PubMed Health⌕ Search

Biomedical subjects

U Williams

Publications and source records attributed to U Williams.

6 recordsLinked to original sources
PubMed1988

Nucleophilic ring-opening in a carbohydrate nitrocyclopropane: a stereospecific approach to chiral isoalkyl structures.

Chemical reactions to open the cyclopropane ring in (1R)-1,2-dideoxy-3,4:5,6-di-O-isopropylidene-1,2-C-methylene-1-nitro-D-m annitol (1) were investigated. Catalytic hydrogenation over Pd-C produced the corresponding 1-amino compound, isolated as its N-acetyl derivative, but failed to cleave the ring. However, ring opening succeeded by nucleophilic addition of sodium thiophenoxide to 1, giving 1,2-dideoxy-3,4:5,6-di-O-isopropylidene-1-nitro-2-C- (phenylthio)methyl-D-mannitol. The latter reacted further with thiophenoxide to furnish phenyl 2-deoxy-3,4:5,6-di-O-isopropylidene-2-C-(phenylthio)methyl-D- mannothiohydroximate. Raney nickel converted both of these thio sugar derivatives into the same product, namely, 1-acetamido-1,2-dideoxy-3,4:5,6-di-O-isopropylidene-2-C-methyl-D-mannito l. The use of these transformations for the design of stereospecific syntheses of chiral isoalkyl structures is proposed.

Alkylation↗
PubMed1984

Selectivity of mixed-function oxygenase enzyme induction in flounder (Pseudopleuronectes americanus) collected at the site of the Baie Verte, Newfoundland oil spill.

A marked level of mixed-function oxygenase (MFO) enzyme induction was observed in kidney but not in liver tissues of winter flounder collected at the site of a spill of No. 2 fuel oil in Newfoundland. A number of MFO-linked, electron transport components including cytochrome P450, cytochrome P450 reductase and cytochrome b5 reductase were also slightly elevated in kidney tissues of fish at the oiled site. The results obtained in this particular field trial demonstrate that reliance on the measurement of liver MFO parameters alone could lead to false negatives in biological monitoring programs. The study also indicates that the exclusive use of liver tissues to investigate the induction potential of various chemicals should be avoided.

Animals↗
PubMed1981

Biosynthesized products of cultured neuroglial cells: I. Selective release of proteins by cells from human astrocytomas.

The proteins synthesized and released by human astrocytoma cells cultured with radiolabeled amino acids were analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and by trichloracetic acid precipitation. A select group of extracellular proteins was released from the astrocytomas. The most abundant extracellular proteins were at least 250,000 daltons. Five other major proteins (P 175, P 125, P 60, P 47, and P 40) were 175,000, 125,000, 60,000, 47,000, and 40,000 daltons, respectively. The complement of proteins retained by the cells was considerably more complex than those released. Clinical efforts to enhance the immunologic response directed against human astrocytomas must distinguish between extracellular and retained antigens. The pattern of proteins released by gliomas might be diagnostically useful if present in cerebrospinal fluid or serum.

Amino Acids↗
PubMed1969

Urinary excretion of glycosaminoglycans in the various forms of gargoylism.

The urinary excretion of glycosaminoglycans in 28 cases of gargoylism, embracing the Hurler, Hunter, Sanfilippo, Morquio, and Scheie syndromes (McKusick, 1966), has been examined using the cetylpyridinium chloride (CPC) turbidity test, the uronic acid/creatinine ratio, and the electrophoretic pattern of urine concentrates, as routine procedures. Ion-exchange column chromatographic techniques were also employed for the fractionation of glycosaminoglycans and aminosugars. Molecular weights were investigated by gel filtration and ultracentrifugation. The CPC turbidity test was positive in every case. The uronic acid/creatinine ratio provided a sensitive index of increased glycosaminoglycan excretion. Cases of the Hurler syndrome showed the highest, and cases of the Morquio and Scheie syndromes the lowest, ratios. A correlation was observed between the uronic acid/creatinine ratio and the clinical severity of the disease. Cellulose acetate electrophoresis differentiated clearly between the two major forms of gargoylism, the Hurler and Sanfilippo syndromes, but differentiation between the Hurler, Hunter, and Scheie syndromes was more difficult on electrophoretic data alone. Results obtained with cases diagnosed as the Morquio syndrome were disappointing. The existence of formes frustes of the Sanfilippo syndrome among the mentally subnormal is predicted. Errors caused by bacterial contamination of urine samples are emphasized. The atypical behaviour of urinary glycosaminoglycans in analytical procedures is discussed. Molecular weight studies suggested heterogeneity. The nature of the basic defect in gargoylism is discussed.

Adolescent↗