Specialized techniques, previously used in surgically prepared goats, which simultaneously measure udder metabolism (arteriovenous difference of milk precursors x udder blood flow) and the whole body turnover of the milk precursors, have been successfully transferred to dairy cows. Methods of obtaining representative samples of arterial and mammary venous blood and of measuring udder blood flow are described.The rates of entry into the circulation, as determined by isotope dilution, of glucose, acetate and plasma free fatty acids were 3-3-4-0, 1-7-2-1 and 0-5 kg/day respectively. Acetate and glucose contributed 32-50 and 4-11% respectively of the total CO a output by the animal.Measurement of the uptake of precursors of milk constituents and their transfer into milk showed that there were substantial arteriovenous differences of glucose, acetate, triglyceride and /?-hydroxybutyrate which were not significantly different between breeds or related to milk yield. Isotopic and balance data confirm that glucose is the main precursor of lactose and that the oxidation and transfer of glucose into lactose accounted for 69-98 % of the glucose entry rate. As in the goat, plasma triglycerides and blood acetate accounted for 35-80 % and 25-50 % of the milk triglycerides respectively. Propionate was extracted from plasma but the uptake was only about 8 % of the value for acetate.There was no net arteriovenous difference of phospholipids, cholesterol esters or free fatty acids, but the fall in specific radioactivity of free fatty acids across the mammary gland indicated there was an exchange of free fatty acids between plasma and mammary tissue. In agreement with previous findings, acetate contributed to all the milk fatty acids up to a chain length of C 14 and part of the C 16 fatty acid. Plasma triglycerides contributed to the remainder of the C 16 fatty acid and all the milk fatty acids with a chain length of C 18 or higher.In contrast to the lactating goat, cow plasma contained very few chylomicrons. The majority of the triglycerides taken up by the udder were derived from the lowdensity lipoprotein fraction.The essential amino acids were extracted from blood in amounts sufficient to account for the essential amino acids secreted into milk protein. Although the plasma level of methionine was low, 52-72 % of the material reaching the mammary gland was taken up. The uptake of arginine was far in excess of the requirement for milk protein synthesis.been difficult to interpret such trials accurately because oi our relative ignorance of the complex The economic importance of the dairy cow has processes involved in the body's mechanisms reguled to numerous studies on the effect of diet on the lating the uptake and metabolism of milk preyield and composition of milk. Frequently it has cursors by the udder. However, in fed and fasted • Present address: Biochemistry Department, Lin-goats important quantitative data have been coin College, University of Canterbury, New Zealand. obtained by simultaneously measuring milk out-

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The present experiment was conducted to determine the effect of muscle temperature during the prerigor and early postrigor period on meat tenderness, postmortem proteolysis, calpain system activity, water-holding capacity, and color. Lamb longissimus muscle (n = 14) from the right and left carcass sides was excised immediately after dressing, divided into an anterior and posterior sample, vacuum-packaged, and stored overnight at 5 to 35 degrees C. Further storage, up to 14 d postmortem, was at 2 degrees C. Tenderness at 1 d postmortem, tenderization during further storage, and postmortem proteolysis were negatively affected by overnight incubation above 25 degrees C. This effect could be explained by an effect of temperature on muscle contraction and activity of the calpain system. Muscle contraction was at a minimum after incubation at 15 degrees C. Water-holding capacity was negatively affected by incubation above 25 degrees C. Color scores improved with increasing incubation temperature at 1 d postmortem. However, after 14 d of postmortem storage, no differences in color scores were observed. Based on the present results and results of other groups, a temperature around 15 degrees C at the onset of rigor seems optimal to maximize tenderness without having detrimental effects on water-holding capacity or color.

SummaryVariation in the nucleotide sequence of the B2 high‐sulfur protein genes has not been reported previously. This paper reports 15 nucleotide substitutions in each of the genes for the B2A and B2C proteins and a length of polymorphism in the B2A gene which translates to the insertion/deletion of one 30‐nucleotide repeat sequence. Evidence is presented for gene conversion occurring within the B2 high‐sulfur multigene family. These DNA polymorphisms may account for some of the microheterogeneity observed in the B2 high‐sulfur proteins and may also be useful genetic markers of the B2 high‐sulfur protein gene loci for future use in analysing wool fibre characteristics.

The design and elaboration of a series of macrocyclic templates that exhibit a propensity to adopt a beta-strand-like peptide-backbone conformation led to potent and selective inhibitors of calpain 2. Macrocycle 1 retarded calcium-induced opacification in an ovine-lens culture assay and is a lead compound for the development of a drug for cataract treatment. Cbz=carbobenzyloxy.