Qualitative and quantitative investigations on t h e hemolymph proteins in t h e adult firebrat Thermobia domestica were performed during an ovarian cycle in inseminated and noninseminated females. Variations of hemolymph protein concentration were determined by Lowry's method. In addition, t h e proteins were studied by gradient slab gel electrophoresis using nondenaturing conditions and microdensitometry. Besides five major protein fractions, which are present in both sexes, three female-specific protein bands (vitellogenins) are found in t h e hemolymph and in maturing oocytes. These vitellogenins have molecular masses of 430, 300 and 240 kiloDalton. In fact, associated with t h e main 300-kD band, there were two smaller bands (320 and 280 kD) indistinguishable by densitometric measurement. Quantitative changes of vitellogenins are linked t o oocyte maturation. These proteins appeared in t h e hemolymph before ecdysis, at t h e same time as t h e first yolk granules in t h e basal oocytes. They increased after ecdysis during t h e intense vitellogenic phase and decreased during chorion formation. In noninserninated females, in which all maturing oocytes are resorbed before chorion formation, t h e level of t h e 300 kD vitellogenin remained lower than in inserninated females. The quantity of vitellogenins fell only after complete oosorption. Thus insemination caused changes in t h e relative quantities of t h e different vitellogenic proteins.
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