Effects of boric acid supplementation on bone histomorphometry,metabolism, and biomechanical properties in aged female F-344 rats

Postmenopausal women may benefit from dietary interventions in order to increase bone strength and prevent fractures. Dietary boron (B) may be beneficial for optimal calcium metabolism and, as a consequence, optimal bone metabolism. The present study evaluated the effects of boron, in the form of boric acid, with or without 17β-estradiol (E₂) supplementation (via subcutaneous implant), in ovariectomized (OVX) aged 13-mo-old F-344 rats. Boric acid was administered by gavage at a subtoxic dose (8.7 mg B/kg/d) for 40 d. Results indicate that serum level of minerals as well as osteocalcin (a marker of bone resorption) are dependent to a greater extent on the hormonal status of the animals than on boron supplementation. Boron treatment increased the E₂-induced elevation of urinary calcium and magnesium. Bone mineral density (BMD) of the L5 vertebra and proximal femur was highest in the E₂-treated groups; no increase in BMD was conferred by boron treatment. By histomorphometry of the proximal tibial metaphysis, osteoblastic, osteoid, and eroded surfaces were significantly suppressed by E₂ treatment, but not by boron treatment. In biomechanical testing of femur and vertebra, neither E₂ nor boron treatment significantly increased bone strength. At the levels given, boron alone provided no protection against OVX-induced osteopenia. In addition, combination therapy (B + E₂) provided no additional benefits over those of 17β-estradiol treatment alone in this aged rat model.     

Cell wall polysaccharides from Gelidium species: physico-chemical studies using MRI techniques

Magnetic resonance imaging (MRI) has already been successively used to investigate polysaccharide matrices. In particular, MRI at microscopic resolution (MR microscopy) is now one of the most powerful techniques for studying the physical properties of natural hydrogels. To contribute to a better understanding of the correlation between chemical and physical properties of agar gels, we report here the measurement of the water magnetic parameters for agar gels extracted from different species of Gelidium: T1 and T2 relaxation times, magnetisation transfer (Ms /M0) and diffusion (D) were measured to evaluate their use for studying the gel characteristics. MR microscopic images were acquired at 7.05 Tesla using various pulse sequences. The results obtained confirmed the possibility to use quantitative MRI for the characterisation of physical parameters correlated with the type of agar chemical structure. In particular, T2 data obtained for gels at different concentrations indicate that this magnetic parameter is very sensitive to the agar concentration and hence particularly useful for the gel strength determination. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct measurement of the adhesive strength of biofilms in pipes by micromanipulation

A novel micromanipulation technique has been developed to measure directly the adhesive strength of biofilms formed in pipe flows. A T-shaped probe was specially designed to pull Pseudomonas fluorescens biofilms away from the inner surface of a pipe to which they were attached. The adhesive strength between biofilms and the substratum was defined as the work required to remove the biofilms per unit area from the substratum. Results showed that the adhesive strength increased with the fluid velocity in which the biofilms were grown, with a typical value of 0.050.2 J/m2. © Rapid Science Ltd. 1998     

An alternative method for serum protein depletion/enrichment by precipitation at mildly acidic pH values and low ionic strength

Serum proteome analysis is severely hampered by the extreme dynamic range of protein concentrations, but tools for the specific depletion of highly abundant serum proteins lack for most farm and companion animals. A well‐established alternative strategy to reduce the dynamic range of plasma protein concentrations, treatment with combinatorial peptide ligand libraries (CPLL), is generally applicable but requires large amounts of sample. Therefore, additional depletion/enrichment protocols for plasma and serum samples from animals are desirable. In this respect, we have tested a protein precipitate that formed after withdrawal of salt from human, bovine, or porcine serum at pH 4.2. The bovine sample was composed of over 300 proteins making it a potential source for biomarker discovery. Precipitation was highly reproducible and the concentrations of albumin and other highly abundant serum proteins were strongly reduced. In comparison to the CPLL treatment, precipitation did not introduce any selection bias based on hydrophathy or pI. However, the composition of both preparations was partially complementary. Salt withdrawal at pH 4.2 is suggested as additional depletion/enrichment strategy for serum samples. Also, we point out that the removal of precipitates from serum samples under the described conditions bears the risk of losing a valuable protein fraction.     

Wind‐mediated horseweed (Conyza canadensis) gene flow: pollen emission,dispersion, and deposition

Horseweed (Conyza canadensis) is a problem weed in crop production because of its evolved resistance to glyphosate and other herbicides. Although horseweed is mainly self-pollinating, glyphosate-resistant (GR) horseweed can pollinate glyphosate-susceptible (GS) horseweed. To the best of our knowledge, however, there are no available data on horseweed pollen production, dispersion, and deposition relative to gene flow and the evolution of resistance. To help fill this knowledge gap, a 43-day field study was performed in Champaign, Illinois, USA in 2013 to characterize horseweed atmospheric pollen emission, dispersion, and deposition. Pollen concentration and deposition, coupled with atmospheric data, were measured in a source field (180 m by 46 m) and its surrounding areas up to 1 km downwind horizontally and up to 100 m vertically. The source strength (emission rate) ranged from 0 to 140 pollen grains per plant per second (1170 to 2.1×10⁶ per plant per day). For the life of the study, the estimated number of pollen grains generated from this source field was 10.5×10¹⁰ (2.3×10⁶ per plant). The release of horseweed pollen was not strongly correlated to meteorological data and may be mainly determined by horseweed physiology. Horseweed pollen reached heights of 80 to100 m, making long-distance transport possible. Normalized (by source data) pollen deposition with distance followed a negative-power exponential curve. Normalized pollen deposition was 2.5% even at 480 m downwind from the source edge. Correlation analysis showed that close to or inside the source field at lower heights (≤3 m) vertical transport was related to vertical wind speed, while horizontal pollen transport was related to horizontal wind speed. High relative humidity prevented pollen transport at greater heights (3–100 m) and longer distances (0–1000 m) from the source. This study can contribute to the understanding of how herbicide-resistance weeds or invasive plants affect ecology through wind-mediated pollination and invasion.     

Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin

doi:10.1111/j.1741‐2358.2009.00292.x
Effect of reline material and denture base surface treatment on the impact strength of a denture base acrylic resin Objective: In this study, the effect of relining and surface treatment on the impact strength (IS) of a heat‐polymerising denture base acrylic resin (Lucitone 550‐L) was evaluated. Materials and methods: Rectangular bars of L were made (60 × 6 × 2 mm) and relined (2 mm) with the relining resins Ufi Gel Hard (UH) and Tokuso Rebase Fast (TR). Specimens relined with L and intact L, TR and UH specimens were also made (60 × 6 × 4 mm), for comparison. Before relining, the L surface was left untreated or wetted with methyl methacrylate monomer and/or the bonding agents (BA) supplied by manufacturers of the reline resins. V‐notches were machined at the midpoint of the length of all specimens. The notches were made either across the width (Nw) or across the thickness of the specimens (Nth). The Charpy impact test was performed using a 0.5‐J pendulum, which had been specially designed and constructed. Data were analysed separately for each notch position using one‐way analysis of variance and Tukey honestly significant difference post‐hoc test (p = 0.05). Results: The IS of L was similar to that of L/L. For the Nw notch, treating the denture base L with TR BA and relining with TR reline material produced the highest IS. Conclusion: The IS of specimens made from heat polymerising acrylic resin Lucitone 550 was increased after relining using the hard chairside reline resin TR with its proprietary BA.     

Beta sheet 2–alpha helix C loop of cytochrome P450 reductase serves as a docking site for redox partners

As a promiscuous redox partner, the biological role of cytochrome P450 reductase (CPR) depends significantly on protein–protein interactions. We tested a hypothesized CPR docking site by mutating D113, E115, and E116 to alanine and assaying activity toward various electron acceptors as a function of ionic strength. Steady-state cytochrome c studies demonstrated the mutations improved catalytic efficiency and decreased the impact of ionic strength on catalytic parameters when compared to wild type. Based on activity toward 7-ethoxy-4-trifluoro-methylcoumarin, CYP2B1 and CPR favored formation of an active CYP2B1•CPR complex and inactive (CYP2B1)₂•CPR complex until higher ionic strength whereby only the binary complex was observed. The mutations increased dissociation constants only for the binary complex and suppressed the ionic strength effect. Studies with a non-binding substrate, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) suggest changes in activity toward cytochrome c and CYP2B1 reflect alterations in the route of electron transfer caused by the mutations. Electrostatic modeling of catalytic and binding parameters confirmed the importance of D113 and especially the double mutant E115 and E116 as mediators in forming charge–charge interactions between CPR and complex partners.     

Immobilization and bone structure in humans

Long-term immobilization is known to result in substantial bone loss. The present review examined the existing evidence for deterioration of bone structure during long-term disuse in humans. Paralysis due to spinal cord injury, long-term exposure to microgravity in space or tightly restricted mobility during bed rest provide reasonable models to assess the influence of immobilization on bone structure. Expectedly, the duration of immobilisation was the major determinant of bone loss, but irrespective of whether the skeletal unloading was due to irrecoverable paralysis, long-term spaceflight or bed rest, the mean pattern of structural deterioration of bone, mainly manifest as substantial cortical thinning and trabecular bone loss, was quite similar. However, skeletal responses to disuse can be highly variable between individuals. Apparently the relative decline in individual’s bone loading in relation to loading prior to immobilization accounts for inter-individual variation.     

Mandibular biomechanics of Crocuta crocuta,Canis lupus,and the late Miocene Dinocrocuta gigantea (Carnivora,Mammalia)

The relative simplicity of the mandible and its functional integration with the upper dentition in carnivorans makes it an ideal subject for functional morphological studies. To compare the mandibular biomechanics of two convergently evolved bone‐cracking ecomorphologies, we used finite element modelling to analyse mandibular corpus stress. The bone‐cracking spotted hyena Crocuta crocuta was used as a living analogue to the late Miocene percrocutid Dinocrocuta gigantea, using the grey wolf Canis lupus as a molar bone‐crushing outgroup. Mandibular stress values during p3, p4, and m1 tooth biting are found to be lowest in Cr. crocuta, and elevated in both Ca. lupus and D. gigantea. However, the stress‐dissipation patterns of the pre‐m1 corpus are similar between Cr. crocuta and D. gigantea. Lastly, D. gigantea has a relatively weaker corpus at the post‐m1 position than either Cr. crocuta or Ca. lupus. These findings suggest that even though stress patterns are similar amongst the bone‐cracking ecomorphs, the extinct D. gigantea had a weaker mandibular structure when performing a comparable bone‐cracking task as in Cr. crocuta because of its slender post‐m1 corpus. Ontogeny could potentially play an important role in strengthening the post‐m1 corpus by growth in the dorsoventral axis, and continuous increase in biting performance through adulthood in living Cr. crocuta suggests the possibility of a relatively more delayed development to full bone‐cracking capability in D. gigantea. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 683–696.     

Trade-off between root porosity and mechanical strength in species with different types of aerenchyma

The objective of this work was to study the existence of a trade-off between aerenchyma formation and root mechanical strength. To this end, relationships among root anatomical traits and mechanical properties were analysed in plant species with contrasting root structural types: Paspalidium geminatum (graminaceous type), Cyperus eragrostis (cyperaceous type), Rumex crispus (Rumex type) and Plantago lanceolata (Apium type). Variations in anatomical traits and mechanical strength were assessed as a function of root diameter by exposing plants to 0, 7, 15 and 30 d of control and flooded conditions. For each species, the proportion of root cortex was positively associated with the increment of root diameter, contributing to the increase in root porosity under both control and flooded conditions. Moreover, cell lysis produced an additional increase in root porosity in most species under flooded conditions (except R. crispus). Both structural types that presented a uniseriate layer (epidermis) to cope with compression (Rumex and Apium types) were progressively weakened as root porosity increased. This effect was significant even when the increment of root porosity was solely because of increased root diameter (R. crispus), as when both processes (root diameter and cell lysis) added porosity to the roots (P. lanceolata). Conversely, structural types that presented a multiseriate ring of cells in the outer cortex (graminaceous and cyperaceous types) maintained mechanical strength over the whole range of porosity, in spite of lysogenic processes registered in the inner cortex. In conclusion, our study demonstrates a strong trade-off between aerenchyma formation and mechanical strength in root structural types that lacked a multiseriate ring of tissue for mechanical protection in the outer cortex. The results suggest that this ring of tissue plays a significant role in maintaining the mechanical strength of roots when flooding induces the generation of additional aerenchyma tissue in the root cortex.