Tsitologiia. ;36(8) [The cultivation features, growth characteristics and oncogenicity of "serum-free" populations of transformed fibroblasts]. [Article in. Agricultural farming systems are a set of strategies to manage the available resource to achieve economic and sustainable agricultural prod. However, few studies have addressed cultivation in the oasis region. Cultivation features and water requirements were examined using the.
Cultivation Features -
On the contrary, turbulent flow is convective mixing dominant flow characterized by the random motion of fluid particles. For a pipe flow, when Reynolds number is less than , it becomes laminar; this value physically means that the viscous effect is comparable to the inertial force. Therefore, convective mixing is much suppressed due to the inherent laminar characteristics mentioned above, and diffusive mixing becomes a dominant phenomenon.
Naturally, most microfluidic systems have been designed in consideration of this fundamental fluid dynamic feature for effective operation [ 41 , 42 ]. Laminar flow is one of the predominant factors in microfluidic systems, and thus the molecular diffusion is the important process. The diffusion is a time-dependent phenomenon. Molecules in the high concentration region diffuse into the low concentration region until an equilibration of concentration is achieved [ 43 ].
The microfluidic system can provide an ability for the control of the concentration gradient of biomolecules, cellular microenvironment by using diffusion phenomenon [ 44 ]. In laminar flow, mixing of different solutions is achieved by diffusion. Since this relationship shows that the diffusion length is controlled by the velocity, various concentration profiles can be made in microfluidic systems by controlling the flow velocity in microchannel where the stem cells grow.
T-channel is one of popular microchannel geometries to have two different solutions from each inlet which come into the main channel to create molecules transportation among the two steams only via diffusion by utilizing laminar flow characteristics Figure 4 a [ 46 , 47 ].
The biological and chemical processes are significantly considered about gradient of solutions properties [ 48 , 49 ]. Many studies have reported that the cells are influenced by concentration gradient of diffusible signalling molecules [ 50 , 51 ].
To confirm the importance of concentration gradient in biology, many methodological approaches have been developed fabricating specific channel shapes [ 52 — 55 ]. This pump provided low and steady flow using osmotic phenomenon between poly ethylene glycol solution and DI water. The efficacy of the device was demonstrated by testing hMSCs; the device enabled hMSCs to change properties such as cells viability, attachment, and morphology according to FBS concentration gradient the attachment of hMSCs is performed in strong concentration of FBS.
The advantage of this system includes portability; the device with pumping unit can be easily kept in conventional incubator. This system was also applied to neuronal progenitor cell to study the influence of cytokine concentration Shh and FGF8 versus BMP4 on neural development differentiated into neurons.
The osmosis pump provided extremely slow flow rate that is enough to create the cytokines gradient concentration and to minimize shear effects to the cells Figure 4 b [ 56 , 57 ]. To mimic in vivo -like 3D microenvironment for human neural stem cell hNSCs , a microfluidic channel array was introduced; this system consists of central channel for cell culture and two side channels for flowing culture media.
Thus, molecular transport was generated between central cell culture channel and two-side culture media supply channels by diffusion. The hNSCs differentiation was confirmed in normoxia and hypoxia conditions Figure 5 a [ 58 ]. Concentration gradient in microchannel is generated by diffusion mechanism since convective mixing is suppressed in low Reynolds number laminar flow. Therefore, it is a favorable feature of microfluidic gradient generation systems for cell biology application because concentration gradient is biological norm in human body.
However, sometimes generation of stratified concentration profiles is needed to test cell characteristics. In this regard, a good example system was introduced to study differentiation of EB cells in stratified biological molecular concentration. A single EB was located at the middle of microchannel. Relationship between shear stress and cells has been studied in microfluidic systems. Various stem cells including ESCs and MSCs were influenced by the shear stress regarding adhesion and differentiation [ 60 — 62 ].
The shear stress is one of mechanical forces applicable to cell mechanics studies and depends on the velocity gradient at the surface [ 63 ]. Although most flow generated in microsystems is laminar flow [ 66 ], the effect of the shear stress on cells has been overlooked in most previously reported microsystems. Thus thorough consideration on the influence of shear stress to cells should be done at the design step of the systems and also at data analysis step [ 9 ].
To investigate how shear stress is influential to morphology of ESC colony, microfluidic device was utilized to control wide range of flow rates. The device has multiple 4 and 16 cell culture chambers with computerized flow resistance controller; ESC colony in each chamber experiences different shear stress levels. Another relationship between shear stress and the hESC morphology and differentiation have been researched utilizing microfluidic bioreactor which generates both shear stress and concentration gradient.
The hESCs were cultured in each chamber 3. The results indicate that vascular differentiation increased under higher shear stress level obtained in microfluidic channel Figure 6 b [ 63 ].
The microreactors were designed with consideration of mass transport and shear stress. Microsystem techniques can be categorized into three different types of techniques. First, microwell is the technique which allows cells to create in vivo -like 3D structure. Finally, microfluidic channel provides dynamic and precise control of mechanical and biochemical cues such as shear stress and biochemical concentration. Table 1 summarizes the related operational principles, target cell types, characteristic of system, performance, and regenerative therapy of these methods.
In this review, various microsystems for stem cell researches were introduced in terms of physical principles structure, diffusion, shear stress, etc. For about 20 years, the microsystem techniques have been rapidly progressed, and a lot of useful microsystems were developed for stem cell research; however, only a few of the existing microsystems have been utilized by biologists or clinicians in practices. The mainly reason for this happening might be the gap of view point and background knowledge between engineering and biology fields.
The newly developed microsystems are usually and mostly reported in the engineering societies [ 22 ], and invisible but strong barrier prevents communications to the people in the biology field. Through this review, we want to provide useful information regarding the microtechniques and applied principles to help understanding for biologists.
We also want engineers to be aware of the gap and the need of conditions for expanding microsystems to practical biology labs; the new microsystems should be able to merge into the existing biolaboratory processes, easy to control, and available to be merged with the other laboratory equipment such as microscope and incubator. Also the challenges for both the engineers and biologists include that many other combinations of physical, chemical, and biological principles should be tested and tried to find better way to reveal the stem cell characteristics and control their functions in the future.
The authors declare that there is no conflict of interests regarding the publication of this paper. Indexed in Science Citation Index Expanded. Subscribe to Table of Contents Alerts.
Ideal plant whether the Ideotype is required for irrigated cultivation or rainfed cultivation. Ideal plant types or model plants have been discussed in several crops like wheat, rice, maize, barley, cotton, and bean. The important features of Ideotype for some crops are briefly described below:.
The term Ideotype was coined by Donald in working on wheat. He proposed Ideotype of wheat with following main features. A short strong stem. It imparts lodging resistance and reduces the losses due to lodging. Such leaves provide better arrangement for proper light distribution resulting in high photosynthesis or CO2 fixation.
Leaves are the important sites of photosynthesis, respiration, and transpiration. Few and small reduce water loss due to transpiration. It will produce more grains per ear. A presence of owns. Awns contribute towards photosynthesis. Thus, Donald included only morphological traits in the Ideotype.
The conclusion was that food items from organic farms had way more nutrients than those sourced from commercial or conventional farms. The study went further to substantiate that five servings of these fruits and vegetables from organic farms offered sufficient allowance of vitamin C. However, the same quantity of fruits and vegetable did not offer the same sufficient allowance.
Statistics show that genetically modified foods GMOs are contaminating natural foods sources at real scary pace, manifesting grave effects beyond our comprehension. What makes them a great threat is they are not even labeled. So, sticking to organic foods sourced from veritable sources is the only way to mitigate these grave effects of GMOs. Those that have tasted organically farmed foods would attest to the fact that they have a natural and better taste. The natural and superior taste stems from the well balanced and nourished soil.
Organic farmers always prioritize quality over quantity. Purchasing foods items from organic farmers is a surefire investment in a cost-effective future. Conventional farming methods have enjoyed great subsidies and tax cuts from most governments over the past years. This has led to the proliferation of commercially produced foods that have increased dangerous diseases like cancer. It all starts with you buying food items from known organic sources. These days, it normal to hear news about extinct species and this should be a major concern.
In the last century alone, it is approximated that 75 percent of agricultural diversity of crops has been wiped out. Slanting towards one form of farming is a recipe for disaster in the future. A classic example is a potato.
There were different varieties available in the marketplace. Today, only one species of potato dominate. This is a dangerous situation because if pests knock out the remaining potato specie available today, we will not have potatoes anymore. This is why we need organic farming methods that produce disease and pest resistant crops to guarantee a sustainable future.
Commercial dairy and meat are highly susceptible to contamination by dangerous substances. According to a report by Environmental Protection Agency EPA , a vast majority of pesticides are consumed by the population stem from poultry, meat, eggs, fish and dairy product since animals and birds that produce these products sit on top of the food chain.
Stem Cells International
Main features of Shifting Cultivation • The following characteristics could be describe/explained • Clearings made in the rainforest by cutting and firing trees. 1School of Mechanical Engineering, College of Engineering, Chung-Ang University, Seoul , Republic of Korea 2Department of. The morphological and physiological features of crop Ideotype is required for irrigated cultivation or rainfed cultivation. Ideal plant whether the Ideotype is.