Prophage F116: Evidence for Extrachromosomal Location in Pseudomonas aeruginosa Strain PAO

F116 is a temperate-generalized transducing phage of Pseudomonas aeruginosa. Genetic evidence leads to the conclusion that F116 prophage DNA is maintained extrachromosomally as a plasmid. Preliminary physical evidence is presented to support this hypothesis.     

Effect of enzymatic methylation on the chemical,physical, and biological properties of DNA

DNA methylase was partially purified from Escherichia coli W and used to methylate DNA from Bacillus subtilis and bacteriophage φ105. The former DNA was methylated 1.17% and the latter 0.87%. The products were 6-methyladenine (85%) and 5-methylcytosine (15%) in both cases. The methylated DNA was stable toward depurination and viscosity loss at elevated temperatures. Methylation led to a 50% decrease in transforming activity in two strains of B. subtilis and no change in a third strain. The ability of phage φ105 DNA to rescue a defective phage strain was decreased 50% by methylation. No changes were observed in the ability of methylated DNA to serve as a template for DNA polymerase or RNA polymerase. The pattern of cleavage of DNA by a variety of restriction endonucleases was not affected by methylation. There were no changes in the physicochemical properties of DNA on methylation as measured by hyperchromicity on heating, formaldehyde denaturation, viscosity, and sedimentation.     

Voluntary control of cardiovascular reactions to demanding tasks

Three groups of 10 normotensives participated in a study exploring voluntary control of cardiovascular reactions to cognitive tasks. Pulse transit time (TT), interbeat interval (IBI), skin conductance level, and respiratory variables were monitored throughout one introductory and four experimental sessions. The groups were matched on the basis of initial TT and IBI responses to the taxing arithmetic and reasoning tasks. During experimental sessions, one group (FB) was provided with visual analogue TT feedback, while the REL group was given detailed relaxation instructions. A third group (CON) performed the same sequence of tasks but was not instructed to modify cardiovascular reactions at any point. Training in voluntary control was carried out in resting (no-task) conditions, and during task administration. Both treatment groups showed lower cardiovascular reactions than controls in task trials. Only REL subjects lengthened TT in no-task conditions, while both FB and REL groups showed smaller cardiovascular reactions than CON during the tasks. Effects were confined to cardiovascular variables, since respiratory and electrodermal reactions during task administration were similar in all groups. The effects of treatments were especially marked among the most reactive subjects.This work was supported by the Medical Research Council, U.K. We are grateful to Derek Johnston for his comments on an earlier draft of this paper.     

Ecological guidelines for designing networks of marine reserves in the unique biophysical environment of the Gulf of California

No-take marine reserves can be powerful management tools, but only if they are well designed and effectively managed. We review how ecological guidelines for improving marine reserve design can be adapted based on an area’s unique evolutionary, oceanic, and ecological characteristics in the Gulf of California, Mexico. We provide ecological guidelines to maximize benefits for fisheries management, biodiversity conservation and climate change adaptation. These guidelines include: representing 30% of each major habitat (and multiple examples of each) in marine reserves within each of three biogeographic subregions; protecting critical areas in the life cycle of focal species (spawning and nursery areas) and sites with unique biodiversity; and establishing reserves in areas where local threats can be managed effectively. Given that strong, asymmetric oceanic currents reverse direction twice a year, to maximize connectivity on an ecological time scale, reserves should be spaced less than 50–200 km apart depending on the planktonic larval duration of target species; and reserves should be located upstream of fishing sites, taking the reproductive timing of focal species in consideration. Reserves should be established for the long term, preferably permanently, since full recovery of all fisheries species is likely to take?>?25 years. Reserve size should be based on movement patterns of focal species, although marine reserves?>?10 km long are likely to protect?~?80% of fish species. Since climate change will affect species’ geographic range, larval duration, growth, reproduction, abundance, and distribution of key recruitment habitats, these guidelines may require further modifications to maintain ecosystem function in the future.     

Effect of short- and medium-term toxicity of doxorubicin on spermatogenesis in adult Wistar rats

Doxorubicin (DXR) is a widely used chemotherapeutic anticancer agent that has potent activity against several solid and non-solid human malignant tumors, including childhood malignancies. However, DXR has serious toxic effects on tissues with rapid cell cycles, such as myeloid and lymphatic tissues, intestinal mucosa, testes and ovaries. In the present study, the short- and medium-term toxic effects of DXR on the reproductive system of male Wistar rats were evaluated using morphometric and stereological tools to quantify damage to the seminiferous epithelium. Adult male Wistar rats were treated with dose of 7.5?mg/kg of DXR and were sacrificed at seven, 14, 21 and 28?days after treatment. The testes were fixed in glutaraldehyde solution, routinely processed and embedded in plastic for evaluation under a light microscope. A significant reduction in testis weight was found as a result of massive germ cell apoptosis. Differences in comparison to the control group were found in the relative frequency of all stages of the seminiferous epithelium cycle, with significant differences for stages VIII–XI. Apoptosis significantly decreased the number of pachytene spermatocytes in the stages evaluated (I, II–III and VIII) at seven and 14?days. At 21 and 28?days after treatment, the testes exhibited the massive loss of germ cells that resulted in a missing cell layer. Moreover, reductions in the height of seminiferous tubules, tubular diameter and tubular compartment as well as an increase in the intertubular compartment were found in the period studied.