305 research outputs found
Linguistic meta-theory the formal and empirical conditions of acceptability of linguistic theories and descriptions
Most linguists acknowledge, explicitly or implicitly,
the relevance of epistemological questions in
linguistics but relatively few have given more than a
cursory, ad hoc or incomplete consideration to them.
The work of one of those few, Jan Mulder, forms the
starting point for much of the present discussion.
Epistemological considerations arise in many contexts
in linguistics and in many guises. It is an epistemological
matter whenever we test the adequacy of a
description or the acceptability of a theory. Epistemological
considerations are latent whenever we discuss
the form or the content of linguistic theories
and descriptions or their interrelations. The comparison
of different approaches to linguistics inevitably
raises epistemological questions concerning our
approach to linguistics or our presuppositions about it.
These questions are of a general nature and transcend
questions about particular linguistic theories and descriptions.
These epistemological questions force us to
consider what we take linguistics to be. In considering
questions of the type mentioned we are forced, for
example, to analyse what we mean by a "linguistic
theory", a "linguistic description" and what phenomena
we are aiming to understand. We are, furthermore,
forced to analyse the constraints which a scientific
attitude places upon linguistic theorising
and description-building. It is these questions concerning
the acceptability of linguistic theories and
descriptions which we call linguistic meta-theory.
This thesis falls into five main parts. Firstly,
in Chapter One, we consider the nature and scope of
linguistic meta-theory. Secondly, in Chapter Two, we
look at a number of previous approaches to the subject.
Other important contributions are discussed as they
arise in the text. Thirdly, in Chapters Three and
Four, we consider in detail the major meta-theoretical
distinctions in linguistics and their consequences.
In particular, we distinguish linguistic theories
from linguistic descriptions and discuss the nature of
linguistic phenomena. The view is put forward that
linguistics is a scientific subject. The meaning of
this assertion is analysed and the interrelations of
linguistic theories, descriptions and phenomena are
considered in the light of this analysis. The main
epistemological requirement that is put forward and
defended is that of the empiricism of linguistics.
Certain changes in our view of the philosophy of science
and in our view of the form of linguistic theories
and descriptions follow from the conjunction of
these major meta-theoretical positions.
Fourthly, we consider the main meta-theoretical
considerations concerning theories (Chapter Five) and
reject a widespread view of linguistic theory as a
non-empirical study (Chapter Six) and we consider the
main meta-theoretical conditions relating to linguistic
descriptions and some practical examples of description
-building consonant with the general positions adopted
in Chapter Seven. In Chapter Eight, we look at a concrete
example of theory-building in the light of the
meta-theoretical conditions of acceptability previously
set up. We are especially concerned to show how a
theory can meet the condition of being "applicable" or
"indirectly scientific" through the establishment of
acceptable empirical descriptions consonant with the
meta-theoretical conditions on descriptions considered
earlier.
The view that linguistics is a science implies
that we must be concerned with the empirical testing of
descriptions and, so, the fifth part of the work is
devoted to methodology. In Chapter Nine, we defend
the role and necessity of methodology in linguistics
and set up the logical framework of relations between
the methodology and theory descriptions and phenomena.
In Chapter Ten, we examine two of the known types of
empirical testing and their shortcomings. Finally, in
Chapter Eleven, we give an example of the successful
and correct application of a methodology in order to
bring out the nature of empirical testing and to demonstrate
its feasibility within a scientific linguistics
of the sort we imagine
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Potential of novel dextran oligosaccharides as prebiotics for obesity management through in vitro experimentation
The energy-salvaging capacity of the gut microbiota from dietary ingredients has been proposed as a contributing factor for the development of obesity. This knowledge generated interest in the use of non-digestible dietary ingredients such as prebiotics to manipulate host energy homeostasis. In the present study, the in vitro response of obese human faecal microbiota to novel oligosaccharides was investigated. Dextrans of various molecular weights and degrees of branching were fermented with the faecal microbiota of healthy obese adults in pH-controlled batch cultures. Changes in bacterial populations were monitored using fluorescent in situ hybridisation and SCFA concentrations were analysed by HPLC. The rate of gas production and total volume of gas produced were also determined. In general, the novel dextrans and inulin increased the counts of bifidobacteria. Some of the dextrans were able to alter the composition of the obese human microbiota by increasing the counts of Bacteroides–Prevotella and decreasing those of Faecalibacterium prausnitzii and Ruminococcus bromii/R. flavefaciens. Considerable increases in SCFA concentrations were observed in response to all substrates. Gas production rates were similar during the fermentation of all dextrans, but significantly lower than those during the fermentation of inulin. Lower total gas production and shorter time to attain maximal gas production were observed during the fermentation of the linear 1 kDa dextran than during the fermentation of the other dextrans. The efficacy of bifidobacteria to ferment dextrans relied on the molecular weight and not on the degree of branching. In conclusion, there are no differences in the profiles between the obese and lean human faecal fermentations of dextrans
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Carbohydrate preferences of Bifidobacterium species isolated from the human gut
The growth of nine species of Bifidobacterium on media containing glucose, xylose, xylooligosaccharides (XOS), xylan or fructooligosaccharides (FOS) as the sole carbon source were compared in pure culture. The bifidobacteria differed in fermentation profiles when tested on different carbohydrates. All species grew to their highest final optical density (OD) on a glucose containing medium, with the exception of B. catenulatum which demonstrated a preference for xylose over glucose, and XOS over FOS. B. bifidum grew to the highest OD on XOS compared to xylose suggesting a specific transport system for the oligosaccharide over the monomer. This is consistent with a lack of β-xylosidase activity present in the culture medium. Lactate, formate and acetate levels were determined and the ratios of these metabolites altered between and within species growing on different carbohydrates. In general, high lactate production correlated with low formate production and low lactate concentrations were obtained at higher levels of formate. Bifidobacteria may alter their metabolic pathways based upon the carbohydrates that are available for their use
Author Correction: Probiotics and prebiotics in intestinal health and disease: from biology to the clinic (Nature Reviews Gastroenterology & Hepatology, (2019), 16, 10, (605-616), 10.1038/s41575-019-0173-3)
© 2019, Springer Nature Limited. In the original article published online, the Competing Interests statement was incorrect and should have stated the following: M.E.S. declares personal fees related to probiotics from the following entities: California Dairy Research Foundation, Clorox, Danone, Danone USA, Dutch Mill, General Mills, JHeimbach, Kelley Drye & Warren, Kellogg, Kerry, Medscape, Nestle, New Chapter, Pepsico, Pfizer, Pharmavite, Probi, Procter & Gamble, Trouw Nutrition, Visalia Dairy Company, Williams Mullen, Winclove Probiotics and Yakult. D.J.M. declares personal fees for consulting for Bayer and Pharmavite. G.R. declares that he helped develop and commercialize probiotic strains GR-1 and RC-14, but has had no financial interest in them for over 10 years. He is Chief Scientific Officer for Seed, a company producing probiotic products. Over the past 3 years, he has consulted on probiotics with Acerus Pharmaceuticals, Altmann, Chr. Hansen, Danone, KGK Science, Kimberly-Clark, Metagenics and Seed. G.R.G. and R.A.R. declare no competing interests. This error has been corrected in the HTML and PDF versions of the article
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Probiotics and prebiotics in intestinal health and disease: from biology to the clinic
Probiotics and prebiotics are microbiota-management tools for improving host health. They target gastrointestinal effects via the gut, although direct application to other sites such as the oral cavity, vaginal tract and skin is being explored. Here, we describe gut-derived effects in humans. In the past decade, research on the gut microbiome has rapidly accumulated and has been accompanied by increased interest in probiotics and prebiotics as a means to modulate the gut microbiota. Given the importance of these approaches for public health, it is timely to reiterate factual and supporting information on their clinical application and use. In this Review, we discuss scientific evidence on probiotics and prebiotics, including mechanistic insights into health effects. Strains of Lactobacillus, Bifidobacterium and Saccharomyces have a long history of safe and effective use as probiotics, but Roseburia spp., Akkermansia spp., Propionibacterium spp. and Faecalibacterium spp. show promise for the future. For prebiotics, glucans and fructans are well proven, and evidence is building on the prebiotic effects of other substances (for example, oligomers of mannose, glucose, xylose, pectin, starches, human milk and polyphenols)
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Prebiotic supplementation of In Vitro fecal fermentations inhibits proteolysis by gut bacteria, and host diet shapes gut bacterial metabolism and response to intervention
Metabolism of protein by gut bacteria is potentially detrimental due to the production of toxic metabolites, such as ammonia, amines, p-cresol, and indole. The consumption of prebiotic carbohydrates results in specific changes in the composition and/or activity of the microbiota that may confer benefits to host well-being and health. Here, we have studied the impact of prebiotics on proteolysis within the gut in vitro. Anaerobic stirred batch cultures were inoculated with feces from omnivores (n = 3) and vegetarians (n = 3) and four protein sources (casein, meat, mycoprotein, and soy protein) with and without supplementation by an oligofructose-enriched inulin. Bacterial counts and concentrations of short-chain fatty acids (SCFA), ammonia, phenol, indole, and p-cresol were monitored during fermentation. Addition of the fructan prebiotic Synergy1 increased levels of bifidobacteria (P = 0.000019 and 0.000013 for omnivores and vegetarians, respectively). Branched-chain fatty acids (BCFA) were significantly lower in fermenters with vegetarians’ feces (P = 0.004), reduced further by prebiotic treatment. Ammonia production was lower with Synergy1. Bacterial adaptation to different dietary protein sources was observed through different patterns of ammonia production between vegetarians and omnivores. In volunteer samples with high baseline levels of phenol, indole, p-cresol, and skatole, Synergy1 fermentation led to a reduction of these compounds
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Metabolism of wheat dextrin, partially hydrolysed guar gum and insulin combined with either Bifidobacterium lactis or Lactobacillus acidophilus in an in vitro gut model fermentation
Combining the fibres wheat dextrin (WD), partially hydrolysed guar gum (PHGG) and inulin with probiotics Lactobacillus acidophilus NCFM (NCFM) or Bifidobacterium lactis HN019 (HN019) may enhance bacterial metabolites leading to a healthier gut community. The aim of this study was to determine whether WD, PHGG and inulin or NCFM and HN019 alone generate a more favourable gut bacterial community than when combined. A secondary aim was to assess organic acid production following prebiotics, probiotics and synbiotic fermentation. An in vitro gut model batch culture fermentation was run for 72 h. Samples were collected for bacterial enumeration (fluorescent in situ hybridisation combined with flow cytometry) and organic acid production (gas chromatography). Inulin and HN019 combination significantly increased bifidobacteria compared to inulin alone. Additionally, a significant increase in lactic acid bacteria, Bacteroides and Clostridium coccoides-Eubacterium rectale was found in the inulin containing probiotic vessels. The WD and PHGG vessels combined with the probiotic did not show any alteration in bacterial metabolism compared to the dietary fibres alone. In conclusion, synbiotic inulin combined with either HN019 or NCFM may help to enhance bacterial metabolites and cross-feeding to lead to a prolonged elevation in Bifidobacterium spp., and lactic acid bacteria
The prebiotic effect of α-1,2 branched, low molecular weight dextran in the batch and continuous faecal fermentation system
The aim of this study was to establish the effect of smaller molecular weight (0.5 and 1.0 kDa) on prebiotic efficacy and its putative sustainability in the human gut. The prebiotic effect of α-1,2 branched, 0.5 and 1 kDa dextrans were evaluated in faecal batch fermentations as compared with inulin. Both dextrans induce similar selectivity towards Bifidobacterium sp., Lactobacillus/Enterococcus and Bacteroides/Prevotella, and producing similar concentrations of short chain fatty acids. However, the 0.5 kDa dextran was fermented faster than the 1 kDa dextran, where both produced lower amount of gas than inulin. The fermentation of 1 kDa dextran was further investigated in continuous gut models. The dextran increased Bifidobacterium and Roseburia sp. populations in the final vessel, while decreasing Clostridium histolyticum and Faecalibacterium prausnitzii. Overall, the α-1,2 branched, 1 kDa dextran induced selective effect on the gut microbiota and stimulated short chain fatty acids, indicating prebiotic sustainability in distal regions of the gut
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Understanding the influence of processing conditions on the extraction of rhamnogalacturonan-I “hairy” pectin from sugar beet pulp
Sugar beet pectin is rich in rhamnogalacturonan-I (RG-I) region, which is a potential source of prebiotics. RG-I
pectin cannot be extracted the same way as commercial homogalacturan-rich pectin using hot acid. Therefore,
this study has explored several alternative methods, including microwave-assisted extraction (MAE) and conventional-
solvent extraction (CSE) at atmospheric pressure using different solvents, and microwave-assisted
hydrothermal extraction (MAHE) under pressure using water. No conclusive differences in microwave and
conventional heating were found with heating rate controlled. The optimum treatment times of both MAE and
CSE at 90 °C atmospheric pressure and regardless of the solvents used were 120 min; however, MAHE at 130 °C
under pressure can dramatically reduce the time to 10 min. Alcohol-insoluble solids (AIS) extracted using pH13
solvent by MAE had both the highest RG-I yield at 25.3% and purity at 260.2 mg/g AIS, followed by AIS extracts
using water by MAHE with 7.5% and 166.7 mg/g AIS respectively
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