Biomedical subjects

Q Zhu

Publications and source records attributed to Q Zhu.

At least 55 records · Page 3Linked to original sources

PubMed2001

Studies toward the total synthesis of clavulactone.

Synthetic studies directed toward a total synthesis of clavulactone are reported. In light of the analysis made in our previous work, cyclopentane 4a (a key intermediate in the present work) was synthesized through a radical-mediated ring closure of a rationally designed substrate 25. Using HWE reactions, the lower and upper side-chains of 4a were converted into an allyl chloride and an allyl cyanohydrin, respectively. Subsequent treatment of the allyl chloride/cyanohydrin in a highly diluted THF solution with sodium bis(trimethylsiliyl)amide led to intramolecular alkylation and thus completed a major endeavor in synthesizing the dolabellane framework, construction of the eleven-membered ring. SmI(2)-mediated lactonization as a model reaction for the formation of the alpha,beta-unsaturated delta-lactone segment of clavulactone is also described.

Animals↗

PubMed2001

Human single-chain Fv intrabodies counteract in situ huntingtin aggregation in cellular models of Huntington's disease.

This investigation was pursued to test the use of intracellular antibodies (intrabodies) as a means of blocking the pathogenesis of Huntington's disease (HD). HD is characterized by abnormally elongated polyglutamine near the N terminus of the huntingtin protein, which induces pathological protein-protein interactions and aggregate formation by huntingtin or its exon 1-containing fragments. Selection from a large human phage display library yielded a single-chain Fv (sFv) antibody specific for the 17 N-terminal residues of huntingtin, adjacent to the polyglutamine in HD exon 1. This anti-huntingtin sFv intrabody was tested in a cellular model of the disease in which huntingtin exon 1 had been fused to green fluorescent protein (GFP). Expression of expanded repeat HD-polyQ-GFP in transfected cells shows perinuclear aggregation similar to human HD pathology, which worsens with increasing polyglutamine length; the number of aggregates in these transfected cells provided a quantifiable model of HD for this study. Coexpression of anti-huntingtin sFv intrabodies with the abnormal huntingtin-GFP fusion protein dramatically reduced the number of aggregates, compared with controls lacking the intrabody. Anti-huntingtin sFv fused with a nuclear localization signal retargeted huntingtin analogues to cell nuclei, providing further evidence of the anti-huntingtin sFv specificity and of its capacity to redirect the subcellular localization of exon 1. This study suggests that intrabody-mediated modulation of abnormal neuronal proteins may contribute to the treatment of neurodegenerative diseases such as HD, Alzheimer's, Parkinson's, prion disease, and the spinocerebellar ataxias.

Amino Acid Sequence↗

PubMed2001

Human homologue of yeast Rad23 protein A interacts with p300/cyclic AMP-responsive element binding (CREB)-binding protein to down-regulate transcriptional activity of p53.

The tumor suppressor protein p53 regulates various cellular responses to DNA damage and plays a significant role in DNA repair. The nuclear p300/cyclic AMP-responsive element binding (CREB)-binding protein (CBP) proteins act as coactivators in supporting the transcription function of p53. We examined the role of the human homologue of yeast Rad23 protein A (hHR23A), one of the two human homologues of the Saccharomyces cerevisiae nucleotide excision repair gene product Rad23, in the p300/CBP-associated regulation of p53 activity. Overexpression of wild-type hHR23A inhibits the p53 transcriptional activity and results in a decreased steady-state protein level of cellular p53. The inhibitory effect of hHR23A can be overcome by the concomitant expression of p300, CBP, and p300 segments harboring C/H1 domain and neutralized by the coexpression of HIV accessory protein Vpr, which binds COOH terminus of hHR23A/B. Additionally, hHR23A was shown to interact in vitro and in vivo with p300 segments harboring C/H1 domain. These studies provide evidence for the involvement of hHR23A in the regulation of p53 activity through p300/CBP. Although the precise direct role of hHR23 proteins in regulation of p53 and DNA repair remains to be elucidated, our data suggest that the interaction between hHR23A and p300/CBP has important implications in cross-talk between the p53 pathway and DNA repair.

Animals↗

PubMed2001

Analysis of a non-functional HNF-1alpha (TCF1) mutation in Japanese subjects with familial type 1 diabetes.

Mutations in the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha; gene symbol TCF1) cause maturity-onset diabetes of the young type 3 (MODY3), a form of diabetes mellitus characterized by autosomal dominant inheritance, early onset, and pancreatic beta-cell dysfunction. Recent genetic studies, however, also found mutations in patients diagnosed with idiopathic (non-autoimmune based) type 1 diabetes. We identified a novel frameshift mutation (142delG) in the TCF1 gene in a family with a strong family history of type 1 diabetes and examined the functional properties of the mutant HNF 1alpha. The expression of the mutant protein was not detected in COS-7 cells by Western blot analysis after transfection of the mutant cDNA. This is the first case of an unstable mutant HNF-1alpha protein. Reporter gene analysis indicated that the mutant HNF-1alpha had no transactivation activity in HeLa and MIN6 cells. Haploinsufficiency for HNF-1alpha may lead to severe forms of diabetes like type 1 diabetes.

Adolescent↗

PubMed2001

A rare polyadenylation signal mutation of the FOXP3 gene (AAUAAA-->AAUGAA) leads to the IPEX syndrome.

The mouse scurfy gene, Foxp3, and its human orthologue, FOXP3, which maps to Xp11.23-Xq13.3, were recently identified by positional cloning. Point mutations and microdeletions of the FOXP3 gene were found in the affected members of eight of nine families with IPEX (immune dysfunction, polyendocrinopathy, enteropathy, X-linked; OMIM 304930). We evaluated a pedigree with clinically typical IPEX in which mutations of the coding exons of FOXP3 were not detected. Our reevaluation of this pedigree identified an A-->G transition within the first polyadenylation signal (AAUAAA-->AAUGAA) after the stop codon. The next polyadenylation signal is not encountered for a further 5.1 kb. This transition was not detected in over 212 normal individuals (approximately 318 X chromosomes), excluding the possibility of a rare polymorphism. We suggest that this mutation is causal of IPEX in this family by a mechanism of nonspecific degradation of the FOXP3 gene message.

Cells, Cultured↗

PubMed2001

Mutation screening of the hepatocyte nuclear factor (HNF)-6 gene in Japanese subjects with diabetes mellitus.

Heterozygous mutations in the genes encoding transcription factors (HNF-1alpha, HNF-1beta and HNF-4alpha) in the hepatocyte nuclear factor (HNF) network are associated with maturity-onset diabetes of the young (MODY). We screened HNF-6 gene for mutations in 34 Japanese subjects with MODY/early-onset diabetes mellitus and 56 subjects with late-onset diabetes mellitus. One single nucleotide polymorphism (SNP) at codon 287 (GGG to GGT) was found in the gene and the frequency was similar among MODY/early-onset diabetes, late-onset diabetes and control subjects. Genetic variations in the HNF-6 gene are not likely to contribute to the susceptibility to diabetes mellitus in Japanese.

Adolescent↗

PubMed2001

Age-related alterations of cardiac tissue microstructure and material properties in Fischer 344 rats.

The cardiac aging process is accompanied by global mechanical dysfunction that reflects increased myocardial stiffness. Accordingly, age-related changes in microscopic material properties of myocardium were delineated with high-frequency ultrasound (US) (30 to 44 MHz) tissue characterization methods for aging Fischer 344 rats at 6 (adult), 18 (aged), and 24 (senescent) months of age. The excised lateral wall of the left ventricle of rats (n = 10 per group) was insonified with a 50-MHz acoustic microscope for determination of integrated backscatter, backscatter coefficient and attenuation coefficient. Histological and biochemical analyses for collagen content and cardiac myocyte diameter were performed. Collagen concentration increased progressively with age, with the greatest increments occurring from 6 to 18 months (38.0 +/- 6.3 to 53.0 +/- 7.1 mg/g dry wt), and leveling off at 24 months (60.0 +/- 7.4 mg/g dry wt). Tissue microscopic material properties also changed progressively from 6 to 24 months of age, as determined by US methods: integrated backscatter increased (-44.7 +/- 1.8 vs. -40.8 +/- 1.9 dB, p < 0.05), attenuation increased (47.1 +/- 5.9 to 65.3 +/- 7.8 dB/cm, p < 0.05), and the backscatter coefficient increased (0.73 +/- 0.16 x 10(-5) to 3.76 +/- 1.6 x 10(-5) cm(-1), p < 0.05), from 6 to 24 months of age in each case. Age-related alterations in indices of cardiac microscopic material properties were closely correlated with the changes in cardiac microstructure. Ultrasonic tissue characterization may prove to be a sensitive tool to monitor changes in the cardiac microstructure, such as increased collagen deposition, that occur within age-related diastolic dysfunction.

Aging↗

PubMed2001

Induction of ErbB-2/neu-specific protective and therapeutic antitumor immunity using genetically modified dendritic cells: enhanced efficacy by cotransduction of gene encoding IL-12.

Overexpression of ErbB-2/neu occurs in 20-30% of patients with breast cancer and indicates a poor prognosis. The presence of a detectable immune response to ErbB-2/neu in some patients suggests that this oncogene may be a useful target for vaccine therapy. We evaluated whether genetic immunization using dendritic cells (DC) transduced ex vivo with an adenovirus expressing the ErbB-2/neu gene (AdNeuTK) could induce protective and therapeutic immunity against a breast tumor cell line overexpressing ErbB-2/neu. Subcutaneous (s.c.) immunization with the DC vaccine elicited protective immunity in an average of 60% of animals. CTL analysis demonstrated specific cytotoxic activity against breast tumor cells, as well as syngeneic fibroblasts transduced with AdNeuTK. In vivo depletion studies demonstrated both CD4+ and CD8+ T cells were required. In a therapeutic setting, immunization with the DC vaccines could cure mice with pre-established tumors and efficacy was further enhanced by cotransducing DCs with a vector expressing murine IL-12 (AdmIL-12). These studies support DC vaccines as a therapeutic strategy for human breast cancer, while emphasizing the importance of optimizing an immune response by combining tumor antigen presentation with immunostimulatory cytokines.

Adenoviridae↗

PubMed2001

Reduction of pacing output coupling capacitance for sensing the evoked response.

Sensing of the intracardiac evoked response (ER) after a pacing stimulus has been used in implantable pacemakers for automatic verification of capture. Reliable detection of ER is hampered by large residual afterpotentials associated with pacing stimuli. This led to the development of various technological solutions, like the use of triphasic pacing pulses and low polarizing electrode systems. This study investigated the effect of reducing the coupling capacitance (CC) in the pacemaker output circuitry on the magnitude of afterpotential, and the ability to automate detection of ventricular evoked response. A CC of 2.2 microF and four different blanking and recharge time settings were clinically tested to evaluate its impact on sensing of the ventricular ER and pacing threshold. Using an automatic step-down threshold algorithm, 54 consecutive patients, aged 70 +/- 10 years with acutely (n = 27) or chronically (n = 27) implanted ventricular pacing leads were enrolled for measurement testing. Routine measurements, using a standard pacing system analyzer (PSA), were (mean +/- SD) impedance 569 +/- 155 omega, R wave amplitude baseline to peak 9.8 +/- 3.7 mV and threshold 0.9 +/- 0.7 V at 0.4-ms pulse width. This new capture verification scheme, based on a CC of 2.2 microF and recharge/blanking timing setting of 10/12 ms, was successful in 52 patients which is equivalent to a success rate of 96%. In a subgroup of 26 patients implanted with bipolar ventricular leads (10 chronic, 16 acute), data were collected in unipolar (UP) and bipolar (BP) pace/sense configurations. Also, ER signals were recorded with two different band-pass filters: a wider band (WB) of 6-250 Hz and a conventional narrow band (NB) of 20-100 Hz. WB sensing from UP lead configuration yielded statistically significant larger signal to artifact ratios (SAR) than the other settings (P < 0.01). A dedicated unipolar ER sensing configuration using a small output capacitor and a wider band-pass filter enables adequate automatic capture verification, without any restrictions on pacing lead models or pacing/sensing configurations.

Aged↗

PubMed2001

Pregnane glycoside, lignan glycosides, triterpene glycosyl ester and flavonoid glycosides from Rubus amabilis.

Two new compounds, 3-O-beta-D-glucopyranosyl-3 beta, 15 alpha-dihydroxypregn-5-en-20-one (1) and (-)-secoisolariciresinol-O-alpha-L-rhamnopyranoside (2), along with six known compounds (3-8), have been isolated from the aerial parts of Rubus amabilis Focke. The structures of the new compounds were elucidated mainly by spectroscopic methods and some chemical transformations.

Drugs, Chinese Herbal↗

PubMed2001

Effects of enamel matrix derivative on gene expression of primary osteoblasts.

OBJECTIVE: The aim of this study was to investigate the effects of enamel matrix derivative (EMD) on gene expression of collagen alpha1 (I), osteocalcin, prostaglandin G/H synthase 2 (PGHS-2), interleukin-6, and insulin-like growth factor I in primary mouse osteoblasts. STUDY DESIGN: Primary osteoblasts were digested from 6- to 8-day-old mouse calvaria. Cells were divided into 4 groups and cultured for 24, 48, and 72 hours with a serum-free modified Eagle medium as negative control, modified Eagle medium with 25 microg/mL EMD, modified Eagle medium with 100 microg/mL EMD, and modified Eagle medium plus 10% fetal bovine serum as positive control. Gene expression was determined by Northern blot and reverse transcription polymerase chain reaction analysis. RESULT: EMD enhanced collagen I, interleukin-6, and PGHS-2 expression and did not stimulate the expression of osteocalcin and IGF-I. CONCLUSION: These results indicate that EMD might regulate certain gene expression during periodontal tissue regeneration.

Animals↗

PubMed2001

Activities of starch hydrolytic enzymes and sucrose-phosphate synthase in the stems of rice subjected to water stress during grain filling.

To understand the effect of water stress on the remobilization of prestored carbon reserves, the changes in the activities of starch hydrolytic enzymes and sucrose-phosphate synthase (SPS) in the stems of rice (Oryza sativa L.) during grain filling were investigated. Two rice cultivars, showing high lodging-resistance and slow remobilization, were grown in the field and subjected to well-watered (WW, psi(soil)=0) and water-stressed (WS, psi(soil)=-0.05 MPa) treatments 9 d after anthesis (DAA) till maturity. Leaf water potentials of both cultivars markedly decreased during the day as a result of WS treatment, but completely recovered by early morning. WS treatment accelerated the reduction of starch in the stems, promoted the reallocation of prefixed (14)C from the stems to grains, shortened the grain filling period, and increased the grain filling rate. More soluble sugars including sucrose were accumulated in the stems under WS than under WW treatments. Both alpha- and beta-amylase activities were enhanced by the WS, with the former enhanced more than the latter, and were significantly correlated with the concentrations of soluble sugars in the stems. The other two possible starch-breaking enzymes, alpha-glucosidase and starch phosphorylase, showed no significant differences in the activities between the WW and WS treatments. Water stress also increased the SPS activity that is responsible for sucrose production. Both V(limit) and V(max), the activities of the enzyme at limiting and saturating substrate concentrations, were enhanced and the activation state (V(limit)/V(max)) was also increased as a result of the more significant enhancement of V(limit). The enhanced SPS activity was closely correlated with an increase of sucrose accumulation in the stems. The results suggest that the fast hydrolysis of starch and increased carbon remobilization were attributed to the enhanced alpha-amylase activity and the high activation state of SPS when the rice was subjected to water stress.

Amylases↗

PubMed2001

Enamel matrix derivative prolongs primary osteoblast growth.

Enamel matrix derivative (EMD) secreted by cells of the epithelial root sheath plays an important role in cementogenesis and periodontal tissue formation. The mechanisms by which EMD influences cell function are not known. The purpose of this study was to determine the effect of EMD on cell growth of primary mouse osteoblasts. Osteoblasts were digested from 6- to 8-day-old mouse calvaria and plated into 6-well cell culture plates at an initial density of 5000 cells/cm2. After 24-h incubation with Dulbecco's modified eagle medium (DMEM) supplemented with 10% fetal bovine serum, cells were incubated in three different groups of media: DMEM only as control, DMEM with 25 microg/ml EMD, and DMEM with 100 microg/ml EMD. At days 3, 7, 10, and 14, the total cell number per well was calculated, and cell morphology was examined. At each observation period the number of cells in the EMD groups was significantly greater (ANOVA, p < 0.01) than that in the control group. EMD had a greater effect on osteoblast survivor in the higher concentration than in the lower concentration. Furthermore normal morphology of the primary osteoblasts was maintained in the EMD groups. These results suggest that EMD prolongs primary osteoblast growth and may have an effect on osteoblasts during periodontal regeneration.

Analysis of Variance↗

PubMed2001

Hormonal changes in the grains of rice subjected to water stress during grain filling.

Lodging-resistant rice (Oryza sativa) cultivars usually show slow grain filling when nitrogen is applied in large amounts. This study investigated the possibility that a hormonal change may mediate the effect of water deficit that enhances whole plant senescence and speeds up grain filling. Two rice cultivars showing high lodging resistance and slow grain filling were field grown and applied with either normal or high amount nitrogen (HN) at heading. Well-watered and water-stressed (WS) treatments were imposed 9 days post anthesis to maturity. Results showed that WS increased partitioning of fixed (14)CO(2) into grains, accelerated the grain filling rate but shortened the grain filling period, whereas the HN did the opposite way. Cytokinin (zeatin + zeatin riboside) and indole-3-acetic acid contents in the grains transiently increased at early filling stage and WS treatments hastened their declines at the late grain filling stage. Gibberellins (GAs; GA(1) + GA(4)) in the grains were also high at early grain filling but HN enhanced, whereas WS substantially reduced, its accumulation. Opposite to GAs, abscisic acid (ABA) in the grains was low at early grain filling but WS remarkably enhanced its accumulation. The peak values of ABA were significantly correlated with the maximum grain filling rates (r = 0.92**, P < 0.01) and the partitioning of fixed (14)C into grains (r = 0.95**, P < 0.01). Exogenously applied ABA on pot-grown HN rice showed similar results as those by WS. Results suggest that an altered hormonal balance in rice grains by water stress during grain filling, especially a decrease in GAs and an increase in ABA, enhances the remobilization of prestored carbon to the grains and accelerates the grain filling rate.

Abscisic Acid↗

PubMed2001

Biphasic poroviscoelastic simulation of the unconfined compression of articular cartilage: II--Effect of variable strain rates.

This study investigated the abilities of the linear biphasic poroviscoelastic (BPVE) model and the linear biphasic poroelastic (BPE) model to simulate the effect of variable ramp strain rates on the unconfined compression stress relaxation response of articular cartilage. Curve fitting of experimental data showed that the BPVE model was able to successfully account for the ramp strain rate-dependent viscoelastic behavior of articular cartilage under unconfined compression, while the BPE model was able to account for the complete viscoelastic response at a slow strain rate, but only the long-term viscoelastic response at faster strain rates. We concluded that the short-term viscoelastic behavior of articular cartilage, when subjected to a fast ramp strain rate, is primarily governed by a fluid flow-independent (intrinsic) viscoelastic mechanism, whereas the long-term viscoelastic behavior is governed by a fluid flow-dependent (biphasic) viscoelastic mechanism. Furthermore, a linear viscoelastic representation of the solid stress was found to be a valid model assumption for the simulation of ramp strain rate-dependent relaxation behaviors of articular cartilage within the range of ramp strain rates investigated.

Animals↗

PubMed2001

Biphasic poroviscoelastic simulation of the unconfined compression of articular cartilage: I--Simultaneous prediction of reaction force and lateral displacement.

This study investigated the ability of the linear biphasic poroelastic (BPE) model and the linear biphasic poroviscoelastic (BPVE) model to simultaneously predict the reaction force and lateral displacement exhibited by articular cartilage during stress relaxation in unconfined compression. Both models consider articular cartilage as a binary mixture of a porous incompressible solid phase and an incompressible inviscid fluid phase. The BPE model assumes the solid phase is elastic, while the BPVE model assumes the solid phase is viscoelastic. In addition, the efficacy of two additional models was also examined, i.e., the transversely isotropic BPE (TIBPE) model, which considers transverse isotropy of the solid matrix within the framework of the linear BPE model assumptions, and a linear viscoelastic solid (LVE) model, which assumes that the viscoelastic behavior of articular cartilage is solely governed by the intrinsic viscoelastic nature of the solid matrix, independent of the interstitial fluid flow. It was found that the BPE model was able to accurately account for the lateral displacement, but unable to fit the short-term reaction force data of all specimens tested. The TIBPE model was able to account for either the lateral displacement or the reaction force, but not both simultaneously. The LVE model was able to account for the complete reaction force, but unable to fit the lateral displacement measured experimentally. The BPVE model was able to completely account for both lateral displacement and reaction force for all specimens tested. These results suggest that both the fluid flow-dependent and fluid flow-independent viscoelastic mechanisms are essential for a complete simulation of the viscoelastic phenomena of articular cartilage.

Animals↗

PubMed2001

Influenza virus infection induces metallothionein gene expression in the mouse liver and lung by overlapping but distinct molecular mechanisms.

Metallothionein I (MT-I) and MT-II have been implicated in the protection of cells against reactive oxygen species (ROS), heavy metals, and a variety of pathological and environmental stressors. Here, we show a robust increase in MT-I/MT-II mRNA level and MT proteins in the livers and lungs of C57BL/6 mice exposed to the influenza A/PR8 virus that infects the upper respiratory tract and lungs. Interleukin-6 (IL-6) had a pronounced effect on the induction of these genes in the liver but not the lung. Treatment of the animals with RU-486, a glucocorticoid receptor antagonist, inhibited induction of MT-I/MT-II in both liver and lung, revealing a direct role of glucocorticoid that is increased upon infection in this induction process. In vivo genomic footprinting (IVGF) analysis demonstrated involvement of almost all metal response elements, major late transcription factor/antioxidant response element (MLTF/ARE), the STAT3 binding site on the MT-I upstream promoter, and the glucocorticoid responsive element (GRE1), located upstream of the MT-II gene, in the induction process in the liver and lung. In the lung, inducible footprinting was also identified at a unique gamma interferon (IFN-gamma) response element (gamma-IRE) and at Sp1 sites. The mobility shift analysis showed activation of STAT3 and the glucocorticoid receptor in the liver and lung nuclear extracts, which was consistent with the IVGF data. Analysis of the newly synthesized mRNA for cytokines in the infected lung by real-time PCR showed a robust increase in the levels of IL-10 and IFN-gamma mRNA that can activate STAT3 and STAT1, respectively. A STAT1-containing complex that binds to the gamma-IRE in vitro was activated in the infected lung. No major change in MLTF/ARE DNA binding activity in the liver and lung occurred after infection. These results have demonstrated that MT-I and MT-II can be induced robustly in the liver and lung following experimental influenza virus infection by overlapping but distinct molecular mechanisms.

Animals↗

PubMed2001

Spot 14 gene deletion increases hepatic de novo lipogenesis.

Previous studies have investigated the relationship between the Spot 14 gene and hepatic lipogenesis. Those studies found that the Spot 14 protein was induced when lipogenesis was induced and suggested that induction of the Spot 14 protein was required for induction of hepatic lipogenesis by thyroid hormone and dietary carbohydrate. Analysis of those findings led us to hypothesize that the Spot 14 gene is required for induced hepatic de novo lipogenesis in vivo. To test this hypothesis, we created an in vivo deletion of the Spot 14 gene in mice using gene-targeting technology. Southern blot analysis showed that the Spot 14 gene was disrupted. Northern blot analysis showed that this disruption ablated expression of intact hepatic Spot 14 mRNA. In contrast to our hypothesis, acute thyroid hormone administration led to comparable induction of hepatic lipogenic enzyme mRNAs between the wild-type and knockout mice. Furthermore, long-term treatment with both thyroid hormone and a diet promoting lipogenesis led to enhanced lipogenic enzyme activity and a greater rate of hepatic de novo lipogenesis in the knockout, compared with the wild-type, mice. Although these data indicate that the Spot 14 protein is not required for induced hepatic de novo lipogenesis, they also suggest that Spot 14 plays some role in this process. It is possible that alternative pathways that complement the loss of the Spot 14 protein are present, and in the absence of Spot 14, these alternative pathways overcompensate to produce an enhanced rate of induced lipogenesis.

Animals↗