Effects of Application Strategies of Fumigant and Nonfumigant Nematicides on Cantaloupe Grown in Deep Sand Soils in Florida

A 2-year study was conducted in which three treatment tactics of oxamyl (at planting application, application every 2 weeks, and rescue applications, as determined by crop symptoms) were compared to fumigant treatments with methyl bromide, 1,3-dichloropropene (1,3-D), and 1,3-D plus chloropicrin for management of Meloidogyne spp. In 2002, treatments that included 1,3-D produced higher yields as determined both by number and weight of marketable fruit. All treatment tactics relying solely on oxamyl, at planting, scheduled treatments, and rescue, were not different from untreated controls for both marketable yield and number of fruit. Gall ratings in 2002 were lowest for 1,3-D at the 112-liters/ha rate, followed by 1,3-D at 84 liters/ha with and without oxamyl. All treatments of oxamyl, except when combined with 1,3-D, had gall ratings not different from untreated plots. In 2004, treatments of methyl bromide and 1,3-D plus chloropicrin had the highest total number of both marketable fruit and highest marketable yields. All treatment strategies relying solely on oxamyl had yields equivalent to the untreated controls. Mean root-gall ratings were lowest for methyl bromide plus chloropicrin and 1,3-D plus chloropicrin treatments. Root-gall ratings for all treatment tactics relying solely on oxamyl were not different from untreated controls.     

Centrally Administered Ghrelin Acutely Influences Food Choice in Rodents

We sought to determine whether the orexigenic hormone, ghrelin, is involved in the intrinsic regulation of food choice in rats. Ghrelin would seem suited to serve such a role given that it signals hunger information from the stomach to brain areas important for feeding control, including the hypothalamus and reward system (e.g. ventral tegmental area, VTA). Thus, in rats offered a choice of palatable foods (sucrose pellets and lard) superimposed on regular chow for 2 weeks, we explored whether acute central delivery of ghrelin (intracerebroventricular (ICV) or intra-VTA) is able to redirect their dietary choice. The major unexpected finding is that, in rats with high baseline lard intake, acute ICV ghrelin injection increased their chow intake over 3-fold, relative to vehicle-injected controls, measured at both 3 hr and 6 hr after injection. Similar effects were observed when ghrelin was delivered to the VTA, thereby identifying the VTA as a likely contributing neurobiological substrate for these effects. We also explored food choice after an overnight fast, when endogenous ghrelin levels are elevated, and found similar effects of dietary choice to those described for ghrelin. These effects of fasting on food choice were suppressed in models of suppressed ghrelin signaling (i.e. peripheral injection of a ghrelin receptor antagonist to rats and ghrelin receptor (GHSR) knock-out mice), implicating a role for endogenous ghrelin in the changes in food choice that occur after an overnight fast. Thus, in line with its role as a gut-brain hunger hormone, ghrelin appears to be able to acutely alter food choice, with notable effects to promote “healthy” chow intake, and identify the VTA as a likely contributing neurobiological substrate for these effects.     

Gender Differentiated Preferences for a Community-Based Conservation Initiative

Community-based conservation (CBC) aims to benefit local people as well as to achieve conservation goals, but has been criticised for taking a simplistic view of “community” and failing to recognise differences in the preferences and motivations of community members. We explore this heterogeneity in the context of Kenya’s conservancies, focussing on the livelihood preferences of men and women living adjacent to the Maasai Mara National Reserve. Using a discrete choice experiment we quantify the preferences of local community members for key components of their livelihoods and conservancy design, differentiating between men and women and existing conservancy members and non-members. While Maasai preference for pastoralism remains strong, non-livestock-based livelihood activities are also highly valued and there was substantial differentiation in preferences between individuals. Involvement with conservancies was generally perceived to be positive, but only if households were able to retain some land for other purposes. Women placed greater value on conservancy membership, but substantially less value on wage income, while existing conservancy members valued both conservancy membership and livestock more highly than did non-members. Our findings suggest that conservancies can make a positive contribution to livelihoods, but care must be taken to ensure that they do not unintentionally disadvantage any groups. We argue that conservation should pay greater attention to individual-level differences in preferences when designing interventions in order to achieve fairer and more sustainable outcomes for members of local communities.     

Computational Investigations of the Chalcogen-Substituted Carboxylic Acids RC(=O)XH and RC(=X)OH and their Dimers [RC(=O)XH]2 and [RC(=X)OH]2 (X=S, Se, Te)

Semiempirical and ab initio theoretical methods have been used to investigate molecular structures of the chalcogen-substituted carboxylic acid isomers RC(=O)XH (chalcogenol acid) and RC(=X)OH (chalcogenon acid). A recent experimental report suggests that the chalcogenon isomers, although less stable at room temperature, predominate at low temperature in polar solvents and that there is only a small barrier to isomerization between the isomers. Theoretical calculations have been used to locate minimum energy structures of chalcogen-substituted carboxylic acid isomers and to calculate energy differences between pairs of isomers. Carboxylic acids are well known to dimerize, especially in the gas phase and in non-polar solvents. We have, therefore, also calculated energies of dimerization of the chalcogen-substituted acids by optimizing the geometries of the symmetric dimers. We note that the PM3 level of theory is only qualitatively correct for sulfur- and selenium-containing species but fails even qualitatively for the tellurium-containing compounds. Ab initio results confirm the experimental observations and provide good estimates of both isomerization and dimerization energies. We conclude that for many functional groups with tautomers RC(=X)YH and RC(=Y)XH, the more acidic tautomer is the one with the acid proton on the smaller, more electronegative atom, although in many cases this may not be the more stable tautomer.Electronic Supplementary Material available.     

Rat cholesterol side-chain cleavage enzyme (P-450scc): use of a cDNA probe to study the hormonal regulation of P-450scc mRNA levels in ovarian granulosa cells

A rat ovarian cDNA library was constructed and screened by differential colony hybridization to detect cDNA clones specific for mRNA induced by follicle-stimulating hormone (FSH). The cDNA clone which demonstrated the greatest degree of induction contained a 766-bp insert which was characterized and sequenced. We conclude that this cDNA is specific for the rat gene coding for cholesterol side-chain cleavage enzyme (P-450scc) by virtue of nucleotide sequence homology to the bovine and human P-450scc cDNA sequences. Southern blotting of rat genomic DNA suggests the presence of a single P-450scc gene. Northern blot analysis indicates that P-450scc mRNA is present in steroidogenic tissues (ovary, adrenal, testis), but not in brain, kidney, liver, lung, or heart. The rat P-450scc mRNA is induced by FSH or pregnant mare's serum gonadotropin in ovaries of estrogen-treated immature rats in vivo. In cultured granulosa cells, estradiol treatment alone did not increase P-450scc mRNA levels, but in combination with FSH or 8-Br-cAMP resulted in three- to four-fold increase in this mRNA.     

The ABC's of diatom identification using laser holography

Biomonitoring systems designed to protect the integrity of aquatic ecosystems must satisfy complementary requirements if they are to be used in a successful management program. First, they must generate reliable information with respect to the current biological status of the ecosystem; and second, they must be capable of reducing the lag time in the feedback of this information. This paper describes a biomonitoring system, currently being developed, that employs coherent optical spatial filtering techniques to rapidly identify diatoms and process species-abundance information. Preliminary results indicate that the optical problems associated with such a system can be overcome satisfactorily, although investigations are continuing into the problem of interfacing a microscope directly to the optical system. We envision that this system can eventually be employed in a management program along with chemical and physical data to obtain full beneficial use of the ecosystem without damage.Co-authors