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The group of chemicals designated organophosphorus compounds have had a significant impact on modern life, including use as pesticides, industrial plasticizers and chemical warfare agents. Exposure to certain organophosphates produces a delayed degeneration of the longest and largest nerve fibers, including those of the ascending and descending tracts of the spinal cord, a condition termed organophosphorus ester-induced delayed neuropathy (OPIDN). Recorded incidents of such an effect in humans have led to research regarding this neurological disease. Among the OPIDN-inducing agents is mipafox, an organophosphate insecticide, the compound we chose to employ in our studies. Although the hen is the primary experimental model in the safety assessment of organophosphates, current research has suggested that the rat may have some validity as an experimental model. We examined the sequential neuropathic effects of a single dose of mipafox (30mg/kg) in rats and hens on a comparative basis to determine the better experimental model. / Master of Science

Laboratory studies were conducted to investigate the mode of action of a new herbicide, isouron (N-(5-(1,1-dimethylethyl)-3-isoxazolyl)-N,N-dimethylurea). These studies included two plant metabolites of isouron, a monomethylurea (N-(5-(1,1-dimethylethyl)-3-isoxazolyl)-N-methylurea) and a urea derivative (N-(5-(1,1-dimethylethyl)-3-isoxazolyl)-urea). The compounds were examined for their effects on four metabolic processes of enzymatically isolated soybean (Glycine max L.) leaf cells. The processes examined were photosynthesis, protein, ribonucleic acid (RNA) and lipid synthesis. Relative incorporation of radiolabeled precursors was the parameter measured to assess herbicidal effects. Results indicate that isouron and its monomethylurea derivative possess similar herbicidal properties. The urea derivative revealed substantially reduced herbicidal effectiveness. The primary mode of action of these compounds appears to be inhibition of photosynthesis. Experiments to determine an I₅₀ value for isouron and experiments to evaluate the influence of an antioxidant EDU (N-(2-(2-oxo-1-imidazolidinyl)ethyl)-N’-phenylurea) and a singlet oxygen quencher DABCO (1,4-diazobicyclo-(2,2,2)-octane) on the photosynthetic inhibition and chlorophyll breakdown induced by isouron were also conducted. An I₅₀ value of 0.51 uM was calculated for isouron. There was no significant influence of EDU or DABCO on isouron toxicity. Greenhouse experiments were conducted to assess the interactions of isouron and four herbicide antidotes on two varieties of corn (Zea mays L.), Dekalb 'XL72AA' and 'XL67', and wheat (Triticum aestivum L.), 'Tyler' and 'McNair 1003'. Antidotes used were naphthalic anhydride (1,8 naphthalic anhydride), R-25788 (N,N-diallyl-2,2-dichloroacetamide), CGA-43089 (α-((cyanomethoxy)imino)benzene acetonitrile) and CGA-92194 (α-((1,3-dioxolan-2-yl-methoxy)imino)benzene acetonitrile. Statistically significant antagonistic interactions between herbicide and antidote were observed in both wheat and corn. Synergistic interactions were also recorded. The order of antidotal effectiveness on corn was determined to be: NA > CGA-43089 > CGA-92194 > R-25788 and in wheat: NA > CGA-43089 > R-25788 (CGA-92194 severely limited germination). Visual observation of both corn and wheat plants indicated that nonantidoted isouron was very toxic to these crops. / Master of Science

The biological actions of the herbicides SC-0224 (trimethylsulfonium carboxymethylaminomethylphosphonate) and glyphosate [N-(phosphonomethyl)glycine] (PMG) were compared. In each study trimethylsulfonium iodide (TMS-I) was included as a treatment because the trimethylsulfonium ion is a constituent of the SC-0224 molecular structure. In inflated duckweed (Lemna gibba L.), both formulated and technical grade forms of SC-0224 were found to be much more phytotoxic to duckweed than either formulated or technical grade forms of glyphosate. The growth inhibition caused by glyphosate was partially prevented by different combinations of the aromatic amino acids phenylalanine, tyrosine, and tryptophan; whereas, the duckweed growth inhibition caused by SC-0224 could not be reduced by the same amino acid combinations. TMS-I and SC-0224 were found to be equally phytotoxic to duckweed. SC-0224 caused larger increases than glyphosate in the pool levels of amino acids; the increases caused by SC-0224 were similar, however, to those caused by trimethylsulfonium iodide. Expressed on a per gram fresh weight basis none of the chemical treatments caused significant changes in soluble protein or the incorporation of ¹⁴C-leucine into soluble protein. On a per flask basis (allowing for decreased growth in treated flasks), both herbicides and TMS-I caused significant decreases in soluble protein and ¹⁴C-leucine incorporation. SC-0224 and TMS-I caused larger decreases than glyphosate in both cases but the SC-0224 and TMS-I treatments were not significantly different. These data indicate that differences in the phytotoxicity of SC-0224 .and glyphosate may be due to the action of the trimethylsulfonium ion of the SC-0224 structure. The effects of these herbicides on the conversion of shikimate to anthranilate in a cell-free extract of Klebsiella pneumoniae ATCC 25306 were also compared. SC-0224 and glyphosate equally inhibited the production of anthranilate indicating that SC-0224 has action similar to glyphosate on the shikimate pathway. The effects of these herbicides on photosynthetic electron transport (the Hill reaction) was determined using isolated thylakoids from Alaska pea (Pisum sativum L.). The action of SC-0224 was compared with the action of glyphosate, TMS-I and diuron [3-(3,4-dichorophenyl)-1,1-dimethylurea]. SC-0224, glyphosate and TMS-I did not inhibit the Hill reaction at concentrations up to 10 mM; whereas, diuron caused an almost total inhibition at 0.10 mM. The results of this study indicate that SC-0224 is not an inhibitor of photosynthetic electron transport. These studies indicate that both constituents of the SC-0224 structure, TMS and PMG, are phytotoxic and may act independently. / Ph. D.

Bermudagrass (<i>Cynodon</i> spp.), when cultured at the northern limit of adaptation for semitropical grasses, is exposed seasonally to temperatures low enough to limit growth and turf quality. Research was conducted to investigate the influence of foliar iron and cytokinin applications on bermudagrass growth during fall and spring. The relationship of photosynthesis, respiration, and nonstructural carbohydrate composition to chilling temperatures was also studied. Foliar applications of Fe in late-summer and fall extended bermudagrass performance during low temperature periods of fall. Frequent Fe applications aided the retention of green bermudagrass turf during prolonged exposure to chilling temperatures. Iron applied the previous season stimulated post-dormancy recovery. Benzyladenine (BA) applied alone was not as effective as Fe for promoting green bermudagrass color retention during fall and BA had few effects on spring growth when applied the previous season. Applications of BA in conjunction with Fe were beneficial for retention of green bermudagrass color during late fall when clear plastic covers were used to prevent frost injury. A 6- to 8-week longer bermudagrass growing season occurred when clear plastic covers were used to prevent frost injury. Iron and BA did not significantly affect the total nonstructural carbohydrate (TNC) levels in Midiron bermudagrass rhizomes and stolons at the onset of dormancy in field studies. Midiron bermudagrass had higher photosynthetic and respiration rates than Tifgreen bermudagrass after 4 days exposure to chilling (10/7°C day/night) temperatures in controlled environment studies. Midiron recovered higher photosynthetic rates than Tifgreen when returned to a warm (30°C) environment after exposure to chilling temperatures. The TNC in leaves of Midiron and Tifgreen increased 88 and 160%, respectively, during 5 days at chilling temperatures. The inability to transport carbohydrate from and the subsequent accumulation of high photoassimilate levels in leaves was associated with the inability of bermudagrass to fully recover high photosynthetic rates following chilling. Reduced respiratory activity was apparently responsible for the accumulation of high TNC levels in leaves. In contrast to photosynthesis, respiration was reversibly inhibited by short term exposure of bermudagrass to chilling temperatures. Rapid recovery of high respiratory activity may be important for maintenance of aesthetically pleasing bermudagrass turf following chilling. Foliar applied Fe or BA generally caused darker green Midiron and Tifgreen turf after exposure to chilling temperatures in a controlled environment, although the enhancement of physiological activity differed with chemical applied and cultivar. Iron stimulated recovery of photosynthetic and respiratory activity in both cultivars after exposure to chilling temperatures. However, during chilling Midiron CO₂ exchange was more responsive to Fe applications. Benzyladenine increased photosynthesis in Tifgreen but not in Midiron and did not significantly affect respiration in either cultivar. Neither Fe nor BA had a consistent effect on TNC levels in bermudagrass leaves, rhizomes, or stolons. These investigations indicate that cultivar selection may play a major role in determining turf quality at chilling temperatures. Iron may modify bermudagrass physiology and enhance performance of bermudagrass exposed to chilling temperatures. / Ph. D. / incomplete_metadata

The effects of high medium temperatures on the growth and mineral nutrition of selected woody plants and on the composition of the medium solution were studied. Medium temperature profiles were established for 3.8-liter black polyethylene containers exposed to solar radiation under Virginia nursery conditions. On clear days in mid-summer, maximum recorded medium temperatures on the southwest side of containers were as high as 45°C and could exceed 40°C for 4 to 5 hours. The high medium temperatures in exposed containers reduced the shoot relative growth rate and the specific rate of nitrogen uptake for Ilex crenata ‘Convexa’ in comparison to that of plants grown in containers insulated from solar radiation. Shoot dry weights of J. crenata ‘Helleri’ , Juniperus chinensis, Buxus microphylla, and Nandina domestica were at least 20% lower in exposed containers than in insulated containers. In a pine bark medium, growth response of J. crenata, J. horizontalis, or N. domestica to increased N application rate was similar when root-zones were at 40°C for 6 hrs/day or more optimal growth temperature. In unlimed pine bark, root-zone temperature of 40°C for 6 hrs/day resulted in higher medium solution pH and NH₄- N:NO₃-N ratio than at lower temperature. Limestone addition to the medium negated these effects and alleviated growth reductions due to high root-zone temperature for N. domestica and J. horizontalis. The higher medium solution pH associated with heated root-zones resulted in lower medium solution and shoot tissue Mn concentrations for I. crenata. A limed pine bark medium periodically fertilized with ammonium N was heated to temperatures of 28°, 34°, 40°, 46°, or 52°C for daily exposure duration of 1, 2, 4, 6, or 24 hours for 20 days. Treatment temperature of at least 40°C with a daily exposure duration of 24 hours resulted in an increase in medium solution NH₄-N concentration. Similar increase in NH₄-N was found for 2 hr/day exposure to 46°C, with further increases in NH₄-N at longer exposure times. The maximum level of NH₄- N occurred after 1 hr/day exposure to 52°C or 24 hr/day exposure to 46°C. Decreases in medium solution NO₃-N concentration generally coincided with the increases in NH₄- N. Results indicate that high container temperature may increase the ratio of NH₄- N:NO₃-N in the medium solution of plants fertilized with predominately ammoniacal N. / Ph. D.

M.Sc. / The increase in industrialisation, mining and agricultural activity along rivers could have a detrimental effect on aquatic environments unless the dangers of pollutants are not taken notice of. Metal ions and industrial effluent have become a source of pollution in the watercourses of South Africa. Pollutants generally have negative effects on the physiology of aquatic biota in polluted waters. The effects of copper and industrial effluent by the exposure of the clawed toad, Xenopus laevis and Tilapia sparrmanii are presented in this study. An experimental static-renewal system with an exposure time of 96 hours was followed at 25±1°C. After copper and effluent exposure, several physiological changes occurred in the two aquatic organisms. The sublethal effects that occurred include changes in hatching, survival, behaviour, growth impairment and developmental limitations. The results of the present study suggest that lethal endpoints can be used as indicators in detecting and evaluating the effects of aquatic pollution, caused by copper and effluent. Individual variation, however, could hamper the conclusions made but the study of aquatic organisms is of practical importance when conducting experimental studies in a laboratory and does not have the same impact as during field studies. Apart from the exposure to sublethal concentrations of copper and effluent, computational derivations of LC50, NOEC values and 95% confidence limits were made. The obtained concentrations were used as assumptions that pollutants should not exceed for the protection of aquatic life. Statistically different differences were found between the chosen derived variables of control and experimental organisms. The advantages of FETAX solution over borehole water can be attributed to the bioavailability of pollutants, which appears to be much less in those solutions. The predicted NOEC values provide some information regarding the concentrations at which no effects will be observed and the Target Water Quality Ranges (TWGR) for water were used to determine if the diluent was correct.

Purpose: The purpose of this thesis is to investigate if abnormal patterns concerning the rates of return during specific weekdays and months are observable for the companies in the OMXS30 during the period 2003-2010. A special focus will be put on the Monday effect anomaly. Background: Investors have a tendency to search for investment opportunities. If errors exist in the pricing of stocks it indicates that anomalies are present and that the stock market is inefficient. Investors then have the possibility to utilize the anomalies in order to receive above average returns. Method: This study is using data of stock prices from Nasdaq OMX in the period of 2003-2010. The strength and existence of the Swedish stock market efficiency is measured through autocorrelation-, chi-square- and regression tests. Average monthly stock returns are calculated on daily-, monthly-, and yearly basis. The returns are compared in order to examine if day-of-the-week and turn-of-the-year anomalies exist. Conclusion: No Monday effect is found in 2003-2010. However, positive Thursday- and positive Friday effects are detected. A negative turn-of-the-year effect as well as a positive April effect is found. The investment opportunities that could be utilized in 2003-2010 due to the specific anomalies in the period do not necessarily imply that the same anomalies can be expected on the OMXS30 in the future.

<p><strong>Purpose: </strong>The purpose of this thesis is to investigate if abnormal patterns concerning the rates of return during specific weekdays and months are observable for the companies in the OMXS30 during the period 2003-2010. A special focus will be put on the Monday effect anomaly.</p><p><strong>Background: </strong>Investors have a tendency to search for investment opportunities. If errors exist in the pricing of stocks it indicates that anomalies are present and that the stock market is inefficient. Investors then have the possibility to utilize the anomalies in order to receive above average returns.<strong> </strong></p><p><strong>Method: </strong>This study is using data of stock prices from Nasdaq OMX in the period of 2003-2010. The strength and existence of the Swedish stock market efficiency is measured through autocorrelation-, chi-square- and regression tests.<strong> </strong>Average monthly stock returns are calculated on daily-, monthly-, and yearly basis. The returns are compared in order to examine if day-of-the-week and turn-of-the-year anomalies exist.</p><p><strong>Conclusion: </strong>No Monday effect is found in 2003-2010. However, positive Thursday- and positive Friday effects are detected. A negative turn-of-the-year effect as well as a positive April effect is found. The investment opportunities that could be utilized in 2003-2010 due to the specific anomalies in the period do not necessarily imply that the same anomalies can be expected on the OMXS30 in the future.</p>

Abstract not available