scholarly journals Liver glucose-6-phosphatase activity is not modulated by physiological intracellular Ca2+ concentrations

1991 ◽  
Vol 275 (3) ◽  
pp. 805-807 ◽  
Author(s):  
R Fulceri ◽  
G Bellomo ◽  
A Gamberucci ◽  
A Benedetti
Keyword(s):  
Phosphatase Activity ◽  
Ionophore A23187 ◽  
Experimental Conditions ◽  
Isolated Liver ◽  
Different Levels

1. In the presence of MgATP and increasing amounts of added Ca2+, isolated liver microsomal vesicles accumulate approx. 10 nmol of Ca2+/mg of protein and buffer ambient free Ca2+ at increasing concentrations (0.22-10.9 microM). Under these experimental conditions, microsomal glucose-6-phosphatase activity is unaffected by the concentration of extravesicular free Ca2+. 2. Different levels of intravesicular Ca2+ were obtained by treating microsomes with the Ca2+ ionophore A23187 and by stimulating active microsomal Ca2+ accumulation with Pi (3 mM). In both instances, microsomal glucose-6-phosphatase activity is unaffected by the level of intravesicular Ca2+.

scholarly journals Influence of saprophages (Isopoda, Diplopoda) on leaf litter decomposition under different levels of humidification and chemical loading

2020 ◽  
Vol 28 (4) ◽  
pp. 384-389
Author(s):  
A. P. Pokhylenko ◽  
O. O. Didur ◽  
Y. L. Kulbachko ◽  
L. P. Bandura ◽  
S. A. Chernykh
Keyword(s):  
Leaf Litter ◽  
Litter Decomposition ◽  
Zinc Content ◽  
Leaf Litter Decomposition ◽  
Absolute Difference ◽  
Average Weight ◽  
Chemical Stress ◽  
Experimental Conditions ◽  
The Common ◽  
Different Levels

The paper presents a study about the influence of two saprophage groups (Isopoda, Diplopoda) on leaf litter decomposition under different levels of humidification and chemical stress. Because of their worldwide distribution, we focused on the common pillbug Armadillidium vulgare (Latreille, 1804) (Isopoda, Armadillidiidae), and the common millipede species Rossiulus kessleri (Lohmander, 1927) (Julida, Julidae). The function of environment creation by the given saprophages, as destructors of dead plant matter, supporting such ecosystem services as soil fertility improvement and nutrients’ turnover, is highlighted. To conduct the experiment, the animals were collected manually and using pitfall trapping. In order to bring the experimental conditions closer to the natural, the individuals were not sexed. The maximum consumption of leaf litter by woodlice was recorded in the conditions with adequate moisture (0.5 mL of distilled water per box) and amounted to 2.52 mg/10 individuals per day, which exceeds its consumption with low and increased moisture, respectively, by 1.82 and 1.24 times. As for the effect of interaction, the consumption of maple litter with optimal moisture (4.77 mg/10 individuals per day) was the greatest. The largest absolute difference between broad-leaved tree species in the average weight of leaf litter consumed by woodlice was between maple leaf litter and oak leaf litter, the minimum – between robinia leaf litter and oak leaf litter. According to the results of the obtained data (Diplopoda), it can be stated that there is a statistically significant effect of chemical stress and discrepancy of the average zinc content in the object of study (in Diplopoda and their faecal pellets). We found that the diet provided did not affect the distribution of zinc in Diplopoda under conditions of chemical stress. According to the results of pairwise comparisons, we determined that the zinc content in the Diplopoda clearly differs for control and almost every concentration of zinc sulfate solution – 0.03 and 0.15 g/L, the samples of which do not form a homogeneous group. The species composition, abundance and distribution in space of soil invertebrates are informative indicators which reflect the ecological state of soils, intensity in development of soil horizons as well as intensity of processes occurring in them.

Dynamics of Species and Size Structures of Phytoplankton at Different Levels of Bottom-Up and Top-Down Effects in Experimental Conditions

2019 ◽  
Vol 12 (3) ◽  
pp. 245-253 ◽  
Author(s):  
E. G. Sakharova ◽  
I. Yu. Feniova ◽  
Z. I. Gorelysheva ◽  
M. Rzepecki ◽  
I. Kostshevska-Shlakovska ◽  
...  
Keyword(s):  
Top Down ◽  
Experimental Conditions ◽  
Bottom Up ◽  
Different Levels

scholarly journals The permeability to calcium of pigeon erythrocyte ‘ghosts’ studied by using the calcium-activated luminescent protein, obelin

1975 ◽  
Vol 152 (2) ◽  
pp. 255-265 ◽  
Author(s):  
Anthony K. Campbell ◽  
Robert L. Dormer
Keyword(s):  
Pyruvate Kinase ◽  
Time Course ◽  
Small Concentration ◽  
Ionophore A23187 ◽  
Erythrocyte Ghosts ◽  
Experimental Conditions ◽  
Bivalent Cation ◽  
Low Concentration ◽  
Triton X ◽  
Obelia Geniculata

1. Obelin, the Ca2+-activated luminescent protein from the hydroid Obelia geniculata, was sealed inside pigeon erythrocyte ‘ghosts’ in order to investigate effects on their permeability of different methods of preparation and of the bivalent cation ionophore A23187. 2. Changes in free Ca2+ within the ‘ghosts’ were studied by following the rate of luminescence of obelin. The possibility that the obelin might have been released from the ‘ghosts’ during an experiment was investigated by studying the release of inulin and pyruvate kinase from the ‘ghosts’. Less than 10% of the inulin or pyruvate kinase sealed within the ‘ghosts’ was released under any of the experimental conditions. 3. Triton X-100 (0.1–10%, v/v) made the ‘ghosts’ highly permeable to Ca2+. In the presence of 1mm-Ca2+ and Triton, 95–100% of the obelin was utilized within 10–20s. 4. A time-course of resealing ‘ghosts’ at 37°C showed that over a period of 90min, the ‘ghosts’ became gradually less permeable to Ca2+. ‘Ghosts’ which remained at 0°C retained only a small concentration of obelin and ATP, and were highly permeable to Ca2+. 5. Erythrocyte ‘ghosts’ resealed for 30min at 20°C rather than 37°C were more permeable to Ca2+, as shown by the fact that 92% of the obelin in the ‘ghosts’ was utilized during the first 60s after the addition of 1mm-Ca2+, as opposed to 44% for ‘ghosts’ resealed at 37°C. 6. Haemolysis at pH6.0 rather than 7.0 resulted in ‘ghosts’ which were highly permeable to Ca2+ after resealing for 60min at 37°C. Of the obelin in the ‘ghosts’, produced by haemolysis at pH6.0, 90% was utilized in the first 60s after the addition of 1mm-Ca2+ compared with 23% for ‘ghosts’ produced at pH7.0. 7. The bivalent cation ionophore A23187 increased the permeability of the ‘ghosts’ to Ca2+. Maximum effects of the ionophore (16μg/ml) were obtained by preincubating the ‘ghosts’ with the ionophore A23187 (16μg/ml) in the presence of a low concentration of Mg2+ and in the absence of Ca2+.

scholarly journals Use of toluene-permeabilized mitochondria to study the regulation of adipose tissue pyruvate dehydrogenase in situ. Further evidence that insulin acts through stimulation of pyruvate dehydrogenase phosphate phosphatase

1986 ◽  
Vol 238 (1) ◽  
pp. 93-101 ◽  
Author(s):  
A P Thomas ◽  
R M Denton
Keyword(s):  
Adipose Tissue ◽  
Phosphatase Activity ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Kinase ◽  
Epididymal Adipose Tissue ◽  
Ionophore A23187 ◽  
Dilute Suspensions ◽  
Dehydrogenase System ◽  
Pyruvate Dehydrogenase Phosphatase

Rat epididymal-adipose-tissue mitochondria were made selectively permeable to small molecules without the loss of matrix enzymes by treating the mitochondria with toluene under controlled conditions. With this preparation the entire pyruvate dehydrogenase system was shown to be retained within the mitochondrial matrix and to retain its normal catalytic activity. By using dilute suspensions of these permeabilized mitochondria maintained in the cuvette of a spectrophotometer, it was possible to monitor changes of pyruvate dehydrogenase activity continuously while the activities of the interconverting kinase and phosphatase could be independently manipulated. Permeabilized mitochondria were prepared from control and insulin-treated adipose tissue, and the properties of both the pyruvate dehydrogenase kinase and the phosphatase were compared in situ. No difference in kinase activity was detected, but increases in phosphatase activity were observed in permeabilized mitochondria from insulin-treated tissue. Further studies showed that the main effect of insulin treatment was a decrease in the apparent Ka of the phosphatase for Mg2+, in agreement with earlier studies with mitochondria made permeable to Mg2+ by using the ionophore A23187 [Thomas, Diggle & Denton (1986) Biochem. J. 238, 83-91]. No effects of spermine were detected, although spermine diminishes the Ka of purified phosphatase preparations for Mg2+. Since effects of insulin on pyruvate dehydrogenase phosphatase activity are not evident in mitochondrial extracts, it is concluded that insulin may act by altering some high-Mr component which interacts with the pyruvate dehydrogenase system within intact or permeabilized mitochondria, but not when the mitochondrial membranes are disrupted.

scholarly journals No evidence for differential biomass and mineral content in adult plants grown from dimorphic seeds of Suaeda aralocaspica

2014 ◽  
Author(s):  
Lei Wang ◽  
Chang-Yan Tian ◽  
Zhen-Ying Huang
Keyword(s):  
Mineral Content ◽  
Seed Traits ◽  
Experimental Conditions ◽  
Significant Difference ◽  
Physiological Dormancy ◽  
Black Seeds ◽  
Nitrogen Phosphorus ◽  
Different Levels ◽  
Adult Plants ◽  
Seed Heteromorphism

Producing two or more types of seeds by a single plant is known as seed heteromorphism. Comparison of seed traits or growth between plants grown from heteromorphic seeds has received considerable attention. However, information is scarce regarding the comparison of mineral content of adult plants from heteromorphic seeds. Here we present biomass and mineral profiles (Nitrogen, Phosphorus, Potassium, Sodium and Chloride) of adult plants grown from dimorphic seeds (non-dormant brown seeds and black seeds with non-deep physiological dormancy) of annual desert halophyte Suaeda aralocaspica at different levels of nutrient and salinity. The results showed that, although nutrient and salinity could affect dry weigh and mineral content, seed-dimorphic plants of S. aralocaspica did not show significant difference under the same experimental conditions. This study is one of the few to compare the physiological responses between seed-heteromorphic plants and suggests that mineral status is exactly consistent with growth performance for these plants.

Development of secretory mechanisms in rat pancreas.

1979 ◽  
Vol 236 (4) ◽  
pp. E446
Author(s):  
S L Werlin ◽  
R J Grand
Keyword(s):  
Calcium Ionophore ◽  
Fetal Tissue ◽  
Calcium Ionophore A23187 ◽  
Intracellular Camp ◽  
Amylase Secretion ◽  
Ionophore A23187 ◽  
Experimental Conditions ◽  
Amylase Release ◽  
Rat Pancreas

Mechanisms and development of secretory function were studied in rat pancreas in vitro. Amylase release from term fetal pancreas was refractory to stimulation by carbamylcholine chloride (carbachol) and cholecystokinin-octapeptide (CCK-OP), but was significantly augmented by calcium ionophore (A23187), DBcAMP, 8-Br-cGMP, and theophylline. The latter agent when combined with either cyclic nucleotide analogue further increased secretory responses. At 1 day and 8 days postnatally, responsiveness to carbachol and CCK-OP had been acquired because amylase secretion stimulated by these agents was brisk and at a level comparable to that found in mature tissue. Increasing extracellular calcium concentrations from 1.23 to 5.28 mM had no effect on basal amylase release in either the fetal or 8-day pancreas. No changes in intracellular cAMP concentrations were found at any age under experimental conditions used. Similarily, in fetal tissue, no changes in cGMP concentrations were found in response to carbachol or A23187. However, at 8 days of age, both agents produced two- to four-fold increases in tissue cGMP levels at 1, 2, and 5 min of incubation. These studies confirm that responsiveness to carbachol and CCK-OP is a maturational process in the pancreas that lags behind the development of intracellular processes involved in stimulus-secretion coupling.

scholarly journals The effect of ionophore A23187 on calcium ion fluxes and α-adrenergic-agonist action in perfused rat liver

1983 ◽  
Vol 214 (2) ◽  
pp. 405-412 ◽  
Author(s):  
P H Reinhart ◽  
W M Taylor ◽  
F L Bygrave
Keyword(s):  
Calcium Ion ◽  
Cellular Level ◽  
Ionophore A23187 ◽  
Respiratory Response ◽  
Adrenergic Agonist ◽  
Experimental Conditions ◽  
Agonist Action ◽  
Total Inhibition ◽  
Hepatic Action ◽  
Alpha Agonist

The effect of ionophore A23187 on cellular Ca2+ fluxes, glycogenolysis and respiration was examined in perfused liver. At low extracellular Ca2+ concentrations (less than 4 microM), A23187 induced the mobilization of intracellular Ca2+ and stimulated the rate of glycogenolysis and respiration. As the extracellular Ca2+ concentration was elevated, biphasic cellular Ca2+ fluxes were observed, with Ca2+ uptake preceding Ca2+ efflux. Under these conditions, both the glycogenolytic response and the respiratory response also became biphasic, allowing the differentiation between the effects of extracellular and intracellular Ca2+. Under all conditions examined the rate of Ca2+ efflux induced by A23187 was much slower than the rate of phenylephrine-induced Ca2+ efflux, although the net amounts of Ca2+ effluxed were similar for both agents. The effect of A23187 on phenylephrine-induced Ca2+ fluxes, glycogenolysis and respiration is dependent on the extracellular Ca2+ concentration. At concentrations of less than 50 microM-Ca2+, A23187 only partially inhibited alpha-agonist action, whereas at 1.3 mM-Ca2+ almost total inhibition was observed. The action of A23187 at the cellular level is complex, dependent on the experimental conditions used, and shows both differences from and similarities to the hepatic action of alpha-adrenergic agonists.

scholarly journals Acid and alkaline phosphatase activity in broiler chicks fed with different levels of phytase and non-phytate phosphorus

2013 ◽  
Vol 41 (2) ◽  
pp. 229-233 ◽  
Author(s):  
Vanessa de Souza Nakagi ◽  
Cecília Maria Costa do Amaral ◽  
Márcia Regina Stech ◽  
Andrea Cristina Frizzas de Lima ◽  
Fátima Aparecida Ribeiro Harnich ◽  
...  
Keyword(s):  
Alkaline Phosphatase ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Broiler Chicks ◽  
Phytate Phosphorus ◽  
Acid And Alkaline Phosphatase ◽  
Different Levels

scholarly journals A simple and rapid method for the reversible removal of lipids from a membrane-bound enzyme

1978 ◽  
Vol 169 (2) ◽  
pp. 305-311 ◽  
Author(s):  
S L Goodman ◽  
M Isern de Caldentey ◽  
K P Wheeler
Keyword(s):  
Phosphatase Activity ◽  
Rapid Method ◽  
Adenosine Triphosphatase ◽  
Complete Loss ◽  
Initial Activity ◽  
Experimental Conditions ◽  
Adenosine Triphosphatase Activity ◽  
Ionic Detergent ◽  
Reproducible Method ◽  
Membrane Bound

A simple, rapid and reproducible method for the reversible removal of lipids from a membrane-bound enzyme is described. Essentially, a membrane preparation containing (Na+ + K+)-dependent adenosine triphosphatase was extracted with the non-ionic detergent Lubrol WX in the presence of glycerol, and partial separation of protein from lipid was achieved with the use of only two centrifugations. About 74% of the endogenous phospholipid and 79% of the cholesterol were removed, concomitant with a virtually complete loss of ouabain-sensitive adenosine triphosphatase activity, but with retention of 60-100% of the K+-dependent phosphatase activity. The addition of pure phosphatidylserine re-activated the enzyme to more than 80% of the initial activity, and up to 30% of the protein was recovered. Excess of phosphatidylserine could be washed off the enzyme to give a stable ‘reconstituted’ preparation. The effects of variation in the experimental conditions were examined, and the results are discussed with respect to the possibility of adapting the method to the study of other lipid-dependent enzymes bound to membranes.

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