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Threshold Tests (threshold + test)

Distribution by Scientific Domains

Life Sciences	30%
Chemistry	15%

Selected Abstracts

Use of an Intracardiac Electrogram Eliminates the Need for a Surface ECG during Implantable Cardioverter-Defibrillator Follow-Up

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2007
KEVIN A. MICHAEL M.B.Ch.B.
Background:A surface electrocardiogram (SECG) for pacing threshold measurements during routine implantable cardioverter-defibrillator (ICD) follow-up can be cumbersome. This study evaluated the use of an intrathoracic far-field electrogram (EGM) derived between the Can and superior vena cava (SVC) electrode,the Leadless electrocardiogram (LLECG), in dual chamber ICDs in performing pacing threshold tests. Methods:The LLECG was evaluated prospectively during atrial and ventricular pacing threshold testing as a substudy of the Comparison of Empiric to Physician-Tailored Programming of Implantable Cardioverter-Defibrillators trial (EMPIRIC) in which dual chamber ICDs were implanted in 888 patients. Threshold tests were conducted at 1 volt by decrementing the pulse width. Follow-up at three months compared pacing thresholds measured using LLECG with those using Lead I of the surface ECG (SECG). The timesaving afforded by LLECG was assessed by a questionnaire. Results:The median threshold difference between LLECG and SECG measurements for both atrial (0.00 ms, P = 0.90) and ventricular (0.00 ms, P = 0.34) threshold tests were not significant. Ninety percent of atrial and ventricular threshold differences were bounded by ± 0.10 ms and ,0.10 to +0.04 ms, respectively. We found that 99% of atrial and ventricular thresholds tests at six and 12 months attempted using LLECG were successfully completed. The questionnaire indicated that 65% of healthcare professionals found LLECG to afford at least some timesaving during device follow-ups. Conclusion:Routine follow-up can be performed reliably and expeditiously in dual chamber Medtronic (Minneapolis, MN, USA) ICDs using LLECG alone, resulting in overall timesaving. [source]

Alternative approaches can greatly reduce the number of fish used for acute toxicity testing

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2006
Conny C. Hoekzema
Abstract Acute toxicity tests with algae, daphnids, and fish are required for the classification and environmental risk assessment of chemicals. The degree of risk is determined by the lowest of these acute toxicity values. Many ecotoxicological programs are seeking to reduce the numbers of fish used in acute toxicity testing. The acute threshold test is a recently proposed strategy that uses, on average, only 10 (instead of 54) fish per chemical. We examined the consequences of reducing the number of fish used in toxicity testing on the ultimate outcome of risk assessments. We evaluated toxicity data sets for 507 compounds, including agrochemicals, industrial chemicals, and pharmaceuticals from our internal database. Theoretical applications of the acute threshold test gave similar results to those obtained with the standard fish median lethal concentration (LC50) test but required only 12% as many fish (3,195 instead of 27,324 fish used for all compounds in the database). In 188 (90%) of the 208 cases for which a complete data set was available, the median effect concentration for algae or daphnids was lower than the LC50 for fish. These results show that replacement of the standard fish LC50 test by the acute threshold test would greatly reduce the number of fish needed for acute ecotoxicity testing without any loss of reliability. [source]

A strategy to reduce the numbers of fish used in acute ecotoxicity testing of pharmaceuticals

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2003
Thomas H. Hutchinson
Abstract The pharmaceutical industry gives high priority to animal welfare in the process of drug discovery and safety assessment. In the context of environmental assessments of active pharmaceutical ingredients (APIs), existing U.S. Food and Drug Administration and draft European regulations may require testing of APIs for acute ecotoxicity to algae, daphnids, and fish (base-set ecotoxicity data used to derive the predicted no-effect concentration [PNECwater] from the most sensitive of three species). Subject to regulatory approval, it is proposed that testing can be moved from fish median lethal concentration (LC50) testing (typically using ,42 fish/API) to acute threshold tests using fewer fish (typically 10 fish/API). To support this strategy, we have collated base-set ecotoxicity data from regulatory studies of 91 APIs (names coded for commercial reasons). For 73 of the 91 APIs, the algal median effect concentration (EC50) and daphnid EC50 values were lower than or equal to the fish LC50 data. Thus, for approximately 80% of these APIs, algal and daphnid acute EC50 data could have been used in the absence offish LC50 data to derive PNECwater values. For the other 18 APIs, use of an acute threshold test with a step-down factor of 3.2 is predicted to give comparable PNECwater outcomes. Based on this preliminary scenario of 91 APIs, this approach is predicted to reduce the total number offish used from 3,822 to 1,025 (,73%). The present study, although preliminary, suggests that the current regulatory requirement for fish LC50 data regarding APIs should be succeeded by fish acute threshold (step-down) test data, thereby achieving significant animal welfare benefits with no loss of data for PNECwater estimates. [source]

ALE meta-analysis: Controlling the false discovery rate and performing statistical contrasts

HUMAN BRAIN MAPPING, Issue 1 2005
Angela R. Laird
Abstract Activation likelihood estimation (ALE) has greatly advanced voxel-based meta-analysis research in the field of functional neuroimaging. We present two improvements to the ALE method. First, we evaluate the feasibility of two techniques for correcting for multiple comparisons: the single threshold test and a procedure that controls the false discovery rate (FDR). To test these techniques, foci from four different topics within the literature were analyzed: overt speech in stuttering subjects, the color-word Stroop task, picture-naming tasks, and painful stimulation. In addition, the performance of each thresholding method was tested on randomly generated foci. We found that the FDR method more effectively controls the rate of false positives in meta-analyses of small or large numbers of foci. Second, we propose a technique for making statistical comparisons of ALE meta-analyses and investigate its efficacy on different groups of foci divided by task or response type and random groups of similarly obtained foci. We then give an example of how comparisons of this sort may lead to advanced designs in future meta-analytic research. Hum Brain Mapp 25:155,164, 2005. © 2005 Wiley-Liss, Inc. [source]

Underestimation of Pacing Threshold as Determined by an Automatic Ventricular Threshold Testing Algorithm

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2006
WILLIAM H. SAUER
In this case report, we describe markedly different pacing thresholds determined by a manual threshold test and the automatic Ventricular Capture Management algorithm. The discrepancy in pacing threshold values reported was due to the difference in the AV intervals used with the different testing methods. We propose that the differences in right ventricular dimensions with altered diastolic filling periods affected the threshold in this patient with a new passive fixation lead in the right ventricular apex. [source]

A strategy to reduce the numbers of fish used in acute ecotoxicity testing of pharmaceuticals

SENSORY FLAVOR PROFILING AND MAPPING OF MARKET SAMPLES OF CUMIN (CUMINUM CYMINUM L.)

JOURNAL OF FOOD QUALITY, Issue 4 2004
ANUPAMA DATTATREYA
ABSTRACT Eight market samples of cumin (R1, R2, R3, R4, R5, R6, R7 and R8) from different regions of India were examined for sensory quality by conducting threshold tests, time-intensity (TI) profiling and flavor profiling. Principal component analysis (PCA) was carried out to group the samples. Threshold values ranged from 0.006 to 0.017% with R7 and R8 lots showing lower values for their thresholds (0.006%). Higher intensity of aroma of R7 and R8 was further confirmed by more of a lingering aroma as shown by the TI study. Flavor profiling by quantitative descriptive analysis showed that the market samples of cumin did not differ significantly (P , 0.05). Mapping of samples using PCA technique showed, based on intensity of attributes, four distinct groups comprising a) R1 and R3, b) R7, c) R2 and R5 and d) R4 and R8. R6 occupied a position in between a and b. [source]

Use of an Intracardiac Electrogram Eliminates the Need for a Surface ECG during Implantable Cardioverter-Defibrillator Follow-Up

Atrial Evoked Response Integral for Automatic Capture Verification in Atrial Pacing

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003
GIUSEPPE BORIANI
BORIANI, G.,et al.:Atrial Evoked Response Integral for Automatic Capture Verification in Atrial Pacing. Beat-by-beat Autocapture is currently limited to operation in the ventricle with bipolar leads. The authors investigated the integral of the negative-going portion of the atrial evoked response integral (AERI) as a potential resource for verification of atrial capture. Intracardiac electrogram signals were collected from 59 patients (ages 67.8 ± 15.1 years) with bipolar, low polarization atrial leads. The signals were collected over a mean period of 6.1 months (minimum 4 days) after lead implantation. St. Jude Medical Affinity pulse generators were used to perform automatic capture threshold tests while the electrogram signals were recorded by a Model 3510 programming device. These signals were transferred to a personal computer in digital form for later analysis. The AERI was calculated at each programmable pacing voltage until capture was lost. The difference between the polarization integral at loss of capture and evoked response integral with successful capture was sufficient to justify enabling the atrial Autocapture feature in 53 of 59 patients in whom bipolar pacing and unipolar sensing was performed. The authors developed a calibration routine to identify automatically those patients in whom atrial Autocapture could be programmed On, based on the polarization integral at loss of capture, the estimated maximum polarization integral, and the AERI. Preliminary analysis indicated that the AERI is a practical resource for beat-by-beat atrial capture detection when used with low polarization leads. (PACE 2003; 26[Pt. II]:248,252) [source]

Synthesis and Anticonvulsant Properties of New Mannich Bases Derived from 3-Aryl-pyrrolidine-2,5-diones.

ARCHIV DER PHARMAZIE, Issue 6 2010
Part
Abstract A series of new Mannich bases of N -[(4-arylpiperazin-1-yl)-methyl]-3-(chlorophenyl)-pyrrolidine-2,5-diones 10,23 have been synthesized and evaluated for their anticonvulsant activity in maximum electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) seizure threshold tests. Their neurotoxicity was determined using a rotorod screen. Several molecules showed a promising anticonvulsant profile especially in the MES-test. In this model of seizures, the most active were N -[{4-(4-chlorophenyl)-piperazin-1-yl}-methyl]-3-(3-chlorophenyl)-pyrrolidine-2,5-dione 16 and N -[{4-(3-trifluoromethylphenyl)-piperazin-1-yl}-methyl]-3-(3-chlorophenyl)-pyrrolidine-2,5-dione 17 with ED50 values of 21.4 mg/kg and 28.83 mg/kg, respectively. Selected derivatives 10, 14, and 16 were tested in the psychomotor seizure 6-Hz test from which N -[{4-(2-chlorophenyl)-piperazin-1-yl}-methyl]-3-(2-chlorophenyl)-pyrrolidine-2,5-dione 10 revealed the highest protection with an ED50 of 78 mg/kg. Compounds 10, 12, and 17 were also tested in the pilocarpine-induced status PIPS test. Furthermore, 17 was examined in the hippocampal kindling screen after i. p. administration to rats. [source]

Epidemic thresholds for infections in uncertain networks,

COMPLEXITY, Issue 4 2009
L. Zager
Abstract Over the last 10 years, the field of mathematical epidemiology has piqued the interest of complex-systems researchers, resulting in a tremendous volume of work exploring the effects of population structure on disease propagation. Much of this research focuses on computing epidemic threshold tests, and in practice several different tests are often used interchangeably. We summarize recent literature that attempts to clarify the relationships among different threshold criteria, systematize the incorporation of population structure into a general infection framework, and discuss conditions under which interaction topology and infection characteristics can be decoupled in the computation of the basic reproductive ratio, R0. We then present methods for making predictions about disease spread when only partial information about the routes of transmission is available. These methods include approximation techniques and bounds obtained via spectral graph theory, and are applied to several data sets. © 2008 Wiley Periodicals, Inc. Complexity, 2009 [source]