Odour-mediated host preference in mosquitoes

The mechanisms underlying host preference in mosquitoes are ultimately a result of optimal foraging on currently available hosts and historical patterns of host availability. The proximate mechanisms are regulated by available host cues and the nature of the mosquitoes’ responses to these cues. Although mosquito host preference has a genetic background and the response to specific host cues are adaptive, mosquitoes exhibit a high degree of plasticity in their host preference. The purpose of this study was to analyse the extent of this variability in the disease vectors Aedes aegypti, Anopheles gambiae and Culex quinquefasciatus, and if their behavioural response is constrained by qualitative and quantitative differences in host cues. I investigated the sensory mechanisms and constraints regulating mosquito behaviour in response to various carbon dioxide (CO2) concentrations, within the range emitted from vertebrate hosts. The temporal capacity of the CO2-ORNs in Ae. aegypti and An. gambiae is higher than in Cu. quinquefasciatus, which translated into behavioural constraints leads to an increased time to take off at high concentrations. The altered sensitivity of CO2-ORNs in transient elevated background levels of CO2 also constrain the host-seeking behaviour in Ae. aegypti. Take off flight was impeded, correlating with a behavioural threshold in the net CO2-ORN response. Hence, sensory limitations of CO2-ORNs induce behavioural constraints at higher CO2 concentrations, which may be partially responsible for species-specific host preferences. The specificity and sensitivity of host volatile blends play a key role in mosquito host recognition and non-host avoidance. I determined that Ae. aegypti and An. gambiae consider (R)-1-octen-3-ol as a host cue, whereas Cu. quinquefasciatus perceives it as a non-host cue, when not in the context of a preferred host. Hence, host recognition is regulated by the perception of specific volatiles in the context of a blend. This specificity appears to be consistent with host preference, as Ae. aegypti is attracted by a wide range of (R)-1-octen-3-ol concentrations, while in Cu. quinquefasciatus it elicits no attraction or even repels at higher concentrations. The behavioural and physiological specificity and sensitivity to (R)-1-octen-3-ol is the output of the sensitivities of the orthologous mosquito odorant receptors, the OR8s. The functional tuning of these receptors and their cognate neurons was reflected in minor differences in the receptors amino acid structure. These findings provide a substrate with which to examine how the sensory system of a mosquito interprets host and non-host odour cues and thus produces host recognition behaviour

Molecular basis for odorant receptor tuning: a short C-terminal sequence is necessary and sufficient for selectivity of mosquito Or8

A birth-and-death evolutionary model for odorant receptor gene repertoires presumes the creation of repertoires with the capacity for high-level diversity and rapid ligand specificity change. This changes the recognised odour space, directly affecting fitnessrelated behaviours and ultimately affecting adaptation to new environments and resources. The proximate molecular mechanisms underlying the tuning of odorant receptor repertoires, and thus peripheral olfaction, are unclear. In the present study, we report a concrete example of this model of odorant receptor evolution leading to rapid changes in receptor tuning that leave the peripheral neuronal circuitry intact. We identified a conserved odorant receptor gene in mosquitoes, Or8, which in Culex quinquefasciatus underwent a duplication and inversion event. The paralogues differ in only minor structural changes manifesting at the C-terminus. We assessed the specificity of the paralogous odorant receptors and receptor neurones. We found that the functional tuning of the receptor was indeed reflected in minor differences in amino acid structure. Specifically, we found that enantiomeric specificity of these mosquito Or8 paralogues relies on eight Cterminal amino acids encoded in the final exon of the gene; thus, the birth of a paralogous odorant receptor can change the tuning of the peripheral olfactory system

Multi-walled Carbon Nanotubes Mixed Matrix Membranes

Mixed matrix membranes (MMMs) are important class of membranes prepared by incorporating nanosized fillers into polymer matrix. During this study Multiwalled carbon nanotubes (MWCNTs) are incorporated into poly(vinylidene fluoride) (PVDF), polyacrylonitrile (PAN), and poly(dimethylsiloxane) (PDMS) to fabricate MMMs. The incorporation of nanofillers is aimed to improve the separation performance and electrical properties of the membranes. Lack of dispersibility of MWCNTs in many common organic solvents is the major problem to obtain well dispersed MWCNTs in polymer composites. Surface functionalization provides a pathway where the surface chemistry of MWCNTs is altered by the introduction of chemical functional groups and improves their dispersion in different desired solvents and polymer matrices. PVDF MMMs are prepared by phase inversion method. The addition of MWCNTs to PVDF leads to the membranes with larger surface pore size but relatively low pore density compared to pure PVDF. PVDF MMMs do not show a significant improvement in separation performance and resistance against compaction. The introduction of MWCNTs leads to PVDF membranes exhibiting electrical conductivity. PAN MMMs are fabricated by phase inversion technique. The membranes incorporated with functionalized MWCNTs show better separation performance along with improved resistance against compaction at a maximum loading of 2 wt. % compared to purified MWCNTs containing membranes. PDMS MMMs are prepared by the solvent evaporation method. Functionalization of MWCNTs has remarkable influence on their dispersion in PDMS membranes. However, the addition of MWCNTs does not change the membrane separation performance significantly. Electrically conductive PDMS thin layered composite membranes are successfully prepared with the addition of MWCNTs

Efficacy of nasal irrigation of normal saline as compared to budesonide following functional endoscopic sinus surgery

Background: Nasal irrigation following Functional endoscopic sinus surgery (FESS) appears to be a nearly universal recommendation. FESS significantly improves the symptoms of the CRS (Chronic rhino sinusitis) and the postoperative endoscopy scores. The primarily objective of our study was to study the efficacy of nasal irrigation of normal saline as compared to budesonide following functional endoscopic sinus surgery. Methods: A total of 100 patients who underwent functional endoscopic sinus surgery were randomly divided into two groups on the basis of computerized generated random table with 50 patients in each group. In group 1 normal saline was used where as in group 2 budesonide solution was used for nasal douching. Post-operative evaluation was done using Lund Kennedy Endoscopic scoring (LKES) at the 7th and 30th postoperative day. Results: On 7th postoperative day, we found that none of our patient in the study groups had polypoidal change. There was decrease in scores of polyposis, discharge mucosal edema, scaring and crusting in both the groups. However, the reduction of discharge in the budesonide group was more significantly decreased than normal saline group (p value<0.05). We also noted that  on 30th postoperative edema, scarring and crusting was significantly decreased in budesonide group as compared to normal saline group (p value <0.05). Conclusions: We concluded that the addition of budesonide in nasal irrigation resulted in improved scores of polyposis, discharge, mucosal edema, crusting and scarring and total score of LKES than normal saline alone

Fatality of salt stress to plants: Morphological, physiological and biochemical aspects

Soil salinity affects various physiological and biochemical processes which result in reduced biomass production. This adverse effect of salt stress appears on whole plant level at almost all growth stages including germination, seedling, vegetative and maturity stages. However, tolerance to salt stress at different plant developmental stages varies from species to species. The plant response to salt stress consists of numerous processes that must function in coordination to alleviate both cellular hyperosmolarity and ion disequilibrium. Salt tolerance and yield stability are complex genetic traits that are difficult to establish in crops since salt stress may occur as a catastrophic episode, be imposed continuously or intermittently and become gradually more severe at any stage during development. The objective of this review is to summarize the morphological, physiological and biochemical aspects of plants under salt stress. It was then concluded that salt stress affects plant physiology at whole plant as well as cellular levels through osmotic and ionic adjustments that result in reduced biomass production. This adverse effect of salt stress appears on whole plant level at almost all growth stages including germination, seedling, vegetative and maturity stages. Despite causing osmotic and ionic stress, salinity causes ionic imbalances that may impair the selectivity of root membranes and induce potassium deficiency.Keywords: Salt stress, ions, osmotic adjustment, morphological, physiological and biochemicalAfrican Journal of Biotechnology Vol. 9(34), pp. 5475-5480, 23 August, 201

Impact of Credit Constraints on Firms Growth: A Case Study of Manufacturing Sector of Pakistan

This study explores the impact of credit constraint on growth by using firm level data of manufacturing sector of Pakistan for the period of 1974-2010 analyzing via Generalized Method of Moments (1991) one step and two step estimation technique. Result of full sample shows that the firms in manufacturing sector for the period from 1974-2010 are not facing external financial constraints and the effect of sale to capital ratio indicates the availability of investment opportunities for the firms in the manufacturing sector of Pakistan. The results for pre and post financial sector reform era shows that firms are facing tight external financial constraints in pre financial reform era as compared to post financial reform era. Results show that growth of firms having small assets is constrained by internal finance whereas firms having medium and large assets are not constrained by internal finance. Similarly, firms’ growth that is less dependent on debt finance is constrained by internal finance whereas results for the firms that are moderately and highly aggressive in financing with debt indicate that the growth of firms belonging to these groups is not constrained by internal finance. Similarly, low dividend paying firms growth is constrained by internal finance whereas high dividend paying firms’ growth is not constrained by internal finance

Detection and perception of generic host volatiles by mosquitoes: responses to CO2 constrains host-seeking behaviour

Natural selection has favoured specialization in anthropophilic mosquito host choice, yet in the absence of human hosts, females feed on a selected range of vertebrates. For host recognition, we hypothesize that mosquitoes primarily rely on generic host volatiles. Detection and perception of such compounds would provide the mosquito with a flexible, yet constrained, odour coding system that could delineate host preference. In this study, we show that the quintessential generic volatile for host-seeking, carbon dioxide, activates and attracts the malaria mosquito, Anopheles coluzzii, and the arbovirus vectors, Aedes aegypti and Culex quinquefasciatus, within boundaries set by the dynamic range and coding capacity of the CO2-sensitive olfactory receptor neurons. These boundaries are sufficiently broad to elicit behavioural responses to various hosts within their preferred host range. This study highlights the significance of the sensitivity of the carbon dioxide detection system and its regulation of host seeking and recognition

Antimicrobial and phytochemical screening of Oligochaeta ramose against different pathogenic microbes- An In vitro study

Biologically active compounds obtained from the medicinal plants are the effective chemotherapeutic agents and offering a broad spectrum of activity with greater emphasis on preventive action. The present study was aimed at evaluating the antimicrobial activities of crude methanolic extract of Oligochaeta ramose (Asteraceae) against pathogenic bacteria species of both G +ve strains (Staphylococcus aureus, Bacillus pumilus, Streptococcus pneumoniae), G -ve strains, (Escherichia coli, Citrobacter freundii, Klebsiella pneumoniae) and fungal species (Candida albicans, Aspergillus niger). In-vitro antimicrobial test was performed by disc diffusion method on nutrient agar and sabouraud dextrose agar for bacteria and fungi respectively, in order to analyze the percentage zone of inhibition and phytochemical screening was also performed. Methanolic extract showed significantly high inhibitory effect against G +ve strains, as compared to G -ve strains, whereas, no effect against C. albicans and A. niger. Modified agar well diffusion method was used to measure the minimum inhibitory concentration (MIC) and MIC values lies within the range of 75 to 150 ?g /ml for the G +ve while 300 to 600 ?g /ml for G-ve. Or.Cr was found to contain alkaloids, tannins, saponins, flavonoids and antraquinones and these agents may be responsible for antibacterial activity of this plant. Keywords: Oligochaeta ramose, Methanolic extract, Antimicrobial assay, Nutrient aga

Assessment of antibacterial potential of Saccharum spontaneum Linn. (family: Poaceae), against different pathogenic microbes- an in vitro study.

In this study, Saccharum spontaneum (Family: Poaceae), was evaluated for its antibacterial potential against human pathogenic bacterial strains. In-vitro antibacterial tests were performed by disc diffusion method on nutrient agar, in order to analyze the percentage zone of inhibition. Whole plant’s extract showed the significant zone of inhibition (mm), against Staphylococcus aureus (17.00), Streptococcus pneumoniae (16.50), Bacillus cereus (15.90), Bacillus pumilus (15.45), Escherichia coli (18.00), Klebsiella pneumoniae (17.10), Pseudomonas aeruginosa (15.20) and Citrobacter freundii (14.00), with relative percentages of inhibition of 76.90, 71.60, 57.40, 56.85, 70.40, 69.90, 61.05 and 54.30 respectively. Modified agar well diffusion method was used to measure the minimum inhibitory concentration (MIC) and MIC values lies within the range of 75 to 300?g /ml for the G+ve strains while 75 to 600?g /ml for G-ve.  Due to presence of tannins and flavonoids, it inhibits the growth of bacteria on most regulatory levels such as peptidoglycan, DNA, RNA and protein synthesis

Hypoglycaemia in Low Birth Weight Babies

Object: Determining the hypoglycaemia prevalence in babies of low birth weight and detection of its beginning in 1st 24 hours.Study Design: Study based on observationPlace and Duration: The current research was carried out from March 2018 to May 2018 at Lahore based Mayo Hospital’s Paediatric Department.Materials and Methods: There was delivery of 200 babies of low birth weight and for the purpose of observation and screening they were shifted to neonatal nursery. The screening was performed on one hourly and four hourly bases for four hours and next twenty hours respectively by Gluco sticks and sample from heel prick was obtained. There was monitoring of levels of Blood Glucose for first twenty-four hours of birth.Results: Study was conducted over 200 babies, hypoglycaemia developed in 15 babies therefore the babies developed asymptomatic hypoglycaemia and symptomatic were found with 5% and 20% of hypoglycaemia prevalence. The hypoglycaemia’s common type symptoms are unwilling to feed. The development of hypoglycaemia in 80 babies was within first four hours of birth and hypoglycaemia development in 20% babies took up to the sixteen hours from birth.Conclusion: The development of hypoglycaemia was in 5% babies and its onset mainly appears within first four hours from birth. Mostly there was development of asymptomatic hypoglycaemia whereas symptomatic hypoglycaemia developed in 20% babies. It was suggested that the screening for hypoglycaemia must be performed in babies with low birth weight within first four hours of birth to avoid the complication and bad results because of hypoglycaemia.Key Words: Low birth weight, hypoglycaemia and prevalence