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Biomedical subjects

S M Li

Publications and source records attributed to S M Li.

At least 19 recordsLinked to original sources
PubMed1998

4-Hydroxybenzoate 3-geranyltransferase from Lithospermum erythrorhizon: purification of a plant membrane-bound prenyltransferase.

Geranyldiphosphate:4-hydroxybenzoate 3-geranyltransferase is a regulatory enzyme in the biosynthesis of shikonin, a phytoalexin and pharmaceutical produced by cell cultures of Lithospermum erythrorhizon Sieb. et Zucc. In Linsmaier-Skoog medium, the activity of this enzyme could be enhanced more than 200-fold by addition of methyl jasmonate, and this culture material was used for the solubilization and purification of the enzyme. Of various detergents examined, digitonin was the most suitable for the solubilization of the enzyme. The solubilized enzyme was purified 800-fold by chromatography over diethylaminoethyl (DEAE)-Sephacel, Heparin-Sepharose, Reactive Green 19-Agarose, and Cholic Acid-Agarose. The purified enzyme required magnesium ions as cofactor and was highly specific for geranyldiphosphate (GPP) and 4-hydroxybenzoate (4HB) as substrates. The K(m) values for 4HB and GPP were calculated by the method of Lineweaver and Burk as 18.4 microM and 13.8 microM, respectively.

Acetates↗
PubMed1998

Effects of metallothionein on action potentials of anoxic and reoxygenated papillary muscles of guinea pigs.

AIM: To study anti-arrhythmic effects of metallothionein (MT). METHODS: Standard microelectrode technique was used to study the effects of MT on action potentials (AP) in anoxic and reoxygenated papillary muscles of guinea pigs. RESULTS: MT (0.02 mmol.L-1) had no effects on AP of the normal papillary muscles; when the muscles were exposed to ischemic solution without MT, there was a marked shortening of action potential duration (APD) at 20%, 50%, and 90% of repolarization (APD20, APD50, APD90) from 82 +/- 7 to 37 +/- 7, 131 +/- 35 to 63 +/- 11, and 167 +/- 12 to 100 +/- 19 ms, respectively, (P < 0.01); and an obvious reduction of resting potential (RP), action potential amplitude (APA), and the maximal upstroke velocity of phase 0 (Vmax) from -92 +/- 9 to -63 +/- 12 mV, 135 +/- 13 to 80 +/- 8 mV, and 286 +/- 55 to 164 +/- 42 V.s-1, respectively (P < 0.01). However, in the presence of MT, the AP parameters (RP, APA, and Vmax) changed from -63 +/- 2 to -82 +/- 1 mV, 80 +/- 8 to 104 +/- 25 mV, and 164 +/- 42 to 237 +/- 43 V.s-1, respectively, (P < 0.01), except that APD20, APD50, and APD90 shortened further from 37 +/- 7 to 12 +/- 3, 63 +/- 11 to 28 +/- 7, and 100 +/- 19 to 82 +/- 11 mV, respectively (P < 0.01). MT decreased the incidence of automaticity during reoxygenation from 91% to 33%. CONCLUSION: MT possesses a calcium regulatory property.

Action Potentials↗
PubMed1997

4-Coumaroyl coenzyme A 3-hydroxylase activity from cell cultures of Lithospermum erythrorhizon and its relationship to polyphenol oxidase.

A 4-coumaroyl-CoA 3-hydroxylase activity was purified 4600-fold from cell cultures of Lithospermum erythrorhizon. The enzyme showed a molecular mass of 42,400 +/- 1700 Da in gel chromatography and required ascorbate, NADH, or NADPH as cofactors. 4-Coumaroyl-CoA, 4-coumarate, p-cresol, and several other phenolic substances, but not tyrosine, were accepted as substrates for the hydroxylation. Besides hydroxylase activity, the enzyme showed diphenol oxidase activity. Both activities were inhibited by diethyldithiocarbamate or beta-mercaptoethanol, although at different concentrations. The enzyme showed striking similarity to a 4-coumaroyl-glucose 3-hydroxylase from sweet potato (Ipomoe batatas) roots, which has reportedly been purified to homogeneity and identified as a specific enzyme of chlorogenic acid biosynthesis. Close examination and comparison to a commercially available polyphenol oxidase, however, suggest that the enzyme activities purified from both Lithospermum and sweet potato are polyphenol oxidases rather than specific enzymes of secondary metabolism.

Adenine Nucleotides↗
PubMed1997

Major origin of mutagenicity of chlorinated drinking water in China: humic acid or pollutants.

Since Loper and Glatz (J. Toxicol. Environ. Health, 4:919-938;1978) discovered the presence of the mutagenicity in drinking water after chlorination in 1978, humic acid (HA) has been considered as an important source. But our research results show that only 1/8 of observed direct frameshift mutagenicity in tap water originated from chlorination of HA isolated from raw water. Contamination from industrial waste and human settlement (night soil) are important potential sources of mutagenicity in chlorinated drinking water. The results show that mutagenicity from night soil after chlorination depended upon pH of sample. Production of mutagenicity at pH 6 is ten times of that at pH 8, and decomposition process is necessary condition for mutagenicity production. Season variation of mutagenicity of tap is also presented in the paper.

China↗
PubMed1997

[Effect of qiangji jianli capsule on metabolism of acetylcholine receptor].

OBJECTIVE: To explore the action mechanism of Qiangji Jianli Capsule (QJJLC) treating myasthenia gravis. METHODS: Internal receptor permeation and degradation test were performed. RESULTS: Volume of receptor permeation in the group with QJJLC at 96 hours was 902.50 +/- 37.48 cpm/mg, while that of control group 738.45 +/- 35.41 cpm/mg. Half-life of receptor degradation in treatment group was 52 hours and that of control 38 hours. Their difference was very significant (P < 0.001). CONCLUSION: QJJLC could accelerate permeation of N-aectylcholine receptor to surface of diaphragm cell membrane and decelerate receptor degradation. It could also increase accumulative amounts of functional receptor in unit time and keep dynamic equilibrium of receptor metabolism in pathologic condition.

Animals↗
PubMed1997

[Effect of puerarin on plasma endothelin, renin activity and angiotensin II in patients with acute myocardial infarction].

OBJECTIVE: To study the changes of endothelin (ET), renin activity (RA) and angiotensin II (AT-II) before and after puerarin treatment in patients with acute myocardial infarction (AMI). METHODS: Forty-three patients with AMI were divided into two groups, and were given puerarin and glucose-insulin-kalium (GIK) treatment respectively. Plasma ET, RA and AT-II were measured by radioimmunoassay (RIA) before and after treatment in different phases. RESULTS: It showed that plasma ET and RA, AT-II levels in AMI were higher than those in control group (P < 0.01). ET level was conversely correlated with RA and AT-II (P < 0.01). After treatment with puerarin, plasma levels of ET, RA and AT-II were recovered to normal in 3 days, but these data recovered to nearly normal until 7-14 days in group with GIK treatment. CONCLUSION: Puerarin might play an important role in regulating the imbalance of ET, RA and AT-II of patients with AMI.

Aged↗
PubMed1996

Effects of long-term administration of octreotide in portal vein-stenosed rats.

The hemodynamic effects of long-term administration of octreotide in portal hypertension has not been established. In addition, whether long-term octreotide treatment prevents the development of portosystemic shunts has not yet been evaluated. Hence, the current study was undertaken to evaluate the effects of long-term administration of octreotide in rats with portal vein stenosis. Immediately after portal vein stenosis or sham operation, rats were given either a long-term octreotide administration of 100 micrograms/kg or a placebo every 12 hours by subcutaneous injection for 14 consecutive days. Systemic hemodynamics and regional blood flows, degree of mesenteric-systemic shunts, and plasma glucagon concentrations were measured after the final dose of octreotide or placebo. A fifth group of portal vein-stenosed rats received hemodynamic and plasma glucagon measurements after 1-day octreotide treatment given at 14 days after surgery. Long-term octreotide treatment modified the hyperdynamic circulation without affecting the degree of mesenteric-systemic shunts, and 1-day octreotide treatment decreased portal tributary blood flow without affecting the portal pressure, systemic hemodynamics, and degree of mesenteric-systemic shunts. Plasma glucagon levels were decreased in portal vein-stenosed rats receiving either long-term or 1-day octreodtide compared with rats receiving placebo. In contrast, chronic octreotide treatment did not affect any of the hemodynamic values or plasma glucagon levels in sham-operated rats. In conclusion, long-term administration of octreotide modified in part the development of portal hypertension and hyperdynamic circulation in portal vein-stenosed rats without affecting the degree of mesenteric-systemic shunts.

Analysis of Variance↗
PubMed1996

Genetic engineering of plant secondary metabolism. Accumulation of 4-hydroxybenzoate glucosides as a result of the expression of the bacterial ubiC gene in tobacco.

The ubiC gene of Escherichia coli encodes chorismate pyruvatelyase, an enzyme that converts chorismate into 4-hydroxybenzoate (4HB) and is not normally present in plants. The ubiC gene was expressed in Nicotiana tabacum L. plants under control of a constitutive plant promoter. The gene product was targeted into the plastid by fusing it to the sequence for the chloroplast transit peptide of the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Transgenic plants showed high chorismate pyruvate-lyase activity and accumulated 4HB as beta-glucosides, with the glucose attached to either the hydroxy or the carboxyl function of 4HB. The total content of 4HB glucosides was approximately 0.52% of dry weight, which exceeded the content of untransformed plants by at least a factor of 1000. Feeding experiments with [1,7-13C2]shikimic acid unequivocally proved that the 4HB that was formed in the transgenic plants was not derived from the conventional phenylpropanoid pathway but from the newly introduced chorismate pyruvate-lyase reaction.

Amino Acid Sequence↗
PubMed1996

Hyperglucagonaemia in cirrhotic patients and its relationship to the severity of cirrhosis and haemodynamic values.

Plasma glucagon concentrations were measured in 160 cirrhotic patients (Pugh's grade A in 52 patients, Pugh's grade B in 64 patients and Pugh's grade C in 44 patients). These values were compared with plasma glucagon concentrations in 57 age and sex-matched healthy subjects. Systemic and portal haemodynamic measurements, effective renal plasma flow and creatinine clearance were recorded for each patient. Plasma glucagon levels were significantly increased in cirrhotic patients compared with healthy subjects. In addition, plasma glucagon levels were higher in cirrhotic patients with ascites than in those without ascites and were increased in relation to the severity of cirrhosis as assessed by Pugh's score. Multiple linear regression found that only Child-Pugh's score was estimated to be an independent predictor of hyperglucagonaemia in cirrhotic patients. However, in patients with different degrees of oesophageal varices and in patients without oesophageal varices, plasma glucagon concentrations were no different among the different groups of patients, but were still higher than plasma glucagon concentrations in healthy subjects. In contrast, plasma glucagon levels were negatively correlated with mean arterial pressure and systemic vascular resistance. The results of the present study suggest that impairment of liver function plays, in part, a role in increased plasma glucagon levels observed in patients with cirrhosis. In addition, these data support the hypothesis that hyperglucagonaemia may contribute, at least in part, to the pathogenesis of peripheral arterial vasodilatation in cirrhosis with portal hypertension.

Adult↗
PubMed1996

Screening of microorganisms for biodegradation of poly(lactic-acid) and lactic acid-containing polymers.

The ability of some microorganisms to use lactic acid stereocopolymers and copolymers with glycolic acid as sole carbon and energy sources was studied under controlled or natural conditions. First, 14 filamentous fungal strains were tested in liquid cultures, adopting total lactic acid consumption, nitrogen source exhaustion, and maximal biomass production as selection criteria. Two strains of Fusarium moniliforme and one strain of Penicillium roqueforti were able to totally assimilate DL-lactic acid, partially soluble racemic oligomers (MW = 1,000), and the nitrogen source. Only one strain of F. moniliforme was able to grow on a poly(lactic acid)-glycolic acid copolymer (MW = 150,000) after 2 months of incubation at 28 degrees C on synthetic agar medium. Mycelium development was examined by scanning electron microscopy. F. moniliforme filaments were observed to grow not only at the copolymer surface but also through the bulk of the copolymer. In a second approach, plates made of a racemic poly(lactic acid) were buried in the soil before being incubated in petri dishes containing mineral agar medium under controlled conditions. Five strains of different filamentous fungi were isolated, and their ability to assimilate racemic poly(lactic acid) oligomers was tested in liquid cultures.

Biodegradation, Environmental↗
PubMed1996

Structural characterization and hydrolytic degradation of a Zn metal initiated copolymer of L-lactide and epsilon-caprolactone.

A bioresorbable aliphatic polyester was synthesized by bulk copolymerization of a 1/1 M/M L,L-lactide/epsilon-caprolactone mixture using zinc metal as initiator. The actual composition of the copolymer was found to be 1.5/1 as deduced from 1H NMR spectra obtained in DMSO-d6 solutions where higher resolution was obtained as compared with chlorinated solvents. Resonances due to L-lactyl units (L) exhibited triads stereosensitivity, epsilon-oxycaproyl units (C) being sensitive to dyads. Average lengths of both poly(lactic acid) and polycaprolactone sequences were evaluated and showed the presence of rather long PLA blocks. Furthermore, no CLC triad signal was found, suggesting the absence of transesterification rearrangements. 10 x 10 x 2 mm specimens made of the copolymer were allowed to age in isoosmolar pH = 7.4 phosphate buffer at 37 degrees C. Degradation was monitored by various analytical techniques such as SEC, X-ray diffractometry, DSC, and 1H NMR. Data were compared with the behaviour of PCL and PLA homopolymers allowed to age under similar conditions. Crystallinity and composition changes are discussed in terms of preferential degradation in L- and C-containing amorphous domains, crystallized long PLA blocks being much more resistant.

Absorption↗
PubMed1994

Attempts to map the structure and degradation characteristics of aliphatic polyesters derived from lactic and glycolic acids.

During the past 5 years, important advances have been accomplished in the understanding of the fate of aliphatic polyesters derived from lactic acid (LA) and glycolic acid (GA) in aqueous media. Hydrolysis of solid LA/GA polymers is now regarded as dependent upon a diffusion-reaction mechanism. Faster central degradation, degradation-induced composition, and morphology changes are three of the most important findings which appeared to be composition-dependent as deduced from the behavior of different LA/GA polymers. An attempt is made to generalize these findings to the whole family and to elaborate a map which could be used to predict degradation characteristics of LA/GA polymers from their initial composition and morphology.

Hydrolysis↗
PubMed1994

[Treatment of femoral trochanteric fracture with intramedullary interlocking nailing: a report of 32 cases].

We improved and made the intramedullary interlocking nail and it's instrument for surgical operation in December 1989 by consulting the reported material of the gamma locking nail. 32 cases of the femoral trochanteric fracture were treated by using this fixation system. The results were satisfactory. The patients could stand up and move about beginning from 6th to 13th day after operation. No mechanical failure of implant, infection and other complications occurred in our series. 29 cases were followed-up for 5 to 19 months and showed all of the fractures were healed. Their hip functions were completely or basically recovered. Coxa vara deformity occurred in two cases and one had a 2.5 cm shortening of the lower limb. We consider that the intramedullary interlocking nail conforms to the principle of human biomechanics and it may be used as an effective surgical treatment with the fracture fixation of superior strength and stability for every type of femoral trochanteric fractures.

Adult↗
PubMed1994

[Quantitative structure-activity relationship of P-amino-diphenyl ether analogues to inhibit cytochrome P-450].

A group of p-amino-diphenyl ether analogues were tested for their activities to prolong the pentobarbital sleeping time in mice and to inhibit the demethylation of p-nitro-anisole catalyzed by untreated mouse hepatic microsomes in vitro. The stepwise multiple regression analyses were used to obtain the quantitative structure-activity relationships between the activities of inhibiting cytochrome P-450 in vitro or in vivo for the analogues and their quantum chemical indexes. The results showed that the inhibiting activities both in vitro and in vivo were correlated with the energy level of the lowest unoccupied molecular orbital (ELUMO), the nucleophilic superdelocalizabilities of the nitrogen (SN(N)) and the oxygen (SN(O)). The inhibiting activities of the analogues to cytochrome P-450 may mainly come from their ability to form cytochrome P-450 metabolic intermediate complex.

Animals↗
PubMed1994

[Comprehensive treatment for diabetes limb gangrene].

Anisodamine was used to improve general circulation and the microcirculation of affected limbs. Measures like local debridement, dressing change, and control of diabetes were applied in 351 patients with diabetic limb gangrene. Of the 351 patients, 301 (85.7%) were cured, 27(7.7%) were improved, 7(2.0%) failed, 6(1.7%) had limb amputated, and 10(2.9%) died. In the treatment, the nail-fold microcirculation was markedly improved. Doppler scan showed increased width and bloodflow of the vessels of the affected limbs. The criteria for the classification and diagnosis of diabetes limb gangrene are suggested.

Adult↗
PubMed1992

Serum steroid hormonal profiles by reversed-phase liquid chromatography in patients with 17-hydroxylase deficiency and in an affected family.

We used an optimized isocratic reversed-phase high-performance liquid-chromatographic procedure to separate and measure 12 steroid hormones, and studied the steroid hormone profiles in sera from three patients with 17-hydroxylase deficiency (17-OHD). Two of the patients were sisters, one of whom (II-3), expressing normotension and primary amenorrhea, was diagnosed on the basis of chromatographic data and followed up for seven years. The untreated patients had obvious abnormalities on chromatograms of serum extracts, characterized by markedly increased corticosterone (B) and decreased or undetectable cortisol (F) and cortisone (E). The concentration of 11-deoxycorticosterone was much greater in the patient with classical symptoms than in the normotensive patient. In all three patients, concentrations of aldosterone were within the normal range, but concentrations of progesterone were much lower than in the patients with 21-hydroxylase deficiency. We evaluated the responses to corticotropin and dexamethasone. HPLC evaluation of the serum steroid profiles before and after corticotropin stimulation in the affected family showed that in the parents and one other sibling, concentrations of F before and after stimulation were within the normal ranges. The sums of the ratio of B to F before and the ratio of B to F after corticotropin stimulation (sigma B/F) in the parents and the other sibling were 0.292, 0.496, and 0.614, respectively, all much higher than the normal value (mean +/- SD: 0.164 +/- 0.038). Thus the sigma B/F value may be a hormonal marker of heterozygotes carrying this defect.

Adolescent↗
PubMed1992

[Reduction of genotoxic damage in oral mucosa with myasthenia gravis by traditional Chinese medicine].

Micronucleated exfoliated cell (MEC) of oral mucosa of 40 patients with myasthenia gravis (MG) and 54 normal controls were observed by means of micronucleus test. The frequency of MEC of two groups were 9.56/1000 and 2.55/1000 respectively, and their difference was remarkably significant (P < 0.001). 22 cases were treated by TCM Qiang Ji Jian Li Capsule. The frequency of MEC after treatment fell from 14.38/1000 to 6.00/1000. The difference was significant (P < 0.002). The frequency of Spleen-asthenia group higher than that of non-Spleen-asthenia (P < 0.05). The results revealed that. The patients with MG had genotoxic damage. (2) The constitution with the Spleen-asthenia and the genotoxic damage was related. (3) Qiang Ji Jian Li Capsule of invigorating the Spleen and benefiting Qi could reduce the genotoxic damage.

Adolescent↗