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Biomedical subjects

I Jardine

Publications and source records attributed to I Jardine.

61 records · Page 4Linked to original sources
PubMed1975

Testosterone and 5alpha-reduced androgen secretion by rabbit testes-epididymides perfused in vitro.

Mass spectrometric determinations confirmed that testosterone, 5alpha-androstan-17betaol-3-one, 5alpha-androstan-3alpha, 17beta-diol and 5alpha-androstan-3beta, 17beta-diol were present in venous effluent of in vitro perfused rabbit testes-epididymides. Testosterone, dihydrotestosterone, 3alpha-androstanediol and 3beta-androstanediol were secreted at 3.1 plus or minus 0.9, 0.7 plus or minus 0.2, 0.4 plus or minus 0.1 and 0.6 plus or minus 0.1 mug/h when testes-epididymides were perfused with an artificial medium containing 2.5 ng/ml NIH-LH-S17, ovine. Surprisingly, testosterone constituted only 64% of the total mass of the four androgens secreted. These results probably reflect in vivo androgen secretion since hourly collections of spermatic vein blood from anesthetized rabbits contained 2.7 plus or minus 0.9, 0.8 plus or minus 0.3, 0.15 plus or minus .04 and 0.5 plus or minus 0.2 mug of testosterone, dihydrotestosterone, 3alpha-androstanediol and 3beta-androstanediol, respectively. Once again testosterone constituted only 64% of the total mass of the four androgens.

Androstanes↗
PubMedDate not supplied

A new peptide in the FMRFamide family isolated from the CNS of the hawkmoth, Manduca sexta.

We have purified a FMRFamide-like peptide from extracts of brain-subesophageal ganglion of the moth, Manduca sexta. The purification was monitored with a new, competitive ELISA, and accomplished with ion exchange and reverse-phase HPLC. The peptide structure was determined by a combination of tandem mass spectrometry and automated Edman degradation. The amino acid sequence of the peptide is less than Glu-Asp-Val-Val-His-Ser-Phe-Leu-Arg-Phe-amide (pEDVVHSFLRF-NH2). In a separate purification, an identical peptide was isolated from extracts of brain-associated neurohemal structures. We have named this peptide ManducaFLRFamide, to indicate its homology with other members of the "FMRFamide" family. In bioassays, chemically synthesized peptide increased the force of neurally evoked contractions in the major power-producing flight muscles, the dorsal longitudinal muscles. This observation suggests that hormonally released ManducaFLRFamide may play a role in sustaining or promoting the flight behavior necessary for mate-seeking (in males) or oviposition (in females) in sphingid moths.

Amino Acid Sequence↗
PubMedDate not supplied

Isolation of 10 cyclosporine metabolites from human bile.

Ten metabolites of cyclosporine were isolate from the ethyl ether extract of bile from four liver transplant patients receiving cyclosporine. Two of the metabolites were unique and previously unidentified. Liquid-liquid partitioning into diethyl ether with subsequent defatting with n-hexane was used for the initial extraction from bile. Separation of the individual metabolites (A-J) was performed using a Sephadex LH-20 column and a gradient high performance liquid chromatographic method. The molecular weights of the isolated metabolites were determined by fast atom bombardment/mass spectrometry. Gas chromatography with mass spectrometric amino acid analysis was also used to identify the amino acid composition and the hydroxylation position of metabolites A, B, C, D, and G. Proton nuclear magnetic resonance spectra were utilized to distinguish the chemical shifts of N-CH3 singlets and NH doublets of metabolites A, B, C, and D. Metabolites A, E, F, H, I, and J were reported previously in human urine and animal bile. Metabolites C and D are dihydroxylated compounds which cannot be clearly described as previously isolated compounds. Metabolites B and G are novel metabolites with a mass fragment which corresponded to a loss of 131 Da from the protonated molecular ion (MH+) in the fast atom bombardment/mass spectrometry, suggesting that the double bond in amino acid 1 has been modified. Metabolites B and G were primarily isolated from the bile of one of the liver transplant patients which contained abnormally high concentrations of these two metabolites. The method described is an efficient procedure for isolating milligram quantities of the major metabolites with greater than 95% purity.

Adult↗
PubMedDate not supplied

The in vitro activity, radioimmunoassay cross-reactivity, and molecular weight of thirteen rabbit cyclosporine metabolites.

Thirteen metabolites of cyclosporine were isolated from the bile of rabbits receiving intravenous cyclosporine. The molecular weights of these metabolites were determined by fast atom bombardment mass spectrometry. These molecular weights were consistent with hydroxylated, N-demethylated, and carboxylated metabolites of cyclosporine as described previously. The in vitro activities of the metabolites were established using mitogen-stimulated lymphocyte proliferation assays. Only the two monohydroxylated metabolites were found to have significant activity, this being between 5 and 10% of that of the parent drug. The metabolites were also compared with cyclosporine in two commercial radioimmunoassay kits. The metabolites were found to cross-react with the parent drug in amounts ranging from 20 to 100%, with the least polar metabolites cross-reacting the most strongly. It is concluded that the cross-reacting metabolites measured by the presently available radioimmunoassays for cyclosporine probably do not represent significant additional immunosuppressive activity in vivo.

Animals↗
PubMedDate not supplied

Foreign compound metabolism studies with human liver obtained as surgical waste. Relation to donor characteristics and effects of tissue storage.

An investigation has been conducted on the foreign compound-metabolizing activity of human liver collected fresh from surgery or at autopsy from cadavers 3 to 18 hr old, and the effects of low temperature storage on the foreign compound-metabolizing activity of fresh human liver. The enzyme activities studied were microsomal cytochrome P-450 content, biphenyl 4-hydroxylation, benzo-(a)pyrene metabolism, halothane reduction, and 4-hydroxybiphenyl UDP-glucuronosyl transferase, as well as cytosolic thiopurine methyltransferase, thermostable (TS) phenolsulfotransferase, thermolabile (TL) phenolsulfotransferase, and 5-fluorouracil dehydrogenase. Cadaver liver was a poor source of material for metabolism studies with the majority of the enzymes investigated. There was an 84% decrease in the yield of microsomal protein, a 64% decrease in cytochrome P-450 content per mg of microsomal protein, and a 36% decrease in the biphenyl 4-hydroxylase specific activity in human cadaver liver that was a few hours old. UDP-glucuronosyl transferase showed a 70% decrease, TS phenolsulfotransferase a 84% decrease, TL phenolsulfotransferase a 97% decrease, and thiopurine methyltransferase no significant change in specific activity. The loss of activity for many of these enzymes could be simulated by keeping fresh human liver at the temperature of the body after death. Surgical waste provided a good source of fresh, histologically normal, human liver for metabolism studies. Microsomal cytochrome P-450 content showed a significant increase with the age of the liver donor. Metabolism of benzo(a)pyrene to 3-hydroxybenzo(a)pyrene and benzo(a)pyrene-7,8- and -9,10-diols showed up to 136% higher rates in fresh liver microsomes from female donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMedDate not supplied

Human erythrocyte membrane thiol methyltransferase. S-methylation of captopril, N-acetylcysteine, and 7 alpha-thio-spirolactone.

Thiol methylation is an important pathway in the biotransformation of sulfhydryl drugs such as captopril. Human red blood cell (RBC) membranes contain a thiol methyltransferase (TMT) activity that catalyzes the S-methylation of 2-mercaptoethanol (2-ME). These experiments were performed to determine whether human RBC membranes contained enzymes that could catalyze the S-methylation of thiol drugs, and, if so, to determine whether those enzymes were similar to the RBC membrane TMT that catalyzes the S-methylation of 2-ME. Human RBC membranes were able to catalyze the methylation of captopril, N-acetylcysteine, and 7 alpha-thio-spirolactone, a sulfhydryl metabolite of spironolactone. Those activities and 2-ME TMT were similar with respect to subcellular distribution, inhibitor sensitivity, and thermal stability. When activities of the methyltransferase enzymes for 2-ME and for the three thiol drugs were measured in RBC membranes from 19 individual subjects, there were highly significant correlations among all four activities (r greater than 0.96 for all comparisons). These observations suggested either that a single enzyme in the human RBC membrane catalyzed the S-methylation of all of these compounds, or, less likely, that these were four separate activities regulated in parallel with similar properties. Experiments were then performed to identify the products of the enzyme reactions. The product of the reaction performed with 7 alpha-thio-spirolactone was the expected S-methyl derivative, 7 alpha-thiomethyl-spirolactone. However, it was found that lipophilic conjugates of the S-methyl derivatives of captopril and N-acetylcysteine were formed during the in vitro enzyme reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcysteine↗