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PubMed2005

A simple model for nitrogen-limited plant growth and nitrogen allocation.

BACKGROUND: and Aims In many studies of nitrogen-limited plant growth a linear relationship has been found between relative growth rate and plant nitrogen concentration, showing a negative intercept at a plant nitrogen concentration of zero. This relationship forms the basis of the nitrogen productivity theory. On the basis of empirical findings, several authors have suggested that there is also a distinctive relationship between allocation and plant nitrogen concentration. The primary aim of this paper is to develop a simple plant growth model that quantifies this relationship in mathematical terms. The model was focused on nitrogen allocation to avoid the complexity of differences in nitrogen concentrations in the different plant compartments. The secondary aim is to use the model for examining the processes that underlie the empirically based nitrogen productivity theory. METHODS: In the construction of the model we focused on the formation and degradation of biologically active nitrogen in enzymes involved in the photosynthetic process (photosynthetic nitrogen). It was assumed that, in nitrogen-limiting conditions, the formation of photosynthetic nitrogen is proportional to nitrogen uptake. Furthermore it was assumed that the degradation of photosynthetic nitrogen is governed by first-order kinetics. Model predictions of nitrogen allocation were compared with data from literature describing four studies of growth. Model predictions of whole plant growth were compared with the above-mentioned nitrogen productivity theory. KEY RESULTS: Allocation predictions agreed well with the investigated empirical data. The ratio of leaf nitrogen and plant nitrogen declines linearly with the inverse of plant nitrogen concentration. Nitrogen productivity is proportional to this ratio. Predictions for whole-plant growth were in accordance with the nitrogen productivity theory. CONCLUSIONS: The agreement between model predictions and empirical findings suggests that the derived equation for nitrogen allocation and its relationship to plant nitrogen concentration might be generally applicable. The negative intercept in the linear relationship between relative growth rate and plant nitrogen concentration is interpreted as being equal to the degradation constant of photosynthetic nitrogen.

Models, Biological↗

PubMed2005

Specific leaf area and dry matter content estimate thickness in laminar leaves.

BACKGROUND AND AIMS: Leaf thickness plays an important role in leaf and plant functioning, and relates to a species' strategy of resource acquisition and use. As such, it has been widely used for screening purposes in crop science and community ecology. However, since its measurement is not straightforward, a number of estimates have been proposed. Here, the validity of the (SLA x LDMC)(-1) product is tested to estimate leaf thickness, where SLA is the specific leaf area (leaf area/dry mass) and LDMC is the leaf dry matter content (leaf dry mass/fresh mass). SLA and LDMC are two leaf traits that are both more easily measurable and often reported in the literature. METHODS: The relationship between leaf thickness (LT) and (SLA x LDMC)(-1) was tested in two analyses of covariance using 11 datasets (three original and eight published) for a total number of 1039 data points, corresponding to a wide range of growth forms growing in contrasted environments in four continents. KEY RESULTS AND CONCLUSIONS: The overall slope and intercept of the relationship were not significantly different from one and zero, respectively, and the residual standard error was 0.11. Only two of the eight datasets displayed a significant difference in the intercepts, and the only significant difference among the most represented growth forms was for trees. LT can therefore be estimated by (SLA x LDMC)(-1), allowing leaf thickness to be derived from easily and widely measured leaf traits.

Climate↗

PubMed2005

The leaf size-twig size spectrum of temperate woody species along an altitudinal gradient: an invariant allometric scaling relationship.

BACKGROUND AND AIMS: The leaf size-twig size spectrum is one of the leading dimensions of plant ecological variation, and now it is under development. The purpose of this study was to test whether the relationship between leaf size and twig size is isometric or allometric, and to examine the relationship between plant allometric growth and life history strategies in the spectrum. METHODS: Leaf and stem characters-including leaf and stem mass, total leaf area, individual leaf area, stem cross-sectional area, leaf number and stem length-at the twig level for 59 woody species were investigated along an altitudinal gradient on Changbaishan Mountain in the temperate zone of China. The environmental gradient ranges from temperate broad-leaved mixed forest at low altitude, to conifer forest at middle altitude, and to sub-alpine birch forest at high altitude. The scaling relationships between stem cross-sectional area and stem mass, stem mass and leaf mass, and leaf mass and leaf area at the twig level were simultaneously determined. KEY RESULTS: Twig cross-sectional area was found to have invariant allometric scaling relationships with the stem mass, leaf mass, total leaf area and individual leaf area, all with common slopes being significantly larger than 1, for three altitudinal-zoned vegetation types under investigation. However, leaf mass was found to be isometrically related to stem mass and leaf area along the environmental gradient. Based on the predictions of previous models, the exponent value of the relationship between twig cross-sectional area and total leaf area can be inferred to be 1.5, which falls between the confidence intervals of the relationship at each altitude, and between the confidence intervals of the common slope value (1.17-1.56) of this study. This invariant scaling relationship is assumed to result from the fractural network and/or developmental constraints of plants. The allometric constants (y-intercepts) of the relationships between the stem cross-sectional area and leaf area (both total leaf area and individual leaf area) were found to decrease significantly along the altitudinal gradient. This suggests that the species would support less leaf area at a given twig cross-sectional area with increasing environmental stress. CONCLUSIONS: This study demonstrated that plants respond to the environmental gradient by changing the y-intercepts of the relationship between leaf size-twig size, while keeping the exponent value of the allometric relationship as an invariant constant. The allometric growth in the twig size-leaf size spectrum is related to many other components of plant life history strategy, including the well established life history trade-off between efficiency and safety in the hydraulic transport of water.

Acclimatization↗

PubMed2006

Above- and below-ground biomass relationships across 1534 forested communities.

BACKGROUND AND AIMS: Prior work has shown that above- and below-ground dry biomass across individual plants scale in a near isometric manner across phyletically and ecologically diverse species. Allometric theory predicts that a similar isometric scaling relationship should hold true across diverse forest-types, regardless of vegetational composition. METHODS: To test this hypothesis, two compendia for forest-level above- and below-ground dry biomass per hectare (M(A) and M(R), respectively) were examined to test the hypothesis that M(A) vs. M(R) scales isometrically and in the same manner as reported for data from individual plants. Model Type II regression protocols were used to compare the numerical values of M(A) vs. M(R) scaling exponents (i.e. slopes of log-log linear relationships) for the combined data sets (n =1534), each of the two data sets, and data sorted into a total of 17 data subsets for community- and biome-types as well as communities dominated by angiosperms or conifers. KEY RESULTS: Among the 20 regressions examined, 15 had scaling exponents that were indistinguishable from that reported for M(A) vs. M(R) across individual plants. The isometric hypothesis could not be strictly rejected on statistical grounds; four of these 15 exponents had broad 95% confidence intervals resulting from small sample sizes. Significant variation was observed in the y-intercepts of the 20 regression curves, because of absolute differences in M(A) or M(R). CONCLUSIONS: The allometries of forest- and individual plant-level M(A) vs. M(R) relationships share strikingly similar scaling exponents, but differ because of considerable variation in y-intercepts. These results support prior allometric theory and provide boundary conditions for the scaling of M(A) and M(R).

Biomass↗

PubMed2002

A two-stage model for multiple time series data of counts.

We propose a two-stage model for time series data of counts from multiple locations. This method fits first-stage model(s) using the technique of iteratively weighted filtered least squares (IWFLS) to obtain location-specific intercepts and slopes, with possible lagged effects via polynomial distributed lag modeling. These slopes and/or intercepts are then taken to a second-stage mixed-effects meta-regression model in order to stabilize results from various locations. The representation of the models from the stages into a combined mixed-effects model, issues of inference and choices of the parameters in modeling the lag structure are discussed. We illustrate this proposed model via detailed analysis on the effect of air pollution on school absenteeism based on data from the Southern California Children's Health Study.

Journal Article↗

PubMed1989

Effect of nalbuphine hydrochloride on the ventilatory and occlusion pressure responses to carbon dioxide in volunteers.

We studied the effect of nalbuphine on the ventilatory and occlusion pressure responses to carbon dioxide rebreathing in six healthy male volunteers (mean age 25.5 yr) in a single-blind laboratory study. On four separate days volunteers were assigned randomly to receive either placebo (0.9% sodium chloride) or three i.v. doses of nalbuphine (15, 30 and 60 mg 70 kg-1), followed 90 min later by naloxone 0.4 mg 70 kg-1. Duplicate rebreathing tests were performed and the mean intercept at PE'CO2 7 kPa and the slopes of the linear relationship between inspiratory minute ventilation (Vl) or occlusion pressure (P0.1) with PE'CO2 were measured. Nalbuphine significantly decreased the mean intercept of the Vl (P less than 0.01) and P0.1 (P less than 0.05) responses, but caused no changes in the slopes. No significant difference between the doses was noted, suggesting that an Effect maximum (E'max) for respiratory depression was reached with a dose of approximately 15 mg 70 kg-1. Naloxone was less effective in antagonizing the depression in Vl at the higher dose of nalbuphine. Similar P0.1 values were associated with the same inspiratory flow rate (1 litre s-1) before and after drug treatment, suggesting that nalbuphine acts centrally to depress ventilation. Sedation increased significantly following each dose of nalbuphine (P less than 0.001). No demonstrable difference between the doses was shown, suggesting an Effect maximum (E'max) for sedation was reached at about 15 mg 70 kg-1. Administration of nalbuphine was associated with pain at the injection site, dizziness, dreaming, nausea and vomiting. Cardiovascular stability was maintained in all subjects.

Adult↗

PubMed2004

Non-invasive assessment of cerebral perfusion pressure in brain injured patients with moderate intracranial hypertension.

BACKGROUND: A non-invasive estimation of cerebral perfusion pressure (CPP) using transcranial Doppler sonography was assessed in brain-injured patients by comparing conventional measurements of CPP (difference between mean arterial pressure and intracranial pressure) (CPPm) with the difference between AP(mean) and the critical closing pressure of the cerebral circulation (CPPe). METHODS: Twenty adults with bilateral and diffuse brain injuries were included in the study. CPPe was estimated using a formula combining the phasic values of flow velocities and arterial pressure. In group A (n=10) the comparison was repeatedly performed under stable conditions. In group B (n=10) the comparison was performed during a CO(2) reactivity test. Covariance analysis was used to assess the relationships. RESULTS: In group A, CPPe and CPPm were correlated (slope, 0.76; intercept, +10.9; 95% CI, -3.5 to +25.4). During the increase in intracranial pressure (group B) (+1.9 (sd 1.5) mm Hg per mm Hg of Pe'(co(2))) the relationship persisted (slope, 0.55; intercept, +32.6; 95% CI, +16.3 to +48.9) but the discrepancy between the two variables increased as reflected by the increase in bias and variability. CONCLUSION: Non-invasive estimation of CPP can be used for brain monitoring of head-injured patients, but the accuracy of the method may depend on the level of intracranial hypertension.

Adult↗

PubMed1977

Left ventricular compliance in acute myocardial infarction in man.

Left ventricular end-diastolic pressure (P) and volume (V) were measured in 12 patients with acute myocardial infarction. It was assumed that the diastolic P-V relationship was exponential and corresponded to the formula P=be KV. In 7 patients submitted to volume loading, several data points of this relationship were obtained and at zero volume, the mean intercept with the ordinates was 0.037+/-0.015 kPa (SEM) (0.28+/-0.12 mmHg). In the other 5 patients, the P-V curve was plotted through this intercept and the pressure and volume co-ordinates obtained by control. The K coefficient (passive elastic modulus) was greater, and the normalised left ventricular compliance index (dV/VdP) was smaller in the infarct group than in the control group. This suggests decreased left ventricular compliance during the acute phase of myocardial infarction. By comparing left ventricular function curves plotted using either end-diastolic pressure or end-diastolic volume as the stretch index it is possible to evaluate the relative participation of decreased compliance and depressed contractility in global left ventricular function.

Acute Disease↗

PubMed1981

Cardiac energetics in short and long term hypertrophy induced by aortic coarctation.

Hypertrophy was induced in rats by constriction of the abdominal aorta proximal to the coeliac trunk. The effects of both short-term, STH. (2 to 4 days) and long term, LTH (40 to 55 days) hypertrophy were studied by mechanical and myothermic measurements on papillary muscles from the left ventricle. In agreement with other studies aortic coarctation increased the left ventricle to body weight ratio. In isometric experiments it was shown that peak stress development was enhanced in the STH group compared with the control and LTH groups. Active heat production was related to active stress development by linear regression in the control and pressure overload groups. There was no significant difference between the mean slopes of the groups but there was a significant increase in the intercept in the STH group and a decrease in the LTH group. This intercept corresponds to the tension-independent heat component. In isotonic experiments load enthalpy relationships were determined for the different groups and the data for each group were pooled. In the LTH group there was a 19% fall in work output per contraction and a 20% fall in total enthalpy. In the STH group there was a 31% increase in work output and a 39% rise in total enthalpy. Because of the parallel changes in work and enthalpy there was no significant change in the mechanical efficiency of the two groups as compared to the controls. The simplest interpretation of the results is that in STH the intracellular free calcium level is raised whereas in LTH it is lowered.

Animals↗

PubMed1984

Diastolic coronary artery pressure-flow velocity relationships in conscious man.

We characterised the diastolic pressure-flow velocity relationship in the normal left coronary artery of conscious man before and after vasodilatation with angiographic contrast medium. Phasic coronary artery pressure and flow velocity were measured in ten patients during individual diastoles (0.5 to 1.0 s) using a 20 MHz catheter-tipped, pulsed Doppler transducer. All pressure-flow velocity curves were linear over the diastolic pressure range of 110 +/- 15 (SD) mmHg to 71 +/- 7 mmHg (r = 0.97 +/- 0.01). In the basal state, values for slope and extrapolated zero flow pressure intercept averaged 0.35 +/- 0.12 cm X s-1 X mmHg-1 and 51.7 +/- 8.6 mmHg, respectively. Vasodilatation resulted in a 2.5 +/- 0.5 fold increase in mean flow velocity. The diastolic pressure-flow velocity relationship obtained during peak vasodilatation compared to that during basal conditions was characterised by a steeper slope (0.80 +/- 0.48 cm X s-1 X mmHg-1, p less than 0.001) and lower extrapolated zero flow pressure intercept (37.9 +/- 9.8 mmHg, p less than 0.05). Mean right atrial pressure for the group averaged 4.4 +/- 1.7 mmHg, while left ventricular end-diastolic pressure averaged 8.7 +/- 2.8 mmHg. These observations in man are similar to data reported in the canine coronary circulation which are consistent with a vascular waterfall model of diastolic flow regulation. In this model, coronary blood flow may be regulated by changes in diastolic zero flow pressure as well as in coronary resistance.

Adult↗

PubMed1987

Effect of alveolar pressure on pulmonary artery pressure in chronically hypoxic rats.

The effect on pulmonary artery pressure of a rise in alveolar pressure differed in chronically hypoxic rats (10% O2 for 3-5 weeks) compared with control rats. Chronically hypoxic rats have newly muscularised walls in arterioles in the alveolar region. Isolated lungs of chronically hypoxic and control rats were perfused with blood under conditions in which alveolar pressure was greater than left atrial pressure during both normoxia and hypoxia. Alveolar pressure was the effective downstream pressure. Pressure-flow lines were measured at low and high alveolar pressure (5 and 15 mmHg). During normoxia pressure-flow lines of chronically hypoxic rats had a steeper slope (higher resistance) and greater extrapolated intercept on the pressure axis (effective downstream pressure) than control rats. In both groups of rats the change from low to high alveolar pressure during normoxia caused an approximately parallel shift in the pressure-flow line similar to the change in alveolar pressure. During hypoxia, which led to an increase in slope and intercept in both groups of rats, the effect of a rise in alveolar pressure differed in chronically hypoxic from control rats. In control rats there was a small parallel shift in the pressure-flow line that was much less than the increase in alveolar pressure; in chronically hypoxic rats there was a large parallel shift in the pressure-flow line that was greater than the increase in alveolar pressure. Thus in chronically hypoxic rats hypoxic vasoconstriction probably occurred mainly in muscular alveolar vessels, whereas in control rats it probably occurred upstream in extra-alveolar vessels. At constant blood flow the relation between pulmonary artery pressure and alveolar pressure was measured while alveolar pressure was reduced from approximately 15 mmHg to zero during both normoxia and hypoxia. In control and chronically hypoxic rats the slope of this line was less than 1. At an alveolar pressure of 2-3 mmHg there was an inflection point below which the line was nearly horizontal in control but negative in chronically hypoxic rats. During hypoxia the inflection point increased in control but not in chronically hypoxic rats, whereas the preinflection slope became negative. Apart from a rise in pulmonary artery pressure at all values of alveolar pressure, which occurred in both groups of rats, there was no change in the form of the curve in chronically hypoxic rats during hypoxia. These results also suggest constriction of extra-alveolar vessels in control rats and alveolar vessels in chronically hypoxic rats during hypoxia.

Animals↗

PubMed1983

Diastolic function in hypertrophic cardiomyopathy: effects of propranolol and verapamil on diastolic stiffness.

In patients with hypertrophic cardiomyopathy (HCM), impaired left ventricular (LV) relaxation and diastolic filling have been reported. Therefore, we determined LV diastolic stiffness in nine patients with HCM before and 10 to 15 min after 0.15 mg/kg propranolol i.v. (group 1) and in six patients with HCM before and 10 to 15 min after 0.1 mg/kg verapamil i.v. (group 2). Simultaneous LV cineangiography and high-fidelity pressure measurements were performed in group 1 and simultaneous M-mode echocardiography and high-fidelity pressure measurements in group 2. Passive LV chamber stiffness was determined in group 1 from the diastolic pressure-volume data using an exponential three-parameter model: P = ae beta V + C, where P = pressure, alpha = intercept, beta = constant of chamber stiffness, V = volume and C = baseline pressure. Passive LV myocardial stiffness was estimated in group 2 from the diastolic stress-strain data using a viscoelastic model: sigma = alpha' (e beta' epsilon -1) + eta epsilon, where sigma = meridional wall stress, alpha = intercept, beta' = constant of myocardial stiffness, epsilon = midwall strain, eta = constant of myocardial viscosity and epsilon = strain rate. LV relaxation was assessed from the time constant of LV pressure decay (T) by plotting LV pressure versus negative dP/dt. LV diastolic filling was evaluated from peak and mean LV filling rate in group 1 and from peak and mean midwall lengthening rate in group 2. LV chamber and myocardial stiffness, respectively, remained unchanged before and after administration of propranolol (beta = 0.054 and 0.047) and verapamil (beta' = 14.8 and 12.6); however, the time constant of LV pressure decay T increased significantly in group 1 from 45 to 66 ms (P less than 0.05) and decreased significantly in group 2 from 53 to 43 ms (P less than 0.05). Parallel to the changes in LV isovolumic relaxation, mean LV diastolic filling rate decreased significantly in group 1 from 257 to 196 ml m-2 s-1 (P less than 0.025) and mean LV midwall lengthening rate increased significantly in group 2 from 2.37 to 4.31 cm/sec (P less than 0.05). It is concluded that LV diastolic stiffness remains unchanged in patients with HCM after propranolol and verapamil. LV relaxation and mean diastolic filling, however, are impaired in patients with HCM following propranolol but are improved after verapamil. Thus, the beneficial effect of verapamil on diastolic mechanics is related to improved relaxation and diastolic filling rather than to changes in LV diastolic stiffness.

Cardiomyopathy, Hypertrophic↗

PubMed1995

Dependence of frequency of homologous recombination on the homology length.

The frequency of homologous recombination is believed to be a linear function of the length (N bp) of homology between DNAs. Here, the N intercept is believed to be determined by a threshold length below which some physical constraint is effective. In the mammalian gene targeting systems, however, the frequency depends more steeply than linearly on the homology length. To explain both the linear dependence and the steeper dependence, we propose a model where the branch point of a reaction intermediate is assumed to "walk randomly" along the homologous region until it is processed. The intermediate is assumed to be destroyed if the branch point ever reaches either end of the homology. In this model, the length dependence is governed by a parameter, h, which is defined as efficiency of processing of the intermediate and reflects unlikelihood of the destruction at either end of the homology. We find that the frequency is proportional to N3 for smaller N and is a linear function of N for larger N. Where the shift from the N3 dependence to the linear dependence takes place is determined by the parameter h. The range of N showing the N3 dependence becomes narrower as h becomes larger. The dependence steeper than linear dependence, which is observed not only in the mammalian gene targeting system but also in bacteriophage T4, Escherichia coli and yeast systems, agrees well with the predicted N3 dependence. The N intercept is determined not by physical (or structural) constraints but only by the parameter h in this model.

Animals↗

PubMed1996

A 15-year longitudinal study of Halstead-Reitan neuropsychological test performance.

Using a two-stage growth curve analysis, change over time in performance on tests in the Halstead-Reitan Battery and Average Impairment Rating (AIR) was assessed for 53 individuals who varied in age and health status. In the first stage of the analysis, estimated slope and intercept values were calculated for each individual by regressing longitudinal data points on time. In the second stage, estimated slope and intercept values obtained in the first-stage analysis were regressed on age at entry into the study with statistical control for health status, education, occupation, and gender. Control for health status had an insignificant influence on magnitude of associations between age and test performance. Age-at-entry into the study was associated with statistically significant increasing change over time (poorer performance) for tests placing relatively heavy demands on speed of psychomotor performance and for AIR.

Adult↗

PubMed2002

Differential age effects in semantic and episodic memory.

Results from 4 experimental tasks and 8 data sets (the 4 tasks involved either multiple sessions or different stimuli) as well as a vocabulary test conducted on the same 80 participants (40 younger and 40 older adults) are reported. The authors employed 2 semantic memory tasks (lexical decision and multiplication verification) using data from 2 sessions (for a total of 4 semantic data sets) and 2 episodic memory tasks (hybrid visual search and memory search with digits and with words as stimuli). Factor analyses using slope and intercept data from the 8 experimental data sets indicated the presence of 3 latent factors: a single intercept factor for both episodic and semantic tasks and separate slope factors for episodic and semantic tasks. A structural equation model with paths from age to 3 different 1st-order latent factors (episodic central processes, semantic central processes, and combined episodic and semantic peripheral processes) fit better than general factor models. These data are consistent with a theoretical framework in which there are age-related dissociations between peripheral and central processes across semantic and episodic memory.

Adolescent↗

PubMed2004

Age differences in central (semantic) and peripheral processing: the importance of considering both response times and errors.

In this project we examined the effect of adult age on visual word recognition by using combined reaction time (RT) and accuracy methods based on the Hick-Hyman law. This was necessary because separate Brinley analyses of RT and errors resulted in contradicting results. We report the results of a lexical decision task experiment (with 96 younger adults and 97 older adults). We transformed the error data into entropy and then predicted RT by using entropy values separately for exposure duration (thought to influence peripheral processes) and word frequency (thought to influence central processes). For exposure duration, the entropy-RT functions indicate that older adults show higher intercepts and slopes than do younger adults, suggesting an encoding decrement for older adults. However, for word frequency, older adults show higher intercepts but not steeper slopes than younger adults. Older adults thus show a peripheral processing decrement but not a central processing decrement for lexical decision.

Adolescent↗

PubMedDate not supplied

Detection of marijuana use by oral fluid and urine analysis following single-dose administration of smoked and oral marijuana.

We compared oral fluid testing to urine testing in subjects who were administered single doses of marijuana by smoked and oral routes. Oral fluid specimens were collected with the Intercept DOA Oral Specimen Collection Device, screened for THC with the Cannabinoids Intercept MICRO-PLATE Enzyme Immunoassay (EIA) utilizing a 1.0-ng/mL cutoff concentration, and confirmed for THC by gas chromatography-tandem mass spectrometry (GC-MS-MS) with a 0.5-ng/mL cutoff concentration. Urine specimens were screened for 11-nor-carboxy-delta9-tetrahydrocannabinol (THCCOOH) by immunoassay utilizing a 50-ng/mL cutoff concentration and confirmed for THCCOOH by GC-MS with a 15-ng/mL cutoff concentration. Oral fluid specimens tested positive following smoked marijuana (N = 10) consecutively for average periods (+/-SEM; range) of 15 (+/-2; 1-24) and 13 h (+/-3; 1-24) by EIA and GC-MS-MS, respectively. The average THC detection times of the last oral fluid positive specimen following smoked marijuana by EIA and GC-MS-MS were 31 (+/-9; 1-72) and 34 h (+/-11; 1-72), respectively. In comparison to oral fluid, urine specimens generally tested negative for THCCOOH immediately after marijuana use. The average times to detection of the first urine specimen positive for THCCOOH by EIA and GC-MS were 6 (+/-2; 1-16) and 4 h (+/-1; 2-8), respectively. Urine specimens tested positive consecutively for average periods of 26 (+/-9; 2-72) and 33 h (+/-10; 4-72) for EIA and GC-MS, respectively. The average THCCOOH detection times of the last specimen by EIA and GC-MS were 42 (+/-10; 2-72) and 58 h (+/-6; 16-72), respectively. Considering the noninvasive nature of oral fluid collection and improved detection of recent marijuana use compared to urine testing, it was concluded that oral fluid testing for THC offers specific advantages over other means of marijuana testing when used in safety-sensitive testing programs.

Administration, Oral↗

PubMed2003

Odor-baited trap trees: a new approach to monitoring plum curculio (Coleoptera: Curculionidae).

We compared a trap approach with a trap-tree approach to determine the need and timing of insecticide applications against overwintered adult plum curculios, Conotrachelus nenuphar (Herbst.), in commercial apple orchards in Massachusetts in 2002. All traps and trap trees were baited with benzaldehyde (attractive fruit odor) plus grandisoic acid (attractive pheromone). Sticky clear Plexiglas panel traps placed at orchard borders, designed to intercept adults immigrating from border areas by flight, captured significantly more adults than similarly placed black pyramid traps, which are designed to capture adults immigrating primarily by crawling, or Circle traps wrapped around trunks of perimeter-row trees, which are designed to intercept adults crawling up tree trunks. None of these trap types, however, exhibited amounts of captures that correlated significantly with either weekly or season-long amounts of fresh ovipositional injury to fruit by adults. Hence, none appears to offer high promise as a tool for effectively monitoring the seasonal course of plum curculio injury to apples in commercial orchards in Massachusetts. In contrast, baiting branches of selected perimeter-row trees with benzaldehyde plus grandisoic acid led to significant aggregation (14-15-fold) of ovipositional injury, markedly facilitating monitoring of the seasonal course of injury to apples. A concurrent experiment revealed that addition of other synthetic fruit odor attractants to apple trees baited with benzaldehyde plus grandisoic acid did not enhance aggregation of ovipositional injury above that of this dual combination. We conclude that monitoring apples on odor-baited trap trees for fresh ovipositional injury could be a useful new approach for determining need and timing of insecticide application against plum curculio in commercial orchards.

Animals↗