Choriocapillaris atrophy after experimental destruction of the retinal pigment epithelium in the rat. A study in thin sections and vascular casts

Rats that receive intravenous injections of sodium iodate develop a retinopathy characterized by the partial loss of the retinal pigment epithelium (RPE). In thin sections examined by transmission electron microscopy the choriocapillaris atrophied adjacent to areas of RPE destruction. The endothelial cells thickened and lost their fenestrae and the lumen of the capillary was reduced. At sites where the RPE remained normal in appearance the choriocapillaris did not atrophy. Scanning electron microscopy of vascular casts of the choriocapillaris showed the coexistence of atrophic and normal choriocapillaris throughout the retina, presumably adjacent to sites where the RPE was destroyed or spared, respectively. Our observations support the concept that the RPE exerts some control over the structure and function of the choriocapillaris.     

Development of the vascular bed in the rabbit ear: scanning electron microscopy of vascular corrosion casts

The development of the vascular bed in the rabbit ear was investigated using vascular corrosion casts from animals of various ages. Examination of the casts revealed that the arrangement of the major auricular arteries and veins was determined before birth and was maintained during postnatal growth of the ear. Furthermore, the number of arteries branching off the central ear artery and the lateral arteries did not increase with increasing ear length. Scanning electron microscopic examination of lateral segments of adult ear casts revealed many anastomoses between marginal arteries and veins. These arteriovenous anastomoses (AVAs) occurred singly, in pairs, or in clusters of three to six. Their size and shape were variable, even in the same cast. The central segment of many AVA casts showed surface impressions of endothelial cell nuclei which were different from the impressions on adjacent arteries and veins. Arteriovenous anastomoses were also detected in ear casts from animals as young as 8 days. The density of AVAs in lateral ear segments ranged from 95-165 cm-2 in 8- to 11-day-old rabbits to 80-115 cm-2 in adults. However, estimates of the total number of AVAs in the lateral ear margin indicated that AVAs continued to be formed at a steady rate during growth of the ear. During the early neonatal period the cutaneous capillary plexuses developed prominent tufts projecting toward the skin surface, which were apparently associated with developing hair follicles. These capillary tufts were not seen in casts from fetal or adult rabbits.     

Blood vessels in Trichinella spiralis infections: a study using vascular casts

Larvae of Trichinella spiralis initiate the transformation of myocytes into nurse cells that become surrounded by elaborate networks of blood vessels. To examine the structure of these networks (i.e., retes), transcardic perfusion was used to clear the vascular tree of Trichinella-infected mice and to inject a plastic that polymerized in situ. Vascular complexes were found only around infected myocytes and were characterized by large circumferential vessels that give rise to the smaller channels of the retes. The secondary vessels vary widely in caliber and are distributed in a random fashion. Three types of network were found: simple, complex, and hypercomplex, and they were distributed normally, with the complex retes the most common. Comparison of the structure of the baskets with that of vessels in surrounding uninfected muscle strongly suggests that the vascular retes are the result of de novo angiogenesis induced during the infection. The parasite may elicit angiogenesis directly through secretion of unique products or may elicit a change in the nurse cell that, in turn, results in growth of new blood vessels.     

Thymic vascular system of the European common frog,Rana temporaria: a scanning electron-microscopic study of vascular casts

Vascular corrosion casts of the thymus of adult individuals of the European common frog, Rana temporaria, were analysed by scanning electron microscopy. The main arterial vessel, which is derived either from the temporal artery or from the auricular ramus, approaches the central territory of the gland and branches into twigs that, on penetrating the parenchyma, give rise to capillaries. Most of these capillaries run vertically towards the surface of the gland; they either join the superficial capillary plexus or follow this plexus for a variable distance and then run back towards the medulla, forming capillary loops. The former capillaries link with the extensive venous plexus composed of irregular meshes, whereas the latter capillaries join the venules at the cortico-medullary boundary and finally escape into collecting veins on the gland surface. The venous twigs, which join together near the gland, form the main thymic vein, which empties into the external jugular vein. The details of the thymic vasculature of the anuran amphibian, R. temporaria, are compared with those described in mammalian species, viz. the mouse, rat and guinea pig.     

Retinal vascularization in the grass goby,Zosterisessor ophiocephalus: a scanning electron-microscopic study of vascular corrosion casts

Synopsis The retinal vascularization ofZosterisessor ophiocephalus is described by scanning electron microscopy of vascular corrosion casts. The retina is vascularized sclerad by the choroidal body and the choriocapillaris, and vitread by the lentiform body and by a dense network of hyaloid vessels. In the bodies there is a parallel arrangement of capillaries indicating a counter current exchange mechanism. The well developed vascularization and its correlation with the hypoxic conditions of the muddy habitat of the species are discussed.     

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.     

Renal microvasculature in the adult pipid frog,Xenopus laevis: A scanning electron microscope study of vascular corrosion casts

We studied the opisthonephric (mesonephric) kidneys of adult male and female Xenopus laevis using scanning electron microscopy (SEM) of vascular corrosion casts and light microscopy of paraplast embedded tissue sections. Both techniques displayed glomeruli from ventral to mid-dorsal regions of the kidneys with single glomeruli located dorsally close beneath the renal capsule. Glomeruli in general were fed by a single afferent arteriole and drained via a single thinner efferent arteriole into peritubular vessels. Light microscopy and SEM of vascular corrosion casts revealed sphincters at the origins of afferent arterioles, which arose closely, spaced from their parent renal arteries. The second source of renal blood supply via renal portal veins varied interindividually in branching patterns with vessels showing up to five branching orders before they became peritubular vessels. Main trunks and their first- and second-order branches revealed clear longish endothelial cell nuclei imprint patterns oriented parallel to the vessels longitudinal axis, a pattern characteristic for arteries. Peritubular vessels had irregular contours and were never seen as clear cylindrical structures. They ran rather parallel, anastomosed with neighbors and changed into renal venules and veins, which finally emptied into the ventrally located posterior caval vein. A third source of blood supply of the peritubular vessels by straight terminal portions of renal arteries (vasa recta) was not found.     

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.     

Microvasculature of the mouse eye: Scanning electron microscopy of vascular corrosion casts

Purpose

For drug safety assessment, ophthalmic fundus examination is of diagnostic importance in experimental animals. Interim blood samples are usually collected from the orbital venous sinus in the mouse. This report characterizes the angioarchitecture of the mouse eye.

Methods

In 10 mice, the microvasculature of the eyes of was investigated using scanning electron micrographs of corrosion casts.

Results

The mouse eye was characterized as having a rich vasculature with many thick retinal arteries and a well-developed orbital venous sinus. The eye receives its primary blood supply from the external ophthalmic artery, which is divided into three branches: the central retinal artery, as well as the medial and lateral long posterior ciliary arteries. The central retinal artery is divided into 8-9 radiating retinal arteries. The mouse has an orbital venous sinus around the orbit rather than a well-developed orbital venous plexus in the retrobulbar space as is in the rat. The orbital venous sinus is formed by the episcleral veins, the ophthalmic vein, the superior palpebral vein, inferior palpebral vein and numerous anastomotic veins among these veins.

Conclusions

The mouse ocular vasculature is quite similar to that of rats. It is recommended that the best location for insertion of a capillary tube for collecting blood is in the lateral canthus around the eye where the sinus is larger and is most readily accessible. Functional significance of the vascular patterns of the eye is discussed.     

The Vascularization of the Anuran Brain: Olfactory Bulb and Telencephalon: A scanning electron microscopical study of vascular corrosion casts

Lametschwandtner, A., Albrecht, U., Adam, H. 1980. The vascularization of the anuran brain. Olfactory bulb and telencephalon. A scanning electron microscopical study of vascular corrosion casts. (Department of Zoology, University of Salzburg, Austria.) — Acta zool. (Stockh.) 61(4): 225–238. The vascularization of the olfactory bulb and the telencephalon of the anuran brain is studied by means of scanning electron microscopy of vascular corrosion casts.—The olfactory bulb is supplied via a terminal branch of the ramus hemisphaerii medialis ventralis, while the drainage is via the lateral telencephalic vein. The vascular plexus which caps the olfactory bulb shows “basket-like” vascular formations facing the rostral olfactory bulb. This plexus is supplied via two sources which are a) terminal branches of the ramus hemisphaerii medialis ventralis and b) a branch of the inner carotid artery. — In the telencephalon the vascular pattern of medial and lateral cortex, the striatum, the septum, and the amygdala are described. It is demonstrated that in the cerebral cortex of the anuran brain the centrifugal blood flow is not present in that strictness found in the other parts of the brain. The arterial supply is via the ramus hemisphaerii medialis ventralis and the posterior telencephalic artery (ramus hemisphaerii medialis dorsalis) and their branches as well as by branches of the preoptic artery. The venous drainage of the telencephalon is by the lateral telencephalic vein.     

Pulmonary vascular disease in a rabbit a high altitude

A male weanling rabbit of the New Zealand White strain, born and living at an altitude of 3800 m in La Paz, Bolivia, developed right ventricular hypertrophy. This was found to be associated with growth of vascular smooth muscle cells in the intima of pulmonary arterioles, and contrasted with muscularization of the walls of pulmonary arterioles, without extension into the intima, found in a healthy, high-altitude control rabbit of the same strain. A low-altitude control showed no such muscularization. It is concluded that alveolar hypoxia, acting directly or through an intermediate agent, is a growth factor for vascular smooth muscle cells in pulmonary arterioles. This is the first report of pulmonary vascular disease due to high altitude in rabbits.     

The Vascularization of the Anuran Brain Rhombencephalon and Medulla spinalis: A scanning electron microscopical study of vascular corrosion casts

Albrecht, U., Lametschwandtner, A., Adam, H. 1980. The vascularization of the anuran brain. Rhombencephalon and medulla spinalis. A scanning electron microscopical study of vascular corrosion casts. (Department of Zoology, University of Salzburg, Austria.) — Acta zool. (Stockh.) 61 (4): 239–246. The vascularization of the rhombencephalon and the medulla spinalis of Bufo bufo (L.) is demonstrated by scanning electron microscopy of vascular corrosion casts. The arterial supply of the rhombencephalon is performed by central arteries. The same is shown in the medulla spinalis. The venous pathways are represented by venae craniales occipitales and by a posterior and bulbar group of the encephaloposthypophysial portal vein, by veins draining into the venae craniales occipitales, by venae spinales ventrales (for the rostral regions of the medulla) and by venae spinales laterales (in the caudal medulla). In the regions examined so far a centrifugal course of the arterial vessels is reported.     

The Vascularization of the Anuran Brain Diencephalon and Choroid Plexus: A scanning electron microscopical study of vascular corrosion casts

Albrecht, U., Lametschwandtner, A., Adam, H. 1979. The vascularization of the anuran brain. Diencephalon and choroid plexus. A scanning electron microscopical study of vascular corrosion casts. (Department of Zoology, University of Saulzburg, Austria.) — Acta zool. (Stockh.) 61(4): 203–220. The vascularization of the diencephalon (with choroid plexus of the third ventricle, epithalamus and pineal region, thalamus and hypothalamus) of the toad, Bufo bufo (L.) has been studied by means of scanning electron microscopy of vascular corrosion casts. To localize angioarchitectonic patterns of distinct diencephalic regions the authors refer to critical point dried specimens and to histological sections. In the choroid plexus a supply via one choroid artery, which arises from the posterior telencephalic artery, was found. Its strict dichotomous branching is pointed out. In generally a similar vascular pattern like that in the choroid plexus of the fourth ventricle has to be reported. Furthermore the epithalamic region with the epiphysial area was under investigation. No special angioarchitecture of the epiphysis was found. There are also no prominent vascular connections with thalamic or hypothalamic regions. The thalamic region is supplied by branches of the posterior telencephalic artery as well as by branches of the preoptic artery. Epithalamic and thalamic regions are drained via the posterior diencephalic vein. Special attention was also paid to the preoptic, the chiasmatic and the retrochiasmatic area. No special vascular connections, however, were found.     

Brain-capillary architecture of the newt,Triturus cristatus carnifex (Caudata: Salamandridae): Scanning electron-microscopical study of vascular corrosion casts

The brain-microvascular architecture of the newt (Triturus cristatus carnifex) was studied by scanning electron-microscopical examination of microvascular corrosion casts. It is characterized at the leptomeningeal level by a superficial network of single vessels that leave the meningeal sheath to form hairpin-shaped capillary loops. These loops penetrate the nervous parenchyma to varying depths and are variously bent, inclined, and twisted. Each hairpin-like loop consists of descending and ascending limbs connected by a distal U-shaped segment. The limbs are of equal diameter and lack physical differentiation. Some loops branch in a secondary loop, but there are no intraparenchymal connections with analogous surrounding structures. On vascular casts we observed detailed imprints of endothelial cell nuclei. This microvascular architecture is present in the whole brain except in leptomeninx and choroidal plexuses. The vascular pattern of T. cristatus carnifex resembles that of apodans. However, it differs from the anuran condition, which is characterized by a three-dimensional parenchymal network and from that of Ambystoma mexicanum which displays an intermediate condition between a single-capillary network and a capillary-loop model. At the level of paired capillaries, a counter-current exchange system may occur between the two limbs of the same loop, an arrangement that could promote uniformity of extracellular fluid composition in parenchyma.