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Biomedical subjects

L Ma

Publications and source records attributed to L Ma.

At least 325 records · Page 18Linked to original sources
PubMed1998

Cloning and sequencing of the gene encoding Toho-2, a class A beta-lactamase preferentially inhibited by tazobactam.

Escherichia coli TUM1083, which is resistant to ampicillin, carbenicillin, cephaloridine, cephalothin, piperacillin, cefuzonam, and aztreonam while being sensitive to cefoxitin, moxalactam, cefmetazole, ceftazidime, and imipenem, was isolated from the urine of a patient treated with beta-lactam antibiotics. The beta-lactamase (Toho-2) purified from the bacteria hydrolyzed beta-lactam antibiotics such as penicillin G, carbenicillin, cephaloridine, cefoxitin, cefotaxime, ceftazidime, and aztreonam and especially had increased relative hydrolysis rates for cephalothin, cephaloridine, cefotaxime, and ceftizoxime. Different from other extended-spectrum beta-lactamases, Toho-2 was inhibited 16-fold better by the beta-lactamase inhibitor tazobactam than by clavulanic acid. Resistance to beta-lactams was transferred by conjugation from E. coli TUM1083 to E. coli ML4909, and the transferred plasmid was about 54.4 kbp, belonging to the incompatibility group IncFII. The cefotaxime resistance gene for Toho-2 was subcloned from the 54.4-kbp plasmid. The sequence of the gene was determined, and the open reading frame of the gene was found to consist of 981 bases. The nucleotide sequence of the gene (DDBJ accession no. D89862) designated as bla(toho) was found to have 76.3% identity to class A beta-lactamase CTX-M-2 and 76.2% identity to Toho-1. It has 55.9% identity to SHV-1 beta-lactamase and 47.5% identity to TEM-1 beta-lactamase. Therefore, the newly isolated beta-lactamase designated as Toho-2 produced by E. coli TUM1083 is categorized as an enzyme similar to Toho-1 group beta-lactamases rather than to mutants of TEM or SHV enzymes. According to the amino acid sequence deduced from the DNA sequence, the precursor consisted of 327 amino acid residues. Comparison of Toho-2 with other beta-lactamase (non-Toho-1 group) suggests that the substitutions of threonine for Arg-244 and arginine for Asn-276 are important for the extension of the substrate specificity.

Amino Acid Sequence↗
PubMed1998

A protein critical for a Theiler's virus-induced immune system-mediated demyelinating disease has a cell type-specific antiapoptotic effect and a key role in virus persistence.

TO subgroup strains of Theiler's murine encephalomyelitis virus (TMEV) induce a persistent central nervous system infection and demyelinating disease in mice. This disease serves as an experimental model of multiple sclerosis (MS) because the two diseases have similar inflammatory white matter pathologies and because the immune system appears to mediate demyelination in both processes. We previously reported (H. H. Chen, W. P. Wong, L. Zhang, P. L. Ward, and R. P. Roos, Nat. Med. 1:927-931, 1995) that TO subgroup strains use an alternative initiation codon (in addition to the AUG used to synthesize the picornavirus polyprotein from one long open reading frame) to translate L*, a novel protein that is out of frame with the polyprotein and which plays a key role in the demyelinating disease. We now demonstrate that L* has antiapoptotic activity in macrophage cells and is critical for virus persistence. The antiapoptotic action of L* as well as the differential translation of L* and virion capsid proteins may foster virus persistence in macrophages and interfere with virus clearance. The regulation of apoptotic activity in inflammatory cells may be important in the pathogenesis of TMEV-induced demyelinating disease as well as MS.

Animals↗
PubMed1998

Drugs affecting phospholipase C-mediated signal transduction block the olfactory cyclic nucleotide-gated current of adult zebrafish.

Amino acid and bile salt odorants are detected by zebrafish with relatively independent odorant receptors, but the transduction cascade(s) subsequently activated by these odorants remains unknown. Electro-olfactogram recording methods were used to determine the effects of two drugs, reported to affect phospholipase C (PLC)/inositol tripohsphate (IP3)-mediated olfactory transduction in other vertebrate species, on amino acid and bile salt-evoked responses. At the appropriate concentrations, either an IP3-gated channel blocker, ruthenium red (0.01-0.1 microM), or a PLC inhibitor, neomycin (50 microM), reduced amino-acid-evoked responses to a significantly greater extent than bile salt-evoked responses. Excised patch recording techniques were used to measure the affects of these drugs on second-messenger-activated currents. Ruthenium red and neomycin are both effective blockers of the olfactory cyclic nucleotide-gated (CNG) current. Both drugs blocked the CNG channel in a voltage-dependent and reversible manner. No IP3-activated currents could be recorded. The differential effects of ruthenium red and neomycin on odor-evoked responses suggest the activation of multiple transduction cascades. The nonspecific actions of these drugs on odor-activated transduction pathways and our inability to record an IP3-activated current do not permit the conclusion that zebrafish, like other fish species, use a PLC/IP3-mediated transduction cascade in the detection of odorants.

Animals↗
PubMed1998

Short report: An imported case of cystic echinococcosis in Japan diagnosed by imaging and serology with confirmation of Echinococcus granulosus-specific DNA sequences.

We report one case of cystic echinococcosis (CE) in Japan in a native of Nepal. Ultrasonography and computed tomography scan of the liver revealed unique cystic lesions with or without daughter cysts of Echinococcus granulosus. Immunoblot analysis using crude antigens of E. multilocularis and cyst fluid of E. granulosus, without reference to these image analyses, strongly suggested this was a case of CE. We found protoscoleces in surgically removed hepatic lesions and analyzed the mitochondrial cytochrome c oxidase subunit I (COI) gene by the polymerase chain reaction. Based on the similarity in DNA sequences of the COI gene of this Echinococcus spp. with that of previously reported sheep-dog strain (GI), the parasite was considered to be the so-called common sheep strain of E. granulosus.

Adult↗
PubMed1998

Novel antigens for neurocysticercosis: simple method for preparation and evaluation for serodiagnosis.

Neurocysticercosis (NCC), which is caused by infection with the larval stage of the pork tapeworm (Taenia solium), is now recognized as a major cause of neurologic diseases in countries where the infection is endemic. Migration of persons from these countries is resulting in diagnosis and local transmission in nonendemic countries at increasing rates. In the present study, immunoblotting and an ELISA were carried out using antigens of T. solium cysticerci fractionated by isoelectric focusing and serum samples from patients with NCC, alveolar (AE) or cystic echinococcosis (CE), and other diseases. Immunoblot analysis revealed antigens fractionated by isoelectric focusing (pH 9.2-9.6) either from cyst fluid of T. solium cysticerci or from intact cysts had unique components (glycoproteins) highly specific and sensitive for detection of NCC exclusively. All confirmed NCC serum samples (53 of 53) recognized at least three major bands of 10-26-kD of fractions with pH 9.2-9.6 from either intact cysts or cyst fluid. These bands were not recognized by sera from patients with other parasitic diseases including AE (0 of 34), CE (0 of 36), or other heterologous parasitoses (0 of 77), patients with hepatoma (0 of 19) or sarcoidosis (0 of 11), or sera from healthy controls (0 of 29). The ELISA using the antigens showed the same sensitivity and specificity for differentiation of NCC (53 of 53) from other diseases (0 of 107) or healthy individuals (0 of 29). Both immunoblotting and the ELISA using the fractionated antigens readily differentiated all NCC from AE or CE in a blind test of 29 serum samples of persons with NCC, CE, and AE. Antigens fractionated from cyst fluid of T. solium cysticerci by a simple, single-step isoelectric focusing (pH 9.2-9.6) are highly specific and sensitive for differential serodiagnosis of NCC in immunoblotting and/or an ELISA.

Animals↗
PubMed1998

Simvastatin, a potent HMG-CoA reductase inhibitor, inhibits the proliferation of human and bovine endothelial cells in vitro.

We investigated in vitro effect of simvastatin, a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on the proliferation of human and bovine endothelial cells (EC) compared to that of bovine smooth muscle cells (SMC). Cells were cultured in a medium supplemented with 10% normal serum (FBS). Simvastatin at concentrations ranging from 0.1 microg/ml to 10 microg/ml were used. In each kind of cells the proliferation was markedly reduced at 1 microg/ml of simvastatin (P<0.01) which was accompanied by morphological changes in the cell shape. We conclude that simvastatin inhibits the proliferation of not only the smooth muscle cells but also the endothelial cells.

Animals↗
PubMed1998

[Strategy on the prevention and treatment of chronic diseases among residents in Dongcheng District, Beijing].

Chronic diseases, in particular, circulatory diseases characterized by high mortality, morbidity, and lack of special treatment have become serious problems to the residents living in the Beijing communities. To learn the above mentioned diseases among people at the community level and to investigate treatment and preventive method concerned studies on chronic circulatory system diseases among people living in communities in Dongcheng where few disease were under special control studies were carried out between 1981 and 1997. We found that the studied residents who had received and adopted a series of preventive measures as health education, giving up smoking, reducing alcohol and salt consumption, diet balance and practicing physical exercises, had greatly improved their health condition. Because of the positive results, we addressed some long-termed suggestions on the treatment and prevention for chronic patients with circulatory system diseases which is believed to have established a solid ground for the future.

Cardiovascular Diseases↗
PubMed1998

Linkage analysis of the genetic markers of the candidate genes with non-insulin dependent diabetes mellitus in Chinese families.

OBJECTIVE: To explore the relationship between the genetic markers of the candidate genes (insulin receptor, glucose transporter 2 and glucokinase) and non-insulin dependent diabetes mellitus (NIDDM) in Chinese pedigrees. METHODS: Genomic DNA of 87 members in 12 Chinese NIDDM pedigrees was amplified using PCR technique. Denaturing polyacrylamide gel electrophoresis was applied to detect short tandem repeat polymorphisms. The linkage program was used under the models of autosomal dominant and recessive. The individuals with impaired glucose tolerance (IGT) of age < or = 45 and age > 45 were counted as affected and unknown status respectively. RESULTS: Linkage of insulin receptor gene and NIDDM was strongly and significantly rejected with total LOD score of-infinity (theta = 0.000). Linkage analysis of glucose transporter 2 gave the result with total LOD score of 2.646 (theta = 0.000) in 4 pedigrees. Linkage of glucokinase and NIDDM was of significance with total LOD score reaching 3.150 in the integration of 6 pedigrees. CONCLUSIONS: Mutations in or near the insulin receptor gene are unlikely to be the major cause of inherited predisposition to NIDDM in Chinese pedigrees that are related in this study, not excluding the principal role in the other Chinese or populations, while the mutations/variations near or at the glucose transporter 2 gene locus might be something of the cause, which needs more data to be ascertained, of familial NIDDM in Chinese pedigrees. However, the variations in or near the glucokinase gene might play a dominant role in the development of NIDDM in some Chinese and represent a subgroup of common NIDDM.

Adult↗
PubMed1998

[Influence of pravastatin therapy on expression of P-selectin].

OBJECTIVE: To study the mechanism of pravastatin enhancing atherosclerosis regression. METHODS: Patients with hypercholesterolemia were treated with pravastatin 10-20 mg/d for 4 and 8 weeks. The changes of blood cholesterol and platelet functions were examined. RESULTS: After 4 weeks and 8 weeks treatment, the expression of platelet membrane P-selectin was decreased from 748 +/- 154 molecular number(MN)/platelet to 478 +/- 110 MN/platelet and 378 +/- 119 MN/platelet, respectively, plasma P-selectin was decreased from 24.3 +/- 9.9 micrograms/L to 16.8 +/- 4.5 and 16.1 +/- 4.0 micrograms/L, respectively, correlative with the lowering of blood cholesterol. Platelet P-selectin was positively correlated with plasma P-selectin(r = 0.8722). CONCLUSION: The early benefit of pravastatin in enhancing atherosclerosis regression was partly due to the improvement of platelet function.

Female↗
PubMed1998

[Expression of opioid-receptor-like receptor (ORL1) gene in rat brain].

In situ hybridization with a digoxigenin-labeled oligonucleotide probe was used to investigate the expression of opioid-receptor-like receptor (ORL1) gene in rat brain. It was observed that ORL1 mRNA is widely expressed in many regions of rat brain, particularly in cerebral cortex, thalamus, hypothalamus, amygdala, hippocampus, septum, habenula, periaqueducted gray, raphe nuclei and locus coeruleus structure. These findings suggest that ORL1 receptor may participate in modulating a number of physiological functions in the brain in addition to pain.

Animals↗
PubMed1998

[A retrospective analysis of autogenous alveolar bone grafting in clefts of the lip and palate].

OBJECTIVE: To analyse factors which are able to influence the result of alveolar bone grafting (AABG). METHODS: A retrospective analysis was performed in a group of 54 alveolar cleft patients (30 males and 13 females, total 66 sides) who received AABG. The age range of the patients was 8-44 years. The cleft area was restored with autogenous cancerous bone from iliac crest. All the patients have been followed up for at least three months postoperatively. The result of the bone grafting was evaluated on the radoigraphs. RESULTS: 1. The overall survival rate of AABG was 94%, and clinical successful rate of AABG was 89%; 2. The successful rate of AABG was correlated with the age of the patients. The successful rate of AABG in group of patients above 18-year-old was significantly lower than other groups; 3. With the exception of cleft palate fistula operation, when the AABG was done simulatneously with other cleft lip and palate operations, the successful rate of AABG was not significantly different from that of the sole AABG operation; 4. The successful rate of AABG in patients with cleft lip or incomplete cleft palate was superior to patients with complete cleft palate. CONCLUSION: Forming of excelent bone grafting bed and closely surturing is the key to the success of AABG.

Adolescent↗
PubMed1998

[Effect of age on mineralization expression of periodontal ligament cell clones].

OBJECTIVE: To evaluate the effect of age on the expression of mineralized tissue progenitors in the peridontium and the effect of basic fibroblast growth factor (bFGF). METHODS: The periodontal ligament (PDL) tissues that derived from three old and 4 young donors were cultured and cells were cloned. The mineralizing ability were detected with or without bFGF treatment in the presence of dexamethasone. The cell cloning technic was employed in present study. RESULTS: The results indicated that the frequency of mineralized tissue progenitors (old donor: 4.1%) and the numbers of cell clones that mineralized with bFGF treated in the PDL cultures derived from old donors (3.4%) is considerably less than that of cultures obtained from young donors (17.7% and 16.9%). bFGF enhanced the mineralization of cell clone but not the parent population. CONCLUSION: It is concluded that the poor stem cell and progenitors in PDL and the low reaction of progenitors to growth factors in PDL are responsible for the limited regenerative capacity of periodontium in old patient.

Adult↗
PubMed1998

[Optimization of non-gel sieving capillary electrophoretic separation of DNA fragments of hundreds of base pairs].

Non-gel sieving capillary electrophoresis has been employed in the biological sciences for the size-based separation of macromolecules such as nucleic acids. In this paper, four factors i.e. electric field strength, capillary length, capillary diameter and hydroxy-propylmethylcellulose (HPMC) concentration were integratively evaluated to select the optimal condition of separating DNA fragments of a few hundreds of base pairs through orthogonal analysis. Conclusion was made through comprehensive analysis: better separation could be achieved in longer capillary, smaller inside diameter of capillary and less field strength. In practical application, effective separation in short time is important. We preferred to employ 8 g/L HPMC in coated capillary (37 cm x 75 microns i.d.) and electric field strength of 324 V/cm in separating DNA fragments of hundreds of base pairs. From sampling to getting results only a few more than ten minutes were needed in capillary electrophoresis. It needs less amount of sample (a few nanoliters) and shows higher sensitivity (0.1 pmol in UV detection) than polyacrylamide gel electrophoresis (PAGE). pBR322/Msp I fragments were completely resolved in both capillary electrophoresis and PAGE, and four-bases resolution was obtained. When the concentration of the PCR product is too low (< 20 mg/L), PCR reaction system is used as a negative control to make sure of the peak generated by the unpurified PCR products, avoiding interference made by PCR buffer and polymerase.

Apolipoprotein B-100↗
PubMed1998

[The chemical constituents of Goniothalamus howii Merr].

Two new compounds were isolated from the chloroform soluble fraction of ethanolic extract of bark of Goniothalamus howii Merr. On the basis of their chemical properties and spectral data (MS, UV, IR, 1H and 13CNMR) they were identified as 6S (1R-hydroxy-2R-cinnamyloxyphenethyl) 5, 6-dihydro-5S-hydroxy-2-pyrone named Howiinol A and 6S-(1S, 2R-epoxyphenethyl-5S-cinnamyloxy) 5, 6-dihydro-2-pyrone named Howiinin A. Howiinol A showed significant antitumor activities toward human tumor cell in vitro and in vivo and less toxic.

Animals↗
PubMed1998

[Detection of Cryptosporidium parvum in fecal samples using polymerase chain reaction combined with non-radioactive labeled DNA probe hybridization].

AIM: To develop a non-radioactive labeled probe hybridization technique for the detection of the PCR products of Cryptosporidium parvum DNA in fecal samples and evaluate its specificity and sensitivity. METHODS: DNA of C. parvum was prepared directly from C. parvum infected patients' fecal samples by the direct lysis method, and was used as the template for PCR. A pair of oligonucleotide primers was synthesized and used to prime the amplification of a 452 bp target fragment specific for C. parvum. The PCR products were directly spotted or transferred on to NC membrane. Then, the PCR products were hybridized with the biotin-labeled oligonucleotide probe and coloured by a substrate BCIP (5-bromo-4-chloro-3-indolyl-phosphate). RESULTS: Positive hybridized signals were only showed in the PCR products of DNA extracted from the fecal samples of C. parvum infected patients, but not in the other DNA of P. yoelii, L. donovani, G. lamblia, C. albicans, E. coli and human leucocytes. The lowest detectable amount of both dot or Southern blotting hybridization was 0.1 pg of C. parvum DNA. CONCLUSION: A combination of PCR and non-radioactive biotin-labeled probe hybridization assay is highly sensitive, specific, and relatively simple and safe for the detection of the PCR products of C. parvum in fecal samples.

Animals↗
PubMed1998

[Identification of crude drugs from genus Leonurus].

The structure in cross section of stem and lamina of 9 species and 1 variety from genus Leonurus, whose herb used as Yimu Cao, were reported. Diagnostic characteristics were listed out in a key for identification.

Drugs, Chinese Herbal↗
PubMed1998

Ovariectomy and estrogen-induced alterations in myocardial contractility in female rabbits: role of the L-type calcium channel.

The effects of ovariectomy and estrogen replacement on myocardial contractility were examined in female rabbits. Ovariectomy failed to alter left ventricular mass, papillary muscle cross-sectional area or isometric force. Estrogen replacement after ovariectomy (0.15 microg/kg/day i.m. 17beta-estradiol acetate for 7 days) increased left ventricular mass and papillary muscle mass, and reduced isometric force compared to control and ovariectomy groups. Ovariectomy did not alter increased isometric force with isoproterenol, but decreased the ED50 for Bay K8644 (compared to control and estrogen groups). Estrogen replacement increased the ED50 for isoproterenol- and Bay K8644-induced isometric force compared to control and ovariectomy groups. Ovariectomy increased and estrogen replacement decreased isometric force associated with increased Ca++o. Acute exposure to 17beta-estradiol or diethylstilbesterol (10(-7) M, 10(-6) M) failed to alter isometric force in control papillary muscles. Estrogen replacement reduced the number, but not the dissociation constant for 3H-nitrendipine binding in plasma membrane preparations (compared to ovariectomy and control groups). Peak L-type calcium currents in isolated ventricular myocytes from the three treatment groups were not significantly different. The data are consistent with an ovariectomy-induced increase and estrogen-induced decrease in L-type calcium channel density in rabbit myocardium. Estrogen-induced alterations in L-type calcium channel expression and contractility are subsequently modified by estrogen-induced cardiac hypertrophy.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗