Nerve terminals and epithelial cell variety in the human lacrimal gland

Abstract

Pieces of tissue taken from three human lacrimal glands were examined electron microscopically. Secretory cells varied according to the electron density and structure of their secretion granules. Secretory cells were arbitrarily categorized as light, medium or dark based on their granule content. Acini were composed of two or all three categories of cells together with myoepithelial cells and lymphocytes. A minority ogic, sympathetic terminals. The appearance of most interstitial and all parenchymal fibres was consistent with that of cholinergic, parasympathetic terminals. Parenchymal terminals were confined to ducts, terminal tubule areas and to serous (dark) cells. A large proportion of parenchymal terminals lay adjacent to myoepithelial cells in the ducts and terminal tubule regions but terminals observed among serous cells were rarely in contact with myoepithelial cells. A possible parasympathetic control of serous secretion, granule production and duct contraction and the autonomy of mucous cells is discussed.

Morphological observations on the Harderian gland of the North American opossum (Didelphis virginiana)

“…Interestingly these may belong to the 7/6 T-cell lineage which has been shown to have a tropism for epithelial microenvironments (Bonneville et al 1988). The unusual dendritiform shape of the cells described in the human lacrimal gland (Ruskell 1975) and in the opossum Harderian gland may support this proposal, as 7/6 T-cells are known to have a dendritic form when situated in epithelia (Stingl et al 1987). More noticeable lymphoid aggregates are evident in the avian Harderian gland (Mueller et al 1971 ;Albini et al 1974;Burns 1979;Schramm 1980) where a greater immune role has been postulated.…”

“…According to Sakai (1989) who has conducted an extensive review of the literature with regard to lacrimal glands in eutherian mammals, true intercellular canaliculi are absent in these glands. Although Ruskell (1975) and others (Iwamato and Jakobiec 1982) have described the presence of intercellular canaliculi in human lacrimal gland, convincing morphological evidcnce has not been presented to support their claims. Thus the presence in true intercellular canaliculi between serous cells of the opossum Harderian gland is apparently the first clear demonstration of these structures in ocular glands.…”

“…This may indicate that this gland synthesises IgA and other antibodies which are important in immune defence on the ocular surface. The presence of moderate numbers of intraepithelial lymphocytes in the human lacrimal gland has been documented (Ruskell 1975). Interestingly these may belong to the 7/6 T-cell lineage which has been shown to have a tropism for epithelial microenvironments (Bonneville et al 1988).…”

Histology, Histochemistry and Fine Structure of the Lacrimal and Nictitans Gland in the South American ArmadilloChaetophractus villosus (Xenarthra, Mammalia)

“…According to Sakai (1989) true intercellular canaliculi are absent in the LG of eutherian mammals. However, several authors claimed the presence of intercellular canaliculi in LG (Ichikawa and Nakajima, 1962;Ku È hnel 1968b,c,d;Ruskell, 1975;Iwamoto and Jakobiec, 1990), although not showing convincing morphologic evidence. Our results, as far as we know, provide the ®rst clear demonstration of intercellular canaliculi in the LG.…”

Regulation of Lacrimal Gland Secretion by Neurotransmitters and the EGF Family of Growth Factors

“…Parasympathetic nerves containing VIP have been identi®ed (Ruskell, 1975;Sibony et al, 1988). VIP also appears to stimulate tear secretion from human lacrimal gland (Gilbard et al, 1988).…”