The adaptive significance of sexuality

A theory of sexuality and polymorphism is proposed in which diversity at the molecular level is the adaptive response of multicellular organisms to the challenge of microparasites that have smaller genomes, shorter generation times and which can evolve more quickly than their hosts. The theory has implications for genetically homogenized crops and other cultivated plants as well as for immunology. A different function of sexuality is proposed for microorganisms that reproduce both asexually and sexually. Several possible experimental tests are discussed. Mathematical modelling techniques are outlined qualitatively and compared with game-theoretical methods which may be interpreted as simplifications of population dynamics of polymorphic host-parasite populations are referenced.     

N-cadherin detected in the membrane fraction of lens fiber cells

Summary N-cadherin was identified as a glycoprotein present in the fiber cell membranes of frog, chick, bovine, rabbit and human lenses. The molecular size of N-cadherin varies with the species. Homogenization of the chick lens in the presence of Ca²⁺ resulted in a decrease in the concentration of N-cadherin. This suggests that the lens contains a Ca²⁺-activated protease which can act on N-cadherin.     

A specific protein in the genusRhynchosciara (Diptera,Sciaridae)

Summary Proteins immunologically related toRhynchosciara americana larval protein 10 occur in the hemolymph and ovaries of five different fly species of the genusRhynchosciara. Electrophoretic analyses showed these proteins to have a mol.wt similar to that of theR. americana protein 10 (43,000), e.g. theR. hollanderi protein 44,300, theR. milleri protein 45,500.     

Communicating junctions between pillar cells in the gills of the atlantic hagfish,Myxine glutinosa

Summary In the respiratory lamellae of the gills of the atlantic hagfish,Myxine glutinosa, pillar cells are coupled by communicating junctions. It is suggested that these cells behave like a functional syncytium.Supported by the DFG, SFB 146. The authors are indebted to Drs F. Walvig and H. Stolte for kindly providing the hagfish. The expert technical assistance of G. Voss-Wermbter, Dipl.-Ing., and H. Heidrich is gratefully acknowledged.     

Elastase digested urokinase (ED-UK)

Summary Elastase digested urokinase (ED-UK) was prepared from human high mol. wt urokinase (HMW-UK). It resembled low mol. wt urokinase (LMW-UK) in its mol. wt, specific activity, and active sites. The steady-state kinetic parameters of each enzyme for the activation of human Glu-plasminogen also resembled each other, as did their amidase parameters (with pyro-Glu-Gly-Arg-pNA).     

Immunohistochemical localization of glutamine synthetase in human liver

Glutamine synthetase (GS) of human liver was recognized with a polyclonal antibody to pig brain GS, but failed to stain with an antibody against rat liver GS. Using the latter antibody GS of human liver was shown to be localized within small rings of 1 to 3 hepatocytes surrounding the terminal hepatic venules. This pattern was analogous to that seen in rat and mouse liver.     

Effects of parathyroid hormone and calcitonin on carbonic anhydrase location in osteoclasts of cultured embryonic chick bone

The ultrastructural location of carbonic anhydrase has been examined in osteoclasts of cultured embryonic chick metatarsi. In untreated cultures and in those to which parathyroid hormone (PTH) was added, the enzyme was found in close association with the plasma membrane of the ruffled border. After brief calcitonin treatment (10 min) the ruffled border disappeared and the association of carbonic anhydrase with the plasma membrane was diminished. The results indicate that the hormones employed act directly on embryonic bone to alter osteoclast structure and the intracellular location of carbonic anhydrase.     

Inhibition of interleukin-1 beta release from cultured human peripheral blood mononuclear cells by prednisolone

Prednisolone, a water-soluble glucocorticoid hormone, suppressed the secretion of interleukin-1 beta from human peripheral blood mononuclear cells in culture. The prednisolone-induced suppression of the monokine release was dose-related and the half maximal response was observed at 0.1 nM.     

Studies on correlations between chloroquine-induced tissue damage and serum enzyme changes in the rat

The administration of chloroquine to rats resulted in a significant elevation of serum enzymes and a corresponding decrease of these enzymes in the tissues. The changes in serum and kidney enzymes were most marked, thus indicating a primary renal dysfunction.