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H Kim

Publications and source records attributed to H Kim.

At least 757 records · Page 42Linked to original sources
PubMed1992

Evidence for elevation of cytochrome P4502E1 (alcohol-inducible form) mRNA levels in rat kidney following pyridine administration.

The effects of pyridine on renal cytochrome P4502E1 (CYP2E1) expression in rat have been examined by immunoblot and Northern blot analyses. Immunoblot analyses revealed that 2E1 protein levels were elevated from 1.4- to 4.6-fold following pyridine administration in a dose- and time-dependent manner. Northern blot analyses revealed that renal 2E1 poly(A)+ RNA levels increased from 1.4- to 3.8-fold following pyridine treatment and that these increases in 2E1 mRNA paralleled the dose- and time-dependent increases in 2E1 protein content. In contrast, hepatic 2E1 poly(A)+ RNA levels failed to increase following these same dosing regimens, suggesting that metabolic alterations, such as those associated with starvation, were not etiologic factors in renal 2E1 induction. These results show that pyridine induced CYP2E1 in kidney and that elevation of renal 2E1 protein levels accompanying pyridine administration occurred at least partly as a consequence of increased 2E1 poly(A)+ RNA levels. The results of this research reveal that regulatory mechanisms governing CYP2E1 expression may differ in hepatic and renal tissues.

Animals↗
PubMed1992

Expression of GABAA receptor polypeptides in clonal rat cell lines.

The neuronal-like cell lines, B35, B65, B103, and B104, previously reported to possess high affinity GABA binding, were analyzed for various cellular properties. They possessed peripheral but lacked central benzodiazepine binding. Only B65 cells possessed [3H-]muscimol binding; none bound [35S]TBPS. None of the cells exhibited GABA-stimulated chloride conductance with patch clamp recordings. By Western blots the cells possessed alpha subunits. Northern blot and polymerase chain reaction analysis showed that out of alpha 1, alpha 4, beta 1 and gamma 2 subunits, only alpha 1 subunit mRNA was present. Thus, GABAA-receptor binding without associated central benzodiazepine receptor sites and without functional chloride channels appears to result from expression of an incomplete subunit composition.

Animals↗
PubMed1992

Isolation and cloning of a voltage-dependent anion channel-like Mr 36,000 polypeptide from mammalian brain.

A polypeptide of M(r) 36,000 (36 kDa) was isolated from detergent-solubilized membrane fractions of mammalian brain on a benzodiazepine affinity column utilized for the purification of the gamma-aminobutyric acid/benzodiazepine receptor protein, followed by preparative gel electrophoresis. Partial protein sequence for two fragments of the 36-kDa polypeptide allowed the isolation of cDNA clones from a rat hippocampal library. An open reading frame coding a sequence of 295 amino acid residues containing the two probe peptide sequences with minor differences, and a putative N-terminal signal peptide of 25 residues was found. Hydropathy index revealed no regions of alpha-helix suitable for membrane spanning, but several areas of alternating hydrophilic and hydrophobic residues consistent with beta-strands. The sequence of this brain protein was 24% identical to that of a yeast mitochondrial protein, the voltage-dependent anion channel (VDAC), and over 70% identical with the VDAC from human B lymphocytes. The gamma-aminobutyric acid type A (GABAA) receptor/36-kDa preparation purified on benzodiazepine affinity column has channel-forming activity in lipid bilayer membranes that is virtually identical to VDAC isolated from mitochondria of various sources, indicating that the 36-kDa protein is a new member of the VDAC family of proteins. An antiserum raised against the purified 36-kDa polypeptide was able to precipitate [3H]muscimol binding activity, indicating a tight association with the GABAA receptor protein in vitro and copurification on the benzodiazepine affinity column due to this association. Further studies are needed to determine whether such an association occurs in vivo.

Amino Acid Sequence↗
PubMed1992

Rat brain expresses an alternatively spliced form of the dihydropyridine-sensitive L-type calcium channel alpha 2 subunit.

We have cloned and sequenced a cDNA (rB-alpha 2) encoding an alpha 2 subunit of the voltage-sensitive L-type calcium channel (dihydropyridine receptor) of rat brain. The cDNA (3823 base pairs) encodes a protein of 1091 amino acids with a Mr of 123,822. The deduced amino acid sequence of rB-alpha 2 cDNA is highly similar (95% amino acid identity) to that of rabbit skeletal muscle alpha 2 subunit. The rB-alpha 2 protein is distinct from the previously cloned skeletal muscle alpha 2-subunit protein [Ellis, S. B., Williams, M. E., Ways, N. R., Brenner, R., Sharp, A. H., Leung, A. T., Campbell, K. P., McKenna, E., Koch, W., Hui, A., Schwartz, A. & Harpold, M. M. (1988) Science 241, 1661-1664] because it contains an insertion of 7 amino acid residues and a deletion of a 19-amino acid segment between putative transmembrane domains 1 and 2. We show that the rB-alpha 2 and skeletal muscle alpha 2-subunit transcripts are the variants produced by alternative splicing of the primary transcript and that they are differentially expressed in brain and skeletal muscle, respectively.

Amino Acid Sequence↗
PubMed1992

The structural organization of the hamster multifunctional protein CAD. Controlled proteolysis, domains, and linkers.

CAD is a multidomain protein that catalyzes the first three steps in mammalian de novo pyrimidine biosynthesis. The 243-kDa polypeptide consists of four functional domains; glutamine amidotransferase (GLNase), carbamyl phosphate synthetase (CPSase), aspartate transcarbamylase (ATCase), and dihydroorotase (DHOase). Controlled proteolysis of hamster CAD was found to cleave the molecule into 18 fragments which successively accumulate and disappear during the course of digestion. Each fragment was isolated and partially sequenced to determine its location in the polypeptide chain. Proteolysis was found to usually occur at the junctions between the domains and sub-domains identified by sequence homology. All proteases of low to moderate specificity cleaved the molecule in a similar fashion. The rate of proteolysis widely varied and the interdomain regions were not always accessible to proteases. Each of the major functional domains is postulated to consist of subdomains. The duplicated halves of the CPSase domain (116 kDa) have a homologous structure consisting of 11-, 25-26-, and 21-22-kDa subdomains. Prolonged digestion cleaved the DHOase domain (36.6 kDa) into two stable species suggesting that this region is comprised of 11.5- and 15.0-kDa subdomains. Similarly, proteolysis of the 21-kDa catalytic subdomain of the GLNase domain (40 kDa) indicated a bilobal structure consisting of 12.3- and 8.5-kDa chain segments. The connecting region between the two ATCase subdomains (16.4 and 18 kDa) was not cleaved. Copurification of many of the domains showed that they remain associated by noncovalent interactions even after the connecting segments have been cleaved. The chain segments, the linkers, which connect the domains and subdomains were conserved in length but not in sequence, were predicted to be relatively hydrophilic and flexible but did not show a tendency to assume a particular secondary structure. These studies provide a more detailed map of the structural organization of the CAD polypeptide.

Amino Acid Sequence↗
PubMed1992

Expression of dihydropyridine-sensitive brain calcium channels in the rat central nervous system.

We have localized dihydropyridine (DHP-sensitive calcium channels in rat brain by in situ hybridization and immunohistochemistry. The mRNA for the dihydropyridine-sensitive calcium channel alpha 1 subunit (DHPR-B) is prominently localized in neuronal cells in the olfactory bulb, dentate gyrus, hippocampus, arcuate nucleus, paraventricular nucleus, ventromedial nucleus, cerebral cortex, superior colliculus and the cerebellar Purkinje cell layer. Strong expression of DHPR-B mRNA was also found in the pituitary and pineal glands. DHP-sensitive calcium channel alpha 1 subunit distribution has also been examined immunohistochemically with polyclonal antibodies raised against synthetic peptides specific for the DHPR-B alpha 1 subunit protein. The results from immunohistochemistry were in good agreement with those from in situ hybridization. Thus, regional distribution and localization of DHPR-B mRNA and alpha 1 subunit protein in rat brain suggest that this type of DHP-sensitive brain calcium channel may play an important role in excitation-secretion coupling functions in the neuroendocrine system.

Amino Acid Sequence↗
PubMed1992

Characterization of two site-specifically mutated human dihydrolipoamide dehydrogenases (His-452----Gln and Glu-457----Gln).

Two site-specifically mutated human dihydrolipoamide dehydrogenases (His-452----Gln and Glu-457----Gln) were expressed in pyruvate dehydrogenase complex-deletion mutant Escherichia coli JRG1342. The expressed mutant E3s were purified to near homogeneity using DEAE-Sephacel and hydroxyapatite columns. The initial velocity measurements in the absence of products for the Gln-452 mutant E3 in the direction of NAD+ reduction showed parallel lines in double-reciprocal plots, indicating that the mutant E3, like wild-type enzyme, catalyzed E3 reaction via a ping-pong mechanism. The specific activity of the Gln-452 mutant E3 was about 0.2% of that of wild-type enzyme. Its Km for dihydrolipoamide was dramatically increased by 63-fold. The substitution of His-452 to Gln resulted in a destabilization of the transition state of human E3 catalysis by about 6.4 kcal mol-1. The Gln-457 mutant E3, unlike wild-type enzyme, catalyzed E3 reaction via a sequential mechanism in the direction of NAD+ reduction based on the intersecting lines shown on double-reciprocal plots. Its specific activity decreased to 28% of that of wild-type enzyme. Its Km for dihydrolipoamide increased about 4.3-fold. The substitution of Glu-457 to Gln resulted in a destabilization of the transition state by about 1.7 kcal mol-1. These results indicate that His-452, which is a possible proton acceptor/donor in human E3 reaction, is critical to human E3 catalysis and that the local environment around His-452 and Glu-457, which are suggested to be hydrogen-bonded, is important in the binding of dihydrolipoamide to the enzyme.

Amino Acid Sequence↗
PubMed1992

Detection of mutations in the insulin receptor gene in patients with insulin resistance by analysis of single-stranded conformational polymorphisms.

We analyzed single-stranded conformational polymorphisms to screen for mutations and polymorphisms in the insulin receptor gene in subjects with or without insulin resistance. Using this new technique, we demonstrated the existence of mutations in the insulin receptor gene which we had identified previously. In addition, a new mutation was found in exon 20 of the insulin receptor gene in a patient with moderate insulin resistance associated with morbid obesity, acanthosis nigricans, and polycystic ovary syndrome. The patient was heterozygous for a mutation substituting Leu (CTG) for Pro (CCG) at codon 1178. Pro1178 is a part of a characteristic sequence motif (D1150 F1151 G1152---A1177 P1178 E1179) common to many protein kinases. Analysis of single-stranded conformational polymorphisms was also used to estimate the frequency of a polymorphism at codon 1058. The two codons CAC (1058 His) and CAT (1058 His) both had a prevalence of 50% in 30 Japanese subjects. These data demonstrate that analysis of single-stranded conformational polymorphisms is a simple and sensitive screening method for mutations and polymorphisms in the insulin receptor gene in subjects with or without insulin resistance. Identification of a mutation in the insulin receptor gene in a patient with a moderate degree of insulin resistance associated with morbid obesity suggests that insulin receptor mutations may exist in patients with Type 2 (non-insulin-dependent) diabetes mellitus associated with a moderate degree of insulin resistance.

Amino Acid Sequence↗
PubMed1992

Fragmentation of dimyristoylphosphatidylcholine vesicles by apomyoglobin.

Previously we have reported results of a preliminary study on the micellization of phosphatidylcholine vesicles by apomyoglobin at pH 4 (J. W. Lee and H. Kim, 1988, FEBS Lett. 241, 181-184). The micellization study has been extended here to investigate the effect of the lipid to protein ratio, temperature, size of vesicles, and pH. The pH-dependent study indicated that micellization occurs when the protein assumes either a molten globular or random coil structure. Time-dependent hydrophobic labeling by 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)-diazirine showed that there is an initial increase in contact between the protein and hydrophobic acyl chain of lipid followed by a decrease in the interaction. This may be explained as the initial stage of vesicle aggregation which is subsequently superseded by the fragmentation. These reactions are discussed in term of protein unfolding at low pH.

Amino Acid Sequence↗
PubMed1992

Indomethacin administration after temporary ischemia causes bowel necrosis in mice.

Several reports have suggested indomethacin administration causes necrotizing enterocolitis (NEC) in infants. Few experimental studies have addressed this relationship. We studied the effects of indomethacin after temporary intestinal ischemia in CD-1 mice, using a previously reported method of simulating NEC in mice. This involved occlusion of both superior mesenteric vessels for 15 minutes. Three groups were studied. In group 1, 12 mice had superior mesenteric vessels occluded for 15 minutes, followed by intravenous (IV) administration of saline for three doses over 3 days. In group 2, 12 mice had sham laparotomy, without occlusion of vessels, followed by IV administration of indomethacin for three doses over 3 days. In group 3, 36 mice had mesenteric vessel occlusion for 15 minutes, followed by IV administration of indomethacin for three doses over 3 days. The results were as follows: group 1, bowel necrosis developed in 1 of 12 animals (8%); group 2, all 12 animals survived without bowel damage (0%); and group 3, 22 of 36 animals developed bowel necrosis (61%) (Fisher's Exact Test: occlusion alone v occlusion and indomethacin, P = .002; indomethacin alone v occlusion and indomethacin, P = .00015.) We conclude that whereas occlusion alone or indomethacin alone does not cause bowel necrosis, temporary intestinal occlusion followed by indomethacin causes bowel necrosis in over 60% of animals studied. In the shocked preterm infant who may have suffered temporary intestinal ischemia, administration of indomethacin may be the second step to development of NEC.

Animals↗
PubMed1992

Endometriosis of bladder.

Vesical endometriosis is the abnormal growth of endometrial tissue in the bladder. Usually small lesions occur. Three cases of endometriosis of the bladder are presented. Each case demonstrates a large intravesical lesion with striking radiographic findings that are indistinguishable from an intravesical neoplasm.

Adult↗
PubMed1992

Variations in characteristic perceptual asymmetry: modality specific and modality general components.

The current study investigates sources of between-subjects variation in asymmetry scores on visual half-field and dichotic listening tasks. For each of these presentation modalities, subjects were given multiple laterality tasks. Results indicate that about 50% of the between-subjects variations in asymmetry scores in each modality is attributable to individual differences in perceptual asymmetries that are not stimulus-specific, referred to as "characteristic perceptual asymmetries" in this paper. In addition, the question of whether individual differences in characteristic perceptual asymmetries are modality specific, modality general, or both was investigated by entering subjects' asymmetry scores from visual half-field and dichotic listening tasks into a principal component analysis. The results of this analysis indicate that there are both modality specific and modality general influences on subjects' characteristic perceptual asymmetries.

Adult↗
PubMed1992

The gene for the dihydropyridine-sensitive calcium channel alpha 2 subunit (CCHL2A) maps to the proximal region of mouse chromosome 5.

A rat brain cDNA probe for the gene encoding the alpha 2 subunit of the dihydropyridine-sensitive L-type calcium channel was used as a hybridization probe for the Southern blot analysis of Chinese hamster x mouse somatic cell hybrids and the progeny of an intersubspecies backcross. This gene, termed Cchl2a, was mapped near the centromeric end of the Chromosome 5 linkage group with gene order: centromere-Pgy-1-Cchl2a-Il-6-Pgm-1.

Animals↗
PubMed1992

Photosensitized formation of ascorbate radicals by chloroaluminum phthalocyanine tetrasulfonate: an electron spin resonance study.

The chloroaluminum phthalocyanine tetrasulfonate sensitized photooxidation of ascorbic acid to ascorbate radical (A.-) was followed by electron spin resonance (ESR) spectroscopy. In air saturated aqueous media, steady-state amounts of A.- are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished--more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of free radical production by direct reaction between ascorbate ion and sensitized phthalocyanine (a Type I mechanism) in competition with the (Type II) reaction of HA- with singlet oxygen, a reaction which does not produce ascorbate radical intermediates.

Ascorbic Acid↗
PubMed1992

Interferon-gamma potentiates the antitumor effect of cyclosporine-induced autoimmunity.

Graft-versus-host-disease (GVHD), which results after allogeneic bone marrow transplantation (BMT), is associated with reduced leukemic relapse. This may be mediated by an immunologic attack with subsequent destruction of residual tumor cells. On the other hand, GVHD does not normally occur after autologous BMT (ABMT), which has an inherently high relapse rate. However, an autoimmune syndrome (AIS) similar to GVHD can be induced after autologous/syngeneic BMT by administration of cyclosporine-A (CsA), resulting in the production of major histocompatibility complex (MHC) class II or Ia autoreactive cytolytic effector cells. Since many hematopoietic malignancies express variable levels of class II molecules, we hypothesized that the adjuvant use of interferon-gamma (IFN-gamma) with CsA-induced autoimmunity after autologous/syngeneic BMT may upregulate class II antigens on residual tumor cells and make them more susceptible to attack by the Ia-reactive cells of CsA-induced AIS. The present studies demonstrated that the CsA-induced autoimmune syndrome mediated an anti-tumor effect, although this effect was dependent on challenge with a minimal number of tumor cells. Further studies clearly demonstrated that the antitumor effect could be markedly enhanced by administration of IFN-gamma which increased the susceptibility of the tumor to recognition and lysis by the CsA induced autoimmune effector cells. The induction of MHC class II-restricted AIS similar to GVHD by administration of CsA together with the ability to manipulate the surface phenotype of residual tumor cells may lead to decreased relapse rates in the ABMT setting.

Animals↗
PubMed1992

pH-sensitive liposomes containing polymerized phosphatidylethanolamine and fatty acid.

With the ultimate aim of targeting cancer drugs to malignant tissues, liposomes containing polymeric phosphatidylethanolamine and a fatty acid were prepared. For this purpose diacetylenic phosphatidylethanolamine (DAPE), a phosphatidylethanolamine containing diacetylene, was synthesized. Liposomes containing DAPE, fatty acid, and either phosphatidylethanolamine (PE) or phosphatidylethanolamine-beta-oleoyl-gamma-palmitoyl (POPE) were then prepared. Polymerization of DAPE was effected by UV illumination. The polymeric liposomes so obtained were stable at physiological pH but became leaky below pH 6.5. Of various compositions studied, the greatest pH-sensitivity was found with liposomes composed of 35 mol% DAPE, 35 mol% POPE, and 30 mol% saturated fatty acid. The presence of blood plasma albumin decreased vesicle stability while apolipoprotein A-I (apo A-I) had the opposite effect and plasma as a whole had a slightly stabilizing effect.

Apolipoprotein A-I↗