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.     

Evolution of Mycobacterium ulcerans and other mycolactone-producing mycobacteria from a common Mycobacterium marinum progenitor

It had been assumed that production of the cytotoxic polyketide mycolactone was strictly associated with Mycobacterium ulcerans, the causative agent of Buruli ulcer. However, a recent study has uncovered a broader distribution of mycolactone-producing mycobacteria (MPM) that includes mycobacteria cultured from diseased fish and frogs in the United States and from diseased fish in the Red and Mediterranean Seas. All of these mycobacteria contain versions of the M. ulcerans pMUM plasmid, produce mycolactones, and show a high degree of genetic relatedness to both M. ulcerans and Mycobacterium marinum. Here, we show by multiple genetic methods, including multilocus sequence analysis and DNA-DNA hybridization, that all MPM have evolved from a common M. marinum progenitor to form a genetically cohesive group among a more diverse assemblage of M. marinum strains. Like M. ulcerans, the fish and frog MPM show multiple copies of the insertion sequence IS2404. Comparisons of pMUM and chromosomal gene sequences demonstrate that plasmid acquisition and the subsequent ability to produce mycolactone were probably the key drivers of speciation. Ongoing evolution among MPM has since produced at least two genetically distinct ecotypes that can be broadly divided into those typically causing disease in ectotherms (but also having a high zoonotic potential) and those causing disease in endotherms, such as humans.     

Infant animal model of pulmonary mycotoxicosis induced by Stachybotrys chartarum

In recent years cases of often fatal pulmonary hemorrhage in infants have been associated with water damaged homes and the toxigenic fungusStachybotrys chartarum. The fungal spores contain mycotoxins which could be injurious to the rapidly developing lung. In order to understand the developmental pathophysiology of this disease we developed an infant rat model of stachybotrytoxicosis describing the effects of fungal spores on survival, growth, histopathology of the lung and respiration. Conidia ofS. chartarum were instilled intratracheally (1.0–8.0 × 10⁵/gm wt.) in 4-dold Sprague-Dawley rat pups. Two control groups received either sterile PBS or a suspension of spores extensively extracted with ethanol to remove toxins. Lethal dose response was determined (LD₅₀ = 2.7 × 10⁵ spores/gm wt.). All dead pups had extensively hemorrhagic lungs. Growth of surviving animals was impaired in a dose-dependent manner. Changes of pulmonary function parameters in rats treated with 1.1 × 10⁵ spores/g were consistent with an increased respiratory resistance. Histology of lungs revealed fresh hemorrhage, sparse hemosiderin-laden macrophages, and evidence of inflammation including thickened alveolar septa infiltrated by lymphocytes and mononuclear cells and intra-alveolar macrophages. Significant increases (p = 0.001) in numbers of macrophages (2-fold), lymphocytes (5-fold) and neutrophils (7-fold) were found in BAL fluid. Hemoglobin was elevated 2-fold (p = 0.004). Proinflammatory mediator IL-1β increased more than 6-fold and TNF-α30-fold (p = 0.001). Extracted spores had a minimal effect on all examined parameters in BAL fluid indicating that mycotoxins are primarily responsible for the hemorrhagic and inflammatory response. This revised version was published online in June 2006 with corrections to the Cover Date.     

Beaver dams maintain fish biodiversity by increasing habitat heterogeneity throughout a low‐gradient stream network

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Bacteria Associated with Cysts of the Soybean Cyst Nematode (Heterodera glycines)

The soybean cyst nematode (SCN), Heterodera glycines, causes economically significant damage to soybeans (Glycine max) in many parts of the world. The cysts of this nematode can remain quiescent in soils for many years as a reservoir of infection for future crops. To investigate bacterial communities associated with SCN cysts, cysts were obtained from eight SCN-infested farms in southern Ontario, Canada, and analyzed by culture-dependent and -independent means. Confocal laser scanning microscopy observations of cyst contents revealed a microbial flora located on the cyst exterior, within a polymer plug region and within the cyst. Microscopic counts using 5-(4,6-dichlorotriazine-2-yl)aminofluorescein staining and in situ hybridization (EUB 338) indicated that the cysts contained (2.6 ± 0.5) × 10⁵ bacteria (mean ± standard deviation) with various cellular morphologies. Filamentous fungi were also observed. Live-dead staining indicated that the majority of cyst bacteria were viable. The probe Nile red also bound to the interior polymer, indicating that it is lipid rich in nature. Bacterial community profiles determined by denaturing gradient gel electrophoresis analysis were simple in composition. Bands shared by all eight samples included the actinobacterium genera Actinomadura and Streptomyces. A collection of 290 bacteria were obtained by plating macerated surface-sterilized cysts onto nutrient broth yeast extract agar or on actinomycete medium. These were clustered into groups of siblings by repetitive extragenic palindromic PCR fingerprinting, and representative isolates were tentatively identified on the basis of 16S rRNA gene sequence. Thirty phylotypes were detected, with the collection dominated by Lysobacter and Variovorax spp. This study has revealed the cysts of this important plant pathogen to be rich in a variety of bacteria, some of which could presumably play a role in the ecology of SCN or have potential as biocontrol agents.     

Inducible expression of <Emphasis Type="Italic">Pisum sativum</Emphasis> xyloglucan fucosyltransferase in the pea root cap meristem,and effects of antisense mRNA expression on root cap cell wall structural integrity

Mitosis and cell wall synthesis in the legume root cap meristem can be induced and synchronized by the nondestructive removal of border cells from the cap periphery. Newly synthesized cells can be examined microscopically as they differentiate progressively during cap development, and ultimately detach as a new population of border cells. This system was used to demonstrate that Pisum sativum L. fucosyl transferase (PsFut1) mRNA expression is strongly expressed in root meristematic tissues, and is induced >2-fold during a 5-h period when mitosis in the root cap meristem is increased. Expression of PsFut1 antisense mRNA in pea hairy roots under the control of the CaMV35S promoter, which exhibits meristem localized expression in pea root caps, resulted in a 50-60% reduction in meristem localized endogenous PsFut1 mRNA expression measured using whole mount in situ hybridization. Changes in gross levels of cell wall fucosylated xyloglucan were not detected, but altered surface localization patterns were detected using whole mount immunolocalization with CCRC-M1, an antibody that recognizes fucosylated xyloglucan. Emerging hairy roots expressing antisense PsFut1 mRNA appeared normal macroscopically but scanning electron microscopy of tissues with altered CCRC-M1 localization patterns revealed wrinkled, collapsed cell surfaces. As individual border cells separated from the cap periphery, cell death occurred in correlation with extrusion of cellular contents through breaks in the wall.