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361.
Dubrovinskaia N Dubrovinsky L Solozhenko VL 《Science (New York, N.Y.)》2007,318(5856):1550; author reply 1550
Chung et al. (Reports, 20 April 2007, p. 436) reported the synthesis of superhard rhenium diboride (ReB2) at ambient pressure. We show that ReB2, first synthesized at ambient pressure 45 years ago, is not a superhard material. Together with the high cost of Re, this makes the prospect for large-scale industrial applications of ReB2 doubtful. 相似文献
362.
Pouchkina-Stantcheva NN McGee BM Boschetti C Tolleter D Chakrabortee S Popova AV Meersman F Macherel D Hincha DK Tunnacliffe A 《Science (New York, N.Y.)》2007,318(5848):268-271
Theory suggests it should be difficult for asexual organisms to adapt to a changing environment because genetic diversity can only arise from mutations accumulating within direct antecedents and not through sexual exchange. In an asexual microinvertebrate, the bdelloid rotifer, we have observed a mechanism by which such organisms could acquire the diversity needed for adaptation. Gene copies most likely representing former alleles have diverged in function so that the proteins they encode play complementary roles in survival of dry conditions. One protein prevents desiccation-sensitive enzymes from aggregating during drying, whereas its counterpart does not have this activity, but is able to associate with phospholipid bilayers and is potentially involved in maintenance of membrane integrity. The functional divergence of former alleles observed here suggests that adoption of asexual reproduction could itself be an evolutionary mechanism for the generation of diversity. 相似文献
363.
Ahlert J Shepard E Lomovskaya N Zazopoulos E Staffa A Bachmann BO Huang K Fonstein L Czisny A Whitwam RE Farnet CM Thorson JS 《Science (New York, N.Y.)》2002,297(5584):1173-1176
The enediynes exemplify nature's ingenuity. We have cloned and characterized the biosynthetic locus coding for perhaps the most notorious member of the nonchromoprotein enediyne family, calicheamicin. This gene cluster contains an unusual polyketide synthase (PKS) that is demonstrated to be essential for enediyne biosynthesis. Comparison of the calicheamicin locus with the locus encoding the chromoprotein enediyne C-1027 reveals that the enediyne PKS is highly conserved among these distinct enediyne families. Contrary to previous hypotheses, this suggests that the chromoprotein and nonchromoprotein enediynes are generated by similar biosynthetic pathways. 相似文献
364.
Vázquez-Carrillo G García-Lara S Salinas-Moreno Y Bergvinson DJ Palacios-Rojas N 《Plant foods for human nutrition (Dordrecht, Netherlands)》2011,66(2):203-208
The maize produced in the highlands of Mexico (>2,400 masl) is generally not accepted by the flour and masa and tortilla industry.
The objective of this work was to evaluate the grain quality and tortilla properties of maize landraces commonly grown in
the highlands of Mexico and compare them with improved germplasm (hybrids). Germplasm analysis included 11 landraces, 32 white
hybrids, and six yellow hybrids. Grain quality was analyzed for a range of physical and chemical factors, as well as for alkaline
cooking quality. Landrace grains tended to be heterogeneous in terms of size, hardness and color. All landraces had soft-intermediate
grains with an average flotation index (FI) of 61%. In contrast, hybrid grains were homogenous in size and color, and harder
than landrace grains, with a FI of 38%. Protein, free sugars, oil and phenolic content in landraces were higher than in the
hybrids. Significant correlations were found between phenolic content and tortilla color (r = −0.60; p < 0.001). Three landraces were identified as appropriate for the masa and tortilla industry, while all the hybrids evaluated
fulfilled the requirements of this industry. 相似文献
365.
366.
Gustavo J. Macchi Marcelo Pjaro María I. Militelli Natalia Radovani Lorena Rivas 《Fisheries Research》2006,80(2-3):345-349
Effects of maternal age–size and condition on oocyte dry weight were analysed for Merluccius hubbsi. Samples of mature females were collected in the Patagonian spawning area during 10 research surveys carried out between 2000 and 2005. Dry weight of 50 hydrated oocytes ranged from 0.80 to 1.90 mg. Relationships of this variable with total length and age were best described by a logarithmic model during the spawning peak. At the beginning and at the end of the reproductive season no significant relationship between these variables was observed, but a decrease in egg dry weight was detected during the spawning period. In general, young spawners (≤5-year-old) showed more variability in egg dry weight, which was associated with a reproductive season shorter than that of old females. Relative condition factor did not shows a significant relationship with oocyte dry weight, and mean values of this index were similar for different months of the spawning seasons analysed. 相似文献
367.
368.
Ji-Min Kim Sung-Chan Shin Yong-Il Cheon Hyung-Sik Kim Gi-Cheol Park Hyoung-Kyu Kim Jin Han Jung-Eun Seol Elena A. Vasileva Natalia P. Mishchenko Sergey A. Fedoreyev Valentin A. Stonik Byung-Joo Lee 《Marine drugs》2022,20(12)
Post-menopausal dry mouth or xerostomia is caused by reduced salivary secretion. This study aimed to investigate the efficacy of echinochrome A (Ech A) in alleviating submandibular gland dysfunctions in ovariectomized rats that mimic menopause. Female rats that were eight-weeks-old were randomly divided into SHAM-6, -12; OVX-6, -12; and ECH-6, -12 groups (consisting of 6- and 12-weeks post-sham-operated, ovariectomized, and Ech A-treated ovariectomized rats, respectively). The ECH groups had lower body weight than OVX but similar food intake and estradiol or estrogen receptor β expression. However, the ECH groups had lower mRNA expression of sterol-regulatory element binding protein-1c (Srebp-1c), acetyl-CoA carboxylase (Acc), fatty acid synthase (Fasn), cluster of differentiation 36 (Cd36), and lipid vacuole deposition than OVX mice. Moreover, reactive oxygen species (ROS), malondialdehyde (MDA), and iron accumulation were lower in the ECH than in the OVX groups. Fibrosis markers, transforming growth factor β (Tgf-βI and Tgf-βII mRNA) increased in the OVX than SHAM groups but decreased in the ECH groups. Aquaporin (Aqp-1 and Aqp-5 mRNA) and mucin expressions were downregulated in the OVX groups but improved with Ech A. In addition, Ech A prevented post-menopausal salivary gland dysfunction by inhibiting lipogenesis and ferroptosis. These findings suggest Ech A as an effective remedy for treating menopausal dry mouth. 相似文献