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G Gazzanelli

Publications and source records attributed to G Gazzanelli.

70 records · Page 4Linked to original sources
PubMed1991

Evidence for a particulate location of ubiquitin conjugates and ubiquitin-conjugating enzymes in rabbit brain.

Conjugate ubiquitin was previously found in the nucleus, cytoplasm, and membranes of eukaryotic cells while the enzymes of the ubiquitin-conjugating system appear to be cytoplasmic. We have prepared the mitochondrial fraction from rabbit brain by discontinuous density gradient ultracentrifugation and by Western blotting, using a specific antibody against conjugate ubiquitin, showing that it contains ubiquitin conjugates in a very wide molecular weight range. Electron microscopy and measurement of specific enzyme markers show that this fraction not only contains mitochondria but also some endoplasmic reticulum vesicles. Immunostaining with anti-ubiquitin IgG followed by immunodecoration with colloidal gold particles provides evidence for the presence of conjugate ubiquitin both in mitochondria and in the endoplasmic reticulum. Furthermore, this "mitochondrial fraction" shows a pronounced ATP-dependent ability to conjugate 125I-ubiquitin into a number of endogenous proteins as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Addition of E1, E2, and E3, the enzymes of the ubiquitin conjugating system purified from rabbit reticulocytes, does not further increase this ubiquitination nor incorporate 125I-ubiquitin into additional protein bands. The same mitochondrial fraction is not able to carry out any ATP-dependent degradation of 125I-albumin; however, it contains an isopeptidase activity able to release the covalently incorporated 125I-ubiquitin and is also able to conjugate 125I-ubiquitin to exogenous proteins as oxidized RNase. By affinity chromatography on ubiquitin-agarose of fraction II of a crude Triton X-100 extract of the mitochondrial fraction, several proteins corresponding in Mr to the E1 and E2s enzymes were obtained. These proteins were also able to form specific ubiquitin-thiol ester bounds on sodium dodecyl sulfate-polyacrylamide gels and to support 125I-ubiquitin conjugation to oxidized RNase. Detergent fractionation of the mitochondrial fraction provided evidence for a possible localization of the ubiquitin conjugating activity in the mitochondrial external membrane and endoplasmic reticulum. The presence of an active ubiquitin protein conjugating system in mitochondria and endoplasmic reticulum may be related to the turnover of organelle proteins as well as to specific cell functions such as import of proteins into mitochondria and ubiquitination of externally oriented membrane-bound proteins.

Animals↗
PubMed1991

[Initial observations on the organization of the testis of Trisopterus minutus capelanus].

Testis of the Teleostean fish Trisopterus minutus capelanus has been examined to study the organization of the seminiferous tubules and the ultrastructural features of the germ cells. The testis is shown to be composed of seminiferous tubules full of cells: only few of them have just a very narrow lumen. Each tubule is divided by thin septa of connective tissue in zones containing homogeneous cells; such an organization is confirmed by ultrastructural images showing groups of synchronously developing germ cells. By morphological characterization of the germ cells found in each zone, 6 maturation stages have been identified. During spermiogenesis, a progressive shrinkage of germ cells and a nuclear chromatin condensation have been observed. Intercellular bridges, homogeneously dispersed granules of glycogen and groups of mitochondria associated with dense granular material have been described. Such features are present in the earlier stages of spermiogenesis and are retained until the later stages of spermatid differentiation. The spermatozoon shows a lack of acrosome as in many other teleosts previously studied.

Animals↗
PubMed1989

Methylazoxymethanol acetate (MAM ac) effects on the ontogenesis of the mouse neocortex.

Methylazoxymethanol acetate (MAM ac) injected prenatally affects development of neocortex in mice. Treatment at 13 days of gestation results in cortical hypoplasia that affects all the cortical layers except the first. Treatment at 15 days of gestation causes a statistically significant reduction in cell density in the superficial layers, while the deepest layers show no significant differences compared to the controls. Treatment at 17 days of gestation causes an alterated arrangement of the cortical layers, not easily separable since MAM ac in limiting perhaps glial cell proliferation, modifies the subsequent migration mechanisms. Fetal MAM exposure prevents proliferation of the various cortical laminae and there aren't subsequent compensatory phenomena.

Alkylating Agents↗
PubMed1988

Biological activity of chitosan: ultrastructural study.

Reparative processes are reconstructive phenomena in which cellular elements and extracellular matrix glycoproteins interact to build the injured tissue. Biomaterials can be used to improve or stimulate reconstruction. In the present experimental investigation, tissue repair induced by chitosan, an 86.8% deacetylated poly(GlcNAc), was monitored by morphological analysis. To evaluate its biological role, chitosan was positioned in contact with dura mater or was used as a dura mater substitute. This polysaccharide, having structural characteristics similar to glycosaminoglycans, seems to mimic their functional behaviour. The inductive and stimulatory activity of chitosan on connective tissue-rebuilding is clearly demonstrated, and it is suggested that chitosan could be considered a primer on which a normal tissue architecture is organized.

Animals↗
PubMed1985

Restricted replication of BK virus in human lymphocytes.

Human lymphocytes from either peripheral blood or continuous cultures (P3HR-1 cells) are able to support the replication of prototype polyomavirus BK (BKV) as well as its related strain BO15 virus (BO15V). Instead, human monocytes from peripheral blood, although able to bind and egulf BKV virions, do not express virus-specific antigens within a 50 day observation period. In the light of these results, a probable role is suggested for human mononuclear blood cells in the mechanism of natural infection by polyomaviruses.

Antigens, Viral↗
PubMed1985

An ultrastructural study of adipocyte precursors from epididymal fat pads of adult rats in culture.

It has been demonstrated that cells with poor or no lipid content, isolated from epididymal fat pads of young rats, develop fully into mature adipocytes in vitro. The ultrastructural feature of these cells during such a development have been studied recently. In the present work the electron microscopic aspects of similarly obtained cells from adult rats have been investigated. It has been found that no morphological differences are present in the cells immediately after isolation between young and adult rats. During culture the cells from both adult and young rats show the same maturative process, but in adult rats this process is generally slower and not homogeneous, suggesting the presence of two populations of adipocyte precursors. The former accumulate lipids quickly and have electron microscopic features very similar to those observed for young rat precursors, however maturation is still faster in the latter cells. The latter have electron microscopic aspects of less differentiated cells (some fibroblast-like features) during the first days of culture; however they show a similar development when longer culture periods are studied. These data suggest that the fibroblast-like cells seen after a period of time in culture probably represent an early stage of adipocyte precursor differentiation. Thus it is suggested that in adult mammals, there may be a population of adipocyte precursors present within the adipose tissue which upon stimulation by as yet unknown factors would develop fully into adipocytes.

Adipose Tissue↗
PubMed1985

Changes in the structure of somato-sensitive neurons in cat following retrograde uptake of HRP.

Neurons of cat cerebral cortex, area S1, labelled by retrograde transport of HRP, have been studied by electron microscopy; the animals were sacrificed 48 h after HRP injection. The cells studied are those in which the enzyme is found both in granular and in diffused form in the cytoplasm (diffuse-granular HRP neurons, DGN), or in diffused form in the cytoplasm (Golgi-like labelled neurons, GLN). The observations have shown that the certain recognition of DGN through electron microscopy, requires a comparison with a semithin section adjacent to the ultrathin section since the labelling granules are light-scattering in dark field. Instead the GLN are not light-scattering in dark field but are directly and unmistakably identifiable even by electron microscopy. The DGN are well preserved on the whole in all their organelles; the GLN show a highly damaged aspect in relation to both the Golgi apparatus and the smooth reticulum, to the cytoplasmic organelles and to the nucleus. Our hypothesis is that the latter neurons take on this appearance because of the combined action of: a) the peripheral mechanical lesions caused by the needle and b) the enormous amount of HRP that the cell is forced to take up (through these pathways) because of its lost integrity and because of the large quantity of marker around the axons. In conclusion intracellular HRP is identifiable by electron microscopy only when it is found in diffused form in the cytoplasm.

Animals↗
PubMed1983

[Ultrastructural observations of cat cortical neurons, labeled by the retrograde method, 8 days after injection of horseradish peroxidase].

The ultrastructural characteristics of cat's cortical neurons labeled by retrograde transport of horseradish peroxidase (HRP) have been studied; the cats were sacrificed 8 days after the injection of the enzyme. The aim of this study was principally to observe the evolution of neurons in which HRP had been assumed in diffused as well as in granular form - "diffuse-granular HRP neurons" -, or only in diffused form - "Golgi-like neurons" -. The results obtained show the scanty presence of diffuse-granular HRP cells and the contemporary presence of two populations of Golgi-like cells. In this study is underlined the difference between the observations conducted on specimens from cats sacrificed 48 hours or 8 days after the injection of the HRP.

Animals↗
PubMed1980

Particular aspects of seminiferous tubules at early puberty.

In the seminiferous tubules of patients at early puberty we have observed Sertoli cells showing an homogeneous aspect. In the cytoplasm of some of these elements dense bodies, which present a particular structure and shape, have been recognized. As far as the germ cells, we can find spermatogonia, spermatocytes and spermatids at various developmental stages. The presence of intercellular bridges among the germ cells and of binucleated spermatids with only one acrosome is a characteristic and fairly frequent finding in our specimens, obtained from normal patients.

Adolescent↗
PubMed1980

Further contributions about the use of the horseradish peroxidase (HRP) in the ultrastructural study of the olivary neurons of cat.

In order to recognize with E.M. the specific aspect of HRP in olivary neurons of cat, we have used newborn animals twenty-four, forty-eight hours old. The observation of these neurons has allowed us to see a numerous series of dense bodies various in size and density; these bodies have never been found in similar neurons from adult cats or from newborn cats not treated with HRP. These structures could represent the equivalent of an intraneuronal storage of enzyme, whose presence had been confirmed by O.M.

Animals↗
PubMed1979

The retrograde transport of horseradish peroxidase: problems in the interpretation of its ultrastructural aspects.

In this study we consider critically the use of HRP in research on the ultrastructure of the Central Nervous System. In fact, although controls make by optical microscope on semi-thin sections made us certain that some of the neurons were definitely marked with the enzyme, when the same specimen was observed by electron microscope, in no case was it possible for us to distinguish any particular aspect of the ultrastructural morphology of labelling within neurons.

Animals↗
PubMed1979

Ultrastructural aspects of Sertoli cells in infancy.

In the present study some aspects of Sertoli cells of testicular-biopsy specimens of children from 0 to 8 years old are examined. We can distinguish two main morphological situations. In the first one, Sertoli cells with monomorphic aspect can be seen; in the second can be shown Sertoli cells with various aspects. In this polimorphic situation we can distinguish three Sertoli cell types differing in cellular shape, cytoplasme electron-density and amount of RER and Golgi complex.

Biopsy↗
PubMedDate not supplied

[Some observations on the ultramicroscopic organization of specialized connections amongst nervous fibres in the inferior olivary nucleus of the cat].

Some observations have been made on inferior olive specimens in the adult cat, with aldehydes fixation techniques through vascular perfusion suitable for electron microscropy. The results made it possible to recognise five types of vesicular structures present in different nerve endings (differences either in type or in number). A possible topographic organization of synaptic connections, between the afferent endings and the dendritic structures of the inferior olive has been considered and it seems that on every large dendrite, nearer the cell body, there is a development of numerous connection. As such connections give a great deal of information to the dendrites with much much interaction it seems possible that there is modulation in the activation of the postsynaptic element. On the other hand, in the periphery of the dendritic branch, many thin branches seem to make contact with few and large endings; this leads us to believe that the regulations of the information is not based only on the afferences but mainly on distribution, origin and number of the postsynaptic elements. A study of the interdendritic connections and of tubulo-vesicular structures showed that their diameter and dense content have a similar morphology with the big granulated vesicles, visible in the terminals, or along the fibres or, frequently, in the Golgi apparatus.

Animals↗