Effect of the Plastoquinone Antagonist Dibromothymoquinone on Electron Transport Reactions in Chloroplast Preparations

1977 ◽  
Vol 4 (2) ◽  
pp. 253 ◽  
Author(s):  
A Stewart ◽  
AWD Larkum
Keyword(s):  
Electron Transport ◽  
Thylakoid Membrane ◽  
Methyl Viologen ◽  
Control Level ◽  
Type A ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Photosynthetic Control ◽  
Type C

The effects of dibromothymoquinone (DBMIB) on electron transport in types A, B, C and D spinach and pea chloroplast preparations have been studied. DBMIB (1 x 10-6M) strongly inhibited electron transport to methyl viologen in all the types of chloroplasts, while electron transport to ferricyanide was inhibited by 60%. Envelope-free (type C) chloroplast preparations with poor photosynthetic control were inhibited more strongly than intact (types A and B) chloroplast preparations at low (< 5 x 10-7M) concentrations of DBMIB. Type C preparations with good photosynthetic control were less strongly inhibited except in the presence of uncoupler or in the absence of ADP. Above 1 x 10-6M DBMIB, inhibition of electron transport to ferricyanide became progressively less and, with type A chloroplast preparations, a large stimulation compared to the control level occurred. Phenylenediamine stimulated high rates of electron transport to ferricyanide in the presence of low concentrations of DBMIB. At higher DBMIB concentrations, the stimulation was completely reversed and envelope-free chloroplasts again showed greater sensitivity to DBMIB compared to intact chloroplasts. DBMIB appears to have a number of sites of interaction with the thylakoid membrane.

Interference by Herbicides with the Transmembrane Potential of Thylakoids

1987 ◽  
Vol 42 (6) ◽  
pp. 718-726 ◽  
Author(s):  
Donald E. Moreland ◽  
William P. Novitzky
Keyword(s):  
Electron Transport ◽  
Thylakoid Membrane ◽  
Transmembrane Potential ◽  
Proton Motive Force ◽  
Cyclic Electron Transport ◽  
Low Concentrations ◽  
High Concentrations ◽  
Proton Shuttling ◽  
Electrical Components ◽  
Spinach Thylakoids

Interferences expressed by herbicides classified as inhibitory uncouplers were measured on the induction and maintenance of ΔpH and ΔΨ, the chemical and electrical components, respectively. of the proton motive force (pmf) generated by light-induced cyclic electron transport in spinach thylakoids. Maintenance of the pmf is required for the synthesis of ATP. The inhibitory uncouplers arc known to inhibit photophosphorylation, but the mechanisms involved remain to be identified. The dinoseb types (dinitrophenols. benzimidazoles. benzonitriles. bromophenoxim. perfluidone. thiadiazoles) of inhibitory uncouplers, most of which contain dissociable protons, were found to discharge ΔpΗ at low concentrations and to collapse ΔΨ at high concentrations. Collapse of ΔpΗ can be attributed to the protonophoric (proton shuttling) action of the herbicides. However, collapse of ΔΨ can be caused by alterations induced to the integrity and loss of semipermeability of the thylakoid membrane. As a result the membrane bccomes permeable to protons and other cations, and the electrical charges across the membrane are neutralized. The non-ionic dicryl types of inhibitory uncouplers (acylanilides. dinitroanilines. diphenylethcrs. bis-carbamates) collapsed ΔΨ at concentrations that were somewhat lower than those required for the collapse of ΔpΗ. These herbicides appear only to alter the integrity and permeability of the thylakoid membrane. Inhibition of photophosphorylation by the inhibitory uncouplcrs correlated with their ability to dissipate the pmf.

Interference by Herbicidal Inhibitors of Electron Transport with Phosphorylation and Permeability Properties of Chloroplast Membranes

1984 ◽  
Vol 39 (5) ◽  
pp. 329-334 ◽  
Author(s):  
Donald E. Moreland ◽  
William P. Novitzky
Keyword(s):  
Electron Transport ◽  
Thylakoid Membrane ◽  
Chloroplast Envelope ◽  
Ortho Position ◽  
Response Patterns ◽  
Chloroplast Membranes ◽  
Semipermeable Membranes ◽  
Low Concentrations ◽  
Maximum Inhibition ◽  
Transport Inhibitors

Many herbicides inhibit chloroplast electron transport by interfering with a proteinaceous component of the Qв complex located in the appressed granal membrane. Certain of these herbicides, designated inhibitory uncouplers, also interfere with photophosphorylation and affect other chloroplast-mediated responses, some of which involve components located in the nonappressed granal membrane. The inhibitory uncouplers can be divided into dinoseb (phenolic) types which contain dissociable protons and dicryl (acylanilide) types which are nonionic. The dinoseb types can function as protonophores and shuttle protons across the thylakoid membrane at low concentrations and can alter the integrity of semipermeable membranes at higher concentrations. However, the dicryl types only alter the integrity of the membranes. The inhibitory uncouplers, but not the DCMU-types of electron transport inhibitors: stimulated electron trans- port from DPIPH2 to methyl viologen; inhibited valifiomycin-induced swelling of intact chloroplasts; increased the permeability of the chloroplast envelope to K+ in the absence of an ionophore; prevented energization of the thylakoid membrane by PS I; and increased the permeability of phosphatidyl choline liposomes to protons. Chlorination response patterns obtained with isomers of N-phenyl-2-methylpentanamides in the above reactions, in general, were similar for interference with the Qв complex, i.e., in all assays, dichlorination in the 3,4 or 3,5 positions was associated with maximum inhibitory potency, whereas substitution in an ortho position decreased inhibitory activity. With a series of 1-alkyl-3-(α,α,α-trifluoro-m-tolyl)ureas, maximum inhibition of electron transport was obtained with the butyl derivative, whereas maximum responses for uncoupling and membrane disturbances were obtained with the hexyl or octyl derivatives. Some of the interferences produced by inhibitory uncouplers may result from interactions with the lipoidal components of chloroplast membranes.

Effects of Indoleacetic Acid on CO2 Fixation, Electron Transport and Phosphorylation in Isolated Chloroplasts

1978 ◽  
Vol 5 (4) ◽  
pp. 425 ◽  
Author(s):  
SP Robinson ◽  
JT Wiskich ◽  
LG Paleg
Keyword(s):  
Electron Transport ◽  
Methyl Viologen ◽  
Co2 Fixation ◽  
Indoleacetic Acid ◽  
Direct Interaction ◽  
Co2 Uptake ◽  
Phenazine Methosulfate ◽  
Short Term ◽  
Intact Chloroplasts ◽  
Isolated Chloroplasts

The effects of indoleactic acid (IAA) on CO2 fixation, electron transport and photophosphorylation were examined. The rate of CO2 fixation by preparations of intact chloroplasts was not significantly increased by the addition of IAA (0.2 - 5 �M). Electron transport and coupled phosphorylations were similarly unaffected when measured with ferricyanide or methyl viologen as the electron acceptor. Cyclic phosphorylntion mediated by phenazine methosulfate was also not increased by IAA. It is concluded that the hormone does not affect photosynthesis by isolated chloroplasts in short-term experiments and that the increased CO2 uptake observed with leaves following application of IAA may result from some effect of the hormone other than a direct interaction with the chloroplasts.

scholarly journals Effects of Cadmium on Carbonic Anhydrase and Activities Dependent on Electron Transport of Isolated Chloroplasts.

1969 ◽  
Vol 63 (2) ◽  
pp. 195-201 ◽  
Author(s):  
Carmen I. Asencio ◽  
Arturo Cedeño-Maldonado
Keyword(s):  
Electron Transport ◽  
Carbonic Anhydrase ◽  
Co2 Fixation ◽  
Strong Inhibition ◽  
Enzyme Preparations ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Isolated Chloroplasts

Low concentrations of Cadmium inhibit the electron transport and CO2 fixation reactions of isolated chloroplasts. CO2 fixation is more sensitive to Cd than electron transport and dark pre-incubation increases the degree of toxicity to both. Carbonic anhydrase, an enzyme associated with CO2 fixation, is very sensitive to Cd either when applied directly to partially purified preparations of the enzyme or when enzyme preparations are obtained from intact chloroplasts previously exposed to Cd. Strong inhibition occurs at Cd concentrations lower than those required to inhibit any of the electron transport dependent reactions studied. These results are interpreted as evidence that carbonic anhydrase is one of the most sensitive sites of Cd action in isolated chloroplasts.

The Slow Phase of the Electrochromic Shift in Relation to the Q-Cycle in Thylakoids

1987 ◽  
Vol 14 (1) ◽  
pp. 29 ◽  
Author(s):  
AB Hope ◽  
DB Matthews
Keyword(s):  
Electron Transport ◽  
Cytochrome B ◽  
Methyl Viologen ◽  
Slow Phase ◽  
Half Time ◽  
Electrochromic Shift ◽  
Q Cycle ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Micromolar Range

The electrochromic signal in oxidising conditions with whole-chain electron transport from water to ferricyanide or methyl viologen was compared with that under reducing conditions with electron transport from duroquinol to methyl viologen. Under oxidising conditions, in a train of flashes at 10 Hz, the slow phase in the growth of the electrochromic signal was not apparent after a few flashes whilst under reducing conditions it persisted. The slow phase of the electrochromic signal was also examined particularly under conditions favouring the operation of an apparent Q-cycle, namely oxidising conditions plus the addition of low concentrations of valinomycin and flashes given at 5-10 Hz. The slow phase was retained in the presence of valinomycin at flash rates up to 10 Hz and its decay was accelerated. The half-time for the slow phase was 18-20 ms (whole-chain), or 3-5 ms (reducing conditions, duroquinol/methyl viologen). There was a lag of 3 ms before the rise of the slow phase with ferricyanide. The onset was accelerated by valinomycin under oxidising conditions. The slow phase was sharply inhibited by 2-n-heptyl- and 2-n-nonyl-4-hydroxyquinoline N-oxide (HQNO and NQNO) to at least half its maximum extent by 0.1 �M (HQNO) or 0.05 �M (NQNO); further inhibition took place in the micromolar range. The slow phase is discussed in terms of probable electrogenic events in the cytochrome b/f complexes and their kinetics. We support the hypothesis that its basic cause is the transverse, intramembrane passage of electrons and show that this passage is controlled by the prevailing intramembrane potential difference, an estimated 85-140 mV sufficing for half inhibition of the slow phase.

Photophosphorylation by Chloroplasts: Effects of Low Concentrations of Ammonia and Methylamine

1982 ◽  
Vol 37 (3-4) ◽  
pp. 242-250 ◽  
Author(s):  
Christoph Giersch
Keyword(s):  
Thylakoid Membrane ◽  
Driving Force ◽  
Proton Motive Force ◽  
Light Illumination ◽  
Low Light ◽  
Atp Production ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Assay Conditions ◽  
Stimulation Of

Abstract Intact chloroplasts exposed to hypotonic assay conditions are capable of photophosphorylating exogenous ADP. The rate of phosphorylation by these unbroken plastids is increased by 10-50% upon the addition of low concentrations (<mм) of NH3 or CH3NH2. Stimulation of phosphorylation is abolished by washing chloroplasts with MgCl2. Evidence is presented that washing removes a factor responsible for amine-induced increase of ATP production and that this factor is associated with the thylakoid membrane. Addition of CH3NH2 increased the proton permeability of the thylakoid membrane of unbroken and washed chloroplasts during the light/dark transition. Hence, differences of the membrane permeability for protons between the two preparations seem not to be responsible for an increase of ATP production upon the addition of amines. Stimulation of photophosphorylation by methylamine is observed even at light itensities which do not saturate the proton motive force, which in turn is reduced upon the addition of the uncoupler. Apparently, phosphorylation can be stimulated, although the limiting driving force is diminished. It is concluded that phosphorylation by unbroken chloroplasts under low light illumination is limited kinetically, not energetically. Consequences of these findings for observation made with intact chloroplasts are discussed.

MRI analysis and surgical treatment of Wassel Type IV duplicated thumbs

2021 ◽  
pp. 175319342098321
Author(s):  
Anyuan Wang ◽  
Jian Ding ◽  
Long Wang ◽  
Tinggang Chu ◽  
Zhipeng Wu ◽  
...  
Keyword(s):  
Type A ◽  
Surgical Reconstruction ◽  
Mri Findings ◽  
Level Of Evidence ◽  
Type D ◽  
Type Iv ◽  
Secondary Operations ◽  
Type C

We present the MRI findings for 39 Wassel Type IV duplicated thumbs in 38 patients. We found that MRI revealed the morphology of the cartilaginous connection between the thumb anlages and the location of the deviation corresponding to the classification of Horii, which allowed precise preoperative planning of corrective osteotomies. All 39 thumbs were available for follow-up after surgical reconstruction at a mean of 29 months (range 25 to 39). Four out of nine Horii Type A cases and all 12 Type B, as well as the six Type C and the six Type D cases, achieved good results according to the Tada scoring system. Five Type A cases achieved fair results with residual stiffness of the interphalangeal joint. No secondary operations were needed. We conclude that MRI proved useful in subclassifying Wassel Type IV duplicated thumbs and may aid in planning the osteotomies needed for their reconstruction. Level of evidence: IV

Inhibition of Photosynthetic Reactions by Aureomycin

1984 ◽  
Vol 39 (6) ◽  
pp. 627-633 ◽  
Author(s):  
Ji-yu Ye ◽  
U. Heber
Keyword(s):  
Membrane Potential ◽  
Proton Gradient ◽  
Effective Inhibitor ◽  
Mesophyll Protoplasts ◽  
Electrochromic Shift ◽  
Low Concentrations ◽  
Intact Chloroplasts ◽  
Photosynthetic Reactions ◽  
Isolated Chloroplasts

The effect of aureomycin on photosynthesis was investigated. This antibiotic which has been reported to stimulate photosynthesis at very low concentrations is an effective inhibitor at higher concentrations. In mesophyll protoplasts and isolated chloroplasts from spinach, 50% inhibition of CO2 reduction required about 20 μᴍ aureomycin. The reduction of 3-phosphoglycerate and of oxaloacetate by intact chloroplasts was also inhibited, but not that of nitrite and methylviologen which was actually stimulated. NADP reduction by broken chloroplasts and methylviologen- dependent photophosphorylation were also sensitive to aureomycin. The electrochromic shift at 518 nm which indicates formation of a light-dependent membrane potential was suppressed in the presence of 200 μᴍ aureomycin and the transthylakoid proton gradient was decreased. The data confirm reports that aureomycin has uncoupling properties, and they indicate that it also acts as an inhibitor of ferredoxin/NADP reductase.

MPTP delta, a putative murine homolog of HPTP delta, is expressed in specialized regions of the brain and in the B-cell lineage

1993 ◽  
Vol 13 (9) ◽  
pp. 5513-5523
Author(s):  
K Mizuno ◽  
K Hasegawa ◽  
T Katagiri ◽  
M Ogimoto ◽  
T Ichikawa ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Lines ◽  
Type A ◽  
Extracellular Domain ◽  
Fine Tuning ◽  
Leader Peptide ◽  
Reticular Nucleus ◽  
Cdna Clones ◽  
Protein Tyrosine ◽  
Type C

Protein tyrosine phosphatases (PTPs), together with protein tyrosine kinases (PTKs), are involved in the regulation of cell activation, growth, and differentiation. To further elucidate the fine tuning of cell growth and differentiation through tyrosine phosphorylation, we tried to isolate mouse receptor-type PTP (RPTP) cDNA clones by screening mouse brain cDNA libraries with mouse CD45 PTP domain probes under reduced-stringency conditions. Characterization of isolated cDNA clones for RPTP showed that the cytoplasmic region contains two tandem repeats of PTP domain of about 230 amino acids with intrinsic phosphatase activity. The extracellular region was composed of immunoglobulin (Ig)-like domains and fibronectin type III (FN-III)-like domains. The gene was highly homologous to human PTP delta (HPTP delta) and thus was named MPTP delta (murine counterpart of HPTP delta). The MPTP delta gene appeared to generate at least three species of mRNA, which differ in the composition of the extracellular domain: type A, one Ig-like and four FN-III-like domains; type B, one Ig-like and eight FN-III-like domains; and type C, three Ig-like and eight FN-III-like domains. Interestingly, the 5' untranslated region and the leader peptide of types A and B were completely different from those of type C. Northern (RNA) blot analysis demonstrated that brain, kidney, and heart cells express three mRNA species of about 7 kb. Antibody directed against part of the extracellular domain of type A MPTP delta recognized a 210-kDa protein in brain and kidney lysates. In situ hybridization of brain samples revealed that MPTP delta mRNA is present in the hippocampus, thalamic reticular nucleus, and piriform cortex, where some Src family PTKs have been also demonstrated to exist. Although MPTP delta mRNA was not detected in lymphoid tissues, all of the pre-B-cell lines tested and one of three B-cell lines tested expressed MPTP delta mRNA, whereas antibody-producing B-cell hybridomas and T-cell and macrophage lines did not. Finally, the MPTP delta locus was tightly linked to the brown (b) locus on mouse chromosome 4.

Abstract 19622: Trans-apical Off-pump Mitral Valve Repair With Neochords Implantation: One Year Clinical and Echocardiographic Follow-up

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Andrea Colli ◽  
Laura Besola ◽  
Lorenzo Bagozzi ◽  
Erica Manzan ◽  
Eleonora Bizzotto ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Type A ◽  
Mitral Valve Regurgitation ◽  
Disease Type ◽  
Reverse Remodeling ◽  
Off Pump ◽  
Single Centre Study ◽  
Type C ◽  
One Year

Introduction: TOP-MINI is a new micro invasive surgical procedure to treat degenerative mitral valve regurgitation due to flail/prolapse. Hypothesis: This prospective single centre study sought to assess the safety and effectiveness of the TOP-MINI procedure up to one year follow-up. Methods: Clinical and Echocardiographic outcomes were evaluated at 1, 3, 6 months and 1 year follow-up for all patients underwent TOP-MINI procedure from November 2013 to March 2015. Procedural success was defined as residual MR≤2+ at any time. Results: Sixty-one patients were treated during study period. One year survival was 96.7±2.3%. Freedom from MR>2+ is shown in figure 1 Panel A, Freedom from MR>2+ according to valve anatomy (Type A isolated P2 disease, Type B posterior multisegment disease, Type C anterior or bileaflet and/or calcified disease) is shown in Figure 1 Panel B. Freedom from MR>2+ according to STS risk profile is shown in Figure 2. The trend of Echocardiographic parameters is shown in Figure 3. Conclusions: TOP-MINI is a safe and effective procedure at 1 year FU. Residual MR is influenced by valve anatomy showing good results in Type A and B patients. Future techniques refinements are needed in order to improve outcomes of Type C patients. The lack of annuloplasty procedure does not influence negatively left ventricle reverse remodeling.

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