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Biomedical subjects

H Kim

Publications and source records attributed to H Kim.

At least 613 records · Page 34Linked to original sources
PubMed1996

Stability and folding of a mutant ribose-binding protein of Escherichia coli.

A mature mutant ribose-binding protein (RBP) of Escherichia coli was obtained by site-directed mutagenesis, replacing Thr-3 in the N-domain of wild-type mature RBP (WT-mRBP) with a Trp residue (N-Trp-mRBP). The equilibrium unfolding properties and the refolding kinetics of this protein were monitored by fluorescence and circular dichroism (CD). The stability of N-Trp-mRBP appears to be the same as that of C-Trp-mRBP, another mutant obtained by replacing Phe-187 with a Trp, and lower than that of WT-mRBP. The overall refolding rate of N-Trp-mRBP is much smaller than that of C-Trp-mRBP, which, in turn, is similar to that of WT-mRBP. For the case of WT-mRBP, the rate constant obtained by Tyr fluorescence is identical to the value obtained by CD. But with C-Trp-mRBP, the rate constant from CD is smaller than the value from the Trp fluorescence and this difference in the rate constants is much greater with the N-Trp-mRBP.

Carrier Proteins↗
PubMed1996

X-ray diffraction, electron microscopy, and Fourier transform infrared spectroscopy of apatite crystals isolated from chicken and bovine calcified cartilage.

Apatite crystals of the calcified zone of the subarticular cartilaginous growth plates of the long bones of young growing chickens and calves were isolated by low temperature reaction with hydrazine and plasma ashing and examined by electron microscopy, electron diffraction and microprobe analysis, and computer-generated deconvolution of the spectra obtained by Fourier transform infrared spectroscopy. The crystal habit was that of wide, very thin, relatively long rectangular plates, which tended to form small clusters of crystals, possibly because reaction with hydrazine alone did not remove all of the organic matrix constituents. Further reaction with low power plasma ashing released more of the isolated crystals although to a lesser extent than was possible with bone. Stereograms of the small clusters showed that many of the crystals in the small isolated aggregates of crystals were bent and/or curved. Together with the resultant overlap of individual adjacent crystals, they also produced images of sharp, very dense lines, reminiscent of the electron-dense needle or rod-like appearances frequently observed by transmission electron microscopy of thin sections of calcified cartilage and thought to represent the habit of the apatite crystals. No true rod or needle-like crystals were observed in the isolated crystals. Although the overall general apatitic structure of the apatite crystals was similar to that of the apatitic crystals of bone, the individual crystals were significantly larger than those of bone from the same specimen, and there were small but significant differences in the concentrations of acid phosphate and carbonate groups and in their short range order.

Animals↗
PubMed1996

Long-term expression of the 35,000 mol. wt fos-related antigen in rat brain after kainic acid treatment.

Systemic injection of kainic acid, a rigid analogue of glutamate, induces both the short-term and the long-term expression of activator protein-1 transcription factors. The short-term responses of activator protein-1 factors such as c-fos and fos-related antigens have been well studied. However, the long-term expression of activator protein-1 factor(s) induced by kainic acid is poorly understood. The present study was designed to document the long-term expression (up to seven months) of the fos-related antigens and to map their distributions in the rat brain after systemic treatment with kainic acid. A single dose of kainic acid (8 mg/kg) was injected i.p. into Fischer 344 rats and their epileptic seizure behaviour was monitored. The rats with full limbic seizures were chosen for long-term study. By using immunocytochemistry with an antibody that cross-reacts with all known fos-related antigens, western blot analysis and a gel mobility-shift assay, we have now shown that a 35,000 mol. wt fos-related antigen was induced by kainic acid treatment and expressed at high levels for up to five months. This fos-related antigen still maintains the activator protein-1 DNA binding activity in the rat brain seven months after kainic acid treatment. The fos-related antigens and activator protein-1 binding activity were continuously expressed at high levels throughout the experimental period in the dentate granule cells where mossy fibre collateral sprouting occurred after kainic acid treatment. Our results suggested that long-term expression of fos-related antigen may reflect the pathophysiological changes after kainic acid administration.

Animals↗
PubMed1996

Ginsenosides stimulate endogenous production of nitric oxide in rat kidney.

Ginsenosides (GS), saponins purified from Panax ginseng, increase renal blood flow in rats. Nitric oxide (NO) is thought to be the substance endogenously released by GS in preconstricted lungs and cultured endothelial cells. The present study aims to determine whether GS could stimulate endogenous release of NO in rat kidney and whether GS affected the activity of NO synthase in kidney tissues. The serum and urine levels of the stable NO metabolites, nitrite (NO2) and nitrate (NO3) and urinary cGMP levels were measured 8 hr after a single intraperitoneal injection of GS (200 mg/kg) into rats. The effects of the NO synthesis inhibitor, N omega-nitro-L-arginine methyl ester and the NO precursor, L-arginine, on the GS-induced changes were also determined. The activity of NO synthase, as determined by conversion of [14C]-L-arginine to [14C]-L-citrulline, in whole kidney, glomeruli and cortical tubules was also investigated. A single injection of GS resulted in endogenous production of NO as reflected by increase in serum and urine levels of NO2/NO3 and urinary cGMP levels, which were inhibited by the addition of N omega-nitro-L-arginine methyl ester and restored by L-arginine. GS also stimulated the activity of NO synthase in whole kidney as well as glomeruli and cortical tubules, and this increase was significantly prevented by N omega-nitro-L-arginine methyl ester. It was concluded that stimulation in endogenous production of NO by GS may contribute to its antinephritic action and may play a protective role in the kidney.

Animals↗
PubMed1996

Transcriptional activation of the dnaA gene encoding the initiator for oriC replication by IciA protein, an inhibitor of in vitro oriC replication in Escherichia coli.

Transcription of the Escherichia coli dnaA gene, encoding DnaA protein required for initiation of chromosomal DNA replication at oriC in E. coli, starts from two promoters, 1P and 2P. Gel-shift and DNase I-protection assays revealed that IciA protein, an inhibitor of initiation of in vitro E. coli chromosomal DNA replication at oriC, bound to two sites in the dnaA promoter region. One site is located upstream of promoter 1P, and the second is located downstream of promoter 2P. Whereas IciA protein did not affect transcription from the promoter 2P, transcription from the promoter 1P was specifically enhanced by IciA protein in vivo and in vitro. DnaA protein bound to the DnaA box between the two promoters 1P and 2P, acts as an transcriptional repressor. Under this condition, IciA protein counteracted the repressive effect of DnaA protein on the promoter 1P. These findings suggest that IciA protein may regulate the initiation of chromosomal DNA replication at oriC by controlling expression of the dnaA gene, as well as by inhibiting the initiation of chromosomal DNA replication at oriC.

Bacterial Proteins↗
PubMed1996

Suppression of in vivo tumor growth and induction of suspension cell death by tissue inhibitor of metalloproteinases (TIMP)-3.

Tissue inhibitor of metalloproteinases-3(TIMP-3), a novel member of TIMP family genes, has been recently cloned and shown to be expressed in preneoplastic but not in neoplastic mouse JB6 epidermal cells (Sun et al. 1994 Cancer Res., 54, 11139). This down regulation of the gene appears to be attributable at least in part to alteration of gene methylation (Sun et al. 1995 J. Biol. Chem., 270, 19312). Little is known, however, about the role of TIMP-3 in human cancers. We screened several human tumor cell lines for TIMP-3 expression and found that a colon carcinoma line, DLD-1, did not express TIMP-3. If down regulation of TIMP-3 is causally related to carcinogenesis, re-expression by transfection may reverse the tumor cell phenotype. We therefore overexpressed human TIMP-3 in DLD-1 cells. TIMP-3 transfectants showed a serum-dependent growth inhibition in monolayer culture and a decreased growth potential in nude mice in a manner dependent on the level of TIMP-3 expression. A transfectant expressing a high level of active hTIMP-3 completely lost the ability to form tumors following s.c. injection into nude mice. We also tested TIMP-3 expressing cells and neocontrol TIMP-3 negative cells for their ability to grow in liquid suspension culture, since both cells grew in semi-solid soft agar. As compared to neocontrol cells, TIMP-3 overexpressors formed large aggregates, followed by cell death. This effect was not mimicked by BB94, a broad MMP inhibitor. We conclude from this study that (i) TIMP-3 overexpression in human colon carcinoma cells induces growth arrest in low serum conditions and inhibits in vivo tumor growth and (ii) the TIMP-3-induced large aggregate formation and subsequent cell death under suspension growth cannot be explained by its MMP inhibitory activity.

Animals↗
PubMed1996

Infectious processes: an infrequent cause of first trimester spontaneous abortions.

A systematic assessment of infections beginning early in pregnancy is necessary to determine the true role of infections in pregnancy loss, given that infections could readily arise only after fetal demise. To this end, we have prospectively determined the frequency of infections in pregnant women who were subjects in a multi-centre US study. Insulin-dependent diabetic subjects and controlled subjects were recruited either before conception (86%) or at the latest within 21 days of conception (14%). We collected data prospectively on all important risk factors and potential confounding variables, seeing 386 diabetic subjects weekly and 432 control subjects every other week during the first trimester. At each visit we inquired about untoward events and explicitly about fever or infections. We found no clinical evidence that infection occurred more often in the 116 subjects experiencing pregnancy loss as compared to the 702 having successful pregnancies. This held both for the 2 week interval in which a given loss was recognized clinically as well as in the prior 2 week interval. Similar findings were not only observed for both the control as well as diabetic subjects but also when data were stratified by genital infection only or by systemic infection only. Our prospective data suggest that the attributable risk of infection in first trimester spontaneous abortion is small.

Abortion, Spontaneous↗
PubMed1996

Management of early-stage Hodgkin's lymphoma. The radiation oncology experience at Northwestern University/Northwestern Memorial Hospital.

Early-stage Hodgkin's lymphoma patients treated with radiotherapy alone or combined modality therapy were retrospectively analyzed for survival, patterns of failure, salvage, and toxicity. Of 75 evaluable patients, 47 were given radiotherapy alone and 28 were given combination radiotherapy and chemotherapy. Of the patients studied, 26 were clinical stage I and 49 were clinical stage II, with nine patients upstaged at laparotomy. Minimum follow-up was 2 years, with a median of 81 months. Complete response rate was 95%. Relapse-free survival and overall survival were 89% and 96%, respectively, at 2 years; 78% and 86% at 5 years; and 76% and 82% at 10 years. Of 16 patients who relapsed (21%), 13/47 patients were treated with radiotherapy and 3/28 were treated with combined modality therapy. Salvage rates were higher in those treated with radiotherapy alone. There were 13 deaths: six from disease, two from treatment-related complications, and five from second primary malignancies. There was a higher incidence of second malignancies and deaths due to complication in patients treated with combined modality therapy. Radiotherapy alone or with chemotherapy is an effective modality in the treatment of Hodgkin's lymphoma. Treatment should be selected properly to optimize results and decrease complications.

Adolescent↗
PubMed1996

alpha 1-antitrypsin deficiency and idiopathic pulmonary fibrosis in a family.

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease of unknown etiology with an estimated prevalence of 3 to 5 per 100,000. We describe a patient with a family history of both IPF and alpha 1-antitrypsin (AAT) deficiency. The patient had a 6-month history of worsening dyspnea when first seen, and he later died of multisystem organ failure and recalcitrant hypoxemia. He had IPF and AAT deficiency, with the phenotype PiSZ. His father and younger brother died of respiratory failure due to IPF. Other family members are heterozygous for AAT deficiency. A variety of inflammatory diseases have been associated with AAT deficiency, and an association between heterozygous AAT deficiency and IPF has been reported in the literature. Most current theories on the pathogenesis of IPF suggest an aberrant inflammatory response to some stimulus. This family cluster and another reported in the literature suggest that AAT deficiency may be a factor predisposing to inflammatory lung disease manifested by interstitial fibrosis.

Adult↗
PubMed1996

Pharmacokinetics and metabolism of genaconazole, a potent antifungal drug, in men.

The pharmacokinetics of genaconazole, a racemic triazole antifungal agent comprising 50% RR and 50% SS enantiomers, were studied in 12 healthy male volunteers after a single oral dose of 200 mg. The serum samples were analyzed for the two enantiomers by using a chiral high-pressure liquid chromatography assay. The concentrations of the RR and SS enantiomers in serum were virtually identical. The mean values for the maximum concentrations in serum (Cmax) (1.7 micrograms/ml), times to Cmax (4.0 to 4.2 h), half-lives (83 h), and areas under the concentration-time curve from 0 h to infinity (195 to 199 micrograms.h/ml) were similar for the two enantiomers. The results showed that the pharmacokinetic profiles of the two enantiomers were similar after a single oral dosing of the racemate. The pharmacokinetics of the RR enantiomer were also evaluated in 12 healthy male volunteers after a single oral dose of 100 or 200 mg. The ratios of the Cmaxs and of the areas under the concentration-time curves from 0 h to infinity for the two doses were about 2, indicating a dose proportionality. In a separate study, six healthy male volunteers received a single oral dose of 50 mg of 14C-labeled genaconazole. The Cmax values for total radioactivity (14C) and intact genaconazole were virtually identical (0.6 micrograms/ml). The mean half-lives in serum were about 73 h for both total radioactivity and genaconazole. The amounts of total radioactivity excreted in the 0 to 240-h interval (representing approximately three half-lives) in urine and feces were 66.6 and 9.3% of the dose, respectively; 64.4% of the dose was excreted in urine as parent drug. There were no detectable metabolites in either serum or urine. The data demonstrate that genaconazole (racemate) is well absorbed, undergoes negligible biotransformation, and is slowly excreted, primarily in the urine.

Administration, Oral↗
PubMed1996

A dual cofactor-specific isocitrate dehydrogenase from Pythium ultimum.

Isocitrate dehydrogenase is considered to be one of the key regulatory enzymes in the conversion of glucose into fatty acids by oleaginous microorganisms. A dual coenzyme-specific isocitrate dehydrogenase (EC 1.1.1.41) (IDH) was isolated from the primitive fungus Pythium ultimum and purified by 211-fold by sequential ion-exchange, affinity, and gel filtration chromatographies. Specific activity of the partially purified enzyme was 76.2 mumol/(min.mg protein) with NAD+ and 40% less active with NADP+. Optimum pH for activity was 8.5-9.5. K(m) values for threo-D-isocitrate and NAD+ were 0.031 and 0.55 mM, respectively. The estimated molecular mass of the IDH was 96 kDa under nondenaturing conditions and 48 kDa under denaturing conditions, suggesting that the enzyme is composed of two subunits of the same size. The enzyme was relatively stable up to 55 degrees C, but no activity was detected after exposure to 65 degrees C for 15 min. Mg2+ or Mn2+ were required for activity.

Cations, Divalent↗
PubMed1996

Expression of LAR-PTP2 in rat lung is confined to proliferating epithelia lining the airways and air sacs.

The LAR family tyrosine phosphatase LAR-PTP2B (RPTP sigma) was previously shown to be expressed in the central and peripheral nervous system. Here we show that LAR-PTP2, the larger alternatively spliced form of the gene, is expressed in proliferating undifferentiated lung epithelia in a developmentally regulated manner: Using in situ hybridization and parallel immunostaining with proliferating cell nuclear antigen to detect proliferating cells, we demonstrate that LAR-PTP2 is expressed exclusively in the undifferentiated epithelial cell layer lining the bronchi, bronchioles, and air sacs in late fetal development and in the neonatal lung. These cells correspond to Clara and fetal alveolar type II cells, as determined by parallel immunostaining with antibodies to surfactant proteins A and B. LAR-PTP2 expression declined progressively with postnatal development, and by adult stage there was no detectable expression in the airways or in the distal (type I and II) mature nonproliferating alveolar epithelial cells. These results suggest that LAR-PTP2 may be involved in the regulation of epithelial cell proliferation/differentiation during lung development.

Aging↗
PubMed1996

Effects of a nitric oxide donor and nitric oxide synthase inhibitors on acid secretion of isolated rabbit gastric glands.

The present study aims to investigate the effect of nitric oxide (NO) on histamine-stimulated acid secretion of gastric glands. An NO donor, sodium nitroprusside (SNP), and inhibitors of NO synthase such as NG-nitro-L-arginine methyl ester (L-NAME) and NG-nitro-L-arginine (L-NNA) with or without L-arginine, a substrate for NO synthase, were added to isolated rabbit gastric glands with the secretagogues. Acid secretion, intracellular concentrations of cGMP and cAMP and lactic dehydrogenase (LDH) release were determined. L-NAME and L-NNA increased stimulated acid secretion, which was reversed by L-arginine. SNP inhibited stimulated acid secretion concentration-dependently; the inhibition was accompanied by an increase in the intracellular cGMP, but neither related to cAMP nor LDH release. In conclusion, NO produced in large quantity by an NO donor inhibits histamine-stimulated acid secretion of isolated rabbit gastric glands.

Animals↗
PubMed1996

Amelioration of impaired cerebral metabolism after severe acidotic ischemia by tirilazad posttreatment in dogs.

BACKGROUND AND PURPOSE: Acidosis may contribute to ischemic injury by mobilizing iron because the iron chelator deferoxamine improves early metabolic recovery from hyperglycermic ischemia. Mobilized iron may then promote oxygen radical-induced lipid peroxidative injury during reperfusion. We tested the hypothesis that administration of the antioxidant tirilazad at the start of reperfusion improves early metabolic recovery after severe acidotic ischemia and ameliorates depletion of the endogenous antioxidant glutathione. METHODS: In anesthetized dogs, arterial glucose concentration was increased to 500 to 600 mg/dL and global incomplete cerebral ischemia was produced for 30 minutes by ventricular fluid infusion to reduce perfusion pressure to 10 to 12 mm Hg. Metabolic recovery and intracellular pH were measured by phosphorus MR spectroscopy. In the first experiment, four groups of eight dogs each received either vehicle or 0.25, 1, or 2.5 mg/kg of tirilizad mesylate at reperfusion. Cerebral blood flow was measured with microspheres. In the second experiment, two groups of eight dogs each each received either vehicle or 2.5 mg/kg of tirilazad at reperfusion, and cortical glutathione was measured at 3 hours of reperfusion. RESULTS: Cerebral blood flow decreased to approximately 6 mL/min per 100 g and intracellular pH decreased to approximately 5.6 during ischemia in all groups. In the vehicle group, ATP recovery was transient and pH remained less than 6.0. Cerebral blood flow, O2 consumption, and ATP eventually declined to near-zero levels by 3 hours. Recovery was improved by tirilazad posttreatment in a dose-dependent fashion. At the highest dose, cerebral blood flow and O2 consumption were sustained near preischemic levels, and five of eight dogs had recovery of ATP greater than 50% and of pH greater than 6.7. Recovery of ATP and phosphocreatine became significantly greater than that in the vehicle group by 17 minutes of reperfusion despite similar levels of early hyperemia, indicating that the drug was acting before the onset of hypoperfusion. Cortical glutathione concentration in the vehicle group was 27% less than that in the tirilazad group and 34% less than that in nonischemic controls. CONCLUSIONS: Decreased depletion of the endogenous antioxidant glutathione is consistent with tirilazad acting as an antioxidant in vivo. Improvement in high-energy phosphate recovery 17 minutes after starting tirilazad infusion during reperfusion is consistent with an early onset of a functionally significant oxygen radical injury. Thus, severe acidosis appears to contribute to early ischemic injury through an oxygen radical mechanism sufficient to impede metabolic recovery.

Acidosis↗