of the potential for Group A beta-hemolytic streptococcal infection.

Chickenpox↗
PubMed1996

Immunocytochemical demonstration of a lipid droplet-specific capsule in cultured Leydig cells of the golden hamsters.

In this report, we provide direct evidence for the presence of a lipid droplet-associated capsule in hamster steroidogenic Leydig cells by using a monoclonal antibody A2. Leydig cells are characterized by containing many lipid droplets and having 3 beta-hydroxysteroid dehydrogenase activity. Immunofluorescence staining with this antibody demonstrated a rim or capsule surrounding the lipid droplets in Leydig cells, a pattern not seen with anti-vimentin antibody. Immunogold labelling confirmed ultrastructurally that antibody binding was distributed on the lipid droplet surface. In order to investigate the possible function of the capsule, we examined the morphological changes induced in the capsule following stimulation with LH or dibutyryl cAMP; the fluorescent intensity of the capsule was seen to gradually decrease, accompanied by a decrease in number and size of lipid droplets, and the response to both reagents was time- and concentration-dependent. We thus conclude that hormonal stimulation resulting in the detachment of certain capsular proteins from the surface of lipid droplets is mediated via the cAMP signaling pathway and may allow cholesterol ester hydrolytic enzyme direct access to its substrate in the lipid droplet.

Animals↗
PubMed1996

Altered expression of the twist gene in young versus senescent human diploid fibroblasts.

We have recently reported the cloning and characterization of the human twist gene (H-twist), which encodes an evolutionarily conserved helix-loop-helix transcription factor. In several species, twist has been shown to play a role in mesoderm differentiation. We now report on the differential expression of H-twist as a function of in vitro life span in human diploid fibroblasts. H-twist was found to be expressed at a relatively high level in quiescent young cells. Addition of fresh serum to young G0 cultures results in a rapid repression of H-twist mRNA expression. This repression depends on the presence of growth factors, specifically EGF, and requires protein synthesis. mRNA stability studies using either actinomycin D or alpha-amanitin indicate a similar decay rate of H-twist mRNA in both young and senescent cells, suggesting that the differential expression of H-twist in young versus old is not primarily regulated at the level of mRNA turnover.

Cell Line↗
PubMed1996

The involvement of PKC in N-cadherin-mediated adherens junction assembly in cultured cardiomyocytes.

Activation of PKC by PMA was shown to promote the separation of chicken cardiomyocytes from each other in culture. Immunofluorescence staining for N-cadherin indicated that PMA, but not its inactive isoform 4 alpha PMA, induces the separation of cardiomyocytes and of co-cultured fibroblasts at intercellular junctional regions. The PMA-induced separation of cardiomyocytes and of co-cultured fibroblasts was inhibited by the PKC inhibitor, H-7. Immunoblot analysis further demonstrated that both PKC iota and PKC lambda were expressed in the cardiomyocyte cultures. While PKC lambda was localized to the cell-cell contact areas between cardiomyocytes, PKC iota was only detectable in the perinuclear cytoplasm of the co-cultured fibroblasts. The present findings suggest the involvement of PKC in regulating N-cadherin-mediated adherens junction formation in chicken cardiomyocytes. The differential distribution of PKC lambda and PKC iota in the cardiomyocytes and in the co-cultured fibroblasts suggests that different PKC isozymes are involved in regulating the assembly of intercellular junctions in these two cell types.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Phytohormone-regulated beta-amylase gene expression in rice.

The expression of beta-amylase genes in rice (Oryza sativa) and its regulation by phytohormones gibberellic acid (GA) and abscisic acid (ABA) were examined. Upon germination beta-amylase is synthesized de novo in aleurone cells and (GA) is not required. Exogenous addition of GA does not enhance the beta-amylase activity, while ABA inhibits the beta-amylase activity, mRNA accumulation, and the germination of rice seeds. GA can reverse ABA inhibition of beta-amylase expression, but not ABA inhibition of seed germination. Such regulation represents a new interaction of ABA and GA.

Abscisic Acid↗
PubMed1996

Immunocytochemical demonstration of a new vimentin-associated protein in 3T3 fibroblasts.

Using a xanthophore cytoskeletal preparation as immunogen, we have produced a monoclonal antibody, A2, which recognized a 160 kDa protein in 3T3 fibroblasts. This protein makes up a cytoplasmic filamentous system, which colocalizes with vimentin filaments. When microtubules and actin filaments are dissolved by high salt extraction, staining with antibody A2 is unaffected. Immunoblot analysis confirms that the 160 kDa protein is co-isolated with vimentin during in vivo high salt extraction. Following vinblastine treatment, both the 160 kDa protein and vimentin become localized to perinuclear caps, as do other intermediate filaments and their associated proteins; after vinblastine removal, the immunostaining produced by A2 becomes filamentous. Immunoelectron microscopy demonstrates that antibody A2 stains a filament system with a diameter of about 10 nm. Our observations suggest that the 160 kDa protein may be a new vimentin-associated protein which differs from the intermediate filament-associated proteins previously reported, and is widely distributed in several cell types.

3T3 Cells↗
PubMed1996

The G1691A mutation of the coagulation factor V gene (factor V Leiden) is rare in Chinese: an analysis of 618 individuals.

To understand the allele frequency of the G1691A mutation of the coagulation factor V gene (factor V Leiden) in Chinese, 618 Chinese individuals, including 54 cases with venous thrombosis, were analyzed. Only one case in the control group was heterozygous for the 1691G allele and the 1691A allele. Our data suggest that the factor V Leiden is rare in Chinese.

Alleles↗