Biomedical subjects

C Pieri

Publications and source records attributed to C Pieri.

104 records · Page 6Linked to original sources

PubMedDate not supplied

Food restriction in female Wistar rats. III. Thermotropic transition of membrane lipid and 5'-nucleotidase activity in hepatocytes.

The effect of diet restriction was measured on the anisotropy parameter of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 5'-nucleotidase enzyme activity in liver plasma membrane preparates. Diet restriction was applied to rats 3.5 months old on an every-other-day schedule (EOD) and the rats were killed at the age of 28-29 months. Six months and 24 months rats, fed ad libitum (AL), were used as controls. The Arrhenius plots of anisotropy parameter of liver membranes from young, old AL and old EOD animals exhibited well defined breakpoints at 16.3 degrees C, 19.5 degrees C and 16.7 degrees C, respectively. The breakpoint temperature of 5'-nucleotidase activity was lower in samples from young rats as compared to those from old AL rats, whereas no difference was observed comparing young and EOD fed rats. Present results support the hypothesis that diet restriction modifies lipid composition of liver plasma membranes in such a way that the appearance of age-dependent alterations is delayed.

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Diet restriction, body temperature and physicochemical properties of cell membranes.

This paper summarizes some recent results of the effect of diet restriction upon body temperature and membrane microviscosity of lymphocytes, hepatocytes and cerebellar cells of diet-restricted female Wistar rats. The treated animals were fed on an every-other-day schedule starting from the age of 3.5 months. It is suggested that a decrease in average body temperature (-1 degree C) of diet-restricted animals as compared to the ad libitum fed ones may stimulate the cells to synthesize more fluid membranes. Together with these the maintenance of the activity of protective enzymes is another key event which helps to prevent the age-dependent deterioration of cell membrane functions.

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Parameters to monitor aging with a possible perspective for intervention - an immunological approach.

Reliable aging markers are very rare, which are better than the chronological age or those symptoms which have such great individual variability that their scientific value is questionable. The effect of aging on immunological behavior of human (and animal) individuals is reasonably well established. In this communication an attempt is made to find an immunological marker of aging at the level of cell surface phenomena. It was observed that ion-channel activities, having a complex regulation, loose their flexible responsiveness in lymphocyte membranes during aging. A recently discovered voltage regulation of the calcium-activated potassium channels showed a distinct change with aging of human lymphocytes. A possibility to find a better marker system in complex regulatory processes is also discussed.

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Food restriction in female Wistar rats, IV. Morphometric parameters of cerebellar synapses.

The effect of food restriction on morphometric parameters of cerebellar synapses has been evaluated. A decrease in the number and surface density of synapses has been observed comparing 6 and 27-28 month old rats. Food restriction prevented the loss of the number and attenuated the reduction of the surface density of synaptic contacts occurring during aging. Present data support the idea that food restriction delays the appearance of age-related modifications of synaptic structures and may explain the improvement of motoric coordination and performance found in dietary restricted old animals.

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Food restriction in female Wistar rats: V. Lipid peroxidation and antioxidant enzymes in the liver.

The activities of antioxidant enzymes as well as the levels of basal and enzyme induced peroxidation have been investigated in liver of female Wistar undernourished rats. Food restriction was applied starting from the age of 3.5 months by feeding the animals on every-other-day schedule (EOD). Diet restriction prevented the age-dependent increase of basal and enzyme induced lipid peroxidation in both mitochondrial and microsomal liver membrane preparations. The activities of antioxidant enzyme, i.e. superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) of liver decreased during aging in ad libitum fed rats. In the diet conditioned animals, a small increase of SOD and a complete recovery of CAT activities were observed. Present data support that food restriction improved the protection against peroxidation, and this may be in close relationship with the life prolonging effect of such a treatment.

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Aging impairs membrane potential responsiveness as well as opening of voltage and ligand gated Na+ channels in human lymphocytes.

Depolarizing effects of increasing concentrations of extracellular K(+), as well as the repolarizing effect of bretylium tosylate (BT) were evaluated in human lymphocytes from young and elderly volunteers. Cells from elderly volunteers were less responsive to depolarization induced by increased extracellular potassium concentrations than those from young volunteers. Upon a near complete depolarization induced by 140 mM K(+) in the extracellular space, a significant amount of non-responding cells were found in samples from elderly volunteers. BT, which opens the otherwise silent Na(+) channels of partially depolarized cells, with subsequent activation of the Na(+)-K(+) pump (Pieri et al., 1989). repolarized both young and old lymphocytes. However, the degree of the repolarization was only 40% in the case of lymphocytes from elderly volunteers than from that of the young. It is suggested that an increase of membrane microviscosity, characteristic of old cells, may be at least partially responsible for the decreased responsiveness of plasma membrane functions which were observed.

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Food restriction in female Wistar rats. VI. Effect of reduced glutathione on the proliferative response of splenic lymphocytes from ad libitum fed and food restricted animals.

The effect of reduced glutathione (GSH) on the proliferative response of splenic lymphocytes from young, adult and old ad libitum (AL) fed as well as from old food-restricted rats was investigated. Food restriction was applied on an every-other-day schedule (EOD) starting from the age of 3.5 months. As was expected, the cells from EOD fed animals responded to concanavalin A (Con A) much better than those from age-matched ad libitum fed rats. The presence of the antioxidant GSH in the culture medium increased the response of lymphocytes in all the models taken into account; furthermore, it decreased the differences due to aging and application of food restriction. According to present knowledge, mitogenic stimulation induces free radical production, and GSH has, among others, a strong antioxidant activity. Thus, present data suggest that splenocytes from EOD animals tolerated the peroxidative stress resulting from mitogenic stimulation better than those from AL fed ones.

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Reduced glutathione recovers the impairment of the proliferative response of splenic lymphocytes from vitamin E-deficient rats.

The effect of reduced glutathione (GSH) on the Con A induce proliferative response of splenic lymphocytes from rats fed a normal or vitamin E-deficient diet has been investigated. The animals were killed when they were 12 months old and after 11 months of dietary treatment. As was expected, a decreased response, measured in terms of blast transformation or [(3)H]thymidine incorporation, was observed in vitamin E-deficient animals when compared with the control group. This pattern can be accounted for by the large number of dead cells found in deficient animals. GSH addition into the culture medium resulted in a strong increase of the response in both groups and it eliminated the difference caused by the different dietary regimens. Taking into account that, during proliferation, an increase of respiration occurs which increases the risk of free radical production, present data suggest that GSH may substitute vitamin E in protecting the cells.

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Effect of reduced glutathione on mitochondrial parameters of proliferating splenocytes from young and old rats.

The time-dependent changes of mitochondrial membrane potential and mass have been investigated on splenocytes from young, adult and old rats stimulated with Con A in the presence and absence of reduced glutathione (GSH). In addition, the basal level as well as the level of GSH during a 3-day culture period has been determined. No age-dependent changes of cellular GSH content were observed in freshly prepared splenocytes; however, in proliferating cells from old animals the expected increase in GSH levels was delayed. As regards the mitochondrial parameters, their membrane potential and mass were measured by means of the fluorescent probes rhodamine-123 (Rh-123) and nonyl acridine orange (NAO), respectively, and flow cytometry. During aging and with time of culture, an increased number of cells showed depolarization and loss of mitochondrial mass. This age-dependent impairment was completely prevented by addition of GSH to the culture medium, which resulted in a sharp increase in intracellular GSH. The present findings support the view that an impairment of the antioxidant defense system may be responsible for the damage observed in the mitochondria of proliferating splenocytes from old animals.

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Melatonin is an efficient antioxidant.

We have compared the peroxyl radical scavenger ability of melatonin with that of vitamin E, ascorbic acid (As.A.), reduced glutathione (GSH) and mannitol. All the antioxidants, except mannitol, prevented the lysis of human erythrocytes exposed to an azo-initiator of peroxyl radicals (2,2'-azo-bis(2-amidinopropane)dihydrochloride) at 37 degrees C. The percentage of this inhibition of erythrocyte lysis varied with the concentration of antioxidants, but the efficiency was melatonin > vitamin E > As.A. > GSH. Based on the assumption that each molecule of vitamin E scavenges two peroxyl radicals, the scavenging capacity of melatonin was four peroxyl radicals/molecule.

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Food restriction in female Wistar rats. VII. Mitochondrial parameters in resting and proliferating splenic lymphocytes.

The effect of food restriction on the mitochondria of resting and proliferating rat splenocytes was examined, measuring the membrane potential and mass of these organelles, by means of the specific fluorescent probes Rhodamine-123 and Nonyl Acridine Orange, respectively. Food restriction was applied on an every-other-day schedule (EOD) starting at the age of 3.5 months. The ad libitum fed (AL) animals were killed when they were 4, 11 and 24 months old, whereas the EOD rats were killed at 11 and 26 months. Resting lymphocytes from AL rats showed an age-dependent increase of both membrane potential and mass of their mitochondria. However, the mitochondrial mass increased to a larger extent when compared with the membrane potential resulting in a decrease of the respiratory quotient (RQ), i.e. of the respiratory activity per unit of mitochondrial mass. In EOD animals, the mitochondrial membrane potential was lower and the mitochondrial mass was higher in the corresponding age-matched controls, resulting in a further decrease of RQ. Following mitogenic stimulation, most of the cells from young and adult AL rat showed an increase of membrane potential and mass of their mitochondria. In contrast about 50% of cells from old AL rats had depolarized organelles after 72 h from the stimulation. Food restriction was able to prevent these alterations allowing the majority of cells, including those from old animals, to maintain the hyperpolarization of their mitochondria during the 3-day culture. In light of the well known sensitivity of mitochondrial membrane potential to peroxidative stress, present data suggest that the increase of respiration occurring during mitogenesis may increase free radical production, which is better tolerated by cells from EOD animals than by those from AL animals.

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The modulation of intracellular glutathione level modulates the mitochondrial response in proliferating rat splenocytes.

We have investigated the effect of intracellular reduced glutathione (GSH) levels on the mitochondrial parameters of proliferating rat splenocytes. The intracellular GSH content of the cells was altered by continuous culture with buthionine-S, R-sulfoximine (BSO), a specific inhibitor of GSH synthesis. BSO decreased the GSH levels, inhibited DNA synthesis and caused depolarization of mitochondria in 52% of cells stimulated to proliferate for 72 h. These data support the proposition that GSH influences the lymphocyte proliferation at more than one site, one of which is the energy producing machinery.

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The c-myc gene regulates the polyamine pathway in DMSO-induced apoptosis.

It is accepted that apoptosis is a gene-controlled process of cellular self-destruction. It occurs during physiological regulation and in pathological situations in the life of a cell. In the immune system, several different intracellular and extracellular factors have been associated with the induction of apoptosis, and the final responses depend on the cell system and the acquired signals. In lymphoid cells, dexamethasone-induced apoptosis is associated with c-myc downregulation in cells that remain in G0-G1 until the point of death. Ornithine decarboxylase (ODC), a key enzyme involved in polyamine biosynthesis, is regulated by c-myc, which is a transcriptional activator implicated not only in the control of cell proliferation and differentiation but also in programmed cell death. As dimethylsulphoxide (DMSO) induces apoptosis in the RPMI-8402 human pre-T cell line, the present study analysed the involvement of the c-myc proto-oncogene and polyamine pathway as mediators of apoptosis. Cell growth, programmed cell death, c-myc expression, ODC activity and intracellular polyamine content were detected after DMSO and difluoromethylornithine (DFMO) treatment. DMSO-treated cells exhibit a decrease in ODC activity and polyamine levels associated with cell growth arrest and programmed cell death induction. The expression of c-myc proto-oncogene, as its mRNA or protein, is specifically down-regulated. DFMO, a well defined polyamine biosynthesis inhibitor, completely blocks ODC activity, resulting in growth inhibition but not apoptosis. Moreover, in these samples no evidence of changes of c-myc expression were found. The results obtained suggest that, in RPMI-8402 cells, DMSO provokes a c-myc-dependent decrease of ODC activity followed by a depletion of intracellular polyamine levels, associated with programmed cell death and cell growth arrest.

Apoptosis↗

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Age-dependent changes of serum oxygen radical scavenger capacity and haemoglobin glycosylation in non-insulin-dependent diabetic patients.

BACKGROUND: Contradictory results have been reported in the literature concerning the correlation between glycosylated haemoglobin (HbA1c) and peroxidation level in serum of diabetic patients. OBJECTIVE: To evaluate this correlation in type 2 diabetic patients by comparing the level of HbA1c with the oxygen radical absorbance capacity (ORAC(OH)) of serum. METHODS: One hundred and five type 2 diabetic patients were enrolled for the study. After having obtained informed consent, venous blood samples were drawn after overnight fast at the time of routine diabetic check-ups. The blood was collected in plain and EDTA (1 mg/ml) tubes. Glycosylated haemoglobin (HbA1c) was determined by cation-exchange chromatography (HPLC), and spectrophotometric detection (Diamat Analyzer, BioRad). Serum was used for biochemical determinations performed by standard laboratory procedures and for ORAC(OH) analysis. This last parameter was determined measuring the loss of beta-phycoerytrin fluorescence due to oxidation by hydroxyl radicals generated by Cu(2+) and H(2)O(2), in the presence and absence of serum. Seventy-eight control age-matched subjects were obtained from the personnel staff of our Research Department and old healthy subjects, selected on the basis of Senieur Protocol, were relatives of the above mentioned personnel. RESULTS: When the population of diabetic patients was taken as a whole, a decrease of ORAC(OH) has been observed compared to the controls. Moreover, negative correlations were found comparing ORAC(OH) either with HbA1c (r = -0.213; p = 0.029) and with the age of patients (r = -0.27; p = 0.005). To better understand the effect of age, the data were re-examined dividing the diabetics into two populations, i.e. under and over 65 years of age. An age-dependent decrease of ORAC(OH) and an increase in HbA1c levels has been observed comparing these two populations; however, the correlation between the two parameters remained statistically significant only in the oldest group (r = -0.31; p = 0.026). CONCLUSIONS: Present data point to an involvement of oxidative stress in the glycation of haemoglobin especially in old diabetic patients, and provide support for the potential use of an antioxidant therapy in these patients, irrespective of their glycaemic control.

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