Biomedical subjects

Lisbeth Marner

Publications and source records attributed to Lisbeth Marner.

5 recordsLinked to original sources

PubMed2005

Increased volume of the pigmented neurons in the locus coeruleus of schizophrenic subjects: a stereological study.

The locus coeruleus is the largest cluster of noradrenaline-producing neurons in the brain and has been involved in regulating attention. The neurotransmitter system contributes to the initiation and maintenance of forebrain activity as well as modulation of the collection and processing of sensory information. This makes locus coeruleus a target of interest in the study of possible structural changes in the brains of subjects with chronic schizophrenia. Uniform sampling and optical disectors were used for estimation of total neuron numbers and the rotator principle for estimation of mean cell volume. This study estimated the bilateral total number of pigmented neurons in the locus coeruleus of schizophrenic and control subjects and found no difference between the two; schizophrenic subjects have 37,400 (coefficient of variation=CV=SD/mean=0.28), control subjects have 35,500 (CV=0.19), p=0.64. The average volume of the cell perikaryon of pigmented neurons was measured in both groups and showed a significant larger cell volume in the locus coeruleus of schizophrenic compared to control subjects; mean locus coeruleus cell volume was 58,400 microm(3) (CV=0.31) in schizophrenic subjects, which is 55% larger than the 37,600 microm(3) (CV=0.33) found in control subjects, a difference of 20,800 microm(3) (p=0.009). The fixation time was significantly longer for the schizophrenic brains with an average of 169 months compared to 88 months for the control brains. No relation was found between total numbers or geometric mean volume of the pigmented cells and fixation time.

Adult↗

PubMed2005

No global loss of neocortical neurons in Parkinson's disease: a quantitative stereological study.

The global total number of neocortical neurons was estimated in 10 patients with Parkinson's disease (PD; mean age, 74.8 years; range, 68-83) and compared to 12 comparison subjects (mean age, 75.8 years; range, 70 - 84). The total mean neocortical neuron number in the patients with PD was 18.6 x 10(9) with a coefficient of variation (CV = SD/mean) of 0.18, which was not statistically significantly different from that of the controls (18.8 x 10(9); CV = 0.16; P = 0.90). In contrast to some studies reporting neocortical atrophy this was not confirmed in our study, where the mean volume of neocortex was the same in the two groups (P = 0.59). No difference was found in the volume of white matter, central gray structures, archicortex, or the ventricular system between the two groups. Most patients with PD develop cognitive disturbances with time, and this study cannot exclude that local neuron loss in specific subpopulations of neocortical neurons or cell loss in small but essential neocortical subregions may be part of the structural defects of PD.

Aged↗

PubMed2003

Marked loss of myelinated nerve fibers in the human brain with age.

The white matter is the structure of the brain that declines most with age-almost 30%, but little is known about the age-effect on the fibers that constitute the white matter. In the present study, the total length of myelinated fibers was measured with a newly developed stereologic method. Specimens came from 36 normal Danes (18 males and 18 females) with an age ranging between 18 and 93 years. Samples were taken systematically and randomly from the white matter, and the biopsy specimens were randomly rotated before sectioning to avoid bias due to the anisotropic nature of nerve fibers. The fibers were counted at light microscopic level at approximately 10,000x magnification, and the diameter of each counted fiber was measured to get the diameter distribution. Males were found to have a total myelinated fiber length of 176,000 km at the age of 20 and 97,200 km at the age of 80, whereas the total length in females was 149,000 km at the age of 20 and 82,000 km at the age of 80. This finding corresponds to a 10% decrease per decade or a total decrease of 45% from the age of 20 to 80 years, and a sex difference of 16%. The fiber diameter distribution showed that primarily the thinner fibers were lost with a relative preservation of the thicker ones. The marked loss of myelinated nerve fibers with age could explain some of the cognitive decline seen in the elderly.

Adult↗

PubMedDate not supplied

Total length of nerve fibers in prefrontal and global white matter of chronic schizophrenics.

It has been suggested that the dysfunction of the prefrontal cortex in schizophrenics is due to dysfunctional connections between the prefrontal cortex and more posterior structures. The present study uses a recent stereological method that allows quantitation of the myelinated nerve fibers in the brain white matter. As especially the prefrontal region is of interest in schizophrenics, the prefrontal white matter was quantitated separately. The total length of nerve fibers in post-mortem brains was estimated from eight male chronic schizophrenics and nine male controls (age-range: 40-81 years). Samples were taken systematically and randomly from both the entire white matter and selectively from the prefrontal white matter. The biopsies were rotated randomly before sectioning to avoid bias due to the anisotropic nature of nerve fibers. The fibers were counted at light microscopic level at about 10,000 x magnification and the fiber diameter of each counted fiber was measured to get the size distribution of the fibers. The schizophrenics had a total of 129,000 km myelinated fibers in the white matter and 25,700 km in the prefrontal white matter, which was non-significantly different from a total of 137,000 km in the entire white matter and 27,600 km in the prefrontal white matter in controls. The size distribution of the fibers in schizophrenics was within normal limits compared to controls. Our results do not show a larger loss of nerve fibers in neither the white matter globally or in the prefrontal white matter of schizophrenics.

Adult↗

PubMedDate not supplied

Aging and the human neocortex.

Neurostereology has been applied to quantitative anatomical study of the human brain. Such studies have included the total neocortical number of neurons and glial cells, the estimated size distribution of neocortical neurons, the total myelinated fiber length in the brain white matter, the total number of synapses in the neocortex, and the effect of normal aging on these structural elements. The difference in total number of neurons was found to be less than 10% over the age range from 20 to 90 years, while the glial cell number in six elderly individuals, mean age 89.2 years, showed an average number of 36 billion glial cells, which was not statistically significantly different from the 39 billion glial cells in the neocortex of six young individuals with a mean age of 26.2 years. The total myelinated fiber length varied from 150,000 to 180,000 km in young individuals and showed a large reduction as a function of age. The total number of synapses in the human neocortex is approximately 0.15 x 10(15) (0.15 quadrillion). Although the effect of aging is seen in all estimated structural elements, the effect of sex is actually higher. The functional relevance of these differences in neuron numbers in both age and gender is not known.

Adult↗