Search

Ca2+-stimulated ATPase activity of sarcoplasmic reticulum (SR) preparations is activated after a short period of preincubation at temperatures between 40 and 45 degrees C, but for temperatures higher than 48 degrees C pronounced denaturation is observed. Heat denaturation is decreased if Mg2+ or K+ are present during heat treatment.

Taurine selectively inhibits the phytohemagglutinin-stimulated incorporation of3H-thymidine by human cultured lymphocytes (50% inhibition by 12.5 mM taurine). Decreasing effects of taurine on Na−K ATPase activity or on calcium accumulation by lymphocytes might be responsible for its action on cell proliferation.

The pink muscle of the carp differs from the white (and red) muscle not only histochemically but also in its myosin isoform, as shown by peptide maps of the myosin heavy chains. Results of an electrophoretic analysis of myosins are discussed in the light of their immunohistochemical properties and histochemical ATPase activity.

Plasma membrane sheets prepared by zonal centrifugation of a premicrosomal pellet obtained from a rat liver homogenate are devoid of HCO-3-ATPase activity. Since the microsomal fraction is also lacking in this ATPase activity, it can be concluded that the HCO-3-ATPase is not involved in the secretion of HCO-3 into bile.

An Mg2+-dependent ATPase activity stimulated by the anions is found in the microsomal fraction prepared from a homogenate of the endopodits of pleopods 4 and 5 ofSphaeroma serratum. This enzyme has an optimal activity for 25 mM whatever the anion and for pH 7.6. Its inhibition is almost complete for 10−3 M of thiocyamate. The stimulation of the enzyme by 2 anions is cumulative if HCO3 − is one of these anions. This anion-stimulated ATPase could be involved with the (Na+−K+) ATPases in the osmoregulation mechanism of this isopod.

In glyzerinierten fibrillaren Muskelfasern vonLethocerus werden schon 20 msec nach maximaler «Dehnungsaktivierung» der ATP-ase (um 5000%) 2 Mol ATP pro Mol Myosin gespalten, worauf die Kontraktionsspannung mit der Wechselzahl von Myosin-ATPase und Querbrucken (etwa 10 Hz) oszilliert.

L'ATP induit la liberation de catecholamines des granules chromaffines medullaires. Nous discutons le role du Cl− dans ce processus vis-a-vis l'activite de l'ATPase et la phosphorylation des membranes. Nos resultats indiquent que la reaction aboutissant a la liberation de catecholamines est un phenomene comportant plusieurs etapes echelonnees apres l'hydrolyse de l'ATP.

L'Autore ha studiato l'influenza della concentrazione degli ioni Ca++ e Mg++ sull'ATPasi degli atri e dei ventricoli di cuore di cavia. Tale attivita e maggiore a pH 9,2 che a pH 6,8. Mentre il Ca++ influisce differenziando decisamente le attivita degli atri da quelle dei ventricoli, il Mg++ accentua piuttosto una differenza tra la parte destra e la sinistra. Il calore distrugge quasi completamente l'attivita enzimatica dopo una permanenza a 60° per 20 min.

Considerable amounts of nonesterified cholesterol were found in human serum freed from lipoproteins. This cholesterol, when incubated with synaptosomal plasma membranes of dog brain, evokes changes of the ouabain-sensitive ATPase activity, as the exogenously added cholesterol does.

Both Mg2+-ATPase and HCO 3 − -stimulated ATPase activity were inhibited by sodium azide and to a lesser extent ethacrynic acid and amiloride. 1 mM DNP stimulated Mg2+-ATPase activity by 22% and HCO 3 − -stimulated ATPase activity by 7%.

In one of two membrane fractions isolated from the homogenate of casein-induced rabbit granulocytes ouabain-sensitive ATPase activity was found definitely. Electrophoretic patterns of these membrane fractions showed no significant differences in staining for carbohydrate and protein.

The enzymic activity of Mg2+- or Ca2+-stimulated ATPase from Escherichia coli was inhibited by one of the troponin components, TN-I, and by mitochondrial ATPase inhibitor (F1-inhibitor). The inhibitory ability of component TN-I against Mg2+-stimulated AtPase activity was lost after digestion of component TN-I with trypsin. The Mg2+-stimulated ATPase activity inhibited by component TN-I was completely restored by the addition of another troponin component TN-C.

The effect of porcine insulin has been tested in vitro on human erythrocyte plasma membrane (Na+−K+) and Mg2+-ATPase activities as well as on membrane fluidity. The results indicate that the hormonal treatment significantly inhibits (Na+−K+)-ATPase activity, and at the same time decreases membrane fluidity.

Eels intoxicated by lethal doses of HgCl2 accumulate mercury in their gills. Mercury inhibits the ouabainsensitive Na+K+ATPase activity of gills involving the rupture of the fish NaCl balance.

Bilirubin in different concentrations was injected in newborn guinea-pigs and the following parameters were determined: serum total and unbound bilirubin, whole brain bilirubin content and oxygen consumption, NADH-cytochrome c reductase and ATPase activities in brain mitochondria. The results showed a significant correlation between decreased rates of brain metabolism and the elevation of serum total and unbound bilirubin.

The time course of ATPase activity and force has been determined during contraction and relaxation in skinned (hyperpermeable) anterior byssus retractor muscle, ABRM, of Mytilus edulis and compared with corresponding measurements on skinned taenia coli of guinea-pigs. Following a calcium-induced contraction, lowering the [Ca++] to 10(-8) M rapidly reduces ATPase activity within 2 min to resting levels while force declines only to about 30-50% of maximal tension within the same time. Thus slow relaxation is due to a 'catch-like-state' which is common to different kinds of smooth muscles and can be reduced with cAMP in ABRM and by Pi in taenia coli.

Mediante l'adsorbimento su Calcio fosfato gel e la successiva eluzione a pH 6,8 con soluzioni a forza ionica crescente si sono riuscite a separare frazioni aventi diverse attivita specifiche 5′-AMPdeaminasica (massima nei campioni eluiti con 1M NaCl) e ATPasica. L'attivita ATPasica e associata alla proprieta della miosina di formare actomiosina.

Behandlung mit 20,25-Diazacholesterin bzw. Triparanol fuhrt bei Ratten zu einer Anhaufung von Desmosterin im Herzmuskel. Gleichzeitig kommt es zu einer Erhohung der spezifischen (Na+, K+)-ATPase Aktivitat des Herzmuskelsakolemm. Der Zusammenhang dieser beiden Phanomene wird diskutiert.

Myosin was isolated from rat ventricular myocardium, and its properties were compared in adult and very old animals. Ca2+ -ATPase activity of ventricular myosin was found to be lower in very old animals as compared with adult ones; K+ -ATPase activity, however, does not change with the aging process. Neither were there any differences between the two age groups in the pattern of ventricular light chains of myosin.

Mg2+-dependent and HCO-3-stimulated ATPase activity was highest in the brush border (microvilli) of rat duodenal mucosa compared with that of the other gastrointestinal mucosa. This ATPase may be useful to neutralize the gastric acid in the duodenal lumen. Carbonic anhydrase seems to accomplish a subsidiary role in the above reaction.

Na+−K+, activated ATPase showed an increase in activity at the beginning of the 5th instar and adult life. This was followed by a relatively constant level of activity which, in larval preparations only, was not maintained but decreased with the onset of metamorphosis.

Divalent metal ions have been found to protect membranes of red beet crown gall tissue more than their adjacent normal regions from thermal or gamma radiation stress, suggesting the possibility of an alteration on the surface charge accompanying tumor formation in plants. Further, tumor tissue has been observed to possess enhanced membrane ATPase activity, a higher tissue sulfhydryl content and increased protein levels, thus suggesting a model of ‘source’ (normal tissue) and ‘sink’ (tumor tissue) relationship.

With a suitable modification of the Farquhar and Palade technique the Na+ + K+-ATPase activity in guinea-pig thyroid is demonstrated. The addition of c-AMP (5 X 10(-6) M or 1.5 X 10(-5) M) to the incubation media produced an apparent intensification of the Na+ + K+ -ATPase activity in the thyroid.

Membranen sekretorischer Granula wurden von der Ohrspeicheldruse (Parotis) der Ratte isoliert und auf Kalzium-ATPase-Aktivitat (Ca2+-ATPase) untersucht und postuliert, dass die gefundene Ca2+-ATPase eine Rolle in der Aufnahme und Abgabe von Kalzium in sekretorischen Granula spielt.

The ATPase activity is inhibited by Colchicin in concentrations of 10−3 m and 10−4 m at a rate of 40 to 20 %, but in no way in the range of 10−7 m and 10−8 m, where Colchicin exerts its typical spindle-blocking action on the mitotic cell division. It is therefore no evidence, that Colchicin acts by influence on the energy yielding ATP-ATPase system, which was proposed to be responsible for the spindle contraction.

The irradiation of the lens by a simple dose of 1400 r, gives a very important and lasting reduction of its hexokinase activity. Its ATPase activity shows an increase during the first four days and a return to normal again. The variations observed here (that isin vivo) are different from the ones noted after irradiation of these enzymesin vitro.

L'autrice ha studiato l'attivita ATPasica dei mitocondri e miofibrille isolate da muscolo e cuore di cavia ed ha trovato: 1) Il progesterone e il desossicorticosterone esercitano una azione inibente su tale attivita. 2) Le miofibrille preparate con tripsina hanno una attivita maggiore di quelle preparate con saccarosio. 3) Non esiste notevole differenza tra attivita ATPasica dei mitochondri e quella delle miofibrille.

The cytoplasma fraction of the bovine choroid plexus epithelial cells was found to contain a considerable ATPase activity. The influence of Na+, K+, Li+, Rb+, Cs+, Co++, Mn++, Zn++ and Fe+++ on the activity of the Mg++-dependent enzyme has been studied. The monovalent cations do not influence the enzymic activity, whereas the effect of the bi- and trivalent cations is characterized by an inhibition of the ATPase.

Mitochondrien aus kleinen und grossen Spontanhepatomen bei F1(C57Bl×C3He) Mausen weisen verschiedene Adenosintriphosphataseaktivitaten auf, was sich 1. an der Hemmung der Fettsaureoxydation normaler Lebermitochondrien nach Zugabe von Tumormitochondrien und 2. an der Fettsaureoxydation der Hepatommitochondrien selbst zeigen lasst. Die Mitochondrien gewisser Tumoren vermochten Caprylsaure nur zu oxydieren, wenn die Adenosintriphosphatase moglichst wenig aktiviert war durch Zugabe von Verseen zum Aufarbeitungsmedium.

Norepinephrin fordert in vitro die Tatigkeit einer Ouabain empfindlichen Na+/K+ ATPase. Diese Wirkung, durch eine geringe Dosis einesβ-adrenergischen Antagonisten eingeschrankt, scheint offenbar von einer 3′,5′-zyklischen AMP unabhangig zu sein. Die Tatigkeit der Brenzkatechin-induzierten ATPase stimmt mit der Auffassung uberein, dass im aktivierten braunen Fettgewebe der Energieumsatz zusammen mit dem vermehrten Sauerstoffverbrauch ansteigt.

A significant portion of the SH-groups of the rat-brain Na+-K+-ATPase preparation is masked; it can be unmasked by the treatment of Triton-X-100. The inhibitory effects of PCMB and NEM on the ATPase activity are different in the detergent-treated and untreated preparations.

The inhibition of cardiac myofibrillar ATPase activity by EDTA can be completely reversed by Ca++ under certain experimental conditions. This shows that there is no fundamental difference between the reaction of cardiac myofibrillar ATPase and the tension development of glycerinated cardiac fibres, as was supposed byBriggs andHannah on account of the results ofParker andBerger.

ATP content shows a cell-age dependent decrease in bovine erythrocytes separated according to Murphy. An important point in the evaluation of results lies in considering differences in the ATP consumption between cells of various age during separation. The decrease in ATP occurs in spite of diminished ATPase activity in older cells.

Die Myofibrillen- und Myosin-ATPase-Aktivitat des schnellen «roten» M. thyroarytenoideus von Kaninchen ist hoher als die ATPase-Aktivitat des «weissen» M. extensor digitorum longus und wesentlich hoher als die ATPase-Aktivitat des «roten» M. soleus. Daraus folgt, dass in Abhangigkeit besonderer funktioneller Anspruche auch rote Muskeln schnell sein konnen.