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Biomedical subjects

C S Hwang

Publications and source records attributed to C S Hwang.

35 records · Page 2Linked to original sources
PubMed1998

D-Erythroascorbic acid is an important antioxidant molecule in Saccharomyces cerevisiae.

D-Arabinono-1,4-lactone oxidase catalysing the final step of D-erythroascorbic acid biosynthesis was purified from the mitochondrial fraction of Saccharomyces cerevisiae. Based on the amino acid sequence analysis of the enzyme, an unknown open reading frame (ORF), YML086C, was identified as the ALO1 gene encoding the enzyme. The ORF of ALO1 encoded a polypeptide consisting of 526 amino acids with a calculated molecular mass of 59493Da. The deduced amino acid sequence of the enzyme shared 32% and 21% identity with that of L-gulono-1,4-lactone oxidase from rat and L-galactono-1,4-lactone dehydrogenase from cauliflower, respectively, and contained a putative transmembrane segment and a covalent FAD binding site. Blot hybridization analyses showed that a single copy of the gene was present in the yeast genome and that mRNA of the ALO1 gene was 1.8kb in size. In the alo1 mutants, D-erythroascorbic acid and the activity of D-arabinono-1,4-lactone oxidase could not be detected. The intracellular concentration of D-erythroascorbic acid and the enzyme activity increased up to 6.9-fold and 7.3-fold, respectively, in the transformant cells carrying ALO1 in multicopy plasmid. The alo1 mutants showed increased sensitivity towards oxidative stress, but overexpression of ALO1 made the cells more resistant to oxidative stress.

Amino Acid Sequence↗
PubMed1997

Adipocyte differentiation and leptin expression.

Adipose tissue has long been known to house the largest energy reserves in the animal body. Recent research indicates that in addition to this role, the adipocyte functions as a global regulator of energy metabolism. Adipose tissue is exquisitely sensitive to a variety of endocrine and paracrine signals, e.g. insulin, glucagon, glucocorticoids, and tumor necrosis factor (TNF), that combine to control both the secretion of other regulatory factors and the recruitment and differentiation of new adipocytes. The process of adipocyte differentiation is controlled by a cascade of transcription factors, most notably those of the C/EBP and PPAR families, which combine to regulate each other and to control the expression of adipocyte-specific genes. One such gene, i.e. the obese gene, was recently identified and found to encode a hormone, referred to as leptin, that plays a major role in the regulation of energy intake and expenditure. The hormonal and transcriptional control of adipocyte differentiation is discussed, as is the role of leptin and other factors secreted by the adipocyte that participate in the regulation of adipose homeostasis.

Adipocytes↗
PubMed1996

Transcriptional activation of the mouse obese (ob) gene by CCAAT/enhancer binding protein alpha.

Like other adipocyte genes that are transcriptionally activated by CCAAT/enhancer binding protein alpha (C/EBP alpha) during preadipocyte differentiation, expression of the mouse obese (ob) gene is immediately preceded by the expression of C/EBP alpha. While the 5' flanking region of the mouse ob gene contains several consensus C/EBP binding sites, only one of these sites appears to be functional. DNase I cleavage inhibition patterns (footprinting) of the ob gene promoter revealed that recombinant C/EBP alpha, as well as a nuclear factor present in fully differentiated 3T3-L1 adipocytes, but present at a much lower level in preadipocytes, protects the same region between nucleotides -58 and -42 relative to the transcriptional start site. Electrophoretic mobility-shift analysis using nuclear extracts from adipose tissue or 3T3-L1 adipocytes and an oligonucleotide probe corresponding to a consensus C/EBP binding site at nucleotides -55 to -47 generated a specific protein-oligonucleotide complex that was supershifted by antibody against C/EBP alpha. Probes corresponding to two upstream consensus C/EBP binding sites failed to generate protein-oligonucleotide complexes. Cotransfection of a C/EBP alpha expression vector into 3T3-L1 cells with a series of 5' truncated ob gene promoter constructs activated reporter gene expression with all constructs containing the proximal C/EBP binding site (nucleotides -55 to -47). Mutation of this site blocked transactivation by C/EBP alpha. Taken together, these findings implicate C/EBP alpha as a transcriptional activator of the ob gene promoter and identify the functional C/EBP binding site in the promoter.

Animals↗
PubMed1996

Deletion of Rb1 gene in late osteosarcoma from survivor of unilateral retinoblastoma--a case report.

It has been well known that the survivors of retinoblastoma are prone to have osteosarcoma. But the secondary tumor usually occurs in bilateral, hereditary type of retinoblastoma. We report one case of osteosarcoma in a survivor of unilateral, sporadic retinoblastoma. A fourteen year old male presented with a painfully swollen distal forearm of 2 month duration. He had enucleated his left eye 10 years ago due to retinoblastoma with no other adjuvant therapy. We managed him with our conventional protocol and identified deletion of Rb gene from his pathological specimen by using the PCR-RFLP method. This result is unusual for unilateral nonhereditable retinoblastoma and may suggest gene level change even in sporadic cases. And Rb gene study may be helpful for unilateral, sporadic retinoblastoma patient in detecting the possibility of late osteosarcoma.

Adolescent↗
PubMed1996

Enhanced expression of cathepsin L in metastatic bone tumors.

Cathepsin L is a kind of cystein proteases which are known to facilitate the invasion and metastasis of tumor cells by degrading the components of basement membrane and extracellular matrix. This study was undertaken to investigate the expression of cathepsin L by Northern blot analysis with radiolabeled cDNA specific for cathepsin L in six normal tissues, two osteosarcoma cell lines, MG-63 and Saos-2, six primary bone tumors and six metastatic bone tumors. In six normal tissues, the highest level of cathepsin L was expressed in liver with the descending order of liver > lung > thymus > ovary > kidney > esophagus. One of the two osteosarcoma cell lines established from the primary sites expressed a high level of cathepsin L mRNA. Out of six primary bone tumors, three (50%) expressed cathepsin L mRNA, while all (100%) of six metastatic bone tumors expressed the mRNA. These results demonstrating the higher frequency of expression of cathepsin L in metastatic bone tumors suggest that cathepsin L may participate in tumor invasion and metastasis.

Adolescent↗
PubMed1995

Regulated expression of the obese gene product (leptin) in white adipose tissue and 3T3-L1 adipocytes.

A mutation within the obese gene was recently identified as the genetic basis for obesity in the ob/ob mouse. The obese gene product, leptin, is a 16-kDa protein expressed predominantly in adipose tissue. Consistent with leptin's postulated role as an extracellular signaling protein, human embryonic kidney 293 cells transfected with the obese gene secreted leptin with minimal intracellular accumulation. Upon differentiation of 3T3-L1 preadipocytes into adipocytes, the leptin mRNA was expressed concomitant with mRNAs encoding adipocyte marker proteins. A factor(s) present in calf serum markedly activated expression of leptin by fully differentiated 3T3-L1 adipocytes. A 16-hr fast decreased (by approximately 85%) the leptin mRNA level of adipose tissue of lean (ob/+ or +/+) mice but had no effect on the approximately 4-fold higher level in obese (ob/ob) littermates. Since the mutation at the ob locus fails to produce the functional protein, yet its cognate mRNA is overproduced, it appears that leptin is necessary for its own downregulation. Leptin mRNA was also suppressed in adipose tissue of rats during a 16-hr fast and was rapidly induced during a 4-hr refeeding period. Insulin deficiency provoked by streptozotocin also markedly down-regulated leptin mRNA and this suppression was rapidly reversed by insulin. These results suggest that insulin may regulate the expression of leptin.

3T3 Cells↗
PubMed1995

Isolation and characterization of genes expressed uniquely during appressorium formation by Colletotrichum gloeosporioides conidia induced by the host surface wax.

Appressorium formation in germinating Colletotrichum gloeosporioides is induced by the surface wax of the host, the avocado fruit. To elucidate the mechanism by which differentiation of appressorium formation is induced, the fungal genes specifically activated by this host signal were sought. From a cDNA library of the transcripts present in appressorium-forming conidia, the clones representing nongerminating conidia were removed by hybridization with cDNAs synthesized from the nongerminating conidia. From this subtracted library, clones that hybridized with cDNA for transcripts from appressorium-forming conidia and not with cDNA for transcripts from germinating conidia were selected. Three such clones were isolated and sequenced. The genes for these three transcripts were also cloned and sequenced. Northern blot analysis showed that transcripts that hybridized with these three clones were expressed in the conidium only during the process of appressorium formation induced by avocado surface wax, and that these transcripts were not detectable when appressorium formation was prevented even in the presence of avocado wax. Nucleotide sequences of the clones revealed that one clone, cap3, contained an open reading frame (ORF) that would code for a 26-amino acid, cysteine-rich peptide with significant homology to Neurospora crassa copper metallothionein. Another clone, cap5, contained an ORF that would code for a 27-amino acid cysteine-rich peptide with less homology to metallothioneins. Cu2+ and Cd2+ also induced the expression of these genes at lower levels. The histochemical analysis of transformants containing the cap5 promoter fused to the beta-glucuronidase (GUS) gene showed that the cap5 gene promoter caused GUS expression exclusively during appressorium formation and most of the gus activity was in the appressorium. The cap22 clone contained an ORF coding for a 227-amino acid polypeptide of 22 kDa, which did not show significant homology to any known proteins. Recombinant CAP22 protein was produced using a pET-19b expression system in Escherichia coli, purified, and used to prepare rabbit antibodies. Western blot analysis of proteins from the appressorium-forming conidia revealed a major cross-reacting protein at 43 kDa and a minor band at 68 kDa, indicating that the potential glycosylation sites found in the primary translation product were probably glycosylated. Results of immunogold localization showed that CAP22 protein was located on the wall of the appressorium.

Amino Acid Sequence↗
PubMed1995

Surface signaling in pathogenesis.

Surface signaling plays a major role in fungal infection. Topographical features of the plant surface and chemicals on the surface can trigger germination of fungal spores and differentiation of the germ tubes into appressoria. Ethylene, the fruit-ripening hormone, triggers germination of conidia, branching of hyphae, and multiple appressoria formation in Colletotrichum, thus allowing fungi to time their infection to coincide with ripening of the host. Genes uniquely expressed during appressoria formation induced by topography and surface chemicals have been isolated. Disruption of some of them has been shown to decrease virulence on the hosts. Penetration of the cuticle by the fungus is assisted by fungal cutinase secreted at the penetration structure of the fungus. Disruption of cutinase gene in Fusarium solani pisi drastically decreased its virulence. Small amounts of cutinase carried by spores of virulent pathogens, upon contact with plant surface, release small amounts of cutin monomers that trigger cutinase gene expression. The promoter elements involved in this process in F. solani pisi were identified, and transcription factors that bind these elements were cloned. One of them, cutinase transcription factor 1, expressed in Escherichia coli, is phosphorylated. Several protein kinases from F. solani pisi were cloned. The kinase involved in phosphorylation of specific transcription factors and the precise role of phosphorylation in regulating cutinase gene transcription remain to be elucidated.

Amino Acid Sequence↗
PubMed1995

Cloning of a gene expressed during appressorium formation by Colletotrichum gloeosporioides and a marked decrease in virulence by disruption of this gene.

Appressorium formation in germinating Colletotrichum gloeosporioides is induced by the surface wax of its host. One of the genes expressed uniquely in C. gloeosporioides during appressorium formation induced by the host signal has been designated cap20, and this gene and its cDNA were cloned and sequenced. Nucleotide sequences of both revealed an open reading frame that could encode a 183-amino acid polypeptide that did not have significant homology with any known proteins. Reverse transcriptase-polymerase chain reaction detected cap20 gene transcripts at the infection front on the surface and within tomato fruits infected by C. gloeosporioides. Gene-disrupted mutants incapable of expressing cap20 showed a drastically decreased virulence on avocado and tomato fruits. These results suggest that cap20 plays a significant role in the infection of the host.

Amino Acid Sequence↗
PubMed1993

Molecular cloning and sequencing of thioesterase B cDNA and stimulation of expression of the thioesterase B gene associated with hormonal induction of peroxisome proliferation.

The primary structure deduced from the cDNA of a medium-chain fatty acyl-CoA hydrolase designated thioesterase B from the uropygial gland of mallard duck was determined. A near full-length thioesterase B cDNA was isolated from a duck uropygial gland cDNA library using a 120-base pair polymerase chain reaction probe generated from first strand of cDNA and primers synthesized on the basis of two segments of the enzyme. The nucleotide sequence of this cDNA showed an open reading frame encoding a polypeptide of 557 amino acids including a 25-amino acid leader sequence. It showed little homology to the thioesterase domain of fatty acid synthase and S-acyl fatty acid synthase thioesterase, but showed homology to some esterases such as carboxylesterases. Northern blot showed one major transcript at 2.4 kilobases. The highest level of this transcript was in the uropygial gland, much less in the liver and kidney, and not detectable in other organs. Elevation of thioesterase B transcript level was associated with peroxisome proliferation occurring in the mating season and the increase in transcript level correlated with peroxisome proliferation and synthesis of 3-hydroxyfatty acid diester pheromones resulting from estradiol treatment. This thioesterase may be associated with peroxisome proliferation or peroxisomal metabolism.

Amino Acid Sequence↗
PubMed1992

[The content of ambulatory family practice in Kaohsiung Medical College Hospital].

To understand the content of ambulatory family practice and find effective ways to improve clinical service, education and research in the Department of Family Medicine of Kaohsiung Medical College Hospital, we surveyed 14,064 patients from Jan. 1984 to Feb. 1991 and analysed (a) their basic demographic data including sex, age, insurance type, source and residential district and (b) clinical health problems covering 25,679 diagnoses and 148,994 diagnostic visits. Clinical health problems were recorded by the ICHPPC-2 code system. Results of basic demographic survey were as follow: 49.1% of patients was male and 50.9% female; 58.9% fell in the age group of 16-40 years and 22.4%, 12.0% and 6.7% of patients fell into the age groups of 41-65, under 16 and over 65 years respectively; 62.8% was insured usually by labor insurance and 26.9% had no insurance; the commonest referrals were other patients, colleagues, company personnel, doctors, media ... etc.; 58.8% lived in Kaohsiung City and 19.6% in Kaohsiung county. As for clinical health problems, the data showed that the commonest thirty diagnoses encountered at our clinic accounted for 69.3% of 25,679 diagnoses and the commonest ten diagnoses in descending order were medical health examination, acute URI, abdominal pain, uncomplicated hypertension, prophylactic immunization, hepatitis B carrier, back pain, anxiety disorder, viral hepatitis and irritable bowel syndrome. By calculating the average value of each diagnosis in a sample of 148,994 diagnostic visits to evaluate the habits of practice, we found that the commonest ten diagnostic visits at clinic in descending order were diabetes mellitus, hypertension involving target organ, uncomplicated hypertension, gout, hyperthyroidism, duodenal ulcer, tuberculosis, lipid metabolism disorder, other peptic ulcer and depressive disorders; all were chronic diseases. We concluded it was very important and helpful for the development of family medicine program and primary care unit to understand the content of their own ambulatory practice.

Ambulatory Care↗
PubMed1991

Multiple brain abscesses as a complication of pulmonary arteriovenous fistula. A case report.

A case of pulmonary arteriovenous fistula (PAVF) complicated by brain abscess is presented. The incidence of this complication has been quoted to be 1-5%. After reviewing all inpatients in Chang Gung Memorial Hospital from 1977 to 1988, we found a total of 9 cases of PAVF; only one case of PAVF complicated by brain abscess was noted. PAVF is often asymptomatic in the early stage, and its diagnosis may sometimes be quite difficult. However, untreated PAVF tends to enlarge and become symptomatic. There is also a continuing risk of severe neurologic complications. For these reasons, early diagnosis and treatment are essential. In a case of brain abscess associated with unexplained hypoxemia and extra-cardiac murmur on auscultation, PAVF should be considered.

Adult↗
PubMed1989

In vivo and in vitro studies on the release of thyrotropin in aging rats.

Effects of aging on the concentration of serum thyrotropin (TSH) and the release of TSH in vitro from anterior pituitary glands (APs) of male and female rats were investigated. Rats with 3-5 (young) and 24-26 (old) months of age were used. Some female rats were ovariectomized (Ovx) 10 weeks before use. After decapitation, trunk blood was collected. APs were bisected and preincubated with Krebs-Ringer phosphate buffer (KRB) at 37 degrees C for 60 min. They were then incubated with or without 10 nM thyrotropin-releasing hormone (TRH) for 30 min. The media were collected and replaced by fresh KRB. Incubations were continued and KRB media were changed three times, once every 30 min. One hemi-AP per flask and 7 or 8 flasks per group were used. The concentration of TSH in the medium and serum samples was measured by radioimmunoassay. The level of serum TSH in the diestrous, estrous and Ovx rats was reduced by aging. Thirty min after incubation with TRH, the release of TSH from APs of old intact female or Ovx rats was significantly (P less than 0.01) less than that of corresponding young rats. The concentration of serum TSH and TRH-stimulated release of TSH from APs of male rats was not altered by aging. There was no difference in the basal release of TSH from APs between old and young animals. These data suggest that the release of TSH from APs in response to TRH is decreased by aging in female but not in male rats.

Aging↗
PubMed1989

Clinical observations of virologically confirmed dengue fever in the 1987 outbreak in southern Taiwan.

Fifty-nine virologically confirmed cases of dengue fever were clinically studied during the 1987 outbreak in southern Taiwan. Viral isolation and serologic studies indicated that type 1 dengue was the cause. Dengue fever has not been on the island of Taiwan for 42 years and nearly all the population under 42 years of age is susceptible. Most patients under age 42 experience primary infection while those over 42 years old experience secondary infection. The majority of 59 cases studied were females in the 21-30-year age group. Classic signs and symptoms ere fever, headache, muscle pain, joint pain, nausea and vomiting, and skin rash. Approximately 80% of the patients had leukopenia (less than 5,000/mm3) and thrombocytopenia (less than 50,000/mm3) and 90% experienced mild to moderate elevation of serum glutamic oxaloacetic transaminase. Hemorrhagic manifestations occurred in 25.4% of patients. No patients under observation in this study developed hypotension or died.

Adolescent↗
PubMedDate not supplied

Detection of human papillomavirus (HPV) in sinonasal inverted papillomas using polymerase chain reaction (PCR).

Paraffin-embedded tissues of 42 sinonasal inverted papillomas were subjected to polymerase chain reaction using type-specific primers pairs of HPV 6, 11, 16, 18, and 33. Two cases of HPV 11 and one of HPV 6 were amplified in 36 samples of benign inverted papilloma, and two cases of HPV 16 were amplified in five samples of inverted papilloma with co-existing squamous cell carcinoma. Inverted papillomas recurred in 1 (16%) of 6 cases exhibiting dysplasia, and in 3 (10%) of 30 cases not exhibiting dysplasia. Inverted papillomas also recurred in 2 (66%) of 3 cases positive for HPV, and in 2 (6%) of 33 cases negative for HPV. These results suggest that HPV may be involved in the pathogenesis of inverted papillomas, may cause malignant transformation of inverted papillomas, and that there may be an apparent relationship between HPV infection and the recurrence of sinonasal inverted papillomas.

Adult↗