Biomedical subjects
Publications and source records attributed to G Spiteller.
A procedure is described to isolate peptides from complex biological fluids (e.g. seminal plasma) in pure form within a short time. The sequence of the isolated peptides was determined by liquid secondary ion mass spectrometry in combination with enzymatic cleavage reactions. The method was used for the structure elucidation of a peptide of molecular weight 2766 u with an N-terminal pyroglutamine residue.
1. After administration of carbamazepine (Tegretal) to an epileptic patient suffering also from uraemia, a previously unknown metabolite was detected in the haemofiltrate. It was identified as the 10,11-dihydro-10-hydroxy-carbamazepine-O-beta-glucuronide. 2. Its identification was accomplished mainly by electron impact (EI), liquid secondary ion (LSI) mass spectrometry and n.m.r. spectroscopy.
Peptides were isolated from the middle molecule fraction of hemofiltrate obtained from uremic patients by adsorption of the organic compounds on RP 18. By stepwise elution an enriched peptide fraction was obtained. This procedure was followed by a combination of ion-exchange-chromatography, gel-chromatography and HPLC. The pure peptides obtained in this way were investigated by liquid secondary ion mass spectrometry (LSIMS)-if necessary after enzymatic digestion. The identified peptides turned out to be fragments of the human serum albumin and beta 2-microglobulin.
Glycerol enol ethers, obtained by the reduction of plasmalogens with lithium aluminum hydride, can be converted into glycerol alk-(1)-enyl ether bismethyl ethers with diazomethane in the presence of silica gel. Their mass spectra allow the position of the enol ether group in glycerol unit to be deduced. Branches in the aldehydic components of the glycerol alk-(1)-enyl ether bismethyl ethers can be identified unequivocally by preparation of the 2-alkyl-1,3-dithiolanes, desulphurization with Raney nickel and deuterium to hydrocarbons and subsequent analysis by gas chromatography-mass spectrometry.
The observation that F-acids (1) occur in rat chow initiated a search for F-acids in human diet. We observed that the amount of F-acids with a pentyl side chain in alpha-position taken up with a one-day diet correlates well with the amount of excreted degradation products, the pentyl urofuran acids (2), (3) and (4). Therefore it can be concluded that F-acids with a pentyl side chain are not produced in the human body but are introduced through the diet. The origin of F-acids carrying an alpha-propyl side chain is less clear. The amount of propyl-urofuran acids (2) and (3) excreted in urine was found in one case out of three to be five times higher than the amount of F-acids carrying a propyl group in alpha-position taken up by the diet. Therefore, it can presently not be excluded that a portion of the propyl F-acids is produced by the body. F-acids found in human food are mainly introduced into the body by vegetables and fruits. F-acids were found also in birch leaves in considerable amounts, as well as in grasses, dandelion and clover leaves. Thus, we can conclude that F-acids are common constituents of plants.
Two previously unknown peptides with a high amount of polar amino acids were isolated from human seminal plasma by a combination of dialysis, gel filtration, ion-exchange chromatography, and RP-HPLC. Their structures were determined by gas-phase sequencing simultaneously considering the different peak intensities.
[MH]+ ions of peptides are degraded in one step to acyl ions, indicating the presence of different [MH]+ species. In contrast to protons, cations are added mainly at the carboxylate function of a peptide zwitterion. These species are degraded by loss of the C-terminal amino acid in the form of CO and an imine.
Practical hints are summarized for the investigation of peptides by soft ionization methods based on liquid secondary ion mass spectrometry. The method aims: to purify the sample; to force a peptide to the surface by ion pair formation; to recover the sample used for mass spectral analysis; to distinguish between Lys and Gln by derivatization; to spot amino acids in the low mass region; and to improve sequence information by use of peptide fragments, not described previously.
The possible role of linoleic acid as a biogenetic precursor of the furan fatty acids (F-acids) was investigated in in vivo experiments in the rat, using a C19 analogue of linoleic acid and gas chromatography-mass spectrometry. No evidence of incorporation of this compound into the F-acids was found. Using an improved analysis procedure by converting F-acids into their tetrahydrofuran derivatives (enabling a separation from the large amounts of normal fatty acids), F-acids (F3, F4 and F6) were detected in rat food, correcting earlier results. Quantification of F-acid intake with food and excretion of furandicarboxylic acids in the urine, suggested the possibility that the F-acids are not produced de novo in the rat, but instead accumulate in tissue after nutritional intake.
The synthesis of C19-androgens oxygenated at carbons 2, 3, 17 and 19 and of their deuterium or deuterium-tritium labeled analogs is described.
Some organic acids that occur in human urine are excreted in very different amounts during the day and the night. The day-night rhythm in the excretion rate of citric acid and propylurofuran acid changes only gradually if the normal rhythm of life is inverted, e.g., if a person sleeps during the day and works at night (shift of 12 h), paralleling the gradual adjustment of steroid metabolism under the same conditions. In contrast, the typical rhythm in the excretion rate of tetrahydrofuran acids and tartaric acid inverts immediately if the sleep-waking rhythm of a person is inverted. In contrast to propylurofuran acid, pentylurofuran acid is excreted unrhythmically. No change in the excretion rate of amino acids was observed if the daily rhythm was inverted. Quantifications were achieved by liquid-liquid extraction, derivatization and gas chromatography computerized peak area integration.
After consumption of onions or garlic, biological profiles of human urine samples show, in the methylated conjugate fraction, peaks corresponding to the methylates of N-acetyl-S-(2-carboxypropyl) cysteine (1), N-acetyl-S-allylcysteine (2) and hexahydrohippuric acid (3). The compounds 1 and 2 are metabolites of peptides introduced with onions or garlic into the body.
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The corticosteroid and androgen metabolites in the urine of 37 test subjects (11 healthy volunteers, 16 patients with eczema, and 10 patients with psoriasis) were investigated by means of gas chromatography and mass spectrometry. In addition, we studied the cortisol and testosterone levels in the plasma by radioimmunoassay. Those patients who had been treated with corticosteroids during the last two weeks were excluded. Our findings revealed that the excretion rate of steroid metabolites was significantly reduced in dermatological patients. The excretion rate of corticosteroids in urine was decreased an average of 25% (eczema) and 29% (psoriasis). The reduction of the androgen metabolites amounted to 26% and 31%. Cortisol and testosterone levels in the plasma were normal in all the cases.
Fractions of dipeptides, obtained from human urine by a combination of cation-exchange chromatography, ligand-exchange chromatography and reversed-phase chromatography, were transformed into their N-heptafluorobutyryl methyl ester derivatives and then subjected to capillary gas chromatography. The profiles obtained indicate the presence of many dipeptides in human urine. For the first time, alpha-Asp-Hyp, Pro-Phe and gamma-Glu-Phe were detected in the urine of healthy individuals.
The excretion of some acids in urine is subject to a circadian rhythm, if diversified nutrition is offered to the body sufficiently. The effect of physical exertion upon the excretion rates of acids in urine is very similar to that of a zero diet, resulting in an increase of final degradation products and a decrease of metabolic intermediates.
A simple procedure to distinguish between urinary acids originating from nutrition and beverages and those produced from compounds stored in the body is described. Acids originating from nutrition disappear in urine samples after a few days of a zero diet, whereas those produced from body compounds do not. The zero diet can be substituted by a diet of peeled rice and water.
In the present study the effects on endogenous hormones of application of topical corticosteroids are investigated. Radioimmunological assays of the hormones cortisol, adrenocorticotrophic hormone (ACTH) and alpha-melanocyte stimulating hormone (alpha-MSH) before, during and after a large-area treatment with topical corticosteroids (30 g/d 0.025% fluocinolone acetonide ointment for 9 days) are performed in eight patients suffering from extensive inflammatory dermatoses (7 cases of eczema, 1 case of psoriasis). Cortisol was measured in plasma daily under treatment. In addition, gas chromatographic and mass spectrometric determinations of urocorticoids and uroandrogens are carried out in 24-h urine. A distinct, treatment-induced suppression of the endogenous steroid production was significant (-42.7%, p less than or equal to 0.05) within the first four days and diminished (-24.4%, p less than or equal to 0.10) after nine days' steroid therapy. The suppression of the plasma ACTH was also significant (-23.1%, p less than or equal to 0.05). The alpha-MSH level did not show any alterations. The measured urocorticoids showed an average fall of -38.9% (p less than or equal to 0.05). It is noteworthy that despite continued steroid treatment the marked initial suppression of the endogenous steroid production diminishes. It is possible that a therapy-induced "normalization" of the epidermis brings about a diminished steroid influx and thus a lower systemic load. Under the therapy conditions chosen here, the androgen metabolites in the urine did not show any significant fluctuations.