RESUMEN
The effectiveness of a ductile fracture model in accurately predicting fracture initiation has been demonstrated. In this study, we concentrate on applying the ductile fracture model to pre-cracked structures constructed from SUS304L stainless steel with experimental and numerical analyses. The Swift hardening law was employed to extend the plastic behavior beyond the onset of necking. Additionally, the Hosford-Coulomb model, integrated with a damaged framework, was utilized to predict ductile fracture behavior, particularly under non-proportional loading conditions. Tension tests were conducted on various specimens designed to illustrate various fracture modes resulting from geometric effects. Numerical analyses were conducted to explore the loading histories, utilizing an optimization process to calibrate fracture model parameters. The proposed fracture model is validated against pre-cracked structures detailed in a reference paper. The results convincingly demonstrate that the fracture model effectively predicts both fracture initiation and propagation in pre-cracked structures.
RESUMEN
Diospyros kaki Thunb. (Ebenaceae) is widely distributed in North-East Asian countries. Almost all parts of this plant have been traditionally used as medicine. Human promyelocytic leukemia cells differentiate into monocytes or granulocytes when treated with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] or all-trans retinoic acid (ATRA). Combination of low doses of ATRA or 1,25-dihydroxyvitamin D3 that do not induce toxicity with another drug is a useful strategy for acute promyelocytic leukemia therapy. Our main aim was to investigate the effect of an acetone extract of D. kaki leaves (KV-1) on HL-60 cell differentiation in combination of ATRA or 1,25-dihydroxyvitamin D3. Treatment of HL-60 cells with zero to 100 microg/ml of KV-1 for 72 h induced a small increase in cell differentiation. Surprisingly, a synergistic induction of differentiation was observed when the HL-60 cells were treated with ATRA or 1,25-(OH)2D3 and the extract. The inhibitors of protein kinase C (PKC) (alpha and betaI) and extracellular signal-regulated kinase (ERK), but not of phosphoinositide 3-kinase (PI3-K) and c-Jun N-terminal kinase (JNK) inhibited the HL-60 differentiation induced by the extract in combination of ATRA or 1,25-(OH)2D3, suggesting that PKC and ERK were involved in the cell differentiation enhancement by the extract. The results indicate that the acetone extract of D. kaki leaves has the ability to enhance HL-60 cell differentiation and suggest that it may be useful in acute promyelocytic leukemia therapy.
Asunto(s)
Diferenciación Celular/efectos de los fármacos , Diospyros/metabolismo , Regulación Neoplásica de la Expresión Génica , Leucemia Promielocítica Aguda/tratamiento farmacológico , Extractos Vegetales/farmacología , Acetona/química , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Calcitriol/metabolismo , Supervivencia Celular , Granulocitos/citología , Células HL-60 , Humanos , Modelos Biológicos , Monocitos/citología , Tretinoina/metabolismoRESUMEN
An extracellular phospholipase D (PLD(St)) was purified from Streptomyces tendae by two successive chromatographic steps on Sepharose CL-6B and DEAE-Sepharose CL-6B. Molecular weight of the PLD(St) was estimated to be approximately 43 kDa by sodium dodecyl sulfatepolyacrylamide gel electrophoresis. Maximal activity was at pH 8 and 60 degrees C, and the enzyme was stable at or below 60 degrees C and between pH 8 and 10, when assayed after 1.5 and 24 h, respectively. The enzyme activity had an absolute requirement of Ca(2+), and the maximum activity was at 2 mM CaCl(2). The Km and Vmax values for phosphatidyl choline were 0.95 mM and 810 micromol min(-1) mg(-1), respectively. More importantly, PLD(St) could not catalyze transphosphatidylation of glycerol, L-serine, myo-inositol and ethanolamine, which have been extensively used to evaluate the activity. The result strongly suggests that PLD( St ) does not have the transphosphatidylation activity, thereby making it the first Streptomyces PLD possessing only hydrolytic activity. PLD(St) may therefore be a novel type of PLD enzyme.
Asunto(s)
Cloruro de Calcio/química , Fosfolipasa D/química , Fosfolipasa D/aislamiento & purificación , Fosfolipasa D/metabolismo , Streptomyces/enzimología , Electroforesis en Gel de Poliacrilamida , Estabilidad de Enzimas , Concentración de Iones de Hidrógeno , Hidrólisis , Cinética , Peso Molecular , Fosfatidilcolinas/química , TemperaturaRESUMEN
A simple and sensitive HPLC method was developed for the quantitative analysis of nargenicin in the culture broth of Nocardia sp. CS682, isolated from Korean soil. Nargenicin, an unusual macrolide antibiotic with potent anti-MRSA (methicilin-resistant Staphylococcus aureus) activity, was extracted from the culture broth with ethylacetate and then analyzed by HPLC using solvent A (0.5 M dipotassium phosphate pH 2.5-water: acetonitrile = 80:20, v/v) and solvent B (100% acetonitrile), at 215 nm. The calibration curve of nargenicin was linear with correlation coefficient greater than 0.99. This method provides precise analysis of the nargenicin amount present in the cell free culture medium, and may be applicable to analyze other bacterial cultures containing similar compounds.