Lead phytoremediation potentials of four aquatic macrophytes under hydroponic cultivation.

Lead (Pb) is a major toxicological concern of the present day that demands immediate attention. The use of aquatic macrophytes with high Pb tolerance and accumulation may be a very convenient and economically viable solution for remediating Pb. We examined the ability of Salvinia cucullata, Alternanthera sessilis, Lemna minor, and Pistia stratiotes to remove 0.12 mM, 0.24 mM, 0.36 mM, and 0.48 mM Pb for 96-h under hydroponic cultivation system. The plants accumulated variable amounts of Pb: S. cucullata > A. sessilis > P. stratiotes > L. minor, with low mobility of Pb from root to shoot. Lead uptake kinetics were monitored up to 96-h. After 96-h, the uptake efficiency for S. cucullata (98-99%), A. sessilis (79-96%), L. minor (45-79%), and P. stratiotes (40-76%) was noted. For S. cucullata and A. sessilis, an extremely high uptake rate was seen within the initial 24-h of trials, followed by slower uptake till 96-h. P. stratiotes and L. minor worked best at 0.12 mM Pb. Pb-Phytotoxicity became prominent at 0.48 mM exposure with biomass loss and morphological changes. The plants had a quick growth rate, extensive root system, high biomass yield, and the ability to tolerate and accumulate Pb that made them suitable for phytoremediation purposes. NOVELTY STATEMENT: Lead phytoremediation potential of four aquatic macrophytes found in Indian waters was evaluated. These macrophytes, often considered as weeds, could be used for phytoremediation purposes that would turn out to be a sustainable means of the utilization of natural resources in developing countries like India. In this study, not only metal accumulation by plants but also the lead uptake kinetics at several time intervals and valuable growth attributes were estimated to establish the suitability of these plants as probable lead phytoremediators. Two of the plant species, Salvinia cucullata, and Alternanthera sessilis, showed excellent Pb accumulation capacities that had not been reported earlier, to the best of our knowledge. The work is all the more significant as there have been needs for identifying Pb-phytoremediators well suited to native climate and growth conditions that could take up large amounts of metal from the substratum.

Morphological transitions of active Brownian particle aggregates on porous walls.

Motility-induced wall aggregation of Active Brownian Particles (ABPs) is a well-studied phenomenon. Here, we study the aggregation of ABPs on porous walls, which allows the particles to penetrate through at large motility. We show that the active aggregates undergo a morphological transition from a connected dense-phase to disconnected droplets with an increase in wall porosity and the particle self-motility, similar to wetting-dewetting transitions in equilibrium fluids. We show that both morphologically distinct states are stable, and independent of initial conditions at least in some parameter regions. Our analysis reveals that changes in wall porosity affect the intrinsic properties of the aggregates and changes the effective wall-aggregate interfacial tension, consistent with the appearance of the morphological transition. Accordingly, a close analysis of the density, as well as orientational distribution, indicates that the underlying reason for such morphological transitions is not necessarily specific to the systems with porous walls, and it can be possible to observe in a larger class of confined, active systems by tuning the properties of confining walls.

Deltamethrin Induced Alteration of Biochemical Parameters in Channa punctata, Bloch and its Amelioration by Quercetin.

We tested the impacts of pyrethroid pesticide deltamethrin and its amelioration by a flavonoid, quercetin, using tissue macromolecules (protein, amino acid, carbohydrate and glycogen) and antioxidant enzymes (superoxide dismutase, catalase and peroxidase) as biomarkers, on fish, Channa punctata, gill and liver. Our study proved that quercetin supplement alone, in the absence of pesticide, might be detrimental to fish health, in terms of depletion of major tissue macromolecules, but, such supplement may be beneficial to fish with pesticide associated oxidative stress. Multivariate analyses predicted that the antioxidant enzymes and lipid peroxidation were closely associated biomarkers; whereas tissue macromolecules formed a different cluster. Hence, oxidative stress biomarkers in fish can be considered a valuable tool in assessment of deltamethrin stress and its amelioration by quercetin. The work can pave the way for further research in establishing quercetin as a probable curative agent.

Copper phytoremediation potential of Calandula officinalis L. and the role of antioxidant enzymes in metal tolerance.

Cu phytoremediation potential of an ornamental plant, Calandula officinalis, was explored in terms of growth responses, photosynthetic activities and antioxidant enzymes such as SOD, CAT and GPX. The results showed that this plant had high Cu tolerance of up to 400 mg/kg, which is far above the phytotoxic range for non hyperaccumulators. It grew normally in soils at all the doses (150-400 mg/kg) without showing external signs of phytotoxicity. At 150 mg/kg, flowering was augmented; root and shoot biomass, root lengths and leaf soluble protein contents remained same as that of the control. However, chlorophyll and carotenoid pigment contents declined significantly along with significant elevations in lipid peroxidation, at all the doses. Elevations of antioxidant enzymes reflected stress as well as probable mitigation of reactive oxygen species due to Cu stress. Except for the highest conc. (400 mg/kg), leaf accumulation of Cu was higher than root accumulations. The Cu accumulation peaked at 300 mg/kg Cu in soil, with leaf and root accumulations to be respectively, 4675 and 3995 µg/g dry wt., far more than the minimum of 1000 µg/g dry wt. for a Cu hyperaccumulator. The plant root at all the doses tolerated Cu, with the tolerance index ranging from 94-62.7. The soil to plant metal uptake capacity, indicated by extraction coefficient and the root to shoot translocation, indicated by translocation factor, at all the doses of Cu were >1, pointed towards efficient phytoremediation potential.

Sublethal effects of pulp and paper mill effluent on two commonly cultured carps: a SEM- and EDS-based hematological biomarker analysis.

Blood being a vehicle for the transport of industrial pollutants in living system, fish hematology is considered as potent biomarker. In the present study, we investigated respective sublethal effects of pulp and paper mill effluents on hematology of two commonly cultured carps, Cyprinus carpio and Ctenopharyngodon idella, using optical, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Irrespective of species, results showed significant decrease in erythrocyte, hematocrit and hemoglobin contents while an increase in white blood cell counts (P < 0.05). We observed an increasing trend of MCV (170.0 ± 3.07 to 193.16 ± 2.5) and MCH (34.31 ± 1.89 to 38.71 ± 3.61) up to 28th day in C. carpio (P < 0.05), while, in C. idella, the highest percent increase in MCV (180.8 ± 2.19) and MCH (32.9 ± 0.62) was observed on seventh exposure day, which subsequently declined, respectively, to 173.1 ± 17.1 and 27.9 ± 2.45 on 28th day. Unlike C. carpio, significant and progressive MCHC declining trend (18.23 ± 0.28 to 16.13 ± 0.31) was observed in C. idella. The most commonly observed abnormalities under SEM include echinocytes, cytoplasmic blebbing, cytoplasmic ring, spherocytes, lobopodial projections and acanthocytes in red blood cells of exposed fishes. EDS further revealed the presence of aluminum, antimony, arsenic, cadmium, mercury, tungsten, zinc and titanium; some of these metals were not even detected in the effluent samples, suggesting the probable metal bio-concentration in fish tissue, and subsequent jeopardization is a major concern particularly in the industrial area. Our study further suggested the use of sensitive and specific techniques like SEM and EDS in fish hematological biomarker analysis along with the conventional approach.

Analysis of heavy metals from water, sediment, and tissues of Labeo angra (Hamilton, 1822), from an Ox-box lake- an wetland site from Assam, India.

The aim of this study was to assess the regional impacts of heavy metals (Mn, Fe, Mg, Ca, Cu, Zn, Cd, Cr, Pb and Ni) on water, sediment and a native, teleost fish species, Labeo angra, inhabiting a flood plain wetland of Barak River in Assam, India. Heavy metal concentrations in the water, sediments and fish were measured; bioaccumulation factor, metal pollution index as well as condition indices were calculated, to assess the pollution load and health status of the fish. Multivariate statistical analysis was used on wetland water and sediment heavy metals to ascertain the possible sources and seasonal variations of the pollutants. Results showed that most heavy metals in the wetland water and sediments exceeded the water (drinking and irrigation) and sediment quality guidelines, respectively. Seasonal variations were observed for geogenic heavy metals, Mn, Fe, Mg and Ca while no seasonal variations were observed for anthropogenic heavy metals, Cu, Cd, Cr, Pb and Ni. Multivariate statistical analysis showed that there was strong correlation between geogenic and anthropogenic heavy metals in water and sediment, both originating from the common anthropogenic sources. Accumulation of most of the metals in all the tissues was above the safe limits as recommended by the Food and Agriculture Organization. High bioaccumulation factors and metal pollution index for these metals in the different tissues revealed that metals were extensively bio-accumulated and bioconcentrated. Condition indices in fish from the wetland suggested metabolic abnormalities.

Anopheles Imd pathway factors and effectors in infection intensity-dependent anti-Plasmodium action.

The Anopheles gambiae immune response against Plasmodium falciparum, an etiological agent of human malaria, has been identified as a source of potential anti-Plasmodium genes and mechanisms to be exploited in efforts to control the malaria transmission cycle. One such mechanism is the Imd pathway, a conserved immune signaling pathway that has potent anti-P. falciparum activity. Silencing the expression of caspar, a negative regulator of the Imd pathway, or over-expressing rel2, an Imd pathway-controlled NFkappaB transcription factor, confers a resistant phenotype on A. gambiae mosquitoes that involves an array of immune effector genes. However, unexplored features of this powerful mechanism that may be essential for the implementation of a malaria control strategy still remain. Using RNA interference to singly or dually silence caspar and other components of the Imd pathway, we have identified genes participating in the anti-Plasmodium signaling module regulated by Caspar, each of which represents a potential target to achieve over-activation of the pathway. We also determined that the Imd pathway is most potent against the parasite's ookinete stage, yet also has reasonable activity against early oocysts and lesser activity against late oocysts. We further demonstrated that caspar silencing alone is sufficient to induce a robust anti-P. falciparum response even in the relative absence of resident gut microbiota. Finally, we established the relevance of the Imd pathway components and regulated effectors TEP1, APL1, and LRIM1 in parasite infection intensity-dependent defense, thereby shedding light on the relevance of laboratory versus natural infection intensity models. Our results highlight the physiological considerations that are integral to a thoughtful implementation of Imd pathway manipulation in A. gambiae as part of an effort to limit the malaria transmission cycle, and they reveal a variety of previously unrecognized nuances in the Imd-directed immune response against P. falciparum.

A study on cadmium phytoremediation potential of water lettuce, Pistia stratiotes L.

Aquatic macrophytes have tremendous potential for remediation of the heavy metal cadmium. The objective of this study was to investigate Cd phytoremediation ability of water lettuce, Pistia stratiotes L. The study was conducted with 5, 10, 15 and 20 mg L(-1) CdCl2 in hydroponic system for 21 days and the Cd concentrations in the root and shoot tissues were estimated by atomic absorption spectroscopy. The values obtained were used to evaluate the bioconcentration factor (BCF), translocation factor (TF) and translocation efficiency of this plant. The plant showed high Cd tolerance of up to 20 mg L(-1) but there was a general trend of decline in the root and shoot biomass. The maximum BCF values for root and shoot tissues were 2,294 and 870 respectively, obtained for 5 mg L(-1) Cd, which indicated that the plant was a Cd hyperaccumulator. The TF maxima was found to be 0.6 and as much as 60 % root to shoot translocation efficiency was observed for 15 mg L(-1) Cd which points towards the suitability of water lettuce for removing Cd from surface waters.

Engineered anopheles immunity to Plasmodium infection.

A causative agent of human malaria, Plasmodium falciparum, is transmitted by Anopheles mosquitoes. The malaria parasite is under intensive attack from the mosquito's innate immune system during its sporogonic development. We have used genetic engineering to create immune-enhanced Anopheles stephensi mosquitoes through blood meal-inducible expression of a transgene encoding the IMD pathway-controlled NF-kB Rel2 transcription factor in the midgut and fat-body tissue. Transgenic mosquitoes showed greater resistance to Plasmodium and microbial infection as a result of timely concerted tissue-specific immune attacks involving multiple effectors. The relatively weak impact of this genetic modification on mosquito fitness under laboratory conditions encourages further investigation of this approach for malaria control.

Effects of cadmium chloride on oxygen consumption and gill morphology of Indian flying barb, Esomus danricus.

Effects of three sub lethal concentrations of cadmium chloride (0.636, 0.063 and 0.006 mg l(-1)) on oxygen consumption and gill morphology in Indian flying barb, Esomus danricus (Hamilton-Buchanan), a teleost fish, were studied. When compared to control, 0.636 mg l(-1) of cadmium chloride after 7,14, 21 and 28 day exposure showed a significant decline in rates of oxygen consumption at 32.98, 28.40, 23.88 and 21.69 ml hr(1) 100 g(-1) of tissue, respectively; while, 0.063 mg l(-1) of cadmium chloride for the same exposure durations showed a significant decline in rates of oxygen consumption at 34.28, 29.30, 28.05 and 26.47 ml hr(1)100 g(-1) of tissue, respectively. However, significant decline in the rate of oxygen consumption at 0.006 mg l(-1) of cadmium chloride could be observed from 21st day of exposure. Gill tissue showed various histopathological changes including epithelial lifting, hyperplasia, mucous secretion, marked leucocyte infiltration in the epithelium after 28 days of cadmium chloride exposure.

An artificial intelligence framework and its bias for brain tumor segmentation: A narrative review.

BACKGROUND: Artificial intelligence (AI) has become a prominent technique for medical diagnosis and represents an essential role in detecting brain tumors. Although AI-based models are widely used in brain lesion segmentation (BLS), understanding their effectiveness is challenging due to their complexity and diversity. Several reviews on brain tumor segmentation are available, but none of them describe a link between the threats due to risk-of-bias (RoB) in AI and its architectures. In our review, we focused on linking RoB and different AI-based architectural Cluster in popular DL framework. Further, due to variance in these designs and input data types in medical imaging, it is necessary to present a narrative review considering all facets of BLS. APPROACH: The proposed study uses a PRISMA strategy based on 75 relevant studies found by searching PubMed, Scopus, and Google Scholar. Based on the architectural evolution, DL studies were subsequently categorized into four classes: convolutional neural network (CNN)-based, encoder-decoder (ED)-based, transfer learning (TL)-based, and hybrid DL (HDL)-based architectures. These studies were then analyzed considering 32 AI attributes, with clusters including AI architecture, imaging modalities, hyper-parameters, performance evaluation metrics, and clinical evaluation. Then, after these studies were scored for all attributes, a composite score was computed, normalized, and ranked. Thereafter, a bias cutoff (AP(ai)Bias 1.0, AtheroPoint, Roseville, CA, USA) was established to detect low-, moderate- and high-bias studies. CONCLUSION: The four classes of architectures, from best-to worst-performing, are TL > ED > CNN > HDL. ED-based models had the lowest AI bias for BLS. This study presents a set of three primary and six secondary recommendations for lowering the RoB.

Role of Artificial Intelligence in Radiogenomics for Cancers in the Era of Precision Medicine.

Radiogenomics, a combination of "Radiomics" and "Genomics," using Artificial Intelligence (AI) has recently emerged as the state-of-the-art science in precision medicine, especially in oncology care. Radiogenomics syndicates large-scale quantifiable data extracted from radiological medical images enveloped with personalized genomic phenotypes. It fabricates a prediction model through various AI methods to stratify the risk of patients, monitor therapeutic approaches, and assess clinical outcomes. It has recently shown tremendous achievements in prognosis, treatment planning, survival prediction, heterogeneity analysis, reoccurrence, and progression-free survival for human cancer study. Although AI has shown immense performance in oncology care in various clinical aspects, it has several challenges and limitations. The proposed review provides an overview of radiogenomics with the viewpoints on the role of AI in terms of its promises for computational as well as oncological aspects and offers achievements and opportunities in the era of precision medicine. The review also presents various recommendations to diminish these obstacles.

A Comparative Cross-Platform Analysis to Identify Potential Biomarker Genes for Evaluation of Teratozoospermia and Azoospermia.

Male infertility is a global public health concern. Teratozoospermia is a qualitative anomaly of spermatozoa morphology, contributing significantly to male infertility, whereas azoospermia is the complete absence of spermatozoa in the ejaculate. Thus, there is a serious need for unveiling the common origin and/or connection between both of these diseases, if any. This study aims to identify common potential biomarker genes of these two diseases via an in silico approach using a meta-analysis of microarray data. In this study, a differential expression analysis of genes was performed on four publicly available RNA microarray datasets, two each from teratozoospermia (GSE6872 and GSE6967) and azoospermia (GSE145467 and GSE25518). From the analysis, 118 DEGs were found to be common to teratozoospermia and azoospermia, and, interestingly, sperm autoantigenic protein 17 (SPA17) was found to possess the highest fold change value among all the DEGs (9.471), while coiled-coil domain-containing 90B (CCDC90B) and coiled-coil domain-containing 91 (CCDC91) genes were found to be common among three of analyses, i.e., Network Analyst, ExAtlas, and GEO2R. This observation indicates that SPA17, CCDC90B, and CCDC91 genes might have significant roles to play as potential biomarkers for teratozoospermia and azoospermia. Thus, our study opens a new window of research in this area and can provide an important theoretical basis for the diagnosis and treatment of both these diseases.

Acetylcholine esterase and antioxidant responses in freshwater teleost, Channa punctata exposed to chlorpyrifos and urea.

We aimed to understand the toxic effects of two crop protecting agents, organophosphate pesticide, chlorpyrifos (CPF) and fertilizer, urea (U), and their binary mixtures at sublethal concentrations for 28-d in a freshwater fish Channa punctata with a battery of biochemical biomarkers in gill and liver. The study has practical value as such mixtures, so often present together in water in the agro-intensive areas, might be predicted to cause cocktail effects. Both CPF and U inhibited AChE, augmented SOD, CAT, GPx activities, and caused lipid peroxidation and depletion in tissue macromolecules in a concentration and duration-dependent manner. While U alone had less severe effects compared to CPF treatments, complex interactions were observed for three combination doses (1CPF + 1U, 2CPF + 1U, 1CPF + 2U). In their mutual effects, antagonism prevailed over other interactions when CPF and U were in equal proportion in the mixture, while synergism was observed for AchE and key antioxidant enzymes when more U was in the mixture. The present study concluded that urea in water bodies might impart adverse effects in combination with pesticides in non-target aquatic organisms such as fish, and there should be a restriction in its excessive usage.

Lead and cadmium exposure network in children in a periurban area in India: susceptibility and health risk.

To investigate the complex Pb-Cd exposure network in school-going children, a thorough investigation of the probable exposure means (diet, water, and school micro-environments such as paint dust and school courtyard soil) and exposure route (ingestion, inhalation and dermal) was carried out in a periurban area spanning three districts in southern Assam, India. Multivariate statistical analysis was carried out to understand the complex data matrices, and the health risk assessments (carcinogenic and non-carcinogenic) based on US EPA Risk Assessment models were also made. We found the median values to be 0.9-4.0 mg Pb/kg and 0.21-6.2 mg Cd/kg in various food items. Groundwater also had Pb (0.13-0.48 mg/L) and Cd (0.11-0.29 mg/L). Pb levels in paint dust were within the permissible limits, but 50% of the samples had higher than permissible levels of Cd. Approximately 23% of the school courtyard soil had Pb above the global background levels, but all the samples had 4-27 times elevated levels of Cd in them. School micro-environment contributed significantly to the metal load in children due to their typical hand-to-mouth behavior and dietary intake (food and water) via ingestion was the most prominent route of exposure in children. The evaluation of the estimated chronic daily intake and the hazard quotient indicated hazardous exposure over a lifetime to both Pb and Cd, but only Cd posed a prominent cancer risk. It could be concluded that chronic insidious effects of metals would be a noteworthy toxicological threat to children when exposed early on.

Transcriptomic and functional analysis of the Anopheles gambiae salivary gland in relation to blood feeding.

BACKGROUND: The Anopheles gambiae salivary glands play a major role in malaria transmission and express a variety of bioactive components that facilitate blood-feeding by preventing platelet aggregation, blood clotting, vasodilatation, and inflammatory and other reactions at the probing site on the vertebrate host. RESULTS: We have performed a global transcriptome analysis of the A. gambiae salivary gland response to blood-feeding, to identify candidate genes that are involved in hematophagy. A total of 4,978 genes were found to be transcribed in this tissue. A comparison of salivary gland transcriptomes prior to and after blood-feeding identified 52 and 41 transcripts that were significantly up-regulated and down-regulated, respectively. Ten genes were further selected to assess their role in the blood-feeding process using RNAi-mediated gene silencing methodology. Depletion of the salivary gland genes encoding D7L2, anophelin, peroxidase, the SG2 precursor, and a 5'nucleotidase gene significantly increased probing time of A. gambiae mosquitoes and thereby their capacity to blood-feed. CONCLUSIONS: The salivary gland transcriptome comprises approximately 38% of the total mosquito transcriptome and a small proportion of it is dynamically changing already at two hours in response to blood feeding. A better understanding of the salivary gland transcriptome and its function can contribute to the development of pathogen transmission control strategies and the identification of medically relevant bioactive compounds.

Aggregate morphology of active Brownian particles on porous, circular walls.

We study the motility-induced aggregation of active Brownian particles (ABPs) on a porous, circular wall. We observe that the morphology of aggregated dense-phase on a static wall depends on the wall porosity, particle motility, and the radius of the circular wall. Our analysis reveals two morphologically distinct, dense aggregates; a connected dense cluster that spreads uniformly on the circular wall and a localized cluster that breaks the rotational symmetry of the system. These distinct morphological states are similar to the macroscopic structures observed in aggregates on planar, porous walls. We systematically analyze the parameter regimes where the different morphological states are observed. We further extend our analysis to motile circular rings. We show that the motile ring propels almost ballistically due to the force applied by the active particles when they form a localized cluster, whereas it moves diffusively when the active particles form a continuous cluster. This property demonstrates the possibility of extracting useful work from a system of ABPs, even without artificially breaking the rotational symmetry.

Quercetin-induced amelioration of deltamethrin stress in freshwater teleost, Channa punctata: Multiple biomarker analysis.

We aimed to ascertain whether ubiquitous plant-based polyphenolic flavonoid compound quercetin (Q) was capable of alleviating deltamethrin (DM) stress in a freshwater teleost, Channa punctata, with emphasis on levels of acetylcholinesterase (AChE), reduced glutathione (GSH), glutathione-S-transferase (GST), DNA/RNA contents and hematological parameters. We measured these parameters in various tissues of fish at 7 and 21 days of exposure to DM doses (0.03 and 0.15 µL L-1), Q (0.14 g L-1) and their combinations (0.03 µL DM L-1 + 0.14 g Q L-1 and 0.15 µL DM L-1 + 0.14 g Q L-1). Both the DM doses altered blood parameters, lowered DNA/RNA contents, AchE activities, GSH levels and augmented GST activities as a mark of neurotoxicity and oxidative stress in fish tissues. We found that 0.14 g L-1 Q ameliorated oxidative stress and AchE inhibitory effects, recovered DM-induced nucleic acid damage and alterations in blood parameters, with some tissue specificity and in duration-dependent manner. Thus, the results indicated that Q was capable of neuroprotection and enhancing the function of antioxidants in fish, which could be predicted to be useful for providing better protection to fish under aquaculture settings with improved Q-rich diets. Through this study with multiple biomarkers in several tissues of fish, valuable information for devising better strategies regarding pesticide risk assessment was obtained and it was recognized that an appropriate dose of Q was essential for its better functioning.

Assessment of lead and cadmium in fifty-four Indian herbal medicine: tribal and marketed varieties.

The objective of this study was to assess the toxic metal content in herbal medicines being used by Indian people. Trace elements, lead (Pb) and cadmium (Cd), in fifty-four herbal medicines (marketed and tribal varieties) of India were estimated, and the potential health risks were characterized by estimating the tolerable daily intake (TDI) and the total hazard quotient (THQ) associated with their consumption. A total of 12% of the marketed varieties had Pb above WHO permissible limits of 10 mg Pb/kg. In tribal varieties, none of the samples exceeded this limit. In contrast, all the marketed varieties and 17% of the tribal varieties exceeded WHO limit of 0.3 mg Cd/kg. Consumption of ~ 0.01 kg of herbal medicine per day contributed almost 20-28% of TDI of Pb and Cd for marketed varieties and < 10% for tribal varieties. Although the consumption of the Indian herbal medicine, especially the tribal varieties, posed no immediate concern as the average THQ was less than 1, 24% of the marketed varieties had a higher metal burden and could pose threat on long-term use. Our findings advocate the use of tribal medicines for therapeutic purposes owing to a relatively lesser metal burden than the marketed varieties. However, for the marketed varieties, appropriate standardization in terms of effective quality control and consistency is needed to ensure the health of the consumers.

Molecular analysis of photic inhibition of blood-feeding in Anopheles gambiae.

BACKGROUND: Anopheles gambiae mosquitoes exhibit an endophilic, nocturnal blood feeding behavior. Despite the importance of light as a regulator of malaria transmission, our knowledge on the molecular interactions between environmental cues, the circadian oscillators and the host seeking and feeding systems of the Anopheles mosquitoes is limited. RESULTS: In the present study, we show that the blood feeding behavior of mosquitoes is under circadian control and can be modulated by light pulses, both in a clock dependent and in an independent manner. Short light pulses (approximately 2-5 min) in the dark phase can inhibit the blood-feeding propensity of mosquitoes momentarily in a clock independent manner, while longer durations of light stimulation (approximately 1-2 h) can induce a phase advance in blood-feeding propensity in a clock dependent manner. The temporary feeding inhibition after short light pulses may reflect a masking effect of light, an unknown mechanism which is known to superimpose on the true circadian regulation. Nonetheless, the shorter light pulses resulted in the differential regulation of a variety of genes including those implicated in the circadian control, suggesting that light induced masking effects also involve clock components. Light pulses (both short and long) also regulated genes implicated in feeding as well as different physiological processes like metabolism, transport, immunity and protease digestions. RNAi-mediated gene silencing assays of the light pulse regulated circadian factors timeless, cryptochrome and three takeout homologues significantly up-regulated the mosquito's blood-feeding propensity. In contrast, gene silencing of light pulse regulated olfactory factors down-regulated the mosquito's propensity to feed on blood. CONCLUSION: Our study show that the mosquito's feeding behavior is under circadian control. Long and short light pulses can induce inhibition of blood-feeding through circadian and unknown mechanisms, respectively, that involve the chemosensory system.