Epidermal cell

Histamine AND histamine antagonists). It is formed from histidine by the enzyme L-histidine decarboxylase. In the periphery, histamine is stored ia mast cells, basophils, cells of the gastric mucosa, and epidermal cells. In the CNS, histamine is released from nerve cells and acts as a neurotransmitter. The actions of histamine ate terrninated by methylation and subsequent oxidation via the enzymes histamine-/V-methyltransferase and monoamine oxidase. 

Air pollutants may enter plant systems by either a primary or a secondary pathway. The primary pathway is analogous to human inhalation. Figure 8-2 shows the cross section of a leaf. Both of the outer surfaces are covered by a layer of epidermal cells, which help in moisture retention. Between the epidermal layers are the mesophyll cells—the spongy and palisade parenchyma. The leaf has a vascular bundle which carries water, minerals, and carbohydrates throughout the plant. Two important features shown in Fig. 8-2 are the openings in the epidermal layers called stomates, which are controlled by guard cells which can open and close, and air spaces in the interior of the leaf. 

Cooper, M.S., Schliwa, M. (1986). Motility of cultured fish epidermal cells in the presence and absence of direct current electric fields. J. Cell Biol. 102, 1384-1399. 

Pantoja, O. Willmer, C.M. (1986). Pressure effects on membrane potentials of mesophyll cell protoplasts and epidermal cell protoplasts of Commelina communis. Journal of Experimental Botany, 37, 315-20. 

Trichloroacetic Acid (TCA) causes precipitation of proteins and coagulative necrosis of epidermal cells [4]. The extent of damage is indeed concentration dependent. Concentrations range from 10 to 50%. Superficial TCA peeling is induced by concentrations of 10-30% whereas higher concentrations cause medium depth or deep peeling. The combination of salicylic acid followed by TCA 10-15% induces superficial wounding. 

Wollenberg A. Kraft S. Hanau D. Bieber T Immuno-morphological and ultrastructural characterization of Langerhans cells and a novel, inflammatory dendritic epidermal cell population in lesional skin of atopic eczema. J Invest Dermatol 1996 106 446-453. 

Enzyme-Mediated Substrate Immunolocalization ofPoIygalacturonic Acid Within Barley Epidermal Cell Walls Utilizing Endopolygalacturonase of Cochliobolus sativus and a Monoclonal Antibody Specific for the Enzyme... 

The EMSIL obtained with the purified EPG on transverse sections of barley leaf epidermal cells taken pependicular to the long axis of the cells and anticlinal to the leaf surface, revealed that EPG substrate is localized primarily in the cell comers and middle lamella of these cells (Fig. 1). 

Figure 1. Transverse section of barley leaf epidermal cells taken perpendicular to the long axis of the cells and anticlinal to the leaf surface. The section has been labeled by the EMSIL technique (see Methods) utilizing purified C. sativus endopolygalacturonase and monoclonal antibody EPG-4, which is specific for this enzyme, in order to localize the substrate of the enzyme at the typical site penetrated by the fungal pathogen. Bar = 1 pm. Inset Comparable cell wall region as in Fig. 1 but labeled with monoclonal antibody JIM 5 to localize non-esterified pectin. Bar = 1 pm. Note the identical labeling patterns obtained with either method.

Immunogold labeling with JIM S exhibited an identical labeling distribution for polygalacturonic acid as was obtained indirectly with the EPG EMSIL (inset of Fig. 1). Control experiments for labeling specificities obtained by the direct or indirect methods resulted in total elimination of specific labeling. The cellulase-gold probe heavily labeled the epidermal cell walls (Fig. 2). 

Figure 2. Advanced stage of barley leaf penetration by C. sativus. The pathogen has penetrated the anticlinal cell wall junction between two host epidermal cells (e). The fungal appressorium (a) is visible above the cell comer. The host cell comer matrix has been displaced by an enlarged hyphal element (h) situated between the thin cell walls of the host epidermal cells. The host epidermal cell walls have been densely labeled with the cellulase-gold probe. An intercellullar hyphal element (ih) is present within the penetrated host cell. Bar = 1 pM.

Of all the epidermal cells studied in vitro with respect to antioxidant status, perhaps keratinocytes are the most important. These cells differentiate as they move upwards through the epidermis and there is evidence that, in... 

Holtzman, M.J., Turk, J. and Pentland, A. (1989). A regiospecific mono-oxygenase with novel stereopreference is the major pathway for arachidonic acid oxygenation in isolated epidermal cells. J. Clin. Invest. 84, 1446-1453. 

Sola, P., Godessart, N., Vila, L., Puig, L. and Moragas, J.M. (1992). Epidermal cell-polymorphonuclear leukocyte cooperation in the formation of leukotriene B4 by transcellular biosynthesis. J. Invest. Dermatol. 98, 333-339. 

Larsson, R. and Cerutti, P. (1989). Translocation and enhancement of phosphotransferase activity of protein kinase C following exposure of mouse epidermal cells to oxidants. Cancer Res. 49, 5627-5632. 

In soil, the chances that any enzyme will retain its activity are very slim indeed, because inactivation can occur by denaturation, microbial degradation, and sorption (61,62), although it is possible that sorption may protect an enzyme from microbial degradation or chemical hydrolysis and retain its activity. The nature of most enzymes, particularly size and charge characteristics, is such that they would have very low mobility in soils, so that if a secreted enzyme is to have any effect, it must operate close to the point of secretion and its substrate must be able to diffuse to the enzyme. Secretory acid phosphatase was found to be produced in response to P-deficiency stress by epidermal cells of the main tap roots of white lupin and in the cell walls and intercellular spaces of lateral roots (63). Such apoplastic phosphatase is safe from soil but can be effective only when presented with soluble organophosphates, which are often present in the soil. solution (64). However, because the phosphatase activity in the rhizo-sphere originates from a number of sources (65), mostly microbial, and is much higher in the rhizosphere than in bulk soil (66), it seems curious that plants would have a need to secrete phosphatase at all. 

Various techniques for collection of root exudates are associated with the risk of root injury by rupture of root hairs and epidermal cells or rapid change of the environmental conditions (e.g., temperature, pH, oxygen availability) during transfer of root systems into trap solutions, application of absorbtion materials onto the root surface, and preparation of root systems for exudate collection. The possible impact of those stress treatments may be assessed by measuring parameters of plant growth in plants either. subjected or not subjected to the collection procedure (6) and by comparing exudation patterns after exposure of roots to the handling procedures with different intensity. 

Endomycorrhizal hyphae adopt a variety of colonization patterns in their penetration of the host root cells. Glomalean fungi are highly dependent on their ho.st and cannot survive for long in its absence. Their hyphae form appressoria on the epidermal cells, penetrate the cortical tissue, and eventually form highly branched structures called arbuscules (Figs. 3-6) (10). 

Keratinocyte The epidermal cell that synthesizes keratin, making up 95% of all epidermal cells commonly called skin cells. ... 

Alteration of Electrical Potential (PD). Study of the Influence of allelochemicals on the electrical potentials across plant cell membranes has been restricted to phenolic acids. Glass and Dunlop (42) reported that at pH 7.2, 500 yM salicylic acid depolarized the electrical potential in epidermal cells of barley roots. The electrical potential changed from -150 mV to -10 mV within 12 min. Recovery of the PD was very slow over about 100 min when the salicylic acid was removed. As the concentration of the allelochemical was increased, the extent of depolarization increased, but the time required for depolarization and recovery were constant. 

Salicylic acid depolarized PD In epidermal cells of oat roots also. At pH 4.5, 500 pM salicylic acid caused a transient hyperpolarization followed by a dramatic depolarization to about -45 mV (Figure 2). Removal of salicylic acid produced a transient, partial repolarization. At pH 6.5, salicylic acid did not affect PD. These results with different pH s are consistent with the Influence of salicylic acid on K+ absorption in oat roots (32). 

Figure 2. Influence of 500 flM salicylic acid on the electrical potential (PD) of epidermal cells of excised oat roots at pH 4.5. Microelectrode was inserted in a cell at 1 min salicylic acid was added at 2.5 min and removed by flushing at 25 min.

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