Insect larvae, analysis

Altstein M., Gazit Y., Ben-Aziz O., Gabay T., Marcus R., Vogel Z. and Barg J. (1996) Induction of cuticular melanization in Spodoptera littoralis larvae by PBAN/MRCH Development of a qualitative bioassay and structure function analysis. Arch. Insect Biochem. Physiol. 31, 355-370. 

Diols have been rarely observed in insect cuticular lipids (Buckner, 1993). Odd-carbon-number diols (C23-C29) were the major lipid class (55%) of the larval cuticular lipids from the flour beetle, Tenebrio molitor (Bursell and Clements, 1967). The major diol constituent was 8, 9-pentacosanediol. For the cuticular lipids of M. sexta larvae, very small amounts (<1%) of 7,8- and 8,9-C27 diols and 8,9- and 9,10-C29 diols were identified (Espelie and Bernays, 1989). Hydroxy n-alkanols are diols with a hydroxyl functional group on the C, position (terminal) of the alkyl chain, but are technically not alcohol derivatives of hydrocarbons. There are a few reports of the occurrence of insect hydroxy -alkanols (Buckner, 1993 Nelson and Blomquist, 1995 Buckner et al., 1996). In a structure analysis study of beeswax, the major alcohol moieties of the diester fraction were identified as 1,23-tetracosanediol (42.2%), 1,27-octacosanediol (26.0%) and 1,25-hexacosanediol (20.2%) (Tulloch, 1971). The hydroxy n-alkanols comprised 16% of the cuticular lipids of FI. zea pupae and were identified as C30-C36 even-chain n-alcohols with hydroxyl groups on carbon numbers 11, 12, 13, 14, or 15 (Buckner et al., 1996). Mass spectral analysis indicated the presence of unsaturation in the alkyl chain of the major diol components. 

In addition to the effects of diflubenzuron on the chitinase and phenoloxidase levels, observed by Ishaaya and Casida (4 6), other biochemical influences of diflubenzuron and Du 19111 have been described in the literature (Table 9) A common feature of all these effects is their analysis one or more days after treatment. As any effects of these benzoyl-phenyl ureas become visible on the living insects only at the time of the next moult, when susceptible larvae die, investigators are prompted to search for defects up to a considerable time after application. In comparison with the very fast inhibition of chitin synthesis discussed above, in our opinion these studies can at the most indicate "secondary" effects. A considerable number of effects of this type can be expected to be found and published in the future. 

Figure 1. Clearance of L-canavanine and L-canaline from insect hemolymph. Clearance was determined by automated amino acid analysis involving a single sample for each time point using the pooled hemolymph of five larvae. The administered dose to H. virescens was 5 mg L-canavanine/g fresh body weight ( ) or 3.8 mg L-canaline/g fresh body weight ( ). Manduca sexta received 1 mg L-canavanine/g fresh body weight ( ). Redrawn from (17).

In the case of stigmasterol (89), the proposed mechanism in Fig. 18 was evaluated as follows. [23- H]-, [24- H]- and [25- H]stigmasterols were synthesized and the fate of the deuterium atoms during the dealkylation was followed by mass spectrometry. The transfer of the deuterium atom from C-25 to C-24 was established in silkworm larvae [162]. Also, the chemically synthesized (24F)- and (24Z)-A -dienes (93 and 94) were found to satisfy the sterol requirement of the silkworm. The A -diene (96) and desmosterol (91) were identified in significant amounts from the insects in accord with the previous observation by the Beltsville group. However, mass fragmentographic analysis of the sterols of insects fed on stigmasterol (89), the... 

The excreta of stored product insects are composed primarily of uric acid. However, in some species, the presence of other purines in lesser proportions has been reported. Ammonia is found in the excreta of larvae of Ephestia kuehniella, urea and allantoin in Tenebrio molitor, and both urea and xanthin in larval excreta of C. cephalonica (Bursell, 1967). Uric acid has been used as an indicator of insect infestation in cereals and cereal products since the 1950s (Subrahmanyan et al., 1955 Venkatrao et al., 1957). Subsequently, several methods have been described to determine uric acid levels in infested foodstuffs (Table VII). Most of these methods are modifications of tests originally developed for analysis in clinical samples. Pachla et al. (1987) have reviewed the methods of uric acid determination in foodstuffs and biological fluids. 

Brader et al. (2002) examined the accuracy of determining insect contamination in wheat by x-ray analysis. It was observed that the x-ray analysis technique is one of the most accurate methods next to ELISA in detecting late instar larvae of S. granarius in wheat. Hurlock (1963) compared the radiographic method with that of staining techniques, flotation method, and C02 analysis to detect hidden infestation of C. chinensis in dried whole green... 

An automated NIRS system capable of scanning individual grains containing late-instar larvae of S. oryzae, R. dominica, or S. cerealella at the rate of 15 kernels/min has been developed in the United Kingdom (Chambers et al., 1998). The system was effective and could detect the infestation irrespective of the type/class of wheat, its protein content (range 11.32 16.2%) and moisture content (range 10.0 13.2%). The minimum detectable size of the insects by NIRS varied between species. As identified by x-ray analysis, the NIRS system has been shown to detect R. dominica as small as 1.1 mm2 with 95% level confidence, whereas for S. oryzae it was 2.0 mm2, and for S. cerealella 2.7 mm2. For a particular insect species, the accuracy of detection increases as insect development proceeds. Accordingly, in S. oryzae the accuracy of detection of first instar larvae was 10%, second instar larvae 24%, third instar larvae 82%, fourth instar larvae 95%, and the accuracy was 100% for pupae and adults. 

HEGEDUS, D BALDWIN, D., O GRADY, M., BRAUN, L., GLEDDIE, S., SHARPE, A., LYDIATE, D., ERLANDSON, M., Midgut proteases from Mamestra configurata (Lepidoptera Noctuidae) larvae Characterization, cDNA cloning, and expressed sequence tag analysis. Arch. Insect Biochem. Physiol, 2003, 53, 30-47. 

Next we considered that the plant material might induce the tobacco budworm to metabolize Compound 10 into an inactive form. TBW were fed Compound 10 on semi-artificial diet and on chickpea leaves. HPLC analysis of the gut, excrement, and carcass showed that the TBW did not metabolize Compound 10 from either food source. These experiments did not address the relative amounts of Compound 10 entering the larvae from the two food sources, but they do demonstrate that ingestion of plant material does not affect the insect s ability to metabolize Compound 10. 

Degradation of suberin was demonstrated by chemical analysis in the case of attack on the periderm of Rubus idaeus by Thomasiniana theobaldi (155). After enzymatic attack by larvae-released enzymes, the periderm was shown to have 52% fewer aliphatic suberin components, and hemicellulose and cellulose were decreased by 28% and 54%, respectively. The cell wall degradation caused by this insect attack was thought to provide subsequent access for fungal infection. 

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