Morphology and glycoconjugate histochemistry of the palpebral glands of the adult newt, Notophthalmus viridescens

Abstract

The eyelids of the newt were studied in 10 microns serial paraffin and 1-2 microns plastic sections using standard histological stains and special stains for glycoconjugates. The eyelids contain four different glands. Simple acinar serous and simple acinar mucous glands occur in the skin; unicellular mucous glands occur in the conjunctiva; and convoluted tubular seromucous glands are present in connective tissue beneath the conjunctiva. The first two are identical to cutaneous glands found elsewhere on the head and body. The simple acinar serous glands are surrounded by myoepithelial cells and release their secretion, which is composed largely of proteins with minimal glycoconjugate content, by a holocrine mechanism. The secretory product of the simple acinar mucous glands is composed of neutral glycoconjugates with a minor content of acidic glycoconjugates; the mucin exhibits strong PAS and PAPD staining and weak staining by AB and PAPS methods. The unicellular conjunctival mucous glands secrete both neutral and acidic glycoconjugates as shown by positive reactions with PAS, PAPD, PAPS, and AB methods. Convoluted tubular seromucous glands in the ventral eyelid synthesize both proteins and neutral glycoconjugates. The mucous secretions of the conjunctival glands probably provide lubrication and protection for the cornea.

The morphology of the dorsal and ventral skin of Triturus karelinii (Caudata: Salamandridae)

“…During the secretory cycle, small granules were subsequently formed. Similar results have been reported in two urodele species by Navas et al (1982) and Reyer et al (1992). In these species, secretory epithelium of serous glands consists of individual large-sized cells with acidophilic cytoplasm and small secretory granules produced at the beginning of the secretory cycle.…”

Light and transmission electron microscopic structure of skin glands and dermal scales of a caecilian amphibian Gegeneophis ramaswamii, with a note on antimicrobial property of skin gland secretion

“…The cell membrane disappears from the core of the gland during the final stage of maturation. It results in a syncytial gland (Navas, Bueno, Hidalgo, Aijon, & Lopez-Campos, 1982;Reyer, Liou, & Pinkstaff, 1992. Syncytial granular glands have already been described in the caecilian amphibians (Lawson, 1963).…”

Three types of cutaneous glands in the skin of the salamandrid Pleurodeles waltl. A histological and ultrastructural study

“…The fact that small, immature, organelle-rich and vesicle-poor cells are located in the apical gland pole and that large, mature, organelle-poor and vesicle-rich cells are found in the basal gland pole, strengths the hypothesis that secretory cells proliferate from apical to basal within the MGs. Earlier authors reported that a myoepithelium in MGs is absent or poorly developed and discontinuous (Dawson, 1920;Quay, 1972;Reyer et al, 1992). Some authors (Helf and Stark, 1941;Quay, 1972;Hoffman and Dent, 1978) also observed glandular secretion in the MG-lumen and argued that MGs secrete in an apocrine way, continuously secreting mucus to the exterior.…”

“…Most authors agree that amphibian skin contains two main glandular types: first, the lumenbearing mucous glands with cells containing flocculent to granular material, second the granular (''serous'') glands which often form syncytia and are built up by cells containing granular material (Reyer et al, 1992;e.g., Duellman and Trueb, 1994;Toledo and Jared, 1995;Fontana et al, 2006). MGs are mainly responsible for producing mucopolysaccharides and mucoproteoglycans.…”