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151.
Treberg JR MacCormack TJ Lewis JM Almeida-Val VM Val AL Driedzic WR 《Physiological and biochemical zoology : PBZ》2007,80(5):542-550
Armored catfish (Liposarcus pardalis), indigenous to the Amazon basin, have hearts that are extremely tolerant of oxygen limitation. Here we test the hypothesis that resistance to hypoxia is associated with increases in binding of selected glycolytic enzymes to subcellular fractions. Preparations of isolated ventricular sheets were subjected to 2 h of either oxygenated or hypoxic (via nitrogen gassing) treatment during which time the muscle was stimulated to contract. The bathing medium contained 5 mM glucose and was maintained at 25 degrees C. Initial experiments revealed increases in anaerobic metabolism. There was no measurable decrease in glycogen level; however, hypoxic treatment led to a twofold increase in heart glucose and a 10-fold increase in lactate content. It is suggested that the increase in heart glucose content is a result of an enhanced rate of facilitated glucose transport that exceeds the rate of phosphorylation of glucose. Further experiments assessed activities of metabolic enzymes in crude homogenates and subsequently tracked the degree of enzyme binding associated with subcellular fractions. Total maximal activities of glycolytic enzymes (hexokinase [HK], phosphofructokinase [PFK], aldolase, pyruvate kinase, lactate dehydrogenase), and a mitochondrial marker, citrate synthase, were not altered with the hypoxic treatment. A substantial portion (>/=50%) of HK is permanently bound to mitochondria, and this level increases under hypoxia. The amount of HK that is bound to the mitochondrial fraction is at least fourfold higher in hearts of L. pardalis than in rat hearts. Hypoxia also resulted in increased binding of PFK to a particulate fraction, and the degree of binding is higher in hypoxia-tolerant fish than in hypoxia-sensitive mammalian hearts. Such binding may be associated with increased glycolytic flux rates through modulation of enzyme-specific kinetics. The binding of HK and PFK occurs before any significant decrease in glycogen level. 相似文献
152.
The interactions between cat-anionic (an acronym indicating surfactant aggregates (micelles and vesicles) formed upon mixing cationic and anionic surfactants in nonstoichiometric amounts) vesicles and DNA have been the subject of intensive studies because of their potential applications in biomedicine. Here we report on the interactions between DNA and cetyltrimethylammonium bromide (CTAB)-sodium octyl sulfate (SOS) cat-anionic vesicles. The study was performed by combining dielectric relaxation spectroscopy, circular dichroism, dynamic light scattering, ion conductivity, and molecular biology techniques. DNA is added to positively charged vesicles until complete charge neutralization of the complex and formation of lipoplexes. This occurs when the mole ratio between the phosphate groups of DNA and positive charges on the vesicle is about 1.8. Above this threshold the nucleic acid in excess remains free in solution. This very interesting new result shows that anionic surfactants are not expelled upon saturation, and therefore, no formation of micelles occurs. Furthermore, vesicle-bound DNA can be released in its native form, as confirmed by dielectric spectroscopy and circular dichroism measurements. The nucleic acid is released upon addition of SOS, which competes with the phosphate groups of the DNA: this results in the demolition of the CTAB-SOS cat-anionic vesicles. These results indicate the possibility of a controlled DNA release and might be of interest in biomedicine. 相似文献
153.
154.
Enhanced Xylitol Production by Precultivation of Candida guilliermondii Cells in Sugarcane Bagasse Hemicellulosic Hydrolysate 总被引:1,自引:0,他引:1
The present work evaluated the key enzymes involved in xylitol production (xylose reductase [XR] and xylitol dehydrogenase
[XDH]) and their correlation with xylose, arabinose, and acetic acid assimilation during cultivation of Candida guilliermondii FTI 20037 cells in sugarcane bagasse hemicellulosic hydrolysate. For this purpose, inocula previously grown either in sugarcane
bagasse hemicellulosic hydrolysate (SBHH) or in semidefined medium (xylose as a substrate) were used. The highest xylose/acetic
acid consumption ratio (1.78) and the lowest arabinose consumption (13%) were attained in the fermentation using inoculum
previously grown in semidefined medium (without acetic acid and arabinose). In this case, the highest values of XR (1.37 U
mg prot−1) and XDH (0.91 U mg prot−1) activities were observed. The highest xylitol yield (∼0.55 g g−1) and byproducts (ethanol and glycerol) formation were not influenced by inoculum procedure. However, the cell previously
grown in the hydrolysate was effective in enhancing xylitol production by keeping the XR enzyme activity at high levels (around
0.99 U·mgprot−1), reducing the XDH activity (34.0%) and increasing xylitol volumetric productivity (26.5%) with respect to the inoculum cultivated
in semidefined medium. Therefore, inoculum adaptation to SBHH was shown to be an important strategy to improve xylitol productivity. 相似文献
155.
Analysis of microbial communities developed on the fouling layers of a membrane-coupled anaerobic bioreactor applied to wastewater treatment 总被引:1,自引:0,他引:1
Calderón K Rodelas B Cabirol N González-López J Noyola A 《Bioresource technology》2011,102(7):4618-4627
The structure of the biofouling layers formed on a pilot-scale membrane-coupled upflow anaerobic sludge blanket bioreactor (UASB) used to treat urban wastewater was analyzed by scanning electron microscopy and electron-dispersive X-ray microanalysis. For comparison, control samples of the membranes were fed either UASB effluent or raw wastewater in a laboratory-scale experiment. Microbial diversity in the fouling materials was analyzed by temperature gradient gel electrophoresis (TGGE) combined with sequence analysis of partial 16S rRNA. Significant differences in structure of the Bacteria communities were observed amongst the different fouling layers analyzed in the UASB membranes, particularly following a chemical cleaning step (NaClO), while the Archaea communities retained more similarity in all samples. The main Bacteria populations identified were evolutively close to Firmicutes (42.3%) and Alphaproteobacteria (30.8%), while Archaea were mostly affiliated to the Methanosarcinales and Methanospirillaceae. Sphingomonadaceae-related bacteria and methanogenic Archaea were persistently found as components of biofouling, regardless of chemical cleaning. 相似文献
156.
157.
Stefania Gessi Stefania Merighi Angela Stefanelli Prisco Mirandola Alessandra Bonfatti Sergio Fini Alberto Sensi Roberto Marci Katia Varani Pier Andrea Borea Fortunato Vesce 《生物化学与生物物理学报:疾病的分子基础》2012,1822(11):1660-1670
Human reproduction is complex and prone to failure. Though causes of miscarriage remain unclear, adenosine, a proangiogenic nucleoside, may help determine pregnancy outcome. Although adenosine receptor (AR) expression has been characterized in euploid pregnancies, no information is available for aneuploidies, which, as prone to spontaneous abortion (SA), are a potential model for shedding light on the mechanism regulating this event. AR expression was investigated in 71 first-trimester chorionic villi (CV) samples and cultured mesenchymal cells (MC) from euploid and TR21 pregnancies, one of the most frequent autosomal aneuploidy, with a view to elucidating their potential role in the modulation of vascular endothelial growth factor (VEGF) and nitric oxide (NO). Compared to euploid cells, reduced A1 and A2B expression was revealed in TR21 CV and MCs. The non-selective adenosine agonist 5′-N-ethylcarboxamidoadenosine (NECA) increased NO, by activating, predominantly, A1AR and A2AAR through a molecular pathway involving hypoxia-inducible-factor-1 (HIF-1α), and increased VEGF, mainly through A2B. In conclusion the adenosine transduction cascade appears to be disturbed in TR21 through reduced expression of A2B and A1ARs. These anomalies may be implicated in complications such as fetal growth restriction, malformation and/or SA, well known features of aneuploid pregnancies. Therefore A1 and A2BARs could be potential biomarkers able to provide an early indication of SA risk and their stimulation may turn out to improve fetoplacental perfusion by increasing NO and VEGF. 相似文献
158.
159.
Ferrão FM Lara LS Axelband F Dias J Carmona AK Reis RI Costa-Neto CM Vieyra A Lowe J 《American journal of physiology. Renal physiology》2012,302(7):F875-F883
ANG II is secreted into the lumens of proximal tubules where it is also synthesized, thus increasing the local concentration of the peptide to levels of potential physiological relevance. In the present work, we studied the effect of ANG II via the luminal membranes of LLC-PK(1) cells on Ca(2+)-ATPase of the sarco(endo)plasmic reticulum (SERCA) and plasma membrane (PMCA). ANG II (at concentrations found in the lumen) stimulated rapid (30 s) and persistent (30 min) SERCA activity by more than 100% and increased Ca(2+) mobilization. Pretreatment with ANG II for 30 min enhanced the ANG II-induced Ca(2+) spark, demonstrating a positively self-sustained stimulus of Ca(2+) mobilization by ANG II. ANG II in the medium facing the luminal side of the cells decreased with time with no formation of metabolites, indicating peptide internalization. ANG II increased heterodimerization of AT(1) and AT(2) receptors by 140%, and either losartan or PD123319 completely blocked the stimulation of SERCA by ANG II. Using the PLC inhibitor U73122, PMA, and calphostin C, it was possible to demonstrate the involvement of a PLC→DAG(PMA)→PKC pathway in the stimulation of SERCA by ANG II with no effect on PMCA. We conclude that ANG II triggers SERCA activation via the luminal membrane, increasing the Ca(2+) stock in the reticulum to ensure a more efficient subsequent mobilization of Ca(2+). This first report on the regulation of SERCA activity by ANG II shows a new mechanism for Ca(2+) homeostasis in renal cells and also for regulation of Ca(2+)-modulated fluid reabsorption in proximal tubules. 相似文献
160.
Azhahianambi Palavesam Felix D. Guerrero Andrew M. Heekin Ju Wang Scot E. Dowd Yan Sun Lane D. Foil Adalberto A. Pérez de León 《PloS one》2012,7(9)
The horn fly, Haematobia irritans, is one of the most economically important pests of cattle. Insecticides have been a major element of horn fly management programs. Growing concerns with insecticide resistance, insecticide residues on farm products, and non-availability of new generation insecticides, are serious issues for the livestock industry. Alternative horn fly control methods offer the promise to decrease the use of insecticides and reduce the amount of insecticide residues on livestock products and give an impetus to the organic livestock farming segment. The horn fly, an obligatory blood feeder, requires the help of microflora to supply additional nutrients and metabolize the blood meal. Recent advancements in DNA sequencing methodologies enable researchers to examine the microflora diversity independent of culture methods. We used the bacterial 16S tag-encoded FLX-titanium amplicon pyrosequencing (bTEFAP) method to carry out the classification analysis of bacterial flora in adult female and male horn flies and horn fly eggs. The bTEFAP method identified 16S rDNA sequences in our samples which allowed the identification of various prokaryotic taxa associated with the life stage examined. This is the first comprehensive report of bacterial flora associated with the horn fly using a culture-independent method. Several rumen, environmental, symbiotic and pathogenic bacteria associated with the horn fly were identified and quantified. This is the first report of the presence of Wolbachia in horn flies of USA origin and is the first report of the presence of Rikenella in an obligatory blood feeding insect. 相似文献