Glial and nerve cell changes in rats with porto-caval anastomosis

Summary Nuclear size and density were determined in brain regions with different glial—neurone composition in rats up to 35 weeks after porto-caval anastomosis.In the white matter, i.e. corpus callosum, both the total cell count and the percentage of astrocytes and oligodendrocytes were unchanged.In the corpus striatum, where the glial/neurone ratio is about 1, the number of nuclei registered as astrocytes increased, and after 35 weeks astrocytes comprised 29% of glial cells (compared with 15% in controls). However, the number of oligodendrogial nuclei decreased simultaneously, leaving the total glial number unchanged. In the animals with longest experimental period there was a 15% loss of neurones.In a region with higher glial/neurone ratio, i.e. the Purkinje cell layer, the neurones showed a similar reduction, whereas the number of Bergmann astrocyte nuclei increased less than striatal astrocytes.A small group of animals with pronounced signs of encephalopathy had a higher loss of neurones and, furthermore, the glial number in corpus striatum and callosum was reduced, due to loss of oligodendrocytes.Despite the use of perfusion fixation, the size of astrocyte nuclei increased, this was reversible, as only slight changes were seen after 35 weeks.A possible explanation of the increase in astrocyte nuclear count and decrease in oligodendroglial count could be that nuclei normally considered to the oligodendroglial are transformed into nuclei with morphological characteristics of astrocytes.     

GLIAL AND NEURONAL ALTERATIONS IN THE CORPUS STRIATUM OF RATS WITH CCl4-INDUCED LIVER DISEASE

The density and size of astrocyte-, oligodendrocyte- and neurone nuclei in corpus striatum were determined in rats with CCl₄-induced liver encephalopathy by means of an electronic image analyzer. After 8 weeks of CCl₄-administration, the astrocyte number had nearly doubled, and astrocytes with increased nuclear size appeared. After 20 weeks, a reduction (appr. 25 per cent) was found in the number of nerve cells and oligodendrocytes. The total number of glial cells, however, was unchanged during the experiment; this demonstrates the need of performing differential counts when evaluating gliosis. Probably, a part of the increase in the number of astrocytes was due to a transformation from precursor cells, usually classified as oligodendrocytes. The increased number and size of astrocyte nuclei are probably connected with an enhanced astrocyte metabolic capacity due to alterations in the ammonia and amino acid metabolism.     

MORPHOMETRIC STUDIES OF RAT GLIAL CELL ULTRASTRUCTURE AFTER UREASE-INDUCED HYPERAMMONAEMIA

The ultrastructure of astrocytes and oligodendrocytes was investigated in hyperammonaemic rats injected daily with urease for 4 days. Glial cells were randomly photographed and magnified x28 000. Cell and nuclear sizes were estimated by planimetry and mitochondrial size and density were measured by image analysis. After 4 days of hyperammonaemia the astrocyte cytoplasmic area was increased by 46%. Mitochondrial area was increased by 20%, but after correction for cytoplasmic oedema the number and size of mitochondria were not significantly increased. The nuclear and cytoplasmic areas of oligodendrocytes were unchanged. The mitochondria of oligodendrocytes were small in the hyperammonaemic group and so was their percentage area to cytoplasmic area, but their numbers were unchanged. It was concluded that hyperammonaemia induces astrocyte oedema and increases the astrocyte mitochondrial content. These findings support the assumption that the astrocytes are the active cells in the brain metabolism of ammonia. The decrease in oligodendrocyte mitochondrial content could be considered a point against an active function of oligodendrocyte mitochondria in ammonia metabolism in hyperammonaemia.     

ASTROCYTE MITOSES AND ALZHEIMER TYPE I AND II ASTROCYTES IN ANOXIC ENCEPHALOPATHY

Astrocyte mitoses and Alzheimer type I and I1 astrocytes in anoxic en-cephalopathy
Numerous astrocyte mitoses, arrested in metaphase, were found in a case of anoxic encephalopathy. The number of chromosomes was not excessive, but in most the mitotic spindles appeared absent. Many Alzheimer type I and II astrocytes were also seen, together with a few cells containing both micronuclei and free chromosomes. The occurrence of such transitional forms supports the hypothesis that astrocyte mitoses arrested in metaphase constitute an intermediate stage in the formation of the tetraploid Alzheimer type I astrocytes from cells of Alzheimer type II.     

Trauma-induced proliferation of astrocytes in the brains of young and aged rats

The time-course and magnitude of astrocyte proliferation following neural trauma was evaluated in young adult (3 months) and mid-aged (16-19 months) male Fischer 344 rats. One to 4 days after a needle wound was made through the cortex and the hippocampus, rats received three intraperitoneal injections of 3H-thymidine at 8 hour intervals and were sacrificed 1 hour after the last injection. For astrocyte quantification, 3H-thymidine autoradiography was combined with immunohistochemical staining for glial fibrillary acidic protein followed by semithin sectioning. In areas of the cortex and hippocampus adjacent to the wound, astrocytes were categorized as unlabeled or labeled with silver grains over the nuclei. Labeling index and numerical density of astrocytes were determined using stereological methods. The results showed that in both young and older rats, astrocyte proliferation is an early glial response to neural trauma, occurring during the first 4 postlesion days and contributing to an increase in astrocyte population. Regional differences in labeling index and numerical density suggest heterogeneity in the proliferative capacity of astrocyte subpopulations in the rat brain. Compared with young animals, older rats demonstrated greater labeling in the cortex but not in the hippocampus. Thus, aging is associated with region-specific increase in astrocyte reactivity to trauma possibly due to increased availability of mitogens or enhanced sensitivity of astrocytes to mitogenic signals.     

Astrocyte decrease in the subgenual cingulate and callosal genu in schizophrenia

Decreases in glial cell density and in GFAP mRNA in the anterior cingulate cortex have been reported in schizophrenia, bipolar disorder and major depressive disorder. Our study examines astrocyte and oligodendrocyte density in the white and grey matter of the subgenual cingulate cortex, and at the midline of the genu of the corpus callosum, in schizophrenia, bipolar disorder, depression and normal control cases. Serial coronal sections were stained with H and E for anatomical guidance, cresyl haematoxylin for oligodendrocyte identification and GFAP immunohistochemistry for astrocyte identification. Oligodendrocyte and astrocyte density was measured using systematic anatomical distinctions and randomised counting methods. A significant decrease in astrocyte density was observed in schizophrenia compared with normal controls in the cingulate grey matter, cingulate white matter and the midline of the corpus callosum (p = 0.025). Bipolar disorder and depression cases showed no significant changes in astrocyte density. Oligodendrocytes did not show any changes between diagnostic groups. In subgenual cingulate cortex, the ratio of oligodendrocytes to astrocytes was decreased between the controls and the three disease groups, suggesting a specific glial cell type specific change in schizophrenia.     

Morphometry of astrocyte and oligodendrocyte ultrastructure after portocaval anastomosis in the rat

Summary The ultrastructure of astrocytes and oligodendrocytes was investigated in rats 10 days, 30 days, and 10 weeks after portocaval anastomosis (PCA). Cell and nuclear sizes were measured by planimetry on randomly sampled cells magnified×24,000. The volume fractions of mitochondria, glia fibrils, and lipofuscin granules were measured in astrocytes by electronic image analysis. The mitochondrial profile area distribution and oligodendrocyte mitochondrial content were likewise estimated. All PCA animals had an increased astrocyte cell and cytoplasmic area, and after correction for cytoplasmic edema all groups had an enhanced mitochondrial fraction and mitochondrial number. The mitochondrial sizes were increased in all PCA groups. The mitochondrial profile area distribution curves did not suggest more than one group of mitochondria. All PCA groups had increased fractions of lipofuscin granules and glia fibrils. The oligodendrocytes had a slight fall in cell, nuclear, and cytoplasmic area after 30 days of shunting, and the mitochondrial fraction was diminished. After 10 weeks of PCA, all changes were reversed to normal values. It is concluded that the astrocytes are the active cells in the brain metabolism of ammonium. The oligodendrocytes seem to be dependent on neuronal integrity and do not contribute to the brain ammonium metabolism. The increase in astrocyte lipofuscin granules content may be explained by a beginning neuronal loss.Abbreviation (PCA) Portocaval anastomosis     

Diversification of glial lineages: a novel method to clone brain cells in vitro on nitrocellulose substratum.

We have developed a novel in vitro method to analyze the diversification of glial cells during development. The primary advantage of the approach is that glial lineages are formed in discrete clones on a nitrocellulose substratum where the relationship of the progeny is strictly defined. This method facilitates the comparison of a large complement of astrocyte and oligodendrocyte lineages under controlled conditions. Clones were formed by plating a brain dissociate on nitrocellulose at very low density (5,000-40,000 cells/154 mm2). However, growth depended on diffusible factors produced by brain cells growing under the nitrocellulose support at high density (feeder layer). The cloning efficiency of cells from mouse forebrain (P0) was 1-3%. This means we can detect 100,000 to 300,000 clonal progenitors in the dissociate (10(7) cells per forebrain) using the clonal culture technique. Cell phenotypes were determined by immunocytochemical staining with anti-glial fibrillary acidic protein (GFAP) to label astrocytes and anti-galactocerebroside (GC) and anti-myelin basic protein (MBP) to label oligodendrocytes. There was a remarkable diversity of glia represented in different lineages. The number of astrocyte clones was greater than the number of oligodendrocyte clones but combined their total was 90%. Clone sizes were distributed over a wide range, which indicated that growth rates varied. Clones appeared compact or dispersed but astrocyte clones exhibited three different morphologies-fibroblast-like, stellate, and elongated. Oligodendrocytes had different morphologies distinct from astrocytes. Although there were different glial lineages the cells in most clones were homogeneous, indicating the progeny had the same fate. However, a small number of the clones, approximately 2%, were heterogeneous and contained both astrocytes and oligodendrocytes. The application of this technique to glial lineages demonstrates that intrinsic factors have a role in determining cell fate since different clones formed under the same external conditions. Finally, these results are consistent with the existence of multiple glial progenitors or the continued presence of multipotential progenitors at the time of birth.     

Differential rearing effects on rat visual cortex synapses.: III. Neuronal and glial nuclei, boutons, dendrites, and capillaries

Morphological measures of neurons, astrocytes, oligodendrocytes, presynaptic boutons, dendrites and capillaries were examined in the upper 4 layers of occipital cortex in rats reared for 30 days postweaning in complex (EC), social (SC) or individual cage (IC) environments. EC rats had a lower numerical density of neuronal nuclei with a comparable volume fraction to SC and IC rats. The volume fraction of astrocyte and oligodendrocyte nuclei was significantly greater for EC rats than IC littermates, and IC rats also had more synapses and neurons/micron3 of glial nuclei. Environmental groups did not differ in the numerical density of presynaptic boutons but the number of boutons per neuron was greater in EC than in IC or SC rats. This result parallels the findings that EC rats have more synapses per neuron than IC rats. Electron microscopic estimates of dendritic volume fraction confirmed estimates from Golgi-impregnated neurons that there is more dendrite per neuron in the occipital cortex of EC rats than IC or SC rats. EC rats also had a larger capillary volume than SC or IC and these capillaries were closer together and had fewer synapses/micron3 of capillary in ECs. Another indicator of metabolic activity, mitochondria volume per neuron, gave similar results with ECs having a greater volume than ICs and SCs intermediate. These results indicate that not only are there more synapses per neuron in the visual cortex of rats from more complex environments but also that the brain appears to adjust to the metabolic requirements of its synapses or neurons, in terms of vascular, mitochondrial and glial support.     

Size and density of glial and neuronal cells within the cerebral neocortex of various insectivorian species

Morphometric measurements were done on frontal sections through the somatosensory neocortex of various insectivorian species. All measured parameters varied with the size of animals; there was a better correlation with the ventriculartopial brain wall thickness than with the brain weight. The following rules were evaluated: with increasing brain wall thickness, 1) lamina I becomes thinner; 2) the nuclei of both neuronal and glial cells become larger; 3) the volume density of neuronal cells decreases greatly; 4) the volume density of glial cells increases slightly; and 5) as a result, the glia:neuron index increases markedly. There was no equal number of neurons under a unit surface area in the cortices of any species studied. Developmental processes that might account for the above-mentioned rules are discussed in this report.     

Glial Cell Lineages in the Rat Cerebral Cortex

I have traced the fates of glial cell progenitors in the rat cerebral cortex marked with a recombinant retrovirus throughout most of the period of corticogenesis, from embryonic (E) day 14 to postnatal (P) day 14. Discrete clusters of clonally related glia were examined in serially cut sections, and their phenotypes identified using reliable light and electron microscopic criteria. Analysis of a large number of clones marked with retrovirus at various stages of embryonic life contained, with very few exceptions, either all astrocytes or all oligodendrocytes. This observation suggests that the ventricular zone contains separate progenitor cells for the two glial cell types. Oligodendrocyte clones were rarely seen in the cortices injected with retrovirus at the early stages of corticogenesis (E14-E16), suggesting that there is a very small number of oligodendrocyte progenitors in the ventricular zone at these early stages. Their frequency increased significantly at later embryonic ages. At these later stages, ventricular zone cells also give rise to progenitor cells that make up the subventricular zone in early postnatal life. Injections of retrovirus in this proliferative zone shortly after birth resulted in the generation of labeled astrocyte and oligodendrocyte clones in the cortical gray and white matter, with the astrocyte clones being in the majority. Injections at increasingly later stages resulted in the presence, predominantly in the white matter of both hemispheres and in the corpus callosum, of progressively more oligodendrocyte clones and fewer astrocyte clones. Injections at P14 generated only oligodendrocyte clones in the white matter of both hemispheres. A small number of clusters (<10%) generated after subventricular zone injections contained both astrocytes and oligodendrocytes, suggesting that single subventricular zone cells can differentiate into both glial cell types.     

Progesterone attenuates astro- and microgliosis and enhances oligodendrocyte differentiation following spinal cord injury

Reactive gliosis, demyelination and proliferation of NG2+ oligodendrocyte precursor cells (OPC) are common responses to spinal cord injury (SCI). We previously reported that short-term progesterone treatment stimulates OPC proliferation whereas chronic treatment enhances OPC differentiation after SCI. Presently, we further studied the proliferation/differentiation of glial cells involved in inflammation and remyelination in male rats with SCI subjected to acute (3 days) or chronic (21 days) progesterone administration. Rats received several pulses of bromodeoyuridine (BrdU) 48 and 72 h post-SCI, and sacrificed 3 or 21 days post-SCI. Double colocalization of BrdU and specific cell markers showed that 3 days of SCI induced a strong proliferation of S100β+ astrocytes, OX-42+ microglia/macrophages and NG2+ cells. At this stage, the intense GFAP+ astrogliosis was BrdU negative. Twenty one days of SCI enhanced maturation of S100β+ cells into GFAP+ astrocytes, but decreased the number of CC1+ oligodendrocytes. Progesterone treatment inhibited astrocyte and microglia /macrophage proliferation and activation in the 3-day SCI group, and inhibited activation in the 21-day SCI group. BrdU/NG2 double labeled cells were increased by progesterone at 3 days, indicating a proliferation stimulus, but decreased them at 21 days. However, progesterone-enhancement of CC1+/BrdU+ oligodendrocyte density, suggest differentiation of OPC into mature oligondendrocytes. We conclude that progesterone effects after SCI involves: a) inhibition of astrocyte proliferation and activation; b) anti-inflammatory effects by preventing microglial activation and proliferation, and c) early proliferation of NG2+ progenitors and late remyelination. Thus, progesterone behaves as a glioactive factor favoring remyelination and inhibiting reactive gliosis.     

Fibroblast growth factor‐9 inhibits astrocyte differentiation of adult mouse neural progenitor cells

Fibroblast growth factor‐9 (FGF9) is expressed in the CNS and is reported to be a mitogen for glial cells, to promote neuronal survival, and to retard oligodendrocyte differentiation. Here we examined the effects of FGF9 on the differentiation, survival, and proliferation of adult neural progenitor cells derived from the adult mouse subventricular zone. FGF9 by itself induced neurosphere proliferation, but its effects were modest compared with those of epidermal growth factor and FGF2. When neurospheres were dissociated and plated for differentiation, FGF9 increased total cell number over time in a dose‐dependent manner. Ki67 immunostaining and bromodeoxyuridine incorporation indicated that this was at least partially due to the continued presence of proliferative nestin‐positive neural progenitor cells and βIII tubulin‐positive neuronal precursors. FGF9 also promoted cell survival as indicated by a decreased number of TUNEL‐positive cells over time. Assessment of differentiation showed that FGF9 increased neuron generation that reflected the increase in total cell number; however, the percentage of progenitor cells differentiating into neurons was slightly decreased. FGF9 had a modest effect on oligodendrocyte generation, although it appeared to slow the maturation of oligodenrocytes at higher concentrations. The most marked effect on differentiation was an almost total lack of glial fibrillary acidic protein (GFAP)‐positive astrocytes up to 7 days following FGF9 addition, indicating that astrocyte differentiation was strongly inhibited. Total inhibition required prolonged treatment, although a 1‐hr pulse was sufficient for partial inhibition, and bone morphogenic protein‐4 could partially overcome the FGF9 inhibition of astrocyte differentiation. FGF9 therefore has multiple effects on adult neural precursor cell function, enhancing neuronal precursor proliferation and specifically inhibiting GFAP expression. © 2009 Wiley‐Liss, Inc.     

A morphological study of glial cells in the hypoglossal nucleus of the cat during nerve regeneration

The cat hypoglossal nerve and nucleus have been used as a model for the study of the occurrence and time course of modifications in the size and composition of the perineuronal glial cell population as they relate to cytological changes in the nerve cell body and the initiation and progress of axon regeneration. Animals were killed at 2, 5, 10, 20, 35, 65, and 115 days after crush injury to the hypoglossal nerve. At 5 days after surgery, growth cones and regenerating unmyelinated axons were present at the lesion site, but no conspicuous changes were apparent in the nerve cell bodies. At 10 days after surgery, the granular endoplasmic reticulum was disaggregated and depleted. The elongation phase appeared to be completed at 20 days, as judged by the bilateral retrograde labeling of the hypoglossal nuclei with horseradish peroxidase. By 35 days, the cytoarchitecture of the nerve cell bodies and maturation of axons, as determined by a comparison of the relative frequency distribution of cross sectional areas proximal and distal to the lesion, were completely restored. Comparative quantitative light microscopic examination of the hypoglossal nuclei of intact and experimental animals failed to reveal any statistically significant differences in the total number of glial cells, number of glial cells/unit area of neuropil, or relative proportions of glial cell types at any of the postoperative time intervals. Moreover, electron microscopic quantitation of the microglial cell population did not reveal any significant alterations in the number, density, location, or morphology of these cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Astrocytes in the hypoglossal nuclei of sudden infant death syndrome (SIDS) infants: a quantitative study

It has been suggested that brain stem hypoxia or ischaemia underlies the sudden infant death syndrome (SIDS), but previous reports of astrocytosis in the brain stems of SIDS infants have been contradictory. A volumetric quantitative technique was, therefore, developed to compare astrocyte numbers and sizes in the hypoglossal nuclei of SIDS and control infancts. In 12 SIDS and eight control infants, serial sagittal sections were taken through the hypoglossal nucleus and every tenth section through the h ypoglossal nucleus and every tenth section was stained for glial fibrillary acidic protein. Astrocytes were counted in the central 4% of a grid stepped throughout the hypoglossal nucleus, and the heights of 100 astrocyte nuclei were measured with a mocrocator. Astrocyte number, corrected for section thickness and nuclear height, was divided by the volume of the hypoglossal nucleus to calculate astrocyte density. Numbers of astrocytes did not differ significantly between SIDS (mean number 44 729, SD 12 096) and control (mean number 46 562, SD 11 060) infants. Astorcyte nuclear height did not differ significantly between groups (SIDS: mean height 3.98μm, SD 0.31). Astrocyte density was similar in SIDS (mean density 24 378 astrocyte/mm³, SD 6155) and control (mean density 23 978 astrocytes/mm³, SD 4031) infants. No quantitative evidence of astrocytosis was found in the hypoglossal nuclei of SIDS infants. This implies that SIDS infants die without previous episodes of hypoxia/ischaemia severe enough to damage the brain stem.     

Development and differentiation of glial precursor cells in the rat cerebellum

The development and differentiation of bipotential glial precursor cells has been studied extensively in tissue culture, but little is known about the distribution and fate of these cells within intact animals. To analyze the development of glial progenitor cells in the developing rat cerebellum, we utilized immunofluorescent, immunocytochemical, and autoradiographic techniques. Glial progenitor cells were identified with antibodies against the NG2 chondroitin-sulfate proteoglycan, a cell-surface antigen of 02A progenitor cells in vitro, and the distribution of this marker antigen was compared to that of marker antigens that identify immature astrocytes, mature astrocytes, oligodendrocyte precursors, and mature oligodendrocytes. Cells expressing the NG2 antigen appeared in the cerebellum during the last 3-4 days of embryonic life. Over the first 10 days of postnatal life, the NG2-labeled cells incorporated ³H-thymidine into their nuclei and their total number increased. At all ages examined, the NG2-labeled cells did not contain either vimentin-like or glial fibrillary acidic protein (GFAP)-like immunoreactivity, suggesting that they do not develop along an astrocytic pathway. NG2-labeled cells of embryonic animals expressed G_D3 ganglioside antigens, a property of oligodendrocyte precursors, whereas NG2-positive cells of postnatal animals did not express G_D3 immunoreactivity. Nevertheless, the NG2-labeled cells of the nascent white matter expressed oligodendrocyte-specific marker antigens. Cells lyingoutside of the white matter continued to express the NG2 antigen. In adult animals, the NG2-labeled cells incorporated ³H-thymidine. Glial cells isolated from adult animals and grown in tissue culture express the NG2 antigen and display the phenotypic plasticity characteristic of 02A progenitor cells. These findings demonstrate that a population of glial progenitor cells is extensive within both young and adult animals.     

Effects of postnatal ethanol exposure on glial cell development in rat optic nerve

This study morphologically evaluated the effects of limited postnatal alcohol exposure on the development of glial cells in the rat optic nerve. Rat pups were artificially reared on Days 5-18 with a supplemented milk diet fed via a chronic gastrostomy tube. Experimental animals received 4% ethanol in their diet on Days 5-9, otherwise the experimental and control animals received identical diets. Optic nerve tissues were prepared for electron microscopy on Days 10, 16, 22, 29, and 90. There were fewer glial cells per cross section and the cross-sectional areas of optic nerves were smaller on Days 10 and 16 in the ethanol-exposed animals. The alcohol caused a delay in the maturation of oligodendroglial cells at 10 days as evidenced by decreases in the total number of oligodendroglia present and by a delay in the appearance of immature cells within the oligodendroglial lineage. All of these effects were compensated for at later ages. There was no evidence of alcohol-induced degeneration of glial cells or their organelles. Thus, postnatal alcohol exposure causes a delay in oligodendrocyte maturation but appears to have no long-term effects on the glial cell population of rat optic nerve.     

Culture and cryopreservation of adult human oligodendrocytes and astrocytes

Summary Human adult oligodendrocytes were bulkisolated from the brains obtained at autopsy by the Percoll density gradient method and cultured in vitro for 2–28 days. Cultured human oligodendrocytes were then scraped from the dishes or coverslips, frozen at –70°C in the presence of 10% dimethyl sulfoxide as a cryoprotectorant, and then stored in liquid nitrogen tank.After the fast thawing, 55%–70% of human oligodendrocytes plus astrocytes were found to survive in the culture. Identification of cell types was established by using antibodies directed against galactocerebroside (oligodendrocyte) and glial fibrillary acidic protein (astrocyte).Supported by grant no. MA 7700 from the Medical Research Council of Canada and grant no. 72 (83-1) from the British Columbia Health Care Research Foundation     

Glial levels determine severity of white matter disease in Alzheimer's disease: a neuropathological study of glial changes

The morphological components of cerebral white matter disease (WMD) were studied in 17 cases of clinically diagnosed dementia and neuropathologically verified Alzheimer's disease (AD) with concomitant WMD. The distribution of grey and white matter changes was evaluated and overall as well as regional severity was graded. Total glial numbers in frontal white matter were counted using a light microscope. Oligodendrocyte and astrocyte quantities as well as astrocytic reactivity were assessed from frontal and parietal lobe white matter using a computer assisted morphometric method. The AD-WMD group was compared with 10 nondemented age-matched controls. Astrocyte/oligodendrocyte ratio (AOR) was calculated, total glial counts and AOR were compared with severity of WMD, and Alzheimer encephalopathy grade was subjectively assessed. Astrocytic numbers, AOR and astrocytic reactivity proved to be significantly higher in the demented group, whereas oligodendrocytic and total glial counts were significantly lower. Furthermore, AOR proved to be positively correlated with severity of WMD, whereas no association was found with Alzheimer encephalopathy. We conclude that WMD in dementia, for example, of the type seen in AD, can easily be detected, measured and graded quantitatively, with AOR being a significant indicator of the severity of changes. This could serve as a tool for differentiating white matter pathologies in dementia and may be the basis for recognition of the mildest white matter changes with new imaging methods, and enable potential clinical intervention.     

Abnormal expression of the proliferating cell nuclear antigen (PCNA) in the spinal cord of the hypomyelinated Jimpy mutant mice

In the present study, assessment of the expression of the proliferating cell nuclear antigen (PCNA), a nuclear acidic protein necessary for DNA replication that is expressed through the cell cycle, was used to investigate the proliferative capability of glial cells in the hypomyelinated Jimpy mutant mice. Spinal cords from 10–12 and 20–22 day Jimpy and normal animals were used for quantitative microscopic image analysis. Simultaneous demonstration of cycling cells and oligodendroglia, astroglia or microglia was achieved through the sequential combination of PCNA immunostaining and selective markers for these glial cells. Our results revealed that the density of PCNA-positive cells was higher in Jimpy than in normal spinal cords, this difference being more pronounced at 20–22 days than at 10–12 days and more so in white than in gray matter. In addition, Jimpy glial cells exhibited an abnormal PCNA expression, as demonstrated by quantification of the intensity of nuclear immunostaining. In comparison to normal animals, the percentage of PCNA-positive cells showing intensely stained nuclei was higher in Jimpy. About 50% of PCNA-positive cells in the Jimpy white matter were identified as cells from the oligodendrocyte line, 30% were microglial cells and 20% were astrocytes. The expression of PCNA in relation to the proliferative capability and possible cell cycle abnormalities of the different glial cell types in Jimpy is discussed.