| Dietary restriction (DR, also termed caloric restriction or food restriction) isthe balanced reduction of the protein, carbohydrate and fat content of the diet.Numerous studies on DR in a wide range of organisms indicate that this nutritionalintervention retards the aging process but reduce daily and lifetime fecundities.The fruit fly Drosophila is very useful as a model organism for our investigationinto effects of DR on longevity and fecundity. Its relatively short generation time,well-characterised molecular biology, genetics and physiology and ease of handling fordemographic analysis are all major strengths. Besides, The Drosophila possesses twoimportant characteristics: one is to have the ability of reproduction in 24 hours aftereclosion that is necessary to weigh senescence and must have broken the limitition ofmaturity; the other is that Drosophia is postmitotic metazoan which doesn't create newcells except for the most germline cells and some gastroenteric cells during the wholeadulthood and loses only few cells. These advantages make for our investigation intothe mechanism of longevity because human being needs to renew cells continually tomaintain our life.Yeast is the basic ingredient in the medium which contains abundant nutrients. Andthe fruit fly favors yeast in rotten fruits in nature. All these suggest that yeast plays animportant role in Drosophila lifecycle. Researches on this issue mainly focus on effectsof DR on the development of Drosophila by controlling the content of yeast in themedium. At present, it is deficient in this tissue in domestic researches, and almost allstudies on this tissue favor the females in foreign researches even if the males playimportant roles in reproductive behavior. We therefore confine our attention to theeffects of DR on longevity, antioxidative ability, reproduction and various stages ofspermatogenesis as well as the relationship among these aspects in male Drosophilamelanogaster that is applied during the whole lifetime.In order to study the effects of DR on longevity, reproductive ability and theirrelationship in male Drosophila melanogaster, we design the experimental plan asfollows: Male flies were fed on five different concentrations of yeast mediumrespectively, 1%, 2%, 4%, 8%, 12%. Then the number of death in male flies wasregistered and the curve of survival was drawn. And the activity of SOD of differentaged male flies in each group was examined. Besides, we also tested the efficient spermnumber fed on five different concentrations of yeast medium in order to examine thatthere are differences in reprpductive ability over the range of yeast level tested. And at the same time, we carried on the immunofluorescence experiment on Drosophila testesin order to examine the differences in special expressed microtubulinβ2-tubulin in thedifferent aged male flies over the range of yeast level tested.The results show that the effects of content of yeast on the longevity and resistanceto oxidation are notably. All these illuminate that dietary restriction can delay aging andimprove the resistance to oxidation in male Drosophila melanogaster. And these areconsistent with free radical-mitochondrial theory of aging. The test results of theefficient sperm number show that there is an enhancement in reproductive ability inmale flies from the low yeast level group to the high yeast level group. Consistently, theimmunofluorescence images of testes illustrate that, along with the increase of yeastcontent in the diet, there are some changes as follows: tubular testes become wider andthicker, the cells in meiosis increase and dense. All these demonstrate that DR candecrease the reproductive ability in male Drosophila melanogaster. All above illuminatethat DR can produce relativity influences on between the longevity and reproductiveability in male Drosophila melanogaster. And these suggest that DR have an effect onthe energy allocation and trade-off between survive and reproduction in maleDrosophila melanogaster. |
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