Ultrastructural localization of monoamines in the epidermis of Lumbricus terrestris (L.)

Summary Receptor cells in the epithelium and the basiepithelial nerve net of the prostomium of Lumbricus terrestris were investigated with electron microscope with special regard to the presence of monoamines. The receptor cells are found in groups of about 40 intermingled with supportive cells. After pretreatment with -methyl-noradrenaline and fixation with potassium permanganate a few receptor cells in each group and some nerve fibres in the basiepithelial nerve net contain small granular vesicles (about400 Å) characteristic for monoaminergic neurons. The distribution and relative number of these receptor cells and nerve fibres coincide well with previous reports on fluorescent receptor cells and varicose fibres. That the monoamine-storing small granular vesicles not are visualized until pretreatment with -methyl-noradrenaline is in accordance with recent microspectrofluorometric analysis, which shows that dopamine is the only primary monoamine present in the epithelium.In the epithelium there are occasional receptor cells and nerve fibres containing large vesicles (1000–1800 Å) which resemble the neurosecretory vesicles in the central nervous system. Photoreceptor cells having an intracellular cavity with microvilli and cilia have infrequently been observed at the base of the epithelium.No synapses on the mucous cells have been noticed. Nor have any synaptic specializations been observed in the basiepithelial nerve net. The morphological conditions necessary for the existence of possible axo-axonal synapses are briefly discussed.This work was supported by grants from the Helge Ax: son Johnson Foundation and the Magn. Bergvall Foundation.     

Auerbach's plexus of mammals and man: Electron microscopic identification of three different types of neuronal processes in myenteric ganglia of the large intestine from rhesus monkeys,guinea-pigs and man

Summary Ganglia from Auerbach's plexus of the large intestine (caecum, appendix vermiformis, colon transversum and rectum) in man, rhesus monkey and guinea-pig are composed of nerve cells and their processes, typical Schwann cells and a vast neuropil. The neuropil consists of dendrites and axons of intrinsic nerve cell perikarya and axons of extrinsic neurons. Axonal profiles in large nerve fibre bundles are of uniform size and appearance, embedded in infoldings of Schwann cell cytoplasm and contain occasional large granular vesicles, mitochondria and neurotubules. Preterminal axons widen into vesicle filled varicosities, some of which establish synaptic contact with intrinsic nerve cell bodies.At least three different types of neuronal processes can be distinguished in the myenteric neuropil according to the size, appearance and commutual proportion of vesicles present in axonal varicosities, and their ability to accumulate exogenous 5- and 6-hydroxydopamine and 5-hydroxydopa: 1. Axonal enlargements containing a major population of small electron lucent synaptic vesicles (350–600 Å in diameter) together with a small number of membrane-bound, opaque granules (800–1,100 Å). These profiles have been identified as cholinergic axons. The boutons establish synaptic contacts with dendritic processes of intrinsic nerve cell bodies; membrane specializations are found at the preand postsynaptic sites. 2. Axonal beads of sometimes very large diameter, containing an approximately equal amount of large granular vesicles (850–1,600 Å) and small, electron lucent or faintly opaque vesicles (400–600 Å). The granular core of the large vesicles is of medium electron density and may either fill the entire vesicle or is separated from the limiting membrane by a more or less clear interspace. The fibres probably belong to intrinsic neurons, and because of the similarity of the large, membrane-bound vesicles with neurosecretory elementary granules, they have been designated p-type fibres (polypeptide fibres). The granular core of the vesicles in these fibres becomes more electron dense after treatment with 5-OH-dopa. The accumulation of an amine precursor analogue in combination with a possible storage of a polypeptide substance (or an ATP-like substance) resembles the situation in several diffusely distributed endocrine cell systems. 3. Varicosities of axons equipped with small (400–600 Å) empty or sometimes granular vesicles, medium sized (500–900 Å) vesicles with highly electron dense cores and occasional large (900–1,300 Å) granular vesicles. Pretreatment with 5-OH-dopamine increases the electron density in almost all medium-sized granular vesicles and some of the large granular vesicles; an osmiophilic core develops in some small vesicles. 6-hydroxydopamine results in degenerative changes in the varicosities of this type of neurons. Concomitantly, both catecholamine analogues markedly reduce neuronal noradrenaline in the large intestine, as demonstrated by fluorescence histochemistry and in fluorimetric determinations. The ultrastructural features of these varicosities and their reaction to 5- and 6-OH-dopamine indicate that they belong to adrenergic, sympathetic nerves. No membrane specializations could be detected at sites of close contact of the adrenergic boutons with dendrites and cell bodies of intrinsic nerve cells.Supported by grants from the Deutsche Forschungsgemeinschaft.Supported by a grant from Albert Pahlsson's Foundation, Sweden. The work was carried out within a research organization sponsored by the Swedish Medical Research Council (projects No. B70-14X-1007-05B, B70-14X-712-05, and B70-14X-56-06).     

Neuronal localization of dopamine,noradrenaline, and 5-hydroxytryptamine in the central and peripheral nervous system ofLumbricus terrestris (L.)

Summary Fluorescence microscopical studies with the procedure of Falck and Hillarp have confirmed previous observations concerning the appearance of neurones with green and yellow specific fluorescence in the central and peripheral nervous system ofLumbricus terrestris.Chemical estimates show that the fluorescent neurones contain the primary catecholamines dopamine and noradrenaline, in addition to an indolamine, presumably 5-hydroxytryptamine. Rude's opinion that dopamine is present in a concentration twice that of noradrenaline is confirmed.Microspectrofluorometric analyses of the neurones displaying green specific fluorescence show two types of neurones, one presumably containing dopamine (mainly the receptor cells, certain small and some of the large cells in the cerebral ganglion). Some of the large cells of the cerebral ganglion and the bipolar cells near the base of the second segmental nerve in the ventral nerve cord show characteristics compatible with the simultaneous presence of both noradrenaline and dopamine in them.This work was supported by grants from the Helge Ax:son Johnson Foundation and was carried out within a reasearch organization sponsored by the Swedish Medical Research Council (projects No. B71-14X-2321-04A, B71-14X-712-06A, and B71-14X-56-07A).     

Fine structure and innervation of the avian adrenal gland

Summary Apart from cholinergic nerve fibers, which make up the main part of efferent fibers to the avian adrenal gland (Unsicker, 1973b), adrenergic, purinergic and afferent nerve fibers occur. Adrenergic nerve fibers are much more rare than cholinergic fibers. With the Falck-Hillarp fluorescence method they can be demonstrated in the capsule of the gland, in the pericapsular tissue and near blood vessels. By their green fluorescent varicosities they may be distinguished characteristically from undulating yellow fluorescent ramifications of small nerve cells which are found in the ganglia of the adrenal gland and below the capsule. The varicosities of adrenergic axons exhibit small (450 to 700 Å in diameter) and large (900 to 1300 Å in diameter) granular vesicles with a dense core which is usually situated excentrically. After the application of 6-hydroxydopamine degenerative changes appear in the varicosities. Adrenergic axons are not confined to blood vessels but can be found as well in close proximity of chromaffin cells. Probably adrenergic fibers are the axons of large ganglion cells which are situated mainly within the ganglia of the adrenal gland and in the periphery of the organ and whose dendritic endings show small granular vesicles after treatment with 6-OHDA.A third type of nerve fiber is characterized by varicosities containing dense-cored vesicles with a thin light halo, the mean diameter (1250 Å) of which exceeds that of the morphologically similar granular vesicles in cholinergic synapses. Those fibers resemble neurosecretory and purinergic axons and are therefore called p-type fibers. They cannot be stained with chromalum-hematoxyline-phloxine. Axon dilations showing aggregates of mitochondria, myelin bodies and dense-cored vesicles of different shape and diameter are considered to be afferent nerve endings. Blood vessels in the capsule of the gland are innervated by both cholinergic and adrenergic fibers.Supported by a grant from the Deutsche Forschungsgemeinschaft (Un 34/1).     

Serotonin-immunoreactive and dopamine-immunoreactive neurones in the terminal ganglion of the cricket,Acheta domestica: Light- and electron-microscopic immunocytochemistry

Summary The distribution and ultrastructure of serotonin- and dopamine-immunoreactive (5-HTi and DAi) neurones have been investigated in the terminal ganglion of the cricket, Acheta domestica, using a pre-embedding chopper technique. Special attention has been paid to the immunoreactive structures in the neuropil. 5-HTi structures are extensively distributed and densely packed throughout the 5 neuromeres of the terminal ganglion and originate from several interneurones and efferent neurones. In contrast, DAi fibres are distributed sparsely although they extend to all neuromeres of the ganglion and originate from 6 interneurons only. For both 5-HTi and DAi neurones characteristic axonal projections and branching patterns can be distinguished. The 5-HTi axons exhibit rich varicose arborizations, whereas DAi neurones possess fewer varicosities in the neuropil. Electron microscopy shows that 5-HTi varicosities contain small ( 60 nm) and large ( 100 nm) agranular vesicles, and large ( 100 nm) granular vesicles, whereas in DAi varicosities small ( 60 nm) agranular and large ( 100 nm) granular vesicles are seen. Both 5-HTi and DAi varicosities form synaptic contacts. We conclude that both serotonin and dopamine may be used as neurotransmitters in the terminal ganglion of the cricket.Fellow of the Alexander von Humboldt-Stiftung     

Brain tissue transplanted to the anterior chamber of the eye

Summary Knowing the ontogenesis of the central monoamine neurons of the rat it is possible to obtain, by free-hand dissection from embryos and newly born animals, pieces containing dopamine (DA), noradrenaline (NA), and 5-hydroxytryptamine (5-HT) neurons that are small enough to permit homologous transplantation to the anterior chamber of the eye of adult animals. With this technique it was established that all three types of immature monoamine neurons are able to survive in the anterior chamber. Fluorescence histochemical analysis of whole mount preparations of the sympathetically denervated host irides revealed that both the catecholamine- and the 5-HT-neurons are able to partly reinnervate the irides, forming networks of varicose nerve terminals similar to the normally present sympathetic adrenergic ground plexus.Monoamine nerve cell bodies are attached to the irides but the majority of fluorescent nerve cell bodies is located within the transplants. Serial sectioning of these transplants showed rather well organized brain tissue, containing groups of fluorescent and non-fluorescent cell bodies, many areas being innervated by monoamine nerve terminals. When brain tissue was transplanted before the normal appearance of fluorescent neuroblasts (embryos with a crown-rump length less than 8 mm) monoamine neurons developed and matured within the eye.The amount of newly formed nerves of central origin recovered on the irides increased with time between the 2nd and 4th postoperative week and persisted after 2 months. The yield of new fibers was better using transplants from embryos with a crown-rump length between 15 and 30 mm than using transplants from larger embryos and newly born animals.If embryonic brain tissue known to be devoid of monoamine nerve cell bodies but containing monoamine nerve terminals in the adult state (cortex cerebri and cerebelli, spinal cord) was transplanted to sympathetically non-denervated eyes, the sympathetic adrenergic fibers seemed to be able to innervate the transplants.This work was supported by grants from the Swedish Medical Research Council (14×–3185), Karolinska Institutets fonder, and Magnus Bergvalls Stiftelse. We thank Miss Monica Eliasson, Mrs. Ulla Flyger, Mrs. Barbro Norstedt and Miss Ingrid Strömberg for skilful technical assistance. The generous gifts of Nialamide, Pfizer, and Pargyline, Abbott are gratefully acknowledged.     

Distribution of indolealkylamine nerve terminals in the ventricles of the rat brain

Summary The density, distribution and the pharmacologically produced changes of a formaldehyde-induced yellow supra-ependymal fluorescence in the lateral and third ventricles and in the aqueduct of the rat brain are described. The fluorescence consists of small spots or a thin spotted layer just above the ependymal cells. The highest fluorescence densities occur in the areas near the tela chorioidea of the third ventricle and in the interventricular foramen. A high to moderate density occurs in the lateral ventricles and in the aqueduct. Little or no fluorescence is seen above the hypothalamic areas bordering the third ventricle. The fluorescence rapidly fades upon irradiation with violet-blue light, disappears after treatment of the rats with reserpine or p-chlorophenylalanine, is intensified after nialamide or reserpine + nialamide, and does not change after -methyl-p-tyrosine.Electron microscopically supra-ependymal varicose nerves containing small (500 Å) and large (1000 Å) vesicles in the varicosities are observed in areas with supra-ependymal yellow fluorescence. A fine-structural cytochemical technique reveals the presence of a specific, chromaffine, reserpine-sensitive electron dense core in the small and large vesicles.The conclusion is drawn that a characteristically distributed population of supra-ependymal efferent nerve terminals containing an indolealkylamine, most probably 5-hydroxytryptamine, exists in the cerebral ventricles of the rat brain.The skilful assistance of Mr. R. Wybrecht and Mrs. G. Gschwind is gratefully acknowledged.     

Evidence for the existence of serotonin-, dopamine-, and noradrenaline-containing neurons in the gut of Lampetra fluviatilis

Summary Monoamine-containing neurons in the gut of Lampetra fluviatilis are characterized by histochemical, electron microscopical and biochemical methods. Strongly yellow fluorescent, probably serotonin-containing intrinsic neurons are found along the entire length of the intestine. Their processes aggregate to form large bundles of mainly non-terminal axons, constituting a subepithelial fibre plexus. This subepithelial, ganglion cell comprising plexus is connected to a wide-meshed subserosal plexus which has ganglion cells of different size and few varicose, single axons. Intermingled with both plexus there occur — in the anterior and middle but not in the preanal portion of the lamprey intestine — scattered green fluorescent intrinsic perikarya, emanating faintly green fluorescent, poorly varicosed axons.The formaldehyde-induced neuronal fluorophores conform to serotonin (yellow fluorescent compound), noradrenaline, and dopamine (green fluorescent substance), as revealed in microspectrofluorimetric recordings. The electron microscopical analysis of the yellow fluorescent intrinsic neurons in the terminal hindgut shows nerve cell pericarya and axons equipped with a typical population of occasional small granular and many large granular vesicles (750–1600 Å). The number and opacity of cores of the small and the osmiophilia of the cores of the large granular vesicles are significantly increased following short-term treatment with 5,6-dihydroxytryptamine. Long-term treatment with 5,6- or 5,7-dihydroxytryptamine provokes severe signs of ultrastructure impairment and eventual degeneration in the supposed serotonin-containing axons, besides indications of piling-up of organelles in the non-terminal axons due to arrest of axonal transport.Chromatography of acid extracts from the lamprey intestine, gills and kidney reveals the presence of serotonin (besides another unidentified indoleamine) and dopamine and noradrenaline in the gut, but only dopamine in the brain. The detection of serotonin, noradrenaline and dopamine in the lamprey gut is confirmed by chemical determinations.The occurrence of intrinsic serotonin-, noradrenaline- and dopamine-containing neurons in the gut of Lampetra fluviatilis deviates from the established pattern of innervation of the vertebrate intestine and is considered to be a remnant of an autonomic innervation principle common in invertebrates.Supported by grants from the Deutsche Forschungsgemeinschaft.Supported by grants from the Swedish Medical Research Council (No. 14X-712 and 14X-56.The authors are indebted to Lilan Bengtsson, Gertrude Stridsberg, Eva Svensson and Rolf Frank for skilful technical assistance.     

Function of Catecholamine-containing Neurones in Mammalian Central Nervous System

SEVERAL chemical substances are involved in synaptic transmission in the mammalian central nervous system^1–3. The Falck-Hillarp technique⁴ has demonstrated noradrenaline, dopamine and 5-hydroxytryptamine within nerve cell bodies and terminals^5,6 and the belief that these amines act as neurohumours is strengthened by observations that nerve fibre activation leads to their release from the terminals^7,8. Histo-chemical evidence suggests that discrete systems of neurones can be identified by their content of particular amines and it seems possible that such neurohumorally homogeneous systems have a functional as well as a chemical identity. Before the anatomical distribution of amine-containing neurones had been described, Brodie and Shore⁹ proposed that noradrenaline functions as the central neurohumour of the sympathetic and 5-hydroxytryptamine of the parasympathetic system. This suggestion has not been supported by anatomical evidence; the amine-containing neurones form systems of small diameter fibres of very diffuse terminal distribution, which do not correspond to recognized ascending or descending pathways^5,6, although amine-containing neurones in invertebrates have been identified as sensory systems¹⁰.     

Ultrastructural evidence for exocytosis in the median eminence of the rat

Summary Exocytosis has been demonstrated by electron microscopy in the external zone of the median eminence of the rat. Exocytotic profiles have been observed in nerve fibres characterized by the presence of granular vesicles with median diameters of 90–103 nm and agranular vesicles of about 50 nm. In addition to the small agranular vesicles, coated vesicles of the same size have been found in many nerve fibres, suggesting that at least part of the agranular vesicles in the median eminence originate by micro-pinocytosis. The nature of the fibres showing exocytosis is discussed. Attention is drawn to the possibility of identifying types of fibres in the median eminence by the occurrence of exocytosis.The technical assistance of Mrs. R. M. Y. Hartsteen is acknowledged with gratitude. We would like to thank Prof. J. Moll for his helpful criticism. We also thank Miss P. Delfos and Mr. W. van den Oudenalder for photographic assistance.     

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.     

Ultrastructural changes in the coronet cells of the saccus vasculosus from rainbow trout,Salmo gairdneri (Richardson), kept in sea water

Summary The coronet cells of saccus vasculosus of fresh-water living and sea-water adapted rainbow trout were studied with the electron microscope, with special regard to changes in the latter group. Only quantitative differences were observed, namely a raised number of mitochondria in the apical region and the head and also a concentration of the agranular endoplasmic reticulum with a higher amount of electron-dense material and vesicles around the Golgi saccules. Together, these findings suggest a secretory function for the coronet cell. A supposed transport of vesicles from the head region of the coronet cell out into the globules is suggested. Interrelation between primary and secondary vesicles is discussed.This work was supported by grants from the Royal Physiographical Society of Lund and the Faculty of Natural Sciences at the University of Lund.—I am greatly indebted to Mrs. Lena Svenre and Miss Inger Norling for excellent technical assistance.     

Ultrastructural effects of parachlorophenylalanine, 5-hydroxytryptamine and the imipramine group on the nerve processes of the small intestine.

The structure of the nerve fibres in the chronically isolated cat ileum was studied by fluorescence and electron microscopy after imipramine group compounds, parachlorophenylalanine, and 5-hydroxytryptamine treatment. Following treatment with parachlorophenylalanine and imipramine group compounds in the nerve fibres of the small intestine, specific granules were selectively decreased (p less than 0.001) in number. In concordance with ultrastructural observations, a marked diminution of fluorescence intensity was demonstrable in the small intestine. In addition, the number of the granular vesicles was significantly increased following 5-hydroxytryptamine treatment, and yellow fluorescent neurones and processes were observed in the myenteric and submucous plexuses. On the basis of these observations, the serotoninergic nature of certain nerve fibres could be demonstrated.     

Submicroscopic morphology of granular vesicles in sympathetic nerves of rat pineal body

Summary In the rat pineal body sympathetic nerve endings are characterized by numerous agranular and granular vesicles. The latter mainly include vesicles of about 450 Å diameter, each of which is bounded by a trilaminar membrane of about 75 Å total thickness. The cores of these granular vesicles appear structurally similar to the bounding membranes and are formed by a less dense, globular or vacuolar component around which a more dense component is distributed. The relative distributions of these two structural elements result in a variety of submicroscopic configurations which suggest a morphological continuum that may be related to the cyclical uptake, storage and release of biogenic amines. A tripartite classification of granular vesicles, such as proposed previously, is not supported by these data.This investigation was supported by United States Public Health Service Research Grants NB 05175-01 and AM-0699802. — The capable technical assistance of Mrs. Caroline Wilner is gratefully acknowledged.     

Vesicle and granule content of sympathetic ganglion cells during limb regeneration of the newt Triturus

Summary Fine structural observations were made on the vesicle and granule content of ganglion cells in the posterior subclavian ganglion and peripheral nerve fibers of the upper forelimb of the newt Triturus. The populations of vesicles and granules in normal ganglion cells and nerve fibers were compared with those observed after limb transection. In normal neurons, clear vesicles range in size from 250 to 1000 Å in diameter, but are most frequently 400–500 Å. Vesicles with dense contents (granules) also vary greatly in size, but most are 450–550 Å in diameter and correspond to dense-core vesicles. Large granules that contain acid phosphatase activity are thought to be lysosomes. During limb regeneration, in both the ganglion cells and peripheral nerves, the ratio of dense vesicles to clear vesicles increases. There is a large increase in number of dense granules with a diameter over 800 Å, particularly in the peripheral regenerating fibers. This study shows that regenerating neurons differ from normal in their content of vesicular structures, especially large, membrane-bounded granules.This work was supported by grants from the National Science Foundation (GB 7912) and from the National Cancer Institute (TICA-5055), National Institutes of Health, United States Public Health Service.     

Lysosomal activation in mouse skeletal muscle induced by protamine in vitro

Summary Incubation of mouse skeletal muscle in a physiological Ringer solution containing protamine (60 g/ml) at +37° C for 1 h induced ultrastructural changes including proliferation of tubular profiles and vesicles at the I-band level close to the A-I junction, formation of numerous acid phosphatase positive lysosomes in the longitudinal sarcoplasmic reticulum and autophagic vacuolation starting at the level of the A-I junction.Biochemical determination of acid phosphatase in the incubated muscles showed that protamine caused an increase in acid phosphatase activity of about 25 % compared to enzyme activities obtained from muscles incubated without protamine at +37°C or with protamine at +4°C.The morphological findings suggest that the vesicles arising adjacent to the A-I junction originate from transverse tubules. Such vesicles, designated as endocytic, may acquire acid phosphatase activity in the longitudinal SR and be active in an autophagic process resulting in large vacuoles. A causal relationship between endocytosis and lysosomal activation is suggested.We wish to thank Miss Britt-Marie Svensson, Miss Ann-Christin Nilsson and Mrs. Lena Kvist for their able technical assistance. This work was supported by grants from the Medical Faculty, University of Lund, Sweden, and the Swedish Medical Research Council, Stockholm, Sweden (04P-4289, 14X-4286, 14X-3112) and from Muscular Dystrophy Association of America, Inc.     

Fine structural localization of acid phosphomonoesterase in the brush border region of osteoclasts

Summary The fine structural localization of acid phosphomonoesterase was studied in osteoclasts of fracture callus in the rat. In addition to being present in the Golgi apparatus and the lysosomes, reaction product was precipitated over tubular elements, vesicles, and vacuoles located subjacent to the brush border. The findings are compatible with the idea that the calcified matrix can be destroyed by the combined effects of absorption with subsequent intracellular digestions in osteoclasts, and actual secretion of lysosomal enzyme to the extracellular space.This study was supported by grants from the Swedish Medical Research Council (Project no. B72-12X-1006-07A) and Konung Gustav V:s åttioårsfond". The assistance of Miss Silwa Mengarelli and Mrs. Britt-Marie Åkerman is gratefully acknowledged.     

The fine structure of cephalopod blood vessels III. Vessel innervation

Summary The cephalic aorta of Octopus vulgaris has a fairly complete endothelium lining the lumen, a thick complete basement membrane, a layer of circularly orientated and a layer of longitudinally orientated muscle fibres. Presumptive synaptic endings are of two types. In the circular muscle, axons containing vesicles, contact club-shaped projections of the muscle. The gap between the pre- and postsynaptic membranes is less than 100 Å and in some places apparently forms a tight junction. The second type of ending has been found in the longitudinal muscle; here axons full of vesicles end on the muscle. The ending is enclosed by a mesaxon of muscle and the synaptic gap is approximately 100 Å. In the smaller blood vessels, axons end on myofilament-containing pericytes of blood vessels (equivalent to small arterioles). The endings contain vesicles and have a synaptic gap of 100 Å. Only some of the pericytes seem to be innervated and transmission between one pericyte to another may be mediated by specialized junctions between the cells. The smaller non-myofilament containing vessels (equivalent to capillaries) are not thought to be innervated.We would like to thank Professor J. Z. Young and Dr. E. G. Gray for advice and encouragement, Mrs. Jane Astafiev for drawing Figs. 1 and 12, Mr. S. Waterman for photography, and Miss Cheryl Martin for secretarial assistance.     

Degeneration of monoamine nerves in anterior byssus retractor muscle of Mytilus induced by 5,6-dihydroxytryptamine

Summary Preliminary ultrastructural studies on the effects of 5,6-Dihydroxytryptamine (5,6-DHT) on the anterior byssus retractor muscle (ABRM) of Mytilus show degeneration of 2 types of monoaminergic nerves after 10 days of drug treatment. One type contained large granular vesicles (560–1,680 Å) while the other had small granular vesicles (200–640 Å). These axons may possibly represent serotonergic and dopaminergic nerves, thought to innervate this muscle.Two other types of profiles seemed to be unaffected by the drug. One conforms to cholinergic nerves while the other has a predominance of large opaque vesicles (1,200–2,500 Å). The significance of these findings is discussed in the light of recent observations on the neurotoxic effects of 5,6-DHT on vertebrate and molluscan nerves.The author is grateful to Professor G. Burnstock for research facilities and Professor B. M. Twarog for advice and encouragement. This work was supported by the Ramaciotti Foundation     

Photoperiodic and osmotic influences on the ultrastructure of the hypothalamic neurosecretory system of the White-crowned sparrow,Zonotrichia leucophrys gambelii

Summary An attempt was made to correlate functional changes in the neurohypophysis of the White-crowned Sparrow, Zonotrichia leucophrys gambelii, with morphologic features on the light- and electron-microscope levels. The aldehyde-fuchsin-staining anterior median eminence possesses essentially the same ultrastructural features as the non-staining posterior median eminence. The axon terminals are characterized by the presence of a large number of small vesicles (approximately 400 Å in diameter) and occasional electron-dense granules. The more-or-less depleted anterior median eminence occasionally evident in the photosensitive bird showing testicular development is indistinguishable ultrastructurally from the more intensely staining median eminence generally characteristic of the photorefractory bird. In the median eminence, stainability and functional state do not seem to be correlated with changes in the type, size or number of vesicles. A slight increase in the number of granules was noted in the photorefractory bird but this was considered insufficient basis to account for differences in stainability.The pars nervosa, on the other hand, responded to osmotic stimuli (saline drinking water) by loss of stainability and decrease in numbers of elementary neurosecretory granules. Small vesicles are also present in the pars nervosa axon terminals, but are intermingled with neurosecretory granules in normal birds. Acute-osmotic birds, however, had axon terminals almost entirely occupied by small vesicles.It is to be emphasized that the pars nervosa and the median eminence are two structurally very different regions of the neurohypophysis. The basis for aldehyde-fuchsin staining in the median eminence appears to differ from that in the pars nervosa. The implications of these findings are considered in regard to hypothalamic control over gonadotropic activity in the White-crowned Sparrow.Dedicated to Professor Dr. W. Bargmann in honor of his 60th birthday.This investigation was supported by grant GB-2484 from the National Science Foundation to Professor Bern, grant GB-2819 from the National Science Foundation to Professor Mewaldt, and grant NB-01353 from the National Institutes of Health to Professor Farner. The authors wish to express their appreciation of the technical assistance of Mrs. Irene Brown, Mr. John Butchart, Sally S. Kibby, Mrs. Carol Nicoll, and Mr. John Striffler. Mrs. Emily Reid kindly prepared the histograms.