Kinetics properties of guaiacol peroxidase activity in Crocus sativus L. corm during rooting

BACKGROUND: Guaiacol peroxidases (GP) are haem-containing enzymes participating in many physiological processes in plants. The expression pattern of these enzymes is organ-specific and developmentally regulated. METHODS: The presence of GP activity in extract samples, prepared from Crocus sativus L. corms that were either dormant or rooting for 3, 6 and 10 days, was investigated. RESULTS: Kinetic studies revealed a significant similarity among GP activities detectable in the corm at different stages of development: in all extract samples, the activity was maximal at pH 7.5 and after preincubation at 30-40 degrees C. When guaiacol was used as the varying substrate, Michaelis-Menten kinetics behavior was observed in all extract samples and resulted in similar KM values; catalytic efficiencies were also very similar. The corm GP activity was inhibited by cyanide, azide and ascorbate. The GP activities from different extract samples had the same sensitivities to azide, cyanide and ascorbate and the type of inhibition by azide and cyanide was competitive and uncompetitive, respectively, while ascorbate inhibited the GP activity non-competitively. Corm extract samples from different stages of rooting similarly responded to temperature treatment and a biphasic Arrhenius plot resulted for each extract sample studied. When dormant, 3-, 6- and 10-days-rooting corm extracts were submitted to non-denaturing polyacrylamide gel electrophoresis, the GP-specific activity staining revealed one band on the gel, with the same migrating distances. CONCLUSION: This finding in combination with kinetic studies demonstrated that at least one form of GP, with an apparent molecular weight of 68 kDa, was expressed during development of Crocus sativus L. corm.     

L-carnitine significantly decreased aging of rat adipose tissue-derived mesenchymal stem cells

Mesenchymal stem cells are undifferentiated cells that have the ability to divide continuously and tissue regeneration potential during the transplantation. Aging and loss of cell survival, is one of the main problems in cell therapy. Since the production of free radicals in the aging process is effective, the use of antioxidant compounds can help in scavenging free radicals and prevent the aging of cells. The aim of this study is evaluate the effects of L-carnitine (LC) on proliferation and aging of rat adipose tissue-derived mesenchymal stem cells (rADSC). rADSCs were isolated from inguinal region of 5 male Rattus rats. Oil red-O, alizarin red-S and toluidine blue staining were performed to evaluate the adipogenic, osteogenic and chondrogenic differentiation of rADSCs, respectively. Flow cytometric analysis was done for investigating the cell surface markers. The methyl thiazol tetrazolium (MTT) method was used to determine the cell proliferation of rADSCs following exposure to different concentrations of LC. rADSCs aging was evaluated by beta-galactosidase staining. The results showed significant proliferation of rADSCs 48 h after treatment with concentrations of 0.2 mM LC. In addition, in the presence of 0.2 mM LC, rADSCs appeared to be growing faster than control group and 0.2 mM LC supplementation could significantly decrease the population doubling time and aging of rADSCs. It seems that LC would be a good antioxidant to improve lifespan of rADSCs due to the decrease in aging.     

Effect of ionic detergents, nonionic detergents, and chaotropic agents on polyphenol oxidase activity from dormant saffron (Crocus sativus L.) corms

Polyphenol oxidase (PPO; EC 1.14.18.1) catalyzes the hydroxylation of monophenols to o-diphenols (cresolase activity) and the oxidation of o-diphenols to o-quinones (catecholase activity), leading to browning in plants and produce. Further interest in the enzyme has been triggered by the active role that it plays in plant defense systems. PPO can be found in latent forms and is activated in vitro by various agents including urea, detergents, and proteases. The activation of PPO from several sources by sodium dodecyl sulfate (SDS) has been extensively investigated, but reports on the effect of other detergents or on the differential effect of detergents on each of PPO's activities are scarce. In addition, investigations on the enzyme in other plant parts besides fruits and vegetables are also scarce. Here, the effect of various detergents and chaotropic agents on PPO from dormant saffron (Crocus sativus L.) corm extract was investigated. SDS and sarkosyl activated the cresolase activity, while only SDS activated the catecholase activity. All other detergents tested, in milli- or micromolar concentrations, inhibited the cresolase activity but barely affected the catecholase activity. In contrast, urea and guanidine-HCl drastically inhibited the catecholase activity but moderately inhibited the cresolase activity. The same effects were obtained on the partially purified enzyme. Results identified a PPO, present in dormant corms, which was activated only by anionic detergents and was inhibited by other reputed activating agents such as urea. Results also emphasized the differences in structure and accessibility of the active sites for cresolase and catecholase activities.     

The influence of corona discharge treatment on the properties of cotton and polyester-cotton knitted fabrics

In this study, the effect of corona discharge treatment on the physical and mechanical properties of bleached cotton and polyester-cotton fabrics were investigated. For this purpose, the samples were treated by corona discharge at two levels of voltage 5 and 10 kV, and at various duration times of plasma, ca. 1.4, 2.1 and 3.5 min. The corona discharge treatment was applied on the fabric samples before and after bleaching treatment. The results show that the corona influences on the surface morphology, breaking strength, air permeability, abrasion resistance, and pilling of cotton and polyester-cotton fabrics. Moreover, the levels of voltage and duration of plasma have a different effect on the properties of fabrics.     

Acute erythroid leukemia with multilineage dysplasia in a cat

Dysplastic features of erythroid and megakaryocytic lineages were observed in a cat with acute erythroid leukemia. We demonstrated that flow cytometry analysis of the expression of glycophorin A and CD71 by neoplastic cells can be helpful in the diagnosis of this type of feline leukemia.     

Electrospinning of silk nanofibers. I. An investigation of nanofiber morphology and process optimization using response surface methodology

Ultra fine fibers were electrospun from regenerated silk fibroin/formic acid solution. Effect of some process parameters on the morphology, diameter and variation in fiber diameter of electrospun fibers were experimentally investigated. Scanning electron microscope was used for the measurement of fiber diameter. Fibers with diameter ranging from 80 to 210 nm were collected depending on the solution concentration and the applied voltages. Response surface methodology (RSM) was used to obtain a quantitative relationship between selected electrospinning parameters and the average fiber diameters and its distribution. It was shown that concentration of silk fibroin solution had a significant effect on the fiber diameter and the standard deviation of the fiber diameter. Applied voltage had no significant effect on the fiber diameter and its standard deviation.     

Photo-oxidation of polypropylene fibers exposed to short wavelength UV radiations

Polypropylene fibers were exposed to short wavelength radiations (λ=253.7 nm). The samples were analyzed by microscopy, staining, FTIR spectroscopy, tensile testing, and X-ray diffraction. The short-wavelength UV irradiation produces much more reactive radicals such as peroxy and alkoxy groups, which speeds up the photo-oxidation process. The products were identified by FTIR spectroscopy to be alcohols, peroxides, ketones, aldehydes, carboxylic acids, and anhydrides. Comparison of the amount of functional groups leads to an estimation of the mechanism of photo-oxidation. The short-range order increases during the photo-oxidation and the long-range order or crystalline fraction remains intact. Transverse cracks appeared on the surface of fibers after a long period of exposure to the radiation. A proposed mechanism for crack formation is the removal of the photo-oxidation products and the restructuring of the residuals. Similar to the thermal oxidation, mass loss and density increase are the main reasons for the crack formation in photo-oxidation.     

Investigation on the Biodegradability and Antibacterial Properties of Nanohybrid Suture Based on Silver Incorporated PGA-PLGA Nanofibers

Polyglycolic acid-poly lactic glycolic acid (PGA-PLGA) electrospun nanofibers containing silver nanoparticles have been produced and twisted into the nanofibrous yarn. The morphology of nanofibers and produced yarns, as well as the mechanical properties of the yarns, were investigated. Furthermore, in vitro antibacterial properties and in vitro degradation behavior of yarns containing various silver nanoparticles were studied. SEM images confirmed that the addition of the silver nanoparticles into the polymer solution increases the fiber diameters. The result of the mechanical test of the yarns alone and used in two different forms of the knots was measured and results showed that the strength of the yarns without the knot was significantly more than that of others. The biodegradability test showed that the mechanical properties and the weight of the yarns were quickly reduced after subjecting to in vitro condition. The result of the antibacterial test indicated that the nanofiber yarns containing %3 silver nanoparticles were the most appropriate sample with a considerably antibacterial activity against both gram-positive bacterium Staphylococcus aureus and gram-negative bacterium Escherichia Coli with inhibition zones of 8.1 and 9.5 mm, respectively; which demonstrated that silver nanoparticles retained their effectiveness after the electrospinning process. Therefore the nanofibrous yarns containing silver nanoparticles could be successfully produced by the electrospinning process with the proper antibacterial property as a candidate for the surgical sutures.     

Mechanical properties and in vitro degradation of PLGA suture manufactured via electrospinning

The current research discusses the efforts to achieve a Poly(lactide-co-glycolide)(PLGA) nanofiber yarn using two differently charged nozzles with potential application as surgery suture. First, electrospinning parameters such as solution concentration, applied voltage, feed rate were optimized to produce yarn with smooth nanofibers. In order to improve the properties of produced suture, heat setting setup was developed. Two heat setting techniques, including hot water and dry heat were applied, and the influence of the heat setting process on the mechanical properties of yarn was studied. The results showed that heat setting with boiling water was the best method. At first strength, E-modulus and extension of prepared suture were 36.6 MPa, 0.9 GPa and 68.8 % respectively. After improvement with heat setting, strength and E-modulus increased to 63.7 MPa, 2.7 GPa respectively and extension decreased to 29.7 %. Finally, in order to analyze knot performance, two types of surgical knot (square and surgeon) were used, and mechanical properties were investigated. The presence of knot lessens mechanical properties for each two type. Square knot showed better mechanical properties than surgeon’s knot. With square knot strength, E-modulus and extension were 62.1 MPa, 2.1 GPa, 28.6 %, respectively. In vitro study of nanofiber yarn degradation behavior showed that the mechanical properties were decreased. This could be due to greater surface area of nanofibers exposed to surrounding environment.