Structural investigations of the extracellular polysaccharides elaborated by Beijerinckia mobilis

The extracellular mucilage from Beijerinckia mobilis, a member of the Azotobacteriaceae, after removal of contaminating protein, was separated into a neutral polysaccharide (N-2, 10%); a neutral, dialysable fraction (N-1, 5%), consisting of glucose and oligosaccharides containing glucose, arabinose, and rhamnose; and an acidic polysaccharide (85%). N-2 (mol. wt, 1900) was highly branched and comprised glucopyranose, mannopyranose, and arabinofuranose residues (1:1:1). The various linkages were determined. The acid fraction was a polymer of high molecular weight composed of L-guluronic acid (65%), D-glucose (15%), and D-glycero-D-mannoheptose (20%), together with acetic and pyruvic acids. From the results of methylation, periodate oxidation, and partial hydrolysis, a branched molecule with a backbone of guluronic acid and heptose, and side chains of glucose and guluronic acid is proposed. Pyruvic acid was found to be acetal-linked to 2?5% of the heptose residues. The similarities between this polysaccharide and that from the related species Azotobacter indicum are discussed.     

Polymorphism and linkage of glutathione reductase in Mus musculus

Using an electrophoretic variant for glutathione reductase, we have been able to map the structural gene for this enzyme to chromosome 8 in Mus musculus.     

Leaf structure and function in evergreen trees and shrubs of Japanese warm temperate rain forest I. The structure of the lamina

Information has been obtained as a part of a wider study of leaf structure, water relations and mineral status, which is to include work on a considerable variety of evergreen forests. Fifteen structural features have been investigated in well-lit leaves of 60 dicotyledonous species of Japanese Warm Temperate Rain Forest, this sample giving an 81% cover of the relevant species (Table 1). The salient features of the average leaf are summarised on p. 200. The leaves of shrubs and small trees have been compared with those of tall and medium trees; some of the differences were unexpected. For example, the leaves of the lower growing species tended to be thicker and to have thicker outer walls. The leaves of the whole Japanese sample were compared with those of 40 species in Tropical Lowland Rain Forest in New Britain. Although the average leaf area of the Japanese species was less than one tenth of that of the species from New Britain, the thickness and internal structure of the leaf and the size and density of the stomata were quite similar in the two sets of leaves (Table 2). The Japanese leaves were somewhat more xeromorphic in that they had thicker outer walls in the upper and lower epidermis.     

Time course changes to structural,mechanical and material properties of bone in rats after complete spinal cord injury

Objective:Characterise the spatiotemporal trabecular and cortical bone responses to complete spinal cord injury (SCI) in young rats.Methods:8-week-old male Wistar rats received T9-transection SCI and were euthanised 2-, 6-, 10- or 16-weeks post-surgery. Outcome measures were assessed using micro-computed tomography, mechanical testing, serum markers and Fourier-transform infrared spectroscopy.Results:The trabecular and cortical bone responses to SCI are site-specific. Metaphyseal trabecular BV/TV was 59% lower, characterised by fewer and thinner trabeculae at 2-weeks post-SCI, while epiphyseal BV/TV was 23% lower with maintained connectivity. At later-time points, metaphyseal BV/TV remained unchanged, while epiphyseal BV/TV increased. The total area of metaphyseal and mid-diaphyseal cortical bone were lower from 2-weeks and between 6- and 10-weeks post-SCI, respectively. This suggested that SCI-induced bone changes observed in the rat model were not solely attributable to bone loss, but also to suppressed bone growth. No tissue mineral density differences were observed at any time-point, suggesting that decreased whole-bone mechanical properties were primarily the result of changes to the spatial distribution of bone.Conclusion:Young SCI rat trabecular bone changes resemble those observed clinically in adult and paediatric SCI, while cortical bone changes resemble paediatric SCI only.     

The Neisseria gonorrhoeae type IV pilus promotes resistance to hydrogen peroxide- and LL-37-mediated killing by modulating the availability of intracellular,labile iron

The Neisseria gonorrhoeae Type IV pilus is a multifunctional, dynamic fiber involved in host cell attachment, DNA transformation, and twitching motility. We previously reported that the N. gonorrhoeae pilus is also required for resistance against hydrogen peroxide-, antimicrobial peptide LL-37-, and non-oxidative, neutrophil-mediated killing. We tested whether the hydrogen peroxide, LL-37, and neutrophil hypersensitivity phenotypes in non-piliated N. gonorrhoeae could be due to elevated iron levels. Iron chelation in the growth medium rescued a nonpiliated pilE mutant from both hydrogen peroxide- and antimicrobial peptide LL-37-mediated killing, suggesting these phenotypes are related to iron availability. We used the antibiotic streptonigrin, which depends on free cytoplasmic iron and oxidation to kill bacteria, to determine whether piliation affected intracellular iron levels. Several non-piliated, loss-of-function mutants were more sensitive to streptonigrin killing than the piliated parental strain. Consistent with the idea that higher available iron levels in the under- and non-piliated strains were responsible for the higher streptonigrin sensitivity, iron limitation by desferal chelation restored resistance to streptonigrin in these strains and the addition of iron restored the sensitivity to streptonigrin killing. The antioxidants tiron and dimethylthiourea rescued the pilE mutant from streptonigrin-mediated killing, suggesting that the elevated labile iron pool in non-piliated bacteria leads to streptonigrin-dependent reactive oxygen species production. These antioxidants did not affect LL-37-mediated killing. We confirmed that the pilE mutant is not more sensitive to other antibiotics showing that the streptonigrin phenotypes are not due to general bacterial envelope disruption. The total iron content of the cell was unaltered by piliation when measured using ICP-MS suggesting that only the labile iron pool is affected by piliation. These results support the hypothesis that piliation state affects N. gonorrhoeae iron homeostasis and influences sensitivity to various host-derived antimicrobial agents.     

Quantification of microtubule stutters: dynamic instability behaviors that are strongly associated with catastrophe

Microtubules (MTs) are cytoskeletal fibers that undergo dynamic instability (DI), a remarkable process involving phases of growth and shortening separated by stochastic transitions called catastrophe and rescue. Dissecting DI mechanism(s) requires first characterizing and quantifying these dynamics, a subjective process that often ignores complexity in MT behavior. We present a Statistical Tool for Automated Dynamic Instability Analysis (STADIA) that identifies and quantifies not only growth and shortening, but also a category of intermediate behaviors that we term “stutters.” During stutters, the rate of MT length change tends to be smaller in magnitude than during typical growth or shortening phases. Quantifying stutters and other behaviors with STADIA demonstrates that stutters precede most catastrophes in our in vitro experiments and dimer-scale MT simulations, suggesting that stutters are mechanistically involved in catastrophes. Related to this idea, we show that the anticatastrophe factor CLASP2γ works by promoting the return of stuttering MTs to growth. STADIA enables more comprehensive and data-driven analysis of MT dynamics compared with previous methods. The treatment of stutters as distinct and quantifiable DI behaviors provides new opportunities for analyzing mechanisms of MT dynamics and their regulation by binding proteins.     

Normalized cDNA libraries from a porcine model of orthopedic implant-associated infection

Staphylococcal infections that result from an alteration in a patient's immune response at the surgical site are a major problem in procedures that incorporate biomaterials in trauma surgery and joint replacement. Diagnosis of infection based on pathogen detection is difficult and exacerbated by increasing numbers of partially or totally resistant strains of nosocomial pathogens, particularly Staphylococcus aureus. Expression profiling of a host's cellular immune response could facilitate the identification of the pathways involved in pathogen recognition and eradication and could lead to more rational design of drugs and therapies. To this end, we constructed and characterized ten individually tagged and directionally cloned cDNA libraries from peripheral blood cells (PBC), spleen (Sp), thymus (Th), lymph node (LN), and bone marrow (BM) from immunologically naive and challenged pigs as part of an implant-associated orthopedic model of deep infection. Three of these libraries were normalized at C _{0 t} values 5, 10, 20, and 30. The libraries comprise more than 20 million primary transformants with an average insert length >1.4 kb. Cluster analysis of 7620 ESTs revealed 1029 clusters containing an average of 3.6 sequences and 3846 singletons. Gene discovery is estimated to be ∼64%. Searches of public databases resulted in 49.3% annotated porcine sequences, of which 22.2% had significant homologies to ESTs from a variety of species, and 28.5% were without a significant match in any public database. We also identified 9.1% ESTs as involved in host cell and organism defense and 11.5% related to cell signaling and communication. These sequences, together with the 28.5% appearing as novel, are of specific interest to the infectious disease process.     

Beyond ecosystem modeling: A roadmap to community cyberinfrastructure for ecological data‐model integration

In an era of rapid global change, our ability to understand and predict Earth's natural systems is lagging behind our ability to monitor and measure changes in the biosphere. Bottlenecks to informing models with observations have reduced our capacity to fully exploit the growing volume and variety of available data. Here, we take a critical look at the information infrastructure that connects ecosystem modeling and measurement efforts, and propose a roadmap to community cyberinfrastructure development that can reduce the divisions between empirical research and modeling and accelerate the pace of discovery. A new era of data‐model integration requires investment in accessible, scalable, and transparent tools that integrate the expertise of the whole community, including both modelers and empiricists. This roadmap focuses on five key opportunities for community tools: the underlying foundations of community cyberinfrastructure; data ingest; calibration of models to data; model‐data benchmarking; and data assimilation and ecological forecasting. This community‐driven approach is a key to meeting the pressing needs of science and society in the 21st century.