A series of neutral mixed-ligand [HB(pz)3]Ag(PR3) silver(I) complexes (PR3 = tertiary phosphine, ... more A series of neutral mixed-ligand [HB(pz)3]Ag(PR3) silver(I) complexes (PR3 = tertiary phosphine, [HB(pz)3]− = tris(pyrazolyl)borate anion), and the corresponding homoleptic [Ag(PR3)4]BF4 compounds have been synthesized and fully characterized. Silver compounds were screened for their antiproliferative activities against a wide panel of human cancer cells derived from solid tumors and endowed with different platinum drug sensitivity. Mixed-ligand complexes were generally more effective than the corresponding homoleptic derivatives, but the most active compounds were [HB(pz)3]Ag(PPh3) (5) and [Ag(PPh3)4]BF4 (10), both comprising the lipophilic PPh3 phosphine ligand. Detailed mechanistic studies revealed that both homoleptic and heteroleptic silver complexes strongly and selectively inhibit the selenoenzyme thioredoxin reductase both as isolated enzyme and in human ovarian cancer cells (half inhibition concentration values in the nanomolar range) causing the disruption of cellular thio...
Metal-based antitumor drugs play a relevant role in antiblastic chemotherapy. Cisplatin is regard... more Metal-based antitumor drugs play a relevant role in antiblastic chemotherapy. Cisplatin is regarded as one of the most effective drugs, even if severe toxicities and drug resistance phenomena limit its clinical use. Therefore, in recent years there has been a rapid expansion in research and development of novel metal-based anticancer drugs to improve clinical effectiveness, to reduce general toxicity and to broaden the spectrum of activity. The variety of metal ion functions in biology has stimulated the development of new metallodrugs other than Pt drugs with the aim to obtain compounds acting via alternative mechanisms of action. Among non-Pt compounds, copper complexes are potentially attractive as anticancer agents. Actually, since many years a lot of researches have actively investigated copper compounds based on the assumption proposal that endogenous metals may be less toxic. It has been established that the properties of copper-coordinated compounds are largely determined by...
This prospective clinical study evaluated the survival rate and the implant-crown success of 201 ... more This prospective clinical study evaluated the survival rate and the implant-crown success of 201 direct laser metal forming (DLMF) implants in different clinical applications, after short-term follow-up of functional loading. At the 1-year scheduled follow-up examination, several clinical, radiographic, and prosthetic parameters were assessed. Success criteria included absence of pain, sensitivity, suppuration, exudation; absence of implant mobility; absence of continuous peri-implant radiolucency, DIB <1.5 mm; absence of prosthetic complications at the implant-abutment interface. A total of 201 implants (106 maxilla, 95 mandible) were inserted in 62 patients (39 males, 23 females; aged between 26 and 65 years) in eight different clinical centers. The sites included anterior (n=79) and posterior (n= 122) implants. The overall implant survival rate was 99.5%, with one implant loss (maxilla: 99.0%, 1 implant failure; mandible: 100.0%, no implant failures). The mean DIB was 0.4±0.2 mm. Among the survived implants (200), five did not fulfill the success criteria, giving an implant-crown success of 97.5%. This 1-year follow-up prospective clinical study gives evidence of very high survival (99.5%) and success (97.5%) rates using DLMF implants.
This study evaluated the 1-year survival and success rate of root-analogue direct laser metal sin... more This study evaluated the 1-year survival and success rate of root-analogue direct laser metal sintering (DLMS) implants, placed into the extraction sockets of 15 patients. DLMS is a technology which allows solids with complex geometry to be fabricated by annealing metal powder microparticles in a focused laser beam, according to a computer-generated three-dimensional (3D) model; the fabrication process involves the laser-induced fusion of titanium microparticles, in order to build, layer-by-layer, the desired object. Cone-beam computed tomography (CBCT) acquisition and 3D image conversion, combined with the DLMS process, allow the fabrication of custom-made, rootanalogue implants (RAIs). CBCT images of 15 nonrestorable premolars (eight maxilla; seven mandible) were acquired and transformed into 3D models: from these, custom-made, root-analogue DLMS implants with integral abutment were fabricated. Immediately after tooth extraction, the RAIs were placed in the sockets and restored with a single crown. One year after implant placement, clinical and radiographic parameters were assessed: success criteria included absence of pain, suppuration, and exudation; absence of implant mobility and absence of continuous peri-implant radiolucency; distance between the implant shoulder and the first visible bone-to-implant contact <1.5 mm from initial surgery; and absence of prosthetic complications. At the 1year follow-up, no implants were lost, for a survival rate of 100 %. All implants were stable, with no signs of infection. The good conditions of the peri-implant tissues were confirmed by the radiographic examination, with a mean DIB of 0.7 mm (±0.2). The possibility of fabricating custom-made, RAI DLMS implants opens new interesting horizons for immediate placement of dental implants.
TWIK1 belongs to a family of K þ channels involved in neuronal excitability and cell volume regul... more TWIK1 belongs to a family of K þ channels involved in neuronal excitability and cell volume regulation. Its tissue distribution suggests a role in epithelial potassium transport. Here we show that TWIK1 is expressed in a subapical compartment in renal proximal tubules and in polarized MDCK cells. In nonpolarized cells, this compartment corresponds to pericentriolar recycling endosomes. We identified EFA6, an exchange factor for the small G protein ADP-ribosylation factor 6 (ARF6), as a protein binding to TWIK1. EFA6 interacts with TWIK1 only when it is bound to ARF6. Because ARF6 modulates endocytosis at the apical surface of epithelial cells, the ARF6/EFA6/TWIK1 association is probably important for channel internalization and recycling.
The small GTP-binding protein Arf6 coordinates membrane traffic at the plasma membrane with aspec... more The small GTP-binding protein Arf6 coordinates membrane traffic at the plasma membrane with aspects of cytoskeleton organization. This function does not overlap with that of other members of the ADP-ribosylation factor (Arf) family, although their switch regions, which are their major sites of interaction with regulators and effectors, have virtually identical sequences. Here we report the crystal structure of full-length, non-myristoylated human Arf6 bound to GTPγS. Unlike their GDP-bound forms, the active forms of Arf6 and Arf1 are very similar. Thus, the switch regions are discriminatory elements between Arf isoforms in their inactive but not in their active forms, a property that may generalize to other families of small G proteins. This suggests that GTP-bound Arfs may establish specific interactions outside the switch regions and/or be recognized in their cellular context rather than as isolated proteins. The structure also allows further insight into the lack of spontaneous GTPase activity of Arf proteins.
The small GTP-binding ADP-ribosylation factor 1 (ARF1) acts as a master regulator of Golgi struct... more The small GTP-binding ADP-ribosylation factor 1 (ARF1) acts as a master regulator of Golgi structure and function through the recruitment and activation of various downstream effectors. It has been proposed that members of the Rho family of small GTPases also control Golgi function in coordination with ARF1, possibly through the regulation of Arp2/3 complex and actin polymerization on Golgi membranes. Here, we identify ARHGAP10 -a novel Rho GTPase-activating protein (Rho-GAP) that is recruited to Golgi membranes through binding to GTP-ARF1. We show that ARHGAP10 functions preferentially as a GAP for Cdc42 and regulates the Arp2/3 complex and F-actin dynamics at the Golgi through the control of Cdc42 activity. Our results establish a role for ARHGAP10 in Golgi structure and function at the crossroads between ARF1 and Cdc42 signalling pathways.
Proceedings of The National Academy of Sciences, 1998
Budding of transport vesicles in the Golgi apparatus requires the recruitment of coat proteins an... more Budding of transport vesicles in the Golgi apparatus requires the recruitment of coat proteins and is regulated by ADP ribosylation factor (ARF) 1. ARF1 activation is promoted by guanine nucleotide exchange factors (GEFs), which catalyze the transition to GTP-bound ARF1. We recently have identified a human protein, ARNO (ARF nucleotide-binding-site opener), as an ARF1-GEF that shares a conserved domain with the yeast Sec7 protein. We now describe a human Sec7 domain-containing GEF referred to as ARNO3. ARNO and ARNO3, as well as a third GEF called cytohesin-1, form a family of highly related proteins with identical structural organization that consists of a central Sec7 domain and a carboxy-terminal pleckstrin homology domain. We show that all three proteins act as ARF1 GEF in vitro, whereas they have no effect on ARF6, an ARF protein implicated in the early endocytic pathway. Substrate specificity of ARNO-like GEFs for ARF1 depends solely on the Sec7 domain. Overexpression of ARNO3 in mammalian cells results in (i) fragmentation of the Golgi apparatus, (ii) redistribution of Golgi resident proteins as well as the coat component -COP, and (iii) inhibition of SEAP transport (secreted form of alkaline phosphatase). In contrast, the distribution of endocytic markers is not affected. This study indicates that Sec7 domain-containing GEFs control intracellular membrane compartment structure and function through the regulation of specific ARF proteins in mammalian cells.
We describe a method for determining the phase and intensity of ultrashort optical pulses in a si... more We describe a method for determining the phase and intensity of ultrashort optical pulses in a single laser shot by analysis of the pulse spectrum after passage through a nonlinear Kerr medium. A demonstration is given using the output of a Ti:sapphire oscillator-amplifier chain.
We report filamentation of subpicosecond UV laser pulses with only millijoule energy in atmospher... more We report filamentation of subpicosecond UV laser pulses with only millijoule energy in atmosphere. The results are in good agreement with a numerical simulation using a quasi-three-dimensional propagation code.
A two-dimensional axisymmetric model of the propagation of intense femtosecond laser pulses throu... more A two-dimensional axisymmetric model of the propagation of intense femtosecond laser pulses through dispersion-free transparent media is described. The effects of diffraction, nonlinear Kerr effect (instantaneous and retarded) and multiphoton ionisation are included. Numerical results concerning air and other gases are discussed. In particular, time self-compression of femtosecond pulses is predicted. Stable self-guided pulses are simulated, in agreement with recent experimental observations.
By studying the conical emission of a blue femtosecond laser filament in air, it is shown that se... more By studying the conical emission of a blue femtosecond laser filament in air, it is shown that selfimprovement of the beams' spatial mode quality occurs for a self-guided laser pulse.
Journal of The Optical Society of America B-optical Physics, 2002
Experiments in which several-meter-long infrared ultrashort laser pulses are guided in air are co... more Experiments in which several-meter-long infrared ultrashort laser pulses are guided in air are compared with numerical simulations. During a first self-focusing stage that is affected by modulational instability, the beam is shown to break up into two channels of light that finally coalesce into a narrow filament that is able to propagate over several Rayleigh lengths. The filament propagation is associated with the generation of an electron plasma, whose density is greater than 10 16 cm Ϫ3 . Electron generation persists well beyond the focal region. The simulations restore the global dynamics of the pulse, including the main stages of Kerr focusing, light guiding driven by ionization, and the ultimate diffraction of the beam.
The propagation of a multi-terawatt femtosecond laser pulse in air is studied as a function of in... more The propagation of a multi-terawatt femtosecond laser pulse in air is studied as a function of initial chirp. The chirp conditions for optimising air ionisation at long distance are presented. Ionisation channels are observed over a distance reaching 400 m.
We report on a new type of permanent damage obtained in bulk fused silica by focusing IR femtosec... more We report on a new type of permanent damage obtained in bulk fused silica by focusing IR femtosecond laser pulses with microjoule energy. It consists of an uniaxial birefringence zone over a lateral size of a few microns and a depth of a few tens of microns. The birefringence zone is followed by sub-micrometer filamentary cracks extending up to 80 μm. Nonlinear pulse propagation plays a crucial role in the onset of this type of damage.
We show that it is possible to organize regular filamentation patterns in air by imposing either ... more We show that it is possible to organize regular filamentation patterns in air by imposing either strong field gradients or phase distortions in the input-beam profile of an intense femtosecond laser pulse. A comparison between experiments and 3+1 dimensional numerical simulations confirms this concept and shows for the first time that a control of the transport of high intensities over long distances may be achieved by forcing this well ordered propagation regime. In this case, deterministic effects prevail in multiple femtosecond filamentation, and no transition to the optical turbulence regime is obtained [Phys. Rev. Lett. 83, 2938 (1999)]].
A series of neutral mixed-ligand [HB(pz)3]Ag(PR3) silver(I) complexes (PR3 = tertiary phosphine, ... more A series of neutral mixed-ligand [HB(pz)3]Ag(PR3) silver(I) complexes (PR3 = tertiary phosphine, [HB(pz)3]− = tris(pyrazolyl)borate anion), and the corresponding homoleptic [Ag(PR3)4]BF4 compounds have been synthesized and fully characterized. Silver compounds were screened for their antiproliferative activities against a wide panel of human cancer cells derived from solid tumors and endowed with different platinum drug sensitivity. Mixed-ligand complexes were generally more effective than the corresponding homoleptic derivatives, but the most active compounds were [HB(pz)3]Ag(PPh3) (5) and [Ag(PPh3)4]BF4 (10), both comprising the lipophilic PPh3 phosphine ligand. Detailed mechanistic studies revealed that both homoleptic and heteroleptic silver complexes strongly and selectively inhibit the selenoenzyme thioredoxin reductase both as isolated enzyme and in human ovarian cancer cells (half inhibition concentration values in the nanomolar range) causing the disruption of cellular thio...
Metal-based antitumor drugs play a relevant role in antiblastic chemotherapy. Cisplatin is regard... more Metal-based antitumor drugs play a relevant role in antiblastic chemotherapy. Cisplatin is regarded as one of the most effective drugs, even if severe toxicities and drug resistance phenomena limit its clinical use. Therefore, in recent years there has been a rapid expansion in research and development of novel metal-based anticancer drugs to improve clinical effectiveness, to reduce general toxicity and to broaden the spectrum of activity. The variety of metal ion functions in biology has stimulated the development of new metallodrugs other than Pt drugs with the aim to obtain compounds acting via alternative mechanisms of action. Among non-Pt compounds, copper complexes are potentially attractive as anticancer agents. Actually, since many years a lot of researches have actively investigated copper compounds based on the assumption proposal that endogenous metals may be less toxic. It has been established that the properties of copper-coordinated compounds are largely determined by...
This prospective clinical study evaluated the survival rate and the implant-crown success of 201 ... more This prospective clinical study evaluated the survival rate and the implant-crown success of 201 direct laser metal forming (DLMF) implants in different clinical applications, after short-term follow-up of functional loading. At the 1-year scheduled follow-up examination, several clinical, radiographic, and prosthetic parameters were assessed. Success criteria included absence of pain, sensitivity, suppuration, exudation; absence of implant mobility; absence of continuous peri-implant radiolucency, DIB <1.5 mm; absence of prosthetic complications at the implant-abutment interface. A total of 201 implants (106 maxilla, 95 mandible) were inserted in 62 patients (39 males, 23 females; aged between 26 and 65 years) in eight different clinical centers. The sites included anterior (n=79) and posterior (n= 122) implants. The overall implant survival rate was 99.5%, with one implant loss (maxilla: 99.0%, 1 implant failure; mandible: 100.0%, no implant failures). The mean DIB was 0.4±0.2 mm. Among the survived implants (200), five did not fulfill the success criteria, giving an implant-crown success of 97.5%. This 1-year follow-up prospective clinical study gives evidence of very high survival (99.5%) and success (97.5%) rates using DLMF implants.
This study evaluated the 1-year survival and success rate of root-analogue direct laser metal sin... more This study evaluated the 1-year survival and success rate of root-analogue direct laser metal sintering (DLMS) implants, placed into the extraction sockets of 15 patients. DLMS is a technology which allows solids with complex geometry to be fabricated by annealing metal powder microparticles in a focused laser beam, according to a computer-generated three-dimensional (3D) model; the fabrication process involves the laser-induced fusion of titanium microparticles, in order to build, layer-by-layer, the desired object. Cone-beam computed tomography (CBCT) acquisition and 3D image conversion, combined with the DLMS process, allow the fabrication of custom-made, rootanalogue implants (RAIs). CBCT images of 15 nonrestorable premolars (eight maxilla; seven mandible) were acquired and transformed into 3D models: from these, custom-made, root-analogue DLMS implants with integral abutment were fabricated. Immediately after tooth extraction, the RAIs were placed in the sockets and restored with a single crown. One year after implant placement, clinical and radiographic parameters were assessed: success criteria included absence of pain, suppuration, and exudation; absence of implant mobility and absence of continuous peri-implant radiolucency; distance between the implant shoulder and the first visible bone-to-implant contact <1.5 mm from initial surgery; and absence of prosthetic complications. At the 1year follow-up, no implants were lost, for a survival rate of 100 %. All implants were stable, with no signs of infection. The good conditions of the peri-implant tissues were confirmed by the radiographic examination, with a mean DIB of 0.7 mm (±0.2). The possibility of fabricating custom-made, RAI DLMS implants opens new interesting horizons for immediate placement of dental implants.
TWIK1 belongs to a family of K þ channels involved in neuronal excitability and cell volume regul... more TWIK1 belongs to a family of K þ channels involved in neuronal excitability and cell volume regulation. Its tissue distribution suggests a role in epithelial potassium transport. Here we show that TWIK1 is expressed in a subapical compartment in renal proximal tubules and in polarized MDCK cells. In nonpolarized cells, this compartment corresponds to pericentriolar recycling endosomes. We identified EFA6, an exchange factor for the small G protein ADP-ribosylation factor 6 (ARF6), as a protein binding to TWIK1. EFA6 interacts with TWIK1 only when it is bound to ARF6. Because ARF6 modulates endocytosis at the apical surface of epithelial cells, the ARF6/EFA6/TWIK1 association is probably important for channel internalization and recycling.
The small GTP-binding protein Arf6 coordinates membrane traffic at the plasma membrane with aspec... more The small GTP-binding protein Arf6 coordinates membrane traffic at the plasma membrane with aspects of cytoskeleton organization. This function does not overlap with that of other members of the ADP-ribosylation factor (Arf) family, although their switch regions, which are their major sites of interaction with regulators and effectors, have virtually identical sequences. Here we report the crystal structure of full-length, non-myristoylated human Arf6 bound to GTPγS. Unlike their GDP-bound forms, the active forms of Arf6 and Arf1 are very similar. Thus, the switch regions are discriminatory elements between Arf isoforms in their inactive but not in their active forms, a property that may generalize to other families of small G proteins. This suggests that GTP-bound Arfs may establish specific interactions outside the switch regions and/or be recognized in their cellular context rather than as isolated proteins. The structure also allows further insight into the lack of spontaneous GTPase activity of Arf proteins.
The small GTP-binding ADP-ribosylation factor 1 (ARF1) acts as a master regulator of Golgi struct... more The small GTP-binding ADP-ribosylation factor 1 (ARF1) acts as a master regulator of Golgi structure and function through the recruitment and activation of various downstream effectors. It has been proposed that members of the Rho family of small GTPases also control Golgi function in coordination with ARF1, possibly through the regulation of Arp2/3 complex and actin polymerization on Golgi membranes. Here, we identify ARHGAP10 -a novel Rho GTPase-activating protein (Rho-GAP) that is recruited to Golgi membranes through binding to GTP-ARF1. We show that ARHGAP10 functions preferentially as a GAP for Cdc42 and regulates the Arp2/3 complex and F-actin dynamics at the Golgi through the control of Cdc42 activity. Our results establish a role for ARHGAP10 in Golgi structure and function at the crossroads between ARF1 and Cdc42 signalling pathways.
Proceedings of The National Academy of Sciences, 1998
Budding of transport vesicles in the Golgi apparatus requires the recruitment of coat proteins an... more Budding of transport vesicles in the Golgi apparatus requires the recruitment of coat proteins and is regulated by ADP ribosylation factor (ARF) 1. ARF1 activation is promoted by guanine nucleotide exchange factors (GEFs), which catalyze the transition to GTP-bound ARF1. We recently have identified a human protein, ARNO (ARF nucleotide-binding-site opener), as an ARF1-GEF that shares a conserved domain with the yeast Sec7 protein. We now describe a human Sec7 domain-containing GEF referred to as ARNO3. ARNO and ARNO3, as well as a third GEF called cytohesin-1, form a family of highly related proteins with identical structural organization that consists of a central Sec7 domain and a carboxy-terminal pleckstrin homology domain. We show that all three proteins act as ARF1 GEF in vitro, whereas they have no effect on ARF6, an ARF protein implicated in the early endocytic pathway. Substrate specificity of ARNO-like GEFs for ARF1 depends solely on the Sec7 domain. Overexpression of ARNO3 in mammalian cells results in (i) fragmentation of the Golgi apparatus, (ii) redistribution of Golgi resident proteins as well as the coat component -COP, and (iii) inhibition of SEAP transport (secreted form of alkaline phosphatase). In contrast, the distribution of endocytic markers is not affected. This study indicates that Sec7 domain-containing GEFs control intracellular membrane compartment structure and function through the regulation of specific ARF proteins in mammalian cells.
We describe a method for determining the phase and intensity of ultrashort optical pulses in a si... more We describe a method for determining the phase and intensity of ultrashort optical pulses in a single laser shot by analysis of the pulse spectrum after passage through a nonlinear Kerr medium. A demonstration is given using the output of a Ti:sapphire oscillator-amplifier chain.
We report filamentation of subpicosecond UV laser pulses with only millijoule energy in atmospher... more We report filamentation of subpicosecond UV laser pulses with only millijoule energy in atmosphere. The results are in good agreement with a numerical simulation using a quasi-three-dimensional propagation code.
A two-dimensional axisymmetric model of the propagation of intense femtosecond laser pulses throu... more A two-dimensional axisymmetric model of the propagation of intense femtosecond laser pulses through dispersion-free transparent media is described. The effects of diffraction, nonlinear Kerr effect (instantaneous and retarded) and multiphoton ionisation are included. Numerical results concerning air and other gases are discussed. In particular, time self-compression of femtosecond pulses is predicted. Stable self-guided pulses are simulated, in agreement with recent experimental observations.
By studying the conical emission of a blue femtosecond laser filament in air, it is shown that se... more By studying the conical emission of a blue femtosecond laser filament in air, it is shown that selfimprovement of the beams' spatial mode quality occurs for a self-guided laser pulse.
Journal of The Optical Society of America B-optical Physics, 2002
Experiments in which several-meter-long infrared ultrashort laser pulses are guided in air are co... more Experiments in which several-meter-long infrared ultrashort laser pulses are guided in air are compared with numerical simulations. During a first self-focusing stage that is affected by modulational instability, the beam is shown to break up into two channels of light that finally coalesce into a narrow filament that is able to propagate over several Rayleigh lengths. The filament propagation is associated with the generation of an electron plasma, whose density is greater than 10 16 cm Ϫ3 . Electron generation persists well beyond the focal region. The simulations restore the global dynamics of the pulse, including the main stages of Kerr focusing, light guiding driven by ionization, and the ultimate diffraction of the beam.
The propagation of a multi-terawatt femtosecond laser pulse in air is studied as a function of in... more The propagation of a multi-terawatt femtosecond laser pulse in air is studied as a function of initial chirp. The chirp conditions for optimising air ionisation at long distance are presented. Ionisation channels are observed over a distance reaching 400 m.
We report on a new type of permanent damage obtained in bulk fused silica by focusing IR femtosec... more We report on a new type of permanent damage obtained in bulk fused silica by focusing IR femtosecond laser pulses with microjoule energy. It consists of an uniaxial birefringence zone over a lateral size of a few microns and a depth of a few tens of microns. The birefringence zone is followed by sub-micrometer filamentary cracks extending up to 80 μm. Nonlinear pulse propagation plays a crucial role in the onset of this type of damage.
We show that it is possible to organize regular filamentation patterns in air by imposing either ... more We show that it is possible to organize regular filamentation patterns in air by imposing either strong field gradients or phase distortions in the input-beam profile of an intense femtosecond laser pulse. A comparison between experiments and 3+1 dimensional numerical simulations confirms this concept and shows for the first time that a control of the transport of high intensities over long distances may be achieved by forcing this well ordered propagation regime. In this case, deterministic effects prevail in multiple femtosecond filamentation, and no transition to the optical turbulence regime is obtained [Phys. Rev. Lett. 83, 2938 (1999)]].
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Papers by Michele Franco