Alterations in factors involved in the regeneration of the neuronal network in the hippocampus of rats with microsphere embolism (ME) were examined. Nine hundred microspheres (48 μm in diameter) were injected into the right hemisphere, and immunochemical and immunohistochemical studies on the hippocampus were performed on the seventh day thereafter. Hematoxylin–eosin staining showed progressive and severe degeneration of the hippocampus after ME. The protein levels of brain-derived neurotrophic factor (BDNF), 43-kDa growth-associated protein (GAP-43), and adhesion protein L1 (L1) in the ipsilateral hippocampus of the ME animal, determined by Western blot analysis or enzyme immunoassay, were increased, unaltered, and decreased, respectively. In contrast, the immunohistochemical study showed increases in a marker of axonal sprouting GAP-43, and a neurotrophic factor BDNF, and a decrease in an adhesion molecule L1 in some areas of the hippocampal ischemic penumbra of such animals. These results suggest that some factors for regeneration of the neuronal network in the ischemic penumbra responded to sustained cerebral ischemia for a certain period, although functional network of the nerve cells in the microsphere-injected hemisphere would be unlikely established after ME.

The impairments of learning and memory function and of the cholinergic system were examined in rats with microsphere embolism. Microsphere embolism was induced by injection of 900 microspheres with a diameter of 48 microm into the right internal carotid artery. The retention latency of a passive avoidance test was shortened and the escape latency of a water maze test was prolonged, when the animals were tested on the 5th to 10th day after the embolism, suggesting learning and memory dysfunction. Cholinergic parameters of the striatum and hippocampus, such as acetylcholine (ACh) content (67 and 60% decrease, respectively), choline acetyltransferase (ChAT) activity (45 and 56% decrease, respectively), and Bmax of muscarinic acetylcholine M1-receptor (43 and 37% decrease, respectively), were reduced on the 11th day after the embolism, suggesting attenuation of ACh synthesis and a decrease in the number of muscarinic acetylcholine M1-receptors mainly in the striatum and hippocampus. Areas not stained with triphenyltetrazolium chloride, an indication of infarction, were detected mainly in the striatum and hippocampus and partly in the frontal cortex on the 11th day after the embolism. The results suggest that an animal with microsphere embolism may be a good ischemic model with relatively sustained impairments of learning and memory function and of the striatal and hippocampal cholinergic system.

The present study was undertaken to test if some cyclohexane dicarboximide derivatives may have a cardioprotective effect against hypoxia/reoxygenation injury. Isolated rat hearts were subjected to 20-min of hypoxia followed by 45-min reoxygenation, and their recovery of post-hypoxic cardiac contractile function was examined. Treatment with agents was carried out from 3 min after the onset of hypoxia to the end of hypoxia (17 min during hypoxia). Among the 17 compounds, 2-[4-[4-(4-chlorophenyl)-4-hydroxy-1-piperidinyl]butyl]hexahydro-1H-i soindol-1,3(2H)-dione (ST-6) showed a significant enhancement of post-hypoxic contractile force. This was associated with attenuation of the releases of creatine kinase and purine nucleosides and bases from the perfused heart. Hypoxia-induced increase in myocardial sodium and decrease in potassium ion content was suppressed by ST-6 treatment. The results suggest that ST-6 is capable of protecting the heart against hypoxia/reoxygenation injury possibly through a mechanism by which sodium overload during hypoxia is suppressed.

Changes in nerve growth factor (NGF) level and type of cells producing NGF were investigated in the rat brain after sustained cerebral embolism. The NGF level was determined by a two-site enzyme immunoassay specific for NGF. The cerebral cortex, striatum, and hippocampus of the embolized hemisphere maximally contained 2.4-, 2.4-, and 1.7-times higher NGF levels than the corresponding regions of the non-embolized hemisphere. A significant increase was transiently observed for 1 week in the cerebral cortex and striatum, whereas the increase was longer lasting, at least of 4 weeks' duration, in the hippocampus. To examine the localization of NGF-like immunoreactivity (NGF-LI), we used a newly developed anti-NGF peptide antiserum that specifically recognized a 30-kDa molecule(s) in the hippocampal extracts or in NGF cDNA-transfected cells, suggesting that the antibody predominantly reacted with the putative NGF precursor protein(s). NGF-LI, which was localized in neurons of the normal or non-embolized hemisphere, was reduced, and on the embolized side new signals emerged in small non-neuronal cells having a round shape. These included cells with common leukocyte antigen CD45 and T-lymphocyte antigen CD3, which did not appear in the normal or non-embolized hemisphere. NGF-LI and CD3 were colocalized in a substantial number of the cells, suggesting that some activated T-lymphocytes produce NGF for neuronal regeneration after sustained cerebral embolism. J. Neurosci. Res. 56:749–761, 1999. © 1999 Wiley-Liss, Inc.

Effects of nebracetam, a novel nootorpic agent, on the synaptosomal uptake of neurotransmitter monoamines of the brain regions were examined. Striatal and hippocampal synaptosomes were isolated by the Percoll gradient method, and the striatal dopamine uptake and hippocampal serotonin uptake were measured in the presence of different concentrations (1 to 1000 microM) of nebracetam in vitro. A significant reduction in dopamine uptake in the striatum and serotonin uptake in the hippocampus was seen at concentrations of 100 microM or above. In in vivo microdialysis study, there were no appreciable changes in the extracellular concentrations of striatal dopamine and hippocampal serotonin when this agent at a dose of 30 mg/kg, which was effective in improving ischemic brain energy metabolism, was applied i.p. to the rat. The ineffectiveness of nebracetam in the in vivo microdialysis may be due to low levels of the concentration of nebracetam when the agent was administered i.p. at a dose of 30 mg/kg, since the brain blood concentration of this agent is pharmacokinetically estimated to be no more than 15 microM when this dose of nebracetam is employed. Thus, it is unlikely that this agent at a pharmacologically effective dose alters dopamine or serotonin uptake in the brain nerve terminal under normal conditions.

Central cholinergic neurons play an important role in learning and memory functions. The present study was undertaken to elucidate the pathological changes in learning function and acetylcholine metabolism of the cerebral cortex and hippocampus, following microsphere embolism in rats. Microspheres (48 μm) were injected into the right internal carotid artery of the rats. Learning function was determined using a passive avoidance task on the seventh day after the embolism. In the biochemical study, acetylcholine and choline contents, and choline acetyltransferase activity were measured in the cerebral cortex and hippocampus. Cortical acetylcholinesterase-containing fibers were quantitatively estimated in the embolized rat. Passive avoidance was impaired in the microsphere-embolized rat. Microsphere embolism decreased the acetylcholine concentration and choline acetyltransferase activity in the cerebral cortex and hippocampus. In the histochemical study, the length of cortical acetylcholinesterase-containing fibers was decreased, but cell density was unchanged in the ipsilateral hemisphere of the microsphere-embolized rat. The results suggest that microsphere embolism induces severe damage to cholinergic neurons, which may be related to the impairment of learning function in the ischemic brain.

1. The effects of delayed treatment with nebracetam, a novel nootropic drug, on neurotransmitters of brain regions were examined in rats with microsphere embolism-induced cerebral ischaemia. 2. Cerebral ischaemia was induced by administration of 900 microspheres (48 microns) into the internal carotid artery. The rats with stroke-like symptoms were treated p.o. with 30 mg kg-1 nebracetam twice daily. The levels of acetylcholine, dopamine, noradrenaline, 5-hydroxytryptamine (5-HT) and their metabolites in the cerebral cortex, striatum and hippocampus of animals with microsphere embolism were determined by high performance liquid chromatography (h.p.l.c.) on the 3rd and 7th days after the operation. 3. Although the microsphere embolism induced significant changes in most of the neurotransmitters and some of their metabolites in the brain regions, the delayed treatment with nebracetam partially restored only the hippocampal 5-HT and the striatal dopamine metabolite contents on the 3rd day. 4. The hippocampal in vivo 5-HT synthesis, but not the striatal dopamine synthesis, was attenuated in rats with microsphere embolism on the 3rd day, but was restored by treatment with nebracetam. In vivo striatal dopamine turnover rate of the rats with microsphere embolism was inhibited on the 3rd day irrespective of treatment with nebracetam. 5. The present study provides evidence for a possible action of nebracetam on 5-HT metabolism in the ischaemic brain.

. The present study was undertaken to examine the effects of delayed treatment with nafronyl oxalate (nafronyl), a cerebral vasodilator, on monoamine neurotransmitters of brain regions in the microsphere‐embolized rat. . Microsphere embolism was induced by injecting 900 microspheres with a diameter of 48 μm into the right internal carotid artery of rats. Microsphere‐embolized rats were treated with nafronyl, 15 mg kg−1, i.p., twice daily from the first to the 5th day. Levels of monoamines and their metabolites in the cerebral cortex, striatum, and hippocampus were measured on days 3 and 5 after the operation by a high‐performance liquid chromatograph with electrochemical detection. In vivo tyrosine or tryptophan hydroxylation was estimated by measurement of the accumulation of 3,4‐dihydroxyphenylalanine or 5‐ hydroxy‐1‐tryptophan after administration of 3‐hydroxybenzylhydrazine dihydrochloride, an inhibitor of aromatic L‐amino acid decarboxylase. . Microsphere embolism induced decreases in dopamine, noradrenaline and 5‐hydroxytryptamine in three brain regions of the right hemisphere on days 3 and 5. In the left hemisphere, the monoamines were reduced, but to a lesser degree than in the right hemisphere. On days 3 and 5, the decrease in the monoamines of the right hemisphere was attenuated by nafronyl treatment except for noradrenaline on day 3. The decrease in the monoamines levels in the left hemisphere was almost completely prevented by nafronyl treatment. . On day 3 after microsphere embolism, in vivo tyrosine and tryptophan hydroxylation was lower than the pre‐embolic value in all three brain regions. Treatment of the embolized rats with nafronyl significantly attenuated the decrease in in vivo tyrosine and tryptophan hydroxylation in the ipsilateral hemisphere, but not hippocampal tryptophan hydroxylation. . The results suggested that treatment with nafronyl improves or attenuates changes in monoamine neurotransmitter metabolism of the brain regions impaired by microsphere embolism. The mechanisms underlying this effect may be attributed to preservation of the ability to synthesize monoamines when the brain is ischaemic or oligaemic.

The present study was undertaken to examine the possible therapeutic effects on nebracetam on the energy metabolism of rat brain regions in microsphere-induced, sustained ischemia. Microsphere embolism was induced by injection of 900 microspheres (48 microns in diameter) into the right internal carotid artery of rats, and changes in the energy metabolism of the cerebral cortex, striatum and hippocampus of the right hemisphere were determined without and with nebracetam treatment. Microsphere embolism induced increases in lactate and glucose contents and decreases of ATP and creatine phosphate contents in these regions, suggesting that sustained impairment of cerebral energy metabolism occurred. These changes were gradually reversed with time after the operation. Treatment of microsphere-injected rats with 30 mg/kg of nebracetam, p.o., twice a day, was started one day after the onset of cerebral ischemia. The effects of treatment with nebracetam on cerebral energy metabolites were determined on the 3rd and 7th day after operation. Treatment of microsphere-injected rats with nebracetam significantly improved these variables on the 3rd day after the onset of ischemia, but the improvement was small on the 7th day, except for reversal of the hippocampal ATP content. These results suggest that nebracetam is a possible therapeutic agent for the restoration of cerebral energy metabolism against microsphere-induced, sustained cerebral ischemia.

Jak3 is a tyrosine kinase mediating cytokine receptor signaling through the association with the common gamma chain of the cytokine receptors such as IL-2, IL-4, IL-7, IL-9, and IL-15. Unlike other members of the Jak family, the expression of Jak3 is highly restricted in hematopoietic cells. To elucidate in vivo function of Jak3, Jak3-deficient mice were generated by homologous recombination. Mice homozygous for Jak3 null mutation showed severe defects, specifically in lymphoid cells. B cell precursors in bone marrow, thymocytes, and both T and B cells in the spleen drastically decreased, although these defects were significantly recovered as aging occurred. Peripheral lymph nodes, NK cells, dendritic epidermal T cells, and intestinal intraepithelial gamma delta T cells were absent. Normal number of hematopoietic stem cells in bone marrow from Jak3-deficient mice and the similar capability to generate myeloid and erythroid colonies as wild-type mice indicated specific defects in lymphoid stem cells. Furthermore, the abnormal architecture of lymphoid organs suggested the involvement of Jak3 in the function of epithelial cells. T cells developed in the mutant mice did not respond to either IL-2, IL-4, or IL-7. These findings establish the crucial role of Jak3 in the development of lymphoid cells.

The present study was undertaken to determine whether naftidrofuryl oxalate, a cerebral vasodilator, may improve or attenuate microsphere embolism-induced damage to the mitochondrial tricarboxylic acid cycle. For this purpose, the intermediates in the tricarboxylic acid cycle were determined using cerebral cortex isolated from microsphere-injected rats with and without naftidrofuryl oxalate treatment. Seven-hundred microspheres, with a diameter of 48 microns were injected into the right hemisphere through the right common carotid artery. The presence of cerebral infarction on the 3rd day after the operation was confirmed by the development of triphenyltetrazolium chloride-unstained areas in brain sections. Succinate, fumarate, malate, citrate and alpha-ketoglutarate, but not oxaloacetate, contents were significantly decreased in the right hemisphere of rats on the 3rd day following microsphere embolism. In the left hemisphere, a similar but smaller decrease in these intermediates was seen. The rats, which showed typical stroke-like symptoms, were treated with 15 mg/kg naftidrofuryl oxalate i.p., twice daily for 2.5 days, resulting in a significant reversal of the intermediate content of both hemispheres toward the control and an increased in the triphenyltetrazolium-stained area of a coronal section of the right hemisphere relative to the untreated animals. The results suggest that naftidrofuryl oxalate attenuates the development of microsphere embolism-induced cerebral infarction and improves microsphere-induced impairment of the mitochondrial tricarboxylic acid cycle. The observed effects provided evidence for a possible site of action of the agent on ischemic brain energy metabolism.

The present study was undertaken to elucidate the possible therapeutic effects of naftidrofuryl on energy metabolism of brain regions impaired for extended periods by microsphere embolism. Nine hundred microspheres (48 microns in diameter) were injected into the right internal carotid artery of rats, and changes in their behavior and energy metabolism of the cortex, striatum and hippocampus of both hemispheres were determined with and without naftidrofuryl treatment. Microsphere embolism induced increases in lactate, glucose and glycogen contents and decreases in ATP and creatine phosphate of these brain regions of the right hemisphere for up to 28 days after the operation, suggesting long-lasting cerebral ischemia or sustained damage to energy metabolism. These changes were gradually reversed with time after the operation. Microsphere-injected rats were treated twice a day with 15 mg/kg naftidrofuryl, and their behavioral and metabolic protection were determined on the 3rd, 5th and 28th days after the operation. Treatment of embolized animals with naftidrofuryl improved these variables appreciably on the 3rd and 28th days, but little on the 5th day. The improvement on the 3rd day was more evident in all brain regions monitored than that on the 28th day. The results suggest that naftidrofuryl exerts beneficial effects on the energy metabolism of brains damaged by microsphere embolism, the mechanism of which may be due to protection against the development of embolism-induced derangement.

Information on sustained damage to cerebral function and metabolism after cerebral ischemia is useful for prophylaxis and therapeutics of cerebral infarction. The purpose of the present study was to induce sustained damage to brain regions after cerebral ischemia in experimental animals. For this purpose, we examined animal behavior and cerebral energy metabolism following microsphere embolism in rats.We injected 900 microspheres (48 microns in diameter) into the right internal carotid artery of 110 rats and determined the time course of changes in the rats' behavior and the energy metabolism of the cortex, striatum, and hippocampus of both hemispheres. We injected the same volume of vehicle, without microspheres, into 28 sham-operated rats; there were 14 nonoperated control rats.Peak increase in lactate content and decrease in adenosine triphosphate and creatine phosphate of these brain regions of the right hemisphere were seen on the first day after microsphere embolism, whereas peak increases in glucose and glycogen contents of these regions were observed on the third day. Most of the metabolic alterations in all these regions continued for up to 28 days after operation, although they recovered toward control levels with time after the operation. The extent and trend of metabolite changes of the right hemisphere after microsphere embolism were similar in the three brain regions. In the left hemisphere, similar metabolic changes were observed, but to a lesser degree. The time course of changes in behavioral scores following microsphere embolism revealed marked stroke-like symptoms on the first day and relatively rapid disappearance of the symptoms with time after embolism.Microsphere embolism is capable of inducing widespread, sustained damage to energy metabolism of brain regions.