Experimental study of tunneling escape through double-barrier resonant-tunneling structures.
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Journal Article↗
Biomedical subjects
X Yang
Publications and source records attributed to X Yang.
Transcriptional analysis of acetylcholine receptor alpha 3 gene promoter motifs that bind Sp1 and AP2.
In this study, we performed an analysis of the neuronal nicotinic acetylcholine receptor alpha 3 subunit gene promoter region, -238/+47, to identify cis and trans elements that are important for basal activity in PC12 cells. Sequence analyses of the alpha 3 promoter and footprint assays revealed an Sp1 binding site between -79 and -57 (termed the alpha 3 GA motif) and an AP2 binding site between -30 and -7. Using mobility shift analysis, we found that PC12 cell extracts contain proteins that specifically bind to the alpha 3 GA motif and are immunologically related to Sp1. Mutation of the alpha 3 GA motif, which prevented binding of Sp1, resulted in a 75% decrease in promoter activity. Mutation of the AP2 site resulted in only a minor loss of promoter activity, which is consistent with the lack of AP2 binding activity in PC12 extracts. In Drosophila Schneider line 2 (S2) cell cotransfection assays, Sp1 activated the alpha 3 promoter in a GA motif-dependent manner. Furthermore, multimerization of the GA motif upstream of the beta-globin TATA box conferred Sp1 responsiveness. Our results indicate that Sp1 can activate transcription through direct interaction with the alpha 3 GA motif and that this motif plays a major role in alpha 3 promoter basal activity in PC12 cells.
Animals↗
An M(r) 7-kDa membrane protein overexpressed in human multidrug-resistant ovarian cancer cells.
We have developed a monoclonal antibody (designated 1D7) which recognizes an M(r) 7-kDa plasma membrane protein overexpressed in ovarian MDR cancer cells. The expression of the M(r) 7-kDa protein in various human multidrug-resistant and drug-sensitive cell lines was analysed by Western blot and flow cytometry methods. The small molecular weight protein was overexpressed in the human ovarian carcinoma cell line, SKVLB which was selected for vinblastine resistance from SKOV3 cells and in OVCAR 4/ADR100 and OVCAR 4/VBL200 which were generated from NIH:OVCAR4 by stepwise selection against adriamycin and vinblastine, respectively. Only a minor amount of the M(r) 7-kDa protein was found in the parent cell line, SKOV3. It was not found in other drug-resistant human cell lines such as the vinblastine-resistant CEM cells (CEM/VLB300), the intrinsic MDR colon cell line HCT15 and the human MDR breast cancer cell line, MCF7/AdrVp. 1D7 specifically inhibited the proliferation of the resistant cells. Our results suggest that the expression of the M(r) 7-kDa protein on the plasma membrane of ovarian MDR cancer cells may be involved in a mechanism related to the proliferation of the drug resistant cancer cells.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Masquerade: a novel secreted serine protease-like molecule is required for somatic muscle attachment in the Drosophila embryo.
Diverse developmental processes, such as neuronal growth cone migration and cell shape changes, are mediated by the interactions of cells with the extracellular matrix. We describe here a secreted molecule encoded by the Drosophila masquerade (mas) gene. Total loss of mas function causes defective muscle attachment. This mutant phenotype suggests that mas normally acts to stabilize cell-matrix interaction and represents a novel functional and limiting component in the adhesion process. mas encodes a 1047-amino-acid preproprotein that is further processed by proteolytic cleavage to generate two polypeptides. The carboxy-terminal polypeptide is highly similar to serine proteases and has an extracellular localization; however, it is unlikely to possess proteolytic activity, because the catalytic site serine has been substituted by a glycine residue. During embryonic development, the mas amino- and carboxy-terminal polypeptides are differentially localized. The mas carboxy-terminal polypeptide accumulates at all somatic muscle attachment sites, which corresponds well with the morphological defect seen in the mas mutants. Our findings demonstrate the involvement of an extracellular component in somatic muscle attachment. We propose that mas acts via its modified serine protease motif, either as a novel adhesion molecule and/or as a competitive antagonist of serine proteases, to stabilize muscle attachment.
Alleles↗
Altered mitochondrial morphology of rat embryos in diabetic pregnancy.
BACKGROUND: Previous studies in vivo and in vitro have suggested that the oxidative metabolism of the embryo may have a role in the teratogenicity of diabetic pregnancy. In particular, the production of reactive oxygen species by the embryonic mitochondria has been implicated in the teratological process. The induction of congenital malformations by the diabetic milieu occurs during the early embryonic development. The present study aimed to estimate the role of the embryonic mitochondria in the teratological process of diabetic pregnancy by studying mitochondrial morphology in the embryos exposed to a diabetic environment in vivo or in vitro during early organogenesis and late fetal development. METHODS: For studies in vivo embryos of control or streptozotocin-diabetic rats were taken at gestational days 9-11 and subjected to light and electron microscopical analysis. The brain, heart, and liver of day-15 fetuses were also observed. For studies in vitro day-9 embryos of normal rats were cultured in a whole-embryo culture system for 48 hours. The culture media were supplied with high concentration of diabetes-related substrates and metabolites, and their effect on structure of embryonic neuroepithelial cells determined. RESULTS: The light microscopical observations demonstrated numerous cytoplasmic vacuoles in the ectoderm of day-9 embryos and in the neuroepithelium and blood cells of day-10 and day-11 embryos of diabetic rats. Ultrastructurally, these vacuoles were found to be mitochondria undergoing large-amplitude swelling with loss of matrix density and disturbed cristae. In contrast, no mitochondrial differences were found in the brain, heart, and liver, when day-15 fetuses from normal and diabetic rats were compared. Ultrastructural analysis of day-9 embryos cultured for 48 hours in the presence of high concentrations of D-glucose, pyruvate, beta-hydroxybutyrate, and alpha-ketoisocaproate also showed high-amplitude mitochondrial swelling in the neuroepithelium. The mitochondrial swelling was, however, not found in embryos cultured in a high concentration of L-glucose, excluding simple osmotic effects of the diabetes-related substrates and metabolites. CONCLUSIONS: The mitochondrial morphological changes appeared in embryos subjected to a diabetic environment during a time period when the congenital malformations in diabetic pregnancy are induced. The results support the notion that embryonic mitochondria are involved in the teratological process of diabetic pregnancy.
Animals↗
Activation of inducible nitric oxide synthase gene in murine macrophages requires protein phosphatases 1 and 2A activities.
The purpose of these studies was to identify phosphatase activities required for the production of nitric oxide in murine macrophages exposed to lipopolysaccharide (LPS), synthetic lipopeptide (LPP), and mouse interferon-gamma (IFN-gamma). The in vitro treatment of macrophages with IFN-gamma and LPS or IFN-gamma and LPP resulted in production of NO, which was inhibited by addition of the specific phosphatase 1 and 2A (PP1/2A) inhibitors okadaic acid (OA), calyculin A, and cantharidin (but not the nonactive analogues okadaic acid tetraacetate and 1,4-dimethylendothall). OA suppressed the accumulation of steady-state inducible NO synthase (iNOS) mRNA and iNOS protein (without alteration of their stability). The cytosol and nuclei of control macrophages contained large amounts of PP1/2A activities that were inhibited by OA in a dose-dependent manner. Taken together, these data indicate that PP1/2A activities are involved in the regulation of iNOS gene expression in murine macrophages.
Amino Acid Sequence↗
Cumulus cell function during bovine oocyte maturation, fertilization, and embryo development in vitro.
Several contemporary micromanipulation techniques, such as sperm microinjection, nuclear transfer, and gene transfer by pronuclear injection, require removal of cumulus cells from oocytes or zygotes at various stages. In humans, the cumulus cells are often removed after 15-18 hr of sperm-oocyte coincubation to assist the identification of the fertilization status. This study was designed to evaluate the function of cumulus cells during oocyte maturation, fertilization, and in vitro development in cattle. Cumulus cells were removed before and after maturation and after fertilization for 0, 7, 20, and 48 hr. The cumulus-free oocytes or embryos were cultured either alone or on cumulus cell monolayers prepared on the day of maturation culture. Percentages of oocyte maturation, fertilization, and development to cleavage, morula, and blastocyst stages and to expanding or hatched blastocysts were recorded for statistical analysis by categorical data modeling (CATMOD) procedures. Cumulus cells removed before maturation significantly reduced the rate of oocyte maturation (4-26% vs. 93-96%), fertilization (0-9% vs. 91-92%), and in vitro development at all stages evaluated. Cumulus cells removed immediately prior to in vitro fertilization (IVF) or 7 hr after IVF reduced the rates of fertilization (58-60% and 71%, respectively, vs. 91-92% for controls), cleavage development (40-47% and 53-54% vs. 74-78% for controls), and morula plus blastocyst development (15% and 24% vs. 45%, P < 0.05). Cumulus cell co-culture started at various stages had no effect on fertilization and cleavage development but significantly improved rates of embryo development to morula or blastocyst stages (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Asymptomatic carotid artery occlusion from a gunshot. The role of angiography in penetrating neck trauma.
Recognition of a carotid artery injury after a gunshot neck wound can be difficult to make in the absence of physical signs. Currently, the usefulness of preoperative angiography in detecting penetrating neck trauma is controversial. We present a case of an angiography proven asymptomatic carotid artery occlusion after a gunshot. Indications for angiography after neck trauma are discussed.
Adult↗
The dynamics of mitochondrial plasmids in a Hawaiian population of Neurospora intermedia.
We analysed the distribution of mitochondrial plasmids among 82 Neurospora intermedia isolates from Hawaii; 74% of the isolates carried the neutral circular plasmid Han-2, whereas 38% contained the linear senescence-causing plasmid kalDNA. The distributions of the two plasmids are independent. There is no significant difference between the Kauaian population of 1972 and that of 1976. To further examine the reasons for this frequency distribution we studied the transmission of both Hawaiian plasmids through the maternal parent in a large series of crosses using non-Kalilo isolates as conidial parents. Plasmids can be lost during the sexual cycle. The Han-2 plasmid is transmitted more efficiently than kalDNA. No clear cases of autonomous or non-autonomous plasmid suppression were observed, so loss can be considered accidental. One Kalilo strain proved to be ineffectual as a maternal parent, and this reduced its ability to transmit kalDNA to the next generation. The dynamic balance of plasmids in natural populations over time is probably a result of the interplay of many forces, including those described in this work and those from several other studies on Neurospora plasmids.
Crosses, Genetic↗
Development of early bovine embryos in co-culture with KSOM and taurine, superoxide dismutase or insulin.
Three experiments, utilizing 2578 embryos, were designed to test the effects of media, taurine, Superoxide dismutase and insulin on the development of embryos produced by in vitro maturation and in vitro fertilization (IVM/IVF). Embryos showing at least 1 cleavage during culture for 40 to 44 h after IVM/IVF were selected for further culture under various conditions for 6 d at 39 degrees C in 5% C0(2):95% air. A Buffalo rat liver (BRL) cell co-culture was used in all 3 experiments. Experiment 1 was a 3 x 2 factorial arrangement with KSOM (a high potassium simplex optimization-derived medium containing only 12 ingredients), Menezo B(2) and TCM-199 media with or without 7 mM taurine. Blastocyst production in the 3 media, respectively, was 48, 36 and 29% (P<0.05). Addition of 7 mM taurine increased the percentage of blastocysts from 34 to 42 (P<0.05). In Experiment 2, Superoxide dismutase (SOD) did not improve blastocyst development (P>0.05). In Experiment 3, insulin (75 ng/ml) added to KSOM resulted in 46% morulae plus blastocysts compared with 35% for the control (P<0.05). These results indicate that the co-culture of embryos in KSOM with taurine or insulin added is superior to commonly used complex media for efficient production of blastocysts following IVM/IVF.
Journal Article↗
Alterations in physical state and expression of human papillomavirus type 18 DNA following crisis and establishment of immortalized ectocervical cells.
Integration of episomal human papillomavirus (HPV) DNA in infected cervical lesions during malignant progression is frequently observed, but the importance of integration is poorly understood. We have studied immortalization by HPV-18 of human cervical cells as an in vitro model system. Here, the status and expression of HPV-18 DNA in precrisis ectocervical keratinocytes was compared with that in the same cells after crisis and establishment of immortalization. Southern blots revealed, and two-dimensional gel analysis confirmed, that the precrisis culture contained more than 100 copies/cell of episomal HPV-18 DNA and no detectable integrated viral DNA. In contrast, the postcrisis cells contained a low copy number of only integrated viral genome. The Northern blot patterns of E6-E7 and E2/E4 RNA expression were also different. Analysis of RNA by RT-PCR indicated that neither culture expressed the unspliced HPV-18 E6 oncogene present in tumor cell lines and that the precrisis, but not postcrisis, culture expressed the full-length E2 repressor. The two cultures displayed a similar keratinocyte morphology in vitro and a similar low grade dysplasia in vivo and both were non-tumorigenic. These results suggest that, although insufficient for complete malignant conversion, viral DNA integration during crisis is associated with the establishment of an immortalized phenotype in which HPV-18 DNA is integrated and HPV-18 RNA expression is altered.
Adult↗
Estrogen dependent expression of heat shock transcription factor: implications for uterine synthesis of heat shock proteins.
Transcriptional induction of heat shock protein genes is generally mediated by binding of heat shock transcription factor(s) to the heat shock element present in the promoters of heat shock genes. Although the steady-state levels of heat shock factor mRNAs vary among different tissues, at present virtually nothing is known regarding the cellular signals responsible for their synthesis and hence the observed variations. In this report we demonstrate that the heat shock transcription factor (HSTF or HSF) is under positive regulation by estrogen. The effect of estrogen was observed with both types of heat shock factors (HSF-1 and HSF-2) and occurred at both the mRNA and protein level. Immunolocalization studies emphasized the potential biological importance of these observations whereby the increase in uterine HSF-1 and HSF-2 due to estrogen was found to be associated with the endometrium, the primary tissue component which is targeted for estrogen action. This is the first demonstration of a cellular factor which can regulate HSF-1 and HSF-2 gene expression. The implications of these findings to uterine heat shock protein gene expression are discussed.
Animals↗
The relationship between an endangered North American tree and an endophytic fungus.
BACKGROUND: The Florida torreya (Torreya taxifolia) began a catastrophic decline in the late 1950s and is now the rarest tree in North America for which a full species designation has been established. The trees have common plant disease symptoms, but the reason for the decline has never been identified. T. taxifolia's imminent extinction gains special poignancy through its close relationship to the Pacific yew (Taxus brevifolia), which produces the potent anticancer agent, taxol. RESULTS: An examination of the endophytic fungal communities of wild torreyas consistently found a filamentous fungus, Pestalotiopsis microspora, associated with diseased trees and also with most symptomless trees. P. microspora can be cultured in the laboratory, and when it is introduced into greenhouse-grown torreyas, it causes disease symptoms similar to those seen in the field. The fungus can then be reisolated from these deliberately infected trees. The phytotoxins pestalopyrone, hydroxypestalopyrone and pestaloside have been isolated and characterized from axenic fungal cultures, and both pestalopyrone and hydroxypestalopyrone can be isolated from artificially infected torreyas. In addition, pestaloside has antifungal activity against other fungal endophytes of T. taxifolia. CONCLUSIONS: The filamentous fungus, P. microspora, has an endophytic-pathologic relationship with T. taxifolia. The fungus resides in the inner bark of symptomless trees, and physiological or environmental factors could trigger its pathological activity. P. microspora produces the phytotoxins pestalopyrone, hydroxypestalopyrone, and pestaloside which give rise to the disease. Pestaloside, which also has antifungal activity, could reduce competition from other fungal endophytes within the host.
Acetylation↗
Beneficial effect of oocyte activation prior to and during nuclear transfer in cattle using in vitro matured oocytes 24 h of age.
This research was designed to study in vitro development of bovine nuclear transferred embryos using enucleated young in vitro matured oocytes 24 h of age as recipient cytoplasts activated prior to nuclear transfer. The oocytes were enucleated and then activated with electric pulse at 24 h of age followed by incubation with cycloheximide for 6-7 h before nuclear transfer and membrane fusion with a blastomere of the 16-32 cell stage. This new protocol effectively improved cleavage (68 vs 17%, p < 0.05) and morula/blastocyst development of reconstructed embryos (29 vs 6%, p < 0.05), compared to similar nuclear transfer procedure without prior activation of recipient oocytes. Corresponding rates of cleavage and morula/blastocyst development for oocytes activated similarly without nuclear transfer were 49 and 19%. Factors affecting nuclear transfer were also compared. Two electric pulses for fusion increased rates of fusion (76 vs 60%, p < 0.05) and subsequent development of cloned embryos (32 vs 11%, p < 0.05). Cytochalasin B treatment following nuclear transfer manipulation seemed not to be beneficial in improving development of cloned embryos (p > 0.05). Both co-culture systems with buffalo rat liver (BRL) cells and cumulus cells promoted development of cloned embryos compared to the controls (28, 21 vs 0%, p < 0.05). The BRL cell system seemed to be better for manipulated embryos by reducing embryolysis.
Animals↗
Analysis of hyperspherical channels of three-electron atomic systems.
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Journal Article↗
Study of the (1/2)g.s.--->(1/2)1+ transition in the 13C(p,n)13N reaction at intermediate energies.
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Journal Article↗
Dipole excitations in p-shell nuclei via (p,n) reactions.
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Journal Article↗
Conversion of glomerular histology from a mesangiopathic to a membranopathic pattern in serum sickness nephritis with prolonged sensitization.
In order to examine the effect of prolonged sensitization on glomerular injury, serum sickness nephritis was induced in Fischer rats by administration of egg albumin (EA). Animals were divided into A, B and C groups with 4-week, 6-week and 8-week sensitization, respectively. The experimental results were as follows: Both group A (4 weeks) and group B (6 weeks) showed mesangial immune complex deposition with proliferation (mesangiopathic pattern), but in the latter both the size and the amount of the deposits were larger than those in the former; while group C (8 weeks) demonstrated predominant distribution of deposition along the capillary walls (membranopathic pattern). It is suggested that such conversion of deposition from mesangiopathic to membranopathic pattern after prolonged repeated sensitization may be the result of the change of the host immune response to antigen, and/or the character of the antibody.
Animals↗