Rapid separation of the plastid,mitochondrial, and cytoplasmic fractions from intact leaf protoplasts of Avena

Purified intact protoplasts were isolated from etiolated and greening leaves of Avena sativa. They were ruptured by forcing them through a 20-m aperture nylon net and immediately thereafter fractionated into a pure pellet of plastids (well above 70% of total plastids), a layer of mitochondria only slightly contaminated by other cellular constituents (about 50% of total mitochondria), and a cytoplasmic supernatant. This was achieved within 60 s by an integrated method of homogenation of protoplasts and centrifugal filtration of the homogenate on a gradient of silicone oils, contained together with the nylon net in 450 l microtubes, and verified by comparing the levels of activity of specific markers within the three fractions obtained. With appropriate modifications to immediately quench metabolic reactions within the fractions, this method allows the determination of metabolite levels within plastids, mitochondria, and the cytoplasmic compartment of intact protoplasts. The applicability of this technique is demonstrated by the determination of ATP in the plastids, mitochondria, and the cytoplasm of protoplasts obtained from etiolated and greening primary leaves of Avena. The levels of ATP, corrected for contamination of the fractions by each other, exhibit a pronounced transient increase during greening, especially within the cytoplasm.Abbreviations BSA bovine serum albumin - Cyt c cytochrome c - EDTA ethylenediamine tetraacetic acid - HEPES N-2-hydroxyethyl-piperazine-N-2-ethane sulphonic acid - MES 2(N-morpholino) ethane sulphonic acid - PGA 3-phosphoglyceric acid - PEP phosphoenol pyruvic acid - RuBP ribulose-1.5-bis-phosphate     

Studies on the size,location and turnover of calcium pools accessible to growing Tetrahymena cells

Tetrahymena pyriformis cells in the logarithmic phase of growth accumulate 2.5–3.75 times as much calcium per unit volume as is present in the growth medium. It appears that most of this calcium is stored in a non-ionic form, with approximately 30% existing in the cilia, near its site of action in effecting ciliary reversal. The exchange of extracellular ⁴⁵Ca²⁺ with the major internal pools is extremely rapid, exhibiting a $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ of less than 0.5 h. Sites located on the cilia are responsible for 35–50% of Ca²⁺ influx, with the remainder entering through other positions on the cell surface.     

Energy metabolism of autotrophically and heterotrophically grown cells of Nitrobacter winogradskyi

The adenine nucleotide pools and the NADH pool were compared in intact Nitrobacter winogradskyi cells grown under different conditions. The NADH pool was highest in nitrite-grown cells (22.0 nmol/mg N), less high in acetategrown cells (15.1 nmol/mg N),and lowest in pyruvate-grown cells (11.9 nmol/mg N).The adenine nucleotide pools and the NADH pool were determined after the transition from anaerobic to aerobic conditions.In both autotrophically and heterotrophically grown cells the ATP pool decreased within the first second after the addition of oxygen and then increased.In cells grown with nitrite or acetate the NADH pool increased the first second after the addition of oxygen then decreased below the initial value. In pyruvate-grown cells the changes in the NADH pool were less obvious.In the presence of rotenone autotrophic cells were able to generate ATP, but the reverse energy-dependent electron transport was inhibited. Consequently, NADH was not synthesized. N,N-dicyclohexylcarbodiimide an inhibitor of ATPase, prevented both ATP and NADH generation.Abbreviations DCCD N,N-dicyclohexylcarbodiimide     

Macrofaunal community types in ponds and small lakes (Overijssel,The Netherlands)

A survey was carried out at 157 sites, situated in pools and small lakes in the province of Overijssel (The Netherlands), to describe the macro-invertebrate community and their environment. A total of 61 environmental viriables was measured at each sampling site. The main aim was to described a regional ecological typology of ponds and small lakes. Multivariate analysis techniques are appropriate in data analysis for typological purposes. Different multivariate analysis techniques (FLEXCLUS, NODES, DCCA, PCA) were used in combination with ecological information on individual taxa to derive and describe site groups in terms of taxon composition and mean environmental conditions. The resulting site groups were termed cenotypes. Nine cenotypes were distinguished among the ponds and small lakes. The main differences between the cenotypes were related to duration of drought, acidity, morphology and nutrient load. In particular, the four cenotypes within the group of stagnant, pH-neutral ponds/lakes showed an overlap in taxon composition. These cenotypes represent a web-shaped continuum dominated by dimensions (relation of width to depth), nutrient load, and bottom composition (especially mesotrophic peat). The most important anthropogenic processes are acidification, eutrophication, and changes in the original hydrology.     

Soil invertebrate and plant responses to mowing and carbofuran application in a North American tallgrass prairie

Relationships between soil invertebrate populations and primary production of a tallgrass prairie were investigated using the insecticide-nematicide carbofuran and a range of mowing intensities to manipulate invertebrate densities and resource quantity and quality. The trophic composition of nematode populations was monitored through each of two growing seasons. Earthworm and macroarthropod densities and primary production were assessed at the end of the second season. Invertebrate densities were generally reduced in carbofuran-treated plots, although individual weights of surviving macroarth-ropod herbivores increased significantly (p<0.05). Carbofuran failed to affect estimates of above- or belowground plant biomass after two years of treatment. Changes in resource quantity and quality resulted in rapid responses by dominant invertebrate consumer populations. A 28% reduction in live root mass and a 24% increase in root detritus following two years of mowing was associated with a 54% decrease in herbivorous nematode densities, a 47% increase in microbivorous nematode densities, and a 41% increase in native earthworm biomass.     

EFFECTS OF ICE ON ASCOPHYLLUM NODOSUM WITHIN THE GREAT BAY ESTUARY SYSTEM OF NEW HAMPSHIRE-MAINE12

The, effects of ice on Ascophyllum nodosum (L.) Le Jolis within the Great Bay Estuary System of New Hampshire-Maine, U.S.A. were assessed during the winter of 1980–81. Approximately 50% of the plants late fall standing crop, or an estimated 136 tonnes dry weight, was removed by ice-rafting. Pieces of Ascophyllum removed averaged 22 cm in length, 15 g in fresh weight and generally represented 2–3 years of growth. Although the winter of 1980–81 wax somewhat extreme, a similar pruning process probably occurs each year contributing to the characteristic bushy habit of attached inner estuarine plants. Ascophyllum fragments rafted in ice and deposited into salt marshes are suggested as a major source of the, ecad scorpioides (Hornemann) Hauck.     

Epilithic periphyton and detritus studies in a subalpine stream

The accumulation of epilithic periphyton in Ward Creek, a permanent stream within the Lake Tahoe basin, California, was measured weekly at three stations from July through September, 1972. Subsamples were analyzed for total carbon and adenosine triposphate content. The mean total carbon content at three stations over the period of investigation was 0.508 ± 0.263 mg carbon cm^–2. Live biomass, as estimated from ATP measurements, averaged 0.121 ± 0.115 mg carbon cm 2. It was estimated that approximately 76% of the organic carbon accumulating on rock substrates was present as detritus. Scanning electron microscopy of rock substrates suggested that much of this detrital accumulation may consist of diatom stalk materials.This work was supported by a grant from the National Science Foundation/RANN GI-22. C. R. Goldman, Principal Investigator.     

On structure and functioning of ecosystem in a Salmon lake

The seasonal dynamics of the main components of the ecosystem as well as the vertical distribution of their biomass and production were studied in the salmon lake Dalnee at Kamchatka Peninsula. The data received were used for the construction of schemes of energy balance during two successive years: 1970 and 1971, which were different by their thermic regime. Analysis of schemes showed that during a colder season the food chain was shorter and more effective in relation of the use of primary production by zooplankton. Through the detritus pool the ecosystem used from 16% (1971) up to 70% (1970) of energy of primary production. Seasonal succession includes two main phases -autotrophic and heterotrophic. The energy balance of the planktonic community at these two phases is given.     

Free tryptophan pool and tryptophan biosynthetic enzymes in Saccharomyces cerevisiae

The free tryptophan pool and the levels of two enzymes of tryptophan biosynthesis (anthranilate synthase and indoleglycerolphosphate synthase) have been determined in a wild type strain of Saccharomyces cerevisiae and in mutants with altered regulatory properties.The tryptophan pool of wild type cells growing in minimal medium is 0.07 mole per g dry weight. Addition of anthranilate, indole or tryptophan to the medium produces a fifteen- to forty-fold increase in tryptophan pool, but causes no repression of the biosynthetic enzymes. Inclusion of 5-methyltryptophan in the growth medium causes a reduction in growth rate and a derepression of the biosynthetic enzymes, and this is shown here not to be correlated with a decrease in the free tryptophan pool.Mutants with an altered anthranilate synthase showing decreased sensitivity to inhibition by l-tryptophan or by the analogue dl-5-methyltryptophan have a tryptophan pool far higher than the wild type strain, but no repression of indoleglycerolphosphate synthase was observed. Mutants with an anthranilate synthase more sensitive to tryptophan inhibition show a slightly reduced tryptophan pool, but no derepression of indoleglycerolphosphate synthase was found.A mutant with constitutively derepressed levels of the biosynthetic enzymes shows a considerably increased tryptophan pool. Addition of 5-methyltryptophan to the growth medium of non-derepressible mutants causes a decrease in growth rate accompanied by a decrease in the tryptophan pool.Abbreviations CDRP 1-(o-carboxyphenylamino)-1-deoxyribulosephosphate - paba paraaminobenzoic acid - PRA N-(5-phosphoribosyl)-anthranilate - tRNA transfer ribonucleic acid; trp1 to trp5 refer to the structural genes for corresponding tryptophan biosynthetic enzymes