Reducing the concentration of selected marker improves efficiency of cotransfer of unselected DNA into SV40-transformed human fibroblasts.

A substantial increase in transfer of unselected DNA to two human SV40-transformed fibroblast cell lines was obtained by reducing the concentration of the cotransferred selected marker DNA. The average amount of unselected DNA transferred, even under favorable conditions, was still low compared to that reported for some rodent cell lines. Our results suggest that in human fibroblasts there is strong competition between exogenous DNA molecules for integration and maintenance, and that more unselected DNA is retained in the presence of only one copy of the selected marker.     

Binding of correolide to K(v)1 family potassium channels. Mapping the domains of high affinity interaction.

Correolide, a novel nortriterpene natural product, potently inhibits the voltage-gated potassium channel, K(v)1.3, and [(3)H]dihydrocorreolide (diTC) binds with high affinity (K(d) approximately 10 nM) to membranes from Chinese hamster ovary cells that express K(v)1.3 (Felix, J. P., Bugianesi, R. M., Schmalhofer, W. A., Borris, R., Goetz, M. A., Hensens, O. D., Bao, J.-M., Kayser, F. , Parsons, W. H., Rupprecht, K., Garcia, M. L., Kaczorowski, G. J., and Slaughter, R. S. (1999) Biochemistry 38, 4922-4930). Mutagenesis studies were used to localize the diTC binding site and to design a high affinity receptor in the diTC-insensitive channel, K(v)3.2. Transferring the pore from K(v)1.3 to K(v)3.2 produces a chimera that binds peptidyl inhibitors of K(v)1.3 with high affinity, but not diTC. Transfer of the S(5) region of K(v)1.3 to K(v)3.2 reconstitutes diTC binding at 4-fold lower affinity as compared with K(v)1.3, whereas transfer of the entire S(5)-S(6) domain results in a normal K(v)1.3 phenotype. Substitutions in S(5)-S(6) of K(v)1.3 with nonconserved residues from K(v)3.2 has identified two positions in S(5) and one in S(6) that cause significant alterations in diTC binding. High affinity diTC binding can be conferred to K(v)3.2 after substitution of these three residues with the corresponding amino acids found in K(v)1.3. These results suggest that lack of sensitivity of K(v)3.2 to diTC is a consequence of the presence of Phe(382) and Ile(387) in S(5), and Met(458) in S(6). Inspection of K(v)1.1-1.6 channels indicates that they all possess identical S(5) and S(6) domains. As expected, diTC binds with high affinity (K(d) values 7-21 nM) to each of these homotetrameric channels. However, the kinetics of binding are fastest with K(v)1.3 and K(v)1.4, suggesting that conformations associated with C-type inactivation will facilitate entry and exit of diTC at its binding site. Taken together, these findings identify K(v)1 channel regions necessary for high affinity diTC binding, as well as, reveal a channel conformation that markedly influences the rate of binding of this ligand.     

Assessing hydraulic redistribution with the compensated average gradient heat-pulse method on rain-fed olive trees

Aims

In this study on hydraulic redistribution (HR) in roots, we aimed to use the calibrated average-gradient (CAG) heat-pulse method, the novelty being the use of a much narrower averaging window for the signal analysis, in order to achieve a more linear calibration curve, allowing the HR quantification.

Methods

The study was conducted in 12 large roots of a rain-fed olive orchard, for 6 months without significant rain, when the predawn leaf water potential decreased to ?2.4 MPa, and immediately following the first autumn rains.

Results

Detailed numerical modelling of the CAG method allowed verification of the response of the measurement system to a range of drivers, improving the linear range of the calibration response function, which has remained stable over the observations period. On average, reverse flow was observed during 30% of the summer nights and, in a conservative estimate, it increased to about 5% of total daily root flow before first autumn rain.

Conclusions

Reverse flow accounted on average for 2.6% of the total daily root flow, enabling upper roots to stay active during the very dry late-summer period. In qualitative terms, our results confirm the CAG method as a reliable tool to identify reverse flow and quantify HR when it occurs.

     

Attachment Anxiety and Avoidance Influence Pet Choice and Pet-directed Behaviors

Attachment theory is a useful lens through which to examine both perceptions and selection of companion animals. Study 1 compared perceptions of dogs and cats, and found that dogs were perceived as having more positive relationship qualities and secure attachment-related characteristics, whereas cats were perceived as having more negative relationship qualities and avoidant attachment-related characteristics. In addition, people perceived relationships with dogs to involve less avoidance and less anxiety relative to relationships with people. In study 2, which built on the findings of study 1, attachment avoidance was negatively associated with wanting to own a pet, whereas attachment anxiety was positive associated with wanting to own a pet. These attachment dimensions were not associated with wanting to own a dog, but lower avoidance and higher anxiety were associated with wanting to own a cat. Study 3 was a longitudinal study of SPCA-type shelter visitors (510 participants, with 169 reporting a recent pet adoption). Lower attachment anxiety predicted recently adopting a dog rather than a cat, though neither anxiety nor avoidance predicted adopting a cat. Individuals who wanted a pet in order to facilitate human relationships were more likely to adopt a dog than a cat. Those high in attachment avoidance reported turning to their pet as a replacement for human companionship, and those high in attachment anxiety reported feeling more concern about their pets requiring more attention. Attachment anxiety and avoidance may influence the decision whether or not to adopt a pet, as well as the motivation underlying the adoption choice. Attachment also may influence the type of pet chosen (i.e., dog versus cat). In addition, attachment may influence the nature of the human–animal relationship, such as the time spent together, and the security felt regarding the relationship.     

Anthropogenic disturbance induces opposing population trends in spotted hyenas and African lions

Large carnivore populations are declining worldwide due to direct and indirect conflicts with humans. Protected areas are critical for conserving large carnivores, but increasing human-wildlife conflict, tourism, and human population growth near these sanctuaries may have negative effects on the carnivores within sanctuary borders. Our goals were to investigate how anthropogenic disturbance along the edge of the Masai Mara National Reserve, Kenya, influences the demography and space-use of two large carnivore species that engage in intense interspecific competition. Here we document, in one disturbed region of the Reserve, a rapid increase in the population size of one large predator, the spotted hyena (Crocuta crocuta), but a striking concurrent decline in numbers of another, the African lion (Panthera leo). Anthropogenic disturbances negatively affected lion populations, and decreasing lion numbers appear to have a positive effect on hyena populations, indicated here by an increase in juvenile survivorship. We also saw an increase in the number of livestock consumed by hyenas. Our results suggest human population growth and indirect effects of human activity along Reserve boundaries may be effecting a trophic cascade inside the Reserve itself. These results indicate both top-down and bottom-up processes are causing a shift in the carnivore community, and a major disruption of guild structure, inside the boundaries of one of the most spectacular protected areas in Africa.     

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.