Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 163 records · Page 9Linked to original sources

PubMed2001

Glatiramer acetate induces a Th2-biased response and crossreactivity with myelin basic protein in patients with MS.

Glatiromer acetate (GA) is an approved treatment for multiple sclerosis (MS). The proposed mechanism of action is the induction of GA-specific T cells characterized by protective anti-inflammatory Th2 response. We tested this hypothesis in 11 MS patients treated with GA from 1-19 months. Interferon-gamma and IL-5 (markers of Th1 and Th2 responses respectively) were assayed by ELISA in GA-specific T-cell lines (TCL) supernatants. Th1/Th2 bias was defined based on the ratio of IFN-gamma/IL-5 secretion. Fifty-eight pre-treatment and 75 on-treatment GA-specific TCL were generated. On-treatment mean IL-5 levels in GA-TCL increased significantly, whereas those for IFN-gamma were markedly reduced. Consequently, the ratio of IFN-gamma IL-5 also shifted in favor of a Th2 response. The percentage of GA-TCL classified as Th1 was decreased, whereas those classified as Th2 increased on-treatment as compared to pre-treatment. Some GA-specific TCL, (approximately 25%) generated during treatment secreted predominantly IL-5 in response to MBP and the immunodominant MBP peptide 83-99, indicating that these crossreactive antigens can act as partial agonists for GA-reactive TCL. These results strongly suggest that the mechanism of action of GA in MS involves the induction of crossreactive GA-specific T cells with a predominant Th2 cytokine profile.

Cell Line↗

PubMed2001

Antioxidant activity of 5-alkoxymethyl-6-chromanols.

The 5-alkoxymethyl-2,2,7,8-tetramethyl-6-chromanols (II) are excellent antioxidants against autoxidising safflower oil (ASO), although not as good as 2,2,5,7,8-pentamethyl-6-chromanol (I), the model compound of alpha-tocopherol. The aim of this work was to determine whether the rate of reaction of (II) with the radicals diphenylpicrylhydrazyl (DPP*) and galvinoxyl (ArO*) was directly proportional to their antioxidant activity against ASO. Compounds (II) reacted faster with DPP* than with ArO* but, in each case, slower than compound (I). The rates of reaction of I and II with both radicals followed the order I > II (R = H) > II (R = CH3) > II (R = other alkyls) and were directly proportional to their antioxidant activity against ASO.

Alkylation↗

PubMed2001

The ASK1 gene regulates B function gene expression in cooperation with UFO and LEAFY in Arabidopsis.

The Arabidopsis floral regulatory genes APETALA3 (AP3) and PISTILLATA (PI) are required for the B function according to the ABC model for floral organ identity. AP3 and PI expression are positively regulated by the LEAFY (LFY) and UNUSUAL FLORAL ORGANS (UFO) genes. UFO encodes an F-box protein, and we have shown previously that UFO genetically interacts with the ASK1 gene encoding a SKP1 homologue; both the F-box containing protein and SKP1 are subunits of ubiquitin ligases. We show here that the ask1-1 mutation can enhance the floral phenotypes of weak lfy and ap3 mutants; therefore, like UFO, ASK1 also interacts with LFY and AP3 genetically. Furthermore, our results from RNA in situ hybridizations indicate that ASK1 regulates early AP3 and PI expression. These results support the idea that UFO and ASK1 together positively regulate AP3 and PI expression. We propose that the UFO and ASK1 proteins are components of a ubiquitin ligase that mediates the proteolysis of a repressor of AP3 and PI expression. Our genetic studies also indicate that ASK1 and UFO play a role in regulating the number of floral organ primordia, and we discuss possible mechanisms for such a regulation.

Arabidopsis↗

PubMed2001

An angiotensin II type 1 receptor blocker, candesartan, increases myocardial apoptosis in rats with acute ischemia-reperfusion.

Angiotensin II (Ang II) and apoptosis contribute significantly to myocardial ischemia-reperfusion (I-R) injury. Evidence indicates that Ang II may activate apoptosis in myocytes. The present study was undertaken to investigate the effects of angiotensin receptor blockers (ARBs), candesartan, on the apoptosis of cardiac myocytes in rats after I-R. Rats were divided into a control group, a candesartan group I (0.015 mg/kg), and a candesartan group II (0.03 mg/kg). Candesartan was intravenously administered 30 min before ischemia. All rats were subjected to 30 min of coronary occlusion followed by 3 h of reperfusion. The data showed that left ventricular (LV) systolic pressure and LV +dp/dt was decreased after administration of candesartan, but increased after reperfusion in the candesartan group II, compared with those in the candesartan group I and control group. LV -dp/dt was decreased after candesartan administration in candesartan group II. The number of apoptotic cells in the candesartan groups (497+/-204 and 543+/-254, respectively) was higher than that in the control group (287+/-166; p<0.05). There was no significant difference in infarct size among the three groups. However, plasma CPK was lower in the candesartan groups than in the control group. Northern blot analysis showed that p53 mRNA was upregulated in the candesartan groups, in association with increased expression of bax mRNA. Immunohistochemical analysis showed that p53 and bax immunoreactivity were increased in both of the candesartan groups. In conclusion, candesartan increased apoptosis in the rat hearts after acute I-R, and this increase was possibly mediated by upregulation of p53 and bax gene expressions. In addition, candesartan was shown to improve LV function, in association with reduction of CPK release.

Acute Disease↗

PubMed2001

Eigenvector based spatial filtering of fetal biomagnetic signals.

In this paper we demonstrate the usefulness of an eigenvector based spatial filtering method for signal processing of multi-channel fetal magnetocardiogram (fMCG) and fetal magnetoencephalogram (fMEG) recordings. This method of filtering can separate signal and interference by exploiting the considerable spatial information contained in multi-channel recordings. Typically, fMCGs and fMEGs suffer from large cardiac interference and low signal-to-noise ratio. To isolate the signal from the interference, we identify their respective subspaces using one portion of the record dominated by the signal and another dominated by the interference. Each subspace is approximately rank two since the sources of the signal and interference can be modeled as current dipoles. The spatial filter consists of a linear transformation that preserves the signal subspace and annihilates the interference subspace. It is easier to implement than a matched filter, preserves the morphology and topography of the fetal signal, and effectively removes maternal cardiac interference, even when the maternal and fetal complexes overlap strongly in time or when small maternal movements or maternal arrhythmias alter the temporal character of the interference.

Evoked Potentials, Auditory↗

PubMed2001

Organ infectivity of Toxoplasma gondii in interferon-gamma knockout mice.

To determine the influence of interferon (IFN)-gamma on the organ infectivity and on the genetic susceptibility of susceptible (C57BL/6) and resistant (BALB/c) strains after peroral infection with cysts of Toxoplasma gondii. IFN-gamma knockout (KO) mice in C57BL/6 and BALB/c backgrounds were utilized. The kinetics of the changes in T. gondii abundance were evaluated with a quantitative competitive polymerase chain reaction assay in various organs at different times after peroral infection. In IFN-gamma KO mice, a T. gondii-specific gene, SAG1, was detected in all organs examined, and the protozoan proliferated much more actively than in wild-type mice. The abundance of T. gondii was much higher in mesenteric lymph nodes and the heart than in other organs. In contrast, in the nervous system organs and kidneys, only a weakly detectable reaction was observed. Toxoplasma gondii grew at a more rapid rate in the organs of IFN-gamma KO C57BL/6 mice than in the organs of IFN-gamma KO BALB/c mice during the course of infection. Destruction of the IFN-gamma gene showed remarkable effects on the infectivity in both susceptible and resistant mice.

Animals↗

PubMed2001

Current progress in the development and use of artemether for chemoprophylaxis of major human schistosome parasites.

Human schistosomiasis, a chronic and debilitating parasitic disease of the tropics, is ranked second after malaria in terms of public health importance. At present, there is no vaccine available, and chemotherapy is the cornerstone of schistosomiasis control. Praziquantel is the drug of choice. Oxamniquine has become difficult to obtain and metrifonate has recently been withdrawn from the market. Rapid re-infection following treatment and concern about praziquantel resistance called for the search of novel drugs for prevention and cure of schistosomiasis. Significant progress has been made with artemether, the methyl ether of dihydroartemisinin, already widely used for the treatment of malaria. The present article reviews the literature that led to the development of artemether for chemoprophylaxis in schistosomiasis, and it summarises the experiences so far obtained with its use to control schistosomiasis in different endemic settings. Topics covered include an overview of the global burden of schistosomiasis and approaches for its control; the nature and features of artemisinin and related derivatives, initially discovered as antimalarials, other bioactivities, and their recent discovery of antischistosomal properties; a historic account disclosing the antischistosomal activity of artemether; in vivo assessment of drug susceptibility of different developmental stages of schistosome parasites; artemether-induced pathology evidenced by scanning and transmission electron microscopy; the possible mechanism of action; in vivo studies with combination therapy of artemether and praziquantel; results of randomised controlled clinical trials of oral artemether for the prevention of patent infection and morbidity; and, ultimately the translation of this knowledge into public health action in different endemic settings towards a more integrated approach of schistosomiasis control.

Animals↗

PubMed2001

[The epidemiology of irritable bowel syndrome and functional constipation of Guangzhou residents].

OBJECTIVE: To investigate the prevalence rates of irritable bowel syndrome (IBS) and functional constipation in Guangzhou City. METHODS: A structured history using a questionnaire on gastrointestinal symptoms during the preceding one year was obtained from random sampling 2,892 residents, 1,006 consecutively patients who visited general practitioner and 495 consecutively patients who visited gastroenterologists. All the questionnaires were filled by trained doctors. RESULTS: The overall prevalence rates of irritable bowel syndrome and functional constipation in Guangzhou City were 5.6% and 3.0%. There were 10.1%, 34.3% and 5.4%, 4.8% visitors who complained IBS and functional constipation in the general internal outpatient department and gastrointestinal outpatient department. The female was predominant in both IBS and functional constipation. The ratio of male to female was 1:1.51 and 1:1.77. With the increase of age, the prevalence rate of functional constipation rose; but IBS did not. There were 23.9% IBS patients and 17.6% functional constipation patients who had ever seen a doctor for these diseases in the community. The percentages of IBS subclasses were as the following: diarrhea predominant: 63.2%; constipation predominant: 27.0%; others: 9.8%. CONCLUSION: The prevalence rates of IBS and functional constipation in Guangzhou City were lower than that in west countries.

Adolescent↗

PubMed2001

Signaling pathway mediated by kappa-opioid receptor is impaired in cardiac hypertrophy.

AIM: The responses of the intracellular calcium ([Ca2+]i) and the intracellular pH (pHi) to kappa-opioid receptor stimulation were determined in the single right ventricular myocytes isolated from the hearts of chronically hypoxic rats which exhibited right ventricular hypertrophy (RVH). METHODS: With the spectrofluorometric method, the electrically-induced [Ca2+]i transient and pHi were measured in myocytes loaded with fura-2 and BCECF [2',7'-bis-(2-carboxyethyl)-5-(and 6)-carboxyfluorscein], respectively. RESULTS: U50,488H, a selective kappa-opioid agonist decreased the electrically-induced [Ca2+]i transient and increased the pHi. The effect of U50,488H was mediated by protein kinase C (PKC). In the RVH, the effect of U50,488H on the [Ca2+]i transient and the pHi were significantly attenuated. In parallel, 4-phorbol 12-myristate 13-acetate (PMA), an activator of PKC, also decreased the [Ca2+]i transient and increased the pHi. In the RVH, the effects of PMA were blunted. The recovery of pHi, which was blocked by ethylisopropyl-amiloride (EIPA), following an acid loading induced by washout of 10 mmol/L NH4)Cl exposing to the cells for 10 min was the same in the RVH and control myocytes. CONCLUSION: kappa-Opioid receptor signaling was impaired in the cardiac hypertrophy due to a defect in the coupling of PKC signaling with its effector.

Animals↗

PubMed2001

[Clinical analysis of nosocomial infection of extended spectrum beta-lactamase-producing bacteria].

OBJECTIVE: To investigate the clinical characteristics of nosocomial infection of extended spectrum beta-lactamase(ESBL)- producing bacteria. METHODS: The data of 50 cases of ESBL(+) E. coli and K. pneumonia from January to November 1999 in Peking Union Medical Hospital were analysed; 45 cases of ESBL (-) infection were randomly selected as controls. t-test and chi-square tests were used for statistical analysis. RESULTS: Long time hospitalization and use of the third generation cephalosporins were risk factors for ESBL(+) pathogen infection(P < 0.02); the prevalence of ESBL(+) bacteria infection in abdominal and pelvic cavity was higher than that of ESBL(-) bacteria(P < 0.02); the outcome of properly treated group(sensitive antibiotics were used within 72 hours) was much better than improperly treated group. All ESBL(+) bacteria were sensitive to imipenam, the resistance rate of ESBL(+) bacteria to cefmetazole, amikacin and piperacillin/tazobactam was low; the in vitro activity of ceftazidim to ESBL(+) bacteria was high but the in vivo activity is still under study. CONCLUSION: The mortality of ESBL(+) bacteria infection was high; the outcome would be improved if sensitive antibiotics were chosen as soon as the diagnosis was made.

Anti-Bacterial Agents↗

PubMed2001

[Diversity of Sinorhizobium fredii strains].

Rhizobial strains were isolated from soils growing with soybean cultivar Heilong 33 and Willimas. Fifty Sinorhizobium fredii strains were chosen, and their biological characteristics including growth velocity, acid-alkali endurance, resistance of intrinsic antibiotics, utilization of carbon and nitrogen sources, absorption of congo red, ability of melanin production, and plasmid profiles were comparatively researched. The dendrogram was described using the method of cluster analysis, and the biodiversity of Sinorhizobium fredii from different soils was proved.

Carbon↗

PubMed2001

[Immunological mechanism of human alpha-interferon gene therapy for treatment of melonoma].

OBJECTIVE: To investigate the possibility of alpha-INF gene therapy for treatment of melonoma. METHODS: An experimental model of fibroblast-mediated human alpha-IFN gene therapy was established for treatment of melonoma and the activity of NK and M phi was determined. RESULTS: The NK and M phi activity was increasing significantly after the implantation of alpha-IFN secreted by cloning the fibroblast in vivo. Good therapeutic results could be achived if the NIH3T3-IFN-alpha+ cells were combined with the IL-2/AK. CONCLUSION: The results has indicated that the fibroblast-mediated gene therapy could be good to use it for the treatment of human melonoma. More effective results could be achieved by using it in combination with IL-2.

3T3 Cells↗

PubMed2001

192Ir endovascular irradiation prevents restenosis after balloon angioplasty in rabbit.

OBJECTIVE: To examine the effect of endovascular irradiation on restenosis after balloon angioplasty in rabbit. METHODS: After the establishment of rabbit iliac atherosclerosis model, balloon angioplasty was performed at the lesion segment of the iliac artery. Rabbits were randomly divided into three groups: control group, 10 Gy irradiated group and 18 Gy irradiated group. Endovascular irradiation was performed for irradiated groups at the dilated sites by introducing the 192Ir radioactive guidewire through a catheter. After four weeks, the animals were killed and the target segments were cut down. Histopathologic and morphometric analyses were carried out. RESULTS: The mean final lumen area in the 18 Gy group was larger than that in the control or 10 Gy group (P < 0.05). The intimal area in the 18 Gy group was smaller (P < 0.05). CONCLUSIONS: 192Ir endovascular irradiation may prevent restenosis after balloon angioplasty. The effect is related to the delivered dose. The mechanism is involved in inhibition of neointimal proliferation.

Angioplasty, Balloon↗

PubMed2001

Clinical and familial study of arrhythmogenic right ventricular cardiomyopathy.

OBJECTIVE: To explore the characteristics of arrhythmogenic right ventricular cardiomyopathy (ARVC). METHODS: Seven patients with arrhythmogenic right ventricular cardiomyopathy and 34 members of three families were studied. All patients and family members underwent history collection, clinical examination, electrocardiogram (ECG), two-dimensional echocardiography (2-DE) and a signal averaging electrocardiogram. Programmed ventricular stimulation was performed in five patients. RESULTS: All patients and family members had normal morphologic characteristics and normal function of the left ventricular by 2-DE. Fourteen persons had abnormal findings indicating ARVC. Five had enlargement of the right ventricular with diffused hypocontractility, eight had thin and systolic bulging in the focal anterior wall with hypokinesia and one had bulging of the inferior wall. Twenty-five persons (seven patients and 18 family members) had abnormal findings in ECG. Positive ventricular late potential was recorded in 13 persons (six patients). Two to three monomorphic ventricular tachycardia (VT) with left bundle branch block (LBBB) configurations were induced in five patients. Ventricular fibrillation was induced in two patients during the electrophysiologic study (EPS). Five patients had very high pacing threshold and/or ineffective pacing in one or many regions of the right ventricle. Two members of one family died suddenly. One member was a dwarf with ARVC. Spontaneous VT with a left bundle branch block (LBBB) configuration was recorded in five patients, polymorphic VT with extremely short coupling interval in one, and premature ventricular complexes with LBBB configuration in 12 (six patients). CONCLUSION: Our familial study strongly suggests that ARVC may be a hereditary disease and it is helpful in the diagnosis and detection of ARVC. The most common manifestations were abnormal structure and function of the right ventricle and abnormal ECG of repolarization and ventricular arrhythmia which originates from the right ventricle.

Adolescent↗

PubMed2001

[Transarterial chemoembolization with high dose iodized oil for the treatment of large hepatocellular carcinoma].

OBJECTIVE: To report the method and result of high dose iodized oil chemoembolization for the treatment of large hepatocellular carcinoma. METHODS: From 1993 to 1998, 163 patients with unresectable hepatocellular carcinoma were treated by transarterial chemoembolization (TACE) with more than 20 ml lipiodol. RESULTS: TACE with high dose lipiodol was well tolerated by the treated patients. In patients whose liver function was of Child A stage, or in patients whose residual indocyanine green level 15 min after injection was less than 20%, the frequency of post-treatment hepatic insufficiency was not significantly different from that of patients treated with routine dose of lipiodol. On CT scan at 4 wk after TACE, more lipiodol was located in the liver. The 1-, 2-,3-year survival rate of patients in Child A stage was 79.8%, 50.3%, and 38.5%, respectively, as compared to 57.5%, 24.8% and 8.37%, respectively in patients treated with routine dose of lipiodol (P = 0.0136). CONCLUSION: High dose lipiodol TACE for the treatment of large hepatocellular carcinoma is practically acceptable with better therapeutic effect but its use should be limited to those patients with compensated liver function.

Abdominal Pain↗

PubMed2001

[Evaluation of methods of detection for prostate neoplasm].

OBJECTIVE: To evaluate the significance of serum prostate specific antigen (PSA), digital rectal examination (DRE), transrectal ultrasound (TRUS) and magnetic resonance imaging (MRI) as guide to perform prostate needle biopsy. METHODS: One hundred forty-eight patients suspicious of prostate neoplasm were undergone transrectal ultrasound-guided prostate needle biopsy. The pathologic diagnosis was analyzed in association with the results of PSA, DRE, TRUS and MRI in various combinations. RESULTS: The positive rate of biopsy was 43.9%. While abnormal DRE or PSA contributed in the detection of prostate cancer, serum PSA became more reliable when combined with DRE, TRUS or MRI, but the contribution of each of the three diagnostic procedures was not significantly different. The sensitivity of MRI was higher than that of DRE or TRUS, whereas TRUS was more specific than PSA or MRI. CONCLUSION: RE and PSA can be used for preliminary screening of prostate cancer. When combined with TRUS and MRI, the positive rate of diagnosis is increased. So is the specificity of the diagnosis which helps avoid unnecessary needle biopsy.

Aged↗

PubMed2001

[Multivariate analysis of prognosis of patients with stage IE non-Hodgkin's lymphomas of the nasal cavity].

OBJECTIVE: To analyze the factors affecting prognosis of patients with primary non-Hodgkin's lymphomas (NHL) of the nasal cavity. METHODS: From Jan. 1968 to Dec. 1997, a total of 71 patients with stage IE(Ann Arbor staging system, 1971) primary non-Hodgkin's lymphomas of the nasal cavity were treated in the Tumor Hospital of Sun Yat-sen University of Medical Sciences. In 37 of the 71 patients, the lesions were limited in the nasal cavity (limited IE), and in 34, the lesions were locally extended involving the adjacent structures (extended IE) Forty-four patients were treated with radiotherapy and 27 with radiotherapy plus chemotherapy. Survival analysis was done by the Kaplan-Meier method, and multivariate analysis was carried out using Cox proportional hazard model. RESULTS: The 5- and 10-year survival rate was 71.9% and 59.7% respectively in patients who had complete response to radiotherapy. The 5- and 10-year survival rate was both 13.9% in patients who had residual tumors after treatment. The 5- and 10-year survival rate was 69.8% and 56.7% in patients with limited IE lesions, but 40.7% and 35.6% in those with extended IE lesions. The prognosis was better in younger (< 44 years) than in older patients. The 10-year survival rate of patients received radiotherapy alone and those combined with chemotherapy was 52.0% and 75.0% respectively for limited IE as compared to 37.6% and 45.0% for extended IE. B symptoms did not significantly affect clinical outcome. Multivariate analysis showed that the immediate response to radiotherapy, invasion of the primary tumor outside of nasal cavity and patients' age were independent prognostic factors. CONCLUSION: Radiotherapy is the main treatment method for stage IE non-Hodgkin's lymphoma of the nasal cavity. Addition of chemotherapy can improve long-term survival. The local tumor response to radiotherapy, clinical staging and age of patients have significant influence on patients' prognosis.

Adolescent↗

PubMed2001

[To select and measure the biomechanical properties of bone of rat].

In the experimental studies designed to evaluate the effects of different factors on the biomechanical properties of bone, careful selection of rats and the scientific indices is very important. The aim of this paper is to recommend some essential methods for testing and calculating the biomechanical properties of rat bone such as tension, compression, bending and torsion.

Algorithms↗