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2.
Ann R Coll Surg Engl ; 100(4): e69-e72, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29543054

RESUMO

Most lumbar intradural schwannomas present initially as radiculopathies with sensory disturbances. However, neurogenic bladder dysfunction may be one of the earliest manifestations and can cause long-term disability. We present the case of a patient with a L3-4 schwannoma (newly diagnosed owing to recurrent urinary retention and urinary tract infection) who finally underwent surgical resection. Improvement of bladder sensation was documented by urodynamic study and the patient was subsequently weaned off her Foley catheter with satisfactory outcome.


Assuntos
Neurilemoma/cirurgia , Neoplasias da Medula Espinal/cirurgia , Bexiga Urinaria Neurogênica/cirurgia , Cateterismo Urinário , Retenção Urinária/cirurgia , Idoso de 80 Anos ou mais , Cistografia , Feminino , Gadolínio/administração & dosagem , Humanos , Laminectomia/instrumentação , Laminectomia/métodos , Dor Lombar/etiologia , Dor Lombar/cirurgia , Vértebras Lombares , Imageamento por Ressonância Magnética/métodos , Neurilemoma/complicações , Neurilemoma/diagnóstico por imagem , Recidiva , Neoplasias da Medula Espinal/complicações , Neoplasias da Medula Espinal/diagnóstico por imagem , Bexiga Urinaria Neurogênica/diagnóstico por imagem , Bexiga Urinaria Neurogênica/etiologia , Retenção Urinária/diagnóstico por imagem , Retenção Urinária/etiologia , Infecções Urinárias/etiologia , Urodinâmica
3.
Phys Rev Lett ; 115(18): 186403, 2015 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-26565480

RESUMO

In a semimetal, both electrons and holes contribute to the density of states at the Fermi level. The small band overlaps and multiband effects engender novel electronic properties. We show that a moderate hydrostatic pressure effectively suppresses the band gap in the elemental semiconductor black phosphorus. An electronic topological transition takes place at approximately 1.2 GPa, above which black phosphorus evolves into a semimetal state that is characterized by a colossal positive magnetoresistance and a nonlinear field dependence of Hall resistivity. The Shubnikov-de Haas oscillations detected in magnetic field reveal the complex Fermi surface topology of the semimetallic phase. In particular, we find a nontrivial Berry phase in one Fermi surface that emerges in the semimetal state, as evidence of a Dirac-like dispersion. The observed semimetallic behavior greatly enriches the material property of black phosphorus and sets the stage for the exploration of novel electronic states in this material.

4.
Genet Mol Res ; 13(4): 8225-33, 2014 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-25299207

RESUMO

Lumbar intervertebral disc degeneration is induced by multiple factors, but few studies have examined the effects of aquaporins on this process. We compared the expression levels of aquaporins 1 and 3 in normal and degenerative lumbar intervertebral discs. Fifteen normal and 15 degenerative lumbar intervertebral disc tissues were excised from lumbar burst fracture patients during orthopedic operations at the Dali College subsidiary hospital. Tissues were stained with hematoxylin-eosin and the expression levels of aquaporins 1 and 3 were measured by immunohistochemistry. Hematoxylin-eosin-staining results illustrated that the structures of the intervertebral disc tissues from the control group were clear, with distinct collagen fiber shapes and slight edema but without mucoid degeneration. Structures of the intervertebral disc tissues from the disease group were obscure and disordered with hyperplastic collagen fibers and tissues of severe inflammatory edemas with necrosis mucoid degeneration. Immunohistochemistry results demonstrated that the average absorbances of aquaporins 1 and 3 in the disease group were significantly lower than those in the control group (P < 0.01), suggesting that the reduction of aquaporins 1 and 3 may be a factor resulting in lumbar intervertebral disc degeneration.


Assuntos
Aquaporina 1/metabolismo , Aquaporina 3/metabolismo , Degeneração do Disco Intervertebral/metabolismo , Disco Intervertebral/metabolismo , Disco Intervertebral/patologia , Adulto , Aquaporina 1/genética , Aquaporina 3/genética , Estudos de Casos e Controles , Feminino , Expressão Gênica , Humanos , Degeneração do Disco Intervertebral/genética , Masculino , Pessoa de Meia-Idade , Adulto Jovem
5.
Eur J Surg Oncol ; 40(3): 330-7, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24373299

RESUMO

BACKGROUND: To assess the safety of transorally-inserted anvil (TOA) for use during esophagojejunostomy (EJ) reconstruction during laparoscopic total gastrectomy (LTG). METHODS: Between March 2009 and December 2011, 39 consecutive open total gastrectomies (OTGs) and 36 LTGs using TOA for gastric cancer were comparatively evaluated. We investigated postoperative complications, using the Clavien-Dindo classification. To evaluate the effect of a learning period in using TOA for LTG, we also investigated shifts in the patterns of complications and changes in total operation time over the course of the study. RESULTS: The patient characteristics at baseline were not different between both groups, except for the extent of lymphadenectomy (P < 0.001) and depth of tumor invasion (P = 0.003). Multivariate analysis revealed that TOA usage elevated the occurrence of infectious complications significantly (OR = 3.32, P = 0.042), but was not associated with EJ-related complications. TOA usage did not need a learning period for the length of time required to complete the operation, or the likelihood of developing an EJ-related or infectious complication. CONCLUSIONS: TOA use for EJ during LTG is relatively simple and easy enough not to require a learning period for surgeons. This procedure did not elevated the occurrence of EJ-related complications compared to circular stapling in open surgery, but it does require special prevention efforts to avoid infectious complications.


Assuntos
Esôfago/cirurgia , Gastrectomia/métodos , Cirurgia Endoscópica por Orifício Natural/instrumentação , Segurança do Paciente , Neoplasias Gástricas/cirurgia , Idoso , Anastomose Cirúrgica/métodos , Estudos de Coortes , Feminino , Gastroscopia/métodos , Humanos , Jejunostomia/métodos , Laparotomia/métodos , Masculino , Pessoa de Meia-Idade , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Cirurgia Endoscópica por Orifício Natural/métodos , Invasividade Neoplásica/patologia , Estadiamento de Neoplasias , Duração da Cirurgia , Estudos Retrospectivos , Neoplasias Gástricas/mortalidade , Neoplasias Gástricas/patologia , Grampeamento Cirúrgico/métodos , Resultado do Tratamento
6.
Transplant Proc ; 45(8): 2949-52, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24157010

RESUMO

BACKGROUND: With the increased numbers of kidney transplantations, more patients return to dialysis after graft loss (DAGL). The aim of this study was to investigate the safety and efficacy of peritoneal dialysis (PD) after graft loss compared with transplant-naive PD patients (TN-PD). METHOD: This study was conducted on 715 patients who started PD between 1988 and 2009, including 47 who started PD after allograft loss (DAGL-PD) and 668 in the (TN-PD) group. RESULT: The mean ages were 40.8 ± 10.7 in DAGL-PD group and 51.03 ± 14.20 in TN-PD group (P < .01). The most common cause of end-stage renal disease in DAGL was primary glomerulonephritis (76.6%), but it was diabetes mellitus (38.9%) in the TN-PD group (P < .05). Patient survival rates at 1, 5, and 10 years were not different: 100%, 86%, and 57% versus 91%, 70%, and 62%, respectively. PD survival rate at 1, 5, and 10 years did not show significant differences: 98%, 95%, and 88% versus 95%, 80%, and 66%, respectively. The most common causes of death in both groups were infection (DAGL, 26.7%; TN-PD, 24.5%) followed by cardiovascular disease (DAGL, 20.0%; TN-PD, 19.6%); the distribution of causes did not differ significantly (P > .05). CONCLUSION: The clinical outcomes of PD in DAGL group were comparable with those of TN-PD patients. Therefore, PD could be considered as a dialysis modality for patients who experience allograft failure.


Assuntos
Rejeição de Enxerto , Falência Renal Crônica/cirurgia , Falência Renal Crônica/terapia , Transplante de Rim , Adulto , Aloenxertos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Taxa de Sobrevida
7.
Diabetologia ; 56(1): 204-17, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23090186

RESUMO

AIMS/HYPOTHESIS: Many of the effects of resveratrol are consistent with the activation of AMP-activated protein kinase (AMPK), silent information regulator T1 (SIRT1) and peroxisome proliferator-activated receptor (PPAR)γ co-activator 1α (PGC-1α), which play key roles in the regulation of lipid and glucose homeostasis, and in the control of oxidative stress. We investigated whether resveratrol has protective effects on the kidney in type 2 diabetes. METHODS: Four groups of male C57BLKS/J db/m and db/db mice were used in this study. Resveratrol was administered via gavage to diabetic and non-diabetic mice, starting at 8 weeks of age, for 12 weeks. RESULTS: The db/db mice treated with resveratrol had decreased albuminuria. Resveratrol ameliorated glomerular matrix expansion and inflammation. Resveratrol also lowered the NEFA and triacylglycerol content of the kidney, and this action was related to increases in the phosphorylation of AMPK and the activation of SIRT1-PGC-1α signalling and of the key downstream effectors, the PPARα-oestrogen-related receptor (ERR)-1α-sterol regulatory element-binding protein 1 (SREBP1). Furthermore, resveratrol decreased the activity of phosphatidylinositol-3 kinase (PI3K)-Akt phosphorylation and class O forkhead box (FOXO)3a phosphorylation, which resulted in a decrease in B cell leukaemia/lymphoma 2 (BCL-2)-associated X protein (BAX) and increases in BCL-2, superoxide dismutase (SOD)1 and SOD2 production. Consequently, resveratrol reversed the increase in renal apoptotic cells and oxidative stress, as reflected by renal 8-hydroxy-deoxyguanosine (8-OH-dG), urinary 8-OH-dG and isoprostane concentrations. Resveratrol prevented high-glucose-induced oxidative stress and apoptosis in cultured mesangial cells through the phosphorylation of AMPK and activation of SIRT1-PGC-1α signalling and the downstream effectors, PPARα-ERR-1α-SREBP1. CONCLUSIONS/INTERPRETATION: The results suggest that resveratrol prevents diabetic nephropathy in db/db mice by the phosphorylation of AMPK and activation of SIRT1-PGC-1α signalling, which appear to prevent lipotoxicity-related apoptosis and oxidative stress in the kidney.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Nefropatias Diabéticas/prevenção & controle , Rim/efeitos dos fármacos , Células Mesangiais/efeitos dos fármacos , Substâncias Protetoras/uso terapêutico , Transdução de Sinais/efeitos dos fármacos , Estilbenos/uso terapêutico , Proteínas Quinases Ativadas por AMP/antagonistas & inibidores , Proteínas Quinases Ativadas por AMP/química , Proteínas Quinases Ativadas por AMP/genética , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Células Cultivadas , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patologia , Ativação Enzimática/efeitos dos fármacos , Rim/metabolismo , Rim/patologia , Rim/fisiopatologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Lipotrópicos/farmacologia , Lipotrópicos/uso terapêutico , Masculino , Células Mesangiais/metabolismo , Células Mesangiais/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Estresse Oxidativo/efeitos dos fármacos , Substâncias Protetoras/farmacologia , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Interferência de RNA , Resveratrol , Sirtuína 1/antagonistas & inibidores , Sirtuína 1/química , Sirtuína 1/genética , Sirtuína 1/metabolismo , Estilbenos/farmacologia , Fatores de Transcrição/agonistas , Fatores de Transcrição/metabolismo
8.
Phys Rev Lett ; 104(13): 137201, 2010 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-20481907

RESUMO

We demonstrate, both theoretically and experimentally, that cation vacancy can be the origin of ferromagnetism in intrinsic dilute magnetic semiconductors. The vacancies can be controlled to tune the ferromagnetism. Using Li-doped ZnO as an example, we found that while Li itself is nonmagnetic, it generates holes in ZnO, and its presence reduces the formation energy of Zn vacancy, and thereby stabilizes the zinc vacancy. Room temperature ferromagnetism with p type conduction was observed in pulsed laser deposited ZnO:Li films with certain doping concentration and oxygen partial pressure.

9.
Phys Rev Lett ; 105(20): 207201, 2010 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-21231259

RESUMO

We report direct evidence of room-temperature ferromagnetic ordering in O-deficient ZnO:Cu films by using soft x-ray magnetic circular dichroism and x-ray absorption. Our measurements have revealed unambiguously two distinct features of Cu atoms associated with (i) magnetically ordered Cu ions present only in the oxygen-deficient samples and (ii) magnetically disordered regular Cu2+ ions present in all the samples. We find that a sufficient amount of both oxygen vacancies (V(O)) and Cu impurities is essential to the observed ferromagnetism, and a non-negligible portion of Cu impurities is uninvolved in the magnetic order. Based on first-principles calculations, we propose a microscopic "indirect double-exchange" model, in which alignments of localized large moments of Cu in the vicinity of the V(O) are mediated by the large-sized vacancy orbitals.

10.
J Paediatr Child Health ; 43(5): 353-8, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17489824

RESUMO

AIM: Because of a high childhood asthma burden in Singapore, assessment of disease control status is essential for formulating school-based strategy of childhood asthma control. The aim of the present study is to assess childhood asthma prevalence and control in Singapore and the socio-demographic and help-seeking correlates. METHODS: School-based survey using parental self-administered questionnaire, conducted from February to April 2004. Four mixed-gender primary schools selected from geographically distinct zones of Singapore. All primary one (modal age - 6.5 years) and six (modal age - 11.9 years) students from selected schools were invited to participate. Questionnaire respondents were the students' parents or guardians. The response rate was 75.2% (2123/2825). RESULTS: Prevalence of current asthma was 8.9% (190/2123). Among them, 26.3% (46/175) were assessed to have inadequate control. Asthma was more prevalent, and less adequately controlled in children from lower socio-economic backgrounds (lower-end housing type). Children with poorly controlled asthma were more likely to be treated by emergency room physicians and hospital specialists, and to be on preventer medications. CONCLUSIONS: In Singapore, poor asthma control is found in a sizeable proportion of school children with asthma, is identifiable for high-risk groups of children from lower socio-economic backgrounds and having asthma-related attendance at the emergency rooms.


Assuntos
Asma/epidemiologia , Asma/terapia , Serviços de Saúde Escolar , Criança , Coleta de Dados , Feminino , Humanos , Masculino , Projetos Piloto , Singapura/epidemiologia
11.
J Biomater Sci Polym Ed ; 14(6): 551-65, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12901437

RESUMO

Lactobionic acid, bearing a beta-galactose group, was coupled with chitosan to provide synthetic extracellular matrices together with poly(vinyl alcohol) (PVA). The hepatocytes encapsulated in Ba-alginate capsules with galactosylated chitosan (GC) and PVA as extracellular matrices showed aggregation morphologies as the incubation time increased. Ba-alginate-encapsulated hepatocytes with GC exhibited a higher metabolic function in albumin secretion compared to those entrapped in Ba-alginate beads and monolayer-cultured on a collagen-immobilized polystyrene dish. The ammonia removal ability of monolayer-cultured hepatocytes decreased with increasing culture time and disappeared completely after three days. In contrast, the ammonia removal ability of encapsulated and entrapped hepatocytes increased with increasing incubation time in the first seven and five days, respectively. Thereafter, the entrapped hepatocytes lost ammonia removal ability quickly while the encapsulated hepatocytes kept a relatively high ammonia removal ability up to 13 days. The trace amount of GC in the core matrices enabled encapsulated cells to enhance their ammonia removal and albumin secretion ability. The results obtained with 3-(3,4-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) also showed that the capsules incorporated with GC can provide a better microenvironment for cell aggregation along with nutrition and metabolite transfer. Due to the nature of the liquid core, the encapsulated hepatocytes showed very good mobility. This facilitated cell-cell interaction and cell-matrix interaction.


Assuntos
Alginatos/metabolismo , Quitina/análogos & derivados , Quitina/metabolismo , Matriz Extracelular/metabolismo , Hepatócitos/metabolismo , Álcool de Polivinil/metabolismo , Animais , Bário/química , Materiais Biocompatíveis , Cápsulas , Células Cultivadas , Quitosana , Galactose/metabolismo , Hepatócitos/citologia , Masculino , Camundongos , Camundongos Endogâmicos ICR , Fatores de Tempo
12.
Water Sci Technol ; 47(9): 65-70, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12830942

RESUMO

The effects of estradiol-17beta, methyltestosterone, tributyltin, bisphenol A and 2,4-dinitrophenol on sex differentiation were investigated in the Korean rockfish, Sebastes schlegeli. The 51 day-old fry with undifferentiated gonads were fed with food containing the chemicals at 0.05, 0.5, 5, 50 and 100 micro/g diet for 29 days. Sex ratio and gonadal abnormality after the chemical treatment were determined by histological examination of gonads. In control group, the sex ratio of fry was 1:1.3 (female:male), and more males than females appeared. The sex of fry fed with estradiol-17beta at 5, 50 and 100 micro/g diet was all females. Feminization of the fry was induced by exogenic estradiol-17beta. In the methyltestosterone group, sex ratio of fry was 1:10.2 in 0.05 micro/g diet, 1:2.4 in 0.5 micro/g diet, 1:3.1 in 5 micro/g diet, 1:1.2 in 50 micro/g diet and 1:2.3 in 100 micro/g diet. Masculinization of the fry was induced by methyltestosterone at the lowest concentration. Furthermore, intersex of the fry was observed. The number of intersex fry was 23.3, 25.0 and 35.3 at 0.5, 5 and 50 micro/g diet of methyltestosterone, respectively. Sex ratio of bisphenol A group showed no difference with that of the control. The sex of fry fed with 2,4-dinitrophenol at 5, 50 and 100 micro/g diet was all females. 2,4-dinitrophenol should be considered as a new member of endocrine disruptors. In tributyltin group, the sex ratio of fry at 100 micro/g diet of tributyltin was 5.4:1. Tributyltin induced the feminization of the fry at the highest dose. Tributyltin showed an estrogenic effect in the Korean rockfish in contrast to an androgenic effect in gastropods.


Assuntos
Sistema Endócrino/efeitos dos fármacos , Peixes/crescimento & desenvolvimento , Diferenciação Sexual/efeitos dos fármacos , Poluentes Químicos da Água/intoxicação , Administração Oral , Animais , Dieta , Feminino , Masculino
13.
Arch Pharm Res ; 24(5): 431-6, 2001 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11693546

RESUMO

The water extract of Cichorium intybus (WECI) showed a remarkable antioxidative effect on LDL, and inhibitory effects on the production of thiobarbituric acid reactive substance and the Degradation of fatty acids in LDL. Vitamin E and unsaturated fatty acids in LDL were protected by adding WECI from the effects of metal catalyzed LDL oxidation. From the results obtained, we conclude that LDL oxidation is inhibited in vitro by the addition of WECI, and that LDL is protected by WECI from oxidative attack, as shown by agarose gel electrophoresis.


Assuntos
Antioxidantes/química , Asteraceae/química , Lipoproteínas LDL/química , Antioxidantes/isolamento & purificação , Cromatografia Gasosa , Cobre/química , Eletroforese em Gel de Ágar , Indicadores e Reagentes , Lipídeos/química , Oxirredução , Extratos Vegetais/química , Raízes de Plantas/química , Substâncias Reativas com Ácido Tiobarbitúrico/química , Vitamina E/química
14.
J Org Chem ; 66(5): 1676-9, 2001 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-11262112

RESUMO

Reaction of various chiral camphor N-enoylpyrazolidinones 2a-g with N-aminophthalimide in the presence of lead tetraacetate in CH(2)Cl(2) proceed smoothly afford the corresponding N-phthalimidoaziridines (3a-e, 4f-g) with excellent material yields (86-95%) at room temperature in 5 min. High levels of diastereoselectivities (up to >95:5 dr) were obtained. The solvent effect was investigated, and the auxiliary can be easily recovered in high yields under mild reaction conditions.

15.
Chem Commun (Camb) ; (17): 1612-3, 2001 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-12240407

RESUMO

Treatment of alpha-naphthyl acrylate with both aliphatic and aromatic aldehydes in the presence of DABCO (30 mol%) afforded the desired (alpha-methylene-beta-hydroxy)esters with reasonable chemical yields (51-88%) within 20 min.

17.
Chem Pharm Bull (Tokyo) ; 48(6): 879-81, 2000 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10866154

RESUMO

Two 3,4-seco-lupane triterpenoids (1, 2) were isolated from the leaves of Acanthopanax divaricatus var. albeofructus (Araliaceae). Based on the spectroscopic data, the chemical structures of 1 and 2 were characterized as 24-hydroxychiisanogenin and 22alpha-hydroxychiisanogenin, respectively. 1 was a new compound and 2 was isolated for the first time from the natural source, although it had been obtained as an enzymatically hydrolyzed artifact from 22alpha-hydroxychiisanoside.


Assuntos
Triterpenos/isolamento & purificação , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Folhas de Planta/química , Triterpenos/química
18.
J Biomater Sci Polym Ed ; 10(5): 543-56, 1999.
Artigo em Inglês | MEDLINE | ID: mdl-10357265

RESUMO

Drug-impregnated polyelectrolyte complex (PEC) sponge composed of chitosan and sodium alginate was prepared for wound dressing application. The morphological structure of this wound dressing was observed to be composed of a dense skin outer layer and a porous cross-section layer by scanning electron microscopy (SEM). Equilibrium water content and release of silver sulfadiazine (AgSD) could be controlled by the number of repeated in situ PEC reactions between chitosan and sodium alginate. The release of AgSD from AgSD-impregnated PEC wound dressing in PBS buffer (PH = 7.4) was dependent on the number of repeated in situ complex formations for the wound dressing. The antibacterial capacity of AgSD-impregnated wound dressing was examined in agar plate against Pseudomonas aeruginosa and Staphylococcus aureus. From the behavior of antimicrobial release and the suppression of bacterial proliferation, it is thought that the PEC wound dressing containing antimicrobial agents could protect the wound surfaces from bacterial invasion and effectively suppress bacterial proliferation. In the cytotoxicity test, cellular damage was reduced by the controlled released of AgSD from the sponge matrix of AgSD-medicated wound dressing. In vivo tests showed that granulation tissue formation and wound contraction for the AgSD plus dihydroepiandrosterone (DHEA) impregnated PEC wound dressing were faster than any other groups.


Assuntos
Alginatos/química , Bandagens , Quitina/análogos & derivados , Animais , Anti-Infecciosos Locais/farmacologia , Linhagem Celular , Quitina/química , Quitosana , Desidroepiandrosterona/administração & dosagem , Desidroepiandrosterona/farmacologia , Ácido Glucurônico , Ácidos Hexurônicos , Camundongos , Camundongos Endogâmicos BALB C , Microscopia Eletrônica de Varredura , Sulfadiazina de Prata/administração & dosagem , Sulfadiazina de Prata/farmacologia , Fatores de Tempo , Ferimentos e Lesões/patologia , Ferimentos e Lesões/terapia
19.
Talanta ; 47(3): 561-7, 1998 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18967358

RESUMO

A novel and robust amperometric enzyme electrode for the determination of glucose was constructed by immobilizing glucose oxidase (GOD) and Os(bpy)(2)Cl-poly(4-vinyl)pyridine (Os-PVP) complex multilayers on thiol self-assembled monolayers surface. The apparent Michaelis-Menton constant K(m)' increased with increasing the number of Os-PVP/GOD multilayers. The concentration range of linear response and detection limit were 0.1-10 and 0.05 mM, the interference of ascorbic acid and uric acid were eliminated by the presence of SAMs and the enzyme electrodes were stable over 3 weeks. The preparation technique may be useful for controlling the performance of multilayer enzyme electrodes by changing the enzyme content.

20.
Eur J Biochem ; 225(3): 1073-9, 1994 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-7957197

RESUMO

D-Erythroascorbic acid was detected from the cell extracts of a dimorphic fungus, Candida albicans. Its concentration in yeast cells grown at 25 degrees C was estimated to be about 0.45 mumol/ml cell water. D-Arabinono-1,4-lactone oxidase, which catalyses the final step in the biosynthesis of D-erythroascorbic acid, was purified 639-fold from the mitochondrial fraction of C. albicans to apparent homogeneity, with an overall yield of 21.2%, by a purification procedure consisting of Triton X-100 solubilisation, ammonium sulphate precipitation, anion-exchange, hydrophobic-interaction, gel-filtration and dye-ligand chromatographies. Gel-filtration chromatography and polyacrylamide-gradient gel electrophoresis in the presence of deoxycholate gave apparent molecular masses of 110 kDa and 84.4 kDa, respectively. SDS/PAGE showed only one protein band corresponding to a molecular mass of 66.7 kDa. Considering the binding of detergents, the enzyme is suggested to be a single polypeptide. The enzyme showed a typical fluorescence excitation spectrum of a flavin-containing enzyme. The flavin was not released by treatment with SDS, CCl3CO2H or boiling, indicating that it may be covalently bound to the enzyme protein. The enzyme was optimally active at 40 degrees C and at pH 6.1. The enzyme was stable in the range pH 7.5-10. An apparent Km value for D-arabinono-1,4-lactone was 44.1 mM. L-Galactono-1,4-lactone, L-gulono-1,4-lactone and L-xylono-1,4-lactone could also serve as substrates. Competitive inhibition was demonstrated with D-glucono-1,5-lactone, L-arabinono-1,4-lactone, D-galactono-1,4-lactone and D-gulono-1,4-lactone. p-Chloromercuribenzoate, N-ethylmaleimide, iodoacetic acid, iodoacetamide and divalent metal ions such as Cd2+, Hg2+, Mn2+ and Zn2+ exhibited inhibitory effects on the enzyme.


Assuntos
Candida albicans/enzimologia , Desidrogenase do Álcool de Açúcar/metabolismo , Ácido Ascórbico/biossíntese , Ligação Competitiva , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Cinética , Mitocôndrias/enzimologia , Peso Molecular , Especificidade por Substrato , Desidrogenase do Álcool de Açúcar/antagonistas & inibidores , Desidrogenase do Álcool de Açúcar/isolamento & purificação , Temperatura
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