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A Matteucci

Publications and source records attributed to A Matteucci.

At least 37 records · Page 2Linked to original sources
PubMed1995

Immunocytochemical detection of phosphatidylinositol 4,5-bisphosphate localization sites within the nucleus.

Phosphatidylinositol 4,5-bisphosphate (PIP2) is a key element of signal transduction, being the preferential substrate of specific phospholipases that produce second messengers such as inositol trisphosphate (IP3) and diacylglycerol (DG). Because PIP2 has been cytochemically identified by monoclonal antibodies not only in the cytoplasmic membranes but also in the nuclear envelope and within the nucleus, we performed a study by immunoblotting and by confocal and electron microscopic immunocytochemistry to identify the nuclear sites of PIP2 localization and to exclude any cross-reactivity of the antibody with other nuclear molecules. The results confirm the specificity of the immunolabeling and indicate that PIP2 is localized at precise intranuclear sites both in in situ and in isolated nuclei. They also show that a significant amount of the phospholipid is retained by the cytoskeleton and by the inner nuclear matrix in in situ matrix preparations. Moreover the sensitivity of the immunocytochemical reaction is capable of detecting quantitative variations of PIP2 nuclear content induced by agonists that modulate the signal transduction system at the nuclear level.

3T3 Cells↗
PubMed1995

Ultrastructural organization of the sperm nuclear matrix.

The organization of DNA-protamine complexes and their association with the nuclear matrix have been analyzed in sperm nuclei by in situ Nick Translation at the electron microscope. The data obtained indicate that the chromatin organization in sperm nuclei is maintained during the sperm condensation by means of interaction with the nuclear matrix at fixed sites. The fine structure of the sperm nucleus and sperm nuclear matrix, investigated by sectioning and replica of freeze-fractured specimens, suggests that the lamellar array observed by freeze-fracturing in the sperm nuclei, could depend on the inner matrix which presents a regular organization of globular structures involved in the maintenance of chromatin domains.

Animals↗
PubMed1994

Nuclear matrix involvement in sperm head structural organization.

In the sperm nuclei the DNA is packaged into a highly condensed form and is not organized into nucleosome and solenoid but is bound and stabilized mainly by the protamines that arrange the DNA in an almost crystalline state. As demonstrated for somatic cells, the sperm DNA has been reported to be organized in loop domains attached to the nuclear matrix structures. However, the possible role of the sperm head matrix in maintaining the loop organization in absence of a typical nucleosomal structures has not been fully elucidated. By using in situ nick translation at confocal and electron microscope level, we analyzed the organization of the DNA-protamine complex and its association with the sperm nuclear matrix. The data obtained indicate that the chromatin organization in sperm nuclei is maintained during the sperm condensation by means of interactions with the nuclear matrix at fixed sites. The fine structure of sperm nucleus and of sperm nuclear matrix, investigated on sections and replicas of freeze-fractured specimens, suggests that the lamellar array, observed by freeze-fracturing in the sperm nuclei, could depend on the inner matrix which presents a regular organization of globular structures possibly involved in the maintenance of chromatin domains in highly condensed sperm nuclei also.

Animals↗
PubMed1993

Bromodeoxyuridine incorporation in corneal epithelium: an immunocytochemical study in rats.

Here we investigate the kinetics of rat corneal epithelium at both single cell and tissue level by means of a BrdU-anti BrdU method. The results obtained have then been compared with those previously obtained by us in rat vocal cord epithelium. In this way two main aspects of BrdU incorporation can be indicated at both light and electron microscopy level. First, we report evidence of a new incorporation pattern corresponding to middle S phase, which is characterized by labelling distribution at the border between interchromatin and heterochromatin at ultrastructural level. Second, by comparing tissue incorporation in rats treated with BrdU at the beginning of light time and at the beginning of dark time, we show an increase of cell proliferation during the last hours of dark time and the first hours of light time. In this way, we demonstrate a different progression of circadian rhythms in peripheral regions of corneal epithelium in comparison with that previously observed in vocal cord epithelium.

Animals↗
PubMed1992

Increased phosphorylation of nuclear substrates for rat brain protein kinase C in regenerating rat liver nuclei.

Protein phosphorylation catalysed by rat brain protein kinase C (PKC) has been studied in nuclei isolated from normal and regenerating rat liver. Histone H1 and a 40,000 molecular weight protein were hyperphosphorylated at all the explored regeneration times, ranging from 3 to 22 h after partial hepatectomy. Phosphorylation of the two substrates was totally dependent on calcium and lipids and was abolished by low concentration of staurosporine. The observed early change of phosphate content of histone H1 and of the 40,000 molecular weight protein on the time scale of liver regeneration suggests that PKC might be involved in the initial nuclear events leading to cell proliferation.

Animals↗
PubMed1991

In vitro phosphorylation of lamin B by protein kinase C in friend erythroleukemia. Effect of chemically induced differentiation.

Nuclear matrix isolated from murine erythroleukemia cells (Friend cells) has been phosphorylated with gamma 32P-ATP and purified protein kinase C in order to identify specific nuclear substrates for the enzyme. HMBA has been employed to induce the cell to differentiate and to compare the changes of phosphorylation profile after erythroid differentiation. Lamin B has been found to be hyperphosphorylated by rat brain PK-C in nuclear matrix purified from uninduced cells. This difference characterizes the cells from 14 to 72 hrs of HMBA treatment and indicates that the ability of lamin B to be phosphorylated by PK-C is linked to the differentiated state. The involvement of PK-C in lamin phosphorylation might represent an early step of the signalling pathway utilized by erythroid differentiating agents to target the cell nucleus.

Acetamides↗
PubMed1991

Dietary treatment for familial hypercholesterolemia--differential effects of dietary soy protein according to the apolipoprotein E phenotypes.

Familial hypercholesterolemia, one form of type IIa hyperlipidemia, usually responds poorly to standard low-lipid diets. To define the responsiveness to a soy-protein diet in this disease, one homozygous and twenty heterozygous type IIa patients were submitted to a 4-wk traditional hypocholesterolemic diet followed by 4 wk in which animal protein was substituted with texturized soy protein. Soy was then withdrawn for a further 4 wk. No significant changes in plasma lipids were observed during low-lipid diets. The soy diet, however, caused a marked decrease in total (-20.8%) and low-density-lipoprotein (-25.8%) cholesterol and in apolipoprotein B (-14.1%). The plasma cholesterol reduction was higher in patients with apolipoprotein E3/E3 or E3/E4 vs an almost negligible effect on E3/E2. These results confirm that soy-protein diets can lower cholesterol in type IIa patients with familial disease. Data on the sensitivity of patients with different apo-E isoforms agree with recent hypotheses suggesting that soy proteins may activate B,E receptors.

Adult↗
PubMed1991

Characterization and cell cycle kinetics of hepatocytes during rat liver regeneration: in vivo BrdUrd incorporation analysed by flow cytometry and electron microscopy.

The incorporation of bromodeoxyuridine (BrdUrd) into newly synthesized DNA has been analysed during hepatocellular regeneration induced by partial hepatectomy in young rats. The kinetic state of the liver has been studied by flow cytometric analysis of the incorporated BrdUrd, while the fine localization of DNA replication sites through the cell cycle has been investigated at the ultrastructural level by the immunogold technique. Eighteen hours after partial hepatectomy flow cytometry revealed an early S phase distribution which corresponded to a specific staining of the interchromatin domains of the hepatocyte nucleus. Thirty-four hours after hepatectomy, on the other hand, when most cells were in late S, a specific staining of heterochromatin domains was observed. The effect of the BrdUrd technique on nuclear aggregation has also been analysed and discussed. The results demonstrate that specific patterns of DNA replication can be recognized during the cell cycle and that flow cytometry and electron microscopy appear to be complementary in the kinetic study of liver regeneration.

Animals↗
PubMed1989

Chromatin organization in rat testis nuclei. Flow cytometric detection of the morphological compaction.

The unusual histone composition of testicular cells generates changes in chromatin organization in order to allow the chromosomal pairing necessary for genetic recombination. Accessibility of testis nuclear DNA was determined by flow cytometry. The observed differences in staining between testis and liver nuclear chromatin, as well as the differences of perpendicular light scatter signal, correlate with alterations in protein composition with the chromatin reorganization.

Animals↗
PubMed1988

Chromatin organization in isolated nuclei: flow cytometric characterization employing forward and perpendicular light scatter.

Flow cytometric perpendicular and forward light scatters have been employed to evaluate whether the changes in chromatin organization due to ionic strength, Mg++ concentration and pH, visible in electron microscopy, can be monitored by flow cytometry. The average intensity of the perpendicular light scatter signal increased as nuclear chromatin became decondensed by lowering the ionic strength or releasing H1 histone at low pH values. These results indicate that flow cytometry signals and in particular the perpendicular light scatter allow the detection of the conformational transitions in chromatin and may therefore be useful for studying cell cycle associated morphological changes in isolated nuclei.

Animals↗
PubMed1987

Flow cytometric analysis of isolated rat liver nuclei during growth.

The development of hepatocyte polyploidy in rats aged up to 4 months was analyzed by flow cytometry using both scatter and fluorescent parameters to distinguish DNA diploid and DNA tetraploid populations and to discriminate between parenchymal and non-parenchymal compartments. The precise origin of each class of nuclei was assessed in whole liver homogenate using purified hepatocytes, obtained by liver perfusion followed by separation on Percoll gradient, and identifying the peaks corresponding to parenchymal nuclei. The results indicate that preparative procedures involving homogenization of the rat liver tissue caused loss of the DNA octaploid population. Data on the relative proportion of the different DNA ploidy elements during rat liver development, which are in good agreement with those observed by cell analysis by means of microspectrophotometry, indicate the usefulness of flow cytometry as a choice method for the analysis of ploidy distribution.

Animals↗
PubMed1987

Influence of phosphatidylserine on endogeneous RNA synthesis in isolated rat liver nuclei.

The possible involvement of anionic phospholipids in the transcriptional process was studied in isolated rat liver nuclei synthesizing RNA in the presence of phosphatidylserine, which was employed in the form of multillamellar liposomes as a means of delivering the lipid to the nuclei in aqueous medium. The divalent ion requirement for RNA synthesis and the properties of the incubation mixture were not significantly modified by the phospholipid, which increased the rate and the extent of the incorporation of 3H-UMP without changing the endogeneous degradation pattern of the product or affecting the activity of a particular RNA polymerase, as indicated by the sensitivity to amanitin. The thin layer chromatography analysis of the alkaline hydrolysates of the RNA showed that the stimulation involved an increase of the total polyribonucleotide elongation rate. The size of the product was essentially unchanged in the presence of phosphatidylserine, as demonstrated by the qualitative overlapping of the sedimentation profiles of control and lipid treated samples in formamide-sucrose gradients. The release of the H1 fraction from intact nuclei occurring with phosphatidylserine indicated that the DNA template availability was increased by a partial removal of the restrictions imposed by histones, as suggested also by the comparison with heparin and Sarkosyl. These evidences, together with the data accumulated on the occurrence of lipids in chromatin and nuclear matrix, and on their changes related to cell growth, differentiation and malignant transformation, allow a better definition of the role that phospholipids might play in regulating the DNA template availability in the cell.

Amanitins↗
PubMed1986

Electron microscopy microsampling of isolated nuclei sorted by flow cytometry.

This paper describes an efficient method to concentrate for electron microscopic examination minute quantities of subcellular particles obtained by cytofluorimetric sorting. The advantages of this micromethod, based on diafiltration on Millipore filters under constant positive nitrogen pressure, are discussed.

Animals↗
PubMed1986

Changes in nucleosome structure and histone H3 accessibility. Iodoacetamidofluorescein labelling after treatment with phosphatidylserine vesicles.

The accessibility of the sulfhydryl-specific dye 6-iodoacetamidofluorescein (IAF) to H3 histone has been studied in isolated rat liver nuclei and mononucleosomal core particles after treatment with phosphatidylserine (PS) multilamellar vesicles (MLV). In isolated nuclei, despite the enhancement of total RNA synthesis and the massive chromatin decondensation produced by liposomes, the amount of histone H3 which can be labelled with the dye remains essentially the same in PS-treated as in control nuclei. However, when mononucleosomal core particles, treated with PS vesicles, are reacted with IAF, H3 becomes derivatized by the dye, while controls do not. These data provide additional evidence that the metabolic and structural changes observed in isolated nuclei treated with PS MLV, are due mainly to the reported removal of histone H1. Moreover, the experiments reported confirm the usefulness of IAF in studying the changes of nucleosome organization, since PS is able to affect the nucleosomal core configuration in isolated nucleosome particles, derivatizing the buried cysteine groups of H3 histone.

Animals↗
PubMed1986

Ultrastructural organization of freeze-fractured interphase nuclei.

The morphology of intact or membrane-deprived interphase nuclei has been analysed by freeze-fracture electron microscopy. This method appears particularly useful for providing information on the distribution and organisation of chromatin and ribonucleoproteins in the absence of dehydration and embedding artifacts of conventional electron microscope techniques which, among other effects, appear to affect heterochromatin distribution, inducing its aggregation along the nuclear envelope. The main levels of chromatin superstructure, from nucleosome to solenoid fibres, are detectable in the replicas of freeze-fractured nuclei on the basis of the size of their shadow, a parameter particularly suitable for automated image analyses.

Animals↗
PubMed1984

Response of isolated nuclei to phospholipid vesicles: analysis of the nuclear proteins after treatment with phosphatidylserine and phosphatidylcholine and comparison with heparin.

Phospholipid liposomes affect the histone pattern of isolated rat liver nuclei. Multilamellar vesicles (MLV) obtained with phosphatidylserine (PS) release a large amount of the lysine rich histones, while those obtained with phosphatidylcholine (PC) do not induce significant changes with respect to controls. This different response has been compared to the effects obtained with Heparin, which slightly modifies the relative ratio of the histone fractions. These data might account for the mode by which phospholipids induce transitions of the chromatin structure and changes of the endogenous RNA polymerase activity.

Animals↗