THE main sites of cytoplasmic protein synthesis in mammalian cells are considered to be the ribonucleoprotein (RNP) particles of ribosomes. The chemical and physical properties of RNP particles have been closely studied in relation to their synthetic function (e.g. KORNER, 1961 ; TAKANAMI, 1960; KIRSCH, SIEKEVITZ and PALADE, 1960; TISSI~RES, SCHLESSINCER and GROS, 1960). Most of these studies have been carried out on ribosomes derived from mammalian liver, while ribosomes derived from brain material have been less extensively investigated. However, some studies on brain ribosomes or microsomes have been carried out using whole brain from rats

Measurements were made of the plasma concentrations of testosterone, progesterone and oestradiol-17 beta during the oestrous cycle of the ewe, and of the plasma concentrations of testosterone and progesterone during the oestrous cycle of the heifer. The maximum concentration of progesterone in the heifer was nearly twice that in the ewe. The maximum concentration of testosterone was similar in both species and occurred at the onset of luteolysis; in the ewe the peak concentration of 19.5 ng/ml plasma was significantly greater (P less than 0.05) than the concentrations of testosterone measured during the remainder of the oestrous cycle.

Six late pregnant and six non-pregnant Finnish Landrace x Dorset Horn ewes were fed a standard diet. Blood and liver samples were taken and the concentrations of the following metabolites measured: adenine monophosphate (AMP), adenine diphosphate (ADP), adenine triphosphate (ATP), citrate, 2-oxoglutarate, phosphoenolpyruvate, pyruvate, lactate, 2-phosphoglycerate, 3-phosphoglycerate, malate, /?-hydroxybutyrate, acetoacetate, glutamate, alanine, NAD+ and NADH. Comparing non-pregnant with pregnant ewes the liver of the pregnant animals had reduced concentrations of lactate, ADP, NAD + and NADH, and in the blood there were reductions in lactate, pyruvate, lactate/pyruvate ratio and urea. The concentrations of the other metabolites of the pregnant ewes receiving adequate nutrition were little changed from those of the non-pregnant ewes. The significance of these findings is discussed.

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