New enzyme-linked immunosorbent digoxin assay on the ADVIA IMS 800i system is virtually free from interference of endogenous digoxin-like immunoreactive factors.

Endogenous digoxin-like immunoreactive factors (DLIF) may crossreact with antidigoxin antibody and falsely elevate immunoassay results. Recently, a new enzyme-linked immunosorbent chemiluminescent assay for digoxin has been available for use on the ADVIA IMS (Integrated Modular System) 800i analyzer (Bayer Diagnostics). We studied potential interference of DLIF with this new digoxin assay. We analyzed 30 serum specimens from patients who have pathologic conditions that may increase serum DLIF concentrations. These patients were never exposed to digoxin or other agents that may lead to a measurable digoxin concentration. We also analyzed 10 specimens from neonates, 10 cord blood specimens, and 10 amniotic fluid specimens. Apparent digoxin concentrations were measured using the new enzyme-linked immunosorbent digoxin assay (IMS-Digoxin), a fluorescence polarization immunoassay (FPIA), and also a chemiluminescent immunoassay (CLIA, run on ACS:180(R) system from Bayer Diagnostics). We observed measurable apparent digoxin levels with the FPIA in 4 uremic patients (range 0.21-0.36 ng/mL, digoxin equivalent), 7 patients with liver disease (range 0.21-0.72 ng/mL), and 3 patients in the third trimester of pregnancy (0.22-0.66 ng/mL). We also observed measurable DLIF concentrations with the FPIA in 2 neonates (0.22 and 0.36 ng/mL), 5 cord blood specimens (range 0.21-1.18 ng/mL), and 5 amniotic fluid specimens (0.21-0.50 ng/mL). None of these DLIF-positive specimens showed any measurable digoxin concentration using the IMS-Digoxin or the CLIA assay. When serum specimens containing elevated concentrations of DLIF but no digoxin (as measured by FPIA) were supplemented with known concentrations of digoxin, we observed falsely elevated digoxin concentrations, as expected, only by the FPIA. In contrast, we observed a good agreement between the target and observed concentrations when the new IMS-Digoxin or the CLIA assay was used. We conclude that the IMS-Digoxin assay is free from interference of DLIF.

Endocrine-dependent accumulation of IGF-I by hypothalamic glia.

Tanycytes are specialized glial cells of the hypothalamus and median eminence. Immunoreactive insulin-like growth factor I (IGF-I) levels fluctuate in tanycytes with the natural variations in sex steroids associated with the ovarian cycle. To determine whether these changes are as a result of differences in IGF-I accumulation, the peptide was labelled with digoxigenin and injected into the lateral cerebral ventricle. Tanycyte-like cells specifically accumulated digoxigenin-labelled IGF-I. This accumulation was mediated by IGF-I receptors and showed marked differences during the oestrous cycle, being low in the afternoon of pro-oestrus and high in the afternoon of oestrus. These results indicate that the accumulation by tanycytes of IGF-I or IGF-I fragments capable of receptor-mediated internalization is under endocrine control, suggesting that hypothalamic glia may be involved in neuroendocrine regulation.

In situ hybridization with digoxigenin-labelled RNA probes for detection procollagen 1 (I)

A localizaçao celular do pró-colágeno 1(I) foi observada na interface de coral natural, sete dias após implante no nosso trabecular de ratos, utilizando-se sondas de RNA marcadas com digoxigenina. A eficácia deste método foi comparada com aquela de sondas de RNA marcadas com enxofre(35). A hibridizaçäo "in situ" realizada utilizando-se sondas de RNA de osteoblastos, marcada com digoxigenina, provou ser täo eficiente quanto aquela marcada com S(35). Embora a porcentagem de fibroblastos marcados com S(35) tenha sido maior do que aqueles marcados com digoxigenina, näo houve diferença significante quanto à eficiência dos dois métodos

Cellular uptake of intracerebroventricularly administered biotin- or digoxigenin-labeled antisense oligodeoxynucleotides in the rat.

1. Antisense oligodeoxynucleotides (ODNs) internally labeled with biotin or digoxigenin were injected into the lateral ventricle of rats and the distribution of the labeled ODNs was examined at several timepoints following the intracerebroventricular (icv) injections. The stability of these injected antisense ODNs, which had no backbone modifications, was also studied by performing recovery experiments. 2. The most intense labeling was observed near the injection site, in periventricular areas, and in perivascular regions. Many of the labeled cells appeared to be neurons, and both the cytoplasm and the nuclei were stained. The labeled cells were detected 15 min after icv injection, demonstrating that the antisense ODNs were taken up rapidly by cells in the parenchyma. The digoxigeninated antisense ODNs were presented in both the cytoplasmic and the nuclear fractions of rat brain extracts, however, the levels appeared to be much lower in the nuclear fractions. 3. Antisense ODNs injected into the lateral ventricle seemed to follow the bulk flow of cerebrospinal fluid (CSF), i.e., from the injection site in the lateral ventricle, through the ventricular system, to the subarachnoid spaces and the perivascular spaces. From the ventricular and perivascular spaces, the antisense ODNs diffused into the extracellular space and were taken up by cells. The full-length digoxigeninated antisense ODNs were detectable within cells after only 15 min, indicating their rapid uptake. In addition, the antisense ODNs appeared to be relatively stable in the brain since the full-length digoxigeninated ODNs were still detectable after 4 hr.