Maria Piera Piacentini

Senescence delay and change of antioxidant enzyme levels in Cucumis sativus L. etiolated seedlings by ELF magnetic fields

We exposed cucumber Cucumis sativus L. etiolated seedlings to a 50 Hz, 1-Gauss magnetic field (MF) 24 h per day for 2 weeks in the dark, starting from complete divarication of cotyledons and observed quickened growth and prolonged life of EMF-exposed seedlings compared to the controls. Since this phenomenon may be due to MF-induced delay in the senescence process which, in turn, is believed to be dependent on the potency of the seedling oxidative defense system, we assayed some related enzymes and found that the combined action of higher levels of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) in MF-exposed seedlings may promote their survival and delay the appearance of signs of decay.

Antibacterial effect of a magnetic field on Serratia marcescens and related virulence to Hordeum vulgare and Rubus fruticosus callus cells

The exposure to a static magnetic field of 80+/-20 Gauss (8+/-2 mT) resulted in the inhibition of Serratia marcescens growth. Callus cell suspensions from Hordeum vulgare and Rubus fruticosus were also examined and only the former was found to be affected by the magnetic field, which induced a decreased viability. S. marcescens was shown to be virulent only toward H. vulgare and this virulence was reduced by the presence of the magnetic field. The modification of glutathione peroxidase activity under the different experimental conditions allowed us to speculate on the possibility of an oxidative-stress response of H. vulgare both to S. marcescens infection and magnetic field exposure. Since the control of microbial growth by physical agents is of interest for agriculture, medicine and food sciences, the investigation presented herein could serve as a starting point for future studies on the efficacy of static magnetic field as low-cost/easy-handling preservative agent.

Automated analysis of morphometric parameters for accurate definition of erythrocyte cell shape

Modification of erythrocyte morphology is clinically important in hematology and medicine. Its detection is routinely performed by subjective microscopic evaluation, which is difficult and strongly dependent on the operators expertise. We developed an original automated methodology to analyze erythrocyte cell shape modification to support and improve the operators capability and expedite measurements.

Glucose-1,6-P2 synthesis, phosphoglucomutase and phosphoribomutase correlate with glucose-1,6-P2 concentration in mammals' red blood cells

Glucose 1,6-biphosphate (G1,6P2) was measured in human, pig, cow, rabbit, rat and sheep red blood cells. Mean values are variable among the species and range from 33 to 122 nmol/ml RBC for pig and rabbit erythrocytes, respectively. The activities of G1,6P2 synthase, phosphoglucomutase (PGM) and phosphoribomutase (PRM) have also been assayed in red cell haemolysates of the same species. The correlations between the biphosphate content and the occurrence of the three enzymatic activities have been studied in order to gain an insight into the regulation of the G1,6P2 turnover in mammalian erythrocytes.

myo-[3H]-inositol loaded erythrocytes and white ghosts: Two models to investigate the phosphatidylinositol synthesis in human red cells

Human erythrocytes were loaded with myo-[(3)H]-inositol in the presence or absence of cytidine trisphosphate to investigate the synthesis of membrane phosphoinositides in the intact red cell. The addition of cytidylic nucleotides to the loading mixture yielded a four-fold increase in the [(3)H]-labeling of the membranes. The [(3)H]-labeling of phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate was distinguished by two chromatographic techniques. Experiments performed on white ghosts demonstrated the presence of CDP-diacylglycerol synthase and phosphatidylinositol synthase. These results and those already reported allow to discuss a possible turnover of the inositol polar head.

Glucose 1,6-bisphosphate-overloaded erythrocytes: A strategy to investigate the metabolic role of the bisphosphate in red blood cells

Human erythrocytes overloaded with glucose 1,6-bisphosphate were prepared in order to establish the metabolic significance of this phosphorylated sugar in the intact red cell. The intracellular glucose 1,6-bisphosphate concentration was increased six- and twofold over the normal level by encapsulating (i) the commercially available compound and (ii) the glucose 1,6-bisphosphate synthase obtained from rabbit skeletal muscle, respectively. In both experimental conditions, a reduction of glucose utilization by the loaded cells was observed after reequilibration to the steady state. At the steady state, the concentrations of the glycolytic intermediates and of the adenine nucleotides appeared substantially unmodified when compared with those of controls, with the exception of a 50% reduction of glucose and fructose 6-phosphate measured in erythrocytes encapsulated with exogenous glucose 1,6-bisphosphate. Under the considered experimental conditions, the elevated intracellular glucose 1,6-bisphosphate appears to display an inhibitory effect on hexokinase that overcomes the possible activation of phosphofructokinase or pyruvate kinase.

Relationships between the age-dependent decay of glucose-1,6-bisphosphate synthesis, phosphoribomutase and phosphoglucomutase in human red cells.

In human red blood cells phosphoglucomutase exists in multiple molecular forms with different isoelectric points determined by two distinct loci called PGM1 and PGM2. With regard to the phosphoglucomutase PGM1 and PGM2 isoenzymes, the latter appear to be more important in erythrocyte metabolism owing to their ability to mutate ribose monophosphates and synthetize glucose-1,6-bisphosphate. In this paper we show that, beside undergoing age-related postranslational modifications, both phosphoglucomutase PGM1 and PGM2 forms decrease their activities as the mean cell age increases. Under the experimental conditions used to separate erythrocytes by age the comparison of the younger erythrocytes with the older shows that total phosphoglucomutase, phosphoribomutase and glucose-1,6-bisphosphate synthetic activities decay by 55%, 26% and 28%, respectively. We consider that these results substantiate the multifunctionality of PGM2 isoenzymes. Furthermore we discuss the role of these forms in the age-related decay of erythrocyte metabolism.

Effects of UV-C irradiation on phosphoinositide turnover in plant cells: similarities with those occurring via the formation of reactive oxygen intermediates in animal cells.

With the aim of examining the response of plant cells to UV-C irradiation, we investigated the behaviour of the phosphatidylinositol 4,5 bisphosphate (PtdIns 4,5-P2) molecule (the precursor of the phosphoinositide signal transduction cascade) by exposing callus cells from Peucedanum verticillare to UV-C (130 J m-2) and by examining the level and the fatty acid composition of PtdIns 4,5-P2 at different times after irradiation. We show that a pathway for the UV-C response includes transient PtdIns 4,5-P2 breakdown. The effect of ultraviolet rays is mimicked by H2O2 suggesting that in this plant it may be brought about by reactive oxygen intermediates (ROI), as already underlined in experimental animal models.

Inositol 1,4,5‐Trisphosphate distribution in Lycopersicon esculentum mill. seedlings cultivated “in vitro” under different conditions

Measurements of inositol 1,4,5‐trisphosphate (Ins 1,4,5‐P3 in cotyledons, epicotyls and roots of tomato seedlings grown “in vitro” either in the light or in the dark indicated that higher concentrations of this signal‐transducing molecule are contained in hypogeous vs. epigeous tissues. The same was observed in induced cotyledon explants grown in the light in the presence of growth regulators. Data concerning phosphatidylinositol metabolism in seedling roots are also reported. Taken together, our results may be helpful in understanding the role of the polyphosphoinositide signal system in plants.

Action of Acetaldehyde on Glucose Metabolism of Newborn and Adult Erythrocytes

This paper reports the effect of acetaldehyde on erythrocytes (RBC) of human adults and newborns. Acetaldehyde increases glucose consumption in adult RBC, but has no effect on that of newborn RBC. The compound stimulates the hexose monophosphate shunt and decreases the pyruvate production of the two RBC suspensions. In newborn RBC, acetaldehyde slightly modifies triose-P and fructose-1,6-bisphosphate but has no effect on the ATP/ADP ratio and glucose-1,6-bisphosphate content, which change markedly in adult RBC. Analysis of aldehyde dehydrogenase reveals nearly one half of enzyme activity in newborn RBC. The data indicate that in both adult and newborn RBC, acetaldehyde causes an intracellular reduced state, but the newborn cells take advantage of their greater pyruvate production for complete removal of the exceeding NADH equivalents.