Morphofunctional restructuring of the nervous system of the lymphoid organs during electrostimulation of the hypothalamus

The intramural nervous apparatus of rabbit lymphoid organs was examined after 15 and 30 sessions of electric stimulation of the posterior hypothalamus. The function of nerve cells was evaluated by cytophotometry according to the content of catecholamines and acetylcholinesterase (ACE) activity. In the mesenteric lymph nodes, stimulation led to a decrease in the activity of both adrenergic and ACE-containing nerve cells. The spleen demonstrated a reduction in the catecholamine content in the perivascular nerve plexuses, with a simultaneous rise of the catecholamine content in the fibers located in the parenchyma, which evidences inhibition of the neurogenous mechanisms of vasomotor control and possible selective activation of the sympathetic mechanisms involved in the regulation of the immunogenesis. Thymic preparations impregnated with silver salts manifested high argyrophilia of the nerve cells, characteristic of the reactive phase of the destructive process. The problems of the hypothalamic effects on the blood supply and functions of the immune system organs are discussed.     

Adrenergic innervation of lymph nodes and the thoracic duct

By means of incubation of slices in 2% solution of glyoxylic acid distribution of adrenergic fibers in the rabbit lymph nodes and in the thoracic lymphatic duct has been studied. Adrenergic fibers get into parenchyma of the lymph nodes via two ways. The first--the perivascular, when the nervous fibers make a plexus and get into the node along the blood vessels, the second--diffuse nervous fibers get together with trabecules in between the lymphoid nodules. The distribution density of the adrenergic fibers is not the same in different groups of the lymph nodes. In the lumbar nodes it is the highest. In the lymph nodes of the cervical part the density of the sympathetic fibers is, as a rule, lower than in the lumbar, but higher than in the axillary nodes. The lowest density of th adrenergic fibers is in the mesenteric, superficial inguinal lymph nodes and in the lymph nodes, situating near the thoracic part of the aorta. In the lymphatic duct wall small amount of adrenergic fibers are revealed, they form a plexus, predominantly in the cranial part.     

Adrenergic innervation of the kidneys in man and various laboratory animals

By means of the neurohistochemical method for slice incubation in 2% solution of glyoxylic acid, innervation of the kidneys of a 57-year-old man after a sudden cardiac death has been investigated, as well as innervation of the kidneys in white rat, rabbit, guinea pig and cat. A rich adrenergic innervation in the organ's blood vessels has been revealed. In particular, adrenergic nervous fibers have been found along the course of afferent glomerular arterioles. Together with innervation of the proximal and distal convoluted tubules, a high density of the terminal adrenergic nervous plexus is revealed along the course of the nephron loops. Adrenergic nervous plexuses of high density are found in the area of the initial part of the urinary excretory pathways and their connection with nervous plexuses of the kidney itself.     

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.     

Functional morphology of the adrenergic innervation and adrenocontaining structures of the lymphoid organs

Topography of adrenergic neural fibres and adrenodependent structures in lymphoid organs of some mammals (rat, cat, dog, guinea-pig, golden hamster) has been studied by means of Falck's method with other histochemical methods applied simultaneously. In thymus, spleen, tonsils, lymph nodes and appendix adrenergic innervation is performed at the expense of adventitial vascular plexus and some neural fibres directed towards the organs' parenchyma. In the parenchyma of the lymphoid organs some fluorescent interfollicular macrophages and intrafollicular cells with serotonin and catecholamines in their cytoplasm were detected spectroscopically. These two types of cells respond differently to increasing amount of free amines in the organism. Orthochromic mast cells and elastic fibres also possess fluoresent properties which are connected with the presence of serotonin and catecholamines in the lymphoid organs.     

Study of the innervation of blood vessels of the digestive organs by fluorescence microscopy]

The blood vessels of the samll intestine and the gallbladder were shown to possess a great amount of adrenergic nerve fibres which, when penetrating the thickness of the wall of the above organs, become thinner and the distributed between the tissue structures of the organs as the thinnest monoaxonal network. The method of Falck--Hillarp--Krokhina was used. Among the vessel nerves there are perivascular nerves accompanying the vessels along their total legnth, juxtavascular and intramural nervous bundles of the sumpathetic nature detected by the fluorescent-microscopy method. Large arteries are disposed in a considerably thicker network of specifically fluorescing fibres than veins and small arteries.     

Reactive changes in adrenergic innervation of the cerebral arteries after activation of the cholinergic mechanisms]

Magistral arteries of the brain and pia mater have been studied in cats 24-72 h after administration of the cholinesterase inhibitor (phosphacol, 600 mcg/kg). Cholinesterase activity in blood has been checked by means of the potentiometric titration method, and acetylcholinesterase (AChE) content in varicosities of the perivascular nervous fibers--cytophotometrically in preparations treated after Karnovsky--Roots histochemical method. Cholinesterase activity of blood homogenates in test animals is 42 +/- 10%, and acetylcholinesterase content in varicosities of the perivascular nervous fibers--23.5 +/- 2.3% in comparison to the norm. Catecholamines in adrenergic nervous elements are revealed treating them with glyoxylic acid. Distribution density (DD) of histochemically active nervous elements is determined, as well as their specific content of the mediator according to luminescent intensity (LI) of varicosities of nervous fibers. The data obtained in intact animals serve as the control. In the experiment DD and LI reach 127 +/- 9% and 154 +/- 15%, respectively, as compared to the control. Signs of the adrenergic nervous apparatus activation in the experiment reflect a compensatory reaction in response to increase of dilatatory cholinergic influences to vessels under conditions of AChE activity.     

The role of adrenergic structures of the posterior hypothalamus in the regulation of the blood coagulation system functions

Under conditions of chronic experiment, the stimulation of alpha- and beta-adrenergic structures of the posterior hypothalamus was performed. The same procedure was repeated after inactivation of these structures. The results of experiments have shown a specificity of the influence of alpha- and beta- adrenergic structures upon the separate blood coagulation phases and the heterogeneity of those structures distribution in the posterior hypothalamic region.     

Innervation of somatostatin synthesizing neurons by adrenergic,phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive axons in the anterior periventricular nucleus of the rat hypothalamus

Summary The adrenergic innervation of somatostatin synthesizing neurons located in the anterior region of the rat hypothalamic periventricular nucleus was studied by means of a light and electron microscopic immunocytochemical double labelling technique. This region which is the source of hypophysiotrophic somatostatin immunoreactive (IR) neurons also receives a dense plexus of adrenergic axons as determined by immunocytochemistry of phenylethanolamine-N-methyltransferase (PNMT), the marker enzyme for the central adrenergic system. The simultaneous detection of PNMT and somatostatin antigens in hypothalamic sections of colchicine pretreated animals revealed a congruency in the distribution of the labelled elements and also close juxtaposition of PNMT-IR axons to somatostatin producing neurons. At the ultrastructural level, axo-somatic and axo-dendritic synaptic connections were found between PNMT-containing axons and somatostatin expressing neurons. These morphological findings support the view that the central adrenergic system might influence the production and secretion of growth hormone in the pituitary gland by a direct monosynaptic interaction with somatostatin synthesizing neurons.     

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.     

Principal features of the nerve supply to the ovary, oviduct and tubal third of the uterus in the golden hamster

The autonomic outflow and sensory structures in the ovary and accessory reproductive organs of the hamster are described by means of specific fluorescence and enzyme histochemical techniques for the demonstration of catecholamine and acetylcholinesterase (AChE), respectively. Sympathetic nerves accompany branches of the major blood vessels in the mesentery of the ovary, oviduct and tubal uterine horn and invest the vascular bed in each of these organs. Vasomotor fibers predominate in the ovary and oviduct, though occasional adrenergic axons supply thecal and interstitial tissues in the ovary and the longitudinal smooth muscle of the oviduct. Fluorescent myomotor axons run in the suspensory ligament and outer myometrial layer of the uterus, but most of the numerous sympathetic and AChE-fibers in the tubal third of the horn supply the intramural and submucosal vascular plexuses. A limited electron microscopic study of the central spiral (preplacental) arteries of the endometrium indicates that the surrounding terminal AChE-fibers are identical to the fluorescent and granular vesicle-bearing adrenergic axons which form neuromuscular junctions with these vessels. Based on the discovery of specialized sensory endings in the walls of the large collecting veins which drain the hamster uterus, a mechanism is proposed to account for the regulation of blood flow through maternal placental vessels which are devoid of an arteriolar neuromuscular apparatus.     

Adrenergic innervation of the myocardium and skeletal musculature of the rabbit exposed to vibration

Innervation of the myocardium and that of foreleg musculature has been studied in rabbits subjected to the local vibration effect. The point where the vibration is applied is the foreleg, because its nerve plexuses are in the tightest way connected with the cardiac nervous apparatus. For treatment of the sections incubation in 2% solution of glyoxylic acid is used, which is followed with luminescent microscopy. While studying adrenergic nerve plexuses of the right auricle, their luminescent activity is stated to decrease more than by a half. In the ventricles only single perivascular adrenergic nerve plexuses remain. A constant reaction of the plexuses mentioned is revealed not only in the right, but in the left extremity subjected to a direct vibration. Taking into account that the vibrational effect is performed as a generalized action and it embraces the whole skeleton of the animal, it is possible to suggest that the activity of the sympathetic nervous plexuses results in a constant influence of noradrenaline on the wall of blood vessels producing their steady spasmodicity.     

Innervation of somatostatin synthesizing neurons by adrenergic, phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive axons in the anterior periventricular nucleus of the rat hypothalamus

The adrenergic innervation of somatostatin synthesizing neurons located in the anterior region of the rat hypothalamic periventricular nucleus was studied by means of a light and electron microscopic immunocytochemical double labelling technique. This region which is the source of hypophysiotrophic somatostatin immunoreactive (IR) neurons also receives a dense plexus of adrenergic axons as determined by immunocytochemistry of phenylethanolamine-N-methyltransferase (PNMT), the marker enzyme for the central adrenergic system. The simultaneous detection of PNMT and somatostatin antigens in hypothalamic sections of colchicine pretreated animals revealed a congruency in the distribution of the labelled elements and also close juxtaposition of PNMT-IR axons to somatostatin producing neurons. At the ultrastructural level, axo-somatic and axo-dendritic synaptic connections were found between PNMT-containing axons and somatostatin expressing neurons. These morphological findings support the view that the central adrenergic system might influence the production and secretion of growth hormone in the pituitary gland by a direct monosynaptic interaction with somatostatin synthesizing neurons.     

A histochemical study of catecholamines and cholinesterases in the autonomic nerves of the human minor salivary glands

Synopsis The cholinergic and adrenergic innervation of human minor sublingual buccal and labial salivary glands has been studied with histochemical techniques for localizing acetylcholinesterase and catecholamines. A rich cholinergic innervation was observed around the acini, blood vessels and some ducts of the three glands.The adrenrgic innervation, however, was virtually absent from the parenchyma although present around the blood vessels, in marked contrast to the dense parenchymal adrenergic innervation observed in the human parotid and submandibular glands. These results suggest that the autonomic nervous mechanism which regulates salivary secretion is more elaborate in the major than in the minor salivary glands.     

Neural connections of the heart and superior vena cava in the rabbit and man

Innervational connections of the heart and the superior vena cava wall have been studied in the rabbit and the man. Besides, series of their embryos, impregnated with silver salts after Cajal-Favorsky have been investigated. Methods of Bielschowsky-Gros, Gomori and Karnovsky-Roots have also been applied. Adrenergic nervous elements have been revealed by means of incubation the slices in 2% solution of glyoxylic acid. Abundant cholinergic and adrenergic nervous plexuses are revealed on the wall of the superior vena cava, they are tightly connected with corresponding plexuses of the heart. Developmental of these nervous connections is followed, when embryogenesis of the cardiac nervous plexuses and large major vessels is studied in serial sections of embryos and fetuses of the rabbit and the man.     

Innervation of the renal vasculature of the toad (Bufo marinus)

The innervation of the dorsal aorta and renal vasculature in the toad (Bufo marinus) has been studied with both fluorescence and ultrastructural histochemistry. The innervation consists primarily of a dense plexus of adrenergic nerves associated with all levels of the preglomerular vasculature. Non-adrenergic nerves are occasionally found in the renal artery, and even more rarely near the afferent arterioles. Many of the adrenergic nerve profiles in the dorsal aorta and renal vasculature are distinguished by high proportions of chromaffin-negative, large, filled vesicles. Close neuromuscular contacts are common in both the renal arteries and afferent arterioles. Possibly every smooth muscle cell in the afferent arterioles is multiply innervated. The glomerular capillaries and peritubular vessels are not innervated, and only 3-5% of efferent arterioles are accompanied by single adrenergic nerve fibres. Thus, nervous control of glomerular blood flow must be exerted primarily by adrenergic nerves acting on the preglomerular vasculature. The adrenergic innervation of the renal portal veins and efferent renal veins may play a role in regulating peritubular blood flow. In addition, glomerular and postglomerular control of renal blood flow could be achieved by circulating agents acting via contractile elements in the glomerular mesangial cells, and in the endothelial cells and pericytes of the efferent arterioles. Some adrenergic nerve profiles near afferent arterioles are as close as 70 nm to distal tubule cells, indicating that tubular function may be directly controlled by adrenergic nerves.     

Adrenergic innervation of the large arteries and veins of the semiarboreal rat snake Elaphe obsoleta

Fluorescence histochemistry was used to study the adrenergic innervation of the large arteries and veins at six points along the body of the semiarboreal rat snake Elaphe obsoleta. Apart from the vessels adjacent to the heart, there was a marked contrast in the density of adrenergic innervation of anterior and posterior systemic arteries and veins. The anterior arteries and veins have little adrenergic innervation in contrast to the extremely dense innervation of the arteries and veins posterior to the heart. The innervation pattern is consistent with known physiological adjustments to gravity and suggests a mechanism for regulating dependent blood flow via sympathetic nerves. In comparison to the posterior systemic arteries, parallel segments of pulmonary artery taken from the same body position of Elaphe contained a much sparser innervation by adrenergic nerves. The sparser innervation can be correlated with less gravitational disturbance in the pulmonary artery, which is relatively short in this and in other arboreal snakes.     

Neuropeptides in the median eminence: Their sources and destinations

By radioimmunoassay and immunocytochemical techniques, 14 neuropeptides have been measured and localized in the rat median eminence. Neuropeptides with inhibitory or stimulatory effects on the anterior pituitary hormones as well as posterior pituitary hormones are present in the median eminence in the highest concentrations of the central nervous system. All these peptides (LH-RH, TRH, somatostatin, CRF, vasopressin, oxytocin) are of preoptic or hypothalamic origin and they are transported to the median eminence by loop-like fiber systems through the lateral retrochiasmatic area. Within the median eminence, the pericapillary space constitutes the main common pathway. Three major transport routes—axons, vessels, liquor spaces—are separated from each others by only basement membranes, which allow free communications downwards to the pituitary but also backwards to the central nervous system.     

The oestrous cycle with particular reference to the neural control of the ovary

The differing types of oestrous cycle found in mammals seem to be manifestations of the degree to which the external environment participates in the control of the three main phases of the ovarian cycle, the follicular phase, ovulation, corpus luteum phase. The question of the importance of the external and the internal environment for the manifestations of cyclicity has been discussed by reference to the factors involved in the control of ovarian function. The control of the ovarian cycle involves an interrelated fluctuation in the secretion of the anterior pituitary gonadotrophins FSH and LH, and in certain species LTH, which are under the control of hypophysiotrophic hormones produced in the hypothalamus. The production of these hormones is modified by other hypothalamic and extra–hypothalamic mechanisms, including a probable preoptic cycling mechanism controlling the ovulatory surge of gonadotrophins. These mechanisms can be triggered and timed by means of nervous reflexes arising from a variety of sensory end organs. Also this brain–hypothalamus–pituitary unit appears to contain sex steroid and gonadotropin sensitive elements through which these factors can influence the system. The additional luteotrophin and luteolytic factors involved in corpus luteum control have not been discussed. A brief idea as to how all these factors are integrated for the control of ovarian cyclicity is presented.