FACTORS AFFECTING THE ACTIVITY OF ALLOXAN IN VITRO

1955 ◽  
Vol 33 (1) ◽  
pp. 780-791
Author(s):  
S. J. Klebanoff
Keyword(s):  
Oxygen Uptake ◽  
Succinic Dehydrogenase ◽  
Selective Toxicity ◽  
Factors Affecting ◽  
Stable Factor ◽  
Heat Stable ◽  
Number Of Factors ◽  
Liver Homogenates ◽  
Insight Into

The effect of alloxan on the oxygen uptake and the succinic dehydrogenase activity of rat liver homogenates has been studied in an attempt to gain some insight into the activity of alloxan within the cell. The increased oxygen uptake on the addition of alloxan to liver homogenates was found to be non-enzymatic in nature and to depend on some heat stable factor or factors in the preparation. The ability of reduced glutathione to substitute for the homogenate suggests that this substance may be concerned. It is thought that alloxan is reduced to dialuric acid by a number of factors in the homogenate, and that the increased oxygen uptake results from the spontaneous reoxidation of this latter substance. Experiments with dialuric acid tend to confirm this hypothesis. The inactivation of succinic dehydrogenase by alloxan is greatly influenced by the pH of the solution in which the alloxan is dissolved, as well as by the pH of the enzyme preparation, with acidity increasing and alkalinity decreasing the effect. The progressive nature of the inactivation with time is shown to depend upon the lowering of the pH which is brought about by the addition of alloxan to an unbuffered enzyme mixture. The experimental results are discussed in relation to the possible importance of pH in the selective toxicity of alloxan.

FACTORS AFFECTING THE ACTIVITY OF ALLOXAN IN VITRO

1955 ◽  
Vol 33 (5) ◽  
pp. 780-791 ◽  
Author(s):  
S. J. Klebanoff
Keyword(s):  
Oxygen Uptake ◽  
Succinic Dehydrogenase ◽  
Selective Toxicity ◽  
Factors Affecting ◽  
Stable Factor ◽  
Heat Stable ◽  
Number Of Factors ◽  
Liver Homogenates ◽  
Insight Into

The effect of alloxan on the oxygen uptake and the succinic dehydrogenase activity of rat liver homogenates has been studied in an attempt to gain some insight into the activity of alloxan within the cell. The increased oxygen uptake on the addition of alloxan to liver homogenates was found to be non-enzymatic in nature and to depend on some heat stable factor or factors in the preparation. The ability of reduced glutathione to substitute for the homogenate suggests that this substance may be concerned. It is thought that alloxan is reduced to dialuric acid by a number of factors in the homogenate, and that the increased oxygen uptake results from the spontaneous reoxidation of this latter substance. Experiments with dialuric acid tend to confirm this hypothesis. The inactivation of succinic dehydrogenase by alloxan is greatly influenced by the pH of the solution in which the alloxan is dissolved, as well as by the pH of the enzyme preparation, with acidity increasing and alkalinity decreasing the effect. The progressive nature of the inactivation with time is shown to depend upon the lowering of the pH which is brought about by the addition of alloxan to an unbuffered enzyme mixture. The experimental results are discussed in relation to the possible importance of pH in the selective toxicity of alloxan.

scholarly journals Formation of cytochrome P-450 containing haem or cobalt-protoporphyrin in liver homogenates of rats treated with phenobarbital and allylisopropylacetamide

1984 ◽  
Vol 222 (2) ◽  
pp. 453-462 ◽  
Author(s):  
H L Bonkovsky ◽  
J F Sinclair ◽  
J F Healey ◽  
P R Sinclair ◽  
E L Smith
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Similar Extent ◽  
Factors Affecting ◽  
Cobalt Protoporphyrin ◽  
Liver Homogenates ◽  
Cytochrome P 450 ◽  
Protein Moiety ◽  
Related Compounds ◽  
Insight Into ◽  
Hepatic Cytochrome

The potent porphyrogen allylisopropylacetamide and related compounds decrease hepatic concentrations of cytochrome P-450. This decrease occurs particularly in phenobarbital-induced cytochrome P-450 and is caused by suicidal breakdown of the haem of cytochrome P-450. Quantitative rocket immunoelectrophoresis showed that the protein moiety of the major phenobarbital-inducible form of hepatic cytochrome P-450 was not diminished up to 1 h, but was markedly decreased (to 43% of that of the phenobarbital-treated control) at 20 h after allylisopropylacetamide treatment. In contrast, the concentration of total cytochrome P-450, measured spectrophotometrically, decreased to 30-40% of the control at both 1 and 20 h after allylisopropylacetamide. Cytochrome P-450-dependent demethylations of ethylmorphine and benzphetamine decreased to a similar extent. When liver homogenates from rats treated with allylisopropylacetamide 1 h before being killed were incubated with haem, functional holocytochrome P-450 could be reconstituted from the apoprotein. Incubation with haem increased spectrophotometrically measurable cytochrome P-450 to 69%, ethylmorphine demethylase to 64% and benzphetamine demethylase to 93% of the activities in rats treated with phenobarbital alone. At 20 h after allylisopropylacetamide treatment, however, little or no reconstitution of cytochrome P-450 occurred after incubation with haem. When liver homogenates were incubated with cobalt and protoporphyrin, and microsomal proteins were then subjected to polyacrylamide-gel electrophoresis, cobalt-protoporphyrin was found specifically associated with proteins of Mr 50 000-53 000. When homogenates from rats given allylisopropylacetamide for 1 h or 20 h were compared, it was found that the extent of this association was higher in livers from the rats containing more apocytochrome P-450, suggesting that cobalt-protoporphyrin had associated with the apocytochrome. The data provide insight into the association of haem with the protein moiety of cytochrome P-450 and factors affecting breakdown of this protein.

Playing in the Virtual Sandbox

2018 ◽  
Vol 8 (3) ◽  
pp. 56-76 ◽  
Author(s):  
Katie Davis ◽  
Julian A. Boss ◽  
Perry Meas
Keyword(s):  
Middle School Students ◽  
Small Groups ◽  
News Media ◽  
Multiplayer Games ◽  
School Students ◽  
Factors Affecting ◽  
Collaborative Processes ◽  
Number Of Factors ◽  
Multiplayer Video Games ◽  
Insight Into

Researchers, teachers, and the news media have touted Minecraft as an effective, engaging way to promote students' 21st century skills, including collaboration. However, little is known about what collaboration looks like in Minecraft, including what factors support and undermine high quality collaboration. The current exploratory study investigated this question through an analysis of middle school students' collaborative processes while playing Minecraft in small groups of 2-4 players. Analyses of the discourse functions used by players during gameplay revealed a number of factors affecting the success of their collaboration, such as prior social ties, gaming experience, and responsiveness to other players. The findings contribute new insight into the nature of more and less effective collaborations in multiplayer video games. These insights will be useful to educators who are interested in using Minecraft and other multiplayer games to promote collaboration among their students.

EFFECT OF COBALT IONS ON MYOCARDIAL METABOLISM

1967 ◽  
Vol 45 (8) ◽  
pp. 1219-1223 ◽  
Author(s):  
G. S. Wiberg ◽  
I. C. Munro ◽  
A. B. Morrison
Keyword(s):  
Oxygen Uptake ◽  
Succinic Dehydrogenase ◽  
Inhibitory Effect ◽  
Cardiac Mitochondria ◽  
Succinic Dehydrogenase Activity ◽  
In Vitro System ◽  
Cobalt Ions ◽  
Rat Heart Mitochondria

Cobalt treatment (4 mg/kg intraperitoneally for 8 days) significantly depressed the oxygen uptake of rat heart mitochondria incubated in pyruvate, octanoate, and stearate media. Cobalt treatment did not, however, affect oxygen uptake in cardiac mitochondria prepared from thiamine-deficient rats. The addition of α-lipoic acid to the in vitro system greatly enhanced the ability of mitochondria from cobalt-treated rats to metabolize pyruvate. Cobalt treatment in vivo did not appear to exert any inhibitory effect on myocardial succinic dehydrogenase activity.

Parallel inhibition of spontaneous and antigen-induced platelet histamine release

1963 ◽  
Vol 205 (2) ◽  
pp. 348-350 ◽  
Author(s):  
P. A. Shore ◽  
H. S. Alpers
Keyword(s):  
Methyl Ester ◽  
Blood Cells ◽  
Spontaneous Release ◽  
High Concentration ◽  
Calcium Dependent ◽  
Stable Factor ◽  
Heat Stable ◽  
Coagulation Mechanism ◽  
Antigen Antibody

Small amounts of histamine and serotonin are released spontaneously in vitro from blood cells of normal rabbits. Similar to release induced by antigen-antibody reaction, spontaneous release is calcium dependent but occurs even in the presence of a high concentration of heparin. Spontaneous release is inhibited by tosylarginine and tosylarginine methyl ester, agents which also inhibit antigen-induced release. Benzoylarginine, benzoylarginine methyl ester, lysine ethyl ester, and arginine have little effect on either spontaneous or antigen-induced release. A heat-stable factor in plasma can effect platelet amine release. The results suggest that factors involved early in the coagulation mechanism may be responsible for platelet amine release under these conditions.

scholarly journals An NMR Metabolomics Approach to Investigate Factors Affecting the Yoghurt Fermentation Process and Quality

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 293
Author(s):  
Alessia Trimigno ◽  
Christian Bøge Lyndgaard ◽  
Guðrún Anna Atladóttir ◽  
Violetta Aru ◽  
Søren Balling Engelsen ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Milk Proteins ◽  
Starter Cultures ◽  
Factors Affecting ◽  
Nmr Metabolomics ◽  
Milk Fermentation ◽  
Number Of Factors ◽  
The Impact ◽  
Insight Into

A great number of factors can influence milk fermentation for yoghurt production such as fermentation conditions, starter cultures and milk characteristics. It is important for dairy companies to know the best combinations of these parameters for a controlled fermentation and for the desired qualities of yoghurt. This study investigates the use of a 1H-NMR metabolomics approach to monitor the changes in milk during fermentation from time 0 to 24 h, taking samples every hour in the first 8 h and then at the end-point at 24 h. Three different starter cultures (L. delbrueckii ssp. bulgaricus, S. thermophilus and their combination) were used and two different heat treatments (99 or 105 °C) were applied to milk. The results clearly show the breakdown of proteins and lactose as well as the concomitant increase in acetate, lactate and citrate during fermentation. Formate is found at different initial concentrations depending on the heat treatment of the milk and its different time trajectory depends on the starter cultures: Lactobacillus cannot produce formate, but needs it for growth, whilst Streptococcus is able to produce formate from pyruvate, therefore promoting the symbiotic relationship between the two strains. On the other hand, Lactobacillus can hydrolyze milk proteins into amino acids, enriching the quality of the final product. In this way, better insight into the protocooperation of lactic acid bacteria strains and information on the impact of a greater heat treatment in the initial matrix were obtained. The global chemical view on the fermentations provided using NMR is key information for yoghurt producers and companies producing starter cultures.

scholarly journals Structure and species as factors affecting the metabolism of some methoxy-6-sulphanilamidopyrimidines

1969 ◽  
Vol 111 (2) ◽  
pp. 167-172 ◽  
Author(s):  
J W Bridges ◽  
M. R. Kibby ◽  
S R Walker ◽  
R T Williams
Keyword(s):  
Rhesus Monkey ◽  
Main Metabolite ◽  
Factors Affecting ◽  
Monkey Liver ◽  
Liver Homogenates ◽  
A Minor ◽  
Minor Extent ◽  
Made In

1. A comparative study was made in man, rhesus monkey, rat and rabbit of the urinary excretion of 2-, 4- and 5-methoxy- and 2,4-, 2,5- and 4,5-dimethoxy-6-sulphanilamidopyrimidines given orally. 2. In the rabbit, 70–80% of the dose of each drug was excreted in 2 days, mainly as N4-acetyl derivatives, except 2,5-dimethoxy-6-sulphanilamidopyrimidine, which was mainly excreted unchanged. 3. In the rat, 50–70% of the dose of each drug was excreted in 2 days, except the 2-methoxy and 2,4-dimethoxy compounds, whose excretion was about 30%. The N4-acetyl derivatives accounted for 20–70% of the drugs excreted, except the 2,5-dimethoxy derivative, which was excreted unchanged. 4. In the rhesus monkey, some 40–60% of the dose of the 2-methoxy, 2,4-dimethoxy and 2,5-dimethoxy compounds was excreted in 2 days, but the 4-methoxy, 5-methoxy and 4,5-dimethoxy compounds were excreted at less than half this rate. The 4-methoxy, 5-methoxy and 4,5-dimethoxy compounds were highly acetylated (80–90%) whereas the 2-methoxy compound was poorly acetylated (17%) and the 2,5-dimethoxy compound hardly at all. The major metabolite of the 2,4-dimethoxy compound in the monkey was the N1-glucuronide. 5. In man, 30% of the dose of the 4-methoxy and 2,4-dimethoxy compounds was excreted in 24 hr., whereas the 4,5-dimethoxy compound (Fanasil) was very slowly excreted (12% in 2 days). The 4-methoxy compound was well acetylated (65%), but the 2,4- and 4,5-dimethoxy compounds were not (20–30%). The main metabolite of the 2,4-dimethoxy compound in man was the N1-glucuronide. 6. N1-Glucuronide formation occurred extensively only with the 2,4-dimethoxy compound and only in man and the rhesus monkey. It did not occur in the rabbit and only to a minor extent in the rat. 7. The 2,5-dimethoxy compound was not significantly acetylated in vivo in the rabbit, rat or monkey, but acetylation occurred in vitro in rabbit or monkey liver homogenates. 8. These findings are discussed.

Cryptosporidiumcell culture infectivity assay design

Parasitology ◽  
2011 ◽  
Vol 138 (6) ◽  
pp. 671-681 ◽  
Author(s):  
B. J. KING ◽  
A. R. KEEGAN ◽  
B. S. ROBINSON ◽  
P. T. MONIS
Keyword(s):  
Developmental Stages ◽  
Gastrointestinal Disease ◽  
Cell Monolayer ◽  
Data Interpretation ◽  
Host Cells ◽  
Specific Gene ◽  
Factors Affecting ◽  
Number Of Factors ◽  
Life Cycle Development

SUMMARYMembers of the genusCryptosporidium, which cause the gastrointestinal disease cryptosporidiosis, still represent a significant cause of water-borne disease worldwide. While intensive efforts have been invested in the development of techniques for parasite culture,in vitrogrowth has been hampered by a number of factors including low levels of infectivity as well as delayed life-cycle development and poor synchronicity. In this study we examined factors affecting the timing of contact between excysted sporozoites and target host cells and the subsequent impact of this upon the establishment of infection. We demonstrate that excystation rate impacts upon establishment of infection and that in our standard assay format the majority of sporozoites are not close enough to the cell monolayer when they are released from the oocyst to successfully establish infection. However, this can be easily overcome by centrifugation of oocysts onto the cell monolayer, resulting in approximately 4-fold increases in sporozoite attachment and subsequent infection. We further demonstrate that excystation procedures can be tailored to control excystation rate to match the assay end purpose and that excystation rate can influence data interpretation. Finally, the addition of both a centrifugation and washing step post-sporozoite attachment may be appropriate when considering the design ofin vitroculture experiments for developmental analysis and stage-specific gene expression as this appears to increase the synchronicity of early developmental stages.

Sign in / Sign up

Export Citation Format

Share Document