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Biomedical subjects

C Chen

Publications and source records attributed to C Chen.

At least 451 records · Page 25Linked to original sources
PubMed1999

Preoperative sonographic diagnosis of midgut malrotation with volvulus in adults: the "whirlpool" sign.

Midgut malrotation and volvulus, found mostly in children, are rare and difficult to diagnose preoperatively in adults. We report 2 cases in which a 68-year-old man and a 75-year-old woman presented with intermittent cramping abdominal pain, abdominal distention, and vomiting. Abdominal sonography demonstrated wrapping of the superior mesenteric vein and bowel loops around the superior mesenteric artery (the "whirlpool sign") in both patients. Abdominal CT revealed similar findings. The diagnoses of midgut volvulus and mesenteric malrotation were made, and the patients underwent laparotomy. The man was confirmed to have duodenojejunal malrotation and volvulus, and the woman had cecal volvulus. The whirlpool sign is valuable for the preoperative diagnosis of mesenteric vessel malrotation and midgut volvulus.

Aged↗
PubMed1999

Study on the isolation, purification and physicochemical properties of polysaccharides from Indocalamus tesselatus.

Polysaccharides prepared from Chinese traditional medicine "Ruoye" (Indocalamus tesselatus), a kind of bamboo leaves, were studied. Eight crude polysaccharides were isolated from the dried leaves by successive extraction with 85% ethanol (FE), 0.9% sodium chloride (FS), hot water (FI), 1% ammonium oxalate (FII), 5% NaOH (FIII-a, FIII-b) and 20% NaOH (FIV-a, FIV-b). They were decolorized by hydrogen peroxide treatment and the protein was removed with Savag's method. The polysaccharides were precipitated by three volumes of absolute ethanol. After further purification by gel filtration chromatography on a Sephadex G-200 column, these polysaccharides were lyophilized. Their physicochemical properties and structural feature were elucidated by modern analytical technique such as UV, elemental analysis and high performance gel permeation chromatography. From the results of partial hydrolysis, FE and FIII-b have a main chain comprised solely of glucuronic acid and xylose residues, respectively.

Chromatography, Gel↗
PubMed1999

Localization of a gene for myoclonus-dystonia to chromosome 7q21-q31.

Essential myoclonus-dystonia is a neurological condition characterized by myoclonic and dystonic muscle contractions and the absence of other neurological signs or laboratory abnormalities; it is often responsive to alcohol. The disorder may be familial with apparent autosomal dominant inheritance. We report a large kindred with essential familial myoclonus-dystonia and map a locus for the disorder to a 28-cM region of chromosome 7q21-q31.

Adolescent↗
PubMed1999

Differences in p16 gene methylation and expression in benign and malignant ovarian tumors.

OBJECTIVE: The aim of this study was to test the hypothesis that DNA methylation is important for silencing the p16 tumor suppressor gene in ovarian epithelial tumors and to compare the prevalence of this mechanism among different ovarian epithelial tumor subtypes. METHOD: Methylation-specific PCR was used to analyze the p16 gene for DNA methylation in 20 ovarian cystadenomas, 15 low malignant potential (LMP) tumors, and 37 carcinomas. p16 expression was determined immunohistochemically in 58 of these tumors (16 cystadenomas, 13 LMP tumors, 29 carcinomas). Differences in methylation or expression rates between specific tumor subgroups were examined by Fisher's exact test. RESULTS: Fragments from the distal promoter and beginning of the first exon of the p16 gene were both methylated in 5 of 15 (33%) LMP tumors compared to 2 of 37 (5%) carcinomas (P = 0. 02). Those sites were also methylated in 5 of 20 (25%) cystadenomas. Lack of p16 expression was present in 7 of 16 cystadenomas, 4 of 13 LMP tumors, and 22 of 29 carcinomas (P [LMPs versus carcinomas] = 0. 01) and correlated with methylation changes in LMP tumors (P = 0.05). p16 expression was correlated with mucinous differentiation in cystadenomas (P = 0.001). CONCLUSION: p16 silencing may be important for the development of ovarian carcinomas and a subset of LMP tumors. Changes in DNA methylation may be more important for inactivation of this gene (and perhaps other tumor suppressor genes) in LMP tumors, which lack many of the alternative mechanisms present in carcinomas. p16 expression is primarily related to mucinous differentiation in cystadenomas.

Carcinoma↗
PubMed1999

Oral administration of L-arginine reduces intimal hyperplasia in balloon-injured rat carotid arteries.

Endogenous nitric oxide (NO) is produced from L-arginine by NO synthase. We evaluated the effect of oral administration of L-arginine on intimal hyperplasia in balloon-injured rat carotid arteries. Thirty Sprague-Dawley rats underwent balloon denudation on the left common carotid artery. Fifteen rats were treated with L-arginine in drinking water (2.5 mg/mL) two days before injury and were continued for 2 weeks. Another 15 rats served as controls. All animals survived without complications or body weight loss. In the treated group, daily intake of L-arginine was 170 +/- 43 mg/day. Plasma arginine levels were 130 +/- 32 micromol/L prior to L-arginine intake, 165 +/- 42 micromol/L at the day of injury, and 162 +/- 26 micromol/L at sacrifice. Intimal hyperplasia developed in all balloon-injured arteries in both control and L-arginine-treated animals. However, L-arginine-treated animals showed a 65% reduction of the intima/media area ratio and a 26% reduction of the intimal cell proliferation compared with control animals. These data indicate that adequate amounts of L-arginine were ingested by the rats and that oral administration of L-arginine significantly reduced intimal hyperplasia of balloon-injured arteries without any detectable toxicity.

Administration, Oral↗
PubMed1999

Different role of antioxidants in endotoxin-induced late myocardial protection.

Previous studies have proposed that endogenous antioxidants play a protective role against cardiac ischemia-reperfusion injury in endotoxin pretreatment. However, the mechanism underlying this effect remains elusive. We therefore evaluated the role of endogenous antioxidants in delayed myocardial protection after different doses of endotoxin administration using cultured rat neonatal cardiomyocytes. Myocytes were treated with normal saline (control) or lipopolysaccharide (Escherichia coli, serotype O111) at doses of 40 and 80 microg/ml (ET40 and ET80). Also, antisense oligodeoxyribonucleotide (1.5 micromol/L) to manganese superoxide dismutase (Mn-SOD) and 3-amino-1,2,4-triazole (25 mg/ml) were added along with a 40 or 80 microg/ml endotoxin pretreatment in the IET40 and IET80 groups. Twenty-four hours later, Cells were subjected to hypoxia (pO2 < 1 kPa, 3 h) and reoxygenation (pO2: 19 kPa, 1 h). Compared with controls, cell viability enhanced significantly (65.3 +/- 5.9, 63.8 +/- 4.6, and 69.7 +/- 5.2% vs 47.2 +/- 4.3%, P < 0.05) and creatine kinase release decreased (7.34 +/- 1.76, 7.11 +/- 1.49, and 6.27 +/- 1.24 U/mg protein vs 11.23 +/- 2.49 U/mg protein, P < 0. 05) in ET40, IET40, and ET80 groups following reoxygenation. No statistically significant difference was found between the control and the IET80 groups. Furthermore, the levels of Mn-SOD (1.12 +/- 0. 31 vs 0.75 +/- 0.15 U/mg. protein, P < 0.05) and catalase activity (1265 +/- 109 vs 996 +/- 85 U/mg. protein, P < 0.05) were higher only in the ET80 group. The results suggest that at a dose of 40 microg/ml, cells were protected by mechanisms other than the augmentation of endogenous antioxidant activity which were more evident at a dose of 80 microg/ml. It seems that different doses of endotoxin pretreatment may induce delayed myocardial protection through various mechanisms.

Animals↗
PubMed1999

Enhanced apoptosis mediates inhibition of EBV-transformed lymphoblastoid cell line proliferation by curcumin.

BACKGROUND: Epstein-Barr virus (EBV)-associated B-cell lymphomas occur more frequently in immunodeficient states such as organ transplantation and HIV infection. We have previously reported that B cell immortalization with EBV was promoted by cyclosporin A (CyA) and that curcumin (Cur), a natural phenol with known antioxidant and antitumor properties, blocked EBV-induced B cell immortalization. In the following experiments we show that Cur inhibits the proliferation of EBV-transformed lymphoblastoid cell lines (LCL) via enhanced apoptosis. METHODS: LCL were generated by infecting freshly isolated human B cells with EBV (B95-8) for 12 h and coculturing with predetermined optimal concentrations of CyA (500 ng/ml) for 4 weeks. LCL were then either frozen for future use or propagated for immediate experiments. These cells were then plated in 96-well plates with 20 microM Cur or 0.1% DMSO (vehicle control). The number of immortalized colonies/well, cell count, and (3)H uptake were used as an index of immortalization. To assess apoptosis rate LCL were cultured with 0.1% DMSO or Cur (20 microM) for 0, 18, and 42 h in culture flasks and then stained with MC540 and H33342, as markers for apoptosis, and analyzed by FACS. RESULTS: A profound inhibition of proliferation was seen in the LCL with 20 microM curcumin compared to 0.1% DMSO control. The colony count reduced from 34.5 +/- 3.4 to 0/well (P = 0.005), cell number reduced from 101,250 +/- 12,093 to 3750 +/- 1500/well (P = 0.002), and (3)H uptake reduced from 40,889 +/- 3669 to 70 +/- 5.2/well (P = 0.001). The apoptosis rate of LCL in the DMSO control at 24.07 and 16.87% increased significantly with 20 microM Cur to 76.4 and 95.1% at 18 and 42 h, respectively (P = 0.02). CONCLUSION: Cur is a potent inhibitor of EBV-transformed LCL. This effect appears to be mediated through enhanced apoptosis. A further investigation of this effect may be useful in prevention and therapy of B-cell lymphoma in immunodeficient patients.

Antineoplastic Agents↗
PubMed1999

Study of chemical species of iodine in human liver.

The distribution and chemical species of iodine in various subcellular fractions of human liver were studied by using epithermal neutron activation analysis combined with chemical and biochemical separation techniques, such as gradient centrifugation and gel chromatography. It was found that the total iodine content orders in various subcellular fractions is as follows: nuclei > cytosol > mitochondria > lysosome > microsome. In the lysosomal fraction, iodine is mainly bound to macromolecules, whereas in the nuclei and mitochondrial fractions, mainly with lower-molecular-weight organic compounds. In the cytosol fraction, iodine is combined with three proteins, in which iodine is chiefly bound with mid- and high-molecular-weight proteins.

Chromatography, Gel↗
PubMed1999

Investigation of selenium distribution in subcellular fractions of human liver by neutron activation analysis.

Selenium is an important and essential trace element to living systems. In the article, two methods of instrumental neutron activation analysis and hydride generation-atomic fluorescence spectrometry were applied to determine Se in biological samples and the accuracy was evaluated by several reference materials. The subcellular distribution of selenium in human liver samples, which were obtained from normal subjects who had an accidental death, was investigated by differential centrifugation combined with INAA. Selenium was mainly enriched in mitochondria, nuclei, and cytosol. Almost half of the total Se content existed in nuclei as a result of the large amount in liver and the high Se concentration. Generally, the highest Se concentration in the mitochondrial fractions of each liver sample suggested that Se had important functions in this liver component.

Adult↗
PubMed1999

Cloning and chromosomal mapping of a gene isolated from thymic stromal cells encoding a new mouse type II membrane serine protease, epithin, containing four LDL receptor modules and two CUB domains.

We cloned and sequenced a mouse gene encoding a new type of membrane bound serine protease (epithin) containing a multidomain structure. The initial cDNA clone was found previously in a polymerase chain reaction (PCR)-based subtractive library generated from fetal thymic stromal cells, and the message was shown to be highly expressed in a thymic epithelial nurse cell line. A clone isolated from a severe combined immunodeficiency (SCID) thymus library and extended to its full length at the 5' end with the RACE technique contains an open reading frame of 902 amino acids. Based on the sequence of this clone, the predicted protein structure is a type II membrane protein with a C-terminal serine protease domain linked to the membrane by four low density lipoprotein receptor modules and two CUB domains. High message expression by northern blotting was detected in intestine, kidney, lung, SCID, and Rag-2(-/-) thymus, and 2-deoxyguanosine-treated fetal thymic rudiment, but not in skeletal muscle, liver, heart, testis, and brain. Sorted MHC class II+ and II- fetal thymic stromal cells were positive for expression by reverse transcriptase-PCR, whereas CD45(+) thymocytes were not. The gene was found in chicken and multiple mammalian species under low stringency Southern hybridization conditions. Under high stringency conditions, only a single gene per haploid genome was identified in the mouse. This gene, Prss14 (protease, serine, 14), was mapped to mouse chromosome 9 and is closely linked to the Fli1 (Friend leukemia integration 1) gene.

Amino Acid Sequence↗
PubMed1999

Single base discrimination of CENP-B repeats on mouse and human Chromosomes with PNA-FISH.

The satellite repeat structure of the mammalian centromere contains the CENP-B protein binding site. Using the peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH), we show by direct PNA-DNA binding that all detectable CENP-B sites in a mammalian genome might have the same sequence. Two species-specific PNA 17-mers, pMm and pMc, were identified from CENP-B binding sites of Mus musculus and M. caroli, respectively. Fluorescence in situ hybridization confirmed that pMc hybridized to M. caroli centromeres only; however, pMm cross-hybridized to M. musculus and human centromeres. By using a series of CENP-B PNA 17-mers containing 1, 2, 3, 5, and 7 base-pair mismatches to their DNA counterparts, we further demonstrate that PNA-FISH can discriminate between two CENP-B DNA sequences that differ by a single base-pair in mouse and human centromeres, suggesting the degree of conservation of CENP-B sequences throughout the genome. In comparison with DNA oligonucleotides, PNA oligomers demonstrate the higher sequence specificity, improved stability, reproducibility, and lower background. Therefore, PNA oligomers have significant advantages over DNA oligonucleotide probes in analyzing microsatellites in a genome.

Animals↗
PubMed1999

A genome-wide scan for loci linked to forearm bone mineral density.

Osteoporosis is a chronic disorder characterized by low bone mass and fragility fractures. It affects more than 25 million men and women in the United States alone. Although several candidate genes, such as the vitamin-D-receptor gene or the estrogen-receptor gene, have been suggested in the pathogenesis of osteoporosis, the genetic dissection of this disorder remains a daunting task. To search systematically for chromosomal regions containing genes that regulate bone mineral density (BMD), we scanned the entire autosomal genome by using 367 polymorphic markers among 218 individuals (153 sibpairs) from 96 nuclear families collected from three townships of Anqing, China. In these 96 families, DNA samples from both parents were available for 82 (85.4%) families. By using age- and gender-adjusted forearm BMD measurements, a peak on chromosome 2 near D2S2141, D2S1400, and D2S405, a region previously linked to spinal BMD, showed evidence of linkage to both proximal and distal forearm BMD (multipoint LOD=2.15 and 2.14 for proximal and distal forearm BMD, respectively). One region on chromosome 13 (multipoint LOD=1.67) in the proximity of D13S788 and D13S800 showed evidence of linkage to distal forearm BMD only. Possible candidate genes included CALM2 (calmodulin 2) at 2p21.3-p21.1, a putative STK (serine/threonine kinase) at 2p23-24, POMC (pro-opiomelanocortin) at 2p23.3, and COL4A1 and COL4A2 (collagen IV alpha-1 and alpha-2 subunits) at 13q34. Because of the limited sample size, the suggestive evidence of linkage of this study should be considered as tentative and needs to be replicated in other larger populations.

Adolescent↗
PubMed1999

Cyclic AMP diffusion coefficient in frog olfactory cilia.

Cyclic AMP (cAMP) is one of the intracellular messengers that mediate odorant signal transduction in vertebrate olfactory cilia. Therefore, the diffusion coefficient of cAMP in olfactory cilia is an important factor in the transduction of the odorous signal. We have employed the excised cilium preparation from the grass frog (Rana pipiens) to measure the cAMP diffusion coefficient. In this preparation an olfactory cilium is drawn into a patch pipette and a gigaseal is formed at the base of the cilium. Subsequently the cilium is excised, allowing bath cAMP to diffuse into the cilium and activate the cyclic nucleotide-gated channels on the plasma membrane. In order to estimate the cAMP diffusion coefficient, we analyzed the kinetics of the currents elicited by step changes in the bath cAMP concentration in the absence of cAMP hydrolysis. Under such conditions, the kinetics of the cAMP-activated currents has a simple dependence on the diffusion coefficient. From the analysis we have obtained a cAMP diffusion coefficient of 2.7 +/- 0.2. 10(-6) cm2 s-1 for frog olfactory cilia. This value is similar to the expected value in aqueous solution, suggesting that there are no significant diffusional barriers inside olfactory cilia. At cAMP concentrations higher than 5 microM, diffusion slowed considerably, suggesting the presence of buffering by immobile cAMP binding sites. A plausible physiological function of such buffering sites would be to prolong the response of the cell to strong stimuli.

Animals↗
PubMed1999

Hyperechoic renal papillae as a physiological finding in neonates.

AIM: The increased echogenicity of medullary pyramids in neonates and children is poorly understood. Hence we conducted a prospective ultrasound study of the kidneys of neonates and fetuses. Hence we conducted a prospective ultrasound study of the kidneys of neonates and fetuses. PATIENTS AND METHODS: Ultrasound images of kidneys in neonates and fetuses in late pregnancy were analysed. RESULTS: Thirteen percent of the studied neonates showed hyperechogenicity in the renal papillae that disappeared spontaneously within 1 week, although no hyperechoic papillae were seen in any of the fetuses. Urine volume of the neonates with hyperechogenicity was significantly less than that of those without it. CONCLUSION: The fact that no hyperechoic findings appeared before the 34th week of gestation suggests that maturation of renal tubules and ability to concentrate urinary substances were contributing factors. Because only the tips of the pyramids were hyperechogenic, however, the term hyperechoic papillae would seem more appropriate than hyperechoic pyramids, the term generally used today.

Birth Weight↗
PubMed1999

ASP147 in the third transmembrane helix of the rat mu opioid receptor forms ion-pairing with morphine and naltrexone.

We tested the hypotheses that the carboxylate side chain of Asp147 of the mu opioid receptor interacts with the protonated nitrogen of naltrexone and morphine and that this interaction is important for pharmacological properties of the two compounds. Mutation of Asp147 to Ala or Asn substantially reduced the affinity of naltrexone and the affinity, potency and efficacy of morphine, while the Glu mutant had similar properties as the wildtype, indicating the significant role of the carboxylate group of Asp147 in receptor binding and activation. This role could be due to its direct interaction with ligands or involvement in interhelical interactions. The unprotonated analogs of naltrexone and morphine, cyclopropylcarbonyl noroxymorphone (CPCNOM) and N-formylnormorphine (NFNM), respectively, were used to discriminate between these mechanisms. CPCNOM was much less potent as an antagonist and had substantially lower affinity for the mu receptor than naltrexone. Similarly, NFNM was unable to activate the mu receptor and had much lower affinity than morphine. These results indicate the importance of the protonated nitrogen. Notably, the D147A and D147N mutations did not appreciably affect the binding affinities of CPCNOM and NFNM. In addition, the D147E mutant had similar affinities for CPCNOM and NFNM as the D147A and D147N mu receptors. Thus, the carboxylate group of Asp147 is not important for binding of the two unprotonated compounds. These results indicate that the carboxylate group of Asp147 of the mu receptor interacts directly with the protonated nitrogen of naltrexone and morphine and this interaction is important for binding and receptor activation.

Animals↗
PubMed1999

P16 gene deletions and point mutations in patients with agnogenic myeloid metaplasia (AMM).

Studies of p16 alterations with homozygous deletions and mutation analysis were done in 32 patients with agnogenic myeloid metaplasia (AMM) including six patients in leukemic phase. No homozygous deletions were found and, one patient was found to have a shift band in exon 2C fragment by PCR-SSCP analysis. Further sequence analysis demonstrated that the mutated band was a point mutation of G to A in exon 2 codon 140 (GCG-->ACG) causing an amino acid substitution of alanine to threonine demonstrating this patient either carried an mutated gene in one allele as a polymorphism (heterozygous carrier of a mutant p16 gene) or carried a mutant p16 gene clone. This study demonstrates that p16 alterations with homozygous deletions and mutations were very rare in patients with AMM. A single patient found to have a shifted band by PCR-SSCP may be represented as a coincidence or as a polymorphism with a heterozygous carrier of mutated p16 gene, predisposable to AMM or as a mutant p16 gene which can be infrequently observed in this disease.

Blast Crisis↗