Application of a U-13C-labeled amino acid tracer in lactating dairy goats for simultaneous measurements of the flux of amino acids in plasma and the partition of amino acids to the mammary gland

A preliminary study was conducted using lactating British Saanen goats (n = 5) at 109 to 213 d in milk that yielded 1.67 to 3.68 kg of milk/d to examine the application of a U-13C-labeled amino acid (AA) mixture obtained from hydrolyzed algal proteins as a tracer for measuring plasma flux (n = 5) and partition to the mammary gland (n = 3; arteriovenous difference) of 13 AA simultaneously. Except for Ile and Ser, there was incomplete (6 to 54%) equilibration of the tracer with AA from packed blood cells (> 90% erythrocytes) during the 6-h infusions. This result agreed with the large ratio of packed cells to gradients for plasma AA concentration that was also observed. However, net mass and isotope removals by the mammary gland were predominantly from plasma, indicating that the erythrocytes did not participate in kinetic exchanges. Plasma AA fluxes (millimoles per kilogram of metabolizable protein intake per kilogram of body weight 0.75) differed among goats that consumed different protein sources; however, overall rates were lowest for Met (5 to 14) and His (8 to 17) and highest for Leu (48 to 70) and Ala (53 to 88). On average, 25% of plasma flux was partitioned to the mammary gland. Less than 20% of His, Ser, Phe, and Ala were directed to the mammary gland; 20 to 30% of Arg, Thr, Tyr, and Leu were directed to the mammary gland; and 30 to 40% of Pro, Ile, Lys, and Val were directed to the mammary gland. The unidirectional AA flux in the mammary gland (AA apparently available for protein syntheses, oxidation, and metabolite formation) did not match the pattern that is required for casein synthesis, suggesting differences in the metabolic requirements of AA for nonmilk protein synthesis.     

Processing of procathepsin from Musca domestica eggs

The major source of amino acids for insect embryos are yolk proteins which accumulate in developing oocytes and are hydrolyzed during embryogenesis. Studies on Musca domestica embryogenesis indicated that a cathepsin B-like proteinase is responsible for yolk protein degradation (Ribolla et al., 1993). In this study, we report the purification of mature cathepsin and show that it is made up of a single 41 kDa polypeptide chain. The Musca domestica cathepsin NH2-terminal 11-residue sequence was determined (Ala-Pro-Lys-Tyr-Val-Asp-Tyr-Gly-Glu-Asn-Glu) and reveals homology with other cathepsins of the papain family. Experiments using serum anti-cathepsin show that the enzyme is stored in oocytes as a 55 kDa zymogen. The activation of the zymogen occurs in vitro only at low pH. In vitro activation in the presence of cysteine protease inhibitors is blocked at an intermediary polypeptide of 48 kDa. Kinetic studies of this activation process at pH 3.5 and 4.6 show that the zymogen is processed in a manner similar to that of pepsin (Foltmann, 1986) and papain (Vernet et al., 1991). We propose that Musca domestica cathepsin zymogen activation occurs in two steps. First, an intramolecular cleavage of the procathepsin polypeptide chain (55,000), induced by low pH gives rise to an intermediary polypeptide (48,000) which then undergoes autolysis to produce the mature enzyme (41,000).     

The value of pancuronium in prolonged intraocular operations

We wished to determine the effectiveness of Pancuronium, a non-depolarizing muscle relaxant, in prolonged intraocular operations. We compared the variations in intraocular pressure when using four different methods of induction of general anesthesia. With Pancuronium the intraocular pressure fell initially and then rose to just below pre-induction levels and remained there. Our study suggests that pancuronium stabilizes intraocular pressure at a level which is highly desirable for intraocular surgery.     

Multiple recurring gastric erosions/aphthous ulcers)

Five patients are described who had repeated endoscopy because of continuing dyspeptic symptoms associated with a negative barium meal. They were found to have multiple recurring gastric erosions (aphthous ulcers). No common aetiological factor could be found, although four of these patients did have a mild or moderatley active superficial chronic gastritis. Conventional peptic ulcer therapy failed to control either symptoms or ulceration. Two patients finally came to gastric surgery (highly selective vagotomy), which resulted in the relief of symptoms and healing of the gastric aphthous ulceration.     

Effect of oral contraceptives on the blood lipid level

Secretion of estrogens in the urine and the content of cholesterol and triglycerides in blood plasma were studied in 36 healthy women 24 of whom took oral contraceptives including estrogenic and gestagenic components to prevent conception. It proved that after the first course of medication the overall estrogen excretion reduces at the expense of all fractions but more so at the expense of the active fraction. Beginning with the 2nd week the cholesterol level in the blood plasma increases and the level of triglycerides grows considerably. The increase in these indices was observed in the first 6 months when the oral contraceptives were taken. With the preparations taken for a longer time the blood plasma cholesterol and triglyceride levels became stable.