The effects of embedding in water-soluble plastics on the final dimensions of liver sections

Identification of Cellular Voids in the Human Otic Capsule

The otic capsule consists of dense highly mineralized compact bone. Inner ear osteoprotegerin (OPG) effectively inhibits perilabyrinthine remodeling and otic capsular bone turnover is very low compared to other bone. Consequently, degenerative changes like dead osteocytes and microcracks accumulate around the inner ear. Osteocytes are connected via canaliculi and need a certain connectivity to sustain life. Consequently, stochastic osteocyte apoptosis may disrupt the osteocytic network in unsustainable patterns leading to widespread cell death. When studying bulk-stained undecalcified human temporal bone, large clusters of dead osteocytes have been observed. Such "cellular voids" may disrupt the perilabyrinthine OPG mediated remodeling inhibition possibly leading to local remodeling. In the common ear disease otosclerosis pathological bone remodeling foci are found exclusively in the otic capsule. We believe the pathogenesis of otosclerosis is linked to the unique bony dynamics of perilabyrinthine bone and cellular voids may represent a starting point for otosclerotic remodeling. This study aims to identify and characterize cellular voids of the human otic capsule. This would allow future cellular void quantification and comparison of void and otosclerotic distribution to further elucidate the yet unknown pathogenesis of otosclerosis.

A simplified method of preparation of mammalian intestine samples for scanning electron microscopy

Due to strong tissue hydration and complex architecture of the mucous membrane, appropriate preparation of inhomogeneous gastrointestinal tissues, especially from the intestine, for scanning electron microscopy is still a challenge and requires constant improvement of preparation techniques. In this article, we describe a simplified method of preparation of small intestinal mucosa tissues for observations in a scanning electron microscope. We emphasized the most important points in the preparation process that, when ignored, may result in formation of numerous artifacts and the inability to analyze the samples reliably. The developed technique facilitates proper animal tissue sampling in the field conditions, reducing the time of tissue collection and sample preparation as well as the total process costs. The fixative of choice, that is, buffered formalin, fixes, and stiffens the processed tissues properly, which is especially important in preservation of long, highly hydrated intestinal villi without shrinkage artifacts. The method described has been successfully used in comparative studies of the development of small intestines in mammals (pigs, mice, rats), reptiles, and birds (hens).

Assessment of cardiac fibrosis: a morphometric method comparison for collagen quantification

Fibrotic remodeling of the heart is a frequent condition linked to various diseases and cardiac dysfunction. Collagen quantification is an important objective in cardiac fibrosis research; however, a variety of different histological methods are currently used that may differ in accuracy. Here, frequently applied collagen quantification techniques were compared. A porcine model of early stage heart failure with preserved ejection fraction was used as an example. Semiautomated threshold analyses were imprecise, mainly due to inclusion of noncollagen structures or failure to detect certain collagen deposits. In contrast, collagen assessment by automated image analysis and light microscopy (LM)-stereology was more sensitive. Depending on the quantification method, the amount of estimated collagen varied and influenced intergroup comparisons. PicroSirius Red, Masson's trichrome, and Azan staining protocols yielded similar results, whereas the measured collagen area increased with increasing section thickness. Whereas none of the LM-based methods showed significant differences between the groups, electron microscopy (EM)-stereology revealed a significant collagen increase between cardiomyocytes in the experimental group, but not at other localizations. In conclusion, in contrast to the staining protocol, section thickness and the quantification method being used directly influence the estimated collagen content and thus, possibly, intergroup comparisons. EM in combination with stereology is a precise and sensitive method for collagen quantification if certain prerequisites are considered. For subtle fibrotic alterations, consideration of collagen localization may be necessary. Among LM methods, LM-stereology and automated image analysis are appropriate to quantify fibrotic changes, the latter depending on careful control of algorithm and comparable section staining.NEW & NOTEWORTHY Direct comparison of frequently applied histological fibrosis assessment techniques revealed a distinct relation of measured collagen and utilized quantification method as well as section thickness. Besides electron microscopy-stereology, which was precise and sensitive, light microscopy-stereology and automated image analysis proved to be appropriate for collagen quantification. Moreover, consideration of collagen localization might be important in revealing minor fibrotic changes.

Collagen network strengthening following cyclic tensile loading

The bulk mechanical properties of tissues are highly tuned to the physiological loads they experience and reflect the hierarchical structure and mechanical properties of their constituent parts. A thorough understanding of the processes involved in tissue adaptation is required to develop multi-scale computational models of tissue remodelling. While extracellular matrix (ECM) remodelling is partly due to the changing cellular metabolic activity, there may also be mechanically directed changes in ECM nano/microscale organization which lead to mechanical tuning. The thermal and enzymatic stability of collagen, which is the principal load-bearing biopolymer in vertebrates, have been shown to be enhanced by force suggesting that collagen has an active role in ECM mechanical properties. Here, we ask how changes in the mechanical properties of a collagen-based material are reflected by alterations in the micro/nanoscale collagen network following cyclic loading. Surprisingly, we observed significantly higher tensile stiffness and ultimate tensile strength, roughly analogous to the effect of work hardening, in the absence of network realignment and alterations to the fibril area fraction. The data suggest that mechanical loading induces stabilizing changes internal to the fibrils themselves or in the fibril–fibril interactions. If such a cell-independent strengthening effect is operational in vivo , then it would be an important consideration in any multiscale computational approach to ECM growth and remodelling.

Thick methacrylate sections devoid of lost caps simplify stereological quantifications based on the optical fractionator design

In neuroscience, the optical fractionator technique is frequently used for unbiased cell number estimations. Although unbiased in theory, the practical application of the technique is often biased by the necessity of introducing a guard zone at one side of the disector to counter lost caps and/or optical limitations. Restricting the disector within the section thickness potentially introduces bias in two ways. First, the need to measure section thickness in order to obtain the disector height/section thickness fraction is challenging since both microcator measurements, microtome block advance, and measurements on re-embedded sections are potentially biased. Second, disector placement is not uniform random within the section thickness resulting in a bias in most sections with inhomogeneous cell distribution along the z axis. Re-embedded 2-hydroxyethylmethacrylate (hereafter methacrylate) sections were inspected for lost caps to evaluate the possibility of whole section thickness counting with the optical fractionator technique and hippocampal granular cell nucleoli density differences along the z axis were assessed with a z axis analysis. No lost caps were found in the examined re-embedded tissue and an inhomogeneous cell distribution through the section thickness was observed. In thick methacrylate sections devoid of lost caps sampling through the entire section thickness could be an acceptable alternative to the use of guard zones and the consequent biases associated with section thickness measurement and non-random placement of disectors.

Relative shrinkage of adipocytes by paraffin in proportion to plastic embedding in human adipose tissue before and after weight loss

Adipocyte size is a major modulator of endocrine functioning of adipose tissue and methods allowing accurate determination of adipocyte size are important to study energy metabolism. The aim of this study was to assess the relative shrinkage of adipocytes before and after weight loss by comparing adipose tissue from the same subjects embedded in paraffin and plastic. 18 healthy subjects (5 males and 13 females) aged 20-50 y with a BMI of 28-38 kg/m² followed a very low energy diet for 8 weeks. Adipose tissue biopsies were taken prior to and after weight loss and were processed for paraffin and plastic sections. Parameters of adipocyte size were determined with computer image analysis. Mean adipocyte size was smaller in paraffin compared to plastic embedded tissue both before (66 ± 4 vs. 103 ± 5 μm, P < 0.001) as after weight loss (62 ± 4 vs. 91 ± 5 μm, P < 0.001). Relative shrinkage of adipocytes in paraffin embedded tissue in proportion to plastic embedded tissue was not significantly different before and after weight loss (73 and 69%, respectively). Shrinkage due to the type of embedding of the adipose tissue can be ignored when comparing before and after weight loss. Plastic embedding of adipose tissue provides more accurate and sensitive results.

Two-exon skipping within MLPH is associated with coat color dilution in rabbits

Coat color dilution turns black coat color to blue and red color to cream and is a characteristic in many mammalian species. Matings among Netherland Dwarf, Loh, and Lionhead Dwarf rabbits over two generations gave evidence for a monogenic autosomal recessive inheritance of coat colour dilution. Histological analyses showed non-uniformly distributed, large, agglomerating melanin granules in the hair bulbs of coat color diluted rabbits. We sequenced the cDNA of MLPH in two dilute and one black rabbit for polymorphism detection. In both color diluted rabbits, skipping of exons 3 and 4 was present resulting in altered amino acids at p.QGL[37-39]QWA and a premature stop codon at p.K40*. Sequencing of genomic DNA revealed a c.111-5C>A splice acceptor mutation within the polypyrimidine tract of intron 2 within MLPH. This mutation presumably causes skipping of exons 3 and 4. In 14/15 dilute rabbits, the c.111-5C>A mutation was homozygous and in a further dilute rabbit, heterozygous and in combination with a homozygous frame shift mutation within exon 6 (c.585delG). In conclusion, our results demonstrated a colour dilution associated MLPH splice variant causing a strongly truncated protein (p.Q37QfsX4). An involvement of further MLPH-associated mutations needs further investigations.

A special construction of subepidermal capillary loops in the hippopotamus (Hippopotamus amphibius)

Based on LM, TEM, and histochemical methods, the study describes the specific structure of subepidemal capillary loops in the integument of the hippopotamus (Hippopotamus amphibius). At 25- 60 µm, the diameter of the capillaries was more than twenty times larger than those found in other mammals, as was the diameter of the epidermal contact area of the hairpin turn, which had enlarged up to 200-400 µm(2). At about 13,400, the number of loops per cm(2) was three times higher than in the few other mammalian species measured to date. The remarkable sheath (thickness 2- 20 µm) of the capillary loops consists of a multitude of fine collagen IV fibres, which were in direct contact with the epidermal stratum (str.) basale, emphasizing an origin from the lamina fibroreticularis of the basement membrane. Additionally, the sheath contained many regions filled with free fatty acids. All observations confirmed the view that the walls of the subepidermal capillaries in the hippopotamus are adapted to withstand high blood pressure, permitting a high rate of blood vesselbased heat transfer from the periphery of the body. Until now this function is only known as an important thermoregulatory response in highly active mammals, e.g. dolphins. However, under hot climatic conditions but without strong exercise for cooling, such ability could be an effective and energy-saving procedure in semi-aquatic mammals.

Demonstration of free fatty acids in the integument of semi-aquatic and aquatic mammals

The sensitive red fluorescence dye BODIPY® 665/676, and embedding in the water-soluble resin Technovit® 7100 were used to demonstrate free fatty acids in the epidermis of seven semi-aquatic and aquatic mammalian species with a sparse or dense hair coat. The staining generally marked lipid layers of varying thickness between the lamellae of the Stratum corneum, as found particularly in very densely haired species (otter), but also in rather sparsely haired animals (beaver, nutria), and especially in the seal. The very sparsely haired capybara contained no free fatty acids in the corneal layer system, but exhibited an accumulation of such substances in the vital epidermis. All haired species showed a strongly positive reaction staining of the sebaceous glands. In the hairless species, a distinct intracellular staining was restricted to cells of the thick vital epidermis in the hippopotamus, whereby in the Str. corneum positive intercellular reactions appeared. In the dolphin, on the contrary, positive intercellular reactions became visible in the vital epidermis, whereas in the Str. corneum the lipids concentrated in large longitudinal intracellular vesicles.

The effects of glycol methacrylate as a dehydrating agent on the dimensional changes of liver tissue

The dimensional changes of liver sections during the course of processing with glycol methacrylate (GMA) or with ethanol are described. Tissue processing with ethanol served as a control. During prolonged processing steps (24 h each), linear shrinkage of tissue specimens dehydrated with GMA at room temperature was 13.2%. Subsequent infiltration with GMA resulted in trivial swelling, and polymerization in slight shrinkage (2.3%). In comparison, processing with cold GMA resulted in shrinkage during dehydration (about 10.8%), a slight swelling in pure GMA, followed by shrinkage during polymerization (2.2%). Short routine processing schedules resulted in similar shrinkage/swelling patterns, although precise values differed slightly. In all experiments, ethanolic dehydration resulted in smaller dimensional tissue changes than did GMA dehydration. The dimensional changes of tissue sections during stretching on water, mounting and drying compensated for the major part of the shrinkage manifested during processing.

Spectral domain optical coherence tomography in mouse models of retinal degeneration

PURPOSE

Spectral domain optical coherence tomography (SD-OCT) allows cross-sectional visualization of retinal structures in vivo. Here, the authors report the efficacy of a commercially available SD-OCT device to study mouse models of retinal degeneration.

METHODS

C57BL/6 and BALB/c wild-type mice and three different mouse models of hereditary retinal degeneration (Rho(-/-), rd1, RPE65(-/-)) were investigated using confocal scanning laser ophthalmoscopy (cSLO) for en face visualization and SD-OCT for cross-sectional imaging of retinal structures. Histology was performed to correlate structural findings in SD-OCT with light microscopic data.

RESULTS

In C57BL/6 and BALB/c mice, cSLO and SD-OCT imaging provided structural details of frequently used control animals (central retinal thickness, CRT(C57BL/6) = 237 +/- 2 microm and CRT(BALB/c) = 211 +/- 10 microm). RPE65(-/-) mice at 11 months of age showed a significant reduction of retinal thickness (CRT(RPE65) = 193 +/- 2 microm) with thinning of the outer nuclear layer. Rho(-/-) mice at P28 demonstrated degenerative changes mainly in the outer retinal layers (CRT(Rho) = 193 +/- 2 microm). Examining rd1 animals before and after the onset of retinal degeneration allowed monitoring of disease progression (CRT(rd1 P11) = 246 +/- 4 microm, CRT(rd1 P28) = 143 +/- 4 microm). Correlation of CRT assessed by histology and SD-OCT was high (r(2) = 0.897).

CONCLUSIONS

The authors demonstrated cross-sectional visualization of retinal structures in wild-type mice and mouse models for retinal degeneration in vivo using a commercially available SD-OCT device. This method will help to reduce numbers of animals needed per study by allowing longitudinal study designs and will facilitate characterization of disease dynamics and evaluation of putative therapeutic effects after experimental interventions.

Demonstration of lipids in plastic resin-embedded sections of skin material

Two different fluorescence stains, green: 5-hexadecanoylaminofluorescein, and red: BODIPY(R) 665/676 [(E,E)-3, 5-bis-(4-phenyl-1,3-butadienyl)-4,4-difluoro-4-bora-3a, 4a-diaza-s-indacene, produced good results regarding the demonstration of glycolipids, free fatty acids and triglycerides in mammalian skin material that had been embedded in a water miscible plastic resin (Technovit(R) 7100). In this way, functional aspects of specific structures (epidermal barrier region, sebaceous glands) could be characterized histochemically in the integument of five mammalian species with sparse or dense hair coats.

A review of state-of-the-art stereology for better quantitative 3D morphology in cardiac research

The aim of stereological methods in biomedical research is to obtain quantitative information about three-dimensional (3D) features of tissues, cells, or organelles from two-dimensional physical or optical sections. With immunogold labeling, stereology can even be used for the quantitative analysis of the distribution of molecules within tissues and cells. Nowadays, a large number of design-based stereological methods offer an efficient quantitative approach to intriguing questions in cardiac research, such as "Is there a significant loss of cardiomyocytes during progression from ventricular hypertrophy to heart failure?" or "Does a specific treatment reduce the degree of fibrosis in the heart?" Nevertheless, the use of stereological methods in cardiac research is rare. The present review article demonstrates how some of the potential pitfalls in quantitative microscopy may be avoided. To this end, we outline the concepts of design-based stereology and illustrate their practical applications to a wide range of biological questions in cardiac research. We hope that the present article will stimulate researchers in cardiac research to incorporate design-based stereology into their study designs, thus promoting an unbiased quantitative 3D microscopy.

Stereologic estimation of the total numbers, the composition and the anatomic distribution of lymphocytes in cone biopsies from patients with stage I squamous cell carcinoma of the cervix uteri

The aim of this study was to present a method to obtain basic biological data on the in situ cellular immune response towards cancer. Using stereology, we estimated the density and frequency of immune cells of 10 different phenotypes in cone biopsies from 20 patients with FIGO stage I cervical squamous cell carcinoma. The anatomic distribution of immune cells with respect to intraepithelial, periepithelial or stromal compartments was recorded in normal epithelium, dysplastic epithelium and carcinoma. We estimated the number of immune cells per cancer cell, and the 3D total number of immune cells, inside cancer tissue. The tumor volume was estimated in 3D and corrected for shrinkage occurring during tissue processing. We found more immune cells in cancer compared to dysplasia and normal epithelia. A median total number of 278 . 10(3) CD3+, 69.1 . 10(3) CD4+ and 113 . 10(3) CD8+ cells were present in the cancers. A median number of 63 CD3+, 11 CD4+ and 29 CD8+ cells were present per cancer cell. The average volume of tumors in stage IA was significantly smaller than that of stage IB. This method was found to be usable and of potential value in clinical pathology research, and for development and evaluation of immunotherapy.

Pineal Gland Post-natal Growth in Rat Revisited

We studied the pineal gland (PG) growth separating two critical moments of the rat post-natal development: the lactation and post-weaning periods. We studied 30 Wistar rats in the post-natal day - PN day 6, 10, 21, 45, 60 and 90 using light microscopy and quantitative methods (allometry and stereology). We estimated the PG volume (using the Cavalieri's principle) and the number of pineal gland cell nuclei (PGCN, using the disector method). We analysed the correlation of the PG volume (y) versus brain weight (x) in the different age groups (the bivariate study used log-transformed data and the allometric model log y = log a + b log x). The PG growth gradually decelerated in older rats than in younger rats. The major increment of the PG growth was observed between PN day 6 and PN day 10, while the minor increment was observed after weaning between PN day 45 and PN day 60. After 60 days of age differences were no more observed. The relative growth of the PG was allometrically positive in all age groups, and growth curves separated the lactation from the after weaning periods. The number of PGCN of rat continuously increased during post-natal life and differences between the lactation and after weaning periods were significant. It is possible that the supporting cells, fibres and new synapses are responsible for that PG late post-natal increase.

Observations on the actual structural conditions in the stratum superficiale dermidis of porcine ear skin, with special reference to its use as model for human skin

The results obtained from the outer ear skin of female pigs (German Landrace) by light microscopy (LM), transmission electron microscopy (TEM), and cryo scanning electron microscopy (cryo SEM) methods, in particular relying on careful and artefact-free tissue processing, exhibited that the stratum superficiale dermidis of the auricle had a very homogeneous and compact construction, especially in one area (central dorsum auriculae). Based upon the important measurements made [average thickness of stratum superficiale dermidis: 94 (+/-16) microm, region A: 81 (+/-10); average thickness of collagen fibre bundles: 12 (+/-2) microm, region A: 13 (+/-0.5); average density of subepidermal capillaries: 3134 (+/-459) loops/cm2, region A: 3497 (+/-247)], this impression was confirmed by low standard deviations for all parameters, in comparison to marginal locations studied. The capillary system present was analysed by LM and TEM for specific structural features, whereby it generally compared to the microvasculature in human skin. Moreover, a regular pattern of diffusion-relevant punctiform contacts of the capillary loop apex with the epidermal basement membrane became obvious. Cryo SEM, particularly offering the advantages of dispensation of chemical fixation, dehydration and solvents during processing, highlighted delicate structures without shrinkage and without loss of soluble sample components. Thus rather real spatial conditions in the region of the epidermo-dermal junction and the upper dermis were visualized, whereby very regular arrangements of the structures present became obvious. This pertained also to a correct demonstration of all components of the epidermal basement membrane, in particular the lamina lucida. In addition, the water-based stable character of the entire stratum superficiale dermidis could be emphasized as a basic feature for controlled diffusion processes.

Stereological study of postnatal development in the mouse utricular macula

This study describes the morphometric changes taking place in the utricular macula of mice with ages in geometric progression from 1 to 512 days after birth. By using design-based stereological methods, the total volume and surface area of the sensory epithelium as well the total number of the hair cells and supporting cells were estimated. Finally, the numerical density, volume density, and mean volume of the individual cell types were determined. The major changes were found in the number of the individual cell types during the first couple of weeks, and a mature composition of cell types was not attained until 16 days after birth. There was no change in the total number of cells and no decline in the number of hair cells within the time period studied.

Embedding of large specimens in glycol methacrylate: Prerequisites for multi-signal detection and high-resolution imaging

Acrylic resin mixtures are commonly used to study microscopic sections of biological specimens, giving the advantage of good morphological preservation. Existing embedding protocols, however, are suitable for tissue blocks, not exceeding 1 mm in thickness. We have developed a protocol to embed larger specimens (up to 2 cm(3)) in Technovit 8100. This medium allowed us to perform classic histological (trichrome), silver, as well as immunohistochemical staining, needed for multi-signal detection at high-resolution imaging to reconstruct a three-dimensional interpretation of a serially sectioned muscle. The technique was applied to reconstruct the semitendinosus muscle of a fetal pig, 44 days post conception, featuring connective tissue, intramuscular nerves, blood vessels, and muscle fibre types. For the reconstruction, a technique was used that enabled us to insert high-resolution images of histological details into low-resolution images of the entire muscle.

Optimization of glycol methacrylate embedding of large specimens in neurological research. Study of rat skull-brain specimens after implantation of polyester meshes

Advances in neuroscience require better anatomical knowledge of neuronal architecture and structural details. Optimal embedding techniques are the basis for precise morphometric studies in section series as well as for the evaluation of tissue specimens or implants of differing hardness. There are very few methods for preparing large specimens by resin embedding, although resins such as polyethylene glycol (PEG) and methyl methacrylate (MMA) are presently in use. However, these methods have proven to be laborious and sometimes unsatisfactory for serial sectioning. While glycol methacrylate embedding (GMA) is suitable for smaller specimens, it results in inadequate infiltration and polymerization in blocks larger than 1 x 1 x 0.2 cm. We present an improved technique using GMA, which permits both standardized embedding of 4 x 2 x 2 cm blocks and preparation of section series. This method was developed for preserving skull-brain specimens from rats with polyester-mesh implants. The excellent preservation of cellular details allowed the assessment of local tissue reaction to foreign-body material in situ. Advantages of this method are: (1) No toxic catalysts or solvents are used (as opposed to MMA and current GMA processes); (2) Laborious routines in stretching and mounting of sections are not necessary (in contrast to PEG and MMA); (3) No deplastination is required before staining (in contrast to PEG and MMA); (4) Excellent morphologic preservation of various tissue is achieved.

A precise and efficient stereological method for determining murine lung metastasis volumes

We have developed a computer-assisted stereological method based on unbiased principles for estimating metastasis volumes in mouse lungs. We evaluated this method using the transplantable Lewis lung carcinoma. Twenty-one days after subcutaneous inoculation of 10(6) Lewis lung cells into C57BL/6J mice, the mice had primary tumors with an average volume of 2300 mm(3). After perfusion fixation, the lungs were removed, embedded in OCT compound, snap-frozen, and processed for stereology. The metastasis volumes were estimated by application of the Cavalieri principle after evaluation of single sections from several evenly distributed tissue levels. The metastasis volume in a group of nine mice varied between 0.01 and 14.4 mm(3), with an average of 6.1 mm(3). The coefficient of variation was 0.9. The coefficient of error of the volume estimation was determined in five cases and varied from 0.08 to 0.23. Thus, the variation on the metastasis volumes that is achieved by this method contributes very little, 2.5%, to the total variance within the group of mice. In conclusion, we have developed an efficient and unbiased method to determine the metastasis burden in mouse lungs.

Stereologic methods and their application in kidney research

Stereologic methods are used to obtain quantitative information about three-dimensional structures based on observations from section planes or--to a limited degree--projections. Stereologic methods, which are used in biologic research and especially in the research of normal and pathologic kidneys, will be discussed in this review. Special emphasis will be placed on modern stereologic methods, free of assumptions of the structure, size, and shape, etc., so-called UFAPP (unbiased for all practical purposes) stereologic methods. The basic foundation of all stereology, sampling, will be reviewed in relation to most of the methods discussed. Estimation of error variances and some of the basic problems in stereology will be reviewed briefly. Finally, a few comments will be made about the future directions for stereology in kidney research.

Embryonal feather growth in the chicken

Prenatal feather growth development in the chicken was studied in 7 body regions in HH stages 27-45, using direct measurements, specific histological and immunohistochemical methods, and scanning electron microscopy. The results from measurements of absolute length values, and, particularly, growth rate development in each HH stage revealed a distinct phase of most intensive growth in HH stage 40-41, which was preceded by feather follicle insertion and accompanied by the occurrence of alpha-keratins in barbule cells. Specific regional evaluation demonstrated that growth in the feather follicles of abdominal skin generally showed the slowest progression from absolute values and that in the feather filaments of the developing wings the most rapid progression occurred during HH stage 40-41 from growth rate values.

Preservation and staining of myelinated nerve fibers

Six procedures are given for preservation of myelinated nerve fibers for light or electron microscopic studies. These procedures fall into two main categories: those with and those without aldehyde fixation. Essentially different effects are attained by application of tannic acid, saline, microwave or conventional heating, or a decreased temperature. All procedures end in osmication. Three main aspects of myelinated fiber morphology are taken into account when judging the quality of their preservation: axon, myelin sheath, and axon/myelin coherence. Each aspect can be preserved excellently, but always in combination with a less superior quality of the other two aspects. Superior myelin quality is attained using microwave irradiation, either with aldehydes to which tannic acid is added or without aldehyde fixatives. Superior axon quality is attained with aldehydes and (conventional) heating. Axon/myelin coherence is best preserved by decreasing the temperature during the rinse with saline. Another two procedures provide good, though less superior, preservation of both axon and axon/myelin coherence. Next, the fixed tissue is embedded in plastic blocks from which semithin and ultrathin plastic sections are cut for light and electron microscopy, respectively. In addition to the standard procedure for toluidine blue staining on semithin sections, two microwave-supported procedures are described, which can be used as alternatives if the staining result is unsatisfactory. Furthermore, a toluidine blue staining procedure is described for glycol methacrylate (GMA)-embedded material, which can be used if larger sections are needed.

Three-dimensional estimation of the glandular volume, and of the number and volume of epithelial cells in two glands from the antral mucosa of five healthy volunteers

Specimens of antral mucosa were taken from five healthy volunteers and processed for microscopic evaluation. Consecutive 50-micron-thick sections were cut to estimate the volume of two antral glands. Two glands in each section were followed throughout by projecting their profiles from two microscopes mounted in parallel. The glandular volume was estimated using Cavalieri's principle. The mean volume of epithelial cells was estimated by systematic random sampling of the sections with an optical disector of known sample volume. The total number of cells per gland was calculated after determination of the volume of the glands and the mean volume of the epithelial cells. The mean volume of the antral glands was 13.6 +/- 1.67.10(6) microns3, whilst the mean volume of the epithelial cells was 1256 +/- 240 microns3. The total number of epithelial cells per gland was 11216 +/- 1104. In conclusion, using stereological methods, the total number of cells as well as the cell volume and the volume of antral glands can be determined in routine biopsy specimens of human stomach provided that the total depth of the mucosa is present in the section.

Upper respiratory tract surface areas and volumes of laboratory animals and humans: considerations for dosimetry models

To facilitate the development of regional respiratory tract dosimetry comparisons between laboratory animal species and humans, published surface area (SA) and volume (VOL) data for the upper respiratory tract (URT) were reviewed. The review of the literature revealed that (1) different studies used different techniques to prepare specimens and make measurements, (2) different areas of the URT were measured, and (3) URT surface areas and volumes have been reported for a limited number of individual subjects within a species but for a relatively wide range of species. The published data are summarized in tables in this article. New measurements made in an F344 rat and in a female human subject are also presented. Despite the differences in experimental protocols, it was possible to fit allometric scaling equations to the data: In(SA, cm2) = -0.34 + 0.52 In(body weight, g) and In(VOL, cm3) = 1.70 + 0.78 In(body weight, g). Separate scaling equations were also fitted for rats alone. To illustrate the use of these scaling equations in quantitative human health risk assessment, two dose metrics (fractional absorption/cm2 URT SA and fractional absorption/g body weight) for predicted URT uptake in laboratory animals and humans were calculated for acrolein and epichlorohydrin. Expressed as an animal-to-human ratio, the 95% confidence interval for URT SA could change the predicted dose ratio by up to a factor of 2. Additional studies are needed to describe the entire URT (from the nares through the larynx) quantitatively and to decrease variability in scaling equation predictions as well as to develop additional species-specific scaling equations. Three-dimensional imaging techniques provide a noninvasive method to obtain URT surface areas and volumes in humans and the larger laboratory animals. Comparisons of magnetic resonance image (MRI) and computed tomography (CT) scans made as part of this study suggest that the greater clarity of the mucosal-air interface in the CT image provides better resolution for the study of anatomic features. Because there is no radiation exposure associated with MRI imaging, however, it is more safely used than CT scans in making repeated measurements in a subject to elucidate changes in URT geometry associated with normal nasal cycling or other physiological changes.

Liver of the brown trout, Salmo trutta (Teleostei, Salmonidae): a stereological study at light and electron microscopic levels

BACKGROUND

A quantitative study was undertaken for the first time on the normal liver of male and female 2-year-old brown trout, Salmo trutta.

METHODS

Liver was fixed by controlled perfusion. Organ-level morphometry provided weight and volume. A two-stage stereological approach was performed at light and electron microscopy levels. Systematic sampling and point-counting morphometry were used for estimating the relative volumes of the structural compartments. Total absolute volumes of these components were obtained by multiplying each volume density by the volume of its reference space.

RESULTS

Liver volume was 3,423.6 mm3 for males and 3,657.4 mm3 for females. Parenchyma accounted for 95% of hepatic volume. Veins and bile ducts occupied, respectively, 76% and 17% of the stroma, whereas arteries, connective tissue, and melanomacrophages together composed only 6%. Hepatocytes occupied 88% of the parenchyma. Nonhepatocytic cells (endothelium, biliary epithelial cells, Ito cells, and macrophages) composed 4% of the parenchyma, the capillary lumen 6%, and other spaces (Disse space, canaliculi, and lumina of preductules and ductules) composed 2%. Significant sexual differences were found: (1) Females showed a greater parenchymal volume density (0.85% vs. 0.35%) and absolute volume (29.5 mm2 vs. 11.7 mm3) of Ito cells; (2) macrophages of females also presented a greater parenchymal volume density (0.94% vs. 0.46%), but not absolute volume.

CONCLUSIONS

The need to analyze both relative and absolute stereological data was stressed. Similarities and differences were detected between brown trout and other species (fishes and mammals); the findings suggest that, despite architectural differences, some quantitative parameters of liver microanatomy were retained during phylogeny. Factors mediating sexual differences in Ito cells and macrophages were discussed and the need for further studies was highlighted.

The use of different fixatives and hydrophilic embedding media (Historesin and Unicryl) for the study of embryonic tissues

The effects of different fixatives, dehydration procedures, and embedding media on the structural and ultrastructural preservation of young chick embryos (Hamburger and Hamilton stages 18-24) have been studied by means of light and electron microscopy techniques. Under the light microscope, the results obtained with the use of Bouin, glutaraldehyde, or glutaraldehyde-paraformaldehyde mixtures, followed by partial dehydration of the samples and the embedding with two different polar resins (Historesin and Unicryl), were compared with the results obtained using conventional paraffin-embedding methods. Cell and tissue shrinkage was determined by comparing blood cells from those embryos embedded in either of resins with those embedded in paraffin. Samples were also compared with blood smears, either methanol-fixed or unfixed, obtained from embryos at the same Hamburger and Hamilton stages. The results obtained when Unicryl and Araldite were used for electron microscopy have also been compared. When ultrastructural images from glutaraldehyde-tannic acid/osmium tetroxide fixed, Unicryl embedded samples were compared with those from araldite embedded samples, the same good results were observed with either of the resins. Araldite embedding requires a complete dehydration of the samples, while Unicryl allows the embedding of partially dehydrated embryos with optimal ultrastructural results. We suggest that these polar resins can be considered as complementary tools for embedding delicate embryonic tissues, allowing partial dehydration of the specimens with an excellent cell and tissue preservation.

Significance of variations in section mounting technique for nuclear stereology and morphology in urinary bladder neoplasms

Owing to its toxicity it would be desirable to avoid xylene in the processing of histological tissue. Consequently, modifications of the section mounting technique excluding xylene have recently been suggested. Changes in tissue preparation might, however, influence histopathological structures used for malignancy grading of tumours. In the current study, we investigated the impact of alterations in the mounting process on the subjectively evaluated quality of nuclear morphology and on the stereologically obtained mean nuclear volume, vv(nuc), of urothelial neoplasms. Paraffin sections from 14 tumours were, after the haematoxylin-eosin staining, mounted with DPX and a coverslip either, 1) from the water bath, 2) after dehydration in ethanol but without clearing, or, 3) after dehydration and xylene clearing. We found that the nuclear morphology of ethanol-treated and xylene-cleared specimens was somewhat more brilliant than that of sections mounted from water. The vv(nuc) of xylene-cleared sections ranged from 142 to 751 microns3, and the mean value of 350 microns3 was not significantly different from that of ethanol-treated sections of 367 microns3 (2p = 0.67). In contrast, the mean vv(nuc) of sections mounted from water was 459 microns3, approximately 30% larger (2p < or = 0.02). Thus, although previous studies have demonstrated the prognostic value of vv(nuc) in patients with bladder cancer, the present study shows that modifications in section mounting technique may significantly influence the results, underscoring the need for standardization of tissue processing. Sections mounted from ethanol seem to be as good as routine xylene-cleared sections, whereas sections mounted from water have a less brilliant morphology and results of nuclear stereology different from those of routine sections.

Prenatal development of the integument in Delphinidae (Cetacea: Odontoceti)

The prenatal development of epidermis, dermis, and hypodermis was studied in embryos of different age of two delphinid species (Stenella attenuata, Delphinus delphis), using light and transmission electron microscopical methods. The delphinid embryo is covered by a multilayered tissue formed by four different epidermal generations (periderm, stratum intermedium-I, str. intermedium-II, str. spinosum) produced by the str. basale. The first layer appears at about 40-50 mm of body length, the second type (s.i.-I) about 60-160 mm, and the third type (s.i.-II) is present at 160-500 mm. The first spinosal cells are produced at 225-260 mm body length; thenceforth, the epidermis increases continuously in thickness. Epidermal ridge formation begins about 400-mm body length. The development of the dermis is characterized by the early production of thin connective tissue fibers (40-70-mm body length) and simultaneously the cutaneous muscle matures in structure. Vascular development intensifies between embryos of 150-225 mm, and collagen production increases markedly in fetuses of 225-260-mm length. These events are paralleled by an increase in dermal thickness. The first elastic fibers can be recognized in the skin from the abdomen at about 600-mm body length. The development of the hypodermis is marked by very rapid and constantly progressing growth, beginning about 60-mm body length. The first typical fat cells appear in animals of 360-400 mm. Regional differences are obvious for all skin layers with regard to the flippers, where structural maturation proceeds more rapidly than in dorsal or abdominal regions.

Estimation of capillary length density in skeletal muscle by unbiased stereological methods: II. Use of vertical slices of unknown thickness

BACKGROUND

The capillary network of the skeletal muscle was analyzed from a quantitative point of view with the purpose of determining the capillary length density--LV(cap/mus). A recent stereological method was applied to estimate this quantity using vertical slices of unknown thickness.

METHODS

First, the whole muscle was systematically sampled according to the fractionator method. The capillary length density was estimated on each chosen field of vision where the vertical axis was always identified as parallel to the major axis of the muscle fibers. Three measurements were performed: count of intersections between capillaries and cycloid test lines, count of intersections between capillaries and straight test lines, and count of capillary end points corresponding to the intersections of capillaries with the parallel planes of the vertical slices.

RESULTS

The estimated capillary length density was 1,578 mm per mm3 of skeletal muscle tissue. The average thickness of the vertical slices was also estimated as 23.4 microns, which is roughly 6% less than the thickness measured using the microcator information on the microscope stage displacement.

CONCLUSIONS

The advantages of this methodology were based on two main features: the method is assumption-free on the degree of capillary and muscle anisotropy, and the thickness of the vertical slices need not be known nor constant.

Estimation of capillary length density in skeletal muscle by unbiased stereological methods: I. Use of vertical slices of known thickness

BACKGROUND

The unbiased estimation of the capillary length density in skeletal muscle tissue Lv(cap/mus) has been performed in this study applying a new stereological methodology based on the use of vertical slices and the intersections of cycloid test curves with capillaries in a three-dimensional space defined by systematically chosen fields of vision and the thickness of the sections.

METHODS

The following simple requirements must be fulfilled: selection of a fixed vertical axis in skeletal muscle, adequate systematic muscle sampling, obtention of vertical slices of constant and known thickness but indifferent in magnitude, superposition of a cycloid test system with the minor axis of cycloid curves positioned perpendicularly to the vertical axis, and counting the intersections between cycloid curves and capillaries. In our study, the vertical axis was defined as that which is parallel to the natural, major axis of the muscle where fibres and capillaries are arranged parallel to this axis. The muscle sampling was performed using the fractionator method, and 25 microns thick sections were chosen.

RESULTS

The application of the equation for estimation of Lv(cap/mus) permits determination of an average of 1,480 mm of capillaries per mm3 of muscle tissue, knowing the number of intersections, section thickness, and the points hitting the muscle with a known ratio between cycloid test curve length to a test point.

CONCLUSIONS

The estimation of Lv(cap/mus) is efficient, unbiasedly obtained, and no assumptions on the degree of capillary anisotropy are required.

Analyzing renal glomeruli with the new stereology

The highly specialized architecture of the renal glomerulus is altered in a variety of disease states. Morphometric methods, including stereological methods, have been widely used to analyze these changes in both animal and human glomeruli. However, many of the methods available until recently were biased and provided incomplete information. The past few years have witnessed the development of a new generation of unbiased stereological methods. Another advantage of these new methods and strategies is that they are less influenced by technical artifacts than the traditional methods. This chapter describes how these new stereological methods can be used to quantify glomerular morphology. Parameters considered include glomerular number and volume; glomerular cell number and size; and the length, surface area, and number of glomerular capillaries. Methods for obtaining data for average glomeruli as well as individual glomeruli are described. Technical details are included wherever possible.

Estimating glomerular number in situ using magnetic resonance imaging and biopsy

In the past researchers have used an estimate of one million as the number of glomeruli in each human kidney. However, recent work on excised kidneys has demonstrated a large variation in glomerular number from one person to another (330,000 to 1,400,000) per kidney. Theoretically an in situ estimate of glomerular number could be obtained if renal cortical volume, volume density of glomeruli per cortex [Vv(glom/cortex)] and mean glomerular volume are known. We used a dog model to demonstrate that an accurate estimate of cortical volume could be obtained in situ using magnetic resonance imaging (MRI). Vv(glom/cortex) and mean glomerular volume were obtained from needle biopsies. An independent and more direct method (the fractionator) was used to validate the estimate of glomerular number obtained using MRI and renal biopsy. On average there was very good agreement between the fractionator method (379,000 +/- 40,000) and the MRI/renal biopsy method (376,000 +/- 108,000) for the 10 dog kidneys measured; however we found up to a 36% difference between the two methods in an individual kidney. Nonetheless, the estimate from the MRI/renal biopsy method has more precision than the assumption that there are one million glomeruli per human kidney.

Combined lectin binding and PAS/alcian blue staining in glycol methacrylate sections

Evaluation of cryofixation and paraffin and glycol methacrylate embedding showed that lectin binding was essentially independent of the embedding medium. Fluorescence intensity increased in the following order: glycol methacrylate, paraffin and cryostat sections. The optical resolution increased in the reverse order. Semi-thin glycol methacrylate sections provided satisfactory fluorescence intensities and the best resolution of all embedding techniques applied. Furthermore the lectin treated sections can be stained further using routine histological or specific histochemical methods. The potassium hydroxide/alcian blue/periodic acid-phenylhydrazine-Schiff method was used successfully to demonstrate sulfated and nonsulfated sialomucins. Lectins combined with mucin histochemistry allowed visualization of specific sugar residues in the same glycol methacrylate plastic section.

Staining myelin and myelin-like degradation products in the spinal cords of chronic experimental allergic encephalomyelitis (Cr-EAE) rats using Sudan black B staining of glycol methacrylate-embedded material

A high-resolution light-microscopical (HRLM) technique is described to visualize myelin, and macrophages containing degradation products of myelin, in the spinal cords of chronic relapsing experimental allergic encephalomyelitis (Cr-EAE) rats. This HRLM technique was developed to optimalize the correlation between nuclear magnetic resonance (NMR) characteristics and histopathological images in this well-established animal model for multiple sclerosis (MS). Spinal cords were fixed by perfusion with a combination of cacodylate-buffered glutaraldehyde and formaldehyde, post-fixed in Dalton's fixative (containing osmium tetroxide), rinsed in water, processed in ethanol, acetone, and embedded in glycol methacrylate resin (Technovit 7100/HistoResin). Semi-thin sections were stained with Sudan Black B and counterstained with Cresyl Fast Violet, resulting in black staining of myelin and its degradation products, with blue/violet staining of demyelinated axons and other tissue elements. These dyes were selected with the aid of a numerical model of staining, which took both access and lipophilicity into account. The staining procedure is simple and highly reproducible. The resulting images are contrast rich, and combine excellent morphology with a high degree of lipid retention.

Integumental Structure in a Friesian Calf with Congenital Hypo-or Atriehosis Combined with Prognathia Inferior

Abstract- The integumental structure in a Friesian calf with congenital hypo-or atrichosis and prognathia is described. The most important feature was the presence of primary hair follicles with full glandular complements but without the hair forming parts (hair bulb with matrix). Résumé- La structure du tégument d'un veau Frison atteinte d'une hypoou atrichose et d'un prognatisme est décrite. La principale caractéristique est l'existance de follicules pileux primaires possédant l'ensemble des glandes annexes, mais dépourvus de partie productrice de poil (bulbe avec matrice). Zusammenfassung- Die Arbeit beschreibt die Hautstruktur eines Schwarzbunte-Kalbes mit Hypo-oder Atrichosis, die mit Prognathia inferior gekoppelt ist. Als wichtigste Beobachtung fällt auf, daß die vorhandenen Primärhaarfollikel die voile Ausstattung mit beiden Drüsentypen zeigen, der gesamte proximale Follikelanteil, der das eigentliche Haar bildet (Haarbulbus mit Haarmatrix), jedoch fehlt. Resumen  Se describe la estructura integumentaria de un ternero frisón que padecía hipo/atricosis acom-pañada de prognosis mandibular. La característica relevante fué la presencia folículosos primarios junto con anexos glandulares completos, pero careciendo de las partes formadoras del pelo (bulbo piloso y matríz).