The occurrence of a glycine cleavage system in mammalian brain

A major catabolic route for glycine in liver is its conversion to methylene tetra-hydrofolate (methylene THF), CO₂ and NH₃, catalysed by the glycine cleavage system described by Yoshida and Kikuchi (1970). In view of the role of glycine as a putative neuro-transmitter, the occurrence of this system in mammalian brain was investigated. Our studies demonstrated: (a) that the production of ¹⁴CO₂ from [1-¹⁴C]glycine required the presence of tetrahydrofolate, NAD, dithiothreitol and pyridoxal phosphate in the reaction mixture; (b) that besides CO₂l -serine was the other major product of the reaction; (c) that glyoxylate did not function as an intermediate in this reaction; and (d) that enzymatic activity appeared to be associated with membranes. All of these properties resembled those previously described for the hepatic system.     

Aerobic biomineralization of alpha-hexachlorocyclohexane in contaminated soil

The factors identified to be important for the aerobic biodegradation of alpha-hexachlorocyclohexane (alpha-HCH) in a soil slurry are temperature, auxiliary carbon source, substrate concentration, and soil inhomogeneities. Temperatures in the range of 20 to 30 degrees C were determined to be most favorable for biodegradation of alpha-HCH. No alpha-HCH biodegradation was detected at temperatures below 4 degrees C and above 40 degrees C. The addition of auxiliary organic carbon compounds showed repressive effects on alpha-HCH biomineralization. Increased oxygen partial pressures reduced the repressive effects of added auxiliary organic carbon compounds. A linear relationship between alpha-HCH concentration and its conversion rate was found in a Lineweaver-Burk plot. Inhomogeneities such as clumping of alpha-HCH significantly affected its biodegradation. Inhomogeneity as an influence on biodegradation has not drawn sufficient attention in the past, even though it certainly has affected both laboratory studies and the application of biotechnological methods to clean up contaminated sites. On the basis of metabolites detected during degradation experiments, the initial steps of aerobic alpha-HCH bioconversion in a soil slurry are proposed.     

Graves' disease: immunological and immunogenetic indicators of relapse

The use of measurements of antibody to the thyroid stimulating hormone receptor and HLA-DR3 phenotype for predicting relapse of hyperthyroidism in patients with Graves'' disease receiving medical treatment is controversial. Fifty eight new patients with Graves'' disease were followed up prospectively for up to 96 months after treatment with antithyroid drugs for 12 months. The presence of antibody to the thyroid stimulating hormone receptor before the start of treatment, measured as immunoglobulins inhibiting binding of thyroid stimulating hormone, was not associated with relapse. Patients who remained positive for antibodies after treatment tended to relapse within six months, but no relation with long term relapse was found. HLA-Cw7 but not HLA-DR3 was significantly associated with relapse. The presence of HLA-DR4 was significantly associated with remission and with absence of antibodies to thyroid stimulating hormone receptor. HLA-DR4 may therefore protect against relapse of thyrotoxicosis by immunomodulation triggered by antithyroid drugs, which results in the synthesis of antibodies to the thyroid stimulating hormone receptor being inhibited.     

Differential hydrogen ion titrations of the histidine residues in Helix pomatia haemocyanin

The properties of the histidine residues in Helix pomatia haemocyanin have been studied by differential hydrogen ion titrations. In oxy-and deoxyhaemocyanin 31 × 10^?5 histidine residues per g protein are titrated in contrast to 35 × 10^?5 residues in apohaemocyanin. The difference corresponds to a stoichiometry of one histidine residue per copper atom bound. Even in apohaemocyanin about 6 × 10^?5 histidine residues per g protein are not titrated in their normal pH region.In the presence of sufficient calcium to displace the dissociation completely out of the titration region the titration curve of apohaemocyanin could he linarized according to the model of Linderstrøm—Lang. In oxy- and deoxyhaemocyanin, however, a distinct deviation from linearity was found under the same conditions. In the absence of calcium the effect of the dissociation adds up to this deviation.The electrostatic interaction factors were determined for the protein at 0.1 M KCl and for the dissociation products: halves and tenths at 1.0 M KCl. The electrostatic interaction factor for the wholes and the halves are much smaller than the values calculated from the Linderstrøm—Lang equation, using the radius of the equivalent sphere either obtained from electron microscopy or from the partial specific volume. This is probably due to solvent penetration. For the tenths at 1.0 M KCl. this effect is small,