EVIDENCE FOR THE OCCURRENCE AND DISTRIBUTION OF INORGANIC POLYPHOSPHATES IN VERTEBRATE TISSUES

Evidence for the occurrence of polyphosphates having apparent chain-lengths ranging from less than 10 to over 5000 orthophosphate units has been found in adult brain as well as in a number of other mammalian tissues which have been examined. There appears to be three times as much polyphosphate in rat brain as there is in rat liver. Adult rat brain appears to contain at least 15 μg of phosphorus as polyphosphate per g of fresh tissue. In addition, neural polyphosphate is extremely labile to catabolic degradation after death whereas hepatic polyphosphate is relatively more stable. The nature of this inorganic polymer was elucidated through use of the technique of ³¹P nuclear magnetic resonance spectroscopy. Further structural evidence was obtained by application of the isotopic dilution technique to ³²P-labelled neural polyphosphate mixed with an abiotically prepared inorganic polyphosphate. The conditions and rates of hydrolysis of the biological polyphosphate and a non-biological polyphosphate were comparable.     

Deductive analysis of a protein-synthesis mutant of Escherichia coli

A mutant of E. coli, T ^s68b, selected as unable to grow at 43 C, is unable to synthesize proteins at 43 C, though it can carry out this function at 30 C. This defect is shown to be in the protein-synthetic rather than the RNA-synthetic machinery by an analysis of the response of the strain to infection with the RNA bacteriophage f2. An analysis of the capacity for RNA synthesis and the polyribosome content of these cells at 44 C indicates that the defect resides in the elongation step of protein synthesis. No defects could be detected in vitro. The results are discussed in light of similar data on other mutants and in relation to the general approach of analyzing complex mutants selected with ill-defined phenotypes.This work was supported by Grant GM14368 from the National Institute of Health.     

A further study on the dietary-regulated biosynthesis of high-sulphur wool proteins

When the diet of sheep is supplemented by the infusion of sulphur-containing amino acids or casein into the abomasum, the newly synthesized wool shows characteristic changes in its amino acid composition, with significant increases in cystine, proline and serine and decreases in aspartic acid and phenylalanine. This modification seems to be due entirely to an alteration in the overall composition of the high-sulphur proteins and to an increase in their proportion in the fibre. These variations are not the result of a change in the composition of individual proteins, but are due to alterations in their relative proportions and to the initiation of the synthesis of `new' proteins, many of which are extremely rich in cystine. It is suggested that the heterogeneity of the high-sulphur proteins may be due, in part, to similar changes in composition caused by natural variations in the nutrition of sheep.     

Metabolism of 35S-labelled Antithyroid Drugs in Man

Differences in the metabolic fate of antithyroid drugs influence the optimal frequency of administration and their therapeutic efficacy. ³⁵S propylthiouracil differed from the ³⁵S imidazoles (carbimazole and methimazole) in the more rapid absorption and excretion and the shorter biological half-life in the plasma of the former. Renal function may have a more important influence on the biological half-life of the drugs than thyroid status. Further work is required to determine the optimal frequency of administration for each compound.     

AN ELECTRON MICROSCOPIC STUDY OF THE PASSAGE OF COLLOIDAL PARTICLES FROM THE BLOOD VESSELS OF THE CILIARY PROCESSES AND CHOROID PLEXUS OF THE RABBIT

The thinnest areas of the capillaries of the choroid plexus and ciliary processes in the eye of the rabbit are characterized by the presence of fenestrae. When various colloidal particles opaque to the electron beam (thorotrast, gold sol, and saccharated iron oxide) were injected into the blood stream, none were found in fenestrae or in areas that might suggest their having passed through fenestrae. The passage of marker particles from the lumen to the surrounding connective tissue does take place on occasion in the areas of thicker walls in the capillaries and venules rather than in the attenuated and fenestrated endothelial walls. The pathway taken by these markers may be either through the cytoplasm of the endothelial cells via membrane-bounded vesicles and vacuoles or through the intercellular spaces of the vessels. An altered aqueous humor (cloudy and plasmoid) was produced by endotoxin injection or by making a draining fistula in rabbit cornea. Both methods gave rise to the same changes in the blood vessels of the ciliary processes. Under such conditions of inflammation the passage of colloidal particles through the thicker walls of the capillaries and venules was greatly increased and occurred primarily as an intercellular passage between the endothelial cells. The attenuated and fenestrated areas of the endothelium of the small capillaries remained unchanged with no particles passing through them. These results on the altered vessels of the ciliary processes parallel those of Majno and Palade (26) on the rat cremaster muscle.