Effect of a potassium-deficient diet on arterial blood pressure, plasma and tissue cations, and tissue norepinephrine in the hypertensive dog

Chronic potassium deficiency in one-kidney one-clip hypertensive dogs significantly reduces blood pressure and plasma potassium, with a simultaneous increase in plasma renin activity. Tissue potassium concentration was decreased and tissue sodium concentration was increased in striated muscle and adrenal glands, which may suggest that the sodium-potassium pump was inhibited. In myocardium the sodium concentration was higher but the potassium concentration was not significantly lower than in control hypertensive dogs on normal diets. Arterial cation concentrations in the potassium-deficient group were not significantly different from those in the control group. Tissue norepinephrine concentration was higher in arteries from potassium-deficient animals, significantly so in the mesenteric and femoral arteries. The conclusion is that potassium deficiency may decrease blood pressure in the one-kidney one-clip hypertensive dogs by impairing the release of norepinephrine.     

Long-acting contraceptive agents: Norethisterone esters of arylcarboxylic acids

The synthesis of esters of norethisterone (17α-ethynyl-17β-hydroxy-estr-4-en-3-one) with acids containing a benzene ring is described, two methods of esterification being compared in terms of yield and convenience. The activities of these esters as long-acting contraceptive agents have been evaluated.     

Reinvestigation of the shape and state of hydration of the skeletal myosin subfragment 1 monomer in solution

Hydrodynamic calculations lead to the conclusion that chymotryptic (or ethylenediaminetetraacetic acid) myosin S1 in solution (hydrated), at 1-5 degrees C, can be modeled as a prolate ellipsoid, with an axial ratio lying between p = 1.0 and 2.5 (major axis between 100.5 A, for p = 1.0, and 162.5 A, for p = 2.5). The degree of hydration is considerable (1.24 g/g for p = 2.5 and 2.02 g/g for p = 1.0). The dehydrated myosin head is pear-shaped under the electron microscope, and its narrowest part is located near the junction with the tail [Elliott, A., & Offer, G. (1978) J. Mol. Biol. 123, 505-519]. Mendelson & Kretzschmar [Mendelson, R. A., & Kretzschmar, K.M. (1980) Biochemistry 19, 4103-4108] have shown that the pear-shaped molecule does not predict the experimental X-ray scattering curve. Nor is this model able to predict the hydrodynamic values. The three-dimensional model for S1 used by Mendelson and Kretzschmar gives a rather good fit to the experimental X-ray scattering curve, but it does not predict the hydrodynamic values. In order to try to reconcile the three models and to fit the X-ray scattering curve and the hydrodynamic data, we suggest that, in solution, the S1 monomer has the shape of a prolate ellipsoid and that an inclusion of bound water exists at one extremity of the protein. The rest of bound water surrounds the protein. As first approximation, the dry protein and the hole are assumed to have the same shape as the hydrated molecule (prolate ellipsoid; p).(ABSTRACT TRUNCATED AT 250 WORDS)     

Protein kinase activity of purified components of the chicken oviduct progesterone receptor

Preparations of the 90K and 110K components of the chick oviduct progesterone receptor (PR) purified to near homogeneity were tested for protein kinase activity. The 90K component was shown to incorporate radioactive phosphate from [γ-³²P]-ATP in the presence of Ca²⁺ but not of Mg²⁺ ions, while the 110K component was phosphorylated in the presence of Mg²⁺, but not of Ca²⁺. The enzymatic activity of the 90K polypeptide appeared selective, since added proteins (histones) did not become phosphorylated. However, all proteins present in the 110K preparations were phosphorylated in the presence of Mg²⁺. These data suggest that components of the chick oviduct PR display protein kinase activity.     

Studies on the fine structure of puffs in Sciara coprophila

Fine structure of RNA and DNA puffs of Sciara coprophila was studied during late developmental stages of the fourth larval instar. In RNA puffs the predominant structure seen seems to be a diffuse, lampbrush-like thread or threads sectioned in a variety of planes. The thread is composed of filamentous and granular material. Three types of RNA puffs, each with a slightly different morphology, are found. In their development DNA puffs pass through a precise sequence of stages, each with its distinct morphologic and metabolic characteristics. At the initial and final stages, when much of the puff chromatin is in the compacted state, DNA puffs resemble condensed chromosomal bands. In contrast, at stages when most chromatin is diffuse, DNA puffs share many structural characteristics of RNA puffs. Most of the expanded puff area is permeated by lampbrush-like threads composed of fibrils and granules. RNA and DNA puffs were compared with respect to granule size and distribution by means of electron micrographs of known magnification. The results of the statistical analysis show that: 1) The coefficient of variation (C.V.) of the method of measurement falls between 5 and 7%. 2) There is a fluctuation in granule sizes within each puff with a C.V. of 24–26%. 3) The average granule diameter is 238 Å for DNA puffs and 310 Å for RNA puffs; the difference is statistically significant. 4) The variation in mean granule size in a sample of DNA puffs is rather small (C.V. 12%), while the variation in granule size between different RNA puffs is somewhat larger (C.V. 20%). 5) The relative spread of granule sizes in DNA puffs is more restricted than that in RNA puffs. It is evident then that, on the average, DNA puff granules are smaller and more uniform than granules found in RNA puffs.     

Helix–coil transition in poly(γ-benzyl-L-glutamate) and poly-ε-carbobenzoxy-L-lysine

In this paper two points are considered: the methods of evaluating the helical content θ and the calculation of the parameters of the transition from experimental data and its interpretation. The parameter ΔH obtained is in good agreement with the calorimetric one and v is found to be independent of temperature and solvent and in agreement with the ordinarily accepted value for poly(γ-benzyl-L -glutamate). The different methods of estimating θ are discussed for both polypeptides.     

Structural and immunological studies on the protoplast membrane of the yeast Candida utilis

Cell membranes of the yeast Candida utilis isolated by lysis of protoplasts have been shown to be lipoprotein in nature. Electron microscopy shows that Mg⁺⁺ is responsible for maintaining the integrity of the membrane. A close serological relationship was found between membranes and cell walls isolated from the yeast. This relationship was exhibited not only by membranes obtained by strepzyme treatment but also by those obtained from the action of helicase enzyme. No such relationship existed between membranes and whole cells. Related data have been obtained by treatment of yeasts with different digestive enzymes. All of the results suggest that the protoplast membrane possesses traces of structural cell wall material. This material is detectable by serological tests, but not by electron microscopy.     

Preparation of protoplast-like structures from conidia ofFusarium culmorum

Protoplast-like structures have been formed by digestion of the cell walls ofFusarium culmorum conidia by lytic enzyme preparations ofMicromonospora AS. Under the test conditions extrusion of the protoplasts was not observed. It seems that digestion of the cell wall occurs in different stages. Digestion of the septa preceded the formation of protoplasts of the individual cells of the multicellularF. culmorum conidia. A few protoplasts survived the lytic enzyme treatment. “Protoplasts” obtained from conidia are much more stable than those obtained from young hyphae and were able to germinate with the formation of normal mycelium. Lysis of some of the protoplast bodies led to the formation of a membranous structure. The protoplasts derived from each of the constituent cells of the conidia could be isolated with the micromanipulator. No differences were found in the ability of the isolated cells to germinate.