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Biomedical subjects

A Sessa

Publications and source records attributed to A Sessa.

At least 37 records · Page 2Linked to original sources
PubMed1998

Transforming growth factor beta blocks cystogenesis by MDCK epithelium in vitro by enhancing the paracellular flux: implication of collagen V.

Transforming growth factor beta (TGFbeta) determines a nearly complete inhibition of cystogenesis by MDCK cells grown in collagen I-enriched matrices in vitro. In order to elucidate the mechanism implicated in this phenomenon, we performed a series of experiments aimed at discovering a relevant role of extracellular matrix. TGFbeta (2 ng/ml) played a marked stimulatory effect on the expression of extracellular matrix by MDCK with a selective effect on collagen V (three to fourfold increase of protein and mRNA) and in parallel inhibited cystogenesis by 95%. Cotreatment with TGFbeta and anti-collagen V antibodies restored a normal cystogenesis. In analogy, when MDCK cells were grown in three-dimensional matrices containing collagen I and minor (10%) amounts of collagen V, cystogenesis was once again inhibited by 95%. To characterize the molecular mechanism activated by TGFbeta and collagen V, we looked at the electrophysiological characteristics of MDCK monolayers and found a drastic fall of transepithelial electrical resistance (TER) in both conditions. In parallel with the decrease in TER, TGFbeta and collagen V also induced the leakage of two high molecular weight tracers, i.e., [3H]-inulin and 150 kD FITC-Dextran, suggesting a perturbation of the paracellular permeability. Finally, TGFbeta at the relevant concentration did not stimulate apoptosis in our cellular model, as judged by propidium iodide staining and by in situ end labeling of DNA fragments. These observations suggest that TGFbeta inhibits cystogenesis by MDCK cells in vitro by altering the collagenic composition of the three-dimensional milieu where MDCK cells grow and form cysts. The molecular mechanism responsible for inhibition of cystogenesis is the increase of paracellular flux which overcomes the active transport of solutes and water inside cysts.

Animals↗
PubMed1998

Electron microscopy study of genesis and dynamics of immunodeposition in IgMk-IgG cryoglobulin-induced glomerulonephritis in mice.

Cryoglobulinemic glomerulonephritis is particularly frequent in type II mixed IgMk-IgG cryoglobulinemia. The typical form is a membranoproliferative glomerulonephritis with a particular monocyte infiltration. In the most severe cases, there is occlusion of the capillary lumina by the same immunoglobulin constituents of the cryoprecipitate. While it is generally accepted that the "hyaline thrombi" are endoluminal aggregates of IgG-IgM immune complexes, probably favored by high endocapillary concentration of cryoglobulins, the modality of generation has not been studied. To study the dynamic formation of such "thrombi," we reproduced an experimental model of cryoglobulinemic glomerulonephritis in mice by injecting them twice a day for 3 days with 4 mg human IgMk-IgG cryoglobulins previously solubilized at 37 degrees C. The dynamic formation of immunodeposits was studied by immunofluorescence and electron microscopy. After 1 day, only mesangial deposits were found; after 3 days, in addition to mesangial deposition, all the capillary lumina were occluded by huge electron-dense bodies. To look for and quantify the contacts between such "thrombi" and mesangial or subendothelial deposits, we obtained serial, ultrathin, 0.5-microm sections that allowed us to reconstruct the whole glomerular tuft. Within each serial section, there was continuity between hyaline thrombi and mesangial or subendothelial deposits ranging from 80% to 85% of the capillary loops. The percentage was 100% for two adjacent serial sections. In conclusion, our data demonstrate directly for the first time that hyaline thrombi follow mesangial deposits. The high percentage of contacts between thrombi and mesangial or subendothelial deposits suggests that they result from in situ build-up of true huge endoluminal immunodeposits after saturation of the clearance capacity of the mesangium.

Aged↗
PubMed1998

Changes in hepatic polyamine catabolism in elderly rats.

AIMS/BACKGROUND: Given the important role of polyamines (putrescine, spermidine, spermine) in the modulation of macromolecular syntheses, gene expression and proteolysis, alterations in their metabolic pathways could be relevant during senescence. Since the few existing data address mainly polyamine biosynthesis, we studied the oxidative catabolism of polyamines in the liver of rats 3-36 months of age. METHODS: Polyamine oxidase activity was fluorimetrically measured using N1-acetylspermine as substrate. Spermidine/spermine N1-acetyltransferase and diamine oxidase were measured by radiochemical methods using labeled acetyl-coenzyme A and putrescine, respectively, as substrate. Polyamines were separated by HPLC and fluorimetrically quantified after post-column derivatization with o-phthaldialdehyde. RESULTS: Spermidine/spermine N1-acetyltransferase activity increased in 36-month-old rats and polyamine oxidase activity in 24- and 36-month-old rats. A decline in spermine and increases in spermidine and putrescine in elderly rats suggested an activation of the interconversion pathway of higher into lower polyamines. The activity of diamine oxidase, which degrades putrescine, was enhanced starting from 12 months of age. CONCLUSION: In the liver of aged rats, an increase in the catabolic enzymes leads to a reconversion of the higher polyamines to putrescine. This increased catabolism may represent an important age-related change and may contribute to impairment of the expression of growth-related genes in senescence.

Acetyltransferases↗
PubMed1997

Ethanol and polyamine metabolism: physiologic and pathologic implications: a review.

This review summarizes the effects of ethanol on the metabolism of polyamines (putrescine, spermidine, and spermine), which are endogenous polycations required for cell physiology, growth, and differentiation. Polyamines regulate DNA, RNA, and protein syntheses; stabilize ribosomes, membranes, and nucleic acids; and protect the cell against lipid peroxidation. Polyamine biosynthesis and catabolism may change after acute and chronic ethanol treatment, thereby playing a negative or positive role in the ethanol-induced injury on liver, extrahepatic tissues, embryo, and fetus.

Alcoholic Intoxication↗
PubMed1997

Transglutaminase activity in rat brain after ethanol exposure.

The effect of acute and chronic ethanol treatment on the activity of tissue transglutaminase (a calcium-dependent enzyme that catalyzes the covalent association between proteins, as well as proteins and polyamines) was studied in homogenate and in the cytosolic fraction of rat brain (telencephalon and diencephalon). A single dose of ethanol (5 g/kg of body weight, by gastric intubation) caused a 2-fold increase in enzyme activity at 6 hr after the ethanol dose, with a return toward the basal values at 24 hr. In vitro experiments with ethanol or acetaldehyde showed that the increase in transglutaminase activity was due to ethanol per se and not to its metabolism. The enzyme stimulation was correlated with a decrease in the levels of the polyamine spermine, a physiological substrate for the enzyme. Similar results were also found in the brain from rats fed on an ethanol diet for 4 months. The enhancement in tissue transglutaminase activity may thus lead to a decline in spermine, a polyamine known to have important protective functions in the cell.

Acetaldehyde↗
PubMed1996

Response of intestinal transglutaminase activity to dietary phytohaemagglutinin.

The behaviour of the activity of tissue transglutaminase, a calcium-dependent enzyme, and the levels of polyamines which are physiological substrates for the enzyme, were studied in rat small intestine induced to grow by lectin phytohaemagglutinin. Transglutaminase activity greatly increased in the homogenates and the cytosolic fractions of the intestinal mucosa of lectin-treated rats compared to that of untreated animals. The measurement of enzyme activity in the presence of monodansylcadaverine, a competitive inhibitor of transglutaminase, testified that the assayed enzyme activity was authentic transglutaminase. As regards polyamines, the level of spermine did not change, whereas putrescine and spermidine contents were enhanced. The activation of transglutaminase, which was probably due to Ca2+ accumulation in enterocytes, could have a role in maintaining enterocyte adhesion and intestinal cell homeostasis, and/or repairing lectin-induced damages of microvilli of the gut epithelium.

Animals↗
PubMed1996

Aging and polyamine acetylation in rat kidney.

The acetylation of polyamines was investigated in rat kidney as a function of age. The activity of cytosolic spermidine/spermine N1-acetyltransferase, the rate-limiting enzyme in polyamine interconversion, increased from 3 to 36 months of age. The activity of cytosolic spermidine N8-acetyltransferase, an enzyme probably related to polyamine excretion, also increased. The activity of polyamine oxidase, which catalyzes the oxidative cleavage of polyamine N1-acetyl derivatives into putrescine, decreased until 24 months, when an accumulation of N1-acetylspermidine occurred. Subsequently, at 36 months, polyamine oxidase activity returned toward high values, in concomitance with the disappearance of N1-acetylspermidine, an increase in spermidine and putrescine, and a decline in spermine was observed. Our results show that in rat kidney during aging there is an activation of the acetylation and interconversion of higher polyamines into putrescine, which is considered an alternative pathway of spermidine and putrescine formation.

Acetylation↗
PubMed1996

X-linked Alport syndrome: an SSCP-based mutation survey over all 51 exons of the COL4A5 gene.

The COL4A5 gene encodes the alpha5 (type IV) collagen chain and is defective in X-linked Alport syndrome (AS). Here, we report the first systematic analysis of all 51 exons of COL4A5 gene in a series of 201 Italian AS patients. We have previously reported nine major rearrangements, as well as 18 small mutations identified in the same patient series by SSCP analysis of several exons. After systematic analysis of all 51 exons of COL4A5, we have now identified 30 different mutations: 10 glycine substitutions in the triple helical domain of the protein, 9 frameshift mutations, 4 in-frame deletions, 1 start codon, 1 nonsense, and 5 splice-site mutations. These mutations were either unique or found in two unrelated families, thus excluding the presence of a common mutation in the coding part of the gene. Overall, mutations were detected in only 45% of individuals with a certain or likely diagnosis of X-linked AS. This finding suggests that mutations in noncoding segments of COL4A5 account for a high number of X-linked AS cases. An alternative hypothesis is the presence of locus heterogeneity, even within the X-linked form of the disease. A genotype/phenotype comparison enabled us to better substantiate a significant correlation between the degree of predicted disruption of the alpha5 chain and the severity of phenotype in affected male individuals. Our study has significant implications in the diagnosis and follow-up of AS patients.

Adult↗
PubMed1996

Nosocomial outbreak of Aspergillus fumigatus infection among patients in a renal unit?

Aspergillus fumigatus is present in the environment worldwide and it is only able to infect debilitated or immunodepressed subjects. Nosocomial outbreaks of A. fumigatus infection have been associated with hospital reconstruction. Spores are released into the environment and are inhaled by immunodepressed patients housed in nearby Medical Units. Specific clinical syndromes are allergic bronchopulmonary aspergillosis and invasive pulmonary aspergillosis with characteristic radiological features. Invasive A. fumigatus infection is commonly fatal, even if promptly diagnosed and treated. Three consecutive cases of A. fumigatus infection occurred in debilitated patients housed in our Renal Unit while building renovation near the Unit was being performed. Two of these patients died and pulmonary and diffuse aspergillosis was found on postmortem examination. The third patient, highly suspected to be infected with Aspergillus, was aggressively and successfully treated with liposomal amphotericin B. Our experience suggests that fungal infections have gained increasing prominence in clinical medicine and they must be considered in chronic debilitated patients including dialysis patients, and that liposomal amphotericin B represents an important advance in the treatment of aspergillosis.

Aged↗
PubMed1995

Transglutaminase activity in rat liver after acute ethanol administration.

The acute effect of ethanol on hepatic transglutaminase (EC 2.3.2.13) activity and polyamine levels were investigated in the rat. A high dose of ethanol (5 g/kg body weight, given by gastric intubation) caused in homogenate and cytosolic fraction an inhibition of 50-70% from 3 to 24 h which thereafter was reversible. Such a decrease may be in part responsible for the observed enhancement in putrescine and spermidine contents observed at the same times. Pyrazole, an inhibitor of alcohol dehydrogenase, prevented the ethanol-induced reduction in transglutaminase activity. Disulfiram, an inhibitor of aldehyde dehydrogenase, allowed detection of an inhibitory effect on enzyme activity even at a low dose of ethanol (2 g/kg), which per se did not modify transglutaminase activity. The hepatic cytosolic fraction, incubated in the presence of various concentrations of acetaldehyde, showed a dose-dependent inhibition of transglutaminase activity. All of these results suggest that acetaldehyde, the first and toxic metabolite of ethanol, inhibits hepatic transglutaminase activity, probably by its binding to the active thiol site of the enzyme. The reduction in transglutaminase may lead to an alteration of cytoskeleton, since the enzyme is known to be involved in tubuline polymerization and microfilament assembly.

Animals↗