Biomedical subjects

M Park

Publications and source records attributed to M Park.

At least 55 records · Page 3Linked to original sources

PubMed2000

The MADS-Box factor CeMEF2 is not essential for Caenorhabditis elegans myogenesis and development.

MEF2 is an evolutionarily conserved MADS (MCM1, Agamous, Deficiens, and serum response factor) box-type transcription factor that plays a critical role in vertebrate and Drosophila melanogaster myogenesis. We have addressed the developmental role of the single MEF2-like factor, CeMEF2, in Caenorhabditis elegans. Using expression assays and two mef-2 deletion alleles, we show that CeMEF2 is not required for proper myogenesis or development. Moreover, a putative null mef-2 allele fails to enhance or suppress the phenotypes of mutants in CeMyoD or CeTwist. Our results suggest that despite its evolutionary conservation of sequence and DNA binding properties, CeMEF2 has adopted a divergent role in development in the nematode compared with Drosophila and vertebrates.

Amino Acid Sequence↗

PubMed2000

Design and synthesis of anticonvulsive agents as gamma-vinyl GABA-based potential dual acting prodrugs and their biological activities.

For the development of new anticonvulsive agents, gamma-vinyl GABA (vigabatrin) and GABA mimetics derivatives were covalently coupled as potential dual acting prodrugs and evaluated for their anticonvulsive activities. Among the prepared compounds, 11 showed the most potent anticonvulsive activity, a shorter onset time and a broader spectrum compared to vigabatrin.

Animals↗

PubMed2000

Constitutive activation of cyclin B1-associated cdc2 kinase overrides p53-mediated G2-M arrest.

Recent studies have suggested that p53 regulates the G2 checkpoint in the cell cycle and that this function is required for the maintenance of genomic integrity. In this study, we investigated a regulatory role of p53 specifically in G2-M transition. Human bladder carcinoma cells lacking functional p53 were synchronized at G1-S, which is preceded by p53-mediated G1 arrest. p53 expression in the synchronized cells was induced by infection with a recombinant adenovirus that encodes p53. After release from the G1-S arrest, the cells progressed to S-phase and G2 but failed to enter mitosis. Biochemical analysis showed that p53 inhibits cell cycle-dependent expression of cdc2 and cyclin B1 and consequently inhibits cdc2 kinase. The role of cyclin B1-associated cdc2 kinase in p53-mediated G2-M arrest was further investigated by expression of both cyclin B1 and cdc2AF, in which inhibitory phosphorylation sites were substituted. The cells expressing both cdc2AF and cyclin B1 showed a constitutive activation of cdc2 kinase during cell cycle progression and passed through G2-M regardless of p53 expression. Therefore, inactivation of cdc2 kinase through cdc2 and cyclin B1 repression is an essential step in p53-mediated G2-M arrest.

CDC2 Protein Kinase↗

PubMed2000

Structural and functional evidence for microglial expression of C1qR(P), the C1q receptor that enhances phagocytosis.

Microglial activation has been associated with several degenerative diseases of the central nervous system (CNS). One consequence of activation is the induction of a more efficient phagocytic response, and it is therefore important to determine what factors regulate microglial phagocytosis and whether this capacity influences the progression of neurodegenerative changes. Previous studies have demonstrated that complement component C1q enhances Fc receptor- and CR1-mediated phagocytosis in cells of the myeloid lineage via a cell surface receptor, C1qRp. Because C1q has been found in the area of lesions in several degenerative CNS diseases, the current investigations were carried out to characterize the effects of C1q on microglial phagocytosis. Neonatal rat microglia were shown to express C1qRp, as assessed by flow cytometry and immunocytochemistry. Interaction of these cells with substrate-bound C1q was shown to enhance both FcR-and CR1-mediated phagocytosis two- to fourfold. In addition, introduction of an antibody raised against the carboxy-terminal, cytoplasmic domain of C1qRp into microglia by electroporation markedly diminished the ability of C1q to enhance uptake of IgG-coated targets, whereas nonspecific IgG had no such effect. These results suggest that C1q in areas of active degeneration may promote the phagocytic capacity of microglia via interaction with microglial C1qRp.

Animals↗

PubMed2000

A broad-spectrum caspase inhibitor blocks concanavalin A-induced hepatitis in mice.

Fulminant hepatic failure (FHF) is a clinical syndrome resulting from massive death of liver cells or sudden and severe impairment of liver function. The causes of FHF are diverse and the overall mortality is very high. Recently, it became clear that apoptosis of hepatocytes is the critical cause of acute hepatic failure in FHF. It is well known that a family of cysteine proteases called caspase is one of the key mediators of the apoptotic pathway. Thus, caspases are attractive potential targets for the treatment of disorders resulting from excessive apoptosis. In this report, we examined the activity of a new caspase inhibitor, Xyz 033 mp. This nonpeptide inhibitor showed broad-spectrum caspase-inhibiting activity and protected primary rat hepatocytes from apoptotic death. In a mouse model of FHF induced by concavalin A (Con A), Xyz 033 mp suppressed elevated AST and ALT and specifically reduced IL-1 beta concentration. Also, Xyz 033 mp rescued mice from lethal experimental hepatitis induced by Con A. In addition, histological examinations indicated that Xyz 033 mp protected hepatocytes from the fatal apoptogenic effect of Con A. These results suggest that Xyz 033 mp may be a candidate therapeutic agent for FHF caused by massive apoptotic death of hepatocytes.

Animals↗

PubMed2000

Stress, coping, and depression in non-ulcer dyspepsia patients.

Thirty adults with upper gastrointestinal symptoms in the absence of structural organic disease diagnosed with non-ulcer dyspepsia (NUD) were compared to 30 healthy adults who had visited the hepatobiliary clinic for medical evaluation of non-organic complaints without NUD. Medical investigation in both groups were negative. Before independent gastrointestinal physicians conducted diagnostic evaluations, all subjects were evaluated for anxiety and depressive symptoms, stressful life events, coping style, and social support. The measures included Symptom Checklist 90-Revised (SCL-90-R), Beck Depression Inventory (BDI), Spielberger State-Trait Anxiety Inventory (STAI), Ways of Coping Checklist, and Interpersonal Support Evaluation List, and a self-report questionnaire, which measured the quantity of perceived stressful life events. The NUD patients reported significantly more symptoms of depression, more perceived stressful life events, less problem-focused coping, and less social support than the control subjects. Depressive symptoms were negatively correlated with interpersonal support, whereas, problem-focused coping was positively correlated with interpersonal support in the NUD patients. The two groups did not differ significantly in terms of anxiety and emotion-focused coping. The implications of these findings for the diagnosis and treatment of NUD are discussed.

Adaptation, Psychological↗

PubMed2000

Characterization of the murine homolog of C1qR(P): identical cellular expression pattern, chromosomal location and functional activity of the human and murine C1qR(P).

Human C1qR(P) is a highly glycosylated transmembrane protein that is the human C1q receptor/receptor component that in vitro mediates enhancement of Fc- and C3b-mediated phagocytosis. A human genomic clone and a murine genomic clone that is 73% identical in sequence with the coding region for human C1qR(P) cDNA have been isolated. Chromosomal localization of the human and murine gene demonstrates that these genes are syntenic. Murine cell lines of diverse myeloid origins are shown to respond to interaction of C1q with the enhancement of phagocytosis similar to that seen previously in human peripheral blood monocytes. Northern blot, RT-PCR, Western blot and FACS analyses demonstrated that mC1qR(P) is expressed in these murine myeloid cell lines, but not in a mouse epithelial cell line, similar to the cell type expression of the human gene product. A polyclonal antibody to a peptide sequence common to the deduced sequence from the both murine and human C1qR(P) inhibited the enhancement of phagocytosis response to C1q when cells were permeabilized to permit access of the antibody to the intracellular milieu. These data support the postulate that the identified murine and human genes are homologs, confirm the previously predicted intracellular location of the C-terminus of the molecule, and indicates the necessary role of this intracellular domain in transducing the signal that leads to enhancement of phagocytic function.

Amino Acid Sequence↗

PubMed2000

The Wnt/Ca2+ pathway: a new vertebrate Wnt signaling pathway takes shape.

Members of the vertebrate Wnt family have been subdivided into two functional classes according to their biological activities. Some Wnts signal through the canonical Wnt-1/wingless pathway by stabilizing cytoplasmic beta-catenin. By contrast other Wnts stimulate intracellular Ca2+ release and activate two kinases, CamKII and PKC, in a G-protein-dependent manner. Moreover, putative Wnt receptors belonging to the Frizzled gene family have been identified that preferentially couple to the two prospective pathways in the absence of ectopic Wnt ligand and that might account for the signaling specificity of the Wnt pathways. As Ca2+ release was the first described feature of the noncanonical pathway, and as Ca2+ probably plays a key role in the activation of CamKII and PKC, we have named this Wnt pathway the Wnt/Ca2+ pathway.

Animals↗

PubMed2000

Postnatal development of the dopaminergic neurons in the rat mesencephalon.

The two mesencephalic dopaminergic systems in the developing rat brain were investigated immunohistochemically by dopamine and tyrosine hydroxylase and the results were quantitatively analyzed with a computer. The number of the dopaminergic neurons in the substantia nigra and the ventral tegmentum area did not change significantly during the postnatal development. Dopaminergic terminals in the lateral septum peaked at postnatal days (PD) 30, when the cell size in middle third of the ventral tegmentum area which was suggested as an origin of this projection system, increased largely. Patchy structures in the striatum were shown most distinctly at PD 7 and disappeared at PD 35 using dopamine antibody, but there were no changes in the cell size of the substantia nigra from PD 14 to 75. Dopaminergic neurons, in general, do not show a transient change in ontogeny.

Age Factors↗

PubMed2000

Ontogeny of (D-Ala(2))-deltorphin I-like immunoreactive neurones in foetal rat brain.

Foetal rat brain from embryonic day (ED) 12-22 was immunohistochemically studied to describe the time of first appearance and further distribution patterns of (D-Ala(2))-deltorphin-I-immunoreactive (DADTI-IR) nerve elements. The primary antiserum used in this study was a polyclonal antibody against DADTI previously used in adult and postnatal rat brain mapping. DADTI-IR nerve elements first appeared in the neuroepithelium of ventral mesencephalon on ED 13. From there, positive cell bodies migrated towards the mantle layer until they invaded the whole ventral mesencephalic tegmentum. They then reached their definitive position, corresponding to a subpopulation of the A8, A9 and A10 dopaminergic neurones that had been constantly observed also in the adult age. From ED 15-17, DADTI-positive nerve fibres appeared in the medial forebrain bundle, the neostriatum anlage, the accumbens nucleus, the olfactory tubercle, the fasciculus retroflexus, and the prefrontal cortex. All these locations have also been found in adult rats. From ED 14 onwards, transient DADTI-IR somata and nerve fibres were observed in retinal neuroepithelium, optic pathways as far as the superior colliculus, CA3 hippocampal field, reticular formation in the medulla oblongata. All these locations gradually disappeared either before birth (medulla oblongata) or within the first 3 weeks after birth. These results suggest that the DADT-like molecule recognised by our antibody has during the embryonic development a regulatory function in neuronal growth and differentiation.

Analgesics, Opioid↗

PubMed2000

In vitro DNA deamination by alpha-nitrosaminoaldehydes determined by GC/MS-SIM quantitation.

The deamination of DNA bases by three alpha-nitrosaminoaldehydes, butylethanalnitrosamine, methylethanalnitrosamine, and N-nitroso-2-hydroxymorpholine (NHMOR), the direct metabolite of potent animal carcinogen N-nitrosodiethanolamine, was demonstrated by a set of in vitro experiments. The deamination of guanine, adenine, and cytosine bases in nucleotides, oligonucleotides, and calf thymus DNA gave xanthine, hypoxanthine, and uracil, respectively. The order of relative reactivities of the bases was as listed above. Deamination of cytosine to uracil was detected by the reaction of (32)P-labeled oligonucleotide ([5'-(32)P]CGAT) followed by enzymatic hydrolysis. Quantitative analysis of deamination of guanine and adenine in calf thymus DNA was performed by a gas chromatography/mass spectrometry-selected ion monitoring method. Both the extent and the rate of the deamination reactions which occur by transnitrosation from the alpha-nitrosaminoaldehyde to the base were determined for formation of xanthine and hypoxanthine. The deamination of guanine by NHMOR remained significant at low substrate levels.

Adenine↗

PubMed2000

Effects of phenethylisothiocyanate on the expression of glutathione S-transferases and hepatotoxicity induced by acetaminophen.

1. The effect of PEITC on the expression of hepatic glutathione S-transferases (GST) and the glutathione (GSH) conjugation has been investigated in the Sprague-Dawley rat, and it has been determined whether hepatotoxicity of acetaminophen (AA) could be inhibited through the induction of GST expression in mouse. 2. The hepatic GST activity and protein levels of alpha class (Ya, Yc) and mu class (Yb1, Yb2) of GST were elevated in a dose-dependent manner after treatment with PEITC (0, 3.16, 10, 31.6, 100 and 200 mg/kg, p.o., 3 days). The mRNA levels of GST Ya and GST Yb1 were also markedly increased 1 day after treatment with PEITC at dosages ranging from 31.6 to 200 mg/kg. The hepatic GSH content was significantly increased to 200% of control at dose of 200 mg/kg PEITC. 3. Pretreatment with 100 mg/kg PEITC significantly enhanced the biliary excretion of glutathione conjugate of AA 2-fold, whereas treatment with 200 mg/kg did not affect it. 4. In mouse, PEITC (100 and 200 mg/kg, 3 days) decreased the lethality and hepatotoxicity caused by AA. 5. These results indicate that (1) the induction of GST by PEITC is presumably under transcriptional regulation, and (2) PEITC may have a protective function against AA-induced hepatotoxicity by induction effect on GST, in combination of enhancement of hepatic GSH.

Acetaminophen↗

PubMed2000

Identification of a new vertebrate nucleoporin, Nup188, with the use of a novel organelle trap assay.

The study of the nuclear pore in vertebrates would benefit from a strategy to directly identify new nucleoporins and interactions between those nucleoporins. We have developed a novel two-step "organelle trap" assay involving affinity selection and in vitro pore assembly. In the first step, soluble proteins derived from Xenopus egg extracts are applied to a column containing a ligand of interest. The bound proteins are then tagged by biotinylation and eluted. In the second step, potential nucleoporins are selected for by virtue of their ability to assemble into annulate lamellae, a cytoplasmic mimic of nuclear pores. The incorporated proteins are then recognized by their biotin tag. Here we use the lectin wheat germ agglutinin (WGA) as ligand; WGA inhibits nuclear transport and has been shown to directly bind three known nucleoporins from Xenopus extract, Nup62, Nup98, and Nup214, all of which contain N-acetylglucosamine residues. Under reduced-stringency conditions, three additional proteins bind to WGA-Sepharose and are revealed by the organelle trap assay. We identified all three as partner nucleoporins. Two were discovered to be Xenopus Nup93 and Nup205. The third is a novel vertebrate nucleoporin, Nup188. This new vertebrate protein, Xenopus Nup188, exists in a complex with xNup93 and xNup205. The Nup93-Nup188-Nup205 complex does not bind directly to WGA but binds indirectly via the N-acetylglucosamine-modified nucleoporins. A gene encoding human Nup188 was also identified. The discovery of vertebrate Nup188, related to a yeast nucleoporin, and its novel protein-protein interactions illustrates the power of the two-step organelle trap assay and identifies new building blocks for constructing the nuclear pore.

Acetylglucosamine↗

PubMed2000

Cbl-transforming variants trigger a cascade of molecular alterations that lead to epithelial mesenchymal conversion.

Dispersal of epithelial cells is an important aspect of tumorigenesis, and invasion. Factors such as hepatocyte growth factor induce the breakdown of cell junctions and promote cell spreading and the dispersal of colonies of epithelial cells, providing a model system to investigate the biochemical signals that regulate these events. Multiple signaling proteins are phosphorylated in epithelial cells during hepatocyte growth factor-induced cell dispersal, including c-Cbl, a protooncogene docking protein with ubiquitin ligase activity. We have examined the role of c-Cbl and a transforming variant (70z-Cbl) in epithelial cell dispersal. We show that the expression of 70z-Cbl in Madin-Darby canine kidney epithelial cells resulted in the breakdown of cell-cell contacts and alterations in cell morphology characteristic of epithelial-mesenchymal transition. Structure-function studies revealed that the amino-terminal portion of c-Cbl, which corresponds to the Cbl phosphotyrosine-binding/Src homology domain 2, is sufficient to promote the morphological changes in cell shape. Moreover, a point mutation at Gly-306 abrogates the ability of the Cbl Src homology domain 2 to induce these morphological changes. Our results identify a role for Cbl in the regulation of epithelial-mesenchymal transition, including loss of adherens junctions, cell spreading, and the initiation of cell dispersal.

Animals↗

PubMed2000

Activation of cdc42, rac, PAK, and rho-kinase in response to hepatocyte growth factor differentially regulates epithelial cell colony spreading and dissociation.

Hepatocyte growth factor (HGF), the ligand for the Met receptor tyrosine kinase, is a potent modulator of epithelial-mesenchymal transition and dispersal of epithelial cells, processes that play crucial roles in tumor development, invasion, and metastasis. Little is known about the Met-dependent proximal signals that regulate these events. We show that HGF stimulation of epithelial cells leads to activation of the Rho GTPases, Cdc42 and Rac, concomitant with the formation of filopodia and lamellipodia. Notably, HGF-dependent activation of Rac but not Cdc42 is dependent on phosphatidylinositol 3-kinase. Moreover, HGF-induced lamellipodia formation and cell spreading require phosphatidylinositol 3-kinase and are inhibited by dominant negative Cdc42 or Rac. HGF induces activation of the Cdc42/Rac-regulated p21-activated kinase (PAK) and c-Jun N-terminal kinase, and translocation of Rac, PAK, and Rho-dependent Rho-kinase to membrane ruffles. Use of dominant negative and activated mutants reveals an essential role for PAK but not Rho-kinase in HGF-induced epithelial cell spreading, whereas Rho-kinase activity is required for the formation of focal adhesions and stress fibers in response to HGF. We conclude that PAK and Rho-kinase play opposing roles in epithelial-mesenchymal transition induced by HGF, and provide new insight regarding the role of Cdc42 in these events.

Actins↗

PubMed2000

Case management model for a community-based multiple sclerosis clinic.

This article describes the process from inception to successful operation of a case management model of a community-based multiple sclerosis clinic. The article includes information regarding the pathophysiology, diagnosis, and clinical manifestations of multiple sclerosis. The assessment, planning, and intervention stages of the process are explained, and a case study of one clinic patient is provided.

Adult↗

PubMed2000

Physiological regulation of uteroglobin/CCSP expression.

Uteroglobin/CCSP is expressed specifically in the Clara cells. This allows the gene to be used as a marker to identify the elements regulating the physiologic and cell-specific expression of this gene. The regulation of UG/CCSP by IFN-gamma was shown to be at the level of the proximal promoter by the upregulation of HNF3 beta. This has allowed the determination of the factors responsible for the expression of UG/CCSP.

Animals↗

PubMed2000

Enhanced transformation by a plasma membrane-associated met oncoprotein: activation of a phosphoinositide 3'-kinase-dependent autocrine loop involving hyaluronic acid and CD44.

A Met-hepatocyte growth factor receptor oncoprotein, Tpr-Met, generated by chromosomal rearrangement, fuses a protein dimerization motif with the cytoplasmic domain of the Met receptor, producing a cytosolic, constitutively activated tyrosine kinase. Although both the Met receptor and the Tpr-Met oncoprotein associate with the same substrates, activating mutations of the Met receptor in hereditary papillary renal carcinomas have different signaling requirements for transformation than Tpr-Met. This suggests differential activation of membrane-localized pathways by oncogenic forms of the membrane-bound Met receptor but not by the cytoplasmic Tpr-Met oncoprotein. To establish which pathways might be differentially regulated, we have localized the constitutively activated Tpr-Met oncoprotein to the membrane using the c-src myristoylation signal. Membrane localization enhances cellular transformation, focus formation, and anchorage-independent growth and induces tumors with a distinct myxoid phenotype. This correlates with the induction of hyaluronic acid (HA) and the presence of a distinct form of its receptor, CD44. A pharmacological inhibitor of phosphoinositide 3' kinase (PI3'K), inhibits the production of HA, and conversely, an activated, plasma membrane-targeted form of PI3'K is sufficient to enhance HA production. Furthermore, the multisubstrate adapter protein Gab-1, which couples the Met receptor with PI3'K, enhances Met receptor-dependent HA synthesis in a PI3'K-dependent manner. These results provide a positive link to a role for HA and CD44 in Met receptor-mediated oncogenesis and implicate PI3'K in these events.

Adaptor Proteins, Signal Transducing↗