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1.
Mult Scler ; 30(7): 899-924, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38357870

RESUMO

BACKGROUND: Epidemiological data reveal that 45% of persons with multiple sclerosis (PwMS) in France are more than 50 years. This population more than 50 is more susceptible to cancer, and this risk may be increased by frequent use of immunosuppressive drugs. Consequently, concerns have arisen about the potential increased risk of cancer in PwMS and how patients should be screened and managed in terms of cancer risk. OBJECTIVE: To develop evidence-based recommendations to manage the coexistence of cancer and multiple sclerosis (MS). METHODS: The French Group for Recommendations in MS collected articles from PubMed and university databases covering the period January 1975 through June 2022. The RAND/UCLA method was employed to achieve formal consensus. MS experts comprehensively reviewed the full-text articles and developed the initial recommendations. A group of multidisciplinary health care specialists then validated the final proposal. RESULTS: Five key questions were addressed, encompassing various topics such as cancer screening before or after initiating a disease-modifying therapy (DMT), appropriate management of MS in the context of cancer, recommended follow-up for cancer in patients receiving a DMT, and the potential reintroduction of a DMT after initial cancer treatment. A strong consensus was reached for all 31 recommendations. CONCLUSION: These recommendations propose a strategic approach to managing cancer risk in PwMS.


Assuntos
Esclerose Múltipla , Neoplasias , Humanos , Esclerose Múltipla/epidemiologia , Esclerose Múltipla/terapia , Neoplasias/epidemiologia , França/epidemiologia , Imunossupressores/uso terapêutico
3.
Neurotherapeutics ; 20(6): 1707-1722, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37882961

RESUMO

Few studies have investigated sustained B-cell depletion after long-term intravenous (IV) anti-CD20 B-cell depleting therapy (BCDT) in multiple sclerosis (MS) with respect to strict and/or minimal disease activity. The main objective of this study was to investigate how sustained B-cell depletion after BCDT influences clinical and radiological stability as defined by "no evidence of disease activity" (NEDA-3) and "minimal evidence of disease activity" (MEDA) status in MS patients at 12 and 18 months. Furthermore, we assessed the frequency of serious adverse events (SAE), and the influence of prior lymphocytopenia-inducing treatment (LIT) on lymphocyte subset counts and gammaglobulins in MS patients receiving long-term BCDT. We performed a retrospective, prospectively collected, study in a cohort of 192 MS patients of all clinical phenotypes treated by BCDT between January 2014 and September 2021. Overall, 84.2% and 96.9% of patients attained NEDA-3 and MEDA status at 18 months, respectively. Sustained CD19+ depletion was observed in 85.8% of patients at 18 months. No significant difference was observed when comparing patients achieving either NEDA-3 or MEDA at 18 months and sustained B-cell depletion. Compared to baseline levels, IgM and IgG levels on BCDT significantly decreased at 6 months and 30 months, respectively. Patients receiving LIT prior to BCDT showed significant CD4+ lymphocytopenia and lower IgG levels compared to non-LIT patients. Grade 3 or above SAEs were rare. As nearly all patients achieved MEDA at 18 months, we suggest tailoring IV BCDT after 18 months given the occurrence of lymphocytopenia, hypogammaglobulinemia, and SAE after this time point.


Assuntos
Linfopenia , Esclerose Múltipla , Humanos , Rituximab/uso terapêutico , Esclerose Múltipla/tratamento farmacológico , Estudos Retrospectivos , Anticorpos Monoclonais Murinos , Depleção Linfocítica/métodos , Imunoglobulina G
4.
Sci Rep ; 13(1): 9251, 2023 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-37286718

RESUMO

Pancreatic ductal adenocarcinoma (PDAC) has a high fatality rate, mainly due to its asymptomatic nature until late-stage disease and therefore delayed diagnosis that leads to a lack of timely treatment intervention. Consequently, there is a significant need for better methods to screen populations that are at high risk of developing PDAC. Such advances would result in earlier diagnosis, more treatment options, and ultimately better outcomes for patients. Several recent studies have applied the concept of liquid biopsy, which is the sampling of a biofluid (such as blood plasma) for the presence of disease biomarkers, to develop screening approaches for PDAC; several of these studies have focused on analysis of extracellular vesicles (EVs) and their cargoes. While these studies have identified many potential biomarkers for PDAC that are present within EVs, their application to clinical practice is hindered by the lack of a robust, reproducible method for EV isolation and analysis that is amenable to a clinical setting. Our previous research has shown that the Vn96 synthetic peptide is indeed a robust and reproducible method for EV isolation that has the potential to be used in a clinical setting. We have therefore chosen to investigate the utility of the Vn96 synthetic peptide for this isolation of EVs from human plasma and the subsequent detection of small RNA biomarkers of PDAC by Next-generation sequencing (NGS) analysis. We find that analysis of small RNA from Vn96-isolated EVs permits the discrimination of PDAC patients from non-affected individuals. Moreover, analyses of all small RNA species, miRNAs, and lncRNA fragments are most effective at segregating PDAC patients from non-affected individuals. Several of the identified small RNA biomarkers have been previously associated with and/or characterized in PDAC, indicating the validity of our findings, whereas other identified small RNA biomarkers may have novel roles in PDAC or cancer in general. Overall, our results provide a basis for a clinically-amendable detection and/or screening strategy for PDAC using a liquid biopsy approach that relies on Vn96-mediated isolation of EVs from plasma.


Assuntos
Carcinoma Ductal Pancreático , Vesículas Extracelulares , MicroRNAs , Neoplasias Pancreáticas , Humanos , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/genética , Neoplasias Pancreáticas/patologia , Carcinoma Ductal Pancreático/diagnóstico , Carcinoma Ductal Pancreático/genética , Carcinoma Ductal Pancreático/patologia , Vesículas Extracelulares/genética , Vesículas Extracelulares/patologia , MicroRNAs/genética , Peptídeos/genética , Análise de Sequência de RNA , Biomarcadores Tumorais/genética , Neoplasias Pancreáticas
5.
Front Immunol ; 13: 755900, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35185870

RESUMO

The key role of B cells in the pathophysiology of multiple sclerosis (MS) is supported by the presence of oligoclonal bands in the cerebrospinal fluid, by the association of meningeal ectopic B cell follicles with demyelination, axonal loss and reduction of astrocytes, as well as by the high efficacy of B lymphocyte depletion in controlling inflammatory parameters of MS. Here, we use a spontaneous model of experimental autoimmune encephalomyelitis (EAE) to study the clonality of the B cell response targeting myelin oligodendrocyte glycoprotein (MOG). In particular, 94% of SJL/j mice expressing an I-As: MOG92-106 specific transgenic T cell receptor (TCR1640) spontaneously develop a chronic paralytic EAE between the age of 60-500 days. The immune response is triggered by the microbiota in the gut-associated lymphoid tissue, while there is evidence that the maturation of the autoimmune demyelinating response might occur in the cervical lymph nodes owing to local brain drainage. Using MOG-protein-tetramers we tracked the autoantigen-specific B cells and localized their enrichment to the cervical lymph nodes and among the brain immune infiltrate. MOG-specific IgG1 antibodies were detected in the serum of diseased TCR1640 mice and proved pathogenic upon adoptive transfer into disease-prone recipients. The ontogeny of the MOG-specific humoral response preceded disease onset coherent with their contribution to EAE initiation. This humoral response was, however, not sufficient for disease induction as MOG-antibodies could be detected at the age of 69 days in a model with an average age of onset of 197 days. To assess the MOG-specific B cell repertoire we FACS-sorted MOG-tetramer binding cells and clonally expand them in vitro to sequence the paratopes of the IgG heavy chain and kappa light chains. Despite the fragility of clonally expanding MOG-tetramer binding effector B cells, our results indicate the selection of a common CDR-3 clonotype among the Igk light chains derived from both disease-free and diseased TCR1640 mice. Our study demonstrates the pre-clinical mobilization of the MOG-specific B cell response within the brain-draining cervical lymph nodes, and reiterates that MOG antibodies are a poor biomarker of disease onset and progression.


Assuntos
Linfócitos B/imunologia , Encefalomielite Autoimune Experimental/imunologia , Glicoproteína Mielina-Oligodendrócito/imunologia , Receptores de Antígenos de Linfócitos T/imunologia , Animais , Autoanticorpos/imunologia , Autoantígenos/imunologia , Linfócitos B/citologia , Encéfalo/metabolismo , Encéfalo/patologia , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/patologia , Encefalomielite Autoimune Experimental/fisiopatologia , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Esclerose Múltipla/imunologia , Esclerose Múltipla/patologia , Glicoproteína Mielina-Oligodendrócito/genética
6.
Artigo em Inglês | MEDLINE | ID: mdl-35091465

RESUMO

BACKGROUND AND OBJECTIVES: Acute optic neuritis (ON) is a classical presenting symptom of multiple sclerosis (MS), neuromyelitis optica spectrum disorders (NMOSD), and anti-MOG-associated disorders. The resulting visual impairment is variable and can be severe. Clinicians are in need of predictive biomarkers to optimize the management of acute ON. In this longitudinal study (IRMANO, NCT03651662), we evaluated the ability of optic nerve lesion length measured on MRI at the acute phase of ON to predict retinal neuro-axonal loss and visual impairment at a chronic stage. METHODS: We conducted a longitudinal study (IRMANO, NCT03651662) of patients who presented a clinical episode of ON (≤8 weeks). All patients underwent a retinal optical coherence tomography (OCT) and a brain/optic nerve MRI, including 3D double-inversion recovery (DIR) sequence at the acute phase of ON and 12 months later. Primary outcomes were optic nerve DIR hypersignal lesion length, macular ganglion cell-inner plexiform layer (GCIPL) volume measured on OCT, and low-contrast monocular visual acuity (LCMVA). RESULTS: The study group included 51 patients (33 women, mean age of 32.4 years ± 7.9). We recruited patients with a clinically isolated syndrome (n = 20), a relapsing-remitting MS (n = 23), an isolated ON (n = 6), and a first clinical episode of NMOSD (n = 2). Optic nerve DIR hypersignal was observed in all but 1 symptomatic optic nerves. At inclusion, the mean optic nerve lesion length (in mm) was 12.35 ± 5.98. The mean GCIPL volume (in mm3) significantly decreased between inclusion (1.90 ± 0.18) and M12 (1.67 ± 0.21; p < 0.0001). Optic nerve lesion length at inclusion was significantly associated with GCIPL thinning (estimate ± SD; -0.012 ± 0.004; p = 0.0016) and LCMVA at M12 (0.016 ± 0.003; p < 0.001). Optic nerve lesion length significantly increased at M12 (15.76 ± 8.70; p = 0.0007). The increase in optic nerve lesion length was significantly associated with the GCIPL thinning between inclusion and M12 (-0.012 ± 0.003; p = 0.0011). DISCUSSION: At the acute phase of ON, optic nerve lesion length is an imaging biomarker predictive of retinal neuro-axonal loss and chronic visual impairment, which can help to stratify future therapeutic strategies in acute ON. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that optic nerve lesion length measured on MRI during the acute phase of a first episode of ON is associated with long-term retinal neuro-axonal loss and visual impairment.


Assuntos
Esclerose Múltipla/patologia , Neurite Óptica/patologia , Neurônios Retinianos/patologia , Doença Aguda , Adulto , Feminino , Humanos , Estudos Longitudinais , Imageamento por Ressonância Magnética , Masculino , Esclerose Múltipla/diagnóstico por imagem , Neuromielite Óptica/diagnóstico por imagem , Neuromielite Óptica/patologia , Neurite Óptica/diagnóstico por imagem , Tomografia de Coerência Óptica
7.
Neurology ; 95(6): e733-e744, 2020 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-32723802

RESUMO

OBJECTIVE: To evaluate the ability of intereye retinal thickness difference (IETD) measured by optical coherence tomography (OCT) to detect asymptomatic optic nerve involvement in clinically isolated syndrome (CIS). METHODS: We conducted a cross-sectional study of patients who recently presented a CIS (≤4.5 months). All patients underwent OCT and brain/optic nerve MRI. Optic nerve involvement was defined clinically (episode of optic neuritis [ON] or not) and radiologically (optic nerve hypersignal on 3D double inversion recovery [3D-DIR]). We evaluated the sensitivity and specificity of previously published IETD thresholds and report the observed optimal thresholds for identifying symptomatic optic nerve involvement but also for identifying asymptomatic optic nerve involvement (optic nerve hypersignal without ON history). Primary outcomes were ganglion cell-inner plexiform layer (GC-IPL) and peripapillary retinal nerve fiber layer IETD. RESULTS: The study group consisted of 130 patients. In the CIS with ON group, 3D-DIR showed a hypersignal in all 41 symptomatic optic nerves and in 11 asymptomatic optic nerves. In the CIS without ON group, 3D-DIR showed a unilateral optic nerve hypersignal in 22 patients and a bilateral optic nerve hypersignal in 7 patients. For the detection of symptomatic and asymptomatic optic nerve lesion, GC-IPL IETD had better performance. We found an optimal GC-IPL IETD threshold ≥2.83 µm (sensitivity 88.2, specificity 83.3%) for the detection of symptomatic lesions and an optimal GC-IPL IETD ≥1.42 µm (sensitivity 89.3%, specificity 72.6%) for the detection of asymptomatic lesions. CONCLUSIONS: Detection of asymptomatic optic nerve lesions in CIS requires lower IETD thresholds than previously reported. GC-IPL IETD represents an alternative biomarker to MRI for the detection of asymptomatic optic nerve lesions. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that OCT accurately identifies asymptomatic optic nerve involvement in patients with CIS.


Assuntos
Esclerose Múltipla/diagnóstico por imagem , Nervo Óptico/diagnóstico por imagem , Tomografia de Coerência Óptica , Adulto , Doenças Assintomáticas , Estudos Transversais , Progressão da Doença , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Esclerose Múltipla/líquido cefalorraquidiano , Bandas Oligoclonais/líquido cefalorraquidiano , Estudos Prospectivos , Retina/diagnóstico por imagem , Retina/ultraestrutura , Síndrome , Acuidade Visual , Adulto Jovem
8.
J Oncol Pharm Pract ; 26(8): 2038-2041, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32281518

RESUMO

An important amount of cytotoxic drug may accumulate in the workplace following the breakage of a vial containing an anticancer drug. Thanks to the monthly monitoring of the surface contamination in our compounding unit, a strong increase of cyclophosphamide contamination was highlighted in the storage area following the breakage of the vial, despite application of the emergency procedure. This study presents an analysis of chemical decontamination in the context of massive contamination. Samples were taken on the floor and on the caster of a storage shelf where the vial broke. The residual contamination was measured with a liquid chromatography-mass spectrometry/mass spectrometry method. An admixture of 10-2 M sodium dodecyl sulfate and 70% isopropanol (SDS/IPA 8:2) was selected as the decontamination solution. High amounts of cyclophosphamide were retrieved. The initial contamination on the floor was over 20 ng/cm2. Three decontaminations with SDS/IPA were carried out at Day 61, Day 68, and Day 71. The amount of cyclophosphamide decreased to 0.45 ng/cm2 at D134. However, high values were still measured on the caster despite successive decontaminations, with a maximal value of 19.78 ng/cm2 observed at Day 106. Continuous monitoring in our unit led us to highlight the inefficiency of our emergency procedure to eliminate high cyclophosphamide contamination. The procedure involving the SDS/IPA admixture was more efficient on the floor compared to the caster, which is a different surface type and porosity. This work highlights the importance of improving the procedures of incident management using contamination monitoring and repeated decontamination procedures adapted to different contaminants and surfaces.


Assuntos
Antineoplásicos Alquilantes/análise , Ciclofosfamida/análise , Descontaminação/métodos , Monitoramento Ambiental/métodos , Humanos , Local de Trabalho
9.
Artigo em Inglês | MEDLINE | ID: mdl-26959037

RESUMO

Women who are generally part of socially disadvantaged and economically marginalized groups are especially susceptible to smoking during pregnancy but smoking rates are underreported in both research and interventions. While there is evidence to support the short-term efficacy of nicotine replacement therapy (NRT) use in pregnancy, long-term abstinence rates are modest. Current health strategies and interventions designed to diminish smoking in pregnancy have adopted a simplified approach to maternal smoking-one that suggests that they have a similar degree of choice to non-pregnant smokers regarding the avoidance of risk factors, and overlooks individual predictors of non-adherence. As a result, interventions have been ineffective among this high-risk group. For this reason, this paper addresses the multiple and interacting determinants that must be considered when developing and implementing effective strategies that lead to successful smoking cessation: socioeconomic status (SES), nicotine dependence, social support, culture, mental health, and health services. Based on our review of the literature, we conclude that tailoring cessation programs for pregnant smokers may ultimately optimize NRT efficacy and reduce the prevalence of maternal smoking.


Assuntos
Comportamento Materno/psicologia , Mães/psicologia , Complicações na Gravidez/prevenção & controle , Abandono do Hábito de Fumar/métodos , Abandono do Hábito de Fumar/psicologia , Fumar/psicologia , Tabagismo/psicologia , Adaptação Psicológica , Feminino , Humanos , Gravidez , Classe Social , Apoio Social , Fatores Socioeconômicos
10.
PLoS One ; 10(8): e0128881, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26248341

RESUMO

Increased blood glucose concentrations promote reactions between glucose and proteins to form advanced glycation end-products (AGE). Circulating AGE in the blood plasma can activate the receptor for advanced end-products (RAGE), which is present on both endothelial and vascular smooth muscle cells (VSMC). RAGE exhibits a complex signaling that involves small G-proteins and mitogen activated protein kinases (MAPK), which lead to increased nuclear factor kappa B (NF-κB) activity. While RAGE signaling has been previously addressed in endothelial cells, little is known regarding its impact on the function of VSMC. Therefore, we hypothesized that RAGE signaling leads to alterations in the mechanical and functional properties of VSMC, which could contribute to complications associated with diabetes. We demonstrated that RAGE is expressed and functional in the A7r5 VSMC model, and its activation by AGE significantly increased NF-κB activity, which is known to interfere with the contractile phenotype of VSMC. The protein levels of the contraction-related transcription factor myocardin were also decreased by RAGE activation with a concomitant decrease in the mRNA and protein levels of transgelin (SM-22α), a regulator of VSMC contraction. Interestingly, we demonstrated that RAGE activation increased the overall cell rigidity, an effect that can be related to an increase in myosin activity. Finally, although RAGE stimulation amplified calcium signaling and slightly myosin activity in VSMC challenged with vasopressin, their contractile capacity was negatively affected. Overall, RAGE activation in VSMC could represent a keystone in the development of vascular diseases associated with diabetes by interfering with the contractile phenotype of VSMC through the modification of their mechanical and functional properties.


Assuntos
Músculo Liso Vascular/citologia , Receptor para Produtos Finais de Glicação Avançada/metabolismo , Transdução de Sinais , Animais , Fenômenos Biomecânicos , Cálcio/metabolismo , Linhagem Celular , Complicações do Diabetes/etiologia , Complicações do Diabetes/metabolismo , Produtos Finais de Glicação Avançada/metabolismo , Humanos , Contração Muscular , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/fisiologia , NF-kappa B/metabolismo , Ratos , Albumina Sérica/metabolismo , Doenças Vasculares/etiologia , Doenças Vasculares/metabolismo , Albumina Sérica Glicada
11.
Anal Biochem ; 478: 73-81, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-25800564

RESUMO

Protein glycation is a ubiquitous process involved in vascular complications observed in diabetes. Glyoxal (GO), an intracellular reactive oxoaldehyde that is one of the most potent glycation agents, readily reacts with amines present on proteins to produce the lysine-derived adduct carboxymethyllysine, which is a prevalent advanced glycation end-product (AGE). Our group previously showed that cell exposure to GO leads to an alteration in the cell contractile activity that could occur as a result of the glycation of various proteins regulating the cell contractile machinery. Here, we measured the extent of glycation on three functionally distinct proteins known to participate in cell contraction and cytoskeletal organization-Rho-kinase (ROCK), actin, and gelsolin (GSN)-using an assay based on the reaction of the cell membrane-permeable fluorescent probe carboxyfluorescein diacetate succinimidyl ester (CFDA-SE), which reacts with primary amine groups of proteins. By combining CFDA-SE fluorescence and Western blot detection, we observed (following GO incubation) increased glycation of actin and ROCK as well as an increased interaction between actin and GSN as observed by co-immunoprecipitation. Thus, we conclude that the use of the fluorescent probe CFDA-SE offers an interesting alternative to perform a comparative analysis of the extent of intracellular protein glycation in live cells.


Assuntos
Fluoresceínas/metabolismo , Corantes Fluorescentes/metabolismo , Glicosilação , Succinimidas/metabolismo , Actinas/análise , Actinas/metabolismo , Western Blotting , Linhagem Celular , Fluoresceínas/análise , Corantes Fluorescentes/análise , Gelsolina/análise , Gelsolina/metabolismo , Glioxal/metabolismo , Humanos , Microscopia de Fluorescência , Succinimidas/análise , Quinases Associadas a rho/análise , Quinases Associadas a rho/metabolismo
12.
Integr Biol (Camb) ; 6(4): 411-21, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24503653

RESUMO

Glyoxal (GO), a highly reactive metabolite of glucose, is associated with diabetic vascular complications via the formation of advanced glycation end-products. Considering its ability to react with proteins' amino acids and its crosslinking potential, we suggest that GO affects cellular mechanical functions such as contractility. Therefore, we tested the effects of GO on cellular contractile response following AngII stimulation of human embryonic kidney cells over-expressing the AT1 receptor (HEK 293 AT1aR). Prior to cell stimulation with AngII, cells exposed to GO exhibited carboxymethyllysine-adduct formation and an increase in cellular stiffness, which could be prevented by pre-treatment with aminoguanidine. The time-dependent cellular contractile response to AngII was measured by monitoring cell membrane displacement by atomic force atomic force microscopy (AFM) and by quantifying myosin light chain phosphorylation (p-MLC) via immunoblotting. Interestingly, short-term GO exposure increased by 2.6 times the amplitude of cell contraction induced by AngII and this was also associated with a sustained rise in p-MLC. This increased response to AngII induced by GO appears to be linked to its glycation potential, as aminoguanidine pre-treatment prevented this increased cellular mechanical response. Our results also suggest that GO could have an impact on ROCK activity, as ROCK inhibition with Y-27632 blocked the enhanced contractile response (p = 0.011) measured under GO conditions. Together, these results indicate that GO enhances the cellular response to AngII and modifies cellular mechanical properties via a mechanism that relies on its glycation potential and on the activation of the ROCK-dependent pathway.


Assuntos
Citoesqueleto de Actina/fisiologia , Actomiosina/metabolismo , Amidas/farmacologia , Angiotensina II/metabolismo , Produtos Finais de Glicação Avançada/metabolismo , Glioxal/metabolismo , Piridinas/farmacologia , Citoesqueleto de Actina/ultraestrutura , Células HEK293 , Humanos , Microscopia de Força Atômica , Microscopia de Fluorescência , Cadeias Leves de Miosina/metabolismo , Fosforilação/fisiologia
13.
J Occup Environ Hyg ; 10(3): 155-72, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23356435

RESUMO

This study assessed the contribution of electron microscopy to the characterization of nanoparticles and compared the degree of variability in sizes observed within each stage when sampled by two cascade impactors: an Electrical Low Pressure Impactor (ELPI) and a Micro-Orifice Uniform Deposit Impactor (MOUDI). A TiO(2) nanoparticle (5 nm) suspension was aerosolized in an inhalation chamber. Nanoparticles sampled by the impactors were collected on aluminum substrates or TEM carbon-coated copper grids using templates, specifically designed in our laboratories, for scanning and transmission electron microscopy (SEM, TEM) analysis, respectively. Nanoparticles were characterized using both SEM and TEM. Three different types of diameters (inner, outer, and circular) were measured by image analysis based on count and volume, for each impactor stage. Electron microscopy, especially TEM, is well suited for the characterization of nanoparticles. The MOUDI, probably because of the rotation of its collection stages, which can minimize the resuspension of particles, gave more stable results and smaller geometric standard deviations per stage. Our data suggest that the best approach to estimate particle size by electron microscopy would rely on geometric means of measured circular diameters. Overall, the most reliable data were provided by the MOUDI and the TEM sampling technique on carbon-coated copper grids for this specific experiment. This study indicates interesting findings related to the assessment of impactors combined with electron microscopy for nanoparticle characterization. For future research, since cascade impactors are extensively used to characterize nano-aerosol exposure scenarios, high-performance field emission scanning electron microscopy (FESEM) should also be considered.


Assuntos
Nanopartículas Metálicas/análise , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Titânio/análise
15.
Colloids Surf B Biointerfaces ; 58(2): 73-90, 2007 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-17509839

RESUMO

Many different processes take place at the cell membrane interface. Indeed, for instance, ligands bind membrane proteins which in turn activate peripheral membrane proteins, some of which are enzymes whose action is also located at the membrane interface. Native cell membranes are difficult to use to gain information on the activity of individual proteins at the membrane interface because of the large number of different proteins involved in membranous processes. Model membrane systems, such as monolayers at the air-water interface, have thus been extensively used during the last 50 years to reconstitute proteins and to gain information on their organization, structure and activity in membranes. In the present paper, we review the recent work we have performed with membrane and peripheral proteins as well as enzymes in monolayers at the air-water interface. We show that the structure and orientation of gramicidin has been determined by combining different methods. Furthermore, we demonstrate that the secondary structure of rhodopsin and bacteriorhodopsin is indistinguishable from that in native membranes when appropriate conditions are used. We also show that the kinetics and extent of monolayer binding of myristoylated recoverin is much faster than that of the nonmyristoylated form and that this binding is highly favored by the presence polyunsaturated phospholipids. Moreover, we show that the use of fragments of RPE65 allow determine which region of this protein is most likely involved in membrane binding. Monomolecular films were also used to further understand the hydrolysis of organized phospholipids by phospholipases A2 and C.


Assuntos
Proteínas de Membrana/fisiologia , Lipossomas Unilamelares/química , Animais , Humanos , Proteínas de Membrana/química , Fosfolipases/química , Fosfolipases/fisiologia
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