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Lin Chen

Publications and source records attributed to Lin Chen.

175 records · Page 10Linked to original sources
PubMed2002

[A method based on independent component analysis for processing fMRI data].

Independent component analysis (ICA) is a new technique in statistical signal processing to extract independent components from multidimensional measurements of mixed signals. In this paper, for the processing of functional magnetic resonance imaging(fMRI) data, two signals of near voxels are used as the mixed signals and are separated by ICA. The correlation coefficients between the reference signal and the separated signals are calculated and those voxels whose correlation coefficients are greater than a threshold are considered to be the activated voxels by the stimulation, and so the functional localization of the stimulation is completed. The validity of the method was primarily proved by trial of real brain functional magnetic resonance imaging data.

Algorithms↗
PubMed2002

[Cloning and expression of Tachypleus tridentatus factor C].

Factor C is an endotoxin-sensitive, intracellular serine protease zymogen which initiates the coagulation cascade system in the horseshoe crab hemolymph. The special lipopolysaccharide (LPS) binding activation of FC makes it a potential drug for anti-LPS treatment and has a high commercial value. Based on the sequence of reported FC from Japan horseshoe crab, two pairs of primers were designed. The total RNA was extracted from amebocytes of Chinese Tachypleus tridentatus and the cDNA was separated into two parts and were cloned using RT-PCR, respectively. FCs from different geographical areas showed high homology in sequence. The whole FC cDNA was cloned into pET-28a (+) containing T7 promoter and recombinant expression plasmid pET-FC was constructed. The recombinant plasmid was transformed into E. coli BL21 (DE3). Recombinant FC was expressed as inclusion body when the expression strain was induced with 1 mmol/L IPTG. Refolded recombinant FC was confirmed to be active by bacteriostatic assay in vitro. The results of Western blot also suggested the recombinant FC may be able to cleave itself partly and produced an extra immunoblot band.

Amino Acid Sequence↗
PubMed2002

Renal cell carcinoma related novel gene, GYLZ-RCC18: cloning and functional studies.

OBJECTIVE: To clone the full length of renal cell carcinoma (RCC) related novel gene GYLZ-RCC18 and study its function. METHODS: SMART RACE technology was used to clone the full length of GYLZ-RCC18. RT-PCR was used to detect its expression in renal cell carcinoma tissue at different stages and grades. We transfected the antisense oligonucleotide of GYLZ-RCC18 to renal cell carcinoma cell line, GRC-1, and analyzed proliferation activity, growth rate, apoptosis, and mortality changes. RESULTS: The full length of GYLZ-RCC18 (GenBank accession number: BE825133) cDNA was about 3.5 kb. GYLZ-RCC18 had a higher expression in higher grades and stages of renal cell carcinoma than in lower ones. The expression of GYLZ-RCC18 in renal cell carcinoma was much higher than in normal kidney. After the transfection of GYLZ-RCC18 antisense oligonucleotide, the mortality of GRC-1 increased significantly, while proliferative activity and growth rate were substantially inhibited at the same time. The antisense oligonucleotide induced apoptosis of GRC-1 through the entire observation time. CONCLUSION: GYLZ-RCC18 is an important novel gene related to renal cell carcinoma. Overexpression of this gene results in higher growth and proliferative activity and has an antiapoptosis effect on renal cell carcinoma cells. Transfection of the antisense oligonucleotide may inhibit the generation and development of renal cell carcinoma.

Apoptosis↗
PubMed2002

Etiological analysis on bacterial ocular disease in northern China (1989-1998).

OBJECTIVE: To review the distribution and trends of bacterial culture specimens in Beijing Institute of Ophthalmology. METHODS: A retrospective analysis of the bacterial culture-positive rate, the distribution of gram' s stain, and the distribution and change of isolates was performed on 4705 specimens during a 10-year period (1989- 1998). RESULTS: Positive cultures numbered 1339 of the 4705 specimens, with a positive rate of 28.6%. Gram-positive cocci constituted 55.6% of the total isolates, followed by gram-positive bacilli 13.1% . Gram-negative cocci accounted for 2.8%, and gram-negative bacilli 28.5% . In the positive bacteria cultures, coagulase-negative Staphylococcus (mainly Staphylococcous epidermidis) was the most common isolate (25.3%), and followed by Pseudomonas 18.8%, Micrococcus 11.7%, Cotynbaccterium 10.1%, and Staphylococcus aureus 8.2% . During the 10-year period, the overall frequency of gram-positive cocci appeared to increase with time while the frequency of gram-negative bacilli decreased. CONCLUSIONS: Gram-positive cocci and gram-negative bacilli are still the predominant pathogens of ocular infection in northern China. The frequency of the former increases annually whereas that of the latter decreases. It is important to comprehend the distribution and trends of ocular pathogenic bacteria for the diagnosis, prevention and treatment of bacterial infectious ocular disease.

Bacteria↗
PubMed2002

[Study on granulocytes derived from induction of committed differentiation of hematopoietic stem/progenitor cells ex vivo].

To evaluated the feasibility of preventing infection after high dose chemotherapy and radiotherapy using the granulocytes derived from differentiated from hematopoietic stem/progenitor cells ex vivo, human CD34-positive cells were isolated from umbilical cord blood by using a high-gradient magnetic cell sorting system (MACS), and the cells committedly differentiated with hematopoietic cytokines (SCF + IL-3 + IL-6 + G-CSF) in a liquid culture system. The expanded cell number, ratio of the viable cells, chromosome and phenotype of the differentiated cells and safety analysis of expanded cells were detected by using cell count, trypan blue exclusion test, karyotype analysis, flow cytometry and tumorigenic model of nude mice, respectively. The results showed that the combination of cytokines increased cell number by (1006.4 +/- 103.2) folds and flow cytometric analysis showed myeloid marker CD11b expressed in the about 60% cells. The growth peak of differentiated cells was at 14 days of culture and decreased at about 33 days. No abnormality was found in the karyotype analysis of expanded cells. No tumor was found in the nude mice injected with expanded cells after 35 days and the expanded cells had the ability of phagocytizing bacteria. It is concluded that the cells, differentiated from CD34(+) cells, expanded ex vivo possess the function of granulocyte and it was safe for clinical trial.

Animals↗
PubMed2002

[Expression of telomerase during induction of committed differentiation of human cord blood hematopoietic stem/progenitor cells in vitro].

To investigate the expression of telomerase in cord blood hematopoietic stem/progenitor cells during their committed differentiation in vitro and provide an index of monitoring the proliferating potential of the hematopoietic stem/progenitor cells and security for clinical application. Human CD34 positive cells were isolated from umbilical cord blood by using magnetic cell sorting system (MACS), and were induced to differentiation with hematopoietic growth factors (SCF + IL3 + IL6 + GCSF and SCF + IL3 + IL6 + EPO) in a liquid culture system. The telomerase activity and the cytalytic subunit of telomerase (hTERT) of the cells were analysed during different periods of culture by using TRAP-PCR, TRAP-ELISA, Western blot and RT-PCR techniques, respectively. The results showed that a peak of cell growth was achieved on day 14 - 21 during induction of differentiation in vitro. Total cell number could increase 1006.4 +/- 103.2 times and could not increase there after. Telomerase activity and hTERT expression were low in freshly isolated cord blood CD34(+) cells and increased after about 7 days of culture in addition of cytokine combinations of SCF + IL3 + IL6 + GCSF and SCF + IL3 + IL6 + EPO, respectively. The telomerase activity and hTERT decreased after 14 days of culture and were not detected after 28 days of culture. It was concluded that the hematopoietic stem/progenitor cells can be expanded in large number in vitro and do not have the character of immortality and the telomerase activity could be a useful index in hematopoiesis regulation.

Antigens, CD34↗
PubMed1999

CT arterial portography and CT hepatic arteriography in detection of micro liver cancer.

AIM:To recognize the characteristic findings of micro-liver cancer (MLC) and to evaluate the effect of CT arterial portography (CTAP) and CT hepatic arteriography (CTHA) in diagnosis of MLC.METHODS:Between April 1996 to December 1998, CTAP and CTHA were performed in 12 patients with MLC, which were not detected by conventional CT examinations. After CTHA, 3mL-5mL mixture of lipiodol, doxorubicin and mitoycin C were injected into hepatic artery through the catheter, and the followed up by CT three or four weeks later (Lipiodol CT Lp-CT).RESULTS:A total of 22 micro-tumors (0.2cm-0.6cm in diameter) were detected in 12 patients, which manifested as small perfusion defects in CTAP and small round enhancement in CTHA. The rate of detectability of CTAP and CTHA was 68.2% (15/22) and 77.3% (17/22) respectively, and the rate of the simultaneous use of both procedures reached 86.4% (19/22).All micro-tumors were demonstrated as punctate lipiodol deposit foci in Lp-CT. After Lp-CT, the elevated serum level of alpha-fetoprotein (AFP) dropped to the normal level in all patients.CONCLUSION:The CTAP and CTHA are the most sensitive imaging methods for detecting micro-liver cancer.Confirmed by the change of the elevated serum AFP level and lipiodol deposit foci in Lp-CT, small perfusion defects in CTAP and puntuate enhancement in CTHA may suggest micro-liver cancer.

Journal Article↗
PubMed1998

Findings of non-pathologic perfusion defects by CT arterial portography and non-pathologic enhancement of CT hepatic arteriography.

AIM:To recognize the characteristic findings of non-pathologic perfusion defects with CT arterial portography (CTAP) and nonpathologic enhancement found in CT hepatic arteriography (CTHA).METHONDS:The manifestations of nonpathologic perfusion defects with CTAP and non pathologic enhancement found in CTHA were analyzed in 50 patients with primary hepatocellular carcinoma.RESULTS:The false-positive rate of perfusion defects detected in CTAP was 15.1% The shapes of perfusion defects were peripheral wedge, small, round, and patchy. The occurrence rate of non-pathologic enhancement found in CTHA was 22.0%. The shapes of non-pathologic enhancement were small, round, irregular, and wedge.CONCLUSION:There was high frequency of non-pathologic perfusion defects detected with CTAP and non-pathologic enhancement found in CTHA. The simultaneous use of both procedures may help decrease the false-positive rate, and increase the veracity of diagnosis for hepatocellular carcinoma.

Journal Article↗
PubMed1996

Synthetic, Mechanistic, and Structural Studies Related to 1,2,4-Dithiazolidine-3,5-dione.

Reaction of O-ethyl thiocarbamate (4) with (chlorocarbonyl)sulfenyl chloride (5) gives 3-ethoxy-1,2,4-dithiazolin-5-one (2) and 3,5-diethoxy-1,2,4-thiadiazole (3), with the relative amounts of 2 and 3 formed depending very much on the solvent (e.g., diethyl ether favors 2; chloroform favors 3). The effects of added base, order of addition, concentration, and temperature were also studied. Mechanisms for the observed transformations have been proposed and are supported by the characterization of relatively unstable acyclic intermediates, e.g., formimidoyl(chlorocarbonyl)disulfane 8, symmetrical bis(formimidoyl)disulfane 10, and ethoxythiocarbonyl imidate 11, which are obtained under alternative conditions. Compound 2 is converted with concentrated aqueous hydrochloric acid upon short reflux to 1,2,4-dithiazolidine-3,5-dione (1), rearranges upon prolonged melting to give principally N-ethyl-1,2,4-dithiazolidine-3,5-dione (13), and is desulfurized with various trivalent phosphorus compounds to yield O-ethyl cyanate (15) plus carbonyl sulfide. X-ray crystallographic structures of 1 and 2 have been solved; the planarity and aromatic character of these molecules help to explain some of their reactions.

Journal Article↗
PubMedDate not supplied

Successful treatment of mucormycosis in the pulmonary artery after cardiac surgery.

Mucormycosis endocarditis after cardiovascular surgery is a rare and usually fatal complication. Here, we report one case of mucormycosis occurring in the pulmonary artery and the residual patent ductus arteriosus (PDA) in a 9-year-old girl, who had been successfully cured with the combination of the emergent surgical removal of infected tissues and the subsequent antifungal drug therapy.

Anti-Bacterial Agents↗
PubMedDate not supplied

Acoustic modulation of electrically evoked otoacoustic emission in chickens.

Electrically evoked otoacoustic emissions (EEOAEs) can be elicited from the chicken inner ear. Since lesion studies implicate hair cells are the source of EEOAEs, we hypothesized that acoustic stimuli would modulate EEOAE amplitude at cochlear locations where the acoustic and electrical stimuli overlap. To assess this interaction, EEOAEs were measured as the frequency and amplitude of the acoustic stimuli were varied. EEOAEs, evoked by AC current (3-250 microA rms) delivered to the round window had a broad band pass response (1-6 kHz) with a peak between 3 and 4 kHz and maximum amplitude of 27 dB SPL. EEOAE suppression/enhancement tuning curves were measured at 2, 3, 4 and 6 kHz by varying the frequency of a 70 dB SPL tone and measuring the change in EEOAE amplitude. EEOAE tuning curves were characterized by a tip; a narrow range of frequencies where EEOAE amplitude was suppressed by as much as 5 dB, and by sidebands, a range of frequencies above and below the tip where EEOAE amplitude was enhanced by as much as 1.5 dB. The best suppression frequency, or characteristic frequency, was close to the frequency of the EEOAE elicited by the 3- or 4-kHz electric stimulus. However, the characteristic frequency was displaced towards higher frequencies for the 2-kHz electric stimulus, and towards lower frequencies for the 6-kHz electric stimulus. EEOAE suppression increased approximately linearly with acoustic level. These results suggest that EEOAEs evoked by round window stimulation are predominantly generated by hair cells near the 3- to 4-kHz region of the cochlea.

Acoustics↗
PubMedDate not supplied

Cue validity and object-based attention.

In a previous study, Egly, Driver, and Rafal (1994) observed both space- and object-based components of visual selective attention. However, the mechanisms underlying these two components and the relationship between them are not well understood. In the present research, with a similar paradigm, these issues were addressed by manipulating cue validity. Behavioral results indicated the presence of both space- and object-based components under high cue validity, similar to the results of Egly et al.'s study. In addition, under low cue validity, the space-based component was absent, whereas the object-based component was maintained. Further event-related potential results demonstrated an object-based effect at a sensory level over the posterior areas of brain, and a space-based effect over the anterior region. The present data suggest that the space- and object-based components reflect mainly voluntary and reflexive mechanisms, respectively.

Adolescent↗