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1.
J Sports Sci ; 40(8): 934-949, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35220909

RESUMO

In the research concerning rational emotive behaviour therapy (REBT) in sport and exercise, irrational beliefs are proposed as a risk factor for health. Concurrent to this, researchers have also indicated that autonomous and controlled motivation, as proposed in organismic integration theory could, together with irrational beliefs, determine individual health. However, research is yet to align irrational beliefs and motivation, and explore how this alignment relates to mental health. The present two study paper identifies individual subgroups, drawn from data concerning irrational beliefs, motivation, and health (psychological distress, and physical health), in a sample of exercisers (study 1) and student athletes (study 2). We examined the latent profile structure of irrational beliefs and motivation, and how these latent profiles relate to psychological distress (studies 1 and 2), and physical health (study 2). Results indicate a two class profile whereby class 1 is characterised by high irrational beliefs, low self-determined motivation, and poor health outcomes. Class 2 is characterised by low irrational beliefs, high self-determined motivation, and better health outcomes. The findings are discussed in relation to the theoretical implications for REBT and organismic integration theory, and the practical implications for key stakeholders in the health of exercise participants and athletes.


Assuntos
Motivação , Angústia Psicológica , Atletas/psicologia , Humanos , Saúde Mental , Autonomia Pessoal
2.
Platelets ; 29(1): 87-90, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28758823

RESUMO

Physical inactivity increases the risk of thromboembolism. However, good standardized human models on inactivity are in short supply and experimental models are few. Our objective was to investigate how standardized bed rest affects platelet aggregation in humans and to investigate if aggregation is altered in a translational model system - the hibernating brown bear (Ursus arctos). We collected blood from (1) healthy male volunteers participating in a 21-day bed rest study in head-down tilt position (-6°) 24 h a day; (2) free-ranging brown bears captured during winter hibernation and again during active state in summer. We analyzed platelet function using multiple electrode platelet aggregometry. In total, 9 healthy male volunteers (age 31.0 ± 6.4 years) and 13 brown bears (7 females and 6 males, age 2.8 ± 0.6 years) were included. In hibernating bears adenosine diphosphate, arachidonic acid, thrombin receptor activating peptide, and collagen impedance aggregometry tests were all halved compared to summer active state. In human volunteers no statistically significant changes were found between baseline and the end of bed rest. In human male volunteers 3 weeks of bed rest did not affect platelet function. In hibernating brown bears platelet aggregation was halved compared to summer and we hypothesize that this is a protective measure to avoid formation of thrombi under periods of low blood flow.


Assuntos
Plaquetas/fisiologia , Exercício Físico , Condicionamento Físico Animal , Ursidae , Adulto , Animais , Biomarcadores , Coagulação Sanguínea , Feminino , Testes Hematológicos , Humanos , Masculino , Agregação Plaquetária , Estações do Ano , Temperatura
3.
J Helminthol ; 94: e6, 2018 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-30369337

RESUMO

This study focused on the spirurid nematode Mastophorus muris in water voles (Arvicola amphibius) trapped in three regions in southern Sweden during spring and fall 2013. The collection of water voles formed part of a larger project (EMIRO) on the cestode Echinococcus multilocularis in rodents. The voles' stomach contents were examined for the presence of M. muris. Prevalence, mean abundance and mean intensity of infection were calculated. A generalized linear model model was used to examine the effects of sex, functional group, season and region on the number of M. muris individuals in each vole. Forty-seven of 181 (26%) voles were infected with M. muris, with up to 74 worms each. The overall mean intensity (worms per infected vole) was 15 (95% CI 10-21), and abundance (mean number of worms in all voles) was 4 (95% CI 2-6). Model output indicated a significant effect of season and region with respect to abundance of nematode infection, which was independent of sex and functional group of the investigated host.


Assuntos
Arvicolinae/parasitologia , Doenças dos Roedores/parasitologia , Infecções por Spirurida/veterinária , Espirurídios/isolamento & purificação , Animais , Masculino , Estações do Ano , Espirurídios/classificação , Espirurídios/genética , Infecções por Spirurida/parasitologia , Suécia
4.
Front Zool ; 13: 7, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-26870151

RESUMO

BACKGROUND: Hibernation has been a key area of research for several decades, essentially in small mammals in the laboratory, yet we know very little about what triggers or ends it in the wild. Do climatic factors, an internal biological clock, or physiological processes dominate? Using state-of-the-art tracking and monitoring technology on fourteen free-ranging brown bears over three winters, we recorded movement, heart rate (HR), heart rate variability (HRV), body temperature (Tb), physical activity, ambient temperature (TA), and snow depth to identify the drivers of the start and end of hibernation. We used behavioral change point analyses to estimate the start and end of hibernation and convergent cross mapping to identify the causal interactions between the ecological and physiological variables over time. RESULTS: To our knowledge, we have built the first chronology of both ecological and physiological events from before the start to the end of hibernation in the field. Activity, HR, and Tb started to drop slowly several weeks before den entry. Bears entered the den when snow arrived and when ambient temperature reached 0 °C. HRV, taken as a proxy of sympathetic nervous system activity, dropped dramatically once the bear entered the den. This indirectly suggests that denning is tightly coupled to metabolic suppression. During arousal, the unexpected early rise in Tb (two months before den exit) was driven by TA, but was independent of HRV. The difference between Tb and TA decreased gradually suggesting that bears were not thermoconforming. HRV increased only three weeks before exit, indicating that late activation of the sympathetic nervous system likely finalized restoration of euthermic metabolism. Interestingly, it was not until TA reached the presumed lower critical temperature, likely indicating that the bears were seeking thermoneutrality, that they exited the den. CONCLUSIONS: We conclude that brown bear hibernation was initiated primarily by environmental cues, but terminated by physiological cues.

5.
Inhal Toxicol ; 28(7): 303-12, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27097835

RESUMO

The many benefits of building "green" have motivated the use of sustainable products in the design and execution of the built environment. However, the use of these natural or recycled materials, some of which have been treated with antimicrobials, provides a growth opportunity for microorganisms with the potential to elicit adverse health effects especially in the presence of an antimicrobial. The focus of this research was to determine the effects of Stachybotrys chartarum (strains Houston and 51-11) grown under different conditions on a macrophage cell line (Raw 264.7) using endpoints, including cytotoxicity, and those associated with immunity specifically inflammation and MHC class II expression. The fungi were grown on four different gypsum products, and macrophages were exposed to whole spores of both strains and fragmented spores of strain 51-11. Whole spores of the Houston strain elicited no cytotoxicity with some level of inflammation, while exposure to whole spores of 51-11 caused variable responses depending on the wallboard type supporting the fungal growth. High concentrations of fragmented 51-11 spores primarily resulted in the apoptosis of macrophage with no inflammation. None of the fungal strains caused elevated levels of major histocompatibility complex (MHC) class II expression on the surface of Raw cells. Mycotoxin levels of 51-11 spores from all of the wallboard types measured >250 ng/µL of T2 equivalent toxin based on activity. Collectively, the data demonstrated that all of the wallboard types supported growth of fungi with the ability to elicit harmful biological responses with the potential to negatively impact human health.


Assuntos
Materiais de Construção/microbiologia , Macrófagos/imunologia , Esporos Fúngicos , Stachybotrys , Animais , Sulfato de Cálcio , Sobrevivência Celular , Interleucina-6/imunologia , Camundongos , Micotoxinas/análise , Células RAW 264.7 , Fator de Necrose Tumoral alfa/imunologia
6.
Anxiety Stress Coping ; 37(6): 721-744, 2024 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-38825960

RESUMO

BACKGROUND AND OBJECTIVES: Examination anxiety is a common occurrence, and is potentially detrimental to student attainment. In recent theorizing, it has been suggested that cognitive appraisals, as put forth in cognitive appraisal theory, and irrational beliefs, as put forth in rational emotive behavior therapy, may interact to predict affectivity. The current research examines the antecedents and associates of examination affect and academic self-concept in undergraduate students. DESIGN: A preliminary study applied confirmatory factor analysis (CFA) to test the factor structure of an irrational beliefs inventory. Study 1 utilized a cross-sectional and correlational approach to testing core theoretical assumptions. Study 2 took a two-wave longitudinal and path analytical approach to examine temporal effects between target variables. METHOD: All self-report data collection took place in the United Kingdom with university students. We recruited n = 1150, n = 362, n = 662 for preliminary, study 1, and study 2, respectively. RESULTS: Across studies, data indicated that a pattern of adaptive cognitive appraisal was associated with more advantageous affectivity, and better academic self-concept. CONCLUSIONS: Reciprocal temporal relationships were revealed between many variables, supporting an interactive and bidirectional view of how cognition and affect are related pertaining to examination anxiety.


Assuntos
Cognição , Autoimagem , Estudantes , Humanos , Feminino , Estudantes/psicologia , Estudantes/estatística & dados numéricos , Masculino , Adulto Jovem , Universidades , Estudos Transversais , Adulto , Ansiedade aos Exames/psicologia , Afeto , Adolescente , Reino Unido , Autorrelato , Ansiedade/psicologia , Estudos Longitudinais
7.
Clin Radiol ; 68(10): 1070-3, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23827085

RESUMO

AIMS: To document the type, location, extent, and complications of brain metastases in patients with breast cancer and identify associations with oestrogen receptor (ER) negative and human epidermal growth factor receptor 2 (HER-2) receptor expression. MATERIALS AND METHODS: Breast cancer patients with known brain metastases were included in this retrospective study, if cross-sectional imaging of the brain [computed tomography (CT)] was available to review and HER-2 and ER status was known. Two neuroradiologists, who were blinded to the receptor status, separately and for each patient, documented on a proforma the location, number, and dimensions of the deposits and the presence or absence of hydrocephalus. Adjudication was sought where there was discrepancy between the two reports. ER status, HER-2 receptor status, and patient age were also documented. The results were analysed using two-sided Fisher's exact tests with Lancaster's mid-P correction and associations were sought between the tumour characteristics and the pattern of brain disease. RESULTS: Sixty patients were included in the study. There was an association between young age (<40 years) and HER-2 positivity [10 of 24 (41.7%) versus three of 36 (8.3%); p = 0.002]. In ER-negative women, HER-2 positivity was found to be associated with a larger number (six or more) of metastases [11 of 18 (61%) versus nine of 25 (36%); p = 0.049], more brain stem metastases [11 of 18 (61%) versus three of 26 (11.5%); p = 0.035], more frequent occurrence of hydrocephalus [7 of 12 (36.8%) versus three of 26 (11.5%); p = 0.049], and a higher incidence of occipital metastases [12 of 18 (66.7%) versus eight of 26 (30.8%); p = 0.029]. CONCLUSION: ER-negative HER-2-positive women are more likely to present with a larger number of lesions, more brain stem/occipital metastases, and hydrocephalus, which may predispose them to unfavourable outcomes following treatment.


Assuntos
Neoplasias Encefálicas/secundário , Neoplasias da Mama/patologia , Receptor ErbB-2/metabolismo , Receptores de Estrogênio/metabolismo , Adulto , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/metabolismo , Neoplasias da Mama/metabolismo , Feminino , Humanos , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Tomografia Computadorizada por Raios X , Reino Unido
8.
Nat Genet ; 16(2): 197-201, 1997 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-9171835

RESUMO

Coronary heart disease, hypertension, non-insulin-dependent diabetes and obesity are major causes of ill health in industrial societies. Disturbances of carbohydrate and lipid metabolism are a common feature of these disorders. The bases for these disturbances and their roles in disease pathogenesis are poorly understood. The spontaneously hypertensive rat (SHR), a widely used animal model of essential hypertension, has a global defect in insulin action on glucose metabolism and shows reduced catecholamine action on lipolysis in fat cells. In our study we used cellular defects in carbohydrate and lipid metabolism to dissect the genetics of defective insulin and catecholamine action in the SHR strain. In a genome screen for loci linked to insulin and catecholamine action, we identified two quantitative trait loci (QTLs) for defective insulin action, on chromosome 4 and 12. We found that the major (and perhaps only) genetic determinant of defective control of lipolysis in SHR maps to the same region of chromosome 4. These linkage results were ascertained in at least two independent crosses. As the SHR strain manifests many of the defining features of human metabolic Syndrome X, in which hypertension associates with insulin resistance, dyslipidaemia and abdominal obesity, the identification of genes for defective insulin and catecholamine action in SHR may facilitate gene identification in this syndrome and in related human conditions, such as type-2 diabetes and familial combined hyperlipidaemia.


Assuntos
Mapeamento Cromossômico , Ácidos Graxos não Esterificados/metabolismo , Glucose/metabolismo , Erros Inatos do Metabolismo/genética , Animais , Modelos Animais de Doenças , Humanos , Escore Lod , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY
9.
Int J STD AIDS ; 16(11): 736-8, 2005 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16303068

RESUMO

Bacterial vaginosis (BV) frequently recurs after treatment. One option in the management of recurrences is to keep the vaginal pH at 4.5 or less, in order to prevent overgrowth of bacteria, until the normal lactobacilli are re-established. We report the outcome of using maintenance acetic acid vaginal gel, after treatment of BV, in a sample of 49 women with frequent recurrences. Half of the women had no further recurrences, and in those who did there was a significant increase in time to first recurrence (4.8 months) after commencing the gel compared with the previous recurrence (2.1 months). Prior to using acidic gel, the mean recurrence rate in 49 women was 4.4 per woman/year, and this was reduced to 0.6 recurrences per woman/year. As there are few effective therapies for women with recurrent BV, we feel this offers an option that can currently be used in clinical practice.


Assuntos
Cremes, Espumas e Géis Vaginais/uso terapêutico , Vaginose Bacteriana/tratamento farmacológico , Vaginose Bacteriana/prevenção & controle , Adulto , Feminino , Humanos , Concentração de Íons de Hidrogênio , Pessoa de Meia-Idade , Recidiva , Resultado do Tratamento , Vagina/química
10.
Hum Mutat ; 18(6): 546-7, 2001 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-11748851

RESUMO

Marfan syndrome (MFS), an autosomal dominant disorder of the extracellular matrix, is due to mutations in fibrillin-1 (FBN1) gene. Investigations carried out in the last decade, unveiled the unpredictability of the site of the mutation, which could be anywhere in the gene. FBN1 mutations have been reported in a spectrum of diseases related to MFS, with no clear evidence for a phenotype-genotype correlation. In this paper we analysed 10 British patients affected by MFS and we were able to characterise five novel missense mutations (C474W, C1402Y, G1987R, C2153Y, G2536R), one novel frameshift mutation (7926delC), one already described mutation (P1424A) and one FBN1 variant (P1148A) classified as a polymorphism in the Asian population. Four out of the five novel missense mutations involved either cysteines or an amino acid conserved in the domain structure. The mutation yield in this study is calculated at 80.0% (8/10), thus indicating that SSCA is a reliable and cost-effective technique for the screening of such a large gene. Our results suggest that this method is reliable to search for FBN1 mutations and that FBN1 screening could be a helpful tool to confirm and possibly anticipate the clinical diagnosis in familial cases.


Assuntos
Síndrome de Marfan/genética , Proteínas dos Microfilamentos/genética , Adulto , Sequência de Bases , Pré-Escolar , DNA/química , DNA/genética , Análise Mutacional de DNA , Feminino , Fibrilina-1 , Fibrilinas , Mutação da Fase de Leitura , Humanos , Masculino , Síndrome de Marfan/patologia , Pessoa de Meia-Idade , Mutação , Mutação de Sentido Incorreto , Polimorfismo Genético , Polimorfismo Conformacional de Fita Simples , Reino Unido
11.
Hum Mutat ; 18(3): 251, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11524736

RESUMO

Marfan syndrome (MFS), an autosomal dominant disorder of the extracellular matrix, is due to mutations in fibrillin-1 (FBN1) gene. Investigations carried out in the last decade, unveiled the unpredictability of the site of the mutation, which could be anywhere in the gene. FBN1 mutations have been reported in a spectrum of diseases related to MFS, with no clear evidence for a phenotype-genotype correlation. In this paper we analysed 10 British patients affected by MFS and we were able to characterise five novel missense mutations (C474W, C1402Y, G1987R, C2153Y, G2536R), one novel frameshift mutation (7926delC), one already described mutation (P1424A) and one FBN1 variant (P1148A) classified as a polymorphism in the Asian population. Four out of the five novel missense mutations involved either cysteines or an amino acid conserved in the domain structure. The mutation yield in this study is calculated at 80.0% (8/10), thus indicating that SSCA is a reliable and cost-effective technique for the screening of such a large gene. Our results suggest that this method is reliable to search for FBN1 mutations and that FBN1 screening could be a helpful tool to confirm and possibly anticipate the clinical diagnosis in familial cases. Hum Mutat 18:251, 2001.


Assuntos
Síndrome de Marfan/genética , Proteínas dos Microfilamentos/genética , Adulto , Sequência de Bases , Pré-Escolar , Feminino , Fibrilina-1 , Fibrilinas , Mutação da Fase de Leitura , Humanos , Masculino , Pessoa de Meia-Idade , Mutação , Mutação de Sentido Incorreto , Deleção de Sequência , Reino Unido
12.
J Endocrinol ; 159(3): 459-67, 1998 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9834463

RESUMO

Angiogenesis and vascular transformation are important processes in the normal development of the placenta. Vascular endothelial growth factor (VEGF) is a potent angiogenic growth factor and is thought to be important for placental development. Recently several new members of this family have been described. In this study we used in situ hybridisation to localise which cells in the placenta expressed mRNA for VEGF, placenta growth factor (PlGF), VEGF-B and VEGF-C. We were unable to find any message for either VEGF-B or VEGF-C in the placenta, suggesting that only low levels are produced which this method was unable to detect. The mRNA encoding VEGF was found to be produced by cells within the villous mesenchyme, decidual macrophages and decidual glands but, in contrast to our previous findings, not by trophoblast. The mRNA encoding PlGF was produced in large amounts by villous cytotrophoblast, syncytiotrophoblast and extravillous trophoblast. The mRNAs encoding VEGF and PlGF were thus not co-localised and it appears that there is unlikely to be any significant production of VEGF/PlGF heterodimer in the placenta.


Assuntos
Fatores de Crescimento Endotelial/metabolismo , Placenta/metabolismo , Gravidez/metabolismo , Proteínas/metabolismo , Northern Blotting , Decídua/metabolismo , Fatores de Crescimento Endotelial/genética , Feminino , Humanos , Hibridização In Situ , Linfocinas/genética , Linfocinas/metabolismo , Proteínas de Membrana , Segundo Trimestre da Gravidez , Terceiro Trimestre da Gravidez , Proteínas/genética , RNA Mensageiro/análise , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Trofoblastos/metabolismo , Fator A de Crescimento do Endotélio Vascular , Fator B de Crescimento do Endotélio Vascular , Fator C de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio Vascular
13.
Am J Med Genet ; 95(2): 99-104, 2000 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-11078557

RESUMO

We describe a family in which non-syndromic mental retardation (MR) and an apparently balanced reciprocal translocation, t(1;17)(p36. 3;p11.2) segregates in eight individuals over three generations. Four children showed psychomotor developmental delay, reduced muscle tone, poor coordination, and learning difficulties. The affected adults had a varying range of behavioral problems and difficulties in social adjustment but no abnormal neurological signs. Most of them were functioning at the borderline learning difficulty level in intellectual abilities with additional specific difficulties in reading in two individuals. The Smith-Magenis and 1p36.3 deletion syndromes were excluded. We propose that this reciprocal translocation has disrupted an autosomal gene with an important function in cognitive development, and this family represents a unique resource for the molecular genetic study on non-syndromic MR.


Assuntos
Cromossomos Humanos Par 17 , Cromossomos Humanos Par 1 , Deficiência Intelectual/genética , Translocação Genética , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Saúde da Família , Feminino , Humanos , Hibridização in Situ Fluorescente , Cariotipagem , Masculino , Pessoa de Meia-Idade , Linhagem
14.
J Dent Res ; 70(2): 137-9, 1991 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-1991871

RESUMO

Prasad et al. (1988) have shown that slow cooling of dental porcelain produces increases in thermal expansion sufficient to make a compatible metal-porcelain system incompatible. The present study was undertaken to determine whether the increase in porcelain thermal expansion might be attributable to crystallization of additional leucite during slow cooling of the porcelain. Eight x-ray diffraction specimens for each of six commercial dental porcelains and for the Component No. 1 frit of the Weinstein and Weinstein (1962) and Weinstein et al. (1962) patents were fabricated and divided into two groups. Specimens in the first group (termed fast-cooled) were cooled in the conventional manner by removing them from the furnace at the maximum firing temperature immediately into room air. Specimens in the second group (termed slow-cooled) were cooled slowly by interrupting power to the furnace muffle and allowing them to cool inside the closed furnace. Quantitative x-ray diffraction was performed on the fast- and slow-cooled porcelain specimens with standards containing leucite volume fractions of 0.111, 0.223, 0.334, and 0.445. Unpaired, one-tailed t tests were performed on the fast- and slow-cool data, and a significant increase (p less than 0.05) in the amount of leucite (as a function of the slow cooling) was found for each of the porcelains. The increases in the leucite volume fractions resulting from the slow cooling ranged from a low of 8.5% to a high of 55.8%, with an average increase of 26.9%.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Compostos de Alumínio , Silicatos de Alumínio/química , Técnica de Fundição Odontológica , Porcelana Dentária/química , Compostos de Potássio , Silicatos , Análise de Variância , Temperatura Baixa , Ligas Dentárias , Temperatura Alta , Teste de Materiais , Fatores de Tempo , Difração de Raios X
15.
J Dent Res ; 65(7): 993-7, 1986 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-3458762

RESUMO

Fatigue in ceramics refers to the subcritical growth of cracks, aided by the combined influence of water and stress. The dynamic fatigue (constant stressing rate) method was used to obtain subcritical crack growth parameters for three dental ceramics: a feldspathic porcelain, an aluminous porcelain, and a fine-grain, polycrystalline core material. The constant stressing rate experiments were carried out at 37 degrees C for all three ceramics in distilled water, and, for the feldspathic porcelain, in artificial saliva as well. Considerable differences were found in the value of the crack growth exponent (n) among the three ceramics. The feldspathic porcelain was lowest in n-value, while the fine-grain ceramic had the highest n-value. No differences were found for the feldspathic porcelain with respect to n measured in water and in the artificial saliva. Lifetime prediction curves in 37 degrees C water, constructed from the n-values and inert strengths, showed that fatigue failure within five years is a good possibility for feldspathic porcelain specimens at stress levels which can reasonably be anticipated to occur in the oral environment. Little likelihood of failure was perceived for the fine-grain ceramic. The aluminous porcelain was intermediate between these two materials with respect to failure probability.


Assuntos
Porcelana Dentária , Antissépticos Bucais , Saliva Artificial , Estresse Mecânico , Água , Humanos , Modelos Biológicos , Propriedades de Superfície , Resistência à Tração
16.
J Dent Res ; 73(6): 1221-7, 1994 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-8046112

RESUMO

Because of the large differential in thermal expansion coefficient between leucite and the surrounding glass matrix, microcracks form around the leucite crystallites during the manufacture of dental porcelain frits. These microcracks decouple leucite from the surrounding glass matrix and affect the bulk thermal expansion of the porcelain frit (Binns, 1983). The purpose of this study was to determine if the microcrack density in a dental porcelain decreased as a result of isothermal heat treatment. Ten specimens of a commercial dental porcelain that had previously exhibited an increase in thermal expansion as a function of isothermal heat treatment were prepared and divided into two groups. The experimental group was heated to 750 degrees C and held for 16 minutes at that temperature. The control group received no anneal. The mean microcrack densities were determined by quantitative stereology to be 575 cm2/cm3 +/- 75 cm2/cm3 (mean +/- SEM) for the control group (no anneal) and 231 cm2/cm3 +/- 25 cm2/cm3 for the experimental group (16-minute anneal at 750 degrees C). The specimens annealed at 750 degrees C had a significantly lower microcrack density (p < 0.001) than those that received no anneal. A model was developed to estimate the effect of microcracking on thermal expansion of the porcelain, and a 6% increase in the coefficient of thermal expansion of the porcelain was predicted from this model as a result of this decrease in microcrack density.


Assuntos
Silicatos de Alumínio/química , Porcelana Dentária/química , Ligas Metalo-Cerâmicas/química , Análise de Variância , Fenômenos Químicos , Físico-Química , Análise Diferencial Térmica , Elasticidade , Temperatura Alta , Teste de Materiais , Microscopia Eletrônica de Varredura , Propriedades de Superfície , Termodinâmica
17.
J Dent Res ; 67(2): 474-8, 1988 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-11039060

RESUMO

The lack of a reliable bond test has hindered the elucidation of the mechanism for porcelain-metal bonding in dental systems, because a test capable of detecting differences among porcelain-metal bonds of various qualities is required before the reasons for these differences may be ascertained. A method was developed in the present study whereby specimens of alloys with differing physical properties may be deformed to a constant strain to yield a fracture surface suitable for measurement of the area fraction of retained porcelain by an x-ray spectrometric technique described previously. The method proved sufficiently discriminating that significant differences could be found in 48 of the possible 66 comparisons among alloys and treatments. Linear regression analysis revealed a strong correlation (r2 = 0.947) between the area fractions of retained porcelain measured in the present study and the oxide adherence strength values measured previously. This strong correlation, when considered in light of the literature evidence for the presence of an oxide layer at the porcelain-metal interface, provides compelling support for the oxide layer theory of porcelain-metal bonding in dental alloy systems.


Assuntos
Colagem Dentária , Ligas Metalo-Cerâmicas/química , Análise do Estresse Dentário , Elasticidade , Microanálise por Sonda Eletrônica , Modelos Lineares , Teste de Materiais , Óxidos/análise , Óxidos/química , Estresse Mecânico , Aderências Teciduais
18.
Br J Ophthalmol ; 86(12): 1359-62, 2002 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12446365

RESUMO

BACKGROUND: Marfan syndrome (MFS), inherited as an autosomal dominant trait, typically affects the cardiovascular, skeletal, and ocular systems. Ectopia lentis (EL) is a clinical manifestation of MFS, with stretching or disruption of the lenticular zonular filaments, leading to displacement of the lenses. EL, with or without minor skeletal changes, exists as an independent autosomal dominant phenotype linked to the same FBN1 locus. METHODS: A consecutive series of 11 patients, affected predominantly by EL, was analysed for FBN1 mutations using PCR, SSCA, and sequencing. RESULTS: Six mutations were identified, of which three are novel and one is recurrent in two patients, thus establishing a mutation incidence in this group of 7/11 (63%). CONCLUSION: The FBN1 variants reported are clustered in the first 15 exons of the gene, while FBN1 mutations reported in the literature are distributed throughout the entire length of the gene. A different type of FBN1 mutation presents in this group of patients, compared with MFS, with arginine to cysteine substitutions appearing frequently.


Assuntos
Ectopia do Cristalino/genética , Proteínas da Matriz Extracelular/genética , Síndrome de Marfan/genética , Proteínas dos Microfilamentos/genética , Mutação/genética , Adulto , Idoso , Criança , Feminino , Fibrilina-1 , Fibrilinas , Humanos , Masculino , Pessoa de Meia-Idade , Conformação de Ácido Nucleico , Reação em Cadeia da Polimerase/métodos , Polimorfismo Genético/genética
19.
Br J Ophthalmol ; 80(9): 831-4, 1996 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-8942382

RESUMO

BACKGROUND: A new technique exists that enables functional mapping of the retina. A control population was examined to obtain normative values and to assess the reproducibility of this new test. METHODS: Twenty healthy volunteers were tested using a 61 hexagonal array stimulus with a 14 minute recording period. Median 5th and 95th percentiles were determined for implicit times and amplitude measures for the 61 test areas. Repeat measurements were performed on 10 individuals. Wilcoxon and Bland and Altman techniques were used to quantify reproducibility of the test. RESULTS: The implicit time of the wave-form components was not found to vary over the retina (peak or b-wave component, 35.52 (1.4) ms; trough or a-wave component, 17.76 (0.8) ms). Reproducibility was found to decrease with eccentricity (coefficient of repeatability 17.4% for the central area increasing to 30.3% for the peripheral ring). CONCLUSIONS: The findings suggest that reproducibility, although variable with eccentricity, is comparable with conventional electrophysiology. These limits of variation were used to assign confidence intervals to individual retinal areas and will be used (future work) in the examination of diseased states.


Assuntos
Eletrorretinografia/métodos , Potenciais Evocados Visuais , Retina/fisiologia , Adolescente , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes
20.
Br J Ophthalmol ; 80(4): 297-303, 1996 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-8703877

RESUMO

AIMS/BACKGROUND: An objective method for detecting hemifield and quadrantic visual field defects has been developed using steady state visual evoked cortical potentials (VECPs), an adaptive noise canceller (ANC), and Hotelling's t2 statistic. The purpose of this study was to determine the sensitivity and specificity of the technique. METHODS: Nine subjects (mean age 44 years) were investigated with field loss due to a variety of causes including both anterior and posterior visual pathway lesions. Dynamic perimetry was performed by means of a Goldmann or Tübingen perimeter. VECP recordings were made from each visual field quadrant (23 degrees X 23 degrees) by means of a steady state reversing checkerboard (7.7 rev/s). The central 5 degrees of the visual field and the vertical and horizontal meridians were masked during these measurements. Recordings were made from three electrode sites, positioned over the visual cortex, relative to a mid frontal electrode. Each recording lasted 2 minutes, during which time fixation was monitored. The data from each recording were divided into 4 second segments, and the amplitude and phase of the VECP signal measured using the ANC. Hotelling's t2 statistic was applied to determine the probability of signal detection. Receiver operating characteristic curves were used to find the optimum signal detection threshold for identification of the visual field defects. RESULTS: The results of the study confirmed patterns of subjective visual field loss. The technique had a sensitivity and a specificity of 81% and 85%, respectively, for detecting 'non-seeing' areas in the inferior visual field, and 82% and 89%, respectively, for detecting 'non-seeing' areas in the superior visual field. CONCLUSION: These results demonstrate that the technique is of potential clinical value to ophthalmologists and neurologists when subjective perimetry is not possible.


Assuntos
Potenciais Evocados Visuais , Transtornos da Visão/diagnóstico , Córtex Visual/fisiopatologia , Testes de Campo Visual/métodos , Campos Visuais/fisiologia , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Sensibilidade e Especificidade
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