Cells species differences

The strength of cell walls differs among bacteria, yeasts, and molds. The strength also varies with the species and the growth conditions, and must Be determined experimentally. Beads of 0.5 mm are typically used for yeast and bacteria. Recommended bead charge is 85 percent for 0.5 mm beads, and 80 percent for 1 mm beads [Schuette et al.. Enzyme Microbial Technology, 5, 143 (1983)]. 

Suppose now that we build a series of cells, alike in all respects save that the (very dilute and completely dissociated) solute has a different concentration in each cell. If the cells are alike in all other respects, the unitary terms must be the same in each coll the values of the e.m.f. for the various cells will differ owing to the difference in the communal terms. In very dilute solutions the contribution made to each communal term by the interionic forces will be small, and the dependence of the e.m.f. on the concentration will arise almost entirely from the cratic term which, for each solute species, may be written — kT In y or — IcT In x. Since we are considering a uni-univalent solute, the numerical values of y+ and t/ for the positive and negative ions will both be the same as the mole ratio of the solute. 

Equation (17) expresses the cell potential difference in a general way, irrespective of the nature of the electrodes. Therefore, it is in particular valid also for nonpolarizable electrodes. However, since

interfacial structure, only polarizable electrodes at their potential of zero charge will be discussed here. It was shown earlier that the structural details are not different for nonpolarizable electrodes, provided no specifically adsorbed species are present. 

Many of the physical changes in membrane structure of cells are reversible and species differences in the degree of disruption of dry membranes may relate to differences in composition, protective mechanisms or to additional damage occurring during desiccation (see below). 

Any bacterial species living in a mixed microbial population, such as that of the rhizosphere, may encounter not only the molecular signal produced by a cell of the. same species but also molecular signals produced by cells of different species. The situation is made more complex by the presence of plant molecular signals, and by the fact that the same AHL molecule can be used to regulate the... 

This process seems to reflect gradual increases in the intensity and density of labelled receptor cell bodies and their axons, followed by regional bulbar staining as synaptogenesis proceeds. However, a more extensive range of lectins needs to be examined before the implications of species differences in the membrane glycoproteins can be satisfactorily interpreted (Salazar and Quinteiro, 1998). 

From an industrial perspective, quantitative knowledge of the existence of different transporters within the cellular system used in screening procedures is of major importance as it can influence both the predictive value of the permeability coefficients and interpretation of the results. In addition, information on species differences or similarities or discrepancies between cell culture models and animals now provide an important basis for the scaling of data during the early phases of drug discovery for animals or humans [48]. 

When applying any of these models it is crucial to understand the main transport mechanisms as well as the metabolic route and characterization of the activity of the transporter/enzyme involved. It is well recognized that the activities of carrier-mediated processes in Caco-2 cells are considerably lower than in vivo [20, 42, 48] therefore, it is crucial to extrapolate in vitro cell culture data to the in vivo situation with great care [18, 20, 42, 48], This is especially important when carrier-mediated processes are involved, as evidenced by a recent report which showed significant differences in gene expression levels for transporters, channels and metabolizing enzymes in Caco-2 cells than in human duodenum [48], If an animal model is used, then potential species differences must also be considered [18, 20, 45],... 

Van den Beukel I, van Kleef RGDM, Oortgiesen M. Differential effects of physostigmine and organophosphates on nicotinic receptors in neuronal cells of different species. NeuroToxicol. 19(6) 777-788, 1998. 

Lymphocytes, the effector cells of the acquired immune system, include morphologically indistinguishable T and B cells, the former divided into CD4+ T helper cells and CD8+ cytotoxic T cells. Since the functions of those cell subsets differ so drastically, it became important to develop tools to distinguish them from each other. Efforts to identify cell subsets according to their expression of different surface antigens have been successful, including various Cluster of Determination (CD) markers (Table 23.1). In addition, cross-reactive monoclonal antibodies, and subsequently developed species-specific polyclonal and monoclonal antibodies towards the major histocompatibility complex (MHC) have been used to label cells in circulation and in tissue sections (Table 23.1). 

Holton Loose coupling would be another explanation. You are working on rabbit bladder. Imaizumi s group have worked on guinea-pig, and in the vas deferens and urinary bladder they see a spark or hotspot within 10 ms of a depolarization. You can either retreat into a species difference argument, or perhaps they selected their cells very heavily. 

Species differences must be considered when choosing a model and, in particular, species-specific immunological differences between the human and the test animal. For example, in humans, an anti-CD4 monoclonal antibody (MAb) will bind to CD4 expressed on monocytes, with subsequent fixing of complement and destruction of antigen-presenting cells. However, since CD4 molecules are not expressed on murine monocytes, these effects would not be evident in a murine model. 

By the early 1960s it was clear that simple experiments on P uptake were inadequate to distinguish different species of RNA in mixed populations of cells at different stages of the cell cycle. The future for labeling experiments with 32P in cell biology was to lie mainly with synchronized cells and for studies on nucleic acids, with molecular biological techniques. 

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