Ultrastructural study of small granule containing (SGC) cells in the lower mesenteric ganglion in drug treated guinea-pigs

Small granule containing cells (SGC or SIF cells) in the lower mesenteric ganglion of the guinea-pig were studied in control and experimental animals. After reserpine administration a decrease of dense population of granular vesicles was found. After injection of nialamide and dopamine to the animals in SGC cells significantly increased the number and density of granular vesicles. No real efferent synapses were found on SGC cell processes, although sites with accumulated synaptic-like vesicles, mostly with a dense core, were often observed.     

The ultrastructure of paraganglia associated with the inferior mesenteric ganglia in the guinea-pig

Summary The paraganglia of the inferior mesenteric ganglia in the guinea-pig are composed of small chromaffin cells containing an abundance of granule-containing vesicles. The chromaffin cells are almost completely surrounded by satellite cells. In areas in which satellite cell processes do not intervene, the membranes of adjacent chromaffin cells are closely apposed and often form specialized attachment zones. The paraganglia contain a dense capillary network, the endothelial cells of which are often extremely attenuated and show areas of fenestration. The processes of chromaffin cells approach close to the capillary walls and are often bare of satellite cells covering on the side facing the capillary. Evidence has been obtained for the exocytotic release of the contents of chromaffin cell vesicles into pericapillary spaces. Synapses of cholinergic and noradrenergic axons are seen on the chromaffin cells. The cholinergic axons degenerate when the praganglia are decentralized, but the noradrenergic axons, which appear to arise from the local inferior mesenteric ganglia, remain intact. The results suggest that the paraganglia have an endocrine function.     

Synaptic contacts between SIF cells immunoreactive to cholecystokinin (CCK-8) in inferior mesenteric ganglia in the guinea-pig

Cell bodies and processes of SIF cells were found to be CCK-like immunoreactive within the mesenteric ganglion of the guinea-pig. Immunoreactivity was contained in granular vesicles, the labeling being chiefly associated with granules, about 100 nm in diameter. Asymmetric synaptic contacts between CCK-like immunoreactive SIF cells have been identified and a possible functional implication regarding intraganglionic connections for these SIF cells is discussed.     

An immuno-electron-microscopic study of the localization of VIP-like immunoreactivity in the adrenal gland of the rat

Summary VIP-like immunoreactivity was revealed in a few chromaffin cells, medullary ganglion cells and a plexus of varicose nerve fibers in the superficial cortex and single varicose fibers in the juxtamedullary cortex and the medulla of the rat adrenal gland. VIP-like immunoreactive chromaffin cells were polygonal in shape without any distinct cytoplasmic processes and they appeared solitarily. Their cytoplasm contained abundant granular vesicles having a round core and the immunoreactive material was localized to the granular core. VIP-immunoreactive ganglion cells were multipolar and had large intracytoplasmic vacuoles. The immunoreactive material was localized not only in a few granular vesicles but also diffusely throughout the axoplasm. VIP-immunoreactive varicose nerve fibers in the superficial cortex were characterized by abundant small clear vesicles and some large granular vesicles, while those in the juxtamedullary cortex and medulla and the ganglionic processes were characterized by abundant large clear vesicles, as well as the same vesicular elements as contained in the nerves in the superficial cortex. The immunoreactive material was localized on the granular cores and diffusely in the axoplasm in both nerves. Based on the similarity and difference in the composition of the vesicles contained in individual nerves, it is likely that the VIP-immunoreactive nerve fibers in the medulla and the juxtamedullary cortex are derived from the medullary VIP-ganglion cells, while those in the superficial cortex are of extrinsic origin. The immunoreactive nerve fibers in both the cortex and the medulla were often in direct contact with cortical cells and chromaffin cells, where no membrane specializations were formed. The immunoreactive nerve fibers were sometimes associated with the smooth muscle cells and pericytes of small blood vessels in the superficial cortex. In addition they were often seen in close apposition to the fenestrated endothelial cells in the cortex and the medulla, only a common basal lamina intervening. Several possible mechanisms by which VIP may exert its effect in the adrenal gland are discussed.     

Electron-microscopic analysis of adrenergic nerve endings in the cat caudal mesenteric ganglion

The ultrastructure of nerve endings of the cat caudal mesenteric ganglion was studied after fixation of the material with 4% lithium permanganate solution by Richardson's method in the modification of Hökfelt et al. [12]. This fixation method was shown to permit the demonstration of numerous adrenergic as well as cholinergic nerve endings. Four types of adrenergic organelles were distinguished in neurons of the ganglion: small and large granular vesicles 30–50 and 70–90 nm in diameter, respectively, a tubular reticulum with electron-dense contents, and small granular vesicles 15–20 nm in diameter. The localization of the adrenergic endings and their relations with other processes and cells of the caudal mesenteric ganglion were studied in detail. The problem of the origin and physiological role of adrenergic nerve endings in this ganglion is discussed.Institute of Physiology, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 86–92, January–February, 1980.     

Different types of small granule-containing cells and neurons in the guinea-pig adrenal medulla

Summary An electron microscopic, histoand biochemical study was carried out on the adrenal medulla of newborn and adult guinea-pigs giving special emphasis to small granule-containing (SGC) cells. Adrenaline (A) was the predominating catecholamine (CA) both in newborn (70–90 % of total CA) and adult (85–90%) guinea-pig adrenals. In analogy to the biochemical findings electron microscopy revealed a high predominance of A cells, which contained large granular vesicles with an average diameter of 180 nm. Most noradrenaline (NA) storing cells showed granular vesicles of a considerably smaller average diameter (80 nm) and had a higher nuclear-cytoplasmic ratio. These cells were termed SGC-NA cells. NA cells with large granular vesicles (average diameter 170 nm) were extremely rare. Another type of SGC cells contained granular vesicles with cores of low to medium electron-density (SGC-NA-negative cells). Biochemical determinations made it unlikely that these cells contained predominantly dopamine (DA). SGC cells were scarcely innervated by cholinergic nerves. They formed processes, which were found both in the adrenal cortex and medulla contacting blood vessels including sinusoid capillaries, steroid producing cells of the reticularis and fasciculata zone and processes, which were interpreted to belong to medullary nerve cells.Two types of neurons were present in the guinea-pig adrenal medulla, one resembling the principal neurons in sympathetic ganglia, the other, which, according to its morphology, occupied an intermediate position between principal neurons and SGC cells.In adrenomedullary grafts under the kidney capsule, which were studied three weeks after transplantation, ordinary A cells resembled SGC-NA negative cells with respect to their ultramorphology. Processes of transplanted principal neurons showed uptake of 5-hydroxydopamine and, hence, were considered to be adrenergic. Despite the lack of extrinsic nerves to the transplants, few principal neurons received cholinergic synapses, the origin of which is uncertain to date.Supported by a grant from Deutsche Forschungsgemeinschaft (Un 34/4)Dedicated to Professor H. Leonhardt in honor of his 60th birthday.     

The origin and distribution of adrenergic nerve fibres in the guinea-pig colon

Summary A detailed study of the origin and distribution of sympathetic fibres in the distal colon of the guinea-pig has been made using the fluorescent histochemical method for localizing catecholamines. The extrinsic adrenergic fibres of the colonie sympathetic nerves follow the inferior mesenteric artery and its branches to the colon. Some of the extrinsic adrenergic fibres are associated with the parasympathetic fibres of the pelvic nerves near the colon. Complete adrenergic denervation follows the removal of the inferior mesenteric ganglion or the destruction of the nerves running with the inferior mesenteric artery.No fluorescent fibres, other than those associated with blood vessels, were observed in air-dried stretch preparations of the isolated longitudinal muscle. However, a substantial number of varicose, terminal fibres, not associated with blood vessels, were observed in the circular muscle. Some varicose fibres, apart from those associated with ganglion cells, were observed in the myenteric plexus. These fibres were seen in the bundles of nerves running between the nodes of the plexus and also as single fibres which branched from the plexus to end in areas free of ganglion cells.Three plexuses of adrenergic nerve fibres have been distinguished in the submucosa: a dense plexus of terminal fibres innervating both the veins and arteries; a plexus consisting of innervated nodes of ganglion cells, connected by bundles of fluorescent and non-fluorescent nerves; and a plexus of varicose and non-varicose fibres, which is not associated with ganglion cells. Some groups of ganglion cells in the submucosa were without adrenergic innervation.A plexus of varicose fibres forms a meshwork in the lamina propria of the mucosa. The muscularis mucosae is sparsely innervated. Most of the blood vessels in the mucosa are not associated with adrenergic fibres.     

Somatostatin-immunoreactive nerve fibers in close association with capillaries in the small intestine

Electron microscopic immunocytochemistry was used to identify somatostatin-immunoreactive nerve profiles around the capillary system of the small intestine in the rat and cat. The highest density of somatostatin-immunoreactive nerve profiles was seen in the mucosa, and 25-30% of all immunoreactive profiles were found immediately adjacent to the endothelial cells of capillary blood vessels. About half of the capillary endothelial cells were fenestrated. The majority of the immunoreactive nerve profiles were varicosities, containing synaptic vesicles. These observations suggest that somatostatin might be released from varicose nerve fibers and may contribute to the elevated levels of the peptide measured in portal blood as compared to peripheral blood.     

Immunocytochemical study of tyrosine hydroxylase and dopamine β-hydroxylase immunoreactivities in the rat pancreas

An immunohistochemical and immunoelectron microscopic study was used to demonstrate tyrosine hydroxylase (TH) and dopamine -hydroxylase (DBH) immunoreactivities in the rat pancreas. Small TH immunoreactive cells were found in close contact with large TH immunonegative ganglion cells among the exocrine glands and were occasionally found in some islets. Some of these TH immunoreactive cells were also DBH immunopositive. The immunoreaction product was seen diffusely in the cytoplasm and in the granule cores of TH immunoreactive cells. All intra-pancreatic ganglion cells were immunoreactive for DBH, but not for TH. The TH immunoreactive cells were identified as small intensely fluorescent (SIF) cells due to their localization and morphological characteristics and showed no insulin, glucagon, somatostatin or pancreatic polypeptide immunoreactivities. These results indicate that SIF cells may release dopamine or noradrenaline to adequate stimuli while the intra-pancreatic ganglion cells with only DBH may not synthesize catecholamines in a normal biosynthetic pathway. TH immunoreactive nerve bundles without varicosities and fibers with varicosities, associated or unassociated with blood vessels, were found in both the exocrine and endocrine pancreas. Close apposition of TH immunoreactive nerve fibers to the smooth muscle and endothelial cells of the blood vessels was observed. A close apposition between TH immunoreactive nerve fibers and exocrine acinar cells and islet endocrine cells was sometimes found in the pancreas. The immunoreaction product was seen diffusely in the axoplasm and in the granular vesicles of the immunoreactive nerve fibers. Since no TH immunoreactive ganglion cells were present in the rat pancreas, the present study suggests that noradrenergic nerve fibers in the pancreas may be extrinsic in origin, and may exert an effect on the regulation of blood flow and on the secretory acitivity of the acinar cells, duct cells and endocrine cells.     

Distribution of enteric nerve cells projecting to the superior and inferior mesenteric ganglia of the guinea-pig

Retrograde tracing, using Fast Blue dye, was employed to determine the distribution of enteric nerve cells that project to the superior mesenteric and inferior mesenteric ganglia of the guinea-pig. Retrogradely labelled neurons were found in the myenteric but not submucous ganglia. When the superior mesenteric ganglion was injected, labelled neurons were found in low frequencies (less than 5 nerve cell bodies/cm²) in the duodenum, jejunum, ileum, caecum and proximal colon. The distal colon was analysed in five segments of equal length (1–5; oral to anal). Segment 1 had about 4 labelled nerve cells/cm², whereas segments 2 to 5 displayed an average of about 25 nerve cells/cm². The rectum contained about 36 labelled neurons/cm². After injection of the inferior mesenteric ganglia with Fast Blue, no labelled neurons were found in the duodenum, jejunum, ileum or caecum. No labelled cells were observed in the gallbladder. A small number of labelled cells occurred in the proximal colon and in segment 1 of the distal colon. The frequency of labelled cells increased markedly in the more anal regions of the distal colon, and reached a peak in the rectum (138 cells/cm²). Both nerve lesions and immersion of the cut nerve in Fast Blue solution showed that the superior mesenteric nerve carries the axons of neurons located in the middle distal colon to the superior mesenteric ganglion. Almost half of the neurons in the rectum that project to the inferior mesenteric ganglia do so via the hypogastric nerves. Of neurons that projected to the inferior or superior mesenteric ganglia from the colon or rectum, similar proportions (about 75–80%) showed immunoreactivity for calbindin or VIP. For each of the prevertebral ganglia (coeliac, superior mesenteric and inferior mesenteric) the great majority of peripheral inputs arise from the large intestine.     

Calcitonin gene-related peptide (CGRP)-like immunoreactivity in scattered chromaffin cells and nerve fibers in the adrenal gland of rats

Summary The present immunohistochemical study reveals that a small number of chromaffin cells in the rat adrenal medulla exhibit CGRP-like immunoreactivity. All CGRP-immunoreactive cells were found to be chromaffin cells without noradrenaline fluorescence; from combined immunohistochemistry and fluorescence histochemistry we suggest that these are adrenaline cells. In addition, all CGRP-immunoreactive cells simultaneously exhibited NPY-like immunoreactivity. CGRP-chromaffin cells were characterized by abundant chromaffin granules with round cores in which the immunoreactive material was densely localized. These findings suggest the co-existence of CGRP, NPY and adrenaline within the chromaffin granules in a substantial number of chromaffin cells.Thicker and thinner nerve bundles, which included CGRP-immunoreactive nerve fibers, with or without varicosities, penetrated the adrenal capsule. Most of them passed through the cortex and entered the medulla directly, whereas others were distributed in subcapsular regions and among the cortical cells of the zona glomerulosa. Here the CGRP-fibers were in close contact with cortical cells. A few of the fibers supplying the cortex extended further into the medulla. The CGRP-immunoreactive fibers in the medulla were traced among and within small clusters of chromaffin cells and around ganglion cells. The CGRP-fibers were directly apposed to both CGRP-positive and negative chromaffin cells, as well as to ganglion cells. Immunoreactive fibers, which could not be found close to blood vessels, were characterized by the presence of numerous small clear vesicles mixed with a few large granular vesicles. The immunoreactive material was localized in the large granular vesicles and also in the axoplasm. Since no ganglion cells with CGRP-like immunoreactivity were found in the adrenal gland, the CGRP-fibers are regarded as extrinsic in origin. In double-immunofluorescence staining for CGRP and SP, all the SP-immunoreactive fibers corresponded to CGRP-immunoreactive ones in the adrenal gland. This suggests that CGRP-positive fibers in the adrenal gland may be derived from the spinal ganglia, as has been demonstrated with regard to the SP-nerve fibers.     

Substance P-like immunoreactivity in adrenal chromaffin cells and intra-adrenal nerve fibers of rats

Summary The present peroxidase-antiperoxidase immunohistochemical study demonstrated a relatively small number of cells with substance P(SP)-like immunoreactivity in the adrenal medulla of rats. These cells were found alone or in small groups, were polygonal in shape and lacked long cytoplasmic processes. At immunoelectron microscopy, the immunoreactive cells were characterized by abundant granular vesicles, and the immunoreactive material was confined to the round core of the vesicles. Thus, it is suggested that SP co-exists with catecholamines in a population of chromaffin cells of the rat adrenal medulla. In addition a few SP-immunoreactive nerve fibers with varicosities were found in the adrenal medulla of rats. They extended between small clusters of chromaffin cells and had their dotlike terminals around and within the cell clusters. The SP-immunoreactive nerve fibers were characterized by the presence of abundant small clear vesicles mixed with a few large granular vesicles; the immunoreactivity appeared in the latter, but was also perfused throughout the entire axoplasm. The nerve fibers formed synapses on nonimmunoreactive chromaffin cells. Judging from the presence of bundles of SP-immunoreactive nerve fibers penetrating the adrenal capsule and cortex as well as the absence of SP-immunoreactive ganglion cells in the medulla, the intramedullary SP-immunoreactive nerve fibers seem to be extrinsic in origin.     

Substance P-like immunoreactivity in adrenal chromaffin cells and intra-adrenal nerve fibers of rats

The present peroxidase-antiperoxidase immunohistochemical study demonstrated a relatively small number of cells with substance P(SP)-like immunoreactivity in the adrenal medulla of rats. These cells were found alone or in small groups, were polygonal in shape and lacked long cytoplasmic processes. At immunoelectron microscopy, the immunoreactive cells were characterized by abundant granular vesicles, and the immunoreactive material was confined to the round core of the vesicles. Thus, it is suggested that SP co-exists with catecholamines in a population of chromaffin cells of the rat adrenal medulla. In addition a few SP-immunoreactive nerve fibers with varicosities were found in the adrenal medulla of rats. They extended between small clusters of chromaffin cells and had their dot-like terminals around and within the cell clusters. The SP-immunoreactive nerve fibers were characterized by the presence of abundant small clear vesicles mixed with a few large granular vesicles; the immunoreactivity appeared in the latter, but was also perfused throughout the entire axoplasm. The nerve fibers formed synapses on nonimmunoreactive chromaffin cells. Judging from the presence of bundles of SP-immunoreactive nerve fibers penetrating the adrenal capsule and cortex as well as the absence of SP-immunoreactive ganglion cells in the medulla, the intramedullary SP-immunoreactive nerve fibers seem to be extrinsic in origin.     

Ultrastructure of the pineal organ of the killifish,Fundulus heteroclitus,with special reference to the secretory function

Summary The pineal organ of the killifish, Fundulus heteroclitus, was investigated by electron microscopy under experimental conditions; its general and characteristic features are discussed with respect to the photosensory and secretory function. The strongly convoluted pineal epithelium is usually composed of photoreceptor, ganglion and supporting cells. In addition to the well-differentiated photosensory apparatus, the photoreceptor cell contains presumably immature dense-cored vesicles (140–220 nm in diameter) associated with a well-developed granular endoplasmic reticulum in the perinuclear region and the basal process. These dense-cored vesicles appear rather prominent in fish subjected to darkness. The ganglion cell shows the typical features of a nerve cell; granular endoplasmic reticulum, polysomes, mitochondria and Golgi apparatus are scattered in the electron-lucent cytoplasm around the spherical or oval nucleus. The dendrites of these cells divide into smaller branches and form many sensory synapses with the photoreceptor basal processes. Lipid droplets appear exclusively in the supporting cell, which also contains well-developed granular endoplasmic reticulum and Golgi apparatus. Cytoplasmic protrusions filled with compact dense-cored vesicles (90–220 nm in diameter) are found in dark-adapted fish. The origin of these cytoplasmic protrusions, however, remains unresolved. Thus, the pineal organ of the killifish contains two types of dense-cored vesicles which appear predominantly in darkness. The ultrastructural results suggest that the pineal organ of fish functions not only as a photoreceptor but also as a secretory organ.We thank Dr. Grace Pickford for the fishes.     

Effect of hydrocortisone on the ultrastructure of the small,intensely fluorescent,granule-containing cells in cultures of sympathetic ganglia of newborn rats

Summary Sympathetic chain ganglia of newborn rats were cultured in Rose chambers with or without hydrocortisone. After one week, the cultures were examined by light microscopy for formaldehyde-induced catecholamine fluorescence and by electron microscopy after fixation in 5% glutaraldehyde solution and thereafter in 1% osmium tetroxide. Hydrocortisone (10 mg/l) caused a great increase in the number of the small, intensely fluorescent (SIF) cells in the ganglion explants, and the fluorescence intensity of these cells was also increased. The SIF cells corresponded to small, granule-containing (SGC) cells in the electronmicros copic preparations, and in addition to an increase in their number there was also an increase in the size and number of granular vesicles in the presence of hydrocortisone. In control cultures the granular vesicles were round (about 100 nm in diameter) or elongated (40–150 nm in cross section and 150–250 nm in length); both types of vesicles contained electron dense cores. In hydrocortisone-containing cultures round granular vesicles up to 200 nm in diameter were also observed; the cores of these vesicles were of variable electron density. It is concluded that in tissue culture, hydrocortisone causes an increased formation of catecholamine-containing granular vesicles in SIF-SGC cells and their precursors and an increase in the number of these cells.This work was supported by grants from the National Heart Foundation, the Australian Research Grants Committee and the Sigrid Juselius Foundation.University of Melbourne Senior Research Fellow, September, 1971 – August, 1972; present address: Department of Anatomy, University of Helsinki, Siltavuorenpenger, Helsinki, Finland, 00170.Holder of a grant from the National Health and Medical Research Council of Australia.Sunshine Foundation and Rowden White Research Fellow in the University of Melbourne, September, 1971 – August, 1972; present address: Department of Anatomy, University of Helsinki, Siltavuorenpenger, Helsinki, Finland, 00170.     

Quantitative immunocytochemical studies of endogenous albumin in rat aortic endothelial and mesothelial cells

Endogenous albumin was revealed over cellular structures of rat ascendent aorta endothelia and mesothelium, with high resolution and specificity, by applying the protein A-gold immunocytochemical approach. This approach allows albumin distribution to be studied under steady-state conditions. The cellular layers evaluated were the aortic endothelium, the capillary endothelium (vasa vasorum), and the mesothelium externally lining the aorta at this level. Gold particles, revealing albumin antigenic sites, were preferentially located over plasmalemmal vesicles and intercellular clefts of endothelial and mesothelial cells, though with different labeling intensities. The interstitial space was also labeled. Morphometrical evaluation of plasmalemmal vesicles demonstrated a higher surface density for these structures in capillary endothelial cells (12%) compared with those in aortic endothelial (5%) and mesothelial cells (2%). Quantitation of gold labeling intensities over these structures revealed a higher labeling over plasmalemmal vesicles of capillary endothelium than over those of aortic endothelium and mesothelium. This result, together with the higher surface density of plasmalemmal vesicles found in capillary endothelium, suggest an important role of these structures in the transendothelial passage of endogenous albumin, particularly for capillary endothelium. On the other hand, labeling densities over mesothelial clefts were found to be higher than those of capillary and aortic endothelia. Results from this study concur with the proposal of a differential passage of albumin according to the cell lining considered, and suggest to a role for mesothelial intercellular clefts in contributing to the presence of albumin in interstitial spaces.     

Galanin-, neuropeptide Y- and enkephalin-like immunoreactivities in catecholamine-storing paraganglia of the fetal guinea pig and newborn pig

Summary The occurrence and distribution of several neuropeptides and transmitter enzymes have been investigated by means of indirect immunofluorescence histochemistry in preaortal and carotid body-like paraganglia of the fetal guinea pig and the newborn pig. Preaortal paraganglia from the celiac and inferior mesenteric ganglion regions in fetal guinea pigs showed cell bodies immunoreactive (IR) for tyrosine hydroxylase (TH), dopamine -hydroxylase (DBH), neuropeptide Y (NPY), galanin (GAL) and metenkephalin (ENK). Almost all cells were IR for TH and DBH, whereas NPY-like immunoreactivity (-LI), GAL-LI and ENK-LI occurred less frequently. Direct double-labeling revealed the coexistence of NPY/GAL, NPY/ENK and GAL/ENK in paraganglion cells from the celiac and inferior mesenteric region. Nerve fibers and terminals were IR for ENK; fibers IR for calcitonin-gene-related peptide (CGRP) were present in the inferior mesenteric ganglion region. Preaortal paraganglia cells from the newborn pig showed TH-LI, DBH-LI, GAL-LI and ENK-LI, the distribution pattern being similar to that seen in the guinea pig; however, NPY-LI was absent. Carotid-body-like paraganglia from the newborn pig showed cell bodies IR to TH, GAL and ENK. Few cells were seen with DBH-LI. A rich supply of nerve fibers with CGRP-LI was present; some fibers exhibited ENK-LI and CCK-LI. In the adjacent superior cervical ganglion, ganglion cell bodies showed immunoreactivity to TH, DBH and NPY. A small number of cells were positive for GAL, CGRP and vasoactive intestinal polypeptide (VIP). Physiological activation of the paraganglia, leading to release or increase in catecholamines, may also change the content of the neuropeptides present in the paraganglia.     

Immunohistochemistry of biogenic polypeptides in nerve cells and fibres of the guinea pig inferior mesenteric ganglion after perturbations

Immunohistochemistry of peptide- and dopamine-beta-hydroxylase-(DBH)-containing varicose nerve fibres and ganglion cells, respectively, in the guinea pig inferior mesenteric ganglion was investigated following a) transsection of mesenteric (colonic) branches, b) transsection of central (lumbar splanchnic, intermesenteric and hypogastric) branches, and c) transplantation into the spleen. The findings indicate that pathways of different opioid peptides are not identical. Met-enkephalin- and met-enkephalin-arg-phe- (cleavage products from pre-proenkephalin) containing fibres course in central branches to make contact in the inferior mesenteric ganglion. Dynorphin- and alpha-neo-endorphin- (deriving from pre-prodynorphin) containing fibres as well as leu-enkephalin- (included in the dynorphin sequence) fibres appear to rise not only from central and from enteric somata, but also from intraganglionic noradrenergic neurons. Similar pathways seem to be used by VIP- and by neurotensin-immunoreactive fibres, although intraganglionic neurotensin-immunoreactive cell bodies are rare. Practically all substance P- and most CGRP-immunoreactive fibres enter the ganglion via central branches and, to a large extent, traverse it, but some CGRP-immunoreactive influx appears to come from the intestine. The origin of intraganglionic substance P- and CGRP-immunoreactive fibres after ganglion transplantation remained unidentified. Somatostatin- and neuropeptide Y-immunoreactive fibres predominantly have an intraganglionic origin as have DBH-immunoreactive noradrenergic fibres. The demonstrated alterations in neuropeptide immunoreactivity of intraganglionic and periganglionic nerve fibres following the applied transsection procedures contribute to the present knowledge on origin and destination of peptidergic transmitter segments in the guinea pig inferior mesenteric ganglion. Moreover, the present study provides evidence that intrinsic participation in intraganglionic fibre supply is more extensive than hitherto believed.     

Fine structure of islet-cell innervation in the pancreas of normal and alloxan-treated rats

Summary The innervation of the islets of Langerhans of normal albino rats and of albino rats treated with several daily doses of 125 mg/kg of alloxan was studied by electron microscopy. In the normal rat, nerve endings containing either agranular vesicles (200–400 Å) alone or in combination with large granular vesicles (500–800 Å) were found on both alpha and beta cells. Infrequently a third type of nerve ending containing small granular synaptic vesicles could be observed. Bundles of unmyelinated axons were also seen, as were typical autonomic ganglion cells. Similar normal neural elements were noted in rats treated with alloxan. However, islets of alloxan-treated animals also possess large elliptical profiles which appear to be dystrophic nerve terminals. These structures most frequently contact degranulated beta cells. Islets of Langerhans fixed with zinc iodide-osmium (ZIO) reported to specifically impregnate synaptic vesicles were also studied. Synaptic vesicles of normal axons and nerve endings as well as of the dystrophic structures were filled with ZIO reactive material. These studies suggest that alloxan may induce autonomic nerve ending changes in the rat endocrine pancreas. This may result from neuronal hyperactivity in an attempt to secrete insulin from the post-alloxan insulin-depleted beta cell.     

Fine structure of the small,granule-containing cells in the superior cervical ganglia of hydrocortisone-treated early postnatal and adult rats

Summary Hydrocortisone injections into rats on postnatal days 3–9 caused an increase in the number of small granulecontaining cells in the superior cervical ganglia. These cells, corresponding to the small, intensely fluorescent cells, showed an extensive rough endoplasmic reticulum, a large Golgi apparatus and a very large number of granular vesicles. In addition to the granular vesicles, 70–160 nm in diameter, in which the dense core filled most of the vesicle, most cells of the hydrocortisone-injected rats contained also larger granular vesicles, up to 350 nm in diameter, in which the dense core was eccentrically located. A minority of the cells contained only granular vesicles 70–100 nm in diameter, which was the only type seen in the saline-treated control rats.Thirty days after discontinuation of the hydrocortisone treatment, most of the cells with large granular vesicles had disappeared, and only two profiles of such cells were seen on day 40. The other small cells contained only granular vesicles 70–160 nm in diameter, and these cells could not be distinguished from the small granule-containing cells of 40-day-old control rats treated early postnatally with saline.Hydrocortisone treatment, first on days 3–9 and subsequently on days 40–46, caused reappearance of the small granule-containing cells with large granular vesicles up to 350 nm in diameter, the dense core of which was eccentrically located. Hydrocortisone treatment on days 40–46 only was not followed by appearance of such cells in rats treated with saline on days 3–9.Abbreviations used in the Text PNMT phenylethanolamine-N-methyltransferase - SIF cell small intensely fluorescent cell - SGC cell small granule-containing cell The author is grateful to Professor Olavi Eränkö and Dr. Seppo Soinila for constructive criticism. Expert technical assistance by Miss Hanna-Liisa Alanen, Mrs. Marja-Leena Piironen and Mrs. Anne Reijula is gratefully acknowledged. This study has been supported by a grant from the Finnish Medical Foundation.