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Induction Frequencies (induction + frequency)
Selected AbstractsEvaluation of tissue culture response from mature seeds of Panicum spp.GRASSLAND SCIENCE, Issue 3 2008Mi-Suk Seo Abstract The genus Panicum contains important warm-season forage grasses and species with potential as biomass crops. We selected Panicum genotypes with high response to tissue culture for genetic improvement. The highest frequency of callus induction from mature seed of Panicum maximum cultivar Natsukaze was obtained on MS medium containing 4.0 mg L,1 2,4-dichlorophenoxyacetic acid and solidified with 0.3% Gelrite. We compared germination frequencies and callus induction capacities among 24 genotypes of 11 Panicum species on this medium. Callus induction frequencies varied among genotypes. Those with high germination frequencies generally had high callus induction frequencies. On the other hand, especially in P. maximum, the callus induction ratio (callus induction frequency/germination frequency) depended on the reproductive mode and ploidy. The callus induction ratio of three sexual accessions of P. maximum were very low compared to apomictic accessions, and besides, a tetraploid sexual accession Noh PL1 had very low germination and callus induction frequencies. Callus induction and regeneration capacities were independent of each other. For shoot regeneration, we transferred callus derived from the 24 genotypes onto MS medium supplemented with 1.0 mg L,1 kinetin and 0.4% Gelrite. Six of the genotypes regenerated plantlets. Among them, Panicum meyerianum produced the highest shoot regeneration frequency of 61.6% and the maximum number of shoots callus,1 in the shortest time. The callus of P. meyerianum also showed vigorous proliferation. We thus selected high-response genotypes of P. meyerianum. [source] Decremental Ramp Atrial Extrastimuli Pacing Protocol for the Induction of Atrioventricular Nodal Re-entrant Tachycardia and Other Supraventricular TachycardiasPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2006BHARAT K. KANTHARIA M.D. Aim: The primary aim of this study was to evaluate the utility of decremental ramp atrial extrastimuli pacing protocol (PRTCL) for induction of atrioventricular nodal re-entrant tachycardia (AVNRT), and other supraventricular tachycardias (SVTs), compared to standard (STD) methods. Methods: The study cohort of 121 patients (age 57.51 ± 14.02 years) who presented with documented SVTs and/or symptoms of palpitations and dizziness, and underwent invasive electrophysiological evaluation was divided into Group I (AVNRT, n = 42) and Group II (Control, n = 79). The PRTCL involved a train of six atrial extrastimuli, delivered in a decremental ramp fashion. The STD methods included continuous burst and rapid incremental pacing up to atrioventricular (AV) block cycle length, and single and occasionally double atrial extrastimuli. Prolongation in the Atrio-Hisian (,-AH) intervals achieved by both methods were compared, as were induction frequencies. Results: In Group I, three categories of responses,(1) induction of AVNRT, (2) induction of echo beats only, and (3) none,were observed in 29 (69%), 11 (26%), and 2 (5%) patients with the PRTCL, when compared with 14 (33%), 16 (38%), and 12 (29%) patients with STD methods in the baseline state without the use of pharmacological agents. The ,-AH intervals for each of these three categories were larger using PRTCL versus STD methods; 293.3 ± 95.2 ms versus 192.9 ± 61.4 ms (P < 0.005), 308.6 ± 68.5 ms versus 189. 9 ± 64.9 ms (P < 0.0005), and 203.0 ± 86.3 ms versus 145.8 ± 58.9 ms (P = NS), respectively. In Group II, in one patient with dual AV nodal physiology but no clinical tachycardia, the PRTCL induced nonsustained (12 beats) AVNRT. Additionally, in this group, both PRTCL and STD methods induced atrial tachycardia in two patients and orthodromic AV re-entrant tachycardia in one patient. Conclusion: Decremental ramp atrial extrastimuli pacing PRTCL demonstrates a superior response for induction of typical AVNRT as compared to STD techniques. Because of easy and reliable induction of AVNRT and echo beats by the PRTCL, we recommend it as a method to increase the likelihood of induction of AVNRT. For induction of other SVTs, the PRTCL and the STD methods are comparable. [source] Clinically relevant radioresistant cells efficiently repair DNA double-strand breaks induced by X-raysCANCER SCIENCE, Issue 4 2009Yoshikazu Kuwahara Radiotherapy is one of the major therapeutic modalities for eradicating malignant tumors. However, the existence of radioresistant cells remains one of the most critical obstacles in radiotherapy and radiochemotherapy. Standard radiotherapy for tumor treatment consists of approximately 2 Gy once a day, 5 days a week, over a period of 5,8 weeks. To understand the characteristics of radioresistant cells and to develop more effective radiotherapy, we established a novel radioresistant cell line, HepG2-8960-R with clinical relevance from parental HepG2 cells by long-term fractionated exposure to 2 Gy of X-rays. HepG2-8960-R cells continued to proliferate with daily exposure to 2 Gy X-rays for more than 30 days, while all parental HepG2 cells ceased. After exposure to fractionated 2 Gy X-rays, induction frequencies of micronuclei and remaining foci of ,-H2AX in HepG2-8960-R were less than those in HepG2. Flow cytometric analysis revealed that the proportion of cells in S- and G2/M-phase of the cell cycle was higher in HepG2-8960-R than in HepG2. These suggest that the response of clinically relevant radioresistant (CRR) cells to fractionated radiation is not merely an accumulated response to each fractionated radiation. This is the first report on the establishment of a CRR cell line from an isogenic parental cell line. (Cancer Sci 2009; 100: 747,752) [source] Involvement of Transcription Factor HNF3, in the Effect of o -Aminoazotoluene on Glucocorticoid Induction of Tyrosine Aminotransferase in Mice Sensitive to its Hepatocarcinogenic ActionMOLECULAR CARCINOGENESIS, Issue 1 2001Konstantin Y. Kropachev Abstract In the rodent liver, hepatocarcinogens inhibit the glucocorticoid induction of several liver-specific genes, including tyrosine aminotransferase (TAT). A distinct positive correlation exists in mice between the extent of inhibition of TAT induction after acute administration of o -aminoazotoluene (OAT) and the frequency of liver tumors after chronic exposure to the carcinogen. To elucidate the mechanism of the carcinogenic action, the effects of OAT on the DNA-binding activity of several transcription factors participating in the glucocorticoid regulation of TAT gene expression were studied. The experimental inbred male mice were sensitive (A/He and SWR/J, tumor induction frequency of 75,100%, TAT induction inhibition of 35,50%) and resistant (CC57BR/Mv and AKR/J, 0,6% and 10,15%, respectively) to OAT. Gel retardation experiments showed that hepatocyte nuclear factor 3 (HNF3), DNA-binding activity was strongly reduced in nuclear extracts from the livers of OAT-treated A/He and SWR/J mice but only slightly reduced in CC57Br/Mv and AKR/J mice. The DNA-binding activities of Ets, AP1 family members, and GME binding proteins were unaffected. HNF3, DNA-binding activity was reduced by 1 h after OAT administration and remained low for 1 mo, as did inhibition of TAT induction in the liver. These results suggested that the inhibitory effect of OAT on the glucocorticoid induction of TAT is mediated by reduced HNF3, DNA-binding activity. © 2001 Wiley-Liss, Inc. [source] | ||||||||||