Observations on the fine structure,enzyme histochemistry,and innervation of parathyroid gland and ultimobranchial body of Chthonerpeton indistinctum (Gymnophiona,Amphibia)

Summary Fine structural and enzyme histochemical observations on ultimobranchial body and parathyroid gland of the caecilian Chthonerpeton are presented. The cell clusters and follicles of the ultimobranchial body consist mainly of granulated cells which are termed C-cells and obviously belong to the APUD cell series. In the larger follicles additional possibly exhausted degranulated cells and replacement cells occur. A rich supply of nerve fibres has been found in this gland. Frequently nerve terminals were observed to come into synaptic contact with the C-cells. Two categories of nerve fibres occur: a) fibres containing large polymorphic electron dense granules (probably purinergic fibres), b) fibres containing small electron transparent vesicles and a few electron dense granules (probably cholinergic fibres). The parathyroid gland consists of elongated cells (one cell type) poor in organelles and often containing fields of glycogen and lipid droplets. The cells are further characterized by fair amounts of lysosomal enzymes; they are interconnected by maculae adhaerentes and occludentes. No nerves and blood vessels have been found in the parathyroid gland of Chthonerpeton. This study has been supported by the Deutsche Forschungsgemeinschaft We 380/5.     

Nature of vesicles associated with the nervous system of cephalopods

Summary The epistellar body on the stellate ganglion of octopods and the parolfactory vesicles on the optic tracts of decapods have been established as potential photoreceptors on the basis of morphology (rhabdomeric processes) and biochemistry (presence of rhodopsin and vitamin A₁). These organs are not to be viewed as neuroglandular, as originally suggested, but rather as possibly contributing to physiological regulation by recording photic information. Layers of nerve fibers are evident around the vesicles in silver-stained preparations, contributing to nerves with central connections. The stellate ganglion of the young Octopus has lens-like optical properties.Dedicated to Professor Berta Scharrer in honor of her 60th birthday.Aided by U.S. National Science Foundation grant GB-2484. We wish to express our thanks to Doctors Pietro Dohrn and Luisa Tosi for the provision of facilities, to Professor A. de Girolamo and Dr. Aldo Cecio of the Istituto di Anatomia, Istologia e Embriologia Veterinaria of the University of Naples for their generous cooperation in allowing us the use of their electronmicroscope laboratory, to Mr. Jeremy Worthington for able technical assistance, and to Miss Margaret Rufener for the drawings.National Science Foundation Senior Postdoctoral Fellow, Stazione Zoologica di Napoli, 1965–1966     

Quantitative differences among the brains of cephalopods

The relative sizes of 30 lobes of the brains of 63 species of cephalopods have been compared. Some of the observed differences could be related to the way of life of the animal and others to the taxonomic relationships. The octopods are separated from the decapods by their larger brachial and other suboesophageal lobes, larger inferior frontal systems and smaller optic lobes. Vampyroteulhis lies somewhat between these two main groups. The vertical lobe system is large in sepioids and loliginids, smaller in decapods from deeper water, but large in Vampyroteuthis. In octopods, it is large in the typical epibenthic forms but smaller in those from deeper water and very small in cirrates. The inferior frontal system is very large in epibenthic octopods and Benthoctopus and in cirrates, but smaller in epipelagic and bathypelagic forms. The optic lobes are larger in decapods than in octopods from comparable depths and are especially large in deep-sea decapods. They are larger in epipelagic octopods than in the typical benthic forms. The photosensitive vesicles vary by nearly two orders of magnitude. They are very small in squids living in surface waters, larger in mesopelagic forms and enormous in some cranchiids and in Balhyteuthis. In Histioteulhis , the side with the larger eye had an optic lobe twice as big as that on the side of the smaller eye, but with only slight differences in other parts of the brain. In the octopods, the inferior frontal system was generally large, being concerned with the tactile memory system, and tends to be inversely related to the size of the optic lobe.     

The statocyst of Vampyroteuthis infernalis (Mollusca: Cephalopoda)

The statocyst shows a remarkable combination of features of decapods and octopods confirming that Vampyroteuthis is a relic somewhere near the ancestor of both groups. The lining of the statocyst separates from the outer wall, forming an inner sac, filled with endolymph, surrounded by perilymph. This is the condition found in octopods, never in decapods. The macula is partly divided into a macula princeps and macula neglecta, as in decapods but never in octopods. There are numerous statoconia, but no large statolith has been seen. The crista has four parts as in decapods, but they are not sharply separated. There are numerous small anticristae, with the general form found in decapods, differentiated into pegs and hooks.
The wall of the inner sac contains numerous hair cells. These hairs protrude between the epithelial cells. The bases of the cells are drawn out into fine processes, presumably some dendritic and some axonal. There is thus a plexus of nerve fibres all over the wall, communicating with the crista nerve.
There is a very large posterior sac of unknown function, lying behind the crista. It contains only one large anticrista and the opening of Kölliker's canal, which is very large.     

Ultrastructural observations on the central innervation of the guinea-pig pineal gland

Summary In the present study the central innervation of the guinea-pig pineal gland was investigated. The habenulae and the pineal stalk contain myelinated and non-myelinated nerve fibres with few dense-cored and electron-lucent vesicles. Some myelinated fibres leave the main nerve fibre bundles, lose their myelin-sheaths and terminate in the pineal gland. Although direct proof is lacking, the non-myelinated fibres appear to end near the site where the bulk of the myelinated fibres are located. Here a neuropil area exists where synapses between non-myelinated fibre elements are abundant. Neurosecretory fibres were also seen. The results support the concept of functional interrelationships between hypothalamus, epithalamus and the pineal gland.     

Structure and innervation of the pineal gland of the rabbit,Oryctolagus cuniculus (L.)

In the rabbit pineal gland two types of postganglionic nerve endings were found which are characterized by the presence of small dense-core vesicles or small clear vesicles. Pharmacological and cytochemical experiments showed then to be noradrenergic and cholinergic, respectively. Both types were often present in the same nerve bundle, occasionally in close opposition. Intrapineal neurons were only rarely observed. They showed cholinergic synapses on their perikaryon and dendrites as well as noradrenergic axo-dendritic close contacts. Bilateral extirpation of the superior cervical ganglia revealed the postganglionic sympathetic origin of the pineal noradrenergic nerve fibres. Moreover, it appeared that these ganglia are hardly, if at all, involved in the pathway of pineal cholinergic innervation. The results obtained from lesions of both facial nerves, taken together with the results reported in the literature, led to the conclusion that the postganglionic cholinergic nerve fibers in the pineal are of parasympathetic origin. A model for the sympathetic and parasympathetic pineal innervation is proposed.     

Scanning electron microscope observations on the muscle innervation of Oikopleura dioica fol (appendicularia,tunicata) with notes on the arrangement of connective tissue fibres

Critical point dried and fractured appendicularia of the species Oikopleura dioica have been examined in the scanning electron microscope. The dorsal nerve cord with ganglion cells and peripheral nerve fibres could easily be observed. Thick peripheral nerve fibres leave the nerve cord as bilateral pairs at constant intervals along the tail. Most of these fibres branch from the naked nerve cord, but some evidently originate in ganglion perikarya bulging out from the nerve cord itself. These paired peripheral nerves always have elaborate end-arborizations on the medial surface of the lateral muscle cells. They are accordingly interpreted as motor axons. Some thinner peripheral nerve fibres originate at irregular intervals from both the nerve cord and the ganglion cells. Due to the numerous extracellular fibrils that connect the bilateral layers of the epidermal fins and the muscle cells to each other, these thin nerve fibres can seldom be traced to their termination. A few ones can, however, be traced ventrally between the notochord and the muscle cells and seem to end in singular bulb-like expansions. Clusters of synaptic vesicles are present in transmission electron micrographs of such nerves, and they are accordingly believed to carry efferent impulses. The extracellular fibrils are arranged in a highly ordered pattern with thick bundles crossing the gap between the structures to be interconnected and with numerous radiating insertions on the surface of the tissues.     

Ultrastructural autoradiographic localization of serotonin in the pituitary of a teleost fish,Poecilia latipinna

Summary Light- and electron-microscopic autoradiographic studies of pituitaries of the molly Poecilia latipinna, after their incubation with tritiated serotonin, revealed the presence of labelled cells in the proximal pars distalis, together with cell processes or nerve fibres throughout all regions of the gland except the prolactin cell zone. The serotonincon-centrating cells and most of the fibres contained small dense-cored vesicles, but some labelled fibres contained larger granules similar in ultrastructure to those of vasotocinergic fibres.This work was supported by a SERC studentship to DJG and SERC grant GR/6379-06 to Professor J.N. Ball     

Some morphological aspects of the innervation of a spider's silk gland

A structure in the ampullate silk gland of an orb-weaving spider, previously thought to be a pressure receptor, was studied by electron microscopy to clarify its sensory function. This lamellated 'bulbous region' is situated between the gland and the beginning duct, which consists of a layered, acellular matrix (muco-protein), surrounded by a flat epithelium and partly covered by connective tissue. The epithelial cells are densely filled by a mesh-work of microtubules and interconnected by extensive cell junctions, both indicating exposure to mechanical stress. The few nerve fibres found to supply the bulbous region do not exhibit specialized dendritic endings and provide no evidence for a receptor function. The abundance of translucent vesicles of 400-500 A (synaptic'?) and dense granules of 1000-1500 A (neurosecretory?) indicate efferent fibres, possibly controlling the secretion of the matrix. The function of the bulbous region remains to be investigated. Similar nerve fibres but with distinct synaptic foci were noted in the adjacent gland duct in large numbers. The neuro-glandular synapses have a characteristic location, namely, opposing the mesaxon-like invagination of the epidermal cells. These nerve fibres are believed to play a role in water uptake and/or secretion of the extra-cellular duct lining.     

Histochemical demonstration of monoaminergic and cholinesterase-positive nerve fibres in regenerating rat submandibular gland autografts

Summary A cholinesterase localization method and a monoamine histofluorescence technique were used to locate nerve fibres in regenerating rat submandibular gland autografts. Experimental rats had a portion of one submandibular gland excised and cut into small fragments which were autografted immediately into the middle one-thrid of the tongue. Control rats had a portion of one submandibular gland removed and discarded, and their tongues were sham-operated. Seven to ten weeks later, the rats were killed and the tongues were removed, frozen and sectioned in a cryostat. A light microscopical study of the tongue sections subjected to the cholinesterase technique showed that the submandibular gland autografts contained many nerve fibres that exhibited cholinesterase activity. These cholinesterase-positive nerve fibres were distributed throughout the autografts. The fibres were associated with the numerous duct-like structures and the less numerous acini. In addition, ultraviolet illumination of tongue sections after treatment with a glyoxylic acid mixture revealed histofluorescent monoaminergic nerves within the autografts. These fibres were less prominent than the cholinesterase-positive fibres and appeared to run primarily along blood vessels within the autografts. The results suggest that autonomic nerves are present within regenerating submandibular gland autografts.     

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).     

Annual variations of the NPYergic innervation of the pineal gland in the European hamster (Cricetus cricetus): a quantitative immunohistochemical study

A prominent innervation of the pineal gland of the European hamster with nerve fibres containing neuropeptide Y (NPY) and tyrosine hydroxylase (TH) was demonstrated by means of immunohistochemistry. Nearly all the TH- and NPY-immunoreactive nerve fibres in the superficial pineal gland disappeared after bilateral superior cervical ganglionectomy, showing that the majority of NPY- and TH-immunoreactive nerve fibres belonged to the sympathetic nervous system. Since, in the European hamster, preliminary studies of the NPY-fibre density in the pineal gland had indicated seasonal changes, the density of NPY-immunoreactive nerve fibre profiles was ascertained in the superficial pineal gland in a series of animals between the first part of November and late April. The highest density of NPY-immunoreactive nerve fibre profiles was observed during midwinter. On the other hand, during the same period of the year, the number of sympathetic TH-immunoreactive sympathetic nerve fibre profiles did not exhibit seasonal variation, nor did substitution of testosterone, during the sexually inactive period, affect the density of NPY-containing nerve fibres in the gland. Our results show the presence of a testosterone-independent annual variation in the content of NPY in the sympathetic nerve fibres innervating the pineal gland of the European hamster. This variation can be correlated with the changes in the daily pattern of melatonin production observed by others in the same species at this period of the year.     

Central innervation of the pineal organ of the Mongolian gerbil

Nerve fibers connecting the brain with the pineal gland of the Mongolian gerbil (central pinealopetal fibers) were investigated by means of light and electron microscopy. Several myelinated fibers penetrate from the brain into the deep pineal gland, extend further into the pineal stalk and continue to the superficial portion of the pineal gland. In the centripetal direction these fibers were traced to the stria medullaris and to the habenular nuclei, where they turned laterad and then occupied a position immediately ventral to the optic tract. As shown in electron micrographs, lesions of the habenular area led to degeneration of myelinated fibers and nerve boutons in the deep pineal gland, the pineal stalk and the superficial pineal gland. Only boutons containing clear transmitter vesicles (devoid of a dense core) were observed to degenerate after the habenular lesions. On the other hand, removal of the superior cervical ganglia resulted in degeneration of boutons containing small (40 to 60 nm in diameter) dense-core vesicles. Several of the nerve fibers that penetrate into the deep pineal directly from the brain (central fibers) exhibited a positive reaction for acetylcholinesterase (AChE). AChE-positive perikarya were located in the projections of the stria medullaris, the lateral portions of the deep pineal, the area of the posterior commissure, and the periventricular gray of the mesencephalon. Such perikarya were found neither in the pineal stalk nor in the superficial pineal gland. These results present anatomical evidence that the pineal organ of the Mongolian gerbil receives multiple nervous inputs mediated by peripheral autonomic (i.e., sympathetic) nerve fibers, on the one hand, and by central fibers, on the other.     

Electron microscopic structure of the cephalic gland of the bee Andrena variabilis Smith (Hymenoptera: Apoidea)

The structure of the glandular tissue located beneath the eye sulcus in Andrena variabilis Smith was studied by means of light and electron microscopy. The glandular tissue was found to be constituted of single-layered, high cylindrical epithelial cells. Electron microscopy revealed strong foldings of the cell membrane on the basal pole of the gland cells. Next to the basal lamina, nerve fibres were found with great frequency. The central, perinuclear zone of the gland cells was rich in cell organelles. The lamellae of the rough-surfaced endoplasmic reticulum (rer) were mostly observed near the nuclear membrane. The vesicles and tubules of the smooth-surface endoplasmic reticulum (ser) were found to be congregated in contiguous compact regions. A well-developed and complicated canalicular system was enclosed between the rer and ser compartments, presumably serving as a passage for the secretory products. Membrane-bound electron-dense granules (secretory granules) were also a characteristic finding in the ser. In a small proportion of the gland cells, strong vacuolization indicated the degradation processes. From the light and electron microscopic characteristics of the gland cells, the existence of pheromone-producing secretory activity of exocrine type in the cephalic gland is presumed.     

Ultrastructure of calcitonin gene-related peptide- and substance P-like immunoreactive nerve fibres in the carotid body and carotid sinus of the guinea pig

Previous studies have demonstrated that substance P- (SP) and calcitonin gene-related peptide-like immunoreactivities (CGRP-LI) coexist in sensory nerve fibres in the guinea-pig carotid body and carotid sinus. In the present study the ultrastructure of these nerve fibres was investigated by means of single- and double-labelling immunocytochemistry. In both, carotid body and carotid sinus immunoreactive fibres were unmyelinated axons of small diameter (0.12-0.56 microns). At the subcellular level, SP- and CGRP-LI were colocalized in intra-axonal dense core vesicles, suggesting corelease and simultaneous action of these two compounds. SP/CGRP-LI nerve fibres within the carotid body were mainly found in the interparenchymal connective tissue, but also occurred in relationship to blood vessels and nests of glomus cells. Neither in the carotid body not in the carotid sinus, SP/CGRP-LI axons corresponded to the large terminals which are generally considered to represent the main chemoreceptor and baroreceptor endings, respectively. Thus, SP/CGRP-LI fibres either belong to the chemo- and baroreceptors of the C-fibre class or constitute a fibre population not directly involved in conduction of baro- and chemoreflexes.     

Are there efferent synapses in fish taste buds?

In fish, nerve fibers of taste buds are organized within the bud's nerve fiber plexus. It is located between the sensory epithelium consisting of light and dark elongated cells and the basal cells. It comprises the basal parts and processes of light and dark cells that intermingle with nerve fibers, which are the dendritic endings of the taste sensory neurons belonging to the cranial nerves VII, IX or X. Most of the synapses at the plexus are afferent; they have synaptic vesicles on the light (or dark) cells side, which is presynaptic. In contrast, the presumed efferent synapses may be rich in synaptic vesicles on the nerve fibers (presynaptic) side, whereas the cells (postsynaptic) side may contain a subsynaptic cistern; a flat compartment of the smooth endoplasmic reticulum. This structure is regarded as a prerequisite of a typical efferent synapse, as occurring in cochlear and vestibular hair cells. In fish taste buds, efferent synapses are rare and were found only in a few species that belong to different taxa. The significance of efferent synapses in fish taste buds is not well understood, because efferent connections between the gustatory nuclei of the medulla with taste buds are not yet proved.     

The innervation of frog's taste organ “A histochemical study”

Morphological investigations on the fungiform papilla of the frog (Rana pipiens) have shown that this taste organ contains two distinct populations of cells: associate and sensory. Messages received by the sensory cells are believed to be transmitted through the mediation of an adrenergic transmitter. This chemical was shown by fluorescence microscopy and electron histochemistry to be stored in synaptic granular vesicles which accumulate at the membrane of the cytoplasmic processes of the sensory cells in typical chemical synaptic complexes. The sensory cell cytoplasmic processes form the presynaptic component of these complexes whose post synaptic components are the nerve fibres supplying the taste buds. These sensory nerve fibres contain agranular vesticles and are probably cholinergic, since they show positive cholinesterase activity at the light and electron microscopical levels.     

Structural re-evaluation of the neurosecretory system in the crayfish eyestalk

Summary The topography of the neurosecretory system in the decapod eyestalk has not been precisely delineated with light microscopy. Cobalt iontophoresis and electron microscopy have proved useful in clarifying the microstructure of this system. The sinus gland (sg) of the crayfish eyestalk consists of aggregated axon terminals which end at or near the blood space, lontophoresing cobalt back through the cut base of the sinus glands reveals proximal cell bodies in the eyestalk only in the X organ (Xo) region. Electron microscopy demonstrates that axons from about 115 neurosecretory cell bodies in the Xo form the Xo-sg tract. Intermingled with these Xo somata are smaller non-neurosecretory cell bodies which do not send axons into the sinus gland. One of these exhibits catecholamine fluorescence. Backfilling also reveals a second group of fibres which run from the brain along the optic tract and into the sinus gland. These brain-sg fibres are smaller in diameter than Xo-sg axons and lack neurosecretory vesicles. From these fibres collaterals extend into the eyestalk neuropil, especially in the proximity of the visual elements. The possible function of these non-neurosecretory processes within the sinus gland is discussed.This work was supported by a National Research Council of Canada grant     

Immunohistochemical properties of nerve fibres supplying accessory male genital glands in the pig. A colocalisation study

 Immunohistochemical studies have been performed to investigate the occurrence and coexistence of two catecholamine-synthesising enzymes, tyrosine hydroxylase and dopamine-β-hydroxylase, and several neuropeptides, including neuropeptide Y, vasoactive intestinal polypeptide, Leu⁵-enkephalin, somatostatin, calcitonin gene-related peptide and substance P, in nerve fibres supplying porcine accessory genital glands, the seminal vesicles, prostate (body and the disseminated part) and bulbourethral glands. Three major populations of nerve fibres supplying non-vascular elements of the glands have been distinguished (from the largest to the smallest one): (1) noradrenergic fibres, the majority of which contain Leu⁵-enkephalin, neuropeptide Y or, to a lesser extent, somatostatin, (2) non-noradrenergic, putative cholinergic fibres containing vasoactive intestinal polypeptide, neuropeptide Y and/or somatostatin and, (3) non-noradrenergic, presumably sensory fibres, containing calcitonin gene-related peptide and substance P. Whilst the coexistence patterns within nerves supplying particular glands are similar, the density of innervation varies between the organs. The innervation of the seminal vesicles and prostatic body is more developed than that of the disseminated part of the prostate and bulbourethral glands. The majority of noradrenergic fibres related to blood vessels contain neuropeptide Y only, while the non-noradrenergic nerves contain mainly vasoactive intestinal polypeptide. The possible function and origin of particular nerve fibre populations are discussed. Accepted: 16 November 1998     

Innervation of the rat pineal gland by pituitary adenylate cyclase-activating polypeptide (PACAP)-immunoreactive nerve fibres

Pituitary adenylate cyclase-activating polypeptide (PACAP)-immunoreactive nerve fibres were demonstrated in the rat pineal gland. These fibres entered the pineal gland through the conarian nerve at the distal tip of the gland. A high density of the fibres was observed in the capsule of the gland, from where the immunoreactive elements penetrated into the pineal perivascular spaces and parenchyma. The majority of PACAP-immunoreactive nerve fibres also contained calcitonin gene-related peptide (CGRP). Some PACAP-immunoreactive nerve fibres contained neuropeptide Y (NPY), but only occasionally was PACAP colocalized with vasoactive intestinal peptide (VIP). After removal of both superior cervical ganglia, a high number of PACAP-containing nerve fibres were still present in the gland. In the nervous system PACAP is present in two isoforms, PACAP-38 and PACAP-27. The concentration of PACAP-38 in the superficial pineal gland was determined by radioimmunoassay to be 20.4 pmol/g tissue at midday and 18.9 pmol/g tissue at midnight. The concentration of PACAP-27 was only about 3% of the concentration of PACAP-38. In summary, this study is the first demonstration of a PACAP-containing innervation of the rat pineal gland. The PACAP concentration in the pineal gland does not exhibit a day-night difference. The colocalization of PACAP with calcitonin gene-related peptide in the pincalopetal nerve fibres indicates that the majority of PACAP-immunoreactive nerve fibres might originate from the trigeminal ganglion.