Biomedical subjects

S C Chen

Publications and source records attributed to S C Chen.

At least 55 records · Page 3Linked to original sources

PubMed2001

The relationship between FTL and NA, DMV or CVLM in central cardiovascular control.

The aim of the present study was to examine the relationship between the lateral tegmental field (FTL), a cardioinhibitory area, with other cardioinhibitory areas, i.e., the ambiguus nucleus (NA) and the dorsal motor nucleus of vagus (DMV) and the caudal ventrolateral medulla (CVLM), a vasopressor inhibitory area. In 55 cats anesthetized with chloralose (40 mg/kg) and urethane (400 mg/kg), the cardiovascular responses of heart rate (HR), systemic arterial blood pressure (SAP) and vertebral nerve activity (VNA) were recorded. The FTL, NA, DMV and CVLM were identified first by stimulation (rectangular pulses in 80 Hz, 0.5 ms, 50-100 microA) and then confirmed by microinjection of sodium glutamate (Glu, 0.25M, 70 nl). In studying the influence of NA, DMV, or CVLM lesion on the Gluinduced responses in FTL, kainic acid (KA, 24 mM, 100 nl) was microinjected into the NA, DMV or CVLM. FTL stimulation produced an average decrease of HR by 55%. After KA lesioning of the ipsilateral NA or the DMV, the decreased HR induced by FTL was significantly diminished. After subsequent lesion of the contralateral DMV or NA, the bradycardia of FTL was abolished. The reduction of resting HR was more intense after lesioning the NA than DMV and with the left side more than that of the right side. These studies suggest that the cardioinhibitory responses of FTL are mediated through both NA and DMV with predominance of the former, while the hypotensive effect of FTL is mediated through CVLM. The precise pathway responsible for the FTL-induced bradycardia and hypotension is to be determined.

Animals↗

PubMed2001

Disruption of neutrophil migration in a conditional transgenic model: evidence for CXCR2 desensitization in vivo.

We developed transgenic mice conditionally expressing the neutrophil chemoattracting chemokine KC and the beta-galactosidase gene in multiple tissues. In these transgenic mice, doxycycline treatment induced a strong up-regulation in the expression of KC in several tissues, including heart, liver, kidney, skin, and skeletal muscle. Expression of KC within these tissues led to a rapid and substantial increase in the serum levels of KC (serum KC levels were higher than 200 ng/ml 24 h after treatment). Accordingly, beta-galactosidase expression was also detected after injection of doxycycline and was highest in skeletal muscle, pancreas, and liver. Surprisingly, despite expression of KC in multiple tissues, no neutrophil infiltration was observed in any of the tissues examined, including skin. Doxycycline treatment of nontransgenic mice grafted with transgenic skin caused dense neutrophilic infiltration of the grafts, but not the surrounding host skin, indicating that the KC produced in transgenic tissues was biologically active. In separate experiments, neutrophil migration toward a localized source of recombinant KC was impaired in animals overexpressing KC but was normal in response to other neutrophil chemoattractants. Analysis of transgenic neutrophils revealed that high concentrations of KC in transgenic blood had no influence on L-selectin cell surface expression but caused desensitization of the receptor for KC, CXCR2. These results confirm the neutrophil chemoattractant properties of KC and provide a mechanistic explanation for the paradoxical lack of leukocyte infiltration observed in the presence of elevated concentrations of this chemokine.

Animals↗

PubMed2001

Ubiquitous transgenic expression of the IL-23 subunit p19 induces multiorgan inflammation, runting, infertility, and premature death.

p19, a molecule structurally related to IL-6, G-CSF, and the p35 subunit of IL-12, is a subunit of the recently discovered cytokine IL-23. Here we show that expression of p19 in multiple tissues of transgenic mice induced a striking phenotype characterized by runting, systemic inflammation, infertility, and death before 3 mo of age. Founder animals had infiltrates of lymphocytes and macrophages in skin, lung, liver, pancreas, and the digestive tract and were anemic. The serum concentrations of the proinflammatory cytokines TNF-alpha and IL-1 were elevated, and the number of circulating neutrophils was increased. In addition, ubiquitous expression of p19 resulted in constitutive expression of acute phase proteins in the liver. Surprisingly, liver-specific expression of p19 failed to reproduce any of these abnormalities, suggesting specific requirements for production of biologically active p19. Bone marrow transfer experiments showed that expression of p19 by hemopoietic cells alone recapitulated the phenotype induced by its widespread expression, pointing to hemopoietic cells as the source of biologically active p19. These findings indicate that p19 shares biological properties with IL-6, IL-12, and G-CSF and that cell-specific expression is required for its biological activity.

Acute-Phase Proteins↗

PubMed2001

Lactococcus garvieae infection in the giant freshwater prawn Macrobranchium rosenbergii confirmed by polymerase chain reaction and 16S rDNA sequencing.

An epizootic bacterial infection in the giant freshwater prawn Macrobranchium rosenbergii occurred in Taiwan from May to June 1999. The cumulative mortality was approximately 30 to 75%. The diseased prawns showed opaque and whitish muscles and were approximately 2 mo old with total lengths from 5 to 6 cm. Histopathologically, they showed marked edema and necrotic lesions with inflammation in the muscles and hepatopancreas. Bacteria isolated using brain heart infusion medium or tryptic soy agar were Gram-positive and ovoid. Three isolates from diseased prawns at different farms were tested using the API 20 Strepsystem and conventional tests and identified as Lactococcus garvieae. Experimental infections with these isolates gave gross signs and histopathological changes similar to those seen in the naturally infected prawns. The LD50 value of isolate MR1 was 6.6 x 10(5) colony forming units/prawn. Identification of MR1 was confirmed by a PCR assay for L. garvieae that gave the expected amplicon of 1100 bp. In addition, its 16S rDNA sequence (GenBank accession number AF283499) gave 99% sequence identity to Enterococcus seriolicida (synonym L. garvieae; GenBank accession number AF061005). This is the first report of confirmed L. garvieae infection in prawn aquaculture.

Animals↗

PubMed2001

Cost-effectiveness analyses: a basic overview for dermatologists.

BACKGROUND: In the current age of limited health care resources, cost-effectiveness analyses are important since they provide information that can be used by decision-makers for prioritizing and setting health care policies. OBJECTIVE: This article gives a conceptual overview of cost-effectiveness analyses (CEAs) by discussing their strengths and limitations, introducing the calculations and variables involved, and outlining the issues in interpreting CEAs using dermatological examples. CONCLUSION: Cost-effectiveness analyses are important tools that dermatologists can use to compare medical interventions using costs, effectiveness, and health outcomes.

Cost-Benefit Analysis↗

PubMed2001

Temporal trends and molecular epidemiology of HIV-1 infection in Taiwan from 1988 to 1998.

Eight hundred and seventy-nine HIV-1-infected patients (comprising 46% of reported HIV-1/AIDS cases in Taiwan) were recruited for this study of the molecular epidemiology of HIV-1 in Taiwan from 1988 to 1998. HIV-1 subtypes were determined using a modified peptide-enzyme immunoassay complemented with DNA sequencing and phylogenetic analysis. Of the 807 HIV-1 infected men, 68.2% were infected with HIV-1B, 29.5% with HIV-1 circulating recombinant form (CRF)01_AE and 2.3% with other subtypes. Of the 72 HIV-1-infected women, 72.2% were infected with HIV-1 CRF01_AE, 13.9% with HIV-1B, and 13.9% with other subtypes. All of 8 foreign-born, Southeast Asian women and 6 of 7 (85.7%) Taiwan-native female commercial sex workers were infected with HIV-1 CRF01_AE. Fourteen of the 33 (42.4%) heterosexual married men with CRF01_AE had transmitted HIV-1 to their wives, whereas only 1 of 17 (5.9%) men with HIV-1 B had transmitted HIV-1 to their spouses (p < .01). Of 18 heterosexual male injecting drug users, 1 of 12 (8.5%) with HIV-1B and 5 of 6 (83.3%) with HIV-1 CRF01_AE had had sexual contact with female commercial sex workers (p < .01). Therefore, in this population, CRF01_AE was preferentially associated with heterosexual risk groups, a finding compatible with differences in transmission capability between B and non-B subtypes.

Adult↗

PubMed2001

Impaired pulmonary host defense in mice lacking expression of the CXC chemokine lungkine.

Lungkine (CXCL15) is a novel CXC chemokine that is highly expressed in the adult mouse lung. To determine the biologic function of Lungkine, we generated Lungkine null mice by targeted gene disruption. These mice did not differ from wild-type mice in their hematocrits or in the relative number of cells in leukocyte populations of peripheral blood or other tissues, including lung and bone marrow. However, Lungkine null mice were more susceptible to Klebsiella pneumonia infection, with a decreased survival and increased lung bacterial burden compared with infected wild-type mice. Histologic analysis of the lung and assessment of leukocytes in the bronchioalveolar lavage revealed that neutrophil numbers were normal in the lung parenchyma, but reduced in the airspace. The production of other neutrophil chemoattractants in the Lungkine null mice did not differ from that in wild-type mice, and neutrophil migration into other tissues was normal. Taken together, these findings demonstrate that Lungkine is an important mediator of neutrophil migration from the lung parenchyma into the airspace.

Animals↗

PubMed2001

A comparison of dermatologists' and primary care physicians' accuracy in diagnosing melanoma: a systematic review.

OBJECTIVE: To compare the accuracy of dermatologists and primary care physicians (PCPs) in identifying pigmented lesions suggestive of melanoma and making the appropriate management decision to perform a biopsy or to refer the patient to a specialist. DATA SOURCES: Studies published between January 1966 and October 1999 in the MEDLINE, EMBASE, and CancerLit databases; reference lists of identified studies; abstracts from recent conference proceedings; and direct contact with investigators. Medical subject headings included melanoma, diagnosis, screening, primary care, family practitioner, general practitioner, internal medicine, dermatologist, and skin specialist. Articles were restricted to those involving human subjects. STUDY SELECTION: Studies that presented sufficient data to determine the sensitivity and specificity of dermatologists' or PCPs' ability to correctly diagnose lesions suggestive of melanoma and to perform biopsies on or refer patients with such lesions. DATA EXTRACTION: Two reviewers independently abstracted data regarding the sensitivity and specificity of the dermatologists and PCPs for diagnostic and biopsy or referral accuracy. Disagreements were resolved by discussion. The quality of the studies was also evaluated. DATA SYNTHESIS: Thirty-two studies met inclusion criteria; 10 were prospective studies. For diagnostic accuracy, sensitivity was 0.81 to 1.00 for dermatologists and 0.42 to 1.00 for PCPs. None of the studies reported specificity for dermatologists; one reported specificity for PCPs (0.98). For biopsy or referral accuracy, sensitivity ranged from 0.82 to 1.00 for dermatologists and 0.70 to 0.88 for PCPs; specificity, 0.70 to 0.89 for dermatologists and 0.70 to 0.87 for PCPs. Receiver operating characteristic curves for biopsy or referral ability were inconclusive. CONCLUSIONS: The published data are inadequate to demonstrate differences in dermatologists' and PCPs' diagnostic and biopsy or referral accuracy of lesions suggestive of melanoma. We offer study design suggestions for future studies.

Clinical Competence↗

PubMed2001

Coil occlusion of patent ductus arteriosus associated with right aortic arch.

Two children with patent ductus arteriosus and associated right aortic arch underwent successful transcatheter coil occlusion. Recognition of ductal anatomy and ensuring that no symptomatic vascular ring is present are important prior to embarking on ductal occlusion. It is concluded that coil occlusion of patent ductus arteriosus in association with right aortic arch is feasible, safe, and effective.

Abnormalities, Multiple↗

PubMed2001

Differential and prolonged expression of Fos-lacZ and Jun-lacZ in neurons, glia, and muscle following sciatic nerve damage.

Fos-lacZ and Jun-lacZ transgenic mice were used to assess the involvement of immediate-early genes in the axotomy-transcription coupling pathway triggered by sciatic nerve injury in neonates and adults. Nerve transection transiently induced Fos-lacZ in degenerating (neonatal) and regenerating (adult) motor, but not sensory, neurons. In contrast, Jun-lacZ was persistently up-regulated in both axotomized motor and sensory neurons in neonates and adults. Thus, expression of these genes did not predict neuronal death or survival. As Jun-lacZ was induced in some undamaged sensory neurons, this gene can be regulated by direct (axotomy) and indirect (transcellular) mechanisms. Indirect mechanisms also mediate expression of both genes in denervated muscle, Schwann cells in the distal and proximal stumps, and satellite cells in the DRG following axotomy. Thus, either these genes may regulate distinct sets of target genes in different cell types or they may subserve a single mechanism that is common to many cell types.

Animals↗

PubMed2001

Hyperthermic pretreatment decreases microvascular protein leakage and attenuates hypotension in anaphylactic shock in rats.

Systemic anaphylaxis is a life-threatening allergic reaction and its pathologic conditions, such as edema, bronchospasm, and hypotension, have been attributed to release of vasoactive mediators. Heat shock protein (HSP) is known to play a protective role in living cells under various stresses. In these studies, we investigated the protective role of heat shock response in anaphylactic shock, focusing on changes of blood pressure (BP) and vascular permeability. Adult sensitized rats were injected intravenously with Evans blue (EB) and challenged with bovine serum albumin (BSA). The rats were treated with whole-body hyperthermia at 41.5 +/- 0.5 degrees for 15 min 24 h before BSA challenge. Vascular protein leakage in tissues was analyzed with the EB technique. The results showed that BSA challenge induced EB extravasation in all sensitized rats. EB values (EB/tissue; microg/g) in heart and lung (112.3 +/- 41 and 244.4 +/- 90.6; mean +/- SD; n = 6) in the nonheated rats were significantly higher than those (33.4 +/- 23.3 and 103.4 +/- 63.9; n = 9) in the heated rats (P < 0.05). The results showed that BSA challenge caused BP to fall drastically in the sensitized rats. BP in the heated rats was significantly higher than BP in the nonheated rats from 4 to 15 min during anaphylactic shock (P < 0.001). Inducible HSP72 appeared overexpressed in heart, lung, and liver tissue in the heated rats tested by Western immunoblotting. The results indicate that reduction of increased protein leakage and attenuation of hypotension may result from induction of HSP by whole-body hyperthermia.

Anaphylaxis↗

PubMed2001

Leukocytes expressing green fluorescent protein as novel reagents for adoptive cell transfer and bone marrow transplantation studies.

Transgenic mice expressing green fluorescent protein (GFP) were generated to provide a source of labeled leukocytes for cell transfer studies. The transgene comprises the GFP coding region under the transcriptional control of the chicken ss-actin promoter and human cytomegalovirus enhancer. Mice expressing this GFP transgene were generated in the B6D2 and in the 129SvEv backgrounds. Flow cytometric analysis of cells from the blood, spleen, and bone marrow of these transgenic mice revealed that most leukocytes, including dendritic cells and memory T cells, express GFP. In allogeneic cell transfers, donor GFP+ splenocytes were detected in the spleen and mesenteric lymph nodes of recipient mice within 2 hours after transfer and for at least 9 days thereafter. In syngeneic experiments using 129-derived GFP+ donor splenocytes, donor cells were detected in multiple tissues of 129 recipients from 2 hours to 3 weeks after transfer. In bone-marrow transplantation experiments using irradiated allogeneic recipients, the percent of GFP+ donor cells in recipients at 3 weeks was comparable to that seen in similar tissues of GFP+ donor mice. These data demonstrate that GFP+ transgenic mice provide a ready source of GFP-expressing primary cells that can be easily monitored after their transfer to recipient animals.

Adoptive Transfer↗

PubMed2001

Application of microbial enumeration technique to evaluate the occurrence of natural bioremediation.

Natural bioremediation is believed to be the major processes that account for both containment of the petroleum-hydrocarbon plume and reduction of the contaminant concentrations. In this study, the feasibility of applying the microbial enumeration technique was assessed for natural biodegradation evaluation at three selected gasoline spill sites. At each site, two monitor wells were installed along the groundwater flow, and one multilevel sampler (MLS) was installed to delineate the vertical distribution of the contaminant plume. Two continuous soil cores were collected at each site to evaluate the horizontal distribution of the microbial activity. Soil samples were used for microbial enumeration, grain-size distribution analysis, and sediment extraction. In situ tracer study was performed using 1,2,4-trimethylbenzene (1,2,4-TMB) as the tracer to study the efficiency of contaminant biodegradation. Investigation results demonstrate the agreement between microbial enumeration and other evaluation techniques for natural bioremediation (e.g., geochemical indicator analysis, tracer study). Results suggest that the microbial enumeration is useful in assessing the occurrence, efficiency, and status of the bioremediation. Because this technique provides insight into factors controlling contaminant biodegradation, it could be performed as the supplemental method for natural bioremediation evaluation at petroleum-hydrocarbon spill sites.

Benzene Derivatives↗

PubMed2001

Development of a biobarrier for the remediation of PCE-contaminated aquifer.

The industrial solvent tetrachloroethylene (PCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system, which includes a peat layer to enhance the anaerobic reductive dechlorination of PCE in situ. Peat was used to supply primary substrate (electron donor) continuously. A laboratory-scale column experiment was conducted to evaluate the feasibility of this proposed system or PCE removal. This experiment was performed using a series of continuous-flow glass columns including a soil column, a peat column, followed by two consecutive soil columns. Anaerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for PCE biodegradation. Simulated PCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for PCE and its degradation byproducts (trichloroethylene (TCE), cis-dichloroethylene (cis-DCE), vinyl chloride (VC), ethylene (ETH), and ethane). Results show that the decrease in PCE concentrations and production of PCE byproducts were observed over a 65-day operating period. Up to 98%, of PCE removal efficiency was obtained in this passive system. Results indicate that the continuously released organics from peat column enhanced PCE biotransformation. Thus, the developed biobarrier treatment scheme has the potential to be developed into a cost-effective in situ PCE-remediation technology, and can be utilized as an interim step to aid in system scale-up.

Biotransformation↗

PubMed2001

Evaluation of TCDD biodegradability under different redox conditions.

Polychlorinated dibenzo-p-dioxins have been generated as unwanted by-products in many industrial processes. Although their widespread distribution in different environmental compartments has been recognized, little is known about their fate in the ultimate environment sinks. The highly stable dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man. In this laboratory microcosm study, TCDD bioavailability was evaluated under five reduction/oxidation (redox) conditions including aerobic biodegradation, aerobic cometabolism, methanogenesis, iron reduction, and reductive dechlorination. Activated sludge and aquifer sediments from a TCDD and a pentachlorophenol (PCP) contaminated site were used as the inocula. Acetate, sludge cake, and cane molasses were used as the primary substrates (carbon sources) in cometabolism and reductive dechlorination microcosms. After a 90-day incubation period, microcosms constructed under reductive dechlorination conditions were the only treatment showing promising remediation results. The highest TCDD degradation rate [up to 86% of TCDD removal (with an initial concentration of 96 microg/kg of soil)] was observed in the microcosms with anaerobic activated sludge as the microbial inocula and sludge cakes as the primary substrates. Except for reductive dechlorination microcosms, no significant TCDD removal was observed in the microcosms prepared under other conditions. Thus, application of an effective primary substrate to enhance the reductive dechlorination process is a feasible method for TCDD bioremediation. Bioremediation expense can be significantly reduced by the supplement of some less expensive alternative substrates (e.g., sludge cakes, cane molasses). Results would be useful in designing a scale-up in situ or on-site bioremediation system such as bioslurry reactor for field application.

Bacteria, Aerobic↗

PubMed2001

Laboratory column studies for evaluating a barrier system for providing oxygen and substrate for TCE biodegradation.

The industrial solvent trichloroethylene (TCE) is among the most ubiquitous chlorinated compounds found in groundwater contamination. The objective of this study was to develop a biobarrier system containing oxygen-organic releasing material to enhance the aerobic cometabolism of TCE in situ. The oxygen-organic material, which contains calcium peroxide and peat, is able to release oxygen and primary substrates continuously upon contact with water. Batch experiments were conducted to design and identify the components of the oxygen-organic releasing material, and evaluate the oxygen and organic substrate (presented as COD equivalent) release from the designed oxygen-organic material. The observed oxygen and chemical oxygen demand (COD) release rates were approximately 0.0246 and 0.052 mg/d/g of material, respectively. A laboratory-scale column experiment was then conducted to evaluate the feasibility of this proposed system for the bioremediation of TCE-contaminated groundwater. This system was performed using a series of continuous-flow glass columns including a soil column, an oxygen-organic material column, followed by two consecutive soil columns. Aerobic acclimated sludges were inoculated in all three soil columns to provide microbial consortia for TCE biodegradation. Simulated TCE-contaminated groundwater with a flow rate of 0.25 l/day was pumped into this system. Effluent samples from each column were analyzed for TCE and other indicating parameters (e.g., pH, dissolved oxygen). Results show that the decreases in TCE concentrations were observed over a 4-month operating period. Up to 99% of TCE removal efficiency was obtained in this passive system. Results indicate that the continuously released oxygen and organic substrates from the oxygen-organic materials enhanced TCE biotransformation. Thus, the biobarrier treatment scheme has the potential to be developed into an environmentally and economically acceptable remediation technology.

Biodegradation, Environmental↗

PubMed2001

Modified approach of hand-assisted laparoscopic nephroureterectomy for transitional cell carcinoma of the upper urinary tract.

Objectives. To report a modified approach for hand-assisted laparoscopic nephroureterectomy (HALNU).Methods. Seven patients with localized transitional cell carcinoma of the upper urinary tract underwent unilateral HALNU. Patients were placed in a 60 degrees oblique position during the entire procedure. Via a 7-cm Gibson incision on the lesion side, the distal ureterectomy and bladder cuff excision were done by an open method without opening the bladder. Then, with the surgeon's hand inserted into the peritoneal cavity by way of the same wound, HALNU was performed with two to three additional laparoscopic ports. The perioperative parameters were compared with those of 15 cases of conventional open nephroureterectomy.Results. Patients in the HALNU group had significantly less mean blood loss (140 versus 455 mL) and earlier resumption of oral intake (33 versus 61 hours), required fewer narcotics (38 versus 70 mg of morphine sulfate equivalent), and were discharged earlier (7.33 versus 9.1 days), with a faster convalescence to normal activity (3.7 versus 5.6 weeks; all P < 0.05). The total mean surgical time was 3.7 hours for the HALNU group.Conclusions. Our approach used the same incision to both excise the distal ureter and apply the hand-assist device. It also preserved the benefits of the minimal invasiveness of laparoscopic surgery compared with its open counterpart.

Aged↗

PubMed2001

Correlations between theoretical and experimental determination of heat of formation of certain aliphatic nitro compounds.

Heats of formation of energetic materials were calculated by Dewar's AM1 and Stewart's PM3 methods. In order to compare the theoretical results with the experimental ones, some correlation models were proposed in this study. Correlations were evaluated by multivariable linear regression method, considering the number of nitro groups and the use of quadratic relations involving the number of carbon, hydrogen, nitrogen, and oxygen atoms. Results indicated very precise correlations. Based on these correlations, heats of formation of some aliphatic nitro compounds can be predicted at 95% predictive interval without experimental analysis.

Journal Article↗