scholarly journals Differences in the thermal inactivation kinetics of Escherichia coli .BETA.-galactosidase in vitro and in vivo.

1997 ◽  
Vol 2 (2) ◽  
pp. 73-78 ◽  
Author(s):  
HIROSHI FUJIKAWA ◽  
TAKESHI ITOH
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Inactivation Kinetics ◽  
Kinetics Of ◽  
Beta Galactosidase

Determination of the Thermal Inactivation Kinetics of Listeria monocytogenes, Salmonella enterica, and Escherichia coli O157:H7 and non-O157 in Buffer and a Spinach Homogenate

2015 ◽  
Vol 78 (8) ◽  
pp. 1467-1471 ◽  
Author(s):  
EMEFA ANGELICA MONU ◽  
MALCOND VALLADARES ◽  
DORIS H. D'SOUZA ◽  
P. MICHAEL DAVIDSON
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Salmonella Enterica ◽  
Thermal Inactivation ◽  
Inactivation Kinetics ◽  
Mild Heat ◽  
Log Reduction ◽  
D Values ◽  
Heat Processes ◽  
Kinetics Of

Produce has been associated with a rising number of foodborne illness outbreaks. While much produce is consumed raw, some is treated with mild heat, such as blanching or cooking. The objectives of this research were to compare the thermal inactivation kinetics of Listeria monocytogenes, Salmonella enterica, Shiga toxin–producing Escherichia coli (STEC) O157:H7, and non-O157 STEC in phosphate-buffered saline (PBS; pH 7.2) and a spinach homogenate and to provide an estimate of the safety of mild heat processes for spinach. Five individual strains of S. enterica, L. monocytogenes, STEC O157:H7, and non-O157 STEC were tested in PBS in 2-ml glass vials, and cocktails of the organisms were tested in blended spinach in vacuum-sealed bags. For Listeria and Salmonella at 56 to 60°C, D-values in PBS ranged from 4.42 ± 0.94 to 0.35 ± 0.03 min and 2.11 ± 0.14 to 0.16 ± 0.03 min, respectively. D-values at 54 to 58°C were 5.18 ± 0.21 to 0.53 ± 0.04 min for STEC O157:H7 and 5.01 ± 0.60 to 0.60 ± 0.13 min for non-O157 STEC. In spinach at 56 to 60°C, Listeria D-values were 11.77 ± 2.18 to 1.22 ± 0.12 min and Salmonella D-values were 3.51 ± 0.06 to 0.47 ± 0.06 min. D-values for STEC O157:H7 and non-O157 STEC were 7.21 ± 0.17 to 1.07 ± 0.11 min and 5.57 ± 0.38 to 0.99 ± 0.07 min, respectively, at 56 to 60°C. In spinach, z-values were 4.07 ± 0.16, 4.59 ± 0.26, 4.80 ± 0.92, and 5.22 ± 0.20°C for Listeria, Salmonella, STEC O157:H7, and non-O157 STEC, respectively. Results indicated that a mild thermal treatment of blended spinach at 70°C for less than 1 min would result in a 6-log reduction of all pathogens tested. These findings may assist the food industry in the design of suitable mild thermal processes to ensure food safety.

Alteration of adipocyte calcium homeostasis by Escherichia coli endotoxin

1985 ◽  
Vol 248 (3) ◽  
pp. R331-R338
Author(s):  
K. M. Nelson ◽  
J. A. Spitzer
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Calcium Homeostasis ◽  
Compartmental Analysis ◽  
In Vitro Exposure ◽  
Exchange Kinetics ◽  
Intracellular Binding ◽  
Kinetics Of

The present study evaluated calcium homeostasis in rat adipocytes after either in vivo or in vitro exposure to Escherichia coli endotoxin. Fat cells from endotoxin-treated rats showed an enhanced uptake of 45Ca. In an attempt to differentiate between 45Ca binding to the cell surface and intracellular 45Ca accumulation, adipocytes were exposed to 5 mM LaCl3. The amount of 45Ca remaining associated with lanthanum-treated adipocytes was taken to be located intracellularly and was increased in adipocytes from endotoxin-treated rats. The amount of 45Ca displaced by lanthanum was also increased in adipocytes from endotoxin-treated rats. This suggested that the endotoxin-induced increase of 45Ca accumulation included both cell surface and intracellular binding sites. Compartmental analysis of the exchange kinetics of cell-associated 45Ca with 40Ca in the medium indicated a 77% increase in the size of the cell surface compartment of adipocytes from endotoxin-treated rats compared with controls. In addition, endotoxin treatment altered the flux of calcium from the cells to the medium. In vitro exposure of freshly prepared adipocytes to 250 or 750 micrograms endotoxin/ml did not produce a perturbation of adipocyte calcium homeostasis. The results indicate that endotoxin induces alterations in the ability of adipocytes to regulate calcium translocations, suggesting that some metabolic and hormonal aspects of endotoxins' actions may be mediated through perturbation of cellular calcium homeostasis.

scholarly journals Interaction of sigma factor σN with Escherichia coli RNA polymerase core enzyme

2000 ◽  
Vol 352 (2) ◽  
pp. 539-547 ◽  
Author(s):  
David J. SCOTT ◽  
Anna L. FERGUSON ◽  
María-Trinidad GALLEGOS ◽  
Melinda PITT ◽  
Martin BUCK ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Rna Polymerase ◽  
Sigma Factor ◽  
Analytical Ultracentrifugation ◽  
Spectroscopic Properties ◽  
Sedimentation Equilibrium ◽  
Equilibrium Binding ◽  
Kinetics Of

The equilibrium binding and kinetics of assembly of the DNA-dependent RNA polymerase (RNAP) σN-holoenzyme has been investigated using biosynthetically labelled 7-azatryptophyl- (7AW)σN. The spectroscopic properties of such 7AW proteins allows their absorbance and fluorescence to be monitored selectively, even in the presence of high concentrations of other tryptophan-containing proteins. The 7AWσN retained its biological activity in stimulating transcription from σN-specific promoters, and in in vitro gel electrophoresis assays of binding to core RNAP from Escherichia coli. Furthermore, five Trp → Ala single mutants of σN were shown to support growth under conditions of nitrogen limitation, and showed comparable efficiency in activating the σN-dependent nifH promoter in vivo, indicating that none of the tryptophan residues were essential for activity. The equilibrium binding of 7AWσN to core RNAP was examined by analytical ultracentrifugation. In sedimentation equilibrium experiments, absorbance data at 315nm (which reports selectively on the distribution of free and bound 7AWσN) established that a 1:1 complex was formed, with a dissociation constant lower than 2µM. The kinetics of the interaction between 7AWσN and core RNAP was investigated using stopped-flow spectrofluorimetry. A biphasic decrease in fluorescence intensity was observed when samples were excited at 280nm, whereas only the slower of the two phases was observed at 315nm. The kinetic data were analysed in terms of a mechanism in which a fast bimolecular association of σN with core RNAP is followed by a relatively slow isomerization step. The consequences of these findings on the competition between σN and the major sigma factor, σ70, in Escherichia coli are discussed.

Effect of pH and inhibitors on beta-amyloid fibril assembly

1996 ◽  
Vol 54 ◽  
pp. 752-753
Author(s):  
Beverly E. Maleeff ◽  
Timothy K. Hart ◽  
Stephen J. Wood ◽  
Ronald Wetzel
Keyword(s):  
Amyloid Fibril ◽  
Peptide Fragment ◽  
Hydrophobic Peptides ◽  
Amyloid Fibril Formation ◽  
Effects Of Ph ◽  
Severity Of The Disease ◽  
Kinetics Of ◽  
The Brain

Alzheimer's disease is characterized post-mortem in part by abnormal extracellular neuritic plaques found in brain tissue. There appears to be a correlation between the severity of Alzheimer's dementia in vivo and the number of plaques found in particular areas of the brain. These plaques are known to be the deposition sites of fibrils of the protein β-amyloid. It is thought that if the assembly of these plaques could be inhibited, the severity of the disease would be decreased. The peptide fragment Aβ, a precursor of the p-amyloid protein, has a 40 amino acid sequence, and has been shown to be toxic to neuronal cells in culture after an aging process of several days. This toxicity corresponds to the kinetics of in vitro amyloid fibril formation. In this study, we report the biochemical and ultrastructural effects of pH and the inhibitory agent hexadecyl-N-methylpiperidinium (HMP) bromide, one of a class of ionic micellar detergents known to be capable of solubilizing hydrophobic peptides, on the in vitro assembly of the peptide fragment Aβ.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Sign in / Sign up

Export Citation Format

Share Document