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Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 1,099 records · Page 61Linked to original sources
PubMed1995

Difference of lifestyle advice between traditional Chinese medical doctors (TCMDs) and Western-style medical doctors (WSMDs) in People's Republic of China.

The role of physicians in providing lifestyle advice is very important in disease prevention and health promotion. This study was designed to examine (a) the difference of lifestyle advice provided for general practice patients between traditional Chinese medical doctors (TCMDs) and Western-style medical doctors (WSMDs), (b) the difference of lifestyle advice provided for cardiovascular disease (CVD) patients between the TCMDs and WSMDs, (c) the difference of lifestyle advice provided for general practice and CVD patients by the TCMDs, and (d) the difference of lifestyle advice provided for general practice and CVD patients by the WSMDs. One thousand four-hundred and thirty general practice patient records and 640 CVD patient records from a Western-style medical hospital, and 1620 general practice records and 830 CVD patient records from a traditional Chinese medical hospital were selected for comparison. Results indicated that TCMDs were more likely to provide nutrition, exercise, and stress management for their patients than WSMDs. On the other hand, WSMDs were more likely to provide smoking and alcohol consumption for their patients than the TCMDs. In addition, both TCMDs and WSMDs were more likely to provide all categories of lifestyle advice for their CVD patients than their general practice patients.

China↗
PubMed1995

Cytolysis of human erythrocytes by a covalent antibody-selenium immunoconjugate.

A selenium (Se)-containing immunoconjugate of a human anti-erythrocyte membrane antibody (Ab-Se) has been synthesized via oxidation of the carbohydrate moieties of the antibody and covalent coupling with selenocystamine. The isolated Ab-Se immunoconjugate is shown to be more hemolytic than is selenocystamine when expressed on equivalent selenium basis. Native antibody preincubated with the human erythrocytes prevented hemolysis induced by the Ab-Se immunoconjugate. As observed microscopically, the Ab-Se immunoconjugate caused extensive damage to the erythrocyte membrane and lysis. The cytotoxicity of Se toward the human erythrocytes is believed to be caused initially by the localized generation of superoxide (O2.-) within the cell membrane. This is the first demonstration of site-directed immunoselectivity of Se cytotoxicity and demonstrates the potential for a free radical pharmacology based on localized Se-generated O2.-.

Cystamine↗
PubMed1995

Melatonin reduces both basal and bacterial lipopolysaccharide-induced lipid peroxidation in vitro.

The protective effect of melatonin against lipopolysaccharide (LPS)-induced oxidative damage was examined in vitro. Lung, liver, and brain malonaldehyde (MDA) plus 4-hydroxyalkenals (4-HDA) concentrations were measured as indices of induced membrane peroxidative damage. Homogenates of brain, lung, and liver were incubated with LPS at concentrations of either 1, 10, 50, 200, or 400 micrograms/ml for 1 h and, in another study, LPS at a concentration of 400 micrograms/ml for either 0, 15, 30, or 60 min. Melatonin at increasing concentrations from 0.01-3 mM either alone or together with LPS (400 micrograms/ml) was used. Liver, brain, and lung MDA + 4-HDA levels increased after LPS at concentrations of 10, 50, 200 or 400 micrograms/ml; this effect was concentration-dependent. The highest levels of lipid peroxidation products were observed after tissues were incubated with an LPS concentration of 400 micrograms/ml for 60 min; in liver and lung this effect was totally suppressed by melatonin and partially suppressed in brain in a concentration-dependent manner. In addition, melatonin alone was effective in brain at concentrations of 0.1 to 3 mM, in lung at 2 to 3 mM, and in liver at 0.1 to 3 mM; in all cases, the inhibitory effects of melatonin on lipid peroxidation were always directly correlated with the concentration of melatonin in the medium. The results show that the direct effect of LPS on the lipid peroxidation following endotoxin exposure is markedly reduced by melatonin.

Aldehydes↗
PubMed1995

Aggressive pattern of angina after successful coronary angioplasty: the role of clinical and angiographic factors.

To assess possible clinical and angiographic factors associated with acute coronary events following PTCA, we performed quantitative angiography in 168 consecutive patients who had undergone successful angioplasty in a native vessel (94 for stable angina, 74 for unstable angina), and who were restudied (24 +/- 15 weeks; range 4 to 52) because of recurrent anginal symptoms. Of the 168 patients, 38 (Group 1) were restudied because the pattern of angina was aggressive (unstable angina in 31, myocardial infarction in 7) and 130 because of effort-related angina (Group 2). the two patient groups were well matched for extent of initial disease but patients in Group 1 were younger (P=0.03). PTCA for unstable angina was originally performed more frequently in Group 1 than in Group 2 (27 of 38 patients (71% vs 47 of 130 patients (36%), P=0.0004). Disease progression in non-dilated segments occurred in 10 patients (26%) in Group 1 compared with eight (6%) in Group 2 (P=0.0004). Disease progression in non-dilated segments occurred in nine patients (24%) in Group 1 and in Group 2 (P=0.0004). Disease progression in non-dilated segments occurred in nine patients (24%) in Group 1 and in 10 (8%) in Group 2 (P=0.0006). Our conclusion is that patients who require re-investigation as a result of angina which has become aggressive following PTCA are usually those who originally underwent PTCA for unstable angina. These patients have a higher incidence of occlusive restenosis or disease progression.

Adult↗
PubMed1995

Deletion analysis of the starch-binding domain of Aspergillus glucoamylase.

The large form of glucoamylase (GAI) from Aspergillus awamori (EC 3.2.1.3) binds strongly to native granular starch, whereas a truncated form (GAII) which lacks 103 C-terminal residues, does not. This C-terminal region, conserved among fungal glucoamylases and other starch-degrading enzymes, is part of an independent starch-binding domain (SBD). To investigate the SBD boundaries and the function of conserved residues in two putative substrate-binding sites, five gluco-amylase mutants were constructed with extensive deletions in this region for expression in Saccharomyces cerevisiae. Progressive loss of both starch-binding and starch-hydrolytic activity occurred upon removal of eight and 25 C-terminal amino acid residues, or 21 and 52 residues close to the N-terminus, confirming the requirement for the entire region in formation of a functional SBD. C-terminal deletions strongly impaired SBD function, suggesting a more important role for one of the putative binding sites. A GAII phenocopy showed a nearly complete loss of starch-binding and starch-hydrolytic activity. The deletions did not affect enzyme activity on soluble starch or thermo-stability of the enzyme, confirming the independence of the catalytic domain from the SBD.

Amino Acid Sequence↗
PubMed1995

3-D structure of the D153G mutant of Escherichia coli alkaline phosphatase: an enzyme with weaker magnesium binding and increased catalytic activity.

The substitution of aspartate at position 153 in Escherichia coli alkaline phosphatase by glycine results in a mutant enzyme with 5-fold higher catalytic activity (kcat) but no change in Km at pH 8.0 in 50 mM Tris-HCl. The increased kcat is achieved by a faster release of the phosphate product as a result of the lower phosphate affinity. The mutation also affects Mg2+ binding, resulting in an enzyme with lower metal affinity. The 3-D X-ray structure of the D153G mutant has been refined at 2.5 A to a crystallographic R-factor of 16.2%. An analysis of this structure has revealed that the decreased phosphate affinity is caused by an apparent increase in flexibility of the guanidinium side chain of Arg166 involved in phosphate binding. The mutation of Asp153 to Gly also affects the position of the water ligands of Mg2+, and the loop Gln152-Thr155 is shifted by 0.3 A away from the active site. The weaker Mg2+ binding of the mutant compared with the wild type is caused by an altered coordination sphere in the proximity of the Mg2+ ion, and also by the loss of an electrostatic interaction (Mg2+.COO-Asp153) in the mutant. Its ligands W454 and W455 and hydroxyl of Thr155, involved in the octahedral coordination of the Mg2+ ion, are further apart in the mutant compared with the wild type.

Alkaline Phosphatase↗
PubMed1995

Pollicization of the mutilated hand by transposition of middle and ring finger remnants.

Traumatic injuries to the thumb are frequently associated with mutilation of one or more of the remaining digits. The most common digital injuries associated with thumb loss are partial or complete amputation of the index finger or index and long fingers. Occasionally, satisfactory index finger function will be preserved with damage or amputation of the middle or ring fingers, making them the best candidates for transposition. Although pollicization of the index finger has received considerable attention in the literature, pollicization of injured middle and ring finger remnants has not. Transposition of these comparatively useless digital stumps, which may be sacrificed without significant functional deficit to the rest of the hand, may be advantageously performed to create a well-functioning thumb. This procedure facilitates the conversion of a useless, mutilated hand into a well-functioning one in a single operation. We present our experience with pollicization of middle and ring finger remnants in four patients including indications, technique, and functional outcome.

Adolescent↗
PubMed1995

An efficient and optimized PCR method with high fidelity for site-directed mutagenesis.

We have developed an efficient method for site-directed mutagenesis using two subsequential rounds of PCR. In this method, PCR conditions are optimized to favor high fidelity of Taq DNA polymerase in the presence of equimolar concentrations of MgCI2 and dNTP in the reaction mixture (pH 5.5-6.2). This method makes use of a pair of universal primers and the multiple cloning site of pUC/M13 vectors. Only one mutagenic primer is required per target site. In the second round of PCR, the 3' extension of the wild-type DNA strand is blocked by the presence of a segment of nonhomologous sequence at its 3' end, and as a consequence, the amplified, full-length DNA fragment is chiefly from the mutant strand. Furthermore, because the mutated DNA fragment has flanking restriction sites different from those of the wild-type DNA fragment, the wild-type DNA fragment is totally excluded in the step involving selective cloning of the mutant DNA fragment. This method was successfully used to introduce four, nonadjacent mutations in the 5' regulatory region of the cytochrome P450BM-3 gene. All 20 analyzed clones from these four cases of mutagenesis carried the desired mutations, and no undesired mutations were observed. We observed that the larger the number of mismatched nucleotide residues in the mutagenic primer, the higher the concentration of MgCI2 was necessary for successful PCR amplification. Our experimental results indicate that this method offers improvements in efficiency, flexibility, and fidelity.

Bacillus megaterium↗
PubMed1995

Bacillus subtilis MrgA is a Dps(PexB) homologue: evidence for metalloregulation of an oxidative-stress gene.

Upon the cessation of exponential growth, Bacillus subtilis enters a transition phase leading to either sporulation or a non-sporulating stationary phase. During this transition period, cells secrete degradative enzymes, become competent for DNA transformation, are motile and acquire resistance to oxidative killing. We now report that mrgA, originally identified as a gene repressed by metal ions, encodes a member of the Dps/PexB family of general stress proteins. Like Escherichia coli Dps(PexB), MrgA forms highly stable, multimeric protein-DNA complexes which accumulate in stationary-phase cells and protect against oxidative killing. MrgA is part of an inducible oxidative stress response in B. subtilis: mrgA is induced by hydrogen peroxide, and a strain lacking MrgA displays increased sensitivity to oxidative killing. In addition, a hydrogen peroxide-resistant mutant, which constitutively overproduces catalase and alkyl hydroperoxide reductase, also overproduces MrgA. These results indicate a complex interplay between metal ions and the expression of the B. subtilis oxidative stress response.

Amino Acid Sequence↗
PubMed1995

Differential effects of phosphoramidon on contractile responses to angiotensin II in rat blood vessels.

1. Cumulative concentration-tension response (C-R) curves to angiotensin II (AII), big endothelin-1 (big ET-1), ET-1 and arginine vasopressin (AVP) were determined in endothelium intact-ring preparations of aorta, mesenteric artery and tail artery isolated from adult male Sprague-Dawley rats in the presence or absence of the neutral metalloprotease inhibitor, phosphoramidon. 2. The order of sensitivity of the three rat vascular smooth muscle preparations to AII, big ET-1 and ET-1 was aorta > mesenteric artery > tail artery whereas that for AVP was reversed, namely, tail artery > mesenteric artery > aorta. 3. Phosphoramidon blocked the responses to AII in a concentration-dependent manner, whereas even very high concentrations of phosphoramidon (100 microM) failed to affect the tension responses evoked by ET-1 and AVP in all three preparations. Low concentrations of phosphoramidon (10 microM) produced significant increases in EC50 values for AII in tail artery (P < 0.01) and mesenteric artery (P < 0.05) but not in aorta. The rank order of sensitivity to the inhibition by phosphoramidon was tail artery > mesenteric artery > aorta. Phosphoramidon-evoked rightward shifts in the C-R curves to AII were much higher than those to big ET-1 in both mesenteric artery and tail artery. 4. In endothelium-denuded preparations, AII failed to evoke any increases in tension in tail artery while the responsiveness of the mesenteric artery to AII was reduced significantly relative to endothelium-intact tissues with a rightward shift in the C-R curve and a decrease in the maximal response. On the other hand, the C-R curve to AII was shifted to the left in aorta following removal of the endothelium.Importantly, ET-1 and AVP evoked vasoconstrictor responses were unaffected by the inclusion of a high concentration of phosphoramidon (100 microM) in endothelium-denuded aorta and mesenteric artery.5. The results suggest that AII-evoked tension responses of blood vessels such as tail artery are completely endothelium-dependent; in relatively larger blood vessels such as mesenteric artery they are partially endothelium-dependent while in much bigger conduit type blood vessel such as aorta, they are endothelium-independent. It is concluded that the vasoconstrictor responses to AII in mesenteric artery and tail artery may be mediated by the release of endothelins from the endothelium by increased formation from big ET, an effect that is blocked by phosphoramidon.

Angiotensin II↗
PubMed1995

Mutations in the SHR5 gene of Saccharomyces cerevisiae suppress Ras function and block membrane attachment and palmitoylation of Ras proteins.

We have identified a gene, SHR5, in a screen for extragenic suppressors of the hyperactive RAS2Val-19 mutation in the budding yeast Saccharomyces cerevisiae. SHR5 was cloned, sequenced, and found to encode a 23-kDa protein not significantly homologous to other proteins in the current data bases. Genetic evidence arguing that Shr5 operates at the level of Ras is presented. We tested whether SHR5, like previously isolated suppressors of hyperactivated RAS2, acts by affecting the membrane attachment and/or posttranslational modification of Ras proteins. We found that less Ras protein is attached to the membrane in shr5 mutants than in wild-type cells and that the Ras proteins are markedly underpalmitoylated, suggesting that Shr5 is involved in palmitoylation of Ras proteins. However, shr5null mutants exhibit normal palmitoyltransferase activity measured in vitro. Further, shr5null mutations attenuate Ras function in cells containing mutant Ras2 proteins that are not palmitoylated or farnesylated. We conclude that SHR5 encodes a protein that participates in the membrane localization of Ras but also interacts in vivo with completely unprocessed and cytosolic Ras proteins.

Acyltransferases↗
PubMed1995

Identification of patients at high risk for adverse coronary events while awaiting routine coronary angioplasty.

BACKGROUND: Identification of patients at risk for progression of coronary stenosis and adverse clinical events while awaiting coronary angioplasty is desirable. OBJECTIVE: To determine the standard clinical or angiographic variables, or both, present at initial angiography associated with the development of adverse coronary events (unstable angina, myocardial infarction, and angiographic total coronary occlusion) in patients awaiting routine percutaneous transluminal coronary angioplasty (PTCA). PATIENTS AND METHODS: Consecutive male patients on a waiting list for routine PTCA. Routine clinical details were obtained at initial angiography. Stenosis severity was measured using computerised angiography. OUTCOME MEASURES: Development of one or more of myocardial infarction, unstable angina, or angiographic total coronary occlusion while awaiting PTCA were recorded as an adverse event. RESULTS: Some 214 of 219 patients underwent a second angiogram. One had a fatal myocardial infarction and four (2%) were lost to follow up. Fifty patients (23%) developed one or more adverse events (myocardial infarction five, unstable angina 35, total coronary occlusion 23) at a median (range) interval of 8 (3-25) months. Twenty (57%) of the 35 patients with unstable angina developed adverse events compared with 30 (17%) of the 180 with stable angina (P = 0.0001). Plasma triglyceride concentration was 2.6 (1.2) mmol/l in patients with adverse coronary events compared with 2.2 (1.1) mmol/l in those without such events (P < 0.05). Patients with adverse events were younger than those without (54 (9) years v 58 (9) years, P < 0.01). The relative risk of an adverse event in patients with unstable angina and increased plasma triglyceride concentrations was 6.9 compared with those presenting with stable angina and a normal triglyceride concentration (P < 0.02). CONCLUSIONS: The study shows that adverse events are not uncommon in patients awaiting PTCA. Patients at high risk for adverse events may be predicted by the presence of acute coronary syndrome, increased concentration of plasma triglyceride, and younger age at the time of the first angiogram.

Adult↗
PubMed1995

Effects of a program to train radiologic technologists to identify abnormalities on mammograms.

PURPOSE: To assess whether radiologic technologists could be successfully trained to identify abnormalities on mammograms. MATERIALS AND METHODS: Eight radiologic technologists from two different institutions took a pretest, underwent an 8-hour training course followed by a period of preceptorship, and then took a posttest. Seven radiologists also took the pretest and posttest, which consisted of evaluating 1,238 two-view screening examinations, including 318 biopsy-proved cancers. RESULTS: Overall, technologists at institution 1 had lower sensitivity (78%) at the pretest, which improved at the posttest (90%). Technologists at institution 2 had lower specificity at the pretest (44%), which improved on the posttest (64%). Hypothetical pairing of radiologists and technologists with use of posttest results revealed an increase in sensitivity (median increase, 12% at institution 1 and 19% at institution 2). CONCLUSION: Formalized training successfully modified the technologists' skills. Radiologic technologists could be used to increase the number of breast cancers detected at screening mammography.

Breast Neoplasms↗