Pulse-chase studies

In a review of feeding and digestion in the Bivalvia [37], it was proposed that the accumulation of metal-bound particulates in the digestive gland was a two-phase process reflecting extracellular and intracellular digestion, and Viarengo [87] has reached similar conclusions. In a pulse chase study of the uptake of radiolabelled metals (Ag, Cd, Cr, Hg, Se) by the zebra mussel Dreissena... 

The pronounced lag observed between labelling of the diether and tetraether polar lipids, in recent [ P]phosphate pulse-chase studies with M. thermoautotrophicum cells [62], is consistent with the generalized mechanism proposed by the authors (Fig. 4 of ref. [62] see also Fig. 13). This mechanism would account for the biosynthesis in M thermoautotrophicum of the three families of heptads of archaeol and caldarchaeol polar lipids containing P-ethanolamine, P-serine and P-inositol, since all of the... 

Both the normal and abnormal forms of PrP are derived from the same gene and have the same amino acid sequence. Pulse-chase studies in Sc+-MNB have demonstrated that PrP-res is in fact posttranslationally derived from mature PrP-sen (Borchelt et al., 1990 Caughey and Raymond, 1991). Unlike PrP-sen, PrP-res is resistant to phospholipases and protease treat-... 

Microsomal fractions of oilseed rape readily incorporated (1- C) oleoyl CoA into PC, PA and TG, indicating the presence of active Kennedy pathway and PC-acyltransferase activities. Acyl transfer to PC was hugely stimulated in the presence of exogenous LPC but, in the presence of exogenous LPA the vast majority of the acyl transfer was to PA (Table 1). In each case the acylation of the added lysophospholipid was virtually the only route for oleate metabol-isation, resulting in the accumulation of labelled PC or PA over the short term. By means of pulse-chase studies, it was possible to observe some flow of label from PA towards TG and PC, which is consistent with the proposed operation of an equilibrium between DG and PC (1-4). It was more difficult to... 

The lysosomal mannosidase has been purified from a munber of species [130, 156-160] and the subunit molecular weights vary significantly between species. The human enzyme can be separated into two forms by ion exchange chromatography, termed A and B, but significant evidence indicates that the two enzymes are differently modified versions of the same gene product [156]. Pulse-chase studies have indicated that the initial translation product of the human gene is a 110 kDa pre-... 

Other sand-based systems using COi pulse-chase procedures have been used to produce carbon budgets for Festuca ovina and Plantago lanceolata seedlings (30) and white lupin (Lupimis albiis) (31). Significantly, CO2 pulse labeling of proteoid roots of white lupin under phosphate-deficient conditions showed that high levels of dark fixation of COi by the roots took place and that 66% of this root-fixed carbon was exuded from the roots (31). Clearly, dark fixation of CO2 by roots and subsequent rhizodeposition is an area that deserves further study in the future. 

The use of pulse-chase methods identifies differences in the timing and efficiency of absorption between the two pathways, enabling the study of uptake in the endocytosis system [83]. 

The biological function of this dolichol-linked oligosaccharide was revealed in pulse-chase experiments which showed that the intact oligosaccharide was transferred, as such, to protein. Subsequent studies, to be discussed, confirmed that the formation of the oligosaccharide linked to the Asn residues of glycoproteins is probably initiated by transfer of the oligosaccharide from the dolichol diphosphate intermediate to the asparagine residue of a nascent polypeptide (see Refs. 35, 49, 50, and 67 for reviews). 

Fig. 5.2. Allocation to ectomycorrhizal fungi correlates with belowground allocation in culture studies. Values are given as a percentage of net primary production (NPP), and are listed in Table 5.2. A linear regression gives an equation of %NPPfungi = 0.43 x %NPPbeiow-ground—12.7%, r = 0.52, /><0.001. One study (Reid et al, 1983) was excluded since the methodology (pulse-chase) was very different than in any other study.

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