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PubMed2003

Utricular sensitivity and preponderance assessed by the unilateral centrifugation test.

Utricular sensitivity and preponderance of the right or left utricle can be assessed by means of the unilateral centrifugation test. In this test, subjects are rotated about an earth vertical axis at a velocity of 400 degrees per second. During the ongoing rotation, the subject is gradually translated 4 cm first to the right, and then to the left, along an interaural axis, to a position at which one utricle becomes aligned with the axis of rotation, and at this point is subjected only to gravitational forces. At this eccentric position, the contralateral utricle is exposed to the combination of gravity and a centrifugal acceleration of 0.4g, corresponding to an apparent roll-tilt of 21.7 degrees. This stimulus induces ocular counterrolling (OCR), which is measured on-line using three-dimensional video-oculography (VOG). We observed that ocular counterrolling appears as a linear function of the gravito-inertial acceleration tilt of the head centre (GIA(HC)) during the lateral translation. We present a theoretical model for this linear relationship that contains two parameters: 1) the slope of the linear regression is a measure for the utricular sensitivity and 2) the intercept of the linear regression is a measure of the preponderance of the right or left utricle. The strength of the model is supported by data obtained from 28 healthy subjects and 14 patients with unilateral vestibular deafferentiation (UVD) due to acoustic neuroma surgery.

Acceleration↗
PubMed2004

[A review of correlation, regression and multiple factors analysis methods.].

In clinical research, the relationships between two factors or among multiple factors are frequently explored. Dependence and covariation are two kinds of relationships between two factors. Regression and correlation analysis are the appropriate methods in measuring and evaluating those factors. Multiple analysis methods are widely used in the studies of risk factors among diseases, data analyses of diagnostic tests, effects evaluation of a prevention and treatment, analyses of prognosis, etc. Multiple analysis methods could interpret the influences of each factor more specifically than single factor analysis, and provide more possibilities to improve the quality of a research. In this review, the fundamental principle and utilities on clinical research of several statistical methods are introduced in this paper, such as linear correlation, linear regression, rank regression, rank correlation, multiple linear regression and logistic regression. It intends to help the clinicians and researchers to select the appropriate statistical methods to collect and analyze the data.

Epidemiologic Studies↗
PubMedDate not supplied

Cross-sectional association between markers of inflammation and serum sex steroid levels in the postmenopausal estrogen/progestin interventions trial.

BACKGROUND: Standard risk factors do not adequately capture cardiovascular risk in postmenopausal women. We sought to determine the associations between levels of sex steroids and levels of inflammatory markers in postmenopausal women. METHODS: We analyzed baseline data from a subset of postmenopausal women aged 45-64 years who had stored samples during a randomized controlled trial. We measured levels of C-reactive protein (CRP), interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9), soluble intercellular adhesion molecule (sICAM), and circulating sex steroids. Multiple linear regression models were created with each of the following hormone levels as the primary exposure variable: estrone, total estradiol, bioavailable estradiol, total testosterone, bioavailable testosterone, progesterone, and sex hormone-binding globulin (SHBG). Sociodemographic and lifestyle covariates were derived from standardized self-report questionnaires and direct measurement (weight, height). RESULTS: Mean age of the 623 women was 56 years. After adjustment for age, body mass index (BMI), physical activity, alcohol consumption, and smoking, the bioavailable testosterone level (p = 0.03) was positively and the SHBG level (p < 0.001) was negatively associated with the logCRP level. The increment in CRP level between the highest and lowest quartile of bioavailable testosterone was 1.28 microg/mL. The increment in CRP level between the lowest and highest quartile of SHBG was 2.62 microg/mL. Compared with SHBG or bioavailable testosterone as predictors of logCRP in separate regression models, when both SHBG and bioavailable testosterone were included in the same multivariate linear regression model, only SHBG remained a statistically significant predictor of logCRP. Progesterone level was positively associated with the logMMP-9 level (p < 0.001); no other sex steroid level was associated with the logMMP-9 level. In multiply adjusted models, no association was found between levels of any sex steroid and IL-6 or sICAM level.

Alcohol Drinking↗
PubMed1998

Respiratory resistive impedance as an index of airway obstruction during nasal continuous positive airway pressure titration.

Esophageal pressure amplitude (DeltaPes), inspiratory pulmonary resistance (RLI) and inspiratory flow limitation score (FS) are used as indices of upper airway obstruction for the titration of nasal continuous positive airway pressure (nCPAP) in patients with obstructive sleep apnea syndrome (OSAS). This study was designed to determine whether oscillatory respiratory resistive impedance at 16 Hz (RFO) might be proposed as an alternative index. Eleven OSAS patients were studied during a night of polysomnography-controlled nCPAP titration. Nasal flow (V) and airway opening and esophageal pressures (Pao and Pes, respectively) were continuously measured during nasal breathing, and forced-flow oscillations (FO) were applied for 5 min at each nCPAP level. RLI was calculated by linear regression analysis of resistive pressure versus V over inspiration. R FO was obtained by linear regression analysis of respiratory resistive impedance versus frequency. Application of FO affected neither sleep nor pulmonary mechanics. RFO correlated with RLI in all patients. RFO did not correlate with DeltaPes in two patients, and was not significantly related to FS in five patients. This study demonstrates the applicability of the FO technique in sleeping patients receiving nCPAP, and the reliability of RFO for assessing pulmonary resistance. RFO might therefore be proposed as a quantitative index of airway obstruction for nCPAP titration.

Aged↗
PubMed2006

Genetic analyses of agronomic and seed quality traits of synthetic oilseed Brassica napus produced from interspecific hybridization of B. campestris and B. oleracea.

The heritability, the number of segregating genes and the type of gene interaction of nine agronomic traits were analysed based on F2 populations of synthetic oilseed Brassica napus produced from interspecific hybridization of B. campestris and B. oleracea through ovary culture. The nine traits-plant height, stem width, number of branches, length of main raceme, number of pods per plant, number of seeds per pod, length of pod, seed weight per plant and 1000-seed weight-had heritabilities of 0.927, 0.215, 0.172, 0.381, 0.360, 0.972, 0.952, 0.516 and 0.987 respectively, while the mean numbers of controlling genes for these characters were 7.4, 10.4, 9.9, 12.9, 11.5, 21.7, 20.5, 19.8 and 6.4 respectively. According to estimated coefficients of skewness and kurtosis of the traits tested, no significant gene interaction was found for plant height, stem width, number of branches, length of main raceme, number of seeds per pod and 1000-seed weight. Seed yield per plant is an important target for oilseed production. In partial correlation analysis, number of pods per plant, number of seeds per pod and 1000-seed weight were positively correlated with seed yield per plant. On the other hand, length of pod was negatively correlated (r = -0.69) with seed yield per plant. Other agronomic characters had no significant correlation to seed yield per plant. In this experiment, the linear regressions of seed yield per plant and other agronomic traits were also analysed. The linear regression equation was y = 0.074x8 + 1.819x9 + 6.72x12- 60.78 (R2= 0.993), where x8, x9 and x12 represent number of pods per plant, number of seeds per pod and 1000-seed weight respectively. The experiment also showed that erucic acid and oil contents of seeds from F2 plants were lower than those of their maternal parents. However, glucosinolate content was higher than that of the maternal plants. As for protein content, similar results were found in the F2 plants and their maternal parents. It was shown that the four quality traits, i.e. erucic acid, glucosinolate, oil content, and protein content, had heritability values of 0.614, 0.405, 0.153 and 0.680 respectively.

Analysis of Variance↗
PubMed2005

Winter-time climatic control on dissolved organic carbon export and surface water chemistry in an Adirondack forested watershed.

Although most of forested watersheds in temperate and boreal regions are snow-covered for a substantial portion of the year, responses of biogeochemical processes under the snow pack to climatic fluctuations are poorly understood. We investigated responses of dissolved organic carbon (DOC) and surface water chemistry in stream and lake discharge waters draining the Arbutus Lake Watershed in the Adirondacks of New York State to climatic fluctuations during the snow-covered months from December through April. Interannual variability in stream discharge corresponded to changes in air temperature and snow pack depth across the winter months. Concentrations of DOC in stream water draining a subcatchment showed immediate positive responses to rising temperatures and subsequent increases in runoff during most snowmelt events. Increases in DOC concentrations usually coincided with decreases in pH and increases in total aluminum (Al) concentrations, while the correlations between concentrations of DOC and SO4(2-) or base cations were negative. Although changes in air temperature, snow pack depth, and runoff were all significantly correlated with stream water concentrations of major solutes, stepwise linear regression found that runoff was the best predictor of solute concentrations. Results of stepwise linear regression with long-term monthly monitoring data collected at the lake outlet showed weaker but still consistent climatic effects on interannual variations in concentrations of DOC and other solutes. Over the 17 winter periods from December 1983 through April 2000, changes in seasonal average concentrations of DOC, H+, and Al in lake discharge generally corresponded to interannual variations in temperature, precipitation, and runoff, while SO4(2-) and base cations displayed an opposite trend. The results suggest that snowmelt-mediated DOC responses to temperature fluctuations during the winter months might offset increases in the surface water pH caused by decreasing acidic deposition and pose a potential hazard of Al toxicity in surface waters.

Air↗
PubMed2005

Comparison of two thiopental infusion rates for the induction of anaesthesia in dogs.

OBJECTIVE: To compare the induction dose requirements of thiopental using two different infusion rates for induction of anaesthesia in dogs. STUDY DESIGN: Prospective, randomized study. ANIMALS: Fifty, healthy (ASA I or II) client-owned dogs with a mean age of 4.1 years and a mean mass of 20.4 kg undergoing elective surgery. MATERIALS AND METHODS: Animals were randomly assigned to receive an infusion of 2.5% thiopental at a rate of either 0.1 ml kg(-1) minute(-1) or 0.4 ml kg(-1)minute(-1), 30-40 minutes after pre-anaesthetic medication with intramuscular acepromazine (0.025 mg kg(-1)) and pethidine (3.5 mg kg(-1)). Thiopental administration was controlled by a precision syringe driver. Statistical analyses of the results, using the outcome 'mg kg(-1) required for induction' (log-transformed) included unpaired t-tests for all categorical data (thiopental infusion rate, breed, sex, obesity, sedation quality) and univariable linear regression for continuous variables (mass, age). All variables were then considered in a multivariable linear regression model. The quality of induction with the two different infusion rates was also assessed. RESULTS: After controlling for quality of sedation, the thiopental induction dose requirement was significantly less (p < 0.001) with the slower infusion rate (median = 7.5 mg kg(-1); range 4.9-13.7) compared with the faster infusion rate (median =11.0 mg kg(-1); range 6.6-18.0). The quality of sedation also affected the dose required (p = 0.03). The slower infusion rate was associated with a significantly poorer induction quality (p = 0.03) [corrected] CONCLUSIONS: Slow thiopental infusion (0.1 ml kg(-1) minute(-1)) for anaesthesia induction after acepromazine/pethidine pre-anaesthetic medication reduced the induction dose requirement, although the quality of induction was inferior. CLINICAL RELEVANCE: The induction dose of thiopental was reduced with a slower administration rate and so slow administration is recommended in thiopental-sensitive animals.

Anesthesia↗
PubMed2000

Combined eye activity measures accurately estimate changes in sustained visual task performance.

Five concurrent eye activity measures were used to model fatigue-related changes in performance during a visual compensatory tracking task. Nine participants demonstrated considerable variations in performance level during two 53-min testing sessions in which continuous video-based eye activity measures were obtained. Using a trackball, participants were required to maneuver a target disk (destabilized by pseudorandom wind forces) within the center of an annulus on a CRT display. Mean tracking performance as a function of time across 18 sessions demonstrated a monotonic increase in error from 0 to 11 min, and a performance plateau thereafter. Individual performance fluctuated widely around this trend - with an average root mean square (RMS) error of 2.3 disk radii. For each participant, moving estimates of blink duration and frequency, fixation dwell time and frequency, and mean pupil diameter were analyzed using non-linear regression and artificial neural network techniques. Individual models were derived using eye and performance data from one session and cross-validated on data from a second session run on a different day. A general regression model (based only on fixation dwell time and frequency) trained on data from both sessions from all participants produced a correlation of estimated to actual tracking performance of R=0.68 and an RMS error of 1.55 (S. D.=0.26) disk radii. Individual non-linear regression models containing a general linear model term produced the cross-session correlations of estimated to actual tracking performance of R=0.67. Individualized neural network models derived from the data of both experimental sessions produced the lowest RMS error (mean=1.23 disk radii, S.D.=0.13) and highest correlation (R=0.82) between eye activity-based estimates and actual tracking performance. Results suggest that information from multiple eye measures may be combined to produce accurate individualized real-time estimates of sub-minute scale performance changes during sustained tasks.

Adult↗
PubMed1985

Correlations for the acute toxicity of multiple nitrogen substituted aromatic molecules.

Twenty-nine compounds, including amino and nitro derivatives of aromatic hydrocarbons as well as azaarenes and indole analogs, were assayed. The biological activity was monitored as population growth to axenic cultures of the ciliate Tetrahymena pyriformis. Structure-activity relationships were examined by linear regression analysis of log biological activity (Y) and log 1-octanol/water partition coefficient (X). Partition coefficients were determined by linear regression analysis of the retention time index of HPLC data. Attempts to generate linear predictive correlations for all the test compounds (n = 29; r2 = 0.325; P greater than 0.0013) and groups, subdivided based on the following chemical classes: aromatic hydrocarbons (n = 13; r2 = 0.122; P greater than 0.2417), azaarenes (n = 9; r2 = 0.348; P greater than 0.0946) and indole analogs (n = 7; r2 = 0.743; P greater than 0.0126), met with little success. Similarly, subdivisions based on the presence of a single (n = 14; r2 = 0.514; P greater than 0.0039) or multiple H-polar groups, i.e., NO2, NH2 (n = 15; r2 = 0.195; P greater than 0.0996), met with little success also. However, if one segregates the compounds which have para oriented H-polar substituents one gets a strong linear predictive correlation (n = 11; r2 = 0.889; P greater than 0.0001). A subdivision of the remaining data set leads to two models (n = 11; r2 = 0.845; P greater than 0.0001) and (n = 7; r2 = 0.965; P greater than 0.0001). An examination of the toxicity partitioning product values suggests the three-line predictive correlation model of these data is valid.

Animals↗
PubMed1997

Effect of uncomplicated chronic hypertension on the risk of small-for-gestational age birth.

This study assesses the effect of chronic hypertension on fetal growth. A cohort of 1,938 pregnant women attending five prenatal clinics in France between August 1991 and May 1993 were enrolled in a prospective study. Chronic hypertension was defined according to blood pressure at enrollment and past history, and cases complicated by preeclampsia were excluded. Adjusted odds ratios of small-for-gestational age birth were estimated by logistic regression. The independent effect of chronic hypertension on mean birth weight was examined through multiple linear regression analysis adjusting for gestational age at delivery and potential confounders. Uncomplicated chronic hypertension was associated with an increased risk of small-for-gestational age birth. Odds ratios increased with age. In women over age 30 years, the association was strong (adjusted odds ratio = 8.5, 95% confidence interval 2.9-24.5). Multiple linear regression showed that mean birth weight was 161 g (95% confidence interval 66-256 g) less in women with chronic hypertension compared with normotensive women. The authors conclude that mean birth weight is reduced and the risk of small-for-gestational age birth is increased in uncomplicated chronic hypertension compared with normotensive pregnancies. Results further suggest that the magnitude of this association increases with age.

Adult↗
PubMed1983

Relation of segmental wall motion to global left ventricular function in acute myocardial infarction.

The relation of left ventricular regional wall motion to global ventricular function was evaluated by radionuclide ventriculography in 127 patients within 18 hours of acute myocardial infarction. No patient had evidence of previous myocardial infarction. The following parameters were measured: (1) wall motion index; (2) percent of abnormally contracting segment; (3) ejection fraction (EF); (4) end-diastolic volume (EDV) and end-systolic volume (ESV); and (5) peak systolic cuff pressure/end-systolic volume ratio (PSP/ESV). The measurements of global function correlated well with wall motion index (r = 0.83, p less than 0.001 for EF; r = -0.69, p less than 0.001 for ESV; and r = 0.061, p less than 0.001 for PSP/ESV), but EDV correlated less well (r = -0.35, p less than 0.001). Multiple linear regression analysis revealed that EF correlated best with wall motion index, and no other parameters of global left ventricular function added significantly to the regression. The correlation of motion in each segment with EF was determined by multiple linear regression analysis. Ejection fraction correlated best with motion in the anterobasal, then in order of correlation, in the apical-septal, inferoapical, anterolateral, and superlateral walls. The relation of EDV, ESV, and degree of percent abnormally contracting segments was as follows: EDV did not increase with a mild regional wall motion abnormality; however, ESV did increase and reduced stroke volume. As percent abnormally contracting segments worsened, enlargement of both EDV and ESV was seen and was associated with further reduction in systolic volume. These data suggest that EF is the best global left ventricular function correlate of the severity of the regional wall motion abnormality, and that abnormal motion in the territory of the left anterior descending coronary best predicts reduction in global left ventricular function. Radionuclide ventriculography is useful in characterizing global and regional left ventricular function in the early hours of acute myocardial infarction.

Aged↗
PubMed2006

Noninvasive measurement of isovolumetric contraction time by Doppler cardiography can be substituted for fetal cardiac contractility: evaluation of a fetal lamb study.

OBJECTIVE: The objective of this study is to clarify whether the isovolumetric contraction time obtained from Doppler cardiography (Doppler ICT) can be an index substituted for fetal cardiac contractility. MATERIALS AND METHODS: In 10 pregnant ewes, fetal hypoxemia was induced by giving a variable mixture of gases. Through experiment, the Doppler ICT, pre-ejection period (PEP), and the maximum first derivative of the left ventricular pressure waveform (Max dp/dt) were simultaneously recorded every 10min. The relationship between both the Doppler ICT and PEP, and the Max dp/dt were analyzed. RESULTS: A significant negative linear regression was founded between the Doppler ICT and the Max dp/dt. A significant negative linear regression was also shown between PEP and the Max dp/dt. Moreover, the regression of Max dp/dt on ICT had significantly less residual variance than the regression of Max dp/dt on PEP (p=0.0004). CONCLUSION: In contrast to PEP, Doppler ICT is a reliable, and non-invasive index which can be substituted for fetal cardiac contractility.

Animals↗
PubMed2001

Are PCBs in the Canadian Arctic atmosphere declining? Evidence from 5 years of monitoring.

A long-term database of weekly air concentrations was examined to establish temporal trends of PCBs in the Arctic atmosphere. Several methods were employed to reduce the intra-annual variability allowing the elucidation of longterm trends for a selection of congeners at Alert located in the Canadian Arctic. These methods included temperature normalization (TN), multiple linear regression (MLR), and digital filtration (DF). Estimation of the slope (m) resulting from the linear regression between the natural logarithm of the partial pressure in air versus reciprocal temperature (In P = m/T + b), required for TN and MLR, proved difficult due to the poor correlation with temperature experienced forthe majority of congeners. Values of m were considerably lower than those obtained from temperate studies, implying that regional air-surface exchange plays a minor role in supporting the observed air concentrations in the Arctic. The lighter congeners generally showed very low slopes, and some even showed positive correlation with 1/T. This might be a result of their relatively fast reaction rates with OH radicals following the onset of 24-h sunlight in spring. Use of DF (in combination with TN and MLR) revealed declining trends for several of the lower chlorinated congeners in the high Arctic atmosphere, with estimated first-order half-lives, t1/2, ranging from approximately 3 to 20 yr. Declining trends of the lower congeners probably reflect falling levels in source regions, as a result of long-range transport to this Arctic site. There were no apparent trends for the higher chlorinated congeners (penta-substituted and above), exceptfor PCB 180, in marked contrast to temperate studies, indicating a lag time for decline between the Arctic and source regions.

Air Pollutants↗
PubMed2003

Simulation of leaf area development based on dry matter partitioning and specific leaf area for cut chrysanthemum.

This work aims to predict time courses of leaf area index (LAI) based on dry matter partitioning into the leaves and on specific leaf area of newly formed leaf biomass (SLA(n)) for year-round cut chrysanthemum crops. In five glasshouse experiments, each consisting of several plant densities and planted throughout the year, periodic destructive measurements were conducted to develop empirical models for partitioning and for SLA(n). Dry matter partitioning into leaves, calculated as incremental leaf dry mass divided by incremental shoot dry mass between two destructive harvests, could be described accurately (R(2 )= 0.93) by a Gompertz function of relative time, R(t). R(t) is 0 at planting date, 1 at the start of short-days, and 2 at final harvest. SLA(n), calculated as the slope of a linear regression between periodic measurements of leaf dry mass (LDM) and LAI, showed a significant linear increase with the inverse of the daily incident photosynthetically active radiation (incident PAR, MJ m(-2 )d(-1)), averaged over the whole growing period, the average glasshouse temperature and plant density (R(2 )= 0.74). The models were validated by two independent experiments and with data from three commercial growers, each with four planting dates. Measured shoot dry mass increase, initial LAI and LDM, plant density, daily temperature and incident PAR were input into the model. Dynamics of LDM and LAI were predicted accurately by the model, although in the last part of the cultivation LAI was often overestimated. The slope of the linear regression of simulated against measured LDM varied between 0.95 and 1.09. For LAI this slope varied between 1.01 and 1.12. The models presented in this study are important for the development of a photosynthesis-driven crop growth model for cut chrysanthemum crops.

Biomass↗
PubMed2001

Effect of the AT1-receptor antagonists losartan, irbesartan, and telmisartan on angiotensin II-induced facilitation of sympathetic neurotransmission in the rat mesenteric artery.

SUMMARY: The effect of the AT1-receptor antagonists losartan, irbesartan, and telmisartan on angiotensin II (Ang II)-induced facilitation of noradrenergic neurotransmission was investigated in the isolated rat mesenteric artery under isometric conditions. Electrical field stimulation (2, 4, and 8 Hz) caused a frequency-dependent increase of contractile force. At stimulation frequencies of 2, 4, and 8 Hz, Ang 11 (10 nM) increased the stimulation-induced vasoconstrictor responses by a factor 4.8 +/- 0.9, 2.9 +/- 0.7, and 1.3 +/- 0.1, respectively (p < 0.05 compared with control for all frequencies). The enhancement could be concentration-dependently antagonized by losartan (1 nM-1 microM), irbesartan (0.1 nM-0.1 microM), and telmisartan (0.01 nM-0.01 microM). At a stimulation frequency of 2 Hz, the relation between stimulation-induced vasoconstrictor responses (in presence of Ang II 10 nM) and the concentration of the AT1-antagonists used could be described by linear regression. The order of potency concerning sympathoinhibition was telmisartan > irbesartan > losartan (p < 0.05 between linear regression lines). Contractile responses to exogenous noradrenaline were unaltered in the presence of Ang II 10 nM. We conclude that the facilitating effect of Ang II on noradrenergic neurotransmission is mediated by presynaptically located AT1-receptors. Conversely, this facilitating effect can be dose-dependently counteracted by blockade of these receptors. Sympathoinhibitory properties are likely to contribute to the therapeutic effect of AT1-blockers, in particular in conditions in which the sympathetic nervous system is activated, such as congestive heart failure and hypertension.

Angiotensin II↗
PubMed2005

Systematic variation normalization in microarray data to get gene expression comparison unbiased.

Normalization removes or minimizes the biases of systematic variation that exists in experimental data sets. This study presents a systematic variation normalization (SVN) procedure for removing systematic variation in two channel microarray gene expression data. Based on an analysis of how systematic variation contributes to variability in microarray data sets, our normalization procedure includes background subtraction determined from the distribution of pixel intensity values from each data acquisition channel and log conversion, linear or non-linear regression, restoration or transformation, and multiarray normalization. In the case when a non-linear regression is required, an empirical polynomial approximation approach is used. Either the high terminated points or their averaged values in the distributions of the pixel intensity values observed in control channels may be used for rescaling multiarray datasets. These pre-processing steps remove systematic variation in the data attributable to variability in microarray slides, assay-batches, the array process, or experimenters. Biologically meaningful comparisons of gene expression patterns between control and test channels or among multiple arrays are therefore unbiased using normalized but not unnormalized datasets.

Algorithms↗
PubMed1984

The use of left ventricular end-ejection pressure and peak pressure in the estimation of the end-systolic pressure-volume relationship.

The end-systolic pressure-volume relationship (ESPVR) as derived from left ventricular pressure-volume loops has gained increasing acceptance as an index of ventricular contractile function. In animal experiments the ESPVR has been defined as a line connecting the upper left corners of several differently loaded pressure-volume (P-V) loops with a slope parameter Ees and a volume axis intercept parameter Vo. In the clinical setting, several variants of the ESPVR have been determined with use of peak left ventricular pressure, end-ejection pressure, and end-ejection volume. The maximum P-V ratio has also frequently been measured. We attempted to determine which of these alternatives resulted in good approximations of the reference ESPVR in eight isolated canine ventricles that ejected into a simulated arterial impedance system with resistance, compliance, and characteristic impedance. We determined various versions of the ESPVR from the same set of beats quickly obtained with little change in inotropic background. To vary ventricular pressure wave forms, each of the arterial impedance parameters was independently controlled at 50%, 100%, and 200% of normal. Against each of the nine combinations of the impedance parameters four P-V loops were obtained under four preloads and from each of the sets of four P-V loops, the reference ESPVR, linear regression of the peak pressure on end-ejection volume (ESPVRPP-EEV), and linear regression of end-ejection pressure on end-ejection volume (ESPVREEPV) were determined. In addition, the maximum P-V ratio (MPVR) was calculated for each P-V loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

An ecologic study of parasuicide in Edmonton and Calgary.

OBJECTIVE: From 1986 to 1999, the suicide rate in the Edmonton Regional Health Authority (RHA) was greater than that in the Calgary RHA (mean rate ratio 1.4). We conducted a study to determine whether a similar relation holds for parasuicide, and if so, whether the pattern can be explained at the ecologic level by sociodemographic factors. METHODS: The Edmonton and Calgary RHAs provided data on emergency department visits for nonfatal intentional self-injury for 1997. We obtained sociodemographic data from the 1996 national census for the Edmonton and Calgary census metropolitan areas (CMAs) from Statistics Canada's public-use files. In each CMA, which is nearly coterminous with the corresponding RHA, we created 10 geographic areas based on average income. We analyzed the data at the ecologic level, using linear regression and multilevel Poisson regression. RESULTS: The parasuicide rate in the Edmonton CMA was greater than that in the Calgary CMA (rate ratio 1.3). In both CMAs, the parasuicide rate decreased as average income increased. In the final regression models, the only independent variables were average income, CMA, and their interaction term (linear regression model R2 = 0.82). CONCLUSIONS: The parasuicide rate in the Edmonton CMA is elevated, compared with that in the Calgary CMA. At the ecologic level, much of the variation in rates can be explained by average income and CMA. The high degree of correlation among the sociodemographic variables suggests that it may not be low income per se that is affecting the parasuicide rate but, rather, the consequences of belonging to a socially disadvantaged stratum of society.

Adolescent↗