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Biomedical subjects

W Gu

Publications and source records attributed to W Gu.

At least 19 recordsLinked to original sources
PubMed2002

Quantitative trait loci for bone density in mice: the genes determining total skeletal density and femur density show little overlap in F2 mice.

Bone mineral density variation is a highly heritable trait and is the best predictor of skeletal fragility. Total skeletal density was determined by PIXIMUS, and femur density was determined by pQCT. The data were analyzed for quantitative trait loci (QTL) to determine if bone density at a specific skeletal site (femur) would identify new gene loci or the same gene loci as total body (PIXIMUS). In order to show concordance and differences in QTL for total body bone density versus femur bone density, we performed a genome-wide scan from 633 (MRL x SJL) F2 mice. The bone mineral density (BMD) data from pQCT were used to identify nine QTL on chromosomes 1, 3, 4, 9, 12, 17, and 18, while nine QTL on chromosomes 1, 2, 4, 9, 11, 14, and 15 were identified by PIXIMUSdata, accounting for 32.5% and 30.4% variation in F2 mice, respectively. QTL on chromosomes 1, 2, 3, 9, 11, 12, 14, 15, 17, and 18 are unique to our study, as they have never been described before. Chromosome 1 (D1Mit33 and D1Mit362) had similar QTL between pQCT and PIXIMUS. Several QTL were identified for both femur and total body BMD but only two QTL were common for both of these phenotypes. This suggests that genes regulating bone density differ depending on the skeletal site analyzed.

Animals↗
PubMed2002

Opposing changes in osteocalcin levels in bone vs serum during the acquisition of peak bone density in C3H/HeJ and C57BL/6J mice.

Our knowledge of the developmental changes in the concentration of serum and bone osteocalcin (OC) is limited. To investigate the interrelationship between skeletal and circulatory OC during acquisition of peak bone density in mice, we examined the temporal changes in the concentration of serum and bone OC from 3 to 12 weeks of age between C3H/HeJ (C3H) and C57BL/6J (B6), two commonly used inbred strains of mice with a large difference in bone density. We have demonstrated an increase in bone and decrease in serum OC during the acquisition of peak bone density in C3H and B6 mice which parallels an increase in bone mineral density. These two strains exhibited differential changes in the concentration of OC. C3H mice retained more OC in bone and secreted less into serum compared with B6, which coincides with the large differences in bone density between these two strains. These opposite changes of OC levels in bone and serum between C3H and B6 stress the importance of defining the genetic mechanisms underlying the differences in OC metabolism, differences that could be relevant to the acquisition and maintenance of bone mass in mice.

Aging↗
PubMed2001

Negative control of p53 by Sir2alpha promotes cell survival under stress.

The NAD-dependent histone deacetylation of Sir2 connects cellular metabolism with gene silencing as well as aging in yeast. Here, we show that mammalian Sir2alpha physically interacts with p53 and attenuates p53-mediated functions. Nicotinamide (Vitamin B3) inhibits an NAD-dependent p53 deacetylation induced by Sir2alpha, and also enhances the p53 acetylation levels in vivo. Furthermore, Sir2alpha represses p53-dependent apoptosis in response to DNA damage and oxidative stress, whereas expression of a Sir2alpha point mutant increases the sensitivity of cells in the stress response. Thus, our findings implicate a p53 regulatory pathway mediated by mammalian Sir2alpha. These results have significant implications regarding an important role for Sir2alpha in modulating the sensitivity of cells in p53-dependent apoptotic response and the possible effect in cancer therapy.

Animals↗
PubMed2001

The emerging periplasm-localized subclass of AroQ chorismate mutases, exemplified by those from Salmonella typhimurium and Pseudomonas aeruginosa.

BACKGROUND: Chorismate mutases of the AroQ homology class are widespread in the Bacteria and the Archaea. Many of these exist as domains that are fused with other aromatic-pathway catalytic domains. Among the monofunctional AroQ proteins, that from Erwinia herbicola was previously shown to have a cleavable signal peptide and located in the periplasmic compartment. Whether or not this might be unique to E. herbicola was unknown. RESULTS: The gene coding for the AroQ protein was cloned from Salmonella typhimurium, and the AroQ protein purified from both S. typhimurium and Pseudomonas aeruginosa was shown to have a periplasmic location. The periplasmic chorismate mutases (denoted *AroQ) are shown to be a distinct subclass of AroQ, being about twice the size of cytoplasmic AroQ proteins. The increased size is due to a carboxy-terminal extension of unknown function. In addition, a so-far novel aromatic aminotransferase was shown to be present in the periplasm of P. aeruginosa. CONCLUSIONS: Our analysis has detected a number of additional *aroQ genes. The joint presence of *AroQ, cyclohexadienyl dehydratase and aromatic aminotransferase in the periplasmic compartment of P. aeruginosa comprises a complete chorismate-to-phenylalanine pathway and accounts for the "hidden overflow pathway" to phenylalanine described previously.

Amino Acid Sequence↗
PubMed2001

Molecular cloning and characterization of chemokine-like factor 1 (CKLF1), a novel human cytokine with unique structure and potential chemotactic activity.

Cytokines are small proteins that have an essential role in the immune and inflammatory responses. The repertoire of cytokines is becoming diverse and expanding. Here we report the identification and characterization of a novel cytokine designated as chemokine-like factor 1 (CKLF1). The full-length cDNA of CKLF1 is 530 bp long and a single open reading frame encoding 99 amino acid residues. CKLF1 bears no significant similarity to any other known cytokine in its amino acid sequence. Expression of CKLF1 can be partly inhibited by interleukin 10 in PHA-stimulated U937 cells. Recombinant CKLF1 is a potent chemoattractant for neutrophils, monocytes and lymphocytes; moreover, it can stimulate the proliferation of murine skeletal muscle cells. These results suggest that CKLF1 might have important roles in inflammation and in the regeneration of skeletal muscle.

Amino Acid Sequence↗
PubMed2001

Quantitative assessment of forearm muscle size, forelimb grip strength, forearm bone mineral density, and forearm bone size in determining humerus breaking strength in 10 inbred strains of mice.

Bone strength is an important clinical endpoint of osteoporosis research. The evaluation of the relative importance of bone and muscle components to bone strength has widespread implications for the understanding and preventing of osteoporosis. The objectives of this study were to understand the interrelationship between the different components of the muscular skeletal system and to determine the effect of forearm muscle size, forelimb grip strength, forearm bone mineral density (BMD), and forearm bone size on the humerus breaking strength among 10 inbred strains of mice. The forearm muscle size was measured using a peripheral quantitative computed tomography (pQCT). The forearm BMD and forearm bone size were measured using a PIXIMUS Densitometer. The forelimb grip strength and humerus breaking strength were measured using an Instron Mechanical Tester. Significant correlations were found among the five regional phenotypes. All variables have a moderately high genetic component with heritability estimates of 0.83 for forelimb grip strength, 0.76 for forearm muscle size, 0.6 for forearm BMD, 0.63 for forearm bone size, and 0.68 for humerus breaking strength. Forward stepwise multiregression analysis showed that the forearm BMD, forelimb grip strength, and forearm bone size were three major determinants of bone strength and explained 61% of the variation in bone breaking strength. These data suggest that evaluation of these three parameters together, rather than BMD alone, is a more effective, noninvasive approach for predicting fracture risk.

Absorptiometry, Photon↗
PubMed2001

An exclusively nuclear RNA-binding protein affects asymmetric localization of ASH1 mRNA and Ash1p in yeast.

The localization of ASH1 mRNA to the distal tip of budding yeast cells is essential for the proper regulation of mating type switching in Saccharomyces cerevisiae. A localization element that is predominantly in the 3'-untranslated region (UTR) can direct this mRNA to the bud. Using this element in the three-hybrid in vivo RNA-binding assay, we identified a protein, Loc1p, that binds in vitro directly to the wild-type ASH1 3'-UTR RNA, but not to a mutant RNA incapable of localizing to the bud nor to several other mRNAs. LOC1 codes for a novel protein that recognizes double-stranded RNA structures and is required for efficient localization of ASH1 mRNA. Accordingly, Ash1p gets symmetrically distributed between daughter and mother cells in a loc1 strain. Surprisingly, Loc1p was found to be strictly nuclear, unlike other known RNA-binding proteins involved in mRNA localization which shuttle between the nucleus and the cytoplasm. We propose that efficient cytoplasmic ASH1 mRNA localization requires a previous interaction with specific nuclear factors.

3' Untranslated Regions↗
PubMed2001

Photo-Fries rearrangements of phenyl phenylacylates in polyethylene films: comparison of reactivity and selectivity with 1-naphthyl phenylacylates.

The fates and kinetics of recombination of singlet radical pairs generated by photolyses of three phenyl phenylacylates have been examined in unstretched and stretched polyethylene films. Comparisons with results from photolyses of analogous 1-naphthyl phenylacylates in the same media lead to the conclusions that (1) phenoxy is less reactive overall than 1-naphthoxy toward a common phenylacyl radical but (2) the constrained cages in which the radical pairs reside exert greater control over the movements of the 1-naphthoxy/phenylacyl pairs. The reasons for these observations are discussed in the context of the shapes and van der Waals volumes of the radical pairs, the void volumes of sites in native polyethylene films, and the electronic properties of the aryloxy radicals.

Journal Article↗
PubMed2001

Analysis of gene expression in the wound repair/regeneration process.

Wound repair/regeneration is a complex process consisting of three stages: inflammation, tissue regrowth, and remodeling, which together involve the action of hundreds of genes. In order to i) identity and analyze the genes that are expressed at the inflammatory stage of repair (i.e., 24 h after injury) and ii) evaluate the molecular basis of fast-wound repair/regeneration in adult mammals. we examined the expression of 8734 sequence-verified genes in response to ear punch in a fast wound-repair/regeneration strain, MRL/MpJ-Fas(lpr) mice, and a slow-wound-repair strain, C57BL/6J mice. Many differentially expressed genes can be assigned to wound-repairing pathways known to be active during the inflammatory phase. whereas others are involved in pathways not previously associated with wound repair. Many genes of unknown function (ESTs) exhibited a more than twofold increase in MRL/ MpJ-Fas(lpr) or C57BL/6J mice, suggesting that current understanding of the molecular events at the inflammatory stage of repair is still limited. A comparison of the differential expression profiles between MRL/MpJ-Fas(lpr) and C57BL/6J mice suggests that fast-wound-repair in MRL/MpJ-Fas(lpr) mice is mediated by a metabolic shift toward a low inflammatory response and an enhanced tissue repair.

Animals↗
PubMed2001

Vascular endothelial growth factor-A and -C protein up-regulation and early angiogenesis in a rat photothrombotic ring stroke model with spontaneous reperfusion.

This study explored the temporal expression pattern of two subtypes of vascular endothelial growth factor (VEGF) proteins and three subforms of their receptors as well as endothelial proliferation in adult rats subjected to photothrombotic ring stroke with spontaneous reperfusion in the cortical region at risk. The exposed crania of halothane-anesthetized, temperature- and blood gas-controlled male Wistar rats were irradiated with a ring laser beam started simultaneously with systemic injection of the photosensitizer erythrosin B. Rats were repeatedly injected with 5-bromodeoxyuridine (BrdU) after stroke induction. Immunohistochemistry of coronal brain sections showed that VEGF protein subtype C increased simultaneously with subtype A in the ring lesion region at 2 h after irradiation. In the cortical region at risk (i.e., the penumbra-like zone), increased VEGF-C and VEGF-A immunostaining was seen at 24 h with sustained appearance up to 72 h after ischemic onset. Correspondingly, the VEGF-C-specific receptor flt-4 and the VEGF-A receptors flt-1 and flk-1 were up-regulated in a temporal sequence similar to that of their agonist proteins in the cortical ring lesion and the region at risk. At 48 h after stroke induction, proliferating BrdU-immunopositive endothelial cells formed microvessels in the post-ischemic cortical region at risk. These vessels became more pronounced at 72 h and were still visible at 100 days after the stroke. This study suggests that VEGF-C and its receptor flt-4 may cooperate with VEGF-A and its receptors flt-1 and flk-1 to promote early angiogenesis after stroke, which may in turn contribute to spontaneous reperfusion in this focal thromboembolic stroke model.

Animals↗
PubMed2001

Progressive and reproducible focal cortical ischemia with or without late spontaneous reperfusion generated by a ring-shaped, laser-driven photothrombotic lesion in rats.

Clinical stroke is mostly of thromboembolic origin, in which the magnitude of brain damage resulting from arterial occlusions depends on the degree and duration of the concomitant ischemia. To facilitate more controllable and reproducible study of stroke-related pathophysiological mechanisms, a photothrombotic ring stroke model was initially developed in adult rats. The ring interior zone comprises an anatomically well confined cortical region-at-risk which is gradually encroached by progressive hypoperfusion, thus mimicking the situation (albeit in inverse fashion) of an ischemic penumbra or stroke-in-evolution. Modification of this model using a thinner ring irradiation beam resulted in late spontaneous reperfusion in the cortical region-at-risk and a remarkable morphological tissue recovery in this ostensibly critically injured region. On the other hand, doubling the thin irradiating beam intensity facilitates a complementary situation in which lack of reperfusion in the region-at-risk after stroke induction leads to tissue pannecrosis. The dual photothrombotic ring stroke model, effectuated either with or without reperfusion and thereby tissue recovery or pannecrosis, may be well suited for the study of events related to postischemic survival or cell death in the penumbra region. To popularize the photothrombotic ring stroke model, we present a detailed protocol of how this model is induced in either version as well as protocols for transcardial carbon black perfusion and laser-Doppler flowmetry experiments.

Animals↗
PubMed2001

Genetic variation in bone-regenerative capacity among inbred strains of mice.

Genetic variation in bone-regenerative capacity has not been studied in any animal model system. We developed a "drill-hole" model in the tail vertebra of inbred strains of mice that allows us to reproducibly introduce an injury with a defined boundary and quantify the rate of bone healing using the combination of high-resolution Faxitron X-ray imaging and the ChemiImager 4000 Low Light Imaging System. Using this model, we demonstrate that bone-regenerative capacity is a genetically controlled trait with an estimated heritability of 72%, and that it differs significantly among inbred strains of mice. Of the 12 inbred strains tested, Sencar/PtJ was identified as the most suitable model for the study of hard-tissue regeneration. This strain regained 73% of bone loss 30 days after injury, in contrast to the slow healer, CBA/J, which recovered only 25% of the bone loss during the same period. Bone-regenerative capacity was not correlated with soft-tissue-regenerative capacity, suggesting that different sets of genes may regulate soft- and hard-tissue regeneration. It was, however, significantly correlated with total bone mineral density (R = 0.49, p < 0.01), indicating that high bone density is associated not only with prevention of bone fracture, but also with promotion of bone regeneration.

Animals↗
PubMed2001

Polymerized lyotropic liquid crystal assemblies for materials applications.

The development of functional materials with nanometer-scale architectures and the effect of these architectures on their chemical and physical properties are currently of great interest in materials design. Polymerizable lyotropic liquid crystal (LLC) assemblies provide a facile entry into this area by allowing one to fix the inherent order in these systems using covalent bonds to create robust, nanostructured materials. The use of the cross-linked inverted hexagonal phase in templated nanocomposite formation and heterogeneous catalysis has been demonstrated. Additionally, the polymerization of LLC mesogens in the regular hexagonal and bicontinuous cubic phases is being targeted for future developments in functional materials. Future directions for new applications of these materials are also discussed.

Journal Article↗
PubMed2001

Genetic control of the rate of wound healing in mice.

There have been few studies of the inheritance of wound healing in mammals. In this study, we demonstrate that inbred strains of mice differ significantly in the rate of wound healing. Of the 20 strains tested, fast healers (MRL/MpJ-Fas(lpr) and LG/J) healed wounds four times faster than slow healers (Balb/cByJ and SJL/J). The genetic basis underlying the difference in the healing capacity was analysed using F2 populations of two different crosses. We show that the wound healing is a polygenically determined quantitative trait with an average estimated heritability of 86%. The modes of gene action in these two crosses are different. In the (MRL/MpJ x SJL/J) cross, genes regulating fast healing in MRL/MpJ mice exhibited additive effects, whereas these effects were suppressed by a dominant repressor gene in CBA/J mice in the (MRL/MpJ-Fas(lpr) x CBA/J) cross. Information gained from this investigation provides insight into further study of molecular mechanisms underlying the rate of wound healing in mammals.

Analysis of Variance↗
PubMed2001

Identification of wound healing/regeneration quantitative trait loci (QTL) at multiple time points that explain seventy percent of variance in (MRL/MpJ and SJL/J) mice F2 population.

Studies on genetic mechanisms of wound healing in mammals are very few, although injury is a leading cause of the global burden of disease. In this study, we performed a high-density, genome-wide scan using 633 (MRL/MPJ x SJL/J) F(2) intercross at multiple time points (days 15, 21, and 25) to identify quantitative trait loci (QTL) involved in wound healing/regeneration. The hypothesis of the study was that QTL and unique epistatic interactions are involved at each time point to promote wound healing/regeneration. Ten QTL were identified from chromosomes 1, 4, 6, 7, 9, and 13. Of the 10 QTL, eight from chromosomes 1, 4, 6, and 9 were novel as compared to QTL identified in the study. The 10 QTL altogether explained 70% of variance in F(2) mice. The same QTL were identified at each time point, with simple linear correlation between days 15, 21, and 25, showing very high significant relationships (R >0.92, P <0.0001). Unique epistatic interactions were identified at each time point except those from chromosomes 4, 6, 9, and 13 that were found at all three time points, showing that some loci are involved at all the three time points of wound healing (days 15, 21, and 25). Therefore, loci-to-loci interactions may play a major role in wound healing. Information from these studies may help in the identification of genes that could be involved in wound healing/regeneration.

Analysis of Variance↗
PubMed2001

Detection of sporadic cases of hepatitis E virus (HEV) infection in China using immunoassays based on recombinant open reading frame 2 and 3 polypeptides from HEV genotype 4.

We reported previously on the complete sequence of hepatitis E virus (HEV) genotype 4, isolated from patients with sporadic cases of acute HEV infection in China. At least eight HEV genotypes have now been described worldwide, and further isolates await classification. Current immunoassays for the detection of anti-HEV antibodies are based on polypeptides from genotypes 1 and 2 only and may be inadequate for the reliable detection of other genotypes. Because genotypes 1 and 4 predominate in China, we wished to investigate the antigenic reactivities of HEV genotype 4 proteins. Four overlapping regions of open reading frame 2 (ORF2) (FB5, amino acids [aa] 1 to 130; E4, aa 67 to 308; F2-2, aa 288 to 461; E5, aa 414 to 672) and the entire ORF3 product were expressed in Escherichia coli as fusion proteins. Enzyme immunoassays based on each of the five purified polypeptides were evaluated with sera from patients with sporadic cases of acute HEV infection. Individual immunoassays derived from HEV genotype 4 detected more cases of acute hepatitis E than a commercial assay. Some serum samples, which were positive for anti-HEV immunoglobulin G only by assays based on HEV genotype 4, were positive for HEV RNA by reverse transcription-PCR. Polypeptide FB5, from the N terminus of ORF2, had the greatest immunoreactivity with sera from patients with acute hepatitis E. These data indicate that the N terminus of ORF2 may provide epitopes which are highly reactive with acute-phase sera and that assays based on genotypes 1 and 2 alone may be inadequate for the detection of HEV infection in China, where sporadic cases of HEV infection are caused predominantly by HEV genotypes 4 and 1.

Acute Disease↗
PubMed2001

Cortical neurogenesis in adult rats after transient middle cerebral artery occlusion.

BACKGROUND AND PURPOSE: This study explored the possible occurrence of newly generated nerve cells in the ischemic cortex of adult rats after middle cerebral artery occlusion and reperfusion. METHODS: Nine- to 10-week-old male Wistar rats were subjected to 2 hours of middle cerebral artery occlusion by the monofilament method. Rats received repeated intraperitoneal injections of the cell proliferation-specific marker 5-bromodeoxyuridine (BrdU) after stroke induction. Brain sections were processed for immunohistochemistry with an avidin-biotin complex-alkaline phosphatase and/or -peroxidase method. Brain sections processed with double-immunofluorescent staining were further scanned by confocal microscopy. RESULTS: Interspersed among the predominantly newly formed glial cells, some cells were double labeled by BrdU and 1 of the neuron-specific markers, Map-2, beta-tubulin III, and Neu N, at 30 and 60 days after stroke onset. These cells were randomly distributed throughout cortical layers II through VI, occurring with highest density in the ischemic boundary zone. Three-dimensional confocal analyses of BrdU and the neuron-specific marker Neu N confirmed their colocalization within the same cortical cells. CONCLUSIONS: This study suggests that new neurons can be generated in the cerebral cortex of adult rats after transient focal cerebral ischemia. Cortical neurogenesis may be a potential pathway for brain repair after stroke.

Animals↗