Search PubMed⌕ Search

Biomedical subjects

T M Mayhew

Publications and source records attributed to T M Mayhew.

At least 127 records · Page 7Linked to original sources
PubMed1980

[Problems with the morphometric-stereologic measurement of biomembranes].

In seeking to draw comparisons between surface density Sv estimates of various organelle membranes, it becomes apparent that main classes of data may be recognised. In the 1st (class A) there is a relatively good agreement between the uncorrected Sv values obtained in different research laboratories, e.g. the boundary membranes of mitochondria, lysosomes and nuclei. In the 2nd class (class B) fall estimates for organelles or organelle sub-compartments whose membrane boundardies cannot be everywhere reliably predicted when they form but vague images on the micrograph, e.g. cristae and membranes of the rough and smooth ER, i.e. class B membranes do not fulfil the assumption for morphometric counting that the identification on section is unambiguous (WEIBEL). For these class B membranes Sv estimates are often more widely discrepant for 2 main reasons. The 1st is connected with the difficulties in finding suitable correction factors which correct either for underestimation of membranes (due to membranes oriented obliquely to the axis of the electron beam) or overestimation due to the Holmes effect. The 2nd equally important reason lies in the subjectivity of the analyser who has to decide to count or not to count vague membrane images. In order to show the insecurities of class B membrane Sv estimates when presenting data it is proposed to abandon the 2nd and 3rd decimal. 2 proposals are made to tackle the problems connected with Sv estimates of class B membranes: Firstly a new method of obtaining a correction factor is presented and secondly, a rigorous standardisation of the criteria used for defining membrane profile intersections. Examples of the latter are shown.

Animals↗
PubMed1979

Ultrastructural morphometry of blastogenesis I: transformation of small lymphocytes stimulated in vivo with dinitrochlorobenzene.

Changes in the volumes and surfaces of subcellular compartments of unstimulated small lymphocytes and immunoblasts in mouse axillary lymph nodes have been established using stereological techniques. Blast transformation was induced in vivo with dinitrochlorobenzene (DNCB). Cell samples were obtained by random sampling regimes applied at light and electron microscopic levels. From electron micrographs the volume densities of euchromatin, heterochromatin, nucleoli, mitochondria, Golgi apparatus and rough endoplasmic reticulum were determined. Cell surface/volume ratios were also computed. By estimating mean nuclear volumes using light microscopy, it was possible to calculate absolute compartmental volumes and to evaluate the plasma membrane surface areas of average cells. Transformation in this model was characterized by a considerable cellular hypertrophy and a substantial increase in plasmalemma surface. Hypertrophy was the consequence of increases in the volumes of all measured intracellular compartments, notably euchromatin and "residual cytoplasm" (including ground cytoplasm and free ribosomes). These changes are discussed in the context of the altered metabolic status of cells.

Animals↗
PubMed1979

Quantitative ultrastructural features of maturing mononuclear phagocytes in rat peritoneal fluids.

Ultrastructural features of the in vivo transformation of macrophage congeners in resident and adjuvant-induced peritoneal populations are evaluated by sterological methods. Maturation involves an increase in cell size by the differential hypertrophy of subcellular compartments, notably remaining cytoplasm, nucleus and lysosome-like granules. Larger cells have more and larger granules, more mitochondria and a greater plasmalemmal surface. In contrast, adjuvant activation tends to produce fewer granules and a nett loss of surface membrane.

Animals↗
PubMed1979

Changes in the plasma membrane surface of lymphocytes stimulated in vivo with DNCB.

Stereological principles have been used to evaluate ultrastructural changes which accompany the transformation of lymphocytes stimulated in vivo with dinitrochlorobenzene (DNCB). Whereas unstimulated lymphocytes and blast cells have slightly more than the minimal containing plasmalemmal surface for their volume, stimulated (blast-derived) lymphocytes have an excess surface area in the order of 30%. This observation is discussed in the context of altered cell function and the biosynthesis of additional membrane components.

Animals↗
PubMed1979

On the problem of counting and sizing mitochondria: a general reappraisal based on ultrastructural studies of mammalian lymphocytes.

The authors ask the question whether the parameters "numbers" and "volume" are suitable for the morphometric analysis of mitochondria. In several types of cell, irregularity of mitochondrial shape makes it technically difficult, if not impossible, to obtain reliable stereological estimates of mean organelle volume or number per unit volume. Of more fundamental concern is whether number of mitochondria per cell is of any real value as a structural correlate of respiratory potential and hence as a measure of cell function. Alternative parameters might serve better for this purpose. Though the problem is illustrated by reference to quantitative studies of lymphocytes, it is also pertinent to the investigation of many other cell types.

Animals↗
PubMed1979

Stereological approach to the study of synapse morphometry with particular regard to estimating number in a volume and on a surface.

The paper presents a system of stereological formulae which are suitable for the quantitative ultrastructural characterization of synapses. Attention is given first to the question of deciding which synaptic feature to adopt as the basis for measurement. Three counting units can be recognized on electron micrographs: the bouton, the total zone of apposition of pre- and postsynaptic membranes, and the zone of paramembranous density. These may provide different numerical results. Possible units of reference are considered also and whilst emphasis is given to a volume of nervous tissue and a membrane surface of postsynaptic element, interesting alternatives are presented for the sake of completeness. Stereological parameters available for quantifying synapses (for example boutons per tissue volume, paramembranous dense zones per soma surface) are described. In addition, some new and previously neglected possibilities are included and some errors found in the literature are corrected. Worked examples of the estimation of synaptic densities are provided.

Animals↗
PubMed1979

Basic stereological relationships for quantitative microscopical anatomy--a simple systematic approach.

There exists in the literature a core of formulations regarded as 'the basic stereological principles' for quantifying cell and tissue morphology. They may be used to obtain information relating component volume, surface area, length and number to a specified containing volume (the so-called component densities in a volume: VV, SV, MV and NV). However, principles may also be formulated for relating these component dimensions to a containing surface (SS, MS and NS), containing length (MM and NM) and a containing number (NN). Methods for estimating these previously neglected stereological relations are presented. Possible biological applications of the principles are also discussed.

Animals↗
PubMed1978

Membrane interiorization by phagocytosing macrophages--an ultrastructural morphometric approach.

Stereological methods have been used to quantify selected membrane compartments of normal and activated rat peritoneal macrophages, before and after phagocytosis of latex beads. Despite being rounder, activated cells are more efficient phagocytes: 30 min after latex challenge they suffer a greater nett depletion of plasma membrane and sequester more and larger phagocytic vacuoles. However, phagocytosis of latex is not the major route of membrane interiorization.

Body Surface Area↗
PubMed1975

Some stereological correction formulae with particular applications in quantitative neurohistology.

The present report furnishes explicit formulations for correcting the observed nucleolar and nuclear volume fractions of neurons sampled on the basis of the presence of nucleolar profiles when sectioned. Such samples, frequently chosen for quantitative studies in neurohistology, can result in the overestimation ov component volume fractions. The correction formulae are derived by considering theoretical spherical models exhibiting "nucleus-nucleolus" concentricity and eccentricity, and are tested by applying them to analogous neuron populations in rat spinal cord. It is concluded that, with certain reservations, the formulae can be usefully applied to data obtained from nucleolar-biased samples, thereby increasing the reliability of quantitative information gleaned from such samples.

Cell Nucleolus↗