Search

PURPOSE: Previous research has shown atrophy of visual cortex can occur in retinotopic representations of retinal lesions resulting from eye disease. However, the time course of atrophy cannot be established from these cross-sectional studies, which included patients with longstanding disease of varying severity. Our aim, therefore, was to measure visual cortical structure over time in participants after onset of unilateral visual loss resulting from AMD. METHODS: Inclusion criteria were onset of acute unilateral neovascular AMD with bilateral dry AMD based on clinical examination. Therefore, substantial loss of unilateral visual input to cortex was relatively well-defined in time. Changes in cortical anatomy were assessed in the occipital lobe as a whole, and in cortical representations of the lesion and intact retina, the lesion and intact projection zones, respectively. Whole brain, T1-weighted magnetic resonance imaging was taken at diagnosis (before antiangiogenic treatment to stabilize the retina), during the 3- to 4-month initial treatment period, with a long-term follow-up approximately 5 (range 3.8-6.1 years) years later. RESULTS: Significant cortical atrophy was detected at long-term follow-up only, with a reduction in mean cortical volume across the whole occipital lobe. Importantly, this reduction was explained by cortical thinning of the lesion projection zone, which suggests additional changes to those associated with normal aging. Over the period of study, antiangiogenic treatment stabilized visual acuity and central retinal thickness, suggesting that the atrophy detected was most likely governed by long-term decreased visual input. CONCLUSIONS: Our results indicate that consequences of eye disease on visual cortex are atrophic and retinotopic. Our work also raises the potential to follow the status of visual cortex in individuals over time to inform on how best to treat patients, particularly with restorative techniques.

Programmes for the surveillance of Aedes aegypti (L.) often focus on residential areas, ignoring non-residential sites. Between November 2003 and October 2004, pupal/demographic surveys were therefore conducted in non-residential sites in the Peruvian city of Iquitos. The sampled sites included schools, factories, ports, public markets, petrol stations, commercial zones, airports, government buildings, animal-production areas, and recreational areas. Compared with the residential sites that had been surveyed a few years earlier, the non-residential sites generally had fewer pupae/ha, even though pupae were found in a high percentage of the sites investigated. Nonetheless, although56 pupae/ha were observed in the industrial, commercial, recreational and school sites, the river boats in the ports and the areas in and around public markets sometimes had pupal abundances (of 122-213 pupae/ha) that were comparable with those previously recorded in the residential sites. When the relative production of Ae. aegypti was calculated by container type and characteristic (lidded/lidless, indoors/outdoors, and water-use patterns), no single container category was found to be a major producer of Ae. aegypti, with the exception of flower vases in cemeteries. In general, almost all (97%) of the pupae collected in the non-residential sites came from unlidded containers, although 91% of those collected in river boats came from lidded storage areas. With the exception of lumber mills, plant nurseries and markets (where only 39%-60% of the pupae were collected outdoors),70% of pupal production was outdoors. In commercial areas, 41% of the pupae came from manually-filled containers, compared with12% in residential sites. These results indicate that non-residential sites can be highly productive for Ae. aegypti and that the role of such sites in dengue transmission requires further investigation.

The present study was conducted to determine the pattern of incorporation of dietary EPA and docosahexaenoic acid (DHA) into milk, and to evaluate consequent changes in milk fat composition and sensory characteristics. Fourteen multiparous cows in early lactation were divided into two groups and were offered supplements for 10 d. While individual stalls after each morning milking, one group was offered a mixture of rumen-protected tuna oil (RPTO)–soyabean supplement (2 kg; 30:70, w/w; +RPTO) and the second group was offered the basal ration without RPTO (−RPTO). Both groups grazed together on a spring pasture after supplementation. Feeding supplemental RPTO increased the concentrations of EPA and DHA in milk fat from undetectable levels in −RPTO cows to 6·9 and 10·1 g/kg milk fat respectively. Total n-3 PUFA concentration in milk fat was increased three- to fourfold by tuna-oil supplementation (8·4 to 32·0 g/kg milk fat). There were no significant effects on milk production (35·4 v. 33·9 l/d), milk protein (28·2 v. 30·1 g/kg) or milk fat (36·2 v. 40·4 g/kg for −RPTO and +RPTO respectively). The concentration of total saturated fatty acids in milk fat was significantly reduced (568 v. 520 g/kg total fatty acids) and there was a 17 % reduction in the atherosclerotic index of milk after tuna-oil supplementation. Untrained consumer panellists (n 61) rated milk from both groups of cows similarly for taste and smell. We conclude that it is possible to enrich milk with n-3 PUFA without deleterious effects on yield, milk composition or sensory characteristics.

Feeding dairy cows with rumen protected n -3 fatty acids (FAs) derived from oilseeds or marine oils significantly increased the proportion of these acids in milk fat. Feeding protected canola/soybean oilseed (70/30, w/w) and soybean oilseed/linseed oil (70/30, w/w) supplements increased the proportions of C 18:3 from 0.8 to 2.49 and 0.64 to 8.45%, respectively. Feeding protected soybean oilseed/tuna oil (70/30, w/w) increased the proportions of eicosapentaenoic (C 20:5 ) and docosahexaenoic (C 22:6 ) from 0 to 0.86 and 0 to 1.41%, respectively, in milk fat. There were also increases in the proportions of linoleic (C 18:2 ) and a simultaneous reduction in the saturated FAs myristic (C 14:0 ) and palmitic, (C 16:0 ) concentration, with no significant change in the proportion of stearic acid (C 18:0 ). These changes in the fatty acid composition had pronounced effects on the thermal characteristics of milk fat with a much higher proportion of liquid fats at lower temperatures, which will improve spreadability of butter. The proportions of n -3 FAs increased in milk fat at higher supplementation rates, however, the efficiency of transfer declined. This relationship between supplementation and transfer rate will determine the optimal feeding regimes necessary to produce the desired proportions of n -3 FAs in milk and dairy products.

A study was conducted to determine the transfer of eicosapentaenoic acid (EPA, 20:5) and docosahexaenoic acid (DHA, 22:6) from fish oil into goats’ milk. Goats were sequentially offered three diets: control (C) pellets (lucerne hay-oat grain: 60/40 w/w), C plus tuna oil protected against ruminal biohydrogenation (PTO pellets), and C plus unprotected tuna oil (UTO pellets). In supplemented diets, tuna oil constituted 3% of total dry matter (DM), and each supplement was fed for 7 days, with 12 days allowed between the two fish oil feeding periods to minimise carry-over effects. Dry matter intake, milk yield, protein and fat yield were reduced by feeding UTO, but not PTO, pellets. Goats produced ω-3 enriched milk (0.3–0.5% EPA and 1.01–1.12% DHA) when fed either supplement. The rate of transfer of dietary EPA and DHA to milk ranged from 3.5 to 7.6%. Significant transfer of EPA and DHA from tuna oil into goat milk, without deleterious effects on intake or milk yield is possible, provided that the oil supplement is substantially protected against ruminal biohydrogenation.

In vitro incubations were used to assess the hydrogenation of conjugated linoleic acid (CLA) isomers 9-cis 11-trans and 10-trans 12-cis present in synthetically produced CLA-60. About 80‐ 90% of the unprotected CLA was hydrogenated when incubated at 388C for 24 h anaerobically with sheep rumen fluid, the main end product of hydrogenation being trans-octadecaenoic acid (C18:1). Encapsulation of the CLA in a matrix of protein provided a protection of about 70% with a 30% hydrogenation of the CLA isomers, resulting in no significant change in the trans-C18:1 but an increase in the level of stearic acid (C18:0). Feeding sheep with unprotected CLA or protected CLA increased the proportion of isomers 9-cis 11-trans and 10-trans 12-cis in abomasal digesta. The concentration of the CLA isomers leaving the abomasum and available for absorption at the small intestine was about 3.5‐4% higher for the protected CLA, confirming protection imparted by encapsulation. Feeding lactating goats with protected CLA increased the proportion of isomers 9-cis 11-trans and 10-trans 12-cis in milk fat. The total CLA levels were enhanced by about 10-fold above the control levels present in milk fat with an efficiency of transfer into milk fat of 36‐41% and 21‐30%, respectively, for the two isomers. # 2000 Published by Elsevier Science B.V.

In vitro anaerobic incubations were used to assess the extent of hydrogenation of eicosapentaenoic acid (C20:5) and docosahexaenoic acid (C22:6) n-3 unsaturated fatty acids found in marine oils. Three sources of marine oils – fish oil, squid oil and max-EPA®(eicosapentaenoic) – were assessed. About 10–15% of the n-3 fatty acids were hydrogenated when incubated at 38°C for 24 h anaerobically with sheep rumen fluid at a level exceeding 5 mg/ml (fish oil/rumen fluid). Results from a dose response experiment with fish oil showed a greater capacity of sheep rumen microorganisms to hydrogenate the C20:5 and C22:6 when the concentration of fish oil was less than 1 mg/ml of rumen fluid. At this level the production of trans C18:1 fatty acid was maximum but at higher concentrations of fish oil these isomers declined indicating an inhibition of biohydrogenation. Feeding lactating goats with either protected or unprotected fish oil increased the proportion of C20:5 and C22:6 n-3 fatty acids in milk. However, further research on the oil quality, level of supplementation and the degree of ruminal protection is required to prevent reduction in feed intake and the resulting suppression in milk fat production.

To study the effect of feeding Slow Ammonia Release and Protected Protein supplement (SARPP) on blood urea nitrogen (BUN) and urinary levels of allantoins as well as on quantity and quality of milk, a feeding trial was conducted on 24 lactating buffaloes. Animals were divided into three similar groups, fed on standard basal ration. Animals in group-I were fed 1.0 kg untreated rapeseed meal containing 50 g untreated urea, animals in group II were fed 1.0 kg treated rapeseed meal containing 50 g untreated urea and animals in group III were fed 1.0 kg treated rapeseed meal containing 50 g treated urea (SARPP supplement), in place of one kg compound cattle feed. Levels of BUN and allantoins in urine were 10.33, 10.48 & 9.64 (P

Nutritional manipulation of the rumen ecosystem provides a strategy to alter the content and composition of milk fat. Dietary fat supplements affect the content and composition of milk fat. The magnitude of changes is influenced by the degree of protection; as protection increases, the deleterious effects fatty acids on microbial activity decreases, and biohydrogenation of C18 unsaturated fatty acids is reduced. In addition, change is influenced by the transfer of dietary fat into milk, which is related to fatty acid composition, degree of ruminal metabolism, and efficiency of digestion. A cascade of metabolic events involving specific nutrients (e.g., trans fatty acids and cyclopropene acids) occurs that regulates the activity of key enzymes in pathways of endogenous fat synthesis within the mammary gland. When cattle are fed oilseeds (e.g., canola and cotton) with > 75% protection from biohydrogenation, the proportion of saturated to unsaturated fatty acids is changed, and the fat content of milk is increased. Human consumption of dairy products containing elevated proportions of C18 mono- and polyunsaturated fatty acids reduces the content of cholesterol in plasma low density lipoproteins. These fat-modified dairy products are more susceptible to autoxidation, which can be controlled by including vitamin E in the diet of lactating cow. These products also have much less solid fat, which improves spreadability of butter. By protecting different oilseeds from ruminal metabolism, demands for energy can be satisfied while producing milk fat that can be designed for consumer and manufacturing requirements.

The effect of feeding dietary fat supplements on the fatty acid composition of goat milk was examined. Inclusion of canola and soybean ( 80 20 ; w w ) oilseed supplement protected from ruminal hydrogenation, significantly increased the proportion of C18:1 (oleic acid), C18:2 (linoleic acid) and decreased the proportion of C16:0 (palmitic acid) and C14:0 (myristic acid), while there was a small increase in C18:0 (stearic acid). Feeding protected cotton seed significantly increased C18:2 and C18:0, but there was a reduction in C18:1 while the C16:0 was unchanged. When combinations of protected cotton seed and protected-canola soybean ( 80 20 ; w w ) were fed, a level of 20–25% incorporation of protected cotton seed was sufficient to inhibit the desaturase enzyme, with an increase in the proportion of C18:0. In contrast, feeding calcium salts of fatty acids, a predominantly saturated fatty acid supplement, increased C16:0 and reduced C10:0 (decanoic acid) and C14:0. Feeding fat supplements of different fatty acid compositions and varying levels of inertness in the rumen will enable significant manipulation of the fatty acid composition of milk fat.

In-vitro anaerobic incubations were used to assess the degree of metabolism or rumen inertness of different fat supplements containing either triacyglycerols and/or free fatty acids. The extent of triacylglycerol lipolysis and biohydrogenation of the unsaturated fatty acids, oleic acid (C18:1) and linoleic acid (C18:2) was monitored after 24h incubation in rumen fluid. These studies indicate that the degree of metabolism of different fat sources varies from 15 to 95%. For untreated oil, extruded oil-seed and pelleted (prilled) fat supplements the degradation values were 95, 70, and 65% respectively. The hydrogenation of calcium salts of C18 monounsaturated fatty acids when mixed with predominately C16 and C18 saturated fatty acids was 45%. The lowest degree of metabolism (

Choline glycerophospholipids and ethanolamine glycerophospholipids of ruminant skeletal muscle contain approximately 40% and 65% plasmalogen, respectively. In the 1,2-diacyl-sn-glycero-3-phosphocholine (diacyl CPG), 16:0-18:2(n-6) and 16:0-18:1(n-9) accounted for about 50% of the total molecular species; in the 2-acyl-1(1-alkenyl)-sn-glycero-3-phosphocholine (alkenyl CPG), 16:0-18:2(n-6) was the predominant species. Fish oil supplementation resulted in a sixfold increase in the proportion of 16:0-20:5(n-3) and a two- to threefold increase in the proportion of 18:1-20:5(n-3) and 16:0-22:6(n-3) in the diacyl CPG, and there was a 40% decrease in the proportion of 16:0-18:1(n-9). In the alkenyl CPG, fish oil supplementation increased the proportion of molecular species containing C20 and C22 polyenoic fatty acids from 34% to 64%; in both sheep and cattle, the proportion of 16:0-20:5(n-3) was greater than any other molecular species. In contrast to the diacyl CPG, there was also an increase in the proportion of 18:0-20:5(n-3) in the alkenyl CPG. In the 1,2-diacyl-sn-glycero-3-phosphoethanolamine (diacyl EPG), 18:0-20:4(n-6) represented about 30% of the molecular species and this was reduced to less than 20% by fish oil supplementation.(ABSTRACT TRUNCATED AT 250 WORDS)

The feeding to dairy cows of canola seed protected from ruminal metabolism by emulsification and encapsulation in a matrix of aldehyde-treated protein resulted in a 10% increase in milk fat and no change in milk yield or protein content. Feeding the protected canola supplement significantly reduced the proportions of saturated fatty acids C 16:0 , C 14:0 , and C 12:0 in milk fat; there were corresponding increases in proportions of C 18:0 , C 18:1 , C 18:2 and C 18:3 . Yield of C 18 monounsaturated and polyunsaturated fatty acids increased by 54%, which is equivalent to 143g/d. Canola seed, enriched in C 18:1 , can be included in the diet and can result in significant changes in the proportions of saturated and unsaturated fatty acids in milk fat.

For the development of community-based vector control programs for dengue prevention, one of the key components is to formulate an adequate classification scheme for the different containers in which immature Aedes mosquitoes develop. Such a standardized scheme would permit more efficient targeting of efforts and resources in the most productive way possible. Based on field data from Kamphaeng Phet, Thailand, we developed a classification method that consists of the shape (S), use (U), and material (M) of the container (SUM-method). We determined that by targeting the four container classes that held the most Ae. aegypti pupae, adult mosquito production could theoretically be reduced by 70%. The classification method may be equally suitable for similar studies elsewhere in the world. Main advantages of the classification scheme are that categorization of containers does not need to be done a priori, that there is no "miscellaneous" class, and that different immature control strategies can be easily and prospectively tested with a local database. We expect that the classification strategy will 1) facilitate comparison of results among different ecological and geographic settings and 2) simplify communication among vector control personnel and affected communities.

Given that tools for dengue emergency control are limited, continuous evaluation of the effectiveness of insecticide applications in the field is of utmost importance. Such studies will provide a sound basis for defining spraying schemes for public health authorities in dengue-affected countries. In this article, we address the following research questions: How do different space spraying strategies affect Aedes aegypti (L.) (Diptera: Culicidae) populations in both space and time? More specifically, how well are these mosquitoes killed, and how quickly do their populations recover and from where? Field trials were carried out with ultralow volume sprayers in Kamphaeng Phet province, Thailand, with a pyrethrin mixture that was applied 1) indoors only, 2) indoors plus outdoors, 3) indoors with a doubled spraying time, and 4) indoors with doubled spraying time plus outdoors. We found that within 7 d, Ae. aegypti populations recovered to approximately 50% of their original numbers. Spraying the outdoor area and doubling the time sprayed per room only had a significant impact on mosquito numbers 1 d after spraying. Two and 7 d after spraying, these effects were no longer detected. By investigating the spatial arrangement of Ae. aegypti numbers, we found that during the first 2 d after spraying immigration from untreated areas extended approximately 15 m into the sprayed area, whereas after 7 d this effect extended up to 50 m. Results are discussed in relation to ongoing dengue control efforts in Thailand.

Mosquito catch in New Jersy light traps (NJLTs) has been declining in recent years, compromising the sensitivity of the California mosquito monitoring program. Centers for Disease Control traps (CDCTs) operated without light and augmented with dry ice have been considered for replacement or augmentation. To provide information on comparative sensitivity and ability to measure abundance over time and space, catch of mosquitoes in NJLTs was compared to catch in CDCTs operated concurrently at 8-10 sites within the Coachella Valley, Kern, San Joaquin County, and Sacramento-Yolo Mosquito and Vector Control Districts. The CDCTs always collected more female mosquitoes than did NJLTs; however, differences in sensitivity varied markedly over time and space precluding the calculation of a universal conversion factor. Regressions of the catch of female Culex tarsalis in CDCTs as a function of catch in NJLTs within districts indicated that the slopes varied markedly, again precluding the derivation of a universal function. Therefore, we recommend that mosquito surveillance programs replace or supplement NJLTs with systematically operated CDCTs to enhance sampling sensitivity for females of most mosquito species. However, both trap types should be operated concurrently at several sites within each district to derive regression functions to convert historical relative abundance data from NJLTs to equivalent counts in CDCTs for retrospective analyses.

We compared the cost effectiveness of enzootic arbovirus surveillance in northern California by antibody detection in sentinel chickens, virus isolation from mosquitoes, and antibody detection in wild avian hosts. Total and annual recurring costs were determined for each method based on estimated personnel and actual material and travel costs for biweekly surveillance at 3 sites in the Sacramento Valley from May 1 through mid-October 1997 and 1998. Serologic detection of antibodies in wild birds was the most expensive method. Total costs associated with sentinel chickens and mosquitoes combined were less than half of those for the wild bird program. Recurring annual costs for the wild bird and mosquito methods were only slightly less than expenses for those methods during the 1st year of operation, which included nonrecurring setup costs. Recurring costs for sentinel chickens were reduced approximately 40% from total costs during the 1st year of the program and were14% of recurring costs for wild bird serology. Exceptions and caveats of our analysis are discussed. When considering data from a companion paper on detection of enzootic virus transmission using the 3 methods, we concluded that the current system that combines sentinel chickens and virus isolation from mosquitoes is the most cost-effective and efficient surveillance program and should be retained. Future research efforts should investigate the costs and surveillance efficiency of modifications in the frequency of specimen collection and the placement of chicken flocks and mosquito traps.

Adult female Aedes aegypti (L.), the vector of dengue and yellow fever viruses, have an affinity for feeding on human blood and a tendency to forego feeding on sugar. This observation challenges two tenets of mosquito biology: (1) mosquitoes imbibe plant carbohydrates for synthesis of energy reserves and blood for reproduction and (2) egg production is reduced when mosquitoes feed on human blood compared with blood from other species. Sub-optimal amounts of the amino acid isoleucine in human blood (particularly free isoleucine in plasma) are thought to be responsible for lowered egg production when human blood is ingested. We tested the hypothesis that feeding on human blood is associated with a selective advantage for Ae. aegypti and is an underlying reason for this mosquito's intimate and epidemiologically important relationship with human beings. Our five experiments examined the effects of different isoleucine concentrations on accumulated energy reserves, frequency of host contact, survival, and egg production. When mosquitoes imbibed blood meals over a 7- to 10-d period and were not fed sugar, increased isoleucine concentration decreased energy reserves and did not increase egg production. Aedes aegypti took smaller but more frequent blood meals when feeding on a low-isoleucine human host daily compared with a high-isoleucine mouse host. Previous reports that isoleucine enhances egg production were confirmed only when females were fed sugar, an unusual behavior for most domestic Ae. aegypti populations. Females fed human blood and water had greater age-specific survival (l(x)), reproductive output (m(x)), and cumulative net replacement (R0) than cohorts fed human blood plus sugar or isoleucine-rich mouse blood with or without access to sugar. The unique isoleucine concentration of human blood is associated with Ae. aegypti's unusual propensity to feed preferentially and frequently on humans--a behavior that increases this mosquito's fitness, synthesis of energy reserves, and contact with human hosts, making it an especially effective disseminator of human pathogens.

Field research with vectors is an essential aspect of vector biology research and vector-borne disease prevention and control. This type of research, which brings experimental vector manipulations into endemic areas, can present risks to human populations. This paper seeks to stimulate a full discussion within the medical entomology community of the risks associated with vector field research. Such discussions will promote development of a consensus, among investigators, sponsoring agencies and the communities within which the work is done, so that appropriate steps can be taken to minimize and manage the risks, and adequate oversight can be maintained.

Laboratory experiments suggest that utilization of blood rather than natural sugar sources for energetic needs affords female Aedes aegypti a reproductive advantage over conspecifics that use sugar. To test this hypothesis under field conditions, we carried out a mark-release-recapture study in Florida, PR. Adult females (F1) reared from field-collected eggs were provided with a diet of human blood alone or human blood plus a 20% honey solution before their release. Backpack aspirators were used to collect mosquitoes from release houses for 5 consecutive days beginning the 2nd day after release. Survival was estimated from the slope of the regression line of the log-transformed daily number of recaptures for each treatment group. To compare fecundity of the treatment groups, each recaptured female was dissected, ovaries were removed, oocytes counted, and Christophers' stages of oocyte development scored. Recapture rates were 30% for the blood-only group and 23% for blood plus honey group. The daily survival rate of the blood-only group (55%) was not statistically different from that of the blood plus honey group (69%) (t = 0.32, P0.05). By analysis of variance, fecundity (average number of stage III-V oocytes) was significantly higher in the females fed human blood alone (n = 103, 109 oocytes/female) than in the group fed on blood and honey (n = 50, 95 oocytes/female) (P = 0.0007). The observed gonotrophic cycle length of the recaptured females ranged from 3 to 7 days. Results from our field study are consistent with laboratory life-table experiments that suggest feeding exclusively on human blood provides a reproductive advantage for female A. aegypti.

The effectiveness of New Jersey (NJ) light, dry ice baited, and gravid female traps for collecting adult mosquitoes was compared at representative habitats in the Coachella, San Joaquin, and Sacramento valleys and the Los Angeles basin of California. The NJ light traps effectively sampled Anopheles freeborni, Culex tarsalis, Psorophora columbiae, and several Aedes when abundance was high in rural areas with minimal competitive illumination. Dry ice-baited encephalitis virus surveillance or CDC style traps collected significantly more females of most species at most localities than did NJ light traps, regardless of background illumination. The Cummings modification of the Reiter gravid female trap baited with a bulrush (Schoenoplectus) infusion was the best method for collecting Culex pipiens complex females in most habitats. In the Los Angeles basin, gravid traps baited with bulrush infusion collected, on average, 4.5 times more Culex quinquefasciatus females than did traps baited with the Reiter infusion. The bulrush infusion in combination with the Cummings trap design seemed to provide resting site cues and collected males as well as empty and bloodfed females. Mosquito surveillance programs in California should include the systematic operation of dry ice-baited and gravid female traps to improve surveillance sensitivity for selected species in appropriate habitats.

Male and female Aedes aegypti fed a 10% sucrose solution and/or blood were tested to determine the duration of fructose detection in their bodies and the volume of sugar solution they ingested. The limit of detection of fructose by the cold anthrone test was investigated in a series of experiments. Results were applied to the interpretation of sugar feeding by Ae. aegypti collected inside houses in Puerto Rico during times of low (cool season) and high (hot season) dengue transmission in 1996. We conclude that, under our experimental conditions, the cold anthrone test can detect a 10% sucrose solution in male and female Ae. aegypti up to approximately 4 days after ingestion, even the smallest volumes of 10% sucrose solution ingested by experimental mosquitoes are detectable, the test is sensitive enough to detect 0.6 microgram of fructose, and the cutoff point for defining positive fructose values in field-collected females should be based on blood-engorged specimens. We confirmed that female Ae. aegypti collected from natural resting sites inside houses in Puerto Rico seldom, compared to males, contain detectable amounts of fructose.

We determined whether size, an indirect measure of teneral energy reserves, modifies the fitness advantage (sigma survival x egg production/female/day) conferred to female Aedes aegypti (L.) maintained on human blood over cohorts fed human blood plus sugar. Different sized females were obtained by rearing them at different larval densities and with different amounts of food per larva. Each female in 4 treatment groups of 23 mosquitoes each was maintained in a separate cage. A 10% sucrose solution was provided ad libitum to mosquitoes in the sugar-plus-blood treatments and water to the blood only groups. Eggs deposited and survival were monitored daily for each mosquito until all had died. Within a size category, survival of mosquitoes in different treatments was not different and mosquitoes fed only human blood laid more eggs than those fed blood plus sugar. The numbers of eggs laid by small mosquitoes fed human blood alone and large mosquitoes fed human blood plus sugar were not different. Mosquitoes fed only human blood had higher net replacement and intrinsic rates of growth than similar sized mosquitoes fed blood plus sugar. Female Ae. aegypti fed only human blood, regardless of the variation in size that we studied and thus energy reserves at emergence, had a fitness advantage over those fed a diet that included sugar.

We used a histologic technique to detect multiple bloodfeeding in a single gonotrophic cycle by Culiseta melanura. In a laboratory study with colonized mosquitoes, 77% (10/13) of known multiple meals were detected when the interval between meals was 24-30 h. Outside that range, known multiple meals were undetectable with this method. No multiple blood meals were detected in 653 wild engorged mosquitoes collected during 3 consecutive years from the Pocomoke Swamp in Maryland. Although previous studies have shown that Cs. melanura will feed twice in the same evening, it rarely, if ever, takes multiple blood meals at 24-h intervals. Our study also indicates that a thorough laboratory standardization is required prior to application of the histologic technique to species for which it has not been studied. This would include a time-series analysis to define species-specific limits for detecting known multiple meals.

Molecular dynamics simulations are reported for the atomic motion of adsorbates at a liquid-solid interface. The rate for physical desorption is analyzed using the potential of mean force to describe adsorbate and transition state energies.

To determine if enemas could be used to simulate oral exposure of Aedes aegypti to dengue-2 virus, we compared infection rates of mosquitoes administered an enema of a blood suspension containing dengue-2 virus to infection rates in mosquitoes that imbibed the same suspension from a drop of blood. In 1 of 4 experiments infection rates were significantly different. More importantly, during 2 of the 4 trials, 100% of the mosquitoes in the enema treatment group were infected. We speculate that the capillary tube used to administer the enemas abraded the hindgut of mosquitoes in the groups with 100% infection rates and, therefore, virus was inoculated directly into the mosquitoes' hemocoel. We conclude that the method we used for administering enemas cannot be used to simulate oral exposure of Ae. aegypti to dengue-2 virus.

Aedes aegypti became infected when inoculated with a mixture of dengue-2 virus and anti-dengue-2 antibodies, but not when they were exposed to the same mixture per os. This phenomenon merits more detailed investigation. Understanding why this difference in mosquito infection rate occurs may lead to improved dengue virus assays or provide insights into the nature of dengue virus-antibody interactions.

This study was designed to determine if transmission rates for dengue-2 virus by Aedes aegypti are altered by mosquitos probing a host for blood or imbibing blood prior to attempting transmission. Aedes aegypti is known to contact multiple hosts during each egg-laying cycle and multiple host contacts might diminish the amount of virus in infected mosquito's salivary glands or ducts and render them functionally uninfective. Probing a host 5, 10, or 20 consecutive times did not significantly alter the infectivity of parenterally infected mosquitoes. However, orally infected Ae. aegypti that probed 20 times transmitted dengue viruses at a significantly higher rate than controls. Infectivity of orally infected Ae. aegypti was unaffected by blood feeding. Our data suggest that (1) dengue virus-infected Ae. aegypti remain infective regardless of their probing or engorging history, and (2) once Ae. aegypti become infective they are extremely efficient disseminators of dengue virus.

A comparative study of 3 ELISA protocols was performed for host blood meal identification in Aedes aegypti. In the sandwich-B ELISA, which used a combination of heavy and heavy+light chain conjugates, specificity was improved to such a degree that conjugates no longer required cross-adsorption with heterologous sera. Using the sandwich-B assay, human blood meals in laboratory reared Ae. aegypti could be detected longer after feeding (100% at 32 h and 80% at 42 h) than with a direct assay (100% at 20 h). Efficacy of the sandwich-B and direct ELISAs in field analyses was studied in parallel) using 80 field collected mosquitoes from Thailand. The sandwich-B assay was superior (88% detection rate) to the direct assay (41% detection rate) and was thus selected as the method of choice for future field studies.

Time resolved surface second harmonic generation has been used to probe the photoreduction kinetics of malachite green adsorbed onto single crystal cadmium sulfide. A detailed analysis is presented of how the adsorbates and the noncentrosymmetric substrate contribute separately to the total second harmonic signal. Conditions under which the adsorbates can be cleanly detected are described. To complement kinetic measurements of adsorbate reduction, the time evolution of conduction band carriers was determined using sum frequency up conversion of the recombination luminescence. In addition, the formation and decay of surface trapped carriers was monitored using near infrared transient absorption. Comparing the time scale for photoreduction with the relaxation kinetics of mobile and trapped charge carriers indicates that short lived mobile carriers rather than longer lived surface trapped carriers dominate interfacial charge transfer in this system.

A Statewide survey of ticks parasitizing white-tailed deer was carried out in Maryland during November 1989 to assess the status of the deer tick, Ixodes dammini Spielman, Clifford, Piesman & Corwin, the major vector of Lyme disease in the northeastern United States. Ticks were collected from deer carcasses brought in by hunters at 23 check stations (one per county). A total of 3,437 I. dammini were collected from 538 of 1,281 deer (42%), together with 2,013 Dermacentor albipictus (Packard) and 23 Amblyomma americanum (L.) from 34 and 0.5% of deer respectively. I. dammini prevalence ranged from 0 to 79% of deer and mean abundance from 0 to 7.3 ticks per deer at different check stations. Lyme spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, infection rates in ticks ranged from 0 to 21%, with a mean of 8%. Deer-tick density and spirochete infection rates varied with physiographic region and were low in the Appalachian, intermediate in the Piedmont, and high in the Western and Eastern Coastal Plains regions. County-based human case rates correlated positively with I. dammini abundance. We concluded that I. dammini was well established except in the mountainous western region of Maryland and was involved in Lyme disease transmission.

We developed an enzyme immunoassay (EIA) for the detection of immunoglobulin M (IgM) and IgG subclass antibodies directed against eastern equine encephalomyelitis (EEE) virus in chickens. The assays were compared with the serum plaque reduction neutralization test (PRNT) and the hemagglutination inhibition (HI) test for ability to detect antibodies against EEE virus in laboratory-infected birds. No cross-reactivity was detected in serum from chickens inoculated with St. Louis encephalitis or Highlands J virus. The interval after infection when EEE virus-specific antibodies were first detected by IgM and IgG EIAs was found to be similar to that determined by the PRNT and HI tests: 2 to 4 days. The IgG EIA, PRNT, and HI test detected antibodies to EEE virus for at least 27 to 30 days after inoculation. In contrast, serum from five of seven chickens did not contain detectable IgM 30 days after infection. Similarly, in all three naturally infected sentinel chickens from Maryland, IgM class antibody was undetectable 1 to 5 weeks after IgM was initially detected. EIAs provide simple and rapid alternatives to traditional tests for monitoring EEE virus infections in sentinel chicken flocks. Moreover, the IgM EIA provides a means to separate recently infected chickens from those infected greater than or equal to 1 month earlier.

The relationship between body size and parity status of adult female Culiseta melanura collected from 3 locations in northeastern United States was studied by measuring wing lengths and examining ovaries of individual mosquitoes. Virus isolation was attempted from Cs. melanura collected in Maryland and in New Jersey. At all 3 locations, the size of Cs. melanura collected varied from large in the spring, to small in the summer. In New Jersey and Maryland mosquitoes collected in the fall were again large. The size of Massachusetts mosquitoes collected in the summer versus the fall was not different. In general, parous mosquitoes were larger than nulliparous mosquitoes in the spring but smaller than nulliparous ones in the fall. Eastern equine encephalomyelitis (EEE) and Highlands J (HJ) viruses were recovered from Cs. melanura only during the late summer when mosquitoes were small or during the fall months when larger mosquitoes were collected. We conclude that there is no detectable association between Cs. melanura size and parity status and that there is no obvious effect of mosquito size on EEE or HJ virus transmission.

We examined susceptibility of a strain of Aedes albopictus from Houston, Texas to experimental infection with eastern equine encephalomyelitis (EEE) virus. After 15 days of extrinsic incubation, all Ae. albopictus examined by the cell culture assay and fluorescent antibody staining were infected but only 57% (4/7) of the mosquitoes that refed transmitted virus by bite. Data supported the concept of a salivary gland infection barrier to EEE virus in Ae. albopictus and the conclusion that virus replicates in fat body following dissemination from the midgut and prior to infection of salivary glands. Assay of adult progeny from females that fed on viremic chicks and fluorescent antibody studies of infected females failed to provide evidence that EEE virus is transmitted vertically by Ae. albopictus.

The nutritional characteristics of rumen-protected protein and fat supplements produced by formaldehyde treatment of oilseeds and meals are reviewed. The proportion of rumen undegraded protein (RUP) in different protein sources can be controlled by this process, bio-available lysine is 82–84% and the proportions of acid detergent and neutral detergent insoluble nitrogen are unchanged by formaldehyde treatment; this is in contrast to heat treatment of proteins where significant increases in these nitrogen components can occur if the RUP content exceeds 60% of the crude protein (CP). A RUP content of 75–80% of CP is optimal when using protein supplements for milk production, and for body growth in steers a lower RUP content is desirable (i.e. 50–55% of CP). Both the fat and protein constituents in rumen-protected fat supplements derived from the emulsification and formaldehyde treatment of oilseeds are highly protected from ruminal metabolism (75–90%) and are readily digested in the small intestine (90% for C18 unsaturated fatty acids, 82% for the essential amino acids). Protected fat/protein supplements are designed and fed to lactating and non-lactating ruminants to increase efficiency of production, enhance product quality, augment n-3, n-6 and n-9 fatty acid content of meat and milk, and to improve reproductive performance. The challenges and potential role for these protected fat/protein supplements in improving productivity and quality of ruminant derived foods are discussed.

To re-evaluate the incorporation of n-3 fatty acids into depot fats and muscle a group of lambs were fed indoors a concentrate ration supplemented (3% DM) with much lower levels than used previously of rumen-protected tuna oil for 42 days. A second group of lambs were fed diets supplemented with tallow (3% DM) to make the diets iso-caloric. There was no difference in final liveweight, average daily gain, hot carcass yield, or dry matter intake (DMI) between lambs fed with tallow and tuna oil-supplemented diets. Both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels in muscle tissue samples from tuna oil-fed lambs were thrice those in tallow-fed lambs (1.81% v. 0.61% for EPA; 1.51 v. 0.44% total fatty acids for DHA). There were also significant incorporations of EPA and DHA into omental and perirenal fat. The level of linolenic acid in both muscle and adipose tissue of tuna oil fed lambs was double that of tallow-fed lambs. Feeding protected tuna oil significantly enhanced the n-3 fatty acid content of lamb meat.

The effect of feeding dehulled cottonseed protected from ruminal metabolism (PCS). Together with supplements of protected sunflower seed meal (PSM), on the performance and fatty acid profile of adipose tissue in feedlot steers was examined. Sixty-two Hereford cross steers, average weight 470 kg, were assigned to 4 groups and fed rations based on barley-corn silage for 150 days. The diets offered contained 10% untreated whole cottonseed +6% untreated sunflower seed meal (Group I), 10% PCS + 10% PSM (Group 11), 15% PCS + 10% PSM (Group 111), or 20% PCS + 10% PSM (Group IV). Inclusion of PCS at the level of 10, 15, and 20% together with 10% PSM resulted in an increase (P < 0.01) in dressing percentage together with an improvement in feed conversion ratio. There was a 5-8-fold increase in the proportion of linoleic acid (C18: 2) in omental, perirenal, and subcutaneous fat from cattle fed the PCS supplement. A significant reduction occurred in the proportion of oleic acid (C18: 1 cis), but the percentage of palmitic acid (C16: 0) was not affected; the proportion of stearic acid (C18 : 0) in subcutaneous fat increased with PCS supplementation.

The effect of feeding protected canola seed (PCS) and protected sunflower seed meal (PSM) supplements on the fatty acid profile and carcass characteristics of feedlot steers was examined. Fifty Hereford cross steers, average weight of 290 kg, were assigned to five groups of 10 and fed the following barley based concentrate rations for 133 days: I, control (containing 15% untreated sunflower seed meal (SSM)); 11, PSM 15%; 111, PCS 10%; IV, PSM 15% plus PCS 10%; V, PSM 15% plus PCS 15%. The inclusion of PCS, with and without PSM, increased the proportion of Cis unsaturated fatty acids in the subcutaneous, perirenal and omental fats; there were threefold increases in the proportion of linoleic (18: 2) acid, fivefold increases in linolenic (18 : 3) acid and smaller increases in the proportion of oleic acid (18 : 1). There was a 20-25% reduction in the proportion of palmitic acid, and the largest decrease was observed in the adipose tissue of steers receiving 15% PCS in the diet. Joint feeding of PCS and PSM significantly increased the dressing percentage of carcasses in Groups IV and V and fat depth in Group IV.

Para explorar las posibilidades de usar los residuos de cosechas como fuentes de N en oxisoles y ultisoles, se hicieron experimentos de rotación de cosechas en tres localidades un oxisol arenoso, un ultisol arcilloso y un oxisol arcilloso . Se usó un diseño de parcelas subdivididas. Los tratamientos principales fueron las tres rotaciones: 1) habichuelas soyas, maíz, maíz; 2) barbecho, maíz, maíz; y 3) maíz, maíz, maíz. Los subtratamientos consistían de dos niveles de N aplicados al maíz después de la cosecha inicial: 0 y 110 kg/ha. En la cosecha inicial se obtuvieron rendimientos medianamente altos de soyas y buenos rendimientos de maíz, especialmente en el suelo Humatas, en el que se obtuvieron 6240 kg/ha. Se obtuvieron rendimientos substancialmente más altos de maíz en los suelos Bayamón y Humatas en la rotación en que el maíz seguía a las soyas o al maíz que en las que este seguía al barbecho, aunque la segunda cosecha de maíz que seguía a maíz y a barbecho fue substancialmente más alta. El efecto del N aplicado como abono fue dramático en todos los sitios, independientemente de la cosecha inicial. No parece que hubo relación entre la cantidad de N que se incorporó al suelo en los residuos y las cosechas subsiguientes de maíz.

Fields studies were conducted in 1984 through 1986 to investigate the release of inorganic N to corn (Zea mays L.) following a winter annual green manure crop of hairy vetch (Vicia villosa Roth) that had either been plowed down to 22 cm (conventional tillage, CT), or killed and left on the surface (no-till, NT). Soil samples were taken regularly throughout the season at three depths (0-7.5 cm, 7.5-22 cm and 22-45 cm) and analyzed for organic N. Crop growth and N uptake, as well as various other plant, soil and environmental parameters were also monitored (...)

En dos siembras de sojas (variedad Júpiter), se estudió el efecto de la cal sobre el rendimiento y sobre los factores de acidez del terreno. Las sojas se sembraron en una arcilla Humatas, un Ultisol típico de la zona montañosa de Puerto Rico. La cal se aplicó a profundidades de 20, 40 y 60 cm. Otro tratamiento consistió de la aplicación de nitrato de calcio sobre la superficie del terreno. Los datos recolectados en las dos cosechas revelaron correlaciones, muy significativas y significativas, entre el rendimiento de la soja y los factores de acidez del suelo en los 60 cm superficiales del perfil. Una ecuación lineal fue la que mejor describió los resultados. Después de 33 meses de las aplicaciones de la cal, en las parcelas tratadas hasta 20 cm de profundidad, todavía se notaban aumentos en pH y en bases. El descenso en aluminio cambiable en la capa entre los 20 y 40 cm indicó movimiento de la cal a través del perfil hasta esta profundidad.

Continuous corn (L.) grown on sloping land and harvested for silage, returns few residues to the soil and leaves the soil unprotected against erosion for most of the year. Three field experiments were conducted on a Lima loam (a fine-loamy, mixed, mesic Glossoboric Hapludalf) to determine the contributions from various intercrops and cover crops towards ground cover, dry matter, and N. In Exp. 1 and Exp. 2, the effects of intercrops and cover crops were measured by determining corn grain yields following the plow down of the various crops. Corn grain yields following the incorporation of various crops were compared to yields of corn where no cover crops had been incorporated but N rates of 0, 56 or 112 kg ha had been applied. In Exp. 3, the effects of intercrops and cover crops on corn yields were measured over a 5-yr period. First-year corn grain yields were neither increased nor decreased as a result of seeding intercrops when the corn was 0.15 to 0.30 m high. All intercrop and cover crop treatments in Exp. 3 provided significantly more ground cover than the control treatment. Annual ryegrass (Lam.), medium red clover (L.), and a combination of the two were the most effective in terms of ground cover and dry matter production.

Techniques are described for assessing the effectiveness with which lipids may be protected against ruminal degradation. A simple in vitro test was developed using pancreatic lipase, and this test may have application in quality control of the commercial production of protected lipid supplements, as it is applicable to supplements containing polyunsaturated or saturated lipids. All the in vitro tests overestimate the actual in vivo biological effectiveness, and this is probably due to mastication and greater microbial activity in vivo than in vitro. The poor biological response of some protected lipid supplements is most probably due to the incomplete entrapment of lipid droplets in the protein matrix.