Neurohistological and histochemical observations on the lung of Francolinus pondicerianus (gray partridge or safed teeter) as revealed by the cholinesterase technique.

An investigation was undertaken to demonstrate the neural elements of the lung of Francolinus pondicerianus, from the point of view of neurohistology and histochemistry. The staining of the neural elements was done by the cholinesterase technique with a maintained pH of 5.2, temperature 40 degrees C and incubation period of 19 h. Distribution of nerves in association with bronchial cartilage, pulmonary vessels and bronchi has been described and discussed. The distribution of the ganglia in association with blood vessels, bronchi, cartilage, various plexuses and the neural terminal terminal network has also been described. The innervation of the bronchi and their branches, and formation of the neural terminal network has been studied, as well as the distribution of cholinesterase in bronchi, blood vessels, muscles, ganglia, and nerve fibres.     

A Working Module for the Neurovascular Unit in the Sexually Dimorphic Nucleus of the Preoptic Area

The neurovascular unit (NVU) can be conceptualized as a functional entity consisting of neurons, astrocytes, pericytes, and endothelial and smooth muscle cells that operate in concert to affect blood flow to a very circumscribed area. Although we are currently in a “golden era” of bioengineering, there are, as yet, no living NVUs-on-a-chip modules available and the development of a neural chip that would mimic NVUs is a seemingly lofty goal. The sexually dimorphic nucleus of the preoptic area (SDN-POA) is a tiny brain structure (between 0.001~0.007 mm³ in rats) with an assessable biological function (i.e., male sexual behavior). The present effort was undertaken to determine whether there are identifiable NVUs in the SDN-POA by assessing its vasculature relative to its known neural components. First, a thorough and systematic review of thousands of histologic and immunofluorescent images from 201 weanling and adult rats was undertaken to define the characteristics of the vessels supplying the SDN-POA: its primary supply artery/arteriole and capillaries are physically inseparable from their neural elements. A subsequent immunofluorescent study targeting α-smooth muscle actin confirmed the identity of an artery/arteriole supplying the SDN-POA. In reality, the predominant components of the SDN-POA are calbindin D28k-positive neurons that are comingled with tyrosine hydroxylase-positive projections. Finally, a schematic of an SDN-POA NVU is proposed as a working model of the basic building block of the CNS. Such modules could serve the study of neurovascular mechanisms and potentially inform the development of next generation bioengineered neural transplants, i.e., the construct of an NVU neural chip.     

Vascular-nervous relationships in the valves of the heart]

Method of silver nitrate impregnation was used in order to study 50 preparations of not-changed atrioventricular valves of the heart of domestic bulls and 30 preparations of the same valves of adult humans. It has been shown that in heart valves there are certain relationships between striated muscle fibres, blood vessels and nerve elements. The nerve structures of the valves are represented by nerve bundles of different thickness. In their composition there are comparatively thin non-myelinated and thicker myelinated fibres. Towards the free edge of cusps the nerve bundles become thinner and the nerve trunks give off separate thin nerve fibres disposed along the vessels of a capillary type and in some places getting around them. In certain portions of cusps the nerve bundles, some of which have zigzag sinuosity, cross blood vessels in different directions. In man the major mass of blood vessels and nerve elements are disposed near the base of the valve cusps, accompanying the muscle fibre bundles penetrating from the base side. In the bull heart valves an amount of blood vessels and nerve elements is found in considerable portions of the cusps not connected with muscle fibres.     

Anatomical, neurohistological and histochemical observations on the tongue of Francolinus pondicerianus (grey partridge or safed teeter).

The staining and demonstration of neural elements in relation with other associated structures was most satisfactory at pH 5.2, incubation period 20 h, and temperature 40degreesC. Ganglia of various shape and size were observed on or near the fungiform, filiform and foliate papillae. In the region of the fungiform papillae, a chain of ganglia (parasympathetic) was observed. The nerve cells of these ganglia showed cholinesterase (ChE) activity. The neural networks of the foliate papillae were connected with the neural terminal network and occasionally to the ganglia. The innervation of blood vessels (artery and vein) was profuse. At times ganglia were noticed on the periphery of the artery. Neuromuscular spindle-like structures were noticed occasionally. Dot-like free nerve endings were also observed. The ChE activity was very marked in the muscle fibres lying in the region of the circumvallate papillae but was less marked in the muscle fibres lying in the region of the filiform and fungiform papillae.     

Effect of taurine on the microvessel exchange function and adrenergic response of veins and arteries in the cat skeletal muscle

In cats anesthetized with Uretan and perfused with a constant blood volume, Taurine induced responses of neither arterial nor venous vessels of the skeletal muscle but increased the capillary filtration coefficient without any significant change of the capillary pressure in the skeletal muscle's microvessels. Taurine also increased both the constrictor and the dilatory responses of the arterial and venous vessels. The mechanism of the Taurine effects upon the smooth muscle elements of arteries and veins as well as upon proper mechanisms of capillary pressure control and capillary filtration coefficient, seems to be calcium-dependent.     

Constitutive expression of preproendothelin in the cardiac neural crest selectively promotes expansion of the adventitia of the great vessels in vivo

Cardiac neural crest cells are essential for normal development of the great vessels and the heart, giving rise to a range of cell types, including both neuronal and non-neuronal adventitial cells and smooth muscle. Endothelin (ET) signaling plays an important role in the development of cardiac neural crest cell lineages, yet the underlying mechanisms that act to control their migration, differentiation, and proliferation remain largely unclear. We examined the expression patterns of the receptor, ET(A), and the ET-specific converting enzyme, ECE-1, in the pharyngeal arches and great vessels of the developing chick embryo. In situ hybridization analysis revealed that, while ET(A) is expressed in the pharyngeal arch mesenchyme, populated by cardiac neural crest cells, ECE-1 expression is localized to the outermost ectodermal cells of the arches and then to the innermost endothelial cells of the great vessels. This dynamic pattern of expression suggests that only a subpopulation of neural crest cells in these regions is responsive to ET signaling at particular developmental time points. To test this, retroviral gene delivery was used to constitutively express preproET-1, a precursor of mature ET-1 ligand, in the cardiac neural crest. This resulted in a selective expansion of the outermost, adventitial cell population in the great vessels. In contrast, neither differentiation nor proliferation of neural crest-derived smooth muscle cells was significantly affected. These results suggest that constitutive expression of exogenous preproET-1 in the cardiac neural crest results in expansion restricted to an adventitial cell population of the developing great vessels.     

Aminergic cellular organization in the gills of Aplysia species

The constituent elements of the gills of Aplysia kurodai and A. juliana were examined for the presence of biogenic amines using histochemical, immunocytochemical, and HPLC techniques. Aminergic elements were revealed by glyoxylic acid-induced fluorescence in the branchial nerve, branchial ganglion, branchial vessels, and pinnules in both species. Three types of fluorescent cells were found in the neural plexus of the gill in each species. Two of them might be sensory neurons. Although HPLC analysis showed the presence of serotonin and dopamine in all gill structures including fluorescent neural elements, there were regional differences in concentrations of the monoamines. It was noted in the pinnules that there was a much higher concentration of dopamine than serotonin. Serotonin immunocytochemistry revealed neural processes which were immunoreactive to antiserotonin antibody, but serotonin immunoreactivity could not be found in a population of branchioganglionic neuron (BGN) somata. Serotonergic elements in the ganglion may be processes of the central ganglion, while dopaminergic elements may be processes of neurons in the neural plexus, located beyond the branchial ganglion. BGNs were activated by bath-applied dopamine and serotonin. These results suggest that dopaminergic sensory inputs from the neural plexus and serotonergic descending inputs from the abdominal ganglion may be among the inputs received by BGNs. It was found that serotonin depressed excitatory junctional potentials in muscle cells of the efferent branchial vessel, which were induced by an identified neuron of the abdominal ganglion. The aminergic cellular organization of the gill may involve serotonergic presynaptic-inhibitory fibers arising from the abdominal ganglion.     

Features of the innervation of fascia and their microcirculatory bed in the rat

By means of silver impregnation, methylene blue staining and using glyoxylic acid, the neural apparatus of the muscle fasciae in the shoulder girdle and back and their microcirculatory bed have been revealed in laboratory white rats. An uneven concentration of neuronal terminals makes the base of neurotissue interactions of the muscle fasciae of the shoulder girdle and the back of the rats. Only a small part of microvessels possesses neural elements. The fasciae and their microvessels are innervated both by sensitive and sympathetic neural fibers and their endings; they differ from each other morphologically and histochemically. The rat fasciae are useful objects for vital observations for behaviour both of the vascular nerves and the avascular areas.     

Neurovascular congruence results from a shared patterning mechanism that utilizes Semaphorin3A and Neuropilin-1

Peripheral nerves and blood vessels have similar patterns in quail forelimb development. Usually, nerves extend adjacent to existing blood vessels, but in a few cases, vessels follow nerves. Nerves have been proposed to follow vascular smooth muscle, endothelium, or their basal laminae. Focusing on the major axial blood vessels and nerves, we found that when nerves grow into forelimbs at E3.5-E5, vascular smooth muscle was not detectable by smooth muscle actin immunoreactivity. Additionally, transmission electron microscopy at E5.5 confirmed that early blood vessels lacked smooth muscle and showed that the endothelial cell layer lacks a basal lamina, and we did not observe physical contact between peripheral nerves and these endothelial cells. To test more generally whether lack of nerves affected blood vessel patterns, forelimb-level neural tube ablations were performed at E2 to produce aneural limbs; these had completely normal vascular patterns up to at least E10. To test more generally whether vascular perturbation affected nerve patterns, VEGF(165), VEGF(121), Ang-1, and soluble Flt-1/Fc proteins singly and in combination were focally introduced via beads implanted into E4.5 forelimbs. These produced significant alterations to the vascular patterns, which included the formation of neo-vessels and the creation of ectopic avascular spaces at E6, but in both under- and overvascularized forelimbs, the peripheral nerve pattern was normal. The spatial distribution of semaphorin3A protein immunoreactivity was consistent with a negative regulation of neural and/or vascular patterning. Semaphorin3A bead implantations into E4.5 forelimbs caused failure of nerves and blood vessels to form and to deviate away from the bead. Conversely, semaphorin3A antibody bead implantation was associated with a local increase in capillary formation. Furthermore, neural tube electroporation at E2 with a construct for the soluble form of neuropilin-1 caused vascular malformations and hemorrhage as well as altered nerve trajectories and peripheral nerve defasciculation at E5-E6. These results suggest that neurovascular congruency does not arise from interdependence between peripheral nerves and blood vessels, but supports the hypothesis that it arises by a shared patterning mechanism that utilizes semaphorin3A.     

Hypertrophic smooth muscle

Summary In adult guinea-pigs, oral to a partial obstruction to the flow of ingesta in the ileum there is a marked increase in the diameter of the intestine and a hypertrophy of the muscle coat. The features of the intramuscular blood vessels and of the extracellular materials were studied by electron microscopy. There is a small increase in the amount of intercellular space measured morphometrically. The basal lamina surrounding the hypertrophic muscle cells is more prominent than in controls. In the intercellular space between muscle cells, in addition to collagen fibrils, there is abundant amorphous material of medium electron density and streak-like, electron-dense material often similar to thickened basal laminae. The total amount of stroma (intercellular materials) present in a unit length of intestine is greatly increased in hypertrophy; a role of the muscle cells in the production of new collagen and other extracellular elements is suggested by the present observations. Many new intramuscular blood vessels (mainly capillaries, some of which are fenestrated) are formed during hypertrophy of the intestinal wall, so that the circular muscle layer remains as well vascularized in the hypertrophic intestine as in the controls. Blood vessels are not formed within the longitudinal muscle layer.     

Development and pathology of the hyaloid, choroidal and retinal vasculature

During embryogenesis, the development and differentiation of the eye requires the concomitant formation of the neural/glial elements along with a dense vascular network. The adult neural retina is supported by two distinct vascular systems, the proper retinal vessels and the choroidal vessels. The two beds differ not only in their pattern of embryonic differentiation, but also in their function in the adult organism. The retinal vasculature has barrier properties similar to those observed in the brain, whereas the choroidal vessels display a highly fenestrated phenotype. The hyaloid vasculature is a transient embryonic vascular bed which is complete at birth in mammals and regresses contemporaneously with the formation of the retinal vasculature. The dependence of the retina on its blood supply makes it highly vulnerable to any vascular changes and indeed ocular diseases, such as proliferative retinopathy, age-related macular degeneration and the hyperplastic primary vitreous, which are associated with abnormalities of the different vascular beds of the eye. A number of factors have been implicated in developmental and pathological changes in vessel formation and regression, including fibroblast growth factors, platelet-derived endothelial growth factor and vascular endothelial growth factor, among others. The purpose of this review is to describe and discuss new insights into the mechanisms and molecular cues involved in the development of the normal and pathological vascular systems of the eye. The characterization of the molecules and cell-cell interactions involved in the formation, stabilization and regression of new vessels has led to the identification of potential control points for therapeutic intervention.     

Ultrastructure of the striated muscle tissue of the iris of birds]

Heteromorphism of the contractile elements of the iris muscular tissue in chick embryos and in chickens has been studied by means of electron microscopical investigation. The leading contractile tissue of the iris is the striated muscular tissue, which is formed as a cellular-simplastic system with its own cambium-myosatellitocytes. Some cells, containing myofilaments in their cytoplasm, are related to myofibroblastic and smooth muscle differons, which functions remain to be studied. A hypothesis is proposed on existence of two sources for development of the iris muscular elements. The first-stem cells for the striated muscular tissue; at early stages of embryonal development they are included into composition of ectomesenchyme of the neural crest and migrate into the area of the muscle anlages. The second-cells migrating from the ocular cup margins and developing into the smooth myocytes of the iris.     

Morphologic aspects of local blood flow regulation in the myocardium

In 67 preparations of the human hearts at the first and second periods of mature age, spatial interrelations between blood vessels and cardiac muscle fibers in the ventricle myocardium have been studied. All the elements of the myocardial blood bed are oriented under a certain angle in relation to the cardiac muscle fibers. Regular arrangement of the arteries and sinusoid dilated veins under endocardium on the top of the papillary muscles and in the muscular trabecules is demonstrated. As proves the mathematical model, the slope orientation of the blood bed elements towards the cardiac muscle fibers ensures and adequate realization of the external influence of the contractile cardiomyocytes to the successive movement of blood along the intramural myocardial vessels. From morphological positions, a conclusion on the mechanism of the intracavitary pressure effect on blood movement along the intramural veins of the ventricular myocardium is argued. A conclusion is made on the leading role of the extravascular factors (intramyocardial and intercavitary pressure) in the local regulation of the blood stream in the myocardium and in development of working cardiac hyperemia.     

AMP deaminase histochemical activity and immunofluorescent isozyme localization in rat skeletal muscle.

The cellular distribution of AMP deaminase (AMPda) isozymes was documented for rat soleus and plantaris muscles, utilizing immunofluorescence microscopy and immunoprecipitation methods. AMPda is a ubiquitous enzyme existing as three distinct isozymes, A, B and C, which were initially purified from skeletal muscle, liver (and kidney), and heart, respectively. AMPda-A is primarily concentrated subsarcolemmally and intermyofibrillarly within muscle cells, while isozymes B and C are concentrated within non-myofiber elements of muscle tissue. AMPda-B is principally associated with connective tissues surrounding neural elements and the muscle spindle capsule, and AMPda-C is predominantly associated with circulatory elements, such as arterial and venous walls, capillary endothelium, and red blood cells. These specific localizations, combined with documented differences in kinetic properties, suggest multiple functional roles for the AMPda isozymes or temporal segregation of similar AMPda functions. Linkage of the AMPda substrate with adenosine production pathways at the AMP level and the localization of isozyme-C in vascular tissue suggest a regulatory role in the microcirculation.     

Immunofluorescent and structural features of cells in the intervascular stroma of the amphibian carotid labyrinth

Summary The amphibian carotid labyrinth consists of a pars cavernosa, the main chamber of which is in communication with both the base of the external carotid artery, and the vessels of the labyrinthine pars capillaris. On the walls of the main chamber is a network of thick strands of connective tissue and modified smooth muscle cells surrounding the openings into the p. capillaris. These openings lead into wide-diameter atrial vessels, which in turn branch to form the short narrow-diameter vessels. The short vessels form the major component of the labyrinth. A few extremely narrow-diameter vessels are also present. The short vessels open into the roots of the internal carotid artery on the ventral aspect of the carotid labyrinth. The intervascular stroma of the p. capillaris contains numerous stellate and bipolar cells. These cells give a positive response to an immunofluorescent technique specific for smooth muscle myosin and tropomyosin. As the ultrastructural features of these cells are comparable in many respects to smooth muscle, they have been designated as modified smooth muscle cells. It is proposed that these cells act in both an active and passive fashion in maintaining the luminal dimensions of the short vessels relatively constant.     

Pericytes and perivascular microglial cells in the basal forebrain of the neonatal rabbit

Summary Three types of pericytes outline the vascular bed in Golgi preparations of the newborn rabbit brain. Elongate cells (Type I) are restricted to capillaries, elements resembling smooth muscle cells (Type II) surround vessels of intermediate size, and large flat forms (Type III) cover the surface of arterioles and venules. Electron microscopy shows all types to be located within a well defined perivascular basement membrane. It also reveals the presence of filaments in the cytoplasm of some pericytes resembling the myofilaments of smooth muscle cells. It suggests the possibility that some pericytes are capable of contraction and may participate in regulating blood flow in small vessels.Microglia cells bear no resemblance to pericytes in terms of their shape, distribution or staining characteristics. Microglia cells are located outside the vascular basement membrane (external basal lamina) in the brain parenchyma, and they vary in form according to their location and the character of the surrounding extracellular space. This study does not support the hypothesis that microglia cells arise from pericytes but indicates that they originate either by in situ division or from hematogenous elements that enter the brain by crossing the vessel wall.Support provided by N.I.H. Grants No. NS 10864 and NS 07938 from the U.S. Public Health Service.     

Electron microscopic research on capillary regeneration in skeletal muscle after mechanical damage

At early stages the regeneration of the capillaries in adult rats in the focus of the skeletal muscle traumatic injury proceeds together with regeneration of muscle elements. However, it is retarded to some extent. The capillaries are formed within the borders of the basal membranes of the destroyed vessels or grow de novo from poorly differentiated interstitial cells.     

Vertebrate head development: Segmentation,novelties, and homology

Vertebrate head development is a classical topic lately invigorated by methodological as well as conceptual advances. In contrast to the classical segmentalist views going back to idealistic morphology, the head is now seen not as simply an extension of the trunk, but as a structure patterned by different mechanisms and tissues. Whereas the trunk paraxial mesoderm imposes its segmental pattern on adjacent tissues such as the neural crest derivatives, in the head the neural crest cells carry pattern information needed for proper morphogenesis of mesodermal derivatives, such as the cranial muscles. Neural crest cells make connective tissue components which attach the muscle fiber to the skeletal elements. These crest cells take their origin from the same visceral arch as the muscle cells, even when the skeletal elements to which the muscle attaches are from another arch. The neural crest itself receives important patterning influences from the pharyngeal endoderm. The origin of jaws can be seen as an exaptation in which a heterotopic shift of the expression domains of regulatory genes was a necessary step that enabled this key innovation. The jaws are patterned by Dlx genes expressed in a nested pattern along the proximo-distal axis, analogous to the anterior–posterior specification governed by Hox genes. Knocking out Dlx 5 and 6 transforms the lower jaw homeotically into an upper jaw. New data indicate that both upper and lower jaw cartilages are derived from one, common anlage traditionally labelled the “mandibular” condensation, and that the “maxillary” condensation gives rise to other structures such as the trabecula. We propose that the main contribution from evolutionary developmental biology to solving homology questions lies in deepening our biological understanding of characters and character states.     

Distribution and the fine structure of serotonin-containing fibers in the rat small intestine

Serotonin immunoreactive fibers were observed under the electron microscopy in all layers of the small intestine, with greatest abundance in the mucosa. Submucosal blood vessels were often surrounded by immuno positive nerves. In the inner circular muscle layer the immunoreactive serotonin positive fibers were closely associated with the smooth muscle cells. In the ganglia of the myenteric and submucous plexuses, labelled fibers surrounded the immunonegative neural cell bodies, but rarely formed conventional synaptic junctions. It is concluded that the serotoninergic system of the small intestine may influence the activity of associated structures in a diffuse non-synaptic manner.