Effects of Raloxifene and tibial loading on bone mass and mechanics in male and female mice.

Purpose: Raloxifene (RAL) is a selective estrogen receptor modulator (SERM) that has previously been shown to cause acellular benefits to bone tissue. Due to these improvements, RAL was combined with targeted tibial loading to assess if RAL treatment during periods of active bone formation would allow for further mechanical enhancements.Methods: Structural, mechanical, and microstructural effects were assessed in bone from C57BL/6 mice that were treated with RAL (0.5 mg/kg), tibial loading, or both for 6 weeks, beginning at 10 weeks of age.Results:Ex vivo microcomputed tomography (CT) images indicated RAL and loading work together to improve bone mass and architecture, especially within the cancellous region of males. Increases in cancellous bone volume fraction were heavily driven by increases in trabecular thickness, though there were some effects on trabecular spacing and number. In the cortical regions, RAL and loading both increased cross-sectional area, cortical area, and cortical thickness. Whole-bone mechanical testing primarily indicated the effects of loading. Further characterization through Raman spectroscopy and nanoindentation showed load-based changes in mineralization and micromechanics, while both loading and RAL caused changes in the secondary collagen structure. In contrast to males, in females, there were large load-based effects in the cancellous and cortical regions, resulting in increased whole-bone mechanical properties. RAL had less of an effect on cancellous and cortical architecture, though some effects were still present.Conclusion: RAL and loading work together to impact bone architecture and mechanical integrity, leading to greater improvements than either treatment individually.

Skeletal manifestations in a streptozotocin-induced C57BL/6 model of Type 1 diabetes.

Diabetes Mellitus is a metabolic disease which profoundly affects many organ systems in the body, including the skeleton. As is often the case with biology, there are inherent differences between the sexes when considering skeletal development and disease progression and outcome. Therefore, the aim of this study was to develop a protocol to reliably induce diabetes in both sexes of the C57BL/6 mouse utilizing streptozotocin (STZ) and to characterize the resulting bone phenotype. We hypothesized that destruction of the ß-cells in the pancreatic islet by STZ would result in a diabetic state with downstream skeletal manifestations. Beginning at 8 weeks of age, mice were injected for 5 consecutive days with STZ (65 mg/kg males, 90 mg/kg females) dissolved in a citrate buffer. The diabetic state of the mice was monitored for 5 weeks to ensure persistent hyperglycemia and mice were euthanized at 15 weeks of age. Diabetes was confirmed through blood glucose monitoring, glucose and insulin tolerance testing, HbA1c measurement, and histological staining of the pancreas. The resulting bone phenotype was characterized using microcomputed tomography to assess bone structure, and whole bone mechanical testing to assess bone functional integrity. Mice from both sexes experienced loss of ß-cell mass and increased glycation of hemoglobin, as well as reduced trabecular thickness and trabecular tissues mineral density (TMD), and reduced cortical thickness and cortical bone area fraction. In female mice the change area fraction was driven by a reduction in overall bone size while in male mice, the change was driven by increased marrow area. Males also experienced reduced cortical TMD. Mechanical bending tests of the tibiae showed significant results in females with a reduction in yield force and ultimate force driving lower work to yield and total work and a roughly 40 % reduction of stiffness. When tissue level parameters were estimated using beam theory, there was a significant reduction in yield and ultimate stresses as well as elastic modulus. The previously reported mechanistic similarity in the action of STZ on murine animals, as well as the ease of STZ administration via IP injection make this model is a strong candidate for future exploration of osteoporotic bone disease, Diabetes Mellitus, and the link between estrogen and glucose sensitivity.

Authorship Trends Over the Past 30-Years in the Annals of Biomedical Engineering.

In academia, manuscripts serve as an important component of career development. The past several years have seen heightened evaluation of the role of the gender gap in career advancement, as well as other bibliometric changes in publications. We therefore analyzed authorship and publication trends in the Annals of Biomedical Engineering over the past three decades (one complete year of manuscripts for each decade; 1986, 1996, 2006, and 2016). The variables analyzed were number of authors per manuscript, numerical position of the corresponding author, number of collaborating institutions and countries, number of references, and number of citations per manuscript. The gender of both the first and corresponding authors was identified and analyzed over time and by region. Globally, the percentage of female first and corresponding authors significantly increased from 0% in 1986 to 28.6% (p = 0.003) and 20.4% (p = 0.0009), respectively, in 2016. Although there were significant differences regarding female first and corresponding author over time, they did not vary by region of origin (p = 0.5 and 0.2, respectively). Overall, these findings highlight the improvements made and the challenges that still exist related to publishing within the bioengineering field.

Influence of reduced electron shuttling compounds on biological H2 production in the fermentative pure culture Clostridium beijerinckii.

Several reports suggest that extracellular electron shuttles influence fermentative metabolism in a beneficial manner for bioremediation and biotechnology strategies. The focus of this research was to characterize the effects of reduced electron shuttling molecules on fermentative H(2) production. Reduced electron shuttles may provide reducing equivalents to generate H(2), which influences alternate cellular processes. Electron shuttling compounds cycle between reduced-oxidized states and influence fermentative physiology. Clostridium beijerinckii fermentation was altered using a physiological approach that resulted in H(2) production with the reduced extracellular electron shuttle anthrahydroquinone-2,6,-disulfonate (AH(2)QDS) and biologically reduced humic substances as the primary electron donors. Cells were suspended in a buffer with an excess of the biological electron transfer molecule NAD(+), with AH(2)QDS (100-1000 microM) or biologically reduced humic substances (0.01-0.025 g/L) as the sole electron source. Increasing concentrations of AH(2)QDS and reduced humics increased H(2) production, while H(2) production was suppressed by Fe(III) hydroxides, which outcompeted the cells for electrons from the reduced shuttles, suggesting that the shuttles are in fact electron donors for H(2) production. Oxidized AQDS/humics did not increase H(2) production. Organic acid production shifted toward butyric acid in the presence of reduced electron shuttles, particularly with growing cells. Growth and hydrogen production rates in growing cells were initially faster in the presence of the reduced electron shuttles; however, the final biomass yield was inversely proportional to the starting AH(2)QDS concentration, which suggests that reduced shuttles may compete with anabolic cell processes for available energetic resources or that the shift to excess butyrate becomes toxic to the cells.

PDILT, a divergent testis-specific protein disulfide isomerase with a non-classical SXXC motif that engages in disulfide-dependent interactions in the endoplasmic reticulum.

Protein disulfide isomerase (PDI) is the archetypal enzyme involved in the formation and reshuffling of disulfide bonds in the endoplasmic reticulum (ER). PDI achieves its redox function through two highly conserved thioredoxin domains, and PDI can also operate as an ER chaperone. The substrate specificities and the exact functions of most other PDI family proteins remain important unsolved questions in biology. Here, we characterize a new and striking member of the PDI family, which we have named protein disulfide isomerase-like protein of the testis (PDILT). PDILT is the first eukaryotic SXXC protein to be characterized in the ER. Our experiments have unveiled a novel, glycosylated PDI-like protein whose tissue-specific expression and unusual motifs have implications for the evolution, catalytic function, and substrate selection of thioredoxin family proteins. We show that PDILT is an ER resident glycoprotein that liaises with partner proteins in disulfide-dependent complexes within the testis. PDILT interacts with the oxidoreductase Ero1alpha, demonstrating that the N-terminal cysteine of the CXXC sequence is not required for binding of PDI family proteins to ER oxidoreductases. The expression of PDILT, in addition to PDI in the testis, suggests that PDILT performs a specialized chaperone function in testicular cells. PDILT is an unusual PDI relative that highlights the adaptability of chaperone and redox function in enzymes of the endoplasmic reticulum.