The measurement of intracellular zinc in human intestinal mucosa using x-ray microanalysis

The zinc content of intestinal epithelial cells in human jejunum and ileum has been measured using X-ray microanalysis. The range of values was wide, the highest being found in stem cells and enterocytes. Significant differences were found in jejunum from gastric carcinoma patients and ileum from Crohn's disease patients compared with patients with non malignant, non inflammatory disease.     

Enantiomeric ratios as an indicator of exposure processes for persistent pollutants in human placentas

The enantiomeric ratios (ER) of alpha-HCH and o,p'-DDT ((+)-isomer concentration/(-)-isomer concentration) and o,p'-DDD (first eluting enantiomer/second enantiomer) were investigated in 112 human placentas from Finnish boys collected 1997-2001. Both o,p'-DDD and alpha-HCH showed changes in their ER depending on the total concentration of the compound in the sample. Their ERs are approaching a value close to racemic mixture (ER=1) at high concentrations. At low concentrations they often differ from 1. The relationship between concentration and ER is clearly identified and it has been shown that it is not affected by analytical uncertainty. This relationship appears to be important for assessing tissue- and species-specific exposure and risk and it may indicate whether net uptake or metabolic activity is dominant in exposure for the resulting exposure of the enantiomers.     

IMPLEMENTATION OF ACUTE CRITERIA FOR CONSERVATIVE SUBSTANCES1

ABSTRACT: Acute criteria are assigned to the fish and wildlife propagation beneficial use in Oklahoma's water quality standards. Dye studies are analyzed to show that these criteria can be implemented through acute regulatory mixing zones. Acute regulatory mixing zones may be defined as areas in receiving streams where acute numerical criteria may be exceeded without causing acute toxicity. Acute regulatory mixing zones are used to obtain acute waste load allocations. If effluent loading does not exceed acute waste load allocation, acute criteria exceedance is confined to the acute regulatory mixing zone and there is no acute toxicity in the receiving stream. Waste load allocations for acute and chronic criteria are compared to determine which is appropriate to develop permit limits for the dye studies.     

Reconciling competing ecological explanations for sexual segregation in ungulates

Sexual segregation in ungulates has important conservation and theoretical implications, but despite numerous studies, the impetus for this behavioral pattern remains a topic of debate. Sexual segregation hypotheses can be broadly grouped into social and ecological explanations, but only ecological explanations can adequately describe why sexes use different areas and habitats. The reproductive strategy hypothesis (RSH) and forage selection hypothesis (FSH) are leading ecological explanations, and although both have received support in the literature, neither the collective basis for that support nor overlap between these hypotheses has been adequately evaluated. This review analyzed seasonal sex comparisons of habitat forage quantity (n=66), quality (n=67), and diet (n=63) from peer-reviewed studies of north temperate ruminants to test predictions of each hypothesis. Empirical data supported predictions of the RSH, but did not support two of three key predictions of the FSH. Males used habitats with greater forage quantity significantly more than females. But, contrary to predictions of the FSH, females did not use habitats with superior forage quality nor consume higher-quality diets more than males. Sexes typically used habitats and consumed diets of similar quality, and when differences were reported, males used higher-quality habitats significantly more than females. Results refute FSH arguments that differences in dietary requirements associated with sexual dimorphism are a universal explanation for sexual segregation in ungulates, but the physiological mechanism on which the FSH is predicated may explain why males consume poorer-quality diets when high-quality forage is scarce. The FSH, therefore, operates at a proximate level because it explains diet and habitat selection by males under certain environmental conditions, but multiple environmental factors may influence sexual segregation, and no single proximate explanation adequately describes this behavioral pattern. The RSH explains sexual segregation as the evolutionary response to differences in reproductive strategies: males choose habitats to maximize energy gains in preparation for rut, and females select habitats with combinations of resources that contribute to offspring survival. Consequently, the RSH provides an ultimate explanation that can be used to explain and interpret studies of sexual segregation in ungulates.     

Kinetic and structural relationships of transition monomeric and oligomeric carboxyl- and choline-esterases

The kinetic and structural relationships of eight electrophoretically pure mammalian serum and liver serine carboxylesterases (CE) and cholinesterases (ChE) have been studied. Eight CE's and ChE's, which were fully resolved but only partially purified, provided additional information. Five of the electrophoretically pure esterases were monomeric, and of these, four belonged to a new and widely distributed class. These four monomeric esterases hydrolyzed choline esters, but at widely differing rates. Thus two were termed monomeric butyrylcholinesterases, mBuChE I and II, and two were monomeric CE's (mCE). The rabbit liver mCE was not a subunit of the oligomeric CE (oCE), although the oCE also hydrolyzed choline esters at a very low rate. The complex kinetics of the mCE's, mBuChE's, oCE's, and of the oligomeric BuChE's of horse and human serum could be interpreted according to a single reaction scheme involving an allosteric site and the equation derived from it. Thus activation and inhibition at high substrate concentrations, together with sigmoidal activity versus substrate concentration plots, all of which characterize the reactions of these esterases, could be interpreted by a single scheme and equation. Structural and kinetic comparisons showed a progressive transition of properties from the oCE's through the mCE's to the oBuChE's. One of the purified mCE's was from horse serum, and it exhibited physical and kinetic properties unlike those of the liver mCE's or oCE's.     

Seed treatments containing neonicotinoids and fungicides reduce aquatic insect richness and abundance in midwestern USA–managed floodplain wetlands

Agrochemicals including neonicotinoid insecticides and fungicides are frequently applied as seed treatments on corn, soybeans, and other common row crops. Crops grown from pesticide-treated seed are often directly planted in managed floodplain wetlands and used as a soil disturbance or food resource for wildlife. We quantified invertebrate communities within mid-latitude floodplain wetlands and assessed their response to use of pesticide-treated seeds within the floodplain. We collected and tested aqueous and sediment samples for pesticides in addition to sampling aquatic invertebrates from 22 paired wetlands. Samples were collected twice in 2016 (spring [pre-water level drawdown] and autumn [post-water level flood-up]) followed by a third sampling period (spring 2017). Meanwhile, during the summer of 2016, a portion of study wetlands were planted with either pesticide-treated or untreated corn seed. Neonicotinoid toxic equivalencies (NI-EQs) for sediment (X??=?0.58 μg/kg), water (X??=?0.02 μg/L), and sediment fungicide concentrations (X??=?0.10 μg/kg) were used to assess potential effects on wetland invertebrates. An overall decrease in aquatic insect richness and abundance was associated with greater NI-EQs in wetland water and sediments, as well as with sediment fungicide concentration. Post-treatment, treated wetlands displayed a decrease in insect taxa-richness and abundance before recovering by the spring of 2017. Information on timing and magnitude of aquatic insect declines will be useful when considering the use of seed treatments for wildlife management. More broadly, this study brings attention to how agriculture is used in wetland management and conservation planning.