Visual and olfactory associative learning in the malaria vector Anopheles gambiae sensu stricto

<p>Abstract</p> <p>Background</p> <p>Memory and learning are critical aspects of the ecology of insect vectors of human pathogens because of their potential effects on contacts between vectors and their hosts. Despite this epidemiological importance, there have been only a limited number of studies investigating associative learning in insect vector species and none on Anopheline mosquitoes.</p> <p>Methods</p> <p>A simple behavioural assays was developed to study visual and olfactory associative learning in <it>Anopheles gambiae</it>, the main vector of malaria in Africa. Two contrasted membrane qualities or levels of blood palatability were used as reinforcing stimuli for bi-directional conditioning during blood feeding.</p> <p>Results</p> <p>Under such experimental conditions <it>An. gambiae </it>females learned very rapidly to associate visual (chequered and white patterns) and olfactory cues (presence and absence of cheese or Citronella smell) with the reinforcing stimuli (bloodmeal quality) and remembered the association for up to three days. Associative learning significantly increased with the strength of the conditioning stimuli used. Importantly, learning sometimes occurred faster when a positive reinforcing stimulus (palatable blood) was associated with an innately preferred cue (such as a darker visual pattern). However, the use of too attractive a cue (e.g. Shropshire cheese smell) was counter-productive and decreased learning success.</p> <p>Conclusions</p> <p>The results address an important knowledge gap in mosquito ecology and emphasize the role of associative memory for <it>An. gambiae</it>'s host finding and blood-feeding behaviour with important potential implications for vector control.</p

Properties Of Lipase (Ec 3.1.1.3) From Different Varieties Of Maize

Lipase activity was studied in four varieties of Corn (Zea mays) namely: Local yellow (LY), Westernyellow (WY), Western white (WW) and Pop corn (POP). Using emulsified olive oil as substrate, lipase was found to be present in the dry seeds of maize. Lipase activity increased with germinationand reached it\'s peak on the first day of germination for WY and LY, third day for POP and sixth dayfor WW. Lipase activity was tested for its ability to hydrolyze different emulsified oils such as groundnut oil, palm kernel oil, and soybean oil. The hghest activity was with soybean oil. This highactivity was correlated with high speciicity of corn lipase on linoleic acid. Thermal inactivation studies showed that the enzyme was stable up to 50oC and showed rapid inactivation above this temperature. Its optimum temperature was 50oC and the optimum pH, 8 Keywords: Lipase, Enzymes, Maize, Thermal stability, Substrate specificitiesAnimal Research International Vol. 4 (2) 2007 pp. 650-65

Appraisal of pig production in Songhai redemption farm, Nekede, Imo State, Nigeria

The objectives of the study are to estimate the costs and returns of pig production in the farm estimate the production function of the enterprise and isolate the factors militating against enhanced production performance of pig enterprises in the farm. Data used for the analysis were collected through well-structured questionnaire and personal interview on the piggery units, costs and revenue items in the farm. The results show that piggery production is a profitable venture. Feeding cost accounted for the largest proportion of the total variable cost incurred in this enterprise. The findings revealed that such variables like number of pigs in stock, labor cost, medication cost and depreciated value of capital implements were positively related to output and statistically significant while feeding cost was negative and significant, but purchasing cost was negative and insignificant. It is recommended that alternative feed sources that will enhance cost reduction and increase output be used. Feed ingredients should be subsidized. More competent workers should be employed and the capacity of piggery production in the establishment should be increased. Workers need motivation and more capital should be made available. Keywords: Pig, production cost, farm, feed, Nigeria > Animal Production Research Advances Vol. 2 (4) 2006: pp. 208-21

Comparative studies on pectinases obtained from Aspergillus fumigatus and Aspergillus niger in submerged fermentation system using pectin extracted from mango, orange and pineapple peels as carbon sources.

Pectinase was produced from Aspergillus species (A. fumigatus, and A. niger) in a submerged fermentation system after 4 and 5 days of fermentation, respectively using pectin extracted from different agro-wastes (mango, orange and pineapple peels) as the carbon sources. The pectin was extracted from mango, orange and pineapplepeels with extractionyields of 17%, 15.5% and 8.33%, respectively. The specific activitiesof the crude pectinases using mango, orange and pineapplepectin extract were found to be 11.20U/mg, 52.9U/mg and 11.14U/mg protein, respectively. The specific activities of precipitated and dialyzed pectinase from A. fumigates were found to be 11.78U/mg and 34.60U/mg, respectively, while that for the enzyme from A. niger using orange and pineapple pectin extract were found to be 33.56U/mg, 92.08U/mg, and 17.26U/mg, 49.42U/mg protein, respectively. The optimum pH for pectinase from A. Fumigates (mango) and A. niger (orange) were found to be 5.5 and 5, respectively with common optimum temperature of 40˚C while pectinase from A. niger (pineapple) had optimum activity at 55˚C, pH 5.5. The maximum velocity, Vmax and Michealis constant, Km obtained from Line weaver-Burk plots of initial velocity data at different concentrations of pectin were found to be625µmol/min and 45.5mg/ml for pectinase from A. fumigatus, 200 µmol/min and 18mg/ml for pectinase from A. niger on orange pectin and 5000µmol/min and 89.5mg/ml for pectinase from A. niger using pineapple pectin, respectively. The result suggests that peels of mango, orange and pineapple can be used for value added synthesis of pectinase, an important enzyme in fruit juice clarification. Keywords: Agro-wastes, pectinase, pectin, Aspergillus fumigatus, Aspergillus niger, submerged fermentation, partial purification and characterizatio