scholarly journals CHANGES IN THE STABILITY AND POTENTIAL OF CELL SUSPENSIONS

1924 ◽  
Vol 6 (5) ◽  
pp. 587-596 ◽  
Author(s):  
Arnold H. Eggerth
Keyword(s):  
Isoelectric Point ◽  
Cell Suspensions ◽  
Acid Solutions ◽  
Progressive Change ◽  
Sheep Erythrocytes ◽  
Buffer Solutions ◽  
Low Concentrations ◽  
The Stability

1. Human and sheep erythrocytes, when placed in 0.01 N buffer solutions at reactions more acid than pH 5.2, undergo a progressive change in potential, becoming less electronegative or more electropositive. This change usually occurs within 2 hours at ordinary room temperatures. It did not occur when rabbit erythrocytes were used. 2. This change is due primarily to the liberation of hemoglobin from some of the cells. 3. Hemoglobin, even in very low concentrations, markedly alters the potential of erythrocytes in the more acid reactions. This is due to a combination between the electropositive hemoglobin and the erythrocytes. The effect of the hemoglobin is most marked in the more acid solutions; it occurs only on the acid side of the isoelectric point of the hemoglobin. 4. The isoelectric point of erythrocytes in the absence of salt, or in the presence of salts having both ions monovalent, occurs at pH 4.7. This confirms the observations of Coulter (1920–21). Divalent anions shift the isoelectric point to the acid side. 5. The effect of salts on the potential of erythrocytes is due to the ions of the salts, and is analogous in every way to the effect of salts on albumin-coated collodion particles, as discussed by Loeb (1922–23).

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.

scholarly journals Assessment of Micral-Test Microalbuminuria Test Strip in the Laboratory and in Diabetic Outpatients

1992 ◽  
Vol 29 (1) ◽  
pp. 96-100 ◽  
Author(s):  
Denis R Jury ◽  
Donald J Mikkelsen ◽  
Deborah Glen ◽  
Peter J. Dunn
Keyword(s):  
Screening Method ◽  
Urine Osmolality ◽  
Test Strip ◽  
Albumin Concentration ◽  
Creatinine Concentration ◽  
Urine Albumin ◽  
Low Concentrations ◽  
Colour Development ◽  
The Stability ◽  
Sodium And Potassium

We have evaluated a semi-quantitative dry immunochemical screening method (Micral-Test) for the detection of low concentrations of albumin in urine. The stability of Micral-Test strips on storage was good, especially with regard to temperature, light and humidity. Changes in urine osmolality (urea and creatinine concentration), pH and sodium and potassium concentration did not have a significant analytical effect on the Micral-Test measurement; extremes of temperature altered the rate of colour development. The depth of dipping the strip into the sample and the timing of reading colour development were critical. We measured the albumin concentration in 184 urine samples from diabetic outpatients by the Micral-Test and by our in-house immunoturbidimetric method; a Micral-Test result of 20 mg/L had a sensitivity of 91% and specificity of 97% to predict a discriminating urine albumin concentration > 30 mg/L by the in house method. The Micral-Test is suitable for use by non-laboratory personnel and is capable of producing analytically acceptable results for use in diabetes clinics and by general practitioners.

Ethanol stability of casein micelles – a hypothesis concerning the role of calcium phosphate

1987 ◽  
Vol 54 (3) ◽  
pp. 389-395 ◽  
Author(s):  
David S. Horne
Keyword(s):  
Ionic Strength ◽  
Skim Milk ◽  
Buffer System ◽  
Casein Micelles ◽  
Buffer Solutions ◽  
Relative Response ◽  
Using Data ◽  
The Stability ◽  
Ethanol Stability

SummaryThe ethanol (EtOH) stability of skim milk and the stability towards aggregation of casein micelles diluted into ethanolic buffer solutions were compared using data obtained from previously published experiments. Differences in absolute stability and in relative response were observed when Ca2+ level and pH were adjusted, the buffer system results lying below those from skim milk in both cases. Increasing the ionic strength of skim milk adjusted to pH 7·0 lowered its EtOH stability whereas increasing the ionic strength of the diluting buffer increased the stability of the casein micelles. The hypothesis is put forward that the differences are due to the simultaneous precipitation of Ca phosphate when EtOH is added to skim milk. This draws calcium from the caseinate sites of the micelle, counteracting the destabilizing effects of the EtOH towards the micelle. Such removal and the consequent restructuring are kinetically controlled and micellar precipitation in skim milk finally occurs when the micellar coagulation time falls within the time scale of the restructuring reactions.

scholarly journals The use of N-methylprotoporphyrin dimethyl ester to inhibit ferrochelatase in Rhodopseudomonas sphaeroides and its effect in promoting biosynthesis of magnesium tetrapyrroles

1982 ◽  
Vol 208 (2) ◽  
pp. 479-486 ◽  
Author(s):  
J D Houghton ◽  
C L Honeybourne ◽  
K M Smith ◽  
H D Tabba ◽  
O T G Jones
Keyword(s):  
Dimethyl Ester ◽  
Cell Suspensions ◽  
Maximum Effect ◽  
Lag Phase ◽  
Rhodopseudomonas Sphaeroides ◽  
Normal Cells ◽  
Low Concentrations ◽  
Cytochrome Content ◽  
Monomethyl Ester ◽  
Substrate Addition

N-Methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membranes of Rhodopseudomonas sphaeroides at low concentrations (around 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of Rps. sphaeroides caused a decrease (near 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of haem into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent Rps. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylphaeoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylphaeophorbide a were excreted, with maximum effect at around 3 microM-inhibitor in the medium. The results are interpreted to suggest that the inhibitor decreases concentration of intracellular haem, which normally controls the activity of 5-aminolaevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells.

The Stability of Nitric Oxide in Acid Solutions

1997 ◽  
Vol 56 (2) ◽  
pp. 171-176 ◽  
Author(s):  
Gabi Gabor
Keyword(s):  
Nitric Oxide ◽  
Acid Solutions ◽  
The Stability

scholarly journals Optimization of the Extraction and Stability of Antioxidative Peptides from Mackerel (Pneumatophorus japonicus) Protein

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Xueqin Wang ◽  
Huahua Yu ◽  
Ronge Xing ◽  
Xiaolin Chen ◽  
Song Liu ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Protein Hydrolysate ◽  
Scientific Basis ◽  
Enzyme Concentration ◽  
Scavenging Activity ◽  
Preparation Conditions ◽  
Low Concentrations ◽  
Dpph Scavenging Activity ◽  
Dpph Scavenging ◽  
The Stability

This study optimizes the preparation conditions for mackerel protein hydrolysate (MPH) by response surface methodology (RSM) and investigates the stability of the antioxidant activity of MPHs (<2.5 kDa). The optimal conditions were as follows: enzyme concentration of 1726.85 U/g, pH of 7.00, temperature of 39.55°C, time of 5.5 h, and water/material ratio of 25 : 1, and the maximum DPPH scavenging activity was 79.14%. The MPHs indicated significant cellular antioxidant activity at low concentrations. Furthermore, the temperature and freeze-thaw cycles had little effect on the antioxidative stability while pH had significant effect on the antioxidative stability. In addition, the MPHs were sensitive to the metal ions, such as Fe2+, Fe3+, Zn2+, and Cu2+. Notably, when the concentrations of Fe2+and Fe3+were 5 mM, the DPPH scavenging activities were only 1.1% and 0.6%, respectively; furthermore, Cu2+at a 5 mM concentration could completely inhibit the DPPH scavenging activity of MPHs. In contrast, K+and Mg2+had no notable effect on the antioxidant activity of MPHs. These results may provide a scientific basis for the processing and application of MPHs.

Thermal Stability of Moniliformin at Varying Temperature, pH, and Time in an Aqueous Environment†

2000 ◽  
Vol 63 (11) ◽  
pp. 1598-1601 ◽  
Author(s):  
GRACIELA PINEDA-VALDES ◽  
LLOYD B. BULLERMAN
Keyword(s):  
Animal Species ◽  
Keshan Disease ◽  
Aqueous Environment ◽  
Buffer Solutions ◽  
Processing Times ◽  
Effects Of Temperature ◽  
The Stability ◽  
Increasing Temperature ◽  
Major Reduction ◽  
Thermal Stability Of

Moniliformin (MON) is a widely occurring mycotoxin, produced mainly by Fusarium proliferatum and Fusarium subglutinans in corn, that has been shown to be acutely toxic for various animal species and is a suspected cause of Keshan disease in China. The effects of temperature (100, 125, and 150°C) and pH (4, 7, and 9) on the stability of MON were determined in aqueous buffer solutions at processing times ranging from 10 to 60 min. The percentage of MON reduction was positively related to increasing temperature and pH. MON was most stable at pH 4. After 60 min at pH 4 and 150°C, MON was reduced by only 5%. Heating at pH 10 caused major reduction of MON. After 60 min at pH 10 and 100, 125, and 150°C, MON was reduced by 56, 72, and 83%, respectively. One trial done at 175°C and pH 10 showed that less than 1% MON remained after 60 min of processing.

scholarly journals CHANGES IN THE STABILITY AND POTENTIAL OF CELL SUSPENSIONS

1923 ◽  
Vol 6 (1) ◽  
pp. 63-71 ◽  
Author(s):  
Arnold H. Eggerth
Keyword(s):  
Soluble Protein ◽  
Negative Charge ◽  
Positive Charge ◽  
Previous Treatment ◽  
Cell Suspensions ◽  
Irreversible Change ◽  
Two Factors ◽  
Alkaline Side ◽  
The Stability ◽  
Original Potential

1. Stability and potential of Bacterium coli suspensions depend, not only on the strain of the organism and the medium in which it is suspended, but also on the previous treatment of the suspension, and the length of time it has been in the medium. 2. When treated at acid reactions, the negative charge on the bacteria is diminished; with some strains, a positive charge is acquired. Changes in stability accompany the changes in potential. 3. Washing acid-treated bacteria at neutral or slightly alkaline reactions does not restore the original potential; the zone of flocculation is moved toward the alkaline side. 4. These changes are due to two factors: the extraction of a soluble protein which combines with the surfaces of the cells, and a further irreversible change of the cell or its membrane.

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