Microvascularization of the interhyoid muscle in larval Xenopus laevis (Daudin): Scanning electron microscopy of vascular corrosion casts and correlative light microscopy

The interhyoid muscle in tadpoles of Xenopus laevis (Daudin) is an important part of the buccal pump, a functional unit that provides unidirectional flow of water through mouth and pharynx. In anuran tadpoles, this flow is crucial in both respiration (gas exchange) and food intake (ingestion). The microvascular anatomy of the interhyoid muscles of 43 tadpoles of X. laevis from developmental stages 49–60 was examined by scanning electron microscopy of vascular corrosion casts and correlative light microscopy of paraplast embedded Goldner stained serial tissue sections. Analysis of vascular corrosion casts of the interhyoid muscle showed that several descending branches of external carotid arteries supplied the interhyoid muscle. Arteries splitted into many arterioles at the dorsal surface of the interhyoid muscle and formed sheaths of longitudinally orientated capillaries around muscle fibers. Postcapillary vessels formed perpendicularly orientated arrays of collecting venules (mean diameter: 15.6 μm), which drained the interhyoid muscle from the ventral surface into external jugular veins. Cast analyses revealed sprouting angiogenesis at the capillary level and nonsprouting angiogenesis at distal domains of the venous system. Both means of angiogenesis that persisted throughout the developmental periods examined are thought to represent a superposition of concurrent developmental and physiological processes. The dense microvascular bed of the interhyoid muscle reflects its high demand for supply with oxygen and nutrients. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Scanning electron microscopy of vascular architecture in the gastric mucosa of the golden hamster

Summary The three-dimensional architectures and the regional differences of the vascular system in the mucosa of the hamster stomach were revealed by scanning electron microscopy of corrosion casts. In the forestomach, the vascular network spreads two-dimensionally in a thin lamina propria. In the corpus and the antrum, the capillaries in the thick lamina propria are well developed, extending three-dimensionally along the gastric pits and glands. In the corpus, the submucosal arteries enter the lamina propria to become ascending capillaries, which project toward the top of the lamina propria and anastomose to create a capillary network beneath the mucosal epithelium. A subepithelial capillary is much wider in diameter than an ascending capillary and is, therefore, a sinusoid capillary. Subepithelial capillaries join descending venules, which are less numerous than the ascending capillaries. Near the gastric lumen, the capillaries in the corpus can be classified into two types: arched type in the cephalic (upper) region and honeycomb type in the caudal (lower) region. In the antrum, the submucosal arterial plexus is less well developed than that in the corpus. The mucosal aspect of the corrosion cast shows many clumps, formed by a unit of capillary network. Functional significances of different vascular architectures in the gastric mucosa of the forestomach, corpus, and antrum are discussed.This study was supported in part by grants from the Research Fund of the Ministry of Education, Science, and Culture, Japan     

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.     

Microvasculature of the epididymis in the boar

Summary Microvasculature of the epididymis was investigated by scanning electron microscopy of vascular corrosion casts. The basic structure of blood supply to the boar epididymis consists of two superimposed vascular networks. Capillaries surrounding the epididymal duct constitute the inner level. They form polygonal meshes around the efferent ductules whereas circular capillaries strongly predominate in the subsequent region of the caput epididymidis. This annulate feature is progressively lost from corpus to cauda, where the capillary network once again has a polygonal appearance. The outer network is composed of feeding and draining vessels. Intertubular arteries pass between the loops of the epididymal duct and give rise to longitudinally oriented vessels attributable to only one adjacent duct segment. They feed the capillary network via circular ramifications debouching in different sectors of its circumference. The sparse veins draining the capillaries encircling the efferent ductules give way to a gradually increasing number of confluent veins up to the cauda.     

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.     

红腹锦鸡和小白鼠肾小球微血管铸型的扫描电镜观察

为了探讨鸟类肾小球微血管构筑与哺乳动物肾小球微血管构筑的异同,用微血管铸型技术和扫描电镜对红腹锦鸡和小白鼠的肾小球微血管做了铸型观察。结果表明：小白鼠肾小球由小球内小叶微动脉,毛细血管网小叶及小叶间交通支和小叶输出血管构成,小叶可分出亚单位;红腹锦鸡肾小球为一簇迂回盘曲的血管团,血管间未见有复杂的分支和吻合;小白鼠和红腹锦鸡入球小动脉和出球小动脉均为一支,但有的出球小动脉有分支。另外,文章还对肾小球微血管构筑与滤过率的关系进行了讨论。     

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.     

Microvascularization of the spleen in larval and adult Xenopus laevis: Histomorphology and scanning electron microscopy of vascular corrosion casts

Microvascular anatomy and histomorphology of larval and adult spleens of the Clawed Toad, Xenopus laevis were studied by light microscopy of paraplast embedded serial tissue sections and scanning electron microscopy (SEM) of vascular corrosion casts (VCCs). Histology showed i) that white and red pulp are present at the onset of metamorphic climax (stage 57) and ii) that splenic vessels penetrated deeply into the splenic parenchyma at the height of metamorphic climax (stage 64). Scanning electron microscopy of VCCs demonstrated gross arterial supply and venous drainage, splenic microvascular patterns as well as the structure of the interstitial (extravasal) spaces representing the “open circulation routes.” These spaces identified themselves as interconnected resin masses of two distinct forms, namely “broccoli‐shaped” forms and highly interconnected small resin structures. Arterial and venous trees were clearly identified, as were transitions from capillaries to interstitial spaces and from interstitial spaces to pulp venules. Venous sinuses were not diagnosed (nonsinusal spleen). The splenic circulation in Xenopus laevis is “open.” It is hypothesized that red blood cells circulate via splenic artery, central arteries, penicillar arteries, and red pulp capillaries primarily via “broccoli‐shaped” interstitial spaces, pulp venules and veins into subcapsular veins to splenic veins while lymphocytes circulate also via the interstitial spaces represented by the highly interconnected small resin structures in vascular corrosion casts. In physiological terms, the former most likely represent the fast route for blood circulation, while the latter represent the slow route. J. Morphol. 277:1559–1569, 2016. © 2016 Wiley Periodicals, Inc.     

Scanning electron microscopy of fruits in the West African Polygonaceae

The fruit morphology of 18 taxa representing seven genera of the family Polygonaceae in West Africa was investigated using scanning electron microscopy. The achenes are trigonous, lenticular, globose, subglobose,heart shaped, ovoid, or cone like. Sizes range from 0.12 × 0.10 cm2 in Polygonum plebeium to 7.87 × 0.58 cm2 in Afrobrunnichia erecta. Colors are brown to black. The cells are isodiametric in P. plebeium, irregular in A. erecta,Antigonon leptopus, and Harpagocarpus snowdenii, and polygonal in other species. The walls are straight, curved,or undulate and are either raised or depressed. Afrobrunnichia erecta is characterized by deeply sinuate lateral walls. The cell surface may be smooth or tuberculate or fibrillate in the family, usually covered with wax deposits.The combination of these characters is mainly taxonomically useful at the tribal level and rarely at the specific or inffaspecific level for the delimitation of the taxa.     

Scanning electron microscopy studies on the first-instar larva of Dermatobia hominis

Abstract. First-instar larvae of Dermatobia hominis collected 1, 4 and 7 days after having penetrated experimentally infected rats, were studied by scanning electron microscope (SEM) observation. On the pseudocephalon there are basiconic and trichoid sensilla (antennal sensory complex), and basiconic, coeloconic and campaniform sensilla (maxillary sensory complex). The thoracic segments bear several rows of small, backwardly pointed, spines, and trichoid, campaniform, coeloconic and pit sensilla. The anterior spiracle is a minute opening. Both small and large spines directed posteriorly are on the first to fourth abdominal segments, which also bear coeloconic and companiform sensilla. These sensilla are present on the unarmed (fifth and sixth) and armed (seventh) abdominal segments. The seventh and the last (eight) abdominal segments have forwardly directed spines. Each spiracular plate has two spiracular openings and four spatulate-like structures called sun rays. The anus and the coeloconic sensilla are proeminent on the last segment. The results are compared with other parasitic dipteran larvae, and emphasize that the multiple types of sensilla on D. hominis larva may have importance in establishing the parasitic phase of the life cycle of this insect.     

Scanning electron microscopy of the zonular fibers in the rat eye

Summary The three-dimensional arrangement of the zonular fibers of Zinn and their ultrastructure was studied with the aid of scanning and transmission electron microscopy.Most of the thicker zonular fibers are arranged in straight bundles between the ciliary body and the lens, while the thinner fibers form a complex three-dimensional network interconnecting all the zonular fibers. These do originate from the limiting membrane covering the ciliary body. The zonular fibers are subdivided close to lens and form a complicated network on the surface of the lens capsule, i. e. the zonular lamella. The latter consists of a dense network of fibers and is from a structural point of view closely related to the zonular fibers and not to the lens capsule.The zonular fibers are continuous with those in the vitreous body close to the ciliary body but never in the lenticular two thirds of the zonular fibers or in the retrolental area.The ground substance is possible to demonstrate in freeze-dried specimens by scanning electron microscopy. It appeared granular or amorphous and coated the zonular fibers. It does not form membranes or fill all available space in contrast to its properties in the vitreous body. The many structural similarities between the zonular fibers and the vitreous body indicate perhaps a common origin.Supported by grants from Magnus Bergwalls Stiftelse and the Swedish Medical Research Council (B70-12 X -2543-02, B71-12 X -2543-03).     

Vascularization of the brains of the Atlantic and Pacific hagfishes, Myxine glutinosa and Eptatretus stouti: a scanning electron microscope study of vascular corrosion casts

The microvascularization of the brains of the hagfishes, Myxine glutinosa L. and Eptatretus stouti, were studied by scanning electron microscopy (SEM) of microvascular corrosion casts. Sections of these casts were used to determine the vascular territories of defined brain areas. Histological serial sections (10 microm) of the brains served for correlation of findings. Analysis of the microvascular casts of both species revealed that the blood supply to and from these brains arose ventrally and dorsally, respectively. Neither species possesses an arterial circle (Circulus Willisi) and both have similar microvascular patterns. The only difference between Myxine and Eptatretus was that the posterior cerebral artery in Myxine divides into mesencephalic and rhombencephalic branches, and in Eptatretus a third branch, termed telencephalic branch, arises from the posterior cerebral artery. 3D-morphometry revealed that luminal diameters of: 1) intracerebral arteries and arterioles range from 35.11 +/- 5.66 microm (mean +/- SEM) in the hypothalamus to 92.69 +/- 14.48 microm in the thalamus; 2) capillaries range from 17.8 +/- 0.44 microm in the olfactory bulb to 21.70 +/- 0.87 microm in the basal ganglia; and 3) intracerebral venules and veins range from 49.38 +/- 4.17 microm in the hypothalamus to 75.58 +/- 6.59 microm in the rhombencephalon. Interbranching distances of arteries and arterioles range from 179.19 +/- 11.32 microm in the optic tectum to 235.19 +/- 94.64 microm in the hypothalamus. Capillaries range from 91.07 +/- 6.22 microm in the hypothalamus to 116.15 +/- 9.45 microm in the thalamus, and venules and veins range from 137.30 +/- 18.11 microm in the hypothalamus to 189.83 +/- 17.47 microm in the optic tectum. Intervascular distances range from 70.58 +/- 3.58 microm in the olfactory bulb to 89.52 +/- 5.74 microm in the optic tectum. Branching angles of arteries and arterioles range from 38.39 +/- 10.9 degrees in the olfactory bulb to 100.73 +/- 9.4 degrees in the optic tectum, and the branching angles of capillaries range from 74.40 +/- 5.42 degrees in the optic tectum to 90.24 +/- 4.66 degrees in the olfactory bulb. Finally, the branching angles of the venules and veins range from 67.84 +/- 6.83 degrees in the tegmentum of the mesencephalon to 92.30 +/- 6.35 degrees in the optic tectum.     

Scanning electron microscopy of the vitreous body in the rat eye

Summary The vitreous body of the rat eye was studied by scanning electron microscopy. The freeze-dried specimens were either unfixed, freshly frozen or fixed and rinsed before being frozen.The vitreous body is surrounded by a coat of intercellular material covering a thin sheath of chiefly parallel fibers. The latter forms the base for a regularly organized three-dimensional network of fibers. The interfibrillar spaces are filled with ground substance and also contain a few cells. The shape of the cells varies from bipolar to polyhedronal. Their interconnected processes are usually undivided. The functional importance of this complex regular organization of the fibers and cells in the vitreous body is stressed.Supported by grants from H. Jeanssons Stiftelse and the Swedish Medical Research Council (B70-12X-2534-02).I would like to thank the Swedish Silicate Research Institute, Göteborg, for using their scanning electron microscope and Miss M. Persson for skilful technical assistance.     

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.