Effects of alkali ions on myosin conformation

We have used two probes to study the effects of alkali ions on the conformation of myosin. One was paramagnetic, the “spin label” N-(1-oxyl-2,2,6,6-tetramethyl-4-piperidinyl)-maleimide, which binds primarily to SH groups; and the other was fluorescent, l-anilino-8-naphthalenesulfonate, which binds to an apolar niche. The bonding of the spin label to myosin was carried out in 0.6M LiCl, 0.6M NaCl, or 0.6M KCl, and the resulting labeled myosin was studied in the same medium in which the myosin was labeled as well as in other alkali chlorides. The electron paramagnetic resonance spectra of the spin label showed that the structure of myosin in the vicinity of the labeled groups differed in the various salts. The protein surface in the region of the labeled groups restricted the rotational freedom of the spin label more in KCl than in any of the other salts. Although ions are known to influence the properties of myosin, our results show that these ions also effect the molecular structure. The fluorescence of l-anilino-8-naphthalenesulfonate, noncovalently attached to myosin in the presence of alkali chlorides, decreased progressively with increasing size of the cations, again showing the protein structure near the probe attachment to be a function of the cation, in the solvent. Ca²⁺ quenched the fluorescence of the bound probe, indicating an interaction between Ca²⁺ and the myosin molecule. The effect of Ca²⁺ on the fluorescence was greatest in KCl.     

Fine Structure Mapping in Yeast with Sunlamp Radiation

The X-ray mapping procedure of Manney and Mortimer (1964) is the most widely applicable and convenient method for fine structure analysis in yeast, but suffers the disadvantage that suitable X-ray machines or gamma ray sources are very expensive. Although many other recombinogens are known, none gives a linear dose-response like X-rays and few are as convenient or give as reproducible results. Experiments with Saccharomyces cerevisiae reported in this paper show, however, that the near-ultraviolet radiation emitted by fluorescent sunlamps gives linear dose-response relations, as reproducible results as ionizing radiations, and map distances which correlate highly with those obtained by using (60)Co gamma rays. It is suggested that this convenient recombinogen may be a suitable low-cost substitute for ionizing radiations in fine structure mapping.     

Red Cell Glucose-6-Phosphate Dehydrogenase Deficiency—A Newly Recognized Cause of Neonatal Jaundice and Kernicterus in Canada

Seven male newborns of Chinese, Greek and Italian origin presented with severe hemolytic jaundice due to red cell glucose-6-phosphate dehydrogenase (G-6-PD) deficiency. In five, the hemolysis was precipitated by inhalation of mothball vapours in the home. Kernicterus was evident upon admission in six infants and was fatal in four of these.G-6-PD deficiency should be suspected as a cause of jaundice in all full-term male infants of these ethnic groups. The diagnosis can be confirmed in any hospital by the methemoglobin reduction test. In areas similar to Toronto, Canada, where these high-risk ethnic groups prevail, the following measures are recommended: (1) detection of G-6-PD deficient newborns by screening cord bloods of all infants of these ethnic groups; (2) protection of affected infants from potentially hemolytic agents such as naphthalene, certain vitamin K preparations, and sulfonamides; and (3) observation of serum bilirubin levels to assess the need for exchange transfusion for hyperbilirubinemia.     

The flow of a viscous liquid in a converging tube

The problem of the viscous flow of an incompressible Newtonian liquid in a converging tapered tube has been solved in spherical polar coordinates. The method of the solution involves the Stokes' stream function and a technique introduced by Stokes in the study of a sphere oscillating in a fluid. The theory for the flow in a rigid tube includes: (1) the pulsatile flow with both radial and angular velocity components; (2) the steady state flow with both radial and angular velocity components and (3) the very slow steady state flow with only a radial velocity component present. For a tapered elastic tube, the velocity of the propagated pulse wave is determined. The solution given is in terms of the elastic constants of the system and the coordinates for this type of geometry. The pulse velocity is then related to the velocity in an elastic cylindrical tube with the necessary correction terms to account for the tapered tube. Supported in part by the American Heart Association (No. 62F4EG). This work was done during the tenure of an Established Investigatorship of the American Heart Association.     

Direct inhibition of the signaling functions of the mammalian target of rapamycin by the phosphoinositide 3-kinase inhibitors, wortmannin and LY294002.

The immunosuppressant, rapamycin, inhibits cell growth by interfering with the function of a novel kinase, termed mammalian target of rapamycin (mTOR). The putative catalytic domain of mTOR is similar to those of mammalian and yeast phosphatidylinositol (PI) 3-kinases. This study demonstrates that mTOR is a component of a cytokine-triggered protein kinase cascade leading to the phosphorylation of the eukaryotic initiation factor-4E (eIF-4E) binding protein, PHAS-1, in activated T lymphocytes. This event promotes G1 phase progression by stimulating eIF-4E-dependent translation initiation. A mutant YAC-1 T lymphoma cell line, which was selected for resistance to the growth-inhibitory action of rapamycin, was correspondingly resistant to the suppressive effect of this drug on PHAS-1 phosphorylation. In contrast, the PI 3-kinase inhibitor, wortmannin, reduced the phosphorylation of PHAS-1 in both rapamycin-sensitive and -resistant T cells. At similar drug concentrations (0.1-1 microM), wortmannin irreversibly inhibited the serine-specific autokinase activity of mTOR. The autokinase activity of mTOR was also sensitive to the structurally distinct PI 3-kinase inhibitor, LY294002, at concentrations (1-30 microM) nearly identical to those required for inhibition of the lipid kinase activity of the mammalian p85-p110 heterodimer. These studies indicate that the signaling functions of mTOR, and potentially those of other high molecular weight PI 3-kinase homologs, are directly affected by cellular treatment with wortmannin or LY294002.     

Chronic Pseudomonas aeruginosa endobronchitis in rhesus monkeys: II. A histopathologic analysis

We have recently established a rhesus monkey model of chronic Pseudomonas aeruginosa (PA) endobronchitis by bronchoscopic instillation of PA-embedded agar beads. All experimental animals developed chronic neutrophilic endobronchitis similar to chronic PA endobronchitis in cystic fibrosis (CF). Histopathologic studies further confirmed similarities to chronic PA endobronchitis in CF, including marked peribronchial inflammation, epithelial damage, presence of degraded cilia and ciliary abnormalities, appearance of PA bacterial clusters, mucosal hyperplasia, goblet cell hypertrophy/hypersecretion, airway obstruction, alveolar abnormalities, bronchiectasis, and fibrosis.