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The metabolism of lactic and pyruvic acids in normal and tumour tissues: Rat liver, brain and testis

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... ), what is known has been derived from manometric studies on testicular tissue (Dickens & Greville, 1933; Elliott, Greig & Benoy, 1937) and the in vitro metabolism of normal and cryptorchid testes has been compared (Tepperman, Tepperman & Dick, 1949). More recently, VanDemark & Ewing (1963) used a simple perfusion procedure in conjunction with in vitro studies to examine the effects of temperature on the metabolic activity of isolated rabbit's testes (Ewing & VanDemark, 1963a, b)Setchell & Waites, 1964). ...
... The important role of glucose in testicular metabolism already demonstrated at normal temperature in anaesthetized rams (Annison, Scott & Waites, 1963), well-nourished conscious rams (Setchell & Waites, 1964) and undernourished anaesthetized rams (Setchell, Waites & Lindner, 1965) was again demonstrated in the present experiments in testes at elevated temperatures. The marked dependence of testicular tissue on glucose for the maintenance of its oxygen uptake in in vitro studies was well recognized (Dickens & Greville, 1933; Elliott, Greig & Benoy, 1937), but fragments of rat testes taken 22 to 28 days after being made cryptorchid, when the spermiogenic epithelium was already damaged, did not utilize more glucose than can be accounted for by glycolysis (Tepperman, Tepperman & Dick, 1949). More recently the effect of temperature elevation has been examined with testis slices and on isolated testes of rabbits perfused with defibrinated blood to which glucose was added (VanDemark & Ewing, 1963; Ewing & VanDemark, 1963a, b). ...
... The in vitro studies are open to criticism because the tissue was incubated in a medium (Locke's) which is unbuffered and because the conclusions are based on results from slices incubated in air; under these conditions the centres of the slices would be completely anaerobic (Dixon, 1952). The experiments on slices incubated in oxygen did not support their conclusion, and the oxygen uptake by this tissue was about half that previously reported for rat testis (Dickens & Greville, 1933; Elliott, Greig & Benoy, 1937). In the per¬ fusion experiments it was claimed that during heating the glucose uptake by the perfused testis was decreased, whereas in fact it increased in the first 2 hr at 39-5° C and fell only in the 3rd hr when the fall was roughly proportional to a simultaneous reduction in perfusate flow. ...
Article
The metabolic effects of elevated temperature on the testes of conscious rams have been investigated. Locally heating the testes above 39° C for 2 to 2½ hr caused moderate or severe seminal degeneration. Blood flow through the testes was not consistently changed by the heating applied. More oxygen was removed from a unit volume of the blood passing through the testes when testicular temperatures were higher than 36 ·3 to 37·2° C, than at control temperatures. The oxygen content of the blood in the spermatic veins fell to 2·7 to 4·9 ml 02/100 ml during heating, and oxygen uptake by the testis and epididymis increased by about 70%. In most testes glucose uptake was increased by heating; there was no consistent change in lactate production. It was concluded that heat sufficient to cause spermatogenic damage results in hypoxia in the testis but does not consistently alter the blood flow or the supply of glucose or the important role of glucose in testicular metabolism.
... The reports of these investigators have suggested that the principal cause of the change in metabolism in vitro after exposure to the elevated temperature in vivo is due to a reduction in the glucose supply. Such a suggestion appears to be consistent with the observations of several investi¬ gators who have shown that mammalian testis tissue suffers a marked decrease in respiration when deprived of exogenous glucose in vitro (Dickens & Greville, 1933a, b;Elliot, Creig & Benoy, 1937;Paul, Paul & Kopko, 1952). ...
Article
Investigations were conducted on the in-vitro metabolic activity of rabbit testicular tissue after exposing the testis to abdominal temperatures for 2, 6 or 24 hr. Metabolic activity increased with the shorter exposure and then significantly decreased as compared with that of normal testicular tissue. Tissue treated in this way recovered its normal metabolic activity when subjected for 30 min to an ice-cold glucose solution. Tissues exposed to abdominal temperature for 24 hr were found to contain 12 % less glucose and 27 % less lactic acid than control tissues. This study suggests that spermatogenic arrest which results from exposure of the testis to elevated temperatures may be caused by reduced levels of substrate in the tissue.
... The quantitative importance of acetate as a peripheral metabolite of ruminants (Reid 1950;McClymont 1951a) has been established. In vitro studies with non-ruminants have shown that acetate is not oxidized by the brain (Elliott, Greig, and Benoy 1937;McGowan and Peters 1937;Elliott, Libet, and McNair Scott 1942) and may in fact be produced by brain tissues when pyruvate is used as the substrate (Long 1938;Elliott et al. 1942). ...
Article
Arteriovonous difforoneo shldios on tho brain of the sheep l1a\'o failed to show an.v utilization or acetate. Tho mean glucose uptake by UlO brain, 6'2~LO'7 mg per 100 ml of blood, was sufficient, assuming complet.e oxidation of the glueose, to aecount for the nWUlI oX~'geJl utilizat.ion of 4·8 J:O·2 vol. pel' 100 IllI of hlood.
... No change in saturation of the blood after it had passed through the internal spermatic artery was observed. Evidence from in vitro studies (Dickens & Greville, 1933; Elliott, Greig & Benoy, 1937) showed that the testis could utilize glucose and the determinations of R.Q. of the testis in vitro (Dickens & S'mer, 1930Dickens & S'mer, , 1931) and in the decerebrate dog (Himwich & Nahum, 1929) suggested that glucose may be a major fuel. Our estimates of R.Q. for the testis and TESTICULAR BLOOD FLOW AND METABOLISM epididymis are in close agreement and the large A-V differences in oxygen and glucose contents reported (Annison et al. 1963) were confirmed and shown by the simultaneous estimates of blood flow to represent considerable uptakes of oxygen and glucose by the testicular and epididymal tissues. ...
... The reports of these investigators have suggested that the principal cause of the change in metabolism in vitro after exposure to the elevated temperature in vivo is due to a reduction in the glucose supply. Such a suggestion appears to be consistent with the observations of several investi¬ gators who have shown that mammalian testis tissue suffers a marked decrease in respiration when deprived of exogenous glucose in vitro (Dickens & Greville, 1933a, b;Elliot, Creig & Benoy, 1937;Paul, Paul & Kopko, 1952). ...
Article
In several investigations of the effect of higher than normal scrotal temperatures on metabolic activity of rabbit testis, oxygen uptake, glucose utilization and lactic acid accumulation of testicular tissues were compared with those of kidney cortex slices. Also, glucose utilization and rate of blood flow through the isolated, perfused rabbit testis were measured. When an adequate amount of substrate (0·055 m glucose) was present, the enzyme systems of neither testis nor kidney cortex slices were deleteriously affected by increased temperature (36·5° C versus 39·0° C) in vitro. An increased temperature in vitro caused a decreased glucose uptake by the isolated, perfused rabbit testis. This decrease in glucose uptake corresponded with a decrease in the amount of glucose available to the tissue, as a result of decreased blood flow and increased metabolic activity. These observations further suggest that spermatogenic arrest due to elevating testicular temperature may be caused by a substrate deficiency to the tissue.
... The conversion of acetaldehyde into acetate has been studied by Reichel and Kohle (15) and Dixon and Lutwak-Mann (16). Elliott et al. (17) have demonstrated the production of pyruvate by liver tissue aerobically from lactate. ...
... The same influence of chloride and a smaller, definite increase in respiration by 0.025 M malate in isotonic glucose were found in bicarbonate-buffered medium in an atmosphere of 5 per cent CO2 in oxygen (Table II). 4 An experiment was carried out in the Dixon-Keilin apparatus with sliced liver in bicarbonate-NaCl medium free of Ca, with and without added malate. The results were exactly like those previously obtained (5) in Krebs' medium containing Ca. The lack of effect of added malate on metabolism of liver slices is, therefore, not due to Ca inhibition. ...
... In humans, the brain represents only 2% of the body mass, yet it uses about 20e25% of the oxygen and glucose consumed at rest ( Kety and Schmidt, 1946;Attwell and Laughlin, 2001;Harris et al., 2012). Glucose is the main energy substrate for the brain, but lactate, pyruvate, and the ketone bodies can also be used in certain situations ( Elliott et al., 1937;Rolleston and Newsholme, 1967;Hawkins et al., 1971;Izumi et al., 1998;Castro et al., 2009;Pellerin and Magistretti, 2012). Ketone bodies are generally consumed in the early stages of development; however, sometimes they can contribute to satisfy energy demands in adults, e.g. during starvation ( Hawkins et al., 1971;Izumi et al., 1998;White and Venkatesh, 2011). ...
... Glucose is the main energy substrate for the brain; however, in some cases, neurons can also utilize pyruvate, lactate, or ketone bodies (Elliott et al., 1937;Rolleston and Newsholme, 1967;Hawkins et al., 1971;Izumi et al., 1998;Castro et al., 2009;Pellerin and Magistretti, 2012). Furthermore, according to the astrocyte-neuron lactate shuttle (ANLS) concept (Pellerin and Magistretti, 2012), neurons have virtually no use of glucose in vivo. ...
Article
Brain tissue is bioenergetically expensive. In humans, it composes approximately 2% of body weight and accounts for approximately 20% of calorie consumption. The brain consumes energy mostly for ion and neurotransmitter transport, a process that occurs primarily in synapses. Therefore, synapses are expensive for any living creature who has brain. In many brain diseases, synapses are damaged earlier than neurons start dying. Synapses may be considered as vulnerable sites on a neuron. Ischemic stroke, an acute disturbance of blood flow in the brain, is an example of a metabolic disease that affects synapses. The associated excessive glutamate release, called excitotoxicity, is involved in neuronal death in brain ischemia. Another example of a metabolic disease is hypoglycemia, a complication of diabetes mellitus, which leads to neuronal death and brain dysfunction. However, synapse function can be corrected with “bioenergetic medicine”. In this review, a ketogenic diet is discussed as a curative option. In support of a ketogenic diet, whereby carbohydrates are replaced for fats in daily meals, epileptic seizures can be terminated. In this review, we discuss possible metabolic sensors in synapses. These may include molecules that perceive changes in composition of extracellular space, for instance, ketone body and lactate receptors, or molecules reacting to changes in cytosol, for instance, K ATP channels or AMP kinase. Inhibition of endocytosis is believed to be a universal synaptic mechanism of adaptation to metabolic changes.
... The decrease in the ATP content of cryptorchid testes may simply be a reflection of the disappearance of the more mature spermatogenic cells. Lactate is known to be rapidly oxidized by the rat testis in vitro (Elliott, Greig & Benoy, 1937). Experiments in vivo on ram testis have also demonstrated that very little lactate is secreted into the venous blood of the testis (). ...
Article
The concentrations of glycogen, glucose, ATP, glucose-6-phosphate and lactate were studied in normal and cryptorchid rat testes using enzymatic pyridine nucleotide methods. With the exception of ATP, all the substrates were significantly higher in the cryptorchid testes. The decrease of the energy metabolites and the accumulation of lactate were also studied in testes incubated in the absence of O2 at the temperatures of 33·6° C and 36·6° C. The metabolic rate of the incubated organs was estimated in terms of the rate of use of high energy phosphate ( ~ P) calculated from changes in ATP, glucose and glycogen. A good parallelism between hexose utilization and lactate production was observed in both normal and cryptorchid testes. A rapid mobilization of glycogen, suggesting activation of phosphorylase, was observed in incubated cryptorchid testes. The calculated oxygen consumption of cryptorchid testes was about 100% higher than that of the normal testes at the same temperature. It is suggested that the basic metabolic rate of the interstitial tissue is higher than that of the seminiferous tubules.
... At the time of the first studies on brain slices, it was already known that ES other than glucose are metabolized by tissues [7,8]. In 1967, Owen et al. [9] reported that a human brain is able to utilize KB. ...
Article
The energy demands of the brain are exceptionally high compared with any other organ of the body. A complex control system maintains brain energy homeostasis, mobilizing appropriate energy substrates to satisfy the energy requirements. It is a common belief that many fundamental neuronal properties, including those governing excitability, are dependent on the energy supply. However, surprisingly little is known about how the specific factors underlying neuronal activity are affected by energy status. Most of these parameters have been studied in acute brain slices, in which the homeostatic system is absent and neurons in the artificial extracellular milieu are arbitrarily supplied with energy substrates. In this paper, we discuss the relationships between availability of energy substrates and neuronal excitability, and suggest that for in vitro studies, it is crucial to optimize the composition of the energy pool in the extracellular milieu.
... min VI) . Similar observations have been made with liver slices (7,29) . It has also been demonstrated that most of the added succinate accumulates as malate or fumarate (29) . ...
Article
Further modifications of the enzymatic technique for the preparation of isolated, intact, parenchymal cells from rat liver as previously described by this laboratory are presented together with a detailed account of several critical factors involved during the procedure. In addition, the fine structure of the cells as revealed by electron microscopy and the characteristics of their respiratory activity in different media and with several added substrates are described. It is shown that cells obtained by adding calcium during the preparative procedure retain approximately 34% more potassium than cells prepared solely in a calcium-free medium. The former cells also demonstrate a higher respiratory activity, which is not due to uncoupling of respiration. Electron microscopy reveals that the cells have an intact plasma membrane and well-preserved intracellular organelles. Glycogen particles are observed in all cells and are particularly abundant when either 20 mM pyruvate is added during the preparation or Eagle's Minimum Essential Medium is employed.
Article
1.1. Hypoglycemia (produced by insulin injection) for 24 hr caused a decreased respiration of chicken testis but no change in rabbit testis slices. This same treatment caused an increased respiration of chicken and rabbit kidney cortex slices.2.2. Oxygen uptake, glucose uptake and lactic acid production of chicken testis slices measured in vitro are higher than those of rabbit testis slices. There was little difference in these criteria between kidney cortex slices from the two species.3.3. Homogenate preparations used to measure glycolysis or Krebs cycle activity also showed a significant species difference of testis tissue.4.4. The species difference in glycolysis of testis tissue was not due to activity of the enzyme lactic dehydrogenase or to temperature stability of this enzyme.
Article
1. An investigation has been made on the stimulation of the anaerobic glycolysis by rat-liver slices caused by previous incubation in oxygen. 2. The stimulation is sustained partly by endogenous carbohydrates and partly by added glucose. The effect of glucose reaches a maximum at a concentration of 20mm; it is more pronounced when glucose is present in the actual glycolytic phase and not during the aerobic preincubation. The conversion of fructose and pyruvate into lactic acid is not affected by the preincubation in oxygen. 3. The stimulation occurs also when preincubation is carried out in a medium that blocks the action of phosphorylase. 4. Preincubation for 2-3min. at 37 degrees is enough to ensure maximum stimulation. The main effect of the aerobic incubation is on the initial velocity of the anaerobic glycolysis. 5. The stimulation depends on the nutritional state of the animal: it is decreased practically to nil in rats starved overnight. In starved animals glycogen content and basal and stimulated glycolysis decline progressively with the same trend. If starved animals are injected with glucose, liver glycogen concentration increases but basal glycolysis remains at a low level; however, the rate of stimulated glycolysis becomes progressively higher and correlates with the amount of liver glycogen. 6. It is suggested that the aerobic preincubation modifies the factors that regulate glycolysis in liver slices at steps above the level of triose phosphates.
Article
Succinate caused a large, temporary stimulation of the respiration of rat-liver slices; the apparent Km for succinate was 5.6 mm. When the Qo2 had returned to a constant level, 85–90% of the added succinate was accounted for as fumarate + l-malate. Similar results were obtained in the presence of Amytal. The succinate oxidation was reduced by depletion of the Ca2+ content of the tissue and medium (by incubation in Ca-free medium containing EDTA), but was little affected by removal of K+ or Mg2+. Endogenous malate and fumarate were retained in the slices against a considerable concentration gradient, but the extra amounts produced by oxidation of succinate appeared largely in the medium. The results are discussed in relation to the ionic exchanges taking place across the plasma membranes and inner-mitochondrial membranes.
Article
Glucose levels are tightly regulated at all times. Gluconeogenesis is the metabolic pathway dedicated to glucose synthesis from non-hexose precursors. Gluconeogenesis is critical for glucose homoeostasis, particularly during fasting or stress conditions. The renal contribution to systemic gluconeogenesis is increasingly recognized. During the post-absorptive phase, the kidney accounts for ∼40% of endogenous gluconeogenesis, occurring mainly in the kidney proximal tubule. The main substrate for renal gluconeogenesis is lactate and the process is regulated by insulin and cellular glucose levels, but also by acidosis and stress hormones. The kidney thus plays an important role in the maintenance of glucose and lactate homoeostasis during stress conditions. The impact of acute and chronic kidney disease and proximal tubular injury on gluconeogenesis is not well studied. Recent evidence shows that in both experimental and clinical acute kidney injury, impaired renal gluconeogenesis could significantly participate in systemic metabolic disturbance and thus alter the prognosis. This review summarizes the biochemistry of gluconeogenesis, the current knowledge of kidney gluconeogenesis, its modifications in kidney disease and the clinical relevance of this fundamental biological process in human biology.
Article
The distribution and relative activities of succinate, lactate, glucose-6-phosphate, malate, glutamate, and fl-hydroxybutyrate dehydrogenases have been histochenlically evaluated in the normal adult bull testis and caput epididymis. In the seminiferous tubule, the spermatogonial cells appear to display fairly high levels of activity in most of the enzymes investigated but, except for glutamate and fl-hydroxybutyrate dehydro- genases, there was a marked decrease of activity in the older spernmtocytes and spermatids. Sertoli cells showed a virtual absence of enzymatic activity. Leydig cells showed very high concentrations of enzymes, particularly glucose-6-phosphate, nmlate, and lactate dehydrogenase. Other enzymes were not very reactive in these cells, and could not be demonstrated in the remainder of the interstitium. Lactate, glucose-6- phosphate, and succinate dehydrogenase showed fairly strong activity in the epithe- lial cells of a portion of the caput epidid- ynfis. The surrounding muscle cells and connective tissue gave very weak reactions for all enzyme substrates tested. Sperlnat- ozoa in both tubular and epididymal lumina showed the presence of some dehydrogena- sea, all activity being confined to the mid- piece section of these cells.
Article
1. Starvation did not affect the rates of glucose utilization or lactate formation by guinea-pig cerebral cortex slices. 2. Palmitate (1mm), butyrate (5mm) or acetoacetate (5mm) did not affect glucose utilization or lactate formation by cerebral cortex slices from guinea pigs starved for 48hr. 3. dl-beta-Hydroxybutyrate (10mm) increased the formation of lactate without affecting glucose utilization by cerebral cortex slices from guinea pigs starved for 48hr. This implies that beta-hydroxybutyrate decreased the rate of glucose oxidation. 4. Metabolism of added ketone bodies can account for 20-40% of observed rates of oxygen consumption. 5. Lactate or pyruvate (5mm) decreased the rates of glucose utilization by guinea-pig cerebral cortex slices.
Article
Cortisone exerted marked effects in vitro on the respiration of mammary gland slices from 20-day-pregnant rats. These effects appear to be such as would be expected if secretory changes had been initiated. On the other hand, the tissue was inert to prolactin at this stage. Conversely, the respiration of tissue taken at days 1–5 of lactation was sensitive in a similar way to prolactin in vitro but inert to cortisone.
The fate of uniformly labelled 14C glucose in rat-brain slices has been followed by a quantitative application of the radio paper-chromatography technique. After 60 min incubation with brain tissue approximately 60% of the glucose disappearing from the medium was accounted for as lactic acid, about 20% as CO2 and most of the remainder as free amino-acids. Of the total glucose metabolized approximately 9% was converted into glutamic acid, 1.5% alanine, 3% gamma -amino-butyric acid and 2.4% aspartic acid. Glutamic acid was the first of the amino-acids to be formed from glucose, and was detectable after 3 min incubation of brain tissue with 14C glucose. Insulin had no effect on glucose metabolism in brain slices. Under anaerobic conditions the total glucose metabolized by brain slices was only about 10% of that found under aerobic conditions; of the total glucose disappearing from the medium anaerobically about 80% was accounted for as lactic acid and the remainder as free unchanged glucose in the tissue cells.
Article
Respiration rates were determined for rat sciatic nerves using the standard Warburg manometric technique. Autoxidation rates of nerves obtained from rats rendered comatose by insulin and of nerves which have been sectioned 8 days previously are diminished by about one-third of the normal rate. The addition of glucose, mannose, fructose, galactose, sucrose, pyruvate, and l-glutamate caused a stimulation of respiratory activity of nerves from normal and insulinized rats and of nerves undergoing Wallerian degeneration. The Schwann cells appear to contribute the major portion of the resting autoxidation rate.
Article
The glucose uptake, lactic acid and pyruvic acid production, glycogen synthesis, oxygen uptake and carbon dioxide production were studied in leucocytes from 54 nondiabetic and 30 diabetic subjects. In normal leucocytes the magnitude of these parameters, except the CO2 production, was influenced by the concentration of leucocytes used in the individual experiments, and decreased with increasing cell concentration. In diabetic leucocytes a similar dependency was found for the oxygen uptake and pyruvic acid production, but not for the glucose uptake, lactic acid production and glycogen synthesis, leading to the situation that these parameters were lower than in normal leucocytes at low cell concentrations, while the reverse was true at high leucocyte concentrations. The lower glucose uptake, lactic acid production and glycogen synthesis of diabetic leucocytes are not thought to be secondary to a defective transport mechanism for glucose.
Article
1.1. The presence of the glycolytic enzymes were demonstrated in testicular tissue.2.2. Chicken tissue predominated in all enzymes in the Embden-Meyerhof pathway with the exception of PK, ‡ whereas rabbit tissue predominated in the various branch-points of glycolysis (G-6-P DH, 6-PG DH, PGM, α-Gly-P DH).3.3. Kidney cortex, regardless of species, was significantly higher in all enzyme activities except hexokinase, G-6-P DH, and PK in which testis was significantly higher.4.4. Three of the enzymes (hexokinase, G-6-P DH, and PK) demonstrated a significantly higher difference in the activity of the testis as compared to that of kidney cortex.5.5. From the above data and previous observations, a hypothesis was constructed in an attempt to explain the difference in metabolism of the abdominal testis (chicken) and the scrotal testis (rabbit).
Article
—Respiration studies in vitro, in which tissue slices were incubated with [1-14C]glucose or [6-14C]glucose and 14CO2 collected, resulted in C-1/C-6 14CO2 ratios that were higher in slices of tumor and newborn brain than in slices of adult brain. In adult brain, the C-1/C-6 14CO2 ratio averaged close to unity. In slices of tumor and newborn brain however, the mean C-1/C-6 ratio was greater than three. Addition of phenazine methosulfate (PMS) increased conversion of [1-14C]glucose to 14CO2 in slices of normal adult brain 5-fold, and in slices of newborn brain and tumor, approx 12-fold. Injection of animals with 6-aminonicotinamide (6-AN) decreased conversion of [1-14C]glucose in slices of normal brain 30% but decreased conversion in tumor slices by 80%. Evidence supports the presence of an active hexose monophosphate pathway (HMP) in tumors of the nervous system regulated in part by available NADP+ levels. Inhibition by 6-AN was more effective in tumors than in normal adult brain.
Article
Further modifications of the enzymatic technique for the preparation of isolated, intact, parenchymal cells from rat liver as previously described by this laboratory are presented together with a detailed account of several critical factors involved during the procedure. In addition, the fine structure of the cells as revealed by electron microscopy and the characteristics of their respiratory activity in different media and with several added substrates are described. It is shown that cells obtained by adding calcium during the preparative procedure retain approximately 34% more potassium than cells prepared solely in a calcium-free medium. The former cells also demonstrate a higher respiratory activity, which is not due to uncoupling of respiration. Electron microscopy reveals that the cells have an intact plasma membrane and well-preserved intracellular organelles. Glycogen particles are observed in all cells and are particularly abundant when either 20 mM pyruvate is added during the preparation or Eagle's Minimum Essential Medium is employed.
Summary Rat liver slices were incubated in cold modified Ringer’s solution. Subsequently, measurements were made of the quantities of water, NaCl and dry substances in the slices, and of the cell size, as a function of incubation time. The water and NaCl content of the tissue increases continuously. The content of dry substance drops to a plateau, remains there until about 30 minutes incubation time, then decreases further. The cell volume raises to a maximum, also at about 30 minutes, and then falls again, while the tissue continues to swell. The values for the extracellular space are at a minimum at 30 minutes.
Chapter
Gasometrische Methoden werden bei biochemischen Untersuchungen häufig angewendet, in erster Linie dann, wenn Stoffwechselvorgänge, die unter Bildung oder unter Verbrauch von Gas ablaufen, gemessen werden sollen. Sie ermöglichen es, den Umsatz selbst sehr geringer Gasmengen quantitativ zu erfassen und — da der Reaktionsablauf durch die Messung im allgemeinen nicht unterbrochen wird — mit kleinen Mengen Versuchsmaterial auch den zeitlichen Verlauf der in Betracht kommenden Reaktionen zu messen. Die Messung der Zellatmung, bei der Sauerstoff verbraucht wird und Kohlendioxyd entsteht, die Messung der pflanzlichen Assimilation, bei der Kohlendioxyd aufgenommen und Sauerstoff freigesetzt wird, oder die Messung der unter Kohlendioxydbildung erfolgenden Gärungen sind hier vor allem zu nennen. Hinzu kommen die hauptsächlich von Bakterien bewirkten Vorgänge, bei denen noch andere Gase als O2 und CO2 umgesetzt werden (z.B. H2, N2), die gasometrisch direkt gemessen werden können. Andere biochemische Vorgänge lassen sich mit gasometrischen Methoden auf eine indirekte Weise verfolgen, z.B. die Glykolyse oder Esterspaltungen, indem man die durch die gebildete Menge Säure aus Hydrogencarbonat freigesetzte Kohlendioxydmenge mißt. Verschiedene Wege werden eingeschlagen, um Reaktionen, an denen Gase nicht unmittelbar beteiligt sind, mit gasbildenden oder gasverbrauchenden Reaktionen zu koppeln und so gasometrisch messen zu können. Auch für die quantitative Bestimmung von Substanzen haben gasometrische Methoden in der Biochemie Bedeutung erlangt.
Chapter
Electrical activity is one of the major ways by which neurons communicate with each other. To understand how the brain works in physiological and pathological conditions, we need to know how the neuron works by monitoring the electrical activities of the neuron at different circumstances. Many electrophysiological techniques are available to obtain information from nerve system. This chapter introduces two techniques that can collect information of synaptic transmission and intrinsic membrane properties from individual neurons. Intracellular recording in vivo can examine the spontaneous firing, evoked postsynaptic potentials, and membrane properties at the cellular level in intact animals. This technique preserves the integrity of the brain, as well as the whole body system of the animal, and therefore is ideal to investigate the electrophysiological changes in various animal models of neurological disorders. Patch-clamp recording on brain slices is a well-control reduced system to examine the electrophysiology at the cellular level with the whole-cell mode. It can also examine the single-ion-channel activities with the cell-attached mode or by isolation of a small piece of cell membrane. Combining pharmacological manipulations, the patch-clamp recording on brain slices significantly expand the horizon of electrophysiological studies on neurons in physiological and pathological conditions.
Chapter
Energy required for vital function whether in the animal, the bacterium or the higher plant is obtained by burning fuel. In most plant tissues the fuel is sugar or one of its storage products (either di- or polysaccharides). In other instances it is fat, and in a few plants, protein storage products may be burned to provide energy. The energy available in these molecules, in the form of bond energy, is derived from the sun either directly or indirectly. For this energy to become available to the cell, a series of transformations must occur which, in the case of the sugars and their related products, and for at least part of the fat molecule, involves the formation of phosphorylated compounds. In short, if substrates are to be used as energy sources they must first undergo phosphorylation. This appears to be true for almost all instances of sugar oxidation. There are, however, a few isolated cases in some animal tissues and especially in bacteria where prior phosphorylation may not be required.
Chapter
The condition sine qua non for the normal activity of the central nervous system is the continuous production of a sufficient amount of energy. Every function of the nerve cells or of the conducting elements requires either direct or indirect energy. The biochemical processes by which the brain cells derive this energy are very similar to those observed in other organs and in lower forms of life, though slight differences are not uncommon. Thus, for example, unlike most other cell types, the brain cells in vivo appear incapable of using any other substance than glucose as their basic energy source [1]. The carbohydrates play such a dominating part in the energy-producing processes of the nerve cells that it appears appropriate to begin this discussion with the metabolism of glucose.
Article
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The review outlines current state of the theoretical, methodological and applies aspects of brains energy homeostasis. Authors suggest reconsidering the exclusive role of glucose as an energy substrate (ES) at both neuronal and systemic levels discussing recent research data on qualitative composition of ES pool in the brain. The role of ES alternative to glucose, e.g., lactate and ketone bodies, is examined. The hypotheses of intracellular and astrocyte-neuron lactate shuttles are discussed along with the hypotheses of astrocyte-neuron shuttle of ketone bodies, the selfish brain theory and suppositions on homeostatic versus non-homeostatic ES supply chains. In conclusion, authors argue that exogenous native ES may be used for prevention and treatment of neurodegenerative diseases.
Article
Influx of alpha-aminoisobutyric acid (AIB) and gamma-aminobutyric acid (GABA) by mouse cerebrum slices incubated with L-lactate or a mixture of succinate, L-malate, and pyruvate (SMP) as the energy source follows the phenomenological rate equation for influx from pyruvate and glucose media: v = Vmax/(1 + Kt/S) + kuS, where v is rate and S is concentration of amino acid. There are two kinetically distinct, parallel components for concentrative uptake, one saturable, and one unsaturable. Rates are less with lactate than with pyruvate and still less with SMP (only GABA was studied), disproving the hypotheses that lower rates with pyruvate compared to glucose are due to an abnormal redox state in the tissue or to a Krebs cycle unbalanced by input at only one point. The carriers for AIB and GABA are qualitatively different. In lactate medium the capacity of each AIB carrier is unchanged but its affinity is reduced to one-third. In lactate and SMP media, the capacity of the saturable GABA carrier is diminished although its affinity is increased. Rates from these media with added glucose or a glucose analog confirm that amino acid and glucose fluxes are not coupled.
EinleitungCitronensäurecyklus und Acetatabbau in der HefeDer Mechanismus der KondensationsreaktionAconitaseOxalbernsteinsäure—Ochoa-ReaktionEffektoren der Fermente des Citronensäurecyklus
IntroductionPyruvate AnabolismPyruvate CatabolismRelationships of Carbohydrate, Protein and Fat Metabolism
Article
—1A procedure has been developed to measure ACh synthesis from [14C]-precursors. As little as 10−9 moles of ACh were detected as the result of de nova synthesis. Following incubation of cortex slices of rat brain with eserine and a tagged metabolite, ACh carrier was added to the incubation medium and to an extract from the slices. ACh was purified by chromatography on Amberlite CG-50, precipitation and recrystallization of ACh chloroaurate.2[U−14C]glucose and [2−14C]pyruvate formed similar amounts of [14C]ACh. Hydrolysis of ACh with subsequent chromatography of the resultant acetic acid demonstrated that all of the label was located in the acetyl moiety. [14C]acetate did not serve as a precursor of the acetyl group of ACh. Equivalent incorporation of carbons 1 and 6 of glucose into ACh indicated that glucose metabolism to ACh occurred via the Embden-Meyerhof pathway.3The amount of ACh detected by bioassay after incubation of cortex slices with [U−14C]glucose was approximately the same as that calculated as labelled ACh; this demonstrates that all of the acetyl groups of ACh formed during incubation were derived from glucose.4[14C]choline, either methyl or chain labelled, formed [14C]ACh while labelled ethanolamine, serine and methionine did not. Synthesis from labelled choline did not occur in the absence of glucose.5When both [U−14C]glucose and [14C]choline were incubated with brain slices, the acetyl and choline moieties of ACh were equally labelled; this demonstrates that the entire molecule was formed from added precursors. Slices supported a high rate of ACh synthesis without addition of choline. The addition of 10−4m-hemicholinium-3 inhibited ACh formation by more than 90 per cent from either [U-14C]glucose or [Me-14C]choline.6Study of the time course of ACh synthesis from glucose demonstrated a rapid formation of [14C]ACh within the slices which reached a maximum during the first hour of incubation. [14C]ACh in the incubation medium accumulated at a linear rate for 3 hr. Replacement of a portion of the sodium chloride of the incubation medium by potassium chloride to a final concentration of 31 mm-KCI markedly increased the formation of [14C]ACh found in the incubation medium. Decreased amounts of [14C]ACh were extracted from the slices by homogenization or by subsequent heating at pH 4 in the high potassium ion medium.
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Experimental FindingsReaction Schemes (Theory of Carbohydrate Oxidation)Problems Related to the Oxidation of Carbohydrate
IntroductionNormal Mechanisms of Energy TransferMethods of AssayAssay ResultsInhibition of Respiratory Enzymes by Carcinogenic Chemicals
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This chapter discusses ion and energy metabolism of the brain at the cellular level. The comparison between metabolism in the brain in vivo and in brain slices and isolated cells has highlighted that ion and energy metabolism of the dissociated cell types corresponds to that in more complex in vitro preparation and under in vivo conditions. Therefore, observations in such preparations of individual cells are relevant for interpretation of physiological and pathological events at the cellular level of the brain cortex. The chapter also focuses the effects of ions (especially K+) on energy metabolism and of adverse metabolic conditions on ion distribution. From a physiological point of view, it is probably of major importance that the potassium concentration in the interstitial fluid becomes considerably increased during neuronal activity. Owing to the pronounced influence of K+ on membrane polarization, efficient and fast removal of excess extracellular potassium is essential.
The respiratory quotient of the stria vascularis was measured in vitro by means of Cartesian diver microgasometry. A value of about 1.2 was found when the incubation medium was phosphate-buffered serum substitute with glucose as the sole substrate. This value suggests that endogenous lipids and amino acids do not contribute significantly to strial respiratory metabolism and that carbohydrate is the primary fuel in vitro. A high activity of the hexose monophosphate pathway may be responsible for raising the respiroatyr quotient above unity.