Cytoplasm Of Clear Cells Research Articles

Ontogeny of small-granule APUD cells in hamster lung: a morphological study.

Development of small-granule APUD cells and cell clusters was studied in 13-day to 15-day fetal hamster lungs by periodic acid-Schiff (PAS)-lead hematoxylin staining, monoamine fluorescence, and transmission electron microscopy. We examined 11-day and 12-day fetal, early postnatal, and adult animals only by PAS-lead hematoxylin. Precursors of small-granule cells first appear as PAS-negative clear cells in proximal airways of 13-day lung, occurring singly or in clusters of 2-25 cells and standing out among their undifferentiated, glycogen-laden, PAS-positive neighbors. By 14 days, developing small-granule cell clusters are prominent in main and lobar bronchi, extending 2-3 airway generations into the periphery. Clear-cell clusters, similar to those seen in 13-day lung, appear in peripheral airways and reach within one generation of developing terminal sacs. By 15 days, a few small, small-granule cell clusters are located at bronchioloalveolar junctions. Comparatively mature clusters occur in proximal airways; they are characterized by specific formaldehyde-induced monoamine fluorescence demonstrable after exposure in vitro to 5-hydroxytryptophan. In early postnatal stages, PAS-positive granules are resolvable toward the base of some endocrine cells. Ultrastructurally, pulmonary APUD cells contain numerous membrane-limited granules (180-nm diameter) of varying electron density. In 13-day lung, granules sparsely populate the cytoplasm of clear cells, but as the cells mature, the granule population increases and becomes concentrated in the basal cytoplasm. Fetal development of small-granule cells is therefore compressed into the last 4 days before birth. Most clusters appearing in neonatal lungs are not yet fully mature, and not all subtypes of this population are present until some time later.

Ultrastructure of the perfused rat epididymis: effect of luminal sodium ion concentration.

The appearance of the rat epididymal epithelium changed when it was perfused in vivo through the lumen with unphysiologically high sodium ion concentrations; dilatation of intercellular spaces (ICS) at threshold concentrations of 30 mM-Na+ in the cauda and about 55 mM-Na+ in the corpus was associated with absorption of water from the lumen. Despite the distended ICS, junctional complexes appeared intact, and their integrity was confirmed by the exclusion of luminal horseradish peroxidase (HRP) from the ICS, and by demonstrating that circulating [3H]inulin did not enter the lumen. Smooth ER and lipid droplets in the principal cells of the corpus epididymidis were well maintained, and the preservation of granular ER in principal cells of the cauda epididymidis lent morphological support to the continued secretion of protein in this segment. However, occasional distension or involution of inner Golgi cisternae was evident in principal cells after 3-6 h perfusion. In contrast to multivesicular bodies of principal cells, the apical and basal vacuoles characteristic of clear cells changed in size with different perfusion. In contrast to multivesicular bodies of principal cells, the apical and basal vacuoles characteristic of clear cells changed in size with different perfusing solutions. When low Na+ concentrations were perfused large translucent vacuoles were frequently found in the apical cytoplasm of clear cells in the corpus and cauda epididymidis, and filled vacuoles became larger and showed a decrease in content density in the cauda epididymidis. These large vacuoles were absent from tissue perfused with high Na+ concentrations. Normal pinocytotic activity of both cell types was demonstrated by perfusing HRP which was taken up by the normal route in principal cells, with some transfer to the Golgi cisternae. By far the most HRP was accumulated in clear cell vacuoles irrespective of the composition of the perfusing solution.

Electron Microscope Studies on the Carpal Organ of the Pig

The eccrine sweat gland located in the subcutaneous tissue at the palmar side of carpal or metacarpal regions of forelegs of the pig (the carpal organ) was studied with the electron microscope. Besides the description of its fine structures, dicussions on the secretion mechanism of this gland are presented in this paper. The results obtained are summarized as follows.1. Two different cell types of the glandular epithelium which were previously pointed out by light microscopy (KITAMURA, 1957), namely the dark and clear cell, are clealy distinguished from each other under the electron microscope. The designation of two cell types may depend on the previous light microscopic observation, though appearances by light- and electron microscopy may often be reverse.2. Within the cytoplasm of the dark cell, there exist a great number of secretory granules or vacuoles. The electron density of these granules or vacuoles is so low that the electron optical appearance of this cell type is rather clear, in contrast to the image by light microscopy of stained preparations, in which the secretory granules are always darkly tinted. The secretory granule is surrounded by a dense smooth membrane (probably one type of the smooth surfaced variety of the endoplasmic reticulum). As it grows and ripens, its internal substance shows a marked decrease in density and the fusing of neighbouring granules occurs, then it converts into the secretory vacuole.3. A small number of mitochondria with high electron density are present in the dark cell cytoplasm. The rough surfaced variety of the endoplasmic reticulum is occasionally observed to be localized at the infranuclear zone. Furthermore, small dense particles (microsomes) and microvesicles are abundant within the cytoplasm, especially in the interstices among the secretory grauules. It was forcibly convinced from many electron micrographs that granules of varying sizes and densities might be transitional forms from one to another of each of the microsomes, microvesicles, secretory granules and secretory vacuoles.The GOLGI apparatus consists of GOLGI vesicles, several pairs of GOLGI membranes and GOLGI vacuoles, which are probably produced either by the expantion of GOLGI vesicles or by the terminal vacuolation of flattened sacs, viz. GOLGI double membranes. It is difficult, in some cases, to distinguish the GOLGI vacuole from the secretory granules.4. The secretory granules of the clear cell are generally opaque to the electron beam and are small in number. These often situate in the vicinity of the crescent-shaped endoplasmic reticulum (rough surfaced). Somtimes, extremely dense granules with irregular outline were observed; they might be identified as fat droplets.5. As compared with the dark cell, far more numerous mitochondria are contained in the clear cell. They have marked limiting membranes and internal ridges (cristae mitochondriales), both of which are electron dense and show a double membraned structure. There have been recognized various transitional steps from the mitochondria to the secretory granules of the clear cell.6. In the clear cell cytoplasm, were observed to be scattered many microsomes and thread-like or tubular structures. The latter may be considered to be produced by chaining of microsomes, and sometimes they aggregate in a compact mass of peculiar crescent shape, which is found to surround the nucleus at the supra- and paranuclear sides maintaining a roughly uniform distance apart the nucleus. This crescent-shaped structure was found under the ordinary light microscope to be strongly basophilic. The constituent elements of such a crescent-shaped mass possess the characteristic of typical endoplasmic reticulum (rough surfaced); but in the case that thread-like or tubular structures are dispersed throughout the cytoplasm, the characteristics of the endoplasmic reticulum are obscure in such distributed bodies.