Slope Of Linear Regression Line Research Articles

Quantitative Assessment of Tendon Backscatter Anisotropy in B-Mode Ultrasound

To test the anisotropy of human tendons in conventional B-mode ultrasound, we prospectively performed ultrasound scans of 40 normal patella tendons and 24 patella tendons with chronic tendinopathy in adults. We scanned all tendons in longitudinal orientation (parallel to tendon fibers) using a linear array transducer (8.5 MHz) with beam steering at 0°, 5°, 10°, 15° and 20°. We used ImageJ histogram analysis to process B-mode images offline for assessing backscatter as a function of angle, known as backscatter anisotropy, between normal tendons and the subcutaneous tissues and between normal tendons and tendons with tendinopathy. We compared the results using the slopes of linear regression lines drawn through the angle-dependent data, and we concluded that the tissue anisotropy was significantly different if the 95% confidence intervals of the line slopes for different tissues did not overlap. We observed significant differences between normal tendons and both the adjacent subcutaneous tissues and tendons with tendinopathy. However, the difference in the regression slopes between tendons with tendinopathy and the adjacent subcutaneous soft tissues was not significant. It appears that changes in anisotropic backscatter could be used to detect tendon abnormalities and in assessing the significance of disease and the effectiveness of therapy.

Central Venous Waveform Analysis and Cardiac Output in a Porcine Model of Endotoxemic Hypotension and Resuscitation.

Cardiac output (CO) is a valuable proxy for perfusion, and governs volume responsiveness during resuscitation from distributive shock. The underappreciated venous system has nuanced physiology that confers valuable hemodynamic information. In this investigation, deconvolution of the central venous waveform by the fast Fourier transformation (FFT) algorithm is performed to assess its ability to constitute a CO surrogate in a porcine model of endotoxemia-induced distributive hypotension and resuscitation. Ten pigs were anesthetized, catheterized, and intubated. A lipopolysaccharides infusion protocol was used to precipitate low systemic vascular resistance hypotension. Four crystalloid boluses (10 cc/kg) were then given in succession, after which heart rate, mean arterial pressure, thermodilution-derived CO, central venous pressure (CVP), and the central venous waveform were collected, the last undergoing fast Fourier transformation analysis. The amplitude of the fundamental frequency of the central venous waveform's cardiac wave (f0-CVP) was obtained. Heart rate, mean arterial pressure, CVP, f0-CVP, and CO were plotted over the course of the boluses to determine whether f0-CVP tracked with CO better than the vital signs, or than CVP itself. Distributive hypotension to a 25% mean arterial pressure decrement was achieved, with decreased systemic vascular resistance (mean 918 ± 227 [SD] dyne/s/cm-5 vs 685 ± 180 dyne/s/cm-5; p = 0.038). Full hemodynamic parameters characterizing this model were reported. Slopes of linear regression lines of heart rate, mean arterial pressure, CVP, f0-CVP, and CO were -2.8, 1.7, 1.8, 0.40, and 0.35, respectively, demonstrating that f0-CVP values closely track with CO over the 4-bolus range. Fast Fourier transformation analysis of the central venous waveform may allow real-time assessment of CO during resuscitation from distributive hypotension, possibly offering a venous-based approach to clinical estimation of volume responsiveness.

Central Venous Pressure Waveform Analysis Predicts Perfusion in a Porcine Model of Endotoxemic Hypotension and Resuscitation

Introduction: Cardiac output (CO), a proxy for perfusion, is a critical measure during sepsis and resuscitation. The understudied venous system has nuanced physiology that confers valuable information. In this investigation, deconvolution of the central venous pressure (CVP) waveform by the fast Fourier transformation (FFT) algorithm is performed to derive a CO surrogate in a “sepsis-like” porcine model of endotoxemic hypotension and resuscitation. Methods: Nine pigs were anesthetized, catheterized and intubated. A lipopolysaccharides infusion protocol was employed to precipitate low systemic vascular resistance (SVR) hypotension. Four subsequent crystalloid boluses (10 cc/kg) were given, after which thermodilution-CO, CVP and the CVP waveform were collected, the latter undergoing FFT analysis. The amplitude of the fundamental frequency of CVP waveform’s cardiac wave (“f0-CVP”) was obtained. Mean CVP, f0-CVP and CO were plotted over the course of the boluses to determine whether f0-CVP tracked with CO better than CVP itself. Results: Distributive hypotension to a 25% mean arterial pressure decrement was achieved, with decreased SVR (918±227 [standard deviation] dynes/seconds/cm-5 vs 685±180 dynes/seconds/cm-5; P = 0.038). Over four boluses, slopes of linear regression lines of CVP (r2=0.27; P < 0.001), f0-CVP (r2=0.15; P = 0.01) and CO (r2=0.08; P = 0.06) were 0.447, 0.148 and 0.178, respectively, demonstrating that f0-CVP constitutes a more accurate CO surrogate than CVP. Conclusion: FFT analysis of CVP waveforms offers a novel paradigm to interpret readily obtainable hemodynamic information. It offers potential for real-time utility in assessing volume responsiveness in sepsis and resuscitation, while further offering potential translation to the less-invasive peripheral venous pressure waveform.

Vertical Drop Jump Biomechanics of Patients With a 3- to 10-Year History of Youth Sport-Related Anterior Cruciate Ligament Reconstruction.

Background:A better understanding of movement biomechanics after anterior cruciate ligament reconstruction (ACLR) could inform injury prevention, knee injury rehabilitation, and osteoarthritis prevention strategies.Purpose:To investigate differences in vertical drop jump (VDJ) biomechanics between patients with a 3- to 10-year history of youth sport–related ACLR and uninjured peers of a similar age, sex, and sport.Study Design:Cross-sectional study. Level of evidence III.Methods:Lower limb kinematics and bilateral ground-reaction forces (GRFs) were recorded for participants performing 10 VDJs. Joint angles and GRF data were analyzed, and statistical analysis was performed using 2 multivariate models. Dependent variables included sagittal (ankle, knee, and hip) and coronal (knee and hip) angles at initial contact and maximum knee flexion, the rate of change of coronal knee angles (35%-90% of the support phase; ie, slopes of linear regression lines), and vertical and mediolateral GRFs (normalized to body weight [BW]). Fixed effects included group, sex, and time since injury. Participant clusters, defined by sex and sport, were considered as random effects.Results:Participants included 48 patients with a history of ACLR and 48 uninjured age-, sex-, and sport-matched controls (median age, 22 years [range, 18-26 years]; 67% female). Patients with ACLR demonstrated steeper negative coronal knee angle slopes (β = –0.04 deg/% [95% CI, –0.07 to –0.00 deg/%]; P = .025). A longer time since injury was associated with reduced knee flexion (β = –0.2° [95% CI, –0.3° to –0.0°]; P = .014) and hip flexion (β = –0.1° [95% CI, –0.2° to –0.0°]; P = .018). Regardless of ACLR history, women displayed greater knee valgus at initial contact (β = 2.1° [95% CI, 0.4° to 3.8°]; P = .017), greater coronal knee angle slopes (β = 0.05 deg/% [95% CI, 0.02 to 0.09 deg/%]; P = .004), and larger vertical GRFs (landing: β = –0.34 BW [95% CI, –0.61 to –0.07 BW]; P = .014) (pushoff: β = –0.20 BW [95% CI, –0.32 to –0.08 BW]; P = .001).Conclusion:Women and patients with a 3- to 10-year history of ACLR demonstrated VDJ biomechanics that may be associated with knee motion control challenges.Clinical Relevance:It is important to consider knee motion control during activities such as VDJs when developing injury prevention and rehabilitation interventions aimed at improving joint health after youth sport–related ACLR.

Contrasting patterns of radial growth rate between Larix principis-rupprechtii and Pinus sylvestris var. mongolica along an elevational gradient are mediated by differences in xylem hydraulics

Species-specific environmental adaptability results in different species having different suitable distribution ranges in nature. Investigating the change of relative advantages in growth performances among tree species along elevational gradients and the underlying mechanism are essential for selecting elevation-specific optimal species in forest management in mountainous regions. Xylem hydraulics has been widely reported to play a key role in tree growth and survival under water-limited environments, but whether and how it regulates tree growth performances at different elevations with contrasting water availability remain unclear. Here we combined tree-ring analyses and measurements of xylem hydraulics to investigate the patterns of tree radial growth and their linkages with water-related physiology for Prince Rupprecht's larch (Larix principis-rupprechtii Mayr) and Mongolian pine (Pinus sylvestris var. mongolica Litvinov) along a 500-m elevational gradient between 1336 and 1825 m a.s.l. in a semi-arid area of northern China where both species were widely used for afforestation. Our results showed that the radial growth rate, reflected by the slope of linear regression line for cumulative basal area increments and tree age, was higher in Prince Rupprecht's larch than in Mongolian pine at higher elevations, which coincided with the advantages in xylem hydraulic efficiency, i.e. higher sapwood area-specific hydraulic conductivity and leaf area to sapwood area ratio for the former species relative to the latter one at the middle and high elevation sites. However, the reversed pattern appeared in comparing radial growth rate for the two conifers at the low elevation sites that might be due to obviously greater loss of hydraulic conductivity caused by drought-induced xylem embolism for Prince Rupprecht's larch. This is corroborated by strong correlations between the tree-ring width indices and water-related climate variables during the growing season in Prince Rupprecht's larch but not in Mongolian pine at low elevations. Our study provides a mechanismic explanation for contrasting growth performances between the two species across elevations and implies a potential risk of growth decline under the influence of climate change in Prince Rupprecht's larch, the currently most widely used species for afforestation in this region, particularly under the drought-prone environment in the low-elevation sites.

Deep-learning-based attenuation correction in dynamic [15O]H2O studies using PET/MRI in healthy volunteers

Quantitative [15O]H2O positron emission tomography (PET) is the accepted reference method for regional cerebral blood flow (rCBF) quantification. To perform reliable quantitative [15O]H2O-PET studies in PET/MRI scanners, MRI-based attenuation-correction (MRAC) is required. Our aim was to compare two MRAC methods (RESOLUTE and DeepUTE) based on ultrashort echo-time with computed tomography-based reference standard AC (CTAC) in dynamic and static [15O]H2O-PET. We compared rCBF from quantitative perfusion maps and activity concentration distribution from static images between AC methods in 25 resting [15O]H2O-PET scans from 14 healthy men at whole-brain, regions of interest and voxel-wise levels. Average whole-brain CBF was 39.9 ± 6.0, 39.0 ± 5.8 and 40.0 ± 5.6 ml/100 g/min for CTAC, RESOLUTE and DeepUTE corrected studies respectively. RESOLUTE underestimated whole-brain CBF by 2.1 ± 1.50% and rCBF in all regions of interest (range −2.4%– −1%) compared to CTAC. DeepUTE showed significant rCBF overestimation only in the occipital lobe (0.6 ± 1.1%). Both MRAC methods showed excellent correlation on rCBF and activity concentration with CTAC, with slopes of linear regression lines between 0.97 and 1.01 and R2 over 0.99. In conclusion, RESOLUTE and DeepUTE provide AC information comparable to CTAC in dynamic [15O]H2O-PET but RESOLUTE is associated with a small but systematic underestimation.

Effects of short-term warm water immersion on cardiac baroreflex sensitivity in healthy men

Warm water immersion (WWI) causes dizziness presumably due to a substantial drop of blood pressure. The aim of this study was to elucidate the effects of short-term WWI on cardiac baroreflex sensitivity (BRS) and the contribution of arterial stiffness to the cardiac BRS. Twelve apparent healthy men (44 ± 12 years) performed the single stand-up test after 5-min sitting in the bathtub without (Control) and with 41 °C warm water at the heart level (WWI). Cardiac BRS gain was evaluated by R–R interval response to the standing-induced drop of systolic blood pressure. In addition, before and 10 min after the single stand-up test, carotid arterial β-stiffness index was evaluated in the supine rest. BRS gain was blunted (2.9 ± 1.6 vs. 1.8 ± 1.1 ms/mmHg, P = 0.005), whereas β-stiffness index was not changed significantly after WWI. BRS gain correlated with β-stiffness index before (r = − 0.626, P = 0.028) and after WWI (r = − 0.672, P = 0.015). ANCOVA revealed that these slopes of linear regression lines remained unchanged after WWI (P = 0.350). These results indicate that a short-term WWI acutely deteriorates cardiac BRS. Individuals with stiffer arteries are relatively more susceptible to WWI because of their poor baseline BRS, which might be one of the causes of bathing-related falling in elderly persons as well as frailty.

Magnetohydrodynamic flow of nano Williamson fluid generated by stretching plate with multiple slips

PurposeThe purpose of this paper is to present an exploration of multiple slips and temperature dependent thermal conductivity effects on the flow of nano Williamson fluid over a slendering stretching plate in the presence of Joule and viscous heating aspects. The effectiveness of nanoparticles is deliberated by considering Brownian moment and thermophoresis slip mechanisms. The effects of magnetism and radiative heat are also deployed.Design/methodology/approachThe governing partial differential equations are non-dimensionalized and reduced to multi-degree ordinary differential equations via suitable similarity variables. The subsequent non-linear problem treated for numerical results. To measure the amount of increase/decrease in skin friction coefficient, Nusselt number and Sherwood number, the slope of linear regression line through the data points are calculated. Statistical approach is implemented to analyze the heat transfer rate.FindingsThe results show that temperature distribution across the flow decreases with thermal conductivity parameter. The maximum friction factor is ascertained at stronger magnetic field.Originality/valueIn the current paper, the magneto-nano Williamson fluid flow inspired by a stretching sheet of variable thickness is examined numerically. The rationale of the present study is to generalize the studies of Mebarek-Oudina and Makinde (2018) and Williamson (1929).

Two-Phase Flow of Dusty Casson Fluid with Cattaneo-Christov Heat Flux and Heat Source Past a Cone, Wedge and Plate

This article addresses the boundary layer flow and heat transfer in Casson fluid submerged with dust particles over three different geometries (vertical cone, wedge and plate). The aspects of Cattaneo-Christov heat flux and exponential space-based heat source (ESHS) are also accounted. At first, the partial differential equations are transformed into a set of ordinary differential equations via appropriate similarity transformations. Resulting equations are solved via shooting method coupled with the Runge-Kutta-Fehlberg-45 integration scheme. The consequences of dimensionless parameters on velocity and temperature fields of both fluid and dust particles phase are analyzed. The rate of increment/decrement in the skin friction as well as the Nusselt number for various values of physical parameters are also estimated via slope of linear regression line using data points.

Effects of Geometries and Substructures of ICMEs on Geomagnetic Storms

To better understand geomagnetic storm generations by ICMEs, we consider the effect of substructures (magnetic cloud, MC, and sheath) and geometries (impact location of flux-rope at the Earth) of the ICMEs. We apply the toroidal magnetic flux-rope model to 59 CDAW CME–ICME pairs to identify their substructures and geometries, and select 20 MC-associated and five sheath-associated storm events. We investigate the relationship between the storm strength indicated by minimum Dst index $(\mathrm{Dst}_{\mathrm{min}})$ and solar wind conditions related to a southward magnetic field. We find that all slopes of linear regression lines for sheath-storm events are steeper ( ${\geq}\,1.4$ ) than those of the MC-storm events in the relationship between $\mathrm{Dst}_{\mathrm{min}}$ and solar wind conditions, implying that the efficiency of sheath for the process of geomagnetic storm generations is higher than that of MC. These results suggest that different general solar wind conditions (sheaths have a higher density, dynamic and thermal pressures with a higher fluctuation of the parameters and higher magnetic fields than MCs) have different impact on storm generation. Regarding the geometric encounter of ICMEs, 100% (2/2) of major storms ( $\mathrm{Dst}_{\mathrm{min}} \leq -100~\mbox{nT}$ ) occur in the regions at negative $P_{Y}$ (relative position of the Earth trajectory from the ICME axis in the $Y$ component of the GSE coordinate) when the eastern flanks of ICMEs encounter the Earth. We find similar statistical trends in solar wind conditions, suggesting that the dependence of geomagnetic storms on 3D ICME–Earth impact geometries is caused by asymmetric distributions of the geoeffective solar wind conditions. For western flank events, 80% (4/5) of the major storms occur in positive $P_{Y}$ regions, while intense geoeffective solar wind conditions are not located in the positive $P_{Y}$ . These results suggest that the strength of geomagnetic storms depends on ICME–Earth impact geometries as they determine the solar wind conditions at Earth.

Mortality following trajectories of physical function: The impact of socio-demographic factors and social relations

Introduction It is important to help older adults maintain a good physical function in old age in order to ensure quality of life, independent living and longevity. To tailor future preventive interventions and rehabilitation, it is necessary to identify how different trajectories of physical function are associated with mortality and whether certain groups of older adults are more vulnerable to negative consequences of adverse trajectories of physical function in old age. The aims of this study are to investigate how trajectories of physical function among older adults are associated with mortality and whether socio-demographic factors and social relations modify the associations. Methods Questionnaire data linked with register data on 2906 older Danish adults aged 75 and 80 years at baseline were included. Physical function was measured by the validated Mobility-help scale (0–6) four times over a 4.5-year period. Trajectories of physical function were based on the baseline measure of physical function and slopes of linear regression lines between the four measures of physical function over time. Four trajectories of physical function were identified by: (1) stable full physical function, (2) full physical function followed by a decrease, (3) stable low physical function and (4) low physical function followed by a decrease. Multivariable additive hazard regression models were used to estimate the association between the four trajectories of physical function and the following 5-year mortality. Results Compared to older adults with a stable full physical function, older adults with a low physical function followed by a decrease were associated with the highest number of additional deaths per 1000-person-years (py) (118.02, 95% CI: 67.40; 168.64). Hereafter older adults who had full physical function followed by a decrease (82.49, 95% CI: 65.22; 99.76) and finally older adults who had a stable low physical function (70.20, 95% CI: 35.33; 105.06). Wald test for global interaction showed significant interactions (P-value Conclusions Trajectories of physical function that included decline were associated with the greatest mortality. The magnitudes of the associations between adverse trajectories of physical function and mortality were greater for men than women and those aged 80 years than those aged 75 years at baseline.

Computer Modeling of Diabetes and Its Transparency: A Report on the Eighth Mount Hood Challenge

ObjectivesThe Eighth Mount Hood Challenge (held in St. Gallen, Switzerland, in September 2016) evaluated the transparency of model input documentation from two published health economics studies and developed guidelines for improving transparency in the reporting of input data underlying model-based economic analyses in diabetes. MethodsParticipating modeling groups were asked to reproduce the results of two published studies using the input data described in those articles. Gaps in input data were filled with assumptions reported by the modeling groups. Goodness of fit between the results reported in the target studies and the groups’ replicated outputs was evaluated using the slope of linear regression line and the coefficient of determination (R2). After a general discussion of the results, a diabetes-specific checklist for the transparency of model input was developed. ResultsSeven groups participated in the transparency challenge. The reporting of key model input parameters in the two studies, including the baseline characteristics of simulated patients, treatment effect and treatment intensification threshold assumptions, treatment effect evolution, prediction of complications and costs data, was inadequately transparent (and often missing altogether). Not surprisingly, goodness of fit was better for the study that reported its input data with more transparency. To improve the transparency in diabetes modeling, the Diabetes Modeling Input Checklist listing the minimal input data required for reproducibility in most diabetes modeling applications was developed. ConclusionsTransparency of diabetes model inputs is important to the reproducibility and credibility of simulation results. In the Eighth Mount Hood Challenge, the Diabetes Modeling Input Checklist was developed with the goal of improving the transparency of input data reporting and reproducibility of diabetes simulation model results.

Comment on Malanson (2017) “Mixed signals in trends of variance in high-elevation tree ring chronologies” published in Journal of Mountain Science

In a recent paper published in Journal of Mountain Science, Malanson (2017) explored variance changes in Rocky Mountains tree-ring chronologies. This commentary points out some methodological issues related to systematic bias in evolving tree-ring chronology variance and suggests that analyzing the slopes of linear regression lines may be suboptimal for identifying temporal changes in variance. The journal editor invited the original article’s authors Dr. Malandson to respond to the comments. Thus Dr. Malandson’s response is attached behind the comments.

Distinct biomarker roles for HbA1c and glycated albumin in patients with type 2 diabetes on hemodialysis

AimsHbA1c and glycated albumin (GA) are used to monitor glycemia, but their accuracy to represent glycemic profiles in hemodialysis remains controversial. MethodsContinuous glucose monitoring in 97 patients with type 2 diabetes (41 on hemodialysis [HD] and 56 without nephropathy) was analyzed to evaluate whether HbA1c and/or GA serve as appropriate glycemic profile markers. ResultsThe average glucose significantly correlated with HbA1c in both HD group and group without nephropathy (r=0.59, P<0.0001; r=0.40, P<0.005). The slopes of linear regression lines were statistically indistinguishable (F=0.30, P=0.744), while the y-intercepts were significantly different (F=57.86, P<0.0001). GA showed strong correlation with the glycemic standard deviation (r=0.68, P<0.0001), and with the average glucose (r=0.42, P<0.001). Least square analysis revealed that only HbA1c, but not GA, was significantly associated with the average glucose (F=10.20, P<0.0005; F=0.38, P=0.5427), while only GA was significantly associated with the glycemic variability in HD group. ConclusionsIn HD participants, HbA1c correlates with the average glucose more than GA, but underestimates it, and a correction formula of HbA1c can be developed as an appreciable marker. GA value itself reflects the average glucose, but less accurately than HbA1c, while it could serve as an indicator for hyperglycemia/hypoglycemia excursion.

Assessment of different pools of organic carbon for better C management in cotton-growing shrink-swell soils of Jalgaon district, Maharashtra

Information on dynamics of soil organic carbon (SOC) in agricultural soils is important for sustained crop productivity, maintenance of soil health and alleviating the climate related stress. Researchers have found that oxidizable soil organic carbon (SOC) fractions are more important in maintaining the soil quality than total organic carbon (TOC). The SOC measured by Walkley and Black method is not sensitive to assess soil quality, but labile fractions of TOC is directly related to the soil productivity and quality. It is therefore, imperative to find out its quantum of SOC and fractions of TOC for better C management and carbon sequestration. In such an endeavour, a case study on carbon dynamics was undertaken for cotton-growing shrink-swell soils of Jalgaon district, Maharashtra, to quantify the SOC and its fractions in TOC and their interrelation with the crop yield. The surface (0-30 cm) soil samples (75) were collected from dominant cotton-growing shrink- swell soils in 2011-12 and analyzed for SOC, very labile carbon (VLC), labile carbon (LC), less labile C (LLC) and non-labile C (NLC). Factorial relationship between SOC with TOC and their relationship with crop yield was worked out. The result indicated that VLC, LC, LLC and NLC contributed to the tune of 15.33%, 11.85%, 51.15% and 21.07% of the TOC, respectively. The dichromate oxidizable SOC (y) was found linearly related to the TOC (x) by the equation, y = 0.782x + 0.025 (R² = 0.932), indicating that oxidizable SOC comprised 78.2 % of the TOC, in other words, a correction factor of 1.278 (inverse of the slope of linear regression line) may be used to convert SOC values in shrink-swell soils of Jalgaon. The crop yield was closely related to the SOC (r = 0.642) compared to TOC (r = 0.610). Considering the maximum and minimum cotton yield, the threshold value and maximum value of SOC were worked out to be 5.688 and 8.312 g C/kg, respectively, reflecting the carbon sequestrations potential of soils. Among the different fractions, VLC was found to be well correlated (r = 0.512) with the crop productivity. The computed threshold and maximum value for VLC were 0.547 and 2.147 g C/kg, respectively. The study thus establishes that only 27.18 % of active carbon (VLC+LC) are important for the crop production in cotton- growing shrink-swell soils.

Differences in antioxidant properties of ginkgo leaves collected from male and female trees.

Total phenolic content and antioxidant capacity (FRAP method) of Ginkgo biloba L. leaves collected from male and female trees were determined and compared. Different water and aqueous ethanolic (water/ethanol 80/20, V/V) extracts were prepared by varying the time of infusing, boiling and steeping in order to determine the effect of the extraction method on the above parameters. Antioxidant activity and phenolic content of ginkgo leaf extracts correlated well with significant correlation coefficients. Slopes of linear regression lines were not statistically different for either sex.

Assessment of Autonomic Function by Phase Rectification of RRInterval Histogram Analysis in Chagas Disease.

BackgroundIn chronic Chagas disease (ChD), impairment of cardiac autonomic function bears prognostic implications. Phase‑rectification of RR-interval series isolates the sympathetic, acceleration phase (AC) and parasympathetic, deceleration phase (DC) influences on cardiac autonomic modulation.ObjectiveThis study investigated heart rate variability (HRV) as a function of RR-interval to assess autonomic function in healthy and ChD subjects.MethodsControl (n = 20) and ChD (n = 20) groups were studied. All underwent 60-min head-up tilt table test under ECG recording. Histogram of RR-interval series was calculated, with 100 ms class, ranging from 600–1100 ms. In each class, mean RR-intervals (MNN) and root-mean-squared difference (RMSNN) of consecutive normal RR-intervals that suited a particular class were calculated. Average of all RMSNN values in each class was analyzed as function of MNN, in the whole series (RMSNNT), and in AC (RMSNNAC) and DC (RMSNNDC) phases. Slopes of linear regression lines were compared between groups using Student t-test. Correlation coefficients were tested before comparisons. RMSNN was log-transformed. (α < 0.05).ResultsCorrelation coefficient was significant in all regressions (p < 0.05). In the control group, RMSNNT, RMSNNAC, and RMSNNDC significantly increased linearly with MNN (p < 0.05). In ChD, only RMSNNAC showed significant increase as a function of MNN, whereas RMSNNT and RMSNNDC did not.ConclusionHRV increases in proportion with the RR-interval in healthy subjects. This behavior is lost in ChD, particularly in the DC phase, indicating cardiac vagal incompetence.

Inactivation of multidrug resistant (MDR)- and extensively drug resistant (XDR)-Mycobacterium tuberculosis by photodynamic therapy

We investigated the effects of photodynamic therapy (PDT) on anti-tuberculosis (TB) activity by measuring inactivation rates, expressed as D-value, of MDR- and XDR-Mycobacterium tuberculosis (M. tb) clinical strains in vitro. Approximately 10(6) colony forming unit per milliliter (CFU/ml) of the bacilli were irradiated with various doses of laser light after exposure to photosensitizers. Survival of M. tb was measured by enumerating CFU in 7H10 medium to measure D-values. No inactivation of M. tb was observed when exposed to photosensitizers (radachlorin or DH-I-180-3) only or laser light only (P>0.1). Treatment with a combination of photosentizer and laser inactivated M. tb although there was a significant difference between the types of photosensitizers applied (P<0.05). Linear inactivation curves for the clinical M. tb strains were obtained up to laser doses of 30 J/cm(2) but prolonged irradiation did not linearly inactivate M. tb, yielding sigmoid PDT inactivation curves. D-values of M. tb determined from the slope of linear regression lines in PDT were not significantly different and ranged from 10.50 to 12.13 J/cm(2) with 670 nm laser irradiation at 100 mW/cm(2) of the fluency rate, except for a drug-susceptible strain among the clinical strains tested. This suggests that PDT inactivated M. tb clinical strains regardless of drug resistance levels of the bacilli. Intermittent and repeated PDT allowed acceleration of the inactivation of the bacilli as a way to avoid the sigmoid inactivation curves. In conclusion, PDT could be alternative as a new option for treatment for MDR- and XDR-tuberculosis.

SU-D-137-07: Verification of the Method Used in Clinical Estimation of Alpha/beta Ratio, Using a Model Simulation Including Proliferation and Hypoxic Effects

Purpose: We hypothesize that the interplay between cell kill, proliferation, and hypoxia make the traditional interpretation of clinically‐derived α/β ratios problematic. In this study, we simulate resulting α/β ratios given a recently developed tumor‐response simulation model that includes the interplay between hypoxia and proliferation, as well as the resulting tumor reoxygenation during a course of radiotherapy. Methods: Using a state‐driven tumor response model, various typical fractionation schemes were simulated until the same level of tumor control probability was achieved (50%). Depending on the inclusion of effects, four different cases were evaluated: (1) neither proliferation nor hypoxia; (2) proliferation only; (3) hypoxia only; and (4) both proliferation and hypoxia. We judge the full model to be most realistic. The resulting α/β ratio was estimated based on the Withers isoeffect equation (as a negative slope of linear regression line in the plot of TD5 0 vs. TD5 0 xd) and compared with the ratio in model input, α/β(model) (=6.63). Results: Without any other effects (case 1), the model estimated an α/β ratio, α/β(est), that equals to the model assigned value. Including proliferation (case 2), smaller fractional doses become less effective due to increased repopulation, resulting in a reduced α/β(est). For case 3, including hypoxia only, longer schedules with smaller fraction sizes become more effective due to reoxygenation and resulted in unrealistic negative α/β(est). Interestingly, in case 4, the two effects, proliferation and hypoxia, approximately cancel each other and unmask the underlying cell‐kill characteristics, resulting in an α/β(est) comparable to the model input value α/β(model). Conclusion: Simulations show that the estimated α/β ratio is dependent on underlying radiobiological effects (including proliferation and hypoxia), and the resulting model estimation may not be an accurate reflection of cell‐kill sensitivity alone, which implies the clinical estimation might be biased if other effects are not properly controlled.

Possible ideas on carbon and nitrogen trophic fractionation of food chains: a new aspect of food‐chain stable isotope analysis in Lake Biwa, Lake Baikal, and the Mongolian grasslands

AbstractTrophic fractionation of carbon and nitrogen isotopes (Δδ13C, Δδ15N) was examined using previously complied databases for food chains in Lake Biwa, Lake Baikal, and Mongolian grassland. The following two features were clarified: (1) For each ecosystem, the ratios of trophic fractionation of carbon and nitrogen isotopes (Δδ15N/Δδ13C) throughout food chain could be obtained as the slope of linear regression line on the δ15N–δ13C plot. (2) Further, analysis of covariance (ANCOVA) revealed the slopes on δ15N–δ13C were not significantly different among these various ecosystems and allowed us to have the regression by setting δ15N as the response variable: δ15N = 1.61 δ13C + [ecosystem specific constant] with standard errors of [±0.41] and [±9.7] for the slope and the intercept, respectively. It was suggested that the slope of the regression (or the ratio Δδ15N/Δδ13C) could be applicable to more complicated food webs in case nitrogen and carbon isotope ratios of primary producers can be assumed constant in space and time within the ecosystems. The results from simple linear regression analyses coincided well with the ANCOVA results for these ecosystems, although there was some discrepancy between the results of the two statistical analyses. Possible factors that govern the linear relationship between δ15N and δ13C along a food chain are discussed together with a new scope for the stable isotope food chain analyses.