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Biomedical subjects

S Hwang

Publications and source records attributed to S Hwang.

At least 109 records · Page 6Linked to original sources
PubMed1996

Epitopes exposed on hepatitis delta virus ribonucleoproteins.

A total of 17 antibodies, raised in several nonhuman species and specific for different regions on the delta antigen (delta Ag), were used to map, via immunoprecipitation, those domains exposed on the surface of the viral ribonucleoprotein (RNP). These studies showed that the domains for the nuclear localization signal and the C-terminal extension, unique to the large form of delta Ag, are exposed. Also exposed is the C-terminal region of the small form of delta Ag. In contrast, reactivity was not found with the coiled-coil domain needed for protein dimerization. When the hepatitis delta virus (HDV) RNA was released by treatment of viral RNP with vanadyl ribonucleoside complexes, no change in the pattern of delta Ag epitope presentation was detected, consistent with the interpretation that a multimeric protein structure persists in the absence of RNA. These RNP studies have implications not only for understanding of the process of HDV assembly but also for evaluation of the immune responses of an infected host to HDV replication.

Animals↗
PubMed1995

Macrophages derived from C3H/HeJ (Lpsd) mice respond to bacterial lipopolysaccharide by activating NF-kappa B.

The effects of bacterial lipopolysaccharide (LPS) on macrophage gene expression are mediated in part by its ability to induce activation of transcription factor NF-kappa B. We compared the ability of LPS-treated macrophages from Lpsn (LPS-responsive) C3H/HeN and Lpsd (LPS-hyporesponsive) C3H/HeJ mice to mobilize NF-kappa B by electrophoretic mobility shift assays with oligonucleotide probes containing a unique NF-kappa B sequence from the promoter of inducible nitric oxide synthase (iNOS). In response to ng/ml concentrations of LPS, this probe bound proteins that appeared rapidly in the nuclei of thioglycollate-elicited macrophages and bone marrow-derived macrophage cell lines from both Lpsn and Lpsd mice. Only in macrophages from Lpsn mice, however, was LPS able to induce iNOS or tumor necrosis factor alpha. NF-kappa B-containing DNA-protein complexes from Lpsd macrophages were formed in lesser amounts than from Lpsn macrophages but shared the same composition, insofar as they displayed the same electrophoretic mobilities and content of heterodimers of p50/RelA (p65) and p50/c-rel. Two conclusions emerge from these findings: (1) NF-kappa B activity alone is not sufficient for induction of certain LPS-responsive genes and (2) An LPS-response pathway involving activation of NF-kappa B is preserved in Lpsd mice. The inability of cells from Lpsd mice to induce gene expression in response to LPS thus cannot be attributed to inability to activate NF-kappa B.

Animals↗
PubMed1995

Novel aspects of the regulation of a cDNA (Arf1) from Chlamydomonas with high sequence identity to animal ADP-ribosylation factor 1.

ADP-ribosylation factor (ARF) is a highly conserved, low molecular mass (ca. 21 kDa) GTP-binding protein that has been implicated in vesicle trafficking and signal transduction in yeast and mammalian cells. However, little is known of ARF in plant systems. A putative ARF polypeptide was identified in subcellular fractions of the green alga Chlamydomonas reinhardtii, based on [32P]GTP binding and immunoblot assays. A cDNA clone was isolated from Chlamydomonas (Arf1), which encodes a 20.7 kDa protein with 90% identity to human ARF1. Northern blot analyses showed that levels of Arf1 mRNA are highly regulated during 12 h/12 h light/dark (LD) cycles. A biphasic pattern of expression was observed: a transient peak of Arf1 mRNA occurred at the onset of the light period, which was followed ca. 12 h later by a more prominent peak in the early to mid-dark period. When LD-synchronized cells were shifted to continuous darkness, the dark-specific peak of Arf1 mRNA persisted, indicative of a circadian rhythm. The increase in Arf1 mRNA at the beginning of the light period, however, was shown to be light-dependent, and, moreover, dependent on photosynthesis, since it was prevented by DCMU. We conclude that the biphasic pattern of Arf1 mRNA accumulation during LD cycles is due to regulation by two different factors, light (which requires photosynthesis) and the circadian clock. Thus, these studies identify a novel pattern of expression for a GTP-binding protein gene.

ADP-Ribosylation Factor 1↗
PubMed1995

Green-fluorescent protein as a new vital marker in plant cells.

The green-fluorescent protein (GFP) from jellyfish Aequorea victoria has been used as a convenient new vital marker in various heterologous systems. However, it has been problematic to express GFP in higher eukaryotes, especially in higher plants. This paper reports that either a strong constitutive or a heat-shock promoter can direct the expression of GFP which is easily detectable in maize mesophyll protoplasts. In this single-cell system, bright green fluorescence emitted from GFP is visible when excited with UV or blue light even in the presence of blue fluorescence from the vacuole or the red chlorophyll autofluorescence from chloroplasts using a fluorescence microscope. No exogenous substrate, co-factor, or other gene product is required. GFP is very stable in plant cells and shows little photobleaching. Viable cells can be obtained after fluorescence-activated cell sorting based on GFP. The paper further reports that GFP can be detected in intact tissues after delivering the constructs into Arabidopsis leaf and root by microprojectile bombardment. The successful detection of GFP in plant cells relies on the use of a universal transcription enhancer from maize or the translation enhancer from tobacco mosaic virus (TMV) to boost the expression. This new reporter could be used to monitor gene expression, signal transduction, co-transfection, transformation, protein trafficking and localization, protein-protein interaction, cell separation and purification, and cell lineage in higher plants.

Animals↗
PubMed1995

Activation of NF-kappa B in murine macrophages by taxol.

Taxol, a plant-derived antimitotic, was recently found to mimic several of the effects of endotoxic bacterial lipopolysaccharide on murine macrophages. However, the mechanisms underlying the cell cycle-independent actions of taxol remain unclear. Here, we report that taxol rapidly activated nuclear factor kappa B (NF-kappa B) in mouse peritoneal macrophages. The intranuclear transcription factor complexes contained two NF-kappa B heterodimers, p50/RelA and p50/c-rel. Taxol-induced nuclear translocation of NF-kappa B was inhibited by pyrrolidine dithiocarbamate, an antioxidant, but not by cycloheximide, a protein synthesis inhibitor. The ability of taxol to activate NF-kappa B may help account for its induction of immunoregulatory and cytotoxic cytokines, which in turn may contribute to its antitumor effects.

Animals↗
PubMed1994

Effect of aging on murine macrophages. Diminished response to IFN-gamma for enhanced oxidative metabolism.

The ability of macrophages to secrete reactive oxygen intermediates, as well as reactive nitrogen intermediates, correlates closely with their capacity to perform two critical effector functions: intracellular killing of microorganisms and lysis of tumor cells. In this study, age-associated changes in the ability of caseinate-elicited peritoneal macrophages to release hydrogen peroxide were determined. Macrophages from aged BALB/c mice produced 50% less hydrogen peroxide than those from young mice in response to PMA or opsonized zymosan. In contrast, the production of macrophage-activating cytokines including IFN-gamma was not diminished in splenocyte supernatants from the aged group. Furthermore, no difference was detected in surface expression of IFN-gamma receptor in old and young mice. Macrophage responses to IFN-gamma, however, declined with aging. In vitro, IFN-gamma-induced release of hydrogen peroxide and nitric oxide was 50% lower in old mice than in young mice. IFN-gamma-induced tyrosine phosphorylation of MAPK, an early activation event, was undetectable in macrophages from the aged mice. These data demonstrate that diminished responses of macrophages to activating signals are one aspect of the impaired immune response in aged mice.

Aging↗
PubMed1994

Simplified nuclear grading of fine-needle aspirates of breast carcinoma: concordance with corresponding histologic nuclear grading and flow cytometric data.

Although histologic grading of breast carcinoma is widely practiced by most pathologists, cytologic grading of fine-needle aspirates (FNA) of this neoplasm is not commonly done. This study addresses the issue of the accuracy of a new classification system, a simplified Nuclear Grading (NG) system based on the criteria proposed by Black et al. (Surg Gynecol Obstet 1955;100:543) in FNA of breast carcinoma. We reviewed 100 cases of breast carcinoma, initially diagnosed by fine-needle aspiration biopsy (FNAB) with subsequent histologic confirmation, consisting of 94 ductal, five lobular, and one medullary carcinoma. NG of Papanicolaou's stained materials were reviewed twice independently by two pathologists and then were compared to the original histologic NG. The concordance rate with histology ranged from 80-90%. Intraobserver reproducibility was 86 and 88%, while interobserver reproducibility ranged from 84-88%. Of the 88 cases with corresponding flow cytometic (FCM) data, there were 35 diploid and 53 aneuploid cases. Fifty-nine (95%) of histologic high NG were aneuploid or diploid with high S-phase fraction (SPF), while 20 (77%) of histologic low NG were diploid with low SPF. This study confirms that nuclear grading of FNA of breast carcinoma using a simplified NG system has a high concordance with histology, has high intraobserver and interobserver reproducibility, and that this grading system correlates well with FCM analysis when tumors are simply divided based on NG as high or low grade.

Biopsy, Needle↗
PubMed1994

Deconvolution method for assessing the absorption of a drug with reversible metabolic pathways.

A method has been established to determine the input rate for a drug with reversible metabolic processes. This method is based on linear system properties without imposing a compartment model for describing the disposition of the drug and the metabolite and their interconnections. The solution is a deconvolution method in N-dimensional space. A general solution has been obtained for calculating the parameters needed to describe the input function. The specific solution for a staircase input function (point-area deconvolution) is explicitly derived. Using a staircase input function is not a robust method and can give negative input values when applied to simulated data sets with a large amount of variability. This suggests the need for more robust functional forms to describe the input function.

Absorption↗
PubMed1994

Control of lhc gene transcription by the circadian clock in Chlamydomonas reinhardtii.

Transcription of nuclear lhc genes has been shown to be under circadian clock control in angiosperms. but many aspects of this regulation have not been elucidated. Unicellular organisms, such as the green alga Chlamydomonas reinhardtii, offer significant advantages for the study of cellular clocks. Therefore, we have asked whether lhc gene expression is regulated by a circadian clock in C. reinhardtii. The mRNA for a photosystem I chlorophyll a/b apoprotein showed a strong diurnal rhythm in cells growing under 12 h/12 h light/dark (LD) cycles; the mRNA accumulated and then declined during the light period reaching very low levels at mid-dark. A similar diurnal pattern was documented for rbcS mRNA. In LD-grown cells shifted to continuous light, the ca. 24 h rhythm of lhca1 mRNA continued for at least 2 cycles. In LD-grown cells shifted to continuous darkness the rhythm of lhca1, but not rbcS2, mRNA also continued, although at lower absolute levels than in LD-grown cells. Also, in the cells shifted to continuous dark, the lhca1 mRNA rhythm persisted in the absence of significant cell division. Pulse-labelling with 32PO4 and sensitivity to actinomycin D demonstrated that control of lhca1 (and rbcS) is mainly transcriptional. However, it was also shown that the half-life of lhca1 mRNA (and rbcS2) is short (1-2 h) and may also vary somewhat during a cycle. We conclude that a cellular, circadian clock regulates lhca1 transcription in C. reinhardtii.

Animals↗
PubMed1994

Tick bites in Korea.

BACKGROUND: Tick bites are dermatoses not commonly encountered in Korea. Recognizing their clinical signs as well as their histopathologic findings is important in making a diagnosis of tick-related dermatoses. The incidence and causative species are different depending on the geographic areas. The histopathologic findings of tick bites are known to be a variable depending on the species of ticks involved and the duration of their bloodsucking. METHODS: Five ticks were collected from five patients and three of them were identified as Ixodes (I.) nipponensis. RESULTS: Histopathologic findings of panniculitis were prominent in four of five cases; septal panniculitis in two cases, and lobular panniculitis in the other cases. CONCLUSIONS: Ixodes nipponensis was the most common causative species of ticks responsible for tick bites in Korea, and tick bite panniculitis must be considered in the differential diagnosis of panniculitis which is mainly composed of neutrophils.

Aged↗
PubMed1993

Immune function in patients with chronic stable congestive heart failure.

The objective of this study was to ascertain whether immune abnormalities were present in a group of patients with chronic stable heart failure at a time when sympathetic drive was not excessive. Elevated sympathetic tone not only plays an important role in the pathophysiologic characteristics of congestive heart failure but may also regulate certain aspects of immune function, which has been shown to be abnormal in patients with severe heart failure. Studies have indicated a high incidence of heterophil antibodies against constituents of the heart, the presence of antibody-mediated cytotoxicity against cultured heart cells, and a decrease in suppressor and natural killer-cell function in patients with idiopathic dilated cardiomyopathy. Lymphocytes were separated over a Ficoll-Hypaque gradient. Lymphocyte subtypes and well as interleukin-2 receptors were detected by means of mouse monoclonal antibodies conjugated with fluorescein or phycoerytherin, and immunofluorescence was measured with a flow cytometer. Mitogen proliferation was assessed by tritiated thymidine incorporation in the presence of either conconavalin A or tetanus toxoid. Serum was used in conjunction with iodine 125-labeled iodopindolol binding to rat cardiac membranes to attempt to detect beta-receptor antibodies. In patients with ischemic (n = 21) and idiopathic (n = 16) cardiomyopathy, the norepinephrine levels were modestly elevated (idiopathic = 482 +/- 70 pg/ml; ischemic = 501 +/- 45 pg/ml) compared with control subjects without heart disease (n = 10; norepinephrine = 252 +/- 70 pg/ml). We found no differences in the number and subtypes of circulating lymphocytes in the three groups, and there was no serum inhibition of beta-binding to rat cardiac membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Role of polyunsaturated fatty acids as signal transducers: amplification of signals from growth factor receptors by fatty acids in mammary epithelial cells.

The growth, morphogenesis and differentiation of milk producing epithelial tissues in the developing mammary glands require interaction with extracellular matrices and stimulation by hormones, growth factors and essential fatty acids. In primary culture, the proliferation of mammary epithelial cells (MEC), induced by epidermal growth factor (EGF), is enhanced and sustained by linoleate and its eicosanoid metabolites. Since a combination of linoleic acid (18:2 omega 6) and prostaglandin E2 or cAMP has synergistic effect on EGF-stimulated growth, it is suggested that additional cAMP-dependent protein kinase A (PK-A) independent pathways may also contribute to the linoleate effect on EGF action. Possible involvement of Ca2+/phospholipid-dependent protein kinase C (PK-C) is explored. Both linoleate and arachidonate can activate Type-II and Type-III protein kinase-C in MEC and a PK-C inhibitor can block growth stimulation by EGF and fatty acids. Like 12-O-Tetradecanoly phorbol-13-acetate (TPA), a PK-C activator which also enhances EGF-stimulated growth of MEC, linoleate can phosphorylate a 40-42 KD protein. EGF itself can stimulate transient phosphorylation of the same protein in MEC cultures but when supplemented with linoleate, which does not influence the ligand binding affinity of EGF-receptors, the transient phosphorylation signal in 40-42 KD protein is sustained.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Prodromal symptoms and signs of bipolar relapse: a report based on prospectively collected data.

Prospectively collected data on 19 recently hospitalized patients with bipolar disorder were examined for prodromal changes preceding relapse. The 4-month periods before six manic and six depressive relapses were compared with each other and with a comparable period for seven patients who did not relapse. The Brief Psychiatric Rating Scale was used to assess symptoms. Significant elevations in unusual thought content were found 1 month before manic relapse. Depressive relapsers evidenced higher levels of conceptual disorganization throughout the prerelapse period. Nonrelapsers showed very stable symptom profiles.

Adult↗
PubMed1991

Changes in patient coping style following individual and family treatment for schizophrenia.

Changes in relatives' affective attitudes are important contributors to the impact of family psychoeducational programmes on the course of schizophrenia. It remains unclear whether similar changes occur in the interactional style of schizophrenic patients participating in psychoeducational treatment. This study examined changes in the interactional style (coping style) of 33 schizophrenic patients in individual or family treatment. Significant changes were seen in the interactional style of the patients participating in the individual treatment. Similar changes were evident, but not significant, in the family treatment group. The quality of patient interactional style before or after treatment did not predict relapse in either group. Changes in relatives' interactional style early in family treatment are necessary to affect the short-term course of schizophrenia. Modification in patient behaviour during the early phase does not have similar predictive value.

Adaptation, Psychological↗