In vitro and in vivo effects of chemotherapeutants on the oyster parasite, Perkinsus marinus

To investigate the potential of chemotherapeutants to control the oyster pathogen Perkinsus marinus, anticoccidial and antifungal compounds were tested in vitro on infected hemolymph and cultured P. marinus cells and in vivo on infected oysters. In addition, acute toxicity to oysters was determined for six anticoccidials. In vitro experiments with infected hemolymph consisted of 24 h exposure of 0.2 mL hemolymph aliquots to concentrations ranging from 100 mg/L to 0.01 mg/L of amphotericin-B, amprolium, arprinocid, cycloheximide, lasalocid, malachite green, monensin, sulfadimethoxine, and a potentiated sulfadimethoxine, followed by incubation in fluid thioglycollate medium (FTM) to determine prezoosporangia abundance. Lasalocid, malachite green, and amphotericin-B were the most effective compounds reducing prezoosporangia abundance, relative to the untreated control group, at concentrations as low as 10 mg/L. Cycloheximide, monensin, and to a lesser extent sulfadimethoxine, were also effective but only at the highest concentration tested (100 mg/L). In vitro experiments with cultured P. marinus consisted of 24 h exposure of 10&\sp5& cells to 100 mg/L, 10 mg/L, and 1 mg/L of amphotericin-B, and 100 mg/L of cimetidine, cycloheximide, fumagillin, 5-fluorocytosine, ketoconazole, lasalocid, and monensin, followed either by incubation in FTM to determine abundance and size of prezoosporangia, or by addition of Neutral Red to determine cell viability. Amphotericin-B, lasalocid, and monensin were effective in reducing prezoosporangia abundance, size, and/or cell viability. No effects of cycloheximide on cultured cells were apparent. Lasalocid, monensin, and malachite green, were toxic to oysters at concentrations below 10 mg/L. The 96-hr. LC50 for lasalocid was 0.59 mg/L. No median lethal dose was determined for monensin or malachite green, but oyster mortality resulted from exposures ranging from 1 mg/L to 10 mg/L of either compound. In three in vivo experiments, infected oysters were exposed to amprolium, arprinocid, cycloheximide, lasalocid, monensin, malachite green, potentiated sulfadimethoxine, and sulfadimethoxine at various concentrations. Only cycloheximide was effective in reducing P. marinus infections. After 15 days of exposure to 10 mg/L of cycloheximide, weighted prevalence significantly declined from 3.78 in untreated controls to 2.10 in treated oysters. Infections progressed after treatment was discontinued as indicated by an increase in weighted prevalence from 0.71 at the end of treatment to 1.31 one month later. (Abstract shortened by UMI.)

Responsibility, Ethics and American Economic Thought, 1776-1900

Nineteenth-century American economic thought offered reflective criticisms and insightful suggestions pertaining to the obligations of corporate enterprise. Although the notion of corporate social responsibility was not featured in the discourse, for-profit entities were held accountable to implicit, and sometimes explicit, codes of social behavior. Attitudes toward corporations/businesses are woven throughout the period’s treatises on political economy. Americans couched their discussion in an intellectual milieu particular to the era. They borrowed from an Anglo-American tradition imbued with republican values, a patriotic fervor that swept the nation following the wars with Britain, and the cosmopolitanism of free-trade liberalism. Protectionists, liberals, republicans, pro-slavery Southerners, and an embryonic breed of anti-market thinkers deliberated over the social obligations of corporations, the dialectic between financial institutions and republican values, the tensions between markets and government, the propriety of slave and free labor, and the consequences of business activities on the moral, political and social fabric of the new nation

Exact time-reversal focusing of acoustic and quantum excitations in open cavities: The perfect inverse filter

The time-reversal mirror (TRM) prescribes the reverse playback of a signal to focalize an acoustic excitation as a Loschmidt echo. In the quantum domain, the perfect inverse filter (PIF) processes this signal to ensure an exact reversion provided that the excitation originated outside the cavity delimited by the transducers. We show that PIF takes a simple form when the initial excitation is created inside this cavity. This also applies to the acoustical case, where it corrects the TRM and improves the design of an acoustic bazooka. We solve an open chaotic cavity modeling a quantum bazooka and a simple model for a Helmholtz resonator, showing that the PIF becomes decisive to compensate the group velocities involved in a highly localized excitation and to achieve subwavelength resolution.Comment: 6 pages, 2 figure

Association of Fungal Secondary Metabolism and Sclerotial Biology

Fungal secondary metabolism and morphological development have been shown to be intimately associated at the genetic level. Much of the literature has focused on the co-regulation of secondary metabolite production (e.g., sterigmatocystin and aflatoxin in Aspergillus nidulans and Aspergillus flavus, respectively) with conidiation or formation of sexual fruiting bodies. However, many of these genetic links also control sclerotial production. Sclerotia are resistant structures produced by a number of fungal genera. They also represent the principal source of primary inoculum for some phytopathogenic fungi. In nature, higher plants often concentrate secondary metabolites in reproductive structures as a means of defense against herbivores and insects. By analogy, fungi also sequester a number of secondary metabolites in sclerotia that act as a chemical defense system against fungivorous predators. These include antiinsectant compounds such as tetramic acids, indole diterpenoids, pyridones, and diketopiperazines. This chapter will focus on the molecular mechanisms governing production of secondary metabolites and the role they play in sclerotial development and fungal ecology, with particular emphasis on Aspergillus species. The global regulatory proteins VeA and LaeA, components of the velvet nuclear protein complex, serve as virulence factors and control both development and secondary metabolite production in many Aspergillus species. We will discuss a number of VeA- and LaeA-regulated secondary metabolic gene clusters in A. flavus that are postulated to be involved in sclerotial morphogenesis and chemical defense. The presence of multiple regulatory factors that control secondary metabolism and sclerotial formation suggests that fungi have evolved these complex regulatory mechanisms as a means to rapidly adapt chemical responses to protect sclerotia from predators, competitors and other environmental stressors.This article is made openly accessible in part by an award from the Northern Illinois University Libraries’ Open Access Publishing Fund

Theoretical study of finite temperature spectroscopy in van der Waals clusters. I. Probing phase changes in CaAr_n

The photoabsorption spectra of calcium-doped argon clusters CaAr_n are investigated at thermal equilibrium using a variety of theoretical and numerical tools. The influence of temperature on the absorption spectra is estimated using the quantum superposition method for a variety of cluster sizes in the range 6<=n<=146. At the harmonic level of approximation, the absorption intensity is calculated through an extension of the Gaussian theory by Wadi and Pollak [J. Chem. Phys. vol 110, 11890 (1999)]. This theory is tested on simple, few-atom systems in both the classical and quantum regimes for which highly accurate Monte Carlo data can be obtained. By incorporating quantum anharmonic corrections to the partition functions and respective weights of the isomers, we show that the superposition method can correctly describe the finite-temperature spectroscopic properties of CaAr_n systems. The use of the absorption spectrum as a possible probe of isomerization or phase changes in the argon cluster is discussed at the light of finite-size effects.Comment: 17 pages, 9 figure

In-Vitro And In-Vivo Effects Of 8 Chemotherapeutants On The Oyster Parasite Perkinsus-Marinus (Mackin, Owen, And Collier)

Eight therapeutants were tested for in vitro inhibition of Perkinsus marinus (Mackin, Owen, and Collier) enlargement and in vivo control of established infections. In addition, acute toxicity of six anticoccidials to oysters was determined. For in vitro experiments 0.2 ml aliquots of infected hemolymph were exposed to 5 concentrations (100 mg/l, 10 mg/l, 1 mg/l, 0.1 mg/l and 0.01 mg/1) of amprolium, arprinocid, cycloheximide, lasalocid, malachite green, monensin, sulfadimethoxine, and a potentiated sulfadimethoxine. Exposure lasted 1 day and was followed by incubation in fluid thioglycollate medium. Lasalocid and malachite green were the most effective compounds, showing significant anti-P. marinus activity at concentrations as low as 10 mg/l. Cycloheximide, monensin, and to a lesser extent sulfadimethoxine, were also effective but only at the highest concentration tested (100 mg/1). At concentrations lower than 10 mg/l, no compound tested had a significant effect on P. marinus. Lasalocid, monensin, and malachite green, were toxic to oysters at concentrations below 10 mg/l. The 96-hr LC50 for lasalocid was 0.59 mg/l. No median lethal dose was obtained for monensin or malachite green, but oyster mortality resulted from exposures ranging from 1 mg/l to 10 mg/l of either compound. In two in vivo experiments, infected oysters were exposed to amprolium, cycloheximide, malachite green, and sulfadimethoxine at various concentrations. Only cycloheximide was effective in reducing P. marinus infections. After 15 days of exposure to 10 mg/l of cycloheximide, weighted prevalence significantly declined from 3.78 in untreated controls to 2. 10 in treated oysters. In addition, infections as measured by repeated hemolymph samples from individual oysters, significantly decreased after treatment. Extension of cycloheximide exposure to 30 days similarly reduced disease prevalence and weighted prevalence. Infections, however, were not completely eliminated even after 30 days of exposure to 10 mg/l of cycloheximide. Furthermore, infections progressed after treatment was discontinued as indicated by an increase in weighted prevalence from 0.71 at the end of treatment to 1.31 one month later