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Biomedical subjects

M C Liu

Publications and source records attributed to M C Liu.

At least 217 records · Page 12Linked to original sources
PubMed1984

Decrease of tyrosine-O-sulfate-containing proteins found in rat fibroblasts infected with Rous sarcoma virus or Fujinami sarcoma virus.

Our interest was aroused by the recent report by Huttner [ Huttner , W. B. (1982) Nature (London) 299, 273-276] on general sulfation of tyrosine residues of proteins in normal and malignantly transformed tissues. Here we report on the reduction of sulfation in embryonic rat fibroblasts, line 3Y1, infected with Rous sarcoma virus or Fujinami sarcoma virus. In view of the instability of tyrosine O-sulfate in strong acid, the protein sulfation was tested for after incubation with [35S]sulfate and exhaustive Pronase hydrolysis. We found in general a reduction of sulfation in transformed tissue. It was greatest in the fibroblasts permanently transformed with Rous sarcoma virus. When fibroblasts transformed by the temperature-sensitive Fujinami sarcoma virus, line ts225 -3Y1, were used for comparison of sulfation at nonpermissive and permissive temperatures, the latter showed a strong reduction. Furthermore, we tested these cells for the uptake of inorganic [35S]sulfate. Uptake appeared highly reduced in the permanently infected fibroblasts, but ts225 -3Y1 grown at permissive and nonpermissive temperatures exhibited no difference. Uptake at both temperatures was comparable to uptake by normal 3Y1 cells. A recently much investigated cell surface protein, fibronectin, was reported to be lost on malignant transformation and to contain sulfate in an undetermined location. We found that ts225 -3Y1 cells grown at permissive temperature released fibronectin that contained tyrosine O-sulfate.

Animals↗
PubMed1984

Human lung macrophages enhance and inhibit lymphocyte proliferation.

To evaluate the effector functions of human lung macrophages, cell preparations containing 70 to 95% macrophages were obtained from surgically resected lungs of cancer patients and were co-cultured with allogeneic or autologous peripheral blood mononuclear cells (PBMC) and Con A. In contrast to previous reports of either marked stimulatory or inhibitory effects of human lung macrophages on lymphocyte function, the present results demonstrate that the proliferative response was a complex function of both the numbers of PBMC and macrophages. In the presence of low numbers of PBMC, small numbers of macrophages enhanced proliferation, whereas larger numbers inhibited proliferation; in the presence of larger numbers of PBMC, macrophages only inhibited. Inhibition was not mediated by cyclo-oxygenase products of arachidonic acid metabolism, because indomethacin did not reverse it. The enhancing effect of macrophages was greater when tested with PBMC depleted of monocytes. Lung macrophages were 10-fold more potent in mediating enhancement than corresponding numbers of peripheral blood monocytes. Both the enhancing and the inhibitory activities could be reproduced by lung macrophage lysates or supernatants derived from macrophages cultured in serum-free medium. Macrophages cultured at high density yielded inhibitory supernatants, which on dilution resulted in enhancing activity. The enhancing activity appeared in supernatants maximally after 24 hr, and its appearance was not inhibited by culturing macrophages in the presence by culturing macrophages in the presence of cycloheximide. Sephacryl S-200 chromatography of such supernatants yielded two peaks of enhancing activity, with apparent m.w. of 160,000 and 40,000, which we call lung macrophage-derived lymphocyte-activating factors (LM-LAF). Fractions with LM-LAF activity contained no IL 1 activity (assessed by augmentation of mitogen-induced proliferation of mouse thymocytes), but IL 1 activity was present in a peak of m.w. of 15,000. The 15,000 m.w. fraction did not enhance the proliferation of human PBMC. These results demonstrate that human lung macrophages are potent modulators of lectin-mediated proliferation of human PBMC. The effects are mediated in part by the release of soluble, pre-formed factors that appear to be distinct from previously described monokines.

Cells, Cultured↗
PubMed1983

Separation of major prostaglandins, leukotrienes, and monoHETEs by high performance liquid chromatography.

A procedure using high performance liquid chromatography (HPLC) is described for the separation of major primary cyclooxygenase metabolites (prostacyclin metabolite-6ketoPGF1 alpha, thromboxane B2, and prostaglandins F2 alpha, E2, and D2), leukotrienes (C4, B4, and D4), monohydroxyeicosatetraenoic acids (15-, 11-, 12-, and 5HETEs), and free arachidonic acid. It is therefore possible to quantitate major arachidonic acid metabolites by a single chromatographic procedure. Using this technique we have determined that a major arachidonic acid metabolite of human lung macrophages co-elutes with leukotriene B4.

Arachidonic Acids↗
PubMed1983

Comparison of cytochromes from anaerobically and aerobically grown cells of Pseudomonas perfectomarinus.

Pseudomonas perfectomarinus (ATCC 14405) is a facultative anaerobe capable of either oxygen respiration or anaerobic nitrate respiration, i.e., denitrification. A comparative study of the electron transfer components of cells revealed five c-type cytochromes and cytochrome cd in the soluble fraction from anaerobically grown cells and four c-type cytochromes in the soluble fraction from aerobically grown cells. Purification procedures yielded three c-type cytochromes (designated c-551, c-554, and acidic c-type) from both kinds of cells as indicated by similarities in absorption spectra, molecular weight, and electrophoretic mobility. Cytochrome cd, a diheme c-type cytochrome (cytochrome c-552), and a split-alpha c-type cytochrome were recovered only from anaerobically grown cells. A c-type cytochrome with a low ratio of alpha to beta absorption peak heights was uniquely present in the aerobically grown cells. Liquid N2 temperature absorption spectroscopy on the membrane fraction from anaerobically grown cells revealed residual cytochrome cd as well as differences in the relative amounts of c-type and b-type cytochromes in membranes prepared from cells grown under the two different conditions.

Aerobiosis↗
PubMed1981

The isolation of a hexaheme cytochrome from Desulfovibrio desulfuricans and its identification as a new type of nitrite reductase.

Desulfovibrio desulfuricans (ATCC 27774), a strictly anaerobic sulfate-reducing bacteria, is able to perform anaerobic nitrate respiration in which nitrate is first reduced to nitrite by the action of nitrate reductase, and nitrite reductase then catalyzes the six-electron reduction of nitrite to ammonia. The nitrite reductase was found to be a membrane-bound enzyme and has been purified to electrophoretic homogeneity. The purified enzyme has a minimal Mr = 66,000 as judged by sodium dodecyl sulfate gel electrophoresis and contains 6 c-type heme groups/molecule. Pure nitrite reductase exhibits a typical c-type cytochrome absorption spectrum with reduced alpha-band at 552.5 nm. NADH and NADPH do not function as direct electron donors for the nitrite reductase. Desulfovibrio vulgaris hydrogenase, however, is able to transfer electrons from H2 to the nitrite reductase using FAD as the electron transfer mediator. The dithionite-reduced nitrite reductase was demonstrated to be auto-oxidizable even in the presence of potassium cyanide. On addition of nitrite, the dithionite-reduced enzyme is re-oxidized immediately. Hydroxylamine, however, can only partially re-oxidize the reduced enzyme. Ascorbate reduces the enzyme to a limited extent and the partially reduced enzyme is neither auto-oxidizable nor re-oxidizable by nitrite or hydroxylamine. Purified nitrite reductase has a pH optimum in the range of 8.0-9.5 and optimal activity at 57 degrees C. Purified nitrite reductase also has hydroxylamine reductase activity, and the Km for nitrite was determined to be 1.14 mM and that for hydroxylamine is 113.5 mM. The difference in Km values seems to exclude the possibility of hydroxylamine being a free intermediate in the reduction of nitrite.

Amino Acids↗
PubMed1976

A predischarge unit in a long-stay hospital for subnormality.

A newly built residential ward in the grounds of a long-stay mental subnormality hospital was converted into a predischarge unit to cater for those patients who could probably be discharged after some special training. So far 31 residents have been trained over the past two years; 18 (58%) have been discharged to community residences, and five were waiting for discharge. The high success rate shows the value and usefulness of a predischage unit in a long-stay hospital, and also shows that a purpose-built building is not necessary so long as the staff have the initiative and will to succeed.

Adolescent↗
PubMedDate not supplied

Quantitative prediction of liquid chromatography retention of N-benzylideneanilines based on quantum chemical parameters and radial basis function neural network.

Based on quantum chemical parameters and a simple numerical coding, the liquid chromatography retention of bifunctionally substituted N-benzylideneaniles (NBA) has been predicted using a radial basis function neural network (RBFNN) model. The quantum chemical parameters involved in the model are dipole moment (m), energies of the highest occupied and lowest unoccupied molecular orbitals (E(homo,) E(lumo)), net charge of the most negative atom (Q(min)), sum of absolute values of the charges of all atoms in two given functional groups (Delta), total energy of the molecule (E(T)), weight of the molecule (W), and numerical coding (N). N was used to indicate the different positions of two substituents. The predictive values are consistent with the experimental results. The mean relative error of the testing set is 1.6%, and the maximum relative error is less than 5.0%. In this work the success of the whole modeling process only depends on the optimization of the spread parameter in network.

Journal Article↗
PubMedDate not supplied

Diagnosing breast cancer based on support vector machines.

The Support Vector Machine (SVM) classification algorithm, recently developed from the machine learning community, was used to diagnose breast cancer. At the same time, the SVM was compared to several machine learning techniques currently used in this field. The classification task involves predicting the state of diseases, using data obtained from the UCI machine learning repository. SVM outperformed k-means cluster and two artificial neural networks on the whole. It can be concluded that nine samples could be mislabeled from the comparison of several machine learning techniques.

Algorithms↗
PubMedDate not supplied

QSAR study of ethyl 2-[(3-methyl-2,5-dioxo(3-pyrrolinyl))amino]-4-(trifluoromethyl) pyrimidine-5-carboxylate: an inhibitor of AP-1 and NF-kappa B mediated gene expression based on support vector machines.

The support vector machine, as a novel type of learning machine, for the first time, was used to develop a QSAR model of 57 analogues of ethyl 2-[(3-methyl-2,5-dioxo(3-pyrrolinyl))amino]-4-(trifluoromethyl)pyrimidine-5-carboxylate (EPC), an inhibitor of AP-1 and NF-kappa B mediated gene expression, based on calculated quantum chemical parameters. The quantum chemical parameters involved in the model are Kier and Hall index (order3) (KHI3), Information content (order 0) (IC0), YZ Shadow (YZS) and Max partial charge for an N atom (MaxPCN), Min partial charge for an N atom (MinPCN). The mean relative error of the training set, the validation set, and the testing set is 1.35%, 1.52%, and 2.23%, respectively, and the maximum relative error is less than 5.00%.

Carboxylic Acids↗
PubMedDate not supplied

Prediction of the isoelectric point of an amino acid based on GA-PLS and SVMs.

The support vector machine (SVM), as a novel type of a learning machine, for the first time, was used to develop a QSPR model that relates the structures of 35 amino acids to their isoelectric point. Molecular descriptors calculated from the structure alone were used to represent molecular structures. The seven descriptors selected using GA-PLS, which is a sophisticated hybrid approach that combines GA as a powerful optimization method with PLS as a robust statistical method for variable selection, were used as inputs of RBFNNs and SVM to predict the isoelectric point of an amino acid. The optimal QSPR model developed was based on support vector machines, which showed the following results: the root-mean-square error of 0.2383 and the prediction correlation coefficient R=0.9702 were obtained for the whole data set. Satisfactory results indicated that the GA-PLS approach is a very effective method for variable selection, and the support vector machine is a very promising tool for the nonlinear approximation.

Amino Acids↗
PubMedDate not supplied

An accurate QSPR study of O-H bond dissociation energy in substituted phenols based on support vector machines.

The support vector machine (SVM), as a novel type of learning machine, was used to develop a Quantitative Structure-Property Relationship (QSPR) model of the O-H bond dissociation energy (BDE) of 78 substituted phenols. The six descriptors calculated solely from the molecular structures of compounds selected by forward stepwise regression were used as inputs for the SVM model. The root-mean-square (rms) errors in BDE predictions for the training, test, and overall data sets were 3.808, 3.320, and 3.713 BDE units (kJ mol(-1)), respectively. The results obtained by Gaussian-kernel SVM were much better than those obtained by multiple linear regression, radial basis function neural networks, linear-kernel SVM, and other QSPR approaches.

Journal Article↗