Transfer of reducing equivalents into mitochondria by the interconversions of proline and Δ1-pyrroline-5-carboxylate

Direct evidence is presented for a proline cycle using a cell-free experimental system which sequentially transfers ³H from [1-³H]glucose to NADP⁺ to Δ¹-pyrroline-5-carboxylate and yields [³H]proline. The formation of [³H]proline depends on the presence of NADP, Δ¹-pyrroline-5-carboxylate, and the enzymes glucose-6-phosphate dehydrogenase and Δ¹-pyrroline-5-carboxylate reductase. The production of [³H]proline from unlabeled proline in the presence of mitochondria provides direct evidence for one complete turn of a proline cycle which transfers reducing equivalents produced by glucose oxidation in the pentose pathway into mitochondria. In this cycle, proline is oxidized to Δ¹-pyrroline-5-carboxylate by mitochondrial proline oxidase. Δ¹-pyrroline-5-carboxylate is released from mitochondria and is recycled back to proline by Δ¹-pyrroline-5-carboxylate reductase with concomitant oxidation of NADPH. At the maximal rate observed, 60% of Δ¹-pyrroline-5-carboxylate produced is recycled back to proline. This cycle provides a mechanism for transferring reducing equivalents from NADPH into mitochondria and is linked to glucose oxidation in the pentose pathway by NADPH turnover.     

Vererbungsstudien

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Hermaphroditismus im Tierreich vom genetischen Standpunkt

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The molecular mechanism for the tetrameric association of glycogen phosphorylase promoted by protein phosphorylation.

The allosteric transition of glycogen phosphorylase promoted by protein phosphorylation is accompanied by the association of a pair of functional dimers to form a tetramer. The conformational changes within the dimer that lead to the creation of a protein recognition surface have been analyzed from a comparison of the crystal structures of T-state dimeric phosphorylase b and R-state tetrameric phosphorylase a. Regions of the structure that participate in the tetramer interface are situated within structural subdomains. These include the glycogen storage subdomain, the C-terminal subdomain and the tower helix. The subdomains undergo concerted conformational transitions on conversion from the T to the R state (overall r.m.s. shifts between 1 and 1.7 A) and, together with the quaternary conformational change within the functional dimer, create the tetramer interface. The glycogen storage subdomain and the C-terminal subdomain are distinct from those regions that contribute to the dimer interface, but shifts in the subdomains are correlated with the allosteric transitions that are mediated by the dimer interface. The structural properties of the tetramer interface are atypical of an oligomeric protein interface and are more similar to protein recognition surfaces observed in protease inhibitors and antibody-protein antigen complexes. There is a preponderance of polar and charged residues at the tetramer interface and a high number of H-bonds per surface area (one H-bond per 130 A2). In addition, the surface area made inaccessible at the interface is relatively small (1,142 A2 per subunit on dimer to tetramer association compared with 2,217 A2 per subunit on monomer-to-dimer association).     

Experiences with reducing point sources of phosphorus to lakes

Experiences over the last 25 years have demonstrated that eutrophication can be reversed, and that phosphorus is most often the nutrient through which control should be exerted.The reduction of the external load of phosphorus to a eutrophic lake is a necessary condition for lake restoration, but may not in itself be sufficient. Three main response patterns to a reduction in external load are identified. These include reduction in lake phosphorus that leads to sufficient reduction in chlorophyll to change the trophic category, to make the lakes less eutrophic or have small or no effect. The factors that determine the actual response are discussed.It is clear that interventions to restore eutrophic lakes have not always given the results expected. Limnological studies are necessary for well-grounded predictions.     

Survival ofPseudomonas syringae pv.lachrymans with cucumber roots

Summary Survival ofPseudomonas syringae pv.lachrymans with seedling cucumber roots, root washings, rhizosphere soil, and nonrhizosphere soil was determined 7–8 days after the soil surface was watered with a cell suspension of the bacterium. Plants were in pots in the green-house and soil was not sterilized. Survival was best with roots and root washings, next best in rhizosphere soil, and poor in nonrhizosphere soil.     

The development of granulation in an upflow floc digester and an upflow anaerobic sludge blanket digester treating cane juice stillage

Summary The use of synthetic polyelectrolytes in the Upflow Floc digester during the treatment of high strength cane juice stillage, resulted in a more rapid accumulation of biomass and promoted granule formation at an earlier stage compared to a control upflow anaerobic sludge blanket digester (UASB). In the Upflow Floc reactor the granules were composed of rod shaped organisms, whereas in the UASB the granules were primarily filamentous. Both types of granules had good settling properties and high activities.     

Coprophagy in larval Culiseta bergrothi (Diptera: Culicidae)

Two experimental groups of Culiseta bergrothi Edw. larvae were kept under laboratory conditions, but in water from the breeding locality. The ‘donors’ were fed on a suspension of charcoal powder and baker's yeast; the ‘receivers’ had access to the faecal pellets of the donors. After 1.5 hours the gut of almost all receivers was more or less filled with charcoal particles. The possible consequences of the added yeast suspension to food choice and feeding behaviour are discussed.     

Lipid composition and food quality of some freshwater phytoplankton for cladoceran zooplankters

The nutritional value of several planktonic algae was testedby means of feeding trials with three cladoceran zooplankters.The algae were monocultures and included two blue-greens, fourgreens and four flagellates with a size range of 5–48µm. The specific growth rates of the zooplankters werechosen as the measure of the nutritional value of the algae.The three cladocerans showed large differences in growth ratein the different algae, but the two cryptomonads were withoutdoubt best suited as food for all. The fatty acid compositionfor the cryptomonads were different from the other algae. Theycontained high percentages of the polyunsaturated fatty acids20:5æ3 (EPA) and 22:6æ3 (DHA), which also are commonin fish. It is suggested that the lipid composition is a probablefactor determining the nutritional quality of the algae.