Viability control and oxygen consumption of isolated hepatocytes from thermally acclimated rainbow trout (Salmo gairdnerii)

Hepatocytes were isolated by collagenase perfusion of the liver from rainbow trout acclimated to 10 and 20 degrees C. The suitability of the stimulation of cellular respiration by succinate as criterion of viability was examined and discussed. Endogenous respiration rates of the hepatocytes were a function of cell size to the power of 0.8. Specific oxygen consumption of the hepatocytes and respiratory control ratios of the mitochondria in situ were independent of acclimation temperature.     

Effects of temperature on glucose release and glycogen metabolism in isolated hepatocytes from rainbow trout (Salmo gairdneri)

Endogenous glucose release and glycogen metabolism were investigated in isolated hepatocytes from rainbow trout acclimated to 10 and 20 degrees C. Thermal acclimation did not significantly affect hepatocyte glycogen contents and the rates of glucose release during substrate-free incubations. In both acclimation groups glucose production and glycogen metabolism exhibited clearly different dependencies on assay temperature. It was concluded, that there are different sources of glucose release in the lower and upper temperature range--gluconeogenesis from endogenous precursors at low temperatures and glycogenolysis at high temperatures. This conclusion was supported by experiments with 3-mercaptopicolinic acid, which stimulated glycogen breakdown especially in the low temperature range.     

The interaction of abscisic acid with growth stimulators in germination of partially after-ripened apple embryos

The effect of abscisic acid (ABA), gibberellin A₄₊₇ and benzyladenine on germination of apple embryos which had been stratified for different periods of time was investigated. The growth stimulators accelerated the germination of non-stratified embryos or those stratified for a short time. After a longer period of stratification, the effect of growth stimulators was visible only when germination of the embryos was artificially inhibited by simultaneous application of synthetic ABA. The sensitivity of stratified apple embryos to the exogenous ABA diminished with the number of hours elapsed between the imbibiting by the embryos of the water or gibberellin and the application of the ABA. This was similar to the change in the sensitivity of apple embryos during stratification due to the increasing concentrations of ABA.     

Influence d'un choc osmotique sur la composition des feuilles de cotonnier en acides amines libres

The effect of water stress on the free amino acids in cotton leaves has been investigated. The water deficit, obtained by lowering of osmotic potential through the use of polyethylene glycol (PEG-600) as the osmotic agent, induces an accumulation of free amino acids.Significant modifications in the composition of this fraction are observed. The major differences from treated and untreated leaves are in the levels of γ-aminobutyric acid, asparagine, proline, and glutamic acid and its amide.     

The influence of leaf traits and deficit irrigation on insect communities in mature green tomato production

1. Drought affects many agriculturally important areas, hampering the cultivation of water intensive crops such as tomatoes.
2. Unlike processing tomatoes, deficit irrigation of fresh market tomatoes is not currently practiced. Deficit irrigation could have negative trade‐offs for yield and pest populations by changing plant nutritional values and the microenvironment.
3. The present study compared crop response and insect populations at two field locations: an on‐farm trial with 0%, 15% and 30% water deficit treatments, and a research station trial with 0%, 10%, 20% and 30% water deficit treatments.
4. At the on‐farm trial, water deficits of 30% affected fruit yield, leaf relative water content (RWC) and leaf δ¹³C, whereas, in the research station trial, water deficits only affected leaf RWC. Treatments did not change the abundance of any insect groups.
5. Sap‐feeding insects such as silverleaf whitefly (Bemisia tabaci) increased with plant traits indicating hydration such as canopy temperature depression (CTD) and RWC. Furthermore, CTD influenced the composition of insect communities.
6. Sap‐feeding insect abundance may vary with traits indicating hydration because of turgor pressure required for feeding, as well as a more suitable microenvironment.

     

The molecular nature of damage by oxygen to freeze-dried Escherichia coli

The damage occurring in freeze-dried bacteria exposed to oxygen is mainly in the bacterial membrane and involves the DNA-initiation complex. This injury occurs in two stages: The primary damage is due to the freeze-drying itself, and is repaired upon reconstitution of bacteria and their subsequent incubation in nutrient broth. The repair process requires protein synthesis. In the next step, the exposure of freezedried bacteria to oxygen, the injury becomes irreversible and the bacteria “die.” The lethal effects of oxygen can be counteracted by either engaging the initiation sites on the membrane (e.g., by colicin E₁), or by arresting the activity of the initiation complex. Such arrest occurs in ts-mutants at nonpermissive temperature, or when appropriate mutants are starved of amino acids or thymine.After freeze drying and storage in vacuo, the reconstituted bacteria grow in filaments and synthetize DNA multifocally; they do not form septa and do not divide. After exposure to oxygen of the freeze-dried bacteria the ability to initiate DNA synthesis is lost.It is assumed therefore that oxygen specifically acts on the initiation complex in the bacterial membrane of the freeze-dried bacteria. When an external DNA synthesis control is provided, e.g., by infection with phage the productivity of the freeze-dried bacteria exposed to oxygen is the same as of the lyophilized controls held in vacuo.     

Asynchrony of erythroblast maturation induced by riboflavin deficiency

Ultrastructural studies indicate that galactoflavin-induced riboflavin deficiency induces asynchrony of rat erythroblast maturation. During the latter stages of maturation erythroblasts retain significantly larger numbers of ribosomes as compared to control cells. Nucleoli are not evident in erythroblasts whose nuclei indicate cells in the latter stages of development. Membrane whorls develop within the mitochondria of plasma cells, eosinophils and neutrophils during the fifth week of riboflavin deficiency. No further evidence of degeneration was noted among additional cell organelles.     

Plant Functional Types Differ in Their Long-term Nutrient Response to eCO2 in an Extensive Grassland

Ecosystems - Increasing atmospheric CO2 enhances plant biomass production and may thereby change nutrient concentrations in plant tissues. The objective of this study was to identify the effect of...