Search PubMed⌕ Search

Biomedical subjects

N Schwartz

Publications and source records attributed to N Schwartz.

At least 37 records · Page 2Linked to original sources
PubMed1983

Immunological evidence for two distinct chondroitin sulfate proteoglycan core proteins: differential expression in cartilage matrix deficient mice.

The expression and core protein structure of two proteoglycans, the major cartilage proteoglycan isolated from a rat chondrosarcoma and a small molecular weight chondroitin sulfate proteoglycan isolated from a rat yolk sac tumor, have been compared. The cartilage proteoglycan was not detectable in the cartilage tissue of cartilage matrix deficient (cmd/cmd) neonatal mice by immunofluorescence, but the cmd cartilage did react with antibodies against the core protein of the yolk sac tumor proteoglycan. Radioimmunoassays showed that the core proteins of these proteoglycans are not cross-reactive with each other. Analysis of the core proteins by sodium dodecyl sulfate/polyacrylamide gel electrophoresis after chondroitinase ABC treatment of the proteoglycan revealed a large difference in their sizes. The cartilage proteoglycan core protein had a molecular weight of about 200,000 while the yolk sac tumor proteoglycan core protein migrated with an apparent molecular weight of about 20,000. In addition, the cultured yolk sac tumor cells that make the small proteoglycan did not react with antiserum against the cartilage proteoglycan. These results indicate that the proteoglycan isolated from the yolk sac tumor is similar to the small chondroitin sulfate proteoglycan species found in cartilage and support the existence of at least two dissimilar and genetically independent chondroitin sulfate proteoglycan core proteins.

Animals↗
PubMed1983

Analysis at the sequence level of mutations induced by the ultimate carcinogen N-acetoxy-N-2-acetylaminofluorene.

The covalent binding of an ultimate carcinogen to the DNA bases or phosphate groups creates a premutational lesion that in vivo is processed by the repair, replication and recombination enzymes, and eventually may be converted into a mutation. Being interested in the way that an initial premutational event is converted into a stable heritable mutation, we have sequenced stable mutations in a gene that has formed covalent adducts in vitro with N-acetoxy-N-2-acetylaminofluorene (N-AcO-AAF, a model for the ultimate metabolite of the rat liver carcinogen 2-acetylaminofluorene, AAF). In vivo studies have shown the mutagenicity of AAF and its derivatives in both bacterial and eukaryotic systems. N-AcO-AAF reacts in vitro with DNA leading mainly to the formation of a guanine adduct, N-2-(deoxyguanosin-8-yl)-acetylaminofluorene (80%) and to at least three minor adducts. Studies by our group showed that binding of N-AcO-AAF to DNA resulted in a local distortion of the DNA helix around the C-8 adduct (the insertion-denaturation model). We describe here the analysis of forward mutations induced in the tetracycline-resistance gene of pBR322 by directing the chemical reaction of the carcinogen to a small restriction fragment (BamHI-SalI) inside the antibiotic-resistance gene. Mutants are selected for ampicillin (Ap) resistance and tetracycline (Tc) sensitivity. The plasmid DNA of such mutants was analyzed for sequence changes in the fragment where the AAF binding had been directed. We show here that the mutations are mainly frameshifts involving GC base pairs and that certain base pairs (hotspots) are affected at high frequencies.

2-Acetylaminofluorene↗
PubMed1981

Preliminary findings on psychiatric patients as research participants: a population at risk?

To determine whether hospitalized mentally ill patients expose themselves to research with high risks more often than hospitalized nonpsychiatric patients, the authors asked patients from both groups if they would be willing to participate in a series of hypothetical research studies. The mentally ill patients did not agree to participate in studies of either high or low risk more frequently than nonpsychiatric patients. Both groups tended to agree to low-risk/high-benefit studies more often than high-risk/low-benefit studies. Although Brief Psychiatric Rating Scale scores clearly differentiated between psychiatric and nonpsychiatric patients, psychopathology did not correlate with willingness to participate in any of the studies.

Humans↗
PubMed1978

2-Pyrrolidinylideneureas, a new class of central nervous system agents.

A series of N-aryl-N'-(1-methyl-2-pyrrolidinylidene)ureas was prepared and screened for pharmacological activity. Congeners possessing either phenyl or phenyl substituted with 4-nitro, 3-bromo, 3-chloro, 3-fluoro, and 3-methyl groups were found to demonstrate anxiolytic activity. 2,6-Disubstitution of the phenyl ring with methyl, chloro, and bromo imparted potent muscle-relaxant properties which appear to be centrally mediated. A significant separation of the anxiolytic and muscle-relaxant properties from other CNS activities, e.g., anticonvulsant, sedative, and hypnotic, was achieved.

Animals↗
PubMed1978

Effect of uremia on tumor growth in mice.

Outbred Swiss mice of the Hebrew University strain were subtotally nephrectomized. The experimental and control animals were both divided into two subgroups, with one group kept on a regular animal house diet and one on a low-protein diet. All the animals were injected with Ehrlich's ascites tumor cells s.c. into the neck region. Two weeks later, the animals were killed and the tumor was excised and weighed to the nearest milligram. Tumor size in the uremic animals--the nephrectomized animals kept on a regular diet--was significantly smaller than in all other groups, which had blood urea nitrogen levels well within the normal range. It is suggested that urea may be a factor responsible for inhibiting tumor growth.

Animals↗