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PubMed1990

[Endocrine cells and Malpighian epithelium. Merkel-type cells? Immunohistochemical and ultrastructural study].

This study was devoted to a peculiar population of argyrophilic cells present among various stratified squamous epithelia. The purpose of the study was to determine the distribution and the nature of these argyrophilic cells, and to reappraise their degree of analogy with the Merkel cells of epidermis. Examples of squamous epithelia from skin, exocervix, anal canal and dermoid cyst of ovary were investigated using histochemical, immunohistochemical and ultrastructural techniques. Melanin-containing cells as well as peculiar argyrophilic cells were revealed in each series of specimens. These peculiar argyrophilic cells expressed EMA, chromogranin A and NCL-5D3 (cytokeratins 19, 18, 8) immunoreactivities. By contrast, they were serotonin negative. An intense staining for EMA was observed. These cells were obviously endocrine cells. Ultrastructural studies confirmed the presence of endocrine cells within the anal canal and the exocervix; moreover, in anal canal, some of these cells appeared to have contacts with a nerve terminal. Through the epidermis, these cells can only correspond to Merkel cells, because of their chromogranin positivity. Throughout other squamous epithelia, this population of endocrine cells (serotonin negative) bear some analogies with Merkel cells of epidermis. Their distribution, morphology, EMA immunoreactivity and ultrastructural appearance were reminiscent of those of the Merkel cells. They could be named Merkel-type cells. Additional studies, using other characteristic or specific markers of Merkel cells, are clearly required to determine the exact degree of analogy between these types of cells. Merkel-type cells could be largely distributed through stratified squamous epithelia from various tissues. They can be easily visualized by their strong EMA immunoreactivity and must be distinguished from Paget cells.

Endocrine Glands↗
PubMed1980

Branched cells in the epidermis: an overview.

Current knowledge concerning the nature, lineage, and function of the Langerhans cell, Merkel cell, and, to a lesser extent, the melanocyte, are reviewed under headings that emphasize the confederate constitution of the epidermis as a compound tissue composed of a variety of cellular elements; the role of the lymphocyte as a component of normal epidermis is also considered. It appears that the function of the Langerhans cell has finally been established, i.e., it serves as a front-line element in immune reactions of the skin. Developmentally, it is of mesenchymal origin. The Merkel cell still presents a number of problems centering around questions of its lineage, the nature of its characteristic granules, and the "synaptic" relationship between it and the associated neurite. The melanocyte continues to hold the attention of investigators, mainly from the point of view of the chemistry of melanin and the rational treatment of pigmentary disorders based upon findings derived from fundamental research into all aspects of its biology.

Animals↗
PubMedDate not supplied

[Cutaneous neuroendocrine carcinoma. Apropos of a case].

Cutaneous neuroendocrine carcinoma (CNEC) is a rare tumour. We report the case of a 75-year old woman affected with a rapidly progressive CNEC of the right cheek which kept recurring despite surgical excision followed by radiotherapy. The clinical features of CNEC are not specific. The tumour is located in the dermis, and the tumoral cells (Merkel cells) have a monotonous appearance. Gould's classification of these carcinomas into three types has a prognostic value. Immunohistochemistry is a mandatory complement to light microscope examination. It is very difficult to distinguish between CNEC and metastasis from a visceral small cell carcinoma. Treatment consists of surgery combined with radiotherapy. Chemotherapy was very successful in our patient and should be considered in other cases.

Aged↗
PubMed2000

Expressions of putative neurotransmitters and neuronal growth related genes in Merkel cell-neurite complexes of the rats.

Reverse transcription-polymerase chain reaction using 32P-labeled dCTP with specific primers for putative neurotransmitters related and neuronal growth-related genes (GAP-43, NGF and BDNF) were used to search for evidence of such substances in the Merkel cell. Merkel cell samples were made from sinus hairs in the facial skin of rats. The relative amount of mRNA in a tissue sample concentrated in Merkel cells was compared semiquantitatively to that from nearby tissue without Merkel cells. mRNAs for VIP, tyrosine hydroxylase, substance P were found in higher concentration in Merkel cells than in control tissues. mRNA for genes encoding pro-enkephalin, GAP-43, CGRP, NGF and BDNF were detected in the Merkel cell samples at concentration statistically equivalent to those found in the control tissues. It was concluded that the relative concentration of mRNAs for VIP, tyrosine hydroxylase and substance P is consistent with the possibility that Merkel cell acts as a possible transduction element in mechanical excitation of sense organs in which Merkel cells are present.

Animals↗
PubMed1994

Immunohistochemical demonstration of keratin 19 expression in isolated human hair follicles.

We examined keratins 19 and 8 in extracted human hair follicles using monoclonal antibodies Ks19.1 and CAM5.2, respectively. Ks19.1 reactivity was found in the bulge and infundibulum. Ks19.1(+) cells were dense in the bulge of vellus and intermediate hair follicles. The intact bulge of terminal hair could not be extracted, but the presence of Ks19.1(+) cells was confirmed in transverse sections. Infundibular Ks19.1(+) cells exhibited a dense network pattern of staining in terminal hair follicle, but only a few cells were labeled in vellus and intermediate hair follicles. CAM5.2(+) cells, i.e., Merkel cells, were found in the same locations as Ks19.1(+) cells but were less dense. These patterns of distribution and staining density were not influenced by different phases of hair cycle. Sequential staining of Ks19.1 and CAM5.2 in the same hair follicle demonstrated that the same cells could be reactive for both. However, considering the large number of Ks19.1(+) cells and rather small number of CAM5.2 in the same locations, it was assumed that only a subset of Ks19.1(+) cells are Merkel cells. It was postulated that the bulge area of human adult hair follicles houses embryonic pluripotential cells characterized by stem cells and post-stem cells and that the Merkel cells in the bulge area arise from these immature cells and may play a role in the maintenance and stimulation of this group of immature cells.

Aged↗
PubMed1992

Calcium-binding proteins in chemoreceptors of Xenopus laevis.

Calcium-binding proteins were investigated immunohistochemically in chemo-receptors of the olfactory epithelium and taste buds of the clawed frog, Xenopus laevis. Calmodulin-, S-100- and calbindin-immunoreactive material were found in sensory cells of the olfactory epithelium; however, parvalbumin-like material was absent in these cells. Taste buds of the palate showed calmodulin-, S-100- and parvalbumin-immunoreactive material in sensory cells, while calbindin-immunoreactive material in supporting cells. Merkel cells, surrounding the base of the taste buds in a ring-like manner, exhibited calmodulin- and S-100-immunoreactive material.

Animals↗