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M Biggiogera

Publications and source records attributed to M Biggiogera.

54 records · Page 3Linked to original sources
PubMed1990

Nucleolar distribution of proteins B23 and nucleolin in mouse preimplantation embryos as visualized by immunoelectron microscopy.

The ultrastructural distribution of proteins B23 and nucleolin in the nucleolus of mouse embryos from the zygote to the early blastocyst has been analyzed by means of specific antibodies and immunocytochemistry using colloidal gold complexes as markers. In parallel, silver staining of nucleoli was carried out on ultrathin sections. Our results show that the compact prenucleolar bodies at 1- and 2-cell stage as well as the compact residual fibrillar masses observed up to the morula stage, are labelled with the two antibodies. These masses, however, are not stained with silver up to the 4-cell stage. In well-developed nucleoli, the two antibodies co-localize in the dense fibrillar component (DFC) and the granular component (GC) while fibrillar centers (FCs) are devoid of label. On the contrary, silver staining occurs in the FCs and DFC but not in the GC. Our observations suggest that there is no direct relationship between the occurrence of silver staining and the distribution of protein B23 or nucleolin. Moreover, neither the localization of the two above proteins nor silver staining are unequivocally related to the nucleolar activity.

Animals↗
PubMed1989

Chromatin arrangement in mouse sperm nuclei: an ultrastructural cytochemical study.

The arrangement of mouse sperm nuclei chromatin and, in particular, of DNA has been studied by electron microscopic cytochemistry. It had been previously shown that, after a Feulgen-type reaction using an osmium ammine complex (OAC), the OAC-stained DNA was distributed in a spotted pattern in the nucleus (Biggiogera: Basic Appl Histochem 30:501-504, 1986). The present chapter shows that this pattern is characteristic of mouse spermatozoa from testis to vas deferens, with the exception of some testicular spermatozoa, in which DNA was homogeneously stained. DNase digestion of thin-sectioned nuclei resulted in a distribution of residual material complementary to the pattern of the unstained zones after the OAC reaction. These findings are discussed considering the role of -S-S- crosslinks, characteristics of this extremely condensed chromatin, in limiting the availability of DNA to acid hydrolysis.

Animals↗
PubMed1989

Ethidium bromide- and propidium iodide-PTA staining of nucleic acids at the electron microscopic level.

Ultra-thin sections of various tissues were stained with ethidium bromide or propidium iodide, two fluorescent markers widely used for quantitation of nucleic acids. The fluorochromes, tested at different concentrations, were then revealed by incubation of the sections with neutralized phosphotungstic acid. We showed that at the electron microscopic level only nucleic acid-containing structures are revealed. Chromatin, nucleolus, and ribosomes appear to be stained by the end-product of the reaction. Furthermore, controls with proteases and nucleases showed that the staining is related to the binding of the fluorochromes to DNA and RNA and to the subsequent detection of the dyes by neutralized PTA.

Animals↗
PubMed1989

Simultaneous immunoelectron microscopic visualization of protein B23 and C23 distribution in the HeLa cell nucleolus.

The intranucleolar distribution of phosphoproteins B23 and C23 was visualized simultaneously by post-embedding immunoelectron microscopy in HeLa cell nucleoli, using specific antibodies. The data show that proteins B23 and C23 co-localize to the same nucleolar compartments, i.e., the dense fibrillar component and the granular component. Neither of the two antibodies is significantly associated with the fibrillar centers in these cells, although the fibrillar centers appear positive after silver staining. These findings suggest that other unidentified components must be responsible for the silver staining observed in the fibrillar centers of interphase nucleoli. The results are discussed in the light of previously reported data obtained by preembedding immunolabeling techniques and by silver staining, which both suggested a localization of protein C23 inside the fibrillar centers.

Antibodies, Monoclonal↗
PubMed1988

Fluorescein mercuric acetate as a dye for fluorescence and electron microscope detection of -SH groups in mouse sperm protamines: a critical evaluation.

Fluorescein Mercuric Acetate (FMA), a specific fluorescent dye for thiols, was tested as a possible reagent for the ultrastructural detection of -SH groups in sperm chromatin protamines. It was shown that FMA may be profitably used for staining at electron microscopy the chromatin -SH groups of caput epididymidis spermatozoa. Like other mercury compounds, FMA proved to be unstable under the electron beam; therefore the use of low beam intensity, and cooling of the specimens are recommended. The main advantages of this staining method are the relatively lower toxicity of FMA, compared to other organic mercurials, and the opportunity to compare the fluorescence patterns on semithin sections with the corresponding ultrastructural findings on thin sections.

Animals↗
PubMed1987

Damage and repair of the immature rat cerebellum after cis-dichlorodiammineplatinum II (cis-DDP) treatment. An ultrastructural study.

The aim of this electron microscopy study was to further investigate the effects of cis-dichlorodiammineplatinum (cis-DDP) on the cerebellum of the immature rat. Ten-day-old animals were treated with cis-DDP subcutaneously and killed after 1, 7, 15 or 21 days. On postinjection day 1, cis-DDP effects were evident mainly in the external granular layer, with nuclear damage in many dividing cells, while their cytoplasm appeared to be less affected. Some binucleate cells were also present. On the contrary, in postmitotic or more differentiated cells, only cytoplasmic alterations were found. At later stages (postinjection day 7), the frequency of damaged cells in the external granular layer decreased, but there was a cellular deficit in the internal granular layer. Many postmitotic neurons underwent coagulative necrosis. Finally (postinjection days 15 and 21), the cellular deficit was partly compensated for by "reactive" structures, e.g., glial cell fibers, which underwent hypertrophy after initial edema. Moreover, packing densities of Bergmann astrocytes and oligodendrocytes were higher.

Animals↗
PubMed1986

Sperm-chromatin maturation in the mouse. A cytochemical approach.

Cytochemical techniques were used to study chromatin during spermiogenesis and sperm maturation in the mouse, starting from the stages at which the substitution of somatic histones by testis-specific proteins occurs. It was possible to distinguish and analyze the different temporal incidence of two processes involved in sperm maturation, i.e. chromatin condensation (a tridimensional highly compacted arrangement) and chromatin stabilization (a tough structure, which protects the genome DNA). The first process, involving a reduction in the nuclear size and a decrease in the amount of sperm DNA accessible to specific cytochemical reactions and stainings, was found to reach its maximum in caput-epididymidis spermatozoa, in which electron microscopy revealed that the sheared chromatin was mainly organized into 120-A-thick knobby fibers. No further changes were found in sperm up to their appearance in the fallopian tubes. On the contrary, chromatin stabilization, the onset of which occurs in the testis (at the late spermatid stage) via the formation of -S-S- cross-links, is completed in the vas deferens, where chromatin has a superstructure consisting of thicker fibers, with diameters of 210 and 350 A. The reductive cleavage of disulfides in vas-deferens spermatozoa does not completely destroy the superstructure of sperm chromatin, which could indicate 'coiling' of the basic knobby fiber. In fact, when the ion concentration was increased, the chromatin of vas-deferens spermatozoa appeared to be organized into fibers with diameters similar to those of the caput epididymidis. This unique organization of mature sperm chromatin should have an essential role in the fast swelling of spermatozoa during fertilization.

Animals↗
PubMed1986

Influence of cis-dichlorodiammineplatinum on the structure of the immature rat cerebellum.

Groups of 6- to 7-day-old and 10- to 11-day-old rats received cis-dichlorodiammineplatinum (cis-DDP) or inactive trans-DDP subcutaneously and were killed after 1, 6, 10, 15, or 21 days. In both age groups the acute effect (postinjection day 1) was most obvious in the germinal external granular layer (EGL), where many cells underwent shrinkage necrosis (pyknosis, apoptosis); the latter were more frequent within the fissures than on the surface of the cerebellar folia. Cell debris were often seen to be engulfed by macrophages, Bergmann cell fibers, and meningocytes. Bergmann cell bodies were swollen and the nuclei of Purkinje cells as well as of surviving cells of the EGL were enlarged. No comparable effects were observed in animals that had received an injection of trans-DDP in the same dose. Toward postinjection (p.i.) day 6, pyknotic cells disappeared from the EGL or, after the larger doses of cis-DDP, substantially decreased in number. Small nests of pyknotic cells appeared, however, at some places of the internal granular layer (IGL). The EGL was discontinuous or thinner in both age groups. In the IGL and molecular layer (ML) multiple focal fresh hemorrhages appeared together with some macrophages. The packing cell density in the IGL was less than in the controls, especially at the top of the cerebellar folia, i.e., contrary to the distribution of the primary damage in the EGL. Later, at p.i. day 10, ectopic nests of the IGL occurred occasionally in animals injected when 10 to 11 days old and severe atrophy of the ML and Purkinje cell population was observed at some places. At p.i. days 15 to 21, invasion of microglia-like cells appeared in the IGL and in some regions of the ML. Occasionally, subpial hemorrhages occurred at this interval. The acute damage caused by cis-DDP is thus similar to the effect of X rays or some, but not all, drugs with a cytostatic action. In addition, a more profound influence on dividing cells of the EGL within the fissures and distinct capillary lesions, indicated by hemorrhages, were found after cis-DDP. As in other experimental models, the acute cis-DDP damage of the immature cerebellum was partly repaired within a few p.i. days. Spatial difference of the repair process was inferred from the packing cell density in the IGL measured at the top and bottom of the cerebellar folia.

Animals↗
PubMed1986

Electron-cytochemical localization of succinic semialdehyde dehydrogenase activity in Purkinje neurons and hepatocytes of the rat.

A method is presented for the ultrastructural demonstration of succinate semialdehyde dehydrogenase (SSADH) activity in cerebellar Purkinje neurons and liver hepatocytes; SSADH is an enzyme involved in the degradation of gamma-aminobutyric acid (GABA). Incubation media originally used for light microscopy were considered. Reaction products were mainly detected when fresh tissue was used. In Purkinje cells, grains ascribable to SSADH activity were localized on the mitochondria (especially on the outer membrane); some extramitochondrial formazan deposits were also found. After brief fixation by immersion or perfusion, only a few formazan granules were detected in the cytoplasm. A similar distribution pattern was observed in hepatocytes, in which extramitochondrial grains and grains on the nuclear membrane were frequent. The actual existence and the possible meaning of extramitochondrial SSADH activity is critically discussed on the basis of the data in the literature.

Animals↗
PubMed1985

Synthesis of myelin proteins and ultrastructural investigations in regenerating rat sciatic nerve.

Myelin protein synthesis, as well as ultrastructural and morphometric changes in regenerating peripheral nerve, was studied. Sciatic nerves of rats were crushed unilaterally; sham-operated nerves of the contralateral side served as controls. For the in vivo experiments, rats were killed at selected periods after the nerves were crushed (30, 60, 90, and 120 days); seven days prior to killing, the animals were injected intravenously with L-[4,5-3H]leucine. For the in vitro experiments, proximal and distal segments of sciatic nerve and equivalent sham-operated nerves were labeled with 3H-amino acid mixture 90 days after axotomy. Purified myelin was isolated from nerve segments; specific radioactivity and gel electrophoretic patterns of proteins were analyzed. Cross-sectional electron microscope (EM) preparations of proximal, distal, and contralateral segments of nerves also were examined. Results showed that the incorporation of labeled amino acids into total myelin proteins was enhanced significantly in the distal segment of sciatic nerves at all of the periods of regeneration studied. The yield of myelin protein per mm distal nerve segment increased as regeneration proceeded. The remyelination of fibers early after nerve crush was weak, whereas it gradually attained the normal range 90-120 days after axotomy. Morphometric analysis of myelin sheath thickness of regenerating axons was consistent with the data obtained for myelin protein synthesis.

Animals↗
PubMed1985

Ultrastructural analysis of mouse sperm chromatin.

Chromatin organization was studied during the maturation processes in the epididymis and vas deferens; these processes lead to a potentially reversible inactivation of the genome. There are progressive increases in resistance to detergent action and -S-S- bridge reduction in both head membranes and chromatin. In all the sites studied, there was a basic "knobby" chromatin fiber of 110 A diameter. In the caput epididymidis only, in addition to the knobby fibers, there were some smooth fibers, which can be considered as markers of a transient situation in which the stabilization of DNA/protamine interactions has not completely been achieved. In the vas deferens, the knobby fibers, the diameters of which are multiples of that of the basic one, can be converted to single units by increasing the ionic strength.

Animals↗
PubMed1983

Effect of Denzimol, a new anticonvulsant drug, on rat cerebellum. Morphological and histochemical patterns of Purkinje cell layer.

The effects of Denzimol, a new anticonvulsant drug, were analyzed in the Purkinje cell layer of rat cerebellum. No modifications in the general histochemical and ultrastructural patterns were induced by chronic administration of the drug. A slight increase in the storage of lipopigments in the cytoplasm of Purkinje neurons was found. No effects on secondary fluorescence (indicative of changes in biogenic amines) were found while an increase in specific SSADH activity, a degradative enzyme in GABA metabolism was present. Some observed histological and ultrastructural alterations (presence of "balloned" Purkinje neurons showing, in particular, enlarged cisternae of the endoplasmic reticulum) may be a stress effect probably due to the gastric tube insertion by which the drug was administered.

Animals↗
PubMed1983

Chromatin organization in frog Purkinje neurons during the annual cycle: cytochemical and ultrastructural studies.

Feulgen-DNA microdensitometric and propidium Iodide-DNA (PI-DNA) microfluorometric evaluations were made in Purkinje cells of cerebella from hibernating frogs and from active frogs. Higher Feulgen-DNA/distribution area ratios and lower PI-DNA values were found in the hibernating frog (both at high and low fluorochrome concentrations). These data indicate a higher degree of chromatin compactness. During the activity period, the Feulgen-DNA/distribution area ratios are lower and the Feulgen-DNA content is higher; the corresponding higher PI-DNA values indicate a lower degree of chromatin condensation. Histochemical and ultrastructural data show clearly different distribution patterns of chromatin and ribosomes in the two periods. The overall results underscore lower activity of neurons and a greater homogeneity within the Purkinje cell population during hibernation.

Animals↗
PubMed1983

Effects of diphenylhydantoin on postnatal ontogenesis in the rat. Ultrastructural analysis of Purkinje neurons and hepatocytes.

An ultrastructural analysis of Purkinje neurons and hepatocytes was carried out at several stages of postnatal ontogenesis in rats born from dams administered diphenylhydantoin (DPH) during pregnancy and nursing. After DPH administration the signs of immaturity in the neurons both at cytoplasmic and nuclear level were particularly evident between the 4th and 17th day of postnatal life, while at the end of histogenesis the normal situation was recovered. Such delayed morphological maturation of the neurons is in agreement with the data showing that anticonvulsant drugs given during pregnancy slow down postnatal growth and mental development. At all stages examined, modifications, mainly concerning the distribution of glycogen and the increase in rough endoplasmic reticulum and free ribosomes, were also observed in hepatocytes. The examination of the placebo group revealed some signs of delayed maturation in Purkinje neurons at early histogenetic stages and some modifications of the normal pattern in the hepatocytes. The rôle of gastric tube in drug administration needs to be verified further.

Animals↗
PubMed1981

The effect of different fixatives on chromatin: cytochemical and ultrastructural approaches.

This study explores the effects of two types of fixative on chromatin. The first type (acrolein, glutaraldehyde) engenders a high degree of ultrastructural preservation. The other type are fixatives that are widely used in cytochemistry and cytogenetics (acetic acid, 3:1 by vol. methanol-acetic acid, methanol alone, formaldehyde). Lymphocytes of adult rats so-fixed in vitro were prepared for electron microscopy or microdensitometric evaluations of smears. Assessments were made of variations in their total protein, nuclear basic protein and DNA contents. DNA was determined both as Feulgen-positive material and by its binding of intercalating dyes (Methyl Green, specific for double-stranded polynucleotides). Our results showed that some fixatives break up the chromatin organization by acting on particular components of chromatin fibres. They can thus be considered to be destructive agents in situ. In addition, a revaluation of some aldehyde fixatives is proposed for both ultrastructural and cytochemical research.

Acrolein↗
PubMedDate not supplied

Ultrastructural analysis of testes from mice fed on genetically modified soybean.

We have considered the possible effects of a diet containing genetically modified (GM) soybean on mouse testis. This organ, in fact, is a well known bioindicator and it has already been utilized, for instance, to monitor pollution by heavy metals. In this preliminary study, we have focussed our attention on Sertoli cells, spermatogonia and spermatocytes by means of immunoelectron microscopy. Our results point out that the immunolabelling for Sm antigen, hnRNPs, SC35 and RNA Polymerase II is decreased in 2 and 5 month-old GM-fed mice, and is restored to normal at 8 months. In GM-fed mice of all ages considered, the number of perichromatin granules is higher and the nuclear pore density lower. Moreover, we found enlargements in the smooth endoplasmic reticulum in GM-fed mice Sertoli cells. A possible role played by traces of the herbicide to which the soybean is resistant is discussed.

Animals↗
PubMedDate not supplied

Reversibility of hepatocyte nuclear modifications in mice fed on genetically modified soybean.

In the literature, the reports on the effects of a genetically modified (GM) diet are scanty and heterogeneous; in particular, no direct evidence has so far been reported that GM food may affect human or animal health. Hepatocytes represent a suitable model for monitoring the effects of a GM diet, the liver potentially being a primary target. In a previous study, we demonstrated that some modifications occur in hepatocyte nuclei of mice fed on GM soybean. In order to elucidate whether such modifications can be reversed, in the present study, 3 months old mice fed on GM soybean since their weaning were submitted to a diet containing wild type soybean, for one month. In parallel, to investigate the influence of GM soybean on adult individuals, mice fed on wild type soybean were changed to a GM diet, for the same time. Using immunoelectron microscopy, we demonstrated that a one-month diet reversion can influence some nuclear features in adult mice, restoring typical characteristics of controls in GM-fed animals, and inducing in control mice modifications similar to those observed in animals fed on GM soybean from weaning. This suggests that the modifications related to GM soybean are potentially reversible, but also that some modifications are inducible in adult organisms in a short time.

Aging↗