Radioautographic investigation of gliogenesis in the corpus callosum of young rats II. Origin of microglial cells

Microglial cells are absent from the corpus callosum of newborn rats. In the hope of finding out when and how microglial cells appear with age, ³H-thymidine was given intraperitoneally as single or three shortly spaced injections to 5-day-old rats weighing about 15 g; and these animals were sacrificed at various time intervals from 2 hours to 35 days later. Pieces of corpus callosum were taken near the superior lateral angle of the lateral ventricles; and semithin sections were radioautographed and stained with toluidine blue. The corpus callosum of 5-day-old rats is composed of loosely arranged unmyelinated fibers and scattered cells. Among these cells, microglia are rare; there are a few astrocytes, many immature glial cells, rare pericytes, and 6-7% of phagocytic “ameboid cells” consisting of a few monocytes and many macrophages. In the animals sacrificed two hours after ³H-thymidine administration, label is present only in immature cells and “ameboid cells.” As time elapses and the fibers of corpus callosum become myelinated, oligodendrocytes and, later, microglial cells appear. At the age of 12 days, microglial cells are present in substantial number; and by 19 days, the number doubles to reach a plateau. Many of the new microglial cells are labeled, e.g., 78.1% in 12-day-old animals (7 days after ³H-thymidine administration). The labeled microglial cells must have come from the transformation of cells that acquired label early, that is, from the immature cells or the “ameboid cells.” The height of the peaks of labeling – 59.8% at nine days for immature cells and 77.8% at 12 days for “ameboid cells” – points to the latter as precursors of the highly labeled microglial cells. Furthermore, the “ameboid cells” disappear as microglial cells appear and there are transitional elements between these two cell types. Cell counts suggest that about a third of the “ameboid cells” transform into microglial cells, while the others degenerate and die. Thus, the microglial cells which appear in the corpus callosum during the first three weeks of life result from transformation of the “ameboid cells” – a group of macrophages showing various stages of transition from monocytes. As for the occasional microglial cell appearing after the third week or in the adult, they presumably come directly from monocytes. In either case, monocytes would be the intial precursors.     

Vault immunofluorescence in the brain: new insights regarding the origin of microglia

The developmental appearance of ameboid and ramified microglia in the rat brain has been examined by immunofluorescent localization of vaults, recently described ribonucleoprotein particles (Kedersha and Rome, 1986a). Vaults are distinct, multiarched structures of unknown function expressed by higher and lower eukaryotic species. Although vaults have been detected in all mammalian cells examined to date, they are highly enriched in macrophages. In the brain, vault antisera is highly specific for both ameboid and ramified microglia. The developmental profile of vault immunoreactivity in rat brain slices suggests that microglia enter the brain at 2 locations, with different time scales for each. The first migration, which begins before embryonic day 15 and subsides between postnatal days 7 and 14, was identified by vault immunoreactivity and Bandeiraea simplicifolia B4-isolectin (a microglia marker) staining. The cells appear to enter from blood vessels and display a ramified morphology as soon as they are detected in the brain. The second microglial migration occurs in the first postnatal week, when ameboid microglia appear in the corpus callosum and other large fiber tracts. Ameboid microglia appear to differentiate into ramified microglia between postnatal days 4 and 14. Vault immunoreactivity, as a very early microglial marker, provides new insight regarding the much-debated origin of the ramified microglia. It is quite clear that ameboid cells are not the sole source of ramified microglia because ramified cells can be detected before the influx of ameboid microglia. Colocalization studies with monocyte/macrophage markers ED1 and OX42 demonstrate that both ramified and ameboid microglia originate from monocyte lineage.     

Carbonic anhydrase II in microglia in forebrains of neonatal rats

In the brains of adult rodents carbonic anhydrase II (CA) immunoreactivity has been observed in the choroid plexus and in oligodendrocytes, astrocytes, and myelin. Localization and functions of CA in the neonatal brain, however, have been controversial. One issue is whether the CAII-immunopositive round and ameboid cells in the corpus callosum and cingulum in the rat CNS during the first postnatal week are oligodendrocytes or microglia. Colocalization of C AH with the microglial antigen, EDI, and the microglia-specific isolectin, BSI-B4, suggested that most (approx. 60%) of the CAII-positive round and ameboid cells in rat brain during the first postnatal week were, indeed, macrophages and microglia. During that initial week, some CAII-positive protoplasmic astrocytes (approx. 40%) were observed as well. At the end of the first postnatal week smooth-surfaced CAII-positive cells began to appear in the corpus callosum. Those cells also bound MAbO4, a marker for the oligodendrocyte cell line. We conclude that during the first postnatal week most of the CAII-positive cells are macrophages and microglia, and that some are protoplasmic astrocytes. During the second postnatal week CAII-positive cells in the oligodendrocyte lineage become apparent, and by the end of that week there are few CAII-positive microglia. Confocal microscopy suggests that in brains of three-day-old rats the ameboid microglia are associated with nerve fibers, where they may perform phagocytosis of axons, directional guidance of axons, or disinhibition of axonal growth.     

The distribution of microglia and cell death in the fetal rat forebrain

The appearance and distribution of microglia in the fetal and early postnatal rat forebrain have been examined with the aid of a peroxidase-conjugated lectin derived from Griffonia simplicifolia. This distribution has in turn been correlated with that of pyknotic figures in the same Nissl-counterstained sections. Round and ameboid microglia may be recognised in the fetal forebrain as early as E11, at a stage when the telencephalic vesicles are beginning to develop. By E13, concentrations of round microglia are found at the dorsal and rostral limits of the diencephalic vesicle (dorsal lamina terminalis) and in the adjacent medial walls of the telencephalic vesicles. These cells are often seen to have pyknotic material within their cytoplasm. Microglia remain concentrated in this region until E17. From E15, blood vessels and round and ameboid microglia concentrate in the region of the future hippocampus and appear to be drawn into the hippocampal fissure as the cortical plate folds to form Ammon's horn. At E15, ameboid microglia are also concentrated in the developing fornix, which first becomes apparent at this age. Microglia remain concentrated in the septomesocortical junction area, and may contribute to the concentrations of microglia previously reported in the region of the developing corpus callosum and cavum septi pellucidi. Microglia probably concentrate in the dorsal lamina terminalis and medial telencephalon at E13 in response to the cell death noted in this region, but other concentrations of microglia in the forebrain are not accompanied by similar aggregations of cell death. These findings indicate that the junction of the telencephalon and rostral diencephalon attracts concentrations of microglia from E13 throughout fetal and early postnatal life, coincident with the infolding of the hippocampus (E13-E19) and several days before the development of the corpus callosum (from E19 onwards).     

Brain mechanisms and feeding behavior in the pigeon (Columba livia). II. Analysis of feeding behavior deficits after lesions of quinto-frontal structures

Strong labeling of the cells in the subependymal layer was produced by stereotaxic injection of 5 μCi of ³H-thymidine into the left lateral ventricle of the brain of one and a quarter month old rats weighing about 100 gm. These animals were sacrificed by glutaraldehyde perfusion from two hours to 21 days later. Blocks of corpus callosum with adjacent subependymal and ependymal layers were excised from the injected and non-injected sides, and embedded in Epon; 0.5 μ thick sections were radioautographed and stained with toluidine blue. In the subependymal region, on both injected and non-injected sides, there was an immediate uptake of label by many cells followed by an increase and later a decrease in the percent cells labeled. In the corpus callosum while at first the percent labeling of glial cells was rather low, it did increase slowly with time and, after seven days, exceeded that in the subependymal region. These results were interpreted as indicating that cells arising in the subependymal layer had migrated into the corpus callosum. Up to four days after injection, most of the label in corpus callosum was present in immature-looking cells resembling the cells of the subependymal layer and referred to as free subependymal cells. With time, the percent labeling decreased in these cells while increasing in some of the glial cells. A labeling peak was observed for light oligodendrocytes at four to seven days and for dark oligodendrocytes at 21 days, whereas labeling of medium shade oligodendrocytes occurred at intermediate times. The succession of labeling peaks indicated a sequence of development from free subependymal cells through light and medium shade to dark oligodendrocytes. Few astrocytes carried label at any time; those which did seemed to have arisen from the transformation of labeled free subependymal cells. Microglia were unlabeled at two hours, but their percent labeling was high at 4–14 days. While the labeling of other glial cells reflected their physiological behavior, the labeling of microglia was a consequence of the trauma produced by the injection 0f tracer into the ventricle. In conclusion, cells coming from the subependymal layer appear to migrate into the corpus callosum where, in 100 gm rats, many of them transform into oligodendrocytes and a few into astrocytes.     

Sex and environmental influences on the size and ultrastructure of the rat corpus callosum

A contested report of sex differences in the size of the splenium of the corpus callosum in humans prompted the present examination of the corpus callosum in the rat. We have previously found that sex differences can vary with the rearing environment. Consequently, male and female rats were raised from weaning to 55 days of age in either a complex or an isolated environment. There were no sex differences in the size of the corpus callosum in sagittal cross section in these rats; however, rats of both sexes had a larger posterior third of the corpus callosum if they were raised in the complex environment. Because the corpus callosum continues to grow in size past 55 days of age, we examined socially housed rats at 113 days and again found no sex differences. The splenium was examined with electron microscopy in complex and isolation reared rats at 55 days of age. The ultrastructural analysis revealed differences at were not apparent from gross size measures. Females had more unmyelinated axons regardless of environment, and females from the complex environment had more myelinated axons than comparably housed males. In contrast, males in the complex environment had larger myelinated axons than females. Rats of both sexes from the complex environment had larger and more unmyelinated axons than isolated rats. In addition in myelinated axons, plasticity in the females occurred through changes in axon number and in males, through axon size. Thus sex differences exist in axonal number and size and the environment influences these differences.     

Migration and fate of newly born cells after focal cortical ischemia in adult rats

Neural cell migration and differentiation may participate in neural repair after adult brain injury; however, the survival and differentiation of newly born cells after different brain lesions are poorly understood. We have examined the migration and fate of bromodeoxyuridine (BrdU)-labeled cells after a highly reproducible focal ischemic lesion restricted to the frontoparietal cortex in adult rats. Thermocoagulation of pial blood vessels induces a circumscribed degeneration of all cortical layers while sparing the corpus callosum and striatum and increases cell proliferation in the subventricular zone (SVZ) and rostral migratory stream (RMS) within 7 days. We now show that, although the rostral migration of the newly born SVZ cells and their differentiation into neurons in the olfactory bulb were not affected by the lesion, numerous cells expressing the neuroblast marker doublecortin migrated laterally in the striatum and corpus callosum 5 days postinjury. In addition to the SVZ, BrdU-labeled cells were seen in the striatum, in the corpus callosum, and around the lesion. One month later, BrdU-labeled cells in the corpus callosum expressed transferrin and the pi isoform of glutathione-S-transferase (GST-pi), markers of oligodendrocytes. Other BrdU+ cells expressed a marker of astrocytes, but none expressed neuronal markers, suggesting that new neurons do not form or survive under these conditions. Numerous BrdU-labeled cells were still observed in the SVZ and RMS. The data show that focal cortical ischemia does not lead to the long-term survival of new neurons in the striatum or cortex but induces long-term alterations in the SVZ and the production of new oligodendrocytes that may contribute to neural repair.     

Blood monocytes and spleen macrophages differentiate into microglia-like cells on monolayers of astrocytes: Morphology

Several morphological and functional properties of microglial cells, the resident immunoeffector cells of the central nervous system (CNS), differ from those of monocytes/macrophages in other tissues. Microglia are assumed to derive from the myelomonocytic lineage, possibly as a distinct subpopulation that diverges from a common cell line early in ontogeny, invades the CNS, proliferates, and differentiates into ameboid and then ramified microglia. We tested the hypothesis that some morphological and functional properties of microglia are induced in myelomonocytic cells by nervous tissue, specifically astrocytes. In the present in vitro studies we compared the differentiation of microglia, blood monocytes, and spleen macrophages on acellular substrates and on monolayers of astrocytes and fibroblasts. On acellular substrates, microglial cells at first acquire an ameboid morphology; later they show a few short, unbranched processes. On monolayers of pure astrocytes, microglial cells at first also differentiate inot ameboid cells, but after 5 to 7 days they start to develop processes with large lamellopodial tips. These lengthen and branch continuously during the next 2 weeks in vitro, demarcating a round to oval territory around the small ellipsoid cell body. By contrast, on monolayers of fibroblasts the microglial cells develop an ameboid morphology, but do not grow the typical long branched processes of the ramified form. Blood monocytes and spleen macrophages behave indistinguishably from microglia both on acellular and cellular substrates, i.e., on astroglia they develop the ramified form, while on fibroblasts they retain the ameboid shape. When microglia, macrophages, or monocytes are cultured on coverslips on top of astrocytic monolayers, i.e., physically separated from the astroglia, but exposed to the medium conditioned by astrocytes, a significant proportion of them also develop the ramified shape. These findings indicate that the ramified shape of microglia is induced by astrocytes. Since this morphology can also be induced in blood monocytes and macrophages, we take this to be further evidence for the proposition that microglial cells are derived from the myelomonocytic lineage, and, moreover, that properties of resident macrophages are largely determined by tissue components of their host organ.     

Investigation of glial cells in semithin sections. II. Variation with age in the numbers of the various glial cell types in rat cortex and corpus callosum

Semithin Epon sections stained with toluidine blue were used to enumerate astrocytes, microglia, the three subtypes of oligodendrocytes, and cells referred to as free subependymal cells, in the corpus callosum and cerebral cortex of male Sherman rats of various ages. The period covered extended from a few days before weaning (3/4 month of age) until the time when growth became negligible (5 months of age). The total number of glial cells increases with age in both cortex and corpus callosum. However, the investigation of individual cell types reveals that the number of microglia remains fairly constant throughout the period under study. The number of astrocytes in corpus callosum increases up to the age of one month, but remains constant thereafter, while their number in the cortex is the same at all investigated times. In the case of oligodendrocytes, the three subtypes behave differently. About two-thirds of the oligodendrocytes in rats aged three-quarters of a month are of the light or medium shade types, but the number of these gradually decreases with age and becomes very low in five-month-old rats. In contrast, the dark cells which constitute about one-third of the oligodendrocytes in young rats make up nearly the whole of this group in adults. Finally, free subependymal cells are absent in cortex throughout the period under study, but are present in corpus callosum, where their number steadily declines with age. In conclusion, the numbers of astrocytes and microglia seem to remain constant in growing rats after the age of one month. Dark oligodendrocytes markedly increase in number with age, while the other types of oligodendrocytes and the free subependymal cells are reduced to negligible numbers by the age of five months.     

Intracerebroventricular transplanted bone marrow stem cells survive and migrate into the brain of rats with Parkinson’s disease

In this study,6-hydroxydopamine was stereotaxically injected into the right substantia nigra compact and ventral tegmental area of rats to establish Parkinson’s disease models.The rats then received a transplantation of bone marrow stromal cells that were previously isolated,cultured and labeled with 5-bromo-2’-deoxyuridine in vitro.Transplantation of the bone marrow stromal cells significantly de-creased apomorphine-induced rotation time and the escape latency in the Morris water maze test as compared with rats with untreated Parkinson’s disease.Immunohistochemical staining showed that,5-bromo-2’-deoxyuridine-immunoreactive cells were present in the lateral ventricular wall and the choroid plexus 1 day after transplantation.These immunoreactive cells migrated to the surrounding areas of the lateral cerebral ventricle along the corpus callosum.The results indicated that bone marrow stromal cells could migrate to tissues surround the cerebral ventricle via the cerebrospinal fluid circulation and fuse with cells in the brain,thus altering the phenotype of cells or forming neuron-like cells or astrocytes capable of expressing neuron-specific proteins.Taken together,the present findings indicate that bone marrow stromal cells transplanted intracerebroventricularly could survive,migrate and significantly improve the rotational behavior and cognitive function of rats with experimentally induced Parkinson’s disease.     

Prolonged seizures recruit caudal subventricular zone glial progenitors into the injured hippocampus

Neurogenesis persists in the adult rat rostral forebrain subventricular zone (SVZ) and is stimulated by status epilepticus (SE). More caudal SVZ (cSVZ) neural progenitors migrate to the hippocampus after ischemic injury and contribute to CA1 pyramidal cell regeneration. Because SE also damages the hippocampus, we examined the effects of SE on cSVZ precursors. SE was induced in adult rats with pilocarpine, and cell proliferation in cSVZ and hippocampus was examined by bromodeoxyuridine (BrdU) and retroviral reporter labeling. Neural precursors were assayed by immunostaining for specfic markers between 1 and 35 days after SE. BrdU-positive cells labeled prior to SE markedly increased in numbers within 1-2 weeks in the cSVZ and infracallosal region, but not in the corpus callosum. Doublecortin-, polysialic acid neural cell adhesion molecule-, and TUC-4 (TOAD/Ulip/CRMP family-4)-immunostained cells with migrating morphology increased with a similar time course after SE and extended from the cSVZ to CA1 and CA3 regions. Retroviral reporters injected into the cSVZ of controls showed labeled cells with oligodendroglial morphology located in the cSVZ and corpus callosum; when injected 2 days prior to SE, many more reporter-labeled cells appeared several weeks later and were located in the cSVZ, corpus callosum, and hippocampus. Labeled cells showed glial morphologies and expressed astrocyte or oligodendrocyte markers. Neither BrdU- nor retroviral reporter-labeled cells coexpressed neuronal markers in controls or pilocarpine-treated rats. These results indicate that SE increases cSVZ gliogenesis and attracts newly generated glia to regions of hippocampal damage. Further study of seizure-induced gliogenesis may provide insight into mechanisms of adult neural progenitor regulation and epileptogenesis.     

Disturbed myelinogenesis and recovery in hyperphenylalaninemia in rats: An immunohistochemical study

Chronic hyperphenylalaninemia (HPA) in rats has been used as an experimental model of the human inborn error of metabolism phenylketonuria (PKU). Impaired brain development in PKU and HPA is reflected in reduced myelin formation. We have used immunohistochemistry, with antibodies to cell-specific antigenic markers, to investigate the cellular basis of the hypomyelination in the corpus callosum and cerebral cortex of rats made hyperphenylalaninemic from Postnatal Days 3-17. The rats were then allowed to recover until Day 59. No effects were seen on the number and differentiation pattern of ganglioside GD3-expressing glial progenitors. Myelin basic protein and 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNP) immunostaining demonstrated a reduction in myelin formation in the corpus callosum and subcortical white matter at 12 and 17 days postnatal. However, numbers of CNP+ oligodendrocytes appeared normal throughout development. No reactive astrogliosis was seen at any stage. The intensity of axonal neurofilament immunostaining was reduced in the corpus callosum at 17 days. In layers II and III of the cortical gray matter there was an increase in the cell packing density and a concomitant decrease in cell body size. Myelination in the corpus callosum was rapid during the recovery period with no difference noted at Day 59. Axonal neurofilament staining also returned to normal in the corpus callosum. However, recovery became increasingly incomplete away from the corpus callosum into the cortical gray matter. Our data suggest a primary effect of HPA on axonal maturation with hypomyelination consequential upon this.     

Human microglial cells: characterization in cerebral tissue and in primary culture, and study of their susceptibility to HIV-1 infection.

Neuropathological studies have shown that human immunodeficiency virus type 1-infected cells within the brain express several markers characteristic of macrophages and could either be microglial cells, or monocytes invading the CNS, or both. To better define the target cells of human immunodeficiency virus type 1 within the brain, we have studied human microglial cells, both in vivo and in vitro, and compared them to monocytes for their antigenic markers and their susceptibility to human immunodeficiency virus type 1 infection. Brain-derived macrophages were isolated from primary cortical and spinal cord cultures obtained from 8 to 12-week-old human embryos. The isolated cells presented esterase activity, phagocyted zymosan particles, expressed several (Fc receptors, and CD68/Ki-M7 and CD11b/CR3 receptors) of the macrophagic antigenic markers, and appeared to be resident microglial cells from human embryonic brain. Conversely, brain-derived macrophages did not express antigens CD4, CD14, or CD68/Ki-M6, which are easily detected on freshly isolated monocytes. Using these antigenic differences between isolated microglial cells and monocytes, we have observed that two populations of macrophages could be individualized. In the normal adult brain, microglial cells were numerous in both the gray and the white matter. The infrequent cells sharing antigens with monocytes were found almost exclusively around vessels. In 8 to 12-week-old human embryos, microglial cells were found in both the parenchyma and the germinative layer. Cells sharing antigens with monocytes were only found at the top of and inside the germinative layer. In brain tissue from patients with human immunodeficiency virus type 1 encephalitis, cells sharing antigens with monocytes are abundant not only around the vessels but also in the parenchyma. In double-labeling experiments, human immunodeficiency virus type 1-infected cells showed monocyte antigens. Finally, microglial cells also differ from monocytes in their in vitro susceptibility to human immunodeficiency virus type 1 infection; after stimulation by r-TNF alpha or GmCSF, monocytes but not microglial cells can replicate human immunodeficiency virus type 1. This in vitro difference in human immunodeficiency virus type 1 susceptibility between monocytes and microglial cells together with the presence of monocytic antigens within the brain tissue of human immunodeficiency virus type 1-infected patients suggest that human immunodeficiency virus type 1-infected cells within the brain are either monocytes that have crossed the blood-brain barrier and spread through the tissue or perivascular microglial cells that, after phagocyting infected blood lymphocytes, subsequently contain viral antigen and migrate to brain tissue.     

Maturation of the corpus callosum of the rat: II. Influence of thyroid hormones on the number and maturation of axons

Quantitative electron microscopy has been used to study the number of callosal axons in the corpus callosum of normal and hypothyroid rats during postnatal development. At birth, the normal corpus callosum contains 4.4 x 10(6) axons. This number increases to 11.4 x 10(6) by 5 days of age (P5) and then, in contrast to cats and primates, remains constant until at least P60, the oldest age examined. The number of axons in the corpus callosum of hypothyroid animals is not significantly different from the values observed in normal rats at all ages studied, although the callosal axons of hypothyroid rats remain structurally immature. As extensive elimination of callosal axons has been shown to occur in normal rats past P5, we conclude that new callosal processes grow through the corpus callosum past this age that compensate numerically for the loss. Moreover, as the number of callosally projecting neurons seems to be higher in hypothyroid rats than in normal controls, it seems that the constant axon number derives from more parent neurons, and thus that there are more axon collaterals per callosal neuron in a normal animal than in a hypothyroid one. Taken together, these data indicate that although hypothyroidism does not alter the total number of callosally projecting axons, it interferes with the normal processes that define or sculpt the projection fields, thereby leading to a numerically normal projection with abnormal topography.     

Allogeneic bone marrow stromal cells promote glial–axonal remodeling without immunologic sensitization after stroke in rats

We evaluated the effects of allogeneic bone marrow stromal cell treatment of stroke on functional outcome, glial–axonal architecture, and immune reaction. Female Wistar rats were subjected to 2 h of middle cerebral artery occlusion. Rats were injected intravenously with PBS, male allogeneic ACI – or syngeneic Wistar –bone marrow stromal cells at 24 h after ischemia and sacrificed at 28 days. Significant functional recovery was found in both cell-treated groups compared to stroke rats that did not receive BMSCs, but no difference was detected between allogeneic and syngeneic cell-treated rats. No evidence of T cell priming or humoral antibody production to marrow stromal cells was found in recipient rats after treatment with allogeneic cells. Similar numbers of Y-chromosome⁺ cells were detected in the female rat brains in both groups. Significantly increased thickness of individual axons and myelin, and areas of the corpus callosum and the numbers of white matter bundles in the striatum were detected in the ischemic boundary zone of cell-treated rats compared to stroked rats. The areas of the contralateral corpus callosum significantly increased after cell treatment compared to normal rats. Processes of astrocytes remodeled from hypertrophic star-like to tadpole-like shape and oriented parallel to the ischemic regions after cell treatment. Axonal projections emanating from individual parenchymal neurons exhibited an overall orientation parallel to elongated radial processes of reactive astrocytes of the cell-treated rats. Allogeneic and syngeneic bone marrow stromal cell treatment after stroke in rats improved neurological recovery and enhanced reactive oligodendrocyte and astrocyte related axonal remodeling with no indication of immunologic sensitization in adult rat brain.     

Presence of labeled monocytes, macrophages and microglia in a stab wound of the brain following an injection of bone marrow cells labeled with 3H-uridine into rats.

To clarify the origin of the cells appearing in a stab wound of the parietal cortex, bone marrow cells from inbred Lewis rats were labeled in vitro with ³H-uridine and injected intravenously into 36 rats of the same strain Just before or after the brain had been stabbed. The animals were sacrificed from 1 to 15 days after the injection of labeled cells. The cells in the wound were examined and the percentage of the various types recorded. Radioautographs were prepared of the wound and the surrounding neuropil, as well as of the corresponding region on the intact side; and they were searched for labeled cells. One day after the stabbing, the wound consisted of a central region containing fluid and red blood cells, and a marginal region of disorganized nervous tissue including granulocytes, monocytes and macrophages. Around the wound, the neuropil appeared normal, except for the perivascular areas appearing more cellular and distended than normally. During the next few days, the granulocytes and monocytes gradually disappeared from the wound. Meanwhile, the macrophages, which initially often showed monocytic features, became increasingly numerous. However, after the seventh day, the macrophages decreased in number, while many small cells appeared in the wound. These displayed a scanty basophilic cytoplasm rich in phagosomes and a nucleus with dense chromatin clumps similar to that seen in microglia A search of the radioautographs revealed no labeled cell on the intact side, but 220 labeled cells on the injured side. Most of these cells were within the wound itself, and a few in the surrounding neuropil. Within the wound, labeled granulocytes and monocytes were common one day after injection, but disappeared after the first three days. Few labeled macrophages were observed at one day but many at three days; none were labeled after the seventh day, however, possibly due to turnover and loss of the ³H-uridine labeled RNA. In the neuropil surrounding the wound, a few labeled cells identified as microglia were observed during the first three days after injection. They were located in perivascular areas, in satellite position to neurons and within the nearby subependymal layer It is concluded that, under the influence of a stab wound, blood cells of bone marrow origin enter the wound and the surrounding neuropil. The presence of macrophages with monocytic features within the wound indicates that the monocytes transform into macrophages. The small cells displaying phagosomes and a microglia-like nucleus, which become numerous after the seventh day, are tentatively interpreted as intermediates in the transformation of the monocytederived macrophages into microglia. Finally, the early labeled cells identified as microglia in the surrounding neuropil are interpreted as a direct transformation of monocytes into microglia.     

Astrogliopathy and oligodendrogliopathy are early events in CNS demyelination

We examined the phenotypic composition of cells and the underlying mechanisms of demyelination following injection of lipopolysaccharide (LPS) into the corpus callosum of rats. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay showed fragmented DNA, which co‐localized with oligodendrocytes in areas of demyelination following intracerebral injection with LPS. Immunostaining showed the presence of caspase 3 in cells which expressed the oligodendrocyte markers, suggesting activation of the apoptotic pathway. Commensurate reduction in glial fibrillary acid protein (GFAP)+/ gap junction protein connexin43+ (Cx43) cells, was also seen in the corpus callosum prior to histochemical evidence of demyelination. Expression of mRNA for proinflammatory cytokines was maximal 3 day postinjection, at a time when the numbers of TUNEL positive cells in the corpus callosum were declining and the total number of CD68+ cells peaked at day 14 postinjection. Our studies suggest that death of oligodendrocytes is an early event in LPS model of demyelination. We believe that the innate immune model of oligodendrocyte death will be useful in the development of neuroprotective agents capable of rescuing oligodendrocytes from apoptosis. GLIA 2013;61:1261–1273     

间歇性θ爆发式磁刺激对高血压大鼠胼胝体髓鞘及局部炎症反应的影响

目的探究间歇性θ爆发式磁刺激对慢性高血压大鼠胼胝体区域髓鞘脱失、星形胶质细胞增生和小胶质细胞活化的改善作用。方法对雄性Sprague-Dawley大鼠随机进行双肾双夹术,制作易卒中型肾血管性高血压大鼠模型。术后22周,模型制备成功的高血压大鼠随机接受连续14 d间歇性θ爆发式磁刺激治疗(intermittent theta burst stimulation,iTBS)(高血压iTBS组,n=6)或假性刺激(高血压假刺激组,n=6),假手术大鼠接受假性刺激(假手术假刺激组,n=6)。HE染色观察胼胝体小动脉形态。免疫荧光染色观察胼胝体MBP标记的髓鞘脱失情况。免疫荧光染色观察GFAP标记的星形胶质细胞数量和IBa-1标记的小胶质细胞数量和形态,以评价星形胶质细胞增生和小胶质细胞活化。结果高血压iTBS组和高血压假刺激组出现明显小动脉管壁增厚。与假手术假刺激组相比,高血压假刺激组胼胝体MBP阳性面积比例减少(P<0.01),GFAP阳性细胞和IBa-1阳性细胞数量明显增加(P<0.01),IBa-1阳性细胞胞体增大,突起变粗,分枝变少。iTBS治疗明显增加了高血压大鼠胼胝体MBP阳性面积比例,降低GFAP阳性细胞和IBa-1阳性细胞数量(P<0.01),IBa-1阳性细胞胞体变小,突起变细,分枝变多。结论iTBS治疗可减轻高血压大鼠胼胝体区域髓鞘脱失,抑制星形胶质细胞增生和小胶质细胞活化。     

Localization of Pi class glutathione-S-transferase in the forebrains of neonatal and young rats: evidence for separation of astrocytic and oligodendrocytic lineages.

The Yp isoform (Pi class) of glutathione-S-transferase has recently been localized in oligodendrocytes in the brains of mature rats. To examine at what postnatal age Pi first appears in oligodendrocytes or precursor cells, antibodies against Pi were used to immunostain tissue sections from the forebrains of neonatal rats and young rats up to 17 days of age. In the brains of neonates Pi immunofluorescence was observed in ovoid cells in the subependymal layer, and in ovoid cells and cells bearing short, thick processes in the corpus callosum and cingulum. These cells did not immunostain for vimentin. During the first postnatal week Pi-positive cells showed positive immunostaining for ganglioside GD3, which is characteristic of oligodendrocyte precursors, and process-bearing Pi-positive cells appeared in the cingulum and at the lateral borders of the corpus callosum in increasing numbers. During the second postnatal week the cytoplasm of Pi-positive cells became more compact, and the processes thinner, and the Pi-positive cells and their processes began to immunostain for 2',3'-cyclic nucleotide-3'-phosphohydrolase, which is characteristic of immature and mature oligodendrocytes and myelin sheaths. By age 17 days Pi was observed in relatively mature oligodendrocytes. The observations suggest that Pi occurs in oligodendrocyte precursors, immature oligodendrocytes, and mature oligodendrocytes in the postnatal through 17 day old rat forebrain. In the accompanying paper (Cammer and Zhang, '92)--if references are permitted in the Abstract a different glutathione-S-transferase isoform, Yb (Mu class), was localized in cells of the astrocyte lineage, beginning in the forebrains of neonatal rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acute Marchiafava‐Bignami Disease with Extensive Diffusion Restriction and Early Recovery: Case Report and Review of the Literature

Marchiafava‐Bignami disease (MBD) is a neurological disorder that has been found to be associated with chronic alcoholism and malnutrition. MBD classically results in acute edema and demyelination of the corpus callosum. Edema of the complete corpus callosum has been described to be an unfavorable prognostic factor. We present an acute onset of MBD with diffusion restriction of the complete corpus callosum and symmetric bilateral extension into the semioval center, that almost completely resolved clinically as well as in MRI only 3 days later. With early detection and treatment, the prognosis of MBD may be good even in cases with severe diffusion restriction of the complete corpus callosum.