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Notes: Abstract: Thirty minutes of insulin-induced reversible hypoglycemic coma (defined in terms of cessation of EEG activity) was produced in anesthetized rats. At the end of the hypoglycemic coma or after recovery for 3, 24, or 72 h induced by glucose infusion, the animals were reanesthetized and their brains frozen in situ. Two control groups were used: untreated controls without prior manipulations, and insulin controls, which received injections of insulin followed by glucose infusion to maintain blood glucose within the physiological range. The brains of these latter animals were frozen 3, 24, or 72 h after glucose infusion. Tissue samples from the cortex, striatum, hippocampus, and thalamus were taken to measure ornithine decarboxylase (ODC) activity, and putrescine and spermidine levels, as well as phosphocreatine (PCr), ATP, glucose, and lactate content. In addition, 20-μm thick coronal sections taken from the striatum and dorsal hippocampus were used for histological evaluation of cell damage and also stained for calcium. Insulin in the absence of hypoglycemia produced a significant increase in ODC activity and putrescine level but had no effect on the profiles of energy metabolites or spermidine. During hypoglycemic coma, brain PCr, ATP, glucose, and lactate levels were sharply reduced, as expected. Energy metabolites normalized after 3 h of recovery. In the striatum, significant secondary decreases in PCr and ATP contents and rises in glucose and lactate levels were observed after 24 h of recovery. ODC activity, and putrescine and spermidine levels were unchanged during hypoglycemic coma. After 3 h of recovery, ODC activity increased markedly throughout the brain, except in the striatum. After 24 h of recovery, ODC activity decreased and approached control values 2 days later. Putrescine levels increased significantly throughout the brain after reversible hypoglycemic coma, the highest values observed after 24 h of recovery (p≤ 0.001, compared with controls). After 72 h of recovery, putrescine levels decreased, but still significantly exceeded control values. Reversible hypoglycemic coma did not produce significant changes in regional spermidine levels except in the striatum, where an approximately 30% increase was observed after 3 and 72 h of recovery (p≤ 0.01 and p≤ 0.05, respectively). Twenty-four hours after hypoglycemic coma, intense calcium staining was apparent in layer III of the cerebral cortex, the lateral striatum, and the crest of the dentate gyrus. After 72 h of recovery, the intense calcium staining included also cortical layer II, the septal nuclei, the subiculum, and the hippocampal CA1-subfield. Changes in polyamine metabolism thus preceded the intense calcium staining in the brain. The results indicate that reversible hypoglycemic coma induces a sharp increase in putrescine level comparable to that observed previously after cerebral ischemia. We, therefore, conclude that the increase in putrescine content is an early biochemical marker of delayed neuronal cell necrosis irrespective of the pathogenesis of this injury. The possible role of polyamines in the manifestation of neuronal necrosis following hypoglycemic coma is discussed.

Notes: Abstract: Biosynthesis and accumulation of the polyamines putrescine, spermidine, and spermine are closely associated with cellular growth processes. We examined polyamine levels and the activity of their first rate-limiting enzyme, ornithine decarboxylase (ODC), in stereotactically induced experimental gliomas of the rat brain 1 and 2 weeks after implantation. Regional ODC activity and polyamine levels were determined in the tumor and in the ipsi- and contralateral striatum, white matter, and cerebral cortex. In the tumor, both ODC activity and polyamine levels markedly increased with progressive tumor growth, as compared to those in the white matter of the opposite hemisphere. In the peritumoral brain tissue, ODC activity did not change, but there was a marked increase of putrescine and, to a lesser degree, of spermidine and spermine almost throughout the whole ipsilateral hemisphere. ODC activity, therefore, seems to be a reliable marker of neoplastic growth in the brain, which may be of use for new clinical concepts of the diagnosis and therapy of brain tumors. The more diffuse distribution of polyamines, however, may be associated with the formation and spreading of edema, which would explain some of the biological effects of tumors on distant brain tissue.

Notes: Abstract Protein synthesis was measured in hippocampal slices which were exposed to glutamate (1 mM or 10 mM) or which were deprived of glucose and oxygen (‘in vitro ischemia’) for 15 min. Glutamate at 1 mM, a concentration estimated to occur duringin vivo ischemia did not affect protein synthesis. Ten mM glutamate inhibited protein synthesis immediately after exposure (50% of control values) and reduced ATP levels to about 30% of the control. After two hours, slices fully recovered their protein synthesis and energy metabolism. The effect of 10 mM glutamate was not receptor-mediated, as NMDA, AMPA, or metabotropic receptor antagonists failed to block the glutamate effect. Immediately after ischemia, protein synthesis was reduced to 30% of control values, and 2 hours later it was still depressed to one-half of control values. Energy charge, however, recovered completely. Ischemic inhibition of protein synthesis was not reversed by glutamate receptor antagonists. The data indicate that inhibition of protein synthesis in hippocampal slices during ischemia is not glutamate-dependent.

Notes: Summary Biosynthesis of the polyamines putrescine, spermidine, and spermine has been found to be activated in tissues with cellular proliferation. In the present study we have investigated polyamine levels and the activity of the first rate-limiting enzyme ornithine decarboxylase (ODC) in tumour samples obtained during operation of 202 patients with gliomas. Biochemical data were closely related to the grading of malignancy and to the morphological characteristics of each sample. Mean ODC activity was significantly higher in all gliomas as compared to peritumoural non-neoplastic brain. Furthermore, it was significantly higher (p ≤ 0.001) in anaplastic gliomas who grade III and IV (9.0 ± 9.6 nmol/g/h) than in gliomas WHO grade I and II (3.3 ± 4.2 nmol/g/h). Highest enzyme activity (58.5 nmol/g/h) was found in solid and vital parts of malignant tumours, whereas predominantly necrotic areas exhibited low ODC activity (〈 1 nmol/g/h). Thus, intra- and interindividual variability of ODC activity corresponded well to histomorphological heterogeneity in high-grade gliomas. Putrescine levels also increased with rising grade of malignancy, whereas spermidine and spermine levels did not correlate with the histological grading. In conclusion, high ODC activity represents a biochemical marker of malignancy in gliomas, but low values do not prove benignity. The present study reinforces the need of further and more extensive tumour sampling closely related to follow-up investigations in the heterogeneous group of gliomas.

Notes: Abstract Reversible cerebral ischemia was produced in Mongolian gerbils by occluding both common carotid arteries. Following 5 min of ischemia brains were recirculated for 8, 24, or 96 hr. At the end of the experiments tissue samples were taken from the cerebral cortex and CA1 subfield of the hippocampus for measuring putrescine content and ornithine decarboxylase (ODC) activity. In 5 of 10 animals subjected to 96 hr of recirculation pentobarbital (50mg/kg) was injected during early recirculation, and the density of ischemic cell damage was determined in the CA1 subfield of the hippocampus in treated and untreated animals. Reversible cerebral ischemia induced a drastic increase in ODC activity after 8 hr of recirculation (about 14-fold in the cortex and 7-fold in the hippocampus), which was markedly reduced following 24 hr of recirculation. Putrescine, in contrast, was high following 8 hr of recirculation and increased even further from 8 to 24 hr of recirculation. Postischemic pentobarbital treatment of animals significantly reduced both the increase in putrescine and the density of ischemic cell damage in the hippocampus. The results are discussed in view of the known activities of putrescine.