جستجوی مقالات مرتبط با کلیدواژه "b" در نشریات گروه "زیست شناسی"

Plant pathogens are a considerable risk to global food security due to the drastic reduction in yield and quality of crops. The deployment of RNA interference (RNAi) machinery for crop protection against plant pathogens agents is showing promising results. It is well set up that small RNA molecules, such as small interfering RNAs (siRNAs) and microRNAs (miRNAs), are included in regulating gene expression, and the process of RNA silencing at both transcriptional and post-transcriptional stages. Using host-induced gene silencing (HIGS), plants are genetically modified to produce small RNAs that infiltrate pathogen cells and deactivate specific genes. Alternatively, spray-induced gene silencing (SIGS) involves directly applying small RNAs onto plants, where they penetrate the pathogens and suppress target genes. This study delves into the roles of small RNAs and examines their potential application in combating a many plant pathogens through either HIGS or SIGS strategies providing an evaluation of their respective benefits and limitations.

Celiac disease in humans is caused by intolerance to the protein part of some grains called gluten. Therefore, food industry researchers have been carried out much researches in the field of gluten-free bread (GFB) production. Among the available solutions to improve gluten-free products's quality and sensory characteristics, sourdough biotechnology can play a prominent role. Sourdough is a mixture of flour and water, which is fermented by an ecosystem of lactic acid bacteria (LAB) and yeasts; and provides conditions for improving the quality and nutritional characteristics of bakery products. Metabolites produced by lactic acid bacteria can play the role of gluten in these products. It is also a cost-effective process with high potential in the field of producing GF products. The effects of sourdough in these products depend on factors such as the characteristics of gluten-free flour, the type of starter culture in fermentation, nutrients in the fermentation medium, fermentation temperature, fermentation time, etc. In this study, we will examine the effects of using sourdough technology in gluten-free breads and the influencing factors of this technology.

Blue-green algae or cyanobacteria are a group of algae that are able to grow rapidly in warm and nutrient-rich waters. The exponential growth of cyanobacteria in water bodies is affected by various factors, including an excess of nutrients, high temperatures, and excessive sunlight. Numerous studies have shown that with the increase in the growth of cyanobacteria in aquatic systems, there is also a possibility of an increase in toxins produced by them, which can have adverse effects on the health of aquatic animals and especially humans. Given the importance of the health of employees and local people in marine environments as well as workers in aquaculture centers, the present study aimed to introduce the most important and common toxins resulting from the growth of cyanobacteria and also to investigate the risks arising from them in order to determine the potential of these toxins in bioterrorism. For this purpose, 12 types of cyanobacterial toxins including including microcystin, nodularin, anatoxin-a, homoanatoxin, oscillatoxin A, cylindrospermopsin, nakienones A-C, aphantoxin, scytophycin/lyngbyatoxin, aplysiatoxin, and debromoaplysiatoxin were investigated. The results showed that among the aforementioned toxins, microcystin has received the most attention in scientific research compared to others, which can be attributed to the global prevalence of this toxin and its effects on human health. The effects of microcystin have often been manifested in the form of gastrointestinal diseases, liver and nerve damage, and cancer. Considering the adverse effects of these toxins, it is essential to employ various techniques to control and reduce the risks arising from the growth of cyanobacteria, as well as to adopt appropriate management decisions and strategies regarding the health of marine workers and people working in aquaculture centers who are exposed to the growth of cyanobacteria and their toxins.

Small mammals, especially rodents, play an important functional role in the ecological processes of the landscape and food chain in the ecosystem. Water vole has a wide distribution and is considered as a pest in parts of its distribution range. The Valley of Shara is a suitable habitat for branch birds, especially of the Arvicola amphibious. This study was conducted from 2018 in the Shara river, Intermediate of between the Duab bridge and the Goshirvan bridge in 2.5km distance from the river, Using of Habitat Biodiversity Modeler (HBM) method, With Modele of Maxent in the Terrset and Arc Gis13.1 softwares , and with variables 8 of such as: slope, elevation, proximity to the river, distance from the road, NDVI, water depth, land use, distance from the village. Results show, The Valley of Shara is the southeastern part of the habitat of the Arvicola amphibious in Iran. The validity of Maxent model is equal to (0.994), which indicates excellent performance. The most important variables affecting the desirability of the water vole habitat is the distance from river. And the variables of slope and distance from road are in the next ranks. The water vole is considered as a key species for Shara valley. that the destruction of the habitat of this species is aggravated by disasters and natural hazards in the valley. Therefore, that providing and protecting the habitat needs of this species will restore and protect the river.

Calcareous nannoplankton, a group of marine microrganisms, play a significant role in producing chalky limestones. They are predominantly associated with microscopic algae known as Haptophytes and can be found in both modern seawater and sediment, as well as in ancient ocean sediments. Selecting the appropriate sample preparation method is crucial for nannoplankton studies. This research explores various standard methods for sediment preparation for a light microscope (LM), such as smear slide, pipette strew slide, gravity settling, and centrifuging, along with methods specific to samples retrieved from seawater. Additionally, a technique for preparing samples for scanning electron microscopy (SEM) to analyze nannofacies is discussed. Furthermore, an innovative sample preparing technique for simultaneous study in LM and SEM is proposed. In addition, methods for determining the absolute abundance, Shannon diversity index, species richness, evenness, nutrient index, and species preservation, which are used in ecological analyses, have been discussed. Consequently, this study serves as a comprehensive guide to standard preparation techniques and studying methods for calcareous nannoplankton, facilitating biological, biostratigraphical, and paleoecological studies.

Increasing the fiber digestibility in the rumen and the total digestive tract of ruminants is very important to improve the feed conversion ratio. One of the methods used for feed processing is electron beam irradiation. Increased fiber digestibility occurred in irradiated feeds, the cause of which is unknown, therefore it is necessary to evaluate the structural condition of fibrous materials pre- and post-processing and also during incubation in the rumen with an electron microscope. The present study was aimed to evaluate the effect of electron beam irradiation on the microscopic structure of wheat straw fibers, the relative abundance of fibrolytic bacteria and the fiber digestibility in the total digestive tract of sheep.

Wheat straw sample was subjected to electron beam irradiation with electron beam power of 10 mega electron volts and electron beam current of 6 mA at doses of 250 and 500 kGy. The straw sample was transferred to bags and then inserted in the rumen for 12 hours, and the structure of the cell wall pre- and post-irradiation, as well as pre- and post-incubation in the rumen, was imaged and analyzed with a scanning electron microscope. The relative abundance of fibrolytic bacteria was evaluated by polymerase chain reaction and horizontal electrophoresis.

The relative abundance of Ruminococcus flavofaciens and Fibrobacter succinogenes in the rumen content showed a significant increase (P0.05) on the relative abundance of Ruminococcus albus. Electron beam irradiation increased (P<0.05) the dry matter digestibility of wheat straw. Dry matter digestibility increased (P<0.05) as irradiation dose increased, and the dose of 500 kg had the greatest effect on dry matter digestibility of wheat straw. Scanning electron microscope showed a huge increase in the destruction of the cell wall structures in 500 kGy irradiated wheat straw, which resulted in an increase of the permeability of fibrolytic bacteria to the internal parts of the cell wall structure. Increasing the permeability of fibrolytic bacteria ultimately led to increased access to the substrate and an increase in the relative abundance of bacteria and higher digestibility of fibers.

Electron beam radiation at dose of 250 kGy can change the structure of the cell wall and improve the digestibility of fibrous materials. Increasing the dose to 500 kGy causes more disruption of the cell wall structure, increasing the relative abundance of fibrolytic bacteria and increasing the digestibility of fibrous materials.

High ambient temperature causes oxidative stress in animals. Selenium is a trace mineral that has an effect on the health and performance of the body in stressful conditions There are limited studies on the effect of different doses of selenium in the conditions of long-term heat stress on immune system response and the expression of genes related to inflammation. The present study was conducted to determine the effects of different doses of selenium from selenium-methionine supplement on immune system response and the expression of interferon gamma, interleukin-2 and 6 genes in rats during the hot season.25 female rats were randomly divided into five groups and five replicates. Five rats were placed in standard temperature during the experiment period and the rest of the rats were placed in heat stress. Rats in the negative control group (without heat stress) and positive control (heat stress) fed with standard pellet without additive and the other three groups fed with standard pellet plus 0.15, 0.30 and 0.45 mg selenium/kg as selenium-methionine supplement for 30 days. Adding selenium supplement to the diet increased the expression of interferon gamma gene in rats under heat stress. The relative expression of the interleukin-2 gene was lower in the groups receiving selenium supplements than in the positive control group. Also, adding selenium supplement to the diet decreased the expression of interleukin-6 gene compared to the positive control treatment. The results indicated an increase in the concentration of immunoglobulin G with the addition of selenium to the diet.

Rhododendron yakusimanum (Rhododendron yakusimanum L.) is one of the ornamental plants in the world that is propagated by the traditional method of cutting leafy stems. Unfortunately, this method is not completely successful and cutting losses are high. Also, in this method, it is possible to spread infected plants. The surface contamination of the samples was removed using 70% alcohol and 2% sodium hypochlorite for 20 seconds and 15 minutes, respectively. For the purpose of callogenesis, the sterilized pieces were cultured in the medium Anderson (1978-1980) containing different concentrations of growth regulators 2,4-D and 2ip, and the largest callus volume was at the concentration of 2ip (5) mg/lit and 2,4-D (0.5 mg/lit) in lighting. For the purpose of organogenesis, the resulting callus were transferred to environments designed with IAA and 2ip hormones in different concentrations, and the best environment for aerial organogenesis was observed at the concentration of 2ip (5 mg/lit and 0.5mg/lit) IAA. became The rooting of the elongated branches was investigated in different environments, and the rooting took place only in the environment outside the glass in the perlite medium.