Biological synthesis of platinum nanoparticles with apoferritin

A novel biological method for the synthesis of platinum nanoparticles using the horse spleen apoferritin (HSAF) is reported. When HSAF was incubated with K₂PtCl₆ at 23°C) for 48 h followed by subsequent reduction with NaBH₄ it resulted in the formation of spherical platinum nanoparticles, size 4.7 ± 0.9 nm, with narrow particle size distribution confirmed by transmission electron microscopy and energy dispersive X-ray analysis. As the initial platinum concentration increased through 0.155, 0.31, 0.465 to 0.62 mM the efficiency of its removal from solution by the apoferritin was 99, 99, 84 and 71% respectively. The maximum uptake of platinum salt per mM apoferritin was estimated at 12.7 mmol l⁻¹ h⁻¹. These results clearly indicate that the HSAF protein cage can successfully serve as a suitable size-constrained support matrix for the biological synthesis of platinum nanoparticles.     

Ectopic expression of a genomic fragment containing a homeobox causes neural defects in the axolotl.

An axolotl (Ambystoma mexicanum) genomic fragment containing the Ahox1 homeobox was placed under the control of the mouse hsp68 promoter, which seems to function constitutively in the axolotl. The resulting construct was injected into fertilized axolotl eggs to see if it would perturb development. Of the injected embryos, 20% showed severe reduction of the anterior neural plate. Later in development, these embryos had small heads, no eyes, and appeared to lack the normal regionalization of the brain. An additional 35% of the embryos were less severely affected, but had reduced or missing eyes. Control embryos, including ones injected with a construct missing the DNA recognition helix of the homeobox, developed normally.     

Distance,flow and PCR inhibition: eDNA dynamics in two headwater streams

Environmental DNA (eDNA) detection has emerged as a powerful tool for monitoring aquatic organisms, but much remains unknown about the dynamics of aquatic eDNA over a range of environmental conditions. DNA concentrations in streams and rivers will depend not only on the equilibrium between DNA entering the water and DNA leaving the system through degradation, but also on downstream transport. To improve understanding of the dynamics of eDNA concentration in lotic systems, we introduced caged trout into two fishless headwater streams and took eDNA samples at evenly spaced downstream intervals. This was repeated 18 times from mid‐summer through autumn, over flows ranging from approximately 1–96 L/s. We used quantitative PCR to relate DNA copy number to distance from source. We found that regardless of flow, there were detectable levels of DNA at 239.5 m. The main effect of flow on eDNA counts was in opposite directions in the two streams. At the lowest flows, eDNA counts were highest close to the source and quickly trailed off over distance. At the highest flows, DNA counts were relatively low both near and far from the source. Biomass was positively related to eDNA copy number in both streams. A combination of cell settling, turbulence and dilution effects is probably responsible for our observations. Additionally, during high leaf deposition periods, the presence of inhibitors resulted in no amplification for high copy number samples in the absence of an inhibition‐releasing strategy, demonstrating the necessity to carefully consider inhibition in eDNA analysis.     

Effective number of breeders provides a link between interannual variation in stream flow and individual reproductive contribution in a stream salmonid

The effective number of breeders that give rise to a cohort (N_b) is a promising metric for genetic monitoring of species with overlapping generations; however, more work is needed to understand factors that contribute to variation in this measure in natural populations. We tested hypotheses related to interannual variation in N_b in two long‐term studies of brook trout populations. We found no supporting evidence for our initial hypothesis that reflects (defined as the number of adults in a population at the time of reproduction). was stable relative to and did not follow trends in abundance (one stream negative, the other positive). We used stream flow estimates to test the alternative hypothesis that environmental factors constrain N_b. We observed an intermediate optimum autumn stream flow for both (R² = 0.73, P = 0.02) and full‐sibling family evenness (R² = 0.77, P = 0.01) in one population and a negative correlation between autumn stream flow and full‐sib family evenness in the other population (r = ?0.95, P = 0.02). Evidence for greater reproductive skew at the lowest and highest autumn flow was consistent with suboptimal conditions at flow extremes. A series of additional tests provided no supporting evidence for a related hypothesis that density‐dependent reproductive success was responsible for the lack of relationship between N_b and N_C (so‐called genetic compensation). This work provides evidence that N_b is a useful metric of population‐specific individual reproductive contribution for genetic monitoring across populations and the link we provide between stream flow and N_b could be used to help predict population resilience to environmental change.     

Pronounced differences in genetic structure despite overall ecological similarity for two Ambystoma salamanders in the same landscape

Studies linking genetic structure in amphibian species with ecological characteristics have focused on large differences in dispersal capabilities. Here, we test whether two species with similar dispersal potential but subtle differences in other ecological characteristics also exhibit strong differences in genetic structure in the same landscape. We examined eight microsatellites in marbled salamanders (Ambystoma opacum) from 29 seasonal ponds and spotted salamanders (Ambystoma maculatum) from 19 seasonal ponds in a single geographic region in west-central Massachusetts. Despite overall similarity in ecological characteristics of spotted and marbled salamanders, we observed clear differences in the genetic structure of these two species. For marbled salamanders, we observed strong overall genetic differentiation (F _ST = 0.091, F′ _ST = 0.375), three population-level clusters of populations (K = 3), a strong pattern of isolation by distance (r = 0.58), and marked variation in family-level structure (from 1 to 23 full-sibling families per site). For spotted salamanders, overall genetic differentiation was weaker (F _ST = 0.025, F′ _ST = 0.102), there was no evidence of population-level clustering (K = 1), the pattern of isolation by distance (r = 0.17) was much weaker compared to marbled salamanders, and there was less variation in family-level structure (from 10 to 36 full-sibling families per site). We suspect that a combination of breeding site fidelity, effective population size, and generation interval is responsible for these marked differences. Our results suggest that marbled salamanders, compared to spotted salamanders, are more sensitive to fragmentation from various land-use activities and would be less likely to recolonize extirpated sites on an ecologically and conservation-relevant time frame.     

Arginine deiminases: Therapeutic tools in the etiology and pathogenesis of Alzheimer's disease

There is, at present, no definitive pre-mortem diagnostic tool for Alzheimer's disease, (AD) which relates to a poor understanding of its etiology. Brains of AD patients contain large amounts of the toxic plaque-forming β-amyloid_1–42 fragment in addition to elevated concentrations of the amino acid l-arginine. This work proposes that lowering levels of arginine in the astrocytes surrounding amyloid plaques may serve as a therapeutic tool in this neurodegenerative disorder. Arginine deiminase (ADI), from Pseudomonas aeruginosa, and peptidylarginine deiminase [PAD II], from bovine brain, are inhibited by amyloid peptides that contain arginine (amyloid_1–42) and those that have no arginine (amyloid_{12–28/22–35}). Enhanced activity of PAD II is noted with free l-arginine.