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Biomedical subjects

I Jardine

Publications and source records attributed to I Jardine.

At least 55 records · Page 3Linked to original sources
PubMed1982

Evidence for a monoglucuronide of 1,25-dihydroxyvitamin D3 in rat bile.

We have isolated and characterized a monoglucuronide fraction of 9,10-secocholesta-5,7,10(19)triene-1 alpha, 3 beta, 25-triol, 5,6-cis isomer (1,25-dihydroxyvitamin D3) from rat bile. Polar radioactive metabolites of 1,25-dihydroxyvitamin D3 were purified by a sequence of chromatographic procedures which utilized Amberlite XAD-2, diethylaminohydroxypropyl Sephadex LH-20, liquid-liquid partition on paper, and reverse phase chromatography on C-18 microparticulate columns. A purified radioactive substance showed maximal absorbance at 264 nm, indicating the presence of a triene in the 5,6-cis configuration. Mass spectrometry by fast atom bombardment of the product demonstrated an ion at m/z 637 atomic mass units that is consistent with a natriated sodium salt of a monoglucuronide of 1,25-dihydroxyvitamin D3 ([MNa]Na+). Following methylation of the carboxylic acid group and formation of trimethylsilyl ethers of the hydroxyl groups, the fragmentation pattern of the product was compatible with that of a monoglucuronide of 1,25-dihydroxyvitamin D3. The intact metabolite was treated with beta-glucuronidase and the aglycon was isolated by chromatography on microparticulate silica. The aglycon co-migrated with authentic 1,25-dihydroxyvitamin D3 during chromatography and it gave a mass fragmentation pattern consistent with 1,25-dihydroxyvitamin D3. The aglycon was bound by an intestinal cytosol receptor with essentially the same affinity as 1,25-dihydroxyvitamin D3. These findings indicate that bile contains a monoglucuronide of 1,25-dihydroxyvitamin D3.

Animals↗
PubMed1982

Presence of plasma branched-chain fatty acids in multineuronal degeneration, hepatosplenomegaly and adrenocortical insufficiency.

We have previously reported a unique disorder in two brothers with multi-system neuronal degeneration, hepatosplenomegaly and adrenocortical deficiency. The clinical features were different from Refsum's disease. Biochemical analysis suggested that a metabolic defect of the omega 6 polyenoic fatty acid pathway may be involved. In the present study, were have further identified by gas chromatography-mass spectrometry two branched-chain fatty acids, phytanate and pristanate, in these two patients' plasma. This small, but unequivocally elevated elevated amount of branched-chain fatty acids were primarily localized in the triacylglycerols of plasma low density lipoprotein. Such branched-chain fatty acids were not detected in skin, liver and sural nerve samples. These two cases may represent an alternative metabolic error to that found in Refsum's disease leading to phytanate accumulation.

Adrenal Cortex Diseases↗
PubMed1982

Synthesis, 470-MHz 1H NMR spectra, and activity of delactonized derivatives of the anticancer drug etoposide.

The anticancer drug etoposide (VP 16-213, 1) contains a highly strained trans-fused gamma-lactone. This functionality is readily metabolized to an inactive ring-opened hydroxy acid (2). To prevent this detoxification of the drug and to investigate whether the lactone is essential for drug activity, we synthesized a cyclic ether analogue of etoposide (3) and tested it in the mouse leukemia L1210 system in vitro and in vivo. This ether analogue of etoposide was found to retain activity in the L1210 system, but the activity was reduced relative to the parent drug. A synthetic intermediate, the ring D opened diol of the reduced lactone (4), was also tested and found to be inactive in the L1210 system. The complete 470-MHz 1H NMR spectra of etoposide and its derivatives are reported. The usefulness of introducing deuterium at C-13 to determine J2,3 is also demonstrated. This coupling constant is characteristic of cis or trans stereochemistry across the C-D ring fusion.

Animals↗
PubMed1981

Metabolism of 6-thiopurines. I. Irreversible binding of a metabolite of 6-thiopurine to mammalian hepatic protein in vitro.

Irreversible binding of a metabolite of 6-thiopurine to mammalian hepatic protein was demonstrated in vitro. Protein binding occurred with rat, hamster, rabbit, pig and human liver microsomes in the presence of NADPH and oxygen. The involvement of the cytochrome P-450 system in the activation of 6-thiopurine to the chemically reactive metabolite was supported by the effects of inhibitors of cytochrome P-450 mediated reactions and phenobarbital induction. The binding of the metabolite appeared to be through formation of a mixed disulfide between 6-thiopurine and protein thiols. In the presence of thiols such as glutathione, the irreversible protein binding of 6-thiopurine was inhibited. No significant binding of 6-thiopurine to other tissues was observed in vitro with rats.

Animals↗
PubMed1981

Metabolism of 6-thiopurines. II. Covalent binding of a 6-thiopurine metabolite to mammalian tissue protein in vivo.

After injection of 6-thio[8-14C]purine i.p. in rats or rabbits radioactivity was shown to be irreversibly bound to protein of all tissues examined except brain. The binding increased with time after a single injection and increased nonlinearly in response to dose. Binding per milligram of protein was most extensive in intestine, spleen and liver. Binding in liver was primarily to microsomal protein with no binding detected in microsomal nucleic acid. Hepatic microsomal protein binding increased in rats fed a protein-free diet to deplete the hepato-cellular glutathione concentration. Binding to hepatic microsomal protein was decreased by pretreatment with phenobarbital or piperonyl butoxide, but not significantly with allopurinol. 6-Thiopurine at therapeutic doses had no apparent negative effects on either hepatocellular glutathione levels or hepatic microsomal aminopyrine N-demethylase activity during this time period. These observations may be significant regarding reported toxic side effects associated with 6-thiopurine.

Animals↗
PubMed1980

Analysis of the anticancer drugs VP 16-213 and VM 26 and their metabolites by high-performance liquid chromatography.

A rapid and convenient high-performance liquid chromatographic procedure for the analysis of the clinically useful anticancer agents VP 16-213 and VM 26 is described. The drugs, which are semi-synthetic derivatives of the natural product podophyllotoxin, are extracted from plasma with chloroform. The extracts are evaporated to dryness, reconstituted in methanol, and chromatographed on a reversed-phase microparticle C18 column using isocratic elution with a mixture of methanol--water (60:40). Each drug is used as the internal standard for the other. Quantitation to 500 ng/ml (0.85 nmole/ml) plasma is based on peak height ratios using UV detection at 254 nm. Patient plasma concentration versus time data agree well with previously published data obtained using radiolabelled drug. Investigations into the nature of the hydroxy acid metabolite of VP 16-213, carried out using paired-ion chromatography with tetrabutylammonium bromide and fluorescence detection, are described. Also, a unique separation of VP 16-213 and a possible metabolite, the isomer, picro VP 16-213, is described.

Adult↗
PubMed1978

Cytochrome P-450 dependent irreversible binding of 6-thiopurine to rat liver microsomal protein in vitro and protection by glutathione.

6-Thiopurine when incubated in the presence of rat liver microsomes and reduced nicotine adenine dinucleotide phosphate (NADPH) binds to microsomal protein. Data support a mechanism involving initial metabolic activation via a cytochrome P450 mediated reaction to an intermediate which binds to protein. Glutathione protects against protein binding of the 6-thiopurine metabolite.

Animals↗
PubMed1978

Quantitation by gas chromatography-chemical ionization mass spectrometry of cyclophosphamide, phosphoramide mustard, and nornitrogen mustard in the plasma and urine of patients receiving cyclophosphamide therapy.

Unambiguous and sensitive methods based on gas chromatography-chemical ionization mass spectrometry have been developed to quantitate cyclophosphamide and two alkylating and cytotoxic metabolites, phosphoramide mustard and nornitrogen mustard. The levels of these materials have been determined in the plasma and urine of five patients receiving cyclophosphamide, 60 or 75 mg/kg i.v. Peak plasma levels of phosphoramide mustard of 50 to 100 nmoles/ml were found at 3 hr after cyclophosphamide administration. Variable levels of nornitrogen mustard were found in the plasma. This product may be arising in part from the decomposition of other metabolites during sample storage and preparation.

Adolescent↗
PubMed1976

Alkylating properties of phosphoramide mustard.

The relative alkylating activities of two of the cytotoxic metabolites of cyclophosphamide, phosphoramide mustard and nornitrogen mustard, have been studied at pH 4.6 and 7.4. The products formed on alkylation of ethanethiol by these metabolites have been identified, confirming that phosphoramide mustard undergoes alkylation reactions as an intact molecule. Deuterated analogs of the two metabolites have been synthesized, namely N,N-bis(2,2-dideutero-2-chloroethyl)-phosphorodiamidic acid and N,N-bis(2,2-dideutero-2-chloroethyl)amine and used to determine that alkylation proceeds directly via an aziridinium intermediate rather than a direct SN2 displacement of the chlorine atom.

Alkylation↗
PubMed1976

Approaches to the pharmacokinetics of cyclophosphamide (NSC 26271): Quantitation of metabolites.

Recent evidence has implicated phosphoramide mustard as a highly active metabolite of cyclophosphamide (CP). This compound has been shown to be produced from CP both in vitro and in vivo. To further study the role of this active metabolite we have devised methods to quantitate the compound in human serum and urine using gas chromatography-chemical ionization mass spectrometry. Tetradeuterated phosphoramide mustard has been synthesized and is used as an internal standard. CP and nor-nitrogen mustard have also been quantitated in human samples using analogous tetradeuterated internal standards.

Chromatography, Gas↗