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M G Reed

Publications and source records attributed to M G Reed.

7 recordsLinked to original sources
PubMed2001

Stereological estimation of eye volume using the Pappus method.

The estimation of object volume from rotationally randomised sections relies on an ancient geometrical principle due to the Alexandrian mathematician Pappus. In this paper we describe two studies that make estimates of eye volume using a stereological version of the Pappus principle. The first study uses a design-based version of the Pappus theorem to make estimates of eye volume in Sprague-Dawley rats and the second uses a model-based implementation for estimating eye volume in juvenile Dover sole. In the sole study we compare the estimates of volume with estimates made using the Cavalieri method and show that the Pappus method gives identical volume estimates with a markedly lower coefficient of variation (2.5%) than the Cavalieri method (13.5%).

Animals↗
PubMed2000

Unbiased and efficient estimation of the total number of terminal bronchiolar duct endings in lung: a modified physical disector.

A novel modification of the physical disector is described which was used to estimate the total number of terminal bronchiolar duct endings (TBDEs) in human infant lung. TBDEs are closed three-dimensional space curves of complex shape that are inherently difficult to count from histological sections. However, careful consideration of the microanatomy of the terminal duct endings provides us with the opportunity to define a very simple and unbiased counting rule. To apply the rule in practice we also need to determine a suitable disector height. Owing to the complex shape of the TBDE we had no prior knowledge of what disector height would be suitable for counting the TBDE structures. Exhaustive serial sectioning of complete TBDE structures was carried out and showed that any disector height under 90 microm would give unbiased counts. A further empirical study was then undertaken to determine the most efficient disector height. This was found to be 50 micro. The total number of TBDEs in the upper lobe of the right lung of six human infants aged between 13 and 25 weeks was also estimated. The estimates of numerical density obtained with our modification of the physical disector were multiplied by estimates of lung lobe volume obtained using Cavalieri's Principle. The total number of TBDEs in the lobes ranged from 15 323 to 57 768, with a mean of 40 306. The average coefficient of error of the number estimates was 19%, which was deemed precise enough given the biological coefficient of variation between TBDE number of 36%.

Bias↗
PubMed1999

Measuring developmental changes in exposure to adversity: a Life Chart and rating scale approach.

The reliability and validity of a comprehensive, integrative strategy for assessing adversity exposure in childhood and adolescence was examined in a community-based longitudinal study of 205 children. Extensive data from multiple measures completed by adolescents and their parents regarding chronic and acute life experiences were aggregated into a Life Chart record of lifetime adversity exposure. Severity of adversity in three nonoverlapping time spans was rated by trained judges with excellent interrater reliability. As hypothesized, Family adversity predominated over all other types of adversity in childhood, remained salient into midadolescence, and showed considerable stability over time. Adversity related to an individual's own behavior and psychological functioning rose to equal prominence by late adolescence. Adversity arising from physical ailments that were independent of the individual's psychological functioning declined over time, while adversity arising from the community rose; physical and community events were uncommon for most individuals but substantial for some. Results suggest that coherent developmental trends in adversity exposure may be identified effectively through judges' ratings of severity of adversity over multiple-year time spans.

Adaptation, Psychological↗
PubMed1999

Stereological estimation of covariance using linear dipole probes.

Classical stereology is capable of quantifying the total amount or 'density' of a geometrical feature from sampled information, but gives no information about the local spatial arrangement of the feature. However, stereological methods also exist for quantifying the 'local' spatial architecture of a 3D microstructure from sampled information. These methods are capable of quantifying, in a statistical manner, the spatial interaction in a structure over a range of distances. One of the key quantities used in a second-order analysis of a volumetric feature is the set covariance. Previous applications of covariance analysis have been 'model-based' and relied upon computerized image analysis. In this paper we describe a new 'design-based' manual method, known as linear dipole probes, that is suitable for estimating covariance from microscopic images. The approach is illustrated in practice on vertically sectioned lung tissue. We find that only relatively sparse sampling per animal is required to obtain estimates of covariance that have low inter-animal variability.

Animals↗
PubMed1998

Surface-weighted star volume: concept and estimation.

The estimation of 'size' for an interconnected nonconvex phase is an ongoing problem in materials science and biomedicine. Examples of this type of phase include the pore space in a porous rock such as sandstone or the marrow space found in cancellous bone. A reasonable definition of size for this type of phase is provided by the mean volume-weighted star volume. This is defined as the average volume of the phase of interest seen unobscured from a typical point within the phase. One practical advantage of this definition of size is that it is easy to estimate stereologically. In this paper we extend the concept of star volume to consider the mean surface-weighted star volume. The mean surface-weighted star volume is the volume of a continuous phase seen unobscured from a typical point of the interface. We expect that this parameter could be useful in biological problems involving mass transfer across an interface. The stereological estimation of mean surface-weighted star volume is described and the method is illustrated on piglet lung tissue.

Animals↗
PubMedDate not supplied

The effect of benomyl on neurite outgrowth in mouse NB2A and human SH-SY5Y neuroblastoma cells in vitro.

The commercial fungicide methyl 1-[(butylamino) carbonyl]-1H-benzimidazol-2-ylcarbamate (benomyl) is teratogenic in rats. Its mode of action is believed to be related to its ability to inhibit the polymerization of brain tubulin. In this study its effects were studied in cultured neuronal cells during differentiation and neurite outgrowth. Mouse NB2a and human SH-SY5Y neuroblastoma cells were induced to differentiate by addition of dibutyryl cyclic AMP and at the same time were exposed to various concentrations of benomyl. Benomyl significantly inhibited neurite outgrowth in both cell lines at concentrations of 10(-8) M and above with IC50 values of 5.9 x 10(-7) M and 1.0 x 10(-6) M in the NB2a and SH-SY5Y cells respectively. The results show that benomyl inhibits neuronal cell differentiation at concentrations likely to be achieved during the development of fetal abnormalities in rats in vivo.

Animals↗