In Vitro Stability and Pharmacokinetics of Novel Antileishmanial Compounds

Leishmaniasis, a disease caused by protozoan parasites of the genus Leishmania, affects millions of people worldwide [6]. Without effective treatment, visceral leishmaniasis is associated with a near 100% fatality rate, whereas other forms can be severely debilitating [6]. Current treatments are not ideal because of toxicity, resistance, expense, and inconvenience [6]. Work to develop new drugs is underway at The Ohio State University and is led by Dr. Karl Werbovetz. Over the past few years Dr. Werbovetz and colleagues have generated a library of antiparasitic compounds known to specifically target Leishmania and trypanosome tubulin. In the first round of derivatization, several dinitroanilines were synthesized and evaluated in in vitro efficacy and stability and in vivo efficacy studies to identify key regions of the molecules for efficacy and metabolism. The most promising of these dinitroaniline compounds, GB-II-150, demonstrates an in vitro selectivity of two orders of magnitude for African trypanosomes over mammalian cell lines [7]. GB-II-150 was further evaluated in an in vivo metabolism study in rats [3] and found to be extensively metabolized with the major products resulting from N1 ring oxidation, N4 alkane oxidation, and N4 oxidation [4]. Although GB-II-150 had a half-life of 170 minutes with intravenous administration, it was determined to be highly unstable with zero oral bioavailability when given via oral gavage [3]. Based on the results of these studies, analogs have been prepared in effort to achieve greater metabolic stability while maintaining selective antiparasitic activity [4]. A second round of derivatization and synthesis yielded another family of dinitroanilines that were again evaluated in vivo and in vitro for efficacy. My work has tested the in vitro stability and metabolism of several of these second generation dinitroaniline compounds that have shown antiparasitic activity. The most promising compound from this second round, TG-II-36, was also tested in an in vivo stability study to determine its pharmacokinetic properties. As a follow-up, ongoing work is being conducted on BTB-06237, an analog of a group of diphenyl thioether compounds that have also shown antiparasitic activity. This highly hydrophobic compound has presented serious challenges at early stages of analytical method development preventing adequate in vitro stability characterization. Advisor: James DaltonNIH grant AI062021 (to KAW

Molecular basis for resistance of acanthamoeba tubulins to all major classes of antitubulin compounds

Tubulin is essential to eukaryotic cells and is targeted by several antineoplastics, herbicides, and antimicrobials. We demonstrate that Acanthamoeba spp. are resistant to five antimicrotubule compounds, unlike any other eukaryote studied so far. Resistance correlates with critical amino acid differences within the inhibitor binding sites of the tubulin heterodimers

The impact of weather variability and climate change on pesticide applications in the US - An empirical investigation

Weather variability and climate change affect the application of pesticides in agriculture, in turn impacting the environment. Using panel data regression for the US, we find that weather and climate differences significantly influence the application rates of most pesticides. Subsequently, the regression results are linked to downscaled climate change scenario the Canadian and Hadley climate change models. We find that the application of most pesticides increase under both scenarios. The projection results vary by crop, region, and pesticide.Climate change, weather variability, pesticide, regression, panel data, North America, US

Структурные механизмы взаимодействия цианоакрилатов с тубулином растений

Структурные механизмы, обусловливающие специфическое связывание соединений цианоакрилатной природы тубулином высших растений, исследованы на примере взаимодействия этил-(2Z)-3-амино-2-циано-4-этилгекса-2-еноата (СА1) и изопропил-(2Z)-3-амино-2-циано-4-этилгекса-2-еноата (СА2) с α-тубулином Arabidopsis thaliana. Выявлено, что цианогруппа в составе цианоакрилатов является функциональным аналогом нитрильной группы, определяющей процессы специфического взаимодействия с тубулином растений у динитроанилиновых соединений. На основании данных флуктуации пространственной структуры, динамики водородных связей и энергии взаимодействия СА1 и СА2 выявлен наиболее вероятный тип связывания этих соединений с растительным α-тубулином и охарактеризован соответствующий сайт взаимодействия. При этом 7 из 10 остатков в составе этого сайта (Глн-133, Асн-249, Вал-250, Асп-251, Вал-252, Асн-253 и Глу-254) являются облигатными компоненттами сайта связывания динитроанилинов на поверхности α-тубулина растений. Таким образом, охарактеризованный нами сайт связывания на поверхности α-тубулина способен распознавать и специфически связывать вещества, кардинально отличные по своей химической природе и не имеющие общих фармакофорных групп, при условии определенного сходства их электростатической топологии.The structural mechanisms underlying the specific binding of cyanoacrylate compounds with tubulin of higher plants have been studied by the example of the interaction of ethyl-(2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA1) and isopropyl-(2Z)-3-amino-2-cyano-4-ethylhex-2-enoate (CA2) with Arabidopsis thaliana α-tubulin. It was revealed that the cyano group of cyanoacrylates is a functional analogue of the nitrile group, which determines the processes of specific interaction with plant tubulin for dinitroaniline compounds. Based on data on spatial structure fluctuations, the dynamics of hydrogen bonds and the interaction energy of CA1 and CA2 (the most probable binding mode for these compounds with plant α-tubulin) was identified and the appropriate site of interaction was characterized. Seven out of ten residues composing this site (Gln-133, Asn-249, Val-250, Asp-251, Val-252, Asn-253, and Glu-254) are obligatory components of dinitroanilines’ binding site on the plant α-tubulin surface. Thus, the binding site on the α-tubulin surface characterized by us is able to recognize and specifically bind substances, which are cardinally different by their chemical nature and have no common pharmacophore groups, under the condition of a certain similarity of their electrostatic topology

Green foxtail (Setaria viridis) resistance to acetolactate synthase inhibitors

Des sétaires vertes (Setaria viridis) présumées résistantes aux inhibiteurs de l'acétolactate synthase (ALS) ont été identifiées en 1999 au Wisconsin, É.-U., dans un champ de soja (Glycine max) issu d'un semis direct. La résistance aux herbicides imidazolinone et sulfonylurée a été caractérisée au niveau de la plante entière et de celui des enzymes. Ces sétaires vertes au stade trois à quatre feuilles étaient respectivement 1020, 53 et 6,5 fois plus résistantes à l'imazethapyr, à l'imazamox et au nicosulfuron que les sétaires sensibles. L'ALS in vivo était respectivement 1300 et 1,7 fois plus résistante à l'imazethapyr et au nicosulfuron. Ces résultats laissent supposer que ce groupe de sétaires vertes était très résistant à l'imazethapyr et à l'imazamox, et que la résistance est associée à un enzyme ALS insensible.Green foxtail (Setaria viridis) plants putatively resistant to acetolactate synthase (ALS) inhibitors were identified in a Wisconsin USA no-tillage soybean (Glycine max) field in 1999. Resistance to imidazolinone and sulfonylurea herbicides was characterized at the whole-plant level and enzyme level. Three- to four-leaf stage green foxtail plants were 1020, 53, and 6.5-fold resistant to imazethapyr, imazamox, and nicosulfuron, respectively, compared to susceptible plants. In vivo ALS was 1300 and 1.7-fold resistant to imazethapyr and nicosulfuron, respectively. These results suggested that this green foxtail accession was highly resistant to imazethapyr and imazamox, and that resistance was associated with an insensitive ALS enzyme

Relative fitnes of herbicide-resistant and susceptible biotypes of weeds

Au cours des dernières années, il y a eu une augmentation rapide du nombre de mauvaises herbes (plus de 100) signalées comme étant résistantes aux herbicides, de même qu'une augmentation du nombre de groupes d'herbicides auxquels la résistance a évolué. Cet article fait état des données qui suggèrent l'existence de différences d'aptitude entre les biotypes résistants et sensibles aux herbicides. Des estimés de l'aptitude sont nécessaires afin d'établir des modèles de population fiables. Ces estimés permettent de prévoir le potentiel de succès évolutif d'un génotype basé sur sa survie, sa compétitivité et en dernier lieu, sur son succès reproductif. Les différences d'aptitude entre les biotypes résistants et sensibles sont généralement dérivées des mesures de productivité relative ou de compétitivité. Pour les mauvaises herbes résistantes aux triazines, des études ont démontré que les plantes résistantes étaient généralement moins compétitives que les plantes sensibles, malgré la présence de certaines exceptions. Bien qu'il y ait moins de données disponibles sur l'aptitude des plantes résistantes aux groupes herbicides autres que les triazines, cet article résume l'information disponible sur les sulfonylurées, les urées substituées, les dinitroanilines, le paraquat, le diclofop et les arsenicaux organiques. Aucune différence d'aptitude constante n'a été observée pour les biotypes résistants et sensibles aux herbicides autres que les triazines. En général, les études ont démontré que l'aptitude relative des biotypes sensibles et résistants d'une espèce donnée dépend des conditions biologiques (incluant la variation à l'intérieur du génotype et de la populationet la compétition inter- et intra-biotypes), et des conditions environnementales telles la température, la qualité lumineuse et les pratiques de gestion.In recent years, there has been a rapid increase in the number of reported cases of herbicide-resistant weed species (over 100), as well as an increase in the types of herbicides to which resistance has evolved. This paper reviews evidence for differential fitness of herbicide-resistant and susceptible biotypes. Fitness estimates are required to produce reliable population models. Fitness measures describe the potential evolutionary success of a genotype based on survival, competitive ability and ultimately reproductive success. Differences in relative fitness between resistant and susceptible biotypes are usually inferred from measures of relative plant productivity or competitiveness. For triazine-resistant weed species, studies have indicated that resistant plants were generally less fit than susceptible plants, although exceptions did exist. Although less data are available on the fitness of plants resistant to non-triazine herbicides, information is summarized for sulfonylureas, substituted ureas, dinitroanilines, paraquat, diclofop, and organic arsenicals. No consistent differences in relative fitness were observed for non-triazine resistant and susceptible biotypes. In general, studies have indicated that the relative fitness of susceptible and resistant biotypes of a single species depends upon biological conditions, including genotype and population variation, intra- and inter-biotype competition, and environmental conditions such as temperature, light quality, and management practices. Future needs for relative fitness studies are discussed

Herbicide resistance in the Canadian prairie provinces : Five years after the fact

La résistance aux herbicides a été reconnue comme un problème pour la première fois dans les Prairies canadiennes, en 1988, quand une sétaire verte (Setaria viridis) résistante à la trifluraline a été détectée au Manitoba, puis une stellaire moyenne (Stellaria média) et un kochia à balais (Kochia scoparia) résistants au chlorsulfuron ont été identifiés en Alberta et en Saskatchewan, respectivement. Depuis lors, le nombre de mauvaises herbes résistantes s'est accru pour inclure la folle avoine (Avena fatua) résistante aux triallates, ainsi qu'aux aryloxyphénoxypropionates et aux cyclohexanediones (herbicides du groupe 1), la sétaire verte aux herbicides du groupe 1, la soude roulante (Salsola pestifer) et la moutarde des champs (Sinapis arvensis) résistantes au sulfonylurées et aux imidazolinones (herbicides du groupe 2), et finalement la moutarde des champs résistante aux herbicides régulateurs de croissance (herbicides du groupe 4). Les niveaux et patrons de résistance croisée aux molécules des groupes 1 et 2 diffèrent énormément entre les différentes populations, avec des facteurs de résistance (rapport de résistant à sensible [R:S]), obtenus à l'aide de courbes de réponse aux doses, se classant de 150. La résistance de la sétaire verte au groupe 1 et la résistance de la stellaire moyenne et du kochia à la classe 2 sont dues à des sensibilités réduites des enzymes-cibles: l'acétyl coenzyme-A carboxylase (ACCase) et l'acétolactate synthase (ALS), respectivement. Les mécanismes de résistance pour les autres espèces, incluant la folle avoine résistante aux inhibiteurs de rACCase (groupe 1) et aux triallate/difenzoquat (groupe 8) sont obscurs. À présent, le seul cas de résistance multiple dans l'ouest canadien est la sétaire verte résistante aux éléments chimiques des groupes 1 et 3 (inhibiteurs de l'ACCase et dinitroanilines). Les préoccupations à venir concernent la sévérité accrue de la résistance aux groupes 1 et 8 dans les Prairies, et la possibilité de sélectionner pour la résistance multiple chez les mauvaises herbes du type de la sétaire verte, contre lesquelles il existe peu d'alternatives efficaces.Herbicide resistance was first recognized as a problem on the Canadian Prairies in 1988 when trifluralin-resistant green foxtail (Setaria viridis) was reported in Manitoba, and chlorsulfuron-resistant chickweed (Stellaria media) and koehia (Kochia scoparia) in Alberta and Saskatchewan, respectively. Since then, the number of resistant weeds has increased to include wild oats (Avena fatua) resistant to triallate and to aryloxyphenoxypropionate and cyclohexanedione (group 1) herbicides, green foxtail to group 1 herbicides, Russian thistle (Salsola pestifer) and wild mustard (Sinapis arvensis) to sulfonylurea and imidazolinone (group 2) herbicides, and wild mustard to growth regulator (group 4) herbicides. The levels and patterns of cross-resistance to chemicals in groups 1 and 2 vary widely among different populations, with resistance factors [resistant to susceptible (R:S) ratios] derived from dose response curves typically ranging from 150. Group 1 resistance in green foxtail and group 2 resistance in chickweed and kochia populations are due to reduced sensitivities of the target enzymes, acetyl coenzyme-A carboxylase (ACCase) and acetolactate synthase (ALS), respectively. The mechanisms of resistance in the other species including wild oats resistant to ACCase inhibitors (group 1 ) and to triallate/difenzoquat (group 8) are unclear. At present, the only instance of multiple resistance in western Canada is green foxtail resistant to chemicals in both groups 1 and 3 (ACCase inhibitors and dinitroanilines). Future concerns focus mainly on the increasing seriousness of group 1 and 8 resistance across the Prairies, and on the possibility of selecting for multiple resistance in weeds such as green foxtail for which there are few remaining effective control options

Registration of N614, A3N615, N616, and N617 Shattercane Genetic Stocks with Cytoplasmic or Nuclear Male Sterility and Juicy or Dry Midribs

Four shattercane [Sorghum bicolor subsp. drummondii (Nees ex Steud.) de Wet ex Davidse] genetic stocks—N614 (Reg. No. GS-652, PI 665684), A3N615 (Reg. No. GS-651, PI 665683), N616 (Reg. No. GS-653, PI 665685), and N617 (Reg. No. GS-654, PI 665686)—with A3 cytoplasmic male sterility or the nuclear male sterility gene ms3 containing either juicy (dd) or dry (DD) culms were developed jointly by the USDA-ARS; the Iowa Agricultural and Home Economics Experiment Station, College of Agriculture and Life Sciences, Iowa State University; and the Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska. The stocks were released in July 2011. The source material for these genetic stocks was isolated from an archetypical shattercane population found near Lincoln, NE. Release of these genetic stocks makes available shattercane lines with both A3 cytoplasmic male sterility, and ms3 genetic (nuclear) male sterility to facilitate crossing. These genetic stocks also contain juicy (dd) or dry (DD) culms, a visible genetic marker to facilitate screening progeny resulting from crosses. The genetic stocks have immediate application for basic research involving gene flow from cultivated sorghum [Sorghum bicolor (L.) Moench] to shattercane and on the fitness of offspring resulting from such crosses