Low level Atrazine exposure effects on crayfish development

Undergraduate Applie

The Effects of Common Herbicide (Atrazine) on Juvenile Crayfish Growth and Development

Undergraduate Basi

Role of insulin-like growth factor binding proteins in human post-nephrectomy proximal tubule cells

In order to determine the role of the insulin-like growth factor-I (IGF-I)/IGF binding protein (IGFBP) axis in the augmentation of tubule growth and function following reductions in nephron mass, primary cultures of human proximal tubule cells (PTCs) were generated from the histologically normal sections of ten surgically removed kidneys.PTC hypertrophy (cellular protein content), DNA synthesis (thymidine incorporation) and apical sodium-hydrogen exchange (NHE) activity (ethylisopropylamiloride-sensitive apical 22Na+ uptake) were measured following 24 h incubation in media supplemented with 10% pre- or post-nephrectomy sera obtained from these patients. The results were compared with the effects of pre- and post-operative control sera collected from seven patients undergoing retroperitoneal operations not involving removal of renal tissue.Day 1 post-nephrectomy sera promoted a significant 73% increase in apical NHE activity, which was accompanied by a significant increase in PTC binding of 125I-IGF-I (post- vs. pre-nephrectomy, 163 ± 6 vs. 142 ± 4 fmol (mg protein)−1; P < 0.05). Subsequent post-nephrectomy sera significantly stimulated PTC protein content and thymidine incorporation, peaking at day 7 (127.7 ± 14.0 and 118.4 ± 9.0% of pre-nephrectomy values, respectively; P < 0.05). The growth effects were cell specific, as they were not observed with renal cortical fibroblasts. No change was detected in any of these measured variables following exposure to control sera.Serum IGF-I and IGFBP-1 levels did not significantly change over time or between groups. IGFBP-3 levels progressively decreased in both control and nephrectomized sera from pre-operative values of 3580 ± 305 and 3360 ± 217 ng ml−1, respectively, to 2670 ± 341 and 2600 ± 347 ng ml−1 at 1 week post-operation. Serum IGFBP-2 levels increased to a comparable extent in both controls (day 0 vs. day 7, 2940 ± 1024 vs. 7010 ± 2520 ng ml−1; P < 0.01) and nephrectomized patients (day 0 vs. day 7, 3070 ± 656 vs. 9130 ± 2010 ng ml−1; P < 0.01).The results indicate that nephrectomy engenders the elaboration of one or more humoral factor(s), which promotes increased binding of IGF-I to PTCs and which may in turn specifically stimulate PTC Na+ transport and growth

Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth