Dosimetric characterization of the 60Co BEBIG Co0.A86 high dose rate brachytherapy source using PENELOPE

⁶⁰Co sources are being used as an alternative to ¹⁹²Ir sources in high dose rate brachytherapy treatments. In a recent document from AAPM and ESTRO, a consensus dataset for the ⁶⁰Co BEBIG (model Co0.A86) high dose rate source was prepared by using results taken from different publications due to discrepancies observed among them. The aim of the present work is to provide a new calculation of the dosimetric characteristics of that ⁶⁰Co source according to the recommendations of the AAPM and ESTRO report. Radial dose function, anisotropy function, air-kerma strength, dose rate constant and absorbed dose rate in water have been calculated and compared to the results of previous works. Simulations using the two different geometries considered by other authors have been carried out and the effect of the cable density and length has been studied.     

The interaction domain of the redox protein adrenodoxin is mandatory for binding of the electron acceptor CYP11A1, but is not required for binding of the electron donor adrenodoxin reductase

Adrenodoxin (Adx) is a [2Fe-2S] ferredoxin involved in electron transfer reactions in the steroid hormone biosynthesis of mammals. In this study, we deleted the sequence coding for the complete interaction domain in the Adx cDNA. The expressed recombinant protein consists of the amino acids 1-60, followed by the residues 89-128, and represents only the core domain of Adx (Adx-cd) but still incorporates the [2Fe-2S] cluster. Adx-cd accepts electrons from its natural redox partner, adrenodoxin reductase (AdR), and forms an individual complex with this NADPH-dependent flavoprotein. In contrast, formation of a complex with the natural electron acceptor, CYP11A1, as well as electron transfer to this steroid hydroxylase is prevented. By an electrostatic and van der Waals energy minimization procedure, complexes between AdR and Adx-cd have been proposed which have binding areas different from the native complex. Electron transport remains possible, despite longer electron transfer pathways.     

Measurement of oxygen concentrations in the intact beating heart using electron paramagnetic resonance spectroscopy: A technique for measuring oxygen concentrationsin situ

Electron paramagnetic resonance (EPR) spectroscopy can be applied to measure oxygen concentrations in cells and tissues. Oxygen is paramagnetic, and thus it interacts with a free radical label resulting in a broadening of the observed linewidth. Recently we have developed instrumentation in order to enable the performance of EPR spectroscopy and EPR oximetry in the intact beating heart. This spectrometer consists of 1–2-GHz microwave bridge with the source locked to the resonant frequency of a specially designed lumped circuit resonator. This technique is applied to measure the kinetics of the uptake and clearance of different free radical labels. It is demonstrated that this technique can be used to noninvasively measure tissue oxygen concentration. In addition, rapid scan EPR measurements can be performed enabling gated millisecond measurements of oxygen concentrations to be performed over the cardiac cycle. Thus, low-frequency EPR spectroscopy offers great promise in the study of tissue oxygen concentrations and the role of oxygen in metabolic control.     

Estimation of electron density,effective atomic number and stopping power ratio using dual-layer computed tomography for radiotherapy treatment planning

PurposeAssess the accuracy for quantitative measurements of electron density relative to water (ρ_e/ρ_e,w), effective atomic number (Z_eff) and stopping power ratio relative to water (SPR_w) using a dual-layer computed tomography (DLCT) system.Methods and MaterialsA tissue characterization phantom was scanned using DLCT with varying scanning parameters (i.e., tube voltage, rotation time, CTDI_vol, and scanning mode) and different reference materials. Then, electron density ρ_e/ρ_e,w and atomic number Z_eff images were reconstructed, and their values were determined for each reference materials. Based on these two values, SPR_w was calculated. Finally, the percent error (PE) against the theoretical values was calculated for reference materials.ResultsSignificant linear relationships (p < 0.001) were observed between the measured and theoretical ρ_e/ρ_e,w (r = 1.000), Z_eff (r = 0.989) and SPR_w (r = 1.000) values. The PE for each reference material varied from –2.0 to 1.2% (mean, <0.1%) for electron density ρ_e/ρ_e,w, from –6.4 to 8.0% (mean, –2.0%) for atomic number Z_eff, and from –2.0 to 1.9% (mean, 0.3%) for stopping power ratio SPR_w. The mean PE of ρ_e/ρ_e,w (<0.1%), Z_eff (<–2.5%) and SPR_w (<0.4%) was verified across the variation of scanning parameters (p > 0.85).ConclusionsDLCT provides a reasonable accuracy in the measurements of ρ_e/ρ_e,w, Z_eff and SPR_w, and could enhance radiotherapy treatment planning and the subsequent outcomes.     

Ostracoda as bioindicators of anthropogenic impact in salt lakes,saltpans, and a lagoon: A case study from the Gulf of Saros coast (NE Aegean Sea), Turkey

The study area consists of wetlands and semi-wetlands (saltpan and salt lakes) that are separated from the Gulf of Saros in the northeastern Aegean Sea by a littoral cordon. Twenty-four samples were collected from the Enez Salt Lake; Dalyan, Enez Gala, Kuvalak, Isik, and Tasalti Lakes; Vakif and Erikli Saltpans; and Karagol Lagoon. The overall distribution of the sediment sizes reveals that they consist predominantly of mud and sand and a mixture of mud, sand, and gravel. The average proportion of gravel size particles is 8.36%. Feldspar and mica are abundant in sand and gravel-sized materials. Ecological conditions of these coastal areas were assessed on the basis of ostracod assemblages that can be considered as useful bioindicators and depend on water depth, temperature, and salinity. In this context, the effects of physical and chemical properties of the environment, geochemistry of the sediment, and anthropogenic impact on the meiofauna, in particular ostracoda, was here evaluated. Cyprideis torosa Jones, a cosmopolitan species of ostracoda, was found in salt lakes. Other species of ostracoda were shown to be affected by environmental conditions. The toxicity of some heavy metals in the saltpans, salt lakes, and hypersaline lagoons was evaluated. Lake Dalyan and Erikli Saltpan display high toxicity for Cu and Cd levels. The distribution of hydrocarbon pollution of terrestrial origin was determined.     

Thermodynamic and kinetic properties of the outer membrane cytochrome OmcF,a key protein for extracellular electron transfer in Geobacter sulfurreducens

Gene knock-out studies on Geobacter sulfurreducens have shown that the monoheme c-type cytochrome OmcF is essential for the extracellular electron transfer pathways involved in the reduction of iron and uranium oxy-hydroxides, as well as, on electricity production in microbial fuel cells. A detailed electrochemical characterization of OmcF was performed for the first time, allowing attaining kinetics and thermodynamic data. The heterogeneous electron transfer rate constant was determined at pH?7 (0.16?±?0.01?cm?s^?1) indicating that the protein displays high electron transfer efficiency compared to other monoheme cytochromes. The pH dependence of the redox potential indicates that the protein has an important redox-Bohr effect in the physiological pH range for G. sulfurreducens growth. The analysis of the structures of OmcF allowed us to assign the redox-Bohr centre to the side chain of His⁴⁷ residue and its pK_a values in the reduced and oxidized states were determined (pK_ox?=?6.73; pK_red?=?7.55). The enthalpy, entropy and Gibbs free energy associated with the redox transaction were calculated, pointing the reduced form of the cytochrome as the most favourable. The data obtained indicate that G. sulfurreducens cells evolved to warrant a down-hill electron transfer from the periplasm to the outer-membrane associated cytochrome OmcF.     

Capillary gas chromatography using electron capture or selected ion monitoring detection for the determination of muramic acid,diaminopimelic acid and the ratio of d/l-alanine in bacteria

Gas chromatographic analyses of muramic acid, diaminopimelic acid and D-alaline, which are specific components of the bacterial cell wall, have been performed using electron capture or selected ion monitoring detection. Intact cells or peptidogylycan preparations were hydrolyzed in HCl and DCl. After purification by cation exchange chromatography, followed by conversion to the N-heptafluobutyrliso-butyl esters, the components were separated on a 25 m fused silica column coated with SE-54 or on a chiral glass capillary column.The detection limits for muramic acid and diaminopimelic acid were about 10 pg using either detection method and the procedure has the potential sensitivity for detecting about 3 × 10⁵ bacterial cells, e.g., Escherichia coli.Mass spectrometric determination of the d/l ratio of alamine in intact cells of Group A streptococci, type M 15 and in peptidogylcan preparations thereof indicated the proportions 10.2% and 10.5% of D-alanine, respectively. The values uncorrected for racemization during acid hydrolysis were 10.3% and 10.7%, respectively.     

Kinetic data for redox reactions of cytochrome c with Fe(CN)5X complexes and the question of association prior to electron transfer

Use of rigorous equilibration kinetics to evaluate rate constants for the Fe(CN)6 4- reduction of horse-heart cytochrome c in the oxidized form, cyt c (III), has shown that limiting kinetics do not apply with concentrations of Fe(CN)6 4- (the reactant in excess) in the range 2-10 x 10(-4) M, I = 0.10 M (NaCl). The reaction conforms to a first-order rate law in each reactant, and at 25 degrees C, pH 7.2 (Tris), it is concluded that K for association prior to electron transfer is less than 200 M-1. From previous studies at 25 degrees C, ph 7.0 (10(-1) M phosphate), I = 0.242 M (NaCl), a value K = 2.4 x 10(3) M-1 has been reported. Had such a value applied, some or all of the redox inactive complexes Mo(CN)8 4-, Co(CN)6 3-, Cr(CN)6 3-, Zr(C2O4)4 4- present in amounts 5-20 x 10(-4) M would have been expected to associate at the same site and partially block the redox process. No effect on rats was observed. With the reductants Fe(CN)5(4-NH2-py)3- and Fe(CN)5(imid)3-, reactions proceeded to greater than 90% completion and rate laws were again first order in each reactant. Rate constants (M-1 sec-1) at 25 degrees C, pH 7.2 (Tris), I = 0.10 M (NaCl), are Fe(CN)6 4- (3.5 x 10(4)), Fe(CN)5(4-NH2py)3- (6.7 x 10(5), and Fe(CN)5(imid)3- (4.2 x 10(5). Related reactions in which cyt c(II) is oxidized are also first order in each reactant, Fe(CN)6 3- (9.1 x 10(6)), Fe(CN)5(NCS)3- (1.3 x 10(6)), Fe(CN)5(4-NH2py)2- (3.8 x 10(6) at pH 9.4), and Fe(CN)5(NH3)2- (2.75 x 10(6) at ph 8). Redox inactive Co(CN)6 3- (1.0 x 10(-3) M) has no effect on the reaction of Fe(CN)6 3- which suggests that a recent interpretation for the Fe(CN)6 3- oxidation of cyt c(II), I = 0.07 M, may also require reappraisal.     

The detection of the sialoglycoprotease gene and assay for sialoglycoprotease activity among isolates of Pasteurella haemolytica A1 strains, serotypes A13, A14, T15 and A16

Abstract Polymerase chain reaction (PCR) using specific primers to the sialoglycoprotease gene ( gcp ) of Pasteurella haemolytica biotype A, serotype 1 amplified a 1-kb fragment from each of P. haemolytica serotypes A7, A13, A14 and A16, but not T15; which was confirmed by Southern blot hybridization analysis. Using a sialoglycoprotease (Gcp) activity assay, Gcp activity was found in serotypes A13, A14 and A16. Inclusion of these three serotypes confirms that all recognized A biotypes are positive for both gcp gene and activity, with the exception of serotype A11 (which has a different genetic organization and exhibits no Gcp activity). Furthermore, all recognized T biotypes are negative for both the gene and Gcp activity.     

伤寒沙门菌与甲、乙、丙副伤寒沙门菌质控血清的制备

应用免疫学原理,将伤寒沙门菌O901、H901和甲、乙、丙型副伤寒沙门菌分别制成全菌体抗原,免疫实验兔获取免疫血清。依据伤寒沙门菌和副伤寒沙门菌的抗原成分的异同性,选择适当的吸收菌除去免疫血清中的交叉反应抗体和类属凝集素,而保留其特异性的抗体。通过对诊断菌液的验证试验,证实吸收充分的免疫血清具有质控血清的特性。具备可靠性能的质控血清,适用于伤寒沙门菌与副伤寒沙门菌的菌种检定及其效价检测;亦有利于肥达氏诊断菌液的质量控制。     

The relationship between the redox state of Q A and photosynthesis in leaves at various carbon-dioxide,oxygen and light regimes

The response of chlorophyll fluorescence elicited by a low-fluence-rate modulated measuring beam to actinic light and to superimposed 1-s pulses from a high-fluence-rate light source was used to measure the redox state of the primary acceptor Q _A of photosystem II in leaves which were photosynthesizing under steady-state conditions. The leaves were exposed to various O₂ and CO₂ concentrations and to different energy fluence rates of actinic light to assess the relationship between rates of photosynthesis and the redox state of Q _A. Both at low and high fluence rates, the redox state of Q _A was little altered when the CO₂ concentration was reduced from saturation to about 600 l·l^-1 although photosynthesis was decreased particularly at high fluence rates. Upon further reduction in CO₂ content the amount of reduced Q _A increased appreciably even at low fluence rates where light limited CO₂ reduction. Both in the presence and in the absence of CO₂, a more reduced Q _A was observed when the O₂ concentration was below 2%. Q _A was almost fully reduced when leaves were exposed to high fluence rates under nitrogen. Even at low fluence rates, Q _A was more reduced in shade leaves of Asarum europaeum and Fagus sylvatica than in leaves of Helianthus annuus and Fagus sylvatica grown under high light. Also, in shade leaves the redox state of Q _A changed more during a transition from air containing 350 l·l^-1 CO₂ to CO₂-free air than in sun leaves. The results are discussed with respect to the energy status and the CO₂-fixation rate of the leaves.Abbreviations and symbols L 1,2 first and second actinic light beam - Q _A primary acceptor of photosystem II - q _Q Q-quenching     

A double-immunostaining procedure using colloidal gold, ferritin, and peroxidase as markers for simultaneous detection of two hypophysial hormones with the electron microscope

For simultaneous ultrastructural localization of intracellular peptides, protein A-gold techniques or immuno-gold techniques have generally been applied. The present study reports a double immunostaining procedure for simultaneous visualization of two hypophysial hormones (prolactin and corticotropin) on a single ultrathin section of the pars distalis of an amphibian. Prolactin and corticotropin antisera were respectively raised in guinea pigs and rabbits and were applied simultaneously to ultrathin sections. Antigenic binding sites were detected under the electron microscope using differently labeled species-specific secondary antisera raised in goats or sheep. Three labels (gold particles, ferritin, peroxidase) were checked for double labeling. The combinations investigated were: 1) two gold preparations or IgG-gold labeled with different-sized gold particles; 2)IgG-gold and IgG-ferritin; 3) IgG-gold and IgG-PAP (peroxidase-antiperoxidase). The double-immunostaining procedures described here have proved useful in the simultaneous ultrastructural localizations of two intracellular antigens on a single tissue section. These procedures constitute a basis for the development of triple immunostaining methods.     

Structural comparison in solution of a native and retro peptide derived from the third helix of Staphylococcus aureus protein A,domain B: retro peptides,a useful tool for the discrimination of helix stabilization factors dependent on the peptide chain orientation

A peptide fragment corresponding to the third helix of Staphylococcus Aureus protein A, domain B, was chosen to study the effect of the main‒chain direction upon secondary structure formation and stability, applying the retro‒enantio concept. For this purpose, two peptides consisting of the native (Ln) and reversed (Lr) sequences were synthesized and their conformational preferences analysed by CD and NMR spectroscopy. A combination of CD and NMR data, such as molar ellipcitity, NOE connectivities, Hα and NH chemical shifts, ³J_αN coupling constants and amide temperature coefficients indicated the presence of nascent helices for both Ln and Lr in water, stabilized upon addition of the fluorinated solvents TFE and HFIP. Helix formation and stabilization appeared to be very similar in both normal and retro peptides, despite the unfavourable charge–macrodipole interactions and bad N-capping in the retro peptide. Thus, these helix stabilization factors are not a secondary structure as determined for this specific peptide. In general, the synthesis and confirmational analysis of peptide pairs with opposite main‒chain directions, normal and retro peptides, could be useful in the determination of secondary structure stabilization factors dependent on the direction. © 1997 European Peptide Society and John Wiley & Sons, Ltd.     

GBF1, a guanine nucleotide exchange factor for ADP-ribosylation factors,is localized to the cis-Golgi and involved in membrane association of the COPI coat

Formation of coated carrier vesicles, such as COPI-coated vesicles from the cis -Golgi, is triggered by membrane binding of the GTP-bound form of ADP-ribosylation factors. This process is blocked by brefeldin A, which is an inhibitor of guanine nucleotide exchange factors for ADP-ribosylation factor. GBF1 is one of the guanine nucleotide-exchange factors for ADP-ribosylation factor and is localized in the Golgi region. In the present study, we have determined the detailed subcellular localization of GBF1. Immunofluorescence microscopy of cells treated with nocodazole or incubated at 15 °C has suggested that GBF1 behaves similarly to proteins recycling between the cis -Golgi and the endoplasmic reticulum. Immunoelectron microscopy has revealed that GBF1 localizes primarily to vesicular and tubular structures apposed to the cis -face of Golgi stacks and minor fractions to the Golgi stacks. GBF1 overexpressed in cells causes recruitment of class I and class II ADP-ribosylation factors onto Golgi membranes. Furthermore, overexpressed GBF1 antagonizes various effects of brefeldin A, such as inhibition of membrane recruitment of ADP-ribosylation factors and the COPI coat, and redistribution of Golgi-resident and itinerant proteins. These observations indicate that GBF1 is involved in the formation of COPI-coated vesicles from the cis -Golgi or the pre-Golgi intermediate compartment through activating ADP-ribosylation factors.     

Preclinical pharmacokinetics of MHAA4549A,a human monoclonal antibody to influenza A virus,and the prediction of its efficacious clinical dose for the treatment of patients hospitalized with influenza A

MHAA4549A is a human immunoglobulin G1 (IgG1) monoclonal antibody that binds to a highly conserved epitope on the stalk of influenza A hemagglutinin and blocks the hemagglutinin-mediated membrane fusion in the endosome, neutralizing all known human influenza A strains. Pharmacokinetics (PK) of MHAA4549A and its related antibodies were determined in DBA/2J and Balb-c mice at 5 mg/kg and in cynomolgus monkeys at 5 and 100 mg/kg as a single intravenous dose. Serum samples were analyzed for antibody concentrations using an ELISA and the PK was evaluated using WinNonlin software. Human PK profiles were projected based on the PK in monkeys using species-invariant time method. The human efficacious dose projection was based on in vivo nonclinical pharmacological active doses, exposure in mouse infection models and expected human PK. The PK profiles of MHAA4549A and its related antibody showed a linear bi-exponential disposition in mice and cynomolgus monkeys. In mice, clearance and half-life ranged from 5.77 to 9.98 mL/day/kg and 10.2 to 5.76 days, respectively. In cynomolgus monkeys, clearance and half-life ranged from 4.33 to 4.34 mL/day/kg and 11.3 to 11.9 days, respectively. The predicted clearance in humans was ～2.60 mL/day/kg. A single intravenous dose ranging from 15 to 45 mg/kg was predicted to achieve efficacious exposure in humans. In conclusion, the PK of MHAA4549A was as expected for a human IgG1 monoclonal antibody that lacks known endogenous host targets. The predicted clearance and projected efficacious doses in humans for MHAA4549A have been verified in a Phase 1 study and Phase 2a study, respectively.