Biomedical subjects

B J Kim

Publications and source records attributed to B J Kim.

At least 37 records · Page 2Linked to original sources

PubMed2003

Biomass accumulation patterns for removing volatile organic compounds in rotating drum biofilters.

A rotating drum biofilter (RDB) with multi-layered foam media was developed for the improvement of current biofiltration technology. The biofilter was used to investigate the effects of organic loadings and influent volatile organic compound (VOC) concentrations on VOC removal efficiency and biomass accumulation. These effects were evaluated using diethyl ether and toluene separately as model VOCs at an empty bed contact time (EBCT) of 30 s. When the toluene loading increased from 2.0 to 4.0 and 8.0 kgCOD m(-3) day(-1), toluene removal efficiency of the biofilter decreased from over 99% to 78% and 74%, respectively. The biomass distribution was found to be more even within the medium when removing toluene than when removing diethyl ether. Higher organic loading also resulted in the more even distribution of the biomass. The ratios of biomass accumulation rates in the medium of the outermost, middle and innermost layers ranged from 1:0.11:0.02 when removing diethyl ether at 2.0 kgCOD m(-3) day(-1) to 1:0.69:0.51 when removing toluene at 8.0 kgCOD m(-3) day(-1). Review of these ratios revealed three biomass accumulation patterns: surface pattern, in-depth pattern and shallow pattern. Different patterns represent different removal mechanisms in the biofiltration process. Improved biofilter design and operation should be based on the biomass accumulation pattern.

Biodegradation, Environmental↗

PubMed2002

Room-temperature ferromagnetism in (Zn1-xMnx)GeP2 semiconductors.

We report on the discovery of a room-temperature ferromagnetic semiconductor in chalcopyrite (Zn1-xMnx)GeP2 with Tc = 312 K. We have also observed that, at temperatures below 47 K, samples for x = 0.056 and 0.2 show a transition to the antiferromagnetic (AFM) state, so that ferromagnetism is well defined to be present between 47 and 312 K. The observation that the AFM phase is most stable at low temperatures is consistent with the predictions of full-potential linearized augmented plane wave total energy calculations and has consequences for other chalcopyrite materials.

Journal Article↗

PubMed2002

Calpeptin suppresses tumor necrosis factor-alpha-induced death and accumulation of p53 in L929 mouse sarcoma cells.

The cytokine tumor necrosis factor (TNF)alpha induces caspase-dependent cell death in a subset of tumor cells. In this report, we show a novel suppressive effect of calpeptin, a calpain inhibitor, on TNFalpha-induced cell death and accumulation of p53 in L929 mouse fibrosarcoma. Exposure to 10 ng/ml TNFalpha induced cell death in >50% of L929 cells within 12 h and stimulated accumulation of p53 (8-fold). Preincubation of cells with calpeptin blocked both TNFalpha-induced cell death and accumulation of p53 as examined with Western blot. TNFalpha-induced accumulation of p53 was in part contributed by increase of p53 mRNA level (2.2-fold) in a calpeptin-insensitive manner. Interestingly, other calpain inhibitors tested did not show these effects like calpeptin and TNFalpha treatment did not increase apparent calpain activity in L929 cells, suggesting that calpeptin may have another function besides targeting calpain. Expression of dominant negative mutant p53Val(135) reduced the incidence of TNFalpha-mediated cell death. Taken together, our findings suggest that TNFalpha induces calpeptin-dependent, but calpain-independent accumulation of p53 protein as a necessary step leading to death in L929 cells.

Animals↗

PubMed2002

Cross-resistance between rifampicin and KRM-1648 is associated with specific rpoB alleles in Mycobacterium tuberculosis.

KRM-1648 resistant Mycobacterium tuberculosis strains were identified from a collection of rifampicin-resistant strains. Several strains had novel rpoB gene mutations in codons 512, 529 and 533 of the rpoB gene. The strains with mutations in codons 526 or 531, major mutation sites in rifampicin-resistant M. tuberculosis, were resistant to KRM-1648. Also, the strains with other mutations in the rpoB gene that were initially susceptible to KRM-1648 were prone to developing KRM-1648 resistance after further mutation. Thus, KRM-1648 is unlikely to be useful for the treatment of rifampicin-resistant tuberculosis.

Alleles↗

PubMed2002

Serial diffusion-weighted MR Imaging in delayed postanoxic encephalopathy. A case study.

We report a case of delayed postanoxic encephalopathy (DPE) studied with serial diffusion weighted imaging five times in a one-year period along with apparent diffusion coefficient (ADC) map as well as ADC values of periventricular white matter. Compared to the normal value, the ADC values of the white matter were initially low on the three (0.68 +/- 0.08 x 10(-3) mm(2)/s) and seven-week images (0.67 +/- 0.08 x 10(-3) mm(2)/s) but gradually recovered to the normal range on the four, six, and twelve-month images (0.78 +/- 0.05, 0.80 +/- 0.05 and 0.87 +/- 0.11 x 10(-3) mm(2)/s, respectively). Among the several pathogenetic mechanisms associated with DPE, these serial changes may be consistent with cytotoxic edema, from apoptosis, triggered by hypoxia.

Activities of Daily Living↗

PubMed2001

Xenobiotic response in humanized double transgenic mice expressing tetracycline-controlled transactivator and human CYP1B1.

The cytochrome P450 enzymes (P450s or CYPs) are a superfamily of hemeproteins that catalyze the monooxygenation of a wide range of endobiotic and xenobiotic substrates. A typical strategy in toxicological research and testing involves applying a toxicant at high doses for a short period to homogeneous animals under controlled conditions. However, the conditions of this approach have very little in common with actual human exposure. Transgenic (Tg) mice carrying human genes encoding a drug-metabolizing enzyme (CYP) offer a solution to many of the difficulties in the evaluation of chemical toxicity. It has been demonstrated that the expression of human CYP transgenes under the control of mammalian-inducible promoters exhibits relatively poor fold increases after induction. In this study, we used the tetracycline-regulated (tet) promoter system to increase the expression of the human CYP1B1 (hCYP1B1) gene in the tissues of transgenic mice. By mating two lineages of transgenic mice, double transgenic (dTg) mice expressing both tTA and hCYP1B1 genes under the control of the tet promoter were successfully produced, into which the two transgenes were introduced in an embryo. The expression pattern of tTA-driven hCYP1B1 transgene featured a fold induction of more than 3 to 12 in the brain, heart, and lung and 2- to 4-fold induction in the liver, kidney, and intestine upon doxycycline removal. Immunohistochemical staining with hCYP1B1 antibody was also increased by the removal of doxycycline. In addition, the activities of CYP liver microsomes in the dTg mice without doxycycline showed an increase compared to that in the dTg mice treated with doxycycline. The level of activities correspond to the levels of human CYP1B1 protein expression in the Tg mice (-dox) that was increased by 2-fold induction as compared to that of the dTg mice with doxycycline. Thus, overproduction in Tg can be purified and the activity of purified human CYP1B1 can be characterized by alterations to the coding sequence in order to solve the physiological function of this enzyme in a humanized in vivo system. It is also possible to examine the activity of purified human CYP1B1 using several environmental toxicants such as procarcinogens.

Animals↗

PubMed2001

XY model in small-world networks.

The phase transition in the XY model on one-dimensional small-world networks is investigated by means of Monte Carlo simulations. It is found that long-range order is present at finite temperatures, even for very small values of the rewiring probability, suggesting a finite-temperature transition for any nonzero rewiring probability. Nature of the phase transition is discussed in comparison with the globally coupled XY model.

Journal Article↗

PubMed2001

Classification of CD and absorption spectra in the Soret band of H(2)TMPyP bound to various synthetic polynucleotides.

The binding mode of porphyrins, namely meso-tetrakis(N-methyl pyridinium-4-yl)porphyrin (H(2)TMPyP), was classified in this work by absorption and circular dichroism(CD) spectroscopy. The three binding modes of intercalation, minor groove binding and external stacking exhibit their own characteristic absorption and CD spectra. Intercalation occurs for this porphyrin when bound to GC-rich polynucleotides at a low mixing ratio, as expected. This binding mode produces hypochromism and a red shift in the absorption band and a negative CD band in the Soret absorption region. When it is complexed with AT-rich polynucleotides at a low mixing ratio, hypochromism and a red shift in the absorption band and a positive CD peak is apparent, and this species can easily be assigned to the minor groove-binding mode. For both AT- and GC-rich polynucleotides at a high binding ratio, an excitonic CD was apparent. The sign of excitonic CD depends on the order of the DNA bases; the CD spectra of H(2)TMPyP complexed with non-alternating homopolymer (disregarding the nature of base pairs, i.e. AT or GC) are characterized by a positive band at short wavelengths followed by a negative band at long wavelengths. In contrast, those complexed with alternating polynucleotide were opposite to those of non-alternating homopolymers.

Chemical Phenomena↗

PubMed2001

Evidence of two distinct dynamic critical exponents in connection with vortex physics.

The dynamic critical exponent z is determined from numerical simulations for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models with relaxational dynamics. It is suggested that the dynamics is characterized by two distinct dynamic critical indices z0 and z related to the divergence of the relaxation time tau by tau proportional to xi(z0) and tau proportional to k(-z), where xi is the correlation length and k the wave vector. The values determined are z0 approximately 1.5 and z approximately 1 for the 3D LCG and z0 approximately 1.5 and z approximately 2 for the 3D XY model. Comparisons with other results are discussed.

Journal Article↗

PubMed2001

FLASH coordinates NF-kappa B activity via TRAF2.

FLASH is a protein recently shown to interact with the death effector domain of caspase-8 and is likely to be a component of the death-inducing signaling complex in receptor-mediated apoptosis. Here we show that antisense oligonucleotide-induced inhibition of FLASH expression abolished TNF-alpha-induced activation of NF-kappaB in HEK293 cells, as determined by luciferase reporter gene expression driven by a NF-kappaB responsive promoter. Conversely, overexpression of FLASH dose-dependently activated NF-kappaB, an effect suppressed by dominant negative mutants of TRAF2, NIK, and IKKalpha, and partially by those of TRAF5 and TRAF6. TRAF2 was co-immunoprecipitated with FLASH from the cell extracts of HEK293 cells or HeLa cells stably expressing exogenous FLASH (HeLa/HA-FLASH). Furthermore, serial deletion mapping demonstrated that a domain spanning the residues 856-1191 of FLASH activated NF-kappaB as efficiently as the full-length and could directly bind to TRAF2 in vitro and in the transfected cells. Taken together, these results suggest that FLASH coordinates downstream NF-kappaB activity via a TRAF2-dependent pathway in the TNF-alpha signaling.

Animals↗

PubMed2001

Secretion of the virulence-associated Campylobacter invasion antigens from Campylobacter jejuni requires a stimulatory signal.

Campylobacter jejuni are a common cause of human diarrheal illness. Previous work has demonstrated that C. jejuni synthesize a novel set of proteins upon coculturing with epithelial cells, some of which are secreted. The secreted proteins have been collectively referred to as Campylobacter invasion antigens (Cia proteins). Metabolic labeling experiments revealed that Cia protein synthesis and secretion are separable and that secretion is the rate-limiting step of these processes. Additional work indicated that Cia protein synthesis is induced in response to bile salts and various eukaryotic host cell components. Host cell components also can induce Cia protein secretion. Culturing C. jejuni on plates supplemented with the bile salt deoxycholate retarded the inhibitory effect of chloramphenicol on C. jejuni invasion, as judged by the gentamicin-protection assay. These data suggest that the coordinate expression of the genes encoding the Cia proteins is subject to environmental regulation.

Antigens, Bacterial↗

PubMed2001

Inactivation of farnesyltransferase and geranylgeranyltransferase I by caspase-3: cleavage of the common alpha subunit during apoptosis.

Caspase plays an important role in apoptosis. We report here that farnesyltransferase/geranylgeranyltransferase (FTase/GGTase)-alpha, a common subunit of FTase (alpha/beta(FTase)) and GGTase I (alpha/beta(GGTase)), was cleaved by caspase-3 during apoptosis. FTase/GGTase-alpha (49 kDa) was cleaved to 35 kDa (p35) in the Rat-2/H-ras, W4 and Rat-1 cells treated with FTase inhibitor (LB42708), anti-Fas antibody and etoposide, respectively. This cleavage was inhibited by caspase-inhibitors (YVAD-cmk, DEVD-cho). Serial N-terminal deletions and site-directed mutagenesis showed that Asp59 of FTase/GGTase-alpha was cleaved by caspase-3. The common FTase/GGTase-alpha subunit, but not the beta subunits, of the FTase or GGTase I protein complexes purified from baculovirus-infected SF-9 cells was cleaved to be inactivated by purified caspase-3. In contrast, FTase mutant protein complex [(D(59)A)alpha/beta(FTase)] was resistant to caspase-3. Expression of either the cleavage product (60-379) or anti-sense of FTase/GGTase-alpha induced cell death in Rat-2/H-ras cells. Furthermore, expression of (D(59)A)FTase/GGTase-alpha mutant significantly desensitized cells to etoposide-induced death. Taken together, we suggest that cleavage of prenyltransferase by caspase contributes to the progression of apoptosis.

Alkyl and Aryl Transferases↗

PubMed2001

Differential distribution of ganglioside GM3 in seminiferous tubule and epididymis of adult rats.

Gangliosides are ubiquitous membrane components in mammalian cells and are suggested to play important roles in various functions such as cell-cell interaction, adhesion, cell differentiation, growth control and signaling. Among all ganglio-series gangliosides, GM3 has the simplest carbohydrate structure, and has been shown as a major ganglioside in male reproductive system. To study GM3 distribution in the seminiferous tubule and epididymis, frozen sections were stained with specific monoclonal antibody (MAb) against ganglioside GM3. In the seminiferous tubule of testis, pachytene spermatocytes and spermatids expressed ganglioside GM3, but not in spermatogonia and sertoli cells. Spermatogonia and sertoli cells near the basement membrane were negatively reacted to anti-GM3. In the epididymis, GM3 was expressed only in some interstitial cells. Taken together, these results suggest that the expression of ganglioside GM3 in rat seminiferous tubule and epididymis is spatio-temporally regulated during spermatogenesis.

Animals↗

PubMed2001

The effects of dexamethasone on insulin release and biosynthesis are dependent on the dose and duration of treatment.

Complex results concerning the effect of glucocorticoids on insulin secretion have been reported. The aim of this study is to clarify the direct effects of glucocorticoids on pancreatic islets and to determine whether the effect of glucocorticoids on insulin biosynthesis or release is dependent on the dose and duration of treatment with glucocorticoid. Studies on insulin secretion and biosynthesis were performed with different concentrations (0, 1, 10, 100 nmol/l) and durations (1 and 6 h) of treatment with dexamethasone (dexa) in rat pancreatic islets. (1) One nmol/l dexa had no inhibitory effect on insulin secretion and biosynthesis. Ten and 100 nmol/l had an inhibitory effect on insulin secretion, which was mainly due to suppression of the first phase of insulin secretion. (2) Insulin content was significantly increased regardless of the concentration in 1-h treated islets. However, insulin content was markedly diminished with 100 nmol/l dexa in 6-h treated islets. (3) The preproinsulin mRNA expression of 6-h treated islets was suppressed in a dose-dependent manner. Our data revealed that, in the condition of short-term and low-dose glucocorticoid exposure, insulin secretion and biosynthesis are not affected. The secretory process of insulin seems to be the initial step of the inhibitory action of glucocorticoid. Both insulin release and biosynthesis are inhibited by chronic exposure to high dose dexamethasone. It can be concluded that glucocorticoid might be involved in the multisteps of insulin release and biosynthesis.

Animals↗

PubMed2001

The roles of intermediates in biodegradation of benzene, toluene, and p-xylene by Pseudomonas putida F1.

Several types of biodegradation experiments with benzene, toluene, or p-xylene show accumulation of intermediates by Pseudomonas putida F1. Under aerobic conditions, the major intermediates identified for benzene, toluene, and p-xylene are catechol, 3-methylcatechol, and 3,6-dimethylcatechol, respectively. Oxidations of catechol and 3-methylcatechol are linked to biomass synthesis. When oxygen is limited in the system, phenol (from benzene) and m-cresol and o-cresol (from toluene) accumulate.

Benzene↗

PubMed2001

A two-step model for the kinetics of BTX degradation and intermediate formation by Pseudomonas putida F1.

A two-step model is developed for the aerobic biodegradation of benzene, toluene, and p-xylene (BTX) by Pseudomonas putida F1. The model contains three unique features. First, an initial dioxygenation step transforms BTX into their catechol intermediates, but does not support biomass growth. Second, the benzene or toluene intermediates are mineralized, which supports biomass synthesis. Third, BTX exhibit competitive inhibition on each other's transformation, while toluene and benzene noncompetitively inhibit the mineralization of their catechol intermediate. A suite of batch and chemostat experiments is used to systematically measure the kinetic parameters for the two-step transformations and the substrate interactions.

Benzene↗

PubMed2001

Moulded photoplastic probes for near-field optical applications.

The inexpensive fabrication of high-quality probes for near-field optical applications is still unsolved although several methods for integrated fabrication have been proposed in the past. A further drawback is the intensity loss of the transmitted light in the 'cut-off' region near the aperture in tapered optical fibres typically used as near-field probes. As a remedy for these limitations we suggest here a new wafer-scale semibatch microfabrication process for transparent photoplastic probes. The process starts with the fabrication of a pyramidal mould in silicon by using the anisotropic etchant potassium hydroxide. This results in an inverted pyramid limited by < 111 > silicon crystal planes having an angle of approximately 54 degrees. The surface including the mould is covered by a approximately 1.5 nm thick organic monolayer of dodecyltrichlorosilane (DTS) and a 100-nm thick evaporated aluminium film. Two layers of photoplastic material are then spin-coated (thereby conformal filling the mould) and structured by lithography to form a cup for the optical fibre microassembly. The photoplastic probes are finally lifted off mechanically from the mould with the aluminium coating. Focused ion beam milling has been used to subsequently form apertures with diameters in the order of 80 nm. The advantage of our method is that the light to the aperture area can be directly coupled into the probe by using existing fibre-based NSOM set-ups, without the need for far-field alignment, which is typically necessary for cantilevered probes. We have evidence that the aluminium layer is considerably smoother compared to the 'grainy' layers typically evaporated on free-standing probes. The optical throughput efficiency was measured to be about 10-4. This new NSOM probe was directly bonded to a tuning fork sensor for the shear force control and the topography of a polymer sample was successfully obtained.

Journal Article↗

PubMed2001

Differential regulation of cAMP-mediated gene transcription and ligand selectivity by MC3R and MC4R melanocortin receptors.

Melanocortins are known to be involved in the regulation of feeding behavior. These hormones mediate their effects through G-protein-coupled receptors by stimulating adenylate cyclase. In this study we describe the functional response of melanocortin 4 receptor (MC4R) and melanocortin 3 receptor (MC3R) in HEK 293T cells, by using a luciferase reporter gene under the transcriptional control of a cAMP-responsive element (CRE) as a monitor of intracellular cAMP levels and cAMP-regulated gene expression. We were able to show that MC4R and MC3R expressed in the human cell line HEK 293T stimulate transcription induced by stimulation with different analogs of alpha-melanocyte-stimulating hormone (alpha-MSH) at different levels. In our assay of CRE-mediated gene transcription activity, alpha-MSH-ND was the most efficient alpha-MSH analog for MC4R whereas NDP-MSH was the most efficient for MC3R. Changing the His6 residue of alpha-MSH-ND to Gln or Lys markedly decreased CRE-mediated luciferase activity for MC3R compared with MC4R. On analysis by modeling the receptor-ligand complex by NMR, [Gln6]alpha-MSH-ND and [Lys6]alpha-MSH-ND showed different conformational interactions between MC3R and MC4R. Furthermore, the maximum coupling efficiency of MC4R and MC3R to G proteins was different; MC4R showed only 30-50% of the maximum activity induced by MC3R. In total, our results suggest that a differential receptor-ligand interaction is involved and that the relative interactions of MC3R and MC4R with G protein are possibly quantitatively and qualitatively different.

Adrenocorticotropic Hormone↗