UNDERGROUND MORPHOLOGY AND HABITAT RELATIONSHIPS OF THREE PAIRS OF FOREST HERBS

To evaluate the ecological importance of differences in underground morphology, ten individuals per species were excavated for three species pairs in a coniferous forest in the Cascade Mountains of Oregon. The two species of each pair had similar aboveground morphologies, divergent underground morphologies, and different geographical ranges and habitat relationships. Erythronium montanum and Clintonia uniflora have one or two elliptic leaves per ramet but E. montanum has a short, segmented rhizome and only one ramet per genet, whereas C. uniflora spreads vegetatively via long rhizomes. Streptopus roseus and Smilacina stellata have similar, determinant aerial shoots and spread by long rhizomes, but S. stellata has a dimorphic root and rhizome system that allows it to occupy a wider range of habitats. Rubus pedatus and Rubus lasiococcus both spread via stolons, but R. lasiococcus has deeper roots and can occupy drier habitats than R. pedatus. The differences in underground morphology within the species pairs are consistent with the species’ geographical ranges and habitats occupied, and may be causal in determining distribution patterns.     

The Impact of Motor Axon Misdirection and Attrition on Behavioral Deficit Following Experimental Nerve Injuries

Peripheral nerve transection and neuroma-in-continuity injuries are associated with permanent functional deficits, often despite successful end-organ reinnervation. Axonal misdirection with non-specific reinnervation, frustrated regeneration and axonal attrition are believed to be among the anatomical substrates that underlie the poor functional recovery associated with these devastating injuries. Yet, functional deficits associated with axonal misdirection in experimental neuroma-in-continuity injuries have not yet been studied. We hypothesized that experimental neuroma-in-continuity injuries would result in motor axon misdirection and attrition with proportional persistent functional deficits. The femoral nerve misdirection model was exploited to assess major motor pathway misdirection and axonal attrition over a spectrum of experimental nerve injuries, with neuroma-in-continuity injuries simulated by the combination of compression and traction forces in 42 male rats. Sciatic nerve injuries were employed in an additional 42 rats, to evaluate the contribution of axonal misdirection to locomotor deficits by a ladder rung task up to 12 weeks. Retrograde motor neuron labeling techniques were utilized to determine the degree of axonal misdirection and attrition. Characteristic histological neuroma-in-continuity features were demonstrated in the neuroma-in-continuity groups and poor functional recovery was seen despite successful nerve regeneration and muscle reinnervation. Good positive and negative correlations were observed respectively between axonal misdirection (p<.0001, r²=.67), motor neuron counts (attrition) (p<.0001, r²=.69) and final functional deficits. We demonstrate prominent motor axon misdirection and attrition in neuroma-in-continuity and transection injuries of mixed motor nerves that contribute to the long-term functional deficits. Although widely accepted in theory, to our knowledge, this is the first experimental evidence to convincingly demonstrate these correlations with data inclusive of the neuroma-in-continuity spectrum. This work emphasizes the need to focus on strategies that promote both robust and accurate nerve regeneration to optimize functional recovery. It also demonstrates that clinically relevant neuroma-in-continuity injuries can now also be subjected to experimental investigation.     

Community development by forest understory plants after prolonged burial by tephra

Several processes bury plants, but sediment can also be subsequently removed, often by delayed erosion. Thus, the ability to survive multiple years of burial and to respond when released are important to vegetation changes and population dynamics. We experimentally evaluated the effects of delayed removal of tephra (aerially transported volcanic ejecta) in an old-growth forest understory near Mount St. Helens, using 1-m² plots assigned to three treatments: tephra removed 4 months after deposition (50 plots), tephra removed 28 months after deposition (the delayed erosion treatment, 50 plots), and undisturbed, natural tephra (100 plots). Prior to tephra removal, species density, cover, shoot density, and shoot size in the delayed erosion treatment were all similar to values in natural plots and significantly less than values in plots cleared initially, indicating that 24 months of additional burial adversely affected understory plants. However, all attributes eventually approached pre-eruption values for shrubs and herbs, indicating that erosion greatly facilitated vegetation recovery. Responses varied substantially among species and growth forms. Overall, our experimental results indicate that some plants of most species can respond effectively after release from burial of at least three growing seasons. In addition, the delay of erosion retards ecosystem recovery relative to early erosion, facilitates recovery relative to no erosion, and modifies the trajectory of post-disturbance vegetation change.

     

The key role of the energized state of Saccharomyces cerevisiae mitochondria in modulations of the outer membrane channels by the intermembrane space proteins

Mitochondria of the yeast Saccharomyces cerevisiae constitute a perfect model to study the outer membrane channel modulation as besides the TOM complex channel they contain only a single isoform of the VDAC channel and it is possible to obtain viable mutants devoid of the channel. Here, we report that the fraction of the intermembrane space isolated from wild type and the VDAC channel-depleted yeast mitochondria, except of the well-known VDAC channel modulator activity, displays also the TOM complex channel modulating activity as measured in the reconstituted system and with intact mitochondria. The important factor influencing the action of both modulating activities is the energized state of mitochondria. Moreover, the presence of the VDAC channel itself seems to be crucial to properties of the intermembrane space protein (s) able to modulate the outer membrane channels because in the case of intact mitochondria quantitative differences are observed between modulating capabilities of the fractions isolated from wild type and mutant mitochondria.     

Predictions of matrix‐assisted refolding of α‐lactalbumin: Process efficiency versus batch dilution method

Protein refolding is an important technique to produce active recombinant proteins from inclusion bodies. Because of the complexity of the refolding process, a trial‐and‐error method is usually used for its design, which is ineffective and time consuming. Therefore, an efficient method for the process prediction is indispensable to optimize the operating conditions. In this article, we suggest a design procedure for matrix‐assisted protein refolding. Three different chromatographic techniques were considered exploiting hydrophobic interaction chromatography, ion‐exchange chromatography, and SEC media. The procedure consisted of quantification of refolding kinetics, analysis of the retention behavior of all protein forms involved in refolding, construction of a dynamic model, and the process simulation. Denatured bovine α‐lactalbumin was used as model protein. The refolding rate was measured for different protein concentration using the batch dilution method. A kinetic scheme for the protein refolding was suggested and incorporated into a dynamic model of chromatographic column and used for predicting the refolding performance. The productivity, yield, and buffer consumption were used as performance indicators for the refolding techniques considered. The matrix‐assisted protein refolding process outperformed batch dilution method with respect to all indicators provided that efficient method for the process design was used.     

Use of polyamidoamine dendrimers to engineer BDNF-producing human mesenchymal stem cells

We report the use of polyamidoamine (PAMAM-NH₂) dendrimers along with other non-viral vehicles for the in vitro transfection of human bone marrow mesenchymal stem cells (hMSCs) and for engineering MSCs to secrete brain-derived neurotrophic factor (BDNF). Different generations of cationic polyamidoamine dendrimers (generations 3–6) were tested on HEK 293T cells. hMSCs were then transfected with PAMAM-NH₂ G4 dendrimers and Lipofectamine 2000, which elicited the expression of GFP reporter in around 6 and 20% of the cells, respectively. Both vehicles were then shown to elicit the expression of BDNF in MSCs from a bicistronic cassette. Non-virally induced neurotrophin expression may be a safe and easy method for adapting autologous stem cells for therapeutic treatment of diseases and neural system injuries.     

Structure and dynamics of an ancient montane forest in coastal British Columbia

Old-growth forests are common in the snowy, montane environments of coastal western North America. To examine dynamics of a stand containing four canopy tree species (Abies amabilis, Chamaecyparis nootkatensis, Tsuga mertensiana and T. heterophylla), we used four stem-mapped, 50 m ×50 m plots. From measurements of annual rings, we obtained ages from basal discs of 1,336 live trees, developed master chronologies for each species, reconstructed early growth rates, and delineated periods of release. The stand was ancient; individuals of all four species exceeded 900 years in age, and the oldest tree exceeded 1,400 years. The four plots differed in the timing of events, and we found no evidence of major, stand-level disturbance. Instead the stand was structured by small-scale patch dynamics, resulting from events that affected one to several trees and initiated episodes of release and relatively rapid early growth. The species differed in age structure and dynamics. A. amabilis and T. heterophylla had a classical reverse-J age structure indicative of stable populations, whereas C. nootkatensis and T. mertensiana appeared to rely on local episodes of increased recruitment, which were often separated by centuries, and were probably related to multiple-tree gaps that occurred infrequently. However, such gaps could be considered normal in the long-term history of the stand, and thus these species with their long life spans can persist. Most individuals of all four species grew extremely slowly, with trees typically spending centuries in the understory before reaching the canopy, where they were able to persist for additional centuries. Thus, the key features of this forest are the very slow dynamics dominated by small-scale events, and the slow growth of stress-tolerant trees.     

Patterns of reproductive effort in male and female shrubs of Oemleria cerasiformis: a 6-year study

1 We monitored flowering and fruiting of individual male and female plants of Oemleria cerasiformis over a 6-year period in a population in western Canada, and calculated fruit set (percentage of pistils maturing) and reproductive effort (RE) (gram of reproductive tissue per gram of leaf).
2 Over 6 years, male O. cerasiformis had on average much lower total RE, but much higher RE at flowering, than females.
3 In males, strong correlations between RE and light suggested that investment in reproduction was largely determined by light levels. There were strong positive correlations of RE between years, with no evidence of periodic fluctuations.
4 In females, in contrast to males, RE at flowering was not related to light. However, fruit set was strongly correlated with light. Flowering RE and fruit set were uncorrelated in females, indicating that these are affected by different factors.
5 Correlations of RE between years in females, although often significant, were lower than in males, indicating that RE fluctuates more between years in females than in males and may respond to past levels of RE. Flowering may reflect adjustments in response to past reproduction, or may be controlled by resources other than light. Fruit set was not significantly related to previous RE.
6 The greater total RE of females and their limited ability to adjust fruit set are probably major factors contributing to the greater mortality rates of females and the male-biased sex ratios in O. cerasiformis .