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PubMed1997

Salivary parameters of relevance for assessing caries activity in individuals and populations.

A review of the non-microbial salivary parameters with respect to their possible association with caries activity is presented. The parameters are limited to those which already are or at least in the near future will obviously be simple enough, also for clinical purposes. Salivary flow rate is undoubtedly the most important single parameter since the cariostatic activity or efficacy of practically all other salivary parameters depends on the flow rate. Flow rate as such has no linear association with dental caries but there seems to exist an individual "threshold" limit which is decisive for enhanced caries activity. This threshold limit varies among different individuals and therefore the so-called normal values for unstimulated or stimulated flow rate are more reliable on a population level than among individuals for screening purposes. In any individual a regular and longitudinal follow-up of the flow rate is of higher clinical value than only a single cross-sectional measurement. Salivary buffer effect has only a weak negative association with caries activity and again, this effect is of greater clinical significance on a population level. Since the decisive processes in caries attack occur within or under the dental plaque, the buffering effect of saliva is limited and obviously more important to screen for erosion-than caries-prone individuals. Although important for dental health, none of the salivary antimicrobial agents as such has shown any strong association with caries activity. The only ones with some evidence of a regulatory role are secretory IgA antibodies, hypothiocyanite ions, and agglutinins. However, the data are controversial and it seems that instead of measuring individual parameters, the assessment of saliva's functional properties (such as the ability to aggregate bacteria, prevent their adhesion to hydroxyapatite or sugar metabolism etc.) is more important for clinical purposes. Of the parameters involved in de- and remineralization process, only salivary fluoride content has some association with caries susceptibility but its diagnostic or predictive value is questionable.

Agglutinins↗
PubMed2006

Development and evaluation of a one-step real-time reverse transcription polymerase chain reaction assay for the detection of salmonid alphaviruses in serum and tissues.

We designed 4 primer pairs to amplify conserved regions of the E1 or nsP4 genes of salmonid alphavirus (SAV) and evaluated their performance in optimized 1-step SYBR green real-time RT-PCR (RRT-PCR) assays. A single primer pair, amplifying a 227 bp segment of E1 was then chosen for further study. This RRT-PCR was shown to be highly repeatable and reproducible over a wide range of RNA dilutions, with a linear relationship between cycle threshold (Ct) value and RNA concentration over a 10(7) dilution range. The limit of detection was calculated to be < or = 1.5 TCID50 ml(-1). When applied to sera previously screened by virus isolation for SAV viraemia, the RRT-PCR correctly identified all 13 culture-positive samples, as well as finding an additional 28 sera positive. Relative semi-quantitation of sera showed a very highly significant relationship between copy number and TCID50 (p < 0.001, R2 = 0.9563). Following experimental infection of salmon, heart samples were consistently positive until 21 d post infection (dpi), with (weak) positive signals still detectable in 50% of fish 70 dpi.

Alphavirus↗
PubMed1997

[Virtual endoscopy with post-processing helical CT data sets].

PURPOSE: The purpose of this work was to test a newly developed, post-processing software for virtual CT endoscopic methods. Virtual endoscopic images were generated from helical CT data sets in the region of the shoulder joint (n = 2), the tracheobronchial system (n = 3), the nasal sinuses (n = 2), the colon (n = 2), and the common carotid artery n = 1). Software developed specifically for virtual endoscopy ("Navigator") was used which, after a previous threshold value selection, makes the reconstruction of internal body surfaces possible by an automatic segmentation process. We have evaluated the usage of the software, the reconstruction time for individual images and sequences of images as well as the quality of the reconstruction. All pathological findings of the virtual endoscopy were confirmed by surgery. RESULTS: The post-processing program is easy to use and provides virtual endoscopic images within 50 seconds. Depending of the extent of the data set, virtual tracheobronchoscopy as a cine loop sequence required about 15 minutes. Through use of the threshold value-dependent surface reconstruction the demands on the computer configuration are limited; however, this also created quality problems in image calculation as a consequence of the accompanying loss of data. CONCLUSIONS: The Navigator software enables the calculation of virtual endoscopic models with only moderate demands on the hardware.

Artifacts↗
PubMed1992

Improved chronic epicardial pacing in children: steroid contribution to porous platinized electrodes.

Although new "low threshold" epicardial electrodes combine steroid with a porous, platinized-platinum surface, the actual contribution of steroid elution has not been established. We evaluated this new electrode surface design with and without steroid in 13 children, ages 1-22 years. Both electrodes are unipolar and of similar surface area. The Medtronic Model 4951-P is a barb design for epimyocardial insertion without steroid while the Model 10295A is a steroid eluting, epicardial disk-shaped design. Both electrodes were implanted for atrial and ventricular pacing. At implant, sensed P and R waves, and pacing impedances were comparable between both electrodes. There were no significant differences between initial measured pulse width or calculated energy thresholds for the first 2 months following implant. Strength-duration curves for both electrodes at 1 month were comparable to implant values. After 2 months, the threshold of the nonsteroid electrode peaked and stabilized at a significantly higher (P less than 0.05) level than the more constant steroid eluting electrode. This difference continued for the first year following implant. We conclude that the new porous, platinized-platinum electrode design intrinsically limits initial electrode-tissue interface reactivity in children and improves epicardial pacing with low chronic threshold values. Steroid elution augments these intrinsic qualities by maintaining fibrous capsule stability with more constant low thresholds over time.

Bradycardia↗
PubMed1998

[Cardiopulmonary exercise testing for evaluation of muscle diseases].

PURPOSE: To evaluate the cardiopulmonary exercise testing (CPX) for the diagnosis of myopathies. METHODS: 27 patients with myopathy were submitted to CPX testing (symptom limited bike protocol). RESULTS: Dystrophic patients and patients with mitochondrial disease, compared with controls, showed significant differences for the power of work perfomed (watt) and the maximum oxygen consumption (VO2 max). Patients with mitochondrial disease presented significantly lower values of anaerobic threshold when compared to controls and elevation of exercise peak respiratory exchange ratio (RER) values when compared to the others groups. CONCLUSIONS: CPX testing may be useful in evaluating degree of physical limitation of patients with myopathy at inicial stage as well on follow-up examinations. Power of work performed, VO2 max, anaerobic threshold and RER at exercise peak may suggest the diagnosis of myopathy and its sub-types and therefore exclude psychologic causes of limitation.

Adolescent↗
PubMed1991

Modeling: optimal marathon performance on the basis of physiological factors.

This paper examines current concepts concerning "limiting" factors in human endurance performance by modeling marathon running times on the basis of various combinations of previously reported values of maximal O2 uptake (VO2max), lactate threshold, and running economy in elite distance runners. The current concept is that VO2max sets the upper limit for aerobic metabolism while the blood lactate threshold is related to the fraction of VO2max that can be sustained in competitive events greater than approximately 3,000 m. Running economy then appears to interact with VO2max and blood lactate threshold to determine the actual running speed at lactate threshold, which is generally a speed similar to (or slightly slower than) that sustained by individual runners in the marathon. A variety of combinations of these variables from elite runners results in estimated running times that are significantly faster than the current world record (2:06:50). The fastest time for the marathon predicted by this model is 1:57:58 in a hypothetical subject with a VO2max of 84 ml.kg-1.min-1, a lactate threshold of 85% of VO2max, and exceptional running economy. This analysis suggests that substantial improvements in marathon performance are "physiologically" possible or that current concepts regarding limiting factors in endurance running need additional refinement and empirical testing.

Fatigue↗
PubMed2001

Evaluation of 5' nuclease assay for detection of Actinobacillus pleuropneumoniae.

Sequence detection by the 5' nuclease TaqMan assay uses online detection of internal fluorogenic probes in closed PCR tubes. Primers and probe were chosen from a part of the omlA gene common to all serotypes of Actinobacillus pleuropneumoniae, which gave an amplicon of 92 bp. The test was evaluated with 73 lung isolates and 120 tonsil isolates of A. pleuropneumoniae as well as with a collection of reference strains. By using a C(t) value (cycle number in which the fluorescence exceeds the threshold defined by the software) of 30 as the cutoff limit, the 5' nuclease assay represents a test with 100% sensitivity and 100% specificity. A high degree of reproducibility of the test was demonstrated. If samples with C(t) values of </=30 are considered positive, the detection limit of the assay was 1 CFU/reaction tube, corresponding to a 10-fold higher number of DNA templates. After cycle 30, nonspecific reactions appeared when testing dilutions of DNA templates or pure cultures of A. pleuropneumoniae, as well as when testing tonsil scrapings from specific-pathogen-free herds. The diagnostic sensitivity, as evaluated with 586 tonsil scrapings from animals infected with A. pleuropneumoniae, is the same level as that of a PCR test based on the omlA gene described previously. The 5' nuclease assay represents a fast method for species-specific detection and identification of A. pleuropneumoniae in pure and mixed cultures. The evaluation shows, however, that a C(t) value cutoff limit of </=30 must be chosen in order to obtain reliable results. The investigation emphasizes that a thorough evaluation of the criteria used to define a positive test result is necessary.

Actinobacillus Infections↗
PubMed1996

Evaluation of formulae for CSF IgG synthesis using data obtained from two methods: importance of receiver operator characteristic curve analysis.

AIMS: To determine the clinical performance of three cerebrospinal fluid (CSF) IgG synthesis formulae using data obtained from two quantitation methods. METHODS: Receiver operator characteristic (ROC) analysis and decision index plots were used to compare a rate nephelometric (RN) and a rocket immunoelectrophoretic (RIEP) method for quantitating albumin and IgG for use in CSF IgG synthesis formulae. Further analysis was used to determine the most clinically accurate of these formulae for a diagnosis of multiple sclerosis with regard to technical accuracy and cost effectiveness. RESULTS: Values for albumin and IgG determined by RN gave better sensitivities and specificities than the RIEP method when applied to all three formulae; however, when the 95% confidence limits were considered, the difference was not significant. Using the RN method with an agreed "rule in" threshold value of 90% specificity, the IgG index gave the best clinical performance. CONCLUSION: ROC curve analysis and decision index plots provide valuable tools in assessing and comparing the clinical performance of new and existing laboratory assays.

Albumins↗
PubMed2003

Ventilatory and cardiovascular responses to exercise in patients with pectus excavatum.

PURPOSE: Uncertainty exists as to whether pectus excavatum causes true physiologic impairments to exercise performance as opposed to lack of fitness due to reluctance to exercise. The purpose of this study was to examine the effect of pectus excavatum on ventilatory and cardiovascular responses to incremental exercise in physically active patients. METHODS: Twenty-one patients with pectus excavatum (age range, 13 to 50 years; mean [+/- SD] age, 23.6 +/- 8.9 years; severity index range, 3.7 to 8.0; mean severity index, 5.1 +/- 1.2) were referred for preoperative evaluation. Eighteen of the patients (85%) had a history of performing aerobic activity ranging from 30 min to 2 h per day (mean duration, 1.0 +/- 0.61 h per day) for 3 +/- 1.5 days per week. Patients performed pulmonary function tests, and submaximal and maximal incremental exercise testing. RESULTS: On maximal exercise testing, the maximum oxygen uptake (O(2)max), and oxygen-pulse were significantly lower than the reference values (t(20) = 6.17 [p < 0.0001] and t(20) = 4.52 [p < 0.0001], respectively). Furthermore, patients exhibited cardiovascular limitation, but not ventilatory limitation. Despite their high level of habitual exercise activity, the overall metabolic threshold for lactate accumulation was abnormally low (ie, 41% of the reference value for O(2)max) especially in those with a pectus severity index (PSI) of > 4.0 (39% of the reference value of O(2)max), which is consistent with cardiovascular impairment rather than physical deconditioning. Patients with a PSI of > 4.0 were also eight times more likely to have reduced aerobic capacity than patients who had a low severity index, despite their level of exercise participation. On submaximal testing, we found that the time constant for O(2) uptake kinetics was 37.4 s for the on-transit and 41.6 s for the off-transit. The observed values for FVC, FEV(1), maximum voluntary ventilation, and diffusing capacity of the lung for carbon monoxide were significantly lower than reference values, but those for total lung capacity and residual volume were not significantly lower than reference values. CONCLUSIONS: The information derived from this study supports the opinion that pectus excavatum is associated with true physiologic impairment and reduced exercise capacity, predominantly due to impaired cardiovascular performance rather than ventilatory limitation. Furthermore, the impairment is not explained by physical deconditioning.

Adolescent↗
PubMedDate not supplied

Interference of exogenous HCG on pregnancy tests.

New urinary tests of pregnancy have recently been developed that are exceptionally sensitive to HCG. Our study was undertaken to explore the possibility that exogenous HCG, administered to induce ovulation, may interfere with these low-threshold tests of pregnancy. Six healthy volunteers participated in our study. Each woman received three sequential 5,000-U doses of HCG by im route on days 3, 5, and 7 after ovulation. Blood and urine for HCG assay were taken daily from each subject. Urine specimens were subjected to a traditional high-threshold pregnancy test (sensitivity limit = 2000 U/L) and to a low-threshold pregnancy test (sensitivity limit = 50 U/L); HCG in plasma and urine was determined by ELISA assay. Plasma HCG levels increased gradually under HCG dosing and attained a peak on day 8 (average = 73.7 U/L; range 24-124 U/L). As regards urinary HCG levels, the average value on days 8, 9, and 10 was above the 50-U/L detection limit of the low-threshold test, which was in fact positive in the majority of patients. Also on days 11 and 12, however, urinary HCG levels were above this limit in a certain proportion of subjects (day 11, 2/6; day 12, 1/6); accordingly the low-threshold pregnancy test was positive with a frequency of 2/6 on day 11 and of 1/6 on day 12. By contrast, the traditional high-threshold pregnancy test was negative in urine samples of all subjects. Our study indicates that the increased sensitivity of modern low-threshold pregnancy tests may cause false positive results in those cases where exogenous HCG has been administered during the luteinic phase.

Adult↗
PubMed2001

Exposure to chemical agents in Swedish aluminum foundries and aluminum remelting plants--a comprehensive survey.

Secondary aluminum melting is mainly performed in sand, die, and static die-casting foundries and remelting plants. In seven Swedish foundries and two remelting plants, the exposure and area concentrations of total dust, metals, organic gases, and vapors were determined mainly as daily, time-weighted averages (TWAs). For most combinations of jobs and agents, the exposure levels were well below the current threshold limits suggested by the American Conference of Governmental Industrial Hygienists (ACGIH). However, high exposure levels of mineral oil mist (geometric mean [GM] = 0.6 mg/m3) were observed in the die-casting process, with a maximum of 4 mg/m3. The findings were similar for total dust (GM = 5.1 mg/m3) and crystalline quartz (GM = 0.05 mg/m3) during molding operations in the sand foundries, maximum air concentrations being 31 mg/m3 and 0.22 mg/m3, respectively. Other agents which occasionally reached high exposure levels included furfuryl alcohol (up to 23 mg/m3 during furan binder use in sand foundries), aniline (up to 2.6 mg/m3 during thermal degradation of cold-box binders), and dimethylethylamine (up to 9 mg/m3) in the cold-box process used in static die-casting and sand foundries. The average aluminum exposure levels (GM = 0.043 mg/m3) were low in all foundries, individual values not exceeding 0.94 mg/m3. The exposures to metals were below 10 percent of their threshold limits. Similarly low levels were detected of polyaromatic hydrocarbons, phenol, formaldehyde, methylenebisphenyl diisocyanate, and phenylisocyanate. In the aluminum remelting plants, a few high exposure levels of total dust (GM = 1.4 mg/m3) up to 8 mg/m3 were detected in furnace workers. Aluminum and other metals were well below 10 percent of their threshold limits, with the exception of a few high concentrations of manganese, up to 0.14 mg/m3. The between-worker variability (GSDB) in the foundries for total dust, aluminum, and oil mist were on the order of 3-4. The heterogenicity of secondary aluminum melting requires assessment of a wide variety of chemical agents. For certain exposures, technical and medical monitoring programs are still needed.

Aluminum↗
PubMed2006

Bayesian detection of abnormal values in longitudinal biomarkers with an application to T/E ratio.

We developed a test that compares sequential measurements of a biomarker against previous readings performed on the same individual. A probability mass function expresses prior information on interindividual variations of intraindividual parameters. Then, the model progressively integrates new readings to more accurately quantify the characteristics of the individual. This Bayesian framework generalizes the two main approaches currently used in forensic toxicology for the detection of abnormal values of a biomarker. The specificity is independent of the number n of previous test results, with a model that gradually evolves from population-derived limits when n = 0 to individual-based cutoff thresholds when n is large. We applied this model to detect abnormal values in an athlete's steroid profile characterized by the testosterone over epitestosterone (T/E) marker. A cross-validation procedure was used for the estimation of prior densities as well as model validation. The heightened sensitivity/specificity relation obtained on a large data set shows that longitudinal monitoring of an athlete's steroid profile may be used efficiently to detect the abuse of testosterone and its precursors in sports. Mild assumptions make the model interesting for other areas of forensic toxicology.

Bayes Theorem↗
PubMed1993

[Determination of limit values for "safe driving" in street traffic with reference to centrally active drugs from the pharmacokinetic and pharmacodynamic viewpoint].

When establishing threshold values for "driving under the influence of centrally acting compounds" it must be considered that many parameters have an important influence on the pharmacokinetic properties (e.g. volume of distribution, the elimination half-life, and the drug concentration in body fluids) and the pharmacodynamic action (e.g. impairment of skills related to driving). This article describes these inter-and intraindividual parameters from the pharmacokinetic (influence of body weight, age, gender, genetics, diseases, other compounds as ethanol and antacids, enzyme induction, enzyme inhibition, first-pass effects, pharmacokinetic interaction, chronopharmacokinetics, mode of application) and pharmacodynamic (tolerance, pharmacodynamic interaction, pharmacogenetic, chronopharmacodynamic, pathological alterations) point of view. The large variabilities clearly indicate, that preliminary threshold values should be chosen high enough to prevent prejudice of traffic participants. A "consensus value" could be established and continuously monitored by a commission. Beside this the high relevance of valid analytical investigations must be regarded.

Adult↗
PubMed2002

Electrical phosphenes: on the influence of conductivity inhomogeneities and small-scale structures of the orbita on the current density threshold of excitation.

Electrical and magnetic phosphenes, perceptions of light as a result of non-adequate stimulation of the eye by electrical current or magnetic induction, respectively, are one of the cornerstones to justify limit values for extreme low-frequency fields specified by statutory regulations. However, the mechanism and place of action, as well as the excitation threshold, remain unknown until now. We suggest that the origin of phosphene excitation is the synaptic layer of the eye. The current density threshold value for electrical phosphene excitation was numerically quantified for this area on the basis of a detailed geometrical model in original submillimetre resolution and specifically measured conductivities in the LF range. The threshold values found were 1.8 A m-2 at 60 Hz and 0.3 A m-2 at 25 Hz. These values are comparable with values of other excitable tissues. It has been shown that the current density threshold for phosphene generation depends on small-scale structures not taken into account by previous models.

Electric Conductivity↗
PubMed1996

A long-term study on the health status and performance of sows on different feed allowances during late pregnancy. II. The total cell content and its percentage of polymorphonuclear leucocytes in pathogen-free colostrum and milk collected from clinically healthy sows.

The main objective of this study was to determine the total cell content, TCC, and the percentage of polymorphonuclear leucocytes, PMNLs, in colostrum and milk collected from sows during the first 22 days of lactation. The pH-values during the same sampling period were also determined. It should be emphasized that all the values obtained emanate from bacteriologically negative colostrum and milk. The potential influence of different levels of late gestation feeding regimes was also evaluated. The TCC-values obtained from milk samples during the first 3 weeks of lactation and exceeding the designated threshold of 10 x 10(6) cells/ml varied between 4% and 21%. Within the TCC-limitation of 10-19.99 x 10(6) cells/ml neither the preceding nor the succeeding cell counts exceeded the threshold in 26.8%. TCC-values above 19.99 x 10(6) cells/ml were preceded and succeeded by cell counts below the threshold in 58.8% and 58.8%, respectively. The TCC-levels below the threshold of 10 x 10(6) cells/ml, expressed as geometric least square means, increased significantly from day 1 to day 3 (1.23 x 10(6) cells/ml versus 1.86 x 10(6) cells/ml) and decreased thereafter gradually to day 22 (1.38 x 10(6) cells/ml). When all values were included, the TCC-values increased in a similar pattern from day 1 to day 3 (1.38 x 10(6) cells/ml versus 3.18 x 10(6) cells/ml). The value on day 22 of lactation was still on a significantly elevated level compared with that of day 1 (2.10 x 10(6) cells/ml versus 1.38 x 10(6) cells/ml). The 2 different feeding regimes were not found to influence the TCC-values during the first 22 days of lactation. In the whole material the PMNL-values, expressed as percentages of the TCC, declined from approximately 60% on day 1 of lactation to between 40% and 50% for the remaining sampling period. This decline was comparable with the one seen in the cell class below the threshold of 10 x 10(6) cells/ml. In the 2 cell classes above 9.99 x 10(6) cells/ml, 78.0% and 88.8% of PMNLs on day 1 declined to about 40% on day 22. This might indicate an inflammatory response on day 1 but without any detectable bacteriological growth. The increase in lactation number, if lactation 1 was compared with the following lactations, revealed a significant rise (p < 0.05) in TCC-level and percentage level of PMNLs. A stepwise and significant increase in pH-level occurred between days 1, 3 and 8 (6.18, 6.56, 7.03) followed by a significant decrease to day 22 (6.91) when pH-values from milk of all cell classes were included.

Animal Feed↗
PubMedDate not supplied

Serum selenium concentration of a healthy northwest Spanish population.

Selenium (Se) is an essential element, cofactor for glutathione peroxidase (GSHPx) activity, whose deficiency may induce modifications in the cellular antioxidative status and induce the appearance of different diseases. Current views suggest that a serum Se concentration inferior to 45 micrograms/L may correlate with an increased risk of coronary hearth diseases, coronary atherosclerosis and cancer. Since the Se concentration in human blood varies between geographical areas, we initiated a study to evaluate the Se status in the general healthy population of Barcelona. Serum Se concentration was investigated in a random sample of 150 subjects (age range 18-70 yr) by graphite furnace atomic spectrometry (FLAAS). L'vov platform, Zeeman background correction, and other specifications of stabilized temperature platform furnace (STPF) concept were followed. The results show that in the general population of Barcelona, Se serum concentration ranges between 60 and 106 micrograms/L (X = 80.7 +/- 10 micrograms/L). These values can be considered within the safe limits, since no subject was found with a concentration lower than the threshold of 45 micrograms/L.

Adolescent↗
PubMed1999

Simple but reliable solutions for spiral MRI gradient design.

The efficiency of gradient design in MRI is limited by the simple fact that the gradient coil current and slew rate cannot exceed hardware threshold values. In spiral MRI, which requires gradients to be very rapidly switched between positive and negative values, minimization of the acquisition time is achieved by maintaining the current and slew rate as high as possible during the entire measurement. Since the current and slew rate compete against each other, an efficient gradient design consists of two parts in which current and slew rate are pushed alternatively to their limits. Values for these types of gradients can be obtained by solving numerically the equation of motion for the spiral trajectory. This paper shows that simple but reasonable mathematical approximations deliver reliable analytical solutions. Images obtained using these analytical solutions do not show evident distortions when compared with images obtained with numerical solutions.

Algorithms↗
PubMed1989

Deactivation kinetics of different components of calcium inward current in the membrane of mice sensory neurones.

1. Deactivation kinetics of different components of calcium inward current were analysed by measuring 'tail currents' in intracellularly perfused sensory neurones isolated from dorsal root ganglia of newborn mice. 2. Deactivation of a low-threshold inactivating component had a mono-exponential time course with time constants that decreased as the potential was made more negative, and reached a limiting value of 1.0-1.2 ms at extreme hyperpolarizations. Replacement of Ca2+ by Ba2+ as a charge carrier decreased this value almost twofold. 3. Deactivation of the high-threshold component of calcium current contained two exponential components with time constants of similar potential dependence. The fast time constant became practically constant (0.1-1.2 ms) during repolarizations beyond -50 mV, and the slow time constant became constant (0.80-0.85 ms) at repolarization beyond -70 mV. 4. Replacement of intracellular aspartate with phosphate, or a depolarized holding potential of -40 mV, abolished reversibly the slow component of the tail current; in parallel, the peak current-voltage relation of the current became shifted by 15-20 mV in the depolarizing direction. 5. Extracellular application of the calcium channel agonist Bay K 8644 (2.5-5 mumol/l) did not change deactivation kinetics of the low-threshold current; however, it increased considerably the slow exponential component of high-threshold current deactivation or induced such a component in conditions when the latter was absent before application (Vh = -40 mV; cell perfusion with Tris phosphate). 6. The data obtained are analysed on the basis of the presence of three types of calcium channels in the neuronal membrane which possess similar kinetic mechanisms of activation and deactivation but differ in the activation thresholds and the time constants of transitions between open and closed states. The three calcium channels differ also in interaction with different permeant ions and calcium channel agonists.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗