Identification of subwatershed sources for chlorinated pesticides and polychlorinated biphenyls in the Ballona Creek watershed

Santa Monica Bay forms part of the western border of the greater Los Angeles region. The Ballona Creek watershed is highly urbanized and past studies indicate that Ballona Creek is the largest source for most pollutants to Santa Monica Bay. This study evaluates the contribution of subwatersheds to PCB and chlorinated pesticide loading during wet weather flow. Fifteen storm drains from these subwatersheds were sampled during three storms during the 2005-2006 winter rainy season. A series of grab samples were taken over the duration of the storms. The suspended solids were analyzed for polychlorinated biphenyls (PCBs) and chlorinated pesticides. A geographic information system (GIS) was used to calculate the runoff volume from each subwatershed to estimate pollution mass loading. There was no statistical difference among subswatersheds; however, a disproportionate mass of PCB loading came from site 5, which had no obvious sources. No specific subwatersheds were identified as key sources for chlorinated pesticides. These results may serve as a model for other locations with concerns for historic PCB and chlorinated pesticides loadings.     

Anthropogenic forcing of estuarine hypoxic events in sub-tropical catchments: landscape drivers and biogeochemical processes

Episodic hypoxic events can occur following summer floods in sub-tropical estuaries of eastern Australia. These events can cause deoxygenation of waterways and extensive fish mortality. Here, we present a conceptual model that links key landscape drivers and biogeochemical processes which contribute to post-flood hypoxic events. The model provides a framework for examining the nature of anthropogenic forcing. Modification of estuarine floodplain surface hydrology through the construction of extensive drainage networks emerges as a major contributing factor to increasing the frequency, magnitude and duration of hypoxic events. Forcing occurs in two main ways. Firstly, artificial drainage of backswamp wetlands initiates drier conditions which cause a shift in vegetation assemblages from wetland-dominant species to dryland-dominant species. These species, which currently dominate the floodplain, are largely intolerant of inundation and provide abundant labile substrate for decomposition following flood events. Decomposition of this labile carbon pool consumes oxygen in the overlying floodwaters, and results in anoxic conditions and waters with excess deoxygenation potential (DOP). Carbon metabolism can be strongly coupled with microbially-mediated reduction of accumulated Fe and Mn oxides, phases which are common on these coastal floodplain landscapes. Secondly, artificial drainage enhances discharge rates during the flood recession phase. Drains transport deoxygenated high DOP floodwaters rapidly from backswamp wetlands to the main river channel to further consume oxygen. This process effectively displaces the natural carbon metabolism processes from floodplain wetlands to the main channel. Management options to reduce the impacts of post-flood hypoxia include i) remodifying drainage on the floodplain to promote wetter conditions, thereby shifting vegetation assemblages towards inundation-tolerant species, and ii) strategic retention of floodwaters in the backswamp wetlands to reduce the volume and rate during the critical post-flood recession phase.     

Salmonella prevalence and antimicrobial susceptibility from the National Animal Health Monitoring System Swine 2000 and 2006 studies

Concern about Salmonella contamination of food is compounded by fear that antimicrobials traditionally used to combat the infection will become useless due to rising antibiotic resistance. Livestock, in particular swine, often are blamed for illnesses caused by Salmonella and for increasing antibiotic resistance due to use of antibiotics in pigs. As part of the National Animal Health Monitoring System Swine 2000 and 2006 studies, swine fecal samples were cultured for Salmonella. These samples were collected from 123 operations in 17 states in 2000 and from 135 operations in 17 states in 2006. At each operation, 50 and 60 fecal samples were collected from late finisher pig pens in 2000 and 2006, respectively. Salmonella isolates were characterized to determine serogroup and serotype and were tested for susceptibility to a panel of 17 and 15 antimicrobial drugs in 2000 and 2006, respectively. A total of 5,470 and 7,788 samples were cultured for Salmonella in 2000 and 2006, respectively. Overall, 6.2% of the samples and 34.2% of the farms were positive for Salmonella in 2000. In 2006, 7.2% of the samples and 52.6% of the farms were positive. Salmonella Derby, Salmonella Typhimurium var. 5- (formerly Salmonella Typhimurium var. Copenhagen), and Salmonella Agona were the three serotypes most often recovered in both study years. The most common antimicrobial resistance pattern for Salmonella Derby in the two study years was resistance to streptomycin, sulfisoxazole, and tetracycline. Most isolates were resistant to tetracycline, sulfisoxazole, and streptomycin in both study years. The proportion of Salmonella isolates that were susceptible to all antimicrobials (pansusceptible) was 38.1% in 2000 and 20.4% in 2006. The proportion of Salmonella isolates that were resistant to three or more antimicrobials (multidrug resistant) was similar in 2000 and in 2006 (52.8 and 57.7%, respectively).     

Influence of colostrum on transepithelial movement of Escherichia coli 055.

The effect of colostrum on transepithelial migration of live Escherichia coli 055:B5:H7 in the neonatal calf intestine was determined by microbiological and microscopic investigations. Colostrum-deprived calves (2 to 6 h old) were given E. coli suspended in saline, E. coli suspended in colostrum, or E. coli in saline 1 h after colostrum. Twenty-four hours after exposure, tissues were collected for examination. Escherichia coli were numerous in mesenteric lymph nodes of calves given this organism in saline. Fewer were recovered from nodes of calves that received the bacteria in colostrum. Escherichia coli were not recovered from mesenteric lymph nodes of calves given colostrum before dosage with the organism. Electron microscopic studies of small intestines from calves that received E. coli in saline revealed bacterial attachment sites surrounded by exfoliation of microvilli. Bacteria appeared to enter epithelial cells by invagination of apical plasma membrane or dilation of apical tubules. Intracellular E. coli were enclosed in a surrounding membrane. The organisms were not observed adhering to or penetrating intestinal epithelium of calves that received E. coli in colostrum or 1 h after colostrum.     

Executive functioning and olfactory identification in young adults with attention deficit-hyperactivity disorder.

Young adults with attention deficit-hyperactivity disorder (ADHD; N?=?105) were compared with a control group (N?=?64) on 14 measures of executive function and olfactory identification using a 2 (group) × 2 (sex) design. The ADHD group performed significantly worse on 11 measures. No Group × Sex interaction was found on any measures. No differences were found in the ADHD group as a function of ADHD subtype or comorbid oppositional defiant disorder. Comorbid depression influenced the results of only 1 test (Digit Symbol). After IQ was controlled for, some group differences in verbal working memory, attention, and odor identification were no longer significant, whereas those in inhibition, interference control, nonverbal working memory, and other facets of attention remained so. Executive function deficits found in childhood ADHD exist in young adults with ADHD and are largely not influenced by comorbidity but may be partly a function of low intelligence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)