Reproduction Methods

Reproduction Methods tài liệu, giáo án, bài giảng , luận văn, luận án, đồ án, bài tập lớn về tất cả các lĩnh vực kinh tế...

Safe carrying methodsCarrying heavy objects can put a strain on your back, arms, shoulders and knees because your body is struggling to support the size and weight of the object. Follow these simple pointers when you have to carry a heavy load. Click the to view the each point.If you cannot view the interaction above, or if it takes a long time to load, have a look at this alternative.Always carry the load close to your body. Never carry a heavy load away from your body as this puts a lot of strain on your shoulders and back.Avoid carrying a heavy load for long distances. This can cause your muscles to get tired and become more vulnerable to strain and injury. Use a trolley, or a similar type of equipment, to move heavy loads over long distances.Back Moving heavy loads safelyYou may need to move loads that are too heavy for you to lift or carry. In these cases, you may need to use some of these methods:• Work with someone to carry the load.• Use a trolley.• Use a forklift or trolley jack to lift loads that are too heavy to lift manually (over 20 kilograms).Back Back to Hazards, Health and Safety homepageHow do hazardous substances enter the body? 3 ways hazardous substances can be harmfulA hazardous substance can be any substance, natural or artificial, solid, liquid or gas, that can potentially injure or harm people in and around their workplace or home.Hazardous substances can enter the body in three ways:• Inhalation (breathing in)• Ingestion (swallowing)• AbsorptionInhalation (breathing into lungs)Gases, vapours, mists, fumes, and dusts are all forms of chemicals and biological agents that can be inhaled. Many of these chemicals give off poisonous fumes and can harm you if inhaled. You should always make sure that you use a respirator when handling chemicals that give off toxic fumes, dusts or gases.Ingestion (swallowing)Not to many people are going to deliberately pick up a chemical and swallow it but have you ever sprayed your lawn or garden with a pesticide and then forgotten to wash your hands before eating, drinking or smoking? Or what about siphoning petrol by mouth? These are common ways in which chemicals can be ingested.Absorption (contact through eyes, mouth, skin) Chemicals can also get into your body by being absorbed though your skin, eyes, and mouth. Back to Hazards, Health and Safety homepage Back to Hazards, Health and Safety homepageThree safety stepsThere are three simple steps you can follow at work to reduce the risk of accidents and injuries at work. Have a look at these steps:• Step 1 - Identify the hazard .• Step 2 - Determine the risk .• Step 3 - Respond .Step 1 - Identify the hazardHazards can happen anywhere and anytime. You need to watch out for hazards and be able to identify them. Click the PLAY button to see what happens to Larrikin Larry. In the workplace, this is as simple as being on the look out for things that may cause injury or harm to a person, for example, wet floors, lifting heavy loads and operating equipment and machinery.BackStep 2 - Determine the riskHave a look at Larrikin Larry trying to cross the street. Click PLAY to see what happens if Larry fails to determine the risk before taking an action. [...]... get lost. Top Back to Hazards, Health and Safety homepage Back to Hazards, Health and Safety homepage Safe feeding Safety points to note while feeding stock Feeding stock is one of the most important jobs you'll do on the farm. Because you feed stock every day it's easy to forget about basic health and safety issues. We'd like you to stay safe while feeding stock, so have a look at... responsibility for safety. 3. Consultation by means of committees or safety representatives discussing and resolving workplace health and safety issues. 4. Penalties in the way of fines for not following workplace health and safety legislation. These principles are controlled by laws that differ from state to state. In Western Reproduction Methods Reproduction Methods Bởi: OpenStaxCollege Animals produce offspring through asexual and/or sexual reproduction Both methods have advantages and disadvantages Asexual reproduction produces offspring that are genetically identical to the parent because the offspring are all clones of the original parent A single individual can produce offspring asexually and large numbers of offspring can be produced quickly In a stable or predictable environment, asexual reproduction is an effective means of reproduction because all the offspring will be adapted to that environment In an unstable or unpredictable environment asexuallyreproducing species may be at a disadvantage because all the offspring are genetically identical and may not have the genetic variation to survive in new or different conditions On the other hand, the rapid rates of asexual reproduction may allow for a speedy response to environmental changes if individuals have mutations An additional advantage of asexual reproduction is that colonization of new habitats may be easier when an individual does not need to find a mate to reproduce During sexual reproduction the genetic material of two individuals is combined to produce genetically diverse offspring that differ from their parents The genetic diversity of sexually produced offspring is thought to give species a better chance of surviving in an unpredictable or changing environment Species that reproduce sexually must maintain two different types of individuals, males and females, which can limit the ability to colonize new habitats as both sexes must be present Asexual Reproduction Asexual reproduction occurs in prokaryotic microorganisms (bacteria) and in some eukaryotic single-celled and multi-celled organisms There are a number of ways that animals reproduce asexually Fission Fission, also called binary fission, occurs in prokaryotic microorganisms and in some invertebrate, multi-celled organisms After a period of growth, an organism splits into two separate organisms Some unicellular eukaryotic organisms undergo binary fission by mitosis In other organisms, part of the individual separates and forms a second individual This process occurs, for example, in many asteroid echinoderms through 1/7 Reproduction Methods splitting of the central disk Some sea anemones and some coral polyps ([link]) also reproduce through fission Coral polyps reproduce asexually by fission (credit: G P Schmahl, NOAA FGBNMS Manager) Budding Budding is a form of asexual reproduction that results from the outgrowth of a part of a cell or body region leading to a separation from the original organism into two individuals Budding occurs commonly in some invertebrate animals such as corals and hydras In hydras, a bud forms that develops into an adult and breaks away from the main body, as illustrated in [link], whereas in coral budding, the bud does not detach and multiplies as part of a new colony Hydra reproduce asexually through budding Link to Learning 2/7 Reproduction Methods Watch a video of a hydra budding Fragmentation Fragmentation is the breaking of the body into two parts with subsequent regeneration If the animal is capable of fragmentation, and the part is big enough, a separate individual will regrow For example, in many sea stars, asexual reproduction is accomplished by fragmentation [link] illustrates a sea star for which an arm of the individual is broken off and regenerates a new sea star Fisheries workers have been known to try to kill the sea stars eating their clam or oyster beds by cutting them in half and throwing them back into the ocean Unfortunately for the workers, the two parts can each regenerate a new half, resulting in twice as many sea stars to prey upon the oysters and clams Fragmentation also occurs in annelid worms, turbellarians, and poriferans Sea stars can reproduce through fragmentation The large arm, a fragment from another sea star, is developing into a new individual Note that in fragmentation, there is generally a noticeable difference in the size of the individuals, whereas in fission, two individuals of approximate size are formed 3/7 Reproduction Methods Parthenogenesis Parthenogenesis is a form of asexual reproduction where an egg develops into a complete individual without being fertilized The resulting offspring can be either haploid or diploid, depending on the process and the species Parthenogenesis occurs in invertebrates such as water flees, rotifers, aphids, stick insects, some ants, wasps, and bees Bees use parthenogenesis to produce haploid males (drones) and diploid females (workers) If an egg is fertilized, a queen is produced The queen bee controls the reproduction of the hive bees to regulate the type of bee produced Some vertebrate animals—such as certain reptiles, amphibians, and fish—also reproduce through parthenogenesis Although more common in plants, parthenogenesis has been observed in animal species that were segregated by sex in ...Master of Computer Science 1 - MOB Mobile Internet and Surrounding1/12 Baey, Fladenmuller – Subject 5MOB Subject 5 –Access methodsStatic and dynamic access techniques1. Static access techniques1.1 Space-division multiple-access (SDMA)When one seeks to cover a broad territory by a whole of cells of the same dimension, oneconsiders that the traffic is uniformly distributed, that the propagation law is the same and that thepower of all the equipment is constant. The same number of carrier will have thus to be allocated toeach basic station.One will often use a hexagonal paving to cut out the zone has to cover, the hexagon being thepolygon nearest to the circle which allows paving the plan. One calls cluster, a set of adjacent cellswhich uses the unit of carriers one and only one time. This cluster is repeated on all surface has tocover.Arithmetic and geometrical considerations allow showing that a cluster having a given numberof carrier is optimal if it is regular. For a hexagonal paving, the size K of cluster verifies the relation:K = i2+ ij + j2(1)with i and j entries positive natural or null.The paving of the zone has to cover is realized of iterative manner in leaving of a cluster givenof K cells. From one cells of this cluster, one moves vertically i cells to one of its sides, then j cellsin a direction forming an angle of +60 degrees with the initial direction. The arrival point definesthen the "homologous" cell of adjacent cluster. By repeating this process for the set of cells of thecluster chosen at the origin while keeping these same directions, one defines an adjacent cluster.One repeats then this process for the five other possible directions (other dimensions of the cell) tofind the set of adjacent clusters. In proceeding secondly little by little on the cluster, one then buildsa paving of the cover zone.Each cell of a cluster is seen allocated a subset of the carrier which is own for it. The homologouscells of all the cluster use the same carrier. The minimal distance between two cells (homologous)using the same carrier is called reuse distance. The size K of the cluster also constitutes the reusefactor of the carrier.1. What is the principle of the reuse of frequencies in the domain of the cellular networks?In a cellular network, the space is divided into cells, each served by a base station (i.e a cell isa portion of the territory covered by a base station).It was affecting to each cell (i.e at each base station), a number of carriers of the totalbandwidth available based on estimated traffic in this cell.It is possible to reuse one even at the same carrier in different cells if they are sufficientlyremote. The reuse of frequencies thus allows an operator has to cover an unlimitedgeographic area by using a frequency band width limited.2. Discuss the advantages and disadvantages to use of cells of small size, in comparing withcells of big size in the cellular networks.Advantages:- greater reuse of frequencies: optimization of bandwidth;- increase battery life because the power of emission decreases; Master of Computer Science 1 - MOB Mobile Internet and Surrounding2/12 Baey, Fladenmuller – Subject 5- if a cell is malfunctioning or cluttered, possibility to switch to a neighboring cell.Disadvantages:- Roaming Management heavier if mobility;- Increasing the level of interference between cells.3. List several manners to increase the capacity of a cellular network:- Adding new carriers: usually when a system is implemented in a region, all carriers are notused. Growth can then be managed using these carriers.- Borrowing frequency: in the simplest case, cells are over-used carrier will temporarilyborrow the adjacent sub-cells used. Methods in Molecular BiologyTMHUMANA PRESSGlycoproteinMethodsand ProtocolsEdited byAnthony P. CorfieldVOLUME 125The MucinsMethods in Molecular BiologyTMHUMANA PRESSEdited byAnthony P. CorfieldThe MucinsGlycoproteinMethodsand Protocols Isolation of Large Gel-Forming Mucins 33From:Methods in Molecular Biology, Vol. 125: Glycoprotein Methods and Protocols: The MucinsEdited by: A. Corfield © Humana Press Inc., Totowa, NJ1Isolation of Large Gel-Forming MucinsJulia R. Davies and Ingemar Carlstedt1. IntroductionThe large gel-forming mucins, which form the major macromolecular componentsof mucous secretions, are members of the mucin “superfamily.” Nine mucin genes(MUC1–MUC4, MUC5AC, MUC5B, and MUC6–MUC8) have been identified (forreviews see refs. 1 and 2), with each gene showing expression in several tissues. Onlythe MUC1, MUC2, MUC4, MUC5, and MUC7 mucins have been sequenced com-pletely (3–11) although large stretches of MUC5AC (12–15) as well as the C-terminalsequences of MUC3 (16) and MUC6 (17) are now known.A characteristic feature of mucins is the presence of one or more domains rich inserine and/or threonine residues that, owing to a high degree of oligosaccharide substi-tution, are resistant to proteolysis. Mucins comprise cell-associated, usually mono-meric species, as well as those that are secreted; the latter can be subdivided into large,gel-forming glycoproteins and smaller, monomeric ones. The gel-forming mucins(Mr= 10–30 million Dalton) are oligomers formed by subunits (monomers) joined viadisulfide bonds (for a review see ref. 18), and treatment with reducing agents willrelease the subunits and cause unfolding of regions stabilized by intramolecular disul-fide bonds. Thus, after reduction, we term the monomers reduced subunits. Reducedsubunits are more sensitive to protease digestion than the intact mucin molecules.The isolation procedures that we use for the large oligomeric mucins depend ontheir source. In secretions such as respiratory tract sputum, tracheal lavage fluid, andsaliva, the material is centrifuged to separate the gel from the sol phase, allowing theidentification of the gel-forming mucins. Repeated extraction of the gel phase solubi-lizes the “soluble” gel-forming species, leaving the “insoluble” mucin complex in theextraction residue. Mucin subunits may be isolated from the “insoluble” glycoproteincomplex following reduction of disulfide bonds. When mucins are isolated from tissuesamples, it may be an advantage to “physically” separate histologically defined areasof the tissue such as the surface and the submucosa of an epithelium. For example,material from the surface epithelium may be enriched by gently scraping the surfacemucosa, thereby allowing gland material to be obtained from the remaining tissue. 4 Davies and CarlstedtTo isolate mucins, the bonds that hold the mucous gel together and those that anchorcell-associated glycoproteins to the plasma membrane must be broken. In our labora-tory, high concentrations of guanidinium chloride are used for this purpose, and high-shear extraction procedures are avoided to minimize the risk of mechanical degradation.Protease inhibitors are used to protect the protein core and a thiol blocking agent isadded to prevent thiol-disulfide bond exchange. However, breaking intermolecularbonds with highly denaturing solvents will most likely cause unfolding of orderedregions within the mucins, and properties dependent on an intact protein core structuremay be lost. Following extraction, mucins are subjected to isopycnic density gradientcentrifugation in the presence of guanidinium chloride. This method allows the groupseparation of large amounts of mucins from nucleic acids and proteins/lipids underdissociative Histological Methods for Detection of Mucin 2929From:Methods in Molecular Biology, Vol. 125: Glycoprotein Methods and Protocols: The MucinsEdited by: A. Corfield © Humana Press Inc., Totowa, NJ3Histologically Based Methods for Detection of MucinMichael D. Walsh and Jeremy R. Jass1. IntroductionMorphologically based studies on mucins allow structural characterization to belinked to specific sites of synthesis and secretion. The histochemical approach to thestudy of mucin is therefore highly informative. There is a correspondingly large bodyof literature documenting the tissue distribution of mucins as demonstrated by mucinhistochemistry, lectin histochemistry, and immunohistochemistry (and various com-binations of these methods). Two principal issues need to be considered in order tomaximize the potential value of morphologically based methodologies: (1) nature andlimitations of the individual techniques, and (2) interpretation and reporting of mucinstaining.1.1. Nature and Limitations of Mucin-Staining MethodsMucin histochemistry, lectin, and immunohistochemistry bring their own advan-tages and disadvantages to the identification and characterization of epithelial mucin.Remember that mucin can be well visualized with hematoxylin; Ehrlich’s hematoxy-lin stains acid mucins (e.g., of salivary glands and intestinal goblet cells) deep blue.The appearance is sufficiently characteristic to allow a mucin-secreting adenocarci-noma to be diagnosed without the use of specific mucin stains.Methods of tissue fixation influence mucin-staining. Formalin fixation is adequatefor most techniques using light microscopy, but fails to preserve the surface mucousgel layer found throughout the gastrointestinal (GI) tract. Alcohol-based fixatives suchas Carnoy’s are required to demonstrate this structure (1). The duration of fixation andnature of fixative used play significant roles in determining optimal protocols for thedemonstration of glycoproteins including mucins. The exact mechanisms of fixation,particularly aldehyde fixation, remain unclear, although it appears that formalin, e.g.,blocks protein amido groups and forms methylene bridges between amino acids, whichdisturb the natural tertiary structure of proteins, rendering epitopes less amenable toantibody binding to varying degrees (2). Since the initial description by Shi et al. 30 Walsh and Jass(3) of a technique for microwave treatment of sections to restore antigenicity, a num-ber of “antigen retrieval” or “antigen unmasking” techniques relying on heat to “unfix”tissues have been rapidly incorporated into the routine histochemical repertoire. Pre-viously efforts to reverse fixation alterations in tissue hinged on the use of proteolyticdigestion of sections with enzymes such as trypsin and pepsin. In all cases, the successor failure of these techniques must be determined empirically. Subheading 3.4. and3.5. discuss a by-no-means exhaustive selection of these techniques.1.1.1. Mucin HistochemistryThe first specific stain to be used for the demonstration of mucin was mucicarmine(4), but this stain has now been largely supplanted by methods based on more strictlyhistochemical approaches that utilize a specific chemical reaction (organic, enzymic,or immunological) in which staining intensity correlates directly with the amount ofsubstrate. Periodic acid-Schiff (PAS) is the quintessential mucin histochemical tech-nique (5), with much of current practice bound up with the PAS reaction. Periodic acidbreaks the C–C bond in 1:2 glycols of monosaccharides, converting the glycol groupsinto dialdehydes that are not oxidized further but localized with Schiff’s reagent. Theintensity of the magenta color reaction is directly proportional to the number of reac-tive glycol structures.Several modifications of the PAS stain have been described. These relate to thevariable structure of sialic acid and specifically to the presence of O-acetyl groups atC4and/or the Detection and Quantitation of Mucins 4545From: Methods in Molecular Biology, Vol. 125: Glycoprotein Methods and Protocols: The MucinsEdited by: A. Corfield © Humana Press Inc., Totowa, NJ4Detection and Quantitation of MucinsUsing Chemical, Lectin, and Antibody MethodsMichael A. McGuckin and David J. Thornton1. IntroductionDetection and quantitation of mucins can be important in both the research andclinical settings. Applications may range from detection of potentially novel mucinspresent during purification from mucus, to quantitation of specific mucin core pro-teins or carbohydrate moieties present in clinical samples. This chapter discusses pro-cedures and limitations of several different strategies available to detect and quantifythese glycoproteins from biological samples, with a view to providing guidelines fromwhich to select the best applicable techniques. Example protocols are then provided togive a starting point for development of a technique. Refer to Chapter 3 for detectionof mucins in histological preparations (1); note, however, that many of the principlesfor selection of detection tools discussed herein are applicable to histological detection.Because of the extreme size and extent of glycosylation of mucins, coupled withthe fact that many secreted mucins are capable of forming gels, these glycoproteinscan be quite difficult to work with biochemically. It is therefore extremely importantbefore attempting to detect mucins that the researcher has a good understanding of thebehavior of these molecules in solution, particularly with regard to their potential lackof solubility in standard physiological buffers. Because of these properties, standardpreparative methods for secreted mucins involve extraction in chaotropic agents (usu-ally 6 M guanidinium chloride) and purification in CsCl density gradients in either thepresence or absence of 4 M guanidinium chloride. Therefore, methods often have to beapplicable to assay in the presence of high concentrations of these agents. Failure toadhere to these considerations may result in embarrassing false-negative results. Read-ers are advised to refer to Chapters 1 and 2 (2,3) of this volume for the preparation ofsecreted and membrane-associated mucins, respectively, and to Chapter 7 (4) for adiscussion of methods for mucin separation. 46 McGuckin and ThorntonSelection of a technique to detect mucins should be influenced by several factors,including knowledge of the core protein sequence of and/or carbohydrate structurespresent on the mucin(s) to be measured, nature of the sample (buffer, presence ofpotential interfering substances), specificity of the data required, availability of spe-cific detection tools, degree of quantitation required, and the number of samples to beprocessed. Owing to the high O-linked carbohydrate content of mucins (as much as90% of the total weight), many assays are targeted toward this portion of the molecule.Although these tend to be useful general methods for detecting mucins, they are notgood tools for distinguishing between specific mucin (MUC) gene products; this iseven true of carbohydrate-specific monoclonal antibodies (MAbs), which can showcrossreactivity between mucins. However, mucin-specific probes are available; theseare commonly antibodies raised against peptide sequences from within the differentmucin polypeptides. Although these are more specific detection tools, note that thedifferent MUC gene products can share regions of homology and therefore cross-reactivity (5). Many of the early MUC-specific probes were generated againstsequences underlying the highly glycosylated tandem repeat regions of the moleculesand, although effective against the protein precursors, were of little use for maturemucins. Nevertheless, chemical and/or enzymatic deglycosylation techniques can beused to increase the effectiveness of these probes for mature mucins (6-8). Detectionof mucin core proteins ... individuals are produced through sexual reproduction 6/7 Reproduction Methods parthenogenesis budding fragmentation A Free Response Why is sexual reproduction useful if only half the animals... males Sexual Reproduction Sexual reproduction is the combination of (usually haploid) reproductive cells from two individuals to form a third (usually diploid) unique offspring Sexual reproduction. .. become female and lay eggs; some oyster species change sex multiple times 5/7 Reproduction Methods Section Summary Reproduction may be asexual when one individual produces genetically identical