Search PubMed⌕ Search

Biomedical subjects

G Li

Publications and source records attributed to G Li.

At least 685 records · Page 38Linked to original sources
PubMed1997

Gallstones and their chemical types in relation to serum lipids and apolipoprotein levels.

OBJECTIVE: To determine the profile of lipidemia in patients with gallstones and the characteristics of lipidemia in different kinds of gallstone in gallbladder for predicting high risk subjects predisposed to gallstone formation by means of some serum parameters. METHODS: Serum lipids and apolipoproteins levels in 47 patients with stone in gallbladder (stone group) were compared with those in 19 inpatients without stone (control group). The characteristics of lipidemia in different kinds of gallbladder stones were also compared. RESULTS: Serum apolipoprotein (Apo) A1, C2 and E levels in the stone group significantly increased as compared with the control group (P < 0.01), but there were no statistically significant differences in TC, TG, LDL-C, HDL-C, HDL-C/TC, LDL-C/HDL-C, Apo A2, B and C3 and Apo A1/Apo B levels between the stone and control groups (P > 0.05). Increased levels of serum LDL-C and Apo B and the LDL-C/HDL-C ratio (P < 0.05) were characterized as an index of cholesterol stones, while elevated levels of serum TG and Apo C2 (P < 0.05) as an index of pigment stones. CONCLUSIONS: Serum apolipoproteins might be more sensitive parameters as compared with serum lipids in distinguishing patients with stones from subjects without stones. There are different profiles of serum lipids and apolipoproteins in different chemical types of gallbladder stones.

Adult↗
PubMed1997

[Distribution of clozapine in poisoned rabbits].

The distribution of clozapine in the body of rabbits died of poison was studied by the method of TLC. The concentration of clozapine in blood, urine, bile, livers, kidneys, spleen, lungs, hearts and brains were 19.4 +/- 6.9, 50.2 +/- 12.6, 75.9 +/- 12.5, 25.9 +/- 4.0, 34.0 +/- 4.7, 13.3 +/- 2.2, 20.0 +/- 4.3, 5.0 +/- 2.3 and 43.6 +/- 43.4 ug/ml or ug/g.respectively. It is concluded that the Clozapine be not well-distributed in poisoned rabbits, Blood, bile, urine, liver and spleen are better samples for the analysis of clozapine than others.

Animals↗
PubMed1997

[Dissociation and culture of primary auditory neurons in postnatal chicken].

In the present study, a primary culture of auditory neurons in 10-16-day old chickens was carried out. We observed the morphologic features of auditory neurons at different culturing stages by using phased-contrast and scanning electron microscope, and particularly described their growth and developmental process. The results indicated that a steady and reliable culturing method established here would contribute to the biological research of inner ear in vitro.

Animals↗
PubMed1997

[Observation of AChE location in chicken cochlea].

The efferent auditory innervation of the chicken was investigated by means of AChE histochemical stain. The localization of AChE in the chicken was observed by use of mounted and freezing microtome in basilar papilla. The positive fibers of AChE stain were distributed over the lateral aspect of the superior cartilaginous plate of the basilar papilla. Radical fibers leave this lontigudinal boundle to supply the hair cells. Two types of efferent synapsis could be distinguished: short hair cells with large cup-like efferent terminal, and tall cells with small, irregular terminal. The characteristics and the significance of experimental study are also discussed.

Acetylcholinesterase↗
PubMed1997

[Effects of selenium supplement on acute lower respiratory tract infection caused by respiratory syncytial virus].

An intervention study was conducted in 75 young children under one year hospitalized with pneumonia or bronchiolitis caused by respiratory syncytial virus (RSV) to evaluate therapeutic effectiveness of selenium (Se) supplement on acute respiratory lower tract infection caused by RSV with randomly controlled and double-masked method. Trial subjects were divided into two groups, one with 37 children in routine treatment and the other with 38 children in routine treatment plus Se supplement. The control group derived from 35 normal children during their physical check-up in the out-patient department. Sodium selenite was supplemented orally with 1 mg on the second day of hospitalization. Results showed that days needed for their relief of symptoms and signs were fewer in Se supplement group than that in controls and recovery in indicators of cell immune was better in the former than that in the latter. Levels of Se and glutathione peroxidase in plasma and white cells could be increased by Se supplement. It suggests that Se supplement can promote recovery from RSV infection.

Bronchiolitis, Viral↗
PubMed1997

[Study of arginase activity in alveolar macrophages from patients with lung cancer].

Alveolar macrophages (AM) were obtained from 20 patients with primary lung cancer and 20 cases with nonmaligment pulmonary disease by BAL and were incubated in vitro in medium with and without BCG and/or IFN-alpha. Then the cell-free supernatants were harvested. The activity of arginase was assayed. It was found that: arginase was produced spontaneously by AM: The spontaneous production of arginase is lower in AMs from the tumor-bearing segments than either nontumor-bearing segments or AMs from the patients with nonmalignant pulmonary diseases (P < 0, .05). The production of arginase was icreased on AMs from the tumor-bearing segments stimulated with BCG and/or IFN-alpha (P < 0.05 or 0.01). The results suggested that (1) There are some function at defects of tumor. (2) The mechanism of anti-tumor and anti-infection activity of BCG and IFN-alpha may possibly increase the production of arginase of AMs.

Adult↗
PubMed1996

In vitro V(D)J recombination: signal joint formation.

The first step of V(D)J recombination, specific cleavage at the recombination signal sequence (RSS), can be carried out by the recombination activating proteins RAG1 and RAG2. In vivo, the cleaved coding and signal ends must be rejoined to generate functional antigen receptors and maintain chromosomal integrity. We have investigated signal joint formation using deletion and inversion substrates in a cell free system. RAG1 and RAG2 alone or in combination were unable to generate signal joints. However, RAG1 and RAG2 complemented with nuclear extracts were able to recombine an extrachromosomal substrate and form precise signal joints. The in vitro reaction resembled authentic V(D)J recombination in being Ku-antigen-dependent.

Animals↗
PubMed1996

Reduction of ferricyanide by thiamine or thiamine pyrophosphate.

The colorimetric assay for the activity of pyruvate dehydrogenase (EC 1.2.4.1) developed by Itokawa is based on a coupled reduction of ferricyanide and the formation of Prussian blue (Brian Research 94, 475-484). In this assay system, we found that the coenzyme, thiamine pyrophosphate, itself reduced ferricyanide independent of both the enzyme and the substrate. Similar effect was also observed with thiamine, but not with thiochrome. The reduction of ferricyanide by thiamine or thiamine pyrophosphate was blocked by trichloroacetic acid. Measurement of the activity of purified pyruvate dehydrogenase based on monitoring the reduction of ferricyanide as described by Schwartz et al (Biochem. Biophys. Res. Commun. 31, 495-500) has been widely used. Our findings clearly disprove the assumption that reduction of ferricyanide is dependent on pyruvate dehydrogenase and invalidate assays for thiamine-dependent dehydrogenases based on the reduction of ferricyanide.

Animals↗
PubMed1996

A new method for the voltammetric response of hemoglobin.

Hemoglobin (Hb) could give a voltammetric response after it was acted on by the surfactant dodecyl benzene sodium sulfonate (DBS) or sodium dodecyl sulfate (SDS). The mechanism might be the enhancement of the adsorption process when there was surfactant in the protein solution. Moreover, the macromolecules might open their electroactive sections after they interacted with the hydrophobic groups of the surfactant. Comparative studies showed that DBS could make Hb present a more welcome result than SDS since it had an extra benzene ring. On the other hand, since surfactant was a denaturant to Hb as well and the electrode surface might be fouled with it, a negative effect of the surfactant should be considered in the meantime.

Benzenesulfonates↗
PubMed1996

Glucose- and GTP-dependent stimulation of the carboxyl methylation of CDC42 in rodent and human pancreatic islets and pure beta cells. Evidence for an essential role of GTP-binding proteins in nutrient-induced insulin secretion.

Several GTP-binding proteins (G-proteins) undergo post-translational modifications (isoprenylation and carboxyl methylation) in pancreatic beta cells. Herein, two of these were identified as CDC42 and rap 1, using Western blotting and immunoprecipitation. Confocal microscopic data indicated that CDC42 is localized only in islet endocrine cells but not in acinar cells of the pancreas. CDC42 undergoes a guanine nucleotide-specific membrane association and carboxyl methylation in normal rat islets, human islets, and pure beta (HIT or INS-1) cells. GTPgammaS-dependent carboxyl methylation of a 23-kD protein was also demonstrable in secretory granule fractions from normal islets or beta cells. AFC (a specific inhibitor of prenyl-cysteine carboxyl methyl transferases) blocked the carboxyl methylation of CDC42 in five types of insulin-secreting cells, without blocking GTPgammaS-induced translocation, implying that methylation is a consequence (not a cause) of transfer to membrane sites. High glucose (but not a depolarizing concentration of K+) induced the carboxyl methylation of CDC42 in intact cells, as assessed after specific immunoprecipitation. This effect was abrogated by GTP depletion using mycophenolic acid and was restored upon GTP repletion by coprovision of guanosine. In contrast, although rap 1 was also carboxyl methylated, it was not translocated to the particulate fraction by GTPgammaS; furthermore, its methylation was also stimulated by 40 mM K+ (suggesting a role which is not specific to nutrient stimulation). AFC also impeded nutrient-induced (but not K+-induced) insulin secretion from islets and beta cells under static or perifusion conditions, whereas an inactive structural analogue of AFC failed to inhibit insulin release. These effects were reproduced not only by S-adenosylhomocysteine (another methylation inhibitor), but also by GTP depletion. Thus, the glucose- and GTP-dependent carboxyl methylation of G-proteins such as CDC42 is an obligate step in the stimulus-secretion coupling of nutrient-induced insulin secretion, but not in the exocytotic event itself. Furthermore, AFC blocked glucose-activated phosphoinositide turnover, which may provide a partial biochemical explanation for its effect on secretion, and implies that certain G-proteins must be carboxyl methylated for their interaction with signaling effector molecules, a step which can be regulated by intracellular availability of GTP.

Acetylcysteine↗
PubMed1996

Effects of modifications of residues in position 3 of dynorphin A(1-11)-NH2 on kappa receptor selectivity and potency.

Tyrosine1 and phenylalanine4 in dynorphin A (Dyn A) have been reported to be important residues for opioid agonist activity and for potency at kappa receptors. The glycine residues in the 2 and 3 positions of dynorphin A may affect the relative orientation of the aromatic rings in positions 1 and 4, but their flexibility precludes careful analysis. To examine these effects on dynorphin A, we previously have synthesized the linear analogues [D-Ala3]Dyn A(1-11)-NH2 (2) and [Ala3]Dyn A(1-11)-NH2 (3) and reported their biological activities. Analogues 2 and 3 displayed affinities for the central kappa opioid receptor (IC50 = 0.76 and 1.1 nM, respectively) similar to that of Dyn A(1-11)-NH2 (1) (IC50 = 0.58 nM) and greatly enhanced selectivities for kappa vs mu and kappa vs delta receptors (IC50 ratios of 350 and 1300 for 2, and 190 and 660 for 3, respectively). These results suggest that the structure and lipophilicity of the amino acid present in position 3 of Dyn A(1-11)-NH2 as well as the conformational changes they induce in the message sequence of dynorphin have important effects on potency and selectivity for kappa opioid receptors. To further investigate structure-activity relationships involving the residue at the 3 position of Dyn A(1-11)-NH2, a series of Dyn A analogues with aromatic, charged, and aliphatic side chain substitutions at the 3 position was designed, synthesized, and evaluated for their affinities for kappa, mu, and delta opioid receptors. It was found that analogues with lipophilic amino acids at the 3 position of Dyn A(1-11)-NH2 generally displayed higher affinity but similar selectivities for the kappa receptor than analogues with charged residues at the same position. It is suggested that the structural, configurational, and steric/lipophilic effects of amino acids at position 3 of Dyn A(1-11)-NH2 may play an important role in potency and selectivity for the kappa receptor.

Amino Acid Sequence↗
PubMed1996

Topographical amino acid substitution in position 10 of glucagon leads to antagonists/partial agonists with greater binding differences.

The role of position 10 in the beta-turn region of glucagon was investigated by substituting chiral constrained amino acids and other modifications in the N-terminal region. A series of glucagon analogues have been designed and synthesized by incorporating beta-methylphenylalanine isomers (2S,3S, 2S,3R, 2R,3R, and 2R,3S) at position 10 in order to explore the structural and topographical requirements of the glucagon receptor, and, in addition, utilizing previous studies which indicated that antagonism could be enhanced by modifications (des-His1, Glu9) and a bulky group at position 5. The structures of the new analogues are as follows: [des-His1,-Tyr5,Glu9]glucagon-NH2 (II), [des-His1,Tyr5,Glu9,Phe10]glucagon-NH2 (III), [des-His1,Tyr5,Glu9,-Ala10]glucagon-NH2 (IV), [des-His1,Tyr5,Glu9,(2S,3R)-beta-MePhe10]glucagon-NH2 (V), [des-His1,-Tyr5,Glu9,(2S,3S)-beta-MePhe10]glucagon-NH2 (VI), [des-His1,Tyr5,Glu9,D-Tyr10]glucagon-NH2 (VII), [des-His1,Tyr5,Glu9,D-Phe10]glucagon-NH2 (VIII), [des-His1,Tyr5,Glu9,D-Ala10]glucagon-NH2 (IX), [des-His1,Tyr5,Glu9,(2R,3R)-beta-MePhe10]glucagon-NH2 (X), and [des-His1,Tyr5,Glu9,(2R,3S)-beta-MePhe10]glucagon-NH2 (XI). These analogues led to dramatically different changes in in vitro binding affinities for glucagon receptors. Their receptor binding potencies IC50 values (nM) are 2.3 (II), 4.1 (III), 395.0 (IV), 10.0 (V), 170.0 (VI), 74.0 (VII), 34.5 (VIII), 510.0 (IX), 120.0 (X), and 180.0 (XI). Analogues II, III, V, VI, and XI were found to be weak partial agonists/partial antagonists with maximum stimulation between 5%-9%, while the other compounds (IV and VII-X) were antagonists unable to activate the adenylate cyclase system even at concentrations as high as 10(-5) M. In competition experiments, all of the analogues caused a right shift of the glucagon-stimulated adenylate cyclase dose-response curve. The pA2 values were 6.60 (II), 6.85 (III), 6.20 (IV), 6.20 (V), 6.10 (VI), 6.50 (VII), 6.20 (VIII), 5.85 (IX), 6.20 (X), and 6.00 (XI). Putative topographical requirements of the glucagon receptor for the aromatic side chain conformation in position 10 of glucagon antagonists are discussed.

Adenylyl Cyclases↗
PubMed1996

Human erythrocytes bearing electroinserted CD4 neutralize infection in vitro by primary isolates of human immunodeficiency virus type 1.

Human erythrocytes bearing electroinserted full-length CD4 (RBC-CD4) can bind and fuse with a laboratory strain of human immunodeficiency virus type 1 (HIV-1) or with T cells infected by HIV-1. Here we show that RBC-CD4 neutralize primary HIV-1 strains in an assay of cocultivation of peripheral blood mononuclear cells (PBMC) from HIV-1-infected persons with uninfected PBMC. RBC-CD4 inhibited viral p24 core antigen accumulation in these cocultures up to 10,000-fold compared with RBC alone. Viral p24 accumulation was inhibited equally well when measured in culture supernatants or in call extracts. The inhibition was dose-dependent and long-lived. Two types of recombinant CD4 tested in parallel were largely ineffective. The neutralization of primary HIV-1 by RBC-CD4 in vitro was demonstrated in PBMC cultures from 21 of a total of 23 patients tested at two independent sites. RBC-CD4 may offer a route to blocking HIV-1 infection in vivo.

Acquired Immunodeficiency Syndrome↗