فهرست مطالب

  • Volume:32 Issue:2, 2007
  • A2
  • تاریخ انتشار: 1386/07/15
  • تعداد عناوین: 8
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  • V. Nazeri Joneghani Pages 89-97
    Pollen morphology of some species of the genus Malus (Rosaceae) was investigated taxonomically. All species are characteristic by tricolpate pollens. Exine sculpturing is variable but is mostly striate. However, species may differ in degree of density of ridges and their orientation. The exine patterns in M. trilobata and M. florentina are very similar and were characterized by short and very branched ridges. These show clear differences from other species, which have pollen grains with long and unbranched or slightly branched ridges.
    Keywords: Pollen morphology, plant systematics, Malus, Rosaceae
  • V. M. Ngole, G. E. Ekosse Pages 99-108
    Soil productivity is generally associated with poor nutrient status and the physical condition of the soil, but the effect of soil mineralogy on soil productivity has received little attention. In this qualitative study, interactions between mineralogy and physico-chemistry and their role on the productivity of two luvisols, an arenosol and a vertisol are investigated. Minerals identified in the soils included smectites in the vertisol, kaolinite, quartz, hydromica, albite and biotite in the luvisols and arenosol. The presence of smectite in the vertisol has resulted in it having a higher organic matter content, higher cation exchange capacity, higher water holding capacity, and low bulk density than both luvisols and the arenosol. Both luvisols and the arenosol were dominated by quartz, feldspars and kaolinite, which are chemically inert compared to smectite and have fewer effects on soil cation exchange capacity, water holding capacity, and bulk density. The effect of soil mineralogy and physico-chemistry on the productivity of these soils is reflected in the yield of spinach (Spinacia oleracea variety Fordhook giant) grown on the different soils where spinach yield on the vertisol was the highest followed by that of the luvisols and then the arenosol.
    Keywords: Cation exchange capacity, kaolinite, organic matter turnover, smectite, spinach yield, water holding capacity
  • H. R. Momeni, M. Soleimani Mehranjani, M. H. Abnosiand M. Kanje Pages 109-116
    Organotypic spinal cord slices from neonatal mammals could be a powerful model for evaluation of cell survival but also cell death mechanisms. The aim of this study was to establish an in vitro model for investigating cell survival and mechanism involved in cell death in neonatal spinal cord slices. The spinal cord was sliced and incubated into culture medium. The MTT assay was carried out to assess the viability of the slices and fluorescent staining was used to study morphological features of apoptosis, where as nucleosomal DNA fragmentation was detected using agarose gel electrophoresis. The results of the present study demonstrated that the slices could be maintained in culture up to 14 days. Both neurons and glial cells died by apoptosis and application of a general caspase inhibitor neither affected slice survival nor nucleosomal DNA fragmentation after 24 h in culture. In addition, the inhibitor failed to block apoptosis in neurons and glial cells in the cultured slices.Our results suggest that in the cultured slices, apoptosis is the main reason for neuron and glial cell death, which occurs by a caspase-independent mechanism.
    Keywords: Apoptosis, MTT assay, neonatal mouse, spinal cord slices
  • E. Heidarian, B. Haghighi Pages 117-127
    Phosphatidate phosphohydrolase (PAP2b,fraction b) was purified from the plasma membrane of rat liver cells. The Km for the surface concentration of phosphatidic acid was 0.43 mol%. The subunit of the enzyme had an M.W. of 33.8 kDa using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The native enzyme shows a molecular weight of 182 kDa in a gel filtration column packed with Sephacryl S300 in the presence of Triton X-100. The pH optima obtained for PAP2b were 5.5 and 7 in imidazole and Tris- HCl buffers, respectively. The membrane homogenate enzyme (PAP2) consumed the lamellar (La) phase of phosphatidate and was activated (approximately 3-fold) by Lubrol PX, CTAB and Tween 80 and inhibited by Zn2+ and Mn2+. The inhibition was concentration dependent. These cations affected PAP2b activity through the phase transition of phosphatidate from lamellar (La) to inverted hexagonal (HII) form. Guanidine hydrochloride and urea increased PAP2 activity (2-fold) up to 20mM concentrations by stabilizing the La phase. Optimum activity of purified PAP2b was obtained at 3% trehalose and 7% sucrose. The data suggested that the stability of the La form of phosphatidate by detergent micelles may take place through surface dilution processes.
    Keywords: Phosphatidate phosphohydrolase, phosphatidic acid
  • F. Rezanejad, A. Chehregani Pages 129-134
    Air pollutants are reported to increase the specific IgE response to allergens. To study allergen proteins and determine the effect of air pollutants on the allergenic potential of pollen extracts, the extracts were injected intraperitoneally and subcutaneously in guinea pigs. The results were analyzed by skin prick test (SPT), ELISA and SDS-PAGE followed by immunoblotting. The pollen extract of Spartium junceum showed positive SPT and increase of specific IgE antibodies than the control (buffer). Two IgE-binding bands were seen in the immunoblots of the pollen extract of this species. In Lagerstroemia indica, the pollen extracts showed no significant difference in wheel diameter compared to those in the control group, but IgE somewhat increased in the pollen extracts. The pollen extracts collected from the polluted region increased the response of SPT and specific IgE in both species. These extracts did not affect IgE-binding bands (proteins). Therefore, these findings indicate that air pollutants show adjuvant activity for the response of SPT and the production of IgE antibodies in guinea pigs by themselves.
    Keywords: Air pollution, allergenecity, Lagerstroemia indica, pollen, Spartium junceum, specific IgE binding proteins
  • B. Shareghi, M. Arabi Pages 135-140
    The thermal denaturation of α-Amylase from Bacillus amyloliquefaciens has been investigated in the presence and absence of sodium dodecyl sulphate (SDS) over the temperature range (293-373) K in 20 mM sodium phosphate buffer, pH 6.9, using temperature scanning spectroscopy. The presence of SDS caused the destabilization of α -Amylase resulting in a decrease in the temperature of unfolding with an increase in SDS concentration. The thermodynamic parameters for unfolding of α-Amylase were determined in terms of the two-state model, using the temperature dependence of the spectroscopic behaviour of the enzyme at 280 nm. The result from specific activity measurements in the presence of SDS is in conformity with the results from thermal studies.
    Keywords: Stability, denaturation, thermodynamic, SDS, α, Amylase
  • T. Radjabian, Sh. Rezazadehand, H. Fallah Huseini Pages 141-146
    Silymarin is a mixture of flavonolignans from the seeds of Silybum marianum (L.) Gaertner, containing silybinin, isosilybinin, silydianin, silychristin and the dihydroflavonol of taxifolin. Flavonolignan components are largely responsible for the medical benefits attributed to silymarin. The aim of this research was to study the variations in composition and content of flavonolignans of silymarin samples from seeds of some native milk thistle ecotypes of Iran, along with a foreign cultivar. Silymarin was extracted by a two-step (defatting and extraction) process using n-hexane, ethyl acetate and methanol in a Soxhlet extraction from the seeds. The content and composition of the main components in different silymarin samples were analyzed by the HPLC method against external standard of silybinin. The HPLC method allowed a good separation between flavonoid components, especially diastereomers of silybinin A and B. The qualitative and quantitative data obtained by HPLC clearly showed that silymarin samples were the same with respect to their flavonolignan composition and they were mainly different based on the content of their components. Silymarin samples from native ecotypes had lower quantities of silybinin as compared to that of silymarin from cultivated ones, but they had higher amounts of other compounds such as silychristin, silydianin and isosilybinin.
    Keywords: Silybum marianum, silymarin, flavonolignans, high performance liquid chromatography
  • A. Ahmadi Moghadam, B. Nowruzi Pages 147-151
    Cyanobacteria were collected and identified in five paddy fields with different soil textures of Golestan province in Iran. It was determined that Nostoc ellipsosporum and Nostoc muscorum were dominant in all sites among 20 species. To assess the ability of atmospheric nitrogen fixation by the species, their pure cultures were provided by growing on BG-11 solid culture medium. Subsequently, each species was grown on Allen liquid culture medium for 21 days and the growth curves were obtained by measuring thallus chlorophyll amount at 1.5 day intervals. The amounts of N fixed by each species were measured by the Indophenol method and by measuring ethylene amounts produced via the acetylene reduction process using gas chromatography. The results showed significantly higher rates in N fixation, cellular doubling time and growth rate in N.ellipsosporum with larger heterocysts than N.muscorum. Therefore, N.ellipsosporum with a higher ability of N and ethylene production is suggested as the superior biological fertilizer.
    Keywords: Heterocystous cyanobacteria, N fixation, acetylene reduction