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Biomedical subjects

J C Chen

Publications and source records attributed to J C Chen.

At least 19 recordsLinked to original sources
PubMed1998

Isolation and characterization of an Enterococcus-like bacterium causing muscle necrosis and mortality in Macrobrachium rosenbergii in Taiwan.

A Gram-positive, ovoid, diplococoid bacterium tentatively identified as Enterococcus-like was isolated from diseased Macrobrachium rosenbergii in Taiwanese aquaculture ponds. The diseased prawns displayed poor growth, anorexia, inactivity, opaque and whitish musculature, and mortality. In histological preparations, melanized hemocytic granulomas were seen in the connective tissue around hemal sinuses together with hemocytic aggregation in necrotic musculature. Five isolates of diplococci were collected from diseased prawns at 4 farms and these were evaluated for 93 characteristics including morphology, physiology, biochemistry and sensitivity to antibiotics. The results indicated that the isolates belonged to a single species. They grew in 0.5 to 6.0% NaCl, at 10 to 40 degrees C, at pH 9.6 and on bile esculin medium, gave positive pyrrolidonylarylamidase, arginine dehydrolase and Voges-Proskauer tests, were resistant to bacitracin and SXT, and were CAMP-negative and non-hemolytic on sheep blood agar. These findings indicated an Enterococcus-like bacterium closely related to Enterococcus seriolicida (recently reduced to synonymy with Lactococcus garvieae). Experimental injection of 3 x 10(5) cells of strain KM002 of this Enterococcus-like bacterium into the ventral sinus of the prawn cephalothorax caused 100% mortality in 11 d, and induced muscular necrosis and hepatopancreatitis, gross signs and histopathology similar to those observed in the naturally infected prawns. It was concluded that this Enterococcus-like bacterium was the etiological agent associated with mortality of the farmed, diseased prawns.

Animals↗
PubMed1998

Structure-activity relationships for a series of bis(phenylalkyl)amines: potent subtype-selective inhibitors of N-methyl-D-aspartate receptors.

A series of bis(phenylalkyl)amines, structural analogues of ifenprodil and nylidrin, were synthesized and tested for antagonism of N-methyl-D-aspartate (NMDA) receptors. Potency and subunit selectivity were assayed by electrical recordings in Xenopus oocytes expressing three binary combinations of cloned rat NMDA receptor subunits: NR1A expressed in combination with either NR2A, NR2B, or NR2C. The bis(phenylalkyl)amines were selective antagonists of NR1A/2B receptors. Assayed under steady-state conditions, the most potent of these, N-[2-(4-hydroxyphenyl)ethyl]-5-phenylpentylamine hydrochloride (20), has an IC50 value of 8 nM and >1000-fold selectivity with respect to NR1A/2A and NR1A/2C receptors. The structure-activity relationship of the bis(phenylalkyl)amine series indicates that the piperidine ring and alkyl chain substitutions common to NR2B-selective antagonists such as ifenprodil, CP 101,606, and Ro 25-6981 are not necessary to generate potent and selective ligands. The primary determinants of potency are the phenolic OH group, acting as a hydrogen bond donor, the distance between the two rings, and an electrostatic interaction between the receptor and the basic nitrogen atom. This study provides a framework for designing structurally novel NR2B-selective antagonists which may be useful for treatment of a variety of neurological disorders.

Animals↗
PubMed1998

The cellular basis of cardiac allograft rejection: VIII. Mechanisms underlying delayed allograft rejection in PVG C6-deficient rats.

BACKGROUND: The delayed allograft rejection in C6-deficient PVG C6- rats compared with normal PVG rats has been attributed to the lack of alloantibody activation of the membrane attack complex of complement. As T cells alone have been shown to effect graft rejection, we examined T-cell responses in PVG C6- rats. METHODS: The cellular infiltrate and its mRNA for cytokines and effector molecules in DA heart allografts to PVG and PVG C6- rats was compared by immunoperoxidase staining and semiquantitative reverse transcriptase polymerase chain reaction. The ability of pure populations of T cells or alloantibody to mediate DA heart graft rejection in irradiated (750 rads) PVG and PVG C6- rats was also compared. RESULTS: The median rejection time of DA heart allografts was 8 days in PVG rats and 17.5 days in PVG C6-. PVG C6- rats sensitized to DA by two skin grafts rejected DA heart grafts in 5-6 days. CD3+, CD4+, CD8+, interleukin-2 receptor-positive T cell, macrophage, and natural killer cell infiltration, as well as class II major histocompatibility complex and intercellular adhesion molecule-1 up-regulation, in grafts was similar in naive PVG and PVG C6- rats. mRNA for T helper 1 cytokine interleukin-2, interferon-gamma, tumor necrosis factor-beta, macrophage molecules tumor necrosis factor-alpha, and inducible nitric oxide synthase, as well as cytotoxic T-cell effector molecules perforin and granzyme A and B, were found to be the same in the grafts from both naive PVG and naive PVG C6- rats. Thus, there appeared to be no difference in the T-cell effector response between the PVG and PVG C6- groups. There were higher alloantibody titers in PVG C6- rats than in PVG hosts. Irradiation ablated rejection and alloantibody responses and reconstitution with naive T cells alone restored rejection in both PVG and PVG C6- rats. Irradiated rats given serum from PVG rats that had rejected DA grafts did not effect rejection of DA grafts even if given naive T cells. Sensitized T cells restored second set. CONCLUSIONS: PVG C6- rats have normal T-cell responses and can mediate allograft rejection in the absence of alloantibody. The failure of PVG C6- to reject allografts rapidly may be a result of the poor clearance of alloantisera leading to enhancement of graft survival rather than a critical role for complement and membrane attack complex in acute rejection.

Animals↗
PubMed1998

Structure of bovine pancreatic cholesterol esterase at 1.6 A: novel structural features involved in lipase activation.

The structure of pancreatic cholesterol esterase, an enzyme that hydrolyzes a wide variety of dietary lipids, mediates the absorption of cholesterol esters, and is dependent on bile salts for optimal activity, is determined to 1.6 A resolution. A full-length construct, mutated to eliminate two N-linked glycosylation sites (N187Q/N361Q), was expressed in HEK 293 cells. Enzymatic activity assays show that the purified, recombinant, mutant enzyme has activity identical to that of the native, glycosylated enzyme purified from bovine pancreas. The mutant enzyme is monomeric and exhibits improved homogeneity which aided in the growth of well-diffracting crystals. Crystals of the mutant enzyme grew in space group C2, with the following cell dimensions: a = 100.42 A, b = 54.25 A, c = 106.34 A, and beta = 104.12 degrees, with a monomer in the asymmetric unit. The high-resolution crystal structure of bovine pancreatic cholesterol esterase (Rcryst = 21.1%; Rfree = 25.0% to 1.6 A resolution) shows an alpha-beta hydrolase fold with an unusual active site environment around the catalytic triad. The hydrophobic C terminus of the protein is lodged in the active site, diverting the oxyanion hole away from the productive binding site and the catalytic Ser194. The amphipathic, helical lid found in other triglyceride lipases is truncated in the structure of cholesterol esterase and therefore is not a salient feature of activation of this lipase. These two structural features, along with the bile salt-dependent activity of the enzyme, implicate a new mode of lipase activation.

Acetylcholinesterase↗
PubMed1998

Glucose deprivation-induced cytotoxicity and alterations in mitogen-activated protein kinase activation are mediated by oxidative stress in multidrug-resistant human breast carcinoma cells.

We previously observed that glucose deprivation induces cell death in multidrug-resistant human breast carcinoma cells (MCF-7/ADR). As a follow up we wished to test the hypothesis that metabolic oxidative stress was the causative process or at least the link between causative processes behind the cytotoxicity. In the studies described here, we demonstrate that mitogen-activated protein kinase (MAPK) was activated within 3 min of being in glucose-free medium and remained activated for 3 h. Glucose deprivation for 2-4 h also caused oxidative stress as evidenced by a 3-fold greater steady state concentration of oxidized glutathione and a 3-fold increase in pro-oxidant production. Glucose and glutamate treatment rapidly suppressed MAPK activation and rescued cells from cytotoxicity. Glutamate and the peroxide scavenger, pyruvate, rescued the cells from cell killing as well as suppressed pro-oxidant production. In addition the thiol antioxidant, N-acetyl-L-cysteine, rescued cells from glucose deprivation-induced cytotoxicity and suppressed MAPK activation. These results suggest that glucose deprivation-induced cytotoxicity and alterations in MAPK signal transduction are mediated by oxidative stress in MCF-7/ADR. These results also support the speculation that a common mechanism of glucose deprivation-induced cytotoxicity in mammalian cells may involve metabolic oxidative stress.

Acetylcysteine↗
PubMed1998

Local treatment of prosthetic vascular graft infection with multivesicular liposome-encapsulated amikacin.

BACKGROUND: Contaminated surgical fields limit the use of prosthetic vascular grafts. We studied the efficacy of sustained-release amikacin applied locally to contaminated grafts in the prevention of infectious complications. MATERIALS AND METHODS: Thirty-one New Zealand white rabbits underwent placement of a polytetrafluoroethylene (PTFE) interposition graft in a 1-cm segment of the descending aorta. The surgical field was infected with application of 10(5) to 10(8) Staphylococcus aureus organisms suspended in normal saline solution. Nineteen rabbits underwent contaminated aortic graft placement without treatment. Twelve rabbits were treated with local application of 2.5 ml of amikacin encapsulated in lipid particle-based sustained-release dosage form. Rabbits were observed for 2 weeks and then evaluated for the presence of graft infection. RESULTS: Seventy-five percent of the treated rabbits survived without evidence of graft infection or systemic sepsis versus 37% in the untreated group (P < 0.04). Cultures verified the absence of organisms in all surviving rabbits without clinical infection. CONCLUSIONS: Sustained-release lipid particle-encapsulated amikacin applied to contaminated PTFE grafts increased survival and decreased postoperative graft infections. Adjunctive use of local, delayed-release antibiotics in contaminated vascular beds may allow wider clinical use of prosthetic grafts.

Amikacin↗
PubMed1998

Effect of lung volume reduction surgery on pulmonary diffusion capacity in a rabbit model of emphysema.

BACKGROUND: While there is renewed interest in lung volume reduction surgery (LVRS) for treatment of emphysema, many aspects of the operation such as patient selection and surgical end points of excision are uncertain. We studied the effects of LVRS on measured lung volumes and diffusion capacity in an animal model to investigate optimal resection volumes. METHODS: Emphysema was induced in 32 New Zealand white (NZW) rabbits using aerosolized elastase. Helium dilution lung volumes and single breath DLCO were measured concurrently at baseline, following induction of emphysema (preop), and 1 week postoperatively (postop) following LVRS. Bilateral upper and middle lobe stapled lung resections were performed through midline sternotomies with excision of variable amounts of lung tissue from 1.8 to 5.8 g. RESULTS: FRC increased following induction of emphysema and decreased postoperatively. DLCO improved with increasing lung tissue resection up to 3 g of tissue and then decreased as even greater amounts were removed (r = 0.54). CONCLUSIONS: Measured lung volumes increase with development of emphysema and appropriately decrease in response to LVRS in this rabbit model. DLCO improves with moderate resection but then decreases with excessive excision of lung quantities and may help define one physiologic operative end point. In this rabbit model, excision of approximately 30% of lung volume was optimal and prevented further decrease in diffusion capacity.

Animals↗
PubMed1998

Anorectal function and endopelvic dissection in patients with repaired imperforate anus.

Fifty-eight patients with anorectal malformations were closely followed up for postoperative anorectal function. Constipation was noted shortly after anorectoplasty in 10 of 28 low anomalies (35.7%) treated with limited sagittal anorectoplasty (LSARP), in 18 of 25 high or intermediate anomalies (72.0%) treated with posterior sagittal anorectoplasty (PSARP), but in none of 5 high or intermediate anomalies treated with Rehbein's mucosa-stripping endorectal pull-through and anterior sagittal perineal anorectoplasty (R-ASAP). The constipation resolved mostly within 1-2 years after repair under conservative management, but persisted beyond 2 years after repair in 3/25 children with LSARP and 10/25 with PSARP. Anal soiling was noted in 1/23 (4.3%) LSARP and 6/22 (27.3%) PSARP patients, but normal anorectal function was attained in 20/23 LSARP (86.9%) and 11/12 PSARP patients (50.0%) by the time of toilet training. Manometric studies disclosed that the resting rectal pressure (RRP) was lower and the anorectal pressure gradient (ARPG) higher in the constipated than the non-constipated children, while the RRP was higher and the ARPG lower in the soiled than the non-soiled patients. The ARPG after R-ASPA was close to that of non-constipated and in between that of the constipated and soiled patients. The rectoanal sphincter inhibitory reflex was not related to defecation status or surgical procedures, but showed a tendency toward positive conversion with time or after exclusion of esctatic terminal bowel in the severely constipated. It is concluded that anorectal function in patients with repaired imperforate anus seems to be more affected by the extent of endopelvic dissection than by preservation of the terminal bowel or sphincter muscles.

Anal Canal↗
PubMed1998

Predictive ability of duplex ultrasonography for internal carotid artery stenosis of 70%-99%: a comparative study.

This study prospectively compared the accuracy of published duplex ultrasonographic criteria for 70%-99% internal carotid artery (ICA) stenosis according to the North American Symptomatic Carotid Endarterectomy Trial (NASCET) method to determine angiographic stenosis. From March 1, 1995 to December 1, 1995, all patients considered for carotid endarterectomy (CEA) were studied with carotid duplex ultrasound and carotid angiography within 1 month of the ultrasound study. Duplex measurements of ICA peak systolic velocity (PSV), end diastolic velocity (EDV), and ratio of the ICA to common carotid artery (CCA) PSVs were recorded. Degree of stenosis on angiography was determined using NASCET criteria. A MEDLINE search to identify duplex ultrasound criteria to predict NASCET defined 70%-99% ICA stenosis was carried out. In addition, the original University of Washington criteria for critical stenosis (> or = 80%) was also examined. The accuracy of these criteria was determined with angiographic results and the positive predictive value (PPV) of each criterion were compared. Ninety-nine patients with 185 carotid bifurcations were available for comparison. The different duplex criteria for determining NASCET defined 70%-99% ICA stenosis were: ICA PSV > 175 cm/sec or PSV < 40 cm/sec, PSV > 230 cm/sec, ratio of ICA to CCA PSVs > 4, PSV > 130 cm/sec plus EDV > 100 cm/sec, and PSV > 270 cm/sec plus EDV > 110 cm/sec. When compared with angiography, the calculated PPVs for these criteria were 71% (73/103), 81% (71/88), 86% (67/78), 88% (62/70), and 90% (57/63), respectively. The University of Washington criteria for critical stenosis (PSV > 125 cm/sec plus EDV > 135 cm/sec) had the highest PPV at 91.6% (55/60). The University of Washington criteria for critical stenosis had the highest PPV to predict a 70%-99% angiographic stenosis.

Blood Flow Velocity↗
PubMed1998

An aggressive local approach to vascular graft infection.

PURPOSE: To present the use of sartorius myoplasty (SM) and superficial femoral vein (SFV) in a graft-sparing approach to vascular graft infection. METHODS: Twenty-five patients were treated for Szilagyi grade III groin infections during the last 10 years. Fifteen presented early (E), mean 2 months; 10 late (L), mean 6.5 years. Bacteria E/L: Staphylococcus epidermidis 1/7, S aureus 6/0, other gram positive 1/0, gram negative 4/1, mixed 6/0 (one pseudomonas). There were 13 aortofemoral (AF), 5 crossover, and 7 femoral distal reconstructions. SM was used to cover exposed grafts after radical debridement. When the graft was free-floating or bleeding, this segment was removed and replaced with SFV. The remaining infection was controlled with antibiotics. RESULTS: One of 10 patients treated by SM alone required SFV replacement for bleeding. Four of 9 AFs treated by partial SFV replacement +/- SM had persistent infection treated by complete graft removal in 3. Six grafts were removed electively in lower risk situations. There was no perioperative mortality, and no early or late limb loss. CONCLUSIONS: This experience supports an attempt at aggressive local treatment in frail patients.

Aged↗
PubMed1998

Hepatocellular carcinoma in children: clinical review and comparison with adult cases.

BACKGROUND: Hepatocellular carcinoma (HCC) in children was rarely reported and usually included with hepatoblastoma in most studies of pediatric liver malignancies despite different clinical behaviors. The authors report their experience in pediatric HCC and discuss its differences from adult HCC. METHODS: A retrospective review of radiographic, laboratory, pathological, and therapeutic data in 55 children with HCC was performed. The liver function was graded by modified Child's classification. Kaplan-Meier survival curves in various therapeutic and Child's groups were plotted, and log-rank test was used to detect differences among survival curves. RESULTS: Although children with HCC mostly presented with advanced disease at diagnosis, disturbances of liver function were unremarkable. Sixty-eight percent of cases concurred with liver cirrhosis. The median survivals for resectable, chemotherapeutic, and untreated HCCs were 23, 3, and 2 months, respectively. Resectable HCC significantly posed a much better prognosis. However, the resectability was unsatisfactory (18.2%). Resection was limited because of anatomic unfeasibility including bilateral involvement (62.5%), portal vein thrombi (41.7%), distant metastasis (29.1%), para-aortic lymphadenopathy (18.8%), inferior vena cava thrombi (16.7%), and hilar invasion (6.3%). Distant metastasis was the most ominous for survival in children with unresectable HCC. CONCLUSIONS: HCC behaved somewhat differently between children and adults. Surgical resection represented the best hope of long-term survival. The outcome in children could not keep up with that in adults because of a diagnostic delay. Hence, alpha-fetoprotein and sonography screening in carrier children should be worthwhile.

Adolescent↗
PubMed1998

Changes in pulmonary physiology after lung volume reduction surgery in a rabbit model of emphysema.

OBJECTIVE: The purpose of this study is to investigate the effects of lung volume reduction surgery on pulmonary compliance, airway flow, and helium lung volumes in an elastase-induced emphysema animal model. METHODS: A 15,000-unit bolus of elastase was aerosolized through an endotracheal tube in 14 New Zealand White rabbits to induce emphysema. Stapled lung volume reduction of bilateral upper and middle lobes was performed through a midline sternotomy at 4 weeks after induction of emphysema. Lung functions were measured at baseline before induction of emphysema, preoperatively at 4 weeks, and 1 week postoperatively. RESULTS: Compliance increased after induction of emphysema and decreased in response to lung volume reduction surgery. Functional residual capacity decreased after lung volume reduction surgery in proportion to the amount of excised lung tissue. Expired flows suggested improvement in response to lung volume reduction surgery. Histologic examination confirmed presence of diffuse heterogeneous emphysema in each animal at necropsy. CONCLUSIONS: The decreased compliance and increased airway flow after volume reduction surgery in this model parallels findings in human studies and suggests that similar mechanisms of increased elastic recoil and airway support contribute to improvement.

Animals↗
PubMed1998

The simulation of hexavalent chromium formation under various incineration conditions.

The formation of hexavalent chromium Cr(VI) during waste incineration processes is of interested because its carcinogenic characteristic. The objective of this study is to simulate the formation of Cr(VI) species under various operating temperatures and input waste compositions during incineration by a thermodynamic model. The results show that the major hexavalent chromium species are CrO2Cl2(g) and CrO3(g). Chlorine and oxygen can increase the formation of Cr(VI) species; while hydrogen, sulfur, sodium, and calcium can inhibit. The input waste composition has greater effect on the formation of hexavalent chromium species than operating temperature.

Calcium↗
PubMed1998

The adsorption of heavy metals by different sorbents under various incineration conditions.

The emission of heavy metals can be controlled by adding solid sorbents into the combustion chamber during incineration processes. The objective of this work was to experimentally study the adsorption efficiency of different sorbents for heavy metals under various incineration conditions. Each sorbent has its optimum operating temperature. Kaolinite and aluminum oxide have the best adsorption efficiency at 800 degrees C, and bauxite is at 700 degrees C. The adsorption efficiencies of the three sorbents for the four heavy metals all follow the sequence of Pb > Cu > Cr > Cd. The presence of inorganic chloride (NaCl) and sulfate (Na2SO4) increases the adsorption efficiency of the sorbents, but organic chloride PVC decreases the adsorption efficiency.

Adsorption↗
PubMed1998

Visual field defect after pars plana vitrectomy.

OBJECTIVE: This study aimed to report the occurrence of visual field defects after pars plana vitrectomy (PPV) for the treatment of each of the following conditions: macular hole (MH), subretinal neovascular membrane (SRNVM), and epiretinal membrane proliferation (EMP). This study also aimed to speculate on the pathogenic mechanisms for the observed field defects. DESIGN: Noncomparative case series. PARTICIPANTS: The study included 48 subjects (50 eyes). Twenty-one of the 50 eyes had stage III MH, 13 eyes had SRNVM, and 16 eyes had EMP. TESTING: Goldmann kinetic perimetry was performed postoperatively. MAIN OUTCOME MEASURE: Visual field defects. RESULTS: Nine (18%) of the 50 eyes had visual field defects. Four (19%) of the 21 eyes with MH and 5 (38%) of the 13 eyes with SRNVM had visual field defects. Of the 16 patients who had epiretinal membrane peeling, none had a visual field defect. An air-fluid exchange had been performed in all patients found to have a postvitrectomy field defect. The difference in rate of visual field defects in eyes that had air-fluid exchange (EMP group) was statistically significant (P < 0.05, chi-square). No significant correlation was found between visual field defect and preoperative intraocular pressure, postoperative intraocular pressure, patient's age, and iatrogenic detachment of the vitreous cortex. The field defects identified were altitudinal (2 eyes), baring of the blind spot (1 eye), inferotemporal (3 eyes), inferonasal (2 eyes), and superonasal (1 eye). CONCLUSIONS: Central and peripheral visual field defects may occur after PPV for the treatment of MHs or SRNVMs. Air-fluid exchange procedure was the common denominator in all of the patients found to have visual field deficit. The etiology is likely to be trauma to the optic nerve region during the air-fluid exchange procedure.

Adult↗
PubMed1998

Detection of fetal red cells in fetomaternal hemorrhage using a fetal hemoglobin monoclonal antibody by flow cytometry.

BACKGROUND: The laboratory determination of the level of fetal cells in maternal circulation remains an important support in the obstetrical management of women with suspected uterine trauma and in the proper dose administration of anti-D for prevention of Rh hemolytic disease of the newborn. Limitations in the sensitivity and precision of the widely used manual Kleihauer-Betke test have prompted an increased utilization of flow cytometric methods for fetal cell detection in maternal blood samples. STUDY DESIGN AND METHODS: Murine monoclonal antibodies directed against fetal hemoglobin (HbF) were developed, conjugated to fluorescein isothiocyanate, and used in a multiparametric flow cytometric assay developed for the quantitation of fetal red cells. A rapid intracellular staining method using brief glutaraldehyde fixation and Triton X-100 permeabilization prior to monoclonal antibody incubation was developed, along with optimization of the flow cytometric analysis protocol for the analysis of 50,000 cells. The performance of the assay was assessed for linearity and precision and correlated with the Kleihauer-Betke acid elution method. RESULTS: The anti-HbF flow cytometric method showed good correlation with the Kleihauer-Betke method (r2 = 0.86) and superior precision with a CV < 15 percent for blood samples with > 0.1 percent fetal cells. Analysis of 150 blood samples from nonpregnant adults, including individuals with elevated HbF due to hemoglobinopathies and hereditary persistence of HbF, gave a mean value of 0.02 percent fetal cells, and all results were less than 0.1 percent. CONCLUSIONS: The anti-HbF flow cytometric method for detection of fetal cells offers a simple, reliable, and more precise alternative to the Kleihauer-Betke manual technique for the assessment of fetomaternal hemorrhage. The method has additional potential applications for the study of HbF levels or frequency of adult red cells with low levels of HbF (F cells) in individuals with hemoglobinopathies.

Adult↗
PubMed1998

The relationship between the quantity of heavy metal and PAHs in fly ash.

Heavy metal and polycyclic aromatic hydrocarbons (PAHs) in flue gas have received considerable attention in recent years due to their mutagenic or carcinogenic properties. The present study is carried out to investigate the influence of the quantity of heavy metals on PAHs formation in fly ash. A fluidized bed incinerator was used in this experiment to obtain fly ash of chemical similarity by incinerating various compositions of waste. The obtained fly ash, both with and without heavy metal, were used to adsorb the PAHs in the flue gas and to investigate the formation of PAHs in fly ash. The results indicate that carbon and heavy metals most greatly influence the formation of PAHs in the fly ash. Carbon is absorptive; heavy metals encourage not only absorption of PAHs but also catalyze PAHs formation.

Air Pollutants, Occupational↗