Independent Effects Of Changes Research Articles

A Conceptual Model for Projecting Coccolithophorid Growth, Calcification and Photosynthetic Carbon Fixation Rates in Response to Global Ocean Change

Temperature, light and carbonate chemistry speciation all influence the growth, calcification and photosynthetic carbon fixation rates of coccolithophores to a similar degree. There have been multiple attempts to project the responses of coccolithophores to changes in carbonate chemistry, but the interaction with light and temperature remains elusive. Here we devise a simple conceptual model to derive a fit equation for coccolithophorid growth, photosynthetic carbon fixation and calcification rates in response to simultaneous changes in carbonate chemistry speciation, temperature and light conditions. The fit equation is able to account for up to 88% of the variability in measured metabolic rates. Equation projections indicate that temperature, light and carbonate chemistry speciation all have different modulating effects on both optimal growth conditions and the sensitivity of responses to extreme environmental conditions. Calculations suggest that a single extreme environmental condition (CO2, temperature, light) will reduce maximum rates regardless of how optimal the other environmental conditions may be. Thus, while the response of coccolithophores to ocean change depends on multiple variables, the one which is least optimal will have the most impact on overall rates. Finally, responses to ocean change are usually reported in terms of cellular rates. However, changes in cellular rates can be a poor predictor for assessing changes in production at the community level. We therefore introduce a new metric, the calcium carbonate production potential (CCPP), which combines the independent effects of changes in growth rate and cellular calcium carbonate content to assess how environmental changes will impact coccolith production. Direct comparison of CO2 impacts on cellular CaCO3 production rates and CCPP shows that while the former is still at 45% of its pre-industrial capacity at 1000 uatm, the latter is reduced to 10%.

Effects Of Changes In Obesity, Fitness, And Physical Activity On Aortic Stiffness In Obese Adults

Aortic stiffness, a precursor to adverse cardiovascular outcomes, is worsened in conditions of general and abdominal obesity, low cardiorespiratory fitness (CRF), and physical inactivity. Elevated carotid-femoral pulse wave velocity (cfPWV) is an indicator of aortic stiffness. Behavioral weight loss interventions promote decreased caloric intake and increased moderate-vigorous physical activity (MVPA), but whether increases in MVPA and CRF have independent or additive effects with weight loss on aortic stiffness remains unclear. PURPOSE: To determine the overall and independent effects of changes in general and abdominal obesity, CRF, and MVPA on cfPWV in overweight and obese adults. METHODS: Eighty three (N=83) sedentary, overweight and obese adults (age 44.5 ± 8.1 years; BMI 32.4 ± 4.0 kg/m2) completed 6 months of a standard behavioral weight loss intervention. Assessments included cfPWV (m/s) by applanation tonometry, abdominal obesity by dual X-ray absorptiometry (DXA), MVPA (min/wk, MET-min/wk) by objective activity monitoring and CRF by graded exercise testing. Changes in systolic and diastolic blood pressure (SBP, DBP) were also evaluated. Multiple linear regression was performed to determine the effect of changes in CRF and MVPA on cfPWV with changes in body weight and abdominal fat as covariates. RESULTS: After 6 months, body weight, BMI, waist circumference, and abdominal fat significantly decreased, while CRF and MVPA significantly increased (all p0.1). Reductions in body weight, BMI, waist circumference, and abdominal fat were not associated with the decrease in cfPWV (all p>0.1). The decrease in cfPWV was moderately correlated with decreases in SBP (r=0.379, p<0.001) and DBP (r=0.317, p=0.004). CONCLUSION: These data did not support that changes in fatness were associated with improved aortic stiffness, however, the significant improvements in CRF and cfPWV suggest that targeting fitness in lifestyle interventions for a sedentary, obese population maybe be important for better vascular health. Supported by NIH (HL103646)

Memory for surface features of unfamiliar melodies: independent effects of changes in pitch and tempo

A melody's identity is determined by relations between consecutive tones in terms of pitch and duration, whereas surface features (i.e., pitch level or key, tempo, and timbre) are irrelevant. Although surface features of highly familiar recordings are encoded into memory, little is known about listeners' mental representations of melodies heard once or twice. It is also unknown whether musical pitch is represented additively or interactively with temporal information. In two experiments, listeners heard unfamiliar melodies twice in an initial exposure phase. In a subsequent test phase, they heard the same (old) melodies interspersed with new melodies. Some of the old melodies were shifted in key, tempo, or key and tempo. Listeners' task was to rate how well they recognized each melody from the exposure phase while ignoring changes in key and tempo. Recognition ratings were higher for old melodies that stayed the same compared to those that were shifted in key or tempo, and detrimental effects of key and tempo changes were additive in between-subjects (Experiment 1) and within-subjects (Experiment 2) designs. The results confirm that surface features are remembered for melodies heard only twice. They also imply that key and tempo are processed and stored independently.

Five-Year Changes in Biologic Risk Factors and Risk of Type 2 Diabetes: Are Attained But Not Initial Risk Factor Levels of Importance?

Independent effects of changes in biologic risk factors on type 2 diabetes incidence remain unclear. The authors examined whether associations between changes in biologic risk factors and diabetes risk are driven by initial or attained risk factor levels. Biologic risk factors were measured at baseline and at each 5-year interval follow-up (rounds 2, 3, and 4) among 4,204 initially healthy men and women, aged 20-59 years, participating in the Dutch Doetinchem Cohort Study (1987-2007). Time-dependent Cox regression analyses were used to analyze associations between changes in waist circumference, blood pressure, and high density lipoprotein cholesterol (HDL cholesterol) and incident diabetes, adjusted for initial or attained levels; 130 diabetes cases occurred during 9 years of follow-up. Five-year increases in waist circumference and blood pressure and decreases in HDL cholesterol were positively associated with risk of diabetes after adjustment for initial levels but no longer after adjustment for attained levels: waist circumference (hazard ratio (HR) = 0.86, 95% confidence interval (CI): 0.69, 1.07), systolic blood pressure (HR = 0.96, 95% CI: 0.84, 1.10), diastolic blood pressure (HR = 0.96, 95% CI: 0.87, 1.06), and HDL cholesterol (HR = 0.91, 95% CI: 0.81, 1.01). In conclusion, the associations between changes in biologic risk factors and risk of diabetes are mainly driven by the attained levels. Hence, not the prior changes, but the attained levels seem to be of importance with regard to diabetes risk.

Neonatal Outcomes After Implementation of Guidelines Limiting Elective Delivery Before 39 Weeks of Gestation

OBJECTIVE: To evaluate the association of a new institutional policy limiting elective delivery before 39 weeks of gestation with neonatal outcomes at a large community-based academic center. METHODS: A retrospective cohort study was conducted to estimate the effect of the policy on neonatal outcomes using a before and after design. All term singleton deliveries 2 years before and 2 years after policy enforcement were included. Clinical data from the electronic hospital obstetric records were used to identify outcomes and relevant covariates. Multivariable logistic regression was used to account for independent effects of changes in characteristics and comorbidities of the women in the cohorts before and after implementation. RESULTS: We identified 12,015 singleton live births before and 12,013 after policy implementation. The overall percentage of deliveries occurring before 39 weeks of gestation fell from 33.1% to 26.4% (P<.001); the greatest difference was for women undergoing repeat cesarean delivery or induction of labor. Admission to the neonatal intensive care unit (NICU) also decreased significantly; before the intervention, there were 1,116 admissions (9.29% of term live births), whereas after, there were 1,027 (8.55% of term live births) and this difference was significant (P.044). However, an 11% increased odds of birth weight greater than 4,000 g (adjusted odds ratio 1.11; 95% confidence interval [CI] 1.01–1.22) and an increase in stillbirths at 37 and 38 weeks, from 2.5 to 9.1 per 10,000 term pregnancies (relative risk 3.67, 95% CI 1.02–13.15, P.032), were detected. CONCLUSION: A policy limiting elective delivery before 39 weeks of gestation was followed by changes in the timing of term deliveries. This was associated with a small reduction in NICU admissions; however, macrosomia and stillbirth increased.

Neonatal Outcomes After Implementation of Guidelines Limiting Elective Delivery Before 39 Weeks of Gestation

To evaluate the association of a new institutional policy limiting elective delivery before 39 weeks of gestation with neonatal outcomes at a large community-based academic center. A retrospective cohort study was conducted to estimate the effect of the policy on neonatal outcomes using a before and after design. All term singleton deliveries 2 years before and 2 years after policy enforcement were included. Clinical data from the electronic hospital obstetric records were used to identify outcomes and relevant covariates. Multivariable logistic regression was used to account for independent effects of changes in characteristics and comorbidities of the women in the cohorts before and after implementation. We identified 12,015 singleton live births before and 12,013 after policy implementation. The overall percentage of deliveries occurring before 39 weeks of gestation fell from 33.1% to 26.4% (P<.001); the greatest difference was for women undergoing repeat cesarean delivery or induction of labor. Admission to the neonatal intensive care unit (NICU) also decreased significantly; before the intervention, there were 1,116 admissions (9.29% of term live births), whereas after, there were 1,027 (8.55% of term live births) and this difference was significant (P=.044). However, an 11% increased odds of birth weight greater than 4,000 g (adjusted odds ratio 1.11; 95% confidence interval [CI] 1.01-1.22) and an increase in stillbirths at 37 and 38 weeks, from 2.5 to 9.1 per 10,000 term pregnancies (relative risk 3.67, 95% CI 1.02-13.15, P=.032), were detected. A policy limiting elective delivery before 39 weeks of gestation was followed by changes in the timing of term deliveries. This was associated with a small reduction in NICU admissions; however, macrosomia and stillbirth increased.

Independent effects of age-related changes in waist circumference and BMI z scores in predicting cardiovascular disease risk factors in a prospective cohort of adolescent females

Cross-sectional data indicate that central adiposity is associated with cardiovascular disease risk, independent of total adiposity. The use of longitudinal data to investigate the relation between changes in fat distribution and the emergence of risk factors is limited. We tested the hypothesis that age-related change in waist circumference (to reflect central adiposity) during adolescence is a significant predictor of longitudinal change in cardiovascular disease risk, after adjustment for change in body mass index (BMI) z score (to reflect total adiposity) in a cohort of postmenarcheal adolescent females. We also tested whether race modified this relation. We analyzed publicly available data from the National Heart, Lung, and Blood Institute Growth and Health Study. Longitudinal regression models were fitted to investigate the independent effects of changes in waist circumference on cardiovascular disease risk factors. Steeper age-related increases in waist circumference over time were associated with a greater increase in LDL-cholesterol concentrations, systolic blood pressure, diastolic blood pressure, and homeostasis model assessment of insulin resistance, after adjustment for BMI z score, in white but not in black females. Change in waist circumference was not a statistically significant predictor of age-related changes in HDL-cholesterol, triglyceride, insulin, and glucose concentrations, after adjustment for changes in BMI z score, in either white or black females. Our research suggests that monitoring waist circumference in addition to BMI z score has the potential to identify adolescents at risk of the emergence of cardiovascular disease risk factors, at least in white females. The data also suggest that race may modify the relation between fat distribution pattern and cardiovascular disease risk factors.

Alcohol outlets, gonorrhea, and the Los Angeles civil unrest: A longitudinal analysis

This study tests the effect of neighborhood changes on gonorrhea rates. Prior studies that indicate gonorrhea rates are associated with alcohol outlet density and neighborhood deterioration have been cross-sectional and cannot establish causality. After the 1992 Civil Unrest in Los Angeles, 270 alcohol outlets surrendered their licenses due to arson and vandalism thus providing a natural experiment. We geocoded all reported gonorrhea cases from 1988 to 1996 in LA County, all annually licensed alcohol outlets, and all properties damaged as a result of the civil unrest. We ran individual growth models to examine the independent effects of changes in alcohol outlets and damaged buildings on gonorrhea. The individual growth model explained over 90% of the residual variance in census tract gonorrhea rates. After the civil unrest, a unit decrease in the number of alcohol outlets per mile of roadway was associated with 21 fewer gonorrhea cases per 100,000 ( p<.01) in tracts affected by the Unrest compared to those not affected. Neighborhood alcohol outlets appear to be significantly associated with changes in gonorrhea rates. The findings suggest that efforts to control sexually transmitted diseases, including gonorrhea and HIV, should address contextual factors that facilitate high-risk behaviors and disease transmission

Did Recent Changes in Medicare Reimbursement Hit Teaching Hospitals Harder?

To inform the policy debate on Medicare reimbursement by examining the financial effects of the Balanced Budget Act of 1997 (BBA) and subsequent adjustments on major academic medical centers, minor teaching hospitals, and nonteaching hospitals. The authors simulated the impacts of BBA and subsequent BBA adjustments to predict the independent effects of changes in Medicare reimbursement on hospital revenues using 1997-2001 Medicare Cost Reports for all short-term acute-care hospitals in the United States. The authors also calculated actual (nonsimulated) operating and total margins among major teaching, minor teaching, and nonteaching hospitals to account for hospital response to the changes. The BBA and subsequent refinements reduced Medicare revenues to a greater degree in major teaching hospitals, but the fact that such hospitals had a smaller proportion of Medicare patients meant that the BBA reduced overall revenues by similar percentages across major, minor, and nonteaching hospitals. Consistently lower margins may have made teaching hospitals more vulnerable to cuts in Medicare support. Recent Medicare changes affected revenues at teaching and nonteaching hospitals more similarly than is commonly believed. However, the Medicare cuts under the BBA probably exacerbated preexisting financial strain on major teaching hospitals, and increased Medicare funding may not suffice to eliminate the strain. This report's findings are consistent with recent calls to support needed services of teaching hospitals through all-payer or general funds.

The effects of ventricular end-diastolic and systolic pressures on action potential and duration in anaesthetized dogs.

1. Although it is known that mechanical events in the heart influence the duration of the cardiac action potential, there is no quantitative information on the effects of independent changes in ventricular end-diastolic and systolic pressures. 2. Experiments were carried out on open-chest anaesthetized dogs in which the autonomic nervous influences on the heart were prevented and monophasic action potentials were recorded form the epicardial surface of the left ventricle. The duration of these action potentials was taken as the interval from the upstroke to the point of 90% repolarization. 3. Elevation of left ventricular peak systolic pressure, at constant end-diastolic pressure, significantly shortened the monophasic action potential. 4. Elevation of end-diastolic pressure at constant peak systolic pressure significantly lengthened the monophasic action potential. 5. Responses were not dependent on release of noradrenaline from sympathetic nerve terminals because they persisted after administration of bretylium tosylate. They were also not due to myocardial ischaemia because they persisted when coronary perfusion pressure was maintained at a constant high level. 6. Simultaneous recordings of changes in myocardial segment length showed the expected responses to changes in ventricular pressures: increases in shortening in response to increases in diastolic pressure and no consistent effect from changes in systolic pressure. 7. These investigations demonstrate the independent effects of changes in systolic and end-diastolic pressures on cardiac action potential duration. This effect is likely to be an effect of the mechanical events, i.e. contraction-excitation feedback. This response may be mediated through changes in myocardial fibre tension, the consequent changes in fibre shortening, or both.

Sensitivity of CO2 washout to changes in acinar structure in a single-path model of lung airways

A numerical solution of the convection-diffusion equation with an alveolar source term in a single-path model (SPM) of the lung airways simulates steady state CO2 washout. The SPM is used to examine the effects of independent changes in physiologic and acinar structure parameters on the slope and height of Phase III of the single-breath CO2 washout curve. The parameters investigated include tidal volume, breathing frequency, total cardiac output, pulmonary arterial CO2 tension, functional residual capacity, pulmonary bloodflow distribution, alveolar volume, total acinar airway cross sectional area, and gas-phase molecular diffusivity. Reduced tidal volume causes significant steepening of Phase III, which agrees well with experimental data. Simulations with a fixed frequency and tidal volume show that changes in blood-flow distribution, model airway cross section, and gas diffusivity strongly affect the slope of Phase III while changes in cardiac output and in pulmonary arterial CO2 tension strongly affect the height of Phase III. The paper also discusses differing explanations for the slope of Phase III, including sequential emptying, stratified inhomogeneity, and the issue of asymmetry, in the context of the SPM.

Effects of acid-base variables on in vitro hepatic metabolism in rainbow trout.

The effects of hypercapnia (1% CO2), and the independent effects of changes in extracellular pH (pHe), PCO2 and [HCO3-] on intracellular pH (measured by the DMO method) and lactate metabolism (measured by utilization of 14C-labelled lactate), were examined in rainbow trout hepatocytes in vitro. Simulated uncompensated hypercapnia (high PCO2, low pHe, moderately increased [HCO3-] led to a substantial depression in the production of CO2 (44%) and glucose (51%) from lactate. In simulated compensated hypercapnia (high PCO2, normal pHe, high [HCO3-], metabolism was still significantly inhibited (18-33%). Subsequent multifactorial design experiments determined that variations in PCO2, pH and [HCO3-] independently affected metabolism; increased PCO2 and decreased pH inhibited metabolism, but increased [HCO3-] stimulated metabolism. These results are interpreted in terms of the effects of acid-base variables on enzymatic and transport pathways, and the possible causes of decreased hepatic glycogen stores during in vivo hypercapnia are discussed.

Responses of left ventricle to changes in aortic input impedance.

In order to evaluate how pressure and flow at the outlet of a ventricle are determined by the interaction between the ventricle and an aortic input impedance, we examined the effects of independent changes in the peripheral resistance and in the aortic compliance using isolated canine left ventricle preparations. There was an inverse linear relationship of mean values between pressure and cardiac output under pure resistance changes when coronary flow was maintained constant. But, when the coronary perfusion pressure depended on mean aortic pressure, the relationship was no longer linear under a critical aortic pressure. When aortic compliance was increased, late systolic flow was enhanced and late systolic pressure decreased such that the stroke volume increased. The top part of the pressure-volume loop showed a configurational change from the right side down to the left side down. Changes in pressure and flow wave forms, and in the pressure-volume loop can be predicted by an electrical model in which time varying capacitance arranged in series with the internal resistance was used as a ventricular model.

Independent effects of changes in H+ and CO 2 concentrations on hypoxic pulmonary vasoconstriction.

Independent effects of changes in H+ and CO 2 concentrations on hypoxic pulmonary vasoconstriction.

The independent effects of changes in H + and CO 2 concentrations on pulmonary hemodynamics of intact dogs.

The hydrogen ion concentration ([H+]) and the carbon dioxide tension [Formula: see text] of the arterial blood were varied independently of the other over a range of values while the respiration was controlled at resting levels. The independent effects of the two variables were examined in intact dogs anesthetized with 30 mg/kg sodium pentobarbital. Increases in [H+] and [Formula: see text] were significantly correlated (r = 0.859 and r = 0.646) with increases in the pulmonary vascular resistance (P.V.R.). The rise in P.V.R. in both cases was associated with rise in pulmonary perfusion pressure and no significant change in pulmonary blood flow. Decrease in [Formula: see text] had no effect on the measured parameters. We have demonstrated the independent pulmonary vasoconstrictor effects of increase in the [H+] and [Formula: see text]. The magnitude of the pulmonary vasoconstrictor response is dependent upon the degree of rise in [H+] and [Formula: see text]. [Formula: see text] does not play a role in maintaining resting pulmonary vasomotor tone.

Bubble coalescence and the simulation of mass transport and chemical reaction in gas fluidized beds

A simulation of a fluidized bed reactor is presented which attempts to represent the effects of vertical coalescence of rising bubbles on a first-order reaction catalyzed by solid particles. Vertical coalescence was studied experimentally for bubbles issuing from a single pulsed injector. A mathematical model of bubble coalescence was developed and shown to agree reasonably well with the experimental data. The coalescence model was then included in an improved theoretical model, along with models for mass transport and chemical reaction, to simulate the performance of a fluidized bed reactor. The simulation provides reactant conversion information using simple formulas containing dimensionless groups to represent reactant transport from the bubbles and the catalytic activity of the solid particles. The model was used to calculate the independent effects of changes in diffusion coefficient, fluidization velocity, bed height, reaction rate constant and reactant feed concentration on conversion. These effects were compared with theoretical predictions.

Effects of raised barometric pressures on respiration in man.

AbstractHesser, C. M. and B. Holmgren. Effects of raised barometric pressures on respiration in man. Acta physiol. scand. 1959. 47. 28—43. – The effects of raised barometric pressures (up to 4.0 atm) on various respiratory functions, hitherto largely neglected, were studied on 8 healthy subjects at rest in a recompression chamber. The independent effects of changes in inspired oxygen and nitrogen pressures were studied by comparing data obtained on air, 100 % oxygen, and 5 % oxygen in nitrogen at various ambient pressures. Breathing air with increasing ambient pressure, respiration became progressively slower and deeper, whereas at 4.0 atm the effective alveolar ventilation was slightly increased. Other observations at 4.0 atm were: Average increase of 33 % in tidal volume; average decreases in respiratory rate of 27 %, respiratory minute volume of 10 %, and functional dead space/tidal volume ratio of 9 %; no demonstrable changes in expiratory reserve volume, functional dead space and respiratory exchange ratio. Evidence is presented that the respiratory changes were caused by the combined effects of increased oxygen tension and of increased breathing resistance due to increased gas density. Thus, nitrogen at high pressures (up to 3.8 atm) exerted little, if any, depressant action on respiration.