Rowett Research Institute

About: Rowett Research Institute is a based out in . It is known for research contribution in the topics: Rumen & Population. The organization has 2986 authors who have published 4459 publications receiving 239472 citations.

Effects of sodium hydroxide on cereal straws in relation to the enhanced degradation of structural polysaccharides by rumen microorganisms

Abstract: The action of sodium hydroxide on the rate and extent of loss of wall polysaccharides from wheat and barley straws incubated in the rumen of the sheep was studied using a nylon bag technique. Cellulose loss reached a maximum in straws treated with 10 g NaOH 100 g−1 straw. Further increase in amounts of alkali applied resulted in additional solubilisation of straw constituents, particularly xylan, but did not further enhance cellulose degradation. Rates of degradation of isolated straw, cotton and wood celluloses correlated with three of four measures of cellulose crystallinity obtained by X-ray diffraction and infrared analysis. Treatment of cellulose samples with 20 g NaOH 100 g−1 cellulose did not affect rates of loss or produce detectable changes to cellulose morphology. Loss of acetic acid esters, which accompanied alkali treatment, did not relate to improvements to digestibility. The rate of loss of cellulose from delignified neutral detergent fibre (NDF) was that shown by the isolated straw cellulose, despite the presence of acetylated hemicellulose. Deacetylation of delignified NDF with NaOH or sodium methoxide did not enhance rates of xylose or cellulose loss. In lignified wall material (NDF) the molar ratio acetyl:xylose (approximately 1:3.5) and proportion of the major phenolic acids (p-coumaric and ferulic acids) remained essentially constant throughout the course of degradation in the rumen. It is suggested that loss of phenolic acids, while not directly contributing to digestibility enhancement, may model the susceptibility of ester linkages formed between polysaccharide and polyphenolic material to alkali. The extent of solubilisation of p-coumaric acid produced by NaOH showed a linear relationship with cellulose digestibility. An upper limit of 40% acid detergent lignin and 55% of total phenolics were released by NaOH, the extent of release closely paralleling cellulose digestibility. Phenolic material resistant to alkali remained associated with wall polysaccharides and was not released from nylon bags until over 50% of cellulose (and hemicellulose) had been degraded.

Inter-individual differences in repair of DNA base oxidation, measured in vitro with the comet assay

Abstract: There is a need for a reliable, robust and sensitive assay for DNA repair, suitable for use with human lymphocyte samples in molecular epidemiological investigations. The comet assay (single cell alkaline gel electrophoresis) has been modified to measure the ability of a simple subcellular extract of lymphocytes to carry out the initial step of repair, i.e. incision, on a DNA substrate carrying specific lesions--namely, oxidized bases introduced by visible light in the presence of photosensitizer. The cell extract is free of non-specific nuclease activity, incising DNA only if the DNA has been treated with photosensitizer and light. The activity varies between individuals, but consistency is seen between samples from each individual taken on occasions several months apart. The lack of activity of extract from Ogg1(-) mouse cells (deficient in the glycosylase that excises 8-oxoguanine) in this assay confirms that the activity measured is predominantly excision repair of oxidized bases. This new DNA repair assay is simple, rapid and requires only small quantities of lymphocyte extract (obtainable from 10 ml blood).

Problems in the measurement of 8-oxoguanine in human DNA. Report of a workshop, DNA Oxidation, held in Aberdeen, UK, 19-21 January, 1997

Abstract: Oxidative DNA damage is widely believed to play a role in cancer aetiology. It is therefore important to be able to assess it, both as an index of cancer risk, and in experiments to test agents with a potential to reduce oxidative damage, such as dietary antioxidants. However, there is an alarming discordance in estimates of concentrations of oxidative damage in human DNA, largely attributable to the kind of method used to measure it. A meeting was held recently at the Rowett Research Institute in Aberdeen to address this problem.

Impact of pH on lactate formation and utilization by human fecal microbial communities.

Abstract: The human intestine harbors both lactate-producing and lactate-utilizing bacteria. Lactate is normally present at <3 mmol liter(-1) in stool samples from healthy adults, but concentrations up to 100 mmol liter(-1) have been reported in gut disorders such as ulcerative colitis. The effect of different initial pH values (5.2, 5.9, and 6.4) upon lactate metabolism was studied with fecal inocula from healthy volunteers, in incubations performed with the addition of dl-lactate, a mixture of polysaccharides (mainly starch), or both. Propionate and butyrate formation occurred at pH 6.4; both were curtailed at pH 5.2, while propionate but not butyrate formation was inhibited at pH 5.9. With the polysaccharide mix, lactate accumulation occurred only at pH 5.2, but lactate production, estimated using l-[U-(13)C]lactate, occurred at all three pH values. Lactate was completely utilized within 24 h at pH 5.9 and 6.4 but not at pH 5.2. At pH 5.9, more butyrate than propionate was formed from l-[U-(13)C]lactate in the presence of polysaccharides, but propionate, formed mostly by the acrylate pathway, was the predominant product with lactate alone. Fluorescent in situ hybridization demonstrated that populations of Bifidobacterium spp., major lactate producers, increased approximately 10-fold in incubations with polysaccharides. Populations of Eubacterium hallii, a lactate-utilizing butyrate-producing bacterium, increased 100-fold at pH 5.9 and 6.4. These experiments suggest that lactate is rapidly converted to acetate, butyrate, and propionate by the human intestinal microbiota at pH values as low as 5.9, but at pH 5.2 reduced utilization occurs while production is maintained, resulting in lactate accumulation.