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Open-path cavity ring-down spectroscopy provides a potential means for sensitive detection of trace gas species in compact, lightweight packages. This contribution presents studies of attainable sensitivity along with details of methane and ammonia sensors.

Purine nucleoside antimetabolites, such as clofarabine, are effective antileukemic agents. However, their effectiveness depends on an initial activation step in which they are monophosphorylated by deoxycytidine kinase (dCK). Some purine nucleoside antimetabolites and their monophosphate derivatives are exported by the ABC transporter ABCG2. Because clofarabine is a dCK substrate, and we show substantial variation in dCK and ABCG2 in myeloid leukemia, we hypothesized that the activity of dCK may modulate ABCG2-mediated resistance to clofarabine by regulating the formation of clofarabine monophosphate. We show that ABCG2 influence on clofarabine cytotoxicity was markedly influenced by dCK activity. When dCK expression was reduced by siRNA, clofarabine cytotoxicity was strongly reduced by enhanced ABCG2-mediated efflux. Conversely, dCK overexpression blunted ABCG2-mediated efflux of clofarabine by increasing the formation of clofarabine nucleotides. The use of an ABCG2 inhibitor confirmed that ABCG2 export of clofarabine is maximal when dCK levels are minimal. Analysis of intracellular clofarabine metabolites suggested that ABCG2 exported clofarabine more readily than clofarabine monophosphate. That ABCG2 primarily effluxes clofarabine, but not chlorfarabine-monophosphate, was confirmed by HPLC analysis of drug exported from ABCG2-overexpressing cells. Because the level and function of dCK and ABCG2 vary substantially among other types of cancer, these findings have important implications not only for clofarabine therapy but for purine nucleoside therapy in general. Therefore, we propose that addition of ABCG2 inhibitors would effectively increase the antitumor efficacy of purine nucleosides by blocking drug efflux that may be a significant mode of resistance when dCK levels are low. Cancer Res; 71(5); 1781–91. ©2011 AACR.

The presence of live and dead emergent vegetation alters the microbial metabolism of communities within the water column of prairie pothole wetlands. To demonstrate the effects, dissolved CH4, dissolved O2, plant densities, and litter densities were measured in transects from emergent vegetation to open water zones. O2 concentrations were consistently lower and CH4 concentrations consistently higher in emergent zones. Plant surface cover most likely interferes with gas flux across the air-water interface in the emergent zone, impeding O2 transport into the water column and impeding CH4 transport out of the water column. Either directly or indirectly, the presence of emergent vegetation may alter aerobic and anaerobic metabolism; since wet and dry cycles can result in emergent plant cover from nearly absent to nearly 100%, understanding these dynamics over the long-term will require studies over a range of wetland stages.

The phosphorus (P) deficiency status of phytoplankton communities was measured using the physiological indicator, alkaline phosphatase activity (APA) and nutrient-addition growth bioassays in field sampled from four northeastern Minnesota lakes and the far western arm of Lake Superior. Phosphorus additions generally reduced APA, while other treatments increased activity. Samples receiving nitrogen (N) and P increased APA after a long lag period. P-addition bioassays of Lake Superior were consistent with phytoplankton P limitation and variations in APA indicated potential seasonal and spatial changes in P deficiency status. The results suggest that APA reliably reflected the phytoplankton P status, but may not provide sufficient information when N or NP limitation is present.

Background and aims – Plant species adapted to metalliferous soil are of high conservation value, and actions for preserving these species (some of them are endemics) are urgent given the threat of mining activities. In the framework of an integrated conservation programme of cuprophytes (plants that tolerate a soil with a high level of copper) in Katanga (D. R. Congo), this study aims at: (1) providing new data on species whose germination has never been studied so far; (2) gaining new insight into the storage behaviour of these species; (3) discussing implications for ex situ conservation of these highly threatened species. Methods – Germination tests were conducted on fresh seeds of nineteen species. These tests were repeated after 6, 12 and 24 months of storage in dry-cold conditions. Key results – Most species kept or increased their germination capacity after 2 years storage in dry-cold conditions. Nine species showed a slight decrease in their viability (from 100% to > 80%) after 2 years storage in dry-cold conditions. The present study gives evidence that at least six of the 19 studied species are desiccation-tolerant (orthodox). Among these, two are strict endemics, Haumaniastrum robertii and Faroa malaissei, and two are broad endemics, Diplolophium marthozianum and Gladiolus robiliartianus . This means that ex situ seed banking of these species could form a useful part of a more comprehensive conservation strategy. Only two species have been identified as desiccation-sensitive (recalcitrant), i.e.inappropriate for conservation in standard seed bank conditions. An orthodox behaviour has not been ruled out for the other species tested, but their response was less clear and needs further investigation.

BACKGROUND: The holmium:YAG laser shrinks stromal collagen and changes corneal refractive power, reportedly without recurrent or persistent epithelial defects, stromal necrosis, or damage to the epithelium and endothelium observed with some other thermokeratoplasty techniques. METHODS: We studied the safety of the holmium:YAG laser using various patterns and energy densities after treating 12 poorly sighted eyes, two immediately prior to corneal transplantation and 10 followed for a mean period of 90 days (range, 60 to 180 days). Visual acuity, intraocular pressure and inflammation, central corneal endothelial cell density and thickness, and intraocular structures of the eye were indices evaluated regularly. Patients were also assessed for specific symptoms during the post-operative period. RESULTS: There were no problems with epithelial healing and no stromal necrosis or evidence of endothelial damage; no significant differences were noted in any of the endothelial cell indices examined. A mean change in corneal curvature of 1.10 diopter (D) was achieved, but varying amounts of regression of this effect was noted. CONCLUSIONS: Holmium:YAG laser thermal keratoplasty appears to be safe over a follow up of up to 180 days. Corneal refractive changes on the order of 1.05 D can be achieved using the parameters employed in this study. Whether or not larger, persistent corneal refractive change can be achieved with a holmium:YAG laser remains to be determined. [J Refract Surg. 1995,11:358-365.]

The Northern Lakes and Forests ecoregion of Minnesota contains thousands of lakes, characterized by their sensitivity to acid rain and typically low productivity. Four acid-sensitive lakes were studied from 1988 to 1991 to determine if phytoplankton were deficient in nitrogen, phosphorus, or both N and P and if the nutrient input via atmospheric deposition could increase primary production. The relative accuracy of predictions based on growth response bioassays, physiological assays, and nutrient deficiency indices was also evaluated. Our results show that (1) N enrichment generally caused a greater biomass response than P, although N + P almost always yielded the greatest effect and co-limitation was likely in two of the lakes, (2) predictions based on DIN:TP ratios generally agreed with the growth bioassays; TN:TP and DIN:SRP were not useful and could be misleading, and (3) atmospheric deposition could satisfy most of the daily algal N demand and increase the fertility of these lakes. These results suggest that although water quality protection based solely on P may not protect against this non-point source of nutrients, without these control strategies, P inputs would be expected to have a disproportionately greater stimulation of phytoplankton growth.