Proteasomal Activity in Synaptosomes Obtained from the Cerebral Structures of Rats Subjected to Long-Lasting Immobilization Stress

We studied the proteasomal activity in synaptosomes obtained from tissues of the cerebral cortex, cerebellum, and hippocampus, as well as in the cytoplasm of cells of these brain structures, of rats subjected to long-lasting immobilization stress. It was demonstrated that the chymotrypsin-like activity of proteasomes in synaptosomes of the cerebral cortex and hippocampus of stressed animals was significantly higher (380 and 560%, respectively) as compared with that observed in control rats. The chymotrypsin-like and peptidylglutamyl peptide hydrolase activities of proteasomes in the cytoplasm of cortical cells under stress conditions also increased (210 and 180%, respectively). These data show that the activity of a multicatalytic proteolytic complex is sharply increased in synaptic terminals of cells of the cerebral cortex and hippocampus of stressed animals. The above complex plays a crucial role in the utilization of short-lived proteins whose molecules form receptors and ion channels; the amount of such proteins is especially great in synaptic terminals.     

Effect of Pasteurization on the Activity of Proteinases in Salmon Roe

We studied the dependence of activity and stability of proteolytic enzymes in salmon roe on pH and temperature. The activity of proteolytic enzymes in roe was primarily determined by proteinases. These enzymes were active at acid pH and had an optimum of 3.6. A study of subclasses of proteolytic enzymes in salmon roe and the published data suggest that the activity of proteinases may be related to the presence of aspartyl proteinases (cathepsin D). Serine proteinases and metalloenzymes were not found in roe. The activity of cysteine proteinases was low. The proposed conditions of pasteurization favored the complete inactivation of salmon roe at pH 6.0–6.4.     

Effects of Ellagic Acid by Oral Administration on N-Acetylation and Metabolism of 2-Aminofluorene in Rat Brain Tissues

Numerous studies have demonstrated that the Acetyl Coenzyme A-dependent arylamine NAT enzyme exist in many tissues of experimental animals including humans, and that NAT has been shown to be exist in mouse brain tissue. Increased NAT activity levels are associated with increased sensitivity to the mutagenic effects of arylamine carcinogens. Attenuation of liver NAT activity is related to breast and bladder cancer processes. Therefore, the effects of ellagic acid (EA) on the in vitro and in vivo N-acetylation of 2-aminofluorene (AF) were investigated in cerebrum, cerebellum and pineal gland tissues from male Sprague-Dawley rats. For in vitro examination, cytosols with or without EA (0.5–500 M) co-treatment decreased 7–72%, 15–63% and 10–78% of AF acetylation for cerebrum, cerebellum and pineal gland tissues, respectively. For in vivo examination, EA and AF at the same time treated groups with all 3 examined tissues did show significant differences (the changes of total amounts of AF and AF metabolites based on the Anova analysis) when compared to the ones without EA cotreatment rats. The pretreatment of male rats with EA (10 mg/kg) 24 hr prior to the administration of AF (50 mg/kg) (one day of EA administration suffice to induce large changes in phase II enzyme activity) resulted in a 76% decrease in total AF and metabolites in pineal gland but did not show significant differences in cerebrum and cerebellum tissues. This is the first demonstration to show that EA decreases the N-acetylation of carcinogens in rat brain tissues.     

Subcellular distribution of carbonic anhydrase and Na+,K+-ATPase in the brain of the hyt/hyt hypothyroid mice

Activities of carbonic anhydrase and Na⁺,K⁺-ATPase in tissue homogenates and in subcellular fractions from different brain regions were studied in inherited primary hypothyroid (hyt/hyt) mice. The body weight, the weight of different brain regions, and the plasma thyroxine and triiodothyronine levels of hyt/hyt mice were significantly lower than those of the age-matched hyt/+ controls. In tissue homogenates of cerebral cortex, brain stem and cerebellum of hypothyroid mice, the activity of carbonic anhydrase (units/mg protein) was 59.2, 57.6, and 43.2%, and the activity of Na⁺,K⁺-ATPase (nmol Pi/mg protein/min) was 73.7, 74.4 and 68.7%, respectively, of that in corresponding regions of euthyroid littermates. The decrease in enzyme activity in tissue homogenates was also reflected in different subcellular fractions. In cerebral cortex and brain stem, carbonic anhydrase activity in cytosol, myelin and mitochondrial fractions of hypothyroid mice was about 45–50% of that in euthyroid mice, while in cerebellum the carbonic anhydrase activity in these subcellular fractions of hyt/hyt mice was only 33–38% of that in hyt/+ controls. Na⁺,K⁺-ATPase activity in myelin fraction of different brain regions of hyt/hyt mice was about 34–42% of that in hyt/+ mice, while in mitochondria, synaptosome and microsome fractions were about 44–52, 46–53, and 66–68%, respectively of controls. These data indicate that the activity of both carbonic anhydrase and Na⁺,K⁺-ATPase was affected more in the myelin than other subcellular fractions and more in the cerebellum than cerebral cortex and brain stem by deficiency of thyroid hormones. A reduction in the activity of transport enzymes in brain tissues as a result of thyroid hormone deficiency during the critical period of development may underlie permanent nervous disorders in primary hypothyroidism.     

Age-related alteration of poly(ADP-ribose) polymerase activity in different parts of the brain

Poly(ADP-ribose) polymerase (PARP) is a conserved enzyme involved in the regulation of DNA repair and genome stability. The role of PARP during aging is not well known. In this study PARP activity was investigated in nuclear fractions from hippocampus, cerebellum, and cerebral cortex of adult (4 months), old adult (14 months) and aged (24-27 months) rats. Concomitantly, the free radical evoked lipid peroxidation was estimated as thiobarbituric acid reactive substances (TBARS). The specific activity of PARP in adult brain was about 25, 21 and 16 pmol/mg protein per min in hippocampus, cerebellum and cerebral cortex, respectively. The enzyme activity was higher in all investigated parts of the brain of old adults. In aged animals PARP activity was lower in hippocampus by about 50%, and was unchanged in cerebral cortex and in cerebellum comparing to adult rats. The concentration of TBARS was the same in all parts of the brain and remained unchanged during aging. There is no direct correlation between PARP activity and free radical evoked lipid peroxidation during brain aging. The lowered enzyme activity in aged hippocampus may decrease DNA repair capacity which subsequently may be responsible for the higher vulnerability of hippocampal neurons to different toxic insults.     

p75 Regulates Purkinje Cell Firing by Modulating SK Channel Activity through Rac1

p75 is expressed among Purkinje cells in the adult cerebellum, but its function has remained obscure. Here we report that p75 is involved in maintaining the frequency and regularity of spontaneous firing of Purkinje cells. The overall spontaneous firing activity of Purkinje cells was increased in p75^−/− mice during the phasic firing period due to a longer firing period and accompanying reduction in silence period than in the wild type. We attribute these effects to a reduction in small conductance Ca²⁺-activated potassium (SK) channel activity in Purkinje cells from p75^−/− mice compared with the wild type littermates. The mechanism by which p75 regulates SK channel activity appears to involve its ability to activate Rac1. In organotypic cultures of cerebellar slices, brain-derived neurotrophic factor increased RacGTP levels by activating p75 but not TrkB. These results correlate with a reduction in RacGTP levels in synaptosome fractions from the p75^−/− cerebellum, but not in that from the cortex of the same animals, compared with wild type littermates. More importantly, we demonstrate that Rac1 modulates SK channel activity and firing patterns of Purkinje cells. Along with the finding that spine density was reduced in p75^−/− cerebellum, these data suggest that p75 plays a role in maintaining normalcy of Purkinje cell firing in the cerebellum in part by activating Rac1 in synaptic compartments and modulating SK channels.     

Neurochemical changes in rats chronically treated with a high concentration of manganese chloride

Several neurochemical parameters were studied in brain regions of rats chronically treated with a high concentration of manganese chloride (20 mg MnCl₂.4H₂O per ml. of drinking water) throughout development until adulthood. Large increases in Mn accumulation were found in all brain regions (hypothalamus, +530%; striatum, +479%; other regions, +152 to +250%) of Mn-treated adult rats. In these animals, Ca levels were decreased (–20 to –46%) in cerebellum, hypothalamus, and cerebral cortex but were increased (+186%) in midbrain. Mg levels were decreased (–12 to –32%) in pons and medulla, midbrain, and cerebellum. Fe levels were increased (+95%) in striatum but were decreased (–28%) in cerebral cortex. Cu levels were increased (+43 to +100%) in pons and medulla and striatum but Zn levels were decreased (–30%) in pons and medulla. Na levels were increased (+22%) in striatum but those of K and Cl remained unchanged. Type A monoamine oxidase activities were decreased (–13 to –16%) in midbrain, striatum, and cerebral cortex, but type B monoamine oxidase activities decreased (–13%) only in hypothalamus. Acetylcholinesterase activities were increased (+20 to +22%) in striatum and cerebellum. The results are consistent with out hypothesis that chronic manganese encephalopathy not only affects brain metabolism of Mn but also that of other metals.We dedicate this paper to Professor Alan N. Davison. Professor Davison has conducted pioneering research in several important areas including: brain development and myelination, aging and Alzheimer's disease, and multiple sclerosis. He encouraged us to investigate the neurochemical mechanisms of neurotoxicity of metal ions, particularly in connection with neurological diseases. His encouragement and continued support facilitated the launching of our multidisciplinary research program in the long-term effects of manganese toxicity on brain development and aging.     

Chronic hypoxia in development selectively alters the activities of key enzymes of glucose oxidative metabolism in brain regions

The immature brain is more resistant to hypoxia/ischemia than the mature brain. Although chronic hypoxia can induce adaptive-changes on the developing brain, the mechanisms underlying such adaptive changes are poorly understood. To further elucidate some of the adaptive changes during postnatal hypoxia, we determined the activities of four enzymes of glucose oxidative metabolism in eight brain regions of hypoxic and normoxic rats. Litters of Sprague-Dawley rats were put into the hypoxic chamber (oxygen level maintained at 9.5%) with their dams starting on day 3 postnatal (P3). Age-matched normoxic rats were use as control animals. In P10 hypoxic rats, lactate dehydrogenase (LDH) activity in cerebral cortex, striatum, olfactory bulb, hippocampus, hypothalamus, pons and medulla, and cerebellum was significantly increased (by 100%–370%) compared to those in P10 normoxic rats. In P10 hypoxic rats, hexokinase (HK) activity in hypothalamus, hippocampus, olfactory bulb, midbrain, and cerebral cortex was significantly decreased (by 15%–30%). Neither -ketoglutarate dehydrogenase complex (KGDHC, which is believed to have an important role in the regulation of the tricarboxylic acid [TCA] cycle flux) nor citrate synthase (CS) activity was significantly decreased in the eight regions of P10 hypoxic rats compared to those in P10 normoxic rats. In P30 hypoxic rats, LDH activity was only increased in striatum (by 19%), whereas HK activity was only significantly decreased (by 30%) in this region. However, KGDHC activity was significantly decreased in olfactory bulb, hippocampus, hypothalamus, cerebral cortex, and cerebellum (by 20%–40%) in P30 hypoxic rats compared to those in P30 normoxic rats. Similarly, CS activity was decreased, but only in olfactory bulb, hypothalamus, and midbrain (by 9%–21%) in P30 hypoxic rats. Our results suggest that at least some of the mechanisms underlying the hypoxia-induced changes in activities of glycolytic enzymes implicate the upregulation of HIF-1. Moreover, our observation that chronic postnatal hypoxia induces differential effects on brain glycolytic and TCA cycle enzymes may have pathophysiological implications (e.g., decreased in energy metabolism) in childhood diseases (e.g., sudden infant death syndrome) in which hypoxia plays a role.     

Age-related increases in superoxide dismutase activity and thiobarbituric acid-reactive substances: Effect of bio-catalyzer in aged rat brain

This study describes, using electron spin resonance spectrometry/spin trapping technique, the increase superoxide dismutase (SOD) activity in the mitochondrial and cytosolic fraction of the cortex, midbrain, pons-medulla oblongata and cerebellum, and in thiobarbituric acid-reactive substances (TBARS) in the cortex, cerebellum and hippocampus of the aged rats. The results show that corresponding to the increased life span and improved physical conditions observed after peroral long-term treatment with Bio-catalyzer, a commercial natural fermented health food supplement marketed in Japan and in the Philippines and earlier reported to be a hydroxyl radical scavenger with weaker scavenging activity on superoxide radical (O ₂ ^– ), SOD which is involved in the metabolic degradation of O ₂ ^– was further increased, whereas TBARS decreased. These findings suggest that the increased SOD activity in the brain as a defense mechanism against age-related accumulation of reactive oxygen species, in particular superoxide radicals, was enhanced with Biocatalyzer treatment while age-related peroxidation of neuronal membrane, as measured by TBARS, was decreased.     

Neuronal interaction in the cat cerebellar cortex: A cross correlation analysis

Neuronal interaction in the cat cerebellum was investigated by cross correlation analysis techniques. Excitatory connections of varying effectiveness were found between neurons of 13 out of 90 pairs investigated (or 14%). Inhibitory interaction was observed in 38 pairs, or 42%. Neurons of 26 pairs (40%) had shared inputs. Effectiveness of connections between cerebellar cortex neurons was demonstrated by changing stimulus parameters. Findings obtained agree with existing data on the functional organization of the cerebellar cortex. Possible reasons for the large numbers of inhibitory connections discovered are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow, Institute of Experimental Biology, Polish Academy of Sciences, Warsaw. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 672–678, September–October, 1987.     

The Proteolytic Activity and Cleavage Specificity of Fibronectin-Gelatinase and Fibronectin-Lamininase

Human plasma fibronectin contains two latent aspartic proteinases, FN-gelatinase and FN-lamininase. Both enzymes can be generated and activated in the presence of Ca²⁺ from the purified cathepsin D-produced 190-kDa fibronectin fragment. We investigated the proteolytic activity and cleavage specificity of both enzymes in a range of pH from 3.5 to 9.0 using the B chain of oxidized bovine insulin and chromogenic peptides as substrates. The inhibition of the enzymes by several natural inhibitors from human plasma was also tested. The specificities of FN-gelatinase and FN-lamininase are similar to other major acidic proteinases, including pepsin, renin, cathepsin D, and HIV-proteinases. Both enzymes mainly hydrolyze three peptide bonds in the oxidized insulin B chain, namely Glu–Ala (residues 13–14), Tyr–Leu (residues 16–17), and Phe–Phe (residues 24–25). For the peptide substrates H-Pro-Thr-Glu-Phe-p-nitro-Phe-Arg-Leu-OH and H-Phe-Gly-His-p-nitro-Phe-Phe-Val-Leu-OMe that were cleaved the respective values of k _cat/K _M were 105.1 and 11.8 mM^–1 sec^–1 for cleavage by FN-gelatinase, and 123.2 and 15.5 mM^–1 sec^–1 for cleavage by FN-lamininase. The maximal activities of both enzymes were observed in a range between pH 5.6 and 6.3 and they became inactivated at a pH value above 8.4. Both FN-gelatinase and FN-lamininase were efficiently inhibited by ₂-macroglobulin.     

Intra- and Interhemispheric Propagation of Electrophysiological Synchronous Activity and Its Modulation by Serotonin in the Cingulate Cortex of Juvenile Mice

Disinhibition of the cortex (e.g., by GABA -receptor blockade) generates synchronous and oscillatory electrophysiological activity that propagates along the cortex. We have studied, in brain slices of the cingulate cortex of mice (postnatal age 14–20 days), the propagation along layer 2/3 as well as the interhemispheric propagation through the corpus callosum of synchronous discharges recorded extracellularly and evoked in the presence of 10 μM bicuculline by electrical stimulation of layer 1. The latency of the responses obtained at the same distance from the stimulus electrode was longer in anterior cingulate cortex (ACC: 39.53 ± 2.83 ms, n = 7) than in retrosplenial cortex slices (RSC: 21.99 ± 2.75 ms, n = 5; p<0.05), which is equivalent to a lower propagation velocity in the dorso-ventral direction in ACC than in RSC slices (43.0 mm/s vs 72.9 mm/s). We studied the modulation of this propagation by serotonin. Serotonin significantly increased the latency of the intracortical synchronous discharges (18.9% in the ipsilateral hemisphere and 40.2% in the contralateral hemisphere), and also increased the interhemispheric propagation time by 86.4%. These actions of serotonin were mimicked by the activation of either 5-HT_1B or 5-HT_2A receptors, but not by the activation of the 5-HT_1A subtype. These findings provide further knowledge about the propagation of synchronic electrical activity in the cerebral cortex, including its modulation by serotonin, and suggest the presence of deep differences between the ACC and RSC in the structure of the local cortical microcircuits underlying the propagation of synchronous discharges.     

Profile of acetylcholinesterase in brain areas of male and female rats of adult and old age

Inhibition of acetylcholinesterase (AChE)-metabolizing enzyme of acetylcholine, is presently the most important therapeutic target for development of cognitive enhancers. However, AChE activity in brain has not been properly evaluated on the basis of age and sex. In the present study, AChE activity was investigated in different brain areas in male and female Sprague-Dawley rats of adult (3 months) and old (18-22 months) age. AChE was assayed spectrophotometrically by modified Ellman's method. Specific activity (micromoles/min/mg of protein) of AChE was assayed in salt soluble (SS) and detergent soluble (DS) fractions of various brain areas, which consists of predominantly G1 and G4 molecular isoforms of AChE respectively. The old male rats showed a decrease (40-55%) in AChE activity in frontal cortex, striatum, hypothalamus and pons in DS fraction and there was no change in SS fraction in comparison to adult rats. In the old female rats the activity was decreased (25-40%) in frontal cortex, cerebral cortex, striatum, thalamus, cerebellum and medulla in DS fraction whereas in SS fraction the activity was decreased only in hypothalamus as compared to adult. On comparing with old male rats, old female rats showed increase in AChE activity in cerebral cortex, hippocampus and hypothalamus of DS fraction and decrease in hypothalamus of SS fraction. There was a significant increase in AChE activity in DS fraction of cerebral cortex, hippocampus, hypothalamus, thalamus and cerebellum in female as compared to male adult rats. However, no significant change in AChE activity was found in the SS fraction, except hypothalamus between these groups. Thus it appears that age alters AChE activity in different brain regions predominantly in DS fraction (G4 isoform) that may vary in male and female. These observations have significant relevance to age related cognitive deficits and its pharmacotherapy.     

Effect of age and monosodium-L-glutamate (MSG) treatment on neurotransmitter content in brain regions from male fischer-344 rats

Peripheral administration of monosodium-L-glutamate (MSG) has been found to be neurotoxic in neonatal rats. When administered in an acute, subconvulsive dose (500 mg/kg i.p.), MSG altered neurotrnnsmitter content in discrete brain regions of adult (6 month old) and aged (24 month old) male Fischer-344 rats. Norepinephrine (NE) content was reduced in both the hypothalamus (16%) and cerebellum (11%) of adult rats, but was increased in both the hypothalamus (7%) and cerebellum (14%) of aged rats after MSG treatment. MSG also altered the dopamine content in adult rats in both the posterior cortex and the striatum, causing a reduction (23%) and an increase (12%), respectively. Glycine content in the midbrain of aged rats increased (21%) after MSG injection. Of particular interest is the widespread monoamine and amino acid deficits found in the aged rats in many of the brain regions examined. NE content was decreased (11%) in the cerebellum of aged rats. Dopamine content was reduced in both the posterior cortex (35%) and striatum (10%) of aged rats compared to adult animals. Cortical serotonergic deficits were present in aged rats with reductions in both the frontal (13%) and posterior cortex (21%). Aged rats also displayed deficits in amino acids, particularly the excitatory amino acids. There were glutamate deficits (9–18% reductions) in the cortical regions (posterior and frontal) as well as midbrain and brain stem. Aspartate, the other excitatory amino acid transmitter, was reduced 10% in the brainstem of aged rats. These data indicate that an acute, subconvulsive, dose of MSG may elicit neurochemical changes in both adult and aged male Fisher-344 rats, and that there are inherent age-related deficits in particular neurotransmitters in aged male Fisher-344 rats as indicated by the reductions in both monoamines and amino acids.     

Evidence for nuclear ornithine decarboxylase activity in different brain regions of the male rat

The subcellular distribution of ornithine decarboxylating activity in nucleus caudatus putamen, hippocampus, parietal cerebral cortex, cerebellum and hypothalamus of male rat brain has been investigated. The 7000 g supernatant (cytosolic fraction), the 7000 g sediment and the 700 g sediment (nuclear fraction) were incubated with (1 − ¹⁴C)-labeled ornithine and the ¹⁴CO₂ released was measured. The results demonstrated that 70–75% of the decarboxylating activity was present in the nuclear fraction (700 g sediment), 10% in the 7000 g sediment and 10–20% was found in the cytosol. With more vigorous homogenization (30 strokes instead of 10) an increase in the 7000 g supernatant was obtained. The activity increased linearly with time and amount of tissue added for the 770 g sediment and the 7000 g sediment. A dose-dependent inhibition was found in the whole brain in nuclear and cytosolic fractions with α-difluoromethylornithine. In all brain areas the nuclear decarboxylating activity was inhibited to 90% with 2.5 mM of α-difluoromethylornithine except in the hypothalamus, where the inhibition amounted to 20%. An equimolar formation of ¹⁴CO₂ and putrescine was found in the nuclear fraction of all brain regions except the nucleus caudatus putamen and the cerebral cortex, where ¹⁴CO₂ formation exceeded that of putrescine with about 50% suggesting that part of the putrescine is rapidly converted into higher polyamines. It is concluded that with the exception of hypothalamus the major decarboxylating activity in the above mentioned brain regions is ornithine decarboxylase activity (ODC, EC 4.1.1.17) and that the most prominent subcellular localization of this enzyme is the nucleus.     

Appearance of Endoproteolytic Enzymes during the Germination of Barley

Barley endoproteolytic enzymes are important to germination because they hydrolyze endosperm storage proteins to provide precursors for new protein synthesis. We recently developed an electrophoretic method utilizing gel-incorporated protein substrates to study the endoproteinases of 4-d-germinated barley (Hordeum vulgare L. cv Morex) grain. This work extends those findings to determine the temporal pattern of the appearance of the endoproteinases during germination, the sensitivities of the proteinases to class-specific proteinase inhibitors, and where, in germinating caryopses, the proteinases reside. Six endoproteinase activity bands (representing a minimum of seven enzymes) were present in 5-d-germinated barley grain extracts subjected to electrophoresis in nondenaturing gels at pH 8.8. The activities of two of the enzyme bands (“neutral” proteinases) increased as the pH was increased from 3.8 to 6.5. The activities of the remaining four (“acidic”) bands diminished abruptly as the pH increased above 4.7. Two proteinase bands hydrolyzed gelatin but not edestin, four of the proteinases hydrolyzed both gelatin and edestin at nearly the same rates, and one enzyme degraded only edestin. One neutral endoproteinase was sensitive to diisopropyl fluorophosphate inhibition, and the other was not inhibited by any of inhibitors tested. Four of acidic enzymes were cysteine proteinases [inhibited by trans-epoxysuccinyl-l-leucylamido(4-guanidino)butane and N-ethylmaleimide]; the other was an aspartic acid endoproteinase (sensitive to pepstatin). Only the aspartic proteinase was detected in either ungerminated or steeped barley grain. During the germination (malting) process, the aspartic endoproteinase activity decreased until the second day of germination and then increased until germination day 5. The first endoproteinase(s) induced during germination was a neutral enzyme that showed activity on the 1st day of the germination phase after steeping. Most of the endoproteinases became active on the 2nd or 3rd germination day, but one cysteine proteinase was not detected until the 5th day. Acid cysteine proteinases were present in the aleurone, scutellum, and endosperm tissues but not in shoots and roots. The aleurone layer and endosperm contained almost exclusively band B1 neutral proteinases, whereas the scutellum, shoots, and roots contained both B1 and B2 bands. This work shows that germinating barley contains a complex set of proteinases whose expression is temporally and spatially controlled. But, at the same time, it also shows that this electrophoretic method for separating and studying individual enzymes of this complex will allow us to more readily characterize and purify them.     

Effects of Thyroxine on Methionine Adenosyltransferase Activity in Rat Cerebral Cortex and Cerebellum During Postnatal Development

Abstract: Methionine adenosyltransferase (MAT) activity was evaluated in cerebral cortex and cerebellum in controls and in rats treated with thyroxine. In controls the enzyme showed a different pattern in cerebral cortex and cerebellum during neonatal and late suckling periods. Hyperthyroid rats showed a significant increase of the enzyme in cerebral cortex only at the 2nd day of the neonatal period; in cerebellum the developmental pattern of MAT in neonatal period was anticipated temporally by 2–4 days. During the late suckling period thyroxine treatment produced in cerebellum a significant decrease in MAT activity at the 15th day after birth. From these data, we propose that hyperthyroidism may cause precocious induction of MAT both in cerebral cortex and in cerebellum and that the increased availability of S -adenosyll-methionine during the neonatal period could be related to its utilization also in polyamine biosynthesis.     

Lithium: Effect on [3H]spiperone binding,ionic content,and amino acid levels in the brain of rats

After prolonged treatment of rats with lithium (pellets, 0.21% lithium carbonate, or 0.5 mg/ml lithium chloride in drinking water) for three months, the level of lithium in plasma was 0.87 meq/liter; in several brain regions, between 1.06–1.39 eq/g wet weight. The content of sodium and potassium in the plasma was normal. The level of potassium in the brain regions tested increased by 13–30% and that of sodium by about 10%. Glycine levels increased significantly in all the regions (cerebral cortex, midbrain, cerebellum, and spinal cord). In the cerebellum GABA was also increased, while glutamine was decreased. In midbrain, apart from increases in glycine levels, alamine, valine, GABA and lysine were also increased. In the spinal cord, glutamic acid was also increased. Changes were largely in the putative neurotransmitters. Long-term treatment with lithium also influenced the high-affinity binding of [³H]spiperone in the cerebral cortex and corpus striatum. Two specific binding sites were found in both brain regions; the main change was the reduction in the lower affinity binding site (B _max2).     

The Evidence for Increased L1 Activity in the Site of Human Adult Brain Neurogenesis

Retroelement activity is a common source of polymorphisms in human genome. The mechanism whereby retroelements contribute to the intraindividual genetic heterogeneity by inserting into the DNA of somatic cells is gaining increasing attention. Brain tissues are suspected to accumulate genetic heterogeneity as a result of the retroelements somatic activity. This study aims to expand our understanding of the role retroelements play in generating somatic mosaicism of neural tissues. Whole-genome Alu and L1 profiling of genomic DNA extracted from the cerebellum, frontal cortex, subventricular zone, dentate gyrus, and the myocardium revealed hundreds of somatic insertions in each of the analyzed tissues. Interestingly, the highest concentration of such insertions was detected in the dentate gyrus—the hotspot of adult neurogenesis. Insertions of retroelements and their activity could produce genetically diverse neuronal subsets, which can be involved in hippocampal-dependent learning and memory.     

Activity of pyruvate- and ketoglutarate dehydrogenase complexes on various regions of the rat brain

The activity of pyruvate dehydrogenase and ketoglutarate dehydrogenase complexes (PDC; EC 1.2.4.1 and KDC; EC 1.2.4.2, respectively) was studied in extracts and lysates of mitochondria isolated from the cortex, cerebellum and stem of the rat brain. In all the mentioned cerebral areas the PDC activity calculating per 1 mg protein noticeably increased that for KDC. Under conditions of solubilization the activity of KDC lowered to a greater extent than that of PDC. The studied brain areas are arranged according to the activity of PDC and KDC in lysates in the following order: stem much much greater than cortex greater than cerebellum, however, the highest stock of the PDC activity manifesting with activation of endogenous phosphatase and dephosphorylation of the complex is observed in cerebellum. When calculating per mitochondria isolated from 1 g of tissue, the value of the PDC activity/KDC activity ratio in all areas of the brain is more than 1, and in cerebellum allowing for the complete PDC activity it exceeds 3. The data obtained emphasize the biochemical originality of the cerebellum and the presence of specific peculiarities in regulation of the pyruvate dehydrogenase complex activity in this cerebral area.