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.     

The effects of dietary macronutrients on flight ability,energetics, and fuel metabolism of yellow‐rumped warblers Setophaga coronata

The catabolism of protein from organs and muscles during migratory flight is necessary to produce glucose, key metabolic intermediates, and water, but may have negative effects on flight range and refueling at stopovers. We tested the hypothesis, suggested by previous studies, that birds that eat high‐protein insect diets use more protein for fuel in flight than those that eat high‐carbohydrate fruits. First, we fed migratory yellow‐rumped warblers synthetic fruit or mixed insect/fruit diets, and measured metabolic rates and fuel mixture under basal conditions and during exercise in a hop/hover wheel respirometer. Birds eating the fruit diet had greater plasma triglyceride and non‐esterified fatty acid concentrations, and the higher protein mixed diet increased plasma uric acid only during feeding. Diet did not affect metabolic rates or the fuel mixture under resting or exercise conditions. We then fed yellow‐rumped warblers synthetic diets that differed only in the relative proportion of carbohydrate and protein (60:15 versus 15:60 as % dry mass) and tested them in wind tunnel flights lasting up to six hours. Birds fed the high carbohydrate diet became heavier and fatter than when fed the high protein diet. Plasma uric acid concentration was increased and plasma phospholipid concentration was decreased by the high protein diet in the pre‐flight state (after a 3 h fast), but diet only affected plasma phospholipids during flight (lower in high protein birds). Neither diet nor amount of body fat affected the rate of loss of lean mass or fat during flight. Inter‐individual or seasonal differences in diet do not appear to influence the amount of protein catabolized during endurance flight. However, birds fed the high carbohydrate diet had greater voluntary flight duration, independent of body fatness, suggesting that there may be other performance benefits of high carbohydrate diets for migratory birds.     

IFITM3 Restricts Influenza A Virus Entry by Blocking the Formation of Fusion Pores following Virus-Endosome Hemifusion

Interferon-induced transmembrane proteins (IFITMs) inhibit infection of diverse enveloped viruses, including the influenza A virus (IAV) which is thought to enter from late endosomes. Recent evidence suggests that IFITMs block virus hemifusion (lipid mixing in the absence of viral content release) by altering the properties of cell membranes. Consistent with this mechanism, excess cholesterol in late endosomes of IFITM-expressing cells has been reported to inhibit IAV entry. Here, we examined IAV restriction by IFITM3 protein using direct virus-cell fusion assay and single virus imaging in live cells. IFITM3 over-expression did not inhibit lipid mixing, but abrogated the release of viral content into the cytoplasm. Although late endosomes of IFITM3-expressing cells accumulated cholesterol, other interventions leading to aberrantly high levels of this lipid did not inhibit virus fusion. These results imply that excess cholesterol in late endosomes is not the mechanism by which IFITM3 inhibits the transition from hemifusion to full fusion. The IFITM3''s ability to block fusion pore formation at a post-hemifusion stage shows that this protein stabilizes the cytoplasmic leaflet of endosomal membranes without adversely affecting the lumenal leaflet. We propose that IFITM3 interferes with pore formation either directly, through partitioning into the cytoplasmic leaflet of a hemifusion intermediate, or indirectly, by modulating the lipid/protein composition of this leaflet. Alternatively, IFITM3 may redirect IAV fusion to a non-productive pathway, perhaps by promoting fusion with intralumenal vesicles within multivesicular bodies/late endosomes.     

RNA and β-Hemolysin of Group B Streptococcus Induce Interleukin-1β (IL-1β) by Activating NLRP3 Inflammasomes in Mouse Macrophages

The inflammatory cytokine IL-1β is critical for host responses against many human pathogens. Here, we define Group B Streptococcus (GBS)-mediated activation of the Nod-like receptor-P3 (NLRP3) inflammasome in macrophages. NLRP3 activation requires GBS expression of the cytolytic toxin, β-hemolysin, lysosomal acidification, and leakage. These processes allow the interaction of GBS RNA with cytosolic NLRP3. The present study supports a model in which GBS RNA, along with lysosomal components including cathepsins, leaks out of lysosomes and interacts with NLRP3 to induce IL-1β production.     

Oncogenic mutations in adenomatous polyposis coli (Apc) activate mechanistic target of rapamycin complex 1 (mTORC1) in mice and zebrafish

Truncating mutations in adenomatous polyposis coli (APC) are strongly linked to colorectal cancers. APC is a negative regulator of the Wnt pathway and constitutive Wnt activation mediated by enhanced Wnt–β-catenin target gene activation is believed to be the predominant mechanism responsible for APC mutant phenotypes. However, recent evidence suggests that additional downstream effectors contribute to APC mutant phenotypes. We previously identified a mechanism in cultured human cells by which APC, acting through glycogen synthase kinase-3 (GSK-3), suppresses mTORC1, a nutrient sensor that regulates cell growth and proliferation. We hypothesized that truncating Apc mutations should activate mTORC1 in vivo and that mTORC1 plays an important role in Apc mutant phenotypes. We find that mTORC1 is strongly activated in apc mutant zebrafish and in intestinal polyps in Apc mutant mice. Furthermore, mTORC1 activation is essential downstream of APC as mTORC1 inhibition partially rescues Apc mutant phenotypes including early lethality, reduced circulation and liver hyperplasia. Importantly, combining mTORC1 and Wnt inhibition rescues defects in morphogenesis of the anterior-posterior axis that are not rescued by inhibition of either pathway alone. These data establish mTORC1 as a crucial, β-catenin independent effector of oncogenic Apc mutations and highlight the importance of mTORC1 regulation by APC during embryonic development. Our findings also suggest a new model of colorectal cancer pathogenesis in which mTORC1 is activated in parallel with Wnt/β-catenin signaling.KEY WORDS: APC, Wnt, mTOR, mTORC1, Zebrafish, Colon cancer, Polyposis, GSK-3     

Distribution and hydraulic significance of large woody debris in a lowland Australian river

The line-intersect technique was used to measure the loading of large woody debris in a 1.8 km reach of the Thomson River, Victoria (catchment area of 3540 km²). A debris census (measuring every item present) was done over 0.775 km of this reach. The transect technique over-estimated the actual loading revealed by the census. The loading of debris 0.01 m in diameter for the total 1.8 km reach was 0.0172 m³ m^–2, which is higher than that measured in many headwater streams in other parts of the world. The volume loading of debris measured from low level aerial photographs was only 4.8% of the value estimated by the line-intersect technique. The line-intersect estimates were biased due to non-random orientation of debris in the stream (causing estimated errors of +8% for volume loading and +16% for surface area loading). It is recommended that to avoid this problem, when using the line-intersect transect technique in lowland rivers, each line should comprise at least two obliquely-angled transects across the channel. The mean item of debris (0.1 m in diameter) had a trunk basal diameter of 0.45 m, a length of 7.4 m, and volume of 0.7 m³. The riparian trees and the in-channel debris were of similar dimensions. The debris tended to be close to the bed and banks and was oriented downstream by the flow at a median angle of 27°. Because of this orientation, most debris had a small projected cross-sectional area, with the median value being only 1 m². Thus, the blockage ratio (proportion of projected area of debris to channel cross-sectional area) was also low, ranging from 0.0002 to 0.1, with a median value of 0.004. The average item of debris, which occupied only 0.4% of the cross-section, would have minimal influence on banktop flow hydraulics, but the largest items, which occupied around 10%, could be significant. Judicious re-introduction of debris into previously cleared rivers is unlikely to result in a large loss of conveyance, or a detectable increase in flooding frequency.     

Microsomal fatty acyl-CoA transacylation and hydrolysis: fatty acyl-CoA species dependent modulation by liver fatty acyl-CoA binding proteins1

Liver and intestinal cytosol contain abundant levels of long chain fatty acyl-CoA binding proteins such as liver fatty acid binding protein (L-FABP) and acyl-CoA binding protein (ACBP). However, the relative function and specificity of these proteins in microsomal utilization of long chain fatty acyl-CoAs (LCFA-CoAs) for sequential transacylation of glycerol-3-phosphate to form phosphatidic acid is not known. The results showed for the first time that L-FABP and ACBP both stimulated microsomal incorporation of the monounsaturated oleoyl-CoA and polyunsaturated arachidonoyl-CoA 8–10-fold and 2–3-fold, respectively. In contrast, these proteins inhibited microsomal utilization of the saturated palmitoyl-CoA by 69% and 62%, respectively. These similar effects of L-FABP and ACBP on microsomal phosphatidic acid biosynthesis were mediated primarily through the activity of glycerol-3-phosphate acyltransferase (GPAT), the rate limiting step, rather than by protecting the long chain acyl-CoAs from microsomal hydrolase activity. In fact, ACBP but not L-FABP protected long chain fatty acyl-CoAs from microsomal acyl-CoA hydrolase activity in the order: palmitoyl-CoA>oleoyl-CoA>arachidonoyl-CoA. In summary, the data established for the first time a role for both L-FABP and ACBP in microsomal phosphatidic acid biosynthesis. By preferentially stimulating microsomal transacylation of unsaturated long chain fatty acyl-CoAs while concomitantly exerting their differential protection from microsomal acyl-CoA hydrolase, L-FABP and ACBP can uniquely function in modulating the pattern of fatty acids esterified to phosphatidic acid, the de novo precursor of phospholipids and triacylglycerols. This may explain in part the simultaneous presence of these proteins in cell types involved in fatty acid absorption and lipoprotein secretion.