The vasculature of Octopus arms: A scanning electron microscope study of corrosion casts

Summary Vascular corrosion casts of the brachial circulation in Octopus were observed under the scanning electron microscope. The angioarchitechture, particularly of the smaller vessels, was revealed with a clarity not previously attained. The casts are very similar in appearance with those obtained from vertebrate tissues, emphasizing the convergent development of the closed system in the two groups, and form a useful basis for further study of vascular structure and function in Octopus.The casting materials were kindly made available by Dr. B. Gannon of Flinders University, South Australia, in whose laboratory the cannulations were performed with the invaluable assistance of Mr. P. Rogers. I also thank Dr. K. Bartusek of the Electron Optical Centre, University of Adelaide, for his assistance with the electron microscopy     

Microvascular anatomy of the esophagus in larval and adult Xenopus laevis Daudin: a scanning electron microscope study of microvascular corrosion casts and correlative light microscopy

Larval to adult microvascular anatomy of the esophagus was studied in the South African Clawed Toad, Xenopus laevis (Daudin) by scanning electron microscopy of vascular corrosion casts and correlative light microscopy of paraplast embedded stained tissue sections. Analyses of vascular corrosion casts of tadpole esophaguses at premetamorphosis revealed a wide‐meshed, but mature looking capillary bed which during following prometamorphosis increased in density and gained the adult‐like pattern during late metamorphic climax by sprouting and nonsprouting angiogenesis. In adult Xenopus, the esophageal mucosa possessed a dense subepithelial capillary bed fed by one or two esophageal arteries that originated from right and/or left thoracic aorta just distal to the origin of the subclavian arteries. In the adult undistended esophagus, esophageal arteries revealed an undulating course, a pattern that guarantees a continuous blood supply when the esophagus is extremely wide expanded as it is the case when adult Xenopus swallows large prey.     

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.     

Microvascular anatomy of testes in the adult pipid frog,Xenopus laevis Daudin: A scanning electron microscopic study of vascular corrosion casts

The three-dimensional microvascular anatomy of the testes of adult Xenopus laevis was studied by scanning electron microscopy of vascular corrosion casts. Results showed that testicular arteries branch off from urogenital arteries and approach the testes via the mesorchium. At the dorsal surface of testes, arteries course towards the medial and lateral surfaces of the ovoid testes, pierce the tunica albuginea and run in the subalbugineal space and then penetrate the testicular parenchyma. In the parenchyma, they branch in all directions. At sites where larger branches arise, sphincters are present. Intimal cushions are found at the origin of smaller branches. Terminal arterioles capillarize and form a wide-meshed capillary network around convoluted seminiferous tubules. Inter- and peritubular capillaries cannot be differentiated reliably. Arterio-venous transition distances are short. Arterio-arterial anastomoses and veno-venous anastomoses are present. Testicular venules empty into a venous subalbugineal plexus which shows veno-venous anastomoses of different lengths and calibres. Signs of the ongoing non-sprouting angiogenesis, particularly intussusceptive branch remodelling, reflect the dynamics of the testicular parenchyma. The present study is the first that demonstrates the testicular microvascular anatomy in an anuran species and shows that X. laevis and men share the intricate convoluted seminiferous tubules with associated vascular patterns as a feature in common.     

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.     

Microvascular anatomy of the brain of the adult pipid frog,Xenopus laevis (Daudin): A scanning electron microscopic study of vascular corrosion casts

To demonstrate the 3D microvascular anatomy of the brain of the model organism Xenopus laevis Daudin scanning electron microscopy of vascular corrosion casts was correlated with light microscopy of stained 7 µm thick serial tissues sections. Results showed that supplying arteries descended from the leptomeningeal surface without remarkable branchings straight to the subventricular zone where they branched and capillarized. Capillaries showed few H‐ and/or Y‐shaped anastomoses during their centrifugal course toward the leptomeningeal surface where they drained into cerebral venules and veins. Apart from the accessory olfactory bulb and the vestibule‐cochlear nucleus where capillaries were densely packed, capillaries formed a wide‐meshed 3D network throughout the brain parenchyma and thus contrasted to urodelian brains where hairpin‐shaped capillaries descend from the leptomeningeal vessels into varying depths of the brain parenchyma. In about two‐third of specimens, a closed arterial circle of Willis was found at the base of the brain. If this circle in Xenopus might serve the same two functions as in men is briefly discussed. Choroid plexuses of third and fourth ventricle were found to have a high venous, but a low arterial inflow via one small choroidal artery only. Findings are compared with previous studies on the vascularization of the anuran brain and discrepancies in respect to presence or absence of particular arteries and/or veins in Ranids, Bufonids, and Pipids studied so far are discussed with particular emphasis on the techniques used in the various studies published so far.     

The prism pattern of rat molar enamel: a scanning electron microscope study.

Rat molar enamel has been studied by sectioning the enamel along various planes, and observing the etched surfaces in the SEM. It was found that the prism pattern was much more variable than in rat incisor enamel. Regions without prism decussation seemed to dominate in the occlusal half of the molars. Where present, prism decussation was of the uniserial lamellar type, but it varied considerably in distribution, extent, and distinctness. Prism decussation seemed to have a predilection for the cervical enamel, and was almost absent in the enamel on the occlusal surface. The interprismatic substance showed a characteristic configuration: In the inner enamel it appeared in the form of radially oriented sheets, which tended to delimit radially directed, single lines of prisms. In regions with prism decussation these single lines of prisms encompassed prisms belonging to different prism lamellae. In the outer part of the enamel the interprismatic substance exhibited a honeycomb appearance. The similarities and differences between the prism patterns of rat incisor and molar enamel may be of importance for understanding the mechanisms of amelogenesis, especially for the recognition of factors controlling the movement of ameloblasts.     

Zinc deficiency in the 11 day rat embryo: a scanning and transmission electron microscope study

Zinc deficient rat embryos were obtained on the 11th day of pregnancy and examined by scanning and transmission electron microscopy. Scanning electron microscopy revealed an increase in the number of deformed embryos, as well as embryonic growth retardation. In addition, the epithelium of zinc deficient embryos displayed a marked increase in surface microvilli, as well as the presence of blebbing. Transmission electron microscopy indicated extensive cell death in the neural epithelium which was apparently more severely damaged by zinc deficiency than were mesenchymal cells. Mitochondrial cristae were affected to a greater degree than any other membrane of the cell and cristael disintigration appeared to represent the principal cellular lesion preceding necrosis of neural cells and neural tube teratology.     

The organization of the mammalian kinetochore: a scanning electron microscope study

Summary A procedure has been developed for scanning electron microscopy that enables the visualization of kinetochores along the surface of isolated chromosomes of the Indian muntjac. Indirect immunofluorescence and thin section analysis of the kinetochores of those isolated chromosomes verified that these structures retained in vivo composition and morphology during the isolation procedure. In scanning electron micrographs the outer surface of the outer kinetochore plate can be visualized as a series of fibers 25–30 nm in diameter that are arranged across the plate. These images are comparable to those obtained by whole mount transmission electron microscopic procedures (Rattner 1986) and are compatible with a model of the kinetochore in which chromatin fiber from the body of the chromosome extend to the outer kinetochore plate.     

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.     

Mechanical wear of the gastropod radula: a scanning electron microscope study

The wear sustained by the teeth of the highly mineralized radula of Patella vulgata and the unmineralized radula of Agriolomax reticulatus has been studied with the scanning electron microscope. The unworn teeth of P. vulgata have tall pointed cusps and wear is first seen as a chipping of the tips then as abrasion. There is a well defined abraded surface giving the worn teeth a chisel shape. In cleaved teeth fibres ˜ 800 Å in diameter are observed parallel to the axis of the tooth. Evidence is presented for chemical etching and for the existence of a surface coat on the tooth. A. reticulatus teeth show wear over their whole surface. With the aid of the grooves in the jaw caused by the teeth the role of the jaw in flattening the radula and protracting and retracting the odontophore is confirmed. From the arrangement of the abraded surfaces on the teeth of P. vulgata it was deduced that the teeth rows are abraded one at a time while on a convex surface at or near the bending plane.     

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: 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.     

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.     

Cosmos pollen ontogeny: A scanning electron microscope study

Summary Ontogenetic data concerning pollen not only clarifies the mode of deposition of the elaborate walls but has considerable functional and taxonomic relevance. Hitherto such studies have used optical or transmission electron microscopy but here a recently devised preparative technique has enabled pollen development inCosmos bipinnatus to be studied using the scanning electron microscope. The technique involves freeze-fracturing of osmium fixed, cryoprotected anthers, maceration in dilute osmium tetroxide, critical point drying, sputter coating and examination. The processes of pollen wall development can then be observed in three dimensions, an important aid to understanding the spatial relationships involved in the determination of ornamentation and apertures. Details of the pollen and tapetum are described at various stages between meiosis and anthesis. A close conformity is demonstrated between the results obtained and those of earlier transmission electron microscopic studies of the same and related species although very different interpretations are made.     

Peritoneal fine structure of inguinal hernia: a scanning electron microscope study

Mesothelial cells of the normal human peritoneum of the anterior abdominal wall are covered with numerous surface microvilli. These cells become partially denuded inside the sacs of direct and indirect inguinal hernias and so lose the protective property the microvillar covering may impart on them. These mesothelial cells of hernial sacs also acquire an extensive surface coat of fibrin-like material, presumably due to the loss of that protective property, which may as a result subject them to adhesions. There is a considerable collagen build-up in the subserosal fibrous tissue of sacs of both direct and indirect inguinal hernias. Such a build-up is at variance with the accepted current surgical concept which suggests a defect in collagen synthesis, rather than a build-up, as the cause of direct hernia.