Mammotrope heterogeneity in the pituitary gland of European ferret, M ustela putorius Juro: An immunoelectron-microscopic study.

Employing the superimposition technique of electron-microscopic immunocytochemistry ultrastructural heterogeneity of the mammοtropes in the pituitary gland of the European ferret, Mustela putorius furo, was studied. On the basis of the size of their secretory granules, the mammotropes were classified into three subtypes, type-I, type-II and type-Ill, which may correspond to different developmental or physiological states of a single cell type. Simultaneous study of mammotropes and somatotropes in several pairs of serial semithin sections demonstrated the occasional occurrence of bihormonal somatomammotropes/ mammosomatotropes which may represent a transitional stage of the progenitor stem-somatotrope during its differentiation into mammotrope; alternatively it may be a functional intermediate during the cross-transformation of somatotrope into mammotrope or vice versa.

Comparison of the determination of insulin by a monoclonal antibody-based immunofluorometric assay and by radioimmunoassay

This paper describes an immunofluorometric assay (IFMA) for insulin and compares it with the classical radioimmunoassay (RIA). Monoclonal antibodies against insulin were produced and used to develop the IFMA. One, immobilized on microtiter plates, was used for capture, the other, labelled with Europium, was used as tracer antibody. The IFMA presentes sensitivity to an amount of insulin of 3 pmol/1 and acceptable valueus for intra- and interassay error. The IFMA presented superimposable curves for human insulin, Arg65/Gly66-split proinsulin and des-Lys64, Arg65, and no cross-reactivity with human proinsulin, Arg32/Glu33 -split and des-Arg31, Arg32. The RIA showed 100 percent cross-reactivity with human proinsulin, 90 pecent with des-Arg31, Arg32 and 170 percent with des-Lys64, Arg65. The assay were used to measure insulin in 300 serum samples from 50 subjects submitted to an oral glucose tolerance test (OGTT). Twenty were normal, 10 had impaired glucose tolerance and 20 non-insulin-dependent diabetes mellitus. The mean value (ñ SEM) obtained bu IFMA was 166.7 ñ 12.1 pmol/1 and the mean value obtained by RIA was 339.6 ñ 18.6, with a correlacion of r = 0.80 (P0.01). Comparison of basal insulin levels of the different groups of individuals using IFMA or RIA led to the same conclusions. The area under curve showed statistically significant differences only for the comparison between normal lean subjects and individuals with impaired glucose tolerance, when measured by RIA...(au)