Gene expression analysis of antioxidant and DNA methylation on the rat liver after 4-week wood preservative chromated copper arsenate exposure.

Our previous 4-week repeated dose toxicity study showed that wood preservative chromated copper arsenate (CCA) induced hepatocellular hypertrophy accompanied by biochemical hepatic dysfunction and an increase in oxidative stress marker, 8-hydroxydeoxyguanosine, in female rats. To further explore the molecular mechanisms of CCA hepatotoxicity, we analyzed 10%-buffered formalin-fixed liver samples from female rats for cell proliferation, apoptosis, and protein glutathionylation and conducted microarray analysis on frozen liver samples from female rats treated with 0 or 80 mg/kg/day of CCA. Chemical analysis revealed that dimethylated arsenical was the major metabolite in liver tissues of male and female rats. CCA increase labeling indices of proliferating cell nuclear antigen and decrease terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling accompanied with increased expression of protein glutathionylation, indicating a decrease in glutathione (GSH) in hepatocytes of female rats. Microarray analysis revealed that CCA altered gene expression of antioxidants, glutathione-S-transferase (GST), heat shock proteins and ubiquitin-proteasome pathway, cell proliferation, apoptosis, DNA methylation, cytochrome P450, and glucose and lipid metabolism in female rats. Increased expression of GSTs, including Gsta2, Gsta3, Mgst1, and Cdkn1b (p27), and decreased expression of the antioxidant Mt1, and DNA methylation Dnmt1, Dnmt3a, and Ctcf were confirmed in the liver of female rats in a dose-dependent manner. Methylation status of the promoter region of the Mt1 was not evidently changed between control and treatment groups. The results suggested that CCA decreased GSH and altered the expression of several genes, including antioxidants, GST, and DNA methylation, followed by impaired cell proliferation in the liver of female rats.

Circadian and Neuroendocrine Basis of Photoperiodism Controlling Diapause in Insects and Mites: A Review.

The photoperiodic system is concealed in the highly complex black-box, comprising four functional subunits: 1) a photo/thermo-sensitive input unit, 2) a photoperiodic clock based on a circadian system, 3) a condenser unit counting the number of inductive signals, and 4) a neuroendocrine switch that triggers a phenotypic shift. This review aims to summarize the research history and current reach of our understanding on this subject to connect it with the molecular mechanism of the circadian clock rapidly being unveiled. The review also focuses on the mode of intersubunit information transduction. It will scan the recent advancement in research on each functional subunit, but special attention will be given to the circadian clock-endocrine conjunct and the role of melatonin signaling in the regulation of insect photoperiodism. Prothoracicotropic hormone (PTTH) probably plays the most crucial role in the regulation of pupal diapause, which is the simplest model system of diapause regulation by hormones investigated so far, particularly in the Chinese oak silkmoth (Antheraea pernyi). A search for the trigger to release the PTTH found some candidates, that is, indoleamines. Indolamine metabolism is controlled by arylalkylamine N-acetyltransferase (aaNAT). Indolamine dynamics and aaNAT enzymatic activity changed according to photoperiods. aaNAT activity and melatonin content in the brain showed not only a photoperiodic response but also a circadian fluctuation. aaNAT had multiple E-boxes, suggesting that it is a clock-controlled gene (ccg), which implies that cycle (cyc, or brain-muscle Arnt-like 1 = Bmal1)/Clock (Clk) heterodimer binds to E-box and stimulates the transcription of aaNAT, which causes the synthesis of melatonin. RNAi against transcription modulators, cyc, or Clk downregulated aaNAT transcription, while RNAi against repressor of cyc/Clk, per upregulated aaNAT transcription. Immunohistochemical localization showed that the circadian neurons carry epitopes of melatonin-producing elements such as aaNAT, the precursor serotonin, HIOMT, and melatonin as well as clock gene products such as cyc-ir, Per-ir, and dbt-ir, while PTTH-producing neurons juxtaposed against the clock neurons showed hMT2-ir in A. pernyi brain. Melatonin probably binds to the putative melatonin receptor (MT) that stimulates Ca2+ influx, which in turn activates PKC. This induces Rab 8 phosphorylation and exocytosis of PTTH, leading to termination of diapause. All the PTTH-expressing neurons have PKC-ir, and Rab8-ir. When diapause is induced and maintained under short days, serotonin binding to 5HTR1B suppresses PTTH release in a yet unknown way. RNAi against this receptor knocked out photoperiodism; short day response is blocked and diapause was terminated even under the short day condition. The result showed that a relatively simple system controls both induction and termination in pupal diapause of A. pernyi: the circadian system regulates the transcription of aaNAT as a binary switch, the enzyme produces a melatonin rhythm that gates PTTH release, and 5HTR1B and MT are probably also under photoperiodic regulation. Finally, we listed the remaining riddles which need to be resolved, to fully understand this highly complex system in future studies.

Involvement of Cis-Acting Elements in Molecular Regulation of JH-Mediated Vitellogenin Gene 2 of Female Periplaneta americana.

Vitellogenins (Vgs) are yolk protein precursors that are regulated by juvenile hormone (JH) and/or 20-hydroxyecdysone (20E) in insects. JH acts as the principal gonadotropin that stimulates vitellogenesis in hemimetabolous insects. In this study, we cloned and characterized the Periplaneta americana Vitellogenin 2 (Vg2) promoter. Multiple sites for putative transcription factor binding were predicted for the 1,804 bp Vg2 promoter region, such as the Broad-Complex, ecdysone response element (EcRE), GATA, Hairy, JH response element (JHRE), and Methoprene (Met)-binding motif, among others. Luciferase reporter assay has identified that construct -177 bp is enough to support JH III induction but not 20E suppression. This 38 bp region (from -177 to -139 bp) contains two conserved response element half-sites separated by 2 nucleotides spacer (DR2) and is designated as Vg2RE (-168GAGTCACGGAGTCGCCGCTG-149). Mutation assay and luciferase assay data using mutated constructs verified the crucial role of G residues in Vg2RE for binding the isolated fat body nuclear protein. In Sf9 cells, a luciferase reporter placed under the control of a minimal promoter containing Vg2RE was induced by JH III in a dose- and time-dependent manner. Nuclear proteins isolated from previtellogenic female fat body cells bound to Vg2RE, and this binding was outcompeted by a 50-fold excess of cold Drosophila melanogaster DR4 and Galleria mellonella JH binding protein response elements (Chorion factor-I/Ultraspiracle). Affinity pull-down experiment with nuclear extracts of previtellogenic female fat body, using 31-bp probe Vg2RE as bait, yielded a 71 kDa candidate nuclear protein that may mediate the regulatory action of the JH III.

Comparative Analysis of Mitochondrial Genomes in Gryllidea (Insecta: Orthoptera): Implications for Adaptive Evolution in Ant-Loving Crickets.

Species of infraorder Gryllidea, or crickets, are useful invertebrate models for studying developmental biology and neuroscience. They have also attracted attention as alternative protein sources for human food and animal feed. Mitochondrial genomic information on related invertebrates, such as katydids, and locusts, has recently become available in attempt to clarify the controversial classification schemes, although robust phylogenetic relationships with emphasis on crickets remain elusive. Here, we report newly sequenced complete mitochondrial genomes of crickets to study their phylogeny, genomic rearrangements, and adaptive evolution. First, we conducted de novo assembly of mitochondrial genomes from eight cricket species and annotated protein-coding genes and transfer and ribosomal RNAs using automatic annotations and manual curation. Next, by combining newly described protein-coding genes with public data of the complete Gryllidea genomes and gene annotations, we performed phylogenetic analysis and found gene order rearrangements in several branches. We further analyzed genetic signatures of selection in ant-loving crickets (Myrmecophilidae), which are small wingless crickets that inhabit ant nests. Three distinct approaches revealed two positively selected sites in the cox1 gene in these crickets. Protein 3D structural analyses suggested that these selected sites could influence the interaction of respiratory complex proteins, conferring benefits to ant-loving crickets with a unique ecological niche and morphology. These findings enhance our understanding of the genetic basis of cricket evolution without relying on estimates based on a limited number of molecular markers.

Clock-controlled arylalkylamine N-acetyltransferase (aaNAT) regulates circadian rhythms of locomotor activity in the American cockroach, Periplaneta americana, via melatonin/MT2-like receptor.

Melatonin (MEL) orchestrates daily and seasonal rhythms (eg, locomotion, sleep/wake cycles, and migration among other rhythms) in diverse organisms. We investigated the effects of pharmacological doses (0.03-1 mM) of exogenous MEL intake in the cockroach, Periplaneta americana, on locomotor activity. As per os MEL concentration increased, cockroach locomotor rhythm in light-dark (LD) cycles became more synchronized. The ratio of night activity to 24-h activity increased and the acrophase (peak) slightly advanced. MEL application also influenced total activity bouts in the free-running rhythm. Since MEL slightly influenced τ in the free-running rhythms, it is not a central element of the circadian pacemaker but must influence mutual coupling of multi-oscillatory system components. Arylalkylamine N-acetyltransferase (aaNAT) regulates enzymatic production of MEL. aaNAT activities vary in circadian rhythms, and the immunoreactive aaNAT (aaNAT-ir) is colocalized with the key clock proteins cycle (CYC)-ir and pigment-dispersing factor (PDF)-ir These are elements of the central pacemaker and its output pathway as well as other circadian landmarks such as the anterior and posterior optic commissures (AOC and POC, respectively). It also partially shares immunohistochemical reactivity with PER-ir and DBT-ir neurons. We analyzed the role of Pamericana aaNAT1 (PaaaNAT1) (AB106562.1) by injecting dsRNAaaNAT1 . qPCR showed a decrease in accumulations of mRNAs encoding PaaaNAT1. The injections led to arrhythmicity in LD cycles and the arrhythmicity persisted in constant dark (DD). Continuous administration of MEL resynchronized the rhythm after arrhythmicity was induced by dsRNAaaNAT1 injection, suggesting that PaaaNAT is the key regulator of the circadian system in the cockroach via MEL production. PaaaNAT1 contains putative E-box regions which may explain its tight circadian control. The receptor that mediates MEL function is most likely similar to the mammalian MT2, because injecting the competitive MT2 antagonist luzindole blocked MEL function, and MEL injection after luzindole treatment restored MT function. Human MT2-ir was localized in the circadian neurons in the cockroach brain and subesophageal ganglion. We infer that MEL and its synthesizing enzyme, aaNAT, constitute at least one circadian output pathway of locomotor activity either as a distinct route or in association with PDF system.

Circadian regulation of night feeding and daytime detoxification in a formidable Asian pest Spodoptera litura.

Voracious feeding, trans-continental migration and insecticide resistance make Spodoptera litura among the most difficult Asian agricultural pests to control. Larvae exhibit strong circadian behavior, feeding actively at night and hiding in soil during daytime. The daily pattern of larval metabolism was reversed, with higher transcription levels of genes for digestion (amylase, protease, lipase) and detoxification (CYP450s, GSTs, COEs) in daytime than at night. To investigate the control of these processes, we annotated nine essential clock genes and analyzed their transcription patterns, followed by functional analysis of their coupling using siRNA knockdown of interlocked negative feedback system core and repressor genes (SlituClk, SlituBmal1 and SlituCwo). Based on phase relationships and overexpression in cultured cells the controlling mechanism seems to involve direct coupling of the circadian processes to E-boxes in responding promoters. Additional manipulations involving exposure to the neonicotinoid imidacloprid suggested that insecticide application must be based on chronotoxicological considerations for optimal effectiveness.

A unique primary structure of RDL (resistant to dieldrin) confers resistance to GABA-gated chloride channel blockers in the two-spotted spider mite Tetranychus urticae Koch.

The primary structure of the second transmembrane (M2) segment of resistant to dieldrin (RDL), an ionotropic γ-aminobutyric acid receptor (GABAR) subunit, and the structure-function relationships in RDL are well conserved among insect species. An amino acid substitution at the 2' position in the M2 segment (Ala to Ser or Gly) confers resistance to non-competitive antagonists (NCAs) of GABARs. Here, a cDNA encoding RDL was cloned from the two-spotted spider mite Tetranychus urticae Koch. Unlike insect homologs, native TuRDL has His at the 2' position (H305) and Ile at 6' (I309) in the M2 segment and is insensitive to NCAs. Single and multiple mutations were introduced in the M2 segment of TuRDL, and the mutant proteins were expressed in Xenopus oocytes and examined for the restoration of sensitivity to NCAs. The sensitivity of a double mutant (H305A and I309T in the M2 segment) was greatly increased but was still considerably lower than that of insect RDLs. We therefore constructed chimeric RDLs consisting of TuRDL and Drosophila melanogaster RDL and examined their sensitivities to NCAs. The results show that the N-terminal region containing the Cys-loop as well as the M2 segment confers functional specificity; thus, our current understanding of the mechanism underlying NCA binding to GABARs requires reappraisal.

Crosstalk among Indoleamines, Neuropeptides and JH/20E in Regulation of Reproduction in the American Cockroach, Periplaneta americana.

Although the regulation of vitellogenesis in insects has been mainly discussed in terms of 'classical' lipid hormones, juvenile hormone (JH), and 20-hydroxyecdysone (20E), recent data support the notion that this process must be adjusted in harmony with a nutritional input/reservoir and involvement of certain indoleamines and neuropeptides in regulation of such process. This study focuses on crosstalks among these axes, lipid hormones, monoamines, and neuropeptides in regulation of vitellogenesis in the American cockroach Periplaneta americana with novel aspects in the roles of arylalkylamine N-acetyltransferase (aaNAT), a key enzyme in indoleamine metabolism, and the enteroendocrine peptides; crustacean cardioactive peptide (CCAP) and short neuropeptide F (sNPF). Double-stranded RNA against aaNAT (dsRNAaaNAT) was injected into designated-aged females and the effects were monitored including the expressions of aaNAT itself, vitellogenin 1 and 2 (Vg1 and Vg2) and the vitellogenin receptor (VgR) mRNAs, oocyte maturation and changes in the hemolymph peptide concentrations. Effects of peptides application and 20E were also investigated. Injection of dsRNAaaNAT strongly suppressed oocyte maturation, transcription of Vg1, Vg2, VgR, and genes encoding JH acid- and farnesoate O-methyltransferases (JHAMT and FAMeT, respectively) acting in the JH biosynthetic pathway. However, it did not affect hemolymph concentrations of CCAP and sNPF. Injection of CCAP stimulated, while sNPF suppressed oocyte maturation and Vgs/VgR transcription, i.e., acting as allatomedins. Injection of CCAP promoted, while sNPF repressed ecdysteroid (20E) synthesis, particularly at the second step of Vg uptake. 20E also affected the JH biosynthetic pathway and Vg/VgR synthesis. The results revealed that on the course of vitellogenesis, JH- and 20E-mediated regulation occurs downstream to indoleamines- and peptides-mediated regulations. Intricate mutual interactions of these regulatory routes must orchestrate reproduction in this species at the highest potency.

A putative direct repeat element plays a dual role in the induction and repression of insect vitellogenin-1 gene expression.

Juvenile hormones (JH) regulate wide-ranging physiological and developmental processes in insects. However, molecular mechanisms underlying JH signaling remain to be determined. Vitellogenin (Vg) is primarily an egg-yolk protein, but recently proposed to serve many functions in insects. In the female American cockroach (Periplaneta americana), vitellogenin (Vg) genes are activated by JH III and suppressed by 20-hydroxyecdysone (20E) via cis-regulatory elements in a dose-dependent manner. In the present study, the upstream promoter region (935 bp) of Vg1 was cloned to elucidate the action of these hormones. A luciferase reporter assay identified an 81 bp region in the promoter region of Vg1 (-120 to -39 bp) that we found to be critical for JH III activation and 20E suppression. This 81 bp region contains a direct repeat separated by a 2-nucleotide spacer-designated Vg1HRE- that is similar to the Drosophila ecdysone response element direct repeat 4. Moreover, nuclear proteins isolated from nymphs, males, females, and Sf9 cells successfully bound to Vg1HRE, while binding was outcompeted by a 100-fold excess of cold probe or dephosphorylated nuclear protein extracts. In addition, binding was outcompeted by other ecdysone and JH response elements with similar half-site sequences (direct repeats) but to varying extents. Ultimately, we postulate that JH III indirectly activates Vg expression by interfering with or inhibiting the phosphorylation of nuclear proteins bound to Vg1HRE. Involvement of JH III in both induction of Vg1 and control of nuclear proteins binding to Vg1HRE suggest the latter to play an important role in JH signaling.

Pathological and Clinical Pathological Changes Induced by Four-week, Repeated-dose, Oral Administration of the Wood Preservative Chromated Copper Arsenate in Wistar Rats.

Chromated copper arsenate (CCA) is used as a wood preservative worldwide. Exposure to it may adversely affect human health. Some events have increased human exposure to CCA, including the Great East Japan Earthquake, which generated a large amount of lumber debris from CCA-treated woods. We elucidated the toxicity due to daily exposure to CCA over a 4-week period at doses of 0, 8, 40, and 80 mg/kg/day in Wistar Hannover rats. Chromium (Cr) and arsenic (As), but not copper, were detected in the plasma samples of rats treated with various doses of CCA. Males and females showed sedation, and males had poor body weight gain. The clinical pathologies observed in both sexes included hypochromic and microcytic anemia, hepatic and renal dysfunction, and changes in lipid and glucose levels. Histopathologically, males and females showed forestomach hyperkeratosis, mucosal epithelial hyperplasia in the small intestine, rectal goblet cell hypertrophy, and lipofuscin deposition in the proximal renal tubule. Females showed diffuse hepatocellular hypertrophy with increased 8-hydroxydeoxyguanosine levels. These results indicated that oral administration of CCA mainly affected hematopoietic, gastrointestinal, hepatic, and renal systems owing to the toxic effects of As and/or Cr. Major toxic effects were observed in both sexes receiving 40 and 80 mg/kg/day.

Molecular and functional characterization of the American cockroach, Periplaneta americana, Rab5: the first exopterygotan low molecular weight ovarian GTPase during oogenesis.

The small Rab GTPases are key regulators of membrane vesicle trafficking. Ovaries of Periplaneta americana (Linnaeus) (Blattodea: Blattidae) have small molecular weight GTP/ATP-binding proteins during early and late vitellogenic periods of oogenesis. However, the identification and characterization of the detected proteins have not been yet reported. Herein, we cloned a cDNA encoding Rab5 from the American cockroach, P. americana, ovaries (PamRab5). It comprises 796 bp, encoding a protein of 213 amino acid residues with a predicted molecular weight of 23.5 kDa. PamRab5 exists as a single-copy gene in the P. americana genome, as revealed by Southern blot analysis. An approximate 2.6 kb ovarian mRNA was transcribed especially at high levels in the previtellogenic ovaries, detected by Northern blot analysis. The muscle and head tissues also showed high levels of PamRab5 transcript. PamRab5 protein was localized, via immunofluorescence labeling, to germline-derived cells of the oocytes, very early during oocyte differentiation. Immunoblotting detected a ∼25 kDa signal as a membrane-associated form revealed after application of detergent in the extraction buffer, and 23 kDa as a cytosolic form consistent with the predicted molecular weight from amino acid sequence in different tissues including ovary, muscles and head. The PamRab5 during late vitellogenic periods is required to regulate the endocytotic machinery during oogenesis in this cockroach. This is the first report on Rab5 from a hemimetabolan, and presents an inaugural step in probing the molecular premises of insect oocyte endocytotic trafficking important for oogenesis and embryonic development.

Three-year lifecycle, large body, and very high threshold temperature in the cricket Gryllus argenteus for special adaptation to desiccation cycle in Malawi.

In temperate climates, the initiation and termination of diapause synchronize the stress-tolerant stage with the stressful season and reproduction with the non-stressful season in many insects. Synchronization is often regulated by photoperiodism.Voltinism and the ultimate size of adults are also important determinants for their lifecycle, and different diapause stages and voltinism patterns are known in crickets.Here, we investigated the life history of the African cricket Gryllus argenteus from Malawi, which is a typical arid tropical highland. The climate is characterized by alternating arid and wet seasons, each of which lasts for half a year, and where the available heat mass is much less than lowlands at the same latitude. We first measured the nymphal duration at each rearing temperature and calculated the lower developmental threshold (t 0) to be 20.19 °C based on Ikemoto and Takai (2000) and 19.38 °C based on a conventional line-fitting method. These values are very high relative to many other insects. The local temperature in winter does not fall below 15 °C, but this is much higher than the lethal limit. This suggested that critical stress in this locality was not coldness but low precipitation in winter. We estimated, based both on local temperature change and the Ikemoto and Takai's t 0, that G. argenteus required 3 years to complete its lifecycle unlike wet lowland species, where univoltinism or multi-voltinism are commonplace. Photoperiodism was observed in this species, but due to a lag between annual cycles in photoperiod, temperature, and humidity, photoperiodism alone cannot atune their lifecycle with local conditions.Synchronization in this species was achieved by three different adaptations: photoperiodism, high t 0, and large body size, which give it a long lifecycle. Although the species cannot achieve a univoltine lifecycle because of its high t0 value, it can escape from dry season by entering diapause at moderate temperatures, probably thereby achieving adaptive synchrony of lifecycle with both favorable and unfavorable seasons. A comparison between a conventional photothermogram and a newly formulated photohydrogram or photohygrogram demonstrates that even though sufficient heat is available, scarcity of water and thus scarcity of foliage should force the cricket to maintain diapause at intermediate temperature. The results suggested that high t 0, large body size, and multi-ennial lifecycle mutually affect each other and formulate a unique adaptation under such an extreme environment.

Localization and functional analysis of the insect-specific RabX4 in the brain of Bombyx mori.

Rab proteins are small monomeric GTPases/GTP-binding proteins, which form the largest branch of the Ras superfamily. The different Rab GTPases are localized to the cytosolic face of specific intracellular membranes, where they function as regulators of distinct steps in membrane trafficking. RabX4 is an insect-specific Rab protein that has no close homolog in vertebrates. There is little information about insect-specific Rab proteins. RabX4 was expressed in Escherichia coli and subsequently purified. Antibodies against Bombyx mori RabX4 were produced in rabbits for western immunoblotting and immunohistochemistry. Western blotting of neural tissues revealed a single band, at approximately 26 kD. RabX4-like immunohistochemical reactivity was restricted to neurons of the pars intercerebralis and dorsolateral protocerebrum in the brain. Further immunohistochemical analysis revealed that RabX4 colocalized with Rab6 and bombyxin in the corpus allatum, a neuronal organ that secretes neuropeptides synthesized in the brain into the hemolymph. RabX4 expression in the frontal ganglion, part of the insect stomatogastric nervous system that is found in most insect orders, was restricted to two neurons on the outer region and did not colocalize with allatotropin or Rab6. Furthermore, RNA interference of RabX4 decreased bombyxin expression levels in the brain. These findings suggest that RabX4 is involved in the neurosecretion of a secretory organ in Bombyx mori.

r/K-like trade-off and voltinism discreteness: The implication to allochronic speciation in the fall webworm, Hyphantria cunea complex (Arctiidae).

North America has distinct types of Hyphantria moths (Arctiidae) characterized by red (RD)- and black (BL)-headed larvae, of which the taxonomic status is unresolved. Genetic divergence of 26 populations, based on 710 bp of the mtCOI sequence, showed two phylogenetic lineages, which could not be connected in the haplotype network with 95% confidence. The two lineages are separated by 3.1% sequence divergence and should be considered for full species status. The estimated split occurred 1.2-1.6 million years ago. The range of the RD type covered most of the continent, whereas that of the BL type was limited to eastern deciduous forests. Several biological characteristics were differentiated in the zone of cohabitation where BL had more annual generations than RD. Spring emergence of BL precedes that of RD in the field by at least 1 month, because the diapause in BL was shallow, whereas it was deep in RD. Voltinism requires discreteness of numbers, which functions as a sink of hybrids between the two parental lines that have distinct but equally adaptive reproductive strategies; BL may be more r-strategist-like and RD more K-strategist-like, because fast-developing BL has multivoltine life cycle, investing less silk proteins as the round-the-clock feeder, and slow-developing RD univoltine one investing more silk as the nocturnal feeder. Also, intensity of diapause, deep in RD and weak in BL, was grossly different, which may enforce segregation of spring adults. Allochronic speciation avoiding coincidental occurrence of adult stages is therefore the most likely scenario. Because the adults never meet in nature, large morphological differentiation is not required.

Toxicity and Carcinogenicity of Dichlorodiphenyltrichloroethane (DDT).

Dichlorodiphenyltrichloroethane (DDT) is still used in certain areas of tropics and subtropics to control malaria and other insect-transmitted diseases. DDT and its metabolites have been extensively studied for their toxicity and carcinogenicity in animals and humans and shown to have an endocrine disrupting potential affecting reproductive system although the effects may vary among animal species in correlation with exposure levels. Epidemiologic studies revealed either positive or negative associations between exposure to DDT and tumor development, but there has been no clear evidence that DDT causes cancer in humans. In experimental animals, tumor induction by DDT has been shown in the liver, lung, and adrenals. The mechanisms of hepatic tumor development by DDT have been studied in rats and mice. DDT is known as a non-genotoxic hepatocarcinogen and has been shown to induce microsomal enzymes through activation of constitutive androstane receptor (CAR) and to inhibit gap junctional intercellular communication (GJIC) in the rodent liver. The results from our previously conducted 4-week and 2-year feeding studies of p,p'-DDT in F344 rats indicate that DDT may induce hepatocellular eosinophilic foci as a result of oxidative DNA damage and leads them to hepatic neoplasia in combination with its mitogenic activity and inhibitory effect on GJIC. Oxidative stress could be a key factor in hepatocarcinogenesis by DDT.

Rab proteins in the brain and corpus allatum of Bombyx mori.

In eukaryotic cells, Rab guanosine triphosphate-ases serve as key regulators of membrane-trafficking events, such as exocytosis and endocytosis. Rab3, Rab6, and Rab27 control the regulatory secretory pathway of neuropeptides and neurotransmitters. The cDNAs of Rab3, Rab6, and Rab27 from B. mori were inserted into a plasmid, transformed into Escherichia coli, and then subsequently purified. We then produced antibodies against Rab3, Rab6, and Rab27 of Bombyx mori in rabbits and rats for use in western immunoblotting and immunohistochemistry. Western immunoblotting of brain tissue revealed a single band at approximately 26 kDa. Immunohistochemistry results revealed that Rab3, Rab6, and Rab27 expression was restricted to neurons in the pars intercerebralis and dorsolateral protocerebrum of the brain. Rab3 and Rab6 co-localized with bombyxin, an insect neuropeptide. However, there was no Rab that co-localized with prothoracicotropic hormone. The corpus allatum secretes neuropeptides synthesized in the brain into the hemolymph. Results showed that Rab3 and Rab6 co-localized with bombyxin in the corpus allatum. These findings suggest that Rab3 and Rab6 are involved in neurosecretion in B. mori. This study is the first to report a possible relationship between Rab and neurosecretion in the insect corpus allatum.

Identification of Proteins Modulated in the Date Palm Stem Infested with Red Palm Weevil (Rhynchophorus ferrugineus Oliv.) Using Two Dimensional Differential Gel Electrophoresis and Mass Spectrometry.

A state of the art proteomic methodology using Matrix Assisted Laser Desorption/Ionization-Time of Flight (MALDI TOF) has been employed to characterize peptides modulated in the date palm stem subsequent to infestation with red palm weevil (RPW). Our analyses revealed 32 differentially expressed peptides associated with RPW infestation in date palm stem. To identify RPW infestation associated peptides (I), artificially wounded plants (W) were used as additional control beside uninfested plants, a conventional control (C). A constant unique pattern of differential expression in infested (I), wounded (W) stem samples compared to control (C) was observed. The upregulated proteins showed relative fold intensity in order of I > W and downregulated spots trend as W > I, a quite interesting pattern. This study also reveals that artificially wounding of date palm stem affects almost the same proteins as infestation; however, relative intensity is quite lower than in infested samples both in up and downregulated spots. All 32 differentially expressed spots were subjected to MALDI-TOF analysis for their identification and we were able to match 21 proteins in the already existing databases. Relatively significant modulated expression pattern of a number of peptides in infested plants predicts the possibility of developing a quick and reliable molecular methodology for detecting plants infested with date palm.

Brain-midgut cross-talk and autocrine metabolastat via the sNPF/CCAP negative feed-back loop in the American cockroach, Periplaneta americana.

Immunohistochemical reactivities against short neuropeptide F (sNPF-ir) and crustacean cardioactive peptide (CCAP-ir) were detected in both the brain-subesophageal ganglion (Br-SOG) and midgut epithelial cells of the male American cockroach, Periplaneta americana. Four weeks of starvation increased the number of sNPF-ir cells and decreased the CCAP-ir cells in the Br-SOG, whereas refeeding reversed these effects. The contents of sNPF in the Br-SOG, midgut and hemolymph titer decreased in response to an injection of CCAP into the hemocoel of normally fed male cockroaches, while CCAP titers/contents decreased in response to an injection of sNPF. The results of a double-labeling experiment demonstrated that sNPF-ir co-existed in CCAP-ir cells in the pars intercerebralis (PI), dorsolateral region of protocerebrum (DL), deutocerebrum (De) and SOG. sNPF-ir and CCAP-ir were also colocalized in the midgut. sNPF and CCAP are neuropeptides and midgut factors that interact with each other. Since the two peptides are known to be secreted by identical cells that affect each other, this constitutes autocrine negative feedback regulation for a quick response to food accessibility/inaccessibility. These peptides not only constitute the switch in the digestive mechanism but also couple digestive adaptation with behavior. A CCAP injection suppressed locomotor activity when cockroaches were starved, whereas sNPF activated it when they were fed.

Structures and functions of insect arylalkylamine N-acetyltransferase (iaaNAT); a key enzyme for physiological and behavioral switch in arthropods.

The evolution of N-acetyltransfeases (NATs) seems complex. Vertebrate arylalkylamine N-acetyltransferase (aaNAT) has been extensively studied since it leads to the synthesis of melatonin, a multifunctional neurohormone prevalent in photoreceptor cells, and is known as a chemical token of the night. Melatonin also serves as a scavenger for reactive oxygen species. This is also true with invertebrates. NAT therefore has distinct functional implications in circadian function, as timezymes (aaNAT), and also xenobiotic reactions (arylamine NAT or simply NAT). NATs belong to a broader enzyme group, the GCN5-related N-acetyltransferase superfamily. Due to low sequence homology and a seemingly fast rate of structural differentiation, the nomenclature for NATs can be confusing. The advent of bioinformatics, however, has helped to classify this group of enzymes; vertebrates have two distinct subgroups, the timezyme type and the xenobiotic type, which has a wider substrate range including imidazolamine, pharmacological drugs, environmental toxicants and even histone. Insect aaNAT (iaaNAT) form their own clade in the phylogeny, distinct from vertebrate aaNATs. Arthropods are unique, since the phylum has exoskeleton in which quinones derived from N-acetylated monoamines function in coupling chitin and arthropodins. Monoamine oxidase (MAO) activity is limited in insects, but NAT-mediated degradation prevails. However, unexpectedly iaaNAT occurs not only among arthropods but also among basal deuterostomia, and is therefore more apomorphic. Our analyses illustrate that iaaNATs has unique physiological roles but at the same time it plays a role in a timezyme function, at least in photoperiodism. Photoperiodism has been considered as a function of circadian system but the detailed molecular mechanism is not well understood. We propose a molecular hypothesis for photoperiodism in Antheraea pernyi based on the transcription regulation of NAT interlocked by the circadian system. Therefore, the enzyme plays both unique and universal roles in insects. The unique role of iaaNATs in physiological regulation urges the targeting of this system for integrated pest management (IPM). We indeed showed a successful example of chemical compound screening with reconstituted enzyme and further attempts seem promising.