Gelatin Embedding of Central Nervous System Tissue Improves the Quality of Vibratome Sections

We have developed a procedure for Vibratome (Oxford Laboratories) sections that is particularly valuable for providing uniformly thick, well preserved CNS tissue sections for morphometric applications.     

Subcellular localization of acetyl-CoA synthetase in leaf protoplasts of Spinacia oleracea

The localization of acetyl-CoA synthetase in the spinach leaf cell was examined. When the different compartments of lysed spinach protoplasts were assayed for marker enzymes and acetyl-CoA synthetase, it was determined that the synthetase was totally localized in the chloroplast compartment. Analysis of spinach leaf for free acetate revealed that this acid was present at a 1 mm level in the leaf cell. It is suggested that free acetate probably derived from a number of sources in the cell diffuses into the chloroplast stroma compartment where it is converted to acetyl-CoA and thence employed for biosynthetic reactions. Thus, free acetate is metabolically inert in the leaf cell until it is transported to the only compartment that contains acetyl-CoA synthetase, namely the chloroplast.     

Response to drought among farmers and herders in southern Kajiado District,Kenya

From 1972 to 1976 rainfall in Kajiado District of Kenya was below normal. The capacity of the farming and herding systems to cope with the consequent reduction in production is discussed within a context of changing land-use patterns and altered resource availability. It is concluded that land-use planning to allocate the available land and water resources and to promote off-farm employment is required to reduce the vulnerability of the population to future drought conditions.     

Photo-oxidative damage in the ripening tomato fruit: Protective role of superoxide dismutase

Factors relating to photo-oxidative damage in tomatoes were investigated during maturation of the fruit and upon induction of sunscald. Superoxide dismutase (SOD) activity passed through a minimum at the mature-green and breaker stages of ripening and availability of zinc and copper did not appear to be a limiting factor in the synthesis of the enzyme. Iron levels were maximal and total carotenoid concentrations were lowest during the same mature-green and breaker stages of maturation, while chlorophyll was starting to decrease but was still present in large amounts. Peroxidase activity decreased steadily during ripening. Artificial induction of tolerance to photodynamic damage by controlled heat treatment was accompanied by an increase in SOD activity, while carotenoid levels and peroxidase activity did not change. These findings support the thesis that the previously reported susceptibility of tomatoes to photodynamic damage, i.e. sunscald, during the mature-green and breaker stages of maturation is related to enhanced formation of superoxide ions, at a time when chloroplast structure begins to break down. SOD, by scavenging the superoxide, appears to supplement the protective action of carotenoids against photo-oxidative injury.     

Contribution of the shunt pathway of mevalonate metabolism to the regulation of cholesterol synthesis in rat liver

The modulation of the shunt pathway of mevalonate metabolism (Edmond, J., and Popják, G. (1974) J. Biol. Chem. 249, 66-71) has been studied in livers from fed, starved, and diabetic rats perfused with a physiological concentration (300 nM) of [5-14C] + [5-3H]mevalonate. Shunt activity was measured by (i) production of 14CO2 (corrected for loss of label by exchange reactions) and (ii) production of 3H2O. Contribution of exogenous mevalonate to total mevalonate production (0.06-0.11%) was assessed in parallel experiments by the incorporation of 3H2O into sterols. Inhibition of non-saponifiable lipid synthesis by starvation and diabetes is not associated with an inhibition of mevalonate production but with a major increase in shunting (7-34%) of sterol-bound mevalonate. The shunt pathway of mevalonate metabolism appears to participate in the regulation of cholesterol synthesis.