Retention of Selenium in Kidneys,Liver and Striated Muscle After Prolonged Feeding of Therapeutic Amounts of Sodium Selenite to Pigs

Sodium selenite was mixed in a commercial pig food so as to increase the original selenium content (0.126 ppm) by 1.2 ppm. The supplemented food was given to 7 pigs during 78 days. A control group of as many pigs was given the non-supplemented commercial food. The pigs were killed, starting 4 hours after the last selenium-supplemented food had been given and then with intervals during the next 14 days. Small but significant increases of tissue selenium were noticed in liver and striated muscle as compared with the control animals. The kidneys showed no increase.     

Studies on in Vitro Erythrocyte Uptake of I131-Labelled 1-Triiodothyronine as A Test of Thyroid Function in Dairy Cattle

Uptake of I¹³¹-labelled triiodothyronine by erythrocytes (EU test) as a test of thyroid function has been studied in cattle. The normal EU value for 141 Swedish Red-and-white cows was 6.99 ± 0.95 (range 4.45–10.23) at an incubation time of one hour. Statistically significantly higher values were obtained for newly-calved cows. The EU values for calves are significantly higher but by 12 to 18 months of age decline to the same level as for older cows.The principle of the test is described and the results obtained compared with those for human beings. The EU test is suitable for screening thyroid function for large groups of animals and for studying associations between thyroid activity and different production qualities.     

STUDIES ON WEED SPECIES OF THE GENUS POLYGONUM L.

Summary. Seeds of Polygonam persiaria were collected from seven localities during 1962. In 1963 plants of these seven populations were grown in the field and sampled at regular intervals over the period 21st June to 13th August. At all samplings there were differences between populations in total dry weight, in leaf area index and in total nitrogen content, and populations also differed in the date of flowering. The populations also differed significantly in relative growth rate, leaf area ratio, net assimilation rate and relative nitrogen absorption rate. The variations in net assimilation rate did not appear to be closely associated with variations in leaf area index. Certain growth attributes were correlated with the latitude of origin, and it is tentatively suggested that the populations may represent genetically distinct latitudinal ecotypes.
Études sur des espèces de mauvaises herbes du genre Polygonum L.     

Methods of analysis for toxic elements in food products. 3. Limit of determination of methods for assuring safety

To evaluate the suitability of the analytical methods used in determining food safety, a new metrological characteristic "MQS" is suggested. MQS is defined as the absolute minimum quantity in micrograms of a substance that can be determined in a test solution (solubilized test portion). MQS accounts for 2 factors: (a) the necessity for a reliable determination of ML (maximum permitted level, i.e., regulatory tolerance), and (b) the optimum quantity of test portion of a food product to be analyzed, and thus assists in evaluating the suitability of a method to assure food safety. The MQS of 8 toxic elements in any food are As, 3; Cd, 0.5; Cu, 20; Fe, 50; Hg, 0.2; Pb, 4; Sn, 200; Zn, 100 micrograms. To characterize the applicability of any given method, the specific minimum limit of determination, MQSM, must be established for each method. The method in question may be used to control food safety only if MQSM is less than MQS. MQSM values are given for the common polarographic and colorimetric methods for determining these elements.     

Seasonal variation in the photosynthetic capacity of a willow (Salix cv. Aquatica gigantea) canopy. 1 Changes in the activity and amount of ribulose 1,5-bisphosphate carboxylase-oxygenase and the content of nitrogen and chlorophyll at different levels in the canopy

The role of ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) in the regulation of photosynthesis in the field was assessed by following changes in the amount and activity of Rubisco and in the amounts of chlorophyll and total nitrogen in a willow (Salix cv. Aquatica gigantea) canopy during two growing seasons. An additional aim of this study was to determine how nitrogen is partitioned in the canopy and whether Rubisco and chlorophyll serve as sources of nitrogen. During both growing seasons, the total activity and the amount of Rubisco were high in young, sun-exposed leaves and decreased as the leaves aged and became shaded. In 1985, the specific activity was low (on average 0.8 micromol mm(-1) mg(-1) Rubisco protein) compared with the values obtained in 1986 (on average 1.8 micromol min(-1) mg(-1) Rubisco protein). These differences in the specific activity of Rubisco between the two years might be associated with changes in partitioning of nitrogen. During the cool summer of 1985, about 20% of the total nitrogen was partitioned to Rubisco compared with about 13% during the warm summer of 1986. Rubisco comprised a high proportion (about 60%) of the total soluble protein throughout the 1985 growing season, whereas during the 1986 growing season, the proportion of Rubisco in the total soluble protein fraction was lower and decreased markedly as the leaves became shaded. Chlorophyll did not serve as a source of nitrogen in the canopy. On the contrary, the proportion of total nitrogen in chlorophyll increased with time, which indicates acclimation of the thylakoid membranes to decreasing irradiance. The degree of activation of Rubisco in samples collected in 1986 was high in young, sun-exposed leaves, which suggests that in these leaves, Rubisco may limit the rate of CO(2) uptake. In the shaded leaves of the lower canopy, the degree of activation of Rubisco was low, which indicates that in these leaves, photosynthesis is limited by factors other than Rubisco.