Biomedical subjects

A Lametschwandtner

Publications and source records attributed to A Lametschwandtner.

At least 19 recordsLinked to original sources

PubMed2006

Spatial growth and pattern formation in the small intestine microvascular bed from larval to adult Xenopus laevis: a scanning electron microscope study of microvascular corrosion casts.

The microvascular anatomy of the small intestine of metamorphosing tadpoles of the South African Clawed Toad, Xenopus laevis (Daudin) is studied from developmental stages 55 to 65 and in adults by scanning electron microscopy (SEM) of vascular corrosion casts (VCCs) and light microscopy. Up to stage 62, VCCs reveal a dense two-dimensional vascular network ensheating the intestinal tube, whose proximal portion forms a clockwise spiralling outer and its distal portion an anti-clockwise spiralling inner coil. Vessels of the intestinal network impose flat and run circularly to slightly obliquely. Locally, dense capillary plexus with small "holes" indicating ongoing intussusceptive microvascular growth (IMG) and vessel maturation, are present. The typhlosole, an invagination along the proximal portion of the small intestine, reveals a dense capillary bed with locally ongoing IMG. VCCs of stages 62/63 for the first time reveal a three-dimensional vascular bed with longitudinal intestinal folds of varying size and heights greatly enlarging the luminal exchange area of the intestinal tube. From stage 65 onwards, longitudinal intestinal folds undulate and, though smaller in size and less mature as indicated in VCCs by the presence of wider, sinus-like vessels with small "holes" interposed between, closely resemble the intestinal folds present in the small intestine of adult Xenopus. Our data suggest that maturation of the vascular pattern in the small intestine of X. laevis tadpoles takes place successively after stages 62-63, and growth during this period is preferentially by intussusception.

Age Factors↗

PubMed2006

Valves in small veins and venules.

It is commonly believed that valves are absent in veins smaller than two millimetres in diameter. Consequently, current investigations on the pathophysiology of chronic venous disease (CVD) consider and evaluate only the valvular competence of large veins. The authors review literature from their own collections as well as from medical database searches to assess the functional relevance of these valves. Microscopic venous valves (MVVs) were first described in 1934 in the human digits and have subsequently been demonstrated in other parts of the human body as well as in many tissues and organs of animals. Their location and arrangement suggests that MVVs prevent blood reflux in small sized veins and restrict flow from postcapillary venules back into the capillary bed. This haemodynamic role of MVVs is strongly supported by the clinical finding that grafting skin rich in MVVs results in long-lasting healing leg ulcers attributable to CVD. The huge body of knowledge available concerning MVVs urges us to correct textbooks of anatomy. Studies on the pathophysiology of CVI should acknowledge that the valvular "chain" is not limited to large veins, but extends down to the venular level where MVVs play an important role in venous haemodynamics.

Humans↗

PubMed2005

Analysis of microvascular trees by means of scanning electron microscopy of vascular casts and 3D-morphometry.

Arterial and capillary trees form by consecutive branching (mostly bifurcations) from a stem vessel, venous trees form by repeated merging of blood vessels. Diameters of stem (parent, mother) vessels and daughter vessels (branches), interbranching distances and branching angles between stem and daughter vessels lastly define the overall three-dimensional structure of the vascular network as well as the basic transport capacity of the system. Here we use scanning electron microscopy and 3D-morphometry to measure these variables from stereo paired images of vascular corrosion casts of the anterior cerebral artery and its main branches and from arteriolar bifurcations of the mesencephalic optic tectum in the actinopterygian fish, Acipenser ruthenus. We then calculate bifurcation indices, area ratios, asymmetry ratios and test for the optimality principles underlying the bifurcations studied. Our results show that arteriolar bifurcations in the optic tectum are in favor of the principles of minimum pumping power and minimum volume rather than the principles of minimum surface and minimum drag. We conclude that scanning electron microscopy of vascular corrosion casts in conjunction with 3D-morphometry is an excellent tool to thoroughly analyze vascular trees in healthy and diseased tissues and organs, as well as on an ontogenetic and phylogenetic scale.

Algorithms↗

PubMed2003

Vasa vasorum of the human great saphenous vein.

The distribution of the vasa vasorum of the human great saphenous vein (GSV) was studied on veins taken both post-mortem and peroperatively. It was found that the stems of feeding vessels approach the venous wall at intervals of 1.5-2.5 cm; their smaller branches first passed the fascial compartments of the GSV and then entered the adventitia at intervals of 0.5-1.5 cm on both the stem and the largest tributaries of the GSV. In the stem regions vasa vasorum arteries and veins ran together but, between neighboring stems, isolated venae vasorum were regularly found which opened individually into terminal segments of the largest tributaries of the GSV. Neither by dissection nor by injection methods were venae vasorum found to open directly into the lumen of the GSV stem. The total thickness of the media ranged between 500 and 1300 micro m, according to the state of constriction of the venous wall before fixation. Two structurally different layers of GSV tunica media were present: an inner loose layer and an outer dense layer, both of similar thickness. The innermost capillaries of the vasa vasorum network were found in all cases on the border between the two layers of media. No lymphatic was found in any of the layers of GSV wall. From the findings the authors recommend extremely careful dissection of the GSV wall during in situ grafting surgery, to ensure the best viability of the venous wall.

Aged↗

PubMed2001

Eurosol versus fetal bovine serum-containing corneal storage medium.

PURPOSE: To evaluate the usability of Eurosol, a new medium-term corneal storage medium without components of bovine origin. METHODS: Ten pairs of human donor corneas were placed in tissue culture at 31 degrees C for 7, 14, 21, 28, or 35 days. One cornea of each pair was cultivated in conventional storage medium on Earls' minimum essential medium base containing 2% fetal bovine serum; the other one was stored in Eurosol. Corneas were examined with inverse light microscopy; corneal thickness was measured; and scanning electron microscopy was performed. RESULTS: No significant difference in corneal thickness and endothelial cell count was found at any time. Scanning electron microscopy showed a complete endothelial cell layer on all corneas. CONCLUSION. The findings indicate a potential clinical applicability of the tested serum-free medium-term storage medium, offering a safer alternative to conventional media containing fetal bovine serum.

Cell Count↗

PubMed2001

Quantitative microvascular corrosion casting by 2D- and 3D-morphometry.

As a system of tubes (blood vessels) the cardiovascular system changes actively and passively diameters to adapt its transport capacities for respiratory gases, nutrients, heat, metabolites and waste products to and off the body's organs, tissues and cells. In most healthy organs blood vessels form a hierarchically arranged three-dimensional network with the geometry defined by vessel diameters, interbranching distances (defining branching frequencies and number of branching sites, i.e. nodes), intervascular distances, and branching angles. In the present study 2D- and 3D-morphometry is applied to quantify these parameters and their changes as they occur in resin casts during metamorphosis of the tadpole lung (2D-morphometry) and filter apparatus vasculature (3D-morphometry). It is shown that 2D-morphometry should be limited to the analysis of high powered images of flat two-dimensional vascular networks (example: tadpole lung alveolar vascular bed) to prevent underestimation of parameters. In contrast, 3D-morphometry can be applied over a wide range of magnifications whereby accuracy of measurements increases with the portion the structure to be measured occupies within the field of view. Together with a careful control of precasting conditions (application of vasoactive drugs, anaesthetics), casting conditions (pressure during rinsing and casting, amount of final shrinkage of casting media), and postcasting conditions (thermal burdening during maceration, sputtering, evaporation, and SEM inspection; thickness of conductive metal layers) 3D-morphometry enables to gain reliable data from resin casts of highly complex real vascular networks in healthy and diseased organs in the developing, juvenile, adult and aged state, as well as in different physiological states.

Aging↗

PubMed2000

Intussusceptive microvascular growth in the lung of larval Xenopus laevis Daudin: a light microscope, transmission electron microscope and SEM study of microvascular corrosion casts.

The remodeling of the uniform wide, plexus-like capillary bed of the lung of metamorphosing tadpoles of the South African clawed toad Xenopus laevis (Daudin) is studied from developmental stages 54 to 65 by scanning electron microscopy (SEM) of microvascular corrosion casts (VCCs), light microscopy (LM) and transmission electron microscopy (TEM). VCCs reveal that the remodeling of the existing uniform, plexus-like lung capillary bed into well-defined alveolar capillary meshworks starts in the caudal lung and then gradually proceeds cranially. Vascular remodeling is entirely by intussusceptive microvascular growth through insertion and enlargement of new and fusion of pre-existing capillary meshes. Analyses of lung tissue serial sections at the LM and TEM level confirm the presence of intracapillary cushions and tissue posts and correlate these structures in respect of size and location to the round to slit-like imprints and tiny "holes" found in VCCs. Additionally, SEM of VCCs give clear evidence that intussusceptive microvascular growth is also involved in the remodeling and maturation of alveolar arterioles and venules.

Animals↗

PubMed2000

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study.

Structural changes of the ventral velum of Xenopus laevis tadpoles from late prometamorphosis (stage 58) to the height of metamorphic climax (stage 62) were examined by light and transmission electron microscopy. Special emphasis was given to the blood vessel regression. Early changes of velar capillaries were formation of luminal and abluminal endothelial cell processes, vacuolation, and cytoplasmic and nuclear chromatin condensation. At the height of metamorphic climax, transmission electron microscopy revealed apoptotic endothelial cells with nuclear condensation and fragmentation, intraluminal bulging of rounded endothelial cells which narrowed or even plugged the capillary, and different stages of endothelial cell detachment ('shedding') into the vessel lumen. These changes explain the 'miniaturisation' of the velar microvascular bed as well as the typical features found in resin-casts of regressing velar vessels which have been observed in a previous scanning electron microscopy study of the ventral velum.

Animals↗

PubMed1999

Pulmonary lymphatic filling is increased in spontaneously hypertensive rats.

Extravascular lung liquid must rely on tissue-space pressure gradients to drive it into the lymphatics because the fluid is outside the lymphatic contractile pumping and valve control. Focal tissue pressure changes could result from muscular contraction in the blood vessel walls. Perivascular lymphatics usually lie within the adventitia of pulmonary blood vessels, and are generally more noticeable in veins than arteries. Spontaneously hypertensive rats have exaggerated focal pulmonary venous muscle (venous sphincters). These muscular tufts are often near initial lymphatics; if their contraction was important for lymph transport, spontaneously hypertensive rats could have more lymphatic filling in the areas of the pulmonary venous sphincters than normotensive rats. Because the focal muscularity is found in pulmonary veins more than arteries, veins may have more focal lymphatic filling than arteries. To test these hypotheses, lung histology and vascular and lymphatic casts of spontaneously hypertensive and normotensive rats were examined. Contracted venous sphincters were found on 108 of 127 veins with lymphatics in the spontaneously hypertensive rats and 5 of 41 in the normotensive rats P<0.01). The spontaneously hypertensive rats had deeper venous contractions and more lymphatic filling around both arteries and veins (P<0.01). In the hypertensive rats, the venous was greater than the arterial lymphatic filling (P<0.01). On the pleural surface, hypertensive rats also had greater lymphatic filling than controls (P<0.01). This anatomic evidence suggests that pulmonary venous sphincters are associated with focal lymphatic filling, and perivascular muscle action might be a component of the pulmonary lymphatic system.

Animals↗

PubMed1999

Three-dimensional morphometry in scanning electron microscopy: a technique for accurate dimensional and angular measurements of microstructures using stereopaired digitized images and digital image analysis.

A method for accurate dimensional and angular measurements of microstructures analysed in the scanning electron microscope is described. The method considers central and parallel projections and involves (a) digital image acquisition of stereopaired images from the scanning electron microscope's photodisplay, (b) generation of 3D-image representations, (c) setting of measuring points in the digitized stereopaired images, (d) computation of exact space coordinates (x/y/z) from the corresponding point coordinates (xL/yL; xR/yR), (e) determination of distances and angles between consecutive corresponding points using vector equations, and (f) transfer of computed data into spreadsheets of the data analysis software using dynamic data exchange with simultaneous graphical display of the frequency distribution of variables. Measurements performed on specimens with known dimensions (grid with 10 microm wide square meshes, polystyrene beads with 0.33 microm diameter) and angles (synthetic crystals of K(Al,Cr)[SO4], CuSO4.5H2O and NaCl) revealed a high accuracy in dimensional as well as angular measurements (total error 1 +/- 0.5%). In Monte Carlo experiments the overall error was found to depend strongly on the size of the measured structure relative to the size of the measurement field (field width).

Image Processing, Computer-Assisted↗

PubMed1996

Vascular regression during amphibian metamorphosis--a scanning electron microscope study of vascular corrosion casts of the ventral velum in tadpoles of Xenopus laevis Daudin.

We used scanning electron microscopy and vascular casting to study gross arterial supply, venous drainage, and microvascular patterns of the fully developed ventral velum of tadpoles of Xenopus laevis Daudin and analyzed changes of the velar vascular bed from prometamorphosis to metamorphic climax in a qualitative and quantitative manner. The multilayered, highly secretory ventral velum is supplied bilaterally by an anterior and a posterior velar artery, branches of the external carotid artery. Velar arterioles branch mainly dichotomously and form a flat two-dimensional capillary meshwork overlying the tops of filterplates I-IV. Thymopharyngeal veins, dorsal branches of the filter plates veins, and the internal jugular veins drain the velum toward the venous sinus of the heart. Location, architecture, and the drainage of the velar microvascular bed into the venous sinus make a significant contribution of the velar capillaries to gas exchange unlikely. Instead, velar capillaries rather serve the nutrition of the secretory epithelium. The overall morphology of velar vessels from prometamorphosis to metamorphic climax--deduced from vascular corrosion casts--points to atonic vessels with increased leakage indicated by adhering globular extravasations, and to obstructed or blind ending vessels evidenced by the tapered and/or rounded blind ending cast vessels. The significant decrease in the size of the ventral velum during the metamorphic cycle was paralleled by a miniaturization of the velar vascular bed. We hypothetize that this miniaturization occurs by a shortening and fusion of capillary mesh elements. Our findings in corrosion casts, particularly the miniaturization of the velar microvascular bed and the morphology of the regressing capillaries, point to profound morphologic and ultrastructural changes in velar vessels; a study on the fine structure of the microvascular bed of the ventral velum in metamorphic tadpoles is in progress.

Analysis of Variance↗

PubMed1995

Microvascularization of corpuscles of Stannius in teleost fishes.

Blood supply and microvascular patterns of Stannius corpuscles were studied by scanning electron microscopy of vascular corrosion casts in the teleost fishes Blennius pavo, Zosterisessor ophiocephalus, and Gasterosteus aculeatus. Microvascular casts demonstrated that Stannius corpuscles--depending on their location--have an arterial supply derived either directly from the dorsal aorta, from the trunk of the first ventral segmental artery of the tail, or from a renal artery. Supplying arteries form a capsular capillary bed and a parenchymal capillary bed; both are composed of fine, freely anastomosing vessels with a homogeneous isotropic distribution. Central venules arise deep in the corpuscles. In the capsule, they form a single vein which drains into a segmental vein or directly into the caudal vein. Stanniocalcin, the hormone of the Stannius corpuscle, enters the renal circulation and reaches its main target organs, the gills, via posterior cardinal veins--heart--ventral aorta. Occasionally, some capsular venules empty into the trunk kidney peritubular venules. Capillaries are fenestrated and are embraced by pericytes with long, slender processes. The perivascular space contains collagen fibrils. Nerve fibers are found close to endothelial cells and pericytes. Vascular patterns of Stannius corpuscles are compared with those of the rat parathyroid glands and are discussed in respect to physiological implications.

Animals↗

PubMed1995

Ontogenic expression of the erythroid-type glucose transporter (Glut 1) in the telencephalon of the mouse: correlation to the tightening of the blood-brain barrier.

Since Glut 1 was shown to be highly abundant in brain microvessels, its distribution during early developmental stages seems of importance in respect to the timing of blood-brain barrier (bbb) formation in the developing CNS. Here we have followed the temporal expression of the erythroid-type glucose transporter Glut 1 in the telencephalon of the embryonic and newborn mouse, beginning at the 9th intrauterine day. Glut 1 immunofluorescence staining was done on cryosections using a rabbit polyclonal antiserum to purified human erythrocyte glucose transporter. Endothelial cells resp. capillaries were detected by staining with a rhodamin-coupled Bandeiraea simplicifolia lectin (BSL). In parallel, the developmental tightening of the embryonic bbb was assessed by perfusion of mouse embryos with Trypan blue and horse radish-peroxidase. At E9, prior to the onset of intraneural neovascularization, strong Glut 1 immunoreactivity was found in the whole neuroectoderm but only minor staining was seen in the perineural domain. Glut 1 expression remained uniformly distributed in the intraneural tissue at E10, the beginning of intraneural neovascularization in the mouse. From E11 onwards, Glut 1 immunoreactivity was invisible in neuroepithelial cells, but appeared tightly associated with intraneural capillaries. Perfusion of E12 embryos using trypan blue solution and HRP revealed that most parts of the CNS and spinal cord were impermeable to the tracer substances at that stage. Thus, we suggest that the bbb is established very early in CNS development, probably in the course of intraneural neovascularization. In addition, our data indicate that the restriction of Glut 1 expression to the intraneural capillaries reflects the onset of bbb function in the mouse embryo.

Animals↗

PubMed1995

Microvascularization of the cerebellum in the turtle, Pseudemys scripta elegans (Reptilia). A scanning electron microscope study of microvascular corrosion casts, including stereological measurements.

Cerebellar blood supply and microvascular patterns were studied in 12 freshwater turtles Pseudemys scripta elegans by scanning electron microscopy (SEM) of microvascular corrosion casts and histology. Vascular densities were estimated by point counting methods from casts and thin sections (7 microns). Short A2-arterioles and recurrent branches from A3-arterioles supply the capillary bed of the molecular layer, while V2 and V3 venules drain it. The Purkinje cell layer is supplied by horizontal branches ("parallel arteries") of A4 and A3 arterioles, which capillarize toward the granular and molecular layers. V2, V3 and V4 venules drain the areas supplied by A3 arterioles. The deep granular and subependymal layers are supplied by A4 arterioles, those adjacent to the Purkinje cell layer also by A3 arterioles. The areas supplied by A4 arterioles drain via V4 venules. The granular and Purkinje cell layers taken together have an estimated vascular density of 4.1%, while in the molecular layer this value is 3.3%. Our findings largely confirm published data from Testudo geometrica and Pseudemys scripta elegans with respect to gross supply and drainage. The microvascular patterns are similar to those of the human cerebellar cortex, particularly the basic patterns of intracortical arterioles and venules. The molecular layer, like that in the human brain, has a circulatory bed largely independent of that of the Purkinje cell and granular layers. In contrast to the human brain, a cerebellar pial capillary network is present in the brain of the turtle.

Animals↗

PubMed1995

The angioarchitecture of the rat mandibular joint synovium.

The synovium (or synovial membrane) lines all intra-articular surfaces of synovial joints except for the articulating surfaces. This study describes the angioarchitecture of the synovium of the adult rat temporomandibular joint using microvascular corrosion casts and scanning electron microscopy. To corroborate findings, India ink-injected, thick-sectioned specimens (200 microns) and haematoxylin and eosin-stained tissue sections (7 microns) were analysed. Rostrally, the synovial membrane was fed by several layers of vessels branching towards the superficial lining of highly convoluted capillary loops. Arterioles were rare, and venules organized in large plexuses. The membrane thinned out in the caudal direction. Villi were present on the surface. They were flat, with a core of two parallel linear feeder vessels, one arteriole and one venule, which were interconnected by capillary loops. At the periphery of the articulating surfaces, the vessels of the synovial layer were flatter. Caudally, the synovial membrane of the richly vascularized retrodiscal pad showed many synovial folds. Feeder vessels were directed rostrally and branched in all directions. The number of subdivisions depended on the size of the synovial fold. Again, venules were organized in plexuses and lining capillaries were convoluted. The densely capillarized synovial membrane with its folds and villi is considered well adapted to serve synovial fluid production and joint dynamics.

Animals↗

PubMed1995

The angioarchitecture of the rat mandibular joint bilaminar zone.

In mammals, temporomandibular-joint articular disc attachments have a bilaminar pattern. The three-dimensional angioarchitecture of the bilaminar zone in the adult rat was described using scanning election microscopy of microvascular corrosion casts (47 specimens) and light microscopy of Indian ink-injected, cleared, thick-sectioned temporomandibular joints (6 specimens). The bilaminar zone had an axial core of feeder vessels composed primarily of flat venules which were organized in plexuses. Arterioles were few and slender. In both laminae, there were usually three branching levels until vessels approached the surface of the lamina, where a dense capillary meshwork was formed. Both laminae ended abruptly at the periphery of the avascular disc with a single, slightly undulating marginal vessel. This marginal vessel, which faced the avascular disc, was definitely larger in diameter than the other superficial capillaries and was rather a postcapillary venule than a capillary. Functionally, this marginal venule might be important in sustaining nutrition of the avascular disc centre by allowing bidirectional blood flow during jaw movements.

Animals↗

PubMed1995

Microvascularization of the pineal gland in the freshwater turtle, Pseudemys scripta elegans (Reptilia): a scanning electron microscopic study of vascular corrosion casts.

Gross supply, microvascular patterns, and drainage routes of the pineal gland and its vascular relations with associated structures (dorsal sac, paraphysis, choroid plexus of the third ventricle) were studied by scanning electron microscopy of microvascular corrosion casts in 10 specimens of the freshwater turtle, Pseudemys scripta elegans. Light microscopy of tissue sections (one transverse and one longitudinal series) served to attribute cast vascular territories to anatomical structures. The tubular pineal gland body is supplied bilaterally by small branches of the saccular artery, a branch of the lateral choroidal artery. Branches of the diencephalic artery supply the pineal stalk. The pineal gland microvascular bed is a two-dimensional network that embraces the tubular gland. The network is made up mainly of venules with few true capillaries. Venules draining the ventral surface of the pineal gland body join those coming from the choroid plexus of the third ventricle and drain into the sagittal sinus. The less dense vascular network embracing the dorsal surface of the pineal body drains directly into the sagittal sinus. The pineal stalk drains into the diencephalic vein or directly into the sagittal sinus. No efferent (venous) vascular connections capable as transport route for pineal secretions toward surrounding telencephalic, diencephalic, or mesencephalic areas were found.

Animals↗

PubMed1995

The fine vasculature of the rat mandibular joint.

There is no detailed description of the fine vasculature of the rat mandibular joint in the literature. The gross vasculature of the cephalic area and of the mandible is known, but without particular emphasis on the joint itself. This article describes the fine vasculature of the rat mandibular joint, using transverse (coronal) and sagittal thick sections of specimens injected with India ink and analyzed with light microscopy. The main vascular supply to the joint comes from the rostral and caudal aspects. Medially, the joint is directly vascularized by vessels from the lateral pterygoid muscle. Rostrally, the synovial membrane and the bilaminar zone of the disc are supplied by articular branches from the rostral deep temporal vessels, terminal branches of the maxillary artery. Caudally, the rich synovium of the retrodiscal pad and the bilaminar zone are supplied by the articular branches of the caudal deep temporal artery, a branch of the maxillary artery. Venous return is into the short, but large retroarticular vein which empties into the maxillary vein together with the vein from the transverse sinus exiting from the postglenoid foramen. Intra-articular synovial membranes own rich venous plexuses, and are lined by a dense capillary network. The central part of the fibrous articular disc is avascular in adult rats, and is circumferentially lined by a rim of capillaries from the bilaminar zone.

Animals↗