DNA damage-induced replication fork regression and processing in Escherichia coli

DNA lesions that block replication are a primary cause of rearrangements, mutations, and lethality in all cells. After ultraviolet (UV)-induced DNA damage in Escherichia coli, replication recovery requires RecA and several other recF pathway proteins. To characterize the mechanism by which lesion-blocked replication forks recover, we used two-dimensional agarose gel electrophoresis to show that replication-blocking DNA lesions induce a transient reversal of the replication fork in vivo. The reversed replication fork intermediate is stabilized by RecA and RecF and is degraded by the RecQ-RecJ helicase-nuclease when these proteins are absent. We propose that fork regression allows repair enzymes to gain access to the replication-blocking lesion, allowing processive replication to resume once the blocking lesion is removed.     

Lead isotopes in North American coals

Lead isotopes in North American coals are equally or much more radiogenic than those in the present continental crust (a mean composition for the continental crust is used). It is practicable to distinguish coal and gasoline lead pollutants by examining their isotopic compositions.     

Location of a major susceptibility locus for familial schizophrenia on chromosome 1q21-q22

Schizophrenia is a complex disorder, and there is substantial evidence supporting a genetic etiology. Despite this, prior attempts to localize susceptibility loci have produced predominantly suggestive findings. A genome-wide scan for schizophrenia susceptibility loci in 22 extended families with high rates of schizophrenia provided highly significant evidence of linkage to chromosome 1 (1q21-q22), with a maximum heterogeneity logarithm of the likelihood of linkage (lod) score of 6.50. This linkage result should provide sufficient power to allow the positional cloning of the underlying susceptibility gene.     

Crossability between some Pelargonium species

Summary Crosses were made between Pelargonium zonale, P.inquinans, P.scandans and P. stenopetalum and any interspecific hybrids obtained were selfed. The species were also selfed. Pelargonium stenopetalum was self-incompatible and cross-incompatible as the pistillate parent with the other species. As the staminate parent, P.stenopetalum was also relatively unsuccessful in interspecific crosses. Crosses between P.zonale and P.inquinans produced relatively high numbers of viable seeds and the hybrids were quite self-fertile. As indicated by the ease of crossability and hybrid self-fertility, reproductive barriers were strong between P.scandens and the other species.     

Crossability between a diploidPelargonium × hortorum Bailey cultivar and some of its putative ancestral species

Summary Crosses were made between Mme. Buchner, a diploid cultivar ofPelargonium × hortorum and four of its putative ancestral speciesP. zonale, P, inquinans, P. scandens andP. stenopetalum. Hybrids derived from these crosses were selfed and records kept of their self-fertility. Crosses between Mme. Buchner andP. inquinans andP. zonale were the most successful.Pelargonium scandens andP. stenopetalum were difficult to cross with the cultivar. Lack of cross- and/or self-fertility appears as low seed set, low germination and, in the hybrids particularly, as partial or complete male-sterility. Partial male-sterility often appears in semi-double florets, a characteristic which seems linked to spurlessness.     

Ecological Compensation to Address Environmental Externalities: Lessons from South American Case Studies

Large development projects commonly cause damage to ecosystems, even after measures have been taken to avoid and reduce impacts on site. Governments are increasingly seeking to offset losses through ecological compensation programs to maintain overall levels of biodiversity and ecosystem services. The key to successful programs are criteria that reduce uncertainty and transaction costs while enhancing ecological equivalency. In South America, the government of Brazil, and Colombia have implemented compensation programs, and Peru has recently published broad guidelines and is developing detailed rules. Brazil emphasizes regulatory simplicity, which mitigates cost uncertainty, over ecological equivalence. Colombia has sophisticated methods for establishing ecological equivalence, but has yet to develop institutions necessary to reduce transaction costs. These experiences suggest a trade-off between rules that rigorously compensate losses with ecologically equivalent areas, and simpler approaches that have low transaction costs but may fail to ensure specific biodiversity goals. The success of Peru’s system will depend on being practical enough to implement at scale and rigorous enough to deliver environmental benefits. We describe a series of mutually compatible recommendations to balance both needs. Ecological compensation is still a nascent effort in the neotropics and policy adjustments will be necessary as better information on success and failure becomes available.     

Forests as Capital: Financial Mechanisms for Tropical Forest Conservation

Tropical forest loss and degradation due to human activities have been persistent and intractable global problems. Model estimates suggest that current levels of finance for conservation and sustainable forest management (SFM) are insufficient and may need to increase by an order of magnitude in order to meet this challenge. This special issue presents select articles from the 2014 Yale International Society of Tropical Foresters (ISTF) Annual Conference, which explored diverse finance mechanisms such as REDD+, sustainability certification, ecological compensation, community forestry, and official development assistance. Each finance mechanism has advantages and disadvantages, which render them effective under specific circumstances. Comprehensive tropical forest conservation will require a diverse portfolio of finance strategies appropriate for local institutional and ecological conditions. Hybrid strategies combining elements of multiple schemes could bolster conservation and SFM efforts by leveraging their respective strengths. Clear and realistic targets and baselines, robust monitoring and measurement-reporting-verification, strong governance and institutions, and periodic evaluation can contribute to the successful application of forest conservation finance. Due to the potentially high damages, especially to the world’s poorest communities from continuing current deforestation trends, substantially greater financing of tropical conservation and SFM is a sound global investment.     

A comparison of two laboratory methods of maintaining field-collected Lymnaea tomentosa for the production of Fasciola hepatica metacercariae

Four replicates of 50 field-collected Lymnaea tomentosa were maintained in two laboratory culture systems and their efficiency and practicability for the production of Fasciola hepatica metacercariae were assessed. There was no significant difference in the total number of metacercariae produced (56 552 from 64 snails in the closed container system and 54 073 from 82 snails in the shallow aquarium system).There was no significant difference between culture systems as assessed by snail survival, the number of infected snails or the number of infected snails harvested for the recovery of metacercariae. Within both systems there was a significant effect of snail size on the number of metacercariae produced. Optimum survival and production of metacercariae was achieved in young adult snails of 5–8 mm shell length at the time of infection.The collection of L. tomentosa from the field habitat and their maintenance in either culture system was shown to be a practical alternative to the breeding of laboratory adapted strains of L. tomentosa for the regular production of large numbers of F. hepatica metacercariae.