Biomedical subjects

I Mariz

Publications and source records attributed to I Mariz.

2 recordsLinked to original sources

PubMed1987

Serum somatomedin binding proteins: physiologic significance and interference in radioligand assay.

Mammalian sera contain binding proteins that specifically complex with somatomedins (insulin-like growth factor I and II) so that there are no detectable free somatomedins. There is immunologic evidence of two distinct types of serum binding proteins. The major binding protein complex (150,000 Mr) is growth hormone dependent. Binding proteins protect somatomedins from proteolytic degradation, retard plasma clearance, and decrease the availability to tissue receptors. The presence of serum binding proteins interferes with radioimmunoassays and radioreceptor assays for somatomedins. Proposed strategies to neutralize the interference from binding proteins without their elimination do not achieve this goal. Extraction of somatomedins by acid ethanol, hydrophobic absorption on C18 silicates (SepPak), and acid gel filtration are effective with human serum, but only acid gel filtration is satisfactory with rat serum. Failure to eliminate binding proteins from assays can lead to serious artifacts in conditions where abnormalities of binding proteins exist.

Acromegaly↗

PubMed1982

Isolation and partial sequence analysis of rat basic somatomedin.

Rat basic somatomedin (Sm) was prepared with an improved purification scheme from the pooled sera of Wistar Furth rats previously inoculated with cells from the pituitary tumor MStT/W15. Amicon hollow fiber diafiltration facilitated the processing of large batches of serum, eliminating the necessity of running smaller portions of material on gel filtration columns to achieve the same qualitative separation. The yield from this technique was excellent. Basic rat Sm was separated from a C3ades Arg component of complement by a narrow pH range isoelectric focusing step. Subsequent chromatography on carboxymethyl-cellulose and Sephadex resins was very efficient, providing a 100-fold purification, with a recovery of Sm activity of approximately 65%. The final product was judged to be pure by a variety of criteria. Structural analysis of this material has demonstrated that the amino-terminal sequences of rat basic Sm and human insulin-like growth factor I are strikingly similar, confirming the homology proposed earlier on the basis of receptor cross-reactivity.

Amino Acid Sequence↗