Biomedical subjects

W Wu

Publications and source records attributed to W Wu.

At least 271 records · Page 15Linked to original sources

PubMed1998

Experimental study on the scavenging effects of ginsenosides on oxygen free radicals using model of heterotopic heart transplantation in rats.

Oxygen-derived free radicals play an important role in myocardial injury associated ischemia and reperfusion. To investigate whether ginsenosides, as an additive agent of cardioplegic solution, can decrease toxicity of oxygen free radicals in myocardial injury, a heterotopic heart transplantation model in Wistar rats was employed. St. Thomas II cold cardioplegia containing ginsenosides 80 mg/l was used in the experimental group. St. Thomas II cold cardioplegia alone was used in the control group. After global ischemia for 60 minutes and reperfusion for 30 minutes of a transplanted heart, SOD activity in the myocardium treated with ginsenosides was significantly higher than that in the control group (N=10, p< 0.01), whereas the MDA in the myocardium treated with ginsenosides were markedly lower than that of the control group (p< 0.01). The amounts of oxygen free radicals in the myocardium treated with ginsenosides were significantly lower than that of the control group (p <0.001). This study demonstrates that ginsenosides, as a proper additive agent of cardioplegic solution, can decrease toxicity of oxygen free radicals, suggesting one of the mechanisms for its protective effects against myocardial ischemia and reperfusion injury.

Animals↗

PubMed1998

Phenotype of an X-linked retinitis pigmentosa family with a novel splice defect in the RPGR gene.

PURPOSE: To assess the clinical phenotype in a Swedish family with X-linked retinitis pigmentosa (XLRP) resulting from a novel splice defect in the RPGR gene. METHODS: RPGR mutation analysis was performed in one family with XLRP, and several individuals from the family were examined clinically. RESULTS: The causative mutation in the family was demonstrated to be a single base-pair change at the splice donor site in intron 7 that resulted in skipping of the complete exon 7 in the mature RPGR transcript. The aberrant mRNA is predicted to produce an RPGR protein with an in-frame deletion of 53 amino acids, corresponding to an RCC1-homology repeat. Clinical studies that included ophthalmological examination and full-field electroretinography showed that this splice mutation resulted in a comparatively less severe form of RP. CONCLUSIONS: Correlation of a causative RPGR genotype with clinical findings in hemizygotes and carrier heterozygotes is an important step toward predictive diagnosis and should assist in the development of gene-based therapies in the future.

Carrier Proteins↗

PubMed1997

Structural features of the kringle domain determine the intracellular degradation of under-gamma-carboxylated prothrombin: studies of chimeric rat/human prothrombin.

Vitamin K antagonists such as warfarin inhibit the vitamin K-dependent gamma-glutamyl carboxylation during protein processing and block the secretion of under-gamma-carboxylated prothrombin (FII) in the rat but not in the human or bovine. Under-gamma-carboxylated prothrombin is also secreted from warfarin-treated human (HepG2) cell cultures but is degraded in the endoplasmic reticulum in warfarin-treated rat (H-35) cell cultures. This differential response to warfarin has been shown to be determined by the structural difference in the proteins rather than by the origin of the cell line. When recombinant rat prothrombin (rFII) and human prothrombin (hFII) were expressed in a transformed human kidney cell line (HEK293), secretion of rFII but not hFII was drastically decreased in response to warfarin. To determine the structural signal required for this differential response, chimeric cDNAs with the propeptide/Gla domains, kringle domain, and serine protease domain exchanged between rFII and hFII were generated (FIIRHH and FIIHRR, FIIRRH and FIIHHR, FIIRHR and FIIHRH) and expressed in both warfarin-treated HEK293 cells and HepG2 cells. The presence of the hFII kringle domain changed the stability of rFII to that of hFII, and the rFII kringle domain changed the stability of hFII to that of rFII. The kringle domain therefore is critical in determining the metabolic fate of under-gamma-carboxylated prothrombin precursors during processing. Prothrombin contains two kringle structures, and expression of additional rFII/hFII chimeras (FIIHrhH and FIIHhrH, FIIRrhR, and FIIRhrR) was used to determine that the first of the two kringles plays a more important role in the recognition process.

Animals↗

PubMed1997

Genetic definition of a protein-splicing domain: functional mini-inteins support structure predictions and a model for intein evolution.

Inteins are protein-splicing elements, most of which contain conserved sequence blocks that define a family of homing endonucleases. Like group I introns that encode such endonucleases, inteins are mobile genetic elements. Recent crystallography and computer modeling studies suggest that inteins consist of two structural domains that correspond to the endonuclease and the protein-splicing elements. To determine whether the bipartite structure of inteins is mirrored by the functional independence of the protein-splicing domain, the entire endonuclease component was deleted from the Mycobacterium tuberculosis recA intein. Guided by computer modeling studies, and taking advantage of genetic systems designed to monitor intein function, the 440-aa Mtu recA intein was reduced to a functional mini-intein of 137 aa. The accuracy of splicing of several mini-inteins was verified. This work not only substantiates structure predictions for intein function but also supports the hypothesis that, like group I introns, mobile inteins arose by an endonuclease gene invading a sequence encoding a small, functional splicing element.

Amino Acid Sequence↗

PubMed1997

Head induction by simultaneous repression of Bmp and Wnt signalling in Xenopus.

The Spemann organizer of the amphibian embryo can be subdivided into two discrete activities, namely trunk organizer and head organizer. Several factors secreted from the organizer that are involved in trunk organization are thought to act by repressing Bmp signalling. With the exception of the secreted factor cerberus, little is known about head-organizer inducers. Here we show that co-expression of a dominant-negative Bmp receptor with inhibitors of the Wnt-signalling pathway in Xenopus leads to the induction of complete secondary axes, including a head. This induction does not require expression of the siamois marker of Nieuwkoop centre signalling, suggesting that cells are directly shifting to head-organizer fate. Furthermore, we find that cerberus is a potent inhibitor of Wnt signalling. Our results indicate that head-organizer activity results from the simultaneous repression of Bmp and Wnt signalling and they suggest a mechanism for region-specific induction by the organizer.

Animals↗

PubMed1997

Identification and functional characterization of a second chain of the interleukin-10 receptor complex.

Interleukin-10 (IL-10) is a pleiotropic cytokine which signals through a specific cell surface receptor complex. Only one chain, that for ligand binding (IL-10Ralpha or IL-10R1), was identified previously. We report here that, although human IL-10 binds to the human IL-10R1 chain expressed in hamster cells, it does not induce signal transduction. However, the co-expression of CRFB4, a transmembrane protein of previously unknown function belonging to the class II cytokine receptor family, together with the IL-10R1 chain renders hamster cells sensitive to IL-10. The IL-10:CRFB4 complex was detected by cross-linking to labeled IL-10. In addition, the IL-10R1 chain was able to be co-immunoprecipitated with anti-CRF antibody when peripheral blood mononuclear cells were treated with IL-10. These results demonstrate that the CRFB4 chain is part of the IL-10 receptor signaling complex. Thus, the CRFB4 chain, which we designate as the IL-10R2 or IL-10Rbeta chain, serves as an accessory chain essential for the active IL-10 receptor complex and to initiate IL-10-induced signal transduction events.

Animals↗

PubMed1997

Multiple dimeric forms of human CD69 result from differential addition of N-glycans to typical (Asn-X-Ser/Thr) and atypical (Asn-X-cys) glycosylation motifs.

CD69 is expressed on the surface of all hematopoietically derived leukocytes and is suggested to function as a multipurpose cell-surface trigger molecule important in the development and activation of many different cell types. Human CD69 contains only a single consensus sequence for N-linked oligosaccharide addition within its extracellular domain (Asn-Val-Thr), yet exists as two distinct glycoforms that are assembled together into disulfide-linked homodimers and heterodimers. The molecular basis for human CD69 heterogeneity has remained elusive. In the current report we show that human CD69 glycoforms are generated before the egress of CD69 proteins from the endoplasmic reticulum to the Golgi and are synthesized under conditions where Golgi processing is inhibited, effectively ruling out the possibility that CD69 heterogeneity results from the differential processing of a single glycosylation site in the Golgi complex. Importantly, these data demonstrate that contrary to current belief, not one but two sites for N-glycan addition exist within the human CD69 extracellular domain and identify the second, "cryptic" CD69 N-glycan attachment site as the atypical Cys-containing glycosylation motif, Asn-Ala-Cys. The results in this study provide a molecular basis for human CD69 heterogeneity and show that multiple dimeric forms of human CD69 result from the variable addition of N-glycans to atypical and typical glycosylation motifs within the CD69 extracellular domain.

Antigens, CD↗

PubMed1997

Action of Taiwan cobra cardiotoxin on membranes: binding modes of a beta-sheet polypeptide with phosphatidylcholine bilayers.

The interaction of Taiwan cobra cardiotoxin (CTX A3), a basic polypeptide consisting of three-fingered loops and five-strand beta-sheet structure, with zwitterionic dipalmitoylphosphatidylcholine (DPPC) has been studied by 31P and 2H NMR to understand the binding modes of CTX in membrane bilayers. The results, in conjunction with DPH fluorescence anisotropy and differential scanning calorimetry studies, show that CTX may penetrate and lyse the bilayers into small aggregates at a lipid/protein molar ratio of about 20 in the ripple Pbeta' phase. Elevating the temperature to that of the liquid crystalline Lalpha phase leads to the fusion of the small aggregates into larger ones as evidenced by the change of the isotropic signal into a magnetically aligned 31P signal with a marked reduction in the chemical shift anisotropy. 2H NMR study on deuterium-labeled DPPC in the head group and fatty acyl region as a function of temperature and CTX concentration reveals a molecular model that CTX undergoes a redistribution between penetrating and peripheral binding states depending on the temperature studied. In addition, both the conformational and dynamic states of the phosphocholine head group of DPPC bilayers are significantly perturbed in the presence of CTX. Structural consideration of the CTX molecule indicates that the penetration binding mode of CTX with the DPPC bilayer may involve a novel membrane-binding motif identified recently in the three-fingered loops of P-type CTX. CTX can only bind to DPPC membrane peripherally in the Lalpha phase due to the mismatch of their hydrophobic lengths.

Calorimetry, Differential Scanning↗

PubMed1997

Evidence for a unique mechanism of strand transfer from the transactivation response region of HIV-1.

We previously found that strand transfer by human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) is promoted at sites where RT pauses during synthesis. In this report, strand transfer is measured within the 5' transactivation response region (TAR) of HIV-1 RNA. We hypothesized that the stable hairpin structure of TAR would induce RT pausing, promoting RNase H-directed cleavage of the template and subsequent transfer at that site. We further predicted that HIV-1 nucleocapsid protein (NC), known to melt secondary structures, would decrease transfer. We show that TAR created a strong pause site for RT, but NC significantly promoted strand transfer. The effect of NC is specific, since other single strand binding proteins failed to stimulate transfer. In another unexpected outcome, preferred positions of internal transfer were not at the pause site but were in the upper stem and loop of TAR. Thus, we propose a new mechanism for transfer within TAR described by an interactive hairpin model, in which association between the donor and the acceptor templates within the TAR stem promotes transfer. The model is consistent with the observed stimulation of strand transfer by NC. The model is applicable to internal and replicative end transfer.

Base Sequence↗

PubMed1997

Transcriptional repression of the growth-associated T alpha1 alpha-tubulin gene by target contact.

In this report, we address the molecular mechanisms that regulate axonal growth by focusing on the gene for one of the major axonal cytoskeletal proteins, T alpha1 alpha-tubulin. During the developmental growth of sympathetic neurons, transcription of a beta-galactosidase transgene driven by the T alpha1 promoter (T alpha1:nlacZ) was high until the time of target innervation and neuronal maturation, when it decreased significantly. In mature animals, T alpha1:nlacZ transcription remained relatively low until target contact was experimentally disrupted; when facial motoneurons were axotomized, T alpha1:nlacZ transgene expression increased, was maximal for 1-7 days, and, if neurons regenerated and reinnervated their target musculature, returned to control levels by 49 days. In contrast, if regeneration and reestablishment of target contact were inhibited, transgene expression remained elevated. To determine whether this increased transcription was due to the loss of target contact or to axonal loss, we transected sympathetic neurons that project to the eye either close to or far from their cell bodies. In both cases, when target contact was severed, T alpha1:nlacZ transcription increased. These experiments indicate that transcription of the T alpha1 alpha-tubulin promoter is repressed by target contact in both developing and mature neurons. We suggest that this repression is due to a target-derived "stop-growth" factor that retrogradely signals to regulate transcription of this and other genes that are required for axonal growth.

Animals↗

PubMed1997

Initial genome scan of the NIMH genetics initiative bipolar pedigrees: chromosomes 1, 6, 8, 10, and 12.

A report on an initial genome screen on 540 individuals in 97 families was collected as part of the NIMH Genetics Initiative on Bipolar Disorder. Families were ascertained to be informative for genetic linkage and underwent a common ascertainment and assessment protocol at four clinical sites. The sample was genotyped for 65 highly polymorphic markers from chromosomes 1, 6, 8, 10, and 12. The average intermarker interval was 16 cM. Genotypic data was analyzed using affected sib pair, multipoint affected sib pair, and pedigree analysis methods. Multipoint methods gave lod scores of approximately two on chromosomes 1, 6, and 10. The peak lod score on chromosome 6 occurred at the end of the q-arm, at some distance from the 6p24-22 area previously implicated for schizophrenia. We are currently genotyping additional markers to reduce the intermarker interval around the signals. The interpretation of results from a genome screen of a complex disorder and the problem of achieving a balance between detecting false positive results and the ability to detect genes of modest effect are discussed.

Bipolar Disorder↗

PubMed1997

Case study of bovine dermatitis caused by oat straw infected with Fusarium sporotrichioides.

A dermatitis characterised by discrete, raised, plaque-like and cracked skin lesions of variable sizes on the udder, the hind quarters, the lips and muzzle of all the cows in a herd was suspected of being caused by the oat straw used in bedding, after initial feed analysis and skin culture were negative for toxins and dermatophytes. Mycological analysis indicated an extensive infestation of the oat straw by Fusarium sporotrichioides, a toxic mould, and an immunochemical assay indicated dermatotoxic trichothecenes in the straw (0.22 microgram/g dried straw). An ethyl acetate extract of the straw induced a necrotic response on shaved rat skin. Ingestion of the toxic bedding straw and inhalation of toxic straw dust probably also caused the internal haemorrhage and lung emphysema observed in the two cows that died. The regression of the dermatitis and the recovery of general herd health after the withdrawal of the oat straw further supported the diagnosis.

Animals↗

PubMed1997

Molecular cloning of the RNA polymerase I transcription factor hUBF/NOR-90 (UBTF) gene and localization to 17q21.3 by fluorescence in situ hybridization and radiation hybrid mapping.

The 90-kDa nucleolus organizer region autoantigen (NOR-90) was previously shown to be identical to human upstream binding factor (hUBF), which has two molecular mass forms of 89 and 93 kDa, respectively. hUBF/NOR-90 is a member of the HMG-box DNA-binding protein family and is known to bind to enhancer regions upstream of the ribosomal RNA genes, which are clustered at NORs. The smaller version of UBF lacks an internal 111-bp region corresponding to 37 amino acids in the second HMG-box of the larger form. We isolated human genomic clones from a phage library and localized one of them by fluorescence in situ hybridization to chromosome 17q21.3. DNA sequence analysis showed that the 111-bp region represented a single exon, consistent with the previous notion that the two isoforms were products of alternative pre-mRNA splicing of a single gene in human. Radiation hybrid mapping placed this STS with very high probability (LOD > 19) to chromosome 17, approximately 3.77 cR distal to MIT framework marker UTR-9641. The order of the markers (a partial list) from this region was UTR-9641, SGC30031, WI-17308, D17S930, NOR53/33, WI-16100, D17S920, WI-16913, and WI-6808.

Alternative Splicing↗

PubMed1997

The Crystallization of Fluorapatite in the Presence of Hydroxyapatite Seeds and of Hydroxyapatite in the Presence of Fluorapatite Seeds

The kinetics of growth of crystals induced by hydroxyapatite (HAP) seed crystals in supersaturated solutions of fluorapatite and of fluorapatite (FAP) seed crystals in supersaturated solutions of hydroxyapatite have been studied using the constant composition method. The reactions were investigated at relative supersaturations ranging from sigmaFAP = 0.99 to 12.0 at pH 6.5 and for HAP, sigmaHAP = 3.6 to 12.6 at pH 7.4. In FAP-supersaturated solutions, this phase was nucleated at the HAP surfaces and underwent growth at a rate more than three times greater than that on FAP seed crystals of equivalent surface area. Transmission electron microscopy (TEM) and electron diffraction imaging clearly demonstrated that the new needle-like HAP phase originated at the FAP surface with the 002 planes of HAP growing on FAP. In contrast, the mutual orientation of FAP crystallization on HAP seed crystals could not be established. Interfacial energies of FAP, HAP, and octacalcium phosphate (OCP) microcrystals against aqueous solutions were obtained by using a thin-layer wicking technique. The interfacial energy values measured in pure aqueous solutions were 18.5, 9.0, and 4.3 mJ m-2 for FAP, HAP, and OCP, respectively. The much smaller value for OCP as compared with the other phases may explain why this phase has been so frequently implicated as a possible precursor to the formation of apatite, especially in biological mineralization reactions.

Journal Article↗

PubMed1997

Inhibition of gluconeogenesis in cultured chicken embryo hepatocytes by Fusarium metabolites.

Four Fusarium metabolites, 2,5-anhydro-D-mannitol, 2,5-anhydro-D-sorbitol, moniliformin, and fumonisin B1, were tested for their ability to inhibit gluconeogenesis and cell viability in a primary chicken embryo hepatocyte culture system. The hepatocyte system was established from fertilized chicken eggs that were incubated for 14 days. The hepatocytes produced and secreted glucose into the supernatant of a Krebs incubation solution amended with 3 mM of either lactate or fructose as a precursor for glucose formation. 2,5-Anhydro-D-mannitol and 2,5-anhydro-D-sorbitol inhibited gluconeogenesis in these cells from both lactate and fructose. The former anhydro sugar was more inhibitory when lactate was the precursor (50% inhibition, IC50, 6 mM) and the latter anhydro sugar more inhibitory when fructose was the precursor (IC50, 12 mM). Moniliformin was more inhibitory to glucose formation from lactate (IC50, 100 microM) than from fructose in these cells. The degrees of inhibition of gluconeogenesis by the two anhydro sugars and moniliformin were greater than their effect on cell viability. Fumonisin B1 as high as 1 mM neither inhibited gluconeogenesis, nor affected cell viability.

Animals↗

PubMed1997

Heterogeneous nucleation of calcium phosphates on solid surfaces in aqueous solution.

The heterogeneous nucleation of calcium phosphates on solid surfaces of poly(methyl methacrylate) (PMMA), poly-(tetrafluoroethylene-co-hexafluoropropylene) (FEP), silicone rubber, mica, and radiofrequency glow discharge (RFGD)-treated PMMA, FEP, and silicone rubber has been studied in solutions supersaturated with respect to hydroxyapatite. The surface properties of the substrates were characterized by contact angle measurements. For the RFGD-treated surfaces, the Lifshitz-Van der Waals surface tension component changes very little, but the Lewis acid-base surface tension parameters vary greatly depending upon the materials. With scanning electron microscopy, nucleation of calcium phosphates was observed only on the surfaces: mica, RFGD-treated PMMA and FEP, with relatively high values of the Lewis base surface tension parameter. The more hydrophobic surfaces having low Lewis acid-base surface tensions, untreated PMMA and FEP, silicone rubber, and even RFGD-treated silicone rubber showed no nucleation.

Biocompatible Materials↗

PubMed1997

Effects of the herbicide molinate on mixotrophic growth, photosynthetic pigments, and protein content of Anabaena sphaerica under different light conditions.

The effects of the carbamate herbicide molinate on growth and chlorophyll a, biliprotein, and protein content of the nitrogen-fixing cyanobacterium Anabaena sphaerica grown mixotrophically under 3000- and 300-lux light intensity were studied. Under two light intensities, the three concentrations of molinate tested (5, 25, and 50 microg ml-1) can significantly inhibit algal growth in a dose-dependent manner. The high concentration of molinate (50 microg ml-1) stimulated the synthesis of chlorophyll a and protein, but inhibited the formation of biliprotein, and these effects appear to be greater at 3000 lux than at 300 lux. The effects of the other two concentrations of molinate (5 and 25 microg ml-1) on chlorophyll a and biliprotein varied with time, but 5 microg ml-1 molinate had an inhibitory effect on the synthesis of protein. It was demonstrated that different concentrations of molinate had different effects on chlorophyll a, biliprotein, and protein content, which varied with light intensity. The results support the suggestion that the physiological mode of molinate toxicity to A. sphaerica is related to its interference with the metabolism of protein, particularly the formation and functional effectiveness of some special protein.

Anabaena↗

PubMed1997

Molecular evolution of cytochrome c oxidase subunit IV: evidence for positive selection in simian primates.

Cytochrome c oxidase (COX) is a multi-subunit enzyme complex that catalyzes the final step of electron transfer through the respiratory chain on the mitochondrial inner membrane. Up to 13 subunits encoded by both the mitochondrial (subunits I, II, and III) and nuclear genomes occur in eukaryotic organisms ranging from yeast to human. Previously, we observed a high number of amino acid replacements in the human COX IV subunit compared to mouse, rat, and cow orthologues. Here we examined COX IV evolution in the two groups of anthropoid primates, the catarrhines (hominoids, cercopithecoids) and platyrrhines (ceboids), as well as one prosimian primate (lorisiform), by sequencing PCR-amplified portions of functional COX4 genes from genomic DNAs. Phylogenetic analysis of the COX4 sequence data revealed that accelerated nonsynonymous substitution rates were evident in the early evolution of both catarrhines and, to a lesser extent, platyrrhines. These accelerated rates were followed later by decelerated rates, suggesting that positive selection for adaptive amino acid replacement became purifying selection, preserving replacements that had occurred. The evidence for positive selection was especially pronounced along the catarrhine lineage to hominoids in which the nonsynonymous rate was first faster than the synonymous rate, then later much slower. The rates of three types of "neutral DNA" nucleotide substitutions (synonymous substitutions, pseudogene nucleotide substitutions, and intron nucleotide substitutions) are similar and are consistent with previous observations of a slower rate of such substitutions in the nuclear genomes of hominoids than in the nuclear genomes of other primate and mammalian lineages.

Amino Acid Sequence↗