The Automatic Proportionator Estimator Is Highly Efficient for Estimation of Total Number of Sparse Cell Populations.

Estimation of total number of a population of cells that are sparsely distributed in an organ or anatomically-defined region of interest represents a challenge for conventional stereological methods. In these situations, classic fractionator approaches that rely on systematic uniform random sampling are highly inefficient and, in many cases, impractical due to the intense sampling of the organ and tissue sections that is required to obtain sufficient counts for an acceptable level of precision. The proportionator, an estimator based on non-uniform sampling theory, marries automated image analysis with stereological principles and is the only estimator that provides a highly efficient and precise method to address these challenging quantification problems. In this paper, the practical considerations of the proportionator estimator and its implementation with Proportionator™ software and digital slide imaging are reviewed. The power of the proportionator as a stereological tool is illustrated in its application to the estimation of the total number of a very rare (~50/vertebrae) and sparsely distributed population of osteoprogenitor cells in mouse vertebral body. The proportionator offers a solution to neuroscientists interested in quantifying total cell number of sparse cell populations in the central and peripheral nervous system where systematic uniform random sampling-based stereological estimators are impractical.

Severe cell reduction in the future brain cortex in human growth-restricted fetuses and infants.

OBJECTIVE: The objective of the study was to test the hypothesis that the total number of cells in the cortical part of the cerebral wall is the same in intrauterine growth-restricted (IUGR) fetuses, compared with normally grown fetuses. STUDY DESIGN: The total cell number in the cerebral wall was estimated in 9 severely affected IUGR fetuses and 15 controls using the optical fractionator. Cell numbers were estimated within 4 developmental zones. The gestational ages were 19-41 weeks. RESULTS: The total cell number in the future cortex was significantly reduced in the IUGR fetuses, compared with controls. The daily increase in brain cells in the future cortex was only half of that of the controls. In the 3 other developmental zones, no significant differences in cell numbers could be demonstrated. CONCLUSIONS: IUGR in humans is associated with a severe reduction in cortical growth and a significant decrease in cell number in the future cortex.

T cell homing to tumors detected by 3D-coordinated positron emission tomography and magnetic resonance imaging.

A general hindrance to progress in adoptive cellular therapy is the lack of detailed knowledge of the fate of transferred cells in the body of the recipient. In this study, we present a novel technique for tracking of 124I-labeled cells in situ, which combines the high spatial resolution of magnetic resonance imaging with the high sensitivity and spatial accuracy of positron emission tomography. We have used this technique, together with determination of tissue radioactivity, flow cytometry, and microscopy, to characterize and quantitate the specific accumulation of transferred CD8+ T cells in tumor tissue in a mouse model. Transgenic CD8+ T cells, specific for the ovalbumin peptide SIINFEKL, were adoptively transferred to recipients carrying a subcutaneous tumor of the ovalbumin-expressing malignant melanoma cell line B16-OVA. The number of SIINFEKL-specific CD8+ cells in the tumor tissue was determined by flow cytometry each day for 8 consecutive days after adoptive transfer. From low levels 1 day after injection, their number gradually increased until day 5 when an average of 3.3x10(6) SIINFEKL-specific cells per gram tumor tissue was found. By applying the combined positron emission tomography/magnetic resonance imaging technique we were able to determine the position of the transferred, 124I-labeled SIINFEKL-specific T cells in 3 dimensions in recipient mice, and could demonstrate a highly significant accumulation of the 124I label in and around the subcutaneous B16-OVA tumors compared with normal tissue. Accumulation of 124I was significantly higher in B16-OVA than in B16 tumors not expressing the OVA antigen.

MRI volume measurements of hypointense objects. A phantom study using stereological methods.

Volume estimates made from thick slabs overestimate the volume of a positive contrast particle in a translucent matrix and underestimate its volume if the particle has negative contrast and the matrix is opaque. For T2-weighted MRI high signal objects the bias can be corrected according to simple geometric models. For negative contrast or hypointense objects the magnitude of the bias is unknown and no corrections have yet been put forward. We wanted to determine the bias of MRI measurements of hypointense objects of known diameter surrounded by a positive contrast solution. One, 3 and 5 mm slices with three different contrast concentrations were obtained according to a stereological MRI protocol. Results were compared with the true object size to estimate the bias. A simple correction for the bias could not be developed due to interslice cross-talk. Cross-talk makes an object appear in more MRI slices than corresponding to its physical size and larger than the true diameter. For phantom measurements an empirical correction could be developed, but for measurements of non-ideal objects such as brain structures the validity of the correction would be unpredictable. Besides avoiding or reducing cross-talk, the best way to deal with this bias is to measure the object's maximal contrast from edge to edge, a solution which is not perfect.