Quantitative investigations on the human entorhinal area: left-right asymmetry and age-related changes

Abstract

Abstract.The total nerve cell numbers in the right and in the left human entorhinal areas have been calculated by volume estimations with the Cavalieri principle and by cell density determinations with the optical disector. Thick gallocyanin-stained serial frozen sections through the parahippocampal gyrus of 22 human subjects (10 female, 12 male) ranging from 18 to 86 years were analysed. The laminar composition of gallocyanin (Nissl)-stained sections could easily be compared with Braak's (1972Braak's ( , 1980 pigmentoarchitectonic study, and Braak's nomenclature of the entorhinal laminas was adopted. Cellsparse laminae dissecantes can more clearly be distinguished in Nissl than in aldehydefuchsin preparations. These cell-poor dissecantes, lamina dissecans externa (dis-ext), lamina dissecans 1 (dis-l) and lamina dissecans 2 (dis-2), were excluded from nerve cell number determinations. An exact delineation of the entorhinal area is indispensable for any kind of quantitative investigation. We have defined the entorhinal area by the presence of pre-alpha cell clusters and the deeper layers of lamina principalis externa (pre-beta and gamma) separated from lamina principalis interna (pri) by lamina dissecans 1 (dis-l). The human entorhinal area is quantitatively characterized by a left-sided (asymmetric) higher pre-alpha cell number and an age-related nerve cell loss in pre as well as pri layers. At variance with other CNS cortical and subcortical structures, the neuronal number of the entorhinal area appears to decrease continuously from the earliest stages analysed, although a secular trend has to be considered. The asymmetry in pre-alpha cell number is discussed in the context of higher human mental capabilities, especially language.

Cortical and striatal neurone number in Huntington's disease

“…Section thickness cannot be directly read from the microtome. It must be optically determined in unstained as well as stained sections (for details see [58]). Due to staining, dehydration, and mounting procedures section thickness linearly decreases by about 20% to 480-540 !-lm.…”

Parahippocampal corpora amylacea and neuronal lipofuscin in human aging

“…Until recently it was generally believed that age-related impairments in cognitive performance are the result of age-related neuron loss, especially within the hippocampus and most neocortical areas. However, with the development of more accurate stereological techniques, it emerged that there is limited neuron loss within the hippocampal region (hilus and subiculum) and that there is no evidence of a more extensive neuronal loss than 10% during normal brain aging in other brain regions [20], including the MTL [21][22][23][24][25].…”

Estimation of the section thickness and optical disector height with a simple calibration method

“…However, such equipment is not readily available in most laboratories. This led investigators either to tailor their sampling design so that the section thickness need not be known (Cruz-Orive, 1987;Pakkenberg & Gundersen, 1989;Guntinas Lichius et al, 1993) or to develop alternative methods for measuring the vertical displacement of the microscope stage (Laroye & Taylor, 1992;Heinsen et al, 1994). One of these alternatives is to calibrate the scale of the fine focus knob with microscope cover glasses.…”

“…The idea is that the vertical distance travelled by the microscope stage during focusing through a cover glass with a known thickness correlates linearly with the angular displacement of the fine focus knob. Such a calibration method has been described by Heinsen et al (1994). They found that one of the 200 gradation marks on the fine focus knob represented a stage movement of 3 .…”

“…In this report, a simple modification that increases the sensitivity of the calibration method of Heinsen et al (1994) is described. The modification is based on the fact that when the boundary of a big circle is divided into a certain number of equally large segments, these segments will gradually become more difficult to see as the radius of the circle becomes shorter.…”