T.J. Shortino

Ecdysones and Analogs: Effects on Development and Reproduction of Insects

Ingestion of certain synthetic ecdysone analogs inhibited larval growth and development in several species of insects, whereas 20-hydroxyecdysone was inactive or considerably less active. Natural 20-hydroxyecdysone and ponasterone A, and a synthetic ecdysone analog inhibited ovarian maturation and egg production in the adult housefly. These effects appeared to be related to hormonal activity.

Assay for ecdysone (Molting hormone) activity using the house fly, Musca domestica L.

Abstract Larvae of the house fly, Musca domestica L., were used as the test insect in a modified assay for ecdysone. The house fly is easily reared by using standard procedures and provides a high yield of organisms suitable for bioassay. The quantity of α-ecdysone needed for about 60% pupation in the abdomens of ligated house fly larvae was 0.005–0.006 μg, one-third to one-fourth the amount needed to effect the same Response in the Calliphora test.

Ecdysones and synthetic analogs: Molting hormone activity and inhibitive effects on insect growth, metamorphosis and reproduction

Abstract Five ecdysones and 19 ecdysone analogs were assessed for molting hormone activity in the house fly assay. When these 5β-steroids were further tested in the house fly, the confused flour beetle, the yellow fever mosquito, and the German cockroach, many of the compounds inhibited growth, development and/or reproduction. The relationship of structure to both the molting hormone and inhibitive activity of these compounds is discussed.

Utilization and metabolism of dietary sterols in the honey bee and the yellow fever mosquito

The honey bee,Apis mellifera, does not convert C28 and C29 phytosterols to cholesterol as found in most previous studies of phytophagous or omnivorous insects, but instead the workers and queens selectively transfer 24-methylenecholesterol, sitosterol and isofucosterol from their endogenous sterol pools to the brood larvae regardless of the sterol in the worker diet. Administering radiolabeled sterols by feeding and injection has made it possible to trace this selective transfer through a second generation of the honey bee. In further comparative sterol metabolism studies, the yellow fever mosquito,Aedes aegypti, was shown to be capable of dealkylating and converting a radiolabeled C29 dietary sterol ([14C] sitosterol) to cholesterol. Metabolic studies with several radiolabeled dietary sterols and an inhibitor of steroid metabolism in the yellow fever mosquito further verified this capability.

The utilization and fate of β-sitosterol in the larva of the housefly, Musca domestica L.

Abstract Using H 3 - β -sitosterol, gas-liquid chromatographic analysis, and a semi-defined diet with aseptic rearing techniques, it was demonstrated that larvae of the houselfy, Musca domestica , do not dealkylate β -sitosterol to form cholesterol. Furthermore, the major sterol (>99 per cent) isolated from insects reared in the above manner on a diet containing pure unlabelled β -sitosterol (100 per cent by GLC) was identified as unchanged β -sitosterol. β -Sitosterol, campesterol, and cholesterol were also compared in nutritional tests in which each of these three sterols served as a sole source of sterol in both the adult and larval diets. β -Sitosterol was only approximately one-fourth as effective as either cholesterol or campesterol in supporting larval growth and development. In addition, only 1·4 per cent of the organisms from the diet containing β -sitosterol emerged as adults and these failed to produce viable eggs. These results demonstrate conclusively that β -sitosterol is not converted to cholesterol in the housefly and that this sterol will not fulfil in entirety the sterol requirement of this insect.

Feeding Stimulants for the Female House Fly, Musca domestica Linneaus

Both casein and yeast hydrolysate contain feeding stimulants for the adult female house fly. Guanosine monophosphate is the major active component in yeast hydrolysate. Several amino acids, including leucine, methionine, lysine, and isoleucine, are also effective feeding stimulants and are presumed to be the active components in the casein hydrolysate. Solution in phosphate buffer is necessary in all instances to obtain maximum activity with the stimulants.

Conversion of cholesterol to 7-dehydrocholesterol in aseptically reared german cockroaches

Abstract The previously reported conversion of cholesterol to 7-dehydrocholesterol by nonaseptically reared German cockroaches has been confirmed using aseptically reared insects. The identity of the 7-dehydrocholesterol was established by UV and infrared spectroscopy and gas-liquid Chromatographie analyses of the free sterol and/or derivatives. This metabolic pathway for cholesterol in the German cockroach is discussed.

Nonsteroidal secondary and tertiary amines: Inhibitors of insect development and metamorphosis and Δ24-sterol reductase system of tobacco hornwormreductase system of tobacco hornworm

Several new branched and straight chain secondary and tertiary amines were shown to have inhibitive effects upon development and metamorphosis and the Δ24-sterol reductase system in larvae of the tobacco hornworm similar to those previously observed with a number of azasteroids. Certain of the amines which are related structurally to compounds with juvenile hormone activity in insects also blocked development and metamorphosis in three other species of insects. These compounds are lethal or inhibit development in all larval stages and thus differ in action from compounds with juvenile hormone activity where the principal effect is to block the penultimate or ultimate molt.

THE STEROL ESTERS OF HOUSEFLY EGGS.

Abstract 1. 1. The free sterols and sterol esters from adult female houseflies and eggs were separated by column chromatography. The sterol ester fraction accounted for about 41 per cent of the total sterol from housefly eggs but only about 8·4 per cent in the female flies. 2. 2. Analysis of the fatty acids from the sterol ester fraction of the eggs showed these to be composed of greater than 90 per cent C16 and C18 mono-unsaturated fatty acids with the C18 acids accounting for about 78 per cent of the total. 3. 3. The fatty acids from the triglyceride fraction of the eggs and female flies differed from the egg sterol esters in that they contained less unsaturation and a predominance of C16 fatty acids.

The conversion of cholestanone to cholestanol by the housefly, Musca domestica L.

Abstract Larvae of the housefly, Musca domestica L., reared aseptically on a semi-defined diet failed to develop when either cholestenone, cholestanone, or cholestanol was used as the sole source of dietary steroid. However, when these three steroids were tested for ‘sparing’ activity (in combination with a subminimal quantity of cholesterol) cholestanone and cholestanol were 66 and 79 per cent, respectively, as effective as an optimum concentration of cholesterol. Under the same conditions cholestenone showed only low biological activity (11 per cent). Biochemical studies with 4-14C-cholestanone indicate that the utilization of this steroid in the housefly larvae proceeds through its partial conversion to cholestanol. The identity of cholestanol as a metabolite of cholestanone was established by radiotracer techniques, gas-liquid chromatographic analysis, and by isolation of crystalline cholestanol from housefly pupae reared aseptically on a semi-defined diet containing cholestanone plus a subminimal amount of cholesterol. Using reverse isotope dilution techniques, no significant conversion of 14C-cholestanone to cholesterol was detected. In studies with adult insects, both males and females converted injected 14C-cholestanone to cholestanol.