Biomedical subjects

Jeong-Hun Kang

Publications and source records attributed to Jeong-Hun Kang.

14 recordsLinked to original sources

PubMed2006

Mass-tag technology responding to intracellular signals as a novel assay system for the diagnosis of tumor.

A novel mass spectrometry-based assay system for determining protein kinase activity employing mass-tagged substrate peptide probes was used for the diagnosis of tumors. Two peptide probes (H-type and D-type) were synthesized containing the same substrate peptide sequence for protein kinase C (PKC). The molecular weights of the two probes differ because of the incorporation of deuterium into the acetyl groups of the D-type probe. The lysates of the normal and tumor tissue were prepared and reacted with the H- and D-type peptide probes, respectively. The PKC activities of the normal and tumor tissues can be compared simply and directly by calculating the phosphorylated ratio to each peptide probe, obtained from the peak intensity of the mass spectrum after mixing of the two reaction solutions. The phosphorylation ratio for the reaction of the H-type peptide probe with the tumor tissue lysate (B16 melanoma) was more than three times higher than that of the D type peptide probe with the normal skin tissue lysate. These results show that the novel assay system for detecting protein kinase activity using mass-tag technology can be a simple and useful means to profile protein kinase activity for cell or tissue lysate samples, and can be applied to the diagnosis of tumors.

Animals↗

PubMed2006

A protein kinase signal-responsive gene carrier modified RGD peptide.

We have previously reported artificial gene-regulation systems responding to cyclic AMP-dependent protein kinase (PKA) using a cationic polymer. However, this polymer alone cannot deliver any gene into living cells. In the present work, we modified the signal-responsive polymer to the RGD peptide for the introduction of a polymer/DNA complex into living cells and succeeded in regulating the gene expression responding to intracellular PKA activation.

Cell Line, Tumor↗

PubMed2006

Phosphorylation of Rho-associated kinase (Rho-kinase/ROCK/ROK) substrates by protein kinases A and C.

Rho-associated kinase (Rho-kinase/ROCK/ROK) is a serine/threonine kinase and plays an important role in various cellular functions. The cAMP-dependent protein kinase (protein kinase A/PKA) and protein kinase C (PKC) are also serine/threonine kinases, and directly and/or indirectly take part in the signal transduction pathways of Rho-kinase. They have similar phosphorylation site motifs, RXXS/T and RXS/T. The purpose of this study was to identify whether sites phosphorylated by Rho-kinase could be targets for PKA and PKC and to find peptide substrates that are specific to Rho-kinase, i.e., with no phosphorylation by PKA and PKC. A total of 18 substrates for Rho-kinase were tested for phosphorylation by PKA and PKC. Twelve of these sites were easily phosphorylated. These results mean that Rho-kinase substrates can be good substrates for PKA and/or PKC. On the other hand, six Rho-kinase substrates showing no or very low phosphorylation efficiency (<20%) for PKA and PKC were identified. Kinetic parameters (K(m) and k(cat)) showed that two of these peptides could be useful as substrates specific to Rho-kinase phosphorylation.

Amino Acid Motifs↗

PubMed2006

Human exposure to bisphenol A.

Bisphenol A (BPA), 2,2-bis(4-hydroxyphenyl)propane, is made by combining acetone and phenol. It has estrogenic activity and is acutely toxic to aquatic organisms. BPA is used mainly as a material for the production of epoxy resins and polycarbonate plastics. Due to an increase in products based on epoxy resins and polycarbonate plastics, human exposure to BPA has increased. The environment (aquatic environment, air and soil) can be one source of human BPA exposure, but the primary route of human exposure is foods. The daily human intake of BPA is <1 microg/kg body weight/day on the basis of several studies, and whether these doses can have an adverse endocrine disruptive effect on humans, especially fetuses, needs to be studied carefully.

Air Pollutants, Occupational↗

PubMed2006

Development of a fluorescence peptide chip for the detection of caspase activity.

Proteases play a key role in cell functions, and it is very important to monitor their activities for drug screening and diagnosis of diseases. In the present study, a new class of fluorescence probe, into which a fluorophore and a quencher have been introduced, was developed and applied to the on-chip detection of caspase-3 activity. This probe is non fluorescent in the absence of caspase-3. However, when it is treated with active caspase-3, the fluorescence intensity increases dependent on the caspase-3 activity due to the cleavage of the quencher-containing moiety on a glass slide. This caspase-dependent increase in the fluorescence intensity was also detected when the glass slide immobilizing the probe peptide was treated with cell lysate stimulated by staurosporine (STP), which is an apoptosis-inducing agent. On the other hand, such an increase was not detected in the case of control cell lysate without STP-stimulation. The developed system is a rapid and sensitive method and is useful for the direct measurement of protease activity on a glass array.

Animals↗

PubMed2005

An intracellular kinase signal-responsive gene carrier for disordered cell-specific gene therapy.

We have previously reported artificial gene-regulation systems responding to cyclic AMP-dependent protein kinase (PKA) using cationic polymer. This cationic polymer (PAK) was a graft-type polymer with an oligopeptide that is a substrate for PKA and could regulate gene-expression in a cell-free system. In the present study, we carried out a detailed characterization of the PAK-DNA complex (AFM observation and DLS measurement) and tried to apply this polymer to living cells. In the unstimulated NIH 3T3 cells, transfection of the PAK-DNA complex showed no expression of the delivered gene. This means that PAK formed a stable complex with DNA in the normal cells to totally suppress gene expression. In contrast, significant expression was seen when the PAK-DNA complex was delivered to forskolin-treated cells. Thus, activated PKA disintegrates the complexes even in living cells, resulting in gene expression. Our results indicate that this type of intracellular signal-responsive polymer will be useful for the cell-specific release of genes.

3T3 Cells↗

PubMed2005

Biodegradation or metabolism of bisphenol A: from microorganisms to mammals.

Bisphenol A (BPA; 2,2-bis(4-hydroxyphenyl)propane; CAS Registry No. 80-05-7) is one of endocrine disruptors and is made by combining acetone and phenol. BPA can be metabolized by extensive organisms. In this review these BPA biodegradations or metabolisms by many organisms from microorganisms to mammals were referred. Though the metabolites of BPA can enhance estrogenicity or toxicity, generally, BPA metabolism by organisms leads to detoxication of BPA.

Animals↗

PubMed2005

Bisphenol A degradation in seawater is different from that in river water.

The purpose of this study was to identify a relationship between changes of bacterial counts and bisphenol A (BPA) degradation in seawater under aerobic or anaerobic conditions, and at temperatures of 4, 25, and 35 degrees C. Water samples (seawater and river water) spiked with 1000 ng/ml of BPA was placed for 60 d. The BPA from water samples was extracted by OASIS HLB cartridges and was detected by high-performance liquid chromatography with fluorescence detection. BPA in river water was degraded under aerobic conditions and was below a detection limit (0.5 ng/ml) on the seventh day at both 25 and 35 degrees C. The more the level of bacterial counts increased, the more BPA degradation decreased. In the case of seawater samples, there was no relationship between BPA degradation and the change of bacterial counts. Bacterial counts at 25 and 35 degrees C increased rapidly at 5 and 3d, respectively, but decreased since then. The concentration of BPA was not changed for 30 d at both 25 and 35 degrees C, but decreased from 40 to 60 d in spite of low levels of bacteria. These results show that the different degradation way for BPA in seawater may exist. Moreover, our study suggest that BPA in seawater than in river water can continue for longer time with no degradation and the possibility of BPA contamination on a marine organism can be higher than that on freshwater organism.

Aerobiosis↗

PubMed2003

Determination of bisphenol A in milk and dairy products by high-performance liquid chromatography with fluorescence detection.

This study was conducted to develop a selective and sensitive method for the determination of bisphenol A (BPA) levels in milk and dairy products. A method based on solvent extraction with acetonitrile and solid-phase extraction (SPE) was developed for the analysis of BPA in milk, yogurt, cream, butter, pudding, condensed milk, and flavored milk, and a method using two SPE cartridges (OASIS HLB and Florisil cartridge) for skim milk was also developed. The developed methods showed good recovery levels (77 to 102%) together with low detection limits (1 microg/liter for milk, yogurt, pudding, condensed milk, flavored milk, and skim milk and 3 microg/liter for cream and butter). These methods are simple, sensitive, and suitable for the analysis of BPA in milk and dairy products. When 40 milk and dairy products were analyzed by the proposed methods, BPA was not identified in noncanned products, but its levels ranged from 21 to 43 microg/kg in canned products, levels that were 60- to 140-fold lower than the migration limits in the European Union and Japan.

Animals↗

PubMed2003

Factors influencing the migration of bisphenol A from cans.

The objective of this study was to determine whether there is a relationship between bisphenol A (BPA) migration from metal cans and container contents (glucose, sodium chloride, and vegetable oil), heating time, and/or temperature. Cans containing 5 to 20% glucose solution, 1 to 10% sodium chloride solution, and vegetable oils (corn, olive, and soybean oil) were heated at 121 degrees C for 30 min. Water samples were heated at 105 degrees C for 30 min and at 121 degrees C for 15, 30, and 60 min, respectively. In the test involving water samples, it was found that temperature's effect on BPA migration from cans can be more extensive than that of heating time. When cans were heated at 121 degrees C, the presence of 1 to 10% sodium chloride or vegetable oils greatly increased the migration of BPA from the cans. Moreover, the presence of 5 to 20% glucose in cans heated to 121 degrees C resulted in increased BPA migration relative to that for water controls.

Benzhydryl Compounds↗

PubMed2002

Determination of bisphenol A in canned pet foods.

Bisphenol A (BPA) contamination of canned foods for human use has been studied, but there are no reports concerning BPA contamination of canned pet foods. The purpose of this study was to identify the levels of BPA in canned pet foods. A total of 26 samples (15 samples of cat food and 11 samples of dog food) were prepared for analysis by high-performance liquid chromatography. BPA in the samples was extracted with acetonitrile and fat in the sample extract was removed with hexane. Solid-phase extraction was used for sample clean-up prior to final analysis. The concentration of BPA ranged from 13 to 136 ng/g in canned cat food and from 11 to 206 ng/g in dog food. Also, to confirm that the BPA had originated from the can coating, distilled water was added to each washed empty can and the cans were autoclaved at 121 degrees C for 30 min. The concentration of BPA leached from empty cans was between 7 and 31 ng/ml.

Animal Feed↗

PubMed2002

Effects of bacterial counts and temperature on the biodegradation of bisphenol A in river water.

Total 15 surface river waters were collected from thirteen different rivers to investigate a relationship of bacterial counts and temperature to the degradation of bisphenol A (BPA). Autoclaved and non-autoclaved river water samples were spiked with 0.2 mg/l BPA. The spiked samples were placed at temperatures of 4, 20, and 30 degrees C and analyzed by high performance liquid chromatography. BPA was degraded at all temperatures in the non-autoclaved samples. However, BPA in the autoclaved samples was not changed at all temperatures for 20 d. These results show that the primary factor of BPA degradation in river water is bacteria. Moreover, three groups [group A (> 10000 CFU/ml), group B (2000-10000 CFU/ml), and group C (< 2000 CFU/ml)], were made on the basis of bacterial counts of the samples. Half-lives for BPA degradation in groups A, B, and C were 2, 3, and 6 d at 30 degrees C and were 4, 5, and 7 d at 20 degrees C, respectively. But at 4 degrees C, the loss of BPA was about 40%, 20%, and 10% in groups A, B, and C for 20 d, respectively. Bacterial counts exerted an influence on BPA degradation in river water with temperature. Our results also show that BPA-degrading bacteria are widely distributed in river waters.

Benzhydryl Compounds↗

PubMed2002

Bisphenol A migration from cans containing coffee and caffeine.

This study was conducted to reconfirm the possibility and level of bisphenol A (BPA) migration from cans containing coffee and test the relationship between caffeine concentration and BPA migration from the can coating. BPA migration from cans containing decaffeinated and non-decaffeinated instant coffee averaged 66.2 and 84.0 ng ml(-1), respectively. In our study, the possibility of BPA migration from cans containing coffee after processing was found. In addition, the more caffeine content in the water solution of caffeine increased, the more BPA migration grew. This means that caffeine can have an effect on BPA migration from the can coating.

Benzhydryl Compounds↗

PubMedDate not supplied

Intracellular signal-responsive gene carrier for cell-specific gene expression.

We designed a peptide-polymer conjugate (CPCCtat) as a novel gene carrier that could control gene expression responding to the intracellular caspase-3 signal. This carrier consists of an uncharged main polymer chain and a cationic peptide side chain, which includes the substrate sequence of caspase-3 and the protein transduction domain sequence of HIV-1 Tat. In the present study, CPCCtat formed a tight complex with DNA through an electrostatic interaction, and in this state the gene expression was totally suppressed. In contrast, the complex disintegrated in the presence of caspase-3 due to cleavage of the cationic portion from CPCCtat. This event led to an activation of gene expression. Our results also indicate that the complex can be delivered into living cells due to the cell-permeable peptide side chain of CPCCtat. This intracellular signal-responsive system with CPCCtat will be useful for the cell-specific gene expression system.

Animals↗