416 research outputs found
L-optimal transportation for Ricci flow
No full textWe introduce the notion of L-optimal transportation, and use it to construct a natural monotonic quantity for Ricci flow which includes a selection of other monotonicity results, including some key discoveries of Perelman [13] (both related to entropy and to L-length) and a recent result of McCann and the author [11]
Vitronectin: growth factor complexes hold potential as a wound therapy approach
No full textTopical administration of growth factors has displayed some potential in wound healing, but variable efficacy, high doses, and costs have hampered their implementation. Moreover, this approach ignores the fact that wound repair is driven by interactions between multiple growth factors and extracellular matrix (ECM) proteins. We report herein that complexes comprising IGF and IGF-binding proteins bound to the ECM protein vitronectin (VN) significantly enhance cellular functions relevant to wound repair in human skin keratinocytes in two- and three-dimensional in vitro cell models and are active, even in the presence of wound fluid. Moreover, these responses require activation of both the IGF receptor and the VN-binding av integrins. Further, we assessed the complexes as a topical agent in the treatment of deep dermal partial thickness burns in a porcine model. This pilot study revealed that the complexes may hold promise as a wound healing therapy. Critically, the significant responses observed in vitro and the encouraging preliminary data in vivo were obtained with nanogram doses of growth factors. This suggests that coupling delivery of growth factors to ECM proteins such as VN may ultimately prove to be a more effective strategy for developing a wound healing therapy.Zee Upton, Leila Cuttle, Anthony Noble, Margit Kempf, Gemma Topping, Jos Malda, Yan Xie, Julie Mill, Damien G Harkin, Olena Kravchuk, David I Leavesley and Roy M Kimbl
Soluble arabinoxylan alters digesta flow and protein digestion of red meat-containing diets in pigs
No full textAbstract not availableDagong Zhang, Barbara A. Williams, Deirdre Mikkelsen, Xiuhua Li, Helen L. Keates, Allan T. Lisle, Helen M. Collins, Geoffrey B. Fincher, Anthony R. Bird, David L. Topping, Michael J. Gidley, Wayne L. Bryde
Effects of topping, stem density, and stage of vine cutting on canopy growth and tuber yield yield of potato (Solanum tuberosum L.)
No full textSeed tubers of ‘Yukon Gold’ potato (Solanum tuberosum L.) exhibit strong apical dominance, resulting in low stem density after planting. After emergence, the terminal buds reimpose apical dominance on the rest of the canopy leading to production of few secondary branches. Therefore, several experiments were conducted at the Virginia Polytechnic Institute and State University Kentland Research Farm, Blacksburg in 1992, 1993, and 1994 to evaluate the effects of topping [(excising 2-3 cm from the terminal buds at 1 to 2 weeks after the date of plant emergence (WAE)], stage of vine cutting at ground level, and main stem density on canopy growth, tuber bulking rate, and tuber yields of potato. Topping (3 years) and vine cutting (2 years) at 1 WAE resulted in more uniform plant stands and increased average yield of US No. 1 tubers of ‘Yukon Gold’ by 16 and 14%, compared to untopped and uncut plants, respectively. When plants of ‘Kennebec’, ’Superior’, and ’Yukon Gold’ were topped in 1994, yield of US No. 1 tubers increased by an average of 10%, indicating that topping could be used to improve tuber yield of potato cultivars exhibiting different growth habits. The increased tuber yields following topping resulted from a combination of increased leaf area duration and increased period of tuber bulking. Cutting vines of ‘Yukon Gold’ at 2, 4, and 6 WAE in 1992 and 1993, decreased yield of US No. 1 tubers by 11, 69, and 38% and by 19, 56, and 48%, respectively. Yield of US No. 1 tubers increased with increased stem density and increased in-row spacing. Interaction effects between in row spacing and topping were significant. Control plants of ’Yukon Gold’ produced higher tuber bulking rates and yield of US No. 1 tubers than topped plants at 15 cm in-row spacing, while topped plants had higher tuber bulking rates and yield of US No. 1 tubers than control plants at 20, 25, and 30 cm in-row spacings. Neither topping nor in-row spacing increased the incidence of hollow heart of tubers in 1994. The results showed that the difference in tuber yield between topped and control plants was greater during long growing season and topped plants should be spaced at 25 cm in-row in order to obtain maximum tuber yield.Ph. D
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Transcriptome analysis reveals key genes involved in the regulation of nicotine biosynthesis at early time points after topping in tobacco (Nicotiana tabacum L.)
No full textBackground Nicotiana tabacum is an important economic crop. Topping, a common agricultural practice employed with flue-cured tobacco, is designed to increase leaf nicotine contents by increasing nicotine biosynthesis in roots. Many genes are found to be differentially expressed in response to topping, particularly genes involved in nicotine biosynthesis, but comprehensive analyses of early transcriptional responses induced by topping are not yet available. To develop a detailed understanding of the mechanisms regulating nicotine biosynthesis after topping, we have sequenced the transcriptomes of Nicotiana tabacum roots at seven time points following topping. Results Differential expression analysis revealed that 4830 genes responded to topping across all time points. Amongst these, nine gene families involved in nicotine biosynthesis and two gene families involved in nicotine transport showed significant changes during the immediate 24 h period following topping. No obvious preference to the parental species was detected in the differentially expressed genes (DEGs). Significant changes in transcript levels of nine genes involved in nicotine biosynthesis and phytohormone signal transduction were validated by qRT-PCR assays. 549 genes encoding transcription factors (TFs), found to exhibit significant changes in gene expression after topping, formed 15 clusters based on similarities of their transcript level time-course profiles. 336 DEGs involved in phytohormone signal transduction, including genes functionally related to the phytohormones jasmonic acid, abscisic acid, auxin, ethylene, and gibberellin, were identified at the earliest time point after topping. Conclusions Our research provides the first detailed analysis of the early transcriptional responses to topping in N. tabacum, and identifies excellent candidates for further detailed studies concerning the regulation of nicotine biosynthesis in tobacco roots.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Butyrylated starch is less susceptible to enzymic hydrolysis and increases large-bowel butyrate more than high-amylose maize starch in the rat
No full textLarge-bowel fermentation of resistant starch produces SCFA that are believed to be important in maintaining visceral function. High-amylose maize starch (HAMS) and acylated starches are sources of resistant starch and are an effective means of increasing colonic SCFA. Cooking increases digestibility of starches but its effects on the capacity of these starches to raise large-bowel SCFA are unknown. We have examined the effects of cooking of HAMS and butyrylated HAMS (HAMSB) on amylolysis in vitro and their capacity to raise caeco-colonic SCFA in rats. The starches were boiled in excess water and microwaved, followed by drying at 100°C. Cooking increased in vitro glucose release for both starches but significantly less from HAMSB. Rat growth rates were unaffected when fed cooked resistant starch. Digesta pH was increased in the caecum and proximal colon of rats fed cooked HAMS. Distal colonic pH was highest in rats fed cooked HAMSB. Factorial analyses (2×2) of caecal SCFA pools showed significant differences between HAMS and HAMSB, and that cooking significantly lowered caecal butyrate pools. Portal venous butyrate concentrations were higher in both HAMSB groups than those fed HAMS. The data suggest that HAMSB is less susceptible to in vitro amylolysis than HAMS following cooking and delivers more butyrate to rat caecum than HAMS. This attribute may be useful in food applications for specific delivery of SCFA to the colon. Preparation of carbohydrates to simulate human food in animal experiments may be important to assess nutritional and physiological effects accurately.Balázs H. Bajka, David L. Topping, Lynne Cobiac and Julie M. Clark
Resistant starch attenuates colonic DNA damage induced by higher dietary protein in rats
No full textEpidemiologic studies suggest that dietary complex carbohydrates are protective against colorectal cancer but dietary protein may increase risk. However, experimental data to support these relationships are scant. We have shown in rats that consumption of a high-protein (25% casein) diet for 4 wk resulted in a twofold increase in damage to colonocyte DNA compared with a low-protein (15% casein) diet. This was associated with thinning of the colonic mucous barrier and increased levels of fecal p-cresol. Addition of resistant starch as a high-amylose maize starch to the diet increased cecal short-chain fatty acid pools and attenuated DNA damage, suggesting protection against genotoxic agents. In humans, this could translate to altered risk of colonic cancer.Shusuke Toden, Anthony R. Bird, David L. Topping, and Michael A. Conlo
Dose-dependent reduction of dietary protein-induced colonocyte DNA damage by resistant starch in rats correlates more highly with caecal butyrate than with other short chain fatty acids
No full textCopyright © 2007 Landes BiosciencePrevious studies have shown increased levels of colonocyte DNA damage (as measured by the comet assay) and thinning of the colonic mucus layer in rats fed higher dietary protein as casein or red meat with highly digestible starch. Feeding resistant starch (RS) as high amylose maize starch (HAMS) opposed these changes. However, the dietary level of HAMS was relatively high (48% by weight) so this study was conducted to establish whether HAMS had the same effects at lower dietary levels. Adult male rats were fed a diet containing 25% casein with 0%, 10%, 20%, 30% or 40% HAMS for 4 wk. DNA single strand breaks and 8-hydroxyguanosine levels were measured in isolated colonocytes by the comet assay. As expected, comet tail moment was greatest and the mucus barrier thinnest in rats fed 0% HAMS. DNA damage was reduced and the mucus barrier thickened in a logarithmic dose-dependent manner by HAMS. There was no significant difference in 8-hydroxyguanosine between dietary groups. Caecal and fecal short chain fatty acid (SCFA) pools rose with the increased level of dietary HAMS. DNA damage of colonocytes correlated negatively with caecal SCFA but the strongest correlation was with caecal butyrate, which is consistent with the proposed role of this SCFA in promoting a normal cell phenotype. These data show that HAMS prevents protein-induced colonic DNA damage in a dose-dependent manner. Inclusion of 10% HAMS was found to be sufficient to oppose colonocyte DNA damage, and to increase caecal and fecal SCFA pools.Shusuke Toden, Anthony R. Bird, David L. Topping and Michael A. Conlo
Resistant starch prevents colonic DNA damage induced by high dietary cooked red meat or casein in rats
No full textIn a previous study we have shown that high levels of dietary protein (as casein) result in increased levels of colonic DNA damage, measured by the comet assay, and thinning of the colonic mucus layer in rats when dietary resistant starch (RS) is negligible. Feeding RS abolishes these effects. This study aimed to establish whether a diet high in protein as cooked red meat would have similar effects and whether RS was protective. Rats were fed a diet containing 15% or 25% casein or 25% cooked lean red beef, each with or without the addition of 48% high amylose maize starch (a rich source of RS) for four weeks. As expected, high dietary casein caused a 2-fold increase in colonic DNA damage compared with a low casein diet and reduced the thickness of the colonic mucus layer by 41%. High levels of cooked meat caused 26% greater DNA damage than the high casein diet but reduced mucus thickness to a similar degree to casein. Addition of RS to the diet abolished the increase in DNA damage and the loss of colonic mucus thickness induced by either high protein diet. Cecal and fecal short chain fatty acid pools were also increased by inclusion of RS in the diet. Because DNA damage is an early step in the initiation of cancer, these findings suggest that increased DNA damage due to high dietary protein as cooked red meat or casein could increase colorectal cancer risk but inclusion of resistant starch in the diet could significantly reduce that risk.Shusuke Toden, Anthony R. Bird, David L. Topping, Michael A. Conlo
MOESM9 of Transcriptome analysis reveals key genes involved in the regulation of nicotine biosynthesis at early time points after topping in tobacco (Nicotiana tabacum L.)
No full textAdditional file 9: Table S4. Differentially transcribed transcription factors after topping
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