Biomedical subjects

Q Wu

Publications and source records attributed to Q Wu.

At least 19 recordsLinked to original sources

PubMed2001

H+-ATPase-mediated cytoplasmic pH-responses associated with elevation of cytoplasmic calcium in cultured rabbit nonpigmented ciliary epithelium.

Studies were conducted to test whether an increase of cytoplasmic calcium concentration influences H+-ATPase activity in cultured rabbit nonpigmented ciliary epithelium (NPE). Cytoplasmic calcium concentration or cytoplasmic pH was measured by a fluorescence ratio technique in cells loaded with either Fura-2 or BCECF. Cytoplasmic calcium was increased in three ways; by exposure to BAY K 8644 (1 microm), by exposure to a mixture of epinephrine (1 microm) + acetylcholine (10 microm) or by depolarization with potassium-rich solution. In each case cytoplasmic pH increased significantly. In all three cases 100 nm bafilomycin A1, a specific H+-ATPase inhibitor, significantly inhibited the pH increase. These results suggest an increase of cytoplasmic calcium might initiate events that lead to activation of proton export from the cytoplasm by a mechanism involving H+-ATPase. This notion is supported by the observation that the pH increase was suppressed when either verapamil or nifedipine was used to prevent the cytoplasmic calcium increase in cells exposed to potassium-rich solution. Protein kinase C activation might also be involved in the mechanism of H+-ATPase stimulation since staurosporine suppressed the pH response to potassium-rich solution. A transient rise of cytoplasmic calcium concentration was observed when cytoplasmic acidification was induced by exposure to high pCO2. This suggests a rise of cytoplasmic calcium might represent part of a physiological mechanism to stimulate H+-ATPase-mediated protein export under acid conditions.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed2001

Intensity-modulated stereotactic radiosurgery using dynamic micro-multileaf collimation.

PURPOSE: The implementation of dynamic leaf motion on a micro-multileaf collimator system provides the capability for intensity-modulated stereotactic radiosurgery (IMSRS), and the consequent potential for improved dose distributions for irregularly shaped tumor volumes adjacent to critical organs. This study explores the use of IMSRS to provide improved tumor coverage and normal tissue sparing for small cranial tumors relative to plans based on multiple fixed uniform-intensity beams or traditional circular collimator arc-based stereotactic techniques. METHODS AND MATERIALS: Four patient cases involving small brain lesions are presented and analyzed. The cases were chosen to include a representative selection of target shapes, number of targets, and adjacent critical areas. Patient plans generated for these comparisons include standard arcs with multiple circular collimators, and fixed noncoplanar static fields with uniform-intensity beams and IMSRS. Parameters used for evaluation of the plans include the percentage of irradiated volume to tumor volume (PITV), normal tissue dose-volume histograms, and dose-homogeneity ratios. All IMSRS plans were computed using previously established IMRT techniques adapted for use with the BrainLAB M3 micro-multileaf collimator. The algorithms comprising the IMRT system for optimization of intensity distributions and conversion into leaf trajectories of the BrainLab M3 were developed at our institution. The ADAC Pinnacle(3) radiation treatment-planning system was used for dose calculations and for input of contours for target volumes and normal critical structures. RESULTS: For all cases, the IMSRS plans showed a high degree of conformity of the dose distribution with the target shape. The IMSRS plans provided either (1) a smaller volume of normal tissue irradiated to significant dose levels, generally taken as doses greater than 50% of the prescription, or (2) a lower dose to an important adjacent critical organ. The reduction in volume of normal tissue irradiated in the IMSRS plans ranged from 10% to 50% relative to the other arc and uniform fixed-field plans. CONCLUSION: The case studies presented for IMSRS demonstrate significant dosimetric improvements for small, irregularly shaped lesions of the brain when compared to treatments using multiple static fields or standard SRS arc techniques with circular collimators. For all cases, the IMSRS plan yielded a smaller volume of normal tissue irradiated, and/or a reduction in the volume of an adjacent critical organ (i.e., brainstem) irradiated to significant dose levels.

Brain Neoplasms↗

PubMed2001

Reversal of spontaneous autoimmune insulitis in nonobese diabetic mice by soluble lymphotoxin receptor.

One striking feature of spontaneous autoimmune diabetes is the prototypic formation of lymphoid follicular structures within the pancreas. Lymphotoxin (LT) has been shown to play an important role in the formation of lymphoid follicles in the spleen. To explore the potential role of LT-mediated microenvironment in the pathogenesis of insulin-dependent diabetes mellitus (IDDM), an LTbeta receptor-immunoglobulin fusion protein (LTbetaR-Ig) was administered to nonobese diabetic mice. Early treatment with LTbetaR-Ig prevented insulitis and IDDM, suggesting that LT plays a critical role in the insulitis development. LTbetaR-Ig treatment at a late stage of the disease also dramatically reversed insulitis and prevented diabetes. Moreover, LTbetaR-Ig treatment prevented the development of IDDM by diabetogenic T cells in an adoptive transfer model. Thus, LTbetaR-Ig can disassemble the well established lymphoid microenvironment in the islets, which is required for the development and progression of IDDM.

Animals↗

PubMed2001

The identification and characterization of hydrazinyl urea-based antibacterial agents through combinatorial chemistry.

An effort to identify novel inhibitors of peptidoglycan synthesis with antibacterial activity resulted in the discovery of a series of biaryl urea-based antibacterial agents through isolation of a by-product from a mixture-based combinatorial library of semi-carbazones and subsequent parallel synthesis efforts. The compounds were shown to possess broad spectrum antibacterial activity against gram-positive drug resistant pathogens, and showed apparent specificity for disruption of the bacterial cell wall biosynthesis pathway.

Anti-Bacterial Agents↗

PubMed2001

Identification of GABA(B) receptor in rat testis and sperm.

gamma-Aminobutyric acid (GABA) can mimic and potentiate the action of progesterone in initiating the acrosome reaction (AR) of mammalian sperm, indicating that sperm contain receptors for GABA. This contention was validated by identifying the receptor (R) subtype, GABA(A)R, in mammalian sperm. In the present study a second subtype, GABA(B)R, was identified in rat testis and sperm. Total RNAs of rat testis and sperm were prepared and used as template to synthesize the respective cDNAs by the RT-PCR method. Two splice variants of the cDNA coding GABA(B)R1 (GABA(B)R1a and GABA(B)R1c) and GABA(B)R2 were identified. Extracts of rat testis, spermatogenic cells and sperm contained two proteins with estimated molecular sizes of 130 and 100 kDa, corresponding to GABA(B)R1a and GABA(B)R1c/lb, respectively, determined by Western blot using polyclonal anti-GABA(B)R1 antibody. By an indirect immunofluorescence technique, GABA(B)R1 was located on the head of rat sperm. The present finding is the first direct demonstration that mammalian sperm contain GABA(B)R.

Alternative Splicing↗

PubMed2001

Cloning and sequence of the gene encoding the muscle fatty acid binding protein from the desert locust, Schistocerca gregaria.

Muscle fatty acid binding protein (FABP) is a major cytosolic protein in flight muscle of the desert locust, Schistocerca gregaria. FABP expression varies greatly during development and periods of increased fatty acid utilization, but the molecular mechanisms that regulate its expression are not known. In this study, the gene coding for locust muscle FABP was amplified by PCR and cloned, together with 1.2 kb of upstream sequence. The sequence coding for the 607 bp cDNA is interrupted by two introns of 12.7 and 2.9 kb, inserted in analogous positions as the first and third intron of the mammalian homologues. Both introns contain repetitive sequences also found in other locust genes, and the second intron contains a GT-microsatellite. The promoter sequence includes a canonical TATA box 24 bp upstream of the transcription start site. The upstream sequence contains various potential myocyte enhancer sequences and a 160 bp segment that is repeated three times. In database searches in the genome database of Drosophila melanogaster, a gene with the same gene organization and promoter structure was identified, likely the dipteran homologue of muscle FABP. Upstream of both insect genes, a conserved 19 bp inverted repeat sequence was detected. A similar but reverse palindrome is also present upstream of all mammalian heart FABP genes, possibly representing a novel element involved in muscle FABP expression.

Amino Acid Sequence↗

PubMed2001

Cloning and characterization of human ubiquitin-processing protease-43 from terminally differentiated human melanoma cells using a rapid subtraction hybridization protocol RaSH.

Defects in growth control and differentiation occur frequently in human cancers. In the case of human melanoma cells, treatment with a combination of fibroblast interferon (IFN-beta) and the protein kinase C activator mezerein (MEZ) results in an irreversible loss of proliferative potential and tumorigenic properties with a concomitant induction of terminal differentiation. These changes in cellular properties are associated with an induction and suppression in specific subsets of genes that occur in a temporal manner. To identify the complete repertoire of gene changes occurring during melanoma reversion to a more differentiated state a number of molecular approaches are being used. These include, subtraction hybridization using temporally spaced cDNA libraries, random cDNA isolation and evaluation by reverse Northern blotting and high throughput microarray analysis of subtracted cDNA clones. In the present study we have used a novel approach, rapid subtraction hybridization (RaSH), to identify and clone an additional gene of potential relevance to cancer growth control and terminal cell differentiation. RaSH has identified a human ubiquitin-processing protease gene, HuUBP43, that is differentially expressed in melanoma cells as a function of treatment with IFN-beta or IFN-beta + MEZ. HuUBP43 is a type I interferon inducible gene that is upregulated in a diverse panel of normal and tumor cells when treated with IFN-beta via the JAK/STAT kinase pathway. This gene may contribute to the phenotypic changes induced by IFN-beta during growth arrest and differentiation in human melanoma cells and other cell types as well as the antiviral and growth inhibitory effects of interferon.

Amino Acid Sequence↗

PubMed2001

Structural basis of caspase-7 inhibition by XIAP.

The inhibitor of apoptosis (IAP) proteins suppress cell death by inhibiting the catalytic activity of caspases. Here we present the crystal structure of caspase-7 in complex with a potent inhibitory fragment from XIAP at 2.45 A resolution. An 18-residue XIAP peptide binds the catalytic groove of caspase-7, making extensive contacts to the residues that are essential for its catalytic activity. Strikingly, despite a reversal of relative orientation, a subset of interactions between caspase-7 and XIAP closely resemble those between caspase-7 and its tetrapeptide inhibitor DEVD-CHO. Our biochemical and structural analyses reveal that the BIR domains are dispensable for the inhibition of caspase-3 and -7. This study provides a structural basis for the design of the next-generation caspase inhibitors.

Apoptosis↗

PubMed2001

Gene targeting in hemostasis. Hepsin.

Hepsin is a type II transmembrane serine protease abundantly expressed on the surface of hepatocytes. Biochemical studies have shown that hepsin is an enzyme of 51 kDa with the trypsin-like substrate specificity. Several in vitro studies have suggested that hepsin may play a role in blood coagulation, hepatocyte growth, and fertilization. To determine the functional importance of hepsin, hepsin-deficient mice were generated by homologous recombination. Homozygous hepsin-/- mice were viable and fertile, and grew normally. When analyzed in hemostasis assays, such as tail bleeding time and plasma clotting times, and in vivo modes, such as disseminated intravascular coagulation, septic shock, and acute liver regeneration, hepsin-/- mice had similar phenotypes as wild-type controls. Liver weight and serum concentrations of liver-derived proteins or enzymes were also similar in hepsin-/- and wild-type mice. No abnormalities were identified in major organs in hepsin-/- mice in histological examinations. These results indicate that hepsin is not an essential enzyme for normal hemostasis, embryogenesis, and maintenance of normal liver function. Unexpectedly, serum concentrations of bone-derived alkaline phosphatase were approximately two-fold higher in both male and female hepsin-/- mice than those in wild-type controls. The underlying mechanism for this phenotype and long-term effects of hepsin deficiency remain to be determined.

Animals↗

PubMed2001

Signal via lymphotoxin-beta R on bone marrow stromal cells is required for an early checkpoint of NK cell development.

NK cells play an important role in the immune system but the cellular and molecular requirements for their early development are poorly understood. Lymphotoxin-alpha (LTalpha)(-/-) and LTbetaR(-/-) mice show a severe systemic reduction of NK cells, which provides an excellent model to study NK cell development. In this study, we show that the bone marrow (BM) or fetal liver cells from LTalpha(-/-) or LTbetaR(-/-) mice efficiently develop into mature NK cells in the presence of stromal cells from wild-type mice but not from LTalpha(-/-) or LTbetaR(-/-) mice. Direct activation of LTbetaR-expressing BM stromal cells is shown to promote to early NK cell development in vitro. Furthermore, the blockade of the interaction between LT and LTbetaR in adult wild-type mice by administration of LTbetaR-Ig impairs the development of NK cells in vivo. Together, these results indicate that the signal via LTbetaR on BM stromal cells by membrane LT is an important pathway for early NK cell development.

Adoptive Transfer↗

PubMed2001

Complementary effects of TNF and lymphotoxin on the formation of germinal center and follicular dendritic cells.

The formation of germinal centers (GC) around follicular dendritic cells (FDC) is a critical step in the humoral immune responses that depends on the cooperative effects of B cells and T cells. Mice deficient in either TNF or lymphotoxin (LT) fail to form both GC and FDC network in B cell follicles. To test a potential complementary effect of TNF and LT, a mixture of bone marrow cells from TNF(-/-) mice and LT alpha(-/-) mice was transferred into irradiated LT alpha(-/-) mice or TNF(-/-) mice. Interestingly, the formation of both GC and FDC clusters in B cell follicles was restored in such chimeric mice, suggesting that TNF and LT from different cells could complement one another. To identify the exact contributions of each subset to the complementary effect of TNF and LT, different sources of T and B cells from LT alpha(-/-) mice or TNF(-/-) mice were used for reconstitution. Our study demonstrates that either T or B cell-derived TNF is sufficient to restore FDC/GC in the presence of LT-expressing B cells. However, TNF itself is not required for GC reactions if the FDC network is already intact. Thus, the development and maintenance of these lymphoid structures depend on a delicate interaction between TNF and LT from different subsets of lymphocytes.

Adjuvants, Immunologic↗

PubMed2001

A new operation for ventricular septal defect with aortic incompetence.

Two boys, 10 years of age, with ventricular septal defect and severe aortic insufficiency were treated using a new method. An autograft of anterior pulmonary artery wall and the adjacent leaflet and subpulmonary muscle was excised. The excised pulmonary artery segment was used to replace the prolapsed right coronary cusp, and the autograft muscle was used to close the ventricular septal defect. The right ventricular outflow tract and pulmonary valve were repaired using an autologous pericardial patch with an autologous single cusp. The results in both cases were satisfactory.

Aortic Valve Insufficiency↗

PubMed2001

Repair of atrial septal defect through a minimal right vertical infra-axillary thoracotomy in a beating heart.

We present a minimally invasive and cosmetic approach to repair atrial septal defect. Fifty-five atrial septal defects were successfully repaired through a minimal right vertical infra-axillary thoracotomy. Every repair was performed on the beating heart with continuous suction through aortic needle vents and with the head of the patient lowered. This approach can be used not only in adults but also in young girls.

Axilla↗

PubMed2001

Purification and characterization of White Spot syndrome virus (WSSV) produced in an alternate host: crayfish, Cambarus clarkii.

Penaeid shrimp is the natural host of White Spot Syndrome Virus (WSSV) that can cause high mortality in the infected hosts. Attempts to obtain sufficient amounts of purified intact WSSV for characterization have been unsuccessful. Using crayfish, Cambarus clarkii as a proliferation system, a large amount of infectious WSSV was reproduced and intact WSSV viral particles were purified with a new isolation medium by ultra-centrifugation. Purified WSSV particles were very sensitive to organic solvents and the detergent, Triton X-100. The size of the rod-shape, somewhat elliptical, intact WSSV was 110-130x260-350 nm with a long, tail-like envelope extension. The naked viral nucleocapsid was about 80x350 nm, and it possessed 15 spiral and cylindrical helices composed of 14 globular capsomers along its long axis, and a 'ring' structure at one terminus. Distinct WSSV genome DNA patterns were obtained when the purified genomic dsDNA of WSSV was digested with five different restriction enzymes (HindIII, XhoI, BamHI, SalI, and SacI). In addition, at least 13 major and distinct protein bands could be observed when purified intact WSSV viruses were separated by SDS-PAGE followed by Coomassie Brilliant R-250 staining. The estimated molecular weights of these proteins were 190, 84, 75, 69, 68, 58, 52, 44, 28, 27.5, 23, 19, and 16 kD, respectively. Both the 44 and 190 kD proteins were easily removed if the hemolymph from the WSSV infected crayfish was transiently treated with 1% Triton X-100 before it was subjected to gradient centrifugation, indicating that both of them are located on the surface of the viral envelope. These characteristics are consistent with WSSV isolated from the penaeid shrimp.

Animals↗

PubMed2001

Dosimetric validation for multileaf collimator-based intensity-modulated radiotherapy: a review.

The creation of intricate dose distributions produced by intensity-modulated radiotherapy (IMRT) depends on complex planning systems and specialized mechanical devices. The many possible sources of inaccuracy and the complexity of the dose maps themselves require that a substantial effort be made to ensure that calculated and delivered dose distributions agree. This review provides an overview of the current status of the validation of dose predictions of IMRT planning systems by comparisons with measurements. Emphasis is placed on multileaf collimator- (MLC) based IMRT. Discrepancies between calculations and measurements may be due to any of 3 causes: errors and uncertainties in the dose calculation algorithm, in measurements, or in beam delivery by the accelerator/MLC combination. Some of the factors affecting dosimetry include: the technique employed for modulating the fluence, the dose calculation algorithm and other aspects of the planning system, mechanical limitations of the MLC hardware, dosimetric characteristics of the MLC, such as MLC leakage and rounded leaf ends, the choice of dosimeter, and the measurement geometry and technique. The advantages and drawbacks of various dosimeters including film, ion chambers, thermoluminescent dosimetry, and electronic portal imaging devices are discussed. The steps involved in validating dosimetrically a planning system are outlined, including the various fields that need to be measured, the phantoms that may be used, and measurement techniques. The achievable accuracy of dosimetry for IMRT is discussed.

Radiometry↗

PubMed2001

Approaches to the remediation of a polychlorinated biphenyl (PCB) contaminated soil--a laboratory study.

A soil that had been historically contaminated with Aroclor 1242, 1248, 1254 and 1260 was decontaminated by two surfactant-mediated cleaning procedures that had been chosen to mimic ex-situ washing and in-situ soil flushing processes. A preliminary screening selected four surfactants (from 17 commercial formulations) for their ability to mobilise PCBs from the soil while suffering minimal losses to the supercritical carbon dioxide (scCO2) that was used in a separate back-extraction procedure. The mobilisation was enhanced, with minimal foam formation, by the presence of 17% (v/v) IBMK in the surfactant suspension. Each of the four surfactants, at 1, 3, or 5% (v/v) concentration, was evaluated by (i) 15 successive 10 min sonication-filtrations and (ii) continuous soil column flushing during 20 h. Each filtrate from (i) and samples, taken at hourly intervals, from (ii) were analysed for their PCB and surfactant content. Both extraction procedures mobilised PCBs efficiently when extended for longer periods and were modelled accurately as the sum of a constant and single-term exponential increase to a maximum. The predicted number of replicate stages required to mobilise 50% of the toxicants (t50) varied from 7 to 3 for sonication-washing of the soil (10 g) or from 6.8 to 2.8 h for column flushing of 30 g soil and decreased as the concentration of surfactant in the aqueous phase was increased. The combined PCB-laden aqueous suspensions were then back-extracted efficiently with scCO2 and the eluate was dechlorinated quantitatively as it traversed a short, heated column of silver-iron bimetallic mixture.

Carbon Dioxide↗

PubMed2001

Analysis of prognostic predictors in idiopathic membranous nephropathy.

We studied clinical and histologic parameters at the time of renal biopsy of 19 patients with idiopathic membranous nephropathy (IMN) to investigate the predictors for prognosis of IMN. Nineteen patients diagnosed by open renal biopsy between 1988 and 1993 and followed for at least 5 years were divided into two groups according to the latest follow-up renal function. Group I included 16 patients with normal renal function at the last follow-up point. Group II included three patients with end-stage renal failure at the last follow-up point. Antibodies to CD68, CD45RO, alpha-SMA, collagen IV, and collagen VI were used to investigate glomerular and interstitial changes in biopsy specimens by the indirect enzyme-labeled antibody method. Degree of global glomerulosclerosis, segmental glomerulosclerosis, adhesion to Bowman's capsule, and crescent formation were evaluated by light microscopy (periodic acid-Schiff, periodic acid-metheramine [PAM] staining). The difference between the two groups was analyzed by Mann-Whitney U: test. The number of interstitial cells, the number of interstitial CD45RO-positive cells, and increases of interstitial collagen IV and VI were found to be the most important factors for prognosis of IMN. These findings suggest that the extent of tubulointerstitial changes (cellular infiltration and fibrosis) determines the prognosis of renal function in IMN.

Adolescent↗

PubMed2001

Comparative DNA sequence analysis of mouse and human protocadherin gene clusters.

The genomic organization of the human protocadherin alpha, beta, and gamma gene clusters (designated Pcdh alpha [gene symbol PCDHA], Pcdh beta [PCDHB], and Pcdh gamma [PCDHG]) is remarkably similar to that of immunoglobulin and T-cell receptor genes. The extracellular and transmembrane domains of each protocadherin protein are encoded by an unusually large "variable" region exon, while the intracellular domains are encoded by three small "constant" region exons located downstream from a tandem array of variable region exons. Here we report the results of a comparative DNA sequence analysis of the orthologous human (750 kb) and mouse (900 kb) protocadherin gene clusters. The organization of Pcdh alpha and Pcdh gamma gene clusters in the two species is virtually identical, whereas the mouse Pcdh beta gene cluster is larger and contains more genes than the human Pcdh beta gene cluster. We identified conserved DNA sequences upstream of the variable region exons, and found that these sequences are more conserved between orthologs than between paralogs. Within this region, there is a highly conserved DNA sequence motif located at about the same position upstream of the translation start codon of each variable region exon. In addition, the variable region of each gene cluster contains a rich array of CpG islands, whose location corresponds to the position of each variable region exon. These observations are consistent with the proposal that the expression of each variable region exon is regulated by a distinct promoter, which is highly conserved between orthologous variable region exons in mouse and human.

Animals↗