Dissecting the fibrillin microfibril: structural insights into organization and function

Force-bearing tissues such as blood vessels, lungs, and ligaments depend on the properties of elasticity and flexibility. The 10 to 12 nm diameter fibrillin microfibrils play vital roles in maintaining the structural integrity of these highly dynamic tissues and in regulating extracellular growth factors. In humans, defective microfibril function results in several diseases affecting the skin, cardiovascular, skeletal, and ocular systems. Despite the discovery of fibrillin-1 having occurred more than two decades ago, the structure and organization of fibrillin monomers within the microfibrils are still controversial. Recent structural data have revealed strategies by which fibrillin is able to maintain its architecture in dynamic tissues without compromising its ability to?interact with itself and other cell matrix components. This review summarizes our current knowledge of microfibril structure, from individual fibrillin domains and the calcium-dependent tuning of pairwise interdomain interactions to microfibril dynamics, and how this relates to microfibril function in health and disease.     

Quantifying the impact of soil compaction on root system architecture in tomato (Solanum lycopersicum) by X-ray micro-computed tomography

Background and Aims

We sought to explore the interactions between roots and soil without disturbance and in four dimensions (i.e. 3-D plus time) using X-ray micro-computed tomography.

Methods

The roots of tomato Solanum lycopersicum ‘Ailsa Craig’ plants were visualized in undisturbed soil columns for 10 consecutive days to measure the effect of soil compaction on selected root traits including elongation rate. Treatments included bulk density (1·2 vs. 1·6 g cm⁻³) and soil type (loamy sand vs. clay loam).

Key Results

Plants grown at the higher soil bulk density exploited smaller soil volumes (P < 0·05) and exhibited reductions in root surface area (P < 0·001), total root volume (P < 0·001) and total root length (P < 0·05), but had a greater mean root diameter (P < 0·05) than at low soil bulk density. Swelling of the root tip area was observed in compacted soil (P < 0·05) and the tortuosity of the root path was also greater (P < 0·01). Root elongation rates varied greatly during the 10-d observation period (P < 0·001), increasing to a maximum at day 2 before decreasing to a minimum at day 4. The emergence of lateral roots occurred later in plants grown in compacted soil (P < 0·01). Novel rooting characteristics (convex hull volume, centroid and maximum width), measured by image analysis, were successfully employed to discriminate treatment effects. The root systems of plants grown in compacted soil had smaller convex hull volumes (P < 0·05), a higher centre of mass (P < 0·05) and a smaller maximum width than roots grown in uncompacted soil.

Conclusions

Soil compaction adversely affects root system architecture, influencing resource capture by limiting the volume of soil explored. Lateral roots formed later in plants grown in compacted soil and total root length and surface area were reduced. Root diameter was increased and swelling of the root tip occurred in compacted soil.     

Factor VII-activating protease is activated in multiple trauma patients and generates anaphylatoxin C5a

Severe tissue injury results in early activation of serine protease systems including the coagulation and complement cascade. In this context, little is known about factor VII-activating protease (FSAP), which is activated by substances released from damaged cells such as histones and nucleosomes. Therefore, we have measured FSAP activation in trauma patients and have identified novel FSAP substrates in human plasma. Mass spectrometry-based methods were used to identify FSAP binding proteins in plasma. Anaphylatoxin generation was measured by ELISA, Western blotting, protein sequencing, and chemotaxis assays. Plasma samples from trauma patients were analyzed for FSAP Ag and activity, nucleosomes, C5a, and C3a. Among others, we found complement components C3 and C5 in FSAP coimmunoprecipitates. C3 and C5 were cleaved by FSAP in a dose- and time-dependent manner generating functional C3a and C5a anaphylatoxins. Activation of endogenous FSAP in plasma led to increased C5a generation, but this was not the case in plasma of a homozygous carrier of Marburg I single nucleotide polymorphism with lower FSAP activity. In multiple trauma patients there was a large increase in circulating FSAP activity and nucleosomes immediately after the injury. A high correlation between FSAP activity and C5a was found. These data suggest that activation of FSAP by tissue injury triggers anaphylatoxin generation and thereby modulates the posttraumatic inflammatory response in vivo. A strong link between C5a, nucleosomes, and FSAP activity indicates that this new principle might be important in the regulation of inflammation.     

Eulemur, me lemur: the evolution of scent-signal complexity in a primate clade

Signal complexity has been linked to social complexity in vocal, but not chemical, communication. To address this gap, we examined the chemical complexity of male and female glandular secretions in eight species of Eulemur. In this diverse clade of macrosmatic primates, species differ by social or mating system and dominance structure. We applied principal component and linear discriminate analyses to data obtained by gas chromatography/mass spectrometry. Beyond the significant effects on chemical signals of gland type, sex, season and species, we found effects of social variables and phylogeny. Notably, female odours were more chemically complex in multimale-multifemale species than pair-bonded species, whereas male odours were more chemically complex in codominant species than female-dominant species. Also, the traditional sexual dimorphism, whereby male signal complexity exceeds that of females, was present in codominant species, but reversed in female-dominant species. Lastly, a positive relationship between the species' pairwise chemical distances and their pairwise phylogenetic distances supported a gradual, but relatively fast mode of signal evolution. We suggest that the comparative method can be a powerful tool in olfactory research, revealing species differences relevant to the understanding of current signal utility and evolutionary processes. In particular, social complexity in lemurs may have selected for olfactory complexity.     

Effects of parents and Brown‐headed Cowbirds (Molothrus ater) on nest predation risk for a songbird

Nest predation limits avian fitness, so ornithologists study nest predation, but they often only document patterns of predation rates without substantively investigating underlying mechanisms. Parental behavior and predator ecology are two fundamental drivers of predation rates and patterns, but the role of parents is less certain, particularly for songbirds. Previous work reproduced microhabitat‐predation patterns experienced by Yellow Warblers (Setophaga petechia) in the Mono Lake basin at experimental nests without parents, suggesting that these patterns were driven by predator ecology rather than predator interactions with parents. In this study, we further explored effects of post‐initiation parental behavior (nest defense and attendance) on predation risk by comparing natural versus experimental patterns related to territory density, seasonal timing of nest initiation, and nest age. Rates of parasitism by Brown‐headed Cowbirds (Molothrus ater) were high in this system (49% nests parasitized), so we also examined parasitism‐predation relationships. Natural nest predation rates (NPR) correlated negatively with breeding territory density and nonlinearly (U‐shaped relationship) with nest‐initiation timing, but experimental nests recorded no such patterns. After adjusting natural‐nest data to control for these differences from experimental nests other than the presence of parents (e.g., defining nest failure similarly and excluding nestling‐period data), we obtained similar results. Thus, parents were necessary to produce observed patterns. Lower natural NPR compared with experimental NPR suggested that parents reduced predation rates via nest defense, so this parental behavior or its consequences were likely correlated with density or seasonal timing. In contrast, daily predation rates decreased with nest age for both nest types, indicating this pattern did not involve parents. Parasitized nests suffered higher rates of partial predation but lower rates of complete predation, suggesting direct predation by cowbirds. Explicit behavioral research on parents, predators (including cowbirds), and their interactions would further illuminate mechanisms underlying the density, seasonal, and nest age patterns we observed.     

Recovery effects of hyperoxic gas inhalation or contrast water immersion on the postexercise cytokine response, perceptual recovery, and next day exercise performance

The effect of different recovery modalities on the postexercise cytokine response, perceptual recovery, and subsequent day athletic performance were investigated. Eight highly trained athletes completed 3 swimming sessions consisting of 20 × 200 m efforts, in a counterbalanced repeated-measures design. At the conclusion of each session, athletes undertook a 30-minute recovery intervention of contrast water therapy (CWT), supplemental oxygen (HYP), or passive rest (CON). Venous blood samples were analyzed for levels of interleukin-6 (IL-6) at the pre-, post-, and 30-minute postswim time points, and a rating of perceived recovery was recorded at the conclusion of the 30-minute intervention and upon returning to the pool 12 hour later. Finally, a 200-m swim time trial was completed as a measure of next day performance. The results showed that there was a significant increase in IL-6 at the completion of exercise, which persisted after 30 minutes of recovery (p < 0.05), with no differences evident between the groups. Additionally, the perception of recovery after the 30-minute intervention was significantly lower in the CON when compared with the CWI and HYP (p < 0.05). However, there were no differences in the 12-hour postrecovery time trial performances. These results suggest that a 30-minute recovery intervention using CWT or HYP has limited influence on the acute-phase response or on improving subsequent day athletic performance. However, strength and conditioning specialists should encourage the use of a structured postexercise recovery procedure because the evidence suggests that the acute perception of recovery is much greater when some form of intervention is implemented in comparison with no recovery procedure at all.     

Measurement of arthropod body composition using quantitative magnetic resonance

Quantitative magnetic resonance (QMR) is a new technology for measuring the body composition (wet lean mass, fat mass, and total body water mass) of unrestrained and unanesthetized animals. We conducted a validation study using two species of crayfish (mass range 5.5–27 g), American lobsters (680–732 g), and Madagascar hissing cockroaches (6.5–14 g) to assess the utility of QMR for quantifying the body composition of crustaceans and other large arthropods. A comparison of crayfish, lobster, and cockroach wet lean, fat, and body water masses calculated by QMR with those obtained from the traditional chemical extraction method demonstrates that QMR is a valid technology for analysis of wet lean mass and body water. Fat mass could not be accurately predicted, although this might be improved with the use of a QMR analyzer designed specifically for animals of low fat content. QMR analysis allows rapid (<4 min) and non‐destructive determination of body composition in field and lab environments, enabling researchers to conduct longitudinal studies and to increase the ethicality and practicality of studying rare or threatened species.