Biomedical subjects

F Chen

Publications and source records attributed to F Chen.

At least 199 records · Page 11Linked to original sources

PubMed2000

Vascular osteomuscular autograft prefabrication using coral, type I collagen and recombinant human bone morphogenetic protein-2.

In 20 male Sprague-Dawley rats, 10 pieces of L-shaped coral combined with type I collagen and recombinant human bone morphogenetic protein-2 (rhBMP-2) and 10 discs (diameter 5 mm) were wrapped in the gracilis muscle, and left pedicled on the femoral vessels. Untreated coral was buried in muscle at a distant control site in 4 animals. After 3 weeks, autografts were examined for the shape of new bone, vascular patency, and induction of bone. In all grafts in viable tissue, heterotopic bone was formed. The shape of the new bone was the same as that of the coral, and there was no significant inflammatory reaction. Part of the coral in the composite was absorbed. Bone was not formed in any of the control sites. Coral and type 1 collagen are effective as a carrier for BMP to prefabricate vascular osteomuscular autografts with designed shape. There is a potential clinical application for BMP to bioengineer microvascular free flaps with intrinsic skeletal muscle for maxillofacial reconstruction.

Animals↗

PubMed2000

The tumor suppressor p53 can both stimulate and inhibit ultraviolet light-induced apoptosis.

We have previously shown that the tumor suppressor p53 can play a protective role against UV-induced apoptosis in human fibroblasts. In the present study, we investigated whether the protective function of p53 expression is established before or after UV irradiation. Using a stable human cell line expressing a murine temperature-sensitive p53 in which p53 function could be tightly and reversibly regulated, we found that functional p53 stimulated the induction of apoptosis when expressed for as little as 4-12 h after UV irradiation and that this induction was not dependent on de novo protein synthesis. In contrast, expression of p53 for 12 h or more before UV irradiation reduced the extent of apoptosis even when functional p53 expression was maintained after irradiation. The protection conferred by p53 required ongoing protein synthesis and correlated with enhanced recovery of mRNA synthesis. Together, these results suggest that p53 induces distinct proapoptotic and antiapoptotic signals and that these opposing activities can be separated both temporally and by their requirement for de novo protein synthesis. These findings may have important implications for the refinement of gene therapy approaches combining p53 with pharmacological agents that target transcription or translation.

Apoptosis↗

PubMed2000

A genetic screen for novel components of the Ras/Mitogen-activated protein kinase signaling pathway that interact with the yan gene of Drosophila identifies split ends, a new RNA recognition motif-containing protein.

The receptor tyrosine kinase (RTK) signaling pathway is used reiteratively during the development of all multicellular organisms. While the core RTK/Ras/MAPK signaling cassette has been studied extensively, little is known about the nature of the downstream targets of the pathway or how these effectors regulate the specificity of cellular responses. Drosophila yan is one of a few downstream components identified to date, functioning as an antagonist of the RTK/Ras/MAPK pathway. Previously, we have shown that ectopic expression of a constitutively active protein (yan(ACT)) inhibits the differentiation of multiple cell types. In an effort to identify new genes functioning downstream in the Ras/MAPK/yan pathway, we have performed a genetic screen to isolate dominant modifiers of the rough eye phenotype associated with eye-specific expression of yan(ACT). Approximately 190,000 mutagenized flies were screened, and 260 enhancers and 90 suppressors were obtained. Among the previously known genes we recovered are four RTK pathway components, rolled (MAPK), son-of-sevenless, Star, and pointed, and two genes, eyes absent and string, that have not been implicated previously in RTK signaling events. We also isolated mutations in five previously uncharacterized genes, one of which, split ends, we have characterized molecularly and have shown to encode a member of the RRM family of RNA-binding proteins.

Amino Acid Sequence↗

PubMed2000

Advanced glycation end-product receptor interactions on microvascular cells occur within caveolin-rich membrane domains.

Advanced glycation end products (AGEs) have an important role in diabetic complications, with many responses mediated through AGE-receptors. The current study has investigated the binding and uptake of AGEs by retinal microvascular endothelium in an attempt to understand the nature of AGE-interaction with receptors on the cell surface. There has been special emphasis placed on the R1, R2, and R3 components of AGE-receptor complex (AGE-RC) and their localization to caveolin-rich membrane domains. Retinal microvascular endothelial cells (RMECs) were exposed to either AGE-modified BSA (AGE-BSA) or native BSA conjugated to colloidal gold (gAGE, gBSA) for various time periods, fixed, and processed for transmission electron microscopy (TEM). Localization of AGE-RC components in caveolae was investigated using confocal microscopy and ultrastructural immunogold labeling. Caveolae were extracted from RMECs using differential Triton X-100 solubility, and Western analysis was conducted to test for caveolae enrichment and the presence of AGE-RC complex components. Ligand blots determined 125I-AGE-BSA binding to caveolae-enriched extracts. Colloidal gold conjugates of AGE-BSA bound to caveolae and were internalized to be trafficked to lysosomal-like compartments. AGE-receptor complex components were significantly enriched within caveolae. The data suggest that AGEs interact with their receptors within caveolae. It is significant that the AGE-R complex localizes to these organelles, because this may have implications for AGE binding, internalization, signal transduction, and the modulation of AGE-receptor-mediated vascular cell dysfunction.

Animals↗

PubMed2000

Radiochemical purity of routinely prepared 99Tcm radiopharmaceuticals: a retrospective study.

Radiochemical purity is an important quality parameter for radiopharmaceuticals. In this study, the radiochemical purity of 2090 samples out of 7000 routine preparations of 20 different 99Tcm radiopharmaceuticals was tested using standard methods over a period of more than 7 years. The mean radiochemical purity was 96.92% (standard deviation = 6.71%). Seventy-four preparations failed to meet radiochemical purity limits; that is, 3.54% of all preparations tested or 1.06% of all preparations in the observation period. The reasons for substandard preparations were mainly related to laboratory-specific conditions. The introduction of a dedicated quality control protocol allowed the elimination of many sources of labelling failures and could reduce the number of administered preparations with an insufficient radiochemical purity. We stress the need for quality control in the preparation of radiopharmaceuticals and provide original radiochemical purity values of routinely prepared 99Tcm radiopharmaceuticals.

Drug Contamination↗

PubMed2000

Chromosome evolution: the junction of mammalian chromosomes in the formation of mouse chromosome 10.

During evolution, chromosomes are rearranged and become fixed into new patterns in new species. The relatively conservative nature of this process supports predictions of the arrangement of ancestral mammalian chromosomes, but the basis for these rearrangements is unknown. Physical mapping of mouse chromosome 10 (MMU 10) previously identified a 380-kb region containing the junction of material represented in human on chromosomes 21 (HSA 21) and 22 (HSA 22) that occurred in the evolutionary lineage of the mouse. Here, acquisition of 275 kb of mouse genomic sequence from this region and comparative sequence analysis with HSA 21 and HSA 22 narrowed the junction from 380 kb to 18 kb. The minimal junction region on MMU 10 contains a variety of repeats, including an L32-like ribosomal element and low-copy sequences found on several mouse chromosomes and represented in the mouse EST database. Sequence level analysis of an interchromosomal rearrangement during evolution has not been reported previously.

Animals↗

PubMed2000

Expression of an expansin is associated with endosperm weakening during tomato seed germination.

Expansins are extracellular proteins that facilitate cell wall extension, possibly by disrupting hydrogen bonding between hemicellulosic wall components and cellulose microfibrils. In addition, some expansins are expressed in non-growing tissues such as ripening fruits, where they may contribute to cell wall disassembly associated with tissue softening. We have identified at least three expansin genes that are expressed in tomato (Lycopersicon esculentum Mill.) seeds during germination. Among these, LeEXP4 mRNA is specifically localized to the micropylar endosperm cap region, suggesting that the protein might contribute to tissue weakening that is required for radicle emergence. In gibberellin (GA)-deficient (gib-1) mutant seeds, which germinate only in the presence of exogenous GA, GA induces the expression of LeEXP4 within 12 hours of imbibition. When gib-1 seeds were imbibed in GA solution combined with 100 microM abscisic acid, the expression of LeEXP4 was not reduced, although radicle emergence was inhibited. In wild-type seeds, LeEXP4 mRNA accumulation was blocked by far-red light and decreased by low water potential but was not affected by abscisic acid. The presence of LeEXP4 mRNA during seed germination parallels endosperm cap weakening determined by puncture force analysis. We hypothesize that LeEXP4 is involved in the regulation of seed germination by contributing to cell wall disassembly associated with endosperm cap weakening.

Abscisic Acid↗

PubMed2000

Left ventricular motion reconstruction based on elastic vector splines.

In medical imaging it is common to reconstruct dense motion estimates, from sparse measurements of that motion, using some form of elastic spline (thin-plate spline, snakes and other deformable models, etc.). Usually the elastic spline uses only bending energy (second-order smoothness constraint) or stretching energy (first-order smoothness constraint), or a combination of the two. These elastic splines belong to a family of elastic vector splines called the Laplacian splines. This spline family is derived from an energy minimization functional, which is composed of multiple-order smoothness constraints. These splines can be explicitly tuned to vary the smoothness of the solution according to the deformation in the modeled material/tissue. In this context, it is natural to question which members of the family will reconstruct the motion more accurately. We compare different members of this spline family to assess how well these splines reconstruct human cardiac motion. We find that the commonly used splines (containing first-order and/or second-order smoothness terms only) are not the most accurate for modeling human cardiac motion.

Computer Simulation↗

PubMed2000

Sound absorption of cellular metals with semiopen cells.

A combined experimental and theoretical study is presented for the feasibility of using aluminum foams with semiopen cells for sound-absorption applications. The foams are processed via negative-pressure infiltration, using a preform consisting of water-soluble spherical particles. An analytical model is developed to quantify the dependence of pore connectivity on processing parameters, including infiltration pressure, particle size, wetting angle, and surface tension of molten alloy. Normal sound-absorption coefficient and static flow resistance are measured for samples having different porosity, pore size, and pore opening. A theory is developed for idealized semiopen metallic foams, with a regular hexagonal hollow prism having one circular aperture on each of its eight surfaces as the unit cell. The theory is built upon the acoustic impedance of the circular apertures (orifices) and cylindrical cavities due to viscous effects, and the principle of electroacoustic analogy. The predicted sound-absorption coefficients are compared with those measured. To help select processing parameters for producing semiopen metallic foams with desirable sound-absorbing properties, emphasis is placed on revealing the correlation between sound absorption and morphological parameters such as pore size, pore opening, and porosity.

Acoustics↗

PubMed2000

Latent membrane protein 2A of Epstein-Barr virus binds WW domain E3 protein-ubiquitin ligases that ubiquitinate B-cell tyrosine kinases.

The latent membrane protein (LMP) 2A of Epstein-Barr virus (EBV) is implicated in the maintenance of viral latency and appears to function in part by inhibiting B-cell receptor (BCR) signaling. The N-terminal cytoplasmic region of LMP2A has multiple tyrosine residues that upon phosphorylation bind the SH2 domains of the Syk tyrosine kinase and the Src family kinase Lyn. The LMP2A N-terminal region also has two conserved PPPPY motifs. Here we show that the PPPPY motifs of LMP2A bind multiple WW domains of E3 protein-ubiquitin ligases of the Nedd4 family, including AIP4 and KIAA0439, and demonstrate that AIP4 and KIAA0439 form physiological complexes with LMP2A in EBV-positive B cells. In addition to a C2 domain and four WW domains, these proteins have a C-terminal Hect catalytic domain implicated in the ubiquitination of target proteins. LMP2A enhances Lyn and Syk ubiquitination in vivo in a fashion that depends on the activity of Nedd4 family members and correlates with destabilization of the Lyn tyrosine kinase. These results suggest that LMP2A serves as a molecular scaffold to recruit both B-cell tyrosine kinases and C2/WW/Hect domain E3 protein-ubiquitin ligases. This may promote Lyn and Syk ubiquitination in a fashion that contributes to a block in B-cell signaling. LMP2A may potentiate a normal mechanism by which Nedd4 family E3 enzymes regulate B-cell signaling.

Amino Acid Motifs↗

PubMed2000

Loss of connectivity in Alzheimer's disease: an evaluation of white matter tract integrity with colour coded MR diffusion tensor imaging.

A novel MRI method--diffusion tensor imaging--was used to compare the integrity of several white matter fibre tracts in patients with probable Alzheimer's disease. Relative to normal controls, patients with probable Alzheimer's disease showed a highly significant reduction in the integrity of the association white matter fibre tracts, such as the splenium of the corpus callosum, superior longitudinal fasciculus, and cingulum. By contrast, pyramidal tract integrity seemed unchanged. This novel finding is consistent with the clinical presentation of probable Alzheimer's disease, in which global cognitive decline is a more prominent feature than motor disturbance.

Aged↗

PubMed2000

Hepatic lesion detection after superparamagnetic iron oxide enhancement: comparison of five T2-weighted sequences at 1.0 T by using alternative-free response receiver operating characteristic analysis.

PURPOSE: To compare the accuracy of five T2-weighted sequences in the detection of liver lesion at magnetic resonance (MR) imaging after superparamagnetic iron oxide (SPIO) enhancement. MATERIALS AND METHODS: Forty-nine candidates for hepatic resection with known coloretal metastases were examined. Before SPIO enhancement, fast spin-echo (SE) images were obtained. After enhancement, the same fast SE sequence and long; TR/short TE, short TE, long TR/TE, and T2-weighted fast low-angle shot (FLASH) sequences were used. All images were viewed independently by four observers who were blinded to the results of the other imaging sequences, the results of the other observers, and the findings at surgery and histopathologic examination. Four weeks after the initial reading, the combined long TR/short TE and long TR/TE dual-echo images were also viewed as an additional set. The alternative free response receiver operating characteristic (ROC) method was used to analyze the results, which were correlated with findings at surgery, intraoperative ultrasonography, and histopathologic examination. RESULTS: Irrespective of lesion size, the accuracy of all sequences after enhancement was significantly greater than that of the nonenhanced fast SE sequence (P < .01). Dual-echo and FLASH sequences were significantly more accurate than the enhanced fast SE sequence (P < .03 or P < .02, respectively). For all lesions, lesions smaller than 1 cm, and lesions 1 cm or larger, mean accuracies were as follows: dual-echo, 0.75, 0.54, and 0.93; FLASH, 0.75, 0.54, and 0.95; and enhanced fast SE, 0.72, 0.49, and 0.92. CONCLUSION: At 1.0 T, dual-echo and FLASH sequences are the most accurate pulse sequences after SPIO enhancement.

Aged↗

PubMed2000

Impairment of NF-kappaB activation and modulation of gene expression by calpastatin.

To address the involvement of the calpain system in both basal and silica-induced nuclear factor (NF)-kappaB activation, several human bronchial epithelial cell lines were established in which an intracellular inhibitor of calpain, calpastatin, was stably expressed. Reduced basal and silica-induced inhibitor (IkappaBalpha) degradation and NF-kappaB activation were observed in cells stably overexpressing calpastatin. In addition, the cells in which calpain was constitutively inhibited by the overexpression of calpastatin exhibited a notable morphological change. Whereas empty vector-transfected cells displayed a morphology indistinguishable from that of parental cells, cells overexpressing calpastatin exhibited a mosaic morphological change with reduced formation of lamella 30 min after the cells were seeded. Genefilter microarray experiments, in which 3,965 human genes can be evaluated for their expression at the same time, showed that calpastatin downregulated genes encoding several membrane-associated proteins or nuclear proteins and upregulated genes of collagen alpha2, DAZ, and mitochondrial capsule selenoprotein. These results suggest that, in addition to their proteolytic activities on cytoskeletal proteins and other cellular regulatory proteins, calpain-calpastatin systems can also affect the expression levels of genes encoding structural or regulatory proteins.

Adrenergic beta-Agonists↗

PubMed2000

Inhibition of endotoxin-induced lung inflammation by interleukin-10 gene transfer in mice.

Interleukin (IL)-10 is an anti-inflammatory cytokine that has great potential for use in the treatment of inflammatory and immune illnesses. In this study, gene transfer was used to induce IL-10 transgene expression in murine lungs for treatment of endotoxin-induced lung inflammation. Gene transfer was performed with a cytomegalovirus (CMV)-IL-10 plasmid with the aid of the liposomal agents LipofectAMINE and N-[1-(2,3-dioleoyl)propyl]-N,N, N-trimethylammonium methylsulfate (DOTAP). Administration of the endotoxin caused a marked increase in lung inflammation as indicated by increased tumor necrosis factor (TNF)-alpha release and neutrophil count. Pretreatment of the mice with IL-10 plasmid with and without LipofectAMINE had no inhibitory effect on lung inflammation and IL-10 transgene expression. LipofectAMINE by itself induced lung inflammation, an effect that was not observed with DOTAP. IL-10 plasmid when codelivered with DOTAP expressed biologically active IL-10 protein and caused a reduction in endotoxin-induced inflammation. Transgene expression was observed as early as 3 h after administration, peaked at 12 h, and declined thereafter. We conclude that IL-10 gene transfer is a feasible approach for the treatment of lung inflammation.

Animals↗

PubMed2000

Pax3 is required for enteric ganglia formation and functions with Sox10 to modulate expression of c-ret.

Hirschsprung disease and Waardenburg syndrome are human genetic diseases characterized by distinct neural crest defects. Patients with Hirschsprung disease suffer from gastrointestinal motility disorders, whereas Waardenburg syndrome consists of defective melanocyte function, deafness, and craniofacial abnormalities. Mutations responsible for Hirschsprung disease and Waardenburg syndrome have been identified, and some patients have been described with characteristics of both disorders. Here, we demonstrate that PAX3, which is often mutated in Waardenburg syndrome, is required for normal enteric ganglia formation. Pax3 can bind to and activate expression of the c-RET gene, which is often mutated in Hirschsprung disease. Pax3 functions with Sox10 to activate transcription of c-RET, and SOX10 mutations result in Waardenburg-Hirschsprung syndrome. Thus, Pax3, Sox10, and c-Ret are components of a neural crest development pathway, and interruption of this pathway at various stages results in neural crest-related human genetic syndromes.

Animals↗

PubMed2000

Migration of cardiac neural crest cells in Splotch embryos.

Pax3 encodes a transcription factor expressed during mid-gestation in the region of the dorsal neural tube that gives rise to migrating neural crest populations. In the absence of Pax3, both humans and mice develop with neural crest defects. Homozygous Splotch embryos that lack Pax3 die by embryonic day 13.5 with cardiac defects that resemble those induced by neural crest ablation in chick models. This has led to the hypothesis that Pax3 is required for cardiac neural crest migration. However, cardiac derivatives of Pax3-expressing precursor cells have not been previously defined, and Pax3-expressing cells within the heart have not been well demonstrated. Hence, the precise role of Pax3 during cardiac development remains unclear. Here, we use a Cre-lox method to fate map Pax3-expressing neural crest precursors to the cardiac outflow tract. We show that although Pax3 itself is extinguished prior to neural crest populating the heart, derivatives of these precursors contribute to the aorticopulmonary septum. We further show that neural crest cells are found in the outflow tract of Splotch embryos, albeit in reduced numbers. This indicates that contrary to prior reports, Pax3 is not required for cardiac neural crest migration. Using a neural tube explant culture assay, we demonstrate that neural crest cells from Splotch embryos show normal rates of proliferation but altered migratory characteristics. These studies suggest that Pax3 is required for fine tuning the migratory behavior of the cardiac neural crest cells while it is not essential for neural crest migration.

Animals↗

PubMed2000

Drying of steamed Asian ginseng (Panax ginseng) roots by microwave-hot air combination.

Steamed Asian ginseng (Panax ginseng) roots were dried by a combined microwave-hot air method in a modified experimental microwave oven. Hot air drying was used as a reference method. The drying time to achieve the desired moisture level (10%) as well as the ginsenoside contents and the color of the final product were determined. The ginsenosides Rb1, Rb2, Rc, Rd, Re, Rf, Rg1 and Ro were analyzed by HPLC. Compared with hot air drying, the combined microwave-hot air drying method resulted in a substantial decrease (approximately 30-40%) in drying time and had little influence on the ginsenoside contents and the color of the final product.

Chromatography, High Pressure Liquid↗

PubMed2000

Effect of chronic ethanol and withdrawal on the mu-opioid receptor- and 5-Hydroxytryptamine(1A) receptor-stimulated binding of [(35)S]Guanosine-5'-O-(3-thio)triphosphate in the fawn-hooded rat brain: A quantitative autoradiography study.

Previous studies have shown that chronic ethanol influences the density of central mu-opioid receptors and serotonin(1A) (5-hydroxytryptamine(1A)) receptors. To determine whether the functional coupling of these two receptors to G proteins in the rat brain, particularly in mesocorticolimbic regions, is affected by ethanol, receptor-mediated [(35)S]guanosine-5'-O-(3-thio)-triphosphate ([(35)S]GTPgammaS) binding stimulated by [D-Ala(2),N-MePhe(4),Gly-ol(5)]-enkephalin (DAMGO) or L694,247 was used. By quantitative autoradiography, receptor-mediated [(35)S]GTPgammaS binding activated by the two agonists was mapped throughout brain sections at the level of the nucleus accumbens and hippocampus from groups of alcohol-preferring Fawn-Hooded (FH) rats after different ethanol consumption paradigms. Significant DAMGO (mu-opioid receptor agonist)-stimulated binding of [(35)S]GTPgammaS was obtained in the striatum, nucleus accumbens, and lateral septum, whereas L694,247 (5-hydroxytryptamine(1A/1B/1D) receptor agonist)-stimulated binding of [(35)S]GTPgammaS was observed in the lateral septum, amygdala, and cingulate cortex. Chronic ethanol self-administration significantly reduced DAMGO-stimulated [(35)S]GTPgammaS binding in the nucleus accumbens (-19%), lateral septum (-15%), and striatum (-23%), which recovered toward control levels after ethanol withdrawal. However, chronic ethanol, as well as ethanol withdrawal, failed to produce any significant alteration in L694,247-stimulated [(35)S]GTPgammaS binding in all tested brain regions. The region-specific and receptor-specific alteration of agonist-stimulated [(35)S]GTPgammaS binding suggests that the change of functional coupling of mu-opioid receptors to G proteins induced by chronic ethanol drinking may have a pathophysiological role in the consequences of ethanol consumption.

Alcohol Drinking↗