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Biomedical subjects

J Wei

Publications and source records attributed to J Wei.

At least 181 records · Page 10Linked to original sources
PubMed1997

[Experimental treatment of rhubarb on mesangio-proliferative glomerulonephritis in rats].

Accumulation of extracellular matrix is a prominent feature of progressive glomerulonephritis (GN). Previously, we have shown that Emodin, an important component of Rhubarb, inhibits the fibronectin (FN) production of cultured mesangial cells. We now provide evidence of the same effect of Rhubarb in immune complex GN induced in rats by injection of anti-thymocyte serum (ATS). Rhubarb ameliorated mesangial matrix expansion on day 7 after ATS administration. Decreased FN level and IL-1 activity were found in the supernatant of cultured glomeruli from Rhubarb-treated animal at the 7th day. Glomerular tissue FN fluorescence staining was also much weaker than that of the untreated rats. These studies demonstrated that Rhubarb-treated anti-Thy-1 animal model should develop significantly less matrix expansion. Rhubarb also inhibited synthesis and secretion of fibronectin, an important component of mesangial extracellular matrix. Decreased IL-1 activity might be involved in the therapeutic effect of Rhubarb on mesangioproliferative glomerulonephritis.

Animals↗
PubMed1996

Isolation and characterization of the chicken m2 acetylcholine receptor promoter region: induction of gene transcription by leukemia inhibitory factor and ciliary neurotrophic factor.

We have isolated the promoter region and determined the start sites of transcription for the gene encoding the chicken m2 (cm2) muscarinic acetylcholine receptor. Transfection experiments, using cm2-luciferase reporter gene constructs, demonstrated that a 789-bp genomic fragment was sufficient to drive high level expression in chicken heart primary cultures, while an additional 1.2-kb region was required for maximal expression in mouse septal/ neuroblastoma (SN56) cells. Treatment of SN56 cells with the cytokines ciliary neurotrophic factor and leukemia inhibitory factor increases expression of endogenous muscarinic acetylcholine receptors and results in a 4- to 6-fold induction of cm2 promoter driven luciferase expression. We have mapped a region of the cm2 promoter that is necessary for induction by cytokines.

Animals↗
PubMed1996

Phenotypic effects of the weaver gene are evident in the embryonic cerebellum but not in the ventral midbrain.

Degeneration of neurons in two structures, the cerebellum and the dopaminergic neurons in the ventral midbrain, is a well characterized action of the weaver gene. In order to see whether the gene has effects prenatally, both the cerebellum and the ventral midbrain were examined in mouse embryos genotyped for the weaver gene (wv, Girk2) on day E19. Anatomically matched sections of the midline cerebellar vermis were quantitatively analyzed 2 h after the dams were given a single injection of [3H]thymidine. A gene-dose effect was seen in the retardation of fissure development. This was more pronounced in homozygotes (wv/wv) and less so in heterozygotes (wv/+) when compared with wild type controls (+/+). Quantitative measures of the following features showed stepwise differences between genotypes so that the wv/wv are most affected and wv/+ are somewhat affected compared with +/+: surface length of the midline vermis, area of the entire midline vermis and the external germinal layer (egl), total number of cells in the egl, [3H]thymidine-labeled and -unlabeled egl cells, cells in the Purkinje cell layer, cells in the region of the deep nuclei, [3H]thymidine-labeled cells in the Purkinje cell layer (presumptive proliferating Bergmann glia), and [3H]thymidine-labeled cells in the region of the deep nuclei. In contrast to the obvious phenotypic effects of wv in the embryonic cerebellum, qualitative immunocytochemical examination of tyrosine hydroxylase staining in the ventral midbrains of the same embryos showed that the position and density of the presumptive dopaminergic neurons was similar in all genotypes.

Animals↗
PubMed1996

A study of the relationship between the DBH activity in serum and a MspI polymorphic site in intron 9 of the human DBH gene in schizophrenia.

Intron 9 of the human dopamine beta-hydroxylase (DBH) gene was amplified using a long PCR procedure in unrelated patients with schizophrenia and unrelated control subjects. MspI digestion of the PCR fragments showed a two allele polymorphism. A1 and A2 Kruskal-Wallis analysis revealed a significant difference in serum DBH activity among the three groups carrying the A1/A2 genotype, the drug-free and drug treated patients, and the control subjects (H = 12.2, df = 2, p < 0.005), and also a significant difference among the three subgroups of drug-treated patients carrying the genotype of A1/A1, A2/A2 or A1/A2 (H = 10.4, df = 2, p < 0.01). The present results suggest that the MspI polymorphic site in intron 9 of the human DBH gene may be associated with alterations of DBH activity in schizophrenia and with the influence of neuroleptic drugs on the DBH activity as well.

Adult↗
PubMed1996

Phosphorylation and inhibition of type III adenylyl cyclase by calmodulin-dependent protein kinase II in vivo.

Inhibition of type III adenylyl cyclase (III-AC) by intracellular Ca2+ in vivo provides a mechanism for attenuation of hormone-stimulated cAMP signals in olfactory epithelium, heart, and other tissues (Wayman, G. A., Impey, S., and Storm, D. R. (1995) J. Biol. Chem. 270, 21480-21486). Although the mechanism for Ca2+ inhibition of III-AC in vivo has not been defined, inhibition is not mediated by Gi, cAMP-dependent protein kinase, or protein kinase C. However, Ca2+ inhibition of III-AC is antagonized by KN-62, a CaM-dependent kinase inhibitor. In addition, constitutively activated CaM kinase II inhibits the enzyme. These data suggest that CaM kinase II regulates the activity of III-AC by direct phosphorylation or by an indirect mechanism involving phosphorylation of a protein that inhibits III-AC. Here we report that III-AC is phosphorylated in vivo when intracellular Ca2+ is increased and that phosphorylation is prevented by CaM-dependent kinase inhibitors. Site-directed mutagenesis of a CaM kinase II consensus site (Ser-1076 to Ala-1076) in III-AC greatly reduced Ca2+-stimulated phosphorylation and inhibition of III-AC in vivo. These data support the hypothesis that Ca2+ inhibition of III-AC is due to direct phosphorylation of the enzyme by CaM kinase II in vivo.

Adenylyl Cyclase Inhibitors↗
PubMed1996

The weaver mutation changes the ion selectivity of the affected inwardly rectifying potassium channel GIRK2.

The weaver mutation in mice has recently been identified as a single base-pair mutation in the Girk2 gene, which encodes a G-protein-activated inwardly rectifying potassium channel, GIRK2. The mutation results in a Gly to Ser substitution at residue 156, in the putative pore-forming region of the potassium channel. In the present study, we used Xenopus oocytes to express mutant GIRK2, and to characterize the effects of the mutation on the channel. The mutation results in a loss of the normal high selectivity for K+ over Na+, with little effect on other channel properties such as activation by the mu opioid receptor. The resulting increase in basal Na+ permeability causes a marked depolarization of oocytes expressing the mutant GIRK2 protein. This result was observed even when the mutant GIRK2 was coexpressed with GIRK1, a situation more analogous to that seen in vivo. Thus, the increased Na+ permeability and resulting depolarization may contribute to the pathology of cerebellar granule cells and substantia nigra dopaminergic neurons observed in the weaver mice.

Analgesics↗
PubMed1996

Determination of hemoglobin adducts in workers exposed to 2,4, 6-trinitrotoluene.

2,4,6-Trinitrotoluene (TNT) is an important occupational and environmental pollutant. TNT can be taken up through the skin and by inhalation. It is therefore essential to have fast and reliable methods to monitor human exposure. In rat experiments, it has been shown that TNT binds covalently to blood proteins and to tissue proteins. Hemoglobin (Hb) adducts of TNT are markers for the internal dose and possibly for the toxic effects of TNT, e.g. cataracts. In the present paper we introduce a new efficient method to quantify Hb adducts of TNT. Precipitated Hb was hydrolyzed with base in the presence of the surrogate internal standard 3,5-dinitroaniline (35DNA). The released 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT) were quantified against 35DNA by gas chromatography-mass spectrometry with negative-ion chemical ionization. Hb of 50 workers and controls from a Chinese munition factory were investigated. The Hb adduct levels ranged from 3.7 to 522 ng for 4ADNT and from 0 to 14.7 ng for 2ADNT per gram of Hb. However, in control samples from Germany no Hb adducts of 4ADNT or 2ADNT could be found.

DNA↗
PubMed1996

Inhibition of immunoglobulin folding and secretion by dominant negative BiP ATPase mutants.

A group of resident ER proteins have been identified that are proposed to function as molecular chaperones. The best characterized of these is BiP/GRP78, an hsp70 homologue that binds peptides containing hydrophobic residues in vitro and unfolded or unassembled proteins in vivo. However, evidence that mammalian BiP plays a direct role in protein folding remains circumstantial. In this study, we examine how BiP interacts with a particular substrate, immunoglobulin light chain (lambda LC), during its folding. Wild-type hamster BiP and several well-characterized BiP ATPase mutants were used in transient expression experiments. We demonstrate that wild-type lambda LCs showed prolonged association with mutant BiP which inhibited their secretion. Both wild-type and mutant BiP bound only to unfolded and partially folded LCs. The wild-type BiP was released from the incompletely folded LCs, allowing them to fold and be secreted, whereas the mutant BiP was not released. As a result, the LCs that were bound to BiP mutants were unable to undergo complete disulfide bond formation and were retained in the ER. Our experiments suggest that LCs undergo both BiP-dependent and BiP-independent folding steps, demonstrating that both ATP binding and hydrolysis activities of BiP are essential for the completion of LC folding in vivo and reveal that BiP must release before disulfide bond formation can occur in that domain.

Adenosine Triphosphatases↗
PubMed1996

Scavenging of Alzheimer's amyloid beta-protein by microglia in culture.

Deposits of amyloid beta-protein (A beta) form the cores of the pathological plaques which characterize Alzheimer's disease. The mechanism of formation of the deposits is unknown; one possibility is failure of a clearance mechanism that would normally remove the protein from brain parenchyma. This study has investigated the capacity of the central nervous system (CNS) phagocytes, microglia cells, to clear exogenous A beta 1-42 from their environment. Cultured microglia from adult rat CNS have a high capacity to remove A beta from serum-free medium, shown by immunoblotting experiments. A beta from incubation medium was attached to the cell surface and could be identified by immunocytochemistry at the light or electron microscopic (EM) level; by EM, A beta also appeared in phagosome-like intracellular vesicles. Light microscopic immunocytochemistry combined with computer-assisted image analysis showed that cells accumulated A beta within 24 hr. from culture medium containing from 1 to 20 micrograms/ml A beta. Microglial accumulation of A beta was substantially reduced in the presence of fetal bovine serum. Addition of the protease inhibitor leupeptin to incubation medium with serum resulted in accumulation of A beta in a membrane-bound intracellular compartment, but not at the cell surface. The increase in intracellular accumulation in the presence of the protease inhibitor indicates a microglial capacity for intracellular degradation of A beta in the absence of inhibition. The change from predominantly cell-surface accumulation in serum-free medium to predominantly intracellular accumulation with serum may be explained by the presence in serum of carrier proteins that complex with A beta and target it to cell surface receptors capable of stimulating endocytosis. Microglia were also cultured on unfixed cryostat sections of human brain tissue containing Alzheimer's plaques. Very little A beta from the tissue was accumulated by the cells, although cultured microglia were found in direct contact with anti-A beta immunopositive plaques. Possibly A beta in tissue sections was complexed with other proteins which either inhibited its uptake by microglia or enhanced its proteolysis, preventing cellular accumulation of immunostainable A beta. The results indicate that cultured microglia effectively remove A beta from tissue culture medium and from the surface of the dish and concentrate monomer and aggregates of A beta either on the cell surface or intracellularly. This process may be modified by proteins present in Alzheimer's brain sections.

Alzheimer Disease↗
PubMed1996

Spatially heterogeneous discrete waves in predator-prey communities over a patchy environment.

A model motivated by the earlier work of J. D. Murray and D. Stirzaker is proposed to describe the dynamics of predator-prey communities over a patchy environment. The model is a system of delay differential equations. It is shown that if only one time lag is incorporated into the model, then a branch of spatially homogeneous periodic solutions occur as a primary Hopf bifurcation. However, if two time lags are used to measure different delayed factors in the process of growth, decay, and predator consumption of the prey population, then stable spatially heterogeneous periodic solutions (discrete waves or phase-locked oscillations) may exist. The utilized method is based on center manifold, normal form, and equivariant Hopf bifurcation theory.

Animals↗
PubMed1996

Protein folding and assembly in the endoplasmic reticulum.

The newly synthesized protein emerging through the ER membrane enters a unique environment for folding and assembly. Unlike the cytosol, the ER provides an oxidizing environment, has high levels of calcium, and contains enzymes for N-linked glycosylation. The growing nascent polypeptide chain is in many cases modified co-translationally with N-linked sugars and begins to fold while still attached to the ribosome. Disulfide bond formation stabilizes the tertiary structure of the protein. The in vivo folding and assembly of nascent proteins requires a delicate balance between allowing folding to occur and preventing incorrect interactions that would ultimately lead to improper folding and/or aggregation. In the past several years, two groups of proteins that interact transiently with incompletely folded and assembled proteins in the ER have been identified and characterized. The first group consists of enzymes that promote or stabilize protein folding. The second is composed of proteins termed "molecular chaperones" that bind transiently to nascent polypeptides and apparently prevent misfolding by masking those regions that could lead to incorrect interactions between protein domains or aggregation.

Calcium-Binding Proteins↗
PubMed1996

A comparison of the early development of ischemic brain damage in normoglycemic and hyperglycemic rats using magnetic resonance imaging.

The early evolution of ischemic brain injury under normoglycemic and streptozotocin-induced hyperglycemic plasma conditions was studied using magnetic resonance imaging (MRI). Male Sprague-Dawley rats were subjected to either permanent middle cerebral artery occlusion (MCAO), or 1-h MCAO followed by reperfusion using the intraluminal suture insertion method. The animals were divided into four groups each with eight rats: normoglycemia with permanent MCAO, normoglycemia with 1-h MCAO, hyperglycemia with permanent MCAO, and hyperglycemia with 1-h MCAO. Diffusion-weighted images (DWIs) and T2-weighted images (T2WIs) were aquired every 1 h from 20 min until 6 h after MCAO, at which time cerebral plasma volume images (PVIs) were acquired. Tissue infarction was determined by triphenyltetrazolium chloride staining at 7 h after MCAO. The ischemic damage, measured as the area of DWI and T2WI hyperintensity and tissue infarction, increased significantly in hyperglycemic rats in both permanent and transient MCAO models. In the permanent MCAO model, the maximal apparent water diffusion coefficient (ADC) decline under either normo- or hyperglycemia was about 40%, but the speed of ADC drop was faster in hyperlgycemic rats than in normoglycemic rats. Reperfusion after 1 h of MCAO in normoglycemic rats partly reversed the decline in ADC, whereas the low ADC area continued to expand after reperfusion in the hyperglycemic group. Between the two hyperglycemic groups with either permanent MCAO or reperfusion, no significant difference was found in the infarct volume measured at 7 h after MCAO. However, reperfusion dramatically increased the extent and accelerated the development rate of vasogenic edema. ADC in the hyperglycemic reperfusion group also dropped to a lower level. A large "no-reflow" zone was found in the ischemic hemisphere in the hyperglycemic reperfusion group. This study provides strong evidence to support that preischemic hyperglycemia exacerbates ischemic damage in both transient and permanent MCAO models and demonstrates, using MRI, that reperfusion under preischemic hyperglycemia accelerates the evolution of early ischemic injury.

Animals↗
PubMed1996

Ferritin gene organization: differences between plants and animals suggest possible kingdom-specific selective constraints.

Ferritin, a protein widespread in nature, concentrates iron approximately 10(11)-10(12)-fold above the solubility within a spherical shell of 24 subunits; it derives in plants and animals from a common ancestor (based on sequence) but displays a cytoplasmic location in animals compared to the plastid in contemporary plants. Ferritin gene regulation in plants and animals is altered by development, hormones, and excess iron; iron signals target DNA in plants but mRNA in animals. Evolution has thus conserved the two end points of ferritin gene expression, the physiological signals and the protein structure, while allowing some divergence of the genetic mechanisms. Comparison of ferritin gene organization in plants and animals, made possible by the cloning of a dicot (soybean) ferritin gene presented here and the recent cloning of two monocot (maize) ferritin genes, shows evolutionary divergence in ferritin gene organization between plants and animals but conservation among plants or among animals; divergence in the genetic mechanism for iron regulation is reflected by the absence in all three plant genes of the IRE, a highly conserved, noncoding sequence in vertebrate animal ferritin mRNA. In plant ferritin genes, the number of introns (n = 7) is higher than in animals (n = 3). Second, no intron positions are conserved when ferritin genes of plants and animals are compared, although all ferritin gene introns are in the coding region; within kingdoms, the intron positions in ferritin genes are conserved. Finally, secondary protein structure has no apparent relationship to intron/exon boundaries in plant ferritin genes, whereas in animal ferritin genes the correspondence is high. The structural differences in introns/exons among phylogenetically related ferritin coding sequences and the high conservation of the gene structure within plant or animal kingdoms of the gene structure within plant or animal kingdoms suggest that kingdom-specific functional constraints may exist to maintain a particular intron/exon pattern within ferritin genes. In the case of plants, where ferritin gene intron placement is unrelated to triplet codons or protein structure, and where ferritin is targeted to the plastid, the selection pressure on gene organization may relate to RNA function and plastid/nuclear signaling.

Amino Acid Sequence↗
PubMed1996

Linkage mapping of microdissected clones from distal mouse chromosome 16.

A total of 38 unique segments generated by microdissection of mouse chromosome 16 (MMU16), sequence independent amplification (SIA) and cloning were sequentially mapped on the distal portion of the chromosome with two mouse backcross panels. Some reference markers from other sources were retyped in the panels and results integrated with those for our microdissected DNA segments. The clone map is most highly refined in its distal portion, which stretches from reference marker D16Mit71 to D16Mit5, and the highest density of clones is in the region defined by markers D16Mit5 and D16Mit141. This map on distal mouse chromosome 16 should be a useful tool for the mouse genome project and for studies of genes in the region.

Animals↗
PubMed1996

Correlated flow cytometric analysis of H-ras p21 and DNA ploidy in acute myelogenous leukemia.

The flow cytometric immunoassay was used to study the correlation between the H-ras oncogene product p21 and the DNA ploidy in 30 de novo cases of acute myelogenous leukemia (AML). The results showed that 17 cases were negative for p21 expression and 13 positive for p21. The patients with positive p21 had higher percentage of bone marrow and peripheral blasts and lower peripheral leukocyte count. The expression of p21 had no influence on the therapeutic effect. Before treatment, DNA diploidy occurred in 18 cases including 13 p21 negative ones, and DNA aneuploidy was revealed in 12 cases including 8 p21 positive ones. Patients with positive p21 or having aneuploidy in complete remission were at risk for early relapse. Our results suggest that p21 may be involved in the process of leukemogenesis and progression in AML.

DNA, Neoplasm↗
PubMed1996

A study of enzymes involved in catecholamine metabolism in parents of patients with schizophrenia.

The concentrations of serum homovanillic acid (HVA), norepinephrine (NE), tyrosine (Tyr), phenylalanine (Phe) and tryptophan (Trp), and the activities of serum dopamine-beta-hydroxylase (DBH), platelet monoamine oxidase (MAO), and erythrocyte catechol-O-methyl transferase (COMT) were measured in 68 healthy parents who had schizophrenic offspring. The results show a significant correlation between the parents of schizophrenic patients in serum HVA (r=0.38, n=34, p<0.05), NE (r=0.40, n=33, p<0.02), Phe (r=0.44, n=34, p<0.0l), Tyr (r=0.43, n = 34, p <0.02) and DBH activity (r=0.51, n = 30, p <0.005), but do not show a significant correlation in erythrocyte COMT (r=0.01, n=27), platelet MAO (r=0.04, n=23) or serum Trp (r=0.10, n=34). There were no significant correlations in these measurements between randomly matched parents. The present study suggests that both parental sides of schizophrenic patients are likely to have similar alleles associated with the catecholamine pathway, and their ill offspring may possess a double dose of the schizophrenogenic alleles.

Adult↗