Renin-positive granulated Goormaghtigh cells. Immunohistochemical and electron-microscopic studies on biopsies from patients with pseudo-Bartter syndrome.

It is difficult to distinguish between Goormaghtigh cells (G-cells) and media cells of the glomerular arterioles at the border of the Goormaghtigh cell field. Consequently, it has been unclear whether renin-positive G-cells are normally present and also whether renin-producing cells are recruited from the pool of renin-negative G-cells upon stimulation of the renin-angiotensin system (RAS). In the present study, immunohistochemical and electron-microscopic experiments have been carried out on serially sectioned kidney biopsies from four patients with pseudo-Bartter syndrome.

Hypothetical interpretation of the calcium paradox in renin secretion.

Most renin-positive cells of the preglomerular arteriole are intermediate in morphological appearence between smooth muscle cells and epithelioid cells. Intermediate cells contain, in addition to secretory granules, contractile proteins arranged as a sublemmal network. The paradoxical (inhibitory) role of calcium in renin secretion is explained, on the basis of these findings, by an increased tone of the sublemmal network; this might impair the preexocytotic access of renin granules to the cell membrane.

Morphology of electrophysiologically identified baroreceptor afferents and second order neurones in the brainstem of the cat.

Baroreceptor afferent fibres and second order baroreceptor neurones were identified by their discharge pattern and were intracellularly injected with horseradish peroxidase. Three afferent fibres and three second order neurones were reconstructed by camera lucida drawings from serial sections of the brainstem. The afferent fibres were classified as A delta-fibres and had terminal arborizations with synaptic boutons in the dorsomedial region of the nuclei of the solitary tract (TS).

Macroautophagic phenomena in renin granules.

The secretory granules of murine epithelioid cells take up and probably degrade mitochondria; they thus appear to have macroautophagic properties. As renin granules also have other properties uncommon for secretory granules, they are suggested to fulfill functions in these cells otherwise reserved for lysosomes.