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Biomedical subjects

Y Kim

Publications and source records attributed to Y Kim.

At least 505 records · Page 28Linked to original sources
PubMed1997

Compensated cirrhosis due to viral hepatitis: using MR imaging to predict clinical progression.

OBJECTIVE: The goal of our study was to determine the relative value of multiple MR features in predicting clinical progression of disease in patients with compensated cirrhosis. MATERIALS AND METHODS: The MR examinations of 23 patients with compensated cirrhosis (Child A) were retrospectively reviewed independently by two radiologists and correlated with clinical progression after follow-up of all patients for more than 12 months each (12-87 months: average, 39 months) by the same experienced hepatologist. Clinical progression was defined as an increase of the Child grade or the Pugh score by at least two points (5- to 15-point scale). In the initial MR study of each patient, the following MR findings were assessed by each radiologist independently: volume indexes of the spleen and each segment of the liver (based on three-axis measurements), nodular surface, regenerative nodules, ascites, iron or fat deposition, and varices or collaterals. RESULTS: The volume index of the spleen was the most accurate predictor of clinical progression (p = .001), the next most accurate was the number of sites of varices or collaterals (p = .002), and the third most accurate was the ratio of caudate lobe to right lobe volume index (p = .02). Other MR findings failed to correlate with clinical progression. CONCLUSION: As revealed on MR imaging, the volume index of the spleen, the severity of varices, and the volume index ratio of caudate lobe to right lobe can be used to help predict clinical progression of disease in patients with compensated cirrhosis.

Adult↗
PubMed1997

Dexamethasone inhibits mucous glycoprotein secretion via a phospholipase A2-dependent mechanism in cultured chinchilla middle ear epithelial cells.

Inhibition or attenuation of mucous hypersecretion in middle ear epithelium is a key step toward resolution of mucoid otitis media. Mucous hypersecretion induced by platelet-activating factor (PAF) in cultured Chinchilla middle ear epithelial cells is dependent on arachidonic acid metabolites via PAF receptors, suggestive of the role of phospholipase A2 (PLA2) in mucous glycoprotein (MGP) secretion. In this study, dexamethasone added to cultured Chinchilla middle ear epithelial cells inhibited baseline and PAF-induced MGP secretion in a concentration-dependent manner. A definite time lag (16 h) was observed between administration of dexamethasone and MGP inhibition. This inhibition was reversed by the addition of exogenous PLA2 (the rate-limiting enzyme of arachidonic acid metabolism) and actinomycin D (an inhibitor of mRNA synthesis). This suggests that dexamethasone inhibits baseline and PAF-induced MGP secretion via a PLA2-dependent mechanism.

Animals↗
PubMed1997

Voiding dysfunction following transurethral resection of the prostate: symptoms and urodynamic findings.

PURPOSE: Persistent voiding dysfunction following transurethral resection of the prostate is not uncommon. We determined the correlation, if any, between the subjective complaints in men with voiding dysfunction after transurethral resection of the prostate and the urodynamic findings. MATERIALS AND METHODS: A total of 50 consecutive men with voiding dysfunction following transurethral resection of the prostate was evaluated with the American Urological Association symptom index and multichannel urodynamics. Patients with urethral stricture, urinary retention or prostate cancer were excluded from the study. Urodynamic parameters assessed included detrusor instability, bladder capacity, sphincteric insufficiency using the Valsalva leak point pressure, voiding pressure-flow studies as determined by the Abrams-Griffiths nomogram (obstructed, unobstructed or equivocal) and post-void residual. RESULTS: Mean patient age was 71 years and mean interval from last transurethral resection of the prostate was 58 months (range 2 to 252). Mean total, obstructive and irritative symptom scores were 16.3, 5.8 and 10.5, respectively. A total of 20 patients (40%) complained of incontinence (14 urge and 6 stress). According to the Abrams-Griffiths nomogram 62% of the cases were unobstructed, 16% obstructed and 22% equivocal. Urodynamic abnormalities were demonstrated in 43 patients (86%), and included detrusor instability (54%), obstruction with or without detrusor instability (16%), sphincteric insufficiency (8%), detrusor hypocontractility (4%) and sensory urgency (4%). There was no difference in the total, irritative or obstructive scores among obstructed, unobstructed or equivocal cases. Similarly there was no difference in scores among patients with and without detrusor instability. Age, number of transurethral resections and interval since last transurethral resection were unrelated to pressure-flow results or detrusor instability. Post-void residual was significantly greater in obstructed cases and bladder capacity was significantly less in those with detrusor instability. The cause of incontinence was demonstrated in 19 of 20 patients (95%): 4 (20%) had sphincteric insufficiency and 15 (75%) had detrusor instability. CONCLUSIONS: Symptoms are unreliable in predicting urodynamic findings with respect to obstruction and detrusor instability. There is a high incidence of detrusor instability in patients with voiding dysfunction after transurethral resection of the prostate. Urodynamic obstruction is a less likely occurrence.

Aged↗
PubMed1997

Structural homology of spinach acyl carrier protein and Escherichia coli acyl carrier protein based on NMR data.

Acyl carrier proteins (ACPs) from spinach and from Escherichia coli have been used to demonstrate the utility of proton NMR for comparison of homologous structures. The structure of E. coli ACP had been previously determined and modeled as a rapid equilibrium among multiple conformational forms (Kim and Prestegard, Biochemistry 28:8792-8797, 1989). Spinach ACP showed two slowly exchanging forms and could be manipulated into one form for structural study. Here we compare this single form to postulated multiple forms of E. coli ACP using the limited amount of NOE data available for the spinach protein. A number of long-range NOE contacts were present between homologous residues in both spinach and E. coli ACP, suggesting tertiary structural homology. To allow a more definitive structural comparison, a method was developed to use spinach ACP NOE constraints to search for regions of structural divergence from two postulated forms of E. coli ACP. The homologous regions of the two protein sequences were aligned, additional distance constraints were extracted from the E. coli structure, and these were mapped onto the spinach sequence. These distance constraints were combined with experimental NOE constraints and a distance geometry simulated annealing protocol was used to test for compatibility of the constraints. All of the experimental spinach NOE constraints could be successfully combined with the E. coli data, confirming the general hypothesis of structural homology. A better fit was obtained with one form, suggesting a preferential stabilization of that form in the spinach case.

Acyl Carrier Protein↗
PubMed1997

Immigration patterns, social support, and adaptation among Korean immigrant women and Korean American women.

There are little empirical data available on the mental health and social functioning of Korean American Women (both native U.S. born and foreign Korean-born U.S. residents, inclusive). State-of-the-art research used to inform social work practice is exploratory descriptive. With the goal of contributing to the social work knowledge base regarding this understudied population, this article uses an emic understanding and approach to examine immigration patterns, social support networks, and issues around adaptation experienced by Korean American women. Issues examined include gender role disruption, limited use of social services, and evidence of depressive symptoms in Korean American women and subsequent risk of substance abuse, suicide, battering, loss of employment, deficits in parenting, and mental health problems. Focus on these areas of functioning suggests the need for development of culturally competent community, family, individual, and organizational-level intervention strategies.

Acculturation↗
PubMed1996

The effect of ouabain (inhibitor of an ATP-dependent Na+/K+ pump) on the pancreas graft during preservation by the two-layer method.

To clarify how synthesized ATP is utilized to maintain cellular integrity during preservation by the two-layer method, we examined the effect of ouabain, inhibitor of ATP dependent Na+/K+ pump, on ATP tissue levels, graft weight, and vascular endothelial cells during 48 hr preservation by the two-layer method and pancreatic tissue perfusion and graft survival after transplantation in a canine model. Ouabain treatment did not affect ATP production but prevented its utilization by the sodium pump, and actually significantly increased ATP levels and decreased the weight loss of the graft. In addition, ouabain caused a significant increase of nuclear trypan-blue staining in vascular endothelial cells and a significant decrease of pancreatic tissue perfusion at reperfusion. Consequently, the grafts did not survive. We conclude that the two-layer method allows sufficient synthesis of ATP to drive the sodium pump and maintains membrane integrity of parenchymal cells and vascular endothelial cells, thus extending the period of preserved pancreatic viability.

Adenosine Triphosphate↗
PubMed1996

Direct evidence of pancreatic tissue oxygenation during preservation by the two-layer method.

The purpose of this study was to measure directly tissue oxygen tension (PO2) of the ischemically damaged pancreas graft during preservation by the two-layer (University of Wisconsin solution/perfluoro-chemical) method at 20 degrees C using Clark-type polarographic oxygen electrodes and to make clear the relationship of tissue PO2 and ATP levels during preservation and graft survival after transplantation in a canine model. During warm ischemia, tissue PO2 and ATP were dramatically decreased. Tissue PO2 continued to decrease, and tissue ATP levels were not elevated during simple storage in oxygenated University of Wisconsin solution at 20 degrees C. On the contrary, during preservation by the two-layer method at 20 degrees C, tissue PO2 promptly increased and reached about 50% of the preprocurement level at 30 min of preservation. Then, tissue PO2 was maintained this level throughout the preservation period. Tissue ATP levels were still low in the first 1 hr, but after that tissue ATP increased in a time-dependent manner. Consequently, the two-layer method at 20 degrees C could restore the viability of pancreas damaged by warm ischemia during 3- and 5-hr preservation. We conclude that the ischemically damaged pancreas grafts were oxygenated, and tissue ATP was increased during preservation by the two-layer (University of Wisconsin solution/pefluorochemical) method at 20 degrees C. Consequently, the graft was resuscitated and survived after transplantation.

Adenosine↗
PubMed1996

Transcription activation at class II CAP-dependent promoters: two interactions between CAP and RNA polymerase.

At Class II catabolite activator protein (CAP)-dependent promoters, CAP activates transcription from a DNA site overlapping the DNA site for RNA polymerase. We show that transcription activation at Class II CAP-dependent promoters requires not only the previously characterized interaction between an activating region of CAP and the RNA polymerase alpha subunit C-terminal domain, but also an interaction between a second, promoter-class-specific activating region of CAP and the RNA polymerase alpha subunit N-terminal domain. We further show that the two interactions affect different steps in transcription initiation. Transcription activation at Class II CAP-dependent promoters provides a paradigm for understanding how an activator can make multiple interactions with the transcription machinery, each interaction being responsible for a specific mechanistic consequence.

Amino Acids↗
PubMed1996

Extending the margin of safety of preservation period for resuscitation of ischemically damaged pancreas during preservation using the two-layer (University of Wisconsin solution/perfluorochemical) method at 20 degrees C with thromboxane A2 synthesis inhibitor OKY046.

We have shown that 5-hr preservation using the two-layer (University of Wisconsin solution/perfluorochemical) method at 20 degrees C allows ATP synthesis and makes it possible to resuscitate a canine pancreas subjected to 90 min of warm ischemia. However, 8 hr of preservation using this method caused a disturbance of vascular microcirculation and did not resuscitate the grafts. The aim of this study was to examine the effect of thromboxane A2 synthesis inhibitor OKY046 on vascular endothelial cells and ATP tissue levels of canine pancreas during preservation using the two-layer (University of Wisconsin solution/perfluorochemical) method at 20 degrees C, and vascular microcirculation and pancreas viability after transplantation. Graft viability was judged by graft survival following autotransplantation. ATP tissue levels were measured by high-performance liquid chromatography at the end of preservation. Viability of the vascular endothelial cells was judged using nuclear trypan blue uptake of the graft after preservation. Pancreatic tissue perfusion was measured using an H2 clearance technique after reperfusion. Pancreas grafts subjected to 90 min of warm ischemia were not viable (0/5). However, 5-hr preservation made it possible to recover the pancreas (5/5); 8-hr preservation was not successful (0/3). ATP tissue levels after 5-hr and 8-hr preservation were 9.40+/-2.09 and 7.37+/-1.06 micromol/g dry weight, respectively, and OKY046 did not affect ATP synthesis during 8-hr preservation (8.44+/-0.92 micromol/g dry weight). The percentage of nuclear trypan blue uptake of endothelial cells in 8-hr-preserved grafts was 37.6+/-11.6% and was significantly higher than the value in 5-hr-preserved grafts (5.0+/-3.0%; P<0.01). However, OKY046 significantly reduced trypan blue uptake in 8-hr-preserved grafts (8.2+/-3.6%; P<0.01). Pancreatic tissue perfusion in 8-hr-preserved grafts after 2 hr of reperfusion was 28.5+/-7.5 ml/min/100 g, and was significantly lower than the value in 5-hr-preserved grafts (57.1+/-4.4 ml/ min/100 g; P<0.01), but OKY046 dramatically improved pancreatic tissue perfusion (97.1+/-14.6 ml/min/100 g; P<0.01). As a consequence, 8-hr-preserved grafts were resuscitated (4/5). We conclude that OKY046 protects the vascular endothelium during preservation by the two-layer method at 20 degrees C and consequently improves vascular microcirculation on reperfusion. Together with ATP synthesis, which is essential for repairing damaged cells, the canine pancreas graft subjected to 90 min of warm ischemia is resuscitated during 8-hr preservation by the two-layer method at 20 degrees C. This method holds promise for pancreas-kidney transplantation from cardiac arrest donors.

Adenosine↗
PubMed1996

Inhibition of phospholipase D by a protein factor from bovine brain cytosol. Partial purification and characterization of the inhibition mechanism.

A specific protein inhibitor of partially purified bovine brain phospholipase D (PLD) was identified from bovine brain cytosol. The PLD inhibitor has been enriched through several chromatographic steps and characterized with respect to size and mechanism of inhibition. The inhibitor showed an apparent molecular mass of 30 kDa by Superose 12 gel exclusion chromatography and inhibited PLD activity with an IC50 of 7 nM. The inhibitor had neither proteolytic activity nor phospholipid-hydrolyzing activity. Because phosphatidylinositol 4,5-bisphosphate (PIP2), which is included in substrate vesicles, is an essential cofactor for PLD, we examined whether the inhibition might be mediated by sequestration of PIP2. PIP2 hydrolysis by phospholipase C (PLC)-beta1 was not affected by the inhibitor and the inhibitor did not bind to substrate vesicles containing PIP2. In contrast, a PH domain derived from PLC-delta1, which could bind to PIP2, showed a nearly identical inhibition of both PLC-beta1 and PLD activities. Thus, the PLD inhibition by the inhibitor is due to the specific interaction with not PIP2 but PLD. The suppression of PLD activity by the inhibitor was largely eliminated by the addition of ADP-ribosylation factor (ARF) and GTPgammaS. We propose that the inhibitor plays a negative role in regulation of PLD activity by PIP2 and ARF.

Animals↗
PubMed1996

Site-directed mutagenesis of residues lining a putative proton transfer pathway in cytochrome c oxidase from Rhodobacter sphaeroides.

Several putative proton transfer pathways have been identified in the recent crystal structures of the cytochrome oxidases from Paracoccus denitrificans [Iwata et al. (1995) Nature 376, 660-669] and bovine [Tsukihara (1996) Science 272, 1138-1144]. A series of residues along one face of the amphiphilic transmembrane helix IV lie in one of these proton transfer pathways. The possible role of these residues in proton transfer was examined by site-directed mutagenesis. The three conserved residues of helix IV that have been implicated in the putative proton transfer pathway (Ser-201, Asn-207, and Thr-211) were individually changed to alanine. The mutants were purified, analyzed for steady-state turnover rate and proton pumping efficiency, and structurally probed with resonance Raman spectroscopy and FTIR difference spectroscopy. The mutation of Ser-201 to alanine decreased the enzyme turnover rate by half, and was therefore further characterized using EPR spectroscopy and rapid kinetic methods. The results demonstrate that none of these hydrophilic residues are essential for proton pumping or oxygen reduction activities, and suggest a model of redundant or flexible proton transfer pathways. Whereas previously reported mutants at the start of this putative channel (e.g., Asp-132-Asn) dramatically influence both enzyme turnover and coupling to proton pumping, the current work shows that this is not the case for all residues observed in this channel.

Carbon Monoxide↗
PubMed1996

Structure of the pcbC gene encoding 2,3-dihydroxybiphenyl dioxygenase of Pseudomonas sp. P20.

Pseudomonas sp. P20 is a soil bacterium growing in biphenyl or 4-chlorobiphenyl as the sole carbon and energy source, where the initial catabolism of biphenyl to form benzoate is catalyzed by four enzymes encoded in the pcbABCD gene cluster. The nucleotide sequence of the 2,3-dihydroxybiphenyl dioxygenase gene corresponding to the pcbC gene was determined. The pcbC gene was composed of 921 base pairs with an ATG initiation codon and a TGA termination codon, which can encode a polypeptide of molecular mass 34 kDa containing 306 amino acids. A promoter-like sequence and ribosome-binding sequence were identified upstream of the initiation codon. The deduced amino acid sequence of 2,3-dihydroxybiphenyl dioxygenase exhibited 47% identity with that of corresponding enzyme of Pseudomonas sp. DJ-12, and less than 35% identity with those of other extradiol-type dioxygenases.

Amino Acid Sequence↗
PubMed1996

Polar residues in helix VIII of subunit I of cytochrome c oxidase influence the activity and the structure of the active site.

The aa3-type cytochrome c oxidase from Rhodobacter sphaeroides is closely related to eukaryotic cytochrome c oxidases. Analysis of site-directed mutants identified the ligands of heme a, heme a3, and CuB [Hosler et al. (1993) J. Bioenerg. Biomembr. 25, 121-133], which have been confirmed by high-resolution structures of homologous oxidases [Iwata et al. (1995) Nature 376, 660; Tsukihara et al. (1995) Science 269, 1069; (1996) 272, 1136]. Since the protons used to form water originate from the inner side of the membrane, and the heme a3-CuB center is located near the outer surface, the protein must convey these substrate protons to the oxygen reduction site. Transmembrane helix VIII in subunit I is close to this site and contains several conserved polar residues that could function in a rate-determining proton relay system. To test this role, apolar residues were substituted for T352, T359, and K362 in helix VIII and the mutants were characterized in terms of activity and structure. Mutation of T352, near CuB, strongly decreases enzyme activity and disrupts the spectral properties of the heme a3-CuB center. Mutation of T359, below heme a3, substantially reduces oxidase activity with only minor effects on metal center structure. Two mutations of K362, approximately 15 A below the axial ligand of heme a3, are inactive, make heme a3 difficult to reduce, and cause changes in the resonance Raman signal specific for the iron-histidine bond to heme a3. The results are consistent with a key role for T352, T359, and K362 in oxidase activity and with the involvement of T359 and K362 in proton transfer through a relay system now plausibly identified in the crystal structure. However, the characteristics of the K362 mutants raise some questions about the assignment of this as the substrate proton channel.

Amino Acid Sequence↗
PubMed1996

Characterization of the gene encoding catechol 2,3-dioxygenase of Alcaligenes sp. KF711: overexpression, enzyme purification, and nucleotide sequencing.

Catechol 2,3-dioxygenase (C23O) is an extradiol-type dioxygenase that catalyzes the aromatic ring fission of catechol to form 2-hydroxymuconic semialdehyde. The C23O gene of Alcaligenes sp. KF711 was overexpressed in Escherichia coli HB101 by using the lac promoter of pUC18, and its gene product was purified by using immunoaffinity chromatography. The purified C23O exhibited a 35-kDa single band on an SDS-polyacrylamide gel, and its ring-fission activity on dihydroxylated aromatics was 4-methylcatechol > 4-chlorocatechol > catechol > 3-methylcatechol >> 2,3-dihydroxybiphenyl. Nucleotide sequence analysis of the C23O gene revealed an open reading frame of 927 bp, which can encode a polypeptide of 308 amino acid residues. The predicted molecular mass of 35 kDa is in agreement with that of purified C23O on an SDS-polyacrylamide gel. The amino acid sequence of the C23O was compared with those of nine other extradiol-type dioxygenases, including 2,3-dihydroxybiphenyl dioxygenase (2,3-DHBD) and 1,2-dihydroxynaphthalene dioxygenase (1,2-DHND). The C23O of Alcaligenes sp. KF711 exhibited 80 to 94% identity in amino acid sequence with other C23Os, and 20 to 25% identity with 1,2-DHND and 2,3-DHBDs. Furthermore, sequence comparison of 10 extradiol-type dioxygenases has led to identifying 19 evolutionarily conserved amino acid residues whose possible catalytic roles are proposed.

Alcaligenes↗
PubMed1996

Structure of catechol 2,3-dioxygenase gene encoded in chromosomal DNA of Pseudomonas putida KF715.

A catechol 2,3-dioxygenase gene in chromosomal DNA of P. putida KF715 was cloned and its nucleotide sequence analyzed. The enzyme gene was composed of 924 base pairs with ATG initiation codon and TGA termination codon, which can encode a polypeptide of molecular weight 35 kDa containing 307 amino acids. A promoter-like sequence and a ribosome-binding sequence were identified upstream the enzyme gene. A deduced amino acid sequence of the catechol 2,3-dioxygenase exhibited 94% identity with that of corresponding enzyme in TOL plasmid and 25% identity with that of 2,3-dihydroxybiphenyl 1,2-dioxygenase from the same strain. Furthermore, sequence comparison of the catechol 2,3-dioxygenase with other extradiol-type dioxygenases has led to identify evolutionally conserved amino acid residues whose possible catalytic roles are proposed.

Amino Acid Sequence↗
PubMed1996

Evidence for a glycosylinositolphospholipid-anchored alkaline phosphatase in the aquatic plant Spirodela oligorrhiza.

Glycosylphosphatidylinositol (GPI)-anchored proteins occur widely, perhaps universally, on the surface of animal cells, where they perform a variety of important functions. However, the existence of GPI-anchored proteins on plant cells has never been established. Evidence is presented in this communication for the occurrence of a 50 kDa GPI-anchored alkaline phosphatase (AP) induced in the duckweed Spirodela oligorrhiza by phosphate deprivation. Triton X-114 partitioning of the Spirodela proteins yielded two forms of AP activity. The detergent-associated form was labeled prominently by [3H]ethanolamine, [3H]myristic acid and [3H]palmitic acid. This amphiphilic form of AP, like authentic GPI-anchored AP from mammals, was clearly resolved from the remaining, water-soluble AP activity by two types of incompletely-denaturing polyacrylamide gel electrophoresis. Lipid covalently bound to the solvent-delipidated amphiphilic AP was resistant to cleavage by phosphatidylinositol-specific phospholipase C. Strong acid or alkaline hydrolysis of the 3H-fatty acid-labeled amphiphilic AP yielded radioactive fatty acids and a radioactive lipid tentatively identified as a long chain base. The more abundant water-soluble AP was also radioactive in plants incubated with [3H]ethanolamine and was labeled to a lesser extent by 3H-fatty acids. The water-soluble AP, unlike its amphiphilic counterpart, could be freed of all fatty acid radioactivity by mild alkaline hydrolysis, indicating the continued presence of an ester-linked fatty acid. All evidence supports the conclusion that Spirodela AP is synthesized as an amphiphilic protein with a ceramide-containing GPI anchor.

Alkaline Phosphatase↗