条背萤成虫与幼虫发光器的超微结构观察

对水生萤火虫——条背萤Luciola substriata(Gorham)成虫和幼虫发光器的超微结构进行研究。结果表明,成虫发光器由明显的2层组成:反射层和发光层。反射层由排列紧密的“尿酸囊泡”构成,具有发达的气管结构,对光起反射作用;发光层由大量发光细胞构成,内含典型的发光颗粒、线粒体、内质网及大量糖原,该层通过发光细胞胞质内的生化反应而发光。2层均由非细胞层膜包被,间距25~30μm。发光器腹节由外向内依次为表皮、发光层、反射层和内部细胞层。幼虫发光器球形,由背射层和发光层构成,由非细胞层膜包被。背射层由单层柱状细胞构成,内含大量“尿酸囊泡”。发光层细胞膜相互绞缠,含有2种类型的发光颗粒:“致密”型和“凋亡”型,含有大量的线粒体和无定形颗粒,发光细胞之间分布着大量的气管、微气管及神经末梢,可观察到神经突触。与条背萤相比,陆生种成虫反射层和发光层均无非细胞层膜包被,2层间无明显间距,发光颗粒形状不规则,气管通常形成2分支;陆栖种幼虫发光层形状差异较大,背射层由单层或2~4层细胞构成;相似点在于,成虫发光器都由均由反射层和发光层构成,发光细胞内都含发光颗粒、线粒体及大量糖原,都具有发达的气管结构,发光颗粒相似。幼虫发光器都由背射层和发光层构成,都具有发达的气管和直接的神经支配,发光颗粒相似,都由非细胞层膜包被。     

The fine structure of the light organ of the New Zealand glow-worm Arachnocampa luminosa (Diptera: Mycetophilidae).

The swollen distal tips of the Malpighian tubules of the glow-worm Arachnocampa luminosa constitute the light organ. The ventral and lateral surfaces are covered by a tracheal ‘reflector’ and the nervous supply to the light organ comes from the ganglion in the penultimate segment. Fine nerve terminals, axons, and glial cells can be seen in close proximity to the basal surface of the cells of the light organ. The epithelial cells of the light organ are large, the cytoplasm dense, homogeneous and acidophilic. The cytoplasm gives a strong positive reaction for protein. The cytoplasm contains a high density of free ribosomes, patches of dense material, smooth endoplasmic reticulum, glycogen and scattered microtubules. Mitochondria are numerous; they are large, randomly distributed and packed with fine cristae. These cells lack the features characteristic of Malpighian tubule epithelial cells; infolding of the apical and basal cell surfaces is reduced and the cytoplasm contains few organelles. These cells do not contain secretory or photocyte granules and the grainy cell matrix is thought to be the luciferin substrate. Oxygen is supplied via the tracheal layer (which may have secondary reflecting properties) and light production controlled by neurosecretory excitation either directly via synapses, or by hormones. There are no other reports of Malpighian tubules of insects producing light and the fine structure of these cells is distinct. Thus, the swollen distal tips of the Malpighian tubules of the glow-worm undoubtedly constitute a unique luminescent organ.     

THE ORGANIZATION AND INNERVATION OF THE LUMINESCENT ORGAN IN A FIREFLY, PHOTURIS PENNSYLVANICA (COLEOPTERA)

The organization of the luminescent organ of an adult firefly has been studied with the electron microscope, and particular attention has been given to the disposition of nerve terminals within the organ. The cytological structure of the cells of the tracheal system, the peripheral and terminal axons, the photocytes and the cells of the dorsal ("reflecting") layer is described. Previous observations on the peripheral course of nerve branches alongside the tracheal trunks at the level of the dorsal layer and photocyte epithelium have been confirmed, and specialised nerve endings containing axoplasmic components structurally identical with "synaptic vesicles" and "neurosecretory droplets" have been identified, not in association with the surface of the photocytes, but lying between the apposed surfaces of two components of the tracheal epithelium: the tracheal end-cell and the tracheolar cell. These cytological findings are discussed in terms of available biochemical and physiological evidence concerning the mechanism of light emission in the firefly, especially with respect to the possible role of chemical "transmitter" action in triggering a response in a luminescent effector system.     

Autonomic nerve terminals in relation to contractile and non-contractile structures in the conduit coronary artery of the dog

The ramus interventricularis anterior (RIA), its first- and second-order branch were prepared for EM (perfused with glutaraldehyde under pressure, or simply fixed with KMnO4). No nerve fibres were found in the tunica media of either of the three consecutive segments. In the tunica adventitia axons with varicosities were found at a distance from the tunica media of 0.5-15 microns (about 50% 0.5-4.5 microns) in the RIA, 0.4-12 microns (about 50% 0.5-3.4 microns) in the first-order branch and 0.3-6.0 microns (about 50% 0.3-2.3 microns) in the second-order branch. Varicosities contain small, dense-cored vesicles (35-60 nm) and large, dense-cored vesicles (70-90 nm, exceptionally up to 120 nm); the other type contains small, clear vesicles (35-60 nm) and few large, dense-cored vesicles (70-90 nm). The remarkably large distance between the nerve terminals and smooth muscle cells fits well with the small range of sympathetic control of the conduit coronary artery. Close apposition of nerve terminals to fibroblasts (30-200 nm) was revealed in all three consecutive coronary portions. Moreover, terminal axons often lose the Schwann cell cover on the abluminal site and face the fibroblast.     

Ultrastructural correlates of luminescence in Porichthys photophores. II. Effects of metabolic inhibitors.

Prolonged, bright luminescent glows in Porichthys photophores are elicited by administration of 2,4-dinitrophenol (DNP) and potassium cyanide (KCN). Ultrastructural alterations of varicose nerve endings precede photocyte changes during such luminescent activity. Common alterations of nerve profiles include mitochondrial disruptions, flattening and depletion of synaptic vesicles, formation of large vacuolar cisternae, and invaginations in the contour of axolemma. Protracted luminescent activity in response to DNP results in depletion of photocyte vesicle material while vesicle and ER membranes accumulate and coil inside coalesced vesicle pools, and photocyte microvilli disappear completely. Although similar photocyte alterations are initially observed in KCN treated luminescing photophores, the early extinction of the response to KCN is related to deleterious, irreversible effects of this chemical on photocytes. These observations, along with some pharmacological manipulations, indicate that at least DNP acts initially and primarily on neural structures, probably the mitochondria, to induced transmitter release and consequent photocyte activity. Based on this and earlier studies, a chain of subcellular events leading to light emission of Porichthys photophores is proposed and discussed.     

Electron microscopic study on the innervation of the pancreas of the domestic fowl

Summary The innervation of the pancreas of the domestic fowl was studied electron microscopically. The extrapancreatic nerve is composed mostly of unmyelinated nerve fibers with a smaller component of myelinated nerve fibers. The latter are not found in the parenchyma. The pancreas contains ganglion cells in the interlobular connective tissue. The unmyelinated nerve fibers branch off along blood vessels. Their synaptic terminals contact with the exocrine and endocrine tissues. The synaptic terminals can be divided into four types based on a combination of three kinds of synaptic vesicles. Type I synaptic terminals contain only small clear vesicles about 600 Å in diameter. Type II terminals are characterized by small clear and large dense core vesicles 1,000 Å in diameter. Type III terminals contain small clear vesicles and small dense core vesicles 500 Å in diameter. Type IV terminals are characterized by small and large dense core vesicles. The exocrine tissue receives a richer nervous supply than the endocrine tissue. Type II and IV terminals are distributed in the acinus, and they contact A and D cells of the islets. B cells and pancreatic ducts are supplied mainly by Type II terminals, the blood vessels by Type IV terminals.This work was supported by a scientific research grant (No. 144017) and (No. 136031) from the Ministry of Education of Japan to Prof. M. Yasuda     

The fine structure of the light organ of the glowworm Lampyris noctiluca

Summary The four main parts of the glowworm light organ are the cuticle, the hypodermis, the photocyte layer and the reflector cell layer. The hypodermis is one cell thick and it contains hypodermic glands. These glandular cells have a lumen that opens to the outside of the cuticle. Projecting into the lumen are numerous microvilli. Between the hypodermis and photocytes are typical insect tunicated nerve fibres. They pass down between the photocyte and reflector layer cells. They do not appear to innervate the photocytes and they are thought to innervate adjacent muscle fibres or to be sensory. Tracheoles are commonly present between the photocytes but no tracheolar end organs are found. The photocytes contain amorphous granules, mitochondria, photocyte granules and a vesiculated reticulum. All, except the mitochondria, are absent from the reflector layer and so probably have some connection with light production. The reflector layer contains glycogen granules, clear spaces thought to be the sites of urate crystals, and membranous granules. The latter granules are sometimes found in photocytes adjacent to the reflector layer whilst amorphous granules are sometimes absent from these adjacent cells. So a cell layer with some features of the photocyte and reflector layer cells is present. These morphological findings are discussed with regard to the unknown function of the reflector layer and the control of light emission. Acknowledgments. We would like to thank Professor J. Z. Young and Dr. E. G. Gray for their advice and encouragement, Mrs. Jane, Astafiev for drawing fig. 1, Mr. S. Waterman for photographic assistance, Miss Cheryl Martin for secretarial assistance, and many colleagues for help in collecting specimens of glowworms.     

The Fine Structure of Photoreceptor Terminals in the Compound Eye of Pandalus borealis (Crustacea)

Seven of the photoreceptor axons of each ommatidium in the compound eye of the prawn Pandalus borealis end in two layers in the optic lamina. They have expanded terminals in the optic cartridges; four distally and three proximally in each cartridge. All seven receptor terminals are presynaptic to one lamina monopolar neuron (M₂) of the cartridge. This monopolar neuron is situated centrally in the cartridge and has a thick axis fibre with radially arranged branches, and its axon has a terminal in medulla externa. At the synapses, an arrowlike presynaptic bar is found facing three postsynaptic profiles. The receptor terminals have several characteristics. Their cytoplasm is filled with empty and coated vesicles, and contains numeorus large mitochondria and clusters of tubular elements. There is a longitudinally arranged fascicle of filaments partly surrounded by electron-dense amorphous material in the terminals. Centrally towards M₂, numerous neural spines invaginate into the terminal. Along the entire terminal periphery, there are invaginations from the glial cells. The terminals also form small knoblike protrusions extending into the surrounding glial cells.     

Catecholamine-rich cells and varicosities in bovine splenic nerve, vesicle contents and evidence for exocytosis.

The bovine splenic nerve trunk contains mast cells, ganglion cells, small intensely fluorescent (SIF) cells, and varicosities which exhibit a brilliant fluorescence characteristic for noradrenaline (NA) and dopamine (DA) after formaldehyde exposure. All these catecholamine-rich structures could contribute particles to isolated nerve vesicle fractions. Mast cells are recognized ultrastructurally by their large (300-800 nm) dense granules. SIF cells may be represented by cells and processes containing dense cored vesicles (120-140 nm) which are larger than the typical vesicles in axons and terminals. Terminal-like areas with typical large dense cored vesicles (LDV, 75 nm) and small dense cored vesicles (SDV, 45-55 nm) probably correspond to the fluorescent varicosities. The LDV constitute about 40% of all vesicles in terminal-like areas and terminals. Their staining properties indicate the presence of protein, phospholipids, and ATP. Tyramine depletes NA without loss of matrix density. The LDV can fuse with the terminal membrane, and released material outside omega profiles is interpreted to depict exocytosis. Large and small vesicles are easily distinguished from the very large mast cell granules and the moderately dense Schwann cell vesicles. Neither appear to contaminate the LDV fractions but the latter may contain a small population of SIF cell vesicles. Golgi vesicles from the Schwann cells mainly occur in the lighter zones of the gradient.     

Catecholamine-rich cells and varicosities in bovine splenic nerve,vesicle contents and evidence for exocytosis

The bovine splenic nerve trunk contins mast cells, ganglion cells, small intensely flurescent (SIF) cells, and varicosities which exhibit a brilliant fluorescence characteristic for noradrenaline (NA) and dopamine (DA) after formaldehyde exposure. All these catecholamine-rich structure could contribute particles to isolated nerve vesicle fractions. Mast cells are recognized ultrastructurally by their large (300–800nm) dense granules. SIF cells may be represented by cells and processes containing dense cored vesicles (120–140 nm) which are larger than the typical vesicles in axons and terminals. Terminal-like areas with typical large dense cored vesicles (LDV, 75 nm) and small dense cored vesicles (SDV, 45–55 nm) probably correspond to the fluorescent varicosities. The LDV constitute about 40% of all vesicle in terminal-like areas and terminals. Their staining properties indicate the presence of protein, phospholipids, and ATP. Tyramine depletes NA without loss of matrix density. The LDV can fuse with the terminal membrane, and released material outside omega profiles is interpreted to depict exocytosis. Large and small vesicles are easily distinguished from the very large mast cell granules and the moderately dense Schwann cell vesicles. Neither appear to contaminate the LDV fractions but the latter may contain a small population of SIF cell vesicles. Golgi vesicles from the Schwann cells mainly occur in the lighter zones of the gradient.     

Adrenergic neurons in the spinal cord of the pike (Esox lucius) and their relation to the caudal neurosecretory system

Summary The lower spinal cord including the caudal neurosecretory system of the pike (Esox lucius) was investigated by means of light and electron microscopy and also with the fluorescence histochemical method of Falck and Hillarp for the visualization of monoamines. A system of perikarya displaying a specific green fluorescence of remarkably high intensity is disclosed in the basal part of the ventrolateral and lateral ependymal lining of the central canal. The area corresponding to the upper half of the urophysis has most cells; their number decreases caudally and cranially. A considerable number of their beaded neurites reach the neurosecretory neurons by different routes but are only occasionally present in the actual neurohemal region. An intensely fluorescent dendritic process is sometimes observed terminating with a bulbous enlargement at the ependymal surface in the central canal. Besides small, electron lucid vesicles in the terminal parts of the axons, the neurons contain numerous large dense-core vesicles which can apparently take up and store 5-hydroxydopa (5-OH-dopa) and 5-hydroxydopamine (5-OH-DA). These neurons are thought to be adrenergic and to contain a primary catecholamine, possibly noradrenaline.The varicosities of the adrenergic terminals are repeatedly observed contiguous to some of the neurosecretory axons, the membrane distance at places of contacts generally ranging from 150–200 Å. Another type of nerve terminals that contain only small empty vesicles, also after pretreatment with 5-OH-dopa or 5-OH-DA, are frequent among the neurosecretory neurons. These axons establish synaptic contacts with membrane thickenings on most of the neurosecretory neurons. Thus it seems that the neurosecretory neurons are innervated by neurons morphologically similar to cholinergic neurons and that part of them receive an adrenergic innervation, which supports the view hat the caudal neurosecretory cells do not constitute a functionally homogeneous population.Supported by the Deutsche Forschungsgemeinschaft and the Joachim-Jungius Gesellschaft zur Förderung der Wissenschaften, Hamburg.Supported by the Swedish Natural Research Council (No. 99-35). This work was in part carried out within a research organization sponsored by the Swedish Medical Research Council (Projects No. B70-14X-56-06 and B70-14X-712-05).Supported by the Deutsche Forschungsgemeinschaft and USPHS Research Grant TW 00295-02.     

Fine-Structural Characterization of the Somatic Innervation of the Tympanic Membrane in Normal,Sympathectomized, and Neurotoxin-Denervated Rats

The pars tensa of the rat tympanic membrane (TM) consists largely of a lamina propria of specialized unbanded collagen bounded on the outer surface by an unusually thin epidermal layer and on the inner surface by a flat, single-cell mucosal layer. The mucosal layer is innervated solely by unmyelinated (C) axons, whereas the cutaneous layer is supplied by both myelinated and C axons. The outer surface differs from general body skin, lacking dermal papillae, hairs, sweat glands, and distinctive dermal corpuscular structures.

Epidermal innervation includes distinctive terminals in the basal layer, unassociated with Merkel cells, and deeper intraepidermal smaller endings containing accumulations of mitochondria and vesicles. The sensory nature of these endings can be inferred by their extensive, but not total, elimination following neonatal capsaicin treatment (a potent neurotoxin for thin sensory fibers) and their preservation following surgical or neurotoxin sympathectomy.

The thin mucosal epithelium displays capillaries and beaded axons close to the free surface of the middle ear. The unmyelinated terminals contain predominantly large, dense-core vesicles (LDCVs). Capsaicin treatment results in extensive elimination of terminals containing LDCVs in surface epithelia. A possible small trophic influence of sensory thin-fiber supply was noted on the development of the epidermal layers. The sensory modalities elicited by natural stimulation of the TM is considered in relation to the pattern of innervation.     

Structure of the intramural nerves of the rat bladder

The bladder of adult female rats receives ～16,000 axons (i.e., is the target of that many ganglion neurons) of which at least half are sensory. In nerves containing between 40 and 1200 axons cross-sectional area is proportional to number of axons; >99% of axons are unmyelinated. A capsule forms a seal around nerves and ends abruptly where nerves, after branching, contain ～10 axons. A single blood vessel is present in many of the large nerves but never in nerves of <600 axons. The number of glial cells was estimated through the number of their nuclei. There is a glial nucleus profile every 76 axonal profiles. Each glial cell is associated with many axons and collectively covers ～1,000 μm of axonal length. In all nerves a few axonal profiles contain large clusters of vesicles independent of microtubules. The axons do not branch; they alter their relative position along the nerve; they vary in size along their length; none has a circular profile. All the axons are fully wrapped by glial cells and never contact each other. The volume of axons is larger than that of glial cells (55%–45%), while the surface of glial cell is twice as extensive as that of axons; there are ～2.27 m² of axolemma and ～4.60 m² of glial cell membrane per gram of nerve. Of the mitochondria of a nerve ～3/4 are in axons and ～1/4 in glial cells.     

Structure of anterior dorsal ventricular ridge in snakes.

Anterior dorsal ventricular ridge (ADVR) is a major subcortical, telencephalic nucleus in snakes. Its structure was studied in Nissl, Golgi, and electron microscopic preparations in several species of snakes. Neurons in ADVR form a homogeneous population. They have large nuclei, scattered cisternae of rough endoplasmic reticulum in their cytoplasm, and bear dendrites from all portions of their somata. The dendrites have a moderate covering of pedunculated spines. Clusters of two to five cells with touching somata can be seen in Nissl, Golgi, and electron microscopic preparations. The area of apposition may contain a series of specialized junctions which resemble gap junctions. Three populations of axons can be identified in rapid Golgi preparations of snake ADVR. Type 1 axons course from the lateral forebrain bundle and bear small varicosities about 1 mu long. Type 2 axons arise from ADVR neurons and bear large varicosities about 5 mu long. The origin of the very thin type 3 axons is not known; they bear small varicosities about 1 mu long. The majority of axon terminals in ADVR are small (1 mu to 2 mu long), contain round synaptic vesicles, and form asymmetric active zones. This type of axon terminates on dendritic spines and shafts and on somata. A small percentage of terminals are large, 5 mu in length, contain round synaptic vesicles, and form asymmetric active zones. This type of axon terminates only on dendritic spines. A small percentage of terminals are small, contain pleomorphic synaptic vesicles, and form symmetric active zones. This type of axon terminates on dendritic shafts and on somata.     

Autonomic nerves terminating on smooth muscle cells of vessels in the pineal organ of various mammals

The significance of autonomic nerves reaching the pincal organ was already investigated in connection to the innervation of pinealocytes and mediating light information from the retina for periodic melatonin secretion. In earlier works we found that some autonomic nerve fibers are not secretomotor but terminate on arteriolar smooth muscle cells in the pineal organ of the mink (Mustela vison). Studying in serial sections the pineal organ of the mink and 15 other mammalian species in the present work, we investigated whether similar axons of vasomotor-type are generally present in the wall of pineal vessels, further, whether they reach the organ via the conarian nerves or via periarterial plexuses. In all species investigated, axons of perivasal nerve bundles were found to form terminal enlargements on the smooth muscle layer of pineal arterioles. The neuromuscular endings contain several synaptic and some granular vesicles. Axon terminals are also present around pineal veins. In serial sections, we found that the so-called conarian autonomic nerves reach the pineal organ alongside pineal veins draining into the great internal cerebral vein. Similar nerves present near arteries of the arachnoid enter the pineal meningeal capsule and septa by arterioles, both perivenous and periarterial nerves form terminals of vasomotor-type. The arteriomotor and venomotor regulation of the tone of the vessels of the pineal organ may serve the vascular support for circadian and circannual periodic changes in metabolic activity of the pineal tissue.     

Synaptin/synaptophysin, p65 and SV2: their presence in adrenal chromaffin granules and sympathetic large dense core vesicles.

The subcellular distribution of three proteins of synaptic vesicles (synaptin/synaptophysin, p65 and SV2) was determined in bovine adrenal medulla and sympathetic nerve axons. In adrenals most p65 and SV2 is confined to chromaffin granules. Part of synaptin/synaptophysin is apparently also present in these organelles, but a considerable portion is found in a light vesicle which does not contain significant concentrations of typical markers of chromaffin granules (cytochrome b-561, dopamine beta-hydroxylase or the amine carrier). An analogous finding was obtained for sympathetic axons. The large dense core vesicles contain most p65 and also SV2 but only a smaller portion of synaptin/synaptophysin. A lighter vesicle containing this latter antigen and some SV2 has also been found. These results establish that in adrenal medulla and sympathetic axons three typical antigens of synaptic vesicles are not restricted to light vesicles. Apparently, a varying part of these antigens is found in chromaffin granules and large dense core vesicles. On the other hand, the light vesicles do not contain significant concentrations of functional antigens of chromaffin granules. Thus, the biogenesis of small presynaptic vesicles which contain all three antigens as well as functional components like the amine carrier is likely to involve considerable membrane sorting.     

Ultrastructural correlates of luminescence in Porichthys photophores. I. Effects of spinal cord stimulation and exogenous noradrenaline.

Light emission induced by electrical stimulation of the spinal cord is associated with ultrastructural alterations of the varicose endings, photocyte organelles and membranes in Porichthys photophores. Changes in nerve profiles appear first and include alterations of the shape, number and distribution of synaptic vesicles, as well as invaginations of the axolemma and mitochondrial swellings. Protocyte vesicles become markedly coalesced and their membranes are incorporated inside vesicular pools, whereas photocyte microvilli become sharply reduced at the cell periphery. Luminescence obtained by administration of noradrenaline is accompanied by similar, but more acute changes in the ultrastructure of photocytes, whereas no marked alteration of nerve profiles is noted after this treatment. These and other observations, such as the presence of specialized synaptic contacts, are discussed in terms of neural activity and processes within the photocytes which may lead to light production.     

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).     

Fine structure of the autonomic nerves of the rabbit myometrium

Summary The fine structure of the preterminal nerve fibers of the rabbit myometrial smooth muscle was studied using potassium permanganate fixation or glutaraldehyde fixation with postosmification. The preterminal fibers were mostly formed by 2–10 axons enveloped by Schwann cells. Two kinds of axons and axon terminals were found. (1) Adrenergic axons, which contained many small, granular vesicles (diameter 300–600 Å) and large granular vesicles (diameter 700–1200 Å) which represented ca. 2% of the total count of the vesicles. (2) Nonadrenergic axons, which contained small agranular vesicles (diameter 300–600 Å) and large granular vesicles (diameter 700–1200 Å). Both types of axons formed preterminal varicosities along their course. The real terminal varicosities, representing the anatomical end of the axons, were usually larger than the preterminal ones and showed close contact to the plasma membranes of the smooth muscle cells. Both adrenergic and nonadrenergic terminals were found close to the smooth muscle cells, but a gap of at least 2000 Å was always present between the two cell membranes. The axons and preterminal varicosities of both types of nerves were in intimate contact with each other within the preterminal nerve fiber. Axo-axonal interactions between the two types of axons are possible in the rabbit myometrium. The relative proportion of the nonadrenergic axons from the total was about one fourth.     

Interneuronal synapses in the local ganglia of the cat urinary bladder.

The interneuronal synapses of the urinary bladder in the cat were studied by electron microscopy. The great majority of the fibres containing vesicles are found within the ganglia occurring in the trigonum area. Morphologically differentiated synaptic contacts could be observed on the surface of the local neurons and between the different nerve processes. The presynaptic terminals can be divided into three types based on a combination of synaptic vesicles. Type I terminals, presumably cholinergic synaptic terminals, contain only small clear vesicles of 40-50 nm in diameter. Type II terminals, presumably adrenergic terminals, are characterized by small granulated vesicles of 40-60 nm in diameter. Type III terminals, probably of local origin, contain a variable number of large granulated vesicles of 80-140 nm in diameter. Occasionally, a single nerve fibre contacted several (two or four) other nerve processes forming a typical synapse. In other cases, on one nerve cell soma or on other nerve processes there are two or three different-type nerve terminals establishing synapses. It might be inferred from these observations that convergence and divergence can occur in the local ganglia and that cholinergic and adrenergic synaptic terminals can modulate the ganglionic activity. However, a local circuit also can play an important role in coordinating the function of the bladder.