Biomedical subjects

M B Moss

Publications and source records attributed to M B Moss.

39 records · Page 3Linked to original sources

PubMedDate not supplied

Recognition memory span in rhesus monkeys of advanced age.

Assessment of recognition memory was performed on eight rhesus monkeys of advanced age (25 to 27 years of age) using the delayed recognition span test (DRST). Their performance was compared to that of five young adult animals (5 to 7 years of age) on two stimulus conditions of the DRST: spatial position and color. Both trial unique and repeating series were used for each of the two conditions. As a group, aged monkeys were impaired on both the spatial and color conditions of the DRST, achieving about two-thirds of the span of the young adult group in each condition. Error analyses revealed that monkeys in the aged group also produced more perseverative responses (i.e., displacing the previously correct disk) than did young adults. Together the findings suggest that monkeys of advanced age are impaired on tasks with memory loading demand characteristics.

Aging↗

PubMedDate not supplied

Increased microglial activation and protein nitration in white matter of the aging monkey.

Activated microglia are important pathological features of a variety of neurological diseases, including the normal aging process of the brain. Here, we quantified the level of microglial activation in the aging rhesus monkey using antibodies to HLA-DR and inducible nitric oxide synthase (iNOS). We observed that 3 out of 5 white matter areas but only 1 of 4 cortical gray matter regions examined showed significant increases in two measures of activated microglia with age, indicating that diffuse white matter microglial activation without significant gray matter involvement occurs with age. Substantial levels of iNOS and 3-nitrotyrosine, a marker for peroxynitrite, increased diffusely throughout subcortical white matter with age, suggesting a potential role of nitric oxide in age-related white matter injury. In addition, we found that the density of activated microglia in the subcortical white matter of the cingulate gyrus and the corpus callosum was significantly elevated with cognitive impairment in elderly monkeys. This study suggests that microglial activation increases in white matter with age and that these increases may reflect the role of activated microglia in the general pathogenesis of normal brain aging.

Aging↗

PubMedDate not supplied

The effects of aging on area 46 of the frontal cortex of the rhesus monkey.

An examination of cortex of area 46 in the floor of the principal sulcus in the frontal lobe of the rhesus monkey has been carried out using three young (4-6 years of age), one middle-aged (12 years of age), and five old (25-32 years of age) rhesus monkeys. Light microscopic examination revealed no age-related change in the thickness of the cortex, and no changes in the frequency of profiles of neurons displaying nuclei and contained in 250-micron-wide strips of 1-micron-thick sections. Since the diameters of the nuclei of the neurons were found to be the same in the young and old monkeys, it was concluded that there was no change in the numbers of neurons beneath similar areas of cortical surface of area 46 with age. This conclusion was reinforced by an electron microscopic examination, since there was no suggestion of degeneration of the cell bodies of the neurons, which accumulated but little lipofuscin in the old monkeys. However, there were signs of degeneration in some of the dendrites in the upper layers of the cortex in the old monkeys, especially in layer 1, in which many of the dendrites had lost organelles from their cytoplasm. The other notable change was a degeneration of myelinated axons in the deep layers and white matter in some of the old monkeys. In contrast to the neurons, the effects of aging on the neuroglial cells and pericytes were very obvious, since in the old monkeys each type of neuroglial cell accumulated large inclusions within its cytoplasm. Prior to fixation, these monkeys had been behaviorally tested using a series of spatial and visual recognition tasks, which revealed that relative to the young monkeys, the old monkeys as a group displayed memory impairment. On one task, the extent of the impairment for each old monkey correlated well with the extent of degeneration of myelinated fibers in the cortex and white matter. Consequently, it is suggested that age-related cognitive changes are unlikely to be a result of a loss of neurons, but might be due to an alteration in connections between the cortex and other brain structures.

Aging↗