Gianfranco Donelli | Fondazione Santa Lucia (original) (raw)
Papers by Gianfranco Donelli
Journal of Biomedical Materials Research Part A, 2007
A series of DNA aptamers bearing triazole internucleotide linkages that bind to thrombin was synt... more A series of DNA aptamers bearing triazole internucleotide linkages that bind to thrombin was synthesized. The novel aptamers are structurally analogous to the well-known thrombin-inhibiting G-quadruplexes TBA15 and TBA31. The secondary structure stability, binding affinity for thrombin and anticoagulant effects of the triazole-modified aptamers were measured. A modification in the central loop of the aptamer quadruplex resulted in increased nuclease resistance and an inhibition efficiency similar to that of TBA15. The likely aptamer-thrombin binding mode was determined by molecular dynamics simulations. Due to their relatively high activity and the increased resistance to nuclease digestion imparted by the triazole internucleotide linkages, the novel aptamers are a promising alternative to known DNA-based anticoagulant agents.
Pathogens, Sep 5, 2014
The Gram-negative opportunistic pathogen, Klebsiella pneumoniae, is responsible for causing a spe... more The Gram-negative opportunistic pathogen, Klebsiella pneumoniae, is responsible for causing a spectrum of community-acquired and nosocomial infections and typically infects patients with indwelling medical devices, especially urinary catheters, on which this microorganism is able to grow as a biofilm. The increasingly frequent acquisition of antibiotic resistance by K. pneumoniae strains has given rise to a global spread of this multidrug-resistant pathogen, mostly at the hospital level. This scenario is exacerbated when it is noted that intrinsic resistance to antimicrobial agents dramatically increases when K. pneumoniae strains grow as a biofilm. This review will summarize the findings about the antibiotic resistance related to biofilm formation in K. pneumoniae.
Giornale di malattie infettive e parassitarie, 1989
Advances in Experimental Medicine and Biology, 2016
The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Oral Diseases, Oct 31, 2013
ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the ... more ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the opportunistic anaerobe Prevotella melaninogenica (PM1), a well‐known causative agent of periodontitis.Materials and MethodsThe inhibitory effect of Lactobacillus CD2 on Prevotella PM1 biofilm was assessed both by exposing the anaerobe to the supernatant of the probiotic strain and by growing the two strains to obtain single or mixed biofilms. The inhibitory effect of CD2 on PM1 was also checked by the agar overlay method.ResultsThe development of PM1 biofilm was strongly affected (56% decrease in OD value) by the CD2 supernatant after 96 h. A dose‐dependent biofilm reduction was also observed at 1/10 and 1/100 dilutions of supernatant. Confocal microscopy on the mixed biofilms revealed the ability of CD2 to prevail on PM1, greatly reducing the biofilm of the latter.ConclusionsIt has been hypothesized a multifactorial nature of the inhibition mechanism, the strong adherence ability of CD2 strain together with the released metabolites presumably contributing to the reduction in the PM1 biofilm detected by confocal microscopy.
Oral Diseases, Oct 31, 2013
ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the ... more ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the opportunistic anaerobe Prevotella melaninogenica (PM1), a well‐known causative agent of periodontitis.Materials and MethodsThe inhibitory effect of Lactobacillus CD2 on Prevotella PM1 biofilm was assessed both by exposing the anaerobe to the supernatant of the probiotic strain and by growing the two strains to obtain single or mixed biofilms. The inhibitory effect of CD2 on PM1 was also checked by the agar overlay method.ResultsThe development of PM1 biofilm was strongly affected (56% decrease in OD value) by the CD2 supernatant after 96 h. A dose‐dependent biofilm reduction was also observed at 1/10 and 1/100 dilutions of supernatant. Confocal microscopy on the mixed biofilms revealed the ability of CD2 to prevail on PM1, greatly reducing the biofilm of the latter.ConclusionsIt has been hypothesized a multifactorial nature of the inhibition mechanism, the strong adherence ability of CD2 strain together with the released metabolites presumably contributing to the reduction in the PM1 biofilm detected by confocal microscopy.
Journal of Molecular Biology, Nov 1, 1972
Abstract With the help of diffraction and optical image reconstruction we have begun to study the... more Abstract With the help of diffraction and optical image reconstruction we have begun to study the arrangement of the protein subunits in the G bacteriophage of Bacillus megatherium . The arrangement of the structural subunits in the tail sheath was completely defined for both the extended and the contracted states. It is basically the same as that observed for the T-even phages, despite their different general architecture. With regard to the process of contraction of the sheath, an unstable intermediate state was observed. This corresponds to a rearrangement of the chemical bonds between the protein subunits before the complete mechanical contraction of the sheath. The process of contraction itself was studied and a simple model proposed.
Infection and Immunity, Jul 1, 1990
Experiments done on in vitro-cultured cells exposed to toxin A from C. difficile showed a series ... more 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 microfflament 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.
Microbial Ecology in Health and Disease, Jun 1, 2000
This review focuses on the main virulence factors characterizing Helicobacter pylori strains. Sev... more This review focuses on the main virulence factors characterizing Helicobacter pylori strains. Several pathogenic factors are important for the establishment and maintenance of H. pylori infection. Among those present in all isolates are the production of urease and phospholipases, the presence of flagella, the ability to attract neutrophils, the expression of ice A gene and a number of adhesins that ensure tissue-specific colonization. In addition, a subset of H. pylori strains is characterized by: i) a potent toxin (VacA) able to cause vacuolar degeneration of target cells by interfering with intracellular membrane fusion; and ii) the pathogenicity island (PAI), named Cag PAI that encodes for a putative secretory mechanism in which the cag A gene encodes an immunodominant antigen that is associated with cytotoxin expression.
Journal of Biological Chemistry, Aug 1, 1997
Cytotoxic necrotizing factor 1 (CNF1), a 110-kDa protein toxin from pathogenic Escherichia coli i... more Cytotoxic necrotizing factor 1 (CNF1), a 110-kDa protein toxin from pathogenic Escherichia coli induces actin reorganization into stress fibers and retraction fibers in human epithelial cultured cells allowing them to spread. CNF1 is acting in the cytosol since microinjection of the toxin into HEp-2 cells mimics the effects of the externally applied CNF1. Incubation in vitro of CNF1 with recombinant small GTPases induces a modification of Rho (but not of Rac, Cdc42, Ras, or Rab6) as demonstrated by a discrete increase in the apparent molecular weight of the molecule. Preincubation of cells with CNF1 impairs the cytotoxic effects of Clostridium difficile toxin B, which inactivates Rho but not those of Clostridium sordellii LT toxin, which inhibits Ras and Rac. As shown for Rho-GTP, CNF1 activates, in a timeand dose-dependent manner, a cytoskeleton-associated phosphatidylinositol 4-phosphate 5-kinase. However, neither the phosphatidylinositol 4,5-bisphosphate (PIP 2) nor the phosphatidylinositol 3,4-bisphosphate (PI 3,4-P 2) or 3,4,5-trisphosphate (PIP 3) cellular content were found increased in CNF1 treated HEp-2 cells. Cellular effects of CNF1 were not blocked by LY294002, a stable inhibitor of the phosphoinositide 3-kinase. Incubation of HEp-2 cells with CNF1 induces relocalization of myosin 2 in stress fibers but not in retraction fibers. Altogether, our data indicate that CNF1 is a toxin that selectively activates the Rho GTP-binding protein, thus inducing contractility and cell spreading. Actin filaments are common targets for several bacterial protein toxins that exert their activities by either directly or indirectly breaking the actin cytoskeleton. Toxins such as Clostridium botulinum C2 or iota from Clostridium perfringens directly modify globular actin by ADP-ribosylating arginine 177 (1). Others toxins, such as C. botulinum C and D exoenzyme C3, or toxins A and B from Clostridium difficile (CdA and CdB, respectively) 1 indirectly disrupt F-actin structures by in
Springer eBooks, 2016
The Advances in Microbiology, Infectious Diseases and Public Health Series will provide microbiol... more The Advances in Microbiology, Infectious Diseases and Public Health Series will provide microbiologists, hygienists, epidemiologists and infectious diseases specialists with well-choosen contributed volumes containing updated information in the areas of basic and applied microbiology involving relevant issues for public health, including bacterial, fungal and parasitic infections, zoonoses and anthropozoonoses, environmental and food microbiology. The increasing threat of the multidrug-resistant microorganisms and the related host immune response, the new strategies for the treatment of biofilm-based, acute and chronic microbial infections, as well as the development of new vaccines and more efficacious antimicrobial drugs to prevent and treat human and animal infections will be also reviewed in this series in the light of the most recent achievements in these fields. Special attention will be devoted to the fast diffusion worldwide of the new findings of the most advanced translational researches carried out in the different fields of microbiological sciences, with the aim to promote a prompt validation and transfer at clinical level of the most promising experimental results. The book series publishes review and original research contributions, short (data) reports as well as guest edited thematic book volumes. All contributions will be published online first and collected in (thematic) book volumes. There are no publication costs. This series is a subseries of Advances in Experimental Medicine and Biology 2014 Impact Factor: 1.958 Advances in Experimental Medicine and Biology has been publishing exceptional works in the field for over 30 years and is indexed in Medline, Scopus, EMBASE, BIOSIS, Biological Abstracts, CSA, Biological Sciences and Living Resources (ASFA-1), and Biological Sciences.
Giornale di malattie infettive e parassitarie, 1981
Veterinary Record, Sep 25, 1993
Search by Subject Search using Medical Subject Headings (< b> MeSH</b>... more Search by Subject Search using Medical Subject Headings (< b> MeSH</b>), a controlled vocabulary for indexing life sciences content.< br/> Note that some records do not have MeSH. These include Patents and the latest PubMed and PubMed Central records.
Journal of urology & nephrology studies, May 1, 2023
Micron, 1973
ABSTRACT The shape of the capsid of phage G, active against B. megatherium, has been studied by e... more ABSTRACT The shape of the capsid of phage G, active against B. megatherium, has been studied by electron microscopy using a variety of approaches including negative staining of whole particles, examination of stereoscopic micrographs, shadowing, observations on capsids devoid of their DNA content ('ghosts'), short and prolonged fixation and the use of single and serial ultra-thin sections. The results were conflicting. With negative staining the appearance of the capsid was not consistent with an icosahedral shape but could be related to that of an octahedron. The shape of the capsid in 'ghost' preparations was definitely octahedral. However, after fixing for 1h or longer and shadowing, the capsids were clearly icosahedral in shape with their sides equal to about half the length of those of the octahedron seen by negative staining. The same results were obtained by the thin sectioning technique. From a study of the two types of geometrical figures it was found that an octahedral container can be transformed into an icosahedral one with sides of half the original length if it is folded inwards on itself at 6 consecutive points. If this type of effect occurred during the preparative procedure it would account for the two apparently conflicting appearances of the capsid. Such an effect would involve a marked change or 'jump' through an intermediate unstable form. While it would reconcile the different results it is emphasized that such an interpretation is essentially speculative. To illustrate the complexities of the problem, an interesting geometrical exercise is presented in the Appendix.
Toxicon, 1989
A comparative study on the effects of toxin A and toxin B from Clostridium difficile on HEp-2 cel... more A comparative study on the effects of toxin A and toxin B from Clostridium difficile on HEp-2 cells was carried out. Both toxins caused cell retraction and rounding and seemed to exert their effect on cell morphology via a rearrangement of actin and alpha-actinin microfilaments. Such a rearrangement occurred at an early stage, when no change in microtubular and cytokeratin systems was detectable. Nevertheless, several structural modifications accompanying the cytopathological process induced by toxins A and B appeared to be quite different. In particular, toxin B-treated cells showed an arborized phenotype as a result of cell retraction and rounding, whereas toxin A caused cell rounding without arborization. Moreover, nuclear polarization following disorganization of the microfilament system was only observed in toxin A-treated cells. The structural features distinguishing intoxication processes induced by the two toxins probably reflect a different mechanism of action and suggest the presence of a distinct subcellular component as a primary target for each toxin.
Infection and Immunity, Mar 1, 1999
Vibrio parahaemolyticus is a marine bacterium known to be the leading cause of seafood gastroente... more Vibrio parahaemolyticus is a marine bacterium known to be the leading cause of seafood gastroenteritis worldwide. A 46-kDa homodimer protein secreted by this microorganism, the thermostable direct hemolysin (TDH), is considered a major virulence factor involved in bacterial pathogenesis since a high percentage of strains of clinical origin are positive for TDH production. TDH is a pore-forming toxin, and its most extensively studied effect is the ability to cause hemolysis of erythrocytes from different mammalian species. Moreover, TDH induces in a variety of cells cytotoxic effects consisting mainly of cell degeneration which often leads to loss of viability. In this work, we examined the cellular changes induced by TDH in monolayers of IEC-6 cells (derived from the rat crypt small intestine), which represent a useful cell model for studying toxins from enteric bacteria. In experimental conditions allowing cell survival, TDH induces a rapid transient increase in intracellular calcium as well as a significant though reversible decreased rate of progression through the cell cycle. The morphological changes seem to be dependent on the organization of the microtubular network, which appears to be the preferential cytoskeletal element involved in the cellular response to the toxin.
Journal of Biomedical Materials Research Part A, 2007
A series of DNA aptamers bearing triazole internucleotide linkages that bind to thrombin was synt... more A series of DNA aptamers bearing triazole internucleotide linkages that bind to thrombin was synthesized. The novel aptamers are structurally analogous to the well-known thrombin-inhibiting G-quadruplexes TBA15 and TBA31. The secondary structure stability, binding affinity for thrombin and anticoagulant effects of the triazole-modified aptamers were measured. A modification in the central loop of the aptamer quadruplex resulted in increased nuclease resistance and an inhibition efficiency similar to that of TBA15. The likely aptamer-thrombin binding mode was determined by molecular dynamics simulations. Due to their relatively high activity and the increased resistance to nuclease digestion imparted by the triazole internucleotide linkages, the novel aptamers are a promising alternative to known DNA-based anticoagulant agents.
Pathogens, Sep 5, 2014
The Gram-negative opportunistic pathogen, Klebsiella pneumoniae, is responsible for causing a spe... more The Gram-negative opportunistic pathogen, Klebsiella pneumoniae, is responsible for causing a spectrum of community-acquired and nosocomial infections and typically infects patients with indwelling medical devices, especially urinary catheters, on which this microorganism is able to grow as a biofilm. The increasingly frequent acquisition of antibiotic resistance by K. pneumoniae strains has given rise to a global spread of this multidrug-resistant pathogen, mostly at the hospital level. This scenario is exacerbated when it is noted that intrinsic resistance to antimicrobial agents dramatically increases when K. pneumoniae strains grow as a biofilm. This review will summarize the findings about the antibiotic resistance related to biofilm formation in K. pneumoniae.
Giornale di malattie infettive e parassitarie, 1989
Advances in Experimental Medicine and Biology, 2016
The use of general descriptive names, registered names, trademarks, service marks, etc. in this p... more The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.
Oral Diseases, Oct 31, 2013
ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the ... more ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the opportunistic anaerobe Prevotella melaninogenica (PM1), a well‐known causative agent of periodontitis.Materials and MethodsThe inhibitory effect of Lactobacillus CD2 on Prevotella PM1 biofilm was assessed both by exposing the anaerobe to the supernatant of the probiotic strain and by growing the two strains to obtain single or mixed biofilms. The inhibitory effect of CD2 on PM1 was also checked by the agar overlay method.ResultsThe development of PM1 biofilm was strongly affected (56% decrease in OD value) by the CD2 supernatant after 96 h. A dose‐dependent biofilm reduction was also observed at 1/10 and 1/100 dilutions of supernatant. Confocal microscopy on the mixed biofilms revealed the ability of CD2 to prevail on PM1, greatly reducing the biofilm of the latter.ConclusionsIt has been hypothesized a multifactorial nature of the inhibition mechanism, the strong adherence ability of CD2 strain together with the released metabolites presumably contributing to the reduction in the PM1 biofilm detected by confocal microscopy.
Oral Diseases, Oct 31, 2013
ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the ... more ObjectiveTo evaluate the ability of the probiotic strain Lactobacillus brevis CD2 to inhibit the opportunistic anaerobe Prevotella melaninogenica (PM1), a well‐known causative agent of periodontitis.Materials and MethodsThe inhibitory effect of Lactobacillus CD2 on Prevotella PM1 biofilm was assessed both by exposing the anaerobe to the supernatant of the probiotic strain and by growing the two strains to obtain single or mixed biofilms. The inhibitory effect of CD2 on PM1 was also checked by the agar overlay method.ResultsThe development of PM1 biofilm was strongly affected (56% decrease in OD value) by the CD2 supernatant after 96 h. A dose‐dependent biofilm reduction was also observed at 1/10 and 1/100 dilutions of supernatant. Confocal microscopy on the mixed biofilms revealed the ability of CD2 to prevail on PM1, greatly reducing the biofilm of the latter.ConclusionsIt has been hypothesized a multifactorial nature of the inhibition mechanism, the strong adherence ability of CD2 strain together with the released metabolites presumably contributing to the reduction in the PM1 biofilm detected by confocal microscopy.
Journal of Molecular Biology, Nov 1, 1972
Abstract With the help of diffraction and optical image reconstruction we have begun to study the... more Abstract With the help of diffraction and optical image reconstruction we have begun to study the arrangement of the protein subunits in the G bacteriophage of Bacillus megatherium . The arrangement of the structural subunits in the tail sheath was completely defined for both the extended and the contracted states. It is basically the same as that observed for the T-even phages, despite their different general architecture. With regard to the process of contraction of the sheath, an unstable intermediate state was observed. This corresponds to a rearrangement of the chemical bonds between the protein subunits before the complete mechanical contraction of the sheath. The process of contraction itself was studied and a simple model proposed.
Infection and Immunity, Jul 1, 1990
Experiments done on in vitro-cultured cells exposed to toxin A from C. difficile showed a series ... more 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 microfflament 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.
Microbial Ecology in Health and Disease, Jun 1, 2000
This review focuses on the main virulence factors characterizing Helicobacter pylori strains. Sev... more This review focuses on the main virulence factors characterizing Helicobacter pylori strains. Several pathogenic factors are important for the establishment and maintenance of H. pylori infection. Among those present in all isolates are the production of urease and phospholipases, the presence of flagella, the ability to attract neutrophils, the expression of ice A gene and a number of adhesins that ensure tissue-specific colonization. In addition, a subset of H. pylori strains is characterized by: i) a potent toxin (VacA) able to cause vacuolar degeneration of target cells by interfering with intracellular membrane fusion; and ii) the pathogenicity island (PAI), named Cag PAI that encodes for a putative secretory mechanism in which the cag A gene encodes an immunodominant antigen that is associated with cytotoxin expression.
Journal of Biological Chemistry, Aug 1, 1997
Cytotoxic necrotizing factor 1 (CNF1), a 110-kDa protein toxin from pathogenic Escherichia coli i... more Cytotoxic necrotizing factor 1 (CNF1), a 110-kDa protein toxin from pathogenic Escherichia coli induces actin reorganization into stress fibers and retraction fibers in human epithelial cultured cells allowing them to spread. CNF1 is acting in the cytosol since microinjection of the toxin into HEp-2 cells mimics the effects of the externally applied CNF1. Incubation in vitro of CNF1 with recombinant small GTPases induces a modification of Rho (but not of Rac, Cdc42, Ras, or Rab6) as demonstrated by a discrete increase in the apparent molecular weight of the molecule. Preincubation of cells with CNF1 impairs the cytotoxic effects of Clostridium difficile toxin B, which inactivates Rho but not those of Clostridium sordellii LT toxin, which inhibits Ras and Rac. As shown for Rho-GTP, CNF1 activates, in a timeand dose-dependent manner, a cytoskeleton-associated phosphatidylinositol 4-phosphate 5-kinase. However, neither the phosphatidylinositol 4,5-bisphosphate (PIP 2) nor the phosphatidylinositol 3,4-bisphosphate (PI 3,4-P 2) or 3,4,5-trisphosphate (PIP 3) cellular content were found increased in CNF1 treated HEp-2 cells. Cellular effects of CNF1 were not blocked by LY294002, a stable inhibitor of the phosphoinositide 3-kinase. Incubation of HEp-2 cells with CNF1 induces relocalization of myosin 2 in stress fibers but not in retraction fibers. Altogether, our data indicate that CNF1 is a toxin that selectively activates the Rho GTP-binding protein, thus inducing contractility and cell spreading. Actin filaments are common targets for several bacterial protein toxins that exert their activities by either directly or indirectly breaking the actin cytoskeleton. Toxins such as Clostridium botulinum C2 or iota from Clostridium perfringens directly modify globular actin by ADP-ribosylating arginine 177 (1). Others toxins, such as C. botulinum C and D exoenzyme C3, or toxins A and B from Clostridium difficile (CdA and CdB, respectively) 1 indirectly disrupt F-actin structures by in
Springer eBooks, 2016
The Advances in Microbiology, Infectious Diseases and Public Health Series will provide microbiol... more The Advances in Microbiology, Infectious Diseases and Public Health Series will provide microbiologists, hygienists, epidemiologists and infectious diseases specialists with well-choosen contributed volumes containing updated information in the areas of basic and applied microbiology involving relevant issues for public health, including bacterial, fungal and parasitic infections, zoonoses and anthropozoonoses, environmental and food microbiology. The increasing threat of the multidrug-resistant microorganisms and the related host immune response, the new strategies for the treatment of biofilm-based, acute and chronic microbial infections, as well as the development of new vaccines and more efficacious antimicrobial drugs to prevent and treat human and animal infections will be also reviewed in this series in the light of the most recent achievements in these fields. Special attention will be devoted to the fast diffusion worldwide of the new findings of the most advanced translational researches carried out in the different fields of microbiological sciences, with the aim to promote a prompt validation and transfer at clinical level of the most promising experimental results. The book series publishes review and original research contributions, short (data) reports as well as guest edited thematic book volumes. All contributions will be published online first and collected in (thematic) book volumes. There are no publication costs. This series is a subseries of Advances in Experimental Medicine and Biology 2014 Impact Factor: 1.958 Advances in Experimental Medicine and Biology has been publishing exceptional works in the field for over 30 years and is indexed in Medline, Scopus, EMBASE, BIOSIS, Biological Abstracts, CSA, Biological Sciences and Living Resources (ASFA-1), and Biological Sciences.
Giornale di malattie infettive e parassitarie, 1981
Veterinary Record, Sep 25, 1993
Search by Subject Search using Medical Subject Headings (< b> MeSH</b>... more Search by Subject Search using Medical Subject Headings (< b> MeSH</b>), a controlled vocabulary for indexing life sciences content.< br/> Note that some records do not have MeSH. These include Patents and the latest PubMed and PubMed Central records.
Journal of urology & nephrology studies, May 1, 2023
Micron, 1973
ABSTRACT The shape of the capsid of phage G, active against B. megatherium, has been studied by e... more ABSTRACT The shape of the capsid of phage G, active against B. megatherium, has been studied by electron microscopy using a variety of approaches including negative staining of whole particles, examination of stereoscopic micrographs, shadowing, observations on capsids devoid of their DNA content ('ghosts'), short and prolonged fixation and the use of single and serial ultra-thin sections. The results were conflicting. With negative staining the appearance of the capsid was not consistent with an icosahedral shape but could be related to that of an octahedron. The shape of the capsid in 'ghost' preparations was definitely octahedral. However, after fixing for 1h or longer and shadowing, the capsids were clearly icosahedral in shape with their sides equal to about half the length of those of the octahedron seen by negative staining. The same results were obtained by the thin sectioning technique. From a study of the two types of geometrical figures it was found that an octahedral container can be transformed into an icosahedral one with sides of half the original length if it is folded inwards on itself at 6 consecutive points. If this type of effect occurred during the preparative procedure it would account for the two apparently conflicting appearances of the capsid. Such an effect would involve a marked change or 'jump' through an intermediate unstable form. While it would reconcile the different results it is emphasized that such an interpretation is essentially speculative. To illustrate the complexities of the problem, an interesting geometrical exercise is presented in the Appendix.
Toxicon, 1989
A comparative study on the effects of toxin A and toxin B from Clostridium difficile on HEp-2 cel... more A comparative study on the effects of toxin A and toxin B from Clostridium difficile on HEp-2 cells was carried out. Both toxins caused cell retraction and rounding and seemed to exert their effect on cell morphology via a rearrangement of actin and alpha-actinin microfilaments. Such a rearrangement occurred at an early stage, when no change in microtubular and cytokeratin systems was detectable. Nevertheless, several structural modifications accompanying the cytopathological process induced by toxins A and B appeared to be quite different. In particular, toxin B-treated cells showed an arborized phenotype as a result of cell retraction and rounding, whereas toxin A caused cell rounding without arborization. Moreover, nuclear polarization following disorganization of the microfilament system was only observed in toxin A-treated cells. The structural features distinguishing intoxication processes induced by the two toxins probably reflect a different mechanism of action and suggest the presence of a distinct subcellular component as a primary target for each toxin.
Infection and Immunity, Mar 1, 1999
Vibrio parahaemolyticus is a marine bacterium known to be the leading cause of seafood gastroente... more Vibrio parahaemolyticus is a marine bacterium known to be the leading cause of seafood gastroenteritis worldwide. A 46-kDa homodimer protein secreted by this microorganism, the thermostable direct hemolysin (TDH), is considered a major virulence factor involved in bacterial pathogenesis since a high percentage of strains of clinical origin are positive for TDH production. TDH is a pore-forming toxin, and its most extensively studied effect is the ability to cause hemolysis of erythrocytes from different mammalian species. Moreover, TDH induces in a variety of cells cytotoxic effects consisting mainly of cell degeneration which often leads to loss of viability. In this work, we examined the cellular changes induced by TDH in monolayers of IEC-6 cells (derived from the rat crypt small intestine), which represent a useful cell model for studying toxins from enteric bacteria. In experimental conditions allowing cell survival, TDH induces a rapid transient increase in intracellular calcium as well as a significant though reversible decreased rate of progression through the cell cycle. The morphological changes seem to be dependent on the organization of the microtubular network, which appears to be the preferential cytoskeletal element involved in the cellular response to the toxin.