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Induction Rate (induction + rate)
Selected AbstractsApical callus formation and plant regeneration controlled by plant growth regulators on axenic culture of the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta)PHYCOLOGICAL RESEARCH, Issue 3 2000Nair S. Yokoya SUMMARY Axenic cultures of Gracilariopsis tenuifrons (Bird et Oliveira) Fredericq et Hommersand (Gracilariales, Rhodophyta) were established in ASP12-NTA solid medium (0.4% agar and 1.0% sucrose) supplemented with plant growth regulators to evaluate the effects on apical callus formation and plant regeneration. Indole-3-acetic acid (IAA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BA) were added individually or in combinations (IAA : BA) over a range of concentrations from 0.5 to 5 mg L,1. Growth of apical and intercalary segments was stimulated by high concentrations of 2,4-D (5 mg L,1) and a high IAA to BA ratio (IAA : BA = 5:1 mg L,1) respectively. Apical calluses were originated from divisions of apical and cortical cells located at apical regions of thallus segments and lateral branches. Low concentration of IAA (0.5 mg L,1) or a high IAA to BA ratio (IAA : BA = 5:1 mg L,1) were the optimal treatments for inducing apical callus formation in apical segments, while high concentration of IAA (5 mg L,1) stimulated the highest callus induction rate in intercalary segments. Conversely, equal parts IAA and BA (IAA : BA = 1:1 mg L,1) and low concentration of 2,4-D (0.5 mg L,1) stimulated growth of apical calluses from apical and intercalary segments, respectively. Two processes of regeneration were observed: direct regeneration (upright axis originated from cells of proximal region of intercalary segments) and indirect regeneration (adventitious plantlet originated from cells of apical calluses). Direct regeneration was promoted significantly by treatment with a low IAA to BA ratio (IAA : BA= 1:5 mg L,1), and treatments with IAA (0.5 mgL,1) or 2,4-D (0.5 or 5 mg L,1) significantly stimulated the elongation of upright axis. Plant growth regulators are essential to inducing indirect regeneration, and a high concentration of IAA (5 mg L,1) and BA (5 mg L,1) were the optimal treatments for inducing the regeneration of plantlets from apical calluses in apical and intercalary segments, respectively. Regenerating plantlets grew into plants morphologically similar to those formed from germinating spores, and became fertile after 6 weeks. The results suggest that auxins and cytokinins are involved in developmental regulatory processes in G. tenuifrons. The regeneration process from calluses in species of Gracilariales was observed for the first time in the present study. The culture system described for G. tenuifrons could be useful for micropropagation and for biotechnological applications in agarophytic algae. [source] Promotion of callus propagation by 5-aminolevulinic acid in a Laminaria japonica sporophyteAQUACULTURE RESEARCH, Issue 1 2009Katsuhiro Tabuchi Abstract The effects of 5-aminolevulinic acid (ALA) on the induction and growth of callus-like cells in Laminaria japonica were investigated in explants obtained from basal, middle and apical portions along the sporophyte. 5-Aminolevulinic acid treatment promoted the induction of callus-like cells in explants obtained from all portions, and the induction rate was higher when a concentration of 50,500 mg L,1 of ALA was used. The promotion was especially remarkable in apical explants, and the induction was 10,14 times higher in the 100,500 mg L,1 range than that in the 0 mg L,1. The cell division rate of callus-like cells showed the highest value in the explants cultured with 500 mg L,1 of ALA for 14 days. The promotion of the cell division rate by culturing with 500 mg L,1 ALA was also observed under white, blue and red lights. The callus-like cells, which were cultured in 500 mg L,1 of ALA for 2 months, had many clear chloroplasts. After 3 months, young thalli occurred. These results suggest that the ALA treatment is effective for stable propagation of callus-like cells in L. japonica. [source] Distinguishing Effects on Tumor Multiplicity and Growth Rate in Chemoprevention ExperimentsBIOMETRICS, Issue 4 2000David B. Dunson Summary. In some types of cancer chemoprevention experiments and short-term carcinogenicity bioassays, the data consist of the number of observed tumors per animal and the times at which these tumors were first detected. In such studies, there is interest in distinguishing between treatment effects on the number of tumors induced by a known carcinogen and treatment effects on the tumor growth rate. Since animals may die before all induced tumors reach a detectable size, separation of these effects can be difficult. This paper describes a flexible parametric model for data of this type. Under our model, the tumor detection times are realizations of a delayed Poisson process that is characterized by the age-specific tumor induction rate and a random latency interval between tumor induction and detection. The model accommodates distinct treatment and animal-specific effects on the number of induced tumors (multiplicity) and the time to tumor detection (growth rate). A Gibbs sampler is developed for estimation of the posterior distributions of the parameters. The methods are illustrated through application to data from a breast cancer chemoprevention experiment. [source] High incidence of obstetric interventions after successful external cephalic versionBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2002Louis Yik-Si Chan Objective To investigate the delivery outcome after successful external cephalic version (ECV). Design Case,control study. Setting University teaching hospital. Population The study group consisted of 279 consecutive singleton deliveries at term over a six-year period, all of which had had successful ECV performed. The control group included 28,447 singleton term deliveries during the same six-year period. Methods Between group differences were compared with the Mann,Whitney U test or Student's t test where appropriate. Odds ratio and 95% confidence interval (CI) were calculated for categorical variables. Main outcome measures Incidence of and indications for obstetric interventions. Results The risk of instrumental delivery and emergency caesarean section was higher in the ECV group (14.3%vs 12.8%; OR 1.4; 95% CI 1.0,2.0, and 23.3%vs 9.4%; OR 3.1; 95% CI 2.3,4.1, respectively). The higher caesarean rate was due to an increase in all major indications, namely, suspected fetal distress, failure to progress in labour and failed induction. The higher incidence of instrumental delivery was mainly due to an increase in prolonged second stage. The odds ratio for operative delivery remained significant after controlling for potential confounding variables. There were also significantly greater frequencies of labour induction (24.0%vs 13.4%; OR 2.0; 95% CI 1.5,2.7) and use of epidural analgesia (20.4%vs 12.4%; OR 1.8; 95% CI 1.4,2.4) by women in the ECV group. The higher induction rate is mainly due to induction for post term, abnormal cardiotocography (CTG) and antepartum haemorrhage (APH) of unknown origin. Conclusion The incidence of operative delivery and other obstetric interventions are higher in pregnancies after successful ECV. Women undergoing ECV should be informed about this higher risk of interventions. [source] Impact of weekend admissions on quality of care and outcomes in patients with acute myeloid leukemia,CANCER, Issue 15 2010Nelli Bejanyan MD Abstract BACKGROUND: Hospital services are expectantly reduced over the weekend, which may result in a delay in treatment or in obtainment of medical procedures. The authors investigated quality of care and clinical outcomes of newly diagnosed acute myeloid leukemia (AML) patients who were hospitalized on weekends versus weekdays and treated with induction chemotherapy. METHODS: This retrospective follow-up study involved 422 AML patients treated with cytarabine-based induction chemotherapy at Cleveland Clinic from 1994-2008. Quality outcome measures included time to triple-lumen catheter (TLC) placement, time to induction chemotherapy, length of stay (LOS), early death (within 15 days of chemotherapy), and 30-day mortality. These were tested for the association with known predictors of AML survival and etiology by the methods of linear, categorical, and survival analyses. RESULTS: Twenty-three percent of all admissions (n = 422) occurred over the weekend (n = 103). Compared with younger (aged <60 years) patients, older patients had higher 30-day mortality (P = .003), early death (P = .025), and time to induction rates (P = .02), but lower complete remission (P = .001) and overall survival (OS) rates (P < .0001). In univariate analyses, time to TLC was delayed for weekend admissions (P < .01). Weekend admissions had lower early mortality (P = .04) and 30-day mortality (P = .02). In multivariate analysis, only time to TLC remained significantly longer for weekend admissions (P < .001). CONCLUSIONS: Weekend admissions significantly delayed placement of TLC without affecting other quality parameters or patient survival. This is likely because of immediate initiation of peripheral chemotherapy with cytarabine even before the placement of TLC for infusion of anthracyclines. Cancer 2010. © 2010 American Cancer Society. [source] | ||||||||||