The microcirculatory bed of the normal rat thyroid and during hypokinesia based on scanning electron microscopy data on corrosion preparations

In 12 mature white rats with body mass of 180-230 g, that are kept in tight pencil-cases for 10, 30 and 90 days (3 rats make the control), by means of scanning electron microscopy of corrosive preparations reorganizations of three-dimensional spatial organization of the thyroid microcirculatory bed are studied. In intact animals single-layered network of the perifollicular capillaries consists of widely anastomotic blood microvessels and makes 68 +/- 7% of the follicular surface. At hypokinesia (Hk) lasting for 10 days, the perifollicular capillaries are sharply dilated, the capillary network area makes 74 +/- 4%. A large amount of processes appear on the capillary walls. On the 30th day of Hk unequal distribution of capillaries on the follicular surface is noted, that is heterogeneity in organization of the perifollicular capillary networks is manifested. In 90 days of Hk reduction of the capillaries is recorded, rarefied pericapillary network prevails, twistedness of the capillaries is clearly manifested, their complex branching decreases. The capillary network area makes 54 +/- 3% of the follicular area. A large amount of pin-shaped protrusions of the capillary wall appear.     

A scanning electron microscopy study of vascular casts from senile human brains.

A scanning electron microscope study was performed of vascular casts from 26 senile human brains. In 15 of these, three types of arterial deformities (glomerular loop formations, vascular wickerworks and bundles) were frequently encountered. They were compared with the appearance in microangiograms and histological sections.     

Architectonics of the vascular bed of the fetal portion of the mature human placenta (based on data of scanning electron microscopy)

Peculiarities of the microangioarchitectonics in the trunks, intermediate and terminal villi of the placenta have been described at a noncomplicated pregnancy. Signs of neovasculogenesis are demonstrated in the microcirculatory bed of the terminal villi. Possible connection between reduction of the paravasal capillary network, as the intermediate villi become mature, and neovasculogenesis is discussed.     

Age-related changes in the circulatory bed of the uterus (data of the scanning electron microscopy

Structure of the blood bed has been studied in normal rat uterus and at ageing. Phenomena of involutive changes in the blood bed have been demonstrated. They depend on the process of sclerosis in the organ and desolation of vessels.     

The microcirculatory bed of the human heart

Using a complex approach in studying microcirculatory bed of the human heart, possibilities of scanning electron microscopy of corrosive preparations, those of silver nitrate impregnation after V. V. Kuprianov are demonstrated. The silver nitrate impregnation makes it possible to study the wall structure of the microcirculatory pathways, to analyse arrangement of nuclei in the endothelial and muscle cells of the microcirculatory links, to reveal together with the vessels the surrounding tissues. Scanograms of the corrosive preparations of the arterioles demonstrate "circulatory strips", that are absent in the venular part. The relief of the luminal casts of the microcirculatory bed vessels in the human heart is presented as impresses of nuclei of the endothelial and smooth muscle cells. Peculiarities in form and distribution of these nuclei in various links of the microbed are demonstrated.     

Ultrastructural characteristics of the microcirculatory bed of the human adrenal cortex in prenatal ontogenesis

By means of transmissive electron microscopy the adrenals have been studied in 25 human embryos and fetuses at the age of 6-36 weeks. Certain stages have been revealed in formation of the adrenal cortex microcirculatory bed. In 6-7-week-old embryos (period of diffuse protocapillary bed) endothelial structure and mesenchymal cells, surrounding the adrenal anlage, resemble one another. A distinguished feature of the endothelium is regularly revealed desmosomes and large vacuoles, often found in cytoplasm of endotheliocytes. In 8-12-week-old fetuses (period when the organospecific microcirculatory bed is forming) sinusoid capillaries differentiate in the internal zone of the adrenal cortex; in endothelium fenestrae, "hatches", "locks" are revealed, the capillary basal membrane is formed. During subsequent time of the intrauterine development perfection of the microcirculatory pathways in the adrenals takes place, the arteriolar link of the subcapsular layer including. By the time of birth morphofunctional maturity of the microcirculatory bed in the adrenal cortex is noted.     

Types of mitochondria destruction in the cardiac myocyte (from the data of scanning electron microscopy)

Scanning electron microscopy has revealed three types of myocardial mitochondria degradation in intact rabbit heart: desquamation of the external membrane, mitochondria swelling with their following destruction, mini-focal ulceration of mitochondrial external membranes. There was a clear-cut daily and seasonal dynamics of the three types of degradation. Mitochondria degradation was much more pronounced in the fibrillating than in intact heart.     

Subendocardial vascular plexus of the human ventricular myocardium in ontogenesis studied by scanning electron microscopy]

By means of scanning electron microscopy of native and corrosive preparations peculiarities of endocardium of the papillary-trabecular apparatus of the human heart ventricle and its vessels have been studied in ontogenesis. Folds of the endocardium increase its contact area with blood and also increase reserve of its elasticity at diastole. The subendocardial vascular plexus is formed by capillary-like venous sinusoids. They situate in the direction to the compact myocardium at the depth of 300-500 mcm. They are supposed to perform resorptive functions of nutritive substances and oxygen from blood, which is in the ventricular cavities and to smooth blood pressure between blood in the ventricular cavities and vessels of the compact myocardium.     

Vascular anastomoses of the blood microcirculatory bed of the human heart

Using a complex of morphological techniques both injective and non-injective, scanning electron microscopy including, the hemomicrocirculatory bed and vascular anastomoses have been studied in various parts of the human heart. In most cases anastomoses between the microcirculatory links are realized at the level of capillaries, precapillary arterioles and postcapillary venules. Venulo-venular anastomoses are demonstrated in the myocardium. Existence of terminal arterioles is discussed.     

Main principles of the organization of the microcirculatory bed of the human greater omentum in early ontogenesis

The formation process of the terminal blood bed of the greater omentum has been studied in 42 human fetuses 14--28-week-old. The main peculiarities of the greater omentum blood bed by the 14th week of development are: paired arrangement of the afferent and deferent blood vessels and loop-shaped type of capillary growth, that joining the arteriole and venule, lend the blood stream a maximally centralized character. In 15--16 weeks of the fetal development in the omentum another type of the vascular growth occurs, characterized with appearance of single angioblastic processes that branch off the apex of the capillary loops. As a result new capillaries form; they connect apices of the capillary loops, that in their turn make bases for developing a true capillary network. Together with this, presence in ontogenesis of an autochthonous way of capillary appearance is proved, their connection with the closed blood stream is followed. Distinguishing of the loop-shaped stage in the capillary growth determines certain difference between vasculogenesis in ontogenesis and the vascular growth at reparative regeneration, since the base for the latter is only the capillary growth by means of single angioblastic processes.     

High resolution scanning electron microscopy of the intracellular surface of intercalated disks in human heart

The three-dimensional architecture of human cardiac intercalated disks was examined by high resolution scanning electron microscopy of osmium-macerated specimens. This methodology permits viewing of in situ intercalated disks from a vantage point inside individual cardiomyocytes. The erose nature of these structures was rendered in stark relief. Areas covered with clusters of particles were present on some membranous projections--these may represent a combination of desmosomes and fasciae adherentes. On the other hand, areas devoid of particles may correspond to gap junctions.     

Microrelief of the internal surface of the thoracic duct in dogs (based on scanning electron microscopy data)

The investigation has been performed on 17 mature dogs. With the aim to investigate the internal surface of the thoracic duct, the methods of scanning electron microscopy of native, impregnated and corrosive preparations have been used. The analysis of the scannograms obtained demonstrates that the valves of the thoracic ducts are mainly bicuspid, have a typical infundibular form, their cuspides are fused, forming a mesentery-like fold on the duct wall. It plays the main role in ensuring unilateral transport of lymph. The microrelief of the thoracic duct endothelium possesses a rather complex organization. The following relief formations are distinguished in endotheliocytes: 1. nuclei-containing eminence, 2. marginal processes, 3. separate microvilli. The dependence of the microrelief on arrangement of endothelial cells in the valvular area or intervalvular fragments is noted. This is also concerned orientation of endotheliocytes; therefore, predominance of stretched endotheliocytes of the postvalvular fragment can be connected with demonstration of viscous friction force in the lymph stream, that produces deforming and orienting influence on the endotheliocytes.     

Microvasculature of the bear heart demonstrated by scanning electron microscopy

Morphological features of the coronary microvasculature were examined in ten Black bears (Ursus americanus). Tissue samples were collected for scanning electron microscopy from five animals, and vascular casts of the coronary vessels were prepared from five. Each portion of the microvasculature examined had specific morphological characteristics which may contribute to the control of blood flow. All indications from the present study suggest that the structure of the coronary microvasculature in the Black bear is similar to that of mammalian species previously examined.     

Protoperidinium (Dinophyceae) from Greece as seen by scanning electron microscopy

The marine dinoflagellates Protoperidinium ventricum (Abé) Balech, P. diaholus (Cleve) Balech, P. tristylum (Stein) Balech and P. divergens (Ehrenberg) Balech, collected from neritic plankton of the gulfs of Saronikos and Korinthiakos, Greece, have been examined by SEM. Morphological characteristics of their thecae are described and evaluated. Results are compared with patterns established by earlier SEM studies on related taxa.     

Pancreatic microcirculation in the common tree shrew (Tupaia glis) as revealed by scanning electron microscopy of vascular corrosion casts.

Pancreatic vascular casts of the common tree shrew (Tupaia glis) were prepared by infusion of Batson's No. 17 plastic mixture into the blood vessels and examined by scanning electron microscopy (SEM). Routine histological study of the pancreas was also performed. It was found that the A and D cells appeared to occupy the core whereas the B cells were found at the periphery of the islets of Langerhans. With SEM, the insular arteriole, a branch of the interlobular artery, was shown to penetrate deeply into the core of the islets before branching off into the glomerular capillary network supplying the islets. These capillaries reunited at the periphery of the islets to become vasa efferentia and then gave off capillaries to anastomose with those in the exocrine part of the pancreas, the insuloacinar portal system. Such an insuloacinar portal system found in the pancreas of the tree shrew was similar to that found in the horse and monkey. However, there were some intralobular arterioles which did not end in the islets but directly branched into the interacinar capillary network and periductular plexus. The capillaries in the exocrine part not only gathered into intralobular venules which confluently formed the interlobular vein but also supplied the duct system. The periductular plexus also collected blood into the intralobular venule and interlobular vein, respectively.     

Scanning electron microscopy of human ocular vascular casts: the submacular choriocapillaris

Vascular casts were prepared from ten human orbits removed at autopsy from patients with no previous history of vascular disease. The ages ranged from 7 months to 68 years. The time interval between death and injection of the orbit was always less than 12 h. The vascular casts were examined under scanning electron microscopy with particular attention to the submacular region. We present photomicrographs of common findings seen in each of our specimens, and discuss our results with respect to current models of the submacular angioarchitecture.     

Healing of microvascular arterial anastomoses, as seen on corrosion casts by scanning electron microscopy.

We made 44 microsurgical anastomoses in the femoral artery in rats. The healing was studied from one day to 4 months, by making an acrylic cast of the lumen of the femoral artery and the surrounding vessels, and examining the cast by scanning electron microscopy. The method proved to be easy and relatively quick, and it limited the possibility of artifacts. The high depth of focus permitted simultaneous study of the main lumen and of the perivascular structures after microvascular anastomoses.     

Hypophyseal angioarchitecture of common tree shrew (Tupaia glis) revealed by scanning electron microscopy study of vascular corrosion casts.

The vascular corrosion cast technique in conjunction with scanning electron microscopy (SEM) was used for the study of pituitary microvascularization in the common tree shrew (Tupaia glis). The pituitary vascular casts were obtained by infusion of low viscosity methyl methacrylate plastic (Batson's no.17) mixture. It was found that the blood supplies to the pituitary complex were from branches of the circle of Willis and could be divided into two groups. The first group consisted of two to four superior hypophyseal arteries (SHAs) branching off from the internal carotid artery supplying each half of the median eminence (ME), infundibular stalk (IS), and pars distalis (PD). The SHAs supplying the ME branched into internal and external capillary plexi. The internal plexus had a larger capillary size (approximately 15 microns in diameter), was deeper in position, and had denser and more complex capillary loops than those in the external plexus. The capillaries of the external plexus were approximately 10 microns in diameter. The two plexi drained into 15-20 hypophyseal portal veins (HPVs) which were located mainly along the ventral and ventrolateral surfaces of the IS before breaking up into large capillaries (approximately 18 microns in diameter) with an anteroposterior arrangement within the PD. The second group consisted of one inferior hypophyseal artery (IHA) on each side branching off from the internal carotid artery. These arteries gave off branches to pierce the dorsolateral and ventrolateral aspects of infundibular process (IP) before branching off to form a capillary network. They also gave rise to radiating capillaries to supply the pars intermedia (PI) surrounding the cortical area of the IP. The hypophyseal cleft separating the PI from the PD was clearly seen with very few blood vessels. The capillaries in both PD and IP joined to form confluent hypophyseal veins draining the blood into the cavernous sinus.     

Circulatory pathways in the sinusal spleen of the dog, studied by scanning electron microscopy of microcorrosion casts

Scanning electron microscopy of microcorrosion casts was used to visualize circulatory pathways in the sinusal spleen of dog. The examination of contracted versus dilated organs and variations of the volume of material injected gave an indication of flow dynamics. Minimal injections of material into contracted spleens produced filling of mainly the fastest routes for flow, whereas injections into dilated spleens primarily filled slower routes. This procedure yielded a more complete, three-dimensional picture of the arterial, intermediate, and venous pathways as a whole, and of the relative amounts of flow through different arterial routes. Evidence of flow from capillary lumina out into ellipsoid sheaths was plentiful in casts from dilated spleens, but rare in casts from contracted organs. The pattern of flow within and out of the marginal sinus has been elucidated: A circumferential filling occurs first, followed by a flow that radiates outward into the marginal zone and red pulp. Venous sinuses filled via two routes in addition to the generally accepted path from the reticular meshwork via fenestrations in sinus walls. First, many venous sinuses extending out from the marginal sinus and surrounding marginal zone originated as open-ended tubes continuous with the reticular spaces of the marginal sinus or marginal zone. Second, direct connections of arterial capillaries with venous sinuses in the red pulp were found. Evidence indicating that some mechanism is controlling the flow via these routes is discussed. The strikingly different arrangement of venous sinuses in the subcapsular region is demonstrated.