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T Henle

Publications and source records attributed to T Henle.

30 records · Page 2Linked to original sources
PubMed1999

Advanced glycated end-products (AGE) during haemodialysis treatment: discrepant results with different methodologies reflecting the heterogeneity of AGE compounds.

BACKGROUND: There has been much recent interest in accumulation of advanced glycation end-products (AGE) in uraemic patients. Analysis of AGE has been difficult, because commonly used methodologies, i.e. immunodetection assays or fluorescence measurements, reflect group reactivity and are not specific for chemically defined substances. Some investigators measured individual AGE compounds, e.g. pentosidine, carboxymethyllysine, pyrraline or imidazolone, but a systematic assessment of known compounds using specific HPLC methods in diabetic and non-diabetic end-stage renal disease (ESRD) patients during treatment has not been performed. METHODS: For the present study, the concentrations of early and late products of the Maillard reaction in plasma and ultrafiltrate were monitored during high-flux dialysis sessions in diabetic and non-diabetic patients. AGE were analysed by fluorescence spectroscopy and size exclusion chromatography with fluorescence detection. Specific HPLC methods were used to quantify the Amadori product fructoselysine and the AGE compounds pentosidine and pyrraline in acid or enzymatic hydrolysates. RESULTS: Using size exclusion chromatography, we confirmed a similar fluorescent peak distribution for diabetic and non-diabetic ESRD patients. Main fractions were found at approximately 70, approximately 14 and <2 kDa, confirming results obtained by other authors. In diabetic patients, the fluorescence intensity of the low molecular weight fraction was higher. Uraemic patients differed from controls mainly by the fluorescence of the low molecular weight fraction. The peak spectrum in ultrafiltrates was similar to that in plasma regarding low molecular weight fractions and the 14 kDa peak, but no protein-bound fluorescence was found at 70 kDa. HPLC analysis revealed a significant reduction of plasma pentosidine during high-flux dialysis in non-diabetic (from 9.1+/-5.1 to 8.5+/-4.7 pmol/mg protein; P<0.05) and diabetic patients (from 10.0+/-9.1 to 6.8+/-4.0 pmol/mg protein; P<0.05). In contrast, plasma fructoselysine showed only a non-significant trend to decrease in diabetic (from 3.24+/-0.88 to 3.05+/-0.77 nmol/mg protein) and non-diabetic patients (from 2.69+/-0.52 to 2.56+/-0.50 nmol/mg protein). Pyrraline, a nonfluorescent late AGE product derived from reaction of 3-deoxyglucosone with lysine, could not be detected (detection limit approximately 40 pmol/mg protein). Comparing HPLC and size exclusion analysis, it was found that pentosidine accumulated in the range of low molecular weight substances and was removed by high-flux dialysis. CONCLUSIONS: High-flux dialysis reduces the plasma concentration of fluorescent AGE compounds, i.e. pentosidine, but the Amadori product fructoselysine is not removed, indicating that this compound is protein associated.

Adult↗
PubMed1996

Synthesis of pyrraline reference material.

A simplified and improved method is described for the preparation of pyrraline, a lysine derivative from the advanced Maillard reaction and potential indicator for heat treatment of foods. The compound was obtained in a high degree of purity and with a yield of 31% from N alpha-t-butyloxycarbonyl-L-lysine after heating with 3-deoxy-D-erythro-hexos-2-ulose for 2 h at 70 degrees C in the dry state, preparative fractionation of the resulting N alpha-t-butyloxycarbonyl pyrraline with reverse-phase liquid chromatography and final deprotection of the intermediate compound with acetic acid.

Cooking↗
PubMed1995

Fast and sensitive determination of furosine.

Sensitive determination of furosine in acid hydrolysates of foods was achieved by isocratic ion-pair reversed-phase HPLC and direct UV-detection within a run time of 5 minutes and levels lower than 1.5 mg per kg of protein. The formation of furosine during hydrolysis of food samples with hydrochloric acid of varying concentration was studied. Furosine formation increased linearly with acid concentration (4 to 8 mol/L).

Animals↗
PubMed1995

Inactivation kinetics of gamma-glutamyltransferase during the heating of milk.

The inactivation of gamma-glutamyltransferase (GGT, E.C.2.3.2.2) during the heating of milk to between 65.0 degrees C and 76.0 degrees C for periods of 5 s to 1000 s follows a first-order reaction (energy of activation 457 kJ/mol) and can be used to monitor the process of milk pasteurisation. GGT activity in raw milks from individual cows showed only little variation (5.92 +/- 0.59 units). Residual GGT activity in 17 commercial milks ranged between 1% and 20%, indicating a heat treatment at the upper limit of the permitted pasteurisation conditions.

Animals↗
PubMed1994

Studies on the formation of lysinomethylalanine and histidinomethylalanine in milk products.

From reaction mixtures consisting of N-acetyldehydroaminobutyric acid methyl ester and N alpha-acetyl-L-lysine or N alpha-acetyl-L-histidine, respectively, distinct amounts of the cross-link amino acids N epsilon-(2-amino-2-carboxy-1-methyl-ethyl)-L-lysine (lysinomethylalanine, LMeAL) and N tau-(2'-amino-2'-carboxy-1'-methyl-ethyl)-L-histidine (histidinomethylalanine, HMeAL) were isolated via preparative ion-exchange chromatography and identified by 1H- and 13C-nuclear magnetic resonance. In the amino acid chromatogram, both compounds eluted clearly separated from other basic amino acids. However, neither LMeAL nor HMeAL could be detected in numerous acid hydrolysates of a range of milk products. In model studies, threonine showed a significantly lower tendency for an alkali-induced beta-elimination reaction compared to serine. The reactivity of the resulting dehydroaminobutyric acid towards nucleophiles was more than tenfold lower as compared to dehydroalanine. Thus, the formation of LMeAL as well as of HMeAL during food processing is negligible.

Animals↗
PubMed1994

A simple method for the preparation of furosine and pyridosine reference material.

After heating N alpha-acetyllysine and glucose for 4 h at 90 degrees C in the dry state and subsequent acid hydrolysis with 7.8 N HCl, preparative fractionation of the dihydrochlorides of furosine and pyridosine was achieved by cation-exchange chromatography. The lysine derivatives could be prepared with high yield and sufficient purity for the use as reference material.

Amino Acids↗
PubMed1994

Structural proteins and DNA characteristics of 14 Listeria typing bacteriophages.

The major structural proteins of 13 temperate and one virulent Listeria typing bacteriophages were analysed and compared using isoelectric focusing in immobilized pH gradients (IPG), ultrathin-layer two-dimensional electrophoresis, amino acid analysis and N-terminal amino acid sequences of selected proteins. Isoelectric points for major capsid and tail proteins of the 12 members of the siphoviridae family included in this study ranged from 4.70 to 5.92, whereas one of the two myoviridae investigated (B054) showed structural proteins in the 6.1 to 6.3 range. In comparison to protein profiles from one-dimensional SDS gels, the IPG technique gave better resolution and improved discrimination of phage proteins. Combination of this technique and SDS gel electrophoresis made it possible to correlate M(r) and isoelectric points of major structural proteins. Tail polypeptides of all siphoviridae are smaller and, with one exception, more acidic than their corresponding capsid counterparts. We also determined the amino acid composition of capsid and tail proteins. When compared with an average protein, they were found to be fairly rich in acidic and short-chain hydrophobic amino acids, as well as in lysine. In addition, the N-terminal amino acid sequences of major capsid and tail proteins of four representative listeriaphages were compared. The base composition of listeriaphage DNAs was between 37% and 39% G + C, reflecting that of their bacterial hosts. Each phage had a distinct restriction endonuclease pattern, and genome sizes ranged from 35 to 116 kb. DNA-DNA hybridization permitted the identification of five DNA homology groups. The two myoviruses studied (A511 and B054) showed no DNA homology to other phages, confirming their unique nature. The 12 siphoviruses were classified into three DNA homology groups with little cross-homology. Furthermore, phage A006 was found to share little DNA homology with the other investigated members of species 2671. Therefore, a new species (A006) is proposed. With respect to phage classification and taxonomy, a good correlation between the various approaches was observed, mostly corresponding to particle morphology.

Amino Acid Sequence↗
PubMed1993

Detection and identification of the cross-linking amino acids N tau- and N pi-(2'-amino-2'-carboxy-ethyl)-L-histidine ("histidinoalanine", HAL) in heated milk products.

An unknown ninhydrin positive compound, X, was detected in acid hydrolysates of heated skim milk samples by amino acid analysis, eluting between phenylalanine and pyridosine in the chromatogram. The formation of X correlated with heating time and temperature. preparative ion-exchange chromatography enabled the isolation of X and a second minor compound from a milk protein hydrolysate and from a model mixture consisting of N alpha-acetylhistidine and methyl-2-acetamidoacrylate (acetyldehydroalaninemethylester), in a relative abundance of 8 to 1. By 1H-NMR spectroscopy, the two compounds could be identified as the N tau- and N pi-isomers of N-(2'-amino-2'-carboxy-ethyl)-L-histidine (histidinoalanine), a cross-link amino acid that has not been described in food proteins up to now. In a number of foods containing milk protein, the N tau-histidinoalanine contents were between 50 and 1800 mg/kg protein, which is in a concentration range comparable to the potential nephrotoxic cross-link lysinoalanine, which was determined simultaneously.

Animals↗
PubMed1993

Localization and concentration of a new bioactive acetic seminal fluid protein (aSFP) in bulls (Bos taurus).

The concentration of the new bioactive acetic seminal fluid protein (aSFP) was determined in body fluids of bulls. An aSFP-specific radioimmunoassay was elaborated and established for routine measurement. No crossreaction of the aSFP antibody was found with other seminal plasma proteins and known growth factors. The 14 kDa aSFP was detected in secretions of ampulla and seminal vesicles by immunoblot analysis, but not in testis, epididymis or blood. Large quantities of aSFP were measured by radioimmunoassay in the fluid from the ampulla (2.6 +/- 0.3 mg ml-1) and seminal vesicles (3.0 +/- 0.4 mg ml-1). Immunohistochemistry techniques demonstrated that aSFP was localized mainly in the secretory epithelium of ampulla and seminal vesicles. Large amounts of aSFP (4.0 +/- 0.4 mg ml-1) were present in seminal plasma of bulls within a range of 1-7 mg ml-1, but aSFP could not be found on membranes of spermatozoa. Concentrations vary considerably among individuals, suggesting that aSFP may have a role in bovine reproduction.

Animals↗
PubMed1991

Evaluation of the extent of the early Maillard-reaction in milk products by direct measurement of the Amadori-product lactuloselysine.

A new method for the evaluation of the extent of lysine modification caused by the Maillard reaction is presented, based on the direct determination of the Amadori product lactuloselysine plus unmodified lysine after complete enzymatic hydrolysis by ion-exchange chromatography. Using a simple mathematical relation, the amount of modified lysine in milk products can be estimated without knowledge of the initial lysine value before heating or storage.

Animals↗
PubMedDate not supplied

3-Deoxyglucosone, a promoter of advanced glycation end products in fluids for peritoneal dialysis.

OBJECTIVE: The accumulation of irreversible formed advanced glycosylation end products (AGE) in the peritoneal cavity might play an important role in the development of ultrafiltration failure and peritoneal membrane destruction. 3-Deoxyglucosone (3-DG), more formally named 3-deoxy-D-erythro-hexos-2-ulose or 3-deoxy-D-erythro-hexosulos is known to be a potent cross-linker responsible for the polymerization of proteins and a precursor of AGE. The purpose of the present study was to determine if the dicarbonyl compound 3-DG, is formed as a glucose degradation product during heat sterilization of fluids for peritoneal dialysis (PD). DESIGN: Four fluids were examined: a commercially available PD fluid Gambrosol (Gambro, Lund, Sweden); Gambrosol-Bio (Gambro), a new PD-fluid produced under conditions that minimize the generation of toxic glucose degradation products; a fluid prepared in the laboratory by sterile-filtration; and a fluid prepared in the laboratory by heat sterilization. METHODS: The concentration of 3-DG was analyzed by measuring the concentration of its diaminonaphthalene derivative by HPLC using a Waters Symmetry C18 column. RESULTS: The 3-DG concentrations in the commercially- and laboratory-prepared heat-sterilized fluids were 118 and 154 micromol/L, respectively. Gambrosol-Bio and the sterile-filtered fluid produced in the laboratory contained 3-DG in concentrations of 12.3 and less than 1.2 micromol/L, respectively. CONCLUSION: Our results demonstrate that during the heat sterilization of conventional PD-fluids, 3-DG is produced as a degradation product of glucose. It was also demonstrated that, through an alteration of the manufacturing condition, the production of 3-DG could be considerably reduced. We speculate that the presence of 3-DG in unused conventional PD-fluid could act as a local promoter, and increase local AGE formation within the peritoneal cavity.

Chromatography, High Pressure Liquid↗