Metabolic activation and toxicity of a DDT-metabolite, 3-methylsulphonyl-DDE, in the adrenal zona fasciculata in mice

Whole-body autoradiography of 14C-labelled 3-methylsulphonyl-DDE (3-MeSO2-DDE) in female C57BL mice revealed a heavy accumulation in the adrenal cortex. Fairly high radioactivity appeared in the nasal mucosa and fat, while the labelling of the liver was intermediate. The adrenal radioactivity remained largely unextracted in tissue-sections treated with organic solvents. In the liver and intestinal contents the radioactivity was partly extracted, whereas in all other tissues almost completely extracted. According to light microscopic autoradiography, the tissue-bound adrenal radioactivity was confined to the zona fasciculata, leaving the other adrenal zones devoid of bound material. Incubation of 3-MeSO2-DDE with adrenal tissue (300 X g supernatant) revealed a dose- and time-dependent covalent binding to protein and formation of water-soluble metabolites. The cytochrome P-450 inhibitors metyrapone and carbon monoxide inhibited both covalent binding and polar metabolite formation. Addition of reduced glutathione decreased binding, while polar metabolite formation was increased. Histopathological examination of adrenals from 3-MeSO2-DDE-treated mice revealed extensive vacuolation and necrosis of the zona fasciculata 1-12 days after single doses down to 25 mg/kg. Degenerative changes were observed at 12.5 mg/kg. In contrast to 3-MeSO2-DDE, 14C-labelled 3,3'-bis(methylsulphonyl)-DDE was not accumulated in the adrenal cortex. 3-MeSO2-DDE is thus a persistent environmental pollutant with a unique ability to produce acute toxicity subsequent to metabolic activation in a mammalian tissue.     

The effect on grain yield of adult plant resistance to mildew in oats

Lines were selected from progeny of the crosses Maldwyn × Milford and Maldwyn × Sun II which consistently exhibited small and large amounts of mildew in similar situations. These are referred to as ‘low’ and ‘high’ mildew lines respectively. In small plot field trials conducted in 1971, 1972 and 1973 the low mildew lines produced substantially more grain each year compared with the high mildew lines in plots where mildew was allowed to develop normally. In plots which were kept comparatively free from infection by spraying with tridemorph, both low and high mildew lines gave similar yield. When the unsprayed plots were compared with the sprayed plots the low mildew lines invariably showed very small losses in grain yield and the high mildew lines usually very large losses. This same trend was evident also in the parent cultivars in 1972. Maldwyn, with only 7·9% mildew cover in the unsprayed plots due to its resistance, suffered a decrease of only 9·2% in grain yield compared with losses of 17·1 and 20·3% in the more susceptible cultivars Milford and Sun II. Certain lines and cultivars sustained heavy levels of mildew without corresponding loss of grain yield, i.e. showed low sensitivity to the disease. The importance of combining low sensitivity (or tolerance) with adult plant resistance to mildew is discussed.     

Optimization of the medium for the yeast synthesis of biotin

In order to increase the yield of biotin produced by the culture Sporobolomyces pararoseus, the medium containing sucrose, asparagine, MgSO4 (NH4)2SO4, KH2PO4, vitamin complex and trace elements was optimized. With the aid of a fractional factor experiment (2(5-1)) and a complete factor experiment (2(4)), the proportion of constituents was chosen in such a way as to double biotin yield, i.e. to increase it to 55.25 micrograms/l. An enrichment of the medium with yeast autolysate, casein hydrolysate and peptone in the presence of adenine increased biotin yield to 105.7 micrograms/l and cell productivity from 6.1 to 8.0 micrograms/l dry biomass.     

A Method for the Isolation of Macronuclei from Paramecium aurelia

SYNOPSIS. A method is described for the isolation of macronuclei from Paramecium aurelia. It has also been successfully employed with Didinium nasutum. The yield is up to 50% with P. aurelia. Some results on the DNA, RNA and protein contents are given. The isolated macronuclei of P. aurelia are able to incorporate ATP and UTP into acid-insoluble material, a process which is probably RNA synthesis mediated by RNA polymerase. The macronuclei were thus highly purified, and retained a measure of biosynthetic activity.     

NAD-dependent formate dehydrogenase from methylotrophic bacteria. Isolation and properties]

NAD-Dependent formate dehydrogenase (FDH) has been isolated from methylotrophyc strain Bacterium sp 1 by (NH4)2SO4 fractionation of cell extract, ion-exchange chromatography and preparative isotachophoresis. Preparation of FDH is homogeneous in analytical polyacrylamide gel electrophoresis and under ultracentrifugation. Sedimentation coefficient of FDH is 4.9S. Mikhaelis constants are 1.1-10(-4) M for NAD and 1.5-10(-2) M for formate. In the absence of sulfhydril compounds FDH is unstable, but it is stable in the presence of mercaptoethanol or ditiotreitol.     

Increased affinity of liposomes derived from total spleen and liver lipids to spleen cells

The interaction of liposomes derived from total lipids of mouse spleen and liver with mouse spleen cells was studied. It was shown that the binding of these liposomes is much higher than the binding of liposomes obtained from a model lipid mixture--phosphatidylcholine--phosphatidylethanolamine--cholesterol (2:1:1). Adherent and nonadherent spleen cells were found to have affinity for liposomes derived from total lipids of spleen or liver. Removal of gangliosides and protein contaminants from the liposomes derived from total spleen lipids caused an increased binding of liposomes to spleen cells. Multilamellar liposomes bound more effectively to ultrasonicated vesicles having a homologous lipid composition than the liposomes with a different lipid composition. The increased affinity of liposomes derived from total lipids of spleen or liver for spleen cells may account for the identical fluidity of the lipid bilayer of liposomes and plasma membranes of spleen cells.