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M Li

Publications and source records attributed to M Li.

At least 1,081 records · Page 60Linked to original sources
PubMed1990

Evidence for identifying fatty acids in rat liver glutathione S-transferase and its possible involvement in the secondary structure.

A rat liver glutathione S-transferase isozyme (GST 3-3) has been purified to apparent electrophoretic homogeneity by procedures including Sephadex G-100, S-hexylglutathione-linked Sepharose, and CM-cellulose column chromatographies. The present study provides evidence for the existence of endogenous fatty acids in the purified GST 3-3 by gas-liquid chromatographic and mass-spectrometric analyses. The liver GST isozyme associated long chain fatty acids such as 14:0, 16:0, 18:0, and 18:1 and the molar ratio of fatty acids to the protein was estimated to be around 3.2. When the enzyme preparation was freed of fatty acids by a mild delipidization technique using Lipidex, the GST activity was significantly decreased. Computer analysis of the circular dichroism spectra revealed that rat liver GST 3-3 contained approximately 49% alpha-helix and 24% random coil. By delipidizing, the enzyme's alpha-helix was decreased to 4% and the random coil was in turn increased to 62%. The enzymatic and structural properties of the delipidized enzyme, however, could be restored to nearly the original levels by recombining with the fatty acids. These findings suggest that weakly bound fatty acids are responsible for the functional capacity of the GST by virtue of changing the protein conformation.

Animals↗
PubMed1990

Increased morbidity in surgical patients undergoing secondary (incidental) cholecystectomy.

Using computerized hospital discharge abstracts for all Vermont residents hospitalized during 1983 and 1984, we examined the question of whether increased morbidity occurs in patients undergoing secondary (incidental) cholecystectomy. Among a cohort of 4183 patients undergoing a primary surgical procedure in which secondary cholecystectomy might have been considered. 69 patients had a secondary cholecystectomy. The surgical wound infection rate was 8.7% in the secondary cholecystectomy group compared to 2.4% in the rest of the cohort (relative risk, 3.7, 95% C.I. 1.7, 8.1). Other postoperative complications occurred in 10.1% of those undergoing secondary cholecystectomy compared to 4.1% in those who did not (relative risk, 2.5, 95% C.I. 1.2, 5.1). The adjusted relative risk for wound infection was 3.3 (95% C.I. 1.4,8.0) and for other surgical complications was 1.7 (95% C.I. 0.8, 3.8). Postoperative length of hospital stay was longer for the secondary cholecystectomy group (mean, 13.8 days) than in the comparison group (mean 8.9 days, p = 0.001). These data suggest that patients undergoing a secondary cholecystectomy may have an increased risk of surgical wound infection and possibly other surgical complications.

Adolescent↗
PubMed1990

Apical membrane Cl- channels in airway epithelia: anion selectivity and effect of an inhibitor.

Previous work has investigated the anion selectivity of transepithelial Cl- secretion by airway epithelia and its inhibition by the Cl(-)-channel blocker 5-nitro-2-(3-phenylpropylamino)benzoate (NPPB). Here we report the anion selectivity of the apical membrane and of the outwardly rectifying Cl- channel and the effect of NPPB on the Cl- channel. The anion selectivity sequence of the apical membrane determined with conventional microelectrodes in the native epithelium was SCN- greater than I- greater than Br- greater than NO3- approximately Cl- much greater than SO(4)2- approximately gluconate-. This contrasts with the observation that Cl- and Br- support transepithelial secretion but that I- does not. Thus the anion selectivity of transepithelial transport is determined by the basolateral membrane Cl- entry step. The anion selectivity of the outwardly rectifying Cl- channel studied in excised patches was the same as that of the apical membrane. We also found that NPPB reversibly blocked the outwardly rectifying Cl- channel from both the internal and external surfaces of the patch. NPPB, 10 microM, completely blocked the channel; lower concentrations caused a decrease in the probability of finding the channel in the open state. NPPB also caused the appearance of a subconductance state of the channel, an occurrence which is rarely observed in the absence of NPPB. These data provide further support for the conclusion that the outwardly rectifying Cl- channel is responsible for Cl- exit from the cell across the apical membrane.

Animals↗
PubMed1990

Calcium-dependent regulation of airway epithelial chloride channels.

To determine how cell calcium ([Ca2+]c) regulates apical Cl- channels, we measured the rate of 125-Iodide (125I-) efflux to assay Cl- channel activity in intact cells and examined cell-free membrane patches from cultured canine tracheal epithelial cells. The Ca2+ elevating agonist bradykinin and the calcium ionophore A23187 increased 125I- efflux. This response did not require prostaglandin production. Under several conditions, changes in [Ca2+]c were temporally dissociated from changes in channel activation: a transient increase in [Ca2+]c caused a prolonged stimulation of 125I- efflux. Neither Cl- channel activation nor open-channel probability was affected by varying internal [Ca2+] in excised membrane patches. Adenosine 3',5'-cyclic monophosphate (cAMP)- and Ca2(+)-dependent channel activation may be independent: cAMP-stimulated 125I- efflux did not require an increase in [Ca2+]c, Ca2(+)-stimulated efflux did not require an increase in cAMP, and simultaneous addition of A23187 and isoproterenol produced additive effects on 125I- efflux. The data suggest that an increase in [Ca2+]c activates Cl- channels, however, the effect of Ca2+ appears to be indirect, not involving a ligand-type interaction with the channel.

Animals↗
PubMed1990

Expression of normal and cystic fibrosis phenotypes by continuous airway epithelial cell lines.

Continuous epithelial cell lines from individuals with cystic fibrosis (CF) and normal controls are required to understand the genetic and cellular defects in CF. We used retroviruses to transduce SV40 large T antigen into nasal epithelial cells. Transformed continuous cell lines were isolated that expressed epithelial markers, cytokeratin, and tight junctions. Northern blot analysis shows that all of the cell lines express the putative CF gene mRNA. Studies of transepithelial electrolyte transport show that CF and normal cell lines develop a transepithelial electrical resistance. Normal but not CF cell lines secreted Cl- in response to agonists that increase cellular levels of adenosine 3',5'-cyclic monophosphate (cAMP) (isoproterenol, forskolin, and a membrane-permeant analogue of cAMP) or in response to a tumor-promoting phorbol ester that activates protein kinase C. In contrast, the Ca2(+)-elevating agonist bradykinin and the Ca2+ ionophore A23187 stimulated secretion in both normal and CF cell lines. The continuous cell lines we have produced maintain their proper phenotypes and will serve as useful tools in understanding the pathophysiology of CF.

Antigens, Polyomavirus Transforming↗
PubMed1990

Interaction of heptanol and pressure on sodium and chloride transport by toad skin.

We examined the interaction of heptanol and hydrostatic pressure on Na+ and Cl- transport in isolated toad skin. In the presence of Cl-, heptanol decreased short-circuit current (Isc) and total transepithelial resistance (Rt). However, in the absence of Cl- in the mucosal bath, heptanol increased Rt, although it retained the same inhibitory effect on Isc. When transepithelial active Na+ transport was blocked by amiloride, heptanol had no effect on Isc whether or not Cl- was present, whereas it decreased the shunt resistance (Rs) only in the presence of Cl- in the mucosal bath. Moreover, this effect of heptanol on Rs was significantly smaller in the presence of diphenylamine-2-carboxylate (DPC), a known Cl- channel blocker. Pressure also decreased Isc through inhibition of active Na+ transport, but it increased Rs. When heptanol and pressure were applied together, their inhibitory effects on Isc were additive, but their effects on Rs were antagonistic. Furthermore, when a transepithelial Cl- current was produced by reducing the Cl- concentration of the serosal bath, heptanol stimulated this current, which was reversibly inhibited by pressure or DPC addition to the mucosal bath. When the heptanol-stimulated Cl- current was first inhibited by pressure, subsequent DPC addition had less or no effect. These results suggest that one site of an antagonistic interaction of heptanol and pressure in toad skin is an apical membrane Cl- conductance.

Alcohols↗
PubMed1990

[Simultaneous determination of brucine and strychnine in semen Strychni by dual wavelength spectrophotometry and studies on processing principles of semen Strychni].

The paper reports the experimental result of the simultaneous quantitative determination of strychnine (ST) and brucine(BR) in Semen Strychni by dual wavelength spectrophotometry. The result shows that there are some deviations in the official method, because the wavelength combination might not have been chosen rightly and the correct coefficient is inconsistent with the facts. We have made a study of the thermal stability of ST and BR, too. On this basis a baking principle for Semen strychni is spelt out.

Drugs, Chinese Herbal↗
PubMed1990

[Reperfusionable focal cerebral ischemia in rats].

Reperfusionable focal cerebral ischemia by embolization to the middle cerebral artery with nylon thread adhered to sponge was studied in rats. It was divided into 2 groups: permanent embolization and embolization for 3 hours. Neurological symptoms, degree of brain swelling and size of cerebral infarction of these animals were observed. The laboratory statistics was no difference between the two groups. But it was found in pathological specimens that infarction area were limited in the basal-ganglion with perivascular hemorrhage in 3 rats after reperfusion. Establishment of the model, symptoms of rats, results of laboratory and it's clinical significances were discussed.

Animals↗
PubMed1990

[Studies on pickled vegetables and cause of esophageal cancer in Linxian. I. Experiments on carcinogenicity of pickled vegetables].

Pickled vegetables are a traditional daily food served in several parts of China where esophageal cancer is prevalent, and the mortality rate due to this cancer appears to be correlated with the time span of consumption and the amount consumed. For the present study epithelial hyperplasia and papillomas of the esophagus and forestomach were induced in mice and rats following administration of condensed juice from or extract of pickled vegetables from Linxian County, Henan Province. Only one case of forestomach carcinoma was observed in a rat subsequent to prolonged treatment with pickled extract, indicating that carcinogens in pickled vegetables alone are probably incapable of inducing carcinogenesis.

Animals↗
PubMed1990

[Analgesic and anti-inflammatory effects and toxicity of houjianxi].

It is effective for acute and chronic laryngopharyngitis clinically. Houjianxi can raise the pain thresholds during hot-plate test in mice, tail flick test in rats, and writhing test in mice with single dose ig 0.125 to 2.0 g/kg. Houjianxi can also inhibit the swelling of hind paw induced by sc 1% carrageenin 0.1 ml in rats as well as the increased vascular permeability induced by ip 0.7% HAC in mice. Toxic side effects were not observed for Houjianxi ig 48 g/kg x 3 within a day in mice and 1.8 g/kg daily for 90 d in rats.

Animals↗
PubMed1990

[The significance of retinal nerve fiber layer examination in the diagnosis of glaucoma].

To evaluate the significance of nerve fiber layer (NFL) changes in the diagnosis of glaucoma, the authors examined 197 cases (347 eyes) of normal subjects, primary open angle glaucoma (POAG), low tension glaucoma (LTG) and suspects of these two types of glaucoma. The sensitivity of NFL atrophy to glaucoma was high: in POAG eyes with field loss, 88.9% (64/72) had NFL atrophy. In 123 normal eyes, NFL atrophy was found in only one eye, the specificity of NFL atrophy being 99.2%. All LTG patients and suspects of LTG had NFL atrophy. In the fellow eyes of POAG with normal fields and eyes of POAG suspects, NFL defects occurred in 53.8% (7/13) and 20.6% (15/73) respectively. The examination of NFL is a simple procedure; the nerve fibers themselves are directly observed rather than their function. When half of the thickness of NFL is lost, it Will be manifested clinically. With its high sensitivity and specificity, NFL atrophy can be regarded as an important indicator in the diagnosis of glaucoma.

Adult↗
PubMed1990

[Conformational changes of rat liver fatty acid binding protein induced by long chain fatty acid].

Rat Liver fatty acid binding protein (FABP) has been purified to homogeneity by the procedures including Sephadex G-100 and DEAE-cellulose column chromatography. FABP was resolved into two peaks of A and B by DEAE-cellulose column chromatography. Each of these fractions exhibited apparent homogeneity upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate with a molecular weight of 16,000 daltons and amino acid analysis of these fractions has revealed that they are identical protein. However, upon isoelectric focusing on polyacrylamide gel, the isoelectric (pl) points were differed considerably showing microheterogeneity. In the present investigation, one isoform (pl = 5.0) of FABP was purified by a successive DEAE-cellulose column chromatography and used for the subsequent experiments of fatty acyl-protein interactions. When the final FABP preparation was partly freed of fatty acids by a mild delipidation technique using Lipidex, the pl shifted toward higher regions of 7.0. However, the pl of the delipidated FABP turned to the original 7.0 by recombining fatty acids. On the other hand, the secondary and tertiary structures were also significantly changed by delipidization, which have been demonstrated by circular dichroism (CD) and nuclear magnetic resonance (1H-NMR) spectroscopy. Furthermore the structural properties of the delipidated FABP also could be restored by recombining fatty acid. These findings suggested that the weakly bound fatty acids are responsible for the functional capacity of the FABP by virtue of changing the protein conformation.

Animals↗
PubMed1990

[Posterior scleral reinforcement operation in the high myopia with macular degeneration].

The authors performed posterior scleral reinforcement operation on 23 cases of high myopia with macular degeneration. One eye underwent surgery and the another eye served as control. Follow-up period ranged from 3 to 24 months. It was found that the corrected vision and refractive degree of the operated eye maintained the original levels and that the control eyes tend to become worse during the follow-up periods. It was also observed that the blood circulation of the macular area of operated eye seemed to be improved, and the bioelectricity was activated. No serious complications were found. Therefore the authors pointed out, for high myopia patients, if the condition advanced constantly, the posterior scleral reinforcement operation is a method of choice before other better therapeutic methods are established.

Adolescent↗
PubMed1990

[A report on systolic hypertension in 1682 elderly peasants in Chengdu area].

Blood pressures of 1682 elderly peasants in Chengdu were measured at cluster random. The prevalence rate of hypertension was 15.7% and higher than that in early elderly (P less than 0.01). The rate of systolic hypertension was 75.4% and increased with the increase of age. The rate in females was higher than that in males (P less than 0.01). Electrocardiograms of these hypertension persons were analyzed with Minnesota code, and the incidence rates of two types were not statistically significant. These results show that the change of heart function resulted from hypertension is related with the rise of systolic pressure as well the rise of diastolic pressure.

Aged↗
PubMed1990

Absence of diuresis during a 7-day saturation dive at 2.5 ATA N2-O2.

Three male divers were studied for 2 days during each of the predive and postdive 1 ATA air control periods and for 7 days at 2.5 ATA (2.3 ATA N2 and 0.2 ATA O2). The chamber temperature was always maintained at a comfort level. Average urine flow remained at 1500 ml.day-1 during both predive and 2.5 ATA periods; urine osmolality also remained constant at around 700 mOSM/kg. On the other hand, daily excretion of Na increased significantly from 139 mEq during the predive period to 178 mEq at 2.5 ATA (P less than 0.05) but returned to the predive level during the postdive period. In contrast, daily K excretion decreased progressively with a significant decrease during the postdive period (P less than 0.05). Plasma osmolality, Na, and K remained unchanged, whereas a 6% reduction of total protein concentration at 2.5 ATA (P less than 0.05) was observed. A quantitatively similar decrease (8%) was observed for hematocrit during the 2.5 ATA period, which did not recover at postdive. These changes were accompanied by a significant increase in urinary excretion of antidiuretic hormone (P less than 0.05) and by decreases in both plasma renin and aldosterone (P less than 0.05) level and urinary excretion of aldosterone (P less than 0.05). Plasma atrial natriuretic factor remained unchanged throughout the entire dive period.

Adult↗