principle which inhibits growth of Krebs-2 carcinoma in 3-4 week old female 

 CF1 mice. Typical mean control tumor weight was about 2,200 mg. Mice 

 receiving mercenene for 7 days had a mean tumor weight of 750 mg. Molecular 

 weight of active principle was less than 1000. - J.L.M. 



1638 



Schmeer, M. Rosarii, Derek Horton, and Akio Tanimura. 1966. 



Mercenene, a tumor inhibitor from Meroenaria: Purification and characterization 

 studies. Life Sci. 5(13): 1169-1178. 



Preparations from tissue of Mereenaria mereenaria possess demonstrated in vivo 

 antitumor activity, ascribed to presence of a biologically active principle 

 named mercenene. In purified preparations mercenene is slowly dialyzable, 

 heat stable, and highly active in tissue culture against human HeLa cancer 

 cells. Samples from 10 independent preparations had these percentage 

 elemental compositions: C 5.9-6.9; H 4.8-5.8; N 10.1-13.2; P 0.1-0.15; S 15.7- 

 16.7; ash (as sulphate) 41.7-42.6%. X-ray powder diffraction patterns of 

 solid samples revealed lines of moderate intensity corresponding to ammonium 

 sulphate and sodium chloride, with a complex pattern of sharp lines indicating 

 a crystalline, organic substance. Tentative estimates of molecular weight were 

 in the range 280-550. Desalted, exhaustively dialyzed mercenene probably has 

 a glycopeptide-type structure, possibly associated with a small proportion of 

 protein. An earlier proposal that the tumor-inhibitory principle of mercenene 

 is a volatile derivative of methylglyoxal appears improbable. - J.L.M. 



1639 



Schmitt, F. 0., R. S. Bear, C. E. Hall, and M. A. Jakus . 1947. 



Electron microscope and X-ray diffraction studies of muscle structure. Ann. 

 N.Y. Acad. Sci. 47(6): 799-813. 



When molluscan adductor muscles, including those of Venus, are macerated with 

 KC1 a viscous mass is obtained from which may be prepared a suspension of 

 needle-shaped fibrils readily observed with a dark field microscope. This 

 fibrous protein forms a considerable portion of the muscle substance. 

 Solubility properties of this protein differ from those of myosin. To 

 distinguish this protein from myosin it has been given the name paramyosin. 

 Unstained paramyosin fibrils appear mottled under the electron microscope, 

 but when they are stained appropriately a structure of great regularity is 

 observed. The whole structure presents a lattice containing an axial period- 

 icity 5 times that of the band separation of transverse bands, or 5xl45=725A. 

 If a line is drawn through any spot representing a transverse band, parallel 

 to the axis, other spots on this line will be separated by 5 bands. If clam 

 adductor muscles are macerated in Edsall's solution (in which paramyosin 

 fibrils dissolve) , fibrous bundles of another type may be obtained by 

 centrif ugation. These bundles are composed of fine filaments closely 

 resembling myosin filaments of skeletal muscle. Closely adhering to the 

 filaments are dense particles which are frequently aligned to give a cross- 

 striated appearance to the bundles. Axial distance between striations is 

 about 1,100A. It seems probable that myosin components are contractile in 

 these muscles, as they are in striated vertebrate skeletal muscle, although 

 there is no morphological evidence that paramyosin fibrils actually shorten. 

 They may have a role in the clutch mechanism (ability to remain shortened for 

 a long time with minimal expenditure of energy) . Except for those features 

 characteristic of paramyosin and collagen, when present, X-ray diffraction 

 patterns of a wide variety of striated and smooth muscles are essentially 

 the same and therefore have been attributed to the myosin filaments. 

 Differences in structure at the light microscope level of resolution are not 

 reflected in X-ray structure of myosin components. Further advances in 

 understanding the contractile mechanism from the structural approach requires 

 more information about internal organization of myosin filaments. - J.L.M. 



454 



