Biomedical subjects

F Bertini

Publications and source records attributed to F Bertini.

At least 19 recordsLinked to original sources

PubMed2006

5 '-Amino-4-imidazolecarboxamide riboside induces apoptosis in human neuroblastoma cells via the mitochondrial pathway.

5'-Amino-4-imidazolecarboxamide (AICA) riboside induces apoptosis in neuronal cell models. In order to exert its effect, AICA riboside must enter the cell and be phosphorylated to the ribotide. In the present work, we have further studied the mechanism of apoptosis induced by AICA riboside. The results demonstrate that AICA riboside activates AMP-dependent protein kinase (AMPK), induces release of cytochrome c from mitochondria and activation of caspase 9. The role of AMPK in determining cell fate is controversial. In fact, AICA riboside has been reported to be neuroprotective or to induce apoptosis depending on its concentration, cell type or apoptotic stimuli used. In order to clarify whether the activation of AMPK is related to apoptosis in our model, we have used another AMPK stimulator, metformin, and we have analysed its effects on cell viability, nuclear morphology and AMPK activity. Five mM metformin increased AMPK activity, inhibited viability, and increased the number of apoptotic nuclei. AICA riboside, which can be generated from the ribotide (an intermediate of the purine de novo synthesis) by the action of the ubiquitous cytosolic 5'-nucleotidase (cN-II), may accumulate in those individuals in which an inborn error of purine metabolism causes both a building up of intermediates and/or an increase of the rate of de novo synthesis, and/or an overexpression of cN-II. Therefore, our results suggest that the toxic effect of AICA riboside on some types of neurons may participate in the neurological manifestations of syndromes related to purine dismetabolisms.

Aminoimidazole Carboxamide↗

PubMed2005

The extension of resin tags in etched dentin: a misinterpretation?

AIM: The morphological characteristics of the filament structure, universally recognized as resin tags, in samples prepared using a new SEM methodology, are analyzed . METHODS: Ten non-carious, human third molars were cut transversally to obtain 10 dentinal surfaces. They were filled using an adhesive restorative technique. Subsequently, the samples were cut lengthwise to be SEM observed, and then randomly divided into 6 main groups according to the preparation modality of the section surface: Group A: EDTA; Group B: H(3)PO(4); Group C1: H(3)PO(4)+NaOCl; Group C2 H(3)PO(4)+NaOCl+H(2)O(2); Group D1: HCl+NaOCl; Group D2: HCl+NaOCl+H(2)O(2). RESULTS: The resin tags which originate from resin penetration and polymerization within the dentinal tubules are small conic-trunk shaped plugs that are a few microns long. The thinner extension of the resin tags is probably due to the persistence of the lamina limitans. CONCLUSIONS: A new method of specimen preparation for SEM visualization is proposed in order to effectively evaluate the penetration capacity of the adhesive in the dentinal substratum. In addition to the use of strong acids and bases, an agent capable of degrading the glycosaminoglycans was employed to completely remove the dentinal organic component.

Acid Etching, Dental↗

PubMed2003

[Use of light-curing composite and adhesive systems for the cementation of tranlucent fiber posts. SEM analysis and pull-out test].

AIM: The purpose of this study was to compare 2 different techniques for the cementation of translucent fiber posts. The comparison was carried out by means of tensile bond strength testing and SEM evaluation of the interfaces morphology post/cement and cement/dentin. METHODS: Twenty upper central extracted incisors were first endodontically treated and then randomly divided into 2 groups of 10 samples each. Twenty translucent Endo Light-posts (RTD) were cemented following 2 different METHODS: In Group 1 Excite (Ivoclar Vivadent) and Tetric Flow (Ivoclar Vivadent) were applied and light-cured. In Group 2: All Bond 2 (Bisco) and RelyX ARC (3M) were applied, light-cured and then self-cured. A tensile bond strength test was carried out on 14 roots, 7 from each group. Subsequently, 2 roots were cut lengthwise and observed using a SEM. The remaining 6 roots (3 from each group) were cut into 5 transversal sections and observed using a SEM. The tensile force required to dislodge the cemented posts from the 7 roots of each group was recorded by means of a testing machine. RESULTS: Group 1 revealed a bonding strength which was slightly inferior to the bonding strength registered in Group 2. SEM evaluation showed a good quality of bond. Without taking into account the curing method used, the polymerization carried out by means of light curing seems to result in a better adaptation of cement. CONCLUSIONS: Self curing cement still represents the most reliable alternative, even if photo-curing cement might guarantee a most efficient stress distribution along the walls of the canal.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2000

[Bilateral adrenal hemorrhage with adrenal insufficiency in the framework of primary antiphospholipid antibody syndrome].

We report a case of acute adrenal insufficiency in a context of probable bilateral adrenal haemorrhage, as revealed by CT-scan in a 52-year-old woman with a history of spontaneous abortion and repeated ischaemic stroke without symptoms or signs of collagen vascular disease. The symptoms began after the patient had successfully been treated for pneumonia. She had persistently high titres of IgG anticardiolipin antibodies, antibodies against beta 2-glycoprotein I and a lupus anticoagulant. The diagnosis of primary antiphospholipid syndrome with adrenal insufficiency was postulated.

Adrenal Gland Diseases↗

PubMed2000

Purification of proteins from rat sperm membranes that interact with ligands other than phosphomannosyl residues.

In this study proteins were purified from rat sperm membranes which might be the high affinity sites for ligands of epididymal fluid other than the mannose-6-phosphate receptors. The sperm membrane proteins were solubilized and passed over an affinity column containing epididymal fluid proteins coupled to a matrix. Two bands in the range of 45-55 kDa were eluted from the column with fructose-6-phosphate but not with mannose-6-phosphate. Although the molecular weight of these proteins are similar to those of the cation-dependent phosphomannosyl receptors they are not related. These two proteins may correspond either to two different receptors or to forms of the same receptor that recognize ligands from rat epididymal fluid. Sequencing and identification of these proteins will be the aim of future studies.

Animals↗

PubMed1998

alpha-Mannosidase from rat epididymal fluid is a ligand for phosphomannosyl receptors on the sperm surface.

This study demonstrates that alpha-mannosidase from rat epididymal fluid is a ligand for phosphomannosyl receptors on the sperm surface. This enzyme was bound to intact epididymal spermatozoa with high affinity and in saturable form, and the binding was inhibited by mannose-6-phosphate but not by phosphorylated derivatives of fructose. Treatment of the enzyme with sodium periodate inhibited the binding of alpha-mannosidase, confirming that a carbohydrate residue is involved in the interaction with spermatozoa. Evidence is also presented that the cation-independent phosphomannosyl receptors are responsible for the interaction with alpha-mannosidase. These findings suggest a new role for extracellular transport mediated by the mannose-6-phosphate receptor.

Animals↗

PubMed1997

Is an ATPase involved in uncoating of plasma membrane adaptor complex AP-2?

The coat of clathrin-coated vesicles mostly consists of clathrin and adaptor complexes AP-1 or AP-2. Clathrin is released from the vesicles in an ATP-dependent fashion prior to their fusion with endosomes. In the present study we found that ATP strongly inhibits in vitro binding of cytosolic AP-2 to membranes of stripped vesicles, and promotes the release of endogenous AP-2 from clathrin-deprived coated vesicles. Both effects required hydrolysis of ATP. In contrast, binding of AP-1 to stripped vesicles was not affected by ATP, but was enhanced by GTP-gamma-S. These results point to an ATPase that promotes the release of AP-2 from clathrin-coated vesicles.

Acyl Coenzyme A↗

PubMed1996

Changes in N-acetyl-beta-D-glucosaminidase binding system in rat liver during growth.

In this paper, we characterize the binding of N-acetyl-beta-D-glucosaminidase to membranes of rat liver during development. Cation-independent phosphomannosyl receptors were shown to be involved in the recognition of the enzyme at the following ages: 18 days of fetal life, 10-, 30- and 90-day-old rats. We remark here two important differences in the binding of the fetal enzyme when compared with that in 90-day-old rats; (a) in addition to an optimal binding at pH 7.0, the fetal enzyme showed another peak of binding at acidic pH (5.0), and (b) the binding of the fetal enzyme was also inhibited by galactose-6-phosphate. This inhibition was higher than that of mannose-6-phosphate at the acidic pH. We concluded that the lysosomal enzymes and their receptors undergo important changes around birth.

Acetylglucosaminidase↗

PubMed1996

Trypanosoma cruzi: involvement of intracellular calcium in multiplication and differentiation.

The possible role of intracellular Ca2+ level on Trypanosoma cruzi differentiation was explored. The addition to epimastigotes of a Triatoma infestans intestinal homogenate, which that triggers off the differentiation to the infective metacyclic form, induced a sudden rise in [Ca2+]i from the basal value, 94 +/- 28 to 584 +/- 43 nmole/liter. This increase was not affected by the presence of EGTA in the medium. Trypsin-treated intestinal homogenate did not alter the [Ca2+]i of epimastigotes. Calmodulin inhibitors (Calmidazolium, Trifluoperazine, and Chlorpromazine) blocked differentiation. Although the calcium ionophore ionomycin increased [Ca2+]i to 342 +/- 29 nmole/liter, it was unable to induce differentiation by itself. BAY K8644 and Methoxyverapamil (agonist and antagonist of Ca2+ channels, respectively) were unable to affect [Ca2+]i by themselves, or when added to stimulated parasites, and did not exert a stimulatory or inhibitory effect on morphogenesis. BAPTA/AM, a Ca2+ chelator, partially blocked the rise in [Ca2+]i and morphogenesis; this effect was reversed by ionomycin. The requirement of intracellular Ca2+ on epimastigote multiplication was also evaluated. The addition of EGTA to the culture medium led to a decrease in epimastigote multiplication till it practically ceased in the sixth passage. When such parasites were transferred to LIT they partially recovered the growth rate. Parasites from passages III, IV, and V in the Ca(2+)-depleted medium maintained their basal [Ca2+]i, but when treated with the intestinal homogenate, the rise in [Ca2+]i was abrogated. Accordingly, the differentiation percentages of such parasites dropped significantly compared with controls.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1996

Electrophoretic analysis of protein selectively extracted with chaotropic agents from membranes of rat sperm.

Sperm from rat cauda epididymis was washed, sonicated and centrifuged to obtain fractions sedimenting at 600 x g for 5 min, 27.000 x g for 5 min, and 100.000 x g for 40 min. All fractions were observed with the electron microscopy and assayed for cytochrome c oxidase activity. The 100.000 x g fraction contained only small membranous vesicles and less than 0.5% of the total enzymatic activity. This fraction was considered to represent sperm plasmalemma and it was extracted with Tris-HCl buffer before treating it with one of the following chemicals: acetate buffer, pH: 4.5; 0.6 M KCl; bicarbonate buffer, pH 11.0; Triton X-100, and Sodium Dodecyl Sulfate (SDS). After centrifuging, the residual sediments were solubilized in hot 2% SDS. The extracts and the solubilized sediments (hot SDS) were analyzed in SDS-PAGE. The extracts obtained with the first three chemicals contained 11,9, and 25% of total proteins respectively. The bicarbonate buffer solubilized 45%, and the detergents 55% and 65% respectively. A total of 30 bands were seen in the extracts and sediments. Acid pH extracted a low number of bands of high mobility and low molecular weight. Instead, the KCl and bicarbonate buffer, extracted a great number of bands over a wide range of molecular weights (23, 38.5, 55, 100, and 140 KD). The detergents had similar effects: both solubilized four new bands. In residual sediments there were no new proteins and the bands corresponded to those extracted with the detergents, but they varied in staining intensity. According to the results obtained with the mild chaotropic agents of 0.6 M KCl and bicarbonate buffer, 50% of the mass of membraneous proteins may be peripheric. Proteins partially extracted with the detergents were also found in the residual sediment, and they may constitute the skeleton of sperm membrane.

Animals↗

PubMed1995

Lysosomal enzyme activity in rat adrenal gland related to the postnatal development.

The activity of five acid hydrolases in the adrenal gland at the perinatal stage in adult rats was measured here and changes in alpha-mannosidase and N-acetyl-beta-D- glucosaminidase activity were detected. These enzymes increase after birth reaching a peak between days 4 and 7. Other enzymes such as beta-glucuronidase, arylsulfatase and beta-glucosidase did not significantly change at the ages studied. These data suggest that the enzymatic activity and development of the adrenal gland may be correlated during the first week after birth; this is critical since most of the changes occur in this organ.

Acetylglucosaminidase↗

PubMed1995

Phosphomannosyl receptors on the surface of spermatozoa from the cauda epididymis of the rat.

This study demonstrates that beta-glucuronidase from rat preputial glands binds with high affinity to spermatozoa from the cauda epididymis. The binding was calcium-independent and was inhibited by mannose-6-phosphate, but not by other phosphorylated or non-phosphorylated sugars. Binding was also inhibited by alpha-mannosidase from Dictyostelium discoideum, an enzyme known to have mannose-6-phosphate as the ligand. From solubilized sperm membranes, a protein of > 200 kDa and one of 45 kDa, were absorbed to a column of D. discoideum enzyme and to a phosphomannan column respectively, and eluted with mannose-6-phosphate. According to histochemical observations at the light and the electron microscopic level, gold particles coated with the enzyme became bound to the external surface of the plasmalemma in the acrosomal region of caudal spermatozoa. Similar labelling was observed using gold particles coated with antibodies against the rat 300 kDa phosphomannosyl receptor. The existence of phosphomannosyl receptors on the sperm plasma membrane, and our previous demonstration of the presence of affinity sites for epididymal beta-galactosidase on these gametes which is inhibited by phosphofructosyl derivatives, suggest strongly that maturing spermatozoa could be a target for glycosidases secreted into the lumen of the cauda epididymis, which then become bound to these cells via different ligand-receptor systems.

Animals↗

PubMed1995

Tubulin aggregates induced by Ni2+ present microtubular characteristics.

Rat brain tubulin in a proper buffered solution became insoluble in the presence of 10 mM NiCl2, and sedimented at centrifugal forces as low as 500 x g for 30 min. Both nickel-sedimented and microtubular tubulin conserved 65% of colchicine binding activity after 25 days of storage at -20 degrees C. However in brain cytosol, only 9% of the initial binding activity was conserved. The electrophoretic mobility of tubulin recovered from aggregates also remained unaltered. Therefore the aggregates formed with Ni2+ share important physicochemical properties with microtubules.

Animals↗

PubMed1995

Organ-specific binding system for beta-galactosidase in the male reproductive tract.

This study reports on the binding of beta-galactosidase obtained from different organs of the rat urogenital tract to membranes of these organs. Homologous and cross binding saturation assays indicated that: (1) high-affinity sites that recognize fructose-6-phosphate derivates (FPR) are present in spermatozoa from the rete testis, epididymal membranes and testes, although the latter may reflect binding to testicular spermatozoa; (2) the membranes of the other organs studied do not have FPR; (3) the FPR of the epididymis does not recognize enzymes purified from other organs of the reproductive tract. These results suggest that the FPR-binding system belongs to a peculiar transport route that permits maturing spermatozoa to acquire hydrolytic enzymes secreted by the epididymal epithelium. In the epididymis and seminal vesicles more than 50% of the enzymatic activity of beta-galactosidase was recovered in cytosol, suggesting that the enzyme is located mainly in the secretory fluid of these organs.

Animals↗

PubMed1994

Affinity sites for N-acetyl-beta-D-glucosaminidase on the surface of rat epididymal spermatozoa.

The binding of N-acetyl-beta-D-glucosaminidase from rat epididymal fluid to the surface of spermatozoa from the cauda epididymis was measured in the presence of sugars, its phosphorylated derivatives, or after treatment of the cells or the enzyme with agents that alter the integrity of proteins or carbohydrates. The binding was saturable, with a Kd in the nanomolar range, was inhibited with phosphorylated derivates of fructose, and did not depend on Ca2+, showing that it is different from the mannose 6-P-recognizing system existing in other tissues for this and other acid hydrolases. Treatment of the cells with sodium periodate or trypsin inhibited the binding, showing that a glycoprotein of the plasmalemma is involved in the affinity site. Fructose or phosphorylated derivates were not detected in the proteins of the epididymal fluid with HPLC. However, with the method used, the presence of these compounds cannot be ruled out, if among the proteins of the fluid there are only a small number of acid hydrolases containing this sugar.

Acetylglucosaminidase↗

PubMed1993

Effect of pH and ATP on the equilibrium density of lysosomes.

Lysosomes are membrane bound structures that accumulate and hydrolyze material internalized by the endocytic pathway. A very conspicuous property of this subcellular compartment is its relatively high equilibrium density. The actual mechanism that regulates lysosomal density is poorly understood. In an attempt to gain knowledge on the factors that regulate lysosomal density we have assessed the equilibrium density of lysosomal markers after in vitro incubation of a lysosome-enriched subcellular fraction. Incubation at pH 6 for 10 min at 37 degrees C causes a density shift of several lysosomal markers to light density regions of Percoll gradients. Addition of ATP was able to prevent the acid-induced density shift. Pretreatment of the vesicles with N-ethylmaleimide (NEM) or trypsin inhibited the effect of ATP. Working in intact cells, ATP depletion, a condition that causes cytoplasmic acidification, also decreases lysosomal density. The results indicate that at low pH lysosomal density is preserved by an active process that requires ATP and membrane associated proteins.

Adenosine Triphosphate↗

PubMed1992

Trypanosoma cruzi: inhibition of metacyclogenesis by mannose.

Metacyclogenesis of Trypanosoma cruzi epimastigotes was evaluated in a medium supplemented with Triatoma infestans intestinal homogenate in the presence of sugars and derivates as are mannose, galactose, fucose, N-acetylglucosamine, mannose 6-P, and fructose 1,6-P at a concentration of 25 mM. Only mannose significantly inhibited metacyclogenesis. Sodium metaperiodate and trypsin treatment of the intestinal homogenate also inhibited differentiation. In our opinion there exists a proteinic factor in the intestine of the vector that promotes metacyclogenesis and is incorporated by the parasite. Treatment of the intestinal homogenate with alkaline phosphatase had no effect. Instead, high ionic strength in the medium (0.4 M NaCl) strongly inhibited metacyclogenesis indicating that, in these conditions, the possible binding of the differentiation factor to the parasite surface was inhibited.

Animals↗

PubMed1992

[A scanning electron microscope assessment of the changes induced by wear on subsonic endodontic instruments].

The aim of the present work was to study the wear of a special kind of subsonic instruments with usage. We have examined with scanning electron microscope new and used instruments: the first to estimate the features and degree of final touches; the second to examine how they wear after 1, 3 and 5 minutes. We tested for each period 3 instruments per size. In all we controlled 72 instruments. The results of the study show that after 5 minutes the instruments are very worn.

Materials Testing↗