ABSTRACT
Genetic models have been used to examine the evolution of insecticide resistance in pest species subject to data and assumptions regarding genetic, biological, and operational parameters. We used time-series data on pyrethroid tolerance and simple genetic models to estimate underlying genetic and biological parameters associated with resistance evolution in tobacco budworm, Heliothis virescens (F.), and bollworm, Helicoverpa zea (Boddie), Louisiana field populations. Assuming pyrethroid resistance is conferred by one gene at one locus in both species, inheritance of pyrethroid resistance was partially dominant in the tobacco budworm and partially recessive in the bollworm. Relative fitness estimates indicated that fitness costs associated with resistance selected against resistance alleles in the absence of selection pressure in the tobacco budworm, but not in the bollworm. In addition, relative fitness estimates obtained using the indirect method outlined in this study were similar in magnitude to estimates obtained using traditional direct approaches.
Subject(s)
Bacillus thuringiensis , Computer Simulation , Insecticides , Models, Genetic , Moths/genetics , Pest Control, Biological , Animals , Insecticide Resistance , Mathematical Computing , Pest Control, Biological/methods , NicotianaSubject(s)
Dentin Permeability , Tooth Permeability , Adolescent , Adult , Humans , Molar/physiology , Osmotic Pressure , Solutions , Surface PropertiesABSTRACT
A technique is described which permits measurements of the ease with which fluid permeates dentin. This value, the hydraulic conductance of dentin, increased as surface area increases and/or as dentin thickness decreases. It increased 32-fold when dentin was acid etched due to removal of surface debris occluding the tubules.
Subject(s)
Dentin Permeability , Tooth Permeability , Acid Etching, Dental , Dentin/anatomy & histology , Dentin/ultrastructure , Humans , Pressure , RheologySubject(s)
Body Fluids/physiology , Dentin/physiology , Adolescent , Adult , Dental Pulp/physiology , Filtration , Humans , In Vitro Techniques , RheologySubject(s)
Dentin Permeability , Dentin/ultrastructure , Tooth Permeability , Adult , Citrates/pharmacology , Dentin/drug effects , Dentin Permeability/drug effects , Female , Humans , In Vitro Techniques , Male , Microscopy, Electron, Scanning , Molar , Oxalates/pharmacology , Tooth Permeability/drug effectsABSTRACT
Iontophoretic currents (0--1.0 mA) were applied to dentin disks prepared from human third molars. A negative electrode increased 125I-permeation 10X, while a positive electrode increased 14C-lidocaine 8X. Iontophoresis appears promising as a method to increase the permeation of dentin by ionized substances of therapeutic interest.
Subject(s)
Dentin Permeability , Iontophoresis , Tooth Permeability , Carbon Radioisotopes/metabolism , Dentin/metabolism , Diffusion , Humans , Iodine Radioisotopes/metabolism , Iontophoresis/methods , Lidocaine/metabolismABSTRACT
A comparison was made between the rate of iodide permeation of dentin by diffusion and by filtration. Before acid etching, filtration only doubled the rate of iodide permeation relative to that obtained by diffusion. After acid etching, filtration produced a 32-fold increase in permeation. Acid etching, by removing occluding debris, facilitates filtration more than diffusion.
Subject(s)
Dentin Permeability , Tooth Permeability , Acid Etching, Dental , Dentin/ultrastructure , Diffusion , Filtration , Humans , Iodine Radioisotopes , PressureABSTRACT
A simple in vitro method has been described for quantitatively measuring the rate at which isotopically labeled substances permeate through dentin in occlusal cavity preparations. The presence or absence of pulp tissue had only a minor effect on the kinetics of permeation. As the dentin was made thinner there was a resulting increase in the rate of iodide permeation. The relative rates of permeation were 3H2O greater than 131I greater than 99mTc greater than 14C-urea, a sequence that follows the molecular dimensions of these substances.
