Biomedical subjects

J Kim

Publications and source records attributed to J Kim.

At least 685 records · Page 38Linked to original sources

PubMed1997

Prediction of transition to chronic atrial fibrillation in patients with paroxysmal atrial fibrillation by signal-averaged electrocardiography: a prospective study.

BACKGROUND: It is well known that paroxysmal atrial fibrillation (PAF) often precedes the establishment of chronic atrial fibrillation (CAF). However, there have been no definite methods to predict the transition from PAF to CAF. The purpose of this report was to determine prospectively whether P-wave-triggered signal-averaged ECG (P-SAE) is useful for the prediction of the transition to CAF in patients with PAF. METHODS AND RESULTS: One hundred twenty-two consecutive patients with PAF were prospectively followed after P-SAE, echocardiography, and 24-hour Holter monitoring at study entry. The duration (Ad) and root-mean-square voltage for the last 30 ms (LP30) of the filtered P wave were measured in P-SAE. The abnormality of P-SAE for the prediction of transition to CAF was defined as Ad > or = 145 ms and LP30 < 3.0 microV. Twenty-three (19%; group 1) of the patients had the abnormality of P-SAE, whereas the others (group 2) did not. During the follow-up period (mean, 26+/-12 months), 10 patients (43%) in group 1 acquired CAF, whereas the transition to CAF was observed in only 4 patients (4%) in group 2. Kaplan-Meier analysis revealed that the transition to CAF was significantly observed more often in group 1 than in group 2 (log-rank test, P<.0001). The Cox proportional hazards regression model identified that the variables most significantly associated with the transition to CAF were Ad (chi2=8.6, P=.003) and LP30 (chi2=5.1, P=.02), although significant differences in the left atrial dimension (40.8+/-5.3 versus 37.3+/-5.5 mm, P<.01) and the number of atrial premature contractions (3641+/-4524 versus 1489+/-2895 beats/d, P<.05) were observed between groups 1 and 2. CONCLUSIONS: These results indicate that P-SAE could be useful to identify patients at risk for the transition from PAF to CAF.

Aged↗

PubMed1997

Repression participates in mammary tissue-specific activation of the caprine beta-lactoglobulin promoter.

Activation of the beta-lactoglobulin (BLG) gene promoter is restricted to overtly differentiated mammary tissue. To understand the mechanism underlying such tissue-specificity, activity of the caprine BLG promoter was analyzed comparatively in cultured mammary HC11 cells and non-mammary HeLa and CV-1 cells. The BLG promoter flanked by the 5'-regulatory sequence below -205 was strongly activated in the cells, regardless of the cell type. In non-mammary HeLa and CV-1 cells, this activation was repressed completely by the upper regulatory sequence. Weak repression was also observed in mammary HC11 cells kept non-confluent. As the mammary HC11 cells grew confluent and maintained the stabilized state, however, repression by the upper regulatory sequence was switched to activation. The repressive upstream flanking sequence was strongly recognized by the binding factors in non-mammary HeLa and CV-1 cells in an in vitro binding assay. Binding intensity and competition strength of the upstream regulatory regions were in a close correlation to their transcriptional repression activities in the cultured cells. The results suggest that the restricted activation of the caprine BLG promoter in differentiated mammary tissue is guaranteed by repression in non-mammary and undifferentiated mammary cells.

Animals↗

PubMed1997

Molecular basis of HLA-C recognition by p58 natural killer cell inhibitory receptors.

NK cells express several inhibitory receptors that recognize class I MHC molecules expressed on target cells. The NK cell inhibitory receptors (KIRs) provide a key regulatory function for NK cells via specific interaction with MHC/peptide complexes, but the molecular details for recognition of class I MHC molecules by KIRs still remain unclear. Here we report cDNA cloning and expression of p58 KIRs and a p50 killer cell activatory receptor (KAR) from a Korean blood donor and demonstrate direct binding between recombinant soluble p58 KIRs and recombinant soluble HLA-C molecules. We identified three p58/p50 killer cell receptors (KAR-K1, KIR-K6, and KIR-K7), which are homologous to p50 cl-39, p58 47.11, and p58 cl-6, respectively. Native gel shift assay revealed that p58 KIR-K6 and KIR-K7 bind both HLA-Cw3 and HLA-Cw6 molecules, but p50 KAR-K1 binds neither of the HLA-C molecules. However, binding of HLA-C molecule by p58 KIR is affected by the antigenic peptide bound on the MHC molecule, suggesting that the p58 KIR binding to the HLA-C molecule may be dependent on the peptide. In addition, the binding interaction requires the presence of both p58 Ig domains, suggesting that the binding mode of HLA-C and p58 KIR may have some similarity to that of the neonatal Fc receptor and the Fc fragment of Ab and may be distinct from that of TCR and MHC.

Amino Acid Sequence↗

PubMed1997

Sera from amyotrophic lateral sclerosis patients reduce high-voltage activated Ca2+ currents in mice dorsal root ganglion neurons.

This study investigated the effects of sera from amyotrophic lateral sclerosis (ALS) patients on high voltage activated (HVA) Ca2+ current in mice dorsal root ganglion (DRG) cells using whole-cell voltage-clamp method. Mice were injected with sera from healthy adults, from patients with other neurological diseases, and from patients with the sporadic form of ALS, for a period of 3 days. Sera from five of six ALS patients reduced HVA Ca2+ current amplitude. The peak Ca2+ current was significantly reduced by ALS sera while the sera from healthy adults and patients with other diseases did not alter Ca2+ current. The inactivation kinetics was altered by ALS sera, and the half-inactivation voltage shifted to more negative potential in ALS group. These results suggest that sporadic ALS serum factors may exert interactions with the HVA Ca2+ channel in DRG cells to reduce the Ca2+ current.

Adult↗

PubMed1997

Brucella abortus arginase and ornithine cyclodeaminase genes are similar to Ti plasmid arginase and ornithine cyclodeaminase.

Brucella abortus arginase and ornithine cyclodeaminase genes have been cloned and sequenced. These gene sequences are located in the same operon and occur in the same order as the homologous genes in Agrobacterium tumefaciens Ti C58 plasmid. The nucleotide sequences of the two genes have 72% and 65% identity to the respective Ti plasmid genes. Both genes are present in a single copy, and expression of arginase is regulated in response to arginine.

Agrobacterium tumefaciens↗

PubMed1997

Analysis of the phosphorylation of human heat shock transcription factor-1 by MAP kinase family members.

The activation of heat shock transcription factor-1 (HSF-1) after treatment of mammalian cells with stresses such as heat shock, heavy metals, or ethanol induces the synthesis of heat shock proteins. HSF-1 is phosphorylated at normal growth temperature and is hyperphosphorylated upon stress. We recently presented evidence that HSF-1 can be phosphorylated by the mitogen activated protein kinase, ERK1, and that such phosphorylation appears to negatively regulate the activity of HSF-1. In this report, we have tested the ability of ERK1 to phosphorylate various HSF-1 deletion mutants. Our results show that ERK1 phosphorylation is dependent on a region of HSF-1 extending from amino acids 280 to 308. This region contains three serine residues that are potential ERK1 phosphorylation sites. The region falls within a previously defined regulatory domain of HSF-1. The possibility of protein kinases other than ERK1 phosphorylating HSF-1 was also examined using in-gel kinase assays. The results show that HSF-1 can be phosphorylated in a ras-dependent manner by other members of the MAP kinase family such as JNK and p38 protein kinases and possibly others.

3T3 Cells↗

PubMed1997

Functional characterization of human nucleosome assembly protein-2 (NAP1L4) suggests a role as a histone chaperone.

Histones are thought to play a key role in regulating gene expression at the level of DNA packaging. Recent evidence suggests that transcriptional activation requires competition of transcription factors with histones for binding to regulatory regions and that there may be several mechanisms by which this is achieved. We have characterized a human nucleosome assembly protein, NAP-2, previously identified by positional cloning at 11p15.5, a region implicated in several disease processes including Wilms tumor (WT) etiology. The deduced amino acid sequence of NAP-2 indicates that it encodes a protein with a potential nuclear localization motif and two clusters of highly acidic residues. Functional analysis of recombinant NAP-2 protein purified from Escherichia coli demonstrates that this protein can interact with both core and linker histones. We demonstrate that recombinant NAP-2 can transfer histones onto naked DNA templates. Deletion mutagenesis of NAP-2 demonstrates that both NH3- and COOH-terminal domains are required for histone transfer activity. Subcellular localization studies of NAP-2 indicate that it can shuttle between the cytoplasm and the nucleus, suggesting a role as a histone chaperone. Given the potential role of the human NAP-2 gene (HGMW-approved symbol NAP1L4) in WT etiology, we have elucidated the exon/intron structure of this gene and have analyzed the mutational status of NAP-2 in sporadic WTs. Our results, coupled with tumor suppression assays in G401 WT cells, do not support a role for NAP-2 in the etiology of WT. A putative role for NAP-2 in regulating cellular differentiation is discussed.

Amino Acid Sequence↗

PubMed1997

Studies on the role of fibroblast growth factor signaling in neurogenesis using conjugated/aged animal caps and dorsal ectoderm-grafted embryos.

Basic fibroblast growth factor (bFGF) has been shown to induce neural fate in dissociated animal cap (AC) cells or in AC explants cultured in low calcium and magnesium concentrations. However, long-term disclosure of the cap may cause diffusion of the secreted molecule bone morphogenetic protein 4 (BMP-4), a neural inhibitor present in the AC. This may contribute to the subsequent neurogenesis induced by bFGF. Here we used conjugated and aged blastula AC to avoid diffusion of endogenous molecules from the AC. Unlike noggin, bFGF failed to induce neural tissue in this system. However, it enhanced neuralization elicited by a dominant negative BMP receptor (DN-BR) that inhibits the BMP-4 signaling. Posterior neural markers were turned on by bFGF in AC expressing DN-BR or chordin. Blocking the endogenous FGF signal with a dominant negative FGF receptor (XFD) mainly inhibited development of posterior neural tissue in neuralized ACs. These in vitro studies were confirmed in vivo in embryos grafted with XFD-expressing ACs in the place of neuroectoderm. Expression of some regional neural markers was inhibited, although markers for muscle and posterior notochord were still detectable in the grafted embryos, suggesting that XFD specifically affected neurogenesis but not the dorsal mesoderm. The use of these in vitro and in vivo model systems provides new evidence that FGF, although unable to initiate neurogenesis on its own, is required for neural induction as well as for posteriorization.

Animals↗

PubMed1997

Differential effects of aging on NADPH-diaphorase and VIP neurons in cerebral cortex of rats.

Age-related changes of NADPH-diaphorase (NADPH-d) and vasoactive intestinal polypeptide (VIP) were examined in the rat brain. Aged (24 months) rats showed a significant decrease in the number of VIP-immunoreactive (IR) neurons in the cerebral cortex when compared with control (4 months) rats. However, the number of NADPH-d-positive neurons was not significantly different in the two groups. Quantitative analysis of cell areas revealed a significant shrinkage of VIP-IR neurons in the aged group, whereas no further cell shrinkage was noted for NADPH-d-positive neurons compared with the control group. These morphometric results demonstrate that NADPH-d-containing neurons are more resistant to aging than the VIP-IR neurons in the cerebral cortex of rats.

Aging↗

PubMed1997

Mechanistic roles of tyrosine 149 and serine 124 in UDP-galactose 4-epimerase from Escherichia coli.

Synthesis and overexpression of a gene encoding Escherichia coli UDP-galactose 4-epimerase and engineered to facilitate cassette mutagenesis are described. General acid-base catalysis at the active site of this epimerase has been studied by kinetic and spectroscopic analysis of the wild-type enzyme and its specifically mutated forms Y149F, S124A, S124V, and S124T. The X-ray crystal structure of Y149F as its abortive complex with UDP-glucose is structurally similar to that of the corresponding wild-type complex, except for the absence of the phenolic oxygen of Tyr 149. The major effects of mutations are expressed in the values of kcat and kcat/Km. The least active mutant is Y149F, for which the value of kcat is 0.010% of that of the wild-type epimerase. The activity of S124A is also very low, with a kcat value that is 0.035% of that of the native enzyme. The values of Km for Y149F and S124A are 12 and 21% of that of the wild-type enzyme, respectively. The value of kcat for S124T is about 30% of that of the wild-type enzyme, and the value of Km is similar to that of the native enzyme. The reactivities of the mutants in UMP-dependent reductive inactivation by glucose are similarly affected, with kobs being decreased by 6560-, 370-, and 3.4-fold for Y149F, S124A, and S124T, respectively. The second-order rate constants for reductive inactivation by NaBH3CN, which does not require general base catalysis, are similar to that for the native enzyme in the cases of S124A, S124T, and S124V. However, Y149F reacts with NaBH3CN 12-20-fold faster than the wild-type enzyme at pH 8.5 and 7.0, respectively. The increased rate for Y149F is attributed to the weakened charge-transfer interaction between Phe 149 and NAD+, which is present with Tyr 149 in the wild-type enzyme. The charge-transfer band is present in the serine mutants, and its intensity at 320 nm is pH-dependent. The pH dependencies of A320 showed that the pKa values for Tyr 149 are 6.08 for the wild-type epimerase, 6.71 for S124A, 6.86 for S124V, and 6.28 for S124T. The low pKa value for Tyr 149 is attributed mainly to the positive electrostatic field created by NAD+ and Lys 153 (4.5 kcal mol-1) and partly to hydrogen bonding with Ser 124 (1 kcal mol-1). The pKa of Tyr 149 is the same as the kinetic pKa for the Bronsted base that facilitates hydride transfer to NAD+. We concluded that Tyr 149 provides the driving force for general acid-base catalysis, with Ser 124 playing an important role in mediating proton transfer.

Bacterial Proteins↗

PubMed1997

Molecular cloning and characterization of the Saccharomyces cerevisiae SAB1 gene that suppresses a temperature-sensitive phenotype of the ARS-binding factor 1 mutant.

A high-copy number suppressor gene of the yeast temperature-sensitive lethal abf1 mutant was isolated and named SAB1 (suppressor of ABF1). Chromoblot hybridization and grid-filter hybridization analyses showed that the SAB1 gene was located on chromosome IV. Deletion analyses of the SAB1 plasmid revealed that the suppressor activity was contained in a 1.1 kb DNA region. The nucleotide sequence of the 1.1 kb DNA fragment was determined and turned out to be identical to that of the yeast phosphoribosylanthranilate isomerase gene (TRP1). A binding site for ARS-Binding Factor 1 was located in the coding sequence of the TRP1 gene, which has been known to be a part of the B domain of yeast autonomously replicating sequence 1 (ARS1). Our results suggest that ABF1 might be important for the transcription of the yeast TRP1 gene in addition to having important roles in the stimulation of replication at the ARS1 locus.

Aldose-Ketose Isomerases↗

PubMed1997

Molecular characterization of a nonsuppressible allele (prC4) of the Drosophila purple gene.

Purple gene encodes 6-pyruvoyl tetrahydropterin synthase (PTP synthase) in Drosophila. The enzyme PTP synthase catalyzes the conversion of dihydroneopterin triphosphate (H2-NTP) to 6-pyruvoyl tetrahydropterin (PTP), an important intermediate for pterin compounds. The extreme purple mutant, prC4, shows a very low activity of PTP synthase. The mutant purple gene has been cloned by screening with the subgenomic library of prC4. The size and expression level of PTP synthase gene transcripts in prC4 were almost the same as those of the wild type. The genomic DNA was also examined in the purple region by Southern blot analysis, but no changes in restriction pattern could be detected. Compared with the wild type PTP synthase sequence, the mutant PTP synthase of prC4 showed three missense mutations: the replacement of alanine 7 by serine (A7S), leucine 9 by phenylalanine (L9P), and aspartic acid 168 by glycine (D168G). Significance of these mutations was discussed in relation to the formation of the oligomeric structure of PTP synthase.

Alleles↗

PubMed1997

Social network characteristics and injecting HIV-risk behaviors among street injection drug users.

As an alternative approach to individually-focused understanding of HIV risk behavior, this study explored the relationship between social network characteristics and HIV-risk injecting behaviors. Subjects were 499 inner-city injection drug users (IDUs) recruited from the streets of Baltimore, Maryland. Analysis of structural and functional network data indicates that a substantial proportion of drug sharing network members also provided social support, often because of family and sexual partner relationships. IDUs with larger drug networks which also provided social support were more likely to share needles, while IDUs with larger drug networks which did not provide social support were more likely to inject in commercial settings. The findings suggest that social support from drug network members has differential effects on injecting HIV-risk behaviors among IDUs. HIV prevention efforts should be expanded to reach drug-sharing networks and should take into account their social support relationships.

Adult↗

PubMed1997

Newborn hearing screening by otoacoustic emissions and automated auditory brainstem response.

The aim of this study is to compare pass rates for two different hearing screening methods in well newborns as a function of age. Hearing screening tests were performed on 400 ears in 200 healthy newborn infants at the University of california-Irvine Medical Center. The screening methods used were automated auditory brainstem response (ABR) and click evoked otoacoustic emissions (EOAE). The infants' ages ranged from 5 to 120 h, with an average age of 24 h. Overall, 88.5% of ears passed the ABR screen, and 79% passed the EOAE screen. There was no significant difference in the ABR pass rate for infants aged 0-24 h of age as compared with infants aged > 24 h compared with the group aged 0-24 h (P < 0.01). Results are compared with earlier studies and implications for universal hearing screening are discussed.

Age Factors↗

PubMed1997

Aluminum-induced structural alterations of the precursor of the non-A beta component of Alzheimer's disease amyloid.

The precursor of the non-A beta component of Alzheimer's disease amyloid (NACP) is a presynaptic protein whose function has been suspected to be tightly involved in neuronal biogenesis including synaptic regulations. NACP was suggested to seed the neuritic plaque formation in the presence of A beta during the development of Alzheimer's disease (AD). Recombinant NACP purified through heat treatment, DEAE-Sephacel anion-exchange, Sephacryl S-200 size-exclusion, and S-Sepharose cation-exchange chromatography steps appeared as a single band on SDS-PAGE with Mr of 19 kDa. Its N-terminal amino acid sequence clearly confirmed that the protein was NACP. Interestingly, however, the protein was split into a doublet on a nondenaturing (ND)-PAGE with equal intensities. The doublet was located slightly above a 45-kDa marker protein on a 12.5% ND-PAGE. In addition, the size of NACP was more carefully estimated as 53 kDa with high-performance gel-permeation chromatography using a TSK G3000sw size-exclusion column. Recently, Lansbury and his colleagues (Biochemistry 35, 13709-13715) have reported that NACP exists as an elongated "natively unfolded" structure which would make the protein more actively involved in protein-protein interactions and Kim (Mol. Cells 7, 78-83) has also shown that the natively unfolded protein is extremely sensitive to proteases. Here, we report that the structure of NACP could be altered by certain environmental factors. Aluminum, a suspected risk factor for AD, converged the doublet of NACP into a singlet with slightly lower mobility on ND-PAGE. Spectroscopic analysis employing uv absorption, intrinsic fluorescence, and circular dichroism indicated that NACP experienced the structural alterations in the presence of aluminum such as the secondary structure transition to generate about 33% alpha-helix. This altered structure of NACP became resistant to proteases such as trypsin, alpha-chymotrypsin, and calpain. Therefore, it is suggested that aluminum, which influences two pathologically critical processes in AD such as the protein turnover and the protein aggregation via the structural modifications, could participate in the disease.

Aluminum↗

PubMed1997

cDNAs derived from primary and small cytoplasmic Alu (scAlu) transcripts.

We have isolated and sequenced twenty-six cDNAs derived from primary Alu transcripts. Most cDNAs (22/26) sequenced end in multiple T residues, known to be at the termination for RNA polymerase III-directed transcripts. We conclude that these cDNAs were derived from authentic, RNA polymerase III-directed primary Alu transcripts. Sequence alignment of the cDNAs with Alu consensus sequences show that the cDNAs belong to different, previously described Alu subfamilies. The sequence variation observed in the 3' non-Alu regions of each of the cDNAs led us to conclude that they were derived from different genomic loci, thus demonstrating that multiple Alu loci are transcriptionally active. The subfamily distribution of the cDNAs suggests that transcriptional activity is biased towards evolutionarily younger Alu subfamilies, with a strong selection for the consensus sequence in the first 42 bases and the promoter B box. Sequence data from seven cDNAs derived from small cytoplasmic Alu (scAlu) transcripts, a processed form of Alu transcripts, also have a similar bias towards younger Alu subfamilies. About half of these cDNAs are due to processing or degradation, but the other half appear to be due to the formation of a cryptic RNA polymerase III termination signal in multiple loci. Using our sequence data, we have isolated a transcriptionally active genomic Alu element belonging to the Ya5 subfamily. In vitro transcription studies of this element suggest that its flanking sequences contribute to its transcriptional activity. The role of flanking sequences and other factors involved in transcriptional activity of Alu elements are discussed.

Base Sequence↗

PubMed1997

Cloning and developmental expression of Xenopus cDNAs encoding the Enhancer of split groucho and related proteins.

The two full-length cDNAs encoding ESG1 (Enhancer of split groucho) and related AES (Amino Enhancer of split) proteins of 767 and 197 amino acids, respectively, were cloned and sequenced from the African frog Xenopus laevis. The amino acid sequence of Xenopus ESG1 protein had 61% identity to the full-length Drosophila groucho. Xenopus AES protein exhibited 91%, 58% and 48% identity to the mouse AES, amino-terminal regions of Xenopus ESG1 and Drosophila groucho, respectively. Northern blot analysis showed that widespread RNA expression of ESG1 of 2.8 kb, ESG2 of 3.6 kb and AES of 2.2 kb transcripts were seen in adult tissues, whereas ESG1 and AES transcripts of 2.8 kb and 2.2 kb, respectively, were ubiquitously expressed in the developing embryos. The overall structural relationships of ESG and AES proteins among human, mouse, rat, Xenopus and Drosophila were analysed.

Amino Acid Sequence↗

PubMed1997

Induction of c-fos gene expression by spinal cord transection in the rat.

Sympathetic nerve activity is maintained after high spinal injury through circuits that remain in question. We evaluated patterns of c-fos gene induction as a monitor of spinal neurons responding to high spinal cord transection in the rat. Rats were anesthetized with isofluorane. Lower cervical or upper thoracic spinal segments were exposed, immersed in warm mineral oil and transected. Spinal cords were exposed but not transected in anesthetized controls. After 2.5 h, spinalized and control rats were perfused for immunocytochemistry. Cervical and thoracolumbar spinal segments and dorsal root ganglia were sectioned coronally. Tissues were incubated in primary, polyclonal antisera raised in rabbit or sheep against a peptide sequence unique to the N-terminal domain of Fos, and processed immunocytochemically. Neurons were induced to express Fos-like immunoreactivity (FLI), bilaterally, in the spinal gray, but not in primary sensory ganglia. Spinal cord transection induced neurons to express FLI in thoracic laminae I, IIo (outer substantia gelatinosa), Vre (lateral reticulated division), VII (lamina intermedia) and X, and the intermediolateral cell column. Lamina VIII was also labeled in spinal-injured but not in control animals. Immunolabeled nuclei were prominent in lumbar segments and were concentrated in the medial third of laminae I and IIo, and in laminae VII and X. Few cells were labeled in upper cervical or sacral segments. FLI was sparse in the spinal gray of controls and expressed mainly within the dorsal root entry zone of upper thoracic segments. Patterns of c-fos gene expression were site-specific and correlated with laminae that respond predominantly to noxious stimulation and that contain sympathetic interneurons. Laminae that are responsive to non-noxious stimuli and activated by walking, IIi, nucleus proprius, medial V and layer VI were not induced to express FLI. We conclude that neurons in specific spinal laminae that process high threshold afferents and that harbor neurons with sympathetic nerve-related activity are activated selectively by spinal cord transections. We hypothesize that peripheral afferents processed by spinal-sympathetic circuit neurons may regulate sympathetic discharge in the absence of supraspinal drive.

Animals↗