Calcitonin gene-related peptide immunoreactive nerve fibers in the developing salivary glands of the rat

Distribution of nerve fibers during the development of palatine glands in rats

BACKGROUND

Salivary gland maturation and function are modulated by the nervous system. Nevertheless, little is known about salivary gland innervation during development, particularly minor salivary glands. This study investigated the development of the innervation of the palatine glands of rat.

MATERIALS AND METHODS

Frozen sections of rat palatine glands at different stages were immunohistochemically labeled for detection of the general nerve markers protein gene product 9.5 (PGP 9.5) and growth associated protein 43 (GAP-43), and the autonomic nerve markers calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY).

RESULTS

PGP 9.5 and GAP-43-immunoreactive fibers (IRF) were present in the mesenchyme and in association with developing acini, ducts and blood vessels. GAP-43-IRF were more abundant and diffuse than PGP 9.5-IRF at early stages, but showed similar distribution with growth, ramifying out from thick bundles in connective tissues until encircling the secretory units observed around postnatal day 21 (PN21). CGRP-IRF were detected in the mesenchyme at embryonic day 20 (E20) and PN0. CGRP-IRF became numerous around PN7 and PN10. They then decreased to the adult level at PN21, mainly located around ducts and infrequently blood vessels. NPY-IRF were sparsely detected in the mesenchyme at E20, then detected in close proximity to acini in addition to blood vessels at PN3. NPY-IRF increased till reaching the adult stage, and were mainly associated with blood vessels and around mucous cells and some serous demilunes.

CONCLUSION

The findings indicated a developmental modification of the sensory and autonomic innervation which may play a role in the functional maturation of the palatine salivary glands.

Distribution of sympathetic and afferent neurones innervating the submandibular gland in the sheep

The distribution of sympathetic and sensory neurones innervating the submandibular gland (SMG) in sheep was studied using retrograde tracing technique. The retrograde tracer Fast Blue (FB) was unilaterally injected into the SMG in five juvenile male sheep under general anaesthesia. After a 4-week survival period, all the animals were reanaesthetized, perfused transcardially with 4% buffered paraformaldehyde and ganglia, which could be considered as a potential sources of sympathetic, and afferent innervation of the gland were bilaterally collected. The FB-labelled sympathetic neurones were found in the ipsilateral superior and middle cervical ganglion. Many labelled neurones were distributed in the ipsilateral jugular and nodose ganglia of the vagus nerve and smaller numbers of the nerve cells were also found in ipsilateral C1-C3 dorsal root ganglia (DRG). No labelled neurones were observed in the ipsilateral stellate ganglion, trigeminal ganglion, C4-C8 DRG and in all contralateral ganglia. The present study revealed that the majority of sympathetic neurones projecting to the sheep SMG are found in the superior cervical ganglion but some of them are also distributed in the middle cervical ganglion. Most of the afferent neurones are located in the jugular and nodose ganglia of vagus nerve but C1-C3 DRG also comprise some of these nerve cells.

Phenotypes in canalicular adenoma of human minor salivary glands reflect the interplay of altered secretory product, absent neuro-effector relationships and the diversity of the microenvironment

AIMS

Uncertainty about the factors influencing phenotypes in salivary canalicular adenoma prompted the present investigation.

METHODS AND RESULTS

Specimens of canalicular adenoma from 15 patients were examined with the use of histology, histochemistry for protein, mucosubstances and pigments, nerve staining and immunocytochemistry for cytoskeleton components. The tumours consisted largely of simple cells lining tubules that were occasionally cystic or branching and budding, and were set in loose, vascular and often haemorrhagic stroma. Other phenotypes recognized were mucous cells, apocrine-like cells, pigmented cells, microliths and stromal macrophages, detected in 26.6%, 20%, 33.3%, 20% and 53. 3% of the patients, respectively. Simple cells showed moderate levels of -SH groups and strong immunoreactivity for 'simple' epithelial phenotype cytokeratin. The simple cells lining cystic tubules showed additional immunoreactivity for 'stratified' epithelial phenotype cytokeratin, possibly an adaptation to mechanical pressure. Lumina showed variable levels of neutral and carboxylated glycoproteins, and chondroitin sulphate. Stroma showed high levels of chondroitin sulphate and hyaluronic acid. Mucous cells showed high levels of -SS- groups and nonsulphated glycoproteins. Apocrine-like cells contained lipofuscin. Pigmented cells contained haemosiderin, possibly a consequence of localized iron overload. Microliths contained mucosubstances. Macrophages often contained lipofuscin. No nerves were found in relation to the tumours.

CONCLUSIONS

The results suggest that, contrary to popular belief, phenotypes in canalicular adenoma do not reflect histogenetic concepts but rather may derive from the interplay between an altered secretory product, consisting of glycosaminoglycan and an immature form of glycoprotein, the lack of neuro-effector relationships and the different microenvironments throughout the tumour.

Localisation of VIP-and CGRP-like substances in the skin and sinus hair follicles of various mammalian species

Using an ultrastructural postembedding immunogold technique, we demonstrated vasoactive intestinal polypeptide (VIP)- and calcitonin gene-related peptide (CGRP)-like immunoreactivity in the Merkel cell dense-cored granules of skin and sinus hair follicles of adult cat and dog. The VIP-like substance was located in cat Merkel cells while both VIP- and CGRP-like substances were colocalised in dog Merkel cells. In cat Merkel cells, the magnitude of labelling of VIP was qualitatively higher than in dog Merkel cells. In the dog Merkel cell, CGRP appeared as the most abundant peptide. Dense-cored granules were labelled for these peptides. In addition, mast cells encountered in the dermal region of dog skin were also found to be immunolabelled by VIP antiserum. The immunoreaction was found to be confined to the secretory granules of the cells. Furthermore, all non-myelinated nerve plexuses encountered in the dermal region of the skin and the sinus hair follicles of the various mammalian species studied were immunolabelled by CGRP antiserum. The specific location was again restricted to the dense-cored granules present in these nerves. As VIP and CGRP have potent vasodilatory effects, our observations suggest that Merkel cells may play a separate or synergistic role in regulatory functions of the skin neuroendocrine cell, exerting their influence by paracrine, endocrine and neurocrine pathways, or a combination of these. Different methodologies of double labelling with different sizes of gold particles are also discussed.

Calcitonin gene-related peptide (CGRP) and its effects on protein release in vitro in the developing submandibular gland of the rat

Indirect immunohistochemical methods were used to study presence and number of CGRP-immunoreactive (CGRP-IR) nerve fibers in the submandibular gland and ganglion cells of the superior cervical, submandibular and trigeminal ganglia of the developing rat. The effect of CGRP on peroxidase and total protein release was also studied in the developing postnatal submandibular glands of 1, 5, 12 and 30-day-old, as well as adult rats by in vitro methods. The possible costimulation of CGRP with SP, NKA or carbachol on 5-day-old and adult rats was also tested. The stimulatory effects of these compounds were compared to the basic release of peroxidase and total amount of proteins from submandibular gland fragments in incubation solution. CGRP-IR nerve fibers were found in relatively high number during post-natal development, mainly around blood vessels and ducts. Some CGRP-IR nerve fibers were also detected around acini. The number of these fibers was quite low and remained constant during the post-natal development. The number of CGRP-IR trigeminal ganglion cells was higher on the 5th and 12th post-natal day than later in development and in adult animals. At the same time, superior cervical- and submandibular ganglion cells were non-reactive for CGRP, suggesting trigeminal origin of CGRP-IR nerve fibers during the development in the submandibular gland. In the secretory studies, CGRP per se stimulated both peroxidase and total protein release in the submandibular gland most effectively on 5th and 12th post-natal days, while there was no clear secretory response in the adult glands. In the 5-day-old submandibular gland CGRP in combination with SP, NKA or carbachol clearly enhanced the total protein secretory response when compared with the release caused by these substances alone. However, in the adult submandibular gland, the combinations did not enhance total protein release more than any of the substances alone. Furthermore, it can be concluded that the presence of a more dense CGRP-IR innervation during the early postnatal period in the developing submandibular gland is accompanied with an increased responsiveness of the secretory elements to CGRP.