[Astrocytic proliferation in the brain adjacent to infarcted lesion: immunohistochemical study of astroprotein (GFAP) and bromodeoxyuridine (BrdU)].

Although cerebral infarction is a destructive process of nerve cells and brain tissue, the nature is not exclusively disintegrating but also includes active cellular reaction which may modify the progression of tissue damage. Most prominent cellular reaction in the area surrounding infarction can be recognized as a trophic or proliferative change of glial cells. In the present study we produced a focal cerebral ischemia in Mongolian gerbils and investigated the dynamic change of astrocytes in the brain adjacent to thalamic infarction. Using immunohistochemical methods, astrocytes were identified with the antibody to astroprotein (GFAP) and the DNA synthesizing (S phase) cells were detected with the antibody to bromodeoxyuridine (BrdU). The posterior communicating artery of a gerbil was occluded by coagulation through the trans-tympanic bulla approach under general anesthesia with ketamine hydrochloride (80 mg/kg, i.p.). Thirty min after intravenous administration of BrdU (200 mg/kg), animals were sacrificed by transcardiac perfusion with 75% ethanol on days 1, 2, 3, 5 and 7 post-infarction. Ethanol-fixed, paraffin-embedded blocks were cut coronally into 6 microns-thick sections at the level of dorsal hippocampus. Double-labeled immunohistochemical technique (avidin biotin peroxidase-complex method) was carried out with each antibody using 3,3'-diaminobenzidine tetrahydrochloride and 4-chloro-1-naphthol as chromogens. The population of GFAP-positive cells and their S-phase fraction (the number of BrdU-positive nuclei divided by the number of GFAP-positive cells expressed in per cent, %) were examined. The data demonstrated that the regional GFAP-positive cells increased continuously between days 1 to 5 (105.9 to 528.8 cells/mm2) postinfarction (44.6 cells/mm2 in normal brain).(ABSTRACT TRUNCATED AT 250 WORDS)

Localization of beta-adrenergic receptors on differentiated cells of the central nervous system in culture.

Hypothalamic neurons and cortical protoplasmic (type 1) astrocytes in dissociated cultures of rat brain express binding sites for antibodies specific for epitopes related to the beta-adrenergic receptor. Undifferentiated glial progenitor cells of the rat optic nerve do not detectably bind these antibodies, but both of the progeny [oligodendroglia and process-bearing (type 2) astrocytes] express immunologically identified beta-adrenergic receptors. Levels of receptor expression are variable: not all cells of each type express receptors nor is expression uniform on a given cell. The data suggest that cells of the central nervous system express beta-adrenergic receptors but that levels of expression may be determined by the differentiated state of the cells.

Short- and long-term consequences of intracranial injections of the excitotoxin, quinolinic acid, as evidenced by GFA immunohistochemistry of astrocytes.

Astroglial reactions to intrastriatal and intrahypothalamic injections of the endogenous excitotoxin quinolinic acid (50 micrograms in 1 microliter) were studied in adult rats, using immunohistochemistry with antiserum to glial fibrillary acidic protein. Animals were sacrificed 6 h, 24 h, 3, 7 and 30 days or 1 year after the injection. Six and 24 h after quinolinic acid, the amount of glial fibrillary acidic protein-like immunoreactivity in the injected striatum was lower than in controls but returned to a normal level at 3 days. Not until 7 days was a clear striatal gliosis apparent, as evidenced by an increased density of glial fibrillary acidic protein-positive structures and brightly fluorescent, clearly hypertrophic cells. This gliosis was even more developed in animals sacrificed 30 days postoperatively. A weak astrocytic reaction was also observed in the ipsilateral corpus callosum at 6 h after quinolinic acid. By 3 days, a marked gliosis restricted to the injected hemisphere was present throughout corpus callosum and cortex cerebri. In animals sacrificed 30 days after quinolinic acid the extrastriatal astrocytic reaction was clearly diminished, although the striatal gliosis was still prominent. One year postinjection, no obvious gliosis could be observed in cortex cerebri or corpus callosum while striatal tissue, now markedly reduced in volume, was clearly gliotic. Using neurofilament antiserum, increased fluorescence intensity was noted in striatal nerve bundles during the first day after an intrastriatal quinolinic acid injection and persisted 1 year postoperatively. Controls were similarly injected with an equimolar amount of nicotinic acid, the non-excitatory, non-neurotoxic decarboxylation product of quinolinic acid. No changes in immunoreactivity of glial fibrillary acidic protein or neurofilament were found in these animals. In animals treated intrahypothalamically, a spherical central area almost devoid of glial fibrillary acidic protein-immunoreactivity was noted around the injection site 7 days after quinolinic acid administration. Around this area, gliosis was observed. Apart from a very restricted gliotic reaction around the needle tract, no astrocytic reaction was observed in nicotinic acid-injected control animals. We conclude that quinolinic acid causes both reversible and long-lasting gliosis when injected into the rat striatum. As a natural brain metabolite, quinolinic acid may constitute a particularly valuable tool for the elucidation of a possible role of glia in neurodegenerative disorders.

Intrauterine growth retardation (malnutrition by vascular ligation) induces modifications in fatty acid composition of neurons and oligodendrocytes.

Intrauterine growth retardation (IUGR) induced by ligation of one uterine artery on day 17 of pregnancy in the rat lead to major abnormalities in the fatty acid content of neurons and oligodendrocytes but not in astrocytes. In neurons from IUGR rats, monounsaturated fatty acids were decreased; in the polyunsaturated series, omega-3 fatty acids were increased and omega-6 fatty acids were decreased. In oligodendrocytes, monounsaturated fatty acids were also decreased, but the modifications in polyunsaturated fatty acids were the opposite of those in neurons: omega-3 being decreased and omega-6 increased. Although the animals received a normal diet after birth, the alterations were still present in adulthood. In addition, fatty acid composition of brain cells is a very indicative criterion of brain maturation.

Structural and microspectrofluorometric studies on glial cells from the periventricular and arcuate nuclei of the rat hypothalamus.

Fluorescence spectroscopy and electron microscopic techniques have been employed to investigate a class of glial cells that is characterized by the presence in their cytoplasm of large fluorescing inclusions that stain with paraldehyde-fuchsin or chrome-hematoxyline-alum. In the periventricular nucleus the cells have been identified as a population of astrocytes whose inclusions emit an orange-red fluorescence. In the arcuate nucleus there are, in addition to an overwhelming majority of such astrocytes, also some microglial cells with similar characteristics. The ability of the latter to emit any kind of fluorescence has not yet been established. The fluorescence maximum of these astrocytic inclusions was found to be at 640 nm when excited at 405 nm. The data obtained suggest that the fluorescence observed is due to the presence of porphyrins in the astrocytic inclusions. In the majority of our electron microscopic pictures the inclusions lack a bounding membrane. By contrast, neuronal lipofuscin has an outer membrane. In cryostat sections, the lipofuscin emits a yellow fluorescence when excited at 400-410 nm.

X-ray microanalytical studies of lead-implanted rat brains.

Various cytoplasmic and intranuclear inclusions found in macrophages and astrocytes of lead-implanted rat brains were studied with an energy dispersive x-ray microanalytical technique. Cytoplasmic inclusions contained large quantities of lead, calcium and phosphorus. The proportions of these elements were different within each inclusion. Intranuclear inclusions also contained small amounts of lead and, occasionally, calcium.