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1.
Z Gastroenterol ; 2023 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-37871633

RESUMO

Liver injury associated with selective androgen receptor modulators (SARMs) is an issue that has not been reported often. We report a case of a previously healthy 24-year-old male, who was referred to our hospital for severe jaundice with intense pruritus. He had previously taken the SARM Enobosarm (also known as Ostarine) for muscle-building purposes. Blood serum levels of total bilirubin exceeded 30 mg/dL with only a slight elevation of liver enzymes. Liver biopsy revealed isolated hepatocellular cholestasis (bland cholestasis) with limited inflammation or necrosis. Supportive treatment was begun in our hospital with molecular adsorbent recirculation system (MARS) albumin dialysis, as well as cholestyramine for pruritus relief. During therapy, bilirubin levels and symptoms regressed, and after five sessions of dialysis, the patient could be released from our clinic in a markedly improved clinical and laboratory condition. However, bilirubin parameters regressed slowly after this, reaching normal levels as late as six months after first intake of the compound. Exome-based genetic testing brought about no pathogenic variants for cholestatic liver disease in our patient. Nevertheless, three common heterozygous polymorphisms associated with an increased risk for intrahepatic cholestasis could be identified. Our case demonstrates that SARMs can cause severe liver injuries not prominently mentioned in safety data sheets. Therefore, these compounds constitute a potential danger to the user's health. This holds especially true when taking SARMs without supervision by a medical professional, which should consist of a thorough monitoring of liver enzyme and bilirubin levels.

2.
Curr Epidemiol Rep ; 7(4): 263-273, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33816056

RESUMO

PURPOSE OF REVIEW: A growing body of evidence suggests adverse neurodevelopmental effects of early-life exposure to fluoride that may differ depending on timing of exposure and sex of the exposed. We conducted a literature search to identify the animal and human epidemiologic studies that examined sex-specific neurodevelopmental differences in response to prenatal and postnatal exposure to fluoride. RECENT FINDINGS: Six of 138 animal studies and 15 of 106 human epidemiologic studies tested for sex-specific effects. Prenatal exposure to fluoride was associated with a male susceptibility to adverse behavioural effects in four of six animal studies and lower IQ in one of three prospective cohort studies. The body of evidence examining sex-effects associated with postnatal fluoride exposure was scarce, and many animal and cross-sectional human studies were considered to have a high risk of bias. SUMMARY: Compared to females, male offspring appear to be more sensitive to prenatal, but not postnatal, exposure to fluoride. We discuss several sex-specific mechanisms and emphasize the need for future research.

3.
Nat Commun ; 10(1): 1350, 2019 03 22.
Artigo em Inglês | MEDLINE | ID: mdl-30902993

RESUMO

Decades of study on volcanic arcs have provided insight into the overarching processes that control magmatism, and how these processes manifest at individual volcanoes. However, the causes of ubiquitous and dramatic intra-arc variations in volcanic flux and composition remain largely unresolved. Investigating such arc-scale issues requires greater quantitative comparison of geophysical and geochemical data, linked through sets of common intensive variables. To work towards these goals, we use observed lava compositions to estimate the heat budget associated with Quaternary volcanism in the Cascades Arc and compare this to the heat required to produce the observed geophysical properties of the crust. Here we show that along-strike volcanic variability in the Quaternary Cascades Arc is primarily related to variations in the flux of basalt into the crust, rather than variations in their crustal storage history. This approach shows promise for studying other large-scale frontier geologic problems in volcanic arcs.

4.
Neurol Sci ; 38(4): 635-642, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28078569

RESUMO

Decreased information processing speed (IPS) is frequently reported in pediatric multiple sclerosis (MS) patients. The computerized version of the Symbol Digit Modalities Test (c-SDMT) measures IPS over eight consecutive trials per session and additionally captures changes in performance within the session. Here, we establish normative c-SDMT performance and test-retest reliability in healthy children (HC) and explore differences in the overall c-SDMT-performance between HC and MS patients. This cross-sectional study included 478 HC (237 female, 49.5%) divided into five age groups (2 years each), and 27 MS patients (22 female, 81.5%) aged 8-18 years. The average time to complete the c-SDMT increased with age (|r| 0.70, 95% CI -0.74, -0.64). Test-retest reliability was high (ICC = 0.91) in HC. The total time to complete the c-SDMT did not differ between children with MS and sex- and age- matched HC (p = 0.23). However, MS patients were less likely to show faster performance across all the successive eight trials compared to HC (p = 0.0001). Healthy children demonstrate faster IPS with increasing age, as well as during successive trials of the c-SDMT. The inability of pediatric MS patients to maintain the increase in processing speed over successive trials suggests a reduced capacity for procedural learning, possibly resulting from cognitive fatigue.


Assuntos
Transtornos Cognitivos/diagnóstico , Diagnóstico por Computador , Esclerose Múltipla/psicologia , Testes Neuropsicológicos , Adolescente , Criança , Transtornos Cognitivos/etiologia , Computadores , Estudos Transversais , Feminino , Humanos , Masculino , Esclerose Múltipla/complicações , Psicologia da Criança , Valores de Referência , Reprodutibilidade dos Testes , Fatores de Tempo
5.
Arch Clin Neuropsychol ; 27(5): 495-509, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22751624

RESUMO

Executive functions (EFs) are vulnerable to disruption in pediatric-onset multiple sclerosis (MS) patients. We describe the pattern and correlates of executive dysfunction in 34 adolescents with MS on neuropsychological tests and the parent version of the Behavior Rating Inventory of Executive Function (BRIEF). The adolescents with MS performed lower than age-matched controls in several areas of executive functioning, with 44% of patients being impaired on the Trail Making Test-Part B. On the BRIEF, problems in working memory and planning/organization were identified in the patient group compared with controls, particularly in patients with a younger age at disease onset. Task performance and parent-ratings of EF skills were strongly related to whole brain and regional brain volume metrics and, to a lesser extent, T(2)-weighted lesion volume. Working memory and attention switching are at greatest risk of impairment. Results support the inclusion of neuropsychological assessment alongside parent-report measures of EF skills in childhood-onset MS.


Assuntos
Encéfalo/patologia , Função Executiva , Esclerose Múltipla/psicologia , Fibras Nervosas Mielinizadas/patologia , Adolescente , Fatores Etários , Atenção , Criança , Feminino , Humanos , Inteligência , Imageamento por Ressonância Magnética , Masculino , Memória de Curto Prazo , Esclerose Múltipla/patologia , Neuroimagem , Testes Neuropsicológicos , Valor Preditivo dos Testes , Adulto Jovem
6.
Mult Scler ; 18(8): 1170-80, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22291032

RESUMO

BACKGROUND: Multiple sclerosis (MS) onset during adolescence has the potential to disrupt a key period of psychosocial maturation. OBJECTIVE: We aimed to examine the prevalence and risk factors associated with emotional and behavioral outcomes in adolescents with MS. METHODS: The Behavioral Assessment System for Children-2nd Edition (BASC-2) was completed by 31 adolescents with MS (mean age = 16.1 years), 31 age-matched controls, and parents of all participants. BASC-2 outcomes were compared between groups. Base rates were examined for scores falling at least one or two standard deviations below norm. Associations between BASC-2 outcomes and features of disease severity and IQ were examined. RESULTS: Youth with MS were reported by their parents to have more symptoms of depression and somatization and lower adaptive skills compared with reports by parents of controls. On the self-report, patients endorsed more problems of inattention/hyperactivity and lower self-reliance relative to controls. Behavioral concerns and reduced adaptive functioning in the MS group were associated with fatigue, poor relations with parents, and perceived social stress. Psychosocial outcomes did not associate with number of relapses, Expanded Disability Status Scale score, disease duration, brain lesion volume or IQ. CONCLUSION: Youth with MS are at risk of difficulties in behavioral and emotional health. Relations with parents emerged as a key factor influencing the emotional well-being of youth with MS, suggesting an important role for family-centered care in this population.


Assuntos
Comportamento do Adolescente , Emoções , Transtornos Mentais/psicologia , Saúde Mental , Esclerose Múltipla/psicologia , Adaptação Psicológica , Adolescente , Fatores Etários , Análise de Variância , Transtorno do Deficit de Atenção com Hiperatividade/epidemiologia , Transtorno do Deficit de Atenção com Hiperatividade/psicologia , Estudos de Casos e Controles , Distribuição de Qui-Quadrado , Criança , Estudos Transversais , Depressão/epidemiologia , Depressão/psicologia , Avaliação da Deficiência , Feminino , Humanos , Inteligência , Testes de Inteligência , Imageamento por Ressonância Magnética , Masculino , Transtornos Mentais/diagnóstico , Transtornos Mentais/epidemiologia , Esclerose Múltipla/diagnóstico , Esclerose Múltipla/epidemiologia , Ontário/epidemiologia , Relações Pais-Filho , Valor Preditivo dos Testes , Prevalência , Escalas de Graduação Psiquiátrica , Medição de Risco , Fatores de Risco , Índice de Gravidade de Doença , Comportamento Social , Transtornos Somatoformes/epidemiologia , Transtornos Somatoformes/psicologia , Adulto Jovem
7.
J Neurol Sci ; 309(1-2): 68-74, 2011 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-21821263

RESUMO

OBJECTIVES: To compare white matter (WM) integrity in children with MS and healthy children using diffusion tensor imaging (DTI), and correlate DTI findings with disease activity, lesion burden, and cognitive processing speed. METHODS: Fractional anisotropy (FA) and mean diffusivity (MD) in normal-appearing white matter (NAWM) were measured in four corpus callosum (CC), eight hemispheric regions, and the normal-appearing thalamus of 33 children and adolescents with MS and 30 age-matched healthy controls. Images were acquired on a GE LX 1.5T scanner. DTI parameters used were 25 directions, b = 1000 s/mm(2), and 5mm slice thickness. MS patients had T2 lesion volumes and Expanded Disability Status Scale (EDSS) scores were measured; all participants underwent two speeded cognitive tasks (Visual Matching and Symbol Digit Modalities Test (SDMT)). RESULTS: MS participants displayed lower FA values in the genu (p<0.005), splenium (p<0.001) and in NAWM of bilateral parietal, temporal, and occipital lobes (p<0.001) versus controls. FA and MD in the thalamus did not differ between groups. Higher lesion volumes correlated with reduced FA in CC and hemispheric NAWM. DTI metrics did not correlate with EDSS. FA values in CC regions correlated with Visual Matching (p<0.001) and SDMT (p<0.005) in MS participants only. INTERPRETATION: DTI analyses indicate widespread NAWM disruption in children with MS-with the degree of abnormality correlating with impaired cognitive processing speed. These findings support an early onset tissue pathology in MS and illustrate its functional consequence.


Assuntos
Cognição/fisiologia , Imagem de Tensor de Difusão , Esclerose Múltipla/metabolismo , Esclerose Múltipla/psicologia , Desempenho Psicomotor/fisiologia , Adolescente , Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/metabolismo , Transtornos Cognitivos/psicologia , Imagem de Tensor de Difusão/métodos , Feminino , Humanos , Masculino , Estimulação Luminosa/métodos , Fatores de Tempo
8.
Neuropsychology ; 25(3): 319-32, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21534686

RESUMO

OBJECTIVE: Brain MRI measures were correlated with neuropsychological function in 35 pediatric-onset multiple sclerosis (MS) patients and 33 age- and sex-matched healthy controls. METHOD: Mean age of MS patients was 16.3 ± 2.3 years with average disease duration of 4.3 ± 3.1 years. Cortical gray matter, thalamic, and global brain volumes were calculated for all participants using a scaling factor computed using normalization of atrophy method to normalize total and regional brain volumes for head size. T1- and T2-weighted lesion volumes were calculated for MS patients. RESULTS: Cognitive impairment (CI) was identified in 29% of the MS cohort. Cognitive deficits predominantly involved attention and processing speed, expressive language, and visuomotor integration. Relative to controls, the MS group showed significantly lower thalamic volume (p < .001), total brain volume (p < .008), and gray matter volume (p < .015). Corpus callosum area and thalamic volume differentiated patients identified as having CI from those without CI (p < .05). Regression models controlling for disease duration and age indicated that thalamic volume accounted for significant incremental variance in predicting global IQ, processing speed, and expressive vocabulary (ΔR2 ranging from .43 to .60) and was the most robust MRI predictor of cognition relative to other MRI metrics. CONCLUSIONS: The robust association between cognitive function and reduced size of thalamus and global brain volume in pediatric-onset MS patients implicate neurodegenerative processes early in the disease course, and suggest that plasticity of an immature central nervous system is not sufficient to protect patients from the deleterious consequences of MS on cognitive neural networks. (PsycINFO Database Record (c) 2011 APA, all rights reserved).


Assuntos
Encéfalo/patologia , Cognição , Imageamento por Ressonância Magnética , Esclerose Múltipla/patologia , Esclerose Múltipla/psicologia , Adolescente , Idade de Início , Estudos de Casos e Controles , Corpo Caloso/patologia , Feminino , Humanos , Masculino , Esclerose Múltipla/diagnóstico , Tamanho do Órgão , Índice de Gravidade de Doença , Tálamo/patologia
9.
Bull Entomol Res ; 100(2): 217-23, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19573253

RESUMO

Field trials were conducted at four Canterbury, New Zealand locations in 2005-06 to determine if the synergistic effects of biological control by natural enemies and standard drenching techniques controlled lettuce aphid populations throughout the entire growing season. Chemical usage significantly lowered aphid densities in the outer, wrapper and heart leaves compared to control plants at most times. However, in mid-summer, natural enemies, such as the brown lacewing (Micromus tasmaniae), 11-spotted ladybird beetle (Coccinella undecimpunctata) and small hoverfly larvae (Melanostoma fasciatum), were more than sufficient to control lettuce aphids without the use of insecticides. Drenching, in addition to natural enemy attack, appears to be required in early spring and late summer to maintain very low levels of lettuce aphid. Given the potential for imidacloprid resistance to develop, it may be advisable to restrict drenches to these key periods in order to allow populations of natural enemies to maintain control of prey populations. We recommend industry support the validation of action thresholds across different regions within New Zealand and focus on the seasonal biology of predators to assist growers with the sustainable long-term control of lettuce aphids. The inclusion of additional data into an economic model to compare pest damage with predator loading would be useful for growers in managing aphid problems. These results will assist in the continued improvement and development of a sustainable IPM strategy for lettuce aphids in New Zealand and elsewhere.


Assuntos
Agricultura/métodos , Afídeos , Inseticidas , Controle Biológico de Vetores , Animais , Nova Zelândia , Estações do Ano
10.
Nature ; 459(7247): 694-7, 2009 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-19494913

RESUMO

The processes that give rise to arc magmas at convergent plate margins have long been a subject of scientific research and debate. A consensus has developed that the mantle wedge overlying the subducting slab and fluids and/or melts from the subducting slab itself are involved in the melting process. However, the role of kinematic variables such as slab dip and convergence rate in the formation of arc magmas is still unclear. The depth to the top of the subducting slab beneath volcanic arcs, usually approximately 110 +/- 20 km, was previously thought to be constant among arcs. Recent studies revealed that the depth of intermediate-depth earthquakes underneath volcanic arcs, presumably marking the slab-wedge interface, varies systematically between approximately 60 and 173 km and correlates with slab dip and convergence rate. Water-rich magmas (over 4-6 wt% H(2)O) are found in subduction zones with very different subduction parameters, including those with a shallow-dipping slab (north Japan), or steeply dipping slab (Marianas). Here we propose a simple model to address how kinematic parameters of plate subduction relate to the location of mantle melting at subduction zones. We demonstrate that the location of arc volcanoes is controlled by a combination of conditions: melting in the wedge is induced at the overlap of regions in the wedge that are hotter than the melting curve (solidus) of vapour-saturated peridotite and regions where hydrous minerals both in the wedge and in the subducting slab break down. These two limits for melt generation, when combined with the kinematic parameters of slab dip and convergence rate, provide independent constraints on the thermal structure of the wedge and accurately predict the location of mantle wedge melting and the position of arc volcanoes.

11.
Nat Mater ; 4(3): 203-6, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15711553

RESUMO

Thin-film technology is widely implemented in numerous applications. Although flat substrates are commonly used, we report on the advantages of using curved surfaces as a substrate. The curvature induces a lateral film-thickness variation that allows alteration of the properties of the deposited material. Based on this concept, a variety of implementations in materials science can be expected. As an example, a topographic pattern formed of spherical nanoparticles is combined with magnetic multilayer film deposition. Here we show that this combination leads to a new class of magnetic material with a unique combination of remarkable properties: The so-formed nanostructures are monodisperse, magnetically isolated, single-domain, and reveal a uniform magnetic anisotropy with an unexpected switching behaviour induced by their spherical shape. Furthermore, changing the deposition angle with respect to the particle ensemble allows tailoring of the orientation of the magnetic anisotropy, which results in tilted nanostructure material.


Assuntos
Magnetismo , Nanoestruturas/química , Cobalto/química , Nanoestruturas/ultraestrutura , Nanotecnologia , Paládio/química
14.
Teratology ; 64(3): 134-41, 2001 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11514943

RESUMO

BACKGROUND: Previous studies in adults and animals with high level exposure to organic solvents suggested impairments in visual functioning. The objective of this pilot study was to examine the effects of maternal occupational exposure to organic solvents during pregnancy on offspring color vision and visual acuity, the development of which may be especially vulnerable to organic solvent exposure. METHODS: We conducted a prospective cohort study of 32 offspring of women who were exposed occupationally to organic solvents during pregnancy compared with 27 nonexposed children. Monocular and binocular color vision and visual acuity were assessed using the Minimalist Test and the Cardiff Cards, respectively. Children with known hereditary color vision loss were excluded. RESULTS: Solvent-exposed children had significantly higher error scores on red-green and blue-yellow color discrimination, as well as poorer visual acuity compared with the control group. Exposure index (an estimated measure of exposure intensity) was not significantly related to color discrimination or visual acuity score. Despite excluding all children with a known family history of color vision loss, clinical red-green color vision loss was found among 3 of the 32 exposed children compared with none of the matched controls. CONCLUSIONS: These preliminary findings suggest that occupational exposure to organic solvents during pregnancy is associated with an increased risk of color vision and visual acuity impairment in offspring. The importance of routine visual function screening in risk assessment after prenatal exposure to chemicals warrants further attention.


Assuntos
Defeitos da Visão Cromática/etiologia , Exposição Materna/efeitos adversos , Exposição Ocupacional/efeitos adversos , Compostos Orgânicos/efeitos adversos , Solventes/efeitos adversos , Visão Ocular/efeitos dos fármacos , Adulto , Criança , Pré-Escolar , Estudos de Coortes , Percepção de Cores/efeitos dos fármacos , Defeitos da Visão Cromática/congênito , Feminino , Humanos , Masculino , Projetos Piloto , Gravidez , Resultado da Gravidez , Fatores de Risco , Fatores de Tempo
15.
Neurotoxicol Teratol ; 23(3): 235-45, 2001.
Artigo em Inglês | MEDLINE | ID: mdl-11418265

RESUMO

The present study compared the cognitive and behavioral functioning of 3- to 7-year-old children (n=33) whose mothers worked with organic solvents during pregnancy with a group of unexposed children (n=28) matched on age, gender, parental socioeconomic status (SES), and ethnicity. Participants were recruited prospectively by the Motherisk Program, an antenatal counseling service in Canada. An exposure index was estimated using questionnaire data obtained at the time of initial contact. Groups were compared on a variety of tasks, including subtests from the NEPSY, a visual CPT, as well as on parent-rated measures of children's behavior. Regression analyses indicated lower composite scores in children with increased exposure on Receptive language (P<.01), Expressive language (P<.01), and Graphomotor ability (P=.001), adjusted for demographics. No group differences were observed on measures of Attention (P=.97), Visuo-spatial ability (P=.33), and Fine-motor ability (P=.33). On the Child Behavior Checklist (CBCL), overall mean differences on broad- and narrow-band scales were not significant, but significantly more exposed children were rated as having mild or severe problem behaviors. The findings suggest that maternal occupational exposure to organic solvents during pregnancy is associated with poorer outcome in selective aspects of cognitive and neuromotor functioning in offspring.


Assuntos
Comportamento/efeitos dos fármacos , Cognição/efeitos dos fármacos , Exposição Ocupacional/efeitos adversos , Efeitos Tardios da Exposição Pré-Natal , Solventes/toxicidade , Adulto , Criança , Desenvolvimento Infantil/efeitos dos fármacos , Pré-Escolar , Relação Dose-Resposta a Droga , Feminino , Crescimento/efeitos dos fármacos , Humanos , Masculino , Testes Neuropsicológicos , Gravidez , Desempenho Psicomotor/efeitos dos fármacos , Caracteres Sexuais
16.
Toxicology ; 149(2-3): 51-61, 2000 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-10967402

RESUMO

The objective of this study was to evaluate the stability of individual, xenobiotic-metabolising, cytochrome P450 proteins in precision-cut rat liver slices cultured for up to 72 h using the multiwell plate system. This was achieved using established diagnostic probes (O-dealkylation of methoxy-, ethoxy- and pentoxy-resorufin, testosterone 2alpha-hydroxylase, debrisoquine 4-hydroxylase, aniline p-hydroxylase and lauric acid hydroxylase) and immunologically using Western blotting. All cytochrome P450 activities declined in culture, the most rapid loss occurring at about 8-12 h of culture; in all cases no detectable activity was present in the 72-h cultured slices. Isoform-specific differences in the stability of various cytochrome P450 proteins were observed, with CYP2E1 being the most stable. When cytochrome P450 expression was determined immunologically, a different picture emerged. High levels of apoprotein were retained in the slices even when activity was very low. In the case of CYP2B, apoprotein levels even increased following the culture of hepatic slices. It is concluded, that for tissue slices to become an acceptable in vitro alternative system for long-term incubations, the culturing conditions must be improved to ensure that cytochrome P450 activities are better maintained.


Assuntos
Hidrocarboneto de Aril Hidroxilases , Sistema Enzimático do Citocromo P-450/metabolismo , Fígado/enzimologia , Animais , Técnicas de Cultura , Citocromo P-450 CYP1A1/metabolismo , Citocromo P-450 CYP1A2/metabolismo , Citocromo P-450 CYP2B6 , Citocromo P-450 CYP3A , Citocromo P-450 CYP4A , Estabilidade Enzimática , Immunoblotting , Microssomos Hepáticos/enzimologia , Oxigenases de Função Mista/metabolismo , Oxirredutases N-Desmetilantes/metabolismo , Ratos , Fatores de Tempo
17.
Appl Environ Microbiol ; 65(9): 4021-7, 1999 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-10473411

RESUMO

The pathways of biotransformation of 4-fluorobiphenyl (4FBP) by the ectomycorrhizal fungus Tylospora fibrilosa and several other mycorrhizal fungi were investigated by using (19)F nuclear magnetic resonance (NMR) spectroscopy in combination with (14)C radioisotope-detected high-performance liquid chromatography ((14)C-HPLC). Under the conditions used in this study T. fibrillosa and some other species degraded 4FBP. (14)C-HPLC profiles indicated that there were four major biotransformation products, whereas (19)F NMR showed that there were six major fluorine-containing products. We confirmed that 4-fluorobiphen-4'-ol and 4-fluorobiphen-3'-ol were two of the major products formed, but no other products were conclusively identified. There was no evidence for the expected biotransformation pathway (namely, meta cleavage of the less halogenated ring), as none of the expected products of this route were found. To the best of our knowledge, this is the first report describing intermediates formed during mycorrhizal degradation of halogenated biphenyls.


Assuntos
Basidiomycota/metabolismo , Compostos de Bifenilo/metabolismo , Basidiomycota/crescimento & desenvolvimento , Biodegradação Ambiental , Radioisótopos de Carbono/metabolismo , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância Magnética
18.
Xenobiotica ; 29(1): 11-25, 1999 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-10078837

RESUMO

1. Objectives were two-fold: (1) to compare the viability of precision-cut liver slices in two culture systems, namely the dynamic organ and the multiwell plate; and (2) to evaluate whether increasing the number of slices per incubation results in a proportional increase in the extent of metabolism. 2. With both culturing systems, the major products of 7-ethoxycoumarin metabolism were the sulphate and glucuronide conjugates of 7-hydroxycoumarin with very low levels of the free compound. When the multiwell plate procedure was used, metabolism increased linearly for at least 10 h, whereas it tended to plateau after 6 h in the dynamic organ culture system. At preincubations > 10 h, significantly more metabolism of 7-ethoxycoumarin was seen in the slices cultured using the multiwell system compared with the dynamic organ system. 3. Morphological evaluation employing light and electron microscopy revealed that liver slices incubated using the multiwell system were structurally better preserved compared with those incubated using the dynamic organ system. 4. Using the multiwell system, increasing the number of slices per incubation from one to two resulted in only a modest increase in the metabolism of 7-ethoxycoumarin. The rate of metabolism of this substrate was much higher with one liver slice when expressed per mg homogenate protein. 5. It is concluded that (1) the multiwell plate culture system for culturing slices is superior to the dynamic organ system in studying the metabolism of xenobiotics following long-term incubations, (2) increasing the number of slices per incubation does not result in a corresponding increase in the rate of metabolism, and (3) in both culture systems optimal viability appears to be within 24 h of incubation.


Assuntos
Cumarínicos/metabolismo , Fígado/metabolismo , Fígado/ultraestrutura , Técnicas de Cultura de Órgãos/métodos , Umbeliferonas/metabolismo , Animais , L-Lactato Desidrogenase/metabolismo , Fígado/citologia , Masculino , Microscopia/métodos , Microscopia Eletrônica , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Fatores de Tempo , Xenobióticos/metabolismo
19.
Chemosphere ; 38(5): 1085-101, 1999 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10028659

RESUMO

The incubation of the model pollutant [U-14C]'-4-fluorobiphenyl (4FBP) in soil, in the presence and absence of biphenyl (a co-substrate), was carried out in order to study the qualitative disposition and fate of the compound using 14C-HPLC and 19F NMR spectroscopy. Components accounted for using the radiolabel were volatilization, CO2 evolution, organic solvent extractable and bound residue. Quantitative analysis of these data gave a complete mass balance. After sample preparation. 14C-HPLC was used to establish the number of 4FBP related components present in the organic solvent extract. 19F NMR was also used to quantify the organic extracts and to identify the components of the extract. Both approaches showed that the composition of the solvent extractable fractions comprised only parent compound with no metabolites present. As the 14C radiolabel was found to be incorporated into the soil organic matter this indicates that metabolites were being generated, but were highly transitory as incorporation into the SOM was rapid. The inclusion of the co-substrate biphenyl was to increase the overall rate of degradation of 4FBP in soil. The kinetics of disappearance of parent from the soil using the data obtained were investigated from both techniques. This is the first report describing the degradation of a fluorinated biphenyl in soil.


Assuntos
Compostos de Bifenilo/metabolismo , Espectroscopia de Ressonância Magnética/métodos , Poluentes do Solo/metabolismo , Biodegradação Ambiental , Biotransformação , Radioisótopos de Carbono , Cromatografia Líquida de Alta Pressão/métodos , Flúor , Cinética , Solventes
20.
Toxicol In Vitro ; 13(3): 459-66, 1999 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20654503

RESUMO

The aim of the present study was to investigate the stability of Phase II conjugation enzymes in precision-cut rat liver slices that have been cultured, using the multiwell plate system, for various periods of time up to 72 hours. The enzyme activities monitored were epoxide hydrolase, glutathione S-transferase and the associated glutathione reductase, sulfotransferase and glucuronyl transferase. The activity of all enzymes studied declined with time when expressed per slice, but the rate of loss differed among the various enzymes. However, in most cases substantial Phase II activity was still present in the liver slices following a 24-hour incubation, and in some cases significant activity was even retained in slices cultured for 72 hours. These studies indicate that precision-cut liver slices maintain Phase II activity for long periods of time, thus allowing metabolic studies involving prolonged incubations to be performed.

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