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Biomedical subjects

X S Wang

Publications and source records attributed to X S Wang.

At least 19 recordsLinked to original sources
PubMed1995

Rescue and replication signals of the adeno-associated virus 2 genome.

The adeno-associated virus 2 (AAV) genome is a single-stranded DNA which contains the inverted terminal repeats (ITRs) of 145 nucleotides. The terminal 125 nucleotides of each ITR form palindromic hairpin structures that serve as primers for AAV DNA replication. These hairpin structures also play a crucial role in the integration, as well as the rescue, of the proviral genome from latently-infected cells, or from the recombinant AAV plasmids. However, the ITRs also contain an additional domain, designated the D-sequence, a 20-nucleotide stretch that is not involved in the formation of hairpins. In order to examine the role of the D-sequence in viral DNA rescue and replication, a number of recombinant AAV plasmids were constructed which contained deletions/substitutions in different regions of the ITRs. The results presented here reveal the existence of additional sequences, other than the hairpin structures, which serve as primers for AAV DNA replication. The results also show that whereas the hairpin structures are sufficient for excision and replication of the viral DNA, the D-sequence is crucial for the high efficiency of rescue and replication of the AAV genome.

Base Sequence↗
PubMed1995

A newly identified 105-kD lower lamina lucida autoantigen is an acidic protein distinct from the 105-kD gamma 2 chain of laminin-5.

A 105-kD lower lamina lucida antigen (p105) has been detected by autoantibodies (anti-p105) from patients with a novel immunobullous disease. To distinguish p105 from other known lamina lucida components, we performed comparative immunoblotting on purified human amniotic laminin-5 (kalinin), 804G matrix (enriched in laminin-5), and keratinocyte and fibroblast proteins using anti-804G matrix antibody (J-18) and anti-p105. J-18 labeled the truncated laminin-5 gamma 2 chain in amniotic laminin-5, 804G matrix, and keratinocyte conditioned medium, but did not label fibroblast cytosol. Conversely, anti-p105 did not label amniotic laminin-5 or 804G matrix, but did label p105 in both keratinocyte conditioned medium and fibroblast cytosol. J-18 labeled the 105-kD laminin-5 gamma 2 chain in reduced keratinocyte proteins and a 400-kD laminin-5 complex under non-reducing conditions. In contrast, anti-p105 labeled p105 under both reducing and non-reducing conditions but did not label a 400-kD protein complex. Similarly, comparative immunoblotting on keratinocyte proteins using anti-p105 and anti-laminin-1 revealed no commonly labeled protein bands. Electrophoretic fractionations by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of these fractions revealed that the peak fractions of keratinocyte proteins reactive with anti-p105 are different from those reactive with J-18. Furthermore, keratinocyte proteins fractionated by Mono Q anion-exchange chromatography revealed fractions immunoreactive with anti-p105, whereas J-18 showed no reactivity with these fractions. Two-dimensional gel electrophoresis and immunoblotting with anti-p105 revealed p105 to be an acidic protein with isoelectric points between 5.7 and 6.3, distinct from the isoelectric points of laminin-5 gamma 2 chain. We conclude that p105 is an acidic protein located in the lamina lucida and distinct from the truncated laminin-5 gamma 2 chain and the laminin-1 family.

Autoantigens↗
PubMed1995

Transcriptional transactivation of parvovirus B19 promoters in nonpermissive human cells by adenovirus type 2.

The pathogenic human parvovirus B19 contains a promoter at map unit 6 (B19p6) of the viral genome, expression from which is largely restricted to human cells in the erythroid lineage, whereas a putative promoter at map unit 44 (B19p44) is inactive during a natural viral infection. Although nonerythroid human cells, such as HeLa and KB, allow expression from the B19p6 promoter but not from the B19p44 promoter following DNA-mediated transfection, little expression from the B19p6 promoter occurs following recombinant virus infection (S. Ponnazhagan, X.-S. Wang, M.J. Woody, F. Luo, L.Y. Kang, M.L. Nallari, N.C. Munshi, S.Z. Zhou, and A. Srivastava, submitted for publication). However, significant expression from the B19p6 promoter as well as the B19p44 promoter could be detected in a human 293 cells line that expresses the adenovirus early gene products, suggesting that coinfection with adenovirus might mediate transcriptional transactivation of the B19 promoters in nonpermissive cells. Expression of the firefly luciferase reporter gene from the B19 promoters was evaluated either following plasmid transfection or following infection with the recombinant adeno-associated virus type 2 vectors. Both B19p6 and B19p44 promoters could be transactivated by coinfection with adenovirus in nonpermissive human cells, although the extent of transactivation of the B19p44 promoter was significantly lower than that of the B19p6 promoter. Expression of the adenovirus E1A proteins was necessary and sufficient for the observed transactivation of the B19 promoters. These studies further illustrate that the underlying molecular mechanisms of transactivation of parvovirus promoters in general by the adenovirus early proteins have similarities with those of the well-documented transactivation of the adeno-associated virus type 2 promoters.

Adenovirus E1A Proteins↗
PubMed1992

Glucocorticoid induction of CRE-binding protein isoform mRNAs in rat C6 glioma cells.

Mammalian cells express several distinct isoforms of transcription factor CREB (cAMP-responsive element binding protein). At least two forms, alpha- and delta CREB, arise through alternative splicing of the CREB gene transcript. In this communication we demonstrate that the mRNAs of several CREB isoforms are expressed in rat C6 glioma cells and that the intracellular levels of these mRNAs are markedly induced by the synthetic glucocorticoid dexamethasone. Nuclear run-off assays show that the induction occurs, at least in part, through a transcriptional mechanism. The enhanced cellular levels of CREB mRNAs are accompanied by increased CREB protein and CRE-binding activity of nuclear extracts as evaluated by immunoblot and Southwestern blot assays.

Animals↗
PubMed1989

Immunohistochemical localization of relaxin in human prostate.

We identified relaxin in human male prostate by use of an anti-human relaxin analogue polyclonal antibody and the avidin-biotin-immunoperoxidase method. The antibody was obtained by immunizing a rabbit with a synthetic human relaxin analogue which has 95% sequence homology with native human relaxin. Human prostate tissues incubated with the anti-human relaxin analogue exhibited positive immunostaining up to an antibody dilution of 1:3200. Inhibition of immunostaining with this antibody by excess relaxin analogue demonstrated specificity of the antibody. The exact role of relaxin in human male reproductive physiology remains to be fully elucidated.

Humans↗
PubMed1989

[Studies on the chemical constituents of Fritillaria in Hubei. X. Isolation and identification of alkaloids from Fritillaria ebeiensis var.purpurea G.D.Yu et P.Li].

The bulb of Fritillaria ebeiensis var. purpurea G.D. Yu et P. Li (Liliaceae) are commercially available as the substitute for the principal Chinese traditional medicine "Beimu". This plant is easily cultivated, has high alkaloid content and conspicuous antitussive and expectorant effects. Seven C-nor-D-homo steroidal alkaloids (I-VII) were isolated from the bulb cultivated in Suizhou district, Hubei. I-IV have been identified as the known alkaloids peimine, peiminine, ebeinine and ebeinone on the basis of spectral data and by TLC and mixed mp comparison with authentic samples. The alkaloid VI, C27H43NO2, mp 186-188 degrees C, named ziebeimine, is a new alkaloid isolated from the title plant. The structure of VI has been established as 5 alpha, 14 alpha-cevanine-13, 17-dehydro-3 alpha, 6 beta-diol on the basis of its IR, 1H-NMR, 13C-NMR and mass spectra. The structure of alkaloids V and VII is still under investigation.

Cevanes↗
PubMed1988

Comparative studies of the sensitization potential of morpholine, 2-mercaptobenzothiazole and 2 of their derivatives in guinea pigs.

The aim of this study was to determine the sensitization potential of morpholine (M), 4,4'-dithiodimorpholine (DTDM), morpholinyl-mercaptobenzothiazole (MMBT) and 2-mercaptobenzothiazole (MBT) in guinea pigs. 5% and 10% DTDM, MMBT and MBT produced irritation reactions. M up to 10% failed to irritate. Sensitization tests showed that all the guinea pigs treated with DTDM and MMBT were sensitized. Cross-sensitization tests showed that 60% of the DTDM-sensitized animals reacted to challenge with MMBT; 30% of the animals sensitized to DTDM reacted to challenge with M; 80% of the MMBT-sensitized animals reacted to challenge with MBT and 10% to challenge with M; 42% of the MBT-sensitized animals reacted to MMBT. The rank order of sensitization potential in guinea pigs observed from this study is DTDM, MMBT and then MBT. It appears that the disulfide bond, sulfur linkage and the sulfhydryl group may each play a role in the sensitizing capacity of these compounds.

Allergens↗
PubMed1988

Studies of the reactivity of morpholine, 2-mercaptobenzothiazole and 2 of their derivatives with selected amino acids.

Previous studies in guinea pigs showed that DTDM, MMBT and MBT were sensitizing agents. The purpose of this study was to investigate the biochemical basis of this sensitization reaction. The reactions of representative amino acids, Cys, Lys & Gly, with morpholine, DTDM, MMBT & MBT were examined. New compounds were found between MMBT and all 3 amino acids. Additional new compounds were seen for Cys/MBT, Cys/DTDM, Lys/MBT & Gly/DTDM. No reaction was observed with morpholine. The new compounds were examined spectroscopically. Results suggest that the sensitizing nature of DTDM is probably a reaction of its disulfide bond with the -SH & -NH2 groups of amino acid moieties. The conjugation of Cys/MMBT may be via the same reaction mechanism. The -SH group of MBT may react either via oxidation and/or thioester formation with the carboxylate group of amino acids. These results also suggest that in vitro tests may predict the sensitizing potential of certain compounds.

Amino Acids↗
PubMed1987

Vitamin A metabolism in primary retinitis pigmentosa.

The serum vitamin A (VA) and retinol body pool response (RBPR) were studied in 28 cases of retinitis pigmentosa (RP), in comparison to 7 unaffected RP family members and 10 normal individuals. Serum VA was found to be normal in all 3 groups, with no significant difference between any 2 groups. The RBPR was also normal in all 3 groups, but the RBPR of the RP patients and their unaffected family members were significantly higher than the normal respectively (P less than 0.001), suggesting that the pigment epithelium or rod photoreceptor of the former groups were deficient in VA, whether from disturbed utilization or abnormalities in their retinol-binding protein, that abnormally high feedback stimuli were sent out calling for a VA supply to the target site with less retention in the liver.

Adolescent↗
PubMed1985

Epidemiologic study on the skin lesions of workers exposed to N,N'-methylene-bis-(2-amino-1,3,4-thiadiazole) and of children in the neighborhood of the factory.

The air in a factory producing N,N' methylene-bis-(2-amino-1,3,4-thiadiazole) (MATDA) and water in a nearby river were often polluted by the intermediate and finished product. The levels of MATDA in the air, soil, and river water were 0.1-0.8 mg/m3, 6-2 650 mg/kg, and 0.5-2 mg/kg, respectively. Seventy-nine workers engaged in MATDA production were observed; 44% of them suffered from contact dermatitis; and 72% showed changes of pigment in the skin (versus 2 and 16%, respectively, for the referents). All of the exposed workers had experienced dermatitis at some time. For 218 pupils of a primary school in the neighborhood of the factory, the incidence of hypopigmentation and pigmentation of the skin was 14 and 72%, respectively, but in the reference group the corresponding incidence rates were 0 and 20%. Pigment changes of workers' children increased with the duration of residence in the neighborhood of the factory. The results of the survey led to a change in the formulation of the product from a powder to an emulsion. Improved technology was also initiated which allowed most of the waste to be reused in the processing. After these control measures the dermatitis of the workers was greatly reduced.

Adolescent↗
PubMed1985

Electrophysiological studies on the nucleus isthmi of the lizards Gekko gekko and Shinisaurus crocodilurus.

This report studies visual responses of the isthmic units in Gekko gekko and Shinisaurus crocodilurus using extracellular recording and cobalt sulfide marking techniques. Our results indicate that: (i) the nucleus isthmi pars magnocellularis (Imc) is a visual center; (ii) there are luxotonic units in Imc; (iii) Imc units respond vigorously to moving contrast targets, of which 35% units burst only at the moment when targets are moving into and out of their receptive fields, none react to either tactile or auditory stimulation; (iv) there exist binocular units in Imc; and (v) visual field is topographically projected onto Imc.

Animals↗
PubMed1983

Neuroanatomy and electrophysiology of the lacertilian nucleus isthmi.

Horseradish peroxidase (HRP) tracings showed a bidirectional connection between the optic tectum (OT) and the ipsilateral nucleus isthmi (NI) pars magnocellularis (Imc) in nocturnal Gekko gekko and diurnal Shinisaurus crocodilurus. We found that, in addition to a direct neuronal pathway, there is an indirect pathway from OT to Imc via the nucleus profundus mesencephali (NPM). The morphology of cells in OT, NPM and NI was studied. Visual units extracellularly recorded from NI were located within Imc based on cobalt sulphide markings. They responded to moving contrast targets, without reacting to tactile and auditory stimulation. HRP and Golgi-Cox studies showed that Imc is a nucleus independent of its parvocellular partner, Ipc.

Animals↗