Factors affecting inosinate synthesis and inosine triphosphate accumulation in human erythrocytes

1977 ◽  
Vol 55 (4) ◽  
pp. 359-364 ◽  
Author(s):  
J. Frank Henderson ◽  
George Zombor ◽  
Joyce H. Fraser ◽  
Ernest E. McCoy ◽  
Vernon Verhoef ◽  
...  
Keyword(s):  
Individual Variation ◽  
Incubation Medium ◽  
Large Degree ◽  
Inhibitory Effect ◽  
Phosphate Concentration ◽  
Human Erythrocytes ◽  
Phosphoribosyl Pyrophosphate ◽  
Factors Affecting

Measurements of rates of inosinate synthesis from radioactive hypoxanthine by human erythrocytes show a large degree of individual variation. Rates of inosinate synthesis also vary with the pH and phosphate concentration of the incubation medium. This may be due to changes in the rate of phosphoribosyl pyrophosphate synthesis, and the stimulatory effect of phosphate on this process seems to be more important than the inhibitory effect of 2,3-diphosphoglycerate. The rate of inosinate synthesis, and especially the extent of accumulation of inosine triphosphate, increase disproportionately with time of incubation up to at least 24 h. Storage of erythrocytes also tends to increase inosinate synthesis and inosine triphosphate accumulation.

The mobility of intramembrane particles in non-haemolysed human erythrocytes. Factors affecting acridine-orange-induced particle aggregation

1986 ◽  
Vol 86 (1) ◽  
pp. 57-67
Author(s):  
G. Lelkes ◽  
I. Fodor ◽  
G. Lelkes ◽  
S.R. Hollan
Keyword(s):  
Acridine Orange ◽  
Intracellular Ph ◽  
Lateral Diffusion ◽  
Inhibitory Effect ◽  
Human Erythrocytes ◽  
Particle Aggregation ◽  
Experimental Conditions ◽  
Factors Affecting ◽  
Cross Links ◽  
Phosphate Buffered Saline

It has previously been shown that reversible intramembrane particle aggregation can be induced in non-haemolysed human erythrocytes. This phenomenon, which can be induced by the cationic dye Acridine Orange, has been further investigated using different experimental conditions that are expected to influence the rate of aggregation of the particles. In addition to the concentration of the dye, the rate of aggregation was also found to be dependent on the extracellular and intracellular pH, as well as on the type of buffer used. While lowering the pH of the Acridine Orange solutions resulted in decreased particle clustering, low intracellular pH increased and elevated intracellular pH decreased particle aggregation. Furthermore, at a given dye concentration and a given pH, Acridine Orange caused more intense aggregation in Tris-buffered saline than in isotonic phosphate buffer or phosphate-buffered saline. Under appropriate conditions Acridine Orange caused significant particle aggregation at concentrations as low as 0.25 mM within 30 s. During this period only discocyte-stomatocyte transformation occurred; neither agglutination nor vesiculation of the erythrocytes could be detected. Treatment of the erythrocytes with Diamide (Serva), which cross-links spectrin via disulphide bridges and thereby reduces lateral diffusion of integral membrane proteins over large distances, had no inhibitory effect on Acridine-Orange-induced particle aggregation. Heating the erythrocytes to 50 degrees C, at which temperature denaturation of spectrin and fragmentation of the erythrocytes occur, and subsequently incubating them in Acridine Orange at room temperature, caused an almost maximal rate of particle aggregation within 10–30 s, without haemolysis. The possible mechanism and significance of the particle aggregation phenomenon are discussed.

Effect of Anticonvulsants on the Uptake of 5-Methyltetrahydrofolic Acid by the Choroid Plexus in Rabbits

1977 ◽  
Vol 53 (1) ◽  
pp. 75-80
Author(s):  
H. Taguchi ◽  
Z. Abdul-Cader ◽  
J. Perry ◽  
E. H. Reynolds ◽  
I. Chanarin
Keyword(s):  
Folic Acid ◽  
Low Temperature ◽  
Choroid Plexus ◽  
Incubation Medium ◽  
Pernicious Anaemia ◽  
Inhibitory Effect ◽  
Anaerobic Conditions ◽  
Acid Therapy ◽  
Pteroylglutamic Acid

1. The isolated choroid plexus of the rabbit takes up 5-methyltetrahydrofolate from the incubation medium. 2. Other folate analogues (pteroylglutamic acid, methotrexate, 5-formyltetrahydrofolate = folinic acid) inhibited the uptake of 5-methyltetrahydrofolate. 3. The uptake of 5-methyltetrahydrofolate was inhibited by low temperature, anaerobic conditions and dinitrophenol. 4. The anticonvulsant drugs, diphenylhydantoin and phenobarbital, had no effect on 5-methyltetrahydrofolate uptake. 5. The inhibitory effect of pteroylglutamic acid on the uptake of 5-methyltetrahydrofolate by the choroid plexus may explain the effect of long-term folic acid therapy in aggravating vitamin B12 neuropathy in pernicious anaemia.

Autoregulation of 3, 3′,5′-triiodothyronine production by rat liver microsomes

1981 ◽  
Vol 98 (2) ◽  
pp. 240-245 ◽  
Author(s):  
T. Kaminski ◽  
J. Köhrle ◽  
R. Ködding ◽  
R.-D. Hesch
Keyword(s):  
Rat Liver ◽  
Incubation Medium ◽  
Liver Microsomes ◽  
Inhibitory Effect ◽  
Incubation Mixture ◽  
Rat Liver Microsomes ◽  
Experimental Conditions ◽  
Physiological Concentration ◽  
Enzyme Binding ◽  
Ph Dependent

Abstract. Conversion of thyroxine (T4) to 3,3′,5′-triiodothyronine (rT3) was studied in rat liver microsomes. Addition of rT3 at a physiological concentration to the incubation medium inhibited the deiodination of thyroxine to rT3. With a concentration of rT3 greater than 37.6 nM no net rT3 production at pH 8.0 was observed. Further increases in rT3 concentration resulted only in degradation of added rT3 and no net synthesis of rT3 from T4 could be detected. The inhibitory effect of rT3 upon its own production from T4 was pH dependent, 5 fold lower amounts of hormone being required to inhibit completely rT3 production at pH 7.4 than at pH 8.0. With the same experimental conditions no significant effect of rT3 on the conversion of T4 to 3,5,3′-triiodothyronine (T3) could be observed at pH 8.0 with all concentrations of added iodothyronine. A linear production of 3,3′-T2 from added rT3 was determined over the whole range of rT3 concentration, suggesting a lack of saturation of deiodinating enzyme. Binding of rT3 by anti-rT3 antibody added to the incubation mixture enhanced rT3 production from T4 by protecting rT3 from being degraded and/or diminishing the inhibitory effect of this iodothyronine on its own production. It was concluded that rT3 influenced its own production and that this effect may represent an important autoregulatory process in the iodothyronine metabolism.

A Method of Measuring Pollinator Populations on Field Crops

1952 ◽  
Vol 84 (10) ◽  
pp. 314-316 ◽  
Author(s):  
M. V. Smith ◽  
G. F. Townsend
Keyword(s):  
Seed Production ◽  
Large Degree ◽  
Factors Affecting ◽  
Field Crops ◽  
Pollinating Insects ◽  
Pollinator Populations

The seed production of many field crops, and in particular of legumes, depends to a large degree upon the number of pollinating insects present in the field during the blooming period. A study of the various factors affecting seed production requires, among other things, a knowledge of the population of pollinating insects present, and a ready means of comparing pollinator populations from one field to another. To obtain this information some means must be employed to count and classify the pollinating insects in the field.

scholarly journals Factors affecting the amount and the mode of merocyanine 540 binding to the membrane of human erythrocytes. A comparison with the binding to leukemia cells

1995 ◽  
Vol 1235 (2) ◽  
pp. 428-436 ◽  
Author(s):  
Johan W.M. Lagerberg ◽  
Karl-Josef Kallen ◽  
Cees W.M. Haest ◽  
John VanSteveninck ◽  
Tom M.A.R. Dubbelman
Keyword(s):  
Human Erythrocytes ◽  
Leukemia Cells ◽  
Factors Affecting ◽  
Merocyanine 540

scholarly journals The counteracting effect of potassium cyanide in sodium azide-inhibited germination of Paulownia tomentosa  Steud. seeds

2005 ◽  
Vol 57 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Suzana Zivkovic ◽  
Dragoljub Grubisic ◽  
Zlatko Giba ◽  
Radomir Konjevic
Keyword(s):  
Seed Germination ◽  
Light Pulse ◽  
Sodium Azide ◽  
Incubation Medium ◽  
Red Light ◽  
Potassium Cyanide ◽  
Inhibitory Effect ◽  
Escape Time ◽  
Paulownia Tomentosa ◽  
Respiratory Inhibitors

The effect of some respiratory inhibitors on light-induced Paulownia tomentosa Steud. seed germination was studied. Millimolar solution of sodium azide was sufficient to completely prevent germination induced by a 5-min red light pulse. The inhibitory effect of azide was absent if seeds were rinsed before phytochrome activation by light. Sodium azide was effective only if present in the period of Pfr activity. The escape time from azide inhibition compared to the escape from far-red light action, was delayed for about 24 hours. When azide was applied after phytochrome activation, its effect depended on how long it was present in the incubation medium. The removal of azide allowed full restoration of germination by another red light pulse and the far-red escape time did not differ from the escape of untreated, i.e. water-imbibed seeds. Potassium cyanide alone did not produce any effect in light-stimulated germination of these seeds. However, it counteracted the inhibitory effect of azide in light-stimulated germination, if applied simultaneously at a concentration three times higher.

Effects of epinephrine on insulin-stimulated glucose uptake and GLUT-4 phosphorylation in muscle

1997 ◽  
Vol 273 (3) ◽  
pp. C1082-C1087 ◽  
Author(s):  
A. D. Lee ◽  
P. A. Hansen ◽  
J. Schluter ◽  
E. A. Gulve ◽  
J. Gao ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Glucose Transporter ◽  
Inhibitory Effect ◽  
Phosphate Concentration ◽  
Intrinsic Activity ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Glut 4

beta-Adrenergic stimulation has been reported to inhibit insulin-stimulated glucose transport in adipocytes. This effect has been attributed to a decrease in the intrinsic activity of the GLUT-4 isoform of the glucose transporter that is mediated by phosphorylation of GLUT-4. Early studies showed no inhibition of insulin-stimulated glucose transport by epinephrine in skeletal muscle. The purpose of this study was to determine the effect of epinephrine on GLUT-4 phosphorylation, and reevaluate the effect of beta-adrenergic stimulation on insulin-activated glucose transport, in skeletal muscle. We found that 1 microM epinephrine, which raised adenosine 3',5'-cyclic monophosphate approximately ninefold, resulted in GLUT-4 phosphorylation in rat skeletal muscle but had no inhibitory effect on insulin-stimulated 3-O-methyl-D-glucose (3-MG) transport. In contrast to 3-MG transport, the uptakes of 2-deoxyglucose and glucose were markedly inhibited by epinephrine treatment. This inhibitory effect was presumably mediated by stimulation of glycogenolysis, which resulted in an increase in glucose 6-phosphate concentration to levels known to severely inhibit hexokinase. We conclude that 1) beta-adrenergic stimulation decreases glucose uptake by raising glucose 6-phosphate concentration, thus inhibiting hexokinase, but does not inhibit insulin-stimulated glucose transport and 2) phosphorylation of GLUT-4 has no effect on glucose transport in skeletal muscle.

EFFECTS OF HYDROXYSTEROID DEHYDROGENASE INHIBITORS ON IN-VITRO AND IN-VIVO STEROIDOGENESIS IN THE OVINE ADRENAL GLAND

1982 ◽  
Vol 92 (2) ◽  
pp. 205-212 ◽  
Author(s):  
P. SINGH-ASA ◽  
G. JENKIN ◽  
G. D. THORBURN
Keyword(s):  
Adrenal Gland ◽  
Incubation Medium ◽  
Bovine Serum ◽  
Hydroxysteroid Dehydrogenase ◽  
Inhibitory Effect ◽  
Bovine Serum Albu ◽  
Stimulatory Action ◽  
Adrenal Steroidogenesis

The effectiveness of trilostane and azastene as inhibitors of adrenal steroidogenesis was compared by in-vitro and in-vivo methods. A radioimmunoassay was developed for the measurement of cortisol in ovine plasma, incubation medium and tissue extract using a specific antiserum raised against cortisol 21-acetate,3-carboxymethyloxime : bovine serum albu Trilostane (20 μmol/l) decreased cortisol synthesis and release both in unstimulated and in ACTH-stimulated adrenal tissues in vitro. The same concentration of azastene had a lesser effect on unstimulated adrenals and was completely ineffective in blocking the stimulatory action of ACTH. In vivo, trilostane suppressed adrenal steroidogenesis in pregnant and cyclic ewes but the suppression in pregnant ewes was over a longer period, and after lower doses. It is concluded that trilostane had an inhibitory effect on ovine adrenal steroidogenesis both in vitro and in vivo.

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