Biomedical subjects

J Yu

Publications and source records attributed to J Yu.

At least 19 recordsLinked to original sources

PubMed2007

Amino acid supplementation reveals differential regulation of aflatoxin biosynthesis in Aspergillus flavus NRRL 3357 and Aspergillus parasiticus SRRC 143.

Aflatoxins are toxic and carcinogenic secondary metabolites produced by the fungi Aspergillus flavus and Aspergillus parasiticus. To better understand the molecular mechanisms that regulate aflatoxin production, the biosynthesis of the toxin in A. flavus and A. parasticus grown in yeast extract sucrose media supplemented with 50 mM tryptophan (Trp) were examined. Aspergillus flavus grown in the presence of 50 mM tryptophan was found to have significantly reduced aflatoxin B(1) and B(2) biosynthesis, while A. parasiticus cultures had significantly increased B(1) and G(1) biosynthesis. Microarray analysis of RNA extracted from fungi grown under these conditions revealed 77 genes that are expressed significantly different between A. flavus and A. parasiticus, including the aflatoxin biosynthetic genes aflD (nor-1), aflE (norA), and aflO (omtB). It is clear that the regulatory mechanisms of aflatoxin biosynthesis in response to Trp in A. flavus and A. parasiticus are different. These candidate genes may serve as regulatory factors of aflatoxin biosynthesis.

Aflatoxins↗

PubMed2007

Bronchial responsiveness to methacholine and adenosine 5'-monophosphate in atopic and non-atopic preschool children with recurrent wheezing.

BACKGROUND: It is well known that atopy is a major determinant of bronchial hyper-responsiveness (BHR) in both asymptomatic and asthmatic children. However, the relationship between atopy and BHR has not been well studied in preschool children with wheezing. BHR is usually measured by bronchial challenges using direct and indirect stimuli. OBJECTIVE: The aim of this study was to investigate whether atopic and non-atopic preschool wheezers display similar or different BHR profiles for direct and indirect stimuli. METHODS: Methacholine and adenosine 5'-monophosphate (AMP) bronchial challenges were performed in 4 to 6-year-old children with recurrent wheezing, using a modified auscultation method. The end-point was defined as the appearance of wheezing and/or oxygen desaturation. Atopy was determined to be present when a child had at least one positive reaction to a panel of 13 common airborne allergens in the presence of positive and negative controls. RESULTS: A positive response to methacholine (an end-point concentration < or =8 mg/mL) was observed in 89.3% (50/56) of atopic wheezers and in 83.8% (31/37) of non-atopic wheezers (P=0.44) for the difference. By contrast, the frequency of a positive response to AMP (an end-point concentration < or =200 mg/mL) was significantly higher in the atopic group (47/56, 83.9%) compared with the non-atopic group (12/37, 32.4%; P<0.01). CONCLUSION: While a majority of both atopic and non-atopic preschool wheezers were hyper-responsive to methacholine, atopic subjects were more hyper-responsive to AMP than non-atopic subjects. These findings suggest that atopic and non-atopic wheeze in preschool children are related to distinctive pathophysiologic pathways.

Adenosine Monophosphate↗

PubMed2006

Novel fast semi-automated software to segment cartilage for knee MR acquisitions.

OBJECTIVE: Validation of a new fast software technique to segment the cartilage on knee magnetic resonance (MR) acquisitions. Large studies of knee osteoarthritis (OA) will require fast and reproducible methods to quantify cartilage changes for knee MR data. In this report we document and measure the reproducibility and reader time of a software-based technique to quantify the volume and thickness of articular cartilage on knee MR images. METHODS: The software was tested on a set of duplicate sagittal three-dimensional (3D) dual echo steady state (DESS) acquisitions from 15 (8 OA, 7 normal) subjects. The repositioning, inter-reader, and intra-reader reproducibility of the cartilage volume (VC) and thickness (ThC) were measured independently as well as the reader time for each cartilage plate. The root-mean square coefficient of variation (RMSCoV) was used as metric to quantify the reproducibility of VC and mean ThC. RESULTS: The repositioning RMSCoV was as follows: VC=2.0% and ThC=1.2% (femur), VC=2.9% and ThC=1.6% (medial tibial plateau), VC=5.5% and ThC=2.4% (lateral tibial plateau), and VC=4.6% and ThC=2.3% (patella). RMSCoV values were higher for the inter-reader reproducibility (VC: 2.5-8.6%) (ThC: 1.9-5.2%) and lower for the intra-reader reproducibility (VC: 1.6-2.5%) (ThC: 1.2-1.9%). The method required an average of 75.4min per knee. CONCLUSIONS: We have documented a fast reproducible semi-automated software method to segment articular cartilage on knee MR acquisitions.

Cartilage, Articular↗

PubMed2006

Thermal stability of cubic boron nitride films deposited by chemical vapor deposition.

Thermal stability of well-crystallized cubic boron nitride (cBN) films grown by chemical vapor deposition has been investigated by cathodoluminescence (CL), Raman spectroscopy, and scanning electron microscopy (SEM) with the cBN films annealed at various temperatures up to 1,300 degrees C. The crystallinity of the cBN films further improves, as indicated by a reduction of the relevant Raman line width, when the annealing temperature exceeds 1,100 degrees C. Structural damage or amorphization was observed on the grain boundaries of the cBN crystals when annealing temperature reaches 1,300 degrees C. The CL spectra are found to be unchanged up to 1,100 degrees C after annealing at 500 degrees C, showing the stability of the cBN films in electronic properties up to this temperature. New features were observed in the CL spectra when annealing temperature reaches 1,200-1,300 degrees C.

Journal Article↗

PubMed2006

A role for neurotrophin-3 in targeting developing cholinergic axon projections to cerebral cortex.

This study examined the relationship between expression of neurotrophin-3 (NT-3) and the ingrowth of cholinergic axonal projections in cerebral cortex. Patterns of expression of NT-3 (defined by beta-galactosidase reporter expression in heterozygous offspring of transgenic NT-3(lacZneo/+) mice) revealed that limbic cortical regions (including frontal, cingulate, and insular cortex, as well as the dentate gyrus) express NT-3 and that these cortical regions receive early and relatively dense cholinergic axons (stained for acetylcholinesterase, AChE). Using the dentate gyrus as a model system, studies revealed that expression of the NT-3 reporter parallels, and precedes by approximately 2 days, the ingrowth of AChE positive cholinergic axons. Studies of forebrain organotypic slice cultures demonstrate that basal forebrain-derived cholinergic axons extend into cortical regions in a pattern that mimics the pattern of expression of the NT-3 reporter. Similarly, chimeric co-cultures, combining wild type septum with a slice of hippocampus from heterozygous NT-3(lacZneo/+) mice, demonstrate that cholinergic axons grow into regions of the dentate gyrus that express the NT-3 reporter. Hemisphere slice cultures made from NT-3 knockout mice reveal cholinergic axonal growth into cortex, but these axons do not form the regional pattern characteristic of slice cultures made from wild type or heterozygous NT-3(lacZneo/+) mice. Further, chimeric co-cultures made using slices of wild type septum combined with slices of hippocampus from NT-3 knockout mice demonstrate robust cholinergic axonal growth into the hippocampus, but the cholinergic axons do not form the characteristic preterminal pattern associated with the dentate gyrus. Slice cultures from limbic cortical tissue from the NT-3 null mice do not display exaggerated levels of cell death. In aggregate, these data support the hypothesis that expression of NT-3 by cortical neurons serves to attract basal forebrain cholinergic projections to their target cells in cerebral cortex.

Acetylcholinesterase↗

PubMed2006

Designing and transgenic expression of melanin gene in tobacco trichome and cotton fiber.

In Streptomyces antibioticus, there are two genes TYRA and ORF438 required for the melanin biogenesis. To investigate whether expression of these two genes in cotton can change cotton fiber colour, we modified the TYRA and ORF438 genes to make their codon usage closer to the codon preference of cotton fiber genes. The resulting versions of these two genes were referred to as DTYRA and DORF438, respectively. Vacuolar targeting signals were also added to their ends. Under the cotton fiber specific LTP3 promoter, DORF438 and DTYRA were first transformed into model plant tobacco (Nicotiana tabacum). Molecular analyses showed that both the DORF438 and DTYRA genes were successfully expressed in transgenic plants, and the melanin deposition was observed in the trichomes of transgenic tobacco. Excitedly, when the same DORF438 and DTYRA expression cassettes were transformed into cotton (Gossypium hirsutum L.) by pollen tube pathway, the colour of cotton fiber changed from white to brown. Molecular analyses confirmed that both genes were transformed into cotton and expressed successfully. All these results indicate that the synthesized DOFR438 and DTYRA genes can work well in tobacco and cotton. Our study may provide a potential method for modifying the colour of cotton fiber.

Amino Acid Sequence↗

PubMed2006

A network of p73, p53 and Egr1 is required for efficient apoptosis in tumor cells.

p73, a transcription factor rarely mutated in cancer, regulates a subset of p53 target genes that cause cells to respond to genotoxic stress by growth arrest and apoptosis. p73 is produced in two main forms; only TAp73 reiterates the roles of p53, while DeltaNp73 can be oncogenic in character. We show that the TAp73 form produced by TP73 P1 promoter has five distinct Egr1-binding sites, each contributing to the transcriptional upregulation of TAp73 by Egr1 in several cell types. In contrast, TP73 P2 promoter transcribes DeltaNp73, is not induced by Egr1, but is induced by TAp73 and p53. Induction of TAp73 by genotoxic stress requires Egr1 in mouse in vivo. Newly discovered non-consensus p53-binding sites in p73, p53 and Egr1 promoters reveal inter-regulating networks and sustained expression by feedback loops in response to stress, resulting in prolonged expression of the p53 family of genes and efficient apoptosis.

Animals↗

PubMed2006

Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China.

The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively -29.8 per thousand to -26.0 per thousand and 1.6 per thousand-5.5 per thousand in the flood season (July), while they were -27.3 per thousand to -25.6 per thousand and 1.7 per thousand-7.8 per thousand in the dry season (February), respectively. The delta(13)C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spatial changes in stable nitrogen isotopes. It was also reflected that delta(15)N and C/N compositions had been obviously modified by organic matter diagenesis and biological processing, and could not be used to trace the sources of organic matter at the study area. In addition, it was considered that the mixing inputs of terrigenous and marine materials generally dominated sedimentary organic matter in the intertidal flat. The contribution of terrigenous inputs to sedimentary organic matter was roughly estimated according to the mixing balance model of stable carbon isotopes.

Carbon Isotopes↗

PubMed2006

Microdissection-based high-resolution genomic array analysis of two patients with cytogenetically identical interstitial deletions of chromosome 1q but distinct clinical phenotypes.

We describe two boys with cytogenetically identical interstitial deletions in the q42.11-q42.13 region of the long arm of chromosome 1 detected by high-resolution G-banding analysis. These children share some phenotypic features but also exhibit distinct morphologic differences. We further characterized the deletions using a new technical strategy--microdissection-based high-resolution genomic array (MHGA) analysis--to define the breakpoints, genomic sizes, and gene contents of the deletions. This showed that the patients had distinguishable deletions that were adjacent but did not overlap, thus explaining the observed phenotypic differences. These results were surprising because we expected at least some degree of overlap to explain the features that were shared. MHGA can quickly give precise and detailed information about any rearrangement in the genome using as little material as a single cell. This novel strategy provides unique advantages for both clinical diagnosis and genomic research.

Child, Preschool↗

PubMed2006

Inheritance and mapping of a powdery mildew resistance gene introgressed from Avena macrostachya in cultivated oat.

The powdery mildew resistance from Avena macrostachya was successfully introgressed into hexaploid oat (A. sativa). Genetic analysis of F(1), F(2), F(3) and BC(1) populations from two powdery-mildew resistant introgression lines revealed that the resistance is controlled by a dominant gene, tentatively designated Eg-5. Molecular marker analysis was conducted using bulked-segregant analysis in two segregating F(3) populations. One codominant simple sequence repeats (SSR) marker AM102 and four AFLP-derived PCR-based markers were successfully developed. The SSR marker AM102 and the STS marker ASE41M56 were linked to the gene Eg-5, with genetic distances of 2 and 0.4 cM, respectively, in both mapping populations. Three STS markers (ASE45M56, ASE41M61, ASE36M55) co-segregated with Eg-5 in one population while two (ASE45M56, ASE36M55) of them linked to Eg-5 with a genetic distance of 1 cM in another population. The gene was further mapped to be in a region corresponding to linkage group 22_44+18 in the Kanota x Ogle (KO) hexaploid oat map by comparative mapping. To our knowledge, this is the first report of mapping powdery-mildew resistance in hexaploid oat. The new resistance source of A. macrostachya, together with the tightly linked markers identified here, could be beneficial in oat breeding programmes.

Ascomycota↗

PubMed2006

Pulmonary sensory and reflex responses in the mouse.

Mouse model research is proliferating because of its readiness for genetic manipulation. Little is known about pulmonary vagal afferents in mice, however. The purpose of this study was to determine whether their pulmonary afferents are similar to those in large animals. Single-unit activity was recorded in the cervical vagus nerve of anesthetized, open-chest, and mechanically ventilated mice. We evaluated airway sensory activity in 153 single units; 141 were mechanosensitive, with 134 inflation receptors and 7 deflation receptors. The remaining 12 receptors were chemosensitive and mechanically insensitive, showing low basal firing frequency and behaving like C-fiber or high-threshold Adelta-receptors. In separate studies, phrenic activity was recorded as an index of respiratory drive to assess pulmonary reflexes. Lung inflation produced a typical Hering-Breuer reflex, and intravenous injection of phenylbiguanide produced the typical chemoreflex resulting in apnea, bradycardia, and hypotension. These reflexes were blocked by bilateral vagotomy. We conclude that mice possess a similar set of airway sensors and pulmonary reflexes as typically found in larger animals.

Action Potentials↗

PubMed2006

Effective treatment of vascular endothelial growth factor refractory hindlimb ischemia by a mutant endothelial nitric oxide synthase gene.

Gene delivery of angiogenic growth factors is a promising approach for the treatment of ischemic cardiovascular diseases. However, success of this new therapeutic principle is hindered by the lack of critical understanding as to how disease pathology affects the efficiency of gene delivery and/or the downstream signaling pathways of angiogenesis. Critical limb ischemia occurs in patients with advanced atherosclerosis often exhibiting deficiency in endothelial nitric oxide production. Similar to these patients, segmental femoral artery resection progresses into severe ischemic necrosis in mice deficient in endothelial nitric oxide synthase (ecNOS-KO) as well as in balb/c mice. We used these models to evaluate the influence of severe ischemia on transfection efficiency and duration of transgene expression in the skeletal muscle following plasmid injection in combination with electroporation. Subsequently, we also explored the potential therapeutic effect of the phosphomimetic mutant of ecNOS gene (NOS1177D) using optimized delivery parameters, and found significant benefit both in ecNOS-KO and balb/c mice. Our results indicate that NOS1177D gene delivery to the ischemic skeletal muscle can be efficient to reverse critical limb ischemia in pathological settings, which are refractory to treatments with a single growth factor, such as vascular endothelial growth factor.

Animals↗

PubMed2006

The G12/13-RhoA signaling pathway contributes to efficient lysophosphatidic acid-stimulated cell migration.

The membrane redistribution and phosphorylation of focal adhesion kinase (FAK) have been reported to be important for cell migration. We previously showed that Lysophosphatidic acid (LPA) induced FAK membrane redistribution and autophosphorylation in ovarian cancer SK-OV3 cells and the signaling pathway consisting of Gi-Ras-MEKK1 mediated LPA-induced FAK membrane redistribution but not FAK autophosphorylation. We also showed that the disruption of the Gi-Ras-MEKK1 pathway led to a significant reduction in LPA-stimulated cell migration. These findings raised the question of whether LPA-induced FAK autophosphorylation was required for LPA-stimulated cell migration and what signaling mechanism was involved in LPA-induced FAK autophosphorylation. In this study, we expressed the membrane anchored wild-type FAK (CD2-FAK) in SK-OV3 cells and found that the expression of CD2-FAK greatly rescued LPA-stimulated cell migration in Gi or Ras-inhibited cells. However, Gi inhibitor pertussis toxin or dominant-negative H-Ras still significantly inhibited LPA-stimulated cell migration in cells expressing the membrane anchored FAK containing a mutation in the autophosphorylation site [CD2-FAK(Y397A)]. These results suggest that FAK autophosphorylation plays a role in LPA-stimulated cell migration. With the aid of p115RhoGEF-RGS, G12 and G13 minigenes to inhibit G12/13, we found that the G12/13 pathway was required for LPA-induced FAK autophosphorylation and efficient cell migration. Moreover, LPA activated RhoA and Rho kinase (ROCK) in a G12/13-dependent manner and their activities were required for LPA-induced FAK autophosphorylation. However, Rho or ROCK inhibitors displayed no effect on LPA-induced FAK membrane redistribution although they abolished LPA-induced cytoskeleton reorganization. Our studies show that the G12/13-RhoA-ROCK signaling pathway mediates LPA-induced FAK autophosphorylation and contributes to LPA-stimulated cell migration.

Cell Membrane↗

PubMed2006

Microarray and phosphokinase screenings leading to studies on ERK and JNK regulation of connective tissue growth factor expression by angiotensin II 1a and bradykinin B2 receptors in Rat1 fibroblasts.

Rat1 fibroblasts stably transfected with the rat angiotensin II (AngII) AT1a and bradykinin (BK) B2 receptor cDNAs gained the ability to bind Ang II and BK. Wild-type Rat1 cells bound neither ligand. Exposure to either effector led to characteristic Galphai and Galphaq signal cascades, the release of arachidonic acid (ARA), and the intracellular accumulation of inositol phosphates (IP). Microarray analyses in response to BK or AngII showed that both receptors markedly induce the CCN family genes, CTGF (CCN2) and Cyr61 (CCN1), as well as the vasculature-related genes, Cnn1 and Egr1. Real time PCR confirmed the increased expression of connective tissue growth factor (CTGF) mRNA. Combined sequence-based analysis of gene promoter regions with statistical prevalence analyses identified CREB, SRF, and ATF-1, downstream targets of ERK, and JNK, as prominent products of genes that are regulated by ligand binding to the BK or AngII receptors. The binding of AngII or BK markedly stimulated the phosphorylation and thus the activation of ERK2, JNK, and p38MAPK. A BKB2R and an AT1aR chimera which displayed only negligible G-protein-related signaling were constructed. Both mutant receptors continued to activate these kinases and stimulate CTGF expression. Inhibitors of ERK1/2 and JNK but not p38MAPK inhibited the BK- and AngII-stimulated expression of CTGF in cells expressing either the WT or mutant receptors, illustrating that ERK and JNK participate in the control of CTGF expression in a manner that appears to be independent of G-protein. Conversely, addition of BK or AngII to the cell line expressing WT AT1aR and BKB2R downregulated the expression of collagen alpha1(I) (COL1A1) mRNA. However, these effectors did not have this effect in cells expressing the mutant receptors. Thus, a robust G-protein related response is necessary for BK or AngII to affect COL1A1 expression.

Animals↗

PubMed2006

Laser microdissection and microarray analysis of breast tumors reveal ER-alpha related genes and pathways.

About 70-80% of breast cancers express estrogen receptor alpha (ER-alpha), and estrogens play important roles in the development and growth of hormone-dependent tumors. Together with lymph node metastasis, tumor size, and histological grade, ER status is considered as one of the prognostic factors in breast cancer, and an indicator for hormonal treatment. To investigate genes and pathways that are associated with ER status and epithelial cells in breast tumor, we applied laser capture microdissection (LCM) technology to capture epithelial tumor cells from 28 lymph node-negative breast tumor samples, in which 17 patients had ER-alpha+ tumors, and 11 patients have ER-alpha- tumors. Gene expression profiles were analysed on Affymetrix Hu133A GeneChip. Meanwhile, gene profiles using total RNA isolated from bulk tumors of the same 28 patients were also generated. In total, 146 genes and 112 genes with significant P-value and having significant differential expression between ER-alpha+ and ER-alpha- tumors were identified from the LCM data set and bulk tissue data set, respectively. A total of 61 genes were found to be common in both data sets, while 85 genes were unique to the LCM data set and 51 genes were present only in the bulk tumor data set. Pathway analysis with the 85 genes using Gene Ontology suggested that genes involved in endocytosis, ceramide generation, Ras/ERK/Ark cascade, and JAT-STAT pathways may play roles related to ER. The gene profiling with LCM-captured tumor cells provides a unique approach to study epithelial tumor cells and to gain an insight into signaling pathways associated with ER.

Breast Neoplasms↗

PubMed2006

Regulation of PUMA-alpha by p53 in cisplatin-induced renal cell apoptosis.

Nephrotoxicity is a major side effect of cisplatin, a widely used cancer therapy drug. Depending on its concentration, cisplatin induces necrosis or apoptosis of tubular cells in the kidneys, whereas the underlying injury mechanism is unclear. Our recent work has suggested a critical role for p53 in cisplatin-induced tubular cell apoptosis; nevertheless, the apoptotic events triggered by p53 remain elusive. The current study has examined Bcl-2 family proteins, critical regulators of apoptosis that may be subjected to p53 regulation. Following cisplatin treatment, the expression of Bcl-xL, an antiapoptotic molecule, was suppressed, while the expression of Bak, a proapoptotic molecule, increased slightly. Of interest, PUMA-alpha, a newly identified p53-responsive proapoptotic Bcl-2 family protein, was drastically induced by cisplatin. PUMA-alpha induction preceded or paralleled the development of apoptosis. Induced PUMA-alpha was localized in mitochondria and appeared to antagonize Bcl-xL via molecular interaction. PUMA-alpha induction during cisplatin treatment was attenuated by pifithrin-alpha, a pharmacological inhibitor of p53, which was accompanied by the amelioration of Bax activation, cytochrome c release and apoptosis. Moreover, PUMA-alpha induction was suppressed by dominant-negative p53. Importantly, cisplatin-induced apoptosis was ameliorated in PUMA-alpha knockout cells. In vivo, cisplatin induced PUMA-alpha in the kidneys, and the inductive response was abrogated in p53-deficient animals. Together, this study has demonstrated the first compelling evidence for the involvement of PUMA-alpha in p53-mediated renal cell apoptosis during cisplatin nephrotoxicity.

Animals↗

PubMed2006

Power of mixed-model QTL mapping from phenotypic, pedigree and marker data in self-pollinated crops.

The power of QTL mapping by a mixed-model approach has been studied for hybrid crops but remains unknown in self-pollinated crops. Our objective was to evaluate the usefulness of mixed-model QTL mapping in the context of a breeding program for a self-pollinated crop. Specifically, we simulated a soybean (Glycine max L. Merr.) breeding program and applied a mixed-model approach that comprised three steps: variance component estimation, single-marker analyses, and multiple-marker analysis. Average power to detect QTL ranged from <1 to 47% depending on the significance level (0.01 or 0.0001), number of QTL (20 or 80), heritability of the trait (0.40 or 0.70), population size (600 or 1,200 inbreds), and number of markers (300 or 600). The corresponding false discovery rate ranged from 2 to 43%. Larger populations, higher heritability, and fewer QTL controlling the trait led to a substantial increase in power and to a reduction in the false discovery rate and bias. A stringent significance level reduced both the power and false discovery rate. There was greater power to detect major QTL than minor QTL. Power was higher and the false discovery rate was lower in hybrid crops than in self-pollinated crops. We conclude that mixed-model QTL mapping is useful for gene discovery in plant breeding programs of self-pollinated crops.

Chromosome Mapping↗

PubMed2006

Laser filaments generated and transmitted in highly turbulent air.

The initiation and propagation of a filament generated by ultrashort laser pulses in turbulent air is investigated experimentally. A filament can be generated and propagated even after the beam has propagated through strongly turbulent regions, with structure parameters C(n)2 as many as 5 orders of magnitude larger than those encountered in the usual atmospheric conditions. Moreover, the filament's position within the beam is not affected by the interaction with a turbulent region. This remarkable stability is allowed by the strong Kerr refractive-index gradients generated within the filament, which exceed the turbulence-induced refractive-index gradients by 2 orders of magnitude.

Journal Article↗