The biochemical pathway of neurofibrillary degeneration in aging and Alzheimer's disease

OBJECTIVE

To determine the spatiotemporal mapping of neurofibrillary degeneration (NFD) in normal aging and the different stages of AD.

BACKGROUND

The pathophysiologic significance of AD lesions, namely amyloid plaques and neurofibrillary tangles, is still unclear, especially their interrelationship and their link with cognitive impairment.

METHODS

The study included 130 patients of various ages and different cognitive statuses, from nondemented control subjects (n = 60, prospective study) to patients with severe definite AD. Paired helical filaments (PHF)-tau and Abeta were used as biochemical and histologic markers of NFD and amyloid plaques, respectively.

RESULTS

NFD with PHF-tau was systematically present in variable amounts in the hippocampal region of nondemented patients age >75 years. When NFD was found in other brain areas, it was always along a stereotyped, sequential, hierarchical pathway. The progression was categorized into 10 stages according to the brain regions affected: transentorhinal cortex (S1), entorhinal (S2), hippocampus (S3), anterior temporal cortex (S4), inferior temporal cortex (S5), medium temporal cortex (S6), polymodal association areas (prefrontal, parietal inferior, temporal superior) (S7), unimodal areas (S8), primary motor (S9a) or sensory (S9b, S9c) areas, and all neocortical areas (S10). Up to stage 6, the disease could be asymptomatic. In all cases studied here, stage 7 individuals with two polymodal association areas affected by tau pathologic states were cognitively impaired.

CONCLUSIONS

The relationship between NFD and Alzheimer-type dementia, and the criteria for a biochemical diagnosis of AD, are documented, and an association between AD and the extent of NFD in defined brain areas is shown.

The evolutionary ecology of insect resistance to plant chemicals

Understanding the diversity of insect responses to chemical pressures (e.g. plant allelochemicals and pesticides) in their local ecological context represents a key challenge in developing durable pest control strategies. To what extent do the resistance mechanisms evolved by insects to deal with the chemical defences of plants differ from those that have evolved to resist insecticides? Here, we review recent advances in our understanding of insect resistance to plant chemicals, with a special emphasis on their underlying molecular basis, evaluate costs associated with each resistance trait, and discuss the ecological and evolutionary significance of these findings.

Contemporary status of insecticide resistance in the major Aedes vectors of arboviruses infecting humans

Both Aedes aegytpi and Ae. albopictus are major vectors of 5 important arboviruses (namely chikungunya virus, dengue virus, Rift Valley fever virus, yellow fever virus, and Zika virus), making these mosquitoes an important factor in the worldwide burden of infectious disease. Vector control using insecticides coupled with larval source reduction is critical to control the transmission of these viruses to humans but is threatened by the emergence of insecticide resistance. Here, we review the available evidence for the geographical distribution of insecticide resistance in these 2 major vectors worldwide and map the data collated for the 4 main classes of neurotoxic insecticide (carbamates, organochlorines, organophosphates, and pyrethroids). Emerging resistance to all 4 of these insecticide classes has been detected in the Americas, Africa, and Asia. Target-site mutations and increased insecticide detoxification have both been linked to resistance in Ae. aegypti and Ae. albopictus but more work is required to further elucidate metabolic mechanisms and develop robust diagnostic assays. Geographical distributions are provided for the mechanisms that have been shown to be important to date. Estimating insecticide resistance in unsampled locations is hampered by a lack of standardisation in the diagnostic tools used and by a lack of data in a number of regions for both resistance phenotypes and genotypes. The need for increased sampling using standard methods is critical to tackle the issue of emerging insecticide resistance threatening human health. Specifically, diagnostic doses and well-characterised susceptible strains are needed for the full range of insecticides used to control Ae. aegypti and Ae. albopictus to standardise measurement of the resistant phenotype, and calibrated diagnostic assays are needed for the major mechanisms of resistance.

Neurosteroid quantification in human brain regions: comparison between Alzheimer's and nondemented patients

Some neurosteroids have been shown to display beneficial effects on neuroprotection in rodents. To investigate the physiopathological significance of neurosteroids in Alzheimer's disease (AD), we compared the concentrations of pregnenolone, pregnenolone sulfate (PREGS), dehydroepiandrosterone, dehydroepiandrosterone sulfate (DHEAS), progesterone, and allopregnanolone, measured by gas chromatography-mass spectrometry, in individual brain regions of AD patients and aged nondemented controls, including hippocampus, amygdala, frontal cortex, striatum, hypothalamus, and cerebellum. A general trend toward decreased levels of all steroids was observed in all AD patients' brain regions compared with controls: PREGS and DHEAS were significantly lower in the striatum and cerebellum, and DHEAS was also significantly reduced in the hypothalamus. A significant negative correlation was found between the levels of cortical beta-amyloid peptides and those of PREGS in the striatum and cerebellum and between the levels of phosphorylated tau proteins and DHEAS in the hypothalamus. This study provides reference values for steroid concentrations determined by gas chromatography-mass spectrometry in various regions of the aged human brain. High levels of key proteins implicated in the formation of plaques and neurofibrillary tangles were correlated with decreased brain levels of PREGS and DHEAS, suggesting a possible neuroprotective role of these neurosteroids in AD.

JNK2 is required for efficient T-cell activation and apoptosis but not for normal lymphocyte development

BACKGROUND

The Jun N-terminal kinase (JNK) signaling pathway has been implicated in cell proliferation and apoptosis, but its function seems to depend on the cell type and inducing signal. In T cells, JNK has been implicated in both antigen-induced activation and apoptosis.

RESULTS

We generated mice lacking the JNK2 isozymes. The mutant mice were healthy and fertile but defective in peripheral T-cell activation induced by antibody to the CD3 component of the T-cell receptor (TCR) complex - proliferation and production of interleukin-2 (IL-2), IL-4 and interferon-gamma (IFN-gamma) were reduced. The proliferation defect was restored by exogenous IL-2. B-cell activation was normal in the absence of JNK2. Activation-induced peripheral T-cell apoptosis was comparable between mutant and wild-type mice, but immature (CD4(+) CD8(+)) thymocytes lacking JNK2 were resistant to apoptosis induced by administration of anti-CD3 antibody in vivo. The lack of JNK2 also resulted in partial resistance of thymocytes to anti-CD3 antibody in vitro, but had little or no effect on apoptosis induced by anti-Fas antibody, dexamethasone or ultraviolet-C (UVC) radiation.

CONCLUSIONS

JNK2 is essential for efficient activation of peripheral T cells but not B cells. Peripheral T-cell activation is probably required indirectly for induction of thymocyte apoptosis resulting from administration of anti-CD3 antibody in vivo. JNK2 functions in a cell-type-specific and stimulus-dependent manner, being required for apoptosis of immature thymocytes induced by anti-CD3 antibody but not for apoptosis induced by anti-Fas antibody, UVC or dexamethasone. JNK2 is not required for activation-induced cell death of mature T cells.

Role of cytochrome P450s in insecticide resistance: impact on the control of mosquito-borne diseases and use of insecticides on Earth

The fight against diseases spread by mosquitoes and other insects has enormous environmental, economic and social consequences. Chemical insecticides remain the first line of defence but the control of diseases, especially malaria and dengue fever, is being increasingly undermined by insecticide resistance. Mosquitoes have a large repertoire of P450s (over 100 genes). By pinpointing the key enzymes associated with insecticide resistance we can begin to develop new tools to aid the implementation of control interventions and reduce their environmental impact on Earth. Recent technological advances are helping us to build a functional profile of the P450 determinants of insecticide metabolic resistance in mosquitoes. Alongside, the cross-responses of mosquito P450s to insecticides and pollutants are also being investigated. Such research will provide the means to produce diagnostic tools for early detection of P450s linked to resistance. It will also enable the design of new insecticides with optimized efficacy in different environments.

Genomic analysis of detoxification genes in the mosquito Aedes aegypti

Annotation of the recently determined genome sequence of the major dengue vector, Aedes aegypti, reveals an abundance of detoxification genes. Here, we report the presence of 235 members of the cytochrome P450, glutathione transferase and carboxy/cholinesterase families in Ae. aegypti. This gene count represents an increase of 58% and 36% compared with the fruitfly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, respectively. The expansion is not uniform within the gene families. Secure orthologs can be found across the insect species for enzymes that have presumed or proven biosynthetic or housekeeping roles. In contrast, subsets of these gene families that are associated with general xenobiotic detoxification, in particular the CYP6, CYP9 and alpha esterase families, have expanded in Ae. aegypti. In order to identify detoxification genes associated with resistance to insecticides we constructed an array containing unique oligonucleotide probes for these genes and compared their expression level in insecticide resistant and susceptible strains. Several candidate genes were identified with the majority belonging to two gene families, the CYP9 P450s and the Epsilon GSTs. This 'Ae. aegypti Detox Chip' will facilitate the implementation of insecticide resistance management strategies for arboviral control programmes.

Increased bone formation and osteosclerosis in mice overexpressing the transcription factor Fra-1

Bone formation by osteoblasts is essential for skeletal growth and remodeling. Fra-1 is a c-Fos-related protein belonging to the AP-1 family of transcription factors. Here we show that transgenic mice overexpressing Fra-1 in various organs develop a progressive increase in bone mass leading to osteosclerosis of the entire skeleton, which is due to a cell-autonomous increase in the number of mature osteoblasts. Moreover, osteoblast differentiation, but not proliferation, was enhanced and osteoclastogenesis was also elevated in vitro. These data indicate that, unlike c-Fos, which causes osteosarcomas, Fra-1 specifically enhances bone formation, which may be exploited to stimulate bone formation in pathological conditions.

The Anopheles gambiae detoxification chip: a highly specific microarray to study metabolic-based insecticide resistance in malaria vectors

Metabolic pathways play an important role in insecticide resistance, but the full spectra of the genes involved in resistance has not been established. We constructed a microarray containing unique fragments from 230 Anopheles gambiae genes putatively involved in insecticide metabolism [cytochrome P450s (P450s), GSTs, and carboxylesterases and redox genes, partners of the P450 oxidative metabolic complex, and various controls]. We used this detox chip to monitor the expression of the detoxifying genes in insecticide resistant and susceptible An. gambiae laboratory strains. Five genes were strongly up-regulated in the dichlorodiphenyltrichloroethane-resistant strain ZAN/U. These genes included the GST GSTE2, which has previously been implicated in dichlorodiphenyltrichloroethane resistance, two P450s, and two peroxidase genes. GSTE2 was also elevated in the pyrethroid-resistant RSP strain. In addition, the P450 CYP325A3, belonging to a class not previously associated with insecticide resistance, was expressed at statistically higher levels in this strain. The applications of this detox chip and its potential contribution to malaria vector insecticide resistance management programs are discussed.

Impact of environment on mosquito response to pyrethroid insecticides: facts, evidences and prospects

By transmitting major human diseases such as malaria, dengue fever and filariasis, mosquito species represent a serious threat worldwide in terms of public health, and pose a significant economic burden for the African continent and developing tropical regions. Most vector control programmes aiming at controlling life-threatening mosquitoes rely on the use of chemical insecticides, mainly belonging to the pyrethroid class. However, resistance of mosquito populations to pyrethroids is increasing at a dramatic rate, threatening the efficacy of control programmes throughout insecticide-treated areas, where mosquito-borne diseases are still prevalent. In the absence of new insecticides and efficient alternative vector control methods, resistance management strategies are therefore critical, but these require a deep understanding of adaptive mechanisms underlying resistance. Although insecticide resistance mechanisms are intensively studied in mosquitoes, such adaptation is often considered as the unique result of the selection pressure caused by insecticides used for vector control. Indeed, additional environmental parameters, such as insecticides/pesticides usage in agriculture, the presence of anthropogenic or natural xenobiotics, and biotic interactions between vectors and other organisms, may affect both the overall mosquito responses to pyrethroids and the selection of resistance mechanisms. In this context, the present work aims at updating current knowledge on pyrethroid resistance mechanisms in mosquitoes and compiling available data, often from different research fields, on the impact of the environment on mosquito response to pyrethroids. Key environmental factors, such as the presence of urban or agricultural pollutants and biotic interactions between mosquitoes and their microbiome are discussed, and research perspectives to fill in knowledge gaps are suggested.

Cross-induction of detoxification genes by environmental xenobiotics and insecticides in the mosquito Aedes aegypti: impact on larval tolerance to chemical insecticides

The effect of exposure of Aedes aegypti larvae to sub-lethal doses of the pyrethroid insecticide permethrin, the organophosphate temephos, the herbicide atrazine, the polycyclic aromatic hydrocarbon fluoranthene and the heavy metal copper on their subsequent tolerance to insecticides, detoxification enzyme activities and expression of detoxification genes was investigated. Bioassays revealed a moderate increase in larval tolerance to permethrin following exposure to fluoranthene and copper while larval tolerance to temephos increased moderately after exposure to atrazine, copper and permethrin. Cytochrome P450 monooxygenases activities were induced in larvae exposed to permethrin, fluoranthene and copper while glutathione S-transferase activities were induced after exposure to fluoranthene and repressed after exposure to copper. Microarray screening of the expression patterns of all detoxification genes following exposure to each xenobiotic with the Aedes Detox Chip identified multiple genes induced by xenobiotics and insecticides. Further expression studies using real-time quantitative PCR confirmed the induction of multiple CYP genes and one carboxylesterase gene by insecticides and xenobiotics. Overall, this study reveals the potential of xenobiotics found in polluted mosquito breeding sites to affect their tolerance to insecticides, possibly through the cross-induction of particular detoxification genes. Molecular mechanisms involved and impact on mosquito control strategies are discussed.

Alternative strategies for mosquito-borne arbovirus control

Background

Mosquito-borne viruses—such as Zika, chikungunya, dengue fever, and yellow fever, among others—are of global importance. Although vaccine development for prevention of mosquito-borne arbovirus infections has been a focus, mitigation strategies continue to rely on vector control. However, vector control has failed to prevent recent epidemics and arrest expanding geographic distribution of key arboviruses, such as dengue. As a consequence, there has been increasing necessity to further optimize current strategies within integrated approaches and advance development of alternative, innovative strategies for the control of mosquito-borne arboviruses.

Methods and findings

This review, intended as a general overview, is one of a series being generated by the Worldwide Insecticide resistance Network (WIN). The alternative strategies discussed reflect those that are currently under evaluation for public health value by the World Health Organization (WHO) and represent strategies of focus by globally recognized public health stakeholders as potential insecticide resistance (IR)-mitigating strategies. Conditions where these alternative strategies could offer greatest public health value in consideration of mitigating IR will be dependent on the anticipated mechanism of action. Arguably, the most pressing need for endorsement of the strategies described here will be the epidemiological evidence of a public health impact.

Conclusions

As the burden of mosquito-borne arboviruses, predominately those transmitted by Aedes aegypti and A. albopictus, continues to grow at a global scale, new vector-control tools and integrated strategies will be required to meet public health demands. Decisions regarding implementation of alternative strategies will depend on key ecoepidemiological parameters that each is intended to optimally impact toward driving down arbovirus transmission.

International public health workers are challenged by the burden of arthropod-borne viral diseases, to include mosquito-borne arboviruses transmitted by Aedes aegypti and A. albopictus due in part to lack of sustainable vector control and insecticide resistance (IR), as well as the inability to scale up and sustain existing interventions for prevention of urban epidemics. As a consequence, there has been increasing interest to advance the development of alternative methods. This review provides a general overview of alternative vector-control strategies under development for the control of arbovirus mosquito vectors and highlights how each could offer innovative public health value. Considerations to regulations, acceptance, and sustainability are also provided.

Insecticide resistance in the dengue vector Aedes aegypti from Martinique: distribution, mechanisms and relations with environmental factors

Dengue is an important mosquito borne viral disease in Martinique Island (French West Indies). The viruses responsible for dengue are transmitted by Aedes aegypti, an indoor day-biting mosquito. The most effective proven method for disease prevention has been by vector control by various chemical or biological means. Unfortunately insecticide resistance has already been observed on the Island and recently showed to significantly reduce the efficacy of vector control interventions. In this study, we investigated the distribution of resistance and the underlying mechanisms in nine Ae. aegypti populations. Statistical multifactorial approach was used to investigate the correlations between insecticide resistance levels, associated mechanisms and environmental factors characterizing the mosquito populations. Bioassays revealed high levels of resistance to temephos and deltamethrin and susceptibility to Bti in the 9 populations tested. Biochemical assays showed elevated detoxification enzyme activities of monooxygenases, carboxylesterases and glutathione S-tranferases in most of the populations. Molecular screening for common insecticide target-site mutations, revealed the presence of the "knock-down resistance" V1016I Kdr mutation at high frequency (>87%). Real time quantitative RT-PCR showed the potential involvement of several candidate detoxification genes in insecticide resistance. Principal Component Analysis (PCA) performed with variables characterizing Ae. aegypti from Martinique permitted to underline potential links existing between resistance distribution and other variables such as agriculture practices, vector control interventions and urbanization. Insecticide resistance is widespread but not homogeneously distributed across Martinique. The influence of environmental and operational factors on the evolution of the resistance and mechanisms are discussed.

Differential roles of neuroticism, extraversion, and event desirability for mood in daily life: an integrative model of top-down and bottom-up influences

Top-down and bottom-up approaches were combined to assess the relative impact of extraversion, neuroticism, and daily events on daily mood. Ninety-six community-residing men completed diaries for 8 consecutive nights. Extraversion predicted positive mood, whereas neuroticism predicted positive and negative mood. Undesirable events predicted negative mood and, more modestly, positive mood. Desirable events predicted positive mood. Negative dispositional and situational factors play a larger role in daily positive affect than positive factors do in daily negative affect.

Exploring the molecular basis of insecticide resistance in the dengue vector Aedes aegypti: a case study in Martinique Island (French West Indies)

BACKGROUND

The yellow fever mosquito Aedes aegypti is a major vector of dengue and hemorrhagic fevers, causing up to 100 million dengue infections every year. As there is still no medicine and efficient vaccine available, vector control largely based on insecticide treatments remains the only method to reduce dengue virus transmission. Unfortunately, vector control programs are facing operational challenges with mosquitoes becoming resistant to commonly used insecticides. Resistance of Ae. aegypti to chemical insecticides has been reported worldwide and the underlying molecular mechanisms, including the identification of enzymes involved in insecticide detoxification are not completely understood.

RESULTS

The present paper investigates the molecular basis of insecticide resistance in a population of Ae. aegypti collected in Martinique (French West Indies). Bioassays with insecticides on adults and larvae revealed high levels of resistance to organophosphate and pyrethroid insecticides. Molecular screening for common insecticide target-site mutations showed a high frequency (71%) of the sodium channel 'knock down resistance' (kdr) mutation. Exposing mosquitoes to detoxification enzymes inhibitors prior to bioassays induced a significant increased susceptibility of mosquitoes to insecticides, revealing the presence of metabolic-based resistance mechanisms. This trend was biochemically confirmed by significant elevated activities of cytochrome P450 monooxygenases, glutathione S-transferases and carboxylesterases at both larval and adult stages. Utilization of the microarray Aedes Detox Chip containing probes for all members of detoxification and other insecticide resistance-related enzymes revealed the significant constitutive over-transcription of multiple detoxification genes at both larval and adult stages. The over-transcription of detoxification genes in the resistant strain was confirmed by using real-time quantitative RT-PCR.

CONCLUSION

These results suggest that the high level of insecticide resistance found in Ae. aegypti mosquitoes from Martinique island is the consequence of both target-site and metabolic based resistance mechanisms. Insecticide resistance levels and associated mechanisms are discussed in relation with the environmental context of Martinique Island. These finding have important implications for dengue vector control in Martinique and emphasizes the need to develop new tools and strategies for maintaining an effective control of Aedes mosquito populations worldwide.

Management of insecticide resistance in the major Aedes vectors of arboviruses: Advances and challenges

BACKGROUND

The landscape of mosquito-borne disease risk has changed dramatically in recent decades, due to the emergence and reemergence of urban transmission cycles driven by invasive Aedes aegypti and Ae. albopictus. Insecticide resistance is already widespread in the yellow fever mosquito, Ae. Aegypti; is emerging in the Asian tiger mosquito Ae. Albopictus; and is now threatening the global fight against human arboviral diseases such as dengue, yellow fever, chikungunya, and Zika. Because the panel of insecticides available for public health is limited, it is of primary importance to preserve the efficacy of existing and upcoming active ingredients. Timely implementation of insecticide resistance management (IRM) is crucial to maintain the arsenal of effective public health insecticides and sustain arbovirus vector control.

METHODOLOGY AND PRINCIPAL FINDINGS

This Review is one of a series being generated by the Worldwide Insecticide resistance Network (WIN) and aims at defining the principles and concepts underlying IRM, identifying the main factors affecting the evolution of resistance, and evaluating the value of existing tools for resistance monitoring. Based on the lessons taken from resistance strategies used for other vector species and agricultural pests, we propose a framework for the implementation of IRM strategies for Aedes mosquito vectors.

CONCLUSIONS AND SIGNIFICANCE

Although IRM should be a fixture of all vector control programs, it is currently often absent from the strategic plans to control mosquito-borne diseases, especially arboviruses. Experiences from other public health disease vectors and agricultural pests underscore the need for urgent action in implementing IRM for invasive Aedes mosquitoes. Based on a plan developed for malaria vectors, here we propose some key activities to establish a global plan for IRM in Aedes spp.

Coping efforts in daily life: role of big five traits and problem appraisals

The role of problem appraisal and Big Five traits in coping with bothersome daily events was investigated. Community-residing men completed diaries regarding stressful events and coping for eight consecutive days. Results of multi-level analyses indicated that lower perceived control over events was associated with greater reliance on distraction, catharsis, acceptance, seeking emotional social support, but less use of direct action. Stressor severity was positively associated with catharsis and religion, but negatively associated with acceptance. Neuroticism, Extraversion, Openness to experience, and Conscientiousness predicted coping strategy use. In addition, broad personality dimensions moderated relations between appraisals (perceived uncontrolability and severity) and coping strategy use. Although previous research implicated perceived control in coping, the present study suggests that both appraisals of stressor severity and individual differences in personality are also important determinants of coping strategy use at the daily level.

Identifying genomic changes associated with insecticide resistance in the dengue mosquito Aedes aegypti by deep targeted sequencing

The capacity of mosquitoes to resist insecticides threatens the control of diseases such as dengue and malaria. Until alternative control tools are implemented, characterizing resistance mechanisms is crucial for managing resistance in natural populations. Insecticide biodegradation by detoxification enzymes is a common resistance mechanism; however, the genomic changes underlying this mechanism have rarely been identified, precluding individual resistance genotyping. In particular, the role of copy number variations (CNVs) and polymorphisms of detoxification enzymes have never been investigated at the genome level, although they can represent robust markers of metabolic resistance. In this context, we combined target enrichment with high-throughput sequencing for conducting the first comprehensive screening of gene amplifications and polymorphisms associated with insecticide resistance in mosquitoes. More than 760 candidate genes were captured and deep sequenced in several populations of the dengue mosquito Ae. aegypti displaying distinct genetic backgrounds and contrasted resistance levels to the insecticide deltamethrin. CNV analysis identified 41 gene amplifications associated with resistance, most affecting cytochrome P450s overtranscribed in resistant populations. Polymorphism analysis detected more than 30,000 variants and strong selection footprints in specific genomic regions. Combining Bayesian and allele frequency filtering approaches identified 55 nonsynonymous variants strongly associated with resistance. Both CNVs and polymorphisms were conserved within regions but differed across continents, confirming that genomic changes underlying metabolic resistance to insecticides are not universal. By identifying novel DNA markers of insecticide resistance, this study opens the way for tracking down metabolic changes developed by mosquitoes to resist insecticides within and among populations.

Insecticide resistance mechanisms associated with different environments in the malaria vector Anopheles gambiae: a case study in Tanzania

BACKGROUND

Resistance of mosquitoes to insecticides is a growing concern in Africa. Since only a few insecticides are used for public health and limited development of new molecules is expected in the next decade, maintaining the efficacy of control programmes mostly relies on resistance management strategies. Developing such strategies requires a deep understanding of factors influencing resistance together with characterizing the mechanisms involved. Among factors likely to influence insecticide resistance in mosquitoes, agriculture and urbanization have been implicated but rarely studied in detail. The present study aimed at comparing insecticide resistance levels and associated mechanisms across multiple Anopheles gambiae sensu lato populations from different environments.

METHODS

Nine populations were sampled in three areas of Tanzania showing contrasting agriculture activity, urbanization and usage of insecticides for vector control. Insecticide resistance levels were measured in larvae and adults through bioassays with deltamethrin, DDT and bendiocarb. The distribution of An. gambiae sub-species and pyrethroid target-site mutations (kdr) were investigated using molecular assays. A microarray approach was used for identifying transcription level variations associated to different environments and insecticide resistance.

RESULTS

Elevated resistance levels to deltamethrin and DDT were identified in agriculture and urban areas as compared to the susceptible strain Kisumu. A significant correlation was found between adult deltamethrin resistance and agriculture activity. The subspecies Anopheles arabiensis was predominant with only few An. gambiae sensu stricto identified in the urban area of Dar es Salaam. The L1014S kdr mutation was detected at elevated frequency in An gambiae s.s. in the urban area but remains sporadic in An. arabiensis specimens. Microarrays identified 416 transcripts differentially expressed in any area versus the susceptible reference strain and supported the impact of agriculture on resistance mechanisms with multiple genes encoding pesticide targets, detoxification enzymes and proteins linked to neurotransmitter activity affected. In contrast, resistance mechanisms found in the urban area appeared more specific and more related to the use of insecticides for vector control.

CONCLUSIONS

Overall, this study confirmed the role of the environment in shaping insecticide resistance in mosquitoes with a major impact of agriculture activities. Results are discussed in relation to resistance mechanisms and the optimization of resistance management strategies.

Glial reaction in the hippocampal formation is highly correlated with aging in human brain

Glial fibrillary acidic protein (GFAP), a biochemical marker of astrocytes and glial reaction, was quantified by immunoblotting in different brain areas from 33 non-demented patients with a Mini Mental State Examination score above 26 and aged from 12 to 98 years. An increase of GFAP with age was first found in the hippocampus and then in the entorhinal cortex. In both regions, GFAP amounts were correlated with age (r = 0.768). In the isocortex, the increase of GFAP as a function of age was also significant (r = 0.672), but less than for the hippocampal region. GFAP levels increased dramatically after the age of 65 years, and more especially in the hippocampal formation. This glial reaction was observed in aged controls that do not show cognitive impairment and the neuropathological hallmarks of Alzheimer's disease.

Transcriptome response to pollutants and insecticides in the dengue vector Aedes aegypti using next-generation sequencing technology

BACKGROUND

The control of mosquitoes transmitting infectious diseases relies mainly on the use of chemical insecticides. However, mosquito control programs are now threatened by the emergence of insecticide resistance. Hitherto, most research efforts have been focused on elucidating the molecular basis of inherited resistance. Less attention has been paid to the short-term response of mosquitoes to insecticides and pollutants which could have a significant impact on insecticide efficacy. Here, a combination of LongSAGE and Solexa sequencing was used to perform a deep transcriptome analysis of larvae of the dengue vector Aedes aegypti exposed for 48 h to sub-lethal doses of three chemical insecticides and three anthropogenic pollutants.

RESULTS

Thirty millions 20 bp cDNA tags were sequenced, mapped to the mosquito genome and clustered, representing 6850 known genes and 4868 additional clusters not located within predicted genes. Mosquitoes exposed to insecticides or anthropogenic pollutants showed considerable modifications of their transcriptome. Genes encoding cuticular proteins, transporters, and enzymes involved in the mitochondrial respiratory chain and detoxification processes were particularly affected. Genes and molecular mechanisms potentially involved in xenobiotic response and insecticide tolerance were identified.

CONCLUSIONS

The method used in the present study appears as a powerful approach for investigating fine transcriptome variations in genome-sequenced organisms and can provide useful informations for the detection of novel transcripts. At the biological level, despite low concentrations and no apparent phenotypic effects, the significant impact of these xenobiotics on mosquito transcriptomes raise important questions about the 'hidden impact' of anthropogenic pollutants on ecosystems and consequences on vector control.

Personality and coping: three generations of research

This article introduces the Journal of Personality's special issue on coping and personality. It first presents a historical overview of the psychological study of how people cope with stress and identifies three generations of theory and research: (a) the psychoanalysts and the ego development school, which tended to equate personality and coping strategies; (b) the transactional approach, which appeared in the 1960s and emphasized situational and cognitive influences on coping while downplaying the role of individual differences; and (c) the most recent, "third generation," whose work is represented in this special issue and focuses on the role of personality in coping while maintaining strong operational distinctions among coping, personality, appraisal, and adaptational outcomes. This introduction concludes with a discussion of unresolved conceptual and methodological issues and a brief orientation to the third-generation articles that follow in this special issue.

Impact of glyphosate and benzo[a]pyrene on the tolerance of mosquito larvae to chemical insecticides. Role of detoxification genes in response to xenobiotics

The effect of exposure of Aedes aegypti larvae for 72h to sub-lethal concentrations of the herbicide glyphosate and the polycyclic aromatic hydrocarbon benzo[a]pyrene on their subsequent tolerance to the chemical insecticides imidacloprid, permethrin and propoxur, detoxification enzyme activities and transcription of detoxification genes was investigated. Bioassays revealed a significant increase in larval tolerance to imidacloprid and permethrin following exposure to benzo[a]pyrene and glyphosate. Larval tolerance to propoxur increased moderately after exposure to benzo[a]pyrene while a minor increased tolerance was observed after exposure to glyphosate. Cytochrome P450 monooxygenases activities were strongly induced in larvae exposed to benzo[a]pyrene and moderately induced in larvae exposed to imidacloprid and glyphosate. Larval glutathione S-transferases activities were strongly induced after exposure to propoxur and moderately induced after exposure to benzo[a]pyrene and glyphosate. Larval esterase activities were considerably induced after exposure to propoxur but only slightly induced by other xenobiotics. Microarray screening of 290 detoxification genes following exposure to each xenobiotic with the DNA microarray Aedes Detox Chip identified multiple detoxification and red/ox genes induced by xenobiotics and insecticides. Further transcription studies using real-time quantitative RT-PCR confirmed the induction of multiple P450 genes, 1 carboxy/cholinelesterase gene and 2 red/ox genes by insecticides and xenobiotics. Overall, this study reveals the potential of benzo[a]pyrene and glyphosate to affect the tolerance of mosquito larvae to chemical insecticides, possibly through the cross-induction of particular genes encoding detoxification enzymes.

Differential toxicity of leaf litter to dipteran larvae of mosquito developmental sites

The relative toxicity of leaf litter to nematocerous dipteran larvae characteristic of mosquito developmental sites was investigated. Culicidae, Chironomidae, and Simuliidae taxa originating from alpine hydrosystems were tested together with two laboratory nonindigenous culicid taxa. Bioassays indicate that ingestion of 10-month-old decaying leaves from Alnus glutinosa, Populus nigra, and Quercus robur by larvae is more deleterious for Aedes aegypti, A. albopictus, Culex pipiens, Simulium variegatum, and Chironomus annularius than for A. rusticus. Histopathological observations reveal that the midgut epithelium is the main target organ of the toxic effect of dietary leaf litter, which appears to be stronger than that of previously reported tannic acid. There is a general response of the nematocerous larval midgut epithelium to dietary tannins-phenolic compounds: clear cells of the anterior midgut showing symptoms of intoxication before dark cells of the posterior midgut.

Different distribution of phosphorylated tau protein isoforms in Alzheimer's and Pick's diseases

Tau proteins aggregate into different neuronal inclusions in several neurodegenerative disorders. In Alzheimer's disease (AD), hyperphosphorylated Tau from paired helical filaments (PHF) of neurofibrillary tangles, named PHF-Tau, have an electrophoretic profile with four main bands (Tau 55, 64, 69, 74 kDa). In Pick's disease, phosphorylated Tau from Pick bodies are made of two major components (Tau 55, 64 kDa) and a minor 69 kDa. Here we show, using specific antibodies against translated exon 2, 3 or 10 of Tau isoforms, that the set of Tau isoforms engaged in the most insoluble part of PHF in AD is made of Tau isoforms with exon 10 while they are lacking in phosphorylated Tau from Pick's disease. Our results suggest that specific sets of Tau isoforms distinguish between typical neuronal inclusions.