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Biomedical subjects

H Aebi

Publications and source records attributed to H Aebi.

At least 19 recordsLinked to original sources
PubMed1981

The role of enzyme variants, polymorphisms and enzyme hybrids in enzyme deficiency conditions.

Based on the heterogeneity observed in two red cell enzymes, i.e. glucose 6-phosphate dehydrogenase (E.C. 1.1.1.49) and catalase (E.C.1.11.1.6), the role of different types of enzyme variants in enzyme deficiency conditions is discussed. For theoretical and practical reasons variants of unusually low specific activity and of low stability have to be distinguished. Whereas in the former type the activity level in blood more or less reflects the situation in other tissues, this is not the case for unstable mutants, e.g. the enzyme variant found in Swiss-type acatalasemia. In heterozygous carriers the situation can be complicated by the fact that variants of oligomer enzymes (e.g. catalase) are present as molecular hybrids exerting almost normal stability and activity.

Acatalasia↗
PubMed1979

[Nestlé Foundation studies of nutritional problems in the 3d world].

An outline is given of the aims and activities of the Nestlé Foundation, notably the inquiries performed at the Study center at Adiopodoumé (Ivory Coast) about the nutrition situation, and the efforts made there to improve the protein intake by introducing new food-stuffs of high protein content.

Child↗
PubMed1979

[Nutritional requirements and parenteral feeding].

1. The nutritional needs of man are governed by the law of the minimum (structural and protective substances) and the isodynamic rule (exchangeability of various energy carriers) There is a tendency to abandon the traditional concept of requirement as an absolute value (g or mg/day) and replace it by 3 graded parameters (minimal - lowest acceptable - desirable supply). Today nutrient density is of utmost importance in the planning and evaluation of food formulas, i.e. the content per 1000 kcal or per MJ = mega-Joule. 2. The metabolism of nutrients proceeds (simplified) in 3 phases: a) digestion (comminution); b) coordination and conversion in intermediary metabolism; c) direct use in synthetic or oxidation processes. This creates problems of balance, of co-ordination and regulation. In the phases b and c the same conformities apply for oral and parenteral feeding. 3. Particular features of parenteral feeding: Exclusion of intestinal flora, limited capacity of uptake by the circulation and, especially, the lowered capacity of biochemical regulatory mechanisms (homeostasis) in patients requiring parenteral feeding necessitate optimal coordination of supply and effective needs. Attempts to comply are made by continuous infusions, diversification of the substrate supply and optimisation of the different components. In principle, priority is given to those nutritional factors which promote anabolism (tissue formation) and counteract catabolism (tissue breakdown). 4. Example: protein needs. --Recapitulation of quantitative and qualitative requirements regarding protein and amino acid supply. --Discussion of the different recommendations and guidelines. --Discussion of the criteria for evaluation and the composition of an optimal amino acid mixture (nitrogen balance and growth as criteria). 5. Conclusions for parenteral feeding. The supply of amino acids should be on the generous side because there is an increased requirement in the "acute phase" and in convalescence. The amino acid composition should correspond to the pattern of a high quality food protein. The E/T ratio (essential AS versus total AS supply) is an indicator. The value proposed as a guideline is E/T approximately 3. However, an exaggerated amino acid cosmetic is not recommended. 6. Diagnostic problems. In the interest of optimal results of treatment, foremost attention should be given to the detection of latent deficiency states and the improvement of nutrition at large. The list of indicators given in the figures should be consulted whenever there is evidence of undersupply. The so-called "hospital malnutrition", as described in recent studies, should obviously not occur.

Amino Acids↗
PubMed1977

Properties of human erythrocyte catalases after crosslinking with bifunctional reagents. Symmetry of the quaternary structure.

Normal erythrocyte catalase, the enzyme present in the blood of Swiss acatalasemic heterozygotes, and their hybrid produced in vitro, were studied after crosslinking with bifunctional reagents. On theoretical grounds [cf. Hajdu, J., Bartha, F. & Friedrich, P. (1976) Eur. J. Biochem. 68, 373--383] it is inferred from the dodecylsulphate gel electrophoretic patterns obtained after treating catalase with diimidates of various chain lengths that the enzyme is an isologous tetramer (D2 symmetry). The minimal distances between crosslinkable primary amino groups across the three domains of bonding are different. Reaction with diimidates causes a moderate loss of enzyme activity in all three enzyme types due to amidination rather than crosslink formation. On the other hand, crosslinking stabilizes the enzyme against urea and heat inactivation. This is most prominent with heterozygote acatalasemic catalase. Crosslinking markedly prevents the development of peroxidase activity that can be elicited in catalases by urea treatment. The role of the quaternary structure of the protein in the relationship between catalase and peroxidase activities is discussed.

Animals↗
PubMed1977

Unstable mutants and molecular hybrids in enzyme deficiency conditions.

Multiple molecular forms contribute to various types of enzyme heterogeneity: "Iso(en)-zymes" and "Allozymes" (enzyme variants) are of genetic origin whereas "Metazymes" represent secondary modifications of epigenetic nature. The concept of variability originates from the discovery of a large number of enzyme variants. Structural gene mutations can lead to enzyme variants of low specific activity or reduced stability and can cause enzyme deficiencies. In heterozygous carriers of oligomeric enzyme defects, the formation of hybrid molecules is possible by random assembly of simultaneously synthetized normal and mutant subunits. The study of normal processes as well as enzyme anomalies contributes essentially to better understanding of biochemical individuality and evolutionary events at a molecular level.

Acatalasia↗
PubMed1976

Properties of erythrocyte catalase from homozygotes and heterozygotes for Swiss-type acatalasemia.

The unstable catalase variant found in the blood of individuals homozygous for Swiss-type acatalasemia and the enzyme species present in heterozygous carriers of this rare defect have been further characterized. The mutant enzyme isolated from acatalasemic red cells is considerably more heat labile and differs in electrophoretic mobility from the normal enzyme. Catalase preparations obtained from heterozygotes consist of an apparently uniform enzyme species, probably representing a molecular hybrid, with properties intermediate to those of the normal and the variant enzyme. However, antigenic identity of catalase from all three sources is observed. Model experiments indicate that hybrid catalase molecules can be produced by recombining normal and variant dimer subunits. Fractionation of erythrocytes according to density and age shows that most of the residual catalase activity is localized in juvenile acatalasemic cells, whereas in normal and heterozygous individuals the catalase activity level does not alter significantly during the life span of the red cells. These findings agree with the observation that there is no gene dosage in heterozygotes, their catalase activity values falling within the normal range.

Acatalasia↗
PubMed1975

Properties of leukocyte catalase in Swiss type acatalasemia: a comparative study of normals, heterozygotes and homozygotes.

Properties of leukocyte catalase from individuals heterozygous and homozygous for Swiss type acatalasemia were found to differ from those of the normal enzyme as well as interindividually in regard to heat stability and electrophoretic mobility. Molecular hybridization is discussed as a possible explanation for the presence of intermediate catalase species. Antigenic identity of catalase from all sources is confirmed.

Animals↗