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Biomedical subjects

G Chen

Publications and source records attributed to G Chen.

At least 73 records · Page 4Linked to original sources
PubMed2004

Lumbar hernia: clinical analysis of 11 cases.

BACKGROUND: Lumbar hernia is a relatively rare phenomenon. The aim of this study was to investigate the clinical manifestation, the diagnosis of lumbar hernia, and the outcome of the surgical procedure. METHODS: Eleven cases of lumbar hernia were studied by clinical observation retrospectively from July 1998 to July 2000. RESULTS: All the patients were diagnosed clinically and confirmed operatively. The typical manifestation was a semi-spherical painful mass in the superior or inferior triangle. If the gut was incarcerated, bowel obstruction may subsequently develop. Ten of the eleven patients were treated successfully. CONCLUSIONS: The clinical symptoms and signs usually allow for easy diagnosis. Excision of the sac and high ligation, followed by repair using either surrounding tissue or prosthetic material, provided satisfactory results.

Aged↗
PubMed2004

Ab initio study on structural and electronic properties of BanOm clusters.

Density-functional calculation within local density approximation, shows that the electronic property of a barium oxide cluster is strongly correlated with its equilibrium structure. The ground-state structures of BanOm (4 < or = n < or = 9,m < or = n) clusters can be classified into four categories: (a) compact, (b) dangling state, (c) F-center, and (d) stoichiometric. The compact cluster is metallic, almost no energy gap exists between the highest occupied and the lowest unoccupied molecular orbitals. The energy gap for the dangling state cluster is larger than that for the F-center cluster, while the stoichiometric cluster has the largest energy gap.

Journal Article↗
PubMed2004

Imaging parallel fiber and climbing fiber responses and their short-term interactions in the mouse cerebellar cortex in vivo.

A major question in the study of cerebellar cortical function is how parallel fiber and climbing fiber inputs interact to shape information processing. Emphasis has been placed on the long-term effects due to conjunctive stimulation of climbing fibers and parallel fibers. Much less emphasis has been placed on short-term interactions and their spatial nature. To address this question the responses to parallel fiber and climbing fiber inputs and their short-term interaction were characterized using optical imaging with Neutral Red in the anesthetized mouse in vivo. Electrical stimulation of the cerebellar surface evoked an increase in fluorescence consisting of a transverse optical beam. The linear relationship between the optical responses and stimulus parameters, high spatial resolution and close coupling to the electrophysiological recordings show the utility of this imaging methodology. The majority of the optical response was due to activation of postsynaptic alpha-amino-3-hydroxyl-5-methyl-4-isoxazole propionate (AMPA) and metabotropic glutamate receptors with a minor contribution from the presynaptic parallel fibers. Stimulation of the inferior olive evoked parasagittal bands that were abolished by blocking AMPA glutamate receptors. Conjunctive stimulation of the cerebellar surface and inferior olive resulted in inhibition of the climbing fiber evoked optical responses. This lateral inhibition of the parasagittal bands extended out from both sides of an activated parallel fiber beam and was mediated by GABA(A) but not GABA(B) receptors. One hypothesized role for lateral inhibition of this type is to spatially focus the interactions between parallel fiber and climbing fiber input on Purkinje cells. In summary optical imaging with Neutral Red permitted visualization of cerebellar cortical responses to parallel fiber and climbing fiber activation. The GABA(A) dependent lateral inhibition of the climbing fiber evoked parasagittal bands by parallel fiber stimulation shows that cerebellar interneurons play a short-term role in shaping the responses of Purkinje cells to climbing fiber input.

Animals↗
PubMed2004

Pathogenesis and pathology of delayed xenograft rejection in pig-to-rhesus monkey cardiac transplantation.

UNLABELLED: It has been recognized that delayed xenograft rejection (DXR) is the major barrier to the acceptance of xenotransplantation after overcoming hyperacute rejection. OBJECTIVES: This study sought to investigate the pathogenesis and pathology of delayed xenograft rejection following pig-to-rhesus monkey heart xenotransplantation. METHODS: Heterotopic xenogeneic heart transplants in the abdominal cavity were performed using piglet donors to four monkey recipients. Complete complement depletion was achieved in the recipients with repetitive doses of high-activity cobra venom factor (Y-CVF). The recipients were immunosuppressed with a combination of cyclosporine, cyclophosphamide, and steroids. Sera were analyzed for C3 and C4 levels and complement activity and anti-pig endothelial xenoantibody. The grafts were examined histopathologically and immunohistochemically for C3, C4;C5b-9, IgM, IgG, tumor necrosis factor-alpha (TNF-alpha), intercellular adhesion molecule-1(ICAM-1), CD57(NK cells), CD68 (macrophages), CD4, and CD8. RESULTS: Xenografts survived 8, 10, 13, and 13 days respectively, all developing DXR. Venous thrombosis was the outstanding feature within DXR xenografts, complicated by interstitial edema, local hemorrhage, myocardial necrosis, and mild to moderate cellular infiltration. The serum C3 levels and complement activity decreased to almost 0 from the day of transplantation due to treatment with Y-CVF. The C4 level began to decrease 2 to 4 days before the cardiac xenografts lost their function. Anti-pig endothelial xenoantibody also decreased after transplantation, slightly increasing during DXR. All rejected xenografts showed C3, C4, C5b-9, IgG, and IgM deposits to various degrees. Large numbers of macrophages (50% of total leukocytes) infiltrated the entire xenograft with a few natural killer cells (8% to 10%), as well as some CD4+ T cells (15%) and CD8+ T cells (25%). Upregulation of ICAM-1 on graft endothelial cells and TNF-alpha in the interstitium were also demonstrated in the rejected heart. CONCLUSION: Both humoral and cell-mediated immunologic reactions may play important roles in the pathogenesis of DXR. Besides C3, C4, C5b-9, IgM, and IgG destroying the xenograft, NK cells, macrophages, and CD4+ and CD8+ T cells may further aggravate the development of DXR.

Animals↗
PubMed2004

High Ca(2+)-phosphate transfection efficiency enables single neuron gene analysis.

Introducing exogenous genes into cells is one of the most important molecular techniques to study gene functions. Comparing to other type of cells, neurons are more difficult to transfect with cDNAs because they are very sensitive to microenvironmental changes. Among various gene transfer techniques, the Ca(2+)-phosphate transfection method is one of the most popular tools in neuroscience research because of its low cell toxicity and easiness to use. However, it is well known that the Ca(2+)-phosphate transfection efficiency in neurons is very low, typically in the range of 1-5%, which has limited its applications in gene functional analyses. Here we report a novel Ca(2+)-phosphate transfection protocol that dramatically increased the transfection efficiency by 10-fold, up to 60%, while maintaining low cell toxicity. The critical factors are the formation of homogenous snow-like precipitate with particle size about 1-3 microm and the subsequent removal of the precipitate. Using this new transfection protocol, we were able to routinely transfect single autaptic neurons in hippocampal microisland cultures and combine it with electrophysiology and fluorescent imaging methods to study gene functions. This high efficiency, low toxicity, and simple to use gene transfer method will have a broad application in gene research at the single cell level.

Animals↗
PubMed2004

Stimulation of methanogenesis in a laboratory scale UASB reactor treating domestic sewage by Fe(0) application.

The effects of application of zero valence Fe (Fe(0)) on the anaerobic digestion of sewage was investigated using two laboratory scale UASB reactors. One reactor had Fe(0) addition in a container found midway along the recycling loop. The other one was a control reactor. In a test run period of 76 days, the Fe(0) application significantly increased the CH, yield by 8.7% and decreased the effluent COD concentration by 21.0% relative to the control reactor. A decrease of the H, concentration of biogas and the CODs/CODt ratio in effluent by Fe(0) application were observed. The obtained results imply that the methanogenesis and COD removal efficiency of the UASB reactor were stimulated by Fe(0) application. The higher performance of the reactor with Fe(0) application arises from the integrated functions of Fe(0) or its ionic state as donor of H2, macronutrient, and flocculant. This study showed that the supply of Fe(0) to a UASB can improve the methanogenesis and the overall COD removal of a UASB reactor treating low-strength domestic waste water.

Bacteria, Anaerobic↗
PubMed2004

Detection of epidermodysplasia verruciformis-associated human papillomavirus DNA in nongenital seborrhoeic keratosis.

BACKGROUND: DNA of epidermodysplasia verruciformis (EV)-associated human papillomaviruses (HPVs) has been widely detected in lesions of malignant skin tumours, benign tumours and other proliferative diseases of epithelial origin. OBJECTIVES: To investigate the presence of EV-associated HPV DNA in nongenital seborrhoeic keratosis (SK) and to elucidate the prevalence of distinct HPV genotypes. METHODS: We investigated HPV DNA in 55 nongenital SK biopsies, which were compared with 48 normal skin biopsies (healthy controls) using a nested polymerase chain reaction (PCR) using consensus primers CP65/CP70 and CP66/CP69. The positive PCR products were retracted and used to prepare recombination clones with T-vector. Distinct clones were analysed with endonucleases, and HPV genotypes were identified by direct sequencing. RESULTS: EV-associated HPV DNA was detected in 42 of 55 (76%) nongenital SK biopsies vs. only 13 of 48 (27%) healthy controls (chi2 = 22.087; P < 0.005). The prevalence was higher in patients with more than five lesions than in those with only one lesion (P < 0.05). Ten distinct HPV genotypes were detected in the nongenital SK biopsies: HPV 20, 23, 5, renal transplant recipient (RTR) X7, HPV 17, 37, 17b, RTRX4, RTRX4b and strain SK3. HPV 20 was found in 26 of 42 (62%) positive specimens, followed by HPV 23 (11 of 42, 26%) and HPV 5 (six of 42, 14%). Existence of multiple HPV genotypes was observed in 12 of 42 (29%) positive specimens. In healthy controls, five genotypes of EV-associated HPV (HPV 20, 23, 5, 17 and RTRX4) were detected, with the same predominant genotype of HPV 20 (five of 13, 38%). Several distinct HPV genotypes were found to coexist in four of 13 (31%) positive specimens. CONCLUSIONS: This study provides some evidence that EV-associated HPVs might play a part in the pathogenesis of nongenital SK.

Adolescent↗
PubMed2004

Radiation synovectomy by 188Re-Sulfide in haemophilic synovitis.

Radiation synovectomy is a safe and effective treatment for chronic haemophilic synovitis causing recurrent haemarthroses. This study reports results of 29 188Re-sulfide radiation synovectomies in knee joint with a follow-up 18 months. Using the absorbed dose factor, three groups of radioactivity dose (555 MBq, 687 MBq and 917 MBq) were used according to the synovium thickness that measured by MRI. Excellent and good results (haemarthrosis reduction from 75 to 100%) were obtained in 71% of cases at 18 months. Comparison of the results, no significant difference was found among the radioactivity dose groups. Radiation was well contained within the knee. There were no observed or identified complications including the detectable harm to the articular cartilage, as shown by MRI.

Adult↗
PubMed2004

Nitrogen removal from sludge reject water by a two-stage oxygen-limited autotrophic nitrification denitrification process.

Nitrogen removal from sludge reject water was obtained by oxygen-limited partial nitritation resulting in nitrite accumulation in a first stage, followed by autotrophic denitrification of nitrite with ammonium as electron donor (similar to anaerobic ammonium oxidation) in a second stage. Two membrane-assisted bioreactors (MBRs) were used in series to operate with high sludge ages and subsequent high volumetric loading rates, achieving 1.45 kg N m(-3) day(-1) for the partial nitritation MBR and 1.1 kg N m(-3) day(-1) for the anaerobic ammonium oxidation MBR. Biomass retention in the nitritation stage ensured flexibility towards loading rate and operating temperature. Nitrite oxidisers were out-competed at low oxygen and high free ammonia concentration. Biomass retention in the second MBR prevented wash-out of the slowly growing bacteria. Nitrite and ammonium were converted to dinitrogen gas in a reaction ratio of 1.05, thereby maintaining nitrite limitation to assure process stability. The anoxic consortium catalysing the autotrophic denitrification process consisted of Nitrosomonas-like aerobic ammonium oxidizers and anaerobic ammonium oxidizing bacteria closely related to Kuenenia stuttgartiensis. The overall removal efficiency of the combined process was 82% of the incoming ammonium according to a total nitrogen removal rate of 0.55 kg N m(-3) day(-1), without adding extra carbon source.

Bacteria, Anaerobic↗
PubMed2004

Removal of Cr(VI) by magnetite nanoparticle.

Magnetite nanoparticles were synthesized by sol-gel method. The highly crystalline nature of the magnetite structure with diameter of around 10 nm was characterized with transmission electron microscopy and X-ray diffractometry. The surface area was determined to be 198 m2/g. Batch experiments were carried out to determine the adsorption kinetics and mechanism of Cr(VI) by these magnetite nanoparticles. The Cr(VI) uptake was mainly governed by physico-chemical adsorption. The adsorption process was found to be pH and temperature dependent. The adsorption data fit well with the Freundlich isotherm equation. The Freundlich constants were calculated at different temperatures. The adsorption capacity increased with rising temperature. Preliminary results indicate that magnetite nanoparticles may be used as an adsorbent for removal of Cr(VI) from wastewater.

Adsorption↗
PubMed2003

Reductive dehalogenation of tetrachloroethylene by microorganisms: current knowledge and application strategies.

Reductive anaerobic dehalogenation is a useful method for remediation of sites contaminated by chlorinated ethylenes, where hydrogen concentration plays the key role. Under anaerobic conditions, dehalogenating bacteria compete best against methanogenic consortia when the hydrogen level is low; and methanogenic consortia outplay dehalogenating bacteria when the hydrogen level is high. Thus, in an anaerobic mixed culture, efficient use of hydrogen for dehalogenation can be achieved by strategies that maintain hydrogen at a certain low concentration. However, due to the role of acetate, expected dehalogenating results cannot be obtained and unexpected methane formation can be encountered in practice.

Anaerobiosis↗
PubMed2003

Agrobacterium-mediated large-scale transformation of wheat (Triticum aestivum L.) using glyphosate selection.

An Agrobacterium-mediated transformation system with glyphosate selection has been developed for the large-scale production of transgenic plants. The system uses 4-day precultured immature embryos as explants. A total of 30 vectors containing the 5-enol-pyruvylshikimate-3-phosphate synthase gene from Agrobacterium strain CP4 (aroA:CP4), which confers resistance to glyphosate, were introduced into wheat using this system. The aroA:CP4 gene served two roles in this study-selectable marker and gene of interest. More than 3,000 transgenic events were produced with an average transformation efficiency of 4.4%. The entire process from isolation of immature embryos to production of transgenic plantlets was 50-80 days. Transgenic events were evaluated over several generations based on genetic, agronomic and molecular criteria. Forty-six percent of the transgenic events fit a 3:1 segregation ratio. Molecular analysis confirmed that four of six lead transgenic events selected from Agrobacterium transformation contained a single insert and a single copy of the transgene. Stable expression of theAROA:CP4 gene was confirmed by ELISA through nine generations. A comparison of Agrobacterium-mediated transformation to a particle bombardment system demonstrated that the Agrobacterium system is reproducible, has a higher transformation efficiency with glyphosate selection and produces higher quality transgenic events in wheat. One of the lead events from this study, no. 33391, has been identified as a Roundup Ready wheat commercial candidate.

Biolistics↗
PubMed2003

Clinically relevant thermal preconditioning attenuates ischemia-reperfusion injury.

INTRODUCTION: Thermal preconditioning has previously been shown to attenuate ischemia-reperfusion induced injuries, possible due to increased expression of heat shock proteins (HSP). The model of thermal preconditioning used, however, was not clinically relevant as preconditioning was to 41 degrees C, leading to cellular damage. Our aim was thus to establish a novel and clinically applicable method of preconditioning. MATERIALS AND METHODS: Twenty-six male Sprague-Dawley rats were split into three groups (nine control, nine ischemia-reperfusion, and eight preconditioned followed by ischemia-reperfusion). To precondition the animals, they were anesthetized and, using a water bath, their core temperature was raised by 1 degrees C for 15 min once a day for five successive days. I/R injury consisted of 30 min of aortic cross-clamping followed by 120 min of reperfusion; control animals had a laparotomy only. Indicators of lung injury were tissue myeloperoxidase, broncho-alveolar lavage protein concentration, and tissue edema. Tissue heat shock protein expression was detected by Western blot analysis. RESULTS: Lower torso ischemia-reperfusion causes significant lung injury versus control, with raised levels of myeloperoxidase 4.53 iu/g to 7.88 iu/g (P < 0.05), raised B.A.L. protein concentration 419 microg/ml to 684 microg/ml (P < 0.05) and altered wet dry ratio 4.63 to 5.50. Clinically relevant thermal preconditioning attenuates all of these parameters back to control levels: myeloperoxidase 3.87 iu/g (P < 0.05 vs I/R), B.A.L. to 284 microg/ml (P < 0.01 vs I/R) and wet dry ratio to 4.44 (P < 0.05 vs I/R). Western blot demonstrated increased expression of H.S.P. 72 in the preconditioned group versus control and I/R alone. Western blot demonstrated increased expression of HSP72 in the preconditioned group vs control and I/R alone. CONCLUSIONS: We conclude that clinically applicable thermal preconditioning can attenuate ischemia-reperfusion induced lung injury, possibly through increased expression of HSP72.

Animals↗
PubMed2003

Inflammatory mechanisms in diabetes: lessons from the beta-cell.

Inflammation plays an important role in the destruction of pancreatic islet beta-cells that leads to type I diabetes. This involves infiltration of T-cells and macrophages into the islets and local production of inflammatory cytokines such as interleukin (IL)-1 beta, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma. Our laboratory has developed several strategies for protecting beta-cells against oxidative stress and cytokine-induced cytotoxicity. These include a cytokine selection strategy that results in cell lines that are resistant to the combined effects of IL-1 beta+IFN-gamma. More recently, we have combined the cytokine selection procedure with overexpression of the antiapoptotic gene bcl-2, resulting in cell lines with greater resistance to oxidative stress and cytokine-induced damage than achieved with either procedure alone. This article summarizes this work and the remarkably divergent mechanisms by which protection is achieved in the different model systems. We also discuss the potential relevance of insights gained from these approaches for enhancing islet cell survival and function in both major forms of diabetes.

Animals↗
PubMed2003

Cellular origin of ionizing radiation-induced NF-kappaB activation in vivo and role of NF-kappaB in ionizing radiation-induced lymphocyte apoptosis.

PURPOSE: To investigate the cellular origin of ionizing radiation (IR)-induced NF-kappaB activation in vivo and the role of NF-kappaB in IR-induced lymphocyte apoptosis. MATERIALS AND METHODS: NF-kappaB activities were analysed by gel shift/supershift assay in isolated murine T- and B-cells, macrophages (MPhi) and tissues from normal and T- and B-cell-deficient Rag1 mice with or without exposure to IR. IR-induced lymphocyte apoptosis was determined by analysis of 3,3'-dihexyloxacarbocyanine iodide (DiOC(6)) uptake, annexin-V staining and the sub-G0/1 population, or by TUNEL assay. RESULTS: The results showed that IR activated NF-kappaB in lymphocytes, including both T- and B-cells, but failed to do so in MPhi. Furthermore, T- and B-cell-deficient Rag1 mice exposed to IR exhibited a significant reduction in NF-kappaB activation as compared with normal mice. Although NF-kappaB1 (p50) gene knockout or NF-kappaB decoy oligonucleotide treatment specifically inhibited IR-induced lymphocyte NF-kappaB activation, they had no significant effect on IR-induced lymphocyte apoptosis. CONCLUSIONS: This finding suggests that lymphocytes are the main cellular origin of IR-induced NF-kappaB activation in vivo. However, NF-kappaB activation has no significant effect on IR-induced lymphocyte apoptosis.

Animals↗
PubMed2003

Possible involvement of the ERK signaling cascade in bipolar disorder: behavioral leads from the study of mutant mice.

Despite the devastating impact that bipolar disorder has on the lives of millions worldwide, little is known for certain about its etiology or pathophysiology. Whereas research has traditionally focused on biogenic amines, it is becoming increasingly more apparent that intracellular pathways are involved in the etiology and treatment of the disease and that a true understanding of the pathophysiology of bipolar disorder must address its neurobiology at different physiological levels, that is, molecular, cellular, systems and behavioral levels. There is now considerable biochemical evidence that the antimanic agents lithium and valproate robustly activate the ERK signaling cascade in therapeutically relevant paradigms. This raises the possibility that this pathway may play a role in the antimanic effects of these agents. The present paper reviews behavioral studies that may shed light on the involvement of the ERK pathway in affective-like behaviors in animals. The available literature suggests that genetic manipulations of the brain-derived neurotrophic factor (BDNF)-ERK kinase pathway produces a variety of changes in affective-like behaviors, with most changes consistent with manic-like behavior. Thus, overall, mice with targeted mutation of the BDNF gene exhibited increased spontaneous locomotion and increased response to acute amphetamine, altered response to chronic cocaine, increased aggression, increase in risk-taking behavior, as demonstrated by time spent in the center of an open field, and changes in eating patterns. Although it has to be acknowledged that the currently available behavioral data from the BDNF-ERK pathway mutants is less than ideal to offer real substantiation relating this pathway to bipolar disorder, the data still supports the possibility that this pathway modulates manic-like behavior in animals, and perhaps mania in humans.

Animals↗
PubMed2002

Hydrogen adsorption on the indium-rich indium phosphide (001) surface: a novel way to produce bridging In-H-In bonds.

The indium phosphide (001) surface provides a unique chemical environment for studying the reactivity of hydrogen toward the electron-deficient group IIIA element, indium. Hydrogen adsorption on the In-rich delta(2 x 4) reconstruction produced a neutral, covalently bound bridging indium hydride. Using vibrational spectroscopy and ab initio cluster calculations, two types of bridging hydrides were identified, a (mu-H)In(2) and a (mu-H)(2)In(3) "butterfly-like" structure. These structures were formed owing to the large thermodynamic driving force for adsorption of H atoms on solid-state indium dimers.

Journal Article↗