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1.
Adv Tech Stand Neurosurg ; 46: 65-94, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37318570

RESUMO

Cerebellar mutism syndrome (CMS) has received increasing attention over the last decades as a complication of posterior fossa tumour surgery in children. Risk factors, aetiological aspects, and treatment measures of the syndrome have been investigated, yet the incidence of CMS remains unchanged. Overall, we are currently able to identify patients at risk, but we are unable to prevent it from occurring.Once CMS sets in, several symptomatic pharmacological treatments have been suggested, but only in smaller case series and not in randomized controlled trials, and it is not clear whether the treatment or time itself had a helpful effect.Within weeks to months, most patients regain their ability to speak after a phase with mutism or severely reduced speech; however, many patients continue to have speech and language deficits. At this point, anti-cancer treatment with chemotherapy and radiotherapy may be of focus more than the prognosis of CMS; however, many patients continue to have speech and language problems for months and years to come, and they are at high risk of other neurocognitive sequelae as well.Without reliable measures to prevent or treat the syndrome, we may look towards improving the prognosis of speech and neurocognitive functioning in these patients. As speech and language impairment is the cardinal symptom and late effect of CMS, the effect of intense and early-onset speech and language therapy as a standard of care in these patients should be investigated in relation to its effect on regaining speech capacity.


Assuntos
Neoplasias Encefálicas , Doenças Cerebelares , Neoplasias Infratentoriais , Mutismo , Criança , Humanos , Mutismo/diagnóstico , Doenças Cerebelares/diagnóstico , Neoplasias Encefálicas/complicações , Neoplasias Infratentoriais/complicações , Medição de Risco , Síndrome , Progressão da Doença , Complicações Pós-Operatórias/diagnóstico
2.
Alzheimer Dis Assoc Disord ; 34(1): 47-53, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31414991

RESUMO

OBJECTIVE: Neuroinflammation may play an important role in the pathogenesis and progression of Alzheimer disease (AD). The aim of the present study was to detect whether increased inflammatory activity at baseline could predict cognitive and functional decline in patients with amnestic mild cognitive impairment (aMCI) or AD dementia after 2 years. METHODS: Serum samples from 242 memory clinic patients with an aMCI (n=88) or AD dementia (n=154) were analyzed for C-reactive protein and for 14 other inflammatory markers [interleukin (IL)-1ß, interleukin-1 receptor antagonist, IL-6, IL-10, IL-12p40, IL-17a, IL-18, IL-22, IL-33, tumor necrosis factor, cluster of differentiation 40 ligand, interferon-γ, chemokine ligand (CCL) 2, and CCL4] by bead-based multiplex immunoassay. Disease progression was measured by the annual increase in the Clinical Dementia Rating Scale Sum of Boxes (CDR-SB) and annual decrease in the score on the Mini-Mental State Examination (MMSE). RESULTS: No association between increased levels of the inflammatory markers and change on the CDR-SB or MMSE score was found, but there was a significant difference in baseline IL-6 and interleukin-1 receptor antagonist levels between aMCI and AD dementia groups. CONCLUSION: Increased levels of inflammatory markers were not associated with faster progression as measured by the annual change on the CDR-SB or MMSE score.


Assuntos
Doença de Alzheimer/epidemiologia , Biomarcadores/sangue , Disfunção Cognitiva/epidemiologia , Progressão da Doença , Inflamação , Idoso , Idoso de 80 Anos ou mais , Doença de Alzheimer/sangue , Disfunção Cognitiva/sangue , Feminino , Humanos , Inflamação/sangue , Interleucinas/análise , Estudos Longitudinais , Masculino , Testes de Estado Mental e Demência/estatística & dados numéricos , Pessoa de Meia-Idade , Testes Neuropsicológicos/estatística & dados numéricos , Noruega/epidemiologia
3.
NPJ Vaccines ; 4: 1, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30622742

RESUMO

Aluminum salts, developed almost a century ago, remain the most commonly used adjuvant for licensed human vaccines. Compared to more recently developed vaccine adjuvants, aluminum adjuvants such as Alhydrogel are heterogeneous in nature, consisting of 1-10 micrometer-sized aggregates of nanoparticle aluminum oxyhydroxide fibers. To determine whether the particle size and aggregated state of aluminum oxyhydroxide affects its adjuvant activity, we developed a scalable, top-down process to produce stable nanoparticles (nanoalum) from the clinical adjuvant Alhydrogel by including poly(acrylic acid) (PAA) polymer as a stabilizing agent. Surprisingly, the PAA:nanoalum adjuvant elicited a robust TH1 immune response characterized by antigen-specific CD4+ T cells expressing IFN-γ and TNF, as well as high IgG2 titers, whereas the parent Alhydrogel and PAA elicited modest TH2 immunity characterized by IgG1 antibodies. ASC, NLRP3 and the IL-18R were all essential for TH1 induction, indicating an essential role of the inflammasome in this adjuvant's activity. Compared to microparticle Alhydrogel this nanoalum adjuvant provided superior immunogenicity and increased protective efficacy against lethal influenza challenge. Therefore PAA:nanoalum represents a new class of alum adjuvant that preferentially enhances TH1 immunity to vaccine antigens. This adjuvant may be widely beneficial to vaccines for which TH1 immunity is important, including tuberculosis, pertussis, and malaria.

4.
BMC Cancer ; 17(1): 439, 2017 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-28637445

RESUMO

BACKGROUND: Central nervous system tumours constitute 25% of all childhood cancers; more than half are located in the posterior fossa and surgery is usually part of therapy. One of the most disabling late effects of posterior fossa tumour surgery is the cerebellar mutism syndrome (CMS) which has been reported in up to 39% of the patients but the exact incidence is uncertain since milder cases may be unrecognized. Recovery is usually incomplete. Reported risk factors are tumour type, midline location and brainstem involvement, but the exact aetiology, surgical and other risk factors, the clinical course and strategies for prevention and treatment are yet to be determined. METHODS: This observational, prospective, multicentre study will include 500 children with posterior fossa tumours. It opened late 2014 with participation from 20 Nordic and Baltic centres. From 2016, five British centres and four Dutch centres will join with a total annual accrual of 130 patients. Three other major European centres are invited to join from 2016/17. Follow-up will run for 12 months after inclusion of the last patient. All patients are treated according to local practice. Clinical data are collected through standardized online registration at pre-determined time points pre- and postoperatively. Neurological status and speech functions are examined pre-operatively and postoperatively at 1-4 weeks, 2 and 12 months. Pre- and postoperative speech samples are recorded and analysed. Imaging will be reviewed centrally. Pathology is classified according to the 2007 WHO system. Germline DNA will be collected from all patients for associations between CMS characteristics and host genome variants including pathway profiles. DISCUSSION: Through prospective and detailed collection of information on 1) differences in incidence and clinical course of CMS for different patient and tumour characteristics, 2) standardized surgical data and their association with CMS, 3) diversities and results of other therapeutic interventions, and 4) the role of host genome variants, we aim to achieve a better understanding of risk factors for and the clinical course of CMS - with the ultimate goal of defining strategies for prevention and treatment of this severely disabling condition. TRIAL REGISTRATION: Clinicaltrials.gov : NCT02300766 , date of registration: November 21, 2014.


Assuntos
Neoplasias Cerebelares/cirurgia , Neoplasias Infratentoriais/cirurgia , Mutismo/fisiopatologia , Complicações Pós-Operatórias/fisiopatologia , Adolescente , Neoplasias Cerebelares/complicações , Neoplasias Cerebelares/epidemiologia , Neoplasias Cerebelares/fisiopatologia , Cerebelo/fisiopatologia , Cerebelo/cirurgia , Criança , Pré-Escolar , Dinamarca/epidemiologia , Feminino , Humanos , Lactente , Neoplasias Infratentoriais/complicações , Neoplasias Infratentoriais/epidemiologia , Neoplasias Infratentoriais/fisiopatologia , Masculino , Mutismo/epidemiologia , Mutismo/etiologia , Procedimentos Neurocirúrgicos , Complicações Pós-Operatórias/epidemiologia , Complicações Pós-Operatórias/etiologia , Fatores de Risco
5.
Toxicol In Vitro ; 27(2): 932-8, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23318728

RESUMO

Cigarette smoking is a leading cause of cardiovascular disease. The cardiovascular effects of smoking are probably multifactorial, including effects on platelets. Previous reports investigating the effects of nicotine and tobacco on platelet function are inconsistent. The present study investigated in vitro effects of nicotine, its major metabolites, tobacco extracts and extract of tobacco-free snuff on human platelets. None of the metabolites cotinine, cotinine-N-oxide, nicotine-1'-N-oxide or trans-3'-hydroxycotinine (0.1-10 µM) affected platelet aggregation or P-selectin expression. Nicotine (10 µM) weakly increased platelet aggregation, whereas trans-3'-hydroxycotinine (0.1 µM) and nicotine-1'-N-oxide (1-10 µM) weakly inhibited adhesion to fibrinogen. To elucidate the influence of other tobacco compounds, we investigated the impact of moist tobacco and smoke extracts on platelet function. Filtered extracts of oral snuff, cigarette smoke and tobacco free snuff inhibited platelet adhesion concentration-dependently. The inhibitory effects of tobacco extracts on platelet adhesion were independent of nicotine content and the nitric-oxide-pathway and not mediated through a platelet-nicotine-receptor. Taken together, tobacco extracts inhibit platelet activation during short-term in vitro challenge. As only limited effects of nicotine and nicotine metabolites were seen, the tobacco-induced platelet inhibition are likely induced by other compounds present in tobacco and tobacco free snuff.


Assuntos
Plaquetas/efeitos dos fármacos , Cotinina/análogos & derivados , Cotinina/toxicidade , Nicotiana , Extratos Vegetais/toxicidade , Plaquetas/fisiologia , Células Cultivadas , Humanos , Nicotina/análise , Nicotina/toxicidade , Extratos Vegetais/química , Agregação Plaquetária/efeitos dos fármacos
6.
Eur Neuropsychopharmacol ; 23(10): 1296-9, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23265955

RESUMO

The self-report Drug Attitude Inventory (DAI), in 30- and 10-item versions, provides unique information of clinical relevance for monitoring treatment adherence among people diagnosed with schizophrenia. The primary purpose of this paper was to evaluate the 10-item version among patients living in sheltered housing. Data were collected among 68 persons living in sheltered housing, most of them (82%) diagnosed with schizophrenia, 6% with non-organic psychoses, and 12% with other diagnoses. The dichotomic response format of the original DAI-10 was replaced by a 4-point Likert scale, in order to improve the resolution of the scale. Over 90% of the participants produced meaningful scores. A factor analysis suggested a 2-factor orthogonal structure: one highly homogenous factor (5 items) reflected wanted effects of the drug and displayed a bimodal distribution; one factor (3 items) reflected side effects. One item concerned the perceived control over one's drug treatment, which is a key clinical issue. One item was conceptually ambiguous and displayed no correlations with the other items. On the basis of the results we suggest cut-off scores which indicate the need for three kinds of adherence-improving interventions. Summing up, by dropping one item and using a Likert scale response format, the resulting instrument, DAI-9, appears to be an easy-to-use self-report instrument for monitoring drug attitudes and to identify needs for treatment adherence interventions among seriously ill patients.


Assuntos
Antipsicóticos/uso terapêutico , Programas de Rastreamento/métodos , Adesão à Medicação , Habitação Popular , Esquizofrenia/tratamento farmacológico , Psicologia do Esquizofrênico , Adulto , Idoso , Antipsicóticos/efeitos adversos , Atitude Frente a Saúde , Análise Fatorial , Humanos , Classificação Internacional de Doenças , Transtornos Mentais/diagnóstico , Transtornos Mentais/tratamento farmacológico , Pessoa de Meia-Idade , Participação do Paciente , Prognóstico , Psicoses Induzidas por Substâncias/diagnóstico , Psicoses Induzidas por Substâncias/tratamento farmacológico , Esquizofrenia/diagnóstico , Autorrelato , Suécia , Adulto Jovem
7.
J Renin Angiotensin Aldosterone Syst ; 12(3): 281-9, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21273224

RESUMO

INTRODUCTION: A polymorphism in the angiotensin-converting enzyme gene (ACE I/D polymorphism) has been associated with increased risk for cardiovascular disease (CVD). This polymorphism affects the level of circulating ACE, but there is great individual variation, even between those with the same genotype. Few previous studies have investigated the link between circulating ACE and cardiovascular risk. The aim of this study was to investigate this association, and to examine the relationship between ACE level, ACE genotype and CVD. MATERIALS AND METHODS: The study population consisted of 322 men and 350 women aged 69-87. Plasma ACE level was determined using enzyme-linked immunosorbent assay (ELISA), and ACE genotype was analysed using PCR followed by gel electrophoresis. RESULTS: In men, ACE levels increased with increasing number of cardiovascular risk factors (p = 0.003). There was a significant association in men between increased ACE level and both diabetes (p = 0.007) and smoking (p = 0.037). CONCLUSIONS: This study shows that cardiovascular risk factors (such as smoking and diabetes) are associated with higher levels of circulating ACE in men. High ACE levels may represent one of the cellular mechanisms involved in producing the vascular damage associated with cardiovascular risk factors.


Assuntos
Doenças Cardiovasculares/sangue , Doenças Cardiovasculares/epidemiologia , Peptidil Dipeptidase A/sangue , Idoso , Idoso de 80 Anos ou mais , Doenças Cardiovasculares/genética , Estudos Transversais , Feminino , Predisposição Genética para Doença , Humanos , Mutação INDEL/genética , Masculino , Peptidil Dipeptidase A/genética , Polimorfismo Genético , Fatores de Risco , Suécia/epidemiologia
8.
Phytother Res ; 24(9): 1297-301, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20148408

RESUMO

Extract from seeds and bark of horse chestnut (Aesculus hippocastanum L) is used as an herbal medicine against chronic venous insufficiency. The effect and mechanism of action on veins, arteries, and platelets are not fully understood. The aim of this study was to investigate the effects and mechanisms of action of horse chestnut on the contraction of bovine mesenteric veins and arteries, and human platelet aggregation. Contraction studies showed that horse chestnut extract dose-dependently contracted both veins and arteries, with the veins being the most sensitive. Contraction of both veins and arteries were significantly inhibited by the 5-HT(2A) receptor antagonist ketanserin. No effect on contraction was seen with the cyclooxygenase inhibitor indomethacin, the alpha(1) receptor antagonist prazosin or the angiotensin AT(1) receptor antagonist saralasin neither in veins nor arteries. ADP-induced human platelet aggregation was significantly reduced by horse chestnut. A further reduction was seen with the extract in the presence of ketanserin. In conclusion, horse chestnut contraction of both veins and arteries is, at least partly, mediated through 5-HT(2A) receptors. Human platelet aggregation is reduced by horse chestnut. The clinical importance of these findings concerning clinical use, possible adverse effects, and drug interactions remains to be investigated.


Assuntos
Aesculus , Contração Muscular/efeitos dos fármacos , Músculo Liso Vascular/efeitos dos fármacos , Extratos Vegetais/farmacologia , Agregação Plaquetária/efeitos dos fármacos , Receptor 5-HT2A de Serotonina/metabolismo , Agonistas do Receptor 5-HT2 de Serotonina/farmacologia , Difosfato de Adenosina , Antagonistas de Receptores Adrenérgicos alfa 1/farmacologia , Bloqueadores do Receptor Tipo 1 de Angiotensina II/farmacologia , Animais , Bovinos , Inibidores de Ciclo-Oxigenase/farmacologia , Relação Dose-Resposta a Droga , Humanos , Ketanserina/farmacologia , Artérias Mesentéricas/efeitos dos fármacos , Veias Mesentéricas/efeitos dos fármacos , Casca de Planta , Inibidores da Agregação Plaquetária/farmacologia , Sementes , Antagonistas do Receptor 5-HT2 de Serotonina/farmacologia
9.
J Agric Food Chem ; 57(11): 4626-9, 2009 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-19441816

RESUMO

This study investigates if the connection between Vaccinium myrtillus and angiotensin-converting enzyme (ACE) might be an explanation of the pharmacological effects on circulation. Cultured endothelial cells from human umbilical veins were incubated with bilberry 25E extract. The main anthocyanidins combined in myrtillin chloride and separately in cyanidin, delphinidin, and malvidin, respectively, were examined concerning their effects on ACE. After 10 min of incubation with bilberry 25E, a significant, dose-dependent inhibition of ACE activity was seen, and after incubation with myrtillin chloride a significant inhibition was seen. No effect was seen with the anthocyanidins. The effect seems to be dependent on this specific mixture of anthocyanins in the bilberry. V. myrtillus may thus have the potential to prevent and protect against cardiovascular diseases.


Assuntos
Inibidores da Enzima Conversora de Angiotensina/farmacologia , Antocianinas/farmacologia , Células Endoteliais/enzimologia , Flavonoides/farmacologia , Peptidil Dipeptidase A/metabolismo , Fenóis/farmacologia , Vaccinium myrtillus/química , Células Cultivadas , Células Endoteliais/efeitos dos fármacos , Humanos , Extratos Vegetais , Polifenóis , Veias Umbilicais/citologia , Veias Umbilicais/enzimologia
10.
APMIS ; 117(1): 1-9, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19161531

RESUMO

Oxidized low-density lipoprotein (LDL) diminishes NO production from activated macrophages. The interaction between LDL and inactivated macrophages is neglected and controversial. This study examines the effect of LDL, 7-oxysterols and iron compounds on NO production in unstimulated J774 macrophages. J774 cells and human umbilical vein endothelial cells (HUVEC) were either incubated for 24 h with native LDL (LDL) or ultraviolet (UV)-oxidized LDL (UVoxLDL), in the absence or presence of an inducible nitric oxide synthase (iNOS)- or an endothelial constitutive nitric oxide synthase (eNOS)-inhibitor. J774 cells were also incubated with lipopolysaccharide (LPS), in the absence or presence of an iNOS- or an eNOS-inhibitor. Nitrite was analysed as a marker of NO production. The mRNA levels of iNOS were evaluated by reverse transcriptase polymerase chain reaction. LDL and UVoxLDL significantly increased NO production from unstimulated J774 macrophages. This increase in NO was accompanied by enhanced expression of iNOS mRNA, and was inhibited by the iNOS inhibitor. Furthermore, NO production was elevated and angiotensin-converting enzyme (ACE) activity was reduced in HUVEC following the exposure to LDL and UVoxLDL. In conclusion, LDL may serve as an important inflammatory activator of macrophages and HUVEC, inducing inducible nitric oxide production but diminishing ACE. After its oxidation, this function of LDL may be further enhanced and may contribute to the regulation and progression of atheroma formation.


Assuntos
LDL-Colesterol/metabolismo , Células Endoteliais/metabolismo , Macrófagos/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Óxido Nítrico/metabolismo , Animais , Células Cultivadas , LDL-Colesterol/farmacologia , LDL-Colesterol/efeitos da radiação , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/enzimologia , Humanos , Macrófagos/efeitos dos fármacos , Macrófagos/enzimologia , Camundongos , Óxido Nítrico Sintase Tipo II/antagonistas & inibidores , Óxido Nítrico Sintase Tipo II/genética , Nitritos/análise , Nitritos/metabolismo , Oxirredução , Peptidil Dipeptidase A/metabolismo , RNA Mensageiro/análise , RNA Mensageiro/genética , Raios Ultravioleta , Cordão Umbilical/citologia , Regulação para Cima
11.
Endothelium ; 15(5-6): 239-45, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-19065315

RESUMO

Nicotine has been shown to induce endothelial dysfunction, which is an early marker of atherosclerosis. Nicotine undergoes extensive metabolism in the liver, forming a number of major and minor metabolites. There are very limited data on the effect of nicotine metabolites on the cardiovascular system. This study investigates the effects of nicotine and the nicotine metabolites, cotinine, cotinine-N-oxide, nicotine-1'-N-oxide, norcotinine, trans-3'-hydroxycotinine, on angiotensin-converting enzyme (ACE) in human endothelial cells. Cultured endothelial cells obtained from human umbilical cord vein (HUVECs) were stimulated with nicotine or nicotine metabolites in concentrations similar to those observed in plasma during smoking. ACE activity and expression were analyzed using commercial kits. The results showed that nicotine and nicotine metabolites can increase both activity and expression of ACE. However, a marked individual variation in the response to the drugs was observed. This variation was not associated with the ACE insertion/deletion polymorphism. Tobacco contains numerous chemical compounds, and the underlying cause for development of atherosclerosis in smokers is probably multifactorial. The results from this study could explain one cellular mechanism by which smoking exerts negative effect on the vascular system.


Assuntos
Aterosclerose/induzido quimicamente , Células Endoteliais/efeitos dos fármacos , Nicotina/farmacologia , Agonistas Nicotínicos/farmacologia , Peptidil Dipeptidase A/efeitos dos fármacos , Aterosclerose/metabolismo , Aterosclerose/fisiopatologia , Células Cultivadas , Cotinina/análogos & derivados , Cotinina/metabolismo , Cotinina/farmacologia , Óxidos N-Cíclicos/metabolismo , Óxidos N-Cíclicos/farmacologia , Células Endoteliais/metabolismo , Ativação Enzimática/efeitos dos fármacos , Ativação Enzimática/genética , Humanos , Nicotina/análogos & derivados , Nicotina/metabolismo , Agonistas Nicotínicos/metabolismo , Peptidil Dipeptidase A/genética , Peptidil Dipeptidase A/metabolismo , Polimorfismo Genético/efeitos dos fármacos , Polimorfismo Genético/genética , Fumar/efeitos adversos , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/fisiologia
12.
J Ethnopharmacol ; 119(1): 17-23, 2008 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-18639398

RESUMO

Melanophores from Xenopus laevis are pigmented cells, capable of quick colour changes through cyclic adenosine 3':5'-monophosphate (cAMP) coordinated transport of their intracellular pigment granules, melanosomes. In this study we use the melanophore cell line to evaluate the effects of Panax ginseng extract G115 on organelle transport. Absorbance readings of melanophore-coated microplates, Correlate-EIA direct cAMP enzyme immunoassay kit, and western blot were used to measure the melanosome movement and changes in intracellular signalling. We show that Panax ginseng induces a fast concentration-dependent anterograde transport of the melanosomes. No significant increase in the cAMP level was seen and pre-incubation of melanophores with the protein kinase C (PKC) inhibitor EGF-R Fragment 651-658 (M-EGF) only partly decreased the ginseng-induced dispersion. We also demonstrate that Panax ginseng, endothelin-3 (ET-3) and alpha-melanocyte stimulating hormone (MSH) stimulate an activation of mitogen activated protein kinase (MAPK). Pre-incubation with M-EGF decreased the MAPK activity induced by ET-3 and MSH, but again only marginally affected the response of Panax ginseng. Thus, in melanophores we suggest that Panax ginseng stimulates an anterograde transport of pigment organelles via a non-cAMP and mainly PKC-independent pathway.


Assuntos
Organelas/efeitos dos fármacos , Panax/química , Pigmentos Biológicos/metabolismo , Extratos Vegetais/farmacologia , Animais , Transporte Biológico/efeitos dos fármacos , Western Blotting , AMP Cíclico/metabolismo , Relação Dose-Resposta a Droga , Endotelina-3/farmacologia , Técnicas Imunoenzimáticas/métodos , Melanóforos/efeitos dos fármacos , Melanóforos/metabolismo , Organelas/metabolismo , Extratos Vegetais/administração & dosagem , Proteína Quinase C/efeitos dos fármacos , Proteína Quinase C/metabolismo , Transdução de Sinais/efeitos dos fármacos , Xenopus laevis , alfa-MSH/farmacologia
13.
Langmuir ; 23(21): 10598-602, 2007 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-17784777

RESUMO

The adsorption of the unsaturated fatty acids oleic, linoleic, and linolenic acid on steel surfaces has been investigated by means of a quartz crystal microbalance (QCM). Two different solvents were used, n-hexadecane and its highly branched isomer, viz., 2,2,4,4,6,8,8-heptamethylnonane. The area occupied per molecule of oleic acid at 1 wt % corresponds to what is needed for adsorption parallel to the surface. At the same concentration, the adsorbed amount of linoleic acid and linolenic acid indicates that they adsorb in multilayers. The chemisorbed amount estimated from static secondary ion mass spectroscopy (SIMS) measurements was found to be similar for the three unsaturated fatty acids. In the case of linolenic acid, it was found that the presence of water significantly alters the adsorption, most likely because of the precipitation of fatty acid/water aggregates. Furthermore, static SIMS results indicate that the amount of water used here inhibits the chemisorption of linolenic acid.


Assuntos
Alcanos/química , Ácidos Graxos Insaturados/química , Aço/química , Adsorção , Soluções , Propriedades de Superfície
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