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Biomedical subjects

J Song

Publications and source records attributed to J Song.

At least 235 records · Page 13Linked to original sources
PubMed1998

Retrograde transport of Golgi-localized proteins to the ER.

The ER is uniquely enriched in chaperones and folding enzymes that facilitate folding and unfolding reactions and ensure that only correctly folded and assembled proteins leave this compartment. Here we address the extent to which proteins that leave the ER and localize to distal sites in the secretory pathway are able to return to the ER folding environment during their lifetime. Retrieval of proteins back to the ER was studied using an assay based on the capacity of the ER to retain misfolded proteins. The lumenal domain of the temperature-sensitive viral glycoprotein VSVGtsO45 was fused to Golgi or plasma membrane targeting domains. At the nonpermissive temperature, newly synthesized fusion proteins misfolded and were retained in the ER, indicating the VSVGtsO45 ectodomain was sufficient for their retention within the ER. At the permissive temperature, the fusion proteins were correctly delivered to the Golgi complex or plasma membrane, indicating the lumenal epitope of VSVGtsO45 also did not interfere with proper targeting of these molecules. Strikingly, Golgi-localized fusion proteins, but not VSVGtsO45 itself, were found to redistribute back to the ER upon a shift to the nonpermissive temperature, where they misfolded and were retained. This occurred over a time period of 15 min-2 h depending on the chimera, and did not require new protein synthesis. Significantly, recycling did not appear to be induced by misfolding of the chimeras within the Golgi complex. This suggested these proteins normally cycle between the Golgi and ER, and while passing through the ER at 40 degrees C become misfolded and retained. The attachment of the thermosensitive VSVGtsO45 lumenal domain to proteins promises to be a useful tool for studying the molecular mechanisms and specificity of retrograde traffic to the ER.

Animals↗
PubMed1998

Regulation of G protein signalling in yeast.

A common property of cell signaling systems is the ability to adapt to chronic stimulation. A genetic analysis of receptor/G protein signaling in yeast has led to the identification of a new class of regulators of G protein signaling (RGS proteins), as well as to new insights about the regulatory role of G protein modifications (myristoylation, palmitoylation). Similar modes of regulation are now known to exist in humans. These discoveries fill some important gaps in our understanding of signal transduction, and provide an instructive example of how model organisms, like yeast, can provide new insights relevant to signal regulation in higher eukaryotes.

Animals↗
PubMed1998

Encoding of acoustic directional information by saccular afferents of the sleeper goby, Dormitator latifrons.

This paper reports on directional response properties of saccular afferents of the sleeper goby, Dormitator latifrons, to 100-Hz acoustic particle motions with a focus on testing the hypothesis that the response directionality of a fish's auditory afferents derives from the morphological polarity of sensory hair cells in the otolithic organs. Spontaneous rates (SR) and best sensitivities (BS) of saccular afferents ranged from 0 to 162 spikes/sec and from 0.2-to 100-nm RMS displacement. SR did not vary with BS. Most saccular afferents were phase-locked to sinusoidal stimulation and had sustained temporal response patterns with some adaptation. All saccular afferents were directionally sensitive to the stimulus, and the sharpness of directional response curves was determined by a directionality index (DI). The DI ranged from 0.64 to 1.50 (mean = 1.02, SE = 0.02, n = 100) and gradually decreased with stimulus level throughout afferents' response dynamic range. Many afferents had approximately symmetric directional response curves relative to their best response axes (BRA). BRA of most afferents remained constant with stimulus level. The BRA distribution had a peak along an axis that correlates closely with the morphological polarity of saccular hair cells. Therefore, our results strongly support the hypothesis.

Acoustic Stimulation↗
PubMed1998

The sensor regions of VDAC are translocated from within the membrane to the surface during the gating processes.

The motion of the sensor regions in a mitochondrial voltage-gated channel called VDAC were probed by attaching biotin at specific locations and determining its ability to bind to added streptavidin. Site-directed mutagenesis was used to introduce single cysteine residues into Neurospora crassa VDAC (naturally lacks cysteine). These were chemically biotinylated and reconstituted into planar phospholipid membranes. In the 19 sites examined, only two types of results were observed upon streptavidin addition: in type 1, channel conductance was reduced, but voltage gating could proceed; in type 2, channels were locked in a closed state. The result at type 1 sites is interpreted as streptavidin binding to sites in static regions close to the channel opening. The binding sterically interferes with ion flow. The result at type 2 sites indicates that these are located on a mobile domain and coincide with the previously identified sensor regions. The findings are consistent with closure resulting from the movement of a domain from within the transmembrane regions to the membrane surface. No single site was accessible to streptavidin from both membrane surfaces, indicating that the motion is limited. From the streptavidin-induced reduction in conductance at type 1 sites, structural information was obtained about the location of these sites.

Amino Acid Sequence↗
PubMed1998

Effect of estrogen on vascular smooth muscle cells is dependent upon cellular phenotype.

To investigate the growth-regulating action of estrogen on vascular smooth muscle cells (SMC), effects of beta-17-estradiol (beta-E2) on phenotypic modulation and proliferation of rabbit aortic SMC were observed in vitro. At 10(-8)M, beta-E2 significantly slowed the decrease in volume fraction of myofilaments (Vv myo) of freshly dispersed SMCs in primary culture, indicating an inhibitory effect of beta-E2 on spontaneous phenotypic modulation of SMC from a contractile to a synthetic phenotype. Freshly dispersed SMCs treated with beta-E2 also had a relatively longer quiescent phase than control cells before intense proliferation occurred. This was in contrast to SMCs in passage 2 3 (synthetic state), where beta-E2-treated cells replicated significantly faster than untreated cells. beta-E2 also markedly enhanced the serum-induced DNA synthesis of synthetic SMCs in a concentration-dependent manner within physiological range (10(-10)to 10(-8)M). These findings indicate that the growth-regulating effect of estrogen on vascular SMC is dependent on the cell's phenotypic state. It delays the cell cycle re-entry of the contractile SMCs by retarding their phenotypic modulation: however, once cells have modulated to the synthetic phenotype, it promotes their replication.

Animals↗
PubMed1998

Changes in three-dimensional architecture of microfilaments in cultured vascular smooth muscle cells during phenotypic modulation.

To investigate changes in the three-dimensional microfilament architecture of vascular smooth muscle cells (SMC) during the process of phenotypic modulation, rabbit aortic SMCs cultured under different conditions and at different time points were either labelled with fluorescein-conjugated probes to cytoskeletal and contractile proteins for observation by confocal laser scanning microscopy, or extracted with Triton X-100 for scanning electron microscopy. Densely seeded SMCs in primary culture, which maintain a contractile phenotype, display prominent linear myofilament bundles (stress fibres) that are present throughout the cytoplasm with alpha-actin filaments predominant in the central part and beta-actin filaments in the periphery of the cell. Intermediate filaments form a meshed network interconnecting the stress fibres and linking directly to the nucleus. Moderately and sparsely seeded SMCs, which modulate toward the synthetic phenotype during the first 5 days of culture, undergo a gradual redistribution of intermediate filaments from the perinuclear region toward the peripheral cytoplasm and a partial disassembly of stress fibres in the central part of the upper cortex of the cytoplasm, with an obvious decrease in alpha-actin and myosin staining. These changes are reversed in moderately seeded SMCs by day 8 of culture when they have reached confluence. The results reveal two changes in microfilament architecture in SMCs as they undergo a change in phenotype: the redistribution of intermediate filaments probably due to an increase in synthetic organelles in the perinuclear area, and the partial disassembly of stress fibres which may reflect a degradation of contractile components.

Actin Cytoskeleton↗
PubMed1998

Retrotransposon-related DNA sequences in the centromeres of grass chromosomes.

Several distinct DNA fragments were subcloned from a sorghum (Sorghum bicolor) bacterial artificial chromosome clone 13I16 that was derived from a centromere. Three fragments showed significant sequence identity to either Ty3/gypsy- or Ty1/copia-like retrotransposons. Fluorescence in situ hybridization (FISH) analysis revealed that the Ty1/copia-related DNA sequences are not specific to the centromeric regions. However, the Ty3/gypsy-related sequences were present exclusively in the centromeres of all sorghum chromosomes. FISH and gel-blot hybridization showed that these sequences are also conserved in the centromeric regions of all species within Gramineae. Thus, we report a new retrotransposon that is conserved in specific chromosomal regions of distantly related eukaryotic species. We propose that the Ty3/gypsy-like retrotransposons in the grass centromeres may be ancient insertions and are likely to have been amplified during centromere evolution. The possible role of centromeric retrotransposons in plant centromere function is discussed.

Amino Acid Sequence↗
PubMed1998

3-Methylcrotonyl-coenzyme A carboxylase is a component of the mitochondrial leucine catabolic pathway in plants

3-Methylcrotonyl-coenzyme A carboxylase (MCCase) is a mitochondrial biotin-containing enzyme whose metabolic function is not well understood in plants. In soybean (Glycine max) seedlings the organ-specific and developmentally induced changes in MCCase expression are regulated by mechanisms that control the accumulation of MCCase mRNA and the activity of the enzyme. During soybean cotyledon development, when seed-storage proteins are degraded, leucine (Leu) accumulation peaks transiently at 8 d after planting. The coincidence between peak MCCase expression and the decline in Leu content provides correlative evidence that MCCase is involved in the mitochondrial catabolism of Leu. Direct evidence for this conclusion was obtained from radiotracer metabolic studies using extracts from isolated mitochondria. These experiments traced the metabolic fate of [U-14C]Leu and NaH14CO3, the latter of which was incorporated into methylglutaconyl-coenzyme A (CoA) via MCCase. These studies directly demonstrate that plant mitochondria can catabolize Leu via the following scheme: Leu --> alpha-ketoisocaproate --> isovaleryl-CoA --> 3-methylcrotonyl-CoA --> 3-methylglutaconyl-CoA --> 3-hydroxy-3-methylglutaryl-CoA --> acetoacetate + acetyl-CoA. These findings demonstrate for the first time, to our knowledge, that the enzymes responsible for Leu catabolism are present in plant mitochondria. We conclude that a primary metabolic role of MCCase in plants is the catabolism of Leu.

Journal Article↗
PubMed1998

Two uterine arterial management methods in laparoscopic hysterectomy.

OBJECTIVE: The purpose of this study was to evaluate whether laparoscopic separation with coagulation of the uterine arteries and uterosacral ligaments can be used in an attempt to improve the operative procedure when hysterectomy is carried out by laparoscopic and vaginal method. METHOD: A prospective study was carried out in 70 women who underwent laparoscopic hysterectomy excluding total laparoscopic hysterectomy. Laparoscopic uterine arterial separation with coagulation (include laparoscopic reperitonization) was performed after laparoscopic detachment of the bladder and resection of the broad ligament (or adnexa) in 39 cases (Group 1). Uterine artery was coagulated by bipolar electrocoagulator and separated from the uterine side wall by scissors. Endoloop tie was applied to the arterial pedicle, if bleeding occurred. Uterine arterial management was performed through the vaginal route (include vaginal reperitonization) after laparoscopic procedure which was finished at the lower part of broad ligament with bladder detachment in 31 cases (Group 2). RESULTS: The average duration of operation was 84.0 min and 101.8 min in Groups 1 and 2, respectively (p < 0.05). The average amount of bleeding was 154.8 ml and 298.4 ml in Groups 1 and 2, respectively (p < 0.05). Hemoglobin decreased in average by 0.9 g/100 ml and 1.6 g/100 ml in Groups 1 and 2, respectively (p < 0.05). CONCLUSION: These results demonstrate that laparoscopic management of uterine arterial pedicles after bladder detachment could reduce the duration of operation time and amount of bleeding in laparoscopic hysterectomy.

Adult↗
PubMed1998

Oxidative stress response and characterization of the oxyR-ahpC and furA-katG loci in Mycobacterium marinum.

Oxidative stress response in pathogenic mycobacteria is believed to be of significance for host-pathogen interactions at various stages of infection. It also plays a role in determining the intrinsic susceptibility to isoniazid in mycobacterial species. In this work, we characterized the oxyR-ahpC and furA-katG loci in the nontuberculous pathogen Mycobacterium marinum. In contrast to Mycobacterium smegmatis and like Mycobacterium tuberculosis and Mycobacterium leprae, M. marinum was shown to possess a closely linked and divergently oriented equivalents of the regulator of peroxide stress response oxyR and its subordinate gene ahpC, encoding a homolog of alkyl hydroperoxide reductase. Purified mycobacterial OxyR was found to bind to the oxyR-ahpC promoter region from M. marinum and additional mycobacterial species. Mobility shift DNA binding analyses using OxyR binding sites from several mycobacteria and a panel of in vitro-generated mutants validated the proposed consensus mycobacterial recognition sequence. M. marinum AhpC levels detected by immunoblotting, were increased upon treatment with H2O2, in keeping with the presence of a functional OxyR and its binding site within the promoter region of ahpC. In contrast, OxyR did not bind to the sequences upstream of the katG structural gene, and katG expression did not follow the pattern seen with ahpC. Instead, a new open reading frame encoding a homolog of the ferric uptake regulator Fur was identified immediately upstream of katG in M. marinum. The furA-katG linkage and arrangement are ubiquitous in mycobacteria, suggesting the presence of additional regulators of oxidative stress response and potentially explaining the observed differences in ahpC and katG expression. Collectively, these findings broaden our understanding of oxidative stress response in mycobacteria. They also suggest that M. marinum will be useful as a model system for studying the role of oxidative stress response in mycobacterial physiology, intracellular survival, and other host-pathogen interactions associated with mycobacterial diseases.

Amino Acid Sequence↗
PubMed1998

NMR for the design of functional mimetics of protein-protein interactions: one key is in the building of bridges.

Using the design of bivalent and bridge-binding inhibitors of thrombin as an example, we review an NMR-based experimental approach for the design of functional mimetics of protein-protein interactions. The strategy includes: (i) identification of binding residues in peptide ligands by differential resonance perturbation, (ii) determination of protein-bound structures of peptide ligands by use of transferred NOEs, (iii) minimization of larger protein and peptide ligands on the basis of NMR structural information, and (iv) linkage of two weakly binding mimetics to produce an inhibitor with enhanced affinity and specificity. This approach can be especially effective for the design of potent and selective functional mimetics of protein-protein interactions because it is less likely that the surfaces of two related proteins or enzymes share two identical binding sites or regions.

Amino Acid Sequence↗
PubMed1998

Localization of endogenous ARF6 to sites of cortical actin rearrangement and involvement of ARF6 in cell spreading.

To study the function of the endogenous ARF6 GTP binding protein in cells, we generated an antibody which specifically recognizes ARF6, and not the other ARF proteins. Using this antibody, ARF6 was detected in all mouse organs tested and in a variety of cultured cell lines including RBL, MDCK, NRK, BHK, COS, and HeLa cells. In NRK cells, by immunofluorescence, ARF6 localized to the plasma membrane, especially at regions exhibiting membrane ruffling, and was also concentrated in a fine punctate distribution in the juxtanuclear region. This pattern of localization of the endogenous protein was similar to the localization of ARF6 when overexpressed in NRK, or HeLa, cells. Treatments which perturb cortical actin in NRK cells, such as replating of cells after trypsinization or treatment with phorbol ester, resulted in the recruitment of endogenous ARF6 to the regions of cortical actin rearrangement. ARF6 activation and subsequent membrane recycling was required for cell spreading activity since expression of the dominant-negative, GTP-binding defective mutant of ARF6, T27N, previously shown to inhibit ARF6-regulated membrane recycling, inhibited cell attachment and spreading in HeLa cells. Furthermore, phorbol ester treatment enhanced the cell spreading activities in NRK cells, and in HeLa cells, but was not observed in cells expressing T27N. Taken together, these observations support a role for endogenous ARF6 in modeling the plasma membrane and cortical actin cytoskeleton.

ADP-Ribosylation Factors↗
PubMed1998

Molecular bases of coronary heart disease in Koreans.

Coronary heart disease (CHD) has been considered as a multifactorial disorder with the involvement of both environmental and genetic factors. The advent of tools to investigate individual variability of DNA has allowed us to perform the association studies of candidate genes. However, an association between genetic trait and phenotypic variations is not easy to demonstrate and several reported association between genetic markers and risk factors or overt CHD have gone unconfirmed. It should not be assumed that for a given genetic trait, the impact on risk will be similar in all populations. In particular, most studies of the molecular bases of CHD have involved Caucasian subjects, so much more work with the Korean population is needed before genetic testing for susceptibility to CHD can be offered to Koreans as a clinical service. In this review, we discuss two aspects of the molecular bases of CHD: i) Molecular bases of the candidate gene related to lipoprotein metabolism including apolipoprotein AI-CIII-AIV gene duster, apolipoprotein B, apolipoprotein E-CI-CII gene cluster, apolipoprotein(a), LDL receptors, lipoprotein lipase, cholesteryl ester transfer protein, and apo B editing protein; ii) Molecular bases of the candidate gene related to thrombotic and other factors including fibrinogen, factor VII, plasminogen activator inhibitor 1, homocysteine, stromelysin, paraoxonase, and angiotensin converting enzyme. Studies involving the Korean population, especially those performed by our teams, are also summarized.

Coronary Disease↗
PubMed1998

[Correction of square face].

OBJECTIVE: This work was to provide an advanced operation method for square face correction. METHODS: The method is characterized by resecting hyperostosis of the mandibular angle, the bulky masseter and the buccal fat pad through intraoral or combined extra-intraoral approach. RESULTS: Good results were obtained in 10 cases after follow-up of 4 to 28 months. CONCLUSION: This operative method proved to be quite ideal and applicable to treat square face.

Adult↗
PubMed1998

[Detection and enrichment of fetal cells in maternal circulation for prenatal diagnosis of fetal sex].

OBJECTIVE: To study fetal cells from maternal peripheral blood for prenatal diagnosis of fetal sex. METHODS: Samples of peripheral blood in 64 women of 8-40 gestational weeks were collected to enrich the fetal nucleated red blood cells by density gradient centrifugation. DNA was extracted from each samples of enriched fetal cell for PCR amplification of Y chromosome specific DNA to determine fetal sex. RESULTS: Fetal nucleated red cells were found in 25 out of 64 maternal samples (39.06%). Y chromosome 149 bp was found in 28 cases of the 33 mothers given birth to male babies. One Y specific DNA sequence was detected in 31 women had female babies. The sensitivity was 84.85% and specificity 96.77%. The overall agreement of the diagnosis was 90.63%. CONCLUSION: Density gradient centrifugation can enrich fetal nucleated red blood cells from maternal peripheral blood. Fetal sex can be determined by PCR amplification of Y chromosome specific DNA with these fetal cells.

Blood Circulation↗
PubMed1998

[Expression of CD44 molecule and its significance in uveal and conjunctival melanomas].

The aim of this study was to evaluate the role of over expression of CD44 molecule in the development and progression of uveal and conjunctival melanomas. Flow cytometry (FCM) and immunofluorescence methods were used for detecting the CD44V expression in uveal malignant melanomas (UMM), conjunctival nevi (CN) and conjunctival malignant melanomas(CMM). The expression content of CD44 in 7 cases of CMM was significantly higher than that in 5 cases of CN (P < 0.05); the CD44V positive expression percentages in 7 cases of CMM and 40 cases of UMM were 71.43% and 62.50% respectively; the expression content of CD44V in UMM was related to scleral invasion (P = 0.0105); there was a negative correlation between the expression content of CD44V and proliferative index (PI), S-phase fraction (SPF) (P < 0.01; P < 0.05). The results suggested that the over expression of CD44V might be involved in the development of CMM and UMM and related to local infiltration ability of UMM and that the CD44V expression content detected by FCM might be helpful in discriminating CN From CMM, but this waited for further research confirmation.

Conjunctival Neoplasms↗