The nonvitellogenic female protein of Musca domestica is an adult-specific hexamerin

During Musca domestica vitellogenesis a protein is preferentially synthesized by the female fat body and accumulates in the haemolymph but not in the ovaries. This protein, designated nonvitellogenic female protein (NVFP), was purified and shown to be a hexamer with an M(r) = 430 kDa, and subunits of M(r) = 70 kDa. The hexamer dissociates into subunits when the pH is elevated from 7.0 to 9.0. Two cDNA clones, F0 and F2, were isolated and analysed. The 2.2 kb F2 clone has an open reading frame that encodes a conceptual translation product that has similarity to the Drosophila melanogaster LSP-2 hexamerin. Recombinant protein from the F2-cDNA is recognized by a specific anti-NVFP serum. The temporal pattern of mRNA expression of the gene represented by the F2 clone follows that determined for the synthesis of NVFP. The data support the conclusion that NVFP is an hexamerin specific to the adult stage of Musca domestica.

Identification of mutations in the housefly para-type sodium channel gene associated with knockdown resistance (kdr) to pyrethroid insecticides

We report the isolation of cDNA clones containing the full 6.3-kb coding sequence of the para-type sodium channel gene of the housefly, Musca domestica. This gene has been implicated as the site of knockdown resistance (kdr), an important resistance mechanism that confers nerve insensitivity to DDT and pyrethroid insecticides. The cDNAs predict a polypeptide of 2108 amino acids with close sequence homology (92% identity) to the Drosophila para sodium channel, and around 50% homology to vertebrate sodium channels, Only one major splice form of the housefly sodium channel was detected, in contrast to the Drosophila para transcript which has been reported to undergo extensive alternative splicing. Comparative sequence analysis of housefly strains carrying kdr or the more potent super-kdr factor revealed two amino acid mutations that correlate with these resistance phenotypes. Both mutations are located in domain II of the sodium channel. A leucine to phenylalanine replacement in the hydro-phobic IIS6 transmembrane segment was found in two independent kdr strains and six super-kdr strains of diverse geographic origin, while an additional methionine to threonine replacement within the intracellular IIS4-S5 loop was found only in the super-kdr strains. Neither mutation was present in five pyrethroid-sensitive strains. The mutations suggest a binding site for pyrethroids at the intracellular mouth of the channel pore in a region known to be important for channel inactivation.

Genetic analysis of factors controlling high-level expression of cytochrome P450, CYP6D1, cytochrome b5, P450 reductase, and monooxygenase activities in LPR house flies, Musca domestica

To understand better the biochemical genetics of cytochrome P450 monooxygenase-mediated insecticide resistance, we examined the microsomal monooxygenases in insecticide-susceptible (aabys) and pyrethroid-resistant (LPR) house fly strains, as well as 15 house fly lines derived from crosses of LPR and aabys. In comparison to the aabys strain, LPR had higher levels of total cytochromes P450, cytochrome b5, P450 reductase, CYP6D1, and three P450 monooxygenase activities: 7-ethoxycoumarin O-deethylase (ECOD), methoxyresorufin O-demethylase (MROD), and aromatic hydrocarbon hydroxylase (AHH). The elevated levels of cytochrome b5 were linked to factors on autosomes 1 and 2. This is similar to previous reports on monooxygenase-mediated resistance and is consistent with the idea that elevated cytochrome b5 levels are involved in monooxygenase-mediated resistance in the LPR strain. Linkage of the elevated P450 reductase is different from that of monooxygenase-mediated resistance. Strains having high levels of CYP6D1 (i.e., like LPR) had high levels of P450 reductase, while strains having intermediate levels of CYP6D1 also had high levels of reductase. Therefore, there is no clear evidence that the elevated P450 reductase in the LPR strain is required for the increased monooxygenase activity. Overexpression of total cytochromes P450, CYP6D1 (mRNA and protein), and CYP6D1-mediated monooxygenase activities (MROD and AHH) in LPR microsomes was linked to a combination of factors on autosomes 1 and 2. This demonstrates that increased expression of CYP6D1 in the LPR strain is both cis regulated by a factor(s) on autosome 1 and trans regulated by a factor(s) on autosome 2. The correlation between the overexpression of CYP6D1 mRNA and protein suggests that CYP6D1 expression is regulated transcriptionally. Monooxygenase-mediated resistance in LPR is controlled by factors on autosomes 1 and 2, which supports previous claims that CYP6D1 is responsible for monooxygenase-mediated resistance in the LPR strain.

Musca domestica hemolymph ferritin

We describe a method for the purification of ferritin from Musca domestica larval hemolymph. Musca ferritin occurs in hemolymph predominantly as a native protein with molecular weight equal to 550,000 and subunits of 26,000. The average iron content of purified ferritin was determined to be 3,000 +/ 600 iron atoms per molecule. The iron contents of ferritin was heterogeneous; both fully iron loaded molecules and apoferritin are probably present in the Musca hemolymph. The anti-ferritin serum raised in rabbit was able to recognize native ferritin but was not reactive with the protein subunits isolated by SDS-PAGE. The ferritin concentration in hemolymph attains a maximum of 0.28 mg/ml in the wandering stage larvae decreasing to 0.13 mg/ml at the middle of pupal stadium. The ferritin contents of midgut and fat bodies were also determined. Fat body ferritin content is greatly reduced when the feeding larva passes into wandering stage.

Processing of procathepsin from Musca domestica eggs

The major source of amino acids for insect embryos are yolk proteins which accumulate in developing oocytes and are hydrolyzed during embryogenesis. Studies on Musca domestica embryogenesis indicated that a cathepsin B-like proteinase is responsible for yolk protein degradation (Ribolla et al., 1993). In this study, we report the purification of mature cathepsin and show that it is made up of a single 41 kDa polypeptide chain. The Musca domestica cathepsin NH2-terminal 11-residue sequence was determined (Ala-Pro-Lys-Tyr-Val-Asp-Tyr-Gly-Glu-Asn-Glu) and reveals homology with other cathepsins of the papain family. Experiments using serum anti-cathepsin show that the enzyme is stored in oocytes as a 55 kDa zymogen. The activation of the zymogen occurs in vitro only at low pH. In vitro activation in the presence of cysteine protease inhibitors is blocked at an intermediary polypeptide of 48 kDa. Kinetic studies of this activation process at pH 3.5 and 4.6 show that the zymogen is processed in a manner similar to that of pepsin (Foltmann, 1986) and papain (Vernet et al., 1991). We propose that Musca domestica cathepsin zymogen activation occurs in two steps. First, an intramolecular cleavage of the procathepsin polypeptide chain (55,000), induced by low pH gives rise to an intermediary polypeptide (48,000) which then undergoes autolysis to produce the mature enzyme (41,000).

Mitochondrial superoxide and hydrogen peroxide generation, protein oxidative damage, and longevity in different species of flies

The objective of this study was to further elucidate the role of oxidative stress in the aging process by determining whether or not the rates of mitochondrial superoxide anion radical and hydrogen peroxide (H2O2) production, the activity of cytochrome c oxidase, and the concentration of protein carbonyls are correlated with the life span potential of different species. A comparison was made among five different species of dipteran flies, namely, Drosophila melanogaster (fruit fly), Musca domestica (house fly), Sarcophaga bullata (flesh fly), Calliphora vicina (blow fly) and Phaenecia sericata (a species of blow flies), which range more than 2-fold in their life span potentials. The average life span potential of these species was found to be inversely correlated with the rates of mitochondrial superoxide and H2O2 production and with the level of protein carbonyls, and to be directly related to the activity of cytochrome c oxidase. The significance of these findings in context of the validity of the oxidative stress hypothesis of aging is discussed. It is inferred that longer life span potential in these insect species is associated with relatively low levels of oxidant generation and oxidative molecular damage. These results accord with our previous findings on different mammalian species.

Sex- and age-related changes in the biophysical properties of cuticular lipids of the housefly, Musca domestica

We examined the biophysical properties of cuticular lipids isolated from the housefly, Musca domestica. Melting temperatures (Tm) of surface lipids isolated from female houseflies decreased from 39.3 degrees C to 35.3 degrees C as the females attained sexual maturity and produced sex pheromone, whereas those prepared from males did not change with age. Lipids melted over a 10-25 degrees C temperature range, and their physical properties were a complex function of the properties of the component lipids. The Tm of total cuticular lipids was slightly below that of cuticular hydrocarbons (HC), the predominant lipid fraction. Hydrocarbons were further fractionated into saturated, unsaturated, and methyl-branched components. The order of decreasing Tm was total alkanes > total HCs > methyl-branched alkanes > alkenes. For 1-day-old flies, measured TmS of hydrocarbons were 1.3-5.5 degrees C lower than TmS calculated from a weighted average of TmS for saturated and unsaturated components. For 4-day-old flies, calculated TmS underestimated Tm by 11-14 degrees C.

An insect model for assessing oxidative stress related to arsenic toxicity

The potential usefulness of an insect model to evaluate oxidative stress induced by environmental pollutants was examined with trivalent arsenic (As3+, NaAsO2) and pentavalent arsenic (As5+, Na2HAsO4) in adult female house flies, Musca domestica, and fourth-instar cabbage loopers, Trichoplusia ni. M. domestica was highly susceptible to both forms of arsenic following 48 h exposure in the drinking water with LC50s of 0.008 and 0.011% w/v for As3+ and As5+, respectively. T. ni larvae were susceptible to dietary As3+ with an LC50 of 0.032% w/w but seem to tolerate As5+ well with an LC50 of 0.794% concentration after 48 h exposure. The minimally acute LC5 dose of both As3+ and As5+ varied considerably but averaged 0.005% for both insects. The potential of both valencies of arsenic for inducing oxidative stress in the insects exposed ad libitum to approximately LC5 levels was assessed. The parameters examined were the alterations of the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST), the peroxidase activity of glutathione transferase (GSTPX), and glutathione reductase (GR), and increases in lipid peroxidation and protein oxidation. SOD (1.3-fold), GST (1.6-fold), and GR (1.5-fold) were induced by As3+ in M. domestica but CAT and GSTPX were not affected. As5+ had no effect on M. domestica. In T. ni, the antioxidant enzyme activities were not affected by As3+ except for SOD which was suppressed by 29.4% and GST which was induced by 1.4-fold. As5+ had no effect except the suppression of SOD by 41.2%. Lipid peroxidation and protein oxidation, which represent stronger indices of oxidative stress, were elevated in both insects by up to 2.9-fold. However, based on the antioxidant enzyme response to the arsenic anions, the mode of action of arsenic induced oxidative stress may differ between the two insects. Until this aspect is further clarified, evidence at this time favors the prospect of As3+ as a pro-oxidant, especially for M. domestica.

Mitochondrial oxidative damage, hydrogen peroxide release, and aging

The objective of this study was to elucidate the possible nature of the mechanism underlying the widely observed phenomenon that the rate of H2O2 production by mitochondria increases during the aging process, using flight muscle mitochondria of the male housefly as a model system. The protein carbonyl content of mitochondria increased linearly with age of the flies, and was also inversely associated with the life expectancy of flies. Exposure of flies to 100% oxygen caused a progressive increase in the level of mitochondrial carbonyl content. The rate of H2O2 release by such oxidatively damaged mitochondria was higher than the controls. Similarly, X-irradiation of submitochondrial particles simultaneously resulted in increased rate of H2O2 production and elevated level of carbonyl content. Results of this and previous studies indicate that oxidative damage to mitochondrial membranes may be responsible for the age-related increase in mitochondrial H2O2 generation.

Constitutive overexpression of the cytochrome P450 gene CYP6A1 in a house fly strain with metabolic resistance to insecticides

Messenger RNA levels of the cytochrome P450 gene CYP6A1 were measured in the insecticide resistant Diazinon-R 'Rutgers' strain and in the susceptible strain sbo of the house fly with a cloned cDNA probe. The constitutive expression of the CYP6A1 gene was at least 10 times higher in the Rutgers strain than in the sbo strain. In both strains, CYP6A1 was inducible by phenobarbital treatment of the flies. Analysis of genomic DNA from the two strains indicated that there was no amplification of the CYP6A1 gene in the Rutgers strain. A developmental analysis revealed that CYP6A1 is expressed larvae and adults, and very low levels of CYP6A1 mRNA were detected in eggs and pupae. The constitutive overexpression of CYP6A1 in the Rutgers strain was observed in both larvae and adults. Crosses between the Rutgers strain and the multiply marked sbo strain revealed that the high constitutive expression of CYP6A1 in the Rutgers strain is controlled by one or more loci located on chromosome II.

Aging and proteolysis of oxidized proteins

The main objective of this study was to investigate the possible cause(s) of the age-related augmentation of oxidatively damaged proteins in animal tissues. The hypothesis that activity of alkaline proteases, involved in the proteolysis of oxidized proteins, declines during aging was tested in the adult male housefly and further explored in the rat. Alkaline protease activity was measured fluorometrically by the release of trichloroacetic acid-soluble fluorescamine-reactive material from X ray-oxidized bovine serum albumin (BSA). Alkaline protease activity in the housefly was linearly related to the number of protein carbonyl groups. Possible involvement of serine or serine and thiol proteases was deduced from a 70% proteolytic inhibition by aprotinin and a 50% inhibition by leupeptin. Protease activity of houseflies for oxidized or native BSA did not alter with age. In contrast, a varied age-related pattern of protease activity was observed in the tissues of the rat. A comparison of 3-, 13-, and 23-month-old Sprague-Dawley rats indicated no age-related decline in alkaline protease activity in the brain, a 50% decline in the liver, and a 20% decline in the heart during 13 to 22 months. Results of this study suggest that in some species or tissues an age-related increase in the oxidized protein content is primarily due to a corresponding increase in the rate of protein oxidation, while in some other tissues a decline in proteolysis may be a contributory factor.

Delphinium alkaloids as inhibitors of alpha-bungarotoxin binding to rat and insect neural membranes

A series of C19-diterpenoid alkaloids purified from Delphinium were evaluated as inhibitors of alpha-bungarotoxin binding to rat and house fly neural membranes. In comparing these diterpenoid analogs, a wide range of inhibition potencies (IC50) were observed, with calculated IC50 values ranging six orders of magnitude. The most potent inhibitory alkaloids in this series possessed the succinimide aromatic ester moiety in the C18 position. Glaudelsine had an IC50 value of 42 pM at the insect nicotinic acetylcholine receptor.

Cytochrome b5 involvement in cytochrome P450 monooxygenase activities in house fly microsomes

The involvement of cytochrome b5 in different cytochrome P450 monooxygenase and palmitoyl CoA desaturase activities in microsomes from insecticide-resistant (LPR) house flies was determined using a specific polyclonal antiserum developed against house fly cytochrome b5. Anti-b5 antiserum inhibited the reduction of cytochrome b5 by NADH-cytochrome b5 reductase. The antiserum also inhibited palmitoyl CoA desaturase, methoxycoumarin-O-demethylase (MCOD), ethoxycoumarin-O-deethylase (ECOD), and benzo[a]pyrene hydroxylase (aromatic hydrocarbon hydroxylase, AHH) activities. However, methoxyresorufin-O-demethylase (MROD) and ethoxyresorufin-O-deethylase (EROD) activities were not affected by this antiserum. These results demonstrate that cytochrome b5 is involved in fatty acyl CoA desaturase activities and in certain cytochrome P450 monooxygenase activities (i.e., MCOD, ECOD, and AHH) in LPR house fly microsomes. Other cytochrome P450 monooxygenase activities (i.e., MROD and EROD) may not require cytochrome b5. The results suggest that cytochrome b5 involvement with cytochrome P450 monooxygenase activities is dependent upon the cytochrome P450 isoform involved.

An insect model for assessing mercury toxicity: effect of mercury on antioxidant enzyme activities of the housefly (Musca domestica) and the cabbage looper moth (Trichoplusia ni)

The effect of mercury as Hg2Cl2 and HgCl2 on the antioxidant enzyme levels and its toxicity was investigated in an insect model comprised of adult females of the common housefly, Musca domestica, and fourth-instar larvae of the cabbage looper moth, Trichoplusia ni. HgCl2 was found to be more toxic than Hg2Cl2 to both M. domestica and T. ni. The LC50s for M. domestica were 1.17% and 0.38% w/v concentration for Hg2Cl2 and HgCl2, respectively. For the more tolerant T. ni, the LC50S were 5.15% for Hg2Cl2 and 0.96% w/w concentration for HgCl2. The minimally acute LC5 dose of both oxidation states of Hg was approximately 0.005% for both insects (w/v for M. domestica and w/w for T. ni). At the LC5, both forms of Hg significantly induced the activity of superoxide dismutase in both insect species. Catalase was induced by both Hg2Cl2 and HgCl2 in M. domestica but was only induced by HgCl2 in T. ni. Glutathione-S-transferase, its peroxidase activity, and glutathione reductase activities were also significantly altered in most cases by Hg in both insects although the pattern of alternation was different between the two insects. It is evident that mercury induces oxidative stress in insects as it does in vertebrates. Our findings suggest that insects may serve as a valuable, non-mammalian model species to assess Hg-induced oxidative stress as a component of environmental toxicity.

Metabolism of insect neuropeptides: properties of a membrane-bound endopeptidase from heads of Musca domestica

A phosphoramidon-sensitive endopeptidase activity has been identified in membranes prepared from heads of Musca domestica. The enzyme hydrolyses the Gly3-Phe4 bond of the enkephalin analogue [D-Ala2,Leu5]enkephalin and the Asn3-Phe4 bond of AKH I. Phosporamidon (10 microM), a selective inhibitor of mammalian endopeptidase 24:11, was able to fully protect AKH I from degradation by head membranes. The breakdown of [D-Ala2,Leu5]enkephalin was only partially inhibited by phosphoramidon (10 microM), suggesting the presence of other enkephalin-degrading enzymes in this preparation. The endopeptidase activity was inhibited by 1 mM EDTA and 1 mM 1,10-phenanthroline and could be partially re-activated in the presence of ZnCl2 but not other divalent metal ions. The enzyme had a neutral pH optimum and behaved like an integral membrane protein when subjected to phase-separation with Triton X-114. Although they have a number of similar properties, the insect and mammalian enzymes could be distinguished by their sensitivity to site-directed inhibitors of endopeptidase 24:11. The fly endopeptidase was much less sensitive to phosphoramidon (IC50, 0.25 microM), thiorphan (IC50, 2.5 microM), SQ 28603 (IC50, 1.0 microM), SCH 39370 (IC50, 2.5 microM) and SCH 32615 (IC50, 30 microM). The fly enzyme is indistinguishable from the endopeptidase activity that is enriched in locust synaptic membranes and that found in membranes from heads of Drosophila melanogaster. In summary, we have identified a rich source of an insect neutral metallo-endopeptidase which is similar to endopeptidase 24:11, an enzyme known to play a key role in the metabolism and inactivation of neuropeptides in mammals.

Aging, cytochrome oxidase activity, and hydrogen peroxide release by mitochondria

The objective of this study was to explore the possible cause(s) underlying the previously observed, age-related increase in the rate of mitochondrial H2O2 release in the housefly. The hypothesis that an imbalance between different respiratory complexes may be a causal factor was tested. Cytochrome c oxidase activity was found to sharply decline in the latter part of the life span of the flies. Effects of different substrates and respiratory inhibitors were determined in order to ascertain if a decrease in cytochrome c oxidase activity could be responsible for the increased H2O2 release. H2O2 was measured spectrofluorometrically using horseradish peroxidase and p-hydroxphenylacetate as an indicator. Neither NADH-linked substrates nor succinate caused a stimulation of H2O2 production. H2O2 release by mitochondria, inhibited with rotenone and antimycin A, was greatly increased upon supplementation with alpha-glycerophosphate; however, the further addition of KCN or myxothiazol, to such preparations, caused a depression of H2O2 generation. In contrast, relatively low concentrations of KCN or myxothiazol were found to stimulate H2O2 release in insect mitochondria supplemented with alpha-glycerophosphate and exposed to rotenone, but not antimycin A. Results are interpreted to suggest that partial inhibition of cytochrome c oxidase activity can lead to the stimulation of mitochondrial H2O2 production in the housefly at site(s) other than NADH dehydrogenase and ubisemiquinone/cytochrome b region; a possible source may be glycerophosphate dehydrogenase.

Regulation of sex pheromone biosynthesis in the housefly, Musca domestica: relative contribution of the elongation and reductive steps

The regulation of production of the sex pheromone (Z)-9-tricosene (Z9-23:Hy) in the housefly, Musca domestica, was studied by examining the chain length specificity of the fatty acyl-CoA elongation reactions and the reductive conversion of fatty acyl-CoAs to alkenes in 1- and 4-day-old male and female houseflies. Microsomal preparations from 4-day-old female insects produced as the predominant alkene Z9-23:Hy when incubated with malonyl-CoA, NADPH, and [9,10-3H2]oleoyl-CoA (18:1-CoA), whereas microsomal preparations from 4-day-old male insects produced predominantly (Z)-9-heptacosene (Z9-27:Hy). These are the major alkenes produced in vivo by Day 4 females and males, respectively. Microsomes prepared from both Day 1 males and Day 1 females produced Z9-27:Hy as the major alkene from labeled 18:1-CoA. This is the major alkene produced in vivo by both sexes at Day 1. An examination of the chain length specificity of the elongation reactions showed that microsomes prepared from Day 4 male insects readily elongated both 18:1-CoA and 15-[15,16-3H2]tetracosenoyl-CoA (24:1-CoA) to 28-carbon moieties, whereas microsomes from Day 4 female insects did not efficiently elongate either substrate beyond 24 carbons. With high substrate concentrations, microsomes prepared from male insects converted 24:1-CoA to Z9-23:Hy more efficiently than did those from females, whereas under lower and presumably more physiological substrate concentrations, microsomes from females had slightly higher activity than did those from males. Taken together, these data show that the regulation of the chain length of the alkenes, and thus sex pheromone production, in the housefly resides predominantly in the elongation reactions and not in the step which converts the fatty acyl-CoA to hydrocarbon.

[35S]t-butylbicyclophosphorothionate binding sites in susceptible and cyclodiene-resistant houseflies

4-aminobutyric acid (GABA)-gated chloride ion channels are important molecular targets for a number of polychlorocycloalkane compounds including cyclodiene insecticides. Previous radioligand binding studies have indicated that cyclodiene insecticides are potent inhibitors of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to housefly thorax and abdomen membranes. In the present study, a laboratory-reared, cyclodiene-resistant (CYW) housefly strain (Musca domestica) showed resistance to a number of cyclodiene insecticides. Specific, saturable [35S]TBPS binding was detected in thorax and abdomen membranes prepared from housefly strains susceptible (CSMA) and resistant (CYW) to cyclodienes. Scatchard analysis of [35S]TBPS binding data from CSMA and CYW membranes revealed no significant differences between the two strains in either the affinity (Kd) or the density (Bmax) of specific, saturable binding sites. There were no differences in the comparative effectiveness of a range of polychlorocycloalkanes, including cyclodiene insecticides, as inhibitors of specific [35S]TBPS binding to CSMA and CYW thorax and abdomen membranes. Therefore, if an alteration in target site is a mechanism for resistance to cyclodienes in the CYW strain, it is not readily measurable using [35S]TBPS.

Pharmacology of insect GABA receptors

A GABA-operated Cl- channel that is bicuculline-insensitive is abundant in the nervous tissue of cockroach, in housefly head preparations and thorax/abdomen preparations, and in similar preparations from several insect species. Bicuculline-insensitive GABA-operated Cl- channels, which are rare in vertebrates, possess sites of action of benzodiazepines, steroids and insecticides that are pharmacologically-distinct from corresponding sites on vertebrate GABAA receptors. The pharmacological profile of the benzodiazepine-binding site linked to an insect CNS GABA-operated Cl- channel resembles more closely that of vertebrate peripheral benzodiazepine-binding sites. Six pregnane steroids and certain polychlorocycloalkane insecticides, which are active at t-butylbicyclophosphorothionate (TBPS)-binding sites, also differ in their effectiveness on vertebrate and insect GABA receptors. Radioligand binding and physiological studies indicate that in insects there may be subtypes of the GABA receptor. Molecular biology offers experimental approaches to understanding the basis of this diversity.

Hydrogen peroxide release by mitochondria increases during aging

The effect of aging on the release of H2O2 by mitochondria was studied in the housefly in order to elucidate the causes of previously observed age-related increase in the level of oxidative stress. Intact flight muscle mitochondria of the housefly, supplemented with alpha-glycerophosphate, produce 1-2 nmol H2O2/min per mg protein, even in the absence of respiratory inhibitors. The rate of H2O2 secretion progressively increases approximately 2-fold during aging of the fly. Neither uncoupling of oxidative phosphorylation nor mechanical damage to mitochondria during the isolation procedure appear to be responsible for the age-related increase in H2O2 production. Activities of NADH-ferricyanide reductase, succinate-ubiquinone reductase, and NADH-, succinate- and alpha-glycerophosphate-cytochrome c reductases, were approximately 2-fold higher in mitochondria from the old than those from the young flies. However, the concentration of enzymatically reducible ubiquinone remained unchanged with age. Infliction of damage by exposure of mitochondria to free radical-generating systems in vitro caused an increase in the rate of H2O2 generation. Glutaraldehyde, an intermolecular crosslinking agent, induced an increase in the rate of H2O2 generation by mitochondria. Results of this study demonstrate that aging in the housefly is associated with an increase in the rate of H2O2 generation by mitochondria probably due, at least in part, to self-inflicted damage by mitochondria. Intermolecular cross-linking in the inner mitochondrial membrane can contribute towards the increased H2O2 generation.

Digestion of bacteria and the role of midgut lysozyme in some insect larvae

1. Lysozyme is absent from tissues other than the midgut in the drug-feeding larvae of Musca domestica (Diptera, Cyclorrhapha, Muscidae) and in the fruit-feeding larvae of Anastrepha fraterculus (Diptera, Cyclorrhapha, Tephritidae), whereas in the detritus-feeding larvae of Trichosia pubescens (Diptera, Nematocera, Sciaridae) lysozyme is only found in the hemolymph and in the fat body. 2. A. fraterculus larvae have a midgut region with a luminal pH of 3.4, and display a pepstatin-inhibited acid proteolytic activity which has a spec. act. (7.2 U/mg protein) similar to that of M. domestica. 3. The midgut lysozyme from M. domestica and A. fraterculus is more active (high ionic strength) at pH 3.5 than at pH 6.0, the contrary being true for a midgut chitinase. 4. The results suggest that the adaptations to digest bacteria in insects are similar to those in vertebrate foregut fermenters, and that these characteristics were probably present in the Cyclorrhapha ancestor, but not in the Diptera ancestor.

Synthesis of omega 9-tetracosynoic and omega 9-octacosynoic acids as entries into tritiated metabolic precursors of cis-9-tricosene and cis-9-heptacosene in the housefly

The syntheses of 15-tetracosynoic acid (omega 9-tetracosynoic acid) and 19-octacosynoic acid (omega 9-octacosynoic acid) are described. These alkynoic acids are to be tritiated to the corresponding alkenoic acids, which will be used as metabolic precursors of housefly pheromone components. The final step in each synthesis involved the coupling of 1-decyne to the lithio-salt of the appropriate omega-bromoacid. Homologation of dibromoalkanes was accomplished with triphasic catalytic displacement of bromide by cyanide ion. Oxidation of a bromo-alcohol to a bromoacid was performed in benzene with KMnO4 and 18-crown-6 ether.

Effect of Altoside (ZR-515) on oxygen consumption, carbon dioxide out put and carbohydrate content of organophosphorus resistant strain of Musca domestica

The effect of applying JHA ZR-515 at a concentration of 50 microliter/liter water in the larval rearing medium from the first larval instar on oxygen consumption, carbon dioxide out put and total carbohydrates was studied. The oxygen consumed by the pupae previously treated as larvae with ZR-515 was decreased and no adult could emerge. The carbon dioxide out put seems to follow a more or less the pattern of oxygen consumption. The concentration of total carbohydrate content in one day old pupae previously treated as larvae was significantly lower than normals. In three days old there was a marked significant increase and in five days old, the carbohydrate content was significantly higher than controls.

Cytochrome P-450-catalyzed formation of 20-hydroxy-ecdysone in larval housefly mitochondria

Six forms of cytochrome P-450 in the mitochondria of larvae from Musca domestica were isolated by solubilization with CHAPS followed by ammonium sulfate fractionation and HPLC on an anion-exchange column. Forms 1, 2, 3, 5, and 6 catalyzed the formation of 20-hydroxy-ecdysone from ecdysone in the presence of NADPH and pig adrenal adrenodoxin and adrenodoxin reductase at rates not much different that observed in mitochondria; whereas, fraction 4 showed an activity which was about 10-fold higher than mitochondria. Forms 4 and 5 were further purified by HPLC on a cation-exchange column followed by removal of excess detergent by hydroxyl apatite column chromatography. In vitro reconstitution of the monooxygenase activity confirmed that form 4 is primarily involved in the formation of 20-hydroxy-ecdysone from ecdysone. SDS-polyacrylamide gel electrophoresis indicated a high degree of purity of both forms 4 and 5, with molecular weights of 56 and 58 KDa, respectively.