Enzymatic hydrolysis combined with mechanical shearing and high-pressure homogenization for nanoscale cellulose fibrils and strong gels

Toward exploiting the attractive mechanical properties of cellulose I nanoelements, a novel route is demonstrated, which combines enzymatic hydrolysis and mechanical shearing. Previously, an aggressive acid hydrolysis and sonication of cellulose I containing fibers was shown to lead to a network of weakly hydrogen-bonded rodlike cellulose elements typically with a low aspect ratio. On the other hand, high mechanical shearing resulted in longer and entangled nanoscale cellulose elements leading to stronger networks and gels. Nevertheless, a widespread use of the latter concept has been hindered because of lack of feasible methods of preparation, suggesting a combination of mild hydrolysis and shearing to disintegrate cellulose I containing fibers into high aspect ratio cellulose I nanoscale elements. In this work, mild enzymatic hydrolysis has been introduced and combined with mechanical shearing and a high-pressure homogenization, leading to a controlled fibrillation down to nanoscale and a network of long and highly entangled cellulose I elements. The resulting strong aqueous gels exhibit more than 5 orders of magnitude tunable storage modulus G' upon changing the concentration. Cryotransmission electron microscopy, atomic force microscopy, and cross-polarization/magic-angle spinning (CP/MAS) 13C NMR suggest that the cellulose I structural elements obtained are dominated by two fractions, one with lateral dimension of 5-6 nm and one with lateral dimensions of about 10-20 nm. The thicker diameter regions may act as the junction zones for the networks. The resulting material will herein be referred to as MFC (microfibrillated cellulose). Dynamical rheology showed that the aqueous suspensions behaved as gels in the whole investigated concentration range 0.125-5.9% w/w, G' ranging from 1.5 Pa to 105 Pa. The maximum G' was high, about 2 orders of magnitude larger than typically observed for the corresponding nonentangled low aspect ratio cellulose I gels, and G' scales with concentration with the power of approximately three. The described preparation method of MFC allows control over the final properties that opens novel applications in materials science, for example, as reinforcement in composites and as templates for surface modification.     

Pancreaticoduodenal arterial rupture and hemoabdomen in ACI/SegHsd rats with polyarteritis nodosa

Many lesions associated with aging have been well-characterized in various strains of rats. Although documented in Sprague-Dawley and spontaneously hypertensive rats, polyarteritis nodosa has not previously been reported in ACI/SegHsd rats. ACII SegHsd rats were maintained on high-fat (40.5%), low-fat (11.6%), and high-fat to low-fat dietary protocols to examine the correlation between dietary fat and the regulation of prostate 5alpha-reductase gene expression and prostate cancer. Seven rats died unexpectedly with hemoabdomen and rupture of the pancreaticoduodenal artery secondary to polyarteritis nodosa (PAN). The purpose of this study was to analyze the pathologic findings in these and the remaining ACI/SegHsd rats and to correlate the level of dietary fat with the presence of PAN, arterial rupture, and hemoabdomen. Approximately 65% of the rats had evidence of PAN by histopathology, with a 24% incidence of arterial rupture. Additional lesions noted included an 88% incidence of chronic progressive nephropathy (CPN) and a 32% incidence of cartilaginous foci in the aortic valve. We found no association between the percentage of dietary fat and incidence of PAN, CPN, or cardiac cartilage. Although arterial rupture is a known complication of polyarteritis nodosa in humans, this case series is the first to document arterial rupture and hemoabdomen in rats with PAN.     

Flaxseed alone or in combination with tamoxifen inhibits MCF-7 breast tumor growth in ovariectomized athymic mice with high circulating levels of estrogen

Flaxseed (FS) is rich in mammalian lignan precursors and alpha-linolenic acid, which have been suggested as having anticancer effects. Previous studies have shown that 10% FS inhibits the growth of human estrogen-dependent breast cancer (MCF-7) in athymic mice, and it enhances the inhibitory effect of tamoxifen (TAM). This study determined whether the effect of FS, alone or in combination with TAM, is dose dependent, and it explored the potential mechanism of action. Ovariectomized athymic mice with estradiol (E2) supplementation (1.7 mg/pellet, 60-day release) and established MCF-7 tumors were treated with basal diet control (0FS), 5% FS (5FS), 10% FS (10FS), and TAM (TAM/ 0FS; 5 mg/pellet, 60-day release), alone or in combination (TAM/ 5FS and TAM/10FS) for 8 weeks. Compared with control, 5FS and 10FS significantly inhibited tumor growth by 26% and 38%, respectively. TAM/0FS had an effect similar to the 10FS. TAM/ 5FS and TAM/10FS, respectively, induced significant 48% and 43% reductions in tumor size compared with 0FS, and 18% and 10% reductions compared with TAM/0FS. The relative uterine weight was significantly lower in all TAM groups compared with the control. The reduction of tumor growth resulted from decreased cell proliferation and increased cell apoptosis. TAM/ 5FS caused a significantly higher expression of estrogen receptor-alpha (ERalpha) compared with 5FS and TAM/0FS, whereas TAM/10FS had a higher ERalpha than 10FS and TAM/0FS. Compared with the control, progesterone receptor (PgR) expression was significantly reduced in all treatment groups, but insulin-like growth factor-1 (IGF-1) expression was reduced only by 10FS, TAM/5FS and TAM/10FS. Tumor cell proliferation was significantly positively associated with expression of PgR and IGF-1 and negatively associated with apoptosis and ERalpha. Apoptosis was only associated with ERalpha. In conclusion, FS inhibited MCF-7 tumor growth in a dose-dependent manner and enhanced the inhibitory effect of TAM due to the modulation of ER and growth factor signal transduction pathways.     

Inhibition of harmful algal blooms caused by Aureococcus anophagefferens (Pelagophyceae) using native (Gracilaria tikvahiae) and invasive (Dasysiphonia japonica) red seaweeds from North America

Journal of Applied Phycology - Harmful algal blooms (HABs) caused by the pelagophyte Aureococcus anophagefferens have spread globally and are a threat to coastal ecosystems. Although some HAB...     

Males Benefit from Mating with Outbred Females in Drosophila littoralis: Male Choice for Female Genetic Quality?

The evolution and expression of mate choice behaviour in either sex depends on the sex‐specific combination of mating costs, benefits of choice and constraints on choice. If the benefits of choice are larger for one sex, we would expect that sex to be choosier, assuming that the mating costs and constraints on choice are equal between sexes. Because deliberate inbreeding is a powerful genetic method for experimental manipulation of the quality of study organisms, we tested the effects of both male and female inbreeding on egg and offspring production in Drosophila littoralis. Female inbreeding significantly reduced offspring production (mostly due to lower egg‐to‐adult viability), whereas male inbreeding did not affect offspring production (despite a slight effect of paternal inbreeding on egg‐to‐adult viability). As inbreeding depressed female quality more than male quality, the benefits of mate choice were larger for males than for females. In mate choice experiments, inbreeding did not affect male mating success (measured as a probability to be accepted as a mate in a large group), suggesting that females did not discriminate among inbred and outbred males. In contrast, female mating success was affected by inbreeding, with outbred females having higher mating success than inbred females. This result was not explained by lower activity of inbred females. Our results show that D. littoralis males benefit from mating with outbred females of high genetic quality and suggest adaptive male mate choice for female genetic quality in this species. Thus, patterns of mating success in mate choice trials mirrored the benefits of choice: the sex that benefited more from choice (i.e. males) was more choosy.     

Rethinking the dispersal of Homo sapiens out of Africa

Current fossil, genetic, and archeological data indicate that Homo sapiens originated in Africa in the late Middle Pleistocene. By the end of the Late Pleistocene, our species was distributed across every continent except Antarctica, setting the foundations for the subsequent demographic and cultural changes of the Holocene. The intervening processes remain intensely debated and a key theme in hominin evolutionary studies. We review archeological, fossil, environmental, and genetic data to evaluate the current state of knowledge on the dispersal of Homo sapiens out of Africa. The emerging picture of the dispersal process suggests dynamic behavioral variability, complex interactions between populations, and an intricate genetic and cultural legacy. This evolutionary and historical complexity challenges simple narratives and suggests that hybrid models and the testing of explicit hypotheses are required to understand the expansion of Homo sapiens into Eurasia.