Erythrocytes, mammalian

In the case of hemoglobin it is well documented that heme or its precursor, ALA, stimulates hemoglobin synthesis when added to preparations of hemolyzed bird erythrocytes, mammalian reticulocytes, or chick embryo blastoderm [6,7]. 

Fauvet B, Mbefo MK, Fares MB, et al. Alpha-synudein in central nervous system and from erythrocytes, mammalian cells, and Escherichia coli exists predominantly as disordered monomer. / Biol Chem. 2012 287(19) 15345-15364. 

In vitro cytotoxicity assays using isolated cells have been applied intermittently to cyanobacterial toxicity testing over several years." Cells investigated for suitability in cyanobacterial toxin assays include primary liver cells (hepatocytes) isolated from rodents and fish, established permanent mammalian cell lines, including hepatocytes, fibroblasts and cancerous cells, and erythrocytes. Earlier work suggested that extracts from toxic cyanobacteria disrupted cells of established lines and erythrocytes," but studies with purified microcystins revealed no alterations in structure or ion transport in fibroblasts or erythrocytes,... 

The processes of electron transport and oxidative phosphorylation are membrane-associated. Bacteria are the simplest life form, and bacterial cells typically consist of a single cellular compartment surrounded by a plasma membrane and a more rigid cell wall. In such a system, the conversion of energy from NADH and [FADHg] to the energy of ATP via electron transport and oxidative phosphorylation is carried out at (and across) the plasma membrane. In eukaryotic cells, electron transport and oxidative phosphorylation are localized in mitochondria, which are also the sites of TCA cycle activity and (as we shall see in Chapter 24) fatty acid oxidation. Mammalian cells contain from 800 to 2500 mitochondria other types of cells may have as few as one or two or as many as half a million mitochondria. Human erythrocytes, whose purpose is simply to transport oxygen to tissues, contain no mitochondria at all. The typical mitochondrion is about 0.5 0.3 microns in diameter and from 0.5 micron to several microns long its overall shape is sensitive to metabolic conditions in the cell. 

In mammalian erythrocytes (red blood-cells) the forward (hydration) reaction occurs during the uptake of CO, by blood in tissue, while the backward (dehydration) reaction takes place when the CO, is subsequently released in the lungs. The enzyme increases the rates of these reactions by a factor of about one million. 

AChE-E (in blue) GPI-anchored dimers to plasma membranes in mammalian muscles, erythrocytes and lymphocytes. 

Microtubules are universally present in eukaryotes from protozoa to the cells of higher animals and plants (Porter, 1966 Hardham and Gunning, 1978 Lloyd, 1987), but they are absent in mammalian erythrocytes and in prokaryotes. Microtubules participate in a number of cellular functions including the maintenance of cell shape and polarity, mitosis, cytokinesis, the positioning of organelles, intracellular transport to specific domains, axoplasmic transport, and cell locomotion. The diversity of microtubule fimctions suggests that not all microtubules are identical and that different classes of microtubules are present in different cell types or are localized in distinct domains in the same cell type (Ginzburg et al., 1989). 

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). 

Certain of these peptoid antibiotics are also selective for bacterial, rather than mammalian, cells. The selectivity of these peptoids has been measured in terms of their capacity to cause hemolysis of human erythrocytes at or near their MIC (Tab. 1.3). Interestingly, the amount of hemolysis induced by these peptoids correlates well with their hydrophobicity as there is an increasing extent of hemolysis as molecular hydrophobicity increases. These results suggest that highly hydro-phobic compounds of this class are poorly selective antibiotics. The most active antibacterial peptoids, T2-15 and T3-12, have quite low hemolytic activity near their MICs. Although highly antibacterial in vitro, T3-17 is also very hemolytic at its MIC value. 

A summary of the steps in the biosynthesis of the porphyrin derivatives from PBG is given in Figure 32-8. The last three enzymes in the pathway and ALA synthase are located in the mitochondrion, whereas the other enzymes are cytosolic. Both erythroid and non-erythroid ( housekeeping ) forms of the first four enzymes are found. Heme biosynthesis occurs in most mammalian cells with the exception of mature erythrocytes, which do not contain mitochondria. However,... 

Homogenates of MetruUum senile, possibly the world s most common large sea anemone, yield extracts that are powerfully hemolytic for washed mammalian erythrocytes (22). The active substance, metridiolysin, is a protein of molecular weight approximately 80,000. In contrast to the sphingomyelin-inhibitable toxins, metridiolysin is an acidic protein having a pi of about 5. It is thermolabile and is inactivat by proteolytic enzymes. The optimal pH for hemolysis is between 5 and 6, and at pH 8 the lysin is inactive. It can be dissociated into two subunits of unequal size. Besides being cytolytic in vitro, metridiolysin is lethal when injected intravenously into mice. As shown in Table IV erythrocytes from the horse or dog are about a hundred times as sensitive to lysis as those from the mouse, and erythrocytes from other animals tested are intermediate in sensitivity. 

By far the most complete study of the kinetics of mammalian passive glucose transporters has been done on the GLUT-1 isoform in the human erythrocyte. The transport of glucose in this cell type is a classic example of facilitated diffusion, the... 

Superoxide dismutases (SODs) are a family of cytosolic metalloenzymes that specifically remove (reviewed by Omar etal., 1992). SOD distribution within the body is ubiquitous, being found in erythrocytes as well as most organs and cell types. Three distinct mammalian SOD forms exist CuZnSOD, MnSOD and extracellular SOD (EC-SOD). Their amino-acid sequences differ as well as the transition metals at their active sites. Rheumatoid synovial fluid contains low levels of SOD activity and hence little protection from ROM generated by infiltrating PMNs (Blake etcU., 1981). Furthermore, leucocytes from patients with RA are deficient in MnSOD, which might promote the extracellular leakage of O2 (Pasquier et al., 1984). 

Another important reason for the significant deviation between calculated and X-ray structures can be the low resolution (2.9 A) of the X-ray structure. It is well known that X-ray structures may miss disordered water molecules inside the enzyme. The X-ray structure of the bovine erythrocyte GPx has a significantly higher resolution (2.0 A) and that structure contains two water molecules in the active site [63], Unfortunately that X-ray structure is not complete. In order to test for the presence of water molecules at the active site of the mammalian GPx, calculations were performed with two additional water molecules at the active site. This reduced the RMS deviation to from 0.97 to 0.19k for ONIOM(B3LYP/6-31G(d) Amber)-ME and suggests the presence of water molecules also in the active site of mammalian GPx. In our investigation of the reaction mechanism, these water molecules turns out to be critical. 

Smith (1996) summarized data on the spontaneous methemoglobin reductase activity of mammalian erythrocytes. Using nitrated RBCs with glucose as a substrate, the data reflect the ratio of the activity of the species to the activity in human RBCs. Activity in rat cells and human cells ranged from 1.3 to 5.0. Activity in cells of the cat and dog was similar to that in human cells, and that of the rabbit was 3.3 to 7.5 times greater. Most studies show that the spontaneous methemoglobin reductase activity of human erythrocytes is within an order of magnitude of that of other mammals (Smith 1996). 

The exact nature of the NO-releasing reaction and the other products of reaction in mammalian tissue are still unclear. The matter has been discussed by a number of authors and a reductive mechanism in rat hepatocytes and human erythrocytes has been suggested in the presence of NADH and NADPH. Nitroprusside can pass through cell membranes and so there is no intrinsic difficulty with this suggestion. There is direct evidence from spin echo NMR studies to show the conversion, by nitroprusside, of glutathione into glutathione disulfide within erythrocytes [49]. 

Reaction (1) is irreversible the enzyme galactokinase has been found in mammalian liver, brain, and erythrocytes, as well as in certain yeasts and other microorganisms. UDPGal, the main product of reaction (2), is the intermediate by means of which the body incorporates galactose into cerebrosides and, probably, other galactolipids, mucopolysaccharides, and lactose galactose-l-phosphate uridyl transferase occurs in the liver, to a lesser extent in red cells, and probably in other tissues. 

The enzymes have been demonstrated to be present in varying amounts in almost all mammalian tissues and in blood (B4, D4, D7, D8, G8, G10, Gil, H13, S12, S14, W5, W18). The highest activities are attributed to erythrocytes and to the other cellular components of blood. Recently, G-6-PDH and 6-PGDH activities in saliva have been described (R5). 

B2. Barron, E. S. G., and Harrop, G. A., The effect of methylene blue and other dyes upon the glycolysis and lactic acid formation of mammalian and avian erythrocytes. J. Biol. Chetn. 79, 65-87 (1028). 

The carbonic anhydrases of mammalian erythrocytes have been the object of extensive study for the last 68 years, and can be considered as the prototype of zinc enzymes that use... 

Fig. 4. Amino acid sequence of several histone HI proteins to illustrate the macroheterogeneity of linker histones. Amino acid sequence of two highly specialized development-specific members of the histone HI family. A. Oocyte specific mammalian histone Hlfo (previously Hloo) [116]. B. PL-I (EM-1/6) protein from the sperm of the razor clam Ensis minor [120]. These two sequences are shown in comparison to the highly specialized histone H5 from chicken erythrocytes. The regions corresponding to the trypsin-resistant (winged helix motif [96]) which is characteristic of the protein members of the histone HI family are indicated by a box and have been aligned to show the sequence similarity.

Mammalian Erythrocyte Micronucleus Test (Updated Guideline, adopted 21 July 1997)... 

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