Search PubMed⌕ Search

Biomedical subjects

J Kim

Publications and source records attributed to J Kim.

At least 631 records · Page 35Linked to original sources
PubMed1998

Mesoderm induction by heterodimeric AP-1 (c-Jun and c-Fos) and its involvement in mesoderm formation through the embryonic fibroblast growth factor/Xbra autocatalytic loop during the early development of Xenopus embryos.

We have previously demonstrated the involvement of AP-1/Jun in fibroblast growth factor (FGF) signaling by loss-of-function assay (Dong, Z., Xu, R.-H., Kim, J., Zhan, S.-N., Ma, W.-Y., Colburn, N. H., and Kung, H. (1996) J. Biol. Chem. 271, 9942-9946). Further investigations by gain-of-function are reported in this study. AP-1 transactivation activity was increased by the treatment of animal cap explants with FGF. Ectopic overexpression of two components of AP-1 (c-jun and c-fos together, but not alone) produced posteriorized embryos and induced mesoderm formation in animal cap explants, indicating that both AP-1 heterodimers are required for mesoderm induction. Since Ras/AP-1 functions downstream of FGF signaling, we then tested the involvement of Ras/AP-1 in mesoderm maintenance mediated by embryonic FGF/Xbra using dominant-negative mutants. Mesoderm maintenance mediated by embryonic FGF/Xbra was blocked by dominant-negative mutants of Ras/AP-1, and AP-1 enhanced the expression of Xbra. Further studies demonstrated the inhibition of Ras/AP-1-mediated mesoderm formation by dominant-negative mutants of the FGF receptor and Xbra. These results indicate that Ras/AP-1 and FGF/Xbra signals are involved in the mesoderm maintenance machinery and mesoderm formation through the synergistic action of the diversified signal pathways derived from the FGF/Xbra autocatalytic loop.

Animals↗
PubMed1998

Role of caspases 1 and 3 and Bcl-2-related molecules in endothelial cell apoptosis associated with thrombotic microangiopathies.

We have defined an in vitro model for the study of microvascular endothelial cell (EC) apoptosis mediated by plasma from patients with various forms of thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS). This system reproduces a variety of histopathologic and ultrastructural features of tissue EC involved in TTP/sporadic HUS, suggesting that apoptotic EC injury is a primary pathophysiologic event in the thrombotic microangiopathies. We now document the ability of tetrapeptide-based inhibitors of interleukin 1beta-converting enzyme (ICE)-like caspase 1 and cysteine protease protein (CPP)-32-like caspase 3, two members of a novel class of cysteine proteases involved in final pathways to apoptosis, to block TTP/sporadic HUS plasma-mediated apoptosis. Overexpression of Bcl-X(L) via gene transfer suppressed this apoptosis by 70%. Transduction of EC with the Bcl-2 homolog A1 had a more limited protective effect. These findings support a role for apoptosis-linked cysteine proteases in the pathophysiology of TTP and sporadic HUS, and raise the possibility that specific apoptosis inhibitors may have a role in the experimental therapeutics of these syndromes.

Apoptosis↗
PubMed1998

Amyotrophic lateral sclerosis: serum factors enhance spontaneous and evoked transmitter release at the neuromuscular junction.

Sera from 30 patients with sporadic amyotrophic lateral sclerosis (ALS) were tested to determine their effects at the neuromuscular junction. Spontaneous transmitter release was significantly increased, as evidenced by a 151% increase in MEPP frequency, by sera from 16 ALS patients. In addition, 16 patients' sera elevated EEP quantal content by an average of 89%. Eleven sera produced both effects. There was no consistent change in MEPP amplitude or time course, indicating the absence of a humoral effect on postjunctional ACh receptors or endplate membrane function. These results suggest that a portion of the sporadic ALS patient population possess serum factors that can alter presynaptic function of the motor nerve terminal. Evidence from the present experiments indicates that alterations at the neuromuscular junction are a result of a combination of increased Ca2+ influx into the cell and an independent increase in intracellular calcium concentration.

Amyotrophic Lateral Sclerosis↗
PubMed1998

Screening of new bioactive materials from microbial extracts of soil microorganism (I). Antimicrobial activity from 200 samples using microdilution assay.

The microdilution assay recommended by NCCLS (National Committee for Clinical Laboratory Standards) is one of the standardized methods of antibiotic susceptibility test. This method has been widely used clinically to obtain MIC values of antibiotics on pathogenic microorganisms. It is more convenient, rapid and simple to test many samples than other test methods such as agar diffusion assay and broth macrodilution assay. The screening of antimicrobial agents from microbial extracts is too laborious in its process. Therefore, a number of screening methods having more simple procedure have been developed. In our laboratory, we applied microdilution assay for screening the antimicrobial agents. This assay showed dose-response results and was more sensitive than disc diffusion assay in our system. We tested 200 samples of microbial extracts originated from 100 microbial strains and selected several samples as potential candidates. In this report, we show that the microdilution assay is more convenient method in screening of antibiotic susceptibility than those previously reported.

Anti-Bacterial Agents↗
PubMed1998

Purification and characterization of Cop, a protein involved in the copy number control of plasmid pE194.

Cop protein has been overexpressed in Escherichia coli using a T7 RNA polymerase system. Purification to apparent homogeneity was achieved by the sequential chromatography on ion exchange, affinity chromatography, and reverse phase high performance liquid chromatography system. The molecular weight of the purified Cop was estimated as 6.1 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). But the molecular mass of the native state Cop was shown to be 19 kDa by an analytical high performance size exclusion chromatography, suggesting a trimer-like structure in 50 mM Tris-HCl buffer (pH 7.5) containing 100 mM NaCl. Cop protein was calculated to contain 39.1% alpha-helix, 16.8% beta-sheet, 17.4% turn, and 26.8% random structure. The DNA binding property of Cop protein expressed in E. coli was preserved during the expression and purification process. The isoelectric point of Cop was determined to be 9.0. The results of amino acid composition analysis and N-terminal amino acid sequencing of Cop showed that it has the same amino acid composition and N-terminal amino acid sequence as those deduced from its DNA sequence analysis, except for the partial removal of N-terminal methionine residue by methionyl-aminopeptidase in E. coli.

Amino Acid Sequence↗
PubMed1998

Mitochondrial dysfunction induced by oxidative stress in the brains of hamsters infected with the 263 K scrapie agent.

Scrapie, one of the prion diseases, is a transmissible neurodegenerative disease of sheep and other animals. Clinical symptoms of prion diseases are characterized by a long latent period, followed by progressive ataxia, tremor, and death. To study the induction of neurodegeneration during scrapie infection, we have analyzed the activities of various antioxidant enzymes and mitochondrial enzymes in cerebral cortex, brain stem, and cerebellum of scrapie-infected hamsters. The activity of mitochondrial Mn-superoxide dismutase (SOD) was decreased, while the activities of cytosolic Cu/Zn-SOD and catalase were not altered in infected brains. The activities of glutathione peroxidase and glutathione reductase were increased in scrapie-infected hamsters. The decreased activity of Mn-SOD might result in increasing oxidative stress in the mitochondria of infected brain; this concept is supported by our findings of a high level of lipid peroxidation, and low levels of ATPase and cytochrome c oxidase activity in the infected cerebral mitochondria. In addition, structural abnormalities of mitochondria have been observed in the neurons of hippocampus and cerebral cortex of infected brain. These results suggest that mitochondrial dysfunction caused by oxidative stress gives rise to neurodegeneration in prion disease.

Adenosine Triphosphatases↗
PubMed1998

Video-assisted thoracic surgery as a primary therapy for primary spontaneous pneumothorax. Decision making by the guideline of high-resolution computed tomography.

BACKGROUND: Because blebs are confirmed in most of the patients undergoing thoracotomy, identification of blebs by high-resolution computed tomography (HRCT) can be proposed as a surgical indication in primary spontaneous pneumothorax (PSP). If an apical bleb is identified, we treat the patient by video-assisted thoracic surgery (VATS). METHODS: From May 1995 to September 1997, 61 patients (21.9 +/- 4.6 years) were seen for initial episodes of PSP. Only seven showed bullae on simple chest radiography. However, by HRCT, 48 had sizable blebs (>5 mm), and 45 were treated surgically by VATS. RESULTS: The mean duration of chest tube use after surgery was 3.2 +/- 1.9 days, and the mean hospital stay was 4.5 +/- 1.9 days. Only one recurrence developed 5 weeks after VATS. CONCLUSIONS: Our protocol is effective in controlling an initial episode of PSP. It shortens the observation time before definitive surgical treatment, shortens the hospital stay, and decreases the likelihood of recurrence.

Adolescent↗
PubMed1998

Surgical resection of lung cancer originating in a tracheal bronchus.

We experienced a case of lung cancer that developed from a tracheal bronchus in an 80-year-old man. The tumor was completely resected by right upper lobectomy and resection of the tracheal bronchus as well as dissection of the mediastinal lymph nodes. Postsurgical pathologic staging was stage IB (T2 N0 M0) adenocarcinoma.

Adenocarcinoma↗
PubMed1998

Surgical resection of mucoepidermoid carcinoma at the carina in a 9-year-old boy.

Mucoepidermoid carcinoma of trachea and bronchi is a rare tumor, especially in children. The authors report a case of 9-year-old boy with mucoepidermoid carcinoma at the carina. His presenting symptoms were hemoptysis of recent onset and intermittent cough of 2 years' duration. Preoperative assessment of the tumor was an intraluminal polypoid mass arising from the carina extending into the trachea and right main stem bronchus. A complete resection with reconstruction of carina was successful. The tumor was 12 mm in size, polypoid with a broad base. It had characteristic features of a low-grade mucoepidermoid tumor, namely, admixture of islands of intermediate cells and glandular components with invasion of submucosa. The patient is now 15 months postsurgery free of disease.

Bronchial Neoplasms↗
PubMed1998

Steroidal glycosides of the 14,15-seco-18-nor-pregnane series from Cynanchum ascyrifolium.

Three new steroidal glycosides named cynascyrosides A-C were isolated from the roots of Cynanchum ascyrifolium. The structures of these compounds were determined on the basis of spectroscopic and chemical evidence as cynajapogenin A 3-O-alpha-D-oleandropyranosyl-(1-->4)-beta-L-cymaropyranosyl -(1-->4)-beta-D- digitoxopyranoside; cynajapogenin A 3-O-beta-D-glucopyranosyl-(1-->4)-alpha-L-cymaropyranosyl- (1-->4)-beta-L-cymaropyranosyl-(1-->4)-beta-L-cymaropyranoside+ ++; cynajapogenin A 3-O-beta-D-glucopyranosyl-(1-->4)-alpha-L-cymaropyranosyl- (1-->4)-beta-D-digitoxopyranosyl-(1-->4)-beta-L-cymaropyranosid e.

Carbohydrate Sequence↗
PubMed1998

Dynamics of a divisive gain control in human vision.

Evidence for a divisive contrast gain control in human vision was obtained using a contrast version of the probe-on-flash technique that has been employed in the light adaptation literature. Thresholds were measured for a briefly flashed (30 ms), vertical test pattern superimposed on a cosine mask as a function of time after mask onset (SOA). Threshold elevations declined monotonically for SOAs up to 150 ms. and exhibited an exponential time course with an average time constant of 51 ms. Increment thresholds for the test as a function of mask contrast provide direct evidence that these effects are due to operation of a divisive gain control within the first 150 ms after stimulus onset. Experiments to measure the spatial spread of this gain control show it to be localized to a region of no more than 45 arc min radius.

Adaptation, Ocular↗
PubMed1998

Open surgery for removal of a failing Gianturco stent with reversed sleeve resection of the right middle and lower lobes.

Although the use of a metallic stent in the treatment of benign tracheobronchial stenosis has been reported as a useful and safe technique, the incorporation of wire stents into the airway may be irreversible and is associated with problems. The authors' experience in a patient with incorrectly positioned metallic stent in the right main bronchus, which was successfully treated with bronchial sleeve resection, is presented.

Adult↗
PubMed1998

Viability of E. coli cells containing phage RNA polymerase and promoter: interference of plasmid replication by transcription.

Strong transcription of phage promoters often renders the host E. coli cells containing the phage RNA polymerase inviable. When expression of the phage SP6 RNA polymerase gene in one plasmid was induced in the E. coli JM109 cells, cells that bear an active SP6 promoter were inviable. When it was not induced (the polymerase was still produced in low levels), viability of the host cells and stability of the promoter-bearing plasmids depended on the orientation of the promoter with respect to that of the replication origin and on the sequence of the origin. A group of SP6 promoter-bearing plasmids (group I plasmids) that had the promoter directed towards the ColE1 replication origin, rendered the polymerase-containing host cells inviable in selective media. When the sequence of the origin was different (group II plasmids), this adverse effect was not observed. When the promoter direction was same as the replication origin and the ampicillin-resistant gene (group III plasmids), many satellites formed around the colonies on ampicillin-containing agar plates. These effects were caused by strong transcription of the phage SP6 promoter by its RNA polymerase, since they were reduced or eliminated by inserting an active terminator just downstream of the promoter. The viability of host cells and copy number of the promoter/terminator-bearing plasmids appear to be quantitatively related with efficiency of initiation and termination of the phage transcription. These systems may be useful for in vivo screening for mutant variants of the phage promoter, polymerase and terminator that are affected in their efficiency.

Bacteriophages↗
PubMed1998

Expression of p21WAF1/CIP1 is unrelated to p53 tumour suppressor gene status in oral squamous cell carcinomas.

The p53 tumour suppressor gene is frequently mutated in oral squamous cell carcinomas. However, the downstream mechanism of p53 during oral carcinogenesis is not fully understood. The cyclin-dependent kinase inhibitor p21WAF1/CIP1 (p21), which can be induced by wild-type p53, functions as a downstream mediator of the antiproliferative and apoptosis-inducing actions of wild-type p53. To learn more about the roles of the p53 gene and its downstream mechanism, we evaluated p53 gene mutation and immunohistochemical expression of p53 and p21 in 20 cases of oral squamous cell carcinoma. p53 gene mutations were observed in 7 cases (35%). Overexpression of p53 was found in 4 of 13 cases with wild-type p53, and in 6 of 7 cases with p53 mutations. p21 expression was detected in 15 of 20 cases (75%). The expression of p21 correlated neither with mutated p53 mutation nor with p53 protein overexpression. p21 was expressed even in carcinomas in which molecular analysis revealed a nonsense mutation. In normal oral mucosa, p21 expression was limited in the differentiating spinous cell layer. However, dysplastic or hyperplastic epithelium adjacent to the tumour demonstrated the increased expression of p21 even in the proliferating basal cell layer. These molecular and immunohistochemical data did not show any correlation with various clinico-pathologic parameters. These results suggest that p53 gene mutations and altered expression of p21 are commonly involved in oral carcinogenesis, but do not correlate with each other or with the clinico-pathologic parameters. They also suggest that p21 expression in oral squamous cell carcinomas may be induced by a p53-independent pathway.

Adult↗
PubMed1998

Phospholipase Cgamma1 inhibitory principles from the sarcotestas of Ginkgo biloba.

Ten phenolic compounds were isolated from the CHCl3 extract of Ginkgo biloba sarcotestas (Ginkgoaceae) as a new class of phosphatidylinositol-specific phospholipase Cgamma1 (PI-PLCgamma1) inhibitors. The substances without the long chain were ineffective. On the other hand, the activities of these compounds were dramatically decreased by acetylation of aromatic hydroxyl groups of cardanol, phenolic acid, and bilobol and by methylation of the aromatic carboxyl group of phenolic acid. The unsaturated long chain as well as the aromatic hydroxyl and carboxyl groups might play a key role for the PI-PLCgamma1 inhibitory activity. These compounds also inhibited the growth of a number of human cancer cell lines, but were less cytotoxic against a human normal colon cell line.

Cells, Cultured↗