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Biomedical subjects

H Kim

Publications and source records attributed to H Kim.

At least 775 records · Page 43Linked to original sources
PubMed1992

Insulin signal transduction: the role of protein phosphorylation.

Recent evidence suggests that the mechanism of insulin action depends in part on protein phosphorylation on tyrosine residues. A cascade of phosphorylation/dephosphorylation reactions is proposed to modulate multiple enzymes involved in metabolism, protein synthesis, and cell growth. Direct evidence is presented for the phosphorylation of myelin basic protein and microtubule-associated protein 2 on tyrosine residues by the insulin receptor.

Animals↗
PubMed1992

Structural determinants in addition to the amino-terminal sorting sequence influence membrane localization of Escherichia coli lipoproteins.

The lipid-modified nine-residue amino-terminal sequence of the mature form of the major outer membrane lipoprotein of Escherichia coli contains information that is responsible for sorting to either the inner or outer membrane. Fusion of this sorting sequence to beta-lactamase is sufficient for localization of the resultant lipo-beta-lactamase to the outer membrane (J. Ghrayeb and M. Inouye, J. Biol. Chem. 259:463-467, 1984). Substitution of the serine adjacent to the amino-terminal lipid-modified cysteine residue of the sorting sequence with the negatively charged residue aspartate causes inner membrane localization (K. Yamaguchi, F. Yu, and M. Inouye, Cell 53:423-432, 1988). Fusion of the aspartate-containing nine-residue inner membrane localization signal to the normally outer membrane lipoprotein bacteriocin release protein does cause partial localization to the inner membrane. However, a single replacement of the glutamine adjacent to the amino-terminal lipid-modified cysteine residue of bacteriocin release protein with aspartate causes no inner membrane localization. Therefore, an aspartate residue itself lacks the information necessary for inner membrane sorting when removed from the structural context provided by the additional eight residues of the sorting sequence. Although the aspartate-containing inner membrane sorting sequence causes an almost quantitative localization to the inner membrane when fused to the otherwise soluble protein beta-lactamase, this sequence cannot prevent significant outer membrane localization when fused to proteins (bacteriocin release protein and OmpA) normally found in the outer membrane. Therefore, structural determinants in addition to the amino-terminal sorting sequence influence the membrane localization of lipoproteins.

Amino Acid Sequence↗
PubMed1992

Intrahippocampal colchicine alters hypothalamic corticotropin-releasing hormone and hippocampal steroid receptor mRNA in rat brain.

The hippocampus appears to be an important modulator of the negative feedback effects of glucocorticoids on the hypothalamic-pituitary-adrenal axis. It is not known if hippocampal subfields CA1-4 or the dentate gyrus differentially alter gene expression of corticotropin-releasing hormone (CRH) in the paraventricular nucleus (PVN) of the hypothalamus. We, therefore, examined the effects of selective destruction of dentate gyrus granule cells, which send excitatory glutaminergic inputs to subfields CA4, CA3 and CA2, on CRH expression in the PVN. To determine the possible involvement of steroid receptors in the regulation of CRH expression, we examined the effects of intrahippocampal colchicine on gene expression of the mineralocorticoid (MR; type I) and glucocorticoid (GR; type II) receptors in hippocampal CA fields and dentate gyrus. Colchicine produced a selective loss of dentate gyrus granule cells without affecting pyramidal cells in CA1-4 as early as 1 day after injection; granule cells were completely destroyed after 3 days. CRH mRNA levels were reduced by 38-48% in the PVN 2-14 days after colchicine. MR mRNA levels were decreased in dorsal and ventral CA fields 1-7 days after colchicine. GR mRNA levels were relatively unchanged, showing a slight decrease only in dorsal CA fields on days 2-7. Unexpectedly, CRH was transiently expressed in dorsal and ventral CA fields 1-3 days after colchicine. In the same time period, mRNA levels of inositol 1,4,5-trisphosphate kinase were decreased, suggesting that increases in neural metabolic activity, indicated by this marker, are not responsible for the transient CRH effect. The results suggest that the dentate gyrus is important for maintenance of steroid hormone receptor mRNA levels in the hippocampus and CRH expression in the hypothalamic PVN, and that CRH gene expression is differentially regulated in the hypothalamus and hippocampus.

Adrenocorticotropic Hormone↗
PubMed1992

Regulated expression of human immunodeficiency virus type 1 in human glial cells: induction of dormant virus.

Human neural cells are susceptible to infection with human immunodeficiency virus type 1 (HIV-1) in vitro; however, virus replication in these cells is strongly restricted. To understand the mechanism of this restriction, we examined the regulation of HIV-1 expression in glial cell cultures expressing high levels of HIV-1 after transfection of infectious viral DNA and selection. In all cases, high HIV-1 expression declined to low basal levels within 4-8 weeks of cultivation. The decrease in HIV-1 protein production wa paralleled by the decline in the relative levels of the 9.2-, 4.3- and 1.8-kilobase HIV-1 transcripts, but not by significant loss of HIV-1 DNA. Analysis of one long-term cell culture revealed 5 full-length unrearranged HIV-1 DNA copies per cell, but no viral transcripts on Northern blots, and minimal production of infectious virus. HIV-1 replication in these cells was markedly augmented by treatment with sodium butyrate (Na But) and to a lesser extent by 5-azacytidine, dibutyryl AMP and human herpes virus type 6. The virus induced by Na But was infectious. Transient expression assays revealed that Na But was more effective than phorbol myristate acetate in increasing the HIV-1 promoter activity in glial cells. Thus, one phase where glial cells can limit HIV infection is the expression of viral RNA from stable HIV provirus. However, such provirus remains responsive to inductive signals and may be activated to produce infectious HIV.

Cells, Cultured↗
PubMed1992

The retrocalcaneal bursa: anatomy and bursography.

The retrocalcaneal bursae, located between the posterior angle of the os calcis and the Achilles tendon, may become inflamed and hypertrophied. There are few objective tests available for the diagnosis of pain syndromes involving the hindfoot and it is often difficult to differentiate Achilles tendinitis and retrocalcaneal bursitis. Retrocalcaneal bursograms can provide further insight into chronic changes in the bursae associated with traumatic and inflammatory conditions. This report describes the anatomy of the retrocalcaneal bursa, the technique of its opacification, and the application of this technique to the diagnosis and treatment of painful hindfoot syndromes. In addition, the anatomy of the retrocalcaneal bursa was investigated further using latex casting techniques. Twelve cadaver limbs were injected with radiopaque latex casting material or renografin into the retrocalcaneal bursae. AP, lateral, and oblique radiographs were then obtained on the specimens. The size, capacity, and configuration of the postmortem bursae were measured and recorded. Subsequently, the cadaver limbs injected with the latex material were cooled and dissection was made of the retrocalcaneal bursae. The latex bursal molds were measured, graphically recorded, and photographed. Fifteen patients with signs and symptoms of retrocalcaneal bursitis and eight asymptomatic patients were selected for this study and injected with radiopaque material into the bursae. Anteroposterior, lateral, and oblique radiographs were then obtained. The size, capacity, and configuration of the retrocalcaneal bursae were measured and recorded. The anatomic characteristics noted from the latex bursal molds correlated well with the findings on bursography. Bursographic findings in patients with retrocalcaneal bursitis can provide insight into the diagnosis and clinical management of this disorder.

Achilles Tendon↗
PubMed1992

Antagonism of medetomidine sedation by atipamezole in pigs.

The efficacy of atipamezole as a medetomidine antagonist was evaluated in pigs. The atipamezole doses (intramuscularly) were 80, 160, 320 and 480 micrograms/kg of body weight, which were one, two, four and six times higher than the preceding medetomidine dose (80 micrograms/kg, intramuscularly). Atipamezole effectively reversed medetomidine-induced sedation, and the optimal action was seen at doses of 160 and 320 micrograms/kg. Recovery from sedation was quick and smooth, and adverse effects such as hyperactivity or tachycardia were minimal with either dose.

Adrenergic alpha-Agonists↗
PubMed1992

Gender role equity and marital satisfaction among Korean couples.

This study examines gender role behaviors and attitudes related to marital satisfaction. Nontraditional attitudes and behaviors are expected to affect negatively marital satisfaction due to the lack of guidelines and due to the other positive alternatives to marital roles. DAta, collected from a survey of 291 married couples in Seoul, Korea in 1991, largely support the hypotheses, which are fairly consistent with the results of studies of American couples. Nontraditional gender role attitudes and wife's employment are related to lower marital satisfaction. However, the housekeeper role has changed somewhat more than the male provider role, so that nontraditional tendencies, in attitudes and behaviors, with respect to the housekeeper role have been related to higher marital satisfaction. Findings of this study show that measures of actual division of household labor are better related to marital satisfaction than are measures of perceived division of household labor. The consistent trends in marital satisfaction in Korea compared with those in the US suggest a further high marital instability in Korea.

Asia↗
PubMed1992

Immortalized hypothalamic GT1-7 neurons express functional gamma-aminobutyric acid type A receptors.

Neuronal cell lines provide a source of pure populations of neurons and allow the properties of many neurotransmitter receptors to be studied. However, none of these cells have been reported to express functional gamma-aminobutyric acid (GABA)A receptors. Indeed, there have been no reports of cell lines expressing functional amino acid receptors. Using biochemical and electrophysiological techniques, we have identified a neuronal cell line expressing functional GABAA receptors. Membranes from immortalized hypothalamic (GT1-7) neurons bound [3H]muscimol but not [3H]flunitrazepam. GABA-activated chloride currents, recorded from GT1-7 cells, were blocked by bicuculline and Zn2+ but were insensitive to diazepam. These results suggest that GABAA receptors on GT1-7 cells lack gamma subunits. The neurosteroid 5 alpha-pregnan-3 alpha-ol-20-one and pentobarbital both modulated GABAA receptors in these cells. Polymerase chain reaction analysis of the cells revealed the presence of mRNAs encoding alpha 1, beta 1, and beta 3 polypeptides. GT1-7 cells provide a useful model system for studying the regulation of GABAA receptor polypeptide expression.

Anesthetics↗
PubMed1992

The conformation of glucagon in dilute aqueous solution as studied by 1H NMR.

The structure of monomeric glucagon in dilute aqueous solution was studied by 500 MHz NMR. Hydrogen-deuterium exchange experiments monitored by NMR showed that the backbone amide NHs form intrastrand hydrogen bonds suggesting the existence of some degree of compact structure. The temperature dependent shift of several amide NH resonances supported the above conclusion. The small J coupling constants arising from the interactions between 6 amide NHs and C alpha Hs (less than 6 Hz) imply a helical structure.

Glucagon↗
PubMed1992

Fusion of phospholipid vesicles induced by phospholipase D in the presence of calcium ion.

Fusion of phospholipid vesicles composed of various combination of phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid was induced by Ca2+ in the presence or absence of phospholipase D from Streptomyces chromofuscus. For the vesicles composed of 20:50:30 molar ratio of phosphatidylcholine/phosphatidylethanolamine/phosphatidic acid, the initial fusion rate was much faster than the expected value when only the conversion of phosphatidylcholine and phosphatidylethanolamine into phosphatidic acid by phospholipase D is taken into account. These observations are discussed in terms of the involvement of outer monolayer of the vesicles and the enzyme activity itself in the fusion process.

Calcium↗
PubMed1991

Structure and conformation of 5-bromo-2',3'-dideoxyuridine.

C9H11BrN2O4, Mr = 291.11, monoclinic, P2(1), a = 11.307 (1), b = 5.954 (1), c = 15.829 (2) A, beta = 93.25 (1) degree, V = 1063.90 A3, Z = 4, Dx = 1.82 g cm-3, lambda(Cu K alpha) = 1.54184 A, mu = 53.58 cm-1, F(000) = 584, T = 295 K, R = 0.034 for 1927 observed reflections [I greater than 3 sigma(I)]. The crystal structure contains two independent molecules forming a dimer linked by a pair of N3--H...O2 hydrogen bonds; the crystal structure is stabilized by four additional hydrogen bonds. Two of these are internal C6--H6...O5' hydrogen bonds, one in molecule A and another in molecule B. These two molecules exhibit two different conformations; their sugar ring puckers are 2'-endo-3'-exo for molecule A and 3'-endo-2'-exo for molecule B. The Cl'--N1 distance, the chi CN torsion angle and the glycosidic conformation are 1.464 (8) A, -130.0 degrees and -anticlinal for molecule A and 1.506 (8) A, -168.9 degrees and -antiperiplanar for molecule B, respectively.

Antiviral Agents↗
PubMed1991

Insulin-sensitive myelin basic protein phosphorylation on tyrosine residues.

Rat brain plasma membranes were solubilized in detergent and a glycoprotein-enriched fraction was obtained by lectin affinity chromatography. This glycoprotein fraction contained insulin receptors, as well as protein kinases capable of phosphorylating some exogenously added substrates such as MAP2 (microtubule associated protein 2) and MBP (myelin basic protein), but not ribosomal protein S6. Phosphoamino acid analysis of MAP2 and MBP showed that phosphotyrosine residues, as well as phosphoserine/phosphotheronine residues, were present in both proteins under basal conditions. Whereas the addition of insulin to the rat brain membrane glycoprotein fraction in vitro had no effect on MAP2 phosphorylation, MBP phosphorylation was stimulated 2.7-fold in response to insulin. This phenomenon was dose-dependent, with half-maximal stimulation of MBP phosphorylation observed with 2 nM insulin. Phosphoamino acid analysis of MBP indicated that insulin stimulated the phosphorylation of tyrosine residues nearly three-fold, whereas the phosphorylation of serine or threonine residues was not increased. These results identify MBP as a substrate for the rat brain insulin receptor tyrosine-specific protein kinase in vitro.

Adenosine Triphosphate↗
PubMed1991

Comparison of the structures of three carboxypeptidase A-phosphonate complexes determined by X-ray crystallography.

The structures of the complexes of carboxypeptidase A (CPA) with two tight-binding phosphonate inhibitors have been determined by X-ray crystallography. The inhibitors, Cbz-Phe-ValP-(O)-Phe[ZFVP(O)F] and Cbz-Ala-GlyP-(O)-Phe[ZAGP(O)F], bind noncovalently to CPA with dissociation constants (Ki's) of 11 fM and 710 pM, respectively. The CPA-ZFVP(O)F complex crystallizes in the space group P2(1)2(1)2(1) with unit cell parameters a = 65.3 A, b = 63.4 A, and c = 76.0 A, and the CPA-ZAGP(O)F complex crystallizes in the space group P2(1)2(1)2(1) with unit cell parameters a = 63.4 A, b = 65.9 A, and c = 74.4 A. Both structures were determined by molecular replacement to a resolution of 2.0 A. The final crystallographic residuals are 0.189 for the CPA-ZFVP(O)F complex and 0.191 for the CPA-ZAGP(O)F complex. The CPA-ZFVP(O)F complex exhibits the lowest Ki yet determined for an enzyme-inhibitor interaction. Comparison of the CPA-ZFVP(O)F structure with that of the CPA-ZAAP(O)F complex [Kim, H., & Lipscomb, W.N. (1990) Biochemistry 29, 5546-5555] indicates the likely important contributions of hydrophobic and weakly polar enzyme-inhibitor interactions to the exceptional stability of the CPA-ZFVP(O)F complex. Among these interactions is a network of four aromatic rings of CPA and ZFVP(O)F in a configuration that allows stabilizing aromatic-aromatic edge-to-face interactions from one ring to the next. A comparison of the structures of the CPA-ZFVP(O)F, CPA-ZAAP(O)F and CPA-ZAGP(O)F complexes shows that all three phosphonates assume a similar binding mode in the active-site binding groove of CPA. For ZAGP(O)F, the glycyl P1 residue does not lead to an anomalous or a partially disordered binding mode as seen in some previous complexes of CPA involving dipeptide analogue inhibitors with glycyl P1 residues. The additional enzyme-inhibitor interactions for these tripeptide phosphonates secure a binding mode in which a Pi portion of the inhibitor is clearly bound by the corresponding Si binding subsite. These three phosphonates have been implicated as transition-state analogues of the CPA-catalyzed reaction. The phosphinyl groups of these phosphonates coordinate to the active-site zinc in a manner that has been proposed as a characteristic feature of the general-base (Zn-hydroxyl or Zn-water) mechanism for the CPA-catalyzed reaction. Further mechanistic proposals are made for Arg-127, whose probable role in binding substrates is apparent in these CPA-phosphonate complexes.

Amino Acid Sequence↗
PubMed1991

Expression of cDNA sequences encoding mature and precursor forms of human dihydrolipoamide dehydrogenase in Escherichia coli. Differences in kinetic mechanisms.

The cDNA sequences encoding mature and precursor forms of human dihydrolipoamide dehydrogenase (E3) were expressed in Escherichia coli using a lambda PL promoter-driven prokaryotic expression vector. The expressed proteins in total cell extracts were identified by Western blot analysis using anti-pig heart E3 antibody and also by measurement of E3 activity. Most of the expressed human E3 polypeptides (five bands) were found in the insoluble pellet while primarily full-length mature E3 was found in the soluble fraction. About 2% of the total soluble protein was mature human E3 when expressed in wild type E. coli AR120. Since wild type E. coli has its own endogenous E3 activity, the expression of human E3 was performed in a pyruvate dehydrogenase complex-deficient strain of E. coli, JRG1342. The expressed recombinant human E3s in JRG1342 were purified to near homogeneity. The amino-terminal amino acid sequence analysis revealed that the recombinant mature E3 had an expected sequence while the recombinant precursor E3 lost 19 amino acid residues of its 35-amino acid leader sequence presumably due to a proteolytic cleavage. The recombinant mature E3 displayed comparable kinetic properties to those reported for highly purified mammalian E3s. The truncated precursor E3 showed about half of the mature E3 activity. The double-reciprocal plot for the mature E3 in the direction of NAD+ reduction showed parallel lines (ping-pong mechanism) while that for the truncated precursor E3 displayed intersecting lines (sequential mechanism). In the direction of NADH oxidation, the kinetic mechanisms of both E3s were apparently a ping-pong mechanism. These kinetic results showed that the partial 16-amino acid extension in the leader sequence changed the kinetic mechanism of human E3 so that it resembled that of glutathione reductase.

Amino Acid Sequence↗
PubMed1991

Life after mandatory insurance: Hawaii providers tide a new wave.

While the nation looks to universal access laws as a solution to hospitals' rising costs of caring for the uninsured, laws covering all workers are standard operating procedure in Hawaii. The state's mandatory insurance law was meant to reduce hospitals' indigent-care losses, but losses have continued to mount at some facilities. Despite the overall benefits of the law, Hawaiian hospitals struggle just like their mainland counterparts to survive.

Evaluation Studies as Topic↗