Harold Brody

The aging brain.

A recent interest in aging of the nervous system is related to the remarkable increase in the numbers of elderly persons throughout the world. As a reflection of the added years, pathologies in the older person have also increased. Primary among those which affect the activities and behavior of these people are the dementias, especially Alzheimers Disease. To focus on such problems, however, requires an understanding of the changes which take place in the normal aging nervous system. This paper reviews some of the accepted criteria for these changes as well as the possible attempts by the nervous system to alter its structure in response to these changes.

Aging in the human brain stem

As a part of a continuing study of the relationship between age and neuronal population within the human brain stem, the nucleus of the trochlear nerve was examined in a total of 20 brains from newbor

Cell Loss with Aging

There have been several techniques developed to determine the number of cells in the central nervous system. Probably the simplest and the most common technique has been the ocular micrometric method. This was originally used by Hammerberg in 1895 and while other techniques may be mentioned, it is at the present time the most consistent and dependable. It involves examination of tissue with the aid of a micrometer disc inserted into the ocular of a compound microscope. Cells which fall within the squares of the disc may then be counted and total counts made as well as graphs showing relative populations within any portion of the section. This is most useful in determining cell numbers within a brain stem nuclear structure since it is possible in serial section counting to obtain an impression of the cell population at any specific point. By examination in several planes, one may obtain a 3-dimensional impression of the nucleus, and to compare specific sites within the nucleus in a number of brain specimens when the nucleus is of similar size. Direct optical examination of tissue by the investigator also makes possible a differentiation of neurons from glial cells and discriminates fairly easily when there is an overlapping of cells.

Mercury in the human brain.

A recently developed technique of neutron activation analysis permitted a sensitive analysis of mercury in over 160 samples of fresh brain tissue from 17 randomly selected autopsies. There was a preferential deposition of mercury in various anatomical loci. Many of these loci are those clinically or histologically affected in poisoning by methyl mercury. The greatest concentration of the metal was generally present in the cerebellum with a mean of 0.28 μMg/g (parts per million). Forty per cent of the cerebellums had concentrations greater than 0.2 ppm. The visual cortex, pons and geniculate bodies contained levels averaging 0.17 to 0.20 ppm. The lowest levels were found in the frontal lobe white matter (mean 0.07 ppm). Two brains from patients with no exceptional exposure to environmental mercury had unusually elevated levels of 1 to 2 ppm in many regions.

An effective surrogate for impact studies

Nineteen unembalmed (fresh) cadavers were used in 21 experiments to test restraint systems in automobile impact studies. Some were mounted in a rearward firing sled; others were placed in standard cars during collisions. Prior to and after testing, each cadaver was evaluated. After each experiment a postmortem examination was performed. High-speed registering cameras (1,000 to 2,000 frames per second) were used and multiple telemetric recordings were made. The radiographic and pathologic changes were similar to those seen in patients following high-velocity accidents. Results were compared with those of car accident victims admitted dead on arrival to one of our hospitals. This study is a progress report. The results are being used to improve existing restraint systems and to evaluate experimental models.