Primary cell defined

Senescence is defined as cellular ageing resulting in an irreversible cell cycle arrest. Primary cells divide about 50 times and then are arrested due to senescence. Senescence is associated with shortening of telomeres. 

In suspension, plant cells are significantly larger than most microbial cells and are typically of the order of 10-100 pm in size. They vary in shape from cylindrical to spherical. The plasma membrane is surrounded by a primary cell wall which defines the cell size and shape. The robustness of plant cells, relative to mammalian cells or to plant protoplasts [18], is usually attributed to the pre-... 

The primary walls of growing plant cells are composed of 90% carbohydrate and 10% protein (51). Carbohydrate in the primary wall is present predominantly as cellulose, hemicellulose, and pectin. The pectic polysaccharides, are defined as a group of cell wall polymers containing a-l,4-linked D-galactosyluronic acid residues (62,76). Pectic polysaccharides are a major component of the primary cell waU of dicots (22-35%), arc abundant in gymnosperms and non-graminaceous monocots, and are present in reduced amounts (-10%) in the primary walls of the graminaceae (27,62). 

Primary batteries, 3 434—469. See also Alkaline primary cells Batteries Carbon-zinc cells Lithium primary cells Secondary batteries defined, 3 409... 

In order to think about the nature and consequences of cell wall polymer phenolic cross-linking, we need a working model of the mode of assembly and the final structure of the primary cell wall. Unfortunately, there is no universally acceptable model that proposed by Albersheim and co-workers (3) is not now widely accepted because the postulated interpolysaccharide glycosidic bonds have not been demonstrated (4) and the warp-weft model of Lamport (5) rests on the assumptions that extensin (i) forms a defined-porosity network (not proven) (ii) is orientated anti-clinally to the cell surface [some evidence against (6)] and (iii) is a major component of all primary cell walls (not true). 

Use of an endothelial cell line should not be considered a substitute for primary endothelial cells such as HUVEC, as different endothelial cell lines may vary in the type and level of adhesion molecules expressed as well as their response to various stimuli such as cytokines. Endothelial cell lines provide a convenient, homogenous, and defined (if not necessarily relevant) cell mono-layer through which leukocytes must migrate in the chemotaxis assay. We find that use of an endothelial cell line to reduce the background migration of primary cells not only improves the signal-to-noise ratio of the assay but also the reproducibility of the assay as compared to HUVEC. 

To summarize pH measurement consists of a hierarchical system of three metrologically defined steps (1) the definition of pH by primary pH(PS) values assigned to primary buffer solutions (PS) in a Harned cell defined as a primary method of measurement, (2) the assignment of pH(SS) to secondary buffer solutions (SS) by tracing them back to pH(PS), and (3) measurement of pH(X) of unknown solutions (X) by comparison with... 

Primary cells can be defined as cells taken directly from an organism and adapted to survive and eventually grow in culture, at least for a limited period. In fact, with the exception of some cells derived from tumors, primary cells have limited lifespans in culture. Cells can be isolated from tissues for ex vivo culture in several ways. They can be released from soft tissues by enzymatic digestion with enzymes such as collagenase, trypsin, or pronase that break down extracellular matrices. Alternatively, in the explant culture method, pieces of tissue are placed in growth media and the cells that grow are available for culture. 

Another field of application for primary cells is their use in target identification and validation studies. To fully understand the importance of a gene as a potential target for a drug discovery campaign, it is crucial to use the appropriate cell type or, when available, a clinically relevant, well defined tissue sample. For reasons of convenience, most pathway analysis utilizes transformed cell lines. 

Stem cells are progenitor cells which are not yet specifically formed. They can multiply almost infinitely and form nearly all 210 tissue types in the human being. Depending on their derivation, they are defined as follows .) embryonal (= taken from the inner cell mass of the blastocysts), (2.) foetal (= isolated from 5-9 week-old abortive foetuses, and (5.) adult (= taken from the tissue of adults or children by means of biopsy or from the umbilical cord of newborns. Adult stem cells are limited in number and life span they do, however, have a broader development potential than so far assumed. They have also been found in the liver. The transformation of stem cells from the bone marrow into hepatocytes has been carried out successfully. Liver stem cells (7-15 gm) can develop both primary cell types of the liver, (7.) mature hepatocytes and (2.) biliary epithelial cells. These stem cells are deemed to be genuine liver stem cells, and not merely derived from the activation of immature oval cells in the liver. (54,59, 60, 81) (s. fig. 2.20)... 

Hemicelluloses have traditionally been defined by extraction procedures, i. e., hemicelluloses are those polysaccharides extracted by alkaline solutions from plant tissues after removal of low-molecular-weight substances with hot aqueous alcohol, removal of waxes and other lipid-soluble substances, delignification, and removal of pectin with an aqueous solution of a calcium ion chelator. The most abundant hemicelluloses in the primary cell walls of dicotyledons are xyloglucans. Xyloglucans have a backbone chain whose chemical stmcture is identical to that of cellulose. About 75% of the 8-D-glucopyranosyl units in that chain are substituted... 

There have been several investigations into the use of hormonally defined medium in order to maintain the differentiation of primary cells, as it is suspected that serum may be a factor in dedifferentiation. The application of defined medium also allows a more standardized approach to cell culture delivering greater reproducibility and transferability. For renal tubular epithelial cells defined medium supplements have been described as far back as 1982 [148], We have been, over the last number of years, successfully cultivating human renal proximal tubular cells (primaries and cell lines) in serum free hormonally defined medium containing EGF, hydrocortisone, insulin, transferrin, and sodium selenite using DMEM-Hams F12 as the base medium [36, 112, 114, 149], Both the HK-2 cell line and the RPTEC/TERT1 have been developed in serum-free conditions. 

The purpose of this chapter is to present overviews of a selection of the major endothelial and epithelial barriers to drug delivery for which there are either primary culture or cell line systems that recapitulate the characteristics of the in vivo barrier. Our objective is to define some general characteristics of cell culture models and highlight the more commonly applied primary cell cultures and cell lines in use today. Specifically, we focus on cell culture models for the intestinal epithelium, blood-brain barrier, pulmonary and nasal epithelium, ocular epithelium, placental barrier, and renal epithelium. Renal epithelium was included here primarily because some cell lines derived from this tissue [e.g., Madin-Darby canine kidney cells (MDCK)] are often used as surrogates for other barriers by pharmaceutical scientists. We have arbitrarily chosen to exclude the skin and liver from the scope of this overview. However, it should be noted that hepatocyte cell culture models, for example, are becoming more widely available and have been the subject of recent reviews.1,2... 

Let us assume a 3-D domain, adequately defined by the general system of curvilinear coordinates (u = iAu, v = jAv, w = kAw). The space is divided into two nonuniform dual meshes. The center of each primary cell is placed at node (i, j, k), while secondary ones are mutually centered at the vertices of the primary grid (i. —, j —, k — ). Following an equivalent process applicable to both lattices, the center of every cell face is obtained by shifting one of its... 

The use of primary cell cultures has certain advantages over perpetuated cell lines as the origin of the cell is defined and inherently represent a better level of differentiation. 

Ninety percent of cancer deaths are caused by metastatic rather than primary tumors. Define metastasis. Explain the rationale for the following new cancer treatments (a) batima-stat, an inhibitor of matrix metalloproteinases and of the plasminogen activator receptor, (b) antibodies that block the function of integrins, integral membrane proteins that mediate attachment of cells to the basal laminae and extracellular matrices of various tissues, and (c) bisphosphonate, which inhibits the function of bone-digesting osteoclasts. 

The compounds were first tested against two panels of human tumour cell lines. The primary cell panel consisted of cells from tumours representative of different tissue types and with different chemosensitivities to cisplatin . Differential cytotoxicity, as opposed to non-selective toxicity, was used as an indicator of potential antitumour activity of test compounds . The second panel was disease-oriented and consisted of cell lines established from human ovarian tumours. This panel included two pairs of cisplatin-sensitive and cisplatin-resistant hnes, with defined mechanisms of resistance (CHl/CHl-R, A2780/A2780-R), and also two inherently resistant cell hnes (HX62 and SK-OV-3). This panel has been used to identify agents with the abihty to circumvent cisplatin resistance . ... 

Potential limitations include the tendency for primary cells in culture to dedifferentiate and lose functional expression of enzymes and membrane transporters during the course of culture. For example, expression of enzymes important for drug metabolism, such as CYPs, tends to readily decrease if culture conditions are not optimized. Plasma membrane transporters, such as many of the OATs, can readily internalize and become nonfunctional dining the course of cultme (Lash et al, 2006). Our strategy to counteract these potential problems has been to use the serum-free, hormonally defined medium that has become standard with primary culture of epithelial cells and then add other supplements to optimize maintenance of differentiated fnnction (Lash et al., 1995 Lash, 2012). 

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