A high dose of long term treatment with deprenyl loses its effect on antioxidant enzyme activities as well as on survivals of Fischer-344 rats

The survival rate of male Fischer-344/Du rats treated chronically with high doses of deprenyl was investigated. Eighteen month old rats were treated with 1 mg/kg s.c. deprenyl 3 times per week for 13 months. At the age of 31 months, treated rats showed a greater mortality rate with three of 12 rats surviving, while in saline-treated control animals seven of 12 animals survived. No significant differences in superoxide dismutase (SOD) or catalase (CAT) activities in brain regions of control and treated animals were seen at 31 months of age. In contrast, when 27 month old rats were treated in the same manner for one month, significant increases in SOD (both Cu,Zn- and Mn-) and CAT activities were found in substantia nigra, striatum and cerebral cortex, but not in hippocampus. This effect was produced with a wide range of deprenyl doses (0.25-2 mg/kg, but not 4 mg/kg). Although a causal relationship between the two different effects of the drug, i.e. 1) increases in antioxidant enzyme activities and 2) the prolongation of survival of animals, has not been directly demonstrated, the loss of both effects with the high dose of the drug in the present experiment may be taken as circumstantial evidence for their causal relationship.     

Leishmania mexicana: participation of NF-kappaB in the differential production of IL-12 in dendritic cells and monocytes induced by lipophosphoglycan (LPG)

Dendritic cells (DC) and macrophages (Mφ) are well known as important effectors of the innate immune system and their ability to produce IL-12 indicates that they possess the potential of directing acquired immunity toward a Th1-biased response. Interestingly, the intracellular parasite Leishmania has been shown to selectively suppress Mφ IL-12 production and are DC the principal source of this cytokine. The molecular details of this phenomenon remain enigmatic. In the present study we examined the effect of Leishmania mexicana lipophosphoglycan (LPG) on the production of IL-12, TNF-α, and IL-10 and nuclear translocation of NF-κB. The results show that LPG induced more IL-12 in human DC than in monocytes. This difference was due in part to nuclear translocation of NF-κB, since LPG induced more translocation in DC than in monocytes. These results suggest that Leishmania LPG impairs nuclear translocation of NF-κB in monocytes with the subsequent decrease in IL-12 production.     

Nutritional symbionts of a putative vector, <Emphasis Type="Italic">Xyleborus bispinatus</Emphasis>, of the laurel wilt pathogen of avocado, <Emphasis Type="Italic">Raffaelea lauricola</Emphasis>

Ambrosia beetles subsist on fungal symbionts that they carry to, and cultivate in, their natal galleries. These symbionts are usually saprobes, but some are phytopathogens. Very few ambrosial symbioses have been studied closely, and little is known about roles that phytopathogenic symbionts play in the life cycles of these beetles. One of the latter symbionts, Raffaelea lauricola, causes laurel wilt of avocado, Persea americana, but its original ambrosia beetle partner, Xyleborus glabratus, plays an uncertain role in this pathosystem. We examined the response of a putative, alternative vector of R. lauricola, Xyleborus bispinatus, to artificial diets of R. lauricola and other ambrosia fungi. Newly eclosed, unfertilized females of X. bispinatus were reared in no-choice assays on one of five different symbionts or no symbiont. Xyleborus bispinatus developed successfully on R. lauricola, R. arxii, R. subalba and R. subfusca, all of which had been previously recovered from field-collected females of X. bispinatus. However, no development was observed in the absence of a symbiont or on another symbiont, Ambrosiella roeperi, recovered from another ambrosia beetle, Xylosandrus crassiusculus. In the no-choice assays, mycangia of foundress females of X. bispinatus harbored significant colony-forming units of, and natal galleries that they produced were colonized with, the respective Raffaelea symbionts; with each of these fungi, reproduction, fecundity and survival of the beetle were positively impacted. However, no fungus was recovered from, and reproduction did not occur on, the A. roeperi and no symbiont diets. These results highlight the flexible nature of the ambrosial symbiosis, which for X. bispinatus includes a fungus with which it has no evolutionary history. Although the “primary” symbiont of the neotropical X. bispinatus is unclear, it is not the Asian R. lauricola.     

Serum inverts and improves the fluorescence response of an aptamer beacon to various vitamin D analytes

A dominant aptamer loop structure from a library of nearly 100 candidate aptamer sequences developed against immobilized 25‐hydroxyvitamin D₃ (calcidiol) was converted into a 5′‐TYE 665 and 3′‐Iowa black‐labelled aptamer beacon. The aptamer beacon exhibited a mild 'lights on' reaction in buffer as a function of increasing concentrations of several vitamin D analogues and metabolites, with a limit of detection of approximately 200 ng/mL, and was not specific for any particular congener. In 10% or 50% human serum, the same aptamer beacon inverted its fluorescence behaviour to become a more intense 'lights off' reaction with an improved limit of detection in the range 4–16 ng/mL. We hypothesized that this drastic change in fluorescence behaviour was due to the presence of creatinine and urea in serum, which might destabilize the quenched beacon, causing an increase in fluorescence followed by decreasing fluorescence as a function of vitamin D concentrations that may bind and quench increasingly greater fractions of the denatured beacons. However, the results of several control experiments in the presence of physiological or greater concentrations of creatinine and urea, alone or combined in buffer, failed to produce the beacon fluorescence inversion. Other possible mechanistic hypotheses are also discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Luteinizing hormone and sexual steroid plasma levels after treatment of European sea bass with sustained-release delivery systems for gonadotropin-releasing hormone analogue

Spermiating male European sea bass Dicentrarchus labrax were treated with gonadotropin-releasing hormone agonists (GnRHa), either a GnRHa injection (IN; 25 μg kg⁻¹ body mass) or one of three types of controlled-release GnRHa-delivery systems: fast release implants (EVAc; 1OO μg kg⁻¹), slow release implants (EVSL; lOO μg kg⁻¹) and slow release microspheres (MC; 50 μg kg⁻¹). Luteinizing hormone (LH) release was highly stimulated by all GnRHa treatments, with elevated plasma levels lasting for 2 days in injected fish (IN) and 2, 4 and 6 weeks in controlled-release-treated fish (EVAc, MC and EVSL, respectively), correlating with a 1, 3, 5 and 5 week period of stimulation of milt production, respectively. Plasma levels of the androgens testosterone (T) and 11-ketotestosterone (11-KT), were not significantly affected by the GnRHa treatments. Plasma T was high at early spermiation and declined sharply near the end of this period. Plasma 11-KT levels declined continuously throughout the experiment. Levels of 17,20 β -dihydroxy-4-pregnen-3-one (17,20 β -P), a proposed maturation-inducing steroid (MIS) in European sea bass, fluctuated around 0.2–1 ng ml⁻¹ and were not greatly affected by the treatments. These results indicated a close correlation between sustained stimulation of LH release, achieved by GnRHa-delivery systems, and long-term enhancement of milt production. They also show an absence of changes in the common sex steroids, associated with elevated LH and enhanced spermiation.     

Electron transport pathway for a Streptomyces cytochrome P450: cytochrome P450 105D5-catalyzed fatty acid hydroxylation in Streptomyces coelicolor A3(2)

Streptomyces and other bacterial actinomycete species produce many important natural products, including the majority of known antibiotics, and cytochrome P450 (P450) enzymes catalyze important biosynthetic steps. Relatively few electron transport pathways to P450s have been characterized in bacteria, particularly streptomycete species. One of the 18 P450s in Streptomyces coelicolor A3(2), P450 105D5, was found to bind fatty acids tightly and form hydroxylated products when electrons were delivered from heterologous systems. The six ferredoxin (Fdx) and four flavoprotein Fdx reductase (FDR) proteins coded by genes in S. coelicolor were expressed in Escherichia coli, purified, and used to characterize the electron transfer pathway. Of the many possibilities, the primary pathway was NADH --> FDR1 --> Fdx4 --> P450 105D5. The genes coding for FDR1, Fdx4, and P450 105D5 are located close together in the S. coelicolor genome. Several fatty acids examined were substrates, including those found in S. coelicolor extracts, and all yielded several products. Mass spectra of the products of lauric acid imply the 8-, 9-, 10-, and 11-hydroxy derivatives. Hydroxylated fatty acids were also detected in vivo in S. coelicolor. Rates of electron transfer between the proteins were measured; all steps were faster than overall hydroxylation and consistent with rates of NADH oxidation. Substrate binding, product release, and oxygen binding were relatively fast in the catalytic cycle; high kinetic deuterium isotope effects for all four lauric acid hydroxylations indicated that the rate of C-H bond breaking is rate-limiting in every case. Thus, an electron transfer pathway to a functional Streptomyces P450 has been established.     

Manipulation of oxidative stress responses as a strategy to generate stress-tolerant crops. From damage to signaling to tolerance

Plants exposed to hostile environmental conditions such as drought or extreme temperatures usually undergo oxidative stress, which has long been assumed to significantly contribute to the damage suffered by the organism. Reactive oxygen species (ROS) overproduced under stress conditions were proposed to destroy membrane lipids and to inactivate proteins and photosystems, ultimately leading to cell death. Accordingly, considerable effort has been devoted, over the years, to improve stress tolerance by strengthening antioxidant and dissipative mechanisms. Although the notion that ROS cause indiscriminate damage in vivo has been progressively replaced by the alternate concept that they act as signaling molecules directing critical plant developmental and environmental responses including cell death, the induction of genes encoding antioxidant activities is commonplace under many environmental stresses, suggesting that their manipulation still offers promise. The features and consequences of ROS effects depend on the balance between various interacting pathways including ROS synthesis and scavenging, energy dissipation, conjugative reactions, and eventually reductive repair. They represent many possibilities for genetic manipulation. We report, herein, a comprehensive survey of transgenic plants in which components of the ROS-associated pathways were overexpressed, and of the stress phenotypes displayed by the corresponding transformants. Genetic engineering of different stages of ROS metabolism such as synthesis, scavenging, and reductive repair revealed a strong correlation between down-regulation of ROS levels and increased stress tolerance in plants grown under controlled conditions. Field assays are scarce, and are eagerly required to assess the possible application of this strategy to agriculture.     

Influence of metazooplankton on interactions of bacteria and phytoplankton in an oligotrophic lake

Commensalism based on organic carbon supplied by phytoplanktonand competition for mineral nutrients are important interactionsbetween bacteria and phytoplankton in oligotrophic clear-watersystems. Both interactions are influenced by zooplankton activity.To examine the relation ship between algae and bacteria in LakeLa Caldera, we studied: the correlations among phyto plankton,bacteria and phosphorus (P) dynamics; the ratio of organic carbonsupplied by algae to organic carbon demand by bacteria; andthe importance of P remineralized by metazooplankton for bothcommunities. Phytoplankton and bacteria had a similar seasonaldynamics, and there was a sig nificant and positive relationshipbetween bacterial abundance and algal biomass (P<0.01). However,the release of organic carbon from phytoplankton was usuallyhigher than the bacterioplankton carbon requirement. P availablevia zooplankton remineralization satisfied between 74 and 316%of the minimum P demands of algae and bacteria. To elucidatewhether zooplankton operate similarly on algae and bacterialgrowth or indirectly influence bacterial growth through phytoplanktonmetab olism, we performed zooplankton manipulation experiments.High zooplankton biomass in these experiments stimulated bothprimary and bacterial production, but release of organic carbonfrom phytoplankton declined. These results suggest a directstimulus of bacterial growth, so algae and bac teria can balancegrazing losses by compensatory growth. Further, the algal decreaseof the organic carbon supply for bacteria could, over time,lead to a change in the algae-bacteria interaction from competitionto commensalism. This reduction in organic carbon excretioncould affect the balance of the competitive interaction.