Biomedical subjects

L Q Luo

Publications and source records attributed to L Q Luo.

6 recordsLinked to original sources

PubMed2001

[Progress in knowledge-based X-ray fluorescence spectrometry].

The review focuses on the expert systems and knowledge engineering in X-ray fluorescence spectrometry. It includes mainly a knowledge-controlled strategy combining the scan-based method with the fixed channel measurements, a XRF interpretation system of spectra with fuzzy logic and pattern recognition, and an expert system for qualitative interpretation of XRF spectra using a certainty factor. In the review, a series of the studies of exploring the knowledge engineering system in XRF are also included, which consists of four parts, i.e. spectra identification, pattern recognition with decision-making, quantitative determination combined with the theoretical alpha coefficients and neural networks, and XRF analysis without standards.

Algorithms↗

PubMed1994

[Enhanced metastasis of a mouse mammary adenocarcinoma after in vitro treatment with gamma-interferon].

gamma-Interferon (IFN-gamma) was detected by ELISA assay in ascitic fluid from a number of ovarian cancer patients. To study its clinical significance, the effect of IFN-gamma on the metastatic potential of a mouse mammary adenocarcinoma, MA-891, was explored. Pretreatment of the tumor cells in vitro for 48hr with recombinant INF-gamma significantly increased the number of lung tumor nodules after i. v. or s. c. inoculation into (TA2 x 615) F1 mice. In contrast, when recombinant IFN-alpha pretreated MA-891 cells were likewise injected into mice significant decrease in metastatic potential was seen. The study in vitro indicated that pretreatment of the tumor cells with IFN-gamma but not with IFN alpha resulted in a decrease in susceptibility to NK cell cytotoxicity. In as much as both IFN-alpha and IFN-gamma can induce MHC class I expression on target cells. The increase in metastatic potential of IFN-gamma-treated tumor cells can be explained only partially on the basis of their reduced NK cells susceptibility.

Adenocarcinoma↗

PubMed1992

[Observation of the in vivo tumor cell lysis mediated by NK cells].

Natural killer cells/large granular lymphocytes (NK/LGL) separated on discontinuous Percoll gradient from rat spleen cells were injected iv to rats (7 x 10(7) cells/rat) 3 days following iv inoculation of 2 x 10(6) Walker-256 cells. Two and 4 hr after NK/LCL injection, animals were sacrificed and the lungs examined by light and immunoelectron microscopy. The latter was done using colloidal gold-labelled polyclonal antibody against purified rat LGL cytoplasmic granules. At 2 hr following iv NK/LGL, in addition to the scattered individual tumor cells and minute tumor foci, many lymphocytes were seen accumulating in the small pulmonary vessels and capillaries. This was not observed in tumor-inoculated control rats. At 4 hr, many extravasated lymphocytes reached the lung parenchyma, some of which had attached to the tumor cells. Immunoelectromicroscopically, lymphocytes were found in intimate contact with the tumor cells with the cytoplasmic gold particles clustering at the cell contact site. Gold particles could also be seen closely adherent to the plasma membrane of degenerating tumor cells. This is the first in vivo demonstration of the role of cytotoxic granules of NK cells in tumor cell lysis.

Animals↗

PubMed1990

Identification, secretion, and neural expression of APPL, a Drosophila protein similar to human amyloid protein precursor.

A Drosophila gene [amyloid protein precursor-like (Appl)] has recently been identified whose predicted amino acid sequence (APPL) shares extensive homology with the beta-amyloid protein precursor (APP) associated with Alzheimer's disease. Characterization of proteins encoded by the Appl gene was initiated with the expectation that this simple model system might help elucidate the basic function provided by APPL and APP proteins. In this report, we identify 2 forms of the APPL protein in embryonic extracts, primary cultures, and transfected cells. APPL is synthesized as a 145-kDa membrane-associated precursor that is converted to a 130-kDa secreted form that lacks the cytoplasmic domain. Both forms are N-glycosylated. Pulse-chase and subcellular localization studies suggest that the conversion is very rapid. The similarities of biogenesis between APP and APPL provide further evidence that APPL and APP might be functionally homologous, and that the secretion event is of physiological significance. Immunocytochemical studies show that the APPL proteins are first detected in developing neurons concomitant with axonogenesis and remain associated with differentiated neurons. APPL immunoreactivity was observed in neuronal cell bodies, axonal tracts, and neuropil regions. In the embryo, APPL proteins are expressed exclusively in the CNS and PNS neurons, consistent with the Appl transcript localization. The expression pattern of APPL proteins suggests an ancestral function for this protein in the nervous system.

Amyloid beta-Peptides↗

PubMed1989

A Drosophila gene encoding a protein resembling the human beta-amyloid protein precursor.

We have isolated genomic and cDNA clones for a Drosophila gene resembling the human beta-amyloid precursor protein (APP). This gene produces a nervous system-enriched 6.5-kilobase transcript. Sequencing of cDNAs derived from the 6.5-kilobase transcript predicts an 886-amino acid polypeptide. This polypeptide contains a putative transmembrane domain and exhibits strong sequence similarity to cytoplasmic and extracellular regions of the human beta-amyloid precursor protein. There is a high probability that this Drosophila gene corresponds to the essential Drosophila locus vnd, a gene required for embryonic nervous system development.

Amino Acid Sequence↗

PubMed1988

Properties of NAD glycohydrolase purified from five-pace snake (Agkistrodon acutus) venom.

NAD glycohydrolase (NADase) (E.C. 3.2.2.5) from five-pace snake (Agkistrodon acutus) venom was purified to electrophoretic homogeneity through a 4-step isolation procedure, including column chromatography using DEAE-Sephadex A-50, Sephadex G-75, CM Sephadex C-50 and Sephadex G-100. The final product was 11.8-fold purified with a 3.9% yield. The pure enzyme showed maximal activity at about 40 degrees C with optimal pH at 7.5. It was a glycoprotein with a pI of 7.6. Its mol. wt was respectively 98,000 as measured by gel filtration and 50,000, by SDS-PAGE. There was only one N-terminal residue, proline. NADase is thus composed of two identical subunits in each molecule. The enzyme contained copper ions. NADase activity was lost when the copper enzyme complex was treated with EDTA. The Km of the enzyme for beta-NAD, NADP and beta-NGP were 0.50 mM, 0.13 mM and 0.16 mM respectively.

Animals↗