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Biomedical subjects

F Li

Publications and source records attributed to F Li.

At least 559 records · Page 31Linked to original sources
PubMed1993

High level expression of Shiga toxin B subunit of Shigella dysenteriae serotype 1 in Escherichia coli.

In this study the gene encoding the Shiga toxin (Stx) was cloned from the chromosomal DNA of Shigella dysenteriae serotype 1 (W30864). The Stx gene was located in a 4.5kb EcoRI fragment. The biological assay revealed that the hybrid plasmid pMGC001 containing the Stx gene could produce Shiga toxin. The amount of Stx was 16 times more than that produced by its parent. The cloned strain showed cytotoxic, entorotoxic and neurotoxic activities. The gene for Stx-B subunit was subcloned into a plasmid vector pJLA503 from the plasmid pMGC001. The B subunit could be expressed at high level in E. coli and has been purified in large quantities. The polyclonal and monoclonal antibodies against B subunit were raised. Western blot showed that they could react specifically to the B subunit.

Bacterial Toxins↗
PubMed1993

Relation of IL-2, IL-3 and IL-4 with allergic asthma induced by spores of mushroom (Pleurotus sapidus).

The effects of IL-2, IL-3, and IL-4 activities on occurrence of allergic asthma induced by spores of mushroom have been studied by measuring the IL-2, IL-3, and IL-4 activities in culture supernatants of spleen lymphocytes from guinea pigs being stimulated with Con A. The IL-4 activity (14.9 +/- 0.18 u) in the culture supernatant was higher than control group (6.7 +/- 1.5 u). The IL-2 and IL-3 activities were all similar to that of the control group. The IL-4 synthesis was similarly raised as the IL-4 activity. These results indicated that there is a relationship between the occurrence of allergic asthma and the increase of IL-4.

Animals↗
PubMed1993

[A clinicopathological and immunohistochemical study of 49 cases of necrotizing lymphadenitis].

A clinicopathological and immunohistiochemical study of 49 cases of necrotizing lymphadenitis was made. Twenty-four patients were male and twenty-five female with the M:F ratio of 0.96:1. The patients ranged in age from 9 to 62 years with a mean of 26. Forty-nine patients had superficial lymphadenopathy, and twenty-two were accompanied by fever. The results also showed that there was multifoci necrosis present in the involved lymph nodes, particularly in the cortex or/and paracortex, with variable numbers of small lymphocytes, immunoblasts, histocytes and phagocytes, the latter with phagocytized nuclear debris derived from necrotizing T lymphocytes. However, granulocytes and plasmacytes were generally absent, and B lymphocytes rare. The pathogenesis of this disease remains unknown and the pathogen has not been found by Gram, Giemsa, PAS, Ziehl-Neelsen and Warthin-Starry stain. The diagnosis, differential diagnosis and etiology of this disease are discussed. We support the suggestion that this entity be called "Kikuchi-Fujimoto's disease" rather than "Histiocytic necrotizing lymphadenitis".

Adolescent↗
PubMed1992

Bryostatin 1 modulates the proliferation and lineage commitment of human myeloid progenitor cells exposed to recombinant interleukin-3 and recombinant granulocyte-macrophage colony-stimulating factor.

The activity of protein kinase C (PK-C) has been implicated in the regulation of the growth and differentiation of both normal and neoplastic hematopoietic cells. We have examined the effects of the PK-C-activating agents phorbol 12,13-dibutyrate (PDBu), mezerein, and bryostatin 1 on the proliferation and lineage commitment of CD34+ human myeloid progenitor cells stimulated by recombinant interleukin-3 (rIL-3) and/or recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). Although each of the PK-C activators administered alone induced no colony formation, coadministration of these agents with plateau concentrations of each cytokine (eg, 50 ng/mL) increased the number of day 14 granulocyte-macrophage colony-forming units by 100% to 150%. The number of pure and mixed neutrophil and macrophage colonies was substantially enhanced in the presence of PK-C activators, whereas the percentage and, in most cases, the absolute number of eosinophilic colonies was significantly reduced. The inhibition of eosinophilic colony formation was not overcome by the addition of rIL-5. Although addition of bryostatin 1 24 hours before rIL-3 abrogated the increase in total colony formation observed with simultaneous administration of factors, the inhibition of eosinophilic colonies and the increase in neutrophil/macrophage colonies persisted under these conditions. The addition of bryostatin 1 for up to 144 hours after rIL-3 continued to potentiate total colony formation, whereas the inhibition of eosinophilic commitment was lost after 120 hours. Together, these results suggest that pharmacologic interventions at the level of PK-C may regulate both the proliferation as well as the lineage commitment of human hematopoietic progenitors exposed to rGM-CSF and rIL-3.

Bryostatins↗
PubMed1992

Hand-eye coordination during sequential tasks.

The small angle subtended by the human fovea places a premium on the ability to quickly and accurately direct the gaze to targets of interest. Thus the resultant saccadic eye fixations are a very instructive behaviour, revealing much about the underlying cognitive mechanisms that guide them. Of particular interest are the eye fixations used in hand-eye coordination. Such coordination has been extensively studied for single movements from a source location to a target location. In contrast, we have studied multiple fixations where the sources and targets are a function of a task and chosen dynamically by the subject according to task requirements. The task chosen is a copying task: subjects must copy a figure made up of contiguous coloured blocks as fast as possible. The main observation is that although eye fixations are used for the terminal phase of hand movements, they are used for other tasks before and after that phase. The analysis of the spatial and temporal details of these fixations suggests that the underlying decision process that moves the eyes leaves key decisions until just before they are required.

Eye Movements↗
PubMed1992

In vitro reaction of ethylene oxide with DNA and characterization of DNA adducts.

Ethylene oxide (EO) is a direct-acting SN2 alkylating agent and a rodent and probable human carcinogen. In vitro reactions of EO with calf thymus DNA in aqueous solution at neutral pH and 37 degrees C for 10 h resulted in the following 2-hydroxyethyl (HE) adducts (nmol/mg DNA): 7-HE-Gua (330), 3-HE-Ade (39), 1-HE-Ade (28), N6-HE-dAdo (6.2), 3-HE-Cyt (3.1), 3-HE-Ura (0.8) and 3-HE-dThd (2.0). Reference (marker) compounds were synthesized from reactions of EO with 2'-deoxyribonucleosides and DNA bases, isolated by paper and high performance liquid chromatography and characterized on the basis of chemical properties and UV, NMR and mass spectra. In agreement with our earlier studies with propylene oxide (PO) (Chem.-Biol. Interact., 67 (1988) 275-294) and glycidol (Cancer Biochem. Biophys., 11 (1990) 59-67), alkylation at N-3 of dCyd by EO under physiological conditions resulted in the rapid hydrolytic deamination of 3-HE-dCyd to 3-HE-dUrd. The hydroxyl group on the alkyl side chain which forms after epoxide alkylation is mechanistically involved in this rapid hydrolytic deamination. These results may provide important insights into the mechanisms of mutagenicity and carcinogenicity exhibited by EO and other SN2 aliphatic epoxides.

Animals↗
PubMed1992

Overexpression of Mos, Ras, Src, and Fos inhibits mouse mammary epithelial cell differentiation.

Mammary epithelial cells terminally differentiate in response to lactogenic hormones. We present evidence that oncoprotein overexpression is incompatible with this hormone-inducible differentiation and results in striking cellular morphological changes. In mammary epithelial cells in culture, lactogenic hormones (glucocorticoid and prolactin) activated a transfected beta-casein promoter and endogenous beta-casein gene expression. This response to lactogenic hormone treatment was paralleled by a decrease in cellular AP-1 DNA-binding activity. Expression of the mos, ras, or src (but not myc) oncogene blocked the activation of the beta-casein promoter induced by the lactogenic hormones and was associated with the maintenance of high levels of AP-1. Mos expression also increased c-fos and c-jun mRNA levels. Overexpression of Fos and Jun from transiently transfected constructs resulted in a functional inhibition of the glucocorticoid receptor in these mouse mammary epithelial cells. This finding clearly suggests that glucocorticoid receptor inhibition arising from oncogene expression will contribute to the block in hormonally induced mammary epithelial cell differentiation. Expression of Src resulted in the loss of the normal organization and morphological phenotype of mammary epithelial cells in the epithelial/fibroblastic line IM-2. Activation of a conditional c-fos/estrogen receptor gene encoding an estrogen-dependent Fos/estrogen receptor fusion protein also morphologically transformed mammary epithelial cells and inhibited initiation of mammary epithelial differentiation-associated expression of the beta-casein and WDNM 1 genes. In response to estrogen treatment, the cells displayed a high level of AP-1 DNA-binding activity. Our results demonstrate that high cellular AP-1 levels contribute to blocking the ability of mammary epithelial cells in culture to respond to lactogenic hormones. This and other studies indicate that the oncogene products Mos, Ras, and Src exert their effects, at least in part, by stimulating cellular Fos and probably cellular Jun activity.

Animals↗
PubMed1992

Apoptotic cell death and tissue remodelling during mouse mammary gland involution.

During post-lactational mammary gland involution, the bulk of mammary epithelium dies and is reabsorbed. This massive cell death and tissue restructuring was found to be accompanied by a specific pattern of gene expression. Northern blot analysis showed that weaning resulted in a dramatic drop in ODC, a gene involved in synthesis of a component of milk, and the nearly simultaneous induction of SGP-2, a gene associated with apoptotic cell death. These changes were followed by decreases in expression of milk protein genes to basal levels and expression of genes associated with regulation of cell proliferation and differentiation, p53, c-myc and TGF-beta 1. Subsequently, additional genes implicated in stress response, tissue remodelling, and apoptotic cell death were transiently expressed, expression peaking at about 6 days post-weaning. A non-random degradation of DNA yielding the oligonucleosomal length fragmentation pattern typical of apoptotic cell death (Wyllie, 1980; Wyllie et al., 1980) was detected in association with morphological changes and gene expression. The correlations between: (a) changes in morphology, (b) pattern of gene expression and (c) changes in DNA integrity suggest that complementary programs for cell death and tissue remodelling direct post-lactational mammary gland involution.

Animals↗
PubMed1992

[A study on origin of the hyperplastic synovial lining cells in rheumatoid arthritis].

The one of striking microscopic feature is synovium hyperplasia in rheumatoid arthritis. The origin of the hyperplastic synovial lining cells in RA remains unsettled. Two marked monoclonal antibodies and two marked antisera are used to run the immunohistochemical study. Our finding revealed that synovial lining cells bear marks for blood monocytes. It is suggested that the increased synovial lining cells population appear to derive from bone marrow. Besides, the results of immunoelectron microscopy showed that synovial lining cells of type A and type C express HLA-DR antigen. HLA positive dendritic cells are distinctly more frequently seen in RA synovium than in that of osteoarthritis.

Arthritis, Rheumatoid↗
PubMed1992

[Preparation of human placenta microvillous membrane and the study of its transferrin receptor].

Human placenta microvillous membrane (PMM) was prepared by differential centrifugation and by sucrose gradient centrifugation, and the transferrin receptor (TfR) was studied using the receptor radioassay with 125I-transferrin as a radioligand. The factors affecting ligand-receptor binding reaction and the characteristics of TfR were also studied. The result showed that there was no significant differences (P > 0.1) in specific binding rates of 125I-transferrin to its receptor between the two membrane preparations, indicating that both of them could be used for TfR analysis, but the method of differential centrifugation was more simple and less time consuming. The study of TfR in sixty cases showed that the TfR binding sites on PMM and Bmax were 3.53 +/- 1.98 x 10(12) sites/mg membrane protein and 6.33 +/- 4.21 x 10(-12) mol/mg membrane protein, respectively. The Kd was 4.95 +/- 3.39 x 10(-9) mol/L, and the highest specific binding was 26% with nonspecific binding less than 3%. The conditions for ligand-receptor binding reaction were optimized when the concentrations of membrane protein and the 125I-transferrin in each test tube were 50 micrograms and 50,000 cpm (specific radioactivity being 2109 kBq/micrograms transferrin) respectively the incubation time was 30 min, and the concentration of polyethylene glycol added for separating B/F was 12% (W/V). transferrin binding to its receptor was characterized by high affinity, high specificity and being saturated.

Cell Membrane↗
PubMed1992

[Scanning electron microscopic observation on Demodex brevis].

This paper presents the first description of the morphology of Demodex brevis examined by scanning electron microscopy. The authors found that D. brevis can be distinguished from D. folliculorum by the characteristic features of the following structures: the flat gnathosoma, the humplike podosoma and the absence of transverse striation on its anterior dorsal surface, the supracoxal spines, the hypostome, the oral opening, the pedipalpal claws and the claws on legs, and the annuli of the terminal part of the opisthosoma. The morphology of the above structures observed are briefly compared with those of D. folliculorum.

Animals↗
PubMed1992

Detection of activated platelets using activation-dependent monoclonal antibody (SZ-51) in clinical disorders.

Platelets may become activated in a number of clinical disorders and participate in thrombus formation. A direct test for activated platelets in whole blood has been developed by radioimmunoassay with 125I labelled SZ-51, an antibody specific for an alpha-granule membrane protein (GMP-140) that associates with the platelet surface during secretion. The assay with sufficient sensitivity can be applied satisfactorily to detect as few as 2% activated platelets. In 50 normal subjects, minimal GMP-140 molecules per platelet were expressed on the surface of circulating platelets. The expression of GMP-140 molecules was increased transiently in 10 patients undergoing cardiopulmonary bypass, especially at the end of bypass. Evaluation of 18 patients with epidemic hemorrhagic fever (EHF) showed that the number of GMP-140 molecules on the platelet surface increased significantly, particularly at the shock phase, and closely related to the four different phases of EHF. In 9 patients suffered from acute myocardial infarction (AMI), the number of GMP-140 molecules changed with the procession of AMI and the highest occurred at the 48th h after AMI. The GMP-140 molecules were also increased in patients with asthma attack (n = 14), but not in patients with idiopathic thrombocytopenic purpura (n = 11). Considered together, these results suggest that activated platelets can be measured reliably in whole blood using radiolabeled SZ-51 antibody and the detection of activated platelets is potentially useful in identifying patients with certain thrombotic disorders.

Acute Disease↗
PubMed1992

[Effects of ginseng volatile oil on cytochemical components of SGC-823 gastric carcinoma in cell culture].

After 24, 48 and 72 hours' treatment of cells of SGC-823 gastric carcinoma in cell cultures with ginseng volatile oil, glycogen, succinate dehydrogenase and DNA in single cells were measured quantitatively with MPV2 microscope photometer. The results show that the inhibition of cancer cell growth by ginseng volatile oil may be due to the action of metabolism of DNA, carbohydrates and energy.

DNA, Neoplasm↗
PubMed1992

Rigidity of half-pins for the Ilizarov external fixator.

The success of the Ilizarov technique is due to the combination of the biomechanics of its external fixator and the biology of distraction osteogenesis. The stability and stiffness of the conventional Ilizarov fixator is attributed to its use of a K-wire cross structure. The disadvantages of this structure include pain, and possible neurologic and vascular injuries when the wires are introduced into crucial neurovascular areas, as well as increased frame complexity and construction. Reducing the number of wires decreases these problems, but also decreases the stiffness of the system. Hybrid (wire and half-pins) Ilizarov fixators and half-pin fixators are also being used in an attempt to alleviate these problems. Half-pins have been described by Fleming et al. and Green as causing minimal transfixation of the surrounding soft tissues and capable of and being inserted into anatomically safe areas. The stiffnesses of the hybrid systems have not been measured. This study reports on the stiffness of different wire and half-pin systems that were biomechanically tested in axial loading, anterior-posterior bending, medial-lateral bending, and torsional loading. The results demonstrated that the conventional Ilizarov fixator with wires possesses a high axial stiffness, whereas the fixator with half-pins possesses higher stiffness under bending and torsional loads. To obtain adequate stability, the use of hybrid Ilizarov frames with one wire and two or more half-pins (5 or 6 mm in diameter), or larger half-pin frames (5 or 6 mm) with three pins is recommended.

Biomechanical Phenomena↗
PubMed1992

[Hypolipodemic action of zhikeqing].

Zhikeqing is a compound prescription of Chinese herbs. It has been proved shown to possess an obvious effect on lipid and lipoprotein cholesterol contents in the serum of hyperlipidemic mice or rats.

Animals↗