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The expression of soluble N-ethyl-maleimide sensitive fusion attachment protein receptor (SNARE) proteins in apocrine glands has not been fully elucidated. In addition to performing ultrastructural observation of the ceruminous glands in goats, our study focuses on the demonstration of β-defensins, SNARE proteins and Rab3D in these glands with the use of immunohistochemical methods. The secretory cells were equipped with two types of vesicles, Golgi apparatus and abundant rough endoplasmic reticulum (ER). Additionally, in some of them, the characteristic concentric structures composed of rough ER were observed in their circum- and infranuclear parts. The expression of phosphorylated inositol requiring enzyme 1a was also detected. These findings may indicate their ability to produce numerous secretory proteins and the maintenance of homeostasis in the glandular cells. Furthermore, β-defensins were demonstrated as products of the ceruminous glands. The present investigation also revealed the presence of SNARE proteins and Rab3D. It is suggested that these proteins are concerned with the secretory machinery of this gland type.

In contrast to the well defined mechanism of merocrine exocytosis, the mechanism of apocrine secretion, which was first described over 180 years ago, remains relatively uncharacterized. We identified apocrine secretory activity in the late prepupal salivary glands of Drosophila melanogaster just prior to the execution of programmed cell death (PCD). The excellent genetic tools available in Drosophila provide an opportunity to dissect for the first time the molecular and mechanistic aspects of this process. A prerequisite for such an analysis is to have pivotal immunohistochemical, ultrastructural, biochemical and proteomic data that fully characterize the process. Here we present data showing that the Drosophila salivary glands release all kinds of cellular proteins by an apocrine mechanism including cytoskeletal, cytosolic, mitochondrial, nuclear and nucleolar components. Surprisingly, the apocrine release of these proteins displays a temporal pattern with the sequential release of some proteins (e.g. transcription factor BR-C, tumor suppressor p127, cytoskeletal β-tubulin, non-muscle myosin) earlier than others (e.g. filamentous actin, nuclear lamin, mitochondrial pyruvate dehydrogenase). Although the apocrine release of proteins takes place just prior to the execution of an apoptotic program, the nuclear DNA is never released. Western blotting indicates that the secreted proteins remain undegraded in the lumen. Following apocrine secretion, the salivary gland cells remain quite vital, as they retain highly active transcriptional and protein synthetic activity.

The present paper describes two distinct morphological features of ovine interdigital sinus, which were examined by means of scanning electron microscopy. In the sweat glandular component, acini with epithelial cells exhibiting a paved appearance and apocrine secretion were observed. In the same gland, other acini with cells exhibiting different luminal surfaces and simultaneous apocrine and merocrine secretion were recorded. The numerous hairs embedded within the waxy material of the sinus exhibited two types. The first type, with a round profile, had a special leaflet structure on the tip, whereas the second type had a convex profile. The comparative differences and probable functional relations of these integumentary structures are discussed. The mixed picture of the epithelial cells of the sweat glands suggests the release of different products. The hair microstructure correlated with the mechanism of hold and release of the secretory material of the interdigital sinus.

This article describes the scanning electron microscopic (SEM) features of the ovine interdigital sinus. The lumen was filled with a dense secretory material and quite a number of hairs embedded in the luminal content. For SEM purposes, the sinus was divided into three parts: base, body and neck. At the cut surface, the wall exhibited significant folds which were almost absent in the base, the very short blind end of the sinus. The wall had three layers: epidermis, dermis and fibrous capsule. Stratified epithelium with a prominent keratin layer faced the lumen. The inner surface was similar to the skin surface; however, it was coarser due to folds. The fibrous capsule was composed mainly of dense connective tissue, constituting the outermost layer of the wall. The dermis contained common skin structures including sebaceous glands, hair follicles, arrector pili muscles and apocrine glands. Sebaceous glands appeared as groups of bubbles if they were not collapsed. Apocrine glands generally appeared as a group of coiled tubules. They frequently exhibited apocrine blebs, which is a feature of apocrine secretion. SEM was able to locate some secretory vesicles in the lumen of apocrine tubules which is frequently filled by secretory content. Thus, the apocrine tubules exhibited classical features of apocrine secretion.

Cytochemistry of glycoconjugates in the apocrine glands in the scrotal skin of the horse was studied using cytochemical methods for electron microscopy, particularly lectin cytochemistry. The secretory cells possessed a variable number of secretory vesicles, a well-developed Golgi apparatus, and abundant cisternae of the rough endoplasmic reticulum. Additionally, the basolateral plasma membrane formed numerous interdigitating folds. Glycoconjugates with vicinal diol groupings were present predominantly in the secretory vesicles, the Golgi apparatus, the surface coat of the plasma membrane, and the majority of the intracellular membranes. With lectin cytochemistry, the secretory vesicles of the glandular cells exhibited glycoproteins with different terminal sugars (alpha-D-mannose, beta-D-galactose beta-N-acetyl-D-glucosamine, and sialic acid). Several sugars were distinctly prominent in the surface coat of the plasma membrane of the secretory cells. The cytochemical properties of the complex glycoconjugates found are discussed in relation to the specific functions of the glandular secretions. These glands may have an important role in not only thermoregulation but protection of the scrotal skin, a specific body region.

The function of the human gland of Moll of the eyelid is not exactly known. We studied the secretory and cytoskeletal components of these apocrine glands in males and females by immunohistochemical methods, and the ultrastructural organization of the glandular cells with an electron microscope. The glands of Moll are exclusively located at the margin of the eyelids and their ducts empty into the lash follicle. Immunohistochemical staining for actin and cytokeratins CK19 and CK7 points to the involvement of actin in the pinching-off mechanism of the apical cell protrusion during apocrine secretion and to a stabilizing role for the cytokeratins in this apical region of the glandular cells. The presence of the bacteriolytic enzyme lysozyme, the membrane-associated mucin 1, and the immunoglobulin A and its secretory component within the gland suggest a function in local immune defense. The presence of a variety of sugar components in the secretory product was verified by lectin histochemistry and periodic acid Schiff and Alcian blue stain. We suppose that these apocrine glands are active from birth in producing agents against pathogenic microorganisms in the eyelid shaft and on the ocular surface.

An apocrine adenocarcinoma was observed in the subcutis of the abdomen of golden hamster. Histologically, the tumor cells irregularly formed multiple layers of cysts and some detached cells were presented in the cystic space. PAS stain with alpha-amylase digestion revealed PAS-positive alpha-amylase-resistant granules in the cytoplasm. Immunohistochemically, cytokeratin was demonstrated in the tumor cells. By electron microscopy, the tumor cells had an oval nucleus with invagination, abundant cytoplasmic organelles and microvilli protruding into the intercellular spaces.

The products of the human apocrine axillary glands contain volatile steroids which act as pheromones. The steroidal structure of these pheromones implies that the axillary glands should be able to synthesize cholesterol which is the essential precursor of these molecules. Since important steps in cholesterol synthesis are localized within peroxisomes, we investigated the occurrence and the putative role of peroxisomes in the axillary glands at protein and mRNA levels by immunocytochemistry, Western blotting, and RT-PCR. Numerous peroxisomes were localized in the cells of the apocrine glands by immunocytochemistry, and the presence of catalase was confirmed by Western blotting and RT-PCR. Additionally, RT-PCR revealed the presence of mRNAs of two peroxisome-associated enzymes of the cholesterol biosynthetic pathway, mevalonate kinase and farnesyl diphosphate synthase. The results suggest that the peroxisomes in the human apocrine axillary glands may play a pivotal role in the biosynthesis of pheromones.

A 13-year-old male Shetland Sheepdog with progressive exophthalmos had a neoplastic mass in the ocular adnexa. Histologically, this neoplasm was composed of duct-forming epithelial cells with decapitation secretion. Tumor cells invaded the globe through the tunica conjunctiva and replaced the vitreous body. The cornea, iris, ciliary body, and retina were extensively destroyed. Both the epithelial and spindle-shaped myoepithelial cells showed nuclear atypia and mitotic activity in the globe. The primary tumor was diagnosed as adenocarcinoma, probably originating from apocrine sweat glands of the eyelid, and the infiltrating intraocular neoplasm was diagnosed as a malignant mixed tumor.

Alkaline phosphatase (ALP) is a membrane-bound enzyme that catalyzes the hydrolysis of inorganic and organic monophosphate esters at alkaline pH. Although the functions of ALP are poorly understood, it is believed to be involved in membrane transport. Because little is known about the functions and distribution of ALP in the sweat glands, we studied the localization of ALP in human sweat glands with light and electron microscopic enzyme cytochemistry. In eccrine sweat glands, ALP was restricted to the cell membranes of intercellular canaliculi. Luminal cell membranes of secretory cells that are in continuity with intercellular canaliculi did not show ALP activity. These results suggest that ALP participates in the production of primary sweat at intercellular canaliculi. In apocrine sweat glands, basal cell membranes of secretory cells and myoepithelial cell membranes that were in apposition with each other showed ALP activity, where as no activity was seen in eccrine sweat glands. These differences in the distribution of ALP in myoepithelial cells between eccrine and apocrine sweat glands might be related to the functional differences of these sweat glands. ALP histochemistry could help to diagnose and to determine the direction of differentiation in sweat gland tumors.

We studied the localization of the epidermal growth factor (EGF) in eccrine and apocrine sweat glands with light microscopic and electron microscopic immunohistochemistry. Anti-human EGF (anti-hEGF) polyclonal antiserum and anti-hEGF monoclonal antibody (MAb) were used for the study. Light microscopic immunohistochemistry with monoclonal and polyclonal antibodies showed that hEGF-like immunoreactivity was strongly positive in the myoepithelial cells and weakly positive in the secretory cells of eccrine sweat glands. In apocrine sweat glands, it was strongly positive in the secretory cells as well as in the myoepithelial cells. Immunoelectron microscopy with polyclonal antibody showed that hEGF-like immunoreactivity was present in secretory granules of apocrine secretory cells. These granules had mitochondrion-like internal structure. No reactivity was observed on the eccrine secretory cells by immunoelectron microscopy. Neither dark cell granules nor mitochondria in eccrine secretory cells were labeled with anti-hEGF antibody. In both eccrine and apocrine sweat glands, hEGF-like immunoreactivity was diffusely present in the cytoplasm of myoepithelial cells. However, nuclei and mitochondria of myoepithelial cells were devoid of immunoreactivity for hEGF. Our observations indicate that apocrine sweat glands may secrete more hEGF in the sweat than eccrine sweat glands.

The secretory portion of the apocrine sweat gland of the human external auditory meatus which is also called the ceruminous gland was observed by transmission and scanning electron microscopy. The secretory glandular cells contain a well developed smooth endoplasmic reticulum and Golgi apparatus. Cisternae of rough endoplasmic reticulum are often closely applied to large round mitochondria. These large mitochondria have no relationship to the secretory granules. Near the concave surface of the Golgi lamellae several tubules can be found. In these golgi-associated tubules a dark substance may accumulate to form specific large dense granules. Many less dense droplets or vacuoles may appear in these dark prosecretory granules and become liberated from their surface. Vacuoles formed in this manner then migrate to the apical cell surface and often discharge their contents into the gland lumen by the mechanism of exocytosis. Also, some of these vacuoles may be released into the lumen by the pinching off of small protrusions of cytoplasm, that is, they are released by the so-called apocrine secretory mechanism. Acid phosphatase activity was demonstrated not only in the dark prosecretory granules but also in clear vacuoles situated at the apical end of the cell and in the gland lumen. Such a histochemical finding may indicate that the secretory substance of the apocrine sweat gland may contain hydrolytic enzymes derived from lysosomes, which are the prosecretory granules of this gland, and these enzymes may play a role in dissolution and break down of the material extruded into the lumen by apocrine secretion. Apocrine secretory process of various sizes were observed on the luminal surface with the scanning electron microscope.

Electron microscopic examination of apocrine glands revealed three types of secretion: merocrine apocrine, and possible holocrine. In the merocrine type of secretion numerous vesicles originating in the Golgi area discharged their granular contents into the lumen of the gland. In the apocrine type of secretion three stages were observed: (1) formation of an apical cap; (2) formation of a dividing membrane at the base of the apical cap; and (3) formation of tubules avove the dividing membrand that extended parallel to the membrane and led to a separation of the apical cap from the underlying cell, In the holocrine type of secretion individual secretory cells or even strands of secretory cells were dischard into the lumen of the gland.

The acrosyringium of human apocrine sweat apparatus has been studied by light and electron microscopy using horizontal continuous serial sections. The apocrine acrosyringium is composed of 3 structurally different portions, a highly keratinizing upper portion, an incompletely keratinizing midportion, and a least keratinizing lower portion. Throughout these 3 portions, there are 2 distinctly different but closely inter-related cellular units, namely (I) a keratinization process lacking membrane-coating granules but containing keratohyalin droplets occurring in its inner cell layer, and (II) a keratinization process rich in membrane-coating granules and containing keratohyalin granules occurring in its outer surrounding concentric cell layers. In contrast to the inner cell layer, the outer cell layer does not belong to the duct proper but rather should be considered as the periacrosyringeal complex layer which is specially differentiated to envelop the intra-epithelial duct. This apocrine acrosyringeal complex in the hair follicle seems to be essentially similar to that of the eccrine apparatus in the epidermis.

Lipid synthesis by freshly isolated human apocrine glands has been measured by the incorporation of [U-14C] acetate. Incorporation is linear over 6 h at 1010 +/- 282 pmol/mg wet weight/h (n = 11; mean +/- sem). The lipid classes, as percentages of the total lipid synthesized, were found by TLC to be cholesterol 12.3 +/- 2.0, mono-glycerides 7.5 +/- 1.5, 1,2 di-glycerides 3.0 +/- 0.9, 1,3 di-glycerides 3.5 +/- 0.5, tri-glycerides 28.4 +/- 1.8, free fatty acids 2.0 +/- 0.4, lysolecithin 15.4 +/- 3.9, sphingomyelin 9.9 +/- 4.3, phosphatidyl-choline 8.4 +/- 0.4, phosphatidyl-ethanolamine -inositol and -serine 1.8 +/- 0.1, phosphatidic acid and cardiolipin 3.3 +/- 0.5, and unidentified 3.3 +/- 0.5 (mean +/- sem, n = 5). Glands were maintained on permeable supports. After 10 d maintenance, electron microscopy showed that the cellular architecture had been preserved, that the ATP contents were the same as in freshly isolated glands, and that [U-14C] acetate incorporation was not significantly altered at 851 +/- 237 pmol/mg/h (n = 18). The addition of 3 microM testosterone had no effect on acetate incorporation at 844 +/- 231 pmol/mg/h (n = 18). The lipid classes and their proportions were similar to the values for fresh glands after 10 d maintenance both with and without testosterone.

The sweat ducts of human eccrine and apocrine (ceruminous) glands were observed with the transmission electron microscope. Both the dermal and epidermal segment of the eccrine as well as apocrine ducts consist of two epithelial layers: luminal cells and peripheral cells. Well-developed microvilli, occurrence of cored vesicles, dense granules, multivesicular bodies and phagosomes in the adluminal filamentous zone, and a strong accumulation of mitochondria in the basal part of the duct epithelium at the dermal segment, as well as an accumulation of small clear vesicles beneath the surface of the luminal cells of the epidermal segment are all prominent in the eccrine duct and concomitant with the special function of the human eccrine duct, i.e., absorption of ions to make the sweat hyotonic and an active endocytosis of some material from the sweat. All of the above enumerated characteristics of the eccrine duct are only rarely or never seen in the apocrine duct. On the other hand, lipid droplets appear in the peripheral cells in a certain level of the apocrine duct near its orifice into the hair follicle, suggesting a kind of metaplasia towards the sebaceous gland. Epidermal duct cells of both eccrine and apocrine sweat glands may keratinize. In the eccrine duct the process in the duct cells precedes the surrounding keratinocytes, while in the apocrine duct the relationship is reversed.

Light microscopic and electron microscopic studies of a lesion displaying a typical histopathological picture of syringocystadenoma papilliferum (S.P.) are reported. Light microscopic serial sections showed that the tumor parenchyma extended to the epithelium just above the intrafollicular sebaceous duct. The tumor thus presumably develops from the epithelial region corresponding to the intrafollicular duct of the apocrine sweat gland. Electron microscopy revealed a non-keratinized intracytoplasmic cavity and intercellular canaliculi apparently formed as a continuation of this cavity. Keratinized cells were absent from the glandular and duct epithelium and even from the superficial epithelial portion of acanthotic areas. Neither myoepithelial cells nor secretory granules were identified in areas showing tubular, glandular, or sinusoidal structures. It was concluded that the tumor differentiates towards both the intrafollicular and intradermal duct of the embryonic apocrine sweat gland apparatus.

The myoepithelial cells of the human ceruminous apocrine gland were observed with transmission and scanning electron microscopes. The myoepithelial cells are long fibrous cells about 100-150 mum in length and 3-5 mum in width. They are arranged in parallel with each other, and their long axes are parallel to that of the secretory tubule itself. The tips of cells are often sharply pointed and their lateral tapering surface may be contiguous with adjacent cells forming a side-by-side contact, while other cells may have a blunt tip which is conjuncted with a similar tip of the next cell forming an end-to-end junction. The myoepithelial cells are joined to each other by desmosomes and there are also desmosomes at their junction with secretory cells. The outer surface of the cell abutting on the basal lamina has some exaggerated densities which are undoubtedly identical to the hemidesmosomes of epidermal cells. There are well developed foldings in the plasma membrane of the secretory cells, but the surface of the myoepithelial cells has very few foldings and projections. The relative shortage of intercellular attachment devices between the secretory and myeopithelial cells makes it easy to peel off the secretory cells to disclose the myoepithelium, a useful feature of scanning electron microscopy. The nucleus-containing part of the cell protrudes slightly upward and invades the secretory epithelium. The cytoplasmic rim surrounding the nucleus contains a small Golgi apparatus and some other organelles. The cytoplasm of the basal half of the cell contains closely packed myofilaments running parallel to the long axis of the cell. There is no definite arrangement of thin and thick myofilaments. Microtubules which often occur in pairs are arranged parallel to the myofilaments.