Effects of E. coli sepsis and myocardial depressant factor on interval-force relations in dog ventricle

1993 ◽  
Vol 264 (5) ◽  
pp. H1402-H1410 ◽  
Author(s):  
P. Jha ◽  
H. Jacobs ◽  
D. Bose ◽  
R. Wang ◽  
J. Yang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Calcium Metabolism ◽  
Calcium Content ◽  
Left Ventricular ◽  
Muscle Preparation ◽  
E Coli ◽  
Calcium Availability ◽  
Fractional Release

We examined whether depressed left ventricular (LV) contractility during Escherichia coli sepsis in dogs was due to a decrease in the fractional release of calcium from the sarcoplasmic reticulum (SR) or a reduction in calcium content in this organelle. To indirectly assess SR calcium availability in a right ventricular (RV) trabecular muscle preparation, we utilized functional indexes of cellular myocardial calcium metabolism, which included rapid-cooling contracture (RCC), an indicator of SR calcium content, and postrest contraction (PRC), an index of calcium availability from the release compartment of the SR. Measurements were made during steady-state stimulation at 0.5 and 1.5 Hz, during which time rest intervals of 30-240 s were periodically imposed. SR calcium availability was measured in RV trabeculae of dogs subjected to 4 h of E. coli sepsis and was compared with calcium availability measured in nonseptic dogs. We further characterized a filterable cardiodepressant substance (FCS), which has been previously shown to be associated with LV depression in this model, to determine whether it produced changes in calcium metabolism similar to those found in sepsis. The results showed that calcium availability from the SR of septic dogs was not impaired. Furthermore, FCS was found in the 10,000- to 30,000-mol wt fraction of plasma and produced changes in PRC in canine trabeculae that were similar to those produced during sepsis. We conclude that, as assessed by PRC and RCC, SR calcium content and release are not impaired in sepsis.

scholarly journals Escherichia coli alkaline phosphatase. Kinetic studies with the tetrameric enzyme

1972 ◽  
Vol 126 (5) ◽  
pp. 1081-1090 ◽  
Author(s):  
S. E. Halford ◽  
M. J. Schlesinger ◽  
H. Gutfreund
Keyword(s):  
Escherichia Coli ◽  
Alkaline Phosphatase ◽  
Steady State ◽  
Analytical Ultracentrifugation ◽  
Kinetic Studies ◽  
Product Formation ◽  
E Coli ◽  
Enzyme Subunits ◽  
Self Association ◽  
The Stability

1. The stability of the tetrameric form of Escherichia coli alkaline phosphatase was examined by analytical ultracentrifugation. 2. The stopped-flow technique was used to study the hydrolysis of nitrophenyl phosphates by the alkaline phosphatase tetramer at pH7.5 and 8.3. In both cases transient product formation was observed before the steady state was attained. Both transients consisted of the liberation of 1mol of nitrophenol/2mol of enzyme subunits within the dead-time of the apparatus. The steady-state rates were identical with those observed with the dimer under the same conditions. 3. The binding of 2-hydroxy-5-nitrobenzyl phosphonate to the alkaline phosphatase tetramer was studied by the temperature-jump technique. The self-association of two dimers to form the tetramer is linked to a conformation change within the dimer. This accounts for the differences between the transient phases in the reactions of the dimer and the tetramer with substrate. 4. Addition of Pi to the alkaline phosphatase tetramer caused it to dissociate into dimers. The tetramer is unable to bind this ligand. It is suggested that the tetramer undergoes a compulsory dissociation before the completion of its first turnover with substrate. 5. On the basis of these findings a mechanism is proposed for the involvement of the alkaline phosphatase tetramer in the physiology of E. coli.

scholarly journals Role of CheB and CheR in the Complex Chemotactic and Aerotactic Pathway of Azospirillum brasilense

2006 ◽  
Vol 188 (13) ◽  
pp. 4759-4768 ◽  
Author(s):  
Bonnie B. Stephens ◽  
Star N. Loar ◽  
Gladys Alexandre
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Azospirillum Brasilense ◽  
Model Organism ◽  
Spatial Gradient ◽  
Wild Type ◽  
Temporal Gradient ◽  
E Coli ◽  
Significant Difference

ABSTRACT It has previously been reported that the alpha-proteobacterium Azospirillum brasilense undergoes methylation-independent chemotaxis; however, a recent study revealed cheB and cheR genes in this organism. We have constructed cheB, cheR, and cheBR mutants of A. brasilense and determined that the CheB and CheR proteins under study significantly influence chemotaxis and aerotaxis but are not essential for these behaviors to occur. First, we found that although cells lacking CheB, CheR, or both were no longer capable of responding to the addition of most chemoattractants in a temporal gradient assay, they did show a chemotactic response (albeit reduced) in a spatial gradient assay. Second, in comparison to the wild type, cheB and cheR mutants under steady-state conditions exhibited an altered swimming bias, whereas the cheBR mutant and the che operon mutant did not. Third, cheB and cheR mutants were null for aerotaxis, whereas the cheBR mutant showed reduced aerotaxis. In contrast to the swimming bias for the model organism Escherichia coli, the swimming bias in A. brasilense cells was dependent on the carbon source present and cells released methanol upon addition of some attractants and upon removal of other attractants. In comparison to the wild type, the cheB, cheR, and cheBR mutants showed various altered patterns of methanol release upon exposure to attractants. This study reveals a significant difference between the chemotaxis adaptation system of A. brasilense and that of the model organism E. coli and suggests that multiple chemotaxis systems are present and contribute to chemotaxis and aerotaxis in A. brasilense.

scholarly journals Different Processing of an mRNA Species inBacillus subtilis and Escherichia coli

2000 ◽  
Vol 182 (3) ◽  
pp. 689-695 ◽  
Author(s):  
Martin Persson ◽  
Elisabeth Glatz ◽  
Blanka Rutberg
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Inverted Repeat ◽  
Fusion Transcript ◽  
Temperature Sensitive ◽  
Rnase Iii ◽  
Transcription Terminator ◽  
E Coli ◽  
Steady State Levels ◽  
The Stability

ABSTRACT Expression of the Bacillus subtilis glpD gene, which encodes glycerol-3-phosphate (G3P) dehydrogenase, is controlled by termination or antitermination of transcription. The untranslated leader sequence of glpD contains an inverted repeat that gives rise to a transcription terminator. In the presence of G3P, the antiterminator protein GlpP binds toglpD leader mRNA and promotes readthrough of the terminator. Certain mutations in the inverted repeat of theglpD leader result in GlpP-independent, temperature-sensitive (TS) expression of glpD. The TS phenotype is due to temperature-dependent degradation of theglpD mRNA. In the presence of GlpP, theglpD mRNA is stabilized. glpDleader-lacZ fusions were integrated into the chromosomes ofB. subtilis and Escherichia coli. Determination of steady-state levels of fusion mRNA in B. subtilis showed that the stability of the fusion mRNA is determined by theglpD leader part. Comparison of steady-state levels and half-lives of glpD leader-lacZ fusion mRNA inB. subtilis and E. coli revealed significant differences. A glpD leader-lacZ fusion transcript that was unstable in B. subtilis was considerably more stable in E. coli. GlpP, which stabilizes the transcript in B. subtilis, did not affect its stability in E. coli. Primer extension analysis showed that theglpD leader-lacZ fusion transcript is processed differently in B. subtilis and in E. coli. The dominating cleavage site in E. coli was barely detectable in B. subtilis. This site was shown to be a target ofE. coli RNase III.

Biosynthetic ornithine and arginine decarboxylases: correlation of rates of synthesis with activities in Escherichia coli during exponential growth and following nutritional shift-up

1982 ◽  
Vol 28 (8) ◽  
pp. 945-950
Author(s):  
Stephen M. Boyle ◽  
Kazuo Adachi
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Ornithine Decarboxylase ◽  
Biological Activities ◽  
Decarboxylase Activity ◽  
Biosynthetic Enzyme ◽  
Guanosine Tetraphosphate ◽  
E Coli ◽  
K 12

Whether guanosine tetraphosphate (ppGpp) has a role in the regulation of the putrescine biosynthetic enzyme, ornithine decarboxylase, in Escherichia coli is controversial. Different laboratories have reported either direct or indirect correlations between ppGpp levels and ornithine decarboxylase activity using different in vivo conditions. In this report, using conditions in vivo to modulate ppGpp levels, experiments are described which bear on the controversy. The rates of synthesis and biological activities of the biosynthetic ornithine and arginine decarboxylases (ODC and ADC) were measured in E. coli K-12 during experimental growth and during nutritional shift-up. There were good correlations between changes in their respective activities and the rates of synthesis of these enzymes during steady state or shift-up. ODC activity or rate of synthesis changed directly in concert with ppGpp levels, while ADC activity or rate of synthesis changed inversely with ppGpp levels. These observations support the contention that ppGpp does not inhibit ODC activity.

scholarly journals Characterization of Neurospora crassa catabolic dehydroquinase purified from N. crassa and Escherichia coli

1982 ◽  
Vol 203 (3) ◽  
pp. 769-773 ◽  
Author(s):  
A R Hawkins ◽  
W R Reinert ◽  
N H Giles
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Neurospora Crassa ◽  
Protein Sequence ◽  
Sequence Data ◽  
E Coli ◽  
Steady State Kinetics ◽  
Electrophoretic Data ◽  
Protein Sequence Data

1. Neurospora crassa catabolic dehydroquinase has been purified from N. crassa and Escherichia coli. 2. Protein-sequence and gel-electrophoretic data show that apparently pure, homogeneous native dehydroquinase is a mixture of intact and proteinase-cleaved enzyme monomers. 3. Protein-sequence data and steady-state kinetics show that the catabolic dehydroquinase gene of N. crassa is expressed with fidelity in E. coli.

Growth kinetics of Escherichia coli with galactose and several other sugars in carbon-limited chemostat culture

1999 ◽  
Vol 46 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Urs Lendenmann ◽  
Mario Snozzi ◽  
Thomas Egli
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Steady State ◽  
Specific Growth Rate ◽  
Growth Kinetics ◽  
Specific Growth ◽  
Chemostat Culture ◽  
Monod Model ◽  
E Coli ◽  
Kinetics Of

Kinetic models for microbial growth describe the specific growth rate (μ) as a function of the concentration of the growth-limiting nutrient (s) and a set of parameters. A typical example is the model proposed by Monod, where μ is related to s using substrate affinity (Ks) and the maximum specific growth rate (μmax). The preferred method to determine such parameters is to grow microorganisms in continuous culture and to measure the concentration of the growth-limiting substrate as a function of the dilution rate. However, owing to the lack of analytical methods to quantify sugars in the microgram per litre range, it has not been possible to investigate the growth kinetics of Escherichia coli in chemostat culture. Using an HPLC method able to determine steady-state concentrations of reducing sugars, we previously have shown that the Monod model adequately describes glucose-limited growth of E. coli ML30. This has not been confirmed for any other sugar. Therefore, we carried out a similar study with galactose and found steady-state concentrations between 18 and 840 μg·L-1 for dilution rates between 0.2 and 0.8·h-1, respectively. With these data the parameters of several models giving the specific growth rate as a function of the substrate concentration were estimated by nonlinear parameter estimation, and subsequently, the models were evaluated statistically. From all equations tested, the Monod model described the data best. The parameters for galactose utilisation were μmax = 0.75·h-1 and Ks = 67 μg·L-1. The results indicated that accurate Ks values can be estimated from a limited set of steady-state data when employing μmax measured during balanced growth in batch culture. This simplified procedure was applied for maltose, ribose, and fructose. For growth of E. coli with these sugars, μmax and Ks were for maltose 0.87·h-1, 100 μg·L-1; for ribose 0.57·h-1, 132 μg·L-1, and for fructose 0.70·h-1, 125 μg·L-1. Key words: monod model, continuous culture, galactose, glucose, fructose, maltose, ribose.

scholarly journals Cation Transport in Escherichia coli

1962 ◽  
Vol 46 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Stanley G. Schultz ◽  
Wolfgang Epstein ◽  
David A. Goldstein
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
E Coli ◽  
Dense Suspension ◽  
K Concentration ◽  
Kinetics Of

The present study is concerned with the measurement of the unidirectional K flux in E. coli. Methods are described by means of which a fairly dense suspension of cells may be maintained in a well defined steady-state with respect to the intracellular K concentration and the pH of the medium. The kinetics of K42 exchange under these conditions are consistent with the presence of a single intracellular K compartment with a unidirectional K flux of 1 pmol/(cm2 sec.). This rate is independent of the extracellular K concentration over the range studied. The simultaneous rate of H secretion averages 16 pmols/(cm2 sec.) indicating that in the steady-state the efflux of metabolically produced H is not linked mole for mole to K movement.

scholarly journals Phase I and phase II of short-term mechanical restitution in perfused rat left ventricles

2002 ◽  
Vol 282 (4) ◽  
pp. H1311-H1319 ◽  
Author(s):  
Cristian Dumitrescu ◽  
Prakash Narayan ◽  
Yuanna Cheng ◽  
Igor R. Efimov ◽  
Ruth A. Altschuld
Keyword(s):  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Phase I ◽  
Phase Ii ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Pressure Development ◽  
Action Potential Prolongation ◽  
Later Phase ◽  
Current Facilitation

We examined the contributions of the Ca2+ channels of the sarcolemma and of the sarcoplasmic reticulum to electromechanical restitution. Extrasystoles (F1) were interpolated 40–600 ms following a steady-state beat (F0) in perfused rat ventricles paced at 2 or 3 Hz. Plots of F1/F0 versus the extrasystolic interval consisted of phase I, which occurred before relaxation of the steady-state beat, and phase II, which occurred later. Phase I exhibited a period of enhanced left ventricular pressure development that coincided with action potential prolongation. Phase I was eliminated by −BAY K 8644 (100 nM) and FPL 64176 (150 nM), augmented by 3 μM thapsigargin plus 200 nM ryanodine and unaffected by KN-93 and KB-R7943. Phase II was accelerated by the Ca2+channel agonists and by isoproterenol but was eliminated by thapsigargin plus ryanodine. The results suggest that phase I of electromechanical restitution is caused by a transient L-type Ca2+ current facilitation, whereas phase II represents the recovery of the ability of the sarcoplasmic reticulum to release Ca2+.

scholarly journals Mapping Stress-Induced Changes in Autoinducer AI-2 Production in Chemostat-Cultivated Escherichia coli K-12

2001 ◽  
Vol 183 (9) ◽  
pp. 2918-2928 ◽  
Author(s):  
Matthew P. DeLisa ◽  
James J. Valdes ◽  
William E. Bentley
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Quorum Sensing ◽  
Interleukin 2 ◽  
Heterologous Proteins ◽  
Induced Expression ◽  
E Coli ◽  
Chemostat Cultures ◽  
K 12

ABSTRACT Numerous gram-negative bacteria employ a cell-to-cell signaling mechanism, termed quorum sensing, for controlling gene expression in response to population density. Recently, this phenomenon has been discovered in Escherichia coli, and while pathogenicE. coli utilize quorum sensing to regulate pathogenesis (i.e., expression of virulence genes), the role of quorum sensing in nonpathogenic E. coli is less clear, and in particular, there is no information regarding the role of quorum sensing during the overexpression of recombinant proteins. The production of autoinducer AI-2, a signaling molecule employed by E. coli for intercellular communication, was studied in E. coli W3110 chemostat cultures using a Vibrio harveyi AI-2 reporter assay (M. G. Surrette and B. L. Bassler, Proc. Natl. Acad. Sci. USA 95:7046–7050, 1998). Chemostat cultures enabled a study of AI-2 regulation through steady-state and transient responses to a variety of environmental stimuli. Results demonstrated that AI-2 levels increased with the steady-state culture growth rate. In addition, AI-2 increased following pulsed addition of glucose, Fe(III), NaCl, and dithiothreitol and decreased following aerobiosis, amino acid starvation, and isopropyl-β-d-thiogalactopyranoside-induced expression of human interleukin-2 (hIL-2). In general, the AI-2 responses to several perturbations were indicative of a shift in metabolic activity or state of the cells induced by the individual stress. Because of our interest in the expression of heterologous proteins in E. coli, the transcription of four quorum-regulated genes and 20 stress genes was mapped during the transient response to induced expression of hIL-2. Significant regulatory overlap was revealed among several stress and starvation genes and known quorum-sensing genes.

Cardiac myocyte volume, Ca2+ fluxes, and sarcoplasmic reticulum loading in pressure-overload hypertrophy

1997 ◽  
Vol 272 (5) ◽  
pp. H2425-H2435 ◽  
Author(s):  
L. M. Delbridge ◽  
H. Satoh ◽  
W. Yuan ◽  
J. W. Bassani ◽  
M. Qi ◽  
...  
Keyword(s):  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Laser Scanning ◽  
Cardiac Myocyte ◽  
Membrane Surface ◽  
Weight Ratio ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Heart Weight ◽  
The Relationship

Alterations in cellular Ca2+ transport and excitation-contraction coupling may contribute to dysfunction in cardiac hypertrophy. Left ventricular myocytes were isolated from rat hearts after 15-18 wk of suprarenal abdominal aortic banding to evaluate the hypothesis that hypertrophy alters the relationship between Ca2+ current (ICa) and sarcoplasmic reticulum (SR) Ca2+ load during steady-state voltage-clamp depolarization. Mean arterial pressure (MAP) and heart weight-to-body weight ratio of banded (B) animals were significantly higher than in control or sham-operated animals (C). Isolated myocyte dimensions and volume increased in parallel with whole heart hypertrophy and elevation in MAP. However, the relationship between membrane surface area (measured by capacitance) and cell volume (measured by laser scanning confocal microscopy) was unaltered (C: 8.9 +/- 0.3; B: 8.5 +/- 0.4 pF/pl). No differences in the voltage dependence of ICa activation, steady-state inactivation, or recovery from inactivation were detected between C and B myocytes. Maximal ICa density for the two groups was also not different either under basal conditions (C: 4.28 +/- 0.98; B: 4.57 +/- 0.60 pA/pF) or in the presence of 1 microM isoproterenol (C: 16.6 +/- 2.3; B: 16.5 +/- 2.3 pA/pF). The fraction of Ca2+ released from the SR by a single twitch was 55.4 +/- 9.4% in C and 37.1 +/- 6.9% in B (not significantly different). Steady-state Ca2+ influx during a twitch was calculated in units of micromoles per liter of nonmitochondrial volume from the integral of ICa (C: 13.4 +/- 0.7 microM; B: 13.3 +/- 0.8 microM). The SR Ca2+ load was similarly calculated by integration of Na+/Ca2+ exchange current induced by rapid caffeine application (C: 140 +/- 9 microM; B: 169 +/- 18 microM). We conclude that significant cellular hypertrophy is associated with proportional increases in sarcolemmal ICa influx, SR Ca2+ loading, and the amount of SR Ca2+ released in this model of pressure overload.

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