The Neuroendocrine System in the Intestinal Tract
and Pancreas of Antarctic Fish
Grazia Tagliafierro, Marina Carlini, Gabriella Faraldi, and Lorenzo Gallus
Istituto di Anatomia Comparata, Universita di Genova, 16132 Genova, Italy
Introduction
The neuroendocrine system (NBS) is composed of endocrine cells and
nerve elements containing a large variety of low molecular weight
peptides; they are generally called neuropeptides or regulatory peptides
and are contained in secretory granules. The endocrine cells can be
grouped to form endocrine glands such as the pancreas, or they can be
found, as single elements, within the epithelial component of different
organs, such as the gut and the respiratory tract. The epithelial endocrine
cells lie on the basement membrane and frequently have a cytoplasmic
process extending to the lumen; this basal-granulated cell is called the
open type endocrine cell. Other basal-granulated cells do not reach the
lumen, and are called the closed type endocrine cell; the latter cell type
lies flat on the basement membrane [1]. In both cases the release of the
granule content occurs at the base of the cell near a blood vessel [2].
There is also the possibility that a small portion of the product of
secretion is released into the gut lumen. The apical release of regulatory
peptides can be compared to the dendritic release of messengers in bipolar
neurons [3]. The peptide-secreting nerve elements, both neuron somata
and nerve fibers, are distributed throughout the central and the peripheral
nervous system. No anatomical boundaries are present between the
endocrine and the nerve compartment, often sharing identical, or nearly
identical, bioactive substances, viewed as the gene products of neuroendocrine cells. The bioactive substances released by the nervous and the
endocrine compartments may function as neurotransmitters and/or
neuromodulators, or they may diffuse to the blood and act as hormones, or
they can also diffuse locally, acting as paracrine messengers on target
neighboring cells.
The Enteropancreatic Neuroendocrine System in Teleosts
The NBS of the enteropancreatic tract is relatively well known, being the
object of research for about 30 years. Most results have been gained on
O. di Prisco, E. Pisano, A. Clarke (Eds)
Fishes of Antarctica. A biological overview
© Springer-Verlag Italia 1998
and Pancreas of Antarctic Fish
Grazia Tagliafierro, Marina Carlini, Gabriella Faraldi, and Lorenzo Gallus
Istituto di Anatomia Comparata, Universita di Genova, 16132 Genova, Italy
Introduction
The neuroendocrine system (NBS) is composed of endocrine cells and
nerve elements containing a large variety of low molecular weight
peptides; they are generally called neuropeptides or regulatory peptides
and are contained in secretory granules. The endocrine cells can be
grouped to form endocrine glands such as the pancreas, or they can be
found, as single elements, within the epithelial component of different
organs, such as the gut and the respiratory tract. The epithelial endocrine
cells lie on the basement membrane and frequently have a cytoplasmic
process extending to the lumen; this basal-granulated cell is called the
open type endocrine cell. Other basal-granulated cells do not reach the
lumen, and are called the closed type endocrine cell; the latter cell type
lies flat on the basement membrane [1]. In both cases the release of the
granule content occurs at the base of the cell near a blood vessel [2].
There is also the possibility that a small portion of the product of
secretion is released into the gut lumen. The apical release of regulatory
peptides can be compared to the dendritic release of messengers in bipolar
neurons [3]. The peptide-secreting nerve elements, both neuron somata
and nerve fibers, are distributed throughout the central and the peripheral
nervous system. No anatomical boundaries are present between the
endocrine and the nerve compartment, often sharing identical, or nearly
identical, bioactive substances, viewed as the gene products of neuroendocrine cells. The bioactive substances released by the nervous and the
endocrine compartments may function as neurotransmitters and/or
neuromodulators, or they may diffuse to the blood and act as hormones, or
they can also diffuse locally, acting as paracrine messengers on target
neighboring cells.
The Enteropancreatic Neuroendocrine System in Teleosts
The NBS of the enteropancreatic tract is relatively well known, being the
object of research for about 30 years. Most results have been gained on
O. di Prisco, E. Pisano, A. Clarke (Eds)
Fishes of Antarctica. A biological overview
© Springer-Verlag Italia 1998