Mechanism of resistance to quinclorac in smooth crabgrass (Digitaria ischaemum)

The mechanism of resistance to quinclorac was investigated in a smooth crabgrass biotype [Digitaria ischaemum (Schreb. ex Schweig) Schreb. ex Muhl] from Tulare County, California. Quinclorac (8.96 kg a.i. ha⁻¹) had no effect (P = 0.18) on the resistant (R) biotype, but reduced fresh weight of a susceptible (S) biotype by 93%. After treatment with 4.48 kg a.i. quinclorac ha⁻¹, the S biotype produced about three times more ethylene than the R biotype and accumulated cyanide in tissues. Similar amounts of endogenous cyanide resulting from treatment with KCN reproduced quinclorac phytotoxicity. Pre-treatment with the ACC synthase inhibitor AVG reduced quinclorac phytotoxicity by 37% and ethylene production by 89%. These data suggest a target site-based mechanism of resistance involving stimulation of ACC synthesis and accumulation of cyanide. Also, the R biotype had four times more β-cyanoalanine synthase activity than the S biotype, suggesting a higher ability to detoxify cyanide.     

Racial, cultural, and ethnic diversity within US veterinary colleges

A comprehensive survey containing 30 questions regarding racial, cultural, and ethnic issues was sent electronically to each of the member colleges within the Association of American Veterinary Colleges (AAVMC) during 2005. Responses were received from 25 of the 28 veterinary colleges in the United States and two foreign colleges. Most colleges had more than one respondent complete the survey. Since the respondents were not identified and were not uniform in regards to position within each college, some responses might have reflected the individual respondent's views rather than the college's actual situation or philosophy. The information gained from this survey demonstrates strong trends in attitudes to and practices with respect to diversity in US veterinary colleges. Three major areas were addressed in the survey-college and university environment and cultures, faculty and curriculum, and recruitment and retention of veterinary students from underrepresented minorities. In many instances, the survey confirmed a lack of knowledge about diversity issues at the respondents' institutions. These survey results will serve as a benchmark for gauging changes in the profession's racial, cultural, and ethnic demographics in the future and as a foundation upon which to build effective diversity programs.     

Plutonium-fission xenon found in Earth's mantle

Data from mid-ocean ridge basalt glasses indicate that the short-lived radionuclide plutonium-244 that was present during an early stage of the development of the solar system is responsible for roughly 30 percent of the fissiogenic xenon excesses in the interior of Earth today. The rest of the fissiogenic xenon can be ascribed to the spontaneous fission of still live uranium-238. This result, in combination with the refined determination of xenon-129 excesses from extinct iodine-129, implies that the accretion of Earth was finished roughly 50 million to 70 million years after solar system formation and that the atmosphere was formed by mantle degassing.     

Assessing the feasibility of sponge aquaculture as a sustainable industry in The Bahamas

Sponge harvesting was a significant part of the Bahamian economy until the late 1930s when disease, hurricanes, and unsustainable harvesting practices reduced the viability of the sponge industry. Current international demands for natural products, increasing regional needs for economic diversification, and the historical foundation of sponging in The Bahamas makes sponge aquaculture a desirable candidate as a sustainable industry. To determine the feasibility of sponge aquaculture in The Bahamas, we deployed growout arrays between February 2006 and September 2009 at two sites off South Eleuthera to examine the survival and growth rates of grass sponge (Spongia tubulifera) and hardhead sponge (Spongia pertusa) cuttings. Complete skin regeneration occurred for both species by the second week following deployment. Following 43 months of growout, both grass and hardhead sponges showed significant positive growth, with cuttings of both species exhibiting faster growth trajectories at the more protected site (Site A) when compared with the site further from shore (Site B). The proportion of sponge cuttings lost during the course of the study was also considerably less for both species at Site A, as was the amount of required maintenance for the arrays. The initial deployment of larger sponge cuttings could help reduce the overall growout period, as would the selection of sites that offered more protection for growout. Based on these results, sponge aquaculture could prove to be a sustainable low-cost industry in The Bahamas; however, further research on site selection, regulations, and market acceptability remains to be done.     

Comparative Histomorphological Review of Rat and Human Hepatocellular Proliferative Lesions

In this comparative review, histomorphological features of common nonneoplastic and neoplastic hepatocyte lesions of rats and humans are examined using H&E-stained slides. The morphological similarities and differences of both neoplastic (hepatocellular carcinoma and hepatocellular adenoma) and presumptive preneoplastic lesions (large and small cell change in humans and foci of cellular alteration in rats) are presented and discussed. There are major similarities in the diagnostic features, growth patterns and behavior of both rat and human hepatocellular proliferative lesions and in the process of hepatocarcinogenesis. Further study of presumptive preneoplastic lesions in humans and rats should help to further define their role in progression to hepatocellular neoplasia in both species.     

Using in situ solid phase microextraction (SPME) for depth profiling in sediments treated with activated carbon

Purpose

Sediment contamination in US waterways is an expensive and complicated issue, and as acceptance of nontraditional sediment remediation strategies broadens, novel and efficient methods to assess and monitor the bioavailability of hydrophobic organic contaminants (HOCs) in contaminated sediments will play an important role.

Materials and methods

In this project, solid phase microextraction (SPME) fibers inside perforated steel tubes were used as in situ passive samplers to measure polycyclic aromatic hydrocarbon (PAH) concentrations in sediment before and after treatment with activated carbon (AC). Two modes of waterjet amendment injection were used to apply the AC. In the first treatment, a single 2-min injection was shot into the center of a test vessel, and in the second treatment, multiple 7-s injections in a grid were placed in sediment.

Results and discussion

In the single injection, no treatment was observed 5 cm away from the injection, while at 2.5 cm, >90 % decrease of PAH pore water concentration was observed, indicating a similar bioavailability decrease. In the multiple injection experiment, >90 % PAH pore water level reductions were observed throughout the test vessel. Highly contaminated and less contaminated sediments were mixed with 0–5 % AC by weight to develop AC treatment curves. Over 99 % reduction in PAH pore water concentrations and bioavailability was observed in the less contaminated sediment at 3 % AC, while 99 % reduction was never reached even at 5 % AC addition in the highly contaminated sediment. Different treatment curves were observed for the different contaminated sediments. In situ equilibration times were 120, 215, and 250 h for phenanthrene, pyrene, and benzo(a)anthracene, respectively.

Conclusions

The results show that in situ SPME is a viable method to observe AC treatment and evaluate reductions in pore water concentrations and bioavailability.     

Weed control and soybean response to preplant tillage and planting time

Clay soils in the southeastern U.S.A. Typically are tilled for seedbed preparation and weed control, prior to seeding soybean (Glycine max (L.).Merr.). However, during extended wet periods when clayey soils cannot be tilled, this practice interferes with timely planting of soybean. Consequently, a 3-year study (1985–1987) investigated the role of tillage and seeding date on irrigated soybean production on Sharkey clay (Vertic Haplaquept) near Stoneville, Mississippi. Plantings were made each year, in early May and late may or early June, in seedbeds subjected to the following treatments: (1) autumn tillage and winter fallow; (2) autumn tillage and winter wheat (Triticum aestivum L.) cover; (3) late winter or early spring tillage; (4) prepared seedbed; or (5) no tillage between harvest and planting. A disk-harrow and spring-tooth harrow were used for all tillage operations. Weeds were effectively controlled during each growing season in all treatments by selected preplant, preemergence, and postemergence herbicides, plus postemergence cultivation. Seedbed tillage had no consistent effect on soybean yield, but in two of the three years, early plantings yielded significantly more seed than late plantings. The increase from early planting was 862 kg ha⁻¹ (3598 vs. 2736 kg ha⁻¹) in 1986, and 381 kg ha⁻¹ (2899 vs. 2518 kg ha⁻¹) in 1987. These results indicate that seedbed tillage of clayey soil should be avoided if it interferes with timely planting of soybean.