PubMed Health⌕ Search

Biomedical subjects

L Riboni

Publications and source records attributed to L Riboni.

At least 55 records · Page 3Linked to original sources
PubMed1989

Formation of ganglioside GD1b-lactone in rat brain from intracisternally administered GD1b.

The presence of ganglioside GD1b, in lactone form GD1b-L, was ascertained in rat brain. The possible formation of GD1b-L from GD1b in brain was explored by the intracisternal injection of GD1b, 3H-labelled at the level of the terminal galactose. This was followed by recognition of the radioactive gangliosides formed at different times (1, 3, and 7 days) after injection. Whereas at 0 time after injection the only radioactive ganglioside was GD1b, after 1, 3, and 7 days other radioactive gangliosides were also found, thus indicating GD1b penetration into the brain tissue, followed by metabolic processing. Besides GD1b, the following radioactive gangliosides were recognized: GM1 and GM2, derived from GD1b degradation; GT1b, formed by the direct sialylation of GD1b; and GD1b-L, produced by metabolic lactonization. The radioactivity carried by GD1b-L was maximal 3 days after injection; its time course was different from that of the other gangliosides, suggesting that the process of lactonization is separate from that of both degradation and glycosylation. Under the same experimental conditions, some radioactive gangliosides also appeared in the liver, although in much smaller amounts than in brain. Radioactive GD1b-L could not be detected in liver, thus indicating that metabolic lactonization is a tissue- or organ-specific process.

Animals↗
PubMed1989

Sprague Dawley rat mutant with tremor, ataxia, tonic immobility episodes, epilepsy and paralysis.

A spontaneous neurological mutation was detected in a colony of Sprague Dawley rats. The animals developed a progressive neurological syndrome characterized by tremor (which appeared at the age of 1 month), ataxia (at 4 months), immobility episodes (after 5-6 months), audiogenic seizures and hindlimb paralysis (after 10 months). Cross breeding experiments indicate that this is an autosomal recessive mutation, which we have named taiep subline.

Animals↗
PubMed1988

Ganglioside content and composition in human gliomas.

Many alterations of ganglioside content and distribution have been described in human and experimental tumours. Our previous data showed the presence of lipid alterations in meningiomas, in particular an increased monosialylganglioside content. Therefore we analyzed the distribution and content of gangliosides in various gliomas. The data show that ganglioside content is inversely proportional to tissue malignancy and that the ganglioside pattern can be described as lacking of polysialylgangliosides with increased GD3 content. The amount of GD3 (as percent of total gangliosides sialic acid) increases from 15% in astrocytomas grade I to 60% in grade IV. The GD3 increase seems to be almost specific of glioma. Because anti-GD3 antibodies could be used to localize immunohistochemically the ganglioside and to help the tumour grading, we used a purified preparation of GD3 to produce monoclonal antibodies in balb/c mice. But because some clones did produce anti-GD3 antibodies the low yield requires further experiments to obtain an antibody useful for this purpose.

Adult↗
PubMed1988

Ouabain uptake by endocytosis in isolated guinea pig atria.

Mammalian cells specifically internalize some molecular species through receptor-mediated endocytosis (RME). We have used four different experimental protocols to investigate whether ouabain enters cardiac cells of guinea pig atrium through this pathway. First, by electron microscope morphometry we found that ouabain increased endocytic vesicles in atrial cells. Second, by scintillation counting we found that [3H]ouabain uptake by the tissue is decreased by three treatments that decrease RME, i.e., NH4Cl, trifluoperazine, and 16 mM [K+]0. Third, by radioautography at the electron microscope level, we checked that in preceding experiments [3H]ouabain was washed out of plasma membrane after 60-min rinse and interiorized into the cardiac cells. Fourth, isometric tension recordings showed that the positive inotropic effect of ouabain was diminished in the presence of inhibitors, whereas that of a hydrophobic analogue, ouabagenin, was not affected. These results suggest that ouabain enters cardiac cells through RME and also that an intracellular site may, at least in part, be responsible for its inotropic effect.

Ammonium Chloride↗
PubMed1988

Morphometric and three-dimensional study of platelets during activation in the rat.

In vivo activation of platelets, produced by damaging an artery in the rat with ultrasound, was studied with the electron microscope. We performed both a three-dimensional reconstruction by thin serial sections and a morphometric study of the activation process. This is characterized by exocytosis of the content of granules, widening of tubules of the open canalicular system, and emission of pseudopodia. The three-dimensional reconstruction suggested that some extended pseudopodia adhere to the arterial intima, and confirmed former observations that a locomotor apparatus differentiates in platelets adhering to the arterial intima. We speculate that the contraction of some pseudopodia may pull the platelet body toward the arterial wall. The morphometric study revealed that during activation the volume of the open canalicular system volume increases and that of the dense granules decreases; all other compartments did not change.

Animals↗
PubMed1987

A computer program for morphometry of circular and elliptical profiles on the microscope.

We describe a short computer program, which is written in Pascal language, to measure the diameter of circular and elliptical profiles in sections. Coordinate pairs on the microscope stage, corresponding to two or three points of a profile, are input to obtain its diameter. The program enables one to take measurements directly on the microscope, thereby reducing photographic work and caliper measurement. While the program is largely designed for electron microscopy, it also may be useful for light microscopy morphometry.

Animals↗
PubMed1987

Pathogenesis of membranous lipodystrophy. Case report and review of the literature.

Membranous lipodystrophy occurred in a 35-year-old woman and membrane-like material was found in her epiphyses and short bones. Electron microscopy allowed a study of the relationship between the pathologic tissue and normal fat, suggesting that the membrane-like material is derived from degenerated cells. Nucleation of hydroxyapatite crystals was also observed in the membranous material. Because basal ganglia calcifications were demonstrated with the use of computed tomography, brain and bone lesions may be assumed to share the same pathogenesis. Lipid and mucopolysaccharide metabolism was found to be normal.

Adipose Tissue↗
PubMed1986

New chemical trends in ganglioside research.

A report is given of recent progress in the methodology for isolation of gangliosides from natural sources, for the preparation of molecular species of gangliosides homogeneous in both the oligosaccharide and ceramide portions of the molecule, for chemical manipulation and derivatization of gangliosides, and for the preparation of gangliosides radiolabelled in different parts of the molecule. Particular emphasis has been given to: high performance liquid chromatographic procedures capable to separate gangliosides on the basis of their oligosaccharide or ceramide moieties and yielding completely homogeneous compounds, that is gangliosides with a single oligosaccharide, a single long chain base and a single fatty acid; two-dimensional thin-layer chromatographic procedures, provided with a fully computerized quantification system, particularly suitable to identifying gangliosides containing alkali-labile linkages, including ganglioside lactones; chemical procedures of high yield for reducing gangliosides at the double bond of long chain base, for selective removal of the fatty acyl moiety and replacement with a novel fatty acid, and for the synthesis of ganglioside lactones; chemical procedures for inserting fluorescent, paramagnetic or photoreactive probes at the fatty acyl part of the ganglioside molecule; procedures for chemical isotopic radiolabelling of gangliosides at the level of sialic acid acetyl group and at the fatty acid moiety. Examples are provided evidencing the significance and potential use of a variety of ganglioside derivatives in the study of ganglioside metabolism and functional implications.

Affinity Labels↗
PubMed1986

Natural occurrence of ganglioside lactones. Isolation and characterization of GD1b inner ester from adult human brain.

A new ganglioside containing an inner ester linkage was extracted from adult brain specimens, obtained at the time of surgery on 51-70-year-old subjects, purified, and analyzed. It contains glucose, galactose, N-acetylgalactosamine, an N-acetylneuraminic acid in the molar ratio 1:2:1:2, but, on ion-exchange chromatography, behaves as a monosialoganglioside. Structural analyses showed its basic neutral glycosphingolipid core to be ganglio-N-tetraose ceramide, carrying a disialosyl residue on the 3-position of internal galactose. Sialidase degradation and chemical analysis of the products obtained after alkaline treatments suggested one sialic acid residue to be involved in an ester linkage. Fast atom bombardment-mass spectrometry indicated the presence of an inner ester linkage between the carboxyl group of the external sialic acid residue and a hydroxyl group of the internal one. On these bases, the new ganglioside can be assumed to be a GD1b in lactonic form. This ganglioside is present only in trace amounts in the brain of infants, but its content increases with age, reaching a value of 3.5% of total sialic acid in 51-70-year-old subjects.

Adult↗
PubMed1985

Correlation between ganglioside distribution and histological grading of human astrocytomas.

Changes in membrane lipid content and composition have been repeatedly detected in experimentally induced as well as spontaneous tumors. Previous data on ganglioside analysis in human astrocytomas suggested a possible correlation between their content and pattern and the histological grading of these tumors. In our study we could definitely prove this correlation: in fact the level of malignancy, passing from grade I to grade IV, is associated with a statistically significant increase of a ganglioside identified as ganglioside GD3. Another important modification in the ganglioside pattern of human astrocytomas is the decrease in polysialylated species with increasing level of malignancy.

Adult↗
PubMed1985

Inhibition of DNA and RNA synthesis in rat liver nuclei by oncogenic and non-oncogenic beta-blockers.

The beta-blocker DL-1-(2-nitro-3-methylphenoxy)-3-tert-butylaminopropan-2-ol (ZAMI 1305), hepatocarcinogenic to the female rat, and the non-oncogenic beta-blockers DL-1-(2-nitro-5-methylphenoxy)-3-tert-butylaminopropan-2-ol (ZAMI 1327), DL-propranolol, and DL-atenolol were studied for their capacity to interfere with hepatic DNA and RNA synthesis. These moieties inhibit DNA and RNA synthesis, in a dose-dependent fashion, when added in vitro to nuclei isolated from the liver of male or female rats. The inhibition is due to a decrease of the initial rate of synthesis and of the total amount of labeled precursor incorporated into the growing chains. When administered in vivo both the oncogenic ZAMI 1305 and its non-oncogenic isomer ZAMI 1327 inhibit hepatic DNA and RNA synthesis in female rats, as evaluated by the determination of nucleic acids synthesis in liver nuclei isolated from female rats 5 and 15 min after the injection of the drug. No influence on hepatic DNA and RNA synthesis is observed when the molecules are administered to male rats. The in vivo administration of DL-propranolol causes an increase of hepatic DNA and RNA synthesis in male rats, while it is uneffective in female rats.

Adrenergic beta-Antagonists↗
PubMed1984

Phospholipid content and composition of human meningiomas.

The content and distribution of phospholipids, as well as their fatty acid composition, were studied in 16 human meningiomas in comparison with normal leptomeninges. The total phospholipid content of tumors (expressed as organic phosphorus/mg DNA) was similar to that of the tissue from which they originated. The same phospholipid classes were present in both tissues, but with a different pattern: an increase of phosphatidylinositol and phosphatidylcholine and a decrease of sphingomyelin and alkenyl-acyl phosphatidylethanolamine were detected in meningiomas. Stearic, palmitic, and oleic acids were the major phospholipid fatty acids in both leptomeninges and meningiomas. However, remarkable differences between the fatty acid composition of the two tissues were shown. The most striking difference is a marked increase of unsaturated fatty acids in tumors associated with a decrease of saturated forms. This feature is common to all major phospholipid classes. The possible significance and role of phospholipid modifications in the functional properties of meningioma plasma membrane is discussed.

Adult↗
PubMed1984

Ganglioside pattern of normal human brain, from samples obtained at surgery. A study especially referred to alkali labile species.

The ganglioside pattern from normal human temporal cortex and cerebellum has been studied in fresh specimens obtained at surgery. The analyses have been performed by two-dimensional thin layer chromatography with an intermediate ammonia treatment which is a methodology particularly suitable for resolving alkali labile gangliosides. Alkali labile gangliosides were detected in all the analyzed specimens and their content contributed to 23% and 11% of total lipid bound sialic acid, in temporal cortex and cerebellum, respectively.

Aged↗
PubMed1983

Modifications of ganglioside patterns in human meningiomas.

Ganglioside content and distribution were determined in control meninges and in 30 human meningiomas belonging to four different histological types. Irrespective of the histological classification all meningiomas showed a ganglioside content significantly higher than that of control meninges. The analysis of ganglioside distribution in each meningioma showed that in the majority of the cases the increase of ganglioside content was primarily the result of selective accumulation of ganglioside GM3; in the remaining cases ganglioside GM1 was present in a significantly higher amount than in the control dura mater and leptomeninges. A common feature of both types of meningiomas is a simplification of ganglioside pattern, with a shift from the polysialylated to the monosialylated forms. A tentative classification of meningiomas into "GM3-rich" and "GM1-rich" types, together with an explanation for the selective accumulation of these two types of ganglioside, is proposed.

Chromatography, Thin Layer↗
PubMed1982

Inhibition in vitro of yeast DNA polymerase I activity by beta-blockers.

The activity of DNA polymerase I from Saccharomyces cerevisiae is inhibited, in a dose-dependent fashion, by the oncogenic beta-blocker 1-(2-nitro-3-methyl-phenoxy)-3-tert-butylamino-propan-2-ol (ZAMI 1305) and by the non-oncogenic beta-blockers 1-(2-nitro-5-methyl-phenoxy)-3-tert-butylamino-propan-2-ol (ZAMI 1327), atenolol, and propranolol, the latter having the highest inhibiting activity. The inhibition is due to an interaction of the beta-blockers with the free enzyme and with the enzyme-DNA complex. The degree of inhibition is directly related to the hydrophobicity of the aromatic moiety and to the length and hydrophilicity of the aliphatic chain of the inhibitor. No relation seems to exist between the in vitro inhibition of yeast DNA polymerase I by beta-blockers and their oncogenic activity.

Adrenergic beta-Antagonists↗
PubMed1982

A non-steroidal gametic factor linked to DNA modulates delta-aminolevulinic acid synthase inducibility acting on liver transcriptional and translational processes.

The effect of an acidic factor of low molecular weight (about 1,000 daltons), extracted from bovine spermatozoan DNA, on the inducibility of delta-aminolevulinic acid synthase by ethanol during aging in rat has been examined. The increased enzyme inducibility in 600-day old rats is supported by stimulation of transcriptional and translational processes; on the contrary, in 30-day old rats, the higher enzyme values induced by ethanol are significantly decreased after factor treatment. The active factor is strongly DNA-bound in the native spermatozoan DNA. This would imply a possible role in regulating gene expression in vivo.

5-Aminolevulinate Synthetase↗
PubMed1982

Is there a cholinergic circadian rhythm throughout the oestrous cycle related to ovulation in the rat?

Rats with a 4-day oestrous cycle were given a single dose of atropine (100, 300, 500 or 700 mg/kg body wt) at 13.00 h on the days of oestrus, dioestrus 1, dioestrus 2 or pro-oestrus and were autopsied on the next expected day of oestrus. The doses of atropine (in mg/kg body wt) necessary to block ovulation during the cycle were 300 at oestrus, 100 at dioestrus 1 or 2 and 700 at pro-oestrus. A single dose of atropine (100 mg/kg) at oestrus, dioestrus 1 or dioestrus 2 was given at 09.00, 13.00, 17.00 or 21.00 h, autopsy again being performed on the next expected day of oestrus. The ability of atropine to block ovulation appeared to have a circadian rhythm, with a maximum blockade at 13.00 h on dioestrus 1 and dioestrus 2 and a minimum at 21.00 h on the same days. Hormone replacement (human chorionic gonadotrophin at oestrus, dioestrus 1 or 2, oestradiol benzoate at dioestrus 2 or progesterone at pro-oestrus) re-established normal ovulation in rats whose ovulation was blocked with atropine (100 mg/kg) on dioestrus 1 at 13.00 h. When ovulation was blocked with atropine but no hormone replacement had been given, rats ovulated 24 h after the next expected day of oestrus. Results obtained in these experiments suggest the existence of a circadian rhythm of gonadotrophin secretion throughout the oestrous cycle and a close relationship between that rhythm and the cholinergic system.

Animals↗