Biomedical subjects

M Li

Publications and source records attributed to M Li.

At least 163 records · Page 9Linked to original sources

PubMed2001

Phosphorylation of p90rsk during meiotic maturation and parthenogenetic activation of rat oocytes: correlation with MAP kinases.

This paper reports on the activation of p90rsk during meiotic maturation and the inactivation of p90rsk after electrical parthenogenetic activation of rat oocytes. In addition, the correlation between p90rsk and MAP kinases after different treatments was studied. We assessed p90rsk activity by examining its electrophoretic mobility shift on SDS-PAGE and evaluated ERK1+2 activity by both mobility shift and a specific antibody against phospho-MAP kinase. The phosphorylation of p90rsk during rat oocyte maturation was a sequential process that may be divided into two stages: the first stage was partial phosphorylation, which was irrelevant with MAP kinases because p90rsk phosphorylation took place prior to activation of MAP kinases. The second stage inferred full activation occurred at the time when MAP kinases began to be activated (3 h after germinal visicle breakdown). Evidence for the involvement of MAP kinases in the p90rsk phosphorylation was further obtained by the following approaches: (1) okadaic acid (OA) accelerated the phosphorylation of both MAP kinases and p90rsk; (2) OA induced phosphorylation of both MAP kinases and p90rsk in the presence of IBMX; (3) when activation of MAP kinases was inhibited by cycloheximide, p90rsk phosphorylation was also abolished; (4) dephosphorylation of p90rsk began to take place at 3 h post-activation, temporally correlated with the completion of MAP kinase inactivation; (5) phosphorylation of both kinases was maintained in oocytes that failed to form pronuclei after stimulation; (6) OA abolished the dephosphorylation of both kinases after parthenogenetic activation. Our data suggest that MAP kinases are not required for early partial activation of p90rsk but are required for full activation of p90rsk during rat oocyte maturation, and that p90rsk dephosphorylation occurs following MAP kinase inactivation after parthenogenetic activation of rat oocytes.

1-Methyl-3-isobutylxanthine↗

PubMed2001

Formation of novel polymeric nanoparticles.

We have found that not only block copolymers but also ionomers can self-assemble in a selective solvent to form surfactant-free nanoparticles. The self-assembly can be induced by chemical reaction, polymer-polymer complexation, and microphase inversion in addition to the temperature. A recently developed microwave method for the preparation of uniform surfactant-free polymeric nanoparticles is also reviewed. Our results have revealed that for a given dispersion, the particle surface area occupied per stabilizer (surfactant, polymer chains, and ionic groups) is close to a constant.

Microspheres↗

PubMed2001

Preparation of pentachlorophenol derivatives and development of a microparticle-based on-site immunoassay for the detection of PCP in soil samples.

Pentachlorophenol (PCP) is used as a herbicide in agriculture and as an insecticide for termite control. Because of the apparent hazard associated with its usage, there is a need for an efficient and economic on-site screening method. A 5-min on-site test has been developed for the detection of PCP based on the OnTrak format, a successful Roche on-site test format for drugs of abuse, utilizing the principle of latex agglutination immunoassay. The test detects 1 ppm of PCP in soil samples.

Agglutination Tests↗

PubMed2001

A novel dimeric diterpene from Salvia prionitis.

A novel dimeric abietane diterpene, hongencaotone (1), has been isolated from the roots of Salvia prionitis, and its structure was determined by spectral data interpretation and X-ray analysis. Hongencaotone (1) is the first ether-linked heterodimeric diterpene to have been isolated from the genus Salvia.

Antineoplastic Agents, Phytogenic↗

PubMed2001

Expression of mRNAs for ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), interleukin-6 (IL-6), and their receptors (CNTFR alpha, LIFR beta, IL-6R alpha, and gp130) in human peripheral neuropathies.

The mRNA levels of neuropoietic cytokines, ciliary neurotrophic factor (CNTF), leukemia inhibitory factor (LIF), and interleukin-6 (IL-6), and their receptor components (CNTFR alpha, LIFR beta, IL-6R alpha, and gp130) were examined in seventy-six patients with various peripheral neuropathies to determine the extent of expression of these cytokines and receptors, and their relationship to nerve fiber pathology and cell infiltration in the diseased nerves. The CNTF mRNA levels were significantly decreased in the diseased nerves and were correlated to residual myelinated fiber population. In contrast, the mRNA levels of LIF, IL-6 and the ligand-binding receptor components (CNTFR alpha, LIFR beta and IL-6R alpha) were elevated to variable extent in the diseased nerves. The CNTFR alpha, LIFR beta, and IL-6R alpha mRNA levels showed a weak positive correlation with the extent of demyelinating pathology and their levels were related to each other. Moreover, the CNTF and LIF mRNA levels were inversely proportional to the extent of macrophage invasion, whereas the CNTFR alpha and IL-6R alpha mRNA expressions were correlated to the increase in macrophage infiltration. The neuropoietic cytokine family and its receptor expressions in the diseased human nerves are regulated by an underlying pathology-related process rather than type of diseases, and could play a role in peripheral nerve regeneration and repair.

Adult↗

PubMed2001

Crystal structure of the complex of concanavalin A and tripeptide.

The X-ray structure analysis of a cross-linked crystal of concanavalin A soaked with the tripeptide molecule as the probe molecule showed electron density corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-related molecules. The crystal structure of the tripeptide complex was refined at 2.4-A resolution to an R-factor of 17.5%, (Rfree factor of 23.7%), with an RMS deviation in bond distances of 0.01 A. The model includes all 237 residue of concanavalin A, 1 manganese ion, 1 calcium ion, 161 water molecules, 1 glutaraldehyde molecule, and 1 tripeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding surface of crystalline protein with a probe molecule that is dissolved in a mixture of organic solvent with water or in neat organic solvent but is hardly dissolved in aqueous solution.

Binding Sites↗

PubMed2001

Glutathione-S-Transferase M1 null genotype in autoimmune hepatitis.

Autoimmune hepatitis is associated with genes located in the major histocompatibility complex. The search for genes at other loci that may play a role in disease susceptibility and/or severity is an area of active investigation in autoimmune liver diseases. Genes for glutathione-S-transferases, enzymes that are widely distributed and collectively metabolize carcinogens, pollutants, drugs, and a broad spectrum of harmful, foreign compounds have been associated with liver disease. The objective of this study was to search for a relationship between the glutathione-S-transferase Ml null genotype and autoimmune hepatitis using polymerase chain reaction analysis. The findings indicate that the frequency of the null genotype is not increased in patients with autoimmune hepatitis when compared to control subjects. These results coupled with similar ones in primary biliary cirrhosis do not support a role for this mutation in autoimmune liver disease.

Adolescent↗

PubMed2001

Crystal structure of the complex of concanavalin A and hexapeptide.

The X-ray structure analysis of a cross-linked crystal of concanavalin A soaked with a hexapeptide molecule as a probe molecule showed an electron density corresponding to full occupation in the binding pocket. The site lies on the surface of concanavalin A and is surrounded by three symmetry-related molecules. The crystal structure of the hexapeptide complex was refined at 1.93-A resolution, to an R-factor of 19% (Rfree factor of 25%), with an RMS deviation in bond distances of 0.01 A. The model includes all 237 residues of concanavalin A, one manganese ion, one calcium ion, 95 water molecules, one glutaraldehyde molecule, one isopropanol molecule, and one hexapeptide molecule. This X-ray structure analysis also provides an approach to mapping the binding surface of crystalline protein with a probe molecule that is dissolved in the mixture of organic solvent with water or in neat organic solvent but is hardly dissolved in aqueous solution.

Binding Sites↗

PubMed2001

In vivo gene electroporation of glial cell line-derived neurotrophic factor (GDNF) into skeletal muscle of SOD1 mutant mice.

Motor neurons degenerate with intracellular vacuolar change and eventually disappear in spinal cords of SOD1 mutant mice, resembling human amyotrophic lateral sclerosis (ALS). The GDNF gene was electroporatically transferred into the leg muscles of SOD1 mutant mice and expressed in muscle cells. This gene therapy with GDNF delayed the deterioration of motor performance, being retrogradely transported into spinal motor neurons. However, the number of the motor neurons and survival of the mutant mice were not improved by GDNF treatment. These results indicate that in vivo gene electroporation of GDNF into muscles could be an appropriate therapeutic approach to ameliorate an early dysfunction of motor neurons in SOD1 mutant mice, but further improvement is needed to use this gene transfer as an effective treatment of ALS.

Animals↗

PubMed2001

Regulation of the PH-domain-containing tyrosine kinase Etk by focal adhesion kinase through the FERM domain.

Etk/BMX, a member of the Btk family of tyrosine kinases, is highly expressed in cells with great migratory potential, including endothelial cells and metastatic carcinoma cell lines. Here, we present evidence that Etk is involved in integrin signalling and promotes cell migration. The activation of Etk by extracellular matrix proteins is regulated by FAK through an interaction between the PH domain of Etk and the FERM domain of FAK. The lack of Etk activation by extracellular matrix in FAK-null cells could be restored by co-transfection with wild-type FAK. Disrupting the interaction between Etk and FAK diminished the cell migration promoted by either kinase. Furthermore, inhibiting Etk expression in metastatic carcinoma cell lines with an antisense oligonucleotide blocks integrin-mediated migration of these cells. Taken together, our data indicate the essential role of the interaction of the PH domain of Etk and the FERM domain of FAK in integrin signalling.

Animals↗

PubMed2001

Regulation of transport of the dopamine D1 receptor by a new membrane-associated ER protein.

Many structural determinants for G protein-coupled receptor (GPCR) functions have been defined, but little is known concerning the regulation of their transport from the endoplasmic reticulum (ER) to the cell surface. Here we show that a carboxy-terminal hydrophobic motif, FxxxFxxxF, which is highly conserved among GPCRs, functions independently as an ER-export signal for the dopamine D1 receptor. A newly identified ER-membrane-associated protein, DRiP78, binds to this motif. Overexpression or sequestration of DRiP78 leads to retention of D1 receptors in the ER, reduced ligand binding, and a slowdown in the kinetics of receptor glycosylation. Our results indicate that DRiP78 may regulate the transport of a GPCR by binding to a specific ER-export signal.

Amino Acid Motifs↗

PubMed2001

Carboxyl proteinase from Pseudomonas defines a novel family of subtilisin-like enzymes.

The crystal structure of a pepstatin-insensitive carboxyl proteinase from Pseudomonas sp. 101 (PSCP) has been solved by single-wavelength anomalous diffraction using the absorption peak of bromide anions. Structures of the uninhibited enzyme and of complexes with an inhibitor that was either covalently or noncovalently bound were refined at 1.0-1.4 A resolution. The structure of PSCP comprises a single compact domain with a diameter of approximately 55 A, consisting of a seven-stranded parallel beta-sheet flanked on both sides by a number of helices. The fold of PSCP is a superset of the subtilisin fold, and the covalently bound inhibitor is linked to the enzyme through a serine residue. Thus, the structure of PSCP defines a novel family of serine-carboxyl proteinases (defined as MEROPS S53) with a unique catalytic triad consisting of Glu 80, Asp 84 and Ser 287.

Amino Acid Sequence↗

PubMed2001

Fusion of two novel genes, RBM15 and MKL1, in the t(1;22)(p13;q13) of acute megakaryoblastic leukemia.

t(1;22) is the principal translocation of acute megakaryoblastic leukemias. Here we show this chromosomal rearrangement to result in the fusion of two novel genes, RNA-binding motif protein-15 (RBM15), an RNA recognition motif-encoding gene with homology to Drosophila spen, and Megakaryoblastic Leukemia-1 (MKL1), a gene encoding an SAP (SAF-A/B, Acinus and PIAS) DNA-binding domain.

Chromosomes, Human, Pair 1↗

PubMed2001

Hamartin and tuberin expression in human tissues.

Tuberous sclerosis (TSC) is a bigenic autosomal dominant disease caused by mutations in one of two tumor-suppressor genes, TSC1 and TSC2, resulting in benign hamartomas and low grade neoplasms in multiple organs including brain, heart, kidney, and skin. We report the results of an immunohistochemical study of the expression of the TSC gene products, tuberin and hamartin, in multiple tissues obtained at autopsy from 12 non-TSC affected patients ranging in age from 20 weeks gestation to 8 years, and surgical specimens from some organs. Tuberin and hamartin are expressed and are colocalized in most tissues. Contrary to a previous report, immunostaining with our antisera detected hamartin in liver, small and large intestine, prostate, and testes. We did not detect significant developmental differences in tuberin or hamartin expression in comparable tissues from patients of different ages. Although tuberin and hamartin colocalize in most tissues and cell types, we provide data that hamartin is more abundantly expressed than tuberin in cells within some tissues including the distal nephron and a population of cells of the endocrine pancreas. These data support the hypothesis that hamartin and tuberin interact and may function together in many tissues where they are co-expressed, but also suggest that hamartin has a discrete and specialized function in certain cell types.

Blotting, Western↗

PubMed2001

Collecting-duct carcinoma of the kidney with prominent signet ring cell features.

We report a case in a 74-year-old woman of collecting-duct carcinoma of the kidney with prominent signet ring cell features. Grossly, the tumor measured 5.5 cm in greatest dimension, occupied the entire upper pole of the kidney, and was well circumscribed. Microscopically, it displayed a predominant tubulopapillary pattern of growth with a hyalinizing stroma. The tumor tubules were lined by a single layer of cells with large, pleomorphic nuclei, some of which had a hobnail appearance. Large intracytoplasmic vacuoles with compression of nuclei (signet ring cells) were present throughout the tumor. Alcian blue, mucicarmine, and periodic acid-Schiff stains failed to identify intracellular mucin or glycogen in the signet ring cells. Enlarged cells with intracytoplasmic vacuoles were also noted in the adjacent collecting ducts. The tumor cells were immunohistochemically positive for cytokeratin including cytokeratin 7, CAM 5.2, AE1/3, and 34 beta E12, vimentin, peanut lectin agglutinin, and Ulex europaeus agglutinin. Electron microscopy revealed that the intracytoplasmic vacuoles were due to intracellular edema. To the best of our knowledge, this is the first reported case of renal collecting-duct carcinoma with prominent signet ring cell features.

Aged↗

PubMed2001

A 1.5 million-base pair inversion polymorphism in families with Williams-Beuren syndrome.

Williams-Beuren syndrome (WBS) is most often caused by hemizygous deletion of a 1.5-Mb interval encompassing at least 17 genes at 7q11.23 (refs. 1,2). As with many other haploinsufficiency diseases, the mechanism underlying the WBS deletion is thought to be unequal meiotic recombination, probably mediated by the highly homologous DNA that flanks the commonly deleted region. Here, we report the use of interphase fluorescence in situ hybridization (FISH) and pulsed-field gel electrophoresis (PFGE) to identify a genomic polymorphism in families with WBS, consisting of an inversion of the WBS region. We have observed that the inversion is hemizygous in 3 of 11 (27%) atypical affected individuals who show a subset of the WBS phenotypic spectrum but do not carry the typical WBS microdeletion. Two of these individuals also have a parent who carries the inversion. In addition, in 4 of 12 (33%) families with a proband carrying the WBS deletion, we observed the inversion exclusively in the parent transmitting the disease-related chromosome. These results suggest the presence of a newly identified genomic variant within the population that may be associated with the disease. It may result in predisposition to primarily WBS-causing microdeletions, but may also cause translocations and inversions.

Adolescent↗

PubMed2001

Minoxidil-induced hair growth is mediated by adenosine in cultured dermal papilla cells: possible involvement of sulfonylurea receptor 2B as a target of minoxidil.

The mechanism by which minoxidil, an adenosine-triphosphate-sensitive potassium channel opener, induces hypertrichosis remains to be elucidated. Minoxidil has been reported to stimulate the production of vascular endothelial growth factor, a possible promoter of hair growth, in cultured dermal papilla cells. The mechanism of production of vascular endothelial growth factor remains unclear, however. We hypothesize that adenosine serves as a mediator of vascular endothelial growth factor production. Minoxidil-induced increases in levels of intracellular Ca(2+) and vascular endothelial growth factor production in cultured dermal papilla cells were found to be inhibited by 8-sulfophenyl theophylline, a specific antagonist for adenosine receptors, suggesting that dermal papilla cells possess adenosine receptors and sulfonylurea receptors, the latter of which is a well-known target receptor for adenosine-triphosphate-sensitive potassium channel openers. The expression of sulfonylurea receptor 2B and of the adenosine A1, A2A, and A2B receptors was detected in dermal papilla cells by means of reverse transcription polymerase chain reaction analysis. In order to determine which of the adenosine receptor subtypes contribute to minoxidil-induced hair growth, the effects of subtype-specific antagonists for adenosine receptors were investigated. Significant inhibition in increase in intracellular calcium level by minoxidil or adenosine was observed as the result of pretreatment with 8-cyclopentyl-1,3-dipropylxanthine, an antagonist for adenosine A1 receptor, but not by 3,7-dimethyl-1-propargyl-xanthine, an antagonist for adenosine A2 receptor, whereas vascular endothelial growth factor production was blocked by both adenosine A1 and A2 receptor antagonists. These results indicate that the effect of minoxidil is mediated by adenosine, which triggers intracellular signal transduction via both adenosine A1 and A2 receptors, and that the expression of sulfonylurea receptor 2B in dermal papilla cells might play a role in the production of adenosine.

ATP-Binding Cassette Transporters↗

PubMed2001

IFN-gamma gene therapy by intrasplenic hepatocyte transplantation: a novel strategy for reversing hepatic fibrosis in Schistosoma japonicum-infected mice.

Liver-targeted gene therapy using hepatocyte as recipient cells has recently been documented to be effective in treatment of numerous hepatic diseases, such as metabolic diseases and liver carcinoma. IFN-gamma elicits antipreliferative and antifibrogenic activity in a variety of mesenchymal cells, including hepatic satellite cells. To investigate the antifibrogenic response of liver gene therapy mediated by intrasplenic transplantation of gene-modified hepatocytes, normal mouse liver cell line BNL CL.2 cells were transfected with murine IFN-gamma gene (BNL.IFN-gamma) in vitro, and transplanted intrasplenically into Schistosoma japonicum-infected mice. The amounts and distribution of IFN-gamma (which inhibits collagen synthesis), TGF-beta (which stimulates collagen synthesis) and extracellular matrix, including type I and III collagen, were detected. In mice infected with S. japonicum and then treated with BNL.IFN-gamma, an increase of IFN-gamma and decrease of TGF-beta1 were detected at 20 weeks postinfection compared to untreated S. japonicum-infected mice. Immunohistochemical analysis showed that S. japonicum infection induced a marked increase of type I and III collagen synthesis. Whereas, 4 weeks after treatment with BNL.IFN-gamma, net synthesis rates of type I and III collagen were markedly decreased in the liver of infected mice. In addition, a decreased expression of TGF-beta1 and its receptor TGF-betaRII in the liver of BNL.IFN-gamma-treated mice was also observed. Moreover, the decrease in TGF-beta1 and TGF-betaRII protein approximately paralleled the decrease in their mRNA expression, which was detected by RNA dot blotting. The data indicate that intrasplenic transplantation of IFN-gamma gene-modified hepatocyte can be a candidate approach to treat hepatic fibrosis.

Animals↗