Hypoxic forebrain cholinergic neuron injury: role of glucose, excitatory amino acid receptors and nitric oxide

Glucose depletion increased sensitivity to hypoxic insult in basal forebrain forebrain cultures in a dose-dependent manner as indicated by reduction of choline acetyltransferase (ChAT) activity, increased lactate dehydrogenase (LDH) release and disrupted morphology. The glutamate receptor antagonists 2-amino-5-phosphonovaleric acid (APV) and 6-cyano-2,3-nitroquinoxoline (CNQX) limited the degree of injury in combination and individually. The nitric oxide synthase (NOS) inhibitor N-nitro-L-arginine (NNLA) also either completely protected against mild injury or attenuated severe injury.

Upregulation of calpain activity in neonatal rat brain after hypoxic-ischemia

Neonatal rats were subjected to transient cerebral hypoxic-ischemia (unilateral occlusion of the common carotid artery plus 7.7% O2 for 2 h) and allowed to recover for 0 min, 30 min or 20 h. The calpain and calpastatin activities were assayed in subcellular fractions of the ipsilateral, hypoxic-ischemic and the contralateral, hypoxic hemisphere. An upregulation of calpain activity occurred in the hypoxic hemisphere, both in the major, cytosolic fraction and in the hypotonic, membrane associated fraction (110% and 133% of controls, respectively). The hypoxic-ischemic hemisphere displayed a decrease in calpain activity in the cytosolic fraction but an increase in the hypotonic fraction (90% and 111% of controls, respectively). The changes in calpastatin activity were less pronounced. This indicates that an upregulation of calpain activity occurs in parallel with development of hypoxic-ischemic damage. However, this upregulation is not necessarily coupled to development of injury as lesions are not seen in the hypoxic hemisphere.

Changes in protein kinase C isozymes in the rat hippocampus following transient hypoxia

The effects of hypoxia on protein kinase C (PKC) isozymes (alpha, beta I, beta II, and gamma) were examined in the hippocampus from rats subjected to hypoxic conditions (5% O2 in 95% N2) for 30 min in a chamber. Western blot analysis revealed that the total amounts of PKC-alpha (-26.0% of control) and -gamma (-32.7% of control) were decreased significantly at the end of hypoxia, which was followed by the reduction of that of PKC-beta II (-23.7% of control at 7 days after hypoxia). Whereas, the PKC activities, which were measured by the incorporation of [gamma-32P] into a specific PKC substrate peptide, in both the cytosolic and the particulate fractions did not change. The reductions of PKC-gamma and -alpha at the end of hypoxia may be related to the following neuronal degeneration.

[Brain bioenergetic parameters in rats with varying resistance to hypoxia]

Spontaneous electrical activity, adenyl nucleotides' and cytochromes' contents, activity of respiratory chain enzymes complex in brain slices, homogenate and isolated mitochondria of rats, preliminary divided into non-resistant (NR) and high resistant (HR) animals by their sensitivity to hypobaric hypoxia have been investigated. It has been shown that in HR animals brain slices high resistant to hypoxia neurons and in NR brain slices non-resistant neurons predominate. ATP content and energetic charge in the HR animals brain slice were maintained at more high level than in NR. The reduction of NAD-depended way of oxidation in low pO2 conditions was greater in brain of NR than in HR animals. Activity of NADH-cytochrome C reductase (rotenon-sensitive) and Km for NADH in HR brain was more higher in the comparison with NR. These data indicate the main role of NADH-oxidase way in the formation of the individual brain resistance to hypoxia.

[Brain-specific creatine kinase (CKBB) in umbilical cord blood. A prognostic parameter in chronic intrauterine hypoxia?]

Elevated levels of brain type creatine isoenzyme (CKBB) have been demonstrated in serum after brain cell injury in neonates. A hypoxic lesion of the membrane permeability of the CKBB rich brain cells may lead to an increased enzyme leakage into the serum. As an increased release from the fetal brain as a result of intermittent compression and decompression of the fetal head during labour and after rupture of membranes may occur without hypoxic damage, only pregnancies which were terminates by cesarean section were studied. No mother went into first stage of labour and no rupture of membranes occurred. Three study groups were defined. The control group (elective cesarean section for breech presentation) showed CKBB enzyme activities below 15 U/l. A group with emergency cesarean sections had low CKBB values too, despite acidotic pH-values (pH < 7.20) at birth. The third group included fetuses which were delivered by cesarean section because of a pathological fetal heart rate tracing and intrauterine growth retardation. 6 out of 40 umbilical cord sera in this group showed elevated CKBB enzyme activities. If there was an additional fetal acidosis an increased neurological morbidity and neonatal mortality was seen.

Effect of graded hypoxia on brain cell membrane injury in newborn piglets

Alterations in brain cell membrane structure and function during cerebral hypoxia were investigated by measuring Na+,K(+)-ATPase activity and levels of lipid peroxidation products in brain cell membranes obtained from newborn piglets following exposure to 60 min of hypoxic hypoxia in vivo. Cerebral hypoxia was documented as a decrease in the ratio of phosphocreatine to inorganic phosphate (PCr/Pi) using 31P-NMR spectroscopy. During hypoxia (FiO2 0.07-0.11), PCr/Pi decreased 28-47% compared to the corresponding baseline value without a decrease in cerebral ATP levels. No change in brain cell membrane Na+,K(+)-ATPase activity was observed for changes in PCr/Pi of less than 30%. When PCr/Pi was at least 30% lower than baseline, Na+,K(+)-ATPase activity decreased linearly as a function of the decrease in PCr/Pi (r = 0.95). Levels of lipid peroxidation products (conjugated dienes and fluorescent compounds) increased significantly as PCr/Pi decreased. These data suggest that below a critical threshold value of oxidative metabolism there are progressive changes in brain cell membrane structure and function during cerebral hypoxia, and demonstrate that membrane alterations occur prior to changes in cellular ATP levels.

[Lactate dehydrogenase in the cerebrospinal fluid in 57 hypoxic neonates]

The authors used assessment of lactic dehydrogenase activity in cerebrospinal fluid to evaluate the severity of hypoxic damage of the CNS of neonates. The highest activity was recorded in infants who died in conjunction with the hypoxic lesion of the CNS. The lowest activity was found in neonates with a permanently normal neurological finding during infancy. From the results ensues the prognostic importance of the above examination for subsequent psychomotor development of children.

Features of the cerebral vascular pattern that predict vulnerability to perfusion or oxygenation deficiency: an anatomic study

In an ongoing study of brain microvasculature in humans at autopsy, we had the opportunity to analyze the overall scheme of this vascular supply. The native endothelial membrane enzyme, alkaline phosphatase, is used to precipitate black lead sulfide salt in the vessel wall, rendering the brain microvasculature visible by both light microscopy and microradiography. There are six distinct patterns of intraparenchymal afferent blood supply to the supratentorial brain: short arterioles from a single source (e.g., those in the cortex); short- to intermediate-length arterioles, single source (anterior two-thirds of the corpus callosum); short- to intermediate length arterioles and arteries, dual source (subcortical U fibers); intermediate-length arterioles and arteries, triple source (extreme/external capsule and claustrum); long arteries and arterioles, single source (centrum semiovale); and large, long muscular arteries, single source (thalamus and basal ganglia). The nature of this arrangement offers some protection to certain regions of the cerebrum from circulatory challenges such as hypotension, while leaving other areas vulnerable. The distal arterioles supplying two of these protected regions, the U-fiber area and the extreme/external capsule and claustrum area, also exhibit the feature of interdigitation, which can offer additional collateral potential from one arteriolar territory to the next. Aging, hypertension, diabetes mellitus, and atherosclerosis can have a significant impact on brain microcirculation. The way in which vascular patterns dictate the distribution of these effects is discussed. The ability to stain the cerebral microvessels and demonstrate the finer points of their patterns in sections and microradiographs has enabled us to resolve some long-standing questions about vascular connections and directions.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain type creatine kinase in relation to oxygen desaturation in the blood of children with congenital heart disease

The concentration of brain type creatine kinase (CK-BB) was measured in blood from the internal jugular vein in 32 children (less than 1 year old) with congenital heart disease. In transposition of the great arteries the CK-BB levels were significantly higher than in children without cyanosis (10.1 +/- 4.1 vs. 3.0 +/- 0.5 ng/ml). A negative correlation was found for CK-BB concentration and arterial oxygen saturation (r = -0.41, p less than 0.02 for all children and r = -0.62, p less than 0.05 for those with tetralogy of Fallot). It is suggested that the increased CK-BB levels in the blood of cyanotic children reflect chronic cerebral hypoxia, which may explain other reports of reduced psycho-intellectual function in patients with cyanotic heart disease.

Adverse effects on the brain in connection with isoflurane-induced hypotensive anaesthesia

As a marker of brain cell injury, adenylate kinase (AK) was measured in cerebrospinal fluid (CSF) in 10 patients given anaesthesia with isoflurane-induced hypotension for corrective surgery of dentofacial deformities. Nine out of 10 patients displayed a marked increase in CSF-AK postoperatively compared with preoperative values. The postoperative mean value displayed a 400% increase compared to the corresponding preoperative value. This difference was statistically significant (P = 0.001). The rise in CSF-AK was most probably the result of an enhanced efflux of AK into CSF subsequent to a presumed hypoxic injury to brain cells.

Serum CPK-BB isoenzyme in the assessment of brain damage in asphyctic term infants

Serum creatine phosphokinase-BB activities were measured at 4 and at 10 hours of life in 33 asphyctic full-term infants. The infants were followed for a mean period of 16 months. Enzyme activities at 4 hours of life were significantly higher in those neonates who died of severe hypoxic-ischemic encephalopathy or developed neurological sequelae than in those who did not present neurological abnormalities during the follow-up time. The specificity of the enzyme assay in order to predict the neurological outcome was inferior to that of cranial computed tomography or a combined clinical-electroencephalographic evaluation. It appears that the presence of elevated serum creatine phosphokinase-BB activity can be a sensitive indicator of conspicuous brain damage, but it is of limited value to predict the neurological outcome after neonatal asphyxia.

Effects of postnatal hypoxia-ischemia on cholinergic neurons in the developing rat forebrain: choline acetyltransferase immunocytochemistry

We studied the effect of early postnatal hypoxia-ischemia on cholinergic neurons in the developing rat forebrain using immunohistochemistry for choline acetyltransferase (ChAT). In 7-day-old rat pups, hypoxia-ischemia was induced in one cerebral hemisphere by combining unilateral carotid ligation with exposure to 8% oxygen for 2.5 h. This procedure caused brain injury in the hemisphere ipsilateral to ligation, most prominent in the corpus striatum, hippocampus and overlying cortex. In animals sacrificed 2-3 weeks after the insult, at approximately 3 weeks of age, the density of cholinergic cell bodies was slightly higher in the lesioned rostral caudate-putamen than the opposite side (+12%, P less than 0.05). In the more caudal portion of caudate-putamen, this effect was greater. In contrast, the size of the cholinergic perikarya in the injured striatum was significantly reduced. Cholinergic neurons in the septum (Ch1, Ch2), globus pallidus and nucleus basalis (Ch4) were relatively unaffected. Considered together with previously reported neurochemical data, these observations suggest that the immature cholinergic neurons are less vulnerable to death from hypoxia-ischemia than other components of the striatum. However, differentiation of surviving cholinergic perikarya and possibly their axonodendritic processes may be disrupted by the early insult.

Mitochondrial and MB isoenzymes of creatine kinase in cerebrospinal fluid from patients with hypoxic-ischemic brain damage

Measurements of cerebrospinal fluid (CSF) creatine kinase (CK, EC 2.7.3.2) isoenzyme activity have been used to predict outcome in patients with acute brain injury following cardiac arrest. We identified two CK isoenzymes previously unreported in CSF from 16 patients with hypoxic-ischemic brain damage. Prior to analysis, the CK in the CSF samples was reactivated with dithiothreitol. CK isoenzymes were identified using electrophoretic and immunologic methods. Total CK activity ranged from 23 to 924 U/L (mean 452). CSF-CK-BB was the predominant isoenzyme present in all cases. In addition to CSF-CK-BB, the authors identified CSF-CK-MM in 6 cases, CSF-CK-MB in 8 cases, and CSF-mitochondrial-CK in 14 cases. The presence of CSF-CK-MM was significantly related to blood contaminating the CSF (P less than 0.02). It is proposed that CSF-CK-MB results from recombination of CK-MM and CK-BB in CSF and that mitochondrial CK is released with CK-BB into the CSF from the damaged brain tissue.

Immunohistochemical localization of glutathione peroxidase in the brain of the rat

The distribution of glutathione peroxidase (GSH-PO) in the brain of rats was studied by using the peroxidase-anti-peroxidase (PAP) immunohistochemical method employing highly specific antibodies raised in rabbits to GSH-PO. The purity of the antigen and the specificity of the antibodies were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and transblot assay, respectively. The specificity of the immunohistochemical staining was confirmed by using a pre-immune serum, eliminating the first to third antibodies in the PAP method and absorption test. Under pentobarbital anesthesia, male Wistar rats were perfused with a mixture of fixatives (paraformaldehyde, glutaraldehyde and picric acid) via the left cardiac ventricle. The brain was immediately removed en masse and fixed in a similar solution but lacking glutaraldehyde, and then thin-sectioned with a cryostat. The sections were stained by the PAP immunohistochemical method. The immunoreactive products were observed chiefly in the nuclei of some nerve cells in the following areas: layers II, IV, VI in the cerebral cortex; CA2, CA1 and CA4, CA3 (listed in descending degree) in the hippocampus; granular and molecular layers in the cerebellar cortex. Few immunoreactive products were observed in the pyramidal cells in layers III, V of the cerebral cortex, and not at all in the Purkinje cells of the cerebellum. The nerve cells where lacking GSH-PO well coincided with the cells vulnerable to hypoxia. During or following hypoxia, lipid peroxides will be generated in the tissues and do harm when they exceed some amount.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain enzyme adaptation to mild normobaric intermittent hypoxia

The adaptation to repeated periods of intermittent normobaric hypoxia (oxygen:nitrogen = 10:90, 12 hr daily for 5 days) of some specific enzymatic activities related to energy metabolism has been observed in different rat brain areas (cerebral cortex, hippocampus, corpus striatum, hypothalamus, cerebellum, and medulla oblongata). The evaluation of the maximum rate (Vmax) of the enzymes was carried out on: the homogenate "in toto," the nonsynaptic mitochondrial fraction, and the crude synaptosomal fraction. The adaptation to intermittent normobaric hypoxic exposure was characterized by significant modifications of some enzyme activities in the homogenate "in toto" (decrease of hexokinase activity in cerebellum), in the nonsynaptic mitochondrial fraction (increase of succinate dehydrogenase activity in corpus striatum and decrease of cytochrome oxidase activity in cerebral cortex), and, particularly, in the synaptosomal fraction (decrease of cytochrome oxidase activity in cerebral cortex, hippocampus, corpus striatum, and cerebellum, and decrease of malate dehydrogenase and lactate dehydrogenase activity in cerebellum). The adaptation to normobaric intermittent hypoxia differs according to the brain area, subcellular fraction, and enzyme activity tested.

The effect of perinatal anoxia on amino acid metabolism in the developing brain. Part I: The effect of experimental anoxia on the free amino acid patterns in the brain of neonatal rats

The effect of perinatal anoxia on the subsequent amino acid pattern in the brain during a period of 2 wks after birth was investigated using neonatal rats. Sixty-nine neonatal albino rats of the Wistar strain were divided into 3 groups: the 1st control group (n = 36), the 2nd anoxic group (n = 30) and the 3rd anoxic-ischemic group (n = 3). In the 1st and 2nd groups, 6 rats out of each group were sacrificed on the each of the following days respectively, the 1st, 3rd, 5th, 7th, 10th and 15th days of life for amino acid assays of brain. In the 3rd group, 3 rats were sacrificed 2 days after ligation of the carotid artery on one side, and free amino acid levels in both cerebral hemispheres were separately measured. In the controls, the levels of GABA, Asp and Glu in the brain increased, those of Tau and Gly decreased and those of PE, Thr, Ser, Gln, Ala and Leu did not change during the experimental period. The total free amino acid level in the brain of the controls remained almost completely unchanged during this period. After anoxic exposure the levels of GABA, Tau, PE, Asp, Thr, Glu, Gln and Ala, and the total free amino acid level in the brain decreased until the 7th day of life and thereafter rapidly increased. The Gly level continuously decreased and the Ser and Leu levels did not change during the experiment. The GABA and Gly levels after anoxia decreased and were still low on the 15th day of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of intermittent hypoxia and pyrimidinic nucleosides on cerebral enzymatic activities related to energy transduction

The effect of intermittent normobaric hypoxia and of biological pyrimidines (uridine and cytidine) on the specific activities of some enzymes related to cerebral energy metabolism were studied. Measurement were carried out on the following: homogenate in toto; purified mitochondrial fraction; crude synaptosomal fraction, in different areas of rat brain: cerebral cortex, hippocampus, corpus striatum, hypothalamus, cerebellum, and medulla oblongata. Intermittent normobaric hypoxia (12 hours daily for 5 days) caused modifications of the enzyme activities in the homogenate in toto (decrease of hexokinase in cerebellum; increase of pyruvate kinase in medulla oblongata), in the purified mitochondrial fraction (increase of succinate dehydrogenase in the corpus striatum) and in the crude synaptosomal fraction (decrease of cytochrome oxidase activity in cerebral cortex, hippocampus, and cerebellum; decrease of malate dehydrogenase in hippocampus and cerebellum; decrease of lactate dehydrogenase in cerebellum). Daily treatment with cytidine or uridine altered some enzyme activities either affected or unaffected by intermittent hypoxia.

Monoacylglycerol lipase. Regulation and increased activity during hypoxia and ischemia

The presence of monoacylglycerol lipase was established in extracts of acetone-dried powders from rat and bovine brains using thioester substrate analogs. At pH 7.4, the apparent Km and Vmax values for 1-S-decanoyl-1-mercapto-2,3-propanediol were 56 microM and 227 nmol/h/mg protein in bovine gray matter. The divalent metal ions Ca2+ and Mg2+ had no effect on enzymic activity, but Zn2+ at 500 microM produced a 50% inhibition of this enzyme. Free fatty acids also caused a marked inhibition of monoacylglycerol lipase activity. Norepinephrine and 5-hydroxytryptamine slightly stimulated the enzymic activity. Hypoxic-hypoxia and 30-s postdecapitation ischemia resulted in a considerable increase in monoacylglycerol lipase activity of rat brain. However, the increased activity of monoacylglycerol lipase returned to normal after 5 min of ischemia. The increased activity of monoacylglycerol lipase during hypoxic-hypoxia and short-time ischemia may be partially responsible for increased levels of free fatty acids during these processes.

Protein-O-methyltransferase in brain synaptosomal fraction under normal, ischemic and hypoxic conditions. Possible role in neuronal function

Activity of protein-O-methyltransferase in synaptosomal fractions was obtained. Km values calculated for S-adenosylmethionine as substrate were 1 microM and Vmax = 4.3 pmoles/mg p/min. In the presence of gelatin (exogenous protein acceptor), activity was about 3 times higher. Without gelatin, activity of endogenous protein-O-methyltransferase decreased by about 20% under hypoxic conditions and by about 15% in ischemia. Exogenous activity under both hypoxic and ischemic conditions did not change. These results can possibly be explained by the changes in methyl acceptor proteins. In normal conditions, after inhibition methylcarboxylation by S-adenosyl-L-homocysteine, the decrease of GABA uptake and increase in the uptake of dopamine were observed. Uptake of serotonine and noradrenaline were unchanged.

The ontogenic development of 2',3'-cyclic nucleotide 3'-phosphohydrolase in the corpus callosum in relation to oligodendroglial proliferation, myelination and the distribution of fat-containing glial cells

The development of CNP'ase activity in the corpus callosum of infants dying from different causes has been compared with myelin formation and oligodendroglial proliferation determined by quantitative histological methods. Cases were classified according to the distribution of neutral lipid in capillary endothelia (Class I), with some fat-containing glial cells (Class II) or extensive occurrence of fatty glia (Class III) and compared with Class O cases, showing no neutral lipid accumulation. For cases in Classes II and III--in which nearly all cases of cardiorespiratory insufficiency were classified--there is a deficit of oligodendroglia and myelin, although the ratio of myelin staining intensity to glial cell numbers is similar to Class O cases. The deficit in myelin is due almost entirely to a reduction in oligodendroglial cell numbers. CNP'ase activity is reduced to a greater extent than myelin and the ratio of CNP'ase to glial cell number is reduced before myelination commences. The defect in expression of CNP'ase activity may be indicative of abnormal glioblast transformation. Fatty glial cells are also acquired before myelination suggesting that the primary insult to oligodendroglia, which may be hypoxia, occurs at the time of their proliferation and differentiation. Nearly half the cases of unexplained death in infancy show deficits in CNP'ase activity, correlating with reduced cell numbers and myelin, and the occurrence of fatty glial cells, all of which could be caused by hypoxia around birth.

Cerebrospinal fluid and serum creatine kinase BB activity after out-of-hospital cardiac arrest

In patients resuscitated from out-of-hospital cardiac arrest, neurologic outcome was compared with creatine kinase isoenzyme BB activity (CKBB) in cerebrospinal fluid (CSF) in 20 patients and in serum in 52 patients. CSF CKBB was 2 units per liter or less in patients with complete neurologic recovery but was significantly elevated in patients without neurologic recovery (mean, 55 units per liter) or with incomplete neurologic recovery (mean, 7 units per liter). Serum CKBB was detected more than 6 hours after cardiac arrest in only 4% of patients with complete neurologic but in all patients without neurologic recovery. These results demonstrate a relationship between CSF and serum CKBB and neurologic outcome after cardiac arrest.