Ultrastructure of the capillaries of nerve tissue transplants growing in the anterior chamber of the eye

Blood capillaries have been studied electron microscopically in the areas of grafts (rat embryonal hippocamp and septal cerebral parts transplanted to mature rats) containing mainly nervous, glial or connective tissue cells. Certain differences in the capillary wall structure have been revealed. In areas with a great concentration of nervous cells, the blood capillaries are characterized by a dense arrangement of cellular elements in their walls, a continuous layer of the glial end-feet, this is specific for the CNS capillaries providing the blood--brain barrier. In peripheral area of the grafts, where glial elements predominate, the capillaries have loose arrangement of the mural cellular elements, great endotheliocyte activity, thick connective tissue tunic, lack of a dense glial surrounding. These characteristics make dubious the statement whether these capillaries possess the blood--brain barrier function. In places where connective tissue cells make aggregates, the capillaries do not possess the barrier properties because of perforations and fenestrae in endothelium and interruptions of the basal membrane, absence of pericapillary glial elements. All types of the capillaries demonstrate certain signs of a high functional activity. Formation of the capillary structure depends on the surrounding tissue.     

Microtopographic relation between the lymphatic capillaries and glands of the small intestine

Microtopographic interrelationships of the lymphatic capillaries and glands of the small intestine have been investigated taking into account new data on the diffuse endocrine system, which includes endocrine cells of the gastro-intestinal tract. An immediate contact of the lymphatic capillaries with the intestinal glands, resembling microtopographic interrelationships of the lymphatic capillaries in the endocrine glands, has been revealed in total translucent and histological preparations. A suggestion is made that the microtopographic interrelationships of the lymphatic capillaries and the intestinal glands can be regarded as a morphologic basis for absorption of hormones produced by the endocrine cells of the intestinal glands.     

The ultrastructure of frog mesenteric capillaries of known filtration coefficient.

The capillaries of the frog mesentery were investigated by transmission electronmicroscopy. The mean diameter of these vessels was 20 micrometers and a single layer of five to six endothelial cells (on average) contributed to each circumference. Their ultrastructure was very similar to that of mammalian capillaries of the continuous type [Bennett, Luft and Hampton, 1959]. The endotherlial cells, which contained many vesicles, were joined by specialized junctions and surrounded by a continuous basement membrane. Eleven capillaries were examined after the filtration coefficient of their walls had been investigated by the microperfusion micro-occlusion technique of Michel, Mason, Curry and Tooke [1974]. No abnormal appearances were observed even after the vessels had been perfused with protein free solutions which have been shown to increase filtration coefficient five fold. No morphological differences between capillaries were seen to accompany large differences in the filtration coefficients.     

Capillaries. A cytologic feature of pulmonary carcinoid tumors

The cytologic features of pulmonary carcinoid tumors have been well described, but most reports have not mentioned capillaries as a prominent finding. Two cases are described in which abundant capillaries in endobronchial brushing and fine needle aspiration specimens were a helpful feature in making the correct diagnosis.     

The formation of the insulo-acinar portal system in the pancreas of human fetuses]

In human fetuses 12-20-week-old peculiarities in creation and development of the pancreatic hemo-microcirculatory bed have been studied in connection of its incretory part formation. The vascular glomerulus begins to form on the 12th-14th week as transformation of capillaries of the exocrinic parenchyma into the glomerular capillaries, which, on their getting out of the glomeruli, turn into vessels. The latter participate in formation of the insulo-acinar portal system. Certain structures have been revealed for adaptation of an elevated volume of the blood stream in the glomeruli place, where the glomerular microvessels pass into the acinar anastomoses. The latter perform shunting of the glomerular capillaries with the arteriole, which brings blood, enriched in insular hormones, to distantly situating acinar cells.     

Identification of lymph and blood capillaries by immunohistochemical staining for various basement membrane components.

In the present report we analyzed the presence and distribution of various basement membrane (BM) proteins in normal blood and lymph vessels with special emphasis on BM-associated heparan sulfate proteoglycan (HSPG) when compared to the BM-components collagen IV, laminin and fibronectin. We found that normal lymph capillaries have a BM that contains only collagen IV and small amounts of laminin, but almost no BM-associated HSPG and fibronectin, while blood capillaries showed a BM comprising of all components tested for. Larger lymphatics, however, were indistinguishable from blood vessels on the basis of BM staining. Lymphangiomas showed a BM pattern similar to that of lymph capillaries. Our findings provide evidence that the differential staining of BM-components may represent a reliable method for morphological distinction between blood and lymph capillaries. A comparison of these results with the BM-pattern in other functionally specialized blood vessels (glomerulus, sinusoids) provides evidence that the BM-composition may have some major impact on the functional properties. Thus, it is conceivable that the lack of HSPG in lymph capillaries may be essential for a free influx of fluid and proteins into these capillaries, which may have been extravasated into the interstitium.     

Identification of lymph and blood capillaries by immunohistochemical staining for various basement membrane components

Summary In the present report we analyzed the presence and distribution of various basement membrane (BM) proteins in normal blood and lymph vessels with special emphasis on BM-associated heparan sulfate proteoglycan (HSPG) when compared to the BM-components collagen IV, laminin and fibronectin. We found that normal lymph capillaries have a BM that contains only collagen IV and small amounts of laminin, but almost no BM-associated HSPG and fibronectin, while blood capillaries showed a BM comprising of all components tested for. Larger lymphatics, however, were indistinguishable from blood vessels on the basis of BM staining. Lymphangiomas showed a BM pattern similar to that of lymph capillaries. Our findings provide evidence that the differential staining of BM-components may represent a reliable method for morphological distinction between blood and lymph capillaries. A comparison of these results with the BM-pattern in other functionally specialized blood vessels (glomerulus, sinusoids) provides evidence that the BM-composition may have some major impact on the functional properties. Thus, it is conceivable that the lack of HSPG in lymph capillaries may be essential for a free influx of fluid and proteins into these capillaries, which may have been extravasated into the interstitium.     

Potential fields and barriers to diffusion in narrow cylindrical capillaries

In this paper, the wall potential along the center line of narrow solid capillaries has been derived. The potential barriers at the open end of such capillaries have been studied in detail. The influence of these potential barriers on the diffusion coefficients and their dependence on temperature and capillary radius have been evaluated. The implications of these energy barriers in the clarification of low pressure hysteresis phenomena have been pointed out.     

Pathogenesis of chronic venous insufficiency and possible effects of compression and pentoxifylline.

It has been recognized for over 2000 years that ulceration of the leg may be associated with visible varices of the lower limb. More recent physiological investigation has shown that the pressure in the veins of the lower limb remains raised in patients with venous ulceration during ambulation, whereas in normal subjects the pressure in superficial veins falls to a low level. This elevated pressure appears to cause damage to the superficial capillaries in the skin culminating in the production of venous ulceration. Events in the dermal capillaries which result in skin destruction have yet to be fully defined. Pericapillary fibrin cuffs have been demonstrated histologically and suggested as a cause of diminished nutrition to the skin. White blood cells have been shown to accumulate in the lower limb of patients with venous disease and these accumulations are particularly located around the dermal capillaries. Activated white blood cells releasing free radicals and destructive enzymes may precipitate skin destruction. An understanding of these mechanisms may help to explain the efficacy of compression hosiery and bandaging as well as some of the new pharmacological agents which have been shown to influence venous ulcer healing.     

Specific endothelial bodies in growing capillaries of the rabbit cornea

Contents of Veibel-Palade corpuscles have been studied in endotheliocytes of vessels of the rabbit eye limb (control) and in the corneal capillaries, growing after burn effect and after a combined effect of burn and colchycin. In the growing capillaries of the cornea the specific endothelial bodies are constant components of the cells and make effect to processes of the vascular new formations.     

Angiogenic effect of colchicine

The effect of colchicine on the microcirculatory vessels of eye perilimbal area was revealed in 2 groups of experimental rabbits. Colchicine was found to promote the growth of capillaries both during intravenous injections of colchicine solution and during local colchicine application as an ointment. The proper substance of cornea was also changed under the influence of colchicine. Changes in the ultrastructure of the capillary wall and endothelial cells forming the capillaries have been noted.     

Changes in the parameters of skin capillaries during the adaptation of students from the countries of Asia, Africa and Latin America

Time-dependent changes in diameters of various parts of the capillaries, distances between loops of the skin papillary capillaries in the nail wall and number of functioning capillaries per 1 mm2 of the skin surface have been studied biomicroscopically in foreign students, arrived from hot countries, during the process of their adaptation. Reorganization of these skin capillary parameters, actively participating in processes of heat exchange, demonstrate a time-dependent character. Therefore, by means of regressive analysis it is possible to approximate dynamics of the initial data using suitable theoretical models. The dynamics of average meanings of the capillary diameters in the arterial part subordinates to the hyperbolic dependence, changes of other parameters approach the rectilinear regression.     

Guidance of vascular and neural network formation

Blood vessels and nerves are structurally similar complex branched systems. Their guidance must be exquisitely regulated to ensure proper wiring of both networks. Recent results showed that specialized endothelial cells, resembling axonal growth cones, form the tips of growing capillaries. These endothelial tip cells guide outgrowing capillaries in response to gradients of extracellular matrix-bound vascular endothelial growth factor. Several axon guidance molecules, including Semaphorins, Netrins, Ephrins and Slits, have also been implicated in vessel pathfinding and network formation. In particular, Semaphorin3E and its receptor plexinD1 in addition to the Netrin receptor UNC5B have recently been shown to direct endothelial tip cell navigation.     

Histoarchitectonics and capillary-glio-neurocytic relationships in the stellate ganglion of cats

By means of injection into the microcirculatory network, section staining with hallocyanine chromic alumen, hematoxylin--eosin, silver impregnation after Bielschowsky--Gross, Baginsky, unequal intensity of microvascularization in cervical and thoracic portions have been stated, as well as different forms of interrelations between capillaries, neurocytes and gliocytes (capillaries are predominantly situated in parallel fashion to the surface of neurocytes, or else surround them). The distance between the capillary and neurocyte does not usually exceed 5--10 mkm. The contact area between neurocytes and capillaries increases with enlargement of neurocyte area. Glial and connective tissue elements are clearly differentiated after staining with acridine orange.     

O2 transport in cerebral microregions (mathematical simulation)

The effects of the circulation rate in capillaries, the intensity of O2 consumption by nerve cells and the capillary network density on the O2 tension distribution in the cerebral cortex have been studied, utilizing a mathematical model simulating actual neuron-capillary relationships. The model has been written as a system of equations in partial derivatives, its solution obtained by the net-point method. Regulatory variations of the capillary circulation rate in certain cerebral microregions have been shown to ensure similar changes in oxygen supply throughout the region. A drop of the pO2 level in a cerebral microregion with a rising O2 consumption by nerve cells is shown to be due, by 75 percent, to the increase of O2 consumption and by 25 percent, to the lower pO2 in the capillaries. Conversely, an increase in pO2 in microregions resulting from a lower O2 consumption by neurons is due by 75 percent, to a pO2 rise in capillaries and by 25 percent, at the expense of an O2 consumption decrease. In cerebral regions differing in capillary network density by 20 percent, changes in the conditions for oxygen supply to tissue are due by 1/3 to pO2 variations in the capillaries and by 2/3 to alterations in the diffusion distances.     

Ultrastructural localization of fibronectin and laminin in human granulation tissue in relation to capillary development

The distribution of fibronectin (FN) and laminin (LM) at developing capillaries during various developmental stages, from capillary sprouts to relatively developed capillaries, was studied by light- and electron-microscopy immunocytochemistry. By light-microscope, FN immunoreactivity was diffusely distributed throughout the stroma of the granulation tissues, while for LM it was preferentially distributed at the perivascular region with the various developmental stages of the immature capillaries. Ultrastructural study revealed that capillary sprouts were closely surrounded by plentiful deposits of immunoreaction with the FN, but only faintly for LM. Relatively developed capillaries with large and tall endothelium were surrounded by plentiful immunoreactive products with both FN and LM, and immunoreactivities in the cisternae of rER of the endothelium and/or the pericytes were also shown. Cytoplasmic interdigitations between the endothelium and the pericyte of developing capillaries were recognized without an immunoreaction for FN and LM. These results mean that the capillary sprouts are associated with a prepatterned FN-rich and LM-poor perivascular matrix, whereas relatively developed capillaries are associated with a FN- and LM-rich perivascular matrix which would have been produced by the capillary endothelium and/or pericytes.     

Capillarization of the myocardium of the yak

Organometric and histometric characteristics of various parts of the heart have been performed in the yak, a permanent inhabitant at altitudes of 3,000-5,000 m above the sea level. Forty hearts of mature animals have been studied. Morphometric investigations of capillaries in the muscle fibers have been carried out in the atrial walls, in the right and left auriculae. in the ventricles and in the papillary muscles. The data are presented for each cardiac part: they describe diameters, density and volume of the capillary network and muscle fibers. In order to estimate the degree of capillarization of the cardiac muscle tissue, a new parameter is suggested to be used, when analyzing the morphometric data. It characterizes ratio of capillaries volume. According to the criterion given, a significant difference is stated between the degree of capillarization in the myocardium of the right and left ventricles. We suppose that this adequately reflects an increased loading experienced by the right cardiac parts under a long-lasting effect of altitude factors.     

Ultrastructural and histochemical investigation of the terminal capillaries in the spleen of the carp (Cyprinus carpio L.)

Summary In the spleen of the carp arterial capillaries of a highly differentiated structure have been studied by light and electron microscopy. These capillaries share various structural characteristics with the sheathed capillaries (ellipsoids of Schweigger-Seidel) of higher vertebrates. The long arterial capillaries of the carp spleen are provided with cuboidal endothelial cells containing filaments approximately 7 nm in diameter. There is no basal lamina. The endothelial cells form various types of cell junctions, but there are also extensive areas without any junctions. Here, a free passage is possible between the capillary lumen and the subendothelial space. The capillaries possess a single-layered sheath of macrophages. Characteristically, the sheath macrophages possess long and slender cell processes forming a loose framework, the meshes of which are filled with lymphocytes and spindle cells. The sheath macrophages show a zone of ectoplasm rich in filaments. They also contain numerous phagolysosomes rich in hydrolytic enzymes, as identified histochemically. The sheath is sharply limited against the pulp by a thick layer of collagen fibers.     

“Seamless” endothelial cells of blood capillaries

Summary The distribution and number of seamless endothelial cells (SE) were studied in various organs and tissues of rats, rabbits and humans (1) by light microscopy after silver impregnation of the endothelial cell boundaries, (2) by electron microscopy, and (3) in three-dimensional reconstructions of duodenal villi and renal glomeruli. Since SE are situated mostly at branching points, the number of SE is roughly correlated to the number of branchings in the capillary system concerned. SE make up about 50% of all endothelial cells in the renal glomerulum and duodenal villi, and about 30% in the cerebral cortex. However, they rarely occur in bradytrophic tissues. SE have been found exclusively in net capillaries (true capillaries). They seem to be absent in most arterio-venous capillaries (capillary parts of thoroughfare channels), in the capillaries of endocrine glands, as well as in the sinusoidal systems of heart muscle, liver, spleen and bone marrow. It is concluded that SE are developed when tube formation is confined to a single endothelial cell. SE are intercalated most frequently in those capillaries that develop lastly in the terminal vascular bed. The seamless segments are canalized by fusion of intraendothelial vacuoles with pre-existing vascular walls. The existence of SE, confirming the dual structural design of capillary systems, may be used as a detector for net capillaries.     

Effect of reduced physical activity on the skeletal muscle

The musculus masseter has been studied in 12 bioptates of 19-24-year-old men after they have been operated on for correction of true progeny which results in a decreasing functional loading on the masticatory musculature. SDG activity, ratio of myons of various types, cross section area of muscle fibres, content ratio of the connective tissue layers, number of blood capillaries around the myons, relative volume of the submicroscopic structures of the muscle fiber have been estimated. Pronounced pathological disorders in the muscle are absent, it is connected with a gradual change in conditions of functioning and a prolonged time for adaptation. The first type myons ratio increases, comparing to that in the control, the number of the capillaries around the myons decreases, while the amount of the connective tissue grows large. Marked quantitative ultrastructural changes of the energy and contractile-myofibrillar apparatus take place.