Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

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

PubMed1991

An assay procedure for solubilized thyroid hormone receptor: use of Lipidex.

A method using Lipidex-1000 is reported for the assay of thyroid hormone receptor activity. The receptor was extracted from rat liver nuclei, incubated with [125I]T3, and applied to 1-ml disposable pipet tip columns containing a small volume of Lipidex. The resin absorbed the free hormone, and the receptor-bound hormone was recovered in the eluate. The method allowed accurate assay of the receptor activity, satisfying a linear relationship between the activity and the receptor protein concentration. The usefulness of this method was demonstrated by determining the pH optimum and the Kd and Bmax of T3 binding by the receptor. The Lipidex column can be used for the preparation of an unoccupied receptor after dissociation of the endogenously bound hormone.

Absorption↗

PubMed1991

Role of sulphation in post-translational processing of rat salivary mucins.

Segments of rat submandibular salivary gland were incubated in MEM supplemented with 10-800 microM sulphate in the presence of [3H]-glucosamine, [3H]-proline and [35S]-Na2SO4, with 0-8 mM chlorate, an inhibitor of 3'-phosphoadenosine-5'-phosphosulphate formation. Incorporation of glucosamine and sulphate depended upon the sulphate content of the medium and reached a maximum at 400 microM sulphate. The introduction of chlorate into the medium, while having no effect on the protein synthesis as shown by [3H]-proline incorporation, caused, at its optimal concentration of 4 mM, a 90% decrease in mucin sulphation and a 29% drop in mucin glycosylation. At low sulphate content in the medium and in the presence of chlorate the incorporation of sulphate and glucosamine was mainly into the low molecular-weight form of mucin. An increase in sulphate in the medium caused an increase in the high molecular-weight form of mucin and in the extent of sulphation in its carbohydrate chain. This effect of sulphate was, however, inhibited by chlorate. The results suggest that sulphation takes place at an early stage of mucin assembly and that sulphate availability is essential for the formation of the high molecular-weight mucin.

Animals↗

PubMed1991

Evidence for platelet-activating factor receptors in several B lymphoblastoid cell lines.

Previous studies have shown that Raji, an Epstein-Barr virus (EBV)-immortalized Burkitt lymphoma B cell line, contains functional platelet-activating factor (PAF) receptors. Twelve other lymphoid cell lines, including Burkitt and non-Burkitt B cell lines, T cell lines, and a non B, non T cell line were tested for the presence of PAF receptors. Radioligand binding studies conducted at 4 degrees C revealed that six lymphoid cell lines of B cell origin (Raji, P3HR-1, BJAB, BJA/HR-1, Dakiki and PB-1) could specifically bind [3H]PAF. Treatment of four (Raji, P3HR-1, Dakiki and PB-1) of the above lymphoid cell lines with PAF resulted in an increase in free intracellular calcium, indicating that these specific PAF binding sites were functional PAF receptors. Other B cell lines (Daudi, B95-8, sfBT, CB-1), T cell lines (MOLT-4, CCRF-CEM) and a non B, non T cell line (NALM-6) had no PAF binding sites and showed no PAF-induced increase in intracellular calcium levels. These studies demonstrate evidence for the presence of PAF receptors on several B lymphocyte cell lines.

Animals↗

PubMed1991

Primary structure of the goat beta-globin locus control region.

The goat beta-globin cluster is composed of a triplicated four-gene set. A locus control region (LCR) containing elements homologous to 5'DNase I hypersensitive sites (HS) 1, 2, and 3 of the human beta-globin LCR has been identified at the 5' end of this locus. We determined 10.2 kb of nucleotide sequence from the goat beta-globin locus control region. Self-comparison of this sequence by dot matrix analysis revealed the presence of six complete and three incomplete artiodactyl repeats. A novel repeated element, termed D repeat, was also identified. Southern blotting analysis demonstrated that these elements exist in the goat genome as a low to medium frequency interspersed repeat family. The absence of any other large region of self-homology (direct or inverted) in the goat LCR suggests that 5'HSs 1, 2, and 3 did not arise through duplication, but rather evolved independently. By comparing goat 5'HS 1 to those of human, rabbit, and mouse, we show a greater than 80% conservation in sequence between the four species. This level of evolutionary conservation suggests that 5'HS 1 plays an important role in the regulation of beta-globin loci.

Animals↗

PubMed1991

Effects of halothane on delayed afterdepolarization and calcium transients in dog ventricular myocytes exposed to isoproterenol.

The effects of halothane on isoproterenol-induced delayed after-depolarizations (DADs) were investigated in canine ventricular myocytes. In addition, the effects of halothane on the intracellular free calcium transient were determined in fura-2-loaded myocytes exposed to isoproterenol to explore the mechanisms underlying halothane effects on DADs. Isoproterenol (100 nM) induced DADs and/or undriven action potentials in myocytes stimulated electrically with the use of trains of 10 stimuli delivered at basic drive cycle lengths of 200-1,000 ms. Isoproterenol (100 nM) increased the peak ratio (350/380 nm excitation) of stimulated myocyte calcium transients; furthermore, isoproterenol induced a second spontaneous component in the calcium transients of 62% of treated myocytes (n = 72). Halothane (1.5%, 0.53 mM) significantly decreased the amplitude of isoproterenol-induced DADs (P less than 0.01). Halothane not only reduced the peak ratio of the stimulated calcium transient, but also eliminated the second spontaneous component in myocytes previously exposed to isoproterenol (n = 14). Elevated extracellular calcium concentrations (5 mM) restored the amplitudes of DADs and the second components of the calcium transients in myocytes exposed to isoproterenol and halothane. These data suggest that halothane opposes isoproterenol-induced DADs by altering intracellular calcium stores. The authors' findings do not support a role for DAD-induced triggered activity in the genesis of anesthetic-catecholamine dysrhythmias.

Animals↗

PubMed1991

Lactate activates ATP-sensitive potassium channels in guinea pig ventricular myocytes.

The functional significance of cardiac ATP-sensitive potassium channels remains controversial because of the discrepancy between the low levels of ATP at which activation of the channels occurs and the much higher levels of ATP maintained during myocardial ischemia. We studied the effects of (+)-lactate, which accumulates in large quantity as a result of increased glycolysis during ischemia, on ATP-sensitive potassium channels in adult guinea pig ventricular myocytes using the whole-cell patch-clamp technique. Lactate at 20-40 mM in the internal solution activated ATP-sensitive potassium channels and shortened action potential duration. Activation of the channels occurred even in the presence of 2-5 mM ATP in the internal solution and was dependent on intracellular free magnesium levels. Our results suggest that intracellular lactate may play a significant role in activating cardiac ATP-sensitive potassium channels and shortening action potential duration even at ATP levels similar to those resulting from moderate to severe myocardial ischemia.

Action Potentials↗

PubMed1991

In vitro evaluation on contact sensitivity from DNCB and DNBS using lymphocyte blastogenesis response test.

To assess the contact allergic potential of sensitizers, an in vitro predictive model was developed. First of all, guinea pigs were sensitized by 1-chloro-2-4,dinitrobenzene (DNCB), and lymph node cells from sensitized and control guinea pigs were cultured in the presence of DNCB, 2,4-dinitrobenzene sulfonic acid sodium salt (DNBS), DNCB plus epidermal cell (DNCB + EC), DNBS + EC and epidermal cell modified hapten (dinitrophenyl-EC, DNP-EC) at 3 x 10(5), 5 x 10(5) and 8 x 10(5) cells/well, respectively. Lymphocyte blastogenesis responses were assessed by uptake of 5H-thymidine. The results indicated that lymphocytes from sensitized guinea pigs responded to the foregoing antigens in vitro to a greater degree than those from control guinea pigs and the blastogenesis response by DNBS was the highest among the challenges of DNBS, DNCB, DNCB + EC, DNBS + EC and DNP-EC. When the number of lymphocytes was sufficient, the blastogenesis response of lymphocytes could be in vitro challenged successfully not only by DNBS, DNCB + EC, DNBS + EC and DNP-EC, but also DNCB alone. There was a cross sensitivity between DNCB and DNBS for in vivo and in vitro challenges. Moreover, significant relationships were observed between lymphocyte blastogenesis response and doses of DNBS used in vitro assay at 5 x 10(5) and 8 x 10(5) cells/well. The results indicate that this assay is an useful in vitro predictive model of contact sensitivity and cross sensitivity of sensitizers.

Animals↗

PubMed1991

Ferritin in astrocytomas.

Ferritin in 119 astrocytoma cases was studied by immunocytochemical PAP and immunogold silver staining (IGSS) methods. In 57% of the cases, ferritin was found in the cytoplasm of the tumor cells. The higher the differentiation of the tumor cells, the less ferritin they contained. Contrary to the reaction of glial fibrillary acidic protein (GFAP), the positive rate of ferritin in various types and grades of astrocytomas was inversely proportional to their degree of differentiation. Electron microscopic observation in 30 cases showed ferritin in the cell sap, cytocavity network, endoplasmic reticulum, Golgi apparatus and also in lysosomes. Some of the cases had extraordinary high level of ferritin in their blood serum.

Astrocytoma↗

PubMed1991

[Investigation of impairment of neutrophil's phagocytosis and bactericidal function in rats with iron deficiency].

Studies were made to determine the neutrophil's phagocytosis and bactericidal function in three groups of rats (control, iron deficiency, and iron supplement). Results showed that there were significant differences in values of chemiluminescence (CL) among three groups. The values of peak CL and five minutes integrated CL were markedly decreased in neutrophils of iron-deficient rats, accounting for only 41% and 32% of the control's values respectively. These suggested that the activity of NADPH oxidase was decreased, and the function of respiratory burst of neutrophils was impaired. The activity of myeloperoxidase in the iron-deficient neutrophils was also significantly lower than that in the control cells. It constituted only 30% of the control's value, indicating that the bactericidal function of neutrophils was injured. One week after iron administration, the low values of the peak CL, the five minutes integrated CL and the activity of myeloperoxidase all went up apparently, but not reached the normal levels yet. The time the function of neutrophils in iron-deficient rats returned to normal may be related to the process of neutrophil maturation in bone marrow.

Anemia, Hypochromic↗

PubMed1991

Characterization of taeniid cestodes by DNA analysis.

High molecular weight DNA samples free of contaminating proteins and RNA obtained from one isolate (of Guangzhou origin) of Cysticercus tenuicollis and five isolates (of Tianjin, Harbin, Lanzhou, Shenyang and Zhengzhou origin) of Cysticercus cellulosae were subjected to thermal denaturation, restriction endonuclease digestion, Southern blotting and hybridization analysis. C. cellulosae DNA showed a melting temperature (Tm) of 82 degrees C corresponding to a 31% GC content whereas C. tenuicollis DNA melted at 85 degrees C suggesting 38.3% GC content. Visual inspection of ethidium bromide-stained gel showed differences not only between the DNAs of the two species of Taeniid cestodes, but also among the five isolates of C. cellulosae. Furthermore, we used two fragments (1.9kb and 5.5kb) of HindIII-derived restriction fragments of C. cellulosae DNA (Harbin origin) and pTS10 as probes to hybridize the DNAs of the Taeniid cestodes from six origins to detect inter- and intra-species genetic variation, the restriction fragment length polymorphisms (RFLPs) were identified.

Animals↗

PubMed1991

[Production and characterization of 3 mcAbs to Mycobacterium tuberculosis].

Three monoclonal antibodies to mycobacterium tuberculosis were produced and designated Ra1, Ra2 and Ra3. The spleen cells of BALB/C mice were immunized with intact, ultrasonicated M. H37Ra and H37Ra culture filtrate and were fused with NS-1 myeloma cells. The monoclonal antibodies were IgG2a, IgM and IgM respectively. The monoclonal antibodies were characterized by ELISA on 14 mycobacterial species. It showed that they reacted with H37Ra and some of mycobacterial species but did not with BCG. McAb Ral was used to prepare immunoabsorbent, and Ag-Ra1 was isolated from unheated H37Ra culture filtrate by affinity chromatography with the absorbent. Ag-Ral was a glycoprotein with MW. of 66 KDa and produced DTH in guinea pigs.

Animals↗

PubMed1991

[Comparison of central stimulating effects between ephedrine and apomorphine].

The potentiation of motor activity caused by ephedrine (Eph) in mice was inhibited by prazosin but not by sulpiride. This potentiation effect caused by apomorphine (Apo) was not inhibited by prazosin. Apo produced stereotyped behavior (including sniffing, licking, and biting) in rodents, but Eph was ineffective except at the toxic dose (400 mg.kg-1 in mice, 200 mg.kg-1 in rats). Apo antagonized haloperidol-induced catalepsy in mice whereas Eph had no such effect. Severe vomiting was evoked by Apo in dogs, but not by Eph even when lethal dose (20 mg.kg-1) was used. Palpebral ptosis induced by prazosin was abolished by intracerebroventricular injection of Eph in mice, but not affected by Apo. The results suggest that the central stimulating action of Eph is mediated by alpha 1-adrenoceptors and not by dopamine receptors.

Animals↗

PubMed1991

[Electrophysiological effects of berbamine on ischemic ventricular tachyarrhythmia].

The effects of berbamine (Ber, 10 mg.kg-1 iv) on ischemic ventricular tachyarrhythmia and electrophysiologic consequences in both normal and ischemic myocardia were studied in the open-chest dogs subjected to programmed electrical stimulation (PES) on 5-8 d after acute myocardial infarction. Its effects were compared with procainamide's (PA). Both drugs distinctly lengthened the QTc interval and the effective refractory period (ERP) of normal and infarct ventricular myocardium, decreased the dispersion of ERP in infarct myocardium (IDR) and the dispersion of ERP in left ventricle (VDR), and increased the diastolic excitability threshold (DET) of normal and infarct ventricular myocardium remarkably. The PES-induced ventricular tachycardia (VT) or ventricular fibrillation (VF) was prevented in 5 out of 6 dogs treated with berbamine and procainamide respectively. (Normal saline did not prevent PES-induced VT or VF). The results suggest that berbamine may be effective in preventing the onset of reentrant ventricular tachyarrhythmia after myocardial ischemic damage.

Alkaloids↗

PubMed1990