Histochemistry and electron microscopy of the three cell types in the adrenal gland of the frog

Histogenesis and morphofunctional characteristics of chromaffin cells

This article reviews the current status of research about the histogenesis and morphofunctional characteristics of chromaffin cells in the adrenal medulla. First, this study reports the selective migration, transcription and activation factors, and the morphological events of the chromaffin cell precursors during adrenal medulla development. Subsequently, the morphofunctional characteristics of adrenergic and non-adrenergic cells are considered, with particular reference to the characteristics of chromaffin granules and their biological steps, including their formation, traffic (storage, targeting and docking), exocytosis in the strict sense and recapture. Moreover, the relationship of chromaffin cells with other tissue components of the adrenal medulla is also revised, comprising the ganglion cells, sustentacular cells, nerves and connective-vascular tissue.

Segmental restriction and target specificity of bullfrog preganglionic neurons that exhibit galanin-like immunoreactivity

These experiments were designed to examine the distribution of galanin-like peptide immunoreactivity (GAL-IR) in bullfrog sympathetic preganglionic neurons and to identify the peripheral target organs affected by these neurons. Cells expressing GAL-IR were observed in the intermediolateral column of segments 7 and 8 only. Apparent GAL-IR innervation is present, but rare, in sympathetic chain ganglia. Double-labelling with retrogradely transported fast blue and galanin antiserum demonstrated that most GAL-IR neurons project via splanchnic nerves to innervate the adrenal gland, which receives a dense plexus of GAL-IR fibers surrounding chromaffin cells. The adrenal gland is also innervated by preganglionic neurons in segments 5 and 6 that do not express GAL-IR. Because nitric oxide is expressed in sympathoadrenal preganglionic neurons in mammals (Anderson, C.R., Neurosci. Lett., 139 (1992) 280), we examined whether it is expressed in bullfrog preganglionic neurons. Nicotinamide adenine dinucleotide phosphate-diaphorase positive neurons are present in bullfrog spinal grey at segments 5 through 8. These neurons were not double-labelled with fast blue retrogradely transported from the sympathetic chain, celiac ganglion, or adrenal gland; nor were they double-labelled with GAL-antiserum. Thus nitric oxide is apparently not expressed in bullfrog sympathetic preganglionic neurons.

Identification of small intensely fluorescent (SIF) cells as chromaffin cells in bullfrog sympathetic ganglia

Small intensely fluoresent (SIF) cells were investigated in the ninth and tenth paravertebral sympathetic ganglia of the bullfrog using histochemical and electron microscopic techniques. Fluorescence histochemistry revealed that clusters of SIF cells are sparsely distributed in the ninth and tenth ganglia; the clusters were usually located in the vicinity of blood vessels. Fluorescent processes were not observed emanating from SIF cells. The clusters stained positively for the chromaffin reaction indicating that SIF cells are chromaffin cells. Ultrastructurally, the SIF-chromaffin cells in the sympathetic ganglia appeared virtually identical to the chromaffin cells in the adrenal gland; this includes two cell types that appear morphologically the same as the epinephrine and norepinephrine containing chromaffin cells in the adrenal gland. Efferent synapses from the SIF-chromaffin cells in sympathetic ganglia to sympathetic ganglia to sympathetic neurons were not observed. The SIF-chromaffin cells in bullfrog sympathetic ganglia did not have the morphological characteristics of interneurons; it is suggested that they may function as extra-adrenal chromaffin tissue.