24 research outputs found
Comparing lactate and glycerol as a single-electron donor for sulfate reduction in fluidized bed reactors.
Among the greatest challenges to the full
implementation of biological sulfate reduction are the
cost and availability of the electron source. With the
development of the biofuel industry, new organic
substrates have become available. Therefore, this
work sought to compare the performance of a sulfidogenic
process utilizing either lactate or glycerol as
the substrate for sulfate-reducing bacteria (SRB)
growth. Although sulfate reduction is energetically
more favorable with lactate, glycerol is a less expensive
alternative because excess production is forecasted
with the worldwide development of the
biodiesel industry. Continuous experiments were
performed in a fluidized bed (FB) reactor containing
activated carbon as a carrier for a mixed bacterial
population composed of sulfate-reducing and fermentative
bacteria. During the lactate-fed phases, incomplete
oxidation of lactate to acetate by SRB was the
dominant metabolic pathway resulting in as much as
90 % sulfate reduction and high acetate concentrations
(2.7 g L-1). Conversely, in the glycerol-fed
phases, glycerol degradation resulted from syntrophic
cooperation between sulfate-reducing and
fermentative bacteria that produce butyrate along with
acetate (1.0 g L-1) as oxidation products. To our
knowledge, this is the first report of butyrate formation
during sulfate reduction in a glycerol-fed continuousflow
reactor. Sulfate concentrations were reduced by
about 90 % (from 2,000 to 100–300 mg L-1) when
glycerol was being fed to the reactor. Since the FB
reactor was able to stand a change from lactate to
glycerol, this reactor is recommended as the preferred
option should glycerol be selected as a cost-effective
alternative to lactate for continuous sulfate reduction
Schistosoma mansoni : functional proteasomes are required for development in the vertebrate host.
Proteasomes are multi-subunit proteases involved in several mechanisms and thought to contribute to the regulation of cellular homeostasis. Here, we report for the Wrst time biochemical evidence for the existence of a ubiquitin–proteasome proteolytic pathway in this parasite. Proteasomes from both cercariae and adult worms exhibited a high preference for hydrolysis of the substrate Suc- LLVY-AMC, although in the cercariae extract the rate of hydrolysis was 50% lower when compared to adult worms extracts. The same diVerence in proteasome activities was observed when endogenous proteins were broken down in the presence of ATP and ubiquitin. Additionally, accumulation of high molecular weight conjugates was observed when cercariae were pre-incubated with proteasome inhibitors. Finally, we present evidence that during experimental schistosomiasis, proteasome inhibitors were able to reduce the number of lung stage schistosomula, reduce the worm burden and consequently decrease the egg output in infected mice
Characterisation of the COP9 signalosome in Schistosoma mansoni parasites.
The COP9 signalosome (CSN) is an eight-subunit
complex found in all eukaryotes and shares structural features
with both the 26S proteasome ‘lid’ and translation factor eIF3.
Recent data have demonstrated that the CSN is a regulator of
the ubiquitin (Ub) proteasome system (UPS). CSN controls
substrate ubiquitination by cullin-RING Ub ligases, a step
which determines substrate specificity of the UPS. Here, we
reconstructed the CSN complex in Schistosoma mansoni and
identified eight homologous components. Among these homologues,
five subunits were predicted with their full-length sequences.
Phylogenetic analysis confirmed the evolutionary
conservation and the architecture of CSN, as well as the 26S
proteasome ‘lid’. We performed quantitative reverse transcrip
tion-polymerase chain reaction to detect the expression of the
SmCSN transcripts. The Smcsn1, Smcsn2, Smcsn3, Smcsn4,
Smcsn5, Smcsn6, Smcsn7 and Smcsn8 genes were upregulated
in adult worms compared to cercariae, and the expression
levels were similar to that of in vitro cultivated
schistosomula. Taken together, these results suggest that the
CSN complex may be important during cercariae, schistosome
and adult worm development and might explain, at
least in part, the differences among UPSs during the parasite
life cycle
Neuropeptide Y in the medial basal hypothalamus and medial preoptic area during the induction of LH surge may be controlled by locus coeruleus.
The multiple control of gonadotropin releasing hormone (GnRH)/luteinizing hormone (LH) secretion involves locus coeruleus
(LC) and neuropeptide Y (NPY). The objective of the present study was to analyze the possible contribution of the LC to the control of NPY activity in the medial basal hypothalamus (MBH) and medial preoptic area (MPOA) during the LH surge induced by estrogen (E2) and progesterone (P4). Ovariectomized adult Wistar rats were submitted to the hormone replacement and to the LC bilateral lesion (lesioned groups) or sham surgery (control groups). On the day of the experiment the rats were decapitated at 11:00, 13:00, 15:00 and 17:00 h for plasma and brain collection. Plasma LH was determined by radioimmunoassay. MBH and MPOA were microdissected for the measurement of NPY by enzyme immunoassay. NPY mRNA levels in MBH were assessed by the ribonuclease protection assay. The results showed that LC lesion: decreased the plasma LH; increased the content of NPY in the MBH and reduced the increase of NPY content in the MPOA during afternoon in which LH surge was induced. The increased NPY content in MBH was not associated with an increase of the respective mRNA content, suggesting the action of postranscriptional and/or posttranslational mechanisms. In conclusion, the NPY activity in the MPOA on LH surge induced by estrogen and progesterone could be controlled by LC through two ways, at least: one direct way, by the release of NPY from LC neurons terminals that innervate the MPOA and they release NA and NPY; one indirect way, by the control of release but not synthesis of NPY from neurons in the MBH which innervate the MPOA
Implications of volatile fatty acid profile on the metabolic pathway during continuous sulfate reduction.
Volatile fatty acid (VFA) profile is an important parameter in anaerobic reactors because it enables the assessment of metabolic pathways. Volatile fatty acids were monitored during sulfate reduction in a UASB (upflow anaerobic sludge blanket) reactor treating 2 g/L sulfate concentration and with the organic loading increasing from 3.5 kg COD/m3 d to 5.9 kg COD/m3 d, for a 1-day residence time. In the absence of recirculation, the best outcome (65% reduction) was noticed with the lowest organic loading (3.55 kg/m3 d). When recirculation was applied, sulfate reduction yields increased to 89%, corresponding to a sulfate removal rate of 1.94 kg SO4 2_/m3 d. The reactor performance was discussed in relation to microbial diversity and metabolic pathways. At high organic loading, two metabolic pathways account for lactate degradation: (i) lactate is oxidized to acetate and carbon dioxide by the incomplete-oxidizer SRB (sulfate-reducing bacteria) Desulfomonas, Desulfovibrio, Desulfolobus, Desulfobulbus and Desulfotomaculum spp.; (ii) lactate is converted to acetate by fermenting bacteria such as Clostridium sp. High propionate concentrations imply that there are low sulfate reduction efficiencies
Computational identification and evolutionary relationships of the MicroRNA gene cluster miR-71/2 in protostomes.
MicroRNAs (miRNAs) are small noncoding
RNA molecules which are processed into *20–24 nt
molecules that can regulate the gene expression posttranscriptionally.
MiRNA gene clusters have been identified
in a range of species, where in miRNAs are often
processed from polycistronic transcripts. In this study, a
computational approach is used to investigate the extent of
evolutionary conservation of the miR-71/2 cluster in animals,
and to identify novel miRNAs in the miRNA cluster
miR-71/2. The miR-71/2 cluster, consisting of copies of the
miR-71 and miR-2 (including miR-13) families, was found
to be Protostome-specific. Although, this cluster is highly
conserved across the Protostomia, the miR-2 family is
completely absent from the Deuterostomia species, while
miR-71 is absent from the Vertebrata and Urochordata. The
evolutionary conservation and clustering propensity of the
miR-71/2 family across the Protostomes could indicate
the common functional roles across the member species of
the Protostomia
Bowman-Birk inhibitors, proteasome peptidase activities and colorectal pre neoplasias induced by 1,2-dimethylhydrazine in Swiss mice.
Bowman-Birk inhibitors (BBIs) are protein molecules containing two inhibitory domains for enzymes similar to trypsin and chymotrypsin. Interest in these inhibitors arose from their properties against the cancer chemically induced by 1,2-dimethylhydrazine (DMH). In this study the effect of two BBI preparations (from Glycine max and Macrotyloma axillare) were evaluated for the prevention of colorectal neoplasia induced by intraperitoneal injections of DMH, given at a dose of 30 mg/kg, during 12 weeks. Mice treated with DMH presented histopathological alterations consistent with tumor development, augmented CD44 expression and increased proteasome peptidase activities. Lysosomal fractions, obtained from the intestines, were chromatographed in a Sepharose-BBI column and increased activity for trypsin and chymotrypsin-like proteases recovered from DMH-treated animals. In parallel, mice treated for eight weeks with BBIs showed a decrease in the chymotrypsin and trypsin-like proteasome activities compared to animals fed on normal diet. For the groups receiving simultaneous treatment with DMH and BBIs, dysplasic lesions were not observed and proteasome peptidase activities were similar to the control group after the 24th week. These results suggest that the mechanism by which BBIs could prevent the appearance of pre neoplastic lesions is associated with inhibition of both the lysosomal and proteasome- dependent proteolytic pathways
Endurance training blocks uncoupling protein 1 up-regulation in brown adipose tissue while increasing uncoupling protein 3 in the muscle tissue of rats fed with a high-sugar diet.
The mitochondrial uncoupling proteins (UCPs) of interscapular brown adipose tissue (iBAT) and of muscles play important roles in energy balance. For instance, the expression of UCP1 and UCP3 are modulated by free fatty acid gradients induced by high-sugar diets and acute exercise that is dependent on sympathetic stimulation. However, the effects of endurance training in animals fed with high-sugar diets are unknown. This study aims to evaluate the long-term effects of diet and exercise on UCP1 and UCP3 levels and energy balance efficiency. Rats fed with standard or high-sugar (HSD) diets were simultaneously subjected to running training over an 8-week period. After the training period, the rats were decapitated, and the iBAT and gastrocnemius muscle tissues were removed for evaluation of the β3-receptor, Ucp1, and Ucp3 mRNA and protein expression, which were analyzed by quantitative reverse transcriptase polymerase chain reaction and Western blot, respectively. Groups fed with an HSD displayed a higher adiposity index and iBAT weight (P < .05), whereas exhibited an up-regulation of Ucp1 mRNA and protein levels (P < .05). Training increased β3-receptor mRNA in iBAT and reduced the Ucp3 mRNA in muscle tissues. In association with an HSD, training restored the increasing β3-receptor mRNA and greatly up-regulated the levels of Ucp3 mRNA. Therefore, training blocked the HSD-induced up-regulation of UCP1 expression in iBAT, whereas it up-regulated the expression of Ucp3 mRNA in muscle. These results suggest that training enhances the relationship between Ucp1/Ucp3 mRNA levels, which could result in higher energy efficiency, but not when HSDinduced elevated sympathetic activity is maintained
Endurance training increases leptin expression in the retroperitoneal adipose tissue of rats fed with a high-sugar diet.
The presence of leptin receptors in white adipose
tissue (WAT) suggests a type of peripheral control
during the development of obesity and other metabolic
disorders. Both diet composition and exercise influence
serum leptin; however, the effect of their combination on
long-term WAT leptin metabolism is unknown. In this
study, rats fed with standard or high-sugar diets (HSD)
were simultaneously subjected to running training for 4-
and 8-week periods, and the retroperitoneal WAT (rWAT)
was evaluated for adipocyte cell size, lipid and catecholamine
content, Lep, OB-Rb and Ucp2 mRNA transcription
levels, and circulating leptin and non-esterified fatty acids
(NEFA). The HSD groups displayed a higher adiposity
index and rWAT weight, Lep mRNA and protein upregulation,
and a period-dependent effect on OB-Rb mRNA
expression. Exercise decreased serum leptin and upregulated
the OB-Rb mRNA levels. However, in rats fed with
an HSD, the increase in OB-Rb mRNA and reduction in
catecholamine levels resulted in a high level of adiposity
and hyperleptinemia. The combination of training and an
HSD decreases the NEFA levels and upregulating the Ucp2
mRNA expression in the 4-week period, while downregulating
the Ucp2 mRNA expression in the 8-week period
without changing the NEFA levels. Our results suggest that
an HSD induces an increase in leptin expression in rWAT,
while reducing adipocytes via leptin-mediated lipolysis
after an 8-week period. In exercised rats fed an HSD, TAG
synthesis and storage overlaps with lipolysis, promoting fat
store development and Lep mRNA and plasma protein
upregulation in adult rats
The 20S proteasome of Schistosoma mansoni : a proteomic analysis.
Proteasomes are molecular machines found in virtually all cells that provide one of the mechanisms
for protein turnover. We have analysed the 20S proteasome of Schistosoma mansoni, the
first multimeric complex isolated from this helminth parasite. Three chromatographic steps
were employed to yield a highly homogeneous preparation. 2-DE of the purified complex
revealed 58 spots, of which 46 could be assigned either an a or a b proteasome signature by MS.
Most of the 14 transcripts (7a and 7b) encoded by the parasite genome were represented by
multiple spots and we suggest that this diversity is due to PTMs of subunits. For most of the
isoforms, variations in pI predominated although alterations in mass were also observed. 2-DE
separations of extracts from infective cercariae and blood-dwelling adult worms probed by
Western blotting, using a human anti-a subunit antibody, revealed different patterns of reactivity,
most probably in a3 and a6 subunits, on the basis of sequence conservation. This difference was
rapidly lost following transformation of the cercaria to the skin schistosomulum stage, suggesting
that changes in the proteasome structure, likely caused by the introduction of a new set of
PTMs, precede remodelling of the parasite body prior to intravascular migration