Kidney Structure Investigations Using Scanning Electron Microscopy of Corrosion Casts - A State of the Art Review

The corrosion casting technique using acrylic resins in the scanning electron microscope (SEM), was originally developed to investigate renal microvascular structure and is now also successfully used in studies on various other organs. However, in the last two decades nearly 100 papers have been published on the renal vascular anatomy of various taxa of vertebrates or on pathomorphological structures of kidneys, using this technique. Analyzing these works, trends and developments in this field can be summed up as follows: The majority of studies are anatomical works on the vascular system of kidneys from all vertebrate classes. In addition, experimental pathological investigations, mostly done using rodents, and documentation of pathologically altered renal structure form another large part of the publications covered in this review. Perspectives for future research on renal systems using this versatile method may be derived from this survey

Scanning Electron Microscopy of Vascular Corrosion Casts in Comparative Studies on Renal Vascular Structure

In comparative microcorrosion casting studies on renal vascular systems the following demands should be met: The preparation procedure (anaesthesia, operation, flushing of the blood vascular system, ...) should be in accord with the specific physiological properties of the animal under investigation and the casting procedure (injection, curing, maceration, ...) should be kept constant as far as possible. If these points are considered, comparative data, even of quantitative nature, can be obtained from corrosion casts. Examples of results at the organ, single vessel and intercellular level as well as correlation of the results with physiological data are given

The Vascularization of the Kidney of the Eel (Anguilla anguilla - Osteichthyes) in the Freshwater Habitat

The renal vascular system of eels (Anguilla anguilla L.) in freshwater has been investigated using light-, transmission electron-, and scanning electron microscopy of vascular corrosion casts and critical-point dried specimens. The morphology of the kidney exhibits a highly evolved, unpaired, spindle-shaped form. The renal tissue extends partially into a recessus dorso-caudal to the anus. Renal glomeruli are comparatively large (100.8 μm +/-17 standard deviation) and well vascularized. They are arranged in grape-like clusters around the intrarenal arteries. Closely neighbouring glomeruli can be surrounded by incompletely separated Bowman\u27s capsules sharing the same renal tubule. The peritubular capillary plexus is mainly supplied from the right posterior cardinal vein (renal portal vein) and is relatively dense (about 30 vol.% - measured from corrosion casts). Conspicuous vascular patterns consisting of a central vein and, at a distance of about 25 μm, a peripheral meshwork of arterioles are frequently found. The nature and function of these structures, however, remains to be studied

The Opisthonephric Blood Vascular System of the Chicken Embryo as Studied by Scanning Electron Microscopy of Microvascular Corrosion Casts and Critical Point Dried Preparations

Microvascular corrosion casts of chicken embryos between four and 19 days after fertilization have been prepared. The developing kidney was investigated with scanning electron microscopy (SEM). The injection technique and resin composition were modified in order to facilitate the complete replication of native blood vascular systems of specimens as small as 15 mm body length. The development of the opisthonephros was followed from near the beginning of its function until a vascular development comparable to the adult situation was reached. Critical point dried glomeruli show the differentiation of the glomerular visceral epithelium (podocytes) from initially epithelioid to highly branched forms. The embryonic kidney (cranial part of the opisthonephros - mesonephros) shows a construction principle resembling amphibians that is entirely different from the definitive excretory organ (caudal part of the opisthonephros - metanephros)

Functional Aspects of Renal Glomeruli Based on Scanning Electron Microscopy of Corrosion Casts, with Special Emphasis on Reptiles and Birds

The glomerular complexity of several species of birds and reptiles is investigated in this study by scanning electron microscopy of vascular corrosion casts. Comparing these results with those of a freshwater teleost and a mammalian species, a trend towards small, simple glomeruli of the avian type, beginning with large, well vascularized glomeruli resembling the type found in fish, can be observed in reptiles. A close correlation between glomerular size and habitat can be established comparing related species having a similar physiological mode of renal function. Entirely different from this sauropsidian evolutionary line of development is the highly complex, large differentiation of the mammalian glomerulus

The Splenic Microvasculature of the Red-Eared Turtle (Chrysemys scripta elegans): A Study Concerning the Question Whether the Circulation is Anatomically Open or Closed

The splenic microvasculature of the turtle Chrysemys scripta elegans was studied by means of scanning electron microscopy of vascular corrosion casts and critical point dried tissue. In addition light- and transmission electron microscopic investigations were carried out. Within the organ the arteries are surrounded by periarterial lymphoid sheaths. The majority of the arterial capillaries, which emerge from these central arteries have open endings within the reticular meshwork of the red pulp. Approximately 10% of the capillaries directly connect with the venous origins. Since these venous capillaries of C. scripta elegans resemble those of nonsinusal mammalian spleens we termed them pulp venules. Several blood cells were seen in passage through the fenestrae of the pulpvenules. The blood cells overcome these wall pores either unimpeded or a striking deformation of the passing cell occurs. In the subcapsular region of the organ radially arranged venous vessels are observed, which drain into a collecting vein

Reply by A. Carretero et al.

Dear Editor, The study of vascular casts in the embryo by means of the scanning electron microscope represents the main subject of our research. We fully agree with DeRuiter and Gittenberger-de Groot in that corrosion casting is a valuable tool to study the early angiogenesis in embryos

Technical Improvements in Corrosion Casting of Small Specimens: A Study on Mesonephric Tubules and Vessels of Chicken Embryos

The injection technique for corrosion casting of small, embryonic material can be improved by using a chemical ligature (cyanocrylate). With this simple method, leakage of the resin at the injection site is prevented and the mechanical stability of the cannula-vessel coupling is improved. The blood vascular system of chicken embryos as small as Hamburger-Hamilton stage 24 (approximately 4.5 days of incubation) has successfully been injected using this procedure. Corrosion casts of the mesonephric tubular system have been made in a similar manner. Additionally, a simple way for secure transport of the fragile casts by immersion in 10% gelatin is suggested

UV spectrophotometry method for the monitoring of galacto-oligosaccharides production

Monitoring the industrial production of galacto-oligosaccharides (GOS) requires a fast and accurate methodology able to quantify, in real time, the substrate level and the product yield. In this work, a simple, fast and inexpensive UV spectrophotometric method, together with partial least squares regression (PLS) and artificial neural networks (ANN), was applied to simultaneously estimate the products (GOS) and the substrate (lactose) concentrations in fermentation samples. The selected multiple models were trained and their prediction abilities evaluated by cross-validation and external validation being the results obtained compared with HPLC measurements. ANN models, generated from absorbance spectra data of the fermentation samples, gave, in general, the best performance being able to accurately and precisely predict lactose and total GOS levels, with standard error of prediction lower than 13 g kg 1 and coefficient of determination for the external validation set of 0.93–0.94, showing residual predictive deviations higher than five, whereas lower precision was obtained with the multiple model generated with PLS. The results obtained show that UV spectrophotometry allowed an accurate and non-destructive determination of sugars in fermentation samples and could be used as a fast alternative method for monitoring GOS production.Fundação para a Ciência e a Tecnologia (FCT) - Bolsa de doutouramento SFRH/BDE/15510/2004Agência da Inovação – Programa IDEIA (Potugal