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In our earlier works, we have shown that the rate-limiting steps, associated with the dark-to-light transition of Photosystem II (PSII), reflecting the photochemical activity and structural dynamics of the reaction center complex, depend largely on the lipidic environment of the protein matrix. Using chlorophyll-a fluorescence transients (ChlF) elicited by single-turnover saturating flashes, it was shown that the half-waiting time (Δτ 1/2) between consecutive excitations, at which 50% of the fluorescence increment was reached, was considerably larger in isolated PSII complexes of Thermostichus (T.) vulcanus than in the native thylakoid membrane (TM). Further, it was shown that the addition of a TM lipid extract shortened Δτ1/2 of isolated PSII, indicating that at least a fraction of the 'missing' lipid molecules, replaced by detergent molecules, caused the elongation of Δ τ1/2. Here, we performed systematic experiments to obtain information on the nature of TM lipids that are capable of decreasing Δ τ1/2. Our data show that while all lipid species shorten Δ τ1/2, the negatively charged lipid phosphatidylglycerol appears to be the most efficient species - suggesting its prominent role in determining the structural dynamics of PSII reaction center. [ABSTRACT FROM AUTHOR]

Photosystem II (PSII) is the pigment–protein complex driving the photoinduced oxidation of water and reduction of plastoquinone in all oxygenic photosynthetic organisms. Excitations in the antenna chlorophylls are photochemically trapped in the reaction center (RC) producing the chlorophyll–pheophytin radical ion pair P+ Pheo−. When electron donation from water is inhibited, the oxidized RC chlorophyll P+ acts as an excitation quencher, but knowledge on the kinetics of quenching is limited. Here, we used femtosecond transient absorption spectroscopy to compare the excitation dynamics of PSII with neutral and oxidized RC (P+). We find that equilibration in the core antenna has a major lifetime of about 300 fs, irrespective of the RC redox state. Two-dimensional electronic spectroscopy revealed additional slower energy equilibration occurring on timescales of 3–5 ps, concurrent with excitation trapping. The kinetics of PSII with open RC can be described well with previously proposed models according to which the radical pair P+ Pheo− is populated with a main lifetime of about 40 ps, which is primarily determined by energy transfer between the core antenna and the RC chlorophylls. Yet, in PSII with oxidized RC (P+), fast excitation quenching was observed with decay lifetimes as short as 3 ps and an average decay lifetime of about 90 ps, which is shorter than the excited-state lifetime of PSII with open RC. The underlying mechanism of this extremely fast quenching prompts further investigation. [ABSTRACT FROM AUTHOR]

Background: A large number of studies have proved that prostate-specific membrane antigen-positron emission tomography/computer tomography (PSMA-PET/CT) provides excellent accuracy in primary staging and restaging of prostate cancer. Less data exist with PSMA-single photon emission computed tomography (SPECT)/CT investigations. Objective: The aim of this study was to evaluate the performance of [99mTc]Tc-PSMA-I&S (for imaging and surgery) in prostate cancer. Design and methods: We retrospectively analysed PSMA-SPECT/CT scans of 20 healthy volunteers and 100 male patients with prostate cancer. All of them had histologically confirmed prostate cancer. In all, 28 patients were examined for primary staging and 72 for biochemical recurrence or progressive disease. Whole body SPECT/CT imaging was carried out 6 h after the intravenous administration of 666 ± 102 MBq [99mTc]Tc-PSMA-I&S. Images were evaluated visually and semi-quantitatively. Results: Patient-based sensitivity, specificity, positive predictive value, negative predictive value and accuracy for primary prostate cancer were 86%, 100%, 100%, 83% and 92%, respectively. For detecting metastases in primary staging, these values were 88%, 100%, 100%, 85% and 93%, respectively. The radiopharmaceutical uptake of primary prostate cancer was significantly higher than in normal prostate. The patient-based sensitivity, specificity, positive predictive value, negative predictive value and accuracy of the method in the visualization of local recurrence were 67%, 100%, 100%, 86% and 89%, and for detecting metastases in restaging were 91%, 92%, 98%, 75% and 91%, respectively. In restaging, detection rates were 37% under prostate-specific antigen level of 1 ng/mL, 74% between 1 and 5 ng/mL and 80% >5 ng/mL. Conclusion: [99mTc]Tc-PSMA-I&S-SPECT/CT can be easily integrated into the routine diagnostic practice, and it provides usable data in primary staging and restaging of prostate cancer. Quantitative assessment of PSMA-SPECT/CT has the potential to be used to differentiate between physiological and pathological intraprostatic tracer uptake. [ABSTRACT FROM AUTHOR]

High soil salinity is a global problem in agriculture that directly affects seed germination and the development of the seedlings sown deep in the soil. To study how salinity affected plastid ultrastructure, leaf segments of 11‐day‐old light‐ and dark‐grown (etiolated) wheat (Triticum aestivum L. cv. Mv Béres) seedlings were floated on Hoagland solution, 600 mM KCl:NaCl (1:1) salt or isosmotic polyethylene glycol solution for 4 h in the dark. Light‐grown seedlings were also treated in the light. The same treatments were also performed on etio‐chloroplasts of etiolated seedlings greened for different time periods. Salt stress induced slight to strong changes in the relative chlorophyll content, photosynthetic activity, and organization of thylakoid complexes. Measurements of malondialdehyde contents and high‐temperature thermoluminescence indicated significantly increased oxidative stress and lipid peroxidation under salt treatment, except for light‐grown leaves treated in the dark. In chloroplasts of leaf segments treated in the light, slight shrinkage of grana (determined by transmission electron microscopy and small‐angle neutron scattering) was observed, while a swelling of the (pro)thylakoid lumen was observed in etioplasts. Salt‐induced swelling disappeared after the onset of photosynthesis after 4 h of greening. Osmotic stress caused no significant alterations in plastid structure and only mild changes in their activities, indicating that the swelling of the (pro)thylakoid lumen and the physiological effects of salinity are rather associated with the ionic component of salt stress. Our data indicate that etioplasts of dark‐germinated wheat seedlings are the most sensitive to salt stress, especially at the early stages of their greening. [ABSTRACT FROM AUTHOR]

Rate-limiting steps in the dark-to-light transition of Photosystem II (PSII) were discovered by measuring the variable chlorophyll-a fluorescence transients elicited by single-turnover saturating flashes (STSFs). It was shown that in diuron-treated samples: (i) the first STSF, despite fully reducing the QA quinone acceptor molecule, generated only an F1(

Photosystem II (PSII) uses solar energy to oxidize water and delivers electrons for life on Earth. The photochemical reaction center of PSII is known to possess two stationary states. In the open state (PSIIO), the absorption of a single photon triggers electron-transfer steps, which convert PSII into the charge-separated closed state (PSIIC). Here, by using steady-state and time-resolved spectroscopic techniques on Spinacia oleracea and Thermosynechococcus vulcanus preparations, we show that additional illumination gradually transforms PSIIC into a light-adapted charge-separated state (PSIIL). The PSIIC-to-PSIIL transition, observed at all temperatures between 80 and 308 K, is responsible for a large part of the variable chlorophyll- a fluorescence (F v) and is associated with subtle, dark-reversible reorganizations in the core complexes, protein conformational changes at noncryogenic temperatures, and marked variations in the rates of photochemical and photophysical reactions. The build-up of PSIIL requires a series of light-induced events generating rapidly recombining primary radical pairs, spaced by sufficient waiting times between these events—pointing to the roles of local electric-field transients and dielectric relaxation processes. We show that the maximum fluorescence level, F m, is associated with PSIIL rather than with PSIIC, and thus the F v /F m parameter cannot be equated with the quantum efficiency of PSII photochemistry. Our findings resolve the controversies and explain the peculiar features of chlorophyll- a fluorescence kinetics, a tool to monitor the functional activity and the structural-functional plasticity of PSII in different wild-types and mutant organisms and under stress conditions. [ABSTRACT FROM AUTHOR]

Copyright of Hungarian Medical Journal / Orvosi Hetilap is the property of Akademiai Kiado and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hungarian Medical Journal / Orvosi Hetilap is the property of Akademiai Kiado and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In response to environmental changes, the photosynthetic bacterium Rubrivivax gelatinosus (Rvx.) can switch from a planktonic lifestyle to a phototrophic biofilm. Like in critical phenomena, the colonization and sedimentation of the cells is abrupt and hard to predict causally, and the underlying biophysics of the mechanisms involved is not known. Herein, we report basic experimental observations and quantitative explanations as keys to understanding microbial turnover of aggregates. (1) The moment of sedimentation can be controlled by the height of the tube of cultivation, by the concentrations of externally added Ficoll (a highly branched polymer) and/or of internally produced polysaccharides (constituents of the biofilm). (2) The observed translational diffusion coefficient of the planktonic bacteria is the sum of diffusion coefficients coming from random Brownian and twitching movements of the bacteria and amounts to 14 (μm)2/s. (3) This value drops hyperbolically with the association number of the cell aggregates and with the concentration of the exopolysaccharides in the biofilm. In the experiments described herein, their effects could be separated. (4) The critical conditions of colonization and sinking of the cells will be achieved if the height of the tube meets the scale height that is proportional to the ratio of the diffusion coefficient and the net mass of the bacterium. The decisive role of the web-like structure of a biofilm, the organization of bacteria from loose cooperativity to solid aggregation, and the possible importance of similar controls in other phototrophic microorganisms are discussed. [ABSTRACT FROM AUTHOR]

99m Tc-PSMA I&S is a prostate-specific membrane antigen (PSMA) tracer that can be used for planar and SPECT/CT γ-imaging and radioguided surgery. The primary aim of this study was to estimate the dosimetry of 99m Tc-PSMA I&S using a hybrid method (sequential γ-planar imaging and 1 single SPECT/CT) in healthy volunteers. The secondary aim was to depict the tracer biodistribution and tumor-to-background ratios (TBRs) in patients with prostate cancer (PCa). Methods: Dosimetry of 99m Tc-PSMA I&S was investigated in 4 healthy volunteers. Whole-body planar imaging was acquired at 1, 2, 3, 6, and 24 h and SPECT/CT at 6 h after tracer injection. Contours of organs were drawn on all acquisitions to determine organ activity at each time point. Absorbed dose was estimated using 2 methods: independent curve-fitting manual method (Levenberg-Marquardt-based algorithm using dose factors from RAdiation Dose Assessment Resource [RADAR] website) and OLINDA/EXM software (version 2.0; HERMES Medical Solutions). Biodistribution of 99m Tc-PSMA I&S was assessed in 10 patients with PCa on SPECT/CT images at 6 h. Tumor uptake (SUV max ), and TBR (tumor SUV max /background organ SUV mean ) using muscle (T/M), bladder (T/B), and intestine (T/I) as background organs were determined. Results: The mean injected activity of 99m Tc-PSMA I&S was 717 MBq (range: 562-828 MBq). No adverse events related to the injection of 99m Tc-PSMA I&S were reported. The average radiation effective dose was 0.0055 mSv/MBq with the RADAR manual method and 0.0052 mSv/MBq with OLINDA/EXM. Total body effective dose ranged between 3.33-4.42 and 3.11-4.23 mSv, respectively. All PCa patients showed high tracer uptake in primary and metastatic lesions with T/M, T/B, and T/I ranging from 5.29-110, 0.11-7.02, and 0.96-16.30, respectively. Conclusion: Effective doses of 99m Tc-PSMA I&S were comparable to those known for most of the 99m Tc tracers and was lower than for the 68 Ga-labeled and 18 F-labeled agents. 99m Tc-PSMA I&S SPECT/CT showed high TBR in PCa patients. This study can provide required data for translation and approval of 99m Tc-PSMA I&S by regulatory agencies., (© 2021 by the Society of Nuclear Medicine and Molecular Imaging.)

This article presents the diagnostic and therapeutic nuclear medicine methods for neuroendocrine tumors in accordance with current guidelines. The paper begins with a general characterization of neuroendocrine tumors, followed by a broad introduction to laboratory and imaging diagnostic techniques, and a detailed discussion of peptide receptor radionuclide therapy and meta-iodobenzylguanidine treatment. Finally, the article provides an insight into current research and future developments.

Introduction: Large-vessel vasculitis has non-specific clinical symptoms, which can delay the diagnosis. Early recognition and treatment of the disease can help to avoid late complications. 18 F-FDG-PET can detect the inflammation of the vessel wall in the early stage of the disease with high sensitivity. CT is used to localize vasculitis. Aim: To examine the performance of 18 F-FDG-PET/CT in patients with suspected large-vessel vasculitis, during relapse and remission, focusing on disease activity and extent. Method: 43 patients were evaluated. They were classified according to the clinical questions: steroid-naive suspected vasculitis, suspected vasculitis on steroid treatment, patients with relapse and in remission. We examined 10 cancer patients in control. We carried out visual and quantitative analysis of the 18 F-FDG uptake of vessel walls. During quantitative evaluation, we determined standardised uptake values (SUVmax) of vessel wall segments compared to liver. Results: We found active disease in 5 patients examined for primary diagnosis, moreover, in 5 patients with relapse. The disease involved 3 or more vessel segments in fifty percent of the active cases. In the visually active group, the SUVmax was significantly lower in patients on steroid treatment than in steroid-naive cases (1.17 ± 0.11 vs. 1.43 ± 0.29; p = 0.005). We confirmed remission in 2 cases after therapy. In the inactive group, we found other types of inflammatory disorders in 8 cases. Conclusion: 18 F-FDG-PET/CT is an effective diagnostic tool for large-vessel vasculitis, and can be used to determine the activity and extent of the disease. Steroid treatment influences the 18 F-FDG-uptake of vessel wall. Orv Hetil. 2020; 161(20): 829-838., (© 2020 Szerző(k)/The Author(s).)

Introduction: The prostate-specific membrane antigen (PSMA) is a transmembrane protein, that is highly expressed on the surface of prostate cancer cells. In the last few years, several PSMA-specific ligands have been developed, that can be successfully used to detect primary prostate cancer, tumor recurrences and metastases as well., Aim: The goal of our work was to examine the clinical application of a 99m technetium-labeled PSMA-radiopharmaceutical as part of the routine diagnostics of prostate cancer., Method: We examined 15 male patients with verified prostate adenocarcinoma with suspicion of progression or recurrence of the disease. We performed whole-body PSMA-SPECT/CTs and multiparametric MRIs of the prostate and the pelvic regions within a week. We used 99m Tc-mas3-y-nal-k(Sub-KuE) for the PSMA-SPECT scans. The images were visually evaluated by independent observers. The results were compared with the follow-up bone scintigraphies as well., Results: Twenty-two PSMA-positive lesions were found. Nine of them were localized outside, 13 were within the MRI's field of view. From these 13 lesions, 7 matched with the SPECT/CT results and in 5 cases the MRI images showed no abnormalities. In one case, bone metastasis was suspected on the MRI scan but there was no corresponding pathological tracer uptake on the SPECT images. In two patients, none of the examinations showed signs of prostate malignancy. Four patients had PSMA-positive bone metastases. One of them had a matching PSMA/SPECT and bone scintigraphy result and in one case the PSMA examination showed metastasis in contrast to the negative bone scintigraphy., Conclusion: PSMA-SPECT/CT with 99m Tc-mas3-y-nal-k(Sub-KuE) is a promising diagnostic tool. This technique is capable of visualizing bone metastases and it can detect local recurrences and visceral metastases as well. Orv Hetil. 2018; 159(35): 1433-1440.