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L Chen

Publications and source records attributed to L Chen.

At least 253 records · Page 14Linked to original sources
PubMed2001

[Evaluation for the regeneration efficiency of activated carbon by wet air oxidation].

It is well known that different regenerating techniques of activated carbon(AC) require the suitable evaluating methods for regeneration efficiency. In this paper, several methods for evaluating the regeneration efficiency of AC were compared and discussed by wet air oxidation(WAO) which were respectively based on different experimental protocols such as iodine value, molasses color adsorption, breckthrough profile, adsorption isotherm and standard reload experiment. The iodine value, molasses color adsorption and breckthrough profile yielded indefinitely PR values for WAO process, so they could not be applied to evaluate regeneration efficiency. And adsorption isotherm experiment was more correct because it compared isotherm loadings at the same equilibrium liquid phase concentrations, but this more laborious and time-consuming method was difficult to be widely used. The results also showed that the standard reload experiment was consequently picked out, easy to use and had high sensibility alternative to adsorption isotherm experiment. When controlling the WAO parameters at 250 degrees C, 0.6 MPa and 1 h, the regeneration efficiency arrived to 55%.

Air↗
PubMed2001

[Analysis of HIV-1 seropositive individual infected with different subtypes].

OBJECTIVE: To investigate whether there existed any individuals infected with different subtypes of human immunodeficiency virus type 1 (HIV-1) and to analyze their source of infection. METHODS: Membrane protein gene (env) of HIV-1 in uncultured single peripheral blood monocytes (PBMCs) from HIV-1 seropositive individuals found in Shenzhen was amplified by nested polymerase chain reaction (PCR). The C2-V3 region and its adjacent region (360 bp) of them were sequenced and analyzed, and their divergence rate and systematic phylogenetic tree (cladogram) were calculated. RESULTS: There existed sequences of B and C or B and E strains of HIV-1 subtype in three infected individuals in Shenzhen. Gene divergence rates between different subtypes and corresponding international subtype reference strains Bcon, Ccon and Econ were 5.07%-7.26%, 3.23% and 5.38%-5.99%, respectively, and those between different subtypes strains in the same individual were 23.52%, 20.69% and 28.44%, respectively. GPGR sequence of typical Europe and America subtype B was found in strain sz46-1 from prostitute with intravenous drug abuse, based on their tetra-peptide sequence characteristics in the crown of gp 120 V3 loop, strain sz8-2 was GPGH and other strains were GPGQ sequence characterized by Thai B (B') and E subtypes. Furthermore, phylogenetic tree analysis showed that strains sz1-2, sz8-1 and sz46-1 were clustered with international reference sequence Bcon, strain sz1-1 clustered with Econ, and strains sz1-1 and sz8-2 clustered with Ccon. CONCLUSION: These findings suggested that an individual could be simultaneously infected with different HIV-1 subtypes, which could probably be caused by his or her own multiple high-risk behavior.

Adult↗
PubMed2001

Attenuation of compensatory right ventricular hypertrophy and heart failure following monocrotaline-induced pulmonary vascular injury by the Na+-H+ exchange inhibitor cariporide.

Pulmonary hypertension results in compensatory right ventricular (RV) hypertrophy. We studied the role of the Na+-H+ exchange (NHE) in the latter process by determining the effect of the NHE-1 inhibitor cariporide after monocrotaline-induced pulmonary artery injury. Sprague-Dawley rats received a control or cariporide diet for 7 days, at which time they were administered either monocrotaline (60 mg/kg) or its vehicle. Twenty-one days later, monocrotaline control, but not cariporide-fed animals, demonstrated increased RV weights and cell size of 65 and 52%, respectively. Monocrotaline alone significantly increased RV systolic pressure and end diastolic pressure by 70 and 94%, respectively, whereas corresponding values with cariporide were significantly reduced to 33 and 42%. Central venous pressure increased by 414% in control animals, which was significantly reduced by cariporide. Monocrotaline treatment produced a decrease in cardiac output of 28 and 8% in the absence or presence of cariporide (P < 0.05 between groups), respectively. Although body weights were significantly lower in both monocrotaline-treated groups compared with vehicle treatment, with cariporide the net gain in body weight was twice that seen in the monocrotaline-treated animals without cariporide. Monocrotaline also increased RV NHE-1 and atrial natriuretic peptide mRNA expression, which was abrogated by cariporide. Monocrotaline-induced myocardial necrosis, fibrosis, and mononuclear infiltration was completely prevented by cariporide. Cariporide had no effect on monocrotaline-induced pulmonary intimal wall thickening. Our results demonstrate that cariporide directly attenuates myocardial dysfunction after monocrotaline administration independent of pulmonary vascular effects. NHE-1 inhibition may represent an effective adjunctive therapy that selectively targets myocardial hypertrophic responses in pulmonary vascular injury.

Animals↗
PubMed2001

Excitatory amino acids in cerebrospinal fluid of patients with acute head injuries.

BACKGROUND: The excitatory amino acids (EAAs) glutamate (Glu) and aspartate (Asp) play a role in the pathogenesis of postischemic and posttraumatic brain insult. The changes of EAAs in cerebrospinal fluid (CSF) of patients with traumatic brain injury are incompletely understood. METHODS: We used reversed-phase HPLC with precolumn derivatization with o-phthalaldehyde and fluorescence detection to measure Glu and Asp in CSF of 42 patients with acute head injury and 9 control adults without neurologic diseases. We assessed the Glasgow Coma Scale (GCS) on admission, the main lesion patterns on computed tomography (CT) scan within 24 h post trauma, and the Glasgow Outcome Scale (GOS) 3 months post injury. RESULTS: The mean concentrations of Glu and Asp in CSF in the brain-injured group were significantly higher than those of the control group (Glu, P <0.001; Asp, P <0.05). In patients admitted within 24 h after severe injury (n = 13), peak Glu values appeared within 48 h in 11 patients (85%), and the mean value remained higher than control values at day 7 (P <0.02). The concentrations of EAAs were higher in patients with severe injuries (GCS < or =8) than in those with milder injuries (Glu, P <0.001; Asp, P <0.05). GCS and peak EAAs correlated negatively (Glu, rs = -0.5706, P <0.001; Asp, rs = -0.5503, P <0.001). The patients with focal brain contusion on initial CT scan (n = 8) had a significantly lower peak Glu value than the patients with other patterns (n = 8-15; P <0.02 to 0.001). The peak value of EAAs in the poor-outcome group (including severe disability, vegetative state, and death) was significantly higher than in the good-outcome group (good recovery and moderate disability; Glu, P <0.001; Asp, P <0.01); GOS was closely correlated to the EAA values (Glu, rs = 0.5737, P <0.001; Asp, rs = 0.5470, P <0.001). CONCLUSIONS: The EAA concentrations in CSF increase after acute head injury and remain higher for at least 1 week post injury in severely injured patients. The more severe the trauma, the more obvious the excitotoxicity induced by EAAs and the worse the outcome.

Acute Disease↗
PubMed2001

[Anatomical study and clinical application of long head of triceps muscle for reconstruction of shoulder abduction].

OBJECTIVE: To study the morphological character of long head of triceps muscle for clinical application in reconstruction of shoulder abduction. METHODS: Forty-four upper extremities of fixed human adult cadavers were carefully dissected. The origins and the pedicles of blood vessels and nerves of long head of triceps muscle, as well as the maximum available size of the muscles, were measured. Six cases of clinical application of long head of triceps muscle for reconstruction of shoulder abduction were followed up for 3 to 11 months. RESULTS: The origins in the dorsal side of long head of triceps muscle were muscular and the ventral side were tendinous, which was 7.6 to 13.3 cm in length and 1.6 to 3.4 cm in width. The distance from the origin to the neurovascular pedicle was 5.7 to 11.4 cm. The radial nerve, which innervated the muscles, could be dissected for 2.9 to 11.8 cm in length. The blood supplies to the triceps muscle were from humeral artery (43.2%), 1.0 to 6.0 cm in length and 1.6 to 2.4 mm in diameter, and from humeral profundus artery (45.5%), 1.5 to 4.4 cm in length and 0.9 to 2.4 mm in diameter, if the vessel was separated to the humeral artery, the length was 1.5 to 6.3 cm. The neurovascular pedicles were multiple branched. In the 6 cases of clinical application of the triceps muscles, the operated shoulder could abduct from 5 degrees preoperatively (0 degree to 10 degrees) to 77.3 degrees (50 degrees to 90 degrees) postoperatively. CONCLUSION: In accordance to the anatomical character of the triceps muscles, the long head of triceps muscle is a suitable choice for reconstruction of shoulder abduction with optimistic outcomes.

Adolescent↗
PubMed2001

Differential telomerase expression and telomere length in primary intracranial tumors.

BACKGROUND: Telomerase activity and telomere length have been shown to be involved in controlling cell proliferation and regulating cell senescence. The authors examined telomerase activity and telomere length in intracranial tumors to determine the clinicopathological behavior of primary intracranial tumors with respect to telomerase expression and alteration of telomere length. METHODS: Telomerase activity was examined in 139 brain tumor samples. Telomere length was examined in 138 of the 139 samples. These tumors included 61 meningiomas, 27 schwannomas, 19 high-grade neuroepithelial tumors, and 32 low-grade neuroepithelial tumors. Telomerase activity was measured with a telomerase polymerase chain reaction, enzyme-linked immunosolvent assay kit. Telomere length was examined by Southern blot analysis for the terminal restriction fragment length. RESULTS: Telomerase activity was detected in 39.2% (20/51) of the neuroepithelial tumors. Detection rates were 47.4% (9/19) for anaplastic astrocytomas and glioblastomas and 34.4% (11/32) for low-grade neuroepithelial tumors. However, detectable telomerase activity was found in 30.8% (4/13) of atypical or malignant meningiomas, but was not detected in any schwannomas. There was a highly significant difference in the telomerase detection rate in neuroepithelial or non-neuroepithelial tumors (p = 0.001). Telomere elongation was found in 11.7% (7/60) of all meningiomas, 46.1% (6/13) of atypical or malignant meningiomas, and 14.8% (4/27) of schwannomas. Elongation of telomere length was detected in 12.6% (11/87) of the cases and 23.5% (12/51) in neuroepithelial tumors. This difference was also significant (p < 0.05). Telomere length was reduced in the majority, (75%, 3/4) of malignant or atypical meningiomas with detectable telomerase activity, but only 45% (9/20) of the neuroepithelial tumors. CONCLUSION: These results indicate that telomerase activation may be a critical step in the pathogenesis of intracranial tumors. Telomere length elongation also indicates a high potential for malignant behavior in these tumors.

Adolescent↗
PubMed2001

[QTL analysis of anther length and ratio of stigma exsertion, two key traits of classification for cultivated rice (Oryza sativa L.) and common wild rice (O. rufipogon Griff.)].

A genetic map including 120 RFLP markers covering 1418.2 cM has been constructed using a BC1 population derived from a cross between common wild rice (Oryza rufipogon Griff.) from Dongxiang, Jiangxi Province, China, and an elite Indica variety Guichao 2. The linkage orders and genetic distances of markers in this map are consistent with the map constructed by Rice Genome Program of Japan except the markers of short arm of Chromosome 1. The QTLs analysis of anther length and ratio of stigma exsertion, two key traits of classification for cultivated rice and common wild rice indicated that there are two QTLs controlling anther length located at the region of C424-G39 of Chromosome 2, and C2807-C1263 of Chromosome 9 respectively. It was also found that there are two QTLs controlling ratio of stigma exsertion, and located at the region of C2289-R1553 of Chromosome 5 and G1149-R1963 of Chromosome 8 respectively. The detected QTLs affecting the key traits of classification for wild rice and cultivated rice will be useful for study of molecular evolution mechanism of cultivated rice.

Chromosome Mapping↗
PubMed2001

[Measurement of chlorodifluoromethane(HCFC-22) in the atmosphere by using an O2-induced electron capture detector (ECD)].

Chlorodifluoromethane (CHClF2, HCFC-22), a typical substitute of dichlorodifluoromethane(CF2Cl2, CFC-12), which atmospheric concentration was only at 10(-12) V/V level. After preconcentrated air sample, O2-Induced method was used to enhance sensitivity of ECD response to HCFC-22. When O2 concentration in carrier gas was 0.54%, there was the greatest value of S/N(signal to noise) and ECD response increased by about 500 times. With the study of other conditions, such as selection of the ECD temperature, programing of the column oven temperature and carrier gas flow, a practicable analysis method with high sensitivity of ECD was established.

Air↗
PubMed2001

[The research of mathematical model for inositol-1,4,5-triphosphate-induced Ca2+ oscillations].

This article mainly illustrates the model for agonist-stimulated Ca2+ oscillations that involves two roles for cytosolic Ca2+: (a) inositol-1.4.5-triphosphate(IP3) inhibits Ca2+ release from the endoplasmic reticulum (ER); (b) IP3 acts on phosphate C, via a Gq protein related mechanism and hence stimulates Ca2+ release from ER. The model assumes that the ER IP3 receptor is a tetramer of independent subunit that can bind both Ca2+ and IP3. The reason for inhibition of Ca2+ oscillations is that IP3-receptor/Ca(2+)-channel slowly comes back to the beginning stable state. The key parameter for Ca2+ oscillations is the ratio of Maximum Ca2+ dependent IP3 input rate (v6) to IP3 decay rate constant (v7): I when v6/v7 < 0.28, no oscillation could be found; II when 0.28 < v6/v7 < 0.572, oscillation starts; III when v6/v7 > 0.572, Ca2+ ceases and arrives at a stable state quickly.

Calcium Channels↗
PubMed2001

Histopathological changes of Macaca mulatta infected with Plasmodium knowlesi.

OBJECTIVE: To study the histopathological changes of relevant internal organs of Macaca mulatta infected with Plasmodium knowlesi (P. knowlesi). METHODS: Histopathological examination of 3 monkeys who died of P. knowlesi infection, 2 P. knowlesi infected monkeys who died of treatment failure with artesunate suppository and 1 P. knowlesi infected monkey that was cured by piperaquine phosphate (PQP) but died of trauma and necrosis of the fore limb. RESULTS: The heart, liver, spleen, lung, kidney, brain, pancreas, parathyroid, pituitary and lymph nodes showed severe pathological changes in 3 monkeys (No. 1, 7 and 12) who died of P. knowlesi infection and 1 infected monkey (No. 72) who died of treatment failure with artesunate suppository. Red blood cells containing malarial parasites and pigments were concentrated in the capillaries of these organs. Malarial pigments were deposited in many organs or phagocytized by macrophages in 1 monkey (No. 131), it was cured by piperaquine phosphate but died of trauma and necrosis of the fore limb; cellular atrophy and disappearance of pancreatic islets, parathyroid and pituitary cells were also observed. One monkey (No. 33) treated with artesunate suppository, showed that blood parasites became negative but recrudesced and pituitary later died from a gavage accident. Its organs showed a significant difference to those of the infected monkeys receiving no treatment. Only the liver Kupffer cells and cerebral matrix contained malarial parasites and pigments; many relevant internal organs showed repair. CONCLUSION: The pathological changes of relevant internal organs of Macaca mulatta infected with P. knowlesi were examined in detail, especially cellular atrophy and the disappearance of pancreatic islets, parathyroid and pituitary cells and myolysis of cardiac muscles. These changes have not previously been reported elsewhere.

Animals↗
PubMed2001

pH-dependent conformational flexibility within the ribosomal peptidyl transferase center.

A universally conserved adenosine, A2451, within the ribosomal peptidyl transferase center has been proposed to act as a general acid-base catalyst during peptide bond formation. Evidence in support of this proposal came from pH-dependent dimethylsulfate (DMS) modification within Escherichia coli ribosomes. A2451 displayed reactivity consistent with an apparent acidity constant (pKa) near neutrality, though pH-dependent structural flexibility could not be rigorously excluded as an explanation for the enhanced reactivity at high pH. Here we present three independent lines of evidence in support of the alternative interpretation. First, A2451 in ribosomes from the archaebacteria Haloarcula marismortui displays an inverted pH profile that is inconsistent with proton-mediated base protection. Second, in ribosomes from the yeast Saccharomyces cerevisiae, C2452 rather than A2451 is modified in a pH-dependent manner. Third, within E. coli ribosomes, the position of A2451 modification (N1 or N3 imino group) was analyzed by testing for a Dimroth rearrangement of the N1-methylated base. The data are more consistent with DMS modification of the A2451 N1, a functional group that, according to the 50S ribosomal crystal structure, is solvent inaccessible without structural rearrangement. It therefore appears that pH-dependent DMS modification of A2451 does not provide evidence either for or against a general acid-base mechanism of protein synthesis. Instead the data suggest that there is pH-dependent conformational flexibility within the peptidyl transferase center, the exact nature and physiological relevance of which is not known.

Base Sequence↗
PubMed2001

Implication of macrophages in tumor rejection induced by CpG-oligodeoxynucleotides without antigen.

Phosphorothioate oligodeoxynucleotides containing CpG motifs (CpG-ODNs) display broad immunostimulating activity and have potential applications in cancer immunotherapy. To investigate the antitumor activity of CpG-ODNs and to study the role of macrophages and lymphocytes in tumor rejection, CpG-ODN's effects on 9 L glioma cells were assessed in Fisher rats, depleted or not in macrophages, in nude mice, and in SCID mice. In nondepleted rats, intratumoral injections with 100 microg of CpG-ODNs on days 5, 12, and 19, after s.c. 9 L cell inoculations, resulted in an 84% reduction of the tumor volumes, when compared with controls injected with saline (P < 0.0001). Whereas all control animals developed tumors, more than one-third of the treated rats remained tumor free. Rejection of established glioma induced a specific long-term immunity, as cured rats were protected against a subsequent 9 L injection, but not a RG2 cell inoculation, another syngenic glioma in Fischer rats. Macrophages played a critical role in the early phase of tumor rejection, because the CpG-ODN's effects were significantly decreased in the rats depleted in macrophages, and none of the macrophage-depleted rats treated with CpG-ODNs rejected the tumor. On the contrary, both nude and SCID mice, which have normal innate immunity, showed a significant decrease of tumor volume when treated with CpG-ODNs when compared with controls. T cells were however involved in a later phase of the tumor rejection, as all nude mice eventually developed tumors despite the initial tumor growth inhibition. Altogether, these data suggest that immunostimulatory CpG-ODNs induced tumor rejections through an early activation of innate immunity and priming of a specific immune response against glioma cells.

Adjuvants, Immunologic↗
PubMed2001

Inhibitory effect of quercetin on cultured neonatal rat cardiomyocytes hypertrophy induced by angiotensin.

AIM: To study the inhibitory effect of quercetin on cultured neonatal rat cardiomyocytes hypertrophy induced by angiotensin II (AngII) and its mechanism. METHODS: DNA, RNA, and protein synthesis were measured by incorporation of [3H]thymidine, [14C]uridine, and [3H]tyrosine, respectively. Protein content were measured by Lowry's method. Protein kinase C (PKC) activity was assayed by incubating PKC with histone IIIS and [gamma-(32)P]ATP. Tyrosine protein kinase (TPK) activity was assayed by incubating TPK with poly glutamate/tyrosine (4:1) and [gamma-(32P]ATP. RESULTS: After treated with AngIIat 10 nmol/L for 24 h, total protein content was greatly increased as compared with untreated group (P < 0.01). Incorporation of [14C]uridine and [3H]tyrosine was also greatly increased (P < 0.01) respectively, while incorporation of [3H]thymidine remained unchanged (P > 0.05). Ang II strongly increased cardiomyocytes PKC and TPK activities at 30 min. Que (1-100 micromol/L) could inhibit the increase of total protein content, incorporation of [14C]uridine and [3H]tyrosine, and PKC and TPK activities induced by Ang II in concentration-dependent manner. CONCLUSION: The inhibitory effect of Que on the cardiomyocytes hypertrophy was related to its inhibitory effect on PKC and TPK.

Angiotensin II↗
PubMed2001

[A comparative study on the sensitivity and specificity of cholinesterase and glutathione s-transferase in Gammarus pulex L].

Studies on the influences of lindane, pirimiphos methyl, permethrin, zinc and dodecyl linear alkybenzene sulfonate (LAS) on the activity and toxicity of cholinesterase (ChE) and glutathione s-transferase (GST) in Gammarus pulex L. showed that only pirimiphos methyl caused a change in ChE activity in Gammarus, with a significant reduction in enzyme activity after 24 h and 48 h exposure. Both lindane and permethrin caused a change in GST activity in Gammarus, with a significant increase in enzyme activity after 48 h exposure. Lindane alos caused a significant increase in GST activity after 24 h exposure. Biomarkers ChE and GST were demonstrated a high degree of specificity and sensitivity in comparison to the lethality assay, but GST activity was less specific than ChE activity.

Animals↗
PubMed2001

[Dynamic surveillance of risk behaviors facilitating sexually transmitted disease/acquired immunodeficiency syndrome transmission among permanent residents in Kunming city in 1996-1999].

OBJECTIVE: To monitor the trends of risk behaviors promoting sexually transmitted disease/Acquired immunodeficiency syndrome (STD/AIDS) transmission among general public in order to develop appropriate intervention strategies and to evaluate impact of intervention programs. METHODS: Two hundred subjects were randomly selected and interviewed every other month in Kunming city from 1996 to 1999. STD-AIDS-related information on knowledge, attitudes and behavior were collected during the interview. RESULTS: The knowledge of STD and AIDS transmission increased from 49.2% to 62.8% (chi 2 = 96.5, P < 0.01) and from 16.6% to 35.2% (chi 2 = 146.5, P < 0.01), respectively. Knowledge on condom use and attitude to AIDS did not change much. Self-reported prevalence of risk behaviors remained low. Residents aged between 15 and 39 had unprotected sex behavior (0.8%-2.5%) and drug use (0.3%-2.4%). CONCLUSION: The awareness on STD and AIDS transmission increased gradually. Risk behavior of STD/HIV infection existed among residents aged between 15 and 39 years, which called for intervention programs in the future.

Acquired Immunodeficiency Syndrome↗
PubMed2001

[Human telomerase RNA (hTR) expression in lung cancer in the Gejiu and Xuanwei regions of Yunnan].

OBJECTIVE: To investigate the correlation between the expression of hTR in and the pathogenesis of lung cancer in Gejiu and Xuanwei regions of Yunnan province. METHODS: By use of in situ hybridization, the expression of hTR gene was observed in 81 cases of lung cancer tissues including 24 cases of Gejiu Tin miners (GTM), 36 cases of Xuanwei farmers (XF) and 21 cases of other regions. RESULTS: hTR was detected in 65.4% (53/81) of the lung cancer cases. The positive rate of hTR in GTM, XF and other regions was 66.7% (16/24), 58.3% (21/36) and 76.2% (16/21) respectively. Positive hTR expression was not found in normal bronchial and alveolar epithelia, but was found in highly proliferating type II alveolar epithelial cells adjacent to the carcinoma (12.3%, 10/81). No significant difference was observed with regard to the positive rate of hTR expression among three different regions. There was no statistically significant correlation between the expression of hTR, the patients' sex, age and the differentiation degree of the tumor, but the expression of hTR was correlated with histological type and lymph node metastasis (P < 0.05). CONCLUSION: The expression of hTR is a prevailing event in lung cancer and therefore can be used as an indicator of lung malignancy.

Adult↗
PubMed2001

[The transfer and expression of human clotting factor IX in muscle mediated by electroporation].

OBJECTIVE: To probe into the feasibility of increasing hFIX cDNA transfer and expression in muscle. METHODS: The high-frequency electric field was used to promote both Lac-Z-encoding plasmid pCMV beta and hFIX-expressing plasmid G1NaMCIX to transfer and express in muscle. The effects of frequency and length of square pulse, as well as eletroporation time on hFIX expression were investigated. RESULTS: Electric stimulation could increase the transfer and expression of pCMV beta in muscle, the number of X-gal positive myofiber cells in electroporation-treated mice is 2.1 times larger than that of mice not treated by electroporation (P<0.01). The most optimal electric simulation condition for hFIX cDNA transfer and expression was obtained, under this condition, the highest level of hFIX antigen in plasma is (40+/- 5.4) ng/ml and 7 times higher than that of mice without electroporation P < 0.001). CONCLUSION: Electroporation is able to enhance hFIX cDNA transfer and expression in muscle efficiently.

Animals↗