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Biomedical subjects

J M Chen

Publications and source records attributed to J M Chen.

At least 37 records · Page 2Linked to original sources
PubMed2006

Removal efficiency of high-concentration H2S in a pilot-scale biotrickling filter.

A pilot-scale biotrickling filter (BTF) packed with polyurethane (PU) foam was installed at one pharmaceutical factory in Zhejiang Province to study the removal of high-concentration H2S from water treatment plant. Experiments were performed at different empty bed residence times (EBRTs), H2S input load, ratio of liquid flow rate to gas inlet rate (L/G) and sulfate concentration in recirculating liquid to examine their effects on the performance of the BTF. The performance of this bioreactor was monitored continuously over a period of 56 days. After the start-up within 8 days, H2S removal efficiency remained between 90% and 100% with inlet concentration fluctuating from 238 to 590 mg m(-3). H2S removal efficiency was consistently greater than 90%, even at a short EBRT of 9 s and inlet H2S load higher than 187 g m(-3) h(-1). Profiles over the height of the reactor indicated that H2S removal took place mostly in the first section of the column. The performance of BTF could be maintained at high and stable levels when L/G was below 0.005 and sulfate concentration down to 28 g l(-1). The results led to the conclusion that BTF is the optimal choice for treating high-concentration H2S.

Air Pollutants↗
PubMed2006

Levels of selenium, zinc, copper, and antioxidant enzyme activity in patients with leukemia.

Essential elements, mainly selenium and zinc, were involved in protection against oxidative stress in cells. Oxidation could lead to the formation of free radicals that have been implicated in the pathogenesis of many diseases, including leukemia. Leukemia is a neoplastic disease that is susceptible to antioxidant enzyme and essential elements alterations. This study was undertaken to examine the levels of essential elements, antioxidant enzymes activities, and their relationships with different types of leukemia. Serum selenium, zinc, and copper concentrations, red blood cell glutathione peroxidase (GPx) activities, plasma Cu-Zn superoxide dismutase (Cu-Zn SOD) activities and lipid peroxidation (LPO) levels were determined in 49 patients with different types of leukemia before initial treatment. Serum selenium and zinc concentrations were lower in leukemia patients than those of controls (p<0.01). Serum copper concentration was higher in leukemia patients than that of controls (p<0.01). The activities GPx and Cu-Zn SOD were significantly increased in leukemia patients, especially with acute leukemia (AL), acute lymphoid leukemia (ALL), and acute nonlymphoid leukemia (ANLL) (p<0.05), whereas no difference was found between those of chronic myelogenous leukemia and the controls. The levels of LPO were normal as controls. Serum selenium concentration was not correlated with GPx, and serum levels of zinc and copper were not related to Cu-Zn SOD. Serum zinc levels had a negative correlation with the absolute peripheral blast cells, whereas serum copper had a positive correlation with the absolute peripheral blast cells. Increased GPx and Cu-Zn SOD activities and normal levels of LPO, which were a protective responses, were an indicator of mild oxidative stress; it might indicate that the essentials elements alterations in leukemia patients were mostly dependent on tumor activity. Changes of their levels demonstrated that there are low selenium, zinc, and high copper status in leukemia patients. The decrease of plasma zinc and increase of the Cu/Zn ratio could be the index that showed an unfavorable prognosis of acute leukemia.

Adolescent↗
PubMed2005

Cochlear implantation in cochlear otosclerosis.

OBJECTIVES/HYPOTHESIS: The objective was to correlate implant performance in cochlear otosclerosis to 1) matched control samples, 2) severity of otic capsule involvement, 3) prior ipsilateral surgery, and 4) programming issues. STUDY DESIGN: Retrospective case controlled study. METHODS: Study cohort comprised 30 individuals. Diagnosis was based on prior ear surgery (stapedectomy [n = 18] or fenestration [n = 2]) and/or pathognomonic radiological findings. High-resolution computed tomography images of the temporal bones were assessed by two radiologists and graded (range, 0-3) for the extent of otosclerosis. Operative records were reviewed. Performance, programming visits, and the number of electrode deactivations at 6 months and at 1 year after implantation were determined for the individuals with otosclerosis and compared with a group of matched control subjects. A within-group comparison correlating severity of otosclerosis to the above was carried out. RESULTS: Implant performance in individuals with cochlear otosclerosis was not significantly different from those without. Previous surgery on the side of implantation did not alter performance. Programming difficulty as reflected in the number of visits and electrode deactivation for sound quality reasons were comparable. Deactivation for facial nerve stimulation occurred exclusively in otosclerotics with the most severe radiological disease (grade 3) and was only with non-modiolar hugging electrodes (n = 5). There was no observed difference between the radiological extent of otosclerosis and implant performance. CONCLUSION: Individuals with severe otosclerosis considering cochlear implantation can be counseled to expect similar benefit to those without, regardless of whether prior surgery occurred on the side of implantation or of severity of otic capsule involvement. There is a significant risk of facial nerve stimulation in otosclerotics with grade 3 disease.

Case-Control Studies↗
PubMed2004

State selective enhanced production of excited fragments and ionic fragments of gaseous Si(CH3)2Cl2 and solid-state analogs following core-level excitation.

State-selective fragmentation dynamics for excited fragments and ionic fragments of gaseous and condensed Si(CH3)2Cl2 following Cl 2p and Si 2p core-level excitations have been characterized. The Cl 2p-->15a1* excitation of Si(CH3)2Cl2 induces significant enhancement of the Cl+ desorption yield in the condensed phase and the Si(CH3)+2 and SiCH+3 yields in the gaseous phase. The core-to-Rydberg excitations at both Si 2p and Cl 2p edges lead to enhanced production of the excited fragments. These complementary results provide deeper insight into the origin of state-selective fragmentation of molecules via core-level excitation.

Journal Article↗
PubMed2004

Two novel severe mutations in the pancreatic secretory trypsin inhibitor gene (SPINK1) cause familial and/or hereditary pancreatitis.

Mutations in the serine protease inhibitor Kazal type 1 gene (SPINK1) encoding pancreatic secretory trypsin inhibitor (PSTI) have recently been found to be associated with chronic pancreatitis. Nevertheless, knowledge of severe mutations is particularly scarce, both in terms of number and in the extent of clinical information. The aim of this study was to expand the known spectrum of such mutations. 46 unrelated families, each including at least two pancreatitis patients and carrying neither cationic trypsinogen (PRSS1) mutations nor the frequent SPINK1 N34S mutation, participated in this study. The four exons and their flanking sequences of the SPINK1 gene were screened by denaturing high performance liquid chromatography analysis (DHPLC); and mutations were identified by direct sequencing. A heterozygous microdeletion mutation (c.27delC), which occurs within a symmetric element, was identified in two families. In one family, c.27delC showed segregation with the disease across two generations, with a penetrance of up to 75%. But in the other family, however, the same mutation manifested as a low-penetrance susceptibility factor. In addition, a novel heterozygous splicing mutation, c.87+1G>A (G>A substitution at nucleotide +1 of intron 2) was found in one family with familial pancreatitis. Our results also helped to resolve the sharply differing views about PSTI's role in pancreatitis.

Adult↗
PubMed2003

Acetylenic TACE inhibitors. Part 1. SAR of the acyclic sulfonamide hydroxamates.

The SAR of a series of potent sulfonamide hydroxamate TACE inhibitors, all bearing a butynyloxy P1' group, was explored. In particular, compound 5j has excellent in vitro potency against isolated TACE enzyme and in cells, good selectivity over MMP-1 and MMP-9, and oral activity in an in vivo model of TNF-alpha production and a collagen-induced arthritis model.

ADAM Proteins↗
PubMed2003

Synthesis and SAR of bicyclic heteroaryl hydroxamic acid MMP and TACE inhibitors.

Potent and selective bicyclic heteroaryl hydroxamic acid MMP and TACE inhibitors were synthesized by a novel convergent route. Selectivity and efficacy versus MMPs and TACE could be controlled by appropriate substitution on the scaffolds and by variation of the P1' group. Select compounds were found to be effective in in vivo models of arthritis.

ADAM Proteins↗
PubMed2002

Facial nerve paralysis and meningioma of the internal auditory canal.

Pathological lesions confined to the internal auditory canal (IAC) commonly present with cochleovestibular symptoms; sensorineural hearing loss, tinnitus and balance disturbance. The commonest lesion of the IAC is vestibular schwannoma. Other lesions include meningioma, facial neuroma, cavernous haemangioma, lipoma and arachnoid cyst. Presentation with facial palsy and an intracanalicular lesion is suggestive of pathology other than acoustic neuroma. Magnetic resonance imaging (MRI) cannot reliably distinguish intracanalicular vestibular schwannomas from meningiomas. Particular care is required for surgery of these lesions: the facial nerve typically does not lie in a protected anterior position within the IAC.

Adult↗
PubMed2001

Discrimination of three mutational events that result in a disruption of the R122 primary autolysis site of the human cationic trypsinogen (PRSS1) by denaturing high performance liquid chromatography.

BACKGROUND: R122, the primary autolysis site of the human cationic trypsinogen (PRSS1), constitutes an important "self-destruct" or "fail-safe" defensive mechanism against premature trypsin activation within the pancreas. Disruption of this site by a missense mutation, R122H, was found to cause hereditary pancreatitis. In addition to a c.365G>A (CGC>CAC) single nucleotide substitution, a c.365 through 366GC>AT (CGC>CAT) gene conversion event in exon 3 of PRSS1 was also found to result in a R122H mutation. This imposes a serious concern on the genotyping of pancreatitis by a widely used polymerase chain reaction-restriction fragment length polymorphism assay, which could only detect the commonest c.365G>A variant. MATERIALS AND METHODS: DNA samples containing either the known c.365G>A or c.365 through 366GC>AT variant in exon 3 of PRSS1 were used as positive controls to establish a denaturing high performance liquid chromatography (DHPLC) assay. RESULTS: DHPLC could readily discriminate the two known different mutational events resulting in the R122H mutation. More importantly, under the same experimental conditions, it identified a further mutational event that also occurs in the R122 primary autolysis site but results in a different amino acid substitution: c.364C>T (CGC>TGC; R122C). CONCLUSIONS: A rapid, simple, and low-cost assay for detecting both the known and new mutations occuring in the R122 primary autolysis site of PRSS1 was established. In addition, the newly found R122C variant represents a likely pancreatitis-predisposing mutation.

Amino Acid Substitution↗
PubMed2001

Site-directed mutagenesis of acyl carrier protein (ACP) reveals amino acid residues involved in ACP structure and acyl-ACP synthetase activity.

Acyl carrier protein (ACP) interacts with many different enzymes during the synthesis of fatty acids, phospholipids, and other specialized products in bacteria. To examine the structural and functional roles of amino acids previously implicated in interactions between the ACP polypeptide and fatty acids attached to the phosphopantetheine prosthetic group, recombinant Vibrio harveyi ACP and mutant derivatives of conserved residues Phe-50, Ile-54, Ala-59, and Tyr-71 were prepared from glutathione S-transferase fusion proteins. Circular dichroism revealed that, unlike Escherichia coli ACP, V. harveyi-derived ACPs are unfolded at neutral pH in the absence of divalent cations; all except F50A and I54A recovered native conformation upon addition of MgCl(2). Mutant I54A was not processed to the holo form by ACP synthase. Some mutations significantly decreased catalytic efficiency of ACP fatty acylation by V. harveyi acyl-ACP synthetase relative to recombinant ACP, e.g. F50A (4%), I54L (20%), and I54V (31%), whereas others (V12G, Y71A, and A59G) had less effect. By contrast, all myristoylated ACPs examined were effective substrates for the luminescence-specific V. harveyi myristoyl-ACP thioesterase. Conformationally sensitive gel electrophoresis at pH 9 indicated that fatty acid attachment stabilizes mutant ACPs in a chain length-dependent manner, although stabilization was decreased for mutants F50A and A59G. Our results indicate that (i) residues Ile-54 and Phe-50 are important in maintaining native ACP conformation, (ii) residue Ala-59 may be directly involved in stabilization of ACP structure by acyl chain binding, and (iii) acyl-ACP synthetase requires native ACP conformation and involves interaction with fatty acid binding pocket residues, whereas myristoyl-ACP thioesterase is insensitive to acyl donor structure.

Acyl Carrier Protein↗
PubMed2001

[Value of transvaginal sonography in diagnosis of placenta previa].

OBJECTIVE: To investigate the value of transvaginal sonography (TVS) in diagnosis of placenta previa. METHODS: Transabdominal sonography(TAS) and TVS localization of the placenta were performed in 78 pregnant women after 35 week's gestation. It was suspected of having placenta previa when the placental edge appeared to be over or within 2 cm in diameter of the internal cervical os demonstrated by TAS or TVS. Final diagnosis depended on diagnosis at delivery. The diagnostic sensitivity, specificity, false-positive rate and coincidence rate were made in comparison between TVS and TAS. RESULTS: The sensitivity, specificity, false-positive rate and coincidence rate of TVS were 100%, 90%, 10% and 93.6%, while that of TAS were 71.4%, 60%, 40% and 64.1%, respectively. The coincidence rate of TVS was better than TAS (p < 0.01). CONCLUSION: TVS is superior to TAS in diagnosis of placenta previa.

Adult↗
PubMed2001

State-specific enhancement of Cl+ and Cl- desorption for SiCl4 adsorbed on a Si(100) surface following Cl 2 p and Si 2 p core-level excitations.

State-specific desorption for SiCl4 adsorbed on a Si(100) surface at approximately 90 K with variable coverage following the Cl 2p and Si 2p core-level excitations has been investigated using synchrotron radiation. The Cl+ yields show a significant enhancement following the Cl 2p-->8a*1 excitation. The Cl- yields are notably enhanced at the 8a*1 resonance at both Cl 2p and Si 2p edges. The enhancement of the Cl- yield occurs through the formation of highly excited states of the adsorbed molecules. These results provide some new dissociation processes from adsorbates on surfaces via core-level excitation.

Journal Article↗
PubMed2001

Toll-like receptor 4 mediates intracellular signaling without TNF-alpha release in response to Cryptococcus neoformans polysaccharide capsule.

Toll-like receptors (TLR) 2 and 4 are cell surface receptors that in association with CD14 enable phagocytic inflammatory responses to a variety of microbial products. Activation via these receptors triggers signaling cascades, resulting in nuclear translocation of NF-kappa B and a proinflammatory response including TNF-alpha production. We investigated whether TLRs participate in the host response to Cryptococcus neoformans glucuronoxylomannan (GXM), the major capsular polysaccharide of this fungus. Chinese hamster ovary fibroblasts transfected with human TLR2, TLR4, and/or CD14 bound fluorescently labeled GXM. The transfected Chinese hamster ovary cells were challenged with GXM, and activation of an NF-kappa B-dependent reporter construct was evaluated. Activation was observed in cells transfected with both CD14 and TLR4. GXM also stimulated nuclear NF-kappa B translocation in PBMC and RAW 264.7 cells. However, stimulation of these cells with GXM resulted in neither TNF-alpha secretion nor activation of the extracellular signal-regulated kinase 1/2, p38, and stress-activated protein kinase/c-Jun N-terminal kinase mitogen-activated protein kinase pathways. These findings suggest that TLRs, in conjunction with CD14, function as pattern recognition receptors for GXM. Furthermore, whereas GXM stimulates cells to translocate NF-kappa B to the nucleus, it does not induce activation of mitogen-activated protein kinase pathways or release of TNF-alpha. Taken together, these observations suggest a novel scenario whereby GXM stimulates cells via CD14 and TLR4, resulting in an incomplete activation of pathways necessary for TNF-alpha production.

Active Transport, Cell Nucleus↗