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S Kim

Publications and source records attributed to S Kim.

At least 919 records · Page 51Linked to original sources
PubMed1995

DNA and RNA-DNA annealing activity associated with the tau subunit of the Escherichia coli DNA polymerase III holoenzyme.

The DNA polymerase III (pol III)holoenzyme is the 10 subunit replicase of Escherichia coli. The 71 kDa tau subunit, encoded by dnaX, dimerizes the core polymerase (alpha epsilon theta) to form pol III'[(alpha epsilon theta)2 tau 2]. tau is also a single-stranded DNA-dependent ATPase and can substitute for the gamma subunit during initiation complex formation. We show here that tau also possesses a DNA-DNA and RNA-DNA annealing activity that is stimulated by Mg2+, but neither requires ATP nor is inhibited by non-hydrolyzable ATP analogs. This suggests the tau may act to stabilize the primer-template interaction during DNA replication.

Adenosine Triphosphatases↗
PubMed1995

The retinoblastoma gene product negatively regulates transcriptional activation mediated by the human cytomegalovirus IE2 protein.

The IE2 gene product of human cytomegalovirus (HCMV) is one of a few viral regulatory proteins expressed immediately upon infection of the host cell. It is a potent transcriptional activator of many viral and cellular promoters. We found that the retinoblastoma susceptibility gene product (Rb) dramatically suppressed this IE2 transactivation of various promoters. However, unlike another tumor suppressor protein, p53, Rb did not have any significant effect on basal levels of transcription, suggesting that Rb specifically interacts with IE2 rather than other cellular factors involved in the general transcription machinery. We found by protein-affinity chromatography that Rb in nuclear extracts or produced by in vitro translation directly bound to IE2. Our results suggest that Rb may regulate the life cycle of HCMV, which is endemic in the human population. Furthermore, these data may provide new insights into the slow rate of HCMV DNA replication in cells and the possible involvement of HCMV in tumorigenesis.

Cell Line↗
PubMed1995

Structural specificity of substrate for S-adenosylmethionine:protein arginine N-methyltransferases.

The enzymatic methylation of polypeptides on the guanidino group of internal arginine residues by S-adenosylmethionine:protein arginine N-methyltransferase (protein methylase I) yields NG-monomethylarginine, NG,NG-dimethylarginine and NG,NG-dimethylarginine. It has commonly been observed that these arginine residues are present in glycine-and-arginine rich motifs. To understand structural features which are essential for serving as the methyl acceptor for protein methylase I, we have investigated substrate capacities of several synthetic oligopeptides whose sequences are homologous and/or analogous to the methyl acceptor region of the naturally occurring arginine-methylated proteins. These studies have led to the following conclusions. (i) The preferred amino-acid sequence of methyl-accepting peptides was shown to be an arginine-containing peptide with glycine in both the N- and C-flanking positions. While a tetrapeptide with such a sequence (residues 106-109 of bovine myelin basic protein) exhibited almost negligible substrate activity, an overlapping hexapeptide was a moderate substrate. (ii) Substitution of the C-flanking glycine in GKGRGL (residues 104-109 of myelin basic protein) with histidine, phenylalanine, lysine or aspartic acid completely abolished the ability of these hexapeptides to serve as substrates. (iii) A heptapeptide with a repeated glycine-arginine motif (GRGRGRG) was an excellent substrate for the enzyme. (iv) A cyclic octapeptide (CGKGRGLC), which was formed by cyclization of GKGRGL by introduction of disulfide bridge to cross-link N- and C-terminus of the hexapeptide, was an even better substrate than the hexapeptide. (v) Upon HPLC amino-acid analysis, all enzymatically methyl-14C-labeled oligopeptides were found to yield predominantly NG-monomethylarginine with a minor fraction of NG,NG-dimethylarginine in certain peptide samples. However, no NG,NG-dimethylarginine formation was detectable. (vi) The recombinant hnRNP protein A1 (residues 1-320) is known to be methylated at arginine-194 by nuclear-protein/histone protein methylase I (Rajpurohit et al. (1994) J. Biol. Chem. 269, 1079-1082). However, the hexapeptide (SSSQRG) which corresponds to residues 189-194 of protein A1 containing the methylatable arginine residue was relatively inert as a substrate. Furthermore, the N-terminal fragment of protein A1 (residues 1-196) generated by controlled trypsin digestion was also completely inactive as a substrate for the enzyme. These results indicate that the remainder of the A1 protein molecule plays an important though not yet understood role in enzymatic methylation of the arginine-194.

Amino Acid Sequence↗
PubMed1995

REST: a mammalian silencer protein that restricts sodium channel gene expression to neurons.

Expression of the type II voltage-dependent sodium channel gene is restricted to neurons by a silencer element active in nonneuronal cells. We have cloned cDNA coding for a transcription factor (REST) that binds to this silencer element. Expression of a recombinant REST protein confers the ability to silence type II reporter genes in neuronal cell types lacking the native REST protein, whereas expression of a dominant negative form of REST in nonneuronal cells relieves silencing mediated by the native protein. REST transcripts in developing mouse embryos are detected ubiquitously outside of the nervous system. We propose that expression of the type II sodium channel gene in neurons reflects a default pathway that is blocked in nonneuronal cells by the presence of REST.

Amino Acid Sequence↗
PubMed1995

Sphingolipid-gated Ca2+ release from intracellular stores of endothelial cells is mediated by a novel Ca(2+)-permeable channel.

Sphingolipid-gated Ca2+ signaling is mediated through Ca(2+)-permeable channels. In this report, we characterize the properties of the channel in a human endothelial cell line (EA.hy926). Ca2+ release from intracellular stores is not antagonized by nifedipine, omega conotoxin G-VIa, or heparin. To further characterize the molecular properties of the channel, we developed a novel assay to directly measure efflux of Ca2+ from intracellular stores of permeabilized Xenopus oocytes. Following size fractionation by sucrose gradient, poly(A)+ RNA from EA.hy926 cells is microinjected into oocytes of Xenopus laevis. We find that the mRNA encoding Ca2+ release activity is approximately 1.5-2.0 kilobases in length. The sphingolipid-gated Ca(2+)-permeable channel is thus likely to be a novel Ca(2+)-permeable channel distinct from other characterized intracellular Ca2+ channels such as the ryanodyne receptor and the inositol 1,4,5-trisphosphate receptor. The method described here provides a new approach to further characterizing this channel and other intracellular Ca2+ channels.

Animals↗
PubMed1995

Okadaic acid stimulates glucose transport in rat adipocytes by increasing the externalization rate constant of GLUT4 recycling.

GLUT4, the major insulin-responsive glucose transporter isoform in rat adipocytes, rapidly recycles between the cell surface and an intracellular pool with two first order rate constants, one for internalization (kin) and the other for externalization (kex). Insulin decreases kin by 2.8-fold and increases kex by 3.3-fold, thus increasing the steady-state cell surface GLUT4 level by approximately 8-fold (Jhun, B. H., Rampal, A. L., Liu, H., Lachaal, M., and Jung, C. (1992) J. Biol. Chem. 267, 17710-17715). To gain an insight into the biochemical mechanisms that modulate these rate constants, we studied the effects upon them of okadaic acid (OKA), a phosphatase inhibitor that exerts a insulin-like effect on glucose transport in adipocytes. OKA stimulated 3-O-methylglucose transport maximally 3.1-fold and increased the cell surface GLUT4 level 3.4-fold. When adipocytes were pulse-labeled with an impermeant, covalently reactive glucose analog, [3H]1,3-bis-(3-deoxy-D-glucopyranose-3-yloxy)-2-propyl 4-benzoylbenzoate, and the time course of labeled GLUT4 recycling was followed, the kex was found to increase 2.8-fold upon maximal stimulation by OKA, whereas the kin remained unchanged within experimental error. These findings demonstrate that OKA mimics the insulin effect on only GLUT4 externalization and suggest that insulin stimulates GLUT4 externalization by increasing the phosphorylation state of a serine/threonine phosphoprotein, probably by inhibiting protein phosphatase 1 or 2A.

Adipocytes↗
PubMed1995

A prospective study of FK506 versus CsA and pig ATG in a porcine model of small bowel transplantation.

Rejection remains a major barrier to successful bowel transplantation, and immunosuppressive protocols are far from standardized. In 88 nonrelated outbred pigs, we compared the effects of two immunosuppressive regimens--one with FK506, the other with cyclosporine (CsA) and pig antithymocyte globulin (ATG)--on incidence and severity of rejection in the early, critical posttransplant period. Group A (n = 14) was nonimmunosuppressed (controls). Group B (n = 17) received pig ATG (10 mg/kg/day x 10 days), CsA (3 mg/kg/day), prednisolone (2 mg/kg/day), and azathioprine (2.5 mg/kg/day); prednisolone and azathioprine were each reduced by 50% at 8 and 15 days posttransplant. Trough CsA whole-blood concentrations were > or = 400 ng/ml for the first 7 days, > or = 200 ng/ml thereafter. Group C (n = 13) received FK506 (0.2 mg/kg/day) and prednisolone (2 mg/kg/day); prednisolone was reduced by 50% at 8 and 15 days. FK506 whole-blood concentrations were > or = 20 ng/ml. All immunosuppression in groups B and C was given intravenously. We performed orthotopic small bowel transplants with systemic venous drainage. Recipient bowel was resected distal to the second portion of the duodenum and proximal to the rectum at transplant; bowel continuity was restored by duodenojejunostomy; ileostomy was created distally to allow access for daily biopsies. We graded interstitial and vascular rejection separately, according to a scoring system (no, mild, moderate, and severe rejection). Rejection-free graft survivals at 7, 14, and 21 days posttransplant were 38%, 19%, and 0% in group A; 93%, 93%, and 62% in group B; and 100%, 91%, and 82% in group C (P < 0.001). Comparing rejection in the immunosuppressed groups, group C (FK506) had a stronger tendency toward rejection than group B (CsA-ATG); significant differences between groups B and C were, however, noted only on individual days posttransplant, not over time. The death rate due to irreversible rejection was not significantly different in groups B and C (P = 0.8), but was significantly better in both of these immunosuppressed groups than in group A (P < 0.001). Pig survival was significantly longer in group C than in B (P = 0.001) due to a lower infection rate in group C. Posttransplant serum interleukin 2 and 7 levels did not correlate with rejection grades. Graft-versus-host reaction was noted only in the skin in 29% of group A, 73% of group B, and 77% of group C pigs; liver and native bowel were not involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Pharmacokinetics of intralumbar DTC-101 for the treatment of leptomeningeal metastases.

PURPOSE: To study the results of intralumbar administration of chemotherapeutic agents for the treatment of neoplastic meningitis and to determine how these results relate to the variable and often subtherapeutic drug concentrations in the ventricular cerebrospinal fluid (CSF) compartment. Ventricular and lumbar pharmacokinetic studies were done following intralumbar administration of DTC-101, an extended-release formulation of cytarabine. PATIENTS AND METHODS: Nine patients (age range, 23 to 67 years; median age, 42 years) with leptomeningeal metastases were treated with 18 courses of intralumbar DTC-101. Eight patients who were treated with 14 courses underwent pharmacokinetic CSF sampling from the lumbar sac and lateral ventricle. Cytarabine concentrations were determined by using high-pressure liquid chromatography. RESULTS: Following intralumbar administration of DTC-101, therapeutic free cytarabine concentrations were achieved rapidly in both of the ventricular and lumbar CSF compartments and maintained for 2 weeks. The mean pharmacokinetic parameters of free cytarabine in the lumbar and ventricular CSF compartments were as follows: maximum concentration, 226 and 6.06 mg/L; half-life, 277 and 130 hours; and area under the concentration vs time curve, 4120 and 598 micrograms/h per milliliter, respectively. CONCLUSIONS: Intralumbar administration of DTC-101 results in extended cytotoxic free cytarabine concentrations in both of the lumbar and ventricular regions of CSF and allows an every-other-week drug-dosing schedule.

Adult↗
PubMed1995

Retroviral-mediated transduction of the fanconi anemia C complementing (FACC) gene in two murine transplantation models.

Fanconi anemia (FA) is a well-known genetic syndrome manifested by bone marrow failure, variable physical anomalies, and cancer susceptibility. This disorder is marked by genotypic and phenotypic heterogeneity and consists of four distinct complementation groups A, B, C, and D. The defective gene responsible for the C group of FA, FACC, was identified by cDNA complementation cloning, and we have recently proposed a trial of gene therapy for group C FA. No animal model yet exists for FA. Consequently, we have studied the effects of constitutive expression of human FACC in two murine transplantation models. In the first model, we demonstrated transduction of FACC to reconstituting stem cells of mutant W/WV mice. In the second model, we demonstrated transduction of FACC to hematopoietic cells transplanted to the bone marrows and spleens of non-myeloablated BALB/c mice. Our data suggest that retroviral-mediated transfer of the normal human FACC cDNA to hematopoietic progenitor and stem cells of mice is feasible and not associated with direct harmful effects to the hematopoietic organ.

Animals↗
PubMed1995

Effect of nicorandil on abnormal coronary flow reserve assessed by exercise 201Tl scintigraphy in patients with angina pectoris and nearly normal coronary arteriograms.

The purpose of the present study is to assess the effect of nicorandil, a coronary vasodilator with a mechanism of potassium channel opening, on the abnormal myocardial 201Tl perfusion evoked by exercise. Eleven patients who had a history of typical angina, positive exercise electrocardiograms, positive 201Tl scintigraphy, nearly normal coronary arteriograms, and negative coronary vasospasm underwent exercise 201Tl scintigraphies under no medication (baseline test) and administration of nicorandil (nicorandil test). 201Tl was injected at a matched workload in both tests. Nicorandil did not alter heart rate, blood pressure, or the rate-pressure product at the end of the exercise, but it significantly improved the extent score from 0.37 +/- 0.22 to 0.20 +/- 0.15 (p < 0.05) and the severity score from 33.9 +/- 32.2 to 13.5 +/- 16.4 (p < 0.05), and also significantly hastened the 201Tl mean washout rate from 30.5 +/- 14.8% to 37.4 +/- 13.1% (p < 0.05). Anginal symptoms disappeared in 3 of 5 cases and ST depression improved in 5 of 7 cases after nicorandil. We conclude that nicorandil augments coronary flow reserve, possibly due to a reduction of vasotone in the small coronary arteries.

Adult↗
PubMed1995

Pharmacokinetics of a single dose of buccal testosterone.

The bioavailability, pharmacokinetics, and metabolism of a novel transbuccal delivery system of testosterone was investigated in five healthy eugonadal men. Total serum testosterone (T), dihydrotestosterone (DHT), and sex hormone-binding globulin (SHBG) concentrations were determined from blood samples obtained at 8:00 a.m. (zero hour), and 30 min and 1, 2, 3, 4, 6, 12 and 24 hours later on day 1, and again on day 2, after dosing. This single transbuccal administration of Buccal T induced a prompt rise in serum T and DHT concentrations. The maximal concentration (Cmax) of T was 19.56 7.64 ng/mL (mean +/- SD; 5.3-fold increase from the baseline) at< 30 min (Tmax) after administration. The elimination half-life of Buccal T was about 1.75 h. Serum DHT peaked at 1 h at a concentration of 1.46 +/- 0.46 ng/mL (2.3-fold increase from the baseline). The drug was well tolerated. This study suggests that the Buccal T is a promising delivery system for natural T.

Administration, Buccal↗
PubMed1995

Inhibition by angiotensin II type 1 receptor antagonist of cardiac phenotypic modulation after myocardial infarction.

The purpose of this study was to examine the cardiac phenotype and remodeling after myocardial infarction and the effect of the angiotensin II type 1 (AT1) receptor antagonist (TCV-116) on the gene expression. Myocardial infarction in rats was produced by ligation of the coronary artery. TCV-116 (10 mg/kg/day) was administered orally to rats from 1 day after myocardial infarction. At 1, 2 and 3 weeks after myocardial infarction, blood pressure and heart rate were measured, and the heart was removed. The left ventricle was measured for infarct size and weight, and then the total RNA from the non-ischemic left ventricle was extracted. mRNAs in the non-ischemic left ventricle were measured by Northern blot analysis. The weight of the non-ischemic left ventricle was significantly increased 3 weeks after infarction. This was completely prevented by TCV-116 treatment. mRNA levels for beta-myosin heavy chain (beta-MHC), atrial natriuretic polypeptide (ANP), collagen types I and III and transforming growth factor-beta 1 (TGF-beta 1) in the non-ischemic left ventricle were increased by a factor of 3.0, 6.7, 7.9, 4.0 and 1.4 (P < 0.01), respectively, 1 week after infarction. There was no increase in alpha-skeletal actin mRNA at 1 and 2 weeks, but it was increased by a factor of 2.9 (P < 0.05) at 3 weeks. On the other hand, there was no change in alpha-MHC mRNA during the 3 weeks. TCV-116 significantly suppressed the increased gene expression of beta-MHC and alpha-skeletal actin in the non-ischemic myocardium at all time points, and also suppressed the expression of ANP at 2 and 3 weeks. However, TCV-116 failed to inhibit the expression of collagen I and III mRNAs at 1 and 3 weeks. These results show that myocardial infarction causes a rapid shift of myocytes to fetal phenotype and a rapid activation of collagen genes in the non-ischemic myocardium. AT1 receptor may be responsible for the phenotypic modulation of myocytes following myocardial infarction.

Actins↗
PubMed1995

Urinary excretion of NG-dimethylarginines in multiple sclerosis patients: preliminary observations.

The concentrations of NG,N'G-dimethylarginine [Me2(sym)Arg] and NG,NG-dimethylarginine [Me2(asym)Arg] were determined in the urine samples from multiple sclerosis (MS) and control subjects, using a highly sensitive HPLC post-column o-phthaldialdehyde derivatization method. The presence of approximately equal amounts of both dimethylarginine isomers, of Arg concentration nearly half of Me2Arg, and of the undetectable amount of NG-monomethylarginine were the characteristic urinary excretion pattern in all human samples studied. The urinary excretion of Me2(asym)Arg and Me2(sym)Arg from MS (n = 9) and control (n = 7) were analyzed: the mean values from the samples were approximately 20% (for all MS) and 33% (for chronic-progressive MS) lower than those from the control for both dimethylarginine-derivatives when compared to the respective compounds. Although there were contrasting trends between controls and MS patients in the relationship of urinary NG-dimethylarginines and myelin basic protein like material (MBPLM), the correlations were not significant. Differences in the ratios of the concentrations of the two dimethyl derivatives, Me2(sym)Arg/Me2(asym)Arg, were not significantly different between MS and control groups. These findings warrant further investigation of possible links between urinary excretion of NG-dimethylarginine and MBPLM in MS. The possible significance of myelin metabolism in relation to urinary NG-dimethylarginines in MS is discussed.

Arginine↗
PubMed1995

Resilience criteria and factors associated with resilience in sexually abused girls.

Alternative measures of resilience and correlates of resilience were examined in a sample of 43 sexually abused girls who were assessed using a self-administered interview at the time of intake for psychotherapy. Results indicated relatively high levels of disagreement as to which girls were resilient using maintenance of social competence and absence of clinical levels of symptomatology as alternative criteria. Most girls that had maintained age-normative levels of social competence were, nonetheless, manifesting clinically significant levels of symptoms. A warm and supportive relationship with a nonoffending parent was a strong correlate of resilience, regardless of which criteria was used. Lower levels of abuse related stress, fewer negative cognitive appraisals of the abusive relationship, and less reliance on aggressive coping behaviors were also significant predictors of resilience based on the absence of clinical levels of symptomatology. However, parental support and level of abuse stress were the only two variables to enter a logistic regression model predicting resilience. The research and clinical implications of these findings are discussed.

Adaptation, Psychological↗
PubMed1995

Characterization of human homologue of 4-1BB and its ligand.

The human homologue of 4-1BB (H4-1BB) cDNA was isolated from PMA plus ionomycin-treated human peripheral T-cell cDNA libraries. The amino acid sequence deduced from the nucleotide sequence showed that the protein is composed of 255 amino acids with 2 potential N-linked glycosylation sites. The molecular weight of its protein backbone is calculated to be 27 kDa. The H4-1BB contains features such as signal sequence and transmembrane domain, indicating that it is a receptor protein. This protein showed 60% identity of amino acid sequence to mouse 4-1BB. In the cytoplasmic domain there are 5 regions of amino acid sequences conserved from mouse to human, indicating that these residues might be important in the 4-1BB function. H4-1BB mRNA was detected in unstimulated peripheral blood T cells and was inducible in T-cell lines such as Jurkat and CEM. H4-1BB-AP, a fusion protein between the H4-1BB extracellular domain and alkaline phosphatase, was used to identify the ligand for the H4-1BB. Although the H4-1BB ligand was detected in both T and B cells of human peripheral blood, the ligand was preferentially expressed in primary B cells and B-cell lines. Daudi, a B-cell lymphoma, was one of the B-cell lines that carried a higher number of ligands. Scatchard analysis showed that the Kd = 1.4 x 10(9) M and the number of ligands in Daudi cell was 4.2 x 10(3).

3T3 Cells↗