Biomedical subjects

K C Chen

Publications and source records attributed to K C Chen.

At least 73 records · Page 4Linked to original sources

PubMed1995

Allelic deletion mapping of putative tumor suppressor genes on 17q in sporadic ovarian cancer.

OBJECTIVES: 1) To study whether the same or different chromosome 17q genes may be involved in the oncogenesis of familial and sporadic ovarian malignancies. 2) To localize the candidate gene in the sporadic ovarian cancers. METHODS (STUDY DESIGN): Using DNA extracted from ovarian tumors and corresponding peripheral leukocyte, we examined the status of loss of heterozygosity (LOH) at 12 loci spanning chromosome 17q12-q25 by Southern hybridization and polymerase chain reaction. RESULTS: Comparison of the extent of LOH among 25 epithelial ovarian tumors showing allele loss at one or more loci on 17q, the smallest overlapping region of allelic deletion is between D17S579 and GIP, with a genetic distance of approximate 2 cM. CONCLUSIONS: From our allelic deletion analysis of chromosome 17q loci, it indicates that there are more than one ovarian cancer candidate genes on chromosome 17q.

Alleles↗

PubMed1995

Distribution of p21ras during primary palate formation of non-cleft and cleft strains of mice.

Cleft lip, with or without cleft palate, is one of the most common defects in craniofacial formation. The primary palatogenesis of mice is similar to that of humans and spontaneous cleft lip is associated with genotype in both mice and humans. To investigate the temporal and spatial expression of ras genes in cleft (A/WySn) and non-cleft strains of mice (BALB/cBy), a broad spectrum ras antibody was used. Positive staining was found in ectodermal, mesenchymal, and neuroepithelial cells of facial prominences before the primary palate formation stage (10 d 20 hr) in both strains. During the primary palate formation stage (11 d 20 hr), positive staining was found in the ectodermal and mesenchymal cells of the facial prominences of the non-cleft strain but not in those of the cleft strain. These results suggest ras genes may play a role in the primary palatogenesis of mice. Cleft lip could be associated with the deficiency of ras gene expression during primary palate formation of mice.

Animals↗

PubMed1995

Identification of a human homologue of yeast nuc2 which interacts with the retinoblastoma protein in a specific manner.

The full-length cDNA clone which encodes a novel 824-amino acid protein was characterized. The predicted protein contains ten 34-amino acid repeats characteristic of the tetratricopeptide repeat protein family. The sequence homology and organization of the 10 repeats are similar to those of the nuc2 protein of fission yeast and bimA protein of Aspergillus, which suggests that the newly identified protein could be the human homologue of nuc2 (H-NUC). Consistent with this notion, the M(r) 95,000 H-NUC is a nuclear protein with DNA binding activity. This protein binds to hypophosphorylated Rb protein in a region indistinguishable from that to which SV40 large T antigen binds. However, Rb also binds to H-NUC at the tetratricopeptide repeat motif, a region which contains sequences different from the binding motifs of either T-antigen or E2F-1. To mimic the temperature-sensitive mutant of yeast nuc2, an H-NUC mutant was made in which the highly conserved glycine 640 residue was changed to aspartic acid. In contrast to wild-type H-NUC, the mutant was temperature sensitive in binding to Rb protein. These results, taken together, suggest that the interaction between H-NUC and Rb may be significant.

Amino Acid Sequence↗

PubMed1994

Fluorescent spot test method for specific detection of beta-lactamases.

A simple, sensitive fluorescent spot test method for specific detection of microbial beta-lactamases has been developed, based on the modification of a previously disclosed method (K. C. S. Chen, October 23, 1990, U.S. Patent 4,965,193). The new fluorescence developer used in the present study consisted of 0.5 mM HgCl2, in 0.5 M sodium citrate buffer, pH 4.5, prepared in 0.5% formaldehyde aqueous solution. A beta-lactam substrate solution consisting of a beta-lactam antibiotic with an acyl side chain containing an alpha-amino group and an alpha-phenyl group, or its derivatives, was incubated with a beta-lactamase-producing organism. One volume of the fluorescence developer was added to 4 vol of the incubated beta-lactam substrate solution, followed by heating the mixture at 45 degrees C for 10 min. The mixture was spotted on filter paper. Production of fluorophore indicated beta-lactamase activity. Each fluorophore was analyzed by TLC and its chemical identity was determined. Using ampicillin as the penicillinase substrate and cephalexin as the cephalosporinase substrate, the new method can be conveniently carried out by using dropping bottles for storing and dispensing the substrate solutions and the fluorescence developer. This modified method also provided more favorable conditions for the penicillinases to remain active during fluorescence development. Therefore, the sensitivity of the test was increased.

Ampicillin↗

PubMed1994

Effects of sodium butyrate on the transfer of arachidonic acid to phosphatidylcholine in a clonal oligodendrocyte cell line (CB-II).

The effect of sodium butyrate on membrane phospholipid metabolism in a neonate rat cerebellum derived clonal oligodendrocyte cell line (CB-II) was investigated. Sodium butyrate is an agent known to induce cell differentiation and morphological transformations. A comparison of the in vivo phospholipid labeling patterns obtained by incubating CB-II cells with [3H]choline, [14C]myristic acid or [3H]arachidonic acid indicated that butyrate altered the route of acylation-deacylation in phosphatidylcholine (PC) biosynthesis. Using an in vitro incubation system containing homogenates of CB-II cells, the largest proportion of radioactivity was found in PC, and addition of sodium butyrate resulted in a further increase in the transfer of arachidonic acid to PC, but not to phosphatidylinositol. Similar results were obtained when this in vitro acylation activity was tested using homogenates from sodium butyrate pretreated cells. The butyrate effect was observed regardless of whether or not exogenous lysophosphatidylcholine (LPC) was added to the incubation system. Addition of butyrate did not result in a change in the activity of LPC:acyl-CoA (coenzyme A) acyltransferase (EC 2.3.1.23) in CB-II cells upon incubating cell homogenates with [1-14C]arachidonoyl-CoA and LPC. However, when cell homogenates were incubated with [3H]arachidonic acid in the presence of 2.5-10 mM sodium butyrate, arachidonoyl-CoA synthesis was stimulated. A time course study demonstrated that significant stimulation occurred after three minutes. Taken together, the results suggest that in CB-II cells, sodium butyrate stimulates the transfer of arachidonic acid into PC and that this effect is at least partially due to a stimulation of arachidonoyl-CoA ligase (EC 6.2.1.3).

Acetyl-CoA C-Acyltransferase↗

PubMed1994

11 alpha-Hydroxylation of progesterone in biphasic media using alginate-entrapped Aspergillus ochraceus gel beads coated with polyurea.

A novel cell-immobilization technique was developed in this study for increasing substrate partition to the gel matrix by coating a polyurea thin layer on the surface of Ca-alginate beads. The proposed method was simple and could be performed under mild conditions. The bioconversion of progesterone to 11 alpha-hydroxyprogesterone with these polyurea-coating alginate-entrapped Aspergillus ochraceus cells was investigated using different organic solvents in biphasic media. The reaction medium of ethyl acetate could markedly enhance the bioconversion rate with the existence of a hydrophobic layer, most likely resulting from the increasing partition of substrate to gel matrix. Bioconversion with higher substrate concentration was possible using an ethyl acetate-water medium. The conversion rate increased almost linearly with increasing substrate concentration from 10 to 80 g l-1. The rate with 80 g l-1 progesterone increased up to six times greater than the rate with the immobilized cells without coating, and also exhibited a much higher rate than that reported in the literature.

Alginates↗

PubMed1994

11 alpha-hydroxylation of progesterone using modified alginate-immobilized cells.

The major disadvantage of using alginate-immobilized Aspergillus ochraceus for 11 alpha-hydroxylation of progesterone is its instability in phosphate solutions. In this study, different gel-hardening methods were used to improve the stability of alginate gels. Addition of Fe3+ and Fe2+ ions increased the activity of hydroxylation, but Fe2+ was not a good gelling agent. Replacement of CaCl2 by FeCl3 as the gelling agent increased the activity of the immobilized cells by about 33%. Hardening the alginate-immobilized cells with polyacrylamide (PAA) increased their stability in a 0.1 M phosphate buffer from 0.35 h to over 36 h. The productivity was increased by a factor of 1.8 compared to those without hardening, and the maximum yield was also increased from 84.3% to 90.8%. The physical properties and biocatalytic characteristics of PAA-hardened, immobilized cells were found to be feasible for application in a steroid bioconversion system.

Acrylic Resins↗

PubMed1994

Molecular characterization of a novel human gene, SEC13R, related to the yeast secretory pathway gene SEC13, and mapping to a conserved linkage group on human chromosome 3p24-p25 and mouse chromosome 6.

We previously described sequence tags from 58 novel directionally cloned human cDNAs from an enriched retinal pigment epithelial cell line library (Gieser and Swaroop, 1992). The nucleotide sequence of one of the cDNA clones, AA35 (D3S1231E), showed strong homology to the yeast SEC13 gene, required for vesicle biogenesis from endoplasmic reticulum during the transport of proteins. We have designated the human gene SEC13R (SEC13-Related). The amino acid sequence of the SEC13R gene product shows 70% similarity to yeast Sec13p, suggesting that SEC13R may be the human homolog of SEC13. The deduced polypeptide sequence contains several beta-transducin like 'WD40' repeats, and is rich in serine and threonine residues. The 1.4 kb transcript of SEC13R is detected by Northern analysis in many human tissues. However, RT-PCR analysis using two primer sets from different regions of the gene suggests differential expression of alternately spliced transcripts in various tissues. Somatic cell hybrid and in situ hybridization studies localized the SEC13R gene to human chromosome 3p24-p25. A related sequence was mapped to chromosome 18q11.2-q12. SEC13R was physically mapped to a yeast artificial chromosome (YAC) clone spanning the D3S720 marker from the region of the Von Hippel-Lindau disease locus. The mouse Sec13r gene was mapped to the conserved linkage group on chromosome 6 that corresponds to human chromosome 3p24-p25.

Amino Acid Sequence↗

PubMed1994

Maternal serum alpha-fetoprotein levels between 13 and 24 weeks' gestation.

Maternal serum alpha-fetoprotein (MSAFP) screening has been widely used and proven valuable in the prediction of a variety of fetal disorders. Any laboratory intending to provide MSAFP screening needs to establish its own reference data. In order to establish a normal MSAFP median value at our own laboratory, 5256 samples of MSAFP were collected from uncomplicated, singleton pregnant women between 13 and 24 weeks' gestation. The MSAFP median levels steadily rise with advancing gestation about 16% per gestational week in average. There were 0.17% and 4.4% of the pregnancies with serum AFP levels less than 0.25 multiple of the median (MoM) and 0.5 MoM respectively, and 4.22% and 1.66% with serum levels above 2.0 MoM and 2.5 MoM. Accurate and satisfactory interpretation of MSAFP screening should be emphasized in the establishment of a well-developed normal median value.

Female↗

PubMed1993

Allelic loss in ovarian cancer.

Loss of heterozygosity (LOH) was examined at 86 loci distributed on every chromosomal arm in 50 human ovarian tumors. Frequent allele losses were observed on chromosomes 13q (42%), 17p (42%), 17q (45%), and Xp (41%). Deletion mapping on chromosome 17 revealed a candidate gene on the long arm distal to D17S41/S74 for ovarian cancer which is distant from the locus for early onset breast cancer. LOH on chromosome 17q was found to be concordant with LOH on chromosomes 3p, 13q, 17p and Xp suggesting that it may be an early event in neoplastic development. These findings indicate that multiple tumor-suppressor genes for ovarian cancer possibly exist on chromosomes 13q, 17, and/or Xp and provide the basis for the identification of candidate gene(s) associated with ovarian cancer. The chromosomal mechanisms resulting in allele losses in ovarian cancer include deletion, deletion/duplication, mitotic recombination and monosomy, in concordance with the developed genetic model.

Alleles↗

PubMed1993

The evolutionary history of the first three enzymes in pyrimidine biosynthesis.

Some metabolic pathways are nearly ubiquitous among organisms: the genes encoding the enzymes for such pathways must therefore be ancient and essential. De novo pyrimidine biosynthesis is an example of one such metabolic pathway. In animals a single protein called CAD carries the first three steps of this pathway. The same three enzymes in prokaryotes are associated with separate proteins. The CAD gene appears to have evolved through a process of gene duplication and DNA rearrangement, leading to an in-frame gene fusion encoding a chimeric protein. A driving force for the creation of eukaryotic genes encoding multienzymatic proteins such as CAD may be the advantage of coordinate expression of enzymes catalyzing steps in a biosynthetic pathway. The analogous structure in bacteria is the operon. Differences in the translational mechanisms of eukaryotes and prokaryotes may have dictated the different strategies used by organisms to evolve coordinately regulated genes.

Animals↗

PubMed1993

The complete nucleotide sequence of parvovirus LuIII and localization of a unique sequence possibly responsible for its encapsidation pattern.

Parvovirus LuIII encapsidates single-stranded DNA of either plus or minus polarity with equal frequency, whereas the rodent parvoviruses MVMp and H-1 encapsidate minus strand DNA only. A full-length, infectious clone of LuIII was constructed and the complete nucleotide sequence of the genome was determined. Comparison of the LuIII sequence with those of MVMp and H-1 revealed that these viruses are virtually identical with respect to the genomic organization, location of regulatory signals, mRNA splicing patterns, and amino acid sequences of viral proteins. However, two regions of the LuIII sequence differ significantly from those of the rodent parvoviruses. At mu 92, LuIII has only one copy of a sequence found as a direct repeat in MVMp and H-1. Upstream of this sequence, at mu 89, there is an A-T-rich region, 47 nucleotides in length, unique to the LuIII genome. This A-T-rich region could represent a signal responsible for the totally different encapsidation patterns observed for these viruses.

Base Sequence↗

PubMed1993

Outcome of pregnancy in patients with organic heart disease in Taiwan.

A total of 122 pregnancies in 101 women with organic heart disease were reviewed. The incidence of organic heart disease in pregnant women was 0.25%. The ratio of rheumatic to congenital heart disease was 1.0 to 1.5. In the congenital heart disease group, IUGR was more frequent in the cyanotic group as were preterm births. Patients with cyanotic lesions had a significantly higher maternal mortality rate than those with acyanotic lesions. The cyanotic group without surgical correction had a significantly higher maternal mortality rate and more IUGR than those with correction. Congestive heart failure was the most common maternal complication, with a rate of 38.1%. The patients with good cardiac status control during pregnancy developed less IUGR, had fewer preterm births, less maternal morbidity and less maternal mortality than those in poor condition. Patients in functional classes I and II before pregnancy carried less risk of maternal morbidity than those in classes III and IV.

Female↗

PubMed1993

Deep vein thrombosis during pregnancy.

Antepartum deep vein thrombosis is quite rare in Chinese women during pregnancy. An adequate diagnosis and early treatment are extremely important as the deep vein thrombosis can embolize, in particular, to the pulmonary vasculature. We present a case of pregnancy at 36 weeks gestation complicated by deep vein thrombosis. The objective diagnosis of deep vein thrombosis for obstetric patients is the noninvasive Doppler ultrasound and plethysmography. An early diagnosis is important to reduce maternal and fetal risks related to embolization. Continuous therapy of low dose intravenous heparin is safe and effective during pregnancy.

Adult↗

PubMed1992

Pregnancy outcome of preterm premature rupture of the membranes before 28 weeks.

From January 1987 to December 1990 at Chang Gung Memorial Hospital, the fetal membrane ruptured in 47 singleton pregnancies at the 20th to the 28th gestational weeks. Sixty-six percent of the patients delivered within three days and 91.5% within one week. Only six (12.8%) patients carried their pregnancies over the 28th week. Of the 47 patients, 16 (34.0%) developed clinical evidence of chorioamnionitis during the latent period. The development of chorioamnionitis was not related to any of clinical factors [gestational age at rupture of the membranes, duration of rupture of the membranes before admission, positive endocervical culture, tocolysis, latent period or the presence of oligohydramnios (p > 0.05)]. The neonatal survival rate was 12.7% (six out of 47). Neonatal death was mainly attributable to prematurity. Gestational age beyond the 28th week and body weight greater than 1000 gm are two factors contributing to fetal survival. When fetal lung maturity has not occurred expectant management in the absence of infection is an alternative treatment.

Chorioamnionitis↗

PubMed1992

[Dento-facial structural characteristics in Angle Class II malocclusion associated with abnormal facial divergency].

Lateral cephalometric radiographs of 60 adult patients with Angle class 11 malocclusion associated with abnormal facial divergency were collected from the Orthodontic Department of the National Taiwan University Hospital. They were divided into a hyperdivergent group (35 cases) and a hypodivergent group (25 case), according to mandibular plane angle (SN-MP). The 19 landmarks on each cephalometric tracing were digitized into a computer, then computer-aided cephalometric analysis was performed to calculate the 17 skeletal measurements and 13 dentoalveolar measurements. The dento-facial structural characteristics of the hyperdivergent and hypodivergent groups were compared. It was found that the subjects of the hyperdivergent group revealed a greater tendency of divergency in the anterior cranial base plane, Frank-fort horizontal plane, palatal plane, occlusal plane, and mandibular plane. Hyperdivergent facial type, supposedly indicating an open bite or a tendency toward an open bite, has a longer lower anterior facial height, shorter posterior facial height, longer upper anterior and posterior dental height. While, the majority of dentofacial characteristics of the hypodivergent facial type observed in is study were directly opposite to those of the hyperdivergent facial type. The relationships of incisor overbite depth and other skeletal and dentoalveolar parameters were illustrated by Pearson's correlation coefficient and stepwise multiple regression analysis by means of the SPSS/PC statistic program. With the incisor overbite depth as the dependent variable, the independent variables included on the regression analysis were the 10 items of skeletal and dentoalveolar parameters. The compared parameters showed a statistically significant correlation with the incisor overbite depth (P < 0.001). By the stepwise method, the variables included on the regression equation were (1) N-Go-Gn, (2) A-Gn-Ar, (3) N-Ans/ans-Me, and (4) U1L1. The value of R square (R2) in the regression analysis was 0.543. It demonstrated that only a 54.3% variation in incisor overbite depth can be explained by variations in those skeletal and dentoalveolar variables.

Adult↗

PubMed1992

In vitro perfusion study of the human placenta at term: preliminary results.

Dual perfusion of the human placental lobule in vitro is a useful method for studying the transfer of molecules across the placenta, including the transfer of endogenous substances and xenobiotics. To establish the first model of in vitro placental dynamic study in our country, we used a dual recirculating perfusion system modified from that described by Miller et al. A placental lobule without tears or gross lesions was chosen. Both the fetal and maternal sides of the placenta were perfused with Medium 199 in addition to heparin, glucose, dextran and antibiotics. Perfusate samples were obtained periodically and analyzed for blood gas, glucose, lactate, human placental lactogen (hPL) and human chorionic gonadotropin (hCG). The stability of this human placental lobule preparation during 10 hours of perfusion was reflected by the stability of the arterial pressure and by the constant volume in the fetal compartment. A constant rate of oxygen was delivered by the maternal circulation system, and a steady rate of oxygen was gained by the fetal circulation system. Neither oxygen nor glucose consumption by the tissue was significantly reduced during the period of perfusion. The releasing rates of hCG and hPL did not change significantly during perfusion. The development of this dual perfusion system for the human placenta can provide for the study of placental hemodynamics and transplacental transport in perinatal medicine in our country.

Female↗

PubMed1992

Rupture of gravid uterus: a eight-year clinical analysis and review of the literature.

Nine cases of ruptured gravid uterus occurred at the Chang Gung Memorial Hospital from July 1983 to June 1991. The incidence is 1/3871. Six (66.7%) of the nine cases of uterine rupture involved rupture of intact uteri. The remaining three (33.3%) occurred in uteri scarred by a previous cesarean-section. The common contributing factor to rupture of an intact uterus was injudicious use of a uterine stimulant; whereas the common etiology of rupture of a scarred uterus was a previous scar rupture or dehiscence. In this series, there was no maternal mortality; however, three (33.3%) of the infants died. The fetal death rate was higher with rupture of an intact uterus, 50.0%, as opposed to 0% with rupture of a scarred uterus. Abnormal labor course and clinical features (palpable fetal part or regression of head, profound shock and cessation of uterine contraction) were the important tools for early diagnosis of uterine rupture. Mortality rates for the mother and fetus can be decreased with a high index of suspicion, early diagnosis, and immediate surgical intervention.

Adult↗