Influence of oxygen inhibition on the surface free energy and enamel bond strength of self-etch adhesives

We compared the surface free energies and enamel bond strengths of single-step self-etch adhesives with and without an oxygen-inhibited layer. The adhesives were applied to the enamel surfaces of bovine incisors, light irradiated, and the oxygen-inhibited layer was either retained or removed with ethanol. The surface free energies and their components (γ(S)(LW), γ(S)(+), and γ(S)(-)) were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths of specimens with and without the oxygen-inhibited layer were measured. For all surfaces, the value of the estimated surface tension component γ(S)(LW) was relatively constant. The value of the γ(S)(+) component increased slightly when the oxygen-inhibited layer was removed, whereas that of the γ(S)(-) component decreased significantly. The enamel bond strengths of the self-etch adhesives were significantly lower in the specimens without an oxygen-inhibited layer. The oxygen-inhibited layer therefore appeared to promote higher enamel bond strength.     

Association between periodontitis and systemic bone mineral density in Japanese community-dwelling postmenopausal women

Objective

The purpose of this cross-sectional study was to evaluate the association between loss of attachment (LA) which is clinical index of periodontitis and bone mineral density (BMD) of the lumbar vertebrae and femur measured with dual energy X-ray absorptiometry (DXA) in Japanese community-dwelling postmenopausal women.

Subjects and methods

Subjects were 347 women aged 55–74. The oral cavity was divided into 6 areas according to the WHO's method for the determination of the clinical attachment level score (CALscore); the LA was measured at 6 sites using a WHO probe in 17, 16, 11, 26, 27, 37, 36, 31, 46, and 47, and the values were recorded in mm. Then, we assessed BMD of the lumbar vertebrae (L2–L4) and femur (femoral neck, proximal part) by DXA. Based on these data, analysis of covariance was used to estimate relation between periodontitis and systemic BMD status excluding effect of age. Multiple linear regression analysis was used to estimate relation between periodontitis and BMD adjusted for 17 variables.

Results

Significant differences were observed in the mean value between the mean CALscore = 0 and CALscore ≥ 1 groups in the Z value in lumbar vertebrate (106.9 ± 18.7 vs. 102.3 ± 1.0, p < 0.05, t-test). Multiple regression analysis was conducted using the mean LA as dependent variable. Lumbar vertebral BMD (regression coefficient: B = −1.039 ± 0.379, p = 0.007), femoral neck BMD (B = −1.332 ± 0.627, p = 0.034), and proximal femoral BMD (B = −1.329 ± 0.536, p = 0.014) all exhibited a significant negative correlation with the mean LA.

Conclusion

A significant negative correlation was observed between periodontal disease and truncal bone BMD in this study.     

Highly enantioselective copper-catalyzed propargylic amination to access N-tethered 1,6-enynes

A highly enantioselective copper-catalyzed propargylic amination starting from benzylic allylic amines has been developed with a new chiral N,N,P ligand. A series of N-tethered 1,6-enynes were synthesized in good to excellent yields with excellent enantioselectivities. Utilization of transition metal-catalyzed cycloisomerization of 1,6-enynes provides several enantioselectively enriched chiral five-membered N-heterocycles efficiently.

A highly enantioselective copper-catalyzed propargylic amination has been developed with a new chiral N,N,P ligand, providing a series of N-tethered 1,6-enynes in good to excellent yields with excellent enantioselectivities.

The N-tethered 1,6-enyne skeleton is a highly versatile motif which plays a key role in organic synthesis.¹ In particular, N-tethered 1,6-enynes are key synthetic precursors of transition metal catalyzed cycloisomerizations, providing diversity of nitrogen-containing heterocycles (N-heterocycles) efficiently.² In the last decades, lots of effort has been dedicated to developing enantioselective methods to synthesize N-tethered 1,6-enynes.^3,4 Among those methods, through C–N bond formation of allylic amines and alkynes was regarded as a promising approach. For examples, addition of alkynylides to N-allyliminium intermediates generated in situ could yield N-tethered 1,6-enynes.^3b,c Using this strategy, Knochel and coworkers disclosed a copper-catalyzed three component reaction for the preparation of N-tethered 1,6-enynes with moderate ees (Scheme 1a).^3b However, this reaction is limited to the synthesis of internal alkynes. In 2010, the Nishibayashi group reported a high enantioselective copper-catalyzed asymmetric propargylic amination, giving the desired product in 87% ee, but only one example was studied (Scheme 1b).⁵ Thus, a general and practical method to synthesize N-tethered 1,6-enynes in high enantioselectivities is highly desirable.Open in a separate windowScheme 1Enantioselective synthesis of N-tethered 1,6-enynes.Copper-catalyzed asymmetric propargylic amination of propargylic esters and amines is a powerful method to construct C–N bond for the preparation of propargylic amines.⁶ Nishibayashi, van Maarseveen and Hu et al. achieved several pioneering works by their asymmetric catalytic systems.⁷ However, those systems are still suffering from low efficiency and limited substrates scope. For instance, both primary and second amines bearing aryl substituted groups were suitable substrates for obtaining excellent ees. However, aryl groups are difficult to remove, thus obstacling its application in organic synthesis. Copper-catalyzed asymmetric propargylic amination of propargylic esters with benzylic amines has not been investigated, probably attributing to their stronger basicity and flexible configuration. It has been well known that benzylic amines not only play important roles in organic synthesis but also are core structures of many pharmaceuticals and bioactive compounds.⁸ Therefore, devising for the asymmetric propargylic amination from benzylic amines are very important, and remains a challenging task.Considering the important role of N-tethered 1,6-enynes in organic synthesis and our continuing effort in propargylic substitutions,⁹ we developed a new catalyst system to realize copper-catalyzed asymmetric propargylic aminations efficiently and mildly. Diverse N-tethered 1,6-enynes could be obtained in excellent enantioselectivities. Furthermore, several N-heterocycles could be synthesized by the transition metal promoted cycloisomerization of thus obtained 1,6-enynes.We began our investigation by using the phenyl-2-propynyl acetate 1a in combination with N-allylbenzylamine 2a as model substrates (10 We then prepared a novel ligand L7 bearing two pyridyl group. This ligand gave an even higher ee (86%) (entry 7). When using Cu(OAc)₂·H₂O as the catalyst instead of CuI, we obtained the product in 87% yield with 93% ee (entry 8). Optimized conditions were finally established by lowering the temperature to −20 °C, the reaction was completed in three hours even with 5 mol% of catalyst loading (entry 9).Optimization of the reaction condition^a

The detoxification mechanisms of low-accumulating and non-low-accumulating medicinal plants under Cd and Pb stress

Recently, the levels of heavy metals in medicinal plants have aroused widespread concern because these elements usually enter the food chain through plants and are gradually passed to the final consumers, greatly threatening human health. To reduce heavy metal pollution, it is necessary to solve the problem from the source to ensure environmental quality during medicinal material production. We use low-accumulating and non-low-accumulating medicinal plants to remediate soil contaminated by Cd and Pb. This experiment aims to study the amino acid levels in root exudates, to study antioxidant enzymes and malondialdehyde (MDA) in leaves, and to discuss the detoxification mechanisms of low-accumulating and non-low-accumulating medicinal plants under Cd and Pb stress. In soil contaminated with Cd or Pb, catnip, thyme and Fineleaf Schizonepeta Herb were cultivated. Enrichment factor (EF) and translocation factor (TF) levels were calculated to determine which are low-accumulating medicinal plants with respect to Cd or Pb. The relationships between the amino acid levels in root exudates, the levels of antioxidant enzymes, the present heavy metal species, heavy metal concentrations, and plant species were discussed. Under Pb and Cd stress, the total amounts of amino acids secreted by plant roots and the level of each amino acid were associated with the heavy metal concentrations and plant species. Plants alleviate Pb and Cd stress via adding malondialdehyde (MDA) and antioxidant enzymes. Thyme can be used as a low-accumulating medicinal plant with any concentration of the heavy metal Pb. These results are of great significance for understanding the chemical behaviors of heavy metals at the root/soil interface under Cd and Pb stress and the detoxification mechanisms of medicinal plants.

Recently, the levels of heavy metals in medicinal plants have aroused widespread concern because these elements usually enter the food chain through plants and are gradually passed to the final consumers, greatly threatening human health.     

Peroxisome Proliferator‐Activated Receptor α Activation Suppresses Cytochrome P450 Induction Potential in Mice Treated with Gemfibrozil

Gemfibrozil, a peroxisome proliferator‐activated receptor α (PPARα) agonist, is widely used for hypertriglyceridaemia and mixed hyperlipidaemia. Drug–drug interaction of gemfibrozil and other PPARα agonists has been reported. However, the role of PPARα in cytochrome P450 (CYP) induction by fibrates is not well known. In this study, wild‐type mice were first fed gemfibrozil‐containing diets (0.375%, 0.75% and 1.5%) for 14 days to establish a dose–response relationship for CYP induction. Then, wild‐type mice and Pparα‐null mice were treated with a 0.75% gemfibrozil‐containing diet for 7 days. CYP3a, CYP2b and CYP2c were induced in a dose‐dependent manner by gemfibrozil. In Pparα‐null mice, their mRNA level, protein level and activity were induced more than those in wild‐type mice. So, gemfibrozil induced CYP, and this action was inhibited by activated PPARα. These data suggested that the induction potential of CYPs was suppressed by activated PPARα, showing a potential role of this receptor in drug–drug interactions and metabolic diseases treated with fibrates.