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M Li

Publications and source records attributed to M Li.

At least 1,045 records · Page 58Linked to original sources
PubMed1992

[Method of producing fusarin C in perlite-liquid culture medium].

For researching the biosynthesis labelled Fusarin C(Fc) by Fuscarium moniliforme, a more quick and convenient method of Fusarin C production and purification were established, and a good liquid culture medium consisted of different kinds organic matters (hydroxy proline, sucrose and glycerin), inorganic salts and perlite replaced corn grit medium. The perlite-liquid culture medium inoculated with the strain of F. moniliforme yields 936mg Fc/kg organic matter with in 14 days of incubation at 28 degrees C. As compared with the corn grit medium, the amount of Fc from perlite-liquid medium was more than that from corn grit medium (831mg Fc/kg corn grit). In all experiments both thin-layer chromatography and high-pressure liquid chromatography were used to confirm the presence of Fc. parameters which were important for the optimal biosynthesis of Fc included hydroxy proline and sucrose concentrations, incubated time/temperature and amount of perlite. The 40g of sucrose/L liquid culture was optimal concentration for Fusarin C production. Of three contained N-matter tested, hydroxy proline was the best sources of N-atom for Fusarin C. Under the absence of hydroxy proline, the Fc wasn't synthesized in perlite-liquid culture medium by F. moniliforme. A culture time/temperature study of Fc production was done, and the optimal Fc amounts was synthesized after incubation for 14 days at 28 degrees C on perlite-liquid culture medium.

Aluminum Oxide↗
PubMed1992

[The construction of rich genomic library of bovine Y chromosome].

According to the fundamentals of DNA renatured kinetics, we made a study in which genomic DNA from male cattle was completely digested with Sau 3A, while female DNA was sheared to an average size of 500 bp fragments. The Y derived DNA sequence rich library of bovine has been contracted with pUC19 plasmid as vector and JM109 as host bacteria by reassociation of male and female DNA. Male and female DNA probes, were used. The result of colony hybridization showed that out of 1000 recombinants analysed, 6 were found to be stronger signal with male probe. Analysis of Pvu' I digested DNA fragment revealed that most of the inserts were in the 90-300 bp.

Animals↗
PubMed1992

Immobilization of aminoacylase from Aspergillus oryzae on synthetic modified polyacrylamides.

A series of acrylamide-bisacrylamide copolymers modified by the Mannich Reaction was prepared. The immobilization of aminoacylase from Aspergillus oryzae on the copolymers was studied. All the polymers adsorbed the enzyme and the activity of the immobilized enzyme dependent on the amine used, viz. secondary amine, diamine, or aniline derivative. However, the activity was also influenced by the degree of crosslinking of the polymer. The surface morphology of the dimethylamine-modified polymer, with varying degrees of crosslinking, was analyzed by scanning electron microscope; the polymers having the largest pore diameter possessed the highest enzyme activity. One of the best polymers (DMA-A9B8) was used for immobilization of aminoacylase and its properties were studied. It had high enzymatic activity and good operational stability, i.e., retaining 90% of its original activity after being used for 42 days. The use of these copolymers for the preparation of immobilized enzymes is discussed.

Acrylic Resins↗
PubMed1992

[Effect of ribosome binding site sequence on the expression level of HBcAg in E. coli].

The recombinant (pKL series) Plasmids showing different levels of HBcAg antigenicity in ELISA were constructed by inserting the HBcAg gene which was randomly deleted at the non-coding region by Bal-31 exonuclease into plasmid vector pKK223-3 containing tac promoter and SD sequence. SDS-PAGE and Western blot experiments indicated that molecular weight of the HBcAg protein generated by these positive clones was 21000D. Three plasmids with high, moderate and low HBcAg expression level were sequenced and the distance between SD sequence and HBcAg gene ATG codon was 12, 13 and 19bp respectively. Computer analysis of secondary structure of the ribosome binding sites on RNA transcripts also revealed energy and structure differences between the low and high level expression plasmids, suggesting the importance of this distance and the mRNA structure to gene expression.

Base Sequence↗
PubMed1992

[Study on binding characteristics of 125I-labeled McAb LC-1 to lung adenocarcinoma cells in vitro and in vivo].

McAb LC-1 was derived from fusion of myeloma cells and murine spleen cells immunized with human lung adenocarcinoma SPC-A-1 cells. The immunoglobulin isotype of LC-1 belonged to IgM. LC-1 was direct against the common epitope of lung cancer. It not only reacted with small cell lung cancer but also with non small cell lung cancer. LC-1 was purified from ascitic fluid by euglobulin precipitation and Sephadex G-200 filtration chromatography, and was iodinated with Iodogen, the specific reactivity of 125I-labeled LC-1 was determined by comparing standard curve with self-displacement curve. The immunoreactive fraction of 125I-LC-1 was determined by its binding to excess of antigen. The RIA data were plotted in Scatchard-form as binding of SPC-A-1 cells to LC-1. The binding constant of LC-1 binding to SPC-A-1 was 4.8 x 10(8) M-1. The LC-1 binding sites on SPC-A-1 were 7.2 x 10(4) per cell. The RIA inhibition test showed that LC-1 and LAC-122 (another IgM isotype McAb reacted only with non small cell lung cancer) had no cross-reactivity. The treatment of SPC-A-1 cells by proteinase and sodium periodate inhibited LC-1 binding to these treated target cells by 39% and 66% respectively. These results suggested that the biochemical nature of antigen recognized by LC-1 was glycoprotein.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1991

Expression of two different forms of fibroblast growth factor receptor 1 in different mouse tissues and cell lines.

The fibroblast growth factor receptors (FGFRs) form a multigene family of at least four members, all having extracellular regions consisting of either two or three immunoglobin-like (Ig-like) domains. By RNase protection analysis we have analyzed the expression of FGFR-1 mRNA in various tissues and cell lines and demonstrated that all of the cell lines studied expressed at least two different forms of the FGFR-1 at similar levels. Although muscle and heart express forms having either two [FGFR-1 short (FGFR-1S)] or three [FGFR-1 long (FGFR-1L)] Ig-like domains, the developing brain and adult brain express only mRNA encoding the longer form. The two forms of the receptor were characterized further by stably introducing expression vectors expressing them into Rat-2 fibroblasts and FDC-P1 myeloid cells. Treatment of the transfected Rat-2 cells with acidic FGF (aFGF) or basic FGF (bFGF) resulted in focus formation. The transformed phenotype was observed even without addition of ligand after growth in culture for greater than 2 months. Cross-linking of 125I-labeled bFGF (125I-bFGF) to Rat-2 cells expressing either FGFR-1L or FGFR-1S yielded two similar complexes of 150 and 110 kDa. Although Rat-2 cells expressing FGFR-1L yielded similar complexes with 125I-labeled aFGF (125I-aFGF), only the 150-kDa complex was formed with cells expressing FGFR-1S. The 150-kDa complex was also observed when 125I-aFGF or 125I-bFGF was cross-linked to FDC-P1 cells expressing FGFR-1L. Significantly, these complexes were only observed when heparin was present in the cross-linking reaction. FDC-P1 cells expressing FGFR-1 bound aFGF and bFGF with high affinity but only in the presence of heparin. The factor dependence of these cells could be switched from interleukin 3 to FGF in the presence of heparin.

Animals↗
PubMed1991

Electroencephalography, magnetic resonance imaging and pathology in patients treated surgically for temporal lobe epilepsy.

In a consecutive series of 40 patients selected by EEG studies for surgical treatment of temporal lobe seizures, magnetic resonance imaging showed structural lesions in 25% and signal abnormalities, usually in the mesial temporal region, in another 35%. Pathological changes included structural lesions in over 30% of patients and sclerosis of the amygdala in almost half of the series. These findings further substantiate the implication of the amygdala in the pathogenesis of temporal lobe seizures with automatism and amnesia.

Amygdala↗
PubMed1991

Isolation and characterization of mannose 6-phosphate/insulin-like growth factor II receptor from bovine serum.

A convenient means was devised for the purification of milligram quantities of a soluble form of the mannose 6-phosphate/insulin-like growth factor II receptor (Man-6-P/IGF II receptor). The receptor was purified to near homogeneity from bovine serum by affinity chromatography on agarose-pentamannosephosphate in the absence of detergent. Approximately 2.5 mg of receptor were obtained from 500 ml of fetal calf serum. The concentration of receptor in serum decreased sharply with development. Fetal calf serum Man-6-P/IGF II receptor was immunologically similar to detergent-solubilized, membrane-bound Man-6-P/IGF II receptor from bovine liver. N-Terminal sequence analysis revealed that the purified serum receptor, but not the solubilized, membrane-associated receptor, contains stoichiometric amounts of bound IGF II. The results of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel chromatography studies suggest that the fetal calf serum receptor (in contrast to the solubilized, membrane-bound bovine testis receptor) does not aggregate. The affinity of the fetal calf serum receptor for bovine testis beta-galactosidase approximated one-half that observed for solubilized, membrane-bound bovine testis receptor.

Aging↗
PubMed1991

Role of the sympathetic nervous system in the onset of hypertension in the rat: the effect of 6-OH-dopamine.

1. The effect of chemical sympathectomy with 6-OH-dopamine (6-OHDA) on the onset of adrenocorticotrophin (ACTH)-induced hypertension was examined in Sprague-Dawley rats (n = 23). 2. 6-OHDA injection produced a fall in systolic blood pressure (SBP) from 100 +/- 5 mmHg control to 74 +/- 4 mmHg post-6-OHDA Treatment Day 1 (P less than 0.001), but did not alter food or water intake, urine volume or electrolyte excretion. 3. Compared with sham injection, ACTH-treated rats showed an increase in blood pressure (sham: 98 +/- 7 mmHg; ACTH: 123 +/- 9 mmHg on Treatment Day 10; P less than 0.01), loss of bodyweight, and increases in water intake and urine volume. 4. The magnitude of the blood pressure rise on ACTH was greater in 6-OHDA-treated rats than in intact control rats. Metabolic changes were similar. 5. Chemical sympathectomy with 6-OHDA did not delay or block the onset of ACTH hypertension in the rat.

Adrenocorticotropic Hormone↗
PubMed1991

The chemiluminescence of amides and monoacyl hydrazides based on firefly dehydroluciferin.

Monoacyl hydrazides based on 5-methyldehydroluciferin and simpler analogs have been synthesized; they proved to be chemiluminescent on treatment with a strong base in DMSO in the presence of oxygen. The light emitters in these cases appear to be the corresponding carboxylate ions; a pathway involving an oxidative decarboxylation was eliminated as a possibility by consideration of the fluorescence wavelengths of the corresponding oxyluciferins. A reaction mechanism for the luminescence involving the possible intermediacy of an azadioxetane is proposed. The corresponding amides were also synthesized; they proved to be equally chemiluminescent to the hydrazides in the dehydroluciferin series.

Acylation↗
PubMed1991

Evidence that M3 muscarinic receptors in rat parotid gland couple to two second messenger systems.

The binding affinities of muscarinic antagonists were compared with their abilities to block carbachol (CCh)-mediated stimulation of Ca2+ mobilization and inhibition of isoproterenol-elicited adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in rat parotid cells. The binding of [3H]quinuclidinyl benzilate (QNB) to membranes was inhibited by antagonists with the following potencies (dissociation constant, nM): atropine (1.1) approximately 4-diphenylacetoxy-N-methylpiperidine methbromide (4-DAMP) (1.6) much greater than pirenzepine (136) greater than 11-[[2-[(diethylamino)methyl-1-piperidinyl]-acetyl]acetyl]-5,11- dihydro-6H-pyrido[2,3-b][1,4]-benzodiazepine-6-one (AF-DX 116) (5,293). AF-DX 116 blocked Ca2+ mobilization and inhibition of cAMP accumulation with low affinities [inhibitory concentration at 50% (IC50) = 3150 and 6,528 nM, respectively], whereas 4-DAMP blocked these responses with considerably higher affinities (IC50 = 4.3 and 11.4 nM, respectively). Schild plots of 4-DAMP and AF-DX 116 antagonism of CCh-stimulated inositol trisphosphate accumulation showed inhibitor constant (Ki) values of 0.85 and 1,585 nM, respectively, whereas Schild plots of 4-DAMP, AF-DX 116, and methoctramine antagonism of CCh-induced inhibition of cAMP accumulation showed Ki values of 1.3, 1,585, and 2,754 nM, respectively. Preincubation of cells with 0.1 mM 3-isobutyl-1-methylxanthine did not prevent the capacity of CCh to inhibit cAMP accumulation. Pertussis toxin blocked the CCh-elicited and Gi-mediated inhibition of cAMP formation. Northern blot analysis showed the presence of mRNA for the M3, but not for the M2, subtype in parotid gland. An immunochemical procedure using m1-m5 specific antibodies was performed in parotid membranes and showed that the m3 receptor accounts for 93% of precipitable receptors. These data suggest that M3 receptors in the rat parotid are coupled to both the stimulation of Ca2+ mobilization and the inhibition of cAMP accumulation.

1-Methyl-3-isobutylxanthine↗
PubMed1991

Epidermal growth factor elevates intracellular pH in chicken granulosa cells.

Many bioregulators, such as epidermal growth factor (EGF), induce intracellular alkalinization by activating a membrane bound Na+/H+ antiporter. The present studies were designed to examine the influence of EGF on intracellular pH (pHi) in chicken granulosa cells. pHi in granulosa cells from the two largest preovulatory follicles of hens was determined spectrofluorometrically using the dye 2',7'-bis(carboxyethyl-5(6)-carboxyfluorescein. The resting pHi was 6.81 +/- 0.006 (n = 30) when the extracellular pH and sodium concentration (Na+o) were 7.3 and 144 mM, respectively. EGF (5-100 ng/ml) induced a concentration-dependent increase in pHi, which reached a maximum of 0.217 +/- 0.009 pH units at a concentration of 100 ng/ml EGF. Cytosolic alkalinization was observed within 10 min of the addition of EGF and lasted over the 60 min observation period. The increase in pHi was dependent upon the presence of Na+o, since the EGF effect was attenuated when Na+o was substituted with equimolar concentrations of nonpermeant choline chloride. The EGF-induced pHi change was also inhibited by amiloride, dimethyl amiloride, and ethylisopropyl amiloride, inhibitors of the Na+/H+ antiporter. The alkalinization effect of EGF was mimicked by transforming growth factor-alpha but not by insulin, insulin-like growth factor-I, or transforming growth factor-beta. These studies suggest for the first time that intracellular alkalinization resulting from activation of the Na+/H+ antiporter may be a part of the transmembrane signaling pathway in the action of EGF on chicken granulosa cells.

Animals↗
PubMed1991

Epidermal growth factor elevates intracellular pH in chicken granulosa cells by activating protein kinase C.

Previous studies from our laboratory have demonstrated that epidermal growth factor (EGF), induces intracellular alkalinization in chicken granulosa cells by activating a sodium-dependent and amiloride-sensitive Na+/H+ antiporter. In the present investigation we have examined the possible involvement of protein kinase C (PKC) in the regulation of intracellular pH (pHi) by EGF in chicken granulosa cells. Intracellular pH in granulosa cells obtained from the two largest preovulatory follicles was determined spectrofluorometrically using the dye 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein. The resting pHi was 6.81 +/- 0.01 (n = 30) when the extracellular pH and sodium concentration were 7.3 and 144 mM, respectively. 12-O-Tetradecanoyl-phorbol-13-acetate (TPA; 50-400 ng/ml) and 1-oleoyl-2-acetylglycerol (OAG; 1-75 micrograms/ml) mimicked the actions of EGF by inducing a concentration-dependent increase in pHi which reached a maximum of 0.25-0.30 pH units. 4 alpha-Phorbol 12,13-didecanoate, a phorbol ester with no tumor promoting activity had no effect on pHi. Cytosolic alkalinization was observed within 10 min of the addition of each agent and increased over the 60-min observation period. Like EGF-induced cytosolic alkalinization, the increases in pHi in response to TPA or OAG were dependent on the presence of sodium concentration and were inhibited by amiloride, an inhibitor of the Na+/H+ antiporter. The effects of EGF, TPA, and OAG were attenuated by the PKC inhibitors 5-isoquinolinylsulfonyl-2-methyl piperazine and trifluoperazine. Down-regulation of granulosa cell PKC by pretreatment with TPA (200 ng/ml) for 2.5 h inhibited EGF-, TPA-, and OAG-induced cytosolic alkalinization. The effects of maximally stimulatory concentrations of EGF and TPA on cytosolic alkalinization were not additive. The increases in pHi induced by TPA and OAG, but not by EGF, were dependent on the presence of extracellular Ca++. These studies suggest that the EGF-induced intracellular alkalinization in chicken granulosa cells involves a PKC-mediated activation of the Na+/H+ antiporter.

Animals↗