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Biomedical subjects

R E McLaughlin

Publications and source records attributed to R E McLaughlin.

At least 37 records · Page 2Linked to original sources
PubMed1991

Effects of ivermectin (MK-933) on the reproductive rate of Aedes aegypti (Diptera: Culicidae).

Aedes aegypti (L.) females were blood fed a single time on rabbits previously injected subcutaneously with ivermectin at 10 or 50 times the labeled dose recommended for cattle (0.2 mg [AI]/kg body weight). Although adult mosquito survival was unchanged by the low dose, fecundity and hatch were depressed slightly. Females fed on rabbits at the high dose exhibited reduced survival and egg production compared with females fed on control rabbits. Eggs from these females also were less likely to hatch, and subsequent larval survival was lower than controls. The effect of ivermectin on these reproductive parameters diminished as the time between drug administration and blood meal increased.

Aedes↗
PubMed1991

Analysis of Haemophilus influenzae type b lipooligosaccharide-synthesis genes that assemble or expose a 2-keto-3-deoxyoctulosonic acid epitope.

We recently isolated a recombinant phage from a Haemophilus influenzae type b (Hib) library that assembles an oligosaccharide with an apparent molecular weight of 1400 (1.4 K) on a 4.1 K Escherichia coli lipopolysaccharide (LPS) structure, producing a 5.5 K LPS species that contains a KDO (2-keto-deoxyoctulosonic acid) epitope. Subcloning and deletional analysis of the 14 kb Haemophilus insert showed that three overlapping restriction fragments contained within a 7.2 kb Pstl-BamHl fragment sequentially modified an E. coli 4.1 K LPS structure, generating novel species of 4.5 K, 5.1 K and 5.5 K. Only the 5.5 K species contained the KDO epitope. We confirmed the relationship between the cloned genes and Hib lipooligosaccharide (LOS) biosynthesis by constructing a mutant that expressed an altered LOS. Thus, the Hib 7.2 kb Pstl-BamHl restriction fragment contained a cluster of at least three genetic loci whose products acted sequentially in LOS biosynthesis.

Blotting, Western↗
PubMed1991

Effect of permethrin treatment of cattle on Psorophora columbiae populations: preliminary field test of a host management concept.

The results of a field test conducted in cooperation with the Jefferson Davis Parish Mosquito Abatement District (JDPMAD) during 1988 in southwestern Louisiana suggested that the biweekly treatment of cattle with permethrin reduced the number of adult Psorophora columbiae in nearby areas. Routine mosquito control operations by JDPMAD were similar from 1987 to 1988 in the cattle-treated area but increased an average of 41% in control areas. In spite of this, during the year of cattle treatment, captures in New Jersey light traps averaged 86 and 26% of the previous 4-year average in control and treated areas, respectively. Similarly, the proportion of trap nights in 1988 when Ps. columbiae captures exceeded 500 averaged 73 and 30% of the previous 4-year average in control and treated areas, respectively. Simulation model projections that took into account differences in JDPMAD operations, weather, cattle density, agricultural practices and the presence of treated cattle were accurate within an average of 9% of observed values for the treated and control areas. The simulation studies indicated that the treatment of cattle with permethrin reduced Ps. columbiae populations by 83%. These results suggest that host management may be a viable method for suppressing populations of Ps. columbiae and that some form of host management be considered for inclusion in integrated control programs in this environment. Further evaluation of this concept is warranted.

Animals↗
PubMed1990

Effect of topically treating cattle with permethrin on blood feeding of Psorophora columbiae (Diptera: Culicidae) in a southwestern Louisiana rice-pasture ecosystem.

The percentage of resting mosquitoes that had fed on blood or were gravid-parous was determined in two pastures associated with the riceland agroecosystem in southwestern Louisiana. In one pasture, all of the cattle were treated with permethrin every 14 d over a 22-wk period, whereas cattle in the other pasture were untreated. The percentage of blood-engorged Psorophora columbiae (Dyar & Knab) was significantly lower in the vicinity of the treated herd. The effectiveness of the permethrin treatment in reducing blood feeding decreased over the interval between applications and as a result of increased rainfall. The proportion of Ps. columbiae that was gravid or parous was not significantly affected by the treatment. Anopheles quadrimaculatus Say engorgement rates also were significantly reduced by the treatment; however, Anopheles crucians Wiedemann and Culex salinarius Coquillett engorgement rates did not differ between the two areas. The results indicate that host management by permethrin treatment has potential for controlling Ps. columbia and An. quadrimaculatus populations in the Louisiana riceland-pasture agroecosystem.

Administration, Topical↗
PubMed1990

Effects of cattle density on New Jersey light trap mosquito captures in the rice/cattle agroecosystem of southwestern Louisiana.

Cattle are the primary host for the major pest mosquito Psorophora columbiae in the rice production region of the Gulf-south. Annual captures of Ps. columbiae, Anopheles crucians and An. quadrimaculatus in New Jersey light traps in Acadia Parish in 1984 were correlated with cattle density within 0.8 km of the trap (R2 = 97, 68 and 74%, respectively). Furthermore, 7 of 10 mosquito species commonly trapped were significantly correlated with cattle density (average R2 = 82%). This work documents host abundance as a key factor in the population dynamics and distribution of most of the important riceland mosquitoes.

Animals↗
PubMed1989

Intramedullary bone repair and ingrowth into porous coated implants in the adult chicken: a histologic study and biochemical analysis of collagens.

A new model was developed to study the histologic and biochemical events during intramedullary bone repair and ingrowth into porous coated implants. Adult chickens were used because of the availability of specific antibody probes. Repair in the metaphysis and diaphysis were compared. Entering through a medial arthrotomy, the distal tibiotarsus was reamed and either implanted with a double-ended porous coated rod or allowed to heal without implantation of a rod. Specimens analyzed histologically at 7, 14, 21, and 70 days postoperatively revealed direct formation of bone by osteoblasts with no evidence of a cartilaginous phase. At 70 days bony ingrowth was observed deep within the porous surface. Analysis of collagens with sodium dodecyl sulfate polyacrylamide gel electrophoresis demonstrated that the synthesis of type I collagen predominated. Biosynthetic data coupled with quantitative immunologic analyses using antibodies to type II and type X collagen showed that neither of these two collagen types, which are characteristic of cartilage undergoing endochondral ossification, were produced during intramedullary bone repair. These results establish that the adult chicken is capable of bony ingrowth into porous coated implants and that this process is through direct bone deposition by osteoblasts without a cartilaginous intermediate.

Animals↗
PubMed1989

Rearing Dictya floridensis (Diptera: Sciomyzidae) in a continuously producing colony and evaluation of larval food sources.

Methods for large-scale continuous propagation of Dictya floridensis Steyskal were developed. A colony originating from 22 specimens of several Dictya species collected in Alachua County, Fla., became a single species colony after several generations because of failure of all but D. floridensis to survive colonization. The colony was maintained as separate generations until the F5, after which new D. floridensis adults were pooled into mass colony cages. During the F7 generation, colony production was in excess of 1,000 neonate larvae per day, the number of adults was continually increasing, and the females had extended longevity and fecundity. At that time, the colony was considered to be continuously producing, and size of the colony was limited only by the availability of food and rearing facilities. Larvae were reared on living, freshly crushed, frozen snails, Physella hendersoni hendersoni (Clench) and Pseudosuccinea columella Say. Larval development and their survival rate to pupariation was the same whether reared on freshly crushed snails or on live food. Larvae reared on frozen snail tissue compared with live snails had the same sex ratio but were lighter in weight and had extended development time to pupariation and lowered survival rates. Larvae fed and developed successfully upon living embryonated snail egg masses but were unable to use egg masses that had been frozen.

Animals↗
PubMed1989

Transposon mutagenesis and complementation of the fructokinase gene in Rhizobium leguminosarum biovar trifolii.

Transposon Tn5 was used to generate a fructokinase mutation in Rhizobium leguminosarum biovar trifolii BAL. The section of the genome containing Tn5 was cloned into the EcoRI site of the vector pHC79 and isolated by direct selection on medium containing kanamycin and tetracycline. Total EcoRI digestion was used to obtain a single fragment containing Tn5 and flanking DNA sequences. The flanking DNA was used as a probe to isolate an intact fructokinase gene from a pLAFR1 cosmid clone bank of the parental strain. A cosmid showing homology to the probe was tri-parentally conjugated into the fructokinase-negative strain, complementing the mutation. The complemented mutant exhibited the wild-type phenotype, with an increase in fructokinase production presumably due to multiple copies of the gene.

Cloning, Molecular↗
PubMed1989

Residual activity of permethrin on cattle as determined by mosquito bioassays.

The residual effectiveness against laboratory-reared female Anopheles quadrimaculatus mosquitoes of a synthetic pyrethroid (permethrin) applied to cattle was determined. Twenty-four-hour postexposure mortality and the degree of successful blood engorgement were determined by exposing mosquitoes for 10 min to cattle. Three replicated assays were conducted and mortality determined at 1, 2, 5, 7, 14 and 21 days after each treatment with an oil-based formulation of permethrin (DeLice) or with an emulsifiable concentrate (Atroban) applied at label rates. Mosquito mortality ranged from 79 to 85% (1 day postapplication) to 12-38% (21 days postapplication).

Animals↗
PubMed1988

Effects of L-364,718, a new cholecystokinin receptor antagonist, on camostate-induced growth of the rat pancreas.

Chronic feeding of rats with camostate results in pancreatic hypertrophy or hyperplasia, or both. Previous studies suggest that this effect of camostate occurs via an increase in endogenous cholecystokinin due to an enteral feedback mechanism involving the inhibition of trypsin in the duodenum. Studies employing proglumide, a weak and relatively nonspecific cholecystokinin antagonist, have failed to fully abolish camostate-induced pancreas growth. We examined the effects of L-364,718, a new and highly potent cholecystokinin receptor antagonist, on camostate-induced pancreas growth in rats. The pancreas weights and the concentrations of ribonucleic acid, protein, and chymotrypsinogen in the pancreas of rats treated with camostate alone were significantly elevated over those of controls. These effects of camostate were completely abolished in rats treated with camostate + L-364,718. The pancreas weights and the concentrations of deoxyribonucleic acid and ribonucleic acid in the pancreas of rats treated with L-364,718 alone were significantly lower than values in control rats. These data indicate that camostate-induced pancreas growth in rats appears to be dependent on the actions of endogenous cholecystokinin and that cholecystokinin may play a role in the maintenance of pancreatic growth in normal rats.

Animals↗
PubMed1988

A dynamic life table model of Psorophora columbiae in the southern Louisiana rice agroecosystem with supporting hydrologic submodel. Part 1. Analysis of literature and model development.

During the past decade, the rice agroecosystem and its associated mosquitoes have been the subject of an extensive research effort directed toward the development and implementation of integrated pest management (IPM) strategies. The objective of this work was to synthesize the literature and unpublished data on the rice agroecosystem into a comprehensive simulation model of the key elements of the system known to influence the population dynamics of Psorophora columbiae. Subsequent companion papers will present a validation of these models, provide an in-depth analysis of the population dynamics of Ps. columbiae, and evaluate current and proposed IPM strategies for this mosquito. This paper describes the development of 2 models: WaterMod: Because spatial and temporal distributions of surface water and soil moisture play a decisive role in the dynamics of Ps. columbiae, an essentially hydrological simulator was developed. Its purpose is to provide environmental inputs for a second model (PcSim) which simulates the population dynamics of Ps. columbiae. WaterMod utilizes data on weather, agricultural practices, and soil characteristics for a particular region to generate a data set containing daily estimates of soil moisture and depth of water table for 12 representative areas comprising the rice agroecosystem. This model could be used to provide hydrologic inputs for additional simulation models of other riceland mosquito species. PcSim: This model simulates the population dynamics of Ps. columbiae by using the computer to maintain a daily accounting of the absolute number of mosquitoes within each daily age class for each life stage. The model creates estimates of the number of eggs, larvae, pupae, and adults for a representative l-ha area of a rice agroecosystem.

Actuarial Analysis↗
PubMed1988

A dynamic life table model of Psorophora columbiae in the southern Louisiana rice agroecosystem with supporting hydrologic submodel. Part 2. Model validation and population dynamics.

In an earlier paper, the development of 2 simulation models designed to describe the interaction between key elements of the rice agroecosystem and the population dynamics of Psorophora columbiae were presented (Focks et al. 1988a). The objective of the work reported herein was to validate these models with field data. The first model (WaterMod) predicts soil hydrology conditions as a function of weather, agricultural practices, and soil characteristics for a variety of habitats found within the rice agroecosystem which are utilized by Ps. columbiae. Using a continuous series of hydrologic data collected in southwestern Louisiana during 1984 and 1985, WaterMod was demonstrated capable of adequately predicting runoff rates and the temporal timing of soil moisture and surface water. The second model (PcSim) simulates the population dynamics of Ps. columbiae based upon a host of variables including the output from WaterMod. This model was validated by comparisons made with density estimates from the literature on the temporal and spatial distribution of various life stages and by correspondence with light trap data gathered during the same time and location as the hydrologic data. PcSim was seen to respond appropriately to host animal densities and unusual meterological events occurring during 1984 and 1985 in southern Louisiana. A discussion is presented of the interaction between agricultural practices and certain key factors of the life history strategy of Ps. columbiae which permit the unusually successful exploitation of the rice agroecosystem by this species. A subsequent paper will use these models to evaluate current and proposed IPM strategies for this mosquito (Focks et al. 1988b).

Actuarial Analysis↗
PubMed1988

Computer simulation of management strategies for Psorophora columbiae in the rice agroecosystem.

Various control strategies were evaluated using a previously-described and validated (Focks et al. 1988a, 1988b) simulation model (PcSim) of the population dynamics of Psorophora columbiae breeding in the rice agroecosystem. As expected from field experience, focally-applied ground or aerial ULV aerosols of insecticides were seen to provide local control of peak populations. Similar control was predicted for larvicides when also used in and around urban and suburban areas. Both of these measures were predicted by simulation to provide only short term control of adults as a result of immigration of adults from surrounding, untreated provide only short term control of adults as a result of immigration of adults from surrounding, untreated areas. Evaluations of the effectiveness of diapause egg control or the elimination of early spring broods to provide lasting, season-long suppression were not encouraging if only conventional methods such as insecticides or tillage were used. This was primarily because the ability of Ps. columbiae to recolonize treated areas during the course of a breeding season would require the treatment of prohibitively large, parish- (i.e., county-) sized areas. Evaluations of host management (either removal or residual insecticide treatment of cattle) in and around urban and suburban areas were more encouraging. This technique, by providing continuing pressure on populations, has the potential to offset the impact of immigration and thereby afford long-term suppression in local areas. Finally, evaluations of the impact of modifications to irrigation practices indicated that this approach warrants consideration as a supplemental control technique. These results suggest that field evaluations of model predictions would be useful. They emphasize the need to better understand the movement and spatial distribution of Ps. columbiae. These factors would bear directly on the cost and therefore, the practicality of several of the long-term suppression strategies evaluated as they determine the size of the treatment area surrounding population centers needed to offset the impact of immigration from surrounding, untreated areas.

Agriculture↗
PubMed1987

The sequential sampling of Psorophora columbiae larvae in rice fields.

Sequential sampling plans were developed for larval populations of Psorophora columbiae developing in rice fields during the growth of rice for a 2nd crop in southwestern Louisiana. Two types of plans were developed: 1) sequential counting plans to estimate the true mean of a population with a prespecified coefficient of variation and 2) sequential decision plans to assist in deciding whether the mean larval count/dip lies outside preselected upper or lower levels. The procedure by which the plans were developed consisted of: 1) conventional larval sampling by dipping along rice field levees that divided each field into pans; 2) counting the number of 2nd through 4th instar larvae observed in two dips taken at each sampling location; and 3) determination of the appropriate statistical parameters from which probability curves, number of samples required, and cumulative larval totals for specific sampling plans could be derived. Both sequential sampling plans are based upon distributions attendant to naturally occurring populations.

Agriculture↗
PubMed1987

Distribution of Anopheles quadrimaculatus and An. crucians larvae within rice field habitats in southwestern Louisiana.

This study, conducted in 3 parishes of Louisiana, documented the distribution pattern of Anopheles quadrimaculatus and An. crucians during the first crop season. Ratios of numbers of 3rd and 4th instar larvae of An. quadrimaculatus to the number of An. crucians 3rd and 4th instar larvae (Q/C), varied both spatially and temporally. The mean Q/C ratio during 1984 was 1.37; during 1985 it was 1.40. The ratios changed from week to week during each year, and increases or decreases in a particular week of 1984 were paralleled by increases or decreases during that same week of 1985. The changes in relative abundance of the 2 species were strongly related to the timing of irrigation practices and to a succession of habitat conditions. Anopheles quadrimaculatus larvae were dominant or exclusively present for several days after fresh water was added to the field. Anopheles crucians larvae then became dominant or exclusively present as the habitat progressed towards a eutrophic condition. Irrigation influenced the conditions of the habitat by freshening and deepening the water, causing a reversion towards a more oligotrophic condition.

Agriculture↗