Biomedical subjects
Publications and source records attributed to S H Bok.
Actinomycin D, C2 and VII, cyclic peptides, inhibited Grb2 SH2 domain association (IC50 5-7 microM) with a phosphotyrosine containing peptide derived from the Shc protein (pTyr317). Actinomycins are the first examples of nonphosphorylated natural ligands of SH2 domain.
In order to identify key genes involved in the development of atherosclerotic lesions, differentially expressed genes in atherosclerotic plaques obtained from diet-induced hypercholesterolemic rabbit aorta were screened using the differential display (DD) RT-PCR technique. Aortic RNAs were isolated from rabbits fed cholesterol-supplemented (2% cholesterol in lab-chow, w/w) chow diet for 12 weeks, followed by the synthesis of cDNAs by reverse-transcription using 2-base anchored oligo (dT) (5'-T11VN) as 3'-primers. Synthesized cDNAs were amplified by PCR using arbitrary 10-mers as 5'-primers and the same 3'-primers used in the reverse-transcription. Amplified cDNAs sized between 0.2 to 0.5kb obtained from control and cholesterol-fed rabbit aortas were displayed on the 6% DNA-sequencing gel for comparisons. The cDNA bands showing distinctive differences in patterns of display or in density of the band were extracted from the gel. A total of 66 differentially displayed cDNAs was isolated and subjected to the reverse-Northern and Northern blot analyses in order to confirm the differences. Through the extensive confirming processes, three cDNAs were finally selected (designated CRGRA-1 through -3) and their nucleotide sequences were determined. Two of those (CRGRA-1 and -2) were determined to be up regulated and the other (CRGRA-3) was down-regulated by the cholesterol-feeding. Upon homology search on databases for the identification of the genes, the first cDNA (CRGRA-1) turned out to be a part of a novel gene, the second one (CRGRA-2) was homologous (82%) to the corresponding segment of mitochondrial NADH dehydrogenase subunits 4 gene, and the last one (CRGRA-2) was identified to be homologous (94%) to a segment of human small GTP-binding protein (Rab7) gene.
Cinnamaldehydes and related compounds were synthesized from various cinnamic acids based on the 2'-hydroxycinnamaldehyde isolated from the bark of Cinnamomum cassia Blume. The cytotoxicity to human solid tumor cells such as A549, SK-OV-3, SK-MEL-2, XF498 and HCT15 were measured. Cinnamic acid, cinnamates and cinnamyl alcohols did not show any cytotoxicity against the human tumor cells. Cinnamaldehydes and related compounds were resistant to A549 cell line up to 15 micrograms/ml. In contrast, HCT15 and SK-MEL-2 cells were much sensitive to these cinnamaldehyde analogues which showed ED50 values 0.63-8.1 micrograms/ml. Cytotoxicity of the saturated aldehydes was much weak compared to their unsaturated aldehydes. From these studies, it was found that the key functional group of the cinnamaldehyde-related compounds in the antitumor activity is the propenal group.
During efforts for cloning disease resistance-responsive genes, a cDNA encoding a putative Nicotiana glutinosa glycine-rich RNA binding protein (ngRBP) was isolated from TMV induced cDNA library. Northern blot hybridization revealed that ngRBP gene is negatively regulated during early hours of TMV induced acute hypersensitive response (HR). Under greenhouse conditions induced expression of ngRBP gene was observed after 24 h following TMV infection. Salicylic acid and copper also induced ngRBP mRNA expression. Our findings are suggestive of some possible role for ngRBP in plant-pathogen interaction.
In the course of a search for acyl-CoA : cholesterol acyltransferase (ACAT) inhibitors from natural sources, new types of ACAT inhibitors were isolated from the extract of Magnolia obovata leaves, and identified as obovatol, honokiol, and magnolol. The active compounds inhibit rat liver ACAT with IC50 values of 42, 71, and 86 microM, respectively.
In the course of our screening program for acyl-CoA : cholesterol acyltransferase (ACAT) inhibitors from Korean herbal medicines, ACAT inhibitors were isolated from the hairy roots of Panax ginseng (Araliaceae) and identified as panaxynol, panaxydol, panaxydiol, and panaxytriol. These active compounds inhibit rat liver ACAT with IC50 values of 94, 80, 45 and 79 microM, respectively.
The cloning and characterization of genes expressed in plant disease resistance could be an initial step toward understanding the molecular mechanisms of disease resistance. A metallothionein-like gene that is inducible by tobacco mosaic virus and by wounding was cloned in the process of subtractive cloning of disease resistance-response genes in Nicotiana glutinosa. One 530-bp cDNA clone (KC9-10) containing an open reading frame of 81 amino acids was characterized. Genomic Southern blot hybridization with the cDNA probe revealed that tobacco metallothionein-like genes are present in few or in one copy per diploid genome. Northern blot hybridization detected strong induction of a 0.5-kb mRNA by wounding and tobacco mosaic virus infection, but only mild induction was detected when copper was tested as an inducer. Methyl jasmonate, salicylic acid, and ethylene were also tested as possible inducers of this gene, but they had no effect on its expression. The possible role of this gene in wounded and pathogen-stressed plants is discussed.
We have isolated cholesteryl ester transfer protein (CETP) inhibitors from the extract of Korean Panax ginseng C. A. Meyer roots and identified them as polyacetylene analogs. These compounds inhibit human CETP with IC50 values of around 20-35 mg/ml.
A new inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), designated GERI-BP002-A, was isolated from the culture broth of Aspergillus fumigatus F93 by acetone extraction, EtOAc extraction, SiO2 column chromatography and reverse phase HPLC. Spectroscopic analyses of the compound identified bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane as the structure and its molecular weight and formula to be 340 and C23H32O2, respectively. GERI-BP002-A inhibited ACAT activity by 50% at the concentration of 50 microM in an enzyme assay system using rat liver microsomes.
Explore the source record for details and available documents.
GERI-BP001 compounds, new inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT), were isolated from a culture broth of Aspergillus fumigatus F37 by acetone extraction, EtOAc extraction, SiO2 column chromatography, and reverse phase HPLC. GERI-BP001 M, A, and B inhibit ACAT activity in an enzyme assay system using rat liver microsomes by 50% at concentrations of 42, 94, and 40 microM, respectively.
Computer-Aided Design and Computer-Aided Manufacture (CAD/CAM) techniques, though often technologically associated with engineering and applied sciences, has opened new horizons in the medical field. In CAD, a product is first geometrically modelled in three dimensions in a computer and it can be viewed and examined from any direction. This model can then be used for many downstream applications such as manufacturing and analysis. In CAM, numerically controlled machining processes are used for cutting out a prosthetic device of the hand for prosthesis. The paper aims at establishing the basis of using CAD/CAM techniques in prostheses in particular, a review of our present work done in the area of below-elbow prostheses using CAD/CAM. A laser scanning device has been used to capture the geometry of human hands. The algorithm used in processing the images is discussed. The processed 3D data file is then interfaced with a CAD modeller where reconstruction, mirroring, scaling, etc., can be performed. The resultant CAD model is then passed on to CAM, which concentrates purely on producing a "positive core" mould for moulding the prosthetic device.
Approximately 260 Streptomyces strains were isolated from neutral pH farmland soil and evaluated for their ability to produce glucose isomerase. The number of acidophilic Streptomyces organisms growing at pH 4.0 was low, i.e., 10 organisms per g of soil. All of the isolates showed glucose isomerase activity when they were grown in a medium containing d-xylose, an inducer for glucose isomerase. More than half of the strains tested developed heavy growth in 24 h, and many produced high titers of glucose isomerase after 24 h of growth in a medium buffered at pH 5.0.
Explore the source record for details and available documents.
A screening procedure was used to isolate from soil a Penicillium sp., two bacterial isolates, and a Streptomyces sp. that produced a new microbial growth factor. This factor was an absolute growth requirement for three soil bacteria. The Penicillium sp. and one of the bacteria requiring the factor, an Arthrobacter sp., were selected for more extensive study concerning the production and characteristics of the growth factor. It did not seem to be related to the siderochromes. It was not present in soil extract, rumen fluid, or any other medium component tested. It appears to be a glycoprotein of high molecular weight, and it has high specific activity. When added to the diets for a meadow vole mammalian test system, it caused an increased consumption of diet without a concurrent increase in rate of weight gain.
Explore the source record for details and available documents.