IRANIAN JOURNAL OF SCIENCE AND TECHNOLOGY TRANSACTION A- SCIENCE
Year:2009 | Volume:33 | Issue:A1|Papers Count:12

With the aim of identifying the Rotifera fauna of Kepektas Dam Lake, samples were collected monthly between January-December 2005. In total 11 rotifer species were identified. As a species-wise percentage, Kellicttia longispina had the highest level with 57%. When the annual abundance of species was taken into consideration Polyarthra vulgaris, Colurella uncinata, Asplanchna priodonta and Keratella cochlearis were determined as dominant species. These species were observed in most months of the year and were well observed in their annual abundance. Notholca squamula was classified as cold steno-thermal species, as this species was recorded only in February and March. Increases in Rotifer individual numbers were observed in spring and summer months.

Brassinosteroids are phytohormones possessing a wide spectrum of antistress activity. To see whether this hormone is able to ameliorate the effects of water stress, the effects of 24-epibrassinolise on plant growth, accumulation of osmolytes (proline, sugars and ions), lipid peroxidation and electrolyte leakage were investigated in Colza (Brassica napus L. cv. Fusia) plants which were under water stress. The seeds were sown in plastic pots containing sand, clay and peat (in a proportion of 1:1:1). Solution of 24-epibrassinolid at 10-7 M concentration containing 0.01% Tween-20 (polyoxyethylene sorbitan) was sprayed on leaves at intervals of 1, 2 and 3 weeks after sowing. Control plants were sprayed with 0.01% Tween-20, and water treatment was applied 26 days after germination, withholding water for 3 or 4 days. One month after sowing, plants were harvested. Lipid peroxidation and electrolyte leakage significantly increased under water stress, but when plants were pretreated with 24-epibrassinolid and put under water stress these parameters decreased, revealing that less oxidative damage occurred in this group. Proline and reduced sugars content was increased when 24-epibrassinolide were applied. FW and DW were significantly decreased under water stress. Water stress also increased the uptake of K and Ca, but the uptake of Na significantly decreased. 24- epibrassinolide considerably increased ions uptake by plants. Taken together, these results showed that 24- epibrassinolide alleviated the effects of water stress and increased the tolerance of plants to stress by increasing osmolytes accumulation and therefore could be used to improve crops in harsh conditions.

Showing the occurrence of glass/rubber transition in bovine serum albumin (a globular protein) at low moisture levels and the occurrence of Maillard crosslinking in gelatin in previous works, the importance of the state of glass or rubber of BSA on the rate and extent of polymerisation, protein solubility, colour and SDS PAGE patterns in the presence and absence of ascorbic acid, diketogulonic acid and dehydroascorbic acid was investigated. BSA on storage with Ascorbic acid and its degradation products at low moisture contents (8.3% and 19.1%) at a relatively low temperature (40oC) can undergo chemical changes resulting in marked increase in molecular weight, solubility decrease and formation of browning colour. The glassy state data established the occurrence of chemical changes (Maillard crosslinking and disulfide crosslinking) in the BSA system on storage below its glass transition temperature.

Geographical, morphological and taxonomic status of Pistacia khinjuk Stocks ex Stocks in Iran was revised. A total of 181 accessions (herbarium materials or specifically collected for this study) were examined geographically and morphologically. The chromosome number of 2n=24, revealed among 15 accessions studied, was taken as evidence to lump the variability observed in P. khinjuk as one taxonomic species. However the states of the leaflet number, i.e. 1 (rarely 3) and 3-7 were taken as the key character in order to subdivide the P. khinjuk material in Iran into two varieties: khinjuk (the autonym variety) with 3-7 and populifolia Boiss. with 1 (rarely 3) leaflet in number. The relative illustrations are prepared and presented. Some nomenclatural corrections are also included.

The goal of this study was to determine whether ghrelin affects the mean plasma concentrations of metabolic parameters such as thyroxine (T4), triiodothyronine (T3), growth hormone (GH), insulin, glucagon, glucose, fatty acid and urea in the goats fed different energy content in diets. Sixteen goats were randomly divided into 4 groups. Animals in groups 1 and 2 were fed 100 % and animals in groups 3 and 4 were fed a 50 % energy content in their diet for 20 days. After 20 days, animals in groups 1 and 3 received a daily infusion of 1 ug ghrelin, while groups 2 and 4 received a daily infusion of 2 ug galanin into their third ventricle for 5 days. Blood samples were collected daily from the jugular veins before infusions on day 4 until 4 days after the last infusions of ghrelin. Samples were assayed for plasma T3, T4, GH, insulin and glucagon concentrations by double-antibody RIA. Glucose, fatty acid, and urea concentrations were also measured. Lower dietary energy intake and infusions of 1 and 2 ug ghrelin significantly (P<0.01) decreased the mean plasma concentrations of T3, T4, insulin, and glucose, and significantly (P<0.01) increased the mean plasma concentrations of GH, glucagon, fatty acid, and urea of the animals in groups 3 and 4. Different dosages of the ghrelin infusions did not change the plasma concentrations of the metabolic parameters in the animals fed a normal energy content in diets. The results of this experiment indicated that ghrelin may negatively affect the T3, T4, insulin, and glucose and increase GH, glucagon, fatty acid, and urea in the goats with a negative energy balance, but not in those with the positive energy balance.

Maharlu saline Lake is located in the SW of Iran. To assess the environmental pollution of the lake, the total concentrations of As, Cr, Co, Cu, Cd, Pb, Zn, Ni, Fe, and Mn were determined in the surface sediments and water of the lake. As and Cr were not detected in the water samples, however, the mean concentrations of other dissolved metals in Maharlu Lake water were 0.28 mg/l for Cu, 0.28 mg/l for Cd, 5.17 mg/l for Pb, 0.37 mg/l for Zn, 2.36 mg/l for Ni, 2.88 mg/l for Co, 10.4 mg/l for Fe, and 1.5 mg/l for Mn. Different water and sediment quality assessment approaches indicated that in this lake, metals can be divided into three different groups: (a) Co, Pb, and Cd. These metals have the highest enrichment factors (the mean values are 35.8, 76.9, and >36.6, respectively), geoaccumulation indexes (the mean values are >3), and contamination factors (11.1, 29, and 8, respectively) compared with other studied elements; thus, the Maharlu Lake is highly polluted with these metals, and they are mainly from anthropogenic sources; (b) Cu, Zn, and Ni. Their mean enrichment factor values are 6.6, 3.4, and 6, respectively; their mean geoacumulation indexes are <1, and their mean contamination factor values are 2, 1.1, and 2, respectively. The enrichment factor of these metals is higher than 10 only north of the lake. The Maharlu Lake is moderately polluted with these metals, and they are from both natural and anthropogenic sources; (c) Cr, As, Fe, and Mn. These elements have the lowest mean enrichment factor (1, 3.5, 2, and 4.2, respectively), geoaccumulation indexes (£0), and contamination factor (0.32, 0.91, 0.63, and 1.5, respectively) values; thus the Maharlu Lake is not polluted with these elements, and they are mainly from natural sources. Results indicated that the Maharlu Lake sediments have a high contamination degree (56.66). Comparisons with consensus-sediment quality guidelines reveal that Ni and Pb pose the greatest environmental threat to aquatic organisms. In order to protect the lake from further contamination, the treatment and recycling of wastewaters discharged into the lake is needed.

The study of tectonic evolution of the Tethyan and SE Asian regions indicates that these two regions have each passed through southwardly progressing sequences of similar tectonic events. Both regions have experienced a southward island-arc subduction and back-arc spreading leading to continental detachment from Gondwanaland, with an earlier southward island arc subduction of Palaeotethys (Tethyan northern ocean), and continental detachment (Early Devonian) which produced the Neo-Tethys Ocean and the land masses of the Tethyan region, compared with a later southward island arc subduction of Tethys II, and continental detachment (Permo-Triassic) which produced Tethys III, and the land masses of the SE Asian region. The northward subduction of Neo-Tethys (Tethyan southern ocean) and formation of the Alpine Orogeny (Late Paleocene-Pliocene) in the Tethyan region was accompanied by the opening of the Red Sea to the south of the Arabian Gondwanaland. Similarly, the northward subduction of Tethys III (SE Asian southern ocean) (Late Oligocene-Present), and arc-continent collision in the SE Asian region was accompanied by the opening of the Southern Ocean to the south of the Australian Gondwanaland. In both regions, the younger oceans are formed sequentially southward. The later occurrence of the southward progressing sequence of tectonic events in the SE Asian region compared with the similar sequence of tectonic events in the Tethyan region indicates an eastward global migration of tectonic events.

Some species of the genus Dunaliella are the major primary producers in Maharlu salt lake, which is polluted with different heavy metals including Hg2+. Short-term (48 h) and prolonged exposure (28 d) of D. tertiolecta to 5, 10, 20, and 50 mM HgCl2 decreased Chlorophyll "a" content, but caused enhanced carotenoid production and increased ascorbate peroxidase (APX) activity, both of which function as antioxidants, buffering oxidative stress by scavenging reactive oxygen species (ROS). Increase in total carotenoids in terms of pictogram per cell (pg cell-1) was higher in prolonged exposure, whereas APX activity was greater in shortterm exposure to HgCl2. In both experiments, despite the increase in antioxidant capacity, algal growth in terms of cell number per ml of culture decreased relative to the control. It seems that generation of ROS in the presence of HgCl2 exceeds the total antioxidant capacity of the cells, which is evident from the increase in cell malondialdehyde (MDA) content and, as a result, reduced cell number. The SDS-PAGE profile of the extracted proteins showed enhanced synthesis of two protein bands of about 29 and 38 kD.

Ferula assa-foetida L. (Apiaceae) is one of the most important endangered medicinal plants, which is rare in nature due to poor seed germination. In an effort to improve and promote the cultivation of this plant, the effects of two temperatures (23oC and 4oC), exogenous GA3 and cytokinins (kinetin and BAP) were investigated on dormancy breaking and germination of F. assa-foetida L. seeds. Among the treatments, cold stratification (4oC) significantly stimulated seed breaking dormancy. The highest mean germination index (2.6 germinated seed per week) was obtained by treatment of seeds with 5 mg/L kinetin at 4oC. But, under no hormone treatment, the highest final percentage germination (73%) was obtained when the seeds were soaked in distilled water and then incubated at 4oC. Also, under this condition the germination index was achieved to 2.5 germinated seeds per week. Treatment of the seeds by GA3 not only could not significantly enhance the germination index and percentage at 23oC, but also the existence of GA3 caused a marked decrease in those values at 4oC. This result demonstrated that GA3 was not effective to overcome dormancy for this species.

Time-dependent Schrodinger equation for a 1-D model of hydrogen molecular ion H2+ in intense laser field linearly polarized along the molecular axis is solved. Ionization rates are calculated for different initial states. The evolution of electronic wavefunction at fixed inter-nuclear separations are simulated and analyzed. The results obtained for the ground state of this 1-D model of H2+ show appreciable qualitative agreement with the results obtained previously in the 2-D and 3-D studies. The Ponderomotive energy effect on the beginning of ionization in different initial states is observed. The above threshold ionization has a large contribution in the ionization of electrons, except for the ground state and at equilibrium inter-nuclear separation. The ionization rates show that at some inter-nuclear separations larger than 4.0 au, resonance enhancement ionization by some higher excited states occur. At inter-nuclear separations shorter than 4.0 au, the ground state does not show any resonance with higher excited states.

The Forumad ophiolite in the northwestern part of the Sabzevar region has embraced the large depleted harzburgites and dunitic bodies associated with podiform chromitites. In some deposits, chromite grains have segregated as nodules. The stretched shape along with high Cr2O3 and TiO2 contents are the characteristics of the nodules. Compared to the other Tethyan nodular chromites, the Forumad nodular chromites show high Cr content. The nodules formation seems to be the result of turbulent picritic magma flows accompanied by the water rich fluids.

A detailed study of Ostracoda changes against the stable isotopes of carbon and oxygen across the Cenomanian-Turonian boundary mass extinction has been fully documented in one section, the South of England. This section comprises the uppermost Cenomanian to lowermost Turonian strata. The comparison between the results obtained in this research and two rival models for the Cenomanian-Turonian boundary mass extinction, famine and high productivity, have been carried out. Low oxygen level has been proposed as the main cause of the Cenomanian-Turonian boundary mass extinction.