125i tracers

IMB labelled with 125I and with nC is an ideal tracer for direct comparison of PET and SPECT (single photon emission computed tomography) for localization and quantification of neuroreceptors in the living human brain. 

Add a constant amount of radioiodinated ligand in a vol of 20 L. For the studies described in this chapter, we are using 5 nM unlabeled MCP-1 (monocyte chemoattractant protein-1), with a tracer concentration of 0.25-0.5 nM [125I]MCP-1. 

Analyte and analyte tracer (structurally similar to analyte, mostly 125I-analyte) compete for a small... 

I-insulin tracer is dissolved in entire volume of label hydrating buffer. 

I-insulin tracer lyophilized, is dissolved in 20 ml H20 bidest. It can be stored up to 24 hours at 2-8 °C after reconstitution. 

The binding values of 20 healthy blood donors were determined e.g. with 125I-human insulin tracer. It can be considered that a binding value higher than the mean value plus 3 standard deviations (e.g. 4.1 % B/T found with a tracer lot for human-insulin tracer binding) indicates the presence of antibodies. 

A commercially available RIA for determination of free anti-insulin antibodies (CIS bio international) was used for method comparison with insulin tracer binding test for Type I diabetic patients. The CIS test uses a 125I-porcine insulin tracer for insulin antibody determination. Linear regression analysis yielded a correlation coefficient of 0.94 for human insulin antibodies. The absolute binding values were 10-15 % lower in the commercial test than in the in-house test. 

Fig. 7. Renal plasma clearance of 125I-cystatin C (Ccy) compared to that of 51 Cr-EDTA (Cq-—edta) in rats with normal glomerular filtration ( ), and in rats with renal blood flow reduced to 25-50% of control by constricting the aorta above the renal arteries (o). The clearance measurements were completed 2.5-6.0 min after tracer injection. Ccy = 0.944 x Ccr-EDTA f = 0.989.

This lipophilic cationic cyanine dye, 339, a tumor specific localizing tracer, labelled with 125I in the 5,5 -positions, has been synthesized324 as outlined in equation 144. 

One of the most useful experimental methods to be applied to protein adsorption in recent years is the radiotracer technique (Mura-matsu, 1973). Proteins labeled with, 31I and 125I (Brash et al., 1974) and [14C]acetyl derivatives of proteins (Phillips et al., 1975) have been used as tracers. As well as measuring adsorption directly, this method has the great advantage that it can detect exchange between interface and bulk even when the total amount adsorbed does not vary. A technique that has been used to obtain independent measurements of the amount of protein adsorbed by measuring film thickness is ellipsometry (Trurnit, 1953). 

Antibodies with high specificity for 4-hydroxy-oestrogens have been obtained by use of a 17-(0-carboxymethyl)oxime-BS A conjugate as antigen the same hapten combined with [125I]iodohistamine was employed as radioactive tracer.135 Antisera... 

It is the responsibility of the individual laboratory to rigorously evaluate each new lot of IA kits for sensitivity, precision, accuracy, and specificity to assure assay reliability. Lot-to-lot variation in kit reagents has been verified by several authors with respect to digoxin RIA kits (187-189). It is necessary to assure the availability of a large number of kits with the same antibody lot from the manufacturer before the evaluation. Once the evaluation is found to be satisfactory, reservation of these kits should be made to cover the entire study. If a tracer lot has to be changed during a study (such as 125I label, which has a short shelf life), QC performance should be checked to ensure that assay performance... 

Fig. 23. Receptor binding affinities of [Thr,Nle]-CCK-9 (O) and DM-CCK ( ) after 45 min incubation with isolated rat pancreatic acini using 125I-BH-IThr.NleJ-CCK-9 as tracer.

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