17 research outputs found
Anaerobic biodegradation of aromatic compounds
1046-1067Many
aromatic compounds and their monomers are existing in nature. Besides they are
introduced in to the environment by human activity. The conversion of these
aromatic compounds is mainly an aerobic process because of the involvement of
molecular oxygen in ring fission and as an electron acceptor. Recent literatures
indicated that ring fission of monomers and obligomers mainly occurs in
anaerobic environments through anaerobic respiration with nitrate, sulphate, Carbon
dioxide or carbonate as electron acceptors. These anaerobic processes will help
to work out the better situation for bioremediation of contaminated
environments. While there are plenty of efforts to reduce the release of these
chemicals to the environment, already contaminated sites need to be remediated
not only to restore the sites but to prevent the leachates spreading to nearby
environment. Basically microorganisms are better candidates for breakdown of
these compounds because of their wider catalytic mechanisms and the ability to
act even in the absence of oxygen. These microbes can be grouped based on their
energy mechanisms. Normally, the aerobic counterparts employ the enzymes like
mono-and-di - oxygenases. The end product is basically catechol, which further
may be metabolised to CO2 by means of quinones reductases cycles. In
the absense of reductases compounds, the reduced catechols tend to become
oxidised to form many quinone compounds. The quinone products are more recalcitrant
and lead to other aesthetic problems like colour in water, unpleasant odour,
etc. On the contrary, in the reducing environment this process is prevented and
in a cascade of pathways, the cleaved products are converted to acetyl co-A to
be integrated into other central metabolite paths.
The central metabolite of
anaerobic degradation is invariably co-Athio-esters of benzoic acid or hydroxy
benzoic acid. The benzene ring undergoes various substitution and addition
reactions to form chloro', nitro', methyl' compounds. For complete degradation
the side chains must be removed first and then the benzene ring is activated by
carboxylation or hydroxylation or co-A thioester formation. In the next step
the activated ring is converted to a form that can be collected in the central
pool of metabolism. The third step is the channeling reaction in which the
products of the catalysis are directed into central metabolite pool. The
enzymes involved in these mechanisms are mostly benzyl co-A ligase, benzyl
alcohol dehydrogenase. Other enzymes involved in this path are yet to be purified
though many of the reactions products that have been theoretically postulated
have been identified. This is mainly due to the instability of intermediate
compounds as well as the association of the enzyme substrate is femoral and
experimental conditions need to be sophisticated further for isolation of these
enzymes. The first structural genes of benzoate and hydroxy benzoate ligases
were isolated from Rhodopseudomonas polustris. This gene cluster of 30
kb size found in Rhodopseudomonas palustris coded for the Bad A protein.
Similarly, some of the bph A,B ,C and D cluster of genes coding for the
degradation of pentachlorobenzenes were located in Pseudomonas pseudoalgaligenes
KF 707.
Magnetic resonance imaging and spectroscopy accurately estimate the severity of steatosis provided the stage of fibrosis is considered
Background/Aims: Currently the diagnosis and severity of hepatic steatosis can be established accurately only by liver biopsy. Previous small studies found that steatosis measured by magnetic resonance spectroscopy (MRS) and imaging (MRI) correlated with histological assessment of liver triglyceride content. However, the accuracy of MRS/MRI for grading the severity of steatosis has not been addressed. The aims of this study were (1) to determine whether MRS and MRI can discriminate grades of steatosis in a large cohort of consecutive patients with a wide spectrum of liver disease aetiology and severity (2) to evaluate the effect of hepatic fibrosis, inflammation and iron on quantitation of intrahepatocellular lipid (IHCL) by these techniques
Macrophage secretory products induce an inflammatory phenotype in hepatocytes
AIM: To investigate the influence of macrophages on hepatocyte phenotype and function