Age-related changes in brain microanatomy: sensitivity to treatment with the dihydropyridine calcium channel blocker darodipine (PY 108-068)

The influence of aging and of treatment with the dihydropyridine Ca2+ antagonist darodipine (PY 108-068) on the age-related microanatomical changes of rat brain were studied in male Wistar rats treated from the 18th to the 24th month of age with an oral dose of 5 mg/kg/day of darodipine. Twelve-month-old untreated rats were used as an adult reference group. A decreased number of nerve cells and of alkaline phosphatase-positive capillaries and an increased lipofuscin deposition were observed in the frontal and occipital cortex, in the hippocampus, and in the cerebellar cortex of rats of 24 months in comparison with 12-month-old animals. The number of nerve cells was higher in the occipital cortex and in the hippocampus, but not in the frontal cortex and in the cerebellar cortex, of darodipine-treated rats in comparison with age-matched untreated animals. Lipofuscin deposition is reduced in all the brain areas investigated. The density of alkaline phosphatase-reactive capillaries is also increased in the frontal and occipital cortex and in the hippocampus of aged rats treated with darodipine. The above results suggest that treatment with darodipine is able to counter some microanatomical changes occurring in the brain of aged rats and involving not only microvascular parameters. The occipital (visual) cortex and the hippocampus were the cerebral areas more sensitive to treatment with darodipine. The possible relevance of these findings is discussed.     

Differential effects of acetylcholine on neuronal activity and interactions in the auditory cortex of the guinea-pig

During normal brain operations, cortical neurons are subjected to continuous cholinergic modulations. In vitro studies have indicated that, in addition to affecting general cellular excitability, acetylcholine also modulates synaptic transmission. Whether these cholinergic mechanisms lead to a modulation of functional connectivity in vivo is not yet known. Herein, the effects were studied of an iontophoretic application of acetylcholine and of the muscarinic agonist, carbachol, on the ongoing activity and co-activity of neurons simultaneously recorded in the auditory cortex of the anaesthetized guinea-pig. Iontophoresis of cholinergic agonists mainly affected the spontaneous firing rates of auditory neurons, affected autocorrelations less (in most cases their central peak areas were reduced), and rarely affected cross-correlations. These findings are consistent with cholinergic agonists primarily affecting the excitability of cortical neurons rather than the strength of cortical connections. However, when changes of cross-correlations occurred, they were usually not correlated with concomitant changes in average firing rates nor with changes in autocorrelations, which suggests a secondary cholinergic effect on specific cortico-cortical or thalamo-cortical connections.     

Local injection of kainic acid causes widespread degeneration of NADPH-d neurons and induction of NADPH-d in neurons, endothelial cells and reactive astrocytes

Nitric oxide (NO), a diffusible gas, is a messenger molecule that mediates vascular dilatation and neural transmission. The enzyme nitric oxide synthase (NOS) present in neurons is activated by Ca2+ influx associated with activation of glutamate receptors. Cultured cortical neurons containing NOS are selectively vulnerable to injury by kainic acid (KA). However, the relationship between NOS neurons and excitotoxicity under in vivo conditions is not entirely clear. In the present study, we examined the time course and spatial distribution of changes in NOS neurons caused by an intracortical microinjection of KA in adult rats. NADPH-diaphorase (NADPH-d) histochemistry was used as a marker for NOS and the neuronal changes were correlated with changes in glial cells and endothelial cells. We demonstrated a rapid loss of NADPH-d neurons in the lesion center and degeneration of NADPH-d neurons and nerve terminals throughout ipsilateral cortex and hippocampus; the striatal neurons appeared to be unaffected. Subsequent to cortical neuronal degeneration, new NADPH-d activity appeared in proliferative reactive astrocytes and in endothelial cells at lesion periphery, and in neuronal groups at lesion periphery, in ipsilateral entorhinal cortex and bilateral hippocampus. These findings indicate that neurons expressing NADPH-d in cerebral cortex and hippocampus are selectively vulnerable to KA toxicity in vivo. The subsequent induction of NOS in neural and non-neural cells may be regarded as an adaptive response to the kainate-induced brain lesion.     

Serotonin promotes the differentiation of glutamate neurons in organotypic slice cultures of the developing cerebral cortex

The monoamines serotonin (5-HT), noradrenaline (NA), and dopamine (DA), which are present in the developing brain apparently before they assume their neurotransmitter functions, are regarded as strong candidates for a role in the maturation of the cerebral cortex. Here we sought to investigate their effects on the generation and differentiation of cortical cell types. Slice cultures, prepared from the cortices of embryonic day (E) 14, E16, and E19 rat fetuses, were kept in defined medium or in defined medium plus 5-HT for 7 d. E16 cortices were also exposed to NA or DA for the same period. At the end of this period, the proportions of the neuronal [glutamate (Glu)-, GABA-, calbindin-, calretinin-labeled], glial (GFAP), and neuroepithelial (nestin) cell types were estimated for all conditions. We found that in E16 cultures, application of 5-HT, but not of NA or DA, significantly increased the proportion of Glu-containing neurons without affecting the overall neuronal population or the proportions of any other cell types. A similar effect was observed in co-cultures of E16 cortex with slices through the midbrain raphe nuclei of E19 rats. The total amount of cortical Glu, as measured with HPLC, was also increased in these co-cultures. To investigate whether the effect of 5-HT was the result of changes in cell proliferation, we exposed slices to bromodeoxyuridine (BrdU) and found that the proportion of BrdU-labeled cells was similar in the 5-HT-treated and control slices. These results indicate that 5-HT promotes the differentiation of cortical Glu-containing neurons without affecting neuroepithelial cell proliferation.     

Magnetic resonance imaging and pathologic studies on lateral fluid percussion injury as a model of focal brain injury in rats

In this study, morphologic changes in brain lesions initiated by moderate lateral fluid percussion injury in rats were investigated chronologically using high-resolution magnetic resonance imaging (MRI) and histopathologic methods. Rats were subjected to moderate fluid percussion injury (average 2.80 +/- 0.48 atmospheres) over the exposed dura overlying the right parietal cortex. MRI obtained in vivo were compared with corresponding pathologic findings at 1, 6, and 24 h and at 3, 6, 14 and 80 days after injury. T2-weighted images showed scattered low-signal intensity in the injured cortex within a few hours after injury, whereas histologic findings revealed intraparenchymal hemorrhages. T2-weighted images of the ipsilateral cerebral cortex and/or corpus callosum showed a high-signal-intensity area 4 h after injury. The high-signal-intensity area became largest in size between 6 and 24 h, then declined gradually, and almost disappeared 14 days after injury. Histologic examination revealed pyknosis, retraction of the cell body of neurons with vacuolated neuropil in the corresponding regions 6 and 24 h after injury, and cystic necrosis 14 days after injury. The location and extent of these pathologic changes were depicted accurately by MRI in vivo. In the hippocampus, pyknosis and retraction of the cell body of pyramidal neurons were observed on the injured side 24 h after injury, and the number of neurons in the CA1 and CA2-CA3 regions decreased significantly on the same side by 14 days after injury. It is concluded that morphologic changes in the brain following experimental traumatic brain injury in rats are detectable in vivo by high-resolution MRI, and that MRI may be useful for the evaluation of treatment effects in experimental brain injury.     

Effect of vagal denervation of the cerebral vessels on cerebellar neurons

Under study were the neurons of the cerebellum cortex of adult cats after a right-side transection of the vagus nerve cranially to its ganglion. The neuron structure was studied in frontal 10-20 mu thick paraffin sections stained with thionine after Nissl 1, 2, 10, 20 days and 1, 2, 3 months after operation. Pathomorphological alterations of neurons were revealed in all layers of the cerebellum cortex. The alterations were of bilateral character, but were more pronounced in the operation side.     

Hyperglycemia and hypercapnia suppress BDNF gene expression in vulnerable regions after transient forebrain ischemia in the rat

Preischemic hyperglycemia or superimposed hypercapnia exaggerates brain damage caused by transient forebrain ischemia. Because high regional levels of brain-derived neurotrophic factor (BDNF) protein correlate with resistance to ischemic damage, we studied the expression of BDNF mRNA using in situ hybridization in rats subjected to 10 minutes of forebrain ischemia under normoglycemic, hyperglycemic, or hypercapnic conditions. Compared with normoglycemic animals, the increase of BDNF mRNA using in situ hybridization in rats subjected to 10 minutes of forebrain ischemia under normoglycemic, or hypercapnic conditions. Compared with normoglycemic animals, the increase of BDNF mRNA in dentate granule cells was attenuated and that in CA3 pyramidal neurons completely prevented in hyperglycemic rats. No ischemia-induced increases of BDNF mRNA levels in the hippocampal formation were detected in hypercapnic animals. Hyperglycemic and hypercapnic rats showed transiently decreased expression of BDNF mRNA levels in the cingulate cortex, which was not observed in normoglycemic animals. The results suggest that suppression of the BDNF gene might contribute to the increased vulnerability of the CA3 region and cingulate cortex in hyperglycemic and hypercapnic animals.     

Opioid-mediated responses of dietary protein on reticular motility and plasma insulin

This study explores the effects of infusion of nerve growth factor (NGF) on behavioral outcome and cell death in the septal region using the clinically relevant model of fluid-percussion brain injury in the rat. Animals were subjected to fluid-percussion brain injury and 24 hours later a miniosmotic pump was implanted to infuse NGF (12 animals) or vehicle (12 animals) directly into the region of maximum injury for 2 weeks. Four weeks postinjury the animals were tested for cognitive function using a Morris Water Maze paradigm. Neurological motor function was evaluated over a 4-week postinjury period. The rats receiving NGF infusions had significantly higher memory scores than vehicle-treated animals. Examination of the cholinergic neurons in the medial septal region using choline acetyltransferase immunohistochemistry demonstrated significant cell loss after injury. Infusion of NGF significantly attenuated loss of these cholinergic neurons. A second group of animals was subjected to fluid-percussion brain injury alone (23 rats) or injury followed by NGF infusion (18 rats). These animals were killed between 24 hours and 2 weeks postinjury and the septal region was examined for the presence of apoptotic cells using the terminal deoxynucleotidyl transferase-mediated biotinylated-deoxyuridinetriphosphate nick-end labeling technique. Apoptotic cells were identified as early as 24 hours postinjury; their numbers peaked at 4 and 7 days, and then declined by 14 days. The NGF-treated animals had some apoptotic cells; however, even at 7 days there were significantly fewer of these cells. No significant motor differences were observed between the NGF- and vehicle-treated groups. These data indicate that NGF administration beginning 24 hours after fluid-percussion brain injury has a beneficial effect on cognition and results in sparing of cholinergic septal neurons. These improvements persist after cessation of NGF administration. The beneficial effects of NGF may be related to its ability to attenuate traumatically induced apoptotic cell death.     

Empirical comparisons of proportional hazards, poisson, and logistic regression modeling of occupational cohort data

Protein deprivation experienced in adult life leads to deficits in the number of hippocampal granule and CA3-CA1 pyramidal cells and to changes in the dendritic domain of granule cells and CA3 pyramids. To obtain a more complete insight into the effects of malnutrition on the limbic system of the adult rat we have analyzed the subiculum and the entorhinal cortex (neuronal layers II, III, and V-VI) in groups of 8-month-old rats fed with a low-protein diet (8% casein) since the age of 2 months and in age-matched control rats. Stereological methods were employed to estimate the total number of neurons in the subiculum and layers II, III, and V-VI of the entorhinal cortex and the volume of the respective cell layers. Moreover, to evaluate whether protein deprivation affects the dendritic domains of the neurons from these regions we have analyzed, in Golgi-impregnated material, the dendritic trees of the pyramidal cells of the subiculum and of the stellate neurons of the entorhinal cortex layer II applying quantitative and metric methods. The volume of the subiculum and the total number of its neurons were reduced in malnourished animals. In these animals we also found marked regressive changes in the apical and basal dendritic trees of the pyramidal subicular neurons. However, the spine density was increased in malnourished rats. No differences in the volume of the neuronal layers of the entorhinal cortex or in the total number of their neurons were found between protein-deprived and control rats, and no alterations were depicted in the dendritic trees of the stellate neurons of layer II. We can thus conclude that the effects of long-term protein deprivation are region specific and that the resulting structural alterations are confined to the three-layered components of the hippocampal region.     

Reduction in the number of NADPH-diaphorase-positive cells in the cerebral cortex and striatum in aged rats

Nitric oxide (NO) plays an important role as a diffusible messenger in learning and memory. To determine whether changes in NO production in the brain may be involved in aging-associated brain dysfunction, we measured the performance of aged rats in a radial arm maze task, and carried out histochemical examination of the changes in NADPH diaphorase (NADPH-d)-containing neurons in the brains of aged rats. The performance of aged rats (30 months old) in a radial arm maze task was significantly impaired compared to the performance of young rats (3 months old). The number of neurons containing NADPH-d reactivity in the cerebral cortex and striatum of aged rats was significantly reduced, by approximately 50 and 30 percent, respectively, compared to that in young rats. NO synthase activity in discrete brain regions of aged rats, i.e., in the cerebral cortex, striatum and hippocampus was not different from that in young rats, although the activity in the cerebellum of aged rats was significantly lower than that in young rats. These results suggest that the reduction in the number of NADPH-d-positive cells in the brains of aged rats may be involved in aging-associated learning impairment in rats.     

NMDA-NR1 receptor subunit mRNA expression in rat brain after 6-OH-dopamine induced lesions: a non-isotopic in situ hybridization study

Antisense digoxigenin-labeled deoxyoligonucleotides probes and non-isotopic in situ hybridization (HIS) techniques have been used to explore the NMDA-NR1 receptor subunit mRNA distribution in different brain areas of rats which had their dopaminergic nigrostriatal pathway previously lesioned with intracerebral administration of 6-OH-dopamine (6-OH-DA). Intense and significant hybridization signals for NR1 mRNA were found in dentate gyrus and regions CA1-CA2-CA3 of the hippocampus, in layers II-III and V-VI of the cerebral cortex, and in the cerebellum of sham-treated rats. Basal ganglia structures such as the striatum exhibited few NR1 mRNA hybridization signals as compared to the hippocampus and cerebral cortex. In contrast, both zona compacta and reticulata of substantia nigra (SN) showed a reduced number of cells with nevertheless intense NR1 mRNA HIS signals. The NR1 mRNA distribution in the brain was affected in a brain regional selective manner by 6-OH-DA induced lesions of DA neuronal systems. A striking increase in NR1 mRNA HIS signals was observed in both striata after unilateral lesioning with 6-OH-DA. Instead, in SN compacta but not in reticulata, a moderate but significant bilateral reduction of NR1 mRNA was observed after unilateral 6-OH-DA injection. No significant changes in NR1 mRNA were detected in cerebral cortex and other brain regions after 6-OH-DA treatment. These studies, and others reported in the literature, support the view that extensive lesions of nigrostriatal DA-containing neurons in the brain may trigger compensatory or adaptative responses in basal ganglia structures such as striatum and substantia nigra which involve glutamateric neurons and the genic expression of NMDA receptors.     

The regulation of hippocampal dynorphin by neural/neuroendocrine pathways: models for effects of aging on an opioid peptide system

Previous research has demonstrated increased messenger RNA expression and peptide content in an opioid system localized to hippocampal dentate granule cells in aged rats. This altered regulation of dynorphin was correlated with the emergence of an age-related impairment in spatial learning. Considerable evidence exists for additional effects of aging on systems that provide input to the dynorphin-containing dentate granule cells. Such changes have been well documented for loss of perforant path innervation from entorhinal cortex, deterioration in septohippocampal cholinergic neurons, and high amounts of glucocorticoids that have, among their targets, receptors located in the dentate gyrus. Similar to the effects of aging on hippocampal dynorphin, age-related changes in each of these systems correlate with the severity of spatial learning impairment in aged rats. This raises the possibility that dysregulation of dynorphin in the aged brain is a reactive response to antecedant change(s) in this circuitry, a hypothesis that was examined by separately manipulating in young rats the three neural/neuroendocrine systems identified above. Of the three models examined only removal of the perforant path reproduced the effect of aging on dynorphin in the hippocampal formation. An immunotoxin was used in Experiment 1 to selectively remove septo-hippocampal cholinergic neurons in young rats. No alteration in hippocampal opioid peptides was produced by this treatment. Experiment 2 examined effects of exposure to excess corticosterone. Adrenalectomized rats exhibited a significant decrease in hippocampal dynorphin-A (1-8) content, which was reversed by corticosterone replacement at a concentration approximating normal basal levels. Dynorphin-A (1-8) content, however, was not reliably increased by exposure to excess corticosterone. In contrast, perforant path removal was found to reproduce the effect of aging on dynorphin content; either aspiration of the entorhinal cortex or knife-cut transections of the perforant path reliably increased hippocampal dynorphin content. These results support the conclusion that age-related deterioration in the septohippocampal cholinergic system and evaluated exposure to corticosterone are not sufficient to induce an elevation in hippocampal dynorphin content. Only removal of the perforant path innervation was found to reproduce the elevation in hippocampal dynorphin content observed in aged rats with hippocampal-dependent learning impairment.     

Experimental brain injury induces regionally distinct apoptosis during the acute and delayed post-traumatic period

The temporal pattern of apoptosis in the adult rat brain after lateral fluid-percussion (FP) brain injury was characterized using terminal deoxynucleotidyl-transferase-mediated biotin-dUTP nick end labeling (TUNEL) histochemistry and agarose gel electrophoresis. Male Sprague Dawley rats were subjected to brain injury and killed for histological analysis at intervals from 12 hr to 2 months after injury (n = 3/time point). Sham (uninjured) controls were subjected to anesthesia with (n = 3) or without (n = 3) surgery. Apoptotic TUNEL-positive cells were defined using stringent morphological criteria including nuclear shrinkage and fragmentation and condensation of chromatin and cytoplasm. Double-labeled immunocytochemistry was performed to identify TUNEL-positive neurons (anti-neurofilament monoclonal antibody RM044), astrocytes (anti-glial fibrillary acidic protein polyclonal antibody), and oligodendrocytes (anti-cyclic nucleotide phosphohydrolase polyclonal antibody). Compared with that seen with sham controls, in the injured cortex, significant apoptosis occurred at 24 hr (65 +/- 19 cells; p < 0.05) with a second, more pronounced response at 1 week after injury (91 +/- 24 cells; p < 0.05). The number of apoptotic cells in the white matter was increased as early as 12 hr after injury and peaked by 1 week (33 +/- 6 cells; p < 0.05). An increase in apoptotic cells was observed in the hippocampus at 48 hr (13 +/- 8), whereas in the thalamus, the apoptotic response was delayed, peaking at 2 weeks after injury (151 +/- 71 cells; p < 0.05). By 2 months, the number of apoptotic cells in most regions had returned to uninjured levels. At 24 hr after injury, TUNEL-labeled neurons and oligodendrocytes were localized primarily to injured cortex. By 1 week after injury, populations of TUNEL-labeled astrocytes and oligodendrocytes were present in the injured cortex, while double-labeled neurons were present predominantly in injured cortex and thalamus, with a few scattered in the hippocampus. DNA agarose gels confirmed morphological identification of apoptosis. These data suggest that the apoptotic response to trauma is regionally distinct and may be involved in both acute and delayed patterns of cell death.     

A decrease of reelin expression as a putative vulnerability factor in schizophrenia

Postmortem prefrontal cortices (PFC) (Brodmann's areas 10 and 46), temporal cortices (Brodmann's area 22), hippocampi, caudate nuclei, and cerebella of schizophrenia patients and their matched nonpsychiatric subjects were compared for reelin (RELN) mRNA and reelin (RELN) protein content. In all of the brain areas studied, RELN and its mRNA were significantly reduced (approximately 50%) in patients with schizophrenia; this decrease was similar in patients affected by undifferentiated or paranoid schizophrenia. To exclude possible artifacts caused by postmortem mRNA degradation, we measured the mRNAs in the same PFC extracts from gamma-aminobutyric acid (GABA)A receptors alpha1 and alpha5 and nicotinic acetylcholine receptor alpha7 subunits. Whereas the expression of the alpha7 nicotinic acetylcholine receptor subunit was normal, that of the alpha1 and alpha5 receptor subunits of GABAA was increased when schizophrenia was present. RELN mRNA was preferentially expressed in GABAergic interneurons of PFC, temporal cortex, hippocampus, and glutamatergic granule cells of cerebellum. A protein putatively functioning as an intracellular target for the signal-transduction cascade triggered by RELN protein released into the extracellular matrix is termed mouse disabled-1 (DAB1) and is expressed at comparable levels in the neuroplasm of the PFC and hippocampal pyramidal neurons, cerebellar Purkinje neurons of schizophrenia patients, and nonpsychiatric subjects; these three types of neurons do not express RELN protein. In the same samples of temporal cortex, we found a decrease in RELN protein of approximately 50% but no changes in DAB1 protein expression. We also observed a large (up to 70%) decrease of GAD67 but only a small decrease of GAD65 protein content. These findings are interpreted within a neurodevelopmental/vulnerability "two-hit" model for the etiology of schizophrenia.     

Specific induction of protein kinase C delta subspecies after transient middle cerebral artery occlusion in the rat brain: inhibition by MK-801

Protein kinase C (PKC) consists of a family of closely related Ca2+/phospholipid-dependent phosphotransferase isozymes, most of which are present in the brain and are differentially activated by second messengers. Calcium-dependent PKC activity may cause neuronal degeneration after ischemic insult. PKC is also involved in trophic-factor signaling, indicating that activity of some PKC subspecies may be beneficial to the injured brain. Therefore, we screened long-term changes in the expression of multiple PKC subspecies after focal brain ischemia. Middle cerebral artery occlusion was produced by using an intraluminal suture for 30 min of 90 min. In in situ hybridization experiments, mRNA levels of PKC alpha, -beta, -gamma, -delta, -epsilon, and -zeta were decreased in the infarct core 4 hr after ischemia and were lost completely 12 hr after ischemia. In areas surrounding the core, PKC delta mRNA was specifically induced 4, 12, and 24 hr after ischemia in the cortex. At 3 and 7 d, the core and a rim around it showed increased mRNA levels of PKC delta. No other subspecies were induced. At 2 d, immunoblotting demonstrated increased levels of PKC delta protein in the perifocal tissue, and immunocytochemistry revealed an increased number of PKC delta-positive neurons in the perifocal cortex. In the core, PKC delta-positive macrophages and endothelial cells were seen. Pretreatment with MK-801, an NMDA antagonist, inhibited cortical PKC delta mRNA induction. The data show that focal brain ischemia induces PKC delta mRNA and protein but not other PKC subspecies through the activation of NMDA receptors and that the upregulation lasts for several days in neurons of the perifocal zone.     

Chronic spinal nerve ligation induces changes in response characteristics of nociceptive spinal dorsal horn neurons and in their descending regulation originating in the periaqueductal gray in the rat

We studied whether a chronic neuropathy induced by unilateral spinal nerve ligation changes the response characteristics of spinal dorsal horn wide-dynamic range (WDR) neurons or their periaqueductal gray (PAG)-induced descending modulation. Experiments were performed in rats with behaviorally demonstrated allodynia induced by spinal nerve ligation and in a group of nonneuropathic control rats. The stimulus-response functions of WDR neurons for mechanical and thermal stimuli and the modulation of their peripherally evoked responses by electrical stimulation of the PAG were determined under pentobarbital anesthesia. The results showed that neuropathy caused a significant leftward shift in stimulus-response functions for mechanical stimuli. In contrast, stimulus-response functions for noxious heat stimuli in the neuropathic limb were, if anything, shifted rightward, although this shift was short of statistical significance. In neuropathic rats, PAG stimulation produced a significantly stronger attenuation of spinal neuronal responses induced by noxious heat in the unoperated than in the operated side. At the intensity that produced attenuation of noxious heat stimuli, PAG stimulation did not produce any significant change in spinal neuronal responses evoked by mechanical stimuli either from the operated or the nonoperated hindlimb of the neuropathic rats. Spontaneous activity of WDR neurons was higher in the operated side of neuropathic rats than in control rats. Afterdischarges evoked by peripheral stimuli were observed in 1/16 of the WDR neurons ipsilateral to spinal nerve ligation and not at all in other experimental groups. The WDR neurons studied were not activated by innocuous or noxious cold stimuli. The results indicate that spinal nerve ligation induces increased spontaneous activity and enhanced responses to mechanical stimuli in the spinal dorsal horn WDR neurons, whereas noxious heat-evoked responses are not significantly changed or if anything, attenuated. Moreover, the inhibition of noxious heat stimuli by PAG stimulation is attenuated in the neuropathic side. It is proposed that the observed changes in the response characteristics of the spinal dorsal horn WDR neurons and in their descending modulation may contribute to the neuropathic symptoms in these animals.     

The neurochemical, molecular and ultrastructural mechanisms of the formation of latent postresuscitation encephalopathy

The content of total RNA and DNA, activity of Ca2+, Mg(2+)-dependent DNA endonuclease, and ultrastructural changes in nerve tissue cells were examined in the brain cortex of narcotized dogs 1 to 3 months after a 4-hour hemorrhagic shock (arterial pressure 40 mm Hg). A new variant of reconstruction of cell membranes and organelles formed by them was revealed, developing in the brain neurons in the course of adaptation during the first-third months of the postshock period. Evidently, the molecular base of development of an atypical variant of cell structure rearrangement in the remote period after shock is the internucleosomal fragmentation of a part of the DNA of nerve cells resultant from DNA endonucleolysis and subsequent information disintegration of a cell as a system. This distorts the process of biosynthesis of supramolecular ensembles, specifically, of nerve cell biomembranes.     

Prolonged and extensive IgG immunoreactivity after severe fluid-percussion injury in rat brain

The relationships between protein extravasation, morphological changes in neurons, and reactive changes in axons were evaluated in rats subjected to right lateral fluid-percussion injury to the brain (4.8-5.6 atm, 20 ms). Serial sections of the brain were immunostained with antibodies to rat immunoglobulin G (IgG) and 68-kDa neurofilament at 1 h to 2 weeks after injury or sham injury. Ischemic changes in neurons were noted in the injured cortex at 6-48 h after injury, and macroscopic hemorrhages were noted in the right corpus callosum and external capsule at 1 h to 1 week after injury. Extracellular IgG immunostaining was observed in the right cortex and right hippocampus at 1 h to 1 week after injury, and in the cortices and hippocampi bilaterally at 2 weeks after injury, but was most prominent in those regions at 24 h after injury. Intracellular IgG staining was noted in the neurons of cortices, hippocampi, brainstem, and cerebellum at 1 h to 2 weeks after injury. The number of IgG immunoreactive neurons was greatest at 1 week after injury. Thickened IgG immunoreactive axons and reactive axonal changes seen with neurofilament immunostaining were both in the similar region of the brainstem at 1 h to 1 week after injury. It appears that prolonged and widespread breakdown of the blood-brain barrier to plasma protein occurs after severe concussive brain injury and that this breakdown is not always accompanied by morphological changes. Intra-axonal IgG immunostaining provides additional clues to the pathogenesis of axonal damage following diffuse brain injury.