Asymmetric and Globular Forms of AChE in Slow and Fast Muscles of 129/ReJ Normal and Dystrophic Mice

Abstract: Acetylcholinesterase activities and molecular forms were studied in normal and dystrophic 129/ReJ mice, focusing on four predominantly fast-twitch muscles and the slow-twitch soleus. The asymmetric and globular forms were analyzed separately so that the effect of dystrophy on each form could be determined. This comparative study showed the following. (1) In the normal condition, each muscle exhibited a distinct distribution of the molecular forms. (2) The diversity among the fast muscles resulted mainly from variations in the proportions of the three globular forms; in contrast, these muscles showed a constant and precise A₁₂/A₈/A₄ ratio. (3) The slow-twitch soleus clearly differed from the other muscles in its low acetylcholinesterase activity and distinct distribution of the molecular forms, characterized by a low level of G₄ and a peculiar ratio among its asymmetric forms, resulting from a relative increase of the A₈ and A₄ forms. (4) In dystrophic mice, the diversity of the acetylcholin esterase distribution was lost; all the fast muscles displayed profiles exhibiting the characteristics typical of the soleus. The fast-twitch extensor digitorum longus, sternomastoid, and plantaris converged towards an identical set of acetylcholinesterase molecules. (5) In contrast, the acetylcholinesterase activity and molecular forms of the soleus were only slightly affected by the disease. These results reveal that the dystrophy modifies both categories of molecular forms of acetylcholinesterase in a very precise manner. Such complex changes, which are highly reproducible in a variety of different muscles, are unlikely to result from nonspecific reactions secondary to the disease.     

Reproduction, growth and mortality of the common bully, Gobiomorphus cotidianus McDowall, in a eutrophic New Zealand lake

Gobiomorphus cotidianus in Lake Waahi, North Island, New Zealand, (37° 34'S; 175° 08'E) spawned continuously between July 1976 and March 1977. Length frequency data indicated that two, and briefly, three year classes, were present, each made up of three groups which were the progeny from successive peaks in spawning activity. Scale examination revealed checks to growth associated with spawning and stressful midsummer conditions. These and length frequency data were used in growth estimates which indicated that bullies reached 3·5-4·0 cm after their first year, 5-6 cm after their second but did not survive a third year. Mortality was associated with spawning and midsummer stress.     

Food sharing: a model of manipulation by harassment

Most analyses of food-sharing behavior invoke complex explanationssuch as indirect and delayed benefits for sharing via kin selectionand reciprocal altruism. However, food sharing can be a moregeneral phenomenon accounted for by more parsimonious, mutualisticexplanations. We propose a game theoretical model of a generalsharing situation in which food owners share because it is in their own self-interest—they avoid high costs associatedwith beggar harassment. When beggars harass, owners may benefitfrom sharing part of the food if their consumption rate islow relative to the rate of cost accrual. Our model predictsthat harassment can be a profitable strategy for beggars if they reap some direct benefits from harassing other than sharedfood (such as picking up scraps). Therefore, beggars may manipulatethe owner's fitness payoffs in such a way as to make sharingmutualistic.