Search results for "cellular respiration"
showing 10 items of 29 documents
Transcriptional regulation and energetics of alternative respiratory pathways in facultatively anaerobic bacteria
1998
Abstract The facultatively anaerobic Escherichia coli is able to grow by aerobic and by anaerobic respiration. Despite the large difference in the amount of free energy that could maximally be conserved from aerobic versus anaerobic respiration, the proton potential and Δg ′ Phos are similar under both conditions. O 2 represses anaerobic respiration, and nitrate represses fumarate respiration. By this the terminal reductases of aerobic and anaerobic respiration are expressed in a way to obtain maximal H + e − ratios and ATP yields. The respiratory dehydrogenases, on the other hand, are not synthesized in a way to achieve maximal H + e − ratios. Most of the dehydrogenases of aerobic respirat…
Effect of changes in the cellular energy state on glucose transport activity in Brevibacterium flavum
2000
Abstract The effect of changes in cellular energy state on 6[14C]glucose uptake and activity of the phosphoenolpyruvate:glucose phosphotransferase system (PTS) in Brevibacterium flavum RC 115 cells was investigated. Energy generation in cells was varied by adding an inhibitor of cellular respiration (potassium cyanide) and an uncoupler of oxidative phosphorylation (pentachlorophenol) to the cell culture as well as by changing thiamine concentration in the bacterial growth medium. The results showed that glucose uptake in ‘respiring’ cells was inversely correlated with bacterial respiration activity: uptake declined with excess ATP generation and increased with lower ATP synthesis caused by …
Aerobic Metabolism: Benefits from an Oxygenated World
2010
In the preceding chapter, we have emphasized the dangers that the advent of dioxygen presented to the existing anaerobic organisms, and the ways they evolved to deal with the problems. However, this is only part of the story and were it to have ended here, we and the world we know would not exist. What happened instead was quite remarkable; for life seized upon an opportunity presented by the presence of free dioxygen to become many-fold more efficient in extracting energy from foodstuffs. As we shall see, this aerobic, oxidative metabolism opened in turn a multitude of new opportunities for growth and diversification.
Cellular and tissue expression of DAPIT, a phylogenetically conserved peptide
2011
DAPIT (Diabetes Associated Protein in Insulin-sensitive Tissues) is a small, phylogenetically conserved, 58 amino acid peptide that was previously shown to be down-regulated at mRNA level in insulin-sensitive tissues of type 1 diabetes rats. In this study we characterize a custom made antibody against DAPIT and confirm the mitochondrial presence of DAPIT on cellular level. We also show that DAPIT is localized in lysosomes of HUVEC and HEK 293T cells. In addition, we describe the histological expression of DAPIT in several tissues of rat and man and show that it is highly expressed especially in cells with high aerobic metabolism and epithelial cells related to active transport of nutrients …
Respiratory plasticity in response to changes in oxygen supply and demand
2011
Aerobic organisms maintain O(2) homeostasis by responding to changes in O(2) supply and demand in both short and long time domains. In this review, we introduce several specific examples of respiratory plasticity induced by chronic changes in O(2) supply (environmental hypoxia or hyperoxia) and demand (exercise-induced and temperature-induced changes in aerobic metabolism). These studies reveal that plasticity occurs throughout the respiratory system, including modifications to the gas exchanger, respiratory pigments, respiratory muscles, and the neural control systems responsible for ventilating the gas exchanger. While some of these responses appear appropriate (e.g., increases in lung su…
Tetrachlorodecaoxide Improves the Oxygenation Status of Multicellular Tumor Spheroids
1986
Insufficient O2 supply to solid tumors has been recognized since many years to be a crucial problem in cancer therapy. Hypoxia and anoxia may increase the resistance of tumor cells to certain antiproliferative drugs or to ionizing radiation. Numerous approaches to overcoming this problem have been reported in the literature. Efforts have been made in mainly two basic directions: (1) the development of therapeutic means which are particularly efficient in hypoxic and nutrient-deprived tissue areas or which are at least independent of the tissue oxygenation, and (2) the development of methods for improving the oxygenation status of solid tumors. Among the former approaches, the cytotoxicity o…
Regulatory O 2 tensions for the synthesis of fermentation products in Escherichia coli and relation to aerobic respiration
1997
In an oxystat, the synthesis of the fermentation products formate, acetate, ethanol, lactate, and succinate of Escherichia coli was studied as a function of the O2 tension (pO2) in the medium. The pO2 values that gave rise to half-maximal synthesis of the products (pO0. 5) were 0.2-0.4 mbar for ethanol, acetate, and succinate, and 1 mbar for formate. The pO0.5 for the expression of the adhE gene encoding alcohol dehydrogenase was approximately 0.8 mbar. Thus, the pO2 for the onset of fermentation was distinctly lower than that for anaerobic respiration (pO0.5/= 5 mbar), which was determined earlier. An essential role for quinol oxidase bd in microaerobic growth was demonstrated. A mutant de…
O2 as the regulatory signal for FNR-dependent gene regulation in Escherichia coli
1996
With an oxystat, changes in the pattern of expression of FNR-dependent genes from Escherichia coli were studied as a function of the O2 tension (pO2) in the medium. Expression of all four tested genes was decreased by increasing O2. However, the pO2 values that gave rise to half-maximal repression (pO(0.5)) were dependent on the particular promoter and varied between 1 and 5 millibars (1 bar = 10(5) Pa). The pO(0.5) value for the ArcA-regulated succinate dehydrogenase genes was in the same range (pO(0.5) = 4.6 millibars). At these pO2 values, the cytoplasm can be calculated to be well supplied with O2 by diffusion. Therefore, intracellular O2 could provide the signal to FNR, suggesting that…
Serine biosynthesis by photorespiratory and nonphotorespiratory pathways: and interesting interplay with unknown regulatory networks
2013
[EN] Photorespiration is a primary metabolic pathway, which, given its energy costs, has often been viewed as a wasteful process. Despite having reached the consensus that one important function of photorespiration is the removal of toxic metabolite intermediates, other possible functions have emerged, and others could well emerge in the future. As a primary metabolic pathway, photorespiration interacts with other routes; however the nature of these interactions is not well known. One of these interacting pathways could be the biosynthesis of serine, since this amino acid is synthesised through photorespiratory and non-photorespiratory routes. At present, the exact contribution of each rout…
Method for functional study of mitochondria in rat hypothalamus
2008
1872-678X (Electronic) Journal Article Research Support, Non-U.S. Gov't; Different roles of mitochondria in brain function according to brain area are now clearly emerging. Unfortunately, no technique is yet described to investigate mitochondria function in specific brain area. In this article, we provide a complete description of a procedure to analyze the mitochondrial function in rat brain biopsies. Our two-step method consists in a saponin permeabilization of fresh brain tissues in combination with high-resolution respirometry to acquire the integrated respiratory rate of the biopsy. In the first part, we carefully checked the mitochondria integrity after permeabilization, defined exper…