Biomedical subjects

Bente Pakkenberg

Publications and source records attributed to Bente Pakkenberg.

25 records · Page 2Linked to original sources

PubMed2003

Neocortical glial cell numbers in Alzheimer's disease. A stereological study.

Most studies agree that specific regions of the hippocampus and specific subcortical regions show neuronal loss in Alzheimer's disease (AD). The aim of the study was to use design-based stereological methods to obtain an estimate of the total glial cell population in 14 AD cases and 20 controls to determine whether brains from AD patients have a different number of neocortical glial cells than controls. The mean total number of neocortical glial cells was 25.9 x 10(9) for the AD group and 29.1 x 10(9) for the control group, 2p = 0.18. The mean total number of neocortical neurons was 18.9 x 10(9) for the AD group and 21.2 x 10(9) for the control group, 2p = 0.059. Estimates of the sum of all glial cells and neurons in the neocortex were in the order of 50 billion cells with a glia to neuron ratio of 1.37 in both groups.

Aged↗

PubMed2003

Stereological quantitation in cerebella from people with schizophrenia.

BACKGROUND: Behavioural and anatomical studies in schizophrenia have pointed to cerebellar involvement. AIMS: To provide stereological estimations of volumes and cell number in the cerebella of people with schizophrenia and a control group using post-mortem material. METHOD: Stereological methods were applied to cerebella taken from eight male patients with a DSM-III diagnosis of chronic schizophrenia with no neurological disorder (mean age 57.5 years) and ten male controls (mean age 56.2 years). The Cavalieri principle was used to provide estimates of volumes, the optical disector method to obtain estimates of the numerical density of Purkinje and granule cells, and a combination of the two to obtain estimates of total cell numbers in the cerebellum. The rotator method was applied to obtain estimates of mean Purkinje cell volume. RESULTS: No global structural difference in major volumes, cell numbers of Purkinje cell volume was found between the groups. CONCLUSIONS: The most frequently reported pathological finding in the cerebellum in schizophrenia is vermal atrophy, which was not found in this small group of heavily affected patients.

Adult↗

PubMed2003

Increased islet volume but unchanged islet number in ob/ob mice.

It is important for our understanding of the pancreatic islets to study whether new islets are able to form in the intact pancreas. We developed a new method to determine the total number and the mean volume of the pancreatic islets, and we used this method to study the expansion of the islet mass in ob/ob mice (n = 8), using ob/+ mice (n = 8) as controls. The total islet volume was increased by a factor of 3.6 in ob/ob mice compared with ob/+ mice, whereas, importantly, the total number of islets did not differ among ob/ob mice and ob/+ mice (3,193 +/- 160 islets in ob/ob mice vs. 3,184 +/- 142 islets in ob/+ mice, P = 0.97). The coefficient of variation in the volume distribution of islets was equal in the two groups, showing that in ob/ob mice, the existing islets expand their volume by the same proportion, without a net formation of new islets. We suggest that the pancreatic islets should be considered as anatomically such complex structures that islet neogenesis does not spontaneously occur in an intact pancreas. Cells within the existing islets are presumably the most important sources for islet cell hyperplasia during expansion of the total islet mass.

Animals↗

PubMed2002

Postnatal development of beta-cells in rats. Proposed explanatory model.

The previously shown wave of beta-cell apoptosis and the apparent plateau in the beta-cell mass in the third week of life in rats are still unexplained events. Using a novel design-based stereological method we investigated the postnatal development of the beta-cell population in Sprague-Dawley rats. The total beta-cell mass increased from postnatal day 4 until day 16, to be followed by a plateau until day 24, after which it increased further. This plateau was caused by beta-cell hypotrophia as well as decreased net beta-cell formation. The beta-cell mass per unit body weight (the relative beta-cell mass) was five times higher at birth compared with the adult constant level that was reached at approximately 24 days of age. We propose an explanatory model for the postnatal development of the beta-cell population in rats. According to this model, beta-cells in the early postnatal period are immature, i.e. are not susceptible to the mechanism that in later life maintains a constant relative beta-cell mass. Within the following weeks the number of mature beta-cells increases, and from approximately day 24 and onwards the beta-cell population is dominated by mature beta-cells that adjust to match the body weight, keeping a constant relative beta-cell mass. Findings of an apoptotic wave, a plateau phase in the total beta-cell mass development, a period with beta-cell hypotrophia, and the disappearance of insulin-like growth factor II positive beta-cells at postnatal day 21 all fit well in the model.

Age Factors↗

PubMedDate not supplied

2D and 3D assessment of neuropathology in rat brain after prenatal exposure to methylazoxymethanol, a model for developmental neurotoxicty.

To evaluate the ability of a tiered quantitative morphological approach to reveal developmental neurotoxicity, morphometric parameters were measured in the offspring of rats treated with methylazoxymethanol (MAM) during days 13-15 of pregnancy. Treatment was aimed at inhibiting the proliferation phase of hippocampal neurons while leaving cerebellar neurons unaffected. 2D and 3D assessment of brain morphology combined with straightforward measurement of brain size, weight and volume, and the usefulness of estimation of total neuron numbers were studied. Each tier indicated major effects of MAM, from macroscopic effects in the cerebrum (first tier) to a considerable loss of neurons in the hippocampal CA1 pyramidal layer (third tier). The cerebellum and the number of cerebellar granular neurons were not changed. Along with each step of the proposed tiered approach (brain size-->linear morphometry-->stereology), the discriminative strength of the endpoints, and thus the probability to pinpoint the extent and location of developmental brain lesions increased.

Abnormalities, Drug-Induced↗

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↗