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Biomedical subjects

G Donelli

Publications and source records attributed to G Donelli.

At least 91 records · Page 5Linked to original sources
PubMed1991

Gangliosides as binding sites in SA-11 rotavirus infection of LLC-MK2 cells.

The chemical nature of receptors involved in the attachment of simian rotavirus (SA-11) to a monkey kidney cell line (LLC-MK2) was investigated. Enzymic treatment of cells before virus infection indicated that membrane proteins and phospholipids are not involved in virus attachment, whereas sialic acid and galactose participate in the receptor structure to differing extents. Incubation of SA-11 with bovine brain gangliosides before infection strongly reduced its ability to bind to cell membranes. Similar experiments with individual purified gangliosides from bovine brain showed that virus infection was prevented by preincubation with GM1. Moreover, desialylated cells regained susceptibility to virus infection when coated with whole gangliosides or GM1 immediately after Clostridium perfringens neuraminidase treatment. The binding of SA-11 to whole gangliosides or GM1 was quantified by an ELISA procedure. The results suggest that gangliosides, mainly GM1, are part of the receptor structure for SA-11 of susceptible LLC-MK2 cells.

Animals↗
PubMed1991

Antimicrobial resistance and production of toxins in Escherichia coli strains from wild ruminants and the alpine marmot.

Escherichia coli strains isolated from 81 fecal samples from red deer (Cervus elaphus), roe deer (Capreoulus capreoulus), chamois (Rupicapra rupicapra) and alpine marmot (Marmota marmota) living in the Stelvio National Park, Italy, were examined for antimicrobial resistance and production of toxic factors. Direct plating of specimens on media containing antimicrobial drugs allowed us to isolate resistant strains of E. coli from 10 of 59 (17%) specimens examined by this technique. Nine of 31 specimens from red deer (29%) contained resistant strains. Different animals were likely colonized by the same resistant strain of E. coli. Conjugative R plasmids were found in four strains isolated from the marmot, roe deer and chamois. A strain from red deer produced heat-stable enterotoxin and another strain produced both hemolysin and cytotoxic necrotizing factor. A marmot isolate produced hemolysin alone. No strains were found to produce heat-labile enterotoxin or verotoxins.

Animals↗
PubMed1991

Capsule-like structures in Clostridium difficile strains.

Fourteen strains of Clostridium difficile, previously characterized by SDS-PAGE, were examined for the presence of surface structures. None of the strains were fimbriated but, when grown in the presence of glucose, all exhibited a thin ruthenium red-positive layer. Two strains, belonging to different electrophoretic groups, were also observed after treatment with homologous and heterologous antisera. The strain belonging to the electrophoretic group 2, usually associated with the disease, showed a 30-80nm thick capsule in ultrathin sections. The strains belonging to group 5, mainly observed in isolates from healthy children, exhibited a thinner polysaccharide layer (10-20 nm). No stabilization was observed when these strains were treated with heterologous antisera. This capsule-like material did not seem to be associated with adhesive properties of C. difficile strains.

Cell Wall↗
PubMed1991

[Principles and application possibilities of cryoultramicrotomy].

This paper reviews the technical aspects of cryoultramicrotomy. The key preparation steps in the technique, namely freezing, sectioning, thawing, and staining are analysed. The application of this method to immunocytochemistry and analytical electron microscopy are discussed with respect to the present possibilities and problems.

Cryoultramicrotomy↗
PubMed1991

[A choledochal diverticulum. A case report].

Due to the rarity of choledochal cystic dilatation, the authors report a clinical case of common bile duct diverticulum. This diverticulum was histologically composed of gastric ectopic mucosa (pyloric type) and it clinically caused chronic abdominal pain (in a young woman). The authors analyse the literature of the above pathology.

Adult↗
PubMed1991

Suicide behavior of target cells after binding with natural killer cells.

Human natural killer (NK) cell activity seems to be related to the integrity and function of the cytoskeletal apparatus. It has been hypothesized that microfilaments and microtubules play a pivotal role. In particular, the binding of the NK cell to the target cell requires microfilament integrity, and the lysis of bound targets seems to depend on microtubule assembly. We focused on the changes occurring in cytoskeletal elements and surface structures of NK cells and of target cells highly sensitive to NK activity (K562). Our observations, performed by fluorescence and scanning electron microscopy, besides confirming a rearrangement of the cytoskeletal apparatus in the effector cell, provide evidence that target cell cytoskeletal elements are involved in NK cell function. In K562 cells, after binding with NK cells, there is marginal rearrangement of actin and polarization of tubulin and vimentin in the contact regions, accompanied by modification of surface structures. These findings suggest that the target cell plays an active role in its own death by participating in the formation of an extended area of intimate contact with the killer cell. In addition, they lend credence to the surprising proposal that NK cells may induce a suicide mechanism in target cells.

Cell Survival↗
PubMed1990

Surface blebbing and cytoskeletal changes induced in vitro by toxin B from Clostridium difficile: an immunochemical and ultrastructural study.

Clostridium difficile toxin B is a powerful cytopathic agent without enterotoxic activity which is believed to be involved in the pathogenesis of pseudomembranous colitis. Up until today, the mechanisms of toxin B cytotoxicity have not been elucidated. The results of in vitro studies performed on different cell lines by means of immunocytochemical and ultrastructural methods are reported here. Low doses (0.15 ng/ml) of toxin B cause cell rounding and arborization. Higher doses (up to 15 micrograms/ml) induce cell rounding and appearance of numerous surface protrusions with blister or bulb-like features. These "blebs" belong to the potocytotic type, the bleb matrix being devoid of cytoplasmic organelles and filled with ribosomes only. Furthermore, a peculiar role of cytoskeletal apparatus in this phenomenon has been detected. In fact, morphological rearrangement occurs in cytoskeletal elements, mainly represented by the presence, in the blebs, of tubulin and of the actin-binding proteins alpha-actinin, filamin, and calmodulin, while actin and intermediate filaments, keratin and vimentin, appear to be absent. Moreover, beta 2-microglobulin, considered as a surface protein marker, seems to undergo changes in its expression, being absent over the blebbing surface. The results of this study may support the view that C. difficile toxin B affects one or more subcellular components that regulate the structure and function of the actin cytoskeleton.

Bacterial Proteins↗
PubMed1990

In vitro effect of synthetic flavanoids on astrovirus infection.

In this study we investigated the activity of halogeno-, cyano- and amidino-isoflavenes, isoflavans and flavans on the multiplication of human astroviruses. These are naked small round viruses which have been recognized as causative agents of human gastroenteritis, and whose capsid proteins are similar to those of picornaviruses. Although all drugs tested caused a dose-dependent reduction of viral antigen synthesis as monitored by immunofluorescence, the chloro derivatives were the most effective.

Animals↗
PubMed1990

On the mechanism of cell internalization of chrysotile fibers: an immunocytochemical and ultrastructural study.

Human breast carcinoma cells (CG5) and human laryngeal carcinoma cells (HEp-2) were exposed to 10 and 50 micrograms/ml of small (about 5 microns) chrysotile asbestos fibers. Morphological and ultrastructural changes were evaluated by means of immunocytochemistry and by scanning and transmission electron microscopy. Our attention was focused on the mechanisms of cell internalization and on transport of chrysotile fibers. The fibers appeared to penetrate the cell cytoplasm and to be translocated in proximity of the nucleus. Small chrysotile fibers could also be found inside the nucleus of interphase cells. Involvement of the main cytoskeletal components, i.e., microfilaments, intermediate filaments, and microtubules, in the cytotoxicity of chrysotile fibers was also evaluated. Our findings suggest that after fiber penetration, a rearrangement of the cytoskeletal apparatus occurs. It has also been observed that small fibers remain associated with the cytoskeletal framework, which can thus play a role in asbestos intracytoplasmic translocation in epithelial cells. Furthermore, after the cell has completely recovered its morphology, fiber internalization ultimately seems to lead to the formation of giant multinucleated cells. These data could be indicative of an interaction occurring between asbestos fibers and the normal mitotic process. The disturbance of the cell cytoskeleton and the close morphologic contact between asbestos fibers and the cell's nuclear region may be of importance in explaining the well-known carcinogenic effects of asbestos mineral fibers.

Asbestos↗
PubMed1990

Interaction of Clostridium difficile toxin A with cultured cells: cytoskeletal changes and nuclear polarization.

Experiments done on in vitro-cultured cells exposed to toxin A from C. difficile showed a series of cytopathologic changes leading to cell retraction and rounding accompanied by the marginalization of the nucleus, which localized at one pole of the cell. Cytoskeleton appeared to be strongly involved in such modifications. In particular, the microfilament system seemed to be involved in cell retraction, while microtubule network integrity and function seemed to be necessary for the nuclear displacement. The carboxylic ionophore monensin completely blocked the cytopathic effect when added with the toxin. The serine protease inhibitor chymostatin appeared to be protective also upon addition long after the end of the binding step. The Ca2(+)-dependent cytosolic protease inhibitors antipain and leupeptin were uneffective in protecting cells. Thus, our results suggest the involvement of an acidic compartment and the action of a serine protease in toxin A-induced cytopathic effect.

Animals↗
PubMed1990

Cellular mechanisms of lymphocyte-mediated lysis of tumor cells.

Both branches, humoral and cellular, of the immune response have specialized mechanisms to lyse tumor cells, virus-infected cells and other targets. The effector components of the humoral response are antibodies and complement, while cytotoxic T lymphocytes (CTL) and natural killer (NK) cells are among the potent effector agents of the cell-mediated immune response. The past few years have witnessed remarkable progress in defining the effector molecules and mechanisms involved in lymphocyte-mediated killing. The recognition of target cells by CTL is antigen specific and restricted through the major histocompatibility complex (MHC). The molecular structure involved in the recognition function is the T cell receptor (TCR), associated with CD3 polypeptides. Conversely, the activity of NK cells in non antigen specific and non MHC restricted. Several surface molecules of cytotoxic lymphocytes have been identified as adhesion-mediating structures. A particular role seems to be played by a family of molecules named lymphocyte function-associated antigens (LFA) and by CD2, CD4 and CD8 antigens. Once the binding between effector and target cell has occurred, a cascade of events can be triggered leading the killer lymphocyte to deliver the lethal hit against the target cell. At least two categories of cytolytic molecules are produced by CTL and NK cells. Perforin is a protein stored in the cytoplasmic granules which forms pores in the plasma membrane of target cell leading to osmotic lysis. The other category of cytolytic factors is the group of soluble mediators which includes lymphotoxin (LT), tumor necrosis factor (TNF) and NK cytotoxic factor (NKCF). Their exact mechanism of action is presently unclear. Several cellular components are involved in the cytolytic mechanism. In particular, the cytoplasmic granules which, upon activation, release a number of cytotoxic factors by directed exocytosis and the cytoskeletal components which, modifying their organization, participate in the binding and killing processes. A growing body of evidence has recently supplied proof that target cells may play an active role in their own lysis supporting the challenging opinion of an induced suicide mechanism.

Animals↗
PubMed1990

Ultrastructural immunolocalization of laminin and fibronectin in human large intestinal mucosa.

The ultrastructural expression of laminin and fibronectin was studied in human colonic mucosa with a pre-embedding immunoperoxidase technique. Both antigens were present in epithelial basement membrane. The lamina densa was uniformly and homogeneously immunostained by both fibronectin and laminin, while the lamina rara showed discrete, positive sites occasionally connecting the lamina densa with the epithelial plasma membrane. In the lamina reticularis, fibronectin was diffusely positive, while laminin showed a discontinuous positivity only in the uppermost region in vicinity of the lamina densa. Collagen fibrils were regularly decorated by fibronectin-positive material. Basement membranes in the capillary wall showed a similar pattern of reactivity both with laminin and fibronectin. These results point out that laminin as well as fibronectin are integral components of intestinal mucosa basement membranes.

Basement Membrane↗
PubMed1989

Haemagglutination and surface structures in strains of Clostridium spiroforme.

Five strains of Clostridium spiroforme were examined for their surface properties. All strains were able to agglutinate human erythrocytes. Electron microscopy showed a ruthenium red-positive capsule mediating the attachment of bacteria to erythrocytes. Two strains, showing the lowest degree of haemagglutination, exhibited an additional external layer of filamentous structures, possibly interfering with the agglutinating activity. In spite of their agglutinating ability, the C. spiroforme strains did not show surface hydrophobicity, thus suggesting the possible existence of a new type of clostridial adhesin.

Animals↗
PubMed1989

An SEM analysis of the interaction between lymphokine-activated killer cells and tumor targets.

The interaction between lymphokine-activated killer (LAK) cells and two types of target cells with different susceptibility to natural killer (NK) activity was investigated by scanning electron microscopy (SEM). In NK-susceptible tumor cells (K562) a different mode of conjugation with the effector was observed as compared with NK-resistant targets (THP-1-0). In LAK-K562 pairs, the contact region was characterized by the presence of long microvilli, blebs and ruffled membranes forming an intertwined and interdigitated binding site. Conversely, when LAK cells were conjugated with THP-1-0 cells, the surface structures of the target cell did not undergo significant modification and the interacting cells did not appear to establish close contact. In addition, cell lysis of the sensitive target was often characterized by plasma membrane blebbing, leading to cell death. In contrast, in the low percentage of resistant targets which underwent lysis after conjugation, cell death always occurred without formation of bulb- or bleb-like structures.

Cytotoxicity, Immunologic↗
PubMed1989

Ultrastructural identification of sulphated glycoconjugates in the Golgi apparatus in human colonic absorptive cells.

The subcellular localization of sulphated glycoconjugates was determined at the ultrastructural level by using the high iron diamine (HID) technique for sulphate groups in the absorptive cells of human colonic mucosa. Stained material was observed on the apical plasma membrane, in intracytoplasmic vesicles and in the Golgi complex. In this organelle, the last two or three cisternae of the trans side and the trans-Golgi network (TGN) were labelled, as well as a variable number of coated and noncoated vesicles facing the trans side and surrounding trans-Golgi network. These findings point to the trans side of the Golgi apparatus and trans-Golgi network as the subcompartments functionally involved in the sulphation of glycoconjugates.

Chlorides↗
PubMed1989

Morphological changes in HAV-infected Frp/3 cells and immunolocalization of HAAg.

Electron and immunoelectron microscopic studies were carried out on HAV-infected Frp/3 cells. The infection led to a distinctive cytopathic effect (CPE) arising on day 3 up to the complete detachment of monolayers on day 7. Infected cells exhibited progressive modifications, beginning from the formation of long helical polyribosomes. Subsequently, hypertrophy, cisternal dilatation and degranulation of the RER could be observed. Furthermore, the formation of concentric membranous bodies (CMB), large myelin-like structures and annulate lamellae could be revealed at later times of infection. 24-27 nm virus-like particles were observed within cytoplasmic vesicles or outside extensively degenerated cells. Indirect immunoperoxidase staining were used to localize HAV antigen (HAAg) in thin sectioned infected Frp/3 cells. Vesicular inclusion bodies, often seen to contain electron-lucent particles, resulted darkly stained as well as tracts of the RER and myelin-like structures. Negatively stained preparations from cell lysates revealed small clusters of HAV particles which sometimes appeared to be still associated with residual membrane fragments. Our findings seem to suggest that HAV replication occurs in close association with cytoplasmic membranes and a direct involvement of the RER seems to be demonstrated.

Antigens, Viral↗