Immunocytochemical demonstration of 5-hydroxytryptamine (serotonin) in the nervous system of the liver fluke, Fasciola hepatica (Trematoda, Digenea)

The localisation and distribution of 5-hydroxytryptamine (5-HT or serotonin) in the nervous system of Fasciola hepatica has been determined by an indirect immunofluorescence technique. Cell bodies and nerve fibres immunoreactive to 5-HT are present in the anterior ganglia, and the longitudinal nerve cords and their commissures in the central nervous system. In the peripheral nervous system, similar immunoreactivity occurs in the nerve plexuses supplying the sub-tegumental muscle layers and the muscular lining of various reproductive ducts, including the ootype, uterus and cirrus pouch. The significance of these results in the light of previous studies on the role of 5-HT in F. hepatica is discussed.

Neuroendocrine tumors. A European view

A center in Belfast, Northern Ireland, has established a register for tumors of the gastroenteropancreatic endocrine system. Carcinoid tumors occur most frequently. Of the non-carcinoid tumors, insulinomas, gastrinomas, and unknown types have the highest incidence, with other types being extremely rare. The potentially remediable nature of the tumors is stressed, and frequently a good quality of life can be experienced even in the presence of metastatic disease. The syndromes are probably underdiagnosed as they present with clinical features for which there are more common explanations, and appropriate diagnostic methods are therefore not used. The management of the syndromes is reviewed with particular emphasis on the treatment of patients with inoperable disease. Histamine (H2)-receptor antagonist therapy has made an impact in Zollinger-Ellison syndrome, and streptozotocin and somatostatin analogues can control tumor growth and endocrine syndromes, respectively.

Neuroendocrine cells within colorectal tumours induced by dimethylhydrazine. An immunocytochemical study

Colorectal adenocarcinomas were induced in male Wistar rats, by weekly subcutaneous administration of 1,2-dimethylhydrazine, classified according to the degree of differentiation and submitted to immunocytochemistry for the peptides cholecystokinin (CCK), gastrin, gastric inhibitory polypeptide (GIP), glucagon, neurotensin, pancreatic polypeptide (PP), peptide YY (PYY), somatostatin and vasoactive intestinal polypeptide (VIP) and the biogenic monoamine 5-hydroxytryptamine. Well- or moderately well-differentiated adenocarcinomas comprised 46% of the tumour population, only 4% were poorly-differentiated adenocarcinomas, and the remaining 50% possessed a mixture of these two morphologies. Glucagon, PYY and 5-hydroxytryptamine immunoreactive cells were frequently observed within well- or moderately well-differentiated tumours and within such regions of tumours possessing a mixed morphological pattern. The tumours contained no cells immunoreactive for any of the peptides not normally located within the colorectum, nor did they contain cells immunoreactive for somatostatin and VIP, although known positive controls did stain. Poorly-differentiated tumours and portions of tumours of mixed type, were consistently negative. 5-hydroxytryptamine was the most frequently located of the three antigens, being detected in 87% of the moderately well-differentiated tumours and 32% of the tumours with mixed morphologies. 11% of moderately well-differentiated tumours possessed 5-hydroxytryptamine positive cells in such profusion that they contributed significantly to the tumour mass. The distribution of glucagon- and PYY-immunoreactive cells was similar, although they occurred with a lower frequency, presumably corresponding to their lower numbers within the normal colorectal mucosa. Additionally, these two peptide immunoreactivities were colocalized in the majority of cells, although some cells contained only one antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Pancreatic polypeptide immunoreactivity in medullary carcinoma of the thyroid: identification and characterisation by radioimmunoassay, immunocytochemistry and high performance liquid chromatography

Pancreatic polypeptide immunoreactivity has been identified in primary medullary carcinoma of thyroid using radioimmunoassay and immunocytochemistry and subsequently characterised by HPLC. Two region-specific PP antisera were used in the study; one C-terminal and one non-C-terminal. These antisera demonstrate variable cross-reactivity with the molecular species of PP identified in the tumours. The immunoreactive material in the tumours corresponded to human PP and not PYY or NPY on the basis of immunoreactivity and HPLC behaviour. It was identified in all patients with familial-type disease but not in the two sporadic cases examined. We propose that estimation of the PP content of medullary carcinoma of thyroid may be a useful means of differentiating familial and sporadic types.

Vincristine-induced abnormalities of gastrointestinal regulatory peptide cells of the rat. An immunocytochemical study

The microtubule-disrupting drug vincristine is a common component of anti-cancer chemotherapeutic regimes, which produces acute constipation as a side effect. Although generally attributed to damage to the myenteric plexus, the precise mechanism of this disturbance is unknown. In addition, vincristine causes marked aberrations in the secretory response of pancreatic endocrine tissue in both man and rats. No information is available on its possible effect on regulatory peptides of the gastrointestinal tract. In this study we have produced vincristine-induced constipation in rats at a dosage comparable with that employed in the treatment of human subjects. Immunocytochemistry revealed concomitant disturbances in cells exhibiting immunoreactivity for gastrin in the antrum, for gastric inhibitory polypeptide and 5-hydroxytryptamine in the duodenum, for enteroglucagon in the colon, and for somatostatin in all three sites. These widespread effects are transient in nature with normal cell numbers and morphology being reestablished within 6 days. It is suggested that the observed effects are a direct result of microtubule disruption and that gastrointestinal regulatory peptide and amine immunoreactive cells have a rapid regeneration potential.

The quest for the inhibitory neurotransmitter in bovine tracheal smooth muscle

The effect of inhibitory nerve stimulation on the mechanical, membrane potential and membrane conductance responses of isolated bovine tracheal smooth muscle has been studied. Membrane responses were measured in a sucrose-gap apparatus. In order to record inhibitory responses, it was necessary to increase tone in the preparation by applying a drug such as histamine. When tone was raised, repetitive field stimulation of intrinsic nerves caused depolarization and contraction, followed by relaxation and a suppression of histamine-induced slow waves. Hyperpolarization of the membrane was only seen following prolonged nerve stimulation, and there was no change in membrane conductance. The inhibitory effect of nerve stimulation was abolished by tetrodotoxin, but was not abolished by atropine, indomethacin, propranolol, naloxone or the purinergic blockers quinidine and theophylline. It was not satisfactorily mimicked by catecholamines, by gamma-amino-n-butyric acid (GABA) or by purines. Nerves with catecholamine fluorescence could not be found in the tracheal muscle layer. Neither adrenergic nor purinergic types of nerve terminal could be found in the tracheal muscle layer during ultrastructural examination of over one thousand nerve profiles. Vasoactive intestinal peptide (VIP) caused relaxation of the histamine-contracted tracheal muscle, suppressed the slow wave and caused slight hyperpolarization at higher concentrations, without affecting the membrane conductance. VIP was found in samples of tracheal muscle at a mean concentration of 1.95 ng/g. When the effluent solution flowing past isolated tracheal muscle strips was assayed for VIP, samples collected during inhibitory nerve stimulation had much higher concentrations of the peptide than samples collected before stimulation, after stimulation, or during stimulation in the presence of tetrodotoxin (10(-6) mol/l). The VIP content of the effluent during control periods was 73.8 pg/ml, and during stimulation was 167.5 pg/ml. It is suggested that VIP might be the non-adrenergic inhibitory neurotransmitter in bovine tracheal smooth muscle.