PubMed Health⌕ Search

Biomedical subjects

J J Krepinsky

Publications and source records attributed to J J Krepinsky.

At least 19 recordsLinked to original sources
PubMed1994

Measuring swainsonine in serum of cancer patients: phase I clinical trial.

Swainsonine, an indolizidine alkaloid and competitive inhibitor of Golgi alpha-mannosidase II (EC 3.2.1.114), reduces tumor growth and stimulates immune function in mice. On the basis of these observations, a phase I clinical trial was initiated to determine whether swainsonine could be administered safely to cancer patients. We describe a method for extraction, acetylation, and quantification of swainsonine in human serum samples. Methyl alpha-D-mannopyranoside and methyl beta-D-galactopyranoside were added to serum samples as internal standards and, after sequential extraction of lipids and proteins with chloroform and acetonitrile, respectively, samples were acetylated with acetic anhydride and 4-dimethylaminopyridine and separated by gas-liquid chromatography. The identity of swainsonine and the internal standards after their extraction from serum and acetylation was confirmed by gas chromatography/mass spectrometry. Swainsonine was recovered at an efficiency of 90%, relative to internal standards, and calibration graphs were rectilinear from 3 to 18 mg/L with a detection limit of approximately 0.1 mg/L. The CV for multiple samples was < or = 6.7%. In patients receiving swainsonine (50-550 micrograms/kg per day) continuously for 5 days by intravenous infusion, serum concentrations of the drug reached 3-11.8 mg/L, 100 to 400 times greater than the 50% inhibitory concentration for Golgi alpha-mannosidase II and lysosomal alpha-mannosidases. Accurate measurements of swainsonine in biological fluids with this method should facilitate further clinical studies with the drug.

Acetylation↗
PubMed1993

Isoglobotetraosylceramide is a marker for highly metastatic cells in rat mammary adenocarcinomas.

We have previously identified a neutral glycolipid antigen which appears to be a surface antigenic marker for the metastatic subpopulation in the R3230AC rat mammary adenocarcinoma (S.A. Carlsen, M. Barry, and K. Newton, Clin. Exp. Metastasis, 8: 141-151, 1990). In this article we describe the structural characterization of this glycolipid antigen. The sequence of the sugars in the saccharide portion of the molecule was determined by specific glycosidase cleavage and further confirmed by mass spectroscopic analysis. The nature of the linkages between the monosaccharide units was determined by methylation analysis. The final structure was confirmed by NMR analysis and found to be isoglobotetraosylceramide (GalNAc beta 1-3Gal alpha 1-3Gal beta 1-4Gle beta 1-O-ceramide). We also present evidence that the cells marked by this antigen have a higher metastatic potential than the cells lacking this glycolipid as measured by the formation of lung colonies after i.v. injection of the cells into the tail vein of the rat. Furthermore, isoglobotetraosylceramide seems to play a direct role in the metastatic process since the blocking of exposed antigen with monoclonal antibodies, or their Fab fragments, results in a highly significant decrease in lung colony formation.

Adenocarcinoma↗
PubMed1989

The involvement of dimethyl sulfoxide in a bacteriotoxic response of the Ames assay tester strains TA98 and TA100.

Dimethyl sulfoxide is a widely accepted and recommended solvent in which to dissolve compounds to be tested for mutagenicity via the Ames Salmonella/mammalian microsome assay. Using tester strains TA98 and TA100, we observed a bacteriotoxic response with various fractions isolated from beer when dissolved in DMSO but not when dissolved in water. Further characterization of the role of solvent in simple model systems consisting of butanol, DMSO and bacteria strongly suggests a chemical reaction occurs between dimethyl sulfoxide and specific chemical constituents of the test substance, nutrient broth, or the Ames bacterial strains. The result of such an interaction could be misinterpreted as a toxic response to the test substance when, in fact, the bacteriotoxicity could be due to another compound, chemically distinct from the test substance.

1-Butanol↗
PubMed1987

The effect of fecapentaenes on nuclear aberrations in murine colonic epithelial cells.

Fecapentaenes, human fecal mutagens of bacterial origin, were intrarectally administered to mice in suppository form. Despite the strong, positive mutagenic response of fecanpentaenes using Ames tester strains TA 98 and TA 100, no increase in nuclear aberrations, taken as a measure of genotoxicity in colonic epithelial cells, was observed over control levels. In fecapentaene treated animals, however, the incidence of mitotic figures was increased above control levels to values comparable to those observed in mice treated with the known colon carcinogen, N-ethyl-N-nitrosourea. Thus, it would appear that fecapentaenes are not cytotoxic to murine colonic epithelia as judged by the nuclear aberration assay.

Animals↗
PubMed1987

Solution conformation of the branch points of N-linked glycans: synthetic model compounds for tri'-antennary and tetraantennary glycans.

The solution conformation of model compounds for the tri'-antennary and tetraantennary (six-arm) branch point of N-linked glycans has been determined through the use of chemical shift, relaxation, and nuclear Overhauser enhancement data. The object was to establish the conformation about the glycosidic linkages in the N-linked substructure GlcNAc(beta 1,6) [GlcNAc(beta 1,2)] Man(alpha)- by estimation of values for the appropriate glycosidic torsional angles. The GlcNAc(beta 1,6) linkage in a trisaccharide model compound was found to be constrained to a narrow rotameric subpopulation about the substituted Man C5-C6 bond (omega = -60 degrees) and a narrow range of possible phi - psi values. Free rotation about the Man C5-C6 bond was obstructed by unfavorable steric interactions between the GlcNAc(beta 1,6) and GlcNAc(beta 1,2) residues. A phi, psi value of 55 degrees, 190 degrees was found to be consistent with the NMR data for the GlcNAc(beta 1,6) linkage. However, the value of psi appears to be "virtual" in that the molecule is in equilibrium between two different values (90 degrees and 252 degrees). For the GlcNAc(beta 1,2) linkage, complete agreement between all the observed NMR parameters and all the calculated ensemble average values could only be obtained with a set of potential energy functions which included hydrogen bonding. Other choices of potentials yielded calculated values that disagreed with at least two of the observed quantities. As a result, we infer that an interresidue hydrogen bond is formed, and we find it to be between the GlcNAc(beta 1,2) ring oxygen and the Man C3 hydroxyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Conformation↗
PubMed1986

Specific deuteration of a trimannoside confirms the existence of a disputed interresidue nuclear Overhauser enhancement.

The relative orientation of the 3-arm of N-linked glycans in solution can be determined, in part, by two interresidue nuclear Overhauser enhancements. The existence of one of these enhancements, that observed to the H5 proton of the (alpha 1,3)-linked mannose (attached to the core beta-linked mannose) upon irradiation of the beta-linked mannose H2 proton, has been disputed by other investigators (Homans, S. W., Dwek, R. A., Fernandes, D. L., and Rademacher, T. W. (1983) FEBS Lett. 164, 231-235). To demonstrate unequivocally the existence of this interresidue enhancement, we have synthesized a mannotrioside to model the corresponding moiety in N-linked glycans. Just as in N-linked glycans, the disputed enhancement cannot be directly observed due to spectral overlap with other enhancements but is detectable by careful quantitative analysis. By employing specifically deuterated derivatives of the mannotrioside, however, the disputed enhancement can be directly visualized.

Magnetic Resonance Spectroscopy↗
PubMed1986

Characterization of cytotoxic steroids in human faeces and their putative role in the etiology of human colonic cancer.

It has been shown previously that chemically induced nuclear abeerrations in the murine colon are correlated with the carcinogenicity of the respective chemicals. Consequently, the nuclear aberration assay was utilized for the identification of putatife carcinogens in human faeces. Human fecal samples were fractionated by several chromatographic methods, and the assay led to the isolation of two substances. A combination of spectroscopic (mass, nuclear magnetic resonance, ultraviolet, and infrared) and chromatographic (HPLC and GLC) methods showed that they are 5-alpha- cholestan-3-one (I) and cholest-4-en-3-one (II). A number of C-27-C-30 steroids isolated from closely related fractions of feces were inactive in this assay. Thus I and II could play a role in etiology of large bowel cancer in humans.

Animals↗
PubMed1984

A model study of fecapentaenes: mutagens of bacterial origin with alkylating properties.

Fecapentaene-14 and -12 are directly acting mutagens that do not require metabolic activation. Their unusual structure suggests a possible mechanism of action. A carbocation that is formed by the addition of an electrophilic species (such as a proton) to the enol ether is most probably the reactive species. A series of model enol ethers with conjugated systems of various lengths was prepared, and a correlation between mutagenicity and increasing reactivity of derived carbocations was found. The glycerol moiety does not play a crucial role in the overall reactivity of the fecapentaenes.

Alkylating Agents↗
PubMed1984

On distribution of different fecapentaenes, the fecal mutagens, in the human population.

It has been shown by an HPLC analysis using a quarternary solvent mixture in an isocratic mode that human excretors of these fecal mutagens excrete both fecapentaene -12 and -14 but the ratios vary greatly between individuals. Since these mutagens are produced by the bacterial flora of the colon, this may indicate differences in the flora between these individuals or differences in the availability of different precursor molecules in their colons. Any relationship of these findings to the etiology of colonic cancer is not clear.

Adult↗
PubMed1983

Colonic mucus in human fetal development.

The labelling behaviour of specimens of human fetal colon at different stages of development was examined using eight fluorescently labelled lectins with preferences for different carbohydrate structures. Peanut agglutinin (PNA) binding can be demonstrated in specimens from fetal colons between the 4th and 5th week and the 5th and 6th lunar month. Since CEA may bind to similar structures as PNA, an answer was sought to the question whether these structures are in fact identical. While there is evidence in favour of non-identity, it is not entirely conclusive. PNA-binding to fetal tissues is of interest since PNA binds to adult transformed colonic tissues, but not to normal ones.

Antigens, Neoplasm↗
PubMed1982

Syntheses of model oligosaccharides of biological significance. Synthesis of methyl 3,6-di-O-(alpha-D-mannopyranosyl)-alpha-d-mannopyranoside and the corresponding mannobiosides.

Methyl 2-O-allyl-4,6-O-benzylidene-3-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl) -alpha-D-mannopyranoside (12) was prepared in 90% yield by Helferich glycosylation of methyl 2-O-allyl-4,6-O-benzylidene-alpha-D-mannopyranoside (9) with tetra-O-acetyl-alpha-D-mannopyranosyl bromide (11). Removal of the benzylidene group and second Helferich glycosylation with 11 led to methyl 2-O-allyl-3,6-di-O-(2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl)-alpha-D-mannopyranoside (14) which, after deallylation and Zemplén deacetylation, gave the title compound 5. The disaccharides methyl 3-O-(alpha-D-mannopyranosyl)-alpha-mannopyranoside (7) and methyl 6-O-(alpha-D-mannopyranosyl)-alpha-D-mannopyranoside (6) have also been synthesized. Complete assignments of the 1H-n.m.r. spectra of the compounds 5, 6, and 7 are given.

Carbohydrate Conformation↗