Na 1 Nachlass Max Horkheimer, 639 - "On the Sociology of Class Relations" und "The Psychology of Nazidom" (p. IX 16.1-2-IX 17.1-2)

"On the Sociology of Class Relations" (GS 12, S.75-104); 1. 1943 Aufsatz. a) Typoskript mit handschriftlichen Korrekturen, 34 Blatt b) Typoskript mit eigenhändigen Korrekturen, 31 Blatt c) Typoskript, 31 Blatt und eigenhändigen Ergänzungen, 1 Blatt d) Typoskript mit eigenhändigen Korrekturen, 26 Blatt; 2. Franz Neumann: 1 eigenhändiger Brief mit Unterschrift an Max Horkheimer mit Anmerkungen zum Aufsatz, ohne Ort, 30.09.1943, 11 Blatt; "The Psychology of Nazidom" (GS 5, S. 354-359); 1. Buchbesprechung von "Is Germany Inucable?" von Richard M. Brickner; veröffentlicht in: "The New Leader", 14.08.1943. a)Typoskript, 7 Blatt b) Typoskript mit eigenhändigen und handschriftlichen Korrekturen, 7 Blatt c) Zeitungsdruck, 3 Exemplare; 2. "What Shall We Do With Germany? A Panel Discussion of 'Is Germany Incurable?'". Zeitungsausschnitte aus : "The Saturday Review of Literature", 29.05.1343, 6 Blatt;

Na 1 Nachlass Max Horkheimer, 682 - "Antisemitism among American Labor" (p. IX 146.2-4 - IX 146.5-23)

"Antisemitism and American Labor. A Research Project of the Institut of Social Research", Januar 1944 (revised June 1944); a) als Typoskript vervielfältigt, 14 Blatt; b) Typoskript, 14 Blatt; Institut of Social Research: "Project an Antisemitism and American Labor", Januar 1944; a) Typoskript, 18 Blatt; b) Typoskript, mit handschriftlichen Korrekturen, 17 Blatt, c) Teilstück, Typoskript mit handschriftlichen Korrekturen, 1 Blatt; d) Teilstück, Typoskript mit handschriftlichen Korrekturen, 1 Blatt; e) Teilstück, Typoskript mit handschriftlichen Korrekturen, 5 Blatt; f) Teilstück, Typoskript mit handschriftlichen Korrekturen, 4 Blatt; "Project on Antisemitism an American Labor", Dezember 1943; a) Typoskript mit handschriftlichen Korrekturen, 18 Blatt; b) Typoskript mit handschriftlichen Korrekturen von Theodor W. Adorno, 17 Blatt; c) Typoskript mit handschriftlichen Korrekturen, 12 Blatt; Memoranden 1941-1949; Adorno, Theodor W. to Löwenthal, Leo: "Supplement to the Memorandum of 7/28/49 by Pollock, Friedrich re Labor Study", 18.09.1949. Typoskript, 6 Blatt; Adorno, Theodor W.: "Memorandum re: Antisemitism among American Labor, as edited by the Bureau of Applied Social Research", 19.07.1949. Typoskript, 8 Blatt; "Expenses for Project: Antisemitism among Labor, june 1, 1944- May 31,1945". Typoskript, 1 Blatt; Institut of Social Research: "Interim Memorandum on Progress of Project on Antisemitism within Labor", 04.09.1944. Typoskript, 11 Blatt; Institut of Social Research: "Re: Project on Labor and Antisemitism. Difficulties to be expected", 21.03.1944. Typoskript, 3 Blatt; "Re: Project on Labor and Antisemitism. Plants to be Contacted", 21.03.1944. Typoskript, 2 Blatt; "Some Remarks to Dr. Gelle's Report 'Der deutsche Progrom, a, 10. November 1938'", 11.03.1944. Typoskript, 12 Blatt; Adorno, Theodor W. ?: "Adress to ameeting of the Jewish Labor Committee, January 20th, 1944, los Angeles". Typoskript mit eigenhändigen Ergänzungen, 2 Blatt; Pollock, Friedrich: "Re: Sherman", 31.12.1943, 1 Blatt; "Memorandum re: Jewish Labor Committee", 23.12.1943. Typoskript mit handschriftlichen Korrekturen, 2 Blatt; "Tentative Budget for a Trial Survey on Antisemitism among American Labor", 23.12.1943. Typoskript, 1 Blatt; "Council for Democracy. Survey on Antisemitism. Hartford, Conn., late 1941". Typoskript, 4 Blatt; "Council for Democracy. Survey on Antisemitism. Terre Haute, Ind.". Typoskript, 2 Blatt; Horkheimer, Max: Eigenhändige Notizen zum Projekt, 3 Blatt; "Some heading lind", handschriftlichen Notizen, 1 Blatt; Institut of Social research: "Instructuins", Fragebogen, als Typoskript vervielfältigt, 3 Blatt; "Instructions for Interviews on Attitudes of Workers and White Collar Workers towards Jews". Als Typoskript vervielfältigt, 1 Blatt; Horkheimer, Max: 1 Briefentwurf an Friedrich Pollock, ohne Ort, ohne Datum, 1 Blatt; Pollock, Friedrich: 3 Briefe an Max Horkheimer, ohne Ort, 1943, 3 Blatt; Sherman, Charles B.: 1 Brief mit Unterschrift an Friedrich Pollock, New York, 23.12.1943; 3 Briefe von Friedrich Pollock, New York, 1943-1944, 5 Blatt;

Na 1 Nachlass Max Horkheimer, 695 - "The Collapse of German Democracy and the Expansion of National Socialism", "Cultural Aspects of National Socialism" u.a. (p. IX 169.1a - IX 170.1-4)

"The Collapse of German Democracy and the Expansion of National Socialism" (1940):; 1. Darstellung des Forschungsprojekts (15.9.1940), b. Typoskript mit handschriftlichen Korrekturen, 78 Blatt; 2. "Research work on recent trends in the history of ideas (parts of the Research project on the Collapse of German Democracy would be included)". Als Memorandum zur Eröffnung zur Eröffnung einer Zweigstelle des Instituts in Los Angeles (12.12.1940): a) Typoskript, 2 Blatt, b) Teilstück, Typoskript mit handschriftlichen Korrekturen, 1 Blatt, c) Teilstück, Typoskript mit handschriftlichen Korrekturen, 1 Blatt, d) Teilstück, Typoskript, 1 Blatt, e) Teilstück, Typoskript, 1 Blatt, f) Entwurf, Typoskript mit handschriftlichen Korrekturen und Manuskript, 3 Blatt; 3. University of California, Los Angeles: 2 Briefe (Abschrift) von Max Horkheimer, o.O., 1940, 2 Briefe (Abschrift) an Max Horkheimer, 1940, 2 Blatt; A.R.L. Gurland: "Survey of Structural Changes in the German Economy, 1933 to 1939. Technological Bases and Organizational Forms of the National Socialist Economic System". Typoskript mit handschriftlichen Korrekturen unter anderem von Theodor W. Adorno, 48 Blatt (formal nicht identisch mit "Technological Trends and Economic Structure under National Socialism", Studies in Philosophy and Social Science, Bd. IX, 1941, S. 226ff.); "Cultural Aspects of National Socialism. A Research Project" (1941):; 1. Institute of Social Research: Mitteilung über das Forschungsprojekt und das 'Supplementary Statement', Typoskript, englisch, 4 Blatt; 2. Supplementary Statement to the Research Project, a) Typoskript, 14.4.1941, 63 Blatt, b) Typoskript, 12.4.1941, mit handschriftlichen Korrekturen, 35 Blatt; 3. "Cultural Aspects of National Socialism. A Research Project" (24.2.1941), a) als Typoskript vervielfältigt, 54 Blatt, b) Typoskript mit handschriftlichen Korrekturen, 34 Blatt, c) Fassung Januar 1941, Typoskript mit handschriftlichen Korrekturen, 40 Blatt; 4. Inhaltsverzeichnisse, mit handschriftlichen Korrekturen, 3 Blatt;

Na 1 Nachlass Max Horkheimer, 707 - "German Refugees from Eastern Zone" (p. IX 183.1-2 - IX 184.2-18)

"German Refugees from the Eastern Zone" 1952; 1. "Outline of a Pilot Study of German Refugees from the Eastern Zone Who are presently in Berlin" a) Typoskript, 4 Blatt; b) Typoskript, 3 Blatt; 2. "Budget for a Pilot Study of German Refugees from the Eastern Zone in Berlin" a) 2 Blatt; b) 1 Blatt; c) 1 Blatt; d) 1 Blatt; "Universität und Gesellschaft" 1952-1956; 1. "Universität und Gesellschaft" Teil III: Expertenbefragung. Forschungsbericht, 1953; als Typoskript vervielfältigt und gebunden, 77 Blatt; 2.-7. Allgemeine Darstellung der Untersuchungen; 2. "Einige wichtige Ergebnisse der Universitätsstudie", 1956. Als Typoskript vervielfältigt, 5 Blatt; 3. "Vorläufige Gliederung für den Bericht der Hochschul-Untersuchung" 2 Blatt; 4. "The German University of Today. Progress Report on a Research Project" 02.11.1955 a) Typoskirpt, 12 Blatt; b) Typoskript mit handschriftlichen Korrekturen, 12 Blatt; 5. "The German University of Today. A Progress Report on a Research Project" a) Typoskript, 7 Blatt; b) Typoskript mit handschriftlichen Korrekturen, 8 Blatt; c) Typoskirpt mit handschriftlichen Korrekturen, 12 Blatt; 6. "Funktion und Wirklichkeit der Universität heute. Zwischenbericht über drei Studien des Instituts für Sozialforschung an der Johann Wolfgang Goethe- Universität". Typoskript, 25 Blatt; 7. "Pläne einer Untersuchung über die Vorstellung von der Finktion der heutigen deutschen Universität bei bestimmten Personenkreisen" a) Typoskirpt, 11 Blatt; b) Typoskript, 11 Blatt; 8.-10. Studentenbefragung; 8. Fagebogen zur Umfrage "Warum studieren Studenten?", als Typoskript vervielfältigt, 19 Blatt; 9. "The Economic Situation of Students at the Johann Wolfgang Goethe- University in Frankfurt am Main" Resultate der Umfrage vom Winter 1952/43; Januar 1956; a) Typoskript, 43 Blatt; b) 43 Blatt; 10. "Students and Parentl Influence. Results of a Survey" a) Typoskript, 25 Blatt; b) Typoskript mit handschriftlichen Korrekturen von Frederick Pollock, 25 Blatt; 11.-14. Aktennotizen; 11. "Bericht über die Verhandlungen zwischen Herrn Professor Baumgarten, Tenbruck und Habermas am 12.12.1956 im Institut für vergleichende Sozialwissenschaften in Stuttgart. Betreff: Professorenstudie" 13.13.1956 vermutlich 13.03.1956. Typoskript, 2 Blatt; 12. Gembardt, Ulrich: Aktennotiz zur Hochschuluntersuchung. 23.05.1955, Typoskript, 3 Blatt; 13. Gembardt, Ulrich: Bemerkungen zur Aktennotiz vom 23.05.1955, Typoskript, 2 Blatt; 14. "Aktennotiz über die Hochschul-Forschungsprojekte des Göttinger Soziologischen Seminars und des Frankfurter Institut für Sozialforschung, die deim Hauptausschuß der Deutschen Forschungsgemeinschaft am 1. August 1953 zur Finanzierung vorgelegt werden" 20.07.1953. Typoskript, 2 Blatt; 15.-18. Briefe; 15. Löwenthal, Leo: 1 Brief mit Unterschrift an MAx Horkheimer, New York, 20.01.1955, 3 Blatt; 16. Horkheimer, Max [?]: 1 Brief an Chauncy D. Harris, ohne Ort, Januar 1955; a) Typoskirpt, 1 Blatt; b) Typoskirpt mit handschriftlichen Korrekturen, 1 Blatt; c) Typoskirpt mit handschriftlichen Korrekturen, 1 Blatt; d) Typoskirpt, 1 Blatt; 17. Horkheimer, Max: Drei gleichlautende Briefe an die Rektoren der Universität Bonn, Heidelberg und Koel, ohne Ort, 15.11.1953; a) Typoskript, 6 Blatt; b) Typoskript mit eigenhändigen KOrrekturen, 3 Blatt; 18. Plessner, Helmuth: 1 Brief mit Unterschrift mit Beilage an Max Horkheimer, Göttingen 02.07.1953, 4 Blatt;

Investigation of Quaternary diatoms in sediment core CRP-1 from the Ross Sea, Antarctica

In the first season of drilling, the Cape Roberts Project (CRP) recovered one drillcore (CRP-l) from Roberts Ridge in western McMurdo Sound, Ross Sea, Antarctica Diatom biostratigraphy places the upper six lithostratigraphic units (Units 1.1, 2.1, 2.2, 2.3, 3.1, and 4.1) of CRP-l (0.0 to 43.15 mbsf) within the Quaternary. Both non-marine and marine Quaternary diatoms occur in variable abundance in the Quaternary interval of CRP- 1 Biostratigraphic data resolve two Quaternary time slices or events within CRP-1. Marine diatom assemblages in Units 4.1 and 3.1 represent sedimentation within the diatom Actinocyclus ingens Zone (1.35 to 0.66 Ma). Further refinement of the age of Unit 3.l places deposition in the interval 1.15 to 0.75 Ma based on the common occurrence of Thalassiosira elliptipora and correlation to the Southern Ocean acme of this taxon The absence of ActiActinocyclus ingens and the presence ot Thalassiosira antarctica in Unit 2.2 require a younger zonal assignment for this interval, within the diatom Thalassiosira lentiginosa Zone (0.66 to 0.0 Ma). A new diatom species. Rouxia leventerae, is described from marine assemblages of Units 2.2, 2.3, 3.1, and 4.l. Lithostratigraphic Unit 3.1 (33.82 to 31.89 mbsf) is a bryozoan-dominated skeletal-carbonate facies. Low abundance of Fragilariopsis curta and Fragilariopsis cylindrus within this unit combined with the relatively high abundance of species associated with open water indicates deposition in waters that remained ice free for much or all of the year Diatom assemblages suggest carbonate deposition in Unit 3.1 is linked to a significant early Pleistocene event in McMurdo Sound, when elevated surface-water temperatures inhibited the formation of sea ice.

FDG-PET Intra-tratamiento como valor pronóstico en el tratamiento del linfoma Hodgkin

Introducción: La utilización de regímenes de tratamiento más individualizados requiere de mejores sistemas de estratificación temprana en Linfoma Hodgkin (LH). El estudio Tomografía por Emisión de Positrones utilizando 2-[18F] fluoro-2-deoxi-Dglucosa (FDG-PET) intra-tratamiento podría jugar un rol muy importante en esta evaluación. Objetivo: Determinar el valor pronóstico del FDG-PET intra-tratamiento en pacientes con LH para predecir sobrevida libre de progresión y sobrevida global. Material y método: El estudio fue llevado a cabo en el Servicio de Hematología del Hospital Central de Mendoza incluyendo pacientes con diagnóstico de LH confirmados por histología. De acuerdo al estadio y sitio de presentación, los pacientes recibieron quimioterapia sola o la combinación de radioterapia y quimioterapia, con el uso del esquema ABVD (adriamicina, bleomicina, vinblastina y dacarbazina) como protocolo estándar. Los estudios FDG-PET fueron practicados como parte de la evaluación intra-tratamiento y a la finalización. Resultados: En total fueron evaluados 8 pacientes, Sexo: F/M: 4/4, Edad: 18-58 años (Mediana: 29 años), Estadios: IIB:1, IIIA:2, IIIB:1, IVA:1, IVB:3, regiones nodales: 2-10 (Mediana:4), compromiso extranodal: 4/8, síntomas B: 5/8, enfermedad bulky 2/8 . Subtipos: Escleronodular: 6/8, Celularidad mixta: 1/8, Depleción linfocítica: 1/8. IPS: 1: 3/8 2: 3/8 3: 1/8 4: 0/8 ≥ 5: 1/8. Tratamientos: ABVD x 6: 6/8, ABVD x 6 + Radioterapia: 2/8. PET intermedio: 8/8 negativos (6/8 PET 3, 2/8 PET 2). PET final: 7/8 PET negativo, 1/8 PET positivo. Recaída: 1/8 (10° mes). Seguimiento: 11-37 meses (mediana de 24 meses). Discusión y Conclusiones: Al momento actual el FDG-PET intra-tratamiento demostró tener un importante valor predictivo negativo dado que todos los pacientes, menos uno, se encuentran en remisión completa sin progresión de enfermedad. Resta aún determinar el rol que esta herramienta pueda tener en el futuro en la terapia adaptada al riesgo de pacientes con LH.

Analysis of spatial microbial properties from experimental plots of the Jena experiment (September 2010)

The study was carried out on the main plots (Main Experiment) of a large grassland biodiversity experiment, the Jena Experiment. In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. This data set consists of standard deviation (SD), mean and stability (stab) of soil microbial basal respiration (µl O2/h/g dry soil) and microbial biomass carbon (µg C/g dry soil). Data were derived by taking soil samples and measuring basal and substrate-induced microbial respiration with an oxygen-consumption apparatus. Samples for calculating the spatial stability of soil microbial properties were taken on the 20th of September in 2010. Oxygen consumption of soil microorganisms in fresh soil equivalent to 3.5 g dry weight was measured at 22°C over a period of 24 h. Basal respiration (µlO2/g dry soil/h) was calculated as mean of the oxygen consumption rates of hours 14 to 24 after the start of measurements. Substrate- induced respiration was determined by adding D-glucose to saturate catabolic enzymes of microorganisms according to preliminary studies (4 mg g-1 dry soil solved in 400 µl deionized water). Maximum initial respiratory response (µl O2/g dry soil/ h) was calculated as mean of the lowest three oxygen consumption values within the first 10 h after glucose addition. Microbial biomass carbon (µg C/g dry soil) was calculated as 38 × Maximum initial respiratory response according to prelimiray studies.

Analysis of temporal microbial properties from experimental plots of the Jena experiment (2003-2014)

The study was carried out on the main plots (Main Experiment) of a large grassland biodiversity experiment, the Jena Experiment. In the main experiment, 82 grassland plots of 20 x 20 m were established from a pool of 60 species belonging to four functional groups (grasses, legumes, tall and small herbs). In May 2002, varying numbers of plant species from this species pool were sown into the plots to create a gradient of plant species richness (1, 2, 4, 8, 16 and 60 species) and functional richness (1, 2, 3, 4 functional groups). Plots were maintained by bi-annual weeding and mowing. This data set consists of standard deviation (SD), mean and stability (stab) of soil microbial basal respiration (µl O2/h/g dry soil) and microbial biomass carbon (µg C/g dry soil). Data were derived by taking soil samples and measuring basal and substrate-induced microbial respiration with an oxygen-consumption apparatus. Samples for calculating the temporal stability were taken every year in May/June from 2003 to 2014, except in 2005. Oxygen consumption of soil microorganisms in fresh soil equivalent to 3.5 g dry weight was measured at 22°C over a period of 24 h. Basal respiration (µlO2/g dry soil/h) was calculated as mean of the oxygen consumption rates of hours 14 to 24 after the start of measurements. Substrate- induced respiration was determined by adding D-glucose to saturate catabolic enzymes of microorganisms according to preliminary studies (4 mg g-1 dry soil solved in 400 µl deionized water). Maximum initial respiratory response (µl O2/g dry soil/h) was calculated as mean of the lowest three oxygen consumption values within the first 10 h after glucose addition. Microbial biomass carbon (µg C/g dry soil) was calculated as 38 × Maximum initial respiratory response according to prelimiray studies.

Elucidation of a PTS–Carbohydrate Chemotactic Signal Pathway in Escherichia coli Using a Time-resolved Behavioral Assay

Chemotaxis of Escherichia coli toward phosphotransferase systems (PTSs)–carbohydrates requires phosphoenolpyruvate-dependent PTSs as well as the chemotaxis response regulator CheY and its kinase, CheA. Responses initiated by flash photorelease of a PTS substrates d-glucose and its nonmetabolizable analog methyl α-d-glucopyranoside were measured with 33-ms time resolution using computer-assisted motion analysis. This, together with chemotactic mutants, has allowed us to map out and characterize the PTS chemotactic signal pathway. The responses were absent in mutants lacking the general PTS enzymes EI or HPr, elevated in PTS transport mutants, retarded in mutants lacking CheZ, a catalyst of CheY autodephosphorylation, and severely reduced in mutants with impaired methyl-accepting chemotaxis protein (MCP) signaling activity. Response kinetics were comparable to those triggered by MCP attractant ligands over most of the response range, the most rapid being 11.7 ± 3.1 s−1. The response threshold was <10 nM for glucose. Responses to methyl α-d-glucopyranoside had a higher threshold, commensurate with a lower PTS affinity, but were otherwise kinetically indistinguishable. These facts provide evidence for a single pathway in which the PTS chemotactic signal is relayed rapidly to MCP–CheW–CheA signaling complexes that effect subsequent amplification and slower CheY dephosphorylation. The high sensitivity indicates that this signal is generated by transport-induced dephosphorylation of the PTS rather than phosphoenolpyruvate consumption.

Blood glutathione synthesis rates in healthy adults receiving a sulfur amino acid-free diet

The availability of cysteine is thought to be the rate limiting factor for synthesis of the tripeptide glutathione (GSH), based on studies in rodents. GSH status is compromised in various disease states and by certain medications leading to increased morbidity and poor survival. To determine the possible importance of dietary cyst(e)ine availability for whole blood glutathione synthesis in humans, we developed a convenient mass spectrometric method for measurement of the isotopic enrichment of intact GSH and then applied it in a controlled metabolic study. Seven healthy male subjects received during two separate 10-day periods an l-amino acid based diet supplying an adequate amino acid intake or a sulfur amino acid (SAA) (methionine and cysteine) free mixture (SAA-free). On day 10, l-[1-13C]cysteine was given as a primed, constant i.v. infusion (3μmol⋅kg−1⋅h−1) for 6 h, and incorporation of label into whole blood GSH determined by GC/MS selected ion monitoring. The fractional synthesis rate (mean ± SD; day-1) of whole blood GSH was 0.65 ± 0.13 for the adequate diet and 0.49 ± 0.13 for the SAA-free diet (P < 0.01). Whole blood GSH was 1,142 ± 243 and 1,216 ± 162 μM for the adequate and SAA-free periods (P > 0.05), and the absolute rate of GSH synthesis was 747 ± 216 and 579 ± 135 μmol⋅liter−1⋅day−1, respectively (P < 0.05). Thus, a restricted dietary supply of SAA slows the rate of whole blood GSH synthesis and diminishes turnover, with maintenance of the GSH concentration in healthy subjects.

Further Studies of the Role of Cyclic β-Glucans in Symbiosis. An ndvC Mutant of Bradyrhizobium japonicum Synthesizes Cyclodecakis-(1→3)-β-Glucosyl1

The cyclic β-(1→3),β-(1→6)-d-glucan synthesis locus of Bradyrhizobium japonicum is composed of at least two genes, ndvB and ndvC. Mutation in either gene affects glucan synthesis, as well as the ability of the bacterium to establish a successful symbiotic interaction with the legume host soybean (Glycine max). B. japonicum strain AB-14 (ndvB::Tn5) does not synthesize β-glucans, and strain AB-1 (ndvC::Tn5) synthesizes a cyclic β-glucan lacking β-(1→6)-glycosidic bonds. We determined that the structure of the glucan synthesized by strain AB-1 is cyclodecakis-(1→3)-β-d-glucosyl, a cyclic β-(1→3)-linked decasaccharide in which one of the residues is substituted in the 6 position with β-laminaribiose. Cyclodecakis-(1→3)-β-d-glucosyl did not suppress the fungal β-glucan-induced plant defense response in soybean cotyledons and had much lower affinity for the putative membrane receptor protein than cyclic β-(1→3),β-(1→6)-glucans produced by wild-type B. japonicum. This is consistent with the hypothesis presented previously that the wild-type cyclic β-glucans may function as suppressors of a host defense response.

Contribution of Malic Enzyme, Pyruvate Kinase, Phosphoenolpyruvate Carboxylase, and the Krebs Cycle to Respiration and Biosynthesis and to Intracellular pH Regulation during Hypoxia in Maize Root Tips Observed by Nuclear Magnetic Resonance Imaging and Gas Chromatography-Mass Spectrometry1

In vivo pyruvate synthesis by malic enzyme (ME) and pyruvate kinase and in vivo malate synthesis by phosphoenolpyruvate carboxylase and the Krebs cycle were measured by 13C incorporation from [1-13C]glucose into glucose-6-phosphate, alanine, glutamate, aspartate, and malate. These metabolites were isolated from maize (Zea mays L.) root tips under aerobic and hypoxic conditions. 13C-Nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry were used to discern the positional isotopic distribution within each metabolite. This information was applied to a simple precursor-product model that enabled calculation of specific metabolic fluxes. In respiring root tips, ME was found to contribute only approximately 3% of the pyruvate synthesized, whereas pyruvate kinase contributed the balance. The activity of ME increased greater than 6-fold early in hypoxia, and then declined coincident with depletion of cytosolic malate and aspartate. We found that in respiring root tips, anaplerotic phosphoenolpyruvate carboxylase activity was high relative to ME, and therefore did not limit synthesis of pyruvate by ME. The significance of in vivo pyruvate synthesis by ME is discussed with respect to malate and pyruvate utilization by isolated mitochondria and intracellular pH regulation under hypoxia.