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L Dini

Publications and source records attributed to L Dini.

At least 73 records · Page 4Linked to original sources
PubMed1991

Ultrastructural analysis of asialoglycoprotein receptor mediated endocytosis in cultured newborn hepatocytes.

We examined the receptor-mediated endocytosis of asialoglycoproteins in thick sections of cultured hepatocytes of newborn rats by high voltage electron microscope. The organelles involved in endocytosis are revealed ultrastructurally using colloidal gold particles coupled to lactosylated bovine serum albumin. Keeping the cells at 4 degrees C the marker binds to the cell surface showing microvilli, and is not internalized. Increasing the temperature to 37 degrees C, we observed that within 5-15 min. the marker enters the intracellular endocytic organelles close to the cell surface. After 60 min. the marker is found in the larger and deeper endocytic organelles and in large lisosome-like vesicles. We find that the process of endocytosis in newborn cultured hepatocytes is similar to that found in cultured cells of adult rats, but the process of internalization is slower.

Animals↗
PubMed1991

[Gastromiro vs gastrografin vs prontobario CAT for computerized tomography. Multicenter study].

The opacification of intestinal loops is mandatory, during CT examination of the abdomen, to prevent the gut from being mistaken for a pathological process or vice versa. The authors compared Gastrografin and Prontobarium-CT with a new, orally administrable, non-ionic contrast medium (Gastromiro) to investigate whether the non-ionic molecule presents any advantages over the other contrast media usually employed with CT. Five hundred ml of water solution/suspension at 11.1% (Gastromiro or Gastrografin) and 1.7% (Prontobarium-CT) were administered 20 minutes before examination to 818 consecutive patients. Different parameters were considered--i.e., patient tolerance as far as "taste and vomiting" were concerned, gut opacification, and any reaction which might have occurred to the patients within 24 hours after examination. The results, statistically analyzed, are the following: no significant difference in the quality of opacification of stomach, duodenum, and large bowel; significant difference in the quality of opacification of small bowel, where Gastromiro proved to have the highest contrast resolution; Gatromiro stimulated diarrhea significantly less than Gastrografin and Prontobarium-CT.

Barium Sulfate↗
PubMed1990

Carbohydrate recognition systems in avian sinusoidal liver cells.

We studied the carbohydrate recognition systems on liver sinusoidal cells of adult chicken and 20-day-old embryos. We localized and quantified the binding sites for glycoproteins exposing terminal N-acetylglucosamine (GlcNAc), mannose and galactose (Gal) residues. Sinusoidal liver cells from animals of both ages express on their cell surfaces binding sites for GlcNAc, mannose and galactose residues, while hepatocytes bind glycoproteins with GlcNAc residues. The gold particles distribution on Kupffer cells depend on the binding sites and the age considered. Binding sites for GlcNAc and Gal residues are generally present as clusters of gold granules, while mannose-specific binding sites are always as single gold granules. Ligand-gold complexes bound on endothelial cells are always present on the coated regions of the cell surface. The number of GlcNAc and Gal-specific receptors expressed on the cell surface of Kupffer cells undergoes modifications between embryonal and adult life.

Acetylglucosamine↗
PubMed1990

Binding and uptake of ligands for mannose-specific receptors in liver cells: an electron microscopic study during development and aging in rat.

The binding and uptake of mannose exposing ligands in rat liver cells during development and aging was studied. The mannose-specific receptors are visualized using 5-nm diameter colloidal gold particles coated with invertase or mannan. It was found that the binding sites are present on sinusoidal liver cells since prenatal life but their quantitative and qualitative cell surface expression changes with age. The number of receptors affects the endocytotic capacity of Kupffer cells which is low during perinatal and aging periods and reaches the values of adult animals between the 11th and the 15th day after birth. Our results indicate that the expression and the activity of mannose-specific receptors on sinusoidal rat liver cells is related to the differentiative stage of the organ.

Aging↗
PubMed1990

The interaction of ceruloplasmin with Kupffer cells.

The binding and uptake of ceruloplasmin was studied with rat liver cells using gold-labeled probes. Ceruloplasmins from either rat or sheep were used, in which different molecular conformations had been induced according to established biochemical criteria. The native protein from either species could bind not only to the endothelium, but also to Kupffer cells, at variance with previous findings. The proteins which had been converted to the conformation typical of stored molecules--which can be considered aged, but not denatured, according to standard activity and spectroscopic assays--were bound by endothelium irrespective of species, while only rat ceruloplasmin was able to bind to rat Kupffer cells. Internalization of sheep ceruloplasmin occurred with either endothelium or Kupffer cells. This property was lost with isolated suspended Kupffer cells. These findings suggest the presence of receptors for ceruloplasmin on Kupffer cells which are different from those present on endothelial cells.

Animals↗
PubMed1989

Electron microscopic evidence for endocytosis of superoxide dismutase by hepatocytes using protein-gold adducts.

Cu, Zn superoxide dismutase, an intracellular, carbohydrate-free protein, was found to bind to hepatocytes and endothelial cells by electron microscopy of liver treated with enzyme-gold conjugates. In cultured hepatocytes, the free enzyme, but not bovine serum albumin, competed for the binding, and at 37 degrees C, the gold-protein complexes were internalized in a typical process of receptor-mediated endocytosis.

Animals↗
PubMed1989

Modulation of asialoglycoprotein binding activity in livers of pregnant or estrogen-treated rats.

This report deals with the modulation of activity and expression of the hepatic asialoglycoprotein receptor, in pregnant or diethylstilbestrol-treated rats. The results show a two-fold increase in the total cell associated binding activity, both in pregnant and in estrogen-treated animals, with respect to normal values. On the contrary the surface expression was shown to be strongly enhanced only in the liver of pregnant rat. Therefore the modulation shown by this receptor system in pregnancy seems to be only partially estrogen-dependent.

Animals↗
PubMed1989

Preclustered receptor arrangement is a prerequisite for galactose-specific clearance of large particulate ligands in rat liver.

We had hypothesized that preclustered arrangement of galactose-specific receptor activity on rat liver macrophages enables these cells to internalize multivalent, particulate ligands in contrast to the clearance of molecules mediated by statistically distributed receptors on hepatocytes. We now took advantage of the nonclustered receptor distribution in newborn rat liver macrophages to study the in vivo clearance of particulate ligands. Gold particles 5, 17, and 50 nm in diameter (Au5, Au17, Au50), coated with lactosylated bovine serum albumin (LacBSA), were injected into the vena cava and livers were perfusion fixed after allowing for binding and uptake for 3 min. In sinusoidal cells from rats 15 days old LacBSA-Au5 and LacBSA-Au17 were taken up by endothelial cells and all sizes by liver macrophages. In newborn rat liver no LacBSA-Au50 or LacBSA-Au17 was retained in liver macrophages. Uptake of LacBSA-Au5 by sinusoidal cells was significant. LacBSA-Au17 was taken up in significant amounts by endothelial cells of newborn rats which correlates to the findings that galactose-specific binding sites on endothelial cells were found to localize as clusters over coated pits irrespective of age. These results demonstrate the crucial role of clustered receptors in binding and uptake of larger particulate ligands via this lectin-like binding activity.

Animals↗
PubMed1989

Age-related changes in the galactose recognition system in rat liver cells.

In the present report, the galactose recognition system in 3- and 24-month-old rat livers has been studied with in vitro and with in situ binding experiments and in vivo ligand uptake. The galactose-specific receptors were visualized by using colloidal gold particles of different sizes (5 nm, 17 nm and 50 nm mean diameter), coated with lactosylated bovine serum albumin (LacBSA) as electron dense ligands. The data show that aging affects the expression of galactose-specific receptors and the rate of endocytosis. In the in vitro and in situ experiments hepatocytes and liver macrophages from old rats on the plasma membrane express a decreased number of binding sites with respect to those present on the adult rat liver cells. Approximately 80% of the total number of liver macrophages from aged rats show a binding distribution which is very different from the typical clustered receptor arrangement: the binding sites appear as single or small clusters of gold granules. As a direct consequence of the altered pattern of the receptor distribution, the capacity of liver macrophages from 24-month-old rats to internalize the larger ligands (17 nm and 50 nm) is decreased, as compared with adult rats. Aging, therefore, influences the galactose recognition system in two ways: (i) by decreasing the number of binding sites expressed on the liver cell surfaces; and (ii) by modifying the receptor distribution on liver macrophages and consequently affecting the internalization of galactose exposing particles.

Aging↗
PubMed1989

Pregnancy-related changes of galactose recognition system on sinusoidal rat liver cells.

We have studied the galactose specific receptor activities of sinusoidal liver cells of pregnant rat from the 13th day of gestation to the 10th day after delivery. Both liver macrophages and endothelial cells modulate the expression of hepatic binding protein during rat pregnancy and lactation. Except for endothelial cells of rats at the 22nd day of gestation, we have measured an overall decrease of binding sites. In addition, in liver macrophages the clustered distribution of galactose specific receptors, which is typical for adult animals, is reduced or completely absent. These results indicate that the galactose specific receptors on non-parenchymal liver cells are modulated in relation with the physiological state of the organ like the asialoglycoprotein receptor of hepatocytes.

Animals↗
PubMed1989

[Importance of a particular formula of soybean milk without S2 globulin, in the treatment of allergy to cow's milk proteins].

Replacing cow's milk with a soybean milk is one of the first measures which are commonly taken with babies suffering from cow's milk protein allergy. Unfortunately soybean can induce sensitization, too, with a variable percentage (ranging from 12 to 80%) according to the different Authors, due to the presence of allergenic proteins, among which the most important one seems to be S2 globulin. An excellent tolerability has been reported in a study carried out with 20 babies suffering from cow's milk protein allergy besides a good palatability of the product with a solution of symptoms in 87.3% of the cases. Only in 16.7% of the treated babies intolerance has been reported and therefore we can conclude that soybean milk has proved to be an excellent substitute of cow's milk in babies suffering from cow's milk protein allergy.

Child, Preschool↗
PubMed1989

High density lipoproteins during rat liver regeneration.

Compositional and maturative parameters of high density lipoproteins (HDL) have been examined during the early stages of rat liver regeneration, when lecithin:cholesterol acyltransferase (LCAT) activity, responsible for the maturation of this lipoprotein class, is markedly decreased. Both HDL subclass distribution and chemical composition are not significantly different from the control, except for a slightly lower cholesterol ester content. Few disc-shaped particles are detectable by electron microscopic observation. Cholesterol ester decrease and presence of immature particles are related, but the entity of the modification is lower than suggested by the deep decrease of LCAT activity. This seems to indicate that proper HDL maturation is assured in the regenerating liver despite low LCAT activity.

Animals↗
PubMed1988

Some features of age-related insulin responsiveness in rat hepatocytes.

Different features of insulin sensitivity have been considered, in rat hepatocytes, with respect to their age-dependence. In particular, plasma membrane-located responses such as (Na/K)-ATPase and Na-dependent aminoacid transport were studied together with cytoplasmic responses such as the insulin-stimulated tyrosine aminotransferase. It appears, as far as the insulin sensitivity is concerned, that the age of the animal does not affect plasma membrane-bound events whereas plasma membrane-mediated intracellular responses are definitely impaired. Insulin binding to intact hepatocytes does not seem to be age-dependent.

Aging↗
PubMed1988

Regulation of amino acid transport in hepatocytes isolated from adult and old rats.

The 2-aminoisobutyric acid transport in hepatocytes isolated from 3- and 24-month-old rats was studied and some age-related differences were observed. The basal uptake appeared to be almost constant in cells from old animals during the incubation time, while, in the cells from adults, it showed a progressive increase, interpreted as being due to a derepression mechanism. Epinephrine and glucagon increased the transport in hepatocytes from animals of both ages, even if with a slightly different pattern; the hormones increased the Vmax, while the Km was unchanged at each age tested. However, the glucagon-induced increase in Vmax was lower in the older animals. The mechanism of hormonal action appeared to be similar in adult and old rats. In fact the uptake stimulation by glucagon and epinephrine showed a dependence on protein synthesis. The epinephrine effect was mediated by alpha-adrenergic receptors. No effect was exerted by extracellular amino acids on hepatocytes from 24-month-old animals, suggesting a loss of adaptative regulation mechanism with aging. This behaviour was reflected in the kinetic parameters; in fact the Vmax was not modified by extracellular amino acids at 24 months of age, while it appeared to be strongly decreased in the adult.

Aging↗
PubMed1987

Regulation of amino acid transport in isolated rat hepatocytes during development.

The effect of amino acid depletion or supplementation and the effect of glucagon and insulin on the amino acid transport mediated by system A were investigated by determining the uptake of either 2-amino [1-14C]isobutyric acid (AIB) or N-methyl 2-amino [1-14C]isobutyric acid (MeAIB) in rat hepatocytes, freshly isolated at different stages of pre- and postnatal development. The data obtained show that the Na+-dependent uptake was higher at the earliest developmental stages, and steadily decreased until the adult level. The hormones increased AlB and MeAIB uptake enhancing the Vmax, while the Km was unchanged. This effect was evident in cells from adult and 18-20-day-old fetuses, while no response was present before the 18th day of fetal life and in the perinatal period. Actinomycin D or cycloheximide abolished this hormone-dependent increase. A decrease in AlB and MeAIB transport after incubation in an amino acid-rich medium was demonstrated at all ages tested, but was particularly evident in the prenatal life. The increase in the activity of the system following amino acid starvation was shown to be mostly dependent from de novo protein synthesis in the fetal life; on the contrary in the adult the increase appeared to be more linked to the release from transinhibition of the transport.

Aging↗
PubMed1987

The galactose-specific receptor system in rat liver during development.

The number and distribution of galactose-specific binding sites were investigated in rat liver cells during perinatal development. Ligand binding to hepatocytes, macrophages and endothelial cells was followed with in vitro and in situ experiments by electron microscopy, using lactosylated bovine serum albumin adsorbed onto 5 nm colloidal gold particles as ligand. Binding capacity, starting at a late stage of fetal development, is very low both on the hepatocyte and on the macrophage surface, which show single particles statistically distributed. By contrast, bound particles are absent from fetal endothelial cells, which also lack the typical coated regions. In vivo, experiments at 37 degrees C show that endocytosis occurs to some extent in prenatal life. These results indicate that the expression of galactose-specific receptors' activity on the different liver cell types follows different developmental patterns, which are independently modulated.

Animals↗