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At least 703 records · Page 39Linked to original sources
PubMed1982

[Use of a synchronous Chlorella population for studying the effect of low-dose stimulation of N-Ninitroso-N-methylurea].

The cycle of Chlorella cells development is shortened under the action of NMU. The effect of stimulation is dependent on the cell developmental stage at the time of treatment with the mutagen. This effect is absent in cells being at the first and final stages of the development. The maximum stimulation is observed after treatment of the 14 hours old culture (the mutagen concentration being 35.10(-7) M) and proceeds during several generations.

Cell Cycle↗
PubMedDate not supplied

The production of hydroxamic acid metabolites of nitrosobenzene by Chlorella pyrenoidosa.

The ability of the green alga Chlorella pyrenoidosa to convert nitrosobenzene (I), phenylhydroxylamine (VI), aniline, and nitrobenzene to hydroxamic acid metabolites was investigated. Only nitrosobenzene and phenylhydroxylamine were partially converted to N-phenylacetohydroxamic acid (Va) and N-phenylglycolhydroxamic acid (Vb), with the latter compound being the major product. The possible mechanisms for the formation of these hydroxamic acid metabolites are discussed. The most plausible explanation for their production is through the interaction of the nitroso group with certain intermediates of thiamine-dependent enzymes. The conversion of phenylhydroxylamine to the hydroxamic acids probably is the result of initial oxidation to nitrosobenzene. Apparently, C. pyrenoidosa lacks nitroreductase and aniline hydroxylase activities, since no metabolic conversions of aniline or nitrobenzene were observed. The potential environmental significance of hydroxamic acid production from nitrosoaromatics is discussed.

Chlorella↗
PubMed1981

[Purification, molecular weight and subunit structure of NAD(NADP)-dependent glyceraldehyde 3-phosphate dehydrogenase from Chlorella].

The NAD(NADP) dependent glyceraldehyde 3-phosphate dehydrogenase was isolated from the thermophylic strain of Chlorella pyrenoidosa Pringsheim 82T. The isolation and purification procedures included fractionation of the proteins with (NH4)2SO4, column chromatography on Bio-Gel A-1,5 m and rechromatography on hydroxyapatite. The enzyme was homogeneous during electrophoresis in polyacrylamide gel. The molecular weight of the oligomeric enzyme is 160 000, that of the subunits is 40 000. The amino acid composition and total number of SH-groups were determined.

Chlorella↗
PubMed1981

[NAD(NADP)-dependent glyceraldehyde 3-phosphate dehydrogenase from Chlorella. Kinetics of inhibition by the reaction products NAD and NADP].

The values of Km and V for NAD(NADP)-dependent glyceraldehyde 3-phosphate dehydrogenase from Chlorella for oxidized and reduced pyridine nucleotides were determined. NAD and NADP competitively inhibit the oxidation of NADH and NADPH, respectively. The NADPH- and NADH-dependent activities were shown to be "cross"-inhibited by NAD and NADP, the inhibition being of a mixed type. It is concluded that the enzyme has independent sites for binding of coenzymes NAD(H) and NADP(H) or at least these coenzymes are linked by different ways at the same site of the enzyme molecule.

Chlorella↗
PubMedDate not supplied

Effect of detergents on radiothermoluminescence of Chlorella.

Radiothermoluminescence (RTL) of Chlorella cells cultivated in a medium in the presence of a detergent was studied as a function of their contact time with the detergent in the temperature range from -196 degrees to +150 degrees C. The concentration of the toxicants blocking cell division caused noticeable changes in the shape of the liminescence curve beginning 1.5 h after adding the detergent to the medium. Additional luminescence peaks were noted in the -95 degrees and +120 degrees temperature region. A correlation was found between the change of luminescence intensity at -95 degrees bleaching of the cells, and their viability as a function of their contact time with the detergent.

Cell Division↗
PubMedDate not supplied

[Effect of adaptation to light of different spectral composition on photosynthesis of Chlorella cells].

Dependence of cell photosynthesis in different spectral regions on illumination conditions of chlorella culture during growing (blue, green and red light) was studied. Change in the shape of action spectra of photosynthesis (measured with interference light filters) was discovered. This change is mostly pronounced in relation to the red and blue maxima. The largest relative value of the blue maximum was observed for the cells grown in the red light.

Adaptation, Physiological↗
PubMedDate not supplied

[Ultrastructure of chloroplasts and activity of amylases in Chlorella cells during space flight].

Ultrastructure of Chlorella cells grown in space flight was studied. Some differences in cell organells, chloroplasts in particular, were found in experimental cells in comparison to control. The considerable reduction in the number of reserve polysaccharides in chloroplasts and some decrease in stroma electron density were detected. Specific activity of amylases enhanced because of an increase in concentrations of mono- and disaccharides. The rearrangements of chloroplast ultrastructure, predominantly a decrease in reserve polysaccharides, are probably due to an increase of hydrolytic processes under microgravity.

Amylases↗
PubMed1978

Extracellular release in Chlorella vulgaris culture and the role of bacteria accompanying - algae in this process.

The effect of different concentrations of nitrogen and phosphorus on extracellular release was investigated. Phosphorus induced the enhanced extracellular release of metabolites by Chlorella vulgaris. No influence of nitrogen on extracellular release was observed. In the initial stages of C. vulgaris culture the algae release was observed. In the initial stages of C. vulgaris culture the algae release compounds readily assimilated by the accompanying bacteria, hence the observed drop of percentage of extracellular release (PER) in culture medium caused by the bacteria. Both, the glycolic acid and the products of photoassimilation released to the environment in the first stages of cultivation were assimilated by the bacteria accompanying-algae at a similar rate. The ageing of C. vulgaris culture resulted in the accumulation of extracellularly released metabolites and increase of PER. These products were not assimilated by the bacteria present in the algal culture.

Chlorella↗
PubMed1993

Change in toxicity effect of mercury at static concentration to Chlorella vulgaris with addition of organic carbon sources.

The effect of mercury on Chlorella vulgaris is influenced to a large extent by organic carbon sources like glucose, glutamate, and 2-oxoglutarate which is exhibited through changes in growth and metabolic processes of the alga in the presence of static dose (0.200 +/- 0.004, p = 0.05) of Hg2+. Addition of the three carbon sources to the Hg(2+)-amended Chu No 10+ medium resulted in an acceleration of pigment biomass, growth, and protein content of the green alga. Glucose at all concentrations was found to be more effective than the other two in reducing the mercury toxicity to C. vulgaris. However, the detoxifying effect is dependent on the type of carbon sources, their concentration and days of incubation. Glucose at 5 mg/l significantly reduced Hg2+ toxicity while glutamate and 2-oxoglutarate, at this concentration, did not show such capacity. Similarly the degree of significance of ameliorative effect increased with increase in incubation period which, however, varied with the carbon source. Availability of additional energy and formation of non-toxic or less toxic mercury are the probable causes of reduction in toxicity effects.

Chlorella↗
PubMed1994

Effect of Cu and Ni on growth, mineral uptake, photosynthesis and enzyme activities of Chlorella vulgaris at different pH values.

A pH dependent reduction in growth, pigment, ATP content, O2- evolution, carbon fixation, photosynthetic electron transport system, nutrient uptake (NO3- and NH4+), nitrate reductase, and ATPase activities and increase in K+ efflux of Chlorella vulgaris was noticed following supplementation of Cu and Ni to the culture medium. PS II was found to be more sensitive to both pH and metals than PS I. Though, nitrate reductase (NR) was more sensitive to both pH and metals, the ATPase was however, more sensitive to metals but less sensitive to acidic pH. Acid pH was found to inhibit the nutrient (NO3- and NH4+) uptake and nitrate reductase in a non-competitive manner. The inhibition produced by the test metals alone was of non-competitive type for NO3- uptake, nitrate reductase and ATPase and competitive for NH4+ uptake. Acidity not only inhibited the metabolic variables directly but also through facilitated uptake of metals and increased membrane permeability. A very low sensitivity of ATPase to acidic pH seems to be responsible for the survival of algae in acid environment.

Adenosine Triphosphatases↗
PubMed1975

[On the composition of fatty acids in Chlorella pyrenoidosa under the influence of dimethyl- and diethylaminoazobenzene (author's transl)].

The composition of bulk fatty acids in Chlorella pyrenoidosa under the influence of the carcinogenic dimethylaminoazobenzene and the non carcinogenic diethylaminoazobenzene was examined. In the presence of dimethylaminoazobenzene cultivated algae showed parallel to morphological changes distinct deviations in the composition of their fatty acids compared with the control. This especially concerns the unsaturated C18-fatty acids as the C16:0-, C16:2- and C16:3-acids respectively. By treatment of algae with diethylaminoazobenzene no morphological variations were observed and only little changes in composition of their fatty acids was demonstrated.

Azo Compounds↗
PubMed1994

In vivo manipulation of the xanthophyll cycle and the role of zeaxanthin in the protection against photodamage in the green alga Chlorella pyrenoidosa.

Chlorella pyrenoidosa was grown in steady-state continuous cultures in either high or low light. Samples of these cultures were incubated in darkness (violaxanthin state) or in saturating light (zeaxanthin state). These samples were kept in the respective preadapted states throughout the entire photodamage treatment. Photodamage involved exposure to single-turnover flashes fired at a low (non-actinic) frequency. The damage caused by the light stress thus applied was monitored by changes in photosynthetic properties and pigment composition. Cells preadapted in the light resisted photodamage better than those kept in darkness. The low light grown cells were more vulnerable to photodamage than the high light grown cells. Our experimental approach permitted the equilibria between the components that participate in the xanthophyll cycle to be set without addition of inhibitors. Regardless of the total amount of violaxanthin being present, its conversion to anthera- and zeaxanthin is a prerequisite for protection. The protection is most effective for photosystem II. It appeared that antheraxanthin accumulates as a result of photodamaging flashes provided that these are fired in the presence of background light, i.e. with zeaxanthin present. From this, it is newly derived that the xanthophyll cycle operates in full in the light, including epoxidation of zeaxanthin. The latter conversion was also demonstrated in vitro, via nonenzymatic oxygen-dependent turnover of zeaxanthin into violaxanthin.

Carotenoids↗
PubMed1993

Effects of 2-alkylthio-6-aminobenzothiazoles and their 6-N-substituted derivatives on photosynthesis inhibition in Chlorella vulgaris and spinach chloroplasts.

2-Alkylthio-6-aminobenzothiazoles and their 6-N-substituted derivatives 3-(2-alkylthio-6-benzothiazolylaminomethyl)-2-benzothiazolineth iones and 3-(2-alkylthio-6-benzothiazolylaminomethyl)-6-bromo-2-benzothia zolinones inhibit photosynthetic processes in spinach chloroplasts and the chlorophyll production in Chlorella vulgaris. The inhibitory activity depends on the alkyl chain length of the thioalkyl substituent. The site of action of the effectors studied is on the donor side of photosystem 2 before the site of action of diphenylcarbazide. The highest antialgal effects were exhibited by compounds containing bromine.

Chlorella↗
PubMed1976

Salt stimulated respiration of Chlorella fusca.

ATP contents have been measured before and after addition of KCl (5 mM final concentration) to suspensions of Chlorella in distilled water under different conditions of energy supply. The levels decreased immediately after salt addition and returned to the original values under conditions both of oxidative phosphorylation and of cyclic photophosphorylation, but not under conditions of fermentation. It appears that this decrease in the ATP level is the cause for salt stimulated respiration (S.S.R.). Furthermore, it is shown that cycloheximide and EDTA, which interact with Rb+ uptake (active and ATP-driven) at low salt concentration, also reduce S.S.R. From this parallelism it is concluded that the ATPase involved in Rb+ uptake at low salt concentration is also responsible for S.S.R. at high salt concentration. As S.S.R. provides far more energy than is required for the small influx of ions it is suggested that the ATPase is decoupled by the salt from ion transport.

Adenosine Triphosphate↗
PubMed1977

[Effect of the light on the biosynthesis of inorganic polyphosphates and some phosphoorganic compounds in Chlorella pyrenoidosa Chick].

The illumination of Chlorella cells is found to affect the biosynthesis of different inorganic polyphosphates (IPP) and phosphoorganic compounds. The synthesis of IPP fractions, extracted with TCA at 0 degrees C and perchloric acid at 100 degrees C, is carried out with the cooperation of photochemical reactions, while the formation of other IPP fractions is light-independent. Ohosphorus incorporation into nucleic acids and phosphoproteins is due to the effect of the light, and phosphorylation of carbohydrates and phospholipids is a dark process.

Chlorella↗
PubMed1995

Post-exposure radioprotection by Chlorella vulgaris (E-25) in mice.

Oral administration of an algal mutant C. vulgaris E-25, 1 hr before or immediately after exposure to sublethal gamma-rays increased the number of endogenous spleen colony forming units (E-CFU). The magnitude of radioprotection was dependent on both, the dose of C. vulgaris fed and the time of administration. An optimal E-CFU was observed when 500 mg/kg body wt. of C. vulgaris was fed 1 hr before or immediately after irradiation. Significant recovery was observed in the number of bone marrow cells and the spleen weight. LD50/30 for Chlorella pre- and post-treated mice were 8.66 and 9.0 Gy, respectively compared to the control value of 7.8 Gy. The dose reduction factor (DRF) was 1.11 and 1.15 for pre-treated and post-treated mice respectively.

Animals↗
PubMed1977

[Effect of dissociating agents on Chlorella glutamate dehydrogenases].

Effect of urea beta-mercaptoethanol and guanidine--hydrochloride on two Chlorella glutamate dehydrogenases (GDH's) have been studied. Both GDH's are inactivated irreversibly by 2-3 M guanidine hydrochloride. Urea above 4 M rapidly inactivates only NH+4-induced NADP--GDH. Constitutive NAD(P)--GDH is stable in 8M urea solution at room temperature for a long time. beta-Mercaptoethanol does not effect significantly the stability of constitutive GDH in 8m urea. Urea above 1M being in reaction mixture inhibits constitutive GDH in a competitive manner to L-glutamate and uncompetitively regards to alpha-oxoglutarate. Taking this into account, one may conclude that L-glutamate and alpha-oxoglutarate seems to bind to different groups on the enzyme molecule.

Chlorella↗