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Biomedical subjects

W Sun

Publications and source records attributed to W Sun.

At least 235 records · Page 13Linked to original sources
PubMed1996

The t(12;21) translocation converts AML-1B from an activator to a repressor of transcription.

The t(12;21) translocation is present in up to 30% of childhood B-cell acute lymphoblastic and fuses a potential dimerization motif from the ets-related factor TEL to the N terminus of AML1. The t(12;21) translocation encodes a 93-kDa fusion protein that localizes to a high-salt- and detergent-resistant nuclear compartment. This protein binds the enhancer core motif, TGTGGT, and interacts with the AML-1-binding protein, core-binding factor beta. Although TEL/AML-1B retains the C-terminal domain of AML-1B that is required for transactivation of the T-cell receptor beta enhancer, it fails to activate transcription but rather inhibits the basal activity of this enhancer. TEL/AML-1B efficiently interferes with AML-1B dependent transactivation of the T-cell receptor beta enhancer, and coexpression of wild-type TEL does not reverse this inhibition. The N-terminal TEL helix-loop-helix domain is essential for TEL/AML-1B-mediated repression. Thus, the t(12;21) fusion protein dominantly interferes with AML-1B-dependent transcription, suggesting that the inhibition of expression of AML-1 genes is critical for B-cell leukemogenesis.

Base Sequence↗
PubMed1996

Na-K-ATPase alpha-isoform expression in heart and vascular endothelia: cellular and developmental regulation.

The Na pump (Na-K-ATPase) is important for regulation of membrane potential and transport in smooth muscle and heart. The alpha (catalytic)-subunit of this pump has three isoforms: alpha 1 is ubiquitous, but alpha 2 and alpha 3 are mainly localized to excitable tissue. Physiological differences between isoforms are not completely understood, but alpha 3 pumps appear to have a lower affinity for intracellular Na and a higher ouabain affinity than alpha 1 pumps. The alpha 2-and alpha 3-isoform mRNAs are expressed at high levels in the normal adult rat cardiac conduction system. Although alpha 1 and alpha 3 are both globally expressed in neonatal rat myocardia, there is a switch in the myocardial isoform pattern from alpha 3 to alpha 2 after birth. There are also important species differences in cardiac isoform patterns. Furthermore, changes in Na-K-ATPase isoforms in heart and vascular tissue have been reported in association with hypertension, but little is known about isoform expression in normal endothelia. We therefore studied the cellular distribution of Na pump protein isoforms in neonatal and adult myocardia and endothelia. Immunohistochemical analysis of rat tissues showed that the alpha 1-isoform was expressed throughout atrial and ventricular myocardium, with alpha 1 the only isoform detectable in the adult t tubule system. Although alpha 2 was also present in ventricular myocytes, the signal was markedly stronger in conduction tissue and papillary muscle. In hearts from neonatal rats, the alpha 3-isoform predominated in the cardiac conduction system, whereas alpha 2 was not detectable in any structure except vascular endothelium. In tissues and in cell lines representing a variety of species and vessel sizes, endothelia of large vessels expressed primarily alpha 1, whereas alpha 2 could be detected in endothelia of small vessels in rat heart. No evidence of alpha 3 expression in endothelium was found. Thus the complex spatial and developmental regulation of Na pump isoform expression in cardiovascular tissues may provide additional correlates to distinct physiological roles of these transporters.

Aging↗
PubMed1996

The alpha3 isoform protein of the Na+, K(+)-ATPase is associated with the sites of cardiac and neuromuscular impulse transmission.

The alpha (catalytic) subunit of the Na+ pump (Na+, K(+)-ATPase) has three isoforms; alpha1 is ubiquitous, skeletal muscle expresses predominantly alpha2, and alpha3 has been localized to specific types of neurons and, possibly, to axonal processes. The alpha3 isoform mRNA is also expressed in the rat cardiac conduction system. Thus, we studied rat heart and quadriceps muscles by immunohistochemistry using isoform-specific antibodies to the Na+ pump alpha subunit and labeled alpha-bungarotoxin as a probe for the neuromuscular junction (NMJ). We found that alpha3 pump protein is localized to three sites important for impulse transmission: the junctional complex between cardiac myocytes, the heart conduction system, and the NMJ. Specifically, all levels of the conduction system expressed alpha3 immunoreactive protein, as assessed by two isoform-specific antibodies and histological conduction system markers. Specific expression at the junctional complex was confirmed by immuno-EM. Double-labeling and denervation analysis indicated that alpha3-positive areas in skeletal muscle were presynaptic and adjacent to postsynaptic bungarotoxin-positive regions, which had the classic morphology of NMJs. Thus, specific Na+,K(+)-ATPase pump isoforms may be adapted to maintenance of membrane potential and/or intracellular ion concentrations required for impulse transmission in both heart and presynaptic motor terminals contacting skeletal muscle.

Animals↗
PubMed1996

[Electroacupuncture at "huatuo jiaji point" inhibits the expression of Fos protein in rat spinal cord induced by traumatic pain].

SD rats were used to study the change of Fos-like immunoreactivity (FLI) in the lumbar spinal cord by traumatic pain following hind limb amputation and the effect of electro-acupuncture (EA) at "Huatuo Jiaji point" on it. The results showed (1) FLI cells induced by amputation were found in all of the I-X laminae of the ipsilateral spinal cord, but most of the labeled cells were located in the laminae I-II and V-VI; (2) EA at "Huatuo Jiaji point" suppressed the Fos expression following amputation, which was indicated by decrease of the number of FLI cells in the spinal cord. It suggests that, the traumatic pain impulse following amputation could activate pain sensitive neurons (PSN) in spinal cord. The impulse of electro-stimulation could suppress activities of these PSN, producing the effect of analgesia.

Acupuncture Points↗
PubMed1996

[Intramedullary spinal teratoma].

We treated 5 cases of intradullary spinal teratomas from 1974 to 1995, accounting 0.636% of all intraspinal tumors and 45.45% of all teratomas of spinal cord admitted in the same time. The origin of this tumor is controversial. It is not easy to differentiate this tumors from other intramedullary spinal tumors on clinical grounds. CT and MR scans of this tumor enabled us to make the preoperative diagnosis of teratoma. Resection is the only treatment of choice.

Adolescent↗
PubMed1996

[An observation on calcium ion overloaded injury and the effect of calcium channel blocker in rabbit retina under acute ocular hypertension].

OBJECTIVE: In order to observe the retinal injury by Ca+2 overload under ocular hypertension and the effect of verapamil treatment. METHODS: Atomic absorption spectrophotometry and phosphate pyroantemonate (PPA) means were used to observe the changes of rabbit retinal Ca+2 content and the therapeutic effects of verapamil under this situation. RESULTS: In the ocular hypertensive group, Ca+2 increased from the moment of intraocular pressure elevation, and with prolongation of time, it tended to increase steadily. In comparison with the control group, there were significant differences (P < 0.01). PPA showed that the longer the time, the more obvious swollen the mitochondria and much more calcium deposition in the mitochondria. In the group of rabbits with ocular hypertension having taken verapamil treatment, the Ca+2 content was markedly lower, the changes of mitochondria milder and the Ca+2 deposition in mitochondria less than that of the ocular hypertension group without treatment. CONCLUSION: Calcium-overload may be one of the reasons of retinal injury under ocular hypertension, while calcium-blocker may alleviate this injury.

Animals↗
PubMed1996

[An analysis of diagnostic errors of uveal melanoma].

OBJECTIVE: The causes of erroneous clinical diagnosis of uveal melanomas were studied METHODS: 18 cases with uveal melanoma diagnosed clinically were analyzed by clinical and histopathological methods. RESULTS: The main causes of the misdiagnosis were the opaque media to prevent from a clear view of the fundus in some cases, and clinicians' insufficient experience and ignorance of the case history. The histological bases of the misdiagnosis were suprachoroidal hemorrhage, subretinal hemorrhage and hemorrhage beneath retinal pigment epithelium, organization and formation of scar tissues. CONCLUSION: It is necessary to take the fluorescein angiography preoperatively and perform local resection of tumor on suitable cases.

Adolescent↗
PubMed1995

Probing sodium channel cytoplasmic domain structure. Evidence for the interaction of the rSkM1 amino and carboxyl termini.

Epitopes for monoclonal antibodies directed against the purified adult rat skeletal muscle sodium channel (rSkM1) were localized using channel proteolysis and fusion proteins. The interactions between these and other monoclonal antibodies with site-specific polyclonal antibodies were used to investigate the spatial relationships among rSkM1 cytoplasmic segments. Competition. between antibodies for binding was performed using a solution-phase assay in which solubilized channel protein retains many of the biophysical characteristics of the rSkM1 protein in vivo. Our results support a model in which: 1) the amino terminus assumes a rigid structure having a fixed orientation with respect to other intracellular segments; 2) the interdomain 2-3 region is centrally located on the cytoplasmic surface of the channel, extends farther into the cytoplasm, and has an intermediate degree of flexibility; 3) the beginning of the amino terminus and end of the carboxyl terminus specifically interact with each other; and 4) domains 1 and 4 are adjacent. The sequences responsible for the interaction of the amino and carboxyl termini were identified by demonstrating the specific binding of a synthetic peptide encompassing the first 30 residues of the rSkM1 amino terminus to a fusion protein containing the rSkM1 carboxyl terminus.

Amino Acid Sequence↗
PubMed1995

Molecular design of the N-methyl-D-aspartate receptor binding site for phencyclidine and dizolcipine.

The N-methyl-D-aspartate receptor (NMDAR), a pivotal entity for synaptic plasticity and excitotoxicity in the brain, is a target of psychotomimetic drugs such as phencyclidine (PCP) and dizolcipine (MK-801). In contrast, a related glutamate receptor, the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate receptor GluR1, is weakly sensitive to these drugs. Three point mutations on GluR1, mimicking homologous residues on the NMDAR, confer the PCP and MK-801 blockade properties that are characteristic of the NMDAR--namely, high potency, voltage dependence, and use dependence. The molecular determinants that specify the PCP block appear confined to the putative M2 transmembrane segment, whereas the sensitivity to MK-801 requires an interplay between residues from M2 and M3. Given the plausible involvement of the NMDAR in the etiology of several neurodegenerative diseases and in excitotoxic neuronal cell death, tailored glutamate receptors with specific properties may be models for designing and screening new drugs targeted to prevent glutamate-mediated neural damage.

Amino Acid Sequence↗
PubMed1995

Effects of exposure to environmental tobacco smoke on a human tracheobronchial epithelial cell line.

BEAS-2B cells, a human bronchial epithelial line immortalized by viral transformation, were exposed to sidestream tobacco smoke (STS) as a surrogate for environmental tobacco smoke (ETS) under biphasic culture conditions where the apical portion of the cells was in direct contact with the gas phase. Dose-dependent cytotoxicity was observed. In addition, induction of an as yet uncharacterized protein of molecular weight 45,000 was associated with exposure to STS. This protein might be part of a protective response of exposed cells, which do not show a classical heat shock response when exposed to STS. We conclude that STS and ETS can be directly cytotoxic to human airway epithelial cells in biphasic culture at concentrations not unreasonable for smoky indoor atmospheres. The model system described in this paper should be useful for studying the detailed mechanisms of cytotoxicity of, and protection from, ETS exposure in the human cells most directly exposed to ETS in vivo.

Bronchi↗
PubMed1995

Borrelia burgdorferi genes selectively expressed in the infected host.

An immunological screening strategy was used to select microbial genes expressed only in the host. Differential screening of a Borrelia burgdorferi (the Lyme disease agent) expression library identified a gene (p21) encoding a 20.7-kDa antigen that reacted with antibodies in serum from actively infected mice but not serum from mice immunized with heat-killed B. burgdorferi. Selective expression of p21 in the infected host was confirmed by Northern blot analysis and RNA PCR. Further differential screening of the expression library identified at least five additional B. burgdorferi genes are selectively expressed in vivo. This screening method can be used to identify genes induced in vivo in a wide variety of pathogenic microorganisms for which a gene transfer system is not currently available.

Amino Acid Sequence↗
PubMed1995

Acute effects of amiodarone on membrane properties, refractoriness, and conduction in guinea pig papillary muscles.

Amiodarone has potent and complex antiarrhythmic effects associated with a rare incidence of proarrhythmia. For a comprehensive understanding of its antiarrhythmic mechanisms in the same preparations, amiodarone (50 microM) was employed as it would be in the clinical setting and applied to guinea pig papillary muscles impaled by microelectrodes, paced at different rates, and superfused with various concentrations of potassium ([K]e). Amiodarone exerted complex actions, as follows: (1) The maximum rate of rise (Vmax) of the fast action potential (i.e., [K]e = 5.4-9.0 mM) as well as that of the slow action potential (i.e., [K]e = 15.0 mM in the presence of 1.0 microM isoproterenol) was suppressed in a rate-dependent manner. (2) Amiodarone exhibited a rate- and [K]e-dependent increase in the ratio of effective refractory period vs action potential duration at 90% repolarization (ERP/APD90), disclosing post-repolarization refractoriness. (3) Amiodarone had no effect on passive cable factors, such as threshold current and tissue resistance, during propagation. These versatile electrophysiological effects of amiodarone may contribute to its unique antiarrhythmic effects, as well as the low incidence of proarrhythmia with this drug.

Action Potentials↗
PubMed1995

Isolation and characterization of RNA from low-biomass deep-subsurface sediments.

Three methods for the isolation of microbial RNA from low-biomass deep-subsurface sediments have been developed and evaluated. RNA was isolated from samples taken from depths ranging from 173 to 217 m, and samples represented a variety of lithologies, including lacustrine, fluvial sand, and paleosol sediments. Cell numbers in these samples were estimated to be between log 4.0 and log 5.1/g on the basis of phospholipid fatty acid analysis. The most efficient method examined is based on the direct lysis of microbial cells followed by the extraction of RNA with alkaline phosphate buffers and subsequent inactivation of nucleases by extraction with guanidinium isothiocyanate. Estimated recoveries of mRNA for this method are approximately 26%. The recovered RNA included both mRNA and rRNA, as evidenced by the detection of sequences homologous to transcripts from the toluene-4-monooxygenase gene of Pseudomonas mendocina KR1 and bacterial, archaeal, and eukaryotic rRNA. An unexpectedly high relative concentration of archaeal rRNA (22 to 40%) was observed for these samples.

Base Sequence↗
PubMed1995

Membrane vesiculation function and exocytosis of wild-type and mutant matrix proteins of vesicular stomatitis virus.

Transfection of mammalian CV1 cells with a recombinant M-gene pTM1 plasmid, driven by vaccinia virus-expressed phage T7 polymerase, resulted in the expression of matrix (M) protein, which is progressively released from the exterior surface of the transfected-cell plasma membrane. Exocytosis of M protein begins 2 to 4 h posttransfection and reaches a peak by 10 to 16 h posttransfection; dye uptake studies reveal that > 97% of cells are alive and have intact membranes at 16 h posttransfection. Density gradient centrifugation and labeling with radioactive palmitic acid revealed that the M protein is released from cells in association with lipid vesicles. Expression of M-gene deletion mutants suggests that exocytosis of M protein requires the presence of a membrane-binding site at N-terminal amino acids 1 to 50. Cells transfected with the pTM1 plasmid containing the M gene of the temperature-sensitive mutant tsO23 expressed ample quantities of the mutant M protein at permissive (31 degrees C) and restrictive (39 degrees C) temperatures, but the exocytosis of the mutant M protein occurred only at the permissive temperature. The tsO23 M gene has three site-specific mutations resulting in amino acid substitutions at residues 21, 111, and 227. Expression of wild-type and mutant M genes with mutations or revertants at each of these sites resulted in exocytosis of M protein at the nonpermissive temperature only when wild-type leucine was present at residue 111, but M-protein exocytosis was restricted (to some extent even at the permissive temperature) when mutant phenylalanine was present at residue 111. Past and present data indicate that a specific structural conformation of the M protein is responsible for the formation and budding of vesicles, a property of the M protein which probably also promotes vesicular stomatitis virus assembly and budding of virions from host cells.

Amino Acid Sequence↗
PubMed1995

Transactivation of the Moloney murine leukemia virus and T-cell receptor beta-chain enhancers by cbf and ets requires intact binding sites for both proteins.

The Moloney murine leukemia virus (Mo-MLV) enhancer contains binding sites (LVb and LVc) for the ets gene family of proteins and a core site that binds the polyomavirus enhancer-binding protein 2/core-binding factor (cbf) family of proteins. The LVb and core sites in the Mo-MLV enhancer contribute to its constitutive activity in T cells. All three binding sites (LVb, LVc, and core) are required for phorbol ester inducibility of the Mo-MLV enhancer. Adjacent binding sites for the ets and cbf proteins likewise constitute a phorbol ester response element within the human T-cell receptor beta-chain (TCR beta) enhancer and contribute to constitutive transcriptional activity of the TCR beta enhancer in T cells. Here we show that the CBF alpha subunit encoded by the mouse Cbfa2 gene (the murine homolog of human AML1) and three ets proteins, Ets-1, Ets-2, and GA-binding protein (GABP), transactivate both the Mo-MLV and mouse TCR beta enhancer in transient-expression assays. Moreover, we show that transactivation by Cbf alpha 2 requires both intact ets and cbf binding sites. Transactivation by Ets-1, Ets-2, and GABP likewise requires intact binding sites for ets proteins and CBF. Supportive biochemical analyses demonstrate that both proteins can bind simultaneously to a composite enhancer element. These findings suggest that ets and cbf proteins cooperate in vivo to regulate transcription from the Mo-MLV and TCR beta enhancers.

Animals↗