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Biomedical subjects

B Pakkenberg

Publications and source records attributed to B Pakkenberg.

At least 19 recordsLinked to original sources
PubMed2001

High levels of CD8-positive lymphocytes expressing CD45R0, granzyme B, and Ki-67 in lymph nodes of HIV-infected individuals are not associated with increased mortality.

Lymph nodes constitute the major site of HIV replication and of immunological response to HIV. To study the role of cytotoxic and mitotic active CD8(+) lymphocytes in lymph nodes during HIV infection we examined 28 formalin-fixed, paraffin-embedded lymph nodes sampled from 1984 to 1986 from 21 HIV-seropositive patients and seven HIV-negative patients. Eleven of the HIV-positive patients died within 78 months of biopsy time and 10 patients were alive on July 1, 1998. Double immunohistochemical staining procedures were developed to identify CD8(+) cells expressing CD45R0, granzyme B, and Ki-67. A stereological method was used to count the different cell types in the lymph nodes. There were no significant differences in the total cell (nucleated) and CD3(+) cell concentrations between the three groups. However, there were significantly higher concentrations of CD3(+)CD8(+), CD8(+)CD45R0(+), and CD8(+)Ki-67(+) lymphocytes in the HIV patients compared with the control group. Furthermore, there was a tendency for the HIV-deceased group to have lower levels of CD8(+)granzyme B(+) and CD8(+)Ki-67(+) lymphocyte concentrations compared with the HIV-alive group. Three HIV patients, who progressed to death within 49 months of biopsy time, were among the patients with the lowest concentrations of CD8(+)granzyme B(+) and CD8(+)Ki-67(+) lymphocytes. This finding allowed us to conclude that CD8(+) lymphocytes expressing high levels of CD45R0, granzyme B, and Ki-67 in lymph nodes of HIV patients are not related to increased mortality, whereas low concentrations of CD8(+) granzyme B(+) and CD8(+)Ki-67(+) lymphocytes may be associated with poor prognosis.

Adult↗
PubMed2001

Size of neocortical neurons in control subjects and in Alzheimer's disease.

The aim of the present study was to estimate mean neuronal volume and absolute size distributions of the neocortical neurons in brains from controls and AD patients using stereological methods based on unbiased principles to determine whether changes in absolute cell size are part of the neuropathological pattern of Alzheimer's disease. The neocortex of 8 patients with Alzheimer's disease (AD), mean age 81.1 (68-94) y was compared with 9 nondemented controls, mean age 80.9 (65-101) y. The brains came from Johns Hopkins University Hospital (JHUH) in Baltimore, USA, the Netherlands Brain Bank (NBB), and from a large brain repository in Denmark. The rotator method was used to obtain an estimate of cell volumes providing absolute size distributions of the volume of both cell perikaryon and cell nuclei. The geometric mean volume of cell nuclei in neocortical neurons was 328 microm3 (interindividual CV = 0.15) in the Alzheimer group compared with 277 microm3 (interindividual CV = 0.17) in controls which was a statistically significant increase (P = 0.049). The perikaryal volume was 1117 microm3 in the Alzheimer group compared with 999 microm3 in controls which was a nonsignificant difference (P = 0.20). There was a highly significant correlation between the nuclear and perikaryal volumes in all individuals. The average slope of the regression lines was significantly higher in the Alzheimer patients than in the controls, illustrating that nuclear hypertrophy was more pronounced in the largest neurons.

Aged↗
PubMed2000

Unchanged total number of neurons in motor cortex and neocortex in amyotrophic lateral sclerosis: a stereological study.

Modern stereological methods provide precise and reliable estimates of the number of neurons in specific regions of the brain. The total number of neurons in the neocortex and motor cortex from eight patients suffering from amyotrophic lateral sclerosis (ALS) and nine controls was estimated. No attempt was made to estimate subpopulations of neurons such as the number of giant pyramidal cells of Betz. No difference was found in the average number of neurons in neocortex in ALS and controls, 21.7 and 22.3 x 10(9), respectively, and 1.33 and 1.29 x 10(9) in motor cortex, respectively. In the light of our stereological measurements, results obtained from in-vivo proton magnetic resonance spectroscopy (1H-MRS), suggesting neuronal loss in ALS, may instead be due to neuronal metabolic dysfunction and/or alteration in the size or the volume fraction of the neurons.

Aged↗
PubMed2000

Stereological studies of the schizophrenic brain.

Stereological studies have contributed with important results to the understanding of brain abnormalities in schizophrenia. The data obtained from stereological studies of brains from schizophrenic patients, including studies of the thalamus, hippocampus, and cortex, are discussed and suggest a central role of the thalamic nuclei in the etiology of the disease. The basic stereological tools are presented and possible biases in quantification studies are discussed.

Brain↗
PubMed2000

Quantitation of regional cerebral blood flow corrected for partial volume effect using O-15 water and PET: I. Theory, error analysis, and stereologic comparison.

Limited spatial resolution of positron emission tomography (PET) can cause significant underestimation in the observed regional radioactivity concentration (so-called partial volume effect or PVE) resulting in systematic errors in estimating quantitative physiologic parameters. The authors have formulated four mathematical models that describe the dynamic behavior of a freely diffusible tracer (H215O) in a region of interest (ROI) incorporating estimates of regional tissue flow that are independent of PVE. The current study was intended to evaluate the feasibility of these models and to establish a methodology to accurately quantify regional cerebral blood flow (CBF) corrected for PVE in cortical gray matter regions. Five monkeys were studied with PET after IV H2(15)O two times (n = 3) or three times (n = 2) in a row. Two ROIs were drawn on structural magnetic resonance imaging (MRI) scans and projected onto the PET images in which regional CBF values and the water perfusable tissue fraction for the cortical gray matter tissue (hence the volume of gray matter) were estimated. After the PET study, the animals were killed and stereologic analysis was performed to assess the gray matter mass in the corresponding ROIs. Reproducibility of the estimated parameters and sensitivity to various error sources were also evaluated. All models tested in the current study yielded PVE-corrected regional CBF values (approximately 0.8 mL x min(-1) x g(-1) for models with a term for gray matter tissue and 0.5 mL x min(-1) x g(-1) for models with a term for a mixture of gray matter and white matter tissues). These values were greater than those obtained from ROIs tracing the gray matter cortex using conventional H2(15)O autoradiography (approximately 0.40 mL x min(-1) x g(-1)). Among the four models, configurations that included two parallel tissue compartments demonstrated better results with regards to the agreement of tissue time-activity curve and the Akaike's Information Criteria. Error sensitivity analysis suggested the model that fits three parameters of the gray matter CBF, the gray matter fraction, and the white matter fraction with fixed white matter CBF as the most reliable and suitable for estimating the gray matter CBF. Reproducibility with this model was 11% for estimating the gray matter CBF. The volume of gray matter tissue can also be estimated using this model and was significantly correlated with the results from the stereologic analysis. However, values were significantly smaller compared with those measured by stereologic analysis by 40%, which can not be explained by the methodologic errors. In conclusion, the partial volume correction was essential in quantitation of regional CBF. The method presented in this article provided the PVE-corrected regional CBF in the cortical gray matter tissue. This study also suggests that further studies are required before using MRI derived anatomic information for PVE correction in PET.

Animals↗
PubMed1999

Preferential loss of large neocortical neurons during HIV infection: a study of the size distribution of neocortical neurons in the human brain.

The infection with human immunodeficiency virus (HIV) is associated with a global and severe loss of neocortical neurons. However, there is limited knowledge concerning whether all neurons are equally susceptible to damage during HIV infection. Other studies have reported low vulnerability of small interneurons and high vulnerability of large motor neurons. Thus, it is natural to suggest that HIV infection, which causes damage to neurons in several ways, may predominantly affect large neurons in the neocortex. In this study we have used three unbiased stereological probes: Cavalieri's principle, the optical dissector and the rotator method, to obtain both total neocortical neuron number and their size distribution in formalin-fixed brains from six male acquired immunodeficiency syndrome (AIDS) patients and six male controls. The material is a selection of a large material choosing the youngest. The number of neurons in neocortex was reduced by 25% from 24.4 x 10(9) in controls to 18.3 x 10(9) in the AIDS patients; the reduction is similar to that of 27% found in the large material. In the normal size distribution of the neocortical neurons most neurons were smaller than 5000 micron3 and no sampled neurons were larger than 28,000 micron3. In addition, the absolute size distribution of neocortical neurons showed a significant decrease of the largest group of neurons by 50% (2p = 0.01) in the AIDS group, while there was no significant difference between controls and AIDS patients in the number of small neurons. The pattern of reduction in the number of large neocortical neurons was found in frontal, temporal, parietal as well as in occipital regions. This suggests that large neurons are more sensitive than small neurons to the destruction caused by the HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Unbiased estimation of total beta-cell number and mean beta-cell volume in rodent pancreas.

We describe a method for unbiased assumption-free estimation of the total number of beta-cells and the mean beta-cell volume in mouse and rat pancreas based on light microscopy. Such a method, which takes advantage of one of the most recent developments in stereology, the fractionator, has not previously been described. It relies on repeated fractionation of the tissue using systematic uniform random sampling combined with an unbiased counting principle. The method was applied to eight BALB/cBom male mice (56 days) and six Lewis/MOL male rats (47 days). In mice, the total number of beta-cells was 1.06 +/- 0.07 x 10(6) (mean +/- SEM) per pancreas with a mean beta-cell volume of 1280 +/- 17 microm3, while in rats the total beta-cell number was 2.76 +/- 0.42 x 10(6) per pancreas with a mean beta-cell volume of 1170 +/- 65 microm3. Furthermore, the results showed that in both species the biological variability in the total beta-cell volume is due to differences in the number of beta-cells rather than variability of the mean beta-cell volume. The method can be used to give a precise description of number and volume of beta-cells at different ages, and will make it possible to estimate the contributions of hyper/hypotrophia and hyper/hypoplasia to a given induced or spontaneous change in the total beta-cell mass.

Animals↗
PubMed1998

The use of a stereological method to estimate the volume of Schistosoma mansoni granulomas: the effect of zinc deficiency.

A quantitative, stereological method to assess the volume of Schistosoma mansoni granulomas is presented and its use demonstrated in a study of zinc-deficient animals. Twenty-six mice were divided into two groups, and given zinc-deficient or control food. After 4 weeks, the mean weight gain and thymus size were lower in the mice on the zinc-deficient diet. Eight mice in each group were then each infected with 60 S. mansoni cercariae and these mice were killed 12 weeks post-infection. There were then more eggs in the livers of the zinc-deficient mice than in those of the infected controls (7400/female worm v. 3300/female worm; P = 0.02), probably because of impaired intestinal egg expulsion and impaired resorption of eggs in the deficient mice. The median proportion of each liver occupied by granulomas was 0.11 among the zinc-deficient mice and 0.09 among the pair-fed, control mice (P = 0.08), and the median liver volumes were 1400 and 1450 microliters (P = 0.49), respectively. The computed median volume of all the granulomas in each liver was 160 microliters in zinc-deficient and 132 microliters in control mice (P = 0.32), while median granuloma volume per egg was 8.6 and 8.7 nl (P = 0.93), respectively. In contrast to conventional methods, modern stereological methods can provide estimates of granuloma volume or granuloma volume fractions without any assumptions about the size, shape, orientation or distribution of the granulomas in the liver.

Animals↗
PubMed1997

Neocortical neuron number in humans: effect of sex and age.

Modern stereological methods provide precise and reliable estimates of the number of neurons in specific regions of the brain. We decided to estimate the total number of neocortical neurons in the normal human brain and to analyze it with respect to the major macro- and microscopical structural components, to study the internal relationships of these components, and to quantitate the influence of important physiological variables on brain structure. The 94 brains reported represent a consecutive collection of brains from the general Danish population. The average numbers of neocortical neurons were 19 billion in female brains and 23 billion in male brains, a 16% difference. In our study, which covered the age range from 20 years to 90 years, approximately 10% of all neocortical neurons are lost over the life span in both sexes. Sex and age were the main determinants of the total number of neurons in the human neocortex, whereas body size, per se, had no influence on neuron number. Some of the data presented have been analyzed by using new mathematical designs. An equation predicting the total neocortical neuron number in any individual in which sex and age are known is provided.

Adult↗
PubMed1997

Total number and size distribution of motor neurons in the spinal cord of normal and EMC-virus infected mice--a stereological study.

The encephalomyocarditis virus of the diabetogenic M-strain (EMC-M) is known to cause diabetes in mice. The EMC-M virus has also been shown to cause paresis in some of the infected animals. The clinical features include an acute ascending predominantly motor paralysis, developing within days. This resembles acute idiopathic polyneuritis. The alpha motor neurons would be a possible target for the virus, so two parameters, the total number and the size distribution of motor neurons, were therefore selected for further investigation in 6 mice with neurological involvement and compared with 6 control mice. The optical fractionator method was applied for estimating the total number of motor neurons and the 3D size distribution was estimated using the rotator method in a vertical design. No difference was found in the total number of motor neurons and the size distributions were similar in the 2 groups. This design can be used as a model for the estimation of the total number of motor neurons and their size distribution in other experimental animal models.

Animals↗
PubMed1996

Muscarinic, N-methyl-D-aspartate (NMDA) and benzodiazepine receptor binding sites in cortical membranes from amyotrophic lateral sclerosis patients.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder causing marked pathology in the motoneuron system. The pathophysiology of the selective degeneration of motor neurons in the disease is as yet unknown, but evidence suggests that excitotoxic mechanisms might be involved. The present study was undertaken to determine whether defects in neurotransmitter receptors are involved in the disease, analyzing uniformly sampled specimens from neocortex and motorcortex. The binding to benzodiazepine, muscarinic cholinergic, and NMDA receptors in ALS brains was compared to that in control brains, using a single radioligand concentration of [3H]Ro 15-1788, [3H]QNB and [3H]MK-801. The benzodiazepine and the muscarinic cholinergic receptor binding was unaffected in any cortical region from the ALS subjects compared to controls. NMDA receptor binding labeled by [3H]MK-801 was significantly increased in several neocortical regions in the ALS group compared to the control group. Scatchard analysis of [3H]MK-801 binding in frontal cortex revealed a single binding site with an unaltered maximal binding capacity but an increased binding affinity of the site in the ALS group compared to the controls. The generalized alteration in the affinity of the binding site for [3H]MK-801 in the ALS cortex may indicate a modification of the NMDA receptor due to different sensitivity for endogenous modulators or to a different subunit composition of the NMDA receptor in ALS with altered functional properties. These findings may reflect a pathophysiological phenomenon in ALS.

Aged↗
PubMed1995

A stereological study of substantia nigra in young and old rhesus monkeys.

The number of pigmented and non-pigmented neurons in the substantia nigra (SN) of 10 old and six young female Macaca mulatta monkeys and in three old alpha male monkeys were estimated using new stereological cell counting methods. No systematic right-left differences were noted, nor were old animals different from young ones with respect to SN volume (68.9 mm3 vs. 62.8 mm3) or absolute number of nerve cells (320,000 vs. 312,000). However, the total number of pigmented neurons was about eight times higher in old animals compared with young ones (166,000 vs. 21,400) while the total number of non-pigmented SN neurons was less than half in old animals compared with young ones (139,000 vs. 285,000). These differences create difficulties in generalizing experimental results from the rhesus animal model to man. It seems unlikely that a simple correlation can be made between pigmented and tyrosine hydroxylase (TH) positive neurons in SN in monkeys. Instead of estimating the total number of pigmented and non-pigmented cells, only SN neurons positive for TH using immunohistochemical techniques might be used an indicator of the total number of dopaminergic neurons in SN in monkeys.

Age Factors↗
PubMed1995

Solutions to old problems in the quantitation of the central nervous system.

New stereological techniques, superior to conventional methods in quantitating macroscopic and microscopic structures in the central nervous system, have been developed within the last decade. By the use of a new counting method, the dissector, it is possible to obtain an efficient and yet precise estimate of the total number of neurons in any specific region, where a delineation of the region can be made, and the cells identified. The method has been applied to brains from patients with different neurological disorders. The latest effort has concentrated on the estimation of the total neocortical neuron number in brains from normal individuals of both sexes in the age from 20 to 90 years to see whether there are differences in total neocortical neuron numbers between males and females.

Adult↗
PubMed1994

Absolute number and size of pigmented locus coeruleus neurons in young and aged individuals.

Significant loss of noradrenergic neurons of the locus coeruleus in aging and Alzheimer's disease has been reported. The interpretation of these analyses, however, is problematic because of the model- and assumption-based nature of conventional sampling and estimation techniques. In the present study, unbiased stereological methods were used to estimate the total number and mean cell volume of pigmented neurons of the locus coeruleus in the brains of young and aged nondemented persons. No side-to-side differences are seen, and there is no change in pigmented cell number or size in the locus coeruleus of nondemented older persons as compared with that of young individuals. In light of previous studies that show severe locus coeruleus cell loss in Alzheimer's disease, these data support further critical investigations into the possible protective role of noradrenaline in normal cognitive functions and emphasize the importance of avoiding methodological bias in quantitative neuroanatomical studies.

Adult↗
PubMed1993

Total nerve cell number in neocortex in chronic schizophrenics and controls estimated using optical disectors.

The total number of neurons was estimated in eight brains from chronic schizophrenic men and compared with 16 gender- and age-matched controls. The average total neocortical nerve cell number was 22.12.10(9) in schizophrenics and 22.06.10(9) in controls. The estimate of total cell numbers can not demonstrate more subtle neuronal losses of specific cell types or cell loss in specific regions, but the result does not indicate that a major cell loss in the neocortex of schizophrenics is part of the disease. The sampling scheme was based on a uniform sampling design, the counting was performed using new stereological principles and the majority of the cerebral cortex was left intact providing the possibility for resampling and further analysis.

Adult↗
PubMed1993

Do alcoholics drink their neurons away?

Although it is commonly believed that chronic alcohol abuse results in loss of neocortical neurons, this assumption has not been properly tested. We used new stereological techniques to make a precise and unbiased estimate of the total number of neurons in the neocortex of brains obtained at necropsy from 11 chronic alcoholic men and 11 control men. The groups were matched with respect to age and height. Total mean neocortical neuron numbers in the two groups did not differ (alcoholics 23.4 x 10(9), controls 23.2 x 10(9)). Estimation of macroscopic brain volumes showed significant reductions in alcoholics compared with controls of the volume/weight ratios of white matter (11%, p = 0.013) and of archicortex (30%, p = 0.028). The volume of the ventricles in the alcoholic group was enlarged by 26%, but this was not statistically significant. There was no difference in the volumes of the neocortices. Our study confirms that chronic alcoholics lose white matter, and this could provide the basis for their functional impairment. However, the results also suggest that the observed brain damage in the alcoholic group is potentially reversible since preserved nerve-cell bodies might allow lost or malfunctioning axons to re-established and restored to function after prolonged abstinence and/or treatment. By contrast, lost neocortical neurons cannot be replaced.

Alcoholism↗