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Biomedical subjects

R E McLaughlin

Publications and source records attributed to R E McLaughlin.

At least 19 recordsLinked to original sources
PubMed1992

Mechanical failure of hydroxyapatite- and polysulfone-coated titanium rods in a weight-bearing canine model.

Three types of material that have shown potential as coatings for orthopaedic implants were studied. Using a weight-bearing canine model, Ti-6A1-4V femoral intramedullary rods coated with (1) sintered titanium beads, (2) plasma-sprayed hydroxyapatite, and (3) silyl coupled polysulfone beads were evaluated for mechanical strength and bone ingrowth. The model was designed to secure optimal prosthetic stability by obtaining maximal bony ingrowth during an initial non-weight-bearing phase, then stressing the implant during a full-weight-bearing phase. None of the rods coated with titanium beads failed. All 17 polysulfone-coated rods failed, 13 of them at the interface between the polysulfone coating and the titanium core. Of 18 rods coated with hydroxyapatite, 15 suffered implant breakdown at the interface between the hydroxyapatite coating and the titanium core. This may be due to dissolution of the plasma-sprayed hydroxyapatite in vivo. Testing of retrieved specimens from both hydroxyapatite- and polysulfone-coated implants showed that the shear strength at the coating-rod interface had decreased to less than 40% of the shear strength at manufacture. Despite mechanical failure, histologic study showed extensive bone ingrowth or apposition onto both the polysulfone and hydroxyapatite coatings.

Animals↗
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↗
PubMed1979

Radionuclide bone imaging as a means of differentiating loosening and infection in patients with a painful total hip prosthesis.

Twenty patients with 23 painful total hip prostheses were examined by radionuclide imaging (20 cases), arthrography (11 cases), needle aspiration (9 cases), and surgery (19 cases) for the purpose of assessing loosening and/or infection. Bone imaging was most accurate, showing three main distributions of activity: (a) ectopic calcification, (b) focal increased activity at the upper and lower ends of the femoral prosthesis, and (c) diffuse activity. These findings suggest that infection and loosening can be differentiated in many instances. None of the patients with focal activity had infection, compared to 2 of the 3 patients with diffuse uptake.

Bone Diseases↗
PubMed1978

Methylmethacrylate: A study of teratogenicity and fetal toxocity of the vapor in the mouse.

To determine possible deleterious effects of methylmethacrylate vapor on mouse gestation, pregnant mice were exposed to average vapor concentrations of 1330 parts per million for two hours twice daily during Day 6 through Day 15 of pregnancy. A slight increase in the average weight of the fetuses of the exposed mothers were demonstrated but no other evidence of fetal toxicity or teratologic effects was found. During three total hip replacements, the concentration of methylmethacrylate in operating-room air never rose above 280 parts per million.

Abnormalities, Drug-Induced↗
PubMed1978

The strength of metal reinforced methylmethacrylate fixation of pathologic fractures.

Fixation of the pathological fracture in terminal patients has in the past added the trauma of an extensive surgical procedure to an already weakened patient. Intramedullary fixation with single and double rods in conjuction with polymethylmethacrylate have been compared to ascertain the effect of different loading conditions using torque and analysis under compression measurements of the strength of repair bone. Extensive intramedullary reaming can be avoided with polymethylmethacrylate. The cement effectively transmits the load from the proximal to the distal fragment. The single large rod method would be more desirable for stiffer bones while the double thin rod technique may be applicable to more flexible bones.

Animals↗
PubMed1977

Porous acrylic cement.

The use of acrylic bone cement has a number of shortcomings, viz., high curing temperatures that can cause thermal necrosis, release of toxic monomer, and a less than perfect cement-to-bone bond. However, by modifying the cement composition through the addition of a soluble, nontoxic filler such as sucrose or tricalcium phosphate which does not impair the workability of the material during surgery, a significant improvement in the performance of the cement can be achieved. Because the filler replaces part of the acrylic components, less heat is generated during curing while the filler itself acts as a heat sink. Also, less monomer, proportional to the amount replaced by the filler, diffuses from the implant site. Upon elution of the filler, a porous cement will be obtained provided that a critical minimum percentage loading is exceeded so that the filler crystals will make physical contact with each other. The value of this percentage depends on both crystal modification and size. In the 125-175 micron sucrose crystal size range, the critical minimum percentage lies in the range of 20-28 wt% loading. Above 30%, the interconnecting pore size increases sharply to a value which allows good tissue ingrowth into the pores. The introduction of filler and pores causes a drop in strength, but the diametral tensile strength of modified cement containing up to 40% pores and sucrose lies between .7 and 1.5 kg/mm2, respectively, which is still in the same range as that of bone.

Acrylic Resins↗