Bundle cells

Automa-ticity. Special cardiac cells, such as SA and AV nodal cells, His-bundle cells, and Purkinje fibers, spontaneously generate an impulse. This is the property of automaticity. Ectopic sites can act as pacemakers if the rate of phase 4 depolarization or resting membrane potential is increased, or the threshold for excitation is reduced. 

Borgstahl GEO, Parge HE, Hickey Ml, et al. 1992. The structure of human mitochondrial manganese superoxide dismutase reveals a novel tetrameric interface of two 4-helix bundles. Cell Press 71 107-118. 

The better efficiency and the more evenly utilization of the Mn02 cathode in bundle cells lowers the loading per cell and leads to an improved cycle life. But if required, the cell can also supply very high currents for special applications, e g. hand tools, video cameras, portable TV s and wheelchairs. Figure 29 shows how the change from I D size cell to a multi-cell... 

C4 plants green plants in which the primary product of CO2 fixation is not 3-phosphoglycerate (cf. C3 plants) but a C4 acid such as oxaloacetate, malate or aspartate. These plants possess two types of photi>-synthesizing cells. In mesophyll cells near the leaf surface, CO2 is fixed into C4-compounds. This prefixation of CO2 is due to the action of the cytosolic enzyme, phosphoeno/pyruvate carboxylase (EC 4.1.1.31), which carboxylates phosphoenolpyruvate to oxaloacetic acid (see Hatch-Slack-Kortschak cycle). The Calvin cycle (see) operates in the the vascular bundle cells of C4 plants, and CO2 for the Calvin cycle is derived from the decarboxylation C4 compounds rather than directly from the atmosphere. This Kranz anatomy , i.e. photosynthetically active bundle sheath cells with a photosynthetically active layer... 

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. 

Figure 10.25 Structure of the dimerization region of MyoD. The a helices HI (red and brown) and H2 (light and dark green) of the two monomers form a four-helix bundle that keeps the dimer together. The loops (yellow and orange) are on the outside of the four-helix bundle. (Adapted from P.C.M. Ma et al.. Cell 77 4S1-4S9, 1994.)...

No superconductivity has yet been found in carbon nanotubes or nanotube arrays. Despite the prediction that ID electronic systems cannot support supercon-ductivity[33,34], it is not clear that such theories are applicable to carbon nanotubes, which are tubular with a hollow core and have several unit cells around the circumference. Doping of nanotube bundles by the insertion of alkali metal dopants between the tubules could lead to superconductivity. The doping of individual tubules may provide another possible approach to superconductivity for carbon nanotube systems. 

Compartmentation of these reactions to prevent photorespiration involves the interaction of two cell types, mescrphyll cells and bundle sheath cells. The meso-phyll cells take up COg at the leaf surface, where Og is abundant, and use it to carboxylate phosphoenolpyruvate to yield OAA in a reaction catalyzed by PEP carboxylase (Figure 22.30). This four-carbon dicarboxylic acid is then either reduced to malate by an NADPH-specific malate dehydrogenase or transaminated to give aspartate in the mesophyll cells. The 4-C COg carrier (malate or aspartate) then is transported to the bundle sheath cells, where it is decarboxylated to yield COg and a 3-C product. The COg is then fixed into organic carbon by the Calvin cycle localized within the bundle sheath cells, and the 3-C product is returned to the mesophyll cells, where it is reconverted to PEP in preparation to accept another COg (Figure 22.30). Plants that use the C-4 pathway are termed C4 plants, in contrast to those plants with the conventional pathway of COg uptake (C3 plants). 

FIGURE 22.30 Essential features of the coinpartinenCation and biochemistry of die Hatch-Slack padiway of carbon dioxide uptake in C4 plants. Carbon dioxide is fixed into organic linkage by PEP carboxylase of meso-phyll cells, forming OAA. Eidier malate (die reduced form of OAA) or aspartate (the ami-iiated form) serves as die carrier transpordiig CO9 to the bundle slieadi cells. Within die bundle slieadi cells, CO9 is liberated by decar-boxyladon of malate or aspartate die C-3 product is returned to die mesophyll cell. 

Eormadon of PEP by pyruvate Pi dikinase reini-dates the cycle. The CO9 liberated in the bundle slieadi cell is used to syndiesize hexose by die convendonal rubisco-Calvin cycle series of reacdons. 

When only one fan and/or exchanger exists per process service, it may be advisable to control with an automatic variable pitch fan, unless a single- or two-speed drive is considered adequate. If the process service consists of several exchanger sections or tube bundles per cell (groups of bundles) and multiple fans are used, see Figure 10-193. If single fans are used per cell, see Figure 10-194. If several... 

The connection of AA-size cells in parallel can replace larger cells (e.g., D-size cells). Four AA cells fit into a D-size can, and six AA-cells are in equivalent weight to a D-cell [27]. The utilization of the Mn02 cathode is considerably improved because the cathode thickness is only 2 mm in a AA cell, but 5 mm in a D-cell. The internal resistance is also lower by a factor of 4 to 6. Figure 11 depicts a 5 PxlO S bundle battery five AA cells in parallel = 1 bundle, 10 bundles in series make a (nominal) 12 V battery. It is used as the power source for a transmitter/receiver service. A typical load profile is 2 A for 1 min, 0.33 A for 9 min average load, 0.5 A per bundle or 0.1 A per cell service, about 15 h. Smaller bundle batteries (with 2x9 cells) are very suitable for notebook-computers 18 AA cells weight 0.36 kg, and the total initial capacity is 32 Wh. 

K. Kordesch, J. Daniel-Ivad, Ch. Faistauer, High power rechargeable alkaline manganese dioxide-zinc batteries, 182nd Meeting of the Electrochem. Soc., Toronto, Oct., 1992, Extended Abstract 92-2, p. 18-18 (6 AA-bundle battery replacement of single D-cell). 

Taxanes (paclitaxel, docetaxel) are derivatives of yew tree bark (Taxus brevifolia). They stabilize microtubules in the polymerized state leading to nonfunctional microtubular bundles in the cell. Inhibition occurs during G2- and M-phases. Taxanes are also radiosensitizers. Unwanted effects include bone marrow suppression and cumulative neurotoxicity. 

Helicobacter Pylori Helix Bundle Helix-loop-helix Motif Helper T Cells Hemangioblast Hematopoiesis... 

Submembranous microtubules are often present in parallel bundles beneath the plasma membrane in the cells of higher plants, particularly during cell wall formation (Hardham and Gimning, 1978). Circular submembranous bundles of microtubules are a feature of bird erythrocytes and mammalian blood platelets, where they maintain the discoid shape of these structures (Dustin, 1980). 

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