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Biomedical subjects

K Wang

Publications and source records attributed to K Wang.

At least 451 records · Page 25Linked to original sources
PubMed1994

[The supplementary effect of consulting vaccination in expanded program on immunization (EPI)].

This study was carried out in 420 of children aged 12-24 months in two counties of Gansu Province, China. The result showed that general consulting rate was 30.24% in county or township hospital. The average consulting time was 2.14. A formula was designed K = R x C (1-V) for detecting the effect of consulting vaccination in EPI. The maximum supplementary coefficients of initial immunization of outpatient children for the vaccines were as follows: BCG 0.3024, TOPV-3 0.0953, DPT-3 0.0929, MV 0.0643. And once immunization were BCG 0.3024, TOPV 0.2643, DPT 0.2381, MV 0.0643. The study also explores the supplementary effect of consulting vaccination in different vaccination times and immunization coverages.

Child, Preschool↗
PubMed1994

[A study on alcohol drinking pattern in freshmen and sophomores].

Alcohol drinking pattern in 871 freshmen and sophomores of Han nationality was studied. Results showed 92.7% of the male and 72.9% of the female students were alcohol drinkers. There were highly significant differences in alcohol drinking pattern and types of alcoholic beverage they drank between males and females (P < 0.0001), and between students specializing in different subjects (P < 0.01). Alcohol drinking pattern of male students was influenced by their academic concerns and the drinking behavior of their fathers and friends.

Adult↗
PubMed1994

Studies on the HDL receptors. I: Evidence for the existence of HDL receptors in Beijing duck liver.

It had been found that Beijing ducks (BD) have a high level of HDL (70%), high LCAT but very low CETP activity and will not develop atherosclerosis on an atherogenic diet, suggesting that cholesterol ester is mainly carried by HDL and metabolized through an HDL receptor pathway in the liver. However, evidence of this receptor's existence in the liver is not yet complete. In this paper, the HDL receptor in BD liver has been studied. Our experiments showed: 1) ApoE-free 125I-HDL could bind specifically to duck hepatic cell membrane with high affinity (Kd = 9.6 micrograms/ml) and was saturable (Bmax = 8.9 micrograms/mg cell membrane protein) at room temperature. 2) Competitive inhibition studies with unlabelled duck, human, rat and chick HDL and duck apo AI and its liposomes formed with PC or DMPC could inhibit the binding of 125I-HDL to duck hepatic cell membranes, but LDL, apo E and their liposomes with PC or DMPC could not with the exception of duck LDL. 3) The receptor could recognize apo AI but not apo B or E. 4) Both phosphorylase A2 and pronase could inhibit the binding activity. The above results give strong evidence for the existence of a specific HDL receptor pathway in the duck liver, supporting our hypothesis that CE in Beijing ducks is metabolized directly through the hepatic HDL receptor instead of being transferred back to VLDL and LDL, then through the LDL receptor pathway. This unique way of metabolizing CE may be behind the Beijing duck's antiatherogenicity.

Animals↗
PubMed1993

Nebulin as an actin zipper. A two-module nebulin fragment promotes actin nucleation and stabilizes actin filaments.

Nebulin is a family of giant muscle proteins (700-900 kDa) that interact with actin to form composite thin filaments in the skeletal muscle sarcomere. This modular protein is composed predominantly of repeating sequence modules of 31-38 residues. To understand the minimum size and number of sequence modules that are required for actin interaction, we studied the behavior of a highly soluble two-module nebulin fragment ND8 that was expressed in Escherichia coli. By fluorescence spectroscopy with pyrenyl-actin and co-sedimentation assays, we observed the following. 1) ND8 greatly accelerated actin nucleation, especially in a buffer that is suboptimal for actin nucleation. The presence of ND8 abolished the lag phase of actin polymerization and increased the net extent of steady state polymerization, thereby reducing the critical concentration of actin polymerization. 2) ND8 reduced the rate of actin depolymerization and might increase the rate of elongation. 3) Cytochalasin E, which caps both ends of actin filaments, inhibited the effect of ND8 on actin polymerization and caused the depolymerization of actin-ND8 complexes. These data suggest that ND8 interacts with actin in such a fashion that it stabilizes the actin nuclei and slows the depolymerization from the ends of actin filaments. 4) The binding stoichiometry of ND8 to F-actin, as estimated by co-sedimentation assays, is 1 to 2 mol of ND8 to 1 mol of actin with an apparent dissociation constant of 20 to 40 microM. Our data suggest that nebulin-actin interaction promotes actin nucleation and stabilizes preformed actin filaments, both of which are desirable attributes of a length-regulating template for actin filaments of the skeletal muscle. Each nebulin molecule may contain as many as 100-200 actin binding domains to form a zipper-like nebulin/actin composite filament.

Actins↗
PubMed1993

Filamentous aggregates of native titin and binding of C-protein and AMP-deaminase.

In solutions of high ionic strength, native titin-2, a large extractable fragment of the sarcomere matrix protein titin, appears as extremely long, flexible, and slender beaded strings. We report here that in solutions of lower ionic strength near neutral pH, titin-2 assembles into higher-order aggregates with surface projections. Solid phase binding assays show that two myosin-binding proteins, C-protein and AMP-deaminase, are also titin-binding proteins. Both proteins decorate titin aggregates, producing filaments of more uniform appearance. Numerical Fourier transforms of these decorated aggregates show approximately 12-nm periodicities. The interaction of titin with myosin-associated proteins such as C-protein may take part in the anchoring mechanism that prevents the stretching and extension of titin filaments in the A band.

AMP Deaminase↗
PubMed1993

Characterization of the human aldose reductase gene promoter.

The promoter region of the human aldose reductase gene has been identified upstream of the translation start ATG codon. The promoter contains a TATA box, a CCAAT promoter element, and three Sp1 protein binding consensus sequences upstream of the capsite. A 640-base pair insert spanning +31 to -609 directs expression of the reporter gene chloramphenicol acetyltransferase in an orientation-specific manner in transfected Hep G2 cells. The promoter activity remained constant with deletions from base pairs -609 to -186. The TATA and the CCAAT consensus sequences show significant promoter activity, whereas the three Sp1 binding consensus sequences, individually, have no significant promoter activity. A GA-rich region (-186 to -146) contains two CGGAAA/G motifs, which show promoter activity and interaction with Hep G2 nuclear extract and GA-binding proteins (GABP alpha and GABP beta 1) as shown by mobility shift assays and DNase I footprinting. Similar cis-elements in herpes simplex virus type 1 interact with rat liver GABP and the viral VP16 protein to mediate the induction of immediate early viral genes. A GC-rich region (-87 to -31) is identified by mobility shift assay, and a consensus sequence of an androgen response element is present at -396 to -382. The human aldose reductase promoter, thus, has regulatory response elements that may be important during early development and puberty. These regulatory elements may play a significant role in the development of certain diabetic complications.

Aldehyde Reductase↗
PubMed1993

Promoter-specific synthetic photoendonuclease: rose bengal-labeled T7 RNA polymerase.

We have constructed a synthetic photoendonuclease composed of T7 RNA polymerase linked to rose bengal. The promoter-specific polymerase confers site-specific binding, and the photosensitizer rose bengal allows light-induced DNA cleavage. Using a gentle labeling procedure, we find that the polymerase can be labeled with 1-30 rose bengals. Polymerase labeled to about 8 rose bengals per molecule retains the same efficiency and specificity of binding to promoter-containing DNA as unlabeled polymerase. At this level of rose bengal substitution, the synthetic endonuclease, in the presence of visible light, specifically cleaves linear or supercoiled DNA containing a T7 promoter. It induces frank single-strand breaks, rather than labile sites convertible to breaks upon additional treatments. Neither the free rose bengal moiety not bonded to polymerase nor the free (not bound to DNA) rose bengal-substituted polymerase cleaves DNA. Although rose bengal is an efficient generator of singlet oxygen, depletion of oxygen from reaction mixtures increases the cleavage rate. This indicates that singlet oxygen cleavage is not a major mechanism of DNA nicking by the synthetic endonuclease. At higher levels of rose bengal substitution, the labeled polymerase shows decreased binding efficiency and increased nonspecific binding to DNA without a T7 promoter; the specificity of DNA cleavage also decreases. These results indicate that the site specificity of rose bengal photocleavage by the synthetic endonuclease results from specific binding of the polymerase, and thus rose bengal photonicking reflects polymerase binding.

Binding Sites↗
PubMed1993

Silver-enhanced copper staining of protein blots.

Copper staining of protein blots has previously been shown to detect proteins rapidly, quantitatively, and sensitively. The sensitivity of this assay can now be enhanced nearly 10-fold with an additional step of silver staining. The silver-enhanced assay retains many of the virtues of copper staining, including a quantitative optical response with the amount of adsorbed protein, low variation between proteins, and reversibility. In addition, both copper staining and silver-enhanced copper staining do not detect nucleic acid, thus allowing for selective measurement of nucleic acid binding proteins or protein contamination in nucleic acid preparations. Silver-enhancement requires only a 5-min incubation with a single reagent. Since copper staining is performed first, it can be used to determine if the greater sensitivity provided by silver enhancement is desirable. For quantitation, an inexpensive reflectance scanning densitometer utilizing optical scanners and NIH Image is described.

Albumins↗
PubMed1993

Identification and physical mapping of a polymorphic human T cell receptor V beta gene with a frequent null allele.

Germline variation in genes that encode the human T cell receptors (TCRs) may have an important influence in shaping the immune T cell repertoire. In this report we describe a frequent null allele of the human V beta 18 gene, resulting from a nucleotide substitution that creates a stop codon (CGA<-->TGA). Approximately 11% of the population tested was homozygous for this null allele, indicating that this is a frequent "hole in the repertoire." We confirmed that there is a greatly reduced (undetectable) level of V beta 18 mRNA in peripheral blood lymphocytes from an individual homozygous for this null allele. In addition, all heterozygous individuals expressed detectable levels of only the functional V beta 18 allele in their peripheral blood lymphocytes. Two other DNA polymorphisms were identified in V beta 18, one of which would result in an amino acid substitution in an expressed V beta 18 gene. Genotypes for all three of these V beta 18 DNA polymorphisms were determined in a group of unrelated individuals. Statistical analyses of the associations between alleles of the V beta 18 polymorphisms and those of other DNA polymorphisms in the TCR beta locus suggested a close physical proximity between the V beta 18 gene and the 3' end of the C beta 2 region. This localization of human V beta 18 had been previously predicted by the sequence homology between human V beta 18 and mouse V beta 14, a V gene segment previously mapped to 3' of the mouse C beta genes. We confirmed this localization of the human V beta 18 gene by isolating a cosmid clone that contains both the V beta 18 and C beta 2 segments. Mapping by restriction enzyme digestion and by the polymerase chain reaction indicated that the V beta 18 gene segment is approximately 9 kb 3' of the C beta 2 gene, making this the only known human V beta gene 3' of the C beta region.

Alleles↗
PubMed1993

Elastic properties of titin filaments demonstrated using a "freeze-break" technique.

A "freeze-break" technique (Trombitás, K.: Acta Biochim. Biophys. Hung. 6:419-427, 1971) and immunoelectron microscopy were used to study the elastic properties of titin filaments. Small bundles of freshly prepared rabbit psoas muscle fibers were quickly frozen and broken under liquid nitrogen to fracture sarcomeres in planes perpendicular to the filament axis, in each of various regions along the sarcomere. The still-frozen specimens were thawed during fixation to allow elastic filaments to retract. The broken specimens were then labelled with monoclonal anti-titin antibodies against an unique epitope in the I-band. The titin epitopes were normally positioned symmetrically about the Z-line. However, in sarcomeres broken at the A-I junction, the epitopes no longer remained symmetrical: the titin filaments in the broken half-sarcomere retracted, independently of the thin filaments, forming a dense band just near the Z-line. The retracted density apparently did not reach the Z-line; retraction stopped at the level of the so-called N1-line. In sarcomeres broken at the Z-line level, the titin filaments retracted in the opposite direction. In this case the titin epitope retracted all the way to the ends of the thick filaments. It appears then that titin molecules form elastic filaments that are independent of thin filaments in most of the I-band. Near the Z-line, however, the titin filaments either have an inelastic domain or associate firmly with the thin filaments at the N1-line level.

Actin Cytoskeleton↗
PubMed1993

Kinetic silver staining and quantification of proteins adsorbed to microtiter plates.

A silver stain was used to detect and quantitate proteins adsorbed to microtiter plate wells. The kinetics of the development of the silver stain were analyzed with an automated microtiter plate reader. The lag time for stain development was found to be a consistent indicator of the amount of protein adsorbed to a microtiter plate well. Protein which was not preadsorbed to the microtiter plate was not effectively stained by silver. Complete adsorption of protein applied to the microtiter plate was possible by drying small amounts of protein in very dilute buffers. Variations in sensitivity for different proteins were less than 30% for the panel of proteins examined. Determinations from kinetic silver staining agreed with those from copper staining for bovine albumin adsorbed to microtiter plates. The precision of kinetic silver staining assay was optimal in the range of 40 to 200 ng per microtiter plate well. In this range, the standard deviations averaged less than 5%. Even smaller amounts of protein can be detected and interpolated down to approximately 10 ng per well. The kinetic silver staining method can be used on standard microtiter plate readers without special filters and is readily adaptable to automated systems.

Adsorption↗