Preoperative estimation of risk in hepatectomy using technetium-99m-galactosyl human serum albumin receptor amount by nonlinear 3-compartment model

BACKGROUND/AIMS

Recently, we developed the method for measurement of the technetium-99m-diethylenetriamine-pentaacetic acid-galactosyl human serum albumin (Tc-GSA) receptor amount (R0) using a nonlinear 3-compartment model. We examined the usefulness of R0 for preoperative estimation of risk in hepatectomy.

METHODOLOGY

Sixty-three patients who underwent hepatectomy in our hospital were examined for R0. These patients consisted of 26 cases of normal liver, 16 cases of liver fibrosis, and 21 cases of cirrhosis. R0 was measured by the nonlinear 3-compartment model of ligand-receptor binding without blood sampling in Tc-GSA scintigraphy. The expected remnant liver R0 after hepatectomy was calculated from CT volumetry before hepatectomy.

RESULTS

The preoperative mean R0 of liver was 15.8 +/- 3.8 mg for Z0, 13.8 +/- 3.9 mg for Z1, and 6.9 +/- 2.3 mg for Z2. R0 in Z2 was significantly lower than Z0 and Z1 (p < 0.0001). Every patient whose remnant liver R0 was over 5 mg tolerated hepatectomy without any postoperative complications. Among 63 cases, 5 patients developed postoperative complications (two liver failures, two postoperative jaundice and one hepatic coma), and remnant liver R0 of these patients were under 5 mg.

CONCLUSIONS

From these results, it can be seen that R0 of remnant liver is a useful parameter to decide indication of hepatectomy and predict postoperative complications.

Receptor-mediated endocytosis of transthyretin by ependymoma cells

Transthyretin (TTR) is involved in the transport of thyroxine (T4) and retinol-binding protein (RBP) in cerebrospinal fluid (CSF) and serum. TTR is secreted in the CSF by the epithelial cells of choroid plexus. The binding of [(125)I]TTR to cultured ependymoma cells which form the brain cerebrospinal barrier, was studied to determine whether these cells carry receptor(s) for TTR. TTR was bound by ependymoma cells in a time-dependent manner reaching equilibrium within 2 h. Scatchard analysis was consistent with a single class of high-affinity binding sites with a K(d) of approximately 18 nM. Saturable high-affinity binding of human TTR has previously been described in rat primary hepatocytes and human renal adenocarcinoma, neuroblastoma, hepatoma and astrocytoma cells, and also transformed lung cells. Endocytosis of fluorescent or biotinylated TTR was observed in ependymoma cells in cytoplasmic vesicles but TTR did not colocalize with clathrin in endocytic coated vesicles. Endocytosis of TTR was inhibited by high sucrose concentration (0.45 M). Finally, ligand blotting and chemical-linking experiments revealed the presence of a approximately 100 kDa putative TTR receptor on the ependymoma cell membrane. Receptor binding of TTR provides a potential mechanism for the delivery of T4 within the central nervous system.

Flow cytometric quantification of surface-displayed recombinant receptors on staphylococci

Surface display of recombinant proteins on bacteria and phages has become an important tool in bioscience. To evaluate the various host systems, a great need exists for quantitative methods to determine the densities of displayed proteins and peptides on the bacteria and phage surfaces. Here we describe how a method previously applied for quantification of surface proteins on mammalian cells has been adapted for quantification of chimeric receptors surface-displayed on bacteria; in this study, the bacteria being recombinant staphylococci. The presented method takes advantage of fluorescence-activated cell sorting (FACS) technology and a new type of nonfluorescent plastic beads, similar in size (2 microns in diameter) to bacterial cells, and thus suitable for generation of calibration curves from which the number of chimeric receptors can be obtained. The method was used to estimate the number of antigenic sites on two types of recombinant staphylococci, both carrying heterologous chimeric receptors, and it was found that the recombinant Staphylococcus carnosus cells carried approximately 10(4) surface-displayed antigenic sites, while recombinant Staphylococcus xylosus exposed approximately 3 x 10(3) sites per cell. The use of the deviced method for different applications is discussed.

[The detection of microalbuminuria by using a recombinant albumin receptor]

Methods of ELISA competitive binding and blotting on nitrocellulose membranes were developed for detecting microalbuminuria in diabetic nephropathy. These methods are based on the use of recombinant albumin receptor. They are highly specific and sensitive and are recommended for everyday clinical use.

Transport of serum transthyretin into chicken oocytes. A receptor-mediated mechanism

Transthyretin (TTR) is involved in the transport of thyroid hormones and, due to its interaction with serum retinol-binding protein, also of vitamin A. The importance of both ligands in vertebrate embryonic development has prompted us to investigate the molecular details of TTR transport function in a powerful germ cell system, the rapidly growing chicken oocytes. Yolk TTR is derived from the circulatory system, since biotinylated TTR was recovered by immunoaffinity chromatography of yolk obtained from a hen previously infused with in vitro biotinylated chicken serum proteins. In concordance with the intraoocytic localization in an endosomal compartment, ligand blotting and chemical cross-linking experiments revealed the presence of a approximately 115-kDa TTR-binding oocyte membrane protein. This putative TTR receptor was not detected in chicken ovarian granulosa cells or embryonic fibroblasts and was different from the previously described oocyte-specific receptor for two estrogen-induced chicken serum lipoproteins, vitellogenin and very low density lipoprotein (Barber, D. L., Sanders, E. J., Aebersold, R., and Schneider, W. J. (1991) J. Biol. Chem. 266, 18761-18770). Furthermore, in contrast to the serum levels of the yolk precursor lipoproteins, those of TTR were not significantly changed by estrogen; thus, TTR represents a newly defined, estrogen-independent class of yolk precursor proteins. These data strongly suggest that oocytic TTR is derived from the circulation, where it is a constitutive component, and deposited into yolk as a result of endocytosis mediated by a specific receptor.

M12 protein from Streptococcus pyogenes is a receptor for immunoglobulin G3 and human albumin

We previously showed that M12 protein from opacity factor-negative Streptococcus pyogenes (group A streptococci) CS24 is responsible for immunoglobulin G3 (IgG3) binding activity. Here, we report that this M protein binds human serum albumin (HSA). Deletion analysis showed that the C repeats are sufficient for binding HSA, although upstream regions may be required for optimal binding. Like protein G, IgG3 and HSA bind to independent domains in the M protein. Experiments showed that bound IgG3 did not inhibit HSA binding to the M protein. The interaction between M12 protein and HSA is specific. M12 protein does not bind chicken egg and bovine serum albumins. Alignments of C1 and C2 repeats of M12 protein to sequences at the carboxy termini of other M proteins and Ig receptors revealed highly homologous sequences in the FcRV, M5, M6, ML2.1, and M57 proteins, suggesting that all could bind HSA. As predicted from the alignment, M5 protein and M6+ streptococci bound HSA, whereas an isogenic M6- mutant did not bind HSA. Furthermore, M2 protein from an opacity factor-positive strain also bound HSA.