Citric Acid Cycle: A series of oxidative reactions in the breakdown of acetyl units derived from GLUCOSE; FATTY ACIDS; or AMINO ACIDS by means of tricarboxylic acid intermediates. The end products are CARBON DIOXIDE, water, and energy in the form of phosphate bonds.Citric Acid: A key intermediate in metabolism. It is an acid compound found in citrus fruits. The salts of citric acid (citrates) can be used as anticoagulants due to their calcium chelating ability.CitratesMalatesIsocitrate Dehydrogenase: An enzyme of the oxidoreductase class that catalyzes the conversion of isocitrate and NAD+ to yield 2-ketoglutarate, carbon dioxide, and NADH. It occurs in cell mitochondria. The enzyme requires Mg2+, Mn2+; it is activated by ADP, citrate, and Ca2+, and inhibited by NADH, NADPH, and ATP. The reaction is the key rate-limiting step of the citric acid (tricarboxylic) cycle. (From Dorland, 27th ed) (The NADP+ enzyme is EC EC Derivatives of OXALOACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that include a 2-keto-1,4-carboxy aliphatic structure.Fumarate Hydratase: An enzyme that catalyzes the reversible hydration of fumaric acid to yield L-malic acid. It is one of the citric acid cycle enzymes. EC Hydratase: An enzyme that catalyzes the reversible hydration of cis-aconitate to yield citrate or isocitrate. It is one of the citric acid cycle enzymes. EC Acids: A family of compounds containing an oxo group with the general structure of 1,5-pentanedioic acid. (From Lehninger, Principles of Biochemistry, 1982, p442)Pyruvic Acid: An intermediate compound in the metabolism of carbohydrates, proteins, and fats. In thiamine deficiency, its oxidation is retarded and it accumulates in the tissues, especially in nervous structures. (From Stedman, 26th ed)Ketoglutarate Dehydrogenase ComplexOxaloacetic Acid: A dicarboxylic acid ketone that is an important metabolic intermediate of the CITRIC ACID CYCLE. It can be converted to ASPARTIC ACID by ASPARTATE TRANSAMINASE.Malate Dehydrogenase: An enzyme that catalyzes the conversion of (S)-malate and NAD+ to oxaloacetate and NADH. EC (si)-Synthase: Enzyme that catalyzes the first step of the tricarboxylic acid cycle (CITRIC ACID CYCLE). It catalyzes the reaction of oxaloacetate and acetyl CoA to form citrate and coenzyme A. This enzyme was formerly listed as EC Coenzyme A: Acetyl CoA participates in the biosynthesis of fatty acids and sterols, in the oxidation of fatty acids and in the metabolism of many amino acids. It also acts as a biological acetylating agent.Succinic Acid: A water-soluble, colorless crystal with an acid taste that is used as a chemical intermediate, in medicine, the manufacture of lacquers, and to make perfume esters. It is also used in foods as a sequestrant, buffer, and a neutralizing agent. (Hawley's Condensed Chemical Dictionary, 12th ed, p1099; McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1851)Carbon Isotopes: Stable carbon atoms that have the same atomic number as the element carbon, but differ in atomic weight. C-13 is a stable carbon isotope.PyruvatesSuccinate Dehydrogenase: A flavoprotein containing oxidoreductase that catalyzes the dehydrogenation of SUCCINATE to fumarate. In most eukaryotic organisms this enzyme is a component of mitochondrial electron transport complex II.Acetates: Derivatives of ACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxymethane structure.GlyoxylatesSuccinate-CoA Ligases: Enzymes that catalyze the first step leading to the oxidation of succinic acid by the reversible formation of succinyl-CoA from succinate and CoA with the concomitant cleavage of ATP to ADP (EC or GTP to GDP (EC and orthophosphate. Itaconate can act instead of succinate and ITP instead of GTP.EC 6.2.1.-.Fluoroacetates: Derivatives of acetic acid with one or more fluorines attached. They are almost odorless, difficult to detect chemically, and very stable. The acid itself, as well as the derivatives that are broken down in the body to the acid, are highly toxic substances, behaving as convulsant poisons with a delayed action. (From Miall's Dictionary of Chemistry, 5th ed)Cell Cycle: The complex series of phenomena, occurring between the end of one CELL DIVISION and the end of the next, by which cellular material is duplicated and then divided between two daughter cells. The cell cycle includes INTERPHASE, which includes G0 PHASE; G1 PHASE; S PHASE; and G2 PHASE, and CELL DIVISION PHASE.Fumarates: Compounds based on fumaric acid.Succinates: Derivatives of SUCCINIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain a 1,4-carboxy terminated aliphatic structure.Glycolysis: A metabolic process that converts GLUCOSE into two molecules of PYRUVIC ACID through a series of enzymatic reactions. Energy generated by this process is conserved in two molecules of ATP. Glycolysis is the universal catabolic pathway for glucose, free glucose, or glucose derived from complex CARBOHYDRATES, such as GLYCOGEN and STARCH.Glutamates: Derivatives of GLUTAMIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the 2-aminopentanedioic acid structure.Gluconeogenesis: Biosynthesis of GLUCOSE from nonhexose or non-carbohydrate precursors, such as LACTATE; PYRUVATE; ALANINE; and GLYCEROL.Ketone Bodies: The metabolic substances ACETONE; 3-HYDROXYBUTYRIC ACID; and acetoacetic acid (ACETOACETATES). They are produced in the liver and kidney during FATTY ACIDS oxidation and used as a source of energy by the heart, muscle and brain.Heptanoates: Salts and esters of the 7-carbon saturated monocarboxylic acid heptanoic acid.Malate Synthase: An important enzyme in the glyoxylic acid cycle which reversibly catalyzes the synthesis of L-malate from acetyl-CoA and glyoxylate. This enzyme was formerly listed as EC Carboxylase: A biotin-dependent enzyme belonging to the ligase family that catalyzes the addition of CARBON DIOXIDE to pyruvate. It is occurs in both plants and animals. Deficiency of this enzyme causes severe psychomotor retardation and ACIDOSIS, LACTIC in infants. EC Acid Transporters: A family of organic anion transporters that specifically transport DICARBOXYLIC ACIDS such as alpha-ketoglutaric acid across cellular membranes.Glucose: A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.GlutaratesMitochondria: Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed)Glutamine: A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells.Acetoacetates: Salts and derivatives of acetoacetic acid.Oxo-Acid-Lyases: Enzymes that catalyze the cleavage of a carbon-carbon bond of a 3-hydroxy acid. (Dorland, 28th ed) EC 4.1.3.Oxygen Consumption: The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)Keto AcidsEnergy Metabolism: The chemical reactions involved in the production and utilization of various forms of energy in cells.Acetic Acid: Product of the oxidation of ethanol and of the destructive distillation of wood. It is used locally, occasionally internally, as a counterirritant and also as a reagent. (Stedman, 26th ed)Magnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Lactic Acid: A normal intermediate in the fermentation (oxidation, metabolism) of sugar. The concentrated form is used internally to prevent gastrointestinal fermentation. (From Stedman, 26th ed)Hydro-Lyases: Enzymes that catalyze the breakage of a carbon-oxygen bond leading to unsaturated products via the removal of water. EC 4.2.1.Carbon: A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.Coenzyme AGlutamic Acid: A non-essential amino acid naturally occurring in the L-form. Glutamic acid is the most common excitatory neurotransmitter in the CENTRAL NERVOUS SYSTEM.Aspartic Acid: One of the non-essential amino acids commonly occurring in the L-form. It is found in animals and plants, especially in sugar cane and sugar beets. It may be a neurotransmitter.Propionates: Derivatives of propionic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxyethane structure.Perfusion: Treatment process involving the injection of fluid into an organ or tissue.Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Aspergillus niger: An imperfect fungus causing smut or black mold of several fruits, vegetables, etc.Tricarboxylic Acids: Organic compounds that are acyclic and contain three acid groups. A member of this class is citric acid which is the first product formed by reaction of pyruvate and oxaloacetate. (From Lehninger, Principles of Biochemistry, 1982, p443)Kinetics: The rate dynamics in chemical or physical systems.Myocardium: The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.NAD: A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage. It is found widely in nature and is involved in numerous enzymatic reactions in which it serves as an electron carrier by being alternately oxidized (NAD+) and reduced (NADH). (Dorland, 27th ed)Menstrual Cycle: The period from onset of one menstrual bleeding (MENSTRUATION) to the next in an ovulating woman or female primate. The menstrual cycle is regulated by endocrine interactions of the HYPOTHALAMUS; the PITUITARY GLAND; the ovaries; and the genital tract. The menstrual cycle is divided by OVULATION into two phases. Based on the endocrine status of the OVARY, there is a FOLLICULAR PHASE and a LUTEAL PHASE. Based on the response in the ENDOMETRIUM, the menstrual cycle is divided into a proliferative and a secretory phase.Cough: A sudden, audible expulsion of air from the lungs through a partially closed glottis, preceded by inhalation. It is a protective response that serves to clear the trachea, bronchi, and/or lungs of irritants and secretions, or to prevent aspiration of foreign materials into the lungs.Taste: The ability to detect chemicals through gustatory receptors in the mouth, including those on the TONGUE; the PALATE; the PHARYNX; and the EPIGLOTTIS.Pyruvate Dehydrogenase Complex: A multienzyme complex responsible for the formation of ACETYL COENZYME A from pyruvate. The enzyme components are PYRUVATE DEHYDROGENASE (LIPOAMIDE); dihydrolipoamide acetyltransferase; and LIPOAMIDE DEHYDROGENASE. Pyruvate dehydrogenase complex is subject to three types of control: inhibited by acetyl-CoA and NADH; influenced by the energy state of the cell; and inhibited when a specific serine residue in the pyruvate decarboxylase is phosphorylated by ATP. PYRUVATE DEHYDROGENASE (LIPOAMIDE)-PHOSPHATASE catalyzes reactivation of the complex. (From Concise Encyclopedia Biochemistry and Molecular Biology, 3rd ed)Lactates: Salts or esters of LACTIC ACID containing the general formula CH3CHOHCOOR.Gas Chromatography-Mass Spectrometry: A microanalytical technique combining mass spectrometry and gas chromatography for the qualitative as well as quantitative determinations of compounds.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Mitochondria, Heart: The mitochondria of the myocardium.Carboxylic Acids: Organic compounds containing the carboxy group (-COOH). This group of compounds includes amino acids and fatty acids. Carboxylic acids can be saturated, unsaturated, or aromatic.Culture Media: Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Oxidoreductases: The class of all enzymes catalyzing oxidoreduction reactions. The substrate that is oxidized is regarded as a hydrogen donor. The systematic name is based on donor:acceptor oxidoreductase. The recommended name will be dehydrogenase, wherever this is possible; as an alternative, reductase can be used. Oxidase is only used in cases where O2 is the acceptor. (Enzyme Nomenclature, 1992, p9)Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Mitochondria, Liver: Mitochondria in hepatocytes. As in all mitochondria, there are an outer membrane and an inner membrane, together creating two separate mitochondrial compartments: the internal matrix space and a much narrower intermembrane space. In the liver mitochondrion, an estimated 67% of the total mitochondrial proteins is located in the matrix. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p343-4)Antitussive Agents: Agents that suppress cough. They act centrally on the medullary cough center. EXPECTORANTS, also used in the treatment of cough, act locally.Fatty Acids: Organic, monobasic acids derived from hydrocarbons by the equivalent of oxidation of a methyl group to an alcohol, aldehyde, and then acid. Fatty acids are saturated and unsaturated (FATTY ACIDS, UNSATURATED). (Grant & Hackh's Chemical Dictionary, 5th ed)Rats, Sprague-Dawley: A strain of albino rat used widely for experimental purposes because of its calmness and ease of handling. It was developed by the Sprague-Dawley Animal Company.Adenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Bacillus subtilis: A species of gram-positive bacteria that is a common soil and water saprophyte.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Taste Threshold: The minimum concentration at which taste sensitivity to a particular substance or food can be perceived.Amino Acids: Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.Iron-Sulfur Proteins: A group of proteins possessing only the iron-sulfur complex as the prosthetic group. These proteins participate in all major pathways of electron transport: photosynthesis, respiration, hydroxylation and bacterial hydrogen and nitrogen fixation.Cell Cycle Proteins: Proteins that control the CELL DIVISION CYCLE. This family of proteins includes a wide variety of classes, including CYCLIN-DEPENDENT KINASES, mitogen-activated kinases, CYCLINS, and PHOSPHOPROTEIN PHOSPHATASES as well as their putative substrates such as chromatin-associated proteins, CYTOSKELETAL PROTEINS, and TRANSCRIPTION FACTORS.IsocitratesOsmeriformes: An order of fish including smelts, galaxiids, and salamanderfish.Aconitic AcidRoot Canal Irrigants: Chemicals used mainly to disinfect root canals after pulpectomy and before obturation. The major ones are camphorated monochlorophenol, EDTA, formocresol, hydrogen peroxide, metacresylacetate, and sodium hypochlorite. Root canal irrigants include also rinsing solutions of distilled water, sodium chloride, etc.Metacercariae: Encysted cercaria which house the intermediate stages of trematode parasites in tissues of an intermediate host.Quinine: An alkaloid derived from the bark of the cinchona tree. It is used as an antimalarial drug, and is the active ingredient in extracts of the cinchona that have been used for that purpose since before 1633. Quinine is also a mild antipyretic and analgesic and has been used in common cold preparations for that purpose. It was used commonly and as a bitter and flavoring agent, and is still useful for the treatment of babesiosis. Quinine is also useful in some muscular disorders, especially nocturnal leg cramps and myotonia congenita, because of its direct effects on muscle membrane and sodium channels. The mechanisms of its antimalarial effects are not well understood.Rats, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Smear Layer: Adherent debris produced when cutting the enamel or dentin in cavity preparation. It is about 1 micron thick and its composition reflects the underlying dentin, although different quantities and qualities of smear layer can be produced by the various instrumentation techniques. Its function is presumed to be protective, as it lowers dentin permeability. However, it masks the underlying dentin and interferes with attempts to bond dental material to the dentin.Acetobacter: A species of gram-negative bacteria of the family ACETOBACTERACEAE found in FLOWERS and FRUIT. Cells are ellipsoidal to rod-shaped and straight or slightly curved.Caproates: Derivatives of caproic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain a carboxy terminated six carbon aliphatic structure.Estrous Cycle: The period of cyclic physiological and behavior changes in non-primate female mammals that exhibit ESTRUS. The estrous cycle generally consists of 4 or 5 distinct periods corresponding to the endocrine status (PROESTRUS; ESTRUS; METESTRUS; DIESTRUS; and ANESTRUS).Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Heart: The hollow, muscular organ that maintains the circulation of the blood.Taste Perception: The process by which the nature and meaning of gustatory stimuli are recognized and interpreted by the brain. The four basic classes of taste perception are salty, sweet, bitter, and sour.Metabolome: The dynamic collection of metabolites which represent a cell's or organism's net metabolic response to current conditions.Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Stars, Celestial: Large bodies consisting of self-luminous gas held together by their own gravity. (From McGraw Hill Dictionary of Scientific and Technical Terms, 6th ed)Sucrose: A nonreducing disaccharide composed of GLUCOSE and FRUCTOSE linked via their anomeric carbons. It is obtained commercially from SUGARCANE, sugar beet (BETA VULGARIS), and other plants and used extensively as a food and a sweetener.TartratesTongue: A muscular organ in the mouth that is covered with pink tissue called mucosa, tiny bumps called papillae, and thousands of taste buds. The tongue is anchored to the mouth and is vital for chewing, swallowing, and for speech.Pentose Phosphate Pathway: An oxidative decarboxylation process that converts GLUCOSE-6-PHOSPHATE to D-ribose-5-phosphate via 6-phosphogluconate. The pentose product is used in the biosynthesis of NUCLEIC ACIDS. The generated energy is stored in the form of NADPH. This pathway is prominent in tissues which are active in the synthesis of FATTY ACIDS and STEROIDS.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)

Activities of glucose metabolic enzymes in human preantral follicles: in vitro modulation by follicle-stimulating hormone, luteinizing hormone, epidermal growth factor, insulin-like growth factor I, and transforming growth factor beta1. (1/1318)

Modulation of glucose metabolic capacity of human preantral follicles in vitro by gonadotropins and intraovarian growth factors was evaluated by monitoring the activities of phosphofructokinase (PFK) and pyruvate kinase (PK), two regulatory enzymes of the glycolytic pathway, and malate dehydrogenase (MDH), a key mitochondrial enzyme of the Krebs cycle. Preantral follicles in classes 1 and 2 from premenopausal women were cultured separately in vitro in the absence or presence of FSH, LH, epidermal growth factor (EGF), insulin-like growth factor (IGF-I), or transforming growth factor beta1 (TGFbeta1) for 24 h. Mitochondrial fraction was separated from the cytosolic fraction, and both fractions were used for enzyme assays. FSH and LH significantly stimulated PFK and PK activities in class 1 and 2 follicles; however, a 170-fold increase in MDH activity was noted for class 2 follicles that were exposed to FSH. Although both EGF and TGFbeta1 stimulated glycolytic and Krebs cycle enzymes for class 1 preantral follicles, TGFbeta1 consistently stimulated the activities of both glycolytic enzymes more than that of EGF. IGF-I induced PK and MDH activities in class 1 follicles but negatively influenced PFK activity for class 1 follicles. In general, only gonadotropins consistently stimulated both glycolytic and Krebs cycle enzyme activities several-fold in class 2 follicles. These results suggest that gonadotropins and ovarian growth factors differentially influence follicular energy-producing capacity from glucose. Moreover, gonadotropins may either directly influence glucose metabolism in class 2 preantral follicles or do so indirectly through factors other than the well-known intraovarian growth factors. Because growth factors modulate granulosa cell mitosis and functionality, their role on energy production may be related to specific cellular activities.  (+info)

Activities of citrate synthase, NAD+-linked and NADP+-linked isocitrate dehydrogenases, glutamate dehydrogenase, aspartate aminotransferase and alanine aminotransferase in nervous tissues from vertebrates and invertebrates. (2/1318)

1. The activities of citrate synthase and NAD+-linked and NADP+-linked isocitrate dehydrogenases were measured in nervous tissue from different animals in an attempt to provide more information about the citric acid cycle in this tissue. In higher animals the activities of citrate synthase are greater than the sum of activities of the isocitrate dehydrogenases, whereas they are similar in nervous tissues from the lower animals. This suggests that in higher animals the isocitrate dehydrogenase reaction is far-removed from equilibrium. If it is assumed that isocitrate dehydrogenase activities provide an indication of the maximum flux through the citric acid cycle, the maximum glycolytic capacity in nervous tissue is considerably greater than that of the cycle. This suggest that glycolysis can provide energy in excess of the aerobic capacity of the tissue. 2. The activities of glutamate dehydrogenase are high in most nervous tissues and the activities of aspartate aminotransferase are high in all nervous tissue investigated. However, the activities of alanine aminotransferase are low in all tissues except the ganglia of the waterbug and cockroach. In these insect tissues, anaerobic glycolysis may result in the formation of alanine rather than lactate.  (+info)

The importance of pyruvate availability to PDC activation and anaplerosis in human skeletal muscle. (3/1318)

No studies have singularly investigated the relationship between pyruvate availability, pyruvate dehydrogenase complex (PDC) activation, and anaplerosis in skeletal muscle. This is surprising given the functional importance attributed to these processes in normal and disease states. We investigated the effects of changing pyruvate availability with dichloroacetate (DCA), epinephrine, and pyruvate infusions on PDC activation and accumulation of acetyl groups and tricarboxylic acid (TCA) cycle intermediates (TCAI) in human muscle. DCA increased resting PDC activity sixfold (P < 0.05) but decreased the muscle TCAI pool (mmol/kg dry muscle) from 1.174 +/- 0.042 to 0.747 +/- 0.055 (P < 0.05). This was probably a result of pyruvate being diverted to acetyl-CoA and acetylcarnitine after near-maximal activation of PDC by DCA. Conversely, neither epinephrine nor pyruvate activated PDC. However, both increased the TCAI pool (1.128 +/- 0.076 to 1.614 +/- 0.188, P < 0.05 and 1.098 +/- 0.059 to 1.385 +/- 0.114, P < 0.05, respectively) by providing a readily available pool of pyruvate for anaplerosis. These data support the hypothesis that TCAI pool expansion is principally a reflection of increased muscle pyruvate availability and, together with our previous work (J. A. Timmons, S. M. Poucher, D. Constantin-Teodosiu, V. Worrall, I. A. Macdonald, and P. L. Greenhaff. J. Clin. Invest. 97: 879-883, 1996), indicate that TCA cycle expansion may be of little functional significance to TCA cycle flux. It would appear therefore that the primary effect of DCA on oxidative ATP provision is to provide a readily available pool of acetyl groups to the TCA cycle at the onset of exercise rather than increasing TCA cycle flux by expanding the TCAI pool.  (+info)

Low oxygen inhibits but complex high-glucose medium facilitates in vitro maturation of squirrel monkey oocyte-granulosa cell complexes. (4/1318)

PURPOSE: The objectives of these in vitro maturation studies in primate cumulus-oocyte complexes (COCs) were to evaluate the effect of a reduced-oxygen environment and to compare medium with a high-glucose concentration to medium with pyruvate but no glucose. METHODS: COCs were retrieved from squirrel monkeys stimulated with 1 mg of follicle-stimulating hormone (FSH) for 4-6 days. Experiment 1 examined maturation after 48 hr in 5% O2/5% CO2/90% N2 compared with 5% CO2/air. The medium was CMRL-1066 containing moderate glucose (5.5 mM) supplemented with 1 mM glutamine, 0.33 mM pyruvate, 0.075 IU/ml human FSH, 5 IU/ml human chorionic gonadotropin, 75 U penicillin G/ml, and 20% fetal bovine serum. Experiment 2 in 5% CO2/air, compared P-1 medium (pyruvate and lactate but no glucose) to Waymouth's medium (27.5 mM glucose), both with identical supplements. RESULTS: Only 3 (8%) of 37 COCs matured in 5% O2, while 39 (49%) of 80 matured in ambient O2. Fourteen (22%) of 64 complexes matured in P-1 medium, compared to 47 (49%) of 96 meiosis II oocytes in Waymouth's medium (P < 0.05). CONCLUSIONS: These are the first primate studies showing detrimental effects of reduced-oxygen culture on in vitro maturation. Additionally, maturation was enhanced with complex high-glucose medium suggesting that the predominant metabolism is aerobic glycolysis.  (+info)

A minimal mechanism for bacterial pattern formation. (5/1318)

Colonies of Escherichia coli or Salmonella typhimurium form geometrically complex patterns when exposed to, or feeding on, intermediates of the tricarboxylic acid (TCA) cycle. In response to the TCA cycle intermediate, the bacteria secrete aspartate, a potent chemo-attractant. As a result, the cells form high-density aggregates arranged in striking regular patterns. The simplest are temporary spots formed in a liquid medium by both E. coli and S. typhimurium. In semi-solid medium S. typhimurium forms concentric rings arising from a low-density bacterial lawn, which are either continuous or spotted, whereas E. coli forms complex patterns arising from a dense swarm ring, including interdigitated spots (also called sunflower spirals), radial spots, radial stripes and chevrons. We present a mathematical model that captures all three of the pattern-forming processes experimentally observed in both E. coli and S. typhimurium, using a minimum of assumptions.  (+info)

The tricarboxylic acid cycle of Helicobacter pylori. (6/1318)

The composition and properties of the tricarboxylic acid cycle of the microaerophilic human pathogen Helicobacter pylori were investigated in situ and in cell extracts using [1H]- and [13C]-NMR spectroscopy and spectrophotometry. NMR spectroscopy assays enabled highly specific measurements of some enzyme activities, previously not possible using spectrophotometry, in in situ studies with H. pylori, thus providing the first accurate picture of the complete tricarboxylic acid cycle of the bacterium. The presence, cellular location and kinetic parameters of citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate oxidase, fumarate reductase, fumarase, malate dehydrogenase, and malate synthase activities in H. pylori are described. The absence of other enzyme activities of the cycle, including alpha-ketoglutarate dehydrogenase, succinyl-CoA synthetase, and succinate dehydrogenase also are shown. The H. pylori tricarboxylic acid cycle appears to be a noncyclic, branched pathway, characteristic of anaerobic metabolism, directed towards the production of succinate in the reductive dicarboxylic acid branch and alpha-ketoglutarate in the oxidative tricarboxylic acid branch. Both branches were metabolically linked by the presence of alpha-ketoglutarate oxidase activity. Under the growth conditions employed, H. pylori did not possess an operational glyoxylate bypass, owing to the absence of isocitrate lyase activity; nor a gamma-aminobutyrate shunt, owing to the absence of both gamma-aminobutyrate transaminase and succinic semialdehyde dehydrogenase activities. The catalytic and regulatory properties of the H. pylori tricarboxylic acid cycle enzymes are discussed by comparing their amino acid sequences with those of other, more extensively studied enzymes.  (+info)

Replenishment and depletion of citric acid cycle intermediates in skeletal muscle. Indication of pyruvate carboxylation. (7/1318)

The effects of various substrates on the concentrations of free amino acids, citric acid cycle intermediates and acylcarnitines were studies in perfused hindquarter of rat in presence of glucose and insulin in order to assess regulatory mechanisms of the level of citric acid cycle intermediates in skeletal muscle. 1. Acetate and acetoacetate effected a significant increase in the level of citrate cycle intermediates and accumulation of acetylcarnitine. These changes were accompanied by a reduction in the level of alanine. The concentration of AMP was significantly elevated. 2. Muscle mitochondria fixed 14CO2 in the presence of pyruvate. The products were identified as malate or citrate when whole and disintegrated mitochondria were used respectively. The fixation was greatly stimulated by acetylcarnitine. 3. Acetylcarnitine inhibited the production of pyruvate from malate by muscle mitochondria. 4. Perfusion with 2-oxoisocaproate and 2-oxoisovalerate promoted increases in the level of citric cycle intermediates, a drop in both alanine and glutamate, and accumulation of branched-chain acylcarnitines. 2-Oxoisocaproate also caused a reduction of alanine released from the muscle. 5. Perfusion with leucine and valine did not change the concentration of citric acid cycle intermediates, but elevated glutamate and still more the concentration of alanine. 6. It is concluded that citric cycle intermediate level in the perfused resting muscle is modified by a) conditions which change the concentration of acetyl-CoA and thereby modify the rate of pyruvate carboxylation and decarboxylation of malate via malic enzyme b) conditions which change the concentration of pyruvate cause changes in alanine and cycle intermediates in the same direction via transamination reactions c) conditions which change the concentrations of 2-oxoacids which are converted to cycle intermediates via oxidation.  (+info)



  • These solutions include lowering serum RBP4 levels, lowering free fatty acid levels, ( hence why Type -2 Diabetes can literally stop the disease by losing weight aka excess fat) and preserving/restoring Beta-cell function. (
  • In the last step of the citric acid cycle, oxaloacetate-the starting four-carbon compound-is regenerated by oxidation of malate. (
  • OMG LOLOLOL above, that really helped man really thnx.i have a head scrather here i learned a mnemonic for kreb's cycle and now i only remember half of it can some plz help me out the last three parts stand for SELL SEX FOR MONEY.i need the first part to [email protected] (
  • Vitamins and coenzymes - Water-soluble vitamins: Thiamine (B1) - Riboflavin (B2) - Pyridoxine (B6) - Folic acid - Cobalamin (B12) - Biotin (H) - Pantothenic acid - Nicotinamide - Ascorbic acid. (
  • The two major products of Citric Acid Cycle are: NADH (the reduced form of nicotinamide adenine dinucleotide) and FADH2 (the reduced form of flavin adenine dinucleotide). (
  • The market for citric acid for application in the pharmaceutical and personal care sectors is emerging with substantial opportunities and is projected to grow at a competitive CAGR from 2015 to 2020. (
  • The global market for citric acid is projected to grow at competitive CAGRs of 5.5% and 5.2%, in terms of value and volume respectively, from 2015 to 2020. (
  • Europe led the market for citric acid in 2014, in terms of value and volume, owing to substantial growth in the processed food & beverage industry and high consumption of citric acid as a vital food additive. (
  • Dec 06, 2008· Best Answer: The citric acid cycle forms the electron carriers which drive the synthesis of ATP. (
  • The cycle is also central to most of the synthesis of biomolecules in you. (
  • Stanley Miller's synthesis of the amino acids by sparking a reducing atmosphere ( 2 ) was the paradigm for prebiotic synthesis for many years, so at first, it was natural to suppose that similar methods would meet with equal success in the nucleotide field. (
  • Exam4Notes - Chapter 11 The Citric Acid Cycle Learning. (
  • Chapter 16: Citric Acid Cycle 134 H C CO 2 O Short Answer Questions Write your answer in the space provided or on a separate sheet of paper. (