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Biomedical subjects

M Yan

Publications and source records attributed to M Yan.

At least 109 records · Page 6Linked to original sources
PubMed1995

[Effects of glucocorticoid on PMN adhesion induced by TNF].

TNF was used as a stimulating factor to study the effects of glucocorticoid (GC) on polymorphonuclear leucocyte (PMN) adhesion. The results showed that tumor necrosis factor (TNF) could increase the PMN adhesion markedly, and Dex could not inhibit the PMN adhesion induced by TNF, but it had a certain effect of prevention. PMN adhesion was increased prominently when Dex and RU 38486 were given after TNF pretreatment.

Animals↗
PubMed1995

The analysis of disparity evoked potentials by a new form of static random-dot stereograms.

PURPOSE: A new form of static random-dot stereograms free of monocular clues was designed as stimulus to elicit disparity evoked potentials. METHODS: Disparity evoked potentials were recorded in 40 stereo-normal subjects. The stimulator was a white-black static random-dot stereograms generated by a computer and had no monocular clues. Every subject was tested in disparity stimulus, zero disparity stimulus, monocular stimulus and wearing prism condition. RESULTS: A characteristic wide positive wave at about 250 ms was consistently recorded in disparity stimulus, which may be regarded as evidence of the presence of stereopsis. In contrast, recordings for zero disparity stimulus, monocular vision, stimulus and wearing prism condition all demonstrated a markedly difference from recording for disparity stimulus.

Adolescent↗
PubMed1995

[Changes of intestinal flora in senile mouse models and the antagonistic activity of the root of Astragalus membraceus (Fisch) Bge].

Inhaled by mice, ozone induced stronger free radical reaction in the organism and led to a series of changes similar to senility. In this way the senility mouse models were established to observe the changes of intestinal flora in senile mice. The senile mice were given the root of Astrogolus membraceus decoction orally. The results showed that the imbalance of intestinal flora in these mice was recovered.

Aging↗
PubMed1994

Crystal structure of recombinant farnesyl diphosphate synthase at 2.6-A resolution.

The synthesis of farnesyl diphosphate (FPP), a key intermediate in the isoprenoid biosynthetic pathway required for the synthesis of cholesterol and in the formation of prenylated proteins, is catalyzed by the enzyme farnesyl diphosphate synthase (FPS). The crystal structure of avian recombinant FPS, the first three-dimensional structure for any prenyltransferase, was determined to 2.6-A resolution. The enzyme exhibits a novel fold composed entirely of alpha-helices joined by connecting loops. The enzyme's most prominent structural feature is the arrangement of 10 core helices around a large central cavity. Two aspartate-rich sequences that are highly conserved among the isoprenyl diphosphate synthase family of prenyltransferases, and are essential for enzymatic activity, were found on opposite walls of this cavity, with the aspartate side chains approximately 12 A apart and facing each other. The location and metal ion binding properties of these sequences suggest that the conserved aspartate residues participate in substrate binding of catalysis.

Alkyl and Aryl Transferases↗
PubMed1994

Identification of 2 serine residues of MEK-1 that are differentially phosphorylated during activation by raf and MEK kinase.

The signal transduction kinase MEK (mitogen-activated protein (MAP) or extracellular signal-regulated (Erk) kinase)-1 is activated via phosphorylation by MEKK (MEK kinase) and raf kinases. We show here that these two kinases phosphorylate rat MEK-1 exclusively on two serine codons, Ser218 and Ser222. Phosphorylation of MEK-1 on serines 218 and 222 is both necessary and sufficient for MEK-1 to be activated and able to phosphorylate MAP kinase. A mutant form of MEK-1 that replaces these two codons with alanine cannot be activated, and one that substitutes glutamic acid residues in place of these 2 serines is active independent of activation by phosphorylation. These sites of activation occur in a region of MEK-1 that is similar to sites of activating phosphorylation in several other serine/threonine kinases, suggesting that this region may represent a conserved "activating domain" of many kinases. MEKK and raf display differences in site preference between these two codons, with MEKK showing preference for the amino acid at codon 218 and raf phosphorylating each residue approximately equally. This site preference might result in differences in the temporal or subsequent substrate patterns of MEK activation that result from these two activation pathways.

Amino Acid Sequence↗
PubMed1994

[Effects of dl-tetrahydropalmatine on blood pressure and norepinephrine and epinephrine contents in peripheral tissues].

Administration of dl-tetrahydropalmatine (THP) i.v., ip, and ig lowered the pressure and concurrently slowed the heart rate in anesthetized rats. The hypotensive and bradycardic effects were not produced by injecting THP into the vertebral artery in anesthetized rabbits. These results suggest that the site of hypotensive action of THP may not be a central one. The HPLC coupled with electrochemical detection showed that the contents of norepinephrine (NE) in the heart, aorta, and femoral artery and epinephrine (E) in the adrenal gland were markedly reduced by THP (P < 0.01). A positive correlation was found between the hypotensive effect and the reduction of NE in the aorta and femoral artery (r = 0.97, P < 0.01).

Animals↗
PubMed1994

[Immunohistochemical study and treatment result of small cell lung carcinoma using combination chemotherapy].

Sixty eight cases of small cell lung carcinoma (SCLC) were treated with Combination chemotherapy regimen of COCE or COMP. Among them, 22 cases received radiotherapy after chemotherapy, and 14 cases were studied with antibodies of NSE (neuron-specific enolase), CCH-A (chromogranin A), CEA (carcino-embryonic antigen) and keratin using an immunohistochemical ABC method. The total remission rate was 58.8% and the MST was 12.8 months. The CR+PR of COCE treated group was 74.3% and the MST was 12.9 months. The CR+PR of COMP treated group was 37.8% and the MST was 10 months. There was statistically significant difference between results of the COCE and COMP-treated groups. The MST of cases who received radiotherapy after chemotherapy was 15 months (COCE 17.3 months, COMP 12 months). It indicated that COCE regimen was more effective than COMP one. The immunohistochemical result showed that 44.4% (6/14) of the cases were positive with NSE and/or CCH-A, and their MAT was longer than that of NSE and/or CCH-A negative cases. It suggests that SCLC with neuroendocrine differentiation has a better prognosis.

Adult↗
PubMed1994

The influence of hydration on the absolute yields of primary free radicals in gamma-irradiated DNA at 77 K. II. Individual radical yields.

In this report we present an electron spin resonance (ESR) investigation of the yields of the individual free radicals formed in gamma-irradiated frozen DNA as a function of hydration and dose at 77 K. Analysis of the ESR spectra taken at low hydration shows that the ion radical composition remains nearly constant with dose and that few secondary radicals are formed even at high doses (above about 50 kGy). For fully hydrated samples, the radical composition changes dramatically with dose. Thymine anion radical (T-.) is found in abundance at low doses but nearly disappears at higher doses, with a corresponding increase in the N-3 deuterated cytosine anion radical (CD.). Guanine cation radical (G+.) decreases at high doses, with a concomitant increase in secondary radical species (S.). Analysis of the dose-response data for G values (the yields in microM/J), k values (the destruction constants) and k' values (a new constant that characterizes the change in G with dose) was performed for each of the DNA base free radicals present at 77 K. The G value for each of the base radicals increases with the hydration level. The k values for CD. and G+. increase slightly with hydration; however, that of T-. increases substantially. Destruction constants for neutral radicals such as TH. and CD. are found to be substantially smaller than those for ion radicals and provide an indication of the radical charge state. A negative k' value for T-. and a positive k' value for CD. are explained in terms of radiation effects that result in the formation of a deuterated cytosine base, i.e., C(N3)D+, which greatly increases cytosine's electron affinity. The ratio of anion radical to cation radical concentrations is found to be about 1.6 and is invariant with hydration. A speculation on the imbalance based on hole-hole combinations in spurs is presented.

DNA↗