Blood Plasma Of Cows Research Articles

659. Factors influencing the vitamin content of milk fat: V. Changes in vitamin A and carotenoid content of the blood plasma of cows and heifers near parturition in relation to secretion of these substances in the milk fat

1. Plasma levels of vitamin A and carotenoids prior to and following parturition have been followed in groups of cows and heifers maintained under typical New Zealand farming conditions.2. Despite the high carotene intake prior to calving, the cows, and to a lesser extent the heifers, showed decreases in plasma vitamin A and carotenoid level at or near to parturition, the decreases in the levels for the cows being of the same order as those reported in Great Britain and the United States.3. Although the concentration of vitamin A and carotenoids was higher in the colostrum of heifers than of cows, the total daily secretion of these components by the cows was much greater over the first few days of lactation.4. Evidence is advanced to support the suggestion that the decrease in plasma components is related to the extra drain of colostrum synthesis rather than to any hormonal changes associated with parturition.We are indebted to the following: the Department of Scientific and Industrial Research for financial assistance towards the cost of this investigation; Mr R. M. Patchell and the farm staff of The Dairy Research Institute for the collection of milk samples; Miss Fay Frecklington for help with much of the analytical work; one of us (S.Y.T.) to the Royal Society, the Nuffield Foundation, and the Board of The Dairy Research Institute (N.Z.) for a travelling fellowship during the tenure of which the work reported here was carried out.

Effect of Raw Soybeans and of Soybean Oil on Plasma Carotene and on Vitamin A as Measured by Activated Glycerol Dichlorohydrin

Summary Feeding raw soybeans in the amount of 9lb. daily to lactating cows caused marked differences in their blood plasma concentration of carotene from that of cows fed a control ration containing no soybean products. During the first 4 weeks the differences increased rapidly, but by 7–9 weeks they seemed to level off at about 250 γ carotene per 100ml. of blood plasma. The reversal in blood plasma concentrations of carotene that took place after a switch-over of rations was made between the cows receiving the control and the raw soybean rations indicates that the causative factor was the feed rather than the individuality of the cows. The feeding of expeller process soybean oil to lactating cows caused differences in their blood plasma concentrations that were intermediate with the concentrations found in the blood plasma of cows fed a control ration containing no soybeans or soybean products and cows fed raw soybeans. The oil apparently depressed the carotene concentrations but not to the extent of the raw soybeans. The differences that occurred in the blood plasma vitamin A concentrations among the cows fed the control, raw soybean and soybean oil rations were small and showed no particular trends. Activated glycerol dichlorohydrin, a new reagent for the determination of vitamin A, proved to be satisfactory for this determination in bovine blood.

Gystine in Normal and Gystinuric Human Blood

It is usually stated that cystine is not present in detectable quantities in normal human blood. The failure of the satisfactory recovery of small amounts of cystine added to blood has been attributed, by Harding and Gary, to difficulties in the preliminary deproteinization necessary prior to cystine determination. They have reported the presence of little, if any, free cystine in cow blood plasma. The amino nitrogen of normal blood (4-7 mg. %) should include small amounts of cystine nitrogen. If loss of cystine in deproteinization could be avoided and if a sufficiently delicate method for the determination of cystine were available, it should be possible to detect cystine in normal blood. By the use of ultrafiltrates of oxalate-fluoride plasma, mechanical loss of cystine by deproteinization has been avoided and the application of the method of Sullivan to the determination of cystine in such ultrafiltrates has been made possible by the use of the Pulf rich photometer. The details of the preparation of the ultrafiltrates and the determination of cystine will be presented elsewhere in connection with studies of the intermediary sulfur metabolism of experimental animals. Recovery of small amounts of cystine added to blood has been satisfactory. Application of the above procedure to normal human blood has indicated the presence of approximately 1.0 mg. % of cystine in plasma ultrafiltrates. Samples of blood of one of us (B.H.B.), taken after fasting periods of 12 to 18 hours, have given values of 0.71, 0.80, 0.92 and 0.93 mg. % of cystine in the plasma ultrafiltrate and values of 0.80, 0.91 and 1.05 mg. after meals. The ultrafiltrate of the blood of the same individual, withdrawn 3 hours after the oral administration of 6 gm. of cystine in gelatine capsules, contained 1.72 and 1.40 mg. % of cystine, respectively in 2 experiments. In a third study, in which 7 gm. of cystine were fed, 1.30 and 0.88 mg. % of cystine were present in the plasma ultrafiltrates of blood samples taken 3 and 5 hours later, respectively. In 4 other normal subjects, cystine values ranging from 0.82 to 1.13 mg. were obtained. The plasma ultrafiltrate of the blood of a cystinuric patient (S.P.) contained 1.13 mg. % of cystine, a value slightly higher than our average normal value, but, we believe, within the upper limit of the range of values for normal human blood. To this subject, 5.6 gm. of methionine were administered in 2 equal portions at the morning and midday meals. The plasma ultrafiltrate of a sample of blood withdrawn at 3 :45 P. M. contained 0.92 mg. % of cystine. It may be noted that, while the isolation of cystine from cystinuric blood has been claimed,, no quantitative data have been reported. It should be noted that no attempt was made to determine the possible presence of cysteine in these ultrafiltrates. The values reported represent “total” cystine, i. e., values obtained by the application of the Sullivan procedure to the ultrafiltrates after reduction with cyanide. This research was made possible by a grant to one of us (H.B.L.) from the Faculty Research Fund of the University of Michigan for the study of cystinuria.