Innervation of submandibular and sublingual glands in elderly donated cadavers: a preliminary histological study of differences in nerve morphology between mucous and serous acini

The human major sublingual gland and its neuropeptidergic and nitrergic innervations

BACKGROUND

What textbooks usually call the sublingual gland in humans is in reality a tissue mass of two types of salivary glands, the anteriorly located consisting of a cluster of minor sublingual glands and the posteriorly located major sublingual gland with its outlet via Bartholin's duct. Only recently, the adrenergic and cholinergic innervations of the major sublingual gland was reported, while information regarding the neuropeptidergic and nitrergic innervations is still lacking.

METHODS

Bioptic and autoptic specimens of the human major sublingual gland were examined by means of immunohistochemistry for the presence of vasoactive intestinal peptide (VIP)-, neuropeptide Y (NPY)-, substance P (SP)-, calcitonin gene related-peptide (CGRP)-, and neuronal nitric oxide synthase (nNOS)-labeled neuronal structures.

RESULTS

As to the neuropeptidergic innervation of secretory cells (here in the form of mucous tubular and seromucous cells), the findings showed many VIP-containing nerves, few NPY- and SP-containing nerves and a lack of CGRP-labeled nerves. As to the neuropeptidergic innervation of vessels, the number of VIP-containing nerves was modest, while, of the other neuropeptide-containing nerves under study, only few (SP and CGRP) to very few (NPY) nerves were observed. As to the nitrergic innervation, nNOS-containing nerves were very few close to secretory cells and even absent around vessels.

CONCLUSION

The various innervation patterns may suggest potential transmission mechanisms involved in secretory and vascular responses of the major sublingual gland.

Tyrosine-hydroxylase, dopamine β-hydroxylase and choline acetyltransferase-like immunoreactive fibres in the human major sublingual gland

OBJECTIVE

To study the innervation of the major sublingual gland by means of immunohistochemistry.

DESIGN

Bioptic and autoptic specimens of the major sublingual gland of humans were examined for the presence of immunoreactivity to tyrosine hydroxylase and dopamine-β-hydroxylase, on one hand, and choline acetyltransferase, on the other, to indicate adrenergic and cholinergic nerves, respectively.

RESULTS

Acini and ducts were supplied by both divisions of the autonomic nervous system.

CONCLUSIONS

Mucous and seromucous cells of the human major sublingual glands may respond with secretion not only to parasympathetic activity but also to sympathetic activity. The major sublingual gland is therefore a potential contributor to the mucin secretion recently reported in the literature in response to high sympathetic activity during physical exercise.

Introduction and validation of a new semi-automated method to determine sympathetic fiber density in target tissues

In recent years, the role of sympathetic nervous fibers in chronic inflammation has become increasingly evident. At the onset of inflammation, sympathetic activity is increased in the affected tissue. However, sympathetic fibers are largely absent from chronically inflamed tissue. Apparently, there is a very dynamic relationship between sympathetic innervation and the immune system in areas of inflammation, and hence a rapid and easy method for quantification of nerve fiber density of target organs is of great value to answer potential research questions. Currently, nervous fiber densities are either determined by tedious manual counting, which is not suitable for high throughput approaches, or by expensive automated processes relying on specialized software and high-end microscopy equipment. Usually, tyrosine hydroxylase (TH) is used as the marker for sympathetic fibers. In order to overcome the current quantification bottleneck with a cost-efficient alternative, an automated process was established and compared to the classic manual approach of counting TH-positive sympathetic fibers. Since TH is not exclusively expressed on sympathetic fibers, but also in a number of catecholamine-producing cells, a prerequisite for automated determination of fiber densities is to reliably distinct between cells and fibers. Therefore, an additional staining using peripherin exclusively expressed in nervous fibers as a secondary marker was established. Using this novel approach, we studied the spleens from a syndecan-3 knockout (SDC3KO) mouse line, and demonstrated equal results on SNS fiber density for both manual and automated counts (Manual counts: wildtype: 22.57 +/- 11.72 fibers per mm²; ko: 31.95 +/- 18.85 fibers per mm²; p = 0.05; Automated counts: wildtype: 31.6 +/- 18.98 fibers per mm²; ko: 45.49 +/- 19.65 fibers per mm²; p = 0.02). In conclusion, this new and simple method can be used as a high-throughput approach to reliably and quickly estimate SNS nerve fiber density in target tissues.

Morphological differences in innervation between mucous glands and serous glands: a quantitative histological study using the sublingual glands of elderly humans

CONCLUSION

In the sublingual gland, the serous lobule usually carried a higher density of NSE-positive nerve elements than the mucous lobule, whereas the mucous acinus in the mucous lobule was larger than the serous acinus in the serous lobule.

OBJECTIVES

To demonstrate quantitative differences in nerve elements between the mucous and serous lobules of sublingual glands.

METHODS

This study investigated using specimens from 14 donated cadavers (mean age = 78 years). Since immunohistochemistry for neuron-specific enolase (NSE) stains all nerves in addition to other mesenchymal cells possibly of nerve origin, the present quantitative evaluation was based on NSE-positive areas per visual field under a ×20 objective lens (0.6 × 0.45 mm when printed).

RESULTS

In mucous lobules, the areas occupied by NSE-positive nerve elements ranged from 5798-16,541 μm(2) (mean ± SD = 9280 ± 2584 μm(2)). In contrast, the corresponding areas in serous lobules ranged from 7853-23,540 μm(2) (mean ± SD = 13,520 ± 4351 μm(2)). The difference in NSE-positive areas was statistically significant (p = 0.0022). However, the mucous acinus in the mucous lobule was 2-times larger than the serous acinus in the serous lobule (2474 ± 1477 μm(2) vs 1119 ± 632 μm(2)).