scholarly journals The use of N-methylprotoporphyrin dimethyl ester to inhibit ferrochelatase in Rhodopseudomonas sphaeroides and its effect in promoting biosynthesis of magnesium tetrapyrroles

1982 ◽  
Vol 208 (2) ◽  
pp. 479-486 ◽  
Author(s):  
J D Houghton ◽  
C L Honeybourne ◽  
K M Smith ◽  
H D Tabba ◽  
O T G Jones
Keyword(s):  
Dimethyl Ester ◽  
Cell Suspensions ◽  
Maximum Effect ◽  
Lag Phase ◽  
Rhodopseudomonas Sphaeroides ◽  
Normal Cells ◽  
Low Concentrations ◽  
Cytochrome Content ◽  
Monomethyl Ester ◽  
Substrate Addition

N-Methylprotoporphyrin dimethyl ester inhibits ferrochelatase in isolated membranes of Rhodopseudomonas sphaeroides at low concentrations (around 10 nm). Full inhibition developed after a short lag phase. The inhibition was non-competitive with porphyrin substrate. Addition of inhibitor to growing cultures of Rps. sphaeroides caused a decrease (near 40%) in cytochrome content and a severe inhibition of ferrochelatase; the excretion of haem into the medium by cell suspensions was also severely inhibited. The addition of N-methylprotoporphyrin dimethyl ester to suspensions of photosynthetically competent Rps. sphaeroides Ga caused excretion of Mg-protoporphyrin monomethyl ester. When added to mutants V3 and O1, magnesium divinylphaeoporphyrin a5 monomethyl ester and 2-devinyl-2-hydroxyethylphaeophorbide a were excreted, with maximum effect at around 3 microM-inhibitor in the medium. The results are interpreted to suggest that the inhibitor decreases concentration of intracellular haem, which normally controls the activity of 5-aminolaevulinate synthetase. Unregulated activity of this enzyme leads to overproduction of protoporphyrin, which is diverted to the bacteriochlorophyll pathway. Further control operates at magnesium protoporphyrin ester conversion in normal cells.

ABOUT SOME PECULIARITIES OF THE PHYSIOLOGICAL HETEROGENEITY OF THE POPULATION OF SCENEDESMUS QUADRICAUDA (TURP.) BREB. IN THE PRESENCE OF LOW CONCENTRATIONS OF METALS

2018 ◽  
pp. 34-43
Author(s):  
V. I. Ipatova ◽  
A. G. Dmitrieva ◽  
О. F. Filenko ◽  
T. V. Drozdenko
Keyword(s):  
Cell Division ◽  
Toxic Effect ◽  
Copper Chloride ◽  
Single Cells ◽  
Physiological State ◽  
Scenedesmus Quadricauda ◽  
Physiological Status ◽  
Lag Phase ◽  
Protective Mechanism ◽  
Low Concentrations

The structure of the laboratory population of green microalgae Scenedesmus quadricauda (Turp.) Breb (=Desmodesmus communis E. Hegew.) was studied at different stages of its growth (lag-phase, log-phase and stationary phase) at low concentrations of copper chloride and silver nitrate by the method microculture, allowing to monitor the state and development of single cells having different physiological status. The response of the culture of S. quadricauda - the change in the number of cells and the fractional composition (the fraction of dividing, «dormant» and dying cells) depended not only on the concentration of the toxicant in the medium, but also on the physiological state of the culture: the level of synchronization and the growth phase. Silver ions at low concentrations had a more pronounced toxic effect on the culture than copper ions at different phases of its development, especially at a concentration of 0.001 mg/l (10-9 M). The main mechanism of the toxic effect of metals is to inhibit the process of cell division. At low concentrations of toxicants, especially at a concentration of 0.001 mg/l, a «paradoxical» effect expressed in the predominance of the fraction of «dormant» cells was revealed. The temporary inhibition of the process of cell division can be regarded as a protective mechanism that allows preserving the integrity of the population and its ability to survive in a changing environment. The obtained data explain the effect of action of low concentrations of substances due to their inclusion in the cell, the subsequent accumulation in the cell and their low excretion.

scholarly journals Utilization of low molecular weight organic compounds by the filterable fraction of a lotic microbiome

2020 ◽  
Author(s):  
Lydia-Ann J Ghuneim ◽  
Marco A Distaso ◽  
Tatyana N Chernikova ◽  
Rafael Bargiela ◽  
Evgenii A Lunev ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Community Dynamics ◽  
Lag Phase ◽  
Minor Role ◽  
Low Molecular Weight ◽  
Freshwater Systems ◽  
North Wales ◽  
Clusters Of Orthologous Groups ◽  
A Minor ◽  
Substrate Addition

Abstract Filterable microorganisms participate in dissolved organic carbon (DOC) cycling in freshwater systems, however their exact functional role remains unknown. We determined taxonomic identity and community dynamics of prokaryotic microbiomes in the 0.22 µm-filtered fraction and unfiltered freshwater from the Conwy River (North Wales, UK) in microcosms and, using targeted metabolomics and 14C-labelling, examined their role in utilization of amino acids, organic acids, and sugars spiked at environmentally-relevant (nanomolar) concentrations. To identify changes in community structure, we used 16S rRNA amplicon and shotgun sequencing. Unlike the unfiltered water samples where the consumption of DOC was rapid, the filtered fraction showed a 3-days lag phase before the consumption started. Analysis of functional categories of clusters of orthologous groups of proteins (COGs) showed COGs associated with energy production increased in numbers in both fractions with substrate addition. The filtered fraction utilized low-molecular-weight (LMW) DOC at much slower rates than the whole community. Addition of nanomolar concentrations of LMW DOC did not measurably influence the composition of the microbial community nor the rate of consumption across all substrate types in either fraction. We conclude that due to their low activity, filterable microorganisms play a minor role in LMW DOC processing within short residence time of lotic freshwater systems.

The adaptation of Bact. coli mutabile to lactose

1954 ◽  
Vol 223 (1154) ◽  
pp. 420-420
Keyword(s):  
Inoculum Size ◽  
Colony Development ◽  
Lag Phase ◽  
Normal Cells ◽  
Adaptive Process ◽  
Large Numbers ◽  
Parent Culture ◽  
Mutation Theory ◽  
Special Circumstances ◽  
New Evidence

When Bact. coli mutabile not previously exposed to lactose is plated on lactose-ammonium sulphate agar the number of normal-sized colonies (lac + ) eventually formed is a complicated function of the inoculum size. For small numbers all the cells plated eventually form colonies; for large numbers the colony yield is determined not by a number of mutants in the parent culture but by plate exhaustion (for which the earlier developing colonies are chiefly responsible). The time of appearance of the lac + colonies is much longer than with a culture previously grown in lactose. Thus lac + mutants could not have been present from the start unless their growth is inhibited by an excess of normal cells. When, however, a small number of previously adapted cells are mixed with an excess of unadapted cells the presence of the latter does not impede the development on agar of lac + colonies from the former. When cells are first placed in a liquid lactose medium and samples are transferred at intervals during the ensuing lag phase, the time needed for colony development on lactose-agar progressively diminishes, once again showing that an adaptive process is occurring during the lag in the liquid medium. In certain special circumstances the adaptation to the liquid lactose medium may occur with abnormal speed. The growth rate of newly adapted strains is at first variable. If interpreted by a mutation theory the observations would demand the assumption of a complex polygenetic system for which current applications of the Luria-Delbrück and Lea-Coulson theories would be invalid. Recent arguments about the mutational nature of these phenomena are criticized in the light of the new evidence.

Characterization and plant regeneration of cell suspension cultures of Lycopersicon chilense

1991 ◽  
Vol 69 (10) ◽  
pp. 2257-2260 ◽  
Author(s):  
Ann Francine Greer ◽  
Zohreh Tabaeizadeh
Keyword(s):  
Plant Regeneration ◽  
Cell Suspension ◽  
Casein Hydrolysate ◽  
Leaf Explants ◽  
Cell Suspension Cultures ◽  
Suspension Cultures ◽  
Cell Suspensions ◽  
Lag Phase ◽  
Petiole Explants ◽  
Lycopersicon Chilense

To produce calli for the establishment of a cell suspension, leaf, stem, and petiole explants of Lycopersicon chilense Dun., grown in vitro and in the soil, were cultured on media containing 15 different combinations of benzylaminopurine, kinetin, and indole acetic acid. Among the three types of tissues, leaf explants showed the best response. Cell suspension cultures of L. chilense were established from leaf callus derived from soil grown plants using Murashige and Skoog's medium supplemented with casein hydrolysate (250 mg/L), coconut water (5%), and 2,4-dichlorophenoxyacetic acid (2 mg/L). Once established, cell suspensions showed a rapid growth rate with no marked lag phase. Shooting via organogenesis occurred from callus derived from cell suspensions on medium containing 2 mg/L benzylaminopurine. Regenerated plants had the same morphology as the original plants. Key words: Lycopersicon chilense, tomato, tissue culture, cell suspensions, organogenesis, plant regeneration.

A vena Coleoptile Segments: Hyperelongation Growth after Anaerobic Treatment

1980 ◽  
Vol 35 (9-10) ◽  
pp. 794-804 ◽  
Author(s):  
A. Hager
Keyword(s):  
Lactic Acid ◽  
Anaerobic Treatment ◽  
Positive Influence ◽  
Elongation Growth ◽  
Lag Phase ◽  
Sodium Arsenate ◽  
Anomalous Increase ◽  
Control Value ◽  
Low Concentrations ◽  
Short Period

Abstract Avena sativa coleoptile segments show an anomalous increase in elongation growth following a short period of oxygen deprivation (tested between 0 and 60 min) lasting 20-30 min (Anaero-biosis-Aerobiosis transition effect = ANA effect). The increase in growth rate is 600% and is commensurate with that observable following an auxin treatment. This hyperelongation growth, in contrast to the auxin-induced growth, begins without a lag phase. The growth “burst” following anaerobiosis is similarly to auxin-induced elongation growth, and is suppressed increasingly by neutral or more alkaline buffers. Hyperelongation growth is suppressed by respiratory inhibitors and uncouplers. A complete inhibition is effected with KCN (0.5 mM) sodium azide (0.5 mM) and CCCP (1 μM); amytal (in the range 0.5 to 1 mM) and sodium arsenate (0.1 to 1 mM) are strong inhibitors. Some of these compounds (KCN, arsenate, amytal) cause a slight increase of the ANA effect in very low concentrations, which is probably due to the K+ or Na+ ions present; on their own, these ions have a strong positive influence on the ANA effect. During anaerobiosis the ATP level sinks around 75% and almost returns to the old value, following the supply of air, within one minute. The cell sap pH drops from 6.3 to 5.9 during anaerobiosis within 20 min. This lowering is mainly due to an increase in lactic acid concentration. Other acids such as citric, malic, and aspartic acids show insignificant changes in concentration. The NADH content increases during anaerobiosis, whereas that of NADPH drops almost as much. The mentioned changes in concentration of lactic acid, NADH and NADPH return to the control value within 20-30 min; thus the differences exist as long as hyperelongation growth is under way. Possible relationships between the mentioned chemical changes and hyperelongation growth are discussed. One of the possible explanations is the following: the lowering of the cytoplasmic pH (normally around pH 7) during anaerobiosis due to the formation of lactic acid causes an activation of H+-ATPases in the plasmalemma and ER, since their optimum activity occurs in a pH of 5.5 to 6.5. This activation causes a greater H+-excretion into the cell wall compartment, and thus hyperelongation growth following supply of air and of ATP.

Base mediated dimerization of 2-tetradecynoic acid

1983 ◽  
Vol 61 (11) ◽  
pp. 2449-2454 ◽  
Author(s):  
Suzanne R. Abrams ◽  
J. Wilson Quail ◽  
Louis T. J. Delbaere
Keyword(s):  
Sodium Salt ◽  
Michael Addition ◽  
Dimethyl Ester ◽  
Crystallographic Analysis ◽  
Strong Base ◽  
X Ray ◽  
Crude Product ◽  
Monomethyl Ester

Under the influence of the very strong base, the sodium salt of 1,2-diaminoethane in 1,2-diaminoethane, 2-tetradecynoic acid is converted to 3-tetradecynoic acid (35%) and a novel dimer 3. Compound 3 ((Z)-2-(1-dodecynyl)-3-undecyl-pent-2-en-1,5-dioic diacid) is isolated as the monomethyl ester 1 after treatment of the crude product with methanolic HCl. The structures of 1 and 3 are deduced from an X-ray crystallographic analysis of the dimethyl ester 2 obtained by reaction of 1 with diazomethane. The dimer 3 is thought to arise from Michael addition of the dianion 4 of 3-tetradecynoic acid with the sodium salt of 2-tetradecynoic acid.

Autophagy is associated with apoptosis in cisplatin injury to renal tubular epithelial cells

2008 ◽  
Vol 294 (4) ◽  
pp. F777-F787 ◽  
Author(s):  
Cheng Yang ◽  
Varsha Kaushal ◽  
Sudhir V. Shah ◽  
Gur P. Kaushal
Keyword(s):  
Cell Death ◽  
Epithelial Cells ◽  
Beclin 1 ◽  
Lag Phase ◽  
Tubular Epithelial Cells ◽  
Renal Tubular Epithelial Cells ◽  
Normal Cells ◽  
Life And Death ◽  
Renal Tubular ◽  
Induced Apoptosis

Autophagy has emerged as another major “programmed” mechanism to control life and death much like “programmed cell death” is for apoptosis in eukaryotes. We examined the expression of autophagic proteins and formation of autophagosomes during progression of cisplatin injury to renal tubular epithelial cells (RTEC). Autophagy was detected as early as 2–4 h after cisplatin exposure as indicated by induction of LC3-I, conversion of LC3-I to LC3-II protein, and upregulation of Beclin 1 and Atg5, essential markers of autophagy. The appearance of cisplatin-induced punctated staining of autophagosome-associated LC3-II upon GFP-LC3 transfection in RTEC provided further evidence for autophagy. The autophagy inhibitor 3-methyladenine blocked punctated staining of autophagosomes. The staining of normal cells with acridine orange displayed green fluorescence with cytoplasmic and nuclear components in normal cells but displayed considerable red fluorescence in cisplatin-treated cells, suggesting formation of numerous acidic autophagolysosomal vacuoles. Autophagy inhibitors LY294002 or 3-methyladenine or wortmannin inhibited the formation of autophagosomes but induced apoptosis after 2–4 h of cisplatin treatment as indicated by caspase-3/7 and -6 activation, nuclear fragmentation, and cell death. This switch from autophagy to apoptosis by autophagic inhibitors further suggests that the preapoptotic lag phase after treatment with cisplatin is mediated by autophagy. At later stages of cisplatin injury, apoptosis was also found to be associated with autophagy, as autophagic inhibitors and inactivation of autophagy proteins Beclin 1 and Atg5 enhanced activation of caspases and apoptosis. Our results demonstrate that induction of autophagy mounts an adaptive response, suppresses cisplatin-induced apoptosis, and prolongs survival of RTEC.

Low Concentrations of Halothane Increase Response to a Noxious Thermal Stimulus and Attenuate the Antinociceptive Effect of Intraventricular but Not Intrathecal Morphine

2001 ◽  
Vol 94 (2) ◽  
pp. 298-302 ◽  
Author(s):  
Kenneth Drasner
Keyword(s):  
Pain Perception ◽  
Intrathecal Morphine ◽  
Antinociceptive Effect ◽  
Maximum Effect ◽  
Tail Flick ◽  
Temperature Threshold ◽  
Thermal Stimulus ◽  
Descending Inhibition ◽  
Low Concentrations ◽  
Tail Flick Latency

Background Classically, the first plane of anesthesia is known as the stage of analgesia. Nonetheless, clinical evidence suggests that low doses of inhaled agents might enhance pain perception. The present experiments test the hypothesis that low concentrations of halothane increase response to a noxious thermal stimulus and attenuate the antinociceptive effect of intraventricular morphine via disruption of descending inhibition. Methods In the first experiment, the temperature at which rats withdraw their tails from a heat source was measured in animals breathing various concentrations of halothane. In the second experiment, the effect of intraventricular or intrathecal morphine on tail-flick latency was assessed in rats breathing either oxygen or 0.23% halothane. Results Low concentrations of halothane decreased the temperature threshold for tail-flick with a maximum effect at 0.06% atmospheres. Halothane attenuated the antinociceptive potency of intraventricular morphine but enhanced the efficacy of intrathecal morphine. Conclusions Subanesthetic concentrations of halothane may enhance response to a noxious stimulus. The differential effect on intraventricular and intrathecal morphine suggests that this enhancement results from disruption of descending inhibition.

scholarly journals Fibrinopeptides A and B release in the process of surface fibrin formation

Blood ◽  
2011 ◽  
Vol 117 (5) ◽  
pp. 1700-1706 ◽  
Author(s):  
Tomas Riedel ◽  
Jiri Suttnar ◽  
Eduard Brynda ◽  
Milan Houska ◽  
Leonid Medved ◽  
...  
Keyword(s):  
Phase Characteristic ◽  
Lag Phase ◽  
Functional Characteristics ◽  
Fibrin Formation ◽  
Low Concentrations ◽  
High Concentrations ◽  
Fibrinogen Adsorption

AbstractFibrinogen adsorption on a surface results in the modification of its functional characteristics. Our previous studies revealed that fibrinogen adsorbs onto surfaces essentially in 2 different orientations depending on its concentration in the solution: “side-on” at low concentrations and “end-on” at high concentrations. In the present study, we analyzed the thrombin-mediated release of fibrinopeptides A and B (FpA and FpB) from fibrinogen adsorbed in these orientations, as well as from surface-bound fibrinogen-fibrin complexes prepared by converting fibrinogen adsorbed in either orientation into fibrin and subsequently adding fibrinogen. The release of fibrinopeptides from surface-adsorbed fibrinogen and from surface-bound fibrinogen-fibrin complexes differed significantly compared with that from fibrinogen in solution. The release of FpB occurred without the delay (lag phase) characteristic of its release from fibrinogen in solution. The amount of FpB released from end-on adsorbed fibrinogen and from adsorbed fibrinogen-fibrin complexes was much higher than that of FpA. FpB is known as a potent chemoattractant, so its preferential release suggests a physiological purpose in the attraction of cells to the site of injury. The N-terminal portions of fibrin β chains including residues Bβ15-42, which are exposed after cleavage of FpB, have been implicated in many processes, including angiogenesis and inflammation.

Sign in / Sign up

Export Citation Format

Share Document