In vivo incorporation ofN-acetyl-d-[U-14C]mannosamine into brain gangliosides of rats with quinolinic acid-induced lesions of the forebrain nucleus basalis magnocellularis

Quinolinic acid, an excitotoxic agent, was applied unilaterally to the nucleus basalis magnocellularis of the rat forebrain, which resulted in neuronal destructions and consequently, loss of cholinergic projections to the cortex. The effects on ganglioside metabolism in brain cortical matter were studied. Total ganglioside contents in lesioned brains (n=8) were found to be significantly decreased (range, 20–60%) but changes in brain ganglioside patterns on thin layer chromatograms were not apparent. On the other hand, in vivo incorporation ofN-acetyl-d-[U-¹⁴C]mannosamine into brain gangliosides ranged from 19 to 36% (mean, 26%) of radiolabel in controls, and 5 to 21% (mean, 13%), a significant reduction in lesioned brains. Labeling of brain glycoproteins or of nonganglioside lipids was not affected. Since central cholinergic hypofunctions are also important neurochemical characteristics of Alzheimer’s disease, abnormal ganglioside metabolism found in the lesioned rats may be of significance in the human disorder, where reduced brain ganglioside contents have also been reported.     

Alterations in the composition of brain lipids in patients with Creutzfeldt-Jakob disease.

Brain lipids were isolated from 3 patients with Creutzfeldt-Jakob (C-J) disease and their chemical constituents were investigated. The total lipid content increased slightly in diseased gray matter. Ganglioside was reduced to less than 20 and 50% of that of control values in gray and white matter of the Creutzfeldt-Jakob brains, respectively, on both a wet and dry weight basis. Abnormal thin-layer chromatography patterns were observed in the gangliosides from the diseased brains. The C₂₀-sphingosine in the gangliosides from the Creutzfeldt-Jakob brains was markedly reduced. The ratio of C₂₀ to C₁₈-sphingosine was 0.03 to 0.23 in the diseased gray matter. An alteration in the fatty acid composition of ganglioside was observed in 1 case of C-J disease. The total cholesterol content increased both in gray and white matter of the Creutzfeldt-Jakob brain, and one-third of the total cholesterol was in the esterified form in gray matter. Major fatty acids of cholesterol ester were palmitic and oleic acids. The total phospholipids were severely decreased in the diseased brains, but the relative proportions of the individual phospholipids were constant. Polyunsaturated fatty acids in phosphatidyl ethanolamine from the diseased gray matter decreased with a moderate increase in oleic acid. Galactolipid levels and types were essentially unchanged. From the above described abnormalities of brain lipids, the pathogenesis of this disease is discussed.     

Effect of Oestrogen Receptors on Brain NMDA Receptors of 1‐Methyl‐4‐Phenyl‐1,2,3,6‐Tetrahydropyridine Mice

Parkinson’s disease (PD) is characterised by the loss of nigrostriatal dopamine (DA) neurones and glutamate overactivity. There is substantial evidence to suggest that oestrogens prevent or delay the disease. 17β‐oestradiol has neuroprotective effects in the 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) mouse model of PD and modulates brain NMDA receptors. In MPTP‐lesioned mice, oestrogen receptor (ER)α and ERβ are important in 17β‐oestradiol‐induced neuroprotection. To evaluate the role of ERs in the response of NMDA receptors to lesion, we compared wild‐type (WT) with ER knockout (KO) C57Bl/6 male mice that received 7, 9 or 11 mg/kg of MPTP. These mice were also treated with MPTP (9 mg/kg) and 17β‐oestradiol. [³H]Ro 25‐6981 specific binding autoradiography was used to label NMDA receptors containing NR2B subunits. In the frontal and cingulate cortex and striatum, vehicle‐treated WT mice had higher [³H]Ro 25‐6981 specific binding compared to ERKO mice. Cortical [³H]Ro 25‐6981 specific binding decreased with increasing doses of MPTP in WT and ERKOα but not ERKOβ mice, whereas a dose‐related decrease was only observed in the striatum of WT mice remaining low in ERKOα and ERKOβ mice. No effect of 17β‐oestradiol treatment in intact or MPTP‐lesioned mice of all three genotypes was observed in the cortex, whereas it increased striatal specific binding of intact ERKOβ and MPTP‐lesioned WT mice. Striatal [³H]Ro 25‐6981 specific binding positively correlated with striatal DA concentrations only in WT mice. MPTP and 17β‐oestradiol treatments had more limited effects in the hippocampus. Only in the CA3 and dentate gyrus did vehicle and 17β‐oestradiol‐treated ERKOα mice have higher [³H]Ro 25‐6981 specific binding than WT and ERKOβ mice, whereas MPTP decreased this specific binding only in the CA1, CA2 and CA3 of ERKOα mice. Hence, brain NMDA receptors were affected by the deletion of ERs, which affect the response to MPTP and 17β‐oestradiol treatments with brain region specificity.     

Type I interferon signaling limits reoviral tropism within the brain and prevents lethal systemic infection

In vivo and ex vivo models of reoviral encephalitis were utilized to delineate the contribution of type I interferon (IFN) to the host’s defense against local central nervous system (CNS) viral infection and systemic viral spread. Following intracranial (i.c.) inoculation with either serotype 3 (T3) or serotype 1 (T1) reovirus, increased expression of IFN-α, IFN-β, and myxovirus-resistance protein (Mx1; a prototypical IFN stimulated gene) was observed in mouse brain tissue. Type I IFN receptor deficient mice (IFNAR^−/−) had accelerated lethality, compared to wildtype (B6wt) controls, following i.c. T1 or T3 challenge. Although viral titers in the brain and eyes of reovirus infected IFNAR^−/− mice were significantly increased, these mice did not develop neurologic signs or brain injury. In contrast, increased reovirus titers in peripheral tissues (liver, spleen, kidney, heart, and blood) of IFNAR^−/− mice were associated with severe intestinal and liver injury. These results suggest that reovirus-infected IFNAR^−/− mice succumb to peripheral disease rather than encephalitis per se. To investigate the potential role of type I IFN in brain tissue, brain slice cultures (BSCs) were prepared from IFNAR^−/− mice and B6wt controls for ex vivo T3 reovirus infection. Compared to B6wt controls, reoviral replication and virus-induced apoptosis were enhanced in IFNAR^−/− BSCs indicating that a type I IFN response, initiated by resident CNS cells, mediates innate viral immunity within the brain. T3 reovirus tropism was extended in IFNAR^−/− brains to include dentate neurons, ependymal cells, and meningeal cells indicating that reovirus tropism within the CNS is dependent upon type I interferon signaling.     

Chronic supranigral infusion of BDNF in normal and MPTP-treated common marmosets

Summary. BDNF or vehicle were administered by unilateral supranigral infusion in normal and chronically lesioned MPTP-treated common marmosets (Callithrix jacchus) for four weeks and locomotor activity, disability and response to apomorphine were assessed with nigral TH, GFAP and GAD immunoreactivity and striatal [³H]mazindol autoradiography. Selective contraversive orientation and ipsilateral neglect evolved in MPTP-treated marmosets receiving BDNF with no significant difference in disability or locomotor activity when compared to the vehicle-infused group. Apomor-phine produced an ipsiversive rotational bias in BDNF-treated animals. In normal animals infused with BDNF contralateral neglect, ipsiversive turning, postural instability and ataxia rapidly evolved. In MPTP-treated marmosets BDNF caused increased ipsilateral striatal [³H]mazindol binding with increased somatic size and staining intensity in GAD-immunoreactive cells and a 10–20% loss of nigral TH-immunoreactive cells with increased GFAP staining. In normal common marmosets, both vehicle and BDNF infusion decreased nigral TH-immunoreactivity. Chronic supranigral infusion of BDNF alters motor behaviour and spatial attention in MPTP-treated marmosets which may reflect altered function in residual nigral dopaminergic neurons and brainstem GABAergic neurons and in normal animals produces behavioural and histological signs of nigrostriatal hypofunction. Received September 1, 1998; accepted December 17, 1998     

Reduction of cerebral edema with GM1 ganglioside

Administration of exogenous gangliosides has been reported to accelerate neurite outgrowth in vitro, and to enhance peripheral nerve regeneration and central nervous system recovery subsequent to damage. After injury, facilitation of CNS recovery with GM1 ganglioside treatment has been postulated to be due to enhanced neuronal regeneration. Since maximal recovery is achieved when experimental animals are treated before injury with GM1 ganglioside, an alternative or parallel mechanism is that gangliosides are "protecting" the CNS by limiting the extent of damage (ie, cell loss, process degeneration, membrane disruption). This may be due to a reduction in the edema subsequent to injury. In this study, rats were treated for 2 days with 20 mg/kg/day of GM1 ganglioside. On the third day they were subjected to a unilateral lesion (mechanical) of one cerebral hemisphere and given another 20 mg/kg of GM1. On the fourth day brains were removed for analysis of edema resulting from the injury. In treated animals there was a significant reduction in edema as measured either in the entire injured hemisphere (23%) or in the area of injury (33%). No effect was seen outside the damaged area. Since exogenous gangliosides can spontaneously "insert" into membranes, it is postulated that the effect of the GM1 may be due to alterations of membrane processes (eg, lipid hydrolysis, phospholipase activation, levels and membrane action of arachidonic acid, ionic permeation) that are characteristic of edema.     

Caspase-3 activation is required for reovirus-induced encephalitis <Emphasis Type="Italic">in vivo</Emphasis>

Reovirus infection of neonatal mice provides a classic experimental system for understanding the molecular pathogenesis of central nervous system (CNS) viral infection. CNS tissue injury, caused by many human neurotropic viruses, including herpes viruses and West Nile virus, is associated with caspase-dependent apoptotic neuronal cell death. We have previously shown that reovirus-induced CNS tissue injury results from apoptosis and is associated with activation of both death-receptor and mitochondrial apoptotic pathways culminating in the activation of the downstream effector caspase, caspase-3. In order to directly investigate the role of caspase-3 in virus-induced neuronal death and CNS tissue injury during encephalitis, we have compared the pathogenesis of reovirus CNS infection in mice lacking the caspase-3 gene (caspase-3 (−/−)) to syngeneic wild-type mice. Prior studies of antiapoptotic treatments for reovirus-infected mice have indicated that protection from reovirus-induced neuronal injury can occur without altering the viral titer in the brains of infected mice. We now show that reovirus infection of caspase-3 (−/−) mice was associated with dramatic reduction in severity of CNS tissue injury, decreased viral antigen and titer in the brain, and enhanced survival of infected mice. Following intracerebral inoculation, the authors also show that virus spread from the brain to the eyes in reovirus-infected caspase-3 (−/−) mice, indicating that viral spread was intact in these mice. Examination of brains of long-term survivors of reovirus infection among caspase-3 (−/−) mice showed that these mice eventually clear their CNS viral infection, and do not manifest residual or delayed CNS tissue injury.     

Loss of Gas6 and Axl signaling results in extensive axonal damage,motor deficits,prolonged neuroinflammation,and less remyelination following cuprizone exposure

The TAM (Tyro3, Axl, and MerTK) family of receptor tyrosine kinases (RTKs) and their ligands, Gas6 and ProS1, are important for innate immune responses and central nervous system (CNS) homeostasis. While only Gas6 directly activates Axl, ProS1 activation of Tyro3/MerTK can indirectly activate Axl through receptor heterodimerization. Therefore, we generated Gas6^–/–Axl^–/– double knockout (DKO) mice to specifically examine the contribution of this signaling axis while retaining ProS1 signaling through Tyro3 and MerTK. We found that naïve young adult DKO and WT mice have comparable myelination and equal numbers of axons and oligodendrocytes in the corpus callosum. Using the cuprizone model of demyelination/remyelination, transmission electron microscopy revealed extensive axonal swellings containing autophagolysosomes and multivesicular bodies, and fewer myelinated axons in brains of DKO mice at 3‐weeks recovery from a 6‐week cuprizone diet. Analysis of immunofluorescent staining demonstrated more SMI32+ and APP+ axons and less myelin in the DKO mice. There were no significant differences in the number of GFAP+ astrocytes or Iba1+ microglia/macrophages between the groups of mice. However, at 6‐weeks cuprizone and recovery, DKO mice had increased proinflammatory cytokine and altered suppressor of cytokine signaling (SOCS) mRNA expression supporting a role for Gas6‐Axl signaling in proinflammatory cytokine suppression. Significant motor deficits in DKO mice relative to WT mice on cuprizone were also observed. These data suggest that Gas6‐Axl signaling plays an important role in maintaining axonal integrity and regulating and reducing CNS inflammation that cannot be compensated for by ProS1/Tyro3/MerTK signaling.     

Gangliosides in the brain in adult Down’s syndrome and Alzheimer’s disease

Quantitative analysis of total gangliosides and of ganglioside composition by HPTLC has been carried out on the gray matter of frontal cerebral cortex of six brains from Down’s syndrome (DS) adults, six age-matched controls, six Alzheimer’s disease (AD) adults, and six controls matched for age with the AD brains, as well as on three DS and six control cerebellum specimens. In addition, the analyses were carried out on specimens of corpus callosum of five adult DS and five control brains. No abnormalities were found in the gangliosides of DS corpus callosum. In DS frontal cortex, the concentration of total gangliosides was reduced, and there was a decrease in the fraction of G_T1b and G_D1b′ and an increase in those of G_T1a′ G_D3′ G_M1 and G_M2; the ratio of total b-series to a-series gangliosides was decreased. Very similar abnormalities were found in the gangliosides of DS cerebellum. In AD frontal cortex, by contrast, the total gangliosides and their composition were normal by comparison with agematched controls, with the minor exception of reductions in the fractions of G_Q1b and G_T1L. It is concluded that abnormalities in gangliosides exist in the brain in DS that are unrelated to AD-type pathology and may reflect developmental disturbances.     

Thioperamide, an H3 Receptor Antagonist Prevents [3H]Glucose Uptake in Brain of Adult Rats Lesioned as Neonates with 5,7-Dihydroxytryptamine

As a first attempt at exploring an association between histaminergic and serotoninergic neuronal phenotypes in glucose regulation, the influence of the histamine H₃ receptor antagonist thioperamide on glucose uptake by brain was determined in rats in which the serotoninergic innervations of brain was largely destroyed perinatally. Male Wistar rats were initially treated on the 3rd day after birth with the serotoninergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) (75 μg icv) or saline vehicle (10 μl icv). At 8 weeks lesioned and control rats were terminated in order to validate the effectiveness of 5,7-DHT: reduction in 5-HT and 5-HIAA by 83–91% and 69–83% in striatum, frontal cortex, and hippocampus (HPLC/ED method). Other groups of rats were pretreated with thioperamide (5.0 mg/kg ip) or saline vehicle 60 min prior to 6-[³H]-D-glucose (500 μCi/kg ip). Fifteen-min later rats were decapitated and brains were excised and dissected to remove frontal cortex, striatum, hippocampus, thalamus/hypothalamus, pons, and cerebellum. Liquid scintillation spectroscopy was used to determine that [³H]glucose uptake, which was enhanced in 5,7-DHT lesioned rats in cortex (by 88%), hippocampus, thalamus/hypothalamus, pons and cerebellum (each by 47–56%), and in striatum (by 35%). In contrast, thioperamide prevented the enhancement in [³H]glucose uptake in all brain regions of 5,7-DHT neonatally lesioned rats; and [³H]glucose levels were significantly different in all brain regions (except thalamus/hypothalamus) in thioperamide-versus saline-treated rats. These findings indicate a functional association between histaminergic and serotoninergic systems in brain in relation to glucose regulation.     

IFN-γ triggers CCR2-independent monocyte entry into the brain during systemic infection by virulent Listeria monocytogenes

Listeria monocytogenes (Lm) is a bacterial pathogen that infects the brain via parasitized monocytes. CCR2 is important for monocyte migration into the brain after it is infected, but the degree of CCR2 involvement in monocyte migration to the CNS during systemic infection is less clear. Our recent data demonstrate that systemic infection with non-neuroinvasive ΔactA Lm mutants triggers IFN-γ-dependent brain influxes of Ly-6C^high monocytes. Studies presented here tested the extent to which CCR2 and IFN-γ are essential for monocyte migration to the brain during systemic infection with virulent Lm. For this, we assessed expression of monocyte-attracting chemokines in brains of normal and IFN-γ mice during infection and tested the degree to which brain influxes of Ly-6C^high monocytes were inhibited in chemokine- and chemokine receptor-deficient mice. In normal mice, systemic infection induced up-regulation of CCR2-binding (CCL2, CCL7, CCL8, CCL12) and CXCR3-binding chemokines (CXCL9, CXCL10). IFN-γ mice had negligible mRNA and protein expression of CXCR3-binding chemokines, whereas expression of CCR2-binding chemokines was reduced, but remained significant. In addition, infection-triggered monocyte influxes were significantly reduced in IFN-γ mice. Remarkably, brain monocyte influxes were normal during infection of CXCR3-, CCL2-, CCR1-, CCR5-, and CX3CR1-deficient mice. Influxes were transiently reduced in CCR2^?/? mice, corresponding with retention of monocytes in the bone marrow but this was eventually overcome during infection. These data show that IFN-γ is critical for triggering brain influxes of Ly-6C^high monocytes during systemic infection with virulent Lm. This initial burst of monocyte migration is largely independent of individual chemokine receptors.     

Fibroblast growth factor 1 (FGFR1) modulation regulates repair capacity of oligodendrocyte progenitor cells following chronic demyelination

The adult mammalian brain contains multiple populations of endogenous progenitor cell types. However, following CNS trauma or disease, the regenerative capacity of progenitor populations is typically insufficient and may actually be limited by non-permissive or inhibitory signals in the damaged parenchyma. Remyelination is the most effective and simplest regenerative process in the adult CNS yet is still insufficient following repeated or chronic demyelination. Our previous in vitro studies demonstrated that fibroblast growth factor receptor 1 (FGFR1) signaling inhibited oligodendrocyte progenitor (OP) differentiation into mature oligodendrocytes. Therefore, we questioned whether FGFR1 signaling may inhibit the capacity of OP cells to generate oligodendrocytes in a demyelinating disease model and whether genetically reducing FGFR1 signaling in oligodendrocyte lineage cells could enhance the capacity for remyelination. FGFR1 was found to be upregulated in the corpus callosum during cuprizone mediated demyelination and expressed on OP cells just prior to remyelination. Plp/CreER^T:Fgfr1^fl/fl mice were administered tamoxifen to induce conditional Fgfr1 deletion in oligodendrocyte lineage cells. Tamoxifen administration during chronic demyelination resulted in reduced FGFR1 expression in OP cells. OP proliferation and population size were not altered one week after tamoxifen treatment. Tamoxifen was then administered during chronic demyelination and mice were given a six week recovery period without cuprizone in the chow. After the recovery period, OP numbers were reduced and the number of mature oligodendrocytes was increased, indicating an effect of FGFR1 reduction on OP differentiation. Importantly, tamoxifen administration in Plp/CreER^T:Fgfr1^fl/fl mice significantly promoted remyelination and axon integrity. These results demonstrate a direct effect of FGFR1 signaling in oligodendrocyte lineage cells as inhibiting the repair capacity of OP cells following chronic demyelination in the adult CNS.     

Imaging of Superoxide Generation in the Dopaminergic Area of the Brain in Parkinson’s Disease,Using Mito-TEMPO

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Absence of oligodendroglial glucosylceramide synthesis does not result in CNS myelin abnormalities or alter the dysmyelinating phenotype of CGT‐deficient mice

To examine the function of glycosphingolipids (GSLs) in oligodendrocytes, the myelinating cells of the central nervous system (CNS), mice were generated that lack oligodendroglial expression of UDP‐glucose ceramide glucosyltransferase (encoded by Ugcg). These mice (Ugcg^flox/flox;Cnp/Cre) did not show any apparent clinical phenotype, their total brain and myelin extracts had normal GSL content, including ganglioside composition, and myelin abnormalities were not detected in their CNS. These data indicate that the elimination of gangliosides from oligodendrocytes is not detrimental to myelination. These mice were also used to asses the potential compensatory effect of hydroxyl fatty acid glucosylceramide (HFA‐GlcCer) accumulation in UDP‐galactose:ceramide galactosyltransferase (encoded by Cgt, also known as Ugt8a) deficient mice. At postnatal day 18, the phenotypic characteristics of the Ugcg^flox/flox;Cnp/Cre;Cgt^−/− mutants, including the degree of hypomyelination, were surprisingly similar to that of Cgt^−/− mice, suggesting that the accumulation of HFA‐GlcCer in Cgt^−/− mice does not modify their phenotype. These studies demonstrate that abundant, structurally intact myelin can form in the absence of glycolipids, which normally represent over 20% of the dry weight of myelin. © 2009 Wiley‐Liss, Inc.     

Measurements of in vivo energy metabolism in experimental cerebral ischaemia using 31P-NMR for the evaluation of protective effects of perfluorochemicals and glycerol

Effects of perfluorochemical (PFC) and glycerol on energy metabolism in cerebral ischaemia were examined by the sequential measurements of in vivo ³¹P-NMR spectrum using topical magnetic resonance (TMR). Experimental cerebral ischaemia was induced in forty-five Wistar rats by a four-vessel occlusion method. The ³¹P-NMR spectrum and the EEG were monitored during preischaemic and ischaemic periods and after circulation was restored for various periods up to 240 min. There were several peaks in the ³¹P-NMR spectrum of the preischaemic rat brain; β-ATP, α-ATP, γ-ATP, phosphocreatine (PCr), phosphodiesters, inorganic phosphate (Pi) and sugar phosphate. As soon as the ischaemia was induced, PCr and ATP decreaseq and Pi increased. The chemical shift of the increased Pi peak decreased, showing acidosis of the brain tissue. After circulation was restored following the 30 min ischaemia, recovery of the ³¹ P-NMR spectrum occurred within 30 min in all sixteen untreated rats. Recovery of the ³¹P-NMR spectrum was induced by recirculation only in half of the six rats in the untreated 60 min ischaemia group. None of the six rats in the untreated group showed recovery of the spectrum after 120 min ischaemia. When 20% Fluosol-DA was administered at a dose of 20 ml/kg before the induction of ischaemia, all eight rats showed recovery of the spectrum after 120 min ischaemia. Moreover, four of six rats treated with both PFC and glycerol showed temporary recovery even after 240 min ischaemia. The results showed that measurements of in vivo ³¹P-NMR spectrum using TMR are very valuable for examining the energy metabolism of cerebral ischaemia, as well as to evaluate the effect of therapeutic drugs on cerebral ischaemia.     

Role for mammalian chitinase 3‐like protein 1 in traumatic brain injury

Traumatic brain injury (TBI) is accompanied by inflammatory infiltrates and CNS tissue response. The astrocytosis associated with TBI has been proposed to have both beneficial and detrimental effects on surviving neural tissue. We recently observed prominent astrocytic expression of YKL‐40/chitinase 3‐like protein 1 (CHI3L1) associated with severity of brain injury. The physiological role of CHI3L1 in the CNS is unknown; however, its distribution at the perimeter of contusions and temporal course of expression suggested that in TBI it might be an important component of the astrocytic response to modulate CNS inflammation. To address this hypothesis, we used serially sectioned brains to quantitatively compare the neuropathological outcomes of TBI produced by controlled cortical impact in wild type (WT) and chi3l1 knockout (KO) mice where the murine YKL‐40 homologue, breast regression protein 39 (BRP‐39/CHI3l1), had been homozygously disrupted. At 21 days post‐injury, chi3l1 KO mice displayed greater astrocytosis (increased GFAP staining) in the hemispheres ipsilateral and contralateral to impact compared with WT mice. Similarly, Iba1 expression as a measure of microglial/macrophage response was significantly increased in chi3l1 KO compared with WT in the hemisphere contralateral to impact. We conclude that astrocytic expression of CHI3L1 limits the extent of both astrocytic and microglial/macrophage facets of neuroinflammation and suggests a novel potential therapeutic target for modulating neuroinflammation.     

Immunohistochemical evidence for degeneration of cholinergic neurons in the forebrain of the rat following injection of AF64A-picrylsulfonate into the dorsal hippocampus

The cholinergic neurotoxin, AF64A-picrylsulfonate, was unilaterally infused into the dorsal hippocampus of Wistar rats (2 nmol/2 μl/4 min; A 6.2, L^s 1.5, H 6.5, Paxinos and Watson). After 19 days the animals' brains were processed for immunohistochemical staining of choline acetyltransferase (ChAT). Morphometry and counting of ChAT-immunoreactive profiles revealed shrinkage and disappearance of cholinergic neurons in the medial septum and diagonal band of Broca at the lesioned brain side. These data indicate a retrograde degeneration of cholinergic neurons following injection of AF64-A-picrylsulfonate into the dorsal hippocampus of the rat.     

Protein kinase C as an early and sensitive marker of ischemia-induced progressive neuronal damage in gerbil hippocampus

In the model of transient brain ischemia of 6-min duration in gerbils we have estimated:

1. The concentration of brain gangliosides: A significant decrease to about 70% of control was observed selectively in the hippocampus at 3 and 7 d after ischemia.
2. The activity of Na⁺,K⁺-ATPase: The enzyme activity was not affected in either hippocampus nor in cerebral cortex.
3. The malonylaldehyde (MDA) concentration: The levels of MDA had increased at 30 min after ischemia up to 123 and 129% of control in hippocampus and cerebral cortex, respectively.
4. Immunoreactivity of protein kinase C detected by Western blotting: In hippocampus the early translocation toward membranes was followed by a decrease in total enzyme content at 6, 24, 72, and 96 h of postischemic recovery. Also, a sharp increase of 50 kDa isoform (PKM) was noticed immediately and at the early recovery times.

The behavior of these biochemical markers of ischemic brain injury in the hippocampus after the short (6 min) insult was contrasted with their reaction in the cerebral cortex as well as after prolongation of the ischemia to 15 min. These results taken together indicate that an early increase in PKC translocation followed by a decrease is the most symptomatic for selective, delayed, postischemic hippocampal injury, resulting from short duration (6 min) ischemia of the gerbil brain.