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Biomedical subjects

M Wu

Publications and source records attributed to M Wu.

At least 595 records · Page 33Linked to original sources
PubMed1982

Malignant transformation of baby hamster lung fibroblasts induced in vitro by a new nitrosamine compound.

A new nitrosamine compound, N-1-methylacetonyl-N-3-methylbutyl-nitrosamine (MAMB-NA), isolated from corn bread inoculated with moulds commonly occurring in Linxian County, a high incidence area for esophageal cancer in North China was tested for its potential carcinogenicity in vitro. Baby hamster lung fibroblasts (BHL) were treated with MAMBNA in tissue culture medium containing liver microsome preparation of Aroclor 1254 treated rat. Cell transformation was assessed by morphological changes, loss of density-dependent inhibition and unlimited growth in vitro, chromosome changes, colony formation on soft agar, growth at low serum concentration, Con A agglutinability and tumor formation after heterotransplantation into immunosuppressed newborn rats. Like the known carcinogens N-methyl-N'-nitro-N-nitroso-guanidine and diethylnitrosamine, MAMBNA was able to cause malignant transformation of cells cultured in vitro.

Animals↗
PubMed1981

Transmission electron microscopic method for gene mapping on polytene chromosomes by in situ hybridization.

A transmission electron microscope method for gene mapping by in situ hybridization to Drosophila polytene chromosomes has been developed. As electron-opaque labels, we use colloidal gold spheres having a diameter of 25 nm. The spheres are coated with a layer of protein to which Escherichia coli single-stranded DNA is photochemically crosslinked. Poly(dT) tails are added to the 3' OH ends of these DNA strands, and poly(dA) tails are added to the 3' OH ends of a fragmented cloned Drosophila DNA. These probe--dA strands are hybridized in situ to polytene chromosome squashes. Gold spheres are linked to the hybridized probe--dA strands by A.T base pairing. The sphere positions relative to the chromosome bands can be observed by transmission electron microscopy. The method shows low background and high resolution.

Animals↗
PubMed1980

Sample sizes for long-term medical trial with time-dependent dropout and event rates.

A general model is formulated that allows for time-dependent dropout and event rates in the determination of sample sizes for long-term medical trials when a therapy group and a control group are to be compared. The need for time-dependent event (dropout) rate is illustrated by using the Framingham Heart Study Mortality data to estimate sample size for the NHLBI (National Heart, Lung, and Blood Institute) Multiple Risk Factor Intervention Trial (MRFIT). A further generalization of the model allows for participants who drop out of the control group (e.g., because of therapeutic measures prescribed by their own physicians) to return (or not return) to the control group at a later date. The question of unequal sample sizes for the therapy and the control groups is also discussed.

Clinical Trials as Topic↗
PubMed1980

Comparison of degrees of coronary arterial luminal narrowing determined by visual inspection of histologic sections under magnification among three independent observers and comparison to that obtained by video planimetry: an analysis of 559 five-millimeter segments of 61 coronary arteries from eleven patients.

The accuracy of determining degrees of luminal narrowing of 559 histologic sections from 61 human coronary arteries was evaluated by visual inspection under magnification (light microscopy) by three independent observers, and the results were compared to those obtained by video planimetry. With the per cent of cross-sectional area narrowing divided into four categories (0 to 25, 26 to 50, 51 to 75, and 76 to 100), both the extent of agreement between each independent observer and video planimetry, i.e., the accuracy of visual inspection under magnification and the extent of agreement among the independent observers, interobserver agreement, evaluated by the Kappa (K) statistic, were excellent. With a K value of 50 per cent indicating reasonably good agreement and values of greater than or equal to 70 per cent indicating strong agreement, the K values between the results of light microscopy and video planimetry by three observers were 61, 67, and 75 percent, respectively, and the extent of interobserver agreement was 72 per cent.

Arteriosclerosis↗
PubMed1979

Electron microscopic mapping of proteins bound to herpes simplex virus DNA.

Exonuclease digestion experiments have suggested that there is a protein(s) bound close to one or both ends of herpes simplex virus-1 (HSV) DNA. The existence of such bound proteins has been positively demonstrated and their positions on the HSV genome determined by application of a newly developed method for electron microscopic mapping of proteins bound to nucleic acids. Purified HSV DNA was treated with dinitrofluorobenzene under conditions that covalently attach the dinitrophenyl (DNP) group to the proteins in a protein-nucleic acid complex. The HSV DNA-protein-(DNP)n complex was treated with rabbit anti-DNP IgG, and, in some cases, additionally treated with monovalent Fab fragments of goat anti-rabbit IgG, and mounted for examination in the electron microscope. Electron opaque dots representing the protein-(DNP)n-(IgG)m complex were seen on the HSV DNA. Direct measurements of the positions of the protein, as well as partial denaturation mapping, indicate that there are four positions for protein bound to HSV DNA: two near but not at the two ends and two at sites corresponding to the internal inverted repeats of the ends. These results suggest that there is a specific protein binding sequence within the direct terminal repeat of HSV DNA. The previous observation that HSV DNA is more sensitive to digestion by a 3' than by a 5' exonuclease then indicates that the bound protein(s) is more intimately associated with one strand of the specific sequence than with the complementary strand.

Binding Sites↗
PubMed1979

Self-stimulation of the nucleus accumbens and ventral tegmental area of Tsai attenuated by microinjections of spiroperidol into the nucleus accumbens.

The contribution of dopaminergic neurons to self-stimulation of the ventral tegmental area, nucleus accumbens and prefrontal cortex was investigated. The ventral tegmental area is the site of non-striatal dopaminergic neurons and their axons project to the nucleus accumbens and prefrontal cortex. Injections of spiroperidol, a dopamine antagonist, into the nucleus accumbens significantly reduced self-stimulation of the ipsilateral ventral tegmental area but did not influence self-stimulation of the contralateral ventral tegmental area. Injections of spiroperidol into the prefrontal cortex did not reduce self-stimulation of the ipsilateral or contralateral ventral tegmental area. Electrical stimulation of sites in the nucleus accumbens positive for self-stimulation antidromically activated neurons of the ventral tegmental area, and a reduction of discharge of these neurons following administration of apomorphine suggested that they were dopaminergic neurons. These observations provide additional evidence implicating dopaminergic neurons in brain-stimulation reward and suggest that dopaminergic neurons contribute to self-stimulation of the nucleus accumbens but not the prefrontal cortex.

Animals↗
PubMed1979

Purification of a colony-stimulating factor from cultured pancreatic carcinoma cells.

Serum-free conditioned medium prepared from an established line of human pancreatic carcinoma (MIA PaCa-2) provides a rich source of colony-stimulating factor (CSF). Two activities distinctly separable by isoelectrofocusing have been identified: a high molecular weight CSF exhibiting greater activity in mouse bone marrow and a low molecular weight CSF more active in human bone marrow. The high molecular weight CSF has been purified 1000-fold to apparent homogeneity by a two-step procedure including isoelectrofocusing and gel filtration chromatography. The purified CSF has a molecular weight of 50,000 and an isoelectric point of 3.7 to 4.6. It is a glycoprotein as shown by periodic acid-Schiff stain and exhibits greater activity in mouse marrow than in human marrow.

Biological Assay↗
PubMed1979

Locomotor activity initiated by microinfusions of picrotoxin into the ventral tegmental area.

Ambulatory activity in rats was increased in a dose-related manner by microinjections of picrotoxin, a GABA antagonist, bilaterally into the ventral tegmental area. Microinjections of strychnine, a glycine antagonist, had no effect on activity. The ambulatory activity induced by microinjections of picrotoxin into the ventral tegmental area was significantly attenuated when the nucleus accumbens was pretreated with spiroperidol, a dopamine antagonist. These findings provide additional evidence that dopaminergic (A10) neurons projecting from the ventral tegmental area to the nucleus accumbens, contribute to locomotor activity. It is suggested that picrotoxin disinhibits the A10 dopaminergic neurons projecting to the nucleus accumbens.

Animals↗
PubMed1979

Electron microscopic mapping of RNA transcribed from the late region of polyoma virus DNA.

The polyoma virus (Py) RNA species transcribed from the L DNA strand of the "late" region of the Py genome in Py-infected mouse cells have been mapped by hybridization with specific fragments of Py DNA followed by electron microscopic visualization of the hybrids. Total cellular polyadenylated Py-specific RNA molecules having an S value in the range of 16S to 20S were purified by oligodeoxythymidylic acidcellulose column chromatography, preparative hybridization with Py DNA, and sucrose gradient centrifugation. Cytoplasmic Py-specific RNA was similarily purified, except that it was not fractionated by sucrose gradient centrifugation. Hybrids of these RNA molecules and Py DNA fragments were spread for electron microscopy by either the cytochrome c technique or the bacteriophage T4 gene 32 protein method. The polyadenylic acid at the 3'-end of the RNA in the hybrids was identified by labeling with simian virus 40 DNA circles to which polybromodeoxyuridylic acid tails had been covalently attached. These experiments revealed the presence of three L DNA strand transcripts in both RNA preparations. Two of these RNA molecules were found to be spliced from chains transcribed from two noncontiguous parts of the late region. The third molecule either is a continuous transcript of the entire late region or contains a splicing feature which is too small to be reliably observed by the electron microscope methods used. The 5'-ends of the three RNA species map within a region extending from 68 to 70 map units on the Py restriction endonuclease map. Each of the two spliced molecules contains a 5'-terminal leader sequence transcribed from a DNA segment with an estimated length of 60 to 110 nuvleotides. The 3'-ends of the leaders map at 66.7 +/- 1.0 and 66.4 +/- 0.50 map units. In these molecules the 5'-ends of the other part (the main body) map at 59.4 +/- 0.90 and 49.4 +/- 2.0 map units, respectively. The 3'-termini of all three RNA species map at 24 to 25 map units.

DNA, Viral↗