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Biomedical subjects

F Li

Publications and source records attributed to F Li.

At least 37 records · Page 2Linked to original sources
PubMed1991

Performance of 133 compounds in the lambda prophage induction endpoint of the Microscreen assay and a comparison with S. typhimurium mutagenicity and rodent carcinogenicity assays.

The Microscreen assay was developed as a means of testing very small samples, as in complex mixture fractionation. It is a multi-endpoint assay which utilizes E. coli WP2s(lambda). Exposure takes place to serial dilutions of the test compound in microtitre wells (250 microliters) followed by sampling from wells in which growth has occurred ('non-toxic wells'). Although a number of different endpoints can be measured, only the prophage induction endpoint (the first one developed) has been extensively tested. Results with 133 compounds are presented. These include 111 compounds which have been tested in the S. typhimurium assay and 66 compounds for which both rodent bioassay and S. typhimurium assay data exists. The concordance for the Microscreen assay and the S. typhimurium assay was 71%. For this group of compounds, the sensitivity of the Microscreen assay in detecting carcinogens was 76% compared with 58% for the S. typhimurium assay. However, the S. typhimurium assay was somewhat more specific (69%) compared with the Microscreen (56%). The overall association between carcinogenicity and Microscreen results was statistically significant (p = 0.029), whereas for the S. typhimurium assay the association with carcinogenicity was non-significant (p = 0.086). The Microscreen assay was able to detect halogenated compounds better than the S. typhimurium assay. The Microscreen assay should prove useful in complex mixture fractionation, or in other situations where sample size is limiting.

Animals↗
PubMed1991

Constitutive and NF-kappa B-like proteins in the regulation of the serum amyloid A gene by interleukin 1.

Serum amyloid A (SAA) is a major acute-phase protein whose chronic production by the liver can lead to the fatal disorder of secondary amyloidosis. Control of SAA is mediated by several inflammatory cytokines, including interleukin 1 (IL-1). To study the cis-acting regulatory elements responsible for constitutive and IL-1-induced expression, DNA constructs containing varying lengths of the promoter region from the human SAA2 beta gene 5' to the bacterial reporter gene, chloramphenicol acetyltransferase (CAT), were generated and transfected into human hepatoma cells, HepG2. Both positive and negative regulatory elements were found in the 5' flanking region of the human SAA2 beta gene. The more proximal region contains an IL-1 enhancer sequence GGGACTTTCC (SAA kappa B1; between -82 and -91), the binding site for the ubiquitous transcription factor NF-kappa B. IL-1 induction of the binding of nuclear factor to this sequence is maximal between 5 min and 30 min after incubation with IL-1 and negative in cells incubated for 60 min or longer. Mutation of the SAA kappa B1 sequence to a nonbinding form of NF-kappa B (CTCACTTTCC) abolishes the IL-1 effect. The SAA 5' region also contained an upstream repressor element, shown by transfection experiments. Within this element, a second NF-kappa B binding site (SAA kappa B2; -626 to -635) was found, and mutation of SAA kappa B2 to a non-NF-kappa B-binding form results in an increase in both constitutive + IL-1 stimulated SAA transcription.(ABSTRACT TRUNCATED AT 250 WORDS)

Amyloid↗
PubMed1991

Polyneuropathy syndromes associated with serum antibodies to sulfatide and myelin-associated glycoprotein.

We studied a series of 64 patients with sensory +/- motor peripheral neuropathies by comparing clinical and physiologic features to serum antibody reactivity against compounds containing sulfated carbohydrate moieties. We determined antibody reactivity by an enzyme-linked immunosorbent assay (ELISA) using purified glycolipids and glycoproteins as antigens, and we used high-performance thin-layer chromatography and Western blotting to test the specificity of results. Twelve patients with high titers of IgM antibodies directed against the myelin-associated glycoprotein (MAG) had sensory-motor polyneuropathies with physiologic evidence of demyelination. IgM antibody reactivity to MAG was associated with an IgM serum M protein in five patients. Eight other patients, most with sensory greater than motor polyneuropathies, had high titers of antibody reactivity to sulfatide but not of IgM to MAG. Two had an associated IgM paraprotein. None of the patients with selective serum antisulfatide activity had predominantly demyelinating features on physiologic testing. We conclude that (1) high ELISA titers of antibodies to MAG may be more common than previously suspected in patients with chronic demyelinating sensory-motor neuropathies, and (2) the presence of high titers of antisulfatide antibodies in serum may provide clues to the pathogenesis of otherwise idiopathic, axonal, predominantly sensory neuropathies.

Adult↗
PubMed1991

Effects of nimodipine on l-glutamate-induced seizures and Ca2+ influx in hippocampus in freely moving rats.

Seizure (EEG) was studied in rats unilaterally injected in the dorsal hippocampus with l-glutamate (Glu). Extracellular Ca2+ content [(Ca2+)e] in the injected area was assessed by brain microdialysis coupled to automatic atomic absorption spectrophotometry. In this experimental epileptic model, an inhibition of Glu-stimulated epileptic activity and a fall in (Ca2+)e by nimodipine (Nim, 100 micrograms.kg-1) were seen. The spike- and wave-burst frequency was reduced from 30 to 5 bursts.min-1 (P less than 0.01, n = 8). Nim 25 and 50 micrograms.kg-1, without anticonvulsant activity, did not prevent the drop in (Ca2+)e. These results indicate that Nim exerts an antiepileptic effect on Glu-induced epilepsy. The mechanisms may be involved in blocking Ca2+ influx into neurons.

Animals↗
PubMed1991

[Cloning and expression of Shiga-toxin gene from Shigella dysenteriae type I].

The chromosomal DNA of S. dysenteriae type I W30864 was isolated and digested by EcoRI. The 3-7 kb DNA fragments were recovered and ligated with vector pUC-19. After transformation, the recombinants were screened by SLT gene probe. The positive clones were obtained. The cloned EcoRI fragment containing both ST-A and ST-B subunit gene was about 4.5 kb. The cloned ST strain was also detected by Hela-S3 cell for cytotoxicity, and detected by rabbit ileal loop test for enterotoxicity. Besides, the cloned strain showed the neurotoxic activity when experimented with mouse. The production of shiga toxin in the cloned strain was 16 times of that of its parent strain S. dysenteriae W30864. The production differences between ST producing stains and SLT producing strain was also tested in our experiment.

Animals↗
PubMed1991

Mammary epithelial differentiation in vitro: minimum requirements for a functional response to hormonal stimulation.

Mammary epithelial differentiation is the culmination of responses to a complex sequence of hormonal stimuli. An in vitro model for this process should retain the basic features of in vivo epithelial differentiation. The IM-2 mouse mammary cell line responds to lactogenic hormone stimulation by synthesizing the milk protein beta-casein. Epithelial and fibroblastic clones derived from IM-2 lack this ability, but cocultures of these clones regain responsiveness to lactogenic hormone stimulation. Studies of the epithelial cell clone 31E under various culture conditions reveal that the role of fibroblastic cells in supporting synthesis and secretion of beta-casein can be supplanted by culture in filter chambers without addition of exogenous extracellular matrix components. Electron microscopic and immunofluorescence studies show that, under these conditions, 31E epithelial cells exhibit the morphology and intercellular organization characteristic of mammary epithelium. Transepithelial electrical resistance measurements indicate that the cells are well polarized. Analysis of glucose metabolism is consistent with this polarization; glucose is utilized from the basal chamber, and lactate is excreted into the basal chamber. Immunoblot analysis demonstrates the vectorial protein secretion expected of polarized mammary epithelium: laminin is secreted into the basal chamber, whereas beta-casein is secreted into the apical chamber in response to lactogenic hormone stimulation from the lower chamber. Thus, the maintenance of a polarized intercellular organization that permits access of the basolateral cell surface to nutrients is sufficient for a pure culture of an established mammary epithelial cell clone to retain differentiated epithelial function in vitro.

Animals↗
PubMed1991

[Observation of curative effect of refined interferon-alpha on viral pneumonia in infants].

Fifteen cases of viral pneumonia in infants were treated with refined interferon-alpha and antibiotics. Clinical symptoms of the cases with IFN-alpha were relieved in 1.40-2.79 days, earlier than those of the control. Clinical recovery time was on the average shorter than that of the control by 1.9 days, and complete recovery by 1.5 days. The difference is statistically significant. It suggested that the clinical effect of IFN-alpha together with antibiotics is better than that of antibiotics alone. There was no significant change between the experimental and control groups in absolute lymphocyte count Ig and T-cell, but OKT3 increased and OKT8 decreased slightly. The study shows that IFN is an effective and safe administration for viral pneumonia.

Anti-Bacterial Agents↗
PubMed1991

Application of uniform design in L-isoleucine fermentation.

Uniform design was employed in our experiments for testing the effects of nine different compositions of the culture media for the production of L-isoleucine in Corynebacterium crenatum A11 fermentation. The most favorable medium was found to be composed of glucose 12%, (NH4)2SO4 2%, KH2PO4 0.1%, K2HPO4 0.45%, MgSO4.7H2O 0.055%, biotin 1 microgram, thiamine 20 micrograms, FeSO4.7H2O 2 ppm, MnSO4.4H2O 2 ppm, CaCO3 4% with pH 7.0-7.2. By using such medium, the amount of L-isoleucine produced by A11 was increased up to 15.1 mg/ml. Uniform design, as compared with orthogonal design, has the advantages of higher efficiency and easier analysis of the factors that affect the production.

Ammonium Sulfate↗
PubMed1991

Treatment of essential hypertension with auriculoacupressure.

Auriculoacupressure was used in the treatment of 291 cases of essential hypertension, in comparison with 51 similar cases treated with Fufang Jiangya (composite hypotensive) Tablets. Analysis of results showed that the therapeutic effects in the 2 groups were similar, while the rate of marked efficacy in the acupressure group was higher than that of the medication group, and the level of blood lipids also significantly dropped (P less than 0.01); there was only minor improvement in blood rheology. In addition, acupressure manifested biphasic regulatory effects on sinus arrythmia. The curative effect of acupressure on essential vascular hypertension was good.

Acupuncture Points↗
PubMed1990

Induction of F9 cell differentiation by transient exposure to retinoic acid.

The F9 cell is a mouse embryonal teratocarcinoma which can be induced to differentiate into visceral endoderm by treatment with retinoic acid (RA). Treatment with RA in conventional studies was carried out in the constant presence of RA. Here we demonstrate that treatment with RA can be as short as 3 hrs to induce differentiation of F9 cells. Morphology, alpha-fetoprotein gene activity, and temporal patterns of F9 cell differentiation are the same with both short- and long-term treatment with RA.

Animals↗
PubMed1990

Coproporphyrinogen oxidase, protoporphyrinogen oxidase and ferrochelatase activities in iron-overloaded and ethanol-treated rats.

The activities of coproporphyrinogen oxidase, protoporphyrinogen oxidase and ferrochelatase in liver homogenates of iron-overloaded and acutely or chronically ethanol-treated rats were assayed by high performance liquid chromatographic methods. Decreased coproporphyrinogen oxidase activity was found in chronically carbonyliron-fed rats while the activities of protoporphyrinogen oxidase and ferrochelatase remained unchanged. Coproporphyrinogen oxidase and protoporphyrinogen oxidase activities in both chronically and acutely ethanol-treated animals were not significantly different from controls. In chronically ethanol-fed rats normal ferrochelatase activity was found.

Animals↗
PubMed1990

Effects of the plant flavonoid baohuoside-1 on cancer cells in vitro.

The novel plant flavonoid 3,5,7,-trihydroxy-4'-methoxyl-8'-prenylflavone-3-O-alpha-L-rham nopranoxide (designated baohuoside-1) was shown to have cytotoxic and cytostatic effects on 6 cancer cell-lines, by means of microscopy, 51Cr-release and growth inhibition. The IC50 on the cells tested ranged from 2.8 to 7.5 micrograms/ml. At tumouricidal concentrations, inhibition of DNA and RNA synthesis, but not protein synthesis was observed.

Animals↗
PubMed1990

Effect of IgG for intravenous use on Fc receptor-mediated phagocytosis by human monocytes.

Polyspecific IgG given intravenously at high doses (IVIG) is used for immunomodulatory therapy in autoimmune diseases such as idiopathic thrombocytopenic purpura and myasthenia gravis. It is assumed that the clinical effect is brought about in part by a modulation of mononuclear phagocyte function, in particular by an inhibition of Fc receptor (FcR) mediated phagocytosis. In the present study, the effect of IVIG on FcR-mediated phagocytosis by monocytes was analysed in vitro. Since monocytes exposed to minute amounts of surface-bound IgG displayed impaired phagocytosis of IgG-coated erythrocytes (EA), the effect of IVIG was studied with mononuclear cells suspended in teflon bags in medium containing 10% autologous serum and IVIG (2-10 mg/ml). Monocytes pre-exposed to IVIG and then washed, displayed impaired ingestion of EA when compared with control cells cultured in 10% autologous serum only. The decrease in phagocytosis was observed with sheep erythrocytes treated with either rabbit IgG or bovine IgG1 and with anti-D-treated human erythrocytes. This suggests that phagocytosis via both FcR type I (FcRI) and type II (FcRII) was decreased. The impairment of phagocytosis was dependent on the presence of intact IgG and was mediated by IVIG from nulliparous donors and from multigravidae to the same extent, suggesting that alloantibodies contained in IVIG have a minor role in modulating FcR-mediated phagocytosis by monocytes. A flow cytometric analysis using anti-FcRI, FcRII and FcRII monoclonal antibodies showed that IVIG treatment upregulated FcRI expression but did not significantly alter the expression of FcRII and FcRIII.

Animals↗
PubMed1990

In vitro reactions of isopropyl methanesulfonate with DNA and with 2'-deoxyribonucleosides.

Isopropyl methanesulfonate (IPMS), an SN1 alkylating agent, is a direct-acting mutagen in bacteria. We recently reported that s.c. and topical administration of IPMS to mice resulted in the rapid induction of thymic lymphomas. Thymic lymphoma induction was not observed following administration of the SN2 alkylating agents methyl methanesulfonate (MMS) and ethyl methanesulfonate (EMS). We have studied the reactions of IPMS with dAdo, dCyd, dGuo and dThd at pH 6.5 to 7.5 and 37 degrees C for 3 h. IPMS formed the following isopropyl (IP) adducts: 7-IP-Gua (4% yield), O6-IP-Gua (8%), O2-IP-Cyt (1%), O2-IP-dThd (2%), 3-IP-dThd (1%), and O4-IP-dThd (0.4%). Adducts were characterized from UV and mass spectra. IPMS was reacted in vitro with calf thymus DNA (pH 6.5 to 7.5, 37 degrees C, 3 h) and yielded (nmol/mg DNA): 7-IP-Gua (22) O6-IP-dGuo (11), O2-IP-Cyt (9), O2-IP-dThd (2), O4-IP-dThd (2), 3-IP-Ade (0.2) and 3-IP-dThd (0.2). The relatively greater alkylation of exocyclic oxygen atoms in DNA by IPMS compared to values for MMS and EMS reported by others, may play a role in the induction of thymic lymphomas in mice by IPMS and the lack of such activity by MMS and EMS.

Alkylating Agents↗
PubMed1990

[Aging-resistant function of soybean phospholipid paste].

Existing chiefly in biomembrane system, phospholipid is a fundamental component in the tissues of all organisms. The ageing of biomembrane is manifested mainly in the changing of phospholipid composition. Experiments have shown that soybean phospholipid paste is obviously helpful in decreasing blood lipids and retarding the ageing process of tissues, thus making a good natural agent for resisting ageing.

Aged↗