Cl Anion-Dependent Mg-ATPase

We studied, in the rat brain, the synaptosomal and microsomal membrane fractions of Cl− ion-activated, Mg2+-dependent ATPase, satisfying the necessary kinetic peculiarities of transport ATPases, by a novel method of kinetic analysis of the multisite enzyme systems: (1) the [Mg-ATP] complex constitutes the substrate of the enzymic reaction; (2) the V = f(Cl−) dependence-reflecting curve is bell-shaped; (3) substrate dependence, V = f(S), curves at a constant concentration of free ligands (Mgf, ATPf, Cl−); (4) as known from the literature, in the process of reaction a phosphorylated intermediate is formed (Gerencser, Crit Rev Biochem Mol Biol 31:303–337, 1996). We report on the Cl-ATPase molecular mechanism and its place in the “P-type ATPase” classification

The effect of EGTA and Ca(++) in regulation of the brain Na/K-ATP-ase by noradrenaline

BACKGROUND: The Na/K-ATPase activity of the brain synaptic plasma membranes (SPM) is regulated by noradrenaline (NA) and the synaptosomal factor SF (soluble protein obtained from the synaptosome cytosol). In the absence of SF, NA inhibits Na/K-ATPase, while, on addition of SF to the reaction medium, there is a NA-dependent activation of Na/K-ATPase . On the other hand, EGTA augments the Na/K-ATPase activity and attenuates the ability of NA to inhibit Na/K-ATPase. RESULTS: Considering that Ca(2+) ion is a Na/K-ATPase modifier, it can be assumed that the effect of NA and SF is a Ca(2+)-dependent process. However, in the presence of 0.3 mM EGTA and 0.1 mM NA, the apparent inhibition constant for Ca(2+) (at [Ca(2+)] > 0.3 mM) is not SF dependent, while the apparent activation constant for SF does not change at increasing Ca(2+) concentration ([Ca(2+)] < 0.3 mM). At various Ca(2+) concentrations (0.06, 0.35 and 0.6 mM), no significant changes occur in the mode of action of NA on the Na/K-ATPase activity in the presence of 5 μg/ml SF. EGTA also has no effect on the NA-independent activation of Na/K-ATPase evoked by high SF concentrations. CONCLUSIONS: Taking into account that in the absence of EGTA similar results have been obtained, it can be concluded that the effect of NA and SF on brain Na/K-ATPase is a Ca(2+)-independent process

Intracellular Reactive Oxygen Species Mediate the Linkage of Na+/K+-ATPase to Hypertrophy and its Marker Genes in Cardiac Myocytes

We showed before that in cardiac myocytes partial inhibition of Na+/K+-ATPase by nontoxic concentrations of ouabain causes hypertrophy and transcriptional regulations of growth-related marker genes through multiple Ca2+-dependent signal pathways many of which involve Ras and p42/44 mitogen-activated protein kinases. The aim of this work was to explore the roles of intracellular reactive oxygen species (ROS) in these ouabain-initiated pathways. Ouabain caused a rapid generation of ROS within the myocytes that was prevented by preexposure of cells to N-acetylcysteine (NAC) or vitamin E. These antioxidants also blocked or attenuated the following actions of ouabain: inductions of the genes of skeletal α-actin and atrial natriuretic factor, repression of the gene of the α3-subunit of Na+/K+-ATPase, activation of mitogen-activated protein kinases, activation of Ras-dependent protein synthesis, and activation of transcription factor NF-κB. Induction of c-fos and activation of AP-1 by ouabain were not sensitive to NAC. Ouabain-induced inhibition of active Rb+ uptake through Na+/K+-ATPase and the resulting rise in intracellular Ca2+ were also not prevented by NAC. A phorbol ester that also causes myocyte hypertrophy did not increase ROS generation, and its effects on marker genes and protein synthesis were not affected by NAC. We conclude the following: (a) ROS are essential second messengers within some but not all signal pathways that are activated by the effect of ouabain on Na+/K+-ATPase; (b) the ROS-dependent pathways are involved in ouabain-induced hypertrophy; (c) increased ROS generation is not a common response of the myocyte to all hypertrophic stimuli; and (d) it may be possible to dissociate the positive inotropic effect of ouabain from its growth-related effects by alteration of the redox state of the cardiac myocyte

Ex Vivo Activity of Cardiac Glycosides in Acute Leukaemia

BACKGROUND: Despite years of interest in the anti-cancerous effects of cardiac glycosides (CGs), and numerous studies in vitro and in animals, it has not yet been possible to utilize this potential clinically. Reports have demonstrated promising in vitro effects on different targets as well as a possible therapeutic index/selectivity in vitro and in experimental animals. Recently, however, general inhibition of protein synthesis was suggested as the main mechanism of the anti-cancerous effects of CGs. In addition, evidence of species differences of a magnitude sufficient to explain the results of many studies called for reconsideration of earlier results. PRINCIPAL FINDINGS: In this report we identified primary B-precursor and T-ALL cells as being particularly susceptible to the cytotoxic effects of CGs. Digitoxin appeared most potent and IC(50) values for several patient samples were at concentrations that may be achieved in the clinic. Significant protein synthesis inhibition at concentrations corresponding to IC(50) was demonstrated in colorectal tumour cell lines moderately resistant to the cytotoxic effects of digoxin and digitoxin, but not in highly sensitive leukaemia cell lines. CONCLUSION: It is suggested that further investigation regarding CGs may be focused on diagnoses like T- and B-precursor ALL

INVESTIGATION OF DEHYDROGENASE ENZYME COMPLEX AMONG SOME INSECTS IN NORM AND UNDER INFLUENCE OF GROWTH REGULATORS

The investigation objects are the flour beetle, American cockroach, house fly and German cockroach. The aim of the work is to study in comparison the activity dynamics of alpha -GFDH, g-6-FDH, SDH, MDH and LDH in the ontogenesis of the flour beetle and American cockroach, to investigate the action of the exogenous morphogenetic hormones and their analogs no less than the peptide hormones on the activity of the enumerated enzymes and also to elucidate the role of the oxidoreductases in the development of the insecticide resistance by the house flies and German cockroachs. The work widens the conception about connection between action of the juveniles and breach of the energy metabolism among insects that one can use at development of the biochemical screening methods of different insecticides. The investigations performed have the great significance in conception of the metabolism regulation among the insects of different groups. The level of both summary activity of alpha -GFDH and SDH and their separate plural forms is recommended as a biochemical resistance evaluation criterion. Application field: biochemistry, entomology, agricultureAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Fathers' experiences accompanying labour and birth

This study aimed to explore the role of first-time fathers during the birthing process and to ascertain their perceptions and experiences within the multi-cultural setting of Nazareth, Israel. Eight fathers participated in retrospective semi-structured interviews 2-6 weeks after the birth of their child. Despite their cultural and religious beliefs, most fathers reported similar experiences concerning their supporting role. Data revealed that all fathers were willing to attend labour and birth, yet expressed feelings of fear and helplessness during the event due to unrealistic expectation, deficiency in antenatal preparation, lack of midwives' guidance, communication and flexibility regarding father's freedom of choic

Fathers' experiences accompanying labour and birth

This study aimed to explore the role of first-time fathers during the birthing process and to ascertain their perceptions and experiences within the multi-cultural setting of Nazareth, Israel. Eight fathers participated in retrospective semi-structured interviews 2-6 weeks after the birth of their child. Despite their cultural and religious beliefs, most fathers reported similar experiences concerning their supporting role. Data revealed that all fathers were willing to attend labour and birth, yet expressed feelings of fear and helplessness during the event due to unrealistic expectation, deficiency in antenatal preparation, lack of midwives' guidance, communication and flexibility regarding father's freedom of choic