Three-dimensional reconstruction of tissue using computer-generated images

A practical three-dimensional reconstruction method to measure the volume of the sexually-dimorphic central nucleus of the medial preoptic area (MPOC) of the rat hypothalamus

Published estimates of the volume of the sexually-dimorphic central nucleus of the medial preoptic area (MPOC) have been quite variable both within and between laboratories. To obtain MPOC volume, most experimenters began with a two-dimensional (2-D) approach. They outlined the MPOC on each of several individual sections; then they added up the area contained on each section and multiplied the total by the section thickness. A 3-D reconstruction approach, although promising, has been somewhat impractical until recently due to the requirements for highly specialized software and massive computing support. Here, we describe the application of commercially-available PC-based software to measure MPOC volume by 3-D reconstruction. Male and female Sprague-Dawley rats, 24 or 50 days of age, were perfusion-fixed with 10% neutral phosphate-buffered formaldehyde. Following processing and embedding, a series of 20-microm sagittal paraffin sections were cut and mounted onto slides. After staining with cresyl violet, they were digitized using a microscope-mounted video camera connected to a frame-grabber in a Pentium-class computer (MCID-M5+). In addition to the MPOC, the anterior commissure, fornix, paraventricular nucleus, medial division of the bed nucleus of the stria terminalis, third ventricle and the bed nucleus of the anterior commissure were identified on the screen image and outlined using a computer mouse. These outlines were then aligned and rendered in 3-D with a solid overlay. The additional areas, such as anterior commissure, form landmarks within 3-D space to improve the accuracy with which the MPOC may be located and outlined. The reconstruction provides a striking illustration of the geometric relations between the structures of the anterior hypothalamus in the male and female rat. Moreover, the volumes determined from the overlays were reproducible between repeated studies in our laboratory. Our volume measurements confirm the sexual dimorphism previously reported for MPOC volumes, and provide a relatively quick, accurate and reliable protocol that should be useful in future experimental studies of environmental estrogenic compounds.

Quantitative study of the effects of maternal hyperthermia on cell death and proliferation in the guinea pig brain on day 21 of pregnancy

On embryonic day 21, pregnant guinea pigs were exposed to a 44 degrees C environment for 1 hour. As a result, all brain ventricular zone cells in M phase of the mitotic cycle when heat-shock occurred became immediately pyknotic and all cell division was stopped for 4-8 hr. The pyknotic cells were removed at a definable rate until mitosis resumed, after which removal occurred in an apparently random manner. Long delays in the return to mitosis were related to increased destruction of S-phase cells deep within the ventricular zone and largely confined to the alar lamina. Upon recovery, a rostrocaudal delay in mitosis was apparent, and the number of mitotic figures was increased compared with control numbers for 1 hr, after which they returned to control numbers. It was evident that up to 40% of the cells within the ventricular zone were destroyed following brief maternal heat stress.

Maternal hyperthermia as a cause of "idiopathic" mental retardation

Maternal hyperthermia of even short duration induces dramatic teratogenic (monster producing) effects in all experimental animals studied. In humans, several studies have reported cases analogous to some laboratory results in animal experiments, e.g., mental retardation, brain and nerve abnormalities and facial deformity. Recent computer-aided 3D reconstructions of pyramidal cells from guinea-pig brains subjected embryonically to a 1 hr stress at 44 degrees C environmental temperature, show that structural changes are induced in dendritic arbors. The alterations are greatest for dendritic segments closest to the cell body and are consistent with several reports linking topological and metrical anomalies with disturbances of brain function. We suggest that many cases of "idiopathic" subnormality are due to maternal hyperthermia during early pregnancy.