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 (10⁷/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 sectionrelated 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.     

Process Technological Develpoments for Improvement of the Castability of High‐Carbon Steels

Steels for rail‐making involve standard requirements concerning oxide cleanness. Castability problems do not generally occur. Due to the extremely high demands on cleanness, roller‐bearing steel 100Cr6 is cast using narrow SENs, which are extremely susceptible to clogging. Problems caused by clogging occur despite the fact that these heats are deoxidized using C, Si and Mn, with no addition of Al. Castability improved significantly after conversion to low‐Al ferrosilicon for deoxidation and rinsing of ladles with carbon‐deoxidized preceding heats. Casting temperature with a superheat of 30°C and a reduction in Al content to less than 20 ppm made it possible to increase sequence length to three heats.     

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

Methods for measuring and evaluating changes in volume of small tissue blocks prepared for transmission electron microscopy are presented. The results indicate: (1) that some blocks swell and others shrink, and (2) that changes in block volume can be explained by inhomogeneous changes occurring in three different tissue compartments. For stereological studies attempting to extrapolate changes in fixed and embedded tissue to those of fresh tissue, consequences of inhomogeneous volume changes in tissue compartments include a decrease in reliability and an increase in statistical variance of stereological density estimates. Since factors could not be found to correct for the changes in individual tissue compartments, alternative strategies are considered for dealing with the volume artifacts of fixation.     

The Genealogy of the Moral Modules

This paper defends a cognitive theory of those emotional reactions which motivate and constrain moral judgment. On this theory, moral emotions result from mental faculties specialized for automatically producing feelings of approval or disapproval in response to mental representations of various social situations and actions. These faculties are modules in Fodor's sense, since they are informationally encapsulated, specialized, and contain innate information about social situations. The paper also tries to shed light on which moral modules there are, which of these modules we share with non-human primates, and on the (pre-)history and development of this modular system from pre-humans through gatherer-hunters and on to modern (i.e. arablist) humans. The theory is not, however, meant to explain all moral reasoning. It is plausible that a non-modular intelligence at least sometimes play a role in conscious moral thought. However, even non-modular moral reasoning is initiated and constrained by moral emotions having modular sources.     

Unexpected activity of novel 9-oxabispidine zinc complexes in lactide polymerization

The zinc dichlorido and zinc diacetato complexes of the chiral tricyclic 9-oxabispidine (1R,2S,9S)-11-methyl-13-oxa-7,11-diazatricyclo [7.3.1.0^2,7] tridecane were prepared and characterized by X-ray crystallography. The latter complex was found to catalyze the solvent-free polymerization of d,l-lactide to give polylactide.     

Experimental Analysis of the Stability of Retained Austenite in a Low-Alloy 42CrSi Steel after Different Quenching and Partitioning Heat Treatments

Quenching and partitioning (Q&P) steels are characterized by an excellent combination of strength and ductility, opening up great potentials for advanced lightweight components. The Q&P treatment results in microstructures with a martensitic matrix being responsible for increased strength whereas interstitially enriched metastable retained austenite (RA) contributes to excellent ductility. Herein, a comprehensive experimental characterization of microstructure evolution and austenite stability is carried out on a 42CrSi steel being subjected to different Q&P treatments. The microstructure of both conditions is characterized by scanning electron microscopy as well as X-ray diffraction (XRD) phase analysis. Besides macroscopic standard tensile tests, RA evolution under tensile loading is investigated by in situ XRD using synchrotron and laboratory methods. As a result of different quenching temperatures, the two conditions considered are characterized by different RA contents and morphologies, resulting in different strain hardening behaviors as well as strength and ductility values under tensile loading. In situ synchrotron measurements show differences in the transformation kinetics being rationalized by the different morphologies of the RA. Eventually, the evolution of the phase specific stresses can be explained by the well-known Masing model.     

Optical absorption and emission spectra of Tb in hexagonal crystals of Na3[Tb(pyridine-2,6-dicarboxylate)3] · NaClO4 · 10H2O

We have measured and analyzed the polarized orthoaxial luminescence and absorption spectra of Tb³⁺ and Eu³⁺ in single crystals of trigonal Na₃[Ln(dpa)₃]·NaClO₄·10H₂O (dpa = 2,6-pyridinedicarboxylate, the dianion of dipicolinic acid). Differential linear polarization (σvs. π) is measured in the orthoaxial luminescence and absorption spectra. A semiempirically derived energy level scheme is developed for the crystal field components of the Tb³⁺ (⁷F_j (J = 0–6), ⁶D₄, ⁶D₃, ⁵G₈, ⁶L₁₀, ⁶D₂) ⁶G₅) and the Eu³⁺ (⁷F_j (J = 0–6), ⁶D_j (J = 0–3) multiplets.     

Stereological method for estimating relative membrane surface area in freeze-fracture preparations of subcellular fractions*

Microsomal fractions from liver cells are a mixture of vesicles derived from a number of different cellular membranes. These can be differentiated on freeze-fracture preparations by their characteristic density of intramembranous particles. A stereological method is developed which allows the estimation of the relative membrane surface of the various membrane types by using freeze-fracture preparations. The sample is restricted to concave profiles without cast shadow. The numerical frequency distribution of vesicles with respect to particle density is determined. The estimation of relative surface area must consider the effects on sampling of (a) variable size distributions of vesicles and (b) loss of small profiles. Correction coefficients are derived which allow a differential vesicle count to be transformed into an estimate of relative membrane surface.     

Computer assisted data collection for stereology: rationale and description of point counting stereology (PCS) software.

The paper describes microcomputer software for point counting stereology. Stereology includes a collection of statistical methods that quantify the images of light and transmission electron microscopy. The methods use test grids placed over images to collect raw data, which includes counts of points, intersections, transections, and profiles. In turn, the counts are included in stereological equations that give estimates of compartmental volumes, surfaces, lengths, or numbers. These parameters describe the composition of a structure in three-dimensional space. The PCS (point counting stereology) System Software III serves as a data collection, storage, and management tool. Users set up point counting protocols without programming, enter data by pressing predefined function (MS-DOS) or alphabetic keys (UNIX), store data in files, select files for analysis, and calculate results as stereological densities. The latest version of the PCS software includes a new user interface and is designed as a research "front end" that can feed data either into the calculation tools of a stereology tutorial (Bolender, 1992, this issue) or into the analysis routines of quantitative morphology databases (Bolender and Bluhm, 1992).     

Metallurgical process engineering for castability‐improvement in steel with elevated sulfur contents

Trouble‐free casting of Al deoxidized steel heats with high sulfur contents necessitates controlled addition of Ca in secondary metallurgy, in order to avoid the nozzle clogging effect. With too little Ca input on the one hand, clogging occurs as a result of the deposition of high melting point calcium aluminates, and at excessively high Ca inputs, on the other hand, precipitation of calcium sulfide occurs. Process engineering for precisely targeted Ca input is developed on the basis of thermodynamic calculations, general steelplant experience, and comprehensive operational tests. The new method reduces the failure rate from casting problems to less than one quarter. Sequence casting of Al killed grades with high sulfur contents is then no longer a problem.