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1.
Medicina (Kaunas) ; 60(1)2023 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-38256287

RESUMO

Background and Objectives: Kidney transplant recipients (KTRs) are at a higher risk of severe COVID-19 development. The course of the infection may vary. Long-term consequences for graft function are still being studied. We investigate whether the clinical course of SARS-CoV-2 infection among KTRs had a long-term effect on graft function. Patients and method: 128 KTRs with confirmed SARS-CoV-2 infection were included in the study. They were divided into two groups: mild (without the need for oxygen therapy; n = 91) and severe (with the need for oxygen therapy; n = 21). Baseline characteristics and medical data, especially creatinine level, estimated glomerular filtration rate (eGFR) CKD-EPI, and proteinuria, were analyzed. The main outcomes were the absolute and relative change in eGFR during the one-year follow-up after COVID-19. In the final models, sex, age, smoking, presence of diabetes mellitus (DM), and cardiovascular disease (CVD) were included. Results: KTRs with severe COVID-19 were older, more likely to smoke, and had DM and CVD more frequently. Our analysis reveals that COVID-19 severity was associated with a significantly more pronounced relative eGFR decline one year after recovery only in males [-13.94 (95% CI: -25.13 to -2.76, p = 0.015) percentage points]. One year after the disease onset, males with a severe course of the infection had a higher eGFR decline than those with a mild one. The COVID-19 severity did not affect eGFR loss in females. Conclusions: In KTRs suffering from COVID-19, deterioration of graft function was noticed. The eGFR decline was associated with disease severity and sex. It indicates a need for further research, observation, and preventive actions for KTRs, especially males.


Assuntos
COVID-19 , Doenças Cardiovasculares , Feminino , Masculino , Humanos , SARS-CoV-2 , Rim , Oxigênio
2.
Entropy (Basel) ; 22(6)2020 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-33286422

RESUMO

This paper studies the leader-following consensus problem in continuous-time multi-agent networks with communications/updates occurring only at random times. The time between two consecutive controller updates is exponentially distributed. Some sufficient conditions are derived to design the control law that ensures the leader-following consensus is asymptotically reached (in the sense of the expected value of a stochastic process). The numerical examples are worked out to demonstrate the effectiveness of our theoretical results.

3.
Int J Immunogenet ; 46(4): 217-231, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31210416

RESUMO

Natural killer (NK) cells make vital contributions to the immune system and the reproductive system. Notably, NK cells of donor origin can recognize and kill residual leukaemic cells and cure malignant patients in hematopoietic stem cell (HSC) transplant setting. NK cell function is regulated by KIRs that recognize cognate HLA class I molecules on target cells, depending on their amino acid residues. In review, we addressed the question of binding capacity and avidity of HLA class I molecules to different killer cell immunoglobulin-like receptors (KIRs) depending on all interacting amino acid residues both on HLA and KIR side. We searched PubMed database and analysed available HLA:KIR crystallographic data for amino acid residues in HLA molecules, those physically involved in binding KIRs (termed here the "entire KIR interface"). Within entire KIR interface, we selected five functional sequence motifs (14-19, 66-76, 77-84, 88-92 and 142-151) and classified them according to the conservation of their amino acid sequences among 8,942 HLA class I molecules. Although some conserved amino acid motifs were shared by different groups of KIR ligands, the HLA motif combinations were exclusive for the ligand groups. In 135 common HLA class I molecules with known HLA:KIR recognition, we found 54 combinations of five motifs in each of the KIR-binding interfaces (C1, C2, Bw4, A3/11) and conserved non-KIR-binding interfaces. Based on the entire KIR interface, this analysis allowed to classify 8,942 HLA class I molecules into KIR specificity groups. This functional and evolutionary classification of entire KIR interfaces provides a tool for unambiguously predicting HLA:KIR interactions for common and those HLA molecules that have not yet been functionally tested. Considering the entire KIR interface in HLA class I molecules, functional interactions of HLA and KIR can be predicted in immune responses, reproduction and allotransplantation. Further functional studies are needed on the HLA:KIR interaction variations caused by the repertoires of peptides presented by HLA molecules and KIR polymorphisms at allelic level.


Assuntos
Motivos de Aminoácidos/genética , Células Matadoras Naturais/imunologia , Receptores KIR/genética , Motivos de Aminoácidos/imunologia , Sequência de Aminoácidos , Antígenos HLA-C/genética , Antígenos HLA-C/imunologia , Antígenos de Histocompatibilidade Classe I/genética , Humanos , Ligantes , Polimorfismo Genético , Receptores KIR/imunologia
4.
Materials (Basel) ; 17(19)2024 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-39410404

RESUMO

The discrete element method (DEM) has emerged as an essential computational tool in geotechnical engineering for the simulation of granular materials, offering significant advantages over traditional continuum-based methods such as the finite element method (FEM) and the finite difference method (FDM). The DEM's ability to model particle-level interactions, including contact forces, rotations, and particle breakage, allows for a more precise understanding of granular media behavior under various loading conditions. However, accurate DEM simulations require meticulous calibration of input parameters, such as particle density, stiffness, and friction, to effectively replicate real-world behavior. This study proposes a simplified calibration procedure, intended to be conducted prior to any granular material flow DEM modeling, based on three fundamental physical tests: bulk density, surface friction, and angle of repose. The ability of these tests, conducted on dry quartz sand, to accurately determine DEM micromechanical parameters, was validated through numerical simulation of cylinder tests with varying height-to-radius ratios. The results demonstrated that this calibration approach effectively reduced computational complexity while maintaining high accuracy, with validation errors of 0% to 12%. This research underscores the efficacy of simplified DEM calibration methods in enhancing the predictive reliability of simulations, particularly for sand modeling in geotechnical applications.

5.
Brain Sci ; 14(4)2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38671972

RESUMO

INTRODUCTION: Methamphetamine is a highly stimulating psychoactive drug that causes life-threatening addictions and affects millions of people around the world. Its effects on the brain are complex and include disturbances in the neurotransmitter systems and neurotoxicity. There are several known treatment methods, but their effectiveness is moderate. It must be emphasised that no drugs have been approved for treatment. For this reason, there is an urgent need to develop new, effective, and safe treatments for methamphetamine. One of the potential treatments is mindfulness meditation. In recent years, this technique has been researched extensively in the context of many neurological and psychiatric disorders. METHODS: This review explores the use of mindfulness in the treatment of methamphetamine addiction. Searches were conducted in the PubMed/Medline, Research Gate, and Cochrane databases. RESULTS: Ten studies were identified that used mindfulness-based interventions in the treatment of methamphetamine addiction. The results show that mindfulness is an effective form of reducing hunger, risk of relapses, stress indicators, depression, and aggression, alone or in combination with transcranial direct current stimulation (tDCS). Mindfulness also improved the cognitive function in addicts. The included studies used only behavioural measures. The potential mechanisms of mindfulness in addiction were explained, and it was proposed that it can induce neuroplasticity, alleviating the symptoms of addiction. CONCLUSIONS: Evidence from the studies suggest that mindfulness may be an effective treatment option for methamphetamine addiction, used alone or in combination with tDCS. However, further high-quality research is required to establish the role of this treatment option in this field. The use of neuroimaging and neurophysiological measures is fundamental to understand the mechanisms of mindfulness.

6.
HLA ; 103(2): e15364, 2024 02.
Artigo em Inglês | MEDLINE | ID: mdl-38312022

RESUMO

Transplantation of HLA and/or KIR mismatched allogeneic hematopoietic stem cells can lead NK cells to different states of activation/inhibition or education/resetting and change anti-tumor immunosurveillance. In this study, we used molecular relapse monitoring to investigate a correlation between either missing ligand recognition or variation of the cognate iKIR-HLA pairs with clinical outcomes in patients with hematological malignancies requiring allogeneic hematopoietic stem cell transplantation (allo-HSCT). Patients (N = 418) with acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphoblastic leukemia (ALL), myelodysplastic syndrome (MDS), or lymphoma receiving T-cell repleted graft from HLA-matched or partly mismatched unrelated donors between 2012 and 2020 in our center were included in this study. Missing-ligand recognition was assessed through the presence or absence of recipients' HLA ligand for a particular inhibitory KIR (iKIR) exhibited by the donor. Inhibitory KIR-HLA pair number variation was defined by loss or gain of a new cognate pair of HLA-KIR within the new HLA environment of the recipient, compared with the donor's one. Considering the results of our research, we drew the following conclusions: (i) loss of iKIR-HLA cognate pair for C1, C2, and/or Bw4 groups led to significant deterioration of disease-free survival (DFS), molecular relapse, overall survival (OS) and non-relapse mortality (NRM) for patients undergoing allo-HSCT in the standard phase of the disease. This phenomenon was not observed in patients who underwent transplantation in advanced hematological cancer. (ii) The missing ligand recognition had no impact if the proportion of HLA mismatches was not considered; however, adjustments of HLA mismatch level in the compared groups highlighted the adverse effect of the missing ligand constellation. (iii) The adverse effect of adjusted missing ligand suggests a predominance of lost NK cell education over lost NK cell inhibition in posttransplant recipients' new HLA environment. Our results suggested that donors with the loss of an iKIR-HLA cognate pair after transplantation should be avoided, and donors who provided an additional iKIR-HLA cognate pair should be preferred in the allo-HSCT donor selection process.


Assuntos
Neoplasias Hematológicas , Transplante de Células-Tronco Hematopoéticas , Leucemia Mielogênica Crônica BCR-ABL Positiva , Humanos , Ligantes , Alelos , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , Células Matadoras Naturais , Neoplasias Hematológicas/genética , Receptores KIR/genética , Doença Crônica , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/terapia , Recidiva
7.
Materials (Basel) ; 17(8)2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38673101

RESUMO

Oxide Dispersion Strengthened (ODS) ferritic steels are promising materials for the nuclear power sector. This paper presents the results of a study on the sintering process using the Spark Plasma Sintering (SPS) technique, focusing on ODS ferritic steel powders with different contents (0.3 and 0.6 vol.%) of Y2O3. The novelty lies in the analysis of the effect of pre-annealing treatment on powders previously prepared by mechanical alloying on the microstructure, mechanical, and thermal properties of the sinters. Using the SPS method, it was possible to obtain well-densified sinters with a relative density above 98%. Pre-annealing the powders resulted in an increase in the relative density of the sinters and a slight increase in their thermal conductivity. The use of low electron energies during SEM analysis allowed for a fairly good visualization of the reinforcing oxides uniformly dispersed in the matrix. Analysis of the Mössbauer spectroscopy results revealed that pre-annealing induces local atomic rearrangements within the solid solution. In addition, there was an additional spectral component, indicating the formation of a Cr-based paramagnetic phase. The ODS material with a higher Y2O3 content showed increased Vickers hardness values, as well as increased Young's modulus and nanohardness, as determined by nanoindentation tests.

8.
Conserv Biol ; 27(4): 644-56, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23692056

RESUMO

Population viability analyses (PVAs) contribute to conservation theory, policy, and management. Most PVAs focus on single species within a given landscape and address a specific problem. This specificity often is reflected in the organization of published PVA descriptions. Many lack structure, making them difficult to understand, assess, repeat, or use for drawing generalizations across PVA studies. In an assessment comparing published PVAs and existing guidelines, we found that model selection was rarely justified; important parameters remained neglected or their implementation was described vaguely; limited details were given on parameter ranges, sensitivity analysis, and scenarios; and results were often reported too inconsistently to enable repeatability and comparability. Although many guidelines exist on how to design and implement reliable PVAs and standards exist for documenting and communicating ecological models in general, there is a lack of organized guidelines for designing, applying, and communicating PVAs that account for their diversity of structures and contents. To fill this gap, we integrated published guidelines and recommendations for PVA design and application, protocols for documenting ecological models in general and individual-based models in particular, and our collective experience in developing, applying, and reviewing PVAs. We devised a comprehensive protocol for the design, application, and communication of PVAs (DAC-PVA), which has 3 primary elements. The first defines what a useful PVA is; the second element provides a workflow for the design and application of a useful PVA and highlights important aspects that need to be considered during these processes; and the third element focuses on communication of PVAs to ensure clarity, comprehensiveness, repeatability, and comparability. Thereby, DAC-PVA should strengthen the credibility and relevance of PVAs for policy and management, and improve the capacity to generalize PVA findings across studies.


Assuntos
Conservação dos Recursos Naturais/métodos , Ecologia/métodos , Modelos Biológicos , Estatística como Assunto/métodos , Comunicação , Conservação dos Recursos Naturais/estatística & dados numéricos , Bases de Dados Factuais , Guias como Assunto , Dinâmica Populacional , Crescimento Demográfico , Incerteza
9.
Artigo em Inglês | MEDLINE | ID: mdl-35162065

RESUMO

Although empirical reports draw attention to the pathological aspects of the functioning of the homeless, recent studies show the benefits related to the elevating roles of different positive phenomena in coping with difficulties for this group of people. The main goal was to verify whether there is a direct relationship between religiosity and gratitude among the homeless, and whether this association is moderated by the reported help-seeking since both religiosity and gratitude seem to play an important role in homeless people's lives. In total, 189 homeless persons participated in the study. Their mean age was M = 56.55 (SD = 12.39; range = 27-86). Most respondents were men (n = 119; 63%). The Scale of Religious Attitude Intensity and the Gratitude Questionnaire were used. The outcomes presented a statistically significant positive correlation between religious attitude and gratitude (r = 0.326***, p = 0.001). Help-seeking played a moderatory role in this relationship. Therefore, it can be assumed that the relationship between religiosity attitude intensity and dispositional gratitude is stronger when homeless persons seek specific help from other people or institutions compared to when they do not look for assistance. Homeless people, overcoming their limitations by actively asking for help, can strengthen their bonds with God (faith, religiosity) and with others (dispositional gratitude).


Assuntos
Pessoas Mal Alojadas , Personalidade , Adaptação Psicológica , Adulto , Humanos , Masculino , Polônia , Religião
10.
Transplant Proc ; 54(4): 884-887, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35501173

RESUMO

BACKGROUND: Kidney transplant recipients (KTRs) are at an increased risk of infection with severe acute respiratory syndrome coronavirus 2, with mortality from 13% to over 30%. However, data concerning the influence of COVID-19 on long-term graft function in convalescents is lacking. The aim of this study was to evaluate the influence of COVID-19 on graft function at 6 months after recovery. METHODS: A longitudinal controlled study was conducted in a group of 1058 KTRs. Of 180 patients with COVID-19 in the past, 77 KTRs (45 male) with a mean age 50.57 ± 13.37 years, Charlson Comorbidity Index of 3 (median; interquartile range [IQR], 3-5), Fragility Score of 3 (median; IQR, 3-3), and minimum 6 months after acute COVID-19 were included. The most common symptoms were weakness (75.33%), fever (74.03%), cough (51.95%), and loss of appetite (48.05%). Thirty-three patients were hospitalized; none required invasive ventilation therapy, but 16 required oxygen support. The treatment of COVID-19 included antibiotics (38.96%), thromboprophylaxis (25.97%), and nonsteroidal anti-inflammatory drugs, or paracetamol (25.97%). RESULTS: The median (IQR) values of serum creatinine 3 months before the onset and 6 months after COVID-19 were 1.25 (0.98-1.86) and 1.26 (1.03-1.78) mg/dL (nonsignificant difference); in strata analysis, there were also no differences with regards to patients with higher and lower comorbidity (3 < Charlson Comorbidity Index < 3) and fragility (3 < Fragility Score < 3). Furthermore, creatinine concentration in KTRs and controls did not differ. CONCLUSIONS: In the group of KTRs with a mild course of COVID-19, no negative impact of the infection on graft function was observed 6 months after transplantation.


Assuntos
COVID-19 , Transplante de Rim , Tromboembolia Venosa , Adulto , Anticoagulantes , Creatinina , Humanos , Rim , Transplante de Rim/efeitos adversos , Masculino , Pessoa de Meia-Idade , Transplantados , Tromboembolia Venosa/etiologia
11.
Nat Nanotechnol ; 17(11): 1192-1197, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36138199

RESUMO

The MXene family of two-dimensional transition metal carbides and nitrides already includes ~50 members with distinct numbers of atomic layers, stoichiometric compositions and solid solutions, in-plane or out-of-plane ordering of atoms, and a variety of surface terminations. MXenes have shown properties that make them attractive for applications ranging from energy storage to electronics and medicine. Although this compositional variability allows fine-tuning of the MXene properties, it also creates challenges during the analysis of MXenes because of the presence of multiple light elements (for example, H, C, N, O, and F) in close proximity. Here, we show depth profiling of single particles of MXenes and their parent MAX phases with atomic resolution using ultralow-energy secondary-ion mass spectrometry. We directly detect oxygen in the carbon sublattice, thereby demonstrating the existence of oxycarbide MXenes. We also determine the composition of adjacent surface termination layers and show their interaction with each other. Analysis of the metal sublattice shows that Mo2TiAlC2 MAX exhibits perfect out-of-plane ordering, whereas Cr2TiAlC2 MAX exhibits some intermixing between Cr and Ti in the inner transition metal layer. Our results showcase the capabilities of the developed secondary-ion mass spectrometry technique to probe the composition of layered and two-dimensional materials with monoatomic-layer precision.

12.
J Clin Med ; 10(21)2021 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-34768725

RESUMO

INTRODUCTION: Patients after SARS-CoV-2 infection frequently face "Post-COVID-19 Syndrome", defined by symptoms that develop during or after COVID-19, continue for more than 12 weeks, and are not explained by an alternative diagnosis. We aimed to evaluate the presence of post-COVID-19 syndrome and its predictors in kidney transplant recipients (KTR) 6 months after the disease. MATERIALS AND METHODS: A total of 67 KTR (38 m) with a mean age of 53.6 ± 14 years, 7.3 ± 6.4 years post-transplant were included in the cohort longitudinal study. Thirty-nine (58.2%) of them were hospitalized, but not one required invasive ventilation therapy. They were interviewed 6 months after being infected, with a series of standardized questionnaires: a self-reported symptoms questionnaire, the modified British Medical Research Council (mMRC) dyspnea scale, EQ-5D-5L questionnaire, and EQ-VAS scale. RESULTS: Post-COVID-19 syndrome was diagnosed in 70.1% of KTR and 26.9% of them reported at least three persistent symptoms. The most common symptoms were fatigue (43.3%), hair loss (31.3%), memory impairment (11.9%), muscle aches, and headaches (11.9%). Dyspnea with an mMRC scale grade of at least 1 was reported by 34.3% patients vs. 14.9% before infection; 47.8% stated that they still feel worse than before the disease. Mean EQ-VAS scores were 64.83 vs. 73.34 before infection. The persistent symptoms are more frequent in older patients and those with greater comorbidity. CONCLUSIONS: Persistent symptoms of post-COVID-19 syndrome are present in the majority of KTR, which highlights the need for long-term follow-up as well as diagnostic and rehabilitation programs.

13.
Psychol Res Behav Manag ; 13: 977-988, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33204190

RESUMO

BACKGROUND: Among many possible variables that can be associated with gratitude, researchers list personality traits. Considering that these relationships are not always consistent, the first purpose of the present study was to verify how the Big Five factors connect to dispositional gratitude in a sample of Polish participants. The second purpose was to assess the unique contribution of personality traits on gratitude with multiple regression analyses. Moreover, because much remains to be learned about whether these associations are indirectly influenced by different personal or social variables, the third goal was to explore the role of emotional intelligence as a potential mediational mechanism implicated in the relationship between personality traits and gratitude. PARTICIPANTS METHODS AND DATA COLLECTION: The sample consisted of 712 Polish respondents who were aged between 17 and 88. Most of them were women (64.3%). They answered questionnaires concerning their personality traits, emotional intelligence, and gratitude. The research was conducted using the paper-and-pencil method through convenience sampling. RESULTS: The results showed that both gratitude and emotional intelligence correlated positively and significantly with extraversion, openness to experience, agreeableness, and conscientiousness. Gratitude and emotional intelligence correlated negatively and significantly with neuroticism. The personality predictor of gratitude with the highest and positive standardized regression value was agreeableness, followed by openness to experience and extraversion. Neuroticism had a negative impact on gratitude. Conscientiousness was the only statistically insignificant predictor in the tested multiple regression model. Moreover, emotional intelligence mediated the relationship between four dimensions of personality (extraversion, openness to experience, agreeableness, and conscientiousness) and gratitude and acted as a suppressor between neuroticism and gratitude. CONCLUSION: The current study broadens our comprehension of the interaction among personality traits, emotional intelligence, and a grateful disposition. Moreover, it imparts a noteworthy foundation not only for the mediatory role of emotional intelligence between four dimensions of personality and gratitude but also for its suppressor effect between neuroticism and being grateful.

14.
Polymers (Basel) ; 12(8)2020 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-32751597

RESUMO

The article describes a systematic investigation of the effects of an aqueous NaOH treatment of 3D printed poly(lactic acid) (PLA) scaffolds for surface activation. The PLA surface undergoes several morphology changes and after an initial surface roughening, the surface becomes smoother again before the material dissolves. Erosion rates and surface morphologies can be controlled by the treatment. At the same time, the bulk mechanical properties of the treated materials remain unaltered. This indicates that NaOH treatment of 3D printed PLA scaffolds is a simple, yet viable strategy for surface activation without compromising the mechanical stability of PLA scaffolds.

15.
HLA ; 94 Suppl 2: 40-48, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31758851

RESUMO

Viral infections are the main cause of increased morbidity and mortality among recipients in allogeneic hematopoietic stem cell transplantation (HSCT). Natural killer (NK) cells fight virally infected cells provided directional activation of cytotoxicity. In this study, we analyzed the role of receptor-ligand pairs that include inhibitory or activating killer cell immunoglobulin-like receptors (KIRs) with their HLA class I ligands in the course of viral infections. The paper also presents an algorithm that allows performing automated inhibitory (i) KIR:HLA pairing and rechecking in the clinical setting. The obtained results indicate a significant adverse roles of reduced number of iKIR:HLA pairs (40% vs 9%; odds ratio [OR] = 6.67; P = .0057; 95% confidence interval [CI] 1.74-25.62) and the presence of activating KIR:HLA pairs (15% vs 5%, OR = 3.58, P = .028, 95% CI 1.19-10.73) in EBV infections post HSCT.


Assuntos
Infecções por Vírus Epstein-Barr/imunologia , Infecções por Vírus Epstein-Barr/metabolismo , Antígenos HLA/metabolismo , Transplante de Células-Tronco Hematopoéticas , Teste de Histocompatibilidade/métodos , Receptores KIR/metabolismo , Linfócitos T/imunologia , Adolescente , Adulto , Criança , Pré-Escolar , Estudos de Coortes , Infecções por Vírus Epstein-Barr/complicações , Infecções por Vírus Epstein-Barr/epidemiologia , Feminino , Seguimentos , Rejeição de Enxerto/epidemiologia , Rejeição de Enxerto/imunologia , Rejeição de Enxerto/virologia , Neoplasias Hematológicas/complicações , Neoplasias Hematológicas/epidemiologia , Neoplasias Hematológicas/imunologia , Neoplasias Hematológicas/terapia , Transplante de Células-Tronco Hematopoéticas/efeitos adversos , Transplante de Células-Tronco Hematopoéticas/métodos , Humanos , Hospedeiro Imunocomprometido/imunologia , Lactente , Células Matadoras Naturais/imunologia , Masculino , Pessoa de Meia-Idade , Ligação Proteica , Imunologia de Transplantes , Transplante Homólogo/efeitos adversos , Doadores não Relacionados , Ativação Viral/fisiologia , Adulto Jovem
16.
Nanoscale ; 10(26): 12497-12504, 2018 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-29931021

RESUMO

Two oppositely charged water-soluble oligosiloxanes with the same main chain were synthesized and used for the formation of multilayer nanocoatings. In spite of low molecular weight of the components, due to entropic reasons, linearly growing and robust films with a hydrophilic surface were formed for the first time. The multilayer films were found to be resistant to high temperature water treatment undergoing only reversible swelling and no surface recovery was observed after prolonged exposure to air indicating permanent water wettability of these silicone-based coatings. High flexibility of the silicone chains resulted in low glass transition temperature (ca. 27 °C) of both dry polyplexes and films as determined using calorimetry and spectroscopic ellipsometry, respectively. Moreover, the thin coating was applied on plasma-treated poly(dimethylsiloxane) preventing surface reconstruction in air and leading to long-lasting hydrophilization of the surface (water contact angles around 65°). Such water-borne systems may be used in common applications of silicones providing high flexibility and at the same time water wettability of the coatings.

17.
Polymers (Basel) ; 10(10)2018 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-30961090

RESUMO

This article describes the synthesis of anionic polymer brushes and their mineralization with calcium phosphate. The brushes are based on poly(3-sulfopropyl methacrylate potassium salt) providing a highly charged polymer brush surface. Homogeneous brushes with reproducible thicknesses are obtained via surface-initiated atom transfer radical polymerization. Mineralization with doubly concentrated simulated body fluid yields polymer/inorganic hybrid films containing AB-Type carbonated hydroxyapatite (CHAP), a material resembling the inorganic component of bone. Moreover, growth experiments using Dictyostelium discoideum amoebae demonstrate that the mineral-free and the mineral-containing polymer brushes have a good biocompatibility suggesting their use as biocompatible surfaces in implantology or related fields.

18.
Colloids Surf B Biointerfaces ; 135: 133-142, 2015 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-26253533

RESUMO

Ultrathin "one-component" multilayer polymeric films for potential biomedical applications were designed based on polyvinyl alcohol,-a non-toxic, fully degradable synthetic polymer. Good uniformity of the obtained film and adequate adsorption properties of the polymeric layers were achieved by functional modification of the polymer, which involved synthesis of cationic and anionic derivatives. Synthesized polymers were characterized by FTIR, NMR spectroscopy, dynamic light scattering measurements and elemental analysis. The layer by layer assembly technique was used to build up a multilayer film and this process was followed using UV-Vis spectroscopy and ellipsometry. The morphology and thickness of the obtained multilayered film material was evaluated by atomic force microscopy (AFM). Preliminary studies on the application of the obtained multilayer film for coating of liposomal nanocarriers containing phenytoin, an antiarrhythmic drug, were performed. The coating effectively stabilizes liposomes and the effect increases with an increasing number of deposited layers until the polymeric film reaches the optimal thickness. The obtained release profiles suggest that bilayer-coated liposomes release phenytoin less rapidly than uncoated ones. The cytotoxicity studies performed for all obtained nanocarriers confirmed that none of them has negative effect on cell viability. All of the performed experiments suggest that liposomes coated with ultrathin film obtained from PVA derivatives can be attractive drug nanocarriers.


Assuntos
Antiarrítmicos/administração & dosagem , Fenitoína/administração & dosagem , Álcool de Polivinil/química , Adulto , Antiarrítmicos/química , Antiarrítmicos/toxicidade , Sobrevivência Celular/efeitos dos fármacos , Preparações de Ação Retardada , Portadores de Fármacos , Sistemas de Liberação de Medicamentos , Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Humanos , Lipossomos , Microscopia de Força Atômica , Fenitoína/química , Fenitoína/toxicidade , Solubilidade
19.
PLoS One ; 9(10): e110219, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25330414

RESUMO

Weather extremes may have strong effects on biodiversity, as known from theoretical and modelling studies. Predicted negative effects of increased weather variation are found only for a few species, mostly plants and birds in empirical studies. Therefore, we investigated correlations between weather variability and patterns in occupancy, local colonisations and local extinctions (metapopulation metrics) across four groups of ectotherms: Odonata, Orthoptera, Lepidoptera, and Reptilia. We analysed data of 134 species on a 1×1 km-grid base, collected in the last 20 years from the Netherlands, combining standardised data and opportunistic data. We applied dynamic site-occupancy models and used the results as input for analyses of (i) trends in distribution patterns, (ii) the effect of temperature on colonisation and persistence probability, and (iii) the effect of years with extreme weather on all the three metapopulation metrics. All groups, except butterflies, showed more positive than negative trends in metapopulation metrics. We did not find evidence that the probability of colonisation or persistence increases with temperature nor that extreme weather events are reflected in higher extinction risks. We could not prove that weather extremes have visible and consistent negative effects on ectothermic species in temperate northern hemisphere. These findings do not confirm the general prediction that increased weather variability imperils biodiversity. We conclude that weather extremes might not be ecologically relevant for the majority of species. Populations might be buffered against weather variation (e.g. by habitat heterogeneity), or other factors might be masking the effects (e.g. availability and quality of habitat). Consequently, we postulate that weather extremes have less, or different, impact in real world metapopulations than theory and models suggest.


Assuntos
Distribuição Animal/fisiologia , Biodiversidade , Insetos/fisiologia , Répteis/fisiologia , Tempo (Meteorologia) , Animais , Demografia , Modelos Biológicos , Países Baixos , Dinâmica Populacional , Especificidade da Espécie
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