[Selective adsorption of homocysteine using HFR-on line technique]. / Estrazione di omocisteina in corso di HFR on-line.

Homocysteine (Hcy) is grossly elevated in hemodialysis (HD) patients. Treatment with folic acid and/or vitamin B12 fails to normalize Hcy levels in the majority of patients. Treatment with various dialyzers with different flux characteristics has produced contrasting results. Hemodiafiltration reinfusion (HFR) on-line (double chamber hemodiafiltration (HDF) with regenerated ultrafiltrate reinfusion) is a novel method combining the processes of diffusion, convection and absorbance. The ultrafiltrate is regenerated through a charcoal-resin device. Our aim was to observe the effect of the HFR on-line technique on removing Hcy. We investigated the effect of this treatment on Hcy levels in 10 patients with a mean Hcy level of 57.6 micromol/L (range 24.1-119.7). We measured Hcy, folate and vitamin B12 pre- and post-dialysis and in the ultrafiltrate pre- and post-cartridge at 10, 120 and 240 min. Mean Hcy levels were 57.6 and 35.3 micromol/L (range 9.9-80.3) (p=0.005) pre- and post-dialysis, respectively, while folate and vitamin B12 were unchanged. Pre- and post-cartridge Hcy levels were 11.6 vs 2.5 (p=0.005), 9.3 vs 3.9 (p=0.005), 7.7 vs 4.6 micromol/L (p=0.012) at three time points considered, while folate and vitamin B12 were essentially undetectable. These preliminary data, which need confirmation in a long-term study, seem to indicate that HFR on-line reduces Hcy levels, not only through a possible reduction in uremic toxins, but also through the actual removal of Hcy by absorbance on the charcoal-resin cartridge.

Agglutinating activity of wheat gliadin peptide fractions in coeliac disease.

The K 562 (S) cell agglutinating activity of peptides obtained from in vitro digestion of bread wheat gliadins has been shown to be associated with a small fraction (coded as Fraction C), that can be easily separated by affinity chromatography of the whole digest on a sepharose 6-B-mannan or sepharose 6-B-oligomers of N-acetyl-glucosamine. Although the whole gliadin digests from 12 durum wheat varieties were unable to agglutinate K 562 (S) cells, all these digests were found to contain an active Fraction C. The lack of agglutinating activity of the whole durum wheat gliadin digests has been shown to be associated with the presence in these digests of another peptide fraction (coded as Fraction B) that is eluted much earlier from the sepharose 6-B-mannan column and is able to inhibit the cell agglutinating activity of Fraction C. Such an active Fraction B is not present in bread wheat gliadin peptides, although peptides with the same elution profile as Fraction B have been detected.

Oxidation of some seleno-diamines by pig kidney diamine oxidase.

The enzymatic deamination of Se-lanthionamine (Se-L), Se-homolanthionamine (Se-HL) and Se-homocystamine (Se-HC) catalyzed by pig kidney diamine oxidase (PKAO) has been studied to collect information about the possible metabolic reactions of selenocompounds in comparison with the sulfur ones. The results indicate that: Se-L, Se-HL and Se-HC are substrates for PKAO. The first product of Se-L, Se-HL and Se-HC oxidative deamination, in analogy with other thio and seleno diamines, may be the cyclized aminoaldehyde. The final product of Se-L, Se-HL and Se-HC degradation are ammonia, elemental selenium and C2 or C3 compounds.

[Oxidative deamination of beta-methylaspartic acid]. / Deaminazione ossidativa dell'acido beta-metilaspartico.

beta-methyl-aspartic acid is a substrate for beef kidney D-aspartate oxidase. The first product of a typical oxidative deamination, undergoes further spontaneous process of decarboxylation which gives as product, the alpha-keto-butyric acid.

Synthesis and chromatographic properties of Se-carboxymethyl-selenohomocysteamine (2-carboxymethyl, 3-aminopropyl selenide).

Details are reported for the synthesis of Se-carboxymethylselenohomocysteamine from selenohomocysteamine and monochloroacetic acid. Data on its behaviour on paper and ion-exchange chromatography are also reported, which allow its identification.

Selective inactivation of catalase during protoporphyrin induced photohemolysis of human red blood cells.

The level of some enzymatic activities in red blood cells before and after photohemolysis induced by protoporphyrin IX was studied. A 30% decrease in catalase activity was found both in normal erythrocytes and those from patients affected by favism. Other proteins though present in larger amounts inside the erythrocytes are not affected by the photohemolytic process.

Oxidation of selenocystamine by diamineoxidase.

Selenocystamine is oxidatively deaminated by pig kidney diamineoxidase. The first product of the reaction is the corresponding cyclized aminoaldehyde, selenocystaldimine, which then undergoes further degradation. The oxidative deamination is thus the first step of a series of cyclic reactions which give rise to extensive cleavage of selenocystamine.

Oxidation of S-e-carboxymethyl-selenocysteine by L-aminoacid oxidase and by D-aspartate oxidase.

Se-Carboxymethyl-DL-selnocysteine (CMSeC) has been prepared in a pure crystalline form from selenocysteine and monochloracetic acid. It has been shown that CMSeC is a substrate for the L-aminoacid oxidase form snake venom and for the D-aspartate oxidase from beef kidney. Oxygen consumption and ammonia production indicate that only the L or the D form of CMSeC ar acted upon respectively by one or the other of the above enzymes. No noticeable differences were shown in the oxidation rate of CMSeC and S-carboxymethylcysteine, an indication that the substitution of a selenium for a sulfur atom in the molecule does not greatly affect the substrate specificity of the two enzymes. Data have been obtained suggesting that the product of the oxidative deamination of CMSeC Is Se-carboxymethyl-selenopyruvic acid.