Metallothionein (MT) has several putative roles in metal detoxification, in Zn and Cu homeostasis, in scavenging free radicals, and in the acute phase response. Mice of mixed 129͞Ola and C57BL͞6J background with targeted disruption of MT-I and MT-II genes are more sensitive to toxic metals and oxidative stress. We noted that these animals were larger than most strains of mice, and we systematically studied aspects of their physiology and biochemistry relating to energy metabolism. During the first 2 weeks after weaning, the growth rates of MT-null and C57BL͞6J mice were similar, but the transgenic mice became significantly heavier at age 5-6 weeks. At age 14 weeks, the body weight and food intake of MT-null mice was 16 and 30% higher, respectively, compared with C57BL͞6J mice. Most 22-to 39-week-old male MT-null mice were obese, as shown by increased fat accretion, elevated obese (ob) gene expression, and high plasma leptin levels, similar to those recorded in Zucker fatty ( fa͞fa) rats. Seven-week-old MT-null mice also had significantly higher levels of plasma leptin and elevated expression of ob, lipoprotein lipase, and CCAAT enhancer binding protein ␣ genes as compared with age-matched C57BL͞6J mice. These observations indicate that abnormal accretion of body fat and adipocyte maturation is initiated at 5-7 weeks of age, possibly coincident with sexual maturation. Targeted disruption of MT-I and MT-II genes seems to induce moderate obesity, providing a new obese animal model. A link between MT and the regulation of energy balance is implied.
This study determined the relative influences of environmental variation versus spatial autocorrelation on benthic macroinvertebrate community composition of temperate headwater streams. We enumerated fauna in riffle zones of 23 separate (i.e., not tributaries to each other) but closely grouped from first-to third-order woodland streams surrounding Zoar Valley Canyon, western New York State, USA, during spring, summer, and fall of 2006. Watershed geomorphology (stream order, catchment area, and forest cover) and semi-quantitative habitat characteristics, the latter of which were incorporated into a Qualitative Habitat Evaluation Index (QHEI), were also recorded for each stream. Non-metric Multidimensional Scaling (NMDS) ordination was used to establish patterns of biotic similarity among these streams. Matrices of biological and environmental Euclidean distances were constructed for all betweenstream pairings. Additionally, a between-stream spatial matrix was constructed based on global position system coordinates of sampling sites. Non-significant partial Mantel coefficients indicated that biological distances were uncorrelated with spatial distances both among all 23 study streams and among 12 first-order streams only. In contrast, biological distances were positively correlated with environmental distances (r M = 0.375 and 0.289 for all streams and for firstorder streams only, respectively; P values \ 0.05). Environmental and spatial distances were uncorrelated (partial Mantel P values [ 0.05), indicating that the measured environmental characteristics were not spatially structured. Each of the geomorphological and habitat variables was statistically associated with NMDS community composition axes (stepwise multiple regression, one-factor MANOVA). These results suggest that environmental filters and niche-based species sorting may operate here between separate streams, and that study sites appear to be effectively insular in their biota despite close physical proximity.
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