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Biomedical subjects

F Li

Publications and source records attributed to F Li.

At least 19 recordsLinked to original sources
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↗
PubMed1992

Biomechanics of the Ilizarov fixator for fracture fixation.

Compression, distraction, and torsion stiffness of the Ilizarov external fixator was measured in two fracture models in autopsy specimens of tibia and fibula. A transverse model was tested in six frame constructions with the osteotomy site preloaded in four different positions. An oblique model was tested in four frame constructions also with four preloaded positions. Stiffness was more dependent on bone preload than wire number, wire type, or frame design. High stiffness was achieved by bone preloading, by compressing the rings together, by increasing the number of wires, and by using olive wires. The stiffness can be decreased (dynamization) by separating the rings and by removing wires. This data is helpful for frame design of the Ilizarov fixator.

Biomechanical Phenomena↗
PubMed1992

Diagnostic exploration of enlarged peripheral nerves in suspected cases of leprosy. An analysis of 55 cases.

In 55 cases presenting with enlarged peripheral nerves without any skin lesions, a rice grain-sized biopsy of the nerve lesion was taken for histopathological examination. As a result definitive diagnoses could be established: leprosy was diagnosed in 32 cases. In 23 cases the cause of nerve enlargement was not leprosy: post-traumatic neuritis 9, cysts 5, hypertrophic neuritis 3, nonspecific 4, neurofibroma 1, and amyloidosis 1. In all of these cases there was a deficit of the nerve function and postoperatively there were no complications. The authors, as a result of this experience, believe that surgical exploration and biopsy is a harmless diagnostic tool for establishing a definitive diagnosis of leprosy in cases presenting with enlarged peripheral nerves without any skin lesions. In 23 out of 55 such cases the nerve enlargement was proved to be other causes than leprosy.

Adolescent↗
PubMed1991

Receptor protein-tyrosine phosphatase gamma is a candidate tumor suppressor gene at human chromosome region 3p21.

PTPG, the gene for protein-tyrosine phosphatase gamma (PTP gamma), maps to a region of human chromosome 3, 3p21, that is frequently deleted in renal cell carcinoma and lung carcinoma. One of the functions of protein-tyrosine phosphatases is to reverse the effect of protein-tyrosine kinases, many of which are oncogenes, suggesting that some protein-tyrosine phosphatase genes may act as tumor suppressor genes. A hallmark of tumor suppressor genes is that they are deleted in tumors in which their inactivation contributes to the malignant phenotype. In this study, one PTP gamma allele was lost in 3 of 5 renal carcinoma cell lines and 5 of 10 lung carcinoma tumor samples tested. Importantly, one PTP gamma allele was lost in three lung tumors that had not lost flanking loci. PTP gamma mRNA was expressed in kidney cell lines and lung cell lines but not expressed in several hematopoietic cell lines tested. Thus, the PTP gamma gene has characteristics that suggest it as a candidate tumor suppressor gene at 3p21.

Animals↗
PubMed1991

A comparison of serum-free media for the support of in vitro mitogen-induced blastogenic expansion of cytolytic lymphocytes.

The high cost and potential dangers of including human AB serum in incubation media used to expand lymphocyte populations in vitro for adoptive immunotherapy have stimulated efforts to develop defined media which can support both the expansion and induction of lymphocytes with tumor cytolytic activity in the absence of serum. Lymphocyte proliferation following exposure to either PHA or the combination of phorbol 12,13-dibutyrate (PDBu) and the calcium ionophore, ionomycin, was evaluated. Although the media tested, X-Vivo 10, HB-104, AIM V, and HL-1, supported the generation of comparable levels of LAK activity after 3-5 days incubation with 10(3) U human recombinant interleukin-2 (rIL-2)/ml, there were striking differences in the ability of each medium to support mitogenically stimulated lymphocytes in the absence of serum, with cells in AIM V and X-Vivo 10 showing the highest levels of DNA synthesis. In long-term cultures (17 days) of blood MNC stimulated by PDBu and ionomycin, X-Vivo 10 and HB-104 yielded the greatest numbers of cells. The addition of 2% AB serum greatly enhanced the ability of each medium to support cell proliferation to equivalent maximum levels. The results indicate that while all four serum-free media were suitable for lymphocyte culture and support the development of LAK activity, they differ in their capacity to support expansion of lymphocyte populations in response to polyclonal mitogenic activation. This latter characteristic should be considered before choosing a particular serum-free formulation as its constituents may affect mechanistic interpretations regarding signal transduction events.

Blood↗
PubMed1991

Autoantibodies to GM1 ganglioside: different reactivity to GM1-liposomes in amyotrophic lateral sclerosis and lower motor neuron disorders.

We studied the ability of anti-GM1 ganglioside antibodies to bind to GM1 in a lipid, "membrane-like" environment. Liposomes containing GM1 were synthesized to simulate this environment. We then compared the binding of anti-GM1 a autoantibodies to GM-1-liposomes and to purified GM1. Antibody binding was quantitated using enzyme-linked immunosorbent assay methodology. Our results showed a 250-fold variation in the ability of anti-GM1 antibodies to bind to GM1-liposomes. There was no correlation between GM-1-liposome binding and the carbohydrate specificities of the anti-GM1 antibodies. However, anti-GM1 antibodies from patients with amyotrophic lateral sclerosis (ALS) showed a 4 fold greater binding to GM1-liposomes than antibodies from patients with lower motor neuron (LMN) syndromes. We conclude that a lipid, presumably "membrane-like", environment may greatly influence the degree of anti-GM1 antibody binding to GM1. The low levels of anti-GM1 antibody binding to GM1-liposomes in patients with LMN syndromes may provide a diagnostic means for distinguishing these patients from those with ALS. Anti-GM1 antibodies from patients with ALS may bind especially well to neuronal membranes containing GM1 in vivo.

Amyotrophic Lateral Sclerosis↗