A study of methods for the classification of bottom deposits of natural waters
The study of the role of bottom sediments of rivers and maturation ponds in the purification of polluted waters which flow over them has been handicapped by lack of suitable methods for classifying sediments according to their physical, chemical and biochemical characteristics . Bottom deposits of lakes, rivers and dams may be regarded as soils which have developed under humid and water-logged conditions . The judicious application of the methods developed by soil scientists for the assessment of agricultural soils to the evaluation of certain important characteristics of sediments is therefore a logical development. Pioneering work in this respect was done by ZULLIG (1955) who applied a number of the methods of soil analysis to bottom deposits of eutrophic and oligotrophic lakes in Switzerland and attempted to correlate the results with the degree of trophy of the lake. Both he and OHLE (1955) pointed out that bottom deposits have ion-exchange properties which can contribute to the removal of ions from the water phase into the muds, but neither of these workers attempted to measure the extent to which this occurs quantitatively. In the present study a number of methods used to determine chemical, physical and biochemical properties of soils have been applied to bottom sediments from the Apies River near Pretoria, including samples taken near its origin where it is free from pollution, below the point of discharge of treated effluent from the Pretoria Sewage Works, where considerable pollution occurs and further
A Single-Solution Method for the Determination of Soluble Phosphate in Sea Water
It has been found that a reagent containing sulphuric acid, ammonium molybdate and ascorbic acid may be used as a single-solution reagent for the determination of phosphate in sea water. Development of the molybdenum-blue colour is complete in 24 h at room temperature and in 30 min at 60° C; the colour is stable for at least 3 days. Beer's law is obeyed closely up to at least 500 μg PO43−-P/1. The salt error is approximately 4% with sea water of chlorinity 19·3%. The interference due to either arsenate or silicate at their concentrations in sea water is negligible.
Quantitative histochemistry of brain tumors and analogous normal tissue
THE BIOCHEMICAL STUDY of brain tumors has been difficult because of the lack of histologic homogeneity of tumor tissue. This lack of homogeneity is the result not merely of variation in neoplastic cell population, but also of normal brain components passing through the tumor, increased vascularity, focal necrosis, and cyst formation. Such diversity in the structure of tumors makes biochemical analysis difficult because of a high degree of scatter in the results.’** However, Lowry’s3 modifications and refinements of Linderstrgm-Lang’s general histochemical technics have made the examination of complex tissue feasible. Using the microscope for direct dissection of lyophilized sections of tumors allows the removal of 0.1 to 0.3 pg. sections composed predominantly of neoplastic cells; extraneous tissue is avoided. Normal brain tissue may be dissected in the same manner, and comparison tissues are obtained which may be looked upon as normal counterparts of the tumors. With this technic, differences in biochemical findings should be those inherent in the neoplastic cells and not the result of random amounts of cellular contaminants. This study presents a comparison of some aspects of cellular glucose metabolism in normal cerebral tissues and in neoplastic tissues. Each of 4 enzymes concerned with a different aspect of glucose metabolism was investigated. These enzymes were measured in 4 human brain tumors and in normal astrocytes, ependymal cells, and dura mater from the brains of healthy, adult Macaca mulatta monkeys. Analyses of normal glial elements in correlation with studies of normal brain metabolism are urgently needed.