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Biomedical subjects

C Li

Publications and source records attributed to C Li.

At least 991 records · Page 55Linked to original sources
PubMed1995

[The adsorption mechanism of Pb2+, Cd2+, Ni2+ and Co2+ onto activated carbon particles].

The adsorption of Pb2+, Cd2+, Ni2+, Co2+ on activated carbon particles was studied as a function of pH and concentrations of adsorbates. These results showed that the adsorption was strongly pH-dependent and all the adsorption isotherms were in agreement with Freundlich equation. The adsorption could be explained by the surface complexation model. Conditional adsorption constants of surface complexes of Pb2+, Cd2+, Ni2+ and Co2+ with activated carbon particles were calculated by a simplified surface complexation model.

Adsorption↗
PubMed1995

[Textual study and resource investigation on traditional Chinese drugs duhuo, jiuyanduhuo and qianghuo].

By means of Bencaological study on traditional Chinese drugs Duhuo, Jiuyanduhuo and Qianghuo, it has been found out that the Duhuo recorded in earlier Bencao works should be Qianghuo, and Duhuo was first used medically in the South-North Dynasty period, whereas Jiuy-anduhuo's medical use started in the Ming Dynasty. Resources of the three drugs were investigated and their main species were found out.

Drug Contamination↗
PubMed1995

[Relationship between the structure--modified N- and C- termini and the biological activity of TNF alpha molecule].

In order to elucidate the relationship between N-, C-termini of TNF alpha and it's biological activity, a TNF alpha derivative 10 (TNF alpha D10) was prepared by changing amino acid at the N-terminus positions Ser(4), Ser(5), Asp(10) and C-terminus position Leu(157) to N-terminus Cys(4), Thr(5), Arg(10) and C-terminus Phe(157) with PCR site-directed mutagenesis. The results showed that the expression level of this mutein has not altered but its cytotoxic activity increased. This might result from trimer formation of TNF alpha D10 by changing N-terminal Ser(4) residue to Cys. HPLC showed that the molecular weight of TNF alpha D10 was 17kD, 35kD, 55kD respectively. In addition, we also found that the stability of TNF alpha D10 was less than that of TNF alpha when to be stored at -20 degrees C for two months. It might be caused by changing Leu(157) to Phe(157).

Base Sequence↗
PubMed1995

Microsomal metabolism of the 5-lipoxygenase inhibitors L-746,530 and L-739,010 to reactive intermediates that covalently bind to protein: the role of the 6,8-dioxabicyclo[3.2.1]octanyl moiety.

Hepatic microsomes from different species were used to study the oxidative metabolism of L-746,530 and L-739,010, two potent and specific 5-lipoxygenase inhibitors. HPLC analysis of the incubates obtained from the microsomal incubations of L-739,010 and L-746,530 showed only traces of metabolites. However, recovery of the starting material in the supernatant was less than quantitative in all of the species studied (approximately 90% in rat, approximately 70% in the dexamethasone-induced rat, approximately 70-90% in humans, and approximately 60% in the rhesus monkey for both compounds). The recovery of the starting material was found to be time- and NADPH-dependent, suggesting that metabolite(s) were formed and reacting with the microsomal proteins. Evidence that the cytochrome P4503A (CYP3A) contributed to the formation of the reactive metabolite(s) was shown by the low recovery of material that was observed upon incubation with microsomes obtained from dexamethasone-treated rats (a CYP3A inducer), compared with microsomes obtained from untreated rats. Also, the recovery of material was improved when troleandomycin, a CYP3A inhibitor, was added to rhesus monkey microsomal incubations (25% more parent compound detected in the supernatant with 100 microM of troleandomycin). Using radiolabeled L-746,530 and gel electrophoresis analysis, it was confirmed that radiolabeled material was covalently bound to the microsomal protein. Incubations of L-739,010 and L-746,530 in the presence of semicarbazide resulted, in both cases, in the formation of two adducts. Using a combination of NMR, liquid secondary-ion MS, and UV techniques, these adducts were identified as isomers of an oxidized metabolite that had been trapped by semicarbazide. The site of oxidation was determined to be on the dioxabicyclo moiety. The importance of this moiety in the formation of reactive metabolite(s) was verified by incubating analogs of the 5-lipoxygenase inhibitors that contained blocking methyl groups at the proposed site of oxidation on the bicyclo moiety. Incubations of these gemdimethyl analogs of L-746,530 and L-739,010 with microsomes from different species resulted in significantly improved recovery of the starting material (approximately 94% in the rat, 85% in the dexamethasone-induced rat, 95% in humans, and 85% in the rhesus monkey for both compounds) and significantly less radioactive binding to the microsomal protein.

Animals↗
PubMed1995

[Apolipoprotein (a) polymorphism in relation to coronary heart disease in Chinese Han nationality].

We investigated the association of apolipoprotein (a) [apo(a)]polymorphism with coronary heart disease in Chinese Han nationality. The effects of the apo(a) phenotypes on lipoprotein [Lp (a)], total cholesterol (TC), high density lipoprotein cholesterol (HDL), and triglyceride (TG) levels were also investigated. The CHD group consisted of 105 patients (85 were survivors from previous myocardial infarction and 20 had > or = 75% narrowing in at least one of the major coronary arteries found by coronary angiography). The control group included 102 healthy individuals who had no symptoms and clinical signs of cardiovascular diseases. Apo(a) phenotype was performed by SDS-polyacrylamide gel electrophoresis (PAGE) under reducing conditions followed by immunoblotting. Determination of (a) Lp(a) and other lipoproteins were also performed. The apo(a) low molecular weight phenotypes (B, S1, S2) were more frequent in the CHD patients than in the healthy individuals (30.5% vs 15.7%, P < 0.05). Lp(a) concentrations were significantly higher in the patients than in the controls (257 +/- 225 mg/L vs 145 +/- 157 mg/L, P < 0.001). The results from stepwise logistic regression analysis indicated that apo(a) phenotype was a significant predictor of CHD, independent of TC, LDL-C and HDL-C. But apo(a) molecular weight was inversely related to Lp(a) levels. The apo(a) low molecular weight phenotypes associated with elevated Lp(a) levels was a primary genetic risk factor for CHD in Han Chinese.

Aged↗
PubMed1995

[Viability and antigenic changes in the skin after preservation under different temperatures].

Oxygen consumption and succinate dehydrogenase contents were determined to compare mean viabilities (%) of human cadaver and guinea pig skin stored under different temperature: 4 C, -20 C, -80 C, and -196 C. The results showed that the mean viability (%) of skin cryopreserved under -196 C was superior to those under 4 C, -20 C, and -80 C (70.8%, 61% respectively for -196 C, P < 0.05 or 0.01). Microimmunoelectrophoresis and rocket immunoelectrophoresis were performed for related antigens and antibodies. The results of microimmunoelectrophoresis showed that the antigenicities were different for four groups. Antigenicity of fresh skin was highest. The higher the storage temperature, the lower the antigenicity of skin was.

Animals↗
PubMed1995

Effect of 3'-untranslated region on expression of TNF alpha cDNA in Escherichia coli.

A construct pRL-rhTNF alpha 2, in which the 110 bp 3'-untranslated region of rhTNF alpha cDNA was deleted, was transformed in E.coli. The expression level of several positive transformants was determined. The results showed that the expression of pRL-TNF alpha 2 was stable and the biological characteristics of the protein product were the same as that of pRL-rhTNF alpha. Furthermore, the expression level of pRL-rhTNF alpha 2 was increased. It is suggested that the 3'-untranslated region may have some effects on gene expression. A TA-rich sequence, TTTATTA, contained in the 3'-untranslated region of pRL-rhTNF alpha may be involved in the inhibitory effect on gene expression.

Base Sequence↗
PubMed1995

Effect of the multiglycoside of Tripterygium Wilfordii Hook f. (Tii) on cornea allograft rejection model in rabbit.

PURPOSE: To examine the effect of Tii treatment of cornea graft survival in a rabbit model. METHODS: Tii was administered orally after eccentrical corneal transplantation. Survival times were determined by biomicroscopy. Cytotoxic T lymphocytes (CTL) and delayed-type hypersensitivity (DTH) responses to donor alloantigens were assessed at day 16 after heterotopic corneal grafts. RESULTS: Administration of Tii reduced the incidence and prolonged the graft survival time. Both CTL and DTH responses to donor alloantigens were severely depressed in hosts treated with Tii. However, combination of Tii and cyclosporine further enhanced the immunosuppressive effects described above. CONCLUSIONS: Tii is a potent immunosuppressant with the ability to prolong allograft survival in the rabbit penetrating keratoplasty model and may have coordinative effects with CsA through different mechanisms. Further studies are necessary to define any potentially coordinative role in the prevention of allograft rejection in human keratoplasty.

Animals↗
PubMed1995

[Retrograde insertion of a spherical headed silicon tube through nasolacrimal duct].

PURPOSE: Chronic dacryocystitis or obstruction of nasolacrimal duct is one of the common and refractory eye diseases. The present operations have large destruction to lacrimal passage and unsatisfactory effects. The purpose of this research is to explore a simple and easy surgical method that makes small injuries and good curative effects. METHODS: Prob a self-made lumbar puncture needle (No. 7) through the lacrimal drainage system, inject fluid and put a thread into the inferior meatus. Guided by the thread, a special robe is retrogradely pulled through the nasolacrimal duct to dilate the meatus to about 3 mm. Then a silicon tube with a spherical head was inserted in the same may. RESULTS: 37 cases with chronic dacryocystitis or obstruction of nasolacrimal duct were treated by the method and followed up from 6 to 17 months. The result showed that the naso meatus was unobstructed postoperatively. The curative rate was 83.7%, which is better than that of other surgical methods. CONCLUSION: This operation is simple and painless for patients; has good curative effects and no severe complications: seldomly injures the normal lacrimal drainage system; can be done repeatedly or replaced by dacryocystorhinostomy if the procedure fails and will become the primarily elected method th treat the patients with chronic dacryocystitis and obstruction of the nasolacrimal duct.

Adult↗
PubMed1995

[Retinal detachment with vitreous hemorrhage].

PURPOSE: To have the knowledge of the diagnosis in time and the choice of operations of retinal detachment with vitreous hemorrhage. METHODS: Sixty eight eyes in 68 cases of retinal detachment with vitreous hemorrhage were reviewed and the main factors affect the operative effect were analysed. RESULTS: Retinal detachment with vitreous hemorrhage usually causes PVR. The successful rate of the operation is low by scleral blucking procedure only, but it can be raised when the operation is combined with vitrectomy. CONCLUSIONS: Owing to the vitreous hemorrhage which has influence on the examination of fundus, it is difficult to make the diagnosis and treatment of retinal detachment. Furthermore, vitreous hemorrhage is easy to cause intraocular inflammatory reaction and PVR. Once the diagnosis is definite, the operation should be taken as soon as possible.

Adolescent↗
PubMed1994

Synaptotagmin I: a major Ca2+ sensor for transmitter release at a central synapse.

Mice carrying a mutation in the synaptotagmin I gene were generated by homologous recombination. Mutant mice are phenotypically normal as heterozygotes, but die within 48 hr after birth as homozygotes. Studies of hippocampal neurons cultured from homozygous mutant mice reveal that synaptic transmission is severely impaired. The synchronous, fast component of Ca(2+)-dependent neurotransmitter release is decreased, whereas asynchronous release processes, including spontaneous synaptic activity (miniature excitatory postsynaptic current frequency) and release triggered by hypertonic solution or alpha-latrotoxin, are unaffected. Our findings demonstrate that synaptotagmin I function is required for Ca2+ triggering of synchronous neurotransmitter release, but is not essential for asynchronous or Ca(2+)-independent release. We propose that synaptotagmin I is the major low affinity Ca2+ sensor mediating Ca2+ regulation of synchronous neurotransmitter release in hippocampal neurons.

Animals↗
PubMed1994

Alcohol action on a neuronal membrane receptor: evidence for a direct interaction with the receptor protein.

For almost a century, alcohols have been thought to produce their effects by actions on the membrane lipids of central nervous system neurons--the well known "lipid theory" of alcohol action. The rationale for this theory is the correlation of potency with oil/water or membrane/buffer partition coefficient. Although a number of recent studies have shown that alcohols can affect the function of certain neuronal neurotransmitter receptors, there is no evidence that the alcohols interact directly with these membrane proteins. In the present study, we report that inhibition of a neuronal neurotransmitter receptor, an ATP-gated ion channel, by a series of alcohols exhibits a distinct cutoff effect. For alcohols with a molecular volume of < or = 42.2 ml/mol, potency for inhibiting ATP-activated current was correlated with lipid solubility (order of potency: 1-propanol = trifluoroethanol > monochloroethanol > ethanol > methanol). However, despite increased lipid solubility, alcohols with a molecular volume of > or = 46.1 ml/mol (1-butanol, 1-pentanol, trichloroethanol, and dichloroethanol) were without effect on the ATP-activated current. The results suggest that alcohols inhibit the function of this neurotransmitter receptor by interacting with a small hydrophobic pocket on the receptor protein.

1-Butanol↗
PubMed1994

Domain structure of a mammalian myosin I beta.

We have determined the primary structure of a myosin I (called mammalian myosin I beta, MMI beta) from bovine brain and identified its functional domains. The protein was previously purified from brain and adrenal gland. Several constructs were generated and expressed in Escherichia coli as glutathione S-transferase fusion proteins and the recombinant proteins were recognized by monoclonal antibodies that recognize either "head" or "tail" domains of native myosin I. A gel overlay method was used to confirm that calmodulin binds to the consensus calmodulin-binding sequence in MMI beta. Binding assays were used to detect interaction with anionic phospholipid vesicles. We conclude that MMI beta consists of an amino-terminal 80.5-kDa domain that contains the ATP- and actin-binding sites, followed by an 8.5-kDa domain with three calmodulin-binding sequences and a basic 30-kDa carboxyl-terminal tail segment that binds to anionic phospholipids and membranes.

Actins↗
PubMed1994

Myelination in the absence of myelin-associated glycoprotein.

The hypothesis that myelin-associated glycoprotein (MAG) initiates myelin formation is based in part on observations that MAG has an adhesive role in interactions between oligodendrocytes and neurons. Furthermore, the over- or underexpression of MAG in transfected Schwann cells in vitro leads to accelerated myelination or hypomyelination, respectively. Here we test this idea by creating a null mutation in the mag locus and deriving mice that are totally deficient in MAG expression at the RNA and protein level. In adult mutant animals the degree of myelination and its compaction are normal, whereas the organization of the periaxonal region is partially impaired. Mutant animals show a subtle intention tremor. Our findings do not support the widely held view that MAG is critical for myelin formation but rather indicate that MAG is necessary for maintenance of the cytoplasmic collar and periaxonal space of myelinated fibres.

Animals↗
PubMed1994

Arachidonyl trifluoromethyl ketone, a potent inhibitor of 85-kDa phospholipase A2, blocks production of arachidonate and 12-hydroxyeicosatetraenoic acid by calcium ionophore-challenged platelets.

Arachidonyl trifluoromethyl ketone (AACOCF3) is a potent and selective slow binding inhibitor of the 85-kDa cytosolic phospholipase A2 (cPLA2) (Street, I. P., Lin, H.-K., Laliberté, F., Ghomashchi, F., Wang, Z., Perrier, H., Tremblay, N. M., Huang, Z., Weech, P. K., and Gelb, M. H. (1993) Biochemistry 32, 5935-5940). AACOCF3 and a number of its structural analogues have been used to investigate the role of cPLA2 in the cellular generation of free arachidonic acid (AA) and in eicosanoid biosynthesis. AACOCF3 inhibited the release of AA from calcium ionophore-challenged U937 cells (IC50 = 8 microM, 2 x 10(6) cells ml-1) and from platelets (IC50 = 2 microM, 4 x 10(7) cells ml-1). Arachidonyl methyl ketone (AACOCH3) and AACH(OH)CF3, both of which are noninhibitory to the purified cPLA2, did not inhibit the production of AA in the ionophore-challenged cells. In addition to the release of AA, AACOCF3 also inhibited the production of 12-hydroxyeicosatetraenoic acid (12-HETE) and thromboxane B2, two of the major metabolites of AA produced by platelets. The inhibition of 12-HETE biosynthesis showed a dose dependence similar to that of AA release in ionophore-challenged platelets; however, when platelet 12-HETE production was stimulated with 10 microM AA to circumvent the PLA2-dependent step, AACOCF3 no longer inhibited the production of 12-HETE. In contrast, AACOCF3 blocked thromboxane B2 formation by both calcium ionophore- and AA-challenged platelets, indicating that the compound affects the cyclooxygenase pathway in addition to AA release. The crude cytosol and membrane fractions from platelets were assayed for calcium-dependent and calcium-independent PLA2 activities and for the susceptibility of each to inhibition by AACOCF3. At AACOCF3 concentrations as high as 10 mol %, only one of the observed PLA2 activities was inhibited by more than 25%. The AACOCF3-susceptible PLA2 (77% inhibition at 1.6 mol %) was found in the cytosolic platelet fraction and showed the functional characteristics of the cPLA2. These results suggest that the cPLA2 plays an important role in the generation of free AA for 12-HETE biosynthesis in platelets.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1994

Pedicle and antler regeneration following antlerogenic tissue removal in red deer (Cervus elaphus).

The physiological control mechanisms underlying the histogenesis of the pedicle, which precedes antler growth, from the frontal bones of male deer are poorly understood. The aim of this study was to investigate the extent of pedicle/antler regeneration after removal (for histological evaluation) of the antlerogenic region or pedicle tissue during pedicle development to determine whether the subsequent pattern of regeneration could contribute to the understanding of pedicle histogenesis and the mechanism of the transition between permanent pedicles and deciduous antlers. The contralateral pedicles of six stags were not removed and these data serve as controls. All deer were observed frequently and measurements of regeneration were made in March after all antler growth had ceased for that season. The development stage of the pedicle was determined by a combination of pedicle height measurements and histological studies. The results showed that pedicle formation histologically covers three stages: a period of intramembranous ossification (when the pedicle is less than 5 mm in height), a period when the ossification pattern changes (when the pedicle is between 5 and 28 mm in height) and a period of modified endochondral ossification (when the pedicle is over 30 mm in height). In all ossification stages some deer regenerated neither antlers nor pedicles. The pedicles which regenerated following the loss of antlerogenic tissue at the intramembranous ossification stage were shorter than the controls (P < 0.01), but longer than the pedicles regenerated after pedicle removal at the transitional stage in the pattern of ossification (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

NN-dimethyl-1,4-phenylenediamine as an alternative reductant for peptidylglycine alpha-amidating mono-oxygenase catalysis.

C-terminal alpha-amidation is a structural feature essential to the biological activity of many peptide hormones. Peptidylglycine alpha-amidating mono-oxygenase (PAM; EC 1.14.17.3) catalyses conversion of glycine-extended peptide hormone precursors into their corresponding alpha-hydroxyglycine derivatives. This reaction is the first step in the C-terminal amidation process. We report here that in the presence of molecular O2, copper and PAM substrate, NN-dimethyl-1,4-phenylenediamine (DMPD) serves as the requisite electron donor for the mono-oxygenase, being oxidized in the process to a stable and highly chromophoric cation radical. By monitoring the rate of increase in absorbance at 515 nm, PAM activity can be easily followed. This provides a spectrophotometric assay for PAM, which represents the first continuous assay reported for this enzyme. DMPD-supported PAM-catalysed mono-oxygenation exhibits normal Michaelis-Menten kinetic behaviour. Steady-state kinetic studies established that both the ascorbate-supported and DMPD-supported PAM reactions exhibit apparent 'Ping Pong' kinetics. In addition, both electron donors give rise to similar pH profiles and identical inhibition patterns towards known competitive inhibitors of PAM. The stoichiometry between formation of the DMPD cation radical and the alpha-hydroxyglycine PAM product was determined to be 2:1, the value expected for a monooxygenase-catalysed reaction. The optimum pH for the DMPD-supported continuous PAM assay was found to be about 5.5. The major advantage of this assay over all previously reported methods is that it is continuous; thus accurate initial rates are easily obtained. Moreover, unlike previous assay methods, 125I-labelled or chromophorically modified substrates are not required. Kinetic parameters for a broad range of PAM substrates and inhibitors have been successfully obtained using this assay.

Amino Acid Sequence↗