THE PRESENCE OF BIOLOGICALLY LABILE COMPOUNDS DURING ISCHEMIA AND THEIR RELATIONSHIP TO THE EEG IN RAT CEREBRAL CORTEX AND HYPOTHALAMUS

—Two surgical methods are described in the present paper, allowing for the approximate determination of in vivo levels of ATP, lactate, glucose, pyruvate and glycogen in anatomically uninjured cortex and hypothalamus from unanaesthetized rats. It was not possible to obtain such levels for P-creatine in the 2 mm thick samples used in the present investigation. No fundamental difference was observed between the cortical and the hypo-thalamic levels of these substrates nor in their fluxes. The substrate fluxes during ischemia were correlated with electrical activity in the rat cortex and hypothalamus, recorded by means of telemetrically transmitted electroencephalograms. The electrical activity declined precipitously at 9.6 s after decapitation in the cortex, and after 12.1 s in the hypothalamus. High levels of glycogen, glucose and ATP were present at this moment, while P-creatine had declined sharply.     

METABOLITE LEVELS IN BRAIN FOLLOWING EXPERIMENTAL SEIZURES: THE EFFECTS OF MAXIMAL ELECTROSHOCK AND PHENYTOIN IN CEREBELLAR LAYERS

Abstract— The effects of maximal electroshock (MES) and phenytoin on metabolites and cyclic nucleotides in layers of frozen-dried cerebellum have been investigated. The four layers (molecular, Purkinje-cell rich, granular and white matter) had remarkably homogeneous distributions of P-creatine, ATP, glucose, glycogen, lactate, GABA and the cyclic nucleotides. MES caused dramatic decreases in P-creatine, ATP, and glucose at 10 s after treatment, followed by a decrease in glycogen at 30 s. Lactate levels were elevated, and GABA was unchanged. Cyclic AMP concentrations were increased at 10s and cyclic GMP at 30 s. Phenytoin modified most of the MES induced changes in all the layers, although white matter was less affected by MES and/or phenytoin. Lactate concentrations were increased by MES and these effects were not altered when phenytoin was administered. The most dramatic effects of phenytoin were on the changes in cyclic nucleotides. Cyclic AMP concentrations were elevated after MES but the values returned to normal more rapidly when phenytoin was present. The drug almost obliterated the MES induced changes in cyclic GMP. The possible relationship of cyclic nucleotide concentrations and the modulation of seizure activity is discussed.     

CARBOHYDRATE AND ENERGY METABOLISM IN PERINATAL RAT BRAIN: RELATION TO SURVIVAL IN ANOXIA

The ability of rats of different ages to survive exposure to anoxia was correlated with rates of high energy phosphate consumption (metabolic rates) of the fore-brain. Fetal rats at term, delivered by hysterotomy following maternal decapitation, survived in nitrogen at 37°C twice as long as 1-day-old neo-nates, 5 times longer than 7-day-old rats, and 45 times longer than adults. During ischemia induced by decapitation, the cerebral concentrations of the labile energy reserves (ATP, ADP, P-creatine, glucose and glycogen) and of lactate were determined in fetuses, 1- and 7-day post-natal animals. From the changes, the cerebral energy use rates were calculated to be 1·57 mmol/kg/min in fetuses, 1·33 mmol/kg/min in 1-day-olds and 2·58 mmol/kg/min in 7-day-olds. Maximal rates of lactate accumulation during ischemia, as a measure of glycolytic capacity, were comparable in fetuses and neonates, but were about twice as great in 7-day-old rats. It is concluded that in post-natal animals survival in anoxia and cerebral energy consumption are inversely, and nearly quantitatively, related. However, the reduced cerebral energy requirement cannot entirely account for the greater anoxic resistance of fetuses.     

An examination of the efficiency of glucose and glutamine as energy sources for cultured chick pigment epithelial cells

Embryonic chick pigment epithelial cells in culture require glucose as their major energy source for long-term growth, pigment formation, and colony organization. Cell number increases with glucose concentration at least up to 5.0 mM. Cells can be grown with glutamine as the major energy source but produce comparable cell numbers for only the first 3 days in culture, after which they cease growing. However, they are able to metabolize glutamine at a two to sixfoid higher rate than cells grown in the presence of glucose as measured by CO₂ release and by incorporation into protein. In cells grown in the presence of both glucose and glutamine, basal ATP levels were 31.1 nmoles/mg protein; P-creatine averaged 15.2 nmoles/mg protein and showed marked variability between experimental groups. During starvation, P-creatine levels fell while ATP levels remained relatively constant. Glucose was required for the recovery of P-creatine to prestarvation levels when measured 5 min after refeeding. Because of these marked changes in P-creatine concentration as a function of nutritional status, the ATP/P-creatine ratio becomes a useful measure of the energy state of the cell.     

CEREBRAL ENERGY METABOLISM DURING TRANSIENT ISCHEMIA AND RECOVERY IN THE GERBIL1

Energy metabolism was studied in the cerebral cortex of gerbils during and following ischemia induced by 1 h of unilateral carotid artery occlusion. An aneurysm clip was applied to the right common carotid artery of 50-70 g gerbils under brief halothane anesthesia, and the clip was removed 1 h later. Clinical state (gait, responsiveness, seizures) was evaluated during carotid occlusion, and 40% of the animals showed clinical evidence of stroke. Cortical energy stores (2 ATP + ADP + P-creatine) were more than half depleted in the ipsilateral cortex of clinically-affected gerbils, and glucose fell by 75%; lactate rose over 7-fold in the same specimens. After release of the carotid clip, clinical state improved, and biochemical abnormalities partially resolved. However, even after 24 h, the concentration of ATP and the total pool of adenine nucleotides remained subnormal. Metabolic activity in the ischemic cortex, assessed as the utilization of high-energy phosphates following decapitation, was normal after 1 h of recovery and decreased (-50%) after 24 h but was increased by more than 50% after 4 h. Cerebral glucose utilization, evaluated from autoradiographs prepared after intravenous administration of 2-[1-¹⁴C]deoxyglucose, was also increased in the cortex, hippocampus, and thalamus after 4 h of recovery. This post-ischemic hypermetabolism in tissue damaged by ischemia may identify a critical period for cell repair, when therapy could be decisive.     

Physiological and biochemical changes in frog sciatic nerve during anoxia and recovery

Frog (Rana pipiens) sciatic nerve was incubated, with and without stimulation, in an oil bath. The correlation between changes in the magnitude of the compound action potential (α and β) and changes in metabolites, particularly energy reserves, during anoxia and recovery from anoxia was studied. The time to extinction of the action potential in anoxia was frequency-dependent. The action potential could not be restored, nor its extinction delayed, by washing the nerve in O₂-free Ringer's solution. Therefore, in this system extracellular K⁺ accumulation was not a significant factor in blocking impulse conduction. At the time of complete nerve block resulting from anoxia (90 min at rest), ATP, P-creatine and glucose were 30, 10 and 10 per cent, respectively, of initial levels. Glycogen did not fall below 42 per cent of control levels even after 5 h of anoxia. Changes in the levels of energy reserves during anoxia were used to calculate the metabolic rate of nerves at rest and during stimulation. In one series of experiments, the resting metabolic rate was 0·12 mequiv. of ‘high-energy phosphate’ (～P)/kg/min. Stimulation increased the metabolic rate to 0·22 mequiv. of ～P/kg/min at 30 Hz and to 0·29 mequiv. of ～P/kg/min at 100 Hz. The change in metabolic rate when the nerve passed from the resting to the stimulated state was quite abrupt, an observation suggesting that the slow transition observed with methods monitoring O₂, consumption was largely instrumental. In nerve stimulated to exhaustion in the absence of O₂, neither ATP nor P-creatine had fully recovered within 60 min after O₂, was readmitted, although the action potential reached supranormal levels 15 min after return to O₂. The ratio of lactate: pyruvate, which increased as expected during anoxia, paradoxically increased even further after O₂, was readmitted. The rate of energy utilization during recovery was 0·30 mequiv. of ～P/kg/min. Nerves stimulated at 100–200 Hz in O₂, exhibited no changes in levels of P-creatine, ATP or lactate, an observation implying that the nerve could not be made to use ～P faster than oxidation of glucose could provide it. This meant that the maximal metabolic rate was not limited by the rate of supply of chemical energy. Instead, the limitation may have arisen as a result of a limited rate at which ionic imbalance can result from stimulation or a limited pump capacity of the axonal membrane. Nerves stimulated at 200 Hz in O₂ for 20 min and then transferred to an O₂-free environment without further stimulation exhibited an increase in the rate of energy utilization (nearly two-fold) over the resting rate, a finding that suggested a metabolic (ionic?) debt as a result of activity which could not be met even though the energy supply was adequate. Therefore, restriction of energy expenditure by a limiting pumping rate seemed to be the most likely explanation. The resting metabolic rate of frog sciatic nerve was only one-quarter to one-third of the rate for rat sciatic nerve, when compared at the same temperature (25°C).     

Quick freezing of the murine CNS: comparison of regional cooling rates and metabolite levels when using liquid nitrogen of Freon-12

Abstract— Murine brains were frozen in situ, either in liquid N₂ or in Freon-12 cooled to its freezing point. The effect of these coolants on cooling rates and times in various CNS regions was determined. In addition, levels of ATP, P-creatine and lactate were measured in selected regions of brains from both intact animals and severed heads frozen in either coolant. For both the intact animals and severed heads, superficial regions of brain cooled to 0°C and deeper regions to 25°C, at the same rate in either liquid N2 or Freon. Subsequent cooling was more rapid in liquid N₂ in both regions. Levels of ATP, P-creatine and lactate were similar in brains frozen in either coolant, probably because CNS utilization of highenergy phosphates decreased markedly as body temperature fell. In brains of animals frozen intact, levels of ATP and P-creatine were higher and levels of lactate were lower than those in brains from heads which were severed prior to freezing. This difference may be a result of the marked stimulation which accompanies decapitation and may also reflect continued cerebral circulation in the intact animal for a brief time after immersing the animal in the coolant.     

LIGHT-INDUCED ALTERATIONS IN RETINAL PYRUVATE AND HIGH-ENERGY PHOSPHATES, IN VIVO

—The effect of illumination upon some metabolic substrates of frog retina was investigated in vivo, using conditions of illumination for which electrophysiological correlates in the retina are well defined. Frogs were frozen immediately after illumination, the tissue was processed for quantitative histochemistry, and the compounds were measured fluorometrically. Levels of P-creatine were lower in flash-illuminated retinas than in either dark- or light-adapted retinas. The high-energy phosphates and pyruvate changed rapidly upon exposure to flashing light, then returned towards the original steady-state level, with ATP preceding pyruvate and P-creatine. ATP and P-creatine were primarily concentrated in the bipolar and ganglion cell layers. The energy reserve of the retina was depleted by an enhanced rate of neural activity in vivo. Levels of P-creatine and ATP decreased in only those cellular layers which initiate neural action potentials. These data suggest that the mechanisms of neural excitation are closely coupled to energy and glucose metabolism in the retina.     

31P-NMR studies of phosphate metabolites in intact red and white swimming muscles of cod (Gadus morhua L.)

31P-NMR was used to characterise intracellular phosphate pools and their post mortem changes at 7 degrees C in intact red and white cod muscles under anaerobic conditions. A total phosphate content of 55 and 60 mM was observed in red and white muscle, respectively. The concentration of P-creatine was 14 mM in the white and 9 mM in the red muscle, while that of inorganic phosphate, Pi (30 mM), ATP (9 mM), and sugar phosphate (5 mM) were similar in both muscles. During the first 90 min after death, the decrease in P-creatine showed a first order breakdown with a concomitant stoichiometric increase in Pi content, whereas the ATP and sugar phosphate remained the same. The intracellular pH decreased from 7.4 to 7.3 in this period. The steady-state rate constant of myosin ATPase was 0.0054 and 0.0022/min for red and white muscles, respectively. Individuals kept under diminished oxygen tension prior to being killed, showed a reduced P-creatine level in both muscles.     

黄瓜去顶苗直接成花的形态学研究

本文对黄瓜0—7天幼苗及去顶后0—8天诱导花芽分化苗与诱导营养芽分化苗的子叶节进行了系统石蜡切片观察,未发现0—7天幼苗的子叶叶腋存在潜伏芽。去顶后1—2天在子叶叶柄基部与切口之间的表皮下细胞分裂形成突起,去顶后6天诱花苗与诱芽苗的突起表现出形态差异,诱花苗突起的上端变钝,而诱芽苗突起的上端成尖锥状。去顶后8天诱花苗在子叶叶柄与切口之间形成完整的花芽。另发现有少量花芽起源于切口处细胞。对去顶后0—6天诱花苗与诱芽苗的子叶节还进行了电镜扫描观察,观察结果与石蜡切片基本一致。     

Loss of cortical function in mice after decapitation, cervical dislocation, potassium chloride injection, and CO2 inhalation

Electroencephalograms (EEG) and visual evoked potentials (VEP) in mice were recorded to evaluate loss of cortical function during the first 30 s after euthanasia by various methods. Tracheal cannulae (for positive-pressure ventilation, PPV) and cortical surface electrodes were placed in mice anesthetized with inhaled halothane. Succinylcholine was used to block spontaneous breathing in the mice, which then underwent continuous EEG recording. Photic stimuli (1 Hz) were presented to produce VEPs superimposed on the EEG. Anesthesia was discontinued immediately before euthanasia. Compared with that obtained before euthanasia, EEG activity during the 30-s study period immediately after euthanasia was significantly decreased after cervical dislocation (at 5 to 10 s), 100% PPV-CO2 (at 10 to 15 s), decapitation (at 15 to 20 s), and cardiac arrest due to KCl injection (at 20 to 25 s) but not after administration of 70% PPV-CO2. Similarly, these euthanasia methods also reduced VEP amplitude, although 100% PPV-CO2 treatment affected VEP amplitude more than it did EEG activity. Thus, 100% PPV-CO2 treatment significantly decreased VEP beginning 5 to 10 s after administration, with near abolition of VEP by 30 s. VEP amplitude was significantly reduced at 5 to 10 s after cervical dislocation and at 10 to 15 s after decapitation but not after either KCl or 70% PPV-CO2 administration. The data demonstrate that 100% PPV-CO2, decapitation, and cervical dislocation lead to rapid disruption of cortical function as measured by 2 different methods. In comparison, 70% PPV-CO2 and cardiac arrest due to intracardiac KCl injection had less rapid effects on cortical function.     

Glycogen, ammonia and related metabolities in the brain during seizures evoked by methionine sulphoximine

Abstract— The levels of ATP, P-creatine, glucose, glycogen, lactate, glutamate and ammonia were measured in mouse brain after administration of the convulsive agent methionine sulphoximine (MSO). No changes were observed in ATP and P-creatine levels either before or during the seizures. Lactate levels were unchanged until the onset of seizures (4–5 hr) at which time the levels increased an average of 65 per cent. Glucose and glycogen levels increased progressively. Just before the onset of seizures the levels had increased 95 and 62 per cent, respectively. During the seizures both substances had increased a total of 130 per cent. Comparable changes were found in cerebral cortex, cerebellum and subcortical forebrain. Through the use of quantitative histochemical methods it was found that the greatest increases in glycogen occurred in layers I and III (layers II and IV were not analysed). Progressively smaller changes were found in layers V and VI and no increase at all was found in the subjacent white matter. Glucose, in contrast to glycogen, increased to about the same degree in all cerebral layers and in subjacent white matter. The increase in glycogen after MSO administration may be related to the fact that MSO also causes an increase in the ratio of brain to serum glucose levels. This would indicate that an increase in intracellular glucose had occurred. Ammonia levels were increased 300–400 per cent in both cerebrum and cerebellum. A time study in cerebellum showed that the increase begins early and reaches maximal levels long before the onset of seizures. Glutamate levels were reduced by small but statistically significant amounts in both cerebrum and cerebellum. Administration of methionine sulphoximine completely prevented seizures and the increase in lactate, but did not prevent the increases in glycogen and glucose. The rise in ammonia was reduced but not prevented. During 20 sec of complete ischaemia (decapitation) ATP, P-creatine and glucose fell somewhat more rapidly than normal in brain of animals undergoing MSO seizures. From the changes it was calculated that the metabolic rate had been increased about 20 per cent by the seizure. A new sensitive and specific enzymic method for determination of tissue ammonia is presented together with evised enzymic procedures for lactate and glutamate.     

Study of the mechanism of the anti-hypoxic action of lithium oxybutyrate using cerebral ischemia as a model

A study was made of energy metabolism and concentration of malonic dialdehyde (MDA) in cerebral tissue of mice given sodium hydroxybutyrate and lithium hydroxybutyrate 30 and 60 s after decapitation. Administration of lithium hydroxybutyrate brought about a more economic consumption of the glycogen pool as compared with "hypoxic" control. The differences were revealed in the action of both salts on ATP. The concentration of MDA declined after their administration, lithium hydroxybutyrate being more efficacious. The possible mechanisms of the action of lithium hydroxybutyrate are discussed.     

THE EFFECTS OF CARBON MONOXIDE INHIBITION ON ATP LEVEL AND THE RATE OF MITOSIS IN THE SEA URCHIN EGG

The requirements for ATP synthesis during the various phases of mitosis were investigated in the oxygen-requiring eggs of the sea urchin, Strongylocentrotus purpuratus. CO in the dark, a specific inhibitor of respiration, was used to inhibit ATP synthesis. The kinetics of respiratory inhibition were determined by analyzing ATP levels with the luciferin-luciferase assay. The kinetics of mitotic inhibition were determined by analysis of the rate of mitosis. It was found that CO inhibition resulted in a decrease in the normal ATP level. Coincident with this decrease was a decrease in the rate of mitosis which stops completely when the ATP drops below 50 per cent of the normal level. With the use of various degrees of CO inhibition, the rate of mitosis is shown to be related to the resultant ATP level. These results contradict the basic premise of the energy reservoir hypothesis, and also disagree with other reports that cells in mitosis are insensitive to inhibitors of energy metabolism. Data are presented which demonstrate that these conflicting reports result from insufficient inhibition of ATP synthesis. The above findings all indicate that mitosis depends on the continuous synthesis and utilization of ATP.     

Adenosine triphosphate and phosphocreatine levels in cochlear structures. Use rate and effect of salicylates.

Guinea pigs were injected with various dosages of salicylate for varying time periods. The temporal bones were removed, frozen quickly, freeze-dried, and the cochlea was dissected into essential auditory component parts and subjected to microchemical analysis for phospho-creatine (P-creatine) and adenosine triphosphate (ATP) levels. It was found that high energy phosphates were not decreased by therapeutic or acutely toxic levels of salicylate. Only when chronic intoxication with salicylate was accomplished was there a reduction in ATP and P-creatine. The data presented do not provide support for the widely held view that uncoupling of oxidative phosphorylation or inhibition of enzymes involved in energy generation in the inner ear structures studied (organ of Corti, stria vascularis, Reissner's membrane, modiolar blood vessels, cochlear nerve and spiral ganglion) are the mechanisms by which salicylates cause reversible hearing loss. The study confirms the existence of a P-creatine gradient opposite to the well known glycogen gradient in the organ of Corti (Krzanowski JJ Jr, Matschinsky M: J Histochem 19:321, 1971) and suggests a relatively uniform energy use rate of this tissue for all four turns (20 mmoles of approximately phosphorus used/kg dry weight/min).     

Influence of Short-Term Relaxation on the Organization of the Brain Electrical Activity of Young Schoolchildren in the State of Quiet Wakefulness

Relaxation-induced changes in characteristics of the functional state of the nervous system (EEG parameters and electrodermal resistance (EDR)) were studied in 30 schoolchildren aged 9–10 years. A multichannel EEG was recorded from the occipital, parietal, temporo-parieto-occipital, central, and frontal areas of both brain hemispheres in three test conditions: quiet wakefulness, R, and recovery of the initial state. Simultaneously, the EDR was monitored. EEG amplitude spectra and coherence were calculated. Prior to and after relaxation, a cognitive test to determine the extent of short-term auditory verbal memory was performed. While changes in the EDR were reversible, relaxation-induced changes in the EEG parameters persisted after relaxation in many subjects. Changes in EEG coherence between distant derivations were most stable. Since short-term auditory verbal memory improved after relaxation, the postrelaxation changes in the EEG parameters were considered to reflect positive changes arising in the brain function and increasing the efficiency of cognitive processes.     

Myoelectrical and mechanical changes linked to length specificity during isometric training

Force generation and ATP utilization under anaerobic conditions were studied in the quadriceps femoris muscle of six volunteers. Electrical stimulation (20 Hz) was used to produce contractions with a duration of 0.8 s in one leg and contractions with a duration of 3.2 s in the other leg. The two procedures were designed to give the same total contraction time of 51 s and used the same number of stimulation pulses. Muscle biopsies were taken at rest and after 22 and 51 s of work and analyzed for ATP, phosphocreatine, and glucolytic intermediates. The results were compared with previous studies on continuous and intermittent stimulation. Fatigue developed significantly faster with contractions of short duration, and the energy cost was higher. Since force at the end of stimulation had a negative correlation to ATP utilization, there is no indication that the energy resources limit force generation. By comparison of stimulations producing the same amount of isometric work but with a different number of contractions, we estimate that the energy cost for activation and relaxation of a 1-s contraction is approximately 37% of the total ATP consumption.     

ATP utilization and force during intermittent and continuous muscle contractions

Energy utilization and force generation under anaerobic conditions were studied in electrically stimulated quadriceps femoris muscle of four volunteers. To investigate the effects of intermittent vs. continuous stimulation one leg was stimulated intermittently and the other continuously during 50 s. The same initial force was produced, and biopsy samples were obtained before the stimulation and after 10, 20, and 50 s and analyzed for energy-rich phosphagens, glycolytic intermediates, and phosphorylase. The ATP utilization and glycolysis were greater during intermittent contraction, but glycogenolysis was equal. ATP content decreased to lower values after intermittent contraction (16.4 compared with 19.6 mmol/kg dry muscle after continuous contraction). Force generation was well preserved during continuous contraction but successively decreased after 20 s of intermittent stimulation down to 50% of initial at end of work. The energy cost per unit work was greater during intermittent stimulation and increased with contraction time, whereas it decreased with time during continuous stimulation. The decrease in force generation in intermittent exercise is suggested to be due to the higher energy cost for contraction resulting in greater changes in the intracellular environment with lower ATP and increased H+ and Pi. These changes would decrease both activation of the contractile system and the cross-bridge turnover rate resulting from activation.     

Effects of duration of convulsions on energy reserves of the brain

Abstract— Rapid administration (0·4 ml in 1 sec) of the convulsant inhalant, flurothyl (hexafluorodiethyl ether, indoklon), to mice induced within 10 sec clonic-tonic seizures that were accompanied by marked decrease of P-creatine, decrease of ATP and glucose, and increase of lactate in the cerebral cortex. In contrast, mice to which flurothyl had been administered slowly (0·05 ml every 30 sec for 10 min) exhibited myoclonic jerks after about 3 min, merging into irregular clonus at about 5 min, and intermittent clonus thereafter until onset of tonic hind limb extension at about 10 min. In these mice, P-creatine in cerebral cortex decreased gradually for 6 min and then remained through 10 min at levels nearly as low as those reached 10 sec after rapidly administered flurothyl. Lactate in cerebral cortex increased much more during the 10 min of slow administration of flurothyl than in 10 sec of rapid administration, the greatest increase occurring at 4–6 min, as myoclonic jerks merged into irregular clonus. Glucose and ATP in cerebral cortex fluctuated somewhat but did not decrease greatly when flurothyl was administered slowly.