Lars-Inge Larsson

Ultrastructural localization of a new neuronal peptide (VIP).

SummaryThe vasoactive intestinal polypeptide (VIP) represents a neuronal peptide of wide-spread occurrence. By electron microscopic immunocytochemistry VIP has been localized to the granules of the terminals of p-type neurons. This localization lends support to the postulate that VIP may be a neurotransmitter.

Effects of antrectomy or porta‐caval shunting on the histamine‐storing endocrine‐like cells in oxyntic mucosa of rat stomach. A fluorescence histochemical, electron microscopic and chemical study.

1. The argyrophil (enterochromaffin‐like) cells in the oxyntic gland area of the rat stomach contain histamine, which can be demonstrated fluorescence microscopically after exposure to gaseous OPT. After administration of L‐dopa (or L‐5‐hydroxytryptophan), these cells produce and temporarily store dopamine (or 5‐hydroxytryptamine), demonstrable by its characteristic formaldehyde‐induced fluorescence. Ultrastructurally, the enterochromaffin‐like cells, which have the appearance of polypeptide hormone‐secreting cells, comprise two main cell types, the most predominant one having vesicular type granules (EGL cells), the second most predominant one having smaller, uniformly electron dense granules (A‐like cells). 2. Rats were subjected to the following surgical treatments: antrectomy; porta‐caval shunting; antrectomy+porta‐caval shunting; or sham‐operation. Three to eight weeks after surgery the histamine‐storing cells (enterochromaffin‐like cells) of the oxyntic mucosa were analysed by fluorescence histochemistry, light and (quantitative) electron microscopy, and fluorometric determination of amines. 3. After antrectomy, fluorescence histochemistry and silver staining revealed a reduced number of enterochromaffin‐like cells. The histamine content in the oxyntic mucosa was reduced by about 50%. As in unoperated injection of pentagastrin seemed to mobilize histamine. Feeding or injection of insulin failed to do so in antrectomized as opposed to control rats. Ultrastructurally, the cytoplasmic granules of both endocrine‐like cell types were less numerous than in the unoperated rats. The reduction in cell number and granularity was particularly conspicuous with regard to the EGL cells. 4. After porta‐caval shunting the number of enterochromaffin‐like cells increased markedly. Chemical determination revealed a twofold increase in the histamine concentration of the oxyntic mucosa. Feeding or injection of insulin or pentagastrin lowered the histamine concentration. As judged by electron microscopy, the proliferation of endocrine‐like cells induced by porta‐caval shunting was restricted to the ECL cell type. Besides occurring in greater number, these cells were larger than those in unoperated controls, and their cytoplasm was densely packed with granules that were increased in size. 5. Following antrectomy of the porta‐caval shunted rats the number of enterochromaffin‐like cells and the oxyntic histamine concentration was reduced. 6. The results support the idea that gastrin exerts trophic as well as excitatory effects on oxyntic endocrine‐like cells.

Comparative localization of enkephalin and cholecystokinin immunoreactivities and heavy metals in the hippocampus.

Abstract The present study is concerned with the cellular origins and identities of the hippocampal enkephalin and CCK-immunoreactive fibers and terminals. In the hippocampus of the rat, the guinea pig and the European hedgehog a system of enkephalin immunoreactive nerves emerges in the hilus of area dentata and can be followed to the apical dendrites of the hippocampal regio inferior pyramidal cells. This pattern of immunoreactive nerves corresponds to the hippocampal mossy fiber system as visualized by the Timm staining. Cholecystokinin immunoreactive nerve fibers and terminals reveal the same distribution in the guinea pig and the European hedgehog whereas in the rat the mossy fiber zone contains little or no cholecystokinin immunoreactivity. In the guinea pig degeneration of the mossy fibers after stereotactic lesions of the mossy fibers causes a complete loss of both enkephalin and cholecystokinin immunoreactivity in the mossy fiber zone. Only a few enkephalin immunoreactive cell bodies were scattered throughout the granular cell layer of area dentata, but inhibition of the axoplasmic transport by colchicine dramatically increased the number of enkephalin immunoreactive granule cell bodies. Enkephalin immunoreactive cell bodies were also detected in the hilus, throughout the pyramidal cell layer as well as in the stratum radiatum and stratum moleculare. Cholecystokinin immunoreactive cell bodies were seen in the hilus of the area dentata and in the stratum oriens, stratum pyramidale and stratum radiatum and the cell-rich layer of subiculum. No cholecystokinin immunoreactive cell bodies were observed in the granular cell layer of area dentata. Even after colchicine treatment the granule cells were devoid of cholecystokinin immunoreactivity. In the rat a system of nerves displaying enkephalin immunoreactivity was also observed in the superficial one-third of the molecular layer of area dentata, a zone which corresponds to the termination of the lateral perforant path. Another observation was that in the rat, but not in the guinea pig and the hedgehog, the terminal zone of both the medial perforant path and the zone of commissural and associational fibers of area dentata contained cholecystokinin immunoreactive molecules. In summary, our data show: (1) that the hippocampal mossy fibers contain enkephalin immunoreactive molecules; (2) that the cholecystokinin immunoreactivity in the mossy fiber zone is most likely also localized in the mossy fibers per se, although the granule cells seem devoid of cholecystokinin immunoreactivity; (3) zinc, here visualized as a Timm-positive substance, is also localized in the mossy fiber terminals; further, (4) other intrinsic cell bodies than the granule cells may contribute to both the enkephalin and cholecystokinin immunoreactive terminals within the hippocampus; (5) in the rat the lateral perforant path may be enkephalinergic; and (6) both the terminal zone of the medial perforant path and the associational and commissural fibers of the rat contain cholecystokinin immunoreactivity.

Ontogeny of peptide-producing nerves and endocrine cells of the gastro-duodeno-pancreatic region

SummaryThe ontogeny of different types of endocrine cells and nerves producing different hormonal peptides was studied by immunocytochemistry. The data indicate that several endocrine cell types are more frequent in the foetal than in the adult gastro-duodeno-pancreatic region. Some cell types were found to show an over-lapping distribution. Such distributional over-laps were more frequent in foetuses and neonates than in adults. Both parallel and non-parallel patterns of development of endocrine cells and peptide-producing nerves were detected. Together with available information on the trophic effects of the gastrointestinal hormonal peptides these findings indicate that foetal and neonatal endocrine cells may participate in the regulation of growth and morphogenesis in the gastrointestinal tract.

A peptide resembling COOH-terminal tetrapeptide amide of gastrin from a new gastrointestinal endocrine cell type

THE gastrointestinal hormones gastrin and cholecystokinin (CCK) share identical COOH-terminal sequences. In both hormones the COOH-terminal tetrapeptide amide constitutes the biologically active region, and the rest of the two molecules determines their potency and selectivity for different target cells. Their similarity in structure and activity may reflect a common phylogenetical origin1. The COOH-terminal tetrapeptide amide is highly immunogenic in each hormone and many gastrin antisera are specific for this sequence and also bind CCK. In order to study the hormones by immunocytochemistry and radioimmunoanalysis, antisera specific for several distinct sequences must be used. Previously, we have used such antisera to characterise antral gastrin cells and intestinal cholecystokinin cells by immunocytochemistry2. We now report the identification of three distinct types of gastrointestinal cells which show COOH-terminal gastrin (or CCK) immunoreactivity. One type corresponds to gastrin-producing G cells, another to CCK-producing I cells and a third type to TG cells which react only with antisera against the COOH-terminal tetrapeptide.

Comparative immunocytochemical localization of putative opioid ligands in the central nervous system

SummaryWe report a detailed comparative immunocytochemical mapping of enkephalin, CCK and ACTH/gb-endorphin immunoreactive nerves in the central nervous system of rat and guinea pig. Enkephalin immunoreactivity was detected in many groups of nerve cell bodies, fibers and terminals in the limbic system, basal ganglia, hypothalamus, thalamus, brain stem and spinal cord. β-endorphin and ACTH immunoreactivity was limited to a single group of nerve cell bodies in and around the arcuate nucleus and in fibers and terminals in the midline areas of the hypothalamus, thalamus and mesencephalic periaqueductal gray with lateral extensions to the amygdaloid area. Cholecystokinin immunoreactive nerve fibers and terminals displayed a distribution similar to that of enkephalin in many regions; but striking differences were also found. An immunocytochemical doublestaining technique, which allowed simultaneous detection of two different peptides in the same tissue section, showed that enkephalin-, CCK- and ACTH/β-endorphin-immunoreactive nerves although closely intermingled in many brain areas, occurred separately. The distributions of nerve terminals containing these neuropeptides showed striking overlaps and also paralleled the distribution of opiate receptors. This may suggest that enkephalin, CCK, ACTH and β-endorphin may interact with each other and with opiate receptors.

Distribution, ontogeny and ultrastructure of the mammalian secretin cell.

SummaryImmunocytochemically, secretin cells have been demonstrated to occur in the duodenum and jejunum of several mammals. Calculations on the relative frequency of such cells indicate that the bulk of secretin occurs in the jejunum, a fact supporting the view that secretin may be released by physiological stimulants other than hydrochloric acid. Electron microscopical identification of cat and pig secretin cells confirmed their identity with the ultrastructurally defined S cells, and staining experiments revealed that secretin cells were argyrophilic both with the method of Grimelius and with that of Hellerström and Hellman. Secretin cells are detected already in the 17-day old fetal rat duodenum and show a developmental pattern similar to that displayed by the gastrin cells. It is suggested that secretin may play a role in the early regulation of growth of the fetal gastrointestinal tract.

Ultrastructural and cytochemical studies on the cytodifferentiation of duodenal endocrine cells

SummaryThe development and cytodifferentiation of endocrine cells that produce the gastrointestinal hormones gastrin, cholecystokinin and secretin have been studied by a combined fluorescence-cytochemical, immunocytochemical and ultrastructural approach. The results show that, during development, several ultrastructurally distinct cell types exhibit COOH-terminal gastrin and cholecystokinin immunoreactivity. Furthermore, some cells simultaneously contain both gastrin- and cholecystokinin-specific antigenic determinants. Studies on the time course of development of gastrin and cholecystokinin cells, together with the above-mentioned data, suggest that gastrin cells may be converted into cholecystokinin cells in development. During this period, gastrin, cholecystokinin and secretin cells store the biogenic monoamine, 5-hydroxytryptamine a feature not displayed by the adult counter-parts of these cells. In the adult duodenum, characteristic enterochromaffin (EC) cells store 5-hydroxytryptamin for which, evidence for a possible hormonal role has been presented. Taken together, our data indicate that the differentiation of duodenal endocrine cells occurs in distinct steps, each involving a restriction in the biosynthetic repertoire of the cell.

Distribution of ACTH-like immunoreactivity in rat brain and gastrointestinal tract.

SummaryImmunocytochemistry reveals ACTH-like immunoreactivity to reside not only in the pituitary but also in central nerves and in antral gastrin cells. In all probability, the central nerves store a peptide identical with or closely resembling true ACTH. Their pattern of distribution is, in some regions, similar to that of enkephalin-immunoreactive nerves. The antiserum demonstrating ACTH-like immunoreactivity in central nerves and in antral gastrin cells is directed towards the COOH-terminal part of the hormone. A peptide corresponding to this part, the corticotrophin-like intermediate peptide (CLIP) is manufactured by the pars intermedia of the pituitary. CLIP is devoid of adrenocortical activity but has recently been shown to possess insulin-releasing activity. The occurrence of CLIP-like peptides in antral gastrin cells may indicate a role for such peptides in the gastrointestinal regulation of insulin release. The simultaneous occurrence of enkephalin-like and ACTH-like immunoreactivity in the antral gastrin cells is of particular interest since a large precursor molecule, containing both the enkephalin and the ACTH sequence has recently been identified.

Suppression of rat stomach histidine decarboxylase activity by histamine: H2‐receptor‐mediated feed‐back

1. Gastrin activates rat stomach histidine decarboxylase. Exogenous histamine suppressed the basal enzyme activity in unoperated, in nephrectomized, in vagally denervated and in antrectomized rats, and counteracted the pentagastrin‐induced enzyme activation in unoperated rats.