Biomedical subjects

M Aragno

Publications and source records attributed to M Aragno.

At least 37 records · Page 2Linked to original sources

PubMed1998

Dehydroepiandrosterone protects bovine retinal capillary pericytes against glucose toxicity.

Pericyte loss is an early feature of diabetic retinopathy and represents a key step in the progression of this disease. This study aimed to evaluate the effect of dehydroepiandro-sterone (DHEA) on glucose toxicity in retinal capillary pericytes. Bovine retinal pericytes (BRP) were cultured in a high glucose concentration, with or without DHEA. After 4 days of incubation the number of BRP was significantly reduced by the high glucose concentration. The addition of DHEA to the medium reversed the adverse effect of high glucose: BRP proliferation partially recovered in the presence of 10 nmol/l DHEA, and completely recovered in the presence of DHEA at concentrations equal to or greater than 100 nmol/l. At physiological glucose concentrations, DHEA had no effect on BRP growth. Data show that DHEA, at concentrations similar to those found in human plasma, protects BRP against glucose toxicity. This effect seems specific for DHEA, since its metabolites, 5-en-androstene-3 beta, 17 beta-diol, dihydrotestosterone and estradiol did not alter BRP growth in normal or high glucose media. Various pieces of evidence link the antioxidant properties of DHEA to its protective effect on glucose-induced toxicity in BRP.

Analysis of Variance↗

PubMed1997

Protective effect of dehydroepiandrosterone against copper-induced lipid peroxidation in the rat.

This study investigates the effectiveness and multitargeted activity of dehydroepiandrosterone (DHEA) as antioxidant in vivo. A single dose of DHEA was given IP to male rats. Liver and brain microsomes, and plasma low density lipoprotein (LDL), were isolated from rats sacrificed 17 h later. Liver and brain microsomes were challenged with CuSO(4) and, as index of lipid peroxidation, the production of thiobarbituric acid reactive substances (TBARS) was measaured. Also, plasma low-density lipoprotein (LDL) were challenged with copper and the time course of lipid peroxidation was evaluated following the formation of conjugated dienes. The onset of TBARS generation induced by copper was marked delayed in both liver and brain microsomes from DHEA-treated animals. Also, the resistance of LDL to oxidation, expressed by the duration of the lag-phase of the kinetic curve, was significantly enhanced in DHEA-treated rats. Results indicate that in vivo DHEA supplementation makes subcellular fractions isolated from different tissues and plasma constituents (LDL) more resistant to lipid peroxidation triggered by copper. The antioxidant effect on plasma LDL might be of special relevance to the proposed antiatherogenic activity of DHEA. Moreover, multitargeted antioxidant activity of DHEA might protect tissues from oxygen radicals damage.

Animals↗

PubMed1997

Fludarabine ability to down-regulate Bcl-2 gene product in CD5+ leukaemic B cells: in vitro/in vivo correlations.

CD5+ B-chronic lymphocytic leukaemia (B-CLL) and mantle cell lymphoma (MCL) in leukaemic phase are characterized by defects in cell death induction that primarily involves the Bcl-2 family of genes. Fludarabine (9-beta-D-arabinofuranosyl-2-fluoradenine, F-ara-A) is a potent inducer of apoptosis in CLL cells. This study aimed to determine whether F-ara-A-induced apoptosis might be related to Bcl-2 modifications and to evaluate in vitro/in vivo correlations. Peripheral blood lymphocytes from eight B-CLL and four leukaemic MCL were cultured in the presence of different concentrations of F-ara-A +/- methylprednisolone (MP). F-ara-A down-regulated the expression of Bcl-2 in 5/12 cases. mRNA down-regulation was maximal at 48 h; protein down-regulation was prominent after 48 h. Both events were dose-dependent. The amount of apoptosis was significantly higher in the samples treated with F-ara-A than in those exposed to MP alone. In the seven remaining cases, no Bcl-2 down-regulation was observed after exposure to F-ara-A and the degree of F-ara-A-induced apoptosis overlapped that induced by MP. The in vivo outcome after treatment with three to six courses of F-ara-A was evaluable in 10 patients: 4/5 cases, whose cells had shown in vitro Bcl-2 down-regulation and prominent apoptosis after exposure to F-ara-A, had a complete response (CR) and a partial response (PR) was observed in the remaining patient. Of the five patients whose cells had shown no in vitro Bcl-2 modulation after exposure to F-ara-A, two had a PR, but the other three did not show any in vivo clinical response.

Aged↗

PubMed1997

Rapid identification of heterotrophic, thermophilic, spore-forming bacteria isolated from hot composts.

The restriction enzyme profiles of 16S ribosomal DNAs (rDNAs) amplified by PCR from thermophilic heterotrophic bacterial strains isolated from composts were compared with those of reference strains. This allowed us to assign all but 1 of 16 strains to four different Bacillus species (namely, Bacillus stearothermophilus, Bacillus pallidus, Bacillus thermoglucosidasius, and "Bacillus thermodenitrificans"). This study showed that PCR restriction analysis of 16S rDNA contributes to rapid and reliable identification of newly isolated strains belonging to recognized species.

Bacillus↗

PubMed1997

Dehydroepiandrosterone administration prevents the oxidative damage induced by acute hyperglycemia in rats.

Free radical overproduction contributes to tissue damage induced by acute hyperglycemia. Dehydroepiandrosterone, which has recently been found to have antioxidant properties, was administered i.p. to rats at different doses (10, 50 or 100 mg/kg body weight) 3 h before treatment with dextrose (5 g/kg). Lipid peroxidation was evaluated on liver, brain and kidney homogenates, measuring both steady-state concentrations of thiobarbituric acid reactive substances, and fluorescent chromolipids, evaluated as hydroxynonenal adducts. Formation of thiobarbituric acid reactive substances was significantly higher in hyperglycemic than in normoglycemic animals. Three hours (but not 1 h) dehydroepiandrosterone-pretreatment protected tissues against lipid peroxidation induced by dextrose; both thiobarbituric acid reactive substances and hydroxynonenal adducts in liver, kidney and brain homogenates were significantly lower in dehydroepiandrosterone-pretreated animals. Dehydroepiandrosterone did not modify the cytosolic level of antioxidants, such as alpha-tocopherol or glutathione, nor the activities of glutathione peroxidase, reductase or transferase. The results of this study indicate that the 'in vivo' administration of dehydroepiandrosterone increases tissue resistance to lipid peroxidation triggered by acute hyperglycemia.

Analysis of Variance↗

PubMed1996

In vivo potentiation of 1,2-dibromoethane hepatotoxicity by ethanol through inactivation of glutathione-s-transferase.

In the rat, a single ethanol (EtOH) pretreatment (2.5 g/kg b.w., per os) was able to strongly enhance the cytotoxicity of 1,2-dibromoethane (DBE)(87 mg/kg b.w., per os). The principal metabolic routes of DBE involve both oxidative and conjugative transformations. Microsomal cytochrome P450 content and dimethyl nitrosamine demethylase activity were not changed, while a significant loss of cytosolic total GSH-transferase was observed in rats killed 6 h after EtOH pretreatment. Pretreatment with methylpyrazole, an inhibitor of alcohol-dehydrogenase prevented the effects provoked by ethanol. The major EtOH metabolite, acetaldehyde. seemed thus to play a fundamental role in the mechanism responsible for the potentiation of DBE toxicity mediated by EtOH. To further support this hypothesis, disulfiram (75 mg/kg b.w.), an inhibitor of aldehyde dehydrogenase, was given i.p. to rats. When DBE was administered to disulfiram- and EtOH-pretreated rats, a marked increase of liver cytolysis was shown and cytosolic GSH-transferase activity was further inhibited if compared to that induced by EtOH treatment alone. The results are consistent with the hypothesis that EtOH given to rats increases DBE liver toxicity because its major metabolite, acetaldehyde, reduces the DBE conjugates to GSH transferase, with consequent shift of DBE metabolism to the oxidative route and accumulation of reactive oxidative intermediates no longer effectively conjugated with GSH.

Alcohol Dehydrogenase↗

PubMed1996

In leukaemic CD5+ B cells the expression of BCL-2 gene family is shifted toward protection from apoptosis.

This study further investigated the mechanisms that control apoptosis in leukaemic CD5+ B cells, and focused on the Bcl-2 gene family. The pattern of expression of Bcl-2, Bcl-xL, Bcl-xS and Bax genes, selected because of their interrelated role in the control of apoptosis, was analysed in a series of CD5+ B-cell chronic lymphoid leukaemias. Cells from 34 patients with chronic lymphoid leukaemia of B-cell type (23 B-chronic lymphocytic leukaemia (B-CLL) and 11 mantle cell lymphoma (MCL) in leukaemic phase) were investigated. High levels of Bcl-2 mRNA were observed by Northern blot and high levels of Bcl-2 protein were detected by cytofluorograph analysis with a specific monoclonal antibody (MAb) in all cases. Strong Bax expression was detected by RT-PCR in 20/23 B-CLL cases; Bax was also observed in 8/11 MCL in leukaemic phase with variable degree of intensity. In both B-CLL and MCL samples the presence of Bax protein was confirmed by cytofluorograph analysis. RT-PCR detected high levels of Bcl-xL in 16/23 B-CLL and in 8/11 MCL in leukaemic phase, whereas Bcl-xS was detectable in low to trace amounts respectively in 13/23 B-CLL and in 6/11 MCL in leukaemic phase. According to the functional role of Bcl-2, Bcl-xL, Bcl-xS and Bax, these data indicate that the pattern of Bcl-2 family genes expression in leukaemic CD5+ B cells is skewed toward prevention of apoptosis and may thus favour the relentless accumulation of CD5+ leukaemic B cells.

Apoptosis↗

PubMed1996

Isolation of Thermus strains from hot composts (60 to 80 degrees C).

High numbers (10(7) to 10(10) cells per g [dry weight]) of heterotrophic, gram-negative, rod-shaped, non-sporeforming, aerobic, thermophilic bacteria related to the genus Thermus were isolated from thermogenic composts at temperatures between 65 and 82 degrees C. These bacteria were present in different types of wastes (garden and kitchen wastes and sewage sludge) and in all the industrial composting systems studied (open-air windows, boxes with automated turning and aeration, and closed bioreactors with aeration). Isolates grew fast on a rich complex medium at temperatures between 40 and 80 degrees C, with optimum growth between 65 and 75 degrees C. Nutritional characteristics, total protein profiles, DNA-DNA hybridization (except strain JT4), and restriction fragment length polymorphism profiles of the DNAs coding for the 16S rRNAs (16S rDNAs) showed that Thermus strains isolated from hot composts were closely related to Thermus thermophilus HB8. These newly isolated T. thermophilus strains have probably adapted to the conditions in the hot-compost ecosystem. Heterotrophic, ovalspore-forming, thermophilic bacilli were also isolated from hot composts, but none of the isolates was able to grow at temperatures above 70 degrees C. This is the first report of hot composts as habitats for a high number of thermophilic bacteria related to the genus Thermus. Our study suggests that Thermus strains play an important role in organic-matter degradation during the thermogenic phase (65 to 80 degrees C) of the composting process.

Environmental Microbiology↗

PubMed1995

The relationship between kinetics of substrate-limited transitions and steady-state growth in continuous cultures of Aquaspirillum autotrophicum limited by pyruvate.

Heterotrophic growth at steady state and during transient states caused by the sudden change of the concentration of the limiting factor in the feed medium was investigated experimentally for continuous cultures of Aquaspirillum autotrophicum limited by pyruvate. A model for describing the growth at steady state was selected from three unstructured models after statistical tests of the data. This model postulates that the growth yield increases linearly with the growth rate. Growth during transitions where the substrate remained limiting at all times was fitted with first-order kinetics. Theoretical predictions of these kinetics were derived from the unstructured models used to describe steady state. The predicted rate coefficients of the transients were compared to the experimental coefficients. It appeared that the model which best described steady-state growth also provided the best predictions for growth during the transient state. It is a widespread opinion that unstructured models are adequate to describe growth under steady-state conditions but not to predict transitions in continuous culture. However, for the particular case studied here, no higher degree of complexity was required to describe transitions, provided the growth of the culture was always limited by the substrate.

Bacteriological Techniques↗

PubMed1995

Growth inhibition of DMBA-induced rat mammary carcinomas by the antiandrogen flutamide.

Antiandrogens have sporadically been reported to exert antitumor activities in both pre- and post-menopausal breast cancer. To explore the possibility of using the pure antiandrogen flutamide (FLU) in breast cancer therapy, rats bearing DMBA-induced mammary tumors were treated with FLU, dihydrotestosterone (DHT), or FLU plus DHT. FLU was administered orally, at doses comparable to those used in the treatment of prostate cancer patients. FLU-treated animals had a significantly smaller average tumor area than controls from day 11 up to the end of the experiment (day 20). A similar reduction of tumor growth was observed in rats given DHT and in those treated with DHT plus FLU. Plasma levels of LH, FSH, P, 17-OH P, E2 and DHEA measured at the end of experiment did not differ between treated animals and controls. Results demonstrate that the antiandrogen FLU and the full androgen DHT exert similar inhibitory effects on the growth of dimethylbenz(a)anthracene (DMBA)-induced rat mammary tumors. Moreover, data show that plasma steroids levels are unaffected by FLU treatment. This finding rules out any antitumor effect dependent on the reduction of adrenal and gonadal steroidosynthesis, and makes it appear more likely that androgen receptors are involved in the antiproliferative effect of FLU.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1995

Osteoclast precursors circulate in the peripheral blood of patients with aggressive multiple myeloma.

Osteolysis resulting in extensive bone damage is a major clinical manifestation of patients with multiple myeloma (MM). The mechanisms of bone resorption in MM are incompletely understood. The final pathway is the generation of activated osteoclasts within bone marrow (BM) microenvironment. To investigate the mechanisms of bone resorption in MM we established an experimental system that, including bone marrow (BM) stromal cells and bone slices, closely mimicks in vitro the in vivo BM microenvironment. Peripheral blood mononuclear cells (PBMC) from nine patients with MM, three monoclonal gammopathy of undetermined significance (MGUS), and nine normal controls were cultured in this system. PBMC from patients with aggressive and bone devastating MM gave rise to multi-nucleated cells with the morphology and phenotype of osteoclasts. These cells induced bone resorption in vitro which was inhibited by the addition of calcitonin. No bone resorption was observed in cultures of PBMC from patients with MM and limited bone damage, with MGUS and from normal subjects. These findings indicate that patients with aggressive MM have a population of circulating precursors that develop into functionally active osteoclast-like cells once they come in contact with the BM microenvironment. These cells may contribute to the wide-spread and generalized bone erosion observed in the patients.

Aged↗

PubMed1995

Ethanol-induced potentiation of rat hepatocyte damage due to 1,2-dibromoethane.

Low amounts of 1,2-dibromoethane (DBE), not able per se to exert pro-oxidant and cytotoxic activity on rat hepatocyte suspensions, become effective when administered with carbon tetrachloride (CCl4), due to impairment of the glutathione transferase detoxication pathway by CCl4. Treatment of rats with a single dose of ethanol (2.5 g/kg body wt) 2 h before liver cell isolation potentiates the effect of DBE alone on both malonaldehyde formation and lactate dehydrogenase release by the hepatocyte. The potentiation of the DBE effects by ethanol may be through a series of mechanisms, such as a strong inactivation of hepatocyte glutathione transferase similar to that caused by CCl4, an increased basal level of lipid peroxidation and a significant loss of total glutathione.

Animals↗

PubMed1995

Acetaldehyde involvement in ethanol-induced potentiation of rat hepatocyte damage due to the carcinogen 1,2-dibromoethane.

Previous experiments with hepatocytes isolated from ethanol-treated rats showed that alcohol potentiates the toxic action of 1,2-dibromoethane (DBE) by inhibiting its metabolism via glutathione-S-transferase. The aim of this study was to investigate whether acetaldehyde, the main product of ethanol metabolism, may be responsible for such inactivation. By pretreatment with 4-methylpyrazole, an inhibitor of acetaldehyde formation, the ethanol inactivation of glutathione transferase was actually prevented. As a consequence of this protective action, 4-methylpyrazole also prevented the high basal lipid peroxidation and the potentiated DBE toxicity observed in hepatocytes from ethanol-dosed animals. Finally, the inactivation of glutathione-S-transferase by concentrations of acetaldehyde likely to occur in the ethanol-intoxicated animal was confirmed in an in vitro model by direct aldehyde addition to hepatocyte suspensions.

Acetaldehyde↗

PubMed1994

Phylogenetic position of the genus Hydrogenobacter.

The genus Hydrogenobacter consists of extremely thermophilic, obligately chemolithotrophic organisms that exhibit anaerobic anabolism but aerobic catabolism. Preliminary studies of the phylogenetic position of these organisms based on limited 16S ribosomal DNA sequence data suggested that they belong to one of the earliest branching orders of the Bacteria. In this study, the complete 16S ribosomal DNA sequences of two type strains, Hydrogenobacter thermophilus TK-6 and Calderobacterium hydrogenophilum Z-829, and another isolate, Hydrogenobacter sp. strain T3, were determined, and the phylogenetic positions of these organisms were examined. Our results revealed that the two type strains are members of a single genus, the genus Hydrogenobacter. Our results also verified the previous conclusion that the Aquifex-Hydrogenobacter complex belongs to a very early branching order, the "Aquificales." Within this order, the relationships among the various organisms are such that only a single family, the "Aquificaceae," can be recognized at this time. Given the early branching point of the "Aquificales," the characteristics of these organisms support the view that the last common ancestor of existing life was thermophilic and suggest that this ancestor may have fixed carbon chemoautotrophically.

Bacteria↗

PubMed1993

Dehydroepiandrosterone pretreatment protects rats against the pro-oxidant and necrogenic effects of carbon tetrachloride.

A single intraperitoneal injection of dehydroepiandrosterone (3 beta-hydroxy-5-androsten-17-one, DHEA) 17 hr before carbon tetrachloride (CCl4) poisoning protects rats against liver injury induced by the haloalkane. In liver homogenates, both the increase in malondialdehyde production and the formation of fluorescent lipid peroxidation products are significantly reduced. Also, liver microsomes obtained from DHEA-pretreated rats incubated in vitro with CCl4 are less susceptible to lipid peroxidation than microsomes from normal animals. The release of liver enzymes into the blood is much reduced in DHEA-pretreated rats, confirming a cause-effect relationship between lipid peroxidation and hepatocyte death. Treatment with DHEA inhibits neither glucose-6-phosphate dehydrogenase activity in the cytosol, nor the microsomal mixed function oxidase system (cytochrome P450 content, aminopyrine demethylase and ethoxycoumarin de-ethylase activities). In animals treated with DHEA, the liver content of total glutathione and vitamin E is not modified. These results support the hypothesis that DHEA protects against CCl4-induced liver injury through its own antioxidant activity, rather than by interfering with the metabolism of the toxin or with the tissue level of primary antioxidants.

Animals↗

PubMed1993

Change of liver metabolism of 1,2-dibromoethane during simultaneous treatment with carbon tetrachloride.

The combination of carbon tetrachloride (CCl4) and 1,2-dibromoethane (DBE) in isolated rat hepatocytes led to a significant potentiation of both lipid peroxidation and of plasma membrane damage observed after a single treatment with CCl4. Such a synergistic effect appeared to be related to the CCl4-induced shift of DBE metabolism from the cytosolic conjugation with glutathione towards the microsomal transformation into toxic intermediates. In fact, CCl4 significantly inactivated hepatocyte total GSH-transferase, i.e. the DBE detoxification pathway. Furthermore, while the microsomal metabolism of CCl4 was not affected by the simultaneous presence of DBE, the amount of DBE reactive metabolites covalently bound to hepatocyte protein was significantly enhanced in the presence of CCl4.

Animals↗

PubMed1992

Linear growth and poly(beta-hydroxybutyrate) synthesis in response to pulse-wise addition of the growth-limiting substrate to steady-state heterotrophic continuous cultures of Aquaspirillum autotrophicum.

Heterotrophic pyruvate-limited steady-state continuous cultures of the bacterium Aquaspirillum autotrophicum were perturbed with a pulse injection of a small volume of concentrated pyruvate solution. These cultures exhibited an instantaneous change in the growth dynamics, turning from steady state to apparently linear growth. These transient growth-responses had no lag phase and were clearly distinct from unlimited exponential growth according to the initial rates of increase of biomass and substrate disappearance kinetics. A linear accumulation with time of poly(beta-hydroxybutyrate) was observed within the cells. Slopes of these linear responses were negatively correlated with the dilution rate. Physiological bases of linear growth are discussed in the light of the models of H. E. Kubitschek. Poly(beta-hydroxybutyrate) synthesis in the absence of exogenous limitation may serve to protect the cells against a transient metabolic overflow.

Bacteriological Techniques↗

PubMed1992

In vivo studies on halogen compound interactions. III. Effect of carbon tetrachloride plus 1,2-dichloroethane on liver necrosis and fatty accumulation.

The effect of a single dose of carbon tetrachloride (CT), 1,2-dichloroethane (DCE) and the mixture on liver toxicity was investigated. The co-presence of both toxins exerts a more than additive effect on liver necrosis and on TBA-reactive substances produced by liver homogenates incubated at 37 degrees C. Both these effects are prevented in animals treated with vitamin E. The liver GSH is not involved in the synergistic action. The liver triglyceride levels of rats treated with the mixture are lower than in those treated with CT alone. This finding cannot be explained either by an improvement in the lipoprotein secretion or by the fact that the liver receives less NEFA. It is thus likely that the apparent protection against liver steatosis is the sign of more severe damage to the liver cell that partially blocks triglyceride synthesis. The mixture composed of CT+DCE exerts a potentiating action on liver toxicity with CT+DCE having the same characteristics as those, as previously reported, exerted by the co-presence of CT+DBE.

Alanine Transaminase↗