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Y Chen

Publications and source records attributed to Y Chen.

At least 811 records · Page 45Linked to original sources
PubMed2000

SM5-1: a new monoclonal antibody which is highly sensitive and specific for melanocytic lesions.

Antibodies such as HMB-45 and anti-S100 protein have been widely used as markers of malignant melanoma despite evidence that HMB-45 has a sensitivity of only 67-93% and S100 is nonspecific for melanoma. Using a subtractive immunization protocol in a mouse model of human melanoma, we have generated several monoclonal antibodies with putative specificity for melanoma. After initial screenings, the antibody SM5-1 was chosen because of its intriguing reactivity with melanocytic tumors in both frozen and paraffin sections. The immunohistochemical staining of SM5-1 was studied in paraffin-embedded specimens of 401 melanomas (n = 401; 250 primary melanomas, 151 metastases), melanocytic nevi of the skin (n = 16), nonmelanocytic neoplasms (n = 84). The results were compared with HMB-45 and anti-S100 staining. All antibodies reacted with nevi and 97-99% with primary melanomas. Whereas both SM5-1 and anti-S100 stained 96% (146/151) of melanoma metastases, HMB-45 correctly identified only 83% (126/151). All HMB-45-negative metastases were positive for SM5-1. Whereas neither SM5-1 nor HMB-45 stained any of 84 specimens from 40 different nonmelanocytic neoplasms, anti-S100 was positive in 21/84 (25%). While the staining pattern of SM5-1 was mostly homogeneous, small tumor areas in some metastases remained unstained. Staining with SM5-1 was also observed in perivascular dendritic cells, in plasma cells, some myofibroblasts and the secretion of eccrine sweat glands. Nonactivated epidermal melanocytes, keratinocytes, endothelial cells, smooth muscle cells and peripheral nerves were all negative for SM5-1. These results suggest that SM5-1 is highly specific, as well as sensitive, for melanocytic lesions and is useful in the immunohistochemical evaluation of melanoma.

Animals↗
PubMed2000

Antimicrobial resistance in gram-negative bacteria isolated from the urinary tract in community-residing persons with spinal cord injury.

OBJECTIVE: To assess the epidemiology of antimicrobial resistance among community-residing persons with spinal cord injury (SCI). DESIGN: Retrospective analysis of existing data. SETTING: Data were obtained from persons with SCI attending clinic for annual examinations. PARTICIPANTS: Two hundred eighty-seven SCI outpatients. INTERVENTION: None. MAIN OUTCOME MEASURE: Occurrence of bacteriuria with gram-negative organisms demonstrating resistance to antimicrobial agents in 2 or more classes. RESULTS: There were 706 gram-negative isolates from 444 urine specimens. Resistance to drugs in 2 or more classes occurred in 33% of bacterial isolates, but did not significantly increase in frequency among those injured for longer periods or more severely. Significantly higher rates of multidrug-resistant bacteria occurred in specimens from males, younger age group (< or =45 yrs), and persons with indwelling and condom catheters. CONCLUSIONS: Antimicrobial resistance in outpatients with SCI is common and is related to widespread use of specific drugs, type of bladder management, and other host factors.

Adult↗
PubMed2000

Probing ligand protein binding equilibria with fluorescence fluctuation spectroscopy.

We examine the binding of fluorescent ligands to proteins by analyzing the fluctuation amplitude g(0) of fluorescence fluctuation experiments. The normalized variance g(0) depends on the molecular brightness and the concentration of each species in the sample. Thus a single g(0) measurement is not sufficient to resolve individual species. Titration of the ligand with protein establishes the link between molecular brightness and concentration by fitting g(0) to a binding model and allows the separation of species. We first apply g(0) analysis to binary dye mixtures with brightness ratios of 2 and 4 to demonstrate the feasibility of this technique. Next we consider the influence of binding on the fluctuation amplitude g(0). The dissociation coefficient, the molecular brightness ratio, and the stochiometry of binding strongly influence the fluctuation amplitude. We show that proteins with a single binding site can be clearly differentiated from proteins with two independent binding sites. The binding of fluorescein-labeled digoxigenin to a high-affinity anti-digoxin antibody was studied experimentally. A global analysis of the fluctuation amplitude and the fluorescence intensity not only recovered the dissociation coefficient and the number of binding sites, but also revealed the molecular heterogeneity of the hapten-antibody complex. Two species were used to model the molecular heterogeneity. We confirmed the molecular heterogeneity independently by fluorescence lifetime experiments, which gave fractional populations and molecular brightness values that were virtually identical to those of the g(0) analysis. The identification and characterization of molecular heterogeneity have far-reaching consequences for many biomolecular systems. We point out the important role fluctuation experiments may have in this area of research.

Antibodies, Monoclonal↗
PubMed2000

Resolving heterogeneity on the single molecular level with the photon-counting histogram.

The diffusion of fluorescent particles through a small, illuminated observation volume gives rise to intensity fluctuations caused by particle number fluctuations in the open observation volume and the inhomogeneous excitation-beam profile. The intensity distribution of these fluorescence fluctuations is experimentally captured by the photon-counting histogram (PCH). We recently introduced the theory of the PCH for diffusing particles (Chen et al., Biophys. J., 77:553-567), where we showed that we can uniquely describe the distribution of photon counts with only two parameters for each species: the molecular brightness of the particle and the average number of particles within the observation volume. The PCH is sensitive to the molecular brightness and thus offers the possibility to separate a mixture of fluorescent species into its constituents, based on a difference in their molecular brightness alone. This analysis is complementary to the autocorrelation function, traditionally used in fluorescence fluctuation spectroscopy, which separates a mixture of species by a difference in their diffusion coefficient. The PCH of each individual species is convoluted successively to yield the PCH of the mixture. Successful resolution of the histogram into its components is largely a matter of the signal statistics. Here, we discuss the case of two species in detail and show that a concentration for each species exists, where the signal statistics is optimal. We also discuss the influence of the absolute molecular brightness and the brightness contrast between two species on the resolvability of two species. A binary dye mixture serves as a model system to demonstrate that the molecular brightness and the concentration of each species can be resolved experimentally from a single or from several histograms. We extend our study to biomolecules, where we label proteins with a fluorescent dye and show that a brightness ratio of two can be resolved. The ability to resolve a brightness ratio of two is very important for biological applications.

Alcohol Dehydrogenase↗
PubMed2000

Chemiluminescence detection of epstein-barr virus DNA with an oligonucleotide probe.

A sensitive and relatively fast chemiluminescence dot blot hybridization assay for Epstein-Barr virus (EBV) DNA was established. A specially designed oligonucleotide probe labeled directly by alkaline phosphatase (AP) and highly sensitive chemiluminescent substrate CDP-star for AP was used in the hybridization assay. About 4 pg purified EBV DNA target can be detected, improved about 10-fold in sensitivity compared with common colorimetric detection. Preliminary EBV clinical testing was carried out on samples of eight cases from patients with nasopharyngeal carcinoma (NPC) (six cases) and nasopharyngeal lymphadenosis (two cases). The detection results in positive rate agreement with control PCR detection indicate that the assay is specific and sensitive for EBV. The whole detection procedure can be finished in 6 h. This method might be useful in EBV clinical diagnosis.

Colorimetry↗
PubMed2000

Mitochondrial gene mutations in gestational diabetes mellitus.

Mitochondrial DNA mutations have been implicated in many diseases including diabetes mellitus. Although gestational diabetes mellitus (GDM) has been suggested to have genetic determinant and to be etiologically indistinct with non-insulin-dependent diabetes mellitus (NIDDM), its association with mitochondrial gene mutations is still unknown. In this study, 137 patients with GDM and 292 non-diabetic pregnant controls were examined for mitochondrial DNA mutations from the nucleotide 3130-4260 encompassing tRNA-Leu gene and adjacent NADH dehydrogenase 1 gene by polymerase chain reaction, single-stranded conformation polymorphism, restriction fragment length polymorphism and DNA sequencing. One heteroplasmic mutation at the position of 3398 (T-C), which changed a highly conserved methionine to threonine in NADH dehydrogenase subunit 1, was identified in 2.9% GDM patients but not in the controls, indicating its association with GDM (P = 0.01). Two novel mutations, a heteroplasmic C3254A and a homoplasmic A3399T, were also found in GDM subjects, the functional meaning of which merits further investigation. G3316A and T3394C mutations implicated in NIDDM, were seen at higher frequencies in patients with GDM than the controls. Our results suggest that mitochondrial DNA mutations may contribute to the development of GDM in some patients.

Adult↗
PubMed2000

Phase II study of tamoxifen, ifosfamide, epirubicin and cisplatin combination chemotherapy in patients with non-small cell lung cancer failing previous chemotherapy.

We conducted a phase II study of tamoxifen, ifosfamide, epirubicin, and cisplatin (TIEP) chemotherapy in patients with non-small cell lung cancer (NSCLC) who had failed previous chemotherapy, in order to assess the response and toxicity of TIEP. Between November 1997 and May 1999, 25 patients were treated. Twelve of the 25 patients (48%) had been previously treated with cisplatin-based combination chemotherapy. TIEP doses were tamoxifen 60 mg oral twice daily on days 1-3; ifosfamide 2.4 g/m(2) intravenous infusion (IV) 60 min with mesna on day 2; epirubicin 40 mg/m(2) IV bolus on day 2; and cisplatin 50 mg/m(2) IV 60 min on day 2 every 4 weeks for up to six cycles. Seventy one cycles were given to 25 patients, with a median of three cycles (range one to six cycles). All patients were evaluable for toxicity profile and response rate. As expected, the major toxicity was myelosuppression. Grade 3 or 4 neutropenia occurred in 15 patients (60%) during treatment, as well as in 31% of the total courses. Febrile neutropenia occurred in two patients. No toxic death occurred in this study. Grade 3 thrombocytopenia occurred in five patients with five cycles. Toxicities other than myelosuppression were few and mild in severity. After two cycles of treatment, five of 25 patients (20%) had a partial response (95% confidence interval 4.3-35.7%). Among 12 patients previously treated with cisplatin-based chemotherapy, three patients (25%) achieved a partial response. The median time to disease progression was 4.9 months and median survival was 7.7 months. The response rate and median survival were better than in our previous study of salvage chemotherapy with ifosfamide, 5-FU, and leucovorin; and with ifosfamide, epirubicin, 5-FU, and leucovorin. In conclusion, TIEP appears to be an active combination regimen with an acceptable toxicity profile in Chinese patients with NSCLC who have failed previous chemotherapy.

Adenocarcinoma↗
PubMed2000

Induction of high level of specific antibody response to the neutralizing epitope ELDKWA on HIV-1 gp41 by peptide-vaccine.

The monoclonal antibody 2F5 recognizing the neutralizing epitope ELDKWA on the C-domain could neutralize 90% of the investigated HIV-1 isolates. Low levels of ELDKWA-epitope-specific antibodies were observed in HIV-1-infected individuals. To induce high levels of antibodies to ELDKW-epitope, C-domain peptide (P2) was conjugated with a carrier peptide (KGGG)(7)-K (K/G). P2-K/G-conjugate induced high level of antibodies in mice by titer 1:25,600 to ELDKWA-epitope. P2-K/G-BSA-conjugate induced antibody response to ELDKWA-epitope (1:320-6400) in mice. The ELDKWA-epitope-specific antibodies of 19.8 and 34.6 microg/per milliliter serum were isolated from two rabbit antiserums (1:25,600). The levels of ELDKWA-epitope-specific antibodies induced in rabbits were greater than 1 microg/ml, a level considered to confer long-term protection. These results demonstrate the potential role of the C-domain peptide of gp41 to develop an effective ELDKWA-based epitope/peptide-vaccine against HIV-1.

AIDS Vaccines↗
PubMed2000

Neuronal activity and stress differentially regulate hippocampal and hypothalamic corticotropin-releasing hormone expression in the immature rat.

Corticotropin-releasing hormone, a major neuromodulator of the neuroendocrine stress response, is expressed in the immature hippocampus, where it enhances glutamate receptor-mediated excitation of principal cells. Since the peptide influences hippocampal synaptic efficacy, its secretion from peptidergic interneuronal terminals may augment hippocampal-mediated functions such as learning and memory. However, whereas information regarding the regulation of corticotropin-releasing hormone's abundance in CNS regions involved with the neuroendocrine responses to stress has been forthcoming, the mechanisms regulating the peptide's levels in the hippocampus have not yet been determined. Here we tested the hypothesis that, in the immature rat hippocampus, neuronal stimulation, rather than neuroendocrine challenge, influences the peptide's expression. Messenger RNA levels of corticotropin-releasing hormone in hippocampal CA1, CA3 and the dentate gyrus, as well as in the hypothalamic paraventricular nucleus, were determined after cold, a physiological challenge that activates the hypothalamic pituitary adrenal system in immature rats, and after activation of hippocampal neurons by hyperthermia. These studies demonstrated that, while cold challenge enhanced corticotropin-releasing hormone messenger RNA levels in the hypothalamus, hippocampal expression of this neuropeptide was unchanged. Secondly, hyperthermia stimulated expression of hippocampal immediate-early genes, as well as of corticotropin-releasing hormone. Finally, the mechanism of hippocampal corticotropin-releasing hormone induction required neuronal stimulation and was abolished by barbiturate administration. Taken together, these results indicate that neuronal stimulation may regulate hippocampal corticotropin-releasing hormone expression in the immature rat, whereas the peptide's expression in the hypothalamus is influenced by neuroendocrine challenges.

Action Potentials↗
PubMed2000

Evaluation of the activity of a novel metabotropic glutamate receptor antagonist (+/-)-2-amino-2-(3-cis and trans-carboxycyclobutyl-3-(9-thioxanthyl)propionic acid) in the in vitro neonatal spinal cord and in an in vivo pain model.

The cyclobutylglycine (+/-)-2-amino-2-(3-cis and trans-carboxycyclobutyl-3-(9-thioxanthyl)propionic acid) (LY393053) has been identified as a functionally potent metabotropic glutamate receptor antagonist. It is most potent on the two group I metabotropic glutamate receptors, 1alpha and 5alpha, with IC50 values of 1.0+/-0.4 microM and 1.6+/-1.4 microM, respectively. In this study, LY393053 has also been evaluated electrophysiologically on native group I metabotropic glutamate receptors in an in vitro spinal cord preparation as well as behaviourally, in a mouse model of visceral pain. LY393053 dose-dependently antagonised group I agonist, (RS)-3, 5-dihydroxyphenylglycine, or a broad-spectrum agonist (1S,3R)-amino-1,3-cyclopentanedicarboxylic acid-induced depolarisation of spinal motoneurons. The apparent Kd values were estimated to be 0.3 microM against (RS)-3, 5-dihydroxyphenylglycine-induced depolarisation and 0.5 microM against (1S,3R)-amino-1,3-cyclopentanedicarboxylic acid-induced depolarisation, respectively. On the other hand, the dorsal root-ventral root potential elicited at 8 x threshold was depressed by LY393053 with IC50 values of 9.0+/-0.7 microM and 12.7+/-1.7 microM on monosynaptic and polysynaptic responses, respectively. When investigated using the mouse acetic acid writhing test, LY393053 showed significant analgesic effects at doses of 1-10 mg/kg intraperitoneally. An ED50 value of 6.0 mg/kg was obtained in this test. By revealing a potent effect of LY393053 in antagonising the native group I metabotropic receptor-mediated responses in the spinal cord in rodents, and an antinociceptive efficacy in a mouse visceral pain model, these results, therefore, provide additional evidence in support of the analgesic potential of metabotropic glutamate receptor antagonists.

Acetic Acid↗
PubMed2000

cDNA microarray technology and its applications.

The cDNA microarray is the most powerful tool for studying gene expression in many different organisms. It has been successfully applied to the simultaneous expression of many thousands of genes and to large-scale gene discovery, as well as polymorphism screening and mapping of genomic DNA clones. It is a high throughput, highly parallel RNA expression assay technique that permits quantitative analysis of RNAs transcribed from both known and unknown genes. This technique provides diagnostic fingerprints by comparing gene expression patterns in normal and pathological cells, and because it can simultaneously track expression levels of many genes, it provides a source of operational context for inference and predication about complex cell control systems. This review describes this recently developed cDNA microarray technology and its application to gene discovery and expression, and to diagnostics for certain diseases.

Journal Article↗