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Biomedical subjects

F Bertini

Publications and source records attributed to F Bertini.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Preliminary research on the prognosis of late reimplants with prior conditioning with a fluoridated solution].

The principal factors that affect the prognosis of a posttraumatic reimplantation are the length of the extra-alveolar persistence and the manner in which the extracted tooth is preserved. Both are fundamental for the maintenance of the fiber vitality of the periodontal ligament. The necrosis of these fibers cause ankylosis. It is observed that the conditioning of the radicular surface with fluoride solutions before the reimplantation is likely to slow down the evolution of radicular resorption. To evaluate the effectiveness of such methodology six cases of traumatic extractions, characterized by a length of extra-alveolar persistency (not longer than 24 hours), and unfavorable conditions of the preserved tooth have been treated by conditioning the radicular surface with the Na-fluoride solution before the reimplantation. Another group of reimplantation cases with the same characteristics have been examined without proceeding first to the radicular conditioning. The results of the study, although preliminary, verified the positive influence of the Na fluoride upon the radicular resorption.

Follow-Up Studies↗
PubMed1991

Fusion of newly formed phagosomes with endosomes in intact cells and in a cell-free system.

Phagosomes are membrane-bound vesicles, formed by the receptor-mediated internalization of particulate ligands, which exchange soluble and membrane proteins with other endocytic compartments as a part of their maturation process. This exchange of material is undoubtedly mediated by fusion of phagosomes with other membrane-bound compartments of the endocytic pathway. By using a particulate probe (fixed Staphylococcus aureus coated with mouse anti-dinitrophenol monoclonal antibody) localized in phagosomes and a soluble probe (dinitrophenol-derivitized beta-glucuronidase) internalized by receptor-mediated endocytosis, we have studied phagosome-endosome and phagosome-lysosome fusion in intact cells and in a cell-free system. Vesicle fusion was assessed by measuring beta-glucuronidase activity associated with S. aureus particles after lysis of the membranes. In intact macrophages, newly formed phagosomes fused with early endosomes and with lysosomes. Fusion with lysosomes was observed to commence after a short lag period of about 5 min. In broken-cell preparations, phagosomes were able to fuse with early endosomes. It was not possible to reconstitute phagosome-lysosome fusion in vitro. In vitro phagosome-endosome fusion required energy and cytosolic- and membrane-associated proteins. A nonhydrolyzable analog of GTP stimulated fusion at low cytosol concentrations and inhibited fusion at high cytosol concentrations. These observations indicate that the mechanisms mediating phagosome-endosome fusion are similar to those described for endosome-endosome fusion. Our results suggest that exchange of material with endosomes is an important step in the process of phagosome maturation.

Cell Fusion↗
PubMed1991

Binding of beta-galactosidase from rat epididymal fluid to the sperm surface by high-affinity sites different from phosphomannosyl receptors.

beta-Galactosidase, known to be secreted by epithelial cells lining the rat epididymal duct, binds to the surface of spermatozoa from the caudal region with high affinity and in a saturable form. The binding was not inhibited by mannose-6-phosphate, but was inhibited by fructose phosphate derivatives, a peculiarity previously demonstrated for the membranes of epididymal tissue. Fructose phosphate derivatives released 55% of beta-galactosidase activity from the spermatozoa. These results suggest that in the epididymis there is a special transport system for hydrolases, which could be involved in the secretion of enzymes destined for spermatozoa. This transport would require receptors that recognize sugar ligands other than mannose-6-phosphate. These receptors were present in the epididymal tissue and on the sperm surface.

Animals↗
PubMed1990

In vitro depolymerization dynamics of brain endogenous microtubules.

A subcellular fraction containing fragments of endogenous microtubules stabilized in 50% glycerol was separated by diferential centrifugation of rat brain homogenates. The pellets were suspended in glycerol-deficient media, and microtubule depolymerization was monitored by measuring the decrease of sedimentable tubulin. Concomitantly, the number and size of microtubules in the suspensions were followed via electron microscopy. Depolymerization was accompanied by a proportional decrease in the number of microtubules, whereas the average size did not change significantly. After approximately 20 min, a subpopulation of microtubules became stable and did not suffer further depolymerization. These results indicate that upon dilution some microtubules completely depolymerize, whereas others remain stable in the glycerol-deficient medium. The degree of depolymerization depended on both the volume of the resuspension media and on the final glycerol concentration. The results suggest that the depolymerization of the remaining microtubules is prevented by stabilizing factors released from depolymerizing microtubules. Tubulin dimers are not one of these factors, since depolymerization was not altered by the addition of colchicine or by changing the concentration of free tubulin in the medium.

Animals↗
PubMed1990

Colchicine binding to tubulin from brain homogenates in the presence of sugars, glycols and metal ions. Effect of nickel ions on the tubulin solubility.

The fact that glycerol preserves microtubules from depolymerizing in vitro, and that some ions such as Ca(II) and Mg(II), regulate the assembly-disassembly process of these structures, induced us to study the effect of several sugars, glycols and metal ions on solubility and colchicine affinity of tubulin in rat brain homogenates, and of purified microtubular protein. Inhibition of colchicine binding was significant with glycerol, polyethylene glycol 1000 (PEG-2) and the ions Al(III), Co(II), Ni(II), while compounds structurally related to glycerol (glucose and sucrose) did not inhibit it. Mannitol, instead, increased the activity a 47% over control. Apparently the presence of some compounds in brain homogenates [PEG-2 (1000) and Ni(II)] favored tubulin sedimentation when these latter were centrifuged at 100,000 x g for 150 min at 20 degrees C, but the form in which tubulin becomes aggregated in the pellet is unknown. Nickel ion made insoluble microtubular protein of homogenates and the purified one by more than 90% without causing significant inhibition of the colchicine binding. The sediment containing nickel-treated two cycles purified microtubular protein observed with the electron microscope did not present microtubules, but it revealed the presence of irregular, wavy and stretched structures bearing highly dense dotted material. The sediments became soluble in phosphate-glutamate buffer (pH 6.8) and, when incubated in polymerizing conditions, gave rise to microtubules undistinguishable from those prepared with untreated purified protein.

Aluminum↗
PubMed1989

[Application of the Ivory separator in dental restoration].

The Ivory widener is practical, quick and without deleterious effects on dental and gingival tissues. It allows a gradual and reproducible effect, good visibility of the operatory field and a better access to the dental cavity with saving of healthy tissue.

Dental Cavity Preparation↗
PubMed1988

Properties of binding sites for chloroquine in liver lysosomal membranes.

Chloroquine (CQ) is an antimalarial and antirheumatic drug that accumulates in lysosomes. We purified liver lysosomal membranes of tritosomes from albino mice injected with Triton WR 1339. The membranes were used for the binding assay with CQ in 0.01 M Tris-HCl buffer (pH 7.4). This binding was saturable, with a KD value of 6.2 microM. To understand the nature of CQ affinity, the binding was done under conditions that alter membrane structure and composition. Changes in pH, high ionic strength, and bivalent cations reversibly decreased the binding, while the effect of non-ionic detergents was partially reversed. The cationic detergent Hyamine strongly decreased the binding, and its effect was trypsin and neuraminidase had no effect. The results indicate the existence of binding sites for CQ in liver lysosomal membranes, which were strongly affected by changes of charge in the molecules involved in the binding. The treatment with the enzymes suggests that loss of polar groups of phospholipids increases the affinity of CQ by exposing protein sites located deep in the membrane, or by permiting a closer interaction between the drug and membrane lipids. CQ lysosomotropism and other effects of CQ on the lysosomal apparatus studied by other authors may be due not only to its accumulation inside the acid milieu of the lysosomes, in the same manner as other weak bases, but also to the affinity of CQ for binding sites in the lysosomal membrane.

Ammonium Chloride↗
PubMed1987

Developmental aspects of the lysosomal apparatus. Membrane affinity of N-acetyl-beta-D-glucosaminidase in developing rat liver.

The affinity of N-acetyl-beta-D-glucosaminidase by membranes of liver was studied in rats of different ages including fetuses at day 18 of gestation. It was found that membrane bound enzyme activity, extractable with 0.6 KCl, increases from fetal life to adulthood reaching a peak 9 days after birth. In binding assays it was found that the enzyme of fetal, 9 days old, or adult rat has high affinity for membranes of the corresponding age. These bindings were saturable and with a similar KD, but the number of receptor sites was lowest in the fetal stage, and reached a peak 9 days after birth. The fetal enzyme did not bind to adult membranes. These results suggest that the transport system of hepatic lysosomal enzymes undergoes post-natal changes which are synchronic with other parameters of lysosomal apparatus maturation studied by us and other authors as total enzyme activity and intracellular digestion of macromolecules.

Acetylglucosaminidase↗
PubMed1987

beta-Galactosidase from rat epididymal fluid is bound by a recognition site attached to membranes of the epididymis different from the phosphomannosyl receptor.

In order to know if the beta-galactosidase of the rat epididymal fluid, as other secreted acid hydrolases, carries a marker in its molecule, we studied the binding of this enzyme to cellular membranes of the epididymal tissue. The binding, like that mediated by the phosphomannosyl receptor, was saturable, did not require calcium, had a Kd in the nM range and was inhibited by phosphatase or metaperiodate treatment of the enzyme. However fructose 6-phosphate derivates were more effective competitive inhibitors than mannose 6-phosphate. The binding capacity of the membranes were extractable with Triton X-100 and incorporable into liposomes. Trypsin inhibited the binding capacity of Triton extracts but it did not affect the affinity of intact cellular membranes for beta-galactosidase. The results suggest that a phosphorylated carbohydrate of the enzyme is bound by a recognizing site of the cellular membranes different from the phosphomannosyl receptor.

Animals↗
PubMed1986

Separation of microtubule populations in rat brain homogenates by differential centrifugation.

Subcellular fractions were separated from rat homogenates at 600 g for 5 min (P1), 15,000 g for 10 min (P2), 48,000 g for 60 min (P3), 100,000 g for 150 min (P4) and a final supernatant (S). They contained 5.0, 14.3, 14.7, 24.7 and 41.3% of the total tubulin in the homogenate measured by colchicine binding. The microtubules recovered in a pool of fractions P1 + P2 + P3 underwent a faster depolymerization than those of P4 when the sediments were suspended in buffered solutions, poor in the stabilizing agent glycerol. As was observed with the electron microscope, P4 was richer than the other fractions in microtubules associated with membranous structures (MTA) by filamentous lateral connections. Subcellular distribution and lability properties may be the result of the connection of microtubules with membranous structures; the attached membranes would decrease the sedimentation velocity of microtubules, and lateral bridges could increase microtubular stability. Differences in length were not a cause of microtubule separation since this parameter did not vary among the microtubule of the different fractions or between MTA and non-associated microtubules of the same fraction.

Animals↗
PubMed1986

The in vivo effect of low body temperatures on the degree of polymerization of tubulin in brain and testes: a comparison among some species of vertebrates.

The tubulin of both brain and testes of the amphibian Bufo spinulosus, Leptodactylus ocellatus and Odontophrynus occidentalis and of the fish Salvelinus fontinalis were partially depolymerized when the animals were maintained on ice for 90 min. Recovery of the animals at room temperature restored the normal degree of polymerization in both organs. The cerebral tubulin of the saurian Phymatura palluma and of the mammalian Myotis chiloensis instead, were not depolymerized in these conditions. The results suggest that the depolymerization in vivo of tubulin by lowering body temperature at 0-2 degrees C, is common to many, but not all species of vertebrates. The existence of a cold stabilizing factor in the brain of some species is suggested. A comparison is made between these results and those of other authors who observed microtubule disaggregation by cold with the electron microscope.

Amphibians↗
PubMed1985

The effect of the lysosomotropic drug chloroquine on the binding of N-acetyl-beta-D-glucosaminidase to mannose-6-phosphate recognizing receptors of rat liver.

The binding of N-acetyl-beta-D-glucosaminidase to rat liver receptors was studied in the presence of chloroquine. The association rate constant was not affected in the presence of the drug, while the dissociation rate constant and consequently the equilibrium dissociation binding constant significatively decreased. This results may explain effects of chloroquine on lysosomal enzyme transport found in cultured cells by other authors.

Acetylglucosaminidase↗
PubMed1985

In vivo interaction between mouse liver lysosomes and chloroquine.

Particles sedimenting at 27,000 g X 10 min (MLCQ) were separated from liver homogenates of mice injected with chloroquine (CQ). The MLCQ contained most of the drug recovered in the organ as well as 50% of the liver aryl sulphatase activity. The release of CQ from MLCQ was studied in some physicochemical conditions, and in the presence of various agents known to modify membrane composition and stability. At pH 7.4, the equilibrium between free and bound CQ depended on the dilution of the MLCQ, and the time to reach equilibrium was strongly influenced by the temperature of incubation. Several agents causing membrane disruption and lysosomal enzyme leakage, such as osmotic shock, sonication and digitonin, had little effect on the CQ release. Acid and alkaline buffers, 0.55 M KCl and 0.1% Triton X-100 caused, instead, the immediate release of most of the bound CQ. Concentrations of digitonin causing the release of aryl sulphatase activity had little effect on bound CQ, suggesting that the drug is retained in lysosomes by forces and/or structures different in nature from those retaining most of the lysosomal enzyme activity. We think that the CQ trapped in lysosomes is bound to high affinity sites in membranous structures which are particularly altered by agents known to extract peripheral proteins from biological membranes or to change the conformation of molecular structures.

Animals↗
PubMed1983

Two populations of acid hydrolase-containing particles in rat epididymis.

Two populations of acid hydrolase-containing particles were distinguished in homogenates of rat epididymis. One of them was rich in acid phosphatase activity, equilibrated at density 1.17 in a sucrose gradient, and it sedimented between 12,000g 2.5 min and 43,000g 60 min (light particles). The other was poor in acid phosphatase activity and rich in N-acetyl-beta-D-glucosaminidase, arylsulphatase, and beta-glucuronidase activity, equilibrated at density 1.20 in a sucrose gradient and it sedimented between 400g 2.5 min and 12,000g 2.5 min (heavy particles). 131I-albumin (RISA) injected into the lumen of the cauda was partially recovered in subcellular particles of homogenates of this region. These particles, incubated at pH 5, were able to digest the engulfed RISA. The subcellular distribution of RISA-containing particles and RISA-digesting particles was similar to that of the heavy hydrolase-containing particles. This suggests that these latter are engaged, at least in part, in heterophagic processes.

Acetylglucosaminidase↗
PubMed1983

Kinin-forming enzymes in vascular tissue.

The present study was undertaken to examine whether there is a kallikrein-like enzyme in vascular tissue. Isolated saline-perfused rat mesenteric arteries were used. A kallikrein-like enzyme and acid protease from saline-perfused mesenteric arteries were separated by CM-cellulose chromatography with a linear NaCl gradient. The separation made it possible to study the optimum pH of the kallikrein-like enzyme and acid protease. The kallikrein-like enzyme showed optimal activity in the range of pH 7-9 and the acid protease in the range of pH 4-5. Both enzymes when acting on a protein plasma substrate release an active peptide that has a similar chemical and pharmacological properties to bradykinin. Using antibodies that specifically inhibit kinins, the biological action was completely abolished. These results indicate that arterial tissue contains two enzymes which generate kinins, the characteristics of one of the enzymes are quite similar to those of a lysosomal protease of the cathepsin-like type of enzyme and the other differs clearly from the acid protease and plasma kallikreins and has physicochemical characteristics quite similar to those of the kallikreins of glandular origin.

Animals↗