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Biomedical subjects

Y Ma

Publications and source records attributed to Y Ma.

At least 595 records · Page 33Linked to original sources
PubMed1989

The 9-fluorenylmethyloxycarbonyl group as a 5'-OH protection in oligonucleotide synthesis.

Oligo-DNAs are synthesized on a solid support using the 9-fluorenylmethyloxycarbonyl group as a 5'-OH base labile protection. The synthesis of the pure protected nucleotides, a relevant phosphoramidite-type strategy of coupling, and the optimization of the deprotection steps are described. This new synthetic method is an alternative to the standard protocol that avoids acidic conditions.

Chromatography, High Pressure Liquid↗
PubMed1989

Expression of ras oncogene p21 during human fetal development as determined by monoclonal antibodies RAP-5, Y13-259, and DWP.

In this report we describe the expression of the ras proto-oncogene p21 protein in various tissues during normal fetal development. Conventional, formalin fixed and paraffin-embedded sections of normal organs were examined from fetuses ranging 9 to 42 weeks of gestation. Immunohistochemical localization of ras p21 was accomplished using the broadly reactive, mouse monoclonal antibodies RAP-5 and Y13-259. The monoclonal antibody DWP, which is specific for a mutated form of ras p21 having a valine/cysteine at amino acid position 12, was also used. Detectable expression of the p21 protein was seen at different time periods during fetal development depending on the tissue. The expression of ras p21 (as detected by RAP-5 and Y13-259) was noted in a wide range of cell types and tissues; intense immunostaining was noted in epithelial cells of the gastrointestinal tract, exocrine and endocrine pancreas, renal tubules and transitional urotheliem, as well as in other tissues. This immunostaining generally, but not invariably, corresponded with patterns previously reported in benign and/or malignant neoplasms of adult tissues. In most instances ras p21 expression, when present, occurred during periods of rapid growth in given organ systems. However, some actively proliferating fetal tissues such as thymus and spleen, failed to express detectable ras p21 suggesting that factors other than cell cycle may influence its expression. No reactivity with DWP was noted in any of the tissues, suggesting that the mutated forms detected by this monoclonal antibody are not expressed during normal human embryogenesis. These data show that there is regulated expression, and broad distribution of this gene product in normal developing human fetal tissue.

Antibodies, Monoclonal↗
PubMed1989

Immunohistochemical analysis of normal and mutated ras oncogene p21 expression in human pulmonary and pleural neoplasms.

In this study we examined 214 cases of primary human pulmonary neoplasms for the expression of a mutated form of the ras oncogene p21 product, recognized by the monoclonal antibody (MCA) DWP. Adjacent serial sections from these same cases had previously been used to demonstrate the frequency of ras p21 expression using the broadly reactive anti-ras p21 MCA RAP-5. Confirmation of the increased expression of p21 was accomplished using MCA Y13-259. The use of adjacent tissue sections from these cases allows the direct comparison of the expression of the mutated and non-mutated forms of ras p21. If reactivity with DWP would prove to be significantly more restrictive than that of the "pan" ras MCAs, RAP-5 and Y13-259, it would lend support to the possibility that DWP (and similar MCAs which detect other specific mutations) could be used to define subsets of these neoplasms based on their specific ras p21 phenotype. Since one would anticipate that the valine/cysteine substitution at position 12 of the ras p21 would occur at only low frequencies in human tumors, our results with DWP are consistent with this hypothesis. As previously reported, RAP-5 reacted with a high proportion of lung tumors (100/214 or 47%). In this report, we demonstrate the selective expression of the mutation recognized by the MCA DWP in only 5% of these same tumors (13/214), and that the expression of this mutated form is not restricted to any of the conventional histological subclasses of pulmonary neoplasms.

Antibodies, Monoclonal↗
PubMed1989

An ESR study of radical kinetics in L-alpha-amino-n-butyric acid hydrochloride containing L-cysteine hydrochloride.

On annealing at temperatures near 100 degrees C, carbon-centered radicals migrate to sulfur-centered radicals in X-irradiated crystals of L-alpha-amino-n-butyric acid hydrochloride, CH3CH2CH(NH3-Cl)COOH, containing L-cysteine hydrochloride, SHCH2CH(NH3Cl)COOH. Samples containing 0, 0.5, 1.0, and 1.5% L-cysteine hydrochloride were studied. When no cysteine is present, the carbon-centered radical formed by X irradiation, CH3CH2CHOOH, decays according to a second-order diffusion-controlled rate equation. In samples containing cysteine, the same carbon-centered radicals are formed, but on annealing, they migrate to cysteine, where a perithiyl radical, RSS, is formed. The transfer of carbon-centered radicals to perthiyl radicals follows a pseudo first-order rate equation with an activation energy of 1.15 eV. A decrease in the initial concentration of the carbon-centered radicals or an increase in the initial concentration of cysteine results in an increase in the transfer efficiency. The rate of growth of the perthiyl radical depends on both the initial concentration of cysteine and the initial concentration of carbon-centered radicals. The pseudo first-order rate constant increases when either the initial carbon-centered radical concentration increases or the initial cysteine concentration increases. The mechanism by which radicals move from one lattice site to another in the crystalline material is most likely hydrogen abstraction from a neighboring molecule.

Aminobutyrates↗
PubMed1988

Pleomorphic carcinoma of the pancreas with osteoclast-like giant cells expressing an epithelial-associated antigen detected by monoclonal antibody 44-3A6.

This article describes a case of pleomorphic adenocarcinoma of the pancreas, metastatic to the adrenal glands and liver, that has unique cytological and histological features. Cytology demonstrated numerous mononuclear and multinucleated tumor giant cells as well as numerous osteoclast-like giant cells. These features were also seen in the histological sections, as were numerous clear cells. Electron microscopy demonstrated features suggesting an epithelial origin of the epulis cells. Prominent immunoreactivity with the monoclonal antibody (MCA) 44-3A6 of these cellular constituents was seen in the aspirate and in the tissue sections. These data provide further evidence to support the epithelial origin of these cellular components.

Adenocarcinoma↗
PubMed1988

Expression of the antigenic determinant recognized by the monoclonal antibody 44-3A6 on select human adenocarcinomas and normal human tissues.

The IgG1 monoclonal antibody, 44-3A6, was raised against the human lung adenocarcinoma cell line, A549. It has been shown to react with a 40,000 MW protein found on the cell surface, which is preserved in formalin-fixed paraffin-embedded tissues. A recent study of pulmonary carcinomas utilizing immunohistochemical methods showed exclusive binding to lung adenocarcinomas, subsets of neuroendocrine tumors, some carcinoids and a subset of large cell carcinomas. Reactivity was not seen in squamous cell carcinomas and small cell neuroendocrine carcinomas. In addition, melanomas, sarcomas and hematologic malignancies do not express this antigen. We now report on the reactivity pattern of 44-3A6 in adenocarcinomas of nonpulmonary primary sites and in normal adults organs. Strong diffuse staining of neoplastic cells in adenocarcinomas of the stomach, colon, pancreas, gallbladder and breast was noted. Adenocarcinomas arising in the endometrium, ovary, kidney, prostate, thyroid and liver were either negative or showed weak and/or focal reactivity. Strong staining patterns were even noted in adenocarcinomas which had an 'undifferentiated' component; i.e., lacking well-defined glandular elements. Immunoreactivity was noted in epithelial cells in several tissues from which these adenocarcinomas arose including the bronchial tract, stomach, small intestine, pancreas and colon, whereas epithelial cells from the endometrium, kidney, ovary, prostate and thyroid were negative or showed diffuse weak immunoreactivity. Our finding indicate that monoclonal antibody 44-3A6 recognizes an epithelial antigen on subsets of normal as well as transformed glandular epithelia. The differential pattern of expression of its target antigen probably reflects differences in tumor genesis and/or differentiation.

Adenocarcinoma↗
PubMed1988

An ESR study of the radicals in X-irradiated L-alpha-amino-n-butyric acid HCl containing 1.5% L-cysteine HCl.

After X-irradiation at room temperature, the radicals in L-alpha-amino-n-butyric acid HCl are CH3CH2CHCOOH. The beta- and alpha-hyperfine constants are typical of those found in amino acid radicals. On annealing at temperatures near 100 degrees C this carbon-centered radical in samples containing 1.5% cysteine converts to a perthiyl radical, RCH2S(1)S(2). The g-values for the perithiyl radical are 2.0024, 2.0257, and 2.0557. When the field is in the minimum g-value direction, the hyperfine splittings are 50 G for 33S(2) and 32 G for 33S(1).

Aminobutyrates↗
PubMed1988

Investigations on methyl mercury contamination of fishes in the Second Songhua River.

Fishes in the middle reaches of the Second Songhua River in Jilin Province were heavily contaminated by methyl mercury, the average content of 61 fish samples being 0.42 mg/kg. The upper and lower reaches were less contaminated and the averages were 0.12 mg/kg (53 samples) and 0.08 mg/kg (20 samples), respectively. The average methyl mercury content of fishes (20 samples) collected from a nearby "nonpolluted" water reservoir was 0.03 mg/kg. In a total of 134 fish samples collected from the Second Songhua River, 41% of the samples had a methyl mercury content exceeding the National Tolerance Limit of 0.2 mg/kg.

Animals↗