Metabolism at several levels of organization in the fruit of the avocado,Persea americana,Mill.

Studies conducted over a number of years offer opportunities for comparisons of oxidative and phosphorylative activities in fruits at the cellular and subcellular levels.In tissue slices placed in moist air as well as in the intact fruit the respiratory rise takes place at the expense of endogenous substrates, while the pattern of respiration in mitochondrial systems is determined by the acid of the Krebs cycle supplied. The change in oxidation rates between the preclimacteric and the climacteric stage is slight in the case of succinate but more striking with malate and with the keto acids. Thiaminepyrophosphate (TPP) plays a key role in determining the rates of oxidation in particles from unripe fruit and in preventing state 3 and state 4 inhibitions in mitochondria from climacteric peak avocados. Oxalacetate was implicated as the inhibitor and the mechanism of the inhibition studied.Inhibitors were used to learn about the electron transport chain in the avocado. When amytal, cyanide, azide and DNP were applied to tissue slices a remarkable stimulation of oxygen uptake was noted, especially in the preclimacteric stage. A return to control rates was achieved by a combination of inhibitors. The response to single inhibitors was explained by mobilization of limiting cofactors to fewer active sites. Coexistence of phosphorylative and non-phosphorylative pathways was also implicated. The use of inhibitors on mitochondrial preparations presented a strikingly different picture by blocking the oxidase and the carriers. In order to resolve the contradiction more knowledge is needed about the relative contributions of the soluble and the particulate systems at the cellular level.The action of 2,4-dinitrophenol (DNP) served as a basis for theories of ripening. When phosphate metabolism was examined in tissue slices the effects of DNP on the incorporation of³²P into esters did not differ materially between the two stages. However the rate of esterification into all esters examined increased greatly with ripening. Similarly, the ADP/O ratios in mitochondrial system increased indicating improvement on phosphorylative activities as the climacteric progresses.The inescapable conclusion is that the machinery for energy generation is in full operation throughout the climacteric. The suggestion was made that for metabolic impairments leading to senescence the search should be directed to protein and nucleic acid metabolism.

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Zusammenfassung Studien über eine Reihe von Jahren geben Gelegenheit zu Vergleichen über die oxidativen und phosphorylativen Aktivitäten in Früchten auf zellularem und subzellularem Niveau.Sowohl in Gewebeschnitten — in feuchter Luft gehalten — als auch in der intakten Frucht wird der Anstieg der Atmung von einer Abgabe endogener Substanzen begleitet, während das Muster der Atmung in den mitochondrischen Systemen bestimmt wird durch die Säure, die vom Krebs-Zyklus zugeführt wird. Die Änderung in den Oxidationsraten während des Vor- und Nachreifestadiums ist gering im Falle von Succinat, aber auffallend grösser bei Malat und den Ketosäuren. Thiaminpyrophosphat (TPP) spielt eine Schlüsselrolle in der Bestimmung der Oxidationsrate in Teilchen unreifer Früchte und bei Verhinderung der Hemmung der Stufen 3 und 4 in Mitochondrien von Avocados, die auf dem Höhepunkt der Nachreife standen. Oxalacetat war als Inhibitor beteiligt und der Mechanismus der Hemmung wurde studiert.Inhibitoren dienten dazu, die Elektronen-Transportkette in der Avocado kennenzulernen. Wurden Amytal, Cyanid, Azid und DNP Gewebeschnitten appliziert, ergab sich eine bemerkenswerte Stimulation der Sauerstoff-Aufnahme insbesondere im Vorreife-Stadium. Ein Abfall auf Kontroll-Werte ergab sich durch eine Kombination von Inhibitoren. Das Ansprechen auf einzelne Inhibitoren wurde mit einer Mobilisierung limitierender Kofaktoren gegenüber weniger aktiven Stellen erklärt. Die Koexistenz phosphorylativer und nicht-phosphorylativer Wege wurde mithin gefolgert. Der Gebrauch von Inhibitoren auf mitochondrischen Präparaten gibt ein auffallend verschiedenes Bild durch Blockieren der Oxidase und des Trägers. Um den Widerspruch zu lösen, ist mehr Kenntnis über die relativen Beiträge des löslichen und der Teilchen-Systeme auf dem zellularen Niveau notwendig.Die Tätigkeit von 2,4-Dinitrophenol (DNP) diente als Basis für die Theorie der Reifung. Wurde der Phosphat-Metabolismus in Gewebeschnitten untersucht, unterschieden sich die Effekte der DNP auf den Einbau von³²P in Ester nicht wesentlich zwischen den beiden Stufen. Nichtsdestoweniger stieg die Veresterungs-Rate in allen geprüften Estern stark mit der Reifung an. Ähnlich nahmen auch die ADP/O-Verhältnisse im mitochondrischen System zu und gaben eine Verbesserung in den phosphorylativen Aktivitäten wie den Nachreife-Fortschritt an.Die unausweichliche Schlussfolgerung ist, dass die Maschinerie für die Energie-Erzeugung während der Nachreife in voller Tätigkeit ist. Die Vorstellung wurde entwickelt, dass für die Beeinträchtigung des Stoffwechsels, die zum Altern führt, die Suche in Richtung Protein- und Nucleinsäuren-Umwandlung gelenkt werden sollte.

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Resume Les travaux menés depuis un certain nombre d'années permettent de comparer les activités d'oxydation et de phosphorylation du fruit aux niveaux cellulaire et subcellulaire.Sur des tranches de tissus placées à l'air humide, aussi bien que dans le fruit intact, l'accroissement de l'activité respiratoire a lieu au détriment de substrats endogènes, tandis que, dans les mitochondries isolées, le type de respiration est déterminé par le type d'acide du cycle de Krebs fourni. La variation de l'intensité des oxydations, lorsque le fruit passe de l'étape préclimactérique à l'étape climactérique, est faible dans le cas où l'acide fourni est le succinate, mais plus forte dans le cas du malate et des cétoacides. La thiaminepyrophosphate (TPP) joue un rôle essentiel dans le déterminisme des vitesses d'oxydation par les particules préparées à partir de fruits non mûrs; elle empêche l'action d'un inhibiteur aux stades 3 et 4 dans le cas des mitochondries préparées à partir des fruits d'avocats se trouvant en pleine crise climactérique. L'oxaloacétate semble être cet inhibiteur; le mécanisme de l'inhibition est étudié.Des inhibiteurs ont été utilisés pour étudier la chaîne de transport d'électrons chez l'avocat. Lorsqu'on applique à des tranches de tissus de l'amytal, du cyanure, de l'azide ou du DNP, une stimulation importante de la consommation d'oxygène est observée surtout dans la période préclimactérique. Un retour aux vitesses témoins a été obtenu en utilisant une combinaison d'inhibiteurs. La réponse à un seul inhibiteur est expliquée par la mobilisation de cofacteurs limitants vers un nombre réduit de sites actifs. La coexistence de voies phosphorylantes et non-phosphorylantes est aussi impliquée. Lorsqu'on applique les inhibiteurs à des préparations de mitochondries, des résultats fort différents sont obtenus: dans ce cas, les inhibiteurs bloquent les oxydases et les transporteurs. Pour résoudre cette contradiction, des études complémentaires sont nécessaires sur les contributions relatives des systèmes solubles et particulaires au niveau cellulaire.L'action du 2,4-dinitrophenol (DNP) a servi de base pour des théories de la maturation. Lorsqu'on examine le métabolisme du phosphate dans les tranches de tissus, on observe que les effets du DNP sur l'incorporation du³²P dans les esters ne different pas entre les 2 étapes de la maturation. Cependant, la vitesse d'incorporation dans tous les esters examinés augmente fortement avec la maturation. De même, les rapports ADP/O dans le système mitochondrial augmente, montrant ainsi une augmentation des activités de phosphorylation au fur et à mesure que progresse le climactérique.La conclusion qu'on est obligé de tirer de ces faits, est que le système de production d'énergie fonctionne à plein rendement tout au long du climactérique. L'auteur suggère que la cause des déficiences métaboliques conduisant à la senescence doit être recherchée du côté du métabolisme des protéines et des acides nucléiques.

     

Identification of spectral regions for the quantification of red wine tannins with fourier transform mid-infrared spectroscopy

Accomplishment of fast tannin measurements is receiving increased interest as tannins are important for the mouthfeel and color properties of red wines. Fourier transform mid-infrared spectroscopy allows fast measurement of different wine components, but quantification of tannins is difficult due to interferences from spectral responses of other wine components. Four different variable selection tools were investigated for the identification of the most important spectral regions which would allow quantification of tannins from the spectra using partial least-squares regression. The study included the development of a new variable selection tool, iterative backward elimination of changeable size intervals PLS. The spectral regions identified by the different variable selection methods were not identical, but all included two regions (1485-1425 and 1060-995 cm(-1)), which therefore were concluded to be particularly important for tannin quantification. The spectral regions identified from the variable selection methods were used to develop calibration models. All four variable selection methods identified regions that allowed an improved quantitative prediction of tannins (RMSEP = 69-79 mg of CE/L; r = 0.93-0.94) as compared to a calibration model developed using all variables (RMSEP = 115 mg of CE/L; r = 0.87). Only minor differences in the performance of the variable selection methods were observed.     

Fluorescence-based method, exploiting lipofuscin, for real-time detection of central nervous system tissues on bovine carcasses

The removal of central nervous system (CNS) tissues as part of bovine spongiform encephalopathy (BSE) risk material is one of the highest priority tasks to avoid contamination of the human food chain with BSE. No currently available method enables the real-time detection of possible CNS tissue contamination on carcasses during slaughter. The fluorescent pigment lipofuscin is a heterogeneous, high-molecular weight material that has been shown to be enriched in high concentrations in neuronal tissues. In this study, lipofuscin fluorescence was investigated as a marker for real-time detection of CNS contamination. Front-faced fluorescence spectra of brain and spinal cord samples from 11 cattle gave identical, reproducible fluorescence signal patterns with high intensities. The specificity of these spectra was assessed by investigating 13 different non-CNS tissues enabling the differentiation of brain and spinal cord by signal intensity and structure of the spectra, respectively. Small quantities of bovine spinal cord were reliably detected in the presence of raw bovine skeletal muscle, fat, and vertebrae. The presented data are a fundamental basis for the development of a prototype device allowing real-time monitoring of CNS tissue contamination on bovine carcasses and meat cuts.     

Rot holes create key microhabitats for epiphytic lichens and bryophytes on beech (Fagus sylvatica)

Identification of trees with key microhabitats as well as knowledge of their ecological formation is important for the conservation of epiphytic bryophytes and lichens on beech. Based on the hypothesis that certain types of stem damage are crucial for the occurrence of epiphytes of conservation concern, we surveyed 145 beech trees (57-280 years) for different types of stem damage and analysed their relationship to other tree characteristics, epiphyte species and wood-inhabiting fungi in a forest landscape on acid soils.Three main types of stem damage were identified; canker, rot hole and surface rot. The incidence of rot holes was highest on trees with a low growth rate during the last 50 years, but was unrelated to tree size or age per se. Bark pH was significantly higher below than above rot holes, whereas no such relationship was found for cankers. Wood mould from rot holes had a very high pH, explaining the higher bark pH below this type of damage. The number of epiphyte species of conservation concern was strongly positively related to rot holes and high bark pH. Cankers had a weaker, yet significant positive effect. The fungus Psathyrella cernua was associated with the rot holes and is suggested to be a key species involved in creating this microhabitat.We conclude that slow-growing trees with rot holes are important for the conservation of epiphytes and should be selected as retention trees in managed forests. The study also highlights a potential for habitat restoration by inducing artificial damage and inoculation of decay fungi in beech trees.     

The role of pair dispersion in turbulent flow

Mixing and transport in turbulent flows-which have strong local concentration fluctuations-are essential in many natural and industrial systems including reactions in chemical mixers, combustion in engines and burners, droplet formation in warm clouds, and biological odor detection and chemotaxis. Local concentration fluctuations, in turn, are intimately tied to the problem of the separation of pairs of fluid elements. We have measured this separation rate in an intensely turbulent laboratory flow and have found, in quantitative agreement with the seminal predictions of Batchelor, that the initial separation of the pair plays an important role in the subsequent spreading of the fluid elements. These results have surprising consequences for the decay of concentration fluctuations and have applications to biological and chemical systems.     

Exploring the potential of providing and feeding pikeperch larvae (Sander lucioperca L.) with euryhaline copepod nauplii: A zoo technical trial

Egg hatching and nauplii success from three euryhaline calanoid copepod species at low salinities suggest a promising alternative initial live feed for pikeperch (Sander lucioperca L.) to the conventional live feed. Acartia bifilosa and Eurytemora affinis are viable candidates with egg hatching down to zero salinity, and Acartia tonsa nauplii survive up to 2 h at zero salinity after transfer from low-salinity seawater. When offered A. tonsa and Artemia, pikeperch larvae equally consumed both prey types. We suggest that euryhaline copepods can be a supplement to or even a substitute for the normal live feed currently used as larval feed for pikeperch.     

Effect of choline chloride premedication on xylazine-induced hypoxaemia in sheep

Objective

To determine the anti-inflammatory efficacy of choline in vivo and in vitro and to investigate the anti-inflammatory mechanisms of choline.