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Biomedical subjects

L Dini

Publications and source records attributed to L Dini.

At least 19 recordsLinked to original sources
PubMed1999

Modulation of cell surface expression of liver carbohydrate receptors during in vivo induction of apoptosis with lead nitrate.

Cell surface expression of carbohydrate receptors (i.e. mannose and galactose receptors) and phagocytosis of apoptotic cells by sinusoidal liver cells was studied. Binding sites and phagocytic activity were quantified at different time intervals (1, 3, 5, 7, 9, 11, 13, 15, 20, 30, 40 and 60 days) after the in vivo administration to rats of a potent liver mitogen, lead nitrate, that also induces apoptosis. The number and distribution of binding sites was receptor and cell-type dependent during the days following the metal injection. The use of competing saccharides in inhibition uptake experiments suggests that sinusoidal liver cells actively phagocytose apoptotic hepatocytes and circulating apoptotic cells by using both receptors. In particular, Kupffer cells at 5 and 15 days after the lead nitrate injection are very active in internalizing apoptotic cells (two- to threefold control). However, phagosomes containing apoptotic hepatocytes are often seen inside the cytoplasm of parenchymal and endothelial cells.

Animals↗
PubMed1999

Citrate carrier and lipogenic enzyme activities in lead nitrate-induced proliferative and apoptotic phase in rat liver.

After in vivo administration of lead nitrate, functional changes of the mitochondrial tricarboxylate carrier and of the cytosolic lipogenic enzymes acetyl-CoA carboxylase and fatty acid synthetase have been detected in rat liver. The rate of citrate transport was greatly reduced in rats during both the proliferative phase (3 days after the lead nitrate administration) and the involutive phase (5 days after the metal injection), which follows hepatic hyperplasia and corresponds to the peak of hepatocyte apoptosis. In both phases, a decrease of the lipogenic enzyme activities has been detected. In treated animals, an alteration of mitochondrial lipid composition has also been found. The modified lipid microenvironment could be responsible for the decreased carrier activity which, in turn, may account for the reduced activities of the lipogenic enzymes.

Acetyl-CoA Carboxylase↗
PubMed1998

Hepatic sinusoidal endothelium heterogeneity with respect to the recognition of apoptotic cells.

The recognition and removal of human apoptotic peripheral lymphocytes in selected populations of periportal and perivenous endothelial cells was studied in in situ and in vitro experiments. Apoptotic peripheral blood lymphocytes once injected into the liver circulation were retained by the sinusoids showing a large heterogeneity of distribution: apoptotic cells are found in the periportal tract double the amount found in the perivenous region. Apoptotic PBL adhesion was lowered to a sixth of the control after preinjection with a sugar mixture (Mannose, N-acetylgalactosamine, N-acetylglucosamine, D-galactose), as suggested by the expression of modified surface glycoconjugates on the plasma membrane of apoptotic cells. A bimodal profile of the distribution of the hepatic sinusoidal cell population, regarding the number of galactose and mannose receptors and the porosity index, was found. Two endothelial cell subsets were present: low porosity cells (average index 14 +/- 6%; periportal tract) with a high number of carbohydrate binding sites, and high porosity cells (average index 26 +/- 7%; perivenous tract), with a low number of carbohydrate binding sites.

Animals↗
PubMed1998

Relationship between cellular shape and receptor-mediated endocytosis: an ultrastructural and morphometric study in rat Kupffer cells.

The relationship between cellular shape (i.e., size, volume, presence of microvilli, pseudopodia, flat or round shape) and receptor-mediated endocytotic activities (i.e., binding and internalization) was investigated using intact liver as well as freshly isolated Kupffer cells and Kupffer cells in culture. The morphological features of Kupffer cells were reconstructed by three-dimensional analysis from in situ experiments and by densitometric analysis of cells in suspension and in culture. By morphometry at the ultrastructural level, different cellular shapes were compared with the respective capacities for binding and internalization of glycoproteins with terminal galactosyl residues. The number of asialoglycoprotein-gold particles bound to the cell surface or internalized into endosomes was calculated. Our data show that differences in cellular shape, mainly related to the reduction of projection and microvilli and to the roundness of cell surface, accompany modulation of galactose-specific receptors in rat Kupffer cells, thus supporting the hypothesis that cell morphology is affected by endocytic activities. In fact, the progressive reduction in microvilli projections and cellular roundness is paralleled by the progressive decrement of both binding and uptake capacity from in situ, freshly isolated and cultured Kupffer cells.

Animals↗
PubMed1998

Interaction between isolated and purified liver cells and small unilamellar liposomes.

AIMS/BACKGROUND: The mechanism of interaction and the role played by the vesicle lipid composition for the selective association between liposomes and liver cells were studied, at the ultrastructural level, by investigating both in situ and in vitro the interaction between hepatocytes, Kupffer and endothelial liver cells with egg-phosphatidylcholine (eggPC) or eggPC/stearylamine (9:1; mol:mol) reverse-phase evaporation (REV) liposomes. METHODS: Liver cells from rats, isolated by enzymatic perfusion and purified by differential centrifugation, were incubated, in a rotating bath at 37 degrees C, with liposomes (2.5 mM final liposomal lipid concentration). Cell aliquots were withdrawn and processed for electron microscope observation at fixed time intervals. Parallel experiments were carried out by in situ liver perfusion with liposome suspensions. RESULTS AND CONCLUSIONS: Our first conclusions are: 1) lipidic composition affects the rate of liposomes uptake and internalization by hepatocytes; 2) liposome uptake by hepatocytes or Kupffer cells is likely an endocytic process; 3) endothelial cells internalize lipid vesicles as well; 4) liposome uptake was due to a phagocytic activity for all isolated liver cells, while in the in situ observation endothelial cells seem to use another mechanism (fusion); and 5) the rate of internalization is related to the viability of the treated cells. Experimental data seem to indicate that differential behaviour in the internalization of lipid vesicles exists among parenchymal, Kupffer and endothelial liver cells. These differences suggest that clearance of liposomes by these cells involves two mechanisms (i.e., endocytosis or fusion) with different rates of uptake and internalization that facilitate the design of carriers that can deliver drugs preferentially to a specific liver cell type.

Animals↗
PubMed1998

[Iatrogenic lesions of the bile ducts in laparoscopic cholecystectomy. Therapeutic potential of interventional radiology].

PURPOSE: We investigated the efficacy of interventional radiology procedures in some patients with iatrogenic injuries of the biliary tree from laparoscopic cholecystectomy. MATERIAL AND METHODS: In the last two years, 8 patients with complications of laparoscopic cholecystectomy were treated in the Department of Radiology of Umberto I Hospital, Ancona, Italy. Five of them had a subhepatic biliary collection due to a cystic duct stump leak, 2 has a leak of the Roux-en-Y hepaticojejunostomy (from a iatrogenic injury of the common biliary duct) and 1 had a right hepatic biliary duct stricture from a clip. In the patients with a cystic duct stump leak, we treated the biloma with percutaneous catheter drainage and the endoscopist positioned a nasobiliary tube, while a percutaneous abdominal catheter was positioned to drain the biloma and a percutaneous transhepatic catheter was positioned through the biliary duct tract or through the hepaticojejunostomy. RESULTS: All injuries were completely repaired within 5-8 weeks of the procedure. There were no maneuver-related complications. All patients had normal serum levels of bilirubin, alkaline phosphatase and transaminase at the monthly follow-up tests performed for 3 months. US and MR cholangiopancreatography at 3 months excluded strictures, fistulas or bilomas of the biliary tree. DISCUSSION: The prompt detection of the injuries is essential to the success of interventional radiology procedures: the patients are less debilitated, small caliber catheters can be used and recovery is quicker. The combined effort of surgeons, endoscopists and radiologists is necessary to optimize the management of patients with laparoscopic cholecystectomy-related biliary complications. CONCLUSIONS: We obtained positive results with minimally invasive procedures costing less than another operation. Thus, we suggest that interventional radiology procedures become the method of choice in patients with iatrogenic injuries of the biliary tree after laparoscopic cholecystectomy.

Adult↗
PubMed1997

Bile acids with differing hydrophilic-hydrophobic properties do not influence cytokine production by human monocytes and murine Kupffer cells.

Bile acids have been proposed to exert immunological effects of potential pathogenic or therapeutic relevance, yet the experimental evidence remains preliminary. We reexamined the effects of a variety of bile salts with differing hydrophilic-hydrophobic properties on the production of interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF alpha) from monocytes and Kupffer cells. Monocytes from healthy human donors and Kupffer cells from 5-week-old mice were incubated for up to 18 hours with or without varying concentrations of bile salts and lipopolysaccharide (LPS). Monocyte viability was > or = 95% with up to 250 mumol/L sodium ursodeoxycholate and < or = 90% with 200 mumol/L chenodeoxycholate, decreasing sharply at higher concentrations. Kupffer cells were more vulnerable, particularly to chenodeoxycholate (viabilities of 25% and 0% at concentrations of 100 mumol/L and 200 mumol/L, respectively). In monocytes incubated in the presence of 20% fetal calf serum, neither ursodeoxycholate and chenodeoxycholate, nor a variety of other unconjugated and conjugated bile acids, tested up to their maximal noncytotoxic concentrations, influenced the IL-6 and TNF alpha production, at any level of LPS stimulation. Similar to monocytes, incubation of murine Kupffer cells with ursodeoxycholate and chenodeoxycholate did not influence cytokine release. In contrast, the addition of 10 nmol/L dexamethasone to monocytes significantly decreased TNF-alpha and IL-6 release (69 +/- 11% and 48 +/- 15%, respectively). When monocytes were incubated with 200 mumol/L chenodeoxycholate in the presence of lower concentrations of fetal calf serum (10% and 5%, respectively) a significant inhibition of cytokine release was observed, whereas incubation with ursodeoxycholate did not cause any effect. Flow cytometry using fluoresceinated LPS showed that chenodeoxycholate does not interact with the CD14 receptor, thus excluding the possibility of an interference with the LPS uptake by monocytes. Incubation with [14C]-chenodeoxycholate showed that the intracellular bile acid uptake was inversely related to the concentration of fetal calf serum, being negligible (< 3 fmol/cell) at the highest level. In conclusion, bile acids with widely different hydrophobicities are incapable of influencing the release of IL-6 and TNF alpha by monocytes and Kupffer cells, provided they are studied at noncytotoxic concentrations and in the presence of physiological amounts of proteins.

Animals↗
PubMed1997

Asialoglycoprotein (ASGP) receptors induced by apoptosis. Their immunohistochemical localization in neonatal rat hepatocytes.

Immunohistochemical detection of asialoglycoprotein (ASGP) receptors has been performed on neonatal rat hepatocytes in primary cultures, incubated with TGF beta, TNF alpha and retinoic acid. These substances account for the increase in the rate of apoptosis of the cell cultures and for the increase of the expression of ASGP receptors. Both modifications are higher at 24 hours of incubation.

Animals↗
PubMed1996

Glutathione inhibits HIV replication by acting at late stages of the virus life cycle.

We investigated the effect of glutathione on the replication of human immunodeficiency virus (HIV) in chronically infected macrophages, a known reservoir of the virus in the body. We found that exogenous GSH strongly suppresses the production of p24gag protein as well as the virus infectivity. This is related to a dramatic decrease in both budding and release of virus particles from chronically infected cells (either macrophages or lymphocytes), together with a selective decrease in the expression of gp120, the major envelope glycoprotein, rich in intrachain disulfide bonds and thus potentially sensitive to the effect of a reducing agent such as GSH. Overall data suggest that GSH can interfere with late stages of virus replication. This would be in agreement with data obtained in cells exposed to herpesvirus type 1 (a DNA virus) or to Sendai (an RNA virus), showing that the suppression of virus replication by GSH is related to the selective inhibition of envelope glycoproteins. These results suggest a potential role of GSH in combination with other antivirals in the treatment of virus-related diseases.

CD4-Positive T-Lymphocytes↗
PubMed1996

Age-related changes in the binding and uptake of Cu, Zn superoxide dismutase in rat liver cells.

The present paper reports the effect of aging on receptor mediated endocytosis of Cu, Zn superoxide dismutase in rat liver cells. The fate of bovine Cu, Zn superoxide dismutase conjugated to colloidal gold was followed by electron microscopy in young (2 months) and old (24 months) rats in situ, in vivo and in vitro experiments. The use of different models for the study of the binding and internalization of the enzyme allowed to discriminate the contribution of each different liver cell type. The data obtained demonstrate that aging of the liver affects binding and uptake of this enzyme. In particular both the number of binding sites and the rate of internalization were depressed in old rats. Therefore, the hypothesis of therapeutic application of superoxide dismutase for age-related diseases needs to be revalued in view of the fact that receptor-mediated endocytosis of this protein is a mechanism affected by senescence.

Age Factors↗
PubMed1996

Human Kupffer cell recognition and phagocytosis of apoptotic peripheral blood lymphocytes.

Cells undergoing apoptosis are recognized and rapidly phagocytosed by macrophages before their degradation, thus preventing the inflammatory reaction and protecting tissues from the damaging effects of released potentially harmful intracellular contents. In spite of growing interest in the mechanisms leading to the engulfment of apoptotic cells, the molecular bases by which an apoptotic cell is recognized are not entirely understood. Among the several potential mechanisms by which a macrophage can identify a cell as apoptotic, the data reported in the present paper support the idea that Kupffer cells phagocytose apoptotic cells by means of lectin-like receptors. Human Kupffer cells, which possess galactose-specific binding sites, can recognize and phagocytose peripheral blood lymphocytes undergoing apoptosis after heat shock (43 degrees C) or cycloheximide treatment, but not normal living peripheral blood lymphocytes. The putative structure by which apoptotic peripheral blood lymphocytes are targeted as "edible" could be the molecular changes in the plasma membrane, In fact, our experiments indicate that the membranes of apoptotic peripheral blood lymphocytes express increased amounts of N-acetylgalactosamine, D-galactose, and mannose residues when compared with membranes of normal PBL. Phagocytosis was inhibited by adding to the culture medium sugar cocktail solution (glucose, N-acetylgalactosamine, methyl mannopyranoside, fucose, 80 mM final concentration) or to a lower extent by desialylated glycoproteins (lactosylated bovine serum albumin, asialofetuin, 2 mg/ml final concentration), but not by nondesialylated glycoproteins (fetuin, 2 mg/ml final concentration, bovine serum albumin, 20% final concentration). In addition, phagocytosis of apoptotic peripheral blood lymphocytes by human Kupffer cells was a very rapid process, being almost entirely completed within 15 min of incubation.

Apoptosis↗
PubMed1996

Multiple pathways for apoptotic nuclear fragmentation.

We analyzed the ultrastructure of apoptotic nuclear fragmentation in U937 cells treated with many different apoptogenic agents. We found that this characteristic apoptotic feature can be achieved through multiple alternative pathways, depending on the apoptogenic inducer, leading to slightly different final nuclear morphologies. In most instances, the irregularly shaped nucleus of U937 rounds up; then, chromatin condenses at the nuclear periphery. Condensed chromatin can form protruding patches, which eventually bud from the nucleus in sealed vesicles through a process which is actin-dependent, since it could be blocked by cytochalasins. Alternatively, chromatin condenses in tiny, nonprotruding crescents, and a cleavage in the nuclear sap forms, beginning from the inner nuclear membrane and growing inward, thus splitting the nucleus. In U937 induced to apoptosis by hydrogen peroxide in the presence of ADP-ribosylation inhibitors, the nuclei fragment in many vesicles before chromatin even begins to condense: chromatin condensation probably occurs as a consequence. While all the apoptotic morphologies described above evolve from interphase cells, a peculiar apoptotic morphology, possibly deriving from mitotic cells, is detected upon oxidative stress, recalling the formation of micronuclei by clastogenic treatments; it shows partially membrane-bound chromatin patches, which look midway between condensed chromosomes and apoptotic condensed chromatin. The existence of these multiple pathways for nuclear fragmentation may indicate an evolutionary convergence, suggesting that this event may play an important physiological role in apoptosis.

Adenosine Diphosphate Ribose↗
PubMed1996

Expression of the asialoglycoprotein receptor in cultured rat hepatocytes is modulated by cell density.

The influence of cell density on expression of the asialoglycoprotein receptor system in primary cultures of rat hepatocytes was evaluated by measuring the level of the receptor specific mRNA. When the hepatocytes are cultured at high cellular density and are not in a proliferative condition, the transcript molecules of the receptor appear increased about 50% with respect to the low plating density, indicating a modulation of asialoglycoprotein receptor expression at transcriptional level. Such control may be dependent on surface molecules involved in cell specific reassociation, since it is well known that cell contacts play a significant regulatory role in differentiated cells.

Animals↗
PubMed1996

Human immunodeficiency virus-induced cell death in cytokine-treated macrophages can be prevented by compounds that inhibit late stages of viral replication.

The basis of the cytopathic effect induced by a laboratory strain and several clinical isolates of human immunodeficiency virus (HIV) in human macrophages cultured in the presence of macrophage colony-stimulating factor was studied. Infected macrophages die of necrosis, the consequence of the production of mature virions in infected cells. Cell death can be prevented by antiviral compounds that interfere with the assembly and budding of virions. Programmed cell death (apoptosis), a potential mechanism of HIV-mediated cell death in CD4 T lymphocytes, does not occur in infected macrophages as shown by electron microscopy, cytofluorometric and gel electrophoretic DNA analysis, and nuclear fluorescent staining by Hoechst and terminal dUTP-nick-end-labeling (TUNEL) assay. The data suggest that macrophage killing by HIV may occur in vivo. Thus, combination therapies that include compounds that inhibit the cytopathic effect of HIV in macrophages should be considered for AIDS patients.

Antiviral Agents↗
PubMed1996

In vivo uptake of Cu, Zn superoxide dismutase. Morphological evidence for preferential endocytosis and accumulation by sinusoidal liver cells.

Bovine Cu, Zn superoxide dismutase (SOD), conjugated to colloidal gold, was intravenously administered to rats and its distribution studied by electron microscopy. Liver was the preferential site of accumulation of gold-labelled SOD. Among liver cells types, Kupffer and endothelial cells showed the presence of the protein earlier than hepatocytes. Uptake by kidney showed slower kinetics than liver. No uptake by heart could be detected. The gold-labelled SOD was localized inside coated pits, coated vesicles and other non-coated endocytic compartments. Absence of binding by BSA-gold complexes and competition between free SOD and the gold-labelled one demonstrated the specificity of the uptake process. Our morphological evidences suggest that in vivo internalization of SOD occurs most likely through receptor-mediated endocytosis.

Animals↗
PubMed1996

Recognition and phagocytosis of apoptotic cells.

Physiological elimination of unwanted cells within the organism occurs via cell death by apoptosis and phagocytosis of these cells represents a key event in the apoptotic process. Macrophages, which are the dedicated phagocytes, and other occasionally phagocytic cells ingest the apoptotic cells while they are still intact, thus preventing the leakage of potentially harmful materials from the dying cells. Although evidence has been presented that the elimination of apoptotic bodies from the tissue operates by means of specific recognition systems, the molecular mechanisms by which an apoptotic cell is recognized are poorly understood. Recent data indicate that phagocyte recognition of apoptotic cells involves at least four classes of receptors on the phagocyte surface. On the other side, dying cells may display different signals to signal their status. Exposure of phosphatidyl serine (PS) on the surface of apoptotic lymphocytes triggers their specific recognition and removal by macrophages. Apoptotic thymocytes are also identified by altered lipid packing on their surface. Different populations of macrophages use either the vitronectin receptor or the PS receptor to recognize and remove apoptotic cells. It has been suggested that the asialoglycoprotein and the galactose-specific receptors of healthy hepatocytes and sinusoidal liver cells are implicated in the engulfment of apoptotic hepatocytes, likely in cooperation with other hepatic carbohydrate-specific receptor systems. The purpose of this review is to examine current knowledge of the mechanisms by which phagocytes recognize and ingest apoptotic cells.

Animals↗