Biochemistry Books

Thyroid hormone status of Atlantic croaker exposed to Aroclor 1254 and selected PCB congeners

April 18, 2010 By biotech-source.com Leave a Comment

Product Description
This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Atlantic croaker (Micropogonias undulatus) were exposed to the polychlorinated biphenyl (PCB) mixture (Aroclor 1254) or one of three individual congeners (planar PCB 77 or ortho-substituted PCB 47 and PCB 153) in the diet for 30 days to investigate the effects of PCBs on circulating thyroid hormones, thyroxine (T”4) and triiodothyronine (T”3). Aroclor 1254 (0.2 and 1.0 mg/kg body mass/day) decreased plasma T”3 levels consistently, but the effects on T”4 levels were inconsistent from year to year. Exposure to PCB 153 (0.1 and 1.0 mg/kg body mass/day) significantly lowered both T”4 and T”3, while PCB 47 at the same doses had no effect on thyroid hormone levels. The lower doses of PCB 77 (0.004, 0.01 and 0.02 mg/kg body mass/day) had no effect on T”4 or T”3, whereas the highest dose (0.1 mg/kg body mass/day) increased T”4 levels significantly. The results of the present study demonstrate that exposure to PCBs at environmentally realistic concentrations can have profound effects on the thyroid status of Atlantic croaker. The ortho-substituted PCB 153 appears to contribute at least partially to the deleterious effects of Aroclor 1254 on thyroid status, whereas the planar PCB 77 at concentrations present in the mixture is unlikely to alter thyroid hormone levels.

Order from Amazon –> Thyroid hormone status of Atlantic croaker exposed to Aroclor 1254 and selected PCB congeners

Filed Under: Biochemistry Books Tagged With: 1254, Amazon, Aroclor, Atlantic, Atlantic Croaker, Body Mass, Comparative Biochemistry And Physiology, Congeners, croaker, Deleterious Effects, Digital Document, exposed, Hormone, Journal Article, Media Library, Micropogonias Undulatus, Pcbs, Planar, Polychlorinated Biphenyl, Profound Effects, selected, status, Thyroid, Thyroid Hormone Levels, Thyroid Hormones, Thyroid Levels, Thyroid Status, Thyroxine, Triiodothyronine

Soil microbial metabolism and nutrient status in a Mediterranean area as affected by plant cover

April 18, 2010 By biotech-source.com Leave a Comment

Product Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
The Mediterranean area of Southern Italy is characterized by different natural plant covers that mainly reflect different successional stages (i.e. low maquis, high maquis, Quercus ilex wood) and managed areas with introduced plant species (such as Pinus species). Soil properties could be affected by plant cover types as well as by plant species. Our objective was to determine the relationships of plant cover types and plant species with the chemical and biological characteristics of the soil. In four neighbouring areas with different plant cover types (low maquis, pure high maquis, high maquis with pines and pinewood, with pines planted by foresters in both cases), soil samples were collected under different plant species in order to evaluate the effect of plant cover types and plant species on soil properties. Soil samples were analyzed for nutrient content, microbial biomass, soil potential respiration and enzymatic activity (phosphatase, arylsulphatase, @b-glucosidase and hydrolase activities) as well as for pH, water holding capacity (WHC) and cation exchange capacity (CEC). Application of cluster analysis and principal component analysis to the data revealed that the plant cover type was the key factor influencing soil properties more than plant species. In fact, the largest differences were observed between pure high maquis soils and all other soils, with pure high maquis soils generally showing the highest values of WHC, CEC, nutrient content, organic and microbial C, soil respiration, phosphatase, arylsulphatase and @b-glucosidase activities. The significantly lower values of these variables in the low maquis relative to the pure high maquis probably reflect the effect of ecological succession on soil. The high maquis with pine, differing from the pure high maquis only for the presence or absence of pine, showed values of soil physical, chemical and biological characteristics similar to those found in the low maquis, thus suggesting that the presence of pine retards soil development.

Order from Amazon –> Soil microbial metabolism and nutrient status in a Mediterranean area as affected by plant cover

Filed Under: Biochemistry Books Tagged With: affected, area, Biological Characteristics, Cation Exchange Capacity, Cluster Analysis, Cover, Digital Document, Enzymatic Activity, Glucosidase, Mediterranean, Mediterranean Area, Metabolism, microbial, Microbial Metabolism, Neighbouring Areas, nutrient, Nutrient Status, Ph Water, Plant, Plant Species, Principal Component Analysis, Soil, Soil Biology And Biochemistry, Soil Properties, Soil Respiration, Soil Samples, Southern Italy, status, Successional Stages, Whc

Birch invasion of heather moorland increases nematode diversity and trophic complexity

April 18, 2010 By biotech-source.com Leave a Comment

Product Description
This digital document is a journal article from Soil Biology and Biochemistry, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
To determine whether successional changes in plant communities may influence belowground community structure, we quantified nematode abundance, trophic structure and diversity along two separate chronosequences from heather moorland to birch woodland in the Scottish uplands. Tree invasion markedly altered plant community composition, and hence litter inputs, both directly, and indirectly through changes in understorey species. In turn, these changes in detrital inputs were reflected in consistent changes in nematode community structure. Nematode abundance increased from moorland to birch woodland, with moorland soils being dominated by a few taxa, notably root-hair and fungal feeders, compared to the more diverse composition of the birch woodland soils. Trophic structure was altered through an increase in the abundance of bacterial feeding relative to fungal-feeding nematodes, and an increase in the abundance of predatory nematodes. The increase in predators during the succession from moorland to woodland was associated with an increase in soil pH, highlighting that not only changes in the plant community, but also changes in soil properties associated with tree invasion may influence soil nematodes. Nematode diversity increased from moorland to birch woodland, with nematode richness being positively related to both plant species richness and soil pH. These results suggest that trees may control soil community structure through the manipulation of resources and the soil physico-chemical environment, promoting greater nematode diversity and trophic complexity.

Order from Amazon –> Birch invasion of heather moorland increases nematode diversity and trophic complexity

Filed Under: Biochemistry Books Tagged With: Amazon, Birch, Chemical Environment, Community Structure, Complexity, Complexity Order, Consistent Changes, Digital Document, Diversity, Heather, Heather Moorland, increases, Invasion, moorland, Nematode, Plant Communities, Plant Community Composition, Plant Species, Predatory Nematodes, Root Hair, Soil Biology And Biochemistry, Soil Community, Soil Nematodes, Soil Ph, Soil Properties, Species Richness, Successional Changes, trophic, Woodland Soils

Influence of @b-carotene on lysosomal hydrolases and their natural substrates in major salivary glands of hamsters treated with 7,12-dimethylbenzanthracene … Biochemistry and Physiology, Part C]

April 18, 2010 By biotech-source.com Leave a Comment

Product Description
This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
We evaluated the effects of @b-carotene, a precursor of vitamin A, on the activity of some lysosomal hydrolases and on the levels of their natural substrates in hamster major salivary glands during experimental oral 7,12-dimethylbenzanthracene (DMBA) carcinogenesis. Sixty-four hamsters (Cricetus auratus) were divided into four groups-group 1: untreated control; group 2: DMBA was painted three times a week in the left buccal pouch; group 3: @b-carotene was painted three times a week in the left buccal pouch; group 4: DMBA and @b-carotene were painted alternatively in the left buccal pouch. After 16 weeks, the animals were sacrificed and the activities of some lysosomal hydrolases and their natural substrates in the major salivary glands were measured. @b-Carotene when administered topically in DMBA treated animals (group 4) reduced the levels of the majority of enzymes and substrates closer to those of the untreated control group, thus outlining a mild protective effect of @b-carotene towards the DMBA carcinogenic stress. Nevertheless, the presence of some enzymes which responded negatively to the combined administration of DMBA and @b-carotene suggests the necessity for future studies on the effect of @b-carotene at different concentrations, the systemic administration and the possibility to combine the topical @b-carotene administration with other chemopreventive drugs.

Order from Amazon –> Influence of @b-carotene on lysosomal hydrolases and their natural substrates in major salivary glands of hamsters treated with 7,12-dimethylbenzanthracene … Biochemistry and Physiology, Part C]