The plasma membrane proton-translocating ATPase

Living cells require membranes and membrane transporters for the maintenance of life. After decades of biochemical scrutiny, the structures and molecular mechanisms by which membrane transporters catalyze transmembrane solute movements are beginning to be understood. The plasma membrane proton-translocating adenosine triphosphatase (ATPase) is an archetype of the P-type ATPase family of membrane transporters, which are important in a wide variety of cellular processes. The H+-ATPase has been crystallized and its structure determined to a resolution of 8 angstrom in the membrane plane. When considered together with the large body of biochemical information that has been accumulated for this transporter, and for enzymes in general, this new structural information is providing tantalizing insights regarding the molecular mechanism of active ion transport catalyzed by this enzyme.     

Inhibition of erythrocyte ATPase activity by aclacinomycin and reverse effects of ascorbate on ATPase activity

We studied the effect of aclacinomycin on human erythrocyte membrane enzymes. Aclacinomycin inhibited ATPase, including Na-K-dependent ATPase, ouabain insensitive ATPase and Ca-ATPase. However acetylcholinesterase was not inhibited by aclacinomycin. The ATPase activities were not inhibited by aclacinomycin if ascorbate was added to the incubation mixture. However other reducing agents, alpha-tocopherol, superoxide dismutase and catalase had no effect on ATPase activity. Ascorbate may protect membrane proteins and lipids from peroxidate damage.     

ATPase activity of two rabbit laryngeal muscles

Zusammenfassung Die Myofibrillen- und Myosin-ATPase-Aktivität des schnellen «roten» M. thyroarytenoideus von Kaninchen ist höher als die ATPase-Aktivität des «weissen» M. extensor digitorum longus und wesentlich höher als die ATPase-Aktivität des «roten» M. soleus. Daraus folgt, dass in Abhängigkeit besonderer funktioneller Ansprüche auch rote Muskeln schnell sein können.     

ATPase activity of guinea pig heart muscle

Riassunto 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 attività è maggiore a pH 9,2 che a pH 6,8. Mentre il Ca⁺⁺ influisce differenziando decisamente le attività 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'attività enzimatica dopo una permanenza a 60° per 20 min.     

ATPase activity in mercury intoxicated eels

Summary 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.The author wishes to express his sincere gratitude to Professor A. Disteche and Professor E. Schoffeniels for discussions during the investigation. This research was carried out in participation in the Belgian National Research and Development Program on the Environment-Water-Sea Project-Office of the Prime Minister-Interministerial Commission for Science Policy and Programmation.     

Chromaffin granules: Effects of ions and ATP on catecholamine content,ATPase activity,and membrane phosphorylation

Résumé L'ATP induit la libération de catécholamines des granules chromaffines médullaires. Nous discutons le rôle du Cl^– dans ce processus vis-à-vis l'activité de l'ATPase et la phosphorylation des membranes. Nos résultats indiquent que la réaction aboutissant à la liberation de catécholamines est un phenomène comportant plusieurs étapes échelonnées après l'hydrolyse de l'ATP.

---

---

Supported by the Medical Research Council of Canada.     

Junctions of polytene chromosomes and the inner nuclear membrane

Summary Polytene chromosomes in salivary gland nuclei from chironomid larvae of defined stages are connected along their entire length, by some 100 chromatin fibers, to the inner nuclear membrane.Dedicated to Professor Friedrich Mechelke on the occasion of his 60th anniversary.     

Intracellular phosphate release by the Na+-K+-activated membrane ATPase

Zusammenfassung An menschlichen Erythrocyten hemmt Phloretin den passiven Austritt von anorganischem Phosphat. Mit Hilfe dieser Wirkung konnte gezeigt werden, dass die Na⁺-K⁺-aktivierte ATPase anorganisches Phosphat nicht direkt nach aussen befördert, sondern im Innern der Zelle freisetzt.     

Effect of heat treatment on the ATPase activity of various sarcoplasmic reticulum preparations

Summary Ca²⁺-stimulated ATPase activity of sarcoplasmic reticulum (SR) preparations is activated after a short period of preincubation at temperatures between 40 and 45°C, but for temperatures higher than 48°C pronounced denaturation is observed. Heat denaturation is decreased if Mg²⁺ or K⁺ are present during heat treatment.Acknowledgments. This work was supported by research grants from Instituto de Alta Cultura (Grant No. CB/2) and the Calouste Gulbenkian Foundation. We are grateful to Drs.A. P. Carvalho andV. M. C. Madeira for many discussions and suggestions during the course of this work.     

On the effect of insulin on lactate permeability through the nuclear membrane

Résumé L'addition d'insuline aux noyaux isolés du thymus de rat peut prévenir les pertes de lactate endogène se produisant à travers de la membrane nucléaire.

---

---

The authors wish to thank Prof. F. J.Loomeijer and Dr. H. M.Klouwen for the stimulating discussions during the work.     

Presence of ATPase on the vesicular membrane ofCysticercus cellulosae. A high resolution cytochemical study

Summary ATPase was demonstrated by high resolution cytochemistry in the microtriches ofC. cellulosae. It is thought that the enzyme is important for the parasite's acquisition of raw materials for surviving and distribution in host tissues.The authors greatfully acknowledge the technical assistant of Miss Jovita Sandoval.     

X-Ray irradiation induced changes of the nuclear membrane of Kirkman-Robbins tumour cells

Riassunto L'osservazione al microscopio electtronico del tumore diKirkman-Robbins irradiato con raggi X dimostrava danni nucleolari, frammentazione, assottigliamento e scollamento dei foglietti dell carioteca. Inoltre, nel citoplasma si osservava cromatina fuoriuscita dal nucleo.