Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 109 records · Page 6Linked to original sources

PubMed2002

A global livestock production and health atlas (GLiPHA) for interactive presentation, integration and analysis of livestock data.

An interactive electronic atlas has been developed with the purpose of providing a scaleable overview of spatial and temporal variation in animal production and health-related information for decision and policy makers in national and international institutions. The information contained in the atlas is currently managed and presented using the Key Indicators Mapping System (KIMS), and will also be integrated using the Key Indicators Database System (KIDS). Both systems were developed by the World Agricultural Information Centre of the FAO (FAO-WAICENT), the former as a stand-alone application and the latter for access via the Internet. Components of the atlas include vector maps, livestock disease and production databases, rules for country-level disease risk classification and 'disease cards' containing basic background information on diseases included in the atlas. The disease data is currently based primarily on Office International des Epizooties (OIE) disease reports, and the livestock production data on the FAO-WAICENT database. The atlas is highly interactive and allows visual presentation of information using maps, tables and charts. It also contains links to relevant resource information on the Internet. Diseases covered in the animal health layer include most OIE List A diseases and a subset of OIE List B diseases. Extensive analyses have been conducted to develop a set of qualitative and semi-quantitative criteria that allow improved disease status classifications based on 5-years cumulative OIE disease reports, and official disease control declarations. Classification rules were determined depending on the epidemiological features of each disease and considering spatial heterogeneity of disease presence in local regions.

Animal Diseases↗

PubMed2002

Polymorphonuclear leukocyte activation induces cerebral hypoperfusion in rats in the absence of previous ischemia-reperfusion damage.

We determined if activation of circulating neutrophils could influence local cerebral blood flow (lCBF) and cerebrovascular reactivity without previous ischemic endothelial activation. After intracarotid infusion of phorbol myristate acetate (PMA, twice in 30 min), Laser-Doppler measurements of lCBF in the parietal cortex of anesthetised rats showed a fall of 34% (P<0.05) at 30 min, but not in the vehicle group nor the group predepleted in polymorphonuclear leukocytes (PMNLs). Blood gases or arterial pressure did not change significantly in any group. The PMNL count fell by 78% at 30 min and reactivity to systemic hypercapnia by 58% at 30-60 min post infusion in the PMA group. These results show that activated PMNLs reduce lCBF and vasoreactivity in the absence of previous cerebral ischemia.

Animals↗

PubMed2002

Very fast hollow-atom decay processes in Xe30+-C60 collisions.

In Xe30+-C60 collisions at low velocity (0.2 a.u.<v<0.4 a.u.), very fast electron ejection is observed not only for frontal collisions but also for near C60 cage collisions. In frontal collisions, the exit-charge distributions obtained with three projectile velocities are reproduced using a multistep exponential decay model. A mean Auger rate of about 0.4 a.u. is estimated for the decay of hollow atoms during the very short interaction time (<3 fs).

Journal Article↗

PubMed2002

Evaluation of HER-2/neu gene amplification and protein expression in non-small cell lung carcinomas.

HER-2/neu gene amplification and cell surface overexpression are important factors in breast cancer for prognosis and prediction of sensitivity to anti-HER-2/neu monoclonal antibody therapy. In lung cancer, the clinical significance of HER-2/neu expression is currently under evaluation. We investigated 238 non-small lung carcinomas for HER-2/neu protein overexpression by immunohistochemistry using the HercepTest. We found 2+ or 3+ overexpression in 39 patients (16%), including 35% in adenocarcinomas and 20% in large cell carcinomas, but only 1% of squamous cell carcinomas. Marked (3+) overexpression was uncommon (4%). The association between protein expression and gene copy number per cell, as determined by fluorescence in situ hybridisation assay, was investigated in 51 of these NSCLC tumours. Twenty-seven tumours (53%) were negative by both tests. Marked (3+) protein expression and gene amplification were present in only 4% of samples. In 11 tumours (21%), gene gain was accompanied by chromosomal aneusomy and did not result in high protein levels while in 7 (14%) the score 2+ was associated with maximum number of signals per cell <9. The prognostic implication of HER-2/neu protein expression was studied in 187 surgically resected tumours. No statistical difference in survival was observed comparing patients with positive (2+/3+) and negative tumours (0/1+), although 3+ patients showed a tendency to shorter survival. The therapeutic implications of protein expression and gene amplification in lung cancer need to be examined in prospective clinical trials.

Aged↗

PubMed2002

Molecular characterization of a calcium binding translationally controlled tumor protein homologue from the filarial parasites Brugia malayi and Wuchereria bancrofti.

We have cloned homologues of the mammalian translationally controlled tumor protein (TCTP) from the human filarial parasites Wuchereria bancrofti and Brugia malayi. TCTP genes from B. malayi and W. bancrofti were expressed in a T7 promoter vector as histidine tagged fusion proteins. Both the recombinant B. malayi TCTP (rBm-TCTP) and recombinant W. bancrofti TCTP (rWb-TCTP) have a molecular mass of approximately 28 kDa with the histidine tag. Sequence analyses showed that there is a 98% similarity between the two filarial TCTPs at amino acid levels and are immunologically cross-reactive. Analysis of soluble proteins from various lifecycle stages of B. malayi suggested that the expression of Bm-TCTP might be differentially regulated and occurs in multimeric form. Recombinant TCTP were found to form multimers in solution under non-reducing conditions. The tendency for filarial TCTPs to become multimers was predicted by the presence of the Lupas coiled coil structure in their sequence. Despite the absence of a signal sequence, Bm-TCTP is present abundantly in the excretory/secretions (ES) of microfilariae. Characterization studies showed that both Bm- and Wb-TCTPs are calcium-binding proteins and have histamine-releasing function in vitro. When injected intraperitoneally both the filarial TCTPs induced inflammatory infiltration of eosinophils into the peritoneal cavity of mice suggesting that the filarial TCTPs may have a role in the allergic inflammatory responses associated with filarial infections.

Amino Acid Sequence↗

PubMed2002

Rotational behavior and electrophysiological effects induced by GABA(B) receptor activation in rat globus pallidus.

GABA is the major neurotransmitter used in the globus pallidus and there is evidence that GABA(B) receptors exist in this nucleus. Here we show that unilateral microinjection of baclofen, a GABA(B) receptor agonist, induced ipsilateral turning in Sprague-Dawley rats. This effect was prevented by preinjection of the GABA(B) receptor antagonist CGP55845A, which itself did not cause rotation. Thus, activation of GABA(B) receptor may suppress the activity of globus pallidus neurons, which is in line with the finding that the glutamate receptor antagonists (+/-)-2-amino-5-phosphonopentanoic acid and 6-cyano-7-nitroquinoxaline-2,3-dione also caused similar ipsilateral turning when injected into globus pallidus. Furthermore, in the presence of these glutamate receptor antagonists, injection of baclofen resulted in fewer rotations. To test the possibility that baclofen reduced glutamate release onto globus pallidus neurons, the effects of baclofen on miniature excitatory postsynaptic currents were studied in rat brain slices. Patch-clamp recordings showed that baclofen at 30 microM significantly reduced the frequency of the miniature excitatory postsynaptic currents. However, baclofen induced a weak outward current only in a minority of globus pallidus neurons. These pre- and postsynaptic effects of baclofen were reversed or prevented by CGP55845A. These results suggest that GABA(B) receptor in globus pallidus plays an important role in the regulation of movement by modulating glutamatergic inputs at a presynaptic site.

Animals↗

PubMed2002

Epidemiological study on obesity and its comorbidities in urban Chinese older than 20 years of age in Shanghai, China.

The aim of this work was to establish the prevalence of overweight and obesity and its associated comorbidities in a Chinese population older than 20 years of age. A group of 2776 randomly selected adults (20-94 years of age) living in the Huayang Community in Shanghai, China, were investigated between 1998 and 2000. Body weight, height, waist and hip circumferences and blood pressure were measured, as were fasting blood glucose, fasting insulin and lipid profile, as well as blood glucose 2 h after a glucose load, and a 75-g glucose tolerance test was performed. The prevalence of overweight was 29.5% and obesity was 4.3%, with a greater number of women being obese than men. More than one-third of the population had abnormal lipid levels. Impaired glucose regulation (IGR) occurred in 10.8%; and 9.8% of the population were classified as having type 2 diabetes mellitus. Hypertension was present in 58.4% of this population. About 21% and 29.3% of the population suffered from high total cholesterol and high triglyceride, respectively. The prevalence of metabolic syndrome was 10.2%. The prevalence of diabetes, IGR and metabolic syndrome increased progressively in association with a body mass index (BMI) of >23 kg m(-2). Hence, although the prevalence of obesity is low in this Chinese population, higher BMI and waist circumference values are clearly associated with an increasing prevalence of comorbidities. The absolute risk of having diabetes, IGR and metabolic syndrome is high in adults with a BMI of > or =23 kg m(-2).

Adult↗

PubMed2002

B7 family molecules: novel immunomodulators at the maternal-fetal interface.

The placenta utilizes both active and passive mechanisms to evade rejection by the maternal immune system. Recently, the mRNA for two newly cloned members of the B7 family of immunomodulatory cell-associated proteins have been identified in the human term placenta. In this article, we review the current knowledge of the B7 family member B7-H1, and discuss how it may participate in modulation of the maternal immune system at the maternal-fetal interface. B7-H1 has been found to possess immunostimulatory or immunoinhibitory properties, and immunohistological examination of first trimester and term placenta has revealed that this protein is abundant in the placenta. B7-H1 is highly expressed by both the syncytiotrophoblast and extravillous cytotrophoblast, both of which lie in direct contact with maternal blood and tissue. Further, treatment of the choriocarcinoma cell line, JEG-3, with recombinant human interferon (IFN)-gamma resulted in a dose-dependent increase in the abundance of the message for B7-H1, suggesting that IFN-gamma could regulate expression of B7-H1 by the trophoblast. These studies document that the positioning of B7-H1 at the maternal-fetal interface is such that it could participate in suppression of activated maternal leukocytes.

Adjuvants, Immunologic↗

PubMed2002

A COUP-TF/Svp homolog is highly expressed during vitellogenesis in the mosquito Aedes aegypti.

In the mosquito Aedes aegypti, vitellogenesis is activated via an ecdysteroid hormonal cascade initiated by a blood meal. The functional ecdysone receptor is a heterodimer composed of the ecdysone receptor (EcR) and ultraspiracle, the homolog of the retinoid X receptor. The precise tuning of this hormonal response requires participation of both positive and negative transcriptional regulators. In Drosophila, Svp, a homolog of chicken ovalbumin upstream promoter transcription factor (COUP-TF), inhibits ecdysone receptor complex-mediated transactivation in vitro and in vivo. Here we report the cloning and characterization of the Svp homolog in mosquito Aedes aegypti, AaSvp. It possesses a high degree of amino acid sequence similarity to the members of the COUP-TF/Svp subfamily. AaSvp transcripts and protein are present in the fat body at high levels from the state of arrest to about 60 h post blood meal. AaSvp binds strongly to a variety of direct repeats of the sequence AGGTCA, but weakly to inverted repeats such as hsp27 EcRE. Transient transfection assays in Drosophila S2 cells showed that AaSvp was able to repress 20-hydroxyecdysone (20E)-dependent transactivation mediated by the mosquito ecdysteroid receptor complex. These data suggest that AaSvp negatively regulates the 20E signaling in the fat body during mosquito vitellogenesis.

Aedes↗

PubMed2001

Oxidative DNA damage in prostate cancer patients consuming tomato sauce-based entrees as a whole-food intervention.

BACKGROUND: Human prostate tissues are vulnerable to oxidative DNA damage. The risk of prostate cancer is lower in men reporting higher consumption of tomato products, which contain high levels of the antioxidant lycopene. We examined the effects of consumption of tomato sauce-based pasta dishes on lycopene uptake, oxidative DNA damage, and prostate-specific antigen (PSA) levels in patients already diagnosed with prostate cancer. METHODS: Thirty-two patients with localized prostate adenocarcinoma consumed tomato sauce-based pasta dishes for the 3 weeks (30 mg of lycopene per day) preceding their scheduled radical prostatectomy. Serum and prostate lycopene concentrations, serum PSA levels, and leukocyte DNA oxidative damage (ratio of 8-hydroxy-2'-deoxyguanosine [8-OHdG] to 2'-deoxyguanosine [dG]) were assessed before and after the dietary intervention. DNA oxidative damage was assessed in resected prostate tissue from study participants and from seven randomly selected prostate cancer patients. All statistical tests were two-sided. RESULTS: After the dietary intervention, serum and prostate lycopene concentrations were statistically significantly increased, from 638 nM (95% confidence interval [CI] = 512 to 764 nM) to 1258 nM (95% CI = 1061 to 1455 nM) (P<.001) and from 0.28 nmol/g (95% CI = 0.18 to 0.37 nmol/g) to 0.82 nmol/g (95% CI = 0.57 to 1.11 nmol/g) (P <.001), respectively. Compared with preintervention levels, leukocyte oxidative DNA damage was statistically significantly reduced after the intervention, from 0.61 8-OHdG/10(5) dG (95% CI = 0.45 to 0.77 8-OHdG/10(5) dG) to 0.48 8-OHdG/ 10(5) dG (95% CI = 0.41 to 0.56 8-OHdG/10(5) dG) (P =.005). Furthermore, prostate tissue oxidative DNA damage was also statistically significantly lower in men who had the intervention (0.76 8-OHdG/10(5) dG [95% CI = 0.55 to 0.96 8-OHdG/10(5) dG]) than in the randomly selected patients (1.06 8-OHdG/10(5) dG [95% CI = 0.62 to 1.51 8-OHdG/10(5) dG]; P =.03). Serum PSA levels decreased after the intervention, from 10.9 ng/mL (95% CI = 8.7 to 13.2 ng/mL) to 8.7 ng/mL (95% CI = 6.8 to 10.6 ng/mL) (P<.001). CONCLUSION: These data indicate a possible role for a tomato sauce constituent, possibly lycopene, in the treatment of prostate cancer and warrant further testing with a larger sample of patients, including a control group.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

The structure of anti-Gal immunoglobulin genes in naïve and stimulated Gal knockout mice.

BACKGROUND: Naturally occurring antibodies (Nabs) that bind to terminal galactose alpha1,3-galactose carbohydrate structures (Gal) are present in humans and Old World monkeys but are negatively regulated in other mammalian species because they express Gal epitopes on their cell surfaces. A Gal knockout mouse (Gal-/-) model, generated by homologous disruption of alpha1,3-galactosyltransferase gene, is capable of producing natural anti-Gal Abs. METHODS: To study the genetic control of the anti-Gal response, we have generated anti-Gal hybridomas from Gal-/- mice and analyzed VH genes of anti-Gal Abs from naïve animals and from mice stimulated by rat heterotopic heart transplantation. RESULTS: Six immunoglobulin (Ig)M anti-Gal hybridomas derived from naïve Gal-/- mice exhibited anti-Gal binding activity with some cross-reactivity to related carbohydrate structures. These naïve anti-Gal Abs used five different VH genes in a germline configuration. Anti-Gal IgM hybridomas isolated after a rat heterotopic heart xenograft (4 days) utilized germline VH gene segments from the VH7183 family and exhibited less cross-reactivity. In contrast to mice 4 days after xenograft, we have predominantly isolated IgG anti-Gal hybridomas from mice 21 days after rat heterotopic heart xenografts, indicating an isotype switch. Nine of the IgG anti-Gal hybridomas secreted IgG3 subclass and one produced IgG1. Sequence analysis of the VH gene usage from the induced anti-Gal IgG antibodies demonstrated a restricted gene utilization (VHJ606-V14A). CONCLUSION: Our results demonstrate that the anti-Gal response in naïve Gal-/- mice is encoded by multiple germline progenitors. In response to a xenograft, the induced anti-Gal Abs exhibited a restricted gene usage and somatic mutations, indicating a positive selection.

Animals↗

PubMed2001

The genome of the natural genetic engineer Agrobacterium tumefaciens C58.

The 5.67-megabase genome of the plant pathogen Agrobacterium tumefaciens C58 consists of a circular chromosome, a linear chromosome, and two plasmids. Extensive orthology and nucleotide colinearity between the genomes of A. tumefaciens and the plant symbiont Sinorhizobium meliloti suggest a recent evolutionary divergence. Their similarities include metabolic, transport, and regulatory systems that promote survival in the highly competitive rhizosphere; differences are apparent in their genome structure and virulence gene complement. Availability of the A. tumefaciens sequence will facilitate investigations into the molecular basis of pathogenesis and the evolutionary divergence of pathogenic and symbiotic lifestyles.

Agrobacterium tumefaciens↗

PubMed2001

Cloning, expression, and crystallization of the fusion protein of Newcastle disease virus.

We have recently reported the X-ray crystal structure of a fragment of the fusion protein (F) of Newcastle disease virus (NDV). This work describes the methodology involved in the production and crystallization of that protein in recombinant form. The full-length cDNA of NDV-F was cloned and the ectodomain expressed in both CHO-K1 and Lec-3.2.8.1 cells. The recombinant protein, secreted as a single-chain polypeptide F0', was purified using a c-myc antibody affinity column followed by gel filtration chromatography. Electron microscopic imaging showed the F0' product to consist of unaggregated club-shaped particles. Trypsin treatment of F0' could be used to produce disulfide-linked F2 and F1' chains. However, imaging revealed extensive rosette-like aggregation of the trypsin-treated material, indicative of a conformational change. Only the non-trypsin-treated product was thus suitable for crystallization and two crystal forms were obtained, diffracting to ca. 3.5 and 4.0 A, respectively. Both crystal forms were used in the structure determination.

Amino Acid Sequence↗

PubMed2001

Primitive deuterostomes from the Chengjiang Lagerstätte (Lower Cambrian, China).

Cambrian fossil-Lagerstätten (sites of exceptional fossil preservation), such as those from Chengjiang (Lower Cambrian) and the Burgess Shale (Middle Cambrian), provide our best window into the Cambrian 'explosion'. Such faunas are known from about 40 localities, and have yielded a widely disparate series of taxa ranging from ctenophores to agnathan fish. Recent excavations of the Chengjiang fossil-Lagerstätte, known from a series of sites near Kunming in Yunnan, south China, have resulted in the discovery of several new forms. In conjunction with material described earlier, these provide evidence for a new group of metazoans, the vetulicolians. Several features, notably a series of gill slits, suggest that this group can throw light on an early stage of deuterostome diversification.

Animals↗

PubMed2001

Neuronal responses in the frontal cortico-basal ganglia system during delayed matching-to-sample task: ensemble recording in freely moving rats.

Electrophysiological recording of single neuron activity has been conducted in rats to investigate the patterns of distributed neuronal responses in the frontal cortico-basal ganglia system that code information during a spatial-delayed matching-to-sample task (DMTSt). Rats were trained to press one of the two retractable levers presented randomly as a sample response. The first valid nose-poke after a delay resulted in the presentation of both levers. Pressing the same lever as the sample lever led to a water reward (match to sample), whereas pressing the lever opposite the sample lever resulted in a time-out (house light turned off). One hundred seventy-one neurons in the medial prefrontal cortex (mPFC), 51 in the dorsal striatum (STR), and 93 in the nucleus accumbens (NAc) were recorded during DMTSt. Different patterns of neuronal responses were observed during different behavioral episodes (sample, delay, and match phases) in all three recording areas. Space-related neuronal responses specific to the side of the lever pressed were more often found in the sample phase than in the match phase in all three areas studied. Neuronal responses specific to either correct or error trials were observed with similar percentages in the mPFC and the NAc, while the incidence of correct/error-coded activity in the STR was lower. Ensemble neuronal activity that coded sample versus match lever presses was observed in three out of five rats in sets of trials with similar speed and trajectory of lever press. The results reveal specific patterns of neural responses in the frontal cortico-basal ganglia system in rats during the DMTSt and suggest the existence of specific neuronal coding for different behavioral events associated with a learned short-term memory process.

Action Potentials↗

PubMed2001

The critical role of LIGHT, a TNF family member, in T cell development.

Negative selection refers to the selective deletion of autoreactive thymocytes but its molecular events have not been well defined. In this study, we demonstrate that a cellular ligand for herpes virus entry mediator and lymphotoxin receptor (LIGHT), a newly identified member of the TNF superfamily, may play a critical role in negative selection. Using TCR transgenic mice, we find that the blockade of LIGHT signaling in vitro and in vivo prevents negative selection induced by peptide and intrathymically expressed Ags, resulting in the rescue of thymocytes from apoptosis. Furthermore, the thymi of LIGHT transgenic mice show severe atrophy with remarkably reduced CD4(+)CD8(+) double-positive cells caused by increased apoptosis, suggesting that LIGHT can delete immature T cells in vivo. Taken together, these results demonstrate a critical role of LIGHT in thymic negative selection of the T cell repertoire.

Animals↗

PubMed2001

[Relationship between basic fibroblast growth factor (bFGF) and cell proliferation, invasion in pituitary adenoma].

Basic fibroblast growth factor (bFGF) and proliferating cell nuclear antigen (PCNA) were examined by immunohistochemistry in fifty-one pituitary adenomas. The results showed that the intensity of bFGF expression was strong or intermediate in twenty-nine adenomas, which was positively related to cell proliferation, there was positive relationship between bFGF expressin and tumor invasion in non-functional adenomas. The data suggest that bFGF may play some role in the origin and progression of pituitary adenomas.

Adenoma↗

PubMed2001

Species-specific differences in the operational RNA code for aminoacylation of tRNA(Trp).

Identity elements play essential roles in the recognition of tRNAs by their cognate aminoacyl-tRNA synthetase. An operational RNA code relates amino acids to specific sequences and structural features of tRNA acceptor stems. In this study, a series of tRNA(Trp) variants was prepared by in vitro transcription and their efficiencies of aminoacylation by tryptophan (k(cat)/K(m)) were measured with the aid of Bacillus subtilis and human tryptophanyl-tRNA synthetases (TrpRS). The identity elements in the operational RNA code of human tRNA(Trp) were found to be: major element, discriminator base A73; minor elements, G1/C72 and U5/G68. From the cross-species aminoacylation assays, we conclude that the identity elements in tRNA(Trp) from B.subtilis and human all contribute to species-specific aminoacylation by TrpRS. Analyses of 22 TrpRS sequences covering three taxonomic domains (bacteria, eukarya and archaea) reveal that the sequences are divided into two evolutionarily distant groups. The same partition is also observed in the analyses of tRNA(Trp) acceptor stem sequences. Our data suggest that the two TrpRS groups may reflect co-adaptations needed to accommodate changes in the operational RNA code for tryptophan.

Acylation↗