Hari C. Agarwal

Site of cholesterol absorption in some insects

Abstract The principal site of cholesterol absorption was studied in a number of insects using 3 H-cholesterol mixed with the diet of the insects. In omnivorous insects ( Gryllodes sigilatus and Camponotus compressus ) and a carnivorous insect ( Dytiscus sp.) cholesterol was absorbed in the foregut, predominantly in the crop. In the phytophagus insects and some others ( Schistocerca gregaria, Hieroglyphus nigrorepletus, Dysdercus koenigii, Belostoma sp., Lucilia sp., Apis sp. Mylabris phalerata and larvae of Papilio demoleus, Prodenia litura , and Earias fabia ) the midgut was the main site of cholesterol absorption.

Lipids of the larvae and adults of trogoderma granarium (Coleoptera)

Abstract 1. 1. The lipids of the larvae and adults of Trogoderma granarium were studied. 2. 2. The larvae and adults consisted od approximately 27 and 10 per cent total lipids respectively on a fresh-weight basis. The decrease in the lipid content of adults was mainly due to a decrease of the neutral lipid fraction, particularly triglycerides which represented more than 90 per cent of the neutral lipids. Monoglycerides, diglycerides, sterols and sterol esters were also detected in both stages. 3. 3. In both stages the phospholipids detected were phosphatidyl inositol, sphingomyelin, phosphatidyl serine, phosphatidyl choline, phosphatidyl ethanolamine and polyglyceryl phosphatide. In larvae, phosphatidyl ethanolamine was the major phospholipid, about 29 per cent. In adults, phosphatidyl choline and phosphatidyl ethanolamine were about equal in proportions and were the major phospholipids. 4. 4. No lyso-phosphatides were detected in any of the two stages.

Sterol requirements of the beetle Trogoderma.

Abstract The khapra beetle, Trogoderma granarium, could not synthesize cholesterol from various known precursors of cholesterol biosynthesis in mammals and was found to require a sterol in the diet. Of the various sterols tested for suitability in the diet, cholesterol, cholestanol, stigmasterol, β-sitosterol, 7-dehydrocholesterol, and ergosterol were satisfactory. Cholesteryl chloride and cholesteryl methyl ether were not utilized by this insect.

INCORPORATION OF THYMIDINE INTO DNA OF THE GONADS IN THE NORMAL AND CHEMOSTERILIZED YELLOW-FEVER MOSQUITO

Effect of the chemosterilants, apholate and hempa, on the incorporation of tritiated thymidine in DNA of the gonads of Aedes aegypti was studied. Larval treatment with sterilizing doses of the chemosterilants caused inhibition of DNA synthesis in the gonads. The inhibition was found to be more in testes than in ovaries. The significance of these findings in relation to the mode of action of these chemosterilants is discussed.

Biology of an egg parasite of Callosobruchus maculatus (Fab.) (Coleoptera: Bruchidae)

Abstract Uscana mukerjii (Mani) (Chalcidoidea, Trichogrammatidae) parasitizes eggs of Callosobruchus maculatus . Mated adult U. mukerjii lived for 5.0 ± 0.8 and 4.7 ± 0.9 days (males and females, respectively) at 27 °C. The female copulated only once, whereas males did so up to 4 times. The maximum parasitization of host eggs took place within the first 24 hours of egg laying and declined thereafter. The parasite completed its development inside the host egg in 7.2 days at 27 °C and 60–63% r.h. and emerged after cutting a circular hole in the chorion of the host egg. Mated and unmated females laid 35.4 ± 1.4 and 36.0 ± 2.2 eggs in their life time of which 27.3 ± 1.8 and 23.2 ± 2.8, hatched respectively. Parasitized host eggs did not hatch and were ultimately destroyed. The degree of parasitization varied with the pulses on which the host eggs were laid. This egg parasite may be useful in controlling the populations of C. maculatus and thus help in reducing the damage caused.

Distribution, excretion, and metabolism of 14C-DDT in the larva and adult Trogoderma granarium in relation to toxicity

Abstract The larvae of the khapra beetle, Trogoderma granarium Everts were completely tolerant to DDT whereas the adults were much less tolerant. The mechanism of this differential toxicity was investigated. Both adults and larvae did not metabolize DDT and only unchanged insecticide was recovered from the insect body and excreta. The adult body retained about one and a half times more DDT and excreted it only at one-half the rate compared to that of the larvae. Further the central nervous system of adults contained two times as much or more DDT than that of the larvae. All of these factors may be responsible for the above-mentioned difference in the DDT toxicity.

Variations in the neutral lipids of Dysdercus koenigii (Hemiptera) during its life cycle

Abstract The total and neutral lipids of the red cotton bug, Dysdercus koenigii F., were studied during its entire life cycle. The lipid content on the fresh weight basis was about 10 per cent. The neutral lipid content varied with age and included monoglycerides, 1,2- and 1,3-diglycerides, triglycerides, free fatty acids, sterols, and sterol esters. In the eggs monoglycerides and 1,3-diglycerides were not detected, whereas, in first and fifth instars only, 1,3-diglycerides were not observed. Triglycerides were the most predominant neutral lipid and accounted for 60 to 90 per cent of the glyceride glycerol. There were always two to three times more 1,2-diglycerides than 1,3-diglycerides.

Lipids of Trogoderma—. III. phospholipid and fatty acid composition during development with a note on fatty acid biosynthesis

Abstract 1. 1. Phospholipid and fatty acid composition of Trogoderma granarium was investigated during its development. A study on the biosynthesis of fatty acids was also carried. 2. 2. Phosphatidyl ethanolamine, phophatidyl choline, sphingomyelin, phosphatidyl inositol, phosphatidyl serine and polyglyceryl phosphatide were generally detected in all developmental stages, except in the fourth and fifth instars. Phosphatidyl ethanolamine and phosphatidyl choline accounted for up to 75 per cent of the total phospholipids. Lysophosphatides were not detected. 3. 3. Oleic and palmitic acids were the most abundant fatty acids forming about 40 and 30 per cent of the total respectively. 4. 4. Fatty acid composition of adult females changed with time. Oleic acid was the dominant fatty acid in 1-day-old adults which was replaced by palmitic acid from the second day onwards. 5. 5. Insects grown on a lipid-free diet, except cholesterol, were able to synthesize oleic, palmitic, palmitoleic, stearic and myristic acids. Fatty acids with two double bonds or more were not synthesized.

EFFECT OF APHOLATE AND HEMPA ON NUCLEIC ACID AND PROTEIN SYNTHESES IN THE YELLOW‐FEVER MOSQUITO

The growth curve, nucleic acid and protein content of the various life stages of Aedes aegypti were studied. The larvae of this mosquito were treated with sterilizing doses of the chemosterilants apholate and hempa, and their effects on the above parameters were also investigated. The body‐weight increased gradually in the earlier instars and showed a sharp rise from late‐fourth instar to the pupa. Adults weighed less than the pupae Females weighed more than the males. In the controls, DNA and RNA content generally followed the growth curve. RNA content was more than DNA up to the late‐fourth instar and the ratio reversed in the later stages. Protein content also followed the growth curve except in adult female, where it was more than in the pupa. In general the treatment with the chemosterilants. apholate and hempa did not seem to alter RNA, DNA and protein content in the whole insect.

Properties and distribution of extra-digestive lipase in the beetle, Trogoderma

Extra-digestive lipase (3.1.1.3) was detected in the female pupa of Trogoderma granarium. The alimentary canal of the insect did not show any lipase activity while the rest of the tissues showed lipase activity. The temperature and pH optima were 37°C. and 7.6 respectively. The Km value was 3.10 × 10−4 M None of the metal ions tested, including calcium, had any effect on enzyme activity. The maximum enzyme activity was found in the pupa, followed by the pharate adult. The enzyme activity declined with age in adults. Enzyme activity was also detected in the larva.