Physarum myosin light chain binds calcium

Myosin from the slime mold Physarum polycephalum contains three sizes of polypeptides: a heavy chain and two light chains, LC-1 and LC-2. Using a simple qualitative test for calcium binding by comparing electrophoretic migration of the polypeptides in sodium dodecyl sulfate (SDS) acrylamide gels in the presence and absence of calcium, we have found that Physarum myosin light chain LC-2 migrates with an apparent molecular weight of 16,900 daltons in the presence of the metal ion chelator ethylene glycol bis (B-aminoethyl ether) N,N'-tetraacetic acid (EGTA). However, if calcium chloride is added to the sample prior to electrophoresis, the apparent molecular weight decreases to 16,100. Lanthanide and cadmium ions, but not magnesium, can substitute for calcium. Because the ionic radii of Ca2+, La3+, and Cd2+ are almost identical, we conclude that Physarum myosin LC-2 possesses a very size-specific binding site for calcium. Physarum myosin LC-1 and the heavy chain give no evidence for binding calcium by this test. Since cytoplasmic streaming in the plasmodium of Physarum requires calcium, our evidence indicates that the calcium-binding property of Physarum myosin LC-2 may be important in regulating the production of force by actomyosin in the ectoplasm. Unexpectedly, the myosin light chain in Physarum capable of binding calcium, LC-2, is the essential light chain, while LC-1 is a member of the regulatory class of myosin light chains [V. T. Nachmias, personal communication]. Until now, essential myosin light chains have not been shown to have high affinity divalent cation binding sites. This means a new version of the myosin-based model for actomyosin regulation by calcium may be required to explain cytoplasmic movement in Physarum, and perhaps in other motile systems involving cytoplasmic myosins as well.

Cephradine in the treatment of infective endocarditis

Ten patients with a mean age of 34.1 years with infective endocarditis (55% of cases due to Staphylococcus aureus) were treated with cephradine. The peak serum levels of cephradine (8-42 microgram/ml) were 3- to 17-fold higher than the minimum inhibitory concentrations of cephradine against pathogenic strains of S aureus (1.2-4 microgram/ml). Patients treated with cephradine became afebrile in 2 to 13 days of therapy, and their white blood cell count returned to a normal level in 3 to 30 days. Cephradine therapy was well tolerated without any incidence of phlebitis. The drug could be administered by three different routes. Cephradine is a useful cephalosporin for treatment of nonenterococcal gram-positive endocarditis in young heroin addicts.

A Method for Optimal Tolerance Selection

This paper introduces and formalizes a method for specifying independent functional tolerances in an optimal least-cost manner. Previous methods have been thwarted by formulation and computational difficulties presented by nontrivial designs. This method is versatile, submits to a diversity of mechanical problems, and relates the production process and cost to process tolerance in the optimization. This tolerance-specification scheme follows Balas’ zero-one algorithm. Generality and efficiency of the method are discussed. Effects of tolerance relaxation on costs are given. Small and large design problems, constructed to satisfy the requirements of the algorithm, show the practical ramifications. The problem is treated with limit, sensitivity, and probability analysis. Widespread adoption of the method throughout industry is encouraged.

Some pharmacological actions of 2,5-dimethoxy-4-ethylamphetamine (DOET) in rats and mice

DOET, like DOM, exhibited pressor action in rats. This increase of blood pressure was blocked by pretreatment with cinanserin. DOET at high doses decreased the spontaneous locomotor activity of mice at the first hour but increased the activity at the second hour; a low dose was less effective. DOET also increased the rectal temperature of rats and this hyperthermic action was suppressed by pretreating the animals with cinanserin or methysergide. These actions of DOET were compared with those of DOM.

Comparative chemistry of 30S ribosomal proteins of Salmonella typhimurium

Individual proteins from the 30S ribosome of Salmonella typhimurium were isolated and compared with their counterparts in Escherichia coli. Amino acid composition data reveal either no significant differences, or only minor differences in a few residues between paired proteins. Tryptic peptide fingerprints were used to amplify any possible differences between protein pairs.