Prenatal development of the intrinsic nerves of the muscles of the human foot

Myelogenesis and blood supply of the intraorganic nerves have been studied in 4-6- and 7-9-month-old human fetuses. At first, the intramuscular nerves are presented as very thick fasciculi (the diameter is more than 90), thick (the diameter is from 50 up to 90) and single muddle neural fasciculi (the diameter is from 30 up to 50 mcm). The microcirculatory blood bed is formed at the expense of branches of the blood vessel-satellites and the blood vessels of the surrounding tissues and is carried out, without any interruption, along the whole extent. In 7-9-month-old fetuses the neural apparatus becomes more complex. The number of the middle neural fasciculi appear. On the background of fine neural fibers in the fasciculi a small part of the middle neural fibers appears, and in the musculus flexor digitorum brevis--single thick neural fibers. The intramuscular nerves have their own hemocirculatory bed presented by microvessels that are on the perineurium surface, in its bulck and among neural fibers.     

Restoration of the innervation of the extremity of the rat after joining the ends of the damaged nerve with a microsurgical suture

Morphofunctional restoration of the cut ischemic nerve has been studied after its connection by means of a microsurgical suture. The investigations have been performed on 20 male rats. In 6 months after the operation the average diameter of the regenerating nervous fibers is 5.0-6.5 mcm and, as in an intact nerve they have a wavy course. Myelin decay products and inflammatory infiltrates are revealed in the nerve but sometimes. All the parts of the plantar skin are well reinnervated. Cutaneous epidermis of the sole and the digital pads possesses an extremely rich innervation. Characteristics of M-responses, registered from the m. gastrocnemius, approaches the norm in 2 months after the operation. In 10% of fibers of the regenerating ischiatic nerve impulse activity begins to be registered in 20-30 days after the operation. Gradually the borders of the receptor fields become wider and in 3 months they spread all over the whole sole. In 5-6 months the impulse reaction of the regenerating nerve fibers does not differ from that in non-operated animals. Thus, use of the microsurgical suture results in a successful regeneration of the rat ischemic nerve and in a rather short time. The restorative dynamics of the extremity tissue innervation can be presented as following: at first somatic muscles get innervation and then, as the afferent fibers grow in the periphery, the plantar skin and the skin of the digital pads is the last to get innervation.     

Comparative study of the cholinergic and adrenergic innervation of the cerebral vessels in humans and various laboratory animals

Choline- and adrenergic innervation of intracerebral branches of the middle and posterior cerebral arteries has been investigated histochemically and electron microscopically in slices, or after their preparation after W. Penfield. The vessels have been studied in the area of the fields 41, 17 of the cerebrum, trunk and spinal cord of the human being, cat and dog. When studying innervation of the intracerebral arteries (ICA), the preparation method has some advantages in comparison with investigation of these vessels in slices of the brain. Around most of the ICA from 200 up to 30 mcm in the diameter choline- and adrenergic nervous conductors are revealed. Using the method for calculating varicosities in nervous plexuses, it is demonstrated that degree of the ICA innervation is two times less than that in the arteries of similar caliber in the cerebral pia mater.     

Innervation of the guinea pig spleen studied by electron microscopy

The innervation of the guinea pig spleen was investigated by electron microscopy. Unmyelinated nerve fibers in the capsulotrabecular and arterial systems were found to contain large and small granular and small agranular synaptic vesicles in their terminals and are thought to be sympathetic adrenergic in nature. They influence the contraction of the smooth muscle cells by diffusion innervation in these systems. These nerve terminals were also scattered in both the red and the white pulp. Pulp nerves wrapped by Schwann cells were further enclosed by myofibroblastic reticular cells. This condition revealed that the pulp nerves pass through the connective-tissue spaces of the reticular fibers, which contain elastic fibers, collagenous fibrils, and lamina densa-like materials of the usual basement laminae. One of the target cells for the pulp nerves is considered to be the myofibroblastic reticular cell in the reticular meshwork. Neurotransmitter substances released from the naked adrenergic nerve terminals travel through the reticular fibers and may play a role, by both close association innervation and diffusion innervation, in the contraction of reticular cells to expose the reticular fibers. At the exposed sides, connective-tissue elements of the reticular fibers are bathed with blood plasma, and the included naked nerve terminals, devoid of Schwann cells but with basement laminae of these cells, face free cells at some distance or are in close association with free cells, especially lymphocytes, macrophages, and plasma cells. The close ultrastructural relationship between the naked adrenergic nerve terminals and immunocytes strongly suggests that there is an intimate relationship between the immune system and the sympathetic nervous system through both close association innervation and diffusion innervation. Thus splenic adrenergic nerves of the guinea pig may play a triple role in 1) contraction of smooth muscle cells to regulate blood flow in the organ, 2) induction of the exposure of reticular fibers by contraction of the reticular cells in order to form a close relationship of the nerve terminals with the immunocytes, and 3) subsequent neuroimmunomodulation of the immunocytes.     

Electron microscopic studies of the innervation of the human spleen

Summary The innervation of four normal human spleens was investigated by electron microscopy. Unmyelinated nerve fibers accompanied the arterial vascular system up to the arterioles of the red pulp. Neither myelinated nerve fibers nor ganglion cells were seen in the splenic hilum or in the splenic tissue itself. The nerve fibers terminated against the smooth muscle cells of the blood vessels in a manner that is typical of the autonomic nervous system. The terminal axons contained small and large granular vesicles and thus were adrenergic nerve fibers. In contrast to the results of previous studies using silver impregnation methods innervation of the red or white pulp could not be demonstrated. The findings on human spleens agree with those on mammalian spleens obtained by other authors using ultrastructural and fluorescence histochemical methods.We are indebted to Prof. Dr. K. Unsicker for his help in discussing the results     

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     

Immunocytochemical evidence of plasticity in the nervous structures of the rat lower lip

In this immunocytochemical study we investigated the distribution of nervous structures in the lower lip of adult rats. The region is characterized by a rich cutaneous and mucosal sensory innervation originating from terminal branches of the trigeminal system. Lower lip innervation was investigated by detection of the general neuronal marker protein gene product 9.5 (PGP 9.5) and the growth-associated protein 43 (GAP-43), a neurochemical marker of neuronal plasticity. The entire neural network of both cutaneous and mucosal aspects was stained by the antibody to PGP 9.5. In particular, nerve fibers were observed in the submucosal and the subepithelial plexuses. Thin immunoreactive fibers were observed within the epithelial layers ending as free fibers or as fibers associated with immunopositive Merkel cells. Well-identified anatomical structures receiving sensory or autonomic innervation were also surrounded by PGP 9.5-ir nerve fibers, in particular, hair follicles, vibrissae, glands, and blood vessels. GAP-43-immunostained nerve fibers were observed in all these structures; however, they were generally less numerous than the PGP 9.5-immunoreactive elements. An equal amount of PGP 9.5 and GAP-43 immunoreactivity occurred, in contrast, in the subepidermal and the submucosal plexuses, or in the epidermis and the mucosal epithelium. The present results show that GAP-43 is normally expressed in the mature trigeminal sensory system of the rat. Skin and oral mucosa are characterized by continuous remodeling that may also involve the sensory nervous apparatus. Continuous neural remodeling, regeneration and sprouting may be the reason for the observed expression of GAP-43.     

Nonconventional innervation of the pancreatic islets of the teleost fish,Gillichthys mirabilis

Summary The innervation of the pancreatic islets of a teleost fish, Gillichthys mirabilis, was investigated with various techniques including axonal iontophoresis of cobalt, light microscopy, and electron microscopy. Two types of postganglionic neurons, the splanchnic and the vagus, innervate the islet parenchyma. The splanchnic fibers originate from the single coeliac ganglion, situated near the third spinal nerve on the right side, and pass caudally to the islet. Postganglionic vagal fibers reaching the islets arise from ganglion cells located at irregular intervals along the vagus nerve.Iontophoresis of cobaltous chloride revealed that both types of nerves send large numbers of fibers to the islet cells. Electron microscopy showed that the granules of the vagal fibers are polymorphic, large (130 mm diameter) and markedly electron dense, whereas the splanchnic granules are smaller (100 nm diameter) and less electron dense than those of the vagus.These granules do not correspond to those seen in postganglionic autonomic neurons of other vertebrates. Rather, they are more like classical neurosecretory granules. Although their chemical nature is unknown, the extent of islet innervation suggests that it must play an important regulatory role.Supported by a grant (AM 17161) from the National Institutes of Health     

Adrenergic innervation of the arteries of different diameters in the human and animal pia mater

The adrenergic nervous plexuses of the pial arteries from 450- to 50 micron in diameter have been studied in dogs, cats and humans from 4 age groups (22-44 years, 55-64 years, 65-74 years and 75-86 years old). It has been found that the decrease in the vessel diameter was accompanied by a marked decline in the absolute number of nervous fibers in the nervous plexuses, however the concentration of the nerve fibers has not revealed any significant differences between human arteries from 450 to 100 micron in diameter and animal arteries from 300 to 80 micron in diameter. The number of varicosities-thickness along the nerve fiber--was the greatest in 200-100 micron human arteries and in 80-60 micron animal arteries. With ageing, the number of varicosities in the adrenergic nervous plexus of human pial vessels decreased faster than in the nerve fibers.     

Comparative study of nerve elements and their relationships with Endocrine glands and muscle retractors in Ommatophores of snails and slugs

A comparative study of the total cytoarchitectonics and structural interrelations of receptor and nerve elements at the area of receptor cell bodies, in tentacular ganglia and their digital outgrowths as well as in the lateral wall of tentacular olfactory organs of several species of terrestrial snails and slugs from different families was carried out using Golgi and Colonnier silver nitrate impregnation technique and horseradish peroxidase labeling. The presence of a peculiar cluster of intraepithelial receptor cells has been established for the first time in sensory epithelium of ommatophores. A connection of endocrine cells of the optic gland with nerve and receptor elements of tentacular ganglia was shown. Peculiarities of innervation of muscle refractors and lateral wall of ommatophores were revealed. FMRFamide-positive nerve fibers were found to participate in innervation of muscle elements of ommatophores. Neurotensin-positive and occasional serotonin-positive nerve elements also were revealed in the tentacular organs. Electron microscopic study showed the presence of complicated synaptic complexes of either convergent or divergent type and of many symmetric synaptic structures in neuropil of tentacular ganglia. Many nervous fibers and synapses contain several types of granular and agranular vesicles, which indicates possible co-localization of several bioactive substances in the same nerve elements.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 40, No. 6, 2004, pp. 556–568.     

Development and ultrastructure of the neuromuscular junction in bronchial smooth muscle tissue

At various stages of pre- and postnatal ontogenesis ultrastructure of contacts of smooth myocytes and nervous terminals in the white mice bronchial wall has been investigated. Nervous fibers grow into the forming tissue of the lung beginning from the 11th day of embryogenesis. By the end of the prenatal development the nervous fibers fasciculi with varicosites and having vesicles are localized at the distance of 100-300 nm from the developing myocytes. Formation of dense neuromuscular junctions with the distance of 35-60 nm between the axonal membranes and the myocyte is observed on the 10-15 day after birth. In mature animals combination of various types of neuromuscular connections is revealed; they ensure local and distant neurotrophic regulation. In the bronchial smooth musculature afferent connections are revealed, as well as connections of myocytic processes with the effectors. Terminals of the cholinergic type predominate, adrenergic effectors occur very seldom. There are terminals, in which combination of vesicles having various structure and diameter are observed.     

On the innervation of the rat and pig adrenal cortex

Summary The innervation of the adrenal cortex of the rat and the pig is investigated with the electron microscope. Nerve fibers containing synaptic and two types of dense-cored vesicles come into contact with endocrine cells. There are no specialized pre- and postsynaptic membranes. The synaptic cleft is about 200 Å wide. Generally the basement membrane between nerve and cell is absent. These observations are discussed on the base of more recent experimental findings. Small fibers having an average diameter of about 0.2 to 0.5 and containing only tubules and filaments are considered to represent parts of an afferent nervous system.Dedicated to Prof. v. Kügelgen on the occasion of his 60th birthday.Supported by the Deutsche Forschungsgemeinschaft.     

Histochemical and ultrastructural studies of the innervation of the lymph-vessel and blood-vessel wall. 1. Adrenergic innervation

The adrenergic innervation of the lymph vascular wall was studied by means of the Falck fluorescence histochemical tecnique and electron microscopy with Tranzer and Richards' histochemical tecnique. The lymph vessels wall, compared with that of blood vessels, shows very few adrenergic nerve fibers located in the adventitia outside the smooth muscle cells. The possible role of the nervous system in the motor control of the lymph vessels is discussed.     

Sensory innervation of the somite in the polychaete worm Nephthys hombergii]

Studies have been made on the peripheral sensory innervation of N. hombergii stained with methylene blue. It was shown that sensory elements of the polychaete are presented by several types of nervous cells which are symmetrically embedded between the circular and longitudinal muscle layers in each of the segments. Peripheral projections of these cells terminate in the epithelium, on muscle fibers and in the connective tissue. Central projections pass to the abdominal nerve chain. All. the observed sensory cells have a constant localization and shape, the latter presumably being determined by their polyvalent functions.     

VIP like immunoreactive nerves in human respiratory tract. Light and electron microscopic study

The present study provides light and electron microscopical evidence of Vasoactive Intestinal Peptide - (VIP) like immunoreactive nerves in human lower respiratory tract. Peroxidase antiperoxidase (PAP) technique was used to localize VIP-like immunoreactivity light microscopically and ultrastructurally. Under light microscopy, VIP-like immunoreactive nerves were observed in the smooth muscle layer of secondary bronchi to small bronchioli, and in bronchial glands. In addition, positive immunoreactive nervous network to VIP was found around nerve cell bodies in small microganglia. The bronchial epithelium of airway tract did not receive any VIP positive nerve fibers. Ultrastructurally VIP-like positive immunoreaction was localized in large granular vesicles ranging from 90 to 210 nm. Usually VIP-like positive immunoreactive nerve profiles contained several immunoreactive large vesicles (100-210). However, nerve profiles containing only a few positive large vesicles (80-150) were also observed. Under electron microscopy VIP-positive nerve profiles corresponded ultrastructurally to nerve profiles containing large granular vesicles observed in conventional electronmicroscopy. The present study provides new information about the innervation of human lower airway tract and widens the concept of their functional regulation on the anatomical basis reported here.     

Hepatocyte innervation in primates

The efferent innervation and some characteristics of nerve fibers of the liver lobule in the tree shrew, a primate, are described. Nerve endings on hepatocytes were encountered regularly and were determined to be efferent adrenergic nerves. Transmission electron microscopy revealed nerve endings and varicosities in close apposition to the hepatocytes adjacent to the connective tissue of the triads as well as within the liver lobule in the space of Disse. Fluorescence microscopy indicated the existence of adrenergic nerves with a similar distribution. Autoradiography of the avid uptake of exogenous [3H]norepinephrine indicated that all intralobular nerves are potentially norepinephrinergic (adrenergic). Chemical sympathectomy with 6-OH-dopamine resulted in the degeneration of all intralobular liver nerve fibers as revealed by fluorescence microscopy and electron microscopy. Substantial regeneration occurred after 60-90 days but was not completed by that time. Some nerves were also observed in close association with von Kupffer cells and endothelial cells. The functional significance of the efferent liver innervation is discussed.     

Three dimensional observation of the nerve fibers along the cerebral blood vessels

Three dimensional observation of the nerve fibers along the cerebral blood vessels was investigated by scanning electron microscopy. Electron probe X-ray microanalysis was also performed in the cerebral blood vessels treated with peroxidase-antiperoxidase immunohistochemistry intensified by nickel ammonium sulfate. Nerve fibers (2-8 microns in diameter) formed a plexus on the outer surface of the adventitia. After branching, the nerve fibers penetrated the blood vessel adventitia. Substance P-immunoreactive nerve fibers showed a meshwork pattern in the outer layer of the adventitia, and vasoactive intestinal polypeptide (VIP)-immunoreactive nerve fibers revealed a spiral running pattern in the inner layer of the adventitia. Taken together with previous studies, these findings suggest that substance P nerve fibers in the cerebral arteries may not be related to arterial dilatation or constriction, but VIP nerve fibers may be vasodilative.     

The loss of sympathetic nerve fibers in the synovial tissue of patients with rheumatoid arthritis is accompanied by increased norepinephrine release from synovial macrophages.

Our objective was to investigate sympathetic and sensory nerve fibers in synovial tissue in rheumatoid arthritis (RA) and osteoarthritis (OA) in relation to histological inflammation and synovial cytokine and norepinephrine (NE) secretion. Immunohistochemistry was used to detect nerve fibers and inflammatory parameters. A superfusion technique of synovial tissue pieces was used to investigate cytokine and NE secretion. In RA, we detected 0.2 +/- 0.04 tyrosine hydroxylase-positive (TH-positive=sympathetic) nerve fibers/mm2 as compared to 4.4 +/- 0. 8 nerve fibers/mm2 in OA (P<0.001). In RA, there was a negative correlation between the number of TH-positive nerve fibers and inflammation index (RRank=-0.705, P=0.002) and synovial IL-6 secretion (RRank=-0.630, P=0.009), which was not found in OA. Substance P-positive (=sensory) nerve fibers were increased in RA as compared to OA (3.5+/-0.2 vs. 2.3+/-0.3/mm2, P=0.009). Despite lower numbers of sympathetic nerve fibers in RA than in OA, NE release was similar at baseline (RA vs. OA: 152+/-36 vs. 106+/-21 pg/ml, n.s.). Basal synovial NE secretions correlate with the number of TH-positive CD 163+ synovial macrophages (RA: RRank=0.622, P=0.031; OA: RRank=0.299, n.s.), and synovial macrophages have been shown to produce NE in vitro. Whereas sympathetic innervation is reduced, sensory innervation is increased in the synovium from patients with longstanding RA when compared to the synovium from OA patients. The differential patterns of innervation are dependent on the severity of the inflammation. However, NE secretion from the synovial tissue is maintained by synovial macrophages. This demonstrates a loss of the influence of the sympathetic nervous system on the inflammation, accompanied by an up-regulation of the sensory inputs into the joint, which may contribute to the maintenance of the disease.     

Substance-P-containing fibers in the incisive papillae of the rat hard palate. Light- and electron-microscopic immunohistochemical study

Substance P (SP)-containing fibers in the incisive papillae of rat hard palates, which include various components of sensory receptors, i.e. mechanoreceptors, free nerve endings and chemosensory corpuscles (taste buds), were examined using immunoperoxidase techniques and light and electron microscopes. Immunolabeled fibers were consistently distributed in the medial part of the orifice of the incisive canals, i.e. in the taste-bud-enriched region. Dense immunolabeled fibers were found in subgemmal regions and in the lamina propria papillae. Some fine fibers entered and ascended the taste buds or occasionally the epithelium outside the taste buds. In addition, a rich innervation by SP-containing fibers close to blood capillaries was clearly identified. Electron microscopy revealed no specialized synaptic contact between the immunolabeled fibers and taste bud cells. Synaptic-like images could be found only between nonimmunolabeled nerve endings and the underlying taste bud cells. In the lamina propria papillae, mechanoreceptors observed in the present study contained no immunoperoxidase end products, whereas free nerve endings with an immunolabeled small-diameter axon (630-730 nm in diameter) were frequent. Similar axons were located at the adventitia of the blood capillaries. The possible functional role of SP-containing fibers in the incisive papillae was given attention.     

Cholinergic nerves in the thyroid gland

Summary The cholinergic innervation of the thyroid gland has been studied in the human. AChE positive nerve fibers are localized in the wall of the thyroid artery, arranged in two plexuses, a superficial (adventitial) and a deep one (medial). The glandular tissue is provided with cholinergic nerve fibers, localized between and around thyroid follicles. The present results suggest that the endocrine activity of the thyroid gland is also under the control of the autonomic nervous system.