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Biomedical subjects

E Kim

Publications and source records attributed to E Kim.

At least 19 recordsLinked to original sources
PubMed2002

Extremely low vertical-emittance beam in the accelerator test facility at KEK.

Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.

Journal Article↗
PubMed2002

Novel genes expressed in subsets of chemosensory sensilla on the front legs of male Drosophila melanogaster.

Detection of courtship-activating female pheromones by contact chemoreceptors on the front legs of male Drosophila melanogaster is thought to play an important role in triggering courtship behavior. However, the chemosensory organs, cells, and molecules responsible are not known. We have isolated two genes, CheA29a and CheB42a, expressed in nonneuronal auxiliary cells within two nested subsets of chemosensory sensilla on the front legs of sexually mature, adult males. The proteins encoded by the CheA29a and CheB42a genes have no sequence similarity to each other or any other known protein, but they belong to two novel families of proteins encoded by the D. melanogaster genome. Members of the two families are predicted to have a single transmembrane domain at their amino terminus, probably to serve as a signal peptide, suggesting that they are soluble and secreted. Finally, in addition to CheA29a and CheB42a, other genes within each family are expressed preferentially in appendages where chemosensory organs are concentrated, in several cases in a male-specific manner. Our data suggest that CheA29a and CheB42a and other members of these two protein families are involved in male-specific chemical senses, perhaps pheromone response.

Amino Acid Sequence↗
PubMed2002

Condensation of 3He and reentrant superfluidity in submonolayer 3He- 4He mixture films on H2.

We have studied the effect of 3He on the superfluid response of submonolayer 4He films adsorbed on H2. In a limited range of 4He coverage, the introduction of 3He brings forth sequentially the normal, superfluid, and the normal phase again. This novel behavior is very likely the consequence of the condensation of the 3He atoms confined near the free surface of the superfluid 4He film into a self-bound 2D liquid.

Journal Article↗
PubMed2002

Effects of risperidone on information processing and attention in first-episode schizophrenia.

Risperidone appears to have a beneficial effect in several areas of cognitive function in schizophrenic patients. In previous studies, however, the clinical characteristics of the subjects differed between studies, and were heterogeneous even in single study. Most of the subjects were previously exposed to different kinds of neuroleptics and some of them were treatment-resistant. The aim of this study is to evaluate the effect of risperidone on attention and information processing in a homogeneous subgroup of schizophrenic patients, i.e. drug-naïve first-episode inpatients. In the patient group (n=17), cognitive tests and clinical assessments were performed before and after 8 weeks of risperidone treatment. The same cognitive tests were administered to the control group (n=24). The delay between test and retest was 8 weeks. Before treatment, the patient group performed significantly worse than control group on the tests measuring continuous attention, vigilance, and the speed of information processing. After treatment (the average dose of risperidone was 7.3mg/day), in spite of significant improvement of the clinical symptoms, the patients did not show any significant improvement or worsening in most of the items of these tests. The control group did not show any practice effect. These results suggest that first-episode schizophrenic patients have deficits in sustained attention and vigilance to visual stimuli, as well as the speed of information processing to visual and auditory stimuli, and these deficits are unrelated to clinical symptoms and remain stable during the early phase of treatment. This study did not receive pharmaceutical company financial support.

Adolescent↗
PubMed2002

Measurement of neutron dose with an organic liquid scintillator coupled with a spectrum weight function.

A dose evaluation method for neutrons in the energy range of a few MeV to 100 MeV has been developed using a spectrum weight function (G-function), which is applied to an organic liquid scintillator of 12.7 cm in diameter and 12.7 cm in length. The G-function that converts the pulse height spectrum of the scintillator into the ambient dose equivalent, H*(10), was calculated by an unfolding method using successive approximation of the response function of the scintillator and the ambient dose equivalent per unit neutron fluence (H*(10) conversion coefficients) of ICRP 74. To verify the response function of the scintillator and the value of H*(10) evaluated by the G-function. pulse height spectra of the scintillator were measured in some different neutron fields, which have continuous energy, monoenergetic and quasi-monoenergetic spectra. Values of H*(10) estimated using the G-function and pulse height spectra of the scintillator were compared with those calculated using neutron energy spectra. These doses agreed with each other. From the results, it was concluded that H*(10) can be evaluated directly from the pulse height spectrum of the scintillator by applying the G-function proposed in this study.

Light↗
PubMed2002

Measurement of lineal-energy distributions for neutrons of 8 keV to 65 MeV by using a tissue-equivalent proportional counter.

The lineal-energy spectra for monoenergetic and quasi-monoenergetic neutrons of 8 keV to 65 MeV were obtained using a tissue-equivalent proportional counter (TEPC). The frequency-mean lineal energy, the dose-average lineal energy and mean quality factor were estimated from the measured data. The neutron absorbed doses obtained with this TEPC were compared with the kerma coefticient for A-150 plastic defined by ICRP 26 and the mean quality factors were compared with the data of ICRP 74. respectively. These comparisons indicated good agreement between them.

Alpha Particles↗
PubMed2002

Morganelliasis pneumonia in a captive jaguar.

Suppurative bronchopneumonia was discovered in a 6-yr-old male jaguar (Panthera onca onca) that died after a 1 wk history of anorexia, depression, and respiratory difficulty. Morganella morganii was isolated as a pure culture from the lung, spleen, and heart blood. This is the first record of M. morganii induced pneumonia in a jaguar.

Animals↗
PubMed2001

Mapping of the interaction sites between apoptosis linked gene ALG-2 and HEED.

The apoptosis linked gene (ALG-2) is a 22 kDa Ca2+-binding protein of the penta EF-hand motif family. ALG-2 was discovered in a "death trap" assay using T-cell receptor-mediated apoptosis. Depletion of ALG-2 using an anti-sense ALG-2 construct inhibits apoptosis that is induced by several stimuli, such as staurosporin, dexamethason, Fas, and glucocorticoid. The Ca2+-dependent function of ALG-2 is consistent with the observation that the cytoplasmic Ca2+ level is elevated in apoptotic cells. We found that ALG-2 interacted specifically with the carboxy-terminal region of HEED using a yeast two-hybrid assay system. The mutants of HEED were constructed by deleting five WD repeat motifs one by one from the C-terminus of the protein. These mutants of ALG-2 were made by combining the EF hand Ca2+ binding motifs in various ways. Mapping of the interaction sites, using each of the mutants, revealed that the interaction between HEED and a third EF-hand motif of ALG-2 was stronger than the other combination.

Apoptosis Regulatory Proteins↗
PubMed2001

Identification of structural domains affecting transactivation potential of Nm23.

The strong transactivation activity of the C-terminal half (amino acids 76-152) of Nm23 was reported previously. Here we examined a structural domain preventing or necessary to its transactivation activity. The C-terminal 1/4 (amino acids 109-152) was sufficient for transactivation, but the C-terminal half with a longer N-terminal extension (amino acids 58-152) caused the loss of the transactivation ability. Furthermore, coexpression of the N-terminal half with the C-terminus of Nm23-H1 blocked the transactivation activity of the C-terminal half, where direct interaction of both truncated proteins was demonstrated in vitro. Transactivation activities in the C-terminal halves of the known mutants (P96S, H118F, S120G, and S120A) exhibiting differential antimetastasis effects were also tested. Significant reduction of transactivation activity was observed only in H118F, indicating that NPD kinase active-site histidine is required. This suggests that transactivation potential of Nm23 is related to NDP kinase activity but not to metastasis suppressor activity.

Binding Sites↗
PubMed2001

Inhibition of the EGF-induced activation of phospholipase C-gamma1 by a single chain antibody fragment.

Phospholipase C-gamma1(PLC-gamma1) is known to play an essential role in various cellular responses, such as proliferation and tumorigenesis, and PLC-gamma1-specific inhibitors are commonly employed to investigate the mechanism of the PLC-gamma1-mediated signaling pathway. In this study, we developed a single chain antibody fragment (scFv) as a blocker for PLC-gamma1 mediated signaling. scFv, designated F7-scFv, specifically bound to PLC-gamma1 with high affinity (K(d)=1.9x10(-8) M) in vitro. F7-scFv also bound to PLC-gamma1 in vivo and altered the distribution pattern of PLC-gamma1 from the cytoplasm to the intracellular aggregates, where F7-scFv was localized. Moreover, F7-scFv interrupted the EGF-induced translocation of PLC-gamma1 from the cytosol to the membrane ruffle and attenuated EGF-induced inositol phosphates generation and intracellular calcium mobilization. These results indicate that F7-scFv blocks EGF-induced PLC-gamma1 activation by causing sequestering of PLC-gamma1 into intracellular aggregates, and may therefore be useful in studies of the PLC-gamma1-mediated signaling pathway.

Amino Acid Sequence↗
PubMed2001

Apoptosis-linked gene 2 binds to the death domain of Fas and dissociates from Fas during Fas-mediated apoptosis in Jurkat cells.

Apoptosis-linked gene 2 (ALG-2) is a member of the family of Ca(2+)-binding proteins with penta-EF-hand and is essential for the execution of apoptosis by various signals including Fas activation. We studied the regulation of ALG-2 during Fas-mediated apoptosis in Jurkat cells. The 22-kDa ALG-2 protein is cleaved and becomes a 19-kDa protein after Fas activation. The appearance of 19-kDa ALG-2 protein increases for 4 h after treatment with 200 ng/ml of anti-Fas Ab treatment and gradually degrades afterward. Confocal microscopic analysis showed that ALG-2 translocated from the plasma membrane to the cytosol during Fas-mediated apoptosis. Therefore, we examined if ALG-2 interacts with Fas. The protein-protein interaction of ALG-2 with Fas was demonstrated using yeast two-hybrid assays as well as in vitro GST pull-down assay. Endogenous ALG-2 was immunoprecipitated with anti-Fas Ab in Jurkat cells without Fas activation. However, the endogenous ALG-2 was no longer immunoprecipitated with anti-Fas Ab 2 h after anti-Fas Ab treatment. This study, for the first time, presents a direct molecular connection of ALG-2 to apoptosis by its direct interaction with Fas, and enlists ALG-2 as a new member of posttranslationally modified proteins during Fas-mediated apoptotic process.

Apoptosis↗
PubMed2001

Apoptosis induced by human Fas-associated factor 1, hFAF1, requires its ubiquitin homologous domain, but not the Fas-binding domain.

FAF1 is a Fas-binding protein without typical death domain. Instead, FAF1 has several domains found in proteins of ubiquitination pathway. Transient overexpression of hFAF1 in BOSC23 cells caused membrane blebbing and cell body condensation which were characteristics of apoptosis. Subsequent analysis revealed that overexpression of hFAF1 induced nuclear condensation, appearance of phosphatidylserines in the outer leaflet of the cellular membrane, and caspase 3 activation. The apoptotic potential of hFAF1 required downstream ubiquitin homologous domain (UB2) and adjacent nuclear localization signal but not the Fas-binding domain. Our data showed that mere intrinsic overexpression of hFAF1 initiated apoptosis in the absence of any extrinsic death signal in BOSC23 cells.

Active Transport, Cell Nucleus↗
PubMed2001

Probing the structure of F-actin: cross-links constrain atomic models and modify actin dynamics.

Cross-links between protomers in F-actin can be used as a very sensitive probe of both the dynamics and structure of F-actin. We have characterized filaments formed from a previously described yeast actin Q41C mutant, where disulfide bonds can be formed between the Cys41 that is introduced into subdomain-2 and Cys374 on an adjacent protomer. We find that the distribution of cross-linked n-mers shows no cooperativity and corresponds to a random probability cross-linking reaction. The random distribution suggests that disulfide formation does not cause a significant perturbation of the F-actin structure. Consistent with this lack of perturbation, three-dimensional reconstructions of extensively cross-linked filaments, using a new approach to helical image analysis, show very small structural changes with respect to uncross-linked filaments. This finding is in conflict with refined models but in agreement with the original Holmes et al. model for F-actin. Under conditions where 94 % of the protomers are linked by disulfide bonds, the distribution of filament twist becomes more heterogeneous with respect to control filaments. A molecular model suggests that strain, introduced by the disulfide, is relieved by increasing the twist of the long-pitch actin helices. Disulfide formation makes yeast actin filaments approximately three times less flexible in terms of bending and similar, in this respect, to vertebrate skeletal muscle F-actin. These observations support previous reports that the rigidity of F-actin can be controlled by the position of subdomain-2, and that this region is more flexible in yeast F-actin than in skeletal muscle F-actin.

Actins↗
PubMed2001

Nephrocystin interacts with Pyk2, p130(Cas), and tensin and triggers phosphorylation of Pyk2.

Juvenile nephronophthisis type 1 is caused by mutations of NPHP1, the gene encoding for nephrocystin. The function of nephrocystin is presently unknown, but the presence of a Src homology 3 domain and its recently described interaction with p130(Cas) suggest that nephrocystin is part of the focal adhesion signaling complex. We generated a nephrocystin-specific antiserum and analyzed the interaction of native nephrocystin with endogenous proteins. Immunoprecipitation of nephrocystin revealed that nephrocystin forms protein complexes with p130(Cas), proline-rich tyrosine kinase 2 (Pyk2), and tensin, indicating that these proteins participate in a common signaling pathway. Expression of nephrocystin resulted in phosphorylation of Pyk2 on tyrosine 402 as well as activation of downstream mitogen-activated protein kinases, such as ERK1 and ERK2. Our findings suggest that nephrocystin helps to recruit Pyk2 to cell matrix adhesions, thereby initiating phosphorylation of Pyk2 and Pyk2-dependent signaling. A lack of functional nephrocystin may compromise Pyk2 signaling in a subset of renal epithelial cells.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Trifluoroacetic acid activates ATP-sensitive K(+) channels in rabbit ventricular myocytes.

Recent in vivo experimental evidence suggests that isoflurane-induced cardioprotection may involve K(ATP) channel activation during myocardial ischemia. The actual effect of isoflurane on cardioprotective ion conductance, however, such as that mediated by the opening of K(ATP) channels, has been the subject of some controversy in the past. The investigation reported here used a patch-clamp technique to test the hypothesis that a metabolite of isoflurane, trifluoroacetic acid (TFA), contributes to isoflurane-induced cardioprotection via K(ATP) channel activation. TFA enhanced channel activity in a concentration-dependent fashion, exhibiting half-maximal activation at 0.03 mM. TFA increased the number of openings of the channel, but did not affect the single channel conductance of K(ATP) channels. Analysis of open and closed time distributions showed that TFA increased the burst duration and decreased the interburst interval without eliciting changes of less than 5 ms in open and closed time distributions. TFA diminished the ATP sensitivity of K(ATP) channels in a concentration-response relationship for ATP. These results imply that TFA could mediate isoflurane-induced cardioprotection via K(ATP) channel activation during myocardial ischemia and reperfusion.

Adenosine Triphosphate↗
PubMed2001

Regulation of dendritic spine morphology by SPAR, a PSD-95-associated RapGAP.

The PSD-95/SAP90 family of scaffold proteins organizes the postsynaptic density (PSD) and regulates NMDA receptor signaling at excitatory synapses. We report that SPAR, a Rap-specific GTPase-activating protein (RapGAP), interacts with the guanylate kinase-like domain of PSD-95 and forms a complex with PSD-95 and NMDA receptors in brain. In heterologous cells, SPAR reorganizes the actin cytoskeleton and recruits PSD-95 to F-actin. In hippocampal neurons, SPAR localizes to dendritic spines and causes enlargement of spine heads, many of which adopt an irregular appearance with putative multiple synapses. Dominant negative SPAR constructs cause narrowing and elongation of spines. The effects of SPAR on spine morphology depend on the RapGAP and actin-interacting domains, implicating Rap signaling in the regulation of postsynaptic structure.

Actins↗
PubMed2001

ARF binds the C-terminal region of the Escherichia coli heat-labile toxin (LTA1) and competes for the binding of LTA2.

Cholera toxin (CT) and the heat-labile enterotoxin (LT) from Escherichia coli are highly related in terms of structure and biochemical activities and are the causative agents of cholera and traveler's diarrhea, respectively. The pathophysiological action of these toxins requires their activity as ADP-ribosyltransferases, transferring the ADP-ribose moiety from NAD onto the stimulatory, regulatory component of adenylyl cyclase, Gs. This reaction is highly dependent on the protein cofactor, termed ADP-ribosylation factor (ARF), that is itself a 20 kDa regulatory GTPase. In this study, we define sites of interaction between LTA and human ARF3. The residues identified as important to ARF binding include several of those previously shown to bind to the A2 subunit of the toxin and those important to the organization of two flexible loops, previously implicated as regulators of substrate entry. A model for how ARF acts to enhance the catalytic activity is proposed. A critical portion of the overlap between ARF and LTA(2) in binding LTA(1) includes a short region of sequence homology between LTA(2) and the switch II region of ARF. LTA(2) also interacted with ARF effectors in two-hybrid assays, and thus, we discuss the possibility that the LTA(2) subunit may function in cells as a partial ARF mimetic to compete for the binding of ARF to LTA(1) or regulate aspects of the toxin's transport from the cell surface to the ER.

ADP-Ribosylation Factors↗