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Biomedical subjects

Y F Li

Publications and source records attributed to Y F Li.

At least 109 records · Page 6Linked to original sources
PubMed1994

Gallbladder contractility in aspirin- and cholesterol-fed prairie dogs.

BACKGROUND/AIMS: Whether aspirin prevents cholesterol gallstone formation is controversial. This study aimed to investigate this issue and determine the depression of gallbladder smooth muscle contractility associated with cholesterol feeding in the prairie dog. METHODS: Prairie dogs were divided into four subgroups. Animals were fed control or 1.2% cholesterol diet and treated with placebo or aspirin for 2 weeks. The presence of crystals and stones was determined, and contractile force in response to cholecystokinin octapeptide (CCK-8) of gallbladder muscle strips was measured. RESULTS: Maximal stress of 2.66 +/- 0.23 x 10(4) N/m2 was measured in muscle strips from animals on control diet. Maximal stress was significantly lower in strips from animals on high-cholesterol diet, being 1.49 +/- 0.16 x 10(4) N/m2 with placebo and 1.62 +/- 0.23 x 10(4) N/m2 with aspirin. The difference in maximal stress between aspirin-treated and placebo-treated animals was not significant. Although none of the animals on control diet had crystals or stones, all animals on the high-cholesterol diet, whether receiving placebo or aspirin, had crystals in the bile, and more than 65% had cholesterol stones. CONCLUSIONS: Aspirin has no effect on stone formation, nor does it prevent the decrease in contractility despite a profound decrease in endogenous gallbladder prostanoid synthesis.

Animals↗
PubMed1994

Nitric oxide is involved in muscle relaxation but not in changes in short-circuit current in rat ileum.

L-Arginine (L-Arg)-nitric oxide (NO) pathways in rat ileum were studied in an Ussing chamber modified so that a strain gauge transducer could be attached longitudinally on the serosal side of the intestine. Ileal segments from 22 rats were mounted as flat sheets and voltage clamped at zero transmural potential (PD). Changes in short-circuit current (delta ISC) in the absence of carbachol and longitudinal muscle relaxations in the presence of carbachol in response to transmural field stimulation (TMS; 5-s trains of impulses, 0.4-ms impulse duration, 1-10 Hz) were recorded during a control period, in the presence of N omega-nitro-L-arginine (L-NNA; 10(-4) M), and in the presence of L-Arg after treatment with L-NNA. In the control period, the delta ISC and muscle relaxation were frequency dependent with maximal responses generated at a frequency of 10 Hz. Tetrodotoxin (5 x 10(-6) M) blocked muscle relaxation and decreased delta ISC by 94% during TMS at 10 Hz. L-NNA blocked the muscle relaxation induced by TMS but failed to alter delta ISC. Muscle relaxation to TMS was restored dose dependently by L-Arg. In segments from another group of eight rats, saturated NO solutions relaxed the muscle but failed to change ISC either in the presence or absence of carbachol. These results support a role for NO as a neurotransmitter mediating relaxation of ileal smooth muscle but not mediating changes in epithelial ISC.

Animals↗
PubMed1994

[Clinical analysis of 5 cases of peritoneal mesothelioma].

Peritoneal mesothelioma is an infrequently encountered tumor that has a poor prognosis. Five female cases are reported in this article: one of epithelial type, one fibrous and three mixed, and there are two benign and three malignant cases. Abdominal mass, pain, ascites and weight loss are main manifestations. The epithelial and mixed types are prone to produce ascites. CT scanning is helpful for preoperation diagnosis. In 3 of the 5 patients the tumors have been thoroughly removed, one patient was treated with a partial removal, and one with biopsy only. Two patients have received chemotherapy after operation. The four patients who were given effective treatment survived each longer than 12 years, 55 months, 26 months and 15 months. One of the 5 patients who received biopsy only at laparotomy died two months later. It is recommended that if the primary tumor of the organs in the peritoneal cavity could be excluded, any patient with an abdominal mass and ascites should be given the benefit of doubt that it might be a case of peritoneal mesothelioma. Laparotomy should be carried out, and all the visible tumor masses should be resected as completely as possible. Cytoreductive surgery should be done in patients with recurrence. If postoperative chemotherapy or radiotherapy is given the prognosis may be improved.

Adult↗
PubMed1994

[Multiple analysis of the factors influencing the result of tilt table test].

Ninety two patients with unexplained syncope and 52 normal controls without history of syncope were divided into three groups respectively. Baseline tilt table test (BTTT), multistage isoproterenol tilt table test (MITTT), and single stage isoproterenol tilt table test (SITTT) were performed in all of them. Logistics regression was used with the result of TTT as independent variable; dependent variables included sex, age, basal heart rate, basal blood pressure, the index of syncope (i) and the difference between basal heart rate and the rate before tilting (h12). The results were as follows: (1) According to the regression for the total population tested, the main factors influencing the result of TTT were i and h12 (P = 0.012 and P = 0.001). Similar result was found in the patient group (P = 0.052 and P = 0.032). (2) In the control group, sex and h12 were the predictors of the result (P = 0.090 and P = 0.016). It is concluded that: (1) The result of TTT is mainly affected by the frequency and degree of syncope, as well as by the use of isoproterenol; (2) Isoproterenol increases the sensitivity of TTT, but decreases the specificity; (3) Sex is probably an important factor affecting the result of TTT.

Adolescent↗
PubMed1994

A report on selective radiofrequency ablation of dual atrioventricular node pathways in 34 cases.

Selective ablation of slow pathway by radiofrequency (RF) current in 34 patients with atrioventricular (AV) node pathways and tachycardia was performed with two methods in our section; posterior approach was used in the first 12 patients, the slow pathways were ablated successfully. Inferior approach was performed in the other 22 patients. Slow pathways were interrupted in 14 patients. Retrograde fast pathways and/or slow pathways were ablated in 6 patients. Retrograde fast pathways and slow pathways were abolished and antegrade fast pathways were injured transitorily in 2 cases. The total procedure time was shorter, RF applications were fewer by inferior approach than by posterior approach (P < 0.05). Both antegrade and retrograde conduction of fast pathways had not been affected after slow pathways were ablated (P > 0.05). After a mean of 8 months follow-up, two patients recurred and were ablated successfully again. We come to the conclusion that inferior approach might be a preferable method compared with posterior approach; the slow pathways is the compact node and its posterior input of transitional cells; the retrograde fast pathway may be the anterior superficial group of transitional cells and is not always in the same location of antegrade fast pathway.

Adult↗
PubMed1994

[Detection of tuberculostearic acid (TBSA) in CSF using gas chromatography in patients with tuberculous meningitis].

By using French's method TBSA in CSFs of 43 patients with tuberculous meningitis and 40 patients with non-tuberculous meningitis were performed. All the patients with tuberculous meningitis were positive and all the patients with non-tuberculous meningitis were negative. So the results showed that the method is a rapid, sensitive and accurate for diagnosis of tuberculous meningitis.

Adolescent↗
PubMed1993

Evidence for lack of DNA photoreactivating enzyme in humans.

Photoreactivating enzyme (DNA photolyase; deoxyribocyclobutadipyrimidine pyrimidine-lyase, EC 4.1.99.3) repairs UV damage to DNA by utilizing the energy of near-UV/visible light to split pyrimidine dimers into monomers. The enzyme is widespread in nature but is absent in certain species in a seemingly unpredictable manner. Its presence in humans has been a source of considerable controversy. To help resolve the issue we used a very specific and sensitive assay to compare photoreactivation activity in human, rattlesnake, yeast, and Escherichia coli cells. Photolyase was easily detectable in E. coli, yeast, and rattlesnake cell-free extracts but none was detected in cell-free extracts from HeLa cells or human white blood cells with an assay capable of detecting 10 molecules per cell. We conclude that humans most likely do not have DNA photolyase.

Base Sequence↗
PubMed1993

Intestinal migrating myoelectric complexes in rats with acute pancreatitis and bile duct ligation.

Intestinal migrating myoelectric complexes (MMC) were studied in rats subjected to common bile duct ligation. Four pairs of bipolar electrodes were implanted on the jejunum and the ileum of 21 rats. Animals were allowed to recover 7 days before electrical recordings were made. Bile duct ligation at the entrance to the duodenum (low) or above the pancreas (high) or sham operation was performed. MMCs were recorded before and 48 and 72 hr after the operation in each animal. MMC intervals were unchanged following high ligation or sham operation. However, 48 hr after low bile duct ligation, the MMC interval (20.6 +/- 2.5 min) was significantly prolonged compared with that before ligation (14.0 +/- 1.2 min). Further prolonged intervals (28.4 +/- 4.2 min) were observed 72 hr after the ligation. There were no significant differences among the slow wave frequencies in any group of animals, being in the range of 34.1 +/- 1.1 to 36.3 +/- 1.0 cycles/min. Thus, the MMC pattern in this rat model may be affected by the development of acute pancreatitis. The mechanism(s) responsible for altering the MMC pattern are not known; however, hepatic biliary secretion alone does not appear to play a primary role.

Acute Disease↗
PubMed1993

[Extraction of cupric intraocular foreign bodies in 108 cases].

The authors report extraction of cupric intraocular foreign bodies in 108 cases with a success rate of 99.07%. The methods utilized and improvements made in localizing the foreign bodies and the procedures of operation were described. Suggestions were also made concerning the timing of operation and the treatment of preoperative and postoperative complications.

Adolescent↗
PubMed1993

[Synthesis and antibacterial action of 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-aroylthiocarbamoyl-1-piperaziny l)-3-quinoline carboxylic acids].

Thirteen new 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-aroyl-thiocarbamoyl-1-piperazinyl)-3- quinoline carboxylic acids were prepared. Their structures were characterized by elemental analysis, IR, HNMR and MS spectra. Preliminary pharmacological tests indicated that some of compounds Ia-m possess strong inhibiting activity against Escherichia coli, Bacillus subtilis and Proteus at concentration of 100 micrograms/ml.

Anti-Infective Agents↗
PubMed1992

Sequence-specific interaction between S1F, a spinach nuclear factor, and a negative cis-element conserved in plastid-related genes.

The nuclear gene rps1 coding for the spinach plastid ribosomal protein CS1 exhibits both a constitutive and leaf-specific expression pattern. In contrast to other chloroplast-related genes like rbcS and cab, the leaf induction of rps1 expression is light-independent. These unique features of rps1 expression provide good models to study the mechanisms regulating plastid development and differentiation in higher plants. We report on the identification of a spinach leaf nuclear factor, designated S1F, interacting with the rps1 promoter. The S1F binding site is conserved in the promoter region of many plastid-related genes, including rbcS, cab, and rpl21. A binding activity similar to S1F was detected in nuclear extract from dark-grown de-differentiated soybean suspension cells. Through site-specific mutagenesis and transient expression in soybean cell protoplasts, we show that the S1F binding site is a negative element down-regulating the promoter activity of rps1. A ligated tetramer of S1F site was able to repress activity of the cauliflower mosaic virus 35 S promoter extending the negative function of the S1F binding site on promoter activity.

Base Sequence↗
PubMed1992

Identification of chromophore binding domains of yeast DNA photolyase.

Photolyases contain two chromophores, flavin plus either methenyltetrahydrofolate (MTHF) or 8-OH-5-deazaflavin (HDF). Amino acid sequence comparison reveals that all photolyases sequenced to date have extensive sequence homology in the carboxyl-terminal half; in the amino-terminal region the folate and deazaflavin class enzymes are more homologous to other members of the same class. This modular arrangement of sequence homologies suggests that the amino-terminal half of photolyase is involved in MTHF or HDF binding whereas the carboxyl-terminal half carries the flavin binding site. In this study we attempted to identify such structural domains of yeast photolyase by partial proteolysis and gene fusion techniques. Partial digestion with chymotrypsin yielded an amino-terminal 34-kDa fragment containing tightly bound MTHF and a carboxyl-terminal 20-kDa polypeptide which lacked chromophore or DNA binding activity. However, a fusion protein carrying the carboxyl-terminal 275 amino acids of yeast photolyase bound specifically to FAD but not to MTHF or DNA. We conclude that the amino-terminal half of yeast photolyase constitutes the folate binding domain and that the carboxyl-terminal half carries the flavin binding site.

Amino Acid Sequence↗
PubMed1992

The third chromophore of DNA photolyase: Trp-277 of Escherichia coli DNA photolyase repairs thymine dimers by direct electron transfer.

Photolyases repair pyrimidine dimers in DNA by converting the light energy of 300- to 500-nm photons into chemical energy. Enzymes from various organisms contain two chromophore cofactors (FADH2 and either methenyltetrahydrofolate or 8-hydroxy-5-deazaflavin) that absorb the low-energy photons and initiate splitting of the cyclobutane ring by a radical mechanism. Here, we show that, in addition to these two chromophores, in the far UV range, direct excitation of one specific tryptophan residue (out of 15 total) in the polypeptide chain of Escherichia coli photolyase leads to splitting of the cyclobutane ring with high quantum yield (phi = 0.56), independent of the other chromophores. The specific tryptophan residue responsible for photosensitized repair was identified as Trp-277 by site-specific mutagenesis.

Catalysis↗
PubMed1992

Is asymptomatic bronchial hyperresponsiveness an indication of potential asthma? A two-year follow-up of young students with bronchial hyperresponsiveness.

To determine the possibility that asymptomatic bronchial hyperresponsiveness (BHR) develops into symptomatic asthma, a two-year follow-up study was conducted in 81 students (48 male, 33 female; 11 to 17 years) who were found to have BHR in a 3,067 population survey (BHR group). Eighty-eight age-matched students (48 male, 40 female) with normal bronchial responsiveness served as control subjects. Daily symptom cards were recorded. Peak expiratory flow rate was measured for 24 h when symptoms occurred. Histamine inhalation tests were performed at the beginning of the study and at the end of the first and the second year. In the BHR group, 58 students remained bronchial hyperresponsive at the end of follow-up. Nine of 31 students with initially diagnosed bronchial asthma had their symptoms relieved entirely, but ten asymptomatic students developed asthma. The incidence of newly diagnosed asthma (12.5 percent in the BHR group or 20 percent in the asymptomatic BHR group) and the total percentage of diagnosed asthma (39.5 percent) in the BHR group were significantly higher than those (2.27 percent, 2.27 percent) in the control group. FVC and FEV1 showed no significant difference between two groups. PD20 FEV1 values in newly diagnosed asthmatics were significantly lower than those in asymptomatic students both at the beginning (3.05 +/- 1.56 mumol vs 6.14 +/- 1.60 mumol, p < 0.05) or the end (3.47 +/- 1.73 mumol vs 6.55 +/- 1.51 mumol, p < 0.05). The percentage of early respiratory illness was significantly higher in those with newly diagnosed asthma (80 percent) than in asymptomatic students (22.3 percent), but atopic index and the percentage of parental asthma showed no difference between two groups. In nine asthmatics whose symptoms were relieved entirely in the two-year follow-up, PD20 FEV1 was undetectable within the cumulative dose of 7.8 mumol of histamine in three students and rose from 4.58 +/- 1.85 mumol to 7.62 +/- 1.02 mumol in the remaining six. The higher the BHR, the more likely the students developed asthma. About 45 percent of asymptomatic students with PD20 < or = 3.2 mumol developed asthma in the following two years and 80 percent of them had a history of early respiratory illness, suggesting that they may have subclinical or potential asthma.

Adolescent↗
PubMed1992

Ultrastructural study on extrahepatic infection of duck hepatitis B virus in ducks.

Kidney and pancreas tissues from congenitally infected Ma ducks with duck hepatitis B virus (DHBV) were examined by immunohistochemical staining technique and electron microscopy. The immunostaining showed that DHBV antigen was localized in the cytoplasm of tubular epithelial cells of kidney and acinar cells of pancreas of infected ducks. Under electron microscope, we found that complete and incomplete DHBV particles existed in the dilated cisternae of rough endoplasmic reticulum of both the cells. The size of complete and incomplete virus particles was nearly uniform in both the cells, 50-65 nm and 40-50 nm in diameter respectively. Therefore, extrahepatic infection and replication of DHBV were directly demonstrated ultrastructurally.

Animals↗
PubMed1991

Cloning, sequencing, expression and characterization of DNA photolyase from Salmonella typhimurium.

We have cloned the phr gene that encodes DNA photolyase from Salmonella typhimurium by in vivo complementation of Escherichia coli phr gene defect. The S.typhimurium phr gene is 1419 base pairs long and the deduced amino acid sequence has 80% identity with that of E. coli photolyase. We expressed the S.typhimurium phr gene in E.coli by ligating the E.coli trc promoter 5' to the gene, and purified the enzyme to near homogeneity. The apparent molecular weight of S.typhimurium photolyase is 54,000 dalton as determined by SDS-polyacrylamide gel electrophoresis, which is consistent with the calculated molecular weight of 53,932 dalton from the deduced phr gene product. S.typhimurium photolyase is purple-blue in color with near UV-visible absorption peaks at 384, 480, 580, and 625 nm and a fluorescence peak at 470 nm. From the characteristic absorption and fluorescence spectra and reconstitution experiments, S.typhimurium photolyase appears to contain flavin and methenyltetrahydrofolate as chromophore-cofactors as do the E.coli and yeast photolyases. Thus, S.typhimurium protein is the third folate class photolyase to be cloned and characterized to date. The binding constant of S.typhimurium photolyase to thymine dimer in DNA is kD = 1.6 x 10(-9) M, and the quantum yield of photorepair at 384 nm is 0.5.

Amino Acid Sequence↗
PubMed1991

Conservation and evolution of the nucleus-encoded and chloroplast-specific ribosomal proteins in pea and spinach.

Two cDNA clones have been isolated from a lambda g11 cDNA library constructed with poly(A)+ mRNAs prepared from spinach seedlings. These nuclear cDNAs encode chloroplast (cp) ribosomal (r) proteins designated L24 and L40. These r-proteins have been identified in the cp 50S r-subunit by immunoblot analysis, amino acid (aa) composition and N-terminal aa sequencing. The L24 r-protein contains a central eubacterial homologous core with the N- and C-terminal polypeptide extensions. The L40 r-protein has no homologous counterpart in bacterial ribosomes. The two nuclear encoded r-proteins have their homologues in pea, a legume, showing that specific elements of cp ribosomes are conserved in higher plants. Surprisingly, the cp-specific r-protein L40 has a higher aa substitution rate than that of other eubacterial-like cp r-proteins identified previously in pea and spinach.

Amino Acid Sequence↗