Uptakes passive

Biosorption is a general phenomenon that can occur in either dead or living biomass. However, this process usually refers to a passive uptake mechanism carried out by nonviable microorganisms (dead yeasts). The biosorption process involves physical-chemical interactions between the yeast surface and the azo dyes, as well as possible passive diffusion inside dead cells. 

Another approach is to determine the effect of contaminating organic compounds on soil fauna such as worms. Although this can be informative, it is often impossible to differentiate between the effects of active uptake and passive uptake or simple exposure [4],... 

Aliphatic carbamates are rapidly absorbed from the colon by passive uptake (Wood et al., 1978) and it is found that there is a linear relationship between log ka and logP for absorption of these carbamates in the colon and the stomach, whereas there is a parabolic relationship between these two values for absorption in the small intestine. The factors to be considered are... 

Special emphasis is placed on the carbohydrate-mediated cell - target system interaction by describing hints and pitfalls of assays for cytoadhesion, specificity, cytoinvasion, and cytoevasion. In addition, basic considerations are presented to discriminate between active and passive uptake as well as to detect lysosomal accumulation. Finally, the pros and cons of two useful analytical techniques, namely, flow cytometry and confocal laser scanning microscopy, are described in detail. 

Figure 10.5 Terms and parameters frequently used to describe accumulation of chemicals in aquatic organisms. Note that the term bioaccumulation (BAF,) is used to describe the total accumulation by all possible routes (e.g., passive uptake, intake by food and digestion, etc.). The term bioconcentration is sometimes...

We should also note that microorganisms have water-filled pores (porins) through their exterior membranes (Fig. 17.13) which permit the passive entrance of small hydrophilic substances (Madigan et al., 2000). In studies of enteric bacteria, passive glucose uptake exhibited transmembrane uptake time scales of less than a millisecond (Nikaido, 1979). Thus, the rate of passive uptake of small, hydrophilic molecules (< 500 molecular mass units) via membrane pores of bacteria is not likely to cause them to avoid biodegradation for prolonged times. 

Once in the gastrointestinal tract, chemicals that have undergone conjugation reactions in the liver may be subject to the action of hydrolytic enzymes that de-conjugate the molecule. De-conjugation results in increased lipophilicity of the molecule and renders them once again subject to passive uptake. Re-absorbed chemicals enter the circulation via the hepatic portal vein, which shunts the chemical back to the liver where... 

Passive uptake Opsonization Recognition Receptor-mediated ( f mRNA / y. oo T o oPro,e,ns 1 5 and 3 UTR Regulation Cell-specificity... 

As the Q10 indicates, the passive uptake of this ion doubles with only a 10°C increase in temperature. Therefore, a passive process can have a rather high Q10 if there is a substantial energy barrier, so such a Q10 for ion uptake does not necessarily indicate active transport. 

Fig. 11.14 Representative imaging studies using SERS labels, (a) An example of cells after passive uptake of silver nanoparticles linked with cresyl violet [91], (b) An example of simultaneous imaging of two biomarkers on tissue surfaces using COINs [70], and (c) An example of in vivo multiplex imaging [92, 93]...

To distinguish diffusible from bound antigens, cryostat sections are often preferred. Pre-fixation diffusion artefacts (e.g., passive uptake of non-specific antigens by cells, particularly of the lymphoid system Mason et al., 1980), which occur quite often, may be revealed by double EIH staining (e.g., k and X chains should normally not be present in the same cell) and counteracted by rapid fixation or removal of diffusible antigens by washing with cold saline. Postfixation diffusion artefacts are also frequently noticeable, e.g. after ethanol fixation (Brandtzaeg, 1982). 

Assuming that the passive uptake and efflux rate constants, k, are equal, we may write the intracellular Rb+ concentration as ... 

The uptake kinetics of C-labelled triadimenol, shown in figure 6 were examined in both the susceptible and triadimenol-resistant strains of the yeast Saccharomycopsis lipolytica. To minimize the effect of unspecific absorption on the cell surface the incubated cells were separated by suction filtration and washed twice with unlabelled triadimenol. The passive uptake curve shows the typical characteristics of saturation by diffusion, equilibrium being reached after about 20 minutes. There are no real differences between the susceptible and resistant isolates, and no indication of transport mutation or induction of efflux transport can be derived from these data. 

Passive uptake by facilitated diffusion into the cell (e.g., Simkiss and Taylor 1989a). 

The high affinity of such metal ions for proteins and other cellular constituents provides the basis for their passive uptake, mediated by carrier proteins, as presented in Figure 7.2. The initial binding with the protein is a passive process, and metal transfer across the membrane into the cell occurs... 

Active transport is more valid for Cd and Cu, while passive uptake through the lipid bilayer membrane is valid for Ag and Hg (Langston and Bryan 1984). 

The relationship between the concentration of a metal in the surrounding water and the concentration in an organism is defined as concentration factor (Baudo 1981). Concentration factors in excess of a thousandfold can be attained (Martincic etal. 1984), and are affected by speciation, active and passive uptake, modalities of uptake, and transformation, transport and distribution between and within tissues, and elimination. 

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