The genetic factors controlling Mixed Function Oxidase (MFO) Activity and malathion resistance was studied in the larva and the adult of a malathion resistant strain of Drosophila melanogaster. In addition, the developmental expression and tissue localization of high MFO activity was characterized in the larva and the adult. Microsomal extracts from a strain with a resistant second chromosome were found to have increased amounts of protein with a relative molecular mass of 52 kD, while a strain with a resistant third chromosome was found to have increased amounts of proteins with relative molecular masses of 51 and 55 kD in the microsomal extract. MFO activity associated with a strain with a resistant second chromosome was found to be most concentrated in the intestine and abdominal wall of the imago, while found primarily in the malpigian tubules and the fat body of the larva. The mapping of genes on the second chromosome associated with larval resistance to malathion suggested two loci, a major resistance gene at 2-64 cM and a second minor resistance gene. The mapping of genes on the second chromosome associated with adult resistance again suggested two loci, one at 2-64 cM and a second just to the left of the marker black (48.5 cM). The mapping of genes on the second chromosome associated with high PNA demethylase activity (an MFO activity) in the adult suggested a locus at 2-64 cM and a second between 54.5 and 60.0 cM. The locus at 2-64 cM and a third locus between 48.5 and 51 cM was found to be associated with high 7-EC hydroxylase activity ( a second MFO activity) in the adult. / Thesis / Master of Science (MS)

To examine the interactions of disease and pollution on amphibian populations around the world, I investigated the effect of infection on contaminant susceptibility in pickerel frog, Rana palustris, larvae. I conducted standard 48-hr toxicity tests to examine effect of trematode parasite, Echinostoma trivolvis, infection (0, 10, or 30 cercaria) on the susceptibility of pickerel frog tadpoles to the widely used organophosphate insecticide malathion. LC50 values ranged from 16.5 – 17.4 mg/L, within the range reported for other amphibian species. I found no differences in susceptibility to malathion among parasite treatments. Nevertheless, this crucial question remains to be tested in other amphibian host-parasite systems. Second, I studied the reverse interaction, the effect of pesticide exposure on susceptibility to parasite infection. I exposed pickerel frog embryos to low doses of malathion, then subjected morphologically normal tadpoles to E. trivolvis later in development. Malathion significantly decreased hatching success and viability rates at concentrations lower than previously documented for anuran embryos. After 7 wk of development in water with no malathion, tadpoles previously exposed to malathion as embryos suffered increased parasite encystment rates compared to controls. My research identifies embryonic development as a sensitive window and the potential for increased susceptibility to infection long after pesticide exposure has ceased. With potential for increased parasite prevalence from eutrophication and climate change, my data underscore the importance of understanding the reciprocal influences of parasites and pesticides in amphibians. / Master of Science

Call number: LD2668 .T4 1956 C73 / Master of Science

Call number: LD2668 .T4 1959 K73

No description available.

The boll weevil (Anthonomus grandis grandis Boheman) is currently under eradication in the U.S. The eradication program is implemented by means of area-wide applications of malathion ULV. Frequent applications of this insecticide result in high mortality of many beneficial insects, and a greater risk of secondary pest outbreaks. Notable among the latter are the outbreaks of beet armyworm (Spodoptera exigua H?bner) and cotton aphid (Aphis gossypii Glover) in the Lower Rio Grande Valley in 1995. The present study (i) compared densities of beneficial and pest insect and spider populations between cotton fields in eradication and non-eradication areas; (ii) evaluated the use of beneficial cotton arthropod population densities as indicators of pest damage risks from cotton aphid, beet armyworm, bollworm (Helicoverpa zea Boddie), and other worms (Estigmene acrea Drury, Pseudoplusia includens Walker, and Trichoplusia ni H?bner); and (iii) evaluated the effects of malathion ULV on the red imported fire ant (Solenopsis invicta Buren) a key arthropod predator in cotton agroecosystems. Studies were conducted in central Texas, in the vicinities of College Station and Dallas, during 2002 and 2003. Results showed that a majority of cotton predators were negatively impacted by malathion ULV applications. However, convergent lady beetle (Hippodamia convergens Gu?rin-M?neville) densities were greater in active eradication fields than inactive fields. Stepwise regression analyses identified densities of lacewing (Chrysoperla carnea Stephens) larvae and lady beetle larvae (H. convergens, Coleomegilla maculata De Geer, Harmonia axyridis Pallas, and Coccinella septempunctata L.) as predictors of cotton aphid density, and density of total spiders as predictors of bollworm density. Predictors of beet armyworm or other worm densities could not be determined. This study demonstrated malathion ULV was highly toxic to fire ants, and could repel ants from treated surfaces. Malathion ULV reduced the number of foraging fire ants in the cotton canopy for three weeks and reduced fire ant predation of beet armyworm eggs. Predictors of secondary pest densities have been suggested which, if utilized, may help to prevent the occurrence of secondary pest outbreaks under boll weevil eradication. Validation of these predictors should be preformed before implementing them into an eradication program.

2,4-D-specific IgE antibodies were detected in serum of BALB/c mice using the rat passive cutaneous anaphylaxis (PCA) test following the second intraperitoneal immunization with 1, 10, or 100 ug of 2,4-D0keyhole limpet hemocyanin (KLH) conjugate administered with aluminum hydroxide adjuvant. The groups that received 1 ug of 2,4-D conjugate had the highest antibody titers (geometric mean of 60). A paper radioallergosorbent test (PRAST) was developed for determination of 2,4-D-specific IgE. The PRAST was equally as sensitive as and showed a positive correlation with the PCA assay. The anhydride of the diacid metabolite of malathion (MMA) coupled to KLH elicited MMA-specific IgE following secondary immunization with 10 and 100 ug and tertiary immunizations with 1, 10, and 100 ug of conjugate. The highest PCA titers (geometric means of 208 and 195) were found after three immunizations with 10 or 100 ug of conjugate, respectively. A PRAST for MMA-specific IgE was developed and yielded results equivelant to those obtained using the PCA procedure. Concurrently with these studies, dinitrophenyl-specific IgE elicited with 1 ug of dinitrophenyl-KLH conjugate was measured by the PCA test at all intervals examined. 2,4-D and malathion applied epicutaneously on two days or over four weeks failed to elicit delayed-type hypersensitivity (DTH). Cptafol produced DTH responses at both dose levels tested. Following two applications, ear thickness, incorporation of 5-[125I]iodo-2'deoxyuridine-labelled cells, and histology of ears indicated swelling and cellular infiltration. Multiple sensitizations over the period of a month also produced DTH as indicated by increases in ear thicknesses. Mice pretreated with cyclophosphamide produced larger responses 24 hours post-challenge but equivalent responses at 48 hours as compared to mice pretreated with saline. Sensitization with a known sensitizer, dinitrofluorobenzene, also elicited DTH. Neither 2,4-D- nor MMA-specific IgE antibodies were detected in serum during the four week epicutaneous sensitization period. Low titers of dinitrophenyl-specific IgE were elicited in mic treated with dinitrofluorobenzene.

No description available.

Malathion-resistance in Drosophila Melanogster was studied in susceptible laboratory strains (CS and OR), a heterogeneous intermediate-resistant strain (C1-39), and a more resistant, artificially selected (with malathion). strain (MH19) by comparing the in vitro metabolism of [¹⁴c]-malathion and [¹⁴c]-malaoxon in crude enzyme preparations made from adult flies. Extracts from all strains were found to contain two enzymatic activities that metabolized malathion and/or malaoxon. One activity degraded malathion to its α- and β-monocarboxylic acids and was designated as malathion-carboxylesterase activity (ME-activity). ME-activity was progressively lost in CS-extracts during reaction with [¹⁴c]-malathion due to inhibition of the enzyme(s) by a tightly bound [¹⁴c]-labeled molecule (not identified) that could not be removed by chromatography on Sephadex G-25. ME-activity, based on initial (0-1 min) rates with or without metyrapone present was similar in all strains and furthermore, the carboxylesterase inhibitors TPP and DEF did not synergize malathion toxicity in either resistant or susceptible strains. It was concluded that carboxylesterase-mediated degradation of malathion was not a factor in the resistance of the C1-39 and MH19 strains. A second enzyme system, microsomal mixed-function oxidases (MFO), converted malathion to malaoxon (activation) and degraded malaoxon to at least two products that were tentatively identified (malaoxon α-and β-monoacids and demethyl-malaoxon). The rate of conversion of malathion to malaoxon was highest in crude extracts of the most resistant MH19 flies, intermediate in C1-39 and could not be detected in the susceptible CS flies while the rate of malaoxon degradation was similar between MH19 and C1-39, but higher than that in the susceptible OR flies. Furthermore, malaoxon (but not malathion) toxicity was most strongly synergized by the MFO-inhibitor MTP in the more resistant strains (MH19 and C1-39) . These results were used along with a previous result that MH19 strain possesses a less sensitive form of the target enzyme, acetylcholinesterase (R.A. Morton, personal communication), to propose a biochemical mechanism that accounts for the increased malathion-resistance of the C1-39 and MH19 strains. / Thesis / Master of Science (MS)

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