The serum component

The factors which affect cells may be produced by the same cell as responds to them (an autocrine response shown by some tumour cells), or may be produced by a neighbouring cell type (a paracrine response mediated by the interleukins). It is sometimes only possible to distinguish autocrine and paracrine responses by cloning cells from a particular tissue, as a factor produced by one cell type may be processed by a second cell type before reacting with receptors on the first cell type. 

Cell growth factors may also be produced by a distant cell or tissue and travel to the responding cell via the blood stream (an endocrine response as shown by insulin). These factors are classically known as hormones. Although endocrine factors are present in serum, conditioned medium is frequently a better source of autocrine and paracrine factors. 

One of the earliest factors to be discovered was platelet derived growth factor (PDGF). This arose from the finding that plasma obtained from unclotted blood could not replace serum in promoting cell growth. PDGF was purified from serum and shown to be the component missing in plasma. 

A large number of peptide growth factors have now been isolated (Table 2.1) and they tend to fall into families exhibiting partial 

Insulin-like growth factors — derived from one polypeptide of 6-12 kDa — 

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Imidazole antimycotics, ketoconazole, clotrimazole, and miconazole are potent inhibitors of various cytochrome P450-isoenzymes that also affect the metabolism of retinoids. They were fust shown to inhibit the metabolism of RA in F9 embryonal carcinoma cells. When tested in vitm liarazole, a potent CYP-inhibitor, suppressed neoplastic transformation and upregulated gap junctional communication in murine and human fibroblasts, which appeared to be due to the presence of retinoids in the serum component of the cell culture medium. Furthermore, liarazole magnified the cancer chemopreventive activity of RA and (3-carotene in these experiments by inhibiting RA-catabolism as demonstrated by absence of a decrease in RA-levels in the culture medium in the presence of liarazole over 48 h, whereas without liarazole 99% of RA was catabolized. In vivo, treatment with liarazole and ketoconazole reduced the accelerated catabolism of retinoids and increased the mean plasma all-irans-RA-concentration in patients with acute promyelocytic leukemia and other cancels. 

Materials. Egg phosphatidylcholine (PC), bovine brain phosphatidylserine (PS) were obtained from Avanti Polar Lipids Inc. (Birmingham, AL) and cholesterol was from Sigma (St. Louis, MO). Ganglioside GMj, bovine, was obtained from Calbiochem (San Diego, CA). Diethylenetriamine pentaacetic acid distearylamide complex (DPTA-SA) was synthesized according to ref. 17 and nlIn-DTPA-SA was prepared as described (7). This lipophilic radiolabel is not transferred to the serum components from liposomes (unpublished data), nor is it rapidly metabolized in vivo (7). The synthesis of N-(glutaryl)phosphatidylethanolamine(NGPE) has been described (18). Dipalmitoyl deoxyfluorouridine(dpFUdR) was synthesized as described (24). 

Carbohydrates are linked to some soluble proteins as well as membrane proteins. In particular, many of the proteins secreted from cells are glycosylated. Most proteins present in the serum component of blood are glycoproteins (Figure 11.20). Furthermore, A-acetylglucosamine residues are O-linked to some intracellular proteins. The role of these carbohydrates, which are dynamically added and removed, is under active investigation. 

A new column design that allowed the separation of serum on G-200 by normal elution technique in conjunction with the application of an electric current so as to retard the serum components and increase resolution, was described by Bundschuh [243]. The technique was termed electro-retardation-filtration , greatly improved resolution was obtained and a general applicability of the technique to protein mixtures was claimed. 

The measurement of warfarin enantiomers in serum using coupled achiral/chiral high-performance liquid chromatography" (110), An assay for the serum concentrations of (fi)-warfarin and (S)-warfarin was developed using the BSA CSF coupled to a Pinkerton internal-surface reverse-phase (ISRP) achiral column. The ISRP column was used to separate (R,S)-warfarin from the serum components and warfarin metabolites and to quantitate the total warfarin concentration. The eluent containing the (A,S)-warfarin was then selectively transferred to the BSA CSR where the enantiomers were enantioselectively resolved (a = 1.19) and the enantiomeric composition determined. 

Q.15.1 What is the ionic strength of the serum component of blood What is the osmolarity of this component Normal Serum composition is Na 140 mil-liequivalents, K 4 milliequivalents, Cl 100 milliequivalents, HCOa 24 milliequivalents. 

The pH of the micellar mobile phase is an important factor for the analysis of ionizable drugs using nonpolar column stationary phases. Fig. 11.7 shows the chromatograms of acetylsalicylic acid (log Kh = 3.5) in a serum sample at pH 3.0 and 6.5, eluted from a CIS column with a 0.08 M SDS mobile phase [20]. It can be seen that at the higher pH, the peak for this drug is not evident. The anionic solute probably eluted with the serum proteins. However, when pH was reduced to 3.5, the neutral form of the drag eluted at approximately 3.5 min, appreciably distinct from the serum components. 

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