Relationships between watershed Stressors and sediment contamination in Chesapeake Bay estuaries

Three methods for assessing the relationships between estuarine sediment contaminant levels and watershed Stressors for 25 Chesapeake Bay sub-estuaries were compared. A geographic information system (GIS) was used to delineate watersheds for each sub-estuary and analyze land use pattern (area and location of developed, herbaceous and forested land) and point source pollution (annual outflow and contaminant loading) using three landscape analysis methods: (1) a watershed approach using the watershed of the estuary containing the sampling station. (2) a partial watershed approach using the area of the watershed within a 10 km radius of the sampling station and (3) a weighted partial watershed approach where Stressors within the partial watershed were weighted by the inverse of their linear distance from the sampling station. Nine sediment metals, 16 sediment organics and seven metals loading variables were each reduced to one principal component for statistical analyses. Relationships between the first principal components for sediment metals and organics concentrations and watershed stressor variables were analyzed using rank correlation and stepwise multiple regression techniques. For both metals and organics, the watershed method yieldedR ² values considerably lower than the partial and weighted partial watershed analysis methods. Regression models using Stressor data generated by the weighted partial watershed landscape analysis method explained 76% and 47% of the variation in the first principal component for sediment metals and organics concentrations, respectively. Results suggest that the area of developed land located in the watershed within 10 km of the sediment sampling station is a major contributing factor in the sediment concentrations of both metals and organics.     

Toxoplasmosis

Infection with T. gondii can have devastating effects on the development of the unborn human fetus. As veterinarians or physicians, we should be able to accurately assess the true risk of exposure of a person to meat-borne tissue cysts or to oocysts based on the age, health, roaming and feeding habits of their cats, and the occupational or recreational activities of the individual. When time precludes an in-depth discussion of preventive measures to decrease exposure to the parasite, the whole client education program can be neatly summarized in the admonition, "When pregnant, wash your hands thoroughly before eating or touching your face, and cook your meat thoroughly." In this way, the risk of exposure to toxoplasmosis and all other meat- or soil-borne diseases is greatly reduced.     

Die Reaktion der Fraßkapazität des BorkenkäferräubersNemosoma elongatum L. (Col., Ostomidae) im Imaginalstadium auf unterschiedliches Beuteangebot in künstlichen Gängen

Feeding capacity of adultN. elongatum was tested at different prey quantities of the bark beetlePityogenes chalcographus L. (Scolytidae) in artificial galleries. Maximum feeding capacity of 2.P. chalcographus/day was observed when 3 prey items/day were offered. There was no increase in prey consumption with further increase of prey quantities, i. e. there was no functional response. Possible reasons for restricted feeding capacity are discussed. It is suggested thatN. elongatum adults exhibit a “threshold strategy” which tends to reach an optimum feeding level instead of a maximum food intake. The consequences of restricted feeding capacity for limiting bark beetle populations are discussed.     

Control of introduced mammalian predators improves kaka Nestor meridionalis breeding success: reversing the decline of a threatened New Zealand parrot

The kaka (Nestor meridionalis) is a threatened, endemic New Zealand parrot that is declining primarily because of predation by introduced mammals. Numbers of female kaka surviving to sexual maturity more than compensated for adult female mortality at three sites with predator control but not at three unmanaged sites. Nesting success at the sites with predator control was significantly greater (?80%) than at unmanaged sites (?38%) while predation on adult females was significantly less (5% c.f. 65%). Predation was the most common cause of nesting failure at all sites. Stoats (Mustela erminea) appeared to be the main predator, although evidence of possum (Trichosurus vulpecula) predation on eggs, nestlings and nesting females was also found. These results suggest that control of stoats and possums can potentially reverse the decline of the kaka on the main islands of New Zealand.     

Taming of a poison: biosynthesis of the NiFe-hydrogenase cyanide ligands

NiFe-hydrogenases have an Ni-Fe site in which the iron has one CO and two CN groups as ligands. Synthesis of the CN ligands requires the activity of two hydrogenase maturation proteins: HypF and HypE. HypF is a carbamoyltransferase that transfers the carbamoyl moiety of carbamoyladenylate to the COOH-terminal cysteine of HypE and thus forms an enzyme-thiocarbamate. HypE dehydrates the S-carbamoyl moiety in an adenosine triphosphate-dependent process to yield the enzyme thiocyanate. Chemical model reactions corroborate the feasibility of this unprecedented biosynthetic route and show that thiocyanates can donate CN to iron. This finding underscores a striking parallel between biochemistry and organometallic chemistry in the formation of an iron-cyano complex.     

Circulatory catecholamines in the eel: origins and functions

While the three catecholamines (CAs) dopamine (DA), norepinephrine (NE) and epinephrine (E), are wide-spread in tissues of the American eel (Anguilla rostrata), the bulk of these CAs in the systemic blood originates from chromaffin cells in the wall of the posterior cardinal veins. In addition, the brain and unidentified structures in the opisthonephric kidney also release appreciable quantities of CAs. The functional realms attributed to systematically circulating CAs in teleosts comprise cardiovascular, respiratory, osmoregulatory, metabolic and endocrinotropic actions. In the eel, cardiovascular and respiratory effects are well established. However, we were unable to prove a physiological role of the CAs in osmoregulation. On the other hand, the eel is the only species among five vertebrates of greatly varying phylogenetic position (the others: hagfish, lamprey, rat, human) in which physiological doses of E were hyperglycemic. As in lamprey and rat, DA and NE are released in the eel by physiological doses of E. In addition, DA and NE also release the respective other two CAs. The physiological significance of the catecholaminotropic (CA-tropic) interactions remains to be established; however, the CA-tropic effect of E does not require the presence of the brain or ‘preganglionic’ nerve cells. In the eel, mild stress causes an immediate ‘unorthodox’ drop of plasma CAs, while stronger stress is followed by the expected increase of plasma CAs.     

EFFECT OF DEFOLIATION AND SOIL MOISTURE ON GRASSLAND RE-GROWTH

The results of field experiments with leys dominated by Festuca pratensis and Dactylis species appear to concur with the theories proposed by Kramer and Jäntti. Complete defoliation, while the soil moisture was at or near permanent wilting percentage down to about 40 cm. depth, arrested growth almost completely but the growth rate of plants with assimilating parts left was 70 to 90 per cent of the corresponding rate on moist soil. The interaction of defoliation and soil moisture, however, seemed to be confined to cases where defoliation was practically complete. When a 4 cm. stubble was left the effect of drought was relatively no more strong than in swards cut to only 12 cm. Defoliation alone causes heavy crop reductions even in moist soil, and these reductions are evidently more important quantitatively than those resulting from the interaction with soil moisture.     

北京鸭迷走背核向脊髓的直接投射——HRP法研究

采用HRP逆行追踪法,对25例北京鸭迷走背核直接投射到脊髓的传导通路的起始部位进行了研究。乌拉坦(Urethane)静脉注射麻醉动物,分别在脊髓的颈中部(C7)、颈膨大部和腰膨大部注时30～50％HRP,灌流固定,取脑做冰冻连续切片,蓝色反应显色,中性红复染,镜检。实验结果:单侧脊髓注射HRP后,在延髓的闩后部分,双侧的迷走背核内发现了标记细胞,对侧的标记细胞数量多于同侧。此外,双侧的疑核和孤束核也有一些标记细胞。在颈中部脊髓引入HRP后,出现的标记细胞较多;在颈膨大部引入HRP后,出现的标记细胞较少;在腰膨大部引入HRP后,迷走背核内不出现标记细胞,而疑核和孤束核仍有少量标记细胞。本文对禽类迷走背核和疑核至脊髓的直接传导通路,结合哺乳类的有关资料进行了讨论。