Influence of tissue composition on the final volume of rat liver blocks prepared for electron microscopy

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).

Quantitative analysis of the developing rat kidney: absolute and relative volumes and growth curves

The development of the permanent kidney, or metanephros, is a complex process. In the present study, stereological methods were used at the light microscopic level to estimate the absolute volumes and volume densities of seven compartments in the developing rat metanephros, from embryonic day 14 (E14) to E21. Metanephroi from time-mated Sprague-Dawley rats were embedded whole in glycolmethacrylate, exhaustively sectioned at 2 microm and stained with PAS. The left metanephros from three embryos from each of three mothers were analysed at each of the ages (a total of 72 metanephroi). Relative volumes were multiplied by total metanephric volume to obtain absolute volumes. Total metanephric volume increased approximately 300-fold during the 7-day period studied. At E14, 92% of the metanephros was composed of undifferentiated mesenchyme, whilst the ureteric epithelium made up approximately 5% of the volume. By E21 the undifferentiated mesenchyme comprised 47% of the kidney, while the ureteric epithelium comprised 9% and the various components of developing nephrons (epithelial vesicles, comma-shaped bodies, S-shaped bodies, glomeruli, tubules) comprised 43%. Equations with prediction intervals describing the growth of the whole kidney as well as the absolute and relative growth of the seven kidney compartments were generated. These data provide a baseline for future studies on the roles of specific molecules in renal development.

Enalapril does not prevent renal arterial hypertrophy in spontaneously hypertensive rats

Angiotensin-converting enzyme inhibitors prevent the development of vessel wall hypertrophy in some vascular beds in spontaneously hypertensive rats (SHR), but their effects on hypertrophy of renal arterial vessels have not been studied. We therefore used stereological techniques to study wall and lumen dimensions of the interlobular (cortical radial) and arcuate arteries in the kidneys of SHR (n = 7), SHR treated from 4 to 10 weeks of age with enalapril (25 to 30 mg/kg per day; SHR-E, n = 7), and Wistar-Kyoto rats (WKY, n = 7). All kidneys were perfusion-fixed at 10 weeks. Systolic blood pressure was 199 +/- 9, 139 +/- 11, and 156 +/- 8 mm Hg in the SHR, SHR-E, and WKY groups, respectively. For the interlobular arteries, the volume density of artery wall, wall-to-lumen ratio, and wall thickness in the untreated SHR were significantly greater than in the WKY (0.84 +/- 0.09 versus 0.69 +/- 0.07 x 10(-3), 0.75 +/- 0.20 versus 0.53 +/- 0.08, and 13.6 +/- 3.3 versus 10.6 +/- 0.8 microns, respectively), but values in the SHR-E were similar to those in the untreated SHR (1.10 +/- 0.20 x 10(-3), 0.88 +/- 0.22, and 14.0 +/- 2.6 microns, respectively). For the arcuate arteries, wall thickness and volume density were significantly greater in SHR than WKY (17.3 +/- 3.0 versus 13.9 +/- 1.7 microns and 1.63 +/- 0.51 versus 1.14 +/- 0.27 x 10(-3), respectively), and values in the SHR-E (15.7 +/- 1.7 microns and 1.69 +/- 0.50 x 10(-3), respectively) were not significantly different from those in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

A rapid, reliable, and valid method for measuring infarct and brain compartment volumes from computed tomographic scans

BACKGROUND AND PURPOSE

Clinical stroke trials require objective and reproducible end point variables. Morphometry of cerebral structures, including infarct volume, provides numerical measures that represent the amount of tissue damaged and potentially salvaged by therapy. However, morphometry may be time-consuming and labor-intensive, and it requires standardization across multiple centers, which may be difficult to achieve in large multicenter trials. We developed a brain morphometry method that is unbiased, rapid, reliable, and based on well-accepted stereological techniques. We now extend this method to analysis of routine computed tomographic (CT) scans such as might be obtained during a clinical stroke trial.

METHODS

We studied CT scans from 18 stroke patients and 14 asymptomatic control patients obtained over 5 years at the San Diego Veterans Administration Medical Center. Three observers independently measured the volume of the cranial vault, cerebrum, cortex, white matter, deep gray structures, ventricle, sulcal cerebrospinal fluid space, visible infarction, and cerebellum/brain stem.

RESULTS

The two patient groups were well matched demographically. The intracranial volume of 1400 +/- 40 mL in control subjects was not different from the 1311 +/- 41 mL in patients. Cerebral volume was 1250 +/- 36 mL compared with 1070 +/- 36 mL (control subjects versus patients, P < .001), and infarction volume was 55 +/- 16 mL in patients. For all structures, intraclass correlation coefficients among the observers ranged from 0.87 to 0.03; the best agreement was found for lesion, ventricle, and intracranial volume. White matter and cortex volume predicted the National Institutes of Health Stroke Scale score but not the late outcome scores on the Barthel Index or Rankin Scale. Each scan required 70 to 90 minutes for analysis.

CONCLUSIONS

We developed a stereological method for cerebral morphometry from CT scans that is reliable, rapid, and simple. The measurements are unbiased, can be made on slices of any known thickness, and are independent of machine variables. Our results are remarkably similar to values obtained with more labor-intensive methods. This method should be of use in large-scale, multicenter trials of stroke therapy.

Postnatal differentiation and development of the rat epididymis: a stereological study

Postnatal development and differentiation of the rat epididymis was studied in the rat from 15 to 120 days of life using stereological techniques. Both the relative volume (volume density) and absolute volume of the epithelial, interstitial, and luminal compartments in the initial segment, caput, corpus, and cauda epididymides were determined. In all segments the volume density of the epithelial compartment increased between days 15 and 30 before falling to adult values at 45 days in the initial segment (0.476 +/- 0.031), at 60 days in the caput (0.258 +/- 0.028) and at 90 days in the corpus (0.245 +/- 0.007) and cauda (0.140 +/- 0.004). The relative volume of the interstitium decreased, whilst that of the lumen increased over the same period with adult values being achieved earlier in the proximal segments than in the distal segments. In contrast to volume fraction the absolute volume of all compartments in all segments increased from day 15 to day 90. Between 90 and 120 days the absolute volumes of compartments in the initial segment and caput showed little volume change. All compartments in the corpus and cauda showed significant increases in volume over the same period. A similar pattern of development was observed with respect to the surface area of both the luminal and basement membrane aspects of the epithelium; surface area per unit volume (surface density) in all segments reached adult values at approximately 60 days, whilst the increase in absolute area of the surfaces ceased at 90 days in the initial segment and caput and continued to 120 days in the corpus and cauda.(ABSTRACT TRUNCATED AT 250 WORDS)

Software for counting cells and estimating structural volumes with the optical disector and fractionator

We describe MS-DOS software for the optical volume fractionator (OVF), a stereological method combining the principles of the optical disector (Gundersen et al.: Acta Pathol. Microbiol. Immunol. Scand., 96:857-881, 1988) and fractionator (Gundersen: J. Microsc., 143:3-45, 1986). The OVF program estimates the volume of a fixed and embedded structure, the numerical density of cells, and the total number of cells in a structure. The hardware requirements include a PC computer (386 or 486 with VGA graphics) and a conventional light microscope fitted with a rotating stage, extension tube, and length gauge. The software includes an introduction, tutorial, simulator, laboratory tool kit, and report generator. The tool kit improves the efficiency of gathering stereological data with light microscopy and offers a convenient link between the data of light and electron microscopy. A novel algorithm, based on fractionator sampling, gives the volume of a fixed and embedded structure from the same set of sections used for cell counting. A laboratory example illustrates the operation of the software.

Total numbers of glomeruli and individual glomerular cell types in the normal rat kidney

Alterations in numbers of glomeruli and glomerular cells occur in various renal disorders. Although values for these parameters have previously been reported for several species, the estimates have often been biased due to assumptions regarding glomerular and/or nuclear size and shape. Other studies have used tedious serial-section reconstruction methods. In the present study, unbiased stereological methods were used to estimate total numbers of glomeruli and individual glomerular cell types in normal rats. The kidneys of seven adult Sprague-Dawley rats were perfused with 4% paraformaldehyde and 1% glutaraldehyde in phosphate buffer and embedded in either glycol-methacrylate (for light microscopy, LM) or Epon/Araldite (for transmission electron microscopy, TEM). Total glomerular number was estimated using an LM physical disector/fractionator combination; the total number of cells per average glomerulus was estimated using an LM optical disector/Cavalieri combination; and TEM physical disectors were used to count individual cell types. The normal rat kidney was found to contain 31,764 +/- 3667 (mean +/- SD) glomeruli. An average glomerulus contained 674 +/- 129 cells, of which 181 +/- 53 were epithelial cells (podocytes), 248 +/- 53 were endothelial cells, and 245 +/- 45 were mesangial cells. An average renal corpuscle contained 117 +/- 27 parietal epithelial cells. Following sectioning and staining, less than 6.5 h was needed to obtain the above estimates for a single animal, with coefficients of variation (SD as a percent of the mean) ranging from 10% to 25%. The unbiased stereological methods used in the present study constitute an unbiased, precise and cost-efficient set of quantitative tools for assessing glomerular morphology in health and disease.

Quantitative morphology for biologists and computer scientists: I. Computer-aided tutorial for biological stereology (version 1.0)

This paper describes a computer-aided tutorial for biological stereology. Stereology, a type of quantitative morphology, includes a collection of statistical methods that quantify the structural compartments that can be viewed in sections with light and electron microscopy. These methods provide volume, surface, length, shape, and number data, and help define the quantitative relationships among the structural compartments of biological hierarchies. Hierarchies, which connect structural data ranging in size from molecules to organs, serve as a central core to which the data of biological databases can be linked. The tutorial focuses on two objectives. It provides the user primarily interested in using quantitative morphology databases with background information, and offers a set of state-of-the-art tools to researchers wishing to use these methods in the laboratory. The main topics of the tutorial include: introduction to quantitative morphology, symbols/terms, data types, sampling, hierarchies, data interpretation, and utilities. The tutorial runs under the MS-DOS operating system and requires at least an IBM PC AT (or compatible), a color monitor (EGA, VGA), 540 KB of RAM, and 3 MB of hard disk space.

The use of the optical disector to estimate the total number of neurons in the developing chick lateral motor column: effects of purified growth factors

Competition between neurons for limited amounts of trophic factors is believed to be the basis for large-scale neuronal death during the normal development of the vertebrate nervous system. In this study, an unbiased stereological counting method, an optical disector/Cavalieri combination, was used to estimate the total number of motor neurons in the lateral motor column of the developing chick and to assess the effects of four growth factors on neuronal numbers. The total number of neurons in lateral motor columns at embryonic day 6 (E6), E8, E10 and E12 were 18,747 +/- 1,369 (mean +/- SD), 15,037 +/- 1,816, 10,245 +/- 940, and 8,802 +/- 797, respectively. Daily exposure from E6 to E9 to three of the growth factors (basic fibroblast growth factor, bFGF; leukemia inhibitory factor, LIF; nerve growth factor, NGF) had no effect on total neuron number at E10. However, exposure to ciliary neurotrophic factor (CNTF) from E6 to E9 significantly increased (P less than 0.05) the number of neurons in the lateral motor column (13,610 +/- 725, compared with 10,058 +/- 204 in normal saline controls). These results are in agreement with previous reports of large scale neuronal death in the developing chick lumbar lateral motor column between E6 and E12 and confirm that exposure to growth factors such as CNTF can mitigate the course of normal ontogenetic cell death. The optical disector/Cavalieri combination is an efficient method for counting neurons: on average, following sectioning and staining, less than 30 min was required to estimate the total number of motor neurons in a lateral motor column with a coefficient of error of approximately 10%.

Dimensional changes in cells and tissues during specimen preparation for the electron microscope

Studies on dimensional changes incurred during preparation of tissue specimens for the transmission and scanning electron microscopes are reviewed, with emphasis on quantitative measurements pertinent to morphometry and three-dimensional reconstruction. The scope of the review includes fixation, dehydration, plastic embedment, critical-point drying, and freeze-drying. Recommendations are presented for monitoring dimensional changes; a strategy for the choice of method of specimen preparation is outlined.

Sources of error in the estimation of Leydig cell numbers in control and atrophied mammalian testes

The effects of assuming (i) that testicular tissue shrinks equally regardless of species or treatment at fixing and processing, (ii) that all Leydig cells in a given testis have spherical nuclei of identical size, and (iii) that testicular volume (i.e. the reference volume) is constant regardless of species or treatment, on the estimation of Leydig cell numbers in mammalian testes were investigated. This was accomplished by comparing the results of stereological analyses of Leydig cell numerical density and Leydig cell number in control testes of hamster, guinea-pig, and rat and in atrophied testes of hamster, and rat, obtained via the disector method which is unbiased with respect to the particle shape under study, and the Floderus equation which assumes that the particles under study are identical spheres. In control hamster, and also in guinea-pig, the effects of the three assumptions on the estimates of Leydig cell number per testis were negligible, because in these two treatment groups, the total shrinkage of testis tissue at fixing and processing (ST%) was low, Leydig cell nuclear profiles were circular in section, and the average volume of a testis was close to unity (i.e. 1 cm3). By contrast, in hamsters, and rats with atrophied testes, these assumptions produced incorrect estimates in Leydig cell number per testis, because the ST% was high, the majority of Leydig cell nuclear profiles were pleomorphic, and the average volume of a testis was lower than control. In summary, this study documents that the assumptions of equal shrinkage in testis tissue at fixing and processing, a constant testicular reference volume, and spheroidal shape of Leydig cell nuclei may contribute significant errors in estimates of Leydig cell number in mammalian testes. The magnitude of the errors introduced by these assumptions depends upon the species and the experimental treatment.

Estimating mean particle volume and number from random sections by sampling profile boundaries

We describe some new shape-independent stereological estimates of particle mean volume and surface area. Finding volumes or surface areas of cell nuclei, from electron micrographs of random thin sections, is a central problem of biological stereology. The well-known point-sampled intercept (PSI) method samples profile interiors to find the volume-weighted mean volume. This can be used in place of the true mean volume, but to do so introduces bias when volumes vary a great deal, as they do in fixed specimens. Jensen and Gundersen quite recently extended the PSI estimator to provide particle surface area, with no bias in the case of uniform surface areas. Here we extend the PSI volume estimator in a different way, sampling profile boundaries rather than their interiors. We obtain a boundary-sampled intercept (BSI) volume estimator, simpler than the PSI surface area estimator, but also unbiased for uniform surface areas. Both of these estimators are attractive, for example, in measuring and counting cell nuclei, where membrane surface area varies less than volume. Furthermore, they have no shape bias whatsoever. This paper also examines the general relationship between boundary- and area-sampled estimates, and we clarify the formal connection between our volume estimator and the PSI surface area estimator. We also calculate and compare their theoretical efficiencies.

Counting cells with stereology: random versus serial sectioning

Counts of cells and nuclei from sections provide information central to studying structural changes in cells, tissues, and organs. This study considers some of the practical problems associated with counting cells with the newer random and serial sectioning methods of stereology and tests the hypothesis that similar cell counts can be obtained with both random and serial sectioning methods. Using irregularly shaped nuclei from alveolar cells of the goat lung, we compared cell counts derived from random (electron microscopic) and serial sectioning (light microscopic) methods. The results showed that both sectioning methods gave similar cell counts (10(7)/cm3 of parenchyma) for type 1 epithelial cells (5.0 vs. 5.0; P=1.0), type 2 epithelial cells (8.6 vs. 9.8; P= 0.42) and interstitial cells (34.6 vs. 33.4; P=0.64), provided that corrections were introduced for section-related biases and that the nuclei of the random sectioning method were corrected for shape. We found counting biases of 5%-7% for nuclear shape and 16% for section compression. These observations support the hypothesis that similar cell counts can be obtained with random and serial sectioning, even when nuclei have irregular shapes.

Determination of Sertoli cell numbers in the developing rat testis by stereological methods

Stereological studies were performed to determine the number of Sertoli cells present during the postnatal development of the rat testes. Sprague-Dawley rats aged from 1 to 70 days were used in two experiments, and in each were fixed by vascular perfusion and embedded in Epon-Araldite, subsequent to which 1 micron sections stained with Toluidine blue were prepared. In the first experiment, rats aged from 1 to 20 days were used in groups of three, and number estimates were made using a direct counting method. In the second, which used groups of four rats aged from 20 to 70 days, a point sampled intercept was used to estimate nuclear volume and thence number. The results of the experiments indicate that the newborn rat testis contains 1.3 +/- 0.2 x 10(6) Sertoli cells and that this number increases to 38.4 +/- 2.7 x 10(6) at day 15. No further increase in Sertoli cell number occurred thereafter up to day 70 of age.