Photosynthetic pathway influences xylem structure and function in Flaveria (Asteraceae)

Higher water use efficiency (WUE) in C(4) plants may allow for greater xylem safety because transpiration rates are reduced. To evaluate this hypothesis, stem hydraulics and anatomy were compared in 16 C(3), C(3)-C(4) intermediate, C(4)-like and C(4) species in the genus Flaveria. The C(3) species had the highest leaf-specific conductivity (K(L)) compared with intermediate and C(4) species, with the perennial C(4) and C(4)-like species having the lowest K(L) values. Xylem-specific conductivity (K(S)) was generally highest in the C(3) species and lower in intermediate and C(4) species. Xylem vessels were shorter, narrower and more frequent in C(3)-C(4) intermediate, C(4)-like and C(4) species compared with C(3) species. WUE values were approximately double in the C(4)-like and C(4) species relative to the C(3)-C(4) and C(3) species. C(4)-like photosynthesis arose independently at least twice in Flaveria, and the trends in WUE and K(L) were consistent in both lineages. These correlated changes in WUE and K(L) indicate WUE increase promoted K(L) decline during C(4) evolution; however, any involvement of WUE comes late in the evolutionary sequence. C(3)-C(4) species exhibited reduced K(L) but little change in WUE compared to C(3) species, indicating that some reduction in hydraulic efficiency preceded increases in WUE.     

Sources of nonlinearity in cDNA microarray expression measurements

Background  

A key assumption in the analysis of microarray data is that the quantified signal intensities are linearly related to the expression levels of the corresponding genes. To test this assumption, we experimentally examined the relationship between signal and expression for the two types of microarrays we most commonly encounter: radioactively labeled cDNAs on nylon membranes and fluorescently labeled cDNAs on glass slides.     

Phylogeography of Sula: the role of physical barriers to gene flow in the diversification of tropical seabirds

We examined mitochondrial cytochrome b sequence variation in masked Sula dactylatra , red-footed S. sula , and brown S. leucogaster boobies sampled from islands in the central and eastern Pacific Ocean and in the Caribbean Sea. Each species showed a different phylogeographic pattern. Whereas haplotypes in masked and red-footed boobies were shared across the central and eastern Pacific (i.e., across the Eastern Pacific Basin), brown booby haplotypes were not shared across the Eastern Pacific Basin. Although most masked booby haplotypes from the Pacific were distinct from those in the Caribbean, one haplotype was shared across the Isthmus of Panama. Red-footed and brown boobies, however, did not share haplotypes across the Isthmus of Panama. We estimate that divergence of these regional populations occurred within the last 560,000 years. Thus, the Isthmus of Panama and the Eastern Pacific Basin (albeit to a lesser degree) appear to have played a role in the diversification of these species.     

Stigmatic Self-Incompatibility and Mating Patterns in Trillium grandiflorum and Trillium erectum(Melanthiaceae)

Post-pollination processes governing mating patterns in Trillium,a well-known genus of insect-pollinated woodland herbs, arepoorly understood. Mechanisms influencing outcrossing were investigatedin T. grandiflorum and T. erectum, two widespread species nativeto eastern North America. In southern Ontario, Canada, the twospecies are often sympatric; they flower in early May, and arepollinated by different assemblages of insects. Controlled cross-and self-pollinations and structural observations of pollengermination and pollen tube growth were conducted to determinewhether the two species possess a self-incompatibility (SI)system and, if so, the specific site(s) of self-rejection. Controlledpollinations indicated that both species set significantly moreseeds from cross-pollination than self-pollination, implicatingthe action of SI. This was confirmed by structural studies whichdemonstrated that self-recognition and rejection reactions occurredon dry-type stigmatic papillae. Observations of pollen hydrationrevealed that self-rejection was rapid, being initiated within10 min of pollination and prior to pollen tube emergence. Finalself-rejection resulted in failure of pollen tube growth atthe base of stigmatic papillae. SI was expressed more weaklyin T. erectum and thereby resulted in considerable self-seedset in some individuals . Estimates of outcrossing rates usingallozyme markers indicated that T. erectum displayed a mixed-matingsystem whereas T. grandiflorum was more highly outcrossed. Structuralstudies of pollen traits indicated that the two species differedwith respect to the size of grains and their aggregation withimplications for pollen dispersal and mating. The ecologicaland evolutionary implications of the variable expression ofSI in Trillium are discussed. Copyright 2001 Annals of BotanyCompany Trillium grandiflorum, Trillium erectum, self-incompatibility, mating     

A validated model of passive skeletal muscle to predict force and intramuscular pressure

The passive properties of skeletal muscle are often overlooked in muscle studies, yet they play a key role in tissue function in vivo. Studies analyzing and modeling muscle passive properties, while not uncommon, have never investigated the role of fluid content within the tissue. Additionally, intramuscular pressure (IMP) has been shown to correlate with muscle force in vivo and could be used to predict muscle force in the clinic. In this study, a novel model of skeletal muscle was developed and validated to predict both muscle stress and IMP under passive conditions for the New Zealand White Rabbit tibialis anterior. This model is the first to include fluid content within the tissue and uses whole muscle geometry. A nonlinear optimization scheme was highly effective at fitting model stress output to experimental stress data (normalized mean square error or NMSE fit value of 0.993) and validation showed very good agreement to experimental data (NMSE fit values of 0.955 and 0.860 for IMP and stress, respectively). While future work to include muscle activation would broaden the physiological application of this model, the passive implementation could be used to guide surgeries where passive muscle is stretched.     

Analysis of the Murine Immune Response to Pulmonary Delivery of Precisely Fabricated Nano- and Microscale Particles

Nanomedicine has the potential to transform clinical care in the 21^st century. However, a precise understanding of how nanomaterial design parameters such as size, shape and composition affect the mammalian immune system is a prerequisite for the realization of nanomedicine''s translational promise. Herein, we make use of the recently developed Particle Replication in Non-wetting Template (PRINT) fabrication process to precisely fabricate particles across and the nano- and micro-scale with defined shapes and compositions to address the role of particle design parameters on the murine innate immune response in both in vitro and in vivo settings. We find that particles composed of either the biodegradable polymer poly(lactic-co-glycolic acid) (PLGA) or the biocompatible polymer polyethylene glycol (PEG) do not cause release of pro-inflammatory cytokines nor inflammasome activation in bone marrow-derived macrophages. When instilled into the lungs of mice, particle composition and size can augment the number and type of innate immune cells recruited to the lungs without triggering inflammatory responses as assayed by cytokine release and histopathology. Smaller particles (80×320 nm) are more readily taken up in vivo by monocytes and macrophages than larger particles (6 µm diameter), yet particles of all tested sizes remained in the lungs for up to 7 days without clearance or triggering of host immunity. These results suggest rational design of nanoparticle physical parameters can be used for sustained and localized delivery of therapeutics to the lungs.     

Complete nucleotide sequence of a cryptic plasmid, pbaw301, from the ruminai anaerobe Ruminococcus flavefaciens R13e2

Abstract The complete nucleotide sequence of a cryptic plasmid designated pBAW301, from the Gram-positive ruminai bacterium Ruminococcus flavefaciens R13e2, has been determined. This plasmid is 1768 bp in size and has an overall G+C content of 43.5%. Computer analysis of the sequence data revealed an open reading frame, ORF1 (256 amino acids), which is similar to the Rep protein of the Bacillus borstelensis plasmid pHT926. ORF1 is preceded by Shine-Dalgarno and Escherichia coli —10 and —35 like sequences. Nine smaller open reading frames showed no significant homologies to known protein sequences. Analysis of replication intermediates and the nucleotide sequence indicate that the plasmid does not replicate by a rolling-circle mode of replication similar to other plasmids from Gram-positive bacteria. Moreover, sequences typical of theta replication origins were not found in the nucleotide sequence of pBAW301. These data suggest that this plasmid either replicates by an as yet undescribed mechanism, or represents a new class of theta replicating plasmids.