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1.
Clin Chim Acta ; 553: 117706, 2024 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-38101466

RESUMO

We report here two patients exhibiting a combination of falsely elevated serum levels of free thyroxine (FT4), free triiodothyronine (FT3), and thyrotropin receptor antibodies (TRAb), measured using Elecsys assay kits (Roche Diagnostics GmbH). The first patient was a 74-year-old man misdiagnosed with Graves' disease and treated with methimazole. The second patient was a 48-year-old woman whose serum FT4 and FT3 concentrations were found to be high during a blood test. These patients denied taking biotin or any other supplements. Further detailed examination, including a heterophilic blocking tube test, revealed the presence of serum antibodies. The abnormal reactions were observed only using the improved assay kits using ruthenium (Ru) sulfonate instead of Ru as a chemiluminescent agent. Therefore, serum antibodies to the Ru sulfonate complex caused the pseudo-high levels of FT4, FT3, and TRAb. To our knowledge, this is the first report showing that antibodies to the Ru sulfonate complex in the electrochemiluminescence immunoassay can cause falsely elevated levels of the combination, leading to discrepant thyroid function test results. We emphasize that in cases of abnormal test results, alternative assay methods should be considered for further examination; unusual test results should not be impulsively interpreted, even when using revised assay kits.


Assuntos
Doença de Graves , Rutênio , Masculino , Feminino , Humanos , Pessoa de Meia-Idade , Idoso , Testes de Função Tireóidea , Tiroxina , Hormônios Tireóideos , Tri-Iodotironina , Anticorpos Antivirais , Tireotropina
2.
Clin Endocrinol (Oxf) ; 91(6): 786-792, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31468541

RESUMO

BACKGROUND: Adult-onset idiopathic isolated adrenocorticotropic hormone deficiency (id-IAD) is a rare disease with unknown aetiology. Recently, numerous cases of anti-PD-1 antibody-induced IAD (PD1-IAD) have been reported, but the clinical course, predictive factors and relationship to id-IAD have not been clarified. Moreover, associations of id-IAD and PD1-IAD with human leucocyte antigen (HLA) require elucidation. METHODS: Clinical characteristics of 13 Japanese patients with id-IAD and eight Japanese patients with PD1-IAD were analysed, and HLA-typing test was performed for each patient. Allele and haplotype frequencies of the patients were compared to those of healthy Japanese controls. RESULTS: In the HLA allele and haplotype analyses of id-IAD, the frequencies of HLA-C*14:02, HLA-DPB1*05:01, HLA-DRB1*04:05-DQB1*04:01-DPB1*05:01 and HLA-DRB1*09:01-DQB1*03:03-DPB1*05:01 were significantly increased. On the other hand, HLA alleles account for PD1-IAD susceptibility as follows: HLA-DQB1*06:01, HLA-DPB1*09:01 and HLA-DRB5*01:02. Moreover, protective effect for HLA-C*03:03 was suggested in combined id-IAD and PD1-IAD patients. Comparison of the effects of HLA on id-IAD and PD1-IAD revealed some differences. Alleles or haplotypes frequencies increased in id-IAD group were as follows: HLA-DPB1*05:01, HLA-DRB1*09:01, HLA-DRB4*01:03:02, HLA-DQB1*03:03 and HLA-DRB1*09:01-DQB1*03:03. In clinical settings, hyponatremia, disturbance of consciousness and hypoglycaemia were less frequently seen in patients with PD1-IAD than in patients with id-IAD. CONCLUSIONS: Distinct clinical characteristics and predisposing HLA allele contributions were proposed between id-IAD and PD1-IAD. Further investigations with greater number of cases are warranted to clarify the detailed mechanisms of id-IAD and PD1-IAD.


Assuntos
Insuficiência Adrenal/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Alelos , Frequência do Gene/genética , Genes MHC Classe I/genética , Genótipo , Cadeias HLA-DRB1/genética , Haplótipos/genética , Humanos , Pessoa de Meia-Idade , Projetos Piloto , Estudos Prospectivos , Estudos Retrospectivos
3.
In Vivo ; 32(2): 345-351, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29475919

RESUMO

BACKGROUND: Immune-checkpoint inhibitors (ICIs) are novel promising agents for the treatment of malignant tumors. However, critical endocrine immune-related adverse events (irAEs) by ICIs often occur. CASE REPORT: A 63-year-old woman with advanced malignant melanoma had received anti-PD-1 antibody (nivolumab, 2 mg/kg every 3 weeks) for 8 cycles (from day 0 to day 147). On day 168, nivolumab was switched to anti-CTLA-4 antibody (ipilimumab, 3mg/kg every 3 weeks). Twenty-eight days later, she was diagnosed with thyrotoxicosis due to painless thyroiditis (day 196). Thirty-five days later (day 231), thyrotoxicosis turned to hypothyroidism. In addition, twenty-five days later (day 256), she was diagnosed with adrenocortical insufficiency due to adrenocortical hormone (ACTH) deficiency. Hormone replacements with levothyroxine and hydrocortisone were administered. She showed eosinophilia, ESR/CRP/LDH elevation, liver dysfunction and hyponatremia before diagnosis of ACTH insufficiency. Eosinophilia, thrombocytopenia, ESR/CRP/LDH elevation, and liver dysfunction might be important for early detection of thyrotoxicosis in our case. CONCLUSION: The present report provides the first detailed presentation of combined thyrotoxicosis and isolated ACTH deficiency induced by ICIs. Since rapidly progressive fatal endocrine system failure may be provoked during ICI therapy, precise diagnosis and prompt treatment as well as close follow-up is critical. We propose routine monitoring of endocrine functions and related symptoms (worsened fatigue, hypoglycemia, hypotension or hyponatremia), as well as other laboratory tests during ICI therapy.


Assuntos
Insuficiência Adrenal/diagnóstico , Insuficiência Adrenal/etiologia , Antineoplásicos Imunológicos/efeitos adversos , Melanoma/complicações , Tireotoxicose/diagnóstico , Tireotoxicose/etiologia , Antineoplásicos Imunológicos/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Antígeno CTLA-4/antagonistas & inibidores , Evolução Fatal , Feminino , Humanos , Imageamento por Ressonância Magnética , Melanoma/diagnóstico , Melanoma/tratamento farmacológico , Pessoa de Meia-Idade , Terapia de Alvo Molecular/efeitos adversos , Terapia de Alvo Molecular/métodos , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Testes de Função Tireóidea , Ultrassonografia
4.
Intern Med ; 55(22): 3295-3299, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27853072

RESUMO

Resistance to thyroid hormone (RTH) is a genetic disorder characterized by reduced tissue responsiveness to thyroid hormone. We herein describe a 60-year old man who presented with the clinical features of cardiomyopathy, diabetes mellitus and elevated thyroid hormones with unsuppressed thyroid stimulating hormone. A genetic analysis of thyroid hormone receptor (TR) revealed a missense mutation (A268D) in the TRß gene. Clinical manifestations of RTH may be variable due to different tissue distributions of TR subtypes and different actions of mutant receptors. The current case demonstrates that patients with a TRß mutation may have impaired his glucose metabolism and a reduced cardiac function, although patients appear clinically euthyroid.


Assuntos
Diabetes Mellitus Tipo 2/complicações , Cardiomiopatias Diabéticas/complicações , Insuficiência Cardíaca/complicações , Receptores beta dos Hormônios Tireóideos/genética , Síndrome da Resistência aos Hormônios Tireóideos/complicações , Síndrome da Resistência aos Hormônios Tireóideos/genética , Diabetes Mellitus Tipo 2/sangue , Humanos , Masculino , Pessoa de Meia-Idade , Mutação de Sentido Incorreto , Receptores dos Hormônios Tireóideos/sangue , Tireotropina/sangue
5.
Endocr J ; 62(8): 711-7, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25994040

RESUMO

Immunoglobulin G4-related disease (IgG4-RD) is characterized by elevated serum IgG4 levels, IgG4-positive plasmacytes, and lymphocyte infiltration into multiple organs. IgG4 thyroiditis is a subset of patients with Hashimoto's thyroiditis (HT) who exhibited histopathological features of IgG4-RD; its source of serum IgG4 is suggested to be the thyroid gland. Although a relationship between IgG4-RD and IgG4 thyroiditis has been reported, the meaning of serum IgG4 in HT is uncertain. In this report, we prospectively evaluated serum IgG4 levels and clinical features of patients with HT. A total of 149 patients with HT were prospectively recruited into this study. According to the comprehensive diagnostic criteria of IgG4-RD, patients were divided into two groups: elevated IgG4 (>135 mg/dL) and non-elevated IgG4 (≤135 mg/dL). Median serum IgG4 levels of HT patients were 32.0 mg/dL (interquartile range, 20.0-65.0), with a unimodal non-normal distribution. Six patients (4.0%) had elevated serum IgG4 levels above 135 mg/dL. The elevated IgG4 group was older and exhibited enlarged hypoechoic areas in the thyroid gland, as revealed by ultrasonography, relative to the non-elevated IgG4 group. Levothyroxine (L-T4) replacement doses and titers of anti-thyroid antibodies did not differ significantly between the two groups. Two out of six HT patients with elevated serum IgG4 levels had extra-thyroid organ involvement as seen in IgG4-RD. In conclusion, HT patients with elevated serum IgG4 levels shared clinical features with both IgG4-RD and IgG4 thyroiditis. Longer follow-up periods and histopathological assessments are needed to further understand the meaning of elevated serum IgG4 levels in HT.


Assuntos
Doença de Hashimoto/sangue , Imunoglobulina G/sangue , Plasmócitos/imunologia , Glândula Tireoide/imunologia , Adulto , Idoso , Feminino , Doença de Hashimoto/diagnóstico , Doença de Hashimoto/imunologia , Humanos , Masculino , Pessoa de Meia-Idade , Plasmócitos/patologia , Glândula Tireoide/patologia
6.
Thyroid ; 24(4): 736-43, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24256421

RESUMO

BACKGROUND: Immunoglobulin G4-related disease (IgG4-RD) is a new clinical entity that affects various organs with increased IgG4 positive plasmacytes and progressive fibrosis. While IgG4-RDs in association with Hashimoto's thyroiditis or Riedel's thyroiditis have been reported, the relationship between IgG4-RD and Graves' disease (GD) is yet unknown. To elucidate the relation of GD to IgG4-RD, serum IgG4 levels and their clinical implications in patients with GD were investigated. METHODS: In this prospective study, serum IgG4 levels were measured in 109 patients with GD and classified into two groups according to the comprehensive diagnostic criteria of IgG4-RD previously established: (i) GD with elevated-IgG4 levels (≥ 135 mg/dL), and (ii) GD with nonelevated IgG4 (<135 mg/dL). RESULTS: Seven out of 109 patients with GD (6.4%) had elevated serum IgG4 levels [mean ± standard deviation (range): 175.0 ± 44.5 (136-266) mg/dL] and elevated ratios of IgG4/IgG [12.7 ± 4.5% (7.6%-21.2%)]. The remaining patients with GD had serum IgG4 levels and IgG4/IgG ratios of 39.6 ± 27.6 (3-132) mg/dL and 3.2 ± 2.2% (0.3%-11.5%), respectively. Ages in the elevated IgG4 group were significantly higher than those of the nonelevated IgG4 group: 54.7 ± 6.2 versus 43.4 ± 15.4 years, respectively. Ultrasound examinations revealed that the elevated IgG4 group had significantly increased hypoechogenic areas in the thyroid in comparison to the nonelevated IgG4 group (low echo scoring: 1.66 ± 0.81 vs. 0.61 ± 0.89, respectively). In the correlation analysis, TSAb (rs=0.385, n=42) titers were significantly correlated with se rum IgG4 levels, while they were not significantly different between the two groups. In the elevated IgG4 group, symptoms were controllable with a small dose of antithyroidal drug (ATD; n=4), a combination treatment with ATD and L-T4 (n=1), or L-T4 administration only one year after the first visit (n=2). CONCLUSIONS: A small portion of GD patients harbored elevated serum IgG4 levels. They were older, had increased hypoechoic areas in the thyroid, and appeared to be responsive or prone to be hypothyroid after ATD treatment. Thus, the present study suggests the presence of a novel subtype of GD. Measuring serum IgG4 levels may help to distinguish this new entity and provide potential therapeutic options for GD.


Assuntos
Doença de Graves/imunologia , Imunoglobulina G/sangue , Adolescente , Adulto , Idoso , Antitireóideos/uso terapêutico , Feminino , Doença de Graves/classificação , Doença de Graves/tratamento farmacológico , Humanos , Imunoglobulinas Estimuladoras da Glândula Tireoide/sangue , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Tiroxina/uso terapêutico , Adulto Jovem
7.
Intern Med ; 52(22): 2545-51, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24240795

RESUMO

A 72-year-old man presented with bilateral eyelid swelling and redness. An orbital CT scan showed bilateral proptosis, extraocular muscle enlargement and swollen lacrimal glands, mimicking thyroid-associated orbitopathy (TAO) with Hashimoto's thyroiditis (HT). During the patient's clinical course, spontaneous remission of lung consolidation (35 × 26 mm) was seen. A diagnosis of IgG4-related disease (IgG4-RD) was made based on an elevated serum IgG4 level (1,020 mg/dL; normal, 4-108), predominance of IgG4-positive plasma cells (IgG4/IgG: 35/70 in HPF) in the lacrimal glands and typical features of Mikulicz's disease. This report provides a novel description of this unusual disease entity among HT, TAO and IgG4-RD.


Assuntos
Doenças dos Anexos/imunologia , Oftalmopatias/imunologia , Imunoglobulina G/sangue , Doenças dos Anexos/diagnóstico , Idoso , Diagnóstico Diferencial , Oftalmopatias/diagnóstico , Feminino , Oftalmopatia de Graves/diagnóstico , Doença de Hashimoto/diagnóstico , Humanos , Imunoglobulina G/metabolismo , Aparelho Lacrimal/imunologia , Aparelho Lacrimal/patologia , Masculino , Doença de Mikulicz/diagnóstico
9.
J Diabetes Investig ; 2(6): 464-73, 2011 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-24843531

RESUMO

UNLABELLED: Aims/Introduction: In order to diagnose diabetic symmetric polyneuropathy (DSPN) more simply and accurately, we identified symptoms that correlated with neurological functions and existed more frequently in diabetic than non-diabetic subjects. MATERIALS AND METHODS: The relationships between 10 symptoms (numbness or paresthesia in toe and sole, numbness in hand, pain in foot or hand, coldness in legs, painful leg cramp, dizziness on standing, sweating restricted to face/trunk and frequent constipation/diarrhea) and clinical background, defined as DSPN and cardiovascular autonomic neuropathy (CAN) by the criteria proposed in the statement of the American Diabetes Association, and seven quantitative nerve function data were evaluated in 593 diabetic patients in Wakayama Medical University Hospital (WMUH). Furthermore, the prevalence of various symptoms was examined by three questionnaires: a WMUH survey (999 diabetic outpatients), a Nationwide survey (1524 male diabetic outpatients under a primary-care physician) and a Control survey (501 non-diabetic subjects). RESULTS: Bilateral 'numbness in toe and sole', 'paresthesia in toe and sole', 'pain in foot' and 'sweating restricted to face/trunk' were significantly associated with diabetes duration, retinopathy, probable and confirmed DSPN, possible and advanced CAN, and all or six nerve functions. Questionnaire surveys clarified that symptoms that are not rare (>15%) and more frequent in diabetic than non-diabetic subjects were bilateral 'numbness in toe and sole', 'paresthesia in toe and sole', 'coldness in legs', 'dizziness on standing' and 'sweating restricted to face/trunk'. CONCLUSIONS: Therefore, bilateral 'numbness in toe and sole', 'paresthesia in toe and sole' and 'sweating restricted to face/trunk' are suitable symptoms useful for the diagnosis of DSPN. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00124.x, 2011).

10.
J Diabetes Investig ; 2(6): 474-82, 2011 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-24843532

RESUMO

UNLABELLED: Aims/Introduction: We have previously reported that the Pro198Leu missense polymorphism in the glutathione peroxidase 1 (GPx-1) gene was associated with frequent macrovascular disease (MVD). Our goal was to examine whether the GPx-1 genotype is associated with diabetic neuropathy. MATERIALS AND METHODS: We determined the GPx-1 genotype in 173 Japanese type 2 diabetic patients who received medical interviews, physical examinations, nerve conduction studies, quantitative vibratory perception (QVP), head-up tilt and heart rate variability tests by polymerase chain reaction-restriction fragment-length polymorphism. Diabetic sensorimotor distal symmetric polyneuropathy (DSPN) and diabetic autonomic neuropathy (DAN) were evaluated separately. DSPN and DAN were defined by two or more abnormalities of neuropathic leg symptoms, diminished Achilles tendon reflexes or impaired QVP in toes, and two autonomic dysfunctions, respectively. The association of the GPx-1 genotype with DSPN, DAN, MVD and other clinical manifestations was analyzed. RESULTS: The prevalence of DSPN, impaired QVP and painful leg cramps in patients having a genotype with Pro/Leu at the codon 198 (Pro/Leu type) was significantly higher than those with Pro/Pro type. As a result of multivariate analyses that contained the GPx-1 genotype as an independent variable, the Pro/Leu type was extracted as a significant risk factor of DSPN, QVP impairment and MVD. The statistical significance did not disappear, even after proteinuria, retinopathy and a history of MVD were introduced as independent variables. In contrast, the GPx-1 genotype was not associated with DAN. CONCLUSIONS: The Pro198Leu missense polymorphism of the GPx-1 gene might have a common genetic predisposition to DSPN and MVD. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2011.00127.x, 2011).

11.
Genes Chromosomes Cancer ; 49(7): 596-609, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20461752

RESUMO

In a single-nucleotide polymorphism array-based analysis of 56 hepatoblastoma (HB) tumors, allelic imbalances were detected in 37 tumors (66%). Chromosome gains were found in 1q (28 tumors), 2q (24), 6p (8), 8q (8), 17q (6), and 20pq (10), and losses in 1p (6), 4q (9), and 16q (4). Fine mapping delineated the shortest overlapping region (SOR) of gains at 1q32.1 (1.3 Mb) and 2q24.2-q24.3 (4.8 Mb), and losses at 4q34.3-q35.2 (8.7 Mb) and 4q32.3 (1.6 Mb). Uniparental disomy of 11pter-11p15.4 (IGF2) and loss of 11pter-p14.1 were found in 11 and 2 tumors, respectively. Expression of HTATIP2 (11p15.1) was absent in 9 of 20 tumors. Amplification was identified in four tumors at 1q32.1, where the candidate oncogene MDM4 is located. In the 4q32.3-SRO, ANXA10S, a variant of the candidate tumor suppressor ANXA10, showed no expression in 19 of 24 tumors. Sequence analysis of ANXA10S identified a missense mutation (E36K, c.106G>A) in a HB cell line. Multivariate analysis revealed that both 4q deletion and RASSF1A methylation (relative risks: 4.21 and 7.55, respectively) are independent prognostic factors. Our results indicate that allelic imbalances and gene expression patterns provide possible diagnostic and prognostic markers, as well as therapeutic targets in a subset of HB.


Assuntos
Desequilíbrio Alélico , Hepatoblastoma/genética , Acetiltransferases , Anexinas , Técnicas de Laboratório Clínico , Genes , Genoma , Humanos , Calicreínas , Polimorfismo de Nucleotídeo Único , Proteínas Proto-Oncogênicas , Pesquisa , Deleção de Sequência , Fatores de Transcrição , Fator Trefoil-1 , Proteínas Supressoras de Tumor , Ubiquitina-Proteína Ligases
12.
Diabetes Care ; 33(1): 150-5, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20040674

RESUMO

OBJECTIVE: Our goal was to ascertain the prevalence of pruritus in diabetic and nondiabetic subjects and the relevance of symptoms, signs, and nerve functions of diabetic polyneuropathy (DPN) of pruritus. RESEARCH DESIGN AND METHODS: A large-scale survey of 2,656 diabetic outpatients and 499 nondiabetic subjects was performed. In diabetic subjects, the relationship between pruritus and age, sex, diabetic duration, A1C, Achilles tendon reflex (ATR), and abnormal sensation in legs was evaluated. In 105 diabetic subjects, nerve conduction studies, quantitative vibratory threshold (QVT), heart rate variability, and a fall of systolic blood pressure at a head-up tilt test (DeltaBP) were performed, and the relationships between pruritus and nerve functions were evaluated. RESULTS: Although the prevalence of truncal pruritus of unknown origin (TPUO) in diabetic subjects was significantly higher than that in age-matched nondiabetic subjects (11.3 vs. 2.9%, P = 0.0001), the prevalence of other pruritus was not different between the two groups. Multiple logistic regression analysis revealed that abnormal sensation and ATR areflexia were independent risk factors for TPUO in age, sex, duration of diabetes, and A1C. DeltaBP in diabetic subjects with TPUO was significantly impaired compared with that in those without TPUO. Larger DeltaBP was identified as a significant risk factor of TPUO independent of other nerve dysfunctions by multiple logistic regression analysis. CONCLUSIONS: TPUO is significantly more frequent in diabetic than in nondiabetic individuals. TPUO is significantly associated with symptoms and signs of DPN, including impaired blood pressure response in a head-up tilt test. TPUO, therefore, might be a newly recognized symptom of DPN.


Assuntos
Neuropatias Diabéticas/diagnóstico , Neuropatias Diabéticas/fisiopatologia , Prurido/etiologia , Prurido/patologia , Adulto , Distribuição por Idade , Idoso , Idoso de 80 Anos ou mais , Neuropatias Diabéticas/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Prurido/epidemiologia , Adulto Jovem
13.
Hepatogastroenterology ; 49(44): 580-4, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-11995502

RESUMO

BACKGROUND/AIMS: Lymphatic flow and the incidence of lymph node metastasis in remnant stomach cancer after distal gastrectomy are obscure. There is consequent controversy about appropriate lymph node dissection in such cases. METHODOLOGY: Thirty-three consecutive patients with remnant stomach cancer and 44 consecutive patients primary gastric cancer in the upper third of the stomach were investigated retrospectively about lymphatic flow by injection of activated carbon particles, and about the incidence of lymph node metastasis. RESULTS: Lymphatic flow and the incidence of lymph node metastasis in remnant stomach cancer after distal gastrectomy without lymph node dissection were the same as those in primary gastric cancer in the upper third of the stomach. Lymphatic flow after distal gastrectomy with lymph node dissection frequently streamed toward the para-aortic lymph nodes through the lymph nodes along the greater curvature and the suprapancreatic lymph nodes. Lymphatic flow toward the jejunal and colonic mesentery was observed regardless of the method of reconstruction. This lymphogenesis was clearly observed, especially in patients with tumors invading the anastomosis site of Billroth-II reconstruction. Station Nos. 110 (lower paraesophageal) and 111 (supradiaphragmatic) lymph nodes were also stained, despite being considered sites of distant metastasis irrespective of the method of reconstruction. CONCLUSIONS: On the basis of the evidence of altered lymphatic flow and the incidence of lymph node metastases in remnant stomach cancer, left upper abdominal evisceration with para-aortic lymph node dissection should be performed in advanced remnant stomach cancer.


Assuntos
Gastrectomia , Coto Gástrico , Excisão de Linfonodo , Neoplasias Gástricas/cirurgia , Idoso , Anastomose Cirúrgica , Feminino , Humanos , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Invasividade Neoplásica , Estudos Retrospectivos , Neoplasias Gástricas/mortalidade , Neoplasias Gástricas/patologia
14.
Nature ; 416(6876): 64-7, 2002 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-11882891

RESUMO

Ceramics are often prepared with surface layers of different composition from the bulk, in order to impart a specific functionality to the surface or to act as a protective layer for the bulk material. Here we describe a general process by which functional surface layers with a nanometre-scale compositional gradient can be readily formed during the production of bulk ceramic components. The basis of our approach is to incorporate selected low-molecular-mass additives into either the precursor polymer from which the ceramic forms, or the binder polymer used to prepare bulk components from ceramic powders. Thermal treatment of the resulting bodies leads to controlled phase separation ('bleed out') of the additives, analogous to the normally undesirable outward loss of low-molecular-mass components from some plastics; subsequent calcination stabilizes the compositionally changed surface region, generating a functional surface layer. This approach is applicable to a wide range of materials and morphologies, and should find use in catalysts, composites and environmental barrier coatings.

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