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Biomedical subjects

X Wu

Publications and source records attributed to X Wu.

At least 703 records · Page 39Linked to original sources
PubMed1997

Presence of IgM antibodies which sensitize HIV-1-infected cells to cytolysis by homologous complement in long-term survivors of HIV infection.

Although human cells are resistant to homologous human complement due to the presence of species-specific membrane inhibitors, a naturally occurring IgM antibody which recognizes an asialo-oligosaccharide can sensitize HIV-1-infected cells for complement-mediated cytolysis. Therefore, we investigated whether long-term survivors of HIV-1 infection harbor such antibodies in their sera. Thirty of 31 sera from HIV-1 seropositive hemophilia patients who have survived HIV-1 infection 10 years or more showed appreciable cytolytic activity, while only 2 sera of 10 seropositive patients presumed to have been infected with HIV-1 (due to sexual contact) more recently showed cytolytic activity. On the other hand, only 7 out of 43 sera from seronegative hemophilia patients showed cytolytic activity. Immunofluorescence staining for IgM on HIV-1-infected cells essentially correlated with the cytolytic capacity of the sera. Therefore, naturally occurring IgM antibodies and/or generated IgM antibodies reactive with the HIV-1-infected cells in patients might have been responsible for long-term survival due to complement-mediated immune cytolysis which may, in conjunction with cytotoxic T lymphocytes, synergistically suppress the infected cells in vivo. Therefore, the transfusion of such IgM antibodies could be effective for the treatment of HIV-1-infected individuals.

Adolescent↗
PubMed1997

Presence of human papillomavirus DNA and expression of L-fucose moiety in some vulvar intraepithelial lesions and vulvar squamous cell carcinoma.

BACKGROUND: Human papillomavirus could reside and play an etiological role in some vulvar epithelial lesions. Human papillomavirus-infected keratinocytes might have certain biochemical changes that could be of significance in helping clinical diagnosis or elucidating the pathogenesis of some vulvar epithelial diseases. OBJECTIVE: To detect the presence of human papillomavirus DNA and observe the expression pattern of L-fucose moiety in some vulvar intraepithelial lesions and vulvar squamous cell carcinoma. METHODS: Nineteen cases of vulvar intraepithelial lesions and 13 cases of vulvar squamous cell carcinoma from the inner aspect of labia majora or the outer aspect of labia minora were selected. Polymerase chain reaction was employed to detect the presence of human papillomavirus DNA in lesional skin. Ulex europeaus agglutinin-1 histochemistry was used to observe the L-fucose expression pattern. RESULTS: A large proportion of vulvar intraepithelial lesions had the presence of human papillomavirus DNA, but the positive rate was low in vulvar squamous cell carcinoma and squamous cell hyperplasia. L-Fucose expression was much more pronounced in human papillomavirus DNA-positive lesions than those negative ones. CONCLUSIONS: Human papillomavirus had an important impact on some vulvar intraepithelial lesions in this Oriental population. The expression pattern of L-fucose may be used as an indicator for vulvar keratinocyte transformation by human papillomavirus.

Adult↗
PubMed1997

Amplification of multiple regions of chromosome 12, including 12q13-15, in chronic lymphocytic leukaemia.

Trisomy 12 is a frequent abnormality in chronic lymphocytic leukaemia (CLL). The biological importance of trisomy 12 is still poorly understood but it has been suggested that one or several genes are duplicated leading to malignant transformation. We present a case with amplification of 12q13-22 found in a clinically aggressive relapse of CLL. A smaller region, 12q13-15, was amplified most frequently and a YAC containing the MDM2 gene gave the highest number of signals. Additionally, in a subclone an amplicon containing at least 5 copies of a cosmid from 12q23-24 was detected. The case shows that small duplications of chromosome 12, not revealed by cytogenetic analysis, may occur in CLL. Also, it shows that cytogenetic clonal evolution can occur in CLL without morphological evidence of blast transformation. Our results indicate that the 12q13-15 region carries an important gene for CLL progression.

Chromosomes, Human, Pair 12↗
PubMed1997

Arterial function in mineralocorticoid-NaCl hypertension: influence of angiotensin-converting enzyme inhibition.

Angiotensin-converting enzyme inhibitors have been suggested to improve the function of arterial endothelium and smooth muscle not only through inhibition of angiotensin II formation and reduction of blood pressure, but also via additional pathways, e.g. potentiation of endogenous kinins and enhancement of endothelial autacoid formation. Therefore, we investigated whether 10-week-long quinapril therapy (10 mg kg-1 day-1) could beneficially influence the function of mesenteric arterial rings in vitro in deoxycorticosterone-NaCl-treated Wistar-Kyoto rats, a model of hypertension which is known to be resistant to angiotensin-converting enzyme inhibition. The quinapril treatment had no long-term blood pressure-lowering effect nor did it reduce the associated cardiac hypertrophy in deoxycorticosterone-NaCl hypertension. In noradrenaline-precontracted arterial rings the endothelium-dependent relaxations to acetylcholine and adenosine 5'-diphosphate as well as the endothelium-independent relaxations to nitroprusside and isoprenaline were clearly attenuated in the deoxycorticosterone-NaCl-treated rats. However, the quinapril therapy was without significant effect on any of these dilatory responses. In the presence of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, the relaxations to acetylcholine in untreated and quinapril-treated hypertensive animals were practically absent, whereas in normotensive rats distinct relaxations to higher concentrations of acetylcholine were still present. Interestingly, when endothelium-dependent hyperpolarization was prevented by precontracting the preparations with potassium chloride, no differences were found in relaxations to acetylcholine and adenosine 5'-diphosphate between the study groups. Exogenous bradykinin induced small comparable contractions in endothelium-intact mesenteric arterial rings from all study groups. In conclusion, the 10-week-long quinapril therapy did not have any significant effects on arterial function in deoxycorticosterone-NaCl hypertensive rats. Therefore, the present results stress the roles of reduced blood pressure and diminished angiotensin II formation in the beneficial vascular effects of long-term angiotensin-converting enzyme inhibition in the present model of hypertension. Furthermore, since the relaxations to acetylcholine and adenosine 5'-diphosphate in the deoxycorticosterone-NaCl-treated rats were attenuated in the absence and presence of nitric oxide synthase inhibition but not under conditions which prevented hyperpolarization, impaired endothelium-dependent relaxation to agonists can be attributed to diminished endothelium-dependent hyperpolarization in this model of hypertension.

Acetylcholine↗
PubMed1997

Arterial responses to bradykinin after ramipril therapy in experimental hypertension.

Angiotensin-converting enzyme inhibitors have been shown to potentiate relaxations to kinins in several arteries, but the effects of long-term therapy on the responses to bradykinin in normotensive and hypertensive animals remain largely unknown. Therefore, the effects of 12-week-long ramipril therapy (1 mg kg-1 day-1) on responses of mesenteric arterial rings in vitro were studied in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats. Endothelium-dependent relaxations of noradrenaline-precontracted rings to acetylcholine were similar in normotensive rats and ramipril-treated hypertensive rats and more pronounced than in untreated hypertensive group. Higher concentrations of bradykinin (0.1-1 microM) induced slight contractions in noradrenaline-precontracted endothelium-intact rings of normotensive groups and untreated hypertensive group, whereas no response or a transient relaxation were observed in ramipril-treated hypertensive rats. Interestingly, in ramipril-treated hypertensive rats but not in the other groups, 20-min. pretreatment of arterial rings with ramiprilat unmasked or potentiated the relaxations to bradykinin, and these bradykinin-induced relaxations were effectively inhibited by the B2-kinin receptor antagonist Hoe-140. In conclusion, ramipril treatment clearly improved endothelium-dependent arterial relaxation to acetylcholine, and potentiated of even unmasked the dilatory response mediated via the endothelial B2-kinin receptor in spontaneously hypertensive rats. Since these enhancing effects on arterial relaxation in vitro could not be attributed to reduced breakdown of bradykinin, the present results suggest that long-term angiotensin-converting enzyme inhibition potentiated the actions of kinins at level of B2-kinin receptors.

Acetylcholine↗
PubMed1997

Parametrization of mammography normalized average glandular dose tables.

Data from existing tables of normalized glandular doses in mammography were parametrized to determine analytical expressions that match tabulated results within known uncertainties. The parametrization was performed for three different target/filter combinations (molybdenum target-molybdenum filter, molybdenum target-rhodium filter, and rhodium target-rhodium filter) and three different breast compositions (100% adipose, 50% adipose-50% glandular, and 100% glandular). The analytical expressions provide the normalized glandular dose for any breast composition within stated ranges of tabulated input parameters (kVp, half-value layer, and breast thickness). The maximum difference between tabulated and parametrized data is 1.29%, which is smaller than the stated 2% uncertainty in tabulated dose data due to uncertainties in the x-ray spectra models used to generate the tables. Analytical expressions are easily coded to create custom functions that return the normalized glandular dose for the set of input parameters. Examples of implementation are presented in Microsoft Visual Basic for Applications (VBA).

Algorithms↗
PubMed1997

Incorporation of functional human immunodeficiency virus type 1 integrase into virions independent of the Gag-Pol precursor protein.

Retroviral integrase (IN) is expressed and incorporated into virions as part of the Gag-Pol polyprotein precursor. IN catalyzes integration of the proviral DNA into host cell chromosomes during the early stages of the virus life cycle, and as a component of Gag-Pol, it is involved in virion morphogenesis during late stages. It is unknown whether the scheme, conserved among retroviruses, for expressing and incorporating IN as a component of the Gag-Pol precursor protein is necessary for its function in the infected cell after viral entry. We have developed human immunodeficiency virus (HIV) virion-associated accessory proteins (Vpr and Vpx) as vehicles to deliver both foreign and viral proteins into the virus particle by their expression in trans as heterologous fusion proteins (X. Wu, et al., J. Virol. 69:3389-3398, 1995; X. Wu, et al., J. Virol. 70:3378-3384, 1996; X. Wu, et al., EMBO J. 16:5113-5122, 1977). To analyze IN function independent of its expression as a part of Gag-Pol, we expressed and incorporated IN into HIV type 1 (HIV-1) virions in trans as a fusion partner of Vpr (Vpr-IN). Our results demonstrate that the Vpr-IN fusion protein is efficiently incorporated into virions and then processed by the viral protease to liberate the IN protein. Virus derived from IN-minus provirus is noninfectious. However, this defect is overcome by trans complementation with the Vpr-IN fusion protein. Moreover, complemented virions are able to replicate through a complete cycle of infection, including formation of the provirus (integration). These results show, for the first time, that full IN function can be provided in trans, independent of its expression and incorporation into virions as a component of Gag-Pol. This finding also indicates that the IN domain of Gag-Pol is not required for the formation of infectious virions when IN is provided in trans. The ability to incorporate functional IN into retroviral particles in trans will provide unique opportunities to explore the function of this critical enzyme in a biologically relevant context, i.e., in infected cells as part of the nucleoprotein/preintegration complex.

Cell Line↗
PubMed1997

Influence of DNA sequence identity on efficiency of targeted gene replacement.

We have developed a system for analyzing recombination between a DNA fragment released in the nucleus from a single-copy plasmid and a genomic target in order to determine the influence of DNA sequence mismatches on the frequency of gene replacement in Saccharomyces cerevisiae. Mismatching was shown to be a potent barrier to efficient gene replacement, but its effect was considerably ameliorated by the presence of DNA sequences that are identical to the genomic target at one end of a chimeric DNA fragment. Disruption of the mismatch repair gene MSH2 greatly reduces but does not eliminate the barrier to recombination between mismatched DNA fragment and genomic target sequences, indicating that the inhibition of gene replacement with mismatched sequences is at least partially under the control of mismatch repair. We also found that mismatched sequences inhibited recombination between a DNA fragment and the genome only when they were close to the edge of the fragment. Together these data indicate that while mismatches can destabilize the relationship between a DNA fragment and a genomic target sequence, they will only do so if they are likely to be in the heteroduplex formed between the recombining molecules.

Base Sequence↗
PubMed1997

The RAD7, RAD16, and RAD23 genes of Saccharomyces cerevisiae: requirement for transcription-independent nucleotide excision repair in vitro and interactions between the gene products.

Nucleotide excision repair (NER) is a biochemical process required for the repair of many different types of DNA lesions. In the yeast Saccharomyces cerevisiae, the RAD7, RAD16, and RAD23 genes have been specifically implicated in NER of certain transcriptionally repressed loci and in the nontranscribed strand of transcriptionally active genes. We have used a cell-free system to study the roles of the Rad7, Rad16, and Rad23 proteins in NER. Transcription-independent NER of a plasmid substrate was defective in rad7, rad16, and rad23 mutant extracts. Complementation studies with a previously purified NER protein complex (nucleotide excision repairosome) indicate that Rad23 is a component of the repairosome, whereas Rad7 and Rad16 proteins were not found in this complex. Complementation studies with rad4, rad7, rad16, and rad23 mutant extracts suggest physical interactions among these proteins. This conclusion was confirmed by experiments using the yeast two-hybrid assay, which demonstrated the following pairwise interactions: Rad4 with Rad23, Rad4 with Rad7, and Rad7 with Rad16. Additionally, interaction between the Rad7 and Rad16 proteins was demonstrated in vitro. Our results show that Rad7, Rad16, and Rad23 are required for transcription-independent NER in vitro. This process may involve a unique protein complex which is distinct from the repairosome and which contains at least the Rad4, Rad7, and Rad16 proteins.

Adenosine Triphosphatases↗
PubMed1997

Demonstration of biphasic effects of docosahexaenoic acid on apolipoprotein B secretion in HepG2 cells.

Oleic acid (OA) stimulates apolipoprotein B (apoB) secretion from HepG2 cells by protecting the nascent protein from rapid intracellular degradation. In contrast, the n-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid, have been shown to reduce apoB secretion by increasing its intracellular degradation in rat hepatocytes. We attempted to determine if OA and DHA have these opposite effects at the same point in the secretory pathway for apoB or if they act at different points in HepG2 cells. Unexpectedly, we found that when DHA (0.2 mmol/L) was incubated with HepG2 cells for 2 hours, it stimulated both triglyceride (TG) synthesis and apoB secretion significantly (the "stimulatory effect"). The stimulatory effect of DHA on apoB secretion was associated with decreased intracellular degradation of newly synthesized apoB. These acute effects of DHA on TG synthesis and apoB secretion paralleled those previously demonstrated with OA. After DHA was removed from the medium, however, both TG synthesis and apoB secretion rapidly decreased to a level that was significantly less than the control level (the "inhibitory effect"). At the same time, intracellular apoB degradation was significantly increased, and this degradation was efficiently prevented by proteasome inhibitors. Removal of DHA from the incubation resulted in inhibition of the incorporation of endogenous fatty acids into TG. In contrast, removal of OA from the media was not associated with any such inhibitory effect. The inhibitory effect of DHA on basal apoB secretion persisted at least 8 hours. These studies suggest that incubation of HepG2 cells with DHA has biphasic effects on TG synthesis and apoB secretion: an initial stimulation of TG synthesis is followed by inhibition of TG synthesis and increased apoB degradation. Although the stimulatory effect of DHA is apparent during short incubations of HepG2 cells, both effects would be expected to occur during long incubations, since fatty acid uptake by cells is rapid and efficient. Thus, long incubations of HepG2 cells with DHA could result in overall reduced apoB secretion compared with cells incubated in bovine serum albumin. If these findings are extrapolated to the in vivo situation, they can explain the ability of dietary n-3 fatty acids, which would be delivered to the liver intermittently, to reduce very low density lipoprotein secretion.

Animals↗
PubMed1997

Event-related potential and intelligence test performance of 50 patients with epilepsy.

The findings of P300 and Wechsler Adult Intelligence Scale in 50 epileptic patients were assessed and compared with those of 38 healthy adult volunteers. The relationships between the course of epilepsy and the WAIS or peak P300 latencies were analyzed. Results showed that the prolonged latencies of P300 were positively correlated with course of epilepsy but not with full scale IQ. P300 peak latency and Arithmetic, Digit Symbol and Picture Arrangement were closely related.

Adolescent↗
PubMed1997

Quantitative pharmaco-EEG of sustained release valproate in epileptics.

The quantitative background EEG effects and serum concentration of the sustained-release form of VPA (SR-VPA) were studied after single-dose administration in 10 previously untreated epileptic patients with generalized tonic-clonic seizures. The result showed an increase of power of alpha 2 band on the occipital areas, a decrease of power of beta band (diffuse and preponderant on posterior scalp areas) with the increase of serum concentration. Both effects were found to reach their maxima and minima respectively when the peak values of serum concentration were reached. A positive correlation between alpha 2 power on the occipital areas and serum concentration was observed, and a negative correlation of serum concentration and beta power were detected on the posterior scalp areas.

Adult↗
PubMed1997

Myosin V associates with melanosomes in mouse melanocytes: evidence that myosin V is an organelle motor.

Mice with mutations at the dilute locus exhibit a 'washed out' or 'diluted' coat color. The pigments that are responsible for the coloration of mammalian hair are produced by melanocytes within a specialized organelle, the melanosome. Each melanocyte is responsible for delivering melanosomes via its extensive dendritic arbor to numerous keratinocytes, which go on to form the pigmented hair shaft. In this study, we show by light immunofluorescence microscopy and immunoelectron microscopy that the myosin V isoform encoded by the dilute locus associates with melanosomes. This association, which was seen in all mouse melanocyte cell lines examined and with two independent myosin V antibodies, was evident not only within completely melanized cells, but also within cells undergoing the process of melanosome biogenesis, where coordinate changes in the distributions of a melanosome marker and myosin V were seen. To determine where myosin V, a known actin-based motor, might play a role in melanosome transport, we also examined the cellular distribution of F-actin. The only region where myosin V and F-actin were both concentrated was in dendrites and dendritic tips, which represent the sole destination for melanosomes and where they accumulate in cultured melanocytes. These results support the idea that myosin V serves as the motor for the outward movement of melanosomes within dendritic extensions, and, together with the available information regarding the phenotype of mutant melanocytes in vitro, argue that coat color dilution is caused by the absense of this myosin V-dependent melanosome transport system.

Actins↗
PubMed1997

beta-Adrenoreceptor antagonistic actions and mutagenicities of R(+)- and S(-)-enantiomers of N-desisopropylpropranolol and its N-acetyl conjugate.

Enantiospecific acetyl conjugation was examined in the rat liver 105000 x g supernatant (cytosol) system using racemic 1-amino-3-(1-naphthyloxy)-2-propanol (NDP), a N-desisopropyl metabolite of propranolol. From the results of chiral separative determination of the samples by HPLC using a Chiralcel OD-R column, more remarkable enantiospecificity was observed in the R(+)-enantiomer on NDP elimination and N-acetyl conjugate (AcNDP) formation. Next, the strength of beta-adrenoceptor antagonistic actions and mutagenicities was compared between R(+)- and S(-)-enantiomers of NDP and AcNDP, respectively. In the case of NDP, both enantiomers possessed weak beta1-adrenoceptor antagonistic effects on isoproterenol-induced positive inotropic and chronotropic actions in the left and right atria isolated from a guinea pig. These actions of R(+)- and S(-)-NDP were 1700-times and 100-times less potent, respectively, than those of propranolol. beta2-Adrenoceptor antagonistic actions of R(+)- and S(-)-NDP in the trachea were 1600-times and 200-times less potent, respectively, than those of propranolol. Enantiospecificity was observed in the beta-adrenoceptor antagonistic action of S(-)-NDP, while R(+)-NDP and both enantiomers of AcNDP appeared to be negligible in this action. On the other hand, the mutagenicities of each enantiomer were examined by the Ames method using 13 kinds of Salmonella typhimurium strains. In the case of AcNDP, the numbers of colonies increased according to the substrate concentration only when rat liver 9000 x g supernatant fraction (S-9 mixture) was added to the plates containing TA100, YG1029, TA104 and YG3003, and then enantiospecificity was observed in the mutagenicity of S(-)-AcNDP. Thus, the ultimate mutagen might be an active metabolite formed mainly from S(-)-AcNDP. Despite of the addition of rat liver S-9 mixture, R(+)-AcNDP and both enantiomers of NDP did not indicate mutagenicity.

Adrenergic beta-Antagonists↗
PubMed1997

Topography of ribosomes and initiation complexes from rat liver as revealed by atomic force microscopy.

Atomic force microscopy (AFM) was used to image ribosomes and ribosomal subunits (60S, 40S and native 40S ribosomal subunits) isolated from rat liver. A variety of topographic images were obtained directly and found to be consistent with models established by other biophysical methods. In addition, the ternary complex of eIF-2 x GTP x Met-tRNA(i) and the 43S preinitiation complex have been discerned by AFM directly. Detailed information about the binding sites for eIF-1A, eIF-2, eIF-3, and Met-tRNA(i) on the 40S ribosomal subunit was derived from the AFM images. Finally, factors which may give rise to artifactual images, namely, convolution of the AFM tip on ribosomes, surface tension collapse effect and dehydration, are discussed. This work demonstrates that AFM is useful for imaging ribosomes and translational complexes and provides valuable information that can be used to complement other well-established techniques.

Animals↗
PubMed1997

[Assessment of sputum culture and serology for detection of chlamydia pneumoniae in patients with symptomatic acute respiratory tract infection].

OBJECTIVE: To evaluate sputum culture and serology for detection of chlamydia pneumoniae (C. pneumoniae) in adult patients with acute respiratory tract infection and normal subjects. METHODS: Microimmunoflorescence (micro-IF) test for IgG and IgM antibodies to C. pneumoniae specific antigen was performed in every subject. Thirty-seven patients also had sputum HEP-2 cell culture tested for C. pneumoniae. RESULTS: Twenty-six patients (29.7%) with micro-IF IgG titres equal to or greater than 1:512 or/and IgM titres equal to or greater than 1:32 indicated recent infection. Eight patients (21.3%) with positive sputum culture of C. pnuemoniae were identified. No similar titer was shown in control normal subjects. CONCLUSIONS: Acute infection of C. pneumoniae was common in symptomatic patients with acute respiratory tract infection and attention should be drawn to this special illness.

Adolescent↗
PubMed1997

[Protein kinase C involved in the protecttve effect of anoxic preconditioning on vascular smooth muscle cells].

It has been known that anoxic preconditioning (APC) has protective effects not only on cardiomyocyte, but also on vasculature. However, the effects of APC on vascular smooth muscle cells (VSMC) is unknown. On the model of anoxia/reoxygenation (A/R) injury of rabbit VSMC, the effect of APC was observed. It was found that APC could increase the survival rate of VSMC after A/R injury, lower the leakage of lactate dehydrogenase (LDH) and protein from cells, and attenuate peroxidation injury and calcium overload of VSMC. The results also showed that PMA, an activator of protein kinase C (PKC), could mimic, but H7 or polymyxin B (inhibitors of PKC) could abolish the above protective effect of APC. It is suggested that the protective effect of APC on VSMC during A/R injury might be due to the activation of PKC.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗