Immunocytochemical characterization of glucagon-immunoreactive cells using monoclonal antibodies to pancreatic glucagon

Colocalization of numerous immunoreactivities in endocrine cells of the chicken proventriculus at hatching

The colocalization of regulatory peptide immunoreactivities in endocrine cells of the chicken proventriculus at hatching has been investigated using the avidin-biotin technique in serial sections and double immunofluorescence in the same section for light microscopy, and double immunogold staining for electron microscopy. In addition to the eight immunoreactivities previously described in this organ, cells immunoreactive for peptide histidine isoleucine (PHI), peptide gene product 9.5 (PGP), and the amidating enzyme, peptidylglycine alpha-amidating monooxygenase (PAM) were observed. All the cells immunoreactive to glucagon were also immunostained by the PHI antiserum. In addition, all the glucagon-like peptide 1, avian pancreatic polypeptide, and some of the neurotensin-like cells costored also glucagon- and PHI-immunoreactive substances. PGP- and PAM-immunoreactivities were also found in the glucagon-positive cells. A small proportion of the somatostatin-containing cells were positive for PHI but not for other regulatory peptides. These results could suggest either the existence of a very complex regulatory system or that the endocrine system of the newborn chickens is not yet fully developed.

Quantitative anatomy, synaptic connectivity and physiology of amacrine cells with glucagon-like immunoreactivity in the turtle retina

Although a wide variety of neuropeptides have been localized in vertebrate retinas, many questions remain about the function of these peptides and the amacrine cells that contain them. This is because many of these peptidergic amacrine cells have been studied using only immunocylochemical techniques. To address this limitation, the present study used a combination of quantitative anatomy, biochemistry and electrophysiology to examine amacrine cells in the turtle retina that contain the neuropeptide glucagon. In the turtle retina, there is a small population of 2500 glucagonergic amacrine cells, which probably represents < 1% of the total number of amacrine cells. Circular distribution statistics indicated that many of these tristratified amacrine cells had asymmetric dendritic arborizations that were radially oriented toward the retinal periphery. The cells were found to have similar dendritic coverage factors, to be distributed in a non-random arrangement in all regions of the retina, and to peak in density in the visual streak region. Electron microscopic studies indicated that glucagonergic amacrine cells made synaptic contacts primarily with other amacrine cells, and small numbers of bipolar cells. The synaptic inputs and outputs were balanced in the inner strata of the inner plexiform layer, and were biased toward synaptic outputs in the outer strata of the inner plexiform layer. These contacts involved small unlabelled synaptic vesicles, and not the large labelled dense core vesicles also found in these neurons. The biochemical studies indicated that glucagon could be released from the retina in a calcium dependent manner by high potassium stimulation. The electrophysiology found no color opponency, and the glucagonergic amacrine cells gave sustained hyperpolarizing responses to small stimulation spots and had antagonistic surrounds. The results of these studies suggest that there are significant regional specializations of glucagonergic amacrine cells, and that they may provide OFF-modulation in interactions between the ON-and OFF-centre visual pathways in the turtle retina.

Release of somatostatin immunoreactivity from human antral D cells in culture

A primary culture of human antral somatostatin cells has been developed and used in release studies. The phorbol ester, phorbol 12 myristate 13-acetate, caused a concentration-dependent increase in immunoreactive somatostatin secretion with a 1-mumol/L concentration resulting in a 40-fold stimulation (basal 0.28% +/- 0.7% total cell content vs. 13.8% +/- 2.2% TCC, P less than 0.005). The calcium ionophore, A23187, resulted in a significant stimulation only at 1 mumol/L (basal 0.28% +/- 0.7% TCC vs. 2.2% +/- 0.5% total cell content, P less than 0.05). However, addition of the ionophore at 1 mumol/L with the phorbol ester resulted in a potentiation of the response at all concentrations tested. Removal of extracellular calcium by chelation with EGTA reduced the response to that seen with the phorbol ester alone. Forskolin at 0.1 mmol/L resulted in a five-fold increase (basal 0.6% +/- 0.2% total cell content vs. 2.8% +/- 0.9% total cell content, P less than 0.02) and was 1000-fold less potent than the phorbol ester. The peptides bombesin and gastrin at concentrations up to 1 mumol/L had no effect on basal secretion. Cholecystokinin-8 significantly stimulated somatostatin secretion with a maximal effect at 0.1 mumol/L resulting in an eightfold increase (basal 0.2% +/- 0.04% total cell content vs. 1.5% +/- 0.4% total cell content, P less than 0.02). These results indicate that human antral D cells are more responsive to agents acting through the c-kinase pathway (phorbol 12 myristate 13-acetate, A23187, and cholecystokinin) than adenylate cyclase (forskolin).

Development of the dorsal pancreatic primordium transplanted into the third ventricle of rats

The dorsal pancreatic primordia of 12.5-day-old rat embryos transplanted into the third ventricle of adult female rats were immunohistochemically examined 10, 20 and 40 days after transplantation. On day 10, the grafts grew into an epithelial sacculus (S) with a thick subepithelial tissue (ST). Tubular and vesicular structures with a single cuboidal epithelium were found within the wall of the S, but they underwent thereafter a regression without allowing the primordia to differentiate into the exocrine acinar tissues. In contrast with this, pancreatic hormone-containing cells existed in the ST, and were arranged like the islands of a mature animal. The tissue also has smooth muscle fibers and neurons. When the primordium was grafted along with its root connected to the duodenum, gut-like tubular structures differentiated, showing mucosa with villi and crypts, submucous mesenchymal tissue and muscle layers. The mucosa possesses epithelial cells immunoreactive for the pancreatic hormones, and the muscle layers have the myenteric plexuses. These findings seem to provide further evidence that in the rat pancreas, pancreatic-hormone-containing cells differ from the acinar cells in origin.

Monoclonal antibodies against calcitonin. Characterization and application in light and electron microscopy immunocytochemistry

Twenty-seven monoclonal antibodies (MAbs) to synthetic human calcitonin (CT) were characterized for their reactivities with human CT peptide fragments by dot-blot analysis on nitrocellulose paper. Most of the antibodies bound to the C-terminus and fewer to the mid-region of CT. We have studied thyroid tissue specimens from several animal species after fixation in paraformaldehyde-, glutaraldehyde- or picric acid-containing mixtures and cryostat sectioning or embedment in paraffin or plastic (Epon 812 or Lowicryl 4KM) using this panel of MAbs. The site of antigen-antibody reaction was revealed either by immunoperoxidase, immunoalkaline phosphatase or by silver-enhanced immunogold staining methods. All MAbs were able to localize CT in human, rat and mouse thyroid C cells. Nineteen MAbs recognizing synthetic salmon CT and synthetic [Asu1,7]-eel CT by dot-blot, reacted with chicken ultimobranchial body C cells. One MAb recognizing native porcine CT by dot-blot, stained C cells in hog thyroid. Immunopositivity was confined to the cytoplasm and ultrastructural immunogold labelling demonstrated that cytoplasmic secretory granules were stained. Surgical specimens from human medullary thyroid carcinoma were also analysed for the presence of CT and a variable number of positive cells was found. Furthermore, Congo red-positive areas were shown to react with the MAbs. All conventional staining and immunoabsorption controls were negative. Hence, these MAbs may be suitable for use in routine immunopathological diagnosis of CT-producing tumors and for immunocytochemical localization of the three major CT variants in different animal species.