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Biomedical subjects

Z Wang

Publications and source records attributed to Z Wang.

At least 703 records · Page 39Linked to original sources
PubMed2000

WdCHS3, a gene that encodes a class III chitin synthase in Wangiella (Exophiala) dermatitidis, is expressed differentially under stress conditions.

Class III chitin synthases are important for hyphal growth in some filamentous fungi but are not found in yeasts. Using a specific PCR product that encodes a portion of the class III chitin synthase of W. dermatitidis as a probe, we isolated the chitin synthase gene, WdCHS3, from this polymorphic melanized pathogen of humans. Northern blotting showed that WdCHS3 was highly expressed under stress conditions, such as the shift of cells to temperatures commensurate with infection, or to conditions that induce cellular morphogenesis in this fungus. Analysis of the 5' upstream sequence of WdCHS3 provided evidence for a negative regulatory element at between -780 and -1600 bp. Western blotting indicated that the production of the WdChs3p was temperature dependent and temporally regulated. Disruption of WdCHS3 in a wild-type strain and in two temperature-sensitive morphological mutants resulted in significantly reduced chitin synthase activities but did not obviously affect their morphologies, growth rates, chitin contents, or virulence. This paradox suggested that the contributions of the high levels of WdCHS3 gene expression and WdChs3p production in strains subjected to stress reside in unknown or unexamined parts of the life cycle of this ecologically poorly known member of the Fungi Imperfecti. Nonetheless, this report presents the first evidence that transcription of a chitin synthase gene is regulated by a negative regulatory element in its 5' upstream sequence.

Amino Acid Sequence↗
PubMed2000

The poly(A)-binding protein and an mRNA stability protein jointly regulate an endoribonuclease activity.

We previously identified a sequence-specific erythroid cell-enriched endoribonuclease (ErEN) activity involved in the turnover of the stable alpha-globin mRNA. We now demonstrate that ErEN activity is regulated by the poly(A) tail. The unadenylated alpha-globin 3' untranslated region (3'UTR) was an efficient substrate for ErEN cleavage, while the polyadenylated 3'UTR was inefficiently cleaved in an in vitro decay assay. The influence of the poly(A) tail was mediated through the poly(A)-binding protein (PABP) bound to the poly(A) tail, which can inhibit ErEN activity. ErEN cleavage of an adenylated alpha-globin 3'UTR was accentuated upon depletion of PABP from the cytosolic extract, while addition of recombinant PABP reestablished the inhibition of endoribonuclease cleavage. PABP inhibited ErEN activity indirectly through an interaction with the alphaCP mRNA stability protein. Sequestration of alphaCP resulted in an increase of ErEN cleavage activity, regardless of the polyadenylation state of the RNA. Using electrophoretic mobility shift assays, PABP was shown to enhance the binding efficiency of alphaCP to the alpha-globin 3'UTR, which in turn protected the ErEN target sequence. Conversely, the binding of PABP to the poly(A) tail was also augmented by alphaCP, implying that a stable higher-order structural network is involved in stabilization of the alpha-globin mRNA. Upon deadenylation, the interaction of PABP with alphaCP would be disrupted, rendering the alpha-globin 3'UTR more susceptible to endoribonuclease cleavage. The data demonstrated a specific role for PABP in protecting the body of an mRNA in addition to demonstrating PABP's well-characterized effect of stabilizing the poly(A) tail.

3' Untranslated Regions↗
PubMed2000

Preferential incorporation of G opposite template T by the low-fidelity human DNA polymerase iota.

DNA polymerase activity is essential for replication, recombination, repair, and mutagenesis. All DNA polymerases studied so far from any biological source synthesize DNA by the Watson-Crick base-pairing rule, incorporating A, G, C, and T opposite the templates T, C, G, and A, respectively. Non-Watson-Crick base pairs would lead to mutations. In this report, we describe the ninth human DNA polymerase, Pol(iota), encoded by the RAD30B gene. We show that human Pol(iota) violates the Watson-Crick base-pairing rule opposite template T. During base selection, human Pol(iota) preferred T-G base pairing, leading to G incorporation opposite template T. The resulting T-G base pair was less efficiently extended by human Pol(iota) compared to the Watson-Crick base pairs. Consequently, DNA synthesis frequently aborted opposite template T, a property we designated the T stop. This T stop restricted human Pol(iota) to a very short stretch of DNA synthesis. Furthermore, kinetic analyses show that human Pol(iota) copies template C with extraordinarily low fidelity, misincorporating T, A, and C with unprecedented frequencies of 1/9, 1/10, and 1/11, respectively. Human Pol(iota) incorporated one nucleotide opposite a template abasic site more efficiently than opposite a template T, suggesting a role for human Pol(iota) in DNA lesion bypass. The unique features of preferential G incorporation opposite template T and T stop suggest that DNA Pol(iota) may additionally play a specialized function in human biology.

Base Pairing↗
PubMed2000

Mooren's ulcer in China: a study of clinical characteristics and treatment.

AIMS: To investigate the clinical characteristics and compare the effects of several methods of treatment of Mooren's corneal ulcer. METHODS: 550 consecutive cases of Mooren's corneal ulcer were analysed in patients, including age, sex, laterality of eye, ulcer location, perforative rate, cure rate of surgeries, recurrent rate, the effects of conjunctiva excision, lamellar keratoplasty (LKP), and LKP plus 1% cyclosporin A eye drops. RESULTS: The average age of onset was 48.4 years of age. The ratio of males to females was 1:0. 74. 165 (30%) cases had the disease bilaterally, of which 52 (31.5%) occurred in the young age group and 113 (68.5%) in the old age group. Ulcers of 501 eyes (70.1%) were located at the limbus of the palpebral fissure. The perforation rate was 13.3%, with perforation of 41 eyes (43.2%) occurring in the young age group and 54 (56.8%) in the old age group. Postoperative recurrence rate was 25.6%. The cure rate of the first procedure of LKP plus 1% cyclosporin A eye drops was 73.7%. The final cure rate was 95.6%, and the postoperative preservation rate of the eye globe was 99.7%. CONCLUSION: This primary study provided the clinical characteristics of patients with Mooren's corneal ulcer in China. LKP plus 1% cyclosporin A eye drops was an effective treatment.

Administration, Topical↗
PubMed2000

Fluid transport by cultured corneal epithelial cell layers.

BACKGROUND/AIMS: Fluid transport across the in vitro corneal epithelium is short lived, hence difficult to detect and characterise. Since stable rates of fluid transport across several cultured epithelial cell layers have been demonstrated, the behaviour of confluent SV40 transformed rabbit corneal epithelial cells (tRCEC) grown on permeable supports was examined. METHODS: Fluid transport was determined with a nanoinjector volume clamp; the specific electrical resistance of the layers was 184 (SEM 9) Omega cm(2). tRCEC layers transported fluid (from basal to apical) against a pressure head of 3 cm H(2)O for 2-3 hours. RESULTS: In the first hour, the rate of fluid transport was 5.2 (0.5) microl/h/cm(-2) (n=23), which is comparable with that found in other epithelia. Fluid transport was completely inhibited in 15-30 minutes by either 100 microM ouabain (n=6), 50 microM bumetanide (n=6), or 1 microM endothelin-1 (ET-1; n=6). Preincubation with 10 microM BQ123 (an ET(A) receptor antagonist) obviated inhibition by ET-1 (n=6). ET-1 also caused a 22% decrease in specific resistance. CONCLUSIONS: Fluid transport appears to depend on transepithelial Cl(- )transport since (1) their directions are the same (stroma-->tear), and (2) both bumetanide and ouabain inhibit it with similar time course. tRCEC appear useful to investigate aspects of the physiology and pharmacology of fluid transport across this layer, including receptor mediated control of this process.

Animals↗
PubMed2000

Attack rates of human papillomavirus type 16 and cervical neoplasia in primiparous women and field trial designs for HPV16 vaccination.

BACKGROUND: Identification of human papillomavirus type 16 (HPV16) as the major risk factor for cervical neoplasia, and mass production of DNA free HPV capsids have paved the way to preventive vaccination trials. Design of such trials requires reliable attack rate data. OBJECTIVE: Determination of (1) HPV16 and (2) cervical neoplasia attack rates in primiparous women. Estimation of actuarial sample sizes for HPV16 vaccination phase IV trials. DESIGN: A longitudinal cohort study. METHODS: Population based Finnish Maternity Cohort (FMC) and Finnish Cancer Registry (FCR) were linked for the identification of two cohorts of primiparous women: (1) a random subsample of the FMC: 1656 women with two pregnancies between 1983-9 or 1990-6 and living in the Helsinki metropolitan area, and (2) all 72,791 primiparous women living in the same area during 1983-94. Attack rate for persistent HPV16 infection (1) was estimated in 1279 seronegative women by proportion of seroconversions between the first and the second pregnancy. Comparable 10 year cumulative incidence rate (CR) of cervical intraepithelial neoplasia grade III and cervical cancer (CIN III+) (2) was estimated based on cases registered at the FCR during 1991-4. RESULTS: The HPV16 attack rates were 13.8% (< 18 years), 7.0% (18-19 years), 2.3% (21 years), 2.4% (23 years), and 4.5% (< 25 years). Number of vaccinees required for a 5 year efficacy trial with persistent HPV16 infection as the end point ranged between 1000 and 3900, assuming 80% power, 90%-70% vaccine efficacy (VE), and misclassification. The CRs of CIN III+ were 0.33% (< 18 years), 0.44% (18-19 years), 0.21% (20-24 years), and 0.28% (< 25 years). Number of vaccinees required for a 10 year efficacy trial with HPV16 positive CIN III+ as the end point was 15,000 assuming 80% power, 90% VE, and 75% aetiological fraction of CIN III+ for HPV16. CONCLUSIONS: The attack rates of HPV16 and CIN III+ identify primiparous women under 25 years of age among target populations for postnatal HPV vaccination at phase II/III trials.

Adolescent↗
PubMed2000

Three different vasoactive responses of rat tail artery to nicotine.

The vasoactive effects of nicotine on isolated rat tail artery tissues were studied. Nicotine transiently contracted rat tail artery tissues (EC50, 55.6 +/- 2 microM) in an extracellular Ca2+ dependent and endothelium-independent fashion. The blockade of alpha1-adrenoceptors, but not alpha2-adrenoceptors or P2X purinoceptors, inhibited the nicotine-induced contraction by 38 +/- 7% (p < 0.05). Nicotine (1 mM) depolarized membrane by 13 +/- 3 mV, but did not affect L-type Ca2+ channel currents, of the isolated rat tail artery smooth muscle cells. The phenylephrine-precontracted tail artery tissues were relaxed by nicotine (EC50, 0.90 +/- 0.31 mM), which was significantly inhibited after the blockade of nicotinic receptors. Simultaneous removal of phenylephrine and nicotine, after a complete relaxation of the phenylephrine-precontracted tail artery strips was achieved by nicotine at accumulated concentrations (> or =10 mM), triggered a Ca2+-dependent rebound long-lasting vasoconstriction (n = 20). This rebound contraction was abolished in the absence of calcium or in the presence of tetracaine in the bath solution. Pretreatment of vascular tissues with a nicotinic receptor antagonist did not affect the nicotine-induced vasoconstriction or nicotine withdrawal induced rebound contraction. The elucidation of the triphasic vascular effects of nicotine and the underlying mechanisms is important for a better understanding of the complex vascular actions of nicotine.

Animals↗
PubMed2000

Resting energy expenditure-fat-free mass relationship: new insights provided by body composition modeling.

The relationship between resting energy expenditure (REE) and metabolically active fat-free mass (FFM) is a cornerstone in the study of physiological aspects of body weight regulation and human energy requirements. Important questions, however, remain unanswered regarding the observed linear REE-FFM association in adult humans. This led us to develop a series of REE-body composition models that provide insights into the widely used simple linear REE-FFM prediction model derived experimentally in adult humans. The new models suggest that the REE-FFM relationship in mammals as a whole is curvilinear, that a segment of this function within a FFM range characteristic of adult humans can be fit with a linear equation almost identical to that observed from a composite review of earlier human studies, and that mammals as a whole exhibit a decrease in the proportion of FFM as high metabolic rate organs with greater FFM. The present study thus provides a new approach for examining REE-FFM relationships, advances in a quantitative manner previously observed albeit incompletely formulated REE-body composition associations, and identifies areas in need of additional research.

Algorithms↗
PubMed2000

Extracellular Ba(2+) blocks the cardiac transient outward K(+) current.

Ba(2+) is widely used as a tool in patch-clamp studies because of its ability to block a variety of K(+) channels and to pass Ca(2+) channels. Its potential ability to block the cardiac transient outward K(+) current (I(to)) has not been clearly documented. We performed whole cell patch-clamp studies in canine ventricular and atrial myocytes. Extracellular application of Ba(2+) produced potent inhibition of I(to) with an IC(50) of approximately 40 microM. The effects were voltage independent, and the inactivation kinetics were not altered by Ba(2+). The potency of Ba(2+) was approximately 10 times higher than that of 4-aminopyridine (a selective I(to) blocker with an IC(50) of 430 microM) under identical conditions. By comparison, Ba(2+) blockade of the inward rectifier K(+) current was voltage dependent; the IC(50) was approximately 20 times lower (2.5 microM) than that for I(to) when determined at -100 mV and was comparable to I(to) as determined at -60 mV (IC(50) = 26 microM). Ba(2+) concentrations of </=1 mM or higher failed to block ultrarapid delayed rectifier K(+) current. Our data suggest that Ba(2+) can be considered a potent blocker of I(to).

4-Aminopyridine↗
PubMed2000

A comparison of transient outward currents in canine cardiac Purkinje cells and ventricular myocytes.

Although abnormalities in Purkinje cell (PC) repolarization are important causes of cardiac arrhythmias, the detailed properties of repolarizing currents in PCs are incompletely understood. We compared transient outward K(+) current (I(to)) in single PCs from canine false tendons with midmyocardial ventricular myocytes (VMs). I(to) reactivation was biexponential, with a similar rapid-phase time constant (30 +/- 5 and 35 +/- 4 ms for VM and PC, respectively) but a large, slow component in PCs with a much greater time constant than VM (1,427 +/- 70 vs. 181 +/- 24 ms, P < 0.001). Tetraethylammonium had no effect on VM I(to) but reversibly inhibited PC I(to) (IC(50) = 2.4 +/- 0.4 mM). PC I(to) was also more sensitive to 4-aminopyridine (IC(50) = 50 +/- 7 vs. 526 +/- 49 microM in VM, P < 0.0001). H(2)O(2) slowed I(to) inactivation in PCs but did not affect VM I(to). We conclude that PC I(to) shows significant differences from VM I(to), with some features, such as tetraethylammonium sensitivity, that have been reported in neither cardiac I(to) of atrial or ventricular myocytes nor cloned K(+) channel subunits (Kv1.4, Kv4.2, or Kv4.3) known to participate in cardiac I(to).

4-Aminopyridine↗
PubMed2000

Lower limb skeletal muscle mass: development of dual-energy X-ray absorptiometry prediction model.

Although magnetic resonance imaging (MRI) can accurately measure lower limb skeletal muscle (SM) mass, this method is complex and costly. A potential practical alternative is to estimate lower limb SM with dual-energy X-ray absorptiometry (DXA). The aim of the present study was to develop and validate DXA-SM prediction equations. Identical landmarks (i.e., inferior border of the ischial tuberosity) were selected for separating lower limb from trunk. Lower limb SM was measured by MRI, and lower limb fat-free soft tissue was measured by DXA. A total of 207 adults (104 men and 103 women) were evaluated [age 43 +/- 16 (SD) yr, body mass index (BMI) 24.6 +/- 3.7 kg/m(2)]. Strong correlations were observed between lower limb SM and lower limb fat-free soft tissue (R(2) = 0.89, P < 0.001); age and BMI were small but significant SM predictor variables. In the cross-validation sample, the differences between MRI-measured and DXA-predicted SM mass were small (-0.006 +/- 1.07 and -0.016 +/- 1.05 kg) for two different proposed prediction equations, one with fat-free soft tissue and the other with added age and BMI as predictor variables. DXA-measured lower limb fat-free soft tissue, along with other easily acquired measures, can be used to reliably predict lower limb skeletal muscle mass.

Absorptiometry, Photon↗
PubMed2000

Dual-energy X-ray absorptiometry: analysis of pediatric fat estimate errors due to tissue hydration effects.

Dual-energy X-ray absorptiometry (DXA) percent (%) fat estimates may be inaccurate in young children, who typically have high tissue hydration levels. This study was designed to provide a comprehensive analysis of pediatric tissue hydration effects on DXA %fat estimates. Phase 1 was experimental and included three in vitro studies to establish the physical basis of DXA %fat-estimation models. Phase 2 extended phase 1 models and consisted of theoretical calculations to estimate the %fat errors emanating from previously reported pediatric hydration effects. Phase 1 experiments supported the two-compartment DXA soft tissue model and established that pixel ratio of low to high energy (R values) are a predictable function of tissue elemental content. In phase 2, modeling of reference body composition values from birth to age 120 mo revealed that %fat errors will arise if a "constant" adult lean soft tissue R value is applied to the pediatric population; the maximum %fat error, approximately 0.8%, would be present at birth. High tissue hydration, as observed in infants and young children, leads to errors in DXA %fat estimates. The magnitude of these errors based on theoretical calculations is small and may not be of clinical or research significance.

Absorptiometry, Photon↗
PubMed2000

Plasmid DNA vaccines: tissue distribution and effects of DNA sequence, adjuvants and delivery method on integration into host DNA.

A variety of factors could affect the frequency of integration of plasmid DNA vaccines into host cellular DNA, including DNA sequences within the plasmid, the expressed gene product (antigen), the formulation, delivery method, route of administration, and the type of cells exposed to the plasmid. In this report, we examined the tissue distribution and potential integration of plasmid DNA vaccines following intramuscular administration in mice and guinea pigs. We compared needle versus Biojector (needleless jet) delivery, examined the effect of aluminum phosphate adjuvants, compared the results of different plasmid DNA vaccines, and tested a gene (the human papilloma virus E7 gene) whose protein product is known to increase integration frequency in vitro. Six weeks following intramuscular injection, the vast majority of the plasmid was detected in the muscle and skin near the injection site; lower levels of plasmid were also detected in the draining lymph nodes. At early time points (1-7 days) after injection, a low level of systemic exposure could be detected. Occasionally, plasmid was detected in gonads, but it dissipated rapidly and was extrachromosomal - indicating a low risk of germline transmission. Aluminum phosphate adjuvant had no effect on the tissue distribution and did not result in a detectable increase in integration frequency. Biojector delivery, compared with needle injection, greatly increased the uptake of plasmid (particularly in skin at the injection site), but did not result in a detectable increase in integration frequency. Finally, injection of a plasmid DNA vaccine containing the human papilloma virus type 16 E7 gene, known to increase integration in vitro, did not result in detectable integration in mice. These results suggest that the risk of integration following intramuscular injection of plasmid DNA is low under a variety of experimental conditions.

Adjuvants, Immunologic↗
PubMed2000

Toxicity of Dutch (E22Q) and Flemish (A21G) mutant amyloid beta proteins to human cerebral microvessel and aortic smooth muscle cells.

BACKGROUND AND PURPOSE: Cerebral amyloid angiopathy (CAA) is characterized by the deposition of amyloid beta protein (Abeta) in cortical and leptomeningeal vessels of patients with Alzheimer's disease and hereditary cerebral hemorrhage with amyloidosis, Dutch type. Smooth muscle cells (SMC) from cerebral microvessels (MV) are of particular interest as a site of Abeta-related injury because CAA is much more pronounced in the tunica media of cortical arterioles than meningeal arteries. Patients carrying point mutations at residues 22 (E22Q) and 21 (A21G) of Abeta show severe CAA with various degrees of brain parenchymal Abeta deposition. The purpose of this study was to investigate the effects of 2 mutant E22Q- and A21G-Abeta peptides on MV and aortic SMC. MERHODS: SMC were isolated from human cerebral MV and aorta. Cell morphology, viability, and proliferation as parameters of Abeta toxicity were investigated after 3 days of peptide treatment by trypan blue exclusion and [(3)H]thymidine incorporation. RESULTS: E22Q-Abeta induced significant decreased cellular proliferation and viability, as well as obvious degeneration of both MV and aortic SMC. A21G-Abeta and wild-type Abeta did not cause significant toxicity, as judged by cell morphology, viability, or cell proliferation, on either type of SMC. CONCLUSIONS: E22Q-Abeta induced greater toxicity in all parameters than A21G-Abeta and wild-type Abeta with respect to both MV and aortic SMC. A21G-Abeta did not show a significant toxic effect on MV and aortic SMC. This differential effect may be linked to cell type-specific processing and metabolism of mutant forms of Abeta. Mutations in amyloid precursor protein may lead to CAA by different pathogenetic mechanisms or share an unknown property that distinguishes them from wild-type Abeta.

Amyloid beta-Peptides↗
PubMed2000

Respiratory syncytial virus stimulation of vascular endothelial cell growth Factor/Vascular permeability factor.

We hypothesized that respiratory syncytial virus (RSV)-induced pathologies could be mediated, in part, by vascular active cytokines elaborated during virus infection. To address this hypothesis, we determined whether RSV stimulated vascular endothelial cell growth factor (VEGF)/vascular permeability factor (VPF) elaboration in vitro. Supernatants from unstimulated A549 cells and normal human bronchial epithelial cells contained modest levels of VEGF. In contrast, supernatants from RSV-infected cells contained elevated levels of VEGF/VPF. This stimulation was seen after as little as 2 h, was still prominent after 48 h, and, by immunoblot, was specific for the 165- and 121-amino acid isoforms of VEGF/VPF. It was not associated with significant cell cytotoxicity or alterations in VEGF messenger RNA. It did, however, require new protein biosynthesis. In accordance with these findings, the 165- and 121-amino acid isoforms of VEGF/VPF were also found in the nasal washings from patients with RSV infections. These studies demonstrate that RSV is a potent stimulator of VEGF/VPF elaboration and that, in vitro, this stimulation is mediated via a noncytotoxic translational and/or post-translational biosynthetic mechanism. VEGF/VPF may play an important role in the pathogenesis of RSV-induced disorders.

Cell Line↗
PubMed2000

Inducible targeting of IL-13 to the adult lung causes matrix metalloproteinase- and cathepsin-dependent emphysema.

Cigarette smoke exposure is the major cause of chronic obstructive pulmonary disease (COPD). However, only a minority of smokers develop significant COPD, and patients with asthma or asthma-like airway hyperresponsiveness or eosinophilia experience accelerated loss of lung function after cigarette smoke exposure. Pulmonary inflammation is a characteristic feature of lungs from patients with COPD. Surprisingly, the mediators of this inflammation and their contributions to the pathogenesis and varied natural history of COPD are not well defined. Here we show that IL-13, a critical cytokine in asthma, causes emphysema with enhanced lung volumes and compliance, mucus metaplasia, and inflammation, when inducibly overexpressed in the adult murine lung. MMP-2, -9, -12, -13, and -14 and cathepsins B, S, L, H, and K were induced by IL-13 in this setting. In addition, treatment with MMP or cysteine proteinase antagonists significantly decreased the emphysema and inflammation, but not the mucus in these animals. These studies demonstrate that IL-13 is a potent stimulator of MMP and cathepsin-based proteolytic pathways in the lung. They also demonstrate that IL-13 causes emphysema via a MMP- and cathepsin-dependent mechanism(s) and highlight common mechanisms that may underlie COPD and asthma.

Animals↗
PubMed2000

Antigen presenting cells expressing Fas ligand down-modulate chronic inflammatory disease in Fas ligand-deficient mice.

We assessed the effect of modified antigen presenting cells (APCs) expressing high levels of Fas ligand (APC-FasL) on post-viral chronic inflammatory disease. FasL-deficient B6-gld/gld mice infected with murine cytomegalovirus (MCMV) cleared the virus from their lungs, kidneys, and livers within 2 weeks of infection. However, inflammation persisted in these organs for more than 8 weeks, with a chronically increased T-cell response to MCMV-infected APCs and production of autoantibodies. Administration of APC-AdFasL at 4 weeks suppressed this inflammation and diminished the T-cell response and autoantibody production. APC-AdFasL that had been transfected with ultraviolet-irradiated MCMV were more effective than uninfected APC-AdFasL in ameliorating the chronic inflammation. APC-AdFasL migrated preferentially to the spleen, where they triggered apoptosis of lymphocytes in the marginal zone of the spleen. These results confirm that Fas-mediated apoptosis is not required for clearance of virus, but is required for down-modulation of the virally induced chronic inflammatory response. This organwide effect of APC-AdFasL appears to be mediated by elimination of activated T lymphocytes in the spleen before their emigration to the target organs.

Adenoviridae↗