Biomedical subjects

W Wu

Publications and source records attributed to W Wu.

At least 217 records · Page 12Linked to original sources

PubMed1999

[Morphological observations of the medial olivocochlear efferents in gerbils with chronic gentamicin ototoxicity].

OBJECTIVE: To determine the possible involvement of the medial olivocochlear efferents (MOC) in chronic aminoglycoside ototoxicity, the morphological changes of the MOC efferents in the cochlea of Mongolian gerbils and their correlations with the impairment of the outer hair cells (OHCs) were observed. METHODS: The animals were given gentamicin in a dose of 150 mg/kg a day for 10 days. The distributions and densities of the MOC efferents were examined using the modified histochemical staining for acetylcholinesterase (AChE) and the numbers of OHCs were numerated with toluidine blue and Ehrlich haematoxylin staining on the surface preparation. RESULTS: Significant damage to the MOC fibers and terminals as well as OHCs was noted in the basal turn of the cochlea, especially in those animals examined in 7th and 11th week after the gentamicin administration. The site of the greatest impairment of OHCs was consistent with that of the MOC efferents. CONCLUSION: The results suggested that damage to the MOC efferents might play an important role in gentamicin-induced impairment of OHCs.

Animals↗

PubMed1998

The interchain disulfide linkage of T-cell antigen receptor-alpha and -beta chains is a prerequisite for T-cell activation.

Complementary DNAs encoding the T-cell antigen receptor (TCR)-alpha and mutant TCR-beta chains, lacking the interchain disulfide bond-related cysteine, were introduced into a TCR-alpha and -beta protein-deficient T-cell line. TCR-alpha and the mutant TCR-beta chains assembled with the CD3-epsilon, -gamma, -delta, and -zeta subunits and were efficiently transported to the cell surface; however, the hybrid TCR molecules exhibited a diminished response to T-cell activation by major histocompatibility complex-bound antigen, superantigen, and TCR cross-linking. These results suggest that the interchain disulfide bond between the TCR clonotypic chains is not required for TCR assembly and cell surface expression, but it plays an important role in maintaining the functional integrity of the TCR complex.

Animals↗

PubMed1998

Overexpression of cdc25A and cdc25B is frequent in primary non-small cell lung cancer but is not associated with overexpression of c-myc.

Cyclin-dependent kinases can be activated by cdc25, which removes inhibitory phosphates from tyrosine and threonine residues. At least three cdc25 genes (cdc25A, cdc25B, and cdc25C) have been identified in humans. Accumulating evidence indicates that cdc25A and cdc25B possess oncogenic properties. Recently, overexpression of cdc25A and of cdc25B was found in many breast and head and neck cancers. To determine potential roles of cdc25s in non-small cell lung cancer (NSCLC), we analyzed primary tumors and corresponding normal lung tissues from 40 patients with NSCLC for relative expression levels of these genes by multiplex reverse transcription PCR (RT-PCR). cdc25A was overexpressed in 60% (24 of 40) of the tumors and cdc25B in 45% (18 of 40) of the tumors, whereas cdc25C was not overexpressed in any of the tumors analyzed. Because c-myc can increase cdc25A and cdc25B expression, it may be a factor in cdc25 overexpression. We found that c-myc was overexpressed in only 18% (7 of 40) of the tumors. We found no association between overexpression of c-myc and cdc25A or cdc25B. We also investigated whether the cdc25B gene was amplified in NSCLC and found this was true in 40% (8 of 20) of the tumors tested. However, this amplification was not correlated with gene expression status. Interestingly, among 24 tumors with cdc25A overexpression and 18 with cdc25B overexpression, 42% (10 of 24) and 44% (8 of 18) were poorly differentiated histological type. In contrast, well or moderately differentiated tumors had lower frequencies of cdc25A and cdc25B overexpression [19% (3 of 16) and 23% (5 of 22), respectively]. These data indicate that overexpression of cdc25A and cdc25B is frequent and that it may play an important role in NSCLC. However, it is unlikely that this overexpression is caused by c-myc stimulation or cdc25B gene amplification.

Adenocarcinoma↗

PubMed1998

The star plot: an alternative display method for multivariate data in the analysis of food and drugs.

The star plot (SP) is a method of displaying multivariate data. It can be used to display data with more than two variables. Combined with principal component analysis (PCA), more than two PCs can be displayed in one plane. Different variants of this method are applied to an atomic absorption spectrometry (AAS) data set and to three near infra-red (NIR) spectral data sets. The results show that SP offers an easy way of visualising the multivariate data for food and drugs in a plane, and it is able to help the analyst to identify and to detect different qualities of food and drug composition. Moreover, when an object is added or removed, the PC's must be computed all over again, which is not the case for the SP-plot. The application of SP to the examples presented in the text suggests that the SP approach can be applied as an alternative method for displaying multivariate chemometric data in place of PCA or, to improve visualisation of the results already obtained with PCA.

Bread↗

PubMed1998

PDGF mediates cardiac microvascular communication.

The diversity of cellular and tissue functions within organs requires that local communication circuits control distinct populations of cells. Recently, we reported that cardiac myocytes regulate the expression of both von Willebrand factor (vWF) and a transgene with elements of the vWF promoter in a subpopulation of cardiac microvascular endothelial cells (J. Cell Biol. 138:1117). The present study explores this communication. Histological examination of the cardiac microvasculature revealed colocalization of the vWF transgene with the PDGF alpha-receptor. Transcript analysis demonstrated that in vitro cardiac microvascular endothelial cells constitutively express PDGF-A, but not B. Cardiac myocytes induced endothelial expression of PDGF-B, resulting in PDGF-AB. Protein measurement and transcript analysis revealed that PDGF-AB, but not PDGF-AA, induced endothelial expression of vWF and its transgene. Antibody neutralization of PDGF-AB blocked the myocyte-mediated induction. Immunostaining demonstrated that vWF induction is confined to PDGF alpha-receptor-positive endothelial cells. Similar experiments revealed that the PDGF-AB/alpha-receptor communication also induces expression of vascular endothelial growth factor and Flk-1, critical components of angiogenesis. The existence of this communication pathway was confirmed in vivo. Injection of PDGF-AB neutralizing antibody into the amniotic fluid surrounding murine embryos extinguished expression of the transgene. In summary, these studies suggest that environmental induction of PDGF-AB/alpha-receptor interaction is central to the regulation of cardiac microvascular endothelial cell hemostatic and angiogenic activity.

Animals↗

PubMed1998

Biochemical characterization and subcellular localization of the mouse retinitis pigmentosa GTPase regulator (mRpgr).

The retinitis pigmentosa GTPase regulator (RPGR) gene encodes a protein homologous to the RCC1 guanine nucleotide exchange factor and is mutated in 20% of patients with X-linked retinitis pigmentosa. We have characterized the full-length and variant cDNAs corresponding to the mouse homolog of the RPGR gene (mRpgr). Comparison with the human cDNA revealed sequence identity primarily in the region of RCC1 homology repeats. As in humans, the mRpgr gene maps within 50 kilobases from the 5'-end of the Otc gene. The mRpgr transcripts are detected as early as E7 during embryonic development and are expressed widely in the adult mice. Variant mRpgr isoforms are generated by alternative splicing and by utilizing two in-frame initiation codons. The products of mRpgr cDNAs migrate aberrantly in SDS-polyacrylamide gels because of a charged domain. In transfected COS cells, the mRpgr protein is isoprenylated and is localized in the Golgi complex. This subcellular distribution is not observed after treatments with brefeldin A or mevastatin and when the conserved isoprenylation sequence (CTIL) at the carboxyl terminus is deleted or mutagenized. These studies suggest a role for the mRpgr protein in Golgi transport and form the basis for investigating the mechanism of photoreceptor degeneration in X-linked retinitis pigmentosa.

Alternative Splicing↗

PubMed1998

Anxiety proneness linked to epistatic loci in genome scan of human personality traits.

A genome-wide scan between normal human personality traits and a set of genetic markers at an average interval of 13 centimorgans was carried out in 758 pairs of siblings in 177 nuclear families of alcoholics. Personality traits were measured by the Tridimensional Personality Questionnaire. We detected significant linkage between the trait Harm Avoidance, a measure of anxiety proneness, and a locus on chromosome 8p21-23 that explained 38% of the trait variance. There was significant evidence of epistasis between the locus on 8p and others on chromosomes 18p, 20p, and 21q. These oligogenic interactions explained most of the variance in Harm Avoidance. There was suggestive evidence of epistasis in other personality traits. These results confirm the important influence of epistasis on human personality suggested by twin and adoption studies.

Anxiety↗

PubMed1998

Increased caveolin-3 levels in mdx mouse muscles.

The density of skeletal muscle caveolae is increased in Duchenne muscular dystrophy and its genetic homologue, the mdx mouse. This structural change is significant as it may indicate muscle regeneration. We identified in mdx mouse tibialis anterior muscles significantly increased levels of caveolin-3, the chief protein in muscle caveolae, and reduced levels of neuronal nitric oxide synthase, an enzyme regulated by caveolin-3. Similar changes occurred in the corresponding mRNA levels. These data suggest that induction of caveolin-3 occurs and this may at least partly be responsible for increased number of caveolae, altered nNOS-caveolin cycle, and regeneration of dystrophic muscles.

Animals↗

PubMed1998

Characterization of spinal motoneuron degeneration following different types of peripheral nerve injury in neonatal and adult mice.

Experimental lesions have been used widely to induce motoneuron (MN) degeneration as a model to test the ability of different trophic molecules to prevent lesion-induced alterations. However, the morphological mechanisms of spinal MN death following different types of lesions is not clear at the present time. In this study, we have characterized the morphological characteristics of MN cell death by examining DNA fragmentation and the ultrastructural and light microscopic morphological features of MNs following different types of spinal nerve injury (i.e., axotomy and avulsion) in the developing and adult mouse. In neonatal mice, axotomy induced cell death as well as the atrophy of MNs that survived the injury. DNA fragmentation could be detected by using the terminal deoxynucleotidyl transferase (TUNEL) method during the cell death process following neonatal axotomy, whereas TUNEL labeling was not observed following either neonatal or adult avulsion. However, with the exception of TUNEL labeling, the morphological characteristics of MN death following neonatal axotomy and avulsion were similar, and both resembled most closely the form of programmed cell death termed cytoplasmic or type 3B, which exhibits similarities as well as differences with currently accepted definitions of apoptosis. By contrast, adult avulsion resulted in a type of degeneration that resembled necrosis more closely. However, even there, the morphology was mixed, showing characteristics of both apoptosis and necrosis. These results indicate that the mode of MN degeneration is complex and is related to developmental age and type of lesion.

Animals↗

PubMed1998

The Streptomyces coelicolor sporulation-specific sigma WhiG form of RNA polymerase transcribes a gene encoding a ProX-like protein that is dispensable for sporulation.

In the non-motile mycelial organism Streptomyces coelicolor A3(2), the sporulation gene whiG encodes a protein that closely resembles RNA polymerase sigma factors such as sigma D of Bacillus subtilis, which mainly control motility and chemotaxis genes. Here, we show that the whiG gene product, purified from an Escherichia coli strain carrying an expression construct, could activate E. coli core RNA polymerase in vitro to transcribe a sigma D-dependent motility-related promoter from B. subtilis. Such RNA polymerase holoenzyme preparations could also transcribe from an S. coelicolor promoter, PTH4, previously shown to require an intact whiG gene for in-vivo transcription. The in-vivo dependence on whiG was therefore shown to be direct. Unusually, the initiation of PTH4 transcription in vitro depended on the provision of appropriate dinucleotides. The whiG-dependent PTH4 transcription unit consisted of a single gene, orfTH4. Sequence comparisons suggested that the gene product was a member of a small group of proteins that include the B. subtilis and E. coli ProX proteins. Though none of these proteins shared more than about 30% of extended primary sequence identity, they had similar size and hydropathy profiles, and could be aligned end to end to reveal a mosaic of similarities. The ProX proteins of B. subtilis and E. coli are implicated in glycine betaine transport in response to hyperosmotic stress. However, disruption of orfTH4 did not cause any obvious phenotypic changes in growth or development on media of varying osmotic strengths.

Amino Acid Sequence↗

PubMed1998

Genome-wide search for genes affecting the risk for alcohol dependence.

Alcohol dependence is a leading cause of morbidity and premature death. Several lines of evidence suggest a substantial genetic component to the risk for alcoholism: sibs of alcoholic probands have a 3-8 fold increased risk of also developing alcoholism, and twin heritability estimates of 50-60% are reported by contemporary studies of twins. We report on the results of a six-center collaborative study to identify susceptibility loci for alcohol dependence. A genome-wide screen examined 291 markers in 987 individuals from 105 families. Two-point and multipoint nonparametric linkage analyses were performed to detect susceptibility loci for alcohol dependence. Multipoint methods provided the strongest suggestions of linkage with susceptibility loci for alcohol dependence on chromosomes 1 and 7, and more modest evidence for a locus on chromosome 2. In addition, there was suggestive evidence for a protective locus on chromosome 4 near the alcohol dehydrogenase genes, for which protective effects have been reported in Asian populations.

Adolescent↗

PubMed1998

Glycosaminoglycans bind to homologous cardiotoxins with different specificity.

We have reported that some cardiotoxins (CTXs), homologous basic polypeptides of cobra venom, bind strongly to heparin. Herein we show that CTXs from spitting cobra venom bind avidly to chondroitin-6-sulfate (CS6) and dermatan sulfate (DS), the glycosaminoglycans (GAGs) abounding in the cornea and elsewhere. We compared the binding strength of Tgamma, a major component of spitting cobra, Naja nigricollis, venom with that of CTX A3, a major component of Naja atra venom to various GAGs including CS6, chondroitin-4-sulfate (CS4), DS, keratan sulfate (KS), hyaluronan (HYA), and heparin. The binding strength of Tgamma followed the order CS6 > KS > HYA > DS > CS4 > heparin, whereas that of CTX A3 was heparin > KS > CS4 > DS > CS6 > HYA. The binding specificity displayed by different CTXs toward GAGs is impressive, given the high homology among CTXs and among GAGs. Strong binding of Tgamma to CS6, rather than to the highly anionic and versatile cousin, heparin, implies specific interaction with CS6. Heparin, at high concentration, displaced CS6 from CS6-Tgamma and CS6-A3 complexes. We also show that corneal CS/DS likely allow Tgamma to bind to corneal epithelium. CTXs of spitting cobra venom are known to cause corneal opacity and/or blindness. Taken together with these observations, our results suggest that corneal CS/DS play a role in the action of CTX in the eye. Most importantly, the present results establish CTXs as cationic, readily available, avidly binding ligands of CS/DS.

Amino Acid Sequence↗

PubMed1998

A phosphatase activity in Xenopus oocyte extracts preferentially dephosphorylates the MPM-2 epitope.

MPM-2 antigens are a large family of mitotic phosphoproteins that contain similar phosphoepitopes recognized by the anti-phosphoepitope antibody MPM-2 (MPM-2 epitopes). These proteins are phosphorylated during M phase induction and dephosphorylated from the onset of anaphase through interphase. Since biochemical characterization of the MPM-2 epitope phosphatase requires a specific assay for its activity, we tested different methods for measurement of the MPM-2 epitope phosphatase activity in crude cell lysates. First, an ELISA-based assay was designed that measured the phosphatase-induced reduction of the MPM-2 reactivity in crude M phase cell lysates. Using this assay to follow the phosphatase activity during sequential chromatography of Xenopus oocyte extracts, one predominant peak of phosphatase activity was detected which was separated from the majority of PP1 and PP2A activities. This phosphatase activity dephosphorylated the MPM-2 epitope on multiple MPM-2 antigens. The second method measured dephosphorylation of cdc25, a known MPM-2 antigen. Two major peaks of cdc25 dephosphorylating activities were detected during the sequential chromatography, one that copurified with the major peak of MPM-2 epitope phosphatase activity, and the other with the major peak of PP2A activity. Finally, we examined whether GST-MPM2, a fusion protein between glutathione S-transferase and a 19-residue peptide that contained two representative MPM-2 epitope sequences, could be dephosphorylated efficiently and specifically by the major MPM-2 epitope phosphatase activity in Xenopus oocyte extracts. Neither the crude extract nor the partially purified MPM-2 epitope phosphatase activity efficiently dephosphorylated the MPM-2 epitope on GST-MPM2. These results demonstrate that the ELISA-based assay preferentially detects the MPM-2 epitope phosphatase activity in crude cell lysates which may represent a physiological MPM-2 epitope phosphatase.

Animals↗

PubMed1998

Time course of NOS expression and neuronal death in Clarke's nucleus following traumatic injury in adult rat spinal cord.

The objective of this study was to investigate the influence of the length of the remaining axons on neuronal survival following axonal injury in the adult rat spinal cord. The relationship between the expression of nitric oxide synthase (NOS) and neuronal death was also studied. The time course of NOS expression and neuronal loss was observed in Clarke's nucleus at segment L1 following hemisection of the cord at either segment C3, T1, or T11. NOS-positive neurons were first observed 3 days after injury, rising significantly after 5 days, and reaching a maximum by 10-20 days post-injury. During the same period the number of neurons surviving in the nucleus decreased. The decrease began at 3 days, rapidly decreased after 5 days, and reached a minimum by 40 days post-injury. Among the three lesioned groups, the highest percentage of NOS expression and neuronal loss was observed in the group with lesions at T11, while the lowest percentage was in the group with lesions at C3. Although the time course of neuronal loss varied following lesion at different spinal levels, in all cases the majority of neurons in Clarke's nucleus had degenerated by 40 days after axotomy.

Animals↗

PubMed1998

Dickkopf-1 is a member of a new family of secreted proteins and functions in head induction.

The Spemann organizer in amphibian embryos is a tissue with potent head-inducing activity, the molecular nature of which is unresolved. Here we describe dickkopf-1 (dkk-1), which encodes Dkk-1, a secreted inducer of Spemann's organizer in Xenopus and a member of a new protein family. Injections of mRNA and antibody indicate that dkk-1 is sufficient and necessary to cause head induction. dkk-1 s a potent antagonist of Wnt signalling, suggesting that dkk genes encode a family of secreted Wnt inhibitors.

Animals↗

PubMed1998

A new 2-base pair deletion in the RPGR gene in a black family with X-linked retinitis pigmentosa.

OBJECTIVE: To report the genetic and ophthalmic findings in a black family with X-linked retinitis pigmentosa resulting from a newly identified mutation in the RPGR (retinitis pigmentosa GTPase regulator) gene. PATIENTS: Four affected hemizygotes with retinitis pigmentosa and 2 obligate carriers were examined. Two unaffected family members, 1 woman and her unaffected son, were also examined. METHODS: Patients underwent a routine ocular examination including slitlamp examination and a dilated fundus examination. Certain patients also underwent testing with Goldmann visual field kinetic perimetry and electroretinography. DNA screening from affected male patients, 2 obligate carriers, and 2 unaffected family members was performed to determine the presence of any mutation in the RPGR gene. RESULTS: A 2-base pair deletion in exon 13 of the RPGR gene that creates a frameshift was found to segregate with the retinal disease in affected males and the carrier state in female heterozygotes in this family. The ophthalmic findings in hemizygotes and carriers were within the spectrum of findings characteristically noted in families with X-linked retinitis pigmentosa. In 2 obligate carriers, a tapetal-like reflex was not clinically apparent. CONCLUSIONS: The described mutation is the first RPGR gene mutation reported in a black family. A 2-base pair deletion in exon 13 segregates with a clinical phenotype of X-linked retinitis pigmentosa.

Adolescent↗

PubMed1998

Characterization of gene-specific DNA repair by primary cultures of rat hepatocytes.

At present, almost all the information on gene-specific DNA repair in mammals comes from studies with transformed cell lines and proliferating primary cells obtained from rodents and humans. In the present study, we measured the repair of specific DNA regions in primary cultures of nondividing rat hepatocytes (parenchymal cells). DNA damage was induced by irradiating the primary cultures of hepatocytes with ultraviolet (UV) light, and the presence of cyclobutane pyrimidine dimers (CPDs) was measured by using T4 endonuclease V in the following: a 21-kb BamHI fragment containing the albumin gene, a 14-kb BamHI fragment containing the H-ras gene, and the genome overall. The frequency of CPDs in the two BamHI fragments and the genome overall were similar and ranged from 0.5 to 1.3 CPDs per 10 kb for UV doses of 5-30 J/m2. However, the removal of CPDs from the DNA fragment containing the albumin gene was significantly higher than from that of the genome overall and the DNA fragment containing the H-ras gene. Within 24 hr, approximately 67% of the CPDs was removed from the DNA fragment containing the albumin gene versus less than 40% for the genome overall and the DNA fragment containing the H-ras gene. The lower repair observed for the 14-kb fragment containing the H-ras gene is probably indicative of repair of the nontranscribed region of this fragment because the H-ras gene makes up only 2.4 kb of the 14-kb fragment. Primary cultures of hepatocytes removed CPDs from the transcribed strand of albumin fragment more efficiently than from the nontranscribed strand; however, no differences were observed in the repair of the two strands of the fragment containing the H-ras gene. These results demonstrate that primary cultures of nondividing rat hepatocytes show differential repair of UV-induced DNA damage that is comparable to what has been reported for transformed, proliferating mammalian cell lines.

Albumins↗

PubMed1998

Interleukin-10 controls neutrophilic infiltration, hepatocyte proliferation, and liver fibrosis induced by carbon tetrachloride in mice.

The role of the anti-inflammatory cytokine interleukin-10 (IL-10) was investigated in the mouse model of liver injury induced by carbon tetrachloride (CCl4). To address the role of endogenous IL-10 production, acute hepatitis was induced by CCl4 in C57Bl/6 IL-10 gene knock out (KO) and wild-type (WT) mice. After CCl4 challenge, serum and liver levels of tumor necrosis factor-alpha (TNF-) and serum levels of transforming growth factor-beta 1 (TGF-beta1) increased and were significantly higher in IL-10 KO mice, whereas IL-6 serum levels were only slightly increased compared with WT mice. At histological examination, the livers disclosed a significantly more prominent neutrophilic infiltration in IL-10 KO mice 12 and 24 hours after CCl4 injection. In contrast, hepatocyte necrosis, evaluated by histological examination and serum alanine aminotransferase levels, was only marginally affected. The proliferative response of hepatocytes, assessed by the proliferating cell nuclear-antigen labeling index, was significantly increased in IL-10 KO mice, compared with WT mice 48 hours after CCl4 injection. Finally, repeated CCl4 injections led to more liver fibrosis in IL-10 KO mice after 7 weeks. In conclusion, endogenous IL-10 marginally affects the hepatocyte necrosis although it controls the acute inflammatory burst induced by CCl4. During liver repair, it limits the proliferative response of hepatocytes and the development of fibrosis.

Animals↗