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Gebru, Elias,Damte, Dereje,Choi, Myung-Jin,Lee, Seung-Jin,Kim, Young-Hoan,Park, Seung Chun Elsevier 2012 Veterinary microbiology Vol.154 No.3
<P><B>Abstract</B></P><P>The antibacterial activity, selection of <I>Escherichia coli</I> (<I>E. coli</I>) mutants and mechanisms of fluoroquinolone resistance were investigated by integrating the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC) and <I>in vitro</I> dynamic model approaches. Difloxacin and orbifloxacin, for which the above information has been scarce, were used. A range of area under curve over a 24h interval (AUC<SUB>24h</SUB>)/MIC ratios and selected <I>E. coli</I> strains were investigated using the dynamic models. Continuous incubation for three days in the presence of difloxacin or orbifloxacin resulted in losses in <I>E. coli</I> susceptibility. An AUC<SUB>24h</SUB>/MIC (AUC<SUB>24h</SUB>/MPC)-dependent fluoroquinolone activity and selection of <I>E. coli</I> mutants was confirmed. Maximum losses in susceptibility occurred at AUC<SUB>24h</SUB>/MIC ratios of 54 (orbifloxacin) and 57.3 (difloxacin). AUC<SUB>24h</SUB>/MIC ratios of 169.8 (orbifloxacin) and 199.5 (difloxacin) were estimated to be protective against the selection of <I>E. coli</I> mutants, and the corresponding ratios based on AUC<SUB>24h</SUB>/MPC predictions were 34 (orbifloxacin) and 36.3 (difloxacin). When integrating our <I>in vitro</I> data with pharmacokinetic data in dogs, the conventional clinical doses of both drugs were found to be inadequate to attain the above protective values for 90% of the mutant subpopulation (AUC<SUB>24h</SUB>/MPC<SUB>90</SUB>). Both target mutations, esp. at codon 83 (Ser to Leu) of <I>gyrA</I>, and overexpression of efflux pumps contributed to resistance development, with mutants also showing decreased susceptibility to enrofloxacin and marbofloxacin. Additional studies would determine the role of mutations found outside the QRDR, at codon 24 of <I>gyrA</I>, and at codon 116 of <I>parC</I>, and establish the significance of these observations <I>in vivo</I>.</P>
Gebru, Elias,Lee, Joong-Su,Chang, Zhi-Qiang,Hwang, Mi-Hyun,Cheng, Henrique,Park, Seung-Chun American Society for Microbiology 2009 Antimicrobial Agents and Chemotherapy Vol.53 No.7
<B>ABSTRACT</B><P>The pharmacokinetics (PK) and pharmacodynamics (PD) of orbifloxacin were studied in beagle dogs after intravenous (i.v.) and intramuscular (i.m.) administration at a dose of 2.5 mg/kg body weight. An absolute bioavailability of 100.1% ± 4.76%, a terminal half-life of 4.23 ± 0.2 h and 3.95 ± 0.15 h after i.v. and i.m. administration, a steady-state volume of distribution of 1.61 ± 0.13 liters/kg, and clearance of 0.31 ± 0.03 liters/h/kg were observed. Orbifloxacin showed rapid, concentration-dependent killing against the <I>Escherichia coli</I>, <I>Staphylococcus aureus</I>, <I>Staphylococcus intermedius</I>, and <I>Proteus mirabilis</I> clinical isolates. Computations based on PK-PD analysis indicated that the recommended dose is unlikely to be clinically effective against some strains like <I>S. intermedius</I>. Therefore, a higher dose of orbifloxacin would be worthy of consideration for treatment of certain bacterial infections in dogs.</P>
Dielectric relaxation and ferroelectric phase transition in Sr4BiRTi4Nb6O30 (R ¼Sm, Eu) ceramics
Gebru Zerihun,Gaoshang Gong,Shuai Huang,Songliu Yuan 한국물리학회 2016 Current Applied Physics Vol.16 No.8
Sr4BiRTi4Nb6O30 (R ¼ Sm, Eu) ceramics with tetragonal tungsten bronze structure were prepared by the conventional solid state reaction method. The crystalline structure, microstructure, dielectric and ferroelectric properties of the ceramics were investigated. Structural analysis using the powder x-ray diffraction patterns revealed the formation of tetragonal tungsten bronze structure in space group P4bm. Columnar grains with a homogeneous distribution were formed in Sr4BiEuTi4Nb6O30 ceramics, while in Sr4BiSmTi4Nb6O30 ceramics the microstructure became inhomogeneous and some abnormal grains were also formed. The dielectric properties of the ceramics exhibited relaxor type phase transition which can be attributed to the random distribution of Bi and Sm/Eu ions at A1-sites and Ti and Nb ions at the B-sites of the TTB structure. The peak temperature shifted towards the higher temperatures and the magnitude of the dielectric constant decreased with increasing frequency. Moreover, the temperature of the dielectric maximum Tm increased as the radius of the R ion getting decreased. From the P-E hysteresis loops, remnant polarization of 0.83 mC/cm2 and 0.6 mC/cm2 were obtained for Sr4BiEuTi4Nb6O30 and Sr4BiSmTi4Nb6O30, respectively.
Effect of 60Co g-ray irradiation on electrical properties of Ti/Au/ GaAs1xNx Schottky diodes
Gebru Zerihun,Gaoshang Gong,Shuai Huang,Songliu Yuan,N. Al Saqri,J.F. Felix,M. Henini 한국물리학회 2016 Current Applied Physics Vol.16 No.8
Current-voltage (I-V), capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G/u-V-f) measurements at room temperature are used to study 50 kGy 60Co g-ray electrical properties irradiation dependence of Ti/Au/GaAs1xNx Schottky diodes with 0.2%; 0.4%; 0.8% and 1.2% nitrogen dilution. This g-ray irradiation induces a permanent damage that has increased ideality factor and series resistance for all samples. It was accompanied by a decrease in Schottky barrier height with nitrogen content up to 0.4%N and remained constant thereafter. Radiation was also found to degrade the reverse leakage current. At high frequency (1 MHz), capacitance and conductance decreased after radiation due to a decrease in net doping concentration. Interface state density and series resistance were determined from C-V-f and G/u-V-f characteristics using Hill-Coleman methods. Interface states density exponentially decreased with increasing frequency confirming the behavior of interface traps response to ac signal. Series resistance increases after irradiation is attributed to carrier's removal effect andmobility degradation. It has two peaks in the accumulation and inversion region for some diodes (0.4%N, 0.8%N). g-ray irradiation produced traps levels and recombination centers that reduce relaxation time. An increase in %N content can impede irradiation damagewith even some compensationwhen the percent of diluted nitrogen is high (1.2%N).
Adaptation and growth performance of different bamboo species in Dryland areas of Northern Ethiopia
Eyasu Gebru,Gebrewahid Yikunoamlak,Darcha Girmay,Kassa Hailemariam 한국산림과학회 2024 Forest Science And Technology Vol.20 No.2
Bamboos are among the large perennial grasses that are renowned for their remarkable vigor and quick development. However, the amount of bamboo available in natural settings is decreasing as a result of shifting agriculture, overexploitation, and forest fires. Furthermore, there is little genetic diversity in our country because just two species are found in a small number of agroecological zones. This makes it difficult to guarantee a steady supply of bamboo, despite its benefits to the environment and economy. Thus, the goal of this study was to evaluate the adaptability and growth performance of four bamboo species: Oxytenanthera abyssinica (A.Rich.) Munro, Phyllostachys edulis (Carrière) J Houz, Bambusa vulgaris Schrad. ex J.C. Wendl, and B-ambusa bambos (L) Voss'. The study was carried out at the Mekelle Agricultural Research Center compound for four years, from 2020 to 2023. Three replications of a strict RCBD design were used in the experiment. There were four plants each plot, for a total of 48 plants, and there was a three-meter gap between each plant and plot. A range of growth indicators, including new shoot emergence, culm diameter, internode length, culm height, and survival rate, were measured at three-month intervals in order to monitor changes among the species. B. bambos, B. vulgaris, and O. abyssinica showed no problems with survival or adaptation in the research locations, with the exception of small growth variances. Significant changes (p≤ 0.05) in the treatment parameters were shown by the statistical analysis. O. abyssinica displayed a noticeably greater quantity of freshly emerging bamboo shoots in comparison to other bamboo species. Conversely, P. edulis showed the lowest growth metrics in terms of internode length, culm height, culm diameter, and survival rate. P. edulis, B. vulgaris, O. abyssinica, and B. bambos had survival rates of 16.67 percent, 66.67 percent, 75 percent, and 91.67 percent, respectively. It is noteworthy that seasonal differences have a substantial impact on the height of culms and the growth of newly emergent shoots. B. vulgaris, B. bambos, and O. abyssinica all showed good growth and survival rates. As a result, it is advised to highlight and promote these species in related agroecological areas, as this can benefit multiple stakeholders’ livelihoods and economies.
Elias gebru,Seungjin Lee,Dereje Damte,Woosik Jo,Seungchun Park 한국버섯학회 2010 한국버섯학회지 Vol.8 No.4
Phellinus gilvus(PG) is a medicinal mushroom belonging to the Hymenochaetaceae basidiomycetes, and has advantages over many Phellinus species due to its short growth period (3 mo), making it cheaper to produce. In the current investigation, we determined the major components of the ethyl acetate extract of PG responsible for its biological activities and further compared the magnitude of the antioxidant/anti-inflammatory activities of components with the various fractional extracts of PG. As the results, the average total DPPH radical scavenging activities of both Fd and Fc of PG was 10 mg/mL, > 95%. Among the fractional extracts of PG, Fd had the greatest inhibitory activity with an IC50 value of 36.70㎍/mL, whereas Fb showed the lowest activity. PCA had even greater activity of NO inhibition than Fd with an IC50 value of 19.46㎍/mL. The mRNA expression of iNOS or COX-2 was nearly undetectable in the absence of LPS. However, LPS- stimulation markedly increased the expression of both iNOS and COX-2 genes. Fd inhibited the effect of LPS in a concentration-dependent manner. Six major compounds were identified from the ethyl acetate extract of PG, and protocatechualdehyde (PCA) was supposed to be the major phenolic compound of PG responsible for its DPPH free radical scavenging activity and its inhibitory effects on LPS-induced NO production in RAW264.7 cells. Further in vitro and in vivo experiments are currently underway to confirm this observation and to investigate the detailed molecular mechanisms involved in the process as well as the biological activities of other fractions of Fd.