Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
122,539
result(s) for
"Stephen, J"
Sort by:
Diet, microorganisms and their metabolites, and colon cancer
Key Points
Colorectal cancer is a so-called westernized disease and the second leading cause of cancer death worldwide; approximately half of those with the disease will die from it
Geographical variation, migration studies and experimental studies provide compelling evidence that environmental factors, rather than genetic dysfunction, are responsible for the development of colorectal cancer
Convincing evidence suggests that risk of colon cancer is increased by processed and unprocessed meat consumption but suppressed by fibre-rich foods
Dietary risk is mediated by the colonic microbiota; carbohydrate residues stimulate production of metabolites that maintain mucosal health, proteinaceous residues and fat-stimulated bile acids might result in pro-inflammatory and carcinogenic metabolites
A moderate intake of meat and fat is part of our omnivorous diet and the carcinogenic potential can be suppressed by the induction of butyrogenesis from fibre-rich foods
Current dietary fibre recommendations need to be reviewed as they are based on the maintenance of cardiovascular health and are below the levels associated with low colon cancer risk
Evidence suggests that food composition affects colonic health and colon cancer risk via its effects on gut microbiota metabolism. In this Review, O'Keefe discusses the mechanisms behind microbial metabolite effects, which could be modified by diet to prevent colorectal cancer in western societies.
Colorectal cancer is one of the so-called westernized diseases and the second leading cause of cancer death worldwide. On the basis of global epidemiological and scientific studies, evidence suggests that the risk of colorectal cancer is increased by processed and unprocessed meat consumption but suppressed by fibre, and that food composition affects colonic health and cancer risk via its effects on colonic microbial metabolism. The gut microbiota can ferment complex dietary residues that are resistant to digestion by enteric enzymes. This process provides energy for the microbiota but culminates in the release of short-chain fatty acids including butyrate, which are utilized for the metabolic needs of the colon and the body. Butyrate has a remarkable array of colonic health-promoting and antineoplastic properties: it is the preferred energy source for colonocytes, it maintains mucosal integrity and it suppresses inflammation and carcinogenesis through effects on immunity, gene expression and epigenetic modulation. Protein residues and fat-stimulated bile acids are also metabolized by the microbiota to inflammatory and/or carcinogenic metabolites, which increase the risk of neoplastic progression. This Review will discuss the mechanisms behind these microbial metabolite effects, which could be modified by diet to achieve the objective of preventing colorectal cancer in Western societies.
Journal Article
Navigating the maze of health insurance choices : a comprehensive look at individual & small business options
\"In one concise book your questions about health insurance are answered in an easy to read format, including the new 2013 Health Insurance Marketplaces.\"--P. [4] of cover.
Book
Highly compressible glass-like supramolecular polymer networks
Supramolecular polymer networks are non-covalently crosslinked soft materials that exhibit unique mechanical features such as self-healing, high toughness and stretchability. Previous studies have focused on optimizing such properties using fast-dissociative crosslinks (that is, for an aqueous system, dissociation rate constant
k
d
> 10 s
−
1
). Herein, we describe non-covalent crosslinkers with slow, tuneable dissociation kinetics (
k
d
< 1 s
−1
) that enable high compressibility to supramolecular polymer networks. The resultant glass-like supramolecular networks have compressive strengths up to 100 MPa with no fracture, even when compressed at 93% strain over 12 cycles of compression and relaxation. Notably, these networks show a fast, room-temperature self-recovery (< 120 s), which may be useful for the design of high-performance soft materials. Retarding the dissociation kinetics of non-covalent crosslinks through structural control enables access of such glass-like supramolecular materials, holding substantial promise in applications including soft robotics, tissue engineering and wearable bioelectronics.
Glass-like supramolecular polymer networks with high compressibility and fast self-recovery are fabricated using host–guest crosslinkers with slow dissociation kinetics.
Journal Article
Coordinate descent algorithms
Coordinate descent algorithms solve optimization problems by successively performing approximate minimization along coordinate directions or coordinate hyperplanes. They have been used in applications for many years, and their popularity continues to grow because of their usefulness in data analysis, machine learning, and other areas of current interest. This paper describes the fundamentals of the coordinate descent approach, together with variants and extensions and their convergence properties, mostly with reference to convex objectives. We pay particular attention to a certain problem structure that arises frequently in machine learning applications, showing that efficient implementations of accelerated coordinate descent algorithms are possible for problems of this type. We also present some parallel variants and discuss their convergence properties under several models of parallel execution.
Journal Article
Local and global regulation of transcription initiation in bacteria
Key Points
Transcription initiation involves the interaction of DNA-dependent RNA polymerase with promoters. In bacteria, this is a highly regulated process.
Many regulators interact directly with the bacterial DNA-dependent RNA polymerase, whereas other regulators interact directly with promoters.
Regulation of transcription initiation occurs in the context of folding and compaction of bacterial chromosomes.
A very wide range of different strategies are used to regulate transcription initiation in bacteria and these differ between species.
In this Review, Browning and Busby describe the advances that have been made in recent years in understanding the molecular details of how transcription initiation is regulated to fine tune gene expression, highlighting factors that relate both to the RNA polymerase and to the promoter.
Gene expression in bacteria relies on promoter recognition by the DNA-dependent RNA polymerase and subsequent transcription initiation. Bacterial cells are able to tune their transcriptional programmes to changing environments, through numerous mechanisms that regulate the activity of RNA polymerase, or change the set of promoters to which the RNA polymerase can bind. In this Review, we outline our current understanding of the different factors that direct the regulation of transcription initiation in bacteria, whether by interacting with promoters, with RNA polymerase or with both, and we discuss the diverse molecular mechanisms that are used by these factors to regulate gene expression.
Journal Article
Phenological sensitivity to climate across taxa and trophic levels
Differences in phenological responses to climate change among species can desynchronise ecological interactions and thereby threaten ecosystem function. To assess these threats, we must quantify the relative impact of climate change on species at different trophic levels. Here, we apply a Climate Sensitivity Profile approach to 10,003 terrestrial and aquatic phenological data sets, spatially matched to temperature and precipitation data, to quantify variation in climate sensitivity. The direction, magnitude and timing of climate sensitivity varied markedly among organisms within taxonomic and trophic groups. Despite this variability, we detected systematic variation in the direction and magnitude of phenological climate sensitivity. Secondary consumers showed consistently lower climate sensitivity than other groups. We used mid-century climate change projections to estimate that the timing of phenological events could change more for primary consumers than for species in other trophic levels (6.2 versus 2.5–2.9 days earlier on average), with substantial taxonomic variation (1.1–14.8 days earlier on average).
An ambitious study has used more than 10,000 datasets to examine how the phenological characteristics—such as the timing of reproduction—of various taxa alter in response to climate change, and suggests that differing levels of climate sensitivity could lead to the desynchronization of seasonal events over time.
The shifting biological seasons
Variations in the phenological responses of different species to climate change have fuelled concerns that key species interactions may desynchronize over time, with consequences for ecosystem functioning. Stephen Thackeray
et al
. examine the climate sensitivity of 812 terrestrial and aquatic taxa across the United Kingdom, using more than 10,000 phenological data sets spanning 1960 to 2012, together with temperature and precipitation data. There was a systematic difference in the magnitude and direction of phenological climate sensitivity across trophic levels, despite marked heterogeneity among organisms sharing taxonomic affinities and trophic position. In particular, secondary consumers showed lower levels of climate sensitivity than primary producers and consumers. The authors suggest that the differential sensitivity of phenology to climate across trophic levels could result in the desynchronization of seasonal events in the future.
Journal Article